Method for preparing silicon carbide material and silicon carbide material

Abstract

The invention relates to the field of semiconductors, and provides a method for preparing a silicon carbide material, which comprises the following steps: pretreating a graphite base; depositing silicon carbide on the pretreated graphite base within 1 hour; the method for pretreating the graphite base comprises the following steps: performing first pretreatment on the graphite base in plasma gas, wherein the plasma gas is oxygen or oxygen and nitrogen; the flow of the plasma gas ranges from 100 sccm to 400 sccm; the flow ratio of the oxygen to the nitrogen is 1: (0.25-1). According to the preparation method, organic matters and metal impurities on the surface of the graphite base can be effectively removed, so that the cleanliness of the surface of the graphite base is improved, the binding force between the graphite base and a silicon carbide coating is improved, and the service life of a silicon carbide material is prolonged.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a method for preparing a silicon carbide material and the silicon carbide material. Background Art

[0002] SiC coated graphite susceptor is commonly used as a component for supporting and heating substrates in metal organic chemical vapor deposition (MOCVD) equipment. Performance parameters such as integrity, thermal stability, and thermal uniformity play a decisive role in the quality of epitaxial material growth and are the core key components of MOCVD equipment.

[0003] At present, the main failure form of SiC coated graphite base in the application process is cracking and shedding of the coating. The cracking and shedding of the coating is partly due to the presence of organic impurities and metal impurities on the surface of the graphite base. The contact between organic matter and graphite on the surface of the graphite base will greatly affect the growth morphology of the SiC epitaxial layer, and easily promote the heterogeneous nucleation of SiC around the organic foreign matter, thereby producing locally protruding SiC particles. When removing SiC particles, damage will be introduced at the SiC particles, thereby reducing the service life of the base product. The contact between organic matter and the graphite base will also reduce the bonding strength between the graphite base and the silicon carbide coating. At present, the graphite base is generally cleaned with deionized water before chemical deposition, but the cleaning strength of deionized water is general and cannot effectively remove the organic and metal impurities on the surface of the graphite base.

[0004] Therefore, in order to improve the bonding strength between the SiC coating and the graphite base, how to improve the cleanliness of the graphite base surface before chemical deposition is an urgent problem to be solved. Summary of the invention

[0005] The purpose of the present invention is to overcome the above-mentioned problems existing in the prior art and provide a method for preparing silicon carbide material. The present invention performs a first pretreatment on a graphite base in a plasma gas, wherein the plasma gas is oxygen and nitrogen. The introduced plasma gas can effectively remove organic matter and metal impurities on the surface of the graphite base, thereby improving the cleanliness of the surface of the graphite base, improving the bonding force between the graphite base and the silicon carbide coating, and improving the service life of the silicon carbide material.

[0006] In order to achieve the above-mentioned object, the first aspect of the present invention provides a method for preparing silicon carbide material, the method comprising: pre-treating a graphite base; depositing silicon carbide on the pre-treated graphite base within 1 hour; the method for pre-treating the graphite base comprises: performing a first pre-treatment on the graphite base in a plasma gas, the plasma gas being oxygen or oxygen and nitrogen;

[0007] The flow rate of the plasma gas is 100-400 sccm.

[0008] The flow ratio of oxygen to nitrogen is 1:(0.25-1).

[0009] In some embodiments, the first pretreatment condition includes: placing the graphite base in a plasma cleaning device, evacuating the device, and then introducing the plasma gas.

[0010] In some embodiments, the graphite base is connected to the negative pole of the power supply, and the vacuum chamber of the plasma cleaning equipment is connected to the positive pole of the power supply.

[0011] In some embodiments, the positive power electrode is a horizontal electrode.

[0012] In some embodiments, the vacuum chamber is evacuated to a pressure of 5×10 -2 Below Pa.

[0013] In some embodiments, the first pretreatment condition further includes: the power of the plasma cleaning equipment is 200-450W.

[0014] In some embodiments, the pulse frequency of the plasma cleaning device is 300-1500 Hz.

[0015] In some embodiments, the pulse width of the plasma cleaning device is 5-30 μm.

[0016] In some embodiments, the cleaning time of the plasma cleaning device is 120-360 seconds.

[0017] In some embodiments, the graphite susceptor further includes pre-processing the graphite susceptor before the first pre-processing, and the pre-processing includes: making the surface roughness Ra≤0.4 and the flatness ≤0.1 mm of the graphite susceptor after the pre-processing.

[0018] In some embodiments, the pretreatment includes: cleaning the graphite base with deionized water, and then drying it, the resistivity of the deionized water is greater than 18MΩ·cm, the drying temperature is 70-200°C, and the time is 20-80min.

[0019] The second aspect of the present invention provides a silicon carbide material prepared by the method for preparing silicon carbide material described in the first aspect, wherein the silicon carbide material includes the graphite base and the silicon carbide coating on the graphite base, the bonding force between the graphite base and the silicon carbide coating is 29-34MPa, the content of organic matter on the surface of the graphite base is less than or equal to 10ppm, and the content of metal impurities is less than or equal to 8ppm.

[0020] In some embodiments, the flatness of the graphite base surface is 0.1-0.32 mm.

[0021] In some embodiments, the water drop angle of the graphite base is ≤40°.

[0022] The present invention adopts the above technical solution to achieve the following beneficial effects:

[0023] The method for preparing the silicon carbide material provided by the present invention can effectively remove organic impurities and metal impurities on the surface of the graphite base, improve the cleanliness of the graphite base, further improve the bonding force between the graphite base and the silicon carbide coating, and increase the service life of the silicon carbide material.

[0024] The endpoints and any values ​​of the range disclosed in this article are not limited to the precise range or value, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article. Herein, in the absence of special instructions, data ranges include endpoints. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The figure shows the morphology of the coating on the surface of the graphite base after plasma cleaning and deionized water cleaning and then deposition in Example 1.

[0026] Figure 2 The figure shows the morphology of the coating on the surface of the graphite base in comparative example 1 which was only cleaned with deionized water and then deposited. DETAILED DESCRIPTION

[0027] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] Unless otherwise defined, all scientific and technical terms used in the present invention have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention relates.

[0029] The first aspect of the present invention provides a method for preparing a silicon carbide material, the method comprising: pre-treating a graphite base; depositing silicon carbide on the pre-treated graphite base within 1 hour; the graphite base pre-treatment method comprises: performing a first pre-treatment on the graphite base in a plasma gas, the plasma gas being oxygen or oxygen and nitrogen; the flow rate of the plasma gas being 100-400sccm; and the flow rate ratio of the oxygen to the nitrogen being 1:(0.25-1).

[0030] After the graphite base is treated with plasma gas, the oxygen plasma gas reacts with the organic pollutants on the surface of the graphite base to generate carbon dioxide and water vapor, which are separated from the graphite base and discharged with the exhaust system. Oxygen itself is an active gas, and the oxygen plasma gas can react with the graphite layer on the surface of the graphite base to generate CO or CO2. Therefore, oxygen has a good etching effect on the graphite base, which can more effectively increase the deposition sites of silicon carbide on the surface of the graphite base; on the other hand, the surface of the graphite base treated with oxygen plasma gas can generate a large number of free radicals, which can improve the bonding force between the graphite base and the silicon carbide coating.

[0031] Nitrogen can clean and etch the graphite surface by physical collision during plasma cleaning without chemically reacting with the graphite base, and its price is cheaper than oxygen. Specifically, when the plasma gas is a mixed gas composed of oxygen and nitrogen, the nitrogen plasma formed by the nitrogen in the mixed gas during the plasma cleaning process can accelerate the cleaning and etching of the graphite surface by oxygen plasma by physical collision, thereby better removing organic impurities and metal impurities on the surface of the graphite base, and the cleaning rate of the graphite surface by oxygen plasma is accelerated by mixing with nitrogen, so time cost is saved; in addition, nitrogen will not chemically react with the graphite base, and its price is cheaper than oxygen, which also helps to save material cost; therefore, by using oxygen and nitrogen as a mixed gas, the cleaning effect and cleaning rate of oxygen plasma can be effectively improved, thereby increasing the removal effect of oxygen on the graphite surface organic impurities and metal impurities during plasma cleaning, and time cost and material cost can also be reasonably regulated.

[0032] Further, the plasma gas is oxygen and nitrogen, and the flow ratio of the oxygen to nitrogen is 1:(0.25-1), such as 1:0.25, 1:0.3, 1:0.35, 1:0.4, 1:0.45, 1:0.5, 1:0.55, 1:0.6, 1:0.65, 1:0.7, 1:0.75, 1:0.8, 1:0.85, 1:0.9, 1:0.95 and 1: 1. When the flow ratio of oxygen to nitrogen is within the above range, the physical modification of nitrogen to oxygen can be better adjusted, so that the effect of nitrogen relative to oxygen is optimal, thereby better removing organic impurities and metal impurities on the surface of the graphite base, and also helping to save costs. After oxygen is introduced into the plasma cleaning equipment, it is excited to generate oxygen plasma. These active particles are accelerated to generate kinetic energy under the action of bias voltage, thereby bombarding the surface of the graphite base, reacting with organic pollutants on the surface of the base to generate carbon dioxide and water vapor, which are separated from the base and discharged with the exhaust system. Oxygen itself is an active gas, and oxygen plasma can react with the graphite layer on the surface of the base to generate CO or CO2. Therefore, oxygen has a better etching effect on the graphite layer than general inert gases, and can more effectively increase the deposition surface area; on the other hand, a large number of free radicals are generated on the surface after oxygen plasma treatment, which can improve the adhesion of the coating after the graphite base is deposited. Nitrogen is an inert gas. During the plasma cleaning process, it can clean and etch the graphite surface by physical collision without chemically reacting with graphite, and its price is cheaper than oxygen. By adjusting the flow ratio of oxygen and nitrogen, further regulation of plasma cleaning time and processing cost is achieved.

[0033] Furthermore, in the present invention, the flow rate of the plasma gas is 100-400sccm, such as 100sccm, 120sccm, 140sccm, 160sccm, 180sccm, 200sccm, 220sccm, 240sccm, 260sccm, 280sccm, 300sccm, 320sccm, 340sccm, 360sccm, 380sccm and 400sccm. The preferred range is 150-300sccm. In some embodiments, the flow rate of the plasma gas is the flow rate of oxygen. In some embodiments, the flow rate of the plasma gas is the sum of the flow rates of oxygen and nitrogen.

[0034] In the present invention, the pretreated graphite base deposits silicon carbide within 1h. The effect of plasma cleaning is time-effective, and the graphite base performs chemical vapor deposition within 1 hour to have a better deposition effect, and the bonding force between the graphite base and silicon carbide will also be higher. In the present application, the reason why the plasma cleaning technology is emphasized to be time-effective is that the active groups introduced into the surface of the graphite base after plasma cleaning are not stable, and the active groups can migrate freely at room temperature, thereby causing the activity of the graphite base surface to decrease with the increase of time, reducing the cleaning effect; in addition, the graphite base surface after plasma cleaning is also easy to adsorb particulate matter (such as dust) in the air, thereby polluting the graphite base surface and reducing the active energy on its surface, controlling chemical vapor deposition within 1 hour, can better ensure the active energy on the surface of the graphite base, and reduce the risk of silicon carbide coating falling off.

[0035] In some embodiments, the first pretreatment conditions include: placing the graphite base in a plasma cleaning device, evacuating the device, and then introducing plasma gas.

[0036] In some embodiments, the purity of the oxygen plasma gas is 99.5%-99.9%; the purity of the nitrogen plasma gas is 99.5%-99.9%.

[0037] In some embodiments, the graphite base is connected to the negative pole of the power supply, and the vacuum chamber of the plasma cleaning equipment is connected to the positive pole of the power supply.

[0038] In some embodiments, the graphite susceptor is placed flat in a plasma cleaning device to help ensure uniformity of plasma cleaning.

[0039] In some embodiments, the vacuum chamber of the plasma cleaning device is evacuated to a pressure of 5×10 -2 Pa or less, such as 5×10 -2 Pa, 1×10 -2 Pa, 5×10 -3 Pa and 1×10 -3 Pa.

[0040] In some embodiments, the positive electrode of the power supply is a horizontal electrode, which helps to ensure uniformity of plasma cleaning.

[0041] In some embodiments, the first pretreatment condition also includes: the power of the plasma cleaning equipment is 200-450W, such as 200W, 220W, 240W, 260W, 280W, 300W, 320W, 340W, 360W, 380W, 400W, 420W and 450W. When the power of the plasma cleaning equipment is within the above range, as the power of the plasma cleaning equipment increases, the cleaning efficiency gradually increases, and the cleaning time can be shortened. When the power of the plasma cleaning is greater than 450W, the surface of the graphite base will be unevenly cleaned, such as the cleaning effect of the edge of the graphite base will be worse than that of the middle area, which will cause the deposition rate of the middle part of the base to be higher than that of the edge during the chemical vapor deposition process, resulting in uneven coating thickness.

[0042] In some embodiments, the pulse frequency of the plasma cleaning device is 300-1500 Hz, such as 300 Hz, 500 Hz, 700 Hz, 900 Hz, 1100 Hz, 1300 Hz and 1500 Hz.

[0043] In some embodiments, the pulse width of the plasma cleaning device is 5-30 μm, such as 5 μm, 10 μm, 15 μm, 20 μm, 25 μm and 30 μm.

[0044] In some embodiments, the cleaning time of the plasma cleaning equipment is 120-360 seconds, such as 120 seconds, 160 seconds, 200 seconds, 240 seconds, 280 seconds, 320 seconds and 360 seconds.

[0045] In some embodiments, the bias voltage of the plasma cleaning equipment is 200-350V, such as 200V, 220V, 240V, 260V, 280V, 300V, 320V, 340V and 350V.

[0046] In some embodiments, the graphite base is pretreated by placing the graphite base in a plasma cleaning device, connecting the graphite base to the negative pole of the power supply, connecting the graphite base vacuum chamber to the positive pole of the power supply, and evacuating the graphite base to 5.0×10 -2 Pa or less; introduce oxygen with a purity of 99.9%, and control the total gas flow rate to 100-400sccm, turn on the power switch, adjust the power bias, pulse frequency, and pulse width, so that the graphite base performs cathode discharge, and the generated oxygen plasma will react with the organic pollutants on the surface of the graphite base to generate carbon dioxide and water vapor, and these gases will be discharged from the cavity with the air pump. The power of plasma cleaning is 200-450W, the cleaning time is 120-360s, the pulse frequency is 300-1500Hz; the pulse width is 5-30μm. After the plasma cleaning is completed, gradually introduce air, and after the indoor and outdoor air pressures are balanced, the graphite base can be taken out of the plasma cleaning chamber.

[0047] In some embodiments, the graphite base is pretreated by placing the graphite base in a plasma cleaning device, connecting the graphite base to the negative pole of the power supply, connecting the graphite base vacuum chamber to the positive pole of the power supply, and evacuating the vacuum chamber to 5×10 -2 Pa or less; introduce a mixed gas of 99.9% pure oxygen and 99.9% pure nitrogen, the flow ratio of oxygen and nitrogen is 1: (0.25-1), and control the total flow of the gas to be 100-400sccm, turn on the power switch, adjust the power bias, pulse frequency, and pulse width, so that the graphite base performs cathode discharge, and the generated oxygen plasma will react with the organic pollutants on the surface of the graphite base to generate carbon dioxide and water vapor, and these gases will be discharged from the cavity with the air pump. The power of plasma cleaning is 200-450W, the cleaning time is 120-360s, the pulse frequency is 300-1500Hz; the pulse width is 5-30μm. After the plasma cleaning is completed, gradually introduce air, and after the indoor and outdoor air pressures are balanced, the graphite base can be taken out of the plasma cleaning chamber.

[0048] In some embodiments, after the deposition is completed, nitrogen can be introduced to replace the remaining gas in the furnace. The nitrogen replacement is to remove the toxic byproduct gas in the furnace to ensure the safety of the operator when opening the furnace.

[0049] In some embodiments, the graphite base is further subjected to pretreatment before the first pretreatment, and the pretreatment includes: making the surface roughness Ra≤0.4 and the flatness ≤0.1mm of the graphite base after the pretreatment, and a smaller flatness can improve the uniformity of deposition. The graphite base is polished so that the roughness and flatness of the graphite base are within the above range. In some embodiments, the graphite base is processed by CNC machine tool machining. The test standard for roughness is GB / T1031-2009. The test method for flatness is probe type, and the standard adopted is GB / T24630.1-2009.

[0050] In some embodiments, the pretreatment includes: cleaning the graphite base with deionized water and then drying. The resistivity of the deionized water is greater than 18MΩ·cm, the drying temperature is 70-200°C, such as 70°C, 100°C, 120°C, 140°C, 160°C, 180°C and 200°C, and the time is 20-80min, such as 20min, 30min, 40min, 50min, 60min, 70min and 80min. Cleaning the graphite base with deionized water helps to remove impurities on the surface of the graphite base and improve the cleanliness of the graphite base to a certain extent.

[0051] In some embodiments, the conditions for depositing silicon carbide on the pretreated graphite base include: a deposition temperature range of 1100°C-1400°C, such as 1100°C, 1200°C, 1300°C and 1400°C, and after keeping warm for 10-20 minutes, argon, methyltrichlorosilane (MTS) and hydrogen are respectively introduced to perform chemical vapor deposition, and the deposition time is determined according to the required coating thickness.

[0052] A second aspect of the present invention provides a silicon carbide material prepared by the method of the first aspect, wherein the silicon carbide material comprises a graphite base and a silicon carbide coating on the graphite base, wherein the bonding force between the graphite base and the silicon carbide coating is 29-34 MPa, such as 29 MPa, 29.5 MPa, 30.2 MPa, 30.5 MPa, 31 MPa, 31.5 MPa, 32 MPa, 32.3 MPa, 32.7 MPa, 33 MPa, 33.1 MPa, 33.5 MPa and 34 MPa; the content of organic matter on the surface of the graphite base is less than or equal to 10 ppm, such as 10 ppm, 9 ppm, 8 ppm, 7 ppm, 6 ppm, 5 ppm, 4 ppm, 3 ppm, 2 ppm and 1 ppm, and the content of metal impurities is less than or equal to 8 ppm, for example, 1 ppm, 2 ppm, 3 ppm, 4 ppm, 5 ppm, 6 ppm, 7 ppm and 8 ppm. The test method for bonding strength is the peel test method, and the reference standard is GB / T 9286-1998.

[0053] In some embodiments, the flatness of the graphite base surface is 0.1-0.32 mm, for example, 0.1 mm, 0.12 mm, 0.14 mm, 0.16 mm, 0.18 mm, 0.2 mm, 0.22 mm, 0.24 mm, 0.26 mm, 0.28 mm, 0.3 mm and 0.32 mm. The roughness test method is GB / T 1031-2009.

[0054] In some embodiments, the water drop angle of the graphite base is ≤40°, for example, 29°, 29.7°, 30°, 30.5°, 31°, 31.5°, 32°, 32.5°, 33°, 33.4°, 34°, 35°, 35.5°, 36°, 37°, 38°, 39° and 40°. The test standard of the water drop angle is ASTM D 1590.

[0055] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0056] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0057] The present invention is described in detail below in conjunction with specific embodiments, which are used to understand but not to limit the present invention.

[0058] Example 1

[0059] S1: Processing the graphite blank into the required base shape, polishing until the roughness and flatness reach the preset standards, the roughness Ra of the graphite blank is 0.2, and the flatness is 0.07mm, to obtain a pre-treated graphite base;

[0060] S2: The graphite base obtained in step S1 after the pretreatment is cleaned with deionized water, and then dried, wherein the resistivity of the deionized water is 20 MΩ·cm, the drying temperature is 150° C., and the drying time is 45 min, thereby obtaining a graphite base cleaned with deionized water;

[0061] S3: Place the graphite base obtained in step S2 and washed with deionized water in a plasma cleaning device, connect the graphite base obtained in step S2 and washed with deionized water to the negative electrode of the power supply, connect the graphite base vacuum chamber to the positive electrode of the power supply, and evacuate to 5×10 -3 Pa;

[0062] S4: Pass oxygen with a purity of 99.9%, and control the total gas flow rate to 200sccm, turn on the power switch, adjust the power bias to 270V, adjust the plasma cleaning power to 400W, the cleaning time to 180s, the pulse frequency to 1000Hz; the pulse width is 10μm. After the plasma cleaning is completed, gradually pass air, and after the indoor and outdoor air pressures are balanced, the graphite base in step S3 can be taken out of the plasma cleaning chamber to obtain a graphite base that has been plasma cleaned; the water drop angle of the graphite base that has been plasma cleaned is measured to be 29.7°;

[0063] S5: performing chemical vapor deposition on the graphite base that has been plasma cleaned in step S4 within one hour after cleaning;

[0064] S6: After the deposition is completed, nitrogen is introduced to replace the remaining gas in the furnace, and the furnace temperature is lowered before the furnace is removed. The bonding force between the graphite base and the silicon carbide coating after the deposition is completed is 33.1 MPa, the content of organic matter on the surface of the graphite base after the deposition is completed is 2 ppm, the content of metal impurities is 2 ppm, and the flatness of the surface of the graphite base after the deposition is completed is 0.12 mm. The morphology of the surface coating of the graphite base obtained is shown in FIG. Figure 1 shown.

[0065] Example 2

[0066] S1: Processing the graphite blank into the required base shape, polishing until the roughness and flatness reach the preset standards, the roughness Ra of the graphite blank is 0.2, and the flatness is 0.07mm, to obtain a pre-treated graphite base;

[0067] S2: The graphite base obtained in step S1 after the pretreatment is cleaned with deionized water, and then dried, wherein the resistivity of the deionized water is 23 MΩ·cm, the drying temperature is 80° C., and the drying time is 30 min, thereby obtaining a graphite base cleaned with deionized water;

[0068] S3: Place the graphite base obtained in step S2 and washed with deionized water in a plasma cleaning device, connect the graphite base obtained in step S2 and washed with deionized water to the negative electrode of the power supply, connect the graphite base vacuum chamber to the positive electrode of the power supply, and evacuate to 5×10 -3 Pa;

[0069] S4: Pass oxygen with a purity of 99.9%, and control the total gas flow rate to 160sccm, turn on the power switch, adjust the power bias to 220V, adjust the plasma cleaning power to 380W, the cleaning time to 120s, the pulse frequency to 300Hz; the pulse width is 5μm. After the plasma cleaning is completed, gradually pass air, and after the indoor and outdoor air pressures are balanced, the graphite base in step S3 can be taken out of the plasma cleaning chamber to obtain a graphite base that has been plasma cleaned; the water drop angle of the graphite base that has been plasma cleaned is measured to be 30.9°;

[0070] S5: performing chemical vapor deposition on the graphite base that has been plasma cleaned in step S4 within one hour after cleaning;

[0071] S6: After the deposition is completed, nitrogen is introduced to replace the remaining gas in the furnace, and the furnace temperature is lowered before exiting the furnace. The bonding force between the graphite base after deposition and the silicon carbide coating is 31.2 MPa, the content of organic matter on the surface of the graphite base after deposition is 4 ppm, the content of metal impurities is 5 ppm, and the flatness of the surface of the graphite base after deposition is 0.11 mm.

[0072] Example 3

[0073] S1: Processing the graphite blank into the required base shape, polishing until the roughness and flatness reach the preset standards, the roughness Ra of the graphite blank is 0.2, and the flatness is 0.07mm, to obtain a pre-treated graphite base;

[0074] S2: The graphite base obtained in step S1 after the pretreatment is cleaned with deionized water, and then dried, wherein the resistivity of the deionized water is 22 MΩ·cm, the drying temperature is 190° C., and the drying time is 70 min, thereby obtaining a graphite base cleaned with deionized water;

[0075] S3: Place the graphite base obtained in step S2 and washed with deionized water in a plasma cleaning device, connect the graphite base obtained in step S2 and washed with deionized water to the negative electrode of the power supply, connect the graphite base vacuum chamber to the positive electrode of the power supply, and evacuate to 5×10 -3 Pa;

[0076] S4: introduce a mixed gas of 99.9% pure oxygen and 99.9% pure nitrogen, with a flow ratio of 1:0.5 between oxygen and nitrogen, and control the total flow of the gas to 280sccm, turn on the power switch, adjust the power bias to 330V, adjust the plasma cleaning power to 420W, the cleaning time to 360s, the pulse frequency to 1500Hz; the pulse width is 30μm. After the plasma cleaning is completed, gradually introduce air, and after the indoor and outdoor air pressures are balanced, the graphite base in step S3 can be taken out of the plasma cleaning chamber to obtain a graphite base that has been plasma cleaned; the water drop angle of the graphite base that has been plasma cleaned is measured to be 31.3°;

[0077] S5: performing chemical vapor deposition on the graphite base that has been plasma cleaned in step S4 within one hour after cleaning;

[0078] S6: After the deposition is completed, nitrogen is introduced to replace the remaining gas in the furnace, and the furnace temperature is lowered before exiting the furnace. The bonding force between the graphite base after deposition and the silicon carbide coating is 32.5 MPa, the content of organic matter on the surface of the graphite base after deposition is 3 ppm, the content of metal impurities is 3 ppm, and the flatness of the surface of the graphite base after deposition is 0.13 mm.

[0079] Example 4

[0080] This example is used to illustrate the preparation of a graphite susceptor when the flow ratio of oxygen to nitrogen is different.

[0081] Example 4-1

[0082] The operation was carried out according to the method described in Example 3, except that the flow ratio of oxygen to nitrogen was 1:0.25.

[0083] Example 4-2

[0084] The operation was carried out according to the method described in Example 3, except that the flow ratio of oxygen to nitrogen was 1:1.

[0085] Example 4-3

[0086] The operation was carried out according to the method described in Example 3, except that the flow ratio of oxygen to nitrogen was 1:2.

[0087] Example 5

[0088] This embodiment is used to illustrate the preparation of a graphite base when the total flow rate of plasma gas is different.

[0089] Example 5-1

[0090] The operation is carried out in accordance with the method described in Example 3, except that the total flow rate of the plasma gas is 120 sccm.

[0091] Example 5-2

[0092] The operation was carried out in accordance with the method described in Example 3, except that the total flow rate of the plasma gas was 370 sccm.

[0093] Example 5-3

[0094] The operation is carried out in accordance with the method described in Example 3, except that the total flow rate of the plasma gas is 500 sccm.

[0095] Example 6

[0096] This embodiment is used to illustrate the preparation of a graphite base when the power of plasma cleaning is different.

[0097] Example 6-1

[0098] The operation was carried out according to the method described in Example 3, except that the power of plasma cleaning was 300W.

[0099] Example 6-2

[0100] The operation was carried out according to the method described in Example 3, except that the power of plasma cleaning was 500W.

[0101] Example 7

[0102] This embodiment is used to illustrate the preparation of a graphite susceptor when the power bias voltage of plasma cleaning is different.

[0103] The operation is carried out according to the method described in Example 3, except that the power bias voltage is 400V.

[0104] Comparative Example 1

[0105] This comparative example is used to illustrate that the graphite base is only treated with deionized water without plasma treatment.

[0106] The operation was carried out according to the method described in Example 3, except that steps S3 and S4 were not performed. The morphology of the coating on the surface of the graphite base obtained is shown in FIG. Figure 2 shown.

[0107] Comparative Example 2

[0108] This comparative example is used to illustrate that the graphite base is not treated by the plasma device.

[0109] The operation is performed according to the method described in Example 3, except that step S3 is not performed.

[0110] Comparative Example 3

[0111] This comparative example is used to illustrate the preparation of a graphite susceptor when the plasma gas introduced is nitrogen.

[0112] The operation was carried out according to the method described in Example 3, except that the gas introduced in step S4 was only nitrogen.

[0113] Test example:

[0114] The graphite susceptor obtained after deionized water cleaning and plasma cleaning in the embodiment was tested, or the graphite susceptor obtained after deionized water cleaning and / or plasma cleaning in the comparative example was tested.

[0115] (1) Content of organic matter and metal impurities on the surface of graphite base: The graphite base obtained after deionized water cleaning and plasma cleaning in the example was tested, or the graphite base obtained after deionized water cleaning and / or plasma cleaning in the comparative example was tested.

[0116] The test was carried out by GDMS glow discharge mass spectrometry, and the test results are shown in Table 1.

[0117] (2) Water drop angle of graphite base: The graphite base obtained after deionized water cleaning and plasma cleaning in the embodiment was tested, or the graphite base obtained after deionized water cleaning and / or plasma cleaning in the comparative example was tested.

[0118] The test was carried out according to ASTM D 1590. The test results are shown in Table 1.

[0119] (3) Adhesion test: The product obtained by depositing silicon carbide on the graphite base is tested.

[0120] The test was carried out in accordance with GB / T 9286-1998. The test results are shown in Table 1.

[0121] (4) Graphite base flatness / mm: The product obtained by depositing silicon carbide on the graphite base was tested.

[0122] The test was carried out in accordance with GB / T24630.1-2009. The test results are shown in Table 1.

[0123] Table 1

[0124]

[0125] In Example 1 and Example 2, the plasma gas is all oxygen, in Example 3, the plasma gas is a mixed gas of oxygen and nitrogen, and in Example 4, the preparation of the graphite base when the flow ratio of oxygen and nitrogen is different. When the plasma gas is all oxygen, it helps to reduce the content of organic matter on the surface of the graphite base and the content of metal impurities, and also helps to reduce the water drop angle on the surface of the graphite base. After silicon carbide is deposited on the surface of the graphite base, it also helps to improve the bonding force between the graphite base and the silicon carbide coating and reduce the flatness of the graphite base. When the plasma gas is a mixed gas of oxygen and nitrogen, and the two meet a certain proportional relationship, the content of organic matter on the surface of the graphite base, the content of metal impurities, and the water drop angle on the surface of the graphite base are small, and after silicon carbide is deposited on the surface of the graphite base, the bonding force between the graphite base and the silicon carbide coating is large, and the flatness of the graphite base is also small. At the same time, it also helps to save costs.

[0126] Comparative Example 1 is a graphite base treated with deionized water only. Comparative Example 2 is a graphite base treated with oxygen after being treated with deionized water, but oxygen is not introduced into the plasma equipment, that is, Comparative Example 2 is not subjected to plasma treatment. Comparative Example 3 is a graphite base also subjected to plasma treatment on the basis of deionized water treatment, but all the gases introduced during the plasma treatment are nitrogen. Comparative Examples 1, 2 and 3 are compared with the test data of Example 1 to show that after the graphite base is treated with deionized water, it is placed in a mixed gas containing oxygen or oxygen and nitrogen for plasma treatment, which does help to reduce the content of organic matter and metal impurities on the surface of the graphite base, and also helps to reduce the water drop angle on the surface of the graphite base. After silicon carbide is deposited on the surface of the graphite base, it also helps to improve the bonding force between the graphite base and the silicon carbide coating and reduce the flatness of the graphite base.

[0127] It should be noted that, in this article, the terms "comprise", "include" or any other variant thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise one..." do not exclude the presence of other identical elements in the process, method, article or device including the element. In addition, it should be pointed out that the scope of the methods and devices in the embodiments of the present application is not limited to performing functions in the order shown or discussed, and may also include performing functions in a substantially simultaneous manner or in reverse order according to the functions involved, for example, the described method may be performed in an order different from that described, and various steps may also be added, omitted, or combined. In addition, the features described with reference to certain examples may be combined in other examples.

[0128] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing silicon carbide material, characterized in that: The method comprises: Pre-treating the graphite base; The pretreated graphite base deposits silicon carbide within 1 hour; The method for pre-treating the graphite susceptor comprises: performing a first pre-treatment on the graphite susceptor in a plasma gas, wherein the plasma gas is oxygen or oxygen and nitrogen; The flow rate of the plasma gas is 100-400 sccm; The flow ratio of the oxygen and the nitrogen is 1:(0.25-1).

2. The method for preparing silicon carbide material according to claim 1, characterized in that: The conditions of the first pretreatment include: placing the graphite base in a plasma cleaning device, evacuating the device, and then introducing the plasma gas.

3. The method for preparing silicon carbide material according to claim 2, characterized in that: The graphite base is connected to the negative electrode of the power supply, and the vacuum chamber of the plasma cleaning equipment is connected to the positive electrode of the power supply; The positive electrode of the power supply is a horizontal electrode; The vacuum chamber is evacuated to a pressure of 5×10 -2 Below Pa.

4. The method for preparing silicon carbide material according to claim 3, characterized in that: The first pretreatment condition also includes: the power of the plasma cleaning equipment is 200-450W; and / or, The pulse frequency of the plasma cleaning equipment is 300-1500 Hz; and / or, The pulse width of the plasma cleaning device is 5-30 μm; and / or, The cleaning time of the plasma cleaning equipment is 120-360s.

5. The method for preparing silicon carbide material according to claim 1, characterized in that: Before the graphite susceptor is subjected to the first pretreatment, the graphite susceptor is also subjected to a pretreatment, and the pretreatment includes: The surface roughness Ra of the graphite base after pretreatment is ≤0.4, and the flatness is ≤0.1 mm.

6. The method for preparing silicon carbide material according to claim 5, characterized in that: The pre-treatment includes: The graphite base is cleaned with deionized water and then dried. The resistivity of the deionized water is greater than 18 MΩ·cm. The drying temperature is 70-200° C. and the drying time is 20-80 minutes.

7. A silicon carbide material obtained by the method for preparing a silicon carbide material according to any one of claims 1 to 6, characterized in that: The silicon carbide material includes the graphite base and the silicon carbide coating on the graphite base, and the bonding force between the graphite base and the silicon carbide coating is 29-34 MPa; The content of organic matter on the surface of the graphite base is less than or equal to 10 ppm, and the content of metal impurities is less than or equal to 8 ppm.

8. The silicon carbide material according to claim 7, characterized in that: The flatness of the surface of the graphite base is 0.1-0.32 mm.

9. The silicon carbide material according to claim 7 or 8, characterized in that: The water drop angle of the graphite base is ≤40°.

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