Method for preparing monocrystalline silicon carbide crystal for chip by using alkylsilane

Abstract

Disclosed is a method for preparing a monocrystalline silicon carbide crystal for a chip by using alkylsilane, which method relates to the technical field of manufacturing special electronic materials. When the alkylsilane precursor in the present invention is used to deposit SiC by means of a CVD process, it will bring a moderate decomposition temperature, simple decomposition products, high deposition efficiency, high levels of usage safety, no spontaneous combustion in air and good storage stability. And stable single crystal SiC crystals can be formed at a temperature of 100-200℃ lower than that of conventional materials, with high crystal growth efficiency and few defects. In addition, the alkylsilane precursor is a non-corrosive and single-source silicon-carbon compound with a small molecular weight. Due to the high proportion of Si and C elements in the precursor molecules, the precursor has a faster deposition rate and a lower deposition temperature, such that SiC with an approximate stoichiometric ratio can be obtained. Compared with a traditional process for preparing a silicon carbide single crystal by means of a "physical vapor transfer method", the deposited silicon carbide crystals are compact, with extremely high purity, few crystal defects and an unlimited crystal size, which can be prepared into silicon carbide crystals of any size.

Description

Method for preparing single crystal silicon carbide crystal for chip using alkylsilane Technical Field

[0001] The present invention relates to the technical field of manufacturing special electronic materials, in particular to a method for preparing single-crystal silicon carbide crystals for chips using alkylsilane. Background Art

[0002] Power semiconductor devices are semiconductor components used to pass high currents under high voltage, and power semiconductor devices using silicon (Si) substrates dominate. However, in recent years, third-generation semiconductor materials represented by single-crystal silicon carbide (SiC) have become one of the most promising semiconductor materials after silicon. The insulation breakdown voltage of single-crystal silicon carbide material itself is an order of magnitude higher than that of silicon-based materials. It has the advantages of high power, high voltage resistance, high temperature resistance, high frequency, low energy consumption, and strong radiation resistance. It can be widely used in modern industrial fields such as new energy vehicles, 5G communications, photovoltaic power generation, rail transportation, smart grids, aerospace, etc.

[0003] The prior art discloses a technique for preparing SiC using a chemical vapor deposition (CVD) process. The precursors used are generally silane, propane, propylene, ethylene, methane, etc. Combinations of gases such as silane + propane, silane + propylene, silane + ethylene, and silane + methane are used. The flow rates of silane and alkanes (propane, propylene, ethylene, and methane) are controlled separately, so that the two precursors react in proportion at a temperature of 2200°C to 2800°C to form SiC.

[0004] Based on the above reasons, the inventors believe that:

[0005] First, using silane + alkanes (propane, propylene, ethylene, methane) as mixed precursors, the thermal decomposition parameters of the two gas raw materials are very different, making the regulation of process parameters such as feed gas flow rate, ratio, and pyrolysis temperature extremely complicated. In addition, there are many unstable by-products, the product purity is difficult to control, and the product consistency is poor.

[0006] Second, silane has a low decomposition temperature (it can decompose at 600°C), making it very easy to form nuclei in the gas phase in the space inside the crystal growth furnace. This can easily lead to an unstable Si / C ratio, the formation of "silicon droplets" on the surface of the SiC crystal, and the resulting SiC crystal form being variable. In addition, both types of raw materials are flammable and explosive gases, which bring many inconveniences to operation and poor safety, and no significant progress has been made. Summary of the Invention

[0007] The purpose of the present invention is to provide a method for preparing single-crystal silicon carbide crystals for chips using alkylsilane, so as to solve the problems of low crystal purity and unstable growth in the prior art of preparing single-crystal silicon carbide crystals in the above-mentioned background technology.

[0008] To achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing single-crystal silicon carbide for chips using alkylsilanes comprises preparing silicon carbide by chemical vapor deposition from a precursor, wherein the precursor is selected from one or more of methylsilane, dimethylsilane, and trimethylsilane of the alkylsilane class. The method for preparing the single-crystal silicon carbide comprises the following steps:

[0010] S1: Seed crystal preparation; S2: Crucible assembly; S3: Crystal growth; S4: Crystal annealing; S5: Unloading step.

[0011] Furthermore, the seed crystal preparation step involves removing the outer packaging of the silicon carbide seed crystal in a Class 10,000 clean area, applying a layer of adhesive evenly to the seed crystal using a glue spreader, and gluing it to the graphite crucible lid. After applying pressure with a rubber sheet to ensure a tight adhesion, the crucible is placed in a vacuum resistance furnace and evacuated to a vacuum of 0.01 to 1×10 -3 Pa, gradually raise the temperature to 300-680℃, keep the vacuum and temperature constant for 8-12 hours, then reduce it to room temperature, take out the graphite crucible cover, put the graphite crucible cover with the seed crystal into an ultrasonic cleaner, and clean it with ultrapure water for 3-5 minutes. Take it out, blow off the surface moisture with high-purity nitrogen, and transfer it to the crystal growth room through the transfer window for use.

[0012] Furthermore, the crucible assembly step is to gently place the crucible cover with the seed crystal attached on the top of the crucible, rotate and align the exhaust hole, slightly open the nitrogen inlet valve and the vacuum suction valve, cover the crystal growth furnace top cover, and evacuate to 0.1-1×10 -5 Pa, maintain for 20-30 minutes.

[0013] Furthermore, the crystals are grown in a closed vertical reactor with a large aspect ratio, nitrogen is introduced at 0.01-10 scm, the temperature is gradually raised to 1300-1800°C, the nitrogen is then stopped and hydrogen is introduced at 0.01-100 scm.

[0014] Afterwards, alkylsilane is continuously introduced into the reactor at a rate of 1-1000sscm controlled by a mass flow meter, maintaining a low vacuum of 0.1Pa~200Pa. Alkylsilane decomposes in the carrier gas atmosphere to generate single-crystalline silicon carbide and deposits on the surface of the seed crystal set at the top of the reactor. Silicon carbide single crystals grow in an orderly manner along the surface of the seed crystal. After 30-100 hours, the precursor is stopped and the temperature is gradually lowered to room temperature. The hydrogen gas is stopped and replaced with nitrogen. The vacuum is stopped, the furnace cover is opened, and the silicon carbide single crystal is taken out together with the crucible cover.

[0015] Furthermore, the crystal is grown in a closed vertical reactor with a large aspect ratio, high-purity (7N) nitrogen is introduced, and the temperature is gradually raised to 1300°C~1800°C, then the high-purity (7N) nitrogen is stopped and hydrogen is introduced, and then alkylsilane is continuously introduced into the reactor controlled by a mass flow meter, and the amount of high-purity (7N) nitrogen introduced is 1 / 30-1 / 100 of the amount of alkylsilane, maintaining a low vacuum of 0.1Pa~200Pa, and the alkylsilane decomposes in the carrier gas atmosphere to generate single-crystalline silicon carbide and deposits on the surface of the seed crystal arranged at the top of the reactor, and grows into silicon carbide single crystals in an orderly manner along the surface of the seed crystal. After 30-100 hours, the precursor is stopped and gradually cooled to room temperature, the hydrogen is stopped and replaced with nitrogen, the vacuum is stopped, the furnace cover is opened, and the silicon carbide single crystal is taken out together with the crucible cover.

[0016] Furthermore, during the crystal growth process, the ratio of alkylsilane to hydrogen is controlled at 1:10 to 200, and the carrier gas is selected from hydrogen, argon or helium.

[0017] Furthermore, the crystal annealing step is to place the taken out crystal into an annealing furnace and maintain a vacuum degree of 1-10×10 -3 Pa, the annealing furnace temperature is raised to 1200-1600℃, kept constant for 30-60 minutes, and protected by inert gas throughout the process, and then gradually cooled to room temperature.

[0018] Furthermore, the step of removing the annealed silicon carbide crystal is to take it out after it cools down to room temperature, and separate the crucible cover from the crystal.

[0019] Furthermore, the precursor further includes alkanes and / or silanes.

[0020] Furthermore, the alkane is selected from methane, propane, ethylene, and propylene, and the silane is selected from silane, trichlorosilane, dichlorosilane, and silicon tetrachloride.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] Compared with the traditional "physical vapor transport method" for preparing silicon carbide single crystals, the method for preparing silicon carbide crystals using alkylsilane disclosed in the present invention is that the deposited silicon carbide crystals are dense, extremely high in purity, have few crystal defects, and are not restricted in crystal size, so silicon carbide crystals of any size can be prepared. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG1 is a schematic diagram of the principle of preparing single-crystal silicon carbide crystal for chips using alkylsilane according to one embodiment of the present application.

[0024] FIG2 is a schematic flow chart of a method for preparing single-crystal silicon carbide crystals for chips using alkylsilane according to one embodiment of the present application. DETAILED DESCRIPTION

[0025] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0026] Semiconductor chips are divided into integrated circuits and discrete devices, and their basic structures can be divided into a "substrate-epitaxial-device" structure. The main form of silicon carbide disclosed in this application in semiconductor chips is as a substrate material. According to different resistivities, silicon carbide wafers are divided into conductive and semi-insulating types. Among them, conductive silicon carbide wafers are mainly used in the manufacture of high-temperature and high-voltage power devices; semi-insulating silicon carbide substrates are mainly used in microwave and radio frequency devices and other fields. This application uses a chemical vapor deposition process to develop a semiconductor silicon carbide single crystal preparation process, the principle of which is as follows:

[0027] H3C-SiH3 →SiC+3H2.

[0028] Referring to Figures 1 and 2, a specific embodiment of the present application proposes a method for preparing single-crystal silicon carbide for chips using alkylsilane. The SiC single crystal is prepared in a closed vertical reactor with a large aspect ratio. The inductor in the reactor is heated by a medium-frequency power supply to maintain the reaction chamber at a reaction temperature of 1300°C to 1800°C. The precursor methylsilane is continuously introduced at a specified flow rate controlled by a mass flow meter. The carrier gas H2 or He is continuously introduced at a specified flow rate controlled by a mass flow meter. The precursor methylsilane decomposes at a high temperature in an atmosphere of carrier gas H2 or He to generate single-crystal silicon carbide, which adheres to the surface of the seed crystal set at the top of the reactor and continues to grow along the surface of the seed crystal, gradually growing into a silicon carbide single crystal of a certain size. The H2 produced by the decomposition reaction and the introduced carrier gas H2 2 The unreacted methylsilane is discharged from the reactor, washed by an alkaline solution washing tower, and then discharged into the atmosphere.

[0029] To produce conductive single-crystal silicon carbide, a calculated amount of N2 must be introduced as the carrier gas. The reaction is carried out under a vacuum of 20-100 Pa. Optimal process conditions are achieved by controlling the reactor gas flow direction, reaction temperature, pressure, and gas flow rate.

[0030] During the growth process of silicon carbide crystals, stress is generated. To eliminate this stress, the crystals need to be heated again for annealing. After annealing, they are naturally cooled in the furnace to a certain temperature. After cooling, the furnace is opened and the crystals are taken out.

[0031] The specific steps include the following:

[0032] S1 Seed crystal preparation: Remove the outer packaging of the seed crystal in a Class 10,000 clean area, apply a layer of adhesive evenly with a glue spreader, and gently glue it to the graphite crucible cover. Apply even pressure with a rubber sheet to ensure a tight bond. Then, place it in a vacuum resistance furnace and evacuate to 0.1-1×10 -3 Pa, gradually raise the temperature to 400-580°C, maintain the vacuum and temperature constant for 8-12 hours, then cool to room temperature and remove the graphite crucible lid. Place the graphite crucible lid with the seed crystal in an ultrasonic cleaner and clean it with ultrapure water for 3-5 minutes. Remove the crucible lid, blow off the surface moisture with high-purity nitrogen, and transfer it to the crystal growth chamber through a transfer window for later use.

[0033] S2 Crucible Assembly: Gently place the crucible cover with the seed crystal on top of the crucible, rotate it to align the exhaust hole, slightly open the nitrogen inlet valve and vacuum suction valve, cover the crystal growth furnace top cover, and tighten the surrounding fastening bolts firmly according to regulations. Evacuate to 0.1-1×10 -5 Pa, maintain for 20-30 minutes to ensure that there is no leakage in the crystal growth furnace.

[0034] S3 crystal growth: A. Open the nitrogen inlet valve of the growth furnace and maintain the nitrogen flow rate at about 50-100

[0035] SCCM, turn on the medium frequency power controller, and gradually increase the temperature of the crystal furnace to 1200-1400℃. Turn on the vacuum system and maintain the vacuum degree in the furnace at 1-10×10 -3Pa. After the furnace temperature reaches 400 Pa, continue to flow nitrogen for 2-5 minutes. Then, close the nitrogen inlet valve and open the hydrogen inlet valve, maintaining a hydrogen flow rate of 50-200 SCCM. Continue to flow hydrogen for 5-10 minutes. B. Adjust the position and power of the heating coils between the seed crystal and the furnace to ensure a temperature difference of 40-70°C. Gradually adjust the hydrogen flow rate to 50-200 SLM. Once the hydrogen flow rate stabilizes, open the precursor inlet valve and adjust the flow rate to 200-1500 SCCM. Maintain a furnace vacuum of 0.5-100 Pa. C. Maintain the above process conditions and the temperature of the furnace circulating cold water stable (temperature fluctuation ±0.2°C), and continue growth for 50-200 hours.

[0036] D. After the growth time is up, close the precursor inlet valve and gradually lower the medium frequency coil heating power (to 0 within 1 hour). After the temperature drops to room temperature, close the hydrogen inlet valve and open the nitrogen inlet valve. After nitrogen replacement for 5-10 minutes, close the nitrogen inlet valve, close the vacuum valve, open the furnace cover, and take out the crystal together with the crucible cover.

[0037] The above is a preferred crystal growth scheme. The applicant also states that the flow rate of the alkylsilane introduced can be controlled between 100 and 10,000 SCCM. In addition to using a single alkylsilane (such as methylsilane) as a precursor, the precursor can also be a combination of methylsilane + dimethylsilane, methylsilane + trimethylsilane, or dimethylsilane + trimethylsilane. The ratio of the introduced alkylsilane to hydrogen can be controlled between 1:10 and 200. In addition to hydrogen, the carrier gas can also be an inert gas such as argon or helium. The vacuum level is controlled between 0.1 and 200 Pa.

[0038] S4 Crystal annealing: Place the taken out crystal (with crucible cap) into the annealing furnace and maintain the vacuum degree of 1-10 ×10 -3 Pa, the annealing furnace temperature rises to 1200-1600℃, and is kept constant for 30-50 minutes. At the same time, the process still requires high-purity nitrogen protection, and the temperature is gradually lowered to room temperature according to the procedure.

[0039] S5: After the annealed silicon carbide crystals cool to room temperature, they are taken out. The crucible cover and the crystals are separated. After the crystals pass inspection, they are packaged and stored.

[0040] Example

[0041] S1 Seed crystal preparation: Power on the system, perform various checks before starting up, vacuum and detect leaks,

[0042] The system was replaced with argon gas, and the circulating cooling water temperature was maintained at 20°C and the pressure at 300 kPa. The SiC crystal furnace system PLC control panel was turned on and the entire system was self-checked. The pH of the alkali solution in the tail gas treatment system was ≥11. The spray tower circulation pump was turned on and the tail gas recovery system was put into normal operation. The outer packaging of the 6-inch seed crystal was removed and a layer of phenolic resin glue was evenly applied using a glue spreader. The seed crystal was bonded to the lid of the 6-inch graphite crucible. The crystal was placed in a vacuum resistance furnace and evacuated to 1×10 -2 Pa, and then heated to 450°C at 10°C / min, maintaining the vacuum and temperature constant for 8 hours, then cooled. The sample was ultrasonically cleaned in ultrapure water for 3 minutes in an ultrasonic cleaning machine, and then surface moisture was blown off with high-purity nitrogen, and then transferred to the crystal growth chamber.

[0043] S2 Crucible Assembly: Place the crucible cover with the seed crystal on top of the crucible, align the exhaust hole, slightly open the nitrogen inlet valve and vacuum valve, cover the crystal growth furnace top cover, and evacuate to 1×10 -4 Pa, maintain for 20 minutes.

[0044] S3 crystal growth: open the nitrogen valve of the growth furnace, maintain the nitrogen flow rate at 30 SCCM, set the medium frequency heating rate to 10 ° C / min, heat the crystal furnace to 1300 ° C, and maintain the vacuum degree in the furnace at 1 × 10 -3 Pa. Close the nitrogen valve, open the hydrogen valve, control the hydrogen flow rate to 80 SCCM, and pass hydrogen for 3 minutes. Control the heating coil power of the seed crystal part and the furnace body to ensure that the temperature difference is 60℃, and adjust the hydrogen flow rate to 5L / min.

[0045] 80 SLM. Open the methylsilane inlet valve and control the flow rate to 600 SCCM. Maintain the furnace vacuum at 40 Pa and circulate cold water at 32°C. Continue growing for 60 hours. Close the methylsilane inlet valve and reduce the heating power to 30°C / min. Once the temperature drops to room temperature, close the hydrogen valve, open the nitrogen valve, and replace the atmosphere with nitrogen at 5 L / min for 5 minutes. Close the nitrogen valve and vacuum valve, open the furnace lid, and remove the crystal.

[0046] S4 Crystal annealing: Place the crystal in an annealing furnace and maintain a vacuum of 1×10 -3 Pa, increase the temperature to 1500℃ at 20℃ / min, keep the temperature constant for 30min, and then cool down to room temperature at 30℃ / min.

[0047] S5: After the annealed silicon carbide crystals cool to room temperature, they are taken out, the crucible cover and the crystals are separated, and they are packaged and put into storage after passing the inspection.

[0048] Example

[0049] S1 Seed crystal preparation: Power on the system, perform various checks before starting up, vacuum and detect leaks,

[0050] The system was replaced with argon gas, and the circulating cooling water temperature was maintained at 20°C and the pressure at 300 kPa. The SiC crystal furnace system PLC control panel was turned on and the entire system was self-checked. The pH of the alkali solution in the tail gas treatment system was ≥12. The spray tower circulation pump was turned on and the tail gas recovery system was put into normal operation. The outer packaging of the 8-inch seed crystal was removed and a layer of melted sucrose was evenly applied using a glue spreader. The seed crystal was bonded to the lid of the 8-inch graphite crucible. The crucible was placed in a vacuum resistance furnace and evacuated to 1×10 -3 Pa, and then heated to 500°C at 15°C / min. Maintain vacuum and temperature for 12 hours, then cool. Place in an ultrasonic cleaner and clean with ultrapure water for 10 minutes. Remove surface moisture with high-purity nitrogen and transfer to the crystal growth chamber.

[0051] S2 Crucible Assembly: Place the crucible cover with the seed crystal on top of the crucible, align the exhaust hole, slightly open the nitrogen inlet valve and vacuum valve, cover the crystal growth furnace top cover, and evacuate to 1×10 -5 Pa, maintain for 30 minutes.

[0052] S3 crystal growth: open the nitrogen valve of the growth furnace, maintain the nitrogen flow rate at 50 SCCM, set the medium frequency heating rate to 15 ° C / min, heat the crystal furnace to 1350 ° C, and maintain the vacuum degree in the furnace at 1 × 10 -4 Pa. Close the nitrogen valve, open the hydrogen valve, control the hydrogen flow rate to 100 sccm, and flow hydrogen for 5 minutes. Control the power of the heating coils between the seed crystal and the furnace to maintain a temperature difference of 55°C. Adjust the hydrogen flow rate to 100 slm at 8 L / min. Open the methylsilane + trimethylsilane inlet valves, control the methylsilane flow rate to 300 sccm, and the trimethylsilane flow rate to 420 sccm. Maintain the furnace vacuum at 20 Pa and the furnace circulating cold water at 32°C. Continue growing for 80 hours. Close the methylsilane + trimethylsilane inlet valves, reduce the heating power by 30°C / min. Once the temperature drops to room temperature, close the hydrogen valve, open the nitrogen valve, and replace the atmosphere with nitrogen at 5 L / min for 15 minutes. Close the nitrogen valve and the vacuum valve, open the furnace lid, and remove the crystal.

[0053] S4 Crystal annealing: Place the crystal in the annealing furnace and maintain the vacuum degree at 1×10- 4 Pa, increase the temperature to 1500℃ at 25℃ / min, keep the temperature constant for 60min, and then cool down to room temperature at 30℃ / min.

[0054] S5: After the annealed silicon carbide crystals cool to room temperature, they are taken out, the crucible cover and the crystals are separated, and they are packaged and put into storage after passing the inspection.

[0055] The embodiments of the present invention are presented for purposes of illustration and description and are not intended to be exhaustive or to limit the invention to the disclosed forms. Many modifications and variations will be apparent to those skilled in the art. The embodiments are chosen and described in order to better illustrate the principles of the invention and its practical application and to enable those skilled in the art to understand the invention and design various embodiments with various modifications as suited for specific applications.

Claims

1. A method for preparing single-crystal silicon carbide for chips using alkylsilane, comprising preparing silicon carbide from a precursor by chemical vapor deposition, characterized in that: The precursor is selected from one of methylsilane, dimethylsilane and trimethylsilane of the alkylsilane class, and the preparation method of the single crystal silicon carbide crystal comprises the following steps: Step: S1: seed crystal preparation; S2: Crucible assembly; S3: crystal growth; S4: crystal annealing; S5: oven removal step.

2. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 1, characterized in that: The seed crystal preparation step is to remove the outer packaging of the silicon carbide seed crystal in a 10,000-level clean area, evenly apply a layer of adhesive on the seed crystal with a glue spreader and adhere it to the graphite crucible cover, apply pressure with a rubber plate to ensure tight adhesion, and then put it into a vacuum resistance furnace and evacuate it to 0.01-1×10 -3 Pa, gradually raise the temperature to 300-680℃, keep the vacuum and temperature constant for 8-12 hours, then drop to room temperature, take out the graphite crucible cover, put the graphite crucible cover with the seed crystal into an ultrasonic cleaner, clean it with ultrapure water for 3-5 minutes, take it out, blow off the surface moisture with high-purity nitrogen, and transfer it to the crystal growth room through the transfer window for use.

3. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 2, characterized in that: The crucible assembly step is to gently place the crucible cover with the seed crystal attached on the top of the crucible, rotate and align the exhaust hole, slightly open the nitrogen inlet valve and the vacuum suction valve, cover the top cover of the crystal growth furnace, and evacuate to 0.1-1×10 -5 Pa, maintain for 20-30min.

4. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 3, characterized in that: The crystal is grown in a closed vertical reactor with a large aspect ratio, and 0.01-10 scm of nitrogen is introduced, and the temperature is gradually raised to 1300-1800°C, and then the nitrogen is stopped and 0.01-100 scm of hydrogen is introduced instead. Then, alkylsilane is continuously introduced into the reactor at 1-1000 sscm controlled by a mass flow meter, and a low vacuum of 0.1Pa-200Pa is maintained. The alkylsilane is decomposed in a carrier gas atmosphere to generate single-crystalline silicon carbide and deposited on the surface of a seed crystal arranged on the top of the reactor, and a silicon carbide single crystal is orderly grown along the surface of the seed crystal. After 30-100 hours, the precursor is stopped and the temperature is gradually lowered to room temperature, the hydrogen is stopped and replaced with nitrogen, the vacuum is stopped, the furnace cover is opened, and the silicon carbide single crystal is taken out together with the crucible cover.

5. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 4, characterized in that: The crystal is grown in a closed vertical reactor with a large aspect ratio, high-purity (7N) nitrogen is introduced, and the temperature is gradually raised to 1300°C-1800°C, then the high-purity (7N) nitrogen is stopped and hydrogen is introduced, and then alkylsilane is continuously introduced into the reactor controlled by a mass flow meter, the amount of high-purity (7N) nitrogen introduced is 1 / 30-1 / 100 of the amount of alkylsilane, and a low vacuum of 0.1Pa-200Pa is maintained. The alkylsilane is decomposed in a carrier gas atmosphere to generate single-crystalline silicon carbide and deposited on the surface of a seed crystal arranged on the top of the reactor, and a silicon carbide single crystal is orderly grown along the surface of the seed crystal. After 30-100 hours, the precursor is stopped and the temperature is gradually reduced to room temperature, the hydrogen is stopped and replaced with nitrogen, the vacuum is stopped, the furnace cover is opened, and the silicon carbide single crystal is taken out together with the crucible cover.

6. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 5, characterized in that: During the crystal growth process, the ratio of alkylsilane to hydrogen is controlled at 1:10-200, and the carrier gas is selected from hydrogen, argon or helium.

7. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 6, characterized in that: The crystal annealing step is to place the taken out crystal into an annealing furnace and maintain a vacuum degree of 1-10×10 -3 Pa, the annealing furnace temperature rises to 1200-1600℃, keeps constant temperature for 30-60 minutes, and is protected by inert gas throughout the process, and then gradually cools down to room temperature.

8. The method for preparing single crystal silicon carbide for chip using alkylsilane according to claim 7, characterized in that: The furnace-out step is to take out the annealed silicon carbide crystal after it cools down to room temperature, and separate the crucible cover from the crystal.

9. The method for preparing single crystal silicon carbide crystal for chip using alkylsilane according to claim 8, characterized in that: The precursor also includes alkanes and / or silanes.

10. The method for preparing single crystal silicon carbide for chip using alkylsilane according to claim 9, characterized in that: The alkane is selected from methane, propane, ethylene, and propylene, and the silane is selected from silane, trichlorosilane, dichlorosilane, and silicon tetrachloride.

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