Silicon carbide single crystal growth equipment and preparation process thereof

Abstract

The invention discloses silicon carbide single crystal growth equipment which comprises a furnace body, a heat preservation layer, crucibles arranged in the heat preservation layer and a resistance heater, the crucibles comprise an upper crucible and a lower crucible, a communicated gas phase conveying pipe is arranged between the upper crucible and the lower crucible, and the gas phase conveying pipe is arranged between an upper crucible body and a lower crucible cover in a communicated mode; the resistance heater comprises an upper heating body arranged on the periphery of the upper crucible, a lower heating body arranged on the periphery of the lower crucible and a middle heating body arranged on the periphery of the gas phase conveying pipe. The crucible comprises the upper crucible and the lower crucible, and the gas phase conveying pipe is arranged between the upper crucible and the lower crucible, so that the area space between the seed crystal and the silicon carbide polycrystalline raw material in the closed space in the crucible becomes smaller, and the temperature gradient is not easy to generate; and meanwhile, the gas-phase silicon carbide in each area with temperature difference in the lower crucible is fully mixed in the gas-phase conveying pipe to form gas-phase silicon carbide with uniform temperature, so that the quality of the silicon carbide single crystal is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide semiconductors, and in particular to a silicon carbide single crystal growth device and a preparation process thereof. Background Art

[0002] As an important third-generation wide bandgap semiconductor material, silicon carbide (SiC) single crystal has broad application prospects in power electronic devices used under extreme conditions such as high frequency, high power, radiation resistance, corrosion resistance, and high temperature resistance because of its advantages such as wide bandgap, high thermal conductivity, high critical breakdown electric field, and high electron saturation migration rate.

[0003] The physical vapor transport method (PVT method) is a commonly used method for growing silicon carbide single crystals. It mainly involves placing silicon carbide polycrystalline raw materials at the bottom of a cylindrical graphite crucible body, covering the graphite crucible body with a graphite crucible cover to form a closed space, and installing silicon carbide seed crystals on the lower surface of the graphite crucible cover. By heating the system consisting of the graphite crucible body and the graphite crucible cover, the silicon carbide polycrystalline raw materials in the graphite crucible body are sublimated, and a suitable temperature gradient is maintained between the silicon carbide polycrystalline raw materials and the silicon carbide seed crystals. The sublimated silicon carbide particles will be deposited and grown on the silicon carbide seed crystals, thereby obtaining silicon carbide single crystals.

[0004] Since the growth of silicon carbide single crystals is particularly affected by temperature differences, the control requirements for the temperature in the crystal growth area are very strict. It is necessary to ensure that the temperature of the shared interface at the same height is consistent and controlled within a very small temperature difference range; especially for large-sized silicon carbide single crystals, the internal space of the crucible is large, resulting in the silicon carbide gas temperature near the center of the crucible being lower than the silicon carbide gas temperature near the crucible wall, causing the crystallization of each area on the seed crystal to be asynchronous, making it difficult to guarantee the quality of the silicon carbide single crystal.

[0005] Constructing a reasonable thermal field structure in the silicon carbide single crystal growth equipment is an important condition for preparing high-quality silicon carbide single crystals. It directly affects the quality, size and final device performance of the crystal. Different thermal field structures will produce different temperature distributions, thus affecting the radial uniformity and axial temperature gradient of the silicon carbide crystal. Existing silicon carbide single crystal growth equipment usually includes two thermal field structures: single crucible induction heating thermal field and single crucible resistance heating thermal field.

[0006] In the prior art, the single crucible induction-heated silicon carbide single crystal growth equipment usually includes an insulation layer arranged in the furnace body, a crucible body and a crucible cover arranged in the insulation layer, and an induction coil arranged outside the insulation layer. A silicon carbide seed crystal is arranged on the lower surface of the crucible cover, and silicon carbide polycrystalline raw materials are placed in the crucible body. By applying high-frequency alternating current to the induction coil, the induction coil generates an alternating magnetic field, thereby generating eddy currents on the crucible body. The crucible body heats the silicon carbide polycrystalline raw materials to sublime them, and re-deposits and crystallizes on the silicon carbide seed crystal to obtain a silicon carbide single crystal. However, this equipment and preparation method cannot achieve multi-zone temperature control, and the growth of silicon carbide single crystals is particularly sensitive to changes in the temperature field. It is impossible to evenly control the temperature distribution of medium and large-sized working areas, resulting in uneven temperature distribution inside the crucible, which is prone to sintering and agglomeration and over-carbonization, affecting the quality and performance of silicon carbide single crystals.

[0007] Compared with the single crucible induction heating silicon carbide single crystal growth equipment, the single crucible resistance heating silicon carbide single crystal growth equipment can achieve multi-zone temperature control. Specifically, the single crucible resistance heating silicon carbide single crystal growth equipment mainly includes an insulation layer arranged in the furnace body, a crucible located in the insulation layer, and a resistance heater arranged between the insulation layer and the crucible. The crucible is heated by the resistance heater, and the crucible is evenly heated to melt the silicon carbide source powder inside, so that it sublimates and recrystallizes at the silicon carbide seed crystal located at the bottom of the crucible cover, thereby obtaining a silicon carbide single crystal. The resistance heater is usually arranged around the crucible, including the side, top and bottom surfaces, to ensure that the crucible is evenly heated.

[0008] Since the growth of silicon carbide single crystal is particularly sensitive to changes in the temperature field, and the central area in the confined space inside the crucible is farther away from the heater than the area near the crucible wall, the temperature of the gas-phase silicon carbide in the central area is slightly lower than the temperature of the gas-phase silicon carbide near the crucible wall, which easily forms a temperature gradient. The crystallization rate of the gas-phase silicon carbide at the seed crystal is inconsistent, which affects the quality of the silicon carbide single crystal, especially the growth of large-sized silicon carbide single crystals. Summary of the invention

[0009] The technical problem to be solved by the present invention is to provide a silicon carbide single crystal growth device which can uniformly heat the silicon carbide gas in various regions of the internal space of the crucible in the silicon carbide single crystal growth device in the prior art, thereby solving the problem that the quality of the silicon carbide single crystal is difficult to ensure due to the uneven heating of the silicon carbide gas in various regions of the internal space of the crucible.

[0010] The technical solution to the technical problem of the present invention is: construct a silicon carbide single crystal growth device, including a furnace body, an insulation layer, a crucible and a resistance heater arranged in the insulation layer, the crucible includes an upper crucible and a lower crucible, a connected gas phase delivery pipe is provided between the upper and lower crucibles, the upper crucible includes an upper crucible body and an upper crucible cover, the lower crucible includes a lower crucible body and a lower crucible cover, and the gas phase delivery pipe is connected and arranged between the upper crucible body and the lower crucible cover.

[0011] Furthermore, the resistance heater includes an upper heating body arranged around the upper crucible, a lower heating body arranged around the lower crucible and an intermediate heating body arranged around the gas phase delivery pipe; further ensuring that the temperature in the gas phase delivery pipe and the upper and lower crucibles is maintained within a consistent range.

[0012] Furthermore, a crucible lifting device is provided at the bottom of the lower crucible body, and the crucible lifting device includes a first lifting guide rod arranged at the bottom of the lower crucible body and passing through the insulation layer and the furnace body, a first driving motor arranged at the bottom of the furnace body, a first screw rod driven by the first driving motor, and a first slider sleeved on the first screw rod, and the first slider is fixed to the bottom end of the first lifting guide rod; the first screw rod is driven to rotate by the first driving motor, so that the first slider is lifted and lowered along the first screw rod, thereby driving the first lifting guide rod to slide up and down, so that the crucible can move up and down as needed to ensure that the crucible is positioned at a suitable position within the heat field generated by the resistance heater.

[0013] Furthermore, it also includes a control system, which is electrically connected to the first drive motor, and the control system controls the first drive motor to drive the first lifting guide rod to rise and fall at a preset speed; thereby, the first lifting guide rod can be automatically controlled according to the preset crystal growth interface position change, so as to control the crystal growth interface of the seed crystal to always be located at a vertical position in the crucible that meets the process temperature, thereby further ensuring the growth quality of the silicon carbide single crystal.

[0014] Furthermore, a crystal heat exchange device is provided directly above the upper crucible cover, and a crystal heat exchange device is provided directly above the upper crucible cover, and the crystal heat exchange device includes a heat exchange plate matching the top surface of the upper crucible cover, a second lifting guide rod passing through the insulation layer and the furnace body and connected to the heat exchange plate, a second drive motor arranged on the top of the furnace body, a second screw rod driven by the second drive motor, and a second slider sleeved on the second screw rod, and the second slider is fixed to the top end of the second lifting guide rod; the second drive motor drives the second screw rod to rotate, so that the second slider is lifted and lowered along the second screw rod, thereby driving the second lifting guide rod to slide up and down, and the second lifting guide rod drives the heat exchange plate to lift and lower, so that the heat exchange plate contacts or separates from the top surface of the upper crucible cover, and timely reduces the temperature of the seed crystal fixed on the bottom surface of the upper crucible cover, and controls the seed crystal temperature to meet the process requirements.

[0015] Furthermore, the crystal heat exchange device also includes a temperature measuring device capable of detecting the temperature of the upper crucible cover, the temperature measuring device including an infrared thermometer with a detection head arranged at the top of the second lifting guide rod, and a temperature measuring channel arranged in the second lifting guide rod, one end of the temperature measuring channel passes through the heat exchange plate and faces the top surface of the upper crucible cover, and the other end matches the infrared thermometer; the temperature of the top surface of the upper crucible cover detected by the detection head of the infrared thermometer through the temperature measuring channel in time can determine the temperature of the seed crystal.

[0016] Furthermore, it also includes a control system, which is electrically connected to the second drive motor and the infrared thermometer. The control system controls the second drive motor to drive the second screw to rotate according to the temperature of the top surface of the upper crucible cover detected by the infrared thermometer, so as to drive the heat exchange plate to rise and fall; the control system can automatically control the heat exchange plate to contact or separate from the top surface of the upper crucible cover according to the temperature detected by the infrared thermometer, thereby realizing automatic adjustment of the seed crystal temperature.

[0017] Furthermore, the insulation layer includes an upper movable insulation block, which is fixed around the second lifting guide rod and the heat exchange plate; so that the upper movable insulation block can be lifted and lowered together with the heat exchange plate, which not only ensures the thermal sealing of the internal space of the insulation layer, but also does not affect the lifting and lowering movement of the heat exchange plate.

[0018] Another technical problem to be solved by the present invention is to provide a process for preparing silicon carbide single crystals in order to solve the problem that the quality of silicon carbide single crystals is difficult to ensure due to uneven heating of silicon carbide gas in the prior art.

[0019] The technical solution of the technical problem of the present invention is: construct a preparation process of silicon carbide single crystal, comprising the following steps: S10. Constructing the silicon carbide single crystal growth apparatus as described above; S20. The silicon carbide seed crystal is fixed to the bottom of the upper crucible cover; the silicon carbide polycrystalline raw material is placed in the lower crucible to complete the furnace; S30. Evacuate the equipment so that the vacuum degree in the furnace reaches below 0.1 Pa; S40. The temperature of the furnace chamber is raised in stages and the vacuum of the furnace is maintained below 0.1 Pa; S50. Maintain the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, and at the same time stop evacuating the furnace chamber and fill it with inert gas, and increase the pressure to 10-60kPa, and maintain the pressure for 3-5 hours; S60. Maintaining the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, while gradually reducing the pressure to reduce the furnace chamber pressure to 100-3000Pa within 3-10 hours; S70. According to the size requirements of silicon carbide single crystal growth, maintaining the temperature and pressure of the furnace chamber unchanged for 50-300 hours; while adjusting the position of the crucible according to the position of the detected crystal growth interface; S80. After the growth of the silicon carbide single crystal is completed, the pressure is released and the temperature is lowered.

[0020] The implementation of the silicon carbide single crystal growth equipment and its preparation process described in the present invention has the following beneficial effects: by setting a crucible including an upper crucible and a lower crucible, and setting a gas phase delivery pipe between the upper and lower crucibles, the area between the seed crystal and the silicon carbide polycrystalline raw material in the closed space in the crucible becomes smaller, the gas phase silicon carbide here is less, and it is not easy to generate a temperature gradient; at the same time, the gas phase silicon carbide in each area with a temperature difference in the lower crucible is fully mixed in the gas phase delivery pipe to form a gas phase silicon carbide with a uniform temperature; thereby ensuring that the crystallization speed of the gas phase silicon carbide at the seed crystal is consistent, improving the radial uniformity of the silicon carbide single crystal, and thus ensuring the quality of the silicon carbide single crystal. In addition, the present invention further enhances the equipment's fine control of the temperature of each area in the crucible by setting an intermediate heating body around the gas phase delivery pipe, setting a crucible lifting device at the bottom of the lower crucible body, and setting a crystal heat exchange device just above the upper crucible cover, thereby avoiding the influence of the temperature difference in each area on the growth quality of the silicon carbide single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Shown is a schematic structural diagram of a preferred embodiment of the silicon carbide single crystal growth device of the present invention; Figure 2 Shown Figure 1 An enlarged schematic diagram of part I; Figure 3 Shown Figure 1 An enlarged schematic diagram of Part II; Figure 4 Shown Figure 1 An enlarged schematic diagram of part III. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] It should also be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they should not be understood as limiting the present invention.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art of the present invention. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0025] like Figure 1 , 2 As shown in Figures 3 and 4, in a preferred embodiment of the silicon carbide single crystal growth device of the present invention, it mainly includes a furnace body 10, a heat preservation layer 20, a crucible 30 and a resistance heater 40. Among them, the furnace body 10 can be provided with an upper furnace cover 11 and / or a lower furnace cover 12 as required. After removing the upper furnace cover 11 and / or the lower furnace cover 12, the furnace body 10 can be quickly opened. Before preparing the silicon carbide single crystal, the silicon carbide polycrystalline raw material 3 is placed in the crucible 30 and the silicon carbide seed crystal 1 is installed in the crucible 30; at the same time, the upper furnace cover 11 and / or the lower furnace cover 12 are reliably sealed on the furnace body 10 to ensure that the space inside the furnace body 10 is airtight during the preparation process to prevent the silicon carbide in the furnace body 10 from being contaminated. A furnace body support 13 can also be provided as required to support the entire furnace body 10. The heat-insulating layer 20 is evenly attached to the inner wall of the furnace body and forms a heat-insulating cavity 21 inside the furnace body. The crucible 30 and the resistance heater 40 are arranged in the heat-insulating cavity 21 , wherein the resistance heater 40 is arranged around the crucible 30 .

[0026] like Figure 1 , 3As shown, in this preferred embodiment, the crucible preferably includes an upper crucible 31 and a lower crucible 32, and a gas phase delivery pipe 33 is provided between the upper crucible 31 and the lower crucible 32. Specifically, the upper crucible 31 can be provided to include an upper crucible cover 31a and an upper crucible body 31b, and the upper crucible cover 31a is sealed and arranged at the upper end opening of the upper crucible body 31b; the lower crucible 32 can be provided to include a lower crucible cover 32a and a lower crucible body 32b, and the lower crucible cover 32a is sealed and arranged at the upper end opening of the lower crucible body 32b. The gas phase delivery pipe 33 is provided to communicate between the bottom of the upper crucible body 31b and the lower crucible cover 32a. The silicon carbide polycrystalline raw material 3 is placed in the lower crucible body 32b of the lower crucible, and the silicon carbide seed crystal 1 is fixedly arranged on the bottom surface of the upper crucible cover 31a. In this preferred embodiment, the upper crucible 31, the lower crucible 32 and the gas phase delivery pipe 33 are preferably made of high-purity graphite material treated with a surface coating to ensure that each area in the crucible can be heated evenly when heated.

[0027] When the lower crucible 32 is heated by the resistance heater 40, the polycrystalline silicon carbide raw material 3 in the lower crucible 32 is sublimated into gaseous silicon carbide, and the gaseous silicon carbide enters the upper crucible body 31b through the gas phase delivery pipe 33 and evenly fills the space in the upper crucible 31. The gaseous silicon carbide gradually cools and recrystallizes at the silicon carbide seed crystal 1 to form a silicon carbide single crystal. When the resistance heater 40 heats the crucible, the gaseous silicon carbide generated in the lower crucible 32 is gathered in the gas phase delivery pipe 33, and the gaseous silicon carbide in each area with a temperature difference in the lower crucible 32 is fully mixed in the gas phase delivery pipe 33 to form gaseous silicon carbide with a uniform temperature. It is best to set the lower crucible cover 32a to a trumpet shape with a small top and a large bottom, so that the gaseous silicon carbide in each area of ​​the lower crucible 32 can be quickly gathered in the gas phase delivery pipe 33. It is best to set the bottom of the upper crucible body 31b to be a trumpet shape with a larger top and a smaller bottom, so that the gas phase silicon carbide with uniform temperature delivered by the gas phase delivery pipe 33 can quickly diffuse into the internal space of the upper crucible 31 and grow evenly on the silicon carbide seed crystal 1.

[0028] In this preferred embodiment, the resistance heater 40 preferably includes an upper heating body 41, a lower heating body 42 and an intermediate heating body 43. The lower heating body 42 is preferably arranged around the lower crucible 32 to heat the lower crucible body 32b so that the silicon carbide polycrystalline raw material 3 in the lower crucible 32 can be sublimated into gas-phase silicon carbide. The intermediate heating body 43 is preferably arranged around the gas-phase delivery pipe 33 so as to control the temperature of the gas-phase silicon carbide in the gas-phase delivery pipe 33 to meet the process requirements. The upper heating body 41 is preferably arranged around the upper crucible 31 to heat the upper crucible 31. After the upper crucible 31 is heated, it can evenly radiate heat to each area in the upper crucible body 31b to maintain the temperature of the gas-phase silicon carbide in the upper crucible 31, control the temperature of the crystallization interface at the silicon carbide seed crystal 1, and ensure the growth quality of the silicon carbide single crystal. A bottom heating body 44 may be provided at the bottom of the lower crucible 32 as required, so that the lower crucible body 32 b is heated evenly, further reducing the temperature difference of gas phase silicon carbide in various regions in the lower crucible 32 .

[0029] The upper heating body 41, the lower heating body 42, the middle heating body 43 and the bottom heating body 44 are all individually controlled by a control system (not shown in the figure) so as to heat each area in the crucible as needed so that the temperature of each area meets the process requirements.

[0030] like Figure 1 , 4 As shown, in this preferred embodiment, a crucible lifting device 50 is preferably provided at the bottom of the lower crucible body 32b to drive the crucible to rise and fall, so as to adjust the height position of the crucible in the heat preservation cavity 21, and control the upper crystal growth interface of the silicon carbide seed crystal 1 in the upper crucible 31 to always be located in the temperature region required by the process. Specifically, the crucible lifting device 50 is preferably provided to include a first lifting guide rod 51, a first drive motor 52, a first screw rod 53, and a first slider 54. The first lifting guide rod 51 is arranged to pass through the heat preservation layer 20 and the furnace body 10, and can slide up and down relative to the heat preservation layer 20 and the furnace body 10, and its top end is arranged at the bottom of the lower crucible body 32b and the other end is located outside the furnace body 10. The first drive motor 52 is arranged at the bottom of the furnace body 10, and can be a servo motor or a variable frequency motor. The first screw rod 53 is rotatably arranged at the bottom of the furnace body 10, and is driven to rotate by the first drive motor 52. Specifically, the first drive motor 52 can be arranged at the end of the first screw rod 53. The first slider 54 is sleeved on the first screw rod 53 and fixed to the bottom end of the first lifting guide rod 51. Specifically, a threaded hole matching the first screw rod 53 can be set at the center of the first slider 54, and the first slider 54 is fixed to the side of the first lifting guide rod 51. When the first driving motor 52 drives the first screw rod 53 to rotate, the first slider 54 can be lifted and lowered along the first screw rod 53, thereby driving the first lifting guide rod 51 to slide up and down, so that the crucible located at the top of the first lifting guide rod 51 can also move up and down.

[0031] In this preferred embodiment, a control system (not shown in the figure) is also included, which is electrically connected to the first drive motor. The process conditions are adjusted to control the growth speed of silicon carbide at a preset speed, thereby obtaining the position information of the growth interface in the upper crucible 31; the control system can automatically control the first drive motor 52 to drive the first lifting guide rod 51 to rise and fall according to the position change of the growth interface, thereby driving the crucible to rise and fall, so as to automatically control the growth interface of the silicon carbide seed crystal 1 to always be in the temperature area required by the process, further ensuring the growth quality of the silicon carbide single crystal 2.

[0032] like Figure 1 , 2 As shown, in this preferred embodiment, a crystal heat exchange device 60 is preferably arranged just above the upper crucible cover 31a, so as to timely adjust the temperature of the upper crucible cover 31a, that is, adjust the temperature of the bottom plate of the silicon carbide seed crystal 1, so that the temperature of the silicon carbide seed crystal 1 meets the process requirements. Specifically, the crystal heat exchange device 60 is preferably arranged to include a heat exchange plate 61, a second lifting guide rod 62, a second drive motor 63, a second screw rod 64, and a second slider 65. Among them, the heat exchange plate 61 is arranged in the insulation layer 20 and is located just above the upper crucible cover 31a, and the bottom surface of the heat exchange plate 61 matches the top surface of the upper crucible cover 31a, that is, the shape of its bottom surface is adapted to the shape of the top surface of the upper crucible cover 31a, so that when the heat exchange plate 61 contacts the upper crucible cover 31a, the bottom surface of the heat exchange plate 61 is completely fitted with the top surface of the upper crucible cover 31a, so as to ensure that the heat of the upper crucible cover 31a can be quickly transferred to the heat exchange plate 61. The second lifting guide rod 62 passes through the insulation layer 20 and the upper cover of the furnace body 10, and can slide up and down relative to the insulation layer 20 and the furnace body 10. Its bottom end is fixedly connected to the heat exchange plate 61 and its top end is located outside the furnace body 10. The second drive motor 63 is arranged on the top of the furnace body 10, and can be a servo motor or a variable frequency motor. The second screw rod 64 is rotatably arranged on the top of the upper furnace cover and driven to rotate by the second drive motor 63. Specifically, the second drive motor 63 can be arranged at the end of the second screw rod 64. The second slider 65 is sleeved on the second screw rod 64 and fixed on the top of the second lifting guide rod 62. Specifically, a threaded hole matching the second screw rod 64 can be arranged at the center of the second slider 65, and the threaded hole of the second slider 65 is sleeved on the second screw rod 64, and the second slider 65 is fixedly arranged on the side of the second lifting guide rod 62. When the second driving motor 63 drives the second screw rod 64 to rotate, the second slider 65 can move up and down along the second screw rod 64, thereby driving the second lifting guide rod 62 to slide up and down, so that the heat exchange plate 61 at the bottom end of the second lifting guide rod 62 can also move up and down.

[0033] Preferably, the crystal heat exchange device 60 further includes a temperature measuring device 70, which can detect the temperature of the upper crucible cover 31a in real time. The temperature measuring device 70 includes an infrared thermometer 71 with a detection head 72 and a temperature measuring channel 73 arranged in the second lifting guide rod 62. Specifically, it is preferable to set the second lifting guide rod 62 to be hollow, and the hollow part thereof is the temperature measuring channel 73. Since the heat exchange plate 61 is fixed at the bottom end of the second lifting guide rod 62, it is preferable to set a through hole matching the temperature measuring channel 73 on the heat exchange plate 61, so that the temperature measuring channel 73 can be directly facing the top surface of the upper crucible cover 31a after passing through the heat exchange plate 61. The infrared thermometer 71 is set at the top end of the second lifting guide rod 62, and it is ensured that the detection head 72 can just pass through the temperature measuring channel 73 to irradiate the top surface of the upper crucible cover 31a. In this way, the detection head 72 of the infrared thermometer 71 can directly detect the real-time temperature of the top surface of the upper crucible cover 31a through the temperature measuring channel 73.

[0034] Similarly, a control system can be set to be electrically connected to the second drive motor 63 and the infrared thermometer 71, and the control system is set to automatically control the second drive motor to drive the second lifting guide rod 62 to slide up and down according to the temperature of the top surface of the upper crucible cover 31a detected by the infrared thermometer 71, thereby driving the heat exchange plate 61 to rise and fall, so that the heat exchange plate 61 is in close contact with or separated from the upper crucible cover 31a, so as to adjust the temperature of the silicon carbide seed crystal 1 located on the bottom surface of the upper crucible cover 31a to ensure that it meets the process requirements. Specifically, when the temperature of the top surface of the upper crucible cover 31a detected by the infrared thermometer 71 is higher than a preset value, the control system automatically controls the heat exchange plate 61 to descend to a preset position, so that the heat exchange plate 61 is in close contact with the upper crucible cover 31a; when the temperature of the top surface of the upper crucible cover 31a detected by the infrared thermometer 71 is lower than a preset value, the control system automatically controls the heat exchange plate 61 to rise to a preset position, so that the heat exchange plate 61 is separated from the upper crucible cover 31a.

[0035] In this preferred embodiment, the thermal insulation layer 20 is preferably provided to include an upper movable thermal insulation block 22, which is fixed around the second lifting guide rod 62 and sleeved on the top of the heat exchange plate 61, so that the upper movable thermal insulation block 22 is lifted and lowered together with the heat exchange plate 61. Specifically, an upper opening 23 matching the outer contour of the upper movable thermal insulation block 22 can be provided at a corresponding position of the thermal insulation layer 20, and when the upper movable thermal insulation block 22 is lifted and lowered together with the heat exchange plate 61, the upper movable thermal insulation block 22 is just embedded in the upper opening 23, thereby ensuring the thermal sealing of the internal space of the thermal insulation layer 20.

[0036] The insulation layer 20 may also include a lower movable insulation block 24, and a lower opening 25 matching the lower movable insulation block is opened at the bottom of the insulation layer 20. The maximum outline size of the lower movable insulation block 24 on the horizontal plane is set to be larger than the maximum outline size of the crucible, so that after opening the lower furnace cover 12, the lower movable insulation block 24 can be taken out and the crucible can be placed in or taken out from the bottom of the furnace body 10.

[0037] In this preferred embodiment, a process gas path system (not shown in the figure) may also be included to control the vacuum degree in the furnace body 10 and to fill the furnace body 10 with process gas; a water cooling system (not shown in the figure) may also be provided as needed to accelerate the cooling speed of the furnace body 10 after the preparation of the silicon carbide single crystal is completed.

[0038] In a preferred embodiment of the process for preparing a silicon carbide single crystal according to the present invention, the following steps are included: S10. A silicon carbide single crystal growth apparatus constructed as described above; S20. The silicon carbide seed crystal is fixed to the bottom of the upper crucible cover; the silicon carbide polycrystalline raw material is placed in the lower crucible to complete the furnace loading process; S30. The equipment is vacuumed so that the vacuum degree in the furnace reaches below 0.1Pa, completing the vacuuming process; S40. The temperature of the furnace chamber is raised in stages and the vacuum of the furnace is maintained below 0.1 Pa to complete the heating process; S50. Maintain the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, stop evacuating the furnace chamber and fill it with inert gas, and increase the pressure to 10-60kPa, maintain the pressure for 3-5 hours, and complete the gas filling and pressurization process; S60. Maintaining the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, while gradually reducing the pressure, reducing the furnace chamber pressure to 100-3000Pa within 3-10 hours, completing the depressurization process; S70. According to the size requirements of the silicon carbide single crystal growth, the temperature and pressure of the furnace chamber are maintained constant for 50-300 hours; at the same time, the position of the crucible is adjusted according to the position of the crystal growth interface detected to complete the crystal growth process; S80. After the growth of the silicon carbide single crystal is completed, the pressure is released, the temperature is lowered, and the finished product is taken out to complete the furnace unloading process.

[0039] In step S10, the equipment includes a vacuum system. In step S30, the vacuum system is controlled by the control system to vacuum the furnace body so that the vacuum degree in the furnace body is below 0.1 Pa. Specifically, a vacuum gauge can be set on the furnace body to monitor the vacuum degree in the furnace body in real time.

[0040] In step S40, the heating stage can be divided into two stages: S41. Control the resistance heater to raise the temperature of the furnace chamber to 1000-1200°C within 2 hours, maintain the vacuum degree in the furnace below 0.1Pa, and keep the temperature constant for 5-10 hours; S43. Control the resistance heater to raise the temperature of the chamber in the furnace to 2000-2500°C within 5 hours, maintain the vacuum degree in the furnace below 0.1 Pa, and keep the temperature constant for 5-10 hours.

[0041] By increasing the temperature in stages and maintaining a constant temperature for a certain period of time in each stage, the crucible can be heated evenly, ensuring that the temperature of all parts of the crucible body is consistent, thereby making the temperature of each area in the crucible basically consistent.

[0042] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in the field without making any creative work, any modifications, equivalent substitutions, improvements, etc. made should be included in the protection scope of the present invention.

Claims

1. A silicon carbide single crystal growth device, comprising a furnace body, a heat preservation layer, a crucible arranged in the heat preservation layer and a resistance heater, characterized in that: The crucible includes an upper crucible and a lower crucible, a gas delivery pipe is provided between the upper crucible and the lower crucible, the upper crucible includes an upper crucible body and an upper crucible cover, the lower crucible includes a lower crucible body and a lower crucible cover, and the gas delivery pipe is provided between the upper crucible body and the lower crucible cover; the resistance heater includes an upper heating body provided around the upper crucible, a lower heating body provided around the lower crucible, and an intermediate heating body provided around the gas delivery pipe.

2. The silicon carbide single crystal growth device according to claim 1, characterized in that: A crucible lifting device is provided at the bottom of the lower crucible body, and the crucible lifting device includes a first lifting guide rod provided at the bottom of the lower crucible body and passing through the insulation layer and the furnace body, a first driving motor provided at the bottom of the furnace body, a first screw rod driven by the first driving motor, and a first slider sleeved on the first screw rod, wherein the first slider is fixed to the bottom end of the first lifting guide rod.

3. The silicon carbide single crystal growth device according to claim 2, characterized in that: It also includes a control system, which is electrically connected to the first drive motor. The control system controls the first drive motor to drive the first lifting guide rod to rise and fall at a preset speed.

4. The silicon carbide single crystal growth device according to claim 1, characterized in that: A crystal heat exchange device is provided directly above the upper crucible cover, and the crystal heat exchange device includes a heat exchange plate matching the top surface of the upper crucible cover, a second lifting guide rod passing through the insulation layer and the furnace body and connected to the heat exchange plate, a second drive motor arranged on the top of the furnace body, a second screw rod driven by the second drive motor, and a second slider sleeved on the second screw rod, wherein the second slider is fixed to the top end of the second lifting guide rod.

5. The silicon carbide single crystal growth device according to claim 4, characterized in that: The crystal heat exchange device also includes a temperature measuring device capable of detecting the temperature of the upper crucible cover, the temperature measuring device includes an infrared thermometer with a detection head arranged on the top of the second lifting guide rod, and a temperature measuring channel arranged in the second lifting guide rod, one end of the temperature measuring channel passes through the heat exchange plate and faces the top surface of the upper crucible cover, and the other end matches the infrared thermometer.

6. The silicon carbide single crystal growth device according to claim 5, characterized in that: It also includes a control system, which is electrically connected to the second drive motor and the infrared thermometer. The control system controls the rotation of the second screw rod according to the temperature of the top surface of the upper crucible cover detected by the infrared thermometer to drive the heat exchange plate to rise and fall.

7. The silicon carbide single crystal growth device according to claim 4, characterized in that: The heat-insulating layer comprises an upper movable heat-insulating block, which is fixed around the second lifting guide rod and sleeved on the top of the heat exchange plate.

8. A process for preparing a silicon carbide single crystal, characterized in that: The following steps are involved: S10. Constructing a silicon carbide single crystal growth apparatus as described in any one of claims 1 to 7; S20. The silicon carbide seed crystal is fixed to the bottom of the upper crucible cover; the silicon carbide polycrystalline raw material is placed in the lower crucible to complete the furnace; S30. Evacuate the equipment so that the vacuum degree in the furnace reaches below 0.1 Pa; S40. The temperature of the furnace chamber is raised in stages and the vacuum of the furnace is maintained below 0.1 Pa; S50. Maintain the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, and at the same time stop evacuating the furnace chamber and fill it with inert gas, and increase the pressure to 10-60kPa, and maintain the pressure for 3-5 hours; S60. Maintaining the temperature of the furnace chamber at 2000-2500°C by controlling the resistance heater, while gradually reducing the pressure to reduce the furnace chamber pressure to 100-3000Pa within 3-10 hours; S70. According to the size requirements of silicon carbide single crystal growth, maintaining the temperature and pressure of the furnace chamber unchanged for 50-300 hours; while adjusting the position of the crucible according to the position of the detected crystal growth interface; S80. After the growth of the silicon carbide single crystal is completed, the pressure is released and the temperature is lowered.

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