Metal carbide coating material

Abstract

To provide a metal carbide coating material that can suppress deterioration in yield of growth of a single crystal when a metal carbide coating material having at least one cross section of which contour line shape is circular is used for producing a single crystal.SOLUTION: A metal carbide coating material includes: a carbon base material containing carbon as the principal component; and a metal carbide coating film that at least partially coats the carbon base material and contains a metal carbide as the principal component. The metal carbide coating material has at least one cross section of which contour line shape is circular, where the circularity of the circle is 0.01 mm or more and 1.2 mm or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a metal carbide coated material including a carbon substrate containing carbon as a main component and a metal carbide coating film containing metal carbide as a main component, which coats at least a portion of the carbon substrate. [Background technology]

[0002] Carbides such as tantalum carbide, niobium carbide, zirconium carbide, hafnium carbide, and tungsten carbide have high melting points and excellent chemical stability, strength, toughness, and corrosion resistance. Therefore, coating a carbon substrate with a carbide can improve the carbon substrate's properties, such as heat resistance, chemical stability, strength, toughness, and corrosion resistance. Carbide-coated materials, in which a carbide film is coated on the surface of a carbon substrate, particularly tantalum carbide-coated materials, are used as components in semiconductor single crystal manufacturing equipment for Si (silicon), SiC (silicon carbide), GaN (gallium nitride), and AlN (aluminum nitride).

[0003] Sublimation recrystallization is a widely known method for producing bulk single crystals of SiC. In this method, a crucible is filled with SiC raw material, and a SiC seed crystal is placed on top of it. A guide is also installed around the SiC seed crystal to guide the sublimation gas to the single crystal. The sublimation gas generated by heating the SiC raw material rises along the inner wall of the guide, and the SiC single crystal grows on the SiC seed crystal.

[0004] Additionally, SiC single crystal substrates used in semiconductor devices and the like are manufactured by epitaxially growing SiC single crystals on SiC substrates made of bulk single crystals. Known methods for epitaxially growing SiC single crystals include liquid phase epitaxy (LPE), vapor phase epitaxy (VPE), and chemical vapor deposition (CVD). The usual method for epitaxially growing SiC single crystals is the CVD method. In the epitaxial growth method using the CVD method, the SiC substrate is placed on a susceptor inside the equipment and raw material gases are supplied at high temperatures of 1500°C or higher to grow the SiC single crystal.

[0005] In such a method for producing a SiC single crystal, in order to obtain a crystal of higher quality, Patent Document 1 discloses a method using a crucible whose inner surface is coated with tantalum carbide and whose graphite base material, and Patent Document 2 discloses a method using a guide member whose inner wall is coated with tantalum carbide. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2019-99453 [Patent Document 2] Japanese Patent Application Publication No. 2019-108611 Summary of the Invention [Problem to be solved by the invention]

[0007] It is known that compound semiconductor single crystals grown using metal carbide-coated materials as crucibles, guide members, and susceptors have significantly improved crystal growth yields compared to when uncoated carbon materials are used. On the other hand, compound semiconductor crystal growth is still in its infancy, and improving yields is an important factor. Generally, bulk single crystals have a cylindrical shape in part, and the wafers obtained by slicing them are also disk-shaped. Therefore, both the metal carbide coating materials used for growing bulk single crystals and the metal carbide coating materials used for epitaxial growth are almost always guide materials or susceptors that have at least one cross section whose outline is circular. When such a metal carbide coating material including a circular portion having a circular cross-sectional outline is used as a component of a manufacturing apparatus used for growing bulk single crystals of compound semiconductors, and as a component of a manufacturing apparatus used for epitaxially growing compound semiconductors, there is a problem in that the yield of the bulk single crystals and the yield of the single crystals obtained by epitaxial growth are reduced. [Means for solving the problem]

[0008] After extensive research, the inventors discovered that the circular portions of a metal carbide-coated material are affected by the gas flow and center misalignment of the raw material gas, resulting in insufficient coverage of the metal carbide coating film on the circular portions of the metal carbide-coated material, and thus reduced crystal growth yields of single crystals produced using manufacturing equipment that uses the metal carbide-coated material as a component. They also discovered that by controlling the circularity of the circular portions of the metal carbide-coated material, which have a circular cross-sectional shape within a predetermined range, the circular portions of the metal carbide-coated material are sufficiently covered with the metal carbide coating film, thereby improving the crystal growth yield of single crystals produced using manufacturing equipment that uses the metal carbide-coated material as a component, and thus completed the present invention. The gist of the present invention is as follows. [1] A metal carbide coated material comprising a carbon substrate containing carbon as a main component and a metal carbide coating film containing metal carbide as a main component, the metal carbide coating film coating at least a portion of the carbon substrate, The metal carbide coating material has at least one cross section whose outline is circular; The metal carbide coated material has a circularity of 0.01 mm or more and 1.2 mm or less. [2] The metal carbide coated material according to [1] above, wherein the circular shape has a circularity of 0.01 mm or more and 0.8 mm or less. [3] The metal carbide coated material according to [1] or [2] above, wherein the circular shape has a circularity of 0.01 mm or more and 0.4 mm or less. [4] The metal carbide coated material according to any one of the above [1] to [3], wherein the circular shape has a circularity of 0.01 mm or more and 0.2 mm or less. [5] The linear thermal expansion coefficient of the carbon substrate is 5.2 × 10 -6 / ℃ or more 7.2×10 -6 The metal carbide coated material according to any one of the above [1] to [4], wherein the temperature is 100°C or lower. [6] The metal carbide coated material according to any one of the above [1] to [5], wherein the arithmetic mean roughness Ra of the surface of the carbon substrate is 0.5 μm or more and 6.0 μm or less. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide a metal carbide coated material that can suppress a decrease in the crystal growth yield of single crystals when used in the production of single crystals, the metal carbide coated material having at least one cross section whose outline shape is circular. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram of an externally heated low-pressure CVD apparatus used to form a tantalum carbide coating film on the surface of a carbon substrate. [Figure 2] FIG. 2 is a schematic diagram for explaining the crucible. [Figure 3] FIG. 3 is a diagram for explaining the susceptor. DETAILED DESCRIPTION OF THE INVENTION

[0011] [Carbide-coated metal materials] The metal carbide-coated material of the present invention is a metal carbide-coated material comprising a carbon substrate primarily composed of carbon and a metal carbide-coated film primarily composed of metal carbide that coats at least a portion of the carbon substrate. The metal carbide-coated material of the present invention has at least one cross section whose outline is circular, and the circularity of the circle is 0.01 mm or more and 1.2 mm or less. This makes it possible to suppress a decrease in the crystal growth yield of a single crystal when a metal carbide-coated material having at least one cross section whose outline is circular is used in the production of a single crystal. The outline is a line that represents the outline of the cross section.

[0012] Examples of metal carbide coating films include coating films of high-melting point metal carbides such as tantalum carbide, niobium carbide, zirconium carbide, hafnium carbide, and tungsten carbide, and composite metal carbide coating films made by combining two or more of these metal carbides. Among these metal carbide coating films, tantalum carbide coating films are preferred. The metal carbide coated material of the present invention will be described below by taking as an example a tantalum carbide coated material using tantalum carbide as the carbide and carbon as the substrate.

[0013] [About tantalum carbide coating materials] Hereinafter, a tantalum carbide coating material according to one embodiment of the present invention will be described with reference to FIG. A tantalum carbide coating material according to one embodiment of the present invention comprises a substrate containing carbon as a main component and a tantalum carbide coating film containing tantalum carbide as a main component provided on the surface of the substrate. The tantalum carbide coating film may coat a portion of the carbon substrate or the entire carbon substrate.

[0014] The carbon substrate 14 may be made of a carbon material such as isotropic graphite, extruded graphite, pyrolytic graphite, or a carbon fiber reinforced carbon composite material (C / C composite). The shape of the carbon substrate 14 is not particularly limited as long as it has at least one cross section whose outline is circular. The carbon substrate 14 can be used by being processed into a shape appropriate for the intended use.

[0015] The tantalum carbide coating material of one embodiment of the present invention can be produced by forming a tantalum carbide coating film on the surface of a carbon substrate. The tantalum carbide coating film can be formed on the surface of the carbon substrate 14 by methods such as chemical vapor deposition (CVD), sintering, and carbonization. Among these, the CVD method is preferred as a method for forming a tantalum carbide coating film because it can form a uniform and dense film.

[0016] Furthermore, CVD methods include, for example, thermal CVD, photo-CVD, and plasma CVD, and thermal CVD, for example, can be used to form a tantalum carbide coating film. Thermal CVD has advantages such as a relatively simple apparatus configuration and no damage caused by plasma. Formation of a tantalum carbide coating film by thermal CVD can be performed, for example, using an externally heated low-pressure CVD apparatus 10 as shown in FIG. 1. In the externally heated low-pressure CVD apparatus 10, a carbon substrate 14 is supported by a support means 15 in a reaction chamber 12 equipped with a heater 13, a raw material supply unit 16, an exhaust unit 17, etc.

[0017] A method for producing a tantalum carbide coated material according to one embodiment of the present invention will be described with reference to FIG. First, the carbon substrate 14 is placed in the reaction chamber 12 of the externally heated low-pressure CVD apparatus 10. The carbon substrate 14 is supported by a support means 15 having a support portion with a pointed tip.

[0018] Next, the reaction chamber 12 is heated. For example, the reaction chamber 12 is heated under conditions of an atmospheric pressure of 10 to 1000 Pa and a temperature of 800 to 2200°C.

[0019] Next, a tantalum carbide coating film is formed on the surface of the carbon substrate 14. As source gases, a gas of a compound containing carbon atoms, such as methane (CH4), and a tantalum halide gas, such as hydrogen (H2) and tantalum pentachloride (TaCl5), are supplied from the source supply unit 16 to the reaction chamber 12. The tantalum halide gas can be generated, for example, by a method of heating and vaporizing tantalum halide, or a method of reacting tantalum metal with a halogen gas. Subsequently, the source gas supplied from the source supply unit 16 is subjected to a thermal CVD reaction at a high temperature of 800 to 2200°C and a reduced pressure of 1 to 1000 Pa, forming a tantalum carbide coating film on the carbon substrate 14.

[0020] A tantalum carbide coated material according to one embodiment of the present invention has at least one cross section whose outline is circular. Hereinafter, the portion of the tantalum carbide coated material whose cross section has a circular outline may be referred to as a circular portion. The dimensions of any circular portion of the produced tantalum carbide coated material are measured. Measurements can be performed using a vernier caliper or micrometer if the object being measured is small, or a contact-type coordinate measuring machine or an optical coordinate measuring machine if the object being measured is large; the measurement method is not limited. In the examples described below, the circularity of the circular portion of the tantalum carbide coated material was measured using a coordinate measuring machine (Crysta-Apex C544) manufactured by Mitutoyo Corporation.

[0021] The value calculated by a coordinate measuring machine may be used as is for the roundness, but it is essentially the difference between the radius of the maximum inscribed circle obtained from the measurement points and the radius of the minimum circumscribed circle (LSC (Least Squares Circle) least squares center method). Other methods for calculating roundness include the MZC (Minimum Zone Circle) minimum zone center method, the MCC (Minimum Circumscribed Circle) minimum circumscribed circle center method, and the MIC (Maximum Inscribed Circle) maximum inscribed circle center method. Although the present invention does not limit the calculation method, it is preferable to apply the relatively widely used LSC least squares center method. It is preferable to measure eight points on the circumference of the circular part of the object to be measured, dividing the circumference into eight equal parts. It is preferable to use the circularity calculated from these eight measurement points using the above method.

[0022] As described above, the tantalum carbide coated material of one embodiment of the present invention has at least one cross section whose outline is circular. For example, when the tantalum carbide coated material of one embodiment of the present invention is a crucible, the crucible has a cylindrical shape, and the outline of the cross section perpendicular to the central axis of the cylindrical shape is circular. Therefore, a cylindrical crucible has at least one cross section whose outline is circular. Furthermore, when the tantalum carbide coated material of one embodiment of the present invention is a susceptor, the susceptor has a disk shape, and the outline of the cross section perpendicular to the central axis of the disk shape is circular. Therefore, a disk-shaped susceptor has at least one cross section whose outline is circular. Furthermore, when the tantalum carbide coated material of one embodiment of the present invention is a guide material, the guide material has a cone shape, and the cross section perpendicular to the central axis of the cone shape is circular. Therefore, a cone-shaped guide material has at least one cross section whose outline is circular. Furthermore, when the tantalum carbide coated material of one embodiment of the present invention is cylindrical, the outer periphery of the cross section perpendicular to the central axis of the cylindrical shape is circular. Therefore, the cylindrical tantalum carbide coated material has at least one cross section whose outer periphery is circular. The tantalum carbide coated material of one embodiment of the present invention is not particularly limited as long as it has at least one cross section whose outer periphery is circular, and may be hemispherical or semi-elliptical.

[0023] A tantalum carbide-coated material according to one embodiment of the present invention has at least one cross section with a circular outline, and the circularity of the circular shape is 0.01 mm to 1.2 mm. If the circularity is greater than 1.2 mm, the flow of the source gas may be uneven when forming the tantalum carbide coating, resulting in insufficient coverage of the circular portion of the metal carbide-coated material with the metal carbide coating. Furthermore, the crystal growth yield of single crystals obtained using a manufacturing apparatus incorporating the metal carbide-coated material may be reduced. If the circularity is less than 0.1 mm, the processing precision of the carbon substrate must be extremely high, increasing the manufacturing cost of the carbon substrate. From this perspective, the circularity is preferably 0.01 mm to 0.8 mm, more preferably 0.01 mm to 0.4 mm, and even more preferably 0.01 mm to 0.2 mm. The circularity of the tantalum carbide coated material of one embodiment of the present invention can be controlled by adjusting the circular cross-sectional circularity of the circular portion of the carbon substrate so that it falls within the above range. Therefore, if the circularity of the cross-sectional outline of the circular portion of the carbon substrate is greater than 1.2 mm, it is preferable to process the carbon substrate so that the circularity of the cross-sectional outline of the circular portion of the carbon substrate is 1.2 mm or less, and then form a tantalum carbide coating film on the surface of the carbon substrate. It has been considered that the circularity of conventional crucibles, guide materials, and susceptors does not need to be increased. Therefore, from the perspective of manufacturing costs, the circularity of the cross-sectional outline of the circular portion of the circular crucible, guide material, and susceptor has been greater than 1.2 mm. Furthermore, when the tantalum carbide coating film covers only a portion of the carbon substrate, it is sufficient that the circularity of the outline of the circular cross section of the portion of the metal carbide coating material that is covered with the tantalum carbide coating film is within the above-mentioned range, and it is not necessary that the circularity of the outline of the circular cross section of all portions of the metal carbide coating material be within the above-mentioned range.

[0024] The tantalum carbide coating material of one embodiment of the present invention has at least one cross section whose outline is circular, and the diameter of the circle is usually 100 mm or more and 400 mm or less, preferably 150 mm or more and 390 mm or less, more preferably 160 mm or more and 380 mm or less, and even more preferably 170 mm or more and 370 mm or less.

[0025] The linear thermal expansion coefficient of the carbon substrate is preferably 5.2 x 10 -6 / ℃ or more 7.2×10 -6 / °C or less. The linear thermal expansion coefficient of the carbon substrate is 5.2 × 10 -6 / ℃ or more 7.2×10 -6 / ° C. or less, the occurrence of microcracks in the tantalum carbide coating film can be further suppressed. The linear thermal expansion coefficient of the carbon substrate can be measured in accordance with JIS R 1618.

[0026] The arithmetic mean roughness Ra of the surface of the carbon substrate affects the growth of semiconductor single crystals and epitaxial growth. The larger the arithmetic mean roughness Ra of the surface of the carbon substrate, the greater the peel strength between the carbon substrate and the tantalum carbide coating film, which is preferable. On the other hand, if the arithmetic mean roughness Ra of the surface of the carbon substrate is too large, the specific surface area increases, which can cause cracks and peeling, shortening the product life when used as a component for the growth of semiconductor single crystals and epitaxial growth. From this perspective, the linear thermal expansion coefficient of the carbon substrate is preferably 5.2 × 10 -6 / ℃ or more 7.2×10 -6 / ° C. or less. The arithmetic mean roughness Ra of the surface of the carbon substrate is a value measured in accordance with JIS B 0633:2001 (ISO 4288:1996).

[0027] The tantalum carbide coating material according to one embodiment of the present invention is an example of the carbide coating material of the present invention, and the carbide coating material of the present invention is not limited to the tantalum carbide coating material. Furthermore, the carbide of the carbide coating material of the present invention is not limited to tantalum carbide. Examples of the carbide of the carbide coating material of the present invention include tantalum carbide, niobium carbide, zirconia carbide, hafnium carbide, and tungsten carbide. These carbides can be used alone or in combination of two or more. Among these carbides, tantalum carbide is preferred because it has the highest melting point and is excellent in chemical stability, strength, and corrosion resistance.

[0028] The products used in the tantalum carbide coated material of one embodiment of the present invention described above are a crucible, a guide material, and a susceptor, but the products used in the metal carbide coated material of the present invention are not limited to a crucible, a guide material, and a susceptor. [Example]

[0029] The present invention will be explained in more detail below by showing examples, but the present invention is not limited to these examples.

[0030] The measurement and evaluation methods in the present examples are as follows. (roundness) The circularity of the circular portions of the tantalum carbide coated materials of the examples and comparative examples was measured using a three-dimensional measuring machine (Crysta-Apex C544) manufactured by Mitutoyo Corporation. Measurements were taken at eight points, dividing the circumference into eight equal parts, for the circular portions of the tantalum carbide coated materials of the examples and comparative examples, and the circularity was calculated from these eight measurement points using the LSC least squares center method.

[0031] (linear thermal expansion coefficient of carbon substrate) The linear thermal expansion coefficient of the carbon substrate was measured in accordance with JIS R 1618. A thermomechanical analyzer (TMA7300) manufactured by Hitachi High-Tech Science Corporation was used, and the linear thermal expansion coefficient value in the temperature range from 200°C to 1200°C was used.

[0032] (Arithmetic mean roughness Ra of the carbon substrate surface) The arithmetic mean roughness Ra of the surface of the carbon substrate was measured based on JIS B 0633:2001 (ISO 4288:1996).

[0033] (SiC single crystal growth yield) <Crucible> The fabricated crucible 21 and guide member 22 were placed in a reduced-pressure heating furnace 20, and a SiC single crystal was grown by sublimation recrystallization. A SiC raw material 25 was placed in the crucible 21, and a SiC seed crystal 24 was placed above it. Argon gas was introduced into the reduced-pressure heating furnace 20 at a flow rate of 10 to 30 SLM, and the pressure was set to 500 to 1000 Pa and the temperature to 2000 to 2500°C. The SiC raw material 25 was sublimated, and a SiC single crystal was grown on the SiC seed crystal 24. If the polytype of the resulting single crystal was 4H-SiC, it was deemed acceptable; otherwise, it was deemed unacceptable. One hundred SiC seed crystals 24 were evaluated as acceptable or unacceptable, and the yield was calculated from the number of acceptable SiC seed crystals 24.

[0034] (SiC single crystal growth yield) <Susceptor> The fabricated susceptor 30 was placed in a vacuum heating furnace, a SiC substrate was placed on the susceptor, and an epitaxial reaction was carried out on the surface of the SiC substrate. After the reaction, a defect inspection was carried out on the SiC seed crystal formed on the SiC substrate. 2 A defect-free area rate of 99% or more in the device area was judged to be pass, and a defect-free area rate of less than 99% was judged to be fail. One hundred SiC substrates were evaluated as pass or fail, and the yield was calculated from the number of pass SiC substrates.

[0035] Tantalum carbide coated materials of Examples 1 to 18 and Comparative Examples 1 and 2 were produced as follows. Example 1 First, isotropic graphite was processed into a cylindrical shape of φ300 (crucible 21 in FIG. 2), which was used as the carbon substrate 14. The arithmetic mean roughness Ra of the surface of this carbon substrate 14 was 6.0 μm, and the linear thermal expansion coefficient of the carbon substrate 14 was 7.2×10 -6 / ℃.

[0036] Next, two carbon substrates 14 were placed in the reaction chamber 12 of the reduced-pressure CVD apparatus 10. The carbon substrates 14 were supported by a support means 15 having three supporting portions with pointed tips. At this time, the tips of the supporting portions were in contact with the outer surface of the carbon substrate 14 in the case of a bottomed cylindrical shape, and with the lower surface of the carbon substrate 14 in the case of a disk shape.

[0037] Next, 0.25 SLM of methane (CH4) gas, 1.0 SLM of argon (Ar) gas, 0.125 SLM of hydrogen (H2) gas as a carrier gas, and 0.25 SLM of tantalum pentachloride (TaCl5) that had been heated to a temperature of 220°C and vaporized were supplied from the raw material supply unit 16, and a reaction was carried out at a pressure of 100 Pa and a temperature of 1250°C in the reaction chamber 12, forming a tantalum carbide coating film on the entire surface of the carbon substrate 14, thereby producing a tantalum carbide-coated material.

[0038] The circularity of the tantalum carbide coated material of Example 1 was measured to be 0.01 mm. When this was used in growing SiC single crystals, the yield was investigated to be 86%.

[0039] Example 2 A tantalum carbide coated material was produced in the same manner as in Example 1, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.19 mm, and the yield of SiC single crystal growth was 56%.

[0040] Example 3 A tantalum carbide coated material was produced in the same manner as in Example 1, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.38 mm, and the yield in growing SiC single crystals was 48%.

[0041] Example 4 A tantalum carbide coated material was produced in the same manner as in Example 1, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.79 mm, and the yield in growing SiC single crystals was 36%.

[0042] Example 5 A tantalum carbide coated material was produced in the same manner as in Example 1, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 1.19 mm, and the yield in growing SiC single crystals was 21%.

[0043] Example 6 Linear thermal expansion coefficient is 5.2 x 10 -6 A carbon substrate 14 having a temperature of 1000 K / °C was used. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 1. The circularity of the circular portion of the tantalum carbide coated material was 0.01 mm, and the yield of SiC single crystal growth was 76%.

[0044] Example 7 Linear thermal expansion coefficient is 5.2 x 10 -6 A carbon substrate with a temperature of 1000 K / °C was used. Except for this, a tantalum carbide-coated material was produced in the same manner as in Example 1. The circularity of the circular portion of the tantalum carbide-coated material was 1.19 mm, and the yield of SiC single crystal growth was 19%.

[0045] Example 8 The arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 0.5 μm. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 1. The circularity of the circular portion of the tantalum carbide coated material was 0.01 mm, and the yield of SiC single crystal growth was 73%.

[0046] Example 9 The arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 0.5 μm. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 1. The circularity of the circular portion of the tantalum carbide coated material was 1.19 mm, and the yield of SiC single crystal growth was 18%.

[0047] (Comparative Example 1) A tantalum carbide coated material was produced in the same manner as in Example 1, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 1.49 mm, and the yield in growing SiC single crystals was 11%.

[0048] Example 10 Isotropic graphite was processed into a roughly circular disk shape (susceptor 30) with a diameter of 300 mm, which was used as the carbon substrate 14. The same procedure as in Example 1 was otherwise performed, and a tantalum carbide coating film was formed on the entire surface of the carbon substrate 14 to produce a tantalum carbide-coated material. The circular portion of the tantalum carbide-coated material had a circularity of 0.01 mm. This was used in growing SiC single crystals, and the yield was investigated and found to be 78%.

[0049] Example 11 A tantalum carbide coated material was produced in the same manner as in Example 10, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.18 mm, and the yield in growing SiC single crystals was 69%.

[0050] Example 12 A tantalum carbide coated material was produced in the same manner as in Example 10, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.39 mm, and the yield in growing SiC single crystals was 63%.

[0051] Example 13 A tantalum carbide coated material was produced in the same manner as in Example 10, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 0.76 mm, and the yield in growing SiC single crystals was 56%.

[0052] Example 14 A tantalum carbide coated material was produced in the same manner as in Example 10, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 1.20 mm, and the yield of SiC single crystal growth was 48%.

[0053] Example 15 Linear thermal expansion coefficient is 5.2 x 10 -6 A carbon substrate 14 having a temperature of 1000 K / °C was used. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 10. The circularity of the circular portion of the tantalum carbide coated material was 0.01 mm, and the yield of SiC single crystal growth was 71%.

[0054] Example 16 Linear thermal expansion coefficient is 5.2 x 10 -6 A carbon substrate 14 having a temperature of 1000 K / °C was used. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 10. The circularity of the circular portion of the tantalum carbide coated material was 1.20 mm, and the yield of SiC single crystal growth was 44%.

[0055] Example 17 The arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 0.5 μm. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 10. The circularity of the circular portion of the tantalum carbide coated material was 0.01 mm, and the yield of SiC single crystal growth was 69%.

[0056] Example 18 The arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 0.5 μm. Except for this, a tantalum carbide coated material was produced in the same manner as in Example 10. The circularity of the circular portion of the tantalum carbide coated material was 1.20 mm, and the yield of SiC single crystal growth was 40%.

[0057] (Comparative Example 2) A tantalum carbide coated material was produced in the same manner as in Example 10, except that the circularity of the carbon substrate 14 was changed when processing the carbon substrate 14. The circularity of the circular portion of the tantalum carbide coated material was 1.51 mm, and the yield in growing SiC single crystals was 32%.

[0058] The evaluation results of the tantalum carbide coated materials of Examples 1 to 18 and Comparative Examples 1 and 2 are shown in Tables 1 and 2. [Table 1]

[0059] [Table 2]

[0060] Comparing the results of Examples 1 to 9 with the results of Comparative Example 1, it was found that when a tantalum carbide coating material was used for the crucible, the yield of SiC single crystal growth could be improved by setting the circularity of the circular part of the crucible to 0.01 mm or more and 1.2 mm or less. Comparing the results of Examples 10 to 18 with the results of Comparative Example 2, it was found that when a tantalum carbide coating material was used for the susceptor, the yield of SiC single crystal growth could be improved by setting the circularity of the circular part of the susceptor to 0.01 mm or more and 1.2 mm or less. [Explanation of symbols]

[0061] 10. Externally heated low-pressure CVD equipment 11 Top Chamber 12 Reaction chamber 13 Heater 14 Carbon substrate 15 Support means 16 Raw material supply department 17 Exhaust section 20 SiC single crystal growth equipment 21 Crucible 22 Guide member 23 Upper lid 24 SiC seed crystal 25 SiC raw material 30 susceptor 31 susceptor edge 32 wafer placement surface

Claims

1. A metal carbide coated material comprising a carbon substrate containing carbon as a main component and a metal carbide coating film containing metal carbide as a main component, the metal carbide coating film coating at least a portion of the carbon substrate, The metal carbide coating material has at least one cross section whose outline is circular; The metal carbide coated material has a circularity of 0.01 mm or more and 1.2 mm or less.

2. 2. The metal carbide coated material according to claim 1, wherein the circular shape has a circularity of 0.01 mm or more and 0.8 mm or less.

3. 2. The metal carbide coated material according to claim 1, wherein the circular shape has a circularity of 0.01 mm or more and 0.4 mm or less.

4. 2. The metal carbide coated material according to claim 1, wherein the circular shape has a circularity of 0.01 mm or more and 0.2 mm or less.

5. The carbon substrate has a linear thermal expansion coefficient of 5.2×10 －６ / ℃ or more 7.2 × 10 －６ 2. The metal carbide coated material according to claim 1, wherein the temperature is 100°C or less.

6. 2. The metal carbide coated material according to claim 1, wherein the arithmetic mean roughness Ra of the surface of the carbon substrate is 0.5 μm or more and 6.0 μm or less.

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