Liquid phase method silicon carbide single crystal growth system and growth method

Abstract

The invention discloses a liquid phase method silicon carbide single crystal growth system and a growth method. The system comprises a furnace body; the heat preservation barrel is located in the furnace body; the crucible is positioned in the heat preservation barrel; the heating body is located in the furnace body and surrounds the periphery of the heat preservation barrel; the upper end of the liftable seed crystal rod penetrates out of the furnace body, and the lower end of the liftable seed crystal rod is connected with the seed crystal disc and can extend into the crucible; and the radar liquid level meter is located at the top of the furnace body, and microwave signals emitted by the radar liquid level meter can reach the liquid level of the melt in the crucible. The growth system can stably work for a long time in a high-temperature, vacuum or inert gas protection environment, and can realize high-precision and real-time monitoring of the liquid level height in a growth cycle of 60-80 hours of the liquid-phase silicon carbide single crystal. By providing reliable liquid level height data for the growth control system, the stability of the solid-liquid interface position can be effectively maintained, and adverse effects of temperature gradient fluctuation on the crystal growth rate and morphology are avoided, so that the growth controllability, the crystal quality and the yield of the liquid phase method silicon carbide single crystal are improved.

Description

Technical Field

[0001] This invention relates to the field of crystal growth technology, and in particular to a liquid-phase silicon carbide single crystal growth system and method. Background Technology

[0002] Silicon carbide (SiC), as a third-generation semiconductor material, has broad application prospects in new energy vehicles, smart grids, high-speed railways, and advanced radar due to its high thermal conductivity, high breakdown field strength, and excellent high-temperature and high-power performance. Liquid-phase growth of silicon carbide single crystals can significantly reduce dislocation density and obtain high-quality silicon carbide, overcoming the high dislocation density drawback of traditional vapor-phase methods. Therefore, liquid-phase growth technology has become a research hotspot in recent years. In the liquid-phase growth of silicon carbide single crystals, silicon and flux elements are placed in a high-purity graphite crucible and heated to a molten state. A temperature gradient is created along the axial direction of the molten liquid by controlling the temperature field. Once the temperature field stabilizes and the carbon concentration in the molten liquid reaches equilibrium, a seed crystal is pushed down and brought into contact with the molten liquid, causing epitaxial precipitation of silicon carbide single crystals on the seed crystal surface.

[0003] The growth cycle of liquid-phase silicon carbide single crystals typically lasts approximately 60-80 hours. During this extended growth process, silicon and carbon are continuously consumed, and significant carbon dissolution occurs at the graphite crucible walls, causing the molten liquid level within the crucible to continuously drop. This leads to changes in the solid-liquid interface conditions. For example, a decrease in liquid level alters the temperature gradient at the solid-liquid interface, affecting carbon supersaturation precipitation and significantly reducing the crystal growth driving force. If the temperature gradient at the solid-liquid interface fluctuates abnormally, the crystal growth rate becomes unstable. Excessive temperature gradients can easily cause quality problems such as crystal surface roughness, inclusion formation, polymorphism, and grain boundary defects. Furthermore, if the seed crystal accidentally detaches from the molten liquid surface during growth due to the drop in liquid level, crystal growth will be interrupted, potentially leading to the formation of unstable crystal structures on the seed crystal surface and causing polymorphic transformations. Therefore, failure to monitor the liquid level in a timely and accurate manner will result in frequent fluctuations at the solid-liquid interface, a significant decrease in crystal growth stability, and may even prevent the single crystal from growing stably for extended periods. High-quality growth of silicon carbide single crystals via liquid phase method depends on the stable control of the solid-liquid interface position over a long period of time, so the liquid level is a key factor affecting interface stability.

[0004] Therefore, existing technologies still need to be improved and developed. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this invention is to provide a liquid phase silicon carbide single crystal growth system and method, which aims to achieve timely and accurate detection of liquid level height.

[0006] The technical solution of the present invention is as follows: A first aspect of the present invention provides a liquid-phase silicon carbide single crystal growth system, wherein the liquid-phase silicon carbide single crystal growth system comprises: Furnace body; The heat-insulating container is located inside the furnace body; The crucible is located inside the insulated container; The heating element is located inside the furnace and surrounds the insulation barrel; The seed crystal rod is adjustable, with its upper end extending out of the furnace body and its lower end connected to the seed crystal plate and able to extend into the crucible; A radar level gauge is located at the top of the furnace body, and the microwave signal emitted by the radar level gauge can reach the surface of the molten liquid in the crucible.

[0007] Optionally, the liquid phase silicon carbide single crystal growth system further includes a heat insulation layer, which is located inside the furnace and is fitted over the heating element and the heat insulation barrel; The radar level gauge is aligned with the molten liquid level in the crucible through a transparent window located on the furnace body, insulation layer, and insulation barrel; the transparent window is made of sapphire or quartz and has a thickness of 5-10 mm.

[0008] Optionally, the crucible is a graphite crucible, the heating element is a graphite heating element, and the insulation layer is a graphite insulation felt; The radar level gauge is installed on the top of the furnace body via a waveguide or waveguide tube. The liquid-phase silicon carbide single crystal growth system also includes: A CCD camera is used to monitor images of the contact between the seed crystal and the molten metal. An infrared temperature sensor is used to monitor the temperature distribution near the crucible in real time.

[0009] Optionally, the liquid-phase silicon carbide single crystal growth system further includes: A seed crystal rod lifting mechanism is connected to the upper end of the seed crystal rod and is used to drive the seed crystal rod to rise or fall. The seed crystal rod weight sensor and the seed crystal rod position sensor are located on the seed crystal rod and are used to measure the total mass of the seed crystal rod, the seed crystal disk and the seed crystal, as well as the position of the seed crystal end face in real time, respectively. A crucible weight sensor, located at the bottom of the crucible, is used to measure the total mass of the crucible and the molten liquid inside the crucible in real time. The host computer and PLC execution unit are connected to the radar level gauge, the seed crystal rod weight sensor and the crucible weight sensor. The host computer is used to determine whether the seed crystal is in contact with the molten liquid surface based on the measurement data of the radar level gauge, the seed crystal rod weight sensor and the crucible weight sensor, and to calculate the seed crystal rod lifting speed and send instructions to the PLC execution unit. The PLC execution unit is connected to the host computer and the seed crystal rod lifting mechanism, respectively, and is used to control the seed crystal rod to rise, fall or change the seed crystal rod lifting speed according to the instructions issued by the host computer.

[0010] Optionally, the host computer has the following calculation formulas (1) to (3) embedded in it. The host computer obtains the result through formula (1). And send an order to the PLC execution unit to lower the seed crystal rod. The instructions; The host computer obtains the results through calculation formulas (2) and (3). and and according to and If all values ​​are equal to a preset positive value, it is determined that the seed crystal has made proper contact with the molten surface, and a command to raise the seed crystal rod for silicon carbide single crystal growth is sent to the PLC execution unit; according to and If all values ​​are 0, it is determined that the seed crystal and the molten liquid surface are not in proper contact, and a command to lower the seed crystal rod is sent to the PLC execution unit. (1) (2) (3) in, This represents the initial height of the seed crystal end face. This is the initial height of the molten liquid surface; The initial height difference between the seed crystal end face and the melt surface; This represents the initial total mass of the crucible and the molten metal; The initial total mass of the seed rod, seed disk, and seed crystal; For seed crystal rod descent Finally, the total mass of the crucible and the molten metal; For seed crystal rod descent Finally, the total mass of the seed crystal rod, seed crystal disk, and seed crystal; Compared to the initial total mass of the crucible and molten metal, the seed rod decreases. The reduction in the total mass of the crucible and molten metal after melting; Compared to the initial total mass of the seed rod, seed disk, and seed crystal, the seed rod decreases. The increase in the total weight of the seed crystal rod, seed crystal disk, and seed crystal.

[0011] Optionally, the host computer calculates the growth thickness of the silicon carbide single crystal based on the measurement data from the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor, calculates the growth rate of the silicon carbide single crystal based on the growth thickness of the silicon carbide single crystal, and calculates the seed crystal rod pulling speed based on the growth rate of the silicon carbide single crystal.

[0012] Optionally, the host computer is embedded with the following calculation formulas (4) and (5), the growth thickness of silicon carbide single crystal is obtained by calculation formula (4), and the growth rate of silicon carbide single crystal is obtained by calculation formula (5). (4) (5) in, To be in the time interval The growth thickness of the internal silicon carbide single crystal; To be in the time interval The apparent weight gain of the inner seed crystal is the weight gain measured by the seed crystal rod weight sensor; The cross-sectional area of ​​the seed crystal end face; Density of the melt; This refers to the density of a single crystal of silicon carbide. To be in the time interval The height by which the inner melt level drops; This represents the growth rate of silicon carbide single crystals.

[0013] Optionally, the host computer has the following calculation formulas (6) and (7) embedded in it, and the seed crystal rod pulling speed is obtained by calculation formulas (6) and (7);

[0014] (7) in, This represents the actual deviation from the interface. The height of the seed crystal end face at time t; Let t be the height of the molten liquid level. The seed crystal rod pulling speed; The growth rate of silicon carbide single crystals; This is the proportionality coefficient; The integral coefficient; These are the differential coefficients; The desired distance Δ0 between the seed crystal end face and the melt surface is defined as follows: The values ​​of Δ0 at different growth stages are as follows: During the meniscus control stage, 0 < Δ0 < 2 mm; during the steady-state growth stage, -2 mm < Δ0 < 0.

[0015] A second aspect of the present invention provides a method for growing a liquid-phase silicon carbide single crystal based on the liquid-phase silicon carbide single crystal growth system described above, comprising the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; The seed crystal rod is lowered to bring the seed crystal into contact with the molten surface. Then, the seed crystal rod is pulled up to grow silicon carbide single crystals. During the growth of silicon carbide single crystals, the height of the molten surface in the crucible is monitored in real time using a radar level gauge.

[0016] A second aspect of the present invention provides a method for growing a liquid-phase silicon carbide single crystal based on the liquid-phase silicon carbide single crystal growth system described above, comprising the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; Before silicon carbide single crystal growth, the host computer uses the measurement data from the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor to determine whether the seed crystal is in proper contact with the molten liquid surface. Once the seed crystal is in contact with the molten liquid surface, the seed crystal rod is pulled up to grow the silicon carbide single crystal. During the growth of the silicon carbide single crystal, the host computer obtains the growth rate of the silicon carbide single crystal and the seed crystal rod pulling speed through the measurement data of the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor, and sends instructions to the PLC execution unit. The PLC execution unit controls the seed crystal rod to rise, fall, or change the seed crystal rod pulling speed according to the instructions issued by the host computer, so as to realize the growth of silicon carbide single crystal. Beneficial Effects: The growth system provided by this invention can monitor the molten liquid level in the crucible in real time using a higher-precision radar level gauge. This non-contact measurement utilizes high-frequency microwave signals to detect the high-temperature molten liquid level in the graphite crucible in real time. The liquid level height is calculated by receiving reflected echo signals and combining them with the time-of-flight principle. This avoids the problems of insufficient measurement accuracy, large surface disturbance, poor repeatability between furnace cycles, and low long-term reliability in high-temperature vacuum environments caused by contact methods (where the probe is in direct contact with the high-temperature molten liquid). It significantly reduces measurement errors caused by probe corrosion, particle shedding, and surface disturbance.

[0017] The growth system provided by this invention can operate stably for extended periods under high temperature, vacuum, or inert gas protection environments, achieving high-precision, real-time monitoring of the liquid level height during the 60-80 hour growth cycle of liquid-phase silicon carbide single crystals. By providing reliable liquid level height data to the growth control system, the stability of the solid-liquid interface can be effectively maintained, avoiding adverse effects of temperature gradient fluctuations on crystal growth rate and morphology, thereby significantly improving the controllability, crystal quality, and yield of liquid-phase silicon carbide single crystal growth. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a liquid-phase silicon carbide single crystal growth system.

[0019] Figure 2 This is a schematic diagram of the liquid-phase silicon carbide single crystal growth process.

[0020] The labels in the attached diagram: 1. Furnace body; 2. Insulation container; 3. Crucible; 4. Heating element; 5. Seed crystal rod; 6. Seed crystal disk; 7. Radar level gauge; 8. Molten liquid; 9. Insulation layer; 10. Seed crystal rod weight sensor; 11. Crucible weight sensor; 12. Support rod. Detailed Implementation

[0021] This invention provides a liquid-phase silicon carbide single crystal growth system and method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0023] The terms used in this document, such as “vertical,” “horizontal,” “up,” “down,” “left,” “right,” and similar expressions, are for illustrative purposes only and do not represent the only possible implementation.

[0024] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0025] If the embodiments of the present invention involve descriptions such as "first" or "second", such descriptions are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0026] Because the molten metal in liquid-phase silicon carbide single crystal growth is highly corrosive and extremely sensitive to impurities, there is currently no commercially available high-precision contact measurement equipment or method suitable for the high-temperature molten metal in a graphite crucible. Existing technologies struggle to achieve reliable measurement without contaminating the molten metal. Furthermore, the liquid level changes continuously over the long growth process. Without real-time monitoring and dynamic control, the temperature gradient and morphological conditions at the solid-liquid interface cannot be effectively controlled, leading to a significant decrease in single crystal yield and crystal quality. Therefore, there is an urgent need to develop a non-contact, high-precision liquid level measurement technology that can operate stably for extended periods in high-temperature, vacuum, or inert gas protected environments. This technology should be able to accurately acquire the real-time position of the liquid level without disturbing the liquid surface, providing reliable data support for the growth control system. This allows for long-term stable control of the solid-liquid interface position through dynamic adjustment of process parameters, ultimately improving the growth quality and yield of liquid-phase silicon carbide single crystals. Based on this, this invention provides a liquid-phase silicon carbide single crystal growth system, wherein, as... Figure 1 As shown, the liquid-phase silicon carbide single crystal growth system includes: Furnace body 1; The heat preservation container 2 is located inside the furnace body 1; The crucible 3 is located inside the insulated container 2; The heating element 4 is located inside the furnace body 1 and surrounds the heat preservation barrel 2; Seed crystal rod 5, with its upper end protruding out of the furnace body 1 and its lower end connected to the seed crystal disk 6 and able to extend into the crucible 3; The radar level gauge 7 is located at the top of the furnace body 1. The microwave signal emitted by the radar level gauge 7 can reach the surface of the molten liquid 8 in the crucible.

[0027] The growth system provided by this invention can monitor the molten liquid level in the crucible in real time using a higher-precision radar level gauge. This non-contact measurement utilizes high-frequency microwave signals to detect the high-temperature molten liquid level in the graphite crucible in real time. The liquid level height is calculated by receiving reflected echo signals and combining them with the time-of-flight principle. This avoids the problems of insufficient measurement accuracy, large disturbance to the liquid surface, poor repeatability between furnace cycles, and low long-term reliability in high-temperature vacuum environments caused by contact methods (where the probe is in direct contact with the high-temperature molten liquid). It significantly reduces measurement errors caused by probe corrosion, particle shedding, and liquid surface disturbance.

[0028] The growth system provided by this invention can operate stably for extended periods under high temperature, vacuum, or inert gas protection environments, achieving high-precision, real-time monitoring of the liquid level height during the 60-80 hour growth cycle of liquid-phase silicon carbide single crystals. By providing reliable liquid level height data to the growth control system, the stability of the solid-liquid interface can be effectively maintained, avoiding adverse effects of temperature gradient fluctuations on crystal growth rate and morphology, thereby significantly improving the controllability, crystal quality, and yield of liquid-phase silicon carbide single crystal growth.

[0029] In some implementations, such as Figure 1 As shown, the liquid phase silicon carbide single crystal growth system also includes a heat insulation layer 9, which is located inside the furnace body 1 and is fitted over the heating element 4 and the heat insulation barrel 2.

[0030] In some embodiments, the crucible is a graphite crucible, the heating element is a graphite heating element, and the insulation layer is a graphite insulation felt.

[0031] In some embodiments, the radar level gauge is installed on the top of the furnace body via a waveguide or waveguide tube; the radar level gauge is aligned with the molten liquid level in the crucible through a transparent window located on the furnace body, insulation layer, and insulation barrel; the transparent window is made of sapphire or quartz, and the thickness of the transparent window is 5-10 mm.

[0032] The high-precision radar level gauge achieves non-contact measurement through a transparent window and can output real-time timestamped liquid level height and echo quality indicators. In this embodiment, the radar level gauge does not come into direct contact with the molten liquid, avoiding problems such as probe corrosion, graphite particle contamination, and liquid surface disturbance. Compared with traditional contact-based liquid level detection methods, the system provided by this invention maintains long-term stable operation in high-temperature environments, significantly improving the accuracy and reliability of liquid level measurement.

[0033] In crystal growth, controlling the crystal growth rate is crucial for ensuring crystal quality and maintaining the stability of the growth process. However, existing technologies typically rely on retrospective calculations based on changes in crystal thickness or mass after growth, failing to provide real-time acquisition of the growth rate or instant feedback control for the seed crystal pulling process. Therefore, the actual crystal growth rate cannot be dynamically determined during growth, making it prone to deviating from the target range, leading to instability at the solid-liquid interface and defects, severely impacting crystal quality and the controllability of the growth process. To address this, this invention provides a mechanism capable of simultaneously fusing data from changes in liquid level height, crucible mass, and seed crystal mass. This mechanism calculates the crystal growth rate and thickness and, in conjunction with a seed crystal rod lifting control mechanism, automatically controls the pulling rate, thereby ensuring long-term stability of the solid-liquid interface and high-quality, controllable growth of silicon carbide single crystals. Specifically, in some embodiments, such as... Figure 1 As shown, the liquid-phase silicon carbide single crystal growth system further includes: Seed crystal rod lifting mechanism ( Figure 1 (Not shown in the diagram), connected to the upper end of the seed crystal rod, used to drive the seed crystal rod to rise or fall; The seed crystal rod weight sensor 10 and the seed crystal rod position sensor are located on the seed crystal rod 5 and are used to measure the total mass of the seed crystal rod, the seed crystal disk and the seed crystal, as well as the position of the seed crystal end face in real time. A crucible weight sensor 11 is located at the lower part of the crucible 3 and is used to measure the total mass of the crucible and the molten liquid inside the crucible; specifically, the crucible weight sensor is located on a support rod 12, which is used to support the crucible 3. The host computer and PLC execution unit (the host computer and PLC execution unit can communicate bidirectionally via industrial Ethernet) are connected to the radar level gauge, seed crystal rod weight sensor, and crucible weight sensor. The host computer is used to determine whether the seed crystal is in contact with the molten liquid surface based on the measurement data of the radar level gauge, seed crystal rod weight sensor, and crucible weight sensor, and to calculate the seed crystal rod lifting speed (specifically, the liquid surface and growth rate fusion calculation unit in the host computer determines whether the seed crystal is in contact with the molten liquid surface based on the measurement data of the radar level gauge, seed crystal rod weight sensor, and crucible weight sensor, and calculates the seed crystal rod lifting speed), and sends instructions to the PLC execution unit. The PLC (Programmable Logic Controller) execution unit is connected to the host computer and the seed crystal rod lifting mechanism, respectively, and is used to control the seed crystal rod to rise, fall or change the seed crystal rod lifting speed according to the instructions issued by the host computer (by driving the seed crystal rod lifting mechanism).

[0034] In this embodiment, a high-precision radar level gauge is used to monitor the molten liquid level in real time. The weight loss of the molten liquid and the weight gain of the seed crystal are obtained through a crucible weight sensor and a seed crystal rod weight sensor, respectively. Combined with changes in liquid level height, the immersion volume of the crystal in the molten liquid and the change in buoyancy are calculated. Based on the principle of mass conservation, the crystal growth thickness and growth rate are accurately calculated. On this basis, the host computer calculates the seed crystal rod pulling speed based on the crystal growth rate and the liquid level height deviation (i.e., the actual interface deviation), and sends this information to the PLC execution unit via industrial Ethernet to achieve automatic raising and lowering adjustment of the seed crystal rod. The system forms a closed-loop link of "liquid level detection—mass feedback—rate calculation—pulling control," enabling stable control of the solid-liquid interface during continuous 60-80 h growth of liquid-phase silicon carbide single crystals. This improves the accuracy of crystal growth rate measurement and single crystal quality, and avoids interface instability caused by crucible dissolution, liquid level fluctuations, and molten liquid evaporation. This invention effectively maintains the stability of the solid-liquid interface, avoiding the adverse effects of temperature gradient fluctuations on crystal growth rate and morphology, thereby significantly improving the controllability, crystal quality, and yield of liquid-phase silicon carbide single crystal growth. The growth system provided by this invention offers strong real-time performance and is suitable for industrial-scale liquid-phase growth of silicon carbide single crystals.

[0035] In some embodiments, the liquid-phase silicon carbide single crystal growth system further includes: CCD camera ( Figure 1 (Not shown in the image), used to monitor the contact between the seed crystal and the molten metal; Infrared temperature sensor ( Figure 1 (Not shown in the image), used for real-time monitoring of the temperature distribution near the crucible.

[0036] A CCD camera is an imaging device with a charge-coupled device (CCD) as its core. The CCD camera can be set inside the top of the furnace (or outside the top of the furnace) and aim at (or aim through a transparent window) the periphery of the seed crystal to collect images of the contact between the seed crystal end face and the liquid surface. The images are used to determine the contact position, surface wettability and interface morphology (such as the appearance of ripples, foam or sputtering abnormalities) through image processing.

[0037] The CCD camera and infrared temperature sensor are connected to the host computer to transmit data.

[0038] In the host computer (specifically the liquid level and growth rate fusion calculation unit), the acquired multi-source data, including liquid level, mass, temperature, and images, undergoes time-series registration and filtering. Based on mass conservation, buoyancy correction, and material density relationships, it calculates the axial thickness and instantaneous growth rate of the crystal in real time and provides a determination of the relative position of the seed crystal and the liquid surface. Furthermore, the host computer obtains the target lifting speed of the seed crystal rod through the instantaneous growth rate and sends the command to the PLC execution unit in real time via industrial Ethernet. Upon receiving the command, the PLC execution unit first performs a safety and legality check (including speed / acceleration limits, travel limits, and collision detection). If it passes the check, it drives the seed crystal rod lifting structure to perform the corresponding rising or falling action, completing the closed-loop regulation. The PLC execution unit can also transmit the execution status and position back to the host computer, which continues to update the calculation based on the latest feedback.

[0039] In some implementations, the host computer is embedded with the following calculation formulas (1) to (3); The host computer obtains the result through formula (1). And send an order to the PLC execution unit to lower the seed crystal rod. The instructions; The host computer obtains the results through calculation formulas (2) and (3). and and according to and If all values ​​are equal to a preset positive value, it is determined that the seed crystal has made proper contact with the molten surface, and a command to raise the seed crystal rod for silicon carbide single crystal growth is sent to the PLC execution unit; according to and If all values ​​are 0, it is determined that the seed crystal and the molten liquid surface are not in proper contact, and a command to lower the seed crystal rod is sent to the PLC execution unit. (1) (2) (3) in, This represents the initial height of the seed crystal end face. This is the initial height of the molten liquid surface; The initial height difference between the seed crystal end face and the melt surface; This represents the initial total mass of the crucible and the molten metal; The initial total mass of the seed rod, seed disk, and seed crystal; For seed crystal rod descent Finally, the total mass of the crucible and the molten metal; For seed crystal rod descent Finally, the total mass of the seed crystal rod, seed crystal disk, and seed crystal; Compared to the initial total mass of the crucible and molten metal, the seed rod decreases. The reduction in the total mass of the crucible and molten metal after melting; Compared to the initial total mass of the seed rod, seed disk, and seed crystal, the seed rod decreases. The increase in the total weight of the seed crystal rod, seed crystal disk, and seed crystal.

[0040] In this embodiment, the growth system achieves automatic and stable alignment between the seed crystal end face and the molten liquid surface, and can maintain a high degree of interface stability during a growth cycle of up to 60 to 80 hours.

[0041] In this embodiment, , These are the initial height of the seed crystal end face and the initial height of the molten liquid surface after a unified reference. Before the seed crystal contacts the molten liquid and the molten liquid surface is in a statically stable state, the growth system automatically records the initial reference data related to the liquid surface and mechanical position. Specifically, this includes: the initial height of the molten liquid surface measured by a radar level gauge, the initial axial position of the seed crystal end face (obtained by a seed crystal rod position sensor (containing an encoder)), and the initial total mass of the crucible and molten liquid. And the initial total mass of the seed rod, seed disk, and seed crystal. Meanwhile, the growth system also acquires inherent parameters of the growth system, such as the installation reference height of the radar level gauge, the geometric dimensions of the crucible, and the allowable stroke of the seed crystal rod, based on the equipment calibration parameters. After completing the initial reference data acquisition, the host computer analyzes the initial data uploaded by the radar level gauge and the seed crystal rod position sensor, and calculates the initial relative height difference between the two based on the spatial relationship between the liquid level height and the seed crystal end face position. Specifically, the host computer first reads the initial height of the molten liquid level uploaded by the radar level gauge and the initial position of the seed crystal end face returned by the seed crystal rod encoder. Then, it establishes a unified spatial coordinate reference, completes the coordinate transformation between the liquid level height and the mechanical position, and obtains the initial height H0 of the molten liquid level and the initial height P0 of the seed crystal end face relative to the unified reference.

[0042] In a unified reference coordinate system, the host computer calculates the initial axial distance (i.e., relative height difference) between the seed crystal end face and the melt surface according to the following formula:

[0043] The relative height difference ΔZ is used to guide the subsequent alignment and descent of the seed crystal rod, and is an important reference parameter before the seed crystal end face contacts the melt.

[0044] Based on this, the host computer further judges the stability of the liquid level signal, and at the same time monitors the liquid surface image of the crucible in real time through a CCD camera to ensure that the liquid level height does not fluctuate significantly.

[0045] Next, the host computer calculates... The PLC execution unit is instructed to lower the seed crystal rod. The command activates the seed crystal rod lifting mechanism, and the seed crystal rod, driven by the seed crystal rod lifting structure, presses... Smooth decline (i.e., decline) This allows the seed crystal's end face to gradually approach the molten surface. During the descent, a slow start and low acceleration control strategy is employed to avoid surface disturbance and thermal shock to the seed crystal. As the seed crystal rod descends... After the distance is reached, the host computer (specifically, the mass change monitoring unit) collects data on the descent of the seed crystal rod. Instantaneous total mass of the crucible and molten metal and seed crystal rod descent Instantaneous total mass of the seed rod, seed disk, and seed crystal The contact state between the seed crystal end face and the liquid surface is determined by the mass change relationship. To accurately determine whether the seed crystal end face and the melt surface are in proper contact, the host computer calculates the changes in the total mass of the crucible and melt, and the total mass of the seed crystal rod, seed crystal disk, and seed crystal relative to the initial measurement values. and When detected A slight increase in weight is sufficient to reach the preset positive value (for example, for a 6-8 inch (approximately 150-200 mm in diameter) seed crystal, when the immersion depth is on the order of 0.05-0.15 mm). The weight is 2-10g, preferably 5g, and When both mass changes occur simultaneously and satisfy the mass conservation trend, it is determined that the seed crystal end face has made contact with the melt surface; if both mass changes remain stable and have no significant increment (i.e., ... and If all values ​​are equal to 0, then it is considered that there is no contact, and the system continues to descend the seed crystal axis in microsteps until the contact condition is met.

[0046] In some embodiments, the host computer calculates the growth thickness of the silicon carbide single crystal based on the measurement data from the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor. It then calculates the growth rate of the silicon carbide single crystal based on its growth thickness and the seed crystal rod pulling speed based on its growth rate. Specifically, the host computer has embedded the following calculation formulas (4) and (5). The growth thickness of the silicon carbide single crystal is obtained through calculation formula (4), and the growth rate is obtained through calculation formula (5).

[0047] (4) (5) in, To be in the time interval The growth thickness of the internal silicon carbide single crystal; To be in the time interval The apparent weight gain of the inner seed crystal is the weight gain measured by the seed crystal rod weight sensor; The cross-sectional area of ​​the seed crystal end face; Density of the melt; This refers to the density of a single crystal of silicon carbide. To be in the time interval The height by which the inner melt level drops; This represents the growth rate of silicon carbide single crystals.

[0048] In this embodiment, after confirming stable contact between the seed crystal end face and the molten liquid surface, the system enters the crystal growth stage. To monitor the crystal growth process in real time, the host computer performs monitoring at the first time t1 and the second time t2 (i.e., =t2-t1) Obtain the following key data, and use the following key data to obtain the instantaneous crystal growth rate: 1. By using a high-precision radar level gauge to output the molten liquid level height H(t1) at time t1 and H(t2) at time t2, the change in molten liquid level height is obtained as: ΔH(t) = H(t1). H(t2); 2. The total mass m of the seed crystal rod, seed crystal disk, and seed crystal at times t1 and t2, as measured by the seed crystal rod weight sensor. s (t1) and m s (t2), the total weight gain obtained: Δm s (t)=m s (t2) m s (t1); 3. Cross-sectional area of ​​the seed crystal end face melt density Silicon carbide single crystal density .

[0049] In this embodiment, ΔH(t) and Δm s (t), crystal displacement volume, buoyancy change, evaporation loss, etc. are all incorporated into the mass conservation relationship. This invention can calculate the crystal growth thickness ΔL and real-time growth rate in millisecond or second-level cycles in real time. This enables the realization of the "real-time visibility of growth rate" problem that has never been solved by existing technologies.

[0050] In this embodiment, the above calculation formula (4) is set based on the following calculation method and principle: The actual increase in solid mass due to seed crystal (or crystal) growth: (41); The change in buoyancy caused by the crystal being immersed in the molten liquid: (42) in, To be in the time interval Within, the volume change of the liquid displaced by the seed crystal (or crystal) entering the molten liquid (i.e., the time interval between t1 and t2 is...) ,but (This is the difference between the volume of liquid displaced by the crystal when it enters the molten liquid at time t2 and the volume of liquid displaced by the crystal when it enters the molten liquid at time t1).

[0051] Therefore, the apparent mass change of the seed crystal (i.e., the apparent weight gain of the seed crystal) measured by the seed crystal rod weight sensor can be obtained from the calculation formulas (41) and (42): Δm s (t)= = - = - (43) The growth thickness can then be obtained using formula (43): .

[0052] Specifically, the host computer has the following calculation formulas (6) and (7) embedded in it, and the seed crystal rod pulling speed is obtained by calculation formulas (6) and (7);

[0053] (7) in, This represents the actual deviation from the interface. The height of the seed crystal end face at time t; Let t be the height of the molten liquid level. The seed crystal rod pulling speed; The growth rate of silicon carbide single crystals; The proportionality coefficient ( Used to provide real-time proportional compensation for actual interface deviations, thereby improving interface adjustment speed. This is the integral coefficient (used to eliminate long-term cumulative bias). The differential coefficient (used to suppress disturbances caused by the rate of change of deviation, which helps to improve the dynamic stability of the growth interface); The desired distance between the seed crystal end face and the melt surface (used to determine the target relative position of the solid-liquid interface) is Δ0, and the values ​​of Δ0 at different growth stages are as follows: During the meniscus control stage, 0 < Δ0 < 2mm (to make the seed crystal end face slightly higher than the liquid surface to avoid excessive interface stress); During the steady-state growth stage, -2mm < Δ0 < 0 (allowing the seed crystal end face to be slightly immersed in the melt to enhance interface stability).

[0054] In this embodiment, to ensure a stable connection between the seed crystal end face and the molten liquid surface, the host computer calculates the current relative height difference ΔZ(t) = P(t) based on the real-time obtained seed crystal end face height P(t) and molten liquid surface height H(t). H(t) is compared with the preset target relative height difference Δ0, and the seed crystal rod pulling speed is adjusted in real time to keep the solid-liquid interface stably at the desired position.

[0055] Subsequently, the actual error e(t) and crystal growth rate of the host computer's integrated interface were analyzed. The target seed crystal rod pulling speed at the current moment is generated according to the above calculation formula (7). .

[0056] In this embodiment, the growth system can significantly improve the accuracy of solid-liquid interface position control, so that the interface deviation can be stably controlled within ±0.5~1 mm, greatly stabilize the crystal growth interface conditions, effectively suppress interface fluctuations, abnormal crystal growth and diameter expansion failure, and improve the crystal yield and quality consistency.

[0057] In the calculation formula (7) The crystal growth rate, calculated based on the change in melt mass and the drop in liquid level, is used as feedforward compensation. , , These are proportional, integral, and derivative parameters, respectively, obtained by analyzing the actual deviation of the interface. By performing proportional, integral, and differential operations, a closed-loop correction of the seed crystal rod pulling speed is achieved, so that the crystal solid-liquid interface is maintained near the preset desired distance Δ0 between the seed crystal end face and the melt surface, thereby improving growth stability.

[0058] In this embodiment, the calculation of the pulling speed follows the control principle of maintaining interface stability: when the actual interface is higher than the target position (e(t)>0), the pulling speed is reduced or the seed crystal rod is driven to descend; when the actual interface is lower than the target position (e(t)<0), the pulling speed is increased so that the seed crystal end face approaches the target relative height again.

[0059] Calculated lifting speed The command is transmitted to the PLC execution unit in real time via industrial Ethernet. The PLC execution unit performs safety checks on the command, including travel limit, speed limit, acceleration limit, and collision protection. After passing the safety checks, it drives the seed crystal rod lifting mechanism to adjust the seed crystal rod along the axial direction, thereby automatically adjusting the interface position and ensuring that the solid-liquid interface is always maintained within the preset position range, achieving stable single crystal growth.

[0060] In addition, during the growth of silicon carbide single crystals, if abnormal fluctuations in the liquid level, abnormal weight loss of the crucible, abnormal weight gain of the seed crystal, or excessive stroke of the seed crystal rod are detected, the fault protection mechanism is triggered and the pulling operation is stopped.

[0061] Specifically, the system monitors key parameters in real time throughout the entire crystal growth cycle, including ΔH(t) and Δm. c (t), Δm s (t), seed crystal rod position and stroke status, etc. When the host computer detects any of the following abnormal conditions, the system immediately triggers the fault protection logic: (1) Abnormal fluctuations in liquid level When the radar level gauge detects an abnormal drop or sudden rise in the liquid level within a short period of time, and the change exceeds the preset fluctuation threshold (e.g., ±2 mm), the host computer determines that there may be disturbance at the molten interface, local condensation, or abrupt dissolution of the crucible wall; the CCD camera identifies sputtering / overflow or abnormal seed crystal end face morphology, or the seed crystal rod is approaching its stroke limit. At this time, the system immediately executes preset protection actions (including adjusting the pulling speed, short-term retraction, alarm, pause, etc.) and enters a protection state to prevent the crystal end face from detaching or deeply immersing in the molten liquid due to interface instability.

[0062] (2) Abnormal weight loss of crucible If the total mass change of the crucible and molten metal changes abruptly beyond the set range within a unit of time (e.g., the crucible's weight loss rate exceeds the upper limit of the normal dissolution rate for three consecutive sampling cycles), it indicates that there may be localized abnormal corrosion of the crucible, leakage, or excessively rapid evaporation of the molten metal. The system will immediately stop the lifting motion and issue an alarm.

[0063] Furthermore, the growth system provided by this invention can be equipped with backup sensors (such as infrared cameras, seed crystal level sensors, gas composition sensors, etc.) and a local data storage unit for long-term trend analysis and process optimization. The modules, connection methods, and detection thresholds can be adjusted according to the specific furnace structure and process requirements, but the basic data flow and control logic are all feasible modifications within the scope of this invention and are protected by the claims.

[0064] This invention also provides a method for growing silicon carbide single crystals using the liquid-phase silicon carbide single crystal growth system described above, comprising the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; The seed crystal rod is lowered to bring the seed crystal into contact with the surface of the molten liquid. Then, the seed crystal rod is pulled up to grow silicon carbide single crystals. During the growth of silicon carbide single crystals, the liquid level in the crucible is monitored using a radar level gauge.

[0065] This invention also provides a method for growing silicon carbide single crystals using the liquid-phase silicon carbide single crystal growth system described above, comprising the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; Before silicon carbide single crystal growth, the host computer uses the measurement data from the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor to determine whether the seed crystal is in proper contact with the molten liquid surface. Once the seed crystal is in contact with the molten liquid surface, the seed crystal rod is pulled up to grow the silicon carbide single crystal. During the growth of the silicon carbide single crystal, the host computer obtains the growth rate of the silicon carbide single crystal and the seed crystal rod pulling speed through the measurement data of the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor, and sends instructions to the PLC execution unit. The PLC execution unit controls the seed crystal rod to rise, fall, or change the seed crystal rod pulling speed according to the instructions issued by the host computer, so as to realize the growth of silicon carbide single crystal.

[0066] Specifically, such as Figure 2 As shown, the liquid-phase silicon carbide single crystal growth method based on the liquid-phase silicon carbide single crystal growth system described above according to the present invention includes the following steps: Once heating is turned on and the temperature reaches the predetermined value, the heating element melts the silicon and metal flux in the crucible to form a molten liquid. Turn on the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor. The host computer obtains initial data through the test data from the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor. , , , ),pass Calculation obtained Then, the host computer sends a message to the PLC execution unit to lower the seed crystal rod. Upon receiving the distance command, the PLC execution unit drives the seed crystal rod lifting mechanism, causing the seed crystal rod to descend. At this point, the host computer obtains the test data from the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor. , ,pass and Calculation obtained and and according to and Determine whether the seed crystal and the molten surface are in proper contact. If they are not in proper contact, continue the above steps until they are in proper contact. If they are in proper contact, proceed to the growth stage.

[0067] During the growth stage, the host computer uses ΔH(t)=H(t1) H(t2) and Δm s (t)=m s (t2) m s (t1) Obtain ΔH(t) and Δm s (t), and the growth thickness is calculated using the above calculation formulas (4) and (5) respectively. and growth rate Then, obtain the preset expected distance. (Also known as the desired height), the actual deviation of the interface is calculated using the above calculation formula (6). Then, the seed crystal rod pulling speed is calculated using the above formula (7). The command is sent to the PLC execution unit, which then drives the seed crystal rod lifting mechanism. The seed crystal rod lifting mechanism servo controls the movement of the seed crystal rod to achieve automatic adjustment.

[0068] If there are no abnormal fluctuations in the liquid level, abnormal weight loss of the crucible, abnormal weight gain of the seed crystal, or excessive stroke of the seed crystal rod during the growth of silicon carbide single crystal, the next cycle will proceed. If there are abnormal fluctuations in the liquid level, abnormal weight loss of the crucible, abnormal weight gain of the seed crystal, or excessive stroke of the seed crystal rod during the growth of silicon carbide single crystal, the fault protection mechanism will be triggered and the pulling operation will be stopped.

[0069] In summary, this invention provides a liquid-phase silicon carbide single crystal growth system and method. Through the fusion of a high-precision radar level gauge, crucible weight sensor, seed crystal rod weight sensor, and host computer calculations, it achieves real-time coordinated monitoring of melt level height, melt mass changes, and crystal weight gain changes. Furthermore, by combining a crystal growth kinetic model, the growth rate and thickness are calculated, thus constructing a complete closed-loop system for automatic liquid level height adjustment. This system exhibits significant technical advantages in the harsh environments of liquid-phase silicon carbide single crystal growth, including long cycles, high temperatures, and high vacuum / inert gas conditions, as detailed below: (1) Achieve non-contact, high-precision real-time measurement of liquid level, avoiding contamination and interference.

[0070] This high-precision radar level gauge achieves non-contact measurement by avoiding direct contact with the molten liquid, thus preventing probe corrosion, molten liquid contamination, and liquid surface disturbance. Compared to traditional contact-based liquid level detection methods, this invention maintains long-term stable operation in high-temperature environments, significantly improving the accuracy and reliability of liquid level measurement.

[0071] (2) Construct a crystal growth rate and growth thickness estimation model based on mass conservation to realize real-time growth rate calculation.

[0072] This invention simultaneously acquires data on crucible weight loss, seed crystal weight gain, and liquid level drop. It integrates factors such as solidification quality changes caused by crystal growth, melt loss due to crucible erosion, and displaced volume changes resulting from crystal immersion in the melt into a unified mass conservation model, thereby accurately calculating crystal growth thickness and growth rate. Compared to existing technologies that can only extrapolate growth rate from the average thickness after growth is complete, this invention significantly improves the real-time performance and accuracy of growth rate measurement.

[0073] (3) Achieve automatic alignment and dynamic stability control between the seed crystal end face and the molten liquid surface.

[0074] By calculating the real-time height difference Δ(Z) = P(t) H(t), combined with the growth rate v(t) and the preset desired distance between the seed crystal end face and the melt surface. This invention enables automatic adjustment of the seed crystal rod pulling speed, ensuring that the seed crystal end face remains near a predetermined position. This closed-loop control avoids interface fluctuations, detachment from the melt, or excessive immersion, improving solid-liquid interface stability, reducing interface nucleation fluctuations, and enhancing crystal surface smoothness. It can maintain high interface stability during growth cycles of up to 60-80 hours, fundamentally reducing defects such as interface disorder, dendrites, inclusions, diameter expansion failures, and abnormal surface roughness, thereby improving the uniformity and smoothness of the crystal structure.

[0075] (4) Construct an automatic control strategy to achieve precise lifting speed control under complex growth conditions.

[0076] This invention constructs a pulling speed calculation model based on the crystal growth rate v(t) to achieve real-time closed-loop adaptive adjustment of the pulling speed. This control strategy can automatically adapt to complex working conditions such as changes in melt composition, temperature fluctuations, and changes in crucible erosion rate, ensuring that the interface movement speed always matches the solidification speed during crystal growth, thereby avoiding problems such as interface accumulation, depressions, or growth disorder.

[0077] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A liquid-phase silicon carbide single crystal growth system, characterized in that, The liquid-phase silicon carbide single crystal growth system includes: Furnace body; The heat-insulating container is located inside the furnace body; The crucible is located inside the insulated container; The heating element is located inside the furnace and surrounds the insulation barrel; The seed crystal rod is adjustable, with its upper end extending out of the furnace body and its lower end connected to the seed crystal plate and able to extend into the crucible; A radar level gauge is located at the top of the furnace body, and the microwave signal emitted by the radar level gauge can reach the surface of the molten liquid in the crucible.

2. The liquid-phase silicon carbide single crystal growth system according to claim 1, characterized in that, The liquid-phase silicon carbide single crystal growth system also includes a heat insulation layer, which is located inside the furnace and is fitted over the heating element and the heat insulation barrel. The radar level gauge is aligned with the molten liquid level in the crucible through a transparent window located on the furnace body, insulation layer, and insulation barrel; the transparent window is made of sapphire or quartz and has a thickness of 5-10 mm.

3. The liquid-phase silicon carbide single crystal growth system according to claim 2, characterized in that, The crucible is a graphite crucible, the heating element is a graphite heating element, and the insulation layer is a graphite insulation felt; The radar level gauge is installed on the top of the furnace body via a waveguide or waveguide tube. The liquid-phase silicon carbide single crystal growth system also includes: A CCD camera is used to monitor images of the contact between the seed crystal and the molten metal. An infrared temperature sensor is used to monitor the temperature distribution near the crucible in real time.

4. The liquid-phase silicon carbide single crystal growth system according to any one of claims 1-3, characterized in that, The liquid-phase silicon carbide single crystal growth system also includes: A seed crystal rod lifting mechanism is connected to the upper end of the seed crystal rod and is used to drive the seed crystal rod to rise or fall. The seed crystal rod weight sensor and the seed crystal rod position sensor are located on the seed crystal rod and are used to measure the total mass of the seed crystal rod, the seed crystal disk and the seed crystal, as well as the position of the seed crystal end face in real time, respectively. A crucible weight sensor, located at the bottom of the crucible, is used to measure the total mass of the crucible and the molten liquid inside the crucible in real time. The host computer and PLC execution unit are connected to the radar level gauge, the seed crystal rod weight sensor and the crucible weight sensor. The host computer is used to determine whether the seed crystal is in contact with the molten liquid surface based on the measurement data of the radar level gauge, the seed crystal rod weight sensor and the crucible weight sensor, and to calculate the seed crystal rod lifting speed and send instructions to the PLC execution unit. The PLC execution unit is connected to the host computer and the seed crystal rod lifting mechanism, respectively, and is used to control the seed crystal rod to rise, fall or change the seed crystal rod lifting speed according to the instructions issued by the host computer.

5. The liquid-phase silicon carbide single crystal growth system according to claim 4, characterized in that, The host computer has the following calculation formulas (1) to (3) embedded in it. The host computer obtains the result through formula (1). And send an order to the PLC execution unit to lower the seed crystal rod. The instructions; The host computer obtains the results through calculation formulas (2) and (3). and and according to and If all values ​​are equal to a preset positive value, it is determined that the seed crystal has made proper contact with the molten surface, and a command to raise the seed crystal rod for silicon carbide single crystal growth is sent to the PLC execution unit; according to and If all values ​​are 0, it is determined that the seed crystal and the molten liquid surface are not in proper contact, and a command to lower the seed crystal rod is sent to the PLC execution unit. （1） （2） （3） in, This represents the initial height of the seed crystal end face. This is the initial height of the molten liquid surface; The initial height difference between the seed crystal end face and the melt surface; This represents the initial total mass of the crucible and the molten metal; The initial total mass of the seed rod, seed disk, and seed crystal; For seed crystal rod descent Finally, the total mass of the crucible and the molten metal; For seed crystal rod descent Finally, the total mass of the seed crystal rod, seed crystal disk, and seed crystal; Compared to the initial total mass of the crucible and molten metal, the seed rod decreases. The reduction in the total mass of the crucible and molten metal after melting; Compared to the initial total mass of the seed rod, seed disk, and seed crystal, the seed rod decreases. The increase in the total weight of the seed crystal rod, seed crystal disk, and seed crystal.

6. The liquid-phase silicon carbide single crystal growth system according to claim 5, characterized in that, The host computer calculates the growth thickness of the silicon carbide single crystal based on the measurement data from the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor. It then calculates the growth rate of the silicon carbide single crystal based on the growth thickness and the seed crystal rod pulling speed based on the growth rate.

7. The liquid-phase silicon carbide single crystal growth system according to claim 6, characterized in that, The host computer is embedded with the following calculation formulas (4) and (5). The growth thickness of silicon carbide single crystal is obtained by calculation formula (4), and the growth rate of silicon carbide single crystal is obtained by calculation formula (5). （4） （5） in, To be in the time interval The growth thickness of the internal silicon carbide single crystal; To be in the time interval The apparent weight gain of the inner seed crystal is the weight gain measured by the seed crystal rod weight sensor; The cross-sectional area of ​​the seed crystal end face; Density of the melt; This refers to the density of a single crystal of silicon carbide. To be in the time interval The height by which the inner melt level drops; This represents the growth rate of silicon carbide single crystals.

8. The liquid-phase silicon carbide single crystal growth system according to claim 7, characterized in that, The host computer has the following calculation formulas (6) and (7) embedded in it. The seed crystal rod pulling speed is obtained by using the calculation formulas (6) and (7). （7） in, This represents the actual deviation from the interface. The height of the seed crystal end face at time t; Let t be the height of the molten liquid surface. The seed crystal rod pulling speed; The growth rate of silicon carbide single crystals; This is the proportionality coefficient; The integral coefficient; These are the differential coefficients; The desired distance Δ0 between the seed crystal end face and the melt surface is defined as follows: The values ​​of Δ0 at different growth stages are as follows: During the meniscus control stage, 0 < Δ0 < 2 mm; during the steady-state growth stage, -2 mm < Δ0 < 0.

9. A method for growing liquid-phase silicon carbide single crystals based on the liquid-phase silicon carbide single crystal growth system according to any one of claims 1-3, characterized in that, Includes the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; The seed crystal rod is lowered to bring the seed crystal into contact with the molten surface. Then, the seed crystal rod is pulled up to grow silicon carbide single crystals. During the growth of silicon carbide single crystals, the height of the molten surface in the crucible is monitored in real time using a radar level gauge.

10. A method for growing liquid-phase silicon carbide single crystals based on the liquid-phase silicon carbide single crystal growth system according to any one of claims 4-8, characterized in that, Includes the following steps: A heating element is used to melt the silicon and metal flux in the crucible to form a molten liquid; Before silicon carbide single crystal growth, the host computer uses the measurement data from the radar level gauge, crucible weight sensor, and seed crystal rod weight sensor to determine whether the seed crystal is in proper contact with the molten liquid surface. Once the seed crystal is in contact with the molten liquid surface, the seed crystal rod is pulled up to grow the silicon carbide single crystal. During the growth of the silicon carbide single crystal, the host computer obtains the growth rate of the silicon carbide single crystal and the seed crystal rod pulling speed through the measurement data of the radar level gauge, the seed crystal rod weight sensor, and the crucible weight sensor, and sends instructions to the PLC execution unit. The PLC execution unit controls the seed crystal rod to rise, fall, or change the seed crystal rod pulling speed according to the instructions issued by the host computer, so as to realize the growth of silicon carbide single crystal.

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