Method for manufacturing tantalum carbide coated carbon material and compound semiconductor growth apparatus

Abstract

To provide a method for producing a carbon material coated with tantalum carbide capable of reducing an impurity concentration in a tantalum carbide coating film and to provide a compound semiconductor growth device using the carbon material coated with tantalum carbide produced by the method.SOLUTION: There is provided a method for producing a carbon material coated with tantalum 10 containing a carbon base material 12 mainly composed of carbon and a tantalum carbide coating film 11 for coating at least a part of the carbon base material 12, which comprises: a first step of generating a tantalum chloride gas by a reaction of a heated tantalum-containing metal and a chlorine-containing gas; and a second step of forming a tantalum carbide coating film on the surface of the carbon base material by reacting the tantalum chloride gas generated in the first step with a hydrocarbon-containing gas. There is provided a compound semiconductor growth device using a carbon material coated with tantalum carbide produced by the production method of the carbon material coated with tantalum carbide.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for producing a tantalum carbide-coated carbon material obtained by coating a tantalum carbide coating film on the surface of a carbon substrate, and a compound semiconductor growth apparatus using the tantalum carbide-coated carbon material produced by the method thereof. [Background technology]

[0002] Carbides such as tantalum carbide and niobium carbide have high melting points and excellent chemical stability, strength, toughness, and corrosion resistance. Therefore, coating a carbon substrate with a carbide can improve the properties of the carbon substrate, such as heat resistance, chemical stability, strength, toughness, and corrosion resistance. Carbide-coated carbon materials, particularly tantalum carbide-coated carbon materials, are used as components in equipment for manufacturing compound semiconductors such as SiC (silicon carbide), GaN (gallium nitride), and AlN (aluminum nitride).

[0003] In particular, in the fabrication of compound semiconductor single crystals as described above, components made of tantalum carbide-coated carbon material are sometimes exposed to environments exceeding 2000°C (Non-Patent Literature 1). Under such conditions, even tantalum carbide, which has a high melting point, sublimes and is consumed, albeit in very small amounts (Non-Patent Literature 2). Furthermore, in order to produce compound semiconductor single crystals with few defects, it is important to control the impurity concentration during crystal growth. Therefore, tantalum carbide-coated carbon material used under such conditions requires a low impurity concentration in the tantalum carbide coating film.

[0004] On the other hand, while there are several methods for producing tantalum carbide, such as carburizing, sintering, and chemical vapor deposition (CVD), the CVD method is advantageous because it allows for film thickness control and minimizes exposure of carbon material. In the case of the CVD method, it is known that a mixed gas of tantalum chloride gas and hydrocarbon gas is used as the growth source for tantalum carbide (Patent Document 1). [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Patent No. 3938361 [Non-patent literature]

[0006] [Non-Patent Document 1] "Sublimation Growth of SiC Single Crystals: Growth Parameters and Defect Generation," FED Journal, Vol. 11, pp. 11-15 (2000), Internet<URL:https: / / sicalliance.jp / data / doc / 1502344086_doc_5_0.pdf> [Non-Patent Document 2] "Carbide Coating," Momentive Technologies Japan Co., Ltd. website, Internet<URL:https: / / www.momentivetech.co.jp / products / carbide-coatings / > [Overview of the project] [Problems that the invention aims to solve]

[0007] When forming the above-mentioned tantalum carbide coating film on a carbon substrate using the CVD method, one method for supplying tantalum chloride gas is to heat and sublimate particulate TaCl5 solid, such as granules or powder (hereinafter referred to as the sublimation method). This method allows the use of already purified TaCl5 solid, and the purity of the raw material, which is a factor that increases the impurity concentration in the tantalum carbide coating film, can be increased.

[0008] On the other hand, solid TaCl5 absorbs moisture significantly, affecting weighing. Furthermore, the presence of moisture and heating in a Cl-containing environment makes the reaction system, including piping, susceptible to corrosion. In addition, if the raw material filling section is opened to the atmosphere after the process is complete, small amounts of chlorine are released into the environment, making tools, equipment, and other parts outside the reaction system susceptible to corrosion.

[0009] Therefore, when handling solid TaCl5, it is necessary to handle it in an environment such as a glove box where moisture has been thoroughly removed by vacuuming or filling with inert gas, which makes it difficult to handle. Furthermore, it is difficult to completely prevent contact between solid TaCl5 and the atmosphere when storing the raw material or introducing it into the reaction system. As a result, equipment inside and outside the reaction system corrodes, impurity elements originating from the equipment enter the reaction system and are incorporated into the tantalum carbide coating film.

[0010] From these perspectives, it is difficult to reduce the impurity concentration in tantalum carbide coatings using the sublimation method. The elemental concentrations of Al, Si, Ti, V, and Mo, which are often found in steel materials used in equipment and tools, are particularly important in tantalum carbide coatings. Because the chlorides of these elements have low boiling points (below 300°C), they are easily mixed into the tantalum chloride gas during the process of heating solid TaCl5 to generate tantalum chloride gas.

[0011] Therefore, the present invention aims to provide a method for producing a tantalum carbide-coated carbon material that can reduce the impurity concentration in the tantalum carbide-coated film, and a compound semiconductor growth apparatus using the tantalum carbide-coated carbon material produced by this method. [Means for solving the problem]

[0012] The inventors diligently researched and experimented to solve this problem, and as a result, discovered that using tantalum chloride gas obtained by supplying chlorine-containing gas to a heated tantalum-containing metal (hereinafter referred to as the reaction method) reduces the impurity concentration in the tantalum carbide coating film more effectively than using tantalum chloride gas obtained by sublimation. This led to the completion of the present invention. The gist of the present invention is as follows. [1] A method for producing a tantalum carbide coated carbon material comprising a carbon substrate mainly composed of carbon and a tantalum carbide coating film covering at least a portion of the carbon substrate, the method comprising: a first step of generating tantalum chloride gas by reacting a heated tantalum-containing metal with a chlorine-containing gas; and a second step of forming a tantalum carbide coating film on the surface of the carbon substrate by reacting the tantalum chloride gas generated in the first step with a hydrocarbon-containing gas. [2] A method for producing a tantalum carbide coated carbon material according to [1] above, characterized in that the heating temperature of the tantalum-containing metal is 200 to 800°C. [3] The method for producing a tantalum carbide coated carbon material according to [1] or [2] above, characterized in that the first step is to react the tantalum-containing metal with the chlorine-containing gas under a pressure of 80 kPa abs or less. [4] A method for producing a tantalum carbide coated carbon material according to any one of [1] to [3] above, characterized in that the tantalum-containing metal used is a tantalum-containing metal having a tantalum content of 99.9% by weight or more. [5] A method for producing a tantalum carbide coated carbon material according to any one of [1] to [4] above, characterized in that the tantalum-containing metal used is particulate or crushed tantalum-containing metal having a maximum particle diameter of 0.5 to 20 mm. [6] A method for producing a tantalum carbide coated carbon material according to any one of [1] to [5] above, characterized in that in the first step, the tantalum-containing metal is held in a container and at least a portion of the material of the container is quartz. [7] A method for producing a tantalum carbide coated carbon material according to any one of [1] to [6] above, characterized in that the hydrocarbon-containing gas is a gas containing at least one alkane gas selected from the group consisting of methane gas, ethane gas, propane gas, and butane gas. [8] A compound semiconductor growth apparatus characterized by using a tantalum carbide-coated carbon material manufactured by the method for manufacturing a tantalum carbide-coated carbon material described in any one of [1] to [7] above. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for manufacturing a tantalum carbide-coated carbon material capable of reducing the impurity concentration in the tantalum carbide coating film, and a compound semiconductor growth apparatus using the tantalum carbide-coated carbon material manufactured by the manufacturing method. In particular, the element concentrations of Al, Si, Ti, V, and Mo in the tantalum carbide coating film are low, which is suitable for use as a semiconductor single crystal growth member.

[0014] Also, in the sublimation method, the rate-determining step of the tantalum chloride gas supply amount is the sublimation of tantalum chloride solid. On the other hand, in the reaction method, the rate-determining step of the tantalum chloride gas supply amount is the reaction between the heated tantalum-containing metal and chlorine. According to the present invention, by increasing the reactivity by increasing the chlorine gas flow rate and the heating temperature, more tantalum chloride can be supplied than in the sublimation method, and the film formation thickness per hour of the tantalum carbide coating film can be increased.

[0015] Furthermore, the tantalum chloride solid serving as a tantalum source in the sublimation method absorbs moisture and easily deteriorates under the atmospheric pressure of normal temperature and pressure. Therefore, it is necessary to handle the tantalum chloride solid in an environment such as a glove box in which moisture has been sufficiently removed by evacuation or filling with an inert gas. On the other hand, in the case of the present invention, the tantalum-containing metal serving as a tantalum source does not absorb moisture under the atmospheric pressure of normal temperature and pressure. Therefore, according to the present invention, the labor of the operator is reduced from the viewpoint of handling such as weighing the tantalum source.

Brief Description of Drawings

[0016] [Figure 1] FIG. 1 is a schematic cross-sectional view illustrating a tantalum carbide-coated carbon material according to the present embodiment. [Figure 2] FIG. 2 is a schematic view of a heating device used when manufacturing the tantalum carbide-coated carbon material according to the present embodiment. [Figure 3] FIG. 3 is a schematic view of the arrangement of pipes, devices, etc. from the raw materials to the reaction furnace used when manufacturing the tantalum carbide-coated carbon material according to the present embodiment. [Modes for carrying out the invention]

[0017] [Method for manufacturing tantalum carbide coated carbon material] Referring to the figure, a method for producing a tantalum carbide-coated carbon material according to one embodiment of the present invention will be described. The present invention is a method for producing a tantalum carbide-coated carbon material comprising a carbon substrate mainly composed of carbon and a tantalum carbide coating film that covers at least a part of the carbon substrate, and is characterized by comprising a first step of generating tantalum chloride gas by reacting a tantalum-containing metal heated at a heating temperature with a chlorine-containing gas, and a second step of forming a tantalum carbide coating film on the surface of the carbon substrate by reacting the tantalum chloride gas generated in the first step with a hydrocarbon-containing gas.

[0018] The tantalum carbide-coated carbon material 10, which is the subject of the method for manufacturing the tantalum carbide-coated carbon material according to one embodiment of the present invention, includes a carbon substrate 12 mainly composed of carbon and a tantalum carbide coating film 11 that covers at least a portion of the carbon substrate 12. The tantalum carbide-coated carbon material 10 has higher durability at high temperatures compared to a carbon material of the same type and shape without the tantalum carbide coating film 11, and can be suitably used in growth apparatuses for compound semiconductor single crystals and growth apparatuses for compound semiconductor substrates.

[0019] As shown in Figure 1, the tantalum carbide coated carbon material 10 is a tantalum carbide coated carbon material comprising a carbon substrate 12 and a tantalum carbide coating film 11 that covers at least a portion of the carbon substrate 12, characterized in that the tantalum carbide coating film 11 is formed of a compound of Ta and C, including TaC and Ta2C.

[0020] The carbon substrate 12 is a substrate whose main component is carbon. Examples of materials for the carbon substrate 12 include isotropic graphite, extruded graphite, pyrolytic graphite, and carbon fiber reinforced carbon composite materials (C / C composite). The shape and properties of the carbon substrate 12 are not particularly limited, and it can be processed into any shape depending on the application.

[0021] The thermal expansion coefficient of the carbon substrate 12 is preferably 0.2 to 9.3 × 10-6 The temperature is / ℃. The thermal expansion coefficient of the carbon substrate 12 is 0.2~9.3 × 10 -6 At a temperature of / °C, the occurrence of microcracks on the surface of the tantalum carbide-coated carbon material can be further suppressed. From this viewpoint, the coefficient of thermal expansion of the carbon substrate 12 is more preferably 3.0 to 9.3 × 10 -6 The temperature is / ℃, and more preferably 5.8~6.5×10 -6 It is / ℃.

[0022] (First step) In the first step, tantalum chloride gas is produced by the reaction of a heated tantalum-containing metal with a chlorine-containing gas. Figure 2 is a schematic diagram of a heating device 21 that carries out the first step of a method for manufacturing a tantalum carbide-coated carbon material according to one embodiment of the present invention. The heating device 21 consists of a container 23, a heater 24, a first step raw material piping 25, a first step product supply piping 26, and a purge piping 27, and the container 23 can be filled with tantalum-containing metal 22.

[0023] As shown in Figure 2, the tantalum-containing metal used in the first step of the method for manufacturing a tantalum carbide-coated carbon material in one embodiment of the present invention is filled into a container 23 and heated by a heater 24. The heater 24 can be heated using resistance heating or induction heating. In Figure 2, insulation materials, valves in the piping, flow meters, etc. are not shown, but by appropriately installing these, it is possible to reduce power consumption and control the introduced gas.

[0024] When heating the tantalum-containing metal in the first step, the heating temperature is preferably 200 to 800°C. If the heating temperature of the tantalum-containing metal is 200°C or higher, the reaction between the tantalum-containing metal and the chlorine-containing gas can proceed sufficiently, and tantalum chloride gas can be sufficiently generated. If the heating temperature of the tantalum-containing metal is 800°C or lower, it is possible to suppress significant corrosion of metal equipment such as piping. From this viewpoint, the heating temperature of the tantalum-containing metal is more preferably 300 to 700°C, and even more preferably 200 to 600°C.

[0025] In the first step, it is preferable to react the tantalum-containing metal with a chlorine-containing gas under negative pressure, particularly at a pressure of 80 kPa abs or less. Specifically, when heating the tantalum-containing metal, it is desirable to maintain a negative pressure inside the container 23. By reducing the pressure, the tantalum chloride produced in the first step is more likely to exist as a gas, preventing solidification of tantalum chloride in the piping and blockage of the piping. In particular, keeping the pressure inside the container 23 at 80 kPa abs or less is preferable because it prevents solidification of tantalum chloride gas and blockage of the piping. From this viewpoint, the pressure when reacting the tantalum-containing metal with the chlorine-containing gas is more preferably 70 kPa abs or less, and even more preferably 60 kPa abs or less. The lower limit of the pressure range when reacting the tantalum-containing metal with the chlorine-containing gas is not particularly limited, but is usually 5 kPa abs.

[0026] It is desirable to use a tantalum-containing metal having a tantalum content of 99.9% by weight or more. If the tantalum purity is low and other metal elements are mixed in with the tantalum-containing metal, these other metal elements will react with chlorine gas and be introduced into the reactor. As a result, the impurity concentration in the tantalum carbide coating increases, and the tantalum carbide-coated carbon material becomes of low quality as a semiconductor single crystal growth material. Therefore, if the tantalum content of the tantalum-containing metal is 99.9% by weight or more, the quality of the tantalum carbide-coated carbon material can be further improved.

[0027] It is preferable to use crushed or granular tantalum-containing metal with a maximum particle diameter of 0.5 to 20 mm as the tantalum-containing metal. In other words, it is preferable that the maximum particle diameter of the tantalum-containing metal is 0.5 to 20 mm. If powdered tantalum-containing metal with a maximum particle diameter of 0.5 mm or more is used, it will be physically blown away by the introduced chlorine gas and reach the inside of the reaction furnace, which can suppress the formation of a non-uniform tantalum carbide film. Furthermore, if crushed tantalum-containing metal with a maximum particle diameter of 20 mm or less is used, it becomes easier to adjust the weight to the target weight when weighing before filling the container. In addition, the void ratio becomes smaller when filling the container, the volume that requires heating can be reduced, and the number of power sources can be reduced. From this viewpoint, the maximum particle diameter of the tantalum-containing metal is more preferably 1 to 10 mm, and even more preferably 2 to 5 mm. The maximum diameter of the tantalum-containing metal particles is determined by randomly selecting 20 tantalum-containing metals from the group, measuring the maximum diameter of each of the selected 20 tantalum-containing metals using calipers, and taking the average of the measured maximum diameters as the maximum diameter of the tantalum-containing metal.

[0028] Examples of chlorine-containing gases used in the first step include hydrogen chloride gas, chlorine gas, TaCl5 gas, and NbCl5 gas. These chlorine-containing gases can be used individually or in combination of two or more. Among these chlorine-containing gases, hydrogen chloride gas and chlorine gas are preferred, with chlorine gas being more preferred.

[0029] It is preferable that at least a portion of the material of the container 23 that holds the tantalum-containing metal 22 used in the first step is quartz. Since the container 23 filled with the tantalum-containing metal 22 is exposed to chlorine, the container material must not be corroded by chlorine from the viewpoint of reducing the impurity concentration mentioned above. Examples of such materials include nickel-based alloys such as Inconel and Hastelloy, and quartz. However, if a nickel-based alloy is used as the container material, it becomes impossible to use a radiation thermometer to measure the temperature of the tantalum-containing metal. In that case, temperature control would have to be done using a thermocouple, but in this case, temperature variations occur depending on the position where the thermocouple is attached and the degree to which the tantalum-containing metal 22 is filled, making control difficult. For this reason, it is desirable to fill the tantalum-containing metal 22 into a container 23 in which at least a portion is made of quartz. This makes it possible to directly measure the temperature of the tantalum-containing metal 22 from the quartz portion using a radiation thermometer.

[0030] In the heating device 21 used in the first process, it is preferable to have a purge pipe 27 installed in parallel with the container 23. The purge pipe 27 is installed to connect the first process raw material supply pipe 25 and the first process product supply pipe 26. When chlorine is passed through common piping materials such as SUS, the pipe may corrode depending on the temperature environment. Furthermore, if a pipe through which chlorine-containing gas has been passed is opened to the atmosphere, the moisture in the atmosphere reacts with the chlorine-containing gas to produce hydrogen chloride, which further accelerates corrosion. Since this occurs inside the pipe, it cannot be judged from the outside, and it is difficult to estimate that it is due to impurities. Therefore, as a countermeasure against this pipe corrosion, when chlorine-containing gas is flowed through the first process raw material supply pipe 25, the container 23, and the first process product supply pipe 26, and then the container 23 is opened to the atmosphere, an inert gas can be introduced into the first process raw material supply pipe 25, the purge pipe 27, and the first process product supply pipe 26. This makes it possible to continue introducing an inert gas into the first process raw material supply pipe 25 and the first process product supply pipe 26 even when the container 23 is opened to the atmosphere, thus avoiding contact between the inside of the pipes exposed to chlorine and moisture in the atmosphere.

[0031] As shown in Figure 2, the container 23 constituting the heating device 21 can be connected to the first process raw material supply pipe 25 and the first process product supply pipe 26. This allows chlorine-containing gas to be introduced from the first process raw material supply pipe 25, and the tantalum-containing metal 22 heated by the heater 24 inside the container 23 reacts with the chlorine-containing gas to produce tantalum chloride. The resulting tantalum chloride is supplied to the reactor through the first process product supply pipe 26.

[0032] (Second step) In the second step, the tantalum chloride gas produced in the first step is reacted with a hydrocarbon-containing gas to form a tantalum carbide coating film on the surface of the carbon substrate.

[0033] Figure 3 shows a schematic diagram of the equipment used to produce a tantalum carbide coated carbon material 10 by forming a tantalum carbide coating film 11 on a carbon substrate 12. Note that the arrangement in Figure 3 is just one example, and configurations with different orientations, such as the orientation of the heating device 21 or the connection positions of each pipe to the reactor 31, are also included as part of one embodiment of the present invention.

[0034] For example, tantalum chloride gas and hydrocarbon-containing gas supplied from the first-step product supply pipe 26 shown in Figure 3 are reacted in a reactor 31 at a high temperature of 1000 to 2500°C under reduced pressure to form a tantalum carbide coating film 11 on a carbon substrate 12.

[0035] It is preferable to use a hydrocarbon-containing gas that contains at least one alkane gas selected from the group consisting of methane, ethane, propane, and butane, and it is more preferable to use a gas containing methane from the viewpoint of high gas diffusivity. The proportion of at least one alkane gas selected from the group consisting of methane, ethane, propane, and butane in the hydrocarbon-containing gas is preferably 70% by volume or more, more preferably 80% by volume or more, even more preferably 90% by volume or more, and even more preferably 95% by volume or more. The upper limit of the range of the proportion of at least one alkane gas selected from the group consisting of methane, ethane, propane, and butane in the hydrocarbon-containing gas is, for example, 100% by volume.

[0036] Multiple heating devices 21 may be installed in relation to the reactor 31. This increases the flow rate of tantalum chloride supplied to the reactor 31, thereby increasing the thickness of the tantalum carbide coating film 11 formed per hour, and thus is cost-effective.

[0037] The method for producing a tantalum carbide-coated carbon material according to one embodiment of the present invention is an example of the method for producing a tantalum carbide-coated carbon material according to the present invention, and does not limit the method for producing a tantalum carbide-coated carbon material according to the present invention.

[0038] [Compound semiconductor growth equipment] The compound semiconductor growth apparatus of the present invention is characterized by using a tantalum carbide-coated carbon material manufactured by the method for manufacturing tantalum carbide-coated carbon material of the present invention. As described above, the tantalum carbide-coated carbon material manufactured by the method for manufacturing tantalum carbide-coated carbon material of the present invention has a low impurity concentration. Therefore, the compound semiconductor growth apparatus of the present invention can further reduce defects in the compound semiconductor compared to a compound semiconductor growth apparatus using conventional tantalum carbide-coated carbon material. [Examples]

[0039] The present invention will be described more specifically below with reference to examples, but the present invention is not limited to these examples.

[0040] The tantalum carbide-coated carbon materials of Examples 1 to 21 and Comparative Example 1 were prepared as follows. (Example 1) First, the carbon substrate 12 was placed inside the reactor 31. A cylindrical member made of isotropic graphite was used as the carbon substrate 12. The surface roughness Ra of the carbon substrate 12 was 5.0 μm. Next, the reactor 31 was heated, and the carbon substrate 12 was heated to 1000°C. Simultaneously, the heater 24 of the heating device 21 was heated, and the tantalum-containing metal 22, which had been pre-filled in the container 23, was heated to 200°C. The heating method was induction heating. The pressure inside the container 23 was set to 78 kPa abs, and the tantalum-containing metal 22 used had a tantalum weight of 99.9% and a maximum particle diameter of 7.0 mm. The maximum particle diameter of the tantalum-containing metal 22 was derived by randomly sampling about 20 particles and calculating the average of the maximum diameters of each particle. Furthermore, container 23 was made of quartz, and temperature control was performed using an infrared thermometer. Next, chlorine-containing gas was introduced into container 23 through the first-process raw material supply pipe 25 to generate tantalum chloride, and the generated tantalum chloride was introduced into reactor 31 through the first-process product supply pipe 26. At the same time, a gas mainly composed of methane gas was introduced into reactor 31 from the hydrocarbon gas supply pipe 32. In addition, Ar gas was introduced from the adjustment gas source 34. Chlorine gas was used as the chlorine-containing gas. The introduced gas was controlled so that the concentrations of chlorine gas in the chlorine-containing gas, methane gas in the hydrocarbon-containing gas, and Ar gas were 0.1 SLM, 1.0 SLM, and 1.0 SLM, respectively. In this example, Ar gas is introduced as a carrier gas from a regulating gas source, but it is also possible to connect and operate multiple regulating gas sources 34. Examples of suitable gases include inert gases such as N2 gas and Ar gas, and H2 gas, which reduces the decomposition rate of tantalum chloride gas. The above state was maintained for 1 hour, and a tantalum carbide coating film 11 was formed on the carbon base material 12 to produce the tantalum carbide-coated carbon material 10 of Example 1.

[0041] Regarding the elemental analysis of the produced tantalum carbide-coated carbon material 10, analysis was performed using glow discharge mass spectrometry (hereinafter referred to as GDMS). In GDMS, trace element analysis can be performed with high sensitivity on a solid tantalum carbide coating film, so this analysis method was selected. In GDMS analysis, sputtering is repeatedly performed from the surface of the tantalum carbide coating film toward the carbon base material, and mass spectrometry of the elements released from the sample is performed. Therefore, it can be said that the elements detected when the sputtering count is small are distributed on the outermost surface side of the tantalum carbide coating film, and the elements detected when the sputtering count is large are distributed on the carbon material side of the tantalum carbide coating film. In the GDMS analysis of this case, it was determined that the depth reached the carbon base material at the sputtering count (denoted as X fin. ) when the C element concentration began to increase. Also, the elements detected in the first sputtering are considered to be located on the outermost surface of the tantalum carbide coating film, and the elements detected in the (X fin. - 1)-th sputtering are considered to be located near the carbon base material of the tantalum carbide coating film. Therefore, using the film thickness T TaC μm of the tantalum carbide coating film obtained as described later, the sputtering resolution during measurement was set to T TaC / (X fin. - 1) μm, and the position of the element measured in the X-th sputtering in the tantalum carbide coating film was set to T TaC × X / (X fin. - 1) μm.

[0042] When GDMS is performed in the depth direction as described above, the impurity concentration is high in the initial stages of the analysis. This is thought to be due to impurities adhering to the sample during handling. Similarly, when the analysis depth reaches the carbon substrate, impurity elements originating from the carbon substrate are detected. Furthermore, the surface of tantalum carbide sputtered in GDMS analysis is not uniform in the depth direction; it is shallower near the sputtering edge and deeper near the center. Therefore, even if you intend to analyze the area corresponding to 1 μm from the outermost surface of the tantalum carbide, you are actually detecting elements contained within 1 μm from the outermost surface.

[0043] Therefore, in the evaluation of GDMS in this invention, the elements detected in the tantalum carbide coating film at a sputtering count corresponding to a thickness of 5 μm from the outermost surface toward the carbon substrate, and at a sputtering count corresponding to 5 μm from the interface between the tantalum carbide coating film and the carbon substrate toward the outermost surface, were excluded from the evaluation, and the average value of the portion excluding the above was taken as the elemental concentration contained in the tantalum carbide coating film. This allows us to exclude the influence of impurity elements that are attached to the outermost surface and not located inside the tantalum carbide film, as well as impurity elements originating from the carbon substrate, and to discuss the elements contained within the tantalum carbide film. In other words, when used as a semiconductor single crystal growth material, it is possible to examine the impurity elements that may be released in conjunction with the consumption of the tantalum carbide film.

[0044] The fabricated tantalum carbide-coated carbon material 10 was cut, and its cross-section was observed using a scanning electron microscope (SEM) to measure the thickness of the tantalum carbide coating film 11. The thickness of the tantalum carbide coating film 11 formed per unit time was also calculated.

[0045] (Example 2) Except for heating the tantalum-containing metal 22 to 400°C, the same procedure as in Example 1 was performed to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0046] (Example 3) Except for heating the tantalum-containing metal 22 to 600°C, the same procedure as in Example 1 was performed to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0047] (Example 4) Except for heating the tantalum-containing metal 22 to 800°C, the same procedure as in Example 1 was performed to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0048] (Example 5) Except for heating the tantalum-containing metal 22 to 180°C, the same procedure as in Example 1 was performed to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0049] (Example 6) Except for heating the tantalum-containing metal 22 to 820°C, the same procedure as in Example 1 was performed to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0050] (Example 7) The same procedure as in Example 1 was followed, except that the pressure inside container 23 was set to 12 kPa abs, to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0051] (Example 8) The same procedure as in Example 1 was followed, except that the pressure inside container 23 was set to 42 kPa abs, to prepare and evaluate a tantalum carbide-coated carbon material 10.

[0052] (Example 9) The same procedure as in Example 1 was performed, except that the pressure inside container 23 was set to 85 kPa abs, to prepare and evaluate the tantalum carbide-coated carbon material 10.

[0053] (Example 10) The same procedure as in Example 1 was followed, except that the pressure inside container 23 was set to 90 kPa abs, to prepare and evaluate the tantalum carbide-coated carbon material 10.

[0054] (Example 11) For the tantalum-containing metal 22, a material with a tantalum content of 99.0% by weight was used. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0055] (Example 12) For the tantalum-containing metal 22, a material with a tantalum content of 95.0% by weight was used. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0056] (Example 13) For the tantalum-containing metal 22, a particle with a maximum diameter of 0.4 mm was used. The maximum diameter of the tantalum-containing metal 22 was adjusted by using a sieve with 0.4 mm holes. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0057] (Example 14) For the tantalum-containing metal 22, a particle with a maximum diameter of 0.6 mm was used. The maximum diameter of the tantalum-containing metal 22 was adjusted by using a sieve with 0.6 mm holes. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0058] (Example 15) For the tantalum-containing metal 22, a particle with a maximum diameter of 3.8 mm was used. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0059] (Example 16) For the tantalum-containing metal 22, grains with a maximum diameter of 19 mm were used. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0060] (Example 17) For the tantalum-containing metal 22, grains with a maximum diameter of 23 mm were used. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0061] (Example 18) A container 23 made of Hastelloy was used as container 23. Temperature control was performed using a thermocouple, and the temperature of container 23 was set to the temperature of the tantalum-containing metal 22. The tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0062] (Example 19) A gas mainly composed of ethane was selected as the hydrocarbon gas to be introduced into the reactor 31. For other aspects, the tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0063] (Example 20) A gas mainly composed of propane was selected as the hydrocarbon gas to be introduced into the reactor 31. For the rest of the process, the tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0064] (Example 21) A gas mainly composed of butane was selected as the hydrocarbon gas to be introduced into the reactor 31. For the rest of the process, the tantalum carbide-coated carbon material 10 was prepared and evaluated using the same procedure as in Example 1.

[0065] (Comparative Example 1) In Comparative Example 1, tantalum carbide-coated carbon material 10 was prepared and evaluated by filling container 23 with tantalum pentachloride (5N) powder instead of tantalum-containing metal 22, using Ar gas instead of chlorine gas, and following the same procedure as in Example 1.

[0066] <Evaluation Result 1> Table 1 summarizes the film thickness of the tantalum carbide coating film 11 per hour and the concentrations of Al, Si, Ti, V, and Mo in the tantalum carbide coating film obtained by GDMS for Examples 1-4, 7-8, 11-12, 14-16, and 18-19, as well as Comparative Example 1.

[0067] [Table 1]

[0068] Comparing Examples 1-4, 7-8, 11-12, 14-16, and 18-19 with Comparative Example 1, Examples 1-4, 7-8, 11-12, 14-16, and 18-19 show a greater film thickness per hour of tantalum carbide coating 11. This is because Examples 1-4, 7-8, 11-12, 14-16, and 18-19, which employ a reaction method, generate a larger amount of tantalum chloride gas in the first step compared to Comparative Example 1, which employs a sublimation method, allowing for a larger supply of tantalum chloride gas to the second step. Furthermore, there was no significant difference in impurity concentration between Example 1 and Comparative Example 1, indicating that the tantalum carbide coated carbon material 10 produced in Example 1 is of comparable quality to the tantalum carbide coated carbon material 10 shown in Comparative Example 1 as a semiconductor single crystal growth member.

[0069] <Evaluation Result 2> The evaluation of Examples 1 to 6 is described below. The results are shown in Table 2. In Examples 1 to 4, the temperatures of the tantalum-containing metal 22 were 200, 400, 600, and 800°C, respectively, and no blockage occurred in the first process product supply piping 26, nor was any deterioration of the first process product supply piping 26 observed. On the other hand, in Example 5, the temperature of the tantalum-containing metal 22 was 180°C, and the first process product supply piping 26 became blocked. Furthermore, in Example 6, the temperature of the tantalum-containing metal 22 was 820°C, and deterioration of the first process product supply piping 26 was observed. These results suggest that a temperature of 200-800°C is appropriate for tantalum-containing metals to ensure stable operation of the equipment.

[0070] [Table 2]

[0071] <Evaluation Result 3> The evaluation of Examples 1 and 7-10 is described below. The results are shown in Table 3. In Examples 1, 7, and 8, the pressure inside the container 23 was 78, 12, and 42 kPa abs, respectively, and the first process product supply pipe 26 did not become blocked. On the other hand, in Examples 9 and 10, the pressure inside the container 23 was 85 kPa abs and 95 kPa abs, respectively, and the first process product supply pipe 26 became blocked. Based on these results, it is preferable that the pressure inside the container 23 be 80 kPa abs or less in order to operate the equipment stably.

[0072] [Table 3]

[0073] <Evaluation Result 4> The evaluation of Examples 1, 11, and 12 is described below. In Examples 1, 11, and 12, tantalum-containing metals 22 with tantalum content of 99.9%, 99.0%, and 95.0% by weight, respectively, were used, and the total elemental concentrations of Al, Si, Ti, V, and Mo obtained from the tantalum carbide coating film are shown in Table 4. From this, it can be said that the higher the tantalum purity of the tantalum-containing metal 22, the lower the concentration of impurities in the tantalum carbide coating film 11, making it suitable as a semiconductor single crystal growth material.

[0074] [Table 4]

[0075] <Evaluation result: 5> The evaluation of Examples 1 and 13-17 is described below. In these examples, tantalum-containing metals 22 with different maximum particle diameters were used. During the introduction of chlorine-containing gas in the first step, particularly in Example 13, the powdered tantalum-containing metal 22 was observed to be violently stirred up. As a result, the tantalum-containing metal 22 could not be properly heated, tantalum chloride gas was not generated, and almost no tantalum carbide coating film 11 was formed in the second step. Furthermore, in Example 17, the maximum diameter of the tantalum-containing metal 22 particles was large, making it difficult to adjust the weight to a specific level by weighing. In addition, the packing rate of the tantalum-containing metal 22 in the container 23 was poor, requiring heating over a wide area to heat the entire mixture, resulting in poor efficiency. On the other hand, in Examples 1 and 14-16, the tantalum-containing metal 22 was appropriately heated, generating tantalum chloride gas in the first step and forming a tantalum carbide coating 11 in the second step. These results are summarized in Table 5, and it can be determined that a maximum particle diameter of 0.5-20 mm for the tantalum-containing metal 22 is appropriate. (Evaluation Criteria) ○: No tantalum-containing metal was observed to become airborne, and it was easy to adjust the weight to a specific level by weighing. ×: Tantalum-containing metal was observed to become airborne, or it was difficult to match the weight to a specific value through weighing.

[0076] [Table 5]

[0077] <Evaluation Result 6> The evaluation of Examples 1 and 18 is described below. The results are shown in Table 6. In Examples 1 and 18, quartz and Hastelloy were used as the material for the container 23, respectively, and accordingly, a radiation thermometer and a thermocouple were used as the temperature measurement methods. In Example 1, the temperature of the tantalum-containing metal 22 can be directly measured using the radiation thermometer, but in Example 18, the temperature is measured through a thermocouple in contact with the container 23, making it impossible to directly measure the temperature of the tantalum-containing metal 22. Furthermore, despite using the same control method, Example 18 showed greater temperature fluctuations, indicating that Example 1 is superior in terms of control.

[0078] [Table 6]

[0079] <Evaluation Result 7> The evaluation of Examples 1 and 19-21 will now be described. In Examples 1 and 19-21, hydrocarbon-containing gases mainly composed of methane, ethane, propane, and butane were used, respectively. From the XRD measurement results of the obtained tantalum carbide coated film 11, it was found that at least 99% of its crystal structure was TaC. This is summarized in Table 7, and in the present invention, methane, ethane, propane, and butane can be used as hydrocarbon-containing gases.

[0080] [Table 7] [Explanation of Symbols]

[0081] 10. Tantalum carbide coated carbon material 11. Tantalum carbide coating 12 Carbon-based substrate 21 Heating device 22 Tantalum-containing metals 23 Container 24 Heater 25 1st process raw material supply piping 26 1st process product supply piping 27 Purge piping 28 valves 31 Reactor 32. Hydrocarbon-containing gas supply piping 33 Exhaust piping 34 Regulating gas source 35 Pedestal

Claims

1. A method for producing a tantalum carbide coated carbon material, comprising a carbon substrate mainly composed of carbon and a tantalum carbide coating film covering at least a portion of the carbon substrate, The first step involves generating tantalum chloride gas by the reaction of a heated tantalum-containing metal with a chlorine-containing gas, The process includes a second step of reacting the tantalum chloride gas produced in the first step with a hydrocarbon-containing gas to form a tantalum carbide coating film on the surface of a carbon substrate, The first step involves reacting the tantalum-containing metal with the chlorine-containing gas under a pressure of 80 kPa abs or less. A method for producing a tantalum carbide-coated carbon material, characterized in that the chlorine-containing gas is chlorine gas.

2. The method for producing a tantalum carbide coated carbon material according to claim 1, characterized in that the heating temperature of the tantalum-containing metal is 200 to 800°C.

3. The method for producing a tantalum carbide coated carbon material according to claim 1, characterized in that the tantalum-containing metal used is a tantalum-containing metal having a tantalum content of 99.9% by weight or more.

4. The method for producing a tantalum carbide coated carbon material according to claim 1, characterized in that the tantalum-containing metal used is a tantalum-containing metal in particulate or crushed form with a maximum particle diameter of 0.5 to 20 mm.

5. In the first step described above, the tantalum-containing metal is held in a container. The method for producing a tantalum carbide-coated carbon material according to claim 1, characterized in that at least a portion of the material of the container is quartz.

6. The method for producing a tantalum carbide coated carbon material according to claim 1, characterized in that the hydrocarbon-containing gas used is a gas containing at least one alkane gas selected from the group consisting of methane gas, ethane gas, propane gas, and butane gas.

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