JP3951300B2 - Light emitting device and method for manufacturing light emitting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light emitting device and a method for manufacturing the same.
[0002]
[Prior art]
[Patent Document 1]
Japanese Patent Laid-Open No. 7-66455 [Patent Document 2]
JP 2001-339100 A [Non-Patent Document 1]
Nikkei Electronics October 21, 2002, pages 124-132
As a result of many years of progress in materials and element structures used in light-emitting elements such as light-emitting diodes and semiconductor lasers, the photoelectric conversion efficiency inside the elements is gradually approaching the theoretical limit. Therefore, when an element with higher luminance is to be obtained, the light extraction efficiency from the element is extremely important. For example, in a light emitting device having a light emitting layer portion formed of AlGaInP mixed crystal, a thin AlGaInP (or GaInP) active layer is sandwiched between an n-type AlGaInP cladding layer and a p-type AlGaInP cladding layer having a larger band gap. By adopting a sandwiched double hetero structure, a high-luminance element can be realized. Such an AlGaInP double heterostructure can be formed by epitaxially growing each layer of an AlGaInP mixed crystal on a GaAs single crystal substrate by utilizing the lattice matching of the AlGaInP mixed crystal with GaAs. When this is used as a light emitting element, a GaAs single crystal substrate is usually used as an element substrate as it is. However, since the AlGaInP mixed crystal constituting the light emitting layer has a larger band gap than GaAs, the emitted light is absorbed by the GaAs substrate, and it is difficult to obtain sufficient light extraction efficiency. In order to solve this problem, a method (for example, Patent Document 1) in which a reflective layer made of a semiconductor multilayer film is inserted between a substrate and a light emitting element has also been proposed. Therefore, only light incident at a limited angle is reflected, and a significant improvement in light extraction efficiency cannot be expected in principle.
[0004]
Therefore, Patent Document 2 discloses a technique in which a growth GaAs substrate is peeled off while a reinforcing element substrate (having conductivity) is bonded to a peeled surface through a reflective Au layer. Yes. This Au layer has an advantage that the reflectivity is high and the dependency of the reflectivity on the incident angle is small. However, as is apparent from the fact that the Au layer appears to be colored yellow under white light, the Au layer has a large absorption with respect to light in a specific wavelength band, and the light emitting device has a peak wavelength set in the wavelength range. There is a problem in that the reflectance decreases due to absorption. On the other hand, Non-Patent Document 1 discloses a light-emitting element in which the reflection intensity is increased by forming a reflection layer with Al whose wavelength dependency of reflectance is smaller than that of Au. In the element structure of Non-Patent Document 1, an Al reflective layer is disposed between a light emitting layer portion and an element substrate made of a silicon substrate, and further, a silicon substrate and a light emitting layer are disposed between the Al reflective layer and the silicon substrate. In order to facilitate the bonding and bonding with the part, an Au layer is interposed. Specifically, an Au layer is formed so as to cover the Al reflective layer formed on the light emitting layer side, and an Au layer is also formed on the other silicon substrate side, and the Au layers are adhered to each other and bonded together. I am doing so.
[0005]
[Problems to be solved by the invention]
However, in the configuration of Non-Patent Document 1, the Al layer and the Au layer are formed in contact with each other. However, even when the bonding is performed at a relatively low temperature, the Al layer forming the reflective layer is alloyed with the Au layer by diffusion. This causes a problem that the reflectance decreases.
[0006]
An object of the present invention is to provide a bonding metal layer in a light emitting device having a structure in which a light emitting layer portion is covered with a reflective metal layer, and the reflective metal layer is bonded to an element substrate through another bonding metal layer. It is an object of the present invention to provide a light emitting element that can effectively prevent the diffusion of components from the metal to the reflective metal layer, and thus hardly causes defects such as a decrease in reflectance due to the diffusion, and a method for manufacturing the same.
[0007]
[Means for solving the problems and actions / effects]
In order to solve the above-described problems, the light-emitting element of the present invention includes:
The first main surface of the compound semiconductor layer having a light emitting layer portion and the light extraction surface, the second main surface side of the compound semiconductor layer, a reflective surface for reflecting light from the light emitting layer portion on the light extraction surface side are reflective metal layer is formed having a said with reflective metal layer is bonded to the element substrate through a bonding metal layer, between the bonding metal layer and the reflective metal layer, said binding metal layer A diffusion preventing layer on the side of the reflective metal layer that prevents the metal component of the metal from diffusing to the reflective metal layer side is interposed, and further, a conductive material is used between the element substrate and the coupling metal layer. In addition, a substrate-side diffusion blocking layer that blocks diffusion of components derived from the element substrate into the bonding metal layer is interposed .
[0008]
In the light emitting device of the present invention, component diffusion occurs from the coupling metal layer to the reflection metal layer by interposing the reflection metal layer side diffusion blocking layer between the reflection metal layer and the coupling metal layer, and thus Therefore, it is possible to effectively suppress a decrease in the reflectance of the reflective metal layer due to the diffusion of the components, thereby realizing a light-emitting element with high luminance.
[0009]
In addition, the method for manufacturing the light emitting device of the present invention includes:
The first main surface of the compound semiconductor layer having the light emitting layer portion is used as a light extraction surface, and a reflection surface that reflects light from the light emitting layer portion to the light extraction surface side is provided on the second main surface side of the compound semiconductor layer. In the method of manufacturing a light emitting device, the reflective metal layer is formed, and the reflective metal layer is bonded to the element substrate through the bonding metal layer.
Reflective metal that prevents the metal component of the reflective metal layer and the bonding metal layer from diffusing to the reflective metal layer side between the bonded main surface of the compound semiconductor layer and the bonded main surface of the element substrate a layer-side diffusion blocking layers, wherein a bonding metal layer, and the substrate-side diffusion barrier layer for preventing diffusion to the bonding metal layer of components derived from the element substrate, in this order from the side of the compound semiconductor layer It is characterized by being laminated and bonded so as to intervene in a stacked form.
[0010]
According to the method for manufacturing a light emitting device of the present invention, since the reflection metal layer side diffusion blocking layer is interposed between the reflection metal layer and the bonding metal layer, the bonding is performed. Component diffusion occurs from the metal layer to the reflective metal layer, and in turn, the reflectance reduction of the reflective metal layer due to the component diffusion can be effectively suppressed, and thus a high-luminance light-emitting element can be easily realized. In particular, the effect of the present invention becomes more remarkable when heat treatment that facilitates diffusion is performed during bonding.
[0011]
The bonding metal layer is interposed between the reflective metal layer and the element substrate to assist the bonding when the reflection metal layer alone is relatively difficult to bond to the element substrate. In many cases, the reflectance itself with respect to light from the light emitting layer is inferior to that of the reflective metal layer. Thus, when a metal having a lower reflectance than the reflective metal layer is used for light from the light emitting layer portion, when the metal component from the bonding metal layer diffuses into the reflective metal layer, the reflectance decreases. It can be said that defects are likely to occur. Therefore, as in the present invention, if a reflection metal layer side diffusion blocking layer is interposed between the coupling metal layer and the reflection metal layer, the effect of suppressing the reduction in reflectance due to the diffusion is particularly remarkable.
[0012]
Specifically, this is a case where the bonding metal layer is composed of an Au-based metal containing Au as a main component (in this specification, “main component” is a component having the highest mass content). Say). Since Au is chemically stable and a thick and strong passive film such as Al is hardly formed, it is suitable as a material for the bonding metal layer. In particular, the metal reflective layer, the reflective metal layer side diffusion blocking layer, and the first Au-based metal layer are formed in this order from the main surface side to the bonding side main surface of the compound semiconductor layer, while the element substrate is bonded. When the second Au-based metal layer is formed on the side main surface and the first Au-based metal layer and the second Au-based metal layer are adhered and bonded together, the affinity between the Au-based metal layers is strong. In addition, there is an advantage that sufficient bonding strength can be easily obtained even at a relatively low temperature.
[0013]
However, as described above, Au exhibits strong absorption with respect to light in a specific wavelength band, and the reflectance with respect to light in the wavelength band is never good. FIG. 4 shows the reflectance on various polished metal surfaces, and the plot point “Δ” is the reflectance of Au. Au has strong absorption in the visible light region with a wavelength of 670 nm or less (especially, absorption is larger at 650 nm or less: 600 nm or less), and when a large amount of diffusion from the Au-based coupling metal layer to the reflective metal layer occurs, the light emitting layer portion In the case where the peak emission wavelength of is present at 670 nm or less, the reflectance is significantly reduced. As a result, the emission intensity is likely to decrease, and the spectrum of the extracted light becomes different from the original emission spectrum due to absorption, and the emission color tone is likely to change. However, if the reflective metal layer side diffusion blocking layer is interposed as in the present invention, the above-described problems can be effectively suppressed.
[0014]
On the other hand, the reflective metal layer can be made of an Al-based metal containing Al as a main component. According to the wavelength dependence of the reflectance of the Al layer shown in FIG. 4 (plot point “♦”), there is no strong absorption like Au even in the visible light region with a wavelength of less than 550 nm, and much more than Au. It is inexpensive and can be suitably used in the present invention as a general-purpose reflective layer. In particular, the reflectance is better than Au for the light emission wavelength range from 400 nm to 550 nm in the range from blue to green, which contributes to the improvement of light extraction efficiency.
[0015]
However, when the Au-based coupling metal layer is formed in direct contact with the Al-based reflective metal layer, the present inventor has examined that the Au-based coupling metal layer is formed even in a relatively low temperature range up to about 115 ° C. It has been found that the diffusion of Au into the Al-based reflective metal layer has progressed significantly, leading to a significant decrease in reflectivity, and in particular, a significant decrease in reflectivity in the blue to green emission wavelength range of wavelengths from 400 nm to 550 nm. did. However, if the reflective metal layer side diffusion blocking layer is interposed as in the present invention, the above problem can be effectively suppressed.
[0016]
Moreover, the part which forms the reflective surface of a reflective metal layer can also be made into Ag type reflective layer which has Ag as a main component. The Ag-based reflective metal layer exhibits better reflectivity than the Au-based metal over almost the entire wavelength range (350 nm to 700 nm) of visible light, and the wavelength dependency of the reflectivity is small. As a result, high light extraction efficiency can be realized regardless of the emission wavelength of the element. Further, when compared with the Au-based reflective metal layer, the reflectance is less likely to be reduced due to the formation of an oxide film or the like for blue to green light emission. The plot point “■” in FIG. 4 indicates the wavelength dependence of the reflectance of Ag. The plotted point “x” is an AgPdCu alloy. The reflectance of Ag is particularly good at a reflectance of 350 nm to 700 nm (and an infrared region longer than that), particularly 380 nm to 700 nm. Naturally, a good reflectance can be obtained even in a blue to green emission wavelength region having a peak wavelength of 400 nm or more and 550 nm or less. The Al-based reflective metal layer described above is less expensive than the Ag-based reflective metal layer, but the reflectance in the visible light region is somewhat lower (for example, 85) because of the decrease in reflectance due to the formation of an oxide film. -92%). On the other hand, since an Ag-based reflective metal film is less likely to form an oxide film than an Al-based reflective metal layer, a higher reflectance than Al can be secured in the visible light region. If the reflection metal layer side diffusion blocking layer is interposed as in the present invention, Au component diffusion from the Au-based coupling metal layer to the Ag-based reflection metal layer can be effectively suppressed.
[0017]
In the case of using the Au-based bonding metal layer, the reflection metal layer side diffusion blocking layer can be specifically a metal layer mainly composed of any one of Ti, Ni and Cr. A metal mainly composed of Ti, Ni, or Cr has a small diffusion coefficient with respect to Au and is excellent in the effect of suppressing the diffusion of the Au component into the reflective metal layer, and thus can be suitably used in the present invention. The thickness of the reflective metal layer side diffusion blocking layer is desirably 1 nm or more and 10 μm or less. If the thickness is less than 1 nm, the diffusion preventing effect is not sufficient, and if it exceeds 10 μm, the effect is saturated, leading to a wasteful increase in manufacturing cost. In addition, the reflective metal layer side diffusion blocking layer can specifically adopt pure Ti, pure Ni or pure Cr for industrial use, but contains subcomponents as long as the effect of preventing diffusion against Au is not impaired. It is possible to make it. For example, addition of an appropriate amount of Pd has an effect of improving the corrosion resistance of a metal mainly composed of Ti, Ni, or Cr. An alloy of Ti, Ni, and Cr can also be used.
[0018]
Next, the light emitting device of the present invention is composed of a conductive material between the element substrate and the bonding metal layer, and prevents the components derived from the element substrate from diffusing into the bonding metal layer. A side diffusion blocking layer can be interposed. According to this structure, component diffusion from the element substrate to the bonding metal layer is blocked by the substrate-side diffusion blocking layer, and as a result, alteration of the bonding metal layer due to the diffusion can be effectively suppressed. As a result, problems such as a decrease in adhesion strength between the bonding metal layer and the element substrate and a decrease in reflectivity due to component diffusion of the element substrate to the reflective metal layer are effectively suppressed. The product yield is not easily reduced.
[0019]
The above configuration is particularly effective when applied when the bonding metal layer is an Au-based metal layer containing Au as a main component and the element substrate is a Si substrate. That is, the Si substrate can easily ensure sufficient conductivity as a light emitting element by doping, and is inexpensive. However, Si and Au are likely to cause a eutectic reaction at a relatively low temperature (the eutectic temperature of the Au—Si binary system is 363 ° C., but the eutectic temperature is further lowered when other alloy components are present. In the case where bonding is performed by heat treatment, the diffusion of Si on the substrate side to the Au-based metal layer side is also likely to proceed. As a result, the Au-based layer in the metal layer tends to cause a decrease in reflectance due to the Si diffusion. However, if a substrate side diffusion blocking layer is provided between the Au-based metal layer and the Si substrate, Si diffusion into the Au-based metal layer can be effectively suppressed.
[0020]
When the Au-based metal layer and the Si substrate are used, specifically, the substrate-side diffusion blocking layer can be a metal layer mainly containing any one of Ti, Ni, and Cr. A metal containing Ti, Ni, or Cr as a main component is particularly excellent in the effect of suppressing the diffusion of Si into the Au-based metal layer, and thus can be suitably employed in the present invention. The thickness of the substrate side diffusion blocking layer is preferably 1 nm or more and 10 μm or less. If the thickness is less than 1 nm, the diffusion preventing effect is not sufficient, and if it exceeds 10 μm, the effect is saturated, leading to a wasteful increase in manufacturing cost. In addition, although the substrate side diffusion blocking layer can specifically employ industrial pure Ti, pure Ni or pure Cr, in a range where the effect of preventing diffusion of Si to the Au-based metal layer is not impaired, Subcomponents such as Pd can be contained, and an alloy of Ti, Ni, and Cr can also be used.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the accompanying drawings.
FIG. 1 is a conceptual diagram showing a light emitting device 100 according to an embodiment of the present invention. The light emitting element 100 has a structure in which a light emitting layer portion 24 is bonded to a first main surface of a Si substrate 7 made of an n-type Si (silicon) single crystal, which is a conductive substrate forming an element substrate, with a metal layer 10 interposed therebetween. Have.
[0022]
The light emitting layer portion 24 includes the active layer 5 made of a non-doped (Al _x Ga _1-x ) _y In _1-y P (where 0 ≦ x ≦ 0.55, 0.45 ≦ y ≦ 0.55) mixed crystal. , the first-conductivity-type cladding layer, in this embodiment the p-type cladding layer 6 made of p-type _{(Al z Ga 1-z)} y in 1-y P ( except x <z ≦ 1), wherein the first conductivity type the second-conductivity-type cladding layer different from the clad layer, in this embodiment interposed by an n-type _{(Al z Ga 1-z)} y in 1-y P ( except x <z ≦ 1) n-type cladding layer 4 made of According to the composition of the active layer 5, the emission wavelength can be adjusted in the green to red region (the emission wavelength (peak emission wavelength) is 550 nm or more and 670 nm or less). In the light emitting device 100, the p-type AlGaInP cladding layer 6 is disposed on the metal electrode 9 side, and the n-type AlGaInP cladding layer 4 is disposed on the coupling metal layer 10k side. Therefore, the conduction polarity is positive on the metal electrode 9 side. The term “non-doped” as used herein means “does not actively add dopant”, and contains a dopant component inevitably mixed in a normal manufacturing process (for example, 10 ¹³ to 10 ¹⁶ / cm 3). It is not excluded that the upper limit is about ³ ).
[0023]
A current diffusion layer 20 made of AlGaAs is formed on the main surface of the light emitting layer 24 opposite to the surface facing the substrate 7, and the light emitting layer 24 emits light at substantially the center of the main surface. A metal electrode (for example, Au electrode) 9 for applying a driving voltage is formed so as to cover a part of the main surface. A region around the metal electrode 9 on the main surface of the current diffusion layer 20 forms a light extraction region from the light emitting layer portion 24. Further, a metal electrode (back electrode: for example, an Au electrode) 15 is formed on the back surface of the Si single crystal substrate 7 so as to cover the entire surface. When the metal electrode 15 is an Au electrode, an AuSb contact metal layer 16 is interposed between the metal electrode 15 and the Si single crystal substrate 7 as a substrate-side contact metal layer. Instead of the AuSb contact metal layer 16, an AuSn contact metal layer may be used as the substrate-side contact metal layer.
[0024]
The Si single crystal substrate 7 is manufactured by slicing and polishing a Si single crystal ingot, and the thickness thereof is, for example, 100 μm or more and 500 μm or less. Then, the light emitting layer portion 24 is bonded with the metal layer 10 interposed therebetween. The metal layer 10 includes a reflective metal layer 10c on the light emitting layer portion 24 side, a coupling metal layer 10a on the light emitting layer portion 24 side, a coupling metal layer 10b on the Si substrate 7 side, and a reflective metal layer 10c. And a reflection metal layer side diffusion blocking layer 10f interposed between the coupling metal layers 10a and 10b (= 10k). In this embodiment, the reflective metal layer 10c is an Al-based metal layer (Al layer), and the coupling metal layers 10a and 10b (= 10k) are Au-based metal layers (for example, Au layers). Further, the reflection metal layer side diffusion blocking layer 10f is a Ti-based metal layer (for example, a Ti layer), and has a thickness of 1 nm to 10 μm (200 nm in this embodiment). The reflective metal layer side diffusion blocking layer 10f may be a Ni-based metal layer (for example, a Ni layer) or a Cr-based metal layer (for example, a Cr layer) instead of the Ti-based metal layer.
[0025]
On the other hand, an AuGeNi contact metal layer 32 (for example, Ge: 15 mass%, Ni: 10 mass%) is formed as the light emitting layer section side contact metal layer between the light emitting layer section 24 and the reflective metal layer 10 c. This contributes to reducing the series resistance of the element. The AuGeNi contact metal layer 32 is dispersedly formed on the main surface of the light emitting layer portion 24 , and the formation area ratio thereof is 1% or more and 25% or less. An AuSb contact metal layer 31 (for example, Sb: 5 mass) as a substrate-side contact metal layer is in contact with the main surface of the Si single crystal substrate 7 between the Si single crystal substrate 7 and the bonding metal layer 10k. %) Is formed. Note that an AuSn contact metal layer may be used in place of the AuSb contact metal layer 31.
[0026]
The entire surface of the AuSb contact metal layer 31 is covered with a substrate side diffusion blocking layer 10d made of a Ti-based metal layer (for example, a Ti layer). The thickness of the substrate-side diffusion blocking layer 10d is 1 nm or more and 10 μm or less (200 nm in this embodiment). The substrate-side diffusion blocking layer 10d may be a Ni-based metal layer (for example, Ni layer) or a Cr-based metal layer (for example, Cr layer) instead of the Ti-based metal layer. A coupling metal layer 10k (Au-based metal layer) is arranged so as to cover the entire surface of the substrate-side diffusion blocking layer 10d so as to be in contact therewith.
[0027]
The light from the light emitting layer portion 24 is extracted in a form in which the light reflected directly from the light extraction surface is superimposed on the light reflected by the reflective metal layer 10c. The thickness of the reflective metal layer 10c is desirably 80 nm or more in order to ensure a sufficient reflection effect. Moreover, although there is no restriction | limiting in particular in the upper limit of thickness, since a reflective effect is saturated, it determines suitably (for example, about 1 micrometer) by balance with cost. The layer thickness of the coupling metal layer 10k is 200 nm or more and 10 μm or less.
[0028]
Hereinafter, a method for manufacturing the light emitting device 100 of FIG. 1 will be described.
First, as shown in Step 1 of FIG. 2, a p-type GaAs buffer layer 2 is made of, for example, 0.5 μm and AlAs on the main surface of a GaAs single crystal substrate 1 which is a semiconductor single crystal substrate forming a light emitting layer growth substrate. The peeling layer 3 is epitaxially grown by, for example, the well-known MOVPE (Metal-Organic Vapor Phase Epitaxy) method in this order, for example, 0.5 μm, and the current diffusion layer 20 made of p-type AlGaAs, for example, 5 μm. Thereafter, a 1 μm p-type AlGaInP cladding layer 6, a 0.6 μm AlGaInP active layer (non-doped) 5, and a 1 μm n-type AlGaInP cladding layer 4 are epitaxially grown in this order as the light emitting layer portion 24.
[0029]
Next, as shown in step 2, AuGeNi contact metal layers 32 are dispersedly formed on the main surface of the light emitting layer portion 24. After forming the AuGeNi contact metal layer 32, an alloying heat treatment is then performed in a temperature range of 350 ° C. or more and 500 ° C. or less. An alloying layer is formed between the light emitting layer portion 24 and the AuGeNi contact metal layer 32 by the alloying heat treatment, and the series resistance is greatly reduced. Thereafter, a reflective metal layer 10c made of an Al-based metal layer is formed so as to cover the AuGeNi contact metal layer 32 (thickness, for example, 300 nm), and then the reflective metal layer-side diffusion blocking layer 10f made of a Ti-based metal layer (thickness: For example, 200 nm). Then, a first Au-based metal layer 10a (thickness: 2 μm, for example) serving as a bonding metal layer is formed so as to further cover the reflective metal layer 10c and the reflective metal layer side diffusion blocking layer 10f. At this time, the Al-based reflective metal layer 10c is formed so as to cover a region excluding the outer peripheral edge portion of the main surface of the light emitting layer portion 24, and the first Au-based metal layer 10a is disposed outside the outer peripheral edge of the reflective metal layer 10c. The peripheral surface of the Al-based reflective metal layer 10c is covered with the first Au-based metal layer 10a.
[0030]
On the other hand, as shown in step 3, AuSb contact metal layers 31 and 16 (which are AuSn contact metal layers as described above) are formed on both main surfaces of a separately prepared Si single crystal substrate 7 (n-type). And alloying heat treatment is performed in a temperature range of 100 ° C. or more and 500 ° C. or less. Then, on the AuSb contact metal layer 31, a substrate side diffusion blocking layer 10d (thickness: for example 200 nm) made of a Ti-based metal layer and a second Au-based metal layer 10b (thickness: for example 2 μm) are arranged in this order. Form. Further, a back electrode layer 15 (for example, made of an Au-based metal layer) is formed on the AuSb contact metal layer 16. In the above steps, each metal layer can be formed by sputtering or vacuum deposition.
[0031]
Then, as shown in step 4, the second Au-based metal layer 10 b on the Si single crystal substrate 7 side is overlapped with the first Au-based metal layer 10 a formed on the light emitting layer portion 24 and pressed, so that 80 The substrate bonded body 50 is formed by performing a bonding heat treatment at a temperature of not less than 500 ° C. and not more than 500 ° C., for example, 200 ° C. The Si single crystal substrate 7 is bonded to the light emitting layer portion 24 via the first Au-based metal layer 10a and the second Au-based metal layer 10b. Further, the first Au-based metal layer 10a and the second Au-based metal layer 10b are integrated by the bonding heat treatment to form a bonding metal layer 10k. Since both the first Au-based metal layer 10a and the second Au-based metal layer 10b are mainly composed of Au that is difficult to oxidize, the bonding heat treatment can be performed without any problem even in the atmosphere, for example.
[0032]
Here, between the first Au-based metal layer 10a and the metal reflective layer 10c made of an Al-based metal, a metal reflective layer side diffusion blocking layer 10f made of a Ti-based metal layer is interposed. When the metal reflection layer 10c is an Al-based metal layer, if the metal reflection layer-side diffusion blocking layer 10f is omitted, the Au component from the first Au-based metal layer 10a to the metal reflection layer 10c even at a low temperature around 115 ° C. This leads to a problem that the reflectance of the metal reflective layer 10c is lowered (particularly, the emission wavelength region from blue to green having a wavelength of 400 nm to 550 nm). However, when the metal reflection layer side diffusion blocking layer 10f is provided as described above, diffusion of the Au component from the first Au-based metal layer 10a to the metal reflection layer 10c during the bonding heat treatment is effectively suppressed, and the metal reflection is suppressed. The reflectance of the layer 10c can be kept good. If the temperature is up to 360 ° C., even if the heat treatment temperature for bonding is increased, the diffusion of Au into the metal reflective layer 10c made of an Al-based metal does not become significant, and as a result, the bonding temperature is increased. Strength can be improved.
[0033]
Further, a substrate-side diffusion blocking layer 10d made of a Ti metal layer is interposed between the second Au metal layer 10b and the Si single crystal substrate 7 (AuSb contact metal layer 31). During the bonding heat treatment, diffusion of the Si component from the Si single crystal substrate 7 toward the second Au-based metal layer 10b is blocked by the substrate-side diffusion blocking layer 10d and integrated by bonding (first metal layer) (Au-based metal layer / second Au-based metal layer) 10a, 10b, and consequently the seepage of the Si component toward the reflective metal layer 10c is effectively suppressed. As a result, the problem that the reflective surface of the finally obtained reflective metal layer 10c is contaminated by the Si component is prevented, and a good reflectance can be realized. Further, due to the thermal history when the second Au-based metal layer 10b (bonding metal layer) is formed by vapor deposition or the like, Si penetrates through the AuSb contact metal layer 31 from the Si single crystal substrate 7, and the second The Si may spring up on the outermost surface of the Au-based metal layer 10b. When the heated Si is oxidized, the bonding of the second Au-based metal layer (bonding metal layer) 10b and the first Au-based metal layer (bonding metal layer) 10a may be significantly inhibited. However, if the substrate side diffusion blocking layer 10d is formed as described above, the Si upwelling and the oxidation are effectively suppressed, and the Si single crystal substrate 7 and the light emitting layer portion (compound) are formed by the bonding metal layer 10k. The bonding strength with the semiconductor layer 24 can be further increased.
[0034]
Next, the process proceeds to step 5, and the substrate bonded body 50 is immersed in an etching solution made of, for example, a 10% hydrofluoric acid aqueous solution, and the AlAs release layer 3 formed between the buffer layer 2 and the current diffusion layer 20 is selected. By etching, the GaAs single crystal substrate 1 (which is opaque to the light from the light emitting layer portion 24) is peeled from the stacked body 50a of the light emitting layer portion 24 and the Si single crystal substrate 7 bonded thereto. . It should be noted that an etch stop layer made of AlInP is formed in place of the AlAs release layer 3, and a GaAs single crystal is used by using a first etching solution (for example, ammonia / hydrogen peroxide mixed solution) having selective etching properties with respect to GaAs. Etch and remove the substrate 1 together with the GaAs buffer layer 2 and then etch stop using a second etchant that has selective etching properties with respect to AlInP (for example, hydrochloric acid: hydrofluoric acid may be added to remove the Al oxide layer) A step of etching away the layer can also be employed.
[0035]
The reflective metal layer 10c made of an Al-based metal layer is enclosed in the first Au-based metal layer 10a, and the outer peripheral surface of the Al-based reflective metal layer 10c is the outer peripheral edge of the first Au-based metal layer 10a having high corrosion resistance. since it is protected by 10e, in step 5, even when etching the light-emitting layer growing substrate (GaAs single crystal substrate 1), the effect is less likely Oyobi the Al-based reflective metal layer 10c. When the GaAs single crystal substrate 1 is used as a light emitting layer growth substrate and dissolved / removed using an ammonia / hydrogen peroxide mixed solution as an etching solution, Al is particularly easily corroded by the etching solution. Can be used to dissolve and remove the GaAs single crystal substrate 1 without problems.
[0036]
Then, as shown in step 6, an electrode for wire bonding (bonding pad: FIG. 1) is formed so as to cover a part of the main surface of the current diffusion layer 20 exposed by removing the GaAs single crystal substrate 1. Thereafter, the semiconductor chip is diced by a usual method, and this is fixed to a support and wire bonding of a lead wire is performed, followed by resin sealing to obtain a final light emitting element.
[0037]
In the above embodiment, the reflective metal layer 10c made of Al-based metal is used. However, the reflective metal layer 10g made of Ag-based metal can be used as in the light emitting element 200 of FIG. In this case, an Ag-based contact metal layer 132 made of AgGeNi (for example, Ge: 15 mass%, Ni: 10 mass%) is dispersedly formed as the light emitting layer portion side contact metal layer. Other parts are the same as those of the light emitting device 100 of FIG.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a first embodiment of a light emitting device of the present invention in a laminated structure.
2 is an explanatory diagram showing an example of a manufacturing process of the light-emitting element shown in FIG.
FIG. 3 is a schematic view showing a second embodiment of the light-emitting element of the present invention in a laminated structure.
FIG. 4 is a diagram showing the reflectance of various metals.
[Explanation of symbols]
1 GaAs single crystal substrate (light emitting layer growth substrate)
4 n-type cladding layer (second conductivity type cladding layer)
5 active layer 6 p-type cladding layer (first conductivity type cladding layer)
7 Si single crystal substrate (element substrate)
9 Metal electrode 10a First Au-based metal layer (binding metal layer)
10b Second Au-based metal layer (bonded metal layer)
10c Reflective metal layer (Al-based metal layer)
10g Reflective metal layer (Ag metal layer)
10d Substrate side diffusion blocking layer (Ti metal layer)
10f Reflective metal layer side diffusion blocking layer (Ti-based metal layer)
24 Light emitting layer part 100,200 Light emitting element

Claims (12)

The first main surface of the compound semiconductor layer having the light emitting layer portion is used as a light extraction surface, and the second main surface side of the compound semiconductor layer is a reflecting surface that reflects light from the light emitting layer portion to the light extraction surface side. A reflective metal layer is formed, and the reflective metal layer is coupled to the element substrate via the coupling metal layer, and the coupling metal layer is interposed between the reflective metal layer and the coupling metal layer. A reflection metal layer side diffusion blocking layer that prevents diffusion of the metal component of the metal component to the reflection metal layer side is inserted,
Further, a substrate-side diffusion blocking layer that is formed of a conductive material between the element substrate and the bonding metal layer and blocks diffusion of components derived from the element substrate into the bonding metal layer. A light-emitting element characterized by being inserted .   The light emitting device according to claim 1, wherein the coupling metal layer is made of a metal having a lower reflectance than the reflective metal layer with respect to light from the light emitting layer portion.   The light-emitting element according to claim 1, wherein the bonding metal layer is an Au-based metal layer containing Au as a main component.   4. The light emitting device according to claim 3, wherein the reflective metal layer is an Al-based metal containing Al as a main component.   4. The light emitting device according to claim 3, wherein the reflective metal layer is made of an Ag-based metal containing Ag as a main component.   6. The light emitting device according to claim 3, wherein the reflection metal layer side diffusion blocking layer is a metal layer mainly composed of any one of Ti, Ni, and Cr. element.   The light emitting device according to claim 6, wherein the reflective metal layer side diffusion blocking layer has a thickness of 1 nm to 10 μm. 2. The light emitting device according to claim 1, wherein the bonding metal layer is an Au-based metal layer containing Au as a main component, and the device substrate is a Si substrate. 9. The light emitting device according to claim 8, wherein the substrate side diffusion blocking layer is a metal layer mainly containing any one of Ti, Ni and Cr. A method for manufacturing a light emitting device according to any one of claims 1 to 9,
The first main surface of the compound semiconductor layer having the light emitting layer portion is used as a light extraction surface, and the second main surface side of the compound semiconductor layer is a reflecting surface that reflects light from the light emitting layer portion to the light extraction surface side. In a method for manufacturing a light emitting device, a reflective metal layer having a reflective metal layer is formed, and the reflective metal layer is bonded to an element substrate through a bonding metal layer.
The metal component of the reflective metal layer and the bonding metal layer diffuses to the reflective metal layer side between the bonded main surface of the compound semiconductor layer and the bonded main surface of the element substrate. A reflection metal layer side diffusion prevention layer that inhibits diffusion, the coupling metal layer, and a substrate side diffusion prevention layer that inhibits diffusion of components derived from the element substrate into the coupling metal layer, the compound semiconductor layer. A method for manufacturing a light-emitting element, wherein the light-emitting elements are stacked and bonded so as to be interposed in the form of being laminated in this order from the side. The method for manufacturing a light-emitting element according to claim 10, wherein heat treatment is performed during the bonding. On the main surface of the compound semiconductor layer, the metal reflective layer, the reflective metal layer side diffusion blocking layer, and the first Au-based metal layer are formed in this order from the main surface side. 12. A second Au-based metal layer is formed on the bonding-side main surface of the first and second Au-based metal layers, and the first Au-based metal layer and the second Au-based metal layer are adhered and bonded together. The manufacturing method of the light emitting element as described in any one of.

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