A method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace.

Abstract

This disclosure relates to a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. The PVT silicon carbide crystal growth furnace includes a cylindrical vertical heating mechanism and a crystal growth furnace body, with the cylindrical vertical heating mechanism coaxially sleeved outside the crystal growth furnace body. The method includes: in an inert atmosphere, controlling the cylindrical vertical heating mechanism to sublimate tantalum powder in a second crucible and coat the inner wall surface of the frustum-shaped graphite part to be coated. This method uses a PVT silicon carbide crystal growth furnace to coat graphite parts. Compared with existing CVD methods, this device has simpler requirements for the materials used and the environment during operation, and can effectively prepare tantalum carbide thin films on the target surface of the graphite part to be coated, reducing the amount of raw materials used.

Description

Technical Field

[0001] This disclosure relates to the field of silicon carbide crystal growth technology, and more specifically, to a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. Background Technology

[0002] Silicon carbide, as a representative of third-generation semiconductor materials, possesses advantages such as a wide bandgap, high thermal conductivity, high critical breakdown field, high electron saturation, and high drift velocity, thus holding immense application potential in the semiconductor manufacturing field. Currently, physical vapor deposition (PVT) is the primary production method for silicon carbide single crystals. The specific growth method involves bonding a silicon carbide seed crystal to a seed stage on top of a graphite crucible, placing silicon carbide powder at the bottom of the crucible, and then heating the graphite crucible in a crystal growth furnace. As the temperature rises, the silicon carbide powder at the bottom of the crucible evaporates, subsequently crystallizing at the top of the graphite crucible, thus growing silicon carbide crystals. During this process, the stability of the graphite components within the graphite crucible significantly impacts silicon carbide crystal growth. Instability in the graphite components can lead to microtube defects such as carbon inclusions and microtube density. Therefore, proposals to replace the internal graphite components with tantalum carbide have gradually emerged. However, tantalum carbide is very expensive, hindering its widespread industrial application.

[0003] Currently, chemical vapor deposition (CVD) is a common method for depositing tantalum carbide thin films on graphite surfaces. However, the equipment required for CVD is extremely expensive, and the method needs to operate at high temperatures, posing safety concerns as many substrates are not thermally stable. Therefore, there is an urgent need for a method to deposit tantalum carbide on graphite surfaces. Summary of the Invention

[0004] The purpose of this disclosure is to provide a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. This method uses a PVT silicon carbide crystal growth furnace to prepare tantalum carbide thin films, uses fewer raw materials, has simple environmental requirements within the PVT silicon carbide crystal growth furnace during the preparation of tantalum carbide thin films, and the resulting tantalum carbide thin films are relatively stable.

[0005] To achieve the above objectives, this disclosure provides a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. The PVT silicon carbide crystal growth furnace includes a cylindrical vertical heating mechanism and a crystal growth furnace body, wherein the cylindrical vertical heating mechanism is coaxially sleeved outside the crystal growth furnace body.

[0006] The crystal growth furnace body includes a heat insulation layer, a first crucible, a second crucible, a top surface, a frustum-shaped graphite part to be coated, and an inverted frustum-shaped flow guide shroud. The heat insulation layer covers the surface of the first crucible facing the inner surface of the cylindrical vertical heating mechanism. The second crucible is disposed in the cavity of the first crucible with its opening facing upward. The top surface is horizontally disposed above the opening of the second crucible. The edge of the top surface is detachably connected to the edge of the upper bottom surface of the frustum-shaped graphite part to be coated, the edge of the lower bottom surface of the frustum-shaped graphite part to be coated is detachably connected to the edge of the lower bottom surface of the inverted frustum-shaped flow guide shroud, and the upper bottom surface of the inverted frustum-shaped flow guide shroud is detachably connected to the edge of the opening of the second crucible. A sealed reaction chamber is formed between the inner wall of the second crucible, the top surface, the inner wall of the frustum-shaped graphite part to be coated, and the inner wall of the inverted frustum-shaped flow guide shroud.

[0007] The method includes: in an inert atmosphere, controlling the cylindrical vertical heating mechanism to sublimate the tantalum powder in the second crucible and coat the inner wall surface of the frustum-shaped graphite part to be coated.

[0008] Optionally, the cylindrical vertical heating mechanism includes an induction coil and a quartz tube, with the induction coil wound around the outer wall of the quartz tube.

[0009] Optionally, the reaction chamber includes an upper chamber and a lower chamber; the upper chamber is formed between the top surface, the inner wall of the inverted frustum-shaped flow guide, the inner wall of the frustum-shaped graphite part to be coated, and the upper part of the opening of the second crucible; the lower chamber is formed between the inner wall of the second crucible and the lower part of its opening; the induction coil includes a first induction coil and a second induction coil, the first induction coil being disposed outside the upper chamber, and the second induction coil being disposed outside the lower chamber; the number of turns of the first induction coil is less than or equal to the number of turns of the second induction coil.

[0010] Optionally, the inner wall of the first crucible has raised steps, which are used to secure the lower bottom edge of the inverted frustum-shaped flow guide and the lower bottom edge of the frustum-shaped graphite part to be coated;

[0011] Preferably, the raised step is a retaining ring coaxial with the first crucible, and the retaining ring protrudes radially from the inner sidewall surface of the first crucible.

[0012] Optionally, the step of sublimating the tantalum powder placed in the second crucible and then coating it onto the inner wall surface of the frustum-shaped graphite part to be coated includes: controlling the cylindrical vertical heating mechanism to perform a first heating treatment and a second heating treatment in sequence, followed by a cooling treatment.

[0013] Optionally, the conditions for the first heating treatment include: the temperature of the reaction chamber is 1750-2000℃, the gas pressure is 0.2-5mbar, and the time is 1-5h; the conditions for the second heating treatment include: the temperature of the reaction chamber is 1800-2200℃, the gas pressure is 0.2-5mbar, and the time is 2-20h; the cooling treatment includes: reducing the pressure in the reaction chamber to 500-600mbar, reducing the power of the cylindrical vertical heating mechanism, and turning off the cylindrical vertical heating mechanism when the temperature in the reaction chamber is less than 1200℃.

[0014] Optionally, the conditions for the first heating treatment include: the temperature of the upper chamber is 1750-1850℃, the temperature of the lower chamber is 1900-2000℃, the gas pressure is 0.2-5mbar, and the time is 1-5h; the conditions for the second heating treatment include: the temperature of the upper chamber is 1800-1900℃, the temperature of the lower chamber is 2000-2200℃, the gas pressure is 0.2-5mbar, and the time is 2-20h.

[0015] Optionally, the insulation layer is an insulation soft felt layer with a thickness of 5-15cm, and a temperature measuring hole is provided on the upper part of the insulation layer.

[0016] Optionally, the first crucible and the second crucible are each independently a graphite crucible or a tantalum carbide crucible; the material of the flow guide is graphite or tantalum carbide; and the material of the top surface is graphite or tantalum carbide.

[0017] Optionally, the number of turns of the first induction coil is 5-8, and the number of turns of the second induction coil is 5-8.

[0018] Through the above technical solution, this disclosure provides a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. This method uses a PVT silicon carbide crystal growth furnace to deposit the film on the graphite parts. Compared with existing CVD methods, this equipment has simpler requirements for the materials used and the environment during operation. It can effectively prepare tantalum carbide thin films on the target surface of the graphite parts to be coated, reducing the amount of raw materials used. The prepared coated graphite parts have good structural stability, and using them in the silicon carbide single crystal growth process can reduce the generation of carbon inclusions and microtube defects during silicon carbide crystal growth.

[0019] Other features and advantages of this disclosure will be described in detail in the following detailed description section. Attached Figure Description

[0020] The accompanying drawings are provided to further illustrate the present disclosure and form part of the specification. They are used together with the following detailed description to explain the present disclosure, but do not constitute a limitation thereof. In the drawings:

[0021] Figure 1 This is a schematic diagram of the structure of the PVT silicon carbide crystal growth furnace used in the method disclosed herein.

[0022] Explanation of reference numerals in the attached figures

[0023] 1. Induction coil 2. Quartz tube 3. Insulation layer

[0024] 4 First crucible; 5 Top surface; 6 Frustum-shaped graphite part to be coated.

[0025] 7. Inverted frustum-shaped flow guide shroud; 8. Lower cavity; 9. Second crucible

[0026] 10 Upper cavity 11 Protruding step Detailed Implementation

[0027] The specific embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are for illustration and explanation only and are not intended to limit this disclosure.

[0028] In this disclosure, unless otherwise stated, directional terms such as "upper" and "lower" generally refer to the upper and lower positions of the PVT silicon carbide crystal growth furnace under normal use. For details, please refer to [reference needed]. Figure 1 The orientation of the drawing, "inside" and "outside" refer to the outline of the PVT silicon carbide crystal growth furnace and the furnace body itself.

[0029] like Figure 1 As shown, this disclosure provides a method for preparing tantalum carbide thin films on the surface of graphite parts using a PVT silicon carbide crystal growth furnace. The PVT silicon carbide crystal growth furnace includes a cylindrical vertical heating mechanism and a crystal growth furnace body. The cylindrical vertical heating mechanism is coaxially sleeved outside the crystal growth furnace body.

[0030] The crystal growth furnace body includes a heat insulation layer 3, a first crucible 4, a second crucible 9, a top surface 5, a frustum-shaped graphite part to be coated 6, and an inverted frustum-shaped flow guide 7. The heat insulation layer 3 covers the surface of the first crucible 4 facing the inner surface of the cylindrical vertical heating mechanism. The second crucible 9 is disposed in the cavity of the first crucible 4 with its opening facing upward. The top surface 5 is horizontally disposed above the opening of the second crucible 9. The edge of the top surface 5 is detachably connected to the edge of the upper bottom surface of the frustum-shaped graphite part to be coated 6, the edge of the lower bottom surface of the frustum-shaped graphite part to be coated 6 is detachably connected to the edge of the lower bottom surface of the inverted frustum-shaped flow guide 7, and the upper bottom surface of the inverted frustum-shaped flow guide 7 is detachably connected to the edge of the opening of the second crucible 9. A sealed reaction chamber is formed between the inner wall of the second crucible 9, the top surface 5, the inner wall of the frustum-shaped graphite part to be coated 6, and the inner wall of the inverted frustum-shaped flow guide 7.

[0031] The method includes: in an inert atmosphere, controlling the cylindrical vertical heating mechanism to sublimate the tantalum powder in the second crucible 9 and coat the inner wall surface of the frustum-shaped graphite part 6 to be coated.

[0032] In this disclosure, a PVT silicon carbide crystal growth furnace is used to coat graphite parts. Compared with existing CVD methods, this apparatus has simpler requirements for the materials used and the environment during operation. It can effectively prepare tantalum carbide thin films on the target surface of the graphite parts to be coated, reducing the amount of raw materials used. The prepared coated graphite parts have good structural stability, and using them in the silicon carbide single crystal growth process can reduce the generation of carbon inclusions and microtube defects in silicon carbide crystals during growth.

[0033] The second crucible of this disclosure forms a sealed reaction chamber between its inner wall, top surface, the inner wall of the frustum-shaped graphite part to be coated, and the inner wall of the inverted frustum-shaped flow guide, which is beneficial for the tantalum powder in the second crucible to sublimate and directly coat the inner wall of the graphite part to be coated.

[0034] According to this disclosure, "in an inert atmosphere" means that the reaction chamber is inert. In one specific embodiment of this disclosure, the method includes: checking the reaction chamber for leaks before filling it with an inert gas to form an inert atmosphere; preferably, the reaction chamber is evacuated for leak checking. This disclosure does not specifically limit the type of inert gas, as long as it is a gas that does not react with tantalum powder, such as including but not limited to nitrogen, helium, argon, etc.

[0035] In this disclosure, the edge of the top surface 5 is detachably connected to the edge of the upper bottom surface of the frustum-shaped graphite part 6 to be coated, the edge of the lower bottom surface of the frustum-shaped graphite part 6 to be coated is detachably connected to the edge of the lower bottom surface of the inverted frustum-shaped flow guide 7, and the upper bottom surface of the inverted frustum-shaped flow guide 7 is detachably connected to the opening edge of the second crucible 9. This disclosure does not specifically limit the detachable connection method; for example, it can be a snap-fit ​​or collapsible connection. In one specific embodiment of this disclosure, the edge of the top surface 5 is snap-fit ​​connected to the edge of the upper bottom surface of the frustum-shaped graphite part 6 to be coated, the edge of the lower bottom surface of the frustum-shaped graphite part 6 to be coated is snap-fit ​​connected to the edge of the lower bottom surface of the inverted frustum-shaped flow guide 7, and the upper bottom surface of the inverted frustum-shaped flow guide 7 is snap-fit ​​connected to the opening edge of the second crucible 9; this facilitates the disassembly of each component.

[0036] In one specific embodiment of this disclosure, the cylindrical vertical heating mechanism includes an induction coil 1 and a quartz tube 2, wherein the induction coil 1 is wound around the outer wall of the quartz tube 2. In the above embodiment, the winding method of the induction coil is not specifically limited; for example, it can be wound in a single layer or in multiple layers.

[0037] In one specific embodiment of this disclosure, the reaction chamber includes an upper chamber 10 and a lower chamber 8; the upper chamber 10 is formed between the top surface 5, the inner wall of the inverted frustum-shaped flow guide 7, the inner wall of the frustum-shaped graphite part to be coated 6, and the upper part of the opening of the second crucible 9; the lower chamber 8 is formed between the inner wall of the second crucible 9 and the lower part of its opening. In the above embodiment, the upper and lower chambers are two connected chambers, so that the tantalum powder in the lower chamber can directly enter the upper chamber after sublimation and react on the surface of the frustum-shaped graphite part to be coated to form a tantalum carbide film.

[0038] In a preferred embodiment of this disclosure, the induction coil 1 includes a first induction coil and a second induction coil. The first induction coil is disposed outside the upper cavity 10, and the second induction coil is disposed outside the lower cavity 8. The number of turns of the first induction coil is less than or equal to the number of turns of the second induction coil. In the above embodiment, the number of turns of the first induction coil outside the upper cavity is less than the number of turns of the second induction coil outside the lower cavity, so that the temperature of the upper cavity is lower than the temperature of the lower cavity when the heating mechanism is running. In a specific embodiment of this disclosure, the number of turns of the first induction coil is set to be less than the number of turns of the second induction coil, so that the temperatures of the upper cavity and the lower cavity are different. In another specific embodiment of this disclosure, the number of turns of the first induction coil is set to be the same as the number of turns of the second induction coil, and the temperature of the upper cavity and the lower cavity is changed by changing the power of the heating mechanism. The second induction coil with a large number of turns generates relatively more heat, while the first induction coil with a small number of turns generates relatively less heat, thereby making the temperature of the lower cavity higher than the temperature of the upper cavity. The higher temperature of the lower cavity is conducive to the sublimation of tantalum powder, and the temperature difference between the upper cavity and the lower cavity is conducive to the sublimated tantalum powder adhering to the inner wall surface of the frustum-shaped graphite part to be coated.

[0039] In one specific embodiment of this disclosure, the inner sidewall of the first crucible 4 has a raised step 11, which is used to secure the lower bottom edge of the inverted frustum-shaped flow guide 7 and the lower bottom edge of the frustum-shaped graphite part 6 to be coated. In the above embodiment, the raised step 11 includes an upper surface and a lower surface. The lower bottom edge of the inverted frustum-shaped flow guide 7 is connected to the lower surface of the raised step by a secured connection, and the lower bottom edge of the frustum-shaped graphite part 6 to be coated is connected to the upper surface of the raised step by a secured connection. This connection method facilitates the disassembly of various components and facilitates the formation of a sealed cavity. In a preferred embodiment of this disclosure, the raised step 11 is a retaining ring coaxial with the first crucible 4, and the retaining ring protrudes radially from the inner sidewall surface of the first crucible 4.

[0040] In one specific embodiment of this disclosure, the step of sublimating the tantalum powder placed in the second crucible 9 and coating it onto the inner wall surface of the frustum-shaped graphite part 6 to be coated includes: controlling the cylindrical vertical heating mechanism to perform a first heating treatment and a second heating treatment in sequence, followed by a cooling treatment.

[0041] In a preferred embodiment of this disclosure, the conditions for the first heat treatment include: a temperature of 1750-2000℃, a gas pressure of 0.2-5 mbar, and a time of 1-5 h; the conditions for the second heat treatment include: a temperature of 1800-2200℃, a gas pressure of 0.2-5 mbar, and a time of 2-20 h; preferably, the conditions for the second heat treatment include: a temperature of 1820-1880℃, a gas pressure of 0.5-3 mbar, and a time of 5-10 h. In the above embodiments, the heat treatment is divided into two stages. The first heat treatment can sublimate a small amount of tantalum powder and internal impurity elements, achieving the purpose of impurity removal. The second heat treatment further increases the temperature, enabling the tantalum powder to sublimate. In a specific embodiment, after the upper and lower chambers reach a preset temperature through the first heat treatment, a vacuum treatment is performed to control the gas pressure in the reaction chamber, thereby promoting the sublimation of tantalum powder into the upper chamber. Vacuuming is a technical means conventionally used by those skilled in the art and will not be described in detail here.

[0042] In a preferred embodiment of this disclosure, the cooling process includes: reducing the pressure inside the reaction chamber to 500-600 mbar, decreasing the power of the cylindrical vertical heating mechanism, and shutting off the cylindrical vertical heating mechanism when the temperature inside the reaction chamber is less than 1200°C. In the above embodiment, the pressure inside the reaction chamber can be controlled to 500-600 mbar by introducing gas; the introduced gas can be an inert gas, such as, but not limited to, N2 and Ar. In one embodiment, the reaction chamber is allowed to cool naturally after the cylindrical vertical heating mechanism is shut off.

[0043] In one specific embodiment of this disclosure, the conditions for the first heating treatment include: the temperature of the upper chamber 10 is 1750-1850℃, the temperature of the lower chamber 8 is 1900-2000℃, the air pressure is 0.2-5 mbar, and the time is 1-5 h; preferably, the temperature of the upper chamber 10 is 1780-1830℃, and the temperature of the lower chamber 8 is 1930-1980℃; the conditions for the second heating treatment include: the temperature of the upper chamber 10 is 1800-1900℃, the temperature of the lower chamber 8 is 2000-2200℃, the air pressure is 0.2-5 mbar, and the time is 2-20 h; preferably, the temperature of the upper chamber 10 is 1830-1880℃, the temperature of the lower chamber 8 is 2050-2200℃, the air pressure is 0.3-2 mbar, and the time is 5-10 h. Under the above conditions, there is a temperature difference between the lower cavity and the upper cavity, and the higher temperature in the lower cavity can cause the tantalum powder to sublimate. The sublimated tantalum powder enters the upper cavity. Since the temperature of the lower cavity is higher than that of the upper cavity, the sublimated tantalum powder is coated on the inner wall surface of the frustum-shaped graphite part to be coated in the upper cavity.

[0044] In one specific embodiment of this disclosure, the insulation layer 3 is an insulating soft felt layer, and the thickness of the insulation layer 3 can vary within a wide range, preferably 5-15 cm. A temperature measuring hole is provided on the upper part of the insulation layer 3 for monitoring the temperature inside the cavity of the crystal growth furnace. This disclosure does not impose specific limitations on the material of the insulating soft felt layer; it can be any material commonly used by those skilled in the art, such as graphite insulating soft felt.

[0045] In one specific embodiment of this disclosure, the first crucible 4 and the second crucible 9 are each independently a graphite crucible or a tantalum carbide crucible. In a preferred embodiment of this disclosure, the first crucible 4 and the second crucible 9 can each be independently a graphite crucible.

[0046] In one specific embodiment of this disclosure, the material of the flow guide is graphite or tantalum carbide; the material of the top surface 5 is graphite or tantalum carbide.

[0047] According to this disclosure, the number of turns of the first induction coil and the number of turns of the second induction coil can vary within a large range. In one specific embodiment of this disclosure, the number of turns of the first induction coil is 5-8, and the number of turns of the second induction coil is 5-8.

[0048] The present invention will be further illustrated by the following examples, but the present invention is not limited thereto.

[0049] Unless otherwise specified, all materials used in this embodiment are commercially available products.

[0050] Example 1

[0051] like Figure 1 As shown, the PVT silicon carbide crystal growth furnace includes a cylindrical vertical heating mechanism and a crystal growth furnace body. The cylindrical vertical heating mechanism is coaxially sleeved on the crystal growth furnace body.

[0052] The crystal growth furnace body includes an insulation layer 3, a first crucible 4, a second crucible 9, a top surface 5, a frustum-shaped graphite part to be coated 6, and an inverted frustum-shaped flow guide 7. The insulation layer 3 covers the surface of the first crucible 4 facing the inner surface of the cylindrical vertical heating mechanism. The second crucible 9 is disposed in the cavity of the first crucible 4 with its opening facing upward. The top surface 5 is horizontally disposed above the opening of the second crucible 9. The edge of the top surface 5 is detachably connected to the edge of the upper bottom surface of the frustum-shaped graphite part to be coated 6. The edge of the lower bottom surface of the frustum-shaped graphite part to be coated 6 is detachably connected to the edge of the lower bottom surface of the inverted frustum-shaped flow guide 7. The upper bottom surface of the inverted frustum-shaped flow guide 7 is detachably connected to the edge of the opening of the second crucible 9. A sealed reaction chamber is formed between the inner wall of the second crucible 9, the top surface 5, the inner wall of the frustum-shaped graphite part to be coated 6, and the inner wall of the inverted frustum-shaped flow guide 7.

[0053] The cylindrical vertical heating mechanism includes an induction coil 1 and a quartz tube 2, with the induction coil 1 wound around the outer wall of the quartz tube 2.

[0054] The reaction chamber includes an upper chamber 10 and a lower chamber 8; the upper chamber 10 is formed between the top surface 5, the inner wall of the inverted frustum-shaped flow guide 7, the inner wall of the frustum-shaped graphite part to be coated 6, and the upper part of the opening of the second crucible 9; the lower chamber 8 is formed between the inner wall of the second crucible 9 and the lower part of its opening.

[0055] The induction coil 1 includes a first induction coil and a second induction coil. The first induction coil is disposed on the outside of the upper cavity 10, and the second induction coil is disposed on the outside of the lower cavity 8. The number of turns of the first induction coil is less than or equal to the number of turns of the second induction coil.

[0056] The inner wall of the first crucible 4 has a raised step 11, which is used to secure the lower bottom edge of the inverted frustum-shaped flow guide 7 and the lower bottom edge of the frustum-shaped graphite part 6 to be coated.

[0057] Specific methods include:

[0058] Weigh 200g of tantalum powder with a purity greater than 99.99% and place it in the second crucible, then shake until the surface is smooth.

[0059] The second crucible is placed inside the first crucible, which is wrapped with a 15cm thick graphite insulation felt. Then, the graphite inverted frustum-shaped flow guide, the frustum-shaped graphite part to be coated, and the graphite sheet are placed in sequence, so that the second crucible, the graphite inverted frustum-shaped flow guide, the frustum-shaped graphite part to be coated, and the graphite sheet are stably matched to form a sealed reaction chamber.

[0060] The first crucible, wrapped with a 15cm thick graphite insulating felt, is placed in a cylindrical vertical heating mechanism, with the upper cavity corresponding to a 5-turn induction coil and the lower cavity corresponding to a 5-turn induction coil.

[0061] The reaction chamber was evacuated to a pressure of 10. -5 Under conditions of mbar, argon gas was introduced and the pressure was controlled at 500 mbar. The cylindrical vertical heating mechanism was turned on for the first heating treatment. The temperature of the upper chamber was 1780℃ and the temperature of the lower chamber was 1930℃. The reaction chamber was evacuated to a pressure of 0.2 mbar in the upper and lower chambers and maintained for 1 hour. Then, the second heating treatment was performed. The temperature of the upper chamber was 1880℃ and the pressure was 0.2 mbar for 4 hours. The temperature of the lower chamber was 2200℃ and the pressure was 0.2 mbar for 4 hours.

[0062] After the heat treatment is completed, N2 is introduced into the reaction chamber to make the pressure in the reaction chamber 500 mbar. At the same time, the power of the cylindrical vertical heating mechanism is reduced. When the temperature drops to 1200℃, the cylindrical vertical heating mechanism is turned off, and the reaction chamber is allowed to cool naturally. A graphite part A coated with a tantalum carbide film is obtained.

[0063] Example 2

[0064] Weigh 280g of tantalum powder with a purity greater than 99.99% and place it in the second crucible, then shake until the surface is smooth.

[0065] The second crucible is placed inside the first crucible, which is wrapped with a 14cm thick graphite insulation felt. Then, the inverted frustum-shaped flow guide, the frustum-shaped graphite part to be coated, and the graphite sheet are placed in sequence, so that the second crucible, the inverted frustum-shaped graphite flow guide, the frustum-shaped graphite part to be coated, and the graphite sheet are stably matched to form a sealed reaction chamber.

[0066] The first crucible, wrapped with a 14cm thick graphite insulating felt, is placed in a cylindrical vertical heating mechanism, with the upper cavity corresponding to a 5-turn induction coil and the lower cavity corresponding to a 5-turn induction coil.

[0067] The reaction chamber was evacuated to a pressure of 10. -5 Under conditions of mbar, argon gas was introduced and the pressure was controlled at 500 mbar. The cylindrical vertical heating mechanism was turned on for the first heating treatment, with the upper chamber temperature at 1780℃ and the lower chamber temperature at 1930℃. The reaction chamber was evacuated to a pressure of 0.2 mbar in both the upper and lower chambers and maintained for 1 hour. Then, the second heating treatment was performed, with the upper chamber temperature at 1880℃ and the pressure at 0.2 mbar for 4 hours, and the lower chamber temperature at 2050℃ and the pressure at 0.2 mbar for 4 hours.

[0068] After the heat treatment is completed, N2 is introduced into the reaction chamber to make the pressure in the reaction chamber 500 mbar. At the same time, the power of the cylindrical vertical heating mechanism is reduced. When the temperature drops to 1200℃, the cylindrical vertical heating mechanism is turned off, and the reaction chamber is allowed to cool naturally. Graphite part B coated with a tantalum carbide film is obtained.

[0069] Example 3

[0070] The graphite part C coated with a tantalum carbide film was prepared using the same method as in Example 2, except that the first crucible was wrapped with a 10 cm thick graphite insulating felt; the reaction chamber was evacuated to a pressure of 10. -5 Under conditions of mbar, argon gas was introduced and the pressure was controlled at 500 mbar. A cylindrical vertical heating mechanism was then activated for the first heating treatment, with the upper chamber temperature at 1700℃ and the lower chamber temperature at 1820℃. A vacuum was then evacuated to a pressure of 0.2 mbar in both chambers and maintained for 1 hour. A second heating treatment was then performed, with the upper chamber temperature at 1800℃ and the pressure at 0.1 mbar for 5 hours, and the lower chamber temperature at 1900℃ and the pressure at 0.1 mbar for 5 hours. This yielded a graphite part C coated with a tantalum carbide film.

[0071] Test case

[0072] The graphite parts A, B, and C coated with tantalum carbide thin film prepared in Examples 1-3, and the graphite parts without tantalum carbide thin film, are applied in the silicon carbide crystal growth process. Specific methods include:

[0073] Example 1 (as shown) Figure 1 The frustum-shaped graphite part 6 to be coated and the inverted frustum-shaped flow guide 7 shown in the figure are both replaced with graphite parts containing tantalum carbide thin film, and the top surface is a wafer.

[0074] Weigh 3000g of silicon carbide powder and place it in the second crucible, then shake until the surface is smooth. Evacuate the reaction chamber to a pressure of 10... -5 Under the condition of mbar, argon gas is introduced and the pressure is controlled at 450 mbar. The cylindrical vertical heating mechanism is turned on for heating treatment. When the temperature of the lower chamber reaches 2250℃, the silicon carbide powder begins to sublimate. The silicon carbide seed crystal is grown in this environment for 7-9 days.

[0075] After the silicon carbide seed crystals are grown, the graphite parts are taken out for observation. The surfaces of graphite parts A and B, which are covered with tantalum carbide film, are flat. The surface of graphite part C, which is covered with tantalum carbide film, is mostly flat with slight defects. The surface of graphite parts without tantalum carbide film is uneven.

[0076] The preferred embodiments of this disclosure have been described in detail above with reference to the accompanying drawings. However, this disclosure is not limited to the specific details of the above embodiments. Within the scope of the technical concept of this disclosure, various simple modifications can be made to the technical solutions of this disclosure, and these simple modifications all fall within the protection scope of this disclosure.

[0077] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, this disclosure will not describe the various possible combinations separately.

[0078] Furthermore, various different embodiments of this disclosure can be combined in any way, as long as they do not violate the spirit of this disclosure, they should also be regarded as the content disclosed in this disclosure.

Claims

1. A method for preparing a tantalum carbide film on the surface of a graphite member using a PVT silicon carbide growth furnace, characterized by, The PVT silicon carbide crystal growing furnace comprises a cylindrical vertical heating mechanism and a crystal growing furnace body, wherein the cylindrical vertical heating mechanism is coaxially sleeved outside the crystal growing furnace body; The crystal growing furnace body comprises a heat preservation layer (3), a first crucible (4), a second crucible (9), a top surface (5), a circular truncated cone-shaped to-be-coated graphite piece (6), and a circular truncated cone-shaped flow guide cover (7); the heat preservation layer (3) is covered on the surface of the first crucible (4) facing the inner surface of the cylindrical vertical heating mechanism; the second crucible (9) is arranged in the cavity of the first crucible (4) and opens upward; The top surface (5) is horizontally arranged above the opening of the second crucible (9), the edge of the top surface (5) is detachably connected with the edge of the upper bottom surface of the circular truncated cone-shaped to-be-coated graphite piece (6), the edge of the lower bottom surface of the circular truncated cone-shaped to-be-coated graphite piece (6) is detachably connected with the edge of the lower bottom surface of the circular truncated cone-shaped flow guide cover (7), and the upper bottom surface of the circular truncated cone-shaped flow guide cover (7) is detachably connected with the edge of the opening of the second crucible (9); a sealed reaction cavity is formed between the inner wall of the second crucible (9), the top surface (5), the inner side wall of the circular truncated cone-shaped to-be-coated graphite piece (6), and the inner side wall of the circular truncated cone-shaped flow guide cover (7); The method comprises the following steps: in an inert atmosphere, the cylindrical vertical heating mechanism is controlled to make the tantalum powder in the second crucible (9) sublimate and cover the inner wall surface of the circular truncated cone-shaped to-be-coated graphite piece (6); The method comprises the following steps: the tantalum powder in the second crucible (9) is sublimated and covers the inner wall surface of the circular truncated cone-shaped to-be-coated graphite piece (6) by controlling the cylindrical vertical heating mechanism to sequentially perform a first heating treatment and a second heating treatment, and then performing a cooling treatment; The first heating treatment comprises the following conditions: the temperature of the reaction cavity is 1750-2000 ℃, the air pressure is 0.2-5 mbar, and the time is 1-5 h; The second heating treatment comprises the following conditions: the temperature of the reaction cavity is 1800-2200 ℃, the air pressure is 0.2-5 mbar, and the time is 2-20 h.

2. The method of claim 1, wherein, The cylindrical vertical heating mechanism comprises an induction coil (1) and a quartz tube (2), and the induction coil (1) is wound on the outer side wall of the quartz tube (2).

3. The method of claim 2, wherein, The reaction cavity comprises an upper cavity (10) and a lower cavity (8); the top surface (5), the inner side wall of the circular truncated cone-shaped flow guide cover (7), the inner side wall of the circular truncated cone-shaped to-be-coated graphite piece (6), and the upper part of the opening of the second crucible (9) form the upper cavity (10); the inner side wall of the second crucible (9) and the lower part of the opening of the second crucible (9) form the lower cavity (8); The induction coil (1) comprises a first induction coil and a second induction coil, the first induction coil is arranged outside the upper cavity (10), and the second induction coil is arranged outside the lower cavity (8); the number of turns of the first induction coil is less than or equal to the number of turns of the second induction coil.

4. The method of claim 1, wherein, The inner side wall of the first crucible (4) has a convex step (11) for fixing the lower bottom edge of the inverted conical fairing (7) and the lower bottom edge of the conical coated graphite piece (6). The convex step (11) is a snap ring coaxial with the first crucible (4), which is radially convex from the inner side wall surface of the first crucible (4).

5. The method of claim 1, wherein, The cooling treatment includes: setting the pressure in the reaction cavity to 500-600 mbar, reducing the power of the cylindrical vertical heating mechanism, and closing the cylindrical vertical heating mechanism when the temperature in the reaction cavity is less than 1200℃.

6. The method of claim 3, wherein, The first heating treatment includes: the temperature of the upper cavity (10) is 1750-1850℃, the temperature of the lower cavity (8) is 1900-2000℃, the air pressure is 0.2-5 mbar, and the time is 1-5 h. The second heating treatment includes: the temperature of the upper cavity (10) is 1800-1900℃, the temperature of the lower cavity (8) is 2000-2200℃, the air pressure is 0.2-5 mbar, and the time is 2-20 h.

7. The method of claim 1, wherein, The heat preservation layer (3) is a heat preservation soft felt layer, the thickness of the heat preservation layer (3) is 5-15 cm, and a temperature measuring hole is arranged at the upper part of the heat preservation layer (3).

8. The method of claim 1, wherein, The first crucible (4) and the second crucible (9) are independently graphite crucibles or tantalum carbide crucibles; the material of the fairing is graphite or tantalum carbide; the material of the top surface (5) is graphite or tantalum carbide.

9. The method of claim 3, wherein, The number of turns of the first induction coil is 5-8, and the number of turns of the second induction coil is 5-8.

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