Preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth

Abstract

The invention relates to the technical field of porous graphite preparation, in particular to a preparation method of fiber porous graphite for semiconductor-grade silicon carbide crystal growth, which comprises the following steps: S1, carbon fiber pretreatment: selecting high-purity PAN (polyacrylonitrile)-based fibers or pitch-based fibers as raw materials, placing the long-fiber raw materials on a high-precision shearing machine, and shearing to obtain carbon fibers; the method comprises the following steps: cutting short-filament fiber bundles with the length of 30-50mm into short-filament fiber bundles, uniformly putting the cut short-filament fiber bundles into a fiber beater which is provided with a toothed claw-shaped structure rotating at a high speed, and mechanically beating the fiber bundles at the rotating speed of 1500-2000r / min by the toothed claw-shaped structure under the driving of a high-power motor, a natural pore structure formed by a carbon fiber bridge is used as a pore-forming mode of porous graphite, a pore-forming agent does not need to be added, and due to the fact that the diameter of carbon fibers is consistent, the pore size of formed pores and the proportion of the formed pores can be accurately controlled by controlling the dispersion degree of the fibers.

Description

Technical Field

[0001] This invention relates to the field of porous graphite preparation technology, specifically to a method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth. Background Technology

[0002] Currently, porous graphite is used as a filter screen for SiC gas during the growth of semiconductor-grade silicon carbide crystals. This serves two purposes: firstly, it removes floating carbon particles and controls the Si / C stoichiometric ratio; secondly, it ensures the homogenization of the high-temperature sublimated SiC gas. Both of these aspects prepare the ground for growing high-quality semiconductor-grade SiC crystals. Traditional porous graphite techniques typically use coke or graphite as aggregate, asphalt or resin as binders, and pore-forming agents to create the porous graphite structure.

[0003] Existing methods for preparing porous graphite often suffer from problems such as uneven fiber dispersion, difficulty in precisely controlling pore structure, insufficient purity, and cumbersome preparation processes, which fail to meet the core requirements of semiconductor-grade applications.

[0004] Secondly, existing methods have not optimized process parameters for silicon carbide crystal growth scenarios, and the prepared porous graphite has poor adaptability to crystal growth requirements, making it difficult to meet the mass production requirements of semiconductor-grade products.

[0005] Third, the structure is not stable. Under the high temperature (1800~2400℃) and inert atmosphere required for silicon carbide crystal growth, it is prone to structural deformation and cracking, which leads to carrier failure and affects the continuity and consistency of crystal growth. Summary of the Invention

[0006] To address the aforementioned shortcomings of existing technologies, this invention provides a method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth. This method effectively solves the problems of insufficient purity, uncontrollable pore structure, poor high-temperature stability, and low adaptability of existing fibrous porous graphite in semiconductor-grade silicon carbide crystal growth applications. It provides a process-controllable and performance-adaptive preparation method to obtain fibrous porous graphite with a purity of 6N, uniform pores, and stable high-temperature structure, meeting the core requirements of silicon carbide crystal growth for carrier materials and ensuring crystal growth quality and mass production stability.

[0007] This invention provides a method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth, comprising the following steps:

[0008] S1: Carbon fiber pretreatment. Select high-purity PAN-based fibers or pitch-based fibers as raw materials. Place the raw materials of long fibers on a high-precision shearing machine and cut them into short fiber bundles. Uniformly put the sheared short fiber bundles into a fiber dispersing machine; simultaneously start the air separation system, adjust the wind speed to 8 - 12 m / s, precisely screen the dispersed single-filament microfibers, and collect them to obtain short fibers.

[0009] S2: Pulp making: Add the short fibers in S1 and binder resin, and at the same time add a dispersant. Put the mixture into a blender to obtain a porous graphite precursor slurry; put the prepared precursor slurry into a sealed high-purity storage tank for standby. Control the storage environment as a clean room to avoid the mixing of external pollutants and ensure the stability of the slurry purity.

[0010] S3: Hot pressing and forming. Use a high-precision four-column press as the forming equipment, and select a high-purity graphite mold for the mold; quantitatively load the precursor slurry in S2 into the mold; the press applies pressure to the mold and heats up at the same time; keep the pressure stable at this temperature point, press the mold to the specified size range, and then keep it warm for 0.5 - 2 h to form a cured fiber body with a dense structure and regular shape; inert gas protection is introduced throughout the hot pressing and forming process.

[0011] S4: High-temperature heat treatment: Transfer the fiber body after hot pressing and forming in S3 to a high-purity heat treatment furnace. High-purity argon is introduced into the furnace as a protective gas, heat up to 2400 - 2600 °C and keep it warm to form a fiber porous graphite structure with a uniform pore size distribution; after the heat treatment is completed, cool it down to room temperature to obtain a fiber porous material.

[0012] S5: Concentrate the fiber porous material in S4 and load it into a special purification furnace. High-purity argon is pre-introduced into the furnace to displace the air; control the heating rate to 2000 - 2400 °C; introduce a special organic gas with halogen elements into the purification furnace to form volatile gaseous metal halides and non-metal halides; and through the high-vacuum system supporting the purification furnace, timely discharge the gaseous impurities outside the furnace; argon is continuously introduced as a protective gas during the purification process to finally achieve 6N-level purification of the fiber porous graphite.

[0013] Furthermore, the length of the short fiber bundles in S1 is 30 - 50 mm, and the fiber dispersing machine is equipped with a high-speed rotating toothed claw structure. Driven by a high-power motor, the toothed claw structure mechanically disperses the fiber bundles at a rotational speed of 1500 - 2000 r / min, quickly dispersing them into single-filament microfibers, with a single-filament diameter of 5 - 10 μm.

[0014] Furthermore, in S2, the adhesive resin is selected from one or more of phenolic resin and asphalt resin. The short filament fiber and the adhesive resin are mixed in a mass ratio of 80%~95%:20%~5%. The dispersant is selected from polyethylene glycol or sodium polyacrylate, and the amount added is 0.5%~1.0% of the fiber mass. The mixer is set to control the stirring speed at 800~1200 r / min and the stirring time at 30~60 min.

[0015] Furthermore, in S3, the material density inside the mold is 1.2~1.5g / cm³, the heating rate is controlled at 5~8℃ / min, the hot pressing temperature is raised to 150~200℃, and the inert gas in the hot pressing process is argon.

[0016] Furthermore, in S4, the temperature in the heat treatment furnace is raised to 2400~2600℃ at a slow heating rate of 10~20℃ / h; and held for 5~13h.

[0017] Furthermore, in S5, the heating rate is 100~200℃ / min, and the temperature is raised to a purification temperature of 2000~2400℃. The total purification time is controlled to be 13~25h, of which the organic gas reaction treatment time is 3~5h and the heat preservation purification time is 10~20h.

[0018] Furthermore, the halogen-containing organic gas is selected from boron trichloride, carbon tetrachloride, or a mixture thereof.

[0019] Furthermore, in S5, the organic gas containing halogen elements is purified in the furnace. The organic gas can be rapidly decomposed at high temperature to produce highly active halogen ions, which react chemically with metallic impurities in the porous fiber material, including Fe, Ni, Cu, etc., as well as non-metallic impurities, and finally form volatile gaseous metal halides and non-metallic halides.

[0020] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention breaks with traditional techniques by using carbon fiber as the skeleton structure and thermosetting resin as the binder. The advantage of this invention is that it utilizes the natural porous structure formed by the carbon fiber bridge as the pore-forming method for porous graphite, without the need for pore-forming agents. Because the diameter of the carbon fibers is uniform, approximately 10 μm, the pore size and pore ratio can be precisely controlled by controlling the degree of fiber dispersion.

[0021] In this device, the fiber shear length, dispersion parameters, and hot pressing and heat treatment processes are optimized to form a porous structure with a pore size of 5~50μm and uniform distribution. This allows for precise control of the argon gas flow rate and heat conduction efficiency during the silicon carbide crystal growth process, providing a stable atmosphere and temperature environment for uniform crystal growth.

[0022] In this invention, the parameters of each process are optimized for the growth requirements of silicon carbide crystals. The prepared porous graphite can be directly used as a support, insulation body or crucible material for growth without secondary processing. The process flow is regular, the parameters are clear and controllable, and the equipment used is conventional equipment in the industry, which facilitates industrial mass production and reduces the preparation cost of semiconductor-grade silicon carbide crystals. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the accompanying drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0024] Figure 1 This is a flowchart of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0026] The present invention will be further described below with reference to embodiments.

[0027] Example 1: A method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth, refer to the attached figure. Figure 1 It includes the following steps:

[0028] S1: Carbon fiber pretreatment. High-purity PAN-based fibers or pitch-based fibers are selected as raw materials. The long fiber raw materials are placed on a high-precision shearing machine and cut into short fiber bundles with a length of 30 mm. The cut short fiber bundles are evenly fed into a fiber dispersing machine, which is equipped with a high-speed rotating toothed claw structure. Driven by a high-power motor, the toothed claw structure mechanically disperses the fiber bundles at a speed of 1500 r / min, rapidly dispersing them into monofilament microfibers with a diameter of 5 μm. Simultaneously, the air classification system is started, and the air speed is adjusted to 8 m / s to accurately screen and collect the dispersed monofilament microfibers, obtaining short fiber.

[0029] S2: Pulping: Mix the short fiber in S1 with binder resin at a mass ratio of 80%:20%. The binder resin is selected from one or more of phenolic resin and asphalt resin. At the same time, add a dispersant, where the dispersant is selected from polyethylene glycol or sodium polyacrylate, and the addition amount is 0.5% of the fiber mass. Put the mixture into a blender, and set the blender to control the stirring speed at 800 r / min and the stirring time at 30 min to obtain a porous graphite precursor slurry. Load the prepared precursor slurry into a sealed high-purity storage tank for standby. Control the storage environment as a clean room to avoid the mixing of external pollutants and ensure the stability of the slurry purity.

[0030] Optimize the fiber shear length, dispersion parameters, and hot pressing and heat treatment processes to form a porous structure with pore sizes of 5 - 50 μm and uniform distribution, which can accurately control the argon flow rate and heat conduction efficiency during the growth process of silicon carbide crystals, providing a stable atmosphere and temperature environment for the uniform growth of crystals.

[0031] S3: Hot pressing and forming: Use a high-precision four-column press as the forming equipment, and select a high-purity graphite mold for the mold. Quantitatively load the precursor slurry in S2 into the mold, and the loading density in the mold is 1.2 g / cm³. The press applies pressure to the mold and heats up simultaneously, with the heating rate controlled at 5 °C / min until the hot pressing and forming temperature of 150 °C is reached. Keep the pressure stable at this temperature point, press the mold to the specified size range, and then keep it warm for 0.5 h to form a cured fiber body with a dense structure and regular shape. Argon is introduced throughout the hot pressing and forming process for protection.

[0032] S4: High-temperature heat treatment: Transfer the fiber body after hot pressing and forming in S3 to a high-purity heat treatment furnace. High-purity argon is introduced into the furnace as a protective gas, and it is heated up to 2400 °C at a slow heating rate of 10 °C / h. Keep it warm for 5 - 13 h to form a fiber porous graphite structure with uniform pore size distribution. After the heat treatment is completed, cool it down to room temperature to obtain a fiber porous material.

[0033] S5: Concentrate the fiber porous material in S4 and load it into a special purification furnace. High-purity argon is pre-introduced into the furnace to displace the air. The heating rate is 100 °C / min, and it is heated up to the purification temperature of 2000 °C. Introduce one or a mixed gas of boron trichloride and carbon tetrachloride into the purification furnace to form volatile gaseous metal halides and non-metal halides. And through the high-vacuum system supporting the purification furnace, timely discharge the gaseous impurities outside the furnace. Argon is continuously introduced as a protective gas during the purification process. Control the total purification treatment time at 13 h, including 3 h for the organic gas reaction treatment time and 10 h for the heat preservation and purification time, finally achieving 6N-level purification of the fiber porous graphite.

[0034] Each process parameter is optimized for the growth requirements of silicon carbide crystals. The prepared porous graphite can be directly used as a growth support, insulation body or crucible material without secondary processing. The process flow is regular, the parameters are clear and controllable, and the equipment used is conventional equipment in the industry, which facilitates industrial mass production and reduces the preparation cost of semiconductor-grade silicon carbide crystals.

[0035] This product is used as a support for silicon carbide crystal growth. It can be used continuously for 100 hours at 2200℃ without deformation or cracking, and the crystal defect rate is reduced compared with traditional carriers.

[0036] Example 2: S1: Carbon fiber pretreatment. High-purity PAN-based fiber or pitch-based fiber is selected as raw material. The long fiber raw material is placed on a high-precision shearing machine and cut into short fiber bundles with a length of 50 mm. The cut short fiber bundles are evenly fed into a fiber dispersing machine, which is equipped with a high-speed rotating toothed claw structure. Driven by a high-power motor, the toothed claw structure mechanically disperses the fiber bundles at a speed of 2000 r / min, rapidly dispersing them into monofilament microfibers with a diameter of 10 μm. Simultaneously, the air classification system is started, and the air speed is adjusted to 12 m / s to accurately screen and collect the dispersed monofilament microfibers, obtaining short fiber.

[0037] S2: Pulping: The short filaments in S1 are mixed with binder resin at a mass ratio of 95%:5%, and the binder resin is one or more of phenolic resin and asphalt resin. A dispersant is added, which is polyethylene glycol or sodium polyacrylate, at an addition amount of 1.0% of the fiber mass. The mixture is put into a mixer, and the mixer is set to control the stirring speed at 1200 r / min and the stirring time at 60 min to obtain a porous graphite precursor slurry. The prepared precursor slurry is stored in a sealed high-purity storage tank for later use. The storage environment is controlled as a clean room to avoid the introduction of external contaminants and ensure the stability of the slurry purity.

[0038] S3: Hot pressing molding, using a high-precision four-column press as the molding equipment, and a high-purity graphite mold; the precursor slurry from S2 is quantitatively loaded into the mold, with a loading density of 1.5 g / cm³; the press applies pressure to the mold while simultaneously heating, with the heating rate controlled at 8℃ / min, until the hot pressing molding temperature reaches 200℃; the pressure is maintained at this temperature to press the mold to the specified size range, followed by holding at this temperature for 2 hours to form a dense and regularly shaped solidified fibrous body; argon gas is introduced for protection throughout the hot pressing molding process;

[0039] S4: High-temperature heat treatment: Transfer the hot-pressed fiber body obtained in S3 into a high-purity heat treatment furnace. Introduce high-purity argon gas into the furnace as the protective gas, and heat it up to 2600 °C at a slow heating rate of 20 °C / h; keep it at a constant temperature for 13 h to form a fiber porous graphite structure with a uniform pore size distribution; after the heat treatment is completed, cool it down to room temperature to obtain the fiber porous material.

[0040] S5: Concentrate and load the fiber porous material in S4 into a special purification furnace. Pre-introduce high-purity argon gas into the furnace to displace the air; the heating rate is 200 °C / min, and heat it up to the purification temperature of 2400 °C; introduce one or a mixed gas of boron trichloride and carbon tetrachloride into the purification furnace to form volatile gaseous metal halides and non-metal halides; and through the high-vacuum system supporting the purification furnace, timely discharge the gaseous impurities out of the furnace; continuously introduce argon gas as the protective gas during the purification process, and control the total purification treatment time to be 25 h, including 5 h for the organic gas reaction treatment time and 20 h for the holding and purification time, finally achieving 6N-level purification of the fiber porous graphite.

[0041] Example 3: S1: Carbon fiber pretreatment. Select high-purity PAN-based fiber or pitch-based fiber as the raw material. Place the raw material of the long fiber on a high-precision shearing machine and shear it into short fiber bundles with a length of 40 mm. Uniformly put the sheared short fiber bundles into a fiber dispersing machine, and the fiber dispersing machine is equipped with a high-speed rotating toothed claw structure. Driven by a high-power motor, the toothed claw structure mechanically disperses the fiber bundles at a speed of 1750 r / min, quickly dispersing them into single-filament micron fibers, with a single-filament diameter of 7 μm; synchronously start the air separation system, adjust the wind speed to 10 m / s, precisely screen the dispersed single-filament micron fibers, and collect them to obtain short fibers.

[0042] S2: Pulp making: Mix the short fibers in S1 and the binder resin in a mass ratio of 90%:10%. The binder resin is selected from one or more of phenolic resin and pitch resin. At the same time, add a dispersant, and the dispersant is selected from polyethylene glycol or sodium polyacrylate, with an addition amount of 0.7% of the fiber mass. Put the mixture into a mixer, and the mixer is set to control the stirring speed at 1000 r / min and the stirring time at 45 min to obtain a porous graphite precursor slurry; put the prepared precursor slurry into a sealed high-purity storage tank for standby, and control the storage environment as a clean room to avoid mixing of external pollutants and ensure the stability of the slurry purity.

[0043] S3: Hot pressing forming. A high-precision four-column press is used as the forming equipment, and a high-purity graphite mold is selected as the mold. The precursor slurry in S2 is quantitatively loaded into the mold, and the loading density in the mold is 1.3 g / cm³. The press applies pressure to the mold while heating up, and the heating rate is controlled at 7 °C / min until the hot pressing forming temperature of 175 °C is reached. At this temperature point, the pressure is kept stable, and the mold is pressed to the specified size range, and then held for 1.5 h to form a solidified fiber body with a dense structure and regular shape. Argon is introduced throughout the hot pressing forming process for protection.

[0044] S4: High-temperature heat treatment: The fiber body after hot pressing forming obtained in S3 is transferred to a high-purity heat treatment furnace. High-purity argon is introduced into the furnace as the protective gas, and it is heated up to 2500 °C at a slow heating rate of 15 °C / h. It is held for 10 h to form a fiber porous graphite structure with a uniform pore size distribution. After the heat treatment is completed, it is cooled to room temperature to obtain the fiber porous material.

[0045] S5: The fiber porous materials in S4 are centrally loaded into a special purification furnace. High-purity argon is pre-introduced into the furnace to displace the air. The heating rate is 100 - 200 °C / min, and it is heated up to the purification temperature of 2000 - 2400 °C. A gas of one or a mixture of boron trichloride and carbon tetrachloride is introduced into the purification furnace to form volatile gaseous metal halides and non-metal halides. And through the high-vacuum system supporting the purification furnace, the gaseous impurities are timely discharged outside the furnace. Argon is continuously introduced as the protective gas during the purification process, and the total purification treatment time is controlled at 18 h, including 3 - 5 h for the organic gas reaction treatment time and 15 h for the heat preservation purification time, finally achieving the 6N-level purification of the fiber porous graphite.

[0046] The fiber porous graphite prepared in the above embodiments, after testing, has a purity of ≥99.9999%, a pore size distribution of 5 - 50 μm, a compressive strength of ≥15 MPa at a high temperature of 2400 °C, and a thermal conductivity of ≥120 W / (m·K), meeting the performance requirements of the carrier material for the growth of semiconductor-grade silicon carbide crystals.

[0047] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features; and these modifications or replacements will not cause the essence of the corresponding technical solutions to deviate from the protection scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth, characterized in that, It includes the following steps: S1: Carbon fiber pretreatment. Select high-purity PAN-based fiber or pitch-based fiber as raw material. Place the raw material of long fiber on a high-precision shearing machine and cut it into short fiber bundles. Uniformly put the sheared short fiber bundles into a fiber dispersing machine. Synchronously start the air separation system, adjust the wind speed to 8 - 12 m / s, precisely screen the dispersed single-filament microfibers, and collect them to obtain short fibers. S2: Pulp making. Add the short fibers in S1 and binder resin into a dispersant simultaneously, and put the mixture into a mixer to obtain a porous graphite precursor slurry. Load the prepared precursor slurry into a sealed high-purity storage tank for standby. Control the storage environment as a clean room to avoid mixing of external pollutants and ensure the stability of the slurry purity. S3: Hot pressing and forming. Use a high-precision four-column press as the forming equipment and select a high-purity graphite mold as the mold. Quantitatively load the precursor slurry in S2 into the mold. The press applies pressure to the mold and heats up simultaneously. Keep the pressure stable at this temperature point, press the mold to the specified size range, and then keep it warm for 0.5 - 2 h to form a cured fiber body with a dense structure and regular shape. An inert gas is introduced throughout the hot pressing and forming process for protection. S4: High-temperature heat treatment. Transfer the fiber body after hot pressing and forming obtained in S3 to a high-purity heat treatment furnace. Introduce high-purity argon gas into the furnace as the protective gas, heat up to 2400 - 2600 °C and keep it warm to form a fiber porous graphite structure with a uniform pore size distribution. After the heat treatment is completed, cool it down to room temperature to obtain a fiber porous material. S5: Concentrate the fiber porous material in S4 and load it into a special purification furnace. Pre-introduce high-purity argon gas into the furnace to displace the air. Control the heating rate to 2000 - 2400 °C. Introduce a special organic gas with halogen elements into the purification furnace to form volatile gaseous metal halides and non-metal halides. And through the high-vacuum system supporting the purification furnace, timely discharge the gaseous impurities outside the furnace. Continuously introduce argon gas as the protective gas during the purification process to finally achieve 6N-level purification of the fiber porous graphite.

2. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, In S1, the length of the short fiber bundle is 30 - 50 mm, and the fiber dispersing machine is equipped with a high-speed rotating toothed claw structure. Driven by a high-power motor, the toothed claw structure mechanically disperses the fiber bundle at a rotational speed of 1500 - 2000 r / min, quickly dispersing it into single-filament microfibers, with the single-filament diameter of 5 - 10 μm.

3. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, In S2, the binder resin is selected from one or more of phenolic resin and asphalt resin. The short fibers and the binder resin are proportioned by a mass ratio of 80% - 95% : 20% - 5%. The dispersant is selected from polyethylene glycol or sodium polyacrylate, and the addition amount is 0.5% - 1.0% of the fiber mass. The mixer is set to control the stirring speed at 800 - 1200 r / min and the stirring time at 30 - 60 min.

4. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, In S3, the loading density in the mold is 1.2 - 1.5 g / cm³, the heating rate is controlled at 5 - 8 °C / min, and the hot pressing and forming temperature is raised to 150 - 200 °C. The inert gas during the hot pressing process is argon.

5. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 4, characterized in that, In S4, the temperature in the heat treatment furnace is raised to 2400-2600℃ at a slow heating rate of 10-20℃ / h; and held for 5-13 hours.

6. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, In S5, the heating rate is 100~200℃ / min, and the temperature is raised to a purification temperature of 2000~2400℃. The total purification time is controlled to be 13~25h, of which the organic gas reaction treatment time is 3~5h and the heat preservation purification time is 10~20h.

7. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, The halogenated organic gas is selected from boron trichloride, carbon tetrachloride or a mixture thereof.

8. The method for preparing fibrous porous graphite for semiconductor-grade silicon carbide crystal growth according to claim 1, characterized in that, In S5, organic gases containing halogens are purified in a furnace. The organic gases can be rapidly decomposed at high temperatures to produce highly active halogen ions. These ions react chemically with metallic impurities in the porous fiber material, including Fe, Ni, Cu, and non-metallic impurities, ultimately forming volatile gaseous metal halides and non-metallic halides.

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