TW202436210A - Titanium carbide coated carbon material - Google Patents

Abstract

The present invention is a tantalum carbide coated carbon material, which is characterized by comprising: a carbon substrate with carbon as a main component, and a tantalum carbide coating covering at least a portion of the carbon substrate; and the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 15 mass ppm or more, and the iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 20 mass ppm or less. According to the present invention, a tantalum carbide coated carbon material with excellent corrosion resistance can be provided.

Description

Titanium carbide coated carbon material

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

Carbides such as tantalum carbide and niobium carbide have high melting points and excellent chemical stability, strength, toughness and corrosion resistance. Therefore, by coating a carbon substrate with carbides, the heat resistance, chemical stability, strength, toughness, corrosion resistance and other properties of the carbon substrate can be improved. Carbide-coated carbon materials, especially tantalum carbide-coated carbon materials, which are formed by coating a carbide film on the surface of a carbon substrate, are used as components of single crystal manufacturing devices for next-generation semiconductors such as SiC (silicon carbide), GaN (gallium nitride), and AlN (aluminum nitride).

The problem of next-generation semiconductors is that the manufacturing cost is higher than that of conventional Si semiconductors. As a method to further reduce the manufacturing cost, for example, the single crystal of the next-generation semiconductor can be manufactured by the HTCVD (High Temperature Chemical Vapor Deposition) method. In this method, since the raw material gas reacts at a high temperature, it is required to further improve the corrosion resistance of the carbon material coated with tantalum carbide. For example, in the HTCVD method that can manufacture single crystals of SiC at a high speed, since gases such as _H2 , _SiH4 , _C3H8 , and HCl are used at a temperature of 2000~ ₂₅₀₀ °C, the carbon material coated with tantalum carbide is required to have excellent corrosion resistance compared to the general SiC sublimation method (see non-patent documents 1 and 2).

So far, attempts have been made to improve the corrosion resistance of tantalum carbide coated carbon materials by various methods. For example, Patent Document 1 improves the corrosion resistance of tantalum carbide coated carbon materials by containing iron at a concentration of 20 to 1000 mass ppm in the tantalum carbide film coated on an isotropic graphite substrate. In addition, Patent Document 2 improves the corrosion resistance by reducing the crystallinity of the tantalum carbide film coated on the carbon substrate. [Prior Technical Document] [Patent Document]

[Patent Document 1] Japanese Patent No. 6888330 [Patent Document 2] Japanese Patent No. 3938361 [Non-patent Document]

[Non-patent document 1] "Current status and prospects of SiC wafers", Onda Masaichi, DENSO TECHNICAL REVIEW Vol.22, pp41-50(2017). [Non-patent document 2] "New materials, energy and semiconductor projects to achieve a low-carbon society", National Research and Development Agency, Electronics, Materials and Nanotechnology Division, ppIII-78-81(2015 data 5-1).

[Problems to be solved by the invention]

However, when using tantalum carbide coated carbon materials as components of next-generation semiconductor single crystal manufacturing equipment, the environment of the tantalum carbide coated carbon materials in the next-generation semiconductor single crystal manufacturing is very harsh. Therefore, after repeated manufacturing of next-generation semiconductor single crystals, the components using tantalum carbide coated carbon materials must be replaced. From the perspective of the manufacturing cost of next-generation semiconductors, the frequency of replacing components using tantalum carbide coated carbon materials is as low as possible. Therefore, it is desired to further improve the corrosion resistance of tantalum carbide coated carbon materials.

Therefore, the object of the present invention is to provide a tantalum carbide-coated carbon material having excellent corrosion resistance. [Means for solving the problem]

As a result of the research conducted by the inventors to solve this problem, they found that by reducing the iron concentration contained in the tantalum carbide film and setting the content of niobium within a specific range, the corrosion resistance of the tantalum carbide-coated carbon material can be significantly improved compared to the previous tantalum carbide-coated carbon material. By developing this result, the present invention described below was completed. The gist of the present invention is as follows. [1] A tantalum carbide-coated carbon material, characterized by comprising: a carbon substrate having carbon as a main component, and a tantalum carbide coating coating at least a portion of the carbon substrate; and the niobium content in the tantalum carbide coating is greater than 15 mass ppm as measured by fluorescence discharge mass spectrometry, and the iron content in the tantalum carbide coating is less than 20 mass ppm as measured by fluorescence discharge mass spectrometry. [2] The tantalum carbide-coated carbon material as described in [1] above, wherein the arithmetic mean roughness Ra of the surface of the tantalum carbide coating is greater than 0.1 μm and less than 10.0 μm. [3] A tantalum carbide-coated carbon material as described in [1] or [2] above, wherein the arithmetic mean roughness Ra of the surface of the carbon substrate is not less than 0.1 μm and not more than 9.5 μm. [4] A tantalum carbide-coated carbon material as described in any one of [1] to [3] above, wherein the number of tantalum atoms contained in the tantalum carbide coating is not less than 0.8 times and not more than 1.2 times the number of carbon atoms contained in the tantalum carbide coating. [5] A tantalum carbide-coated carbon material as described in any one of [1] to [4] above, wherein the thickness of the tantalum carbide coating is 10 to 100 μm. [Effect of the Invention]

According to the present invention, a tantalum carbide-coated carbon material having excellent corrosion resistance can be provided.

[Carbon material coated with titanium carbide]

The present invention is a tantalum carbide coated carbon material, comprising: a carbon substrate with carbon as a main component, and a tantalum carbide coating covering at least a portion of the carbon substrate; and the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 15 mass ppm or more, and the iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 20 mass ppm or less. Thus, the tantalum carbide coated carbon material of the present invention has excellent corrosion resistance.

(Carbon substrate) The carbon substrate in the tantalum carbide-coated carbon material 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 material include isotropic graphite, extruded graphite, pyrolytic graphite, and carbon fiber reinforced carbon composites (C/C composites). The shape and properties of the carbon substrate are not particularly limited, and the carbon substrate may be processed into any shape according to the application, etc.

<Arithmetic surface roughness Ra> The arithmetic average roughness Ra of the carbon substrate surface is preferably 0.1 μm to 9.5 μm. Since the surface roughness of the carbon substrate is reflected in the surface roughness of the tantalum carbide coating, if the arithmetic average roughness Ra of the carbon substrate surface is 0.1 μm to 9.5 μm, it is easy to make the arithmetic average roughness Ra of the surface of the tantalum carbide coating be 0.1 μm to 10.0 μm. Based on this viewpoint, the arithmetic average roughness Ra of the carbon substrate surface is more preferably 1.0 μm to 8.0 μm, and more preferably 2.0 μm to 6.0 μm. 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).

(Titanium carbide coating) The titanium carbide coating in the titanium carbide-coated carbon material of the present invention has titanium carbide as a main component and contains niobium. In addition, the titanium carbide coating does not contain iron, or when the titanium carbide coating contains iron, the iron content in the titanium carbide coating is very small.

<Niobium content> The niobium content in the tantalum carbide film measured by fluorescence discharge mass spectrometry is 15 mass ppm or more. If the niobium content in the tantalum carbide film is less than 15 mass ppm, the effect of niobium on the corrosion resistance of the carbon material coated with tantalum carbide may become insufficient. As a result, when the carbon material coated with tantalum carbide is used as a component of a single crystal manufacturing device for next-generation semiconductors such as SiC (silicon carbide), GaN (gallium nitride), and AlN (aluminum nitride), the replacement frequency of the component may not be sufficiently reduced, and the manufacturing cost of the next-generation semiconductor may not be reduced. Based on this viewpoint, the niobium content in the tantalum carbide film measured by fluorescence discharge mass spectrometry is preferably 20 mass ppm or more, more preferably 50 mass ppm or more, further preferably 100 mass ppm or more, further more preferably 200 mass ppm or more, further more preferably 300 mass ppm or more, further more preferably 400 mass ppm or more. In addition, the upper limit of the range of the niobium content in the tantalum carbide film measured by fluorescence discharge mass spectrometry is not particularly limited, but the niobium content in the tantalum carbide film measured by fluorescence discharge mass spectrometry is preferably 1000 mass ppm or less. Furthermore, from the viewpoint of further improving the corrosion resistance of the tantalum carbide coated carbon material, the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is preferably 900 mass ppm or less, further preferably 800 mass ppm or less, further preferably 700 mass ppm or less, further preferably 600 mass ppm or less, further preferably 500 mass ppm or less.

Fluorescence discharge mass spectrometry refers to the following method: in an argon environment, a sample is used as a cathode to generate a glow discharge, the sample surface is sputtered in plasma, the sputtered sample is ionized in the glow discharge, and the generated ions are analyzed by mass spectrometry. In this manual, the content of niobium in the tantalum carbide film is the average value of the content of niobium relative to the tantalum carbide film in the range of 20-80 mass% of the tantalum carbide film in the depth direction of the sputtered tantalum carbide film. In the range where the proportion of the sputtered tantalum carbide film is less than 20 mass%, it may be affected by impurities attached to the surface of the tantalum carbide film. On the other hand, when the ratio of the sputtered tantalum carbide film is greater than 80% by mass, there is a possibility that it will be affected by impurity elements originating from the carbon substrate. By setting the range of the niobium content in the tantalum carbide coating measured by EDS to the range of 20-80% by mass of the ratio of the sputtered tantalum carbide film, the influence of impurities attached to the surface of the tantalum carbide coating and the influence of impurity elements originating from the carbon substrate can be removed.

Specifically, the fluorescence discharge mass spectrometry method uses VG9000, ElementGD, and Astrum manufactured by VG Scientific, and performs analysis in the depth direction by Ar ⁺ sputtering. Here, when the horizontal axis is the number of sputtering times in the depth direction and the vertical axis is the impurity concentration, the point where the tantalum element concentration begins to decrease is regarded as the point where Ar ⁺ reaches the carbon substrate, that is, the point where the tantalum carbide film in the depth direction is completely sputtered, and the proportion of the sputtered tantalum carbide film at this point is set to 100 mass %. Next, the number of sputtering times within the range of 20 to 80% of the number of sputtering times at this time is regarded as equivalent to the ratio of the sputtered tantalum carbide film being in the range of 20 to 80 mass %, and the niobium content in the tantalum carbide coating film measured by the sputtering in the number of sputtering times is used to define the niobium content in the tantalum carbide coating film. For example, when the tantalum element concentration begins to decrease at the 60th sputtering, the 60th sputtering is regarded as 100 mass % of the tantalum carbide film being sputtered. Next, the average value of the niobium content in the tantalum carbide coating film measured at the 12th to 48th sputtering times corresponding to a ratio of the sputtered tantalum carbide film of 20 to 80 mass % is defined as the niobium content in the tantalum carbide coating film.

In the analysis of EDMS, the elements detected by one sputtering are the average values of all elements contained from the surface before the sputtering to the depth dug by the sputtering. Therefore, in the analysis value of the outermost surface after the analysis starts, not only the elements contained in the tantalum carbide film near the outermost surface, but also the elements derived from the outermost surface attachments may be detected. Similarly, when the sputtering depth reaches the carbon material of the substrate, impurity elements derived from the carbon substrate may also be detected. Therefore, in order to avoid the influence of the outermost surface attachments and the influence from the carbon substrate, the evaluation of the impurity concentration contained in the tantalum carbide coating is evaluated based on the detection value of the ratio of the sputtered tantalum carbide film in the range of 20~80 mass %, as described above.

The reason why the tantalum carbide-coated carbon material exhibits excellent corrosion resistance when the tantalum carbide coating contains niodium in the above-mentioned range is not clear, but is speculated as follows. It is known that in the case of a crystal structure in which the crystal orientation of tantalum carbide constituting the tantalum carbide coating is relatively uniform and specific crystal planes are developed, chemical and physical properties will be anisotropic. Therefore, when the tantalum carbide-coated carbon material is used for a long time at high temperature and in a reducing gas or reactive gas environment, a chemically or physically weak specific portion of the tantalum carbide coating will become a starting point for cracks or other damage caused by consumption, etc. (for example, refer to Patent Document 2). The carbon material coated with a tantalum carbide film of the present invention has a chaotic crystallinity compared to previous materials due to the presence of niobium in the tantalum carbide film, and the tantalum carbide film as a whole has a low crystallinity, close to a so-called amorphous state. Therefore, the anisotropy of chemical and physical properties is also reduced, and it is not easy for chemically or physically weak parts to exist on the surface of the tantalum carbide film. As a result, it can be inferred that the surface of the tantalum carbide film is not easily consumed even if it comes into contact with reducing gas or reactive gas, and it is not easy to produce cracks or damage caused by consumption. In addition, it is believed that the corrosion resistance of the tantalum carbide film is improved, and as a result, the corrosion resistance of the carbon material coated with tantalum carbide is also improved. Furthermore, the niobium in the tantalum carbide coating is not limited to its existing form. Niobium can exist in the tantalum carbide coating in any form, such as a niobium monomer or a niobium compound.

<Iron content> The iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 20 mass ppm or less. If the iron content in the tantalum carbide coating is greater than 20 mass ppm, the corrosion resistance of the tantalum carbide coated carbon material may be reduced. As a result, when the tantalum carbide coated carbon material is used as a component of a single crystal manufacturing device for next-generation semiconductors, the replacement frequency of the component becomes high, and the manufacturing cost of the next-generation semiconductors may increase. From this point of view, the iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is preferably 10 mass ppm or less, more preferably 1 mass ppm or less, further preferably 0.1 mass ppm or less, and further preferably 0.01 mass ppm or less. In addition, the lower limit of the range of the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is not particularly limited, for example, it is 0 mass ppm. In addition, the iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry can be measured in the same manner as the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry.

When the tantalum carbide coating contains iron in an amount exceeding the above range, the reason why the corrosion resistance of the carbon material coated with tantalum carbide deteriorates is not clear, but it is speculated as follows. It is speculated that when the iron content in the tantalum carbide coating is greater than 20 mass ppm, the tantalum carbide coating reacts with HCl and vaporizes under the high temperature of the HTCVD environment and in a reducing gas or reactive gas environment, and the tightness of the tantalum carbide coating is lost.

<Arithmetic mean roughness Ra> The arithmetic mean roughness Ra of the surface of the tantalum carbide coating is preferably 0.1 μm to 10.0 μm. If the arithmetic mean roughness Ra of the surface of the tantalum carbide coating is 0.1 μm to 10.0 μm, the adhesion to the substrate can be improved while maintaining the compactness of the tantalum carbide coating. From this point of view, the arithmetic mean roughness Ra of the surface of the tantalum carbide coating is more preferably 1.0 μm to 8.5 μm, and more preferably 2.0 μm to 6.5 μm. In addition, the arithmetic mean roughness Ra of the surface of the tantalum carbide coating 11 is a value measured based on JIS B 0633:2001 (ISO 4288:1996).

The arithmetic average roughness Ra of the surface of the tantalum carbide coating can be adjusted, for example, by adjusting the surface roughness of the carbon substrate. For example, when the film thickness of the tantalum carbide coating is about 20 μm, the surface roughness of the carbon substrate directly becomes the surface roughness of the tantalum carbide coating. In addition, after the tantalum carbide coating is formed on the carbon substrate, the arithmetic average roughness Ra of the surface of the tantalum carbide coating can be adjusted by grinding the surface of the tantalum carbide coating with an abrasive or a file.

<Thickness> The thickness of the tantalum carbide coating is preferably 10~1000μm. When the thickness of the tantalum carbide coating is 10μm or more, the corrosion resistance of the carbon material coated with tantalum carbide can be further improved. When the thickness of the tantalum carbide coating is 1000μm or less, the film forming time of the tantalum carbide coating can be shortened, and the production efficiency of the carbon material coated with tantalum carbide can be improved. From this point of view, the thickness of the tantalum carbide coating is more preferably 20~500μm, and more preferably 30~200μm.

<Multiples of the number of tantalum atoms relative to the number of carbon atoms> The number of tantalum atoms contained in the tantalum carbide coating is preferably 0.8 times or more and 1.2 times or less relative to the number of carbon atoms. When the number of tantalum atoms contained in the tantalum carbide coating is 0.8 times or more and 1.2 times or less relative to the number of carbon atoms, the corrosion resistance of the carbon material coated with tantalum carbide can be further improved. From this point of view, the number of tantalum atoms contained in the tantalum carbide coating is preferably 0.85 times or more and 1.15 times or less relative to the number of carbon atoms, and more preferably 0.9 times or more and 1.1 times or less. The number of tantalum atoms and the number of carbon atoms contained in the tantalum carbide coating can be estimated from the peak intensity measured by X-ray diffraction (XRD).

<XRD half-value width> The intensity of X-ray diffraction rays of the tantalum carbide coating can be obtained by 2θ/θ measurement (Out-of-Plane) using an X-ray diffraction device (XRD). A peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating can be observed near 2θ=40˚. The size of the crystallites constituting the tantalum carbide coating can be indicated by the half-value width of the peak. The half-value width increases due to the decrease in crystallinity (approaching amorphous), the refinement of the crystallites, and the unevenness of the composition. However, when the composition is stable, the crystallinity is good, and the crystallites are of a certain size, as in the tantalum carbide coating in the tantalum carbide-coated carbon material of the present invention, the half-value width falls within a certain range. As an index for specifying the tantalum carbide coating in the tantalum carbide-coated carbon material of the present invention, the half-value width is optimal.

The half-value width (FWHM) in X-ray diffraction is the angle difference of 2θ in half the value (fmax/2) of the maximum value (fmax) of the peak when the diffraction peak obtained from the (hkl) plane of the X-ray diffraction spectrum is fitted by the pseudo Voigt function. In this specification, including the embodiments described later, the half-value width is specified by this method. The half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating obtained in this way is preferably 0.6˚ or less, 0.5˚ or less, and more preferably 0.4˚ or less. When the half-value width is too large, the crystal grains are too small and the propagation of cracks etc. cannot be sufficiently prevented, or the low-crystallization amorphous structure crystallizes in a high-temperature environment and causes structural changes, which is not good. The lower limit of the half-value width is not particularly limited, and is preferably 0.01˚, and more preferably 0.1˚. If the half-value width is too small, the crystal grains become too large, and it is difficult to form a granular structure that is layered in a non-oriented manner. In addition, when the content of niobium in the tantalum carbide coating measured by fluorescence discharge mass spectrometry increases, the half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystals in the tantalum carbide coating increases.

(Manufacturing method of carbon material coated with tantalum carbide) Hereinafter, an example of the manufacturing method of the carbon material coated with tantalum carbide for heating of the present invention is described. The carbon material coated with tantalum carbide of the present invention can be manufactured, for example, by forming a tantalum carbide layer on the surface of a carbon substrate. The tantalum carbide layer can be formed on the surface of the carbon substrate by methods such as chemical vapor deposition (CVD), sintering, and carbonization. Among them, the CVD method is preferred as a method for forming a tantalum carbide layer because it can form a uniform and dense film.

In addition, among the CVD methods, there are thermal CVD methods, photo CVD methods, plasma CVD methods, and the like. For example, thermal CVD methods can be used to form a tantalum carbide layer. The thermal CVD method has advantages such as a relatively simple device structure and no damage caused by plasma. The formation of a tantalum carbide coating using the thermal CVD method can be performed, for example, using an external heating type reduced pressure CVD device 11 as shown in FIG. 1 . In the external heating type reduced pressure CVD device 11, 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, and the like.

An example of a method for manufacturing a tantalum carbide-coated carbon material of the present invention is described with reference to FIG. 1 and FIG. 2. First, a carbon substrate 14 is placed in a reaction chamber 12 of an externally heated reduced-pressure CVD device 11. The carbon substrate 14 is supported by a supporting means 15 having three supporting portions with pointed tips. As described above, the surface roughness Ra of the carbon substrate 14 is preferably greater than 0.1 μm and less than 9.5 μm.

Next, the reaction chamber 12 is heated. For example, the reaction chamber 12 is heated under reduced pressure and at a temperature of 1000 to 2500°C.

Then, a tantalum carbide layer 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 ) 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, for example, by reacting tantalum metal with a halogen gas. For example, in the metal chloride production device 21 shown in FIG. 2 , tantalum metal and a small amount of niobium metal 25 are filled into a container 24 and heated to 300° C. to 1200° C. by a heating device 23. At least one gas of chlorine gas and hydrogen chloride gas is supplied thereto, so that tantalum halide gas and niobium halide gas can be produced.

Next, the raw material gas supplied from the raw material supply unit 16 shown in FIG. 1 is subjected to a thermal CVD reaction at a high temperature of 1000 to 2500°C under reduced pressure to form a niobium-containing tantalum carbide layer on the carbon substrate 14. [Example]

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

The tantalum carbide-coated carbon materials of Examples 1 to 7 and Comparative Examples 1 to 2 were prepared as follows. (Example 1) First, a carbon substrate 14 was placed in a reaction chamber of an external thermal reduced pressure CVD device 11 shown in FIG. 1 . A cylindrical member made of isotropic graphite was used as the carbon substrate 14. The carbon substrate 14 was supported by a supporting means 15 having three supporting portions with pointed tips. The surface roughness Ra of the carbon substrate 14 was 5.0 μm.

Next, after the reaction chamber 12 is heated to a temperature of 1550°C, a mixed gas of TaCl ₅ gas and NbCl ₅ gas, CH ₄ gas and Ar gas are mixed and the resulting mixed gas is supplied to the reaction chamber 12 to form a tantalum carbide layer on the surface of the carbon substrate 14, thereby producing the tantalum carbide-coated carbon material of Example 1. The film formation time of the tantalum carbide layer is 3 hours. In addition, the flow rates of CH ₄ gas and carrier gas (Ar gas) are controlled to 1.0 SLM and 1.0 SLM respectively by mass flow controllers.

The mixed gas of TaCl ₅ gas and NbCl ₅ gas is produced as follows. In the metal chloride production device 21 shown in FIG. 2 , a quartz container 24 containing 1000 g of Ta metal and 0.10 g of Nb metal is arranged. Then, the Ta metal and the Nb metal are heated to 850° C. by the heating device 23, and the mixed gas of HCl gas and Cl ₂ gas is supplied to the metal chloride production device 21, so that the Ta metal and the Nb metal react with the mixed gas of HCl gas and Cl ₂ gas (HCl gas:Cl ₂ gas=1:1 (molar ratio)) to produce the mixed gas of TaCl ₅ gas and NbCl ₅ gas. The mixed gas of TaCl ₅ gas and NbCl ₅ gas is controlled to 0.25 SLM and supplied to the reaction chamber 12. Ta metal and Nb metal used have a purity of 99.999%. The thickness of the tantalum carbide layer is 40μm.

(Example 2) A titanium carbide-coated carbon material of Example 2 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 0.50 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Example 3) A tantalum carbide-coated carbon material of Example 3 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 1.00 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Example 4) A tantalum carbide-coated carbon material of Example 4 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 2.00 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Example ₅ ) A titanium carbide-coated carbon material of Example 5 was prepared in the same manner as in Example 1, except that 1000 g of Ta metal and 3.00 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Example 6) A tantalum carbide-coated carbon material of Example 6 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 4.00 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Example 7) A tantalum carbide-coated carbon material of Example 7 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 5.00 g of Nb metal _were placed in a quartz container 24 in order to generate a mixed gas of TaCl 5 gas and NbCl 5 gas.

(Comparative Example 1) A tantalum _{carbide -} coated carbon material of Comparative Example 1 was prepared in the same manner as in Example 1, except that 1000 _g of Ta metal and 5.00 g of Fe metal were placed in a quartz container 24 in order to produce a mixed gas of TaCl 5 gas and FeCl 3 gas instead of a mixed gas of TaCl _{5 gas and NbCl 5} gas.

(Comparative Example 2) A tantalum _carbide - _coated carbon material of Comparative Example 2 was prepared in the same manner as in Example 1, except that 1000 g of Ta metal was placed in the quartz container 24 in order to generate TaCl ₅ gas instead of the mixed gas of TaCl 5 gas and NbCl 5 gas.

The following evaluations were performed on the titanium carbide-coated carbon materials of Examples 1 to 7 and Comparative Examples 1 to 2 prepared in the above manner.

(Surface roughness Ra of tantalum carbide coating) The surface roughness Ra of tantalum carbide coating is measured based on JIS B 0633:2001 (ISO 4288:1996).

(Surface roughness Ra of carbon substrate) The surface roughness Ra of carbon substrate is measured based on JIS B 0633:2001 (ISO 4288:1996).

(The number of tantalum atoms in the tantalum carbide coating relative to the number of carbon atoms) The number of tantalum atoms and carbon atoms contained in the tantalum carbide coating is determined based on the peak intensity measured by X-ray diffraction (XRD).

(The content of niobium in the tantalum carbide coating measured by fluorescence discharge mass spectrometry) According to the method described in the above manual, the content of niobium in the tantalum carbide coating was measured by fluorescence discharge mass spectrometry.

(Iron content in tantalum carbide coating measured by fluorescence discharge mass spectrometry) According to the method described in the above manual, the iron content in tantalum carbide coating was measured by fluorescence discharge mass spectrometry.

(Half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating) The half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating was measured according to the method described in the above manual.

(Evaluation of durability in HTCVD) A schematic diagram of an HTCVD apparatus 30 is shown in FIG3 . First, a SiC single crystal 32 is grown on a seed crystal 33 in close contact with a supporting surface of a pedestal 35. Specifically, a raw material gas is thermally decomposed in a gas decomposition chamber in the HTCVD apparatus 30 and supplied to the seed crystal 33. Among the raw material gases, SiH ₄ gas, C ₃ H ₈ gas and HCl gas are used, and H ₂ gas is further used as a carrier gas. The C/Si ratio is set to about 1.0, and the growth pressure is set to 53 kPa. The surface temperature of the seed crystal 33 is 2200~2400°C, the reaction time is set to 6 hours, and the temperature of the crucible 31 of the gas decomposition chamber is set to 2300~2500°C. The carbon material coated with tantalum carbide of Examples 1 to 7 and Comparative Examples 1 to 2 was used as the crucible 31 of the gas decomposition chamber. The production of SiC single crystal was repeated many times, and the number of times the SiC single crystal was produced until the carbon material coated with tantalum carbide became unusable due to peeling of the tantalum carbide film was measured.

(Concentration of niobium in SiC single crystals produced by HTCVD) The concentration of niobium in SiC single crystals was calculated by secondary ion mass spectroscopy (SIMS).

(Iron concentration in SiC single crystal produced by HTCVD) The iron concentration in SiC single crystal was calculated by secondary ion mass spectrometry (SIMS).

The evaluation results are shown in Table 1. In addition, as an example of the distribution of the content of tantalum, carbon, niobium and iron in the tantalum carbide coating film from the surface to the depth direction measured by fluorescence discharge mass spectrometry, the measurement result of the tantalum carbide coating film of Example 4 is shown in FIG4. In addition, as an example of the XRD measurement result of the carbon material coated with tantalum carbide, the XRD measurement result of the carbon material coated with tantalum carbide of Example 4 is shown in FIG5. In addition, the relationship between the content of niobium in the tantalum carbide coating film measured by fluorescence discharge mass spectrometry and the half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating film is shown in FIG6. FIG. 7 shows the relationship between the content of niobium in the tantalum carbide coating film measured by fluorescence discharge mass spectrometry and the number of SiC single crystals produced until the tantalum carbide-coated carbon material became unusable.

From the evaluation results of the tantalum carbide-coated carbon materials of Examples 1 to 7 and Comparative Examples 1 to 2 shown in Table 1 and FIG. 7 , it can be seen that when the content of niobium in the tantalum carbide coating film measured by fluorescence discharge mass spectrometry is greater than 15 mass ppm and the content of iron in the tantalum carbide coating film measured by fluorescence discharge mass spectrometry is less than 20 mass ppm, the number of SiC single crystals produced until the tantalum carbide-coated carbon material cannot be used increases. It can be seen from this that when the content of niobium in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 15 mass ppm or more and the content of iron in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 20 mass ppm or less, the corrosion resistance of the carbon material coated with tantalum carbide is improved.

From the relationship between the niobium content in the tantalum carbide film measured by fluorescence discharge mass spectrometry and the half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystals in the tantalum carbide film shown in FIG6 , it can be seen that the niobium content in the tantalum carbide film can be inferred by measuring the half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystals in the tantalum carbide film.

11: External heating type decompression CVD device 12: Reaction chamber 13: Heater 14: Carbon substrate 15: Support means 16: Raw material supply unit 17: Exhaust unit 21: Metal chloride generation device 23: Heating device 24: Container (quartz container) 25: Tungsten metal and a small amount of Niobium metal 30: HTCVD device 31: Crucible 32: SiC single crystal 33: Seed crystal 35: Pedestal

[Figure 1] is a schematic diagram of an external heating type reduced pressure CVD device. [Figure 2] is a schematic diagram of a metal chloride generation device. [Figure 3] is a schematic diagram of an HTCVD device. [Figure 4] is a diagram showing the measurement results of the tantalum carbide coated carbon material in Example 4 obtained by fluorescence discharge mass spectrometry. [Figure 5] is the XRD measurement results of the tantalum carbide coated carbon material in Example 4. [Figure 6] is a diagram showing the relationship between the niobium content in the tantalum carbide coating film measured by fluorescence discharge mass spectrometry and the half-value width of the peak corresponding to the (200) plane of the tantalum carbide crystal in the tantalum carbide coating film. [Figure 7] is a graph showing the relationship between the content of niobium in the tantalum carbide coating measured by fluorescence discharge mass spectrometry and the number of SiC single crystals produced until the tantalum carbide-coated carbon material becomes unusable.

Claims (5)

A tantalum carbide coated carbon material, characterized in that it comprises: a carbon substrate with carbon as the main component, and a tantalum carbide coating covering at least a portion of the carbon substrate, the niobium content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 15 mass ppm or more, the iron content in the tantalum carbide coating measured by fluorescence discharge mass spectrometry is 20 mass ppm or less. The titanium carbide-coated carbon material of claim 1, wherein the arithmetic average roughness Ra of the surface of the titanium carbide coating is not less than 0.1 μm and not more than 10.0 μm. The titanium carbide-coated carbon material of claim 1 or 2, wherein the arithmetic average roughness Ra of the surface of the carbon substrate is not less than 0.1 μm and not more than 9.5 μm. The tantalum carbide-coated carbon material of claim 1 or 2, wherein the number of tantalum atoms contained in the tantalum carbide coating is 0.8 times or more and 1.2 times or less of the number of carbon atoms contained in the tantalum carbide coating. The tantalum carbide coated carbon material of claim 1 or 2, wherein the thickness of the tantalum carbide coating is 10-100 μm.