2H-SiC film and preparation method thereof

Abstract

The invention relates to a 2H-SiC film and a preparation method thereof.The preparation method comprises the steps that mixed gas of methyl trichlorosilane, argon and hydrogen is introduced, chemical vapor deposition is conducted on a graphite substrate, and the 2H-SiC film is formed on the surface of the graphite substrate; in the mixed gas, the conveying flow ratio of the hydrogen to the methyl trichlorosilane is greater than 15: 1. According to the preparation method, controllable adjustment of the 2H-SiC phase is achieved, the large-area 2H-SiC thin film can be prepared, meanwhile, the preparation cost is low, and commercial application of the 2H-SiC thin film can be popularized easily.

Description

Technical Field

[0001] This application relates to the field of silicon carbide manufacturing technology, and in particular to a 2H-SiC thin film and its preparation method. Background Technology

[0002] Silicon carbide (SiC) possesses excellent electrical properties such as a wide bandgap, high voltage resistance, and high temperature resistance, making it widely used in aerospace, semiconductors, and new energy vehicles. SiC has over 200 polymorphs, with common phases including cubic 3C-SiC, hexagonal 2H-SiC, 4H-SiC, and 6H-SiC. Among these, 3C-SiC has a bandgap of approximately 2.2 eV and an electron mobility of approximately 900 cm⁻¹. 2 / (V·s); The band gap of 2H-SiC is approximately 3.33 eV, and the electron mobility is approximately 1200 cm⁻¹. 2 / (V·s); The band gap of 4H-SiC is approximately 3.26 eV, and the electron mobility is approximately 720 cm⁻¹. 2 / (V·s); The band gap of 6H-SiC is approximately 3.00 eV, and the electron mobility is approximately 370 cm⁻¹. 2 / (V·s). It can be seen that 2H-SiC has a wider band gap and higher carrier mobility compared to other crystal forms of silicon carbide. In addition, 2H-SiC also has a wurtzite structure. Therefore, 2H-SiC is a semiconductor material compatible with wurtzite-type group III semiconductors (such as AlN, GaN and ZnO) and has rich application potential.

[0003] Currently, methods for preparing 2H-SiC include solvothermal methods, carbothermal reduction methods, molten salt methods, and laser-assisted chemical vapor deposition (LAD). However, thermal reduction and molten salt methods can only produce whiskers or nanowires that are a mixture of 3C-SiC and 2H-SiC phases. Only LAD can produce 2H-SiC thin films. However, this method requires laser irradiation and the use of the organic precursor 3DMAS (SiH(N(CH3)2)3), resulting in high raw material and equipment costs. Furthermore, the limited laser spot area makes it difficult to prepare large-size 2H-SiC thin films, thus restricting the commercial application of 2H-SiC thin films. Summary of the Invention

[0004] Therefore, it is necessary to provide a 2H-SiC thin film and its preparation method to address the above problems. The preparation method described in this application achieves controllable adjustment of the 2H-SiC phase, can produce large-area 2H-SiC thin films, and has a low preparation cost, which is conducive to promoting the commercial application of 2H-SiC thin films.

[0005] A method for preparing a 2H-SiC thin film includes the following steps:

[0006] A mixture of methyltrichlorosilane, argon, and hydrogen is introduced to perform chemical vapor deposition on a graphite substrate, forming a 2H-SiC thin film on the surface of the graphite substrate.

[0007] In the mixed gas, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is greater than 15:1.

[0008] In one embodiment, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is less than or equal to 10000:1.

[0009] In one embodiment, the hydrogen delivery flow rate is 1 L / min to 100 L / min.

[0010] In one embodiment, the argon gas flow rate is 1 L / min to 100 L / min.

[0011] In one embodiment, the distance between the graphite substrate surface and the gas inlet of the mixed gas is 10mm to 100mm.

[0012] In one embodiment, the chemical vapor deposition temperature is 1200°C to 1500°C and the pressure is 10 kPa to 10000 kPa.

[0013] In one embodiment, the mixed gas also includes a protective gas selected from nitrogen.

[0014] In one embodiment, the sum of the flow rates of the protective gas and the argon gas is 1 L / min to 100 L / min.

[0015] In one embodiment, argon is introduced first, followed by hydrogen, during the heating process, before the mixed gas is introduced.

[0016] In one embodiment, during the heating process, argon gas is introduced when the temperature reaches 800°C to 1000°C, and hydrogen gas is introduced when the temperature reaches 1200°C to 1500°C.

[0017] A 2H-SiC thin film prepared by the method described above.

[0018] The method for preparing 2H-SiC thin films described in this application uses methyltrichlorosilane as a precursor for chemical vapor deposition (CVD). Argon and hydrogen are used as carrier gases to introduce the evaporated methyltrichlorosilane into the CVD reaction chamber. By controlling the flow rate ratio of hydrogen to methyltrichlorosilane in the mixed gas, the types of decomposition products of methyltrichlorosilane in the reaction chamber are optimized, suppressing the formation of silicon dichloride. Simultaneously, highly saturated methane undergoes a polymerization reaction to form highly reactive acetylene, placing the reaction in a carbon-rich environment. On one hand, the high density of silicon vacancies can... On the one hand, the formation energy of 2H-SiC is reduced. On the other hand, since the carbon-silicon ratio in silicon carbide formed in a carbon-rich environment is greater than 1:1, additional carbon atoms are inserted into the silicon carbide lattice to generate stress. Stress release is used to promote phase transformation, thereby realizing the orientation adjustment of 3C-SiC to 2H-SiC. A 2H-SiC thin film with (100) preferred orientation is successfully prepared. The size of the 2H-SiC thin film can be up to 12 inches, realizing the large-area preparation of 2H-SiC thin film. At the same time, the preparation cost is low, which is conducive to promoting the commercial application of 2H-SiC thin film. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a SEM image of the sample surface obtained in Example 1 of this application;

[0021] Figure 2 The XRD pattern of the sample prepared in Example 1 of this application;

[0022] Figure 3 The Raman spectrum of the sample obtained in Example 1 of this application;

[0023] Figure 4 This is a SEM-EDS image of the sample prepared in Example 1 of this application;

[0024] Figure 5 SEM image of the surface of the sample obtained in Comparative Example 3 of this application;

[0025] Figure 6 The XRD pattern of the sample prepared in Comparative Example 3 of this application;

[0026] Figure 7 The Raman spectrum of the sample prepared in Comparative Example 3 of this application;

[0027] Figure 8This is a SEM-EDS image of the sample prepared in Comparative Example 3 of this application. Detailed Implementation

[0028] To facilitate understanding of this application, it will be described in more detail below. However, it should be understood that this application can be implemented in many different forms and is not limited to the embodiments or examples described herein. Rather, these embodiments or examples are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0029] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. The terminology used herein in the specification of this application is for the purpose of describing particular implementations or embodiments only and is not intended to limit the application. The optional range of the term "and / or" as used herein includes any one of two or more of the related listed items, as well as any and all combinations of the related listed items, including any two related listed items, any more related listed items, or a combination of all related listed items. In this application, when numerical ranges are involved, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, and every value between such minimum and maximum values. Further, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Furthermore, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges to which they are incorporated.

[0030] Through long-term and in-depth research and testing, the applicant discovered that 2H-SiC is a metastable phase, less stable under normal pressure than cubic 3C-SiC and hexagonal 4H-SiC and 6H-SiC. During growth, nuclei of 3C-SiC and 2H-SiC may form simultaneously. However, because 3C-SiC grows faster and is more stable, the 2H nuclei are suppressed, resulting in the final product usually being 3C-SiC or its polycrystalline mixture, rather than pure 2H-SiC.

[0031] In traditional chemical vapor deposition (CVD) processes using methyltrichlorosilane, silicon chloride, and hydrocarbon gases as precursors, silicon chloride, being a highly reactive halide precursor, reacts violently with hydrocarbon gases at high temperatures, generating numerous SiC nuclei. However, this rapid nucleation process is difficult to control, leading to the formation of polycrystalline or amorphous films. Furthermore, due to the rapid and disordered growth of nuclei, a large amount of gas-phase pre-reaction occurs: silicon chloride and hydrocarbon gases generate silicon carbide particles before reaching the graphite substrate surface. These particles settle on the graphite substrate, roughening the film surface and introducing numerous defects, severely impacting film quality. More importantly, the high reactivity of the silicon chloride system and the strong adsorption of chlorine atoms cause silicon carbide to tend to form the thermodynamically more stable 3C phase rather than the metastable 2H phase during growth. Therefore, traditional CVD processes struggle to produce high-quality 2H-SiC films.

[0032] To address the aforementioned technical challenges, this application provides a method for preparing 2H-SiC thin films, comprising the following steps:

[0033] A mixture of methyltrichlorosilane, argon, and hydrogen is introduced to perform chemical vapor deposition on a graphite substrate, forming a 2H-SiC thin film on the surface of the graphite substrate.

[0034] In the mixed gas, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is greater than 15:1.

[0035] The method for preparing 2H-SiC thin films described in this application uses methyltrichlorosilane as a precursor for chemical vapor deposition (CVD). Argon and hydrogen are used as carrier gases to carry the evaporated methyltrichlorosilane into the CVD reaction chamber. By controlling the flow rate ratio of hydrogen to methyltrichlorosilane in the mixed gas, the types of decomposition products of methyltrichlorosilane in the reaction chamber are optimized, and the formation of silicon dichloride is suppressed. At the same time, highly saturated methane undergoes a polymerization reaction to form highly reactive acetylene, so that the reaction is in a carbon-rich environment. On the one hand, the high density of silicon vacancies can reduce the formation energy of 2H-SiC. On the other hand, since the carbon-silicon ratio in silicon carbide formed in the carbon-rich environment is greater than 1:1, additional carbon atoms are inserted into the silicon carbide lattice to generate stress. Stress release is used to promote phase transformation, thereby achieving the directional regulation of 3C-SiC to 2H-SiC.

[0036] Meanwhile, hydrogen can also react with chlorine-containing substances in the decomposition products, effectively reducing the Cl / H ratio in the gas phase and significantly enhancing the surface mobility of silicon atoms, carbon atoms, or silicon-carbon groups adsorbed on the graphite substrate, thus laying the foundation for the formation of a high-quality, ordered 2H crystal structure.

[0037] Furthermore, unlike traditional chemical vapor deposition processes where gas feedstocks are introduced separately, this application optimizes the process by mixing methyltrichlorosilane with argon and hydrogen before introducing it. This ensures that the methyltrichlorosilane, argon, and hydrogen form a homogeneous mixture before entering the reaction chamber. This not only suppresses gas-phase pre-reactions but also ensures that the partial pressure of methyltrichlorosilane, the ratio of hydrogen to methyltrichlorosilane, and the argon concentration are consistent at any point on the growth surface of the graphite substrate. This provides a stable and repeatable thermodynamic and kinetic environment for the nucleation and growth of 2H-SiC, effectively suppressing the random generation of stable phase nuclei. This is more conducive to the large-area, uniform epitaxial growth of metastable 2H-SiC and further improves the phase purity of the 2H-SiC film.

[0038] Therefore, the preparation method provided in this application can successfully prepare 2H-SiC thin films with (100) preferred orientation. The size of the 2H-SiC thin films can be up to 12 inches, realizing the large-area preparation of 2H-SiC thin films. At the same time, the preparation cost is low, which is conducive to promoting the commercial application of 2H-SiC thin films.

[0039] It is understood that the ratio of the hydrogen to the methyltrichlorosilane flow rate in the mixed gas includes, but is not limited to, any one of the following values ​​or any range between two: 16:1, 18:1, 20:1, 25:1, 30:1, 40:1, 50:1, 100:1, 1000:1, 10000:1, etc., such as 20:1, 50:1, 100:1, 50:1~1000:1, 100:1~10000:1, etc.

[0040] In one embodiment of this application, preferably, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is less than or equal to 10000:1, that is, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is greater than 15:1 and less than or equal to 10000:1.

[0041] In one embodiment of this application, the hydrogen delivery flow rate is 1L / min to 100L / min. Based on the fact that the delivery flow rates of hydrogen and methyltrichlorosilane in the mixed gas meet a specific ratio, by adjusting the hydrogen delivery flow rate, hydrogen can selectively etch crystal planes with higher surface energy or structurally unstable regions in the carbon-rich environment unique to this application, thereby directionally retaining 2H-SiC regions with good structural matching and lower surface energy, and achieving the effect of "phase selection".

[0042] It is understood that the hydrogen delivery flow rate includes, but is not limited to, any one of 1L / min, 20L / min, 40L / min, 60L / min, 80L / min, 100L / min or any range between two of them.

[0043] In one embodiment of this application, the argon gas flow rate is 1 L / min to 100 L / min. Unlike adjusting the hydrogen flow rate, argon does not participate in the chemical reaction during chemical vapor deposition. Based on the fact that the flow rates of hydrogen and methyltrichlorosilane in the mixed gas meet a specific ratio, by adjusting the argon gas flow rate, on the one hand, the partial pressure of methyltrichlorosilane and hydrogen in the reaction chamber can be changed, avoiding homogeneous nucleation and inhibiting polycrystalline growth. At the same time, the rate at which active groups reach the surface is slowed down, allowing atoms or molecules adsorbed on the graphite substrate surface more time to migrate. By controlling the surface migration ability of adsorbed atoms or molecules and the deposition rate through surface dynamics, a delicate balance is achieved, thereby directionally forming a 2H-SiC crystal phase with a precise stacking sequence.

[0044] On the other hand, the argon gas flow rate can change the overall heat capacity in the reaction chamber, which can fine-tune the local temperature field near the graphite substrate. Under a more stable and uniform temperature field, it is more conducive to the uniform epitaxial growth of 2H-SiC crystal phase, thereby further improving the size of 2H-SiC thin films.

[0045] Therefore, by changing the argon flow rate, the thermodynamic conditions of the reaction environment and the surface processes at the atomic scale can be precisely controlled, thereby creating a kinetic window conducive to the formation and growth of the metastable 2H-SiC phase.

[0046] It is understood that the argon gas delivery flow rate includes, but is not limited to, any one of the following values ​​or a range between any two: 1 L / min, 10 L / min, 20 L / min, 50 L / min, 60 L / min, 80 L / min, and 100 L / min.

[0047] It should be noted that this application does not impose restrictions on parameters such as the purity of methyltrichlorosilane, argon, and hydrogen; any commercially available product may be used.

[0048] In one embodiment of this application, the distance between the graphite substrate surface and the gas inlet position of the mixed gas is 10mm~100mm. By adjusting the distance between the graphite substrate surface and the gas inlet position of the mixed gas, the transport, decomposition and surface reaction kinetics of the reactants can be precisely controlled. This, along with the control conditions such as methyltrichlorosilane, hydrogen and their proportions, temperature and pressure, can regulate the competitive relationship between gas phase chemistry and surface reaction, further forming a kinetic window that is favorable for the epitaxial growth of metastable 2H-SiC phase.

[0049] It is understood that the distance between the graphite substrate surface and the gas inlet of the mixed gas includes, but is not limited to, any one of 10mm, 20mm, 50mm, 80mm, 100mm or any range between two.

[0050] In one embodiment of this application, the temperature of the chemical vapor deposition is preferably 1200℃~1500℃, including but not limited to any one of 1200℃, 1300℃, 1400℃, 1500℃ or any range between two; the pressure is preferably 10kPa~10000kPa, including but not limited to any one of 10kPa, 100kPa, 1000kPa, 5000kPa, 10000kPa or any range between two.

[0051] In one embodiment of this application, the mixed gas further includes a protective gas selected from nitrogen. On the one hand, nitrogen decomposes at high temperature to produce nitrogen atoms. Based on the high adsorption and high migration capacity of nitrogen atoms, they can preferentially occupy specific surface active sites, selectively increasing the surface energy of 3C-SiC while relatively decreasing the surface energy of 2H-SiC, thereby achieving directional regulation from 3C-SiC to 2H-SiC. On the other hand, nitrogen can also change the partial pressure of methyltrichlorosilane and hydrogen in the reaction chamber, avoiding homogeneous nucleation, inhibiting polycrystalline growth, and slowing down the rate at which active groups reach the surface, allowing atoms or molecules adsorbed on the graphite substrate surface more time to migrate. By controlling the surface migration capacity and deposition rate of adsorbed atoms or molecules through surface dynamics, a clever balance is achieved, thereby directionally forming a 2H-SiC crystal phase with a precise stacking sequence.

[0052] In one embodiment of this application, the sum of the flow rates of the protective gas and the argon gas is 1L / min to 100L / min, including but not limited to any one of 1L / min, 10L / min, 20L / min, 50L / min, 60L / min, 80L / min, 100L / min or any range between the two.

[0053] In one embodiment of this application, the graphite substrate is preferably polished before chemical vapor deposition, followed by ultrasonic cleaning to remove surface impurities and drying.

[0054] In one embodiment of this application, it is preferable to perform a pressure test on the reaction apparatus before chemical vapor deposition to ensure that there is no gas leakage in the reaction chamber.

[0055] In one embodiment of this application, before introducing the mixed gas, argon gas is first introduced during the heating process to achieve "oxygen-free protection and physical purification" by utilizing the inertness of argon gas. Then, hydrogen gas is introduced to achieve "chemical cleaning and surface activation" by utilizing the activity of hydrogen gas. This provides a clean and orderly graphite substrate surface for the nucleation and growth of 2H-SiC in a step-by-step manner.

[0056] In one embodiment of this application, during the heating process, argon gas is preferably introduced when the temperature reaches 800°C to 1000°C, and hydrogen gas is introduced when the temperature reaches 1200°C to 1500°C. It is understood that the temperature at which hydrogen gas is introduced is the deposition process temperature.

[0057] It should be noted that this application does not impose any restrictions on the specific equipment used in the chemical vapor deposition process.

[0058] The present invention also provides a 2H-SiC thin film prepared by the method described above.

[0059] The 2H-SiC thin film and its preparation method will be further described below through specific embodiments. However, those skilled in the art will understand that the following embodiments are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified, specific conditions in the embodiments are performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments used without specified manufacturers are all commercially available conventional products.

[0060] Example 1

[0061] The graphite substrate is ground and polished, then ultrasonically cleaned to remove surface impurities, and finally placed in an oven to dry at 120°C for 6 hours.

[0062] Using a low-pressure chemical vapor deposition (LPCVD) system, the pretreated graphite substrate was placed on a support rod, and after the chamber door was closed, a vacuum of 10 °C was applied. -4 After Pa, close the cavity outlet valve and conduct a one-hour pressure holding test to ensure there is no gas leakage in the cavity.

[0063] Turn on the heating power supply and heat the reaction chamber through the graphite electrode. When the temperature reaches 900°C, argon gas is introduced. When the temperature reaches 1200°C, hydrogen gas is introduced. Turn on the sample stage rotary switch to keep the flow and thermal fields inside the chamber stable. The chamber is kept at a pressure of 10 kPa, and the temperature of the chamber is monitored by thermocouples.

[0064] Methyltrichlorosilane was introduced into a mixing tank and mixed thoroughly with hydrogen, argon, and nitrogen. The inlet valve at the front of the chamber was opened to allow the mixed gas to enter. The flow rates of methyltrichlorosilane, hydrogen, argon, and nitrogen were adjusted to 0.5 L / min, 15 L / min, 3 L / min, and 1 L / min, respectively. The distance between the graphite substrate and the inlet was approximately 10 mm. The reaction time was 100 min. After the reaction was completed, the inlet valve was closed, the heating power was turned off, and the temperature was allowed to drop to room temperature. The sample stage rotation was then stopped, the inlet valve was closed, and argon gas was introduced into the sealed chamber to open the chamber door and remove the sample.

[0065] The sample prepared in Example 1 was characterized and tested, and the results are as follows: Figures 1-4 As shown. According to Figure 1 The SEM image shown indicates that its surface morphology is an irregular plateau; according to Figure 2 The XRD pattern shown and Figure 3 The Raman spectra shown indicate that the (100) plane diffraction peak of 2H-SiC is around 33.6°, while the Raman peak of hexagonal SiC is around 788 cm⁻¹. -1 Nearby, it can be proven that the material obtained in Example 1 is 2H-SiC; according to Figure 4 As shown in the SEM-EDS image, Si and C elements are evenly distributed in the coating, and the C / Si ratio is close to 1:1.

[0066] Example 2

[0067] The graphite substrate is ground and polished, then ultrasonically cleaned to remove surface impurities, and finally placed in an oven to dry at 120°C for 6 hours.

[0068] Using a low-pressure chemical vapor deposition (LPCVD) system, the pretreated graphite substrate was placed on a support rod, and after the chamber door was closed, a vacuum of 10 °C was applied. -4 After Pa, close the cavity outlet valve and conduct a one-hour pressure holding test to ensure there is no gas leakage in the cavity.

[0069] Turn on the heating power supply and heat the reaction chamber through the graphite electrode. When the temperature reaches 900°C, argon gas is introduced. When the temperature reaches 1300°C, hydrogen gas is introduced. Turn on the sample stage rotary switch to keep the flow and thermal fields inside the chamber stable. The chamber is kept at a pressure of 100 kPa, and the temperature of the chamber is monitored by thermocouples.

[0070] Methyltrichlorosilane was introduced into a mixing tank and mixed thoroughly with hydrogen, argon, and nitrogen. The inlet valve at the front of the chamber was opened to allow the mixed gas to enter the chamber. The flow rates of methyltrichlorosilane, hydrogen, argon, and nitrogen were adjusted to 1 L / min, 100 L / min, 50 L / min, and 3 L / min, respectively. The distance between the graphite substrate and the inlet was approximately 30 mm. The reaction time was 100 min. After the reaction was completed, the inlet valve was closed, the heating power was turned off, and the temperature was allowed to drop to room temperature. The sample stage rotation was then stopped, the inlet valve was closed, and argon gas was introduced into the chamber under sealed conditions to open the chamber door and remove the sample.

[0071] The sample was characterized using the same method as in Example 1, which proved that the sample prepared in Example 2 was 2H-SiC, a disk with a diameter of approximately 50 mm.

[0072] Example 3

[0073] The graphite substrate is ground and polished, then ultrasonically cleaned to remove surface impurities, and finally placed in an oven to dry at 120°C for 6 hours.

[0074] Using a low-pressure chemical vapor deposition (LPCVD) system, the pretreated graphite substrate was placed on a support rod, and after the chamber door was closed, a vacuum of 10 °C was applied. -4 After Pa, close the cavity outlet valve and conduct a one-hour pressure holding test to ensure there is no gas leakage in the cavity.

[0075] Turn on the heating power supply and heat the reaction chamber through the graphite electrode. When the temperature reaches 900°C, argon gas is introduced. When the temperature reaches 1400°C, hydrogen gas is introduced. Turn on the sample stage rotary switch to keep the flow and thermal fields inside the chamber stable. The chamber is kept at a pressure of 500 kPa, and the temperature of the chamber is monitored by thermocouples.

[0076] Methyltrichlorosilane was introduced into a mixing tank and mixed thoroughly with hydrogen, argon, and nitrogen. The inlet valve at the front of the chamber was opened to allow the mixed gas to enter. The flow rates of methyltrichlorosilane, hydrogen, argon, and nitrogen were adjusted to 2 L / min, 50 L / min, 50 L / min, and 3 L / min, respectively. The distance between the graphite substrate and the inlet was approximately 50 mm. The reaction time was 100 min. After the reaction was completed, the inlet valve was closed, the heating power was turned off, and the temperature was allowed to drop to room temperature. The sample stage rotation was then stopped, the inlet valve was closed, and argon gas was introduced into the sealed chamber to open the chamber door and remove the sample.

[0077] The sample was characterized using the same method as in Example 1, which proved that the sample prepared in Example 3 was 2H-SiC, with a diameter of approximately 50 mm.

[0078] Example 4

[0079] The graphite substrate is ground and polished, then ultrasonically cleaned to remove surface impurities, and finally placed in an oven to dry at 120°C for 6 hours.

[0080] Using a low-pressure chemical vapor deposition (LPCVD) system, the pretreated graphite substrate was placed on a support rod, and after the chamber door was closed, a vacuum of 10 °C was applied. -4 After Pa, close the cavity outlet valve and conduct a one-hour pressure holding test to ensure there is no gas leakage in the cavity.

[0081] Turn on the heating power supply and heat the reaction chamber through the graphite electrode. When the temperature reaches 900°C, argon gas is introduced. When the temperature reaches 1500°C, hydrogen gas is introduced. Turn on the sample stage rotary switch to keep the flow and thermal fields inside the chamber stable. The chamber is kept at a pressure of 700 kPa, and the temperature of the chamber is monitored by thermocouples.

[0082] Methyltrichlorosilane was introduced into a mixing tank and mixed thoroughly with hydrogen, argon, and nitrogen. The inlet valve at the front of the chamber was opened to allow the mixed gas to enter the chamber. The flow rates of methyltrichlorosilane, hydrogen, argon, and nitrogen were adjusted to 5 L / min, 90 L / min, 90 L / min, and 5 L / min, respectively. The distance between the graphite substrate and the inlet was approximately 80 mm. The reaction time was 100 min. After the reaction was completed, the raw material inlet valve was closed, the heating power was turned off, and the temperature was allowed to drop to room temperature. The sample stage rotation was then stopped, the inlet valve was closed, and argon gas was introduced into the chamber under sealed conditions to open the chamber door and remove the sample.

[0083] The sample was characterized using the same method as in Example 1, which proved that the sample prepared in Example 4 was 2H-SiC, and the size was approximately 50 mm in diameter.

[0084] Comparative Example 1

[0085] A quartz tube furnace was used, with silica powder placed near the gas inlet as the silicon source. Methane was introduced into the chamber through the gas inlet as the carbon source, and hydrogen was used as the carrier gas. The graphite substrate was placed away from the gas inlet. The quartz tube was heated by a silicon carbide rod. The gaseous silicon generated by the heated silica powder was transported to the graphite substrate through the carrier gas and reacted with methane on the substrate surface to generate silicon carbide. However, because the silica introduced oxygen, the obtained silicon carbide had a high oxygen content and was not a continuous thin film, but rather silicon carbide nanowires.

[0086] Comparative Example 2

[0087] Tris(dimethylamino)silane (SiH(N(CH3)2)3) was used as the silicon source, and argon was used as the carrier gas to carry the tris(dimethylamino)silane vapor into the chamber. Methane was used as the carbon source and introduced into the chamber separately through a dual-tube nozzle. The entire substrate was irradiated by a continuous wave Nd:YAG laser (μ=1064nm) using laser-assisted chemical vapor deposition. However, tris(dimethylamino)silane is expensive, the reaction requires additional laser assistance, the coating area is small, and the equipment cost is high.

[0088] Comparative Example 3

[0089] The difference between Comparative Example 3 and Example 1 is that the flow rate of methyltrichlorosilane was adjusted to 2 L / min and the flow rate of hydrogen was adjusted to 20 L / min.

[0090] The sample prepared in Comparative Example 3 was characterized and tested, and the results are as follows: Figures 5-8 As shown. According to Figure 5 The SEM image shown indicates that its surface morphology is tetrahedral pyramidal; according to Figure 6 The XRD pattern shown and Figure 7The Raman spectra shown indicate that the (111) plane diffraction peak of 3C-SiC is around 35.5°, while the Raman peak of tetragonal SiC is around 798 cm⁻¹. -1 Nearby, it can be proven that the material obtained in Comparative Example 3 is 3C-SiC; according to Figure 8 As shown in the SEM-EDS image, the C / Si ratio of the SiC coating increases compared to Example 1, indicating that the coating was deposited in a carbon-rich environment.

[0091] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above 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.

[0092] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A method for preparing a 2H-SiC thin film, characterized in that, Includes the following steps: A mixture of methyltrichlorosilane, argon, and hydrogen is introduced to perform chemical vapor deposition on a graphite substrate, forming a 2H-SiC thin film on the surface of the graphite substrate. In the mixed gas, the ratio of the flow rate of hydrogen to that of methyltrichlorosilane is greater than 15:

1.

2. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The ratio of the flow rate of hydrogen to that of methyltrichlorosilane is less than or equal to 10000:

1.

3. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The hydrogen delivery flow rate is 1L / min to 100L / min.

4. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The argon gas flow rate is 1L / min to 100L / min.

5. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The distance between the graphite substrate surface and the gas inlet of the mixed gas is 10mm to 100mm.

6. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The chemical vapor deposition temperature is 1200℃~1500℃, and the pressure is 10kPa~10000kPa.

7. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, The mixed gas also includes a protective gas, which is selected from nitrogen.

8. The method for preparing 2H-SiC thin films according to claim 7, characterized in that, The sum of the flow rates of the protective gas and the argon gas is 1 L / min to 100 L / min.

9. The method for preparing 2H-SiC thin films according to claim 1, characterized in that, Before introducing the mixed gas, argon gas is introduced first during the heating process, followed by hydrogen gas.

10. The method for preparing 2H-SiC thin films according to claim 9, characterized in that, During the heating process, argon gas is introduced when the temperature reaches 800℃~1000℃, and hydrogen gas is introduced when the temperature reaches 1200℃~1500℃.

11. A 2H-SiC thin film prepared by the method of any one of claims 1 to 10.

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