A superconducting magnet and a magnetic-controlled Czochralski single crystal growth apparatus

Abstract

The present invention belongs to the technical field of semiconductor manufacturing, and specifically relates to a superconducting magnet and a magnetic-controlled Czochralski single crystal device, which includes a support and installation assembly. The support and installation assembly includes a support frame plate and support ear plates, and the support ear plates are fixedly installed on the outer side of the support frame plate. A superconducting magnet assembly and a rotating Czochralski assembly are installed on the top of the support frame plate. A Czochralski furnace shell is fixedly installed inside the support frame plate, and a rotating crucible assembly is installed inside the Czochralski furnace shell. By means of the thermistor provided, the subtle changes in the temperature inside the liquid helium cavity are captured in real time. When the thermistor detects that the temperature rises and causes the resistance value to drop, it compensates for the magnetic field fluctuations that may be caused by temperature changes. Through this feedback mechanism, even if the temperature inside the liquid helium cavity fluctuates, the magnetic field can remain relatively stable, making the composition of the crystal more uniform and reducing the segregation effect in the crystal.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor manufacturing, and specifically relates to a superconducting magnet and a magnetic-controlled Czochralski single crystal growth device. Background Art

[0002] The methods for manufacturing single crystal silicon are divided into the Czochralski method and the floating zone melting method. At present, the vast majority of single crystal silicon is prepared by the Czochralski method, which uses a single crystal furnace to grow rod-shaped single crystal silicon from a melt. During the crystal growth process by the Czochralski method, the thermal convection of the melt causes macroscopic and microscopic inhomogeneities of impurities, thereby affecting the physical and chemical properties of the crystal. Therefore, suppressing the melt convection is one of the important ways to improve the quality of single crystals. To solve the above problems, the magnetic-controlled Czochralski technology has been gradually developed. Based on the Czochralski method, by applying a strong magnetic field outside the single crystal furnace, the thermal convection of the melt is suppressed, the impurity content of the crystal is reduced, the longitudinal and radial impurity distribution uniformity is improved, and high-quality single crystals are obtained.

[0003] The magnetic field generating devices of traditional magnetic-controlled Czochralski methods generally use permanent magnetic materials and conventional electromagnets. Due to the limitations of the saturation magnetization intensity of permanent magnetic materials and the power of conventional electromagnets, the generated magnetic field intensity is often not high, and the suppression effect on the thermal convection of the melt is relatively ordinary. With the development of superconducting magnet technology, more and more superconducting magnets have replaced traditional conventional electromagnets, which can generate stronger magnetic fields and have a more obvious suppression effect on the thermal convection of the melt. Then, combined with the corresponding crystal pulling process, single crystal silicon with larger size or higher quality can be prepared.

[0004] When the existing superconducting magnet is in use, its interior will be affected by the temperature of the Czochralski furnace. The Czochralski furnace will generate extremely high temperatures during operation, and this high temperature will act directly or indirectly on the superconducting magnet through various ways such as heat conduction and thermal radiation. Due to the structural characteristics and material properties of the superconducting magnet, its interior will be significantly and directly affected by the temperature of the Czochralski furnace, and then the temperature inside the superconducting magnet will inevitably increase accordingly. Once the temperature inside the superconducting magnet increases, the low-temperature environment where the superconducting core is located will be damaged, resulting in the transformation or loss of the superconducting state. This transformation will directly affect the stability and distribution of the current in the superconducting core, and then cause a significant change in the magnetic force, interfering with the forming process of the silicon rod, resulting in uneven growth rate, inconsistent diameter, increased internal defects of the silicon rod, and even problems such as the fracture of the silicon rod, seriously affecting the product quality and production efficiency of the silicon rod.

[0005] Therefore, the present invention provides a superconducting magnet and a magnetic-controlled Czochralski single crystal growth device. Summary of the Invention

[0006] In order to make up for the deficiencies of the existing technology and solve at least one of the technical problems proposed in the background art.

[0007] The technical solution adopted by the present invention to solve its technical problems is as follows: A superconducting magnet and a magnetic-controlled Czochralski single crystal device according to the present invention include a support and installation assembly. The support and installation assembly includes a support frame plate and support ear plates, and the support ear plates are fixedly installed on the outer side of the support frame plate. A superconducting magnet assembly and a rotating Czochralski assembly are installed on the top of the support frame plate. A Czochralski furnace shell is fixedly installed inside the support frame plate. A rotating crucible assembly is installed inside the Czochralski furnace shell. A driving assembly is fixedly installed at the bottom of the support frame plate and the support ear plates. The driving assembly is used to drive the rotating Czochralski assembly and the rotating crucible assembly to operate. The driving assembly includes a driving motor, and a driving gear is fixedly installed at the output end of the driving motor. The superconducting magnet assembly includes a central heat-insulating and magnetic-resisting shell, an upper heat-insulating and magnetic-resisting shell, and a lower heat-insulating and magnetic-resisting shell. The central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell are all located outside the Czochralski furnace shell. The upper heat-insulating and magnetic-resisting shell is fixedly installed on the top of the central heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell is fixedly installed on the bottom of the central heat-insulating and magnetic-resisting shell. Liquid filling valves are fixedly installed on the outer sides of the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell. Liquid helium cavities are opened inside the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell. Superconducting cores are fixedly installed inside the liquid helium cavities. Coils are wound around the outer sides of the superconducting cores. The number of turns of the coils wound around the superconducting cores inside the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell is in a ratio of 2:1:1.

[0008] Preferably, a heat-insulating and magnetic-passing shell is fixedly installed inside the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell, and the distance between the heat-insulating and magnetic-passing shell and the outer wall of the Czochralski furnace shell is five centimeters. A support bending rod is fixedly installed at the bottom of the lower heat-insulating and magnetic-resisting shell, and the end of the support bending rod away from the lower heat-insulating and magnetic-resisting shell is fixedly connected to the top of the support frame plate.

[0009] Preferably, heat-insulating connection blocks are fixedly installed on the outer sides of the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell. Thermistors are fixedly installed inside the three heat-insulating connection blocks, and the temperature measuring parts of the thermistors are located inside the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell. An electricity connection frame is fixedly installed on one side of the three heat-insulating connection blocks away from the central heat-insulating and magnetic-resisting shell, the upper heat-insulating and magnetic-resisting shell, and the lower heat-insulating and magnetic-resisting shell.

[0010] Preferably, the rotating straight-pull assembly includes a lifting straight-pull assembly and a rotating assembly, the lifting straight-pull assembly includes a straight-pull traction head, a rotating pull rod is fixedly installed on the top of the straight-pull traction head, a connecting rod is rotatably installed on the top of the rotating pull rod, an end of the connecting rod away from the rotating pull rod is fixedly connected to a lifting rope, an end of the lifting rope away from the connecting rod is fixedly connected to a winding rod, a steering gear is fixedly installed on the top of the support ear plate, an output end of the steering gear is fixedly connected to one end of the winding rod, a driven gear is fixedly installed on the input end of the steering gear, and the outer side of the driven gear is meshed with the outer side of the driving gear.

[0011] Preferably, the rotating assembly includes a limit frame, which is fixedly mounted on the inner side of the straight-pull furnace shell and movably mounted on the outer side of a rotating pull rod, a rotating guide groove is provided on the outer side of the rotating pull rod, a rotating guide block is fixedly mounted on the inner side of the limit frame, and the rotating guide block is slidably mounted on the inner side of the rotating guide groove.

[0012] Preferably, the rotating crucible assembly includes a crucible, which is located directly below the lower thermal insulation and magnetic resistance shell, an insulation ring plate is fixedly installed on the outer side of the crucible, an anti-slip ring is fixedly installed on the outer side of the insulation ring plate, and the anti-slip ring is fixedly installed on the inner side of the vertical pulling furnace shell, a driven gear ring is fixedly installed on the outer side of the insulation ring plate, the outer side of the driven gear ring is meshed with the outer side of the driving gear, a swinging assembly is installed inside the crucible, the swinging assembly is used to swing the material in the bottom area of ​​the crucible to the top area of ​​the crucible, and a magnetic ring lifting assembly is also installed inside the crucible, the magnetic ring lifting assembly is used to reduce heat convection inside the crucible.

[0013] Preferably, the swing assembly includes four pressure push rods and four U-shaped seats, one end of the four pressure push rods is fixedly connected to the inner side of the vertical pulling furnace shell, and a toggle plate is rotatably installed inside the four U-shaped seats. One end of the four pressure push rods away from the supporting bending rod is located on the inner side of the crucible, and the height of the one end of the pressure push rod away from the supporting bending rod is located between the top of the U-shaped seat and the top of the toggle plate, and a liquid diversion plate is fixedly installed on the bottom of the toggle plate.

[0014] Preferably, the liquid-repelling plate is five-step-type and shrinks from bottom to top, a rectangular through groove is provided inside the liquid-repelling plate, one side of the liquid-repelling plate is flat, and the other side of the liquid-repelling plate is arc-shaped.

[0015] Preferably, the magnetic ring lifting assembly includes a magnetic ring, four connecting rods are fixedly installed on the top of the magnetic ring, and lifting plates are fixedly installed on the top of the four connecting rods. The central axes of the four lifting plates are respectively in the same vertical plane as the central axes of four liquid-draining plates, and four limiting slide bars are slidably installed inside the connecting rods, and the bottom of the limiting slide bar is fixedly installed on the bottom of the crucible.

[0016] Preferably, a heat insulation material is installed on the outer side of the magnetic ring, and the heat insulation material is short fiber alumina, and the magnetic ring is made of alnico magnet.

[0017] The beneficial effects of the present invention are as follows:

[0018] 1. For the superconducting magnet and magnetic-controlled Czochralski single crystal equipment of the present invention, the fine changes in the temperature inside the liquid helium cavity are captured in real time by the thermistor arranged. When the thermistor detects that the temperature rises and the resistance value drops, the current in the coil connected in series with it will increase to compensate for the magnetic field fluctuation that may be caused by the temperature change. Through this feedback mechanism, even if the temperature inside the liquid helium cavity fluctuates, the magnetic field can remain relatively stable, making the composition of the crystal more uniform and reducing the segregation effect in the crystal.

[0019] 2. For the superconducting magnet and magnetic-controlled Czochralski single crystal equipment of the present invention, when the same current is passed, the magnetic field intensities generated by the superconducting cores and coils inside the central heat insulation and magnetic resistance shell, the upper heat insulation and magnetic resistance shell, and the lower heat insulation and magnetic resistance shell first increase and then decrease from bottom to top, and the magnetic field intensities at the top and bottom are the same, while the magnetic field intensity in the middle is twice that of the top and bottom magnetic field intensities. When the single crystal passes through the magnetic field that changes from low to high, the convective motion in the melt can be more effectively suppressed, making the heat conduction more uniform, reducing the defects and impurities in the crystal. Then, when passing through the magnetic field that changes from high to low, it may help that there is a buffer interval when the formed crystal leaves the magnetic field, preventing the formed crystal from leaving the magnetic field instantaneously and triggering a new convective mode, which has an adverse impact on the crystal quality, and ensuring continuous growth under more stable conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The present invention will be further described below with reference to the drawings.

[0021] Figure 1 is the three-dimensional external view of the present invention;

[0022] Figure 2 is the bottom three-dimensional view of the present invention;

[0023] Figure 3 is the sectional structural schematic diagram of the Czochralski furnace shell in the present invention;

[0024] Figure 4 is the three-dimensional structural schematic diagram of the superconducting magnet group in the present invention;

[0025] Figure 5 is the bottom three-dimensional view of the superconducting magnet assembly in the present invention;

[0026] Figure 6 is the sectional structural schematic diagram of the superconducting magnet assembly in the present invention;

[0027] Figure 7 It is a schematic diagram of the three-dimensional structure of the rotating crucible assembly in the present invention;

[0028] Figure 8 It is a schematic diagram of a local three-dimensional structure in the present invention;

[0029] Figure 9 It is a schematic diagram of the three-dimensional structure of the limiting frame in the present invention;

[0030] Figure 10 It is a circuit connection diagram of the superconducting magnet assembly in the present invention;

[0031] In the figure: 1, central heat-insulating magnetic-resisting shell; 2, upper heat-insulating magnetic-resisting shell; 3, lower heat-insulating magnetic-resisting shell; 4, liquid-adding valve; 5, heat-insulating connecting block; 6, thermistor; 7, power connection rack; 8, liquid helium chamber; 9, superconducting core; 10, coil; 11, steering gear; 12, winding rod; 13, lifting rope; 14, straight-pull furnace shell; 15, connecting rod; 16, rotating rod; 17, rotating guide groove; 18, driven gear; 19, support frame plate; 20, support Ear support plate; 21. Driving motor; 22. Driving gear; 23. Crucible; 24. Driven gear ring; 25. Insulation ring plate; 26. Anti-slip ring; 27. Limiting slide bar; 28. Limiting frame; 29. ​​Rotating guide block; 30. Straight-pull traction head; 31. Support bending rod; 32. Insulation magnetic shell; 33. Push rod; 34. U-shaped seat; 35. Toggle plate; 36. Liquid-discharging plate; 37. Magnetic ring; 38. Connecting vertical pole; 39. Lifting plate. DETAILED DESCRIPTION

[0032] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further explained below in conjunction with specific implementation methods.

[0033] like Figures 1 to 10As shown in the figure, a superconducting magnet and a magnetic-controlled Czochralski single crystal device according to an embodiment of the present invention include a support and installation assembly. The support and installation assembly includes a support frame plate 19 and support ear plates 20, and the support ear plates 20 are fixedly installed on the outer side of the support frame plate 19. A superconducting magnet assembly and a rotating Czochralski assembly are installed on the top of the support frame plate 19. A Czochralski furnace shell 14 is fixedly installed inside the support frame plate 19, and a rotating crucible assembly is installed inside the Czochralski furnace shell 14. A driving assembly is fixedly installed at the bottom of the support frame plate 19 and the support ear plates 20. The driving assembly is used to drive the rotating Czochralski assembly and the rotating crucible assembly to operate. The driving assembly includes a driving motor 21, and a driving gear 22 is fixedly installed at the output end of the driving motor 21. The superconducting magnet assembly includes a central heat-insulating and magnetic-resisting shell 1, an upper heat-insulating and magnetic-resisting shell 2, and a lower heat-insulating and magnetic-resisting shell 3. The central heat-insulating and magnetic-resisting shell 1, the upper heat-insulating and magnetic-resisting shell 2, and the lower heat-insulating and magnetic-resisting shell 3 are all located outside the Czochralski furnace shell 14. The upper heat-insulating and magnetic-resisting shell 2 is fixedly installed on the top of the central heat-insulating and magnetic-resisting shell 1, and the lower heat-insulating and magnetic-resisting shell 3 is fixedly installed on the bottom of the central heat-insulating and magnetic-resisting shell 1. Liquid filling valves 4 are fixedly installed on the outer sides of the central heat-insulating and magnetic-resisting shell 1, the upper heat-insulating and magnetic-resisting shell 2, and the lower heat-insulating and magnetic-resisting shell 3. Liquid helium cavities 8 are opened inside the central heat-insulating and magnetic-resisting shell 1, the upper heat-insulating and magnetic-resisting shell 2, and the lower heat-insulating and magnetic-resisting shell 3. Superconducting cores 9 are fixedly installed inside the liquid helium cavities 8. Coils 10 are wound around the outer sides of the superconducting cores 9. The number of turns of the coils 10 wound around the outer sides of the superconducting cores 9 inside the central heat-insulating and magnetic-resisting shell 1, the upper heat-insulating and magnetic-resisting shell 2, and the lower heat-insulating and magnetic-resisting shell 3 is in a ratio of 2:1:1;During operation, first, liquid helium can be injected into the liquid helium chamber 8 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 through the liquid filling valve 4. The liquid helium keeps the inside of the liquid helium chamber 8 at a low temperature, so that the superconducting core 9 and the coil 10 located inside the liquid helium chamber 8 are both at a low temperature, and the superconducting core 9 and the coil 10 are both in a superconducting state. In addition, the number of turns of the coil 10 wound around the outside of the superconducting core 9 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 is in the ratio of 2:1:1. When the same current is passed, the magnetic field intensity generated by the superconducting core 9 and the coil 10 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 first increases and then decreases from bottom to top, and the magnetic field intensity at the top and the bottom is the same, while the magnetic field intensity in the middle is twice that of the top and the bottom. When the single crystal passes through the magnetic field that changes from low to high, it can more effectively suppress the convective movement in the melt, make the heat conduct more evenly, reduce the defects and impurities in the crystal. Then, when passing through the magnetic field that changes from high to low, it may help there to be a buffer zone when the formed crystal detaches from the magnetic field, preventing the formed crystal from detaching from the magnetic field instantly and triggering a new convective mode, which has an adverse effect on the crystal quality, and ensuring continuous growth under more stable conditions. Moreover, the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 are all made of heat-insulating materials, which can greatly delay the heating rate of the liquid helium inside the liquid helium chamber 8, keep the inside of the liquid helium chamber 8 at a low temperature for a long time, ensure that the superconducting core 9 is in a superconducting state for a long time, and ensure the use effect of the device.

[0034] Such as Figures 1 to 10As shown, an insulating and magnetic - permeable shell 32 is fixedly installed inside the central insulating and magnetic - resistant shell 1, the upper insulating and magnetic - resistant shell 2, and the lower insulating and magnetic - resistant shell 3. The distance between the insulating and magnetic - permeable shell 32 and the outer wall of the Czochralski furnace shell 14 is five centimeters. A support bending rod 31 is fixedly installed at the bottom of the lower insulating and magnetic - resistant shell 3. One end of the support bending rod 31 away from the lower insulating and magnetic - resistant shell 3 is fixedly connected to the top of the support plate 19. During operation, the provided insulating and magnetic - permeable shell 32 can delay the heat transfer from the Czochralski furnace shell 14 to the inside of the central insulating and magnetic - resistant shell 1, the upper insulating and magnetic - resistant shell 2, and the lower insulating and magnetic - resistant shell 3, greatly delaying the heating rate of the liquid helium inside the liquid helium chamber 8, keeping the inside of the liquid helium chamber 8 at a low temperature for a long time, ensuring that the superconducting core 9 remains in a superconducting state for a long time, and guaranteeing the use effect of the device. In addition, the insulating and magnetic - permeable shell 32 is made of a magnetic - permeable material, which can ensure that the magnetic force and magnetic field generated by the superconducting core 9 can act on the Czochralski furnace shell 14 in an accurate and controllable direction, thereby effectively having an expected impact on the silicon rod being grown by Czochralski method inside the Czochralski furnace shell 14, and thus greatly reducing the thermal stress generated during the growth of the silicon rod. A five - centimeter spacing space is specifically designed between the insulating and magnetic - permeable shell 32 and the Czochralski furnace shell 14. This ingenious arrangement not only effectively avoids direct contact between the insulating and magnetic - permeable shell 32 and the Czochralski furnace shell 14, thus significantly reducing direct heat transfer on the one hand, but on the other hand, this five - centimeter spacing also provides a buffer distance for the magnetic force and magnetic field during action, enabling the magnetic field lines to act more evenly and stably on the silicon rod inside the Czochralski furnace shell 14, further optimizing the regulation effect of the magnetic field on the silicon rod growth process and ensuring the quality and stability of the silicon rod growth.

[0035] As Figures 1 to 10As shown, heat-insulating connection blocks 5 are fixedly installed on the outer sides of the central heat-insulating and magnetic-blocking shell 1, the upper heat-insulating and magnetic-blocking shell 2, and the lower heat-insulating and magnetic-blocking shell 3. Thermistors 6 are fixedly installed inside the three heat-insulating connection blocks 5, and the temperature-measuring parts of the thermistors 6 are located inside the central heat-insulating and magnetic-blocking shell 1, the upper heat-insulating and magnetic-blocking shell 2, and the lower heat-insulating and magnetic-blocking shell 3. On one side of the three heat-insulating connection blocks 5 away from the central heat-insulating and magnetic-blocking shell 1, the upper heat-insulating and magnetic-blocking shell 2, and the lower heat-insulating and magnetic-blocking shell 3, an electricity-connecting frame 7 is fixedly installed; during operation, the externally connected current can be transmitted to the thermistors 6 and the superconducting core 9 through wires. The three thermistors 6 are arranged to change their resistance values according to the temperature inside the liquid helium chamber 8 inside the central heat-insulating and magnetic-blocking shell 1, the upper heat-insulating and magnetic-blocking shell 2, and the lower heat-insulating and magnetic-blocking shell 3. The three thermistors 6 are all negative temperature coefficient thermistors 6. When the temperature inside the liquid helium chamber 8 rises, the resistance value of the thermistor 6 decreases, which can change the current passing through the coil 10 inside the central heat-insulating and magnetic-blocking shell 1, the upper heat-insulating and magnetic-blocking shell 2, and the lower heat-insulating and magnetic-blocking shell 3, so as to ensure the stability of the magnetic field generated by the superconducting core 9 and the coil 10 when the temperature inside the liquid helium chamber 8 changes. The thermistor 6 can be used as a highly sensitive temperature sensor to capture the subtle changes in the temperature inside the liquid helium chamber 8 in real time. When the thermistor 6 detects that the temperature rise causes the resistance value to drop, the current in the coil 10 connected in series with it will increase to compensate for the magnetic field fluctuations that may be caused by the temperature change. Through this feedback mechanism, even if the temperature inside the liquid helium chamber 8 fluctuates, the magnetic field can remain relatively stable, making the composition of the crystal more uniform and reducing the segregation effect in the crystal.

[0036] As Figures 1 to 10As shown in the figure, the Czochralski rotation assembly includes a Czochralski lifting assembly and a rotation assembly. The Czochralski lifting assembly includes a Czochralski traction head 30. A rotation pull rod 16 is fixedly installed at the top of the Czochralski traction head 30. A connecting rod 15 is rotatably installed at the top of the rotation pull rod 16. One end of the connecting rod 15 away from the rotation pull rod 16 is fixedly connected to a lifting rope 13. One end of the lifting rope 13 away from the connecting rod 15 is fixedly connected to a winding rod 12. A steering gear 11 is fixedly installed at the top of the support ear plate 20. The output end of the steering gear 11 is fixedly connected to one end of the winding rod 12. An input end of the steering gear 11 is fixedly installed with a driven gear 18. The outer sides of the driven gear 18 and a driving gear 22 are meshed with each other. During operation, after the driving motor 21 is started, the output end of the driving motor 21 can drive the driving gear 22 to rotate, thereby driving the driven gear 18 to rotate. And after being steered by the steering gear 11, the winding rod 12 is driven to rotate, thereby winding the lifting rope 13, so as to pull the connecting rod 15 to move upward, thereby driving the rotation pull rod 16 to move upward, and finally pulling the Czochralski traction head 30 to move upward. A Czochralski silicon rod is formed at the bottom of the Czochralski traction head 30. The Czochralski traction head 30 is lifted by winding the lifting rope 13. As the number of turns of the lifting rope 13 wound on the outer side of the winding rod 12 increases, the length of the lifting rope 13 that can be wound in one turn of the winding rod 12 increases, so that the rising speed of the Czochralski traction head 30 can be slowly increased. In the initial stage of silicon rod growth, a lower pulling speed helps to stabilize the growth interface and reduce the generation of defects. As the growth progresses, gradually increasing the pulling speed can maintain the stable growth of the crystal and improve the production efficiency at the same time.

[0037] As Figures 1 to 10 shown in the figure, the rotation assembly includes a limit frame 28. The limit frame 28 is fixedly installed inside the Czochralski furnace shell 14, and the limit frame 28 is movably installed on the outer side of the rotation pull rod 16. A rotation guide groove 17 is formed on the outer side of the rotation pull rod 16. A rotation guide block 29 is fixedly installed inside the limit frame 28, and the rotation guide block 29 is slidably installed inside the rotation guide groove 17. During operation, when the rotation pull rod 16 is rising, the limit frame 28 located on the outer side of the rotation pull rod 16 can ensure the stability of the rising of the rotation pull rod 16, so that the rotation pull rod 16 will not swing, reducing or eliminating the shaking phenomenon, so as to ensure the quality of the crystal and the stability of the growth process. In addition, when the rotation pull rod 16 is rising, the rotation guide block 29 can move inside the rotation guide groove 17, so that the rotation pull rod 16 rotates. The rotation can homogenize the component and temperature distribution in the molten pool, and can also avoid the uneven stress generated by the friction between the crystal and the graphite rod, and can also promote the mass transfer between the gas and the molten pool, so as to better control the content and form of impurities in the crystal.

[0038] As Figures 1 to 10As shown, the rotating crucible assembly includes a crucible 23, which is located directly below the lower heat-insulating and magnetic-resistant shell 3. An insulating ring plate 25 is fixedly installed on the outer side of the crucible 23. An anti-disengagement ring 26 is fixedly installed on the outer side of the insulating ring plate 25, and the anti-disengagement ring 26 is fixedly installed on the inner side of the Czochralski furnace shell 14. A driven gear ring 24 is fixedly installed on the outer side of the insulating ring plate 25, and the outer side of the driven gear ring 24 meshes with the outer side of the driving gear 22. A swinging assembly is installed inside the crucible 23, and the swinging assembly is used to swing the materials in the bottom area of the crucible 23 to the top area of the crucible 23. A magnetic ring lifting assembly is also installed inside the crucible 23, and the magnetic ring lifting assembly is used to reduce the heat convection inside the crucible 23. During operation, when the driving motor 21 is started, it can drive the driving gear 22 to rotate, thereby driving the driven gear ring 24 to rotate, and driving the crucible 23 to rotate through the insulating ring plate 25. The rotating crucible 23 can make the melt evenly distributed inside the crucible, and the centrifugal force generated by the rotation helps to discharge the bubbles in the melt, reduce the voids between the melts, so that the reactants are more closely combined together, which is beneficial to the mass transfer and heat transfer between the reactants, and further accelerates the progress of the chemical reaction. Moreover, when the crucible 23 rotates, the temperature distribution inside the melt can be made more uniform, reduce the temperature gradient, which helps to reduce the thermal stress during the single crystal growth process and reduce the generation of crystal defects. In addition, both the driven gear ring 24 and the driven gear 18 are driven to rotate by the driving gear 22. When pulling a silicon rod with a large diameter, the rotation speed of the driving motor 21 can be reduced, so that the rotation speeds of the driving gear 22, the driven gear ring 24 and the driven gear 18 are all reduced, so that the rotation speed of the crucible 23 and the rising speed of the Czochralski pulling head 30 are both reduced, and the pulling is carried out slowly to ensure the stable growth of the silicon rod. When pulling a silicon rod with a small diameter, the rotation speed of the driving motor 21 can be increased, so that the rotation speeds of the driving gear 22, the driven gear ring 24 and the driven gear 18 are all increased, so that the rotation speed of the crucible 23 and the rising speed of the Czochralski pulling head 30 are both increased, and the pulling is carried out quickly to ensure the pulling efficiency of the silicon rod. The rotation speed of the crucible 23 and the rising speed of the Czochralski pulling head 30 are both controlled by the driving motor 21, and there is no need for excessive adjustment of equipment, and it can be stably applied to the pulling of silicon rods with different diameters. In addition, the provided insulating ring plate 25 can play a role in heat insulation, preventing the support frame plate 19 from directly contacting the crucible 23 and preventing the staff from being affected by the high temperature of the crucible 23 during operation.

[0039] As Figures 1 to 10As shown, the swinging assembly includes four pressing push rods 33 and four U-shaped seats 34. One end of each of the four pressing push rods 33 is fixedly connected to the inner side of the direct-pulling furnace shell 14. A shifting plate 35 is rotatably installed inside each of the four U-shaped seats 34. One end of each of the four pressing push rods 33 away from the supporting bent rod 31 is located inside the crucible 23, and the height of the end of the pressing push rod 33 away from the supporting bent rod 31 is between the top of the U-shaped seat 34 and the top of the shifting plate 35. A liquid shifting plate 36 is fixedly installed at the bottom of each shifting plate 35. During operation, when the crucible 23 rotates, it can drive the shifting plate 35 to rotate through the U-shaped seat 34. When the shifting plate 35 passes by the pressing push rod 33, the pressing push rod 33 can push one end of the shifting plate 35 towards the inner wall of the crucible 23, and make the liquid shifting plate 36 at the other end of the shifting plate 35 move away from the inner wall of the crucible 23, thus shifting the materials deposited at the bottom of the crucible 23 upwards, avoiding excessive accumulation of the melt at the bottom of the crucible 23. This uniform distribution helps to ensure that the reactants can fully contact and mix, thereby improving the uniformity of the reaction.

[0040] As Figures 1 to 10 shown, the liquid shifting plate 36 is of a five-stage stepped type and is in a shrinking state from bottom to top. A rectangular through groove is formed inside the liquid shifting plate 36. One side of the liquid shifting plate 36 is flat, and the other side is arc-shaped. During operation, the five-stage stepped liquid shifting plate 36 in a shrinking state from bottom to top can shift the melt at different positions inside the crucible 23 to different degrees, ensuring the uniformity of the shifting. In addition, the rectangular through groove inside the liquid shifting plate 36 can reduce the resistance of the liquid shifting plate 36 during upward shifting, and also prevent the melt from splashing during shifting, ensuring the safety of the shifting. In addition, the flat side of the liquid shifting plate 36 can ensure the shifting effect and prevent the melt from quickly detaching from one side of the liquid shifting plate 36. In addition, the arc-shaped side of the liquid shifting plate 36 can prevent the liquid shifting plate 36 from shifting the melt downwards when the liquid shifting plate 36 approaches the inner wall of the crucible 23 under the action of gravity, ensuring the uniformity of the melt inside the crucible 23. By shifting the melt with the liquid shifting plate 36, the friction force between the melts increases and it is not easy to form lumps. During the direct-pulling single-crystal growth process, preventing the formation of lumps helps to grow high-quality single crystals without dislocations and defects.

[0041] As Figures 1 to 10As shown in the figure, the magnetic ring lifting assembly includes a magnetic ring 37. Four connecting vertical rods 38 are fixedly installed at the top of the magnetic ring 37. Lifting plates 39 are fixedly installed at the tops of the four connecting vertical rods 38. The central axes of the four lifting plates 39 and the central axes of the four liquid deflecting plates 36 are in the same vertical plane. Four limiting sliding rods 27 are slidably installed inside the connecting vertical rods 38. The bottoms of the limiting sliding rods 27 are fixedly installed at the bottom of the crucible 23. During operation, when the liquid deflecting plate 36 moves away from the inner wall of the crucible 23, it can push up the lifting plate 39, thereby pulling the connecting vertical rod 38 to move upward, and then pulling the magnetic ring 37 to move upward outside the limiting sliding rod 27. By adding a magnetic ring 37 that moves up and down in the crucible 23, a changing magnetic field can be generated. This magnetic field can more effectively suppress the convection of the silicon melt, thereby reducing the heat flow. When the magnetic field acts on the melt, the conductors in the melt will cut the magnetic induction lines, thereby generating an induced electromotive force. Under the action of the induced electromotive force, an induced current will be generated in the silicon melt, and the induced current will generate a Lorentz force under the action of the magnetic field. The direction of this Lorentz force is opposite to the flow direction of the melt, so it can hinder the flow of the melt, that is, suppress convection.

[0042] As Figures 1 to 10 shown, a heat insulation material is installed on the outside of the magnetic ring 37. The magnetic ring 37 is made of an alnico magnet; during operation, in addition, the outside of the magnetic ring 37 is wrapped with a heat insulation material, and the heat insulation material is alumina short fiber, which can significantly slow down the transfer of external heat to the magnetic ring 37. And the magnetic ring 37 is an alnico magnet, and its Curie temperature is higher than the sintering temperature of 900 °C, and it can still maintain magnetism at high temperatures.

[0043] Working principle: First, liquid helium can be injected into the liquid helium chamber 8 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 through the liquid filling valve 4. The liquid helium makes the inside of the liquid helium chamber 8 in a low-temperature state, so that the superconducting core 9 and the coil 10 located inside the liquid helium chamber 8 are both in a low temperature, and the superconducting core 9 and the coil 10 are both in a superconducting state. Then, the externally connected current can be transmitted to the thermistor 6 and the superconducting core 9 through the wire. The three set thermistors 6 change their resistance values according to the temperature inside the liquid helium chamber 8 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3. The three thermistors 6 are all negative temperature coefficient thermistors 6. When the temperature inside the liquid helium chamber 8 rises, the resistance value of the thermistor 6 decreases, which can change the current passing through the coil 10 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3, so as to ensure the stability of the magnetic field generated by the superconducting core 9 and the coil 10 when the temperature inside the liquid helium chamber 8 changes. The thermistor 6 can be used as a highly sensitive temperature sensor to capture the subtle changes in the temperature inside the liquid helium chamber 8 in real time. When the thermistor 6 detects that the temperature rises and the resistance value drops, the current in the coil 10 connected in series with it will increase to compensate for the magnetic field fluctuations that may be caused by the temperature change. Through this feedback mechanism, even if the temperature inside the liquid helium chamber 8 fluctuates, the magnetic field can remain relatively stable, making the composition of the crystal more uniform and reducing the segregation effect in the crystal. In addition, the number of turns of the coil 10 wound around the outside of the superconducting core 9 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 is in the ratio of 2:1:1. When the same current is passed through, the magnetic field intensity generated by the superconducting core 9 and the coil 10 inside the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 first increases and then decreases from bottom to top, and the magnetic field intensity at the top and bottom is the same, while the magnetic field intensity in the middle is twice that of the top and bottom. When the single crystal passes through the magnetic field from low to high, it can more effectively suppress the convective motion in the melt, make the heat conduct more evenly, and reduce the defects and impurities in the crystal. Then, when passing through the magnetic field from high to low, it may help the formed crystal to have a buffer interval when leaving the magnetic field, preventing the formed crystal from leaving the magnetic field instantly and triggering a new convective mode, which has an adverse impact on the crystal quality and ensuring continued growth under more stable conditions. And the central heat-insulating and magnetic-resistant shell 1, the upper heat-insulating and magnetic-resistant shell 2, and the lower heat-insulating and magnetic-resistant shell 3 are all made of heat-insulating materials, which can greatly delay the heating rate of the liquid helium inside the liquid helium chamber 8, keep the inside of the liquid helium chamber 8 in a low-temperature state for a long time, ensure that the superconducting core 9 is in a superconducting state for a long time, and ensure the use effect of the device. After the driving motor 21 is started, the output end of the driving motor 21 can drive the driving gear 22 to rotate, thereby driving the driven gear 18 to rotate, and after being steered by the steering gear 11, it drives the winding rod 12 to rotate, thereby winding the lifting rope 13, thereby pulling the connecting rod 15 upward, thereby driving the rotating rod 16 upward, and finally pulling the direct pulling head 30 upward.A straight-pull silicon rod is formed at the bottom of the straight-pull traction head 30, and the straight-pull traction head 30 is lifted by means of a winding and lifting rope 13. As the number of turns of the lifting rope 13 on the outer side of the winding rod 12 increases, the length of the lifting rope 13 that can be wound up when the winding rod 12 rotates one circle increases, thereby slowly increasing the rising speed of the straight-pull traction head 30. In the initial stage of silicon rod growth, a lower pulling speed helps to stabilize the growth interface and reduce the generation of defects. As the growth proceeds, gradually increasing the pulling speed can maintain the stable growth of the crystal and improve production efficiency at the same time. During the rising process of the rotating pull rod 16, the limit frame 28 located on the outer side of the rotating pull rod 16 can ensure the stability of the rising of the rotating pull rod 16, so that the rotating pull rod 16 will not swing, reducing or eliminating shaking. In addition, the rotating guide block 29 can move inside the rotating guide groove 17 during the rising process of the rotating pull rod 16, so that the rotating pull rod 16 can rotate. The rotation can evenly distribute the components and temperature in the molten pool, avoid the uneven stress caused by the friction between the crystal and the graphite rod, and promote the mass transfer between the gas and the molten pool, so as to better control the content and form of impurities in the crystal. When the driving motor 21 is started, it can drive the active gear 22 to rotate, thereby driving the driven gear ring 24 to rotate, and driving the crucible 23 to rotate through the heat insulation ring plate 25. The rotating crucible 23 can make the melt evenly distributed inside the crucible, and the centrifugal force generated by the rotation has It helps to discharge bubbles in the melt, reduce the gaps between the melts, and make the reactants more closely combined, which is beneficial to mass transfer and heat transfer between the reactants, thereby accelerating the chemical reaction. When the crucible 23 rotates, the temperature distribution inside the melt can be made more uniform, reducing the temperature gradient, which helps to reduce the thermal stress in the single crystal growth process and reduce the generation of crystal defects. In addition, the driven gear ring 24 and the driven gear 18 are driven to rotate through the driving gear 22. When it is necessary to straight-pull a silicon rod with a large diameter, the speed of the drive motor 21 can be reduced, thereby reducing the speeds of the driving gear 22, the driven gear ring 24 and the driven gear 18, thereby reducing the rotation speed of the crucible 23 and the rising speed of the straight-pull traction head 30, and the straight-pull is performed slowly. , to ensure the stable growth of silicon rods. When it is necessary to pull silicon rods with small diameters, the speed of the driving motor 21 can be increased, so that the speeds of the driving gear 22, the driven gear ring 24 and the driven gear 18 are all increased, so that the rotation speed of the crucible 23 and the rising speed of the straight-pull traction head 30 are all increased, and the straight-pull is performed quickly to ensure the efficiency of the straight-pull of silicon rods. The speed of the crucible 23 and the rising speed of the straight-pull traction head 30 are both controlled by the driving motor 21, and there is no need to adjust too much equipment. It can be stably applied to the straight-pull of silicon rods of different diameters. When the crucible 23 rotates, the toggle plate 35 can be driven to rotate by the U-shaped seat 34. When the toggle plate 35 passes through the pressing push rod 33, the pressing push rod 33 can push one end of the toggle plate 35 toward the end close to the inner wall of the crucible 23.And the liquid deflecting plate 36 at the other end of the toggling plate 35 is moved towards the end away from the inner wall of the crucible 23, so as to toggle the material deposited at the bottom of the crucible 23 upwards, avoiding excessive accumulation of the melt at the bottom of the crucible 23. This uniform distribution helps to ensure sufficient contact and mixing of the reactants, thereby improving the uniformity of the reaction.

[0044] The foregoing has shown and described the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments, and what is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements all fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A superconducting magnet and a magnetron CZ single crystal pulling device, characterized in that: The invention comprises a support installation component, wherein the support installation component comprises a support frame plate (19) and a support ear plate (20), and the support ear plate (20) is fixedly mounted on the outer side of the support frame plate (19); a superconducting magnet component and a rotating straight-pull component are mounted on the top of the support frame plate (19); a straight-pull furnace shell (14) is fixedly mounted inside the support frame plate (19); a rotating crucible component is mounted inside the straight-pull furnace shell (14); a driving component is fixedly mounted on the bottom of the support frame plate (19) and the support ear plate (20); the driving component is used to drive the rotating straight-pull component and the rotating crucible component to operate; the driving component comprises a driving motor (21); a driving gear (22) is fixedly mounted on the output end of the driving motor (21); the superconducting magnet component comprises a central heat-insulating magnetic-resistance shell (1), an upper heat-insulating magnetic-resistance shell (2) and a lower heat-insulating magnetic-resistance shell (3); the central heat-insulating magnetic-resistance shell ( 1), an upper heat-insulating magnetic-resistance shell (2) and a lower heat-insulating magnetic-resistance shell (3) are both located on the outside of the vertical pulling furnace shell (14), the upper heat-insulating magnetic-resistance shell (2) is fixedly mounted on the top of the central heat-insulating magnetic-resistance shell (1), and the lower heat-insulating magnetic-resistance shell (3) is fixedly mounted on the bottom of the central heat-insulating magnetic-resistance shell (1), and a liquid filling valve (4) is fixedly mounted on the outside of the central heat-insulating magnetic-resistance shell (1), the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3), and the central heat-insulating magnetic-resistance shell (1) is fixedly mounted on the outside of the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3). The thermal-resistance magnetic shell (1), the upper thermal-insulation magnetic-resistance shell (2) and the lower thermal-insulation magnetic-resistance shell (3) are each provided with a liquid helium cavity (8), a superconducting core (9) is fixedly mounted inside the liquid helium cavity (8), the outer side of the superconducting core (9) is wound with a coil (10), and the number of turns of the coil (10) wound around the outer side of the superconducting core (9) inside the central thermal-insulation magnetic-resistance shell (1), the upper thermal-insulation magnetic-resistance shell (2) and the lower thermal-insulation magnetic-resistance shell (3) is 2:1:1; A heat-insulating magnetic-resistance shell (32) is fixedly installed inside the central heat-insulating magnetic-resistance shell (1), the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3), and the distance between the heat-insulating magnetic-resistance shell (32) and the outer wall of the vertical pull furnace shell (14) is five centimeters. A support bending rod (31) is fixedly installed at the bottom of the lower heat-insulating magnetic-resistance shell (3), and one end of the support bending rod (31) away from the lower heat-insulating magnetic-resistance shell (3) is fixedly connected to the top of the support frame plate (19); The outer sides of the central heat-insulating magnetic-resistance shell (1), the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3) are all fixedly mounted with heat-insulating connecting blocks (5); the interiors of the three heat-insulating connecting blocks (5) are all fixedly mounted with thermistors (6); and the temperature measuring parts of the thermistors (6) are located on the inner sides of the central heat-insulating magnetic-resistance shell (1), the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3); and the sides of the three heat-insulating connecting blocks (5) away from the central heat-insulating magnetic-resistance shell (1), the upper heat-insulating magnetic-resistance shell (2) and the lower heat-insulating magnetic-resistance shell (3) are fixedly mounted with an electrical connection frame (7).

2. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 1, characterized in that: The rotary straight-pull assembly comprises a lifting straight-pull assembly and a rotary assembly, wherein the lifting straight-pull assembly comprises a straight-pull traction head (30), a rotary pull rod (16) is fixedly mounted on the top of the straight-pull traction head (30), a connecting rod (15) is rotatably mounted on the top of the rotary pull rod (16), a lifting rope (13) is fixedly connected to one end of the connecting rod (15) away from the rotary pull rod (16), a winding rod (12) is fixedly connected to one end of the lifting rope (13) away from the connecting rod (15), a steering gear (11) is fixedly mounted on the top of the support ear plate (20), an output end of the steering gear (11) is fixedly connected to one end of the winding rod (12), and a driven gear (18) is fixedly mounted on the input end of the steering gear (11), and the outer side of the driven gear (18) is meshed with the outer side of the driving gear (22).

3. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 2, characterized in that: The rotating assembly comprises a limit frame (28), wherein the limit frame (28) is fixedly mounted on the inner side of the straight-pull furnace shell (14), and the limit frame (28) is movably mounted on the outer side of a rotating pull rod (16), a rotating guide groove (17) is provided on the outer side of the rotating pull rod (16), a rotating guide block (29) is fixedly mounted on the inner side of the limit frame (28), and the rotating guide block (29) is slidably mounted on the inner side of the rotating guide groove (17).

4. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 3, characterized in that: The rotating crucible assembly comprises a crucible (23), the crucible (23) being located directly below the lower heat-insulating and magnetic-resisting shell (3), a heat-insulating ring plate (25) being fixedly mounted on the outer side of the crucible (23), a fall-off prevention ring (26) being fixedly mounted on the outer side of the heat-insulating ring plate (25), the fall-off prevention ring (26) being fixedly mounted on the inner side of the vertical-pulling furnace shell (14), a driven gear ring (24) being fixedly mounted on the outer side of the heat-insulating ring plate (25), the outer side of the driven gear ring (24) being meshed with the outer side of the driving gear (22), a swinging assembly being mounted inside the crucible (23), the swinging assembly being used to swing the material in the bottom area of ​​the crucible (23) to the top area of ​​the crucible (23), and a magnetic ring lifting assembly being mounted inside the crucible (23), the magnetic ring lifting assembly being used to reduce the heat convection inside the crucible (23).

5. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 4, characterized in that: The swing assembly comprises four push rods (33) and four U-shaped seats (34), one end of the four push rods (33) is fixedly connected to the inner side of the vertical pull furnace shell (14), and a toggle plate (35) is rotatably installed inside the four U-shaped seats (34). One end of the four push rods (33) away from the supporting bending rod (31) is located on the inner side of the crucible (23), and the height of the end of the push rod (33) away from the supporting bending rod (31) is located between the top of the U-shaped seat (34) and the top of the toggle plate (35), and a liquid diverting plate (36) is fixedly installed at the bottom of the toggle plate (35).

6. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 5, characterized in that: The liquid-discharging plate (36) is of five-stage stepped type and is in a shrinking state from bottom to top. A rectangular through groove is provided inside the liquid-discharging plate (36). One side of the liquid-discharging plate (36) is flat, and the other side of the liquid-discharging plate (36) is in an arc shape.

7. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 6, characterized in that: The magnetic ring lifting assembly comprises a magnetic ring (37), four connecting rods (38) are fixedly mounted on the top of the magnetic ring (37), and a lifting plate (39) is fixedly mounted on the top of each of the four connecting rods (38), the central axes of the four lifting plates (39) are respectively in the same vertical plane as the central axes of the four liquid-discharging plates (36), and four limiting slide bars (27) are slidably mounted inside the connecting rods (38), and the bottom of the limiting slide bars (27) is fixedly mounted on the bottom of the crucible (23).

8. A superconducting magnet and a magnetron CZ single crystal pulling device according to claim 7, characterized in that: A heat-resistant material is installed on the outer side of the magnetic ring (37), and the heat-resistant material is short aluminum oxide fibers. The magnetic ring (37) uses an aluminum-nickel-cobalt magnet.

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