JP2002118293A - Light emitting device and method for forming the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable conversion type light emitting device having good productivity and excellent optical characteristics, and a method for forming the same. A light-emitting element having a semiconductor layer on a substrate;
A fluorescent substance capable of absorbing a part of light from the light emitting element and emitting light of a longer wavelength than the fluorescent substance; and a translucent mold member having the fluorescent substance and surrounding the surface of the light emitting element. In a light emitting device, at least one bump is provided on an electrode of the light emitting element, and an upper surface of the bump is substantially flush with an upper surface of the light transmitting mold member.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting device which can be used for a backlight of a liquid crystal, an illuminating light source, various indicators, a traffic light, and the like, and relates to a semiconductor light emitting element and a fluorescent material capable of emitting light of a longer wavelength than that. And a method for forming the same.

[0002]

2. Description of the Related Art Semiconductors capable of emitting blue light with high luminance today
Nitride semiconductors (In _xGa_yAl
_1-xyN, L using 0 ≦ x ≦ 1, 0 ≦ y ≦ 1)
ED chips have been developed. Light emission using nitride semiconductor
The device uses other GaAs, AlInGaP, etc. materials
Output compared to a light-emitting element that emits red to yellow-green light
High, with little color shift due to temperature
But have so far wavelengths above green
High output in the long wavelength region
You. On the other hand, emission from the LED chip onto this LED chip
Absorbs at least a part of the blue light and emits yellow light
YAG: Ce phosphor, which is a possible fluorescent substance, is arranged.
This opens a light emitting diode that can emit white light.
Was issued. (International publication number WO98 / 5078)

In this light emitting diode, for example, an LED chip is arranged at the bottom of a cup of a mount lead,
The ED chip is electrically connected to the mount lead and the inner lead by a gold wire or the like. After the connection, the cup is filled with a translucent mold resin containing a fluorescent substance that absorbs blue light from the LED chip and emits complementary yellow light. Finally, a convex lens is formed at the tip of both leads by using a translucent resin or the like. Thus, the LED
An LED lamp that emits white light composed of a mixture of light from the chip and the fluorescent substance via the convex lens is obtained.

In the above-described LED lamp, a light-transmitting mold resin containing a fluorescent substance is provided in advance around a chip, and then a convex lens member is formed of a light-transmitting resin or the like. As a result, the light from the chip becomes a desired mixed color light when it passes through the translucent mold resin containing the fluorescent substance filled in the cup. Therefore, the color-converted light can be satisfactorily extracted in the front direction. Further, by adjusting the shape of the cup, light scattering can be suppressed and light emission output can be improved, and desired light emission characteristics can be easily obtained.

[0005]

However, it has been difficult to produce such LED lamps at a high yield with a noticeable unevenness in luminescence and uneven chromaticity as the size of the LED lamps is reduced.

Accordingly, an object of the present invention is to provide a chip type long wavelength conversion type light emitting device having good productivity and excellent optical characteristics, and a method of forming the same.

[0007]

That is, a light-emitting device according to the present invention comprises a light-emitting element having a semiconductor layer on a substrate, and a part of light from the light-emitting element which absorbs part of the light and has a longer wavelength. A light emitting device comprising: a fluorescent substance capable of emitting light; and a translucent mold member having the fluorescent substance and surrounding a surface of the light emitting element, wherein at least one light emitting element is provided on an electrode of the light emitting element.
And a top surface of the bump is substantially flush with an upper surface of the translucent mold member. As a result, a light emitting device having high reliability and capable of uniformly emitting desired mixed light can be obtained.

The thickness of the bump is 5 μm to 150 μm.
μm. Thereby, a light emitting device capable of emitting light with high output is obtained.

[0009] Further, the upper surface of the light emitting device comprising the upper surface of the bump and the upper surface of the translucent mold member is substantially parallel to the bottom surface on the substrate side. As a result, a light emitting device having good directivity characteristics can be obtained.

The fluorescent substance is a yttrium-aluminum-garnet-based fluorescent substance activated with Ce, Eu.
And / or Cr-activated CaO-Al ₂ O activated with Cr
_3, characterized in that one selected from -SiO _2. As a result, a highly reliable light-emitting device that can easily perform mixed-color light emission with high luminance can be obtained.

[0011] Further, the light emitting device has a continuous reflection film at least on the substrate side. As a result, a light emitting device having good luminous efficiency and less luminance unevenness can be obtained.

Further, according to the method for forming a light emitting device of the present invention, a light emitting element having a semiconductor layer on a substrate can absorb a part of light from the light emitting element and emit light having a longer wavelength than the light emitting element. A method for forming a light-emitting device, comprising: a fluorescent material; and a translucent mold member having the fluorescent material and surrounding the surface of the light-emitting element, wherein a bump is formed on an electrode of the light-emitting element in a wafer state. A first step of coating, a second step of coating the semiconductor layer side of the light emitting element with a material to be the translucent mold member so as to cover the bumps, and curing the material to be the translucent mold member. After this, a third step of exposing the upper surface of the bump from the semiconductor layer side in parallel with the bottom surface of the wafer by polishing, and a fourth step of cutting the wafer by dicing and scribing. Thus, a light-emitting device can be formed with high productivity.

In the third step, each of the bumps is polished so as to have a thickness of 5 μm to 150 μm. Thereby, the fluorescent material in the mold member formed in the second step can be polished well without being destroyed, and a light emitting device which can emit light with high reliability and uniformity can be obtained.

Further, after the fourth step, a continuous translucent mold member is formed at least on the substrate side of the light emitting element. The light emitting device thus obtained can have a translucent mold member containing a fluorescent substance on the entire outer peripheral surface other than the upper surface of the bump electrically connected to the external electrode, and thus has high reliability and high color purity. Is obtained.

Further, after the fourth step, a continuous reflection film is formed on at least the substrate side of the light emitting element. Thus, light emitted from the substrate side of the light emitting element can be guided to the semiconductor layer side, and a light emitting device with less color unevenness and high light emission output can be obtained.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a result of various experiments, the present inventor has found that a fluorescent material-containing translucent mold member, which is a color conversion member, is provided before an element is electrically connected, so that a subsequent mounting process can be performed. The inventors have found that a color conversion type light emitting device which can be simplified and has high reliability can be obtained, and the present invention has been accomplished.

Conventionally, when forming a wavelength conversion type LED lamp, it has been necessary to provide a mold member containing a fluorescent substance in advance for each of the divided elements separately from the convex lens member. Specifically, the following process is required.

Each chip-shaped element is placed on the bottom of the cup of the mount lead, and each electrode of the element is electrically connected to the lead electrode by a wire or the like. First, the element is placed in the cup so as to cover the element and the wire. A resin containing a fluorescent substance is dropped and injected with a dispenser or the like, and is heated and cured to form a color conversion member. Thus, the first mold member is formed.

Thereafter, the resin as the material of the convex lens member is poured into the casting case, and the tip of the lead on which the color conversion member is formed is immersed. This is placed in an oven and cured by heating to form a convex lens member as a second mold member.
An ED lamp is formed.

In order to form one light emitting device as described above, a step of filling each element with a resin and curing the element is required twice, the waiting time for the resin effect is relatively long, and further production is required. There is a demand for improved performance.

Further, as the size of the light emitting device becomes smaller, the amount of the first mold member becomes inevitably smaller, and it is difficult to arrange the amount of fluorescent substance necessary to obtain desired mixed light with high accuracy for each element. It is extremely difficult, and chromaticity variation occurs in each light emitting device, and the yield is poor.

Further, the light emitting device has a wire or the like in the color converting member in order to provide the color converting member after the light emitting element is electrically connected with the semiconductor layer as the upper surface. It is considered that such an electrical connection member has an adverse effect on the arrangement of the fluorescent substance, reduces the light extraction efficiency of the fluorescent substance and the light emitting element, and causes color unevenness and output reduction.

Therefore, in order to solve the above-mentioned problem, the present invention provides a light-emitting element itself with a color conversion member. Specifically, the electrode portion of the light emitting element is raised in a wafer state before being divided into individual light emitting elements, and a color conversion member is provided around the light emitting element. With such a configuration, a color conversion light-emitting device having sufficiently high reliability and excellent optical characteristics can be formed with high productivity.

An embodiment according to the present invention will be described below with reference to the drawings. FIG. 1 is a schematic sectional view of a light emitting diode according to one embodiment of the present invention. On an insulating substrate 1, at least an n-type nitride semiconductor layer 2, an active layer (not shown), and a p-type nitride semiconductor layer 3 are sequentially laminated and formed on almost the entire surface of the p-type nitride semiconductor layer 3. The formed transparent first positive electrode 4, the second positive electrode 5 for bonding formed on a part of the first positive electrode 4, and the p-type nitride semiconductor layer 3 exposed by etching or the like from the p-type nitride semiconductor layer 3 side. A light emitting device having a negative electrode 6 on the n-type nitride semiconductor layer 2 and an insulating protective film 7 formed except for a bonding surface of each electrode is used. Bumps 8 are respectively provided on the bonding surfaces of the respective electrodes of such a light emitting element, and the upper surfaces of these bumps are exposed to form a light-transmitting mold member 9 containing a fluorescent substance on the upper surface and side surfaces of the light emitting element on the semiconductor layer side. Provided. Hereinafter, each configuration of the present invention will be described in detail.

(Light Emitting Element) In the present invention, it is efficient if the light from the light emitting element has a shorter wavelength than the light emitted from the fluorescent substance. Therefore, as a semiconductor element capable of emitting visible light with high emission luminance with high efficiency, a nitride semiconductor (I
_{n x Ga y Al 1-x} -y N, 0 ≦ x ≦ 1,0 ≦ y ≦
One using (1) for the active layer is preferred. A light emitting element using a nitride semiconductor can be formed on a sapphire substrate, a spinel (MgAi ₂ O ₄ ) substrate, SiC, GaN single crystal, or the like. Preferably, it is used. Therefore, in the present invention, a light-emitting element in which n-type and p-type nitride semiconductor layers are formed on a sapphire substrate which is an insulating substrate and has both electrodes on the semiconductor layer side is used.

More specifically, the light emitting device comprises an n-type nitride semiconductor layer 2 composed of one or more layers on a sapphire substrate 1, an active layer (not shown), and one or more layers. A p-type nitride semiconductor layer 3 is laminated, and positive and negative electrodes are formed as follows. That is, the positive electrode is composed of the first positive electrode 4 formed on almost the entire surface of the p-type nitride semiconductor layer and the second positive electrode 5 for bonding formed on a part of the first positive electrode, The negative electrode 6 is formed on the surface of the n-type nitride semiconductor layer where a part of the p-type nitride semiconductor layer is removed by dry etching or the like and exposed.

In the present invention, the n-type nitride semiconductor layer 2 and the p-type nitride semiconductor layer 3 are not particularly limited, and may have any layer configuration.

In the case of emitting a white light in the light emitting device of the present invention, the main emission peak of the light emitting element is 400 nm or more in consideration of the complementary color relationship with the fluorescent substance and the deterioration of the resin.
It is preferably 0 nm or less, more preferably 420 nm or more and 490 nm or less. In order to improve the efficiency of each of the light emitting element and the fluorescent substance, 450 nm or more and 470 nm
It is more preferable to use a light-emitting element having a main emission peak below.

On the other hand, in the light-emitting device of the present invention, when a light-transmitting mold member containing a fluorescent substance is provided around the light-emitting element, a resin or glass, which is relatively resistant to ultraviolet light, is used.
A light-emitting device capable of emitting white light can be obtained by using a light-emitting element which can emit ultraviolet light having a main emission peak at a short wavelength around 00 nm. Red,
A fluorescent substance capable of emitting blue and green light, for example, Y ₂ O ₂ S: Eu as a red fluorescent substance, and Sr ₅ (PO
₄ ) ₃ Cl: Eu and as green phosphor (SrEu)
White light can be obtained by incorporating O.Al ₂ O ₃ into the ultraviolet-resistant resin or the like and applying it as a color conversion layer on the surface of a light emitting element that emits short wavelength light.

In one embodiment of the present invention, a light-transmitting mold member as a color conversion layer is provided around the entire periphery of the light emitting element with the surface of the bump disposed on the electrode of the light emitting element as an opening. As a result, light emitted from all directions of the light emitting element is efficiently absorbed by a fluorescent substance disposed therearound, wavelength-converted, and then emitted. Therefore, a highly reliable white light emitting device can be obtained without deterioration of the light emitting device due to ultraviolet rays.

As a fluorescent substance used in combination with a light emitting element capable of emitting ultraviolet light to obtain white light, in addition to the above, 3.5MgO.multidot.
0.5MgF ₂ · GeO ₂ : Mn, Mg ₆ As
₂ O ₁₁ : Mn, Gd ₂ O ₂ : Eu, LaO ₂ S: E
u, as a blue phosphor, Re ₅ (PO ₄ ) ₃ Cl: Eu
(However, Re is at least one selected from Sr, Ca, Ba, and Mg), BaMg ₂ Al ₁₆ O ₂₇ : Eu, etc. are preferably used. Since these fluorescent materials are remarkably excellent in light emission by ultraviolet light, a white light emitting device capable of emitting light with high luminance can be obtained.

In the present invention, the first positive electrode 4 is not particularly limited as long as it is an electrode material that can make ohmic contact with the p-type nitride semiconductor layer. For example, Au, Pt, Al, Sn, C
One or more of r, Ti, Ni, Co and the like can be used. In addition, the first positive electrode can be adjusted to be light-transmitting or non-light-transmitting by adjusting the film thickness in accordance with the mounting form. However, in the present invention, the first positive electrode is light-transmitting. The film thickness is adjusted as follows. In order to be translucent, the film thickness should be 10
It is set to be between Angstroms and 500 Angstroms, preferably between 10 Angstroms and 200 Angstroms.

The second positive electrode 5 includes Au, P
One or more types of metal materials such as t, Al, Sn, Cr, Ti, and Ni can be used. The thickness of the second positive electrode is 1
It is preferable that the thickness be set to 2,000 angstroms to 2 μm.

In the present invention, the negative electrode 6 is not particularly limited as long as it is an electrode material that can make ohmic contact with the n-type nitride semiconductor. For example, Ti, Al, Ni, Au, W, V
One or more types of metal materials such as
Ti / Al, W / A based on i, W and V respectively
It is preferable to have a multilayer structure such as 1 / W / Au, W / Al / W / Pt / Au, V / Al and the like. By using an electrode material that can make ohmic contact with the n-type nitride semiconductor layer, _Vf can be reduced. The thickness of the negative electrode 7 is 2
000 Å to 5 μm, preferably 5000
Angstrom to 1.5 μm.

In the present invention, a short circuit between the positive and negative electrodes is prevented.
In order to stop it, the bump formation surface of each electrode is
It is preferable to provide an insulating protective film 7 on the surface of the conductor layer.
No. Also, slightly apply an insulating protective film on the upper surface of each electrode.
When it is formed in such a way, it peels off from the underlying layer that each electrode is in contact with
Can be suppressed. Insulating protective film material
As a result, the transmittance is good at the main wavelength and the first positive
Good adhesion to the electrode, the second positive electrode, and the negative electrode
It is not particularly limited. It also cuts light in the short wavelength region.
It is preferable to use such a material. For example, alkali silicate
Glass, soda-lime glass, lead glass, barium glass, etc.
Glass composition, or SiO₂, TiO ₂, Ge
O₂, And Ta₂O₅Oxides are preferably formed
You. Further, the film thickness is not particularly limited.
It is preferable that the transmittance in the length is adjusted to 90% or more.
New

(Bump) In the present invention, the light emitting element has at least one bump on the electrode, and the upper surface of the bump is substantially the same as the upper surface of the light-transmitting mold member arranged in contact with the side surface of the bump. It is a plane. As described above, by forming substantially the same plane on the upper surface of the bump and the upper surface of the translucent mold member, a light emitting device that is easy to mount and has high reliability can be obtained.

The bumps are formed on the bonding surfaces of the electrodes of each element in a wafer state before the light emitting elements are individually cut (first step). If a metal material such as Au or Pt is used as the material of the bump, a bump excellent in adhesion to each electrode and conductivity can be obtained. The metal material is pressure-formed on each of the bonding surfaces by a bump bonder. When the protrusion formed at the center front end of the bump upper surface is pressed by a leveler and flattened, a bump having substantially the same width from the bottom surface to the upper surface can be formed. The shape of the side surface of the bump can be adjusted by adjusting the pressure. It is preferable that the side surfaces of the bumps have a tapered shape, and that the light emitted from the fluorescent substance and the light emitting element in the translucent mold member can be reflected and scattered on the side surfaces to improve the light extraction efficiency. it can.

In the case of the metal material, the bumps are 20 to 50.
It is preferable to form it with a height of μm. Further, the bumps can be formed in a thick film by using a material such as plating. For example, it can be formed at a height of 5 to 150 μm by electroless Ni plating. In addition, bumps made of electroless Ni
A two-layer structure in which electroless Au plating is provided on the plating may be employed. For example, 5-100 μm of electroless Ni plating
m, and electroless A is formed on the electroless Ni plating.
It is preferable to form the u-plate at a height of 5,000 Å or less, since the bonding property becomes good. A light-transmissive mold member containing a fluorescent substance is provided on the semiconductor layer side of the device on which the bumps are formed in this way (second step). So that the upper surfaces of the bumps are substantially coplanar, and the thickness of the entire bump is 5 μm to 150 μm, preferably 5 μm to 10
The translucent mold member and the bump are simultaneously polished so as to have a thickness of 0 μm, more preferably 50 μm to 100 μm, to expose the surface of the bump (third step). As described above, by setting the height of the bumps in the above range, the color tone unevenness is suppressed, and a light emitting device having excellent optical characteristics can be obtained.

Also, in the case of a light emitting element which has a pair of positive and negative electrodes on the same surface side and emits visible light, like the light emitting element used in this embodiment, the current density near the negative electrode is increased and the color is increased. Unevenness tends to occur. In the present invention, a bump is provided on each electrode of the light emitting element, and the upper surface of the bump is formed so as to be substantially flush with the upper surface of the light-transmitting mold member, which is a light extraction surface, so that the bump is generated between the electrodes. A light emitting device capable of improving color unevenness and emitting light uniformly can be obtained.

(Fluorescent Material) The fluorescent material used in the light emitting device of the present invention is yttrium activated with cerium which can emit light by exciting light emitted from a semiconductor light emitting element having a nitride semiconductor as a light emitting layer. It is based on an aluminum oxide-based fluorescent substance. Specific yttrium / aluminum oxide-based fluorescent materials include YAlO
₃ : Ce, Y ₃ Al ₅ O ₁₂ Y: Ce (YAG: Ce)
And Y ₄ Al ₂ O ₉ : Ce, and a mixture thereof. The yttrium / aluminum oxide-based fluorescent substance may contain at least one of Ba, Sr, Mg, Ca, and Zn. In addition, by containing Si, the crystal growth reaction can be suppressed and the particles of the fluorescent substance can be made uniform.

In the present specification, the yttrium / aluminum oxide-based fluorescent material activated by Ce shall be interpreted in a particularly broad sense, and a part or the whole of yttrium is composed of Lu, Sc, La, Gd and Sm. At least one element selected from the group or a part or the whole of aluminum is replaced with Ba, Tl, Ga, I
The term “n” is used in a broad sense including a phosphor having a fluorescent action in which either or both are substituted.

More specifically, the general formula (Y_zGd_1-z)
₃Al₅O₁₂: Ce (however, 0 <z ≦ 1)
Photoluminescent phosphors and general formulas (Re_1-aSm
_a) ₃Re ‘₅O₁₂: Ce (provided that 0 ≦ a <1, 0 ≦
b ≦ 1, Re is selected from Y, Gd, La, Sc
At least one of Re 'is selected from Al, Ga, and In
Is at least one kind. Photoluminum indicated by)
It is a luminescent phosphor.

Since this fluorescent substance has a garnet structure,
Resistant to heat, light and moisture, and has a peak in the excitation spectrum of 45
It can be set to around 0 nm. Also, the emission peak is near 580 nm and has a broad emission spectrum extending down to 700 nm.

In addition, the photoluminescent phosphor contains Gd (gadolinium) in the crystal, so that 460
It is possible to increase the excitation light emission efficiency in a long wavelength region of not less than nm. Due to the increase in the Gd content, the emission peak wavelength shifts to a longer wavelength, and the entire emission wavelength shifts to the longer wavelength side.
That is, when a reddish luminescent color is required, it can be achieved by increasing the replacement amount of Gd. On the other hand, as Gd increases, the emission luminance of photoluminescence due to blue light tends to decrease. Further, Tb, Cu, Ag, Au, Fe, Cr, Nd, Dy, C
o, Ni, Ti, Eu and the like can be contained.

Moreover, in the composition of the yttrium-aluminum-garnet-based phosphor having a garnet structure, the emission wavelength shifts to the shorter wavelength side by partially replacing Al with Ga. Further, by substituting a part of Y in the composition with Gd, the emission wavelength shifts to the longer wavelength side.

When a part of Y is substituted with Gd, the substitution with Gd is less than 10%, and the content (substitution) of Ce is 0.0%.
It is preferable to set the value to 3 to 1.0. 2 substitutions with Gd
Below the percent, the green component is large and the red component is small,
By increasing the content of Ce, the red component can be supplemented, and 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. In addition, when a photoluminescent phosphor adjusted to have many red components is used, a light emitting device capable of emitting an intermediate color such as pink can be formed.

Such a photoluminescent phosphor is
An oxide or a compound that easily becomes an oxide at a high temperature is used as a raw material for Y, Gd, Al, and Ce, and these are sufficiently mixed in a stoichiometric ratio to obtain a raw material. Or Y, Gd,
A coprecipitated oxide obtained by calcining a solution obtained by dissolving a rare earth element of Ce in an acid at a stoichiometric ratio with oxalic acid,
A mixed raw material is obtained by mixing with aluminum oxide. An appropriate amount of a fluoride such as barium fluoride or ammonium fluoride is mixed into the crucible as a flux, and the mixture is placed in a crucible.
Calcined in a temperature range of 0 to 1450 ° C. for 2 to 5 hours to obtain a calcined product, then ball-milled in water, washed,
It can be obtained by separating, drying and finally passing through a sieve.

In the light emitting diode of the present invention, such a photoluminescent phosphor may be a mixture of two or more kinds of yttrium aluminum garnet phosphor activated with cerium and other phosphors.

Other phosphors capable of absorbing blue, blue-green or green to emit red light include sapphire (aluminum oxide) phosphor activated with Eu and / or Cr, and Eu.
And / or Cr-activated Ca-Al ₂ O ₃ activated with Cr
—SiO ₂ phosphor (oxynitride fluorescent glass) and the like. Using these phosphors, white light can also be obtained by mixing colors of light from the light emitting element and light from the phosphors.

The viscosity of the translucent mold member containing the phosphor and the particle size of the phosphor affect the mass productivity at the time of formation. That is, when the viscosity of the material forming the light-transmitting mold member is low or when the particle size of the phosphor is large, the separation and sedimentation due to the difference in specific gravity from the material forming the light-transmitting mold member tends to be promoted. Also, due to crystal destruction in the grinding process,
In the case of inorganic phosphors, the conversion efficiency tends to decrease as the particle size decreases. Further, when the particle size is too small, an aggregate is formed, so that the dispersibility in the translucent mold member is reduced, and color unevenness and luminance unevenness from the light emitting device tend to be caused. Therefore, the average particle size of the phosphor is preferably from 1 to 100 μm, more preferably from 5 to 50 μm, depending on the material of the translucent mold member and the phosphor. Here, the average particle diameter indicates an average particle diameter measured by a sub-sieving sizer based on the air transmission method as a basic principle.

In order to improve the luminous output, the fluorescent material used in the present invention has an average particle size of 10 μm to 50 μm.
μm is preferable, and more preferably 15 μm to 30 μm. A fluorescent substance having such a particle size has high light absorption and conversion efficiency and a wide excitation wavelength range. As described above, by including a large-diameter fluorescent substance having excellent optical characteristics, it becomes possible to satisfactorily convert and emit light around the main wavelength of the light-emitting element, thereby increasing the mass productivity of the light-emitting device. Be improved.

It is preferable that the fluorescent substance having the average particle diameter is contained frequently, and the frequency is preferably 20%.
% To 50% is preferred. By using a fluorescent substance having a small variation in particle diameter, color unevenness is suppressed and a light-emitting device having a favorable color tone can be obtained.

As a specific fluorescent substance used in the present invention, a YAG-based fluorescent substance (Y, Lu, S
Garnet-based phosphor activated with cerium containing at least one element selected from c, La, Gd, and Sm and at least one element selected from the group consisting of Al, Ga, and In) Are listed. The YAG-based phosphor precipitates a solution obtained by dissolving rare earth elements of Y, Gd, and Ce in an stoichiometric ratio in an acid with oxalic acid. A co-precipitated oxide obtained by calcining this is mixed with aluminum oxide to obtain a mixed raw material. The mixture was mixed with ammonium fluoride as a flux and packed in a crucible.
The product is fired for a minute to obtain a fired product. The fired product can be ball-milled in water, washed, separated, dried, and finally passed through a sieve to form a YAG phosphor.

Similarly, another specific phosphor used in the present invention is a nitrogen-containing CaO—Al ₂ O ₃ —SiO ₂ phosphor activated with Eu and / or Cr. Nitrogen-containing CaO-Al activated by Eu and / or Cr
_{The 2} O ₃ —SiO ₂ phosphor is prepared by mixing a powder obtained by mixing a rare earth material with a material such as aluminum oxide, yttrium oxide, silicon nitride, and calcium oxide at a predetermined ratio in a nitrogen atmosphere at 1300 ° C. to 1900 ° C. (more preferably 150 ° C.).
(0 ° C. to 1750 ° C.) and molded. The molded article can be ball-milled, washed, separated, dried, and finally passed through a sieve to form the phosphor. This gives 450
an Eu- and / or Cr-activated Ca-Al-Si-ON-based oxynitride fluorescent glass capable of emitting red light by an excitation spectrum having a peak at nm and blue light having a peak at about 650 nm. can do.

It should be noted that C activated by Eu and / or Cr
By increasing or decreasing the nitrogen content of the a-Al-Si-ON-based oxynitride fluorescent glass, the peak of the emission spectrum can be continuously shifted from 575 nm to 690 nm. Similarly, the excitation spectrum can be shifted continuously. Therefore, white light can be emitted by combined light of a gallium nitride-based compound semiconductor containing GaN or InGaN doped with an impurity such as Mg or Zn in a light-emitting layer and light of a phosphor of about 580 nm. In particular, I which can emit light of about 490 nm with high luminance
Light emission can be obtained ideally in combination with a light-emitting element made of a gallium nitride-based compound semiconductor containing nGaN in the light-emitting layer.

Further, the above-described YAG-based phosphor activated with Ce and the nitrogen-containing Ca-activated with Eu and / or Cr are used.
Combination with Al-Si-ON-based oxynitride fluorescent glass makes use of a light-emitting element capable of emitting blue light to emit light with extremely high color rendering properties including RGB (red, green, blue) components at high luminance. A diode can also be formed. For this reason, an arbitrary intermediate color can be formed very simply by adding a desired pigment. In the present invention, any of the phosphors is an inorganic phosphor, and a light emitting diode having both high contrast and excellent mass productivity can be formed by using an organic light scattering agent or SiO ₂ .

(Translucent Mold Member) Such a fluorescent substance is contained in a translucent mold member. As a material of the light-transmitting mold member, a material having high light resistance to light from a light-emitting element and a fluorescent substance and excellent in light-transmitting property is preferable.
Also, when working as a protective film for covering the light emitting element,
Some rigidity is required. As the material of the translucent mold member, specifically, epoxy resin, silicone resin,
A non-solvent such as a urethane resin, an unsaturated polyester resin, an acryl urethane resin, and a polyimide resin, or a solvent-type liquid translucent thermosetting resin is preferably used. Similarly, a solvent-type liquid translucent thermoplastic resin such as an acrylic resin, a polycarbonate resin, and a polynorbornene resin can be used. Furthermore, not only organic substances but also inorganic substances such as silicon dioxide, or hybrid resins obtained by mixing silicon dioxide formed by a sol-gel method and acrylic resins can be suitably used. When the translucent mold member such as a convex lens member is further covered with a resin or the like, the resin can be selected from the above-described resins in consideration of the adhesion to the convex lens member and the like.

In the present invention, the translucent mold member 9 containing a fluorescent substance is provided on the upper surface and side surfaces of the device in a wafer state. By performing in the state of a wafer in this way,
Polishing can be performed later to adjust the film thickness to a preferable value, so that a light-emitting device having an ideal color tone can be formed.
Further, by providing the translucent mold member containing the fluorescent substance so as to cover up to the side surface of the device, light from the side surface of the device can be converted into color and emitted, thereby suppressing color tone unevenness. Further, the light emitting diode of the present invention,
Since there is no thing such as a wire necessary for electrical connection in the translucent mold member containing the fluorescent substance, there is nothing to block the light, and the light extraction efficiency is good.

In the present invention, the upper surface of the light-transmitting mold member serving as the light emitting surface is substantially flush with the upper surface of the bump on the electrode of the light emitting element. Here, in the present specification, the term “substantially the same plane” has a broad meaning as long as the entire side surface of the bump is coated with the translucent mold resin. By covering the bump with the translucent mold member without exposing the side surface of the bump in this manner, it is possible to prevent moisture from being absorbed from the interface between the bump and the translucent mold member. preferable. Further, the shape of the upper surface of the mold member is not particularly limited, and may have a curved shape or may have irregularities. In such a configuration, a lens effect is obtained and good directivity characteristics are obtained. Is obtained.

In the light emitting device thus obtained, the upper surface of the light emitting device comprising the upper surface of the bump 8 and the translucent molding member 9 containing the fluorescent substance is substantially parallel to the lower surface of the light emitting device on the substrate side. Various implementations are possible and preferred. Further, it is preferable that the light emitting device is a substantially rectangular parallelepiped because a plurality of light emitting devices can be easily mounted densely. In particular, when a light emitting element having both electrodes on the same surface side is used, a bump is provided on each of the electrodes, and the conductive connection portions of each of the positive and negative electrodes have the same height from the element bottom side, so that lead electrodes and the like can be obtained. When conducting electrical connection between the external electrode and the light emitting device using a wire, the loop shape and the approach angle of each wire can be made equal. As a result, the strength of the wire is improved, and breakage of the wire due to external force or the like can be prevented.

Further, as shown in FIG. 5, the light-transmissive mold member containing the fluorescent material is covered with the upper surface of the bump provided on each electrode of the light-emitting device as an opening so as to cover the periphery of the light-emitting device. It may be provided in all directions. With such a structure, all light emitted from the light emitting element can be favorably converted, and a light emitting device capable of emitting light uniformly can be obtained. In particular, if a translucent mold member containing a fluorescent substance is provided also on the bottom surface on the substrate side, flip mounting becomes possible and output can be improved. On the other hand, in the case where the substrate side of the light emitting device is fixed to the mounting substrate with the die bonding resin facing the mounting substrate, the light emitted from the substrate bottom side of the light emitting element is favorably converted by including the fluorescent substance in the die bonding resin. And can be taken out.

(Reflection film) Reflection film 11 used in the present invention
Is for suppressing emission of light emitted from the substrate side to the outside, improving light extraction efficiency, and obtaining better light emission. Preferred materials for the reflective film include an oxide film formed of a multilayer film and various metals. It is particularly preferable to use a metal film from the viewpoint of ease of formation. As a metal film, specifically, Ag, A having a high reflectance
l and their alloys. These metal films can be formed by a sputtering method, a vacuum evaporation method, or the like. In the present invention, the reflection film may be formed so as to cover at least the bottom surface of the substrate, and is preferably formed continuously so as to cover the side and bottom surfaces of the chip.

[0063]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a light emitting diode according to an embodiment of the present invention will be described. Note that the present invention is not limited to only the examples described below.

Example 1 Each of the semiconductor layers 2 and 3 and blue (470n) were placed on an insulating substrate 1 made of sapphire (C-plane).
m) a light emitting layer (not shown) capable of emitting light by MOVP
It is formed by the E method. After the annealing, the wafer is taken out of the reaction vessel, an insulating film made of a predetermined SiO ₂ or the like is formed on the surface of the uppermost p-type nitride semiconductor layer, and a resist film having a predetermined shape is formed on the insulating film surface. Forming, RI
Etching is performed from the p-type nitride semiconductor layer side by an E (reactive ion etching) device to expose the surface of the n-type nitride semiconductor layer forming the negative electrode. Next, after the insulating film is peeled off with an acid, the first positive electrode 4 made of Ni / Au is formed on almost the entire surface of the uppermost p-type nitride semiconductor layer by 47.
The light transmittance at a wavelength of 0 nm is 40% and the surface resistivity is 2
It is formed with a film thickness of 200 Å so as to be Ω / □. Next, a second positive electrode 5 made of Au is formed on the first positive electrode to a thickness of 0.7 μm by a lift-off method. On the other hand, on the surface of the n-type nitride semiconductor layer exposed by etching, W / Al /
Forming a negative electrode 6 made of W / Au with a film thickness of 0.8 μm;
LED elements.

Next, by patterning, only the bonding portion of each electrode is exposed to cover the entire device.
_The insulating protective film 7 made of 2 is formed with a thickness of 2 μm so that the light transmittance becomes 90% at a wavelength of 470 nm.

In the nitride semiconductor wafer formed as described above, as shown in FIG. 3A, a concave portion for forming a fluorescent material-containing transparent mold member is formed on the side surface of the semiconductor layer by dicing. . Dicing in this manner is preferable because a translucent mold member containing a fluorescent substance can be disposed on the side surface of the light emitting layer of the light emitting element, and color unevenness can be suppressed. In addition, when the wafer is scribed, the pressure applied to the wafer can be reduced, and the warpage and cleavage of the substrate can be suppressed. After dicing, Au, which is the material of the bump 8, is pressed on each bonding surface of each electrode with a bump bomber at a height of 50 μm. (First step).

On the other hand, (Y _0.8 Gd
_{0.2) 3 Al 5 O 12:} 80 parts by weight of Ce, epoxy resin 100 parts by weight of an acid anhydride, an SiO ₂ sufficiently allowed to stir at 65 ° C. as a curing accelerator and diffusing agent, light-transmitting fluorescent substance containing A material for forming the conductive mold member 9 is formed. At this time, the viscosity of the epoxy resin is 700 cp. The material for the phosphor-containing translucent mold member formed as described above is coated with a film having a thickness of 1 so as to cover the bumps by dipping.
Coating at 50 μm (second step). 85 ℃ 1
It is cured by primary curing for 80 minutes and secondary curing at 140 ° C. for 240 minutes.

Next, the bumps 8 and the fluorescent material-containing light-transmitting mold member 9 are polished together from the semiconductor layer side so that the upper surface of the light-transmitting mold member is 40 μm from the light-emitting surface of the light-emitting element. 8 is exposed (third step). Further, the substrate is ground and polished from the substrate side so as to have a thickness of 120 μm.

Finally, after the light-transmitting mold member at the position where the nitride semiconductor wafer is cut is removed by dicing, the scribe line is drawn by a scriber and cut into 300 μm square chips by an external force (fourth step). .

When a white LED lamp is formed using the light emitting diode formed as described above, the yield is 95%. Thus, by using the light emitting diode of the present invention, a light emitting device can be produced with good mass productivity,
A light emitting device with high reliability and less color tone unevenness can be provided.

(Comparative Example 1) On the other hand, after providing an insulating film, the nitride semiconductor layer semiconductor wafer was cut into chips, and the individual light emitting devices were arranged on the bottom surface in the cup of the mount lead, and the wires were electrically connected. After the connection, the light-emitting diode is formed in the same manner as in Example 1 except that the translucent mold member containing the fluorescent substance is first filled in the cup so as to cover the light-emitting element, and thereafter a translucent convex lens member is provided. Then, the yield is 85%. Further, as compared with the light emitting diode of Example 1, the color tone is uneven.

(Embodiment 2) After the fourth step, the reflection film 11 is formed on the sapphire substrate side by a sputtering method using the sheet expand 10 for each light emitting diode.
When the light emitting diode is formed in the same manner as in the first embodiment except that the step is performed, the same effect as in the first embodiment can be obtained. Further, light from the end face can be favorably extracted to the light emitting surface, so that a high output light emitting diode can be obtained.

(Embodiment 3) After the fourth step, a light-emitting diode is formed in the same manner as in Embodiment 1 except that a light-transmitting mold member containing a fluorescent substance is formed on each of the light-emitting diodes from the substrate side to the periphery of the substrate. Is formed, a light emitting device having the phosphor-containing translucent mold member on the entire outer periphery other than the exposed surface of the bump provided on the light emitting element is obtained, and the same effects as those of the first embodiment are obtained. Since the light emitted from the light emitting element in all directions can be favorably color-converted, color unevenness is suppressed and more uniform light emission can be obtained.

On the other hand, (Y _0.8 Gd
_0.2 ) ₃ Al ₅ O ₁₂ : 80 parts by weight of Ce, 100 parts by weight of silanol (Si (OEt) 3 OH), and ethanol at twice the weight of the silanol are mixed to form a slurry. After discharging from the nozzle to the wafer and applying the material of the translucent mold member containing the fluorescent material, the silanol is heated at 300 ° C. for 3 hours to convert the silanol to SiO 2
When the light emitting device is formed in the same manner as in the first embodiment except that the fluorescent substance is fixed on the wafer, the same effect as in the first embodiment can be obtained.

[0075]

As described above in detail, in the light emitting device according to the present invention, before cutting the wafer into chips, bumps are formed on each electrode to increase the conductive portion, and the phosphor-containing light-transmitting light is transmitted. By providing the conductive mold member on the semiconductor layer side, a color conversion type light emitting device having high reliability and excellent optical characteristics can be efficiently produced.

Further, since the light emitting device of the present invention has a transparent mold member containing a fluorescent substance over the entire surface of the light emitting element with the bump exposed surface as an opening, light from the light emitting element can be efficiently emitted by the fluorescent substance. It can be converted, and a desired color tone can be emitted uniformly. Therefore, external deterioration due to light from the light emitting element can be suppressed.

Further, by providing a continuous insulating reflection film on the substrate side, a light emitting device having good light extraction efficiency and less emission unevenness can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a light emitting diode according to an embodiment of the present invention.

FIG. 2 is a schematic plan view of a light emitting diode according to another embodiment of the present invention.

FIG. 3 is a method for forming a light emitting diode according to an embodiment of the present invention.

FIG. 4 is a step of another method for forming a light emitting diode according to the embodiment of the present invention.

FIG. 5 is a schematic sectional view of another light emitting diode according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... N-type nitride semiconductor layer 3 ... P-type nitride semiconductor layer 4 ... 1st positive electrode 5 ... 2nd positive electrode 6 ... Negative electrode 7 ... -Insulating film 8-Bump 9-Transparent mold member containing fluorescent material 10-Sheet expand 11-Reflective film

 ────────────────────────────────────────────────── ─── Continued on the front page F term (reference) 4H001 CA07 XA07 XA08 XA13 XA14 XA20 XA39 YA24 YA58 YA63 5F041 AA14 AA41 AA47 CA34 CA40 CA46 CA76 CA82 CA92 CA93 CA98 DA43 DA44 DA45 DB09 EE23 EE25

Claims (8)

[Claims] A light emitting element having a semiconductor layer on a substrate;
A fluorescent substance capable of absorbing a part of light from the light emitting element and emitting light of a longer wavelength than the fluorescent substance; and a translucent mold member having the fluorescent substance and surrounding the surface of the light emitting element. A light emitting device, comprising: at least one bump on an electrode of the light emitting element, wherein an upper surface of the bump is substantially flush with an upper surface of the translucent mold member. 2. The bump has a thickness of 5 μm to 150 μm.
The light emitting device according to claim 1, wherein: 3. The light emitting device according to claim 1, wherein an upper surface of the light emitting device including an upper surface of the bump and an upper surface of the translucent mold member is parallel to a bottom surface on the substrate side. 4. The phosphor is a yttrium-aluminum-garnet-based phosphor activated with Ce, Eu.
And / or Cr-activated CaO-Al ₂ O activated with Cr
The light emitting device according to claim 1, wherein the light emitting device is one selected from a _3- SiO ₂ fluorescent material. 5. The light emitting device according to claim 1, further comprising a continuous reflection film on at least the substrate side of the light emitting element. 6. A light emitting element having a semiconductor layer on a substrate;
A fluorescent substance capable of absorbing a part of light from the light emitting element and emitting light of a longer wavelength than the fluorescent substance; and a translucent mold member having the fluorescent substance and surrounding the surface of the light emitting element. A method of forming a light-emitting device, comprising: a first step of forming a bump on an electrode of the light-emitting element in a wafer state; and a step of forming the light-transmitting mold member so as to cover the bump on a semiconductor layer side of the light-emitting element. And a third step of exposing the upper surface of the bump in parallel with the bottom surface of the wafer from the semiconductor layer side by polishing.
And a fourth step of cutting by dicing and scribing the wafer. 7. The method according to claim 6, wherein, after the fourth step, a continuous translucent mold member is formed on at least the substrate side of the light emitting element. 8. The method according to claim 6, wherein, after the fourth step, a continuous reflective film is formed on at least the substrate side of the light emitting element.