Method for manufacturing compound semiconductor junction substrate

Abstract

The present invention relates to a method for manufacturing a compound semiconductor junction substrate, the method comprising: (1) a step for epitaxially growing a compound semiconductor functional layer on a starting substrate; (2) a step for temporarily bonding a support substrate to an epitaxial growth surface to form a first compound semiconductor junction substrate; (3) a step for removing the starting substrate from the first compound semiconductor junction substrate to form a second compound semiconductor junction substrate; (4) a step for finally bonding the surface, from which the starting substrate has been removed, of the second compound semiconductor junction substrate, to a permanent substrate to form a third compound semiconductor junction substrate; and (5) a step for removing the support substrate from the third compound semiconductor junction substrate to form a fourth compound semiconductor junction substrate, wherein the temporary bonding is performed via a thermosetting resin, the thermosetting resin is maintained in a softened state without being cured, and the final bonding is performed via a silicon oxide film or a silicon nitride film. Thus, provided is a method for manufacturing a compound semiconductor junction substrate having an improved degree of freedom in designing a device or a device system.

Description

[Technical field]

[0001] The present invention relates to a technique for epitaxially growing a compound semiconductor functional layer on a starting substrate, separating only the epitaxially grown layer, and transferring it to another substrate. [Background technology]

[0002] The technology to separate only the epitaxial functional layer from the starting substrate and transfer it to another substrate is important for alleviating the constraints imposed by the physical properties of the starting substrate and increasing the design freedom of the device system. To achieve this transfer, a technology is required to temporarily bond and hold the epitaxial functional layer on a temporary support substrate, bond it to a permanent substrate, and then release the temporary bond to realize the transfer.

[0003] Patent Document 1 discloses a technique for separating a temporary support substrate and an epitaxial functional layer by wet etching. However, in Patent Document 1, a separation groove is required to separate the temporary support substrate and the epitaxial functional layer by wet etching.

[0004] Because peeling by wet etching requires the formation of isolation grooves, there was a problem in that the presence of the isolation grooves restricted design freedom in cases such as when non-uniform device patterns exist within a single wafer or when the isolation grooves need to be narrow. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2021-27301 Summary of the Invention [Problem to be solved by the invention]

[0006] The present invention has been made in consideration of the above problems, and has an object to provide a method for manufacturing a compound semiconductor junction substrate which does not require a separation groove to separate an epitaxial functional layer from a supporting substrate, thereby improving the freedom in designing a device or device system. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides (1) epitaxially growing a compound semiconductor functional layer on a starting substrate; (2) temporarily bonding a support substrate to the epitaxial growth surface to form a first compound semiconductor bonded substrate; (3) removing the starting substrate from the first compound semiconductor junction substrate to obtain a second compound semiconductor junction substrate; (4) bonding the surface of the second compound semiconductor junction substrate from which the starting substrate has been removed to a permanent substrate to form a third compound semiconductor junction substrate; and (5) removing the support substrate from the third compound semiconductor junction wafer to obtain a fourth compound semiconductor junction wafer; A method for manufacturing a compound semiconductor junction substrate, comprising: The temporary bonding in the step (2) is performed via a thermosetting resin, and the thermosetting resin is maintained in a softened state without being hardened, and The present invention provides a method for producing a compound semiconductor junction substrate, in which the main bonding in the step (4) is performed via a silicon oxide film or a silicon nitride film.

[0008] In this way, a thermosetting resin is used for the temporary bond, and by maintaining the resin in a softened state without hardening it, the temporary bond can be easily peeled off. Also, by using a silicon oxide film for the main bond, the thermosetting resin does not harden due to the high temperatures that occur when the silicon oxide film is formed, which increases the freedom in designing devices or device systems.

[0009] It is also preferable that the thermosetting resin is applied to a thickness greater than 1.0 μm and equal to or less than 30 μm.

[0010] A thickness of more than 1.0 μm improves dissolvability and peelability, and from the standpoint of cost and ensuring flatness after bonding, a thickness of 30 μm or less is preferable.

[0011] The thermosetting resin is preferably a benzocyclobutene (BCB) resin, a fluororesin, or a polyimide (PI) resin.

[0012] These resins can reliably maintain a softened state and can be easily dissolved and peeled off.

[0013] It is also preferable that the surface roughness of the silicon oxide film or silicon nitride film is set to Ra=1 nm or less.

[0014] Such a surface roughness is preferable for realizing stable bonding.

[0015] In addition, it is preferable that the support substrate is made of any one of AlN, Al2O3, Cu, GaAs, GaN, GaP, InP, Si, SiC, and SiO2.

[0016] In the present invention, such a support substrate can be suitably used.

[0017] The present invention also provides a compound semiconductor bonded substrate in which a compound semiconductor functional layer is bonded to a supporting substrate via a thermosetting resin, the thermosetting resin being bonded in a softened state.

[0018] In the case of such a compound semiconductor substrate, the compound semiconductor functional layer can be permanently bonded and the support substrate can be easily peeled off.

[0019] It is also preferable that the thermosetting resin has a thickness of more than 1.0 μm and not more than 30 μm.

[0020] A thickness of more than 1.0 μm improves dissolvability and peelability, and from the standpoint of cost and ensuring flatness after bonding, a thickness of 30 μm or less is preferable.

[0021] The thermosetting resin is preferably a benzocyclobutene (BCB) resin, a fluororesin, or a polyimide (PI) resin.

[0022] These resins can reliably maintain a softened state and can be easily dissolved and peeled off.

[0023] It is also preferable that a silicon oxide film or a silicon nitride film is formed on the surface of the compound semiconductor functional layer to which the support substrate is not bonded.

[0024] By forming the silicon oxide film in this manner, permanent bonding can be easily achieved.

[0025] The silicon oxide film or silicon nitride film preferably has a surface roughness Ra of 1 nm or less.

[0026] Such a surface roughness is preferable for realizing stable bonding.

[0027] It is also preferable that the support substrate is made of any one of AlN, Al2O3, Cu, GaAs, GaN, GaP, InP, Si, SiC, and SiO2.

[0028] In the present invention, such a support substrate can be suitably used. Effect of the Invention

[0029] As described above, the present invention can provide a method for manufacturing a compound semiconductor junction substrate that does not require a separation groove when separating an epitaxial functional layer from a supporting substrate, thereby improving the degree of freedom in designing a device or device system. [Brief description of the drawings]

[0030] [Figure 1] FIG. 2 is a flow chart showing an example of a method for producing a compound semiconductor junction substrate according to the present invention. [Diagram 2] 1 is a schematic diagram showing a compound semiconductor functional layer epitaxially grown on a starting substrate in the first and second embodiments of the present invention. FIG. [Diagram 3] FIG. 11 is a schematic diagram showing a first compound semiconductor junction substrate formed by temporarily bonding a support substrate onto a grown epitaxial layer via BCB resin in the first and second embodiments of the present invention. [Figure 4] FIG. 4 is a schematic diagram showing a state where a second compound semiconductor junction substrate is obtained by removing the starting substrate in the first and second embodiments of the present invention. [Diagram 5] FIG. 4 is a schematic diagram showing a state where a silicon oxide film is formed on a surface from which a starting substrate has been removed in the first and second embodiments of the present invention. [Figure 6] FIG. 11 is a schematic diagram showing a third compound semiconductor bonded substrate obtained by permanently bonding a silicon oxide film surface to a permanent substrate in the first and second embodiments of the present invention. [Figure 7] FIG. 11 is a schematic diagram showing a fourth compound semiconductor junction wafer obtained by removing the support substrate in the first and second embodiments of the present invention. [Figure 8] 1 is a graph showing the relationship between the thickness and surface roughness (Ra) of a silicon oxide film (SiO2). [Figure 9] 1 is a graph showing the relationship between removal amount and surface roughness (Ra) when a silicon oxide film (SiO2) is polished. [Figure 10] 1 is a graph showing the relationship between the thickness of a silicon oxide film (SiO2) and the peeled area ratio when immersed in a dissolving solution, with the thickness of the BCB resin as a parameter. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] As described above, there has been a demand for a method of manufacturing a compound semiconductor junction substrate that does not require a separation groove in separating an epitaxial functional layer from a supporting substrate and that improves the degree of freedom in designing a device or device system.

[0032] After extensive research, the inventors discovered that a thermosetting resin is used for temporary bonding, which is maintained in a softened state without being hardened, and that main bonding is performed via a silicon oxide film, thereby enabling temporary bonding and main bonding to be performed without providing a separation groove, and allowing the support substrate to be easily peeled off, thereby completing the present invention.

[0033] That is, the present invention provides: (1) epitaxially growing a compound semiconductor functional layer on a starting substrate; (2) temporarily bonding a support substrate to the epitaxial growth surface to form a first compound semiconductor bonded substrate; (3) removing the starting substrate from the first compound semiconductor junction substrate to obtain a second compound semiconductor junction substrate; (4) bonding the surface of the second compound semiconductor junction substrate from which the starting substrate has been removed to a permanent substrate to form a third compound semiconductor junction substrate; and (5) removing the support substrate from the third compound semiconductor junction wafer to obtain a fourth compound semiconductor junction wafer; A method for manufacturing a compound semiconductor junction substrate, comprising: The temporary bonding in the step (2) is performed via a thermosetting resin, and the thermosetting resin is maintained in a softened state without being hardened, and In the method for producing a compound semiconductor junction substrate, the main bonding in the step (4) is performed via a silicon oxide film or a silicon nitride film.

[0034] <Method of manufacturing compound semiconductor junction substrate> DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The method for producing a compound semiconductor junction substrate of the present invention will now be described in more detail with reference to the drawings with respect to embodiments thereof, but the present invention is not limited thereto.

[0035] First embodiment A first embodiment of a method for temporarily bonding semiconductor substrates will be described with reference to FIGS.

[0036] First, as shown in Fig. 2, a first-conductivity type GaAs buffer layer 2 is laminated on a first-conductivity type GaAs starting substrate 1 in an MOCVD apparatus, and then a first-conductivity type GaInP first etch-stop layer 3, a first-conductivity type GaAs second etch-stop layer 4, a first-conductivity type AlGaInP first cladding layer 5, a non-doped AlGaInP active layer 6, a second-conductivity type AlGaInP second cladding layer 7, a second-conductivity type GaInP intermediate layer 8, and a second-conductivity type GaP window layer 9 are sequentially grown as epitaxial functional layers to prepare an epitaxial wafer having a light-emitting device structure (step (1) in Fig. 1). Here, the first cladding layer 5 to the second cladding layer 7 are referred to as a double hetero (DH) structure.

[0037] It should be noted that the present invention is not limited to an AlGaInP-based light-emitting diode structure, but can also be applied to any AlGaInP-based light-emitting element structure lattice-matched to a GaAs substrate, an AlGaAs-based light-emitting element structure, an AlGaAs-based HEMT structure, an InGaP-based HBT structure, an InGaP / GaAs-based solar cell structure, etc. Also applicable are an (Al)InGaAs(P)-based light-emitting element structure lattice-matched to an InP substrate, an (Al)InGaAs(P)-based light-receiving element structure, an (Al)InGaAs(P)-based HEMT structure, an (Al)InGaAs(P)-based HBT structure, etc.

[0038] 3, a thermosetting resin, for example, benzocyclobutene (BCB) resin 10 is spin-coated onto the epitaxial wafer, and then the epitaxial wafer is placed face-to-face on a support substrate, for example, a silicon wafer 11, and then thermocompression-bonded to produce a first compound semiconductor bonded substrate 101 in which the epitaxial wafer and silicon wafer 11 are bonded (temporarily bonded) via the BCB resin 10 (step (2) in FIG. 1). Bonding is performed under conditions such that the temperature of the BCB resin 10 is 150° C. or less.

[0039] In addition, it is also preferable to use a fluororesin or a polyimide (PI) resin as the thermosetting resin. It is also preferable to apply the thermosetting resin to a thickness of more than 1.0 μm and less than 30 μm. By making the thickness more than 1.0 μm, the dissolving and peeling properties are improved, and by making the thickness less than 30 μm, the cost can be reduced and the flatness after bonding can be improved.

[0040] The support substrate may be made of any one of AlN, Al2O3, Cu, GaAs, GaN, GaP, InP, Si, SiC, and SiO2.

[0041] Next, as shown in Fig. 4, the GaAs starting substrate 1 is removed by wet etching to expose the first etch stop layer 3, and the etchant is switched to remove the second etch stop layer 4 to expose the first cladding layer 5, thereby producing a second compound semiconductor junction substrate 102 that retains only the DH layer and the window layer (step (3) in Fig. 1). At this time, since the ammonia / hydrogen peroxide etchant has etching selectivity for GaInP-based materials, the etching stops when it reaches the GaInP layer, and therefore only the GaAs starting substrate can be selectively removed.

[0042] Next, as shown in FIG. 5, a silicon oxide film 12 (SiO2) is formed on the surface of the first cladding layer 5 by sputtering to a thickness of 50 nm or less.

[0043] In this embodiment, the SiO2 film is formed by sputtering, but the method is not limited to sputtering as long as the temperature of the substrate is not higher than 150° C. and the flatness can be ensured. For example, PLD (pulsed laser deposition) and ALD (atomic layer deposition) can be selected.

[0044] Film formation by P-CVD is also possible, but requires application of a higher temperature than around 250°C. At a temperature of 250°C, the BCB film hardens even in a short time, so in order to achieve film formation while suppressing the hardening of the BCB resin, a very short processing time is required. Although it is possible, it cannot be said to be preferable.

[0045] Evaporation using an electron gun can form a SiO2 film while suppressing the rise in substrate temperature. Film formation using electron gun evaporation has a large distribution of film thickness, and the in-plane distribution of roughness also becomes large accordingly. Although film formation is possible, it cannot be said to be preferable.

[0046] Also, even if the bonding to the permanent substrate is not performed via SiO2, it is possible to bond the substrate to the permanent substrate after plasma activation processing without providing SiO2. However, by providing SiO2 and bonding the substrate, it is possible to accommodate various process designs.

[0047] Next, as shown in FIG. 6, the surface of the silicon oxide film 12 (SiO2) and the surface of the permanent substrate 13 (wafer to be bonded) are both subjected to plasma activation treatment, and then they are stacked in a vacuum atmosphere and bonded (main bonding) by applying pressure to produce a third compound semiconductor bonded substrate 103 (step (4) in FIG. 1).

[0048] Finally, as shown in FIG. 7 , third compound semiconductor bonded substrate 103 is immersed in a BCB dissolving solution to dissolve BCB resin 10, and silicon wafer 11 is separated from third compound semiconductor bonded substrate 103 to obtain fourth compound semiconductor bonded substrate 104.

[0049] When the peeling of the silicon wafer 11 (support substrate) does not proceed smoothly, applying rotational pressure to the bonded silicon wafer 11 side makes the peeling proceed more easily.

[0050] In addition, by selecting the sputtering method in forming the silicon oxide film (SiO2) described above and setting the thin film condition of 2 nm to 50 nm, it is possible to suppress the temperature rise of the BCB resin film accompanying the film formation, and film formation at 150°C or less can be achieved. Since BCB resin hardens when maintained at a temperature condition above 150°C, hardening of the BCB resin can be prevented by maintaining a temperature of 150°C or less. Preventing hardening of the BCB resin can improve the peelability of the silicon wafer from the third compound semiconductor junction substrate.

[0051] Also, as shown in Figure 8, if the thickness of the silicon oxide film (SiO2) is 50 nm or less, the surface roughness (Ra) can be made 1 nm or less. When bonding (main bonding) is performed via a silicon oxide film (SiO2), it is preferable to make Ra = 1 nm or less in order to achieve a more stable bond. There is no particular limit to the lower limit of the surface roughness (Ra), but it can be 0 nm or more.

[0052] Second Embodiment A second embodiment of the method for temporarily bonding semiconductor substrates will be described with reference to FIGS.

[0053] First, as shown in Fig. 2, a first-conductivity type GaAs buffer layer 2 is laminated on a first-conductivity type GaAs starting substrate 1 in an MOCVD apparatus, and then a first-conductivity type GaInP first etch-stop layer 3, a first-conductivity type GaAs second etch-stop layer 4, a first-conductivity type AlGaInP first cladding layer 5, a non-doped AlGaInP active layer 6, a second-conductivity type AlGaInP second cladding layer 7, a second-conductivity type GaInP intermediate layer 8, and a second-conductivity type GaP window layer 9 are sequentially grown as epitaxial functional layers to prepare an epitaxial wafer having a light-emitting device structure (step (1) in Fig. 1). Here, the first cladding layer 5 to the second cladding layer 7 are referred to as a double hetero (DH) structure.

[0054] It goes without saying that the present invention is not limited to an AlGaInP-based light-emitting diode structure, but can also be applied to any AlGaInP-based light-emitting element structure lattice-matched to a GaAs substrate, an AlGaAs-based light-emitting element structure, an AlGaAs-based HEMT structure, an InGaP-based HBT structure, an InGaP / GaAs-based solar cell structure, etc. Also applicable are an (Al)InGaAs(P)-based light-emitting element structure and an (Al)InGaAs(P)-based light-receiving element structure lattice-matched to an InP substrate.

[0055] 3, a thermosetting resin, for example, benzocyclobutene (BCB) resin 10 is spin-coated onto the epitaxial wafer, and then the epitaxial wafer is placed face-to-face with a silicon wafer 11 and thermocompression-bonded to produce a first compound semiconductor bonded substrate 101 in which the epitaxial wafer and silicon wafer 11 are bonded (temporarily bonded) via the BCB resin 10 (step (2) in FIG. 1). Bonding is performed under conditions such that the temperature of the BCB resin 10 is 150° C. or less.

[0056] Preferable specific examples of the thermosetting resin and the supporting substrate are as described in the first embodiment.

[0057] Next, as shown in FIG. 4, the GaAs starting substrate 1 is removed by wet etching to expose the first etch stop layer 3, and the etchant is switched to remove the second etch stop layer 4 to expose the first cladding layer 5, thereby producing a second compound semiconductor junction substrate 102 retaining only the DH layer and the window layer (step (3) in FIG. 1).

[0058] Next, as shown in FIG. 5, a silicon oxide film 12 (SiO2) is formed on the surface of the first cladding layer 5 by sputtering to a thickness of more than 50 nm and less than 5 μm. At this time, it is possible to form a film up to about 5 μm in one go, but if it is deposited in one go, the temperature of the substrate rises and the hardening of the BCB resin progresses, so it is preferable to limit the film formation to about 2 to 3 μm at a time, and when forming a film of a thickness greater than this, it is preferable to cool the substrate to prevent the substrate temperature from exceeding 100°C and deposit it again. This makes it possible to suppress the temperature rise of the BCB film accompanying the film formation. Since the hardening of the BCB resin progresses when it is maintained at a temperature condition of more than 150°C, the hardening of the BCB resin can be prevented by forming the film at 150°C or less. By preventing the hardening of the BCB resin, the peelability of the silicon substrate from the permanent substrate can be ensured.

[0059] The surface of this silicon oxide film 12 (SiO2) is polished so that Ra is 1 nm or less. When bonding via a silicon oxide film (SiO2), it is preferable to set Ra to 1 nm or less in order to achieve a more stable bond. Figure 9 shows the relationship between the removal amount and surface roughness (Ra) when the silicon oxide film (SiO2) is polished. As can be seen from Figure 9, it is possible to achieve Ra = 1 nm or less by removing 200 nm or more. Therefore, it is preferable to perform polishing with a removal amount of 200 nm or more.

[0060] In addition, by polishing to reduce the Ra to 0.1 nm or less, the bonding yield after plasma activation processing can be improved.

[0061] In this embodiment, the SiO2 film is formed by sputtering, but it goes without saying that the method is not limited to sputtering as long as the substrate is not exposed to a temperature of more than 150° C. For example, PLD (pulsed laser deposition), ALD (atomic layer deposition), and deposition using an electron gun can also be selected.

[0062] Film formation by P-CVD is also possible, but requires application of a higher temperature than around 250°C. At a temperature condition of 250°C, the BCB film hardens even in a short time of a few seconds, so in order to achieve film formation while suppressing the hardening of the BCB resin, a very short processing time is required. Although it is possible, it cannot be said to be preferable.

[0063] Also, even if the bonding to the permanent substrate is not performed via SiO2, it is possible to bond the substrate to the permanent substrate after plasma activation processing without providing SiO2. However, by providing SiO2 and bonding the substrate, it is possible to accommodate various process designs.

[0064] Next, as shown in FIG. 6, the surface of the silicon oxide film 12 (SiO2) and the surface of the permanent substrate 13 (wafer to be bonded) are both subjected to plasma activation treatment, and then they are stacked in a vacuum atmosphere and bonded (main bonding) by applying pressure to produce a third compound semiconductor bonded substrate 103 (step (4) in FIG. 1).

[0065] Finally, as shown in FIG. 7, third compound semiconductor bonded wafer 103 is immersed in a BCB dissolving solution to dissolve BCB resin 10, and silicon wafer 11 is separated from third compound semiconductor bonded wafer 103 to obtain fourth compound semiconductor bonded wafer 104 (step (5) in FIG. 1).

[0066] When the peeling of the silicon wafer does not proceed smoothly, applying rotational pressure to the bonded silicon wafer 11 side makes the peeling proceed more easily.

[0067] Figure 10 shows the relationship between the thickness of the silicon oxide film (SiO2) and the peeled area ratio when immersed in a dissolving solution, with the thickness of the BCB resin as a parameter. As can be seen from Figure 10, when the BCB resin is thin (0.5 μm), the peeled area ratio decreases as the thickness of the silicon oxide film (SiO2) increases. Therefore, it is preferable to make the thickness of the BCB resin thicker than 1 μm. Also, considering cost and flatness, it is preferable to set the upper limit to 30 μm.

[0068] Furthermore, by selecting the sputtering method, it is possible to suppress the temperature rise of the BCB film compared to other film formation methods such as P-CVD, and film formation at 150°C or less can be achieved. Since BCB resin hardens when maintained at temperatures above 150°C, hardening of the BCB resin can be prevented by maintaining a temperature of 150°C or less. Preventing hardening of the BCB resin can improve the peelability of the silicon wafer from the third compound semiconductor junction substrate.

[0069] <Compound semiconductor junction substrate> The present invention also provides a compound semiconductor bonded substrate in which a compound semiconductor functional layer is bonded to a supporting substrate via a thermosetting resin, the thermosetting resin being bonded in a softened state.

[0070] Specific embodiments of the compound semiconductor junction substrate of the present invention are those shown in the first and second embodiments of the method for producing a compound semiconductor junction substrate of the present invention described above. With such a compound semiconductor substrate, the compound semiconductor functional layer can be fully bonded and the support substrate can be easily peeled off. EXAMPLES

[0071] The present invention will be specifically described below using examples and comparative examples, but the present invention is not limited to these.

[0072] Example 1 Using an MOCVD device, a 0.5 μm first conductivity type GaAs buffer layer was laminated on a first conductivity type GaAs starting substrate, and then a 0.1 μm first conductivity type GaInP first etch stop layer, a 0.1 μm first conductivity type GaAs second etch stop layer, a 1 μm first conductivity type AlGaInP first cladding layer, a 0.5 μm non-doped AlGaInP active layer, a 1 μm second conductivity type AlGaInP second cladding layer, a 0.1 μm second conductivity type GaInP intermediate layer, and a 3 μm second conductivity type GaP window layer were grown in this order to produce an epitaxial wafer with a light emitting element structure as the epitaxial functional layer (Figure 2).

[0073] Next, BCB resin was dropped onto the epitaxial wafer and spin-coated at 5000 rpm to form a 1 μm BCB film on the epitaxial wafer. A silicon wafer was prepared as a support substrate, and the epitaxial wafer was stacked with the BCB film side facing the polished surface of the silicon wafer. The two were then introduced into a bonding machine and temporarily bonded by thermocompression in a vacuum atmosphere to produce the first compound semiconductor bonded substrate (Figure 3).

[0074] Here, the temperature of the BCB resin was kept at around 150°C to soften the BCB resin, and the bonding was achieved by lowering the temperature.

[0075] Next, the first compound semiconductor junction substrate was immersed in an ammonia / hydrogen peroxide based etchant to remove the GaAs starting substrate by wet etching to obtain a second compound semiconductor junction substrate, and then the first etch stop layer was removed by a hydrochloric acid based etchant.

[0076] Next, after exposing the second etch stop layer, the GaAs second etch stop layer was removed with a sulfuric acid / hydrogen peroxide etchant. By carrying out the above steps, the first cladding layer was exposed, and a second compound semiconductor junction substrate was fabricated that retained only the DH layer and the window layer (Figure 4).

[0077] Next, SiO2 was deposited on the surface of the first cladding layer at a temperature of 150°C or less by sputtering to a thickness of 50 nm or less (Figure 5).

[0078] Next, both the SiO2 film surface and the silicon wafer surface that would become the permanent substrate were irradiated with nitrogen plasma in a vacuum to activate the surfaces, and then the two were stacked and pressure was applied to bond them together, producing a third compound semiconductor bonded substrate (Figure 6).

[0079] Next, the third compound semiconductor bonded substrate was immersed in a BCB dissolving solution (mesitylene) to dissolve the BCB resin, and the silicon wafer supporting substrate was separated from the third compound semiconductor bonded substrate to obtain a fourth compound semiconductor bonded substrate (Figure 7).

[0080] Example 2 In an MOCVD apparatus, a 0.5 μm first-conductivity type GaAs buffer layer is deposited on a first-conductivity type GaAs starting substrate. x In 1-x P(0.4≦x≦0.6) first etch stop layer 0.1 μm, first conductivity type GaAs second etch stop layer 0.1 μm, first conductivity type (Al y Ga 1-y ) x In 1-xAn epitaxial wafer having a light emitting device structure was produced by sequentially growing a P(0.4≦x≦0.6, 0.6≦y≦1) first cladding layer of 1 μm, a non-doped AlGaInP active layer of 0.5 μm, a second conductivity type AlGaInP second cladding layer of 1 μm, a second conductivity type GaInP intermediate layer of 0.1 μm, and a second conductivity type GaP window layer of 3 μm (Figure 2).

[0081] Next, BCB resin was dropped onto the epitaxial wafer and spin-coated at 5000 rpm to form a 1 μm BCB film on the epitaxial wafer. A silicon wafer was prepared as a support substrate, and the BCB film side of the EPW was placed opposite the polished surface of the silicon wafer, which was then placed inside a bonding machine and temporarily bonded by thermocompression in a vacuum atmosphere to produce the first compound semiconductor bonded substrate (Fig. 3).

[0082] Here, the temperature of the BCB resin was kept at around 150°C to soften the BCB resin, and the bonding was achieved by lowering the temperature.

[0083] Next, the first compound semiconductor junction substrate was immersed in an ammonia / hydrogen peroxide based etchant, and the GaAs starting substrate was removed by wet etching to obtain a second compound semiconductor junction substrate. The first etch stop layer was then removed by a hydrochloric acid based etchant.

[0084] Next, after exposing the second etch stop layer, the GaAs second etch stop layer was removed with a sulfuric acid / hydrogen peroxide etchant. By carrying out the above steps, the first cladding layer was exposed, and a second compound semiconductor junction substrate was fabricated that retained only the DH layer and the window layer (Figure 4).

[0085] Next, SiO2 was deposited to a thickness of 5 μm on the surface of the first cladding layer using the sputtering method at a temperature of 150°C or less. Although it is possible to deposit a film up to 5 μm in one go, depositing it all at once will raise the temperature of the bonding substrate and accelerate the hardening of the BCB resin. For this reason, the film was deposited at one time to a thickness of about 2 to 3 μm, and when depositing a film thicker than that, the substrate was cooled before depositing again. After deposition, the SiO2 surface was polished and processed until the Ra of the SiO2 surface was 0.1 nm or less (Figure 5).

[0086] Next, both the SiO2 film surface and the silicon wafer surface that would become the permanent substrate were irradiated with nitrogen plasma in a vacuum to activate the surfaces, and then the two were stacked and pressure was applied to bond them together, producing a third compound semiconductor bonded substrate (Figure 6).

[0087] Next, the third compound semiconductor bonded substrate was immersed in a BCB dissolving solution (mesitylene) to dissolve the BCB resin, and the silicon wafer supporting substrate was separated from the third compound semiconductor bonded substrate to obtain a fourth compound semiconductor bonded substrate (Figure 7).

[0088] As described above, with the method for manufacturing a compound semiconductor junction substrate of the present invention, wet etching is not required when separating the supporting substrate and the epitaxial functional layer, and therefore formation of a separation groove is not required.

[0089] In Comparative Example 1 described later, it is necessary to add a BCB removal process after removing the support substrate, but this is not necessary in Examples 1 and 2. Therefore, a plasma atmosphere (such as a dry etching atmosphere or an ashing atmosphere) is not required in the process of peeling the support substrate from the mounted permanent substrate, and essentially no new damage is caused to the permanent substrate.

[0090] Similarly, because BCB removal is performed by dissolving and peeling, the peeling ability is higher than that of laser ablation, and the yield after peeling can be made higher than in Comparative Example 1. In addition, because no laser process is required, no laser equipment is required, and the total cost, including depreciation and operating costs, can be made lower than in Comparative Example 1.

[0091] Comparative Example 1 In an MOCVD apparatus, a 0.5 μm first-conductivity type GaAs buffer layer is deposited on a first-conductivity type GaAs starting substrate. x In 1-x P(0.4≦x≦0.6) first etch stop layer 0.1 μm, first conductivity type GaAs second etch stop layer 0.1 μm, first conductivity type (Al y Ga 1-y ) x In 1-x An epitaxial wafer having a light emitting device structure was manufactured by sequentially growing an epitaxial functional layer of a P(0.4≦x≦0.6, 0.6≦y≦1) first cladding layer of 1 μm, a non-doped AlGaInP active layer of 0.5 μm, a second conductivity type AlGaInP second cladding layer of 1 μm, a second conductivity type GaInP intermediate layer of 0.1 μm, and a second conductivity type GaP window layer of 3 μm.

[0092] BCB resin was dropped onto the epitaxial wafer and spin-coated at 5000 rpm to form a 1 μm BCB film on the epitaxial wafer. A sapphire substrate was prepared as a support substrate, and the epitaxial wafer was stacked with the BCB film side facing the polished surface of the sapphire substrate, introduced into a bonding machine, and temporarily bonded by thermocompression in a vacuum atmosphere to produce an EPW bonded substrate.

[0093] When preparing the epitaxial wafer bonded substrate, the temperature of the BCB resin was kept at about 300°C to completely harden the BCB resin and achieve strong bonding.

[0094] The epitaxial junction substrate was immersed in an ammonia / hydrogen peroxide based etchant, and the GaAs starting substrate was removed by wet etching. The first etch stop layer was then removed with a hydrochloric acid based etchant.

[0095] After the second etch stop layer was exposed, the GaAs second etch stop layer was removed with a sulfuric acid / hydrogen peroxide etchant. By carrying out the above steps, the first cladding layer was exposed and an epitaxial junction substrate was fabricated that retained only the DH layer and the window layer.

[0096] The surface of the first cladding layer was spin-coated with BCB resin and bonded to a permanent substrate. Next, a short-pulse laser was irradiated from the sapphire substrate side and focused on the BCB layer at the temporary bond, destroying the BCB to form a peeled section, and the sapphire substrate was separated from the permanent substrate.

[0097] In this way, even if the temporary bonding BCB resin is completely cured, it is possible to separate the sapphire substrate from the permanent substrate by using laser lift-off without wet etching. However, laser lift-off is an ablation process, and the BCB resin does not completely evaporate during the ablation process, and the first cladding layer is not exposed on its entire surface. BCB residue is inherently generated.

[0098] Although BCB residue can be easily removed by dry etching, the dry etching process must be performed after mounting, which causes damage to the mounting board. It is not impossible to remove it by ashing to avoid the damage caused by dry etching, but the effect of removing BCB by ashing is small and it takes a long time to remove it. Therefore, even if the plasma output is smaller than that of dry etching, it has the disadvantage of causing damage to the mounting board.

[0099] The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included in the technical scope of the present invention.

Claims

1. (1) epitaxially growing a compound semiconductor functional layer on a starting substrate; (2) temporarily bonding a support substrate to the epitaxial growth surface of the compound semiconductor functional layer to form a first compound semiconductor bonded substrate; (3) removing the starting substrate from the first compound semiconductor junction substrate to obtain a second compound semiconductor junction substrate; (4) a step of permanently bonding the surface of the second compound semiconductor junction substrate from which the starting substrate has been removed to a permanent substrate to obtain a third compound semiconductor junction substrate; and (5) removing the support substrate from the third compound semiconductor junction wafer to obtain a fourth compound semiconductor junction wafer; A method for manufacturing a compound semiconductor junction substrate, comprising: The temporary bonding in the step (2) is performed via a thermosetting resin, and the thermosetting resin is maintained in a softened state without being hardened, and 4. A method for producing a compound semiconductor junction substrate, wherein the main bonding in the step (4) is performed via a silicon oxide film or a silicon nitride film.

2. 2. The method for manufacturing a compound semiconductor junction substrate according to claim 1, wherein the thermosetting resin is applied to a thickness greater than 1.0 [mu]m and equal to or less than 30 [mu]m.

3. 3. The method for manufacturing a compound semiconductor junction substrate according to claim 1, wherein the thermosetting resin is a benzocyclobutene (BCB) resin, a fluororesin, or a polyimide (PI) resin.

4. 4. The method for manufacturing a compound semiconductor junction substrate according to claim 1, wherein the surface roughness of the silicon oxide film or silicon nitride film is set to Ra=1 nm or less.

5. The support substrate is made of AlN, Al ２ O ３ , Cu, GaAs, GaN, GaP, InP, Si, SiC, and SiO ２ 5. The method for manufacturing a compound semiconductor junction substrate according to claim 1, wherein the compound semiconductor junction substrate is made of any one of the following materials:

Images