Junction-type light-emitting element wafer and method for manufacturing same

Abstract

The present invention is a bonded light-emitting element wafer in which a light-emitting element epitaxial wafer having an epitaxial layer including an active layer is bonded to a transparent substrate with an adhesive layer interposed therebetween, the transparent substrate being visible-light-transmissive and ultraviolet-light-transmissive. The adhesive layer is visible-light-transmissive and ultraviolet-light-impermeable, and the height at which spinous inclusions contained in the epitaxial layer protrude from the epitaxial layer is equal to or less than the thickness of the adhesive layer. The present invention thereby provides a bonded light-emitting element wafer in which an epitaxial wafer having thorn-like inclusions is bonded to a transparent substrate with an adhesive layer interposed therebetween, the adhesive layer being visible-light-transmissive and ultraviolet-light-impermeable, and the transparent substrate being visible-light-transmissive and ultraviolet-light-transmissive, the range of defective parts caused by spiny inclusions is narrow.

Description

Technical Field

[0001] The invention relates to a junction type light emitting element wafer and a manufacturing method thereof. Background Art

[0002] Conventionally, as a wafer for AlGaInP-based micro light-emitting diodes (micro LEDs, μLEDs), a technology of a bonded wafer (bonded light-emitting element wafer) with benzocyclobutene (BCB) interposed therebetween has been disclosed (for example, Patent Document 1).

[0003] Since the bonded wafer is formed by bonding two wafers to each other, poor bonding may occur due to the surface condition of each wafer (e.g., a substrate having an AlGaInP-based light-emitting element layer and a bonded substrate bonded to the substrate) or the presence of foreign matter at the bonding interface.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2022-013244 Summary of the invention

[0007] 1. Technical issues to be resolved

[0008] In particular, one of the two wafers to be bonded is an epitaxial wafer, so the presence of convex defective parts caused by foreign matter falling during the growth of the epitaxial layer of the epitaxial wafer is a problem. The origin of foreign matter falling during the growth process is mostly due to precipitates in the epitaxial growth furnace. During the growth process, gas containing raw materials is continuously supplied from the raw material gas inlet of the epitaxial growth furnace. It is difficult to completely block the radiant heat from the heating part at the inlet, and a small amount of raw material gas is decomposed and precipitated at the inlet.

[0009] The precipitate is not precipitated in the state of semiconductor, but precipitated in the state close to metal. In particular, the precipitate with In or Ga as the main component has a relatively low melting point, which is equal to or lower than the decomposition temperature of the organic metal as the raw material. Therefore, in the growth process, the precipitate is often in a state that is easy to peel off from the introduction port. The precipitate peeled off from the introduction port is transported by carrier gas and falls to the surface of the epitaxial layer. When peeling off, it will peel off along the carrier gas flow direction, so the precipitate is mostly in a spear-shaped shape, and is inserted into the surface of the epitaxial layer in a state that maintains the shape.

[0010] Therefore, the precipitates falling onto the epitaxial surface penetrate the epitaxial surface in a state of having a size (height) of several μm to tens of μm, directly forming an abnormal growth portion around it, and epitaxial growth is performed at the same time. In the case of smaller precipitates, they will be buried and form a hillock as the epitaxial growth progresses, or cause growth inhibition to form a hillock, but larger precipitates reaching tens of μm will not be buried in the epitaxial layer, but will remain as an abnormal growth portion with a spike-like convex portion after epitaxial growth.

[0011] Hereinafter, the precipitate is referred to as a "spike-shaped inclusion" or simply "inclusion". When an epitaxial wafer having a spike-shaped inclusion is attempted to be joined or bonded to a substrate to be joined, the inclusion is mechanically very fragile and thus is broken by the pressure applied during joining. With this destruction, particles are scattered around the inclusion, and joining or bonding is performed with the scattered particles sandwiched at the interface.

[0012] When the joined substrate or the joining layer / adhesive layer is made of a non-light-transmitting material such as metal, the particles sandwiched between the joining interface / adhesive interface are only a problem with the mechanical strength of the joining interface / adhesive interface, and there will be no problem as long as it does not cause problems during device processing or grain processing.

[0013] However, when the bonded substrate and the bonding layer / adhesive layer are made of a light-transmitting material, particles present at the bonding interface / adhesive interface absorb light and cause light scattering. In the chip where the increase in light scattering or absorption corresponds to the position where the increase in light scattering or absorption occurs, the chip has a significant difference in characteristics from the adjacent chip, so the uniformity of the distribution of the characteristics of the components formed in the wafer decreases, resulting in a decrease in yield.

[0014] In addition, particles scattered due to the destruction of the thorn-like inclusions (thorn-like protrusions) will be scattered over a relatively wide range, so the number of poorly joined parts will increase to a level greater than the influence of the height of the thorn-like inclusions, which will also become a major factor in reducing the yield.

[0015] Patent document 1 discloses a technique for bonding an epitaxial wafer having convexoconcave (convex) surfaces to a bonded wafer. However, the technique disclosed in Patent document 1 is a technique for a case where convexoconcave (convexoconcave) portions are formed roughly uniformly on the entire surface of a wafer, and does not disclose a technique for solving problems that occur when bonding to discrete, irregular, and thorn-like convexoconcave portions.

[0016] The present invention is completed in order to solve the above-mentioned problems, and its purpose is to provide a bonded light-emitting element wafer, which is formed by bonding an epitaxial wafer with thorn-like inclusions to a transparent substrate via an adhesive layer, wherein the adhesive layer is visible light transmissive and ultraviolet light opaque, and the transparent substrate is visible light transmissive and ultraviolet light transmissive, wherein the range of defective parts caused by the thorn-like inclusions is relatively narrow; and to provide a method for manufacturing a bonded light-emitting element wafer that suppresses the generation of particles generated by the thorn-like inclusions during the bonding, wherein the range of defective parts caused by the thorn-like inclusions in the bonded light-emitting element wafer is relatively narrow.

[0017] (II) Technical solution

[0018] The present invention is completed to achieve the above-mentioned purpose, and provides a junction type light-emitting element wafer, which is a junction type light-emitting element wafer in which an epitaxial wafer for a light-emitting element having an epitaxial layer including an active layer is bonded to a transparent substrate via an adhesive layer, the transparent substrate is visible light transmissive and ultraviolet light transmissive, the adhesive layer is visible light transmissive and ultraviolet light opaque, and the junction type light-emitting element wafer is characterized in that a thorny inclusion built into the epitaxial layer protrudes from the epitaxial layer to a height less than the thickness of the adhesive layer, and the front end of the thorny inclusion is destroyed.

[0019] In such a junction type light emitting element wafer, since the inclusion parts existing in the form of thorns on the surface of the epitaxial wafer protrude to a thickness less than that of the adhesive layer, the expansion of the poor junction portion can be suppressed, and thus the area of ​​the poor junction portion can be reduced.

[0020] At this time, it is preferable that the adhesive layer is selected from the group consisting of benzocyclobutene, silicone resin, epoxy resin, spin-on-glass (SOG), polyimide, and amorphous fluorine resin.

[0021] Such a material is suitable as the material of the adhesive layer of the junction type light emitting element wafer.

[0022] In addition, the present invention provides a method for manufacturing a junction-type light-emitting element wafer, which has the following steps: a step of making an epitaxial wafer for a light-emitting element having an epitaxial layer including an active layer on a starting substrate; a step of preparing a transparent substrate, wherein the transparent substrate is visible light transmissive and ultraviolet light transmissive; and a step of bonding the epitaxial wafer for the light-emitting element to the transparent substrate via an adhesive layer, wherein the adhesive layer is visible light transmissive and ultraviolet light opaque. In the method for manufacturing a junction-type light-emitting element wafer, before the bonding step, the epitaxial layer of the epitaxial wafer is placed opposite to a dummy wafer via a protective film and pressure is applied, thereby destroying the front end of a portion of a thorny inclusion built into the epitaxial layer that protrudes from the epitaxial layer until the height of the protrusion from the epitaxial layer is less than the thickness of the adhesive layer, thereby reducing the height of the thorny inclusion protruding from the epitaxial layer, and using the epitaxial wafer with the height of the thorny inclusion protruding from the epitaxial layer reduced to perform the bonding step.

[0023] Such a method for manufacturing a junction type light emitting element wafer can pre-destroy the tip of the thorn-like inclusion, thereby suppressing the generation of particles generated by the thorn-like inclusion during bonding, and can manufacture a junction type light emitting element wafer with a narrow range of defective parts generated by the thorn-like inclusion.

[0024] In this case, the thickness of the protective film can be set to 0.01 μm or more and 10 μm or less.

[0025] When the thickness of the protective film is such, the thorn-like inclusions can be effectively destroyed.

[0026] Furthermore, at this time, it is preferable that the thickness of the protective film be set to 0.05 μm or more and 10 μm or less.

[0027] When the protective film has such a thickness, the thorn-like inclusions can be effectively destroyed, and damage to the surface of the epitaxial layer can be suppressed.

[0028] Furthermore, in the method for manufacturing a junction-type light-emitting element wafer of the present invention, the adhesive layer is made of a material selected from the group consisting of benzocyclobutene, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluororesin.

[0029] Such a material can be suitably used as the material of the adhesive layer of the junction type light emitting element wafer.

[0030] (III) Beneficial effects

[0031] The junction type light emitting element wafer of the present invention can suppress the expansion of the poorly bonded portion because the inclusion portion existing in the form of a thorn on the surface of the epitaxial wafer protrudes less than the thickness of the adhesive layer, thereby reducing the area of ​​the poorly bonded portion.

[0032] In addition, the method for manufacturing a junction-type light-emitting element wafer of the present invention can suppress the generation of particles generated by thorn-like inclusions during bonding, and can manufacture a junction-type light-emitting element wafer having a narrower range of defective parts generated by thorn-like inclusions. In particular, by pre-destroying the inclusion part existing in the form of a thorn on the surface of the epitaxial wafer before bonding, the number of particles originating from the inclusion part generated during bonding can be reduced. In addition, by pre-destroying the inclusion part existing in the form of a thorn on the surface of the epitaxial wafer before bonding, the area of ​​the defective bonding part can be reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic cross-sectional view showing a part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0034] Figure 2 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0035] Figure 3 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0036] Figure 4 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0037] Figure 5 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0038] Figure 6 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0039] Figure 7 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0040] Figure 8 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0041] Fig. 9 It is a schematic cross-sectional view showing another part of the first embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention.

[0042] Fig.10This is an enlarged photograph showing the state of bonding of the inclusion portion after the treatment in the method for manufacturing a junction type light emitting element wafer of the present invention.

[0043] Fig.11 This is an enlarged photograph showing the state of bonding of an inclusion portion in a conventional bonding type light emitting element wafer manufacturing method.

[0044] Fig.12 It is a graph showing the width of the BCB thickness defective region in the example and the comparative example. DETAILED DESCRIPTION

[0045] Hereinafter, the present invention will be described in detail, but the present invention is not limited to these descriptions.

[0046] The junction type light emitting element wafer of the present invention is a junction type light emitting element wafer in which an epitaxial wafer for light emitting element having an epitaxial layer including an active layer is bonded to a transparent substrate via an adhesive layer, the transparent substrate is visible light transmissive and ultraviolet light transmissive, the adhesive layer is visible light transmissive and ultraviolet light non-transmissive, and the junction type light emitting element wafer is characterized in that the height of the thorn-like inclusions built into the epitaxial layer protruding from the epitaxial layer is less than the thickness of the adhesive layer. In the junction type light emitting element wafer of the present invention, the front end of the thorn-like inclusion is particularly broken.

[0047] Such a junction-type light-emitting element wafer can be manufactured using the method for manufacturing a junction-type light-emitting element wafer of the present invention. The method for manufacturing a junction-type light-emitting element wafer of the present invention has the following steps: a step of making an epitaxial wafer for a light-emitting element having an epitaxial layer including an active layer on a starting substrate; a step of preparing a transparent substrate, the transparent substrate being visible light-transmissive and ultraviolet light-transmissive; and a step of bonding the epitaxial wafer for a light-emitting element to the transparent substrate via an adhesive layer, the adhesive layer being visible light-transmissive and ultraviolet light-opaque. In the method for manufacturing a junction-type light-emitting element wafer, before the bonding step, the epitaxial layer of the epitaxial wafer is placed opposite to a filling sheet via a protective film and pressure is applied, thereby destroying the front end of the part of the thorn-like inclusion built into the epitaxial layer that protrudes from the epitaxial layer, reducing the height of the thorn-like inclusion protruding from the epitaxial layer, and performing the bonding step using the epitaxial wafer with the reduced height of the thorn-like inclusion protruding from the epitaxial layer. In the manufacturing method of the junction type light emitting element wafer of the present invention, the destruction of the front end of the part protruding from the epitaxial layer is carried out until the height protruding from the epitaxial layer is less than the thickness of the adhesive layer. In addition, in the present invention, "joining" means integrating two wafers by using an adhesive or the like, and includes the concepts of "bonding" and "laminating".

[0048] Hereinafter, the method for manufacturing a junction-type light-emitting element wafer of the present invention will be described by way of example using the first embodiment, the second embodiment, and the third embodiment. Similar components in each embodiment are described by being labeled with the same reference numerals in the drawings. In addition, repeated descriptions are omitted.

[0049] [First embodiment]

[0050] First, the first embodiment will be described.

[0051] First, if Figure 1 As shown, epitaxial growth is sequentially performed on a starting substrate 11 to form each layer, thereby manufacturing an epitaxial wafer 20. Thus, an epitaxial layer 18 including an etching stop layer 12 or an active layer 14 is grown. More specifically, the epitaxial growth of each layer can be performed in the following manner.

[0052] like Figure 1 As shown, an etching stop layer 12 is epitaxially grown on a starting substrate 11 of a first conductivity type, for example, made of GaAs. For example, a first conductivity type GaAs buffer layer is stacked and then a first conductivity type GaAs is formed. x In 1－x P (0.4 ≤ x ≤ 0.6) is grown as a first etching stop layer, for example, 0.1 μm, and a second etching stop layer of GaAs of the first conductivity type is grown as 0.1 μm, so that the etching stop layer 12 can be formed. Further, a light emitting element epitaxial wafer 20 (hereinafter sometimes simply referred to as "epitaxial wafer") having a light emitting element structure as an epitaxial layer (epitaxial functional layer) 18 is prepared. The light emitting element epitaxial wafer 20 is formed by sequentially growing, for example, a first conductivity type (AlAs) on the etching stop layer 12. y Ga 1－y )xIn 1－x The first cladding layer 13 is grown to 1.0 μm, for example, to make the undoped (Al y Ga 1－y )xIn 1－x P (0.4≤x≤0.6, 0≤y≤0.5) active layer 14, second conductivity type (Al y Ga 1－y )xIn 1－x The second cladding layer 15 is grown to a thickness of, for example, 1.0 μm, so that the second conductivity type Ga x In 1－xThe P (0.5≤x≤1.0) intermediate layer (not shown) is grown to a thickness of, for example, 0.1 μm, and the second conductivity type GaP window layer 16 is grown to a thickness of, for example, 5 μm. Here, the first cladding layer 13 to the second cladding layer 15 are referred to as a double heterogeneous (DH) structure. There are thorn-like inclusions 22 on the epitaxial wafer 20, which are formed by peeling off from the growth furnace and falling on the epitaxial wafer 20 (see Figure 1 ).

[0053] In the present invention, the thorn-like inclusion 22 is a foreign object embedded in the epitaxial layer 18, and refers to an amorphous spear-like object as described above. The "protrusion height" of the thorn-like inclusion 22 refers to the height of the thorn-like inclusion 22 from the surface of the epitaxial layer 18 (in Figure 1 In the case of , it is the height of the protrusion from the surface of the window layer 16).

[0054] The film thicknesses described above are merely examples, and the film thickness is only a parameter that changes according to the operating specifications of the device, and is of course not limited to the film thickness described here. In addition, each layer is not a single composition layer, and of course, it is conceptually included that there are multiple composition layers within the composition range described above. In addition, the level of carrier concentration is not uniform in each layer, and of course, it is conceptually included that there are multiple levels in each layer.

[0055] The active layer may be composed of a single composition, and even a structure in which a plurality of barrier layers and active layers are alternately laminated has similar functions, and both can be selected.

[0056] As described below, the epitaxial wafer 20 prepared in this manner is bonded to a transparent substrate as a bonding target wafer. In the present invention, before the bonding step described below, the epitaxial layer 18 of the epitaxial wafer 20 is placed opposite to the filling sheet via a protective film and pressure is applied.

[0057] Figure 2 The filling piece 41 can be set as a silicon wafer, for example. In the first embodiment, a protective film 42 is formed on the filling piece 41 (see Figure 2 ). The protective film 42 can be made of, for example, a photosensitive resist. It is preferred that after the protective film 42 formed of a photosensitive resist is coated on the filling sheet 41, a prebaking treatment is performed at about 90°C to remove the solvent contained in the resist in advance. The filling sheet 41 only needs to be flat and have a mechanical strength capable of destroying the thorn-like inclusions 22 and be inexpensive. As a material, in addition to the above-mentioned silicon, for example, quartz, GaP, GaAs, InP, GaN, SiC, etc. can be selected.

[0058] In addition, although a photosensitive resist is exemplified as the protective film 42, any material can be selected as long as it is a material required for protecting the surface of the epitaxial wafer 20 and has good wettability. Polyvinyl acetate, wax, various resists, HogoMax (registered trademark, propylene glycol monomethyl ether / polyvinyl alcohol containing material), benzocyclobutene (BCB), amorphous fluorine-based resin (for example, CYTOP (registered trademark)), silicone resin, epoxy resin, etc. can be selected.

[0059] Figure 3 The following situation is shown in the figure: Figure 2 The filling sheet 41 shown is formed with a protective film 42 , and the epitaxial layer 18 of the epitaxial wafer 20 is placed opposite to the filling sheet 41 via the protective film 42 , and pressure is applied.

[0060] The growth surface of the epitaxial wafer 20 (the surface with the thorn-like inclusions 22) is made to face the surface of the filling sheet 41 with the protective film 42, and pressure is applied to the epitaxial wafer in the same manner as in the following bonding to push the filling sheet 41 (see Figure 3 ). At this time, pressure is selectively applied to the thorn-like inclusion 22, and the front end is broken and the height is reduced. The portion of the height of the inclusion 22 that passes through the thickness of the protective film 42 and hits the filling sheet 41 is broken, and the height of the inclusion 22 equivalent to the thickness of the protective film 42 remains. Therefore, in order to reduce the remaining height, it is more appropriate that the protective film 42 is thinner. The viscosity of the protective material can be adjusted so that it can be applied thinner, and the remaining height can be further reduced.

[0061] Since the protrusion height of inclusions 22 is often 10 μm or more, the thickness of protective film 42 is preferably at least 10 μm or less. If the thickness of protective film 42 is greater than the protrusion height of inclusions 22, pressure cannot be applied to inclusions 22, resulting in inclusions 22 not being broken.

[0062] On the other hand, the protective film 42 also has the function of preventing the surface of the epitaxial wafer 20 from being damaged by embedding the fragments (particles) generated by the destruction of the inclusions 22 into the protective film 42. If it is too thin, the risk of damaging the surface of the epitaxial wafer 20 increases. Therefore, in order to protect the surface of the epitaxial wafer 20, it is preferably 0.05 μm or more thick.

[0063] When the thickness of the protective film 42 is made thinner (for example, less than 0.05 μm), the particles generated by the destruction of the inclusions 22 may damage the surface of the epitaxial wafer 20. In order to improve the brightness, the surface of the epitaxial wafer 20 is often roughened. At this time, the damage to the surface of the epitaxial wafer 20 caused by the particles will not become a problem, so that a thin film of about 0.01 μm can be made, for example.

[0064] In addition, if the remaining height (height protruding from the epitaxial layer 18) after the inclusion 22 is destroyed is lower than the thickness of the bonding layer during bonding in the subsequent process, the remaining part of the inclusion is contained in the bonding layer (BCB, etc.) and does not collide with the bonded substrate, so that the bonding defect area can be suppressed to a minimum. Therefore, by setting the thickness of the protective film 42 to be less than the thickness of the bonding layer, it is expected to reduce the bonding defect caused by the inclusion 22. For example, when the thickness of the bonding layer is 0.6μm, it is more appropriate to design the thickness of the protective film 42 to be less than 0.6μm.

[0065] In such Figure 3 After the step of destroying the inclusions 22 by using the filling sheet 41 as shown, the epitaxial wafer 20 is removed from the filling sheet 41, and the protective film 42 and residual particles attached to the epitaxial wafer 20 are removed (see Figure 4 ). To remove them, when a photosensitive resist or wax is selected as the protective film 42, washing is performed with an organic solvent, when a water-insoluble BCB, CYTOP, or silicone is selected as the protective film 42, washing is performed with a rinse solution, such as a thinner or a stripping solution, and when a water-soluble HogoMax is selected as the protective film 42, washing is performed with pure water. By washing in this manner, the protective film 42 and particles are removed, thereby obtaining an epitaxial wafer 20 with reduced height of the thorn-like inclusions 22 (see Figure 4 ).

[0066] The epitaxial wafer 20 in which the height of the thorn-like inclusions 22 protruding from the epitaxial layer 18 is reduced in the above manner is bonded to a transparent substrate 30 as a bonding wafer via an adhesive layer 25 (see Figure 5 ). More specifically, the bonding process can be performed in the following manner.

[0067] As an adhesive layer, an adhesive layer 25 that is transparent to visible light and opaque to ultraviolet light is used. In the description of the present invention, opaque to ultraviolet light refers to having a light absorption edge in a wavelength region of 170 nm to 360 nm and a transmittance of 50% or less under the light absorption edge. As a bonded wafer, i.e., a transparent substrate, a transparent substrate made of a material that is transparent to visible light and opaque to ultraviolet light is used. Benzocyclobutene (BCB) is spin-coated on the epitaxial wafer 20 as a bonding material that is transparent to visible light and opaque to ultraviolet light (preferably a thermosetting bonding material), and then overlapped with a transparent substrate 30 (e.g., a sapphire wafer) as a bonded substrate in a relative manner, and thermocompression bonding is performed, thereby making a bonded light-emitting element wafer (epitaxial wafer bonding substrate) in which the epitaxial wafer 20 and the transparent substrate 30 (e.g., a sapphire wafer) are bonded via an adhesive layer 25 (e.g., BCB). When BCB is applied by spin coating, the designed film thickness can be set to 0.6 μm, for example.

[0068] In the present embodiment, the case where the substrate to be bonded is sapphire is exemplified, but any material may be used as long as it has flatness and visible light transmittance and UV light transmittance, and quartz or the like can be selected.

[0069] In addition, in this embodiment, BCB is exemplified as a bonding material for forming the adhesive layer 25, but it is not limited to BCB, and any material can be selected as long as it is visible light transmissive and UV light opaque. The bonding material is preferably a thermosetting material, and in addition to BCB, silicone resin, epoxy resin, SOG, polyimide, and amorphous fluorine resin (such as CYTOP) can also be used.

[0070] Furthermore, in this embodiment, Figure 5 The case where BCB is applied in a layered state is exemplified, but it is not limited to the layered state. Of course, even if photosensitive BCB is used and patterned into isolated islands, lines, or other shapes and then the bonding process is performed, the same result can be obtained.

[0071] Can be manufactured by the above method Figure 5 The junction type light emitting element wafer shown in the figure is formed by bonding an epitaxial wafer 20 for light emitting element having an epitaxial layer 18 including an active layer 14 and a transparent substrate 30 via an adhesive layer 25, wherein the transparent substrate is visible light transparent and ultraviolet light transparent, and the adhesive layer is visible light transparent and ultraviolet light non-transparent. Figure 5 In the junction-type light-emitting device wafer, the height of the thorn-like inclusions 22 embedded in the epitaxial layer 18 protruding from the epitaxial layer 18 is less than or equal to the thickness of the adhesive layer 25 .

[0072] In addition, the junction type light emitting element wafer of the present invention can be further processed in the following manner. Figure 6 Specifically, the GaAs starting substrate 11 is removed by wet etching to expose the first etching stop layer 12, and the second etching stop layer is removed by switching the etchant to expose the first cladding layer 13. By performing the above process, an epitaxial bonding substrate ( Figure 6 ) In this embodiment, a BCB thickness of 0.6 μm is exemplified, but the thickness is not limited to this.

[0073] Furthermore, the device separation can be continued as described below to form electrodes of each device. The following methods of device separation and electrode formation are exemplified.

[0074] First, if Figure 7As shown, the element separation is performed, for example, in the following manner. A pattern is formed by photolithography, and the element separation process is performed by inductively coupled plasma (ICP). The gases used for ICP are chlorine and argon. The ICP process is performed twice: a process of exposing the BCB layer and a process of exposing the second cladding layer 15.

[0075] In this embodiment, the case where the second cladding layer 15 is exposed is illustrated, but it is of course not limited to the case where the second cladding layer 15 is exposed. As long as at least the active layer 14 is separated, the processing purpose can be achieved. Therefore, even if it is not the second cladding layer 15 that is exposed but the GaP window layer 16 that is exposed, the same effect can be obtained.

[0076] After the components are separated and processed, Figure 8 As shown, a light emitting element protection film 52 is formed as the end surface treatment. In this embodiment, SiO2 can be used as the light emitting element protection film 52. The protection film is not limited to SiO2, and any material can be selected as long as it can protect the end surface and has insulating properties. SiN x Or titanium oxide, magnesium oxide, etc.

[0077] After forming the light emitting element protection film 52, Fig. 9 As shown, the electrode 54 of the element is formed. For example, by forming the electrode 54 that contacts the first conductive type layer or the second conductive type layer, and applying heat treatment, an ohmic contact is formed. In this embodiment, the first conductive type can be designed as an N type, the second conductive type can be designed as a P type, a metal containing Au and Si is used as an electrode in contact with the N type layer, and a metal containing Au and Be is used as an electrode in contact with the P type layer.

[0078] In this embodiment, as an N-type electrode, for example, a metal of Au and Si can be used, but it is not limited to this material, and a metal containing Au and Ge can also be used. In addition, as a P-type electrode, for example, a metal of Au and Be can be used, but it is not limited to this material, and a metal containing Au and Zn can also be used.

[0079] In this embodiment, the case of a bonded wafer obtained by using an AlGaInP-based light-emitting element is illustrated, but it is not limited to this material and function. When manufacturing a bonded light-emitting element wafer that will produce a defective epitaxial wafer 20 caused by thorny inclusions 22 (thorny protruding foreign matter), of course, any material system can be used.

[0080] [Second embodiment]

[0081] Next, a second embodiment of the method for manufacturing a junction type light emitting element wafer of the present invention is described. The steps and structures until the epitaxial wafer 20 is formed are the same as those of the first embodiment. Figure 3 The protective film 42 when the pressure is applied using the filling sheet 41 shown is formed on (not the filling sheet 41 but) Figure 1 On the surface of the epitaxial wafer 20 shown ( Figure 1 Using such epitaxial wafer 20 and filler sheet 41, pressure is applied to the surface of epitaxial wafer 20 via protective film 42. The method of destroying thorn-like inclusions 22 and the subsequent steps are the same as those of the first embodiment.

[0082] [Third embodiment]

[0083] Next, a third embodiment of the method for manufacturing a junction-type light-emitting element wafer of the present invention is described. The steps and structures until the epitaxial wafer 20 is formed are the same as those of the first embodiment. Figure 3 The protective film 42 is formed on the epitaxial wafer 20 shown in the figure when the pressure is applied using the filling sheet 41, and also formed Figure 2 That is, the protective film 42 is formed on the surface of the epitaxial wafer 20 ( Figure 1 At this time, by making the total thickness of the protective film (the total thickness of the protective film formed on the surface of the epitaxial wafer 20 and the thickness of the protective film formed on the surface of the filling sheet 41) less than the thickness of the adhesive layer, it is expected to reduce the bonding defects caused by the inclusions 22. The method of destroying the thorn-like inclusions 22 and the subsequent steps are the same as those in the first embodiment.

[0084] In any of the first to third embodiments, according to the present invention, the influence of the thorn-like inclusions 22 (thorn-like protrusions) caused by the epitaxial growth of the epitaxial wafer 20 and difficult to completely eliminate during bonding can be reduced, thereby reducing the area of ​​the bonding defective portion.

[0085] [Example]

[0086] Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples, but these examples do not limit the present invention.

[0087] (Example 1)

[0088] According to the first embodiment, a junction type light-emitting element wafer is manufactured.

[0089] First, if Figure 1 As shown, after stacking a first conductive type GaAs buffer layer on a first conductive type GaAs starting substrate 11, the first conductive type GaAsx In 1－x P (0.4 ≤ x ≤ 0.6) first etching stop layer is epitaxially grown to 0.1 μm, and GaAs second etching stop layer of the first conductivity type is epitaxially grown to 0.1 μm to form etching stop layer 12. y Ga 1－y )xIn 1－x The first cladding layer 13 is grown by 1.0 μm, and the undoped (Al y Ga 1－y )xIn 1－x P (0.4≤x≤0.6, 0≤y≤0.5) active layer 14, second conductivity type (Al y Ga 1－y )xIn 1－x The second cladding layer 15 is grown by 1.0 μm, and the second conductivity type Ga x In 1－x The epitaxial wafer 20 having a light emitting element structure as the epitaxial layer (epitaxial functional layer) 18 is prepared by growing a P (0.5≤x≤1.0) intermediate layer (not shown) by 0.1 μm and growing a second conductive type GaP window layer 16 by 5 μm. The epitaxial wafer 20 has a thorn-like inclusion 22 formed by peeling off from the growth furnace and falling on the epitaxial wafer (refer to Figure 1 ).

[0090] Then, if Figure 2 As shown, a silicon wafer was prepared as a filler sheet 41, and a photosensitive resist was applied on the filler sheet to form a 0.5 μm protective film 42. After the application, a pre-baking process was performed at about 90° C. to remove the solvent contained in the resist.

[0091] Then, if Figure 3 As shown, the growth surface of the epitaxial wafer 20 (the surface having the thorn-like inclusions 22 ) is made to face and overlap the surface of the filling sheet on which the protective film 42 is formed, and pressure is applied to the epitaxial wafer 20 to push against the filling sheet 41 .

[0092] After the pressure treatment, Figure 4 As shown, the epitaxial wafer 20 is removed from the filling sheet 41, and the coating film (protective film 42) and residual particles attached to the epitaxial wafer 20 are removed.

[0093] Then, if Figure 5As shown, benzocyclobutene (BCB) is spin-coated on the epitaxial wafer 20 as the adhesive layer 25, and the epitaxial wafer 20 is overlapped with the sapphire wafer (transparent substrate 30) as the substrate to be bonded in a relative manner, and thermocompression bonding is performed, thereby bonding the epitaxial wafer 20 and the sapphire wafer (transparent substrate 30) through the BCB (adhesive layer 25). The coating of BCB involves a film thickness of 0.6μm.

[0094] Then, if Figure 6 As shown, the GaAs starting substrate 11 is removed by wet etching to expose the first etching stop layer, and the etchant is switched to remove the second etching stop layer to expose the first cladding layer 13, thereby manufacturing an epitaxial bonding substrate with only the DH layer and the window layer 16.

[0095] Then, if Figure 7 As shown, the pattern was formed by photolithography, and the element separation process was performed by ICP. The gas used for ICP was chlorine gas and argon gas. The ICP process was performed twice: a process of exposing the BCB layer (adhesive layer 25) and a process of exposing the second cladding layer 15.

[0096] After the components are separated and processed, Figure 8 As shown, a light emitting element protection film 52 including SiO2 is formed as an end surface treatment.

[0097] Then, if Fig. 9 As shown, after forming the light emitting element protection film 52, an electrode 54 is formed to contact the first conductive type layer or the second conductive type layer, and a heat treatment is applied, thereby forming an ohmic contact. In this embodiment, the first conductive type is designed to be N-type, the second conductive type is designed to be P-type, a metal containing Au and Si is used as an electrode in contact with the N-type layer, and a metal containing Au and Be is used as an electrode in contact with the P-type layer.

[0098] (Example 2)

[0099] The steps and structures until the epitaxial wafer 20 is formed are the same as those in Example 1. Except for forming the protective film 42 on the epitaxial wafer 20, the same method as in Example 1 is used to destroy the thorn-like inclusions 22, peel off the filler sheet 41, clean the epitaxial wafer 20, bond it to the sapphire wafer (transparent substrate 30) through the BCB, remove the starting substrate 11, and form the element.

[0100] (Example 3)

[0101] The steps and structures until the epitaxial wafer 20 is formed are the same as those in Example 1. Except that the protective film 42 is formed on both the epitaxial wafer 20 and the filling sheet 41, the same method as in Example 1 is used to destroy the thorny inclusions 22, peel off the filling sheet 41, clean the epitaxial wafer 20, bond it to the sapphire wafer (transparent substrate 30) through the BCB, remove the starting substrate 11, and form the element.

[0102] (Comparative Example)

[0103] The steps and structures until the epitaxial wafer 20 are formed are the same as those of Examples 1 to 3. A device is fabricated in the same manner as in Examples 1 to 3 except that the destruction of the thorn-like inclusions 22 shown in Examples 1 to 3 is not performed (ie, the filler sheet 41 is not used).

[0104] (Comparison between Example and Comparative Example)

[0105] Fig.10 FIG. 2 shows the state of the joint at the position where the inclusion 22 exists after the treatment of Example 1 is applied. Fig.11 The figure shows the location of inclusions in the comparative example when the bonding is performed according to the conventional process. In either case, inclusions exist near the center of the figure, the coating film in the area where the inclusions exist is uneven, and the film thickness near the inclusions becomes thicker. Compared with the comparative example, the diameter of the area where the film thickness distribution occurs in the embodiment (the part indicated by the solid arrow) is about half. In particular, the area ratio of the area with significantly thicker film thickness (the part indicated by the dotted arrow) is less than 1 / 3 compared with the comparative example.

[0106] In addition, in previous examples ( Fig.11 ), a large number of black spots and annular areas surrounding the black spots can be confirmed around the inclusions. The black spots are particles that are broken and scattered during the joining process, and the annular area around the black spots is the area where the BCB is locally thickened. In the previous examples, particles originating from inclusions are scattered around the inclusions, but in the examples, such particles originating from inclusions do not exist or are significantly reduced.

[0107] Fig.12 1 and 2 show the width of the BCB thickness defective region in the example and the comparative example when the total thickness of the protective film 42 is 0.5 μm. The defective portion diameters in Examples 1 to 3 are smaller than those in the comparative example.

[0108] In Example 1, a 0.5 μm thick BCB protective film 42 was applied on the filler sheet, in Example 2, a 0.5 μm thick BCB protective film 42 was applied on the epitaxial wafer, and in Example 3, the viscosity was adjusted and a 0.25 μm thick BCB protective film 42 was applied on both the epitaxial wafer and the filler sheet. In Example 3, the improvement effect was slightly reduced. It is believed that this is because the protective film 42 was applied on these two wafers, resulting in the protective film 42 being actually thicker than in the case of applying a single film, and the effect of reducing the remaining height of inclusions was reduced.

[0109] The present invention is not limited to the above-mentioned embodiments. The above-mentioned embodiments are illustrative, and any technical solution having substantially the same structure and exerting the same function and effect as the technical concept described in the claims of the present invention is included in the technical scope of the present invention.

Claims

1. A bonded light emitting element wafer, wherein an epitaxial wafer for a light emitting element having an epitaxial layer including an active layer is bonded to a transparent substrate via an adhesive layer, the transparent substrate being transparent to visible light and transparent to ultraviolet light, the adhesive layer being transparent to visible light and non-transparent to ultraviolet light, the bonded light emitting element wafer being characterized in that: The height of the thorn-like inclusions embedded in the epitaxial layer protruding from the epitaxial layer is less than the thickness of the adhesive layer, and the tip end of the thorn-like inclusions is broken.

2. The junction type light emitting element wafer according to claim 1, characterized in that: The adhesive layer is selected from the group consisting of benzocyclobutene, silicone resin, epoxy resin, spin-coated glass, polyimide, and amorphous fluorine resin.

3. A method for manufacturing a junction type light emitting element wafer, characterized in that: It has the following processes: A step of manufacturing an epitaxial wafer for a light-emitting element having an epitaxial layer including an active layer on a starting substrate; A step of preparing a transparent substrate, wherein the transparent substrate is transparent to visible light and ultraviolet light; and The step of bonding the epitaxial wafer for the light emitting element to the transparent substrate via an adhesive layer, wherein the adhesive layer is transparent to visible light and opaque to ultraviolet light, In the method for manufacturing the junction type light emitting element wafer, Before the bonding step, the epitaxial layer of the epitaxial wafer is placed opposite to a filling sheet via a protective film and pressure is applied. Thus, the tip of the part of the thorn-like inclusion built into the epitaxial layer that protrudes from the epitaxial layer is destroyed until the height of the protrusion from the epitaxial layer is less than the thickness of the adhesive layer, thereby reducing the height of the thorn-like inclusion that protrudes from the epitaxial layer. The bonding step is performed using an epitaxial wafer in which the height of the thorn-like inclusions protruding from the epitaxial layer is reduced.

4. The method for manufacturing a junction type light emitting element wafer according to claim 3, characterized in that: The thickness of the protective film is set to be 0.01 μm or more and 10 μm or less.

5. The method for manufacturing a junction type light emitting element wafer according to claim 4, characterized in that: The thickness of the protective film is set to 0.05 μm or more and 10 μm or less.

6. The method for manufacturing a junction-type light-emitting element wafer according to any one of claims 3 to 5, characterized in that: The adhesive layer is selected from the group consisting of benzocyclobutene, silicone resin, epoxy resin, spin-coated glass, polyimide, and amorphous fluorine resin.

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