Silicon carbide and preparation method thereof, silicon carbide ceramic and semiconductor device

Abstract

The present invention relates to silicon carbide and a preparation method thereof, silicon carbide ceramics and semiconductor devices. The preparation method of silicon carbide comprises the following preparation steps: under inert atmosphere conditions, silicon powder and carbon powder are mixed by acoustic resonance mixing, and then pressed to obtain a mixed material blank, wherein the average particle size of the silicon powder is 10 μm to 200 μm; the mixed material blank is solid-phase carbonized under vacuum conditions; the solid-phase carbonization treatment conditions include a preheating stage, a silicon powder melting stage and a solid-phase carbonization reaction stage performed in sequence, the vacuum pressure of the silicon powder melting stage is greater than the vacuum pressure of the initial heating stage, and the vacuum pressure of the silicon powder melting stage is greater than the vacuum pressure of the solid-phase carbonization reaction stage. Silicon powder and carbon powder are mixed and pressed under inert atmosphere conditions, and the vacuum pressures of the preheating, silicon powder melting and solid-phase carbonization reaction stages are controlled during the solid-phase carbonization treatment process to obtain silicon carbide with higher purity and lower nitrogen content, while the Si / C ratio of the silicon carbide is precisely controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of material preparation, and in particular to silicon carbide and a preparation method thereof, silicon carbide ceramics and semiconductor devices. Background Art

[0002] Silicon carbide (SiC) is an inorganic non-metallic material with excellent mechanical properties, thermal conductivity, thermal stability, wear resistance and chemical stability. In recent years, with the development of science and technology, the application fields of high-purity silicon carbide powder have become more and more extensive, especially in the fields of semiconductors, ceramics and refractory materials. The silicon carbide single crystal substrate material used to make devices has put forward higher requirements on the purity, particle size and crystal form of SiC powder. Although the purity of the commercially produced high-purity SiC powder raw materials can reach 99.999%, the nitrogen content is mostly above 15ppm, which seriously affects the comprehensive performance of silicon carbide single crystals. Therefore, the development of a low-cost method for high-purity, low-nitrogen silicon carbide powder is of great significance for the preparation of high-purity semi-insulating silicon carbide crystals and the promotion of the development of key semiconductor materials in my country.

[0003] High-temperature solid-phase synthesis is a commonly used method for preparing silicon carbide. In this method, silicon powder and carbon powder are mixed evenly by using ball mills and grinding balls made of other materials through mechanical impact. Such a uniform powder mixture can ensure the completeness of the subsequent solid-phase carbonization reaction, thereby producing silicon carbide. However, in this method, there is a problem that the powder surface easily absorbs oxygen and nitrogen, resulting in the low purity and high nitrogen content of the silicon carbide powder prepared by the traditional high-temperature solid-phase synthesis method, making it difficult to obtain high-quality and high-purity silicon carbide powder. Summary of the invention

[0004] Based on this, it is necessary to provide silicon carbide with higher purity and lower nitrogen content and its preparation method, silicon carbide ceramics and semiconductor devices.

[0005] A first aspect of the present invention provides a method for preparing silicon carbide, comprising the following preparation steps:

[0006] Under inert atmosphere conditions, silicon powder and carbon powder are mixed by acoustic resonance mixing, and then pressed to obtain a mixed material blank, wherein the average particle size of the silicon powder is 10 μm to 200 μm;

[0007] The mixed material blank is solid-phase carbonized under vacuum conditions; the solid-phase carbonization treatment conditions include a pre-heating stage, a silicon powder melting stage and a solid-phase carbonization reaction stage performed in sequence, the vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the initial heating stage, and the vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the solid-phase carbonization reaction stage.

[0008] Under inert atmosphere conditions, silicon powder and carbon powder are mixed and pressed by acoustic resonance mixing. The acoustic resonance mixing method can avoid the introduction of new impurities due to ball milling and other methods, and further improve the purity of silicon carbide products; the use of acoustic resonance mixing can also improve the distribution uniformity of the two phases of the mixed powder, reduce the temperature required for the solid phase carbonization reaction stage, and then reduce the volatilization of liquid silicon, so that the Si / C ratio of silicon carbide can be more accurately controlled, and silicon carbide powder with more uniform particle size can also be obtained. In addition, mixing by acoustic resonance can also effectively reduce the water vapor, oxygen and nitrogen physically adsorbed on the surface of solid silicon powder and carbon powder. Pressing treatment can also further improve the uniformity of the mixed powder, increase the carbonization rate during the solid phase carbonization treatment process, and improve the uniformity of silicon carbide product particles. Controlling the average particle size of silicon powder within a specific range can effectively regulate the carbonization rate of silicon powder and carbon powder on the premise of obtaining good uniformity of the mixture, and control the content of oxygen, nitrogen and water vapor adsorbed by silicon powder. Further, in the solid phase carbonization process, the vacuum pressure value of the preheating stage, the silicon powder melting stage and the solid phase carbonization reaction stage is controlled, wherein the preheating stage makes the furnace pressure in a vacuum condition to reduce the residual nitrogen content in the sintering furnace; in the silicon powder melting stage, the silicon powder becomes a liquid phase, the vapor pressure in the furnace increases, and there are a large number of pores in the blank, and the vacuum pressure value in the furnace is further increased, which can reduce the volatilization loss of liquid silicon, and effectively accelerate the liquid silicon to infiltrate the carbon powder particles, greatly improve the density of the reaction blank, and then improve the density of silicon carbide; in the solid phase carbonization reaction stage, silicon carbide powder is rapidly synthesized, and the vacuum pressure value in the furnace is appropriately reduced at this time, the internal liquid silicon is not easy to volatilize, and only the surface liquid silicon volatilizes, which can more accurately control the Si / C ratio in silicon carbide; and under high vacuum pressure conditions, the nitrogen content in silicon carbide powder can be further reduced. Silicon carbide with high purity and low nitrogen content can be obtained by the above method, and the density of silicon carbide can also be improved.

[0009] In some embodiments, the vacuum pressure in the preheating stage is less than or equal to 1×10 -3 Pa; and / or

[0010] The vacuum pressure of the silicon powder melting stage is 1×10 -2 Pa~5×10 -2 Pa; and / or

[0011] The vacuum pressure of the solid phase carbonization reaction stage is 5×10 -3 Pa~4.9×10 -2 Pa.

[0012] In some embodiments, the initial heating stage includes heating to a first temperature and keeping the temperature at the first temperature, wherein the first temperature is 1200° C. to 1300° C.; and / or

[0013] The silicon powder melting stage includes a heating stage from the first temperature to a second temperature and a process of keeping the temperature at the second temperature, wherein the second temperature is 1350° C. to 1600° C.; and / or

[0014] The solid phase carbonization reaction stage includes a heating stage from the second temperature to a third temperature and a process of keeping the temperature at the third temperature, wherein the third temperature is 1850°C to 2000°C.

[0015] In some embodiments, the first temperature is kept for 1.5 hours to 3 hours; and / or

[0016] The second temperature keeping time is 1h~3h; and / or

[0017] The third temperature insulation time is 1.5h~3h.

[0018] In some embodiments, the silicon powder melting stage includes the following stages:

[0019] The temperature is raised from the first temperature to 1350° C. to 1450° C. and kept at this temperature for 0.5 h to 2 h, and then raised to 1500° C. to 1600° C. and kept at this temperature for 0.5 h to 1 h.

[0020] In some embodiments, the resonance frequency of the acoustic resonance mixing is 60 Hz to 70 Hz, the vibration mixing time is 5 min to 30 min, and the acceleration is 60 to 90 gravitational acceleration (g); and / or

[0021] When performing acoustic resonance mixing, the vacuum pressure of the inert atmosphere is 1×10 -3 Pa~1×10 5 Pa.

[0022] In some embodiments, the pressure of the pressing treatment is 20 MPa to 50 MPa.

[0023] In some embodiments, the average particle size of the carbon powder is 0.5 μm to 20 μm.

[0024] In some embodiments, the purity of the silicon powder is ≥ 99.999%; the purity of the carbon powder is ≥ 99.999%; and / or

[0025] The molar ratio of the silicon powder to the carbon powder is 1:(1-1.8).

[0026] A second aspect of the present invention provides silicon carbide, which is prepared according to the above method.

[0027] In some embodiments, the purity of the silicon carbide is 99.9990% to 99.9996%, and the nitrogen content in the silicon carbide is 2 ppm to 8 ppm.

[0028] A third aspect of the present invention provides a silicon carbide ceramic, wherein the preparation material of the silicon carbide ceramic includes the above-mentioned silicon carbide.

[0029] A fourth aspect of the present invention provides a semiconductor device, wherein the manufacturing material of the semiconductor device includes the above-mentioned silicon carbide. DETAILED DESCRIPTION

[0030] In order to facilitate the understanding of the present invention, the present invention will be described more comprehensively below, and preferred embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. It should be understood that the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0032] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of the present invention, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0033] In one embodiment of the present application, a method for preparing silicon carbide is provided, characterized in that it includes the following preparation steps:

[0034] Under inert atmosphere conditions, silicon powder and carbon powder are mixed by acoustic resonance mixing, and then pressed to obtain a mixed material blank, wherein the average particle size of the silicon powder is 10 μm to 200 μm;

[0035] The mixed material blank is solid-phase carbonized under vacuum conditions; the solid-phase carbonization treatment conditions include a pre-heating stage, a silicon powder melting stage and a solid-phase carbonization reaction stage performed in sequence, the vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the initial heating stage, and the vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the solid-phase carbonization reaction stage.

[0036] Under inert atmosphere conditions, silicon powder and carbon powder are mixed and pressed by acoustic resonance mixing. The acoustic resonance mixing method can avoid the introduction of new impurities due to ball milling and other methods, and further improve the purity of silicon carbide products; the use of acoustic resonance mixing can also improve the distribution uniformity of the two phases of the mixed powder, reduce the temperature required for the solid phase carbonization reaction stage, and then reduce the volatilization of liquid silicon, so that the Si / C ratio of silicon carbide can be more accurately controlled, and silicon carbide powder with more uniform particle size can also be obtained. In addition, mixing by acoustic resonance can also effectively reduce the water vapor, oxygen and nitrogen physically adsorbed on the surface of solid silicon powder and carbon powder. Pressing treatment can also further improve the uniformity of the mixed powder, increase the carbonization rate during the solid phase carbonization treatment process, and improve the uniformity of silicon carbide product particles. Controlling the average particle size of silicon powder within a specific range can effectively regulate the carbonization rate of silicon powder and carbon powder on the premise of obtaining good uniformity of the mixture, and control the content of oxygen, nitrogen and water vapor adsorbed by silicon powder. Further, in the solid phase carbonization process, the vacuum pressure of the preheating stage, the silicon powder melting stage and the solid phase carbonization reaction stage is controlled, wherein the preheating stage makes the furnace pressure in a vacuum condition to reduce the residual nitrogen content in the sintering furnace; in the silicon powder melting stage, the silicon powder becomes a liquid phase, the vapor pressure in the furnace increases, and there are a large number of pores in the blank, and the vacuum pressure in the furnace is further increased, which can reduce the volatilization loss of liquid silicon, and effectively accelerate the liquid silicon to infiltrate the carbon powder particles, greatly improve the density of the reaction blank, and then improve the density of silicon carbide; in the solid phase carbonization reaction stage, silicon carbide powder is rapidly synthesized, and the vacuum pressure in the furnace is appropriately reduced at this time, the internal liquid silicon is not easy to volatilize, and only the surface liquid silicon volatilizes, which can more accurately control the Si / C ratio in silicon carbide; and under high vacuum pressure conditions, the nitrogen content in silicon carbide powder can be further reduced. Silicon carbide with high purity and low nitrogen content can be obtained by the above method, and the density of silicon carbide can also be improved.

[0037] The apparent value of the vacuum pressure in the present application is a positive value. The comparison of the magnitude of the vacuum pressure in the present application refers to the comparison of the magnitude of its apparent value. "The vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the initial heating stage, and the vacuum pressure in the silicon powder melting stage is greater than the vacuum pressure in the solid-phase carbonization reaction stage" means that the apparent value (i.e., positive value) of the vacuum pressure in the container where the silicon powder is located in the silicon powder melting stage is greater than the apparent value of the vacuum pressure in the container where the silicon powder is located in the initial heating stage. Similarly, the apparent value (i.e., positive value) of the vacuum pressure in the container where the silicon powder is located in the silicon powder melting stage is greater than the apparent value of the vacuum pressure in the container where the reaction materials are located in the solid-phase carbonization reaction stage.

[0038] In some embodiments, the vacuum pressure during the preheating stage is less than or equal to 1×10 -3 As an example, the vacuum pressure during the preheating stage can be 1×10 -3 Pa, 5×10-4 Pa, 4×10 -4 Pa, 3×10 -4 Pa, 2×10 -4 P or 1×10 -4 Pa. It can also be any other value less than 1×10 -3 The value of Pa.

[0039] In some embodiments, the vacuum pressure during the silicon powder melting stage is 1×10 -2 Pa~5×10 -2 Pa. It can be understood that the vacuum pressure during the silicon powder melting stage can be 1×10 -2 Pa, 2×10 -2 Pa, 3×10 -2 Pa, 4×10 -2 Pa or 5×10 -2 Pa. Furthermore, the vacuum pressure during the silicon powder melting stage may be a range of values ​​formed by any two of the above-mentioned points.

[0040] In some embodiments, the vacuum pressure during the solid phase carbonization reaction is 5×10 -3 Pa~4.9×10 -2 Pa. It can be understood that the vacuum pressure during the solid-phase fireworks reaction stage can be 5×10 -3 Pa, 6×10 -3 Pa, 8×10 -3 Pa, 1×10 -2 Pa, 2×10 -2 Pa, 3×10 -2 Pa, 4×10 -2 Pa, 4.5×10 -2 Pa or 4.9×10 -2 Pa.

[0041] In some embodiments, the initial temperature rise stage includes a process of heating to a first temperature and keeping the temperature at the first temperature, and the first temperature is 1200° C. to 1300° C. It is understood that the first temperature may be 1200° C., 1220° C., 1250° C., 1260° C., 1280° C. or 1300° C. Further, the first temperature may be a range value consisting of any two of the above point values.

[0042] In some embodiments, the first temperature insulation time is 1.5h~3h. It is understood that the first temperature insulation time is 1.5h, 2h, 2.5h or 3h. Further, the first temperature insulation time can be a range value composed of the above arbitrary point values. Preferably, the first temperature insulation time is 2h~2.5h.

[0043] In some embodiments, the silicon powder melting stage includes a heating stage from the first temperature to the second temperature and a process of keeping the temperature at the second temperature, and the second temperature is 1350° C. to 1600° C. It can be understood that the second temperature can be 1350° C., 1400° C., 1450° C., 1500° C., 1550° C. or 1600° C. Further, the second temperature can be a range value consisting of any two of the above point values.

[0044] In some embodiments, the second temperature insulation time is 1 hour to 3 hours. It is understood that the second temperature insulation time is 1 hour, 1.5 hours, 2 hours, 2.5 hours or 3 hours. Further, the second temperature insulation time can be a range value composed of the above arbitrary point values.

[0045] In some embodiments, the silicon powder melting stage includes heating from the first temperature to 1350° C. to 1450° C. and keeping the temperature for 0.5 h to 2 h, and then heating to 1500° C. to 1600° C. and keeping the temperature for 0.5 h to 1 h.

[0046] In some embodiments, the solid phase carbonization reaction stage includes a heating stage from the second temperature to the third temperature and a process of keeping the temperature at the third temperature, and the third temperature is 1850° C. to 2000° C. It can be understood that the third temperature can be 1850° C., 1900° C., 1950° C. or 2000° C. Further, the third temperature can be a range value consisting of any two of the above point values.

[0047] In some embodiments, the third temperature insulation time is 1.5h~3h. It can be understood that the third temperature insulation time is 1.5h, 2h, 2.5h or 3h. Further, the third temperature insulation time can be a range value composed of the above arbitrary point values.

[0048] In some embodiments, the inert atmosphere may be argon, helium or xenon.

[0049] In some embodiments, the resonance frequency of the acoustic resonance mixing is 60 Hz to 70 Hz, the vibration mixing time is 5 min to 30 min, and the acceleration is 60 to 90 gravitational acceleration (g).

[0050] In some embodiments, the acoustic resonance mixing is performed in a mixing vessel.

[0051] In some embodiments, the material of the mixing container may be phenolic resin or polypropylene.

[0052] In some embodiments, before performing the acoustic resonance mixing, it is necessary to cycle through the steps of evacuating the container and introducing an inert gas multiple times.

[0053] In some embodiments, the method of vacuuming and introducing inert gas each time is to first perform vacuuming until the vacuum pressure in the container is 5×10 -4 Pa~5×10 -3 Pa, and then introduce inert gas until the pressure in the container is 1×10 -3 Pa~1×10 5 Pa.

[0054] In some embodiments, before performing the acoustic resonance mixing, the container needs to be evacuated and inert gas introduced for 2-6 cycles.

[0055] In some embodiments, the inert gas is high-purity argon gas. Further, the purity of the high-purity argon gas is 99.9999%.

[0056] In some embodiments, the pressure during the pressing process is 20 MPa to 50 MPa.

[0057] In some embodiments, the pressing process may be performed in a high-purity graphite mold, wherein the purity of the high-purity graphite is greater than or equal to 99.999%.

[0058] In some embodiments, the average particle size of the silicon powder is 10 μm to 200 μm. It is understood that the average particle size of the silicon powder can be 10 μm, 15 μm, 20 μm, 30 μm, 50 μm, 80 μm, 100 μm, 150 μm or 200 μm. Further, the average particle size of the silicon powder can be a range value consisting of any two of the above point values. Preferably, the average particle size of the silicon powder is 10 μm to 100 μm. Further, the average particle size of the silicon powder is 10 μm to 60 μm. Further, the average particle size of the silicon powder is 40 μm to 60 μm. By controlling the average particle size of the silicon powder, it is beneficial to effectively regulate the carbonization rate of the silicon powder and the carbon powder under the premise of obtaining good uniformity of the mixture, and control the content of oxygen, nitrogen and water vapor adsorbed by the silicon powder.

[0059] In some embodiments, the average particle size of the carbon powder is 0.5 μm to 20 μm. It is understood that the average particle size of the carbon powder can be 0.5 μm, 2 μm, 5 μm, 8 μm, 10 μm, 15 μm, 18 μm or 20 μm. Further, the average particle size of the carbon powder can be a range value consisting of any two of the above point values. Preferably, the average particle size of the carbon powder is 2 μm to 15 μm. Further, the average particle size of the carbon powder is 5 μm to 12 μm. Further, the average particle size of the carbon powder is 9 μm to 11 μm.

[0060] In some embodiments, the purity of the silicon powder is ≥ 99.999%.

[0061] In some embodiments, the purity of the carbon powder is ≥ 99.999%.

[0062] In some embodiments, the molar ratio of silicon powder to carbon powder is 1:(1-1.8). It can be understood that the molar ratio of the above silicon powder to carbon powder can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, 1:1.5, 1:1.6, 1:1.7 or 1:1.8. Further, the molar ratio of the above silicon powder to carbon powder can be a range value composed of the above arbitrary point values. Preferably, the molar ratio of silicon powder to carbon powder is 1:(1.1-1.5). More preferably, the molar ratio of silicon powder to carbon powder is 1:(1.1-1.2).

[0063] In one embodiment of the present application, there is provided silicon carbide, which is prepared according to the above preparation method.

[0064] In some embodiments, the purity of the silicon carbide is 99.9990% to 99.9996%. Further, the purity of the silicon carbide is 99.9992% to 99.9996%.

[0065] In some embodiments, the nitrogen content of the silicon carbide is 2ppm to 8ppm. The nitrogen content refers to the mass content of nitrogen in the silicon carbide. Further, the nitrogen content of the silicon carbide is 2ppm to 5ppm.

[0066] In one embodiment of the present application, a silicon carbide ceramic is provided, and the preparation material of the silicon carbide ceramic includes the above-mentioned silicon carbide.

[0067] In one embodiment of the present application, a semiconductor device is provided, and the manufacturing material of the semiconductor device includes the above-mentioned silicon carbide.

[0068] In order to make the purpose, technical solutions and advantages of the present invention more concise and clear, the present invention is described with the following specific embodiments, but the present invention is by no means limited to these embodiments. The embodiments described below are only preferred embodiments of the present invention, which can be used to describe the present invention and cannot be understood as limiting the scope of the present invention. It should be pointed out that any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0069] In order to better illustrate the present invention, the present invention is further described below in conjunction with the embodiments. The following are specific embodiments.

[0070] The products used in the examples are as follows:

[0071] Commercial high-purity silicon powder with a purity of 99.999% and commercial high-purity carbon powder with a purity of 99.999% were used. The acoustic resonance equipment was from Shenzhen Huasheng Strengthening Technology Co., Ltd., and the model was experimental HAM-100. Other products are conventional products on the market.

[0072] Example 1

[0073] (1) High-purity silicon powder and carbon powder with a molar ratio of 1:1.1 are placed in a phenolic resin container, and vacuumed and introduced with high-purity argon gas for multiple cycles, and then mixed by acoustic resonance to obtain a mixed powder of silicon powder and carbon powder. The average particle size of the high-purity silicon powder is 15 microns, and the average particle size of the high-purity carbon powder is 5.0 microns. The container is vacuumed for multiple cycles until the pressure inside the container is 5×10 -4 Pa, argon gas with a purity of 99.9999% was introduced until the pressure reached 1×10 5 Pa. Repeat the above vacuuming and introducing high-purity argon gas for 5 cycles. The resonance frequency of the acoustic resonance mixing is 70 Hz, the vibration mixing time is 25 min, and the acceleration is 70 gravitational acceleration (g).

[0074] Then, the mixed powder is sealed.

[0075] (2) The mixed powder is briquetting in a glove box protected by an inert atmosphere, and is pressed in a high-purity graphite mold at a pressing pressure of 50 MPa.

[0076] (3) The above-mentioned block-shaped mixed powder compact is placed in a high-purity graphite crucible and placed in a vacuum sintering furnace with a graphite heating element to carry out a solid-phase carbonization reaction. The solid-phase carbonization reaction is divided into the following four stages: Stage 1: The temperature in the sintering furnace is raised to 1300°C at a rate of 10°C / min and kept at this temperature for 2 hours. The vacuum pressure in the furnace is set to 5×10 -4 Pa; Stage 2: heating from 1300°C to 1400°C at 5°C / min, keeping warm for 1h, and the vacuum pressure in the furnace was set to 1×10 -2 Pa; Stage 3: Heating to 1600°C at 3°C / min, keeping warm for 30 min, and setting the vacuum pressure in the furnace to 1×10 -2 Pa; Stage 4: Raise the temperature to 1900°C at 5°C / min, keep warm for 2h, and set the vacuum pressure in the furnace to 5×10 -3 Pa.

[0077] (4) After the solid phase carbonization reaction is completed, the furnace is cooled to obtain silicon carbide powder with a purity of 99.9992% and a nitrogen content of 5 ppm.

[0078] Example 2

[0079] (1) High-purity silicon powder and carbon powder with a molar ratio of 1:1.15 are placed in a phenolic resin container, and vacuumed and introduced with high-purity argon gas for multiple cycles, and then mixed by acoustic resonance to obtain a mixed powder of silicon and carbon black. The average particle size of the high-purity silicon powder is 30 microns, and the average particle size of the high-purity carbon powder is 8.0 microns. The container is vacuumed for multiple cycles until the pressure in the container is 5×10-4 Pa, argon gas with a purity of 99.9999% was introduced until the pressure reached 1×10 5 Pa. Repeat the above vacuuming and gas introduction for 4 cycles. The resonance frequency of the acoustic resonance mixing is 65 Hz, the vibration mixing time is 15 min, and the acceleration is 65 gravitational acceleration (g).

[0080] Then, the mixed powder is sealed.

[0081] (2) The mixed powder is briquetting in a glove box protected by an inert atmosphere, and is pressed in a high-purity graphite mold at a pressing pressure of 40 MPa.

[0082] (3) The above-mentioned block-shaped mixed powder compact is placed in a high-purity graphite crucible and placed in a vacuum sintering furnace with a graphite heating element to carry out a solid-phase carbonization reaction. The solid-phase carbonization reaction is divided into the following four stages: Stage 1: The temperature in the sintering furnace is raised to 1300°C at a rate of 10°C / min and kept at this temperature for 2 hours. The vacuum pressure in the furnace is set to 2×10 -4 Pa; Stage 2: heating from 1300°C to 1400°C at 5°C / min, keeping warm for 1h, and the vacuum pressure in the furnace was set to 5×10 -2 Pa; Stage 3: heating to 1600°C at 3°C / min, keeping warm for 30 min, and setting the vacuum pressure in the furnace to 5×10 -2 Pa; Stage 4: Raise the temperature to 1950°C at 5°C / min, keep warm for 2h, and set the vacuum pressure in the furnace to 1×10 -2 Pa.

[0083] (4) After the solid phase carbonization reaction is completed, the furnace is cooled to obtain silicon carbide powder with a purity of 99.9994% and a nitrogen content of 4 ppm.

[0084] Example 3

[0085] (1) High-purity silicon powder and carbon powder with a molar ratio of 1:1.2 are placed in a phenolic resin container, and vacuumed and introduced with high-purity argon gas for multiple cycles, and then mixed by acoustic resonance to obtain a mixed powder of silicon and carbon black. The average particle size of the high-purity silicon powder is 50 microns, and the average particle size of the high-purity carbon powder is 10.0 microns. The container is vacuumed for multiple cycles until the pressure in the container is 5×10 -4 Pa, argon gas with a purity of 99.9999% was introduced until the pressure reached 1×10 5 Pa. Repeat the above vacuuming and gas introduction for 3 cycles. The resonance frequency of the acoustic resonance mixing is 60 Hz, the vibration mixing time is 10 min, and the acceleration is 60 gravitational acceleration (g).

[0086] Then, the mixed powder is sealed.

[0087] (2) The mixed powder is briquetting in a glove box protected by an inert atmosphere, and is pressed in a high-purity graphite mold at a pressing pressure of 20 MPa.

[0088] (3) The above-mentioned block-shaped mixed powder compact is placed in a high-purity graphite crucible and placed in a vacuum sintering furnace with a graphite heating element to carry out a solid-phase carbonization reaction. The solid-phase carbonization reaction is divided into the following four stages: Stage 1: The temperature in the sintering furnace is raised to 1300°C at a rate of 10°C / min and kept at this temperature for 2 hours. The vacuum pressure in the furnace is set to 1×10 -3 Pa; Stage 2: heating from 1300°C to 1400°C at 5°C / min, keeping warm for 1h, and the vacuum pressure in the furnace was set to 5×10 -2 Pa; Stage 3: heating to 1600°C at 3°C / min, keeping warm for 30 min, and setting the vacuum pressure in the furnace to 5×10 -2 Pa; Stage 4: Raise the temperature to 2000°C at 5°C / min and keep warm for 2h. The vacuum pressure in the furnace is set to 5×10 -3 Pa.

[0089] (4) After the solid phase carbonization reaction is completed, the furnace is cooled to obtain silicon carbide powder with a purity of 99.9996% and a nitrogen content of 2 ppm.

[0090] Example 4

[0091] (1) High-purity silicon powder and carbon powder with a molar ratio of 1:1.1 are placed in a phenolic resin container, and vacuumed and introduced with high-purity argon gas for multiple cycles, and then mixed by acoustic resonance to obtain a mixed powder of silicon powder and carbon powder. The average particle size of the high-purity silicon powder is 150 microns, and the average particle size of the high-purity carbon powder is 15 microns. The container is vacuumed for multiple cycles until the pressure in the container is 5×10 -4 Pa, argon gas with a purity of 99.9999% was introduced until the pressure reached 1×10 5 Pa. Repeat the above vacuuming and introducing high-purity argon gas for 5 cycles. The resonance frequency of the acoustic resonance mixing is 70 Hz, the vibration mixing time is 25 min, and the acceleration is 70 gravitational acceleration (g).

[0092] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the average particle size of the high-purity silicon powder used in this embodiment is 150 microns, and the average particle size of the high-purity carbon powder is 15 microns. Other conditions and process parameters are the same as those of embodiment 1.

[0093] The purity of the silicon carbide prepared in this embodiment is 99.9990% and the nitrogen content is 8 ppm.

[0094] Comparative Example 1

[0095] (1) High-purity silicon powder and carbon powder with a molar ratio of 1:1.1 are placed in a phenolic resin ball mill. The grinding medium is deionized water with a purity of 99.9% (the water-to-material mass ratio is 0.8:1). The grinding is performed using grinding balls made of phenolic resin for 2 hours. The average particle size of the high-purity silicon powder is 15 microns, and the average particle size of the high-purity carbon powder is 5.0 microns. Subsequently, the mixed powder is sealed.

[0096] (2) The mixed powder is briquetting in a glove box protected by an inert atmosphere, and is pressed in a high-purity graphite mold at a pressing pressure of 50 MPa.

[0097] (3) The above-mentioned block-shaped mixed powder compact is placed in a high-purity graphite crucible and placed in a vacuum sintering furnace with a graphite heating element to carry out a solid-phase carbonization reaction. The solid-phase carbonization reaction is divided into the following four stages: Stage 1: The temperature in the sintering furnace is raised to 1300°C at a rate of 10°C / min and kept at this temperature for 2 hours. The vacuum pressure in the furnace is set to 5×10 -4 Pa; Stage 2: heating from 1300°C to 1400°C at 5°C / min, keeping warm for 1h, and the vacuum pressure in the furnace was set to 1×10 -2 Pa; Stage 3: Heating to 1600°C at 3°C / min, keeping warm for 30 min, and setting the vacuum pressure in the furnace to 1×10 -2 Pa; Stage 4: Raise the temperature to 1900°C at 5°C / min, keep warm for 2h, and set the vacuum pressure in the furnace to 5×10 -3 Pa.

[0098] (4) After the solid phase carbonization reaction is completed, the furnace is cooled to obtain silicon carbide powder with a purity of 99.996% and a nitrogen content of 10 ppm.

[0099] Comparative Example 2

[0100] The preparation method of this embodiment is basically the same as that of embodiment 1, except that the vacuum pressure in the furnace is 1×10 -2 Pa. After cooling, the purity of the obtained silicon carbide powder was 99.998% and the nitrogen content was 9 ppm.

[0101] Comparative Example 3

[0102] The preparation method of this comparative example is basically the same as that of Example 1, except that the average particle size of the high-purity silicon powder is different. The average particle size of the high-purity silicon powder selected in this comparative example is 5 microns, and the other process conditions and parameters are the same as those of Example 1. The purity of the obtained silicon carbide powder is 99.995%, and the nitrogen content is 10 ppm.

[0103] Comparative Example 4

[0104] The preparation method of this comparative example is basically the same as that of Example 1, except that the powder mixed by acoustic resonance is not subjected to briquetting, but is directly charged into a graphite crucible for reaction synthesis. After cooling, the purity of the obtained silicon carbide powder is 99.992%, and the nitrogen content is 15 ppm.

[0105] Performance Testing

[0106] The purity test method of silicon carbide powder is: measured according to the method specified in the national standard GB / T 3045-2017.

[0107] The test method for the nitrogen content in silicon carbide powder is: measured according to the method specified in the national standard GB / T 41153-2021.

[0108] The performance test data of the above embodiments and comparative examples are shown in Table 1 below:

[0109] Table 1

[0110]

[0111] From the data in Table 1, it can be seen that Examples 1-4 use the preparation method of the present application to obtain silicon carbide with a purity of 99.9990% to 99.9996%, and a nitrogen content of 2ppm to 8ppm. Specifically, the purity of silicon carbide prepared in Example 1 is 99.9992% and the nitrogen content is 5ppm.

[0112] When preparing silicon carbide in Comparative Example 1, silicon powder and carbon powder were mixed by ball milling, and the purity of the obtained silicon carbide was 99.996% and the nitrogen content was 10 ppm. It can be seen that the quality of the silicon carbide prepared in Comparative Example 1 is inferior to that of Example 1.

[0113] When preparing silicon carbide in Comparative Example 2, during the solid phase carbonization process, the vacuum pressure in each stage was controlled to be the same, and the purity of the obtained silicon carbide was 99.998% and the nitrogen content was 9 ppm. It can be seen that the quality of the silicon carbide prepared in Comparative Example 2 is inferior to that of Example 1.

[0114] In the silicon carbide prepared in Comparative Example 3, the particle size of the high-purity silicon powder used was 5 μm, the purity of the obtained silicon carbide was 99.995%, and the nitrogen content was 10 ppm. It can be seen that the quality of the silicon carbide prepared in Comparative Example 3 is inferior to that of Example 1.

[0115] In Comparative Example 4, no pressing treatment was performed before the solid-phase carbonization reaction of the mixed powder of silicon powder and carbon powder. The purity of the obtained silicon carbide was 99.992% and the nitrogen content was 15 ppm. It can be seen that the quality of the silicon carbide prepared in Comparative Example 4 is inferior to that of Example 1.

[0116] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0117] The above-mentioned embodiments only express several implementation methods of the present invention, and the description is relatively specific and detailed, but it cannot be understood as limiting the scope of the invention patent. It should be pointed out that for ordinary technicians in this field, several modifications and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims, and the description can be used to interpret the content of the claims.

Claims

1. A method for preparing silicon carbide, characterized in that: The method comprises the following preparation steps: Under inert atmosphere conditions, silicon powder and carbon powder are mixed by acoustic resonance mixing, and then pressed to obtain a mixed material blank, wherein the average particle size of the silicon powder is 10 μm to 200 μm; The mixed material blank is subjected to solid-phase carbonization treatment under vacuum conditions; the solid-phase carbonization treatment conditions include a preheating stage, a silicon powder melting stage, and a solid-phase carbonization reaction stage performed in sequence, the vacuum pressure of the silicon powder melting stage is greater than the vacuum pressure of the preheating stage, and the vacuum pressure of the silicon powder melting stage is greater than the vacuum pressure of the solid-phase carbonization reaction stage; The preheating stage includes heating to a first temperature and keeping the temperature at the first temperature, wherein the first temperature is 1200°C to 1300°C; the first temperature keeping time is 1.5h to 3h; the vacuum pressure in the preheating stage is less than or equal to 1×10 -3 Pa; The silicon powder melting stage includes a heating stage from the first temperature to the second temperature and a heat preservation process at the second temperature, wherein the second temperature is 1350°C to 1600°C; the heat preservation time of the second temperature is 1h to 3h; the vacuum pressure of the silicon powder melting stage is 1×10 -2 Pa~5×10 -2 Pa; The solid phase carbonization reaction stage includes a heating stage from the second temperature to a third temperature and a process of keeping the temperature at the third temperature, wherein the third temperature is 1850°C to 2000°C; the time of keeping the temperature at the third temperature is 1.5h to 3h; the vacuum pressure of the solid phase carbonization reaction stage is 5×10 -3 Pa~4.9×10 -2 Pa.

2. The method for preparing silicon carbide according to claim 1, characterized in that: The silicon powder melting stage includes the following stages: The temperature is raised from the first temperature to 1350° C. to 1450° C. and kept at this temperature for 0.5 h to 2 h, and then raised to 1500° C. to 1600° C. and kept at this temperature for 0.5 h to 1 h.

3. The method for preparing silicon carbide according to claim 1, characterized in that: The resonance frequency of the acoustic resonance mixing is 60 Hz to 70 Hz, the vibration mixing time is 5 min to 30 min, and the acceleration is 60 to 90 gravitational accelerations.

4. The method for preparing silicon carbide according to claim 1, characterized in that When performing acoustic resonance mixing, the vacuum pressure of the inert atmosphere is 1×10 -3 Pa~1×10 5 Pa.

5. The method for preparing silicon carbide according to any one of claims 1 to 4, characterized in that: The pressure of the pressing treatment is 20 MPa to 50 MPa.

6. The method for preparing silicon carbide according to any one of claims 1 to 4, characterized in that: The average particle size of the carbon powder is 0.5 μm to 20 μm.

7. The method for preparing silicon carbide according to any one of claims 1 to 4, characterized in that: The purity of the silicon powder is ≥99.999%; the purity of the carbon powder is ≥99.999%.

8. The method for preparing silicon carbide according to any one of claims 1 to 4, characterized in that: The molar ratio of the silicon powder to the carbon powder is 1:(1-1.8).

9. Silicon carbide, characterized in that: The silicon carbide is prepared according to the method according to any one of claims 1 to 8.

10. The silicon carbide according to claim 9, characterized in that The purity of the silicon carbide is 99.9990% to 99.9996%, and the nitrogen content in the silicon carbide is 2ppm to 8ppm.

11. A silicon carbide ceramic, characterized in that: The preparation material of the silicon carbide ceramic includes the silicon carbide as claimed in any one of claims 9 to 10.

12. A semiconductor device, characterized in that: The manufacturing material of the semiconductor device includes the silicon carbide according to any one of claims 9 to 10.

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