Method, device and system for growing silicon carbide by top temperature regulation type liquid phase method

Abstract

The invention provides a method, a device and a system for growing silicon carbide by a top temperature regulation type liquid phase method. The device for producing silicon carbide by the top temperature regulation type liquid phase method comprises a graphite crucible; the heating assembly comprises a heating coil wound on the side surface of the graphite crucible; the top temperature adjusting assembly comprises a liquid cooling disc and a heat exchange pipe arranged in the liquid cooling disc in a winding mode, and the two ends of the heat exchange pipe are located outside the liquid cooling disc; and the graphite crucible, the heating coil and the liquid cooling disc are all positioned in the crystal growth furnace body. And the heat exchange tube is internally provided with flowing heat exchange liquid. The flow and the liquid pressure of the heat exchange liquid in the heat exchange tube in the re-melting step are respectively lower than the flow and the liquid pressure of the heat exchange liquid in the heat exchange tube in the crystal growth step.

Description

Technical Field

[0001] The present application relates to the technical field of silicon carbide single crystal production, and in particular to a method, device and system for growing silicon carbide by a top temperature-controlled liquid phase method. Background Art

[0002] As a wide bandgap semiconductor material, silicon carbide (SiC) has become an ideal material in many fields because of its high potential, wide bandgap (3.23eV, about three times that of silicon), large breakdown field (3MV / cm, about ten times that of silicon), high thermal conductivity (4.9W / cm·K, about three times that of silicon), excellent radiation resistance and good chemical stability. These characteristics make silicon carbide (SiC) show great potential in the manufacture of high-frequency, high-voltage, and high-power power electronic devices, and show important application value in electric vehicles, rail transportation, 5G communications, and aerospace. The supply of high-quality, large-size, and low-cost silicon carbide (SiC) single crystal substrates is a prerequisite for the large-scale application of silicon carbide (SiC).

[0003] High temperature solution growth (HTSG) is one of the growth methods of silicon carbide (SiC). Due to its advantages such as low dislocation density of grown crystals and low crystal growth cost, HTSG has gradually attracted attention in the industry in recent years and is used to produce high-quality silicon carbide (SiC) single crystals. The driving force for the growth of silicon carbide (SiC) single crystals by high temperature solution growth (HTSG) is the temperature gradient in the solution. Silicon alloy melt is added to the graphite crucible, and carbon is dissolved from the graphite crucible at high temperature. Through solute convection diffusion, the area near the seed crystal reaches a supersaturated state of carbon from supercooling, so that carbon precipitates on the seed crystal and grows silicon carbide (SiC) crystals.

[0004] In the step of growing silicon carbide crystals by the liquid phase method, the key melting back step before crystal growth usually requires the high temperature area to be located at the upper part of the crucible, that is, near the solid-liquid interface, to ensure the uniform elimination of surface defects of the seed crystal and provide stable and excellent starting conditions for crystal growth. In the crystal growth step, the high temperature area must be changed to the lower part of the crucible, usually located at the bottom of the solution to form a stable temperature gradient, to ensure the supercooling of the seed crystal area so that the carbon in the solution is evenly deposited on the seed crystal, and to achieve stable crystal growth.

[0005] One method known to the inventor is to change the relative position of the heating coil and the crucible to achieve the movement of the high-temperature area. Specifically, by mechanically moving the heating coil or the crucible up and down and changing the position of the coil relative to the crucible, the concentrated area of ​​the heating energy can be controlled, thereby affecting the temperature distribution of the solution in the crucible. In the remelting step, the heating energy center is usually adjusted to a higher position of the crucible, close to the solid-liquid interface, to ensure sufficient remelting of the seed crystal surface; in the crystal growth step, the heating energy center position is lowered to be closer to the bottom of the crucible to ensure the high temperature at the bottom of the solution and promote uniform growth of the crystal.

[0006] However, the existing technology for adjusting the temperature distribution of the solution also has problems such as inconvenient adjustment, slow response, and difficulty in precise control. Because the relative position of the coil and the crucible is mechanically adjusted, the temperature field reacts slowly and cannot respond to the need for fast and precise switching from the remelting step to the crystal growth step, which in turn affects the crystal quality and overall growth efficiency.

[0007] Precise control of temperature distribution is crucial to the quality of silicon carbide single crystals. Imprecise position adjustment may lead to uneven temperature gradients, insufficient or excessive temperature control, and the low temperature zone fluctuates with temperature and composition, thereby introducing crystal defects such as polymorphs and inclusions. Therefore, the mechanical adjustment method has a greater impact on the stability of the thermal field, and the actual impact of the crystal growth step on the thermal field is difficult to monitor and adjust in real time. After setting the relative position of the heating coil and the crucible, once the solution temperature distribution cannot be flexibly adjusted in this way during the crystal growth process, the crystal growth rate during the crystal growth process cannot be flexibly adjusted as needed.

[0008] In summary, an effective regulation mechanism for stably maintaining the optimal thermal field conditions is crucial. Rapidly switching modes at the critical stage of crystal growth and flexibly regulating the growth temperature distribution during long-term crystal growth to regulate the growth rate and ensure crystal quality are the keys to improving the economic benefits of the entire growth process.

[0009] In fields such as automation and energy storage, if the system usually needs to maintain temperature stability during long-term operation, the heat dissipation design in these fields usually adopts water cooling solutions, such as embedded tube cooling plates, which use copper or aluminum tubes embedded in metal plates to form an internal fluid channel network. The cooling medium flows in these pipes, transferring heat from the plate to the external environment or heat exchanger to ensure that the equipment can still effectively manage heat under long-term high-load operation. However, the semiconductor crystal growth process requires rapid adjustment of temperature distribution at different production stages, especially when switching from remelting to crystal growth mode, rapid adjustment of solution temperature is crucial. This is different from the pursuit of continuous and stable cooling and heat dissipation needs in the fields of automation and energy storage.

[0010] The Chinese utility model patent with the announcement number "CN214032755U" discloses a "silicon carbide growth device with radially adjustable temperature gradient". The device is provided with a water cooling mechanism above the seed crystal and placed parallel to the top of the seed crystal. The water cooling mechanism has a relatively high heat exchange efficiency, but the utility model patent lacks further elaboration on how to implement what kind of heat exchange means and heat exchange efficiency at different stages of the silicon carbide growth process. Summary of the invention

[0011] This application is made in view of the above-mentioned state of the prior art. This application aims to solve or alleviate at least one of the above-mentioned problems.

[0012] In a first aspect, the purpose of the present application is to provide a method for producing silicon carbide by a top temperature-controlled liquid phase process.

[0013] The technical solution adopted by the present application to solve its technical problem is: a method for producing silicon carbide by a top temperature-adjusting liquid phase method, comprising: a feeding step: putting a solid silicon alloy material into a graphite crucible, and placing the graphite crucible in a crystal growth furnace; a heating step: heating the graphite crucible to melt the solid silicon alloy material in the graphite crucible, and keeping the temperature for a period of time after reaching a predetermined growth temperature until the solid silicon alloy material is completely melted; a remelting step: adjusting a top temperature-adjusting component located above the graphite crucible so that the temperature at the solid-liquid interface of the seed crystal at the upper part of the graphite crucible is higher than the solution temperature at the lower part of the graphite crucible, and remelting and etching the seed crystal; Crystal growth step: lowering the top temperature of the graphite crucible to supercool the seed crystal to form a carbon supersaturation zone, and the carbon in the carbon-silicon solution in the graphite crucible is deposited on the seed crystal to achieve crystal growth; discharging step: after the crystal growth is completed, lowering the temperature of the crystal growth furnace and taking out the crystal; wherein the top temperature control component includes a liquid cooling plate arranged above the graphite crucible, a heat exchange tube is pre-buried in the liquid cooling plate, and a heat exchange liquid is flowing in the heat exchange tube; in the remelting step, the flow rate and liquid pressure of the heat exchange liquid in the heat exchange tube are respectively lower than the flow rate and liquid pressure of the heat exchange liquid in the heat exchange tube in the crystal growth step.

[0014] As a further improvement of the present application, in the feeding step, the crystal growth furnace body is first evacuated and then an inert gas is introduced; in the heating step, the graphite crucible is heated by the electric current thermal effect of electromagnetic induction heating or resistance heating; the crystal growth furnace body includes a seed crystal rod and a graphite holder that cooperate with each other, and the seed crystal is adhered to the graphite holder; in the remelting step, the surface defects of the seed crystal are eliminated to improve the smoothness of the crystal grown from the seed crystal.

[0015] As a further improvement of the present application, in the remelting step, the remelting height of the seed crystal is in a range of 0.1 mm to 2.0 mm, and the duration is in a range of 5 minutes to 30 minutes.

[0016] As a further improvement of the present application, in the remelting step, the liquid pressure range of the heat exchange liquid in the heat exchange tube is 0.1MPa to 0.3MPa, and the flow rate is 0.5L / min to 1.0L / min; in the crystal growth step, the liquid pressure range of the heat exchange liquid in the heat exchange tube is 0.7MPa to 1.0MPa, and the flow rate is 3L / min to 5L / min.

[0017] As a further improvement of the present application, the top opening diameter range of the graphite crucible is 40mm to 50mm, and the pressure range of the graphite crucible after the inert gas is introduced is 0.5 standard atmosphere to 1 standard atmosphere; after the temperature in the graphite crucible reaches the range of 1850°C to 1900°C, it is kept warm for 25 minutes to 30 minutes, and the flow range of the heat exchange liquid is adjusted to 0.5 liters / minute to 0.6 liters / minute, and the pressure range of the heat exchange liquid is 0.2MPa to 0.3MPa; the remelting height range of the remelting step is 1mm to 1.5mm, and the remelting duration is 10 minutes to 15 minutes; after the remelting step is completed, the flow rate of the heat exchange liquid is adjusted to the range of 3 liters / minute to 4 liters / minute, and the pressure range of the heat exchange liquid is 0.7MPa to 0.9MPa; the heating power range of the crystal growth step is 9KW to 10KW, and the crystal growth duration is 40 hours to 60 hours.

[0018] In a second aspect, a device for producing silicon carbide by a top temperature-controlled liquid phase method is provided, comprising: a graphite crucible; a heating assembly, comprising a heating coil wound around the side of the graphite crucible; a top temperature-controlled assembly, comprising a liquid cooling plate and a heat exchange tube arranged in a winding manner in the liquid cooling plate, wherein both ends of the heat exchange tube are located outside the liquid cooling plate; and a crystal growth furnace body, wherein the graphite crucible, the heating coil, and the liquid cooling plate are all located inside the crystal growth furnace body.

[0019] As a further improvement of the present application, the two ends of the heat exchange tube include a liquid inlet and a liquid outlet located outside the crystal growth furnace body; the heat exchange tube also includes an embedded section located inside the liquid cooling plate and a lead-out section located outside the liquid cooling plate, the embedded section includes horizontal sections arranged parallel to each other and spaced apart, and the same ends of adjacent horizontal sections are connected through the elbow section of the heat exchange tube.

[0020] As a further improvement of the present application, the top of the graphite crucible is provided with a graphite crucible top cover, and the top temperature-controlled liquid phase method for producing silicon carbide also includes a seed crystal, a graphite tray, a seed crystal rod and an insulation layer, the insulation layer is arranged around the graphite crucible, the upper surface of the seed crystal is the graphite tray, and the upper surface of the graphite tray is provided with the seed crystal rod extending upward; the graphite crucible top cover, the insulation layer, the liquid cooling plate, and the crystal growth furnace body all have through holes that allow the seed crystal rod to pass through.

[0021] As a further improvement of the present application, a gap is formed between adjacent horizontal sections of the heat exchange tube, and the heat exchange tube has an avoidance zone that avoids the seed crystal rod and expands the width of the gap; the liquid cooling plate enables the through hole through which the seed crystal rod passes to be located at the centroid of the liquid cooling plate, and the avoidance zone does not contact or interfere with the inner wall of the through hole of the liquid cooling plate.

[0022] As a further improvement of the present application, the outside of the graphite crucible and the top temperature adjustment component are both wrapped with an insulation layer; the heating coil heats the graphite crucible by electromagnetic induction, and the heating coil is located outside the insulation layer.

[0023] As a further improvement of the present application, the material of the heat exchange liquid in the heat exchange tube is liquid gallium-indium-tin alloy, liquid gallium or water; the material of the liquid cooling plate is aluminum alloy, copper alloy or stainless steel; the material of the heat exchange tube is oxygen-free copper or tantalum.

[0024] As a further improvement of the present application, the diameter range of the through hole of the liquid cooling plate through which the seed rod passes is 30mm to 60mm, and the thickness range of the liquid cooling plate is 33mm to 60mm; the straight-line distance between the two ends of the embedded section is 300mm to 500mm, the vertical distance from the outer wall of the heat exchange tube to the lower surface of the liquid cooling plate is 0mm to 10mm, the outer diameter range of the heat exchange tube is 12mm to 33mm, and the inner diameter range of the embedded section of the heat exchange tube is 10mm to 30mm; the inner diameters of the liquid inlet and the liquid outlet at both ends of the heat exchange tube are smaller than the inner diameter of the embedded section, the outer diameters of the liquid inlet and the liquid outlet range from 12mm to 32mm, and the inner diameters of the liquid inlet and the liquid outlet range from 10mm to 29mm.

[0025] In a third aspect, a system for producing silicon carbide by a top temperature-controlled liquid phase method is provided, comprising the device for producing silicon carbide by the top temperature-controlled liquid phase method, wherein the system for producing silicon carbide by the top temperature-controlled liquid phase method comprises: an air-cooled heat exchange module, wherein both ends of the heat exchange tube are connected to the air-cooled heat exchange module and together constitute a circulation pipeline, wherein the heat exchange liquid in the circulation pipeline is driven by a liquid transmission pump; and a control system, comprising a pressure sensor, a flow meter, and a temperature sensor arranged on the circulation pipeline at both ends of the heat exchange tube.

[0026] As a further improvement of the present application, the circulation pipeline is provided with an electric regulating valve, and the electric regulating valve remotely controls the opening or closing of the circulation pipeline.

[0027] As a further improvement of the present application, the crystal growth furnace body is connected to a vacuum pump via a vacuum valve; the crystal growth furnace body is also connected to an argon gas tank.

[0028] The beneficial effects of the top temperature-controlled liquid phase method for producing silicon carbide of the present application include: meeting the demand for rapid switching between relatively high and relatively low temperatures in the furnace in the semiconductor industry. That is, rapid adjustment of the temperature distribution of the solution when switching from the remelting step to the crystal growth step. By setting a liquid cooling plate above the graphite crucible, the flow rate and pressure of the heat exchange liquid in the liquid cooling plate are adjusted, and then the heat value taken away from the vicinity of the liquid cooling plate per unit time is changed, so as to flexibly adjust the different temperature distributions of the upper and lower sections of the graphite crucible in different steps to ensure efficient growth of crystals.

[0029] The design of the liquid cooling plate can have higher adjustment flexibility and response speed. By allowing a large amount of heat exchange liquid to pass through the liquid cooling plate and take away the heat around the liquid cooling plate, the temperature around the liquid cooling plate can be reduced, that is, the temperature of the upper half of the graphite crucible is relatively low, and then the temperature required for crystal growth is met. By allowing a smaller amount of heat exchange liquid to pass through the liquid cooling plate, less heat is taken away from the liquid cooling plate, and the temperature around the liquid cooling plate can be maintained at a higher level, that is, the temperature of the upper half of the graphite crucible is also higher, and then the temperature required for remelting is met. The flow rate and liquid pressure of the heat exchange liquid can accurately correspond to their ability to take away heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions in the embodiments, the drawings of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0031] Figure 1 It is a structural schematic diagram of an embodiment of the device for producing silicon carbide by the liquid phase method of the present application;

[0032] Figure 2 is a perspective view of an embodiment of an apparatus for producing silicon carbide by a liquid phase method of the present application;

[0033] Figure 3 is a quarter cross-sectional view of an embodiment of the device for producing silicon carbide by a liquid phase method of the present application;

[0034] Figure 4 is a top view of an embodiment of the device for producing silicon carbide by a liquid phase method of the present application;

[0035] Figure 5 yes Figure 4 AA section view;

[0036] Figure 6 is an exploded view of an embodiment of the device for producing silicon carbide by a liquid phase method of the present application;

[0037] Figure 7 It is a three-dimensional diagram of a heat exchange tube of one embodiment of the device for producing silicon carbide by a liquid phase method of the present application;

[0038] Figure 8 1 is a schematic diagram of an embodiment of a system for producing silicon carbide by a liquid phase method of the present application.

[0039] Description of Reference Numerals

[0040] 1-liquid inlet; 2-cooling medium; 3-graphite crucible top cover; 31-first through hole; 4-graphite support; 5-seed crystal; 6-carbon silicon solution; 7-graphite crucible; 8-liquid outlet; 9-insulation layer; 91-second through hole; 92-wrapping cavity; 10-heating coil; 11-crystal growth furnace body; 111-third through hole; 12-seed crystal rod; 13-liquid cooling plate; 131-fourth through hole; 14-air-cooled heat exchange module; 15-electric regulating valve; 16-liquid transfer pump; 17-temperature sensor; 18-flow meter; 19-pressure sensor; 20-vacuum valve; 21-vacuum pump; 22-argon tank; 23-thermocouple; 24-heat exchange tube; 241-lead-out section; 242-horizontal section; 243-elbow section; 244-gap; 245-avoidance area. DETAILED DESCRIPTION

[0041] The exemplary embodiments of the present application are described below with reference to the accompanying drawings. It should be understood that these specific descriptions are only used to teach those skilled in the art how to implement the present application, and are not intended to exhaust all possible methods of the present application, nor to limit the scope of the present application.

[0042] The method for growing silicon carbide by a top temperature-controlled liquid phase method, the device for growing silicon carbide by a top temperature-controlled liquid phase method, and the system for growing silicon carbide by a top temperature-controlled liquid phase method of the present application are further described in detail below in conjunction with specific embodiments.

[0043] The method for growing silicon carbide by top temperature-controlled liquid phase method of the present application comprises: step S1, feeding step: feeding solid silicon alloy material into graphite crucible 7 (see for example Figure 1), placing the graphite crucible 7 in the crystal growth furnace body 11. Step S2, heating step: heating the graphite crucible 7 according to the set power to melt the solid silicon alloy material in the graphite crucible 7. When the predetermined growth temperature is reached, the temperature is kept constant for a period of time until the solid silicon alloy material is completely melted. Step S3, remelting step: adjusting the top temperature regulating component located above the graphite crucible 7 so that the temperature at the solid-liquid interface of the seed crystal 5 on the upper part of the graphite crucible 7 is higher than the temperature of the solution at the lower part of the graphite crucible 7, and remelting and etching the seed crystal 5. Step S4, crystal growth step: lowering the top temperature of the graphite crucible 7 so that the seed crystal 5 is overcooled to form a carbon supersaturated zone, and the carbon in the carbon-silicon solution 6 in the graphite crucible 7 will be deposited on the seed crystal 5 to achieve crystal growth. Step S5, discharging step: when the crystal growth is completed, the temperature of the crystal growth furnace body 11 is cooled to room temperature, and the crystal is finally taken out. The top temperature control assembly includes a liquid cooling plate 13 suspended above the graphite crucible 7, and a heat exchange tube 24 is embedded in the liquid cooling plate 13 (see, for example, Figure 6 ), the heat exchange tube 24 has a flowing heat exchange liquid as the cooling medium 2; the flow rate of the heat exchange liquid in the heat exchange tube 24 in the remelting step is lower than the flow rate of the heat exchange liquid in the heat exchange tube 24 in the crystal growth step; the liquid pressure of the heat exchange liquid in the heat exchange tube 24 in the remelting step is lower than the liquid pressure of the heat exchange liquid in the heat exchange tube 24 in the crystal growth step.

[0044] The beneficial effect of adopting the above embodiment is: by simply adjusting the flow rate and pressure of the heat exchange liquid to accurately control the temperature gradient inside the graphite crucible 7, a rapid temperature mode switch from remelting to crystal growth can be achieved. In addition, the method can adjust the longitudinal temperature gradient during the crystal growth process, ensure the uniformity of the radial temperature distribution of the crystal, enhance the controllability and economic benefits of the production process, and provide an efficient and reliable method for the growth of silicon carbide single crystals. The controllability of the temperature field of the heating body is ensured, and the mode switching is ensured to be achieved quickly at the critical stage of crystal growth. The silicon carbide growth temperature gradient can be flexibly changed during the crystal growth process, so that the crystal growth rate can be adjusted as needed, and the crystal growth process is optimized in thermodynamics and kinetics, which helps to generate silicon carbide (SiC) single crystals with higher quality and fewer defects, and improve production capacity.

[0045] In one embodiment, in step S1, the crystal growth furnace body 11 is first evacuated, and then an inert gas is introduced. In step S2, the graphite crucible 7 is heated by the electric current thermal effect of electromagnetic induction heating or resistance heating to increase the temperature inside the graphite crucible 7. The crystal growth furnace body 11 includes a seed crystal rod 12 and a graphite tray 4 that cooperate with each other, and the seed crystal 5 is adhered to the graphite tray 4; in step S3, the surface defects of the seed crystal 5 are eliminated to improve the smoothness of the growing crystal of the seed crystal 5. In this embodiment, the seed crystal 5 is first baked and then immersed in the melt. After the solid silicon alloy material is melted, in order to avoid the instantaneous thermal shock of contacting the liquid causing excess thermal stress to the seed crystal 5, and excessive temperature fluctuations at the growth interface, the seed crystal 5 needs to be fully preheated, and the seed crystal 5 is placed 10 mm above the surface of the melt after the solid silicon alloy material is melted for baking. However, the solution evaporates at high temperature and solidifies on the growth surface of the seed crystal 5, resulting in polymorphic nucleation points (i.e., 6H / 15R-SiC) in the locally saturated silicon carbide (SiC), which easily leads to defects such as solvent encapsulation and polymorphic inclusions in the early stage of growth. There are two different polymorphs of silicon carbide (SiC), each with a unique crystal structure and properties. Among them, 6H-SiC belongs to the hexagonal system, and 15R-SiC belongs to the trigonal system. By immersing the seed crystal 5 in the superheated solution for remelting, the polymorphic nucleation points deposited on the growth surface of the seed crystal 5 caused by baking are eliminated, and through-screw dislocations (TSDs) are revealed. Through-screw dislocations (TSDs) refer to a linear, spiral defect formed by the dislocation or slip of atoms or molecules inside the crystal during the growth or processing of the crystal due to various factors. This defect will run through multiple crystal faces of the crystal, have a significant impact on the physical and chemical properties of the crystal, and provide an initial spiral step source for the growth of the seed crystal 5. In addition, the melting back step can also suppress dislocation proliferation and eliminate processing damage on the surface of the seed crystal 5, further improving the crystal quality.

[0046] In step S3, the melting height of the seed crystal 5 ranges from 0.1 mm to 2.0 mm, and the duration ranges from 5 minutes (min) to 30 minutes (min). The melting height refers to the depth or height of the melting phenomenon on the surface of the seed crystal 5 during the high-temperature melting process.

[0047] An embodiment of the specific steps of the method for growing silicon carbide by the top temperature-controlled liquid phase method of the present application is as follows:

[0048] Step S1: Put solid silicon alloy material into a graphite crucible 7 with an opening at the top, wherein the solid silicon alloy material can be one of silicon-chromium alloy (SiCr), silicon-chromium-aluminum alloy (SiCrAl), silicon-chromium-aluminum-cerium alloy (SiCrAlCe) or a combination thereof, and place the graphite crucible 7 in a crystal growth furnace body 11. Then, open the vacuum valve 20 of the vacuum pump 21 connected to the crystal growth furnace body 11 (see, for example, Figure 8), the gas in the growth chamber in the crystal growth furnace body 11 is evacuated, and then an inert gas is introduced for protection. The inert gas can be one of helium (He) or argon (Ar) or a combination thereof.

[0049] Step S2: Turn on the heating power supply, and heat the graphite crucible 7 according to the set power by using a heater based on the induction heating principle or the resistance heating principle to melt the solid silicon alloy material in the graphite crucible 7, and the molten silicon alloy melt dissolves the inner wall of the graphite crucible 7, thereby providing the carbon required for the synthesis of the silicon carbide single crystal. When the predetermined growth temperature is reached, keep the temperature for a period of time to ensure that the silicon alloy material is completely melted.

[0050] Step S3: By adjusting the flow rate and pressure of the heat exchange liquid in the top temperature control component, using low flow rate and low water pressure to weaken the heat exchange effect, the insulation effect of the insulation layer 9 in the crystal growth furnace body 11 is maintained, ensuring that the temperature at the solid-liquid interface of the seed crystal 5 in the upper half of the graphite crucible 7 is higher than the solution temperature in the lower half of the graphite crucible 7, and the silicon carbide seed crystal 5 is glued to the graphite holder 4. The graphite holder 4 is threaded with a seed crystal rod 12, and the seed crystal rod 12 extends into the graphite crucible 7 with a top opening and filled with silicon alloy melt, and the seed crystal 5 is melted back and etched to ensure that the surface defects of the seed crystal 5 are uniformly eliminated, and the surface smoothness of the produced seed crystal 5 is improved. During this period, the melting back height is 0.1mm to 2.0mm, and the duration ranges from 5 minutes (min) to 30 minutes (min).

[0051] Step S4: After the remelting is completed, the flow rate and pressure of the cooling medium 2 in the top temperature control component are adjusted, and a high flow rate and high water pressure are used to quickly weaken the insulation effect of the insulation layer 9, reduce the top temperature of the graphite crucible 7, and move the high-temperature area down to the lower half of the graphite crucible 7, so that the seed crystal 5 area is supercooled to form a carbon supersaturated area, and the mode is switched to enter the crystal growth step, and the carbon in the solution is deposited on the seed crystal 5 to achieve crystal growth.

[0052] Step S5: Cooling and taking out of the furnace. When the crystal growth is completed, the temperature is slowly lowered according to the set cooling program until the temperature of the crystal growth furnace body approaches or reaches room temperature, and then the crystal is taken out.

[0053] In one embodiment, during the remelting step, the liquid pressure of the heat exchange liquid in the heat exchange tube 24 is in the range of 0.1 MPa to 0.3 MPa, and the flow rate is in the range of 0.5 liters / minute (L / min) to 1.0 liters / minute (L / min). During the crystal growth step, the liquid pressure of the heat exchange liquid in the heat exchange tube 24 is in the range of 0.7 MPa to 1.0 MPa, and the flow rate is in the range of 3 liters / minute (L / min) to 5 liters / minute (L / min).

[0054] The top opening diameter of the graphite crucible 7 is in the range of 40 mm to 50 mm, and the pressure of the graphite crucible 7 after the inert gas is introduced is in the range of 0.5 standard atmosphere (atm) to 1 standard atmosphere (atm). After the temperature in the graphite crucible 7 reaches the range of 1850° C. to 1900° C., it is kept warm for 25 minutes (min) to 30 minutes (min), and the flow rate of the heat exchange liquid is adjusted to reach 0.5 liters / minute (L / min) to 0.6 liters / minute (L / min). At the same time, the pressure of the heat exchange liquid is in the range of 0.2 MPa to 0.3 MPa, the remelting height is in the range of 1 mm to 1.5 mm, and the remelting duration is 10 minutes (min) to 15 minutes (min). After the remelting is completed, the flow rate of the heat exchange liquid is adjusted to the range of 3 liters / minute (L / min) to 4 liters / minute (L / min), and the pressure range of the heat exchange liquid is 0.7MPa to 0.9MPa; during the crystal growth stage, the heating power range is 9KW to 10KW, and the crystal growth duration is 40 hours to 60 hours.

[0055] According to the parameter selection range in the previous paragraph, an embodiment of the parameter selection in the method for growing silicon carbide by the top temperature-adjusted liquid phase method of the present application is as follows:

[0056] Put the silicon-chromium-aluminum alloy material into a graphite crucible 7 with a top opening diameter of 50 mm. The silicon content of the silicon-chromium-aluminum alloy material in the alloy or material is about 60%, the content of the chromium content in the alloy or material is about 36%, and the content of the aluminum content in the alloy or material is about 4% (i.e., Si0.6Cr0.36Al0.04). Place the graphite crucible 7 in a crystal growth furnace body 11, open the vacuum pump 21 and the vacuum valve 20 to evacuate the gas in the growth chamber, and then introduce argon (Ar) for protection. The pressure in the growth chamber is 0.5 standard atmosphere (atm), turn on the heating power supply, and heat the graphite crucible 7 at a power of 15KW by induction heating to melt the silicon-chromium-aluminum alloy material in the graphite crucible 7, and the molten silicon alloy melt dissolves the inner wall of the graphite crucible 7, thereby providing the carbon required for the synthesis of silicon carbide single crystals. When the temperature reaches 1850°C, keep warm for 30 minutes (min) to ensure complete melting of the silicon alloy material. The heat exchange liquid can be cooling water. The cooling water flow rate is adjusted to 0.6 liters / minute (L / min) and the water pressure is 0.2 MPa. Low flow rate and low water pressure weaken the heat exchange effect, and the insulation effect of the insulation layer 9 is maintained to ensure that the temperature at the solid-liquid interface of the seed crystal 5 in the upper half of the graphite crucible 7 is higher than the solution temperature in the lower half of the graphite crucible 7. The silicon carbide seed crystal 5 is glued to the graphite holder 4 that is threadedly matched with the seed crystal rod 12, and the seed crystal rod 12 and the graphite holder 4 are extended into the graphite crucible 7. The seed crystal 5 is melted back and etched to ensure uniform elimination of surface defects of the seed crystal 5 and improve the surface smoothness of the growing crystal. The melt-back height is 1 mm and the duration is 15 minutes (min). After the remelting is completed, the cooling water is adjusted to a flow rate of 4L / min and a water pressure of 0.9Mpa. The high flow rate and high water pressure quickly weaken the insulation effect of the upper part of the insulation layer 9, reduce the temperature of the upper part of the graphite crucible 7, and quickly move the high temperature area down to the lower part of the graphite crucible 7, so that the seed crystal 5 area is supercooled to form a carbon supersaturated area. The mode is switched to enter the crystal growth step, and a heating power of 9KW is provided. The carbon in the solution is deposited on the seed crystal 5. After the crystal grows for 60 hours (h), the heating power is gradually reduced to 0KW, and the temperature is slowly lowered until the temperature of the crystal growth furnace body 11 reaches room temperature, and the crystal is completed and taken out.

[0057] Another embodiment of the parameter selection in the method for growing silicon carbide by the top temperature-controlled liquid phase method of the present application is as follows:

[0058] A silicon-chromium-aluminum alloy material (Si0.6Cr0.33Al0.07) is put into a graphite crucible with a top opening of 40 mm. The content of silicon in the silicon-chromium-aluminum alloy material is about 60%, the content of chromium in the alloy or material is about 33%, and the content of aluminum in the alloy or material is about 7% (i.e., Si0.6Cr0.33Al0.07). The graphite crucible 7 is placed in a crystal growth furnace body 11, and the vacuum pump 21 and the vacuum valve 20 are turned on to evacuate the gas in the growth chamber. Subsequently, argon (Ar) is introduced for protection. The pressure in the growth chamber is 1 standard atmosphere (atm). The heating power supply is turned on, and the graphite crucible 7 is heated at 15KW by induction heating to melt the silicon-chromium-aluminum alloy material in the graphite crucible 7. The molten silicon alloy melt dissolves the inner wall of the graphite crucible 7 to provide the carbon required for the synthesis of silicon carbide single crystals. After reaching 1900°C, the temperature is kept for 25 minutes (min) to ensure that the silicon alloy material is completely melted. The heat exchange liquid can be liquid metal gallium indium tin alloy (GaInSn). The flow rate of the liquid metal gallium indium tin alloy (GaInSn) is adjusted to 0.5L / min and the pressure is 0.3Mpa. Low flow rate and low pressure weaken the heat exchange effect, and the insulation effect of the insulation layer 9 is maintained to ensure that the temperature at the solid-liquid interface of the seed crystal 5 on the upper part of the graphite crucible 7 is higher than the solution temperature at the lower part of the graphite crucible 7. The silicon carbide seed crystal 5 is adhered to the graphite holder 4 threadedly matched with the seed crystal rod 12. The seed crystal rod 12 and the graphite holder 4 are extended into the graphite crucible 7, and the seed crystal 5 is melted back and etched to ensure that the surface defects of the seed crystal 5 are uniformly eliminated and the surface smoothness of the growing crystal is improved. The melt-back height is 1.5mm and the duration is 10 minutes (min). After the remelting is completed, the flow rate of the liquid metal gallium indium tin alloy (GaInSn) is adjusted to 3L / min and the pressure is 0.7Mpa. The high flow rate and high pressure quickly weaken the insulation effect of the upper insulation layer 9, reduce the temperature at the top of the graphite crucible 7, and quickly move the high temperature area down to the lower part of the graphite crucible 7, so that the seed crystal 5 area is supercooled to form a carbon supersaturated area. The mode is switched to enter the crystal growth step, and a heating power of 10KW is provided. The carbon in the solution is deposited on the seed crystal 5. After the crystal grows for 40 hours (h), the heating power is gradually reduced to 0KW, and the temperature is slowly lowered until the temperature of the crystal growth furnace body 11 reaches room temperature, and the crystal is completed and taken out.

[0059] Compared with the existing liquid phase method for growing silicon carbide crystals, the present application uses an embedded pipe liquid cooling plate 13 as the top temperature control component and is placed in the upper part of the insulation layer 9. The liquid inlet 1 and the liquid outlet 8 connected to the liquid cooling plate 13 allow the heat exchange liquid as the cooling medium 2 to flow therein. By simply adjusting the flow rate and pressure of the heat exchange liquid, the insulation effect of the upper insulation layer 9 can be quickly changed, so as to achieve the effect of flexibly regulating the temperature distribution of the solution. In the remelting step, the heat exchange liquid is set to low flow and low hydraulic pressure, and the high temperature area will be located in the seed crystal 5 area at the top of the graphite crucible 7. When entering the crystal growth step, the heat exchange liquid is adjusted to high flow and high hydraulic pressure, which can quickly take away a large amount of heat, reduce the temperature of the upper part of the graphite crucible 7, and quickly move the high temperature area to the lower part of the graphite crucible 7, thereby realizing a fast mode switch from the remelting step to the crystal growth step.

[0060] See also Figure 1 The present application also provides a device for producing silicon carbide by a top temperature-controlled liquid phase method, which comprises: a heating component, comprising a heating coil 10 wound around the side of the graphite crucible 7; a top temperature-controlled component, comprising a heat exchange tube 24 arranged in a winding manner in the liquid cooling plate 13 (see, for example, Figure 6 , 7 ), both ends of the heat exchange tube 24 are located outside the liquid cooling plate 13; the graphite crucible 7, the heating coil 10, and the liquid cooling plate 13 are all located inside the crystal growth furnace body 11.

[0061] In one embodiment, both ends of the heat exchange tube 24 include a liquid inlet 1 and a liquid outlet 8 located outside the crystal growth furnace body 11; the liquid inlet 1, the liquid outlet 8 and the heat exchange tube 24 are used to allow the heat exchange liquid as the cooling medium 2 to pass through, and the cooling medium 2 is used to control the temperature of the liquid cooling plate 13. Figure 7 As shown, the heat exchange tube 24 also includes an embedded section located inside the liquid cooling plate 13 and an extraction section 241 located outside the liquid cooling plate 13. The embedded section includes horizontal sections 242 arranged in parallel and spaced apart from each other. The same ends of adjacent horizontal sections 242 are connected through an elbow section 243 of the heat exchange tube 24. The two ends of the elbow section 243 can be parallel and in the same direction. Figure 7 As shown, the lead-out section 241 is L-shaped, and the bottom end of the lead-out section 241 is parallel to the axis of the liquid cooling plate 13. The top ends of the two lead-out sections 241 are in opposite directions.

[0062] The beneficial effects of adopting the above embodiment are: the embedded section of the heat exchange tube 24 actually participates in the heat transfer, there is enough contact area between the embedded section and the liquid cooling plate 13, the embedded section and the liquid cooling plate 13 directly conduct solid heat to each other, and the outer surface of the liquid cooling plate 13 conducts heat to the high-temperature gas in the crystal growth furnace body 11. The lead-out section 241 of the heat exchange tube 24 is convenient for leading out the end of the heat exchange tube 24 and docking with other external equipment. In addition, the horizontal section 242 and the elbow section 243 of the embedded section indicate that the embedded section is arranged in an approximately S-shaped winding arrangement in the liquid cooling plate 13, so that the embedded section can have a longer length, and finally there is sufficient area and time for heat exchange between the heat exchange liquid and the liquid cooling plate 13.

[0063] In one embodiment, the graphite crucible 7 and the top temperature adjustment component are both wrapped with an insulation layer 9, which includes at least an upper insulation layer, a side insulation layer and a lower insulation layer. The highest point of the insulation layer 9 is higher than the top surface of the liquid cooling plate 13, and the lowest point of the insulation layer 9 is lower than the bottom surface of the graphite crucible 7. The heating coil 10 is located outside the side insulation layer. Figure 5 As shown, the insulation layer 9 includes a wrapping cavity 92 wrapping the liquid cooling plate 13 and the graphite crucible 7, the liquid cooling plate 13 and the graphite crucible 7 may be spaced a certain distance apart, and there may be no solid partition plate between the liquid cooling plate 13 and the graphite crucible 7. The insulation layer 9 may also include an insulation jacket passing through the crystal growth furnace body 11, and the insulation jacket wraps and protects the lead-out section 241 of the heat exchange tube 24.

[0064] In one embodiment, the heat exchange liquid in the heat exchange tube 24 is made of liquid gallium-indium-tin alloy, liquid gallium or water; the liquid cooling plate 13 is made of aluminum alloy, copper alloy or stainless steel; the heat exchange tube 24 is made of oxygen-free copper or tantalum. Oxygen-free copper refers to copper with an oxygen content of no more than 0.003%, a total impurity content of no more than 0.05%, and a copper purity of more than 99.95%.

[0065] The beneficial effect of the above embodiment is that the melting point of gallium indium tin alloy ranges from 5°C to 30°C, so gallium indium tin alloy is liquid at room temperature and is suitable as cooling medium 2 just like water. Oxygen-free copper or tantalum ensures the thermal conductivity and corrosion resistance of the heat exchange tube 24.

[0066] In one embodiment, the top of the graphite crucible 7 is provided with a graphite crucible cover 3, the upper surface of the seed crystal 5 is a graphite tray 4, and the upper surface of the graphite tray 4 is provided with a seed crystal rod 12 extending upward; the graphite crucible cover 3, the insulation layer 9, the liquid cooling plate 13, and the crystal growth furnace body 11 are all provided with through holes that allow the seed crystal rod 12 to pass through, and the seed crystal rod 12 drives the seed crystal 5 to extend into the graphite crucible 7. The actual assembly operation sequence is: the solid silicon alloy material is first placed in the graphite crucible 7 that is not covered with the graphite crucible cover 3, the graphite tray 4 is connected to the seed crystal rod 12, and then the seed crystal rod 12 is placed in the graphite tray 4, and then the graphite crucible cover 3 is covered to close the furnace and start vacuuming. Figure 3As shown, in order to facilitate the display of the internal structure, from the visual effect of the attached figure, Figure 3 A quarter of the fan-shaped area of ​​the top temperature-controlled liquid phase method for producing silicon carbide is cut off. From bottom to top, the seed crystal rod 12 passes through the first through hole 31 of the graphite crucible top cover 3, the fourth through hole 131 of the liquid cooling plate 13, the second through hole 91 on the top of the insulation layer 9, and the third through hole 111 on the top of the crystal growth furnace body 11. Among them, the inner diameters of the first through hole 31, the second through hole 91, and the third through hole 111 can be equal.

[0067] The beneficial effect of the above embodiment is that the seed crystal rod 12 facilitates external driving of the seed crystal 5 to change its position state in the graphite crucible 7. In addition, the first through hole 31, the second through hole 91, and the third through hole 111 also ensure sealing when the seed crystal rod 12 slides through.

[0068] like Figure 7 As shown, a gap 244 is formed between adjacent horizontal sections 242 of the heat exchange tube 24, and the heat exchange tube 24 has an avoidance area 245 that avoids the seed crystal rod 12 and expands the width of the gap 244. The heat exchange tubes 24 next to the avoidance area 245 are all arc-shaped. The fourth through hole 131 of the liquid cooling plate 13 is located at the centroid of the liquid cooling plate 13, and the avoidance area 245 does not contact or interfere with the inner wall of the fourth through hole 131.

[0069] The beneficial effects of the above embodiment are: the avoidance area 245 does not interfere with the fourth through hole 131 of the liquid cooling plate 13. First, the seed rod 12 is ensured to pass through the liquid cooling plate 13, and second, the arrangement density of the heat exchange tube 24 in the liquid cooling plate 13 is taken into consideration.

[0070] In one embodiment, the diameter range of the through hole of the liquid cooling plate 13 through which the seed rod 12 passes is 30mm to 60mm, and the thickness range of the liquid cooling plate 13 is 33mm to 60mm; the straight-line distance between the two ends of the embedded section is 300mm to 500mm, the vertical distance from the outer wall of the heat exchange tube 24 to the lower surface of the liquid cooling plate 13 is 0mm to 10mm, the outer diameter range of the heat exchange tube 24 is 12mm to 33mm, and the inner diameter range of the embedded section of the heat exchange tube 24 is 10mm to 30mm; the inner diameters of the liquid inlet 1 and the liquid outlet 8 at both ends of the heat exchange tube 24 can be smaller than the inner diameter of the embedded section, the outer diameters of the liquid inlet 1 and the liquid outlet 8 are in the range of 12mm to 32mm, and the inner diameters of the liquid inlet 1 and the liquid outlet 8 are in the range of 10mm to 29mm.

[0071] In one embodiment, the heat exchange tube 24 is buried in the lower half of the liquid cooling plate 13, close to the lower surface of the liquid cooling plate 13, to ensure that the heat exchange tube 24 can effectively absorb the heat from the top of the graphite crucible 7 and take away the heat through the flow of the heat exchange liquid.

[0072] In one embodiment, the junction of the lead-out section 241 of the heat exchange tube 24 and the embedded section is located on the outermost circumferential surface of the liquid cooling plate 13, ensuring that the heat exchange liquid path can flow through the entire liquid cooling plate 13, so as to maximize the heat exchange effect. In addition, the heat exchange tube 24 is integrally formed from the liquid inlet 1 to the liquid outlet 8, forming a continuous heat exchange liquid flow path, ensuring that the heat exchange liquid as the cooling medium 2 flows in the entire liquid cooling plate 13 for heat exchange, and then is discharged from the liquid outlet 8.

[0073] See also Figure 8 The present application also provides a system for producing silicon carbide by a top temperature-controlled liquid phase method. It includes: an air-cooled heat exchange module 14, both ends of a heat exchange tube 24 are connected to the air-cooled heat exchange module 14 and form a circulation pipeline, and the circulation pipeline is driven by a liquid transmission pump 16; a control system, and the circulation pipelines at both ends of the heat exchange tube 24 are provided with pressure sensors 19, flow meters 18, and temperature sensors 17.

[0074] The beneficial effect of adopting the above embodiment is that the pressure sensor 19 and the flow meter 18 are used to provide a dynamic heat exchange liquid with pressure and flow that meet the requirements. The heat exchange liquid first passes through the pressure sensor 19, the flow meter 18, and the temperature sensor 17 at the liquid inlet 1 to enter the liquid cooling plate 13, and after flowing out, passes through the pressure sensor 19, the flow meter 18, and the temperature sensor 17 at the liquid outlet 8, and then passes through the air-cooled heat exchange module 14 on the circulation pipeline to cool down, and then circulates back and forth, and the recycling of the heat exchange liquid ensures economic efficiency.

[0075] A high-precision pressure sensor 19 is installed at the liquid inlet 1 and the liquid outlet 8 to monitor the pressure change of the heat exchange liquid in real time. The output signal of the pressure sensor 19 is used for feedback regulation. A high-precision flow meter 18 is installed at the liquid inlet 1 and the liquid outlet 8 to monitor the flow of the heat exchange liquid in real time. The output signal of the flow meter 18 is also used for feedback regulation of the control system. A high-precision temperature sensor 17 is installed at the liquid inlet 1 and the liquid outlet 8 to monitor the temperature of the heat exchange liquid in real time, which is also used for feedback regulation of the control system. It is convenient to accurately calculate the heat taken away by the heat exchange liquid per unit time.

[0076] In one embodiment, the circulation pipeline is provided with an electric regulating valve 15, and the electric regulating valve 15 remotely controls the opening or closing of the circulation pipeline.

[0077] In one embodiment, the crystal growth furnace body 11 is connected to a vacuum pump 21 via a vacuum valve 20 ; the crystal growth furnace body 11 is also connected to an argon gas tank 22 via a gas valve.

[0078] The liquid transmission pump 16 is a water pump, a liquid metal pump, etc., which can work stably under high temperature conditions and provide stable flow and pressure. The material of the liquid transmission pump 16 can be high temperature resistant and corrosion resistant, such as stainless steel or tantalum.

[0079] The air-cooled heat exchange module 14 is made of a high-temperature resistant, high-thermal conductivity metal material. The air-cooled heat exchange module 14 includes heat dissipation fins to maximize the air contact area, thereby improving the heat exchange efficiency. In the cooling cycle, the hot cold liquid medium flows out from the liquid outlet 8 of the heat exchange tube 24, and the heat is transferred to the fins. When the air flows through these fins, the heat is effectively taken away, causing the temperature of the cooling medium 2 to drop rapidly, and then the cooling medium 2 with a lowered temperature is sent back. The air-cooled heat exchange module 14 and the circulation pipeline can help the cooling process of the cooling medium 2 without relying on additional cooling equipment, and make full use of the natural temperature of the ambient air, which not only improves the overall energy efficiency of the system, but also reduces operating costs and environmental impacts.

[0080] In one embodiment, if Figure 8 As shown, a thermocouple 23 may be provided inside the heat-insulating layer 9 , and the thermocouple 23 has a higher high temperature resistance than a general thermometer. The measured temperature of the thermocouple 23 is convenient for comparison with the temperature measured by the temperature sensor 17 .

[0081] like Figure 8 As shown, the circulation pipeline is connected with the liquid inlet 1 and the liquid outlet 8 of the heat exchange tube 24. Figure 8 is Figure 1 Based on the above, a variety of graphic symbols are used to represent the system of producing silicon carbide by top temperature-controlled liquid phase method.

[0082] The above embodiments are only for illustrating the technical concept and features of the present application, and their purpose is to enable people familiar with this technology to understand the content of the present application and implement it. They cannot be used to limit the scope of protection of the present application. All equivalent changes or modifications made according to the spirit of the present application should be included in the scope of protection of the present application.

Claims

1. A method for producing silicon carbide by a top temperature-controlled liquid phase method, characterized in that: include: The step of feeding: feeding solid silicon alloy material into a graphite crucible (7), and placing the graphite crucible (7) in a crystal growth furnace body (11); Heating step: heating the graphite crucible (7) to melt the solid silicon alloy material in the graphite crucible (7), and maintaining the temperature for a period of time after reaching a predetermined growth temperature until the solid silicon alloy material is completely melted; Melting back step: adjusting the top temperature adjustment component located above the graphite crucible (7) so that the temperature at the solid-liquid interface of the seed crystal (5) at the top of the graphite crucible (7) is higher than the solution temperature at the bottom of the graphite crucible (7), and performing melting back etching on the seed crystal (5); Crystal growth step: lowering the top temperature of the graphite crucible (7) so that the seed crystal (5) is supercooled to form a carbon supersaturation zone, and the carbon in the carbon-silicon solution (6) in the graphite crucible (7) is deposited on the seed crystal (5) to achieve crystal growth; Discharging step: after the growth of the crystal is completed, lowering the temperature of the crystal growth furnace (11) and taking out the crystal; The top temperature control component comprises a liquid cooling plate (13) arranged above the graphite crucible (7), a heat exchange tube (24) is pre-buried in the liquid cooling plate (13), and a flowing heat exchange liquid is provided in the heat exchange tube (24); in the remelting step, the flow rate and liquid pressure of the heat exchange liquid in the heat exchange tube (24) are respectively lower than the flow rate and liquid pressure of the heat exchange liquid in the heat exchange tube (24) in the crystal growth step.

2. The method for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 1, characterized in that: In the feeding step, the crystal growth furnace body (11) is first evacuated and then an inert gas is introduced; In the heating step, the graphite crucible (7) is heated by utilizing the electric current thermal effect of electromagnetic induction heating or resistance heating; The crystal growth furnace body (11) comprises a seed crystal rod (12) and a graphite holder (4) that cooperate with each other, and the seed crystal (5) is adhered to the graphite holder (4); in the remelting step, the surface defects of the seed crystal (5) are eliminated to improve the smoothness of the crystal grown by the seed crystal (5).

3. The method for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 1, characterized in that: In the remelting step, the remelting height of the seed crystal (5) ranges from 0.1 mm to 2.0 mm, and the duration ranges from 5 minutes to 30 minutes.

4. The method for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 1, characterized in that: In the remelting step, the liquid pressure of the heat exchange liquid in the heat exchange tube (24) ranges from 0.1 MPa to 0.3 MPa, and the flow rate ranges from 0.5 L / min to 1.0 L / min; During the crystal growth step, the liquid pressure of the heat exchange liquid in the heat exchange tube (24) ranges from 0.7 MPa to 1.0 MPa, and the flow rate ranges from 3 liters / minute to 5 liters / minute.

5. The method for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 1, characterized in that: The diameter of the top opening of the graphite crucible (7) is in the range of 40 mm to 50 mm, and the pressure of the graphite crucible (7) after the inert gas is introduced into the graphite crucible (7) is in the range of 0.5 standard atmosphere to 1 standard atmosphere; After the temperature in the graphite crucible (7) reaches a range of 1850° C. to 1900° C., the temperature is maintained for 25 to 30 minutes, and the flow rate of the heat exchange liquid is adjusted to a range of 0.5 liters / minute to 0.6 liters / minute, and the pressure of the heat exchange liquid is adjusted to a range of 0.2 MPa to 0.3 MPa; The melting back step has a melting back height ranging from 1 mm to 1.5 mm and a melting back duration ranging from 10 minutes to 15 minutes; After the remelting step is completed, the flow rate of the heat exchange fluid is adjusted to a range of 3 liters / minute to 4 liters / minute, and the pressure range of the heat exchange fluid is 0.7 MPa to 0.9 MPa; The heating power of the crystal growth step ranges from 9KW to 10KW, and the crystal growth duration ranges from 40 hours to 60 hours.

6. A device for producing silicon carbide by a top temperature-controlled liquid phase method, characterized in that: The device for producing silicon carbide by the top temperature-adjusting liquid phase method comprises: Graphite crucible (7); A heating assembly, comprising a heating coil (10) wound around the side of the graphite crucible (7); A top temperature control component comprises a liquid cooling plate (13) and a heat exchange tube (24) arranged in a winding manner in the liquid cooling plate (13), wherein both ends of the heat exchange tube (24) are located outside the liquid cooling plate (13); A crystal growth furnace body, wherein the graphite crucible (7), the heating coil (10), and the liquid cooling plate (13) are all located inside the crystal growth furnace body (11).

7. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 6, characterized in that: Both ends of the heat exchange tube (24) include a liquid inlet (1) and a liquid outlet (8) located outside the crystal growth furnace body (11); The heat exchange tube (24) further comprises an embedded section located inside the liquid cooling disk (13) and a lead-out section (241) located outside the liquid cooling disk (13); the embedded section comprises horizontal sections (242) arranged in parallel and spaced relation to each other; the same ends of adjacent horizontal sections (242) are connected via an elbow section (243) of the heat exchange tube (24).

8. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 7, characterized in that: The top of the graphite crucible (7) is provided with a graphite crucible top cover (3); The device for producing silicon carbide by the top temperature-adjusting liquid phase method further comprises a seed crystal (5), a graphite holder (4), a seed crystal rod (12) and a heat-insulating layer (9), wherein the heat-insulating layer is arranged around the graphite crucible (7). The upper surface of the seed crystal (5) is the graphite holder (4), and the upper surface of the graphite holder (4) is provided with the seed crystal rod (12) extending upward; The graphite crucible top cover (3), the heat-insulating layer (9), the liquid cooling plate (13), and the crystal growth furnace body (11) all have through holes through which the seed crystal rod (12) can pass.

9. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 8, characterized in that: A gap (244) is formed between adjacent horizontal sections (242) of the heat exchange tube (24), and the heat exchange tube (24) is provided with an avoidance area (245) for avoiding the seed crystal rod (12) and enlarging the width of the gap (244); The liquid cooling plate (13) enables the through hole through which the seed rod (12) passes to be located at the centroid of the liquid cooling plate (13), and the avoidance zone (245) does not contact or interfere with the inner wall of the through hole of the liquid cooling plate (13).

10. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 7, characterized in that: The graphite crucible (7) and the top temperature adjustment component are both wrapped with a heat-insulating layer (9); The heating coil (10) heats the graphite crucible (7) by electromagnetic induction, and the heating coil (10) is located outside the thermal insulation layer (9).

11. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 6, characterized in that: A method for producing silicon carbide by a top temperature-controlled liquid phase method according to any one of claims 1 to 5, The heat exchange liquid in the heat exchange tube (24) is made of liquid gallium-indium-tin alloy, liquid gallium or water; The liquid cooling plate (13) is made of aluminum alloy, copper alloy or stainless steel; The heat exchange tube (24) is made of oxygen-free copper or tantalum.

12. The device for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 8, characterized in that: The diameter of the through hole of the liquid cooling plate (13) through which the seed crystal rod (12) passes is in the range of 30 mm to 60 mm, and the thickness of the liquid cooling plate (13) is in the range of 33 mm to 60 mm; The straight-line distance between the two ends of the embedded section ranges from 300 mm to 500 mm, the vertical distance from the outer wall of the heat exchange tube (24) to the lower surface of the liquid cooling plate (13) ranges from 0 mm to 10 mm, the outer diameter of the heat exchange tube (24) ranges from 12 mm to 33 mm, and the inner diameter of the embedded section of the heat exchange tube (24) ranges from 10 mm to 30 mm; The inner diameters of the liquid inlet (1) and the liquid outlet (8) at both ends of the heat exchange tube (24) are smaller than the inner diameter of the embedded section; the outer diameters of the liquid inlet (1) and the liquid outlet (8) range from 12 mm to 32 mm; and the inner diameters of the liquid inlet (1) and the liquid outlet (8) range from 10 mm to 29 mm.

13. A system for producing silicon carbide by a top temperature-controlled liquid phase method, comprising the device for producing silicon carbide by a top temperature-controlled liquid phase method according to any one of claims 6 to 12, characterized in that: The system for producing silicon carbide by the top temperature-controlled liquid phase method comprises: An air-cooled heat exchange module (14), wherein both ends of the heat exchange tube (24) are connected to the air-cooled heat exchange module (14) and together form a circulation pipeline, and the heat exchange liquid in the circulation pipeline is driven by a liquid transmission pump (16); The control system comprises a pressure sensor (19), a flow meter (18), and a temperature sensor (17) arranged on the circulation pipeline at both ends of the heat exchange tube (24).

14. The system for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 13, characterized in that: The circulation pipeline is provided with an electric regulating valve (15), and the electric regulating valve (15) remotely controls the opening or closing of the circulation pipeline.

15. The system for producing silicon carbide by a top temperature-controlled liquid phase method according to claim 13, characterized in that: The crystal growth furnace body (11) is connected to a vacuum pump (21) via a vacuum valve (20); the crystal growth furnace body (11) is also connected to an argon gas tank (22).

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