JP2013048199A - GaN-BASED LED ELEMENT - Google Patents

Abstract

A GaN-based LED element having an increased current flowing through an n-type conductive layer through an extending portion of an n-side metal electrode is provided.
A GaN-based LED element has a semiconductor stacked body including a plurality of GaN-based semiconductor layers. The plurality of GaN-based semiconductors include a p-type conductive layer having a top surface and a bottom surface, and a p-type. An active layer 122 disposed on the bottom surface side of the conductive layer 123 and an n-type conductive layer 121 disposed so as to sandwich the active layer 122 between the p-type conductive layer 123 are included. Is provided with a p-side electrode, and an n-side electrode is provided on the surface of the n-type conductive layer 121 partially exposed on the p-type conductive layer 123 side. The n-side electrode has a connection portion and an extending portion extending from the connection portion, and an area of an ohmic contact interface formed between the connection portion of the n-side electrode and the n-type conductive layer 121 is It is smaller than the area of the part.
[Selection] Figure 1

Description

The present invention relates to a GaN-based LED element having a pn-junction light-emitting structure configured using a GaN-based semiconductor. A GaN-based semiconductor is a compound semiconductor represented by a general formula Al _a In _b Ga _1-ab N (0 ≦ a ≦ 1, 0 ≦ b ≦ 1, 0 ≦ a + b ≦ 1), such as a nitride semiconductor Also called.

  A GaN-based LED element having a pn junction type light-emitting structure, in particular, a double hetero-type GaN-based LED element having an active layer between an n-type conductive layer and a p-type conductive layer, has a wavelength range of near ultraviolet to green. Light can be generated with high efficiency. A white light emitting device configured by combining a phosphor with a highly efficient GaN-based LED element has been put into practical use as a light source for a backlight unit of a liquid crystal display or a light source for illumination.

  A general GaN-based LED element is manufactured through a process of epitaxially growing a GaN-based semiconductor on a sapphire substrate by the MOVPE method. In this step, an n-type conductive layer is formed on the sapphire substrate via a buffer layer, and an active layer and a p-type conductive layer are sequentially formed on the n-type conductive layer. The electrodes are respectively formed on the surface of the p-type conductive layer and the surface of the n-type conductive layer exposed on the p-type conductive layer side. The n-side electrode is usually a metal electrode. The p-side electrode is configured by a combination of a translucent electrode made of a conductive oxide and a metal electrode. The metal electrode is provided with a connecting portion so that a bonding wire or the like can be connected. In a large LED element, in order to assist in spreading the current in the lateral direction (direction perpendicular to the thickness direction of the GaN-based semiconductor film) in the element, either or both of the metal electrodes on the n side and the p side are applied to the metal electrode. In addition to the connecting portion, an extending portion is provided (Patent Documents 1 to 5). The extending portion can be formed in various shapes such as a line shape, a comb shape, and a net shape. The line-shaped extending portion may be likened to an arm or a finger.

JP 2000-164930 A Special Table 2003-524295 JP 2001-345480 A JP 2004-221529 A JP 2004-56109 A JP 2006-196692 A

L.W.Wu et al., Solid-State Electronics, 47, 2027 (2003)

In a GaN-based LED element in which an n-side metal electrode having a connecting portion and an extending portion is provided so as to be in contact with the n-type conductive layer as a whole, the n-side metal electrode is supplied from a bonding wire joined to the connecting portion. It is considered that most of the current flows directly from the connection portion into the n-type conductive layer, and the current flowing through the extending portion to the n-type conductive layer is small. This is because an n-type GaN-based semiconductor has a relatively high conductivity and a low contact resistance with an electrode material, and the GaN-based LED element is made of such an n-type GaN-based semiconductor. This is because the n-type conductive layer is formed relatively thick (usually 2 μm or more). If simplified, since the resistance of the n-type conductive layer is low, current easily flows from the n-side electrode to the n-type conductive layer.

  The present invention has been made based on such consideration, and a main object is to provide a GaN-based LED element in which the current flowing through the n-type conductive layer through the extending portion of the n-side metal electrode is increased.

According to a preferred embodiment of the present invention, the following GaN-based LED element is provided.
(1) It has a semiconductor laminated body including a plurality of GaN-based semiconductor layers, and the plurality of GaN-based semiconductors are arranged on a p-type conductive layer having a top surface and a bottom surface, and on the bottom surface side of the p-type conductive layer An n-type conductive layer disposed so as to sandwich the active layer between the active layer and the p-type conductive layer. A p-side electrode is provided on the upper surface of the p-type conductive layer, and the p-type conductive layer is provided. A GaN-based LED element in which an n-side electrode is provided on a surface of the n-type conductive layer partially exposed on the layer side; the n-side electrode has a connecting portion and an extending portion extending from the connecting portion. A GaN-based LED element, wherein an area of an ohmic contact interface formed between the connection portion of the n-side electrode and the n-type conductive layer is smaller than an area of the connection portion.
(2) The area of the ohmic contact interface formed between the extending portion of the n-side electrode and the n-type conductive layer is formed between the connection portion of the n-side electrode and the n-type conductive layer. The GaN-based LED element according to (1), which is larger than the area of the formed ohmic contact interface.
(3) The GaN-based LED element according to (1), wherein no ohmic contact interface is formed between the connection portion of the n-side electrode and the n-type conductive layer.
(4) An ohmic contact interface and a contact interface whose interface resistance is relatively higher than the ohmic contact interface are formed between the extending portion of the n-side electrode and the n-type conductive layer. The GaN-based LED element according to any one of 1) to (3).
(5) An insulating film having an opening is inserted between the n-side electrode and the n-type conductive layer, and the n-side electrode and the n-type conductive layer are in contact through the opening. The GaN-based LED element according to any one of 1) to (3).
(6) In the extending portion, an area of an ohmic contact interface formed between the n-side electrode and the n-type conductive layer is increased continuously or stepwise as the distance from the connection portion increases. The GaN-based LED element of any one of (1) to (5).
(7) The extending portion includes a line-shaped first portion having a certain width, the ohmic contact interface in the first portion is a line shape parallel to the longitudinal direction of the first portion, and the line width is The GaN-based LED element according to any one of (1) to (6), which is narrower than the line width of the first portion.
(8) The GaN-based LED element according to (7), wherein in the first portion, the line width of the ohmic contact interface is constant or becomes wider continuously or stepwise as the distance from the connection portion increases.
(9) The GaN-based LED element according to any one of (1) to (8), wherein the extending portion includes a highly conductive layer formed of Au, Ag, Cu, or Al.

  In the GaN-based LED element according to the embodiment of the present invention, the current supplied from the n-side metal electrode to the n-type conductive layer is sufficiently distributed through the extending portion to a site away from the connecting portion.

The structure of the GaN-type LED element which concerns on 1st Embodiment is shown, Fig.1 (a) is a top view, FIG.1 (b) is sectional drawing in the position of the X1-X1 line | wire of Fig.1 (a). The structure of the GaN-type LED element which concerns on 1st Embodiment is shown, FIG.2 (c) is sectional drawing in the position of the Y11-Y11 line | wire of Fig.1 (a), FIG.2 (d) is FIG. It is sectional drawing in the position of Y12-Y12 line | wire of a), FIG.2 (e) is sectional drawing in the position of Y13-Y13 line | wire of Fig.1 (a). FIG. 3A shows a plan view of the n-side metal electrode, and FIG. 3B shows a plan view of the p-side metal electrode. FIG. 3A shows only the metal electrode included in the GaN-based LED element according to the first embodiment. FIG. It is a top view which extracts only the metal electrode contained in the GaN-type LED element which concerns on 1st Embodiment, and displays the bottom face (surface which is in physical contact with an n-type conductive layer). It is process sectional drawing for demonstrating the manufacturing method of the GaN-type LED element which concerns on 1st Embodiment. It is process sectional drawing for demonstrating the manufacturing method of the GaN-type LED element which concerns on 1st Embodiment. It is process sectional drawing for demonstrating the formation procedure of the n side metal electrode contained in the GaN-type LED element which concerns on 1st Embodiment. It is process sectional drawing for demonstrating the formation procedure of the n side metal electrode contained in the GaN-type LED element which concerns on 1st Embodiment. 9 (a) and 9 (b) respectively show only the metal electrode included in the GaN-based LED element according to the modification of the first embodiment, and the bottom surface (physical contact with the n-type conductive layer). It is a top view which displays the surface to perform. FIG. 10C and FIG. 10D respectively show only the metal electrode included in the GaN-based LED element according to the modification of the first embodiment, and the bottom surface (physical contact with the n-type conductive layer). It is a top view which displays the surface to perform. The structure of the GaN-type LED element which concerns on 2nd Embodiment is shown, Fig.11 (a) is a top view, FIG.11 (b) is sectional drawing in the position of the X2-X2 line | wire of Fig.11 (a). However, the contact limiting film 280 is provided with an opening pattern shown in FIG. Only the metal electrode included in the GaN-based LED element according to the second embodiment is extracted and displayed. FIG. 12A is a plan view of the n-side metal electrode, and FIG. 12B is a plane of the p-side metal electrode. FIG. It is a top view which illustrates the opening pattern provided in a contact limiting film. The structure of the GaN-type LED element which concerns on 2nd Embodiment is shown, Fig.14 (a) is sectional drawing in the position of the Y21-Y21 line | wire of Fig.11 (a), FIG.14 (b) is FIG. It is sectional drawing in the position of Y22-Y22 line | wire of a). However, the contact limiting film 280 is provided with an opening pattern shown in FIG. It is a top view which illustrates the opening pattern provided in a contact limiting film. It is sectional drawing which shows the structure of the GaN-type LED element which concerns on the deformation | transformation of 2nd Embodiment.

(First embodiment)
The structure of the GaN-based LED element 100 according to the first embodiment is shown in FIGS. FIG. 1A is a plan view, and FIG. 1B is a cross-sectional view taken along line X1-X1 in FIG. FIGS. 2C, 2D, and 2E are cross-sectional views taken along lines Y11-Y11, Y12-Y12, and Y13-Y13 in FIG. 1A, respectively. The GaN-based LED element 100 has a semiconductor stacked body 120 on a substrate 110. The semiconductor stacked body 120 includes an n-type conductive layer 121, an active layer 122, and a p-type conductive layer 123 each made of a GaN-based semiconductor in order from the substrate 110 side. Each of these layers may have a laminated structure.

A translucent electrode 140 patterned in a predetermined shape is provided on the upper surface of the semiconductor stacked body 120. In the region where the translucent electrode 140 is not provided, a part of the semiconductor stacked body 120 is removed by etching, and the n-side metal electrode 130 is formed on the surface of the n-type conductive layer 121 exposed in the region. Yes. A p-side metal electrode 150 is partially formed on the translucent electrode 140. Translucent electrode 140 and p-side metal electrode 150 constitute a p-side electrode.

  3A is a plan view in which only the n-side metal electrode 130 is extracted and displayed, and FIG. 3B is a plan view in which only the p-side metal electrode 150 is extracted and displayed. The n-side metal electrode 130 includes a connection part 131 and a line-shaped extending part 132 extending from the connection part. The p-side metal electrode 150 includes a connecting portion 151 and two extending portions 152 extending from the connecting portion. The extending portion 152 of the p-side metal connecting portion 150 is patterned into a shape in which two straight line-shaped portions 152a and 152b are combined so as to form a right angle. Note that a line in the present invention or the present specification includes not only a straight line but also a bent line.

  When the LED element 100 is mounted, bonding wires, solder, conductive paste, metal bumps, and the like are connected to the connection portions 131 and 151 included in the n-side metal electrode 130 and the p-side metal electrode 150, respectively. The planar shape of the connecting portions 131 and 151 is not limited to a rectangle, and may be a circle or an ellipse. When the planar shape of the connection parts 131 and 151 is a square, it is preferable that the one side exists in the range of 60-120 micrometers. When the planar shape of the connecting portion is circular, the diameter is preferably in the range of 60 to 120 μm.

  The extending portions 132 and 152 of the n-side metal electrode 130 and the p-side metal electrode 150 preferably include a highly conductive layer formed of a metal having high conductivity such as Au, Ag, Cu, and Al. The thickness of the highly conductive layer is preferably 1 μm to 10 μm, particularly 2 μm to 5 μm. Moreover, although the width | variety (line width) of a highly conductive layer can be 7 micrometers-30 micrometers, Preferably they are 10 micrometers-20 micrometers. From the viewpoint of mechanical stability, it is preferable that the extending portions 132 and 152 have a width larger than the height (thickness).

  FIG. 4 is a plan view that displays only the n-side metal electrode 130 and displays the bottom surface thereof, that is, the surface that physically contacts the n-type conductive layer 121. As shown in this figure, the ohmic metal M1 and the non-ohmic metal M2 are exposed on the bottom surface of the n-side metal electrode 130 so as to exhibit a predetermined pattern. Here, the ohmic metal is a metal that can form an ohmic contact with an n-type GaN-based semiconductor. For example, Al (aluminum), Ti (titanium), W (tungsten), V (vanadium), and Cr (chromium). Etc. On the other hand, the non-ohmic metal is a metal having high contact resistance with respect to the n-type GaN-based semiconductor. For example, a platinum group such as Pt (platinum), Pd (palladium), and Rh (rhodium), Au (gold), Ag. (Silver), Cu (copper), Ni (nickel), Co (cobalt), and the like.

  In the example shown in FIG. 4, the ohmic metal M <b> 1 exposed on the bottom surface of the n-side metal electrode 130 exhibits a line pattern having a constant width parallel to the longitudinal direction of the extending portion 132. This pattern is equal to the pattern of the interface (ohmic contact interface) between the ohmic metal M1 and the n-type conductive layer 121. In order to reduce the current flowing directly from the connection part 131 to the n-type conductive layer 121, the area of the ohmic contact interface formed between the connection part 131 and the n-type conductive layer 121 is smaller than the area of the connection part 131. Has been. In addition, the bottom surface of the extending portion 132 is configured to include more exposed portions of the ohmic metal M <b> 1 than the bottom surface of the connecting portion 131. In other words, the area of the ohmic contact interface formed between the extending portion 132 of the n-side metal electrode 130 and the n-type conductive layer 121 is equal to the connection portion 131 of the n-side metal electrode 130 and the n-type conductive layer 121. It is larger than the area of the ohmic contact interface formed therebetween. With this configuration, most of the current supplied to the n-side metal electrode 130 through the bonding wire, solder, conductive paste, metal bump, etc. connected to the connection part 131 is transferred to the n-type conductive layer 121 via the extension part 132. Will be injected.

Further, the current injected from the n-side metal electrode 130 into the n-type conductive layer 121 is changed to the extended portion 132.
In order to flow into the n-type conductive layer 121 after flowing through as far as possible from the connection portion 131, the line width of the ohmic metal M1 exposed on the bottom surface of the n-side metal electrode 130 must be reduced. desirable. The line width is preferably 0.5 to 5 μm, more preferably 1 to 3 μm. It should be noted that if the width of the stretched portion 132 itself is narrowed so far, the electrical resistance increases, and the action of spreading the current in the stretched portion 132 in the lateral direction is significantly reduced.

  A current blocking layer 170 that prevents contact between the translucent electrode 140 and the p-type conductive layer 123 is provided immediately below the connection portion of the p-side metal electrode 123. Immediately below the current blocking layer 170, p-type carrier injection is suppressed, and thus no light emission occurs in the active layer 122. Since the light generated in the region is strongly shielded and absorbed by the connecting portion of the p-side metal electrode 123, it is desirable to suppress the generation from the viewpoint of improving the light emission efficiency.

  Hereinafter, an example of a manufacturing procedure of the GaN-based LED element 100 will be described with reference to process cross-sectional views. Actually, when a plurality of LED elements are formed on a wafer-sized substrate, only a cross section of one LED element is shown in the process sectional view for convenience.

First, a substrate 110 having a wafer size (for example, 2 inches in diameter) that can be used for epitaxial growth of a GaN-based semiconductor is prepared (FIG. 5A). As a substrate that can be preferably used, a single crystal substrate made of sapphire, spinel, silicon carbide, zinc oxide, magnesium oxide, GaN, AlGaN, AlN, NGO (NdGaO ₃ ), LGO (LiGaO ₂ ), LAO (LaAlO ₃ ), or the like can be given. It is done. One particularly preferable substrate is PSS (Patterned Sapphire Substrate) in which a convex portion or a concave portion for generating light scattering is formed by etching on the surface on which a GaN-based semiconductor is to be grown.

  Next, an n-type conductive layer 121, an active layer 122, and a p-type conductive layer 123 are sequentially grown on the prepared substrate 110 by an epitaxial growth method to form the semiconductor stacked body 120 (FIG. 5B). As the epitaxial growth method, a MOVPE method, an HVPE method, an MBE method, a sputtering method, a reactive sputtering method, and other known methods can be appropriately used. When the MOVPE method is used, if the temperature at which the p-type conductive layer 123 is grown is set to a low temperature of about 800 ° C., the surface can be a textured surface on which a large number of pits are formed (non-surface). Patent Document 1).

For the types of impurities that can be added to impart n-type conductivity or p-type conductivity to the GaN-based semiconductor, known techniques can be referred to. The n-type conductive layer 121 is preferably Al _x Ga _1-x N (0 ≦ x ≦ 0.05) to which Si (silicon) is added at a concentration of 3 × 10 ^{18 to} 5 × 10 ¹⁹ cm ⁻³ . It is formed to a thickness of 2 to 6 μm. The active layer 122 is preferably a multiple quantum well layer in which In _x Ga _1-x N (0 <x) well layers and In _y Ga _1-y N (0 ≦ y <x) barrier layers are alternately stacked. To do. For the kind and concentration of impurities that can be added to the active layer, the thickness of the well layer and the barrier layer, etc., known techniques can be referred to.

The p-type conductive layer 123 is preferably Al _x Ga _1-x N (0 ≦ x ≦ 0.05) to which Mg (magnesium) is added at a concentration of 5 × 10 ¹⁹ to 1 × 10 ²¹ cm ⁻³ . A thickness of 0.05 to 2 μm is formed.

GaN having various functions between the substrate 110 and the n-type conductive layer 121, between the n-type conductive layer 121 and the active layer 122, and between the active layer 122 and the p-type conductive layer 123 with reference to known techniques. A system semiconductor layer can be inserted. For example, a defect reduction layer, a strain relaxation layer, a cap layer (decomposition prevention layer), a carrier block layer, and the like. The GaN-based semiconductor layer to be inserted may have a multilayer structure such as a superlattice.

  When the formation of the semiconductor stacked body 120 is completed, as shown in FIG. 5C, a part of the semiconductor stacked body 120 is removed by dry etching using an etching gas containing chlorine. The etching depth is set so that the n-type conductive layer 121 is exposed in a region where the semiconductor stacked body 120 is partially removed. Even when the surface of the p-type conductive layer 121 is a roughened surface, the surface of the n-type conductive layer 121 can be exposed flat by applying an etch back method (Patent Document 6) to this step. Is possible. Note that the step of removing a part of the semiconductor stacked body 120 by dry etching may be performed after the formation and patterning of the light-transmitting electrode 140 described later.

  Following the dry etching, a current blocking layer 170 is formed as shown in FIG. As the material of the current blocking layer 170, various metal oxides or metal nitrides can be used without particular limitation. For example, silicon oxide, magnesium oxide, spinel, aluminum oxide, zirconium oxide, tantalum oxide, niobium oxide, titanium oxide, silicon nitride, silicon oxynitride, and the like.

  After the formation of the current blocking layer 170, the translucent electrode 140 is formed on the surface of the p-type conductive layer 123 as shown in FIG. As a material for the translucent electrode 140, a transparent conductive oxide (TCO) can be preferably used. Indium oxide based TCO such as ITO and IZO (indium zinc oxide), zinc oxide based TCO such as AZO (aluminum zinc oxide) and GZO (gallium zinc oxide), oxidation such as FTO (fluorine doped tin oxide) Any tin-based TCO can be used. There is no limitation on the method of forming the translucent electrode 140, sputtering method, reactive sputtering method, vacuum deposition method, ion beam assisted deposition method, ion plating method, laser ablation method, CVD method, spray method, spin coating method, A known method such as a dip method can be used as appropriate. The translucent electrode 140 may be patterned using either a subtractive method or an additive method (lift-off method).

  After the formation of the translucent electrode 140, the n-side metal electrode 130 and the p-side metal electrode 140 are formed as shown in FIG. The order of formation is not particularly limited, and the n-side metal electrode 130 may be formed before the p-side metal electrode 140 or may be formed later. It is also possible to form the n-side metal electrode 130 and the p-side metal electrode 150 at the same time.

  In order to expose a pattern composed of ohmic metal and non-ohmic metal on the bottom surface of the n-side metal electrode 130, first, as shown in FIG. 7A, the ohmic metal M1 is formed on the surface of the n-type conductive layer 121 with a predetermined pattern. Then, as shown in FIG. 7B, the surface of the ohmic metal M1 and the surface of the n-type conductive layer 121 exposed around the surface may be covered with the non-ohmic metal M2. Alternatively, as shown in FIG. 8A, first, a non-ohmic metal M2 is formed in a pattern having an opening OP of a predetermined shape on the surface of the n-type conductive layer 121, and then, as shown in FIG. 8B. In addition, the surface of the n-type conductive layer 121 exposed in the opening OP may be covered with the ohmic metal M1. In the latter method, the pattern of the opening OP provided in the non-ohmic metal M2 is equal to the pattern exhibited by the ohmic metal M1 on the bottom surface of the n-side metal electrode 130.

Examples of suitable ohmic metals include Al (aluminum), Ti (titanium), W (tungsten), Cr (chromium), V (vanadium), and alloys containing these metals. Al and Al alloys are particularly preferred ohmic metals because of their high reflectance in the near ultraviolet to blue wavelength region. Examples of the Al alloy include those containing additive elements such as Ti, Nd (neodymium), Si (silicon), Cu (copper), Mg (magnesium), Mn (manganese), and Cr.

In one example, the n-side metal electrode 130 can be provided by the following procedures (S1) to (S3):
(S1) As the ohmic metal M1, an Al film having a thickness of 0.05 to 0.2 μm is formed in a predetermined pattern on the surface of the n-type conductive layer 121 using a lift-off method. In order to reduce the contact resistance with the n-type conductive layer 121, heat treatment is performed on the formed Al film at 350 to 500 ° C.
(S2) A lift-off mask provided with an opening having the shape of the n-side metal electrode 130 to be formed is used to cover the Al film formed in (S1) with a thickness of 0.1 to 0.5 μm. Deposition of an Ag film and a Cu film having a thickness of 0.5 μm or more is sequentially performed to form a laminated film.
(S3) The lift-off mask is lifted off so that the laminated film formed in (S2) exhibits the shape of the n-side metal electrode 130.

  In this example, the Ag film and the Cu film formed in (S2) correspond to the non-ohmic metal M2 and the high conductive layer, respectively. If necessary, it is possible to form a thick Ag film so that the non-ohmic metal M2 can also be used as a highly conductive layer. In order to form the p-side metal electrode 150 simultaneously with the n-side metal electrode 130, an opening for forming the p-side metal electrode 150 may be added to the lift-off mask used in (S2). The p-side metal electrode 150 thus formed has a structure in which a Cu film is laminated on an Ag film.

In another example, the n-side metal electrode 130 can be formed by the following procedures (T1) to (T3):
(T1) An Rh film having a thickness of 0.05 to 0.2 μm is formed as a non-ohmic metal M2 in a pattern having an opening on the surface of the n-type conductive layer 121. Patterning can be performed using a lift-off method.
(T2) Using a lift-off mask provided with an opening having the shape of the n-side metal electrode 130 to be formed, the surface of the n-type conductive layer 121 exposed in the opening of the Rh film formed in (T1) and the A multilayer film is formed by sequentially depositing a Cr film having a thickness of 0.05 to 0.5 μm and an Au film having a thickness of 0.5 μm or more so as to cover the surface of the Rh film.
(T3) The lift-off mask is lifted off so that the laminated film formed in (T2) exhibits the shape of the n-side metal electrode 130.

  In this example, the Cr film and the Au film formed in (T2) correspond to the ohmic metal M1 and the high conductive layer, respectively. The p-side metal electrode 150 can be formed simultaneously with the n-side metal electrode 130 by adding an opening for forming the p-side metal electrode 150 to the lift-off mask used in (T2). The p-side metal electrode 150 thus formed has a structure in which an Au film is laminated on a Cr film.

  The material of the surface layer of the n-side metal electrode 130 and the p-side metal electrode 150 can be selected in consideration of the bondability of the bonding wire. In order to increase the bondability of the Au wire, the surface layer is preferably formed of Au or Al. Solder may be bonded to the n-side metal electrode 130 and the p-side metal electrode 150 instead of the bonding wire. In order to increase the wettability of the solder, it is preferable to form the surface layer of these electrodes with a metal that is difficult to oxidize, such as Au or Pt, or a component metal contained in solder that is scheduled to be used. In the case where a surface layer made of a different material is provided on the above-described highly conductive layer, both layers of barrier layers made of a refractory metal are formed so that an undesired alloying reaction does not occur between these layers. You may provide between. A surface layer for improving wire bondability and solder wettability can be provided only at the connection portions 131 and 151.

  Although not shown, before the dicing process of dividing the wafer into LED elements as chips (also referred to as dies), the surface of the wafer on which the semiconductor laminate 120 is formed (excluding the surface of the connection portion of the metal electrode). ), An insulating and translucent protective film is formed. Preferred materials for this protective film are silicon oxide, silicon nitride, silicon oxynitride and the like. For the dicing method, known techniques can be referred to as appropriate.

  The GaN-based LED element 100 obtained by the above procedure can be mounted on a package by face-up or face-down (flip chip). After the face-down (flip chip) mounting, the substrate 110 can be further detached from the semiconductor stacked body 120 by using a laser lift-off technique.

(Modification of the first embodiment)
In a preferred embodiment, in the extension portion 132, the area of the ohmic contact interface formed between the n-side electrode 130 and the n-type conductive layer 123 is increased continuously or stepwise as the distance from the connection portion 131 increases. be able to. In other words, the area of the exposed portion of the ohmic metal M1 on the bottom surface of the n-side electrode 130 can be increased continuously or stepwise as the distance from the connecting portion 131 increases in the extending portion 132. By adopting such a configuration, a larger amount of current is injected into the n-type conductive layer 121 via the extending portion 132 of the n-side metal electrode 130.

  FIG. 9A shows an example in which the area of the ohmic metal M <b> 1 exposed on the bottom surface of the n-side electrode 130 is continuously increased in the extending portion 132 as the distance from the connecting portion 131 increases. On the other hand, FIG. 9B shows an example in which the area of the ohmic metal M <b> 1 exposed on the bottom surface of the n-side electrode 130 is gradually increased as the distance from the connection portion 131 increases in the extending portion 132.

  10 (a) and 10 (b) are examples in which the area of the ohmic metal M1 exposed on the bottom surface of the n-side electrode 130 is gradually increased as the distance from the connecting portion 131 increases in the extending portion 132. is there. In these examples, unlike the example shown in FIG. 9B, the exposed portion of the ohmic metal M <b> 1 on the bottom surface of the n-side electrode 130 is discontinuous along the longitudinal direction of the extending portion 132.

In any of the examples shown in FIGS. 9 and 10, the line width of the extending portion 132 of the n-side metal electrode 130 is constant, so that the action of spreading the current of the extending portion 132 in the lateral direction is not impaired. If necessary, the line width of the extending portion 132 may decrease as the distance from the connecting portion 131 increases.
In the example of FIGS. 9A and 9B, the line width of the line-shaped ohmic metal M1 exposed on the bottom surface of the n-side electrode 130 is the line width of the extending portion 132 at a portion farthest from the connecting portion 131. It is preferable to make it wide to the same extent. On the other hand, on the connection portion 131 side where the line width of the ohmic metal M1 is the narrowest, the line width can be reduced to 1 μm or less, and further to 0.5 μm or less. From the technical point of view, there is no particular lower limit to the line width, but if it is too fine, the production cost will increase, so it is preferably 0.5 μm or more.

  The same applies to the case where the exposed portion of the ohmic metal M1 on the bottom surface of the n-side electrode 130 shown in FIGS. 10A and 10B is discontinuous. In the portion farthest from the connecting portion 131, the exposed portion The width (the width of the extending portion 132 in the line width direction) is preferably increased to the same extent as the line width of the extending portion 132. From a technical point of view, there is no particular lower limit to the width of the exposed portion on the connection portion 131 side. However, if it is too fine, the manufacturing cost increases, and therefore it is preferably 0.5 μm or more.

(Second Embodiment)
A structure of a GaN-based LED element 200 according to the second embodiment is shown in FIG. FIG. 11A is a plan view, and FIG. 11B is a cross-sectional view taken along line X2-X2 in FIG. 11A. The GaN-based LED element 200 has a semiconductor laminate 220 on a substrate 210. The semiconductor stacked body 220 includes an n-type conductive layer 221, an active layer 222, and a p-type conductive layer 223, each of which is made of a GaN-based semiconductor in order from the substrate 210 side.

  In a part of the semiconductor stacked body 220, the p-type conductive layer 223 and the active layer 222 are removed, and the n-type conductive layer 221 is exposed. A contact limiting film 280 is formed on the exposed surface of the n-type conductive layer 221, and an n-side metal electrode 230 is formed thereon. A translucent electrode 240 is formed almost entirely on the upper surface of the p-type conductive layer 223, and a p-side metal electrode 250 is partially formed thereon. The translucent electrode 240 and the p-side metal electrode 250 constitute a p-side electrode.

  FIG. 12A is a plan view in which only the n-side metal electrode 230 is extracted and displayed, and FIG. 12B is a plan view in which only the p-side metal electrode 250 is extracted and displayed. The n-side metal electrode 230 includes a connecting portion 231 and a line-shaped extending portion 232 extending from the connecting portion. Similarly, the p-side metal electrode 250 includes a connecting portion 251 and a line-shaped extending portion 252 extending from the connecting portion. In the n-side metal electrode 230, at least a portion in contact with the n-type conductive layer 221, that is, a portion including the bottom surface may be formed of ohmic metal.

  A structural feature of the GaN-based LED element 200 according to the second embodiment resides in a contact limiting film 280 provided between the n-type conductive layer 221 and the n-side metal electrode 230. The contact limiting film 280 is insulative and is formed in a pattern having an opening. The contact between the n-type conductive layer 221 and the n-side metal electrode 230 is limited to the contact through the opening of the contact limiting film 280. By appropriately setting the shape, size, number, arrangement, and the like of the opening, the contact area between the n-side metal electrode 230 and the n-type conductive layer 221 is made larger than the connection portion 231 in the extending portion 232. With this configuration, the ratio of the current injected through the extending portion 232 to the current injected from the n-side metal electrode 230 into the n-type conductive layer 221 is increased.

  An example of a planar shape of the contact limiting film 280 included in the GaN-based LED element 200 is shown in FIG. In the contact limiting film 280 of FIG. 13A, a plurality of circular openings OP are provided. The cross-sectional view of the GaN-based LED element 200 shown in FIG. 11B is a cross-sectional view when the contact limiting film 280 has the planar shape shown in FIG.

In the contact limiting film 280 of FIG. 13B, the slit-shaped opening OP is provided substantially parallel to the extending portion 232 of the n-side metal electrode. FIG. 14 shows a cross-sectional view of the GaN-based LED element 200 when the contact limiting film 280 has the planar shape shown in FIG. 14A is a cross-sectional view taken along the line Y21-Y21 in FIG. 11A, and FIG. 14B is a cross-sectional view taken along the line Y22-Y22 in FIG.
The slit width of the opening OP is preferably 0.5 to 5 μm, more preferably 1 to 3 μm.

If the contact limiting film 280 is used, it is possible to limit the contact area between the n-side metal electrode 230 and the n-type conductive layer 221 without reducing the width of the extending portion 232 of the n-side metal electrode 230. Will be understood. That is, the current flowing into the n-type conductive layer 221 at or near the connecting portion 231 can be reduced without increasing the electrical resistance in the longitudinal direction of the extending portion 232. If the electrical resistance of the stretched portion 232 is high, this effect cannot be sufficiently exhibited. Therefore, the stretched portion 232 includes a highly conductive layer formed of a metal having high conductivity such as Au, Ag, Cu, and Al. Is preferred. The thickness of this highly conductive layer is preferably 1 μm to 10 μm,
Particularly, it is 2 μm to 5 μm. Moreover, although the width | variety (line width) of this highly conductive layer can be 7 micrometers-30 micrometers, Preferably it is 10 micrometers-20 micrometers. From the viewpoint of mechanical stability, the highly conductive layer preferably has a width larger than the height (thickness). However, since the metal material becomes an absorber of light generated in the active layer 222, the light output of the LED element 200 is lowered when the width of the highly conductive layer is excessively widened.

  In order to further enhance the above effect, it is possible to employ a configuration in which the contact area between the n-side metal electrode and the n-type conductive layer in the extending portion increases as the distance from the connection portion of the n-side metal electrode increases. In order to realize this configuration, as the contact limiting film 280 shown in FIGS. 15A to 15C, the width of the opening OP increases as the distance from the connecting portion of the n-side metal electrode formed thereon increases. A contact limiting film may be used. When such a contact limiting film 280 is used, the contact area between the extending portion 232 and the n-type conductive layer 221 is changed according to the distance from the connecting portion 231 without changing the line width of the extending portion 232 of the n-side metal electrode. Can be changed.

When the contact limiting film 280 is configured as shown in FIG. 15A, the slit width of the opening OP can be increased to the same level as the line width of the extending portion 232 in the portion farthest from the connecting portion 231. preferable. On the other hand, on the connection portion 231 side where the slit width is the narrowest, the slit width can be reduced to 1 μm or less, and further to 0.5 μm or less. From the technical point of view, there is no particular lower limit to the slit width, but if it is too fine, the manufacturing cost increases, and therefore it is preferably 0.5 μm or more.
In the case where the contact limiting film 280 is configured as shown in FIG. 15B or FIG. 15C, the preferred width of the opening OP (the width of the extending portion 232 in the line width direction) is also the same as in FIG. It is the same.

  Various metal oxides or metal nitrides can be used for the material of the contact limiting film 280 without any particular limitation. For example, silicon oxide, magnesium oxide, spinel, aluminum oxide, zirconium oxide, tantalum oxide, niobium oxide, titanium oxide, silicon nitride, silicon oxynitride, and the like. The thickness of the contact limiting film 280 can be set to, for example, 50 nm to 500 nm. The patterning of the contact limiting film 280 can be performed using a normal photolithography technique.

  A configuration in which the contact limiting film 280 also serves as a protective film for protecting the surface of the semiconductor stacked body 220 can be adopted as in the example shown in the cross-sectional view of FIG.

  The preferable aspect of each other site | part of the GaN-type LED element 200 which concerns on 2nd Embodiment is the same as that of the GaN-type LED element 100 which concerns on 1st Embodiment.

  As mentioned above, although this invention was demonstrated according to specific embodiment, this invention is not limited to the said embodiment, A various deformation | transformation is possible within the range which does not deviate from the meaning.

It should be noted that the following GaN-based LED elements are included in the preferred embodiment of the present invention.
(A1) It has a semiconductor laminated body including a plurality of GaN-based semiconductor layers, and the plurality of GaN-based semiconductors are arranged on a p-type conductive layer having a top surface and a bottom surface, and on a bottom surface side of the p-type conductive layer An n-type conductive layer disposed so as to sandwich the active layer between the active layer and the p-type conductive layer. A p-side electrode is provided on the upper surface of the p-type conductive layer, and the p-type conductive layer is provided. A GaN-based LED element in which an n-side electrode is provided on a surface of the n-type conductive layer partially exposed on the layer side; the n-side electrode has a connecting portion and an extending portion extending from the connecting portion. And the area of the ohmic contact interface formed between the n-side electrode and the n-type conductive layer is larger than the connection part in the extending part, and the area of the ohmic contact interface in the extending part Is smaller than the physical contact area between the n-side electrode and the n-type conductive layer. D element.
(A2) In the extending portion, the area of the ohmic contact interface formed between the n-side electrode and the n-type conductive layer is increased continuously or stepwise as the distance from the connection portion increases. (A1) GaN-based LED element.
(A3) The extending portion includes a line-shaped first portion having a constant width, the ohmic contact interface in the first portion is a line shape parallel to the longitudinal direction of the first portion, and the line width is The GaN-based LED element according to (a1), which is narrower than the line width of the first portion.
(A4) The GaN-based LED element according to (a3), wherein in the first portion, the line width of the ohmic contact interface is constant or becomes wider continuously or stepwise as the distance from the connection portion increases.
(A5) The GaN-based LED element according to any one of (a1) to (a4), wherein the extending portion includes a highly conductive layer formed of Au, Ag, Cu, or Al.

(B1) A semiconductor stacked body including a plurality of GaN-based semiconductor layers, wherein the plurality of GaN-based semiconductors are arranged on a p-type conductive layer having a top surface and a bottom surface, and on a bottom surface side of the p-type conductive layer. An n-type conductive layer disposed so as to sandwich the active layer between the active layer and the p-type conductive layer. A p-side electrode is provided on the upper surface of the p-type conductive layer, and the p-type conductive layer is provided. A GaN-based LED element in which an n-side metal electrode is provided on a surface of the n-type conductive layer partially exposed on the layer side; the n-side metal electrode includes a connecting portion and an extending portion extending from the connecting portion. An insulating contact limiting film having an opening patterned so that a contact area between the n-side metal electrode and the n-type conductive layer is larger than the connection portion in the extended portion. A GaN-based LED element provided between a conductive layer and the n-side metal electrode.
(B2) The extending portion includes a line pattern, and the contact limiting film is provided at a position corresponding to the line pattern, and is a slit-like opening that is substantially parallel to the line pattern and narrower than the line pattern. (B1) GaN-based LED element having
(B3) The GaN-based LED element according to (b1) or (b2), wherein a contact area between the n-side metal electrode and the n-type conductive layer in the extending portion increases as the distance from the connection portion increases.
(B5) The GaN-based LED element according to any one of (b1) to (b4), wherein the second extending portion includes a highly conductive layer formed of Au, Ag, Cu, or Al.

100, 200 GaN-based LED elements 110, 210 Substrate 120, 220 Semiconductor laminates 121, 221 n-type conductive layers 122, 222 active layers 123, 223 p-type conductive layers 130, 230 n-side metal electrodes 131, 231 connection portion 132, 232 Stretched portion 140, 240 Translucent electrode 150, 250 P-side metal electrode 151, 251 Connection portion 152, 252 Extension portion 170 Current blocking layer 280 Contact limiting film

Claims (9)

  A semiconductor laminate including a plurality of GaN-based semiconductor layers, the plurality of GaN-based semiconductors including a p-type conductive layer having a top surface and a bottom surface, and an active layer disposed on a bottom surface side of the p-type conductive layer; And an n-type conductive layer disposed so as to sandwich the active layer with the p-type conductive layer, and a p-side electrode is provided on the upper surface of the p-type conductive layer, and on the p-type conductive layer side A GaN-based LED element in which an n-side electrode is provided on a partially exposed surface of the n-type conductive layer; the n-side electrode having a connection portion and an extending portion extending from the connection portion; A GaN-based LED element in which an area of an ohmic contact interface formed between the connection portion of the n-side electrode and the n-type conductive layer is smaller than the area of the connection portion.   The ohmic contact interface area formed between the extending portion of the n-side electrode and the n-type conductive layer is an ohmic formed between the connection portion of the n-side electrode and the n-type conductive layer. The GaN-based LED element according to claim 1, wherein the GaN-based LED element is larger than an area of the contact interface.   The GaN-based LED element according to claim 1, wherein an ohmic contact interface is not formed between the connection part of the n-side electrode and the n-type conductive layer.   The ohmic contact interface and the contact interface whose interface resistance is relatively higher than the ohmic contact interface are formed between the extending portion of the n-side electrode and the n-type conductive layer. The GaN-based LED element according to any one of the above.   An insulating film having an opening is inserted between the n-side electrode and the n-type conductive layer, and the n-side electrode and the n-type conductive layer are in contact through the opening. The GaN-based LED element according to any one of the above.   In the extending portion, an area of an ohmic contact interface formed between the n-side electrode and the n-type conductive layer increases continuously or stepwise as the distance from the connection portion increases. The GaN-based LED element according to any one of 5.   The extending portion includes a line-shaped first portion having a constant width, the ohmic contact interface in the first portion is a line shape parallel to the longitudinal direction of the first portion, and the line width is the first width. The GaN-based LED element according to claim 1, which is narrower than the line width of the portion.   8. The GaN-based LED element according to claim 7, wherein in the first portion, a line width of the ohmic contact interface is constant or becomes wider continuously or stepwise as the distance from the connection portion increases.   The GaN-based LED element according to any one of claims 1 to 8, wherein the extending portion includes a highly conductive layer formed of Au, Ag, Cu, or Al.

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