Automatic liquid level contact detection system for liquid phase method silicon carbide single crystal growth furnace

Abstract

The invention provides an automatic liquid level contact detection system for a liquid phase method silicon carbide single crystal growth furnace. The automatic liquid level contact detection system comprises a seed crystal measuring point unit, a crucible measuring point unit, a high-precision resistance detector and a PLC (Programmable Logic Controller) programmable crystal growth control system, the electronic change characteristic curve between the seed crystal and the liquid level can be directly measured, the contact position of the seed crystal and the liquid level can be rapidly, accurately and reliably detected, the successful state of the seed crystal in contact with the liquid level is automatically judged, and the contact judgment success rate of the seed crystal and the liquid level is 100%; the liquid phase method silicon carbide crystal automatically grows, manual operation is not needed, and the production efficiency is greatly improved.

Description

Technical Field

[0001] The invention relates to the field of automatic control of electromechanical equipment, and in particular to an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace. Background Art

[0002] Liquid phase carbide single crystal growth has very strict requirements on the temperature distribution in the thermal field. The temperature is about 1750 degrees. Due to the thermal insulation environment of the thermal field, it is impossible to open a window to observe the crystal growth state. When growing crystals in a blind box state, there are usually two ways to judge whether the seed crystal is in contact with the liquid surface:

[0003] Method ①: Manually calculate the contact position and manually determine the liquid contact. This cannot effectively determine the critical state of the liquid surface and the seed crystal combination, and may result in misjudgment and failure to contact the liquid surface, resulting in material and time cost losses.

[0004] Method ②: Infrared temperature measurement is used to measure the temperature change of the seed crystal graphite drag, and the temperature difference is used to determine the liquid connection. The volatile matter of silicon carbide causes inaccurate temperature measurement, and there are many unstable factors. Manual liquid connection is inefficient and has poor reliability.

[0005] Current problems: Liquid phase silicon carbide cannot accurately determine the contact position between the seed crystal and the liquid surface, has poor production stability, cannot grow automatically, and has low production efficiency. Summary of the invention

[0006] In view of the problems existing in the prior art, the present invention provides an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, which can directly measure the electronic change characteristic curve between the seed crystal and the liquid surface, quickly, accurately and reliably detect the contact position between the seed crystal and the liquid surface, and automatically judge the successful state of the seed crystal contacting the liquid surface. The success rate of judging the contact between the seed crystal and the liquid surface is 100%. The liquid phase method silicon carbide crystal grows automatically without manual operation, and the production efficiency is greatly improved.

[0007] The technical solution of the present invention is: an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, comprising a seed crystal measurement point unit, a crucible measurement point unit, a high-precision resistance detector and a PLC programmable crystal growth control system;

[0008] The seed crystal measurement point unit includes a seed crystal measurement point, a seed crystal rod, a first ceramic insulating sheet and a seed crystal high temperature resistant cable; the seed crystal measurement point is a copper terminal, which is installed on the cavity by adding a Teflon gasket, so that the center of the copper terminal of the seed crystal measurement point is insulated from the cavity; the seed crystal rod is a stainless steel seed crystal rod, which is designed to be divided into two sections, upper and lower, and can be lifted and rotated. The first ceramic insulating sheet is used to isolate and insulate the middle of the upper and lower sections of the stainless steel seed crystal rod, and the lower section of the stainless steel seed crystal rod is insulated from the cavity, and the measured resistance is greater than 1MΩ; the seed crystal in the furnace is connected to the seed crystal measurement point by a seed crystal high temperature resistant cable;

[0009] The crucible measurement point unit includes a crucible measurement point, a crucible rod, a second ceramic insulating sheet and a crucible high temperature resistant cable; the crucible measurement point is a copper terminal, which is installed on the cavity by adding a Teflon gasket, so that the center of the copper terminal of the crucible measurement point is insulated from the cavity; the crucible rod is a stainless steel crucible rod, which is designed to be divided into two sections, upper and lower, and can be lifted and rotated. The middle of the upper and lower sections of the stainless steel crucible rod is isolated and insulated by a second ceramic insulating sheet, and the upper section of the stainless steel crucible rod is insulated from the cavity, and the measurement resistance is greater than 1MΩ; the crucible high temperature resistant cable is used to connect the solution in the furnace to the crucible measurement point;

[0010] The high-precision resistance detector is connected to the seed crystal measurement point and the crucible measurement point respectively through external cables;

[0011] The PLC programmable crystal growth control system is connected to the high-precision resistance detector, which detects the resistance value between the seed crystal and the liquid level in the furnace in real time, records the data to generate a current and resistance trend curve, determines the position where the seed crystal contacts the liquid level, and automatically jumps to the step of starting crystal growth.

[0012] The present invention also provides an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, comprising a seed crystal measurement point unit, a high-precision resistance detector and a PLC programmable crystal growth control system;

[0013] The seed crystal measurement point unit includes a seed crystal measurement point, a seed crystal rod, a first ceramic insulating sheet and a seed crystal high temperature resistant cable; the seed crystal measurement point is a copper terminal, which is installed on the cavity by adding a Teflon gasket, so that the center of the copper terminal of the seed crystal measurement point is insulated from the cavity; the seed crystal rod is a stainless steel seed crystal rod, which is designed to be divided into two sections, upper and lower, and can be lifted and rotated. The first ceramic insulating sheet is used to isolate and insulate the middle of the upper and lower sections of the stainless steel seed crystal rod, and the lower section of the stainless steel seed crystal rod is insulated from the cavity, and the measured resistance is greater than 1MΩ; the seed crystal in the furnace is connected to the seed crystal measurement point by a seed crystal high temperature resistant cable;

[0014] The high-precision resistance detector is connected to the seed crystal measurement point via an external cable;

[0015] The PLC programmable crystal growth control system is connected to the high-precision resistance detector to measure the current characteristic curves of the seed crystal and the cavity.

[0016] Further, the seed crystal measurement point unit also includes a seed crystal sliding wire ring; the seed crystal sliding wire ring includes an outer ring of the seed crystal sliding wire ring, an inner ring of the seed crystal sliding wire ring, a fixed ring on the outer ring side of the seed crystal scribing ring, and a seed crystal limiting rod;

[0017] The fixed ring on the outer ring side of the seed crystal sliding wire ring is connected to the cavity by lifting and sliding using a seed crystal limiting rod, that is, the outer ring of the seed crystal sliding wire ring is relatively fixed and does not rotate with the cavity, and the first seed crystal high temperature resistant cable is used on the outer ring wiring side of the seed crystal sliding wire ring to connect the inner side connection point of the cavity of the seed crystal measurement point copper terminal;

[0018] The inner ring of the seed crystal slide wire ring is locked with the upper stainless steel seed crystal rod by using a top screw, and the inner ring of the seed crystal slide wire ring rotates and runs synchronously with the upper stainless steel seed crystal rod; the second seed crystal high temperature resistant cable is used to connect the lower stainless steel seed crystal rod on the wiring side of the inner ring of the seed crystal slide wire ring, so that the seed crystal measurement point terminal and the lower stainless steel seed crystal rod are connected to the same circuit;

[0019] The outer ring of the seed crystal slide wire ring and the inner ring of the seed crystal slide wire ring are insulated from the internal circuit of the seed crystal slide wire ring.

[0020] The present invention also provides an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, comprising a crucible measurement point unit, a high-precision resistance detector and a PLC programmable crystal growth control system;

[0021] The crucible measurement point unit includes a crucible measurement point, a crucible rod, a second ceramic insulating sheet and a crucible high temperature resistant cable; the crucible measurement point is a copper terminal, which is installed on the cavity by adding a Teflon gasket, so that the center of the copper terminal of the crucible measurement point is insulated from the cavity; the crucible rod is a stainless steel crucible rod, which is designed to be divided into two sections, upper and lower, and can be lifted and rotated. The middle of the upper and lower sections of the stainless steel crucible rod is isolated and insulated by a second ceramic insulating sheet, and the upper section of the stainless steel crucible rod is insulated from the cavity, and the measurement resistance is greater than 1MΩ; the crucible high temperature resistant cable is used to connect the solution in the furnace to the crucible measurement point;

[0022] The high-precision resistance detector is connected to the crucible measurement point via an external cable;

[0023] The PLC programmable crystal growth control system is connected to the high-precision resistance detector to measure the current characteristic curves of the solution and the cavity in the furnace.

[0024] Furthermore, the crucible measurement point unit also includes a crucible sliding line ring; the crucible sliding line ring includes a crucible sliding line ring outer ring, a crucible sliding line ring inner ring, a crucible scoring ring outer ring side fixing ring, and a crucible limiting rod;

[0025] The fixing ring on the outer ring side of the crucible sliding wire ring is connected to the cavity by lifting and sliding using a crucible limiting rod, that is, the outer ring of the crucible sliding wire ring is relatively fixed and does not rotate with the cavity, and the first crucible high temperature resistant cable is used on the outer ring wiring side of the crucible sliding wire ring to connect the inner side connection point of the cavity of the copper terminal of the crucible measurement point;

[0026] The inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod are locked with a top screw, and the inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod rotate and run synchronously together; the second crucible high temperature resistant cable is used on the wiring side of the inner ring of the crucible sliding wire ring to connect the upper stainless steel crucible rod, so that the crucible measurement point terminal and the upper stainless steel crucible rod are connected to the same circuit;

[0027] The outer ring of the crucible sliding wire ring and the inner ring of the crucible sliding wire ring are insulated from the internal circuit of the crucible sliding wire ring.

[0028] The beneficial effects of the present invention are as follows: providing an automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, a seed crystal rod and a crucible rod are designed with a new structure, and a ceramic insulating sheet is used to insulate the seed crystal rod from the cavity, or to insulate the crucible from the cavity. A high temperature resistant sliding wire ring is added to the seed crystal rod or the crucible rod, and the relevant connecting cable uses a high temperature resistant cable to connect the seed crystal detection circuit. Two high-precision resistance detection systems between the seed crystal and the crucible and between the seed crystal and the cavity are designed, which can monitor the resistance change curve between the seed crystal and the liquid surface in the furnace in real time. Before and after the seed crystal contacts the liquid surface, the resistance change curve has a step response change characteristic to judge, confirm the seed crystal lifting position, and detect the contact state between the seed crystal and the liquid surface. In the process of liquid phase method silicon carbide crystal growth, the liquid contact state is detected in real time as a key factor in judging the processing flow, so as to realize accurate and automatic jump of the crystal growth process. The growth cycle of liquid phase method silicon carbide is about 7 days, and in this process, no manual supervision is achieved, which improves production efficiency and more importantly, improves the reliability of crystal growth. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a schematic diagram of the seed crystal and liquid surface contact detection system;

[0030] Figure 2 This is a schematic diagram of the seed crystal slide line ring structure;

[0031] Figure 3 This is the main structural diagram of the liquid surface contact system;

[0032] Figure 4 This is the circuit diagram for detecting the resistance of the seed crystal and the crucible;

[0033] Figure 5 This is the circuit diagram for detecting the resistance of the seed crystal and the cavity;

[0034] Figure 6 This is the circuit diagram for detecting resistance of crucible and cavity.

[0035] In the figure: 1 is the seed crystal measurement point, 2 is the seed crystal rod, 3 is the seed crystal sliding wire ring, 4 is the first ceramic insulating sheet, 5 is the seed crystal high temperature resistant cable, 6 is the second ceramic insulating sheet, 7 is the crucible high temperature resistant cable, 8 is the seed crystal sliding wire ring, 9 is the crucible rod, 10 is the crucible measurement point, 11 is the first external connection cable, 12 is the second external connection cable, 13 is the high-precision resistance detector, 14 is the cavity, 15 is the seed crystal in the furnace, 16 is the solution in the furnace, 17 is the PLC programmable crystal growth control system, 20 is the outer ring of the seed crystal sliding wire ring, 21 is the inner ring of the seed crystal sliding wire ring, 23 is the second seed crystal high temperature resistant cable, 24 is the outer ring side fixing ring of the seed crystal sliding wire ring, 25 is the seed crystal limiting rod, 27 is the first seed crystal high temperature resistant cable, 29 is the upper stainless steel seed crystal rod, and 30 is the lower stainless steel seed crystal rod. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] An automatic liquid surface contact system for a liquid phase method silicon carbide single crystal growth furnace. Figure 1 As shown, it is used for rapid and accurate detection of the contact state between the seed crystal and the raw material solution. The structure consists of four parts: a seed crystal measurement point unit, a crucible measurement point unit, a high-precision resistance detector 13, and a PLC crystal growth control system 17, which can accurately monitor the contact state between the seed crystal and the liquid surface.

[0038] The main structure of the liquid surface contact system is as follows: Figure 3 shown.

[0039] Seed crystal measurement point unit: mainly realizes the insulation isolation between the seed crystal and the furnace body circuit, and the electronic characteristic data of the seed crystal can be measured outside the furnace. Seed crystal measurement point 1 is a copper terminal with a Teflon gasket to insulate the center of the terminal from the cavity and achieve the sealing of the connection. Seed crystal rod 2 is a stainless steel seed crystal rod, which is designed to be divided into two sections, which can be lifted and rotated. The first ceramic insulating sheet 4 is used for isolation in the middle to insulate the lower stainless steel seed crystal rod from the cavity. The measured resistance is greater than 1 MΩ to achieve circuit insulation isolation. The seed crystal 15 in the furnace is connected to the seed crystal measurement point 1 using a seed crystal high temperature resistant cable 5: This cable uses a special engineering plastic PEEK customized high temperature resistant cable. When the seed crystal is lifted and lowered in the high temperature environment of the furnace, the cable is guaranteed to be used normally, and the seed crystal can be effectively isolated from the cavity.

[0040] When the seed crystal rotates, a seed crystal sliding wire ring 3 is added to realize the dynamic electrical connection between the seed crystal and the seed crystal connection point at the upper part of the cavity when the seed crystal rod rotates; the sliding wire ring shell is insulated from the internal circuit. Figure 2As shown, the fixed ring 24 on the outer ring side of the seed crystal slide wire ring is connected to the cavity 14 by lifting and sliding using the seed crystal limit rod 25, that is, the outer ring of the seed crystal slide wire ring is relatively fixed and does not rotate with the cavity, and the first seed crystal high temperature resistant cable 27 is used on the wiring side of the outer ring 20 of the seed crystal slide wire ring to connect the inner connection point of the cavity of the copper terminal of the seed crystal measurement point 1, so as to keep the connection cable 27 from being damaged by rotation. The inner ring 21 of the seed crystal slide wire ring is locked with the upper stainless steel seed crystal rod 29 by the top screw, and the inner ring 21 of the seed crystal slide wire ring rotates and runs synchronously with the upper stainless steel seed crystal rod 29; the second seed crystal high temperature resistant cable 23 is used on the wiring side of the inner ring 21 of the slide wire ring to connect the lower stainless steel seed crystal rod 30, so that the seed crystal measurement point terminal and the lower stainless steel seed crystal rod are connected to the same circuit.

[0041] The upper stainless steel seed crystal rod 29 and the lower stainless steel seed crystal rod 30 are isolated by the first ceramic insulating pad 4, and the sliding wire ring housing is insulated from the internal circuit. Figure 3 The seed crystal 15 is insulated from the cavity 14 and other components. When the seed crystal is lifted, lowered and rotated, the electrical characteristic data of the seed crystal in the furnace can be detected in real time at the seed crystal measurement point 1.

[0042] Crucible measurement point unit: mainly realizes the insulation isolation between the crucible and the furnace body circuit, and can measure the electronic characteristics data of the solution outside the furnace. The basic principle is the same as the above-mentioned seed crystal unit. The crucible measurement point 10 is a copper terminal with a Teflon gasket to insulate the center of the terminal from the cavity and achieve the sealing of the connection. The crucible rod 9 is a stainless steel crucible rod, which is designed to be divided into two sections, which can be raised and lowered and rotated. The second ceramic insulating sheet 6 is used in the middle to insulate and insulate the upper stainless steel crucible rod from the cavity. The measured resistance is greater than 1MΩ to achieve circuit insulation isolation. The crucible high temperature resistant cable 7 is used to connect the solution 16 in the furnace to the crucible measurement point 10: This cable uses a special engineering plastic PEEK customized high temperature resistant cable. When the crucible is raised and lowered in the high temperature environment of the furnace, the cable is guaranteed to be used normally, and the crucible and the cavity can be effectively isolated.

[0043] When the crucible rotates, a crucible wire slide ring 8 is added; the crucible wire slide ring 8 includes an outer ring of the crucible wire slide ring, an inner ring of the crucible wire slide ring, a fixing ring on the outer ring side of the crucible marking ring, and a crucible limiting rod; the fixing ring on the outer ring side of the crucible wire slide ring is connected to the cavity by a crucible limiting rod for lifting and sliding, that is, the outer ring of the crucible wire slide ring is relatively fixed to the cavity and does not rotate, and the first crucible high-temperature resistant cable is used on the wiring side of the outer ring of the crucible wire slide ring to connect the inner side connection point of the cavity of the crucible measuring point 10 copper terminal; the inner ring of the crucible wire slide ring and the lower stainless steel crucible rod are locked with a top screw, and the inner ring of the crucible wire slide ring rotates and runs synchronously with the lower stainless steel crucible rod; the second crucible high-temperature resistant cable is used on the wiring side of the inner ring of the crucible wire slide ring to connect the upper stainless steel crucible rod, so that the crucible measuring point terminal and the upper stainless steel crucible rod are connected to the same circuit; the outer ring of the crucible wire slide ring and the inner ring of the crucible wire slide ring are insulated from the internal circuit of the crucible wire slide ring.

[0044] A high temperature resistant custom cable is used on the outside of the crucible sliding wire ring 8 to connect the connection point inside the cavity of the copper terminal of the crucible measurement point 10. The high temperature resistant cable 7 on the inside of the sliding wire ring is connected to the upper stainless steel crucible rod on the upper end of the crucible insulation gasket 6. The crucible measurement point terminal and the upper stainless steel crucible rod of the crucible are connected to the same circuit. The crucible and silicon carbide solution 16 are insulated from the cavity 14 and other components, and the electrical characteristic data of the crucible solution in the furnace can be detected in real time at the crucible measurement point 10.

[0045] The high-precision resistance detector 13 is combined into three detection circuits through the first external connection cable 11 and the second external connection cable 12:

[0046] 1. Detect the contact resistance between the silicon carbide seed crystal 15 and the silicon carbide solution 16 in the crucible to determine the contact state. The electrical circuit is as follows: Figure 4 As shown (seed crystal measurement point unit and crucible measurement point unit are used at the same time).

[0047] 2. Detect the contact resistance between the silicon carbide seed crystal 15 and the cavity 14 to determine the contact state. The electrical circuit is as follows: Figure 5 As shown (only the seed crystal measurement point unit is used, the crucible measurement point unit is cancelled, the crucible rod is an integrated structure, and the crucible is connected and conductive with the cavity).

[0048] 3. Detect the contact resistance between the silicon carbide solution 16 in the silicon carbide crucible and the cavity 14 to determine the contact state. Figure 6 As shown (only the crucible measurement point unit is used, the seed crystal measurement point unit is cancelled, the seed crystal rod is an integrated structure, and the seed crystal is connected and conducted with the cavity).

[0049] The PLC programmable crystal growth control system 17 detects the resistance value between the seed crystal and the liquid surface in real time, records the data to generate a current and resistance trend curve, accurately determines the position where the seed crystal contacts the liquid surface, and automatically jumps to the step of starting crystal growth.

[0050] The specific inspection method of the automatic liquid surface contact system of the liquid phase silicon carbide single crystal growth furnace is as follows:

[0051] In the liquid phase silicon carbide crystal growth furnace, after the raw materials are added and melted, there are volatile silicon carbide gases, which cause the seed crystal to have a conductor-like resistance characteristic when there is no contact between the liquid surface and the crystal. Different raw material process formulas result in inconsistent conductive properties of the volatile gas. To address this difficulty, the above three detection circuits are designed to achieve effective and reliable measurement of the electronic properties of the seed crystal and the solution when the furnace environment is different.

[0052] 1. Conventional thermal environment, when there are few volatiles: use Figure 4The seed crystal and crucible resistance detection circuit directly measures the seed crystal and solution current characteristic curves, calculates the resistance change curve, observes the change trend, and records the liquid contact characteristics. At this time, the influence of the cavity and other external interferences is eliminated.

[0053] 2. When the space below the thermal field is limited: When the crucible wire loop 8 cannot be installed and the crucible measurement point unit cannot be used, only the seed crystal measurement point unit can be used. Figure 5 The seed crystal and cavity resistance detection circuit measures the current characteristic curve of the seed crystal and the cavity, and calculates the resistance change curve. At this time, the cavity and the solution circuit are connected. When there are more volatiles, adjust the adjustable resistance parameters, observe the change trend, and record the liquid contact characteristics.

[0054] 3. When the upper space of the thermal field is limited: the customer needs to use the visual measurement sensor CCD to observe the top of the thermal field. The upper space in the furnace requires a larger observation field of view. When the seed crystal slide ring 3 cannot be installed and the seed crystal measurement point unit cannot be used, only the crucible measurement point unit can be used. Figure 6 The resistance detection circuit of the crucible and the cavity measures the current characteristic curve of the solution in the crucible and the cavity, and calculates the resistance change curve. At this time, the cavity and the seed crystal circuit are connected, the adjustable resistance parameters are adjusted, the change trend is observed, and the liquid contact characteristics are recorded.

[0055] The liquid phase silicon carbide crystal growth furnace uses an automatic liquid surface contact detection system to quickly and efficiently detect the resistance and current change characteristic curves between the seed crystal and the solution. Through curve trend analysis, the contact status between the seed crystal and the liquid surface can be accurately and reliably detected. In the above three processing environment, the three detection methods are switched, which has been applied in batches in the automatic production of silicon carbide.

[0056] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. An automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, characterized in that: It includes a seed crystal measuring point unit, a crucible measuring point unit, a high-precision resistance detector (13) and a PLC programmable crystal growth control system (17); The seed crystal measurement point unit comprises a seed crystal measurement point (1), a seed crystal rod (2), a first ceramic insulating sheet (4) and a seed crystal high temperature resistant cable (5); the seed crystal measurement point (1) is a copper terminal, which is installed on the cavity (14) by adding a Teflon gasket, so that the center of the copper terminal of the seed crystal measurement point (1) is insulated from the cavity (14); the seed crystal rod (2) is a stainless steel seed crystal rod, which is designed to be divided into two sections, upper and lower, and can be lifted and rotated. The first ceramic insulating sheet (4) is used to isolate and insulate the middle of the upper and lower sections of the stainless steel seed crystal rod, and the lower section of the stainless steel seed crystal rod is insulated from the cavity, and the measured resistance is greater than 1MΩ; the seed crystal (15) in the furnace is connected to the seed crystal measurement point (1) by a seed crystal high temperature resistant cable (5); The crucible measurement point unit comprises a crucible measurement point (10), a crucible rod (9), a second ceramic insulating sheet (6) and a crucible high temperature resistant cable (7); the crucible measurement point (10) is a copper terminal, which is installed on the cavity (14) by adding a Teflon gasket, so that the center of the copper terminal of the crucible measurement point (10) is insulated from the cavity (14); the crucible rod (9) is a stainless steel crucible rod, which is designed to be divided into two sections, upper and lower, and can be raised and lowered and rotated. The middle of the upper and lower sections of the stainless steel crucible rod is isolated and insulated by a second ceramic insulating sheet (6), and the upper section of the stainless steel crucible rod is insulated from the cavity, and the measured resistance is greater than 1MΩ; the crucible high temperature resistant cable (7) is used to connect the solution (16) in the furnace to the crucible measurement point (10); The high-precision resistance detector (13) is connected to the seed crystal measurement point (1) and the crucible measurement point (10) respectively via external cables; The PLC programmable crystal growth control system (17) is connected to the high-precision resistance detector (13) to detect the resistance value between the seed crystal and the liquid surface of the solution in the furnace in real time, record the data to generate a current and resistance trend curve, and determine the position where the seed crystal contacts the liquid surface.

2. The automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace according to claim 1, characterized in that: The seed crystal measurement point unit further comprises a seed crystal sliding line ring (3); the seed crystal sliding line ring (3) comprises a seed crystal sliding line ring outer ring (20), a seed crystal sliding line ring inner ring (21), a seed crystal scoring ring outer ring side fixing ring (24), and a seed crystal limiting rod (25); The fixed ring (24) on the outer ring side of the seed crystal sliding wire ring is connected to the cavity (14) by lifting and sliding using a seed crystal limiting rod (25), that is, the outer ring of the seed crystal sliding wire ring and the cavity are relatively fixed and do not rotate, and the first seed crystal high temperature resistant cable (27) is used on the wiring side of the outer ring of the seed crystal sliding wire ring (20) to connect the inner side connection point of the cavity of the copper terminal of the seed crystal measurement point (1); The inner ring (21) of the seed crystal slide wire ring and the upper stainless steel seed crystal rod (29) are locked by using a top screw, and the inner ring (21) of the seed crystal slide wire ring and the upper stainless steel seed crystal rod (29) rotate together and run synchronously; the wiring side of the inner ring (21) of the seed crystal slide wire ring is connected to the lower stainless steel seed crystal rod (30) by using a second seed crystal high temperature resistant cable (23), so that the seed crystal measurement point terminal and the lower stainless steel seed crystal rod are connected to the same circuit; The seed crystal slide wire ring outer ring (20) and the seed crystal slide wire ring inner ring (21) are insulated from the internal circuit of the seed crystal slide wire ring.

3. The automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace according to claim 1, characterized in that: The crucible measurement point unit further comprises a crucible sliding line ring (8); the crucible sliding line ring (8) comprises a crucible sliding line ring outer ring, a crucible sliding line ring inner ring, a crucible marking ring outer ring side fixing ring, and a crucible limiting rod; The fixing ring on the outer ring side of the crucible sliding wire ring is connected to the cavity by lifting and sliding using a crucible limiting rod, that is, the outer ring of the crucible sliding wire ring is relatively fixed and does not rotate with the cavity, and the first crucible high temperature resistant cable is used on the outer ring wiring side of the crucible sliding wire ring to connect the inner side connection point of the cavity of the copper terminal of the crucible measurement point (10); The inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod are locked with a top screw, and the inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod rotate and run synchronously together; the second crucible high temperature resistant cable is used on the wiring side of the inner ring of the crucible sliding wire ring to connect the upper stainless steel crucible rod, so that the crucible measurement point terminal and the upper stainless steel crucible rod are connected to the same circuit; The outer ring of the crucible sliding wire ring and the inner ring of the crucible sliding wire ring are insulated from the internal circuit of the crucible sliding wire ring.

4. An automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, characterized in that: It includes a seed crystal measuring point unit, a high-precision resistance detector (13) and a PLC programmable crystal growth control system (17); The seed crystal measurement point unit comprises a seed crystal measurement point (1), a seed crystal rod (2), a first ceramic insulating sheet (4) and a seed crystal high temperature resistant cable (5); the seed crystal measurement point (1) is a copper terminal, which is installed on the cavity (14) by adding a Teflon gasket, so that the center of the copper terminal of the seed crystal measurement point (1) is insulated from the cavity (14); the seed crystal rod (2) is a stainless steel seed crystal rod, which is designed to be divided into two sections, upper and lower, and can be raised and lowered and rotated. The first ceramic insulating sheet (4) is used to isolate and insulate the middle of the upper and lower sections of the stainless steel seed crystal rod, and the lower section of the stainless steel seed crystal rod is insulated from the cavity, and the measured resistance is greater than 1 MΩ; the seed crystal (15) in the furnace is connected to the seed crystal measurement point (1) by a seed crystal high temperature resistant cable (5); The high-precision resistance detector (13) is connected to the seed crystal measurement point (1) via an external cable; The PLC programmable crystal growth control system (17) is connected to the high-precision resistance detector (13) to measure the current characteristic curves of the seed crystal and the cavity.

5. The automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace according to claim 4, characterized in that: The seed crystal measurement point unit further comprises a seed crystal sliding line ring (3); the seed crystal sliding line ring (3) comprises a seed crystal sliding line ring outer ring (20), a seed crystal sliding line ring inner ring (21), a seed crystal scoring ring outer ring side fixing ring (24), and a seed crystal limiting rod (25); The fixed ring (24) on the outer ring side of the seed crystal sliding wire ring is connected to the cavity (14) by lifting and sliding using a seed crystal limiting rod (25), that is, the outer ring of the seed crystal sliding wire ring and the cavity are relatively fixed and do not rotate, and the first seed crystal high temperature resistant cable (27) is used on the wiring side of the outer ring of the seed crystal sliding wire ring (20) to connect the inner side connection point of the cavity of the copper terminal of the seed crystal measurement point (1); The inner ring (21) of the seed crystal slide wire ring and the upper stainless steel seed crystal rod (29) are locked by using a top screw, and the inner ring (21) of the seed crystal slide wire ring and the upper stainless steel seed crystal rod (29) rotate together and run synchronously; the wiring side of the inner ring (21) of the seed crystal slide wire ring is connected to the lower stainless steel seed crystal rod (30) by using a second seed crystal high temperature resistant cable (23), so that the seed crystal measurement point terminal and the lower stainless steel seed crystal rod are connected to the same circuit; The seed crystal slide wire ring outer ring (20) and the seed crystal slide wire ring inner ring (21) are insulated from the internal circuit of the seed crystal slide wire ring.

6. An automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace, characterized in that: It includes a crucible measuring point unit, a high-precision resistance detector (13) and a PLC programmable crystal growth control system (17); The crucible measurement point unit comprises a crucible measurement point (10), a crucible rod (9), a second ceramic insulating sheet (6) and a crucible high temperature resistant cable (7); the crucible measurement point (10) is a copper terminal, which is installed on the cavity (14) by adding a Teflon gasket, so that the center of the copper terminal of the crucible measurement point (10) is insulated from the cavity (14); the crucible rod (9) is a stainless steel crucible rod, which is designed to be divided into two sections, upper and lower, and can be raised and lowered and rotated. The middle of the upper and lower sections of the stainless steel crucible rod is isolated and insulated by a second ceramic insulating sheet (6), and the upper section of the stainless steel crucible rod is insulated from the cavity, and the measured resistance is greater than 1 MΩ; the crucible high temperature resistant cable (7) is used to connect the solution (16) in the furnace to the crucible measurement point (10); The high-precision resistance detector (13) is connected to the crucible measurement point (10) via an external cable; The PLC programmable crystal growth control system (17) is connected to the high-precision resistance detector (13) to measure the current characteristic curves of the solution and the cavity in the furnace.

7. The automatic liquid surface contact detection system for a liquid phase method silicon carbide single crystal growth furnace according to claim 6, characterized in that: The crucible measurement point unit further comprises a crucible sliding line ring (8); the crucible sliding line ring (8) comprises a crucible sliding line ring outer ring, a crucible sliding line ring inner ring, a crucible marking ring outer ring side fixing ring, and a crucible limiting rod; The fixing ring on the outer ring side of the crucible sliding wire ring is connected to the cavity by lifting and sliding using a crucible limiting rod, that is, the outer ring of the crucible sliding wire ring is relatively fixed and does not rotate with the cavity, and the first crucible high temperature resistant cable is used on the outer ring wiring side of the crucible sliding wire ring to connect the inner side connection point of the cavity of the copper terminal of the crucible measurement point (10); The inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod are locked with a top screw, and the inner ring of the crucible sliding wire ring and the lower stainless steel crucible rod rotate and run synchronously together; the second crucible high temperature resistant cable is used on the wiring side of the inner ring of the crucible sliding wire ring to connect the upper stainless steel crucible rod, so that the crucible measurement point terminal and the upper stainless steel crucible rod are connected to the same circuit; The outer ring of the crucible sliding wire ring and the inner ring of the crucible sliding wire ring are insulated from the internal circuit of the crucible sliding wire ring.

Images