Deposition silicon carbide coating and preparation method and application thereof

Abstract

The invention relates to the technical field of inorganic functional coatings, in particular to a deposited silicon carbide coating and a preparation method and application thereof.The preparation method comprises the following steps that firstly, trichloromethylsilane-hydrogen-argon serves as a precursor atmosphere system, and a first silicon carbide coating is deposited on the surface of a base material through a chemical vapor deposition method; in the deposition process, the introduction rate of trichloromethylsilane is adjusted, the trichloromethylsilane is progressively decreased, then is at a constant speed and then is progressively increased, the silicon carbide coating of a gradient structure can be obtained by utilizing atmosphere switching of high and low MTS, and a micropore or nano structure can be formed in the coating; introducing an atmosphere with the oxygen volume concentration of 5-30%, carrying out aerobic treatment at the temperature of 1100-1200 DEG C, and washing with hydrofluoric acid to obtain a first silicon carbide base material; and then the second silicon carbide coating continues to be deposited on the surface of the first silicon carbide base material, a transition layer does not need to be prepared, the bonding force between the silicon carbide coatings is high, and the problems that at present, the bonding strength between the silicon carbide coatings is low, and the silicon carbide coatings are prone to falling off and cracking are solved.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic functional coatings, and in particular to a deposited silicon carbide coating and a preparation method and application thereof. Background Art

[0002] With the rapid development of optoelectronic technology and the semiconductor industry, CVD chemical vapor deposition technology has gradually become one of the main methods for preparing high-quality semiconductor films and coatings. In the preparation of silicon carbide coatings, CVD technology has attracted much attention because it can prepare coatings with high density, high purity and fine grains. In recent years, with the continuous improvement of material performance requirements, CVD silicon carbide coating technology has also been continuously developed and improved. At present, the silicon carbide coating obtained by CVD deposition has many excellent properties: 1) High melting point and high hardness: Silicon carbide has extremely high melting point and hardness, which makes the CVD silicon carbide coating have excellent wear resistance and high temperature resistance; 2) Good thermal conductivity: Silicon carbide has good thermal conductivity, which helps to maintain temperature stability and uniformity during the use of the coating; 3) Excellent corrosion resistance and oxidation resistance: Silicon carbide coatings can resist the erosion of various corrosive gases and high-temperature oxidizing environments, thereby extending the service life of the coating. Therefore, the current CVD silicon carbide coating has broad application prospects in aerospace, weapons and equipment, tool industry, mold industry and automotive industry.

[0003] However, the current CVD silicon carbide coating still has the following problems after multiple depositions: 1) When CVD coating is performed on the silicon carbide surface, since both the substrate and the deposited layer are silicon carbide, the chemical bonding at the interface is relatively weak; 2) The deposited multi-layer silicon carbide coating has high density. High density means that the atoms on its surface are tightly arranged, which may lead to a decrease in the diffusion rate of the deposited material on the silicon carbide surface, because the deposited material needs to diffuse and react on the surface of the substrate to form a continuous deposited layer. If the diffusion rate is reduced, it may affect the uniformity and growth rate of the deposited layer; in addition, the high density of silicon carbide may also affect the interface reaction between the deposited material and the substrate, because the deposited material needs to chemically react with the active sites on the surface of the substrate to form chemical bonds. If the substrate surface is too dense, the number of active sites may be reduced, thereby reducing the interface reaction rate and the bonding strength between the deposited layer and the substrate.

[0004] In view of this, it is indeed necessary to provide a technical solution to the above problems. Summary of the invention

[0005] One of the purposes of the present invention is to provide a method for preparing a deposited silicon carbide coating in view of the deficiencies in the prior art, so as to solve the problem of low bonding strength between layers due to the high density of silicon carbide deposition during the current CVD deposition of multi-layer silicon carbide coatings.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for preparing a deposited silicon carbide coating comprises the following steps:

[0008] S1. Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the substrate by chemical vapor deposition, wherein the rate of introduction of trichloromethylsilane is first decreasing, then uniform, and then increasing, the molar ratio of hydrogen to argon is (3-6):1, the reaction temperature is 1100-1350°C, the reaction time is 3-7h, and the pressure is 150-250Torr;

[0009] S2, introducing an atmosphere with an oxygen volume concentration of 5% to 30%, aerobically treating the first silicon carbide coating obtained in step S1 at 1100 to 1200° C., washing with hydrofluoric acid after oxidation treatment, to obtain a first silicon carbide substrate;

[0010] S3, continuing to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of step S1 to obtain a multi-layer silicon carbide coating.

[0011] Preferably, in step S1, the reaction temperature is 1200-1350° C.; the process of introducing trichloromethylsilane is as follows: when the introduction starts, the molar ratio of hydrogen to trichloromethylsilane is (2-5):1; when decreasing to a uniform rate, the molar ratio of hydrogen to trichloromethylsilane is (10-20):1; when increasing to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (2-5):1.

[0012] Preferably, when the introduction starts, the molar ratio of hydrogen to trichloromethylsilane is (3-5):1; when the speed decreases to a uniform rate, the molar ratio of hydrogen to trichloromethylsilane is (10-15):1; when the speed increases to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (3-5):1.

[0013] Preferably, in step S1, the time taken for the introduction rate of trichloromethylsilane to decrease from a constant rate is 0.4 to 0.6 h; and the introduction rate of trichloromethylsilane begins to increase to a maximum rate within 0.4 to 0.6 h before the end of deposition.

[0014] Preferably, in step S2, the aerobic treatment reaction conditions are: introducing an atmosphere with an oxygen volume concentration of 10% to 30%, heating to 1100 to 1200° C. at a rate of 5 to 10° C. / min, and maintaining the temperature for 3 to 4 hours.

[0015] Preferably, in step S2, the mass concentration of hydrofluoric acid used is 5% to 10%.

[0016] Preferably, in step S1, the substrate is selected to have a thermal expansion coefficient of 5×10 -6 / ℃~7×10 -6 / ℃ graphite substrate.

[0017] Preferably, the graphite substrate is pretreated and dried before the first silicon carbide coating is deposited. The pretreatment method is: grinding the surface of the graphite substrate and then washing it to obtain the pretreated graphite substrate.

[0018] A second object of the present invention is to provide a silicon carbide coating, which is prepared by the above-mentioned method for preparing the deposited silicon carbide coating.

[0019] A third object of the present invention is to provide an application of the above-mentioned silicon carbide coating in semiconductors.

[0020] The beneficial effects of the present invention are as follows: in the silicon carbide coating deposition method provided by the present invention, the first silicon carbide coating is a porous silicon carbide coating with a gradient structure, the rate of introduction of trichloromethylsilane (MTS) is adjusted during the deposition process, and a silicon carbide coating with a gradient structure can be obtained by switching the atmosphere between high MTS and low MTS, and micropores or nanostructures can be formed in the coating, thereby increasing the specific surface area of ​​the coating, improving the surface activity of the coating, and more active sites ensure the chemical reaction between the coating and the substrate, thereby enhancing the bonding force between the coating interfaces; in addition, high-temperature oxidation and hydrofluoric acid washing treatment are continued to be performed, so that the surface of the first silicon carbide coating has more porous structures, providing an excellent deposition basis for the deposition of the second silicon carbide coating, and the second silicon carbide coating can be directly deposited on the surface of the first silicon carbide substrate without re-preparing a transition layer, and the bonding force between the silicon carbide coatings is strong, which solves the problem of low bonding strength between layers due to the high density of silicon carbide, causing cracking and peeling between the silicon carbide coatings. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 This is an EDS test result diagram of the element content in the first silicon carbide substrate of Example 1 of the present invention.

[0022] Figure 2 This is the XRD diagram of the first silicon carbide substrate in Example 1 of the present invention.

[0023] Figure 3 This is a SEM image of the first silicon carbide substrate of Example 1 of the present invention.

[0024] Figure 4 This is a SEM image of the multilayer silicon carbide coating of Example 1 of the present invention. DETAILED DESCRIPTION

[0025] In order to make the technical solutions and advantages of the present invention more clear, the present invention and its beneficial effects are described in further detail below, but the embodiments of the present invention are not limited thereto.

[0026] At present, multi-layer silicon carbide coatings prepared by CVD generally need to add transition layers between silicon carbide coatings to improve the bonding strength between layers due to the high density between layers. If the silicon carbide coatings are not added, the product is prone to peeling and cracking after a period of use due to insufficient bonding strength, which limits the widespread application of silicon carbide coatings.

[0027] Based on this, the present invention provides a method for preparing a deposited silicon carbide coating, and the obtained multi-layer silicon carbide coating has high bonding strength between layers and exhibits excellent performance in the semiconductor field. Of course, it can also be used in aerospace, weapons and equipment, tool industry, mold industry, automotive industry, etc. as needed.

[0028] The method for preparing the deposited silicon carbide coating comprises the following steps:

[0029] S1. Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the substrate by chemical vapor deposition, wherein the rate of introduction of trichloromethylsilane is first decreasing, then uniform, and then increasing, the molar ratio of hydrogen to argon is (3-6):1, the reaction temperature is 1100-1350°C, the reaction time is 3-7h, and the pressure is 150-250Torr;

[0030] S2, introducing an atmosphere with an oxygen volume concentration of 5% to 30%, aerobically treating the first silicon carbide coating obtained in step S1 at 1100 to 1200° C., washing with hydrofluoric acid after oxidation treatment, to obtain a first silicon carbide substrate;

[0031] S3, continuing to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of step S1 to obtain a multi-layer silicon carbide coating.

[0032] Compared with the current conventional CVD method for depositing silicon carbide, the above-mentioned multilayer deposition method does not need to add a transition layer between the silicon carbides to improve the bonding force between the silicon carbide coatings. Silicon carbide can be directly deposited on the silicon carbide coating. The obtained multilayer silicon carbide material has good stability and effectively improves the cracking and peeling problems between conventional pure silicon carbide coatings. This is mainly due to the breakthrough in the CVD coating process of the present invention. By periodically switching between high MTS and low MTS atmospheres, the silicon carbide coating can form a gradient structure, and micropores or nanostructures can be formed in the coating. In the high MTS concentration stage, the precursor molecules react chemically on the surface of the substrate and are deposited to form a carbon-rich coating. As the MTS concentration decreases, the reaction rate decreases, but some substances in the deposited coating may volatilize or decompose due to lack of sufficient reactants, thereby forming micropores or nanostructures in the coating. At the same time, high-temperature aerobic oxidation reaction and hydrofluoric acid pickling are used to make the surface structure of the first silicon carbide coating more porous, laying the foundation for the subsequent deposition of the second silicon carbide coating. First, the porous structure increases the specific surface area of ​​the first silicon carbide coating and increases the surface activity of the coating. The second silicon carbide coating can have more surface active sites to react chemically with it during the deposition process. The coatings are bonded by chemical bonds and have stronger bonding force. Second, the porous structure provides more attachment points and growth space for the deposition of the second silicon carbide coating, which can make the diffusion rate faster and the second silicon carbide coating deposited more evenly. The uniform coating can reduce stress concentration and crack generation. The porous structure increases the possibility of generation, thereby improving the overall performance and stability of the coating; thirdly, the porous structure helps the second silicon carbide coating to better penetrate into the first coating, forming a tighter bond, thereby improving the adhesion of the overall coating; fourthly, the porous structure also helps to improve the wear resistance of the coating. On the one hand, the pore structure increases the area of ​​the coating, thereby increasing the contact area between the coating and the friction pair, thereby improving the wear resistance of the coating; on the other hand, the existence of the pore structure can also accommodate some debris generated by wear, thereby reducing further damage to the coating and the substrate caused by wear. Therefore, the multilayer silicon carbide coating obtained by the present invention has better overall performance and broader application prospects.

[0033] For the deposition of the first silicon carbide coating, the reaction temperature may be 1100-1150° C., 1150-1200° C., 1200-1250° C., 1250-1300° C. or 1300-1350° C. Preferably, the reaction temperature may be 1200-1350° C.

[0034] The molar ratio of hydrogen to argon in the precursor atmosphere system may be 3:1, 4:1, 5:1 or 6:1. Preferably, the molar ratio of hydrogen to argon is 3:1.

[0035] By switching the pulse atmosphere to high MTS or low MTS, the specific amount of introduction can be adjusted based on the amount of hydrogen. Specifically, the process of introducing trichloromethylsilane is as follows: when the introduction begins, the molar ratio of hydrogen to trichloromethylsilane is (2-5):1; when it decreases to a uniform speed, the molar ratio of hydrogen to trichloromethylsilane is (10-20):1; when it increases to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (2-5):1.

[0036] Preferably, the process of introducing trichloromethylsilane is as follows: at the beginning of introduction, the molar ratio of hydrogen to trichloromethylsilane is (3-5):1; when decreasing to a uniform rate, the molar ratio of hydrogen to trichloromethylsilane is (10-15):1; when increasing to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (3-5):1.

[0037] More preferably, the process of introducing trichloromethylsilane is as follows: at the beginning of introduction, the molar ratio of hydrogen to trichloromethylsilane is 5:1; when decreasing to a uniform rate, the molar ratio of hydrogen to trichloromethylsilane is 10:1; when increasing to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is 5:1.

[0038] In some embodiments, in step S1, the time taken for the rate of introduction of trichloromethylsilane to decrease to a uniform rate is 0.4 to 0.6 hours; the rate of introduction of trichloromethylsilane begins to increase to a maximum rate within 0.4 to 0.6 hours before the end of deposition. The amount of trichloromethylsilane introduced is adjusted within a period of time before the beginning and the end. Compared with the entire reaction process, which is changing, there is a uniform introduction process in the middle, which can ensure the full reaction of the system, and the density of the deposited silicon carbide will not be too dense or too loose. At the same time, the interface contacting the graphite substrate and the interface coating contacting the second silicon carbide coating have a higher bonding strength.

[0039] In some embodiments, during the aerobic oxidation treatment, the volume concentration of oxygen introduced into the atmosphere may be 5% to 10%, 10% to 15%, 15% to 20%, 20% to 25% or 25% to 30%, preferably, the volume concentration of oxygen is 10% to 30%; more preferably, the volume concentration of oxygen is 20%. Avoid introducing too much oxygen to generate too much silicon dioxide. Although more pore structures can be obtained after etching, excessive oxygen will also cause the silicon carbide to be too loose as a whole, affecting the bonding strength between the coatings.

[0040] In the aerobic oxidation treatment, the temperature is increased to 1100-1200°C at a rate of 5-10°C / min. Specifically, the heating rate includes but is not limited to 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min or 10°C / min. Preferably, the heating rate is 5-8°C / min. The temperature of the insulation treatment can be 1100-1150°C or 1150-1200°C. The insulation treatment time can be 3-4h.

[0041] In some embodiments, in step S2, the mass concentration of hydrofluoric acid used is 5% to 10%. Specifically, the mass concentration of hydrofluoric acid can be 5%, 6%, 7%, 8%, 9% or 10%. Preferably, the mass concentration of hydrofluoric acid is 5%.

[0042] After depositing the first silicon carbide coating, the present invention also performs high-temperature aerobic oxidation treatment on it, so that a portion of silicon dioxide is generated on the surface, and then etching is performed by washing with hydrofluoric acid, so that more pore structures can be reserved on the surface of the first silicon carbide substrate, and more active sites can be reacted, and then the second silicon carbide coating is deposited. Compared with the conventional dense silicon carbide coating, the second silicon carbide coating of the present invention can be deposited on the surface of the first silicon carbide substrate faster, forming a more stable chemical bond. The two treatment processes are performed in sequence, and neither is indispensable.

[0043] In some embodiments, in step S3, the thickness of the first silicon carbide coating is less than or equal to the thickness of the second silicon carbide coating. Specifically, when the thickness of the second silicon carbide coating is greater, it can be obtained by extending the deposition time to increase its deposition time, such as the deposition time of the first silicon carbide coating CVD is 3h, and the deposition time of the second silicon carbide coating can be 5h. Setting the thickness of the second silicon carbide coating to be relatively thicker and being located in the outer layer can make the multi-layer silicon carbide coating have higher stability and longer service life.

[0044] In addition, the number of silicon carbide coating layers can be increased according to actual needs, such as 3 layers, 4 layers, 5 layers, etc. When adding silicon carbide coating, the above-mentioned CVD deposition, high-temperature aerobic oxidation treatment, and hydrofluoric acid cleaning can be repeated, which will not be elaborated here.

[0045] In some embodiments, in step S1, the substrate is selected to have a thermal expansion coefficient of 5×10 -6 / ℃~7×10 -6 / ℃ graphite substrate. Selecting this type of graphite as the deposition substrate and cooperating with the silicon carbide deposition process of the present invention can obtain a multilayer silicon carbide material with a stronger bonding force between silicon carbide and the graphite substrate. Preferably, the substrate is selected to have a thermal expansion coefficient of 5×10 -6 / ℃~6×10 -6 More preferably, the substrate is a graphite substrate with a thermal expansion coefficient of 5×10 -6 / ℃ graphite substrate.

[0046] In some embodiments, the graphite substrate is pretreated and dried before the first silicon carbide coating is deposited, and the pretreatment method is: grinding the surface of the graphite substrate, and then cleaning to obtain the pretreated graphite substrate. The surface of the pretreated graphite substrate is free of impurities, which is conducive to the subsequent uniform deposition of silicon carbide.

[0047] The present invention and its beneficial effects will be described in further detail below in conjunction with specific embodiments and the accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0048] Example 1

[0049] A method for preparing a deposited silicon carbide coating comprises the following steps:

[0050] 1) Select the thermal expansion coefficient of 5×10 -6 / ℃ graphite is used as the substrate, and the substrate is pretreated by using sandpaper to remove the roughness and attachments on the surface of the graphite substrate, and then ultrasonic cleaning is performed with solvents such as anhydrous ethanol;

[0051] 2) Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the graphite substrate by chemical vapor deposition, wherein the molar ratio of hydrogen to argon is 3:1, the reaction temperature is 1200°C, the reaction time is 3 hours, and the pressure is 150 Torr; and the process of introducing trichloromethylsilane is as follows: at the beginning of the introduction, the molar ratio of hydrogen to trichloromethylsilane is 5:1; within 0.5 hours, the amount of MTS introduced is gradually reduced by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 10:1; 0.5 hours before the end of the reaction (i.e., after 2.5 hours of reaction), the amount of MTS introduced is increased by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is 5:1, and sample 1 is obtained;

[0052] 3) placing sample 1 in a muffle furnace, introducing an atmosphere with an oxygen volume concentration of 20%, heating to 1100° C. at a rate of 5° C. / min, and maintaining the temperature for 3 hours for aerobic oxidation treatment, and washing with hydrofluoric acid with a mass concentration of 5% after oxidation treatment to obtain a first silicon carbide substrate;

[0053] 4) Continue to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of the first silicon carbide coating to obtain a carbon-porous silicon carbide-silicon carbide multilayer coating.

[0054] Example 2

[0055] Different from Example 1, when depositing the first silicon carbide coating, the content of trichloromethylsilane is increased at the beginning of the introduction, and the molar ratio of hydrogen to trichloromethylsilane is 3:1; and 0.5h before the end of the reaction (i.e., 2.5h after the reaction), the amount of MTS introduced is also increased by pulse atmosphere to a molar ratio of hydrogen to trichloromethylsilane of 3:1.

[0056] For the rest, please refer to Example 1 and will not be described again here.

[0057] Example 3

[0058] Different from Example 1, when depositing the first silicon carbide coating, the content of trichloromethylsilane is increased at the beginning of the introduction, and the molar ratio of hydrogen to trichloromethylsilane is 2:1; and 0.5h before the end of the reaction (i.e., 2.5h after the reaction), the amount of MTS introduced is also increased by pulse atmosphere to a molar ratio of hydrogen to trichloromethylsilane of 2:1.

[0059] For the rest, please refer to Example 1 and will not be described again here.

[0060] Example 4

[0061] Different from Example 1, when depositing the first silicon carbide coating, the content of trichloromethylsilane is increased at the beginning of the introduction, and the molar ratio of hydrogen to trichloromethylsilane is 7:1; and 0.5h before the end of the reaction (i.e., 2.5h after the reaction), the amount of MTS introduced is also increased by pulse atmosphere to a molar ratio of hydrogen to trichloromethylsilane of 7:1.

[0062] For the rest, please refer to Example 1 and will not be described again here.

[0063] Example 5

[0064] The difference from Example 1 is that the amount of trichloromethylsilane introduced during the deposition of the first silicon carbide coating is as follows: when the introduction is started, the molar ratio of hydrogen to trichloromethylsilane is 5:1; within 0.5 h, the amount of MTS introduced is gradually reduced by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 15:1; 0.5 h before the end of the reaction (i.e., 2.5 h after the reaction), the amount of MTS introduced is increased by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is 5:1.

[0065] For the rest, please refer to Example 1 and will not be described again here.

[0066] Example 6

[0067] The difference from Example 1 is that the amount of trichloromethylsilane introduced during the deposition of the first silicon carbide coating is as follows: when the introduction is started, the molar ratio of hydrogen to trichloromethylsilane is 3:1; within 0.5 h, the amount of MTS introduced is gradually reduced by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 20:1; 0.5 h before the end of the reaction (i.e., after 2.5 h of reaction), the amount of MTS introduced is increased by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is 3:1.

[0068] For the rest, please refer to Example 1 and will not be described again here.

[0069] Example 7

[0070] Different from Example 1, the reaction temperature during the deposition of the first silicon carbide coating is 1300°C.

[0071] For the rest, please refer to Example 1 and will not be described again here.

[0072] Comparative Example 8

[0073] Different from Example 1, the reaction temperature during the deposition of the first silicon carbide coating is 1100°C.

[0074] For the rest, please refer to Example 1 and will not be described again here.

[0075] Example 9

[0076] A method for preparing a deposited silicon carbide coating comprises the following steps:

[0077] 1) Select the thermal expansion coefficient of 5×10 -6 / ℃ graphite is used as the substrate, and the substrate is pretreated by using sandpaper to remove the roughness and attachments on the surface of the graphite substrate, and then ultrasonic cleaning is performed with solvents such as anhydrous ethanol;

[0078] 2) Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the graphite substrate by chemical vapor deposition, wherein the molar ratio of hydrogen to argon is 4:1, the reaction temperature is 1350°C, the reaction time is 5 hours, and the pressure is 170 Torr; and the process of introducing trichloromethylsilane is as follows: at the beginning of the introduction, the molar ratio of hydrogen to trichloromethylsilane is 5:1; within 0.6 hours, the amount of MTS introduced is gradually reduced by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 10:1; 0.6 hours before the end of the reaction (i.e., after 2.4 hours of reaction), the amount of MTS introduced is increased by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is 5:1, and sample 1 is obtained;

[0079] 3) placing sample 1 in a muffle furnace, introducing an atmosphere with an oxygen volume concentration of 5%, heating to 1150° C. at a rate of 7° C. / min, and maintaining the temperature for 4 hours for aerobic oxidation treatment, and washing with hydrofluoric acid with a mass concentration of 7% after oxidation treatment to obtain a first silicon carbide substrate;

[0080] 4) Continue to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of the first silicon carbide coating to obtain a carbon-porous silicon carbide-silicon carbide multilayer coating.

[0081] Example 10

[0082] A method for preparing a deposited silicon carbide coating comprises the following steps:

[0083] 1) Select the thermal expansion coefficient of 5×10 -6 / ℃ graphite is used as the substrate, and the substrate is pretreated by using sandpaper to remove the roughness and attachments on the surface of the graphite substrate, and then ultrasonic cleaning is performed with solvents such as anhydrous ethanol;

[0084] 2) Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the graphite substrate by chemical vapor deposition, wherein the molar ratio of hydrogen to argon is 6:1, the reaction temperature is 1250°C, the reaction time is 7h, and the pressure is 200Torr; and the process of introducing trichloromethylsilane is as follows: at the beginning of the introduction, the molar ratio of hydrogen to trichloromethylsilane is 5:1; within 0.4h, the amount of MTS introduced is gradually reduced by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 10:1; 0.4h before the end of the reaction (i.e., after 2.6h of reaction), the amount of MTS introduced is increased by pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is 5:1, and sample 1 is obtained;

[0085] 3) placing sample 1 in a muffle furnace, introducing an atmosphere with an oxygen volume concentration of 30%, heating to 1200° C. at a rate of 10° C. / min, and maintaining the temperature for 3 hours for aerobic oxidation treatment, and washing with hydrofluoric acid with a mass concentration of 10% after oxidation treatment to obtain a first silicon carbide substrate;

[0086] 4) Continue to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of the first silicon carbide coating to obtain a carbon-porous silicon carbide-silicon carbide multilayer coating.

[0087] Embodiment 11

[0088] The difference from Example 1 is that the thermal expansion coefficient is 6×10 -6 / ℃ graphite as the substrate.

[0089] For the rest, please refer to Example 1 and will not be described again here.

[0090] Example 12

[0091] The difference from Example 1 is that the thermal expansion coefficient is 7×10 -6 / ℃ graphite as the substrate.

[0092] For the rest, please refer to Example 1 and will not be described again here.

[0093] Comparative Example 1

[0094] Different from Example 1, the introduction rate of trichloromethylsilane was not adjusted during the deposition of the first silicon carbide coating, and hydrogen and trichloromethylsilane were directly introduced continuously at a molar ratio of 10:1 for reaction.

[0095] For the rest, please refer to Example 1 and will not be described again here.

[0096] Comparative Example 2

[0097] Different from Example 1, the introduction rate of trichloromethylsilane was not adjusted during the deposition of the first silicon carbide coating, and hydrogen and trichloromethylsilane were directly introduced continuously at a molar ratio of 5:1 for reaction.

[0098] For the rest, please refer to Example 1 and will not be described again here.

[0099] Comparative Example 3

[0100] The difference from Example 1 is the preparation of the first silicon carbide substrate. In this comparative example, no high-temperature aerobic oxidation treatment at 1100° C. is performed. The obtained sample 1 is directly washed with hydrofluoric acid, and then the second silicon carbide coating is deposited.

[0101] For the rest, please refer to Example 1 and will not be described again here.

[0102] Comparative Example 4

[0103] The difference from Example 1 is the preparation of the first silicon carbide substrate. In this comparative example, when the high-temperature aerobic oxidation treatment is performed at 1100° C., the volume concentration of oxygen introduced into the atmosphere is 40%.

[0104] For the rest, please refer to Example 1 and will not be described again here.

[0105] Comparative Example 5

[0106] The difference from Example 1 is the preparation of the first silicon carbide substrate. In this comparative example, hydrofluoric acid is not used for washing. Instead, a mixed solution of sulfuric acid (H2SO4) and hydrogen peroxide (H2O2) is used for washing instead of hydrofluoric acid.

[0107] For the rest, please refer to Example 1 and will not be described again here.

[0108] Comparative Example 6

[0109] Different from Example 1, the introduction rate of trichloromethylsilane during the deposition of the first silicon carbide coating first decreases and then becomes uniform: at the beginning of the introduction, the molar ratio of hydrogen to trichloromethylsilane is 5:1; within 1 hour, the introduction amount of MTS is gradually reduced through the pulse atmosphere until the molar ratio of hydrogen to trichloromethylsilane is maintained at 10:1.

[0110] For the rest, please refer to Example 1 and will not be described again here.

[0111] Comparative Example 7

[0112] Different from Example 1, the introduction rate of trichloromethylsilane during the deposition of the first silicon carbide coating was first uniform and then increasing: at the beginning of the introduction, the molar ratio of hydrogen to trichloromethylsilane was 10:1. After 2.5 hours of reaction, the introduction amount of MTS was increased by pulse atmosphere to a molar ratio of hydrogen to trichloromethylsilane of 5:1.

[0113] For the rest, please refer to Example 1 and will not be described again here.

[0114] The multilayer silicon carbide coatings obtained in the above-mentioned Examples 1 to 11 and Comparative Examples 1 to 7 were subjected to morphological characterization and performance tests, wherein the performance tests included: 1) Film layer adhesion test: Referring to GB / T 8642-2002, the film layer adhesion test was performed using a universal mechanical testing machine, with at least three samples in each group, and the average value was taken; 2) Thermal shock resistance test: The sample was heated to 1000°C and kept warm for 10 minutes, then quickly taken out and naturally cooled at room temperature of 20 to 25°C for 5 hours, and the surface changes of the film layer were recorded, and the action was repeated until the first crack appeared on the surface. There were at least three samples in each group, and the average value was taken as the test result.

[0115] The morphology characterization results of Example 1 are shown in Tables 1 and Figures 1 to 4 shown.

[0116] Depend on Figures 1-2 It can be seen that the first silicon carbide substrate prepared by the present invention has a gradient structure. Figure 1 The C and Si element contents of the selected points are shown in Table 1. When more trichloromethylsilane is introduced at the beginning, the amount of deposited carbon is higher, forming a carbon-rich coating; as the amount of trichloromethylsilane introduced decreases, the reaction rate decreases, there are not enough reactants to react with the carbon, part of the carbon volatilizes or decomposes, and the carbon proportion of Spectrum 5 corresponding to the EDS detection is relatively reduced; in the final stage, as the amount of trichloromethylsilane introduced increases, the amount of deposited carbon increases.

[0117] Table 1 Carbon and silicon content ratio

[0118] element Spectrum 4 Spectrum 5 Spectrum 6 C 61.16％ 53.13％ 60.32％ Si 38.84％ 47.87％ 39.68％

[0119] In addition, by Figures 3-4 It can also be seen that the multi-layer silicon carbide coating obtained by the present invention has a firm bond between the silicon carbide coating and the graphite substrate, and between the silicon carbide and the silicon carbide coating, without cracking, and the coating is deposited evenly.

[0120] The performance test results are shown in Table 2.

[0121] Table 2 Multilayer silicon carbide coating performance test results

[0122]

[0123]

[0124] It can be seen from the test results of the above-mentioned Examples 1 to 12 and Comparative Examples 1 to 2 that, compared with the conventional CVD method for preparing silicon carbide coatings, the present invention improves the CVD coating process to form a porous silicon carbide coating, and directly deposits silicon carbide on the porous silicon carbide coating to obtain a multilayer silicon carbide coating with high bonding strength between the two without adding other transition layers between the two, thereby solving the problem of low bonding strength between layers due to the excessively high density of silicon carbide deposition when currently depositing multilayer silicon carbide coatings by CVD.

[0125] Among them, by comparing Examples 1 to 6 and Comparative Examples 6 to 7, the inventors found that the regulation of the amount of trichloromethylsilane introduced during deposition affects the bonding strength between the coatings. When the amount of trichloromethylsilane introduced at the beginning is significantly different from the amount introduced at a uniform speed, although a gradient structure and a porous structure can be formed, the uniformity of the deposition is insufficient, and the deposition layer is too loose, and the bonding strength between the coatings cannot be improved well; and if the amount of trichloromethylsilane introduced at the beginning is slightly different from the amount introduced at a uniform speed, more pore structures cannot be formed in the system, and the overall density of the silicon carbide coating is still relatively high, resulting in the deposition of the silicon carbide coating on the silicon carbide substrate. There is still a problem of low bonding strength between the two. After investigation, it was found that the molar ratio of hydrogen to trichloromethylsilane was preferably controlled at (3-5):1 at the beginning. When it was reduced to a uniform speed, the molar ratio of hydrogen to trichloromethylsilane was (10-15):1. When it was increased to the highest rate, the molar ratio of hydrogen to trichloromethylsilane was (3-5):1. A porous gradient structure first silicon carbide substrate with relatively excellent performance can be obtained to ensure the bonding strength between the two when the silicon carbide coating is subsequently deposited.

[0126] In addition, it can be seen from the comparison between Example 1 and Comparative Examples 3 to 5 that after the first silicon carbide coating is deposited, it is equally important to subject it to high-temperature aerobic oxidation treatment and hydrofluoric acid cleaning. When high-temperature aerobic oxidation treatment is lacking, as shown in the results of Comparative Example 3, the bonding strength between the first silicon carbide substrate and the second silicon carbide coating is weak, cracks appear when the number of thermal cycles is small, and the stability of the multilayer silicon carbide coating is poor. When hydrofluoric acid cleaning is replaced with other acid cleaning, as shown in the results of Comparative Example 4, the bonding strength between the first silicon carbide substrate and the second silicon carbide coating is still weak. This is mainly because hydrofluoric acid cleaning is a subsequent step of high-temperature aerobic oxidation treatment, which is used to etch the silicon dioxide formed by oxidation, thereby ensuring the porous structure of the deposition surface of the first silicon carbide substrate. On the one hand, sufficient active sites can be obtained for the deposition of the second silicon carbide coating, enhancing the bonding ability between the silicon carbide coatings, and the second silicon carbide coating can better penetrate into the first coating, and the overall coating has stronger adhesion; on the other hand, the diffusion rate of the second silicon carbide coating is faster and the deposition is more uniform, reducing the possibility of stress concentration and crack generation. At the same time, the porous structure of the surface also improves the wear resistance of the coating.

[0127] According to the disclosure and teaching of the above description, those skilled in the art to which the present invention belongs can also change and modify the above embodiment. Therefore, the present invention is not limited to the above specific embodiment, and any obvious improvement, replacement or modification made by those skilled in the art on the basis of the present invention belongs to the protection scope of the present invention. In addition, although some specific terms are used in this specification, these terms are only for the convenience of description and do not constitute any limitation to the present invention.

Claims

1. A method for preparing a deposited silicon carbide coating, characterized in that: The following steps are involved: S1. Using trichloromethylsilane-hydrogen-argon as the precursor atmosphere system, a first silicon carbide coating is deposited on the surface of the substrate by chemical vapor deposition, wherein the rate of introduction of trichloromethylsilane is first decreasing, then uniform, and then increasing, the molar ratio of hydrogen to argon is (3-6):1, the reaction temperature is 1100-1350°C, the reaction time is 3-7h, and the pressure is 150-250Torr; S2, introducing an atmosphere with an oxygen volume concentration of 5% to 30%, aerobically treating the first silicon carbide coating obtained in step S1 at 1100 to 1200° C., washing with hydrofluoric acid after oxidation treatment, to obtain a first silicon carbide substrate; S3, continuing to deposit a second silicon carbide coating on the surface of the first silicon carbide substrate under the preparation conditions of step S1 to obtain a multi-layer silicon carbide coating.

2. The method for preparing a deposited silicon carbide coating according to claim 1, characterized in that: In step S1, the reaction temperature is 1200-1350° C.; the process of introducing trichloromethylsilane is as follows: when the introduction starts, the molar ratio of hydrogen to trichloromethylsilane is (2-5):1; when it decreases to a uniform rate, the molar ratio of hydrogen to trichloromethylsilane is (10-20):1; when it increases to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (2-5):

1.

3. The method for preparing a deposited silicon carbide coating according to claim 2, characterized in that: When the introduction begins, the molar ratio of hydrogen to trichloromethylsilane is (3-5):1; when the speed decreases to a constant rate, the molar ratio of hydrogen to trichloromethylsilane is (10-15):1; when the speed increases to the maximum rate, the molar ratio of hydrogen to trichloromethylsilane is (3-5):

1.

4. The method for preparing a deposited silicon carbide coating according to claim 2, characterized in that: In step S1, the time taken for the introduction rate of trichloromethylsilane to decrease from a constant rate is 0.4 to 0.6 h; the introduction rate of trichloromethylsilane begins to increase to a maximum rate within 0.4 to 0.6 h before the end of deposition.

5. The method for preparing a deposited silicon carbide coating according to any one of claims 1 to 4, characterized in that: In step S2, the aerobic treatment reaction conditions are: introducing an atmosphere with an oxygen volume concentration of 10% to 30%, heating to 1100 to 1200° C. at a rate of 5 to 10° C. / min, and maintaining the temperature for 3 to 4 hours.

6. The method for preparing a deposited silicon carbide coating according to claim 1, characterized in that: In step S2, the mass concentration of hydrofluoric acid used is 5% to 10%.

7. The method for preparing a deposited silicon carbide coating according to any one of claims 1 to 4, characterized in that: In step S1, the substrate is selected to have a thermal expansion coefficient of 5×10 -6 / ℃~7×10 -6 / ℃ graphite substrate.

8. The method for preparing a deposited silicon carbide coating according to claim 7, characterized in that: The graphite substrate is pretreated and dried before the first silicon carbide coating is deposited. The pretreatment method is: grinding the surface of the graphite substrate and then cleaning to obtain the pretreated graphite substrate.

9. A silicon carbide coating, characterized in that: The silicon carbide coating is prepared by the method for preparing the deposited silicon carbide coating according to any one of claims 1 to 8.

10. Use of the silicon carbide coating according to claim 9 in semiconductors.

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