TW202505050A - Carbon material coated with carbide metal - Google Patents

Abstract

The present invention relates to a metal carbide-coated carbon material containing a carbon base material of which carbon is the main component and a metal carbide coating film which coats at least part of the carbon base material, wherein: the metal carbide constituting the metal carbide coating film is at least one metal carbide selected from the group consisting of tantalum carbide, niobium carbide, zirconium carbide, hafnium carbide, and tungsten carbide; the carbon base material contains at least one element selected from the group consisting of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur; and the total concentration made up of the concentrations of the aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur in the carbon base material is 10-10,000 mass ppm. The present invention makes it possible to provide a metal carbide-coated carbon material that can inhibit the generation of gas in a high-temperature environment.

Description

Carbon material coated with metal carbide

The present invention relates to a metal carbide-coated carbon material in which a metal carbide coating film is coated on the surface of a carbon substrate.

Wide band gap semiconductors, such as SiC and GaN, have higher insulation destructive electric field strength and excellent heat resistance than Si semiconductors, and are low loss, so they are suitable for power semiconductors. On the other hand, compared with Si semiconductors, the manufacturing cost of wide band gap semiconductor wafers is higher. Therefore, it is necessary to reduce the manufacturing cost of wide band gap semiconductor wafers. The cost of the crystallization growth step and epitaxial growth step of wide band gap semiconductors has a significant impact on the manufacturing cost of wide band gap semiconductor wafers. In order to reduce the manufacturing cost of wide band gap semiconductor wafers, it is necessary to improve the yield of these steps.

There are several factors that reduce the yield of the crystal growth step and epitaxial growth step of wide-gap semiconductors. One of them is the gas generated from the carbon substrate used as a crucible, guide member, and susceptor. It is believed that the gas is generated by the sublimation of the carbon substrate itself and the desorption of the hydrocarbon gas adsorbed on the carbon substrate. This gas is the cause of the change in crystal orientation during crystal growth, resulting in a reduction in yield.

As a countermeasure, a method of coating a carbon substrate with a metal carbide film can be cited. Metal carbides such as tantalum carbide, niobium carbide, zirconium carbide, tungsten carbide, etc. have high melting points and excellent chemical stability, strength, toughness and corrosion resistance. Therefore, by coating a carbon substrate with a metal carbide, the heat resistance, chemical stability, strength, toughness and corrosion resistance of the carbon substrate can be improved while suppressing gas generation.

Furthermore, it is known that the generation of gas can be suppressed by subjecting the carbon substrate itself to high-purity treatment. In fact, in Patent Document 1, a carbon substrate subjected to high-purity treatment is used, and in Non-Patent Document 1, it is shown that the gas desorbed from the carbon substrate when the temperature is increased can be reduced by subjecting the carbon substrate to high-purity treatment. [Prior Art Document] [Patent Document]

Patent document 1: Japanese Patent No. 5502721 [Non-patent document]

Non-patent document 1: Toyo Tan Co., Ltd. Special Graphite Products Catalog, URL: https://www.toyotanso.co.jp/Products/download/

[The problem that the invention wants to solve]

However, when the carbon substrate described in Patent Document 1 and the carbon substrate described in Non-Patent Document 1 coated with a metal carbide film are used in a wide-bandgap semiconductor manufacturing device, it is not possible to sufficiently suppress gas generation in the crystal growth step and the epitaxial growth step.

Therefore, the purpose of the present invention is to provide a carbon material coated with a carbide metal that can suppress the generation of gas in a high-temperature environment. [Means for solving the problem]

As a result of diligent research, the inventors of the present invention have found that by setting the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the carbonized substrate of the carbonized metal-coated carbon material to 10 mass ppm or more and 10000 mass ppm or less, the generation of gas from the carbonized metal-coated carbon material in a high temperature environment can be suppressed, thereby completing the present invention. The gist of the present invention is as follows. [1] A carbon material coated with a metal carbide, comprising: a carbon substrate having carbon as a main component, and a metal carbide coating covering at least a portion of the carbon substrate, the metal carbide constituting the metal carbide coating is at least one metal carbide selected from the group consisting of tantalum carbide, niobium carbide, zirconium carbide, tungsten carbide, the carbon substrate comprises at least one element selected from the group consisting of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur, The total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the carbon substrate is 10 mass ppm to 10,000 mass ppm. [2] The metal carbide-coated carbon material as described in [1] above, wherein the iron concentration in the carbon substrate is 1 mass ppm to 10,000 mass ppm. [3] The metal carbide-coated carbon material as described in [1] or [2] above, wherein the titanium concentration in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [4] A carbon material coated with a metal carbide as described in any one of [1] to [3] above, wherein the concentration of magnesium in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [5] A carbon material coated with a metal carbide as described in any one of [1] to [4] above, wherein the concentration of silicon in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [6] A carbon material coated with a metal carbide as described in any one of [1] to [5] above, wherein the concentration of calcium in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [7] A carbon material coated with a metal carbide as described in any one of [1] to [6] above, wherein the concentration of vanadium in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [8] A carbon material coated with a metal carbide as described in any one of [1] to [7] above, wherein the concentration of sodium in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [9] A carbon material coated with a metal carbide as described in any one of [1] to [8] above, wherein the concentration of potassium in the carbon substrate is 0.1 mass ppm to 10,000 mass ppm. [10] A carbon material coated with metal carbide as described in any one of [1] to [9] above, wherein the concentration of sulfur in the carbon substrate is 0.1 mass ppm or more and 10000 mass ppm or less. [11] A carbon material coated with metal carbide as described in any one of [1] to [10] above, wherein the thickness of the metal carbide coating is 10 μm or more and 100 μm or less. [12] A carbon material coated with metal carbide as described in any one of [1] to [11] above, wherein the arithmetic average roughness Ra of the surface of the metal carbide coating is 0.1 μm or more and 9.5 μm or less. [13] A carbon material coated with metal carbide as described in any one of the above [1] to [12], wherein the arithmetic average roughness Ra of the surface of the carbon substrate is not less than 0.1 μm and not more than 10.0 μm. [14] A carbon material coated with metal carbide as described in any one of the above [1] to [13], wherein the metal carbide constituting the metal carbide coating is tantalum carbide. [Effect of the Invention]

According to the present invention, a carbon material coated with a carbided metal capable of suppressing the generation of gas in a high-temperature environment can be provided.

The metal carbide-coated carbon material of the present invention is described by taking a tantalum carbide-coated carbon material as an example.

[Titanium carbide coated carbon material] The tantalum carbide coated carbon material of one embodiment of the present invention comprises: a carbon substrate having carbon as a main component, and a tantalum carbide coating coating at least a portion of the carbon substrate, the carbon substrate comprising at least one element selected from the group consisting of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur, and the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the carbon substrate is not less than 10 mass ppm and not more than 10000 mass ppm.

(Carbon substrate) The carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is a substrate having carbon as the main component. The carbon substrate may further contain chlorine. Examples of the carbon substrate include isotropic graphite, extruded graphite, pyrolytic graphite, carbon fiber reinforced carbon composite (C/C composite), etc. The shape and properties of the carbon substrate are not particularly limited, and any shape processed according to the application can be used.

<Total concentration of elements> The carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention contains at least one element selected from the group consisting of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur. Then, the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the carbon substrate is 10 mass ppm or more and 10000 mass ppm or less. If the total concentration of the above-mentioned elements is greater than 10,000 mass ppm, the amount of gas generated from the carbon substrate in a high temperature environment increases, and as a result, when the tantalum carbide-coated carbon material using the carbon substrate is used in a wide bandgap semiconductor manufacturing device, the yield of the wide bandgap semiconductor may decrease. In addition, if the total concentration of the above-mentioned elements is less than 10 mass ppm, the amount of gas generated from the carbon substrate in a high temperature environment cannot be reduced as much as when the total concentration of the above-mentioned elements is 10 mass ppm. That is, since the manufacturing cost of the carbon substrate increases due to setting the total concentration of the above-mentioned elements to less than 10 mass ppm, the cost of wafer manufacturing of wide bandgap semiconductors may not be sufficiently reduced. From this point of view, the total concentration of the above elements is preferably 15 mass ppm or more and 5000 mass ppm or less, and more preferably 20 mass ppm or more and 1000 mass ppm or less. In addition, the concentration of the above elements in the carbon substrate can be measured by the method described in the embodiment described below. In addition, the total concentration of the above elements can be adjusted, for example, by heating the carbon substrate at about 2000°C in a halogen gas to volatilize the above elements in the carbon substrate in the form of low-boiling halides. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Iron concentration> The iron concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 1 mass ppm or more and 10000 mass ppm or less. If the iron concentration is 10000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the iron concentration is 1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the iron concentration can be suppressed. From this point of view, the iron concentration is more preferably 1 mass ppm or more and 4000 mass ppm or less, more preferably 1 mass ppm or more and 1000 mass ppm or less, further preferably 1 mass ppm or more and 100 mass ppm or less, and further preferably 1 mass ppm or more and 50 mass ppm or less. In addition, the concentration of iron in the carbon substrate can be measured by the method described in the following embodiment. In addition, the concentration of iron can be adjusted, for example, by heating the carbon substrate at about 2000°C in a halogen gas to volatilize the iron in the carbon substrate in the form of low-boiling halides. Specifically, the method of removing impurities by chlorine is described in reference 1 (Nagata Kazuhiro, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

< Titanium concentration > The titanium concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10000 mass ppm or less. If the titanium concentration is 10000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the titanium concentration is 0.1 mass ppm or more, the cost increase of the carbon substrate caused by reducing the titanium concentration can be suppressed. From this point of view, the concentration of titanium is more preferably 0.1 mass ppm to 2000 mass ppm, more preferably 0.1 mass ppm to 1000 mass ppm, further preferably 0.1 mass ppm to 500 mass ppm, further preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm, further preferably 0.1 mass ppm to 3 mass ppm. In addition, the concentration of titanium in the carbon substrate can be measured by the method described in the examples described below. Furthermore, the concentration of titanium can be adjusted, for example, by heating the carbon substrate at about 2000°C in a halogen gas to volatilize the titanium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in Reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Magnesium concentration> The magnesium concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10000 mass ppm or less. If the magnesium concentration is 10000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the magnesium concentration is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the magnesium concentration can be suppressed. From this point of view, the concentration of magnesium is more preferably 0.1 mass ppm to 100 mass ppm, more preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm, further preferably 0.1 mass ppm to 2 mass ppm. In addition, the concentration of magnesium in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of magnesium can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the magnesium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Silicon concentration> The silicon concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the silicon concentration is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the silicon concentration is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the silicon concentration can be suppressed. From this point of view, the concentration of silicon is preferably 0.1 mass ppm to 1000 mass ppm, more preferably 0.1 mass ppm to 500 mass ppm, further preferably 0.1 mass ppm to 200 mass ppm, further preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 30 mass ppm. In addition, the concentration of silicon in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of silicon can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the silicon in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Calcium concentration> The calcium concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the calcium concentration is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the calcium concentration is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the calcium concentration can be suppressed. From this point of view, the concentration of calcium is more preferably 0.1 mass ppm to 2000 mass ppm, more preferably 0.1 mass ppm to 1000 mass ppm, further preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm. In addition, the concentration of calcium in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of calcium can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the calcium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Valium concentration> The vanadium concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the vanadium concentration is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the vanadium concentration is 0.1 mass ppm or more, the cost increase of the carbon substrate caused by reducing the vanadium concentration can be suppressed. From this point of view, the concentration of vanadium is more preferably 0.1 mass ppm to 1000 mass ppm, more preferably 0.1 mass ppm to 500 mass ppm, further preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm. In addition, the concentration of vanadium in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of vanadium can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the vanadium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Concentration of sodium> The concentration of sodium in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm to 10,000 mass ppm. If the concentration of sodium is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the concentration of sodium is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the concentration of sodium can be suppressed. From this point of view, the concentration of sodium is more preferably 0.1 mass ppm to 100 mass ppm, more preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, and further preferably 0.1 mass ppm to 5 mass ppm. In addition, the concentration of sodium in the carbon substrate can be measured by the method described in the following embodiment. In addition, the concentration of sodium can be adjusted, for example, by heating the carbon substrate at about 2000°C in a halogen gas to volatilize the sodium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Nagata Kazuhiro, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Potassium concentration> The potassium concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the potassium concentration is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the potassium concentration is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the potassium concentration can be suppressed. From this point of view, the concentration of potassium is preferably 0.1 mass ppm to 100 mass ppm, more preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm, further preferably 0.1 mass ppm to 2 mass ppm, further preferably 0.1 mass ppm to 1 mass ppm. In addition, the concentration of potassium in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of potassium can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the potassium in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Sulfur concentration> The sulfur concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10000 mass ppm or less. If the sulfur concentration is 10000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the sulfur concentration is 0.1 mass ppm or more, the cost increase of the carbon substrate caused by reducing the sulfur concentration can be suppressed. From this point of view, the sulfur concentration is preferably 0.1 mass ppm to 100 mass ppm, more preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, further preferably 0.1 mass ppm to 10 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm, further preferably 0.1 mass ppm to 2 mass ppm, further preferably 0.1 mass ppm to 1 mass ppm. In addition, the sulfur concentration in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the sulfur concentration can be adjusted, for example, by hydrogenating the carbon substrate to volatilize the sulfur in the carbon substrate in the form of hydrogen sulfide.

<Concentration of aluminum> The concentration of aluminum in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the concentration of aluminum is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the concentration of aluminum is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the concentration of aluminum can be suppressed. From this point of view, the concentration of aluminum is more preferably 0.1 mass ppm to 1000 mass ppm, more preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm. In addition, the concentration of aluminum in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of aluminum can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the aluminum in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Nickel concentration> The nickel concentration in the carbon substrate in the tantalum carbide-coated carbon material of one embodiment of the present invention is preferably 0.1 mass ppm or more and 10,000 mass ppm or less. If the nickel concentration is 10,000 mass ppm or less, the generation of gas from the carbon substrate in a high temperature environment can be further suppressed. In addition, if the nickel concentration is 0.1 mass ppm or more, the increase in the cost of the carbon substrate caused by reducing the nickel concentration can be suppressed. From this point of view, the concentration of nickel is more preferably 0.1 mass ppm to 1000 mass ppm, more preferably 0.1 mass ppm to 100 mass ppm, further preferably 0.1 mass ppm to 50 mass ppm, further preferably 0.1 mass ppm to 20 mass ppm, further preferably 0.1 mass ppm to 5 mass ppm. In addition, the concentration of nickel in the carbon substrate can be measured by the method described in the embodiments described below. In addition, the concentration of nickel can be adjusted, for example, by heating the carbon substrate at about 2000° C. in a halogen gas to volatilize the nickel in the carbon substrate in the form of a low-boiling halide. Specifically, the method of removing impurities by chlorine is described in reference 1 (Kazuhiro Nagata, Iron and Steel, Vol. 73, No. 9, pp1077-1081 (1987)).

<Arithmetic surface roughness Ra> The arithmetic average roughness Ra of the carbon substrate surface affects semiconductor single crystal growth and epitaxial growth. The larger the arithmetic average roughness Ra of the carbon substrate surface, the greater the peeling strength between the carbon substrate and the tantalum carbide coating, and the better. On the other hand, if the arithmetic average roughness Ra of the carbon substrate surface is too large, the specific surface area increases, which becomes a cause of cracking and peeling, and there is a possibility that the product life is shortened when used as a component for semiconductor single crystal growth and epitaxial growth. Therefore, from the perspective of the product life of the tantalum carbide-coated carbon material, the arithmetic average roughness Ra of the carbon substrate surface is preferably 10.0μm or less. If the cracking and peeling rate of the carbon substrate and the tantalum carbide coating are taken into consideration, the arithmetic average roughness Ra of the carbon substrate surface is preferably 0.1μm to 10.0μm, and more preferably 2.0μm to 6.0μm. In this way, the peeling strength of the carbon substrate and the tantalum carbide coating can be increased, which may extend the product life when used as a component for semiconductor single crystal growth and epitaxial growth. In addition, the arithmetic average roughness Ra of the carbon substrate surface is a value measured based on JIS B 0633: 2001 (ISO 4288: 1996).

<Linear thermal expansion coefficient> The linear thermal expansion coefficient of the carbon substrate is preferably 3.5×10 ^-6 /°C to 8.2×10 ^-6 /°C. If the linear thermal expansion coefficient of the carbon substrate is 3.5×10 ^-6 /°C to 8.2×10 ^-6 /°C, the microcracks in the tantalum carbide coating can be further suppressed. From this point of view, the linear thermal expansion coefficient of the carbon substrate is more preferably 5.0×10 ^-6 to 7.5×10 ^-6 /°C. In addition, the linear thermal expansion rate of the tantalum carbide coating is about 6.3×10 ^-6 /°C. The linear thermal expansion coefficient of the carbon substrate can be measured according to JIS R 1618.

(Titanium carbide coating) Titanium carbide coating is a film with tantalum carbide as the main component. In addition, the tantalum carbide coating may cover a part of the carbon substrate or the entire carbon substrate. In addition, the tantalum carbide coating may contain trace amounts of carbon and atoms other than tantalum within a range that does not hinder the effect of the present invention. For example, the tantalum carbide coating may contain impurity elements and doping elements other than carbon and tantalum at a concentration of 10,000 ppm by mass or less.

<Film thickness> If the thickness of the tantalum carbide coating is too thin, there is a concern that the gas generated from the carbon substrate passes through the tantalum carbide coating and has an adverse effect on the semiconductor single crystal. On the other hand, if the thickness of the tantalum carbide coating is too thick, the film formation time is prolonged and the film formation cost increases. Taking all these into consideration, the thickness of the metal carbide coating is preferably 10 μm to 100 μm, and more preferably 20 μm to 50 μm. In addition, the thickness of the tantalum carbide coating is a value measured based on observing the cross section of the tantalum carbide coating using a scanning electron microscope (SEM). Specifically, the film thickness of the cross section of the tantalum carbide film at any five locations is measured from an image of the cross section of the tantalum carbide film taken using a scanning electron microscope (SEM), and the average value is taken as the film thickness of the tantalum carbide film.

<Arithmetic surface roughness Ra> The arithmetic average roughness Ra of the surface of the tantalum carbide coating is preferably 0.1 μm to 9.5 μm, and more preferably 2.0 μm to 5.5 μm. If the value of the arithmetic average roughness Ra of the surface of the tantalum carbide coating is large, it may cause cracking and peeling in the same way as the carbon substrate, and there is a possibility that the product life will be shortened when used as a component for semiconductor single crystal growth and epitaxial growth. The arithmetic average roughness Ra of the surface of the newly formed tantalum carbide coating varies according to the arithmetic average roughness Ra of the surface of the carbon substrate, and tends to be slightly smaller than the arithmetic average roughness Ra of the surface of the carbon substrate. The arithmetic average roughness Ra of the surface of the tantalum carbide coating can also be controlled by polishing, etc., but the number of manufacturing steps increases, so it is better to select the arithmetic average roughness Ra of the surface of the carbon substrate according to the desired arithmetic average roughness Ra of the surface of the tantalum carbide coating. In addition, the arithmetic average roughness Ra here is a value measured based on JIS B0633: 2001 (ISO4288: 1996).

<Manufacturing method of tantalum carbide coated carbon material> The tantalum carbide coated carbon material of one embodiment of the present invention can be manufactured by forming a tantalum carbide layer on the surface of a carbon substrate. The tantalum carbide coating can be formed on the surface of the carbon substrate by, for example, chemical vapor deposition (CVD), sintering, carbonization, etc. Among them, the CVD method can form a uniform and dense tantalum carbide coating, and therefore is a preferred method for forming a tantalum carbide coating.

Furthermore, there are thermal CVD method, photo CVD method, plasma CVD method, etc. in the CVD method. For example, the thermal CVD method can be used to form the tantalum carbide layer. The thermal CVD method has a relatively simple apparatus structure and has advantages such as no damage to the carbon substrate caused by plasma. In the formation of the tantalum carbide coating using the thermal CVD method, for example, an external heating type reduced pressure CVD apparatus 10 can be used as shown in FIG. 1. In the external heating type reduced pressure CVD apparatus 10, a carbon substrate 14 is supported by a supporting means 15 in a reaction chamber 12 equipped with a heater 13, a raw material supply unit 16, an exhaust unit 17, etc.

Referring to FIG. 1 , a method for manufacturing a tantalum carbide-coated carbon material according to an embodiment of the present invention is described. First, a carbon substrate 14 is placed in a reaction chamber 12 of an external heating type reduced pressure CVD device 10. The carbon substrate 14 is supported by a supporting means 15 having three support portions with pointed front ends.

Next, the reaction chamber 12 is heated. For example, the reaction chamber 12 is heated at a pressure of 10-1000 Pa and a temperature of 800-2200°C.

Next, a tantalum carbide film is formed on the surface of the carbon substrate 14. As raw material gases, a gas of a compound containing carbon atoms such as methane (CH ₄ ), a hydrogen (H ₂ ) gas, and a tantalum halide gas such as tantalum pentachloride (TaCl ₅ ) are supplied from the raw material supply unit 16 to the reaction chamber 12. The tantalum halide gas can be produced by, for example, a method of heating and vaporizing tantalum halide or a method of reacting tantalum metal with a halogen gas. Next, the raw material gas supplied from the raw material supply unit 16 is subjected to a thermal CVD reaction at a high temperature of 800 to 2200° C. and a pressure of 1 to 1000 Pa to form a tantalum carbide film on the carbon substrate 14.

The tantalum carbide coated carbon material of one embodiment of the present invention described above is an example of the metal carbide coated carbon material of the present invention, and the metal carbide coated carbon material of the present invention is not limited to the tantalum carbide coated carbon material of one embodiment of the present invention. In the metal carbide coated carbon material of the present invention, the metal carbide constituting the metal carbide coating coating the carbon substrate is not limited to tantalum carbide. For example, carbides such as niobium carbide, zirconium carbide, arsenic carbide, and tungsten carbide can be used as the metal carbide constituting the metal carbide coating coating the carbon substrate. Furthermore, a combination of two or more metal carbides selected from the group consisting of tantalum carbide, niobium carbide, zirconium carbide, beryllium carbide and tungsten carbide can be used as a metal carbide constituting a carbide metal coating on a coated carbon substrate. In addition, among tantalum carbide, niobium carbide, zirconium carbide, beryllium carbide and tungsten carbide, tantalum carbide is preferred because it has the highest melting point, excellent chemical stability, strength and corrosion resistance. [Example]

Hereinafter, the present invention will be described in more detail with reference to embodiments, but the present invention is not limited thereto.

The carbon materials coated with carbide metal of Examples 1 to 14 and Comparative Examples 1 to 4 were prepared as follows. (Example 1) First, isotropic graphite doped with aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur was prepared. The isotropic graphite was processed into a cylindrical shape with an outer diameter of 40 mm, an inner diameter of 30 mm, and a height of 30 mm, and the same was made into a carbon substrate 14. The arithmetic mean roughness Ra of the surface of the carbon substrate was 6.0 μm, and the linear thermal expansion coefficient of the carbon substrate 14 was 7.0×10 ^-6 /°C. In addition, regarding the linear thermal expansion coefficient of the carbon substrate, a thermal mechanical analyzer (TMA7300) manufactured by Hitachi Advanced Technologies Co., Ltd. was used to measure the thermal expansion coefficient value in the temperature range from 200° C. to 1200° C.

Next, as shown in FIG. 1 , a carbon substrate 14 is placed in a reaction chamber 12 of an external heating type reduced pressure CVD apparatus 10. The carbon substrate 14 is supported by a supporting means 15 having three supporting portions with pointed tips. At this time, the front end of the supporting portion contacts the outer surface of the carbon substrate 14 in a conical cylindrical shape, contacts the outer surface of the carbon substrate 14 in a bottomed cylindrical shape, contacts the lower surface of the carbon substrate 14 in a disc shape, and contacts the outer surface in a cylindrical shape.

Next, methane (CH ₄ ) gas is supplied at a flow rate of 0.25 SLM, argon (Ar) gas as a carrier gas is supplied at a flow rate of 1.0 SLM, hydrogen (H ₂ ) gas is supplied at a flow rate of 0.125 SLM, and tantalum pentachloride (TaCl ₅ ) heated to a temperature of 220° C. and vaporized is supplied at a flow rate of 0.25 SLM from the raw material supply unit 16, and reacts at a pressure of 100 Pa and a temperature of 1250° C. in the reaction chamber 12, thereby forming a tantalum carbide coating on the entire carbon substrate 14.

The carbon substrate 14 coated with the tantalum carbide film is taken out from the reaction chamber 12, and a cylinder composed of the tantalum carbide coated carbon material is completed.

(Examples 2 to 5) Isotropic graphite doped with different amounts of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur was prepared. In addition, a cylinder was made in the same way as in Example 1 and the evaluation was performed.

(Example 6) A cylinder was produced in the same manner as in Example 1 except that the flow rate of hydrogen (H ₂ ) gas was changed to 0.15 SLM, the flow rate of tantalum pentachloride (TaCl ₅ ) was changed to 0.3 SLM, and the film formation time was shortened to set the film thickness to 10 μm, and the evaluation was performed.

(Example 7) A cylinder was produced in the same manner as in Example 1 except that the flow rate of hydrogen (H ₂ ) gas was changed to 0.15 SLM, the film forming time was prolonged and the film thickness was set to 50 μm, and the evaluation was performed.

(Example 8) The surface of the carbon substrate 14 was polished, and the arithmetic average roughness Ra of the surface of the carbon substrate 14 was set to 0.1 μm. In addition, a cylinder was made in the same way as in Example 1 and the evaluation was performed.

(Example 9) The surface of the carbon substrate 14 was subjected to sandblasting treatment by projecting an abrasive agent, and the arithmetic average roughness Ra of the surface of the carbon substrate 14 was set to 10 μm. In addition, a cylinder was made in the same way as in Example 1, and the evaluation was performed.

(Example 10) A cylinder was produced in the same manner as in Example 1 except that the metal chloride was changed from tantalum pentachloride (TaCl ₅ ) to niobium pentachloride (NbCl ₅ ) and supplied at a flow rate of 0.25 SLM, and the evaluation was performed.

(Example 11) A cylinder was produced in the same manner as in Example 1 except that the metal chloride was changed from tantalum pentachloride (TaCl ₅ ) to tantalum tetrachloride (HfCl ₄ ) and supplied at a flow rate of 0.25 SLM, and the evaluation was performed.

(Example 12) A cylinder was produced in the same manner as in Example 1 except that the metal chloride was changed from tantalum pentachloride (TaCl ₅ ) to zirconium tetrachloride (ZrCl ₄ ) and supplied at a flow rate of 0.25 SLM, and the evaluation was performed.

(Example 13) A cylinder was produced in the same manner as in Example 1 except that the metal chloride was changed from tungsten pentachloride (WCl ₅ ) to tungsten pentachloride (WCl ₅ ) and supplied at a flow rate of 0.25 SLM, and the evaluation was performed.

(Example 14) As the metal chloride, a mixture of tantalum pentachloride (TaCl ₅ ) and niobium pentachloride (NbCl ₅ ) (TaCl ₅ :NbCl ₅ =100:1) was supplied at a flow rate of 0.25 SLM. Otherwise, a cylinder was prepared in the same manner as in Example 1 and evaluated.

(Comparative Example 1) Isotropic graphite doped with different amounts of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur was prepared, the flow rate of hydrogen (H ₂ ) gas was changed to 0 SLM, the flow rate of tantalum pentachloride (TaCl ₅ ) was changed to 0.5 SLM, and a cylinder was made in the same manner as in Example 1, and the evaluation was performed.

(Comparative Example 2) Isotropic graphite doped with different amounts of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur was prepared, the film forming time was shortened, the film thickness of the tantalum carbide coating was changed to 2μm, and a cylinder was made in the same way as in Example 1, and the evaluation was performed.

(Comparative Example 3) Isotropic graphite doped with different amounts of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur was prepared, and the arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 32 μm. In addition, a cylinder was prepared in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

(Comparative Example 4) Isotropic graphite doped with different amounts of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur was prepared, and the arithmetic mean roughness Ra of the surface of the carbon substrate 14 was set to 0.05 μm. In addition, a cylinder was prepared in the same manner as in Example 1 and evaluated. The results are shown in Table 1.

The following evaluations were performed on the cylinders of Examples 1 to 14 and Comparative Examples 1 to 4. [Thickness of metal carbide coating] The cross section of the metal carbide coating was observed using a scanning electron microscope (SEM), and the thickness of the metal carbide coating was measured.

[Arithmetic average roughness Ra of the surface] Using SURFTEST SJ-210 manufactured by Mitutoyo Corporation, the arithmetic average roughness Ra of the surface of the carbon substrate and the surface of the metal carbide coating formed on the surface of the carbon substrate was measured.

[Element concentration in carbon substrate] <Determination of sulfur concentration> The sulfur concentration in the carbon substrate was determined using a trace sulfur analyzer (manufactured by Nitto Seiko Analytical Technology Co., Ltd., trade name "TS-100"). (1) Sample preparation method Cut the carbon material coated with metal carbide after film formation, peel off the metal carbide coating to make a state where only the carbon substrate exists. Wrap it in Teflon (registered trademark) sheets and coarsely crush it with a hammer. Then, pulverize the coarse powder with a _B4C mortar to prepare a sample for measurement. (2) Determination of sulfur concentration Burn 10 mg of the sample for measurement at 1000°C in an oxygen environment, analyze the generated SOx, and calculate the sulfur concentration in the carbon substrate.

<Concentration of Elements Other Than Sulfur> The metal concentration of the carbon substrate underlying the carbon material after the tantalum carbide coating was peeled off was measured using an ICP-MS analyzer (inductively coupled plasma mass spectrometer) (900°C thermal decomposition/gas analysis) (manufactured by Agilent Technologies, trade name "Agilent 7900") to measure the concentration of elements other than sulfur in the carbon substrate. (1) Measurement The carbon material coated with metal carbide was cut using the sample conditioning method, and the metal carbide coating was peeled off to form a state where only the carbon substrate was present. After it was wrapped in Teflon (registered trademark) sheets and coarsely crushed with a hammer, the coarse powder was finely pulverized with a _B4C mortar. More than 0.1 g of the fine powder was weighed into a microwave decomposition container and decomposed according to the following decomposition formula. In addition, air cool until the temperature drops to 40℃ between STEP. (Decomposition formula) STEP.1: HNO ₃ : 5 mL + H ₂ SO ₄ : 2.5 mL (80℃*2min, 60℃*3min, 220℃*20min, 230℃*30min) STEP.2: Add HClO ₄ : 0.5 mL (240℃*25min, 240℃*25min) Transfer the obtained solution to a 30mL crucible, heat at 380℃ and dry solidify. After drying and solidification, dissolve the metal residue with a small amount of nitric acid and cool it, then add a small amount of hydrofluoric acid and pure water to 10mL to prepare the measurement solution. (2) Concentration determination Using ICP-MS analysis equipment, the concentration of elements in the carbon substrate was determined from the obtained measurement solution under the following conditions. (Measurement conditions) Alkali and alkaline earth metals: Cool Plasma (RF power: 600W) Elements other than the above: Hot Plasma (RF power: 1500W)

[Measurement method of corrosion amount of carbon substrate] Figure 2 shows a cross-sectional view of the corrosion test device. Prepare a cylindrical carbon material 21 coated with carbide metal with an outer diameter of 40mm, an inner diameter of 30mm, and a height of 30mm. Cover it with a heat-resistant material 22 and place it in a quartz tube 23. Use high-frequency induction heating to raise the temperature to 2300℃, maintain the temperature for 2 hours after reaching the temperature, and then cool it down for 2 hours. The temperature of the heating element is measured by a radiation thermometer. At the beginning of heating, nitrogen is flowed in at a flow rate of 1.0SLM until the temperature starts to drop. Measure the weight of the carbon material coated with carbonized metal before and after heating, and take (weight after heating - weight before heating) × 100 as the weight change (mg) of the carbon material coated with carbonized metal.

In addition, the measurement temperature range of thermal desorption gas analysis (TDS) is up to 1500℃, and it is impossible to investigate the gas generated in the high temperature environment of 1600~2300℃ in the crystallization growth step and epitaxial growth step of wide-gap semiconductors. Therefore, by measuring the weight change of the carbon substrate, the gas generation in the high temperature environment is indirectly measured. In other words, if the weight change of the carbon substrate is large, the gas generation in the high temperature environment is also large. From the research results so far, it is understood that if the carbon substrate is heated to about 2200℃, the carbon substrate reacts with nitrogen to generate cyan, dicyan and other gases, resulting in the carbon substrate being corroded. Reference 2 (GJ TENNENHOUSE, JA MANGELS, JOURNAL OF MATERIALS SCIENCE LETTERS, 1, 1982, 282-284.) also records that cyanide gas is generated by the reaction of N ₂ and carbon. In addition, according to the above-mentioned non-patent document 1, it is believed that the result of TDS has reached saturation at 1500°C, and the generated gas such as hydrocarbons adsorbed on the carbon substrate itself will not cause such an impact in a high temperature environment of 1600~2300°C. Therefore, the weight change at 2300°C is observed to be generated by the reaction of N ₂ and carbon. In addition, it is believed that the difference in the amount of weight change is related to the metal contained in the substrate as a catalyst for the reaction.

[Method for measuring the adhesion strength of metal carbide coating] The adhesion strength of metal carbide coating is measured using a thin film adhesion strength tester (manufactured by Quad Group, trade name "Romulus"), as shown in Figure 3. The metal carbide coating 41 and the pin 46 are bonded with an adhesive 45, and the pin 46 is pressed with a pressing jig 44 to stretch the pin 46, and the stress when the metal carbide coating 41 is peeled off is measured. The measurement is performed 5 times, and the average value calculated 5 times is set as the adhesion strength of the metal carbide coating.

The manufacturing conditions of Examples 1 to 14 and Comparative Examples 1 to 4 are shown in Table 1.

The evaluation results of Examples 1 to 4 and Comparative Example 1 are shown in FIG. 4 , and the evaluation results of Examples 1 to 14 and Comparative Examples 1 to 4 are shown in Table 2.

Comparing the results of Examples 1 to 14 with the results of Comparison Examples 1 to 4, if the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the carbon substrate is greater than 10 mass ppm and less than 10,000 mass ppm, the weight change of the carbon material coated with the carbided metal is suppressed.

The results of Examples 1 to 4 and Comparative Example 1 are plotted against the weight change per corrosion test (2h) and the number of times used, and are shown in FIG4. When these are compared, when the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur in the carbon substrate is 10 mass ppm or more and 10000 mass ppm or less, the weight loss per test is almost unchanged even if the number of tests is increased. On the other hand, in the case of a composition such as Comparative Example 1, it is shown that the amount of weight loss becomes larger as the number of tests increases.

When comparing the results of Examples 1, 6, and 7 with the results of Comparative Example 2, when the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur in the carbon substrate is 10 mass ppm or more and 10000 mass ppm or less, and the film thickness of the tantalum carbide film is 10 μm or more and 100 μm or less, the weight change of the carbon material coated with the metal carbide is further suppressed. When the film thickness of the tantalum carbide film is less than 10 μm, the weight loss amount becomes larger. Furthermore, when the film thickness of the tantalum carbide coating exceeds 100 μm, the film formation time increases and the film formation cost increases, which is not preferable. Therefore, the film thickness of the tantalum carbide coating is preferably in the range of 10 μm to 100 μm.

Comparing the results of Examples 1, 8, and 9 with the results of Comparison Examples 3 and 4, when the total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium, and sulfur in the carbon substrate is from 10 mass ppm to 10,000 mass ppm, and the arithmetic average roughness Ra of the surface of the metal carbide coating is from 0.1 μm to 9.5 μm, or the arithmetic average roughness Ra of the surface of the carbon substrate is from 0.1 μm to 10.0 μm, the weight change of the carbon material coated with the metal carbide is further suppressed. When the arithmetic mean roughness Ra of the surface of the carbon substrate is greater than 10 μm, the weight loss amount becomes larger. When the arithmetic mean roughness Ra of the surface of the carbon substrate is less than 0.1 μm, the weight loss amount also becomes larger.

Comparing the results of Example 1 with those of Examples 10 to 14, when the metal carbide coating is a tantalum carbide coating, the weight change of the carbon material coated with the metal carbide is further suppressed.

10: External heating type decompression CVD device 11: Chamber top 12: Reaction chamber 13: Heater 14: Carbon substrate 15: Support means 16: Raw material supply unit 17: Exhaust unit 20: Schematic diagram of the installation of the corrosion resistance test device 21: Carbon material coated with metal carbide 22: Heat-resistant material 23: Quartz tube 24: Coil 41: Metal carbide coating 42: Carbon substrate 44: Pressing jig 45: Adhesive 46: Pin

[Figure 1] is a schematic diagram of an external thermal reduced pressure CVD device of this embodiment. [Figure 2] is a schematic diagram of the installation of the corrosion resistance test method of this embodiment. [Figure 3] is a schematic diagram used to illustrate the method for measuring the adhesion strength of the metal carbide coating of this embodiment. [Figure 4] is the result of the corrosion resistance test of the tungsten carbide coated carbon material of Examples 1 to 4 and Comparative Example 1.

Claims (14)

A carbon material coated with metal carbide, comprising: a carbon substrate with carbon as the main component, and a metal carbide coating covering at least a portion of the carbon substrate, The metal carbide constituting the metal carbide coating is at least one metal carbide selected from the group consisting of tantalum carbide, niobium carbide, zirconium carbide, tungsten carbide, The carbon substrate comprises at least one element selected from the group consisting of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur, The total concentration of aluminum, iron, magnesium, titanium, silicon, calcium, vanadium, nickel, sodium, potassium and sulfur in the aforementioned carbon substrate is not less than 10 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of iron in the carbon substrate is not less than 1 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of titanium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The carbon material coated with a carbide metal as claimed in claim 1, wherein the concentration of magnesium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of silicon in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The carbon material coated with metal carbide as claimed in claim 1, wherein the concentration of calcium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The carbon material coated with a carbide metal as claimed in claim 1, wherein the concentration of vanadium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of sodium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of potassium in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The metal carbide-coated carbon material of claim 1, wherein the concentration of sulfur in the carbon substrate is not less than 0.1 mass ppm and not more than 10000 mass ppm. The metal carbide coated carbon material as claimed in claim 1, wherein the thickness of the metal carbide coating is not less than 10 μm and not more than 100 μm. A carbon material coated with metal carbide as claimed in claim 1, wherein the arithmetic average roughness Ra of the surface of the metal carbide coating is not less than 0.1 μm and not more than 9.5 μm. The metal carbide-coated carbon material of claim 1, wherein the arithmetic average roughness Ra of the surface of the carbon substrate is not less than 0.1 μm and not more than 10.0 μm. A carbon material coated with metal carbide as claimed in claim 1, wherein the metal carbide constituting the aforementioned metal carbide coating is tantalum carbide.

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