Composite seed crystal and method of manufacturing single crystal

Abstract

This composite seed crystal is provided with a seed crystal, and a protective layer formed on a surface other than a growth surface of the seed crystal. The protective layer: is formed on all or part of at least a reverse surface of the seed crystal; comprises a formed body, a debound body, or a pre-sintered body containing a main powder of at least one selected from the group consisting of high-melting-point metals, high-melting-point metal carbides, high-melting-point metal nitrides, and high-melting-point metal carbonitrides; and has a thickness of 50 to 500 μm. This method of manufacturing a single crystal comprises: a first step for installing a composite seed crystal in a container for growing a single crystal; and a second step for heating the seed crystal to a growth temperature of the single crystal, supplying a raw material gas to a growth surface of the seed crystal, and causing the single crystal to grow on the growth surface.

Description

Method for manufacturing composite seed crystal and single crystal

[0001] The present invention relates to a method for manufacturing a composite seed crystal and a single crystal, and more particularly to a composite seed crystal capable of suppressing sublimation decomposition of the seed crystal and deterioration of the quality of the grown crystal due to thermal stress during single crystal growth, and a method for manufacturing a single crystal using the same.

[0002] Conventionally, single crystals of SiC or group III nitride semiconductors (e.g., AlN) have been manufactured by adhering and fixing a seed crystal on the surface of a pedestal, supplying a raw material gas to the surface of the seed crystal, and growing a new crystal on the surface of the seed crystal. As a method of adhering the seed crystal, for example, (a) a method of adhering an AlN seed crystal and a pedestal (holder plate) with an AlN-based adhesive composed of a mixture of AlN ceramics and a silicate solution (Patent Document 1), (b) a method of adhering a SiC seed crystal and a pedestal with a phenolic resin-based adhesive (Patent Document 2), etc. are known.

[0003] However, if the seed crystal and the pedestal are firmly fixed, thermal stress may be generated in the seed crystal and the grown crystal due to the difference in thermal expansion coefficient between the seed crystal and the pedestal during single crystal growth, and cracks may occur in the seed crystal and the grown crystal.

[0004] Further, if the adhesion between the seed crystal and the pedestal is non-uniform, a gap will occur between the seed crystal and the pedestal. When the temperature of the seed crystal is raised to the growth temperature in this state, sublimation from the surface of the seed crystal and re-precipitation of the sublimated component on the surface of the pedestal occur in the gap. As a result, the defects generated on the back surface of the seed crystal may progress toward the growth surface of the seed crystal, and the defects may be exposed on the growth surface. The defects exposed on the growth surface cause micro-pipe defects in the grown crystal. See Non-Patent Document 1.

[0005] Therefore, various proposals have been made to solve this problem. For example, Patent Document 3 discloses a method of protecting the non-growth surface of a SiC seed crystal with a carbon film in order to suppress sublimation decomposition of the back surface of the SiC seed crystal. Patent Document 4 discloses a method of protecting the back surface of a SiC seed crystal with a photosensitive resin film or a carbon film obtained by carbonizing the photosensitive resin film. <Patent Document 5 discloses a method for protecting the back surface of a SiC seed crystal with a coating made of metals such as W, Ta, and Mo, or metal compounds such as WC, TaC, MoC, and TaN, using methods such as vapor deposition and CVD. Patent Document 6 discloses a method for inserting a stress buffer made of a flexible graphite sheet between the seed crystal and the base in order to reduce the thermal stress generated in the seed crystal.

[0007] Patent Document 7 discloses (a) a method for forming a carbon layer or a dense high-melting-point metal carbide layer on the back surface of a SiC seed crystal, and (b) a method for mechanically holding the SiC seed crystal with a hook-shaped member.

[0008] Patent Document 8 discloses (a) a method for forming a high-melting-point metal carbide layer on the back surface of a SiC seed crystal using a sputtering method or a screen printing method, and (b) a method for placing a SiC seed crystal on the upper end opening of a conical holding part.

[0009] Furthermore, Patent Document 9 discloses a method in which (a) the back surface of the SiC seed crystal and the surface of the graphite lid are mirror polished, (b) the SiC seed crystal and the graphite lid are placed on top of each other so that their mirror polished surfaces face each other, and (c) the ends of the SiC seed crystal are fixed with graphite screws.

[0010] Patent documents 3 and 4 propose the use of a carbon film as a protective film for SiC seed crystals. However, when a carbon film is used as a protective film for SiC seed crystals, the carbon film reacts with Si vapor in the growth atmosphere and gradually deteriorates and degrades with high-temperature, long-term use. Furthermore, when a carbon film is used as a protective film for seed crystals other than SiC seed crystals, its protective function may be insufficient. For example, carbon is known to corrode severely in Al vapor. Therefore, tantalum crucibles or tungsten crucibles, rather than carbon crucibles, are used as growth crucibles for growing AlN single crystals. See Non-Patent Documents 2 and 3.

[0011] Patent documents 5, 7, and 8 suggest the use of high-melting-point metal carbide films as protective films for SiC seed crystals. However, these documents only suggest the use of high-melting-point metal carbides and do not describe in detail the protective film that can suppress the deterioration of the quality of the grown crystal, nor do they describe the method of forming it. For example, if the protective film is formed by vapor deposition, there is a difference in the coefficient of thermal expansion between the protective film and the SiC seed crystal, so when the temperature is raised from room temperature to the growth temperature of approximately 2000°C, there is a risk that cracks may occur in the seed crystal and the grown crystal due to thermal stress.

[0012] Patent documents 6 to 9 disclose methods for reducing thermal stress generated in seed crystals during single crystal growth using flexible graphite sheets and mechanical holding methods. However, flexible graphite sheets may be altered or deteriorated during single crystal growth. Furthermore, the method of mirror polishing the back surface of the seed crystal and the surface of the graphite lid increases processing costs. Moreover, mirror polishing the back surface of the seed crystal leaves polishing marks on the polished surface, which can cause sublimation decomposition of the seed crystal.

[0013] U.S. Patent No. 7,638,346, U.S. Patent Application Publication No. 2012 / 0006255, JP A-09-268096, JP A-2003-226600, JP H11-510781

[0014] Japanese Patent Publication No. 2004-269297, Japanese Patent Publication No. 2002-201097, Japanese Patent Publication No. 2011-184209, Japanese Patent Publication No. 2002-308697

[0015] A. Stein, Physica B, vol. 185(1993) pp211-216E. N. Mokhov et al., J. Cryst. Growth 281(2005)pp.93-100P. Lu et al., J. Cryst. Growth 312(2009)pp.58-63

[0016] The problem that this invention aims to solve is to provide a composite seed crystal that can suppress the sublimation decomposition of the seed crystal and the deterioration of the quality of the grown crystal due to thermal stress during single crystal growth. Another problem that this invention aims to solve is to provide a method for manufacturing a single crystal using such a composite seed crystal.

[0017] To solve the above problems, the composite seed crystal according to the present invention comprises a seed crystal and a protective layer formed on a surface other than the growth surface of the seed crystal, wherein the protective layer is formed on at least all or part of the back surface of the seed crystal and consists of a molded body, degreased body, or calcined body containing at least one main powder selected from the group consisting of high-melting-point metals, high-melting-point metal carbides, high-melting-point metal nitrides, and high-melting-point metal carbonitrides, and has a thickness of 50 μm or more and 500 μm or less. However, the "high-melting-point metal" refers to a metal whose melting point at 1 atmosphere is 2000°C or higher.

[0018] A method for manufacturing a single crystal according to the present invention comprises: a first step of placing a composite seed crystal according to the present invention in a container for growing a single crystal; and a second step of heating the seed crystal to the growth temperature of the single crystal, supplying a raw material gas to the growth surface of the seed crystal, and growing the single crystal on the growth surface. Preferably, the first step includes a step of placing the composite seed crystal in the container such that all or part of the back surface of the composite seed crystal is not restrained by other members.

[0019] A composite seed crystal is fabricated with a low-density protective layer formed on its back surface. When this composite seed crystal is held in a container for single-crystal growth and heated to the growth temperature, the protective layer sintersects in place. As a result, the back surface of the seed crystal is protected by the dense protective layer, and the sublimation decomposition of the seed crystal is suppressed. Using this method, the thermal stress generated in the seed crystal during single-crystal growth is reduced compared to when a dense protective layer is formed on the back surface of the seed crystal at room temperature. Therefore, the deterioration of the quality of the grown crystal due to thermal stress can also be suppressed. Furthermore, if a method is used to hold the composite seed crystal in which all or part of the back surface of the composite seed crystal is not constrained by other components, the thermal stress generated in the seed crystal and the grown crystal is further reduced.

[0020] Figure 1(A) is a schematic diagram of the first method of holding a composite seed crystal. Figure 1(B) is a schematic diagram of the second method of holding a composite seed crystal. Figure 2(A) is a schematic diagram of the third method of holding a composite seed crystal. Figure 2(B) is a schematic diagram of the fourth method of holding a composite seed crystal. Figure 3(A) is a schematic diagram of the fifth method of holding a composite seed crystal. Figure 3(B) is a schematic diagram of the fifth method of holding a composite seed crystal. This is a flowchart of the manufacturing method for composite seed crystals and single crystals. This is a diagram showing the relationship between the temperature of the protective layer in each step and the thermal stress generated in the seed crystal at that time.

[0021] [Configuration 1] A composite seed crystal comprising a seed crystal and a protective layer formed on a surface other than the growth surface of the seed crystal, wherein the protective layer is formed on all or part of the back surface of at least the seed crystal and consists of a molded body, degreased body, or calcined body containing at least one main powder selected from the group consisting of high-melting-point metals, high-melting-point metal carbides, high-melting-point metal nitrides, and high-melting-point metal carbonitrides, and has a thickness of 50 μm or more and 500 μm or less. However, the "high-melting-point metal" refers to a metal whose melting point at 1 atmosphere is 2000°C or higher.

[0022] [Configuration 2] The composite species crystal according to Configuration 1, wherein the high melting point metal comprises at least one selected from the group consisting of Nb, Hf, Ta, and W.

[0023] [Configuration 3] The composite species crystal according to Configuration 1 or 2, wherein the main powder comprises at least one selected from the group consisting of (a) Nb powder, Hf powder, Ta powder, W powder, (b) TaC powder, WC powder, (c) TaN powder, and (d) Ta(C,N) powder.

[0024] [Configuration 4] The protective layer is a composite species crystal according to any one of Configurations 1 to 3, wherein the relative density is 50% or more and 80% or less.

[0025] [Configuration 5] The protective layer is a composite species crystal according to any one of Configurations 1 to 4, further comprising a sintering aid.

[0026] [Configuration 6] The composite species crystal according to Configuration 5, wherein the sintering aid comprises at least one selected from the group consisting of (a) a transition metal having a melting point below the sintering temperature of the protective layer, (b) a carbide of the transition metal, and (c) an oxide of the transition metal.

[0027] [Configuration 7] A method for manufacturing a single crystal, comprising: a first step of placing a composite seed crystal described in any one of Configurations 1 to 6 in a container for growing a single crystal; and a second step of heating the seed crystal to the growth temperature of the single crystal, supplying a raw material gas to the growth surface of the seed crystal, and growing the single crystal on the growth surface.

[0028] [Configuration 8] The method for manufacturing a single crystal according to Configuration 7, wherein the first step is to place the composite seed crystal in the container such that all or part of the back surface of the composite seed crystal is not restrained by other members.

[0029] [Configuration 9] The first step is to (a) arrange a holding member A having a cylindrical portion and a hollow plate portion having a housing portion at the upper end of the cylindrical portion that can accommodate the composite seed crystal, with the hollow plate portion facing upward, and to house the composite seed crystal in the housing portion so that the growth surface of the seed crystal faces upward, or to adhere and fix a part of the back surface of the composite seed crystal to the upper surface of the housing portion; (b) arrange a holding member B having a cylindrical portion and a hollow plate portion having a housing portion at the lower end of the cylindrical portion that can accommodate the composite seed crystal, with the hollow plate portion facing downward, and to house the composite seed crystal in the housing portion so that the growth surface of the seed crystal faces downward, or to adhere and fix a part of the surface of the composite seed crystal to the upper surface of the housing portion; (c) arrange the composite seed crystal so that the growth surface of the seed crystal faces downward, and to hold the seed crystal by hooking the tips of the hooks onto the growth surface of the seed crystal using a holding member C having three or more hooks. (d) Arranging a holding member D having a cylindrical portion whose inner dimensions are larger than the outer dimensions of the composite seed crystal and a hollow plate portion having a through hole at the lower end of the cylindrical portion whose inner dimensions are smaller than the outer dimensions of the composite seed crystal, with the hollow plate portion facing downwards, and inserting the composite seed crystal into the cylindrical portion so that the growth surface of the seed crystal faces downwards, or a step of adhesively fixing a part of the surface of the composite seed crystal to the upper surface of the hollow plate portion; (e) Placing the composite seed crystal on the upper surface of a flat plate-shaped or hollow plate-shaped holding member E so that the growth surface of the seed crystal faces upwards, or adhesively fixing all or part of the back surface of the composite seed crystal to the upper surface of the holding member E, or (f) A method for manufacturing a single crystal according to configuration 7 or 8, comprising the steps of: arranging a holding member F having a cylindrical portion and a hollow plate portion having an internal hole smaller than the external dimensions of the composite seed crystal at the upper end of the cylindrical portion so that the hollow plate portion faces upward; placing the composite seed crystal on the upper surface of the hollow plate portion so that the growth surface of the seed crystal faces upward; or bonding and fixing a part of the back surface of the composite seed crystal to the upper surface of the hollow plate portion.

[0030] [Configuration 10] A method for producing a single crystal according to any one of Configurations 7 to 9, wherein the second step is to grow the single crystal using a sublimation method, a high-temperature CVD method, a CVD method, or a halide chemical vapor deposition (HCVD) method.

[0031] An embodiment of the present invention will be described in detail below. [1. Composite Seed Crystal] The composite seed crystal comprises a seed crystal and a protective layer formed on a surface other than the growth surface of the seed crystal.

[0032] [1.1. Seed Crystal] The material of the seed crystal is not particularly limited, and the most suitable material can be selected according to the purpose. Examples of seed crystal materials include SiC single crystals, AlN single crystals, sapphire, and substrates on which an epitaxial layer or buffer layer made of the same or different material as the growth crystal is formed on the substrate surface. The shape and dimensions of the seed crystal are also not particularly limited, and the most suitable shape can be selected according to the purpose. For example, the seed crystal may be a substrate-shaped seed crystal with a thickness thin relative to the size of the growth surface, or it may be a block-shaped seed crystal with a thickness equal to the size of the growth surface. When the seed crystal is substrate-shaped, the thickness of the seed crystal is usually about 300 μm to 1000 μm, and the maximum dimension of the growth surface of the seed crystal is usually about 25 mm to 200 mm.

[0033] [1.2. Protective Layer] [1.2.1. Position of Protective Layer Formation] The protective layer is intended to protect the surface of the seed crystal other than the growth surface (hereinafter also referred to as the "non-growth surface"). During the process of raising the temperature of the seed crystal to the single crystal growth temperature, if sublimation decomposition of the seed crystal occurs on the non-growth surface of the seed crystal, defects will occur on the non-growth surface. If sublimation decomposition continues, the defects will progress from the non-growth surface toward the growth surface, and the defects may become exposed on the growth surface. Defects exposed on the growth surface will be carried over to the grown crystal, causing a decrease in the quality of the grown crystal. In order to suppress the occurrence of defects caused by such sublimation decomposition of the seed crystal, it is necessary to protect the non-growth surface of the seed crystal with a protective layer.

[0034] The protective layer must be formed on at least the surface opposite to the growth surface (hereinafter also referred to as the "back surface"). The protective layer may be formed on a part of the back surface, or on the entire back surface. Even if the protective layer is formed on a part of the back surface, the sublimation decomposition of the seed crystal can be suppressed in the region where the protective layer is formed. In order to effectively suppress the sublimation decomposition of the seed crystal on the back surface, it is preferable that the protective layer be formed on the entire back surface.

[0035] Furthermore, sublimation decomposition of the seed crystal also occurs on the sides of the seed crystal. Therefore, if the seed crystal is thick, sublimation decomposition from the sides may not be negligible. In such cases, it is preferable to form a protective layer not only on the back surface of the seed crystal but also on the sides of the seed crystal.

[0036] [1.2.2. Materials for the protective layer] The protective layer contains at least one main powder selected from the group consisting of high-melting-point metals, high-melting-point metal carbides, high-melting-point metal nitrides, and high-melting-point metal carbonitrides. In the present invention, "high-melting-point metal" refers to a metal whose melting point at 1 atmosphere is 2000°C or higher. Examples of high-melting-point metals include Nb, Hf, Ta, and W. The protective layer may contain one of these high-melting-point metals, or it may contain two or more.

[0037] Examples of the main powders that make up the protective layer include: (a) Nb powder, Hf powder, Ta powder, W powder, (b) TaC powder, WC powder, (c) TaN powder, (d) Ta(C,N) powder, etc. The protective layer may contain one of these main powders, or it may contain two or more.

[0038] [1.2.3. Average particle size of main powder] "Average particle size" refers to the average value of the maximum dimensions of 50 or more randomly selected powders measured under microscopic observation. The protective layer must be capable of in-situ sintering and densification during the heating process. For this purpose, the smaller the average particle size of the main powder contained in the protective layer, the better. To promote in-situ sintering during the heating process, the average particle size of the main powder is preferably 5 μm or less. More preferably, the average particle size is 3 μm or less, or 2 μm or less.

[0039] [1.2.4. Thickness of the protective layer] If the thickness of the protective layer is too thin, it may become difficult to suppress the sublimation decomposition of the seed crystal. Therefore, the thickness of the protective layer must be 50 μm or more. Preferably, the thickness is 100 μm or more, or 200 μm or more. On the other hand, if the thickness of the protective layer is too thick, the thermal stress generated between the protective layer and the seed crystal will increase, and the protective layer may peel off from the seed crystal. Therefore, the thickness of the protective layer must be 500 μm or less. Preferably, the thickness is 400 μm or less, or 300 μm or less.

[0040] "Thickness ratio (%)" refers to the thickness (t) of the seed crystal. s ) thickness of the protective layer (t p The ratio of (= t p ×100 / t s This refers to the thickness ratio, which affects the stress generated in the seed crystal. To reduce the stress generated in the seed crystal, a thickness ratio of 100% or less is preferable. More preferably, the thickness ratio is 80% or less, 60% or less, or 40% or less.

[0041] [1.2.5. Relative density of the protective layer] The protective layer is composed of the above-described green compact, degreased body, or calcined body of the main powder. Here, the "protective layer composed of a green compact" refers to a layer in which the main powders are bonded via an organic binder. The "protective layer composed of a degreased body or a calcined body" refers to a layer obtained by heat-treating a protective layer containing an organic binder at a temperature not lower than the thermal decomposition temperature of the organic binder and lower than the sintering temperature of the main powder. When the green compact is heated, first, the organic binder thermally decomposes, and then, in order to reduce the surface area of the main powder, substances move and diffuse on the particle surface to form a bonding portion called necking with adjacent particles. When the temperature is further increased, densification proceeds to form a complete sintered layer. In other words, the "protective layer composed of a degreased body or a calcined body" refers to a layer at a stage before such complete sintering occurs, that is, a layer in a state where the main powders are physically in contact with each other, or a layer in a state where necking is formed between the main powders. The "relative density of the protective layer" refers to the ratio of the actual density of the protective layer to the theoretical density of the protective layer.

[0042] When a dense protective layer is formed on the non-growth surface of the seed crystal at room temperature, when the composite seed crystal is heated from room temperature to the growth temperature of the single crystal, a large thermal stress is generated between the seed crystal and the protective layer. Due to this thermal stress, cracks may occur in the seed crystal and the grown crystal. On the other hand, the protective layer composed of a green compact, degreased body, or calcined body has a low relative density. When a composite seed crystal containing such a low-density protective layer is heated from room temperature to the growth temperature of the single crystal, the thermal stress generated during the heating process is reduced. Further, at the heating process or the growth temperature of the single crystal, the low-density protective layer is sintered in place to form a dense protective layer. As a result, sublimation decomposition on the non-growth surface of the seed crystal and the progress of defects to the growth surface are suppressed. In particular, the green compact is easy to handle and has a small thermal stress generated during the heating process, so it is suitable as a protective layer.

[0043] The relative density of the protective layer can be selected as an optimal value according to the purpose. Generally, the lower the relative density of the protective layer, the more the thermal stress generated in the heating process can be reduced. However, if the relative density of the protective layer becomes too low, the densification of the protective layer may be insufficient during the heating process or at the growth temperature of the single crystal. Therefore, the relative density of the protective layer is preferably 50% or more. More preferably, the relative density is 55% or more.

[0044] On the other hand, if the relative density of the protective layer becomes too high, a large thermal stress may be generated between the seed crystal and the protective layer during the heating process or at the growth temperature of the single crystal. Therefore, the relative density of the protective layer is preferably 80% or less. More preferably, the relative density is 70% or less.

[0045] [1.2.6. Sintering Aid] [A. Material] The protective layer may contain a sintering aid or may not contain a sintering aid. Even when the protective layer does not contain a sintering aid, the densification of the protective layer proceeds to some extent during the heating process. However, when the main powder is made of a difficult-to-sinter material such as a high melting point metal carbide, a high melting point metal nitride, or a high melting point metal carbonitride, the densification of the protective layer may be insufficient. In such a case, it is preferable to add a sintering aid to the protective layer.

[0046] The optimal material for the sintering aid can be selected according to the type of the main powder. Examples of the sintering aid include (a) transition metals having a melting point below the sintering temperature of the protective layer, (b) carbides of the transition metals, and (c) oxides of the transition metals. The protective layer may contain any one of these sintering aids or may contain two or more of them.

[0047] Examples of the transition metals that can be used as the sintering aid include Ti, Cr, Fe, Co, Ni, etc. Examples of the transition metal carbides that can be used as the sintering aid include TiC, Cr 25 C6, Fe3C, Co2C, Ni2C, etc. Examples of the transition metal oxides that can be used as the sintering aid include TiO2, Cr2O3, CrO2, FeO, Fe3O4, Fe2O3, Co3O4, Co2O3, etc.

[0048] [B. Amount of Addition] The "amount of sintering aid added" refers to the ratio of the mass of the sintering aid to the total mass of the main powder and the sintering aid. The amount of sintering aid added is not particularly limited, and the optimal amount can be selected according to the purpose. In general, if the amount of sintering aid added is too small, the densification of the protective layer may be insufficient. Also, in order to suppress the sublimation decomposition of the seed crystal when the protective layer is low density, it is necessary to make the protective layer thicker. However, if the protective layer is thicker, the thermal stress generated in the seed crystal may increase. Therefore, the amount of sintering aid added is preferably 0.2 mass% or more. More preferably, the amount added is 1.0 mass% or more, or 3.0 mass% or more.

[0049] On the other hand, adding more sintering aid than necessary does not make a difference in effect and is not beneficial. Also, if the amount of sintering aid added is excessive, a large amount of sintering aid will remain in the protective layer. As a result, the sintering aid may be incorporated into the grown crystal as an impurity during single crystal growth. Therefore, the amount of sintering aid added is preferably 10.0 mass% or less. More preferably, the amount added is 8.0 mass% or less, or 6.0 mass% or less.

[0050] [2. Method for Manufacturing Composite Seed Crystals] The method for manufacturing composite seed crystals according to the present invention is not particularly limited, and the most suitable method can be selected depending on the purpose. Examples of methods for manufacturing composite seed crystals include: (a) preparing a slurry containing a main powder, an organic binder, and optionally a sintering aid, applying the slurry to the non-growth surface of a seed crystal, and drying the coating; (b) molding raw material powder containing a main powder, an organic binder, and optionally a sintering aid, and attaching the molded body to the non-growth surface of a seed crystal via an organic binder; and (c) forming a protective layer containing an organic binder on the non-growth surface of a seed crystal, and heating the protective layer to a temperature above the thermal decomposition temperature of the organic binder and below the sintering temperature of the main powder.

[0051] In particular, the method of applying slurry to the non-growth surface is suitable as a method for forming a protective layer because it facilitates the formation of a protective layer. In this case, the method of applying the slurry is not particularly limited, and the most suitable method can be selected according to the purpose. Methods of applying slurry include: (a) a spray method in which slurry is sprayed onto the non-growth surface of the seed crystal; (b) a spin coating method in which the seed crystal is rotated and slurry is dropped onto the back surface of the rotating seed crystal; and (c) a dip coating method in which the seed crystal is immersed in slurry while the growth surface of the seed crystal is protected with a protective film.

[0052] When heating a protective layer containing an organic binder, the heating temperature is not particularly limited, as long as it allows for the handling of the composite seed crystals and the desired relative density is achieved. Depending on the type of main powder and organic binder, and the presence or absence of sintering aids, the degreasing temperature is usually 150°C to 600°C. The calcination temperature is usually 600°C to 1000°C.

[0053] [3. Method for Manufacturing Single Crystals] The method for manufacturing single crystals according to the present invention comprises: a first step of placing a composite seed crystal according to the present invention in a container for growing single crystals; and a second step of heating the seed crystal to the growth temperature of the single crystal, supplying a raw material gas to the growth surface of the seed crystal, and growing the single crystal on the growth surface.

[0054] [3.1. First Step] First, the composite seed crystal according to the present invention is held in a container for growing a single crystal. The method for holding the seed crystal substrate is not particularly limited, and the most suitable method can be selected depending on the purpose.

[0055] Because the protective layer of the composite seed crystal according to the present invention is low density, cracks in the seed crystal and grown crystal due to thermal stress can be suppressed to some extent even when the composite seed crystal is held in a state in which the back surface of the composite seed crystal is constrained by other members. However, in order to further reduce thermal stress, it is preferable that the first step includes a step of holding the composite seed crystal in a container so that all or part of the back surface of the composite seed crystal is not constrained by other members. Specifically, it is preferable that the first step includes the following steps.

[0056] [3.1.1. First Holding Method] Figure 1(A) shows a schematic diagram of the first holding method for composite seed crystals. The lower part of Figure 1(A) is a plan view, and the upper part of Figure 1(A) is a cross-sectional view taken along line A-A' in the lower part. Note that in Figure 1, the dimensions of each part have been enlarged or reduced from their actual dimensions for clarity. The same applies to Figures 2 and 3, which will be described later.

[0057] In Figure 1(A), the holding member A20 comprises a cylindrical portion 20a, a hollow plate portion 20b provided at the upper end of the cylindrical portion 20a, and a flange portion 20c provided at the lower end of the cylindrical portion 20a. A through hole 20d having an inner dimension smaller than the outer dimension of the composite seed crystal 10 is provided at the lower part of the hollow plate portion 20b. Furthermore, a housing portion 20e capable of housing the composite seed crystal 10 is provided at the upper part of the hollow plate portion 20b.

[0058] When using such a retaining member A20, the first step preferably includes: (a) arranging the retaining member A20 so that the hollow plate portion 20b faces upward, and housing the composite seed crystal 10 in the housing portion 20e so that the growth surface of the seed crystal 12 faces upward; or (b) bonding and fixing a part of the back surface of the composite seed crystal 10 to the upper surface of the housing portion 20e. In this case, the raw material gas is supplied from above the composite seed crystal 10. The method of bonding the composite seed crystal 10 and the retaining member A20 is not particularly limited, and the most suitable method can be selected according to the purpose.

[0059] [3.1.2. Second Holding Method] Figure 1(B) shows a schematic diagram of the second holding method for the composite seed crystal. The lower part of Figure 1(B) is a plan view, and the upper part of Figure 1(B) is a cross-sectional view taken along line A-A' in the lower part. In Figure 1(B), the holding member B22 comprises a cylindrical portion 22a, a hollow plate portion 22b provided at the lower end of the cylindrical portion 22a, and a flange portion 22c provided at the upper end of the cylindrical portion 22b. A through hole 22d is provided at the lower part of the hollow plate portion 22b, having an inner dimension smaller than the outer dimension of the composite seed crystal 10. Furthermore, a housing portion 22e capable of housing the composite seed crystal 10 is provided at the upper part of the hollow plate portion 22d.

[0060] When using such a retaining member B22, the first step preferably includes: (a) arranging the retaining member B22 so that the hollow plate portion 22b faces downward, and housing the composite seed crystal 10 in the housing portion 22e so that the growth surface of the seed crystal 12 faces downward and the protective layer 14 faces upward; or (b) bonding and fixing a part of the surface of the composite seed crystal 10 to the upper surface of the housing portion 22e. In this case, the raw material gas is supplied from below the composite seed crystal 10. The method of bonding the composite seed crystal 10 and the retaining member B22 is not particularly limited, and the most suitable method can be selected according to the purpose.

[0061] [3.1.3. Third Holding Method] Figure 2(A) shows a schematic diagram of the third holding method for composite seed crystals. The lower part of Figure 2(A) is a plan view, and the upper part of Figure 2(A) is a front view. In Figure 2(A), the holding member C24 is equipped with three hooks 24a, 24b, and 24c whose tips are bent in an L shape.

[0062] When using such a holding member C24, the first step preferably includes the step of arranging the composite seed crystal 10 such that the growth surface of the seed crystal 12 faces downward and the protective layer 14 faces upward, and then using the holding member C24 to hook the tips of the hooks 24a, 24b, and 24c onto the growth surface of the seed crystal 12 and hold it in place. In this case, the raw material gas is supplied from below the composite seed crystal 10. The base ends of the hooks 24a, 24b, and 24c are fixed to any part inside the container for growing the single crystal. The method of fixing the base ends of the hooks 24a, 24b, and 24c is not particularly limited, and the most suitable method can be selected according to the purpose.

[0063] In Figure 2(A), the total number of hooks is three, but this is merely an example. The number of hooks is not particularly limited, as long as they can stably support the composite seed crystal 10. To stably support the composite seed crystal 10, it is preferable to have three or more hooks.

[0064] [3.1.4. Fourth Holding Method] Figure 2(B) shows a schematic diagram of the fourth holding method for the composite seed crystal. The lower part of Figure 2(B) is a plan view, and the upper part of Figure 2(B) is a cross-sectional view taken along line A-A' in the lower part. In Figure 2(B), the holding member D26 comprises a cylindrical portion 26a, a hollow plate portion 26b provided at the lower end of the cylindrical portion 26a, and a flange portion 26c provided at the upper end of the cylindrical portion 26a. The inner dimensions of the cylindrical portion 26a are larger than the outer dimensions of the composite seed crystal 10. The hollow plate portion 26b is provided with a through hole 26d having an inner dimension smaller than the outer dimensions of the composite seed crystal 10.

[0065] When using such a retaining member D26, the first step preferably includes: (a) a step of arranging the retaining member D26 so that the hollow plate portion 26b of the retaining member D26 faces downward, and inserting the composite seed crystal 10 into the cylindrical portion 26a so that the growth surface of the seed crystal 12 faces downward and the protective layer 14 faces upward; or (b) a step of bonding and fixing a part of the surface of the composite seed crystal 10 to the upper surface of the hollow plate portion 26b. In this case, the raw material gas is supplied from below the composite seed crystal 10.

[0066] [3.1.5. Fifth Holding Method] Figure 3(A) shows a schematic diagram of the fifth holding method for the composite seed crystal. The lower part of Figure 3(A) is a plan view, and the upper part of Figure 3(A) is a cross-sectional view taken along line A-A' in the lower part. In Figure 3(A), the holding member E28 is made of a flat plate. The holding member E28 may also be a hollow plate-shaped member having a through hole with an inner dimension smaller than the outer dimension of the composite seed crystal 10.

[0067] When such a retaining member E28 is used, the first step preferably includes: (a) a step of placing the composite seed crystal 10 on the upper surface of the flat retaining member E28 such that the growth surface of the seed crystal 12 faces upward and the protective layer 14 faces downward; or (b) a step of adhesively fixing all or part of the back surface of the composite seed crystal 10 to the upper surface of the retaining member E28. In this case, the raw material gas is supplied from above the composite seed crystal 10.

[0068] Since the back surface of the composite seed crystal 10 has a low-density protective layer 14, thermal stress can be suppressed to some extent even when the entire back surface of the composite seed crystal 10 is bonded and fixed to the upper surface of the holding member E28. However, when bonding the composite seed crystal 10 to the holding member E28, it is preferable to bond and fix a portion of the back surface of the composite seed crystal 10 to the holding member 28E in order to reduce thermal stress.

[0069] [3.1.6. Sixth Holding Method] Figure 3(B) shows a schematic diagram of the sixth holding method for the composite seed crystal. The lower part of Figure 3(B) is a plan view, and the upper part of Figure 3(B) is a cross-sectional view taken along line A-A' in the lower part. In Figure 3(B), the holding member F30 comprises a cylindrical portion 30a, a hollow plate portion 30b provided at the upper end of the cylindrical portion 30a, and a flange portion 30c provided at the lower end of the cylindrical portion 30a. The hollow plate portion 30b is provided with a through hole 30d having an inner dimension smaller than the outer dimension of the composite seed crystal 10.

[0070] When such a holding member E30 is used, the first step preferably includes: (a) a step of arranging the holding member E30 so that the hollow plate portion 30b of the holding member E30 faces upward, and placing the composite seed crystal 10 on the upper surface of the hollow plate portion 30b so that the growth surface of the seed crystal 12 faces upward and the protective layer 14 faces downward; or (b) a step of adhesively fixing a part of the back surface of the composite seed crystal 10 to the upper surface of the hollow plate portion 30b. In this case, the raw material gas is supplied from above the composite seed crystal 10.

[0071] [3.2. Second Step] Next, the seed crystal is heated to the single crystal growth temperature, and the raw material gas is supplied to the growth surface of the seed crystal to grow the single crystal on the growth surface. If the protective layer contains an organic binder, the organic binder decomposes thermally during the heating process. Also, during the heating process or during single crystal growth, the protective layer sintersects in place and becomes denser. As a result, sublimation decomposition of the non-growth surface of the seed crystal is suppressed.

[0072] In the present invention, the method for growing single crystals is not particularly limited, and the most suitable method can be selected depending on the purpose. Examples of single crystal growth methods include sublimation, high-temperature CVD, CVD, and halide chemical vapor deposition (HCV). Any of these methods may be used in the present invention.

[0073] Here, "sublimation method" refers to a method in which sublimation gas is generated by heating a sublimation raw material, and the sublimation gas is supplied onto the growth surface of a seed crystal to grow a single crystal on the growth surface. "High-temperature CVD method" refers to a method in which high-purity gas raw material is heated to a temperature range of approximately 1800°C to 2500°C under reduced pressure, and the heated gas raw material is supplied onto the growth surface of a seed crystal to grow a single crystal on the growth surface. "CVD method" refers to a method in which high-purity gas raw material is heated to a temperature range of approximately 800°C to 1900°C under reduced pressure, and the heated gas raw material is supplied onto the growth surface of a seed crystal to grow a single crystal on the growth surface. "Halogenated chemical vapor deposition (HCVD) method" refers to a method in which a raw material gas consisting of halides together with a carrier gas such as H2 or N2 is supplied onto the growth surface of a seed crystal to grow a single crystal on the growth surface.

[0074] [4. Flowchart] Figure 4 shows a flowchart of the manufacturing method for composite seed crystals and single crystals. First, in step 1 (hereinafter also simply referred to as "S1"), a protective layer is formed on the non-growth surface of the seed crystal. As described above, the method of forming the protective layer is not particularly limited, and the most suitable method can be selected according to the purpose. Next, in S2, the composite seed crystal is held in a holding member and placed in a container for growing the single crystal. As described above, it is preferable to place the composite seed crystal in the container so that the back surface of the composite seed crystal is not restrained by other members.

[0075] Next, in S3, the heating of the composite seed crystal is started. If the composite seed crystal contains an organic binder, the organic binder is removed during the heating process. In S4, as the temperature inside the container rises further, the protective layer sintersects in place, forming a dense protective layer. Furthermore, in S5, when the temperature inside the container reaches the single crystal growth temperature, a new crystal grows on the growth surface of the seed crystal.

[0076] [5. Mechanism of Operation] Conventionally, single crystals were manufactured by bonding and fixing a seed crystal to the surface of a base, supplying a raw material gas to the surface of the seed crystal, and growing a new crystal on the surface of the seed crystal. However, if the seed crystal and the base are firmly fixed, thermal stress may be generated in the seed crystal and the grown crystal due to the difference in thermal expansion coefficients between the seed crystal and the base during single crystal growth, which may cause cracks in the seed crystal and the grown crystal. In addition, if the seed crystal is exposed to high temperatures, the back surface of the seed crystal may sublimate and decompose, and defects may be generated on the growth surface of the seed crystal.

[0077] In contrast, a composite seed crystal is fabricated with a low-density protective layer formed on the back surface of the seed crystal. When this composite seed crystal is held in a container for single crystal growth and heated to the growth temperature, the protective layer sintersects in place. As a result, the back surface of the seed crystal is protected by the dense protective layer, and the sublimation decomposition of the seed crystal is suppressed. Furthermore, using this method reduces the thermal stress generated in the seed crystal during single crystal growth compared to when a dense protective layer is formed on the back surface of the seed crystal at room temperature. Therefore, the deterioration of the quality of the grown crystal due to thermal stress can also be suppressed. Moreover, if a method is used to hold the seed crystal in which the back surface of the composite seed crystal is not constrained by other components, the thermal stress generated in the seed crystal and the grown crystal is further reduced.

[0078] Figure 5 shows the relationship between the temperature of the protective layer at each stage of the process and the thermal stress generated in the seed crystal at that time. Note that whether the stress generated at each stage is tensile or compressive depends on the relative thermal expansion coefficients of the protective layer and the seed crystal, so only the absolute values ​​are qualitatively shown in Figure 5. As shown in Figure 5, the seed crystal is substantially stressed only after the sintering of the protective layer has begun. Before the sintering of the protective layer begins, the protective layer can stretch to match the seed crystal, so virtually no stress is generated.

[0079] The thermal stress generated in the seed crystal during crystal growth is determined by the temperature difference between the start of sintering of the protective layer and the growth temperature, and the difference in thermal expansion coefficients between the seed crystal and the protective layer. For example, if crystal growth is performed at 2000°C, if the protective layer can be sintered in situ at 1500°C, the thermal stress can be significantly reduced compared to when a dense protective layer is formed on the seed crystal at room temperature using methods such as vapor deposition or welding.

[0080] Furthermore, if the protective layer contains a sintering aid, the protective layer can be easily densified during the heating process, suppressing the sublimation decomposition of the seed crystal. As a result, the protective layer can be made thinner, further reducing the thermal stress applied to the seed crystal.

[0081] (Examples 1.1-1.4, Comparative Examples 1.1-1.2: Growth of AlN single crystals, TaC only) [1. Sample preparation] AlN single crystals were grown by sublimation. A 500 μm thick AlN single crystal was used as the seed crystal. The slurry used to form the protective layer had the following composition (main powder: TaC, sintering aid: none): TaC: 75.0 mass% PVB (organic binder): 0.6 mass% Dibutyl phthalate: 0.6 mass% Ethanol: 10.0 mass% Toluene: 10.0 mass% Terpineol: 3.8 mass%

[0082] A protective layer was formed by spraying a slurry onto the back surface of a seed crystal. To prevent contamination of the seed crystal's growth surface, the growth surface was covered with a silicone sheet. By adjusting the amount of slurry applied, protective layers of different thicknesses were formed. The thicknesses of the protective layers were 30 μm (Comparative Example 1.1), 50 μm (Example 1.1), 100 μm (Example 1.2), 300 μm (Example 1.3), 500 μm (Example 1.4), or 700 μm (Comparative Example 1.2). The seed crystals with the protective layer formed were heated to 200°C on a hot plate to evaporate the solvent contained in the protective layer.

[0083] A composite seed crystal was placed in a seed crystal holder (holding member) located inside the growth crucible. The seed crystal holder was hook-shaped, and the composite seed crystal was not fixed by adhesive. See Figure 2(A). AlN powder, the sublimation raw material, was packed into the growth crucible at a position opposite the growth surface of the seed crystal. The growth crucible was placed in the growth furnace, and a temperature gradient was created so that the seed crystal was at a lower temperature than the sublimation raw material. The AlN powder was sublimated, and an AlN single crystal was grown on the growth surface of the seed crystal. At this time, the raw material temperature was 2300°C, and the seed crystal temperature was 2200°C. The growth atmosphere was an N2 gas atmosphere, and the furnace pressure was 80 kPa. This state was maintained for 40 hours. After that, it was cooled to room temperature, and the seed crystal and grown crystal were removed.

[0084] [2. Test Method and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. (1) When the thickness of the protective layer was 30 μm (Comparative Example 1.1), sublimation decomposition due to inadequate protection occurred in the seed crystal. Hollow through holes were also observed in the grown crystal. (2) When the thickness of the protective layer was 700 μm (Comparative Example 1.2), cracks thought to be caused by thermal stress during growth occurred in the seed crystal. Furthermore, the portion that grew on the cracks was polycrystalline. (3) In Examples 1.1 to 1.4, no defects such as voids were observed in the grown crystals. Furthermore, no cracks due to thermal stress occurred in the seed crystals or grown crystals. However, traces of sublimation due to inadequate protection were observed in some seed crystals with protective layer thicknesses of 50 μm and 100 μm.

[0085] (Examples 2.1-2.2: Growth of AlN single crystals, TaC + Co) [1. Sample preparation] AlN single crystals were grown by sublimation. A 500 μm thick AlN single crystal was used as the seed crystal. The slurry used to form the protective layer had the following composition (main powder: TaC, sintering aid: Co): TaC: 72.0 mass% Co: 3.0 mass% PVB (organic binder): 0.6 mass% Dibutyl phthalate: 0.6 mass% Ethanol: 10.0 mass% Toluene: 10.0 mass% Terpineol: 3.8 mass%

[0086] A protective layer was formed by spraying a slurry onto the back surface of the seed crystal. At this time, the growth surface of the seed crystal was covered with a silicone sheet to prevent contamination. By adjusting the amount of slurry applied, protective layers of different thicknesses were formed. The thickness of the protective layer was 50 μm (Example 2.1) or 100 μm (Example 2.2). AlN single crystals were then grown in the same manner as in Example 1.1.

[0087] [2. Test Methods and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. In both Examples 2.1 and 2.2, no defects such as voids were found in the grown crystals. However, traces of sublimation due to inadequate protection were observed in some seed crystals with a protective layer thickness of 50 μm.

[0088] (Examples 3.1-3.2, Comparative Example 2: Long-term growth of AlN single crystal, TaC + Co) [1. Sample preparation] AlN single crystals were grown by sublimation. A 500 μm thick AlN single crystal was used as the seed crystal. The slurry used to form the protective layer was the same as in Example 2.1 (main powder: TaC, sintering aid: Co).

[0089] A protective layer was formed by spraying a slurry onto the back surface of the seed crystal. To prevent contamination of the seed crystal's growth surface, the growth surface was covered with a silicone sheet. By adjusting the amount of slurry applied, protective layers of different thicknesses were formed. The thickness of the protective layer was 30 μm (Comparative Example 2), 100 μm (Example 3.1), or 300 μm (Example 3.2). AlN single crystals were grown in the same manner as in Example 2.1, except that the growth time was set to 100 hours.

[0090] [2. Test Method and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. (1) In Comparative Example 2, sublimation, which appeared to be due to poor protection, occurred in the seed crystal. In addition, hollow through holes were observed in the grown crystal. In Comparative Example 2, no cracks due to thermal stress occurred in the seed crystal or grown crystal. (2) In Examples 3.1 to 3.2, no defects such as voids were observed in the grown crystals. In addition, no cracks due to thermal stress occurred in the seed crystal or grown crystal.

[0091] (Example 4: Growth of SiC single crystal, TaC + Co) [1. Sample preparation] A SiC single crystal was grown by sublimation. A SiC single crystal with a thickness of 500 μm was used as the seed crystal. The slurry used to form the protective layer was the same as that used in Example 2.1 (main powder: TaC, sintering aid: Co). A protective layer was formed on the back surface of the seed crystal in the same manner as in Example 1.1. The thickness of the protective layer was 300 μm.

[0092] A composite seed crystal was held inside a growth crucible with hooks. SiC powder, the sublimation raw material, was packed into the growth crucible at a position opposite the growth surface of the seed crystal. The growth crucible was placed in a growth furnace, and a temperature gradient was created so that the seed crystal was at a lower temperature than the sublimation raw material. The SiC powder was sublimated, and a SiC single crystal was grown on the growth surface of the seed crystal. At this time, the raw material temperature was 2200°C, and the seed crystal temperature was 2100°C. The growth atmosphere was an N2 gas atmosphere, and the furnace pressure was 500 kPa. This state was maintained for 40 hours. After that, it was cooled to room temperature, and the seed crystal and grown crystal were removed.

[0093] [2. Test Method and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. In Example 4, no sublimation decomposition due to inadequate protection was observed in the seed crystal. Furthermore, no defects such as voids were observed in the grown crystal. In addition, no cracks were found in either the seed crystal or the grown crystal.

[0094] (Example 5: Heteroepitaxial growth of AlN single crystal, TaC + Co) [1. Sample preparation] An AlN single crystal was grown by sublimation. A 500 μm thick SiC single crystal was used as the seed crystal. The same slurry as in Example 2.1 (main powder: TaC, sintering aid: Co) was used to form the protective layer. A protective layer was formed on the back surface of the seed crystal in the same manner as in Example 1.1. The thickness of the protective layer was 300 μm.

[0095] A composite seed crystal was held inside a growth crucible with a hook. The growth crucible was filled with AlN powder, the sublimation raw material, in a position opposite the growth surface of the seed crystal. The growth crucible was placed in a growth furnace, and a temperature gradient was created so that the seed crystal was at a lower temperature than the sublimation raw material. The AlN powder was sublimated, and an AlN single crystal was grown on the growth surface of the seed crystal. At this time, the raw material temperature was 2100°C, and the seed crystal temperature was 1900°C. The growth atmosphere was an N2 gas atmosphere, and the furnace pressure was 80 kPa. This state was maintained for 100 hours. After that, it was cooled to room temperature, and the seed crystal and grown crystal were removed.

[0096] [2. Test Method and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. In Example 5, no sublimation decomposition due to inadequate protection was observed in the seed crystal. Furthermore, no defects such as voids were observed in the grown crystal. In addition, no cracks were found in either the seed crystal or the grown crystal.

[0097] (Example 6: Growth of AlN single crystal, WC only) [1. Sample preparation] An AlN single crystal was grown by sublimation. A 500 μm thick AlN single crystal was used as the seed crystal. The slurry used to form the protective layer had the following composition (main powder: WC, sintering aid: none): WC: 75.0 mass% PVB (organic binder): 0.6 mass% Dibutyl phthalate: 0.6 mass% Ethanol: 10.0 mass% Toluene: 10.0 mass% Terpineol: 3.8 mass%

[0098] The protective layer was formed and the AlN single crystal was grown in the same manner as in Example 1.1. The thickness of the protective layer was 300 μm.

[0099] [2. Test Method and Results] Seed crystals and grown crystals were observed visually and under a stereomicroscope. The results are shown in Table 1. In Example 6, no sublimation decomposition due to inadequate protection was observed in the seed crystal. Furthermore, no defects such as voids were observed in the grown crystal. In addition, no cracks were found in either the seed crystal or the grown crystal.

[0100]

[0101] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0102] The composite seed crystal according to the present invention can be used in the production of single crystals made of compound semiconductors such as SiC and AlN.

[0103] 10 Composite seed crystal 12 Seed crystal 14 Protective layer

Claims

Seed crystal and, A protective layer formed on a surface other than the growth surface of the seed crystal, Equipped with, The aforementioned protective layer is It is formed on at least all or part of the back surface of the seed crystal, It consists of a molded body, degreased body, or calcined body containing at least one main powder selected from the group consisting of high-melting-point metals, high-melting-point metal carbides, high-melting-point metal nitrides, and high-melting-point metal carbonitrides. The thickness is between 50 μm and 500 μm. Composite seed crystal. However, the term "high melting point metal" refers to a metal whose melting point at 1 atmosphere is 2000°C or higher. 　 The composite species crystal according to claim 1, wherein the high melting point metal comprises at least one selected from the group consisting of Nb, Hf, Ta, and W. 　 The main powder is, (a) Nb powder, Hf powder, Ta powder, W powder, (b) TaC powder, WC powder, (c) TaN powder, and (d) Ta(C,N) powder A composite species crystal according to claim 1, comprising at least one selected from the group consisting of the following. 　 The protective layer is a composite species crystal according to claim 1, wherein the relative density is 50% or more and 80% or less. 　 The composite species crystal according to claim 1, wherein the protective layer further comprises a sintering aid. 　 The sintering aid is (a) A transition metal having a melting point below the sintering temperature of the protective layer, (b) Carbides of the transition metals, (c) The oxide of the transition metal A composite species crystal according to claim 5, comprising at least one selected from the group consisting of the following. 　 A first step involves placing the composite seed crystal described in claim 1 in a container for growing a single crystal, A second step involves heating the seed crystal to the single crystal growth temperature, supplying a raw material gas to the growth surface of the seed crystal, and growing the single crystal on the growth surface. A method for manufacturing single crystals equipped with [the necessary components]. 　 The first step includes placing the composite seed crystal in the container such that all or part of the back surface of the composite seed crystal is not restrained by other members. The method for producing a single crystal according to claim 7. 　 The first step is, (a) A holding member A having a cylindrical portion and a hollow plate portion having a housing portion capable of housing the composite seed crystal provided at the upper end of the cylindrical portion, is positioned with the hollow plate portion facing upward, and the composite seed crystal is housed in the housing portion with the growth surface of the seed crystal facing upward, or a part of the back surface of the composite seed crystal is bonded and fixed to the upper surface of the housing portion. (b) A holding member B comprising a cylindrical portion and a hollow plate portion having a housing portion at the lower end of the cylindrical portion that can accommodate the composite seed crystal, is positioned with the hollow plate portion facing downward, and the composite seed crystal is housed in the housing portion with the growth surface of the seed crystal facing downward, or a part of the surface of the composite seed crystal is bonded and fixed to the upper surface of the housing portion. (c) A step of arranging the composite seed crystal so that the growth surface of the seed crystal faces downward, and holding the seed crystal by hooking the tips of the hooks onto the growth surface of the seed crystal using a holding member C equipped with three or more hooks. (d) A holding member D having a cylindrical portion whose inner dimensions are larger than the outer dimensions of the composite seed crystal and a hollow plate portion having a through hole at the lower end of the cylindrical portion whose inner dimensions are smaller than the outer dimensions of the composite seed crystal is positioned with the hollow plate portion facing downward, and the composite seed crystal is inserted into the cylindrical portion with the growth surface of the seed crystal facing downward, or a part of the surface of the composite seed crystal is bonded and fixed to the upper surface of the hollow plate portion. (e) A step of placing the composite seed crystal on the upper surface of a flat or hollow plate-shaped holding member E such that the growth surface of the seed crystal faces upward, or a step of adhesively fixing all or part of the back surface of the composite seed crystal to the upper surface of the holding member E, (f) A holding member F comprising a cylindrical portion and a hollow plate portion having a through hole at the upper end of the cylindrical portion whose inner dimensions are smaller than the outer dimensions of the composite seed crystal, is positioned with the hollow plate portion facing upward, and the composite seed crystal is placed on the upper surface of the hollow plate portion with the growth surface of the seed crystal facing upward, or a part of the back surface of the composite seed crystal is bonded and fixed to the upper surface of the hollow plate portion. A method for producing a single crystal according to claim 7, including the method described above. 　 The second step includes growing the single crystal using sublimation, high-temperature CVD, CVD, or halide chemical vapor deposition (HCVD). The method for producing a single crystal according to claim 7.

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