HK1128820B - Nitride semiconductor device having support substrate and its manufacturing method - Google Patents

Description

Nitride semiconductor device with supporting substrate and method for manufacturing the same

This application is a divisional application of an application entitled "nitride semiconductor device with supporting substrate and method for manufacturing the same" filed on 30/6/2004 under the international application number PCT/JP2003/000757, application number 03801898.5.

Technical area

The present invention relates to a nitride semiconductor device used for a light emitting element such as a Light Emitting Diode (LED) or a Laser Diode (LD), a light receiving element such as a solar cell or an optical sensor, or an electronic device such as a transistor or a power device, and a method for manufacturing the same. The adhesive structure is adopted as one of the manufacturing methods.

Background

Although nitride semiconductors are promising semiconductor materials as direct transition type semiconductors, the fabrication of bulk single crystals is difficult. Therefore, a heteroepitaxial growth technique for growing GaN on a hetero-substrate such as sapphire or SiC by Metal Organic Chemical Vapor Deposition (MOCVD) is currently used. Among them, sapphire has been confirmed to be a preferable substrate for growing a high-efficiency nitride semiconductor light-emitting element due to stability in a high-temperature ammonia atmosphere of an epitaxial growth process. The method used in the case of using a sapphire substrate is: AlGaN is formed as a transition layer (buffer layer) on a sapphire substrate at a low temperature of about 600 ℃, and a nitride semiconductor layer is grown thereon. This can improve the crystallinity of the nitride semiconductor layer.

Specifically, nitride semiconductor devices grown on sapphire substrates are used for blue LEDs, pure green LEDs, and LDs (laser diodes) having higher luminance than ever before, and they are used for full-color display devices, media such as DVDs for storing large-capacity information such as light sources for oscilloscopes, image scanners, optical disks, light sources for communications, printing devices, and the like. And even for electronic devices such as Field Effect Transistors (FETs).

(patent document 1)

Japanese unexamined patent publication No. 9-129932

However, sapphire is an insulator having poor thermal conductivity, and thus the construction of a nitride semiconductor device is limited. For example, if the semiconductor device is a conductor substrate such as GaAs or GaP, 1 electrical contact (electrode) may be provided on the upper surface of the semiconductor device, and 1 contact may be provided on the bottom surface, but a light-emitting element grown on sapphire must have 2 electrical contacts on the upper surface (same surface). Therefore, if an insulator substrate such as sapphire is used, the effective light emitting area on the same substrate area is reduced as compared with a conductor substrate. Further, in the case of using an insulator substrate, the number of elements (chips) obtained from a wafer of the same diameter is reduced.

Further, nitride semiconductor devices using an insulator substrate such as sapphire have a face-up type and a face-down type, and since they have two electrodes on the same surface, the current density locally increases, heat is generated in the element (chip), and element degradation is accelerated. In addition, since the pn two electrodes need to be connected to each other in the wire bonding step of the counter electrode, the chip size increases, and the yield of the chip decreases. Further, sapphire has a high hardness and a hexagonal crystal structure. Therefore, when sapphire is used as a growth substrate, the sapphire substrate needs to be separated by dicing, and the number of manufacturing steps must be increased compared to other substrates.

Further, in recent years, an LED emitting light in an ultraviolet region has been put to practical use. The ultraviolet region means that the emission wavelength is 400nm or less. The band gap of GaN is 365nm, and if the wavelength is shorter than 365nm, the light extraction efficiency is significantly reduced by absorption of GaN by a contact layer or the like.

In view of the above, the present invention provides a nitride semiconductor device that can realize a facing electrode structure in which two electrodes face each other and that can provide high output without increasing voltage, and a method for manufacturing the same. And is a nitride semiconductor device that realizes high light emission output also in the ultraviolet region.

Disclosure of Invention

The nitride semiconductor device of the present invention comprises a supporting substrate, and at least a conductive layer, a 1 st electrode, a nitride semiconductor having a light-emitting layer, and a 2 nd electrode in this order, wherein the conductive layer comprises the 1 st electrode and a 1 st conductivity type nitride semiconductor layer with a 1 st insulating protective film as an intermediate. The nitride semiconductor is composed of a 1 st conductivity type nitride semiconductor layer, a light-emitting layer, and a 2 nd conductivity type nitride semiconductor layer in this order from the support substrate side, and a 2 nd electrode is formed on the 2 nd conductivity type nitride semiconductor layer. Since the supporting substrate is conductive, a nitride semiconductor device having an opposed electrode structure can be obtained. Further, if the 1 st electrode is a p-type electrode, the light extraction efficiency is improved. This means that the 2 nd conductivity type nitride semiconductor layer formed on the 2 nd electrode (n-type electrode) side which becomes the upper part of the nitride semiconductor layer becomes an n-type nitride semiconductor. That is, the n-type nitride semiconductor side becomes a light output surface. Since the nitride semiconductor (particularly, GaN semiconductor) has low resistance of the n-type layer, the size of the n-type electrode as the 2 nd electrode can be reduced. The light extraction efficiency is improved because the area for blocking light can be reduced by making the n-type electrode small. Further, since the conventional nitride semiconductor device has a structure in which two electrodes are provided on the same surface and a P-pad electrode is required for a P-type electrode, the present invention uses a conductive support substrate and performs die bonding with a conductive material on a package such as a lead frame to enable conduction, and thus a light emitting area can be increased without using the P-pad electrode. Further, since the 1 st insulating protective film is provided, short-circuiting and the like can be prevented, and thus yield and reliability can be improved. The manufacturing process can be simplified.

The 1 st electrode and the 1 st insulating protective film are characterized in that: is in contact with the 1 st conductivity type nitride semiconductor layer. The 1 st electrode may be formed on the entire surface of the 1 st conductivity type nitride semiconductor layer, but the contact area between the 1 st electrode and the 1 st conductivity type nitride semiconductor layer can be adjusted by forming a part of the 1 st electrode and burying the opening with the 1 st insulating protective film. Further, the 1 st electrode is formed in a pattern such as a rectangle, a stripe, a square, a grid, a dot, a diamond, a parallelogram, a mesh, a stripe, or a branch divided into 1 to a plurality of parts, thereby improving the light output efficiency. The above-mentioned 1 st conductivity type nitride semiconductor layer may be a p-type nitride semiconductor or an n-type nitride semiconductor as long as it can form ohmic contact with the 1 st electrode. The 1 st conductivity type nitride semiconductor layer is not limited to a single layer or a plurality of layers.

The 1 st electrode has at least 1 kind selected from the group consisting of Ag, Rh, Ni, Au, Pd, Ir, Ti, Pt, W, and Al. The specific values of the reflectivity are Ag-89%, Al-84%, Rh-55%, Pd-50% and Au-24%. From the above data, Ag is the most preferable material for reflectance, but Rh is preferable in terms of ohmic properties when the 1 st conductivity type nitride semiconductor layer is p-type. By using the above materials, the resistance can be reduced and the light extraction efficiency can be improved. The conductive layer is formed of a eutectic crystal containing at least 1 kind selected from the group consisting of Au, Sn, and In. The conductive layer is made of the eutectic material, and layer formation at low temperature is possible. In the case of eutectic bonding, sticking at a low temperature has a relaxation effect on warpage. Further, the conductive layer has a structure of an adhesive layer, a barrier layer and a eutectic layer from the 1 st electrode side, such as Au, Sn, Pd, In, Ti, Ni, W, Mo, Au-Sn, Sn-Pd, In-Pd, Ti-Pt-Au, Ti-Pt-Sn, etc., and deterioration due to diffusion with the 1 st electrode (for example, a p-type electrode) can be prevented.

The 1 st electrode and the 2 nd electrode are opposed electrodes having different surfaces, and the 2 nd electrode is not present above the 1 st electrode. This means that the electrodes on both sides do not overlap when viewed from the electrode forming surface. If the 1 st electrode and the 2 nd electrode do not overlap each other when viewed from the electrode forming surface, the emitted light is not blocked by the 2 nd electrode (for example, an n-type electrode), and the light can be efficiently extracted. The absorption of the light emitted from the 2 nd electrode can be suppressed. When the nitride semiconductor layer of type 2 is N-type, the above-mentioned electrode 2 preferably contains Al, and is composed of Ti — Al or W — Al, for example. In the present invention, the opposed electrode structure means a structure in which the 1 st electrode and the 2 nd electrode are formed by sandwiching a nitride semiconductor.

In the nitride semiconductor device, the nitride semiconductor has a 2 nd conductivity type nitride semiconductor layer on an uppermost layer, and the 2 nd conductivity type nitride semiconductor layer is provided with a concave-convex portion. The concave-convex (dimple processing) formed portion becomes the light extraction side of the nitride semiconductor. Since the surface is formed with irregularities, light that is not emitted by total reflection of light can be extracted by changing the angle of the surface. The formation of the irregularities is expected to improve the output by 1.5 times or more as compared with the formation without irregularities. The planar shape is a circular shape, or a polygonal shape such as a hexagon or a triangle. The irregularities may be formed in a stripe shape, a grid shape, or a rectangular shape. In order to improve the light extraction efficiency, a pattern as thin as possible is preferable. The wave shape is better than the flat surface as the cross-sectional shape. This is because the light extraction efficiency can be improved more than that of the angular unevenness. The depth of the recess is 0.2 to 3 μm, more preferably 1.0 to 1.5 μm. The reason for this is that if the depth of the concave portion is shallower than 0.2 μm, the effect of light extraction is not enhanced; if it is deeper than the above range, the resistance in the lateral direction is increased. Further, by forming the recess in a circular or polygonal shape, the resistance can be maintained low and the output can be improved.

In the nitride semiconductor, the nitride semiconductor layer other than the light-emitting layer is characterized in that: has a band gap larger than that of the light emitting band gap. More preferably, the nitride semiconductor layer other than the light-emitting layer has a band gap larger than the light-emitting band gap by 0.1eV or more. Thus, the emitted light can be extracted without being absorbed.

The nitride semiconductor device is characterized in that the linear thermal expansion coefficient of the supporting substrate is 4 to 10 (x 10)^-6K) is added. The thermal expansion coefficient of the supporting substrate is in the above range, and the warping and cracking of the nitride semiconductor device can be prevented. The difference in thermal expansion coefficient with GaN must be controlled to 4X 10^-6The reason why the value is not more than/K is that if the value exceeds this range, the strain increases and the rate of cracking of the supporting substrate and the nitride semiconductor device increases rapidly.

In the nitride semiconductor device, the supporting substrate contains at least 1 kind selected from the group consisting of Cu, Mo, and W. The characteristics of the support substrate are conductive and have a thermal expansion coefficient close to that of the nitride semiconductor. The support substrate composed of the above-mentioned metal satisfies these characteristics. Further, the characteristics of the LED and LD, such as high heat dissipation and easy chip separation, can be improved.

The nitride semiconductor device is characterized in that the Cu content in the supporting substrate is 50% or less. If the Cu content is large, the thermal conductivity is improved, but the thermal expansion coefficient is also increased. Therefore, the Cu content is more preferably 30% or less. In order to alloy with Cu, it is preferable to reduce the thermal expansion coefficient. In contrast to the Cu content, when Mo is alloyed, the Mo content is 50% or more. Mo is inexpensive. In contrast to the Cu content, when W is alloyed, the W content is set to 70% or more. W is easy to dice. Such a support substrate has a thermal expansion coefficient close to that of the nitride semiconductor, and thus has excellent thermal conductivity. Since the support substrate is conductive, a large current can be applied.

The 1 st insulating protective film is formed with at least one metal layer selected from the group consisting of Al, Ag, and Rh on a side not in contact with the nitride semiconductor. That is, the metal layer is present between the conductive layer and the 1 st insulating protective film (fig. 4). Since the metal film is formed at this position, the light extraction efficiency is improved. This is because the LED light that has propagated a lot of lateral light is reflected on the light extraction surface side. The metal film is characterized in that: connected with the conductive layer.

A semiconductor light-emitting device comprising a 1 st electrode 3, a semiconductor multilayer body 2 having a light-emitting layer, and a 2 nd electrode in this order on a supporting substrate 11. Here, the 1 st electrode 3 is located on the bonding surface side with the supporting substrate 11 provided on the semiconductor 2. The 2 nd electrode 6 is provided on the light extraction surface side of the semiconductor 2. In such a semiconductor light emitting device, light emitted from the light emitting layer is not only emitted upward as a light extraction surface but emitted in all directions, and therefore, light emitted downward from the light emitting layer is absorbed by other layers or the like. When a semiconductor device is formed, the thickness of the semiconductor 2 is in the range of several μm to 10 μm, and the length in the lateral direction is 200 μm or more and 1mm or more. Therefore, the light propagating in the lateral direction has a longer distance to be reflected by the side surface of the semiconductor or the like than the light propagating in the longitudinal direction, and is absorbed by the material constituting the semiconductor, so that the light extraction efficiency is lowered.

Accordingly, the semiconductor light emitting device of the present invention has, on the supporting substrate 11, at least in this order: a conductive layer 13; 1 st electrode 3; a semiconductor 2 having a 1 st conductivity type semiconductor layer 2a on the side of a contact interface with the 1 st electrode, a light emitting layer 2b thereon, and a 2 nd conductivity type semiconductor layer 2c on the side of a light extraction surface thereon; and, a 2 nd electrode 6 characterized by: there is a 1 st protective film 4, and the 1 st protective film 4 has a contact interface area with the semiconductor 2 and/or an area laterally protruding from the contact interface to the semiconductor 2.

The 1 st protective film 4 having a contact interface region with the semiconductor 2 means that the 1 st protective film 4 is optically connected to the semiconductor multilayer body 2 so as to be capable of propagating light, or an intermediate layer is provided between the 1 st protective film 4 and the semiconductor 2. In the 1 st protective film 4, the region projecting laterally from the contact interface toward the semiconductor 2 is a region in which the 1 st protective film 4 does not contact the semiconductor 2 on the light extraction surface side and extends outward of the semiconductor 2 (fig. 3C, 3E, 3F, 4C, and the like). The 1 st protective film 4 is sufficient as a light-transmitting film as long as it has a function of transmitting light emitted from the light-emitting layer. In addition, it has an insulating property and serves as a film having a leakage current preventing effect and a current limiting effect. The convex region is a light extraction surface provided outside the semiconductor 2, and is intended to allow light downward from the light-emitting layer 2b to pass through the 1 st protective film 4, reflect the transmitted light at an interface with the layer having a reflection function, and extract the reflected light as upward emitted light. Light propagating through the light-emitting layer 2b of the semiconductor 2 enters the 1 st protective film 4, is repeatedly reflected by the side walls and the bottom surface of the 1 st protective film 4, and is emitted upward from most of the upper surface of the convex region, and therefore, the film thickness of the 1 st protective film is smaller than the film thickness in the semiconductor growth direction, so that absorption and loss in the light-emitting device are suppressed, and the light extraction efficiency from the semiconductor light-emitting device is improved. The 1 st protective film 4 is preferably made of a material having a low absorption coefficient. The light outgoing path, i.e., the protruding region, for outgoing light emitted from the light-emitting layer 2b incident on the 1 st protective film 4 optically connected to the semiconductor 2 has a function of repeating internal reflection of the emitted light in the semiconductor multilayer body and taking out the light to the outside before internal absorption occurs. This not only combines the main (main) light coming out from the upper portion of the 1 st electrode 3 but also the sub (sub) light coming out from the above-mentioned convex region corresponding to the outside of the semiconductor light emitting device, thereby increasing the external quantum efficiency from the semiconductor light emitting device. Specifically, the layer having a reflecting action is the conductive layer 13, but it is preferable to interpose a reflecting film between the 1 st protective film 4 and the conductive layer 13, so that the loss during the reflection in the 1 st protective film 4 can be reduced.

If a rough surface is formed on the upper surface of the convex region of the 1 st protective film 4 by etching or the like, the amount of light extraction from the surface can be increased. As another configuration, there is a configuration in which the upper surface of the convex region is formedThe surface has a refractive index n₃The protective film 40. If the protective film 4b is formed and is constituted such that the refractive index n of the protective film 40 and the 1 st protective film 4₂Is smaller than the refractive index n of the semiconductor 2₁And refractive index n of the 1 st protective film 4₂Since the refractive index difference of (a) is small, a large amount of light can be extracted on the side where the refractive index difference is small, and the large amount of light enters the 1 st protective film 4 having an exposed surface to the outside, the light extraction efficiency is improved.

In the semiconductor light emitting device of the present invention, at least 1 or more of the 1 st electrode 3 and the 1 st protective film 4 are alternately formed on the surface of the nitride semiconductor on the supporting substrate side. Preferably, a reflective film is provided on the lower surface of the 1 st protective film 4 (fig. 12D). Light from the light-emitting layer is reflected on the interface a between the 1 st conductivity type semiconductor layer 2a and the 1 st electrode 3. Light from the light-emitting layer is transmitted through the interface between the 1 st conductive semiconductor layer 2a and the 1 st protective film 4, and light from the light-emitting layer is reflected at the interface b between the 1 st protective film 4 and the conductive layer 13. Since the 1 st electrode 3 absorbs light, the 1 st protective film 4 is intentionally transmitted with light in order to reduce such light absorption, and light is reflected at the interface b with the reflective film or the conductive layer 13 formed on the lower surface of the 1 st protective film 4, thereby improving the light extraction efficiency (fig. 12E). For this reason, the reflectance at the interface between the semiconductor 2 and the 1 st protective film 4 is reduced, and the reflectance at the above-mentioned interface b is improved. In order to make the light reflectance of the 1 st protective film 4 smaller than the light reflectance of the 1 st electrode 3, the 1 st protective film 4 is preferably made of a material having high light transmittance.

It is characterized in that a concave-convex portion is formed on the interface a between the 1 st conductive semiconductor layer 2a and the 1 st electrode 3 and the interface b between the 1 st protective film 4 and the conductive layer 13. Here, the interfaces a and b are surfaces that function as light reflecting surfaces that reflect light from the light emitting layer 2b in cooperation with each other. The 1 st protective film 4 is a light-transmitting film, but light can be reflected at the interface b between the 1 st electrode 3 in contact with the side surface of the protective film 4 and the conductive layer 13 in contact with the bottom surface of the protective film 4. Concave and convex portions, in which the interface b is a concave portion and the interface a is a convex portion, are provided laterally below the light-emitting layer 2c of the semiconductor light-emitting device (fig. 12D). The reflective film shown in fig. 12D and the like may be omitted.

Since the uneven portion is provided, the light extraction efficiency of light output from the semiconductor to the outside can be further improved. The reason for this is that light that originally propagates downward is reflected at the interface or is refracted to become light whose longitudinal component is enhanced, that is, before light propagates for a long distance in the lateral direction, light is diffusely reflected at the uneven portion and guided upward. Although most of the light having a large lateral component is absorbed in the semiconductor, if there are irregularities, the light from the light-emitting layer is diffusely reflected by the irregularities to become small light in the upper, lower, left, and right directions, and becomes light having a vertical component. If such a concave-convex portion is optically connected to the convex region formed on the 1 st protective film 4, the light extraction efficiency is further improved.

The 1 st electrode 3 and the 1 st protective film 4 are provided on the lower surface of the 1 st conductivity type semiconductor layer 2a on the same surface. Here, the 1 st conductive type semiconductor layer 2a may be formed with a step of unevenness or subjected to appropriate microfabrication in an as-growth state on the 1 st electrode 3 formation surface, but is preferably a flat structure. This is because, if the semiconductor is formed with the concave-convex portion by etching, the semiconductor is damaged at a large amount, and the life characteristics are inevitably degraded. The invention is not the concave-convex processing part formed by etching, but the concave-convex part is formed by the combination of materials, thereby having no etching damage, not reducing the service life characteristic and improving the light extraction efficiency.

The 1 st protective film 4 has a multilayer structure including at least 2 layers, and is characterized in that: the interface between the layers is a concave-convex surface. The concave-convex surface is preferably inclined. In the lateral direction of the semiconductor 2, the 1 st protective film 4 occupies a larger area on the semiconductor than the 1 st electrode 3. Therefore, the ratio of light transmitted through the 1 st protective film to total light emission is high. Thus, the light incident into the 1 st protective film 4 is converted into a longitudinal component at one endLight extraction is an extremely important issue. The 1 st protective film 4 has a multilayer structure of at least 2 layers, and the above object is achieved by forming irregularities in the 1 st protective film 4, and converting light incident on the 1 st protective film 4 into a vertical component by causing diffuse reflection at the interface between the respective layers. The material of the No. 1 protective film is SiO₂、Al₂O₃、ZrO₂、TiO₂、Nb₂O₅And the like. For example, the 1 st protective film is made Nb at the interface side 4b with the nitride semiconductor 2₂O₅The lower layer 4a is SiO₂The 2-layer structure of (1) can actively diffuse light in the protective film by providing a concave-convex portion between the 2 layers (fig. 12F).

In the nitride semiconductor device of the present invention, the 1 st electrode 3 and the 2 nd electrode 6 are formed in the opposed electrode structure (fig. 3, fig. 12, and the like), and as described above, it is preferable that the 2 nd electrode 6 is not present on the 1 st electrode 3, but this is not necessarily a limitation, and a part of the 2 nd electrode 6 may be overlapped on the 1 st electrode 3. In fig. 3D, if the 2 nd electrode 6 is made to be an n-electrode, the dispersion of current is large in the nitride semiconductor on the 2 nd electrode side, i.e., n-type nitride semiconductor 2c, and conversely, the dispersion of current is small in the p-type nitride semiconductor 2a that is a nitride semiconductor on the 1 st electrode 3 side, and therefore, the formation range of the 1 st electrode in the plane of the nitride semiconductor is large. Therefore, in order to actively extract external light, the 2 nd electrode is preferably formed so as to surround the light extraction portion on the upper surface of the semiconductor 2, but since the electrode formation area of the 2 nd electrode 3 may be small, both electrodes may be partially overlapped with each other through a nitride semiconductor if light is not blocked (fig. 12E).

In the present invention, the shape of the convex portion and the concave portion of the uneven portion formed on the light extraction surface includes: squares and rectangles with right angles, trapezoids with inclinations and inverted trapezoids. It is preferable that the shape of the concave-convex portion is a shape having an inclination.

The semiconductor 2 is characterized in that: is a nitride semiconductor. The nitride semiconductor is a compound semiconductor containing nitrogen. Since the nitride semiconductor is a direct transition type semiconductor, the light emission efficiency is far higher than that of an indirect transition type semiconductor, and a compound semiconductor is formed with In, Ga, Al, and other group III elements, whereby a semiconductor light-emitting device having a short wavelength region (300nm to 550nm) including an ultraviolet region can be provided.

The light-emitting layer may contain at least Al_aIn_bGa_1-a-bA well layer composed of N (0. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.1, a + b. ltoreq.1) and Al_cIn_dGa_1-c-dAnd N (c is more than or equal to 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to 1, and c + d is less than or equal to 1). A light-emitting element having a quantum well structure, which can achieve high light emission efficiency, may have a single quantum well structure or a multiple quantum well structure. In the well layer, the In composition b is preferably 0 < b.ltoreq.0.3, so that high output can be realized. This is because if the In mixture ratio b is increased, the crystallinity varies In the plane due to the segregation of the crystal or the like, and the crystal is dispersed In the plane In a good region, and when the current density is increased, the linearity of the current-output characteristic becomes weak, and saturation tends to be facilitated, and In the In composition range, the large current input of the present invention is facilitated.

The light-emitting layer at least contains Al_aIn_bGa_1-a-bWell layer composed of N (0 < a < 1, 0 < b < 1, a + b < 1), and well layer composed of Al_cIn_dGa_1-c-dThe quantum well structure of the barrier layer formed by N (c is more than 0 and less than or equal to 1, d is more than 0 and less than or equal to 1, and c + d is less than 1) is characterized in that: the 2 nd conductivity type nitride semiconductor layer is a nitride semiconductor containing Al. And, In the range of In composition b of 0 < b < 0.1 at 420nm (near ultraviolet region) or less where the visual sensitivity is low; under 380nm (ultraviolet region), the Al composition a is more than or equal to 0.01 and less than or equal to 0.2.

The above-mentioned 2 nd conductive nitride semiconductor layer is composed of at least 2 layers, and the 2 nd electrode side of the 2 nd conductive nitride semiconductor layer is Al_eGa_1-eN, one side of the luminescent layer is Al_fGa_1-fN，Al_eGa_1-eImpurity concentration ratio of N layer to Al_fGa_1-fThe N layer is high.

In the invention, the active layer is made of Al_aIn_bGa_1-a-bThe nitride semiconductor device composed of N (0. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.1, and a + b. ltoreq.1) is applicable to a device which emits light of various wavelengths, and is particularly effective for a nitride semiconductor device in an ultraviolet region of 380nm or less. The present invention is a method for manufacturing a nitride semiconductor device, which has an active layer having a quantum well structure including a well layer composed of an InAlGaN quaternary mixed crystal and a barrier layer composed of a nitride semiconductor containing at least Al, and which can be applied to a short wavelength region of 380nm or less. Since the well layer is formed of an InAlGaN quaternary mixed crystal, the number of constituent elements can be minimized to suppress deterioration of crystallinity, and light emission efficiency can be improved. Further, since the barrier layer is made of a nitride semiconductor containing at least Al, the band gap energy is increased as compared with the well layer, and an active layer having a quantum well structure matching the emission wavelength can be formed, and good crystallinity in the active layer can be maintained.

In particular, in a nitride semiconductor device in an ultraviolet region of 380nm or less, it is necessary to grow a GaN layer at a high temperature on a substrate or a buffer layer in order to obtain a nitride semiconductor device having good crystallinity. If a light-emitting layer (active layer) or the like is grown without growing such a layer, crystallinity is very poor, and the light emission output is very weak in a nitride semiconductor light-emitting element or the like, which is not practical. Although a nitride semiconductor device having good crystallinity can be obtained by providing a high-temperature growth layer composed of GaN, when GaN is included as the underlying layer and the high-temperature growth layer, a part of light from the active layer is absorbed by the GaN layer due to self-absorption of GaN in the ultraviolet region, and the light emission output is reduced. In the present invention, after bonding to the conductive substrate, the GaN in the growth substrate, the transition layer, and the high-temperature growth layer is removed, and therefore, the self-absorption can be suppressed while maintaining good crystallinity of the nitride semiconductor constituting the device.

A composition gradient layer may be further provided on the high-temperature growth layer. In particular, the composition gradient layer is effective for an LED emitting light in an ultraviolet region where GaN having an action of recovering crystallinity is not present, and a nitride semiconductor layer having very few defects and good crystallinity can be stacked. The composition gradient layer may be formed by modulated doping in which a gradient is provided for impurities that determine conductivity. For example, when the nitride semiconductor layer grown on the upper surface is Si-doped AlGaN, the nitride semiconductor layer having good crystallinity can be stacked with fewer defects by making the composition gradient layer have a structure in which the Si concentration is increased from the non-doped state to the n-type cladding layer (confinement layer). In addition, the composition gradient layer may be graded from the high-concentration impurity concentration region to the undoped layer.

In the nitride semiconductor device, particularly the light emitting element of the present invention, since the coating layer containing the fluorescent substance that absorbs a part or all of the light from the active layer and emits light of different wavelengths and the sealing member are formed on the nitride semiconductor device formed by bonding to the supporting substrate, light of various wavelengths can be emitted. An example of the fluorescent substance is shown below. As the green light-emitting phosphor, there is SrAl₂O₄:Eu；Y₂SiO₅:Ce，Tb；MgAl₁₁O₁₉:Ce、Tb；Sr₇A₁₂O₂₅Eu; ga (at least 1 of Mg, Ca, Sr and Ba)₂S₃Eu. As the blue light-emitting phosphor, there is Sr₅(PO₄)₃Cl:Eu；(SrCaBa)₅(PO₄)₃Cl:Eu；(BaCa)₅(PO₄)₃Cl is Eu; (at least 1 or more of Mg, Ca, Sr and Ba)₂B₅O₉Cl is Eu, Mn; (at least 1 or more of Mg, Ca, Sr and Ba) (PO₄)₆Cl₂Eu and Mn. Further, as the red-based light-emitting phosphor, Y is given₂O₂S:Eu；La₂O₂S:Eu；Y₂O₃:Eu；Gd₂O₂And S is Eu. In particular, by containing YAG, white light can be emittedThe light source is especially widely used. YAG is (Y)_1-xGd_x)₃(Al_1-yGa_y)₅O₁₂R (R is at least 1 or more selected from Ce, Tb, Pr, Sm, Eu, Dy and Ho. 0 < R < 0.5.), e.g., (Y)_0.8Gd_0.2)₃Al₅O₁₂:Ce；Y₃(Al_0.8Ga_0.2)₅O₁₂Ce. Further, fluorescent substances that absorb part or all of light and emit light of different wavelengths are limited to materials that absorb visible light and emit light of different wavelengths, and there is a problem in material selectivity. However, there are many materials that absorb ultraviolet light and emit different light, and the material can be selected according to various uses. One of the main reasons that materials can be selected is that fluorescent substances that absorb ultraviolet light are said to have higher light conversion efficiency than visible light. In particular, with respect to white light, there is a greater possibility of obtaining white light having high color rendering properties, for example. The present invention provides a nitride semiconductor light emitting device which emits light in the ultraviolet region, wherein a nitride semiconductor light emitting element having little self-absorption can be obtained, and a white light emitting element having a very high conversion efficiency can be obtained by coating a fluorescent substance.

[ fluorescent substance ]

The fluorescent substance used in the present invention is described in detail below. The phosphor having a particle diameter, preferably a center particle diameter in the range of 6 to 50 μm, more preferably 15 to 30 μm, has high light absorption and conversion efficiency and a wide excitation wavelength range. Fluorescent substances smaller than 6 μm are relatively likely to form aggregates and become denser and precipitated in the liquid resin, and therefore, in addition to reducing the light transmission efficiency, the light absorption and conversion efficiency also deteriorate, and the range of the excitation wavelength also becomes narrow.

Here, in the present invention, the particle size of the fluorescent substance is a value obtained from a volume-based particle size distribution curve obtained by measuring the particle size distribution of the fluorescent substance by a laser diffraction/scattering method. Specifically, the fluorescent substance was dispersed in an aqueous solution of sodium hexametaphosphate having a concentration of 0.05% in an environment of an air temperature of 25 ℃ and a humidity of 70%, and the distribution was measured in a particle size range of 0.03 to 700 μm by a laser diffraction particle size distribution measuring apparatus (SALD-2000). The center particle diameter of the fluorescent substance in the present invention is a particle diameter value at which the cumulative value on the volume-based particle size distribution curve is 50%. Preferably, the fluorescent substance having the central particle size is contained at a high frequency, and the frequency is preferably 20% to 50%. By using such a fluorescent substance having a small particle size variation, a light-emitting device with good contrast can be obtained with suppressed color unevenness.

(Yttrium/aluminum oxide fluorescent substance)

The fluorescent substance used in the present embodiment may be a fluorescent substance (YAG fluorescent substance) based on an yttrium/aluminum oxide fluorescent substance activated with cerium (Ce) or praseodymium (Pr) and emitting light when excited by light emitted from a semiconductor light-emitting element in which a nitride semiconductor is used as a light-emitting layer. Specific examples of the yttrium/aluminum oxide fluorescent substance include YAlO₃:Ce；Y₃Al₅O₁₂Ce (YAG: Ce) or Y₄Al₂O₉Ce, and mixtures thereof. The yttrium/aluminum oxide phosphor may contain at least one of Ba, Sr, Mg, Ca, and Zn. Further, by containing Si, the reaction of crystal growth can be suppressed and the particles of the fluorescent substance can be unified.

In the present specification, an yttrium/aluminum oxide fluorescent substance activated with Ce is used In a very broad sense, including a fluorescent substance having a fluorescent action, In which a part or the whole of yttrium may be substituted with at least 1 element selected from the group consisting of Lu, Sc, La, Gd and Sm, or a part or the whole of aluminum may be substituted with any one of Ba, Tl, Ga and In, or both of them.

More specifically represented by the general formula (Y)_zGd_1-z)₃Al₅O₁₂A photoluminescent phosphor represented by Ce (wherein, 0 < z.ltoreq.1), or a photoluminescent phosphor represented byGeneral formula (Re)_1-aSm_a)₃Re’₅O₁₂A photoluminescent phosphor represented by Ce (wherein 0. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.1, Re is at least one selected from Y, Gd, La and Sc, and Re' is at least one selected from Al, Ga and In). The fluorescent substance has a garnet structure, has high adaptability to heat, light and moisture, and can make the peak of an excitation spectrum fall in the vicinity of 450 nm. Further, the emission spectrum has a broad emission spectrum with an emission peak around 580nm and a side portion extending to 700 nm.

In addition, since the photoluminescent phosphor contains Gd (gadolinium) in the crystal, the excitation light emission efficiency in a long wavelength region of 460nm or more can be improved. By increasing the Gd content, the emission peak wavelength is shifted to a longer wavelength, and the entire emission wavelength is also shifted to a longer wavelength side. That is, when a red-light emission color is required, the amount of Gd substitution can be increased. On the other hand, the emission luminance of blue photoluminescence tends to decrease with an increase in Gd. Further, Tb, Cu, Ag, Au, Fe, Cr, Nd, Dy, Co, Ni, Ti and Eu may be contained in addition to Ce as desired. In addition, in the composition of the yttrium/aluminum/garnet-based phosphor having a garnet structure, a part of Al may be replaced with Ga to shift the emission wavelength to a short wavelength side; a part of the composition Y is substituted with Gd to shift the emission wavelength toward the long wavelength side.

In the case of replacing a part of Y with Gd, it is preferable that Y replaced with Gd is less than 1 and Ce content (replacement) is 0.03 to 1.0. If Y substituted with Gd is less than 2, the green component increases and the red component decreases, but the red component can be supplemented by increasing the Ce content, so that a desired color tone can be obtained without lowering the luminance. With such a composition, the temperature characteristics are improved, and the reliability of the light emitting diode can be improved. Further, if a photoluminescent phosphor adjusted to have a large red component is used, a light-emitting device capable of emitting light of an intermediate color such as pink can be obtained.

Such a photoluminescent phosphor uses an oxide or a compound that easily becomes an oxide at high temperature as raw materials of Y, Gd, Al, Ce, and Pr, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or dissolving rare earth elements Y, Gd, Ce and Pr in a stoichiometric ratio in acid, co-precipitating the dissolved solution with oxalic acid, firing the co-precipitate, and mixing the obtained co-precipitated oxide with alumina to obtain a mixed raw material. Mixing a proper amount of barium fluoride and ammonium fluoride serving as cosolvents, putting the mixture into a crucible, firing the mixture in air at 1350-1450 ℃ for 2-5 hours to obtain a fired product, performing ball milling on the fired product in water, cleaning, separating, drying, and finally sieving to obtain the product.

In the light-emitting diode of the present invention, 2 or more kinds of cerium-activated yttrium/aluminum/garnet-based phosphors and other phosphors may be mixed with the photoluminescent phosphor. By mixing 2 kinds of yttrium/aluminum/garnet-based phosphors having different amounts of substitution from Y to Gd, light of a desired color tone can be easily realized. In particular, when a fluorescent substance having a large substitution amount is used as the fluorescent substance, and a fluorescent substance having a small or zero substitution amount is used as the medium-particle-diameter fluorescent substance, it is possible to improve color rendering properties and luminance at the same time.

(nitride-based phosphor)

The fluorescent substance used in the present invention may contain a nitride-based phosphor activated with at least one element selected from rare earth elements, wherein the nitride-based phosphor contains N, at least one element selected from Be, Mg, Ca, Sr, Ba, and Zn, and at least one element selected from C, Si, Ge, Sn, Ti, Zr, and Hf. The nitride-based phosphor used in the present embodiment is a phosphor that absorbs visible light or ultraviolet light emitted from a light-emitting element or light emitted from a YAG-based phosphor and is excited to emit light. Particularly, the phosphor of the present invention is obtained by adding Mn to Sr-Ca-Si-N, Eu, Ca-Si-N:eu, Sr-Si-N, Sr-Ca-Si-O-N, and Sr-Si-O-N, Eu-based silicon nitride. The basic constituent element of the phosphor is represented by the general formula L_XSi_YN_(2/3X+4/3Y)Eu or L_XSi_YOZN_{(2/3X+4/3Y-2/3Z)}Eu (L is any one of Sr, Ca, Sr and Ca). In the general formula, X and Y are preferably 2 and 5, or 1 and 7, but may be any values. Specifically, the basic constituent element is preferably Mn-added (Sr)_xCa_1-x)₂Si₅N₈:Eu、Sr₂Si₅N₈:Eu、Ca₂Si₅N₈:Eu、Sr_xCa_1-xSi₇N₁₀:Eu、SrSi₇N₁₀:Eu、CaSi₇N₁₀Eu, but the phosphor composition may also contain at least 1 or more selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr and Ni. However, the present invention is not limited to the embodiment and examples.

L is any one of Sr, Ca, Sr and Ca. The Sr and Ca may be mixed in a ratio which is changed as desired.

Since Si is used for the composition of the phosphor, a phosphor having excellent crystallinity can be provided at low cost.

Europium (Eu), which is a rare earth element, is used in the luminescence center. Europium has predominantly valence 2 and 3 energy levels. The phosphor of the present invention is Eu²⁺Used as an activator for the parent alkaline earth metal silicon nitride. Eu (Eu)²⁺Is easily oxidized, so that Eu having a valence of 3 is commercially available₂O₃. However, Eu is commercially available₂O₃The participation of medium O is so deep that it is difficult to obtain a good phosphor. Therefore, it is preferable to use Eu₂O₃A substance in which O is removed out of the system. For example, europium monomer or europium nitride is preferably used. However, the addition of Mn is not limited to this.

As additivesMn is for promoting Eu²⁺The light emitting efficiency such as the light emitting brightness, the energy efficiency, the quantum efficiency and the like is improved. Mn is contained in the raw material, or a Mn monomer or a Mn compound is added in the production process and fired together with the raw material. However, Mn is not contained in the basic constituent elements after firing, or even if Mn is contained, only a small amount of Mn remains as compared with the initial content. This is considered to be because Mn is scattered in the firing step.

The phosphor contains at least 1 or more selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O and Ni in or together with the basic constituent elements. These elements have an effect of increasing the particle diameter or improving the light emission luminance. B, Al, Mg, Cr and Ni have an action called afterglow control.

Such a nitride-based phosphor absorbs a part of the blue light emitted from the light-emitting element and emits light in a yellow to red region. In the light-emitting device having the above-described configuration, the nitride-based phosphor is used together with the YAG-based phosphor, and blue light emitted from the light-emitting element and yellow to red light from the nitride-based phosphor are mixed, whereby a light-emitting device that emits warm white light can be obtained. The phosphor other than the nitride-based phosphor preferably contains an yttrium/aluminum oxide fluorescent substance activated with cerium. This is because the color tone can be adjusted to a desired color tone by including the yttrium/aluminum oxide fluorescent substance. The yttrium/aluminum oxide fluorescent substance activated by cerium absorbs a part of the blue light emitted from the light-emitting element and emits light in the yellow region. Here, blue light emitted from the light emitting element and yellow light of the yttrium/aluminum oxide fluorescent substance are mixed to emit blue-white light. Therefore, a light-emitting device which emits a white mixed color light can be provided by mixing the yttrium/aluminum oxide fluorescent substance with a red-emitting fluorescent substance in a color conversion layer and combining the mixed color light with blue light emitted from a light-emitting element. Particularly preferably, the chromaticity is a white light emitting device on the black body radiation locus in the chromaticity diagram. However, in order to provide a light emitting device of a desired color temperature, the amount of the yttrium/aluminum oxide fluorescent substance and the amount of the red-emitting fluorescent substance may be appropriately changed. A light-emitting device that emits such white mixed-color light is intended to improve the special color rendering evaluation number R9. In a light-emitting device which emits white light only by combining a conventional light-emitting element which emits light of a blue color system and a cerium-activated yttrium/aluminum oxide fluorescent substance, the number of special color rendering evaluations R9 is approximately in the vicinity of 0 in the vicinity of the color temperature Tcp 4600K, and the red component is insufficient. Therefore, although it is a problem to increase the number of special color rendering evaluations R9, in the present invention, since a red-emitting phosphor is used together with an yttrium/aluminum oxide fluorescent substance, the number of special color rendering evaluations R9 can be increased to around 40 in the vicinity of the color temperature Tcp 4600K.

Next, the phosphor of the present invention ((Sr)_xCa_1-x)₂Si₅N₈Eu), however, the present invention is not limited to this production method. The phosphor contains Mn and O.

Firstly, raw materials Sr and Ca are crushed. The raw materials Sr and Ca are preferably monomers, but compounds such as imine compounds and amide compounds may be used. In addition, the raw materials Sr and Ca contain B, Al, Cu, Mg, Mn and Al₂O₃And so on. Raw materials Sr and Ca were pulverized in an argon atmosphere in a glove box. The average particle size of Sr and Ca obtained by pulverization is preferably from about 0.1 μm to 15 μm, but is not limited to this range. The purity of Sr and Ca is preferably 2N or more, but not limited thereto. In order to further improve the mixing state, at least 1 or more of Ca metal, Sr metal, and Eu metal may be alloyed, nitrided, and then pulverized to be used as a raw material.

② crushing the raw material Si. The raw material Si is preferably a monomer, but a nitride compound, an imine compound, an amide compound, or the like may be used. For example, Si₃N₄、Si(NH₂)₂、Mg₂Si, etc. The purity of the raw material Si is preferably 3N or more, but Al may be contained₂O₃Mg, metal boride (CO)₃B、Ni₃B. CrB), manganese oxide, H₃BO₃、B₂O3、Cu₂O, CuO, and the like. Si is also pulverized in a glove box in an argon atmosphere or a nitrogen atmosphere, similarly to Sr and Ca as raw materials. The average particle diameter of the Si compound is preferably from about 0.1 μm to 15 μm.

Thirdly, the raw materials Sr, Ca are nitrided in a nitrogen atmosphere. The following formulae 1 and 2 are each a reaction formula.

3Sr+N₂→Sr₃N₂... (formula 1)

3Ca+N₂→Ca₃N₂... (formula 2)

Nitriding Sr and Ca in a nitrogen atmosphere at 600 to 900 ℃ for about 5 hours. Sr and Ca may be mixed and nitrided, or may be nitrided separately. Thus, nitrides of Sr and Ca can be obtained. Nitrides of Sr and Ca are preferably of high purity, but commercially available ones can also be used.

Nitriding the raw material Si in a nitrogen atmosphere. The following formula 3 represents the reaction formula.

3Si+2N₂→Si₃N₄... (formula 3)

Similarly, the Si is nitrided in a nitrogen atmosphere at 800 to 1200 ℃ for about 5 hours. Thus, silicon nitride is obtained. The silicon nitride used in the present invention is preferably of high purity, but may be used commercially.

Fifthly, crushing nitride of Sr, Ca or Sr-Ca. The nitride of Sr, Ca, Sr-Ca is pulverized in an argon atmosphere or a nitrogen atmosphere in a glove box.

Also, the Si nitride is pulverized. Also, Eu, a compound of Eu₂O₃And (4) crushing. Europium oxide is used as Eu compound, but metal europium, europium nitride, or the like may be used. In addition, the raw material Z may beAmine compounds and amide compounds. Europium oxide is preferably of high purity, but commercially available europium oxides can also be used. The average particle diameter of the ground nitride of an alkaline earth metal, silicon nitride and europium oxide is preferably from about 0.1 to 15 μm.

The raw material may contain at least 1 or more selected from the group consisting of Mg, Sr, Ca, Ba, Zn, B, Al, Cu, Mn, Cr, O and Ni. In the following mixing step, the above-mentioned elements such as Mg, Zn, and B may be mixed after adjusting the mixing amounts. These compounds may be added to the starting materials individually, but are usually added in the form of compounds. Among such compounds are H₃BO3、Cu₂O₃、MgCl₂、MgO·CaO、Al₂O₃Metal boride (CrB, Mg)₃B₂、AlB₂、MnB)、B₂O₃、Cu₂O, CuO, etc.

Sixthly, after the pulverization, the nitride of Sr, Ca, Sr-Ca, the nitride of Si and the compound Eu of Eu are made₂O₃Mixing was performed, and Mn was added. These mixtures are easily oxidized and are therefore mixed in an Ar atmosphere or a nitrogen atmosphere in a glove box.

Seventhly, firing Sr, Ca, Sr-Ca nitrides, Si nitrides and Eu compound Eu in an ammonia atmosphere₂O₃A mixture of (a). By firing, Mn-added (Sr) compounds can be obtained_xCa_1-x)₂Si₅N₈Eu, as a phosphor. Here, the composition of the target phosphor can be changed by changing the blending ratio of each raw material.

Firing can be performed using a tube furnace, a small-sized furnace, a high-frequency furnace, a metal furnace, or the like. Firing may be carried out at a firing temperature in the range of 1200 to 1700 ℃, however, a firing temperature of 1400 to 1700 ℃ is preferred. Firing is preferably carried out in one stage by gradually raising the temperature and firing at 1200 to 1500 ℃ for several hours, but firing in the first stage at 800 to 1000 ℃ may be carried outThen, the mixture is gradually heated, and second firing (multi-stage firing) is performed at 1200 to 1500 ℃. The phosphor is preferably fired from a crucible or pot made of Boron Nitride (BN). Alumina (Al) may be used in addition to the boron nitride crucible₂O₃) Crucible made of material.

By using the above production method, the target phosphor can be obtained.

In the present embodiment, a nitride-based phosphor is particularly used as the phosphor that emits reddish light, but in the present invention, a light-emitting device including the YAG-based phosphor and a phosphor that can emit red-based light may be used. The phosphor capable of emitting red light is excited by light having a wavelength of 400 to 600nm to emit light, and examples thereof include Y₂O₂S:Eu；La₂O₂S is Eu; CaS is Eu; SrS is Eu; ZnS is Mn; ZnCdS is Ag and Al; ZnCd S, Cu, Al and the like. In this way, the color rendering properties of the light-emitting device can be improved by using a YAG phosphor together with a phosphor capable of emitting red light.

The YAG phosphor and the nitride phosphor formed in the above manner can emit red light, and two or more kinds of phosphors can be present in the color conversion layer formed of one layer on the side end surface of the light emitting element; one or more than two color conversion layers may be present in the color conversion layer composed of two layers. With this configuration, it is possible to obtain a mixed color light obtained by mixing light from different types of phosphors. In this case, in order to achieve better color mixing and reduction of color unevenness of light emitted from each fluorescent material, it is preferable that the average particle size and shape of each fluorescent material are made similar. In view of absorbing a part of light wavelength-converted by the YAG phosphor, the nitride phosphor is preferably provided closer to the side end surface of the light-emitting element than the YAG phosphor to form a color conversion layer. With this configuration, a part of the light wavelength-converted by the YAG phosphor is not absorbed by the nitride phosphor any more, and color rendering properties of the mixed light of the YAG phosphor and the nitride phosphor can be improved as compared with a case where both phosphors are mixed.

The method for manufacturing a nitride semiconductor device of the present invention is a method for manufacturing a nitride semiconductor device having at least a conductive layer, a 1 st electrode, a nitride semiconductor having a light emitting layer, and a 2 nd electrode in this order on a supporting substrate, and includes: a step of growing a nitride semiconductor having at least a 2 nd conductivity type nitride semiconductor layer, a light emitting layer and a 1 st conductivity type nitride semiconductor layer on a foreign substrate; thereafter, a step of bonding a support substrate to the 1 st conductivity type nitride semiconductor layer side of the nitride semiconductor with the 1 st electrode as an intermediate; and a step of exposing the 2 nd conductivity type nitride semiconductor layer by removing the foreign substrate. For example, in the case where a nitride semiconductor layer is formed on a hetero-substrate in the order of an n-type layer and a p-type layer, the hetero-substrate (sapphire or the like) is removed after being bonded to a supporting substrate, and the surface of the n-type layer is exposed. On the surface of the n-type layer, a damaged layer is formed by removing the foreign substrate by polishing or the like, but since the damaged layer can be removed by chemical polishing, the characteristic is not degraded by removing the foreign substrate.

The above-mentioned bonding process is characterized in that: the conductive layer is formed by eutectic bonding. The above-mentioned bonding process is characterized in that: thermocompression bonding is used. The temperature of the thermocompression bonding is preferably 150 to 350 ℃. When the temperature is 150 ℃ or higher, the metal diffusion of the conductive layer is promoted, a eutectic crystal having a uniform density distribution is formed, and the adhesion between the nitride semiconductor device and the supporting substrate is improved. If the temperature is more than 350 ℃, the diffusion range is extended to the bonding region and the adhesiveness is lowered. The foreign substrate removing step is characterized in that: by laser irradiation, grinding, chemical polishing. The exposed surface of the nitride semiconductor as a mirror surface is formed by the above steps.

Characterized in that: after the foreign substrate removing step, there is a step of providing a concave-convex portion on the 2 nd conductivity type nitride semiconductor layer which is an exposed surface of the nitride semiconductor. The purpose is to diffuse the emitted light at the concave-convex part, guide the totally reflected light upward, and take out the light to the outside of the device.

Characterized in that: after the foreign substrate removing step, there is a step of forming a 2 nd insulating protective film on the 2 nd conductivity type nitride semiconductor layer to be an exposed surface of the nitride semiconductor. Thus, short-circuiting at the time of dicing or the like at the time of chipping can be prevented. The protective film contains SiO₂、TiO₂、Al₂O₃、ZrO₂. Characterized in that: the method comprises a step of providing a concave-convex portion on the 2 nd insulating protective film. The refractive index of the 2 nd insulating protective film is preferably 1 to 2.5. This is because the refractive index of the 2 nd insulating protective film is set to a refractive index between the nitride semiconductor and the atmosphere, and the light extraction efficiency is improved. More preferably 1.4 to 2.3. With the above configuration, the light extraction efficiency is 1.1 times or more higher than that in the case where the protective film is not provided. The protective film also has a surface deterioration prevention effect.

Characterized in that: after the foreign substrate removing step, there is a step of separating the nitride semiconductor into chips by etching the exposed surface of the nitride semiconductor. In the semiconductor light emitting device of the present invention, first, the semiconductor 2 is etched from the light extraction surface side until the 1 st insulating protective film 4 is etched, and the chip-shaped semiconductor light emitting device is formed on the support substrate 11. This is to form the convex region of the 1 st insulating protective film 4. Here, within the wafer, the individual semiconductors 2 have been separated, but the support substrate has not yet been separated. Thereafter, the 2 nd insulating protective film 7 is formed on the semiconductor 2 and on the projection region of the 1 st insulating protective film 4 except for the wire bonding region of the 2 nd electrode 6. The 2 nd insulating protective film 7 is formed on the side wall and the upper surface of the semiconductor 2, and thus physical damage due to current short circuit and dust adhesion can be suppressed. Next, after the 2 nd insulating protective film 7 is formed, the 2 nd insulating protective film 7 is formed into a chip by dicing or the like from the support substrate 1 side. According to the above method, a single semiconductor light emitting device can be obtained.

Then, a light emitting device is formed. The semiconductor light emitting device described above is first mounted on a heat sink having a lead frame, and conductive wires are connected from the semiconductor light emitting device to the lead frame. Thereafter, encapsulation was performed with transparent glass, thereby forming a light-emitting device (fig. 19).

When manufacturing another light emitting device, an encapsulating resin having a heat sink is prepared, a semiconductor light emitting device is formed on the heat sink, and a conductive wire is connected from the semiconductor light emitting device to a lead frame. Thereafter, a sealing resin such as silicone is applied to the semiconductor light emitting device. Then, a lens is formed thereon, thereby forming a light emitting device (fig. 20).

In the above light emitting device, it is preferable that the semiconductor light emitting device includes a protection device for protecting the semiconductor light emitting device from static electricity.

Drawings

Fig. 1 is a schematic cross-sectional view illustrating a manufacturing process of the present invention.

Fig. 2 is a schematic cross-sectional view illustrating a manufacturing process of the present invention.

Fig. 3 is a schematic sectional view and a perspective view illustrating an embodiment of the present invention.

Fig. 4 is a schematic cross-sectional view illustrating an embodiment of the present invention.

Fig. 5 is a schematic cross-sectional view illustrating an embodiment of the present invention.

Fig. 6 is a plan view illustrating an embodiment of the present invention.

Fig. 7 is a plan view illustrating an embodiment of the present invention.

Fig. 8 is a plan view illustrating an embodiment of the present invention.

Fig. 9 is a plan view illustrating an embodiment of the present invention.

Fig. 10 is a plan view illustrating an embodiment of the present invention.

Fig. 11 is a schematic cross-sectional view and a schematic top view illustrating an embodiment of the present invention.

Fig. 12 is a schematic cross-sectional view and a schematic top view illustrating an embodiment of the present invention.

Fig. 13 is a schematic cross-sectional view illustrating a manufacturing process of the present invention.

Fig. 14 is a schematic cross-sectional view illustrating a manufacturing process of the present invention.

Fig. 15 is a plan view illustrating an embodiment of the present invention.

Fig. 16 is a plan view illustrating an embodiment of the present invention.

Fig. 17 is a plan view illustrating an embodiment of the present invention.

Fig. 18 is a graph showing current output characteristics of an embodiment of the present invention, together with a comparative example.

Fig. 19 is a perspective view, a plan view, and a schematic cross-sectional view illustrating a light-emitting device of the present invention.

Fig. 20 is a perspective view, a plan view, and a schematic cross-sectional view illustrating a light-emitting device of the present invention.

Detailed Description

The nitride semiconductor device according to the embodiment of the present invention is a nitride semiconductor device including at least a conductive layer, a 1 st electrode, a nitride semiconductor having a light emitting layer, and a 2 nd electrode in this order on a supporting substrate, and the nitride semiconductor device includes a 1 st conductive type nitride semiconductor layer on the conductive layer with the 1 st electrode and the 1 st insulating protective film interposed therebetween. In the nitride semiconductor device, the 1 st electrode and the 2 nd electrode have a facing electrode structure. Preferably, the 2 nd electrode is not present above the 1 st electrode. In the above nitride semiconductor, the nitride semiconductor layer other than the light-emitting layer is a nitride semiconductor device having a band gap larger than the light-emitting band gap.

Embodiment mode 1

The following drawings show the manufacturing process of the nitride semiconductor device according to the present embodiment.

A nitride semiconductor 2 having at least a 2 nd conductivity type nitride semiconductor layer, a light emitting layer and a 1 st conductivity type nitride semiconductor layer is grown on a hetero substrate 1 of sapphire or the like (fig. 1A). Thereafter, a 1 st electrode (e.g., p-type electrode) 3 is formed on the nitride semiconductor layer. Next, a 1 st insulating protective film 4 is formed in the opening of the 1 st electrode, i.e., the exposed portion of the nitride semiconductor (fig. 1B). And a conductive layer 5 for alloying at the time of bonding is formed (fig. 1C). The conductive layer preferably has a 3-layer structure including an adhesive layer, a barrier layer, and a eutectic layer. On the other hand, a support substrate 11 is prepared. It is preferable to form the conductive layer 12 also on the surface of the supporting substrate (fig. 2A). Thereafter, the nitride semiconductor device and the supporting substrate are bonded by thermocompression bonding (fig. 2B). The adhesion surface is alloyed as each conductive layer to form a conductive layer 13 after adhesion. Thereafter, the foreign substrate is removed (fig. 2C). After the foreign substrate is removed, the nitride semiconductor layer is divided into chips, and the 2 nd electrode is formed on the exposed surface of the 2 nd conductivity type nitride semiconductor layer (fig. 3A). Here, irregularities may be formed on the exposed surface of the 2 nd conductivity type nitride semiconductor layer other than the 2 nd electrode (fig. 4A). Thereafter, the upper surface of the nitride semiconductor device except for the wire bonding region was covered with a 2 nd insulating protective film (fig. 3B and 4B), and the nitride semiconductor device was diced by dicing to obtain a nitride semiconductor device. Further, a concave-convex shape may be formed on the 2 nd insulating protective film (fig. 5 and 11).

The foreign substrate 1 may be any substrate that can be used to epitaxially grow the nitride semiconductor 2, and may be of a size corresponding to the foreign substrateAnd the thickness and the like are not particularly limited. As the foreign substrate, there can be mentioned: such as sapphire and spinel (MgAl) having any of the C-plane, R-plane and A-plane as a main surface₂O₄) Such an insulating substrate; or an oxide substrate of silicon carbide (6H, 4H, 3C), silicon, ZnS, ZnO, Si, GaAs, diamond, or lithium niobate or neodymium gallate lattice-bonded to a nitride semiconductor. In addition, if the film is thick enough to be processed into a device (several tens μm or more), a nitride semiconductor substrate such as GaN or AIN may be used. The foreign substrate may have a bias angle in the range of 0.1 to 0.5 °, preferably 0.05 to 0.2 °, in the case of a sapphire C-plane.

Also, the nitride semiconductor grown on the foreign substrate is grown through the transition layer. As the transition layer, a transition layer of the general formula Al is used_aGa_1-aThe nitride semiconductor represented by N (0. ltoreq. a. ltoreq.0.8), and more preferably, Al is used_aGa_1-aA nitride semiconductor represented by N (0. ltoreq. a. ltoreq.0.5). The thickness of the transition layer is preferably 0.002 to 0.5. mu.m, more preferably 0.005 to 0.2. mu.m, and still more preferably 0.01 to 0.02. mu.m. The growth temperature of the transition layer is preferably 200 to 900 ℃, and more preferably 400 to 800 ℃. Thus, dislocations and pits on the nitride semiconductor layer can be reduced. Further, Al may be grown on the foreign substrate by an ELO (atomic layer growth) method_xGa_1-XN (X is more than or equal to 0 and less than or equal to 1) layers. This ELO method is a method of reducing dislocations by causing a nitride semiconductor to grow in a lateral direction to thereby strain and confine threading dislocations.

After the low-temperature grown transition layer was formed on the nitride semiconductor layer, the following nitride semiconductor layer of the 2 nd conductivity type was formed. It is preferable to form a high-temperature growth layer grown at a high temperature on the transition layer. As the high-temperature growth layer, undoped GaN or GaN doped with n-type impurities may be used. Preferably, good crystallinity can be grown by using undoped GaN. The film thickness of the high-temperature growth layer is 1 μm or more, more preferably 3 μm or more. The growth temperature of the high-temperature growth layer is 900 to 1100 ℃, preferably 1050 ℃ or higher.

Next, an n-type contact layer is grown. The n-type contact layer is formed with a composition having a band gap energy larger than that of the active layer, and preferably Al_jGa_1-jN (j is more than 0 and less than 0.3). The thickness of the n-type contact layer is not particularly limited, but is preferably 1 μm or more, and more preferably 3 μm or more. The n-type impurity concentration of the n-type cladding layer is not particularly limited, but is preferably 1 × 10¹⁷～1×10²⁰/cm³More preferably 1X 10¹⁸～1×10¹⁹/cm³. Further, a gradient may be added to the n-type impurity concentration. Also, the additional Al composition gradient also acts as a carrier confining cladding.

The light-emitting layer (active layer) used in the present invention has a structure containing at least Al_aIn_bGa_1-a-bA well layer composed of N (0. ltoreq. a.ltoreq.1, 0. ltoreq. b.ltoreq.1, a + b. ltoreq.1) and Al_cIn_dGa_1-c-dAnd N (c is more than or equal to 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to 1, and c + d is less than or equal to 1). More preferably, the well layer and the barrier layer are each made of Al_aIn_bGa_1-a-bN (a is more than 0 and less than or equal to 1, b is more than 0 and less than or equal to 1, and a + b is less than 1) and Al_cIn_dGa_{1 -c-d}N (c is more than 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to 1, and c + d is less than 1). The nitride semiconductor used for the active layer may be any one of undoped, n-type impurity doped, and p-type impurity doped, but it is preferable to use a nitride semiconductor doped with undoped or n-type impurity, which enables the light emitting element to have high output. More preferably, the well layer is undoped, and the barrier layer is doped with n-type impurities, whereby the output and light-emitting efficiency of the light-emitting element can be improved.

By including Al in the well layer used in the light emitting element, a wavelength band which is difficult for the well layer of the conventional InGaN, specifically, a wavelength around 365nm or shorter as the band gap energy of GaN can be obtained.

The thickness of the well layer is preferably 1nm to 30nm, more preferably 2nm is 20nm or more, more preferably 3.5nm or more and 20nm or less. This is because, if less than 1nm, it cannot function well as a well layer; if the diameter exceeds 30nm, the crystallinity of the InAIGAN quaternary mixed crystal is lowered, and the device characteristics are lowered. In addition, in the case of 2nm or more, the film thickness does not vary greatly, and a relatively uniform layer of film quality can be obtained; at 20nm or less, the occurrence of crystal defects can be suppressed, and crystal growth can proceed. Further, the output can be improved by making the film thickness 3.5nm or more. This is because, when the thickness of the well layer is increased, light emission recombination is caused by high light emission efficiency and internal quantum efficiency in the injection of majority carriers as in the case of a large current-driven LD, and this is particularly effective in the multiple quantum well structure. In the single quantum well structure, the effect of improving the output can be obtained as described above by setting the film thickness to 5nm or more. The number of well layers is not particularly limited, but it is preferable that the film thickness of the well layer is 10nm or less to reduce the film thickness of the active layer when 4 or more is used. If the thickness of each layer constituting the active layer is increased, the thickness of the entire active layer is increased, resulting in V_fIs increased. In the multiple quantum well structure, it is preferable that at least 1 layer of the multiple wells have a film thickness in the above-described range of 10nm or less, and it is more preferable that all the well layers are made to be 10nm or less.

As in the case of the well layer, the barrier layer is preferably doped with a p-type impurity or an n-type impurity, or is undoped, and more preferably doped with an n-type impurity or is undoped. For example, in the case of doping an n-type impurity in the barrier layer, the concentration thereof must be 5 × 10¹⁶/cm³The above. For example, for an LED, 5 × 10 is preferred¹⁶/cm³2X 10 above¹⁸/cm³The following. Further, for a high output LED or LD, it is 5X 10¹⁷/cm³1X 10 above²⁰/cm³Hereinafter, more preferably 1X 10¹⁸/cm³5X 10 above¹⁹/cm³The following. In this case, it is preferable that the well layer contains substantially no n-type impurity, or is grown in a non-doped manner. When the n-type impurity is doped in the barrier layer, the entire barrier layer in the active layer may be doped, or a part of the barrier layer may be doped and a part of the barrier layer may be undoped. Here, when an n-type impurity is doped in a part of the barrier layer, it is preferable that the barrier layer disposed on the n-type layer side is doped in the active layer. For example, doping is performed in the n-th blocking layer Bn (n is a positive integer) counted from the n-type layer side, so that electrons are efficiently injected into the active layer, and a light emitting element having excellent light emitting efficiency and internal quantum efficiency is obtained. In the well layer, the mth well layer W counted from the n-type layer side_mThe same effect as in the case of the barrier layer described above can be obtained by doping (m is a positive integer). The same effect can be obtained by doping both the barrier layer and the well layer.

In the light emitting element of the present invention, it is necessary to use a nitride semiconductor in which the barrier layer has a larger band gap energy than the well layer. In particular, in the region where the well layer emits light having a wavelength of 380 or less, it is preferable to use Al of the general formula_cIn_dGa_1-c-dAnd (c is more than 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to 1, and c + d is less than or equal to 1) or AlGaN ternary mixed crystal. The barrier layer has an Al composition ratio c larger than that a of the well layer, i.e., c > a, and sufficient band gap energy is provided between the well layer and the barrier layer, so that a quantum well structure having good light emission efficiency can be formed as a light emitting element. When the barrier layer contains In (d > 0), the In composition ratio d is 0.1 or less, more preferably 0.05 or less. If the In composition ratio d exceeds 0.1, the reaction between Al and In is promoted during growth, and the crystallinity is deteriorated, so that a good film cannot be formed. When the In composition ratio d is 0.05 or less, the crystallinity can be further improved and a favorable film can be formed.

Further, the difference In band gap energy is set mainly by the Al composition ratio, and a composition ratio of the In composition ratio d of the barrier layer to the In composition ratio b of the well layer can be made wider, so that d.gtoreq.b. In this case, since the critical film thicknesses of the well layer and the barrier layer can be changed, the film thicknesses can be freely set in the quantum well structure, and an active layer having desired characteristics can be designed. The thickness of the barrier layer is preferably 1nm to 30nm, more preferably 2nm to 20nm, as in the case of the well layer. If it is less than 1nm, a uniform film cannot be obtained, and the function as a barrier layer cannot be sufficiently exerted; in addition, if it exceeds 30nm, the crystallinity is deteriorated.

Next, a 1 st conductivity type nitride semiconductor layer is formed on the light emitting layer. Here, the following layers are formed for the p-type nitride semiconductor layer. First, the p-type cladding layer has a composition larger than the band gap energy of the active layer, is not particularly limited as long as it can confine carriers of the active layer, and Al can be used_kGa_1-kN (0 < k < 1), particularly preferably Al_kGa_{1 -k}N (k is more than 0 and less than 0.4). The thickness of the p-type clad layer is not particularly limited, but is preferably 0.01 to 0.3. mu.m, more preferably 0.04 to 0.2. mu.m. p-type impurity concentration of the p-type cladding layer is 1 × 10¹⁸～1×10²¹/cm³、1×10¹⁹～5×10²⁰/cm³. When the p-type impurity concentration is in the above range, the bulk resistance can be reduced without lowering the crystallinity. The p-type cladding layer may be a single layer or a multilayer film (superlattice structure). In the case of a multilayer film, the film is made of Al as described above_kGa_1-kA multilayer film layer composed of a nitride semiconductor layer having N and a smaller band gap energy than that is sufficient. For example, as In the case of the n-type clad layer, In can be cited as the layer having a small band gap energy_lGa_1-lN(0≤l＜1)、Al_mGa_1-mN (m is more than or equal to 0 and less than 1, and m is more than 1). The thickness of each layer forming the multilayer film layer is preferably one layer in the case of a superlattice structureHereinafter, it is further preferable thatHereinafter, it is more preferable thatIn the case where the p-type cladding layer is a multilayer film layer including a layer having a large band gap energy and a layer having a small band gap energy, at least one of the layer having a large band gap energy and the layer having a small band gap energy may be doped with a p-type impurity. When doping is performed on both the layer having a large band gap energy and the layer having a small band gap energy, the doping amounts may be the same or different.

Next, a p-type contact layer is formed on the p-type cladding layer. The p-type contact layer can be made of Al_fGa_{1 -f}N (0. ltoreq. f < 1), especially Al_fGa_1-fN (0. ltoreq. f < 0.3) can maintain a good ohmic contact with the 1 st electrode as an ohmic electrode. The p-type impurity concentration is preferably 1X 10¹⁷cm³The above. The p-type contact layer preferably has a high p-type impurity concentration on the conductive substrate side and a composition gradient in which the mixed crystal ratio of Al is small. In this case, the composition gradient may be such that the composition changes continuously, or the composition may be such that the composition changes discontinuously in a stepwise manner. For example, the p-type contact layer may be formed of a 1 st p-type contact layer having a high p-type impurity concentration and a low Al composition ratio and a 2 nd p-type contact layer having a low p-type impurity concentration and a high Al composition ratio so as to be in contact with the ohmic electrode. Good ohmic contact can be obtained by the 1 st p-type contact layer, and self-absorption can be prevented by the 2 nd p-type contact layer.

In the present invention, a nitride semiconductor is grown by a vapor phase growth method such as a Metal Organic Chemical Vapor Deposition (MOCVD) method, a Halide Vapor Phase Epitaxy (HVPE) method, or a Molecular Beam Epitaxy (MBE) method.

Next, in the case where the nitride semiconductor is formed in the order of an n-type nitride semiconductor layer and a p-type nitride semiconductor layer, after the nitride semiconductor 2 is grown on the hetero-substrate 1 (fig. 1A), the wafer is taken out from the reaction apparatus, and thereafter, heat treatment is performed at 450 ℃ or higher in an atmosphere containing oxygen. In this way, hydrogen bonded to the p-type nitride semiconductor layer is removed, and a p-type nitride semiconductor layer exhibiting p-type conductivity is formed.

Thereafter, a 1 st electrode is formed in ohmic contact with the surface of the p-type nitride semiconductor layer as the 1 st conductivity type nitride semiconductor layer. The 1 st electrode 3 is made of Ni, Au, W, Pt, Ti, Al, Ir, Rh, Ag, Ni-Au-RhO, Rh-Ir-Pt, etc. It is preferable that the 1 st electrode is formed of Rh, Ag, Ni, Au, or the like having high reflectance. Next, heat treatment is performed in an atmosphere containing oxygen. The film thickness of the No. 1 electrode is 0.05 to 0.5 μm.

Next, a 1 st insulating protective film 4 is formed on the exposed surface of the nitride semiconductor 2 on which the 1 st electrode 3 is formed (fig. 1B). SiO can be used as the material of the 1 st insulating protective film₂、Al₂O₃、ZrO₂、TiO₂Etc. single layer films or multilayer films. Further, a metal film having a high reflectance such as Al, Ag, Rh, etc. may be formed on the surface to be bonded to the supporting substrate. Since the metal film increases the reflectance, the light extraction efficiency can be improved. Thereafter, a conductive layer 5 made of an alloy containing at least 1 selected from the group consisting of Au, Sn, Pd, and In is formed on the surface to be bonded to the support substrate (fig. 1C). In the case where the 1 st electrode is made of Ag, although a high light extraction effect is obtained, the Ag is likely to migrate during high-temperature and high-humidity operation. If migration occurs, leakage current occurs. Therefore, when the 1 st electrode is Ag, the 1 st insulating protective film 4 is not formed, and the 1 st layer of the conductive layer 5 is formed of RhO. If RhO is formed on the entire surface, Ag is covered, and migration of Ag is suppressed, thereby achieving a high light extraction effect.

On the other hand, a supporting substrate 11 (fig. 2A) to be bonded to the conductive layer formation surface of the nitride semiconductor device is prepared. Specific examples thereof include a composite of a metal such as Cu-W, Cu-Mo, AlSiC, AlN, Si, SiC and Cu-diamond and a ceramic. For example, it can be represented by the general formula Cu_xW_1-x(0. ltoreq. x. ltoreq.30), or Cu_xMo_1-x(x is more than or equal to 0 and less than or equal to 5). If AlN is used as a supporting substrate, it is an insulating substrate, and therefore, it is advantageous to mount a chip on a circuit such as a printed circuit board. And alsoIn some cases, the use of Si is advantageous in that it is inexpensive and easy to be formed into chips. The preferable film thickness of the supporting substrate is 50 to 500 μm. By reducing the thickness of the supporting substrate to the above range, heat dissipation can be improved. The supporting substrate may have a structure having irregularities on the surface to be bonded to the nitride semiconductor or on the surface opposite thereto. Preferably, the adhesive surface has a structure including an adhesive layer, a barrier layer, and a eutectic layer. This is to prevent diffusion with the 1 st electrode. They are the conductive layer 12 on the side of the support substrate. For example, a metal film such as Ti-Pt-Au, Ti-Pt-Sn, Ti-Pt-Pd, or Ti-Pt-AuSn, W-Pt-Sn, RhO-Pt-Au, RhO-Pt- (Au, Sn) is formed. The metal film is alloyed by eutectic crystals and becomes the conductive layer 13 in a subsequent step. Also, it is preferable that the surface metal to be bonded is different on the support substrate side than on the nitride semiconductor device side. The reason for this is to ensure that a eutectic crystal can be formed at a low temperature and the melting point of the eutectic crystal is increased.

Next, the conductive layer forming surface of the supporting substrate 11 and the conductive layer forming surface of the nitride semiconductor device are bonded to each other in an opposed manner, and thermocompression bonding is performed (fig. 2B). Heating to 150 ℃ or higher while applying pressure. In order to form a eutectic by adhesion, it is preferable that an adhesive layer, a barrier layer, and a eutectic layer are provided on the adhesive surface on the support substrate side and the nitride semiconductor side, respectively. The adhesion layer is a layer that ensures high adhesion to the 1 st electrode, and is preferably any one of Ti, Ni, W, and Mo. The barrier layer is a layer for preventing diffusion of the metal constituting the eutectic layer into the adhesion layer, and is preferably Pt or W. Further, in order to prevent the diffusion of the metal in the eutectic layer into the adhesive layer, an Au film having a thickness of about 0.3 μm may be formed between the barrier layer and the eutectic layer. When bonding, the first electrode/Ti-Pt-AuSn-Pt-Ti/supporting substrate is formed, and the other electrodes are the first electrode/RhO-Pt-AuSn-Pt-Ti/supporting substrate, the first electrode/Ti-Pt-PdSn-Pt-Ti/supporting substrate and the first electrode/Ti-Pt-AuSn-Pt-RhO/supporting substrate. This enables the formation of an alloy that is difficult to exfoliate. When the conductive layer is eutectic, adhesion can be performed at a low temperature, and the adhesion is also enhanced. Bonding at low temperature has the effect of mitigating warping.

Thereafter, the foreign substrate is removed by irradiating Excimer (Excimer) laser or grinding from the foreign substrate side (fig. 2C). After the foreign substrate is removed, CMP (chemical mechanical polishing) is performed on the surface of the exposed nitride semiconductor layer to expose the 2 nd conductive nitride semiconductor layer, which is a desired film. In this case, since the GaN film grown at a high temperature is removed, the LED having an emission wavelength in the ultraviolet region can be protected from absorption. By this treatment, the damaged layer can be removed, the thickness of the nitride semiconductor layer can be adjusted, and the roughness of the surface can be adjusted. Thereafter, in order to chip the nitride semiconductor device, the outer periphery is etched by RIE or the like to remove the nitride semiconductor layer on the outer periphery.

Next, a 2 nd electrode 6 is formed on the exposed surface of the 2 nd conductivity type nitride semiconductor layer (fig. 3A). The No. 2 electrode has Ti-Al-Ni-Au, W-Al-W-Pt-Au, Al-Pt-Au, etc., in the case of using an n-type electrode. The second electrode has a thickness of 0.1 to 1.5 μm. In order to improve light extraction efficiency, the exposed surface of the 2 nd conductivity type nitride semiconductor layer may be formed with irregularities (dimpling) by RIE or the like (fig. 4A). The 2 nd electrode forming surface is preferably a removal region. The cross-sectional shape of the concave-convex is a mesa shape or an inverted mesa shape, and the planar shape thereof is an island shape, a grid shape, a rectangular shape, a circular shape, or a polygonal shape.

Next, the 2 nd insulating protective film 7 is formed so as to cover the region other than the pad electrode forming region of the 2 nd electrode on the exposed surface (fig. 3B, 4B). The 2 nd insulating protective film 7 is SiO₂、Nb₂O₅、Al₂O₃、ZrO₂、TiO₂And the like. Thereafter, in order to improve the light extraction efficiency, the exposed surface of the protective film may be formed into a concave-convex shape by RIE or the like (fig. 5). The method for forming the unevenness is performed by RIE or wet etching, and can be controlled to 0.1 μm level. The convex part of the protective film has a trapezoidal, triangular or semicircular cross section. That is, the occurrence probability of diffuse reflection is increased by providing a slope to the convex portion. The inclination angle as the inclination of the convex portion is preferably at 30More than 60 degrees. The planar shape of the protective film is an island shape, a grid shape, a rectangular shape, a circular shape, or a polygonal shape.

If the cross section of the light extraction surface of the 2 nd insulating protective film is uneven, light that cannot be extracted by total reflection of light can be transmitted by changing the angle of light at the uneven surface (light extraction interface). Therefore, the light extraction efficiency is 1.5 times or more higher than that in the case where the protective film has no irregularities. The shape of the convex portion of the protective film in the nitride semiconductor light-emitting element is as follows: the cross section is at least 1 selected from the group consisting of trapezoid, triangle, and semicircle. Also, if the corners are configured to have circular arcs, the probability of diffuse reflection increases, thereby further improving the light extraction efficiency. The depth of the recess is 0.2 to 3 μm, more preferably 1.0 to 1.5 μm. The reason for this is that if the depth of the concave portion is too shallow than 0.2 μm, the effect of improving light extraction is not obtained; if the thickness is deeper than 3 μm, the resistance value is not changed, but the film does not function as a protective film. Further, when the recess is formed in a circular or polygonal shape, the output can be improved while maintaining a low resistance value. By forming the uneven shape on the protective film on the nitride semiconductor layer, the light extraction efficiency can be improved without increasing the voltage. The reason for this is that the nitride semiconductor is not thinned by processing, and therefore the resistance is not increased. Further, there is no damage due to direct etching of the nitride semiconductor. In addition, when the protective film is subjected to the unevenness processing, a material having good etching processability such as RIE (reactive ion etching) may be selected and subjected to the microfabrication, as compared with the case of performing the unevenness processing on the nitride semiconductor layer. By forming the cross-sectional shape, efficient diffuse reflection can be performed. Preferably, the difference in refractive index between the protective film and GaN is in the range of 0.5. According to the above configuration, the voltage is not increased and the light extraction efficiency is 1.5 times or more as compared with the configuration without the protective film. The protective film also has an effect of preventing surface deterioration. Since the protective film is insulating, it is possible to prevent a short circuit due to chipping or the like.

Further, the nitride semiconductor device is separated into chips by dicing or the like.

Fig. 18 is a graph showing current output characteristics of a nitride semiconductor device using a conventional sapphire substrate and one embodiment of a supporting substrate used by bonding. Since the nitride semiconductor device using the supporting substrate has low thermal resistance, a large current of 2000mA or more can be applied, and the output is 350mA or more. In contrast, a nitride semiconductor device using a conventional sapphire substrate cannot expect high output because of high thermal resistance and poor heat dissipation. In addition, the conditions are the same for nitride semiconductor devices, electrodes, and the like.

Another nitride semiconductor light-emitting device according to embodiment 1 is described below. A support substrate is provided with a conductive layer, a 1 st electrode and a nitride semiconductor in this order. The nitride semiconductor has a 2 nd electrode thereon. For the 2 nd electrode, pad electrode forming regions are formed at the opposite corners of the four corners, and the 2 nd electrode is further formed in a mesh shape between the pad electrode forming regions. The pad electrode forming region is not limited to 2 on the diagonal direction, and may be formed entirely at four corners. Also, the 1 st electrode and the 2 nd electrode do not overlap when viewed from above. The 2 nd electrode has a protective film thereon. The protective film may be formed not only on the nitride semiconductor layer but also on the 2 nd electrode except for the pad electrode forming region of the 2 nd electrode. By forming the 2 nd electrode in a mesh shape, a grid shape, or the like over the entire surface of the light emission range, the resistance of the nitride semiconductor layer can be reduced.

In the nitride semiconductor light-emitting device shown in fig. 12A, when viewed in cross section (fig. 12B), the 1 st electrode 3 in contact with the nitride semiconductor 2 has an opening, and a 1 st insulating protective film 4 is formed in the opening, and the protective film 4 preferably has a 2-layer structure with a reflective film (not shown). The material of the protective film 4 adopts SiO₂、Al₂O₃、ZrO₂、TiO₂Etc. single layer films or multilayer films. Can prevent short due to the film with insulation propertyAnd the like, thereby improving the yield and reliability. On the side not in contact with the nitride semiconductor 2, on the protective film 4The aboveBy forming a reflective film (not shown) of Al, Ag, Rh, or the like in the following film thickness, light propagating in the lateral direction can be efficiently extracted.

As described above, since the face-down configuration (the n-side is the surface) is adopted, the light extraction efficiency is improved. This is because the back surface reflectance of the nitride semiconductor layer is high. Further, since the opposed electrodes are structured, the light emitting area can be enlarged. Furthermore, the support substrate used in the present invention has improved heat dissipation. If a conductive substrate is used, a 1-lead structure can be obtained. This embodiment mode can also be applied to a laser diode.

Another structure of the nitride semiconductor device obtained in embodiment 1 is described below. The figure is given from above. Fig. 6 is a type having the 2 nd electrode on the diagonal line. The shape and size of the 1 st electrode are not particularly limited in the region not overlapping with the 2 nd electrode. The 2 nd electrode may be formed at all of the four corners except the 2 nd position. Fig. 7 shows a type in which the 2 nd electrode extends to the center. Fig. 8 shows a type in which the 1 st electrode has a pad electrode. Fig. 9 shows a type in which the 2 nd electrode is covered with an L-shape in order to form the 1 st electrode over a wide range. Other types have the 2 nd electrode in the central portion as shown in fig. 10. The 1 st electrode is formed on the outer periphery and does not overlap with the 2 nd electrode.

As described above, since the face-down configuration (the n-side is the surface) is adopted, the light extraction efficiency is improved. Further, since the opposed electrodes are structured, the aperture can be increased. Further, the heat dissipation is improved by the choice of the substrate. Further, since a conductive substrate can be used, a 1-lead structure can be provided. This embodiment mode can also be applied to a laser diode.

Embodiment mode 2

On the hetero substrate 1, a nitride semiconductor is formed in the order of a 2 nd conductivity type nitride semiconductor layer, a light emitting layer and a 1 st conductivity type nitride semiconductor layer. The surface is first partially etched using RIE or the like. Thereafter, heat treatment is performed in an atmosphere containing oxygen. Ohmic contact with the surface of the 1 st conductivity type nitride semiconductor layer is obtained on a part of the unetched surface, and a 1 st electrode pattern having a high reflectance is formed. Then, a 1 st insulating protective film is formed on a portion where the 1 st electrode is not formed. The protective film can be made of SiO₂And the like, and may be a multilayer structure thereof. Further, a metal film having a high reflectance such as Al may be formed thereon. Thereafter, a conductive layer composed of an adhesive layer, a barrier layer, and a eutectic layer is formed on the entire surface of the wafer or an unetched portion. The conductive layer becomes eutectic when bonded. For example, Ni-Pt-Au-Sn-Au, RhO-Pt-Au-Sn-Au, Ti-Pt-Au-Sn-Au, and Ti-Pt-Sn-Sn are formed into a film.

On the other hand, a support substrate 11 on which a metal film has been formed is prepared. The metal film forming surface of the support substrate and the 1 st electrode surface formed on the nitride semiconductor layer are opposed to each other and joined, and heated while being pressurized. Thereafter, polishing, etching, electromagnetic wave irradiation, or a combination thereof is performed from the reaction substrate side. As an example of the electromagnetic wave irradiation, excimer laser irradiation is given. After the exposure, the nitride semiconductor is subjected to CMP processing to expose a desired film. This enables removal of the damaged layer, adjustment of the GaN thickness, and adjustment of the surface roughness.

Thereafter, the exposed surface of the 2 nd conductivity type nitride semiconductor layer is stepped by an etching method such as RIE. The 2 nd electrode 6 is formed of Ti-Al-Ni-Au, W-Al-W-Pt-Au, or the like on the surface of the nitride semiconductor layer. Next, SiO is formed to cover the exposed surface of the nitride semiconductor layer₂、Al₂O₃、ZrO₂、TiO₂And the like, and covers the 2 nd electrode (e.g., n-type electrode) and the other parts. And thereafter separated into chip shapes by dicing or the like.The characteristics of the nitride semiconductor device obtained in this embodiment are equivalent to those of embodiment 1.

Embodiment 3 of the invention

The nitride semiconductor device of the present embodiment is an element in which the bonding step is performed 2 times (fig. 13). A method for manufacturing a nitride semiconductor light emitting device having at least a 1 st electrode, a nitride semiconductor having a light emitting layer, and a 2 nd electrode on a supporting substrate, comprising: a 1 st step of growing a nitride semiconductor having the light-emitting layer on a 1 st substrate and bonding a 2 nd substrate to a growth surface of the nitride semiconductor; thereafter, removing the 1 st substrate to form an exposed surface of the nitride semiconductor layer; thereafter, forming a step on the exposed surface of the nitride semiconductor layer in step 3; thereafter, a 4 th step of bonding a supporting substrate to the exposed surface of the nitride semiconductor layer via a 1 st electrode; and a 5 th step of removing the 2 nd substrate.

In the step 1, a 2 nd substrate is bonded to the growth surface of the nitride semiconductor layer via a 2 nd electrode. In the 4 th step, the 1 st electrode is formed by eutectic alloying at the time of bonding the support substrate and the nitride semiconductor layer. In the nitride semiconductor light-emitting element, the 1 st electrode has aluminum at an interface with the nitride semiconductor, and the interface has a stepped shape. The 1 st electrode has a eutectic layer. The step of the interface between the 1 st electrode and the nitride semiconductor layer is 0.1 μm or more.

The nitride semiconductor light-emitting device of the present embodiment is a nitride semiconductor light-emitting device including at least a 1 st electrode, a nitride semiconductor layer having a light-emitting layer, and a 2 nd electrode on a supporting substrate, and is characterized in that: the 1 st electrode has aluminum at an interface of the nitride semiconductor layer, and the interface has a stepped shape. In this way, the aluminum formed on the interface prevents light from the light-emitting element from transmitting through the support substrate, and therefore, the light extraction efficiency from the light extraction surface can be improved. Further, since aluminum is in ohmic contact with the n-type nitride semiconductor, the voltage can be reduced. Forming aluminum on the interface of a nitride semiconductor device is difficult because nitride substrates such as GaN and AlN cannot be mass-produced. In the present invention, 2 times of bonding technique is adopted, so that aluminum can be formed on the interface with the 1 st electrode. Further, the 1 st electrode has an effect of obtaining conductivity to the supporting substrate because it has a eutectic layer. The 1 st electrode has aluminum at the interface with the nitride semiconductor, and thus can generate high reflection.

Further, since the interface between the 1 st electrode and the nitride semiconductor layer is formed in a stepped shape, light extraction efficiency can be improved. This is because light that originally entered the total reflection angle due to total reflection of light and did not exit is extracted by changing its angle due to the step of the interface. If the step of the interface is provided, the light extraction efficiency becomes 1.5 times or more as compared with the case where there is no step on the interface. The step size of the interface is 0.1 μm or more, preferably 0.3 μm or more.

Since the supporting substrate is conductive, a nitride semiconductor light-emitting device having an opposed electrode structure is formed. The 1 st electrode contains at least 1 kind selected from the group consisting of Pd, Au, Sn and In for forming a eutectic layer. If the 1 st electrode is used as the n-side electrode, the P-side electrode contains at least 1 kind selected from the group consisting of Al, Ag, Rh, Ni, Au, and Pd. In order to improve the extraction efficiency, the P electrode is formed of Ag, Rh, or the like in a mesh structure, or a material having light transmittance such as a Ni and/or Au thin film is used. When such a material is used, the electric resistance can be reduced and the light extraction efficiency can be improved.

The above-mentioned 4 th step is characterized in that: the 1 st electrode is connected by an alloy eutectic at the time of bonding the supporting substrate and the nitride semiconductor layer. Due to the eutectic crystal, adhesion can be achieved at low temperature, and the adhesion strength is also enhanced. Since the bonding is performed at a low temperature, the effect of alleviating the warpage is obtained.

Formed in the order of the supporting substrate/1 st electrode (eutectic layer + aluminum)/nitride semiconductor.

The bonding step in the step 1 is: after forming a nitride semiconductor on a 1 st substrate (sapphire, SiC, GaN, etc.) in the order of an n-type nitride semiconductor layer, a light-emitting layer, and a p-type nitride semiconductor layer, the 2 nd substrate is bonded on the growth surface of the p-type nitride semiconductor layer by thermocompression bonding. The step 1 is characterized in that: a2 nd substrate is bonded on the growth surface of the nitride semiconductor layer through a 2 nd electrode. Here, the 2 nd substrate is Cu — W, invar, stainless steel, or the like, and is bonded with a material that can be bonded at a relatively low temperature, such as an epoxy film. When the 2 nd substrate is bonded to the nitride semiconductor with the epoxy film, it is preferable to sandwich the diffusion preventing layer. The resist coated as the temporary protective film on the nitride semiconductor side and the organic substance of the epoxy resin film on the 2 nd substrate side are subjected to the adhesion process through the metal film having the diffusion preventing effect, so that the 2 nd substrate is easily removed in the subsequent process. The metal film having the diffusion preventing effect is Ti or the like. Next, in step 2, the first substrate 1 is removed by polishing, laser irradiation, chemical polishing, or the like to expose the surface of the n-type nitride semiconductor layer. On the surface of the n-type layer, a damaged layer is formed because the foreign substrate is removed by grinding, but the damaged layer can be removed by chemical polishing. Therefore, deterioration of characteristics due to removal of the foreign substrate is avoided. Next, in the 3 rd step, a step is formed on the exposed surface of the nitride semiconductor layer. The step is 0.1 μm or more. Since the step is formed by a dry etching method (RIE) or a wet etching method, the step can be controlled to be on the order of 0.1 μm. Next, in the 4 th step, a supporting substrate is formed on the exposed step surface of the nitride semiconductor layer via the 1 st electrode. The 1 st electrode is characterized in that: the nitride semiconductor layer has aluminum or silver at an interface with the nitride semiconductor layer. Further features are: a low-melting-point metal containing Sn and In is formed on the uppermost surface of the 1 st electrode. The support substrate is preferably a thermally conductive substrate. The conditions for the adhesion of the support substrate are: on the supporting substrate, the 1 st electrode is hot-pressed at 100 to 500 ℃ with at least 1 material selected from the group consisting of Ti-Pt-Au and Ti-Pt-Pd as an intermediary, so as to form eutectic bonding. Next, in the 5 th step, the 2 nd substrate is removed from the adhesive layer by losing its adhesive strength by heating at 200 ℃ or higher, or by melting the eutectic portion with an organic solvent or an acid solution, or the like, thereby forming a nitride semiconductor light emitting element. As described above, the nitride semiconductor light emitting device has a structure including, from the support substrate side, the support substrate, Ti-Pt-AuSn, Ti-Pt-PdSn, and the like, the 1 st electrode, the nitride semiconductor, and the 2 nd electrode.

Hereinafter, the steps of manufacturing the nitride semiconductor light emitting device according to embodiment 3 will be described with reference to the drawings.

(step 1)

First, a nitride semiconductor 102 is grown on a 1 st substrate 101 (fig. 13A). Thereafter, the nitride semiconductor layer is etched (fig. 13B). This etching is performed to expose the n-type nitride semiconductor layer in order to prevent cracking of the nitride semiconductor layer and facilitate chip separation. Since the nitride semiconductor after etching has a film thickness of 1 μm or more, it is possible to suppress the occurrence of cracking when removing the 1 st substrate. Next, a 2 nd electrode (P-side electrode) 103 is formed in an unetched region of the nitride semiconductor 102 (fig. 13C). Thereafter, a 2 nd substrate 105 is bonded on the nitride semiconductor 102 (fig. 13D). The adhesive layer 104 for bonding the 2 nd substrate 105 is bonded by hot pressing using a polymer material such as an epoxy resin or a polyamide resin, or a resist. The hot pressing is carried out at 100-200 ℃.

Since the 2 nd substrate 105 is to be removed in a subsequent step, it is sufficient if it has a certain flatness and strength, and a good material is not particularly limited, but it is preferable that the value of the thermal expansion coefficient should be close to that of the 1 st substrate. The reason for this is that no difference in thermal expansion occurs during bonding in the 4 th step. Further, a substance which can be easily removed is preferable, and examples thereof include Cu-W, W, Mg, kovar (iron cobalt nickel) alloy, invar material, polyimide-based resin, polyester-based resin, and epoxy-based resin. The area of the 2 nd electrode as the active layer is S (μm)²) When the sum of the outer peripheral lengths of the 2 nd electrodes is L (. mu.m),then L/S is more than or equal to 0.02. Within this range, the light extraction efficiency is 1.2 times or more. The 2 nd electrode is made of at least one selected from the group consisting of Ni, Co, Fe, Ti, Cu, Rh, Au, Ru, W, Zr, Mo, Ta, Pt, Ag, and oxides and nitrides thereof.

(step 2)

Next, the 1 st substrate is removed to form an exposed surface of the nitride semiconductor 102 (fig. 13E). The 1 st substrate 101 is removed by grinding or excimer laser irradiation. The exposed surface of the nitride semiconductor 102 after the 1 st substrate is removed is then chemically polished to form a flat surface.

(step 3)

Next, a step is formed on the exposed surface of the nitride semiconductor layer (fig. 13F). Here, the step means that the interface step is 0.1 μm or more, and the step shape is a tapered shape or an inverted tapered shape. The pattern of the planar shape of the stepped shape has convex portions and/or concave portions in a stripe shape, a grid shape, an island shape, or a circular shape, and thus can be selected from a rectangular shape, a comb shape, and a mesh shape. For example, if a circular projection is formed, the diameter of the circular projection should be 5 μm or more and the interval between the concave grooves should be 3 μm or more. The provision of the steps is effective for improving the light extraction efficiency of the LED, and the introduction of aluminum having a high light reflectance at the interface in the subsequent step makes it possible to achieve a light extraction efficiency 1.5 times or more higher than that of a nitride semiconductor light-emitting element having no steps.

(step 4)

Next, the 1 st electrode 106 is formed on the step formation surface (fig. 14A), and next, the supporting substrate 111 is bonded (fig. 14B). The supporting substrate 111 on which a metallization material such as AuSn, PdSn, or inp is formed and the nitride semiconductor 102 on which the 1 st electrode 106 is formed are bonded to each other in an opposed manner, and heated while being pressurized. A conductive layer 113 is formed on the adhesive surface. The bonding temperature in this case is 120 ℃ or higher, preferably 150 ℃ or higher and 300 ℃ or lower. The 1 st electrode has aluminum at an interface with the nitride semiconductor layer. In order to bond the support substrate 8 and the 1 st electrode through eutectic alloy, a metal for forming eutectic such as Sn or In is formed on the surface of the 1 st electrode 106. In order to prevent the metal for forming the eutectic crystal from alloying with aluminum, a barrier layer made of a high-melting-point metal such as Pt, W, Ni, Ti, or the like may be formed.

The 1 st electrode 106 is made of Al-Pt-Sn, Al-W-In, or the like. The No. 1 electrode is formed to have a total film thicknessThe following. The thickness of the aluminum film is 500 or moreThe following. If the aluminum is within the above film thickness range, the film thickness becomes uniform in the chip even after 2 times of the bonding process. For example, the thickness of the 1 st electrode 106 is set to

If AlN is used as a support substrate, it is an insulating substrate, and therefore, it is advantageous to mount a chip on a circuit such as a printed wiring board. Further, the use of Si has advantages of low cost and easy chipping. The preferable film thickness of the supporting substrate is 50 to 500 μm. When the supporting substrate is thinned to the above range, heat dissipation is improved. The adhesive surface of the support substrate preferably has a structure of an adhesive layer, a barrier layer, and a eutectic layer, which are alloyed by eutectic crystals in a subsequent step. For example, a metal film such as Ti-Pt-Au, Ti-Pt-Pd, or Ti-Pt-AuSn, W-Pt-Sn, RhO-Pt-Au, RhO-Pt- (Au, Sn) or the like. Further, the surface metal to be bonded is preferably different between the support substrate side and the nitride semiconductor layer side. The reason for this is that eutectic crystallization is possible at low temperatures, and the melting point after eutectic crystallization is increased.

(step 5)

Thereafter, in the 5 th step, the 2 nd substrate 105 is removed (fig. 14C). Which is heated to a higher temperature than during bonding. When heated to 200 ℃ or higher, the bonding force is reduced, and the 2 nd substrate 5 is removed together with the adhesive layer 4. This method is effective for removing the adhesion using an epoxy resin. The adhesive layer may be dissolved with an organic solvent such as acetone or N-methyl-2-pyrrolidone. When eutectic crystals are formed by AuSn or the like, the eutectic crystals are immersed in an acid to melt the bonding portions, and the bonding portions are separated. Combinations of these methods with milling may also be employed.

After the removal of the 2 nd substrate, an insulating protective film 107 is formed on the exposed surface of the nitride semiconductor layer (fig. 14D). Next, a pad electrode is formed in the opening of the protective film (fig. 15A).

Thereafter, the chip is diced by dicing, thereby producing a nitride semiconductor light emitting element. The 1 st electrode is an n-side electrode, but the present invention is not limited thereto. Since the nitride semiconductor device using the supporting substrate has low thermal resistance, it is possible to apply a large power of 2W or more and output 200mA or more. According to the present embodiment described above, an LED element having high light extraction efficiency can be manufactured without increasing the voltage. In contrast, conventional nitride semiconductor devices using a sapphire substrate have high thermal resistance and poor heat dissipation, and therefore cannot be expected to have high output.

A nitride semiconductor light-emitting device according to embodiment 3 other than the above will be described below. A1 st electrode and a nitride semiconductor layer are provided in this order on a support substrate. The nitride semiconductor layer has a 2 nd electrode thereon. The 2 nd electrode is formed in a mesh shape on the light extraction surface (fig. 16). The area of the opening is 1 to 100 μm². The 2 nd electrode is formed with a pad electrode forming region at a diagonal of four corners. The pad electrode forming region is not limited to 2 on the diagonal direction, and all four corners may be formed. The support substrate is an insulating substrate and is formed on the same surfaceA two-electrode configuration is formed (fig. 17). Further, it is preferable that the second electrode 2 has a layer of SiO₂、Al₂O₃、ZrO₂、TiO₂、Nb₂O₅、Ta₂O₅And the like, a single layer film or a multilayer film. The insulating film is a single-layer film or a multilayer film. The protective film also has an effect of preventing surface deterioration. The protective film is characterized by having an insulating property. Since the protective film is insulating, it is possible to prevent a short circuit at the time of dicing due to dicing or the like at the time of dicing. Since the insulating film is provided, short-circuiting and the like can be prevented, and thus yield and reliability can be improved. Since the 2 nd electrode is formed over the entire light-emitting region in a mesh shape, a grid shape, or the like, the resistance of the nitride semiconductor layer can be reduced.

According to the above-described manufacturing method, aluminum having high reflectance can be formed at the interface between the 1 st electrode and the nitride semiconductor layer. Thus, the light extraction efficiency is improved. Further, since the opposed electrodes are structured, the light emitting area can be enlarged. Furthermore, the support substrate used in the present invention improves heat dissipation. If a conductive substrate is used, a 1-lead structure can be formed. The present embodiment can be applied to a laser diode.

A semiconductor light emitting device having a concave-convex portion at an interface between a 2 nd electrode 106 and a semiconductor 102, characterized in that: the 2 nd electrode forms a mirror on the bottom surface and/or the inclined surface of the recess (fig. 15B). The reflector is made of a material having the above-mentioned reflecting action. The light can be actively scattered at the interface by the reflecting mirror, and the light extraction efficiency is improved.

Examples

Various embodiments of the present invention will be described below, but the present invention is not limited thereto.

[ example 1]

The following describes a method for manufacturing the LED element of example 1. First, a foreign substrate 1 made of sapphire (C-plane) was placed in a MOVPE reaction vessel, and the substrate was purged by raising the temperature of the substrate to 1050 ℃ while introducing hydrogen.

(transition layer)

Then, the temperature was lowered to 510 ℃, hydrogen was used as a carrier gas, ammonia, TMG (trimethylgallium) and TMA (trimethylaluminum) were used as a source gas, and Al with a film thickness of about 100 angstroms was grown on the substrate 1_0.25Ga_0.75N, a transition layer.

(nitride semiconductor layer of the 2 nd conductivity type)

After the growth of the transition layer, the 1 st conductivity type nitride semiconductor layer was grown in the following order. First, only TMG was stopped and the temperature was raised to 1050 ℃. After reaching 1050 ℃, the undoped GaN layer 103 with a film thickness of 1.5 μm was grown using TMG and ammonia gas as the raw material gases. Then, TMG and ammonia gas were used as raw material gases and silane gas as impurity gas were used at 1050 ℃ to grow Si-doped silicon particles of 2.25 μm thickness of 4.5X 10¹⁸/cm³An n-type contact layer of GaN. The thickness of the n-type contact layer may be 2 to 30 μm.

Next, only the silane gas was stopped, a 3000 ANGSTROM thick undoped GaN layer was grown at 1050 ℃ using TMG and ammonia gas, and then silane gas was added at the same temperature to grow a 300 ANGSTROM thick Si-doped layer of 4.5X 10¹⁸/cm³Then, only the silane gas was stopped, and an undoped GaN layer having a thickness of 50 angstroms was grown at the same temperature, and the total thickness of 3 layers was 3350 angstroms. This was used as a 2 nd conductivity type nitride semiconductor layer.

Secondly, growing 40 angstrom non-doped GaN layer at the same temperature, secondly, setting the temperature to 800 ℃, and growing 20 angstrom non-doped In by adopting TMG, TMI and ammonia_0.13Ga_0.87And N layers. By repeating this operation, 10 layers were alternately stacked, and finally, a 40 angstrom GaN layer was grown to grow a 640 angstrom thick superlattice structure layer.

Next, 200 angstroms of undoped Ga is grownN barrier layer, then, the temperature was set to 800 ℃, and 30 angstroms thick undoped In was grown using TMG, TMI, and ammonia_0.4Ga_0.6A well layer of N. Barrier layers 5 and well layers 4 were alternately stacked in the order of barrier + well + barrier + well … + barrier, and an active layer having a multiple quantum well structure with a total film thickness of 1120 angstroms was grown. In addition, the active layer and the n-side 2 nd multilayer film laminated below the active layer (substrate side) are all formed of a laminated layer of a GaN layer and an InGaN layer, and the composition of the InGaN layer contained In the active layer is In_0.4Ga_0.6N。

(nitride semiconductor layer of the 1 st conductivity type)

Secondly, TMG, TMA, Ammonia, Cp were used at 1050 deg.C₂Mg (cyclopentylmagnesium) 1X 10 as a 40 ANGSTROM-thick Mg-doped film²⁰/cm³P-type Al of (1)_0.2Ga_0.8N layer, then, the temperature was set to 800 ℃ and TMG, TMI, Ammonia, Cp were used₂Mg, 1X 10 Mg doped with 25 angstrom thickness²⁰/cm³In (2) of_0.03Ga_0.97And N layers. Repeating the above operation, alternately stacking 5 layers, and finally growing the p-type Al film with a thickness of 40 angstroms_0.2Ga_0.8N layers, thereby growing a multilayer film having a superlattice structure with a film thickness of 365 ANGSTROM.

Then, TMG, ammonia, CP were used at 1050 deg.C₂Mg of 1X 10 by growing 1200 angstrom thick²⁰/cm³A p-type contact layer made of p-type GaN.

After the reaction, the temperature was lowered to room temperature, and the wafer was annealed in a nitrogen atmosphere in a reaction vessel at 700 ℃ to further lower the resistance of the p-type layer.

After the annealing, the wafer was taken out from the reaction vessel to form a p-type electrode as the 1 st electrode. Rh is added on the p-type electrodeAnd (4) film forming. Thereafter, ohmic annealing was performed at 600 ℃ to form a 2 nd insulating layer having a film thickness of 0.3 μmProtective film SiO₂. Thereafter, to form the conductive layer 5, the film thickness is set in the order of Ti-Pt-Au-Sn-AuAn adhesion layer, a barrier layer, and a eutectic layer are formed.

On the other hand, a support substrate 11 is prepared. On the surface of a supporting substrate having a film thickness of 200 μm and consisting of Cu 15% and W85%, the film thickness was determined in the order of Ti-Pt-PdAnd forming a conductive layer.

Next, the conductive layer 5 formed on the p-type electrode as the 1 st electrode and the 2 nd insulating protective film is bonded to the metal film formation surface of the support substrate. The heating set temperature was set to 280 ℃ and the extrusion pressure was applied. At this time, eutectic crystals were formed. Thereafter, the sapphire substrate is removed by polishing and exposed, and then the n-type contact layer, which is the exposed surface of the 2 nd conductivity type nitride semiconductor layer, is polished to remove surface roughness.

Next, by RIE apparatus, with SiO₂The mask separates the GaN into chips. Then, the n-type contact layer is formed with Ti-Al-Ti-Pt-Au in the order of film thicknessAn n-type electrode is formed as the 2 nd electrode 6. Thereafter, after the supporting substrate was ground to 100 μm, Ti-Pt-Au was applied to the back surface of the supporting substrateForming a film, namely forming the film,thereafter, dicing is performed. The thus obtained LED element had a size of 1mm × 1mm, and emitted 460nm blue light at a forward current of 20mA, and outputted 4mW, and Vf was 2.9 v.

[ example 2]

In example 1, a p-type electrode as the 1 st electrode was formed using Ag. The p-type electrode has a film thickness ofOther conditions were the same as in example 1. The LED element thus obtained outputted 6mW and had Vf of 3.3V.

[ example 3]

In example 1, a supporting substrate having a film thickness of 200 μm and composed of Cu 50% and Mo 50% was used. Other conditions were the same as in example 1. The LED element thus obtained outputted 4mW, and Vf was 2.9V.

[ example 4]

In example 1, after the n-type electrode is formed, stripe-shaped irregularities are formed on the surface of the exposed n-type contact layer. The depth of the concave portion was 1.5 μm, the width of the concave portion was 34 μm, and the width of the convex portion was 3 μm. Other conditions are the same. After the dimple processing, when the forward current is 20mA, 5.4mW is output, and Vf is 3.18V. When the forward current is 100mA, 21.3mW is output, and Vf is 3.44.

[ example 5]

In example 1, after the n-type electrode is formed, irregularities are formed on the surface of the exposed n-type contact layer. The planar shape of the convex part is made into a hexagon. The width of the convex portion was 8 μm, the width of the concave portion was 2 μm, and the depth of the concave portion was 1.5 m. Other conditions are the same. After the dimple processing, when the forward current is 20mA, 6mW is output, and Vf is 3.29V. When the forward current was 20mA, 23.4mW was outputted and Vf was 3.52.

[ example 6]

In example 1, after the n-type electrode is formed, irregularities are formed on the surface of the exposed n-type contact layer. A recess is formed by digging and the planar shape of the recess is made into a hexagon. The width of the convex portion was 2 μm, the width of the concave portion was 8 μm, and the depth of the concave portion was 1.5 μm. Other conditions are the same. When the dimple processing is performed, the output of 6.1mW is performed when the forward current is 20mA, and Vf is 3.1V. When the forward current was 20mA, 24.7mW was outputted, and Vf was 3.41.

[ example 7]

In example 1, a 1 st insulating protective film SiO with a film thickness of 0.3 μm was formed on the exposed surface of the nitride semiconductor located in the opening of the p-type electrode₂. Then forming an insulating film on the substrateAl as the reflective film.

Further, after forming the 2 nd electrode which is an n-type electrode, ZrO is used₂(refractive index 2.2) and a 2 nd insulating protective film having a film thickness of 1.5pm was formed. The protective film was further formed into irregularities at intervals of 3 μm. The planar shape of the convex portion was circular, and the depth of the concave portion was 1.0. mu.m. After that, the supporting substrate was ground to 100 μm, and then LED elements were manufactured by dicing. The thus obtained LED element had a size of 1mm × 1mm, and emitted 460nm blue light at a forward current of 20mA, and outputted 6mW, and Vf was 2.9V. In the LED element of this example, the light extraction efficiency was 1.5 times higher than that of the structure having no irregularities on the protective film.

[ example 8]

In example 7, the protective film ZrO₂The convex part of the angle adjusting part is made into a shape with a cone angle of 60 degrees. Other conditions are the same. Both the output and Vf have equal characteristics. In the LED element of this example, the light extraction efficiency was 1.5 times higher than that of the structure having no irregularities on the protective film.

[ example 9]

In example 7, Nb₂O₅(refractive index 2.4) and a 2 nd insulating protective film having a film thickness of 1.5pm was formed. The protective film was further formed into irregularities at intervals of 3 μm. The planar shape of the convex portion was circular, and the depth of the concave portion was 1.0. mu.m. Other stripsThe piece was the same as in example 1. The LED element thus obtained has equivalent characteristics in both output and Vf. Further, the LED element and the protective film Nb of the present embodiment₂O₅The light extraction efficiency is 1.5 times or more compared with the structure having no concavities and convexities.

[ example 10]

In example 7, TiO was used₂(refractive index 2.7) and a 2 nd insulating protective film having a thickness of 1.5 μm was formed. The protective film was further formed into irregularities at intervals of 3 μm. The planar shape of the convex portion was circular, and the depth of the concave portion was 1.0. mu.m. Other conditions were the same as in example 1. The LED element thus obtained has equivalent characteristics in both output and Vf. Also, the LED element and the protective film TiO of the present example₂The light extraction efficiency is 1.5 times or more compared with the structure having no concavities and convexities.

[ example 11]

As the foreign substrate, a substrate made of sapphire (C-plane) was used, and surface purification was performed at 1050 ℃ in a hydrogen atmosphere in an MOCVD reaction vessel. Transition layer: next, in a hydrogen atmosphere, ammonia and TMG (trimethyl gallium) were grown on the substrate at 510 ℃ in the presence of hydrogenA thick buffer layer 2 made of GaN. Growing a layer at a high temperature: after the growth of the transition layer, only the TMG was stopped, the temperature was raised to 1050 ℃ and 1050 ℃ was reached, and then the high-temperature grown nitride semiconductor composed of undoped GaN with a film thickness of 5 μm was grown by using TMG and ammonia as the raw material gas.

Next, a 3 μm-thick Si-doped Si film was grown at 1050 ℃ using TMG, TMA, ammonia, and silane to form a 5X 10 film¹⁷/cm³N-type Al of (1)_0.07Ga_0.93N-type cladding layer 5.

Secondly, setting the temperature at 800 ℃, adopting TMI (trimethyl indium), TMG and TMA as raw material gas, and sequentially laminating Si-doped Al on the barrier layer (I)/well layer (I)/barrier layer (II)/well layer (II)/barrier layer (III)_0.1Ga_0.9A barrier layer of N inThereon with undoped In_0.03Al_0.02Ga_0.95A well layer of N. At this time, formA thick barrier layer,Film-thick barrier layers (c) and (c),Well layers (i) and (ii) having a film thickness. The total thickness of the active layer is aboutMultiple quantum well structures (MQW).

Next, TMG, TMA, ammonia, Cp were used at 1050 ℃ in a hydrogen atmosphere₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.2Ga_0.8A p-type cladding layer 7 of N. Next, on the p-type cladding layer, TMG, TMA, Ammonia, Cp₂Mg of 0.1 μm thickness and formed by doping with Mg1 × 10¹⁹/cm³Al of (2)_0.07Ga_0.93N, thereafter, the flow rate of the gas was adjusted to grow a 0.02 μm-thick Mg-doped 2X 10 film²¹/cm³Al of (2)_0.07Ga_0.93N, a 2 p-type contact layer.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer. After annealing, the wafer is taken out of the reaction vessel and a film thickness is formed on the p-type contact layerThe Rh film of (1) was formed into a P electrode as a 1 st electrode. Thereafter, ohmic annealing was performed at 600 ℃ to form a film thickness of 0 on the exposed surface except the P electrode3 μm of insulating protective film SiO No. 1₂。

Then, on the P electrode, the film thickness is setA multilayer film of Ni-Pt-Au-Sn-Au is formed as a conductive layer. Here, Ni is an adhesion layer, Pt is a barrier layer, Sn is a 1 st eutectic formation layer, an Au layer between Pt and Sn serves to prevent Sn from diffusing into the barrier layer, and an Au layer on the outermost layer serves to improve adhesiveness.

On the other hand, a metal substrate having a thickness of 200 μm and composed of a composite of Cu 30% and W70% was used as a supporting substrate, and the thickness of the metal substrate was set to be equal to the thickness of the metal substrateAn adhesion layer made of Ti, a barrier layer made of Pt, and a conductive layer made of Au on the side of the support substrate are formed in this order.

Next, the nitride semiconductor device and the supporting substrate were thermocompression bonded by pressing with a press at a heating temperature of 250 ℃ in a state where the surfaces on which the conductive layers were formed were opposed to each other. In this way, the conductive layers are made to diffuse into each other, thereby forming a eutectic. After the sapphire substrate is removed by polishing, the exposed transition layer or high-temperature growth layer is polished and polished until the AlGaN layer of the n-type clad layer is exposed, and the surface roughness is removed.

Then, the surface of the n-type cladding layer is polished and then the n-type cladding layer is coated with the filmA multilayer electrode composed of Ti-Al-Ti-Pt-Au was formed to make an n-electrode as a 2 nd electrode. Thereafter, after grinding the support substrate to 100 μm, the support substrate was set on the back surface thereofA multilayer film made of Ti-Pt-Au was formed as a pad electrode for a P electrode. Next, the elements are separated by dicing.

The obtained LED element has a size of 1mm × 1mm, emits 373nm ultraviolet light at a forward current of 20mA, and has an output of 4.2mW and Vf of 3.47V.

[ example 12]

The foreign substrate was removed under the same conditions as in example 11 except that the polishing method was replaced with the laser irradiation method.

Using KrF excimer laser with wavelength of 248nm from the opposite side of the base layer side of the sapphire substrate to output 600J/cm²The laser beam was made into a beam shape of 1mm × 50mm, and the entire surface of the opposite surface was scanned and irradiated with the laser beam. The laser irradiation decomposes the nitride semiconductor of the underlying layer, thereby removing the sapphire substrate.

The LED device obtained showed an emission peak wavelength of 373nm, a Vf of 3.47V, and an emission output of 4.2mW at a forward current of 20 mA. Further, since it is not necessary to polish the sapphire substrate, the time required for manufacturing can be significantly shortened as compared with example 1. The light emission output is greatly improved as compared with the conventional element.

[ example 13]

The nitride semiconductor device was manufactured under the same conditions as those in example 11. And then SiO containing YAG as a fluorescent substance is formed on the entire surface of the nitride semiconductor device₂As a coating layer.

Thus, a nitride semiconductor light-emitting element which is white, has little self-absorption, and has high conversion efficiency is obtained.

[ example 14]

A nitride semiconductor device was produced under the same conditions as those in example 13, but in this example, a plurality of nitride semiconductor devices were formed on a conductive substrate in a dot-like arrangement. The plurality of nitride semiconductor devices are partially provided with an exposed surface and packaged. SiO containing YAG as fluorescent substance is formed on the exposed surface₂As a coating layer.

Thus, a plurality of white nitride semiconductor devices are arranged, and a nitride semiconductor light-emitting device that emits white light over a large area is realized. It can be used as a light source for illumination.

[ example 15]

A substrate made of sapphire (C-plane) was used as a foreign substrate, and surface purification was performed at 1050 ℃ in a hydrogen atmosphere in an MOCVD reaction vessel.

Next, ammonia and TMG (trimethyl gallium) were grown on the substrate in a hydrogen atmosphere at 510 deg.CA thick buffer layer 2 made of GaN. After the growth of the transition layer, a 2 nd conductivity type nitride semiconductor layer was produced, only TMG was stopped, the temperature was raised to 1050 ℃, and after the temperature was raised to 1050 ℃, a high temperature grown nitride semiconductor composed of undoped GaN was grown with a film thickness of 5 μm by using TMG and ammonia as raw material gases. Next, TMG, TMA, ammonia, and silane were used to form a 2.5 μm thick film of 1X 10 Si doped at 1050 deg.C¹⁹/cm³Al of (2)_0.1Ga_0.9N-type cladding layer 5.

Secondly, setting the temperature at 900 ℃, adopting TMI (trimethyl indium), TMG and TMA as raw material gas, and sequentially laminating a barrier layer (I)/a well layer (I)/a barrier layer (II)/a well layer (II)/a barrier layer (III)/a well layer (III)/a barrier layer (III) by doping Si of 1 multiplied by 10¹⁹/cm³Al of (2)_0.08Ga_0.92N structureBarrier layer of undoped In on top of the barrier layer_0.01Ga_0.92A well layer of N. At this time, respectively formThick barrier layers (first, second, third and fourth) are formedWell layers (i), (ii), and (iii) of film thickness. Only the barrier layer is undoped, the active layer becomes about the total film thicknessMultiple quantum well structures (MQW).

Next, a nitride semiconductor layer of the 1 st conductivity type is formed. In hydrogen atmosphere, at 1050 deg.C, TMG, TMA, ammonia, Cp₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.2Ga_0.8A p-type cladding layer 7 of N. Next, on the p-type cladding layer, TMG, TMA, Ammonia, Cp₂Mg, 1X 10 as a 0.1 μm film thickness doped Mg¹⁹/cm³Al of (2)_0.07Ga_0.93N layer, thereafter, the flow rate of the gas was adjusted, and Mg-doped layer of 2X 10 was grown to a film thickness of 0.02 μm²¹/cm³Al of (2)_0.07Ga_0.93And N layers.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer.

After annealing, the wafer was taken out from the reaction vessel and the Al on the outermost surface of the 1 st conductivity type nitride semiconductor layer was formed_0.07Ga_0.93Thickness of N layerAs a P electrode. Thereafter, ohmic annealing is performed at 600 DEG CThen, a 1 st insulating protective film SiO with a film thickness of 0.3 μm was formed on the exposed surface except the P electrode₂。

On the other hand, a substrate having a thickness of 200 μm and composed of a composite of Cu 30% and W70% was used as a supporting substrate, and the thickness of the supporting substrate was set to be equal to the thickness of the supporting substrateAn adhesion layer made of Ti, a barrier layer made of Pt, and a conductive layer made of Pd on the side of the support substrate are formed in this order.

Next, the nitride semiconductor device and the supporting substrate were thermocompression bonded by pressing with a press machine at a heating temperature of 250 ℃ in a state where the conductive layers were opposed to each other. This causes the conductive layers to diffuse into each other, thereby forming a eutectic crystal.

Next, after bonding the supporting substrates, a KrF excimer laser having a wavelength of 248nm was used from the opposite side of the base layer side of the sapphire substrate to output 600J/cm²The laser beam was made into a beam shape of 1mm × 50mm, and the entire surface of the opposite surface was scanned and irradiated with the laser beam. The laser irradiation decomposes the nitride semiconductor of the underlying layer, thereby removing the sapphire substrate. Then mixing with n-type Al_0.1Ga_0.9The residual thickness of the N-type clad layer made of N was polished to 2.2 μm, and the surface roughness was removed.

Next, a multilayer electrode made of Ti-Al-Ni-Au was formed as an n-electrode on the n-type clad layer. Thereafter, a support substrate was polished to 100 μm and then formed on the back surface of the support substrateThe multilayer film of Ti-Pt-Au-Sn-Au as the pad electrode for the P electrode. Next, the elements are separated by dicing. The n-electrode and the P-electrode are formed in a grid shape on the entire surface of the semiconductor layer. In this case, the openings between the grids are formed so as not to overlap each other, with the n-side and P-side alternating.

The obtained LED element has the size of 1mm multiplied by 1mm, emits 365nm ultraviolet light when the forward current is 20mA, and has the output of 2.4mW and Vf of 3.6V.

[ example 16]

The present embodiment relates to a blue LED element.

As the foreign substrate, a substrate made of sapphire (C-plane) was used, and surface cleaning was performed at 1050 ℃ in a hydrogen atmosphere in an MOCVD reaction vessel.

Next, ammonia and TMG (trimethyl gallium) were grown on the substrate in a hydrogen atmosphere at 510 deg.CA thick buffer layer 2 made of GaN. After the growth of the transition layer, only TMG was stopped, the temperature was raised to 1050 ℃ and 1050 ℃ was reached, then the Si-doped layer of 1X 10 thickness of 5 μm was grown by using TMG, ammonia and silane as raw material gases¹⁸/cm³An n-type contact layer made of n-type GaN. Secondly, at 1050 ℃, TMG, TMA, ammonia, silane are used to formThe thickness of the film is 5X 10 times of Si-doped¹⁷/cm³N-type Al of (1)_0.18Ga_0.82N-type cladding layer 5.

Next, the temperature was set to 800 ℃, and the barrier layer composed of GaN doped with Si and the well layer composed of InGaN undoped thereon were laminated in the order of barrier layer/well layer/barrier layer using TMI, TMG, TMA as the source gas. At this time, formA barrier layer of film thickness,A thick well layer. The total thickness of the active layer is aboutMultiple quantum well structures (MQW).

Next, TMG, TMA, ammonia, Cp were used at 1050 ℃ in a hydrogen atmosphere₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.2Ga_0.8A p-type cladding layer 7 of N. Then, on the cladding, TMG, ammonia, Cp₂Mg with a thickness of 0.15 μm and a thickness of 2X 10²¹/cm³A p-type contact layer of GaN.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer.

After annealing, the wafer is taken out of the reaction vessel and a film thickness is formed on the p-type contact layerAs a P electrode. Thereafter, ohmic annealing was performed at 600 ℃ to form a 1 st insulating protective film SiO with a film thickness of 0.3 μm on the exposed surface except the P electrode₂。

Next, on the P electrode, films of respective thicknessesThe Ni-Pt-Au-Sn-Au multilayer film of (1) as a conductive layer. Here, Ni is an adhesion layer, Pt is a barrier layer, Sn is a 1 st eutectic formation layer, an Au layer between Pt and Sn serves to prevent Sn from diffusing into the barrier layer, and an Au layer on the outermost layer serves to improve adhesion with a 2 nd eutectic formation layer.

On the other hand, as the supporting substrate, a substrate having a film thickness of 200 μm and composed of a composite of Cu 30% and W70% was used, and films were sequentially formed on the surface of this substrateEach thickness isAn adhesive layer of Ti, a barrier layer of Pt, and a conductive layer of Au on the side of the support substrate.

Next, thermocompression bonding of the nitride semiconductor device and the conductive layer of the supporting substrate is performed by pressing and pressurizing at a heating temperature of 250 ℃. In this way, the conductive layer causes the metals to interdiffuse, thereby forming a eutectic.

Next, the multilayer body for bonding to the supporting substrate was bonded to the sapphire substrate from the opposite side of the substrate layer, using KrF excimer laser having a wavelength of 248nm, to output 600J/cm²The laser beam was made into a beam shape of 1mm × 50mm, and the entire surface of the opposite surface was scanned and irradiated with the laser beam. The laser irradiation decomposes the nitride semiconductor of the underlying layer, thereby removing the sapphire substrate. Polishing until the n-type contact layer is exposed, and removing the surface roughness.

Then, on the n-type contact layer, the films with the thickness ofThe multilayer electrode composed of Ti-Al-Ti-Pt-Au is used as the n electrode, namely the 2 nd electrode. Thereafter, the conductive substrate was polished to 100 μm, and then formed on the back surface of the conductive substrateThe multilayer film of Ti-Pt-Au as a pad electrode for a P electrode. Next, the elements are separated by dicing.

The resulting LED element had a size of 1mm × 1mm and emitted 460nm blue light at a forward current of 20 mA.

[ example 17]

The same procedure as in example 16 was adoptedTo manufacture a nitride semiconductor device. And then SiO containing YAG as a fluorescent substance is formed on the entire surface of the nitride semiconductor device₂As a coating layer. Thus, a white nitride semiconductor light-emitting element was obtained.

[ example 18]

A nitride semiconductor device was produced under the same conditions as in example 17, but in this example, a plurality of nitride semiconductor devices were formed on a conductive substrate in a dot-like arrangement. The plurality of nitride semiconductor devices are partially provided with an exposed surface and packaged. SiO containing YAG as fluorescent substance is formed on the exposed surface₂As a coating layer.

Thus, a plurality of white nitride semiconductor devices are arranged, and a nitride semiconductor light-emitting device that emits white light over a large area is realized. It can be used as a light source for illumination.

[ example 19]

As the foreign substrate, a substrate made of sapphire (C-plane) was used, and surface purification was performed at 1050 ℃ in a hydrogen atmosphere in an MOCVD reaction vessel.

Next, ammonia and TMG (trimethyl gallium) were grown in a hydrogen atmosphere at 510 ℃ to aboutA thick transition layer made of GaN. After the growth of the transition layer, only the TMG was stopped, the temperature was raised to 1050 ℃ and 1050 ℃ was reached, and then a high-temperature grown nitride semiconductor composed of undoped GaN having a thickness of 5 μm was grown by using TMG and ammonia as raw material gases.

After the high-temperature growth layer was grown, an AlGaN layer having a composition gradient and a film thickness of 0.4 μm was grown at the same temperature using TMG, TMA, and ammonia as raw material gases. The composition gradient layer is used for relaxing lattice mismatch between the high-temperature growth layer and the n-type cladding layer, and the lattice mismatch is 1 × 10 from undoped GaN to Si¹⁹/cm³N-type Al of (1)_0.07Ga_0.93Until now, the mixed crystal ratio of Al and the doping amount of Si were gradually increased.

Next, TMG, TMA, ammonia, and silane were used to form a 2.5 μm thick film of 1X 10 Si doped at 1050 deg.C¹⁹/cm³N-type Al of (1)_0.07Ga_0.93N-type cladding layer 5.

Secondly, setting the temperature at 900 ℃, adopting TMI (trimethyl indium), TMG and TMA as raw material gas, and sequentially laminating a barrier layer (I)/a well layer (I)/a barrier layer (II)/a well layer (II)/a barrier layer (III)/a well layer (III)/a barrier layer (III) by doping Si of 1 multiplied by 10¹⁹/cm³Al of (2)_0.09Ga_0.91Barrier layer of N, In on top of it_0.01Ga_0.99A well layer of N. At this time, respectively formThick barrier layers (first, second, third and fourth) are formedWell layers (i), (ii), and (iii) of film thickness. Only the barrier layer (iv) is undoped.

Next, TMG, TMA, ammonia, Cp were used at 1050 ℃ in a hydrogen atmosphere₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.38Ga_0.62A p-type cladding layer 7 of N. Next, TMG, TMA, Ammonia, Cp were used as the cladding layer of the p-type₂Mg, 4X 10 by growing 0.1 μm thick film¹⁸/cm³Al of (2)_0.07Ga_0.93A 2 nd p-type contact layer composed of N layers, and thereafter, the flow rate of the gas was adjusted to grow a 0.02 μm-thick 1X 10 Mg-doped layer²⁰/cm³Al of (2)_0.07Ga_0.93N, a 2 p-type contact layer.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer.

After annealing, the wafer is taken out of the reaction vessel and a film thickness is formed on the p-type contact layerAs a P electrode. Thereafter, ohmic annealing was performed at 600 ℃ to form an insulating protective film SiO with a film thickness of 0.3 μm on the exposed surface except the P electrode₂。

On the other hand, as the supporting substrate, a substrate having a film thickness of 200 μm and composed of a composite of Cu 15% and LW 85% was used, and on the surface thereof, a film thickness of each of them was formed in orderThe adhesion layer made of Ti, the barrier layer made of Pt, and the 2 nd eutectic formation layer made of Pd.

Next, the nitride semiconductor device and the supporting substrate were thermocompression bonded to the conductive layer by pressing with a press at a heating temperature of 230 ℃. In this way, the conductive layer causes the metals to interdiffuse, thereby forming a eutectic.

Next, from the opposite side of the base layer side of the sapphire substrate, KrF excimer laser having a wavelength of 248nm was used to output 600J/cm²The laser beam was made into a beam shape of 1mm × 50mm, and the entire surface of the opposite surface was scanned and irradiated with the laser beam. The laser irradiation decomposes the nitride semiconductor of the underlying layer, thereby removing the sapphire substrate. Then a substrate layer, a high temperature growth layer, a composition gradient layer and n-type Al_0.3Ga_0.7The residual thickness of the N-type clad layer made of N was polished to 2.2 μm, and the surface roughness was removed.

Next, a multilayer electrode made of Ti-Al-Ni-Au was formed on the n-type contact layerThe electrode is an n-electrode which is the 2 nd electrode. The n-electrode is not formed on the entire surface in consideration of light extraction efficiency, but is formed so that the aperture ratio is 70%. After polishing the conductive substrate to 100 μm, it was formed on the back surface of the conductive substrateThe multilayer film of Ti-Pt-Au-Sn-Au as the pad electrode for the P electrode. Next, the elements are separated by dicing. The n-electrode and the P-electrode are respectively distributed on the whole surface of the semiconductor layer and formed in a grid shape. In this case, the openings between the grids are formed so as to alternate with each other on the n-side and the P-side without overlapping.

When the element is at room temperature and under the condition of pulse current of 500mA (pulse width of 2 musec and duty ratio of 1%), 365nm ultraviolet light is emitted, the output is 118mW, the driving voltage is 4.9V, and the external quantum efficiency is 6.9%; at room temperature and under the condition of direct current of 500mA, 365nm ultraviolet light is emitted, the output is 100mW, the driving voltage is 4.6V, and the external quantum efficiency is 5.9%.

[ example 20]

A nitride semiconductor was grown on a sapphire substrate, and annealing was performed at 700 ℃. Thereafter, RIE was used to etch the surface of the nitride semiconductor to a depth of 4.5 μm. Thereafter, a film thickness is formed by using Ni-Au as a material1 st electrode (P-side electrode). Thereafter, heat treatment was performed at 600 ℃ in an atmosphere containing oxygen.

Next, a Cu — W substrate (Cu 15%) as a 2 nd substrate was prepared, and thermocompression bonded to the 1 st electrode formation surface of the nitride semiconductor device at 150 ℃. Next, the back surface of the sapphire substrate is mirror-polished, and then an excimer laser is irradiated from the back surface of the sapphire substrate to separate the nitride semiconductor from the sapphire substrate. Thereafter, the Si-doped GaN surface was exposed by CMP. Next, a grid pattern was formed on the exposed GaN surface with a resist, and GaN was etched to a depth of 1 μm by RIE. The planar shape of GaN was a 6-sided mesh with 5 μm convex portions.

Thereafter, the etched surface of the nitride semiconductor was subjected to a surface treatment with BHF, and then formed to have thicknesses of, respectively, GaN and GaNAnd a 2 nd electrode (n-side electrode) 6 made of Al-Pt-Sn. CuW (Cu 15%) substrates as supporting substrates were prepared and formed to have thicknesses ofAs the eutectic layer 7, Ti-Pt-Pd. Thereafter, the nitride semiconductor having the above-described 2 nd substrate and the above-described support substrate were subjected to thermocompression bonding at 250 ℃.

The nitride semiconductor bonded with the supporting substrate is put into a boiling acetone solution. Thereafter, the 2 nd substrate is separated from the epoxy film as the adhesive layer 4. Thus, a nitride semiconductor layer is formed on the supporting substrate.

Next, SiO was formed on the 2 nd electrode (P-side electrode) except for the pad electrode forming region₂And a protective film 9. Forming a layer of a thickness ofThe pad electrode 10 made of Ni — Au.

Thereafter, the supporting substrate 8 was polished to 100 μm, and then, dicing was performed to produce an LED element. The thus obtained LED element had a size of 1mm × 1mm, and emitted 460nm blue light at a forward current of 20mA, and outputted 6mW or more, and Vf was 2.9V. In the LED element of the present example, the light extraction efficiency was 1.5 times or more higher than that of the LED element having no uneven step in the nitride semiconductor.

[ example 21]

In the above-described embodiment 20, the ultraviolet LED element is formed on the nitride semiconductor 2. Other conditions were the same as in example 20. The conditions of nitride semiconductor 2 are shown below.

Film thickness formation with GaNForming a 5 μm thick undoped GaN layer using Si-doped Al_0.18Ga_0.82N (Si-doped amount: 5X 10)¹⁷/cm³) Film thickness is formedIn the thickness of the n-type cladding layerSi-doped Al of_0.1Ga_0.9N/film thicknessIn (2) of_0.03Al_0.02Ga_0.95N/film thicknessSi-doped Al of_0.1Ga_0.9N/film thicknessIn (2) of_0.03Al_0.02Ga_0.95N/film thicknessSi-doped Al of_0.1Ga_0.9N, total film thicknessAn active layer is formed. Secondly, with Mg-doped Al_0.2Ga_0.8Thickness of N formation filmForming Mg-doped Al with a film thickness of 0.1 μm_0.04Ga_0.96N (Mg doping amount: 1X 10)¹⁹/cm³) And Mg-doped Al with a film thickness of 0.02 μm_0.01Ga_0.99N (Mg doping amount: 2X 10)²¹/cm³) A p-type contact layer of (1).

The obtained LED element has the size of 1mm multiplied by 1mm, emits 373nm ultraviolet light when the forward current is 20mA, outputs 4.2mW and has Vf of 3.5V.

[ example 22]

In the above example 20, Rh was used for the 2 nd electrode. The 2 nd electrode was 6-sided mesh-like with a gap of 5 μm between meshes, and had a film thickness ofOther conditions were the same as in example 20. The LED element thus obtained exhibited characteristics equivalent to those of example 1.

[ example 23]

The supporting substrate was made into an insulating AlN substrate, and two electrodes were formed on the same surface (FIG. 17). Other conditions were the same as in example 23. The LED element thus obtained emitted 460nm blue light at a forward current of 20mA, and outputted 5mW or more, and had Vf of 3.0V.

[ example 24]

In example 1 above, after the LED element and the external electrode were electrically conducted by the lead wire, a coating layer containing a fluorescent substance was formed on the LED element according to the following method.

First, a film of a resist or polyimide is formed on an electrode of an LED element. Secondly, a mixed solution of a cerium-activated yttrium aluminum garnet phosphor, a hydrolysis solution of ethyl silicate and a high boiling point solvent is prepared as described above, and the mixture is stirred to uniformly disperse the phosphor, thereby preparing a coating solution. And thirdly, the coating liquid is attached to the supporting substrate and the upper surface and the side surface of the LED element except the part for forming the protective film by adopting the spraying method. Fourthly, drying the mixture for 30 minutes at the temperature of 150 ℃ to carry out primary curing, and forming a layer with the thickness of tens of microns. Immersing the layer in the hydrolytic solution of ethyl silicate without phosphor. Sixthly, removing the film of the resist or the polyimide, and drying the film for 30 minutes at the temperature of 240 ℃ to perform secondary hardening. Through the above processes, the nitride-based semiconductor layer having a total film thickness of 5 to 10 μm has a continuous layer at least on the exposed surface, and is disposed on the upper surface, side surfaces and corners of the LED element except the electrodes, thereby forming the coating layer 14 having a substantially uniform film thickness of 20 to 30 μm.

The present embodiment can provide the following light emitting device: the phosphor is fixed to the light emitting element by using an inorganic substance as a material which does not deteriorate even when used together with the light emitting element emitting light in the blue to ultraviolet regions, and the variation in emission color is not large even when used for a long time. Further, since the coat layer 14 is formed to have a substantially uniform thickness so as to cover at least the emission observation surface of the light emitting element, the light emitting device of the present embodiment can be a light emitting device in which the color temperature does not change much even if the emission observation direction is different. Further, since the coating layer containing the phosphor is formed on all the surfaces where light emission from the light emitting element can be observed, light does not pass through the support substrate, and thus, the efficiency of extracting light whose wavelength is converted by the phosphor is improved as compared with a light emitting element using a conventional sapphire substrate. Further, since a support substrate having high thermal conductivity is used, heat dissipation is improved as compared with a light-emitting element using a conventional sapphire substrate.

[ example 25]

The coating layer was formed by screen printing using the coating liquid prepared in the same manner as in example 24 or a material in which a cerium-activated yttrium aluminum garnet phosphor was contained in a silicone resin. Here, when a material containing a phosphor in a silicone resin is used, curing is performed at a temperature of 150 ℃ for 1 hour. The semiconductor wafer thus completed is placed on a scribe line and then divided by dicing, thereby forming LED chips as light emitting elements.

Since the coating layer 14 containing the phosphor is formed in a wafer state, inspection and sorting of emission colors can be performed at a stage before the LED chip is placed on a metal package or the like to form a light emitting device, that is, at a stage of the LED chip after the coating layer containing the phosphor is formed, and thus the product yield of the light emitting device is improved. The LED chip of the present embodiment can be a light-emitting element that does not greatly change the color temperature even if the LED chip forming the coating layer 14 has a different light emission observation direction.

[ example 26]

In example 24, the exposed surface of the nitride semiconductor device may be mesa-shaped or inverted mesa-shaped, and the planar shape may be island-shaped, grid-shaped, rectangular-shaped, circular-shaped, or polygonal-shaped. The exposed surface and the side surface of the semiconductor layer subjected to the dimple processing were coated in the same manner as in example 25. The thickness of the coating layer is preferably substantially equal to the top surface, the side surface, and the corners of the light-emitting element.

Thus, the light-emitting device can be provided which has improved light extraction efficiency from the light-emitting element and which does not cause a large variation in emission color even when used for a long period of time.

[ example 27]

In example 19, an insulating protective film SiO was formed on the exposed surface other than the P electrode₂Then, a eutectic-formed layer of Rh-Ir-Pt was formed on the P electrode. Other conditions were the same as in example 20. The LED element thus obtained exhibited characteristics equivalent to those of example 1.

[ example 28]

In example 19, an n-type clad layer was produced in the same manner as described below, and an LED was produced.

At 1050 deg.C, TMG, TMA, ammonia, siliconAlkane to form a film of 1.7 μm thickness and 1X 10 by doping Si¹⁹/cm³Al of (2)_0.07Ga_0.93A 1N-type clad layer of N, and a Si-doped layer of 2X 10 thickness of 0.8 μm¹⁷/cm³Al of (2)_0.07Ga_0.93And a 2 nd N-type cladding layer composed of N, wherein the 1 st N-type cladding layer and the 2 nd N-type cladding layer are used as N-type cladding layers.

The LED device thus obtained had a driving voltage lower by about 0.3V than that of example 19, and also exhibited little deterioration in the device even when light emission was carried out for a long period of time.

[ example 29]

Growing on the substrate at 510 deg.CA thick buffer layer 2 made of GaN. Next, the temperature was raised to 1050 ℃ and then 1050 ℃, and then a high-temperature grown nitride semiconductor composed of undoped GaN with a thickness of 5 μm was grown by using TMG and ammonia as the source gases.

(nitride semiconductor layer of the 2 nd conductivity type)

Secondly, at 1050 ℃, TMG, TMA, ammonia, silane are used to formThe thickness of the film is 5X 10 times of Si-doped¹⁷/cm³Al of (2)_0.18Ga_0.82N-type cladding layer.

(active layer)

Secondly, setting the temperature at 800 ℃, adopting TMI (trimethyl indium), TMG and TMA as raw material gas, and sequentially laminating Si-doped Al on the barrier layer (I)/well layer (I)/barrier layer (II)/well layer (II)/barrier layer (III)_0.1Ga_0.9Barrier layer of N and In thereon which is undoped_0.03Al_0.02Ga_0.95A well layer of N. In this case, the barrier layer isThe film thickness of the barrier layers isFilm thickness of well layers ofAnd (5) film thickness. The total thickness of the active layer is aboutMultiple quantum well structures (MQW).

(nitride semiconductor layer of the 1 st conductivity type)

Next, TMG, TMA, ammonia, Cp were used at 1050 ℃ in a hydrogen atmosphere₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.2Ga_0.8A p-type cladding layer 7 of N. Next, on the p-type cladding layer, TMG, TMA, Ammonia, Cp₂Mg, 1X 10 by growing 0.1 μm thick film¹⁹/cm³Al of (2)_0.04Ga_0.96N, and thereafter, the flow rate of the gas was adjusted to grow a 2X 10 Mg-doped layer having a film thickness of 0.02 μm²¹/cm³Al of (2)_0.01Ga_0.99N, and a 2 nd p-type contact layer.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer.

After annealing, the wafer is taken out of the reaction vessel and a film thickness is formed on the p-type contact layerThe Rh film of (3) to prepare a P electrode. Thereafter, ohmic annealing was performed at 600 ℃ to form an insulating protective film SiO with a film thickness of 0.3 μm on the exposed surface except the P electrode₂。

Next, on the P electrode, films of respective thicknessesAnd (3) a conductive layer 5 of Ni-Pt-Au-Sn-Au. Here, Ni is an adhesion layer, Pt is a barrier layer, Sn is a 1 st eutectic formation layer, an Au layer between Pt and Sn serves to prevent Sn from diffusing into the barrier layer, and an Au layer on the outermost layer serves to improve adhesion to the conductive layer 12 on the support substrate side.

On the other hand, a metal substrate having a film thickness of 200 μm and composed of a composite of Cu 30% and W70% was used as a supporting substrate, and the metal substrate was formed on the surface thereof in this order to have film thicknesses of 200 μmAn adhesive layer made of Ti, a barrier layer made of Pt, and a conductive layer 12 made of Au.

Next, the nitride semiconductor device and the supporting substrate were thermocompression bonded by pressing with a press machine at a heating temperature of 250 ℃ in a state where the above conductive layers were opposed to each other. In this way, the conductive layers are made to diffuse into each other, thereby forming a eutectic.

Next, after the sapphire substrate is removed by polishing, the exposed transition layer or high-temperature growth layer is polished until the AlGaN layer of the n-type clad layer is exposed, and the surface roughness is removed.

Then, on the n-type contact layer, the films are formed to be respectively thickAs the n-electrode, a multilayer electrode (n-electrode) composed of Ti-Al-Ti-Pt-Au. Thereafter, after polishing the conductive substrate to 100 μm, on the conductive substrateBack side formationThe multilayer film of Ti-Pt-Au as a pad electrode for a P electrode. Next, the elements are separated by dicing.

The obtained LED element has a size of 1mm × 1mm, emits 373nm ultraviolet light at a forward current of 20mA, and has an output of 4.2mW and Vf of 3.47V.

[ example 30]

A nitride semiconductor device was produced under the same conditions as in example 29. And then SiO containing YAG as a fluorescent substance is formed on the entire surface of the nitride semiconductor device₂As a coating layer.

Thus, a nitride semiconductor light-emitting element which is white, has little self-absorption, and has high conversion efficiency is obtained.

[ example 31]

A nitride semiconductor device was produced under the same conditions as in example 29, but in this example, a plurality of nitride semiconductor devices were formed on a conductive substrate in a dot-like arrangement. The plurality of nitride semiconductor devices are partially provided with an exposed surface and packaged. SiO containing YAG as fluorescent substance is formed on the exposed surface₂As a coating layer.

Thus, a plurality of white nitride semiconductor devices are arranged, and a nitride semiconductor light-emitting device that emits white light over a large area is realized. It can be used as a light source for illumination.

[ example 32]

A foreign substrate made of sapphire (C-plane) was used, and surface cleaning was performed at 1050 ℃ in a hydrogen atmosphere in an MOCVD reaction vessel.

Next, ammonia and TMG (trimethyl gallium) were grown on the substrate in a hydrogen atmosphere at 510 deg.CA thick buffer layer 2 made of GaN. After the growth of the transition layer, only the TMG was stopped, the temperature was raised to 1050 ℃ and 1050 ℃ was reached, and then a high-temperature grown nitride semiconductor composed of undoped GaN having a thickness of 5 μm was grown by using TMG and ammonia as raw material gases.

(nitride semiconductor layer of the 1 st conductivity type)

Next, TMG, TMA, ammonia, and silane were used to form a 2.5 μm thick film of 1X 10 Si doped at 1050 deg.C¹⁹/cm³Al of (2)_0.3Ga_0.7N-type cladding layer 5.

(active layer)

Secondly, setting the temperature at 900 ℃, adopting TMI (trimethyl indium), TMG and TMA as raw material gas, and sequentially laminating a barrier layer (I)/a well layer (I)/a barrier layer (II)/a well layer (II)/a barrier layer (III)/a well layer (III)/a barrier layer (III) by doping Si of 1 multiplied by 10¹⁹/cm³Al of (2)_0.08Ga_0.92Barrier layer of N and In thereon which is undoped_0.1Ga_0.9A well layer of N. At this time, respectively formThick barrier layers (first, second, third and fourth) are formedThe film thickness well layers are first, second and third. Only the barrier layer is undoped, the active layer becomes about the total film thicknessMultiple quantum well structures (MQW).

(nitride semiconductor layer of the 2 nd conductivity type)

Next, TMG, TMA, ammonia, Cp were used at 1050 ℃ in a hydrogen atmosphere₂Mg (cyclopentylmagnesium), growthThe thickness of the film is 1X 10 from Mg doping²⁰/cm³Al of (2)_0.2Ga_0.8A p-type cladding layer 7 of N.

Next, on the p-type cladding layer, TMG, TMA, Ammonia, Cp₂Mg, 1X 10 by growing 0.1 μm thick film¹⁹/cm³Al of (2)_0.07Ga_0.93N, and thereafter, the flow rate of the gas was adjusted to grow a 0.02 μm-thick 2X 10 Mg-doped layer²¹/cm³Al of (2)_0.07Ga_0.93N, and a 2 nd p-type contact layer.

After the growth, the wafer was annealed at 700 ℃ in a reaction vessel in a nitrogen atmosphere to further lower the resistance of the p-type layer.

After annealing, the wafer is taken out of the reaction vessel and a film thickness is formed on the p-type contact layerAs a P electrode. Thereafter, ohmic annealing was performed at 600 ℃ to form an insulating protective film SiO with a film thickness of 0.3 μm on the exposed surface except the P electrode₂. Next, on the P electrode, a conductive layer is formed with a multi-layer film composed of Rh-Tr-Pt.

On the other hand, a metal substrate having a film thickness of 200 μm and composed of a composite of Cu 30% and W70% was used as a supporting substrate, and the metal substrate was formed on the surface thereof in this order to have film thicknesses of 200 μmAn adhesion layer made of Ti, a barrier layer made of Pt, and a conductive layer made of Pd on the side of the support substrate.

Next, the nitride semiconductor device and the supporting substrate were thermocompression bonded by pressing with a press machine at a heating temperature of 250 ℃ in a state where the conductive layers were opposed to each other. In this way, the metals of the conductive layers are interdiffused, thereby forming a eutectic.

The laminate for bonding to the supporting substrate was subjected to KrF excimer laser with a wavelength of 248nm from the opposite side of the sapphire substrate from the base layer side to output 600J/cm²The laser beam was made into a beam shape of 1mm × 50mm, and the entire surface of the opposite surface was scanned and irradiated with the laser beam. The laser irradiation decomposes the nitride semiconductor of the underlying layer, thereby removing the sapphire substrate. Then, a substrate layer, a high temperature growth layer, and n-type Al are formed_0.3Ga_0.7The residual thickness of the N-type clad layer made of N was polished to 2.2 μm, and the surface roughness was removed.

Next, a multilayer electrode made of Ti — Al — Ni — Au was formed as an n-electrode on the n-type contact layer. Thereafter, the conductive substrate was polished to 100 μm, and then formed on the back surface of the conductive substrateThe multilayer film of Ti-Pt-Au-Sn-Au as the pad electrode for the P electrode. Next, the elements are separated by dicing. The n-electrode and the P-electrode are respectively distributed on the whole surface of the semiconductor layer and formed in a grid shape. In this case, the openings between the grids are formed so as to alternate with each other on the n-side and the P-side without overlapping.

The obtained LED element has the size of 1mm multiplied by 1mm, emits 365nm ultraviolet light when the forward current is 20mA, and has the output of 2.4mW and Vf of 3.6V.

(example 33)

With the semiconductor light-emitting device obtained in example 1, the semiconductor light-emitting device was die-bonded with an epoxy resin on the bottom surface of the opening of the heat sink (package). Here, the bonding material used for die bonding is not particularly limited, and resin or glass containing Au — Sn alloy or conductive material can be used. The contained conductive material is preferably Ag, and if Ag paste with a content of 80% to 90% is used, a light-emitting device with excellent heat dissipation and low stress after bonding can be obtained. Next, the electrodes of the die-bonded semiconductor light-emitting device and the lead-out electrodes exposed from the bottom surface of the package opening are electrically connected by Au wires (fig. 20).

Next, the benzyl silicone resin composition 100 wt% (refractive index 1.5) containing 3 wt% as a diffusing agent, light calcium carbonate (refractive index 1.62) with an average particle diameter of 1.0 μm and an oil absorption of 70ml/100g, was stirred for 5 minutes by a rotary and rotary stirrer. Next, in order to stir the heat generated by cooling, standing 30 minutes, so that the resin to return to the normal temperature, thereby making it stable.

The curable composition thus obtained is filled into the opening of the package until the curable composition is flush with the upper surfaces of the two ends of the opening. Finally, heat treatment was performed at 70 ℃ for 3 hours and at 150 ℃ for 1 hour. Thus, a parabolic concave light emitting surface having a substantially bilateral symmetry from the upper surface of the opening portion at both end portions to the central portion is obtained. The sealing member composed of a cured product of the curable composition is separated into 2 layers of a first layer containing a large amount of the diffusing agent and a second layer containing less or no diffusing agent than the first layer, and the surface of the semiconductor light-emitting device is covered with the first layer. Thus, the light emitted from the semiconductor light emitting device can be efficiently extracted to the outside, and good light uniformity can be obtained. The first layer is preferably formed continuously from the bottom surface of the opening to the surface of the semiconductor light-emitting device, so that the light-emitting surface can be formed into a smooth opening.

The light emitting device of the present embodiment can efficiently emit light from the light emitting element from the main surface side, and can be made thinner and can make light enter the light incident surface of the light guide plate in a wide range compared to the conventional light emitting devices.

(example 34)

In example 33, a light-emitting device was formed in the same manner as in example 33 except that a fluorescent substance was contained in the sealing member.

In the case of a fluorescent substance,a mixed raw material is obtained by mixing alumina and a coprecipitated oxide obtained by coprecipitating a solution in which rare earth elements Y, Gd, and Ce are dissolved in an acid at a stoichiometric ratio with oxalic acid and firing the coprecipitated oxide. After mixing barium fluoride as a co-solvent, the mixture was placed in a crucible and fired in air at 1400 ℃ for 3 hours to obtain a fired product. Ball-milling the fired product in water, washing, separating, drying, and sieving to obtain (Y) with a central particle diameter of 8 μm_0.995Gd_0.005)_2.750Al₅O₁₂:Ce_0.250A fluorescent substance.

Since the light-emitting device contains the phosphor, it is possible to obtain a light-emitting device that obtains mixed light of light from the semiconductor light-emitting device and light obtained by wavelength-converting a part of the light-emitting device with the phosphor.

(example 35)

The semiconductor light-emitting device obtained in example 19 was formed into a light-emitting device according to the same conditions as in the above-described embodiment example 33. The light emitting device of the present embodiment can efficiently emit light from the light emitting element from the main surface side, can be made thinner than the conventional light emitting device, and can allow light to enter the light incident surface of the light guide plate in a wide range.

As described above, the present invention can greatly improve the light extraction efficiency without increasing the voltage. Since the opposed electrodes are formed, the heat dissipation property can be improved by selecting the support substrate, and the life characteristics can be improved. Since the conductive substrate is used as a support substrate, a 1-wire structure can be obtained. Further, since a package such as a lead frame is die-bonded with a conductive material using a conductive support substrate, conduction can be achieved, and therefore, a pad electrode is not required for the 1 st electrode, and the light emitting area is increased. As described above, since the face-down configuration (the n-side is the surface) is adopted, the light extraction efficiency is improved. Further, since the opposed electrodes are structured, the diameter can be increased. Due to the concave-convex steps and the aluminum on the step interface, light is highly reflected, and the light extraction efficiency is improved.

The method for manufacturing a nitride semiconductor device according to the present invention can provide a nitride semiconductor device having excellent heat dissipation properties with less chipping and cracking of a nitride semiconductor layer during peeling.

The nitride semiconductor device of the present invention has a coating layer containing a fluorescent substance that absorbs a part or all of light from the active layer and emits light of different wavelengths, and thus can emit light of various wavelengths. In particular, when YAG is contained, white light can be emitted, and the fluorescent material is suitable for a light source for illumination.

Industrial applicability

As described above, the nitride semiconductor device having a supporting substrate and the method for manufacturing the same according to the present invention are suitably used for light emitting devices such as LEDs and LDs, light receiving devices such as solar cells and optical sensors, electronic devices such as transistors and power devices, and media such as DVDs and communication light sources, printing devices, illumination light sources, etc. for storing large amounts of information such as full color displays, oscilloscopes, image scanners, and light sources for optical disks using the same.

Claims (11)

1. A nitride semiconductor device, having in order: a support substrate, a conductive layer formed on the support substrate, and a nitride semiconductor provided on the conductive layer, the nitride semiconductor device being characterized in that,

the nitride semiconductor includes a p-type nitride semiconductor layer, a light-emitting layer, an n-type nitride semiconductor layer,

the p-type nitride semiconductor layer, the light-emitting layer, and the n-type nitride semiconductor layer are sequentially stacked on the conductive layer,

a 1 st electrode is formed between the conductive layer and the p-type nitride semiconductor layer,

a 2 nd electrode is formed on the n-type nitride semiconductor layer,

the surface side of the n-type nitride semiconductor layer is provided with irregularities,

the 2 nd electrode is formed in a mesh-like or grid-like pattern,

an overcoat layer containing a fluorescent substance is provided on the surface side of the semiconductor layer on which the irregularities are formed.

2. The nitride semiconductor device according to claim 1,

the planar shape of the irregularities on the surface of the n-type nitride semiconductor layer is a circle, a polygon, a bar, or a grid.

3. The nitride semiconductor device according to claim 2,

the depth of the concave portion of the unevenness is 0.2 to 3 μm.

4. The nitride semiconductor device according to claim 3,

the depth of the concave portion of the unevenness is 1.0 to 1.5 μm.

5. The nitride semiconductor device according to any one of claims 1 to 4,

the surface of the n-type nitride semiconductor layer has a concave-convex shape in a figure shape, and is formed above the 1 st electrode.

6. The nitride semiconductor device according to claim 1,

the 2 nd electrode has 2 or more pad electrode forming regions, and the 2 nd electrode is formed in a mesh or grid shape on the entire surface of a light emitting range between the 2 or more pad electrode forming regions.

7. The nitride semiconductor device according to claim 6,

the 1 st electrode and the 2 nd electrode have a facing electrode structure, and the 2 nd electrode is not present above the 1 st electrode.

8. The nitride semiconductor device according to claim 1,

the light-emitting layer at least contains Al_aIn_bGa_1-a-bWell layer of N and Al_cIn_dGa_1-c-dAnd the quantum well structure of the barrier layer is formed by N, wherein a is more than or equal to 0 and less than or equal to 1, b is more than or equal to 0 and less than or equal to 1, a + b is less than or equal to 1, c is more than or equal to 0 and less than or equal to 1, d is more than or equal to 0 and less than or equal to 1, and c + d is less than or.

9. The nitride semiconductor device according to claim 8,

the n-type nitride semiconductor layer is composed of at least 2 layers, and the 2 nd electrode side layer of the 2 layers is Al_eGa_1-eN, Al being one of the 2 layers on the side of the light-emitting layer_fGa_1-fN，Al_eGa_{1 -e}The N layer has a specific Al content_fGa_1-fN layer high impurity concentration.

10. The nitride semiconductor device according to claim 9,

the nitride semiconductor device is a nitride semiconductor device that emits light having a wavelength in the ultraviolet region.

11. The nitride semiconductor device according to claim 8,

the light-emitting layer at least contains Al_aIn_bGa_1-a-bWell layer of N and Al_cIn_dGa_1-c-dA quantum well structure of a barrier layer composed of N, wherein a is more than 0 and less than or equal to 1,0 < b.ltoreq.1, a + b.ltoreq.1, 0 < c.ltoreq.1, 0 < d.ltoreq.1, and c + d.ltoreq.1, wherein the p-type nitride semiconductor layer is provided on one main surface of the light-emitting layer, and the n-type nitride semiconductor layer is provided on the opposite main surface, and the n-type nitride semiconductor layer is a nitride semiconductor containing Al.