Single crystal furnace and crystal pulling method

Abstract

The invention relates to a single crystal furnace and a crystal pulling method, the single crystal furnace comprises a shell, a heat shield assembly and a driving member, the heat shield assembly comprises a first heat shield and a second heat shield, the driving member comprises a first driving member and a second driving member, and a driving chain can drive the heat shield assembly to switch between a first state and a second state. The circulation opening of the shell, the first cavity of the first heat shield and the second cavity of the second heat shield can be used for forming a channel. By means of the design, the area of the heat shield assembly can be increased, the position of the heat shield assembly can be adjusted in the crystal pulling process, and the cooling efficiency of the single crystal furnace and the quality of a crystal bar can be improved.

Description

Technical Field

[0001] The present application relates to the field of crystal pulling technology, and in particular to a single crystal furnace and a crystal pulling method. Background Art

[0002] With the development of technology, the application of photovoltaic modules is becoming more and more extensive. Photovoltaic modules absorb light energy through cells and convert it into solar energy. The substrate of silicon wafers is usually silicon wafers. During production, silicon rods are pulled by single crystal furnaces and then cut and processed to obtain silicon wafers. However, the cooling effect of single crystal furnaces on crystal rods is poor, resulting in poor quality of crystal rods, which will affect the quality of cells and photovoltaic modules. Summary of the invention

[0003] In view of this, the present application provides a single crystal furnace and a crystal pulling method for improving the cooling effect of the single crystal furnace.

[0004] The present application provides a single crystal furnace for producing crystal rods, the single crystal furnace comprising:

[0005] A housing having a receiving cavity;

[0006] A heat shield assembly, wherein the heat shield assembly is located in the accommodating cavity;

[0007] a driving member, the driving member being used to drive the heat shield assembly to move relative to the housing;

[0008] Wherein, the heat shield assembly comprises a first heat shield and a second heat shield, the driving member comprises a first driving member and a second driving member, the shell is provided with a circulation port, the first heat shield has a first cavity, the second heat shield has a second cavity, the circulation port, the first cavity and the second cavity are connected to form a channel, the driving member comprises a first driving member and a second driving member, the first driving member is used to drive the first heat shield to move along the height direction of the single crystal furnace, the second driving member is used to drive the second heat shield to move along the height direction of the single crystal furnace, the driving member is used to drive the heat shield assembly to move in a direction away from the circulation port, so that the heat shield assembly is converted from a first state to a second state, and the driving member is used to drive the heat shield assembly to move in a direction close to the circulation port, so that the heat shield assembly is converted from a second state to a first state;

[0009] When the heat shield assembly is in the first state, at least a portion of the second heat shield is sleeved on the outside of the first heat shield;

[0010] When the heat shield assembly is in the second state, at least a portion of the second heat shield is located on a side of the first heat shield away from the flow opening, and the first heat shield is movable between the second heat shield and the flow opening.

[0011] In a possible implementation manner, the cross-sectional area of ​​the second cavity gradually decreases in a direction away from the flow port.

[0012] In a possible implementation, the second cavity includes a first flow section and a second flow section that are interconnected, and the first flow section is located on a side of the second flow section away from the flow port;

[0013] The angle between the side wall of the first flow section and the height direction of the single crystal furnace is a, and 15°≤a≤25°, and the angle between the side wall of the second flow section and the height direction of the single crystal furnace is b, and 10°≤b≤15°.

[0014] In a possible implementation manner, the diameter of one end of the second cavity close to the circulation port is 520 mm to 540 mm, and the diameter of one end of the second cavity away from the circulation port is 300 mm to 320 mm;

[0015] The outer diameter of the first heat shield is 360 mm to 380 mm, and the diameter of the first cavity is 300 mm to 320 mm.

[0016] In a possible implementation manner, the diameter of the first cavity is c, the diameter of the crystal rod is d, and they satisfy 20 mm≤cd≤80 mm.

[0017] In a possible implementation manner, along the height direction of the single crystal furnace, the length of the first heat shield is 50 mm to 450 mm, and the length of the second heat shield is 100 mm to 500 mm.

[0018] In a possible implementation manner, the single crystal furnace further includes a heat sink, the heat sink is fixedly connected to the shell and has a third cavity, and the third cavity is communicated with the flow port;

[0019] When the heat shield assembly is in a first state, the first heat shield is sleeved on the outside of the heat sink, and the second heat shield is sleeved on the outside of the first heat shield;

[0020] When the heat shield assembly is in the second state, at least a portion of the first heat shield is located on a side of the heat sink away from the flow opening, and at least a portion of the second heat shield is located on a side of the first heat shield away from the heat sink.

[0021] In a possible embodiment, the single crystal furnace includes an outer guide tube and an insulation tube, the outer guide tube is sleeved on the outside of the second heat shield, and the end of the outer guide tube close to the flow port has a flange, when the single crystal furnace is in the second state, along the height direction of the single crystal furnace, the lower edge position of the flange coincides with the upper edge position of the insulation tube.

[0022] The present application also provides a crystal pulling method for manufacturing a crystal rod by using the single crystal furnace according to any one of claims 1 to 8, the manufacturing method comprising:

[0023] In the charging stage, the first heat shield is driven to move to a position 0 mm to 300 mm away from the flow opening, and the second heat shield is driven to move to a position 100 mm to 300 mm away from the flow opening, so as to charge the single crystal furnace;

[0024] In the temperature control stage, the second heat shield is driven to move in a direction away from the flow port to a position where the distance between the lower edge of the flange of the outer guide tube and the upper edge of the insulation tube is 100 mm to 200 mm, and the silicon material is heated and melted. When the linear diameter of the silicon material does not exceed 150 mm, the second heat shield is driven to descend to a position where the flange of the outer guide tube and the upper edge of the insulation tube are at the same height, and the first heat shield is driven to descend to a position where the lower edge of the first heat shield is 60 mm above the upper edge of the second heat shield and the lower edge of the first heat shield extends into the second heat shield by 60 mm. At this time, the first heat shield is at the 0th position of the first heat shield, and the second heat shield is at the 0th position of the second heat shield;

[0025] During the stages of placing the crucible, seeding and shouldering, the positions of the first heat shield and the second heat shield remain stationary;

[0026] In the equal diameter stage, when the equal diameter length of the crystal rod is less than 800 mm, driving the first heat shield to descend by 30 mm to 100 mm;

[0027] After the length of the crystal ingot exceeds 800 mm, driving the first heat shield to rise to a position no greater than 100 mm above the zero position of the first heat shield;

[0028] During the finishing phase, the first heat shield and the second heat shield remain stationary.

[0029] In a possible implementation, the crystal pulling method further includes:

[0030] During the shutdown phase, the first heat shield is driven to move to a position 0 mm to 300 mm away from the flow opening, and the second heat shield is driven to move to a position 100 mm to 300 mm away from the flow opening.

[0031] The embodiment of the present application provides a single crystal furnace and a crystal pulling method, wherein the single crystal furnace comprises a shell, a heat shield assembly and a driving member, wherein the heat shield assembly comprises a first heat shield and a second heat shield, wherein the driving member comprises a first driving member and a second driving member, wherein the driving chain can drive the heat shield assembly to switch between a first state and a second state, and wherein the flow port of the shell, the first cavity of the first heat shield and the second cavity of the second heat shield can be used to form a channel. Through such a design, the area of ​​the heat shield assembly can be increased and the position of the heat shield assembly can be adjusted during the crystal pulling process, which is beneficial to improving the cooling efficiency of the single crystal furnace and the quality of the crystal rod.

[0032] It should be understood that the foregoing general description and the following detailed description are exemplary only and are not restrictive of the present application. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0034] Figure 1 A schematic diagram of a single crystal furnace provided in an embodiment of the present application;

[0035] Figure 2 A cross-sectional view of a single crystal furnace when the heat shield assembly provided in an embodiment of the present application is in a first state;

[0036] Figure 3 A cross-sectional view of a single crystal furnace when the heat shield assembly provided in an embodiment of the present application is in a second state;

[0037] Figure 4 A cross-sectional view of a second heat shield provided in an embodiment of the present application;

[0038] Figure 5 for Figure 4 A partial enlarged view of the middle Ⅰ position;

[0039] Figure 6 A cross-sectional view of a single crystal furnace provided in an embodiment of the present application;

[0040] Figure 7 for Figure 6 A partial enlarged view of the middle II position.

[0041] Reference numerals

[0042] 1- housing;

[0043] 11- circulation port;

[0044] 12-accommodating chamber;

[0045] 2- Heat shield assembly;

[0046] 21- first thermal screen;

[0047] 211-first cavity;

[0048] 22 - second thermal screen;

[0049] 221- second cavity;

[0050] 222-first circulation section;

[0051] 223-second circulation section;

[0052] 3- heat sink;

[0053] 31- third cavity;

[0054] 4-external guide tube;

[0055] 41-Flanging;

[0056] 5-Insulation tube;

[0057] 6-Crystal rod. DETAILED DESCRIPTION

[0058] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0059] It should be clear that the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work are within the scope of protection of the present application.

[0060] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0061] It should be understood that the term "and / or" used in this article is only a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " in this article generally indicates that the associated objects before and after are in an "or" relationship.

[0062] With the development of technology, the application of photovoltaic modules is becoming more and more extensive. Photovoltaic modules include solar cells, which convert light energy into electrical energy. The substrate of the solar cell is usually a silicon wafer. During processing, the crystal rod 6 is first pulled, the crystal rod 6 is cut into silicon wafers, and the silicon wafers are processed to obtain the solar cell. The silicon wafer is an important component of the solar cell, and the quality of the crystal rod 6 will directly affect the quality of the silicon wafer. Therefore, how to improve the quality of the crystal rod 6 is a key factor in improving the overall quality of the photovoltaic module. When producing the crystal rod 6, it is produced by a single crystal furnace, and the crystal rod 6 is obtained through the steps of melting, seeding, shouldering, equal diameter, and finishing. Generally, the cooling efficiency of the single crystal furnace for the crystal rod 6 is low, resulting in a long cooling time. The crystal rod 6 will produce more oxygen donors during the cooling period, and the generation of oxygen donors will affect the resistivity of the crystal rod 6. At the same time, there will be a certain distance between the throat of the single crystal furnace and the water cooling period. When argon gas is introduced from the throat into the single crystal furnace to cool the crystal rod 6, the argon gas will flow around, resulting in a low utilization rate, which will affect the cooling efficiency. Moreover, the argon gas will form a vortex. As the argon gas flows, impurities attached to the insulation tube 5, solid felt and other components will be drawn into the argon gas flow and fall into the crucible, resulting in an increase in the impurity content of the straightened crystal rod 6, affecting the overall quality of the crystal rod 6, and increasing the possibility of the crystal rod 6 breaking, resulting in reduced production quality and increased production costs.

[0063] In view of this, an embodiment of the present application provides a single crystal furnace and a method for manufacturing a crystal rod 6 , which are used to improve the cooling efficiency of the crystal rod 6 , thereby improving the quality of the crystal rod 6 .

[0064] like Figure 1 As shown, the embodiment of the present application provides a single crystal furnace for producing a crystal rod 6, such as Figure 2As shown, the single crystal furnace includes a shell 1, a heat shield assembly 2 and a driving member, the shell 1 has a receiving cavity 12, the heat shield assembly 2 is located in the receiving cavity 12, and the driving member is connected to the heat shield assembly 2, and is used to drive the heat shield assembly 2 to move relative to the shell 1. The heat shield assembly 2 includes a first heat shield 21 and a second heat shield 22, and the driving member includes a first driving member and a second driving member, wherein the first driving member is connected to the first heat shield 21, and the second driving member is connected to the second heat shield 22, the first driving member is used to drive the first heat shield 21 to move along the height direction of the single crystal furnace, and the second driving member is used to drive the second heat shield 22 to move along the height direction of the single crystal furnace. The shell 1 is provided with a flow port 11, and the flow port 11 can be set at the top of the single crystal furnace. The first heat shield 21 has a first cavity 211, and the second heat shield 22 has a second cavity 221. The flow port 11 can be connected with the first cavity 211 and the second cavity 221 to form a channel. In the process of producing the crystal rod 6, the drawn crystal rod 6 can move along the channel formed by the flow port 11, the first cavity 211 and the second cavity 221. At the same time, argon and other gases can be introduced into the single crystal furnace from the flow port 11, and the crystal rod 6 located in the channel can be cooled by the flow of gas. The first driving member and the second driving member can respectively drive the first heat shield 21 and the second heat shield 22 to move independently. By driving the heat shield assembly 2 to move by the driving member, the state of the heat shield assembly 2 can be changed. Figure 2 As shown, when the heat shield assembly 2 is in the first state, at least a portion of the second heat shield 22 is sleeved on the outside of the first heat shield 21. The driving member can drive the heat shield assembly 2 to move away from the flow opening 11, so that the heat shield assembly 2 can be transformed from the first state to the second state. Figure 3 As shown, when the heat shield assembly 2 is in the second state, at least part of the second heat shield 22 is located on a side of the first heat shield 21 away from the flow opening 11 , and the first heat shield 21 can move between the second heat shield 22 and the flow opening 11 .

[0065] Through such a design, the heat shield assembly 2 can form a telescopic structure. When it is necessary to add material to the single crystal furnace, the heat shield assembly 2 can be driven by the driving member to be in the first state, that is, the heat shield assembly 2 is in a contracted state, and the first heat shield 21 and the second heat shield 22 are located on the side close to the flow port 11. Such a design can reduce the influence of the heat shield assembly 2 on the material addition, and the placement of the heat shield assembly 2 interferes with the operation of adding material. During the production process of the crystal rod 6, the first heat shield 21 and the second heat shield 22 are driven by the driving member to move in a direction away from the flow port 11, that is, move in a direction close to the crucible, so that the heat shield assembly 2 is in an extended state to form a channel. The first heat shield 21 can move between the second heat shield 22 and the flow port 11. In the initial stage of the production of the crystal rod 6, since the length of the crystal rod 6 is short, that is, the distance between the crystal rod 6 and the flow port 11 is far, the first heat shield 21 can be moved in a direction away from the flow port 11, so that the first heat shield 21 can be used to cool the crystal rod 6. As the production of the crystal rod 6 proceeds, the length of the crystal rod 6 gradually increases. As the crystal rod 6 rises (the crystal rod 6 moves in the direction of the crucible pointing to the flow port 11), the position of the first heat shield 21 can be adjusted by the first driving member. According to the needs of the crystal rod 6 production process, the first heat shield 21 is adjusted to a corresponding position to cool the crystal rod 6. The flow port 11, the first cavity 211 and the second cavity 221 are used to form a channel. The channel can guide the flow of gas when the gas is introduced, thereby reducing the possibility of gas flowing around, which is conducive to improving the utilization rate of the gas. At the same time, it can also reduce the possibility of the gas blowing impurities attached to the insulation tube 5, the solid felt and other components to the crystal rod 6 and the crucible, thereby helping to reduce the impurity content of the crystal rod 6 and improve the quality of the crystal rod 6.

[0066] The first heat shield 21 and the second heat shield 22 may be hollow structures, that is, the first heat shield 21 and the second heat shield 22 respectively have cavities, and flow channels are provided in the cavities. Heat exchange medium is introduced into the cavities of the first heat shield 21 and the second heat shield 22 through pipelines. The heat exchange medium can flow along the flow channels and absorb the heat of the crystal rod 6 located in the channels, thereby cooling the crystal rod 6.

[0067] like Figure 4 As shown, in a possible implementation manner, the cross-sectional area of ​​the second cavity 221 gradually decreases in a direction away from the flow port 11 .

[0068] Such a design can improve the flow rate of the gas in the second cavity 221 , thereby facilitating the use of the flow of gas to carry away the heat of the crystal rod 6 , thereby improving the heat dissipation efficiency of the second heat shield 22 .

[0069] like Figure 5As shown, in a possible implementation, the second cavity 221 includes a first flow section 222 and a second flow section 223 that are interconnected, and the first flow section 222 is located on a side of the second flow section 223 away from the flow port 11. The angle between the side wall of the first flow section 222 and the height direction of the single crystal furnace is a, and satisfies: 16°≤a≤24°. The angle between the side wall of the second flow section 223 and the height direction of the single crystal furnace is b, and satisfies: 8°≤b≤16°.

[0070] The angle between the first flow section 222 and the height direction of the single crystal furnace can be 15°, 16°, 17°, 18°, 19°, 20°, 21°, 22°, 23°, 24°, 25°, etc. The angle between the second flow section 223 and the height direction of the single crystal furnace can be 10°, 11°, 12°, 13°, 14°, 15°, etc.

[0071] This design can further adjust the flow rate of the gas in the second cavity 221. Compared with the second flow section 223, the side wall of the first flow section 222 has a larger inclination angle, so the flow rate of the gas in the second flow section 223 can be further improved. In the process of producing the crystal rod 6, the first flow section 222 is closer to the crucible, so the temperature of the crystal rod 6 located in the first flow section 222 is higher. By increasing the flow rate of the gas in the first flow section 222, it is beneficial to improve the cooling efficiency of the first flow section 222, thereby improving the overall cooling efficiency.

[0072] In a possible implementation, the diameter of the second cavity 221 at one end close to the flow opening 11 is 520 mm to 540 mm, and the diameter of the second cavity 221 at one end away from the flow opening 11 is 300 mm to 320 mm. The outer diameter of the first heat shield 21 is 360 mm to 380 mm, and the diameter of the first cavity 211 is 300 mm to 320 mm.

[0073] The diameter of the end of the second cavity 221 close to the circulation port 11 can be 520 mm, 521 mm, 522 mm, 523 mm, 524 mm, 525 mm, 526 mm, 527 mm, 528 mm, 529 mm, 530 mm, 531 mm, 532 mm, 533 mm, 534 mm, 535 mm, 536 mm, 537 mm, 538 mm, 539 mm, 540 mm, etc. The diameter of the end of the second cavity 221 away from the circulation port 11 can be 300 mm, 301 mm, 302 mm, 303 mm, 304 mm, 305 mm, 306 mm, 307 mm, 308 mm, 309 mm, 310 mm, 311 mm, 312 mm, 313 mm, 314 mm, 315 mm, 316 mm, 317 mm, 318 mm, 319 mm, 320 mm, etc. The outer diameter of the first heat shield 21 may be 360 ​​mm, 361 mm, 362 mm, 363 mm, 364 mm, 365 mm, 366 mm, 367 mm, 368 mm, 369 mm, 370 mm, 371 mm, 372 mm, 373 mm, 374 mm, 375 mm, 376 mm, 377 mm, 378 mm, 379 mm, 380 mm, etc. The diameter of the first cavity 211 may be 300 mm, 301 mm, 302 mm, 303 mm, 304 mm, 305 mm, 306 mm, 307 mm, 308 mm, 309 mm, 310 mm, 311 mm, 312 mm, 313 mm, 314 mm, 315 mm, 316 mm, 317 mm, 318 mm, 319 mm, 320 mm, etc.

[0074] Through such a design, part of the first heat shield 21 can be extended into the second cavity 221, so that the first heat shield 21 and the second heat shield 22 are nested. At the same time, the size of the second cavity 221 close to the first heat shield 21 is larger than the size of the first heat shield 21. When matched, a gap can be formed between the side walls of the first heat shield 21 and the second cavity 221. Such a design can reduce the obstruction of the CCD viewing angle by the heat shield assembly 2, making it convenient for operators to observe the state of the crystal rod 6, which is more in line with actual usage needs.

[0075] In a possible implementation, the diameter of the first cavity 211 is c, the diameter of the crystal rod 6 is d, and 20 mm ≤ cd ≤ 80 mm. That is, there is a gap between the first cavity 211 and the crystal rod 6, and the distance of the gap can be 10 mm, 12 mm, 14 mm, 16 mm, 18 mm, 20 mm, 22 mm, 24 mm, 26 mm, 28 mm, 30 mm, 32 mm, 34 mm, 36 mm, 38 mm, 40 mm, etc.

[0076] When the distance between the crystal rod 6 and the side wall of the first cavity 211 is less than 10 mm, the crystal rod 6 is easily in contact with the first heat shield 21 during the lifting process, resulting in damage to the crystal rod 6 and affecting the quality of the crystal rod 6. When the distance between the crystal rod 6 and the side wall of the first cavity 211 is greater than 40 mm, the first heat shield 21 is far away from the crystal rod 6, resulting in a decrease in the heat exchange capacity of the first heat shield 21, thereby affecting the cooling efficiency of the first heat shield 21. During cooling, it is necessary to reduce the lifting speed of the crystal rod 6 to allow the crystal rod 6 to be fully cooled. Due to the decrease in the lifting speed of the crystal rod 6, the portion of the crystal rod 6 at 450°C stays for a longer time, resulting in the generation of oxygen donors, affecting the resistivity of the crystal rod 6, and thus affecting the quality of the crystal rod 6.

[0077] In a possible implementation, along the height direction of the single crystal furnace, the length of the first heat shield 21 is 50 mm to 450 mm, and the length of the second heat shield 22 is 100 mm to 500 mm.

[0078] The length of the first heat shield 21 along the height direction of the single crystal furnace can be 50 mm, 75 mm, 100 mm, 125 mm, 150 mm, 175 mm, 200 mm, 225 mm, 250 mm, 275 mm, 300 mm, 325 mm, 350 mm, 375 mm, 400 mm, 425 mm, 450 mm, etc. The length of the second heat shield 22 along the height direction of the single crystal furnace can be 100 mm, 150 mm, 200 mm, 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, etc.

[0079] When the size of the first heat shield 21 and the second heat shield 22 is too large, the space occupied by the first heat shield 21 and the second heat shield 22 is too large, and it is easy to interfere with other components in the single crystal furnace, affecting the process of adding materials, etc. When the size of the first heat shield 21 and the second heat shield 22 is too small, the heat dissipation capacity of the heat shield assembly 2 decreases, resulting in reduced heat dissipation efficiency, affecting production efficiency, and at the same time causing the generation of oxygen donors, affecting the quality of the crystal rod 6.

[0080] like Figure 3As shown, in a possible embodiment, the single crystal furnace further includes a heat sink 3, which is fixedly connected to the shell 1 and has a third cavity 31, and the third cavity 31 is connected to the flow port 11. The first cavity 211 located at the first heat shield 21 can be connected to the flow port 11 through the third cavity 31, and the second cavity 221 located at the second heat shield 22 can be connected to the third cavity 31 through the first cavity 211, and then connected to the flow port 11. When the heat shield assembly 2 is in the first state, the first heat shield 21 is sleeved on the outside of the heat sink 3, and the second heat shield 22 is sleeved on the outside of the first heat shield 21. When the heat shield assembly 2 is in the second state, at least part of the first heat shield 21 is located on the side of the heat sink 3 away from the flow port 11, and at least part of the second heat shield 22 is located on the side of the first heat shield 21 away from the heat sink 3.

[0081] The heat sink 3 may be a water-cooled component and is fixedly mounted on the housing 1. The heat sink 3 may be provided to further improve the heat dissipation capacity of the single crystal furnace. The first heat shield 21 may move between the heat sink 3 and the second heat shield 22 to adjust the position of the first heat shield 21 according to different heat dissipation requirements during the production of the crystal rod 6, thereby improving the heat dissipation efficiency of the heat shield assembly 2.

[0082] like Figure 6 and Figure 7 As shown, in a possible implementation, the single crystal furnace includes an outer guide tube 4 and a heat preservation tube 5, the outer guide tube 4 is sleeved on the outside of the second heat shield 22, and one end of the outer guide tube 4 close to the flow port 11 has a flange 41. When the single crystal furnace is in the second state, along the height direction of the single crystal furnace, the lower edge of the flange 41 of the outer guide tube 4 coincides with the upper edge of the heat preservation tube 5.

[0083] When the height of the second heat shield 22 is too high, the distance between the second heat shield 22 and the crucible of the single crystal furnace is too far, and the heat dissipation effect of the second heat shield 22 on the crystal rod 6 is poor. When the height of the second heat shield 22 is too low, the distance between the second heat shield 22 and the crucible is too close, and it is easy to interfere with the crucible and other components.

[0084] When the first heat shield 21 extends into the second cavity 221 too small, the distance between the first heat shield 21 and the crystal rod 6 is large, resulting in poor cooling effect of the first heat shield 21 on the crystal rod 6. When the first heat shield 21 extends into the second cavity 221 too large, the first heat shield 21 is likely to interfere with the second heat shield 22, and the observation angle of the CCD will be affected.

[0085] Generally, the cooling capacity of the first heat shield 21 may be higher than that of the second heat shield 22. When in use, different heat exchange media may be introduced into the first heat shield 21 and the second heat shield 22 to improve the heat exchange effect of the first heat shield 21, thereby improving the cooling capacity of the first heat shield 21. The cooling capacity of the first heat shield 21 may also be higher than that of the second heat shield 22 by adjusting the flow rate of the heat exchange medium between the first heat shield 21 and the second heat shield 22.

[0086] Based on the single crystal furnace provided in the above embodiments, the embodiment of the present application further provides a method for manufacturing a crystal rod 6, and the single crystal furnace involved in any of the above embodiments can be used to produce the crystal rod 6. The manufacturing method includes: in the charging stage, driving the first heat shield 21 to move to a position 0 mm to 300 mm away from the flow port 11, driving the second heat shield 22 to move to a position 100 mm to 300 mm away from the flow port 11, and charging the single crystal furnace;

[0087] During the temperature control stage, the second heat shield 22 is driven to move in a direction away from the flow port 11 to a position where the distance between the lower edge of the flange 41 of the outer guide tube 4 and the upper edge of the insulation tube 5 is 100 mm to 200 mm, and the silicon material is heated and melted. When the linear diameter of the silicon material does not exceed 150 mm, the second heat shield 22 is driven to descend to the same height position as the flange 41 of the outer guide tube 4 and the upper edge of the insulation tube 5, and the first heat shield 21 is driven to descend to a position where the lower edge of the first heat shield 21 is 60 mm above the upper edge of the second heat shield 22 and the lower edge of the first heat shield 21 extends into the second heat shield 22 by 60 mm. At this time, the position of the first heat shield 21 is recorded as the 0 position of the first heat shield 21, and the position of the second heat shield 22 is recorded as the 0 position of the second heat shield 22. In the subsequent crystal pulling process, the 0 position of each heat shield can be used as the reference position corresponding to each heat shield. In the subsequent crystal pulling process, when the position of the heat shield assembly 2 needs to be adjusted, the 0 position of the heat shield can be used as a reference for adjustment. For example, adjusting the first heat shield 21 to (-100, -30) can indicate that the first heat shield 21 is lowered by 30 mm to 100 mm relative to the 0 position, and adjusting the first heat shield 21 to a position not exceeding +100 can indicate that the position of the first heat shield 21 is not higher than 100 mm above the 0 position. Similarly, the 0 position of the second heat shield 22 can also be used as the reference position of the second heat shield 22. When the position of the second heat shield 22 needs to be adjusted, the distance adjusted relative to the 0 position can be used to indicate it. Usually, adjustment parameters can be indicated by symbols and numbers. Numbers are used to indicate the absolute value of the distance. When the sign before the number is a negative sign, it indicates that the position is lower than the 0 position. When the sign before the number is a positive sign, it indicates that the position is higher than the 0 position.

[0088] During the stages of placing the crucible, seeding, and shouldering, the positions of the first heat shield 21 and the second heat shield 22 remain stationary;

[0089] In the equal diameter stage, when the equal diameter length of the crystal rod 6 is less than 800 mm, the first heat shield 21 is driven to descend by 30 mm to 100 mm;

[0090] After the length of the crystal rod 6 exceeds 800 mm, the first heat shield 21 is driven to rise until the first heat shield 21 is no more than 100 mm above the zero position of the first heat shield 21;

[0091] In the closing phase, the first heat shield 21 and the second heat shield 22 remain stationary.

[0092] During production, the above steps can be repeated to carry out repeated production. In the shutdown stage, the first heat shield 21 and the second heat shield 22 can both rise to the upper limit position, that is, drive the first heat shield 21 to move to a position with a distance of 0 mm to 300 mm from the flow port 11, and drive the second heat shield 22 to move to a position with a distance of 100 mm to 300 mm from the flow port 11, so as to reduce the possibility of interference between the heat shield assembly 2 and other components of the single crystal furnace, and facilitate the feeding of the single crystal furnace during the next production.

[0093] During the production process, the first heat shield 21 and the second heat shield 22 move to the upper limit position in the feeding stage to reduce the interference of the heat shield assembly 2 on the feeding, which is conducive to reducing the difficulty of feeding and improving the feeding efficiency. After the second heat shield 22 drops to the lower limit position in the temperature control stage, the lower edge of the first heat shield 21 blocks half of the CCD viewing angle, so that the first heat shield 21 is at position 0. In the equal diameter stage, when the CCD is only used to observe the diameter of the crystal rod 6, usually when the equal diameter length is less than 800 mm, the first heat shield 21 drops to a position 30 mm to 100 mm below the 0 position. At this time, the length of the crystal rod 6 is relatively short, and driving the first heat shield 21 to drop can enable the first heat shield 21 to better cool the crystal rod 6. As the length of the crystal rod 6 increases, the first heat shield 21 gradually rises, and the rising position of the first heat shield 21 does not exceed 100 mm above 0. When the rising height of the first heat shield 21 is too large, a gap will appear between the first heat shield 21 and the second heat shield 22, that is, part of the crystal rod 6 is not within the cooling range of the heat shield assembly 2, resulting in a decrease in cooling efficiency. When argon is introduced, the argon will flow out from the gap between the first heat shield 21 and the second heat shield 22, reducing the cooling effect of the argon. At the same time, the argon will form a cyclone, blowing the surrounding impurities, causing the impurities to enter the crystal rod 6, affecting the quality of the crystal rod 6.

[0094] As shown in Table 1 below, the length is the equal length of the crystal rod 6, the pulling speed is the lifting speed of the crystal rod 6 after the single crystal furnace is improved, the original pulling speed is the lifting speed of the crystal rod 6 before the single crystal furnace is improved, the compensation power is the compensation power after the single crystal furnace is improved, and the original compensation power is the compensation power before the single crystal furnace is improved. Since the single crystal furnace provided in the embodiment of the present application has a strong cooling capacity and a better cooling effect, the temperature of the crystal rod 6 drops faster and the cooling time is shorter during crystal pulling, thereby increasing the lifting speed of the crystal rod 6 and further increasing the production efficiency of the crystal rod 6. Since the heat shield assembly 2 has a good cooling and heat dissipation capacity, when the heat shield assembly 2 is working, it will absorb the heat above the crucible, causing the temperature above the crucible to drop, and the heat at the liquid level of the crucible will be transferred above the crucible. Therefore, it is necessary to compensate for the temperature by increasing the power of the heating element.

[0095] In the initial stage of crystal pulling, when the length of the crystal rod 6 is short, the crystal can be cooled by introducing argon gas along the flow port 11. As the length of the crystal rod 6 increases, the first heat shield 21 and the second heat shield 22 are used to cool the crystal rod 6, and the cooling efficiency is improved, so that the later pulling speed can be increased to a higher level, and the final target pulling speed can be controlled at 125mm / h. In the scheme provided in the embodiment of the present application, a channel can be formed by the heat sink 3, the first heat shield 21 and the second heat shield 22, so that the argon gas can be more concentrated and the cooling effect of the argon gas on the crystal rod 6 can be improved. Taking the production of a crystal rod with a diameter of 263 mm as an example, during the shouldering process, the total cooling amount is controlled at 7-9kw, and the parameter settings for equal diameter are as shown in Table 1. The heat dissipation capacity of the lower part of the thermal field is not significantly different from before, so the power supplement of the equal diameter rear drive heater is slightly increased to supplement the heat taken away by the first heat shield 21 and the argon gas. After actual measurement, by using the single crystal furnace provided in the embodiment of the present application to produce the crystal rod 6, the cooling efficiency of the crystal rod 6 can be improved, so the time required for the heat shield assembly 2 to cool the crystal rod 6 can be reduced, so that during the crystal pulling process, a higher crystal pulling rate can be achieved, thereby improving the crystal pulling efficiency. The unit yield can be increased by 3kg / d to 7kg / d. At the same time, since the heat sink 3, the first heat shield 21 and the second heat shield 22 can form a channel, the possibility of argon gas diffusing outward can be reduced, and the possibility of argon gas blowing impurities such as stains in the single crystal furnace to the crystal rod 6 when flowing can be reduced, thereby improving the quality of the crystal rod 6. The reduction of impurities in the crystal rod 6 can reduce the possibility of the crystal rod 6 breaking during the production process. The breakage rate of the crystal rod 6 can be reduced by 8% to 12%. Due to the reduction of impurities in the crystal rod 6, the overall quality of the crystal rod 6 is improved, the crystal rod 6 is processed into a silicon wafer, and then the silicon wafer is processed into a battery cell, the electrical performance of the battery cell is also improved, and the efficiency of the battery cell can be increased by 0.01% to 0.03%.

[0096] Table 1

[0097]

[0098]

[0099] The above description is only the preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A single crystal furnace for producing crystal rods, characterized in that: The single crystal furnace comprises: A housing (1), wherein the housing (1) has a receiving chamber (12); A heat shield assembly (2), wherein the heat shield assembly (2) is located in the accommodating cavity (12); A driving member, the driving member being used to drive the heat shield assembly (2) to move relative to the housing (1); The heat shield assembly (2) comprises a first heat shield (21) and a second heat shield (22); the driving member comprises a first driving member and a second driving member; the housing (1) is provided with a circulation port (11); the first heat shield (21) has a first cavity (211); the second heat shield (22) has a second cavity (212); the circulation port (11), the first cavity (211) and the second cavity (212) are connected to form a channel; the driving member comprises a first driving member and a second driving member; the first driving member is used to drive the first heat shield (21) to move along the height direction of the single crystal furnace; the second driving member is used to drive the second heat shield (22) to move along the height direction of the single crystal furnace; the driving member is used to drive the heat shield assembly (2) to move in a direction away from the circulation port (11) so that the heat shield assembly (2) is converted from a first state to a second state; and the driving member is used to drive the heat shield assembly (2) to move in a direction close to the circulation port (11) so that the heat shield assembly (2) is converted from the second state to the first state; When the heat shield assembly (2) is in a first state, at least a portion of the second heat shield (22) is sleeved on the outside of the first heat shield (21); When the heat shield assembly (2) is in a second state, at least a portion of the second heat shield (22) is located on a side of the first heat shield (21) away from the flow opening (11), and the first heat shield (21) is capable of moving between the second heat shield (22) and the flow opening (11).

2. The single crystal furnace according to claim 1, characterized in that: In a direction away from the flow port (11), the cross-sectional area of ​​the second cavity (212) gradually decreases.

3. The single crystal furnace according to claim 2, characterized in that: The second cavity comprises a first flow section and a second flow section which are interconnected, wherein the first flow section is located on a side of the second flow section away from the flow port; The angle between the side wall of the first flow section and the height direction of the single crystal furnace is a, and 15°≤a≤25°, and the angle between the side wall of the second flow section and the height direction of the single crystal furnace is b, and 10°≤b≤15°.

4. The single crystal furnace according to claim 2, characterized in that: The diameter of the second cavity at one end close to the circulation port is 520 mm to 540 mm, and the diameter of the second cavity at one end away from the circulation port is 300 mm to 320 mm; The outer diameter of the first heat shield is 360 mm to 380 mm, and the diameter of the first cavity is 300 mm to 320 mm.

5. The single crystal furnace according to claim 1, characterized in that: The diameter of the first cavity (211) is c, the diameter of the crystal rod is d, and the relationship 20 mm≤cd≤80 mm is satisfied.

6. The single crystal furnace according to claim 1, characterized in that: Along the height direction of the single crystal furnace, the length of the first heat shield (21) is 50 mm to 450 mm, and the length of the second heat shield (22) is 100 mm to 500 mm.

7. The single crystal furnace according to claim 1, characterized in that: The single crystal furnace further comprises a heat sink (3), the heat sink (3) being fixedly connected to the housing (1) and having a third cavity (31), the third cavity (31) being in communication with the flow port (11); When the heat shield assembly (2) is in a first state, the first heat shield (21) is sleeved on the outside of the heat sink (3), and the second heat shield (22) is sleeved on the outside of the first heat shield (21); When the heat shield assembly (2) is in the second state, at least a portion of the first heat shield (21) is located on a side of the heat sink (3) away from the flow opening (11), and at least a portion of the second heat shield (22) is located on a side of the first heat shield (21) away from the heat sink (3).

8. The single crystal furnace according to any one of claims 1 to 7, characterized in that: The single crystal furnace comprises an outer guide tube (4) and a heat preservation tube (5), wherein the outer guide tube (4) is sleeved on the outside of the second heat shield (22), and the end of the outer guide tube (4) close to the flow port (11) has a flange (41), and when the single crystal furnace is in a second state, along the height direction of the single crystal furnace, the lower edge position of the flange (41) coincides with the upper edge position of the heat preservation tube (5).

9. A crystal pulling method for manufacturing a crystal rod (6) by using the single crystal furnace according to any one of claims 1 to 8, characterized in that: The manufacturing method comprises: In the charging stage, the first heat shield (21) is driven to move to a position between 0 mm and 300 mm away from the flow opening (11), and the second heat shield (22) is driven to move to a position between 100 mm and 300 mm away from the flow opening (11), so as to charge the single crystal furnace; In the temperature control stage, the second heat shield (22) is driven to move in a direction away from the flow port (11) to a position where the distance between the lower edge of the flange (41) of the outer guide tube (4) and the upper edge of the insulation tube (5) is 100 mm to 200 mm, and the silicon material is heated and melted. When the linear diameter of the silicon material does not exceed 150 mm, the second heat shield (22) is driven to descend to a position where the flange (41) of the outer guide tube (4) and the upper edge of the insulation tube (5) are at the same height, and the first heat shield (21) is driven to descend to a position where the lower edge of the first heat shield (21) is 60 mm above the upper edge of the second heat shield (22) and the lower edge of the first heat shield (21) extends 60 mm into the second heat shield (22). At this time, the first heat shield (21) is at the 0th position of the first heat shield (21), and the second heat shield (22) is at the 0th position of the second heat shield (22); During the stages of placing the crucible, seeding and shouldering, the positions of the first heat shield (21) and the second heat shield (22) remain stationary; In the equal diameter stage, when the equal diameter length of the crystal rod (6) is less than 800 mm, the first heat shield (21) is driven to descend by 30 mm to 100 mm; After the length of the crystal rod (6) exceeds 800 mm, the first heat shield (21) is driven to rise until the first heat shield (21) is no more than 100 mm above the zero position of the first heat shield (21); In the closing phase, the first heat shield (21) and the second heat shield (22) remain stationary.

10. The crystal pulling method according to claim 9, characterized in that: The crystal pulling method further comprises: During the shutdown phase, the first heat shield (21) is driven to move to a position between 0 mm and 300 mm away from the flow port (11), and the second heat shield (22) is driven to move to a position between 100 mm and 300 mm away from the flow port (11).

Images