JP2005056956A - Method of manufacturing light emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a light emitting element by which a substrate for growth is handled easily even when the substrate is removed from a compound semiconductor layer having a light emitting layer and, in addition, the reflectance of a metallic layer is hardly lowered even when alloying heat treatment is performed on metallic junction layers. <P>SOLUTION: After the compound semiconductor layer 24 is epitaxially grown on the first principal surface of the substrate 1 for growth, a temporary supporting substrate 110 is stuck to the first principal surface of the compound semiconductor layer 24 through a polymer binding material 111 and, in addition, the substrate 1 for growth is removed by chemical etching etc. Then, after the metallic junction layers 31 are formed on the second principal surface of the compound semiconductor layer 24 from which the substrate 1 is removed, alloying heat treatment is performed on the layers 31 and, thereafter, an element substrate 7 is stuck to the second principal surface of the compound semiconductor layer 24 through the metallic layer 10. A polymer binding material having a vapor pressure of ≤10 torr in the temperature range (300-450°C) within which the alloying heat treatment is performed is selected as the polymer binding material 111. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for manufacturing a light emitting device.

JP-A-7-66455 JP 2002-217450 A

  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. A light emitting device in which a light emitting layer portion is formed of a III-V compound semiconductor, for example, an AlGaInP mixed crystal, includes a thin AlGaInP (or GaInP) active layer, an n-type AlGaInP cladding layer having a larger band gap, and a p-type AlGaInP. By adopting a double hetero structure sandwiched between clad layers, 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. And when using this as a light emitting element, usually a GaAs single crystal substrate is often used as it is as a substrate. 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.

  Therefore, in Patent Document 2, the growth GaAs substrate is removed from the compound semiconductor layer composed of the current diffusion layer and the light emitting layer portion, and instead of the element substrate for reinforcement composed of Si or the like, the reflectance is high. A technique for bonding to a compound semiconductor layer via a metal layer is disclosed. Specifically, as described in paragraph 0041, an AlGaInP light emitting layer portion having a double hetero structure is grown on a GaAs substrate, a current diffusion layer made of GaP is further grown by a MOVPE method, and then a GaAs substrate is formed. It is removed by mechanical polishing and chemical etching.

  Further, in order to make ohmic contact between the light emitting layer portion and the metal layer, it is essential to dispose a bonding metal layer (contact layer) between them and alloy them by heat treatment. In Patent Document 2, after the growth GaAs substrate is peeled from the compound semiconductor layer, a contact layer is formed on the peeled surface of the light emitting layer portion, and alloying heat treatment is performed. A process of covering with a layer is employed. If the alloying heat treatment is performed after the formation of the reflective metal layer and then after the element substrate is bonded, the alloy component of the contact layer diffuses in the in-plane direction of the metal layer forming the reflective surface, thereby reducing the reflectance. However, according to the above process, since the alloying heat treatment is completed before the formation of the metal layer, there is an advantage that the reflectance is not easily lowered by diffusion.

  In order to sufficiently spread the current in the in-plane direction, the current diffusion layer is generally formed to have a certain thickness, for example, a thickness larger than that of the light emitting layer. In particular, in the process of Patent Document 2, since the element substrate is bonded through the metal reflective layer after removing the GaAs substrate, the light emitting layer portion is usually formed very thin to improve the light emission efficiency (for example, In consideration of the fact that the total thickness is less than 10 μm), it is necessary to grow the current diffusion layer into a thick film up to at least about 50 μm in order to improve the handling property of the light emitting layer at the time of bonding.

  However, the MOVPE method is a high-temperature treatment, and it takes a very long time to grow a current diffusion layer having a sufficient thickness. As a result, the light emitting layer portion on which the current diffusion layer is formed is exposed to a high temperature thermal history during the growth of the current diffusion layer for a long time, and a p-type dopant for forming a pn junction, The concentration profile in the layer thickness direction of the n-type dopant collapses due to thermal diffusion, causing a problem that leads to a decrease in internal quantum efficiency of the light emitting layer portion. In particular, in the case of a light emitting layer portion adopting a double heterostructure, when the dopant from the clad layers on both sides penetrates into the active layer formed by non-doping by diffusion, the probability of electron / hole emission recombination decreases, The emission intensity is significantly deteriorated. That is, even if the metal reflective layer is formed in the light emitting layer portion, the light emitting performance of the entire device cannot be improved because the internal quantum efficiency of the light emitting layer portion itself has deteriorated.

  Naturally, when the thickness of the current diffusion layer is reduced so that such a problem does not occur, the total thickness of the compound semiconductor layer including the current diffusion layer and the light emitting layer portion becomes small, and after removing the growth substrate, the element Handling for bonding substrates becomes difficult. When the thickness of the compound semiconductor layer is particularly small (for example, 10 μm or more and 30 μm or less), since the mechanical strength of the compound semiconductor layer that has lost its support is extremely small as the growth substrate is removed in the etching solution, In response to the attack of bubbles generated by the etching reaction, there is a problem that the bubbles are broken into pieces like algae while floating in the liquid.

  The problem of the present invention is that even if the growth substrate is removed from the compound semiconductor layer having the light emitting layer portion, the handling can be easily performed, and the reflectance of the metal layer is reduced by the alloying heat treatment of the bonding metal layer. An object of the present invention is to provide a method for manufacturing a light-emitting element that does not easily occur.

Means for Solving the Problems and Effects of the Invention

In the method for producing a light emitting device of the present invention, a first main surface of a compound semiconductor layer made of a III-V group compound semiconductor having a light emitting layer portion is used as a light extraction surface, and a light emitting layer is formed on the second main surface of the compound semiconductor layer. The element substrate is coupled through a metal layer having a reflection surface that reflects light from the light-extraction surface side, and the compound semiconductor layer and the metal layer are interposed between the metal layer and the compound semiconductor layer. In order to solve the above-mentioned problem, the light emitting device is provided with a bonding alloying layer that reduces the contact resistance of
A compound semiconductor layer growth step of epitaxially growing the compound semiconductor layer on the first main surface of the growth substrate;
With the growth substrate attached to the second main surface side of the compound semiconductor layer, the temporary support substrate is bonded to the first main surface of the compound semiconductor layer via the polymer material bonding layer, and then the growth substrate is attached. A temporary support bonded body forming step of forming a temporary support bonded body in which the compound semiconductor layer and the temporary support substrate are bonded by removing,
A bonding metal layer forming step of forming a bonding metal layer on the second main surface of the compound semiconductor layer exposed by removing the growth substrate;
An alloying heat treatment step of alloying the bonding metal layer with the compound semiconductor layer to form a bonding alloyed layer in the state of the temporary support laminate;
After the completion of the alloying heat treatment, the compound semiconductor layer is handled in the state of the temporary support bonded body, and the bonding process is performed at a temperature lower than that of the alloying heat treatment, whereby a metal is applied to the second main surface of the compound semiconductor layer. An element substrate bonding step of creating an element substrate bonded body in which the element substrates are bonded through the layers;
A temporary support substrate separation step of heating and softening the polymer material bonding layer to separate the temporary support substrate from the element substrate bonded body is performed in this order,
The alloying heat treatment is performed in an inert gas atmosphere in a temperature range of 300 ° C. or higher and 450 ° C. or lower, and as a polymer material bonding layer used for the temporary support bonded body, at a temperature of 300 ° C. or higher and 450 ° C. or lower. A vapor pressure of 10 torr (1.33 × 10 ⁻² Pa) or less is used.

  According to the method of the present invention, after the compound semiconductor layer is epitaxially grown on the first main surface of the growth substrate, the temporary support substrate is bonded to the first main surface of the compound semiconductor layer via the polymer material bonding layer. Further, the growth substrate is removed by chemical etching or the like. Since the temporary support substrate is bonded to the compound semiconductor layer as a reinforcing body even if the growth substrate is removed, the compound semiconductor layer is damaged by a bubble attack or the like during etching. Defects can be effectively prevented. In addition, after removing the growth substrate, when the compound semiconductor layer is subjected to the subsequent bonding process, etc., the temporary support substrate is bonded, which makes it extremely easy to handle the compound semiconductor layer, resulting in a handling failure. This reduces the probability of breakage of the compound semiconductor layer due to, thereby contributing to an improvement in the manufacturing yield of the light emitting elements. When the total thickness of the compound semiconductor layer incorporated in the temporary support bonded body is as thin as 7 μm or more and 30 μm or less, the effect of using the temporary support substrate is particularly remarkable.

  In the case of a compound semiconductor layer made of a III-V group compound semiconductor, the bonding metal layer has, for example, Au, Ag or Al as a main component (50% by mass or more), and Ge, Sb, Sn, Be and What contains 1 type (s) or 2 or more types of Zn can be used. AuGe, AuGeNi, AuSn, and AuSb are excellent in the contact resistance reduction effect with the n-type semiconductor layer, and AuZn and AuBe are excellent in the contact resistance reduction effect with the p-type semiconductor layer. Generally, the alloying heat treatment for such a bonding metal layer is performed at a temperature of 300 ° C. or higher and 450 ° C. or lower. If the alloying heat treatment temperature is less than 300 ° C., alloying between the compound semiconductor layer and the bonding metal layer does not proceed sufficiently, leading to an increase in contact resistance. On the other hand, the effect of alloying is saturated at a temperature higher than 450 ° C., but rather, the temperature is unnecessarily high from the viewpoint of preventing diffusion of alloy components into the light emitting layer and diffusion deterioration of the dopant concentration profile in the light emitting layer. Since it is not a good idea to set, the upper limit of the temperature of the alloying heat treatment is set to 450 ° C. Also, since the alloying heat treatment temperature is relatively high, the treatment is performed in an inert gas atmosphere such as argon or nitrogen in order to prevent oxidative degradation of the compound semiconductor layer.

  In the present invention, after a bonding metal layer is formed on the second main surface of the compound semiconductor layer from which the growth substrate has been removed, an alloying heat treatment is first performed, and then the metal layer is formed on the second main surface of the compound semiconductor layer. The element substrate is bonded via As a result, the heat history of the alloying heat treatment is not added to the bonding metal layer in contact with the bonding metal layer, and the effect of reducing the reflectivity by diffusing the components of the bonding metal layer into the metal layer surface is effective. Can be prevented. Furthermore, in the present invention, the alloying heat treatment is performed in the state of a temporary support bonded body in which the temporary support substrate is bonded to the compound semiconductor layer via the polymer material bonding layer. As the polymer material bonding layer, one having a vapor pressure of 10 torr or less in a temperature range (300 ° C. or higher and 450 ° C. or lower) in which alloying heat treatment is performed is selected. As a result, even if the alloying heat treatment is performed with the polymer material bonding layer interposed, rapid vaporization of the polymer material bonding layer does not occur during the heat treatment. Problems such as separation or damage of the compound semiconductor layer from the combined body can be effectively suppressed, and a light-emitting element can be manufactured with high yield.

  When the vapor pressure of the polymer material bonding layer in the above temperature range exceeds 10 torr, it leads to a problem that the compound semiconductor layer is separated or damaged from the temporary support bonded body by the vapor of the vaporized polymer material bonding layer. . In addition, the lower the vapor pressure of the polymer material bonding layer in the above temperature range, the better, as long as the polymer material can be softened at an appropriate temperature when forming the temporary support bonded body.

The polymer material has a glass transition temperature, and when the glass transition temperature is exceeded, the polymer material is softened. The alloying heat treatment temperature range (300 ° C. or more and 450 ° C. or less) is much higher than the glass transition temperature (for example, about 80 to 90 ° C.) of ordinary polymer materials, and may be in a liquid state. Many. In this case, if the temporary support bonded body is tilted carelessly, the temporary support substrate and the compound semiconductor layer may slip relative to each other, or the thin compound semiconductor layer may be damaged. . Therefore, it is necessary to perform an alloying heat treatment while holding the temporary support bonded body so that relative movement in the in-plane direction between the temporary support substrate and the compound semiconductor layer does not occur. In this case, for example, the following method is effective:
(1) Hold the temporary support bonded body as horizontally as possible to perform heat treatment;
(2) performing heat treatment in a state where the temporary support bonded body is housed in a holder that prevents relative movement in the in-plane direction;
(3) A load imparting body that reinforces the adhesion between the temporary support substrate and the compound semiconductor layer is placed on the temporary support bonded body, and heat treatment is performed.

Next, when a bonding metal layer is formed using a well-known technique such as sputtering or vapor deposition, it is difficult to avoid a constant temperature rise even if the substrate is cooled, and the adsorbed moisture in the film formation container is evaporated and removed. In view of this, it is desirable to form a bonding metal layer by raising the temperature to 60 ° C. or higher. On the other hand, the effect of removing moisture is almost saturated at 150 ° C., and it is not always a good idea to perform an unnecessary temperature increase beyond that. On the other hand, the formation of a metal film by a vapor deposition method such as sputtering or vapor deposition is naturally performed in a vacuum atmosphere in order to ensure the quality of the film. In this case, the polymer material bonding layer used for the temporary support bonded body has a vapor pressure of 1 × 10 ⁻⁶ torr (1.33 × 10 ⁻⁴ Pa) or less at the temperature of 60 ° C. or more and 150 ° C. or less. It is desirable to use something. When a polymer material bonding layer having a vapor pressure higher than 10 ⁻⁶ torr in the temperature range is used, the quality of the metal layer to be formed may be deteriorated by a gas generated from the polymer material bonding layer in a vacuum atmosphere. . In order to form a good bonding metal layer, it is desirable to set the pressure of the vacuum atmosphere to be used to 1 × 10 ⁻⁴ torr (1.33 × 10 ⁻² Pa) or less.

Next, the bonding of the element substrate to the compound semiconductor layer through the metal layer can be easily performed as follows. That is, the first Au-based metal layer that should be a part of the metal layer is formed on the second main surface of the compound semiconductor layer in the state of the temporary support bonded body, while the metal layer is formed on the bonded surface of the element substrate. A second Au-based metal layer to be a part is formed, and the first Au-based metal layer and the second Au-based metal layer are bonded in the element substrate bonding step. In this case, since the affinity between Au-based metal layers is strong, there is an advantage that sufficient bonding strength can be easily obtained even at a relatively low temperature. However, in this case, the first Au-based metal layer formed on the temporary support bonded body side is formed by sputtering, vapor deposition, or the like. From the viewpoint of evaporation / removal of adsorbed moisture and the like in the film formation container, Similarly, it is desirable to form in a vacuum atmosphere at a temperature of 60 ° C. or higher and 150 ° C. or lower. As the polymer material bonding layer, the vapor pressure at a temperature of 60 ° C. or higher and 150 ° C. or lower is 1 × 10 ⁻⁶ torr ( It is desirable to use the following 1.33 × 10 ⁻⁴ Pa) or less.

  Hereinafter, an embodiment of a method for manufacturing a light emitting device according to the present invention will be described with reference to the drawings. FIG. 1 is a conceptual diagram of a light emitting element to which the present invention is applied. The light-emitting element 100 includes an Au-based metal layer 10 as a metal layer on a first main surface of a silicon substrate 7 (in this embodiment, n-type but may be p-type) made of silicon single crystal as an element substrate. It has a structure in which the light-emitting layer portion 24 is bonded via. In the present embodiment, the main surfaces of the layers and the substrate, as shown in FIG. 1, are defined as a state where the light extraction surface PF of the light emitting element 100 is on the upper side, and a surface appearing on the upper side of the drawing in the normal state is a first main surface. The surface, the surface appearing on the lower side, is uniformly described as the second main surface. Therefore, for convenience of description of the process, when the drawing is performed in a transposed state that is upside down with respect to the normal state, the vertical relationship between the first main surface and the second main surface in the drawing is also reversed.

The light emitting layer portion 24 is an 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. a 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), 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) p-type clad 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).

  A current diffusion layer 20 made of AlGaAs (AlInP or GaInP) is formed on the first main surface of the light emitting layer portion 24, and the compound semiconductor layer 50 is configured together with the light emitting layer portion 24. A light extraction surface side electrode 9 (for example, an Au electrode) for applying a light emission driving voltage to the light emitting layer portion 24 is formed substantially at the center of the first main surface of the current diffusion layer 20. Between the light extraction surface side electrode 9 and the current diffusion layer 20, an AuBe bonding alloyed layer 9a as a light extraction side bonding alloyed layer is disposed. A region around the light extraction surface side electrode 9 on the first main surface of the current diffusion layer 20 forms a light extraction region PF from the light emitting layer portion 24.

The thicknesses of the n-type cladding layer 4 and the p-cladding layer 6 are, for example, 0.8 μm or more and 4 μm, respectively.
The thickness of the active layer 5 is, for example, not less than 0.4 μm and not more than 2 μm (desirably not less than 0.4 μm and not more than 1 μm). The total thickness of the light emitting layer portion 24 is, for example, 2 μm to 10 μm (desirably 2 μm to 5 μm). Furthermore, the thickness of the current spreading layer 20 is, for example, 5 μm or more and 28 μm or less (desirably 8 μm or more and 15 μm or less). Therefore, the thickness of the compound semiconductor layer 50 is, for example, 7 μm or more and 30 μm or less (desirably 5 μm or more and 15 μm or less). If the thickness of the current diffusion layer 20 is less than 5 μm, the in-plane current diffusion effect may be reduced and the light extraction efficiency may be reduced. On the other hand, when the thickness of the current diffusion layer 20 exceeds 28 μm, dopant diffusion into the active layer 5 of the light emitting layer portion 24 proceeds due to thermal history when the current diffusion layer 20 is epitaxially grown, leading to a decrease in light emission efficiency. There is. In the present embodiment, the p-type cladding layer 6 is a laminated form in which the light-extracting surface is located, but the n-type clad layer 4 may be in a laminated form in which it is located on the light-extracting side (in this case, current diffusion). The layer 20 must be n-type, and the bonded alloying layer 9a is made of AuGeNi or the like).

  On the other hand, a back surface electrode (for example, an Au electrode) 15 is formed on the back surface of the silicon substrate 7 so as to cover the whole. An AuSb bonding alloyed layer 16 is interposed between the back electrode 15 and the silicon substrate 7 as a substrate side bonding alloyed layer. Instead of the AuSb bonding alloyed layer 16, an AuSn bonding alloyed layer may be used as the substrate side bonding alloyed layer.

  The silicon 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, it is bonded to the light emitting layer portion 24 with the Au-based metal layer 10 interposed therebetween. The Au-based metal layer 10 is formed by laminating a first Au-based metal layer 10a in contact with the compound semiconductor layer 50 and a second Au-based metal layer 10b in contact with the silicon substrate 7, and is apparently simple. One Au-based metal layer. The first Au-based metal layer 10a and the second Au-based metal layer 10b (and thus the Au-based metal layer 10) are made of pure Au or an Au alloy having an Au content of 95% by mass or more.

  An AuGeNi bonding alloyed layer 31 (for example, Ge: 15% by mass, Ni: 10% by mass) is formed between the light emitting layer part 24 and the first Au-based metal layer 10a as a bonding side bonding alloyed layer. This contributes to reducing the series resistance of the element. The AuGeNi bonding alloyed layer 31 is dispersedly formed on the first main surface of the first Au-based metal layer 10a, and the formation area ratio (AuGeNi bonding alloying with respect to the entire first main surface area of the first Au-based metal layer 10a) is formed. The ratio of the total area of the layer 31 is 1% or more and 25% or less. Further, an AuSb bonding alloyed layer 32 (for example, Sb: 5% by mass) is interposed between the silicon substrate 7 and the second Au-based metal layer 10b as a substrate-side bonding alloyed layer. Instead of the AuSb bonding alloyed layer 32, an AuSn bonding alloyed layer may be used.

  Further, in the present embodiment, the entire surface of the AuSb bonding metal layer 32 is a diffusion blocking layer that prevents the Si component from the silicon substrate 7 from diffusing into the Au-based metal layer 10 during the bonding heat treatment described later (specifically, Is a Ti layer). The thickness of the diffusion blocking layer 10c is 1 nm to 10 μm (600 nm in this embodiment). The diffusion blocking layer may be composed of a Ni layer or a Cr layer instead of the Ti layer. Further, the Au-based metal layer 10 (second Au-based metal layer 10b) is disposed so as to be in contact with the entire surface of the diffusion blocking layer 10c.

  In this embodiment, the Au-based metal layer 10 that forms the metal layer also serves as a reflective layer. The light from the light emitting layer portion 24 is extracted in a form in which the light reflected directly from the Au-based metal layer 10 is superimposed on the light emitted directly to the light extraction surface side. The thickness of the Au-based metal layer 10 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 reflection effect is saturated, it determines suitably (for example, 1 micrometer or less) by balance with cost. Note that an Ag-based layer can be used as the metal layer that also serves as the reflective layer. For example, instead of the first Au-based metal layer 10a and the second Au-based metal layer 10b, a first Ag-based layer and a second Ag-based layer can be formed and bonded together. In this case, the bonded side bonded alloyed layer can also be composed of an Ag-based material such as AgGeNi.

Hereinafter, a specific example of the method for manufacturing the light emitting device 100 will be described.
First, as shown in step 1 of FIG. 2, an n-type GaAs buffer layer 2 is 0.5 μm, for example, and a release layer 3 made of AlAs is 0.5 μm, for example, on the main surface of a GaAs single crystal substrate 1 that is a growth substrate. Then, epitaxial growth is performed in this order. Thereafter, as the light emitting layer portion 24, an n-type cladding layer 4 (thickness: for example 1 μm), an AlGaInP active layer (non-doped) 5 (thickness: for example 0.6 μm), and a p-type cladding layer 6 (thickness: for example 1 μm). ) In this order. The total thickness of the light emitting layer portion 24 is 2.6 μm. Further, a current diffusion layer 20 made of p-type AlGaAs is epitaxially grown by 5 μm, for example. Epitaxial growth of each of these layers can be performed by a known MOVPE method. The following can be used as a source gas that is a component source of Al, Ga, In, P, and As;
Al source gas; trimethylaluminum (TMAl), triethylaluminum (TEAl), etc .;
Ga source gas; trimethylgallium (TMGa), triethylgallium (TEGa), etc .;
In source gas; trimethylindium (TMIn), triethylindium (TEIn), etc.
P source gas; tertiary butyl phosphine (TBP), phosphine (PH ₃ ), etc.
As source gas; tertiary butyl arsine (TBA), arsine (AsH ₃ ), etc.

Moreover, as a dopant gas, the following can be used;
(P-type dopant)
Mg source: biscyclopentadienyl magnesium (Cp ₂ Mg), etc.
Zn source: dimethyl zinc (DMZn), diethyl zinc (DEZn), etc.
(N-type dopant)
Si source: silicon hydride such as monosilane.

As a result, the compound semiconductor layer 50 including the light emitting layer portion 24 and the current diffusion layer 20 is formed on the GaAs single crystal substrate 1. The thickness of the compound semiconductor layer 50 is 7.6 μm. When the GaAs single crystal substrate 1 is removed, it is practically impossible to handle it alone without being damaged. Note that the bonding metal layer 9 a ′ and the light extraction surface side electrode 9 covering the bonding metal layer 9 a ′ are formed by patterning on the first main surface of the compound semiconductor layer 50 at this stage. Subsequently, the alloying heat treatment may be performed to make the bonding metal layer 9a ′ as the bonding alloying layer 9a. However, in this embodiment, the alloying heat treatment is performed on the bonding alloying layer 31 on the Au-based metal layer 10a side described later. This is also used for heat treatment for alloying when forming.

  Next, as shown in step 2, the polymer material bonding layer 111 is applied and formed on the first main surface of the compound semiconductor layer 50 so as to cover the light extraction surface side electrode 9, and as shown in step 3, In a state where the polymer material bonding layer 111 is heated and softened, a separately prepared temporary support substrate 110 is superposed and adhered, and then cooled to cure the polymer material bonding layer 111, whereby the compound semiconductor layer 50 and A temporary support bonded body 120 is prepared by bonding the temporary support substrate 110 to the polymer material bonding layer 111 (step 3). At this time, the GaAs single crystal substrate 1 as a growth substrate is attached to the second main surface side of the compound semiconductor layer 50.

  The material of the temporary support substrate 110 is made of a material that maintains rigidity even during an alloying heat treatment described later and that generates less gas. Specifically, a silicon substrate, a ceramic plate (for example, an alumina plate), or a metal plate can be used. The thickness is, for example, 100 μm or more and 500 μm or less, but may be thicker. On the other hand, hot-melt adhesives and waxes can be used as the polymer material bonding layer 111. Specifically, an alloy described later in a temperature range of 300 ° C. to 450 ° C. in an inert gas atmosphere. When performing the chemical heat treatment, a vapor pressure in the temperature range of 300 ° C. to 450 ° C. (equilibrium vapor pressure measured under a constant volume condition) is 10 torr or less.

  For example, when a hot-melt adhesive is used, the adhesive force required for bonding to the base resin that ensures the shape retention of the polymer material bonding layer 111 in the cured state and the base resin that has been softened by increasing the temperature. A blended material with a tackifying polymer material that imparts odor is used. As the material of the base resin, it is necessary to use a material having a thermal decomposition temperature higher than the set alloying heat treatment temperature, considering that the alloying heat treatment temperature is set to 300 ° C. or higher and 450 ° C. or lower. Examples include polypropylene or polyethylene (thermal decomposition temperature: 330 ° C. to 450 ° C.), polystyrene (thermal decomposition temperature: 300 ° C. to 400 ° C.), nylon (thermal decomposition temperature: 310 ° C. to 380 ° C.), and the like. In addition, polyester resins, polyolefin resins, and the like can be used. On the other hand, as tackifying polymer materials, various terpene resins (terpene polymers, aromatic modified terpene polymers, terpene hydrogenated resins, terpene phenol copolymers, etc.), α-pinene resins, β-pinene resins, etc. Can be used. In order to keep the vapor pressure at the heat treatment temperature as a whole of the adhesive, it is desirable to use a tackifying polymer material having a molecular weight as large as possible. On the other hand, if the molecular weight is too large, the tackiness imparting power is low. Thus, the function as the polymer material bonding layer 111 is hindered. Accordingly, the molecular weight of the tackifying polymer material to be used and the blending amount with respect to the base resin need to be appropriately selected in consideration of the balance between vapor pressure and adhesive strength. In order to give a suitable adhesive force necessary for bonding to the polymer material binding layer, it is often necessary to select a tackifying polymer material having a lower thermal decomposition temperature than the base resin, In this case, it is desirable to keep the content ratio of the tackifying polymer material relative to the total amount of the base resin and the tackifying polymer material to a necessary minimum (for example, 1% by mass to 30% by mass).

  Examples of commercially available waxes for forming the polymer material bonding layer 111 suitable for the present invention include Apiezon Wax W (manufactured by M & I Materials Ltd.), Space Liquid (manufactured by Nikka Seiko Co., Ltd.), and protect wax. It can be illustrated. All of these waxes have a glass transition temperature of 80 ° C. or higher and 90 ° C. or lower (for example, 85 ° C.).

  Next, as shown in step 4 of FIG. 3, the GaAs single crystal substrate 1 as a growth substrate attached to the temporary support bonded body 120 is removed. For this removal, for example, the temporary support bonded body 120 (see step 3) is immersed in an etching solution (for example, a 10% aqueous hydrofluoric acid solution) together with the GaAs single crystal substrate 1 and formed between the buffer layer 2 and the light emitting layer portion 24. The GaAs single crystal substrate 1 can be peeled from the temporary support bonded body 120 by selectively etching the AlAs release layer 3 thus formed. 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. In addition, it is desirable to use the polymer material bonding layer 111 having a corrosion resistance to the above etching solution, and the above-mentioned commercially available products can be suitably employed in the present invention from the viewpoint of the corrosion resistance. .

  In this way, the compound semiconductor layer 50 from which the GaAs single crystal substrate 1 has been removed is bonded to the temporary support substrate 110 via the polymer material bonding layer 111 to form a temporary support bonded body 120. Therefore, even though the compound semiconductor layer 50 is very thin, it is difficult to cause a problem of being destroyed by an impact such as bubbles when the GaAs single crystal substrate 1 is removed by etching, and temporary support sticking is performed even after the GaAs single crystal substrate 1 is removed. Since it is reinforced in the form of the mating body 120, it is possible to easily handle when it is used in the subsequent steps.

  Next, as shown in step 5, in the state of the temporary support bonded body 120, an AuGeNi bonding metal layer is dispersedly formed on the second main surface of the compound semiconductor layer 50 exposed by removing the GaAs single crystal substrate 1, Further, an alloying heat treatment is performed so that the AuGeNi bonded metal layer becomes the AuGeNi bonded alloyed layer 31. At this time, alloying of the bonding metal layer 9 a ′ with respect to the light extraction surface side electrode 9 can be performed at the same time.

The AuGeNi bonding metal layer is formed by sputtering or vacuum deposition in a vacuum atmosphere. Specifically, the film formation is performed under the conditions of a temperature of 60 ° C. or more and 150 ° C. or less and a degree of vacuum (pressure) of 1 × 10 ⁻⁶ torr or more and 1 × 10 ⁻⁴ torr or less (if necessary, temporary support bonding is performed) The laminated body 120 can be heated by a heater (not shown)). By adopting a polymer material bonding layer 111 having a vapor pressure of 1 × 10 ⁻⁶ torr or less in the above temperature range (the above-mentioned commercial product also satisfies this condition), The gas can effectively prevent a problem that the quality of the bonding metal layer to be formed is deteriorated.

The alloying heat treatment is performed in an inert gas atmosphere at a temperature of 300 ° C. or higher and 450 ° C. or lower. Specifically, the alloying heat treatment can be performed in an inert gas atmosphere such as N _{2 at the} same level as atmospheric pressure. . Since the polymer material bonding layer 111 to be used has a vapor pressure of 10 torr (1.33 × 10 ⁻² Pa) or less in the above temperature range, the compound semiconductor layer 50 is formed by the rapid vaporization of the polymer material bonding layer 111. It is possible to effectively prevent breakage. In addition, since the said temperature of alloying heat processing is higher than the glass transition temperature (about 80-90 degreeC) of the polymeric material coupling layer 111, the polymeric material coupling layer 111 softens during a process. Therefore, in order to prevent slipping during the alloying heat treatment, the temporary support bonded body 120 is placed so that the compound semiconductor layer 50 side is on the upper side and the temporary support substrate 110 side is on the lower side (that is, step 5 in FIG. It is desirable to place them horizontally, and to place a load applying body such as a ceramic substrate or a silicon substrate.

  Further, by separately preparing the silicon substrate 7, forming AuSb bonding metal layers on both main surfaces, and further performing alloying heat treatment in a temperature range of 250 ° C. or higher and 360 ° C. or lower, respectively, the AuSb bonding alloyed layer 32 is obtained. , 16. Among these, on the AuSb bonding alloying layer 32, a diffusion blocking layer 10c is formed that prevents the components of the silicon substrate 7 from diffusing into the second Au-based metal layer 10b in the subsequent element substrate bonding step. On the other hand, the back electrode 15 is formed on the AuSb bonding alloying layer 16.

Next, an element substrate bonding step is performed. Specifically, as shown in Step 6 of FIG. 3, the first Au-based metal layer 10a is formed on the second main surface of the compound semiconductor layer 50 in the state of the temporary support bonded body 120, while the element substrate. A second Au-based metal layer 10 b is formed on the first main surface side of 7. Each Au-based metal layer can be formed in a vacuum atmosphere (by sputtering or vacuum vapor deposition). Specifically, film formation is performed under conditions of a temperature of 60 ° C. or more and 150 ° C. or less and a degree of vacuum (pressure) of 1 × 10 ⁻⁶ torr or more and 1 × 10 ⁻⁴ torr or less. When the first Au-based metal layer 10a on the temporary support bonded body 120 side is formed, a polymer material bonding layer 111 having a vapor pressure of 1 × 10 ⁻⁶ torr or less in the above temperature range is adopted. Therefore, it is possible to effectively prevent a problem that the quality of the Au-based metal layer formed by the gas from the polymer material bonding layer 111 is deteriorated.

  Next, as shown in Step 7 of FIG. 4, the first Au-based metal layer 10a formed on the compound semiconductor layer 50 side is overlaid on the second Au-based metal layer 10b formed on the silicon substrate 7 side. Bonding heat treatment is performed at 180 ° C. or higher and 360 ° C. or lower (lower temperature than the above alloying heat treatment), for example, 250 ° C. As a result, the first Au-based metal layer 10 a and the second Au-based metal layer 10 b are bonded together with sufficient strength to form the Au-based metal layer 10. In addition, the compound semiconductor layer 50 and the silicon substrate 7 are bonded together via the Au-based metal layer 10 to form a bonded bonded body 130. Since both the first Au-based metal layer 10a and the second Au-based metal layer 10b are mainly composed of Au that is not easily oxidized, the bonding heat treatment can be performed without any problem even in the atmosphere, for example. At this stage, the alloying heat treatment on the light extraction side and the bonding side has already been completed, and the bonding heat treatment is performed at a temperature lower than that, so that the alloy component from the bonded alloying layer becomes the Au-based metal layer. Accordingly, it is possible to effectively suppress the diffusion within the surface of the reflection surface made of 10 and to obtain a reflection surface with higher reflectivity.

  When the bonding heat treatment is completed, a temporary support substrate separation step is performed. In the temporary support substrate separation step, as shown in Step 8 of FIG. 4, the polymer material bonding layer 111 is heated and softened, and the temporary support substrate 110 is separated and removed. Note that this separation can be performed simultaneously with the bonding heat treatment in step 7. Thereafter, as shown in Step 9, the polymer material bonding layer 111 remaining on the first main surface of the compound semiconductor layer 50 is dissolved and removed using an organic solvent such as toluene or methyl ethyl ketone (MEK).

  In the above, for the purpose of facilitating understanding, the process of forming the bonded assembly 130 has been described in the form of a single element stack, but in practice, a plurality of element chips are arranged in a matrix. A bonded wafer formed in a lump is created. Then, the bonded wafer is diced by an ordinary method to form an element chip, which is fixed to a support and subjected to wire bonding of a lead wire, etc., and then sealed with a resin to obtain a final light emitting element. can get.

  As shown in FIG. 5, the Au-based metal layer 10 (first Au-based metal layer 10a + second Au-based metal layer 10b) is exclusively used for bonding, and a reflective metal layer different from the Au-based metal layer 10 is used. 10r can also be provided between the Au-based metal layer 10 and the compound semiconductor layer 50. As such a reflective metal layer 10r, an Ag-based reflective layer mainly composed of Ag or an Al-based reflective layer mainly composed of Al can be used. In this case, the bonding-side bonded alloyed layer can be composed of an Ag-based material such as AgGeNi in the case of an Ag-based reflective layer, or an Al-based material such as AlGeNi in the case of an Al-based reflective layer. . The manufacturing process is substantially the same except that the bonding alloyed layer 31 is covered with the reflective metal layer 10r and then covered with the first Au-based metal layer 10a.

  Moreover, the light emitting layer part 24 can also be comprised as an active layer and a clad layer having a double hetero structure comprised of InAlGaN or MgZnO.

The schematic diagram which shows an example of the light emitting element used as the application object of this invention. Process explanatory drawing which shows an example of the manufacturing method of the light emitting element of this invention. Process explanatory drawing following FIG. Process explanatory drawing following FIG. The schematic diagram which shows another example of the light emitting element used as the application object of this invention.

Explanation of symbols

1 GaAs single crystal substrate (growth substrate)
7 Silicon substrate (element substrate)
10 Au-based metal layer (metal layer)
DESCRIPTION OF SYMBOLS 10a 1st Au type metal layer 10b 2nd Au type metal layer 20 Current diffusion layer 24 Light emitting layer part 50 Compound semiconductor layer 100 Light emitting element 110 Temporary support substrate 111 Polymer material coupling | bonding layer 120 Temporary support bonding body 130 Bonding bonded body

Claims (4)

The first main surface of a compound semiconductor layer made of a III-V group compound semiconductor having a light emitting layer portion is used as a light extraction surface, and the light from the light emitting layer portion is emitted to the second main surface of the compound semiconductor layer on the light extraction surface side. In order to reduce the contact resistance between the compound semiconductor layer and the metal layer between the metal layer and the compound semiconductor layer, while the element substrate is bonded through a metal layer having a reflective surface to be reflected on In order to manufacture a light emitting device having a bonding alloying layer of
A compound semiconductor layer growth step of epitaxially growing the compound semiconductor layer on the first main surface of the growth substrate;
With the growth substrate attached to the second main surface side of the compound semiconductor layer, a temporary support substrate is bonded to the first main surface of the compound semiconductor layer via a polymer material bonding layer, and then the A temporary support bonded body forming step of forming a temporary support bonded body in which the compound semiconductor layer and the temporary support substrate are bonded by removing the growth substrate;
A bonding metal layer forming step of forming a bonding metal layer on the second main surface of the compound semiconductor layer exposed by removing the growth substrate;
An alloying heat treatment step of alloying the bonding metal layer with the compound semiconductor layer to form the bonding alloyed layer in the state of the temporary support bonded body; and
After completion of the alloying heat treatment, the compound semiconductor layer is handled at a temperature lower than the alloying heat treatment while the compound semiconductor layer is handled in the state of the temporary support bonded body, whereby the second main layer of the compound semiconductor layer is obtained. An element substrate bonding step of creating an element substrate bonded body in which an element substrate is bonded to the surface via a metal layer;
The polymer material bonding layer is heated and softened, and the temporary support substrate separation step of separating the temporary support substrate from the element substrate bonded body is performed in this order,
The alloying heat treatment is performed in an inert gas atmosphere in a temperature range of 300 ° C. or more and 450 ° C. or less, and the polymer material bonding layer used for the temporary support bonded body is 300 ° C. or more and 450 ° C. or less. A method for producing a light-emitting element, wherein a vapor pressure at a temperature of 10 torr or less is used.   2. The method for manufacturing a light-emitting element according to claim 1, wherein the total thickness of the compound semiconductor layer incorporated in the temporary support bonded body is 7 μm or more and 30 μm or less. The bonding metal layer is formed in a state of the temporary support bonded body in a vacuum atmosphere at a temperature of 60 ° C. or higher and 150 ° C. or lower, and the polymer material bonding layer is formed at a temperature of 60 ° C. or higher and 150 ° C. or lower. The method for manufacturing a light-emitting element according to claim 1, wherein a vapor pressure of 1 × 10 ⁻⁶ torr or less is used. In the state of the temporary support bonded body, a first Au-based metal layer to be a part of the metal layer is formed on the second main surface of the compound semiconductor layer, and on the other side of the bonded surface of the element substrate Forming a second Au-based metal layer to be a part of the metal layer, and bonding the first Au-based metal layer and the second Au-based metal layer in the element substrate bonding step;
The first Au-based metal layer is formed in a vacuum atmosphere at a temperature of 60 ° C. to 150 ° C., and the vapor pressure at a temperature of 60 ° C. to 150 ° C. is 1 × 10 ⁻⁶ torr as the polymer material bonding layer. The method for manufacturing a light-emitting element according to claim 1, wherein the following is used.

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