Substrate including a tantalum coating

Abstract

In a first aspect, the present disclosure relates to a vapor deposition method for coating a carbonaceous substrate with a tantalum carbide coating, the method including a coating process. The coating process includes placing a carbonaceous substrate in a reaction chamber and heating the reaction chamber to a temperature of about 1100 °C to about 1500 °C for a time of about 1 hour to about 24 hours. The coating process is supplying a process gas to the reaction chamber, the process gas including a halide-containing species, and the process gas including less than 4 atomic % carbon and less than 10 volume % H2 for at least 15 minutes after the start of the method. Further, the coating process includes supplying a tantalum-containing species to the reaction chamber or placing a solid containing tantalum in the reaction chamber. Alternatively, the method includes placing a solid containing tantalum halide in the reaction chamber.

Description

Technical Field

[0001] The present invention relates to the field of substrates coated with tantalum carbide. More specifically, the present invention relates to carbonaceous substrates coated with tantalum carbide coatings.

Background Art

[0002] Graphite materials have high heat resistance, specifically high melting points and thermal conductivities, and moreover low coefficients of thermal expansion, so they can be used in many high-temperature processes. Furthermore, graphite can be used as a susceptor. A susceptor can absorb electromagnetic energy and convert it into heat, or re-emit the electromagnetic energy as infrared thermal radiation. Graphite can be used as a wafer carrier in the semiconductor industry due to its function as a susceptor, relatively high chemical purity, and high heat resistance. For example, a wafer carrier can be used to grow a GaN layer on a wafer by metalorganic vapor phase epitaxy (MOVPE) to manufacture a blue light-emitting diode (LED) or a high electron mobility transistor (HEMT).

[0003] In addition, graphite can be used as a crucible material for the physical vapor transport process of semiconductor materials such as SiC. Since graphite crucibles have high temperature stability, they can be used over a wide temperature range. Furthermore, due to the high thermal conductivity of graphite, it becomes possible to more precisely control the temperature of the material placed inside the graphite crucible, and then it may become possible to control the growth of semiconductor crystals for making wafers. In particular, due to the high thermal conductivity of graphite, it may become possible to apply a temperature gradient to the material placed inside the crucible while reducing the temperature delay.

[0004] However, since graphite contains or consists essentially of carbon, it can be susceptible to chemical attack. For example, graphite can be attacked by hydrogen or ammonia used in semiconductor manufacturing. Further, graphite may still contain contaminants such as boron, and it is undesirable for this to migrate to the semiconductor wafer during high-temperature processes. In fact, carbon itself can be a contaminant in many semiconductor processes.

[0005] Furthermore, the surface of graphite can release graphite particles, which can damage the wafer or the film grown on the wafer. For example, the surface of graphite can release graphite particles when the wafer placed therein moves, such as rotates. A coating can be applied to the graphite surface to improve chemical resistance, mechanical resistance, and to encapsulate contaminants and particles in the graphite. In particular, a metal carbide coating, such as a tantalum carbide coating, can be used to improve the chemical resistance of graphite and seal its surface. However, known methods for depositing tantalum carbide on a wafer carrier can sometimes result in a layer that is prone to peeling from the underlying graphite. Peeling is thought to occur because the thermal expansion coefficients of the tantalum carbide coating and the graphite substrate are different. Further, in some processes, the pores of a porous graphite substrate can be completely filled with tantalum carbide. Since the thermal expansion coefficients of tantalum carbide and the graphite substrate are different, the tantalum carbide in the pores may expand excessively compared to the surrounding graphite substrate, which can lead to local destruction of the graphite substrate. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] The present disclosure aims to address the aforementioned problems in a substrate including a tantalum carbide coating. MEANS FOR SOLVING THE PROBLEMS

[0007] Method In a first aspect, the present disclosure relates to a vapor deposition method for coating a carbonaceous substrate with a tantalum carbide coating, the method including a coating step. The coating step includes placing the carbonaceous substrate in a reaction chamber and heating the reaction chamber to a temperature of about 1100 °C to about 1500 °C for a time of about 1 hour to about 24 hours. The coating step further includes supplying a process gas to the reaction chamber, the process gas including a halide-containing species, and the process gas including less than 4 atomic % carbon and less than 10 volume % H2 for at least 15 minutes after the start of the method. Further, the coating step includes supplying a tantalum-containing species to the reaction chamber or placing a solid containing tantalum in the reaction chamber. Alternatively, the method includes placing a solid containing tantalum halide in the reaction chamber.

[0008] In some embodiments, the solid containing tantalum or tantalum halide may be in the form of a powder.

[0009] In some embodiments, the solid containing tantalum may include tantalum in metallic form.

[0010] In some embodiments, the tantalum-containing species and the halide-containing species may be the same, and in particular, the process gas may include TaCl5.

[0011] In some embodiments, the solid containing tantalum halide may include tantalum halide in the form of TaCl5 and / or other TaCl x species.

[0012] In some embodiments, the coating step may include first and second coating steps, the first coating step being performed at a first temperature and the second coating step being performed at a second temperature, and in particular, the first temperature may be lower than the second temperature.

[0013] In some embodiments, the first temperature may be from about 1150°C to about 1250°C, and / or the second temperature may be from about 1250°C to about 1350°C.

[0014] In some embodiments, the coating process may include a third coating process, and the third coating process may be performed at a third temperature, particularly where the third temperature is higher than the first and / or second temperature.

[0015] In some embodiments, the third temperature may be at least about 1350°C, more specifically from about 1350°C to about 1600°C, particularly from about 1350°C to about 1450°C.

[0016] In some embodiments, the time for each of the first and / or second coating processes may be at least about 15 minutes, more specifically from about 30 minutes to about 120 minutes, particularly from about 45 minutes to about 90 minutes.

[0017] In some embodiments, the time for the third coating process may be at least about 60 minutes, more specifically at least about 180 minutes, particularly at least about 300 minutes.

[0018] In some embodiments, the process gas in the first coating process may contain less than 4 atomic %, more specifically less than 1 atomic %, particularly less than 0.1 atomic % carbon, based on the total number of atoms in the process gas.

[0019] In some embodiments, the process gas in the first coating process may contain less than 4 volume %, more specifically less than 1 volume %, particularly less than 0.1 volume % H2, based on the total volume of the process gas.

[0020] In some embodiments, the process gas in the first coating process may contain a halide, particularly chlorine, at a maximum ratio of 1:0.05, more specifically 1:0.01, particularly 1:0.001, relative to carbon.

[0021] In some embodiments, the process gas in the first coating step may contain a halide, particularly chlorine, at a maximum ratio of 1:0.05, more specifically 1:0.01, and particularly 1:0.001 with respect to H2.

[0022] In some embodiments, the process gas in the second coating step may contain carbon in an amount exceeding 0.1 atomic %, more specifically exceeding 1 atomic %, and particularly exceeding 4 atomic % with respect to the total number of atoms in the process gas.

[0023] In some embodiments, the process gas in the third coating step may contain carbon in an amount exceeding 0.1 atomic %, more specifically exceeding 1 atomic %, and particularly exceeding 4 atomic % with respect to the total number of atoms in the process gas.

[0024] In some embodiments, the halide-containing species may be chloride-containing species, more specifically the chloride-containing species may be Cl2 or HCl, and particularly the halide-containing species may be HCl.

[0025] In some embodiments, the process gas may additionally contain an inert gas, more specifically nitrogen or argon, and particularly argon.

[0026] In some embodiments, the pressure in the reaction chamber may be from about 0.001 bar to about 1.1 bar, more specifically from about 0.001 bar to about 0.5 bar, and particularly from about 0.1 bar to about 0.2 bar.

[0027] In some embodiments, the method may additionally include an annealing step after the coating step.

[0028] In some embodiments, the annealing process may include placing the coated carbonaceous substrate in an annealing chamber, heating the annealing chamber to a temperature of about 900 °C to about 1800 °C, more specifically 1200 °C to about 1500 °C for a time of about 10 minutes to about 5 hours, and supplying a process gas to the reaction chamber. The process gas may include carbon-containing species, more specifically carbon and hydrogen-containing species, particularly C2H4.

[0029] In some embodiments, the annealing process may include placing the coated carbonaceous substrate in an annealing chamber and heating the reaction chamber to a temperature of about 1900 °C to about 2300 °C for a time of about 0.5 hours to about 3 hours in an inert gas atmosphere.

[0030] Substrate In a second aspect, the present disclosure relates to a carbonaceous substrate including a first tantalum carbide coating layer, the first tantalum carbide coating layer being disposed on an outer surface of the carbonaceous substrate, the carbonaceous substrate including a plurality of pores including a TaC pore coating, and the plurality of pores not being completely filled by the tantalum carbide pore coating.

[0031] In some embodiments, the plurality of pores may be disposed less than 182 μm, particularly less than 100 μm, from the outer surface.

[0032] In some embodiments, the TaC pore coating may have a thickness of less than 20 μm, more specifically less than 10 μm, particularly less than 8 μm.

[0033] In some embodiments, the TaC pore coating at a depth of about 20 μm to about 60 μm may have a thickness of about 0.5 μm to about 8 μm, more specifically about 0.8 μm to about 3 μm, particularly about 1 μm to about 2.5 μm.

[0034] In some embodiments, the ratio of the thickness of the first tantalum carbide coating layer to the thickness of the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm may be about 2:1 to about 30:1, more specifically about 3:1 to about 20:1, and particularly about 5:1 to about 15:1.

[0035] In some embodiments, the plurality of pores may have a maximum diameter of about 5 μm to about 100 μm, more specifically about 10 μm to about 50 μm, and particularly 15 μm to about 25 μm.

[0036] In some embodiments, at least 50%, more specifically at least 75%, and particularly at least 90% of the plurality of pores having a maximum diameter of about 5 μm to about 100 μm may not be completely filled by the tantalum carbide pore coating.

[0037] In some embodiments, the volume of the plurality of pores in the carbonaceous substrate may be about 1% by volume to about 20% by volume, more specifically about 5% by volume to about 15% by volume, and particularly about 7% by volume to about 13% by volume.

[0038] In some embodiments, the carbonaceous substrate may contain TaC to a penetration depth of at least 20 μm, more specifically at least 40 μm, and particularly at least 60 μm.

[0039] In some embodiments, the first tantalum carbide coating layer and / or the tantalum carbide pore coating may have a ratio of Ta to C of about 1.3:1 to about 1:1.3, more specifically about 1.1:1 to about 1:1.1, and particularly about 1.05:1 to about 1:1.05.

[0040] In some embodiments, the first tantalum carbide coating layer may have a thickness of about 0.1 μm to about 40 μm, more specifically about 5 μm to about 35 μm, and particularly about 10 μm to about 30 μm.

[0041] In some embodiments, the first tantalum carbide coating layer may include tantalum carbide in the form of tantalum carbide crystals, and the tantalum carbide crystal orientations of each group of

[0111] ,

[0200] ,

[0220] ,

[0311] , and

[0311] are from the maximum peak intensity of the X-ray diffraction pattern detected by CuKα rays with a wavelength of 1.5406 Å, according to the following formula:

[0042] [Number]

[0043] (wherein I i is correspondingly selected from the maximum intensity of the crystal orientation, n = 5, I 111 is the maximum intensity at 2θ in the range of 33.9° to 35.9°, I 200 is the maximum intensity at 2θ in the range of 39.4° to 41.4°, I 220 is the maximum intensity at 2θ in the range of 57.6° to 59.6°, I 311 is the maximum intensity at 2θ in the range of 69.0° to 71.0°, I 222 is the maximum intensity at 2θ in the range of 72.6° to 74.6°, I i,0 is the intensity of the crystal orientation expected when the crystal orientation of the tantalum carbide crystal is random), and the texture coefficient TC of about 0.5 to about 1.5 is calculated according to this formula. i is shown.

[0044] In some embodiments, the first tantalum carbide layer may have a porosity of less than 5% by volume, more specifically less than 1% by volume, and particularly less than 0.1% by volume.

[0045] In some embodiments, the first tantalum carbide layer may contain less than 1 atomic %, more specifically less than 0.1 atomic %, and particularly less than 0.01 atomic % of impurities.

[0046] In some embodiments, the carbonaceous substrate comprises, consists essentially of, or consists of graphite.

[0047] In some embodiments, the carbonaceous substrate may include a second tantalum carbide coating layer, the second tantalum carbide coating layer may be located adjacent to the first tantalum carbide coating layer, and in particular, the first tantalum carbide coating layer may be located between the second tantalum carbide coating layer and the outer surface of the carbonaceous substrate.

[0048] Use In a third aspect, the present disclosure relates to the use of a carbonaceous substrate according to any one of the preceding claims as a component of an epitaxial growth system, more specifically a GaN or SiC growth system, and in particular as a wafer carrier of a GaN or SiC growth system, or as a component of a physical vapor transport (PVT) system, more specifically as a component of a SiC PVT physical vapor transport system, and in particular as a crucible or hot wall of a PVT system.

Brief Description of the Drawings

[0049]

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Mode for Carrying Out the Invention

[0050] Hereinafter, a detailed description of the present disclosure will be given. Terms or words used in this specification and aspects of the present disclosure should not be construed as limited to having only a common language or dictionary meaning, but should be construed as having their ordinary technical meanings established in the relevant technical field, unless specifically defined otherwise in the following description. In the detailed description, specific embodiments will be referred to in order to better explain the present disclosure, but it should be understood that the present disclosure is not limited to these specific embodiments.

[0051] Method As described above, the thermal expansion coefficients of the tantalum carbide coating and the graphite substrate are different, and it is considered that peeling of the tantalum carbide coating disposed on the graphite substrate may occur due to insufficient "fixing" of the tantalum carbide coating to the graphite substrate. Further, in some processes, the pores of the porous graphite substrate may be completely filled with tantalum carbide. Since the thermal expansion coefficients of tantalum carbide and the graphite substrate are different, the tantalum carbide in the pores may expand excessively compared to the surrounding graphite substrate, which may lead to local destruction of the graphite substrate.

[0052] Tantalum carbide necessarily contains tantalum and carbon, and in known methods for depositing tantalum carbide on a substrate, a tantalum source and a carbon source are generally used. The tantalum source and the carbon source can also exist as a single molecule. It has surprisingly been found that a tantalum carbide coating can be grown on a carbonaceous substrate at low carbon and hydrogen concentrations in a process gas using tantalum halide. The tantalum halide may be supplied to the reaction together with the process gas or generated in the reaction chamber. Without wishing to be bound by theory, the tantalum halide can then react with the carbon of the carbonaceous substrate, leading to the formation of tantalum carbide on the carbonaceous substrate without the need for a significant amount of carbon source in the process gas. Since tantalum carbide is formed directly from the carbon provided by the carbonaceous substrate, the fixing of the tantalum carbide coating to the carbonaceous substrate can be improved.

[0053] Furthermore, it was observed that the resulting coating can also be present within the pores of the carbonaceous substrate, but does not entirely fill the pores. Although not wishing to be bound by theory, it is theorized that the growth of the tantalum carbide coating on the carbonaceous coating can be limited by the access of halide species to the carbon of the carbonaceous substrate. When the tantalum carbide coating is formed in the conventional manner from a gas phase containing significant amounts of both a carbon source and a tantalum source, the tantalum carbide coating may preferentially form on the outer surface of the substrate, which may also rapidly clog any access paths to the pores beneath the outer surface, leading to poor fixation of the tantalum carbide coating. Additionally, or alternatively, unfilled pores, particularly those close to the surface, may be overfilled, which can lead to subsequent local destruction as described above.

[0054] Furthermore, the presence of significant amounts of dihydrogen H2 in the process gas can inhibit the formation of TaC. In particular, the presence of H2 in the process gas can lead to the formation of metallic tantalum on the surface of the carbonaceous substrate, which may then require subsequent carbonization to obtain a tantalum carbide coating. The term "carbonization" refers to the process of reacting a precursor, such as a pure metal, with a carbon source to obtain a carbide, particularly a metal carbide, such as reacting metallic tantalum with a carbon source to obtain tantalum carbide. Metallic tantalum may form within the pores of the carbonaceous material and may fill the pores. During subsequent carbonization of the metallic tantalum, its volume increases, which can lead to overfilling of the pores with tantalum carbide.

[0055] As used herein, the term "outer surface" may refer to a surface on which no other surface of the carbonaceous substrate is disposed in a direction perpendicular to the surface. Alternatively, or in addition, the term "outer surface" as used herein may refer to a surface on which at least one reference point on the surface is not surrounded by at least 50% by a wall segment extending away from the bulk. Alternatively, or in addition, the term "outer surface" may refer to a surface on which at least one reference point on the surface is not surrounded by a wall segment having a height of at least 1 cm extending away from the bulk within a radius of at least 2.5 cm, more specifically at least 3.5 cm, and particularly at least 4 cm. For example, the carbonaceous substrate may include a disk-shaped depression with a radius of the depression of 100 mm. The interior of the depression may also be regarded as an outer surface and not necessarily regarded as a recess.

[0056] Furthermore, the term "wall segment" refers to a part of a wall, more specifically a part of a wall having a length of at least 100 μm, and particularly a part of a wall having a length of at least 100 μm and a width of at least 10 μm. The width can also be measured along a curved surface along a curved wall segment.

[0057] By supplying tantalum in the form of tantalum halide and carbon from the carbonaceous substrate, it has been found that the growth of the tantalum carbide coating may slow down as the thickness of the tantalum carbide coating increases, so that the formation of the tantalum carbide coating may not occur predominantly on the outer surface. As a result, the tantalum halide can penetrate into the pores, where a tantalum carbide pore coating can also be formed. Furthermore, since the formation of the tantalum carbide coating slows down with increasing thickness, excessive filling of the pores by the tantalum carbide coating is prevented, and pores that are only partially filled can be obtained. Furthermore, although the tantalum halide can initially approach the pores, as the tantalum coating grows on the outer surface, the access path to the pores is blocked, and excessive growth of the tantalum carbide pore coating can be prevented.

[0058] Accordingly, in a first aspect, the present disclosure relates to a vapor deposition method for coating a carbonaceous substrate with a tantalum carbide coating, the method including a coating process. The coating process includes placing the carbonaceous substrate in a reaction chamber and heating the reaction chamber to a temperature of about 1100 °C to about 1500 °C for a time of about 1 hour to about 24 hours. The coating process further includes supplying a process gas to the reaction chamber, the process gas including a halide-containing species. Further, for at least 15 minutes after the start of the method, the process gas includes less than 4 atomic (at)% carbon and less than 10 volume (vol)% H2. Tantalum can be introduced into the reaction chamber in three different ways.

[0059] First, the coating process may include supplying a tantalum-containing species to the reaction chamber. For example, the tantalum-containing species and the halide-containing species may be the same, particularly when the process gas includes TaCl5 and / or other TaCl x species. TaCl5 and / or other TaCl x species may be formed in a separate chamber and then supplied to the reaction. For example, TaCl5 and / or other TaCl x species may be formed by reacting tantalum metal with a halide, such as HCl or Cl2, in a separate chamber.

[0060] Alternatively, or in addition, the coating process may include placing a solid containing tantalum in the reaction chamber. For example, the solid containing tantalum may include tantalum in metallic form. A halide-containing species, such as hydrogen chloride HCl, may be supplied to the reaction chamber by the process gas. The halide-containing species may then react with tantalum to form, for example, gaseous tantalum(V) chloride, TaCl5 and / or other TaCl x species. TaCl5 and / or other TaCl x species may then react with the carbonaceous substrate to form a tantalum carbide coating and chlorine gas Cl2. Other TaCl xThe species may be, for example, tantalum(IV) chloride, TaCl4, or tantalum(III) chloride, TaCl3. The solid may be, for example, a solid plate of metallic tantalum. Alternatively, the solid may be a powder containing metallic tantalum. The powder may exhibit a high specific surface area compared to the plate and can thus react with the halide at an increased rate.

[0061] The term "process gas" shall refer to the entire gas supplied to the reaction chamber. For example, the reaction chamber may include one gas inlet, and the term "process gas" can be related to the entire gas stream supplied to the reaction chamber through that one gas inlet. In another example, the reaction chamber may include a plurality of gas inlets, and the entire gas supplied to the reaction chamber through the plurality of gas inlets shall be regarded as the "process gas". The term "process gas" may also include the precursor gas formed within the reaction chamber. For example, when the reaction chamber contains a tantalum halide solid, the term "process gas" may also include the gaseous tantalum halide generated from the tantalum halide solid.

[0062] In addition, or alternatively, the solid containing tantalum halide may contain TaCl5 and / or other forms of tantalum halide. x TaCl x evaporates due to the temperature rise within the reaction chamber and can then react with the carbonaceous substrate. TaCl x may also be in the form of a powder. When the tantalum halide solid is placed in the reaction chamber, the process gas may also contain less than 4 atomic % carbon and less than 10 volume % H2 for at least 15 minutes after the start of the method.

[0063] Alternatively, when using solid TaCl x placed within the reaction chamber, the reaction chamber may be sealed and a continuous process gas may not be used. For example, TaCl xWhen using a sealed reaction chamber, since both tantalum-containing species and halide-containing species are already present in the reaction chamber, the reaction chamber may be pre-filled with a process gas containing less than 4 atomic % carbon and less than 10 volume % H2.

[0064] Alternatively, when using gaseous TaCl x , for example TaCl5, the reaction chamber may be filled with TaCl x and an inert gas, such as argon, and then sealed. Thereafter, the reaction in the reaction chamber may then be carried out, for example, for 1 minute to 10 minutes. After carrying out the reaction, the reaction chamber may be flushed, and the method may be repeated by introducing TaCl x gas and an inert gas again and sealing the chamber to carry out the reaction.

[0065] It should be noted that TaCl5 can decompose into other TaCl x species due to the high temperature of the reaction chamber or the process gas. Therefore, when using TaCl5, the process gas may contain a plurality of TaCl x species, or any one of the TaCl x species. Without wishing to be bound by theory, it is contemplated that some of the TaCl x species may temporarily form metallic tantalum on the surface of the reaction chamber. The metallic tantalum on the surface of the reaction chamber may then react with a halide, such as Cl2, present in the gas in the reaction chamber to form TaCl x species again, which can then react with carbon from the carbonaceous substrate to form TaC.

[0066] In some embodiments, the coating process may include first and second coating steps, the first coating step is performed at a first temperature, the second coating step is performed at a second temperature, and in particular, the first temperature may be lower than the second temperature. As described above, the reaction between tantalum halide and the carbonaceous substrate slows down as the thickness of the tantalum carbide coating increases. Without wishing to be bound by theory, it is believed that the limiting factor may be the diffusion of carbon to the outer surface that can react with tantalum-containing species through the tantalum carbide coating from the carbonaceous substrate. By increasing the temperature, the diffusion rate of carbon through the carbide coating can be increased, thereby increasing the growth rate of the tantalum carbide coating. By first operating the method at a lower first temperature, the tantalum coating can efficiently penetrate the pores and at the same time not overly fill them. Then, when the coating is fixed to the carbonaceous substrate and the access path to the pores is partially blocked, a second coating step at a higher second temperature can be performed to increase the growth rate of the tantalum carbide coating on the outer surface.

[0067] As described above, without wishing to be bound by theory, it is considered that an improved tantalum carbide coating can be achieved by reacting the carbon contained in the carbonaceous substrate with tantalum-containing species as opposed to supplying an additional carbon source into the process gas. Thus, in some embodiments, the process gas in the first coating step may contain less than 4 atomic percent, more specifically less than 1 atomic percent, and in particular less than 0.1 atomic percent carbon, based on the total number of atoms in the process gas. For example, the process gas in the first coating step may contain a halide, in particular chlorine, in a maximum ratio of 1:0.05, more specifically 1:0.01, and in particular 1:0.001 with respect to carbon. The maximum ratio shall refer to the maximum relative amount of carbon. Thus, a ratio of 1 part chlorine to 1 part carbon shall be considered a higher ratio compared to a ratio of 1 part chlorine to 0.5 part carbon. Thus, the maximum ratio of chlorine to carbon of 1:0.05 relates to all ratios in the range from 1 part chlorine to 0 parts carbon to a maximum of 1 part chlorine to 0.05 parts carbon.

[0068] In the second coating step, the process gas may also contain less than 4 atomic percent, more specifically less than 1 atomic percent, and particularly less than 0.1 atomic percent carbon, based on the total number of atoms in the process gas. For example, the process gas in the second coating step may contain a halide, particularly chlorine, with respect to carbon, at a maximum ratio of 1:0.05, more specifically 1:0.01, and particularly 1:0.001. Thus, an increase in the growth of tantalum carbide can be induced by an increase in temperature.

[0069] Alternatively, an additional carbon source may be added to the process gas of the second coating step to increase the growth rate of the tantalum carbide coating on the outer surface. Since the access path is blocked by the tantalum carbide coating formed in the first coating step, the carbon source may not significantly penetrate into the pores of the carbonaceous substrate in the second coating step, thereby preventing excessive filling of the pores. Further, the tantalum carbide coating is sufficiently fixed in the pores by the first coating step, and the risk of peeling can be reduced even when the thickness of the carbide coating on the outer surface increases in the second coating step. Thus, in some embodiments, the process gas in the second coating step may contain more than 0.1 atomic percent, more specifically more than 1 atomic percent, and particularly more than 4 atomic percent carbon, based on the total number of atoms in the process gas.

[0070] In some embodiments, the process gas in the first coating step may contain less than 4 volume percent, more specifically less than 1 volume percent, and particularly less than 0.1 volume percent H2, based on the total volume of the process gas. As described above, a substantial amount of H2 may prevent the formation of the tantalum carbide coating and may result in the formation of a metallic tantalum coating.

[0071] In some embodiments, the process gas in the first coating step may contain a halide, particularly chlorine, in a maximum ratio of 1:0.05, more specifically 1:0.01, and particularly 1:0.001 with respect to H2.

[0072] In some embodiments, the first temperature may be about 1150 °C to about 1250 °C, and / or the second temperature may be about 1250 °C to about 1350 °C.

[0073] In some embodiments, the time for each of the first and / or second coating steps may be at least about 15 minutes, more specifically about 30 minutes to about 120 minutes, and particularly about 45 minutes to about 90 minutes.

[0074] In some embodiments, the coating step may include a third coating step, and the third coating step may be performed at a third temperature, particularly where the third temperature is higher than the first and / or second temperatures. In some embodiments, the third temperature may be at least about 1350 °C, more specifically about 1350 °C to about 1600 °C, and particularly about 1350 °C to about 1450 °C. The third coating step can be used to further increase the thickness of the tantalum carbide coating on the outer surface, particularly at a substantially increased growth rate. The third coating step can also be performed immediately after the first coating step.

[0075] It should be noted that the first, second, and third temperatures may not be stationary. The method can also be performed with a temperature gradient within the ranges presented for the first, second, and third temperatures above. For example, the first coating step may include a temperature increase from 1150 °C to 1250 °C within 1 hour.

[0076] In some embodiments, the time for the third coating step may be at least about 60 minutes, more specifically at least about 180 minutes, and particularly at least about 300 minutes.

[0077] The tantalum carbide coating formed by the first and second coating processes can effectively prevent tantalum in the process gas from approaching the carbon of the carbonaceous substrate. Therefore, in the third coating process, an additional carbon source in the process gas may be required. Thus, in some embodiments, the process gas in the third coating process may contain carbon in excess of 0.1 atomic %, more specifically in excess of 1 atomic %, particularly in excess of 4 atomic %, based on the total number of atoms in the process gas.

[0078] In some embodiments, the halide-containing species may be chloride-containing species. More specifically, the chloride-containing species may be Cl2 or HCl, and particularly the halide-containing species may be HCl. Cl2 and HCl can form TaCl5 and / or other TaCl x species when reacted with metallic tantalum, particularly tantalum metal powder. TaCl5 and / or other TaCl x species can react with the carbonaceous substrate to form a tantalum carbide coating.

[0079] In some embodiments, the process gas may additionally contain an inert gas, more specifically nitrogen or argon, particularly argon.

[0080] In some embodiments, the pressure in the reaction chamber may be from about 0.001 bar to about 1.1 bar, more specifically from about 0.001 bar to about 0.5 bar, particularly from about 0.1 bar to about 0.2 bar.

[0081] In some embodiments, the method may additionally include an annealing process after the coating process.

[0082] Tantalum carbide may exist in a stoichiometry deviating from 1:1 ratio of tantalum to carbon, for example pure TaC. For example, the ratio of tantalum to carbon may vary from 1:0.4 to 1:1. Thus, tantalum carbide may be TaC xIt may exist in the form of, and x varies from 0.4 to 1. Furthermore, tantalum carbide may also be formed in the form of Ta2C.

[0083] Surprisingly, it has been found that coating a carbonaceous substrate using the process parameters of the first coating step can result in a tantalum carbide coating with a ratio of tantalum to carbon close to 1. However, it has been observed that at higher temperatures, for example above 1500 °C, the stoichiometry can change to a higher proportion of tantalum. In particular, with increasing temperature and increasing coating thickness, the proportions of Ta2C and metallic tantalum increased. In particular, the proportions of Ta2C and metallic tantalum were higher in the part of the tantalum carbide coating located further away from the carbonaceous substrate. Without wishing to be bound by theory, it is thought that higher temperatures increased the reaction rate at the surface of the coating. In particular, the reaction rate at the surface may have increased more significantly compared to the diffusion rate of carbon. Furthermore, metallic tantalum may have been deposited on the coating by self-decomposition of TaCl5 and / or other TaCl x species at high temperatures. It has surprisingly been found that two annealing methods can be used to increase the proportion of TaC in the tantalum carbide coating and / or to decrease the proportions of Ta2C and metallic tantalum. TaC, also known as tantalum monocarbide, and Ta2C, also known as tantalum hemicarbide, can exhibit different properties. In particular, TaC can exhibit increased hardness compared to Ta2C and metallic tantalum. Furthermore, TaC is chemically more stable than Ta2C. For example, in a process for the epitaxial growth of SiC, residues of Ta and Ta2C in the coating may react with the carbonaceous precursor intended for the growth of SiC, which in turn can change the reaction rate of the process and lead to poor process results. Furthermore, Ta2C and Ta may react with other process gases, such as Cl2 or HCl, which can lead to deterioration of the coating properties.

[0084] In some embodiments, the annealing process may include placing the coated carbonaceous substrate in an annealing chamber, heating the annealing chamber to a temperature of about 900 °C to about 1800 °C, more specifically 1200 °C to about 1500 °C for a time of about 10 minutes to about 5 hours, and supplying a process gas to the reaction chamber. The process gas may include carbon-containing species, more specifically carbon and hydrogen-containing species, particularly C2H4. The carbon-containing species can provide carbon to the tantalum carbide coating to form TaC from Ta2C and metallic tantalum. Further, the elevated temperature may also enable a higher rate of carbon diffusion from the carbonaceous substrate to the tantalum carbide coating.

[0085] In another embodiment, the annealing process may include placing the coated carbonaceous substrate in an annealing chamber and heating the reaction chamber to a temperature of about 1900 °C to about 2300 °C for a time of about 0.5 hours to about 3 hours under an inert gas atmosphere. The annealing process carried out at a temperature of 1900 °C to about 2300 °C may be performed without supplying carbon in the process gas. Without wishing to be bound by theory, it is believed that the temperature range of about 1900 °C to about 2300 °C may significantly increase the mobility or diffusion rate of carbon in the tantalum carbide coating. Thus, carbon may move from the carbon-rich portions of the carbonaceous substrate and / or the tantalum carbide coating towards the carbon-poor portions of the tantalum carbide coating.

[0086] Furthermore, the tantalum carbide in the tantalum carbide coating may form tantalum carbide crystallites. The annealing process at a temperature of about 1900 °C to about 2300 °C may lead to an increase in the particle size of the tantalum carbide crystallites. As a result, the number and / or the absolute length of the grain boundaries in the tantalum carbide coating may decrease, which may lead to a decrease in the gas permeability of the tantalum carbide coating. The decrease in gas permeability may result in improved protection of the carbonaceous material against chemical attack.

[0087] In some embodiments, the method may be performed under a continuous flow of process gas. A continuous flow process may result in a higher growth rate of the tantalum carbide layer compared to a static atmosphere.

[0088] In some embodiments, the reaction chamber may be sealed or semi-sealed. In some embodiments, the reaction chamber may be disposed within a process cell. The process cell may be sealed. In an unsealed reaction chamber, for example, a reaction chamber with a continuous flow of process gas, the process gas enters the reaction chamber through an inlet and then exits the reaction chamber after reacting at least partially with the carbonaceous substrate. For example, Cl2 or HCl enters the reaction chamber through an inlet and reacts with tantalum metal powder disposed within the reaction chamber to form TaCl5 and / or other TaCl x species. Then TaCl5 and / or other TaCl x species can react with the carbonaceous substrate to form a tantalum carbide coating and Cl2. However, it is possible that not all of the TaCl5 and / or other TaCl x species react with the carbonaceous substrate and are carried out of the reaction chamber, leading to a loss of relatively expensive tantalum. A sealed reaction chamber or a sealed process cell can be used by supplying HCl or Cl2 through a gas inlet to the reaction chamber or the surrounding process cell at the start of the reaction, then stopping the flow of the process gas and closing the gas inlet and outlet. Then HCl or Cl2 can react with the supplied solid tantalum metal, particularly tantalum metal powder, to form TaCl5 and / or other TaCl x species, which can react again with the carbonaceous substrate to form a tantalum carbide coating. Since the reaction chamber or the process cell is sealed, the unreacted TaCl5 and / or other TaCl x species do not exit the reaction chamber, preventing loss of tantalum. Further, TaCl5 and / or other TaCl xSince the Cl2 formed when the species reacts with the carbonaceous substrate can react again with the solid tantalum metal to reform TaCl5, the growth of the tantalum carbide coating can continue. As a result, the yield of tantalum can be improved.

[0089] Similarly, when using solid TaCl5 placed in the reaction chamber as a precursor, a sealed reaction chamber configuration or a process cell can also be used. In this configuration, by heating the reaction chamber, the process gas can be directly formed inside the reaction chamber. By keeping the reaction chamber or the process cell sealed, TaCl5 and / or other TaCl x species do not exit the reaction chamber, and TaCl5 and / or other TaCl x species can only react with the carbonaceous substrate to form a tantalum carbide coating. As a result, the yield of tantalum can be improved.

[0090] In a semi-sealed reaction chamber, a continuous flow of the process gas may flow around the reaction chamber, for example, inside the process cell. A part of the process gas, particularly the halide-containing species, enters the semi-sealed reaction chamber and reacts with the solid tantalum metal to form TaCl x can be formed. Since the reaction chamber is semi-sealed, the residence time of the halide-containing species and the formed TaCl x can increase, which can result in less tantalum being lost to the waste stream compared to an open configuration, thus leading to a higher yield of tantalum.

[0091] The process cell and / or reaction chamber may comprise a stirrer configured to stir the gas within the process cell and / or reaction chamber. For example, the process cell and / or reaction chamber may comprise a fan. The stirrer can increase the growth rate of the tantalum carbide coating by reducing, for example, dead zones that may form at the corners of the process cell and / or reaction chamber. Further, the gas exchange rate at the surface of the carbonaceous surface can be increased, thereby also increasing the reaction rate. As described above, on the surface of the carbonaceous substrate, tantalum halide, such as TaCl x can react with the carbonaceous substrate to form TaC and a halide, such as Cl2. For example, the stirrer can increase the rate at which Cl2 replaces TaCl x on the surface of the carbonaceous substrate. Then TaCl x can react with the carbonaceous substrate again. Further, by the stirrer, Cl2 can more rapidly contact the solid tantalum metal, if present, to reform TaCl x again.

[0092] substrate In a second aspect, the present disclosure relates to a carbonaceous substrate comprising a first tantalum carbide coating layer, wherein the first tantalum carbide coating layer is disposed on an outer surface of the carbonaceous substrate, the carbonaceous substrate comprises a plurality of pores including a tantalum carbide pore coating, and the plurality of pores are not completely filled by the tantalum carbide pore coating.

[0093] In some embodiments, the plurality of pores may be disposed less than 182 μm, particularly less than 100 μm, from the outer surface. It should be noted that the pores may be present in a carbonaceous portion that is further removed from the outer surface than 182 μm or 100 μm. However, pores further away from the outer surface may not be related to the fixation of the first tantalum carbide coating layer. Additionally, pores disposed further away from the outer surface may not significantly contact tantalum halide species and, thus, may not exhibit a significant tantalum carbide pore coating after the coating process.

[0094] In some embodiments, the tantalum carbide pore coating may have a thickness of less than 20 μm, more specifically less than 10 μm, particularly less than 8 μm.

[0095] In some embodiments, the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm may have a thickness of about 0.5 μm to about 8 μm, more specifically about 0.8 μm to about 3 μm, particularly about 1 μm to about 2.5 μm. As described above, an excessive thickness of the tantalum carbide pore coating can lead to local destruction of the carbonaceous substrate at elevated temperatures due to the expansion of tantalum carbide. However, applying a tantalum carbide pore coating with a minimum thickness can improve the fixation of the first tantalum carbide coating layer to the carbonaceous substrate and enhance the resistance of the pores to chemical attack.

[0096] In some embodiments, the ratio of the thickness of the first tantalum carbide coating layer to the thickness of the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm may be about 2:1 to about 30:1, more specifically about 3:1 to about 20:1, particularly about 5:1 to about 15:1. The term "depth" is well-known and is to be taken in its ordinary meaning in the art. Further, or alternatively, the term "depth" may refer to the direction extending into the bulk of the material perpendicular to the outer surface of the material.

[0097] The thickness of the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm can be measured by the following protocol. a) Create a SEM overview image showing a substrate depth of about 20 μm to about 60 μm. Select the width of the created SEM overview image such that there are at least 30 pores with a maximum diameter of at least 5 μm. The SEM overview image may be formed from a plurality of SEM images juxtaposed next to each other. b) Identify all pores with a maximum diameter of at least 5 μm in the SEM overview image as a subset of pores. c) Determine the thickness of the tantalum carbide pore coating perpendicular to the underlying carbonaceous substrate at five positions equally distributed along the circumference of each pore in the subset of pores. d) Calculate the thickness of the tantalum carbide pore coating by averaging the thicknesses of the tantalum carbide pore coating determined in step c) at all five positions of all pores in the subset of pores.

[0098] It has been found that the above process may enable coating pores with a smaller maximum diameter as compared to known processes. In some embodiments, the plurality of pores may have a maximum diameter of from about 5 μm to about 100 μm, more specifically from about 10 μm to about 50 μm, particularly from 15 μm to about 25 μm. The pores in the carbonaceous substrate may exhibit smaller or larger diameters, but these are not considered to belong to the plurality of pores defined herein. However, the volume of the plurality of pores can account for at least 50%, more specifically at least 75%, particularly at least 90% of the total volume of the pores located less than 182 μm, particularly less than 100 μm, from the outer surface. The volume of the tantalum carbide pore coating is considered to be part of the pore volume of the plurality of pores. For the same proportion of pore volume, smaller pores can provide more fixation sites compared to larger pores, thereby improving the fixation of the first tantalum carbide coating. However, if pores smaller than 5 μm are present to a high degree, they may be overly filled by the tantalum carbide pore coating, which may lead to partial destruction of the aforementioned carbonaceous substrate. As described above, the method according to the first aspect may enable coating pores with a smaller maximum diameter with a tantalum carbide pore coating as compared to known methods.

[0099] In some embodiments, at least 50%, more specifically at least 75%, particularly at least 90% of the plurality of pores having a maximum diameter of from about 5 μm to about 100 μm may not be completely filled with tantalum carbide, particularly at a depth of from about 20 μm to about 60 μm. Some of the plurality of pores, particularly those located near the outer surface, may be completely filled by the tantalum carbide pore coating.

[0100] In some embodiments, the volume of the plurality of pores in the carbonaceous substrate may be from about 1% to about 20% by volume, more specifically from about 5% to about 15% by volume, particularly from about 7% to about 13% by volume. Substrates with higher porosity can improve the fixation of the first tantalum carbide coating layer.

[0101] However, carbonaceous substrates with lower porosity can exhibit improved mechanical properties. In addition, carbonaceous substrates with a smaller pore volume, particularly isotropic graphite, may exhibit a smaller pore diameter, which can improve fixation as outlined above. However, it is possible to create carbonaceous substrates with a larger volume of the plurality of pores, particularly isotropic graphite. Thus, in some embodiments, the carbonaceous substrate can include from about 7% to about 20% by volume of the plurality of pores, and at least 50%, more specifically at least 75%, particularly at least 90% of the plurality of pores have a maximum diameter of from about 5 μm to about 100 μm.

[0102] In some embodiments, the carbonaceous substrate may include TaC to a depth of at least 20 μm, more specifically at least 40 μm, particularly at least 60 μm. As described above, by the above method, tantalum halide species can penetrate deeper into the carbonaceous substrate, thereby improving the fixation of the first tantalum carbide coating layer and the chemical resistance of the carbonaceous substrate.

[0103] In some embodiments, the first tantalum carbide coating layer and / or the tantalum carbide pore coating may have a Ta to C ratio of from about 1.3:1 to about 1:1.3, more specifically from about 1.1:1 to about 1:1.1, and particularly from about 1.05:1 to about 1:1.05. As described above, it has been unexpectedly found that coating a carbonaceous substrate using the process parameters of the first coating step can result in a tantalum carbide coating having a ratio of tantalum carbide close to 1. Further, in contrast to Ta2C or metallic tantalum, a tantalum coating predominantly containing TaC can exhibit improved properties, such as improved mechanical hardness and chemical resistance, as described above. Coatings containing more carbon compared to tantalum may, for example, contain domains of crystalline graphite, which may also exhibit a decrease in mechanical properties and chemical resistance.

[0104] In some embodiments, the first tantalum carbide coating layer may have a thickness of from about 0.1 μm to about 40 μm, more specifically from about 5 μm to about 35 μm, and particularly from about 10 μm to about 30 μm. The thickness of the first tantalum carbide coating layer can be determined perpendicular to the outer surface.

[0105] The tantalum carbide coating layer typically exists in crystalline form. The tantalum carbide layer produced by the method according to the first aspect may exhibit a characteristic distribution of tantalum carbide crystals as measured by X-ray diffraction. In particular, the process according to the first aspect can result in a tantalum carbide layer containing tantalum carbide crystals, and the tantalum carbide crystals do not exhibit a preferred orientation, and thus the orientation of the tantalum carbide crystals is mainly random. Thus, in some embodiments, the first tantalum carbide coating layer may contain tantalum carbide in the form of tantalum carbide crystals, and each tantalum carbide crystal orientation in the group of

[0111] ,

[0200] ,

[0220] ,

[0311] , and

[0311] is determined from the maximum peak intensity of the X-ray diffractogram detected with CuKα radiation having a wavelength of 1.5406 Å by the following formula:

[0106]

Equation

[0107] (wherein I i is selected corresponding to the maximum intensity of the crystal orientation, n = 5, and I 111 is the maximum intensity at 2θ in the range of 33.9° to 35.9°, I 200 is the maximum intensity at 2θ in the range of 39.4° to 41.4°, I 220 is the maximum intensity at 2θ in the range of 57.6° to 59.6°, I 311 is the maximum intensity at 2θ in the range of 69.0° to 71.0°, I 222 is the maximum intensity at 2θ in the range of 72.6° to 74.6°, I i,0 is the texture coefficient TC of about 0.5 to about 1.5 calculated according to (the intensity of the crystal orientation expected when the crystal orientation of the tantalum carbide crystal is random)), i is shown.

[0108] A tantalum carbide coating showing a substantially random crystal orientation can exhibit higher chemical resistance.

[0109] A tantalum carbide coating containing a substantially random crystal orientation can also be produced, for example, by sintering tantalum carbide particles on a substrate surface. However, the tantalum carbide coating formed by sintering can be porous. To reduce the porosity, a sintering aid may be mixed with the tantalum carbide particles. However, the sintering aid can introduce unnecessary impurities into the tantalum carbide coating.

[0110] In some embodiments, the first tantalum carbide layer may have a porosity of less than 5% by volume, more specifically less than 1% by volume, particularly less than 0.1% by volume.

[0111] In some embodiments, the first tantalum carbide layer may contain less than 1 atomic %, more specifically less than 0.1 atomic %, and particularly less than 0.01 atomic % of impurities. As used herein, the term "impurities" refers to elements other than tantalum and carbon.

[0112] In some embodiments, the distribution of the tantalum carbide crystal orientation may exhibit a texture coefficient of from about 0.35 to about 0.6, more specifically from about 0.35 to about 0.55, and particularly from about 0.4 to about 0.52.

[0113] In some embodiments, the carbonaceous substrate comprises, consists essentially of, or consists of graphite, particularly isotropic graphite. As described above, graphite can exhibit high heat resistance, a high melting point, high thermal conductivity, and a low coefficient of thermal expansion, and can thus be used in many high-temperature processes. Further, graphite can be used as a susceptor and can exhibit relatively high chemical purity. Further, graphite consists mainly of carbon and can thus provide carbon for the formation of the first tantalum carbide coating layer and the tantalum carbide pore coating. In particular, isotropic graphite can have improved mechanical properties compared to other types of graphite, such as extruded or vibration-molded graphite. Further, isotropic graphite can have pores with an average smaller maximum pore diameter. As described above, the methods described herein can enable coating pores with a smaller maximum pore diameter and can enable fixing the first tantalum carbide coating layer to isotropic graphite.

[0114] The term "graphite" is well-known and has its common meaning in the relevant technical field. More specifically, the term "graphite" may refer to a material containing crystalline carbon with a hexagonal crystal structure. Alternatively, or in addition, the term "graphite" may refer to a material containing at least about 60 atomic %, more specifically at least about 80 atomic %, particularly at least about 83 atomic % of crystalline carbon with a hexagonal crystal structure. Alternatively, or in addition, the term "graphite" may refer to a material having a graphitization degree of at least about 46 atomic %, more specifically about 69 atomic %, even more specifically at least about 80 atomic %, particularly at least about 83 atomic %.

[0115] The graphitization degree of a carbonaceous substrate can be measured by XRD. The crystalline carbon in graphite forms a plurality of honeycomb lattices. XRD can be used to measure the interplanar distance d 001 thereof. Accordingly, the term "graphite" may additionally or alternatively refer to a carbonaceous material having an interplanar distance of about 0.3400 to about 0.3354, more specifically 0.3381 to about 0.3354, even more specifically about 0.3371 to about 0.3354, particularly about 0.3369 to about 0.3354. In order to perform XRD measurement on a graphite substrate according to the present disclosure, the tantalum carbide coating layer and the tantalum carbide pore coating must be removed, and only the underlying carbonaceous material is used for the measurement.

[0116] The graphitization degree can also be calculated by the following formula using the interplanar distance.

[0117]

Equation

[0118] 0.3340 corresponds to the interplanar distance of turbostratic graphite, and 0.3354 corresponds to the interplanar distance of a perfect graphite crystal.

[0119] In some embodiments, the carbonaceous substrate may exhibit a graphitization degree of from about 46 atomic % to about 83 atomic %, more specifically from about 46 atomic % to about 69 atomic %. The thermal expansion coefficient of graphite with a lower degree of graphitization may be closer to the thermal expansion coefficient of tantalum carbide as compared to graphite with a higher degree of graphitization. As a result, graphite with a lower degree of graphitization can provide higher thermal stability of the carbonaceous substrate.

[0120] In some embodiments, the carbonaceous substrate may include carbon fiber reinforced carbon CFRC, and more specifically, the carbonaceous substrate may include at least about 90% by mass of CFRC based on the total mass of the carbonaceous substrate, and in particular, the carbonaceous substrate may include at least about 99% by mass of CFRC. CFRC can exhibit improved mechanical properties as compared to other carbonaceous substrates. Furthermore, CFRC also consists mainly of carbon and thus can provide carbon for the formation of the first tantalum carbide coating layer and the tantalum carbide pore coating. The term "CFRC" is well-known and is to have its common meaning in the art. More specifically, the term "CFRC" may refer to a composite material containing carbon fibers in a graphite matrix. In particular, the term "CFRC" may refer to a composite material consisting of carbon fibers in a graphite matrix.

[0121] In some embodiments, the carbonaceous substrate may include a second tantalum carbide coating layer, which may be positioned adjacent to the first tantalum carbide coating layer. In particular, the first tantalum carbide coating layer may be positioned between the second tantalum carbide coating layer and the outer surface of the carbonaceous substrate. The second tantalum carbide coating layer may be disposed on the first tantalum carbide coating layer. For example, the first tantalum carbide coating layer may be formed by a first coating process. Thereafter, a second or third coating process may be used to deposit a second tantalum carbide coating layer on the first tantalum carbide coating layer. The first tantalum carbide coating layer may be formed on the carbonaceous substrate by a first coating process to achieve improved fixation and only partially fill a plurality of pores. However, in order to improve, for example, the mechanical properties and chemical resistance of the carbonaceous substrate, it may be preferable to dispose a tantalum carbide layer having a greater thickness than that provided by the first tantalum carbide coating layer on the outer surface of the carbonaceous substrate. However, as described above, the growth of the first tantalum carbide coating layer by the first coating process may become very slow with an increase in the thickness of the first tantalum carbide coating layer. As a result, in order to increase the overall thickness of the tantalum carbide coating applied on the carbonaceous substrate, a second or third coating process at an elevated temperature and / or using an additional carbon source in the process gas can be used. The properties of the second tantalum carbide coating layer may be different from those of the first tantalum carbide coating layer. For example, the second tantalum carbide coating layer may exhibit a different stoichiometry of tantalum and carbon and / or a different tantalum carbide crystal orientation. However, the second tantalum carbide coating layer may also grow epitaxially on the first tantalum carbide coating layer or align with the first tantalum carbide coating layer during an annealing process and thus exhibit the above-described tantalum carbide crystal orientation.In addition, as described above, the annealing process can also shift the stoichiometry of tantalum and carbon towards carbon so that the second tantalum carbide coating layer can then exhibit a stoichiometric ratio of tantalum to carbon close to 1.

[0122] Use In a third aspect, the present disclosure relates to the use of a carbonaceous substrate according to any one of the preceding claims as a component of an epitaxial growth system, more specifically a GaN or SiC growth system, in particular as a wafer carrier of a GaN or SiC growth system, or as a component of a physical vapor transport system (PVT), more specifically as a component of a SiC PVT system for growing single crystal SiC, in particular as a crucible or hot wall of a PVT system.

[0123] In a fourth aspect, the present disclosure relates to a method for annealing a carbonaceous substrate comprising a tantalum carbide coating. The annealing process according to the fourth aspect comprises placing the coated carbonaceous substrate in an annealing chamber, heating the annealing chamber to a temperature of about 900 °C to about 1800 °C for a time of about 10 minutes to about 5 hours, and supplying a process gas to the reaction chamber, the process gas comprising a carbon-containing species, more specifically a carbon and hydrogen-containing species, in particular C2H4.

[0124] In a fifth aspect, the present disclosure relates to a method for annealing a carbonaceous substrate comprising a tantalum carbide coating. The annealing process according to the fifth aspect comprises placing the coated carbonaceous substrate in an annealing chamber and heating the reaction chamber to a temperature of about 1900 °C to about 2300 °C for a time of about 0.5 hours to about 3 hours under an inert gas atmosphere.

Examples

[0125] Experimental section Sample preparation In each of the following examples, a graphite substrate was used. The graphite used was isotropic graphite, grade R6810, which can be purchased from SGL Carbon GmbH, Germany. The dimensions of the cubic graphite substrate were 10 cm × 6 cm × 0.15 cm.

[0126] Experimental setup All of the following examples were conducted in a laboratory-scale low-pressure CVD reactor. The CVD reactor was equipped with a cell in which the gas inlet and outlet were arranged on opposite sides. The reaction chamber itself was placed inside the cell and was equipped with an induction-heated graphite susceptor with dimensions of 20 cm × 8 cm × 2 cm. The time-series test was conducted by placing four graphite samples in the reaction chamber and removing one sample after one-fourth of the total process time had elapsed.

[0127] First experiment The configuration of the first experiment can be seen in Figure 1. In the first experiment, tantalum metal powder (140) was loaded into the reaction chamber (100). A graphite substrate (130) was placed next to the metal powder (140), and the graphite substrate (130) was arranged in the downstream direction of the metal powder (140). Then the cell and the reaction chamber (100) were evacuated, and the susceptor was heated to a temperature of 1200 °C under a gas flow (110) of argon Ar as the carrier gas. When the temperature of 1200 °C was reached, HCl was added to the gas flow (110) to form the process gas. The flow rate of Ar was 1000 sccm, and the flow rate of HCl was 100 sccm. Since the reaction chamber was not sealed, the process gas could exit the reaction chamber (100) as waste gas (120). The pressure inside the reaction chamber (100) was maintained at 150 mbar, and the reaction was carried out for 3 hours.

[0128] The thickness of the obtained tantalum carbide coating was 3.7 μm. As shown in Figures 2a and 2c, the obtained coating was dense and smooth on the surface.

[0129] The results of X-ray diffraction of the coated samples are shown in Table 1.

[0130]

Table 1

[0131] As can be derived from Table 2, the tantalum carbide coating layer did not show a significant preferred crystal orientation.

[0132] The Second Experiment The configuration of the second experiment corresponded to that of the first experiment. In the second experiment, the temperature was increased to 1300 °C, while all other parameters remained unchanged.

[0133] The thickness of the obtained tantalum carbide coating was 3.3 μm. It was found that using a higher temperature led to the formation of a crust on the tantalum metal powder, which may have reduced the growth rate of the tantalum carbide coating compared to lower temperatures. Therefore, when using tantalum metal powder, a lower temperature can be used for the coating process. As shown in Figures 2b and 2d, the obtained coating was dense and smooth on the surface. The tantalum carbide crystals obtained in the second experiment were larger in size compared to those in the first experiment.

[0134] The results of the X-ray diffraction method for the coated samples are shown in Table 2.

[0135]

Table 2

[0136] As can be derived from Table 2, the tantalum carbide coating layer did not show a significant preferred crystal orientation.

[0137] The Third Experiment In the third experiment, a semi-closed reaction chamber was used. The configuration of the third experiment can be seen in Figure 4. Here too, tantalum metal powder (240) was charged into the reaction chamber (200). The graphite substrate (230) was placed on top of the tantalum metal powder (240) and supported by four support pieces of graphite felt (250). The cell and the reaction chamber (200) were evacuated and then heated to 1300 °C under an Ar flow of 1000 sccm at a pressure of 150 mbar. Once the temperature of 1300 °C was reached, a flow rate of 1000 sccm of Ar and 100 sccm of HCl was applied as process gases at a pressure of 150 mbar. The reaction was carried out for 3 hours. As shown in Figure 4, the process gas (210) flowed around the semi-closed reaction chamber inside the cell. However, a part of the gas flow (210) entered the semi-closed reaction chamber before exiting as waste gas (220) and reacted with the tantalum metal powder to form TaCl x species could be formed.

[0138] In this configuration, after TaCl x reacted with graphite, the resulting Cl2 reacted again with the tantalum metal powder to form TaCl x again, it is considered.

[0139] The thickness of the obtained tantalum carbide coating was 3.7 μm. As shown in Figure 5b, the coating was dense and smooth on the surface. However, cracks were observed as shown in Figure 5a. As can be seen in Figure 3c, the pores were only partially coated.

[0140] The results of X-ray diffraction of the coated sample are shown in Table 3.

[0141]

Table 3

[0142] As can be derived from Table 3, the tantalum carbide coating layer showed no significant preferred crystal orientation.

[0143] Fourth Experiment In the fourth experiment, a sealed process cell equipped with a semi-closed reaction chamber was used. The test configuration corresponded to that of the third experiment and can thus be seen in Figure 4. Again, tantalum metal powder was charged into the reaction chamber, and a graphite substrate supported by four support pieces of graphite felt was placed on top of the tantalum metal powder. The reaction chamber and the process cell were evacuated and then filled with Ar at a flow rate of 1000 sccm and HCl at a flow rate of 100 sccm until a pressure of 150 mbar was reached. Subsequently, the gas inlet and outlet of the process cell were closed to seal the process cell. The process gas containing HCl could enter the semi-closed reaction chamber again. Then, the reaction chamber was heated to a temperature of 1200 °C for 3 hours to perform the coating process.

[0144] The thickness of the obtained tantalum carbide coating was 1.5 μm. As shown in Figure 6b, the coating was of high density. However, cracks were observed as shown in Figure 6a. As can be seen in Figure 3b, the pores were only partially coated.

[0145] The results of X-ray diffraction of the coated sample are shown in Table 4.

[0146] [Table 4]

[0147] As can be derived from Table 4, the tantalum carbide coating layer showed no significant preferred crystal orientation.

[0148] Fifth Experiment In the fifth experiment, a sealed process cell with a semi-closed reaction chamber was used. The test configuration was the same as that of the fourth experiment. However, in the fifth experiment, a mixture of tantalum metal powder and TaCl5 was charged into the reaction chamber, and a graphite substrate supported by four support pieces of graphite felt was placed on top of the powder mixture. The reaction chamber and the process cell were evacuated, and then the process cell was filled only with Ar at a flow rate of 1000 sccm until a pressure of 150 mbar was reached. No HCl or other gaseous halide source was added. Then the gas inlet and outlet of the process cell were closed to seal the process cell. Thereafter, the reaction chamber was heated to a temperature of 1300 °C for 3 hours to perform the coating process.

[0149] Both TaCl5 powder and tantalum metal powder reacted with the graphite substrate during the process. The TaCl5 powder evaporated and reacted with the graphite substrate to form tantalum carbide, releasing Cl2 simultaneously, which then reacted with the tantalum metal powder to form TaCl x is thought to have formed.

[0150] The thickness of the obtained tantalum carbide coating was 2.2 μm. As shown in FIGS. 7a and 7b, the coating was of high density. As can be seen in FIG. 3a, the pores were only partially coated.

[0151] The results of X-ray diffraction of the coated samples are shown in Table 5.

[0152] [Table 5]

[0153] As can be derived from Table 5, the tantalum carbide coating layer showed no significant preferred crystal orientation.

[0154] The sixth experiment The configuration of the sixth experiment was the same as that of the first experiment. Therefore, the configuration of the sixth experiment can be seen in Figure 1. In contrast to the first experiment, tantalum metal powder was not loaded into the reaction chamber. The cell and the reaction chamber were evacuated, and the susceptor was heated under a gas flow of argon Ar as the carrier gas until a temperature of 1300 °C was reached. Once the temperature of 1300 °C was reached, TaCl5 was added to the gas flow to form the process gas. The flow rate of Ar was 1000 sccm. The flow rate of TaCl5 was approximately 5 sccm. TaCl5 was generated in an external evaporator. Since the reaction chamber was not sealed, the process gas could exit the reaction chamber as waste gas. The pressure inside the chamber was maintained at 150 mbar, and the reaction was carried out for 12 hours.

[0155] The thickness of the obtained tantalum carbide coating was 8.8 μm. As shown in Figure 8b, the coating was dense and smooth on the surface. However, as shown in Figure 8a, the coating also showed cracks.

[0156] The results of the X-ray diffraction method of the coated sample are shown in Table 6.

[0157]

Table 6

[0158] As can be derived from Table 6, the tantalum carbide coating layer did not show a significant preferred orientation.

[0159] By the method, as shown in Figure 13, a high-purity TaC coating is obtained.

[0160] The Seventh Experiment In the seventh experiment, the same configuration as in the sixth experiment was used. However, the temperature was set at 1500 °C. Four samples were placed in the reaction chamber, and one sample was taken out and analyzed every 3 hours. The coating thickness after 12 hours was 35 μm. However, the coating stoichiometry changed from TaC to Ta2C and Ta with the increase in the coating thickness. The change in the ratio of Ta2C, Ta, and TaC was determined by performing X-ray diffraction on the four samples. The results of the X-ray diffraction are shown in Figure 10.

[0161] The eighth experiment In the eighth experiment, the effect of annealing at 2100 °C without using a carbon source was tested. The samples from the third, fourth, sixth, and seventh experiments were annealed in an annealing furnace at a temperature of 2100 °C for 1 hour in an Ar atmosphere.

[0162] Figures 9a, 9c, 9e, and 9g show the samples before annealing, and Figures 9b, 9d, 9f, and 9h show the samples after annealing. Figures 9a and 9b show the samples of the third experiment coated for 3 hours before and after annealing at 2100 °C. Figures 9c and 9d show the samples of the fourth experiment coated for 3 hours before and after annealing at 2100 °C. Figures 9e and 9f show the samples of the sixth experiment coated for 12 hours before and after annealing at 2100 °C. Figures 9g and 9h show the samples of the seventh experiment coated for 6 hours before and after annealing at 2100 °C. As can be derived from Figures 9a to 9h, the crystal size increased and the number of grain boundaries decreased.

[0163] Furthermore, annealing the sample of the seventh experiment resulted in the conversion of Ta2C and Ta species to TaC, and a pure TaC coating was obtained. The results of the X-ray diffraction after the eighth experiment are shown in Figures 14 and 15.

[0164] The ninth experiment In the 9th experiment, the effect of annealing at 1200 °C using an additional carbon source was tested. The sample of the 7th experiment was annealed in an annealing furnace at 1200 °C for 10 minutes in an atmosphere of Ar and C2H4. The flow rate of Ar was 5000 sccm, and the flow rate of C2H4 was 25 sccm. Annealing resulted in the conversion of Ta2C and Ta species to TaC, and a pure TaC coating was obtained. The results of the X-ray diffraction method for the 9th experiment are shown in Fig. 16.

[0165] It should be understood that the present invention is defined in the appended claims, but the present invention may also (alternatively) be defined in accordance with the following embodiments.

[0166] 1. A carbonaceous substrate comprising a first tantalum carbide coating layer, wherein the first tantalum carbide coating layer is disposed on the outer surface of the carbonaceous substrate, and the carbonaceous substrate comprises a plurality of pores including a tantalum carbide pore coating, and the plurality of pores are not completely filled by the tantalum carbide pore coating.

[0167] 2. The carbonaceous substrate according to claim 1, wherein the plurality of pores are disposed less than 182 μm, particularly less than 100 μm, from the outer surface.

[0168] 3. The carbonaceous substrate according to claim 1 or 2, wherein the tantalum carbide pore coating has a thickness of less than 20 μm, more specifically less than 10 μm, particularly less than 8 μm.

[0169] 4. The tantalum carbide pore coating at a depth of about 20 μm to about 60 μm has a thickness of about 0.5 μm to about 8 μm, more specifically about 0.8 μm to about 3 μm, particularly about 1 μm to about 2.5 μm, according to any one of claims 1 to 3.

[0170] 5. The ratio of the thickness of the first tantalum carbide coating layer to the thickness of the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm is from about 2:1 to about 30:1, more specifically from about 3:1 to about 20:1, and particularly from about 5:1 to about 15:1. The carbonaceous substrate according to any one of claims 1 to 4.

[0171] 6. The plurality of pores have a maximum diameter of about 5 μm to about 100 μm, more specifically about 10 μm to about 50 μm, and particularly 15 μm to about 25 μm. The carbonaceous substrate according to any one of claims 1 to 5.

[0172] 7. At least 50%, more specifically at least 75%, and particularly at least 90% of the plurality of pores having a maximum diameter of about 5 μm to about 100 μm are not completely filled by the tantalum carbide pore coating. The carbonaceous substrate according to any one of claims 1 to 6.

[0173] 8. The volume of the plurality of pores of the carbonaceous substrate is from about 1% by volume to about 20% by volume, more specifically from about 5% by volume to about 15% by volume, and particularly from about 7% by volume to about 13% by volume. The carbonaceous substrate according to any one of claims 1 to 7.

[0174] 9. The carbonaceous substrate contains TaC to a penetration depth of at least 20 μm, more specifically at least 40 μm, and particularly at least 60 μm. The carbonaceous substrate according to any one of claims 1 to 8.

[0175] 10. The first tantalum carbide coating layer and / or the tantalum carbide pore coating has a ratio of Ta to C of from about 1.3:1 to about 1:1.3, more specifically from about 1.1:1 to about 1:1.1, and particularly from about 1.05:1 to about 1:1.05. The carbonaceous substrate according to any one of claims 1 to 9.

[0176] 11. The first tantalum carbide coating layer has a thickness of from about 0.1 μm to about 40 μm, more specifically from about 5 μm to about 35 μm, and particularly from about 10 μm to about 30 μm. The carbonaceous substrate according to any one of claims 1 to 10.

[0177] 12. The first tantalum carbide coating layer contains tantalum carbide in the form of tantalum carbide crystals, and each tantalum carbide crystal orientation in the group of

[0111] ,

[0200] ,

[0220] ,

[0311] , and

[0311] , from the maximum peak intensity of the X-ray diffraction pattern detected by CuKα rays with a wavelength of 1.5406 Å, according to the following formula:

[0178]

Equation

[0179] (where I i is correspondingly selected from the maximum intensity of the crystal orientation, n = 5, and I 111 is the maximum intensity at 2θ in the range of 33.9° to 35.9°, I 200 is the maximum intensity at 2θ in the range of 39.4° to 41.4°, I 220 is the maximum intensity at 2θ in the range of 57.6° to 59.6°, I 311 is the maximum intensity at 2θ in the range of 69.0° to 71.0°, I 222 is the maximum intensity at 2θ in the range of 72.6° to 74.6°, I i,0 is the intensity of the crystal orientation expected when the crystal orientation of the tantalum carbide crystal is random), the texture coefficient TC of about 0.5 to about 1.5 calculated according to this formula i is shown. The carbonaceous substrate according to any one of claims 1 to 11.

[0180] 13. The carbonaceous substrate according to any one of claims 1 to 12, wherein the carbonaceous substrate contains graphite, consists essentially of graphite, or consists of graphite.

[0181] 14. The carbonaceous substrate includes a second tantalum carbide coating layer, the second tantalum carbide coating layer is located adjacent to the first tantalum carbide coating layer, and in particular, the first tantalum carbide coating layer is located between the second tantalum carbide coating layer and the outer surface of the carbonaceous substrate. The carbonaceous substrate according to any one of claims 1 to 13.

[0182] 15. A vapor deposition method for coating a carbonaceous substrate with a tantalum carbide coating, including a coating process, the coating process being - placing the carbonaceous substrate in a reaction chamber; - heating the reaction chamber to a temperature of about 1100 °C to about 1500 °C for a time of about 1 hour to about 24 hours; - supplying a process gas to the reaction chamber, the process gas containing a halide-containing species, and the process gas containing less than 4 atomic % carbon and less than 10 vol % H2 for at least 15 minutes after the start of the method, and supplying a tantalum-containing species to the reaction chamber, or placing a solid containing tantalum in the reaction chamber, or placing a solid containing tantalum halide in the reaction chamber and including.

[0183] 16. The method according to claim 15, wherein the solid containing tantalum contains tantalum in a metallic form, in particular tantalum metal powder.

[0184] 17. The tantalum-containing species and the halide-containing species are the same, and in particular, the process gas contains TaCl5 and / or other TaCl x species. The method according to claim 15.

[0185] 18. The solid containing tantalum halide contains tantalum halide in the form of TaCl5 and / or other TaCl x species, in particular tantalum halide in the form of TaCl5 and / or TaCl x powder. The method according to claim 15.

[0186] 19. The coating process includes first and second coating steps, the first coating step is performed at a first temperature, the second coating step is performed at a second temperature, and in particular, the first temperature is lower than the second temperature. The method according to any one of claims 15 to 18.

[0187] 20. The first temperature is about 1150 °C to about 1250 °C, and / or the second temperature is about 1250 °C to about 1350 °C. The method according to claim 20.

[0188] 21. The coating process includes a third coating step, the third coating step is performed at a third temperature, and in particular, the third temperature is higher than the first and / or second temperature. The method according to any one of claims 15 to 20.

[0189] 22. The third temperature is at least about 1350 °C, more specifically about 1350 °C to about 1600 °C, and in particular about 1350 °C to about 1450 °C. The method according to claim 21.

[0190] 23. The time of each of the first and / or second coating steps is at least about 15 minutes, more specifically about 30 minutes to about 120 minutes, and in particular about 45 minutes to about 90 minutes. The method according to claim 19 or 20, or if dependent on claim 18, according to claim 21 or 22.

[0191] 24. The time of the third coating step is at least about 60 minutes, more specifically at least about 180 minutes, and in particular at least about 300 minutes. The method according to claim 21 or 22.

[0192] 25. The process gas in the first coating step contains less than 5 atomic%, more specifically less than 1 atomic%, and in particular less than 0.1 atomic% carbon, based on the total number of atoms in the process gas. The method according to claim 19 or 20, or if dependent on claim 18, according to any one of claims 21 to 24.

[0193] 26. The process gas in the first coating step contains less than 4% by volume, more specifically less than 1% by volume, and particularly less than 0.1% by volume of H2 with respect to the total volume of the process gas. The method according to any one of claims 19 or 20, or claims 21 to 25 when dependent on claim 18.

[0194] 27. The process gas in the first coating step contains a halide, particularly chlorine, with a maximum ratio of 1:0.05, more specifically 1:0.01, and particularly 1:0.001 with respect to carbon. The method according to any one of claims 19 or 20, or claims 21 to 26 when dependent on claim 18.

[0195] 28. The process gas in the first coating step contains a halide, particularly chlorine, with a maximum ratio of 1:0.05, more specifically 1:0.01, and particularly 1:0.001 with respect to H2. The method according to any one of claims 19 or 20, or claims 21 to 27 when dependent on claim 18.

[0196] 29. The process gas in the second coating step contains more than 0.1 atomic %, more specifically more than 1 atomic %, and particularly more than 5 atomic % of carbon with respect to the total number of atoms in the process gas. The method according to any one of claims 19 or 20, or claims 21 to 28 when dependent on claim 18.

[0197] 30. The halide-containing species is a chloride-containing species, more specifically the chloride-containing species is Cl2 or HCl, and particularly the halide-containing species is HCl. The method according to any one of claims 15 to 29.

[0198] 31. The process gas additionally contains an inert gas, more specifically nitrogen or argon, and particularly argon. The method according to any one of claims 15 to 30.

[0199] 32. The method according to any one of claims 15 to 31, wherein the pressure in the reaction chamber is from about 0.001 bar to about 1.1 bar, more specifically from about 0.001 bar to about 0.5 bar, particularly from about 0.1 bar to about 0.2 bar.

[0200] 33. The method according to any one of claims 15 to 32, further comprising an annealing step after the coating step.

[0201] 34. The annealing step comprises: - placing the coated carbonaceous substrate in an annealing chamber; - heating the annealing chamber to a temperature of about 900 °C to about 1800 °C for a time of about 10 minutes to about 5 hours; and - supplying a process gas to the reaction chamber, the process gas comprising a carbon-containing species, more specifically a carbon and hydrogen-containing species, particularly C2H4. The method according to claim 33, comprising the above steps.

[0202] 35. The annealing step comprises: - placing the coated carbonaceous substrate in an annealing chamber; and - heating the reaction chamber to a temperature of about 1900 °C to about 2300 °C for a time of about 0.5 hours to about 3 hours in an inert gas atmosphere. The method according to claim 33, comprising the above steps.

[0203] Use 36. Use of the carbonaceous substrate according to any one of claims 1 to 14, as a component of an epitaxial growth system, more specifically a GaN or SiC growth system, particularly as a wafer carrier of a GaN or SiC growth system, or as a component of a physical vapor transport (PVT) system, more specifically as a component of a SiC PVT system for growing SiC single crystals, particularly as a crucible or hot wall of a PVT system.

Description of the reference numerals

[0204] 100 reaction chamber 110 gas flow 120 waste gas 130 graphite substrate 140 metal powder 200 reaction chamber 210 process gas 220 waste gas 230 graphite substrate 240 metal powder 250 graphite felt

Claims

1. A carbonaceous substrate comprising a first tantalum carbide coating layer, wherein the first tantalum carbide coating layer is disposed on an outer surface of the carbonaceous substrate, and the carbonaceous substrate includes a plurality of pores including a tantalum carbide pore coating, and the plurality of pores are not completely filled by the tantalum carbide pore coating.

2. The carbonaceous substrate according to claim 1, wherein the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm has a thickness of about 0.5 μm to about 8 μm, more specifically about 0.8 μm to about 3 μm, particularly about 1 μm to about 2.5 μm.

3. The carbonaceous substrate according to claim 1 or 2, wherein a ratio of a thickness of the first tantalum carbide coating layer to a thickness of the tantalum carbide pore coating at a depth of about 20 μm to about 60 μm is about 2:1 to about 30:1, more specifically about 3:1 to about 20:1, particularly about 5:1 to about 15:

1.

4. The carbonaceous substrate according to any one of claims 1 to 3, wherein at least 50%, more specifically at least 75%, particularly at least 90% of the plurality of pores having a maximum diameter of about 5 μm to about 100 μm are not completely filled by the tantalum carbide pore coating.

5. The carbonaceous substrate according to any one of claims 1 to 4, wherein a volume of the plurality of pores in the carbonaceous substrate is about 1% by volume to about 20% by volume, more specifically about 5% by volume to about 15% by volume, particularly about 7% by volume to about 13% by volume.

6. The first tantalum carbide coating layer includes tantalum carbide in the form of tantalum carbide crystals, and each tantalum carbide crystal orientation of the group of [111], [200], [220], [311], and [311] is from a maximum peak intensity of an X-ray diffractogram detected by CuKα radiation having a wavelength of 1.5406 Å, the following formula: 【Number 1】 (wherein I ｉ is selected corresponding to the maximum intensity of the crystal orientation, n = 5, and I １１１ is the maximum intensity at 2θ in the range of 33.9° to 35.9°, I ２００ is the maximum intensity at 2θ in the range of 39.4° to 41.4°, and I ２２０ is the maximum intensity at 2θ in the range of 57.6° to 59.6°, I ３１１ is the maximum intensity at 2θ in the range of 69.0° to 71.0°, I ２２２ is the maximum intensity at 2θ in the range of 72.6° to 74.6°, I ｉ，０ is a texture coefficient TC of about 0.5 to about 1.5 calculated according to (which is the intensity of the crystal orientation expected when the crystal orientation of the tantalum carbide crystal is random). ｉ The carbonaceous substrate according to any one of claims 1 to 5, showing this.

7. A vapor deposition method for coating a carbonaceous substrate with a tantalum carbide coating, the method including a coating step, the coating step including: - disposing the carbonaceous substrate in a reaction chamber; - heating the reaction chamber to a temperature of about 1100 °C to about 1500 °C for a time of about 1 hour to about 24 hours. - Supplying a process gas to the reaction chamber, wherein the process gas contains a halide-containing species, and for at least 15 minutes after the start of the method, the process gas contains less than 4 atomic % carbon and less than 10 volume % H ２ including, supplying, and supplying a tantalum-containing species to the reaction chamber, or disposing a solid containing tantalum in the reaction chamber, or disposing a solid containing tantalum halide in the reaction chamber

8. The tantalum-containing species and the halide-containing species are the same, and in particular the process gas is TaCl ５ and / or other TaCl ｘ species, the method according to claim 7.

9. The coating process includes a first coating process and a second coating process, the first coating process is performed at a first temperature, the second coating process is performed at a second temperature, and in particular, the first temperature is lower than the second temperature. The method according to claim 7 or 8.

10. The method according to claim 9, wherein the first temperature is about 1150 °C to about 1250 °C, and / or the second temperature is about 1250 °C to about 1350 °C.

11. The method according to claim 9 or 10, wherein the time of each of the first coating process and / or the second coating process is at least about 15 minutes, more specifically about 30 minutes to about 120 minutes, and in particular about 45 minutes to about 90 minutes.

12. The method according to any one of claims 9 to 11, wherein the process gas in the first coating process contains less than 5 atomic%, more specifically less than 1 atomic%, and in particular less than 0.1 atomic% carbon based on the total number of atoms in the process gas.

13. The process gas in the first coating step contains less than 4% by volume, more specifically less than 1% by volume, and particularly less than 0.1% by volume of H with respect to the total volume of the process gas. ２ The method according to any one of claims 9 to 12, comprising the above.

14. The method according to any one of claims 7 to 13, wherein the pressure in the reaction chamber is about 0.001 bar to about 1.1 bar, more specifically about 0.001 bar to about 0.5 bar, and in particular about 0.1 bar to about 0.2 bar.

15. Use of a carbonaceous substrate according to any one of claims 1 to 6, as a component of an epitaxial growth system, more specifically a GaN or SiC growth system, and in particular as a wafer carrier of a GaN or SiC growth system, or as a component of a physical vapor transport (PVT) system, more specifically as a component of a SiC PVT system for growing single crystal SiC, and in particular as a crucible or hot wall of a PVT system.

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