阅读说明：本技术 具有高纯工作表面的SiC陶瓷器件及其制备方法和应用 (SiC ceramic device with high-purity working surface and preparation method and application thereof ) 是由 杨勇 刘盟 黄政仁 刘学建 姚秀敏 于 2020-12-22 设计创作，主要内容包括：本发明公开具有高纯工作表面的SiC陶瓷器件及其制备方法和应用。所述SiC陶瓷器件包括低B、C残余的SiC陶瓷基体和位于SiC陶瓷基体表面的高纯CVD-SiC薄膜；所述SiC陶瓷基体的致密度高于98%；所述SiC陶瓷基体的纯度高于99.5wt%；所述CVD-SiC膜的纯度高于99.9wt%。本发明通过在低B、C残余SiC陶瓷表面镀制一层高纯CVD SiC薄膜,将有效减少B元素扩散进晶圆中,减少对晶圆的不利影响。(The invention discloses a SiC ceramic device with a high-purity working surface and a preparation method and application thereof. The SiC ceramic device comprises a low B, C residual SiC ceramic matrix and a high-purity CVD-SiC film positioned on the surface of the SiC ceramic matrix; the density of the SiC ceramic matrix is higher than 98%; the purity of the SiC ceramic matrix is higher than 99.5 wt%; the CVD-SiC film has a purity of greater than 99.9 wt%. According to the invention, a high-purity CVD SiC film is plated on the surface of the low B, C residual SiC ceramic, so that B element is effectively reduced from diffusing into the wafer, and the adverse effect on the wafer is reduced.)

1. A SiC ceramic device having a high purity working surface, characterized in that the SiC ceramic device comprises a low B, C residual SiC ceramic matrix and a high purity CVD-SiC thin film on the surface of the SiC ceramic matrix; the density of the SiC ceramic matrix is higher than 98%; the purity of the SiC ceramic matrix is higher than 99.5 wt%; the CVD-SiC film has a purity of greater than 99.9 wt%.

2. The SiC ceramic device according to claim 1, wherein the CVD-SiC thin film has a thickness of 10 to 1000 μm.

3. The method of manufacturing a high purity working surface SiC ceramic device according to claim 1 or 2, comprising the steps of:

(1) performing ball milling mixing on alpha-SiC powder, a sintering aid and a solvent to obtain SiC slurry, and drying and molding the slurry to prepare a SiC green compact;

(2) carrying out vacuum debonding on the SiC green compact and then sintering at normal pressure to obtain a low B, C residual SiC ceramic matrix;

(3) the SiC ceramic matrix with low B, C residue is placed in a CVD reaction chamber, and a high-purity CVD-SiC film is plated on the surface of the SiC ceramic matrix.

4. The preparation method according to claim 3, wherein the sintering aid comprises a B source and a C source, the B source addition amount in the sintering aid is 0.1-1 wt% of the quality of the alpha-SiC powder, and the C source addition amount in the sintering aid is less than 5wt% of the quality of the alpha-SiC powder; preferably, the B source is selected from at least one of boric acid, boron oxide and boron carbide, and the C source is selected from at least one of D-fructose, glucose and phenolic resin.

5. The production method according to claim 3 or 4, wherein the solid content of the SiC slurry is 20 to 60 wt%.

6. The production method according to any one of claims 3 to 5, wherein the solvent is absolute ethanol.

7. The production method according to any one of claims 3 to 6, wherein the molding manner is dry press molding and/or cold isostatic press molding; the dry pressing pressure is 5-100 MPa; the cold isostatic pressing pressure is 150-200 MPa; the pressure maintaining time is 1-3 minutes.

8. The preparation method according to any one of claims 3 to 7, wherein the temperature of the vacuum de-bonding is 600 to 1200 ℃, the holding time is 30 to 120 minutes, and the vacuum degree is less than 100 Pa.

9. The method according to any one of claims 3 to 8, wherein the sintering temperature is 2050 to 2250 ℃, the holding time is 30 to 120 minutes, and the sintering atmosphere is an inert atmosphere.

10. The method according to any one of claims 3 to 9, wherein the CVD-SiC thin film is produced by chemical vapor deposition at a deposition temperature of 1000 to 1400 ℃ under a deposition pressure of 1 to 20 kPa.

11. The method according to claim 10, wherein a mixed gas of trichloromethylsilane and hydrogen is used as a gas source in the chemical vapor deposition process, wherein trichloromethylsilane is a silicon carbide gas source, and hydrogen is a carrier gas; preferably, the trichloromethylsilane accounts for 5-20 mol% of the mixed gas of trichloromethylsilane and hydrogen.

12. Use of a SiC ceramic component with a high-purity working surface according to claim 1 or 2 in the semiconductor field, in particular in the processing of large-size wafers.

Technical Field

The invention relates to a SiC ceramic device with a high-purity working surface and a preparation method thereof, belonging to the field of materials.

Background

Chip manufacturing is mainly divided into chip design, wafer manufacturing, and package testing. In the semiconductor industry in china, wafer fabrication is the weakest link. With the increasing emphasis of the country on the semiconductor industry, a large number of wafer factories establish production lines in China in recent years, and the relevant ones are various devices required in semiconductor processing. Among them, high-purity silicon carbide (SiC) ceramic materials occupy a large specific gravity in the fabricated devices due to many excellent properties such as high strength, hardness, rigidity, chemical stability, excellent oxidation resistance and wear resistance, and the like.

At present, the SiC ceramic device widely applied to semiconductor processing is mainly prepared by a recrystallization sintering method. Although the recrystallized SiC has extremely high purity and does not contain any metal phase and glass phase, the density and the strength are lower because the recrystallization sintering is gas phase mass transfer, the volume shrinkage is almost not generated in the sintering process, and the density of the prepared SiC ceramic is equivalent to that of a biscuit. Although the compactness and the bending strength of the recrystallized SiC ceramic can be improved by a precursor impregnation cracking method, the bending strength is still lower than 200MPa, and the requirements of the semiconductor industry are difficult to meet. With the further development of the semiconductor industry, the performance of recrystallized SiC ceramic devices has not been able to meet the requirements of larger-sized wafers for processing devices. Although high-density SiC ceramics can be prepared without adding a sintering aid by hot-press sintering or spark plasma sintering, the sintering conditions are severe. For example, when a sintering aid is not used, the temperature and pressure of hot-pressing sintering need to reach 2500 ℃ and 5GPa, and the temperature and pressure of discharge plasma sintering need to reach 2100 ℃ and 70MPa to prepare SiC ceramics with the density of more than 98%. In addition, the two methods generally place SiC powder in a graphite mold for sintering, so that the prepared SiC ceramic has simple shape and small size, and is not suitable for preparing ceramic parts with large size and complex shape.

In addition, the current more solution is to plate high purity CVD-SiC films on the surfaces of other devices such as graphite, recrystallized SiC, reaction sintered SiC, and atmospheric pressure solid phase sintered SiC to obtain high purity working surfaces. The graphite is used as a matrix, so that the problem of unmatched thermal expansion coefficients exists, the SiC film is peeled off after repeated temperature rise and drop, and the service life is extremely short. Recrystallized SiC as a matrix has disadvantages of low strength, high cost, and causing fine particles after exfoliation of the SiC film. The reaction sintered SiC contains more free Si, which can reduce the high-temperature mechanical property and can not be used under the conditions of strong oxidation and strong corrosion, and in addition, the existence of the free Si can cause poor combination of a matrix and a film layer. Residual B and C exist in the normal-pressure solid-phase sintered SiC, and impurity elements can diffuse into the CVD-SiC during long-time use to finally pollute the wafer.

Disclosure of Invention

Although the content of the B element in the low B, C residual SiC ceramic is greatly reduced compared with the content of the B element in the common normal-pressure solid-phase sintering method, the content of the B element is still 1136ppm, and the B atoms are likely to diffuse into a wafer during the semiconductor processing process, particularly at higher temperature, so that the yield is reduced. Therefore, the existing high-density low B, C residual SiC ceramic still has difficulty in meeting the requirements of the semiconductor industry.

In order to solve the problem, the invention adopts a method of combining a film material and a bulk material to prepare the SiC ceramic device with a high-purity working surface, namely, the SiC ceramic with low B, C residual which is sintered in a solid phase at normal pressure is taken as a matrix, and a high-purity CVD-SiC coating is plated on the surface of the SiC ceramic device. By plating a high-purity CVD SiC film on the surface of the low B, C residual SiC ceramic, the diffusion of B element into the wafer is effectively reduced, and the adverse effect on the wafer is reduced. The method can reduce the manufacturing cost to a great extent, and provides powerful technical support for 'curve overtaking' in the semiconductor industry of China.

In a first aspect, the present invention provides a SiC ceramic device having a high purity working surface. The SiC ceramic device comprises a low B, C residual SiC ceramic matrix and a high-purity CVD-SiC film positioned on the surface of the SiC ceramic matrix; the density of the SiC ceramic matrix is higher than 98%; the purity of the SiC ceramic matrix is higher than 99.5 wt%; the CVD-SiC film has a purity of greater than 99.9 wt%.

The invention realizes the effective composition of the SiC ceramic matrix with low B, C residual and the high-purity CVD-SiC film. The compound mode avoids the existence of free silicon and improves the bonding force between the SiC matrix and the CVD-SiC film. In addition, the normal pressure solid phase sintered SiC is adopted as the matrix, and compared with the reaction sintered SiC, the SiC has better physical and chemical properties, such as higher strength (the strength of the normal pressure sintered silicon carbide matrix used by the invention can reach 440MPa, and the strength of the reaction sintered SiC matrix is about 350 MPa). In addition, reaction sintered SiC substrates contain a large amount of free Si, which may result in a mismatch in the thermal expansion coefficients of the substrate and the thin film, and the bonding force between the free Si portion and the CVD-SiC is poor, resulting in easy peeling of the film.

Preferably, the thickness of the CVD-SiC film is 10 to 1000 μm.

In some technical schemes, the SiC phase of the SiC ceramic matrix with low B, C residual is 4H-SiC and 6H-SiC, and the SiC phase of the high-purity CVD-SiC film is 3C-SiC.

In a second aspect, the present invention provides a method of making a high purity working surface SiC ceramic device as described in any one of the above. The preparation method comprises the following steps:

(1) performing ball milling mixing on alpha-SiC powder, a sintering aid and a solvent to obtain SiC slurry, and drying and molding the slurry to prepare a SiC green compact;

(2) carrying out vacuum debonding on the SiC green compact and then sintering at normal pressure to obtain a low B, C residual SiC ceramic matrix;

(3) the SiC ceramic matrix with low B, C residue is placed in a CVD reaction chamber, and a high-purity CVD-SiC film is plated on the surface of the SiC ceramic matrix.

Preferably, the sintering aid comprises a B source and a C source, the addition amount of the B source in the sintering aid is 0.1-1 wt% of the mass of the alpha-SiC powder, and the addition amount of the C source in the sintering aid is less than 5wt% of the mass of the alpha-SiC powder; preferably, the B source is selected from at least one of boric acid, boron oxide and boron carbide, and the C source is selected from at least one of D-fructose, glucose and phenolic resin.

Preferably, the solid content of the SiC slurry is 20-60 wt%.

Preferably, the solvent is absolute ethyl alcohol.

Preferably, the forming mode is dry pressing and/or cold isostatic pressing; the dry-pressing forming pressure is 5-100 MPa, the cold isostatic pressing forming pressure is 150-200 MPa, and the pressure maintaining time is 1-3 minutes.

Preferably, the temperature of the vacuum de-bonding is 600-1200 ℃, the heat preservation time is 30-120 minutes, and the vacuum degree is less than 100 Pa.

Preferably, the sintering temperature is 2050-2250 ℃, the heat preservation time is 30-120 minutes, and the sintering atmosphere is an inert atmosphere.

Preferably, the CVD-SiC film is prepared by a chemical vapor deposition method, the deposition temperature is 1000-1400 ℃, and the deposition pressure is 1-20 kPa.

Preferably, the mixed gas of trichloromethylsilane and hydrogen is used as a gas source in the chemical vapor deposition process, wherein trichloromethylsilane is a silicon carbide gas source, and hydrogen is a carrier gas; preferably, the trichloromethylsilane accounts for 5-20 mol% of the mixed gas of trichloromethylsilane and hydrogen. In some embodiments, argon may also be added as a dilution gas.

In a third aspect, the invention also provides the use of any of the above-described SiC ceramic devices having a high purity working surface in the semiconductor field, in particular in the processing of large-size wafers.

Drawings

FIG. 1 is an SEM image of a low B, C residual SiC ceramic prepared in example 1 after etching;

FIG. 2 is an SEM photograph of a cross section of a SiC film prepared in example 1;

FIG. 3 is an XRD pattern of CVD-SiC prepared in example 1;

FIG. 4 is an SEM image of a cross section of a SiC film prepared in example 2;

FIG. 5 is an XRD pattern of CVD-SiC prepared in example 2.

Detailed Description

The invention is further illustrated below with reference to the accompanying drawings and the following embodiments. It is to be understood that the drawings and the following detailed description are illustrative of the invention only and are not restrictive thereof. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Although the normal pressure sintered SiC ceramic has excellent physicochemical properties, the wafer is contaminated by an excessive amount of the sintering aid. Based on the problem, the invention provides a SiC ceramic device with a high-purity working surface applied to the semiconductor processing industry and a preparation method thereof. The SiC ceramic device adopts the combination of membrane materials and bulk materials, takes low B, C residual SiC ceramic which is subjected to normal pressure solid phase sintering as a matrix, prepares compact SiC ceramic by a normal pressure solid phase sintering method, can easily prepare ceramic parts with large size and complex shape, and is suitable for industrial production. Further, a high-purity CVD-SiC coating is plated on the surface of the compact SiC ceramic matrix, so that the requirements of semiconductor processing application are met. In addition, the substrate and the film layer in the silicon carbide ceramic device of the invention use the same type of materials, thereby avoiding the peeling or cracking of the film layer caused by the inconsistency of the thermal expansion coefficients of the substrate and the film layer. Preferably, the thermal expansion coefficients of the SiC substrate and the CVD-SiC film both in the normal pressure solid phase sintering are 2 to 4X 10^-6and/K. The bending strength of the low B, C residual SiC ceramic matrix was 443. + -.27 MPa.

The following is an exemplary description of the method of making a high purity working surface SiC ceramic device according to the present invention.

Preparing alpha-SiC powder, a sintering aid and a solvent. The average particle size of the alpha-SiC powder is 0.1-1 mu m. In some embodiments, the alpha-SiC powder has an average particle size of 0.6 μm and a purity of 99.86%. The sintering aid comprises a source B and a source C. The source of B may be selected from at least one of boric acid, boron oxide and boron carbide. The addition amount of the B source is 0.1-1 wt% of the quality of the alpha-SiC powder. The C source may be selected from at least one of D-fructose, glucose and phenolic resin. The addition amount of the C source is 0-5 wt% of the quality of the alpha-SiC powder. In some embodiments, the sintering aid is a mixture of boric acid and D-fructose in a mass ratio of 1 (4-6). By way of example, the mass ratio of the alpha-SiC powder, the boric acid and the D-fructose is 50: 1: 5. also, the solvent may be absolute ethanol.

And performing ball milling and mixing on the alpha-SiC powder, the sintering aid and the solvent to obtain SiC slurry. The solid content of the SiC slurry is 20-60 wt%, and preferably 30-50 wt%. The ball milling process may use a planetary ball mill with SiC grinding balls. The rotating speed in the ball milling process can be 100-400 r/min, and the ball milling time can be 4-48 hours. As an example, the ball milling process time is 24 hours and the rotational speed is 300 revolutions per minute.

And drying and molding the SiC slurry to prepare a SiC green body. The drying temperature is 60-100 ℃, and the drying time is 3-24 hours. As an example, the drying temperature is 60 ℃ and the drying time is 6 hours. The molding mode is dry pressing molding and/or cold isostatic pressing molding. The dry pressing pressure is 5-100 MPa. The cold isostatic pressing pressure is 150-200 MPa, and the pressure maintaining time is 1-3 minutes. As an example, the dry-press molding pressure is 20 MPa; the pressure of cold isostatic pressing is 200MPa, and the pressure maintaining time is 2 minutes.

And placing the SiC green compact in a debonding furnace for vacuum debonding, and then placing the debonding furnace in a normal pressure sintering furnace for sintering to obtain the low B, C residual SiC ceramic. The temperature of the vacuum de-bonding is 600-1200 ℃, the heat preservation time is 30-120 minutes, and the vacuum degree is less than 100 Pa. As an example, the temperature of vacuum debonding is 900 ℃, the holding time is 30 minutes, and the vacuum degree is less than 20 Pa. The sintering temperature is 2050-2250 ℃, the heat preservation time is 30-120 minutes, and the sintering atmosphere is inert atmosphere. As an example, the normal pressure sintering temperature is 2100 ℃, the holding time is 60 minutes, and the sintering atmosphere is inert atmosphere.

And processing the SiC ceramic to obtain a flat working surface. The sintered SiC ceramic has a rough surface, may have graphite deposited on the surface, and may have a small amount of deformation. The purpose of processing is to remove pollutants on the surface, so that the size of the ceramic meets the use requirement, and a relatively flat surface is obtained to facilitate film coating.

And placing the processed SiC ceramic in a CVD reaction chamber, and plating a high-purity CVD-SiC film on the surface of the SiC ceramic.

The CVD-SiC film is prepared by a chemical vapor deposition method. The CVD method is easy to prepare the high-purity SiC film with high density and isotropy. For example, trichloromethylsilane (MTS) is used as a silicon carbide gas source, hydrogen is used as a carrier gas, and argon is used as a diluent gas. MTS and H₂The MTS accounts for 5-20 mol% of the mixed gas. By way of example, the MTS and H₂The molar ratio of MTS in the mixed gas of (4) was 10 mol%. In some embodiments, H₂The flow rate is 200-800 mL/min, and the flow rate of Ar is 100-400 mL/min. The deposition temperature is 1000-1400 ℃, and the deposition pressure is 1-20 kPa. By way of example, the deposition temperature is 1200 deg.C and the deposition pressure is 5 kPa. The deposition time is adaptively adjusted according to the thickness of the CVD-SiC film, and the deposition time can be 5 to 24 hours.

The thickness of the CVD-SiC film is not less than 10 μm. If the thickness of the CVD-SiC film is too low, it becomes difficult to block the impurity elements of the substrate from entering the wafer.

In the SiC ceramic device, the thickness ratio of the residual SiC ceramic matrix of low B, C and the CVD-SiC film is adaptively changed according to different use scenes in practical application. According to the invention, a high-purity SiC film is plated on the surface of the low B, C residual SiC ceramic, so that impurity elements in a matrix are reduced from entering a wafer, and the pollution of excessive sintering aids to the wafer can be avoided.

In some embodiments, the low B, C residual SiC ceramics produced have a flexural strength of 443 + -27 MPa, an elastic modulus of 420 + -1 GPa, and a coefficient of thermal expansion of 3.84 × 10^-6K (RT-600 ℃). The composite member obtained after the surface of the SiC ceramic substrate having low B, C residual was coated substantially maintains the excellent physical properties of the ceramic substrate.

Tests show that the prepared film is tightly combined with a matrix and has no peeling. The density of the SiC ceramic matrix is obtained by testing through an Archimedes drainage method. The purity of the SiC ceramic matrix was obtained by GDMS testing. The purity of the CVD-SiC film was obtained by XRF testing.

The present invention will be described in detail by way of examples. It is also to be understood that the following examples are illustrative of the present invention and are not to be construed as limiting the scope of the invention, and that certain insubstantial modifications and adaptations of the invention by those skilled in the art may be made in light of the above teachings. The specific process parameters and the like of the following examples are also only one example of suitable ranges, i.e., those skilled in the art can select the appropriate ranges through the description herein, and are not limited to the specific values exemplified below.

Example 1

(1) Preparation of the blank

100g of alpha-SiC powder, 2g of boric acid, 10g D-fructose, 150g of absolute ethyl alcohol and 150g of SiC grinding balls are weighed and placed in a nylon ball milling tank together. The average particle size of the alpha-SiC powder was 0.6. mu.m. And placing the ball milling tank in a planetary ball mill for ball milling. The diameter of the SiC grinding ball is 5mm, the rotating speed of the ball mill is 300 r/min, and the ball milling time is 24 hours. And (3) placing the ceramic slurry subjected to ball milling in an electric heating air blast drying box for drying, and then grinding and sieving to obtain raw material powder. The temperature of the drying oven is 80 ℃, the drying time is 8 hours, and a sieve used for sieving is a 100-mesh sieve. The raw material powder is subjected to dry pressing forming and cold isostatic pressing forming to prepare a blank. The dry pressing forming pressure is 20MPa, the cold isostatic pressing forming pressure is 200MPa, and the pressure maintaining time is 2 minutes.

(2) Preparation of ceramics

And placing the blank in a debonding furnace for vacuum debonding, and then placing in a normal pressure sintering furnace for sintering to obtain the low B, C residual SiC ceramic. The vacuum de-bonding temperature is 900 ℃, the heat preservation time is 30 minutes, and the vacuum degree is less than 20 Pa. The sintering temperature is 2100 ℃, the heat preservation time is 60 minutes, and the sintering atmosphere is normal-pressure argon atmosphere.

The density of the prepared SiC ceramic is 98.63%, the content of free carbon is 0.13 wt%, the content of B element is 0.11 wt%, and the content of O element is 0.13 wt%.

(3) Preparation of films

And (3) placing the low B, C residual SiC ceramic into a CVD reaction chamber, and plating a high-purity CVD-SiC film on the surface of the SiC ceramic. The deposition temperature was 1200 ℃, MTS ratio was 10 mol%, deposition pressure was 5kPa, and deposition time was 5 hours. The thickness of the prepared SiC film is about 33 μm.

FIG. 1 is an SEM image of a low B, C residual SiC ceramic prepared in example 1 after etching, showing that: the prepared SiC ceramic has clean crystal boundary and no obvious second phase.

FIG. 2 is an SEM image of a cross section of the SiC film prepared in example 1, showing that: the prepared SiC film is well combined with a substrate, and the thickness of the film is about 33 mu m.

FIG. 3 is an XRD pattern of CVD-SiC prepared in example 1, showing: the main crystal phase of the prepared CVD-SiC film is 3C-SiC.

Table 1 shows XRF test results of the CVD-SiC film prepared in example 1, which shows that the purity of the prepared CVD-SiC film is higher than 99.9%.

Table 1 shows the XRF (X-ray fluorescence Spectroscopy) test results of CVD-SiC prepared in example 1

Example 2

(1) Preparation of the blank

100g of alpha-SiC powder, 2.5g of boric acid, 15g D-fructose, 150g of absolute ethyl alcohol and 150g of SiC grinding balls are weighed and placed in a nylon ball milling tank together. The average particle size of the alpha-SiC powder was 0.2. mu.m. And placing the ball milling tank in a planetary ball mill for ball milling. The diameter of the SiC grinding ball is 5mm, the rotating speed of the ball mill is 250 r/min, and the ball milling time is 36 hours. And (3) placing the ceramic slurry subjected to ball milling in an electric heating air blast drying box for drying, and then grinding and sieving to obtain raw material powder. The temperature of the drying oven is 60 ℃, the drying time is 12 hours, and a sieve used for sieving is a 100-mesh sieve. The raw material powder is subjected to dry pressing forming and cold isostatic pressing forming to prepare a blank. The dry pressing forming pressure is 50MPa, the cold isostatic pressing forming pressure is 200MPa, and the pressure maintaining time is 3 minutes.

(2) Preparation of ceramics

And placing the blank in a debonding furnace for vacuum debonding, and then placing in a normal pressure sintering furnace for sintering to obtain the low B, C residual SiC ceramic. The vacuum de-bonding temperature is 1100 ℃, the heat preservation time is 60 minutes, and the vacuum degree is less than 20 Pa. The sintering temperature is 2050 ℃, the heat preservation time is 120 minutes, and the sintering atmosphere is normal-pressure argon atmosphere.

The density of the prepared SiC ceramic is 98.22%, the content of free carbon is 0.14 wt%, the content of B element is 0.14 wt%, and the content of O element is 0.15 wt%.

(3) Preparation of films

And (3) placing the low B, C residual SiC ceramic into a CVD reaction chamber, and plating a high-purity CVD-SiC film on the surface of the SiC ceramic. The deposition temperature was 1100 deg.C, MTS ratio was 8 mol%, deposition pressure was 10kPa, and deposition time was 5 hours. The thickness of the prepared SiC film is about 28 μm.

FIG. 4 is an SEM image of a cross section of the SiC film prepared in example 2, showing that: the prepared SiC film is well combined with a substrate, and the thickness of the film is about 28 mu m.

FIG. 5 is an XRD pattern of CVD-SiC prepared in example 2, showing: the main crystal phases of the prepared CVD-SiC film are 3C-SiC and 6H-SiC.

Example 3

(1) Preparation of the blank

100g of alpha-SiC powder, 1g of boric acid, 8g D-fructose, 150g of absolute ethyl alcohol and 150g of SiC grinding balls are weighed and placed in a nylon ball milling tank. The average particle size of the alpha-SiC powder was 0.5. mu.m. And placing the ball milling tank in a planetary ball mill for ball milling. The diameter of the SiC grinding ball is 5mm, the rotating speed of the ball mill is 400 r/min, and the ball milling time is 12 hours. And (3) placing the ceramic slurry subjected to ball milling in an electric heating air blast drying box for drying, and then grinding and sieving to obtain raw material powder. The temperature of the drying oven is 100 ℃, the drying time is 6 hours, and a sieve used for sieving is a 100-mesh sieve. The raw material powder is subjected to dry pressing forming and cold isostatic pressing forming to prepare a blank. The dry pressing forming pressure is 80MPa, the cold isostatic pressing forming pressure is 200MPa, and the pressure maintaining time is 3 minutes.

(2) Preparation of ceramics

And placing the blank in a debonding furnace for vacuum debonding, and then placing in a normal pressure sintering furnace for sintering to obtain the low B, C residual SiC ceramic. The vacuum de-bonding temperature is 700 ℃, the heat preservation time is 30 minutes, and the vacuum degree is less than 20 Pa. The sintering temperature is 2200 ℃, the heat preservation time is 30 minutes, and the sintering atmosphere is normal-pressure argon atmosphere.

The density of the prepared SiC ceramic is 98.13%, the content of free carbon is 0.13 wt%, the content of B element is 0.13 wt%, and the content of O element is 0.14 wt%.

(3) Preparation of films

And (3) placing the low B, C residual SiC ceramic into a CVD reaction chamber, and plating a high-purity CVD-SiC film on the surface of the SiC ceramic. The deposition temperature was 1300 ℃, MTS ratio was 15 mol%, deposition pressure was 15kPa, and deposition time was 24 hours. The thickness of the prepared SiC film is about 800 μm.