Sapphire crystal growing furnace and thermal field regulation and control method

Abstract

The invention relates to the field of crystal growth, in particular to a sapphire crystal growth furnace and a thermal field regulation and control method. The sapphire crystal growing furnace comprises an outer furnace body, a hollow heat preservation cavity and a crucible, wherein a lifting shaft penetrates through the top of the outer furnace body, the heat preservation cavity is formed in the outer furnace body, and the crucible is arranged in the heat preservation cavity. The heat preservation cavity comprises an inner layer arranged outside the crucible in a sleeving mode and arranged in a cylindrical shape, a side adjusting layer arranged outside the inner layer in a sleeving mode and used for blocking heat transfer and an outer layer arranged outside the side adjusting layer in a sleeving mode. The side adjusting layer comprises a plurality of adjusting modules, and the adjusting modules are arranged in the axis direction of the crucible; the adjusting module is used for adjusting the heat conductivity of the corresponding module according to the sapphire crystal growth state in the crucible. The heat conductivity of the corresponding adjusting modules is changed according to different working conditions, and therefore the heat preservation effect in the axis direction of the crucible is adjusted. And when the liquid level of the molten liquid in the crucible descends, the heat conductivity above the liquid level of the molten liquid is increased, so that the quality and efficiency of crystal growth in the equal-diameter process can be improved.

Description

Technical Field

[0001] This application relates to the field of crystal growth, and in particular to a sapphire crystal growth furnace and a method for controlling the thermal field. Background Technology

[0002] A sapphire crystal growth furnace is the core equipment used to prepare sapphire single crystals. Based on crystal growth techniques such as the Czochralski method and the Czochralski method, it achieves the growth of sapphire crystals and the formation of crystal rods at high temperatures exceeding 2000 degrees Celsius. The operation process of a sapphire crystal growth furnace is as follows: high-purity alumina raw material is melted to form a molten solution through a heating system; a seed crystal is lowered to contact the molten solution surface through a pulling shaft; under temperature control, the molten solution begins to crystallize at the end of the seed crystal to form a sapphire crystal, a process called crystal introduction; the pulling shaft is slowly raised to gradually increase the diameter of the sapphire crystal to the target size, a process called shoulder formation; maintaining a stable temperature and pulling speed keeps the diameter of the sapphire crystal constant and eventually grows it into a crystal rod, a process called constant diameter.

[0003] In the process of sapphire crystal growth, the temperature gradient control along the axial direction of the sapphire crystal growth furnace is particularly important. The temperature below the melt surface needs to be maintained to stabilize the growth of the sapphire crystal, but the temperature above the melt surface needs to be reduced to make the grown sapphire crystal more stable.

[0004] Currently, sapphire crystal growth furnaces utilize insulated chambers to maintain the axial temperature gradient. The insulated chamber is a closed cylindrical structure formed by a combination of top, side, and bottom insulation plates. The side insulation plates are composed of multiple layers to enhance insulation performance. Once installed, the side insulation plate structure provides stable insulation. However, the molten metal level changes during sapphire crystal growth, and the furnace cannot adjust the insulation effect of the side insulation plates according to the growth status of the sapphire crystals within the furnace.

[0005] Therefore, there is a need to provide a sapphire crystal growth furnace and a method for controlling the thermal field, which can change the insulation effect of the insulation cavity according to different working conditions. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, one of the objectives of this application is to provide a sapphire crystal growth furnace that can change the heat preservation effect of the heat preservation cavity according to different working conditions.

[0007] To achieve the above objectives, this application adopts the following technical solution: A sapphire crystal growth furnace, comprising The outer furnace body has a lifting shaft inserted at the top; A heat-insulating cavity is disposed inside the outer furnace body and is hollow; and A crucible is disposed inside the heat-insulating cavity, and the bottom of the lifting shaft is located inside the crucible; The feature is that the heat-insulating cavity includes The inner layer is sleeved on the outside of the crucible and is arranged in a cylindrical shape; Side conditioning layers, fitted over the inner layer, are used to block heat transfer; and The outer layer is fitted over the side adjustment layer. The side adjustment layer includes multiple adjustment modules, which are arranged along the axis of the crucible. The adjustment modules are used to adjust the thermal conductivity of the corresponding modules according to the growth state of the sapphire crystal in the crucible.

[0008] With the above setup, multiple adjustment modules are arranged along the crucible axis. These modules can adjust the thermal conductivity, and by changing the thermal conductivity of the corresponding module according to different operating conditions, the heat preservation effect along the crucible axis can be adjusted. When the molten liquid level inside the crucible drops, increasing the thermal conductivity above the molten liquid level can improve the quality and efficiency of crystal growth during the constant diameter process.

[0009] Preferably, the adjustment module includes By adjusting the material layer, the thermal conductivity can be adjusted according to the electric field strength; A positive electrode layer is disposed on one side of the conditioning material layer; and A negative electrode layer is disposed on the other side of the regulating material layer; The positive electrode layer and the negative electrode layer are electrically connected to a power supply, and the adjustment module is externally wrapped with an insulating layer.

[0010] With the above setup, an electric field is applied to the regulating material layer between the positive and negative electrode layers via a power supply. Different electric fields are applied based on varying thermal conductivity requirements, thus achieving different insulation effects. The insulating layer protects the regulating module from the risk of voltage breakdown at high temperatures.

[0011] Preferably, a grounding layer is provided between the top of the insulating layer and the regulating material layer, and between the bottom of the insulating layer and the regulating material layer.

[0012] With the above setup, the grounding layer can effectively absorb the electric field at the edge, thereby reducing the interference of the electric field on the outside world and the interference of the outside world on the electric field of the regulating material layer.

[0013] Preferably, the regulating material layer is silicon carbide doped with electric field responsive elements. The corresponding element of the electric field is nitrogen and / or aluminum.

[0014] With the above setup, the high-temperature resistance of silicon nitride can operate stably on the inner layer away from the crucible. Doping of silicon carbide can be achieved through ion implantation or other methods. Doping silicon carbide with nitrogen and / or aluminum can change the internal carrier concentration and conductivity. Changes in conductivity will affect thermal conductivity by influencing electronic thermal conduction and electron and phonon scattering, thereby changing the heat insulation effect of the conditioning material layer.

[0015] Preferably, the adjustment module includes By adjusting the material layers, the thermal conductivity can be adjusted according to the magnetic field strength; and An electromagnetic generation structure is disposed on the side of the regulating material layer away from the crucible; The electromagnetic generator structure is electrically connected to a power supply.

[0016] Preferably, the electromagnetic generating structure includes an electromagnetic coil wound around the outer wall of the regulating material layer and a magnetic yoke disposed on the side of the electromagnetic coil away from the regulating material layer.

[0017] With the above setup, different currents are supplied to the electromagnetic coil by the power supply, so that the electromagnetic coil applies magnetic fields of different intensities to the regulating material layer, thereby changing the thermal conductivity of the regulating material layer and achieving different insulation effects of the insulation cavity.

[0018] The magnetic yoke can confine the magnetic field generated by the electromagnetic coil within its own path, reducing the impact of the magnetic field on external leakage, thereby reducing the mutual interference of magnetic fields between adjacent regulating material layers.

[0019] Preferably, the regulating material layer is a composite material of magnetocaloric oxide and ceramic, wherein the ceramic is a high-temperature resistant heat-insulating material.

[0020] By using the above settings, high-temperature resistant and heat-insulating ceramics are selected as the base, and magnetocaloric oxides are added as composite materials. The magnetic sensitivity effect can be adjusted according to the changes in the type, concentration, and morphology factor of the magnetocaloric oxides, resulting in stronger operability and adaptability to working conditions.

[0021] Preferably, the adjustment modules are arranged at intervals along the axial direction of the crucible, and a heat insulation screen is provided between adjacent adjustment modules; or The adjustment modules are arranged in close contact with the crucible axis.

[0022] Through the above setup, placing heat shields between the adjustment modules enables multi-regional control while reducing mutual interference between the modules. Simultaneously, the heat shields possess excellent insulation capabilities, allowing for gradient changes in the insulation effect along the crucible's axis by selecting appropriate heat shield materials and coordinating them with the adjustment modules. The adjustment modules are arranged closely along the crucible's axis, enabling better control of the temperature gradient along this direction.

[0023] The second objective of this application is to provide a thermal field control method that can achieve the technical effect of adjusting the thermal conductivity of the module by changing the electric field.

[0024] To achieve the above objectives, this application adopts the following technical solution: A method for controlling a thermal field, implemented through the aforementioned heat-insulating cavity, includes the following steps: Initially, the molten liquid level is located between two adjacent adjustment modules; During the crystal pulling and shoulder formation process, the power supply of the regulating module located above the molten surface is set to the first voltage to improve the thermal conductivity of the regulating material layer in the regulating module. During the constant diameter process, the power supply of the regulating module located above and close to the molten surface is set to the second voltage to reduce the thermal conductivity of the regulating material layer in the regulating module; and the regulating module located above the aforementioned regulating module is set to the third voltage to increase the thermal conductivity of the regulating material layer in the regulating module.

[0025] The third objective of this application is to provide a thermal field control method that can achieve the technical effect of adjusting the thermal conductivity of the module by changing the electric field.

[0026] To achieve the above objectives, this application adopts the following technical solution: A method for controlling a thermal field, implemented through the aforementioned heat-insulating cavity, includes the following steps: Initially, the molten liquid level is located between two adjacent adjustment modules; During the crystal pulling and shoulder formation process, the power supply of the regulating module located above the molten surface is set to the first current to improve the thermal conductivity of the regulating material layer in the regulating module. During the constant diameter process, the power supply of the regulating module located above and close to the molten surface is set to the second current to reduce the thermal conductivity of the regulating material layer in the regulating module; and the regulating module located above the aforementioned regulating module is set to the third current to increase the thermal conductivity of the regulating material layer in the regulating module.

[0027] In summary, this application includes at least one of the following beneficial technical effects: This application achieves the effect of changing the heat preservation effect along the crucible axis according to different working conditions by setting up multiple modular adjustment modules. Furthermore, by adjusting the thermal conductivity of the corresponding heat preservation material layer through electric or magnetic fields, the heat preservation effect at different locations can be adjusted to adapt to the heat preservation requirements of different temperature gradients during the sapphire crystal growth process. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the cross-sectional structure of a sapphire crystal growth furnace; Figure 2 This is an exploded structural diagram of the insulation cavity; Figure 3 This is a partial cross-sectional structural diagram of the side adjustment layer in one embodiment; Figure 4 This is a partial cross-sectional view of the side adjustment layer in another embodiment; Figure 5 This is a partial cross-sectional structural diagram of the adjustment module in one embodiment; Figure 6 This is a partial cross-sectional view of the adjustment module in another embodiment.

[0029] Explanation of reference numerals in the attached figures: 1. Outer furnace body; 11. Lifting shaft; 2. Insulation cavity; 3. Crucible; 100. Inner layer; 200. Side adjustment layer; 210. Adjustment module; 211. Adjustment material layer; 212. Positive electrode layer; 213. Negative electrode layer; 214. Insulation layer; 215. Grounding layer; 216. Electromagnetic generation structure; 2161. Electromagnetic coil; 2162. Magnetic yoke; 220. Heat insulation screen; 300. Outer layer; 310. Top insulation board; 320. Bottom insulation board; 400. Power supply. Detailed Implementation

[0030] The serial numbers assigned to components in this document, such as "first" and "second," are used solely to distinguish the described objects and have no sequential or technical meaning. The terms "connection" and "linkage" used in this application, unless otherwise specified, include both direct and indirect connections (linkages). It should be understood that the terms "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," and "counterclockwise," indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings and are used solely for the convenience of describing this application and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application.

[0031] In this application, unless otherwise expressly 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," "on top of," and "over" 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.

[0032] like Figure 1 As shown in the figure, this application provides a sapphire crystal growth furnace, including an outer furnace body 1 with a lifting shaft 11 inserted at the top, a hollow heat-insulating cavity 2 disposed inside the outer furnace body 1, and a crucible 3 disposed inside the heat-insulating cavity 2. The bottom of the lifting shaft 11 is located inside the crucible 3. The operation process of the sapphire crystal growth furnace is as follows: high-purity alumina raw material is melted to form a molten liquid through a heating system; a seed crystal is lowered to contact the molten liquid surface through the lifting shaft 11; through temperature control, the molten liquid begins to crystallize at the end of the seed crystal to form a sapphire crystal, this process is called crystal seeding; the lifting shaft 11 is slowly raised to gradually increase the diameter of the sapphire crystal to the target size, this process is called shoulder formation; the temperature and lifting speed are kept stable to keep the diameter of the sapphire crystal constant and finally grow into a crystal rod, this process is called constant diameter.

[0033] Combination Figure 2 The heat-insulating cavity 2 comprises a cylindrical inner layer 100, a side adjustment layer 200, and an outer layer 300, which are nested sequentially. The crucible 3 is located inside the space surrounded by the inner layer 100. The top and bottom of the outer layer 300 are respectively equipped with a top heat-insulating plate 310 and a bottom heat-insulating plate 320 to reduce heat loss from the top and bottom of the crucible 3. The inner layer 100 is made of tungsten or molybdenum, which maintains structural stability at high temperatures; the outer layer 300 can be made of alumina hollow spherical bricks or other metal materials or structures. The side adjustment layer 200 blocks heat transfer, thus insulating the space inside the inner layer 100, i.e., the space containing the crucible 3, and ensuring the stable operation of the sapphire crystal pulling process.

[0034] Combination Figure 3 and Figure 4 The side adjustment layer 200 includes multiple adjustment modules 210, which are arranged along the axial direction of the crucible 3. The adjustment modules 210 are used to adjust the thermal conductivity of the corresponding modules according to the growth state of the sapphire crystal in the crucible 3.

[0035] like Figure 3As shown, in some embodiments, the adjustment modules 210 are arranged at intervals along the axis of the crucible 3, with heat insulation screens 220 positioned at these intervals. Specifically, the heat insulation screens 220 can be made of other high-temperature resistant, low-thermal-conductivity materials, such as zirconia sand combined with a molybdenum screen or other composite materials. Optionally, one side of the heat insulation screen 220 is attached to the inner layer 100, while the other side has a gap between it and the outer layer 300. This gap can be filled with nitrogen gas, ensuring the safety of the internal environment while allowing for fine-tuning of the insulation effect by adjusting the nitrogen flow rate or content.

[0036] like Figure 4 As shown, in some other embodiments, the adjustment module 210 is arranged in close contact with the crucible 3 along the axial direction.

[0037] Specifically, when there are two adjustment modules 210, the initial position of the molten liquid surface inside the crucible 3 corresponds to the area between the two adjustment modules 210. Specifically, if there is a heat shield 220 between adjacent adjustment modules 210, the initial molten liquid surface inside the crucible 3 corresponds to the middle of the heat shield 220; if there is a seam between adjacent adjustment modules 210, the initial molten liquid surface inside the crucible 3 corresponds to the vicinity of the seam. The vertical distance between the molten liquid surface and the seam should conform to the requirements of actual operation.

[0038] When there are three or more adjustment modules 210, the initial position of the molten liquid level inside the crucible 3 corresponds to the position between the two uppermost adjustment modules 210. The specific positional relationship is the same as when there are two adjustment modules 210.

[0039] In some implementations, combined Figure 5 The adjustment module 210 controls the heat preservation effect through electric field adjustment. Specifically, the adjustment module 210 includes an adjustment material layer 211 whose thermal conductivity can be adjusted according to the electric field strength, a positive electrode layer 212 disposed on one side of the adjustment material layer 211, and a negative electrode layer 213 disposed on the other side of the adjustment material layer 211. The positive electrode layer 212 and the negative electrode layer 213 are led out to the outside of the outer furnace body 1 through high-temperature wires and electrically connected to a power supply 400. By adjusting the voltage of the power supply 400, the electric field strength between the positive electrode layer 212 and the negative electrode layer 213 can be adjusted. The adjustment module 210 is wrapped with an insulating layer 214, which is selected as a high-temperature resistant ceramic insulator to prevent high-voltage breakdown.

[0040] Optionally, to reduce electric field interference between adjacent adjustment modules 210, a grounding layer 215 is provided between the top of the insulating layer 214 and the adjustment material layer 211, and between the bottom of the insulating layer 214 and the adjustment material layer 211. The grounding layer 215 can be a metal foil, such as molybdenum foil. The grounding layer 215 can effectively conduct away the edge electric field between adjacent adjustment modules 210, achieving electrostatic decoupling.

[0041] Optionally, the adjustment material layer 211 can be selected as silicon carbide doped with an electric field-responsive element, namely nitrogen and / or aluminum. The doping method can be ion implantation or material composite, such as a silicon nitride-silicon carbide composite material, where the nitrogen doping concentration reaches 4 × 10¹. 8 cm - At 3, the resistivity and thermal conductivity of silicon carbide will decrease significantly.

[0042] In other embodiments, combined Figure 6 The adjustment module 210 controls the heat preservation effect through magnetic field adjustment. Specifically, the adjustment module 210 includes an adjustment material layer 211 whose thermal conductivity can be adjusted according to the magnetic field strength, and an electromagnetic generating structure 216 disposed on the side of the adjustment material layer 211 away from the crucible 3. The electromagnetic generating structure 216 is electrically connected to a power supply 400. By adjusting the current of the power supply 400, the magnetic field generated by the electromagnetic generating structure 216 is adjusted, thereby changing the thermal conductivity of the adjustment material.

[0043] Optionally, the electromagnetic generating structure 216 includes an electromagnetic coil 2161 wound around the outer wall of the regulating material layer 211 and a magnetic yoke 2162 disposed on the side of the electromagnetic coil 2161 facing away from the regulating material layer 211. The electromagnetic coil 2161 is connected to a power supply 400 via leads, and the power supply 400 is selected as a constant current power supply. The outer contour of the magnetic yoke 2162 matches the outer contour of the regulating material layer 211 and completely covers the electromagnetic coil 2161. In order to ensure the normal operation of the electromagnetic coil 2161 and the magnetic yoke 2162, a water-cooling structure (not shown in the figure) is provided on the magnetic yoke 2162, such as cooling channels, pipes, etc. Specifically, the water-cooling structure can be integrated inside or on the outer wall of the magnetic yoke 2162. Optionally, the electromagnetic coil 2161 can also be replaced with a magnet or other structure that can generate a magnetic field based on electromagnetic induction.

[0044] Optionally, the adjustment material layer 211 can be a composite material of magnetocaloric oxide and ceramic, where the ceramic is a high-temperature resistant heat-insulating material. Specifically, the ceramic can be zirconium oxide or alumina, and the magnetocaloric oxide can be ferrite; the ferrite is incorporated into the zirconium oxide or alumina in a specific phase form to form a composite ceramic material.

[0045] This application also provides a thermal field control method, which is specifically described by selecting two methods: electric field control and magnetic field control of the material layer 211.

[0046] When the material layer 211 is selected to be controlled by an electric field, the thermal field control method is as follows: Initially, the molten liquid level is located between the two uppermost adjacent adjustment modules 210; During the crystal pulling and shoulder formation process, the power supply 400 electrically connected to the adjustment module 210 located above the molten surface is set to the first voltage to improve the thermal conductivity of the adjustment material layer 211 in the adjustment module 210. During the equal diameter process, the power supply 400 electrically connected to the regulating module 210, which is located above and close to the molten surface, is set to a second voltage to reduce the thermal conductivity of the regulating material layer 211 in the regulating module 210; and the regulating module 210 located above the aforementioned regulating module 210 is set to a third voltage to increase the thermal conductivity of the regulating material layer 211 in the regulating module 210.

[0047] When the material layer 211 is selected to be controlled and adjusted using a magnetic field, the thermal field control method is as follows: Initially, the molten liquid level is located between the two uppermost adjacent adjustment modules 210; During the crystal pulling and shoulder formation process, the power supply 400 electrically connected to the adjustment module 210 located above the molten surface is set to the first current to improve the thermal conductivity of the adjustment material layer 211 in the adjustment module 210. During the equal diameter process, the power supply 400 electrically connected to the regulating module 210, which is located above and close to the molten surface, is set to the second current to reduce the thermal conductivity of the regulating material layer 211 in the regulating module 210; and the regulating module 210 located above the aforementioned regulating module 210 is set to the third current to increase the thermal conductivity of the regulating material layer 211 in the regulating module 210.

[0048] Although preferred embodiments of this application have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this application.

[0049] Obviously, those skilled in the art can make various modifications and variations to this application without departing from the spirit and scope of this application. Therefore, if such modifications and variations fall within the scope of the claims of this application and their equivalents, this application also intends to include such modifications and variations.

Claims

1. A sapphire crystal growth furnace, comprising: The outer furnace body (1) has a lifting shaft (11) inserted through its top. The heat-insulating cavity (2) is disposed inside the outer furnace body (1) and is hollow; and The crucible (3) is located inside the heat-insulating cavity (2), and the bottom of the lifting shaft (11) is located inside the crucible (3); Its features are, The heat-insulating cavity (2) includes The inner layer (100) is sleeved on the outside of the crucible (3) and is arranged in a cylindrical shape; A side conditioning layer (200), fitted over the inner layer (100), is used to block heat transfer; and The outer layer (300) is fitted over the side adjustment layer (200); The side adjustment layer (200) includes multiple adjustment modules (210), which are arranged along the axis of the crucible (3). The adjustment modules (210) are used to adjust the thermal conductivity of the corresponding modules according to the growth state of the sapphire crystal in the crucible (3).

2. The sapphire crystal growth furnace according to claim 1, characterized in that, The adjustment module (210) includes The thermal conductivity of the adjustable material layer (211) can be adjusted according to the electric field strength; A positive electrode layer (212) is disposed on one side of the conditioning material layer (211); and A negative electrode layer (213) is disposed on the other side of the regulating material layer (211); The positive electrode layer (212) and the negative electrode layer (213) are electrically connected to a power supply (400), and the adjustment module (210) is wrapped with an insulating layer (214).

3. The sapphire crystal growth furnace according to claim 2, characterized in that, A grounding layer (215) is provided between the top of the insulating layer (214) and the regulating material layer (211) and between the bottom of the insulating layer (214) and the regulating material layer (211).

4. The sapphire crystal growth furnace according to claim 2, characterized in that, The regulating material layer (211) is silicon carbide doped with electric field responsive elements. The corresponding element of the electric field is nitrogen and / or aluminum.

5. The sapphire crystal growth furnace according to claim 1, characterized in that, The adjustment module (210) includes The adjustable material layer (211) can adjust the thermal conductivity according to the magnetic field strength; and An electromagnetic generating structure (216) is disposed on the side of the regulating material layer (211) away from the crucible (3); The electromagnetic generating structure (216) is electrically connected to a power supply (400).

6. The sapphire crystal growth furnace according to claim 5, characterized in that, The electromagnetic generating structure (216) includes an electromagnetic coil (2161) wound around the outer wall of the regulating material layer (211) and a magnetic yoke (2162) disposed on the side of the electromagnetic coil (2161) away from the regulating material layer (211).

7. The sapphire crystal growth furnace according to claim 5, characterized in that, The regulating material layer (211) is a composite material of magnetocaloric oxide and ceramic, wherein the ceramic is a high-temperature resistant heat insulation material.

8. The sapphire crystal growth furnace according to claim 2 or 5, characterized in that, The adjustment modules (210) are arranged at intervals along the axis of the crucible (3), and a heat insulation screen (220) is provided between adjacent adjustment modules (210); or The adjustment module (210) is arranged in close contact with the crucible (3) along the axial direction.

9. A method for controlling a thermal field, characterized in that, This is achieved through the thermal insulation cavity (2) as described in any one of claims 2, 3, 4, and 8, and the thermal field control method includes the following steps: Initially, the molten liquid level is located between two adjacent adjustment modules (210); During the crystal pulling and shoulder formation process, the power supply (400) electrically connected to the adjustment module (210) located above the molten liquid surface is set to the first voltage to improve the thermal conductivity of the adjustment material layer (211) in the adjustment module (210); During the equal diameter process, the power supply (400) electrically connected to the regulating module (210) located above and close to the molten liquid surface is set to the second voltage to reduce the thermal conductivity of the regulating material layer (211) in the regulating module (210); and the regulating module (210) located above the aforementioned regulating module (210) is set to the third voltage to increase the thermal conductivity of the regulating material layer (211) in the regulating module (210).

10. A method for controlling a thermal field, characterized in that, This is achieved through the thermal insulation cavity (2) as described in any one of claims 5, 6, 7, and 8, and the thermal field control method includes the following steps: Initially, the molten liquid level is located between two adjacent adjustment modules (210); During the crystal pulling and shoulder formation process, the power supply (400) electrically connected to the adjustment module (210) located above the molten liquid surface is set to the first current to improve the thermal conductivity of the adjustment material layer (211) in the adjustment module (210); During the equal diameter process, the power supply (400) electrically connected to the regulating module (210) located above and close to the molten liquid surface is set to the second current to reduce the thermal conductivity of the regulating material layer (211) in the regulating module (210); and the regulating module (210) located above the aforementioned regulating module (210) is set to the third current to increase the thermal conductivity of the regulating material layer (211) in the regulating module (210).

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