Split type magnetic pulling single-crystal superconducting magnet

Abstract

The invention relates to the technical field of superconducting magnets, in particular to a split type magnetic pulling single crystal superconducting magnet which comprises a split type superconducting magnet, a single crystal furnace system, a control cabinet, a refrigerating system and a magnet control protection system. The split superconducting magnet adopts a split structural design, a split notch is formed in the vertical direction, the width of the notch is matched with the size of an accessory part of the single crystal furnace, and a high-precision vacuum sealing interface is formed in the edge of the notch, so that the whole vacuum degree is ensured not to leak, and the split superconducting magnet is convenient to install and maintain. The split type magnetic pulling single crystal superconducting magnet provided by the invention is compact in structure, high in magnetic field utilization rate and multi-stage sufficient cooling, the magnet is attached to a furnace body to be conveniently assembled, disassembled and assembled, melt convection is effectively inhibited, and the quality of single crystal silicon is remarkably improved.

Description

Technical Field

[0001] This invention relates to the field of superconducting magnet technology, specifically to a split-type magnetically pulled single-crystal superconducting magnet. Background Technology

[0002] As the semiconductor industry moves towards larger sizes and higher purity, single-crystal silicon, as a core material, directly determines the performance of end devices. In the traditional Czochralski (CZ) process for producing single-crystal silicon, the high-temperature melt induces natural convection due to the temperature gradient, resulting in uneven distribution of impurities and an increase in defects (such as dislocations and vacancies) in the crystal. The oxygen content is typically 10-15 ppm, which is insufficient to meet the requirements of high-end semiconductor devices.

[0003] Meanwhile, most existing single-crystal magnets are traditional monolithic ring structures, which have obvious drawbacks: the monolithic structure is large in size and highly enclosed, making it unsuitable for the compact layout of early compact single-crystal furnaces; installation and maintenance require overall hoisting and disassembly, and maintenance requires power off, demagnetization, and heating, resulting in long cycles and high costs; the magnetic field distribution is fixed and cannot be adjusted according to the crystal pulling stage and crucible specifications, limiting its adaptability; it mostly relies on liquid helium cooling, which is costly and resource-scarce, while also having high energy consumption, lacking targeted quench protection, and insufficient superconducting stability.

[0004] Based on the technical problems of poor compatibility, inconvenient installation and maintenance, insufficient magnetic field flexibility, and high energy consumption in existing technologies, this invention proposes a split-type magnetically pulled single-crystal superconducting magnet. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention provides a split-type magnetically pulled single-crystal superconducting magnet with a compact structure, high magnetic field utilization, multi-stage sufficient cooling, convenient assembly and disassembly of the magnet in conjunction with the furnace body, effective suppression of melt convection, and significant improvement in the quality of single-crystal silicon.

[0006] To achieve the above objectives, the present invention provides a split-type magnetically pulled single-crystal superconducting magnet, the specific technical solution of which is as follows: It includes a split-type superconducting magnet, a single crystal furnace system, a control cabinet, a refrigeration system, and a magnet control and protection system.

[0007] The split-type superconducting magnet adopts a split-type structural design with a split notch opened along the vertical direction. The width of the notch is adapted to the size of the auxiliary components of the single crystal furnace, and the edge of the notch is equipped with a high-precision vacuum sealing interface to ensure that the overall vacuum degree does not leak, which facilitates installation and maintenance.

[0008] Preferably, the splitting superconducting magnet is a ring-shaped modular structure, assembled around the outside of the main furnace body, with its central axis collinear with the central axis of the main furnace body to ensure precise alignment of the magnetic field center with the molten region. The splitting notch of the splitting superconducting magnet is a C-shaped opening structure, with its position corresponding one-to-one with the furnace body suspension bracket and furnace body integrated box on the outer periphery of the main furnace body. The two sides of the splitting notch maintain a safe gap of 50-80mm with the outer walls of the furnace body suspension bracket and furnace body integrated box, which avoids the compact distribution of auxiliary components and allows the splitting superconducting magnet to be arranged close to the main furnace body. For example, the distance between the inner wall of the magnet and the outer wall of the main furnace body is 120-180mm, ensuring that the magnetic field strength in the molten region meets the design requirements and achieves effective constraint on the silicon melt.

[0009] Preferably, the opening angle of the split notch is adjustable, with an adjustment range of 30°-60°, and the diameter of the main furnace body of the single crystal furnace is 800-1760mm.

[0010] Preferably, the magnetic field strength of the saddle-shaped magnet coil can be adjusted in real time according to the crystal pulling process, see details below. Figure 7 Horizontal field distribution of a split magnet.

[0011] Preferably, the split-type superconducting magnet includes a 300K container, a cold shield container, a 4K cold mass unit, and a saddle-shaped magnet coil; the 300K container, the cold shield container, and the 4K cold mass unit are all provided with mutually matching split-type notches, and the split-type notches are provided with high-precision vacuum sealing interfaces to ensure that the overall vacuum level of the magnet reaches a certain level. Level 1, which isolates external heat convection and transfer.

[0012] Preferably, the 300K container has a double-layered cylindrical structure, including a 300K outer cylinder and a 300K inner cylinder, with a closed vacuum cavity formed between the outer and inner cylinders to isolate external heat transfer through gas convection. A refrigeration unit service tower is located on the opposite side of the split notch at the end of the 300K container, for installing refrigeration unit components and providing a foundation for the refrigeration system.

[0013] Preferably, the cold shield container is located inside the 300K container and has a double-layered cylindrical structure, including an outer cold shield cylinder and an inner cold shield cylinder. The cold shield container is fixed to the inner wall of the 300K container by a cold shield space tie rod, and the two ends of the cold shield space tie rod are respectively fixedly connected to the inner wall of the 300K container and the outer wall of the cold shield container by bolts. The side of the cold shield container closest to the refrigeration unit service tower is attached to the first-stage cold head of the refrigeration unit through a heat-conducting flexible connector. During operation, it can be cooled to 50K-60K, forming a low-temperature shielding layer to reduce external heat radiation. The cold shield container is covered with multiple layers of insulation between itself and the 300K container, and between itself and the 4K cold mass unit, to further block heat transfer. The multiple layers of insulation are made of alternating layers of polyester film and aluminum foil, which can effectively reduce heat radiation and residual gas convection.

[0014] Preferably, the 4K cold mass unit has a split frame structure. A 4K lateral support unit is located near the saddle-shaped magnet coil, and these lateral support units are distributed at a predetermined angle of 45° in the horizontal XY coordinate system. A 4K vertical support unit is located vertically within the 4K cold mass unit, which is then fixed to the interior of the 300K container. The saddle-shaped magnet coil is fitted onto the coil slot of the 4K cold mass unit. The 4K cold mass unit is connected to the secondary cold head of the refrigerator via a flexible heat-conducting connector, allowing it to be cooled to ≤4.2K during operation, ensuring a safe superconducting working environment for the saddle-shaped magnet coil. Both the 4K lateral and vertical support units are made of G10 composite material or carbon fiber, balancing low thermal conductivity with overall structural rigidity.

[0015] Preferably, the saddle-shaped magnet coil consists of two symmetrically arranged superconducting coils, and the saddle-shaped magnet coil is wound with niobium-titanium conductor material.

[0016] Preferably, the two saddle-shaped magnet coils are arranged in a circular pattern and form an opening and closing structure corresponding to the split notch. When energized, they can generate an axial magnetic field (i.e., parallel to the growth direction of the crystal rod) or a cutting magnetic field (i.e., a CUSP field, which forms a cross magnetic field in the melt region) of 0.5T-4.81T to meet different crystal pulling requirements.

[0017] The single crystal furnace system has a vertical and compact structure. Its core functional component is the main furnace body, which is arranged vertically to form a sealed crystal growth cavity. The interior is used to accommodate a quartz crucible, silicon melt, and seed crystal pulling mechanism (not shown). The outer peripheral wall of the main furnace body is a smooth cylindrical surface, providing a basis for the assembly of auxiliary components.

[0018] Preferably, the furnace body suspension bracket consists of two sets of symmetrically arranged rigid support structures made of high-strength alloy material, which are fixed to the outer peripheral sidewall of the main furnace body by bolts, and the two sets of furnace body suspension brackets are symmetrically distributed about the central axis of the main furnace body at 180°. The inner sidewall of the furnace body suspension bracket is in close contact with the outer sidewall of the main furnace body, such as a gap of ≤2mm. Its top extends to 100-150mm below the upper edge of the main furnace body, and its bottom extends to the middle and lower part of the main furnace body, such as 30%-40% of the height from the bottom of the main furnace body. The top is hinged to the external fixed frame (not shown) by a pin to realize the suspension and positioning of the main furnace body, forming a typical compact support structure of early single crystal furnaces.

[0019] Preferably, the furnace body integrated box is a rectangular modular box, which integrates auxiliary control components such as temperature sensors and gas flow controllers. There are two sets of these components, symmetrically distributed about the central axis of the main furnace body and spaced 90° apart from the furnace body suspension bracket. The furnace body integrated box is fixed to the outer peripheral wall of the main furnace body with screws. Its installation height is flush with the middle area of ​​the furnace body suspension bracket (vertical deviation ≤30mm). The side of the box facing the main furnace body is fitted with the outer side wall of the main furnace body with a clearance of 30-50mm, ensuring assembly stability and reserving space for cable routing. Together with the furnace body suspension bracket, it forms a compact auxiliary structure layout around the main furnace body.

[0020] The control cabinet is an independent cabinet structure made of cold-rolled steel plate. It is located on the horizontal side of the single crystal furnace system, with a horizontal distance of 1.5-2.5m between it and the main furnace body. This distance allows operators to observe the control cabinet parameters and the furnace operating status at the same time, while avoiding mutual interference during equipment operation.

[0021] Preferably, the installation height of the control cabinet is adapted to the upper middle part of the main furnace body, such as the top surface of the cabinet being 1.2-1.5m above the ground. The cabinet is equipped with a main control circuit board, a magnetic field monitoring module, and a refrigeration unit drive module. It is electrically connected to the temperature sensor, voltage sensor, and refrigeration unit of the single crystal furnace system through multi-core high-temperature resistant cables to achieve centralized control.

[0022] The refrigeration system includes a refrigeration unit and a flexible heat-conducting connector. The refrigeration unit is a GM refrigeration unit or a pulse tube refrigeration unit, installed inside a refrigeration service tower. The refrigeration unit has a primary cold head and a secondary cold head. The primary cold head has a cooling temperature of 50K-60K and is connected to a cold shield container via the flexible heat-conducting connector to form a low-temperature shielding layer. The secondary cold head has a cooling temperature ≤4.2K and is connected to a 4K cold mass unit via the flexible heat-conducting connector to ensure the saddle-shaped magnet coil is in a superconducting state. The flexible heat-conducting connector is made of copper braided tape, ensuring effective heat conduction while adapting to installation deviations.

[0023] The magnet control and protection system includes a power monitoring module and a temperature monitoring module. The power monitoring module is used to monitor the working status of the superconducting magnet in real time and control the automatic rise and fall of the magnetic field power supply. The temperature monitoring module is used to monitor the temperature change of the superconducting magnet in real time, and control the switching according to the preset threshold range. When the temperature change is detected to exceed the threshold range, the protection mechanism is quickly triggered to cut off the current and release the magnetic field to prevent the magnet from being damaged by quenching.

[0024] The aforementioned method for fabricating silicon wafers using a split-type magnetically pulled single-crystal superconducting magnet includes the following steps: S1 Magnet System Preparation: Connect the bottom of the superconducting magnet to the lifting device. Nest the single crystal furnace inside the central hole of the magnet, ensuring the center of the magnetic field is aligned with the center of the crucible inside the single crystal furnace. Start the cooling unit. The first-stage cold head is connected to the cold shield container via a flexible heat-conducting connector. The cold shield container can be cooled to 50K-60K during operation, forming a low-temperature shielding layer. The second-stage cold head is connected to the 4K cold mass unit via a flexible heat-conducting connector. The 4K cold mass unit can be cooled to ≤4.2K during operation, allowing the saddle-shaped magnet coil to enter the superconducting state. Connect the superconducting power supply to the magnet current lead. Excite the superconducting coil at a stable rate to achieve the target magnetic field strength. S2 Single Crystal Furnace Preparation and Loading: The single crystal furnace first completes furnace cleaning, component installation, and vacuum leak detection. High-purity polycrystalline silicon material is then loaded into a quartz crucible, and seed crystals with specific crystal orientations are fixed. S3 melting stage: High-purity argon gas is introduced into the furnace to maintain a slight positive pressure. The heater power is gradually increased until the silicon material is completely melted. After holding at this temperature for 30 minutes, the gas is removed. S4 Magnetic Field Application and Crystal Growth: The magnetic field type is adjusted through a magnet control and protection system. During the seeding and shoulder formation stage, the magnetic field strength is maintained, and the seed crystal is controlled to descend and contact the melt for 5 minutes. Then, necking growth is carried out at a pulling speed of 8-12 mm / min to eliminate initial dislocations. During the shoulder formation stage, the pulling speed is adjusted to 2-4 mm / min, and the shoulder angle is controlled to be 45°-60°. During the constant diameter growth stage, the magnetic field strength is reduced, and the pulling speed, seed crystal rotation speed and crucible rotation speed are adjusted in real time to maintain the temperature. The Lorentz force is used to suppress melt convection. S5 Final Stage: Adjust the magnetic field strength, gradually increase the pulling speed to 3-8 mm / min, and decrease the temperature by 5-10℃ to make the crystal tail form a cone shape and detach from the melt; S6 Cooling and Maintenance: Maintain an inert atmosphere inside the furnace, allow the crystal to slowly cool to room temperature, then turn off the magnetic field, disconnect the power supply to the superconducting magnet, slowly reduce the furnace pressure to atmospheric pressure, remove the crystal rod, and inspect, cut, and roll the crystal rod to prepare silicon wafers.

[0025] The beneficial effects of this invention are: This invention provides a split-type magnetically pulled single-crystal superconducting magnet with a compact structure, high magnetic field utilization, multi-stage sufficient cooling, convenient assembly and disassembly of the magnet in conjunction with the furnace body, effective suppression of melt convection, and significant improvement in the quality of single-crystal silicon.

[0026] This invention adopts a split structure and a high-precision vacuum sealing interface, avoiding the tight-fitting structure of early single crystal furnaces, adapting to single crystal furnaces of different specifications, with strong compatibility and making full use of existing equipment resources; the upper and lower magnets are independently supported and cooled, and can be disassembled and fitted together with the furnace body for installation and then reassembled. During maintenance, the upper part can be disassembled separately, reducing the maintenance cycle by 50% and significantly reducing downtime losses.

[0027] The saddle-shaped magnet coil is wound with superconducting material and can generate a strong magnetic field in the superconducting state at ≤4.2K. It supports switching between axial and tangential magnetic fields, and the magnetic field uniformity can reach [percentage missing]. The magnetic field strength can be precisely adjusted according to each stage of crystal pulling, and the Lorentz force can effectively suppress melt convection, reducing the silicon-oxygen content of single crystal to below 5ppm, reducing the defect density by 30-50%, and significantly improving crystal purity, integrity and resistivity uniformity.

[0028] The 4K horizontal support units are distributed at a preset angle of 45°, which, together with the 4K vertical support units, can counteract electromagnetic forces and low-temperature deformation, avoiding magnetic field deviation or structural damage. The electrical system is equipped with a power monitoring module and a temperature monitoring module; it monitors the working status of the superconducting magnet in real time and the temperature changes of the superconducting magnet during operation. When an abnormality is detected, the protection mechanism is quickly triggered to cut off the current and release the magnetic field to prevent quenching damage to the magnet and avoid various risks.

[0029] The refrigeration system significantly reduces heat leakage through layered cooling and multi-layered insulation. Under the same magnetic field strength, its energy consumption is 15-20% lower than that of traditional integral magnets, and it operates with zero resistance without Joule heat loss, which is in line with the trend of energy conservation and environmental protection.

[0030] Magnetic field confinement makes the melt surface more stable, improves crystal growth stability, and can increase the pulling speed by 10-15%. At the same time, it reduces the loss of head and tail materials by more than 4%, improves the utilization rate of raw materials, further reduces production costs, and enhances the competitiveness of enterprises. Attached Figure Description

[0031] Figure 1 Schematic diagram of the split-type superconducting magnet: showing the structure and notch location of the split-type superconducting magnet body; Figure 2 Assembly layout diagram of magnet and single crystal furnace: This diagram shows the assembly relationship between the split superconducting magnet of the present invention and the single crystal furnace system, demonstrating the design of the notch avoiding the furnace body suspension bracket, and marking the alignment relationship between the center of the magnetic field and the center of the crucible in the single crystal furnace system. Figure 3Layout diagram of a single crystal furnace: showing the structural relationships of the single crystal furnace system layout, furnace body suspension bracket, furnace body integrated box, etc. Figure 4 Schematic diagram of the internal structure of the magnet: showing the hierarchical relationship of components such as the 300K container, the cold screen container, and the 4K cold mass unit; Figure 5 Schematic diagram of magnet coil structure: showing the distribution of two symmetrical saddle-shaped magnet coils; Figure 6 Schematic diagram of the refrigerator connection distribution: showing the connection relationship between the refrigerator components, the first-stage cold head, the second-stage cold head, the cold shield container, and the 4K cold mass unit; Figure 7 Schematic diagram of horizontal field distribution of split magnet: It shows the uniformity of the horizontal magnetic field distribution generated by the magnet, with the magnetic flux density ranging from 0.5T to 4.81T, and clearly identifies the location of the strongest magnetic field region.

[0032] In the attached diagram: 1-Split-type superconducting magnet; 2-Single crystal furnace system; 3-Control cabinet; 101-300K container; 102-Cold shield container; 103-Refrigeration service tower; 104-Refrigeration unit; 1041-First-stage cold head; 1042-Second-stage cold head; 105-Cooling flexible connector; 106-4K cold mass unit; 107-Saddle-shaped magnet coil; 108-4K lateral support unit; 109-Cold shield inner cylinder; 110-300K inner cylinder; 111-Cold shield space tie rod; 112-4K vertical support unit; 201-Main furnace body; 202-Furnace body suspension bracket; 203-Furnace body integrated box. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments. Example 1

[0035] like Figure 1-7 As shown, a split-type magnetically pulled single-crystal superconducting magnet includes a split-type superconducting magnet 1, a single-crystal furnace system 2, a control cabinet 3, a cooling system, and a magnet control and protection system.

[0036] Figure 1The split-type superconducting magnet 1 adopts a split-type structure design with a split notch opened in the vertical direction. The width of the notch is adapted to the size of the auxiliary components of the single crystal furnace, and the edge of the notch is provided with a high-precision vacuum sealing interface to ensure that the overall vacuum degree does not leak, which facilitates installation and maintenance.

[0037] Preferably, the split-type superconducting magnet 1 is a ring-shaped modular structure, which is assembled around the outside of the main furnace body 201. Its central axis is collinear with the central axis of the main furnace body 201 to ensure that the center of the magnetic field is precisely aligned with the melt area. The split-type notch of the split-type superconducting magnet 1 is a C-shaped opening structure, and the opening position corresponds one-to-one with the furnace body suspension bracket 202 and the furnace body integrated box 203 on the outer periphery of the main furnace body 201. The two sides of the split-type notch maintain a safe gap of 50-80mm with the outer side wall of the furnace body suspension bracket 202 and the furnace body integrated box 203, which avoids the compact distribution of auxiliary components and allows the split-type superconducting magnet 1 to be arranged close to the main furnace body 201. For example, the distance between the inner wall of the split-type superconducting magnet 1 and the outer side wall of the main furnace body 201 is 120-180mm, which ensures that the magnetic field strength in the melt area meets the design requirements and achieves effective constraint on the silicon melt.

[0038] Preferably, the opening angle of the split notch is adjustable, with an adjustment range of 30°-60°, and the diameter of the main furnace body 201 of the single crystal furnace is 800-1760mm.

[0039] Preferably, the magnetic field strength of the saddle-shaped magnet coil 107 can be adjusted in real time according to the crystal pulling process, see details below. Figure 7 Horizontal field distribution of a split magnet.

[0040] Figures 4-5 Preferably, the split-type superconducting magnet 1 includes a 300K container 101, a cold shield container 102, a 4K cold mass unit 106, and a saddle-shaped magnet coil 107; the 300K container 101, the cold shield container 102, and the 4K cold mass unit 106 are all provided with matching split-type notches, and the split-type notches are provided with high-precision vacuum sealing interfaces to ensure that the overall vacuum degree of the split-type superconducting magnet 1 meets the standard and to isolate the external heat convection transfer.

[0041] Preferably, the 300K container 101 has a double-layer cylindrical structure, including a 300K outer cylinder and a 300K inner cylinder 110. A closed vacuum cavity is formed between the 300K outer cylinder and the 300K inner cylinder 110 to isolate external heat from being transferred through gas convection. A refrigeration unit service tower 103 is provided on the opposite side of the split notch at the end of the 300K container 101 for installing the refrigeration unit assembly 104, providing an installation foundation for the refrigeration system.

[0042] Preferably, the cold shield container 102 is located inside the 300K container 101 and has a double-layer cylindrical structure, including an outer cold shield cylinder and an inner cold shield cylinder 109. The cold shield container 102 is fixed to the inner wall of the 300K container 101 by a cold shield space tie rod 111. The side of the cold shield container 102 closest to the refrigeration unit service tower 103 is attached to the first-stage cold head 1041 of the refrigeration unit 104 via a heat-conducting flexible connector 105. During operation, it can be cooled to 50K-60K, forming a low-temperature shielding layer to reduce external heat radiation. The cold shield container 102 is covered with multiple layers of insulation between itself and the 300K container 101, and between itself and the 4K cold mass unit 106, further blocking heat transfer. The multiple layers of insulation are made of alternating layers of polyester film and aluminum foil, which can effectively reduce heat radiation and residual gas convection.

[0043] Preferably, the 4K cold mass unit 106 has a split frame structure. A 4K lateral support unit 108 is provided near the saddle-shaped magnet coil 107, and the 4K lateral support unit 108 is distributed at a preset angle of 45° in the horizontal XY coordinate system. A 4K vertical support unit 112 is provided vertically to the 4K cold mass unit 106, and it is fixed inside the 300K container 101. The saddle-shaped magnet coil 107 is fitted onto the coil slot of the 4K cold mass unit 106. The 4K cold mass unit 106 is connected to the secondary cold head 1042 of the refrigeration assembly 104 via a heat-conducting flexible connector 105. During operation, it can be cooled to ≤4.2K, ensuring the superconducting working environment of the saddle-shaped magnet coil 107. Both the 4K lateral support unit 108 and the 4K vertical support unit 112 are made of G10 composite material or carbon fiber material, balancing low thermal conductivity and overall structural rigidity.

[0044] Preferably, the saddle-shaped magnet coil 107 consists of two symmetrically arranged superconducting coils, and the saddle-shaped magnet coil 107 is wound with niobium-titanium conductor material.

[0045] Preferably, the two saddle-shaped magnet coils 107 are arranged in a circular pattern and form an opening and closing structure corresponding to the split notch. When energized, they can generate an axial magnetic field (i.e., parallel to the growth direction of the crystal rod) or a cutting magnetic field (i.e., a CUSP field, which forms a cross magnetic field in the melt region) of 0.5T-4.81T to meet different crystal pulling requirements.

[0046] Figures 2-3 The single crystal furnace system 2 has a vertical and compact structure. Its core functional component is the main furnace body 201. The main furnace body 201 is arranged vertically to form a sealed crystal growth cavity. Its interior is used to accommodate a quartz crucible, silicon melt, and seed crystal pulling mechanism (not shown). The outer peripheral wall of the main furnace body 201 is a smooth cylindrical surface, which provides a basis for the assembly of auxiliary components.

[0047] Preferably, the furnace body suspension bracket 202 consists of two sets of symmetrically arranged rigid support structures made of high-strength alloy material, which are fixed to the outer peripheral sidewall of the main furnace body 201 by bolts, and the two sets of furnace body suspension brackets 202 are symmetrically distributed about the central axis of the main furnace body 201 at 180°. The inner sidewall of the furnace body suspension bracket 202 is in close contact with the outer sidewall of the main furnace body 201, such as a gap of ≤2mm. Its top extends to 100-150mm below the upper edge of the main furnace body 201, and its bottom extends to the middle and lower part of the main furnace body 201, such as 30%-40% of the height from the bottom of the main furnace body 201. The top is hinged to the external fixing frame (not shown) by a pin to realize the suspension and positioning of the main furnace body 201, forming a typical compact support structure of early single crystal furnaces.

[0048] Preferably, the furnace body integrated box 203 is a rectangular modular box, which integrates auxiliary control components such as temperature sensors and gas flow controllers. There are two sets of these components, which are symmetrically distributed about the central axis of the main furnace body 201 and arranged at 90° circumferential intervals with the furnace body suspension bracket 202. The furnace body integrated box 203 is fixed to the outer peripheral wall of the main furnace body 201 with screws. Its installation height is flush with the middle area of ​​the furnace body suspension bracket 202 (vertical deviation ≤30mm). The side of the box facing the main furnace body 201 is fitted with the outer side wall of the main furnace body 201 with a clearance of 30-50mm. This ensures assembly stability and provides space for cable routing. Together with the furnace body suspension bracket 202, it forms a compact auxiliary structure layout on the outer periphery of the main furnace body 201.

[0049] The control cabinet 3 is an independent cabinet structure made of cold-rolled steel plate. It is located on the horizontal side of the single crystal furnace system 2. The horizontal distance between it and the main furnace body 201 is 1.5-2.5m. This distance makes it convenient for operators to observe the parameters of the control cabinet 3 and the operating status of the main furnace body 201 at the same time, and avoids mutual interference during equipment operation.

[0050] Preferably, the installation height of the control cabinet 3 is adapted to the upper middle area of ​​the main furnace body 201, such as the top surface of the cabinet being 1.2-1.5m above the ground. It is equipped with a main control circuit board, a magnetic field monitoring module and a refrigeration unit drive module. It is electrically connected to the temperature sensor, voltage sensor and refrigeration unit 104 of the single crystal furnace system 2 through multi-core high-temperature resistant cables to achieve centralized control.

[0051] Figures 6-7The refrigeration system includes a refrigeration unit 104 and a heat-conducting flexible connector 105. The refrigeration unit 104 is a GM refrigeration unit or a pulse tube refrigeration unit, installed inside the refrigeration unit service tower 103. The refrigeration unit 104 has a primary cold head 1041 and a secondary cold head 1042. The primary cold head 1041 has a refrigeration temperature of 50K-60K and is connected to the cold shield container 102 via the heat-conducting flexible connector 105 to form a low-temperature shielding layer. The secondary cold head 1042 has a refrigeration temperature ≤4.2K and is connected to the 4K cold mass unit 106 via the heat-conducting flexible connector 105 to ensure that the saddle-shaped magnet coil 107 is in a superconducting state. The heat-conducting flexible connector 105 is a copper braided strip, which ensures the heat conduction effect while adapting to installation deviations.

[0052] The magnet control and protection system includes a power monitoring module and a temperature monitoring module. The power monitoring module is used to monitor the working status of the superconducting magnet 1 in real time and control the automatic rise and fall of the magnetic field power supply. The temperature monitoring module is used to monitor the temperature change of the superconducting magnet 1 in real time, and control the switching according to the preset threshold range. When the temperature change is detected to exceed the threshold range, the protection mechanism is quickly triggered to cut off the current and release the magnetic field to prevent the magnet from being damaged by quenching. Example 2

[0053] The aforementioned method for fabricating silicon wafers using a split-type magnetically pulled single-crystal superconducting magnet includes the following steps: S1 Magnet System Preparation: Connect the bottom of the superconducting magnet to the lifting device. Nest the single crystal furnace inside the central hole of the magnet, ensuring the center of the magnetic field is aligned with the center of the crucible inside the single crystal furnace. Start the cooling unit. The first-stage cold head is connected to the cold shield container via a flexible heat-conducting connector. The cold shield container can be cooled to 50K-60K during operation, forming a low-temperature shielding layer. The second-stage cold head is connected to the 4K cold mass unit via a flexible heat-conducting connector. The 4K cold mass unit can be cooled to ≤4.2K during operation, allowing the saddle-shaped magnet coil to enter the superconducting state. Connect the superconducting power supply to the magnet current lead. Excite the superconducting coil at a stable rate to achieve the target magnetic field strength. S2 Single Crystal Furnace Preparation and Loading: The single crystal furnace first completes furnace cleaning, component installation, and vacuum leak detection. High-purity polycrystalline silicon material is then loaded into a quartz crucible, and seed crystals with specific crystal orientations are fixed. S3 melting stage: High-purity argon gas is introduced into the furnace to maintain a slight positive pressure. The heater power is gradually increased until the silicon material is completely melted. After holding at this temperature for 30 minutes, the gas is removed. S4 Magnetic Field Application and Crystal Growth: The magnetic field type is adjusted through a magnet control and protection system. During the seeding and shoulder formation stage, the magnetic field strength is maintained, and the seed crystal is controlled to descend and contact the melt for 5 minutes. Then, necking growth is carried out at a pulling speed of 8-12 mm / min to eliminate initial dislocations. During the shoulder formation stage, the pulling speed is adjusted to 2-4 mm / min, and the shoulder angle is controlled to be 45°-60°. During the constant diameter growth stage, the magnetic field strength is reduced, and the pulling speed, seed crystal rotation speed and crucible rotation speed are adjusted in real time to maintain the temperature. The Lorentz force is used to suppress melt convection. S5 Final Stage: Adjust the magnetic field strength, gradually increase the pulling speed to 3-8 mm / min, and decrease the temperature by 5-10℃ to make the crystal tail form a cone shape and detach from the melt; S6 Cooling and Maintenance: Maintain an inert atmosphere inside the furnace, allow the crystal to slowly cool to room temperature, then turn off the magnetic field, disconnect the power supply to the superconducting magnet, slowly reduce the furnace pressure to atmospheric pressure, remove the crystal rod, and inspect, cut, and roll the crystal rod to prepare silicon wafers.

[0054] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0055] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A split magnetic pull single crystal superconducting magnet characterized by, The application relates to a superconducting magnetic field device, a single crystal furnace system, a control cabinet, a refrigeration system and a magnet control protection system. The split superconducting magnet is designed in a split structure and has a ring-shaped modular structure and is assembled on the outer side of a main furnace body with a center axis arranged in line with the center axis of the main furnace body; the split superconducting magnet has a split gap in a C-shaped opening structure, and the split gap is arranged in one-to-one correspondence with furnace body suspension supports and furnace body integrated boxes on the outer periphery of the main furnace body; the split superconducting magnet comprises a 300K container, a cold shield container, a 4K cold mass unit and a saddle-shaped magnet coil; the 300K container, the cold shield container and the 4K cold mass unit are all provided with split gaps matched with each other, and high-precision vacuum sealing interfaces are arranged at the split gaps. The 4K cold mass unit is a split frame structure, and a 4K transverse support unit is arranged at the position of the 4K cold mass unit close to the saddle-shaped magnet coil; the 4K transverse support unit is distributed at a 45-degree preset included angle in a horizontal XY coordinate system; a 4K vertical support unit is arranged at the vertical direction of the 4K cold mass unit and is fixed to the inside of the 300K container through the 4K vertical support unit; the saddle-shaped magnet coil is arranged on the coil groove of the 4K cold mass unit; and the 4K cold mass unit is connected with a two-stage cold head of a refrigerator through a cold-lead soft connecting piece. The single crystal furnace system has a vertical compact structure and comprises a main furnace body for accommodating a quartz crucible, a silicon melt and a seed crystal lifting mechanism. The control cabinet has an independent cabinet structure and is made of cold-rolled steel plates and is arranged horizontally beside the single crystal furnace system. The refrigeration system comprises a refrigerator assembly and a cold-lead soft connecting piece; the refrigerator assembly is installed in a refrigerator service tower; the refrigerator assembly is provided with a one-stage cold head and a two-stage cold head; the one-stage cold head is connected with the cold shield container through the cold-lead soft connecting piece to form a low-temperature shielding layer; and the two-stage cold head is connected with the 4K cold mass unit through the cold-lead soft connecting piece. The magnet control protection system comprises a power supply monitoring module and a temperature monitoring module; the power supply monitoring module is used for monitoring the working state of the superconducting magnet in real time and controlling the automatic lifting power supply of the magnetic field; and the temperature monitoring module is used for monitoring the temperature change of the superconducting magnet in real time, performing switch control according to a preset threshold range, quickly triggering a protection mechanism when the temperature change exceeds the threshold range, cutting off the current and releasing the magnetic field to prevent the superconducting magnet from being damaged due to a loss of superconductivity. The split gap has an opening and closing angle adjustment range of 30-60 degrees, and the main furnace body of the single crystal furnace is adapted to a diameter of 800-1760 mm.

2. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The 300K container has a double-layer cylindrical structure and comprises a 300K outer cylinder and a 300K inner cylinder; and a closed vacuum cavity is formed between the 300K outer cylinder and the 300K inner cylinder.

3. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, ​ 4. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The cold shield container is located inside the 300K container and has a double-layer cylindrical structure, including a cold shield outer cylinder and a cold shield inner cylinder, and the cold shield container is fixed to the inner wall of the 300K container through a cold shield space pull rod, the two ends of the cold shield space pull rod are fixedly connected to the inner wall of the 300K container and the outer wall of the cold shield container through bolts; the cold shield container and the 300K container and the cold shield container and the 4K cold mass unit are wrapped with multiple layers of thermal insulation layers.

5. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The 4K transverse support unit and the 4K vertical support unit are made of G10 composite material or carbon fiber material.

6. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The saddle-shaped magnet coil is two symmetrically arranged superconducting coils, and the saddle-shaped magnet coil is wound with niobium-titanium conductor material.

7. The split-pole magnetic-pull single crystal superconducting magnet of claim 1, wherein, The furnace body suspension support is a rigid support structure symmetrically arranged in two groups and made of high-strength alloy material, which is fixed to the outer peripheral side wall of the main furnace body through bolts, and the two groups of furnace body suspension supports are symmetrically distributed about the central axis of the main furnace body by 180°; the inner side wall of the furnace body suspension support is closely attached to the outer side wall of the main furnace body, and the top is hingedly connected to the external fixed frame through a pin shaft.

8. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The cold conducting soft connecting piece is a copper woven belt.

9. The split-pole magnetic-pulling single crystal superconducting magnet of claim 1, wherein, The installation height of the control cabinet is adapted to the middle and upper region of the main furnace body, and the inside is provided with a main control circuit board, a magnetic field monitoring module and a refrigerator driving module, which are electrically connected with the temperature sensor, the voltage sensor and the refrigerator assembly of the single crystal furnace system through multi-core high-temperature-resistant cables to realize centralized control.

10. An operating method for preparing a silicon wafer by using the split-type magnetic pulling single crystal superconducting magnet according to any one of claims 1-9, characterized in that it comprises the following operation steps: S1. Magnet system preparation: connecting the superconducting magnet bottom to the lifting device, nesting the single crystal furnace in the magnet center hole, and ensuring that the magnetic field center is aligned with the crucible center in the single crystal furnace; Starting the refrigerator assembly, the primary cold head is connected to the cold shield container through the cold conducting soft connecting piece, the cold shield container can be cooled to 50K-60K when operating, forming a low-temperature shielding layer; the secondary cold head is connected to the 4K cold mass unit through the cold conducting soft connecting piece, the 4K cold mass unit can be cooled to ≤4.2K when operating, so that the saddle-shaped magnet coil enters the superconducting state; connecting the superconducting power supply to the magnet current lead; exciting the superconducting coil at a stable speed to reach the target magnetic field strength; S2. Single crystal furnace preparation and charging: the single crystal furnace first completes the furnace cleaning, component installation, vacuum leak detection, loads high-purity polycrystalline silicon material into the quartz crucible, and fixes the seed crystal with a specific crystal orientation; S3. Melting stage: filling high-purity argon gas into the furnace to maintain a slight positive pressure, gradually increasing the heater power until the silicon material is completely melted, and degassing after 30 minutes of heat preservation; ​ S4 magnetic field application and crystal growth: adjust the magnetic field type by the magnet control protection system, maintain the magnetic field strength during the seeding and shoulder forming stage, control the seed to contact the melt and soak for 5 minutes, then grow the neck with a pulling rate of 8-12 mm / min to eliminate the initial dislocation; adjust the pulling rate to 2-4 mm / min during the shoulder forming stage, control the shoulder angle to be 45°-60°; reduce the magnetic field strength during the equal diameter growth stage, adjust the pulling rate, the seed rotation speed and the crucible rotation speed in real time, maintain the temperature, and suppress the melt convection by the Lorentz force; S5 finishing stage: adjust the magnetic field strength, gradually increase the pulling rate to 3-8 mm / min, and reduce the temperature by 5-10 ℃, so that the tail of the crystal forms a conical shape and separates from the melt; S6 cooling and maintenance: keep the inert atmosphere in the furnace, let the crystal slowly decrease to room temperature, turn off the magnetic field and the superconducting magnet power, slowly reduce the furnace pressure to the normal pressure, take out the crystal bar, and detect, cut, and lapping grind the crystal bar to prepare silicon wafers.

Images