Process and device for preparing P-type silicon carbide crystal by vapor deposition method

Abstract

The invention discloses a process and a device for preparing a P-type silicon carbide crystal by a vapor deposition method, and relates to the technical field of silicon carbide crystal preparation. The device for preparing the P-type silicon carbide crystals through the vapor deposition method comprises a reaction cavity, an air supply mechanism is fixedly connected to the outer wall of the reaction cavity, a discharging mechanism is movably connected to the top of the reaction cavity, and an exhaust pipe is fixedly connected to the bottom of the reaction cavity. According to the process and the device for preparing the P-type silicon carbide crystals by the vapor deposition method, mixed gas uniformly enters the reaction cavity from the open pores in the reaction cavity, and the rotating connecting pipe drives the inner spiral plate to rotate, so that the mixed gas is pushed to be dispersed to the periphery at the top of the rotating disc; the gas in the reaction chamber generates a slight circulation effect, by-product gas at the bottom layer is dispersed in the reaction chamber, the gas is prevented from hindering the reaction of the substrate in the reaction chamber, and the preparation speed of silicon carbide is further improved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide crystal preparation technology, specifically to a process and apparatus for preparing P-type silicon carbide crystals by vapor deposition. Background Technology

[0002] The semiconductor industry has developed through three stages. The first generation of semiconductor materials was represented by silicon; the second generation, gallium arsenide, is also widely used; and the third generation, represented by silicon carbide, has significant performance advantages over the previous two generations. Currently, commercially available silicon carbide crystals, and the silicon carbide substrates used to fabricate wafers, are mainly N-type, primarily used to manufacture power devices such as Schottky diodes and metal-oxide-semiconductor field-effect transistors. The patent published in China with publication number 202311024386.5 discloses a process and apparatus for preparing P-type silicon carbide crystals by vapor deposition, including a vapor deposition furnace component, a gas supply component and a vacuum pump. The vapor deposition furnace component includes a furnace body and a furnace cover. A deposition box is fixedly connected to the center of the furnace body. The top of the deposition box has an open structure. A substrate assembly is provided on the top inner side of the deposition box. The substrate assembly includes a cross bar. Multiple uprights are vertically fixed to the bottom surface of the cross bar.

[0003] Existing silicon carbide crystal preparation processes all employ a spray-type process to introduce mixed gas into contact with the substrate for reaction. During this process, the byproduct gas produced by the reaction will be near the substrate, causing the substrate to come into contact with the reaction gas and the reaction to become slower, thus affecting the silicon carbide production efficiency. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a process and apparatus for preparing P-type silicon carbide crystals by vapor deposition, thereby solving the problems mentioned in the background section.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a process and apparatus for preparing P-type silicon carbide crystals by vapor deposition, comprising a process for preparing P-type silicon carbide crystals by vapor deposition: S1. Substrate pretreatment: Select a substrate and sequentially perform ultrasonic cleaning with organic solvent, etching with hydrofluoric acid-nitric acid mixture, and high-temperature treatment with high-purity hydrogen to obtain a clean substrate with a surface roughness Ra < 0.1 nm. S2. Preparation of reaction chamber: Fix the pretreated substrate on the base inside the corresponding device, seal the reaction chamber and evacuate to ≤0.001Pa, introduce high-purity hydrogen and heat to 1400-1450℃ at 5-10℃ / min for in-situ etching for 20-30min. S3. Buffer layer growth: Adjust the chamber pressure to 50-500 mbar and the temperature to 1550-1600℃, and introduce a first mixed gas containing silicon source, carbon source, hydrogen chloride and hydrogen to grow an intrinsic silicon carbide buffer layer with a thickness of 1-5 μm, wherein the carbon-silicon ratio is 1.0-1.3. S4. Alternating doping epitaxial growth: Maintain the temperature at 1550-1680℃, alternately introduce the first mixed gas and the second mixed gas containing Al doping source, cycle 5-50 times to form an epitaxial layer. In a single cycle, the first mixed gas grows a 2-100nm undoped layer and the second mixed gas grows a 2-50nm doped layer. S5. Cooling and wafer removal: Stop the supply of silicon source, carbon source and doping source, keep hydrogen flowing and cool down to below 1000℃ at 5-10℃ / min, switch to Ar gas to cool to room temperature, pressurize and remove the P-type silicon carbide crystal.

[0006] Preferably, the organic solvent ultrasonic cleaning is performed by ultrasonication of acetone for 15 min + ultrasonication of isopropanol for 15 min, the volume ratio of hydrofluoric acid-nitric acid mixture is 1:3:10, and the high-purity hydrogen high-temperature treatment is performed at 1500℃ for 30 min.

[0007] An apparatus for preparing P-type silicon carbide crystals by vapor deposition, the apparatus comprising a reaction chamber (1), a gas supply mechanism (6) fixedly connected to the outer wall of the reaction chamber (1), a discharge mechanism (7) movably connected to the top of the reaction chamber (1), an exhaust pipe (3) fixedly connected to the bottom of the reaction chamber (1), an extraction pipe (4) fixedly connected to the bottom of the reaction chamber (1), a composite pump (5) fixedly connected to the back of the extraction pipe (4), and an electric heater (2) fixedly connected to the outer wall of the reaction chamber (1). The gas supply mechanism (6) includes: A rotating motor (68) is fixedly connected to the bottom of the reaction chamber (1); Rotating disk (69) is located at the bottom of the reaction chamber (1), and the top output shaft of the rotating motor (68) passes through the bottom of the reaction chamber (1) and is fixedly connected to the bottom of the rotating disk (69). Five bases are provided on the top of the rotating disk (69).

[0008] Preferably, a first solenoid valve (31) is fixedly connected to the left side of the exhaust pipe (3), and an outlet (32) is fixedly connected to the left side of the first solenoid valve (31).

[0009] Preferably, the outer wall of the reaction chamber (1) is fixedly connected to an annular guide groove (61), and the inner wall of the reaction chamber (1) is provided with multiple air inlet holes at the corresponding positions of the annular guide groove (61). The outer wall of the annular guide groove (61) is fixedly connected to a second solenoid valve (62), and the right side of the second solenoid valve (62) is fixedly connected to an air supply pipe (63). The right end of the air supply pipe (63) is fixedly connected to a mixing chamber (64), and the top of the mixing chamber (64) is fixedly connected to a third solenoid valve (65). The top of the third solenoid valve (65) is fixedly connected to an air inlet (66).

[0010] Preferably, a gas supply motor (641) is fixedly connected to the bottom of the gas mixing chamber (64), and a stirring rack (642) is provided inside the gas mixing chamber (64). The top output shaft of the gas supply motor (641) passes through the bottom of the gas mixing chamber (64) and is fixedly connected to the bottom of the stirring rack (642).

[0011] Preferably, a connecting pipe (72) is fixedly connected to the top of the rotating disk (69), and an inner spiral plate (67) is fixedly connected to the inner wall of the connecting pipe (72). The outer wall of the connecting pipe (72) has openings at the top and bottom of the inner spiral plate (67).

[0012] Preferably, the discharge mechanism (7) includes a gear base (77), five of which are fixedly connected to the top of the corresponding gear base (77). The top of each gear base (77) is provided with a limiting structure on the outside of the base. The inner wall of the reaction chamber (1) is provided with an inner ring tooth (78) at the corresponding position of the gear base (77), which meshes with the gear base (77). The bottom of each gear base (77) is provided with a circular protrusion. The top of the rotating disk (69) is provided with a groove that mates with the bottom of the gear base (77).

[0013] Preferably, a rotating cover (71) is movably connected to the top of the reaction chamber (1). The rotating cover (71) is rotatably connected to the reaction chamber (1) through a sealed bearing. The bottom of the rotating cover (71) is fixedly connected to the top of the connecting pipe (72). Five rotating cylinders (73) are movably connected inside the rotating cover (71) through a sealed bearing. A closing cover (74) is movably connected to the top of the rotating cylinder (73) through a thread.

[0014] Preferably, a guide rod (75) is movably connected to the top of the gear base (77), and the guide rod (75) is rotatably connected to the gear base (77). The guide rod (75) is movably connected to the rotating cylinder (73). A sealing structure is provided on the guide rod (75) to prevent gas from flowing through the connection between the guide rod (75) and the rotating cylinder (73). A threaded rod (76) is movably connected to the top of the gear base (77), and the threaded rod (76) is rotatably connected to the gear base (77). The threaded rod (76) is movably connected to the rotating cylinder (73) by a thread. A sealing structure is provided between the rotating cylinder (73) and the gear base (77) to prevent gas from flowing through the connection between the rotating cylinder (73) and the threaded rod (76).

[0015] This invention provides a process and apparatus for preparing p-type silicon carbide crystals by vapor deposition. It has the following beneficial effects: 1. The process and apparatus for preparing P-type silicon carbide crystals by vapor deposition involves uniformly introducing a mixed gas into the reaction chamber through an opening. The rotating connecting pipe drives the inner spiral plate to rotate, pushing the mixed gas to spread outwards from the top of the rotating disk. This creates a slight circulation effect within the reaction chamber, dispersing the byproduct gas located at the bottom layer within the reaction chamber. This prevents the gas from hindering the reaction of the substrate within the reaction chamber, thereby increasing the preparation speed of silicon carbide.

[0016] 2. The process and apparatus for preparing P-type silicon carbide crystals by vapor deposition involves rotating disk 69 to drive gear substrate 77 to revolve around the center while rotating itself. This combined rotation makes the growth rate of each site on the substrate surface tend to be consistent, and the growth stress no longer accumulates in a specific direction, but is uniformly distributed throughout the substrate. At the same time, the centrifugal force generated by the rotation makes the grown silicon carbide lattice more compact, reduces lattice vacancies, reduces the defect rate of the product, and thus improves the preparation speed of silicon carbide.

[0017] 3. The process and apparatus for preparing P-type silicon carbide crystals by vapor deposition, after the reaction is completed, by turning the threaded rod, the top of the gear substrate is brought into contact with the bottom of the rotating cylinder, and the closed cover is opened. The reacted crystal can be taken out by the suction cup, which is convenient for placing a new substrate. In this process, the reaction chamber is not opened in a large area, the heat loss inside the reaction chamber is reduced when the substrate is taken out, and the reheating time is saved, which can indirectly improve the preparation speed of silicon carbide. Attached Figure Description

[0018] Figure 1 This is a front-view stereoscopic structural diagram of the present invention; Figure 2 for Figure 1 Schematic diagram of cross-section structure; Figure 3 This is a schematic diagram of the rear three-dimensional structure of the present invention; Figure 4 for Figure 2 Enlarged structural diagram of section B; Figure 5 for Figure 1 Enlarged structural diagram of section A in the middle; Figure 6 for Figure 2 Enlarged structural diagram of section C; Figure 7 for Figure 2 Enlarged structural diagram of section D in the middle; Figure 8 This is a schematic diagram of the rotating cylinder structure of the present invention.

[0019] In the diagram: 1. Reaction chamber; 2. Electric heater; 3. Exhaust pipe; 31. First solenoid valve; 32. Exhaust port; 4. Suction pipe; 5. Compound pump; 6. Gas delivery mechanism; 61. Ring guide groove; 62. Second solenoid valve; 63. Gas delivery pipe; 64. Mixing chamber; 641. Gas delivery motor; 642. Stirring rack; 65. Third solenoid valve; 66. Air inlet; 67. Inner spiral plate; 68. Rotating motor; 69. Rotating disc; 7. Discharge mechanism; 71. Rotating cover; 72. Connecting pipe; 73. Rotating cylinder; 74. Closing cover; 75. Guide rod; 76. Threaded rod; 77. Gear base; 78. Inner ring gear. Detailed Implementation

[0020] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0021] Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the invention, and should not be construed as limiting the invention.

[0022] Example 1: Please refer to Figure 1 This invention provides a technical solution: a process and apparatus for preparing P-type silicon carbide crystals by vapor deposition, comprising a process for preparing P-type silicon carbide crystals by vapor deposition: S1. Substrate pretreatment: Select a substrate and sequentially perform ultrasonic cleaning with organic solvent, etching with hydrofluoric acid-nitric acid mixture, and high-temperature treatment with high-purity hydrogen to obtain a clean substrate with a surface roughness Ra < 0.1 nm. S2. Preparation of reaction chamber: Fix the pretreated substrate on the base inside the corresponding device, seal the reaction chamber and evacuate to ≤0.001Pa, introduce high-purity hydrogen and heat to 1400-1450℃ at 5-10℃ / min for in-situ etching for 20-30min. S3. Buffer layer growth: Adjust the chamber pressure to 50-500 mbar and the temperature to 1550-1600℃, and introduce a first mixed gas containing silicon source, carbon source, hydrogen chloride and hydrogen to grow an intrinsic silicon carbide buffer layer with a thickness of 1-5 μm, wherein the carbon-silicon ratio is 1.0-1.3. S4. Alternating doping epitaxial growth: Maintain the temperature at 1550-1680℃, alternately introduce the first mixed gas and the second mixed gas containing Al doping source, cycle 5-50 times to form an epitaxial layer. In a single cycle, the first mixed gas grows a 2-100nm undoped layer and the second mixed gas grows a 2-50nm doped layer. S5. Cooling and wafer removal: Stop the supply of silicon source, carbon source and doping source, keep hydrogen flowing and cool down to below 1000℃ at 5-10℃ / min, switch to Ar gas to cool to room temperature, pressurize and remove the P-type silicon carbide crystal.

[0023] The organic solvent ultrasonic cleaning consisted of acetone ultrasonication for 15 min + isopropanol ultrasonication for 15 min, the volume ratio of hydrofluoric acid-nitric acid mixture was 1:3:10, and the high-purity hydrogen high-temperature treatment was carried out at 1500℃ for 30 min.

[0024] A 4-inch 4-hydrogen silicon carbide substrate was selected and immersed in acetone solution for ultrasonic cleaning at 28 kHz for 15 min to remove surface oil. It was then transferred to isopropanol solution and ultrasonically cleaned at 40 kHz for 15 min, rinsed three times with deionized water (3 min each time), and dried with nitrogen. Next, a mixed etching solution with a volume ratio of hydrofluoric acid:nitric acid:hydrogen = 1:3:10 was prepared, and the substrate was immersed in it for 5 min at room temperature to remove the natural oxide layer. It was then rinsed with deionized water until pH=7 and dried with nitrogen. The substrate was placed in a quartz boat in a tube furnace, and high-purity hydrogen was introduced at a flow rate of 100 SLM. The temperature was raised to 1500℃ and held for 30 min, then naturally cooled to room temperature to obtain a clean substrate with a surface roughness Ra=0.08 nm.

[0025] The pretreated substrate was fixed on the pedestal, then the CVD reaction chamber was closed, and the mechanical pump was started to evacuate to a vacuum level. 0.0005 Pa, maintained for 30 min, to capture water vapor and volatile impurities in the chamber using a liquid nitrogen cold trap; High-purity hydrogen gas (flow rate 80 SLM) was introduced to increase the chamber pressure to 100 mbar, and the temperature was increased to 1420°C at a rate of 8°C / min. Hydrogen gas was kept flowing while in-situ etching was performed for 25 min to remove residual trace contaminants on the substrate surface. Adjust the chamber pressure to 200 mbar, increase the temperature to 1580°C at 5°C / min, and pass the mixed gas through: Silicon source: silicon tetrachloride, flow rate 500 sccm; Carbon source: propane (99.999% purity), flow rate 600 sccm; Hydrogen chloride (purity 99.99%), flow rate 1500 sccm; Hydrogen (carrier gas), flow rate 120 SLM; Control the carbon-silicon ratio to 1.2; The above parameters were maintained for 20 min to form an intrinsic silicon carbide buffer layer with a thickness of 3 μm, at a growth rate of 15 μm / h. Maintaining a chamber pressure of 200 mbar and a temperature of 1620 °C, the alternating doping mode was activated and cycled 20 times. The first mixed gas was continuously introduced to grow an intrinsic silicon carbide isolation layer with a thickness of 50 nm for 2 min. The process was then switched to the second mixed gas, in which silicon tetrachloride flow rate was 500 sccm, propane flow rate was 600 sccm, and hydrogen flow rate was 120 SLM. Trimethylaluminum (TMA, purity 99.999%) was delivered by bubbling hydrogen at a bubbling temperature of 25 °C and a TMA flow rate of 100 sccm to grow an Al doped layer with a thickness of 30 nm for 1.2 min. The total epitaxial growth time was 64 min, forming a P-type silicon carbide epitaxial layer with a total thickness of 1.6 μm, and the average growth rate was 15 μm / h.

[0026] Stop the flow of silicon tetrachloride, propane, and TMA. Maintain a hydrogen flow rate of 120 SLM and a chamber pressure of 300 mbar, and cool down to 900°C at a rate of 8°C / min. Switch to high-purity Ar gas (99.999% purity) at a flow rate of 100 SLM and use forced convection cooling. The cooling rate is 5 K / min in the 900-500°C range, and the temperature is allowed to cool naturally to room temperature below 500°C. Slowly introduce Ar gas to atmospheric pressure (pressure increase rate ≤ 0.05 MPa / min), open the reaction chamber, and remove the P-type silicon carbide crystal through a ring-shaped edge vacuum chuck (negative pressure 0.03 MPa).

[0027] Example 2: Please refer to Figure 1-4 Based on Embodiment 1, the present invention provides a technical solution: An apparatus for preparing P-type silicon carbide crystals by vapor deposition, the apparatus includes a reaction chamber 1, a gas supply mechanism 6 fixedly connected to the outer wall of the reaction chamber 1, a material discharge mechanism 7 movably connected to the top of the reaction chamber 1, an exhaust pipe 3 fixedly connected to the bottom of the reaction chamber 1, an extraction pipe 4 fixedly connected to the bottom of the reaction chamber 1, a composite pump 5 fixedly connected to the back of the extraction pipe 4, an electric heater 2 fixedly connected to the outer wall of the reaction chamber 1, and the gas supply mechanism 6 includes: Rotary motor 68 is fixedly connected to the bottom of reaction chamber 1; A rotating disk 69 is located at the bottom of the reaction chamber 1, and the top output shaft of the rotating motor 68 passes through the bottom of the reaction chamber 1 and is fixedly connected to the bottom of the rotating disk 69. Five bases are provided on the top of the rotating disk 69.

[0028] The pretreated substrate is placed on top of the substrate, and then reaction chamber 1 is sealed. The compound pump 5 is started to extract the gas inside the reaction chamber 1 through the gas extraction pipe 4, and the gas pressure inside the reaction chamber 1 is reduced to the corresponding value by the electric heater 2. Then, the gas is delivered into the reaction chamber 1 through the gas delivery mechanism 6 to carry out the reaction; During the reaction, the rotating disk 69 is driven to rotate by the rotating motor 68, which in turn drives the five corresponding substrates to rotate, thereby causing the substrates to rotate and detach from the byproduct gas at the original reaction site, thus preventing the gas from inhibiting the reaction.

[0029] A first solenoid valve 31 is fixedly connected to the left side of the exhaust pipe 3, and an outlet 32 ​​is fixedly connected to the left side of the first solenoid valve 31.

[0030] After the reaction is completed, inert gas is sent into the reaction chamber 1 through the gas supply mechanism 6 by connecting the outlet 32 ​​with the corresponding waste gas treatment device, and the first solenoid valve 31 is opened so that the gas squeezes the waste gas in the reaction chamber 1 through the outlet 32 ​​into the waste gas treatment device.

[0031] The uniform delivery of the mixed gas into the reaction chamber 1 facilitates contact between the gas and the substrate, promoting the reaction. An annular guide groove 61 is fixedly connected to the outer wall of the reaction chamber 1. Multiple air inlets are located on the inner wall of the reaction chamber 1 at positions corresponding to the annular guide groove 61. A second solenoid valve 62 is fixedly connected to the outer wall of the annular guide groove 61. An air supply pipe 63 is fixedly connected to the right side of the second solenoid valve 62. A mixing chamber 64 is fixedly connected to the right end of the air supply pipe 63. A third solenoid valve 65 is fixedly connected to the top of the mixing chamber 64. An air inlet 66 is fixedly connected to the top of the third solenoid valve 65.

[0032] The device for feeding the mixed gas is connected to the air inlet 66, and the mixing chamber 64 is opened to allow the mixed gas to enter the mixing chamber 64. Then the third solenoid valve 65 is closed, and then the second solenoid valve 62 is opened. Due to the negative pressure inside the second solenoid valve 62, the mixed gas inside the mixing chamber 64 is drawn into the reaction chamber 1 through the opening on the reaction chamber 1, so that the mixed gas can react.

[0033] A gas supply motor 641 is fixedly connected to the bottom of the gas mixing chamber 64, and a stirring rack 642 is installed inside the gas mixing chamber 64. The top output shaft of the gas supply motor 641 passes through the bottom of the gas mixing chamber 64 and is fixedly connected to the bottom of the stirring rack 642.

[0034] After the mixed gas is fed into the mixing chamber 64, the gas supply motor 641 is started, which drives the stirring frame 642 to stir the mixed gas, so that the various gases in the mixed gas are evenly distributed and the gas reaction is promoted.

[0035] After the mixed gas enters the reaction chamber 1, it reacts with the substrate, and the reaction byproducts remain near the substrate, which will inhibit the reaction. A connecting pipe 72 is fixedly connected to the top of the rotating disk 69, and an inner spiral plate 67 is fixedly connected to the inner wall of the connecting pipe 72. Openings are provided on the outer wall of the connecting pipe 72 at the top and bottom of the inner spiral plate 67.

[0036] During the rotation of the rotating disk 69, the connecting pipe 72 will rotate synchronously, which in turn will cause the inner spiral plate 67 inside the connecting pipe 72 to rotate. The rotation of the inner spiral plate 67 pushes the gas to the bottom, so that the opening above the connecting pipe 72 draws in the mixed gas entering from the top of the reaction chamber 1 and discharges the gas through the bottom of the connecting pipe 72. This creates a slight circulation effect in the gas inside the reaction chamber 1, pushing the mixed gas to spread outwards from the top of the rotating disk 69 and dispersing the by-product gas located at the bottom layer inside the reaction chamber 1, thus preventing the gas from hindering the reaction of the substrate inside the reaction chamber 1.

[0037] Example 3: Please refer to Figure 1-8 Based on Embodiment 1 and Embodiment 2, the present invention provides a technical solution: The reaction requires extremely high temperatures. When the substrate is removed from the reaction chamber 1, the temperature inside the reaction chamber 1 will drop. When the next reaction is carried out, the temperature needs to be raised back to the corresponding position. This process will consume a lot of time and resources.

[0038] The discharge mechanism 7 includes a gear base 77, of which five gear bases 77 are provided. Each base is fixedly connected to the top of the corresponding gear base 77. The top of each gear base 77 is provided with a limiting structure on the outside of the base. The inner wall of the reaction chamber 1 is provided with an inner ring tooth 78 at the corresponding position of the gear base 77. The inner ring tooth 78 meshes with the gear base 77. The bottom of each gear base 77 is provided with a circular protrusion. The top of the rotating disk 69 is provided with a groove that mates with the bottom of the gear base 77.

[0039] The pre-treated substrate is placed on the top of the gear substrate 77 and secured in the corresponding mating groove. When the rotating disk 69 rotates, the gear substrate 77 rotates through the engagement of the groove with the protrusion at the bottom of the gear substrate 77. At the same time, the gear substrate 77 contacts the inner ring tooth 78 during rotation, which further causes the gear substrate 77 to rotate. During this process, the resulting composite rotation makes the growth rate of each site on the substrate surface tend to be consistent, and the growth stress no longer accumulates in a directional manner, but is uniformly distributed throughout the substrate. Meanwhile, the centrifugal force generated by the rotation makes the grown silicon carbide lattice more compact, reduces lattice vacancies, and reduces the defect rate of the product.

[0040] A rotating cover 71 is movably connected to the top of the reaction chamber 1. The rotating cover 71 is rotatably connected to the reaction chamber 1 through a sealed bearing. The bottom of the rotating cover 71 is fixedly connected to the top of the connecting pipe 72. Five rotating cylinders 73 are movably connected inside the rotating cover 71 through sealed bearings. A closing cover 74 is movably connected to the top of the rotating cylinder 73 through a thread.

[0041] A guide rod 75 is movably connected to the top of the gear base 77, and the guide rod 75 is rotatably connected to the gear base 77. The guide rod 75 is movably connected to the rotating cylinder 73. A sealing structure is provided on the guide rod 75 to prevent gas from flowing through the connection between the guide rod 75 and the rotating cylinder 73. A threaded rod 76 is movably connected to the top of the gear base 77, and the threaded rod 76 is rotatably connected to the gear base 77. The threaded rod 76 is movably connected to the rotating cylinder 73 via a thread, and a sealing structure is provided between the rotating cylinder 73 and the gear base 77 to prevent gas from flowing through the connection between the rotating cylinder 73 and the threaded rod 76. A corresponding notch is provided at the top of the threaded rod 76, and the threaded rod 76 is rotated by turning it with a corresponding tool. Sealing strips are provided at the bottom and bottom of the rotating cylinder 73, which can play a sealing role when in contact with the rotating cylinder 73 and the gear base 77.

[0042] After the reaction is complete, the threaded rod 76 is turned so that the threaded rod 76 lifts the gear base 77 through the thread. The gear base 77 is rotated continuously so that the top of the gear base 77 fits against the bottom of the rotating cylinder 73. At this time, the closing cover 74 is opened so that the reacted crystal can be taken out by the suction cup and then a new substrate can be placed in. After that, the closing cover 74 can be closed again and the threaded rod 76 is turned again so that the gear base 77 is lowered. During the process of lowering the gear base 77, the rotating cylinder 73 is pushed to rotate, so that the edge of the gear base 77 re-engages with the inner ring tooth 78. In this process, the reaction chamber 1 is not opened to a large extent, the heat loss inside the reaction chamber 1 is reduced when the substrate is removed, and the reheating time is saved.

[0043] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for preparing P-type silicon carbide crystals by a vapor deposition method, characterized in that: S1, substrate pretreatment: selecting a substrate, sequentially performing ultrasonic cleaning with an organic solvent, etching with a hydrofluoric acid-nitric acid mixture, and high-temperature treatment with high-purity hydrogen, to obtain a clean substrate with a surface roughness Ra < 0.1 nm; S2, reaction chamber preparation: fixing the pretreated substrate on a susceptor inside a corresponding device, sealing the reaction chamber, vacuumizing to ≤0.001 Pa, introducing high-purity hydrogen, and heating at 5-10 ℃ / min to 1400-1450 ℃ for in-situ etching for 20-30 min; S3, buffer layer growth: adjusting the chamber pressure to 50-500 mbar and the temperature to 1550-1600 ℃, introducing a first mixed gas containing a silicon source, a carbon source, hydrogen chloride, and hydrogen, and growing a 1-5 μm thick intrinsic silicon carbide buffer layer with a carbon-silicon ratio of 1.0-1.3; S4, alternating doping epitaxial growth: maintaining the temperature at 1550-1680 ℃, alternatingly introducing the first mixed gas and a second mixed gas containing an Al doping source, and forming an epitaxial layer by 5-50 cycles, in which the first mixed gas grows a 2-100 nm undoped layer and the second mixed gas grows a 2-50 nm doped layer in each cycle; S5, cooling and wafer removal: stopping the supply of the silicon source, the carbon source, and the doping source, maintaining the hydrogen flow, cooling at 5-10 ℃ / min to below 1000 ℃, switching to Ar cooling to room temperature, and removing the P-type silicon carbide crystal after pressurization. The ultrasonic cleaning with the organic solvent is acetone ultrasonic cleaning for 15 min + isopropyl alcohol ultrasonic cleaning for 15 min, the volume ratio of the hydrofluoric acid-nitric acid mixture is 1:3:10, and the high-purity hydrogen high-temperature treatment temperature is 1500 ℃ with a 30 min holding time. The device comprises a reaction chamber (1), a gas feeding mechanism (6) fixedly connected to the outer wall of the reaction chamber (1), a discharge mechanism (7) movably connected to the top of the reaction chamber (1), an exhaust pipe (3) fixedly connected to the bottom of the reaction chamber (1), an air suction pipe (4) fixedly connected to the bottom of the reaction chamber (1), a compound pump (5) fixedly connected to the back of the air suction pipe (4), an electric heater (2) fixedly connected to the outer wall of the reaction chamber (1), and the gas feeding mechanism (6) comprises: a rotating motor (68) fixedly connected to the bottom of the reaction chamber (1); a rotating disc (69) arranged at the inner bottom of the reaction chamber (1), wherein the top output shaft of the rotating motor (68) penetrates the bottom of the reaction chamber (1) and is fixedly connected to the bottom of the rotating disc (69), and the top of the rotating disc (69) is provided with five substrates. A first electromagnetic valve (31) is fixedly connected to the left side of the exhaust pipe (3), and a discharge port (32) is fixedly connected to the left side of the first electromagnetic valve (31).

2. The process for preparing P-type silicon carbide crystal by vapor deposition method according to claim 1, wherein: ​ 3. An apparatus for producing P-type silicon carbide crystals by a vapor deposition method, characterized by comprising: ​ ​ ​ 4. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 3, wherein: ​ 5. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 3, wherein: The outer wall of the reaction cavity (1) is fixedly connected with a ring guide groove (61), a plurality of gas inlet holes are arranged on the inner wall of the reaction cavity (1) at positions corresponding to the ring guide groove (61), the outer wall of the ring guide groove (61) is fixedly connected with a second electromagnetic valve (62), the right side of the second electromagnetic valve (62) is fixedly connected with a gas supply pipe (63), the right end of the gas supply pipe (63) is fixedly connected with a gas mixing chamber (64), the top of the gas mixing chamber (64) is fixedly connected with a third electromagnetic valve (65), and the top of the third electromagnetic valve (65) is fixedly connected with a gas inlet (66).

6. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 5, wherein: The bottom of the gas mixing chamber (64) is fixedly connected with a gas supply motor (641), and the inside of the gas mixing chamber (64) is provided with a stirring frame (642). The top output shaft of the gas supply motor (641) penetrates through the bottom of the gas mixing chamber (64) and is fixedly connected with the bottom of the stirring frame (642).

7. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 3, wherein: The top of the rotating disc (69) is fixedly connected with a connecting pipe (72), the inner wall of the connecting pipe (72) is fixedly connected with an inner spiral plate (67), and the outer wall of the connecting pipe (72) is provided with openings at the top and the bottom of the inner spiral plate (67).

8. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 3, wherein: The discharge mechanism (7) comprises gear bases (77), five gear bases (77) are arranged, the top of each gear base (77) is fixedly connected with a corresponding base, limit structures are arranged on the outside of the top of each gear base (77), the inner wall of the reaction cavity (1) is provided with inner ring teeth (78) at positions corresponding to the gear bases (77), the inner ring teeth (78) are engaged with the gear bases (77), the bottom of each gear base (77) is provided with a circular protrusion, and the top of the rotating disc (69) is provided with a groove matched with the bottom of the gear base (77).

9. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 8, wherein: The top of the reaction cavity (1) is movably connected with a rotating cover (71), the rotating cover (71) is rotatably connected with the reaction cavity (1) through a sealing bearing, the bottom of the rotating cover (71) is fixedly connected with the top of the connecting pipe (72), and the inside of the rotating cover (71) is movably connected with five rotating cylinders (73) through sealing bearings.

10. The apparatus for preparing P-type silicon carbide crystal by vapor deposition method according to claim 9, wherein: The top of the gear base (77) is movably connected with a guide rod (75), and the guide rod (75) is rotatably connected with the gear base (77), the guide rod (75) is movably connected with the rotating cylinder (73), a sealing structure is arranged on the guide rod (75), so that gas flow can be avoided at the connection between the guide rod (75) and the rotating cylinder (73), the top of the gear base (77) is movably connected with a threaded rod (76), and the threaded rod (76) is rotatably connected with the gear base (77), the threaded rod (76) is movably connected with the rotating cylinder (73) through threads, and a sealing structure is arranged between the rotating cylinder (73) and the gear base (77), so that gas flow can be avoided at the connection between the rotating cylinder (73) and the threaded rod (76).

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