Method for preparing silicon carbide coating and substrate with silicon carbide coating

Abstract

The present invention relates to a method for preparing a silicon carbide coating and a substrate with the silicon carbide coating, the method for preparing the silicon carbide coating comprising the following steps: S1, depositing a first layer of silicon carbide coating on the surface of the substrate by chemical vapor deposition reaction; S2, detecting the thickness of the first layer of silicon carbide coating; S3, changing the placement of the substrate, adjusting the reaction time of the chemical vapor deposition reaction according to the detection result, and continuing to deposit the silicon carbide coating by chemical vapor deposition reaction; S4, detecting the total thickness of the silicon carbide coating on the surface of the substrate, if the total thickness reaches a preset thickness, then end, if the total thickness is less than the preset thickness, then looping steps S3-S4 until the total thickness of the silicon carbide coating reaches a preset thickness. The method for preparing the silicon carbide coating can not only enable the silicon carbide coating to accurately reach the preset thickness, but also enable the silicon carbide coating to completely wrap the substrate to avoid the risk of contamination.

Description

Technical Field

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

[0002] As a high-performance coating material, silicon carbide coating is widely used in many fields such as high-temperature components of single crystal furnaces, rocket engine nozzles, semiconductor equipment, etc. When preparing silicon carbide coatings through chemical vapor deposition (CVD) reactions, in order to make the silicon carbide coating reach the preset thickness, the traditional practice is to estimate the deposition rate of the silicon carbide coating before the chemical vapor deposition reaction, and prepare the silicon carbide coating by controlling the deposition time; however, since the chemical vapor deposition reaction is easily affected by factors such as flow field and thermal field, and the appearance of various products varies greatly, the deposition rate of the silicon carbide coating is difficult to accurately estimate, which ultimately leads to the thickness of the silicon carbide coating being often quite different from the preset thickness. In addition, the traditional practice will inevitably leave uncoated areas on the supporting parts of the substrate, and the exposed substrate may cause contamination, which limits the application scenarios. Summary of the invention

[0003] Based on this, it is necessary to provide a method for preparing a silicon carbide coating and a substrate with a silicon carbide coating to address the above problems. The method for preparing a silicon carbide coating can not only enable the silicon carbide coating to accurately reach a preset thickness, but also enable the silicon carbide coating to completely wrap the substrate to avoid the risk of contamination.

[0004] The present invention discloses a method for preparing a silicon carbide coating, comprising the following steps:

[0005] S1, depositing a first layer of silicon carbide coating on the surface of the substrate by chemical vapor deposition reaction;

[0006] S2, detecting the thickness of the first layer of silicon carbide coating;

[0007] S3, changing the placement posture of the substrate, adjusting the reaction time of the chemical vapor deposition reaction according to the detection result, and continuing to deposit the silicon carbide coating through the chemical vapor deposition reaction;

[0008] S4, detecting the total thickness of the silicon carbide coating on the surface of the substrate, and if the total thickness reaches a preset thickness, the process ends; if the total thickness is less than the preset thickness, the process repeats steps S3 to S4 until the total thickness of the silicon carbide coating reaches the preset thickness;

[0009] Wherein, the duration of the chemical vapor deposition reaction satisfies the following conditions:

[0010] ,

[0011] Tn represents the duration of the nth chemical vapor deposition reaction, represents the total duration from the 1st chemical vapor deposition reaction to the n-1th chemical vapor deposition reaction, H represents the preset thickness, H' represents the total thickness of the silicon carbide coating after n-1 chemical vapor deposition reactions, and n≥2.

[0012] In one embodiment, the thickness of the first silicon carbide coating layer is 10%-50% of the preset thickness.

[0013] In one embodiment, the step of the chemical vapor deposition reaction includes: introducing a dilution gas, a silicon source and a reducing gas to carry out a chemical vapor deposition reaction, wherein, between any two chemical vapor deposition reactions, the flow rate of the dilution gas differs within 40 slm, the flow rate of the silicon source differs within 60 g / min, the flow rate of the reducing gas differs within 20 slm, the reaction temperature differs within 200°C, and the reaction pressure differs within 10 kPa.

[0014] In one embodiment, the flow rate of the dilution gas is 20slm-80slm, the flow rate of the silicon source is 50g / min-150g / min, the flow rate of the reducing gas is 20slm-80slm, the reaction temperature is 1150°C-1400°C, and the reaction pressure is 1kPa-20kPa.

[0015] In one embodiment, in step S1, the chemical vapor deposition reaction time is 10 min-120 min.

[0016] In one embodiment, the number of cycles is 1, 2, 3, 4 or 5 times.

[0017] In one embodiment, between any two chemical vapor deposition reactions, HCl gas is introduced and high-temperature treatment is performed.

[0018] In one embodiment, in the step of introducing HCl gas and performing high temperature treatment, the reaction temperature is 800° C.-1400° C., the reaction pressure is 1 kPa-10 kPa, the reaction time is 1 min-60 min, and the flow rate of the HCl gas is 1 slm-20 slm.

[0019] In one embodiment, the step of changing the placement posture of the base includes rotating the base by 5°-180°.

[0020] A substrate with a silicon carbide coating comprises a stacked substrate and a silicon carbide coating, wherein the silicon carbide coating is prepared by the above-mentioned method for preparing the silicon carbide coating, and the silicon carbide coating completely covers the substrate.

[0021] The method for preparing a silicon carbide coating provided by the present invention firstly measures the thickness of the silicon carbide coating on the surface of a substrate after each chemical vapor deposition reaction, thereby accurately estimating the deposition rate of the silicon carbide coating; secondly, adjusts the reaction time of a subsequent chemical vapor deposition reaction according to the detection result, thereby preventing the thickness of the silicon carbide coating from exceeding a preset thickness; and finally improves the accuracy of the thickness of the silicon carbide coating by means of multiple cycles of deposition, thereby meeting the stringent requirements for the thickness of the silicon carbide coating in special fields, and is well suited for the manufacture of core components in high-precision and advanced equipment.

[0022] In addition, the method for preparing the silicon carbide coating provided by the present invention changes the placement of the substrate after each chemical vapor deposition reaction, thereby depositing the silicon carbide coating on the supporting part of the substrate, thereby achieving full coverage of the silicon carbide coating and avoiding impurity contamination from the substrate.

[0023] Therefore, the substrate with silicon carbide coating provided by the present invention can not only achieve a preset thickness accurately, but also completely wrap the substrate to avoid contamination risks. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A schematic diagram of a process for preparing a silicon carbide coating provided by the present invention;

[0026] Figure 2 This is a scanning electron microscope image of the cross section of the silicon carbide coating prepared in Example 1;

[0027] Figure 3 This is a thickness curve of the silicon carbide coating prepared in Example 1 obtained by sampling at different positions;

[0028] Figure 4 This is a scanning electron microscope image of the cross section of the silicon carbide coating prepared in Example 7. DETAILED DESCRIPTION

[0029] For ease of understanding of the present invention, the present invention will be described in more detail below. However, it should be understood that the present invention can be implemented in many different forms and is not limited to the embodiments or examples described herein. On the contrary, the purpose of providing these embodiments or examples is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0030] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the technical field of the terminology of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific implementation methods or embodiments and are not intended to limit the present invention.

[0031] like Figure 1 As shown, the present invention provides a method for preparing a silicon carbide coating, comprising the following steps:

[0032] S1, depositing a first layer of silicon carbide coating on the surface of the substrate by chemical vapor deposition reaction;

[0033] S2, detect the thickness of the first layer of silicon carbide coating;

[0034] S3, changing the placement of the substrate, adjusting the reaction time of the chemical vapor deposition reaction according to the detection result, and continuing to deposit the silicon carbide coating through the chemical vapor deposition reaction;

[0035] S4, detecting the total thickness of the silicon carbide coating on the substrate surface, if the total thickness reaches the preset thickness, then the process ends, if the total thickness is less than the preset thickness, then looping steps S3-S4 until the total thickness of the silicon carbide coating reaches the preset thickness.

[0036] The method for preparing a silicon carbide coating provided by the present invention firstly measures the thickness of the silicon carbide coating on the surface of a substrate after each chemical vapor deposition reaction, thereby being able to accurately estimate the deposition rate of the silicon carbide coating; secondly, adjusts the reaction time of a subsequent chemical vapor deposition reaction according to the detection result, thereby preventing the thickness of the silicon carbide coating from exceeding a preset thickness; and finally improves the thickness accuracy of the silicon carbide coating by means of multiple cycles of deposition, thereby meeting the stringent requirements for thickness control of the silicon carbide coating in special fields, and being well suited for the manufacture of core components in high-precision and advanced equipment.

[0037] In step S1, the present invention does not limit the material of the substrate. In one embodiment, the material of the substrate is selected from at least one of graphite, carbon-carbon material or ceramic.

[0038] In order to improve the bonding strength between the substrate and the silicon carbide coating, the substrate is pretreated before depositing the first layer of silicon carbide coating on the surface of the substrate by chemical vapor deposition reaction. Preferably, the pretreatment step includes: immersing the substrate in water for ultrasonic cleaning and then drying.

[0039] In order to better improve the accuracy of the silicon carbide coating thickness, preferably, the thickness of the first layer of silicon carbide coating is 10%-50% of the preset thickness, including but not limited to 10%, 20%, 30, 40% or 50%.

[0040] In one embodiment, the predetermined thickness of the silicon carbide coating is 80 μm-120 μm, including but not limited to 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 105 μm, 110 μm, 115 μm or 120 μm.

[0041] In one embodiment, the step of chemical vapor deposition reaction includes: introducing a diluent gas, a silicon source and a reducing gas to carry out a chemical vapor deposition reaction; including but not limited to, the diluent gas includes at least one of argon or nitrogen, the silicon source includes at least one of chlorosilane or silicon tetrachloride, and the reducing gas includes at least one of hydrogen or chlorine.

[0042] In order to better control the thickness of the first layer of silicon carbide coating to be 10%-50% of the preset thickness, in one embodiment, the flow rate of the dilution gas is 20slm-80slm, including but not limited to 20slm, 30slm, 40slm, 50slm, 60slm, 70slm or 80slm, the flow rate of the silicon source is 50g / min-150g / min, including but not limited to 50g / min, 60g / min, 70g / min, 80g / min, 90g / min, 100g / min, 110g / min, 120g / min, 130g / min, 140g / min or 150g / min, and the flow rate of the reducing gas is 20slm-80slm, including but not limited to At 20slm, 30slm, 40slm, 50slm, 60slm, 70slm or 80slm, the reaction temperature is 1150°C-1400°C, including but not limited to 1150°C, 1200°C, 1250°C, 1300°C, 1350°C or 1400°C, the reaction pressure is 1kPa-20kPa, including but not limited to 1kPa, 5kPa, 10kPa, 15kPa or 20kPa, and the chemical vapor deposition reaction time is 10min-120min, including but not limited to 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, 90min, 100min, 110min or 120min.

[0043] In step S2, a dimension detection device is used to detect the thickness of the first silicon carbide coating layer. In one embodiment, the dimension detection device is selected from a three-coordinate measuring machine.

[0044] In step S3, the duration of the chemical vapor deposition reaction satisfies the following conditions:

[0045] ,

[0046] T n represents the duration of the nth chemical vapor deposition reaction, represents the 1st to n-1th chemical vapor deposition reactions, H represents the preset thickness, H' represents the total thickness of the silicon carbide coating after n-1 chemical vapor deposition reactions, and n≥2.

[0047] In order to better control the thickness of the silicon carbide coating by the duration of the chemical vapor deposition reaction, in one embodiment, the step of the chemical vapor deposition reaction includes: introducing a dilution gas, a silicon source and a reducing gas to carry out a chemical vapor deposition reaction, wherein, between any two chemical vapor deposition reactions, the flow rate of the dilution gas differs within 40 slm, the flow rate of the silicon source differs within 60 g / min, the flow rate of the reducing gas differs within 20 slm, the reaction temperature differs within 200°C, and the reaction pressure differs within 10 kPa.

[0048] Including but not limited to: between any two chemical vapor deposition reactions, the flow rate of the dilution gas differs by 0slm, 1slm, 2slm, 3slm, 4slm, 5slm, 6slm, 7slm, 8slm, 9slm, 10slm, 15slm, 20slm, 25slm, 30slm, 35slm or 40slm. It can be understood that when the flow rate of the dilution gas differs by 0slm, the flow rate of the dilution gas is equal between any two chemical vapor deposition reactions;

[0049] Between any two chemical vapor deposition reactions, the flow rate of the silicon source differs by 0 g / min, 1 g / min, 2 g / min, 3 g / min, 4 g / min, 5 g / min, 6 g / min, 7 g / min, 8 g / min, 9 g / min, 10 g / min, 15 g / min, 20 g / min, 25 g / min, 30 g / min, 35 g / min, 40 g / min, 45 g / min, 50 g / min, 55 g / min or 60 g / min. It can be understood that when the flow rate of the silicon source differs by 0 g / min, the flow rate of the silicon source is equal between any two chemical vapor deposition reactions.

[0050] Between any two chemical vapor deposition reactions, the flow rate of the reducing gas differs by 0 slm, 1 slm, 2 slm, 3 slm, 4 slm, 5 slm, 6 slm, 7 slm, 8 slm, 9 slm, 10 slm, 15 slm or 20 slm. It can be understood that when the flow rate of the reducing gas differs by 0 g / min, the flow rate of the reducing gas is equal between any two chemical vapor deposition reactions.

[0051] The reaction temperature difference between any two chemical vapor deposition reactions is 0°C, 1°C, 2°C, 3°C, 4°C, 5°C, 6°C, 7°C, 8°C, 9°C, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C or 200°C. It can be understood that when the reaction temperature difference is 0°C, the reaction temperature between any two chemical vapor deposition reactions is equal;

[0052] The reaction pressure difference between any two chemical vapor deposition reactions is 0Pa, 1Pa, 2Pa, 3Pa, 4Pa, 5Pa, 6Pa, 7Pa, 8Pa, 9Pa or 10Pa. It can be understood that when the reaction pressure difference is 0Pa, the reaction pressure between any two chemical vapor deposition reactions is equal.

[0053] In one embodiment, the flow rate of the dilution gas is 20 slm-80 slm, including but not limited to 20 slm, 30 slm, 40 slm, 50 slm, 60 slm, 70 slm or 80 slm, and the flow rate of the silicon source is 50 g / min-150 g / min, including but not limited to 50 g / min, 60 g / min, 70 g / min, 80 g / min, 90 g / min, 100 g / min, 110 g / min, 120 g / min, 130 g / min, 140 g / min n or 150g / min, the flow rate of reducing gas is 20slm-80slm, including but not limited to 20slm, 30slm, 40slm, 50slm, 60slm, 70slm or 80slm, the reaction temperature is 1150℃-1400℃, including but not limited to 1150℃, 1200℃, 1250℃, 1300℃, 1350℃ or 1400℃, and the reaction pressure is 1kPa-20kPa, including but not limited to 1kPa, 5kPa, 10kPa, 15kPa or 20kPa.

[0054] In one embodiment, HCl gas is introduced and high-temperature treatment is performed between any two chemical vapor deposition reactions, thereby removing impurity elements in the deposited silicon carbide coating, enhancing the bonding strength between the silicon carbide coatings, and improving product purity.

[0055] In one embodiment, in the step of introducing HCl gas and performing high temperature treatment, the reaction temperature is 800° C.-1400° C., the reaction pressure is 1 kPa-10 kPa, the reaction time is 1 min-60 min, and the flow rate of HCl gas is 1 slm-20 slm.

[0056] In one embodiment, the number of cycles is 1, 2, 3, 4 or 5. It can be understood that when the number of cycles is 1, the method for preparing the silicon carbide coating provided by the present invention undergoes a total of 2 chemical vapor deposition reactions, n=2; when the number of cycles is 2, the method for preparing the silicon carbide coating provided by the present invention undergoes a total of 3 chemical vapor deposition reactions, n=2 or 3; when the number of cycles is 3, the method for preparing the silicon carbide coating provided by the present invention undergoes a total of 4 chemical vapor deposition reactions, n=2, 3 or 4; when the number of cycles is 4, the method for preparing the silicon carbide coating provided by the present invention undergoes a total of 5 chemical vapor deposition reactions, n=2, 3, 4 or 5; when the number of cycles is 5, the method for preparing the silicon carbide coating provided by the present invention undergoes a total of 6 chemical vapor deposition reactions, n=2, 3, 4, 5 or 6.

[0057] After each chemical vapor deposition reaction, the substrate is changed in position, so that the silicon carbide coating is deposited on the supporting part of the substrate, thereby achieving full coverage of the silicon carbide coating and avoiding contamination by impurities from the substrate. In one embodiment, the step of changing the substrate's position includes rotating the substrate by 5°-180°, including but not limited to 5°, 15°, 25°, 35°, 45°, 55°, 65°, 75°, 85°, 95°, 105°, 115°, 125°, 135°, 145°, 155°, 165°, 175° or 180°.

[0058] The present invention also provides a substrate with a silicon carbide coating, comprising a stacked substrate and a silicon carbide coating, wherein the silicon carbide coating is prepared by the above-mentioned method for preparing the silicon carbide coating, and the silicon carbide coating completely covers the substrate.

[0059] Hereinafter, the preparation method of the silicon carbide coating and the substrate with the silicon carbide coating will be further described through the following specific examples.

[0060] Example 1

[0061] Example 1 provides a method for preparing a graphite substrate with a silicon carbide coating, wherein the preset thickness H of the silicon carbide coating is 100 μm.

[0062] S1, immersing the graphite substrate in pure water for ultrasonic cleaning for 60 min, then taking it out and baking it in an oven at 150°C for 60 min.

[0063] The pretreated graphite substrate was placed in a vacuum furnace, which was evacuated and heated, and 5slm of argon was introduced to replace the residual gas in the furnace. When the temperature in the furnace was heated to 1200°C, 20slm of argon was introduced into the furnace to make the pressure in the furnace reach 20kPa. After the pressure in the furnace was stabilized, 60slm of hydrogen and 50g / min of liquid chlorosilane were introduced into the furnace for 60 minutes to carry out the first chemical vapor deposition reaction to prepare the first layer of silicon carbide coating.

[0064] S2, after the first chemical vapor deposition reaction is completed, the heating is turned off, and the graphite substrate is taken out after the vacuum furnace is cooled to room temperature. The size of the graphite substrate with silicon carbide coating is detected using a three-coordinate measuring instrument. The test results show that the thickness H' of the first layer of silicon carbide coating is 40μm.

[0065] S3, the graphite substrate is rotated 45 degrees and installed again. After the installation is completed, the vacuum furnace is evacuated and heated. When the temperature is heated to 900°C, 10 slm of argon gas is introduced into the furnace to make the pressure in the furnace reach 2 kPa. After the pressure in the furnace is stable, the argon gas is turned off, and 10 slm of HCl is introduced into the furnace for high-temperature treatment. The treatment time is 30 minutes. After the treatment is completed, the HCl gas is turned off.

[0066] H is 100μm, H' is 40μm, so T2 should meet the following conditions T2:60≤60:40, T2 should be less than or equal to 90min. Raise the temperature of the vacuum furnace to 1100℃, introduce 20slm argon gas into the furnace to make the pressure in the furnace reach 20kPa, and after the insulation is completed, introduce 60slm hydrogen and 50g / min liquid chlorosilane into the furnace to perform chemical vapor deposition reaction again to form the second layer of silicon carbide coating, and the reaction time T2 is 90min.

[0067] S4, after the vacuum furnace is cooled to room temperature, the graphite substrate with the silicon carbide coating is taken out.

[0068] The scanning electron microscope image of the cross section of the silicon carbide coating prepared in Example 1 is as follows: Figure 2 As shown, from Figure 2 It can be found that no obvious stratification is observed between the first layer of silicon carbide coating and the second layer of silicon carbide coating. The thickness curve of the silicon carbide coating prepared in Example 1 measured by sampling at different positions is as follows: Figure 3 As shown, from Figure 3 It can be seen that the thickness of the silicon carbide coating is 100±0.5μm, the thickness error is 0.5μm, the error is extremely small and the distribution is uniform.

[0069] Comparative Example 1

[0070] Comparative Example 1 provides a method for preparing a graphite substrate with a silicon carbide coating, wherein the preset thickness H of the silicon carbide coating is 100 μm; according to Example 1, the deposition rate of the silicon carbide coating is estimated to be 40 μm / h, so the theoretical duration of the chemical vapor deposition reaction is 150 min.

[0071] The graphite substrate was immersed in pure water for ultrasonic cleaning for 60 min, and then taken out and baked in an oven at 150°C for 60 min.

[0072] The pretreated graphite substrate was placed in a vacuum furnace, and the vacuum furnace was evacuated and heated, and 5slm of argon was introduced to replace the residual gas in the furnace. When the temperature in the furnace was heated to 1100°C, 20slm of argon was introduced into the furnace to make the pressure in the furnace reach 20kPa. After the pressure in the furnace was stabilized, 60slm of hydrogen and 50g / min of liquid chlorosilane were introduced into the furnace for 150min for chemical vapor deposition reaction to prepare the silicon carbide coating. The heating was turned off, and the graphite substrate was taken out after the vacuum furnace was cooled to room temperature.

[0073] Test Example 1

[0074] The thickness of the silicon carbide coatings at different positions prepared in Example 1 and Comparative Example 1 was measured using a three-coordinate measuring instrument. The test results are shown in Table 1. The unit of the thickness at each position in Table 1 is μm.

[0075] Table 1

[0076]

[0077] In Table 1, position 4 of comparative example 1 is the supporting position of the graphite substrate. Since the placement posture of the graphite substrate is not changed during the preparation process, silicon carbide is not deposited on the supporting position, and the thickness of the silicon carbide coating at position 4 is 0.

[0078] Example 2

[0079] Example 2 is carried out with reference to Example 1, except that, in step S1, the duration of the first chemical vapor reaction is 75 minutes, and the thickness of the first layer of silicon carbide coating is 50 μm.

[0080] In step S3, in the second chemical vapor reaction step, the temperature of the vacuum furnace is 1200° C., the duration is 75 minutes, and the thickness of the second layer of silicon carbide coating is 50 μm.

[0081] Example 3

[0082] Example 3 is carried out with reference to Example 1, except that, in step S1, the duration of the first chemical vapor reaction is 30 minutes, and the thickness of the first layer of silicon carbide coating is 20 μm.

[0083] In step S3, in the second chemical vapor reaction step, the temperature of the vacuum furnace is 1200° C., the duration is 120 min, and the thickness of the second layer of silicon carbide coating is 80 μm.

[0084] Test Example 2

[0085] Referring to Test Example 1, a three-coordinate measuring instrument was used to perform dimensional inspection on the silicon carbide coatings prepared in Examples 2-3. The test results are shown in Table 2. The thickness units at each position in Table 2 are μm.

[0086] Table 2

[0087]

[0088] Example 4

[0089] Example 4 is carried out with reference to Example 1, except that in step S1, the duration of the first chemical vapor reaction is 30 minutes, and the thickness of the first silicon carbide coating is 20 μm. In step S3, the temperature of the second chemical vapor reaction vacuum furnace is 1200° C., the duration is 60 minutes, and the thickness of the second silicon carbide coating is 40 μm.

[0090] The third chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 60 minutes, and the thickness of the third silicon carbide coating being 40 μm.

[0091] Example 5

[0092] Example 5 is carried out with reference to Example 1, except that in step S1, the duration of the first chemical vapor reaction is 30 minutes, and the thickness of the first silicon carbide coating is 20 μm. In step S3, the temperature of the second chemical vapor reaction vacuum furnace is 1200° C., the duration is 30 minutes, and the thickness of the second silicon carbide coating is 20 μm.

[0093] The third chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 30 minutes, and the thickness of the third silicon carbide coating being 20 μm.

[0094] The fourth chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 60 minutes, and the thickness of the fourth silicon carbide coating being 40 μm.

[0095] Example 6

[0096] Example 6 is carried out with reference to Example 1, except that in step S1, the duration of the first chemical vapor reaction is 15 minutes, and the thickness of the first silicon carbide coating is 10 μm. In step S3, the duration of the second chemical vapor reaction is 30 minutes, and the thickness of the second silicon carbide coating is 20 μm.

[0097] The third chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 30 minutes, and the thickness of the third silicon carbide coating being 20 μm.

[0098] The fourth chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 60 minutes, and the thickness of the fourth silicon carbide coating being 40 μm.

[0099] The fifth chemical vapor reaction was carried out with the temperature of the vacuum furnace being 1200°C for 15 minutes, and the thickness of the fifth silicon carbide coating being 10 μm.

[0100] Example 7

[0101] Example 7 provides a method for preparing a graphite substrate with a silicon carbide coating, wherein the preset thickness H of the silicon carbide coating is 100 μm.

[0102] S1, immersing the graphite substrate in pure water for ultrasonic cleaning for 60 min, then taking it out and baking it in an oven at 150°C for 60 min.

[0103] The pretreated graphite substrate was placed in a vacuum furnace, which was evacuated and heated, and 5slm of argon was introduced to replace the residual gas in the furnace. When the temperature in the furnace was heated to 1200°C, 20slm of argon was introduced into the furnace to make the pressure in the furnace reach 20kPa. After the pressure in the furnace was stabilized, 60slm of hydrogen and 50g / min of liquid chlorosilane were introduced into the furnace for 60 minutes to carry out the first chemical vapor deposition reaction to prepare the first layer of silicon carbide coating.

[0104] S2, after the first chemical vapor deposition reaction is completed, the heating is turned off, and the graphite substrate is taken out after the vacuum furnace is cooled to room temperature. The size of the graphite substrate with silicon carbide coating is detected using a three-coordinate measuring instrument. The test results show that the thickness H' of the first layer of silicon carbide coating is 40μm.

[0105] S3, H is 100 μm, H' is 40 μm, so T2 should satisfy the following condition T2:60≤60:40, T2 should be less than or equal to 90 min.

[0106] The graphite substrate was rotated 45° and installed again. After the installation was completed, the vacuum furnace was evacuated and heated until the temperature inside the furnace reached 1100°C. 20slm of argon was introduced into the furnace to make the pressure inside the furnace reach 20kPa. After the insulation was completed, 60slm of hydrogen and 50g / min of liquid chlorosilane were introduced into the furnace for chemical vapor deposition reaction again. After 90 minutes, the second layer of silicon carbide coating was formed.

[0107] S4, after the vacuum furnace is cooled to room temperature, the graphite substrate with the silicon carbide coating is taken out.

[0108] The scanning electron microscope image of the cross section of the silicon carbide coating prepared in Example 7 is as follows: Figure 4 As shown, from Figure 4 It can be found that there is obvious stratification between the first silicon carbide coating and the second silicon carbide coating.

[0109] Test Example 4

[0110] Referring to Test Example 1, the dimensions of the silicon carbide coatings prepared in Examples 4-7 were measured using a three-coordinate measuring instrument. The test results are shown in Table 3. The unit of thickness at each position in Table 3 is μm.

[0111] Table 3

[0112]

[0113] 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.

[0114] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preparing a silicon carbide coating, characterized in that: The following steps are involved: S1, depositing a first layer of silicon carbide coating on the surface of the substrate by chemical vapor deposition reaction, wherein the thickness of the first layer of silicon carbide coating is 10%-50% of a preset thickness; S2, detecting the thickness of the first layer of silicon carbide coating; S3, changing the placement of the substrate, introducing HCl gas and performing high temperature treatment, adjusting the reaction time of the chemical vapor deposition reaction according to the detection result, and continuing to deposit the silicon carbide coating through the chemical vapor deposition reaction, wherein the step of changing the placement of the substrate includes rotating the substrate by 5°-180°; S4, detecting the total thickness of the silicon carbide coating on the surface of the substrate, and if the total thickness reaches a preset thickness, the process ends; if the total thickness is less than the preset thickness, the process repeats steps S3 to S4 until the total thickness of the silicon carbide coating reaches the preset thickness; Wherein, the duration of the chemical vapor deposition reaction satisfies the following conditions: ， T n represents the duration of the nth chemical vapor deposition reaction, represents the total duration from the 1st chemical vapor deposition reaction to the n-1th chemical vapor deposition reaction, H represents the preset thickness, H' represents the total thickness of the silicon carbide coating after n-1 chemical vapor deposition reactions, and n≥2.

2. The method for preparing a silicon carbide coating according to claim 1, characterized in that: The steps of the chemical vapor deposition reaction include: introducing a dilution gas, a silicon source and a reducing gas to carry out a chemical vapor deposition reaction, wherein, between any two chemical vapor deposition reactions, the flow rate of the dilution gas differs within 40 slm, the flow rate of the silicon source differs within 60 g / min, the flow rate of the reducing gas differs within 20 slm, the reaction temperature differs within 200°C, and the reaction pressure differs within 10 kPa.

3. The method for preparing the silicon carbide coating according to claim 2, characterized in that: The flow rate of the dilution gas is 20slm-80slm, the flow rate of the silicon source is 50g / min-150g / min, the flow rate of the reducing gas is 20slm-80slm, the reaction temperature is 1150°C-1400°C, and the reaction pressure is 1kPa-20kPa.

4. The method for preparing a silicon carbide coating according to claim 2 or claim 3, characterized in that: In step S1, the chemical vapor deposition reaction time is 10 min-120 min.

5. The method for preparing a silicon carbide coating according to any one of claims 1 to 3, characterized in that: The number of cycles is 1, 2, 3, 4 or 5.

6. The method for preparing a silicon carbide coating according to claim 5, characterized in that: In the step of introducing HCl gas and performing high temperature treatment, the reaction temperature is 800° C.-1400° C., the reaction pressure is 1 kPa-10 kPa, the reaction time is 1 min-60 min, and the flow rate of the HCl gas is 1 slm-20 slm.

7. A substrate with a silicon carbide coating, characterized in that: It comprises a stacked substrate and a silicon carbide coating, wherein the silicon carbide coating is prepared by the method for preparing the silicon carbide coating according to any one of claims 1 to 6, and the silicon carbide coating completely covers the substrate.

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