Method for manufacturing a nitride semiconductor substrate

Abstract

To provide a nitride semiconductor substrate having small warp and less dislocation, excellent crystallinity and including a group III nitride semiconductor layer, and a method for manufacturing the same.SOLUTION: A nitride semiconductor substrate includes a group III nitride semiconductor layer including GaN on a support substrate. The support substrate includes: a composite substrate obtained by laminating a plurality of layers including a polycrystal ceramic core, a first adhesive layer bonded to the entire polycrystal ceramic core, a second adhesive layer laminated on the entire first adhesive layer and a barrier layer bonded to the entire second adhesive layer; and a group III nitride semiconductor seed crystal layer bonded on the composite substrate through a planarization layer and including at least GaN. The group III nitride semiconductor layer is formed on the group III nitride semiconductor seed crystal layer, and the crystallinity of the GaN (0002) growth plane of the group III nitride semiconductor seed crystal layer is 550 arcsec or less in a XRD half value width.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a nitride semiconductor substrate and a method for manufacturing the nitride semiconductor substrate.

Background Art

[0002] The MOCVD method, which is one of the semiconductor thin film manufacturing methods, is excellent in terms of large diameter and mass productivity, and can form a homogeneous thin film crystal, so it is widely used. Nitride semiconductors typified by GaN are expected as next-generation semiconductor materials that exceed the limits of silicon single crystal materials.

[0003] Due to the characteristic that GaN has a high saturated electron velocity, it is possible to fabricate devices capable of high-frequency operation. Also, due to its high breakdown electric field, it is possible to operate at high power. In addition, weight reduction, size reduction, and low power consumption can be expected.

[0004] In recent years, due to the high-speed increase in communication speed represented by 5G and the accompanying requirement for high output power, GaN HEMTs capable of operating at high frequency and high output power have attracted attention. to

[0005] As a substrate used for a GaN epitaxial wafer for manufacturing a GaN device, a silicon single crystal substrate is the cheapest and is advantageous for increasing the diameter. Also, due to its high thermal conductivity and good heat dissipation, SiC substrates are also used. However, since these substrates have different coefficients of thermal expansion from GaN, stress is applied in the cooling process after epitaxial film formation, and cracks are likely to occur. Also, due to the strong stress applied, wafer cracking may occur during the device process. In addition, it is impossible to form a thick GaN film, and even if a complex stress relaxation layer is formed in the epitaxial layer, the limit for crack-free is only about 5 μm at most.

[0006] Since the GaN substrate has the same (or very close) coefficient of thermal expansion as the GaN epitaxial growth layer, problems such as the above-mentioned crack problems and wafer cracking due to warping are less likely to occur. In addition, since the GaN substrate and the GaN layer to be epitaxially grown have a very small lattice constant difference, problems such as the generation of dislocations and the deterioration of crystallinity due to the lattice constant difference are also solved.

[0007] However, not only is it difficult to fabricate a self-supporting GaN substrate, but it is also extremely expensive and large-diameter substrates cannot be fabricated, making it unsuitable for mass production.

[0008] Therefore, large-diameter substrates for GaN epitaxy (hereinafter referred to as GaN support substrates or simply growth substrates) with a large diameter and a coefficient of thermal expansion close to that of GaN have been developed. A general GaN support substrate is composed of a support structure including a polycrystalline ceramic core, a first adhesive layer, a conductive layer, a second adhesive layer, and a barrier layer, a planarization layer laminated on one side of the support structure, and a single-crystalline silicon layer laminated on the planarization layer. Note that the conductive layer may not be formed or may be formed only on one side. Alternatively, a conductive layer may be formed on the back surface of the barrier layer.

[0009] By using this GaN support substrate, a GaN epitaxial substrate with a large diameter, a thick epitaxial film thickness, and no cracks can be fabricated. In addition, since the difference in the coefficient of thermal expansion from GaN is extremely small, warping is less likely to occur during GaN growth or cooling. Therefore, not only can the warping of the substrate after film formation be controlled to be small, but also there is no need to provide a complex stress relaxation layer in the epitaxial growth layer, resulting in a shorter epitaxial film formation time and a significant reduction in the cost required for epitaxial growth.

[0010] Furthermore, since most of the GaN support substrate is ceramics, in addition to the fact that the substrate itself is very hard and difficult to plastically deform, wafer cracking that occurs when growing a nitride semiconductor on a large-diameter single-crystalline silicon substrate does not occur.

[0011] Patent Document 1 discloses a technology of a bonding substrate (support substrate for GaN) having a coefficient of thermal expansion close to that of GaN.

[0012] Although it is difficult for the support substrate for GaN to have problems of warping during growth due to the difference in the coefficient of thermal expansion, since the surface layer is composed of a silicon layer, a difference in lattice constant occurs with the GaN layer and crystal defects (dislocations) are likely to occur. As a result, the crystallinity of the GaN epitaxial layer formed on the support substrate for GaN does not differ significantly from the case where a single-crystalline silicon substrate is used as the support substrate.

[0013] Patent Document 2 describes a method of separating a sapphire substrate and a GaN layer by irradiating a pulsed laser beam.

[0014] Patent Document 3 describes a method of separating a semiconductor thin film by laser beam processing or the like and bonding it to another substrate.

Prior Art Documents

Patent Documents

[0015]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0016] However, none of Patent Documents 1 to 3 describe or suggest any measures for improving the crystallinity of the GaN epitaxial layer formed on the support substrate for GaN.

[0017] The present invention has been made to solve the above problems, and an object thereof is to provide a nitride semiconductor substrate including a group III nitride semiconductor layer having little warpage, little generation of dislocations, and good crystallinity, and a method for manufacturing the same.

Means for Solving the Problems

[0018] In order to solve the above problems, the present invention provides a nitride semiconductor substrate in which a group III nitride semiconductor layer containing GaN is formed on a support substrate, wherein the support substrate is a composite substrate including a polycrystalline ceramic core, a first adhesive layer joined to the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier layer bonded to the entire second adhesive layer, and a plurality of layers are laminated, and a group III nitride semiconductor seed crystal layer containing at least GaN joined via a planarization layer on the composite substrate, and includes wherein the group III nitride semiconductor layer is formed on the group III nitride semiconductor seed crystal layer, and the crystallinity of the (0002) growth plane of GaN in the group III nitride semiconductor seed crystal layer is 550 arcsec or less in terms of the XRD half-value width. A nitride semiconductor substrate is provided.

[0019] If it is a nitride semiconductor substrate in which a group III nitride semiconductor layer is formed on a group III nitride semiconductor seed crystal layer having a crystallinity of the (0002) growth plane of GaN of 550 arcsec or less in terms of the XRD half-value width, is it can be made to have a group III nitride semiconductor layer with an extremely low dislocation density and good crystallinity, and the characteristics of the device can be improved.

[0020] In addition, in the case of the nitride semiconductor substrate of the present invention, by including a support substrate including a composite substrate in which a plurality of layers are stacked, it is possible to reduce the warping during the epitaxial growth of the group III nitride semiconductor layer due to the difference in the coefficient of thermal expansion. Therefore, a group III nitride semiconductor layer having a large thickness without cracks can be obtained. Therefore, the group III nitride semiconductor layer can be finally peeled off from the support substrate and used as a free-standing substrate.

[0021] In addition, in the present invention, there is provided a nitride semiconductor substrate in which a group III nitride semiconductor layer containing GaN is formed on a support substrate, wherein the support substrate includes a composite substrate including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a barrier layer bonded to the entire first adhesive layer, a second adhesive layer bonded to the back surface of the barrier layer, and a conductive layer bonded to the back surface of the second adhesive layer, and at least a group III nitride semiconductor seed crystal layer bonded via a planarization layer bonded only to the surface of the composite substrate on the composite substrate, and the group III nitride semiconductor layer is formed on the group III nitride semiconductor seed crystal layer, and the crystallinity of the (0002) growth surface of GaN in the group III nitride semiconductor seed crystal layer is 550 arcsec or less in terms of the XRD half-value width.

[0022] In the case of a nitride semiconductor substrate in which a group III nitride semiconductor layer is formed on a group III nitride semiconductor seed crystal layer having a crystallinity of the (0002) growth surface of GaN of 550 arcsec or less in terms of the XRD half-value width as described above, is it can be assumed that the group III nitride semiconductor layer has an extremely low dislocation density and good crystallinity, and the characteristics of the device can be improved.

[0023] In addition, in the case of this nitride semiconductor substrate, by including a support substrate including a composite substrate in which a plurality of layers are stacked, warping during epitaxial growth of the group III nitride semiconductor layer due to the difference in thermal expansion coefficient can be reduced, so that a group III nitride semiconductor layer having a large thickness without cracks can be obtained. Therefore, the group III nitride semiconductor layer can finally be peeled off from the support substrate and used as a free-standing substrate.

[0024] And in the case of the nitride semiconductor substrate of the present invention including the above support substrate, a leakage path due to the surface-side conductive layer of the support substrate does not occur, and excellent high-frequency characteristics can be achieved.

[0025] Further, in the present invention, there is provided a nitride semiconductor substrate in which a group III nitride semiconductor layer containing GaN is formed on a support substrate, wherein the support substrate includes a composite substrate in which a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a conductive layer bonded to the back surface of the first adhesive layer, a second adhesive layer bonded to the back surface of the conductive layer, and a barrier layer bonded to the front and side surfaces of the first adhesive layer, the side surface of the conductive layer, and the side and back surfaces of the second adhesive layer are stacked with a plurality of layers, and on the composite substrate, a group III nitride semiconductor seed crystal layer containing at least GaN bonded through a planarization layer bonded only to the surface of the composite substrate, and the group III nitride semiconductor layer is formed on the group III nitride semiconductor seed crystal layer, and the crystallinity of the (0002) growth surface of GaN in the group III nitride semiconductor seed crystal layer is 550 arcsec or less in terms of the XRD half-value width.

[0026] Thus, a group III nitride semiconductor layer is formed on a group III nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth surface of GaN of the seed crystal is 550 arcsec or less in terms of the XRD half-value width. isIn the case of a formed nitride semiconductor substrate, it can be made to have a group-III nitride semiconductor layer with an extremely low dislocation density and good crystallinity, and the characteristics of the device can be improved.

[0027] Also, in the case of such a nitride semiconductor substrate, by including a support substrate including a composite substrate in which a plurality of layers are stacked, the warpage during the epitaxial growth of the group-III nitride semiconductor layer due to the difference in thermal expansion coefficient can be reduced. Therefore, a group-III nitride semiconductor layer with a large thickness and no cracks can be obtained. Therefore, the group-III nitride semiconductor layer can finally be peeled off from the support substrate and used as a free-standing substrate.

[0028] And, in the case of the nitride semiconductor substrate of the present invention including the above support substrate, no leakage path is generated by the surface-side conductive layer of the support substrate, and it can be made to have excellent high-frequency characteristics.

[0029] The group-III nitride semiconductor layer can include one or more of AlN and AlGaN in addition to GaN.

[0030] Thus, the group-III nitride semiconductor layer can also include nitrides other than GaN.

[0031] It is preferable that the polycrystalline ceramic core includes aluminum nitride.

[0032] If the polycrystalline ceramic core includes aluminum nitride, the difference in thermal expansion coefficient can be made extremely small.

[0033] Each of the first adhesive layer and the second adhesive layer preferably includes tetraethyl orthosilicate and / or silicon oxide, and the barrier layer preferably includes silicon nitride.

[0034] The first adhesive layer and the second adhesive layer can contain, for example, the above compound. Further, if the barrier layer contains the above compound, the movement of impurities from the inside of the composite substrate to the group III nitride semiconductor layer can be sufficiently blocked.

[0035] Each of the first adhesive layer and the second adhesive layer preferably has a thickness of 50 to 200 nm, and the barrier layer preferably has a thickness of 100 nm to 1500 nm.

[0036] If the thickness of each of the first adhesive layer and the second adhesive layer is within the above range, the upper and lower layers can be adhered with sufficient force, and warpage can be more reliably suppressed. Further, if the thickness of the barrier layer is within the above range, the movement of impurities from the inside of the composite substrate to the group III nitride semiconductor layer can be sufficiently blocked.

[0037] The planarization layer preferably contains at least one selected from the group consisting of tetraethyl orthosilicate, silicon oxide, aluminum oxide, silicon nitride, and silicon oxynitride, and has a thickness of 500 nm to 3000 nm.

[0038] If it includes such a planarization layer, warpage can be more reliably suppressed, and a group III nitride semiconductor layer having better crystallinity can be included. Further, the unevenness on the surface can be sufficiently planarized.

[0039] The group III nitride semiconductor seed crystal layer may have a thickness of 100 nm or more.

[0040] The group III nitride semiconductor seed crystal layer can have a thickness of, for example, 100 nm or more.

[0041] Preferably, the composite substrate further has a conductive layer laminated on the whole or one side of the first adhesive layer between the first adhesive layer and the second adhesive layer.

[0042] By including such a conductive layer, a nitride semiconductor substrate including a portion having conductivity can be obtained.

[0043] The conductive layer preferably has a thickness of 50 nm to 500 nm.

[0044] If the thickness of the conductive layer is within this range, a nitride semiconductor substrate including a portion having excellent conductivity can be obtained while suppressing the occurrence of warping.

[0045] The composite substrate preferably further has a backside conductive layer laminated on the backside surface where the group-III nitride semiconductor species crystal layer is not joined.

[0046] If it further has such a backside conductive layer, a nitride semiconductor substrate having conductivity on the backside can be obtained.

[0047] Further, the present invention provides a method for manufacturing a nitride semiconductor substrate including epitaxially growing a group-III nitride semiconductor layer on a group-III nitride semiconductor species crystal layer containing at least GaN, (1) To manufacture a bonding group-III nitride semiconductor substrate, a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single crystal substrate or a starting composite substrate in which a plurality of layers are laminated is prepared as a growth substrate; (2) A bonding group-III nitride semiconductor substrate including the group-III nitride semiconductor species crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of the XRD half-value width is manufactured by epitaxially growing a group-III nitride semiconductor species crystal layer containing at least GaN on the growth substrate; (3) A step of forming a separation layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the bonding group-III nitride semiconductor substrate and the group-III nitride semiconductor species crystal layer; (4) As a composite substrate different from the starting composite substrate, prepare a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer joined to the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier layer bonded to the entire second adhesive layer are laminated, and laminate a planarization layer on the composite substrate; (5) A step of bonding the planarization layer laminated on the composite substrate prepared in step (4) to the group III nitride semiconductor layer of the group III nitride semiconductor substrate for bonding to obtain a bonded substrate; (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding with the release layer, and peeling a part of the growth substrate from the bonded substrate; (7) By polishing the peeled surface, removing the portion remaining on the bonded substrate of the silicon single crystal substrate or the silicon single crystal thin film, and obtaining a support substrate including the composite substrate and the group III nitride semiconductor layer bonded to the composite substrate via a planarization layer; and (8) A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor layer containing GaN on the support substrate to manufacture a nitride semiconductor substrate provided is a method for manufacturing a nitride semiconductor substrate, characterized by including the above steps.

[0048] In such a method for manufacturing a nitride semiconductor substrate, since a group III nitride semiconductor layer containing GaN is epitaxially grown on a group III nitride semiconductor layer containing GaN and having a crystallinity of the (0002) growth surface of GaN of 550 arcsec or less in terms of XRD half-value width, no lattice mismatch occurs between the seed crystal layer and the group III nitride semiconductor layer which is an epitaxial growth layer, and a group III nitride semiconductor layer with a low dislocation density, that is, a good crystallinity, can be formed. Further, by repeating this, a group III nitride semiconductor layer with fewer dislocations can be formed.

[0049] In addition, since the group-III nitride semiconductor layer formed by this method has few dislocations, it can be thickly laminated. Then, since a support substrate including a composite substrate in which a plurality of layers are laminated is used as the support substrate, warping during the growth of the group-III nitride semiconductor layer due to the difference in the coefficient of thermal expansion can be reduced, and a group-III nitride semiconductor layer with a large thickness can be formed without cracks. Therefore, the group-III nitride semiconductor layer can be finally peeled off from the support substrate and used as a free-standing substrate.

[0050] Also, when the above starting support substrate is used as the growth substrate, since the starting support substrate is peeled off by dividing the silicon single crystal thin film from the bonding substrate, the substrate obtained by bonding the silicon single crystal again to the surface layer of the peeled starting support substrate can be used again as the starting support substrate, and the merit of cost reduction can be obtained.

[0051] In step (4), it is preferable to prepare, as the composite substrate, one having a conductive layer laminated on the whole or one side of the first adhesive layer between the first adhesive layer and the second adhesive layer.

[0052] In this way, a nitride semiconductor substrate including a conductive portion can be manufactured.

[0053] Further, the present invention is a method for manufacturing a nitride semiconductor substrate including epitaxially growing a group-III nitride semiconductor layer on a group-III nitride semiconductor seed crystal layer containing at least GaN, (1) A step of preparing, as a growth substrate, a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single crystal substrate or a starting composite substrate in which a plurality of layers are laminated, for manufacturing a bonding group-III nitride semiconductor substrate. (2) A step of manufacturing a bonding group-III nitride semiconductor substrate including the group-III nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in the XRD half-value width, by epitaxially growing a group-III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate. (3) A step of irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the III-nitride semiconductor substrate for bonding and the III-nitride semiconductor species crystal layer to form a release layer; (4) As a composite substrate different from the starting composite substrate, a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a barrier layer bonded to the entire first adhesive layer, a second adhesive layer bonded to the back surface of the barrier layer, and a conductive layer bonded to the back surface of the second adhesive layer are laminated, and a step of laminating a planarization layer only on the surface of the composite substrate; (5) A step of bonding the planarization layer laminated on the composite substrate prepared in step (4) and the III-nitride semiconductor species crystal layer of the III-nitride semiconductor substrate for bonding to obtain a bonded substrate; (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the III-nitride semiconductor substrate for bonding with the release layer and peeling off a part of the growth substrate from the bonded substrate; (7) By polishing the peeled surface, removing the remaining portion of the silicon single crystal substrate or the silicon single crystal thin film on the bonded substrate to obtain a support substrate including the composite substrate and the III-nitride semiconductor species crystal layer bonded to the composite substrate via a planarization layer, and (8) A step of epitaxially growing a III-nitride semiconductor layer containing GaN on the III-nitride semiconductor species crystal layer of the support substrate to manufacture a nitride semiconductor substrate provided is a method for manufacturing a nitride semiconductor substrate, characterized by including the above steps.

[0054] In such a method for manufacturing a nitride semiconductor substrate, in order to epitaxially grow a group-III nitride semiconductor layer containing GaN on a group-III nitride semiconductor seed crystal layer containing GaN and having crystallinity of the (0002) growth plane of GaN with an XRD full width at half maximum of 550 arcsec or less, no lattice mismatch occurs between the seed crystal layer and the group-III nitride semiconductor layer which is an epitaxial growth layer, and a group-III nitride semiconductor layer with a low dislocation density, that is, good crystallinity, can be formed. Further, by repeating this, a group-III nitride semiconductor layer with fewer dislocations can be formed.

[0055] In addition, since the group-III nitride semiconductor layer formed by this method has few dislocations, it can be thickly laminated. And since a support substrate including a composite substrate in which a plurality of layers are laminated is used as the support substrate, warping during the growth of the group-III nitride semiconductor layer due to the difference in thermal expansion coefficient can be reduced, and a group-III nitride semiconductor layer with a large thickness and no cracks can be formed. Therefore, the group-III nitride semiconductor layer can be finally peeled off from the support substrate and used as a free-standing substrate.

[0056] In addition, when the above starting support substrate is used as the growth substrate, since the starting support substrate is peeled off by dividing the silicon single crystal thin film from the bonding substrate, the substrate obtained by bonding the silicon single crystal again to the surface layer of the peeled starting support substrate can be used again as the starting support substrate, and the merit of cost reduction can be obtained.

[0057] And in such a method for manufacturing a nitride semiconductor substrate, no leakage path is generated by the surface-side conductive layer of the support substrate, and a nitride semiconductor substrate with excellent high-frequency characteristics can be manufactured.

[0058] Further, the present invention is a method for manufacturing a nitride semiconductor substrate including epitaxially growing a group-III nitride semiconductor layer on at least a group-III nitride semiconductor seed crystal layer containing GaN, (1) To manufacture a III-nitride semiconductor substrate for bonding, prepare a starting support substrate in which a silicon single-crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single-crystal substrate or a starting composite substrate having a plurality of layers laminated thereon, as a growth substrate; (2) On the growth substrate, epitaxially grow a III-nitride semiconductor seed crystal layer containing at least GaN to manufacture a III-nitride semiconductor substrate for bonding including the III-nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of XRD full width at half maximum; (3) Irradiate a laser near the interface between the silicon single-crystal substrate or the silicon single-crystal thin film of the III-nitride semiconductor substrate for bonding and the III-nitride semiconductor seed crystal layer to form a release layer; (4) As a composite substrate different from the starting composite substrate, prepare a composite substrate in which a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a conductive layer bonded to the back surface of the first adhesive layer, a second adhesive layer bonded to the back surface of the conductive layer, and a plurality of layers including a barrier layer bonded to the front surface and side surfaces of the first adhesive layer, side surfaces of the conductive layer, and side surfaces and back surface of the second adhesive layer are laminated, and laminate a planarization layer only on the surface of the composite substrate; (5) Bond the planarization layer laminated on the composite substrate prepared in step (4) and the III-nitride semiconductor seed crystal layer of the III-nitride semiconductor substrate for bonding to obtain a bonded substrate; (6) Divide the silicon single-crystal substrate or the silicon single-crystal thin film of the III-nitride semiconductor substrate for bonding with the release layer to peel off a part of the growth substrate from the bonded substrate; (7) By polishing the peeled surface, remove the remaining part of the silicon single-crystal substrate or the silicon single-crystal thin film on the bonded substrate to obtain a support substrate including the composite substrate and the III-nitride semiconductor seed crystal layer bonded to the composite substrate via a planarization layer, and (8) Epitaxially grow a III-nitride semiconductor layer containing GaN on the III-nitride semiconductor seed crystal layer of the support substrate to manufacture a nitride semiconductor substrate. Provided is a method for manufacturing a nitride semiconductor substrate, characterized by including

[0059] In such a method for manufacturing a nitride semiconductor substrate, for epitaxially growing a group III nitride semiconductor layer containing GaN on a group III nitride semiconductor seed crystal layer containing GaN and having crystallinity of the (0002) growth surface of GaN of 550 arcsec or less in terms of XRD half-value width, no lattice mismatch occurs between the seed crystal layer and the group III nitride semiconductor layer which is an epitaxial growth layer, and a group III nitride semiconductor layer with a low dislocation density, that is, good crystallinity can be formed. Further, by repeating this, a group III nitride semiconductor layer with fewer dislocations can be formed.

[0060] In addition, since the group III nitride semiconductor layer formed by this method has few dislocations, it can be thickly laminated. And, since a support substrate including a composite substrate in which a plurality of layers are laminated is used as the support substrate, warping during the growth of the group III nitride semiconductor layer due to the difference in thermal expansion coefficient can be reduced, and a group III nitride semiconductor layer with a large thickness and no cracks can be formed. Therefore, the group III nitride semiconductor layer can be finally peeled off from the support substrate and used as a free-standing substrate.

[0061] Also, when the above starting support substrate is used as the growth substrate, since the starting support substrate is peeled off by dividing the silicon single crystal thin film from the bonding substrate, the substrate obtained by bonding a silicon single crystal again to the surface layer of the peeled starting support substrate can be used again as the starting support substrate, and the merit of cost reduction can be obtained.

[0062] And, even in such a method for manufacturing a nitride semiconductor substrate, no leakage path is caused by the surface-side conductive layer of the support substrate, and a nitride semiconductor substrate with excellent high-frequency characteristics can be manufactured.

[0063] Preferably, the wavelength of the laser used in step (3) is 360 nm or more and 1100 nm or less.

[0064] In this way, the release layer can be surely formed targeting the vicinity of the interface of the silicon single crystal thin film or the silicon single crystal substrate of the growth substrate.

Advantages of the Invention

[0065] As described above, in the case of the nitride semiconductor substrate of the present invention, it can be made to include a group III nitride semiconductor layer with little warpage, few dislocations generated, and good crystallinity.

[0066] Also, in the case of the method for manufacturing a nitride semiconductor substrate of the present invention, a nitride semiconductor substrate including a group III nitride semiconductor layer with little warpage, few dislocations generated, and good crystallinity can be manufactured.

Brief Description of the Drawings

[0067]

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Embodiments for Carrying Out the Invention

[0068] As described above, there has been a demand for the development of a nitride semiconductor substrate including a group III nitride semiconductor layer with less warpage, less generation of dislocations, and good crystallinity, and a method for manufacturing the same.

[0069] As a result of intensive studies on the above problems, the present inventors have found that a nitride semiconductor substrate including a composite substrate, a group III nitride semiconductor species crystal layer bonded via a planarization film on the composite substrate, and having a crystallinity of the (0002) growth surface of GaN of 550 arcsec or less in terms of XRD half-value width, and a group III nitride semiconductor layer formed on the group III nitride semiconductor species crystal layer can have a group III nitride semiconductor layer with an extremely low dislocation density and good crystallinity, and can be a nitride semiconductor substrate with less warpage, and thus completed the present invention.

[0070] That is, the present invention is a nitride semiconductor substrate in which a group III nitride semiconductor layer containing GaN is formed on a support substrate, wherein the support substrate is a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier layer bonded to the entire second adhesive layer are laminated, and a group III nitride semiconductor species crystal layer containing at least GaN bonded via a planarization layer on the composite substrate and the group III nitride semiconductor layer is formed on the group III nitride semiconductor species crystal layer, and the crystallinity of the (0002) growth surface of GaN in the group III nitride semiconductor species crystal layer is 550 arcsec or less in terms of XRD half-value width.

[0071] The present invention also relates to a nitride semiconductor substrate having a group-III nitride semiconductor layer containing GaN formed on a support substrate, wherein the support substrate is a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a barrier layer bonded to the entire first adhesive layer, a second adhesive layer bonded to the back surface of the barrier layer, and a conductive layer bonded to the back surface of the second adhesive layer are laminated, and a group-III nitride semiconductor seed crystal layer containing at least GaN, which is bonded via a planarization layer bonded only to the surface of the composite substrate, is provided on the composite substrate, and the group-III nitride semiconductor layer is formed on the group-III nitride semiconductor seed crystal layer, and the crystallinity of the (0002) growth surface of GaN in the group-III nitride semiconductor seed crystal layer is 550 arcsec or less in terms of the XRD full width at half maximum. The nitride semiconductor substrate is characterized by this.

[0072] The present invention also relates to a nitride semiconductor substrate having a group-III nitride semiconductor layer containing GaN formed on a support substrate, wherein the support substrate is a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a conductive layer bonded to the back surface of the first adhesive layer, a second adhesive layer bonded to the back surface of the conductive layer, and a barrier layer bonded to the front and side surfaces of the first adhesive layer, the side surface of the conductive layer, and the side and back surfaces of the second adhesive layer are laminated, and a group-III nitride semiconductor seed crystal layer containing at least GaN, which is bonded via a planarization layer bonded only to the surface of the composite substrate, is provided on the composite substrate, and the group-III nitride semiconductor layer is formed on the group-III nitride semiconductor seed crystal layer, and the crystallinity of the (0002) growth surface of GaN in the group-III nitride semiconductor seed crystal layer is 550 arcsec or less in terms of the XRD full width at half maximum. The nitride semiconductor substrate is characterized by this.

[0073] The present invention also relates to a method for manufacturing a nitride semiconductor substrate, which includes epitaxially growing a group III nitride semiconductor layer on a group III nitride semiconductor seed crystal layer containing at least GaN, (1) To manufacture a bonding group III nitride semiconductor substrate, a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single crystal substrate or a starting composite substrate in which a plurality of layers are laminated is prepared as a growth substrate; (2) By epitaxially growing a group III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate, a bonding group III nitride semiconductor substrate including the group III nitride semiconductor seed crystal layer having crystallinity of the (0002) growth plane of GaN with an XRD half-value width of 550 arcsec or less is manufactured; (3) A laser is irradiated near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the bonding group III nitride semiconductor substrate and the group III nitride semiconductor seed crystal layer to form a separation layer; (4) As a composite substrate different from the starting composite substrate, a composite substrate including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier layer bonded to the entire second adhesive layer is prepared, and a planarization layer is laminated on the composite substrate; (5) The planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor seed crystal layer of the bonding group III nitride semiconductor substrate are bonded together to obtain a bonded substrate; (6) The silicon single crystal substrate or the silicon single crystal thin film of the bonding group III nitride semiconductor substrate is divided by the separation layer, and a part of the growth substrate is peeled off from the bonded substrate; (7) By polishing the peeled surface, the remaining portion of the silicon single crystal substrate or the silicon single crystal thin film on the bonded substrate is removed to obtain a support substrate including the composite substrate and the group III nitride semiconductor seed crystal layer bonded to the composite substrate via a planarization layer, and (8) A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor seed crystal layer of the support substrate to produce a nitride semiconductor substrate A method for manufacturing a nitride semiconductor substrate, characterized by including the above.

[0074] Further, the present invention is a method for manufacturing a nitride semiconductor substrate including epitaxially growing a group III nitride semiconductor layer on at least a group III nitride semiconductor seed crystal layer containing GaN, (1) A step of preparing a growth substrate, which is a silicon single crystal substrate or a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a starting composite substrate in which a plurality of layers are laminated, in order to manufacture a group III nitride semiconductor substrate for bonding. (2) A step of manufacturing a group III nitride semiconductor substrate for bonding including the group III nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in XRD half-value width by epitaxially growing a group III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate. (3) A step of forming a separation layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding and the group III nitride semiconductor seed crystal layer. (4) As a composite substrate different from the starting composite substrate, a composite substrate in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a barrier layer bonded to the entire first adhesive layer, a second adhesive layer bonded to the back surface of the barrier layer, and a conductive layer bonded to the back surface of the second adhesive layer are laminated is prepared, and a planarization layer is laminated only on the surface of the composite substrate. (5) A step of bonding the planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor seed crystal layer of the group III nitride semiconductor substrate for bonding to obtain a bonded substrate. (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding with the separation layer and peeling off a part of the growth substrate from the bonded substrate. (7) By polishing the separation surface, removing the portion remaining on the bonding substrate of the silicon single crystal substrate or the silicon single crystal thin film, to obtain a support substrate including the composite substrate and the group III nitride semiconductor species crystal layer bonded via a planarization layer on the composite substrate, and (8) A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor species crystal layer of the support substrate to manufacture a nitride semiconductor substrate A method for manufacturing a nitride semiconductor substrate, characterized by including the above.

[0075] Further, the present invention is a method for manufacturing a nitride semiconductor substrate including epitaxially growing a group III nitride semiconductor layer on at least a group III nitride semiconductor species crystal layer containing GaN, (1) To manufacture a bonding group III nitride semiconductor substrate, prepare a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single crystal substrate or a starting composite substrate in which a plurality of layers are laminated, as a growth substrate, (2) By epitaxially growing a group III nitride semiconductor species crystal layer containing at least GaN on the growth substrate, manufacturing a bonding group III nitride semiconductor substrate including the group III nitride semiconductor species crystal layer having crystallinity of the (0002) growth plane of GaN of 550 arcsec or less in XRD half-value width, (3) A step of forming a separation layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the bonding group III nitride semiconductor substrate and the group III nitride semiconductor species crystal layer, (4) As a composite substrate different from the starting composite substrate, prepare a composite substrate in which a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a conductive layer bonded to the back surface of the first adhesive layer, a second adhesive layer bonded to the back surface of the conductive layer, and a barrier layer bonded to the front surface and side surfaces of the first adhesive layer and the side surfaces of the conductive layer and the side surfaces and back surface of the second adhesive layer are laminated, and laminate a planarization layer only on the surface of the composite substrate, Step of bonding the planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor crystal layer of the group III nitride semiconductor substrate for bonding to obtain a bonded substrate. Step (6) of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding with the release layer, and peeling a part of the growth substrate from the bonded substrate. Step (7) of removing the remaining part of the silicon single crystal substrate or the silicon single crystal thin film on the bonded substrate by polishing the peeling surface to obtain a support substrate including the composite substrate and the group III nitride semiconductor crystal layer bonded to the composite substrate via the planarization layer, and Step (8) of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor crystal layer of the support substrate to manufacture a nitride semiconductor substrate. A method for manufacturing a nitride semiconductor substrate, characterized by including the above steps.

[0076] Hereinafter, the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

[0077] [Nitride Semiconductor Substrate] FIG. 1 shows a schematic cross-sectional view of an example of the nitride semiconductor substrate of the present invention.

[0078] The nitride semiconductor substrate 100 shown in FIG. 1 includes a support substrate 10 and a group III nitride semiconductor layer 20 formed on the support substrate 10.

[0079] The support substrate 10 includes a composite substrate 6 and a group III nitride semiconductor crystal layer 8 bonded to the composite substrate 6 via a planarization film 7.

[0080] The composite substrate 6 includes a polycrystalline ceramic core 1, a first adhesive layer 2 bonded to the entire polycrystalline ceramic core 1, a second adhesive layer 4 laminated on the entire first adhesive layer 2, and a barrier layer 5 bonded to the entire second adhesive layer 4, with a plurality of layers laminated. In the example shown in FIG. 1, the composite substrate 6 further has, as an optional layer, a conductive layer 3 laminated on the entire first adhesive layer 2 between the first adhesive layer 2 and the second adhesive layer 4.

[0081] In the example shown in FIG. 1, a group-III nitride semiconductor seed crystal layer 8 is bonded via a planarization layer 7 only to one side of the composite substrate 6.

[0082] The group-III nitride semiconductor seed crystal layer 8 contains at least GaN. Also, the crystallinity of the (0002) growth plane of GaN in the group-III nitride semiconductor seed crystal layer 8 is 550 arcsec or less in terms of the XRD (X-ray Diffraction) full width at half maximum.

[0083] On such a group-III nitride semiconductor seed crystal layer 8, a group-III nitride semiconductor layer 20 is formed. The group-III nitride semiconductor layer 20 contains GaN.

[0084] In the nitride semiconductor substrate 100 of the present invention, since the group-III nitride semiconductor layer 20 is epitaxially formed on the group-III nitride semiconductor seed crystal layer 8 in which the crystallinity of the (0002) growth plane of the seed crystal GaN is 550 arcsec or less in terms of the XRD full width at half maximum, the dislocation density is extremely low and good crystallinity can be exhibited. As a result, in the nitride semiconductor substrate 100 of the present invention, the characteristics of the device can be improved.

[0085] Further, the nitride semiconductor substrate 100 of the present invention includes a support substrate 10 including the composite substrate 6 in which a plurality of layers are laminated as described above, so that the warpage during the epitaxial growth of the group-III nitride semiconductor layer 20 due to the difference in the coefficient of thermal expansion can be reduced, and thus a group-III nitride semiconductor layer 20 having a large thickness without cracks can be obtained. Therefore, the group-III nitride semiconductor layer 20 can finally be peeled off from the support substrate 10 and used as a self-supporting substrate.

[0086] Hereinafter, the nitride semiconductor substrate 100 shown in FIG. 1 will be described in more detail.

[0087] The polycrystalline ceramic core 1 can include, for example, aluminum nitride. If the polycrystalline ceramic core 1 includes aluminum nitride, the difference in thermal expansion coefficients can be made extremely small.

[0088] Such a polycrystalline ceramic core 1 is sintered at a high temperature of, for example, 1800° C. with a sintering aid and can have a thickness of about 600 to 1150 μm. Basically, it is often formed with the thickness of the SEMI (Semiconductor Equipment and Materials International) standard of a silicon substrate.

[0089] The first adhesive layer 2 and the second adhesive layer 4 can be, for example, layers containing a tetraethyl orthosilicate (TEOS) layer or a silicon oxide (SiO2) layer, or both. The first adhesive layer 2 and the second adhesive layer 4 are respectively deposited by an LPCVD (Low-Pressure Chemical Vapor Deposition) process, a CVD (Chemical Vapor Deposition) process, etc., and can have a thickness of approximately 50 to 200 nm.

[0090] The conductive layer 3 includes, for example, polysilicon and is deposited by, for example, an LPCVD process. The conductive layer 3 is a layer for imparting conductivity, and is doped with, for example, boron (B), phosphorus (P), etc. The conductive layer 3 containing this polysilicon is provided as needed, may not be provided, and may be formed only on one side of the first adhesive layer 2.

[0091] Any conductive layer 3 preferably has a thickness of 50 nm to 500 nm. If the thickness of the conductive layer 3 is within this range, a nitride semiconductor substrate 100 including a portion having excellent conductivity can be obtained while suppressing the occurrence of warpage.

[0092] The barrier layer 5 contains, for example, silicon nitride, is deposited by an LPCVD process or the like, and has a thickness of about 100 nm to 1500 nm. The barrier layer 5 is a layer that blocks impurities from inside the substrate such as ceramics.

[0093] The planarization layer 7 is deposited by, for example, an LPCVD process or the like, and has a thickness of, for example, about 500 nm to 3000 nm. This planarization layer 7 is deposited for planarization of the upper surface. As the material of the planarization layer 7, for example, tetra ethyl orthosilicate, or silicon oxide (SiO2), aluminum oxide (Al2O3), silicon nitride (Si3N4), or silicon oxynitride (Si x O y N z ; 0 < x < 1, 0 < y < 2, 0 ≦ z ≦ 0.6), etc., ordinary ceramic film materials, etc. are selected.

[0094] In the nitride semiconductor substrate 100 of the present invention, the crystallinity of the (0002) growth surface of the seed crystal GaN in the group III nitride semiconductor seed crystal layer 8 is 550 arcsec or less in terms of the XRD half-value width. It is more preferable that the crystallinity of the (0002) growth surface of the seed crystal GaN is 300 arcsec or less in terms of the XRD half-value width.

[0095] The group III nitride semiconductor seed crystal layer 8 can contain, in addition to GaN, for example, one or more of AlN and AlGaN.

[0096] Also, the thickness of the group III nitride semiconductor seed crystal layer 8 is not particularly limited because it is changed depending on the application, but can be, for example, 100 nm or more.

[0097] The group III nitride semiconductor layer 20 contains GaN, but can also contain, in addition to GaN, for example, one or more of AlN and AlGaN.

[0098] Since the GaN in the Group-III nitride semiconductor layer 20 is epitaxially grown on the crystalline Group-III nitride semiconductor species crystal layer 8 as described above, it can exhibit the same good crystallinity as that of the GaN in the Group-III nitride semiconductor species crystal layer 8. Further, the Group-III nitride semiconductor layer 20 can have a thickness of, for example, 10 μm or more without including cracks.

[0099] Although not shown, in the nitride semiconductor substrate 100 of the present invention, the composite substrate 6 may further have a back surface conductive layer laminated on the back surface side surface where the Group-III nitride semiconductor species crystal layer 8 is not joined, instead of the conductive layer 3. The back surface conductive layer contains, for example, polysilicon and is deposited by, for example, an LPCVD process or the like, similar to the conductive layer 3. Further, the back surface conductive layer can have a thickness of, for example, 50 nm to 500 nm.

[0100] The nitride semiconductor substrate 100 of the present invention can be manufactured, for example, by the method for manufacturing a nitride semiconductor substrate of the present invention, which will be described with examples below. However, the nitride semiconductor substrate 100 of the present invention may be manufactured by a method other than the method for manufacturing a nitride semiconductor substrate of the present invention.

[0101] As the support substrate, the composite substrate 10 schematically shown in FIG. 10 or FIG. 11 can also be used for the nitride semiconductor substrate of the present invention.

[0102] The support substrate 10 shown in FIG. 10 includes a composite substrate 6 and a Group-III nitride semiconductor species crystal layer 8 containing at least GaN, which is joined to the composite substrate 6 via a planarization layer 7 joined only to the surface (front side surface) of the composite substrate 6. The composite substrate 6 is a composite substrate 6 in which a plurality of layers including a polycrystalline ceramic core 1, a first adhesive layer 2 joined to the entire polycrystalline ceramic core 1, a barrier layer 5 joined to the entire first adhesive layer 2, a second adhesive layer 4 joined to the back surface of the barrier layer 5, and a conductive layer 3 joined to the back surface of the second adhesive layer 4 are laminated.

[0103] The support substrate 10 shown in FIG. 11 includes a composite substrate 6 and at least a group III nitride semiconductor species crystal layer 8 containing GaN, which is bonded on the composite substrate 6 via a planarization layer 7 bonded only to the surface (front - side surface) of the composite substrate 6. The composite substrate 6 is a composite substrate in which a plurality of layers are laminated, including a polycrystalline ceramic core 1, a first adhesive layer 2 bonded to the entire polycrystalline ceramic core 1, a conductive layer 3 bonded to the back surface of the first adhesive layer 2, a second adhesive layer 4 bonded to the back surface of the conductive layer 3, and a barrier layer 5 bonded to the front and side surfaces of the first adhesive layer 2, the side surface of the conductive layer 3, and the side and back surfaces of the second adhesive layer 4.

[0104] Each layer of the composite substrate 6 shown in FIGS. 10 and 11 can be the same as those described above.

[0105] The nitride semiconductor substrate 100 including the support substrate 10 having a structure in which the conductive layer 3 as shown in FIGS. 10 and 11 is formed only on the back - side, in addition to the effects described above with reference to FIG. 1, when manufacturing a high - frequency device, there is no leakage path due to the conductive layer on the surface side of the support substrate 10, and it can have excellent high - frequency characteristics.

[0106] [Method for manufacturing a nitride semiconductor substrate] Hereinafter, as examples of the method for manufacturing a nitride semiconductor substrate of the present invention, the first and second embodiments will be described with reference to the drawings. However, the method for manufacturing a nitride semiconductor substrate of the present invention is not limited to the examples described below.

[0107] (First Embodiment) The first embodiment of the method for manufacturing a nitride semiconductor substrate of the present invention will be described with reference to FIGS. 2 to 6.

[0108] (Step (1): Step of preparing a starting support substrate as a growth substrate) In step (1), in order to manufacture a III-nitride semiconductor substrate for bonding, as shown in Fig. 2(a), a starting support substrate 30 is prepared as a growth substrate, on which a silicon single-crystal thin film is bonded as a starting seed crystal layer 38 via a starting planarization layer 37 on a starting composite substrate 36. The starting support substrate 30 can also be called a support substrate for GaN.

[0109] The starting composite substrate 36 can have a configuration schematically shown in Fig. 3, for example. Specifically, the starting composite substrate 36 shown in Fig. 3 is a support structure including a polycrystalline ceramic core 31, a first adhesive layer 32 integrally bonded to the polycrystalline ceramic core 31, a conductive layer 33 integrally bonded to the entire first adhesive layer 32, a second adhesive layer 34 integrally bonded to the entire conductive layer 33, and a barrier layer 35 integrally bonded to the entire second adhesive layer 34.

[0110] Each of the polycrystalline ceramic core 31, the first adhesive layer 32, the conductive layer 33, the second adhesive layer 34, and the barrier layer 35 can be the same as each layer of the composite substrate 6 included in the nitride semiconductor substrate 100 of the present invention described with reference to Fig. 1, for example. The starting composite substrate 36 can be manufactured by the method described in the description of the composite substrate 6. Note that the starting composite substrate 36 only needs to be a laminate of a plurality of layers and is not limited to that shown in Fig. 3. For example, the conductive layer 33 and the first adhesive layer 32 are formed as needed and do not necessarily exist, and may be formed on only one side in some cases.

[0111] In the examples shown in Figs. 2(a) and 3, the planarization film 37 is bonded to only one side of the starting composite substrate 36. The planarization film 37 can be the same as the planarization film 7 described with reference to Fig. 1, for example, but is not limited thereto.

[0112] The silicon single-crystal thin film 38 is bonded to the planarization film 37 and can also be called a substantially silicon layer. The silicon single-crystal thin film 38 has a thickness of about 50 nm to 1000 nm, for example, and is used for epitaxial growth of a III-nitride semiconductor seed crystal layer containing GaN in step (2).

[0113] The silicon single crystal thin film 38 which is the starting seed crystal layer is preferably a silicon single crystal thin film with an axial orientation of <111>, but the resistivity etc. are not limited.

[0114] The silicon single crystal thin film 38 can be formed, for example, by bonding it to the planarization layer 37 by a bonding process and then peeling it off while leaving the necessary thickness by an ion irradiation method or the like.

[0115] (Step (2): Step of manufacturing a III-nitride semiconductor substrate for bonding) Next, as step (2), a step of manufacturing the III-nitride semiconductor substrate 200 for bonding shown in Fig. 2(b) is performed. In this step (2), on the starting support substrate 30 which is a growth substrate, more specifically, on the silicon single crystal thin film 38 which is the starting seed crystal layer, at least a III-nitride semiconductor seed crystal layer 8 containing GaN is epitaxially grown, thereby manufacturing a III-nitride semiconductor substrate 200 for bonding including a III-nitride semiconductor seed crystal layer 8 in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of the XRD full width at half maximum.

[0116] This step (2) can be performed, for example, in a MOCVD (Metal Organic Chemical Vapor Deposition) reactor.

[0117] In this step (2), epitaxial growth of a III-nitride semiconductor seed crystal layer (epitaxial layer) 8 such as AlN, AlGaN, and GaN is performed on the silicon single crystal thin film 38 of the starting support substrate 30. The structure of the III-nitride semiconductor seed crystal layer 8 is not limited to this, and there may be cases where AlGaN is not deposited, or where AlN is deposited after depositing AlGaN. Also, there may be cases where a plurality of layers of AlGaN with a changed Al composition are deposited. On the other hand, in step (2), GaN is always grown. The film thickness is not particularly limited as it is changed according to the application.

[0118] During epitaxial growth, for example, trimethylaluminum (TMAl) is used as the Al source, trimethylgallium (TMGa) is used as the Ga source, and NH3 is used as the N source. Also, the carrier gas can be, for example, N2 and H2, or either of them, and the process temperature can be about 900 to 1200 °C.

[0119] By controlling the conditions in step (2), for example, by epitaxially growing the group III nitride semiconductor seed crystal layer 8 on the silicon single crystal thin film 38 with a <111> axial orientation, a group III nitride semiconductor substrate 200 for bonding including the group III nitride semiconductor seed crystal layer 8 with the crystallinity of the (0002) growth plane of GaN being 550 arcsec or less in XRD full width at half maximum can be manufactured.

[0120] (Step (3): Step of forming a release layer on the silicon single crystal thin film by laser irradiation) Next, as shown in Fig. 2(c), a laser is irradiated near the interface between the silicon single crystal thin film 38 of the group III nitride semiconductor substrate 200 for bonding manufactured in step (2) and the group III nitride semiconductor seed crystal layer 8 to form the release layer 38a shown in Fig. 4(d).

[0121] At this time, the wavelength of the laser is preferably longer than the wavelength of light equal to the bandgap energy of GaN and shorter than the wavelength of light equal to the bandgap energy of the silicon single crystal. Specifically, about 360 nm or more and 1100 nm or less is preferable. By doing so, the release layer 38a can be formed targeting the silicon single crystal thin film 38, so damage to the group III nitride semiconductor seed crystal layer 8 containing GaN can be suppressed. Also, the power of the laser is not particularly limited as long as the release layer 38a can be formed, but about 5 W to 20 W is suitable. The pitch of laser irradiation is preferably 30 μm or less. By setting the irradiation pitch to 30 μm or less, a release layer 38a that can sufficiently perform the peeling in step (6) described below can be formed.

[0122] By using a method of forming a release layer (damage layer) 38a by laser irradiation and then peeling it off, the difference in the ease of laser focusing between the group-III nitride semiconductor seed crystal layer 8 containing GaN and the single-crystalline silicon can be utilized. Since the release layer 38a can be formed on the single-crystalline silicon thin film 38 by the laser that has passed through the group-III nitride semiconductor seed crystal layer 8 containing GaN, damage to the group-III nitride semiconductor seed crystal layer 8 containing GaN can be suppressed. Also, since the laser can be focused at a deep position from the surface, even when the group-III nitride semiconductor seed crystal layer 8 containing GaN is formed to a thickness of several μm, the release layer 38a can be formed near the interface between the single-crystalline silicon thin film 38 and the group-III nitride semiconductor seed crystal layer 8.

[0123] On the other hand, in a peeling method by ion irradiation such as the Smart Cut method (registered trademark), the penetration depth is greatly limited, and when a group-III nitride semiconductor seed crystal layer of several μm or more is formed, ions often cannot penetrate and peeling cannot be achieved. Also, ion irradiation damages the crystal.

[0124] (Step (4): Preparing a composite substrate different from the starting composite substrate and laminating a planarization layer on the composite substrate) Next, a composite substrate 6 shown below in FIG. 4(e) is prepared. This composite substrate 6 is a support base substrate different from the starting composite substrate 36 prepared in step (1).

[0125] The composite substrate 6 prepared in this step (4) is the same as the composite substrate included in the nitride semiconductor substrate of the present invention. That is, the composite substrate 6, similar to the composite substrate 6 shown in FIG. 1, is a composite substrate 6 in which a plurality of layers including a polycrystalline ceramic core 1, a first adhesive layer 2 joined to the entire polycrystalline ceramic core 1, a second adhesive layer 4 laminated on the entire first adhesive layer 2, and a barrier layer 5 bonded to the entire second adhesive layer 4 are laminated.

[0126] Next, a planarization layer 7 is laminated on the prepared composite substrate 6.

[0127] For the manufacturing methods of the composite substrate 6 and the planarization layer 7, refer to the description in the nitride semiconductor of the present invention.

[0128] (Step (5): A step of bonding a planarization layer and a group III nitride semiconductor seed crystal layer to obtain a bonded substrate) Next, as shown in FIG. 4(e), the planarization layer 7 laminated on the composite substrate 6 prepared in step (4) and the group III nitride semiconductor seed crystal layer 8 of the group III nitride semiconductor substrate 200 for bonding (a release layer 38a is formed on the silicon single crystal thin film 38) are bonded together to obtain the bonded substrate 300 shown in FIG. 5(f).

[0129] (Step (6): A step of peeling a part of the growth substrate (starting support substrate) from the bonded substrate) Next, in the bonded substrate 300 fabricated in step (5), the silicon single crystal thin film 38 of the group III nitride semiconductor substrate 200 for bonding is divided into a part 38b and another part 38c as shown in FIG. 5(g) by the release layer 38a shown in FIG. 5(f), and a part of the starting support substrate 30 which is the growth substrate is peeled from the bonded substrate 300.

[0130] Regarding this peeling, the method is not particularly limited. For example, by fixing the front and back surfaces of the bonded substrate 300 shown in FIG. 5(f) to a jig with adhesiveness and applying a force to the opposite side, it is possible to divide and peel the silicon single crystal thin film 38 at the release layer 38a.

[0131] (Step (7): A step of removing the remaining portion of the silicon single crystal thin film on the bonded substrate to obtain a support substrate) Next, by polishing the peeling surface of the remaining portion 38c of the silicon single crystal thin film on the bonded substrate 300 shown in FIG. 6(h), a part 38c of the silicon single crystal thin film is removed. By doing so, the support substrate 10 including the composite substrate 6 and the group III nitride semiconductor seed crystal layer 8 as the group III nitride semiconductor seed crystal layer bonded to the composite substrate 6 via the planarization layer 7 shown in FIG. 6(i) is obtained. As shown in FIG. 6(i), the surface layer of the support substrate 10 is the group III nitride semiconductor seed crystal layer 8 containing GaN.

[0132] By going through these steps, a support substrate 10 (a support substrate for GaN) can be fabricated, which includes a nitride semiconductor species crystal layer 8 containing GaN and having a crystallinity of the (0002) growth plane of GaN with an XRD half-value width of 550 arcsec or less as the surface layer.

[0133] (Step (8): A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor species crystal layer of the support substrate to manufacture a nitride semiconductor substrate) Next, as shown in FIG. 6(j), a group III nitride semiconductor layer 20 containing GaN is epitaxially grown on the group III nitride semiconductor species crystal layer 8 of the support substrate 10. The conditions for epitaxial film formation can be the same as those in step (2).

[0134] By the steps (1) to (8) described above, the nitride semiconductor substrate 100 shown in FIG. 6(j) can be manufactured.

[0135] (Second Embodiment) Next, a second embodiment of the method for manufacturing a nitride semiconductor substrate of the present invention will be described with reference to FIGS. 7 to 9.

[0136] The second embodiment is significantly different from the first embodiment in that a silicon single crystal substrate 40 shown in FIG. 7(a) is used as the growth substrate instead of the starting support substrate 30. Hereinafter, the differences from the first embodiment will be mainly described.

[0137] In step (1), as described above, a silicon single crystal substrate 40 shown in FIG. 7(a) is prepared as the growth substrate.

[0138] The silicon single crystal substrate 40 is preferably a silicon single crystal substrate with an axial orientation of <111>, but the resistivity and the like are not particularly limited.

[0139] In step (2), in the same manner as in the first embodiment, at least a group-III nitride semiconductor seed crystal layer 8 containing GaN is epitaxially grown on a silicon single crystal substrate 40 which is a growth substrate, thereby manufacturing a group-III nitride semiconductor substrate 200 for bonding including a group-III nitride semiconductor seed crystal layer 8 in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of the XRD full width at half maximum, as shown in Fig. 7(b).

[0140] In step (3), as shown in Fig. 7(c), a laser is irradiated in the vicinity of the interface between the silicon single crystal substrate 40 which is a growth substrate and the group-III nitride semiconductor seed crystal layer 8 to form a separation layer. The formation of the separation layer can be performed in the same manner as in the first embodiment.

[0141] Step (4) is the same as in the first embodiment.

[0142] In step (5), the planarization layer 7 laminated on the composite substrate 6 prepared in step (4) is bonded to the group-III nitride semiconductor seed crystal layer 8 of the group-III nitride semiconductor substrate 200 for bonding (a separation layer 40a is formed on the silicon single crystal substrate 40), thereby obtaining a bonded substrate 300 as shown in Fig. 8(d).

[0143] In step (6), in the bonded substrate 300 manufactured in step (5), the silicon single crystal substrate 40 of the group-III nitride semiconductor substrate 200 for bonding is divided into a part 40b and another part 40c as shown in Fig. 8(e) by the separation layer 40a shown in Fig. 8(d), and a part 40b of the silicon single crystal substrate which is a growth substrate is peeled off from the bonded substrate 300. The peeling can be performed in the same manner as in the first embodiment.

[0144] In step (7), by polishing the peeling surface of the remaining portion 40c on the bonding substrate 300 of the single-crystalline silicon substrate shown in Fig. 9(f), a part 40c of the single-crystalline silicon thin film is removed. By doing so, a support substrate 10 including a composite substrate 6 and a group-III nitride semiconductor species crystal layer 8 as a group-III nitride semiconductor species crystal layer bonded via a planarization layer 7 on the composite substrate 6, as shown in Fig. 9(g), is obtained. As shown in Fig. 9(g), the surface layer of the support substrate 10 is a group-III nitride semiconductor species crystal layer 8 containing GaN.

[0145] Step (8) is the same as that in the first embodiment.

[0146] By the steps (1) to (8) described above, a nitride semiconductor substrate 100 shown in Fig. 9(h) can be manufactured.

[0147] In the method for manufacturing a nitride semiconductor substrate of the present invention described by way of example above, since the lattice constant difference between the group-III nitride semiconductor layer (for example, GaN epitaxial layer) 20 containing GaN and the support substrate 10 can be made extremely small, a group-III nitride semiconductor layer 20 containing GaN with few dislocations and good crystallinity can be formed. Further, by repeating this, a group-III nitride semiconductor layer 20 with even fewer dislocations can be formed.

[0148] In addition, since the group-III nitride semiconductor layer 20 formed by this method has few dislocations, it can be thickly laminated. And since the support substrate 10 including the composite substrate 6 with a plurality of layers laminated is used as the support substrate, the warpage during the growth of the group-III nitride semiconductor layer 20 due to the difference in thermal expansion coefficient can be reduced, and a group-III nitride semiconductor layer 20 with a large thickness and no cracks can be formed. Therefore, the group-III nitride semiconductor layer 20 can be finally peeled off from the support substrate 10 and used as a free-standing substrate.

[0149] On the other hand, conventionally, even when a group III nitride semiconductor species crystal containing GaN was formed on a composite substrate in which a plurality of layers were laminated, the lattice constant could not be made appropriate, and a group III nitride semiconductor species crystal layer having a crystallinity of the (0002) growth plane of GaN of 550 arcsec or less in terms of the XRD full width at half maximum could not be formed.

[0150] Further, in the first embodiment, as shown in FIG. 5(g), in order to peel the starting support substrate 30 from the bonding substrate 300 by dividing the single-crystal silicon thin film 38, the substrate obtained by bonding a single-crystal silicon again to the surface layer of the peeled starting support substrate 30 can be used again as the starting support substrate, and the merit of cost reduction can be obtained. If necessary, a part 38b of the single-crystal silicon thin film 38 remaining on the surface layer may be removed, SiO2 may be deposited, and then a single-crystal silicon may be bonded. When removing by grind etching or the like, the substrate cannot be reused.

[0151] In addition, as the composite substrate 6 prepared in step (4), instead of the composite substrate 6 shown in FIG. 1, the composite substrate 6 shown in FIG. 10 or FIG. 11 may be prepared, and the planarization layer 7 may be laminated only on the surface (front-side surface) of this composite substrate 6.

[0152] In the manufacturing method of the nitride semiconductor substrate of this modification, a leakage path due to the surface-side conductive layer of the support substrate does not occur, and a nitride semiconductor substrate excellent in high-frequency characteristics can be manufactured.

[0153] In addition, above, an example using the one shown in FIG. 3 as the starting composite substrate 36 has been described, but the structure of the starting composite substrate is not limited to that in FIG. 3, and for example, it may have the same structure as the composite substrate 6 shown in FIGS. 10 and 11.

Examples

[0154] Hereinafter, the present invention will be specifically described using examples and comparative examples, but the present invention is not limited thereto.

[0155] (Example 1) In Example 1, a nitride semiconductor substrate was manufactured according to the manufacturing flow of the first embodiment shown in FIGS. 2 and 4 to 6.

[0156] (Step (1)) First, the starting support substrate (support substrate for GaN) 30 described above with reference to FIGS. 2(a) and 3 was produced as a growth substrate.

[0157] In Step (1), a silicon single crystal having an axial orientation of <111> was bonded to the planarization layer 37, and then a silicon single crystal thin film 38 was formed by leaving a thickness by ion irradiation and peeling.

[0158] (Step (2)) This starting support substrate 30 was placed in an MOCVD reactor, and epitaxial growth of a group III nitride semiconductor seed crystal layer containing AlN, AlGaN, and GaN was performed on the starting support substrate 30. The starting support substrate 30 was placed in a wafer pocket called a satellite. During epitaxial growth, TMAl was used as the Al source, TMGa was used as the Ga source, and NH3 was used as the N source.

[0159] Also, either N2 or H2 was used as the carrier gas. The process temperature was set to 1200°C.

[0160] In Step (2), a support substrate for GaN was placed on the satellite, and when epitaxial growth was performed, the epitaxial layer was formed with AlN and AlGaN in order from the substrate side in the growth direction, and then GaN was epitaxially grown.

[0161] As a result, as shown in FIG. 2(b), a group III nitride semiconductor seed crystal layer (epitaxial layer) 8 was formed on the silicon single crystal thin film 38 of the starting support substrate 30, and a bonding group III nitride semiconductor substrate (support substrate for GaN on GaN) 200 was produced. The total film thickness of the group III nitride semiconductor seed crystal layer (epitaxial layer) 8 was set to 1 μm.

[0162] (Step (3)) Next, as shown in Fig. 2(c), a laser was irradiated near the interface between the silicon single-crystal thin film 38 of the group-III nitride semiconductor substrate 200 for bonding fabricated in step (2) and the group-III nitride semiconductor seed crystal layer (epitaxial layer) 8.

[0163] At this time, the wavelength of the laser was 1064 nm, the irradiation pitch was 5 μm, and the power of the laser was 12 W. By this step (3), a release layer 38a shown in Fig. 4(d) was formed.

[0164] (Step (4)) Separate from the starting composite substrate 36 prepared in step (1), a composite substrate 6 as a support base substrate shown below Fig. 4(e) was prepared. Further, a planarization layer 7 was laminated on this composite substrate 6. The composite substrate 6 and the planarization layer 7 were fabricated by a method that does not perform the step of bonding the surface silicon single-crystal thin film 38 in the fabrication method of the starting support substrate 30 in step (1).

[0165] (Step (5)) Next, as shown in Fig. 4(e), the group-III nitride semiconductor substrate 200 for bonding fabricated in steps (1) to (3) was bonded to the planarization layer 7 formed on this composite substrate 6 to obtain a bonded substrate 300 shown in Fig. 5(f). The bonding step was carried out at room temperature.

[0166] (Step (6)) In the bonded substrate 300 fabricated in step (5), the silicon single-crystal thin film 38 of the group-III nitride semiconductor substrate 200 for bonding was divided into a part 38b and another part 38c as shown in Fig. 5(g) by the release layer 38a shown in Fig. 5(f), and a part of the starting support substrate 30 which is a growth substrate was peeled off from the bonded substrate 300. Here, the top and bottom of the bonded substrate 300 were fixed with jigs, and an external force in the opposite direction was applied to divide the silicon single-crystal thin film 38 by the release layer.

[0167] (Step (7)) After the separation in step (6), a part 38c of the silicon single crystal thin film remaining on the surface layer of the bonded substrate 300, as shown in FIG. 6(h), was polished. By polishing about 100 nm, the silicon single crystal thin film was completely removed. As a result, a support substrate 10 including a composite substrate 6 and a group III nitride semiconductor seed crystal layer 8 bonded via a planarization layer 7 on the composite substrate 6, as shown in FIG. 6(i), was obtained.

[0168] The crystallinity of the (0002) growth plane of GaN in the group III nitride semiconductor seed crystal layer 8 on the surface layer of the support substrate 10 was 540 arcsec in terms of the XRD full width at half maximum.

[0169] (Step (8)) On the support substrate 10 fabricated up to step (7), as shown in FIG. 6(j), a GaN layer was epitaxially grown as a group III nitride semiconductor layer 20. The epitaxial growth conditions at this time were the same as those in step (2) except for the film thickness. Regarding the film thickness of the GaN layer 20, the film was formed to be 5 μm in total together with the GaN layer already present in the group III nitride semiconductor seed crystal layer 8. As a result, a nitride semiconductor substrate 100 of Example 1, as shown in FIG. 6(j), was manufactured.

[0170] Thereafter, when the crystallinity of GaN contained in the GaN layer 20 was measured, the crystallinity of the (0002) growth plane of GaN was 250 arcsec in terms of the XRD full width at half maximum.

[0171] Also, the GaN layer 20 did not contain cracks.

[0172] (Example 2) In Example 2, a nitride semiconductor substrate was manufactured according to the manufacturing flow of the second embodiment shown in FIGS. 7 to 9. shown in That is, in the manufacturing flow of the second embodiment, a nitride semiconductor substrate was manufactured.

[0173] (Step (1)) First, as a growth substrate, a silicon single crystal substrate 40 shown in FIG. 7(a) was prepared. The silicon single crystal substrate 40 had an axial orientation of <111>.

[0174] (Step (2)) This silicon single crystal substrate 40 was placed in a MOCVD reactor, and an epitaxial growth of a group III nitride semiconductor seed crystal layer containing AlN, AlGaN, and GaN was performed on the silicon single crystal substrate 40. The silicon single crystal substrate 40 was placed in a wafer pocket called a satellite. During the epitaxial growth, TMAl was used as the Al source, TMGa was used as the Ga source, and NH3 was used as the N source.

[0175] Also, either N2 or H2 was used as the carrier gas. The process temperature was set to 1200 °C.

[0176] In step (2), a support substrate for GaN was placed on the satellite. When performing epitaxial growth, the epitaxial layer was formed with AlN and AlGaN in order from the substrate side in the growth direction, and then GaN was epitaxially grown.

[0177] As a result, as shown in FIG. 7(b), a group III nitride semiconductor seed crystal layer (epitaxial layer) 8 was formed on the silicon single crystal substrate 40, and a group III nitride semiconductor substrate for bonding (GaN on Si substrate) 200 was fabricated. The total film thickness of the group III nitride semiconductor seed crystal layer (epitaxial layer) 8 was set to 1 μm.

[0178] (Step (3)) Next, as shown in FIG. 7(c), a laser was irradiated near the interface between the silicon single crystal substrate 40 of the group III nitride semiconductor substrate for bonding 200 fabricated in step (2) and the group III nitride semiconductor seed crystal layer 8.

[0179] At this time, the wavelength of the laser was 1064 nm, the irradiation pitch was 5 μm, and the power of the laser was 12 W. By this step (3), a release layer was formed on the silicon single crystal substrate 40.

[0180] (Step (4)) In the same manner as in step (4) of Example 1, a composite substrate 6 and a planarization layer 7 were fabricated.

[0181] (Step (5)) Next, the III-nitride semiconductor substrate 200 for bonding fabricated in steps (1) to (3) was bonded to the planarization layer 7 formed on the composite substrate 6 fabricated in step (4) to obtain a bonded substrate 300 shown in FIG. 8(d). The bonding process was carried out at room temperature.

[0182] Subsequent steps (6) to (8) were the same as those in Example 1.

[0183] The crystallinity of the GaN (0002) growth plane of the III-nitride semiconductor seed crystal layer 8 on the surface layer of the support substrate 10 obtained in step (7) was 540 arcsec in terms of the XRD full width at half maximum.

[0184] Also, when the crystallinity of the GaN in the GaN layer 20, which is the surface layer of the nitride semiconductor substrate 100 shown in FIG. 9(h) and obtained in step (8), was measured, the crystallinity of the GaN (0002) growth plane was 450 arcsec in terms of the XRD full width at half maximum.

[0185] Also, the GaN layer 20 did not contain cracks.

[0186] (Comparative Example) In the comparative example, in step (2) of Example 1, a GaN layer with a total film thickness of 5 μm was formed to fabricate a support substrate for GaN on GaN. This support substrate was used as the nitride semiconductor substrate of the comparative example.

[0187] When the crystallinity of the GaN on the surface layer of the nitride semiconductor substrate of the comparative example was measured, the crystallinity of the GaN (0002) growth plane was 600 arcsec in terms of the XRD full width at half maximum.

[0188] As is clear from the above results, the III-nitride semiconductor layer 20, which is the surface layer of the nitride semiconductor substrates 100 of Examples 1 and 2 of the present invention, has suppressed generation of dislocations, and the crystallinity of the GaN (0002) growth plane is 550 arcsec or less in terms of the XRD full width at half maximum, and is superior to the crystallinity of the GaN on the surface layer of the nitride semiconductor substrate of the comparative example.

[0189] In addition, in the group-III nitride semiconductor layer 20 which is the surface layer of the nitride semiconductor substrates 100 of Examples 1 and 2, warpage was not observed.

[0190] Note that the present invention is not limited to the above-described embodiments. The above-described embodiments are examples, and any structure that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits the same operational effects is included in the technical scope of the present invention.

Description of Reference Numerals

[0191] 1, 31... polycrystalline ceramic core, 2, 32... first adhesive layer, 3, 33... conductive layer, 4, 34... second adhesive layer, 5, 35... barrier layer, 6... composite substrate, 7... planarization layer, 8... group-III nitride semiconductor seed crystal layer, 10... support substrate, 20... group-III nitride semiconductor layer (GaN layer), 30... starting support substrate (growth substrate), 36... starting composite substrate, 37... starting planarization layer, 38... starting seed crystal layer (silicon single crystal thin film), 38a, 40a... release layer, 38b, 38c... part of the starting seed crystal layer, 40... silicon single crystal substrate, 40b, 40c... part of the silicon single crystal substrate, 100... nitride semiconductor substrate, 200... group-III nitride semiconductor substrate for bonding, 300... bonding substrate.

Claims

1. A method for manufacturing a nitride semiconductor substrate, comprising epitaxially growing a group III nitride semiconductor layer on a group III nitride semiconductor seed crystal layer containing at least GaN, (1) A step of preparing a starting support substrate, in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a silicon single crystal substrate or a starting composite substrate in which a plurality of layers are laminated, as a growth substrate, for manufacturing a group III nitride semiconductor substrate for bonding, (2) A step of manufacturing a group III nitride semiconductor substrate for bonding, which includes a group III nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of the XRD half-value width, by epitaxially growing a group III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate, (3) A step of forming a separation layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding and the group III nitride semiconductor seed crystal layer, (4) A step of preparing a composite substrate, which is a composite substrate different from the starting composite substrate, and includes a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a second adhesive layer laminated on the entire first adhesive layer, and a barrier layer bonded to the entire second adhesive layer, and laminating a planarization layer on the composite substrate, (5) A step of obtaining a bonded substrate by bonding the planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor seed crystal layer of the group III nitride semiconductor substrate for bonding, (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding with the separation layer, and peeling off a part of the growth substrate from the bonded substrate, (7) A step of obtaining a support substrate including the composite substrate and the group III nitride semiconductor seed crystal layer bonded to the composite substrate via a planarization layer by removing the remaining part of the silicon single crystal substrate or the silicon single crystal thin film on the bonded substrate by polishing the separation surface, and (8) A step of manufacturing a nitride semiconductor substrate by epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor seed crystal layer of the support substrate characterized by including the above steps.

2. In step (4), as the composite substrate, a substrate having a conductive layer laminated on the whole or one side of the first adhesive layer between the first adhesive layer and the second adhesive layer is prepared, and the method for manufacturing a nitride semiconductor substrate according to claim 1 is characterized in that.

3. A method for manufacturing a nitride semiconductor substrate including epitaxially growing a group III nitride semiconductor layer on a group III nitride semiconductor seed crystal layer containing at least GaN, (1) To manufacture a group III nitride semiconductor substrate for bonding, a silicon single crystal substrate, or a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a starting composite substrate in which a plurality of layers are laminated is prepared as a growth substrate. (2) By epitaxially growing a group III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate, a group III nitride semiconductor substrate for bonding including the group III nitride semiconductor seed crystal layer having crystallinity of the (0002) growth plane of GaN of 550 arcsec or less in XRD half-value width is manufactured. (3) A step of forming a release layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding and the group III nitride semiconductor seed crystal layer. (4) As a composite substrate different from the starting composite substrate, a composite substrate in which a polycrystalline ceramic core, a first adhesive layer bonded to the whole of the polycrystalline ceramic core, a barrier layer bonded to the whole of the first adhesive layer, a second adhesive layer bonded to the back surface of the barrier layer, and a conductive layer bonded to the back surface of the second adhesive layer are laminated is prepared, and a planarization layer is laminated only on the surface of the composite substrate. (5) A step of bonding the planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor seed crystal layer of the group III nitride semiconductor substrate for bonding to obtain a bonded substrate. (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding by the release layer and peeling off a part of the growth substrate from the bonded substrate. (7) By polishing the peeled surface, the portion remaining on the bonded substrate of the silicon single crystal substrate or the silicon single crystal thin film is removed to obtain a support substrate including the composite substrate and the group III nitride semiconductor seed crystal layer bonded to the composite substrate via a planarization layer, and (8) A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor seed crystal layer of the support substrate to manufacture a nitride semiconductor substrate A method for manufacturing a nitride semiconductor substrate, comprising the above. **Claim 4** A method for manufacturing a nitride semiconductor substrate, comprising epitaxially growing a group III nitride semiconductor layer on at least a group III nitride semiconductor seed crystal layer containing GaN, (1) A step of preparing a growth substrate, which is a silicon single crystal substrate or a starting support substrate in which a silicon single crystal thin film is bonded as a starting seed crystal layer via a starting planarization layer on a starting composite substrate in which a plurality of layers are laminated, in order to manufacture a group III nitride semiconductor substrate for bonding; (2) A step of manufacturing a group III nitride semiconductor substrate for bonding, which includes a group III nitride semiconductor seed crystal layer in which the crystallinity of the (0002) growth plane of GaN is 550 arcsec or less in terms of the XRD full width at half maximum, by epitaxially growing a group III nitride semiconductor seed crystal layer containing at least GaN on the growth substrate; (3) A step of forming a release layer by irradiating a laser near the interface between the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding and the group III nitride semiconductor seed crystal layer; (4) A step of preparing a composite substrate, which is a composite substrate different from the starting composite substrate, in which a plurality of layers including a polycrystalline ceramic core, a first adhesive layer bonded to the entire polycrystalline ceramic core, a conductive layer bonded to the back surface of the first adhesive layer, a second adhesive layer bonded to the back surface of the conductive layer, and a barrier layer bonded to the front surface and side surfaces of the first adhesive layer and the side surfaces and back surface of the conductive layer and the second adhesive layer are laminated, and laminating a planarization layer only on the surface of the composite substrate; (5) A step of obtaining a bonded substrate by bonding the planarization layer laminated on the composite substrate prepared in step (4) and the group III nitride semiconductor seed crystal layer of the group III nitride semiconductor substrate for bonding; (6) A step of dividing the silicon single crystal substrate or the silicon single crystal thin film of the group III nitride semiconductor substrate for bonding with the release layer and peeling a part of the growth substrate from the bonded substrate (7) By polishing the peeling surface, the portion remaining on the bonding substrate of the silicon single crystal substrate or the silicon single crystal thin film is removed to obtain a support substrate including the composite substrate and the group III nitride semiconductor species crystal layer bonded via a planarization layer on the composite substrate, and (8) A step of epitaxially growing a group III nitride semiconductor layer containing GaN on the group III nitride semiconductor species crystal layer of the support substrate to manufacture a nitride semiconductor substrate A method for manufacturing a nitride semiconductor substrate, comprising the steps of:

5. The method for manufacturing a nitride semiconductor substrate according to any one of claims 1 to 4, wherein the wavelength of the laser used in step (3) is 360 nm or more and 1100 nm or less.

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