Single crystal furnace and crystal pulling method

Abstract

The application relates to the technical field of semiconductor manufacturing, and discloses a single crystal furnace and a crystal pulling method. The single crystal furnace comprises a furnace body, a crucible, a heat shield, a flow guide cylinder, a first magnetic field device and a second magnetic field device. The crucible is arranged in the furnace body. The heat shield is arranged in the furnace body and is provided with a cavity. The flow guide cylinder is arranged in the furnace body and surrounds the heat shield. The first magnetic field device is located in the cavity and is provided with a channel through which a crystal bar passes, and the first magnetic field device is used for forming a horizontal magnetic field in the channel. The second magnetic field device is located at the periphery of the first magnetic field device and is used for forming a hook-shaped magnetic field at the periphery of the first magnetic field device. The single crystal furnace and the crystal pulling method provided by the application can be beneficial to ensuring the quality of the crystal bar.

Description

Technical Field

[0001] This application relates to the field of semiconductor manufacturing technology, and in particular to a single crystal furnace and a crystal pulling method. Background Technology

[0002] With the continuous development of photovoltaic power generation technology, the installed capacity of photovoltaic modules is constantly increasing. A photovoltaic module is formed by encapsulating solar cells. A PN junction is formed on the silicon wafer of the solar cell, enabling it to generate current under sunlight. The silicon wafer is the fundamental component in solar cell manufacturing; it is obtained by cutting crystal rods.

[0003] A single crystal furnace is a device used to produce crystal ingots. The molten silicon formed inside the furnace can be used to obtain crystal ingots via the Czochralski method, which are then cut into silicon wafers. The quality of the crystal ingots is a crucial factor affecting the performance of solar cells. Therefore, ensuring the quality of the crystal ingots is an important issue. Summary of the Invention

[0004] The purpose of this application is to provide a single crystal furnace and a crystal pulling method that can help ensure the quality of crystal rods.

[0005] To address the aforementioned technical problems, this application provides a single crystal furnace. The single crystal furnace includes a furnace body, a crucible, a heat shield, a flow guide tube, a first magnetic field device, and a second magnetic field device. The crucible is disposed within the furnace body. The heat shield is disposed within the furnace body and has a cavity. The flow guide tube is disposed within the furnace body and surrounds the heat shield. The first magnetic field device is located within the cavity and has a channel for the crystal rod to pass through, and is used to form a horizontal magnetic field within the channel. The second magnetic field device is located around the first magnetic field device and is used to form a hook-shaped magnetic field around the first magnetic field device.

[0006] This application also provides a crystal pulling method. The crystal pulling method includes: A single crystal furnace is obtained, which is the single crystal furnace described above; Add silicon material into the crucible and heat the crucible to melt the silicon material and form a silicon solution; The seed crystal is controlled by the pulling device of the single crystal furnace to generate crystals, form shoulders and equal diameters, and a horizontal magnetic field is applied by the first magnetic field device and a hook-shaped magnetic field is applied by the second magnetic field device.

[0007] The single crystal furnace and crystal pulling method provided in this application include a first magnetic field device disposed within the internal space of a heat shield, and a second magnetic field device disposed around the first magnetic field device. The first magnetic field device can generate a horizontal magnetic field during crystal rod growth, while the second magnetic field device can generate a hook-shaped magnetic field during crystal rod production. By utilizing the combination of different types of magnetic fields, heat convection can be effectively suppressed, thereby controlling temperature fluctuations during crystal rod production and ensuring the quality of the crystal rod.

[0008] In some embodiments, the first magnetic field device is provided with a first magnetic shielding layer located on the side of the first magnetic field device closer to the second magnetic field device, and / or the second magnetic field device is provided with a second magnetic shielding layer located on the side of the second magnetic field device away from the first magnetic field device.

[0009] In some embodiments, a first magnetic field device and / or a second magnetic field device are movably disposed within the furnace body along a first direction parallel to the direction of movement of the crystal rod.

[0010] In some embodiments, the heat shield is movably disposed inside the furnace along a first direction, and the side of the first magnetic field device away from the channel is connected to the heat shield.

[0011] In some embodiments, the furnace body is provided with a movable component that can move along a first direction, and the movable component is connected to a second magnetic field device.

[0012] In some embodiments, the guide tube includes a cylinder and an extension at one end of the cylinder, the extension having a through hole through which a movable element passes and connects to a second magnetic field device.

[0013] In some embodiments, the second magnetic field device is located on the side of the guide tube away from the heat shield, and the second magnetic field device is spaced apart from the guide tube, with the distance between the second magnetic field device and the guide tube being 30mm~50mm.

[0014] In some embodiments, the size of the first magnetic field device is 250mm to 350mm along the first direction, and the size of the second magnetic field device is 250mm to 350mm. Attached Figure Description

[0015] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0016] Figure 1 This is a schematic diagram of the structure of a single crystal furnace provided in some embodiments of this application; Figure 2This is a schematic diagram of the magnetic field formed by the first magnetic field device in the single crystal furnace provided in some embodiments of this application; Figure 3 This is a schematic diagram of the structure of the second magnetic field device in a single crystal furnace provided in some embodiments of this application; Figure 4 This is a schematic diagram of the magnetic field formed by the second magnetic field device in the single crystal furnace provided in some embodiments of this application; Figure 5 This is a flowchart of a crystal pulling method provided in some embodiments of this application. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the various embodiments of this application will be described in detail below with reference to the accompanying drawings. However, those skilled in the art will understand that many technical details have been presented in the various embodiments of this application to enable readers to better understand this application. However, even without these technical details and various changes and modifications based on the following embodiments, the technical solutions claimed in this application can be implemented. The division of the various embodiments below is for the convenience of description and should not constitute any limitation on the specific implementation of this application. The various embodiments can be combined with and referenced by each other without contradiction.

[0018] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0019] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0020] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A exists, A and B exist simultaneously, and B exists. In addition, the character " / " in this document generally indicates that the related objects before and after it have an "or" relationship.

[0021] In the description of the embodiments of this application, the technical 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 only for the convenience of describing the embodiments of this application 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 the embodiments of this application.

[0022] In the description of the embodiments of this application, unless otherwise expressly specified and limited, technical terms such as "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; 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; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0023] In the accompanying drawings corresponding to the embodiments of this application, the thickness and / or area of ​​layers, films, panels, regions, etc., are enlarged for better understanding and ease of description. Throughout the specification, the same reference numerals denote the same elements. It should be understood that when describing a component (such as a layer, film, region, or substrate) on or on the surface of another component, the component may be "directly" located on the surface of the other component, or there may be an intermediate component between the two components. Conversely, when describing a component on the surface of another component, or a component "directly" on another component, or a component surface on which another component is formed or disposed, it indicates that there is no intermediate component between the two components. Furthermore, when describing a component as "generally" formed on another component, it means that the component is not formed on the entire surface (or front surface) of the other component, nor is it formed on a portion of the edge of the entire surface.

[0024] In the semiconductor manufacturing field, particularly in the preparation of single-crystal silicon cells, the minority carrier lifetime and oxygen content of single-crystal silicon rods are key factors affecting the electrical properties of silicon materials and cell efficiency. Therefore, improving the quality of single-crystal silicon rods is crucial for enhancing photovoltaic cell performance. Under high-temperature conditions, intense thermal convection occurs in the silicon melt. This convection not only causes temperature fluctuations at the crystal growth interface, affecting crystal quality, but also erodes the crucible walls, causing oxygen molecules in the crucible to precipitate into the silicon melt. Ultimately, this results in excessively high oxygen content in the pulled single-crystal silicon rods, severely impacting the resistivity uniformity and minority carrier lifetime of the single-crystal silicon. To suppress melt thermal convection, the Magnetic Field Applied Czochralski (MCZ) method has been widely researched and applied. By applying a magnetic field around the single-crystal furnace, the Lorentz force damping effect formed by the magnetic field on the conductive melt can effectively suppress thermal convection. Magnetic field types include horizontal, vertical, and hook-shaped magnetic fields.

[0025] The arrangement of the magnetic field is crucial for effectively suppressing heat convection. In this regard, some embodiments of this application provide a single-crystal furnace. The single-crystal furnace utilizes different magnetic field devices to form different types of magnetic fields. These different types of magnetic fields can effectively suppress heat convection during crystal growth, thereby suppressing temperature fluctuations at the crystal growth interface and ensuring the quality of the crystal rod.

[0026] The following is combined with Figures 1 to 4 This application describes the structure of a single crystal furnace provided in some embodiments.

[0027] like Figures 1 to 4 As shown, some embodiments of this application provide a single crystal furnace including a furnace body 11, a crucible 12, a heat shield 13, a flow guide tube 14, a first magnetic field device 15, and a second magnetic field device 16. The crucible 12 is disposed within the furnace body 11. The heat shield 13 is disposed within the furnace body 11 and has a cavity 131. The flow guide tube 14 is disposed within the furnace body 11 and surrounds the heat shield 13. The first magnetic field device 15 is located within the cavity 131 and has a channel 151 through which the crystal rod passes, forming a horizontal magnetic field within the channel 151. The second magnetic field device 16 is located around the first magnetic field device 15 and forms a hook-shaped magnetic field around the first magnetic field device 15.

[0028] The furnace body 11 provides a space for crystal growth. The furnace chamber within the furnace body 11 can accommodate components such as the crucible 12 and form a thermal field, providing favorable temperature conditions for crystal growth. The furnace body 11 may include a main furnace chamber and an auxiliary furnace chamber. The main furnace chamber provides a space for crystal growth, and the auxiliary furnace chamber provides a space for crystal transfer. After crystal growth is completed, the crystal is transferred into the auxiliary furnace chamber for removal.

[0029] The crucible 12 provides space within the furnace body 11 to hold solid silicon material. Upon heating, the solid silicon material forms molten silicon, which can grow into a crystal rod under the action of a seed crystal. The crucible 12 can be rotated and raised / lowered using a linkage mechanism located at the bottom of the single-crystal furnace to adapt to the process requirements during crystal rod growth. The crucible 12 can be a quartz crucible.

[0030] The heat shield 13 facilitates the formation of a thermal field within the furnace body 11. The cavity 131 of the heat shield 13 allows a seed crystal to pass through, enabling the crystal rod formed on the seed crystal to pass through the interior of the heat shield 13. The heat shield 13 can be cooled by water for temperature control. Water-cooling pipes can be introduced from the top of the furnace body 11 and connected to water-cooling channels within the heat shield 13. Water-cooling channels can be formed on the inner or outer surface of the heat shield 13, or between the inner and outer surfaces of the heat shield 13.

[0031] The flow guide tube 14 is located outside the heat shield 13 and serves to guide the gas flow inside the furnace body 11. During the crystal rod processing, inert gas is introduced into the furnace body 11 to carry out impurities. The flow guide tube 14 can guide the flow of inert gases such as argon, thereby preventing impurities such as oxygen from entering the crystal rod and affecting its quality.

[0032] The first magnetic field device 15 and the second magnetic field device 16 are arranged in a ring, and can respectively form a horizontal magnetic field (magnetic field lines such as...). Figure 2 (as shown) and hook-shaped magnetic field (also known as Cusp magnetic field, magnetic field lines as shown) Figure 4 (As shown). During the crystal rod production process, the magnetic field can suppress thermal convection in the melt, thereby preventing temperature fluctuations within the melt; this is also known as magnetron crystal pulling. During crystal rod growth, the first magnetic field device 15 is located inside the heat shield 13 and can form a horizontal magnetic field during crystal rod growth. The first magnetic field device 15 can use a permanent magnet or an excitation coil to form the magnetic field. The horizontal magnetic field formed by the first magnetic field device 15 can effectively suppress vertical thermal convection, thus suppressing thermal convection around the crystal rod. The second magnetic field device 16 can also use a permanent magnet or an excitation coil to form the magnetic field. The hook-shaped magnetic field formed by the second magnetic field device 16 can effectively suppress internal and external thermal convection, thus suppressing thermal convection around the crucible 12.

[0033] The single-crystal furnace provided in some embodiments of this application includes a first magnetic field device 15 disposed within the internal space of a heat shield 13, and a second magnetic field device 16 disposed around the first magnetic field device 15. The first magnetic field device 15 can generate a horizontal magnetic field during crystal rod growth, while the second magnetic field device 16 can generate a hook-shaped magnetic field during crystal rod production. By utilizing the combination of different types of magnetic fields, heat convection can be effectively suppressed, thereby controlling temperature fluctuations during crystal rod production and ensuring the quality of the crystal rod.

[0034] In some embodiments, reference Figure 2 The first magnetic field device 15 may be provided with a first magnetic shielding layer 152, which is located on the side of the first magnetic field device 15 closer to the second magnetic field device 16, and / or, refer to Figure 3 The second magnetic field device 16 may be provided with a second magnetic shielding layer 161, which is located on the side of the second magnetic field device 16 away from the first magnetic field device 15.

[0035] In other words, a first magnetic shielding layer 152 can be provided on the outside of the first magnetic field device 15, or a second magnetic shielding layer 161 can be provided on the outside of the second magnetic field device 16, or a first magnetic shielding layer 152 can be provided on the outside of the first magnetic field device 15 and a second magnetic shielding layer 161 can be provided on the outside of the second magnetic field device 16.

[0036] The first magnetic shielding layer 152 can shield the magnetic field outside the first magnetic field device 15, thereby controlling the first magnetic field device 15 to form a horizontal magnetic field inside, and avoiding mutual interference between the magnetic fields formed by the first magnetic field device 15 and the second magnetic field device 16.

[0037] The second magnetic shielding layer 161 can shield the magnetic field outside the second magnetic field device 16, thereby controlling the second magnetic field device 16 to form a hook-shaped magnetic field on the inside, and preventing the second magnetic field device 16 from being interfered with by external factors.

[0038] In practice, refer to Figure 3 The second magnetic field device 16 may include a first coil 162 and a second coil 163 spaced apart along a first direction. The first coil 162 and the second coil 163 are arranged in different regions along the height direction of the furnace body 11, i.e., the first coil 162 and the second coil 163 are distributed vertically. (Refer to reference...) Figure 3 and Figure 4 When the first coil 162 and the second coil 163 are energized, they form a hook-shaped magnetic field. That is, the second magnetic field device 16 can be composed of two sets of excitation coils and a second magnetic shielding layer 161. The excitation coils are the driving source for generating magnetic induction intensity. The second magnetic shielding layer 161 surrounds the upper and lower excitation coil sets, maintaining the uniformity of the magnetic field strength and magnetic field line distribution in the hot field region, while reducing external interference to the magnetic field and thus maintaining its stability. The excitation coils can be made of copper coils, creating a favorable magnetic field environment for crystal growth. Alternatively, the excitation coils can be made of superconducting materials, which can generate a stronger magnetic field. The magnetic field lines distributed in the hot field can better cope with the intense molten thermal convection within the large-size crucible 12, resulting in more uniform crystal growth and more efficient production of large-size single-crystal silicon rods.

[0039] Furthermore, the hook-shaped magnetic field can be classified as symmetrical or asymmetrical based on the ratio of the number of longitudinal layers of the upper and lower coils. When the number of longitudinal layers of the upper and lower coils is the same, the hook-shaped magnetic field is symmetrical. The hook-shaped magnetic field can simultaneously generate radial and axial field strength components. The radial magnetic field component generated by the hook-shaped magnetic field can suppress thermal convection in the molten silicon, reducing the erosion of the inner wall of the crucible 12 by the molten silicon. The thermal convection in the molten silicon can be effectively suppressed by increasing the number of layers of the lower coil. For example, the ratio of the number of longitudinal layers of the upper and lower coils can be controlled to 2:3 to increase the magnetic field strength provided by the lower coil.

[0040] In addition, different magnetic field devices can be equipped with high-temperature resistant protective layers to ensure normal operation in high-temperature environments.

[0041] In some embodiments, the first magnetic field device 15 and / or the second magnetic field device 16 may be along a first direction ( Figure 1 The direction indicated by the middle arrow A) is movably disposed within the furnace body 11, with the first direction parallel to the lifting direction of the crystal rod.

[0042] The movement of the first magnetic field device 15 and / or the second magnetic field device 16 can adapt to the growth position of the crystal rod, thereby better matching the liquid surface position within the crucible 12. During the crystal rod growth process, the liquid level in the crucible 12 continuously decreases. By controlling the movement of the first magnetic field device 15 or the second magnetic field device 16, the distance between the first magnetic field device 15 or the second magnetic field device 16 and the liquid surface can be controlled, thereby enabling the first magnetic field device 15 or the second magnetic field device 16 to play a role in suppressing thermal convection in an optimal position.

[0043] The first direction corresponds to the lifting direction of the crystal rod, and also to the height direction during crystal rod processing in the single crystal furnace. The first magnetic field device 15 moves along the first direction, meaning the first magnetic field device 15 can be raised and lowered within the furnace body 11. The second magnetic field device 16 moves along the first direction, meaning the second magnetic field device 16 can be raised and lowered within the furnace body 11.

[0044] In practice, the single crystal grows continuously from the molten silicon under the rotational pull of the seed crystal, causing the molten silicon level in crucible 12 to drop. Crucible 12 rises via a connecting rod, generating a rotational speed opposite to that of the seed crystal, ensuring the stability of the relative position between the thermal field and the molten surface. However, in actual crystal pulling, the time required to pull a single crystal rod in a single-crystal furnace is relatively long, resulting in a prolonged period for the liquid outlet distance (the distance between the lower edge of the thermal shield 13 and the surface of the molten silicon) to reach a stable state. Fluctuations in the liquid outlet distance indirectly alter the relative position of the magnetic field lines acting on the molten silicon surface, easily causing the magnetic field to generate a reaction force on the thermal convection of the molten silicon, affecting the solid-liquid interface temperature gradient and oxygen impurity content. By raising and lowering the magnetic field device with the molten silicon level, not only can the stability of the relative position between the magnetic field lines and the molten silicon be ensured, but the performance of the magnetic field in regulating the thermal field can also be improved.

[0045] Furthermore, by placing the first magnetic field device 15 and the second magnetic field device 16 inside the furnace body 11, the space within the furnace body 11 can be utilized to arrange the first magnetic field device 15 and the second magnetic field device 16, allowing them to directly generate different types of magnetic fields within the furnace body 11, ensuring magnetic field strength. Simultaneously, this avoids the problems of space occupation and reduced magnetic field effectiveness that would occur if the magnetic field devices were placed outside the furnace body 11. In practice, the second magnetic field device 16 can also be placed outside the furnace body 11.

[0046] In some embodiments, the heat shield 13 may be movably disposed within the furnace body 11 along a first direction, and the side of the first magnetic field device 15 away from the channel 151 is connected to the heat shield 13.

[0047] The heat shield 13 moves along the first direction, meaning it can be raised and lowered within the furnace body 11. This raising and lowering effectively controls the thermal field and adjusts the distance between the lower edge of the heat shield 13 and the liquid surface, ensuring a heat preservation effect in the crystal growth area. Furthermore, before the crystal rod leaves the main furnace chamber, it is cooled down using water cooling.

[0048] The outer side of the first magnetic field device 15 is connected to the heat shield 13, and it can rise and fall synchronously with the heat shield 13, thereby reducing the difficulty of raising and lowering the first magnetic field device 15 and simplifying the position control structure of the first magnetic field device 15. When controlling the rise and fall of the heat shield 13, the first magnetic field device 15 can be raised and lowered synchronously, that is, the first magnetic field device 15 can be driven to complete the position adjustment.

[0049] like Figure 1 As shown, the furnace body 11 may be provided with a movable part 17 that can move along the first direction, and the movable part 17 is connected to the second magnetic field device 16.

[0050] The movable component 17 can move along a first direction, meaning it can be raised and lowered relative to the furnace body 11. The movable component 17 extends downwards from above the furnace body 11 to connect with the second magnetic field device 16. By controlling the raising and lowering of the movable component 17, the second magnetic field device 16 can be raised and lowered. The raising and lowering of the movable component 17 can be achieved by a drive component located above the furnace body 11. The top of the movable component 17 can be connected to a lifting device, or it can be connected to the output end of the drive component via a transmission mechanism.

[0051] like Figure 1As shown, the movable component 17 can be configured as a rod to reduce its space occupation and weight. Multiple movable components 17 can be configured to ensure stability when controlling the raising and lowering of the second magnetic field device 16. Multiple movable components 17 can be arranged around the central axis of the guide tube 14, and can connect to the second magnetic field device 16 at different positions, enabling stable position control of the second magnetic field device 16 and ensuring its structural stability.

[0052] In some embodiments, the guide tube 14 may include a tube body 141 and an extension 142 located at one end of the tube body 141. The extension 142 is provided with a through hole 1421, through which the movable member 17 passes and connects to the second magnetic field device 16.

[0053] The cylinder 141 forms the main body of the guide tube 14, and the extension 142 forms the protruding part of the guide tube 14 and is located at the top of the cylinder 141. The hollow part inside the cylinder 141 allows inert gas to flow, and the second magnetic field device 16 can be arranged on the periphery of the bottom of the cylinder 141. The through hole 1421 provided in the extension 142 allows the movable member 17 to pass through, so that the bottom of the movable member 17 passes through the through hole 1421 and connects with the second magnetic field device 16, enabling the movable member 17 to drive the second magnetic field device 16 to move synchronously.

[0054] Furthermore, by allowing the movable part 17 to pass through the through hole 1421 on the extension 142, it can play a guiding role when the movable part 17 moves, thus preventing the movable part 17 from shifting laterally relative to the guide tube 14.

[0055] In some embodiments, the second magnetic field device 16 may be located on the side of the guide tube 14 away from the heat shield 13. The second magnetic field device 16 is spaced apart from the guide tube 14, and the distance between the second magnetic field device 16 and the guide tube 14 is 30mm to 50mm.

[0056] By maintaining a distance between the second magnetic field device 16 and the guide tube 14, interference between them can be avoided. Simultaneously, controlling the distance between the second magnetic field device 16 and the guide tube 14 to 30mm~50mm avoids the second magnetic field device 16 becoming too large due to a larger distance, thus preventing increased difficulty in controlling the hook-shaped magnetic field. It also avoids the second magnetic field device 16 having a limited magnetic field range due to a smaller distance, thus preventing ineffective suppression of heat convection. Furthermore, it prevents interference between the second magnetic field device 16 and other components such as the guide tube 14.

[0057] In practice, the distance between the second magnetic field device 16 and the guide tube 14 can be 30mm, 35mm, 40mm, 45mm or 50mm.

[0058] In some embodiments, along the first direction, the size of the first magnetic field device 15 can be 250mm to 350mm, and the size of the second magnetic field device 16 can be 250mm to 350mm.

[0059] The dimension of the first magnetic field device 15 along the first direction corresponds to its height. The dimension of the second magnetic field device 16 along the first direction corresponds to its height. By controlling the height dimensions of the first magnetic field device 15 and the second magnetic field device 16, the increased cost of the magnetic field device due to a large height can be avoided, as can the inability to effectively suppress heat convection due to a small height.

[0060] In practice, the dimensions of the first magnetic field device 15 along the first direction can be 250mm, 270mm, 290mm, 300mm, 320mm, 340mm, or 350mm. The dimensions of the second magnetic field device 16 along the first direction can be 250mm, 270mm, 290mm, 300mm, 320mm, 340mm, or 350mm.

[0061] In addition, the strength of the magnetic field can be increased by increasing the size or number of magnetic field devices. Increasing the size or number of magnetic field devices can also increase the range of influence of the magnetic field, effectively suppressing thermal convection of the melt.

[0062] Some embodiments of this application also provide a crystal pulling method, such as Figure 5 As shown, the crystal pulling method includes the following steps: Step S110: Obtain a single crystal furnace, which is the single crystal furnace described above.

[0063] A single crystal furnace is a device used for growing crystal rods. It provides the necessary spatial environment and temperature conditions for crystal rod growth. The magnetic field device within the furnace generates a magnetic field during the crystal pulling process. This magnetic field effectively suppresses heat convection during the crystal rod pulling process, thereby reducing temperature fluctuations and improving the quality of the crystal rod.

[0064] Step S120: Add silicon material into the crucible and heat the crucible to melt the silicon material and form a silicon solution.

[0065] The silicon material inside the crucible can form a silicon solution upon heating. During the production of single-crystal silicon rods, single-crystal silicon material can be added to the crucible. During feeding, the crucible can be rotated at a low speed to ensure uniform heating of the silicon material. For example, the crucible can be rotated at a speed of 1 rpm to 2 rpm. Simultaneously, the main heater and bottom heater can be turned on to rapidly heat the silicon material. The power of the main heater can be controlled between 90W and 110W, and the power of the bottom heater can be controlled between 80W and 100W. During the feeding stage, the magnetic field device can be turned off to facilitate heat convection and allow the silicon material to melt rapidly.

[0066] Step S130: The seed crystal is controlled by the pulling device of the single crystal furnace to perform crystal pulling, shoulder formation and equal diameter, and a horizontal magnetic field is applied by the first magnetic field device and a hook-shaped magnetic field is applied by the second magnetic field device.

[0067] By using a magnetic field device inside the single-crystal furnace, different types of magnetic fields can be generated during the crystal pulling process, thereby suppressing melt thermal convection and improving the quality of the crystal rod. The first magnetic field device can be placed inside the heat shield to form a horizontal magnetic field. The second magnetic field device can be placed outside the flow guide tube to form a hook-shaped magnetic field. During crystal pulling, the synergy of different magnetic fields increases the range of magnetic field influence. The hook-shaped magnetic field can suppress thermal convection, and the horizontal magnetic field can work in conjunction with the hook-shaped magnetic field to optimize the thermal gradient and flow field at the crystal growth interface, more effectively suppressing melt thermal convection. Actual testing shows that crystal rods obtained through magnetic field control during the pulling process can reduce the oxygen content to 5 ppma, achieve a dislocation-free ratio exceeding 97%, improve resistivity uniformity by 10%, and increase minority carrier lifetime by 15%.

[0068] In some embodiments, the magnetic field device can be raised and lowered to keep the relative position of the magnetic lines of force and the liquid surface stable, thereby better suppressing molten thermal convection and improving the quality of the crystal rod.

[0069] In practice, different magnetic field parameters can be set according to the different stages of crystal pulling to maximize the effect of the magnetic field.

[0070] For example, when controlling the seed crystal for crystal pulling through the pulling device, the magnetic field strength of the horizontal magnetic field can be controlled to be 5mT~8mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled to be 10mT~16mT; along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 20mm~30mm, and the distance between the second magnetic field device and the surface of the silicon solution is 20mm~30mm.

[0071] During crystal development, the crucible rotation speed can be controlled at 3 rpm to 5 rpm, and the power of the main heater can be controlled at 60 W to 70 W. The seed crystal rotation speed can be controlled at 7 rpm to 9 rpm, and the furnace pressure can be controlled at 6 Torr to 8 Torr.

[0072] During the crystal pulling stage, the magnetic field strength of the horizontal magnetic field and the hook-shaped magnetic field can be controlled within a small range. The weak magnetic field is used to stabilize the liquid surface, ensure the liquid surface temperature is stable, and improve the quality of the crystal rod during the crystal pulling stage.

[0073] When the seed crystal is raised by the lifting device, the magnetic field strength of the horizontal magnetic field can be controlled to be 8mT~12mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled to be 16mT~24mT. Along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 30mm~40mm, and the distance between the second magnetic field device and the surface of the silicon solution is 40mm~50mm.

[0074] During shoulder placement, the crucible rotation speed can be controlled at 4 rpm to 6 rpm, and the main heater power can be controlled at 50 W to 60 W. The seed crystal rotation speed can be controlled at 7 rpm to 9 rpm, and the furnace pressure can be controlled at 6 Torr to 8 Torr.

[0075] During the shoulder formation stage, the magnetic field strength of the horizontal magnetic field and the hook-shaped magnetic field is increased to suppress the thermal convection of the melt and ensure the stability of the interface during the shoulder formation stage.

[0076] When controlling the seed crystal to achieve the same diameter using the lifting device, the magnetic field strength of the horizontal magnetic field can be controlled to be 5mT~20mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled to be 10mT~40mT; along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 40mm~50mm, and the distance between the second magnetic field device and the surface of the silicon solution is 60mm~70mm.

[0077] When the diameter is constant, the crucible rotation speed can be controlled at 3 rpm to 5 rpm, and the power of the main heater can be controlled at 60 W to 70 W. The seed crystal rotation speed can be controlled at 7 rpm to 9 rpm, and the furnace pressure can be controlled at 6 Torr to 8 Torr.

[0078] Furthermore, more precise control can be achieved at different stages of the equal diameter process. For example, in the early stage of equal diameter processing, the magnetic field strength of the horizontal magnetic field can be controlled at 15mT~20mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled at 30mT~40mT. The crucible rotation speed can be controlled at 5rpm, and the power of the main heater can be controlled at 45W~55W. In the middle stage of equal diameter processing, the magnetic field strength of the horizontal magnetic field can be controlled at 8mT~12mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled at 16mT~24mT. The crucible rotation speed can be controlled at 6rpm, and the power of the main heater can be controlled at 44W~54W. In the later stage of equal diameter processing, the magnetic field strength of the horizontal magnetic field can be controlled at 5mT~8mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled at 10mT~16mT. The crucible rotation speed can be controlled at 7rpm, and the power of the main heater can be controlled at 45W~55W.

[0079] During the final stage of ingot growth, the crucible rotation speed can be controlled at 4 rpm to 6 rpm, and the main heater power can be controlled at 50 W to 55 W. The magnetic field strength of the horizontal magnetic field can be controlled at 5 mT to 8 mT, and the magnetic field strength of the hook-shaped magnetic field can be controlled at 10 mT to 16 mT. Along the first direction, the distance between the first magnetic field device and the silicon solution surface can be controlled at 40 mm to 50 mm, and the distance between the second magnetic field device and the silicon solution surface can be controlled at 60 mm to 70 mm. The seed crystal rotation speed can be controlled at 7 rpm to 9 rpm, and the furnace pressure can be controlled at 6 Torr to 8 Torr.

[0080] In the early stages of the constant diameter phase, temperature fluctuations can be suppressed and the temperature stabilized by increasing the strength of the horizontal and hook-shaped magnetic fields, thus controlling oxygen levels. In the middle stages, the strength of the horizontal and hook-shaped magnetic fields can be appropriately reduced to dynamically compensate for the drop in liquid level. In the later stages of the constant diameter phase, and in the final stages, as the amount of silicon solution decreases and melt thermal convection reduces, the strength of the horizontal and hook-shaped magnetic fields can be further reduced.

[0081] Those skilled in the art will understand that the above embodiments are specific implementations of this application, and in practical applications, various changes can be made in form and detail without departing from the spirit and scope of this application.

Claims

1. A single crystal furnace, characterized in that, include: Furnace body; A crucible is disposed inside the furnace body; A heat shield is installed inside the furnace body, and the heat shield is provided with a cavity; A flow guide tube is disposed inside the furnace body and surrounds the heat shield; A first magnetic field device is located inside the cavity. The first magnetic field device is provided with a channel through which the crystal rod passes, and the first magnetic field device is used to form a horizontal magnetic field in the channel. The second magnetic field device is located around the first magnetic field device, and the second magnetic field device is used to form a hook-shaped magnetic field around the first magnetic field device.

2. The single crystal furnace according to claim 1, characterized in that, The first magnetic field device is provided with a first magnetic shielding layer, which is located on the side of the first magnetic field device closer to the second magnetic field device, and / or the second magnetic field device is provided with a second magnetic shielding layer, which is located on the side of the second magnetic field device away from the first magnetic field device.

3. The single crystal furnace according to claim 1, characterized in that, The first magnetic field device and / or the second magnetic field device are movably disposed in the furnace body along a first direction, which is parallel to the direction of movement of the crystal rod.

4. The single crystal furnace according to claim 3, characterized in that, The heat shield is movably disposed inside the furnace along the first direction, and the side of the first magnetic field device away from the channel is connected to the heat shield.

5. The single crystal furnace according to claim 3, characterized in that, The furnace body is provided with a movable component that can move along the first direction, and the movable component is connected to the second magnetic field device.

6. The single crystal furnace according to claim 5, characterized in that, The guide tube includes a cylinder body and an extension portion located at one end of the cylinder body. The extension portion is provided with a through hole, and the movable member passes through the through hole and is connected to the second magnetic field device.

7. The single crystal furnace according to claim 1, characterized in that, The second magnetic field device is located on the side of the guide tube away from the heat shield. The second magnetic field device is spaced apart from the guide tube, and the distance between the second magnetic field device and the guide tube is 30mm~50mm.

8. The single crystal furnace according to claim 1, characterized in that, Along the first direction, the size of the first magnetic field device is 250mm~350mm, and the size of the second magnetic field device is 250mm~350mm.

9. A crystal pulling method, characterized in that, include: A single crystal furnace is obtained, wherein the single crystal furnace is the single crystal furnace according to any one of claims 1 to 8; Silicon material is added into a crucible and heated to melt the silicon material and form a silicon solution. The seed crystal is controlled by the pulling device of the single crystal furnace to perform crystal pulling, shoulder formation and equal diameter, and a horizontal magnetic field is applied by the first magnetic field device and a hook-shaped magnetic field is applied by the second magnetic field device.

10. The crystal pulling method according to claim 9, characterized in that, When the seed crystal is pulled by the lifting device, the magnetic field strength of the horizontal magnetic field is 5mT~8mT, and the magnetic field strength of the hook-shaped magnetic field is 10mT~16mT; along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 20mm~30mm, and the distance between the second magnetic field device and the surface of the silicon solution is 20mm~30mm.

11. The crystal pulling method according to claim 9, characterized in that, When the seed crystal is controlled to form a shoulder by the lifting device, the magnetic field strength of the horizontal magnetic field is 8mT~12mT, and the magnetic field strength of the hook-shaped magnetic field is 16mT~24mT; along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 30mm~40mm, and the distance between the second magnetic field device and the surface of the silicon solution is 40mm~50mm.

12. The crystal pulling method according to claim 9, characterized in that, When the seed crystal is controlled to be of equal diameter by the lifting device, the magnetic field strength of the horizontal magnetic field is 5mT~20mT, and the magnetic field strength of the hook-shaped magnetic field is 10mT~40mT; along the first direction, the distance between the first magnetic field device and the surface of the silicon solution is 40mm~50mm, and the distance between the second magnetic field device and the surface of the silicon solution is 60mm~70mm.

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