A magnetic crystal pulling device

Abstract

This application provides a magnetron crystal pulling device, including a single crystal furnace, a crucible, and a magnetron assembly. The crucible is disposed within the single crystal furnace and is used to hold molten silicon. The magnetron assembly is positioned above the molten silicon. The magnetron assembly includes a ring magnet with a crystal pulling channel for inserting a single crystal silicon rod. The ring magnet is positioned close to the molten silicon to form a hook-shaped magnetic field within the molten silicon. The magnetic field strength of the hook-shaped magnetic field at the surface of the molten silicon is greater than or equal to 0.1 millitrile. The hook-shaped magnetic field inside the molten silicon can effectively suppress longitudinal thermal convection, lateral thermal convection, and thermal convection in other directions, thus reducing the scouring of the crucible wall by the molten silicon, lowering the impurity content in the molten silicon, and improving the crystal pulling quality. Moreover, the magnetron crystal pulling device has a simple structure and can be implemented with only minor modifications to existing crystal pulling devices, making it widely applicable and cost-effective.

Description

Technical Field

[0001] This application belongs to the field of photovoltaic technology, specifically relating to a magnetically controlled crystal pulling device. Background Technology

[0002] In the field of photovoltaic technology, in order to improve the quality of crystals during the production of monocrystalline silicon, magnetic field applied crystal pulling equipment is usually used to pull crystals using the magnetic field applied crystal pulling method (MCZ).

[0003] In existing technologies, a magnetic field generator is installed in the magnetron crystal pulling apparatus. The magnetic field generated by the generator passes through the molten silicon in the crucible, causing the molten silicon to interact with the magnetic field and generate a Lorentz force. This suppresses thermal convection of the molten silicon and its erosion of the crucible wall, thereby reducing the impact of uneven crystal pulling and reducing impurities in the molten silicon. Therefore, magnetron crystal pulling apparatus has a significant impact on the production of monocrystalline silicon.

[0004] However, during their research into existing technologies, the inventors discovered that magnetic field generating devices can only suppress thermal convection of molten silicon in a single longitudinal or transverse direction, and the suppression effect is relatively limited. Furthermore, existing magnetic field generating devices are mostly installed outside the furnace body, resulting in complex and bulky structures that require significant modifications to the existing crystal pulling equipment, leading to substantial engineering work, long development cycles, and significantly increased production costs. Summary of the Invention

[0005] In view of the above problems, the present invention is proposed to provide a magnetic crystal pulling apparatus that overcomes or at least partially solves the above problems.

[0006] To solve the above-mentioned technical problems, this application is implemented as follows:

[0007] This application provides a magnetically controlled crystal pulling device, which includes a single crystal furnace, a crucible, and a magnetic control component.

[0008] The crucible is placed inside the single crystal furnace and is used to hold molten silicon; the magnetron assembly is placed above the molten silicon.

[0009] The magnetic control component includes a ring magnet, which has a crystal pulling channel for inserting a single crystal silicon rod. The ring magnet is positioned close to the molten silicon to form a hook-shaped magnetic field within the molten silicon.

[0010] The hook-shaped magnetic field has a magnetic field strength greater than or equal to 0.1 millitrile on the surface of the molten silicon.

[0011] Optionally, the annular magnet is a one-piece molded structure.

[0012] Optionally, the annular magnet has a split structure, comprising multiple magnetic components that are sequentially distributed circumferentially to form the crystal pulling channel.

[0013] Optionally, among the plurality of magnetic elements, two adjacent magnetic elements abut against each other.

[0014] Optionally, among the plurality of magnetic elements, adjacent magnetic elements are arranged at intervals.

[0015] Optionally, in the plurality of magnetic elements, each of the magnetic elements has the same magnetic pole distribution.

[0016] Optionally, the annular magnet includes an inner sidewall and an outer sidewall disposed opposite to each other, and a top surface and a bottom surface respectively connected to the inner sidewall and the outer sidewall;

[0017] The annular magnet has a first magnetic pole and a second magnetic pole, wherein the first magnetic pole is opposite to the second magnetic pole.

[0018] The first magnetic pole is disposed on the inner sidewall and the second magnetic pole is disposed on the outer sidewall, or the first magnetic pole is disposed on the top surface and the second magnetic pole is disposed on the bottom surface.

[0019] Optionally, the single crystal furnace is equipped with a heat exchanger, which is located above the crucible, and the magnetron assembly is connected to the heat exchanger.

[0020] Optionally, the distance between the inner wall of the annular magnet and the outer wall of the single-crystal silicon rod includes any value between 2 and 10 centimeters.

[0021] Optionally, the magnetron assembly further includes a cooling layer and a heat insulation layer;

[0022] The cooling layer covers the annular magnet, the heat insulation layer covers the cooling layer, and a cooling medium flows through the cooling layer.

[0023] In this embodiment, the magnetron crystal pulling device includes a single crystal furnace, a crucible, and a magnetron assembly. The crucible is disposed within the single crystal furnace and is used to hold molten silicon. The magnetron assembly is disposed above the molten silicon. The magnetron assembly includes a ring magnet with a crystal pulling channel for inserting a single crystal silicon rod. The ring magnet is positioned close to the molten silicon to form a hook-shaped magnetic field within the molten silicon. The magnetic field strength of the hook-shaped magnetic field at the surface of the molten silicon is greater than or equal to 0.1 millitrile. The magnetron assembly in this embodiment is connected to the heat exchanger. The ring magnet is located within the magnetron assembly, with at least a portion of it situated within the crucible, allowing the ring magnet to be positioned close to the molten silicon within the crucible and to form the hook-shaped magnetic field within the molten silicon. In practical applications, when the magnetic field strength of the hook-shaped magnetic field on the surface of the molten silicon is greater than or equal to 0.1 holodes, the hook-shaped magnetic field inside the molten silicon can effectively suppress longitudinal, lateral, and other directional thermal convection, thus inhibiting thermal convection in multiple directions. This reduces the scouring of the crucible wall by the molten silicon, lowers the impurity content in the molten silicon, and improves the crystal pulling quality. Furthermore, the magnetically controlled crystal pulling device has a simple structure, requiring only minor modifications to existing crystal pulling devices, making it widely applicable and cost-effective.

[0024] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0025] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0026] Figure 1 This is a schematic diagram of the structure of a magnetically controlled crystal pulling device according to an embodiment of this application;

[0027] Figure 2 This is a partial schematic diagram of the magnetic field lines of a magnetically controlled crystal pulling device according to an embodiment of this application;

[0028] Figure 3 This is a partial structural schematic diagram of a magnetically controlled crystal pulling device according to an embodiment of this application;

[0029] Figure 4 This is one of the structural schematic diagrams of a ring magnet described in the embodiments of this application;

[0030] Figure 5 This is a second schematic diagram of the structure of a ring magnet as described in the embodiments of this application;

[0031] Figure 6 This is the third schematic diagram of the structure of a ring magnet described in the embodiments of this application;

[0032] Figure 7 This is the fourth schematic diagram of the structure of a ring magnet described in the embodiments of this application;

[0033] Figure 8 This is the fifth schematic diagram of the structure of a ring magnet described in the embodiments of this application;

[0034] Figure 9 This is the sixth schematic diagram of the structure of a ring magnet described in the embodiments of this application;

[0035] Figure 10 This is a schematic diagram of the structure of a magnetic control component described in an embodiment of this application.

[0036] Figure reference numerals: 10 - Single crystal furnace; 20 - Crucible; 30 - Magnetically controlled assembly; 11 - Heat exchanger; 12 - Heater; 13 - Support rod; 31 - Ring magnet; 311 - Magnetic field lines; 21 - Liquid silicon; 22 - Single crystal silicon rod; 23 - Crystal pulling channel; 32 - Magnetic component; 33 - Inner wall; 34 - Outer wall; 35 - Top surface; 36 - Bottom surface; 37 - Cooling layer; 38 - Insulation layer; 301 - Ring-shaped body; 302 - Water inlet pipe; 303 - Water outlet pipe. Detailed Implementation

[0037] Embodiments of the present invention will now be described in detail. Examples of these embodiments are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0038] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0039] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0040] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0041] Monocrystalline silicon is typically produced in a single-crystal furnace 10 using the Czochralski method to obtain monocrystalline silicon rods 22. To improve the quality of the monocrystalline silicon rods 22 during production and avoid adverse effects such as high impurity content and uneven distribution, magnetic pulling is generally employed. Specifically, during the Czochralski process, a magnetic field is applied to a portion of the molten silicon 21 using a magnetic pulling device. The thermal convection of the molten silicon 21 cuts the magnetic field lines 311 generated by the magnetic field, producing a Lorentz force that suppresses the thermal convection of the molten silicon 21. This process yields monocrystalline silicon rods 22 with lower impurity content and more uniform distribution.

[0042] Reference Figures 1 to 10 This diagram illustrates the structure of a magnetically controlled crystal pulling device according to an embodiment of this application. Specifically, it may include a single-crystal furnace 10, a crucible 20, and a magnetic control assembly 30. The crucible 20 is disposed within the single-crystal furnace 10 and is used to hold molten silicon 21. The magnetic control assembly 30 is disposed above the molten silicon 21. The magnetic control assembly 30 includes a ring magnet 31, within which a crystal pulling channel 23 for the single-crystal silicon rod 22 is provided. The ring magnet 31 is positioned close to the molten silicon 21 to form a hook-shaped magnetic field within the molten silicon 21. The magnetic field strength of the hook-shaped magnetic field at the surface of the molten silicon 21 is greater than or equal to 0.1 millitrile.

[0043] In this embodiment, the magnetron crystal pulling device is equipped with a magnetron assembly 30, which is connected to the heat exchanger 11. A ring magnet 31 is disposed within the magnetron assembly 30, with at least a portion of the ring magnet 31 located within the crucible 20. This allows the ring magnet 31 to be positioned close to the molten silicon 21 within the crucible 20, forming a hook-shaped magnetic field 311 within the molten silicon 21. Specifically, the magnetic field generated by the ring magnet 31 within the molten silicon 21 has its maximum magnetic field strength at the surface of the molten silicon 21. By setting the maximum magnetic field strength of the hook-shaped magnetic field at the surface of the molten silicon 21 to be greater than or equal to 0.1 millitrile (mT), the ring magnet 31 provides a good thermal convection suppression effect on all molten silicon 21, avoiding a weaker magnetic field at a distance from the ring magnet 31 that would be difficult to suppress significantly and thus uneconomical. In this way, the hook-shaped magnetic field inside the molten silicon 21 can effectively suppress longitudinal, transverse, and other directional thermal convection in the molten silicon 21, thus suppressing thermal convection in multiple directions. This reduces the scouring of the crucible 20 wall by the molten silicon 21, lowers the impurity content in the molten silicon 21, and improves the crystal pulling quality. Moreover, the magnetically controlled crystal pulling device has a simple structure, requiring only minor modifications to existing crystal pulling devices, making it widely applicable and cost-effective.

[0044] Specifically, in the embodiments of this application, the magnetic field strength of the ring magnet 31 refers to its "remanence", symbol Br; the magnetic field strength at the surface of the silicon liquid 21 refers to the "magnetic flux density" at that point, which is a vector. The magnitude refers to the magnitude of its absolute value, commonly represented by the symbol B. The internationally accepted unit for both is Tesla (symbol T).

[0045] In practical applications, a crystal pulling apparatus typically consists of a single crystal furnace 10, a heater 12, a heat exchanger 11, a crucible 20, and a support rod 13. The heater 12 is positioned close to the crucible 20 to heat the silicon material inside the crucible 20 into molten silicon 21 and maintain the molten silicon 21 at a temperature suitable for growing crystal rods. The support rod 13 is connected to the bottom of the crucible 20 to support it. For example, the crucible 20 may specifically include at least one of a quartz crucible and a graphite crucible; however, the specific material of the crucible 20 is not limited in this embodiment.

[0046] Reference Figure 2 The diagram illustrates a schematic of the magnetic field lines of a hook-shaped magnetic field as described in an embodiment of this application. Figure 2As shown, the magnetic field lines 311 of the hook-shaped magnetic field within the molten silicon 21 are arc-shaped. Thus, some of the magnetic field lines 311 can cut through the longitudinal thermal convection in the molten silicon 21, generating a Lorentz force, which suppresses longitudinal thermal convection in the molten silicon 21. Simultaneously, another portion of the magnetic field lines 311 can cut through the transverse thermal convection in the molten silicon 21, generating a Lorentz force, which also suppresses transverse thermal convection in the molten silicon 21. Furthermore, the magnetic field lines 311 can also cut through thermal convection in other directions besides longitudinal and transverse, generating a Lorentz force. For example, these other directions can be at an angle of 45°, 60°, etc., to the transverse direction. In this way, thermal convection in multiple directions within the molten silicon 21 can be suppressed, the utilization rate of the magnetic field is almost constant, resulting in high utilization and improving the suppression effect of the magnetic control component 30 on thermal convection in the molten silicon 21.

[0047] In some optional embodiments of this application, the heat exchanger 11 includes a top end and a bottom end that are opposite to each other, and the magnetron control assembly 30 can be connected to the bottom end of the heat exchanger 11. In this way, without adding other installation structures, the magnetron control assembly 30 can be positioned as close to the liquid surface as possible, so that the magnetron control assembly 30 has a better suppression effect on the thermal convection of the silicon liquid 21.

[0048] Specifically, in the embodiments of this application, the magnetic control component 30 can be installed inside the heat exchanger 11 or outside the heat exchanger 11. The specific installation method of the magnetic control component 30 in the embodiments of this application is not limited.

[0049] For example, the specific structure of the magnetic control component 30 is as follows: Figure 3 As shown, the magnetic control assembly 30 may include a heat exchanger 11 and an annular magnet 31. The heat exchanger 11 includes an annular body 301, a water inlet pipe 302, and a water outlet pipe 303. An annular cavity is provided within the annular body 301, which is used to contain a cooling medium. The water inlet pipe 302 communicates with the annular cavity and is used to introduce the cooling medium into the annular cavity. The water outlet pipe 303 communicates with the annular cavity and is used to discharge the cooling medium from the annular cavity. The annular magnet 31 is connected to the side of the annular body 301 closest to the crucible 20.

[0050] During the pulling process of the single-crystal silicon rod 22, the heat released during the crystallization of the single-crystal silicon rod 22 can be quickly removed through the circulation of the cooling medium within the annular cavity, thereby increasing the pulling speed of the single-crystal silicon rod 22. Specifically, the annular body 301 can be made of a metal material with a certain strength. A channel is provided inside the annular body 301, which communicates with the crystal pulling channel 23, allowing the single-crystal silicon rod 22 to pass along the crystal pulling channel 23. Since the cooling medium can be continuously circulated into the annular cavity of the annular body 301, when the single-crystal silicon rod 22 passes through the channel of the annular body 301 and the crystal pulling channel 23, it can exchange heat with the cooling medium within the annular cavity, rapidly removing the latent heat of crystallization of the single-crystal silicon rod 22 and increasing the pulling speed of the single-crystal silicon rod 22.

[0051] Specifically, the inlet pipe 302 can be connected to the bottom of the annular cavity, and the outlet pipe 303 can be connected to the top of the annular cavity. In this way, the cooling medium can enter from the bottom of the annular cavity through the inlet pipe 302, flow through the annular cavity, and then flow out from the top outlet pipe 303, thus realizing heat conduction.

[0052] In this embodiment, the annular magnet 31 can be disposed on the side of the annular cavity near the crucible 20, and at least a portion of the annular magnet 31 can extend into the crucible 20, so that the annular magnet 31 can be disposed close to the silicon liquid 21 in the crucible 20 and form a hook-shaped magnetic field in the silicon liquid 21.

[0053] For example, in the embodiments of this application, the annular magnet 31 can be a permanent magnet, such as an iron boron magnet, or an electromagnet, or a combination of a permanent magnet and an electromagnet, etc. The specific form of the annular magnet 31 is not limited in the embodiments of this application.

[0054] Optionally, in the embodiments of this application, such as Figure 4 As shown, the annular magnet 31 is a one-piece molded structure, which facilitates the processing of the annular magnet 31, reduces material loss and manufacturing processes, and enables the annular magnet 31 to have a strong magnetic field.

[0055] In some alternative embodiments of this application, such as Figures 5 to 7 As shown, the annular magnet 31 can be a modular structure. Specifically, the annular magnet 31 may include multiple magnetic elements 32, which are sequentially distributed circumferentially to form the crystal pulling channel 23. This allows for flexible arrangement of the annular magnet 31, making it suitable for various single crystal furnaces 10 with different structures, and also avoids some structural distributions within the single crystal furnace 10.

[0056] Specifically, the magnetic component 32 can be a ferromagnetic component or an electromagnetic coil module. The specific type of the magnetic component 32 is not limited in this embodiment. For example... Figures 4 to 7The diagram illustrates different distributions of the magnetic component 32 as a ferromagnetic component. When the magnetic component 32 is a ferromagnetic component, it can include, but is not limited to, any one of samarium cobalt magnets, neodymium iron boron magnets, and iron oxide magnets. Because ferromagnetic components are simple in structure and low in cost, using ferromagnetic components as the magnetic component 32 allows for a relatively simple structure and lower cost. When the magnetic component 32 is an electromagnetic coil module, the electromagnetic coil module can generate a magnetic field when energized, and each electromagnetic coil module resembles a magnetic block.

[0057] Optionally, in the embodiments of this application, such as Figure 5 As shown, among the multiple magnetic components 32, adjacent magnetic components 32 abut against each other. This facilitates the formation of a complete circular ring by the multiple magnetic components 32, resulting in better stability and enabling the ring magnet 31 to generate a strong magnetic field.

[0058] In this embodiment of the application, optionally, among the plurality of magnetic elements 32, such as Figures 6 to 7 As shown, adjacent magnetic components 32 are spaced apart. This allows for compatibility with various single-crystal furnace 10 structures, facilitating the avoidance of potentially interfering structural distributions within the furnace 10 during installation. Furthermore, it saves on the material used for the ring magnet 31, reducing production costs.

[0059] For example, in this embodiment of the application, the cross-section of the magnetic component 32 includes at least one of an arc-shaped surface and a rectangular surface, which facilitates its application to different scenarios and improves the compatibility of the magnetic control assembly 30. Figure 6 As shown, the cross-section of the magnetic component 32 includes an arc-shaped surface. Multiple arc-shaped magnetic components 32 are arranged to form a ring magnet. The arc-shaped magnetic components 32 can form a ring magnet 31 more effectively with a smaller number of components. Figure 7 As shown, the cross-section of the magnetic element 32 includes a rectangular surface. Multiple rectangular magnetic elements 32 are arranged to form a ring magnet, which has a more flexible distribution and is easy to apply to single crystal furnaces 10 with various structures. In addition, the ring magnet 31 may also include a combination of arc-shaped magnetic elements 32 and rectangular magnetic elements 32, but this application embodiment does not limit this.

[0060] Optionally, in this embodiment, the magnetic poles of each of the plurality of magnetic elements 32 are distributed in the same way. This results in the ring magnet 31 formed by the axial distribution of the plurality of magnetic elements 32 having a large magnetic field strength, which in turn provides better suppression of the thermal convection effect of the magnetic assembly on the molten silicon 21.

[0061] Specifically, in this embodiment, the identical magnetic pole distribution of each magnetic element 32 means that if one magnetic element 32 has an N pole at the end near the crystal pulling channel 23 and an S pole at the end away from the crystal pulling channel 23, then the other magnetic element 32 also has an N pole at the end near the crystal pulling channel 23 and an S pole at the end away from the crystal pulling channel 23. Similarly, if one magnetic element 32 has an S pole at the end near the crystal pulling channel 23 and an N pole at the end away from the crystal pulling channel 23, then the other magnetic element 32 also has an S pole at the end near the crystal pulling channel 23 and an N pole at the end away from the crystal pulling channel 23. This continues in a similar manner, with each magnetic element 32 having an N pole at the end near the crystal pulling channel 23 and an S pole at the end away from the crystal pulling channel 23, or vice versa. The specific magnetic pole distribution of each magnetic element 32 is not limited in the embodiments of this application.

[0062] It should be noted that the magnetic pole distribution of each magnetic component 32 can also be different. That is, the magnetic pole of one magnetic component 32 is N pole at the end closer to the crystal pulling channel 23 and S pole at the end farther away from the crystal pulling channel 23; the magnetic pole of another magnetic component 32 can be S pole at the end closer to the crystal pulling channel 23 and N pole at the end farther away from the crystal pulling channel 23.

[0063] Optionally, in this embodiment, the annular magnet 31 includes an inner sidewall 33 and an outer sidewall 34 disposed opposite to each other, and a top surface 35 and a bottom surface 36 respectively connected to the inner sidewall 33 and the outer sidewall 34. The magnetic poles of the annular magnet 31 include a first magnetic pole and a second magnetic pole, wherein the first magnetic pole is opposite to the second magnetic pole. Wherein, as... Figure 9 As shown, the first magnetic pole is disposed on the inner sidewall 33, and the second magnetic pole is disposed on the outer sidewall 34. Alternatively, as... Figure 8 As shown, the first magnetic pole is disposed on the top surface 35, and the second magnetic pole is disposed on the bottom surface 36. Thus, in this embodiment of the application, ring magnets 31 with different magnetic pole distributions can be used in different practical application scenarios, improving the compatibility of the magnetic control component 30.

[0064] For example, in this embodiment of the application, when the first magnetic pole is the N pole and the second magnetic pole is the S pole, the inner sidewall 33 can be set as the N pole and the outer sidewall 34 as the S pole to form a radially distributed magnetic field. Alternatively, the top surface 35 can be set as the N pole and the bottom surface 36 as the S pole to form a longitudinally distributed magnetic field. When the first magnetic pole is the S pole and the second magnetic pole is the N pole, the inner sidewall 33 can be set as the S pole and the outer sidewall 34 as the N pole to form a radially distributed magnetic field. Alternatively, the top surface 35 can be set as the S pole and the bottom surface 36 as the N pole to form a longitudinally distributed magnetic field.

[0065] In this embodiment, the first magnetic pole can be set to the N pole and the second magnetic pole to the S pole, or the first magnetic pole can be set to the S pole and the second magnetic pole to the N pole. This embodiment does not limit this specific configuration.

[0066] Furthermore, the annular magnet 31 can be tilted at a certain angle, such as 45°, 60°, etc., to form magnetic field distributions in various directions. In this embodiment, the tilt angle of the annular magnet 31 is not limited.

[0067] Referring to Table 1 below, in the simulation experiment, the magnetic field distribution was set to radial distribution, longitudinal distribution, magnetic field with the toroidal magnet 31 tilted at a 45° angle, and without the magnetic control component 30 for control experiments. As shown in Table 1, with the magnetic field strength set to 1.2T (Tesla), the highest flow velocity of the silicon liquid 21 was 0.013 m / s in the radial distribution magnetic field, 0.027 m / s in the longitudinal distribution magnetic field, 0.034 m / s in the magnetic field distribution with the toroidal magnet 31 tilted at a 45° angle, and 0.055 m / s in the absence of magnetic field distribution.

[0068]

[0069] Table 1

[0070] Therefore, all three magnetic field distributions described above can effectively suppress thermal convection in the molten silicon 21. Among them, the radially distributed magnetic field is more effective in suppressing thermal convection in the molten silicon 21. That is, the radial magnetic field formed by setting the inner wall 33 of the annular magnet 31 as the N pole and the outer wall 34 as the S pole, or by setting the inner wall 33 of the annular magnet 31 as the S pole and the outer wall 34 as the N pole, is more effective.

[0071] In this embodiment, optionally, the distance between the inner wall of the annular magnet 31 and the outer wall of the single-crystal silicon rod 22 includes any value from 2 to 10 cm. That is, if the inner diameter of the annular magnet 31 is D1 and the outer diameter of the single-crystal silicon rod 22 is D2, then 4cm ≤ D2 - D1 ≤ 20cm, so that the annular magnet 31 can have a good suppression effect on the thermal convection of the silicon liquid 21 without affecting crystal pulling. This avoids a small distance between the inner wall of the annular magnet 31 and the outer wall of the single-crystal silicon rod 22, which would hinder the flow of protective gas along the crystal pulling channel 23 and impede the observation of the solid-liquid growth interface during crystal growth. It also avoids a large distance between the inner wall of the annular magnet 31 and the outer wall of the single-crystal silicon rod 22, which would weaken the suppression effect of the magnetron control component 30 on the thermal convection of the silicon liquid 21.

[0072] In this embodiment, if the outer diameter of the annular magnet 31 is D3 and the inner diameter of the crucible 20 is D4, setting D3 < D4 allows the annular magnet 31 to be positioned inside the crucible 20 close to the surface of the molten silicon 21, resulting in a stronger magnetic field generated by the magnetocontrol component 30.

[0073] Specifically, in this embodiment, when the annular magnet 31 is installed outside the bottom of the heat exchanger 11, the distance between the annular magnet 31 and the surface of the molten silicon 21 includes any value between 2 and 10 centimeters (cm). This ensures that the annular magnet 31 has a good crystal pulling effect on the single-crystal silicon rod 22 without affecting its growth. It avoids a small distance between the annular magnet 31 and the surface of the molten silicon 21, which would hinder the flow of protective gas along the crystal pulling channel 23 and impede observation of the solid-liquid growth interface during crystal growth. It also avoids a large distance between the annular magnet 31 and the surface of the molten silicon 21, which would weaken the suppression effect of the magnetocontrol component 30 on the thermal convection of the molten silicon 21.

[0074] Optionally, in this embodiment, the magnetic control component 30 further includes a cooling layer 37 and a heat insulation layer 38. The cooling layer 37 covers the annular magnet 31, and the heat insulation layer 38 covers the cooling layer 37. A cooling medium is circulated in the cooling layer 37 to prevent the magnetic properties of the annular magnet 31 from failing and to improve the service life of the magnetic control crystal pulling device.

[0075] In practical applications, high temperatures are required within the single crystal furnace 10 during the crystal pulling process. The molten silicon 21, being in a molten state, also has a high temperature, exceeding 1400°C within the furnace 10, which can easily damage the magnetron assembly 30. For example, this can cause the energized coil to burn out or the permanent magnet to demagnetize. Therefore, the heat insulation layer 38 blocks the high temperature generated by the molten silicon 21 from affecting the annular magnet 31, and the cooling medium within the cooling layer 37 lowers the temperature of the annular magnet 31 to prevent magnetic failure.

[0076] For example, the material of the insulation layer 38 may include at least one of metal, ceramic, and refractory materials with low thermal conductivity, etc., with a thermal conductivity of less than 50 W / (m*K) and a temperature resistance of more than 1000℃, exhibiting good high-temperature resistance. The insulation layer 38 may be made entirely of any one of the above materials, or any combination of the above materials; this application embodiment does not limit this.

[0077] Specifically, a flowing cooling medium or a non-flowing cooling medium can be introduced into the cooling layer 37 for periodic replacement; however, this embodiment of the application does not impose such limitations. For example, the material of the cooling medium may include water, gas, or other liquids, etc., to cool the annular magnet 31 so that its temperature is less than or equal to 300°C, thus not affecting the magnetic field it generates.

[0078] In summary, the magnetically controlled crystal pulling apparatus described in the embodiments of this application may include at least the following advantages:

[0079] In this embodiment, the magnetron crystal pulling device includes a single crystal furnace, a crucible, and a magnetron assembly. The crucible is disposed within the single crystal furnace and is used to hold molten silicon. The magnetron assembly is disposed above the molten silicon. The magnetron assembly includes a ring magnet with a crystal pulling channel for inserting a single crystal silicon rod. The ring magnet is positioned close to the molten silicon to form a hook-shaped magnetic field within the molten silicon. The magnetic field strength of the hook-shaped magnetic field at the surface of the molten silicon is greater than or equal to 0.1 millitrile. The magnetron assembly in this embodiment is connected to the heat exchanger. The ring magnet is located within the magnetron assembly, with at least a portion of it situated within the crucible, allowing the ring magnet to be positioned close to the molten silicon within the crucible and to form the hook-shaped magnetic field within the molten silicon. In practical applications, when the magnetic field strength of the hook-shaped magnetic field on the surface of the molten silicon is greater than or equal to 0.1 holodes, the hook-shaped magnetic field inside the molten silicon can effectively suppress longitudinal, lateral, and other directional thermal convection, thus inhibiting thermal convection in multiple directions. This reduces the scouring of the crucible wall by the molten silicon, lowers the impurity content in the molten silicon, and improves the crystal pulling quality. Furthermore, the magnetically controlled crystal pulling device has a simple structure, requiring only minor modifications to existing crystal pulling devices, making it widely applicable and cost-effective.

[0080] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0081] Although embodiments of the invention have been shown and described, those skilled in the art will understand 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 claims and their equivalents.

Claims

1. A magnetron puller apparatus, characterized by, The magnetic control crystal pulling device comprises a single crystal furnace, a crucible and a magnetic control assembly; The crucible is arranged in the single crystal furnace and used for containing silicon liquid, and the magnetic control assembly is arranged above the silicon liquid; The single crystal furnace is provided with a heat exchanger, the heat exchanger is arranged above the crucible, and the magnetic control assembly is connected to the heat exchanger; The magnetic control assembly comprises a ring-shaped magnet, a crystal pulling channel for passing through a single crystal silicon rod is arranged in the ring-shaped magnet, the ring-shaped magnet is arranged close to the silicon liquid and used for forming a hook-shaped magnetic field in the silicon liquid; The magnetic field strength of the hook-shaped magnetic field at the liquid surface of the silicon liquid is greater than or equal to 0.1 millitesla. The magnetic control assembly further comprises a cooling layer and a heat insulation layer, the cooling layer is wrapped on the ring-shaped magnet, the heat insulation layer is wrapped on the cooling layer, and a cooling medium is passed through the cooling layer.

2. The magnetron puller of claim 1, wherein The ring-shaped magnet is an integral structure.

3. The magnetron puller of claim 1, wherein The ring-shaped magnet is a split structure, the ring-shaped magnet comprises a plurality of magnetic pieces, and the plurality of magnetic pieces are sequentially distributed in a circumferential direction to form the crystal pulling channel.

4. The magnetron puller of claim 3, wherein Among the plurality of magnetic pieces, two adjacent magnetic pieces abut each other.

5. The magnetron puller of claim 3, wherein Among the plurality of magnetic pieces, two adjacent magnetic pieces are arranged in a spaced manner.

6. The magnetron puller of claim 4, wherein, Among the plurality of magnetic pieces, the magnetic poles of each magnetic piece are distributed in the same way.

7. The magnetron crystal pulling apparatus as set forth in claim 1 further including, The ring-shaped magnet comprises an inner side wall and an outer side wall arranged oppositely, and a top surface and a bottom surface connected to the inner side wall and the outer side wall respectively; The magnetic poles of the ring-shaped magnet comprise first magnetic poles and second magnetic poles, the first magnetic poles are opposite to the second magnetic poles; The first magnetic poles are arranged on the inner side wall, and the second magnetic poles are arranged on the outer side wall, or the first magnetic poles are arranged on the top surface, and the second magnetic poles are arranged on the bottom surface.

8. The magnetron puller of claim 1, wherein, The spacing between the inner wall of the ring-shaped magnet and the outer wall of the single crystal silicon rod comprises any value in the range of 2-10 cm.

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