Method for producing group III compound substrate and substrate produced by the same

Abstract

The method for manufacturing a Group III compound substrate of the present invention includes the following steps: a base substrate formation step of forming a Group III nitride base substrate by vapor phase synthesis; a seed substrate formation step of forming a seed substrate on the base substrate; and a Group III compound crystal formation step of forming a Group III compound crystal on the seed substrate by hydride vapor phase growth. The Group III compound substrate of the present invention is characterized by being manufactured by the method for manufacturing a Group III compound substrate of the present invention. According to the present invention, while leveraging the advantages of the hydride vapor phase growth method, namely, its high film formation rate, a larger, high-quality Group III compound substrate can be obtained at low cost.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a large-scale, high-performance, high-quality GaN-based, AlN-based, or other group III compound substrate with minimal warping, voids, or lattice defects, and to a substrate manufactured using the manufacturing method. In particular, the present invention relates to a method for manufacturing a large-scale, high-quality GaN substrate or a large-scale, high-quality AlN substrate, and to a GaN substrate or AlN substrate manufactured using the manufacturing method. Background Art

[0002] Crystalline Group III compound substrates, such as those based on GaN and AlN, have wide bandgaps, exhibit extremely short-wavelength luminescence, high withstand voltage, and excellent high-frequency characteristics. Consequently, Group III compound substrates are expected to be used in devices such as lasers, Schottky diodes, power devices, and high-frequency devices. However, the current situation is that growing large, high-quality crystals of these Group III compounds is difficult, resulting in high costs and hindering the expansion and widespread adoption of these substrates.

[0003] For example, looking at GaN substrates, bulk GaN substrates obtained by growing GaN crystals in liquids such as liquid ammonia or Na flux are generally of higher quality. However, because high-temperature and high-pressure equipment is required, it is difficult to scale up (large diameter, thick objects). In contrast, if GaN is grown heteroepitaxially or homoepitaxially on single crystal substrates such as sapphire substrates, GaAs substrates, SiC substrates, SCAM (ScAlMgO4) substrates, GaN substrates, and AlN substrates using a metal organic vapor phase epitaxy method (MOCVD method) or a hydride vapor phase epitaxy method (HVPE method, THVPE method, etc.) for crystal growth by a vapor phase method, then in principle, large-scale, i.e., large and high-quality substrates can be manufactured. However, in reality, the current situation is that single crystal substrates such as GaN substrates or SCAM substrates with lattice constants and thermal expansion coefficients that are the same or relatively close to those of GaN crystals have only manufactured small substrates, and there are no large single crystal substrates, so it is difficult to scale up by epitaxial film formation.

[0004] As a solution, non-patent document 1 describes: a plurality of tile-shaped substrates obtained by cutting a GaN single crystal obtained by a Na flux method into a honeycomb shape are bonded to a pyrolytic graphite (PG) base, the GaN single crystal is enlarged, and the enlarged GaN single crystal is used as a seed substrate, and GaN is grown thereon by a method such as HVPE to obtain a large GaN substrate. In addition, patent document 1 describes: a plurality of tile-shaped substrates obtained by cutting a GaN single crystal obtained by a known method such as a vapor phase method into a honeycomb shape are bonded to a pyrolytic graphite (PG) base, the GaN single crystal is enlarged, and the enlarged GaN single crystal is used as a seed substrate, and GaN is grown thereon by a method such as HVPE to obtain a large GaN substrate. However, these methods have a large difference in thermal expansion coefficient between the PG base, which can also be called a base substrate, the alumina-based adhesive or zirconia-based adhesive material used when attaching the PG base to the seed substrate, and the tile-shaped GaN single crystal or SCAM single crystal serving as the seed substrate. Therefore, due to temperature changes, the base substrate expands / contracts, moves or peels off, warps, etc. on the seed substrate, and it is difficult to maintain the crystal orientation or the same planarity during the film formation reaction, making it difficult to form a film with consistent orientation.

[0005] Attempts have also been made to produce large GaN substrates by using single-crystal substrates such as Si, sapphire, SiC, and GaAs, which offer larger diameters, as both base and seed substrates. However, due to the significant mismatch in lattice constant and thermal expansion coefficient between these single-crystal substrates and the GaN crystal, the resulting GaN substrates grown through epitaxial growth experience an increase in defects, and are prone to warping and cracking, which poses a problem.

[0006] As a solution to this problem, the following attempt has been proposed: a sintering aid is added to polycrystalline powders of GaN or AlN with the same or similar lattice constant or thermal expansion coefficient, or to powders composed of mullite as described in Patent Document 2, and the mixture is sintered to produce a ceramic. The resulting ceramic is used as a base substrate, and a single crystal thin film such as a Si substrate, sapphire substrate, SiC substrate, GaAs substrate, GaN substrate, or AlN substrate is transferred or bonded to the base substrate. These substrates are then used as seed substrates, and GaN is further heteroepitaxially grown on the seed substrates to produce large GaN substrates. However, in this method, metallic impurities from the ceramic raw materials or the sintering aid diffuse and contaminate the epitaxial GaN film, making it difficult to obtain a high-performance substrate.

[0007] Therefore, as one of the improvement measures, Patent Document 3 proposes the following proposal: using AlN ceramics with a thermal expansion coefficient close to that of GaN as a base substrate, then wrapping and sealing the entire substrate with a multilayer film of inorganic materials such as Si, SiO2, and Si3N4, stacking SiO2 on it, and then transferring / bonding the Si of the seed substrate. <111> The GaN film is then epitaxially grown to prevent the diffusion of metallic impurities from the base substrate. However, sealing with multiple layers of inorganic materials requires multiple steps, which is costly and uneconomical. In addition, it is very difficult to ensure the complete sealing of the multilayer film.

[0008] Prior art literature

[0009] Patent Literature

[0010] Patent Document 1: Japanese Patent No. 6203460;

[0011] Patent Document 2: Japanese Patent No. 6331553;

[0012] Patent document 3: USP9997391B2;

[0013] Non-patent literature

[0014] Non-patent document 1: Phys. Status Solidi B 254, No.8, 1600671 (2017). Summary of the Invention

[0015] Problems to be solved by the invention

[0016] The present invention has been completed in view of the above situation, and its purpose is to provide: a method for manufacturing a large and high-quality GaN-based or AlN-based group III compound substrate; and a group III compound substrate, especially a GaN substrate or an AlN substrate, obtained by this method.

[0017] Means for solving problems

[0018] In order to achieve the above-mentioned object, the present invention provides the following method for manufacturing a group III compound substrate and the substrate thereof.

[0019] [1] A method for manufacturing a group III compound substrate, the method comprising the following steps: a base substrate forming step of forming a group III nitride base substrate by a vapor phase synthesis method; a seed substrate forming step of forming a seed substrate on the base substrate; and a group III compound crystal forming step of forming a group III compound crystal on the seed substrate by a hydride vapor phase growth method.

[0020] [2] The method for manufacturing a group III compound substrate described in [1] above is characterized in that the hydride vapor phase epitaxy method used in the group III compound crystal formation step is a THVPE method.

[0021] [3] The method for manufacturing a group III compound substrate according to [1] or [2], wherein the group III nitride of the base substrate is GaN or AlN, and the seed substrate is Si <111> , sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN substrate, in the above-mentioned seed substrate forming step, by transferring the above-mentioned seed substrate film to the above-mentioned base substrate, forming the above-mentioned seed substrate on the above-mentioned base substrate,

[0022] In the group III compound crystal forming step, the group III compound crystal is formed on the seed substrate using group III chloride and NH 3 as vapor phase growth raw materials.

[0023] [4] The method for manufacturing a Group III compound substrate according to any one of [1] to [3] above, wherein the base substrate is a substrate of at least one substance selected from the group consisting of amorphous, polycrystalline, single crystal and ceramic Group III nitrides, and the total content of metal impurities other than the Group III metal element in the base substrate is 5000 mass ppm or less in terms of metal.

[0024] [5] The method for producing a group III compound substrate according to any one of [1] to [4] above, wherein in the base substrate forming step, the group III nitride base substrate is formed by a hydride vapor phase epitaxy method.

[0025] [6] The method for manufacturing a group III compound substrate according to any one of [1] to [5] above, wherein the base substrate is a substrate obtained by molding a powder of a group III nitride obtained by a hydride vapor phase growth method to produce a molded body, causing the molded body to contain a group III metal by an impregnation method, and then sintering the molded body; or a substrate obtained by molding a powder of a group III nitride obtained by a hydride vapor phase growth method to produce a molded body, causing the molded body to contain a group III compound that becomes a group III metal when reduced by an impregnation method, and then nitriding and sintering the molded body.

[0026] [7] The method for manufacturing a group III compound substrate as described in any one of [1] to [5] above, wherein the base substrate is a substrate obtained by adding / mixing a group III metal to a powder of a group III nitride obtained by a hydride vapor phase epitaxy method to prepare a mixture, molding the mixture to prepare a molded body, and then nitriding and sintering the molded body.

[0027] [8] The method for producing a group III compound substrate according to any one of [1] to [7] above, wherein the group III compound crystal is a gallium nitride (GaN) crystal or an aluminum nitride (AlN) crystal.

[0028] [9] The method for manufacturing a group III compound substrate as described in any one of [1] to [8] above, further comprising, between the seed substrate forming step and the group III compound crystal forming step, an N-face group III nitride layer forming step of forming an N-face group III nitride layer on the seed substrate.

[0029]

[10] The method for manufacturing a group III compound substrate as described in [9] above, wherein, in the step of forming the N-face group III nitride layer, the N-face group III nitride layer is formed on the seed substrate by a low-temperature MOCVD method at a temperature of 400 to 800°C or by a THVPE method.

[0030]

[11] The method for manufacturing a group III compound substrate as described in

[10] above, wherein, in the step of forming the N-face group III nitride layer, the N-face group III nitride layer is formed on the seed substrate by a low-temperature MOCVD method at a temperature of 500 to 600°C.

[0031]

[12] The method for manufacturing a group III compound substrate according to any one of [1] to

[11] above, wherein the thickness of the seed substrate, or the total thickness of the seed substrate and the thickness of the N-face group III nitride layer formed in the N-face group III nitride layer formation step, is 50 to 2000 nm.

[0032]

[13] The method for manufacturing a Group III compound substrate according to any one of [1] to

[12] above, further comprising: a peeling layer forming step of forming a peeling layer composed of a peelable and cleavable substance on the above base substrate; and in the above seed substrate forming step of forming a seed substrate on the above peeling layer.

[0033]

[14] The method for manufacturing a group III compound substrate described in

[13] above, wherein the above-mentioned peelable cleavage-capable substance is at least one substance selected from SCAM (ScAlMgO4) crystal, boron nitride (BN) and graphite.

[0034]

[15] The method for manufacturing a group III compound substrate as described in

[13] or

[14] above, further comprising: an intermediate layer forming step of forming an intermediate layer on the above-mentioned peeling layer, wherein the intermediate layer is a film of a Si-based compound, and in the above-mentioned seed substrate forming step, a seed substrate is formed on the above-mentioned intermediate layer.

[0035]

[16] The method for manufacturing a group III compound substrate as described in any one of [1] to

[14] above, further comprising: an intermediate layer forming step of forming an intermediate layer on the above base substrate, wherein the intermediate layer is a film of a Si-based compound; and in the above seed substrate forming step, forming a seed substrate on the above intermediate layer.

[0036]

[17] A group III compound substrate, characterized in that it is manufactured using the method for manufacturing a group III compound substrate according to any one of [1] to

[16] above.

[0037] Effects of the Invention

[0038] According to the present invention, while effectively utilizing the advantages of the hydride vapor phase epitaxy method, namely its high film deposition rate, larger, high-quality Group III compound substrates can be produced at low cost. Specifically, large-diameter, uniformly thick Group III compound substrates can be produced, making it easy to produce large-diameter Group III compound substrates with excellent crystallographic properties at low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] [ Figure 1 ] Figure 1 This is a diagram for explaining a reaction apparatus for producing a base substrate and forming a crystal on a seed substrate in Example 1.

[0040] [ Figure 2 ] Figure 2 This is a diagram for explaining a reaction apparatus for producing a base substrate and forming a crystal on a seed substrate in Example 1. DETAILED DESCRIPTION

[0041] [Method for producing a group III compound substrate]

[0042] The method for manufacturing a Group III compound substrate of the present invention includes the following steps: a base substrate formation step in which a Group III nitride base substrate is formed by vapor phase synthesis; a seed substrate formation step in which a seed substrate is formed on the base substrate; and a Group III compound crystal formation step in which a Group III compound crystal is formed on the seed substrate by hydride vapor phase growth. This allows for the production of a high-purity, large-scale Group III nitride base substrate, enabling the fabrication of large-diameter, uniform, and extremely thick Group III compound substrates. This makes it possible to easily produce large-diameter Group III compound substrates with excellent substrate crystal properties at low cost. Each step is described in detail below.

[0043] (Base Substrate Forming Step)

[0044] In the base substrate formation step, a base substrate of a group III nitride is formed by a vapor phase synthesis method. This allows for a high-purity base substrate to be obtained, thereby suppressing the diffusion / contamination of metal impurities from the base substrate into the group III compound crystals when forming group III compound crystals on the seed substrate by a hydride vapor phase growth method. From the perspective of obtaining a high-purity base substrate, a base substrate of a group III nitride formed by a hydride vapor phase growth method is particularly preferred. The group III nitride of the base substrate is preferably GaN or AlN.

[0045] The base substrate is preferably a substrate of at least one material selected from the group consisting of amorphous, polycrystalline, single crystal, and ceramic Group III nitrides. In particular, when the desired Group III compound substrate is a GaN substrate or an AlN substrate, the base substrate is preferably an amorphous, polycrystalline, single crystal, or ceramic GaN or AlN substrate, or a mixture thereof, as the thermal expansion coefficient is closer to that of the GaN or AlN substrate.

[0046] The base substrate is preferably a substrate obtained by molding a Group III nitride powder obtained by hydride vapor phase growth to form a molded body, impregnating the molded body with a Group III metal by impregnation, and then sintering the molded body. Alternatively, a substrate obtained by molding a Group III nitride powder obtained by hydride vapor phase growth to form a molded body, impregnating the molded body with a Group III compound that becomes a Group III metal upon reduction by impregnation, and then nitriding and sintering the molded body. Alternatively, a substrate obtained by adding / mixing a Group III metal to a Group III nitride powder obtained by hydride vapor phase growth to form a mixture, molding the mixture to form a molded body, and then nitriding and sintering the molded body can be used. This allows for the production of large-diameter, high-purity base substrates at low cost.

[0047] Instead of forming a Group III nitride using hydride vapor phase epitaxy, the base substrate can be formed using gallium nitride powder produced by heating high-purity Ga2O3 powder in an ammonia atmosphere. In this case, the base substrate formation step uses Group III nitride powder obtained by nitriding Group III oxide powder. Furthermore, the base substrate can be formed by molding Group III nitride powder obtained by nitriding Group III oxide powder to form a compact, impregnating the compact with a Group III metal using an impregnation method, and then sintering the compact. Alternatively, the base substrate can be formed by molding Group III nitride powder obtained by nitriding Group III oxide powder to form a compact, impregnating the compact with a Group III compound that becomes a Group III metal upon reduction using an impregnation method, and then nitriding and sintering the compact. Furthermore, the base substrate can be formed by adding or mixing a Group III metal to Group III nitride powder obtained by nitriding Group III oxide powder to form a mixture, molding the mixture to form a compact, and then nitriding and sintering the compact. By using high-purity Group III oxides, a large-diameter, high-purity base substrate can be produced at low cost.

[0048] When the base substrate is a GaN substrate or AlN, the base substrate can be produced using GaN or AlN powder produced as follows, for example.

[0049] As a method for producing GaN or AlN powder, GaN or AlN powder can be produced by directly nitriding Ga metal or Al metal in an NH3 atmosphere, and GaN or AlN powder can be produced by causing Ga metal or Al metal to undergo an arc plasma reaction in NH3.

[0050] Alternatively, GaN powder or AlN powder can be produced by nitriding Ga metal or Al metal while crushing it in N2 or NH3.

[0051] A GaN or AlN substrate can be manufactured by adding a sintering aid such as SiO2 or a binder to the GaN powder or AlN powder obtained in this manner, mixing, molding, and sintering.

[0052] However, these methods may introduce impurities from the pulverizing container or pulverizing medium used during manufacturing, especially when pulverizing the raw metal, or produce a large amount of electrode component contaminants due to the consumption of the arc electrode, etc., and may introduce a large amount of metal impurities other than Ga or Al, making them unsuitable for the base substrate forming step in the manufacturing method of the group III compound substrate of the present invention.

[0053] On the other hand, as a method for producing a base substrate suitable for the method for producing a group III compound substrate of the present invention, there is, for example, the following method: Ga metal or Al metal or its halide is subjected to a gas-phase oxidation reaction to obtain Ga2O3 powder or Al2O3 powder, which is then formed into a molded body, and then nitrided under a reducing atmosphere such as N2 or NH3. However, in this method for producing a base substrate, it is difficult to control the incorporation of oxygen into the base substrate. Therefore, as a particularly suitable method for producing a base substrate, there is the following method, which does not have the problem of controlling the incorporation of oxygen as described above and can produce a GaN substrate or AlN substrate with a total metal impurity content of 5000 mass ppm or less, excluding Ga or Al.

[0054] Particularly suitable methods for preparing a base substrate include the following: a method of directly obtaining a GaN or AlN substrate by performing a hydride vapor phase growth method under reduced pressure using high-purity Ga chloride or Ga bromide or Al chloride or Al bromide and NH3 as raw materials; a method of performing the above-mentioned vapor phase growth method at a pressure above normal pressure to obtain a high-purity GaN or AlN powder, and then pressurizing and sintering the powder to obtain a GaN or AlN substrate; and a method of performing a sintering process to improve the formability of the above-mentioned GaN or AlN powder. Methods for obtaining a GaN or AlN substrate by adding high-purity Ga metal or high-purity Al metal in a single step, mixing, then press-molding to form a molded body, sintering the molded body, and simultaneously nitriding the Ga metal or Al metal in the molded body; and methods for obtaining a high-purity GaN or AlN powder, press-molding the powder to form a molded body, infiltrating Ga metal or Al metal into the molded body, and then sintering, while simultaneously nitriding the Ga metal or Al metal in the molded body, to obtain a GaN or AlN substrate. Furthermore, if the substrate obtained by such an operation is low-density and porous, a step may be provided in which high-purity Ga metal or high-purity Al metal is infiltrated into the pores of the substrate, followed by nitriding and sintering for densification. It should be noted that high-purity GaN powder or high-purity AlN powder can be obtained by heating high-purity Ga2O3 powder or Al2O3 powder in an ammonia atmosphere, instead of implementing the above-mentioned vapor phase growth method above normal pressure to obtain high-purity GaN or AlN powder, which can be used to obtain a GaN or AlN base substrate.

[0055] The total amount of metal impurities other than the group III metal elements in the base substrate is preferably 5000 mass ppm or less in terms of metal conversion. If the total amount of metal impurities other than the group III metal elements in the base substrate is 5000 mass ppm or less in terms of metal conversion, the diffusion of impurities from the base substrate into the group III compound crystal can be suppressed, resulting in a high-performance group III compound substrate. For example, in the case where the base substrate is a GaN substrate, the total amount of metal impurities other than Ga is preferably 5000 mass ppm or less in terms of metal conversion. In addition, in the case where the base substrate is an AlN substrate, the total amount of metal impurities other than Al is preferably 5000 mass ppm or less in terms of metal conversion.

[0056] (Seed substrate forming process)

[0057] In the seed substrate forming step, the seed substrate is formed on the base substrate. Preferably, the seed substrate is formed on the base substrate by transferring the seed substrate film onto the base substrate. In addition, the seed substrate is preferably Si <111> , sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN substrate. Moreover, the thickness of the seed substrate is preferably 50 to 2000 nm. If the thickness of the seed substrate is more than 50 nm, the effect of the seed substrate can be fully exerted, and at the same time, many defects generated during film formation can be suppressed. In addition, if the thickness of the seed substrate is less than 2000 nm, the warping of the seed substrate can be suppressed, or the cracking or peeling of the seed substrate can be suppressed. It should be noted that if the seed substrate is formed on the base substrate, the seed substrate can be directly formed on the base substrate, or at least one layer can be interposed between the seed substrate and the base substrate to form the seed substrate on the base substrate.

[0058] In particular, when the base substrate is a GaN substrate or an AlN substrate, the seed substrate is preferably a Si substrate. <111> , sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN substrate. The reason is that Si <111> , sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN is the same as GaN or AlN, or has a similar crystal structure.

[0059] As a method of thin film transfer, various methods can be adopted. However, the following operation is particularly suitable: <111> The invention relates to a process of injecting ions of hydrogen, Ar, etc. into the surface of a seed substrate supplying a substrate of sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN; a process of bonding the surface portion into which the ions have been implanted to a base substrate; and a process of peeling off the surface portion into which the ions have been implanted and bonded to the base substrate from the seed substrate supplying substrate, thereby transferring a uniform thin film to the base substrate.

[0060] (Group III Compound Crystal Formation Step)

[0061] In the III compound crystal formation process, III compound crystal is formed on the above-mentioned seed substrate by hydride vapor phase growth method. In particular, in the III compound crystal formation process, it is preferred to use III chloride and NH3 as vapor phase growth raw materials to form III compound crystal on the seed substrate. It is further preferred that the III compound crystal is gallium nitride (GaN) crystal or aluminum nitride (AlN) crystal. In addition, in order to improve the characteristics of the substrate, it can also be a multi-component III compound crystal of a binary system or a ternary system with Al, In, Ga, etc. added. As needed, the III compound crystal can further include various dopants. It should be noted that if the III compound crystal is formed on the seed substrate, the III compound crystal can be directly formed on the seed substrate, or at least one layer can be between the III compound crystal and the seed substrate to form the III compound crystal on the seed substrate.

[0062] For example, in the case of manufacturing large and high-quality group III compound single crystals of GaN or AlN by hydride vapor phase epitaxy, it is preferred to mainly use GaCl3 or AlCl3 and NH3 as vapor phase growth raw materials to grow GaN or AlN crystals. The hydride vapor phase epitaxy method can be selected from the HVPE method and the THVPE method according to the required crystallization characteristics, and can also be combined with the metal organic vapor phase epitaxy method (MOCVD method) according to the circumstances. Generally, the THVPE method is particularly preferred because the crystal growth rate is fast and the crystal diameter increases with growth. The produced crystal can be used directly as a substrate, or the produced crystal can be processed and the processed crystal can be used as a substrate. In addition, the produced crystal can also be used as a base substrate according to the circumstances.

[0063] (N-face Group III Nitride Layer Formation Step)

[0064] The method for manufacturing a Group III compound substrate of the present invention may further include an N-face Group III nitride layer formation step. In the N-face Group III nitride layer formation step, an N-face Group III nitride layer is formed on the seed substrate between the seed substrate formation step and the Group III compound crystal formation step. It should be noted that the N-face Group III nitride layer refers to a Group III nitride layer having a surface with nitrogen atoms arranged thereon. This allows the production of a large, high-quality Group III compound substrate with minimal warping, voids, or lattice defects, resulting in high performance.

[0065] In the N-face III-nitride layer formation step, the N-face III-nitride layer is preferably formed on the seed substrate using a low-temperature MOCVD method at a temperature of 400-800°C or a THVPE method. This facilitates the formation of the N-face III-nitride layer on the seed substrate. Furthermore, when forming the N-face III-nitride layer on the seed substrate using a low-temperature MOCVD method, it is more preferably formed at a temperature of 500-600°C.

[0066] Generally, HVPE easily forms a surface with Ga atoms or Al atoms arranged thereon, while THVPE, which uses GaCl3 or AlCl3 as a raw material, easily forms a surface with N atoms arranged thereon. Therefore, when the N-faced Group III nitride layer is an N-faced GaN layer or an N-faced AlN layer, it is preferable to form the N-faced Group III nitride layer on the seed substrate using THVPE. In this case, from the perspective of the effect of the seed substrate, the combined film thickness of the seed substrate and the N-faced Group III nitride layer is preferably 50 to 2000 nm.

[0067] Furthermore, an N-faced Group III nitride layer can be formed on a seed substrate using a low-temperature MOCVD method at a film formation temperature preferably between 400°C and 800°C, more preferably between 500°C and 600°C. If the film formation temperature of the low-temperature MOCVD method is 400°C or higher, the N-faced Group III nitride layer can be formed on the seed substrate in a short time, while also improving the film quality of the N-faced Group III nitride layer. If the film formation temperature of the low-temperature MOCVD method is 800°C or lower, the formation of a surface having Ga atoms or a surface having Al atoms arranged on the surface of the Group III nitride layer can be suppressed, allowing the N-faced Group III nitride layer to be easily formed.

[0068] (Peeling Layer Forming Step)

[0069] The method for producing a Group III compound substrate of the present invention may further include a peeling layer forming step, in which a peeling layer composed of a peelable, cleavable substance is formed on the base substrate. Providing the peeling layer between the base substrate and the seed substrate facilitates separation of the Group III compound crystals grown on the seed substrate from the base substrate, allowing for the reuse of the base substrate without loss. It should be noted that when the method for producing a Group III compound substrate of the present invention further includes the peeling layer forming step, the seed substrate is formed on the peeling layer during the seed substrate forming step.

[0070] The above-mentioned peelable cleavable material is preferably selected from the group consisting of SCAM (ScAlMgO4) crystals with cleavable properties, boron nitride (BN) with a crystal structure that is easily peeled into a layered structure, i.e., hexagonal crystals, graphite, PBN (pyrolytic boron nitride) and PG (pyrolytic graphite), and more preferably at least one material selected from the group consisting of SCAM crystals, boron nitride and graphite. If these materials are used in the peeling layer, after the crystals of the group III compound grow, the seed substrate and the produced group III compound crystals can be easily peeled off from the surface layer of the peeling layer, and the seed substrate and the group III compound crystals can be easily recovered. In addition, the peeling layer remaining on the base substrate after recovery can be polished to a smooth surface and reused as needed, which is more economical. It should be noted that when the peeling layer is provided on the base substrate, the peeling layer can be bonded to the base substrate using a common heat-resistant inorganic adhesive, or a peeling layer of any thickness can be laminated on the base substrate by a physical method such as a reduced pressure vapor phase method or sputtering.

[0071] (Intermediate Layer Formation Step)

[0072] The method for manufacturing a group III compound substrate of the present invention may further include an intermediate layer forming step. In the intermediate layer forming step, between the base substrate forming step and the seed substrate forming step, Si, SiO2, Si3N4, SiO2, SiO ... x N y A film of a Si-based compound such as SiO2 is used as a substrate for the seed substrate. This further suppresses contamination from metal impurities in the base substrate or the peeling layer, and enables the production of a large, high-performance, and high-quality Group III compound substrate with minimal warping, voids, or lattice defects. Among these Si-based compounds, SiO2 and Si3N4 are preferred, with SiO2 being more preferred. The method for forming the intermediate layer is not particularly limited, but is preferably formed by a plasma CVD (chemical vapor deposition) method or the like. In addition, after the intermediate layer is formed, it is preferably polished by a CMP (chemical mechanical polishing) method or the like.

[0073] [Group III compound substrate]

[0074] The Group III compound substrate of the present invention is characterized in that it is produced by the method of producing a Group III compound substrate of the present invention.

[0075] The present method for producing a Group III compound substrate makes it possible, for the first time, to produce a large-diameter, uniform, and extremely thick Group III compound substrate. This results in a low-cost substrate with excellent crystal properties. This enables the use of Group III compound substrates in devices such as lasers, power devices, and high-frequency devices, which have been previously limited due to performance and cost considerations. Example

[0076] Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

[0077] [Example 1]

[0078] (1) Fabrication of base substrate

[0079] Reference Figure 1 and Figure 2 The preparation of the base substrate in Example 1 is described below. A mat-shaped alumina heat insulating material 10 is placed in a stainless steel reactor (not shown) with an inner diameter of 1500 mm and a height of 1800 mm (the inner surface of which is pre-sprayed and coated with an extremely thin layer of zirconia) and equipped with a water cooling jacket and an exhaust port. Inside the reactor, a cylindrical heating device 9 (inner diameter 1000 mm and height 1300 mm) with a rod-shaped SiC heater and a gas supply pipe 5 (made of the same material as the above-mentioned reactor, with a center pipe 6: inner diameter 1000 mm and height 1300 mm) are installed. ϕ 30mm, second tube 8: inner diameter ϕ 40mm, outermost tube 7: inner diameter ϕ 50mm). On the other hand, prepare ϕ 520mm PBN coated / graphite base revolution fixture 4, the fixture is arranged and stored at 120° intervals ϕ Three bases 3 are made of 170mm PBN (pyrolytic boron nitride) (PBN is manufactured by changing the pressure in the furnace in a pulsed manner during the manufacture of PBN. As a result, PBN can be peeled and has cleavage properties). The base surface is heated to 1250°C by a heater, and at the same time, the base revolution fixture 4 rotates at 10 rpm to make the base 3 revolve, and the force of its revolution gear is used to make each of the three bases 3 rotate at 30 rpm. After confirming that the temperature and rotation of the base are stable, GaCl3 gas is supplied from the central tube 6 of the triple tube, NH3 gas is supplied from the outermost tube 7, and N2 gas is supplied from the second tube 8 between the central tube 6 and the outermost tube 7 to the inside of the reaction device 1, so that the pressure inside the reaction device reaches 2Torr, and the THVPE reaction is started. As the GaN film grows, the pressure is about 30 m The film growth rate was m / hour and the reaction lasted for 30 hours, and GaN crystal 2 was formed on PBN.

[0080] After cooling, the GaN crystal is peeled off from the PBN base at the part where the PBN interlayer peeling is easy. Then, the peeled GaN crystal is made into ϕ 155mm disc. The disc was polished using a fixed grindstone to completely remove the PBN layer of the disc. The disc was further polished on both sides using a grindstone until the disc thickness was 750mm. m m. Then, the GaN surface was mirror-finished by CMP to smooth the surface of the disk, and a GaN base substrate was produced. When the difference in thermal expansion coefficient between the GaN base substrate and the GaN single crystal was measured, it was as small as about 0.1×10 -6 It should be noted that the thermal expansion coefficient of GaN single crystal at 500°C is about 5.6 ppm / K.

[0081] (2) SiO2 film formation (intermediate layer formation)

[0082] A 0.5 layer was stacked on the base substrate using a plasma CVD device. m m of SiO2 to form a SiO2 film, which was gently polished by CMP to a thickness of 0.4 m m.

[0083] (3) Thin film transfer to substrates

[0084] The hydrogen ions are injected to 0.5 m The hydrogen ion implantation surface of the C-surface sapphire wafer with a depth of 0.5 m is attached to the base substrate formed with a SiO2 film. After bonding with the base substrate, the C-surface sapphire film is peeled off from the C-surface sapphire wafer and the 0.5 m thick m The C-plane sapphire film of m is transferred to the base substrate.

[0085] (4) Formation of the III-nitride layer on the N-side

[0086] On this substrate, trimethyl gallium (TMG) and NH3 were used as raw materials, and a low-temperature MOCVD reaction was carried out at a film forming temperature of 550°C for 3 hours to stack 0.6 m The total thickness of the substrate and the N-face GaN crystal is 1.1 m m.

[0087] (5) Fabrication of large and high-quality GaN substrates

[0088] The THVPE reaction was continued for 40 hours using the seed substrate under the same conditions as those used to prepare the base substrate, except that the pressure was kept at normal pressure using the apparatus used to prepare the base substrate. GaN crystals were formed on the seed substrate. The obtained GaN crystals did not warp or deform after cooling, and large and thick GaN crystals were obtained. The GaN crystals were processed into ϕ 150mm x 10mm thick, diamond cutting and double-sided polishing were performed to produce 7 pieces. ϕ 150mm×thickness 625 m m's GaN substrate of Example 1.

[0089] (6) Evaluation of the obtained GaN substrate

[0090] Of the seven GaN substrates obtained, the topmost GaN substrate (the GaN substrate farthest from the seed substrate) had an average of 15 arcsec (arcseconds) and a deviation of 1 arcsec for any three points within the plane of the FWHM (Full Width at Half Maximum) X-ray rocking curve on the (100) plane for the average of 55 arcsec and a deviation of 8 arcsec for any three points within the plane of the FWHM X-ray rocking curve on the (100) plane for the bottommost GaN substrate (the GaN substrate closest to the seed substrate). Although slightly inferior in crystallinity to that of the topmost GaN substrate, this substrate also had good crystallinity. Incidentally, chemical analysis of the surfaces of the aforementioned substrates revealed that metal contamination in both the topmost and bottommost GaN substrates was below the detection limit.

[0091] Furthermore, observation of stacking defects using monochromatic cathodoluminescence imaging revealed no stacking defects at all in the uppermost GaN substrate. On the other hand, very minor stacking defects were observed in the lowermost GaN substrate, at a level comparable to that observed in MOCVD-derived GaN substrates, which are considered to have good crystallinity. These results demonstrate that the GaN substrate of Example 1 is a large, high-quality GaN crystal substrate.

[0092] [Comparative Example 1]

[0093] GaN powder was produced by reacting Ga metal in NH3 under arc plasma. The GaN powder was molded into a substrate using a press to produce a molded body. The molded body was fired at a firing temperature of 1300°C in an NH3 atmosphere to produce a base substrate. Except for this, the GaN substrate of Comparative Example 1 was produced in the same manner as the method for producing the GaN substrate of Example 1. The metal contamination of the uppermost GaN substrate was measured, and the results showed that a total of 8500 mass ppm of metal impurities such as Cu and Fe, which are believed to come from the Cu electrode of the arc plasma device, were mixed into the GaN substrate. GaN substrates with such high metal impurity content could not be introduced into the production line due to concerns about contamination of the device manufacturing line. In addition, when the FWHM of the GaN substrate of Comparative Example 1 was measured, the average value of any three points in the plane was 7800 arcsec and the deviation was 3000 arcsec due to the influence of metal impurities. The GaN substrate of Comparative Example 1 had very poor crystallinity.

[0094] [Example 2]

[0095] (1) Fabrication of base substrate

[0096] Using the apparatus used to produce the GaN substrate of Example 1, high-purity GaN powder was produced by a hydride gas phase reaction using GaCl3 and NH3 as raw materials at a pressure of 3 Torr in gauge pressure, i.e., atmospheric pressure + 3 Torr. To 100 parts by mass of GaN powder, 1 part by mass of Ga metal was added and mixed to produce a mixture. The mixture was heated at 30 kg / cm 2 The mixture was press-molded using a press under conditions of 10% pressure and 25°C temperature to produce a compact. The compact was then nitrided and sintered at 1200°C in a mixed gas atmosphere of 10% by volume N2 gas and 90% by volume NH3 gas to produce a base substrate.

[0097] (2) Thin film transfer to substrates

[0098] use ϕ 6-inch Si <111> Instead of the C-surface sapphire wafer, the Si <111> Transfer to the base substrate.

[0099] (3) Formation of the III-nitride layer on the N-side

[0100] The N-face GaN crystal was stacked on the seed substrate by THVPE reaction at 800°C for 1 hour. It should be noted that the total thickness of the seed substrate and the N-face GaN crystal is 0.7 m m.

[0101] (4) Fabrication of large and high-quality GaN substrates

[0102] In the same manner as in Example 1, a GaN crystal was formed on a seed substrate, and the obtained GaN crystal was processed to produce the GaN substrate of Example 2.

[0103] (5) Evaluation of the obtained GaN substrate

[0104] Of the seven GaN substrates obtained, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the top GaN substrate was 20 arcsec, with a deviation of 1 arcsec, indicating that this substrate has very good crystallinity. On the other hand, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the bottom GaN substrate was 45 arcsec, with a deviation of 4 arcsec. Although its crystallinity was slightly worse than that of the top GaN substrate, this substrate also had good crystallinity. Incidentally, the results of chemical analysis of the surfaces of the above-mentioned substrates showed that the metal contamination in the GaN substrate of the top GaN substrate was below the detection limit. On the other hand, the Al detected in the bottom GaN substrate was near the detection limit, but the Al detection level is not a problem for using the GaN substrate in a device. The other metal impurities were also below the detection limit.

[0105] Furthermore, the stacking defects were observed by monochromatic cathodoluminescence imaging. The results showed that there were no stacking defects in the uppermost and lowermost GaN substrates, indicating that both were excellent crystals. The above results show that the GaN substrate crystal of Example 2 is a large and high-quality GaN crystal substrate. It should be noted that the GaN substrate of Example 2 has good crystallinity and few metal impurities. It is speculated that this is due to the Si layer stacked on the seed substrate. <111> Effect of the GaN layer on the N-side.

[0106] [Example 3]

[0107] (1) Fabrication of base substrate

[0108] Using the apparatus used to produce the GaN substrate of Example 1, high-purity GaN powder was produced by a hydride gas phase reaction using GaCl3 and NH3 as raw materials at a total pressure of 3 Torr in gauge pressure, i.e., atmospheric pressure + 3 Torr. 2 Under the conditions of pressure and temperature of 1050℃, the mixture was heated and pressed in a N2 gas atmosphere to produce ϕ6-inch wafer-shaped base substrate.

[0109] (2) SiO2 film formation (intermediate layer formation)

[0110] A 0.5 layer was stacked on the base substrate using a plasma CVD device. m m of SiO2 to form a SiO2 film, which was gently polished by CMP to a thickness of 0.4 m m.

[0111] (3) Thin film transfer to substrates

[0112] Multiple pieces ϕ 2-inch SCAM substrate (thickness 220 m m) Processing into honeycomb shape. Use inorganic adhesive material to attach multiple honeycomb SCAM substrates to a glass substrate prepared separately to form ϕ 7-inch disk. Then, hydrogen ions are injected into the SCAM substrate to 1 m The hydrogen ion implantation surface of the SCAM substrate that has been implanted with hydrogen ions is attached to the base substrate formed with the SiO2 film and bonded to the base substrate. Then, the SCAM film is peeled off from the SCAM substrate and a thickness of 1 m is formed. m The SCAM film of 0.7 μm is transferred to the base substrate. The transferred SCAM film is gently polished by CMP to a thickness of 0.7 μm. m m, which serves as the seed substrate. It should be noted that in Example 3, no N-face GaN crystal is stacked on the seed substrate. Furthermore, after peeling off the SCAM film, the SCAM substrate remaining on the glass substrate can be reused as the seed substrate.

[0113] (4) Fabrication of large and high-quality GaN substrates

[0114] In the same manner as in Example 1, GaN crystals were formed on the seed substrate and the obtained GaN crystals were processed to produce the GaN substrate of Example 3. It should be noted that the obtained GaN crystals could not be easily peeled off from the SCAM film serving as the seed substrate. In addition, when the obtained GaN crystals were several hundred meters away from the seed substrate, the GaN crystals were not easily peeled off from the SCAM film serving as the seed substrate. m In the region m, the GaN crystal is slightly colored yellow, but in other regions, the GaN crystal is not colored.

[0115] (5) Evaluation of the obtained GaN substrate

[0116] Of the seven GaN substrates obtained, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the top GaN substrate was 13 arcsec, with a deviation of 2 arcsec, indicating that the substrate had very good crystallinity. On the other hand, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the bottom GaN substrate among the seven substrates was 20 arcsec, with a deviation of 3 arcsec, indicating that the crystallinity of the bottom GaN substrate was almost the same as that of the top GaN substrate. This is presumably because when GaN was formed on the SCAM film as the seed substrate, the SCAM film peeled off, causing stress relaxation in the GaN being formed. Incidentally, the results of chemical analysis of the surfaces of the above-mentioned substrates showed that the metal contamination in the GaN substrate of the top GaN substrate was below the detection limit. In the bottommost GaN substrate, although Al, Mg, and Sc were detected near the detection limit, the detection levels of these elements are not problematic for use in devices. Other metal impurities were also below the detection limit.

[0117] [Comparative Example 2]

[0118] (1) Fabrication of base substrate

[0119] At 100°C, under a mixed gas flow of 20% by volume N₂ gas and 80% by volume NH₃ gas, Al metal was nitrided and pulverized for 300 hours to produce AlN powder. SiO₂ and Al₂O₃ as sintering aids, and Poval (polyvinyl alcohol) as a binder were added to the resulting AlN powder, mixed, molded, and fired to produce a base substrate.

[0120] (2) Thin film transfer to substrates

[0121] A 2-inch GaN substrate made with Na flux was used as a seed substrate to replace ϕ 2-inch SCAM substrate. It should be noted that the GaN substrate manufactured using Na flux does not show the same cleavage as the SCAM substrate. ϕ 6-inch seed substrate.

[0122] (3) Fabrication of large and high-quality GaN substrates

[0123] The GaCl3 gas was replaced with GaCl gas, and the film formation method was changed from THVPE to HVPE. A GaN crystal was formed on the seed substrate in the same manner as in Example 3, and the resulting GaN crystal was processed to produce the GaN substrate of Comparative Example 2. However, the flow rate of the GaCl gas was changed so that the supply amount of the Ga element remained the same as in the case of the GaCl3 gas.

[0124] (4) Evaluation of the obtained GaN substrate

[0125] Among the 7 GaN substrates obtained, the diameter of the GaN substrate at the bottom layer was about 6 inches, and the diameter of the GaN substrate at the top layer was about 4 inches. Therefore, in Comparative Example 2, the GaN crystals formed on the seed substrate became smaller as they went up. Therefore, it was not possible to obtain multiple GaN substrates. ϕ The diameter of the obtained GaN substrate is not uniform for the target GaN substrate of 6 inches.

[0126] Of the seven GaN substrates obtained, the average value of the FWHM of the X-ray rocking curve for the (100) plane at any three points within the topmost GaN substrate was 1350 arcsec, with a deviation of 200 arcsec, indicating that this substrate had very poor crystallinity. Incidentally, chemical analysis of the surfaces of these substrates revealed that the metal impurity content in the topmost GaN substrate was 5300 mass ppm, while that in the bottommost GaN substrate was 95000 mass ppm, both of which were high. GaN substrates with such high metal impurity content were not introduced into the device manufacturing line due to concerns about contamination.

[0127] Furthermore, stacking defects were observed by monochromatic cathodoluminescence imaging, and as a result, many stacking defects were observed in both the uppermost GaN substrate and the lowermost GaN substrate.

[0128] [Example 4]

[0129] (1) Fabrication of base substrate

[0130] In addition to replacing GaCl3 gas with AlCl3 gas and changing the reaction temperature from 1250°C to 1500°C, the same method as in Example 1 was used to prepare ϕ A 155 mm AlN substrate was used as the base substrate. It should be noted that the thermal expansion coefficient of the AlN substrate at 500°C is approximately 5.7 ppm.

[0131] (2) SiO2 film formation (intermediate layer formation)

[0132] A 0.6-layer stack was stacked on the base substrate using a plasma CVD device. mm of SiO2 to form a SiO2 film, which was gently polished by CMP to a thickness of 0.5 m m.

[0133] (3) Thin film transfer to substrates

[0134] Multiple pieces were made by flux method ϕ 2-inch AlN substrate (thickness 200 m m). Put multiple pieces ϕ 2-inch AlN substrate is processed into honeycomb shape. Multiple honeycomb AlN substrates are attached to a glass substrate prepared separately using an inorganic adhesive to form a ϕ 6-inch disk. Then, hydrogen ions are implanted into the AlN substrate to 1 m The hydrogen ion implantation surface of the AlN substrate that has been implanted with hydrogen ions is attached to the base substrate formed with the SiO2 film and bonded to the base substrate. After that, the AlN film is peeled off from the AlN substrate and a thickness of 1 m is formed. m The AlN film is transferred to the base substrate. Then, the transferred AlN film is gently polished by CMP to a thickness of 0.9 m m, and use it as a seed substrate.

[0135] (4) Fabrication of large and high-quality AlN substrates

[0136] Using the same equipment used in the preparation of the base substrate, the THVPE reaction was continued for 40 hours using the seed substrate under the same conditions as the base substrate, and AlN crystals were formed on the seed substrate. The AlN crystals obtained did not warp or deform after cooling, and large and thick AlN crystals were obtained. The AlN crystals were processed into ϕ 150mm x 10mm thick, diamond cutting and double-sided polishing were performed to produce 7 pieces. ϕ 150mm×thickness 625 m m is the AlN substrate of Example 4.

[0137] (5) Evaluation of the obtained AlN substrate

[0138] Of the seven AlN substrates obtained, the average value of the FWHM of the X-ray rocking curve for the (100) plane at any three points within the plane of the topmost AlN substrate was 23 arcsec, with a deviation of 3 arcsec, indicating that this substrate had very good crystallinity. On the other hand, the average value of the FWHM of the X-ray rocking curve for the (100) plane at any three points within the plane of the bottommost AlN substrate was 45 arcsec, with a deviation of 8 arcsec. Although slightly inferior in crystallinity to that of the topmost AlN substrate, this substrate also had good crystallinity. Incidentally, chemical analysis of the surfaces of these substrates revealed that metal contamination in both the topmost and bottommost AlN substrates was below the detection limit.

[0139] Furthermore, stacking defects were observed by monochromatic cathodoluminescence imaging, and no stacking defects were observed in the uppermost and lowermost AlN substrates. The above results show that the AlN substrate of Example 4 is a large and high-quality AlN substrate.

[0140] [Example 5]

[0141] (1) Fabrication of base substrate

[0142] According to the same method as Example 3, ϕ 6-inch wafer-shaped base substrate.

[0143] (2) Si3N4 film formation (intermediate layer formation)

[0144] A 0.5 layer was stacked on the base substrate using a plasma CVD device. m m of Si3N4 to form a Si3N4 film, which was gently polished by CMP to a thickness of 0.4 m m.

[0145] (3) Thin film transfer to substrates

[0146] As in Example 3, multiple ϕ 2-inch SCAM substrate (thickness 220 m m) Processing into honeycomb shape. Use inorganic adhesive material to stick multiple honeycomb SCAM substrates on a glass substrate prepared separately to form ϕ 7-inch disk. Then, hydrogen ions are injected into the SCAM substrate to 1 m The hydrogen ion implantation surface of the SCAM substrate that has been implanted with hydrogen ions is attached to the base substrate formed with the Si3N4 film and bonded to the base substrate. Then, the SCAM film is peeled off from the SCAM substrate and a thickness of 1 m is formed. mThe SCAM film of 0.7 μm is transferred to the base substrate. The transferred SCAM film is gently polished by CMP to a thickness of 0.7 μm. m m, and use it as a seed substrate.

[0147] (4) Fabrication of large and high-quality GaN substrates

[0148] A GaN crystal was formed on a seed substrate and processed to produce a GaN substrate in the same manner as in Example 1. It should be noted that the GaN crystal can be easily peeled off from the SCAM film serving as the seed substrate.

[0149] (5) Evaluation of the obtained GaN substrate

[0150] Of the seven GaN substrates obtained, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the topmost GaN substrate was 16 arcsec, with a deviation of 2 arcsec, indicating that the substrate had good crystallinity. On the other hand, the average value of the FWHM of the X-ray rocking curve of the (100) plane at any three points within the plane of the bottommost GaN substrate among the seven substrates was 22 arcsec, with a deviation of 3 arcsec, indicating that the crystallinity of the bottommost GaN substrate was almost equivalent to that of the topmost GaN substrate. Incidentally, chemical analysis of the surfaces of the above-mentioned substrates showed that metal contamination in the GaN substrates was below the detection limit in both the topmost and bottommost GaN substrates.

[0151] [Example 6]

[0152] (1) Fabrication of base substrate

[0153] Using GaCl3 and NH3 as raw materials, under the same conditions as in Example 1, a ϕ 8 inches, thickness 800 m m GaN base substrate.

[0154] (2) Formation of the peeling layer

[0155] Multiple pieces ϕ 2-inch SCAM substrate (thickness 600 m m) Processed into a honeycomb shape, the honeycomb is spread over the base substrate and bonded with an alumina-based inorganic adhesive to form a peeling layer.

[0156] (3) SiO2 film formation (intermediate layer formation)

[0157] A sputtering device was used to deposit 2 on the surface of the peeling layer. mThe surface of the SiO2 film is polished by CMP to make the surface roughness Ra of the SiO2 film 0.5 m m.

[0158] (4) Thin film transfer to substrates

[0159] The hydrogen ions have been injected to 0.35 m m depth ϕ 8-inch Si <111> The hydrogen ion implantation surface of the wafer is attached to a base substrate on which a SiO2 film is formed on a peeling layer, and after bonding with the base substrate, the Si <111> The ion implantation part of the wafer is stripped of Si <111> Film, thickness 0.35 m mSi <111> The film is transferred to the base substrate.

[0160] Three such GaN base substrates / SCAM peeling layers / SiO2 films / Si <111> A composite substrate having a structure of a substrate.

[0161] On this substrate, trimethyl gallium (TMG) and NH3 are used as raw materials, and a low-temperature MOCVD reaction is carried out at a film forming temperature of 550°C for 3 hours to stack 0.6 m The total thickness of the substrate and the N-face GaN crystal is 1.1 m m.

[0162] (5) Fabrication of large and high-quality GaN substrates

[0163] Using the apparatus used in the preparation of the base substrate, under the same conditions as when preparing the base substrate, the seed substrate was used and the crystal growth rate was about 200. m m / hour, and the THVPE reaction was continued for 100 hours to form GaN crystals on the seed substrate.

[0164] After cooling, the resulting GaN crystals and Si <111> The seed crystal is integrated with the SCAM crystal and can be easily peeled off from the SCAM crystal by utilizing the cleavage property of the peeling layer. The SCAM of the peeling layer is suitable for recycling and reuse. On the other hand, first, the peeled GaN crystal and Si <111> The seed crystal is cylindrically ground and then polished to remove Si <111> After seed crystal is cut into 800 m The thickness of the 16 GaN substrates was obtained by grinding and polishing to the final CMP polishing, and a thickness of 625 mIncidentally, the GaN substrate immediately after crystal growth absorbs thermal stress by cleaving gradually during the reaction due to the action of the SCAM of the exfoliation layer, resulting in almost no warping and no cracking.

[0165] (6) Evaluation of the obtained GaN substrate

[0166] The FWHM of the (100) plane X-ray rocking curves for the 16 GaN substrates obtained had an average in-plane center value of 30 arcsec and a deviation of 3 arcsec. Furthermore, the average value for any three points on these substrates was 53 arcsec with a deviation of 6 arcsec, indicating good crystallinity. Incidentally, chemical analysis of the surfaces of these substrates revealed that metal contamination in all GaN substrates was below the detection limit.

[0167] Furthermore, observation of stacking defects using monochromatic cathodoluminescence imaging revealed virtually no stacking defects in the surface layer of the resulting GaN substrate. These results demonstrate that the resulting GaN substrate exhibits no warping and little deviation, demonstrating a uniform, high-quality GaN crystal substrate.

[0168] [Example 7]

[0169] (1) Fabrication of base substrate

[0170] High-purity GaN powder was prepared in the same manner as in Example 2. 10 parts by mass of Ga metal was added to 100 parts by mass of the GaN powder and mixed to prepare a mixture. 2 The mixture was press-molded using a press under conditions of 10% pressure and 25°C temperature to produce a compact. The compact was nitrided and sintered at 1200°C in a mixed gas atmosphere of 10% by volume N2 gas and 90% by volume NH3 gas to produce a base substrate.

[0171] (2) Formation of the peeling layer

[0172] Use alumina-based inorganic adhesive ϕ 8-inch PBN substrate (thickness 600 m m) is attached to the surface of the base substrate to form a peeling layer.

[0173] (3) Si3N4 film formation (intermediate layer formation)

[0174] A Si3N4 film was stacked on the surface of the peeling layer using a plasma CVD device, and the surface of the Si3N4 film was polished to a surface roughness Ra of 0.5. m m.

[0175] (4) Thin film transfer to substrates

[0176] The hydrogen ions have been injected to 0.35 m m depth ϕ The hydrogen ion implanted surface of an 8-inch sapphire wafer was attached to the Si3N4 film of the intermediate layer on the base substrate, and the sapphire wafer and the base substrate were bonded. Then, the sapphire film was peeled off from the ion implanted part of the sapphire wafer and a 0.35 mm thick m m sapphire film is transferred to the base substrate.

[0177] Three composite substrates having the structure of GaN base substrate / PBN peeling layer / Si3N4 film / sapphire seed substrate were produced.

[0178] On this substrate, trimethyl gallium (TMG) and NH3 were used as raw materials, and a low-temperature MOCVD reaction was carried out at a film forming temperature of 550°C for 3 hours to stack 0.6 m The total thickness of the substrate and the N-face GaN crystal is 1.1 m m.

[0179] (5) Fabrication of large and high-quality GaN substrates

[0180] Using the apparatus used in the preparation of the base substrate, GaN crystals were grown on the seed substrate under the same conditions as those used in the preparation of the base substrate. m m / hour, and the GaN film growth was continued for 100 hours.

[0181] After cooling, the resulting GaN crystals are easily peeled off from the PBN layer of the debonding layer, forming a single unit with the seed substrate. The thermal stress that might have been caused by cooling is absorbed by the interlayer debonding. As a result, the GaN crystals experience no cracking and little warping.

[0182] (6) Evaluation of the obtained GaN substrate

[0183] The average value of the FWHM of the X-ray rocking curve of the (100) plane of the obtained GaN substrate at any three points within the plane was 55 arcsec, with a deviation of 6 arcsec. The analysis value of metal impurities was below the measurement limit. In addition, stacking defects were observed by monochromatic cathodoluminescence imaging, and the results showed that stacking defects were almost absent in the surface layer of GaN. From the above measurements and observations, it can be seen that the obtained GaN crystal is a very uniform and good crystal substrate with no deviation.

[0184] Explanation of symbols

[0185] 1: Inside the reaction device;

[0186] 2: GaN crystal;

[0187] 3: base;

[0188] 4: Base revolution fixture;

[0189] 5: Gas supply pipe;

[0190] 6: Central tube;

[0191] 7: outermost tube;

[0192] 8: 2nd tube;

[0193] 9: Heating device;

[0194] 10: Thermal insulation material.

Claims

1. A method for manufacturing a group III compound substrate, the method comprising the following steps: a base substrate forming step of forming a base substrate of group III nitride by a vapor phase synthesis method; a seed substrate forming step of forming a seed substrate on the base substrate; and The group III compound crystal forming step is to form a group III compound crystal on the seed substrate by a hydride vapor phase growth method, wherein: The base substrate is the following substrate: A substrate obtained by forming a molded body by molding a powder of a group III nitride obtained by a hydride vapor phase epitaxy method, impregnating the molded body with a group III metal by an impregnation method, and then sintering the molded body; A substrate obtained by forming a molded body by molding a powder of a group III nitride obtained by a hydride vapor phase growth method, impregnating the molded body with a group III compound that becomes a group III metal when reduced by an impregnation method, and then nitriding and sintering the molded body; or A substrate obtained by adding or mixing a Group III metal to a Group III nitride powder obtained by a hydride vapor phase epitaxy method to prepare a mixture, molding the mixture to prepare a molded body, and then nitriding and sintering the molded body.

2. The method for manufacturing a group III compound substrate according to claim 1, wherein: The hydride vapor phase epitaxy method used in the above-mentioned group III compound crystal formation step is the THVPE method.

3. The method for producing a group III compound substrate according to claim 1, wherein: The group III nitride of the base substrate is GaN or AlN, The above substrate is Si <111> , sapphire, SiC, GaAs, SCAM (ScAlMgO4) or GaN substrates, In the seed substrate forming step, the seed substrate film is transferred onto the base substrate to form the seed substrate on the base substrate. In the group III compound crystal forming step, the group III compound crystal is formed on the seed substrate using group III chloride and NH 3 as vapor phase growth raw materials.

4. The method for producing a group III compound substrate according to claim 1, wherein: The base substrate is a substrate of at least one material selected from the group consisting of amorphous, polycrystalline and single crystal Group III nitrides. The total content of metallic impurities other than the Group III metal element in the base substrate is 5000 ppm by mass or less in terms of metal.

5. The method for producing a group III compound substrate according to claim 1, wherein: The base substrate is a ceramic substrate of group III nitride. The total content of metallic impurities other than the Group III metal element in the base substrate is 5000 ppm by mass or less in terms of metal.

6. The method for producing a group III compound substrate according to claim 1, wherein: The Group III compound crystal is a gallium nitride (GaN) crystal or an aluminum nitride (AlN) crystal.

7. The method for producing a group III compound substrate according to claim 1, wherein: The method further includes, between the seed substrate forming step and the group III compound crystal forming step, an N-face group III nitride layer forming step of forming an N-face group III nitride layer on the seed substrate.

8. The method for producing a group III compound substrate according to claim 7, wherein: In the N-face III-nitride layer forming step, the N-face III-nitride layer is formed on the seed substrate by low-temperature MOCVD at a temperature of 400 to 800° C. or by THVPE.

9. The method for producing a group III compound substrate according to claim 8, wherein: In the N-face group III nitride layer forming step, the N-face group III nitride layer is formed on the seed substrate by a low-temperature MOCVD method at a temperature of 500 to 600°C.

10. The method for producing a group III compound substrate according to claim 7, wherein: The thickness of the seed substrate, or the total thickness of the seed substrate and the thickness of the N-face group III nitride layer formed in the N-face group III nitride layer forming step, is 50 to 2000 nm.

11. The method for manufacturing a Group III compound substrate according to claim 1, further comprising: a peeling layer forming step of forming a peeling layer made of a peelable cleavable material on the base substrate; In the seed substrate forming step, a seed substrate is formed on the release layer.

12. The method for producing a group III compound substrate according to claim 11, wherein: The above-mentioned peelable cleavable substance is at least one substance selected from SCAM (ScAlMgO4) crystal, boron nitride (BN) and graphite.

13. The method for manufacturing a Group III compound substrate according to claim 11, further comprising: an intermediate layer forming step of forming an intermediate layer on the peeling layer; The above-mentioned intermediate layer is a film of Si-based compound, In the seed substrate forming step, a seed substrate is formed on the intermediate layer.

14. The method for manufacturing a Group III compound substrate according to claim 1, further comprising: an intermediate layer forming step of forming an intermediate layer on the base substrate; The above-mentioned intermediate layer is a film of Si-based compound, In the seed substrate forming step, a seed substrate is formed on the intermediate layer.

15. A group III compound substrate, characterized in that: The substrate is produced by the method for producing a Group III compound substrate according to any one of claims 1 to 14.

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