CN114686969A - Device and process for preparing silicon carbide by PVT (polyvinyl dichloride) method - Google Patents

Device and process for preparing silicon carbide by PVT (polyvinyl dichloride) method Download PDF

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CN114686969A
CN114686969A CN202210365694.3A CN202210365694A CN114686969A CN 114686969 A CN114686969 A CN 114686969A CN 202210365694 A CN202210365694 A CN 202210365694A CN 114686969 A CN114686969 A CN 114686969A
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crucible
furnace body
silicon carbide
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刘源
陈鹏飞
梁刚强
苗浩伟
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Beijing Qingyan Semi Guide Technology Co ltd
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    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/10—Inorganic compounds or compositions
    • C30B29/36—Carbides
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B23/00—Single-crystal growth by condensing evaporated or sublimed materials

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Abstract

The invention discloses a device and a process for preparing silicon carbide by a PVT method, which relate to the technical field of silicon carbide production and mainly comprise a furnace body, a heat insulation layer, a growth crucible, a raw material crucible and a porous breathable layer; a heat insulation layer is arranged in the furnace body, a growth crucible is arranged in the heat insulation layer, the raw material crucible is positioned in the growth crucible, and the porous breathable layer is arranged at an opening at the top of the raw material crucible; the furnace body is communicated with a furnace body vacuum system, and the bottom of the growth crucible is communicated with a crucible vacuum system. The crucible is completely sealed, so that the crucible and an external heat insulation material are not etched in the silicon-rich atmosphere, external impurities are prevented from entering the growth crucible, and defects such as micropipes and carbon wrapping are reduced; the service life is prolonged, and the cost is reduced; a porous and breathable layer is arranged on the upper part of the raw material crucible, the raw material crucible is arranged on the upper part of the growth crucible, and the silicon-rich atmosphere is adsorbed while the air is ensured to be uniformly diffused to the upper part of the raw material crucible from two sides of the growth crucible, so that the doping stability and the resistivity distribution uniformity are ensured.

Description

Device and process for preparing silicon carbide by PVT (polyvinyl dichloride) method
Technical Field
The invention relates to the technical field of silicon carbide production, in particular to a device and a process for preparing silicon carbide by a PVT method.
Background
Silicon carbide is used as a third-generation semiconductor material, compared with the first-generation and second-generation semiconductor materials, the third-generation semiconductor material such as silicon carbide has wider forbidden bandwidth, higher breakdown field strength, higher thermal conductivity, higher electronic saturation rate and higher radiation resistance, is more suitable for manufacturing high-temperature, high-frequency, large-frequency and radiation-resistant devices, can be widely applied to the fields of high voltage, high frequency, high temperature, high reliability and the like, and comprises radio frequency communication, radars, satellites, power management, automotive electronics, industrial power electronics and the like.
The preparation method of silicon carbide is mainly Physical Vapor Transport (PVT), Liquid Phase (LPE), High Temperature Chemical Vapor Deposition (HTCVD), etc., the most mature and commonly used method being PVT, in a typical PVT silicon carbide preparation process, a crucible is made of graphite, and appropriate coils and thermal insulation materials are placed by induction or resistance heating to establish and control the required temperature gradient. The raw material powder is silicon carbide and the seed crystal is also silicon carbide. The crucible is vertically arranged at the lower part of the seed crystal, silicon carbide powder is sublimated along with the rise of the temperature, and gas-phase components are condensed at the seed crystal and finally grow into silicon carbide crystals.
The silicon carbide single crystal substrate structure prepared by the PVT method still has some defects, including micropipes, carbon inclusions, polycrystalline forms, hexagonal cavities and the like, and the defects can influence the performance stability and long-term working performance of the later device manufacturing process. How to solve the defects and obtain high-quality silicon carbide crystal ingots is a problem which needs to be solved at present.
Chinese patent CN212610986U discloses a crucible for reducing carbon inclusions in silicon carbide crystals, wherein an airflow homogenizing member and a cover plate are arranged above a silicon carbide polycrystal material in the crucible, so that the mode of mainly diffusion is changed from convection to mainly diffusion for airflow transmission, carbon particles are deposited, and then carbon inclusions in the silicon carbide crystals are reduced. However, this method cannot guarantee carbon inclusion caused by an externally introduced carbon source.
Chinese patent CN214300468U discloses a crucible and a device for growing silicon carbide single crystal, wherein the sidewall of the crucible is made of air-permeable graphite material, and nitrogen gas is permeated into the sidewall of the crucible, so that the nitrogen doping stability and the resistivity uniformity of the large-size N-type silicon carbide single crystal are improved.
In the patent that publishes at present, the crucible is not completely sealed, and the crucible is in threaded fit or porous, which not only can cause the silicon-rich atmosphere to escape to etch the crucible and the heat insulating material, but also can introduce foreign impurities when the crystal grows, which causes growth defects such as micropipes and carbon coating. Therefore, it is very important to provide a device and a process for preparing silicon carbide by PVT, which have the advantages of no impurity introduction, prolonged service life of raw materials and reduced production cost.
Disclosure of Invention
In order to solve the technical problems, the invention provides a device and a process for preparing silicon carbide by a PVT method, which ensure the stability and controllability of sublimation of atmosphere during crystal growth.
In order to achieve the purpose, the invention provides the following scheme:
the invention provides a device for preparing silicon carbide by a PVT method, which comprises a furnace body, a heat insulation layer, a growth crucible, a raw material crucible and a porous breathable layer; the furnace body is internally provided with the heat insulation layer, the growth crucible is arranged in the heat insulation layer, the raw material crucible is positioned in the growth crucible, and the porous breathable layer is arranged at an open top of the raw material crucible; the furnace body is communicated with a furnace body vacuum system, and the bottom of the growth crucible is communicated with a crucible vacuum system.
Optionally, the furnace body comprises an upper furnace cover, a main furnace body and a lower furnace cover; the main furnace body is of a cavity structure which is communicated up and down; the upper furnace cover is arranged at the top of the main furnace body, and the lower furnace cover is arranged at the bottom of the main furnace body.
Optionally, the main furnace body is a quartz tube, or the main furnace body is made of stainless steel materials, and the upper furnace cover and the lower furnace cover are made of stainless steel.
Optionally, the growth crucible is made of ultra-high-purity high-density isostatic pressing graphite, and the volume density is 1.84-1.95 g/cm3The average particle size is 2-5 μm; the raw material crucible is made of ultra-high-purity high-density isostatic pressing graphite or ultra-high-purity breathable graphite, and the volume density of the raw material crucible is less than or equal to 1.84g/cm3The average particle size is 3 to 10 μm.
Optionally, the porous gas-permeable layer is a porous graphite sheet and/or a porous metal carbide sheet or a porous graphite sheet with a metal carbide coating layer on the surface, wherein when the porous gas-permeable layer is a porous graphite sheet and a porous metal carbide sheet, the porous graphite sheet and the porous metal carbide sheet have the same shape, and the porous graphite sheet is located below the porous metal carbide sheet; the thickness of the porous air-permeable layer is 2-5 mm, the average porosity is 20-50%, and the average pore diameter is 2-5 μm.
Optionally, the metal carbide adopted by the porous metal carbide sheet or the porous graphite sheet with the metal carbide coating layer arranged on the surface is one or more of tantalum carbide, hafnium carbide and niobium carbide.
Optionally, the joint between the growth crucible and the crucible vacuum system and the joint between the furnace body and the furnace body vacuum system are connected by bolts and/or adhesives.
Optionally, the furnace vacuum system keeps the vacuum degree of the furnace body at 1.0 × 10-4～1.0×10-5pa, the vacuum system of the growth crucible makes the vacuum degree of the crucible 1.0 x10-4～1.0×10-5pa。
Optionally, in the crystal growth process, the vacuum degree of the furnace body is 1.0 multiplied by 10-3～1.0×10-4pa, the vacuum degree of the growth crucible is 150-1500 pa.
The invention also provides a preparation process of the device for preparing silicon carbide based on the PVT method, which comprises the steps of charging a raw material crucible, placing the raw material crucible into a growth crucible, then placing the raw material crucible, the growth crucible and a heat insulation material into a furnace body, heating, adjusting the pressure difference between the inside and the outside of the crucible in the crystal growth stage, and ensuring that the vacuum degree of the furnace body is 1.0 multiplied by 10 in the crystal growth process-4～1.0×10- 5pa, wherein the vacuum degree of the growth crucible is 150-1500 pa, and then the crystal ingot is taken out and annealed to obtain the silicon carbide crystal.
Compared with the prior art, the invention has the following technical effects:
1. the crucible is completely sealed and is completely separated from the heat insulation material in the furnace body, so that the crucible and the external heat insulation material are not etched in the silicon-rich atmosphere, and foreign impurities including external environment and heat insulation material impurities are prevented from entering the growth crucible, so that the defects of micropipes, carbon wrapping and the like are reduced;
2. the ultra-pure heat-insulating material is replaced by the heat-insulating material with low cost, and the heat-insulating material is not polluted, so that the cost is reduced while the service life is prolonged;
3. a porous breathable layer is arranged on the upper part of the raw material crucible, the raw material crucible is arranged on the upper part of the growth crucible, and the silicon-rich atmosphere is adsorbed while the air is uniformly diffused to the upper part of the raw material crucible from two sides of the growth crucible, so that the doping stability and the resistivity distribution uniformity are ensured.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a schematic structural diagram of an apparatus for preparing silicon carbide by a PVT process according to the present invention;
FIG. 2 is a view of a silicon carbide ingot prepared by a first embodiment of an apparatus and process for preparing silicon carbide by the PVT method according to the present invention;
FIG. 3 is a diagram of a silicon carbide wafer prepared by the first embodiment of the device and process for preparing silicon carbide by PVT method of the present invention.
FIG. 4 is a diagram of temperature measuring holes in the crystal growth process of the device for preparing silicon carbide by the PVT method and the preparation process of the invention;
FIG. 5 is a diagram of temperature measurement holes during a prior art crystal growth process;
FIG. 6 is a diagram of the thermal field etching after the crystal growth of the device for preparing silicon carbide by the PVT method and the preparation process of the invention is finished;
FIG. 7 is a graph of thermal field etching after completion of prior art nucleation.
Description of reference numerals: 1. growing a crucible cover; 2. silicon carbide seed crystals; 3. a porous, breathable layer; 4. an air inlet; 5. a furnace vacuum system; 6. a thermal insulation material; 7. growing a crucible; 8. a raw material crucible; 9. silicon carbide powder; 10. a furnace body; 11. a vent; 12. crucible vacuum system.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example one
As shown in fig. 1, the present embodiment provides an apparatus for preparing silicon carbide by PVT method, comprising a furnace body 10, a heat insulating layer, a growth crucible 7, a raw material crucible 8 and a porous gas permeable layer 3; a heat insulation layer is arranged in the furnace body 10, a growth crucible 7 is arranged in the heat insulation layer, a raw material crucible 8 is positioned in the growth crucible 7, and a porous breathable layer 3 is arranged at an opening at the top of the raw material crucible 8; the furnace body 10 is communicated with a furnace body 10 vacuum system 5, and the bottom of the growth crucible 7 is communicated with a crucible vacuum system 12. A silicon carbide seed crystal 2 is grown on the bottom of growth crucible cover 1 at the top of growth crucible 7.
In this embodiment, the furnace body 10 includes an upper furnace cover, a main furnace body 10, and a lower furnace cover; the main furnace body 10 is a cavity structure which is communicated up and down; the upper furnace cover is arranged at the top of the main furnace body 10, and the lower furnace cover is arranged at the bottom of the main furnace body 10. The main furnace body 10, the upper furnace cover and the lower furnace cover are all made of stainless steel. The upper furnace cover and the lower furnace cover are connected with the main furnace body 10 by bolts.
The growth crucible 7 is made of ultra-high-purity high-density isostatic pressing graphite, and the volume density is 1.84-1.95 g/cm3The average particle size is 2 to 5 μm. The raw material crucible 8 is made of ultra-high-purity high-density isostatic pressing graphite or ultra-high-purity air-permeable graphite, and the volume density is less than or equal to 1.84g/cm3The average particle size is 3 to 10 μm.
The porous air-permeable layer 3 is used for filtering particles in silicon-rich gas generated by heating silicon carbide powder 9 in the raw material crucible 8, so that the stability and controllability of atmosphere sublimation during crystal growth are ensured, and crystal growth defects such as micropipes, carbon wrapping, hexagonal cavities, dislocation density and the like are greatly reduced.
Porous ventilative layer 3 can adopt porous graphite piece, also can adopt porous metal carbide piece, also can adopt the porous graphite piece that the surface was provided with the metal carbide coating, can also adopt porous graphite piece and porous metal carbide piece simultaneously.
When the porous ventilating layer 3 is made of porous graphite flakes, the porous graphite flakes need to be made of non-powdering high-quality graphite materials, so that the influence of dust generated by the graphite flakes on the crystallization quality is prevented. The porous graphite sheet made of common graphite material can be added with a metal carbide coating on the surface. And a porous sheet made of metal carbide can be covered above the porous graphite sheet made of common graphite, and the porous sheet made of metal carbide is used for filtering graphite powder, so that the porous sheet made of metal carbide with the thickness of 50 microns can meet the requirement. If only the porous sheet made of metal carbide is used, the thickness of the porous sheet needs to be increased to 1mm to meet the strength requirement of the porous sheet.
The metal carbide adopted by the porous metal carbide sheet or the porous graphite sheet with the metal carbide coating arranged on the surface is one or more of tantalum carbide, hafnium carbide and niobium carbide.
The joints between the growth crucible 7 and the crucible vacuum system 12 and between the furnace body 10 and the furnace body 10 vacuum system 5 are connected by bolts and are connected by adhesives such as epoxy glue, phenolic resin, graphite glue and the like so as to enhance the sealing effect of the joints.
The vacuum system 5 of the furnace body 10 keeps the vacuum degree of the furnace body 10 at 1.0 multiplied by 10-4～1.0×10-5pa crucible vacuum system 12 to maintain growth crucible 7 at a vacuum of 1.0X 10-4～1.0×10-5pa. Preferably, the vacuum degree of the furnace body 10 is 1.0X 10 in the crystal growth process-4～1.0×10-5pa, the vacuum degree of the growth crucible 7 is 150-1500 pa.
The invention also aims to prolong the service life of the material, and the common heat-insulating material 6 is used for replacing the expensive ultra-high-purity heat-insulating material 6, so that the crystal growth cost is reduced, and the low-cost and high-quality silicon carbide crystal is obtained. The heat insulating material 6 is graphite, graphite soft felt or graphite hard felt.
Fig. 2 and 3 are views of a conductive silicon carbide ingot and wafer prepared by the apparatus and process for preparing silicon carbide by the PVT method according to the present invention.
The device in the embodiment is used for preparing the conductive silicon carbide crystal, and the steps are as follows:
1. adding self-made high-purity silicon carbide powder 9 into a raw material crucible 8, wherein the particle size of the silicon carbide powder 9 ranges from 5 meshes to 200 meshes, the purity is more than 99.9999 percent, and the bulk density is 1.2g/cm3. After the charging, a graphite sheet having a thickness of 2mm and a tantalum carbide coating was placed over the powder.
2. Placing a raw material crucible 8 in a growth crucible 7, and sealing the growth crucible 7 by bolts and glue;
3. the thermal field composed of the growth crucible 7 and the heat insulation material 6 is placed in the furnace body 10, the bottom of the growth crucible 7 is connected and sealed with an air inlet pipeline and an air outlet pipeline, and the sealing mode is that bolts are padded with graphite paper.
4. Closing the upper furnace cover and the lower furnace cover, and sealing by a flange;
5. opening the vacuum system to ensure that the vacuum inside the furnace body 10 and the crucible reaches 9 multiplied by 10-5pa。
6. Introducing a mixed gas of argon and nitrogen into the growth crucible 7 through the gas inlet 4 and the gas vent 11, wherein the ratio is 100: 1, the flow rate of argon gas was 1200sccm, so that the vacuum in the growth crucible 7 was 1300pa and the vacuum in the furnace body 10 was 5X 10-3pa, simultaneously raising the furnace temperature from room temperature to 2000 ℃, keeping stable growth for 120h under the pressure after raising the furnace temperature to the set pressure and temperature, and finishing the crystal growth stage.
7. After the crystal growth is finished, the pressure in the crucible and the pressure in the furnace body 10 are slowly increased to atmospheric pressure, the temperature is reduced at the same time, the temperature is slowly cooled to room temperature, and finally the silicon carbide crystal ingot with the thickness of 22mm is obtained, wherein the average growth rate is 183 mu m/h. The defects of carbon wrapping, polymorphism and the like are avoided through positive observation, and the utilization rate can reach more than 98%.
8. The obtained ingot was subjected to an annealing treatment for 60 hours. The annealing temperature was 2200 ℃, and the annealed ingot was sliced, ground, polished, and cleaned to obtain the wafer shown in fig. 3.
The density of the 4H silicon carbide wafer micropipe prepared by the method can reach 0.2/cm2No polytype and hexagonal cavity defects exist, the carbon coating is less than or equal to 0.05 percent, and the resistivity is 0.02 omega cm.
Example two
The device in the first embodiment is adopted to prepare the semi-insulating silicon carbide crystal, and the steps are as follows:
1. adding self-made high-purity silicon carbide powder 9 into a raw material crucible 8, wherein the particle size of the silicon carbide powder 9 is 5-200 meshes, the purity is more than 99.9999%, and the bulk density is 1.2g/cm3. After the charging, a graphite sheet having a thickness of 2mm and a tantalum carbide coating was placed over the powder.
2. Placing a raw material crucible 8 in a growth crucible 7, and sealing the growth crucible 7 by bolts and glue;
3. the thermal field composed of the growth crucible 7 and the heat insulation material 6 is placed in the furnace body 10, the bottom of the growth crucible 7 is connected and sealed with an air inlet pipeline and an air outlet pipeline, and the sealing mode is that bolts are padded with graphite paper.
4. Closing the upper furnace cover and the lower furnace cover, and sealing by a flange;
5. opening the vacuum system to ensure that the vacuum inside the furnace body 10 and the crucible reaches 9 multiplied by 10-5pa。
6. Introducing mixed gas of argon and hydrogen into the growth crucible 7 through the gas inlet 4 and the gas vent 11, wherein the concentration of the nitrogen and the hydrogen is less than 1ppb, and the volume ratio is 2: 1, the flow rate of argon gas was 800sccm, so that the vacuum in the growth crucible 7 was 1400Pa, and the vacuum in the furnace body 10 was 5X 10-3pa, simultaneously raising the furnace temperature from room temperature to 2100 ℃, keeping the furnace temperature at the set pressure and temperature, and stably growing for 120h under the pressure, thus completing the crystal growth stage.
7. After the crystal growth is finished, the pressure in the crucible and the pressure in the furnace body 10 are slowly increased to atmospheric pressure, meanwhile, the temperature is reduced, and the silicon carbide crystal ingot with the thickness of 20mm is obtained after the temperature is slowly cooled to the room temperature, and the average growth rate is 166 mu m/h. The defects of carbon wrapping, polymorphism and the like are avoided through positive observation, and the utilization rate can reach more than 98%.
8. The obtained ingot was subjected to an annealing treatment for 60 hours. The annealing temperature is 2200 ℃, and the ingot after annealing is cut, ground, polished and cleaned.
The density of the 4H silicon carbide wafer micropipe prepared by the method can reach 0.2/cm2No polytype and hexagonal cavity defect, less than or equal to 0.05% of carbon coating and 8.29x10 of resistivity10Ω·cm。
The silicon carbide crystals with small micropipe density, no multi-type and hexagonal cavity defects and small carbon inclusions can be prepared by adopting the first embodiment and the second embodiment of the device disclosed by the invention, and compared with the silicon carbide crystals prepared by a single set of vacuum system, the macroscopic defects are greatly reduced, so that the crystal defects can be reduced, and the high-quality silicon carbide single crystals can be prepared.
Fig. 4 and 5 are pictures of temperature measuring holes in the first embodiment and the prior art in the growth process, and it is found that black flaky substances are arranged on the temperature measuring holes in the prior art to block the temperature measuring holes, so that the temperature measuring precision is affected.
Fig. 6 and 7 are images of the thermal field after the growth of the first embodiment and the prior art, which show that there is gas volatilization outside the thermal field of the prior art, and there is no gas volatilization outside the thermal field of the first embodiment, which illustrate that the present invention can prevent the gas from escaping to etch the external thermal insulation material, prolong the service life of the thermal insulation material, and have a beneficial effect on reducing the process cost.
Table 1 shows SIMS results and crystal resistivity with respect to B, N element measured in the first and second examples using the apparatus of the present invention.
Figure BDA0003585772820000081
In Table 1, the number of atoms per cubic centimeter of the crystal has reached the requirement of high purity, and the N atom content in example one is higher because N element is added as a dopant to the crystal. According to the industrial high-purity conductive silicon carbide with the resistivity of 15-30m omega cm, the deviceThe resistivity of a semi-insulator silicon carbide crystal with minimized back gate insulation effect is greater than 1x105The product in the first embodiment meets the requirement of conductivity and the product in the second embodiment meets the requirement of semi-insulation, so that the invention successfully prepares the high-purity conductive and semi-insulating silicon carbide single crystal.
It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrative embodiments, and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein, and any reference signs in the claims are not intended to be construed as limiting the claim concerned.
The principle and the implementation mode of the present invention are explained by applying specific examples in the present specification, and the above descriptions of the examples are only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, the specific embodiments and the application range may be changed. In view of the above, the present disclosure should not be construed as limiting the invention.

Claims (10)

1. A device for preparing silicon carbide by a PVT method is characterized by comprising a furnace body, a heat insulation layer, a growth crucible, a raw material crucible and a porous breathable layer; the furnace body is internally provided with the heat insulation layer, the growth crucible is arranged in the heat insulation layer, the raw material crucible is positioned in the growth crucible, and the porous breathable layer is arranged at an opening at the top of the raw material crucible; the furnace body is communicated with a furnace body vacuum system, and the bottom of the growth crucible is communicated with a crucible vacuum system.
2. The PVT method for preparing silicon carbide according to the claim 1, wherein the furnace body comprises an upper furnace cover, a main furnace body and a lower furnace cover; the main furnace body is of a cavity structure which is communicated up and down; the upper furnace cover is arranged at the top of the main furnace body, and the lower furnace cover is arranged at the bottom of the main furnace body.
3. The PVT method silicon carbide preparing device according to claim 2, wherein the main furnace body is a quartz tube, or the main furnace body is made of stainless steel material, and the upper furnace cover and the lower furnace cover are made of stainless steel.
4. The PVT method for preparing silicon carbide according to claim 1, wherein the growth crucible is made of ultra-high-purity high-density isostatic-pressure graphite, and the volume density of the growth crucible is 1.84-1.95 g/cm3The average particle size is 2-5 μm; the raw material crucible is made of ultra-high-purity high-density isostatic pressing graphite or ultra-high-purity breathable graphite, and the volume density is less than or equal to 1.84g/cm3The average particle size is 3 to 10 μm.
5. The PVT process for preparing silicon carbide according to claim 1, wherein said porous gas-permeable layer is a porous graphite sheet and/or a porous metal carbide sheet or a porous graphite sheet having a metal carbide coating layer provided on the surface thereof, wherein when said porous gas-permeable layer is a porous graphite sheet and a porous metal carbide sheet, said porous graphite sheet and said porous metal carbide sheet have the same shape, and said porous graphite sheet is located below said porous metal carbide sheet; the thickness of the porous air-permeable layer is 2-5 mm, the average porosity is 20-50%, and the average pore diameter is 2-5 μm.
6. The PVT method for preparing silicon carbide according to claim 5, wherein the metal carbide adopted by the porous metal carbide sheet or the porous graphite sheet with the metal carbide coating layer arranged on the surface is one or more of tantalum carbide, hafnium carbide and niobium carbide.
7. The PVT method for preparing silicon carbide according to claim 1, wherein the joints between the growth crucible and the crucible vacuum system and between the furnace body and the furnace body vacuum system are connected by bolts and/or adhesives.
8. The PVT method for preparing silicon carbide according to claim 1, wherein the furnace vacuum system maintains the furnace vacuum degree at 1.0 x10-4～1.0×10-5pa, the vacuum system of the growth crucible makes the vacuum degree of the crucible 1.0 x10-4～1.0×10-5pa。
9. The PVT method for preparing silicon carbide according to claim 8, wherein the vacuum degree of the furnace body is 1.0 x10 during the crystal growth process-3～1.0×10-4pa, the vacuum degree of the growth crucible is 150-1500 pa.
10. A production process for preparing silicon carbide by the PVT method according to any one of claims 1 to 9, characterized in that a raw material crucible is charged, the raw material crucible is placed in a growth crucible, then the raw material crucible, the growth crucible and a heat insulating material are placed in a furnace body, heating is carried out, in a crystal growth stage, the pressure difference between the inside and the outside of the crucible is adjusted, and the vacuum degree of the furnace body in the crystal growth process is ensured to be 1.0 x10-4～1.0×10-5pa, wherein the vacuum degree of the growth crucible is 150-1500 pa, and then the crystal ingot is taken out and annealed to obtain the silicon carbide crystal.
CN202210365694.3A 2022-04-08 2022-04-08 Device and process for preparing silicon carbide by PVT (polyvinyl dichloride) method Pending CN114686969A (en)

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