Efficient crystal growing furnace

Abstract

The utility model discloses an efficient crystal growing furnace, which relates to the technical field of crystal growth, and comprises a rack and a crystal growing cavity positioned above the rack, the rack comprises a movable disc capable of lifting up and down, the movable disc is provided with a turntable, the turntable is provided with a buffer cavity and a feeding cavity side by side, and the buffer cavity and the feeding cavity are communicated with each other. The buffering cavity and the feeding cavity are both located below the crystal growth cavity and are symmetrical about the rotating axis of the rotating disc; when the turntable rotates to a certain angle, the buffer cavity or the feeding cavity can be aligned with the crystal growth cavity up and down; the machine frame further comprises an upper-layer frame body located above the movable disc, a lower-layer frame body located below the movable disc and a lifting mechanism located between the upper-layer frame body and the lower-layer frame body, the movable end of the lifting mechanism is fixed to the movable disc, a plurality of guide rods are further supported between the upper-layer frame body and the lower-layer frame body, and the guide rods penetrate through the upper bottom face and the lower bottom face of the movable disc. The crystal growth furnace solves the technical problem of low production efficiency of the crystal growth furnace in the prior art.

Description

Technical Field

[0001] The utility model relates to the technical field of crystal growth, in particular to a high-efficiency crystal growth furnace. Background Art

[0002] In the 21st century, wide bandgap semiconductor materials such as silicon carbide and gallium nitride have developed rapidly. These materials have many advantages, such as large bandgap, high thermal conductivity, small on-resistance, high electron saturation drift rate, etc. These advantages make these materials widely used in rail transportation, aerospace, household appliances, new energy vehicles and other fields.

[0003] At present, there are three main methods for preparing high-quality single-crystal silicon carbide: physical vapor transport, liquid phase method and high-temperature chemical vapor deposition. Among them, physical vapor transport has become the most mainstream preparation method in current industrial applications due to its low manufacturing cost and simple equipment structure.

[0004] The crystal growth furnace is a key equipment for preparing silicon carbide crystals using the physical vapor transport method. At present, only one growth chamber is usually used inside the crystal growth furnace. Before growing the crystal, the growth chamber needs to be preheated; after the crystal growth is completed, the growth chamber needs to be slowly cooled down. Both of the above stages require a lot of time, which seriously restricts the production efficiency of the crystal growth furnace. Utility Model Content

[0005] The present application provides a high-efficiency crystal growth furnace to solve the technical problem of low production efficiency of crystal growth furnaces in the prior art.

[0006] In order to solve the above technical problems, the utility model adopts the following technical scheme: a high-efficiency crystal growth furnace, comprising a frame and a crystal growth chamber located above the frame, the frame comprising a movable plate that can be lifted up and down, a turntable is installed on the movable plate, a cache chamber and a loading chamber are installed side by side on the turntable, the cache chamber and the loading chamber are both located below the crystal growth chamber and are symmetrical about the axis of rotation of the turntable; when the turntable rotates to a certain angle, the cache chamber or the loading chamber can be aligned with the crystal growth chamber up and down; the frame also comprises an upper frame body located above the movable plate, a lower frame body located below the movable plate, and a lifting mechanism located between the upper frame body and the lower frame body, the moving end of the lifting mechanism is fixed to the movable plate, and a plurality of guide rods are also supported between the upper frame body and the lower frame body, and the guide rods pass through the upper and lower bottom surfaces of the movable plate.

[0007] The high-efficiency crystal growth furnace adopts a three-chamber structure of crystal growth chamber, buffer chamber and loading chamber. When the crystal growth is completed, the crucible tray in the crystal growth chamber can be sent to the buffer chamber for cooling through the lifting and rotating mechanism, and then the turntable is rotated to dock the loading chamber with the crystal growth chamber and load the material. In this way, the slow cooling stage can be carried out simultaneously with the next round of crystal growth process. In addition, the cooperation of the upper frame, the lower frame and the guide rod realizes the guidance of the moving plate during the up and down movement, making the lifting and lowering of the moving plate smoother and improving the operation accuracy and flexibility of the equipment.

[0008] Furthermore, the lifting mechanism includes a nut fixed on one side of the movable disk and a lead screw cooperating with the nut, the two ends of the lead screw are respectively connected to the upper frame and the lower frame, and a drive motor is also installed on the upper frame or the lower frame, and the output end of the drive motor is connected to one end of the lead screw via a coupling.

[0009] Furthermore, the lower end of the crystal growth chamber, the upper end of the loading chamber and the upper end of the buffer chamber are all provided with flanges, and a clamping mechanism is fixed to the flange at the lower end of the crystal growth chamber; the clamping mechanism can make the crystal growth chamber more reliably connected to the loading chamber or buffer chamber below it, so that better airtightness can be achieved during vacuuming or inflation.

[0010] Furthermore, a support frame is provided on the frame, and a positioning mechanism is installed on the upper end of the support frame, and the positioning mechanism includes a pressure cover, a spring and a ball head; wherein, the pressure cover is fixed to the support frame, the spring is installed in the pressure cover, and the ball head is located above the spring; correspondingly, positioning holes are provided on the flange at the top of the loading chamber or the top of the buffer chamber, and the positioning holes can cooperate with the ball head; thereby, precise positioning support can be provided for the loading chamber or the buffer chamber after the turntable rotates, so that the loading chamber or the buffer chamber can be accurately aligned with the crystal growth chamber.

[0011] Furthermore, the crystal growth chamber is equipped with a gate valve A, the loading chamber is equipped with a gate valve B, and the buffer chamber is equipped with a gate valve C. The inner wall of the chamber above the gate valve A is provided with a tray support frame, and the inner wall of the chamber below the gate valves B and C are also provided with tray support frames, respectively, and the crucible tray can be placed on the tray support frame; the bottom of the loading chamber and the buffer chamber are also respectively equipped with lifting and rotating mechanisms, and the top of the lifting and rotating mechanisms can cooperate with the crucible tray; the gate valve A, gate valve B, and gate valve C can play a role in isolating gas, thereby enabling the loading chamber to directly feed material into the crystal growth chamber through vacuum extraction and inflation operations, thereby reducing the heat loss inside the crystal growth chamber and improving the work efficiency of crystal growth production.

[0012] Furthermore, the lifting and rotating mechanism includes a telescopic cylinder, the bottom of the telescopic cylinder is connected to the rotating cylinder through a bracket, and the bottom of the buffer chamber and the loading chamber are respectively connected to the corresponding telescopic cylinders, wherein a rotating shaft is installed on the piston rod of the telescopic cylinder, and a magnetic liquid linear sealing mechanism is installed on the outer side of the rotating shaft; thereby, smooth rotation can be achieved while ensuring air tightness.

[0013] Furthermore, a spline is installed on the top of the lifting and rotating mechanism, and a spline groove is provided at the bottom of the crucible tray, and the spline groove cooperates with the spline; a groove is provided on the outer periphery of the crucible tray, and correspondingly, a boss is provided on the inner circle of the tray support frame, and when the crucible tray is rotated to a certain angle, the groove and the boss are aligned up and down; when the groove of the crucible tray is aligned up and down with the groove of the tray support frame, the crucible tray can move up and down through the tray support frame, thereby, driven by the lifting and rotating mechanism, the crucible tray in the loading chamber can be delivered to the crystal growth chamber, or the crucible tray in the crystal growth chamber can be delivered to the cache chamber.

[0014] It can be seen from the above technical solutions that the utility model has at least the following technical effects or advantages:

[0015] The utility model adopts a three-chamber structure of a crystal growth chamber, a buffer chamber and a loading chamber. When the crystal growth is completed, the crucible tray in the crystal growth chamber can be sent to the buffer chamber for cooling through a lifting and rotating mechanism, and then the turntable is rotated to dock the loading chamber with the crystal growth chamber and load the material. In this way, the slow cooling stage can be carried out simultaneously with the next round of crystal growth process, which improves the work efficiency of crystal growth production. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solution of the utility model, the following is a brief introduction to the drawings required for the description. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work:

[0017] Figure 1 It is a schematic diagram of the overall structure of the utility model;

[0018] Figure 2 It is a structural schematic diagram of the cooperation between the tray support frame and the crucible tray;

[0019] Figure 3 It is a schematic diagram of the local structure of the positioning mechanism;

[0020] Figure 4 It is a structural schematic diagram of the lifting and rotating mechanism;

[0021] Figure 5 It is a schematic diagram of the structure of the spline;

[0022] Figure 6 It is a structural schematic diagram of the clamping mechanism.

[0023] Explanation of the reference numerals in the accompanying drawings: 1. crystal growth chamber; 2. tray support frame; 3. gate valve A; 4. clamping mechanism; 5. positioning pin; 6. feeding chamber; 7. gate valve B; 8. support frame; 9. frame; 10. guide rod; 11. turntable; 12. movable plate; 13. lifting and rotating mechanism; 14. movable plate lifting mechanism; 15. turntable bearing; 16. lead screw; 17. driving motor; 18. gate valve C; 19. positioning mechanism; 20. cache chamber; 21. crucible tray; 22. groove; 23. boss; 24. spline groove; 25. spline; 26. rotating shaft; 27. magnetic liquid linear sealing mechanism; 28. telescopic cylinder; 29. ​​bracket; 30. rotating cylinder; 31. ball head; 32. pressure cover; 33. spring. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

[0025] The utility model discloses a high-efficiency crystal growth furnace, which structure includes a crystal growth chamber 1, a loading chamber 6 and a buffer chamber 20. The crystal growth chamber 1 is located above the loading chamber 6 and the buffer chamber 20. The buffer chamber 20 and the loading chamber 6 are arranged in parallel on a rotatable turntable 11, and are arranged symmetrically about the rotation axis 26 of the turntable 11. The turntable 11 is installed on a movable plate 12 that can move up and down, so as to realize the lifting and lowering of the loading chamber 6 and the buffer chamber 20.

[0026] like Figure 1 As shown, in each cavity, a gate valve is provided to achieve the sealing of the cavity. Specifically, the crystal growth chamber 1 is equipped with a gate valve A3, the loading chamber 6 is equipped with a gate valve B7, and the buffer chamber 20 is equipped with a gate valve C18. In addition, a tray support frame 2 is provided on the inner wall of the cavity above the gate valve A3 and below the gate valves B7 and C18. The tray support can provide a placement plane for the crucible tray 21 to ensure safety and reliability during operation. In addition, the bottom of the loading chamber 6 and the buffer chamber 20 are both equipped with a lifting and rotating mechanism 13, and the top of the lifting and rotating mechanism 13 can cooperate with the crucible tray 21 to drive the lifting and lowering of the crucible tray 21.

[0027] like Figure 1As shown, the crystal growth furnace also includes a frame 9, and the frame 9 includes an upper frame and a lower frame, and a plurality of guide rods 10 are supported between the upper frame and the lower frame, and the guide rods 10 are located near the edge of the frame 9 and are vertically arranged. The guide rods 10 penetrate the upper and lower bottom surfaces of the movable plate 12, and can be guided by the guide rods 10 during the process of the movable plate 12 moving up and down, so that the movable plate 12 can be lifted and lowered more smoothly, and the operation accuracy and flexibility of the equipment are improved. A movable plate lifting mechanism 14 is connected to one side of the movable plate 12, and the movable plate lifting mechanism 14 includes a lead screw 16 and a nut. Among them, the nut is fixed to the movable plate 12 and cooperates with the lead screw 16, and the upper and lower ends of the lead screw 16 are respectively connected to the frame 9, and the output end of the drive motor 17 is connected to one end of the lead screw 16 through a coupling. Thus, the movable plate 12 can be driven to lift and lower by the rotation of the drive motor 17. Preferably, a turntable bearing 15 is provided between the turntable 11 and the movable plate 12 , and the turntable bearing 15 can realize rapid switching between the loading chamber 6 and the buffer chamber 20 .

[0028] The lower end of the crystal growth chamber 1 is provided with a flange, and correspondingly, the upper ends of the loading chamber 6 and the buffer chamber 20 are also provided with flanges. When the loading chamber 6 or the buffer chamber 20 rotates to the bottom of the crystal growth chamber 1, the flange at the lower end of the crystal growth chamber 1 can dock with the flange at the upper end of the loading chamber 6 or the buffer chamber 20. In addition, a clamping mechanism 4 is installed at the flange at the lower end of the crystal growth chamber 1, and the clamping mechanism 4 is provided in plurality and is arranged along the outer periphery of the flange at the lower end of the crystal growth chamber 1. The clamping mechanism 4 can make the crystal growth chamber 1 more reliably connected to the loading chamber 6 or the buffer chamber 20 below it. In this way, better airtightness can be achieved during the vacuuming or inflation process, which helps to improve the operating efficiency of the overall equipment and the quality of the crystal.

[0029] A support frame 8 is also fixed on the frame 9, the lower part of the support frame 8 is firmly connected to the frame 9, and the upper end of the support frame 8 is equipped with a positioning mechanism 19. The positioning mechanism 19 includes a pressure cover 32, a spring 33 and a ball head 31. Figure 2As shown, the gland 32 is fixed to the support frame 8 to form a cavity, the upper end of which is open, and the gland 32 spring 33 and the ball head 31 are located in the cavity of the gland 32, wherein the spring 33 is in a compressed state, and the ball head 31 is located above the spring 33, so that the top of the ball head 31 is located outside the gland 32. Correspondingly, positioning holes are also provided on the flanges at the top of the loading chamber 6 or the top of the buffer chamber 20, respectively. When the loading chamber 6 or the buffer chamber 20 is coaxially aligned with the crystal growth chamber 1, the ball head 31 of the positioning mechanism 19 is located in the positioning hole. In this way, accurate positioning support can be provided for the loading chamber 6 or the buffer chamber 20 after the turntable 11 rotates, so that the loading chamber 6 or the buffer chamber 20 can be accurately aligned with the crystal growth chamber 1, thereby improving the operating convenience of the equipment. In addition, at least two positioning pins 5 are also provided at the flange at the lower end of the growth chamber, and the positioning pins 5 face downward.

[0030] On the other hand, Figure 3 As shown, the lifting and rotating mechanism 13 includes a telescopic cylinder 28 to realize the transmission of materials. The bottom of the telescopic cylinder 28 is connected to the rotating cylinder 30 through a bracket 29, and the rotating cylinder 30 can be rotated by the rotating cylinder 30. The bottoms of the buffer chamber 20 and the feeding chamber 6 are respectively connected to the corresponding telescopic cylinders 28, wherein a rotating shaft 26 is installed on the piston rod of the telescopic cylinder 28, and a magnetic liquid linear sealing mechanism 27 is installed on the outer side of the rotating shaft 26. The lifting and rotating mechanism provides a sealing effect through the viscous nature of the magnetic liquid, which can allow its own rotation.

[0031] like Figure 5 , Figure 6 As shown, a spline 25 is installed on the top of the lifting and rotating mechanism 13, a spline groove 24 is provided at the bottom of the crucible tray 21, a groove 22 is provided on the outer periphery of the crucible tray 21, and correspondingly, a boss 23 is provided on the inner circle of the tray support frame 2, and when the crucible tray 21 rotates to a certain angle, the groove 22 is aligned with the boss 23 up and down. When the groove 22 of the crucible tray 21 is aligned with the groove 22 of the tray support frame 2 up and down, the crucible tray 21 can move up and down through the tray support frame 2, thereby, driven by the lifting and rotating mechanism 13, the crucible tray 21 in the loading chamber 6 can be sent to the crystal growth chamber 1, or the crucible tray 21 in the crystal growth chamber 1 can be sent to the buffer chamber 20.

[0032] The high-efficiency crystal growth furnace disclosed in the utility model has the following working process during operation:

[0033] S1. Loading: Place the material on the crucible tray 21 inside the loading chamber 6, then rotate the turntable 11 until the upper flange positioning hole of the loading chamber 6 cooperates with the buffer chamber positioning mechanism 19 to achieve alignment between the loading chamber 6 and the crystal growth chamber 1. The moving plate lifting mechanism 14 makes the loading chamber 6 rise, and then the lower end flange of the crystal growth chamber 1 contacts and seals with the upper end flange of the loading chamber 6. The clamping mechanism 4 is actuated to press the two flanges tightly. After the interior of the loading chamber 6 is evacuated, H2, N2 and Ar gases are introduced until the vacuum degree of the crystal growth chamber 1 and the loading chamber 6 is the same as the content of the above gas components. At this time, open the plug plate Valve A3, the loading chamber 6 is sent to the tray support frame 2 in the crystal growth chamber 1 through the crucible tray lifting and rotating device 13, then the crucible tray lifting and rotating device 13 descends, the gate valve A3 is closed, H2, N2 and Ar gases are introduced into the loading chamber 6 until the pressure is equal to the atmospheric pressure, then the clamping mechanism 4 is released, the loading chamber 6 descends and separates from the crystal growth chamber 1. At this time, the crystal growth chamber 1 has just finished the previous round of crystal growth process, the temperature is high and the vacuum environment is maintained, which can effectively reduce the time required for preheating and vacuuming of the crystal growth, quickly preheat, improve the heat utilization rate of the crystal growth chamber 1, and reduce energy loss;

[0034] S2, reset: rotate the loading chamber 6 to restore it to the original loading position, at which time the buffer chamber 20 is aligned with the crystal growth chamber 1 in the vertical direction;

[0035] S3, crystal growth: H2, N2 and Ar gases are introduced into the crystal growth chamber 1, and heating enters the crystal growth stage;

[0036] S4, cooling: When the crystal growth is completed and the temperature is lowered and cooled, the movable plate lifting mechanism 14 pushes the movable plate 12 to move upward until the lower flange of the crystal growth chamber 1 contacts the upper flange of the buffer chamber 20, the end faces are sealed, and the clamping mechanism 4 is actuated to press the two flanges tightly. At this time, the gate valve C18 is opened, and the buffer chamber 20 is evacuated and H2, N2 and Ar gases are introduced until the vacuum degree of the crystal growth chamber 1 and the buffer chamber 20 is the same as the content of the above gas components. At this time, the gate valve A3 is opened, the crystal growth chamber 1 and the buffer chamber 20 are connected, and the rotating shaft 26 in the crucible tray lifting and rotating device 13 rises and contacts the crucible tray 21. At this time, the spline groove 24 and the spline 25 cooperate, and the crucible inside the crystal growth chamber 1 is After the tray 21 is higher than the tray support frame 2, the crucible tray lifting and rotating device 13 drives the crucible tray 21 to rotate (the groove 22 and the boss 23 are aligned up and down), and the crucible tray 21 descends to the cache chamber 20 and is placed on the tray support frame 2 in the cache chamber 20 by rotation. At this time, the gate valve C18 is closed, the gate valve A3 is closed, the clamping mechanism 4 is released, and the movable plate lifting mechanism 14 pushes the movable plate 12 to move downward, and the crystal growth chamber 1 and the cache chamber 20 are separated. At this time, the crystal inside the cache chamber 20 enters a slow cooling stage, and the crystal cooling is parallel to the next round of crystal growth, which greatly shortens the crystal growth time, improves the utilization rate of the crystal growth chamber 1, and significantly improves the efficiency of crystal growth;

[0037] S5, unloading: the crystal cooling in the buffer chamber 20 and the crystal growth stage of the next round of crystal growth chamber 1 are carried out in parallel. After the crystal in the buffer chamber 20 is cooled, the buffer chamber 20 is rotated to the loading position, the crystal is taken out, and the buffer chamber 20 is rotated to the buffer station to wait for the next round of crystal cooling. At this time, the loading chamber 6 is located at the loading position, waiting for the next round of loading.

[0038] In the description of the present invention, the terms "upper", "lower", "front", "back", "left", "right", "top", "bottom", "vertical", "horizontal", etc. (if any) indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, which are only for the purpose of describing the present invention and do not require that the present invention must be constructed or operated in a specific position, and therefore cannot be understood as a limitation on the present invention. The terms "connected" and "connected" in the present invention should be understood in a broad sense, for example, it can be connected or detachably connected; it can be directly connected or indirectly connected through an intermediate component. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0039] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in their embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novelties disclosed herein.

Claims

1. A high-efficiency crystal growth furnace, comprising a frame (9) and a crystal growth chamber (1) located above the frame (9), characterized in that: The frame (9) comprises a movable plate (12) capable of being raised and lowered, a rotating plate (11) being mounted on the movable plate (12), a buffer chamber (20) and a loading chamber (6) being mounted side by side on the rotating plate (11), the buffer chamber (20) and the loading chamber (6) being both located below the crystal growth chamber (1) and symmetrical about an axis of rotation of the rotating plate (11); when the rotating plate (11) is rotated to a certain angle, the buffer chamber (20) or the loading chamber (6) can be aligned with the crystal growth chamber (1) in the vertical direction; The frame (9) further comprises an upper frame body located above the movable plate (12), a lower frame body located below the movable plate (12), and a lifting mechanism located between the upper frame body and the lower frame body, wherein the movable end of the lifting mechanism is fixed to the movable plate (12), and a plurality of guide rods (10) are supported between the upper frame body and the lower frame body, wherein the guide rods (10) penetrate the upper and lower bottom surfaces of the movable plate (12).

2. A high-efficiency crystal growth furnace according to claim 1, characterized in that: The lifting mechanism comprises a nut fixed on one side of the moving plate (12) and a lead screw (16) matched with the nut, the two ends of the lead screw (16) are respectively connected to the upper frame and the lower frame, and a driving motor (17) is also installed on the upper frame or the lower frame, and the output end of the driving motor (17) is connected to one end of the lead screw (16) via a coupling.

3. A high-efficiency crystal growth furnace according to claim 2, characterized in that: The lower end of the crystal growth chamber (1), the upper end of the material loading chamber (6) and the upper end of the buffer chamber (20) all have flanges, and a clamping mechanism (4) is fixed to the flange at the lower end of the crystal growth chamber (1).

4. A high-efficiency crystal growth furnace according to claim 3, characterized in that: A support frame (8) is provided on the frame (9), and a positioning mechanism (19) is installed on the upper end of the support frame (8), and the positioning mechanism (19) includes a pressure cover (32), a spring (33) and a ball head (31); wherein the pressure cover (32) is fixed to the support frame (8), the spring (33) is installed in the pressure cover (32), and the ball head (31) is located above the spring (33); correspondingly, a positioning hole is provided on the flange at the upper end of the feeding chamber (6) or the upper end of the buffer chamber (20), and the positioning hole can cooperate with the ball head (31).

5. A high-efficiency crystal growth furnace according to any one of claims 1 to 4, characterized in that: The crystal growth chamber (1) is provided with a gate valve A (3), the loading chamber is provided with a gate valve B (7), and the buffer chamber is provided with a gate valve C (18); a tray support frame (2) is provided on the inner wall of the chamber above the gate valve A (3), and a tray support frame (2) is also provided on the inner wall of the chamber below the gate valve B (7) and the gate valve C (18); a crucible tray (21) can be placed on the tray support frame (2); and a lifting and rotating mechanism (13) is also provided on the bottom of the loading chamber (6) and the buffer chamber (20), and the top of the lifting and rotating mechanism (13) can cooperate with the crucible tray (21).

6. A high-efficiency crystal growth furnace according to claim 5, characterized in that: The lifting and rotating mechanism (13) comprises a telescopic cylinder (28), the bottom of which is connected to a rotating cylinder (30) via a bracket (29), and the bottoms of the buffer chamber (20) and the feeding chamber (6) are respectively connected to the corresponding telescopic cylinders (28), wherein a rotating shaft (26) is installed on the piston rod of the telescopic cylinder (28), and a magnetic liquid linear sealing mechanism (27) is installed on the outer side of the rotating shaft (26).

7. A high-efficiency crystal growth furnace according to claim 6, characterized in that: A spline (25) is installed on the top of the lifting and rotating mechanism (13), and a spline groove (24) is arranged at the bottom of the crucible tray (21), and the spline groove (24) cooperates with the spline (25); a groove (22) is arranged on the outer periphery of the crucible tray (21), and correspondingly, a boss (23) is arranged on the inner circle of the tray support frame (2), and when the crucible tray (21) rotates to a certain angle, the groove (22) and the boss (23) are aligned up and down.

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