Heat-resistant materials

Abstract

To provide a heat-resistant member with a higher total emissivity and a smaller temperature dependence of the total emissivity compared to a conventional heat resistant member.SOLUTION: A heat-resistant member of the present invention includes a base material made of isotropic graphite and an ultra-porous.high emissivity layer formed on all or part of the surface of the base material. However, the term "ultra-porous.high emissivity layer" refers to a layer with a porosity of 60% or more and a total emissivity of 60% or more at 25°C. The ultra-porous.high emissivity layer has a total emissivity change rate ΔεT (=(εT2500-εT25) / εT25) of 0.6 or less. Note that εT2500 is the total emissivity of the ultra-porous.high emissivity layer at 2500°C and εT25 is the total emissivity of the ultra-porous.high emissivity layer at 25°C. The heat-resistant member may further be provided with a dense or porous layer formed in all or in part at the interface between the base material and the ultra-porous.high emissivity layer. However, the term "porous layer" refers to a layer with a porosity of 10% or more to less than 60%, and the term "dense layer" refers to a layer with a porosity of less than 10%.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present invention relates to a heat-resistant member, and more particularly to a heat-resistant member having a high total emissivity and a small temperature dependency of the total emissivity. [Background technology]

[0002] Semiconductor processes such as bulk single crystal growth and epitaxial film formation of SiC and group III nitride semiconductors are subject to severe processing conditions. Components used in these processes, such as crucibles and susceptors (hereinafter collectively referred to as "heat-resistant components"), are exposed to high temperatures and highly corrosive atmospheres during the processes. Conventionally, SiC-coated graphite materials and pBN-coated graphite materials have been used for such heat-resistant components. However, these materials have a problem of short life span in the current semiconductor processing environment.

[0003] Therefore, various proposals have been made in the past to solve this problem. For example, Patent Document 1 discloses a high-temperature heat-resistant member including a graphite substrate made of isotropic graphite and a TaC coating made of a non-oriented granular structure that coats the surface of the graphite substrate. The same document states: (A) The TaC coating has a non-oriented granular structure, which makes it difficult for cracks to propagate. (B) As a result, the graphite substrate is protected even when the high-temperature resistant component is used for a long time in a high-temperature atmosphere; and (C) Such high-temperature resistant components can be used as susceptor components for MOCVD epitaxial growth of III-nitrides. is stated.

[0004] Patent Document 2 discloses a high-temperature heat-resistant member including a graphite substrate having chamfered corners and a TaC coating that covers the surface of the graphite substrate. The same document states: (A) If there are corners on the surface of the graphite substrate, the TaC coating is likely to crack, peel, or peel off locally during deposition or use; and (B) Chamfering the corners of the graphite substrate can prevent cracking, lifting, peeling, etc. of the TaC coating during deposition or use. is stated.

[0005] Patent Document 3 states: (a) A slurry containing TaC particles is applied to the surface of a graphite substrate to form a coating film; (b) drying the coating film to form a formed film; (c) polishing the surface of the formed film to reduce the surface roughness or surface waviness of the formed film; (d) The formed film is heated to sinter the TaC particles, thereby obtaining a sintered film. A method for manufacturing a heat-resistant graphite member is disclosed. The same document states: (A) When the sintered film is subjected to processing such as polishing or grinding, there is a risk of microcracks occurring in the sintered film, and (B) Polishing is easier when polishing a molded film instead of a sintered film. is stated.

[0006] In Patent Document 4, a TaC film is formed on the surface of a graphite substrate, and the coefficient of thermal expansion (CTE) of the graphite substrate is 5.8 to 6.4 × 10 -6 / K and a bulk density of 1.83 to 2.0 g / cm 3 A heat-resistant graphite member is disclosed. The document describes that when a TaC coating is formed on the surface of a graphite substrate, the durability and heat resistance are improved by optimizing the CTE and bulk density of the graphite substrate.

[0007] Patent Document 5 discloses a high heat-resistant member in which the surface of a substrate made of isotropic graphite is coated with a TaC film, and the TaC film has an iron content of 20 to 1000 mass ppm. The document describes that optimizing the amount of iron in TaC suppresses the occurrence of cracks in the TaC film and improves the heat resistance of the TaC coating.

[0008] Patent Document 6 discloses a crystal growth member including a substrate made of a carbon-based material, a protective layer made of TaC or SiC formed on the surface of the substrate, and a parasitic reaction prevention layer made of W, Mo, Ru, and / or Ir formed on the surface of the protective layer. The document describes that by forming a protective layer and a parasitic reaction prevention layer on the surface of a substrate, a crystal growth member having both a protective function and a parasitic reaction suppression function can be obtained.

[0009] Patent Document 7 discloses an auxiliary heating member in which a coating layer having a lower emissivity than graphite is formed on the surface of graphite. The same document states: (A) Simply heating the peripheral wall of the crucible by induction heating from the outer periphery of the crucible lowers the temperature of the region near the central axis of the crucible, preventing sufficient sublimation of the raw material powder located near the central axis of the crucible, resulting in a slower growth rate of the single crystal; and (B) When an auxiliary heating element is placed opposite the bottom wall of the crucible, the bottom wall of the crucible is heated by radiant heat from the auxiliary heating element, and the temperature of the region near the central axis of the crucible rises, so that the sublimation of the raw material powder located in the region near the central axis of the crucible proceeds sufficiently. is stated.

[0010] Patent Document 8 discloses a heat-resistant member in which a dense WC layer having a porosity of less than 3% is formed on the surface of a substrate made of isotropic graphite, and a porous WC layer having a porosity of 20 to 50% is formed on the surface of the dense WC layer. The same document states: (A) When a dense WC layer is formed on the surface of the substrate, the underlying graphite can be protected from corrosive gases for a longer period of time, and (B) When a porous WC layer is formed on the outermost surface of the coating, the emissivity becomes higher than that of a coating consisting only of a dense WC layer. is stated.

[0011] Patent Document 9 discloses a heat-resistant member in which a carbide coating is formed on the surface of a substrate made of isotropic graphite, the coverage of the impurity film adhering to the surface of the carbide coating is less than 3%, and the arithmetic mean roughness Ra of the carbide coating is 1.5 μm or less. The document describes that when a heat-resistant component having a carbide coating formed on the surface of a substrate and an impurity film attached to the surface of the carbide coating is subjected to a blasting treatment (soft blasting treatment) in which soft media is collided with the surface of the carbide coating, the impurity film on the carbide coating can be easily and inexpensively removed without damaging the carbide coating.

[0012] Patent Document 10 discloses a sintered body, which is not a heat-resistant component, obtained by adding 0.02 mass % of SiO2 to TaC, molding the raw material mixture, and sintering it under atmospheric pressure. The document states that this method allows for the production of a TaC sintered body with a relative density of 95.1%.

[0013] Non-Patent Document 1 discloses a TaC-coated graphite crucible produced by a wet ceramics method. The same document states: (A) When growing SiC single crystals by sublimation, the growth rate can be increased for a long period of time by using a TaC-coated graphite crucible instead of a graphite crucible; and (B) This increases the crystal size by approximately 1.2 times. is stated.

[0014] Furthermore, Non-Patent Document 2 discloses a TaC-coated graphite member produced by powder molding and sintering. The same document states: (A) The difference in thermal expansion coefficient Δα from TaC is approximately 2×10 -6 When a TaC layer is formed on the surface of graphite, cracks are formed in the TaC layer. (B) The difference in thermal expansion coefficient Δα from TaC is approximately 0.02×10 -6When a TaC layer is formed on the surface of graphite, the warpage of the component is minimized. is stated.

[0015] As mentioned above, the process conditions for bulk single crystal growth (mainly sublimation growth) of III-nitride semiconductors, including SiC and GaN, are high temperatures and corrosive atmospheres. Therefore, when graphite is used for heat-resistant components (e.g., crucibles) used for growth, the graphite is gradually etched during the process, shortening its lifespan. This has been an issue in terms of manufacturing costs. On the other hand, heat-resistant components made of TaC-coated graphite are expected to have a long life due to their chemical stability (see, for example, Non-Patent Document 1). However, it has been reported that TaC-coated graphite components have a lower emissivity than uncoated graphite components, and therefore it may be difficult to replace graphite components with TaC-coated graphite components (see Non-Patent Document 2).

[0016] To solve this problem, Patent Document 8 discloses a method in which the outermost surface of the coating is made of a porous WC layer with a porosity of 20 to 50%, thereby increasing the emissivity of the coating. The method described in Patent Document 8 makes it possible to simultaneously improve the corrosion resistance of the heat-resistant member and achieve high emissivity. However, during the crystal growth process, the heat-resistant member is exposed to large temperature changes from room temperature to high temperatures (approximately 2500°C). This large temperature change also causes a large change in the total emissivity of the heat-resistant member. Therefore, with conventional heat-resistant members, precise temperature control is difficult when large temperature changes are involved. [Prior art documents] [Patent documents]

[0017] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-075814 [Patent Document 2] Japanese Patent Application Laid-Open No. 2013-193943 [Patent Document 3] Japanese Patent Application Laid-Open No. 2015-044719 [Patent Document 4] Japanese Patent Application Laid-Open No. 2017-075075 [Patent Document 5] Japanese Patent Application Publication No. 2018-145022

[0018] [Patent Document 6] Japanese Patent Publication No. 2020-063175 [Patent Document 7] Japanese Patent Application Laid-Open No. 2016-037441 [Patent Document 8] Patent Publication No. 2021-084826 [Patent Document 9] Patent Publication No. 2021-138578 [Patent Document 10] International Publication No. 2019 / 159851 [Non-patent literature]

[0019] [Non-Patent Document 1] D. Nakamura: Appl. Phys. Express 9 (2016) 055507 [Non-patent document 2] D. Nakamura and K. Shigetoh: Jpn. J. Appl. Phys. 56 (2017) 085504 Summary of the Invention [Problem to be solved by the invention]

[0020] The problem to be solved by the present invention is to provide a heat-resistant member having a higher total emissivity and a smaller temperature dependency of the total emissivity than conventional heat-resistant members. Another problem to be solved by the present invention is to provide a heat-resistant member that has a higher total emissivity and a smaller temperature dependency of the total emissivity than conventional heat-resistant members, and that also has high corrosion resistance against high-temperature corrosive gases. [Means for solving the problem]

[0021] In order to solve the above problems, the heat-resistant member according to the present invention has the following configuration. (1) The heat-resistant member is a substrate made of isotropic graphite; an ultra-porous, high-emissivity layer formed on all or part of the surface of the substrate; It is equipped with: However, the above-mentioned "ultra-porous high-emissivity layer" refers to a layer having a porosity of 60% or more and a total emissivity at 25°C of 60% or more. (2) The ultra-porous high-emissivity layer has a total emissivity change rate Δε T is less than 0.6. Δε T =(ε T2500 -ε T25 ) / ε T25 …(1) however, ε T2500 is the total emissivity of the ultraporous high-emissivity layer at 2500°C, ε T25 is the total emissivity of the ultra-porous high-emissivity layer at 25°C.

[0022] The heat-resistant member preferably further comprises a dense or porous layer formed on all or part of the interface between the substrate and the ultra-porous high-emissivity layer. however, The "porous layer" refers to a layer having a porosity of 10% or more and less than 60%. The "dense layer" refers to a layer having a porosity of less than 10%. [Effects of the Invention]

[0023] When an ultra-porous, high-emissivity layer is formed on the outermost surface of a heat-resistant material, the total emissivity of the heat-resistant material becomes relatively high, and Δε T Furthermore, if a dense or porous layer is further formed on all or part of the interface between the substrate and the ultra-porous high-emissivity layer, the total emissivity of the heat-resistant member becomes relatively high, and Δε T In addition, the corrosion resistance of the heat-resistant member is further improved. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a cross-sectional view of a heat-resistant member according to a first embodiment of the present invention. [Figure 2] FIG. 4 is a cross-sectional view illustrating a heat-resistant member according to a second embodiment of the present invention. [Figure 3] FIG. 2 is a cross-sectional view of a heat-resistant member of Comparative Example 1. [Figure 4] FIG. 10 is a cross-sectional view of a heat-resistant member of Comparative Example 3. [Figure 5] Fig. 5(A) is an SEM image of the surface of the porous TaC layer (A) obtained in Comparative Example 1. Fig. 5(B) is an SEM image of the surface of the porous TaC layer (B) obtained in Comparative Example 2. Fig. 5(C) is an SEM image of the surface of the ultraporous TaC layer obtained in Example 1. [Figure 6] FIG. 10 is a diagram showing the relationship between porosity and total emissivity. [Figure 7] FIG. 1 is a graph showing the porosity dependence of ΔεT. DETAILED DESCRIPTION OF THE INVENTION

[0025] An embodiment of the present invention will be described in detail below. [1. Heat-resistant materials] The heat-resistant member according to the present invention has the following configuration. (1) The heat-resistant member is a substrate made of isotropic graphite; an ultra-porous, high-emissivity layer formed on all or part of the surface of the substrate; It is equipped with: (2) The ultra-porous high-emissivity layer has a total emissivity change rate Δε T is less than 0.6.

[0026] [1.1. Base material] [1.1.1. Materials] The base material is made of isotropic graphite. "Isotropic graphite" refers to polycrystalline graphite material produced by cold isostatic pressing (CIP). Graphite is a hexagonal crystal system, so its properties are anisotropic. On the other hand, isotropic graphite has the advantage that the crystal orientation of each crystal grain is unoriented, so there is no difference in properties depending on the cutting direction. In the present invention, the shape, size, etc. of the substrate are not particularly limited, and an optimum shape can be selected depending on the purpose.

[0027] 1.1.2. Average coefficient of thermal expansion "Average thermal expansion coefficient" refers to the average value of the thermal expansion coefficient in the temperature range from room temperature to 500°C. The average thermal expansion coefficient of the substrate affects the durability of the coating (ultra-porous / high-emissivity layer, porous layer, and / or dense layer) formed on the surface of the substrate. Generally, the greater the difference in thermal expansion coefficient between the substrate and the coating, the more likely it is that the substrate will warp or the coating will peel off. The average thermal expansion coefficient of isotropic graphite is usually 3.8 to 7.0 × 10 depending on its manufacturing method and composition. -6 / K. Therefore, it is preferable to select a material with an appropriate average thermal expansion coefficient from among various isotropic graphites as the material for the substrate.

[0028] [1.2. Ultra-porous / high emissivity layer] [1.2.1. Definition] An ultra-porous, high-emissivity layer is formed on all or part of the surface of the substrate. "Ultra-porous high-emissivity layer" refers to a layer with a porosity of 60% or more and a total emissivity of 60% or more at 25°C.

[0029] [1.2.2. Porosity] The porosity of the ultra-porous high-emissivity layer is related to the total emissivity and the rate of change in total emissivity Δε at 25°C. T In general, the larger the porosity, the higher the total emissivity at 25°C. Also, in areas where the porosity is relatively high, the larger the porosity, the lower the Δε Tbecomes small. Relatively high total emissivity and relatively low Δε T To achieve this, the porosity must be 60% or more, preferably 70% or more, and more preferably 80% or more. On the other hand, if the porosity is too high, the strength of the ultra-porous high-emissivity layer will be significantly reduced. Therefore, the porosity is preferably 95% or less. The porosity is more preferably 90% or less.

[0030] [1.2.3. Total emissivity at 25°C] Graphite has one of the highest total emissivities among practical materials. Therefore, in order to easily replace graphite components with the heat-resistant component of the present invention, the higher the total emissivity of the ultra-porous, high-emissivity layer that covers the surface of the substrate, the better. The total emissivity of an ultra-porous, high-emissivity layer at 25°C mainly depends on the material and porosity (particularly the porosity) of the layer. If the structure of the ultra-porous, high-emissivity layer is optimized, the total emissivity of the ultra-porous, high-emissivity layer at 25°C will be 60% or more. If the structure is further optimized, the total emissivity at 25°C will be 65% or more.

[0031] [1.2.4. Total emissivity change rate] "Total emissivity change rate Δε T " refers to the value expressed by the following formula (1). Δε T =(ε T2500 -ε T25 ) / ε T25 …(1) however, ε T2500 is the total emissivity of the ultraporous high-emissivity layer at 2500°C, ε T25 is the total emissivity of the ultra-porous high-emissivity layer at 25°C.

[0032] During the crystal growth process, the heat-resistant material is exposed to large temperature changes from room temperature to high temperatures (approximately 2500°C). Generally, this large temperature change often results in a large change in the total emissivity of the heat-resistant material. However, if the total emissivity fluctuates greatly with temperature change, precise temperature control can become difficult.

[0033] In contrast, when the surface of the substrate is coated with an ultra-porous, high-emissivity layer, the Δε T The Δε of the ultra-porous high-emissivity layer can be reduced. T depends mainly on the material and porosity (particularly the porosity) of the ultra-porous high-emissivity layer. By optimizing the structure of the ultra-porous high-emissivity layer, the Δε T is less than 0.6. By further optimizing the structure, Δε T is less than 0.3 or less than 0.1.

[0034] [1.2.5. Materials] The material of the ultra-porous high-emissivity layer is not particularly limited as long as it satisfies the above-mentioned conditions. Examples of materials for the ultra-porous high-emissivity layer include tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide. The ultra-porous high-emissivity layer may be made of any one of these materials, or may be a mixture or laminate film made of two or more materials.

[0035] [1.2.6. Number of layers] The ultra-porous high-emissivity layer may be a single layer or may be a multi-layer, so long as it satisfies the above-mentioned conditions.

[0036] Here, the term "single layer" refers to a layer that can be considered to have a substantially uniform composition and relative density. In other words, a "single layer" refers to a layer manufactured by a single manufacturing process using the same manufacturing method and conditions. Within a layer manufactured by a single manufacturing process, fluctuations in composition and relative density due to the manufacturing process may occur. Alternatively, a reaction layer may form at the interface between the substrate and the ultra-porous, high-emissivity layer. In the present invention, even in such cases, the layer is considered to be a "single layer." "Multilayer" refers to a stack of layers that differ in composition and / or relative density.

[0037] [1.2.7. Formation location, area ratio, thickness] The position where the ultra-porous high-emissivity layer is formed is not particularly limited, and the optimum position can be selected depending on the purpose. The ultra-porous high-emissivity layer is particularly (a) Where it is desired to promote the radiation of heat from the heat-resistant component to the outside, or (b) Areas where you want to promote the absorption of heat from outside It is preferable to provide it at

[0038] The ultra-porous, high-emissivity layer may be formed on the entire surface of the substrate, or may be formed on only a portion of the surface of the substrate. When the ultra-porous, high-emissivity layer is formed on only a portion of the surface of the substrate, the ratio of the area of ​​the ultra-porous, high-emissivity layer to the total surface area of ​​the substrate is not particularly limited, and an optimal area ratio can be selected depending on the purpose. Furthermore, the thickness of the ultra-porous, high-emissivity layer is not particularly limited, and an optimum thickness can be selected depending on the purpose. The thickness of the ultra-porous, high-emissivity layer is typically 20 μm to 100 μm.

[0039] [1.3. Porous layer] [1.3.1. Definition] In the present invention, a porous layer may be formed on all or part of the interface between the substrate and the ultra-porous high-emissivity layer. The term "porous layer" refers to a layer having a porosity of 10% or more and less than 60%.

[0040] [1.3.2. Porosity] If the substrate surface is covered only with an ultra-porous, high-emissivity layer, corrosive gases may reach the substrate surface, accelerating corrosion of the substrate. In contrast, the porous layer has a lower porosity than the ultra-porous, high-emissivity layer. Therefore, forming a porous layer between the substrate surface and the ultra-porous, high-emissivity layer can suppress corrosion of the substrate compared to when the substrate surface is covered only with an ultra-porous, high-emissivity layer.

[0041] The porosity of the porous layer is not particularly limited, and an optimum value can be selected depending on the purpose. Generally, the smaller the porosity of the porous layer, the greater the effect of suppressing corrosion of the substrate. The porosity of the porous layer is preferably 50% or less, more preferably 30% or less.

[0042] [1.3.3. Total emissivity at 25°C] The total emissivity of a heat-resistant component at 25°C is determined by the total emissivity of the ultra-porous, high-emissivity layer on the outermost surface. Therefore, the total emissivity of the porous layer formed underneath at 25°C is not particularly limited, and an optimal value can be selected depending on the purpose.

[0043] [1.3.4. Total emissivity change rate Δε T ] Δε of heat-resistant material T is the Δε of the ultra-porous, high-emissivity layer on the outermost surface. T Therefore, the Δε of the porous layer formed thereunder is T is not particularly limited, and an optimum value can be selected depending on the purpose.

[0044] [1.3.5. Materials] The material of the porous layer is not particularly limited as long as it satisfies the above-mentioned conditions. Examples of the material for the porous layer include tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide. The porous layer may be made of any one of these materials, or may be a mixture or laminate film made of two or more materials. Furthermore, the material of the porous layer may be the same as or different from the material of the ultra-porous high-emissivity layer.

[0045] [1.3.6. Number of layers] The porous layer may be a single layer or may be a multi-layer, as long as it satisfies the above-mentioned conditions. However, a multi-layer porous layer is often not practical and may even result in increased costs. Therefore, a single layer porous layer is preferred.

[0046] [1.3.7. Formation location, area ratio, thickness] The position where the porous layer is formed is not particularly limited, and the optimal position can be selected depending on the purpose. For example, the porous layer may be formed over the entire interface between the substrate and the ultra-porous, high-emissivity layer, or may be formed over only a portion of the interface. Furthermore, the porous layer may be formed only at the interface between the substrate and the ultra-porous, high-emissivity layer, or may be formed on the surface of the substrate where the ultra-porous, high-emissivity layer is not formed.

[0047] When the porous layer is formed on a part of the surface of the substrate, the ratio of the area of ​​the porous layer to the total surface area of ​​the substrate is not particularly limited, and an optimal area ratio can be selected depending on the purpose. Furthermore, the thickness of the porous layer is not particularly limited, and an optimum thickness can be selected depending on the purpose. The thickness of the porous layer is usually 20 μm to 100 μm.

[0048] [1.4. Dense layer] [1.4.1. Definition] In the present invention, a dense layer may be formed on all or part of the interface between the substrate and the ultra-porous high-emissivity layer. A "dense layer" refers to a layer having a porosity of less than 10%.

[0049] [1.4.2. Porosity] If the substrate surface is covered only with an ultra-porous, high-emissivity layer, corrosive gases may reach the substrate surface, causing corrosion of the substrate. Even if the substrate surface is covered with a porous layer, corrosion of the substrate may still occur. In contrast, a dense layer has an even lower porosity than a porous layer. Therefore, forming a dense layer between the substrate surface and the ultra-porous, high-emissivity layer can further suppress corrosion of the substrate.

[0050] The porosity of the dense layer is not particularly limited, and an optimum value can be selected depending on the purpose. Generally, the smaller the porosity of the dense layer, the greater the effect of inhibiting corrosion of the substrate. The porosity of the dense layer is preferably 5% or less.

[0051] [1.4.3. Total emissivity at 25°C] The total emissivity of a heat-resistant component at 25°C is determined by the total emissivity of the ultra-porous, high-emissivity layer on the outermost surface. Therefore, the total emissivity of the dense layer formed underneath at 25°C is not particularly limited, and an optimal value can be selected depending on the purpose.

[0052] [1.4.4. Total emissivity change rate Δε T ] Δε of heat-resistant material T is the Δε of the ultra-porous, high-emissivity layer on the outermost surface. T Therefore, the Δε of the dense layer formed underneath T is not particularly limited, and an optimum value can be selected depending on the purpose.

[0053] [1.4.5. Materials] The material of the dense layer is not particularly limited as long as it satisfies the above-mentioned conditions. Examples of materials for the dense layer include tantalum carbide, titanium carbide, vanadium carbide, chromium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide. The dense layer may be made of any one of these materials, or may be a mixture or laminate film made of two or more materials. Furthermore, the material of the dense layer may be the same as or different from the material of the ultra-porous high-emissivity layer or the porous layer.

[0054] [1.4.6. Number of layers] The dense layer may be a single layer or may be a multi-layer, as long as it satisfies the above-mentioned conditions. However, a multi-layer dense layer is often not practical and may even result in increased costs. Therefore, a single layer dense layer is preferred.

[0055] [1.4.7. Formation location, area ratio, thickness] The position where the dense layer is formed is not particularly limited, and the optimal position can be selected depending on the purpose. For example, the dense layer may be formed over the entire interface between the substrate and the ultra-porous, high-emissivity layer, or may be formed over only a portion of the interface. Furthermore, the dense layer may be formed only at the interface between the substrate and the ultra-porous, high-emissivity layer, or may be formed on the surface of the substrate where the ultra-porous, high-emissivity layer is not formed.

[0056] Furthermore, only a dense layer may be formed at the interface between the substrate and the ultra-porous high-emissivity layer, or both a dense layer and a porous layer may be formed. When both a dense layer and a porous layer are formed at the interface between the substrate and the ultra-porous high-emissivity layer, the layers may be stacked in the following order: substrate / dense layer / porous layer / ultra-porous high-emissivity layer, or substrate / porous layer / dense layer / ultra-porous high-emissivity layer.

[0057] When the dense layer is formed on a part of the surface of the substrate, the ratio of the area of ​​the dense layer to the total surface area of ​​the substrate is not particularly limited, and an optimal area ratio can be selected depending on the purpose. Furthermore, the thickness of the dense layer is not particularly limited, and an optimum thickness can be selected depending on the purpose. The thickness of the dense layer is usually 20 μm to 100 μm.

[0058] [1.5. Usage] The heat-resistant member according to the present invention can be used for various purposes. The heat-resistant member according to the present invention is particularly suitable as a member exposed to a growth atmosphere when growing a compound semiconductor single crystal. Specific examples of such members include: (a) a crucible for holding the raw material; (b) a pedestal for holding a seed crystal; (c) a heat shield disposed between the crucible and the base; (d) Support for holding the heat shield etc.

[0059] [1.6. Specific Examples] [1.6.1. Example 1] Fig. 1 shows a cross-sectional schematic diagram of a heat-resistant member according to a first embodiment of the present invention. In Fig. 1, the dimensions of each part are drawn larger or smaller than their actual dimensions to make it easier to see. This also applies to Figs. 2 to 4, which will be described later. In Fig. 1, a heat-resistant member 10a includes a substrate 20 made of isotropic graphite and an ultraporous high-emissivity layer 30 formed on a portion of the surface of the substrate 20.

[0060] 1, the ultra-porous high-emissivity layer 30 is formed only on the top surface of the substrate 20, but this is merely an example. The ultra-porous high-emissivity layer 30 may be formed on a surface other than the top surface of the substrate 20. Other aspects of the substrate 20 and the ultra-porous high-emissivity layer 30 are as described above, and therefore will not be described here.

[0061] [1.6.2. Example 2] A cross-sectional view of a heat-resistant member according to a second embodiment of the present invention is shown in Fig. 2. In Fig. 2, the heat-resistant member 10b includes a substrate 20 made of isotropic graphite, an ultra-porous high-emissivity layer 30 formed on a portion of the surface of the substrate 20, and a dense layer 40 formed at the interface between the substrate 20 and the ultra-porous high-emissivity layer 30.

[0062] 2, the heat-resistant member 10b has a three-layer structure of the substrate 20 / dense layer 40 / ultra-porous high-emissivity layer 30, but this is merely an example. The heat-resistant member 10b may have a porous layer formed thereon instead of or in addition to the dense layer 40. Other aspects of the substrate 20, the ultra-porous high-emissivity layer 30, and the dense layer 40 are as described above, and therefore will not be described here.

[0063] [2. Manufacturing method of heat-resistant components] The heat-resistant member according to the present invention can be manufactured by various methods, among which the sintering method is suitable as a manufacturing method for the heat-resistant member because it is easy to adjust the porosity.

[0064] Here, the "sintering method" means (a) applying a first slurry containing raw materials for forming a dense layer and / or a second slurry containing raw materials for forming a porous layer to all or part of the surface of a substrate made of isotropic graphite, as needed, and drying the slurry to form a first molded film and / or a second molded film on the surface of the substrate; (b) forming a third formed film on all or part of the surface of the substrate by scattering raw material powder for forming an ultra-porous high-emissivity layer on all or part of the surface of the substrate; (c) The substrate on which the third molded film and, if necessary, the first molded film and / or the second molded film are formed is heated in an inert atmosphere to sinter the first to third molded films. It means a method.

[0065] [2.1. 1st step] First, a first slurry containing raw materials for forming a dense layer and / or a second slurry containing raw materials for forming a porous layer is applied to all or part of the surface of a substrate made of isotropic graphite, as needed, and then dried (first step). This allows a first molded film and / or a second molded film to be formed on the surface of the substrate. Note that if neither the first molded film nor the second molded film is formed, the first step can be omitted.

[0066] 2.1.1. First Slurry The first slurry is a raw material for forming the dense layer. The first molded film is a layer that becomes the dense layer after sintering. If the raw material for forming the dense layer is difficult to sinter, an appropriate amount of sintering aid is added to the first slurry. For example, if TaC or WC is used as the raw material for the dense layer, it is preferable to use Co as the sintering aid. The first slurry may further contain an organic binder, a dispersant, etc., as necessary.

[0067] The average particle size of the raw material powder, the type and amount of the sintering aid, the composition of the first slurry, etc. are not particularly limited and can be selected optimally depending on the purpose. For example, to facilitate densification, the average particle size of TaC or WC is preferably 1 to 3 μm. Generally, if the amount of sintering aid added to the first slurry is too small, densification will not proceed sufficiently, resulting in a large porosity. On the other hand, if the amount of sintering aid added is excessive, the sintering aid will remain in the dense layer and may leak during use, becoming a source of contamination. The appropriate amount of sintering aid to be added varies depending on the type of sintering aid. For example, if the sintering aid is Co, the amount of sintering aid to be added is preferably 0.1 to 5 mass%.

[0068] [2.1.2. Second Slurry] The second slurry is a raw material for forming the porous layer. The second molded film is a layer that becomes the porous layer after sintering. The composition of the second slurry is not particularly limited, and an optimal composition can be selected depending on the purpose. For example, if the raw material for forming the porous layer is a difficult-to-sinter material such as TaC or WC, the second slurry does not need to contain a sintering aid. In fact, using a second slurry that does not contain a sintering aid makes it easier to form the porous layer. Other aspects of the second slurry are the same as those of the first slurry, so a description thereof will be omitted.

[0069] 2.1.3. Application of Slurry After preparing the first slurry and / or the second slurry, one or both of them are applied to the surface of the substrate. When both the first slurry and the second slurry are applied to the surface of the substrate, the order in which the first slurry and the second slurry are applied is not particularly limited, and an optimal order can be selected depending on the purpose. Furthermore, the application area of ​​the first slurry and the application area of ​​the second slurry do not necessarily have to be the same, and the application area may be changed depending on the purpose.

[0070] [2.2. 2nd process] Next, raw material powder for forming an ultra-porous, high-emissivity layer is scattered over all or part of the surface of the substrate (second step), thereby forming a third molded film over all or part of the surface of the substrate.

[0071] The third molded film is a layer that will become the ultra-porous, high-emissivity layer after sintering. If necessary, by sprinkling raw material powder for forming the ultra-porous, high-emissivity layer on the surface of the substrate on which the first molded film and / or second molded film have been formed, a third molded film with a higher porosity than the second molded film can be formed. By sintering this, an ultra-porous, high-emissivity layer with a higher porosity than the porous layer can be formed. The raw material may be sprinkled directly on the surface of the substrate, or on the surface of the first molded film and / or second molded film.

[0072] [2.3. Third step] Next, the substrate on which the third molded film and, if necessary, the first molded film and / or the second molded film are formed is heated in an inert atmosphere to sinter the first to third molded films (third step), thereby obtaining the heat-resistant member according to the present invention. The optimum sintering conditions are selected depending on the compositions of the first to third molded films. The optimum sintering conditions vary depending on the properties of the raw material powder, the composition of the slurry, etc. For example, when the raw material powder is TaC or WC, it is preferable to heat it at 2000°C to 2300°C for about 0.5 to 1.0 hour.

[0073] [3. Effect] When an ultra-porous, high-emissivity layer is formed on the outermost surface of a heat-resistant material, the total emissivity of the heat-resistant material becomes relatively high, and Δε T Furthermore, if a dense or porous layer is further formed on all or part of the interface between the substrate and the ultra-porous high-emissivity layer, the total emissivity of the heat-resistant member becomes relatively high, and Δε T In addition, the corrosion resistance of the heat-resistant member is further improved.

[0074] It exhibits high total emissivity in the temperature range from room temperature to approximately 2500°C, and has a low Δε T By selectively coating the surface of a graphite substrate with a corrosion-resistant coating material with low corrosion resistance, it is possible to more accurately control the temperature distribution during high-temperature processes, such as the growth of compound semiconductor single crystals. Therefore, when such a heat-resistant component is used in, for example, a SiC single crystal growth process, it is possible to improve the sublimation efficiency of the SiC raw material powder, improve the cooling efficiency of the seed crystal, and reduce thermal stress within the growing crystal. This also makes it possible to achieve high-speed growth of single crystals, larger single crystals, and higher-quality single crystals. [Example]

[0075] (Example 1, Comparative Examples 1 to 3) 1. Sample Preparation 1.1. Example 1 The heat-resistant member 10a shown in FIG. 1 was fabricated. The base material 20 had an average CTE of 3.5 to 7.0 × 10 in the temperature range from room temperature to 500°C.-6 The raw material for forming the ultra-porous high-emissivity layer 30 was TaC powder with an average particle size of about 1 to 3 μm.

[0076] TaC powder was spread on the surface of the substrate 20 using a sieve with openings of 50 to 150 μm to form a third molded film with a thickness of approximately 50 μm. The substrate 20 on which the third molded film had been formed was held in an inert gas (main component: Ar) atmosphere at 2000°C or higher for 1 hour to sinter the third molded film, thereby obtaining a heat-resistant member 10a equipped with an ultraporous high-emissivity layer 30 (hereinafter also referred to as an "ultraporous TaC layer").

[0077] 1.2. Comparative Example 1 Fig. 3 shows a schematic cross-sectional view of the heat-resistant member of Comparative Example 1. As shown in Fig. 3, a heat-resistant member 10c was produced in which a porous layer 50 was formed on the surface of a substrate 20. The substrate 20 was made of the same isotropic graphite as in Example 1. The raw material for forming the porous layer 50 was the same TaC powder as in Example 1.

[0078] TaC powder, an organic binder, and an organic solvent were mixed in a predetermined ratio to obtain a second slurry. The obtained second slurry was spray-coated onto the surface of the substrate 20 to obtain a second molded film. The thickness of the second molded film was set to a thickness that would result in a film thickness of 50 to 100 μm after sintering. Furthermore, in order to remove the organic solvent from the second molded film, the substrate 20 on which the second molded film had been formed was heated on a hot plate at 150°C for 30 minutes. Thereafter, the second molded film was sintered in the same manner as in Example 1 to obtain a heat-resistant member 10c provided with a porous layer 50 (hereinafter also referred to as "porous TaC layer (A)").

[0079] 1.3. Comparative Example 2 In order to form a porous layer 50 with a larger porosity than that of Comparative Example 1, one of the organic solvents used in the second slurry was changed to one with a melting point of 20 to 30° C. Thereafter, in the same manner as in Comparative Example 1, a heat-resistant member 10c provided with a porous layer 50 (hereinafter also referred to as a “porous TaC layer (B)”) was obtained.

[0080] 1.4. Comparative Example 3 Fig. 4 shows a schematic cross-sectional view of the heat-resistant member of Comparative Example 3. As shown in Fig. 4, a heat-resistant member 10d was produced in which a dense layer 40 was formed on the surface of a substrate 20. The substrate 20 was made of the same isotropic graphite as in Example 1. The raw material for forming the dense layer 40 was the same TaC powder as in Example 1.

[0081] TaC powder, Co powder as a sintering aid, an organic binder, and an organic solvent were mixed in a predetermined ratio to obtain a first slurry. The obtained first slurry was spray-coated onto the surface of the substrate 20 to obtain a first molded film. The thickness of the first molded film was set to a thickness that would result in a film thickness of 50 to 100 μm after sintering. Furthermore, in order to remove the organic solvent from the first molded film, the substrate 20 on which the first molded film had been formed was heated on a hot plate at 150°C for 30 minutes. Thereafter, the first molding film was sintered in the same manner as in Example 1 to obtain a heat-resistant member 10d having a dense layer 40 (hereinafter also referred to as a "dense TaC layer").

[0082] 2. Test Method [2.1. Measurement and calculation of total emissivity] The temperature dependence of total emissivity was measured and calculated using an indirect measurement method (JIS R1693-2:2012) using a Fourier transform infrared spectrophotometer (FT-IR) at room temperature (25°C), 500°C, 1000°C, 1500°C, 2000°C, and 2500°C.

[0083] 2.2. Calculation of void ratio Samples for cross-sectional observation were prepared from the sintered heat-resistant components 10a to 10d, and cross-sectional SEM images were taken using a scanning electron microscope (SEM). The porosity of each layer was calculated using the obtained cross-sectional SEM images. The porosity was calculated using the following formula. Porosity={1-M / (ρ×V)}×100 however, M is the mass of each layer, ρ is the true density of each layer calculated based on the composition of each layer, V is the apparent volume of each layer calculated from the thickness of each layer.

[0084] [3. Results] [3.1. Dependence of total emissivity on porosity] FIG. 5(A) shows an SEM image of the surface of the porous TaC layer (A) obtained in Comparative Example 1. FIG. 5(B) shows an SEM image of the surface of the porous TaC layer (B) obtained in Comparative Example 2. FIG. 5(C) shows an SEM image of the surface of the ultraporous TaC layer obtained in Example 1. FIG. 6 shows the relationship between porosity and total emissivity. Furthermore, Table 1 shows the porosity and total emissivity at each temperature. The following can be seen from FIGS. 5 and 6 and Table 1.

[0085] (1) The porosity of Example 1 was 82.8%. Furthermore, the total emissivity of Example 1 was higher than those of Comparative Examples 1 to 3 at all temperatures. (2) The porosity of Comparative Example 1 was 27.9%. On the other hand, the porosity of Comparative Example 2 was 33.0%. Therefore, the total emissivity of Comparative Example 2 was higher than those of Comparative Examples 1 and 3 at all temperatures. (3) The porosity of Comparative Example 3 was 0.5%, so the emissivity of Comparative Example 3 was the lowest at any temperature.

[0086] [Table 1]

[0087] [3.2. Δε T porosity dependence] Based on the results in Table 1, the total emissivity ε at 25°C versus porosity (x) T25 and the total emissivity ε at 2500℃ versus porosity (x). T2500 The approximate curve of ε was calculated using the following equations (1) and (2). T25 Approximation curve of and ε T2500 The approximate curve of Equation (1) is shown below. 2 =0.999, and equation (2) is R 2 =1. ε T25 =0.0182x 2 -0.2306 x+1 2.874 …(1) ε T2500 =-0.0008x 2 +0.6966x+20.888 …(2)

[0088] Using equations (1) and (2), ε when the porosity (x) is 10 to 70% T25 , ε T2500 , and Δε T The results are shown in Table 2. Also, Δε T Table 2 and Figure 7 show the porosity dependency of Δε T ≦0.6. This means that the total emissivity does not fluctuate significantly from room temperature (25°C) to high temperatures (2500°C), making temperature control easier than with conventional materials.

[0089] [Table 2]

[0090] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications are possible within the scope of the gist of the present invention. [Industrial Applicability]

[0091] The heat-resistant member according to the present invention can be used for a crucible for growing crystals or thin films made of compound semiconductors, a susceptor, a heater material, a deposition boat, a reflector material, and the like. [Explanation of symbols]

[0092] 10a, 10b heat-resistant member 20 Base material 30 Ultra porous / high emissivity layer 40 Layer compacta

Claims

1. A heat-resistant member having the following configuration: (1) The heat-resistant member is a substrate made of isotropic graphite; an ultra-porous, high-emissivity layer formed on all or part of the surface of the substrate; a porous layer and / or a dense layer formed at all or part of the interface between the substrate and the ultra-porous high-emissivity layer; It is equipped with: however, The "ultra-porous high-emissivity layer" refers to a layer having a porosity of 70% or more and 95% or less, and a total emissivity at 25°C of 60% or more. The "porous layer" refers to a layer having a porosity of 10% or more and less than 60%. The "dense layer" refers to a layer having a porosity of less than 10%. (2) The ultra-porous high-emissivity layer has a total emissivity change rate Δε expressed by the following formula (1): T is 0.6 or less. No T =(e T2500 -e T25 ) / e T25 …(1) however, ε T2500 is the total emissivity of the ultra-porous high-emissivity layer at 2500°C, ε T25 is the total emissivity of the ultra-porous high-emissivity layer at 25°C. (3) The ultra-porous high-emissivity layer contains at least one selected from the group consisting of tantalum carbide, titanium carbide, vanadium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide.

2. The heat-resistant member comprises the dense layer, 2. The heat-resistant member according to claim 1, wherein the dense layer contains at least one selected from the group consisting of tantalum carbide, titanium carbide, vanadium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide.

3. The heat-resistant member comprises the porous layer, 3. The heat-resistant member according to claim 1, wherein the porous layer contains at least one selected from the group consisting of tantalum carbide, titanium carbide, vanadium carbide, zirconium carbide, niobium carbide, molybdenum carbide, hafnium carbide, and tungsten carbide.

4. 4. The heat-resistant member according to claim 1, which is used as a member exposed to a growth atmosphere when growing a compound semiconductor single crystal.

5. The member is (a) a crucible for holding the raw material; (b) a pedestal for holding a seed crystal, or (c) a heat shield disposed between the crucible and the base; The heat-resistant member according to claim 4, wherein

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