Single crystal furnace and crystal pulling process

Abstract

The invention relates to a single crystal furnace and a crystal pulling process. The single crystal furnace comprises a furnace body, a crucible and a guide cylinder, the furnace body defines a furnace cavity with an opening in the top end, the opening is used for introducing protective gas into the furnace cavity, the crucible is arranged in the furnace cavity and used for containing silicon liquid, and the guide cylinder is arranged in the furnace cavity and located on the side, in the axis direction of the furnace cavity, of the crucible. The guide cylinder is provided with a channel which is arranged in a penetrating mode in the axis direction of the furnace chamber, protective gas flows towards the crucible through the channel, the inner side wall of the channel is provided with a plurality of guide grooves, the guide grooves are distributed in the circumferential direction of the furnace chamber at intervals and are spirally distributed, and the extending direction of the guide grooves intersects with the axis direction of the furnace chamber. According to the single crystal furnace, the airflow path of the protective gas can be optimized, the airflow of the protective gas generates vortexes, so that the temperature of the liquid level of the silicon liquid is more uniform, the oxygen reduction effect is better, and the impurity removal effect is better.

Description

Technical Field

[0001] This application relates to the technical field of single crystal silicon manufacturing, and particularly to a single crystal furnace and a crystal pulling process. Background Art

[0002] With the rise of the photovoltaic industry, the demand for single crystal silicon, which is the main raw material for manufacturing photovoltaic cells, has gradually increased. Generally, the Czochralski method can be used to produce single crystal silicon rods in a single crystal furnace. During the pulling process of the single crystal silicon rod, argon gas is usually introduced into the single crystal furnace to balance and reduce the oxygen content in the single crystal furnace.

[0003] In the related art, argon gas is usually directly introduced, which easily leads to uneven oxygen content everywhere in the furnace and the introduced argon gas is likely to directly impact the liquid surface of the silicon melt in the crucible. For example, when the argon gas flow rate is too large, it will inhibit the volatilization of oxygen in the liquid surface, affecting the oxygen reduction effect. And the introduced argon gas will cause temperature fluctuations in each region of the liquid surface. Combining with the rotation and rising of the crucible and the design of the internal heat field of the single crystal furnace itself, there are also differences in the temperatures of each region of the liquid surface, making it difficult to ensure a good balance point at the crystallization interface and affecting the quality of crystal pulling.

[0004] That is, the oxygen reduction effect of the single crystal furnace in the related art is poor, and there are problems such as uneven oxygen content everywhere in the furnace and uneven temperature everywhere in the furnace, which affect the quality of crystal pulling. Summary of the Invention

[0005] Based on this, it is necessary to provide a single crystal furnace and a crystal pulling process for the problems in the related art that the oxygen reduction effect of the single crystal furnace is poor, there is uneven oxygen content everywhere in the furnace, and there is uneven temperature everywhere in the furnace, affecting the crystal pulling process.

[0006] According to one aspect of the present application, a single crystal furnace is provided, and the single crystal furnace includes:

[0007] A furnace body defining a furnace cavity with an open top, and the opening is used to introduce a protective gas into the furnace cavity;

[0008] A crucible disposed in the furnace cavity and used to hold silicon material; and

[0009] A flow guiding cylinder disposed in the furnace cavity and located on one side of the crucible along the axial direction of the furnace cavity; a channel is provided on the flow guiding cylinder and penetrates along the axial direction of the furnace cavity, and the protective gas flows towards the crucible through the channel;

[0010] Wherein, a plurality of flow guiding grooves are formed on the inner side wall of the channel, and the plurality of flow guiding grooves are arranged at intervals along the circumferential direction of the furnace cavity and are arranged in a spiral shape; the extending direction of the flow guiding groove intersects with the axial direction of the furnace cavity.

[0011] In one embodiment, the draft tube includes a first draft portion, a second draft portion, and a third draft portion. Along the axial direction of the furnace chamber and away from the crucible, the first draft portion, the second draft portion, and the third draft portion are arranged in sequence;

[0012] The channel sequentially penetrates through the first draft portion, the second draft portion, and the third draft portion; and the draft groove includes a first draft groove, a second draft groove, and a third draft groove that communicate with each other. The first draft groove is formed on the first draft portion, the second draft groove is formed on the second draft portion, and the third draft groove is formed on the third draft portion;

[0013] Along the radial direction of the furnace chamber, the size of the first draft portion is smaller than that of the second draft portion, and the size of the second draft portion is smaller than that of the third draft portion.

[0014] In one embodiment, the draft groove is recessed on the inner side wall of the channel. The recessed depth h of the draft groove satisfies: 5 mm ≤ h ≤ 8 mm; the notch width d of the draft groove satisfies: 8 mm ≤ d ≤ 12 mm.

[0015] In one embodiment, the draft groove includes two groove edges that are parallel to each other. The two groove edges are respectively located on both sides of the notch of the draft groove and jointly define the notch;

[0016] On the side of the inner side wall of the first draft portion facing away from the second draft portion, there is a first circular edge. The included angle a1 between the first circular edge and the groove edge of the draft groove provided on the first draft portion satisfies: 10° ≤ a1 ≤ 50°;

[0017] At the junction of the inner side wall of the first draft portion and the inner side wall of the second draft portion, there is a second circular edge. The included angle a2 between the second circular edge and the groove edge of the draft groove provided on the second draft portion satisfies: 10° ≤ a2 ≤ 50°;

[0018] At the junction of the inner side wall of the third draft portion and the inner side wall of the second draft portion, there is a third circular edge. The included angle a3 between the third circular edge and the groove edge of the draft groove provided on the third draft portion satisfies: 10° ≤ a3 ≤ 50°.

[0019] In one embodiment, along the axial direction of the furnace chamber, the radial dimension of the first flow guiding portion remains unchanged. Along the axial direction of the furnace chamber and away from the crucible, the radial dimensions of the second flow guiding portion and the third flow guiding portion both gradually increase; and the radial dimension b1 of the first flow guiding portion satisfies: 300 ≤ b1 ≤ 365; the radial dimension b2 of the second flow guiding portion satisfies: 305 mm ≤ b2 ≤ 370 mm, and the radial dimension b3 of the third flow guiding portion satisfies: 310 mm ≤ b3 ≤ 370 mm.

[0020] In one embodiment, along the axial direction of the furnace chamber, the dimension H of the flow guiding cylinder satisfies: 165 mm ≤ H ≤ 330 mm, the dimension h1 of the second flow guiding portion satisfies: 150 mm ≤ h1 ≤ 300 mm, and the dimension h2 of the third flow guiding portion satisfies: 15 mm ≤ h2 ≤ 30 mm.

[0021] In one embodiment, the single crystal furnace further includes a thermal insulation cover shell, which is arranged around the central axis of the furnace chamber and is annularly arranged outside the flow guiding cylinder;

[0022] And the thermal insulation cover shell and the flow guiding cylinder jointly define a thermal insulation cavity, and the thermal insulation cavity is filled with thermal insulation materials.

[0023] In one embodiment, the thermal insulation cover shell includes a bottom shell and a side shell. The bottom shell is connected between the side shell and the flow guiding cylinder. The outer side surface of the bottom shell faces the crucible opening of the crucible, and the included angle k between the outer side surface of the bottom shell and the axial direction of the furnace chamber satisfies: 60° ≤ k ≤ 82°.

[0024] According to another aspect of the present application, a crystal pulling process is provided. The single crystal furnace described in any of the above embodiments is used for crystal pulling. The crystal pulling process includes:

[0025] Add silicon material into the crucible and place the crucible into the furnace body of the single crystal furnace;

[0026] Introduce a protective gas into the single crystal furnace. The flow rate Q of the protective gas satisfies: 80 liters / minute ≤ Q ≤ 120 liters / minute, and the furnace pressure P after introducing the protective gas into the single crystal furnace satisfies: 4 Torr ≤ P ≤ 6 Torr;

[0027] Heat the crucible to fully melt the silicon material in the crucible to form silicon liquid;

[0028] Immerse the seed crystal into the silicon liquid and sequentially perform crystal seeding, shoulder forming, and equal diameter growth to obtain single crystal silicon.

[0029] In one embodiment, during the equal diameter growth process, control the rotation speed r1 of the crucible to satisfy: 4 revolutions / minute ≤ r1 ≤ 5 revolutions / minute.

[0030] In the above-mentioned single crystal furnace and crystal pulling process, during the crystal pulling process, the protective gas introduced from the top of the furnace body flows into the crucible through the channel opened on the guide tube. The guide groove can guide the protective gas. And the extension direction of the guide groove and the axial direction of the furnace chamber intersect each other. It can be understood that the guide groove is inclined relative to the axial direction of the furnace chamber, or it can be understood that the guide groove is spirally arranged along the axial direction of the furnace chamber. In this way, when the protective gas guided by the guide groove flows to the crucible, it is in a spiral airflow state, and its motion trajectory is a spiral trajectory. Thereby, the protective gas can be delivered to the surface of the silicon material in the crucible in a more dispersed manner, so that the coverage of the protective gas on the surface of the silicon material can be expanded, which is conducive to improving the uniformity of oxygen reduction at various places on the surface of the silicon material, and is conducive to improving the oxygen reduction effect in the single crystal furnace. And it is conducive to making the heat transfer on the surface of the silicon material more uniform, and making the temperature distribution of the entire silicon material surface more uniform. At the same time, it is also conducive to more effectively stirring the airflow on the surface of the silicon material, which is conducive to the protective gas to carry away more impurities on the surface of the silicon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the structure of a single crystal furnace in one embodiment of the present application.

[0032] Figure 2 It is a schematic diagram of the structure of a guide tube in one embodiment of the present application.

[0033] Figure 3 for Figure 2 An enlarged schematic diagram of point A is shown.

[0034] Figure 4 The present invention is a flow chart of a crystal pulling process for performing crystal pulling using a single crystal furnace in one embodiment of the present application.

[0035] Description of Figure Numbers:

[0036] 10. Single crystal furnace;

[0037] 100, furnace body; 110, opening; 200, crucible;

[0038] 300, guide tube; 310, first guide part; 320, second guide part; 330, third guide part; 340, channel; 350, guide groove; 351, first guide groove; 352, second guide groove; 353, third guide groove;

[0039] 400, thermal insulation cover; 410, bottom shell; 420, side shell; 500, thermal insulation material; 600, crystal rod. DETAILED DESCRIPTION

[0040] To make the above objects, features, and advantages of the present application more apparent and understandable, the following provides a detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings. A lot of specific details are set forth in the following description to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without departing from the connotation of the present application. Therefore, the present application is not limited by the specific embodiments disclosed below.

[0041] In the description of the present application, it should be understood that if terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or positional relationship indicated by these terms is based on the orientation or positional relationship shown in the accompanying drawings. These are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation to the present application.

[0042] In addition, if terms such as "first" and "second" appear, these terms are only for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of the present application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise specifically and clearly defined.

[0043] In the present application, unless otherwise clearly specified and limited, if terms such as "install", "connect", "couple", "fix", etc. appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or integrated; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, and it can be the communication inside two elements or the interaction relationship between two elements, unless otherwise clearly limited. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0044] In this application, unless otherwise clearly specified and defined, when a first feature is described as being "on" or "under" a second feature or the like, it may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "over" and "on top of" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply indicates that the first feature has a higher horizontal height than the second feature. The first feature being "under", "beneath" and "underneath" the second feature may be that the first feature is directly below or obliquely below the second feature, or simply indicates that the first feature has a lower horizontal height than the second feature.

[0045] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or there may also be an intermediate element. If an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. If present, the terms "vertical", "horizontal", "up", "down", "left", "right" and similar expressions used in this application are only for the purpose of illustration and do not represent the only implementation.

[0046] Oxygen will combine with boron elements in single-crystalline silicon to form boron-oxygen complexes, which are one of the main causes of the photoinduced degradation of photovoltaic modules. Therefore, it is crucial to reduce the oxygen content in single-crystalline silicon to improve the service life of photovoltaic modules. Moreover, the reduction of the oxygen content can significantly improve the minority carrier lifetime of single-crystalline silicon, which is crucial for improving the conversion efficiency of photovoltaic modules. Among them, the improvement of the minority carrier lifetime can increase the current output of photovoltaic modules, thereby improving the overall performance of photovoltaic modules. Oxygen may form oxygen precipitates or other defects during the single-crystal growth process. These defects will affect the mechanical and electrical properties of the silicon wafer and may even cause the silicon wafer to warp or break. Reducing the oxygen content in single-crystalline silicon can reduce the formation of these defects, thereby improving the quality and reliability of single-crystalline silicon.

[0047] Reducing the oxygen content in the single-crystal furnace can reduce the oxygen content in the prepared single-crystalline silicon and can effectively improve the stability and long-term performance of photovoltaic modules using single-crystalline silicon with a lower oxygen content.

[0048] Therefore, the oxygen reduction process in the single-crystal furnace is very important. Usually, argon is introduced into the single-crystal furnace, and the argon is used to carry the oxygen impurities in the single-crystal furnace to float and discharge. However, the structure of introducing argon into the single-crystal furnace in the related technology is likely to cause the introduced argon to directly impact the liquid surface of the silicon melt in the crucible, which is likely to result in uneven oxygen content everywhere in the furnace and poor oxygen reduction effect. There are also problems such as uneven temperature everywhere in the furnace, affecting the quality of crystal pulling.

[0049] Based on this, the present application provides a single crystal furnace, which has a better oxygen reduction effect, and the oxygen uniformity and temperature uniformity at various positions inside the single crystal furnace are significantly increased, and the quality of the single crystal silicon formed by using the single crystal furnace is significantly improved.

[0050] Referring to Figure 1 and Figure 2 shown, Figure 1 is a schematic structural view of a single crystal furnace 10 in an embodiment of the present application. Figure 2 is a schematic structural view of a deflector tube 300 in an embodiment of the present application.

[0051] The single crystal furnace 10 provided by the present application includes a furnace body 100, a crucible 200, and a deflector tube 300. The furnace body 100 defines a furnace cavity with an opening 110 at the top. The opening 110 is used to introduce a protective gas into the furnace cavity, and the protective gas can be argon. The crucible 200 is disposed in the furnace cavity and is used to contain silicon material. The silicon material in the crucible 200 forms silicon liquid after being heated in the single crystal furnace. When using the single crystal furnace 10 to prepare single crystal silicon, a seed crystal is suspended on a rotatable seed crystal rod in the furnace cavity and immersed in the silicon liquid, so that the single crystal silicon can continue to grow to form a crystal rod 600.

[0052] The deflector tube 300 is disposed in the furnace cavity and is located on one side of the crucible 200 along the axial direction of the furnace cavity. The deflector tube 300 is provided with a channel 340 penetrating along the axial direction of the furnace cavity, and the protective gas flows toward the crucible 200 through the channel 340. The channel 340 on the deflector tube 300 is also used for the crystal rod 600 to pass through, so that the crystal rod 600 is suspended in the furnace cavity, and the crystal rod 600 extends longitudinally along the furnace cavity.

[0053] Among them, a plurality of flow guiding grooves 350 are formed on the inner side wall of the channel 340. The plurality of flow guiding grooves 350 are arranged at intervals along the circumferential direction of the furnace cavity and are arranged in a spiral shape. The extending direction of the flow guiding groove 350 intersects with the axial direction of the furnace cavity. When the protective gas flows from top to bottom toward the crucible 200 through the channel 340, the flow guiding grooves 350 on the inner side wall of the channel 340 can guide the protective gas, so that the gas flow of the protective gas finally flowing to the surface of the silicon liquid in the crucible 200 is in a spiral shape. The spiral gas flow can form a more complex gas flow pattern on the liquid surface, producing an effect similar to a vortex.

[0054] Compared with the related art, in the related art, argon gas is directly blown, and the direction of the gas flow directly impacts the surface of the silicon liquid in the crucible 200. The direction of the gas flow is relatively single, and it is easy to form a relatively concentrated impact area on the surface of the silicon liquid. The coverage range of argon gas on the surface of the silicon liquid is relatively narrow, and a "columnar" gas flow impact effect is easily formed on the surface of the silicon liquid. This easily leads to a poor oxygen reduction effect on the surface of the silicon liquid and uneven temperatures at various parts of the silicon liquid surface. In this application, a spiral gas flow is formed. On the one hand, it can make the gas flow on the surface of the silicon liquid more sufficient, and the oxygen-containing surface of the silicon liquid is exposed to the gas flow, which is beneficial to the volatilization of oxygen in the silicon liquid in the form of silicon oxide and is conducive to improving the deoxygenation effect. Moreover, the spiral gas flow will form a relatively stable gas flow rotation field above the liquid surface, which can more effectively carry away substances such as volatilized silicon oxide from near the surface of the silicon liquid, reducing the possibility of the volatilized silicon oxide returning to the silicon liquid, thereby reducing the oxygen content in the silicon liquid and the oxygen content of the finally formed ingot 600, which is beneficial to improving the quality of the ingot 600. On the other hand, the spiral gas flow can make the temperatures at various parts of the silicon liquid surface more uniform. After the protective gas passes through the guide cylinder 300 with a spiral guide groove 350, the gas flow will obtain a rotational momentum. The protective gas is blown out from the channel 340 of the guide cylinder 300, and the spiral gas flow formed on the surface of the silicon liquid can diffuse more evenly on the surface of the silicon liquid, expanding the coverage range of the protective gas on the surface of the silicon liquid. It plays a role in agitating the gas on the surface of the silicon liquid, thereby driving the circulation of the gas on the surface of the silicon liquid, which is beneficial to improving the uniform distribution of temperatures at various parts of the silicon liquid surface.

[0055] In the single crystal furnace 10 of this application, during the crystal pulling process, the protective gas introduced from the top of the furnace body 100 flows through the channel 340 opened on the guide cylinder 300 into the crucible 200. The guide groove 350 plays a spiral guiding role for the protective gas, making the gas flow spiral on the surface of the silicon liquid, so that the protective gas can be delivered to the surface of the silicon liquid in the crucible 200 in a more dispersed manner, thereby being able to expand the coverage range of the protective gas on the surface of the silicon liquid, being beneficial to improving the uniformity of oxygen reduction at various parts of the surface of the silicon liquid, and being beneficial to improving the oxygen reduction effect and the uniformity of the temperature distribution on the surface of the silicon liquid in the single crystal furnace 10. At the same time, it is also beneficial to more effectively agitate the gas flow on the surface of the silicon liquid, being beneficial to the protective gas carrying away more impurities on the surface of the silicon liquid and improving the quality of crystal pulling.

[0056] In some embodiments, referring to Figure 1 、 Figure 2 and Figure 3 as shown, Figure 3 is Figure 2An enlarged schematic view of the position A shown. The draft tube 300 includes a first draft portion 310, a second draft portion 320, and a third draft portion 330. Along the axial direction of the furnace cavity and away from the crucible 200, the first draft portion 310, the second draft portion 320, and the third draft portion 330 are arranged in sequence, and the channel 340 sequentially passes through the first draft portion 310, the second draft portion 320, and the third draft portion 330. By arranging three draft portions for gradual draft, the movement trajectory of the protective gas can be gradually changed, avoiding the situation that the gas flow direction of the protective gas is too single due to the draft of a single draft portion, which is conducive to the full mixing of the protective gas and is beneficial to further expanding the coverage range of the protective gas on the surface of the silicon liquid, thereby improving the oxygen reduction uniformity and temperature distribution uniformity at various positions on the surface of the silicon liquid.

[0057] In this embodiment, along the radial direction of the furnace cavity, the size of the first draft portion 310 is smaller than that of the second draft portion 320, and the size of the second draft portion 320 is smaller than that of the third draft portion 330. Herein, the size of the draft portion refers to the diameter size of the inner wall of the draft portion. Compared with the first draft portion 310 and the second draft portion 320, the third draft portion 330 has the largest size, which is conducive to receiving more protective gas and improving the utilization rate of the protective gas. Moreover, the overall trend of the draft tube 300 is in an inverted conical shape, which is conducive to reducing the risk of the protective gas flowing outside the crucible 200, enabling the introduced protective gas to flow into the crucible 200 as much as possible. At the same time, in cooperation with the spiral draft of the draft groove 350, the gas flow of the protective gas flowing into the crucible 200 is in a spiral shape. Therefore, while being conducive to improving the utilization rate of the protective gas, it is also conducive to making the gas flow of the protective gas in a spiral shape, thereby improving the oxygen reduction uniformity and temperature distribution uniformity at various positions on the surface of the silicon liquid.

[0058] In this embodiment, continue to refer to Figure 2 and Figure 3 As shown, the draft groove 350 includes a first draft groove 351, a second draft groove 352, and a third draft groove 353 that are communicated with each other. The first draft groove 351 is opened on the first draft portion 310, the second draft groove 352 is opened on the second draft portion 320, and the third draft groove 353 is opened on the third draft portion 330. Or it can be understood that a draft groove structure is opened on each draft portion, and the groove structures at corresponding positions of adjacent draft portions are communicated with each other. In this way, the draft groove 350 is arranged on the inner wall of the entire draft tube 300 from top to bottom or along the axis of the furnace cavity. Therefore, compared with the case where a draft groove structure is arranged on a single draft portion, the draft groove 350 arranged on the inner wall of the entire draft tube 300 from top to bottom is beneficial to increasing the draft path of the protective gas and improving the draft effect on the protective gas.

[0059] In some embodiments, refer to Figure 1 、 Figure 2 and Figure 3As shown, the guide groove 350 is recessed on the inner wall of the channel 340, and the recess depth h of the guide groove 350 satisfies: 5mm≤h≤8mm, and the notch width d of the guide groove 350 satisfies: 8mm≤d≤12mm. Among them, the bottom wall of the guide groove 350 can be a curved surface structure or the like, and the recess depth h of the guide groove 350 means that the depth at any point of the guide groove 350 satisfies the above range. If the recess depth h and the notch width d of the guide groove 350 meet the above range, it is beneficial for the guide groove 350 to guide the flow of the protective gas more stably, so that the protective gas can flow smoothly in the guide groove 350, reducing the risk of poor flow or local accumulation of the protective gas, and also helping to improve the diversion efficiency. And the guide groove 350 of this depth can effectively guide the flow direction of the protective gas and prevent the protective gas from overflowing.

[0060] In some embodiments, Figure 2 and Figure 3 As shown, the guide groove 350 includes two groove edges parallel to each other, which are respectively located on both sides of the groove opening of the guide groove 350 and define the groove opening together. The two sides of the guide groove 350 at the groove opening are parallel to each other, so that the protective gas passing through the guide groove 350 flows in a spiral shape.

[0061] In this embodiment, the inner side wall of the first guide portion 310 has a first circular edge on the side facing away from the second guide portion 320, and the angle a1 between the first circular edge and the groove edge of the first guide groove 351 provided in the first guide portion 310 satisfies: 10°≤a1≤50°. Among them, the shape of the first circular edge infinitely approaching the groove edge of the first guide groove 351 of the first guide portion 310 can be approximately regarded as a straight line, and the angle between the straight line and the groove edge of the first guide groove 351 is the above-mentioned angle a1. In this way, the above-mentioned range reflects the spiral inclination angle of the first guide groove 351 of the first guide portion 310. The spiral inclination angle of the first guide groove 351 satisfies the above-mentioned range, which is conducive to reducing airflow turbulence, reducing the risk of the protective gas directly impacting the liquid surface of the silicon liquid in the crucible 200, and making the protective gas on the liquid surface of the silicon liquid in the crucible 200 form a stable and uniform spiral airflow, thereby making the temperature in various places in the furnace more uniform, and improving the oxygen reduction effect in various places in the furnace.

[0062] In this embodiment, at the junction of the inner sidewall of the first flow guiding portion 310 and the inner sidewall of the second flow guiding portion 320, there is a second circular edge, and the included angle a2 between the second circular edge and the edge of the second flow guiding groove 352 provided in the second flow guiding portion 320 satisfies: 10° ≤ a2 ≤ 50°. The above range reflects the spiral inclination angle of the second flow guiding groove 352. Among them, the shape of the second circular edge infinitely approaching the edge of the second flow guiding groove 352 can be approximately regarded as a straight line, and the included angle between the straight line at this position and the edge of the second flow guiding groove 352 is the above-mentioned included angle a2. The spiral inclination angle of the second flow guiding groove 352 satisfying the above range is beneficial to reducing the air flow turbulence of the shielding gas, and enabling the shielding gas to enter the first flow guiding groove 351 more smoothly and stably.

[0063] In this embodiment, at the junction of the inner sidewall of the third flow guiding portion 330 and the inner sidewall of the second flow guiding portion 320, there is a third circular edge, and the included angle a3 between the third circular edge and the edge of the third flow guiding groove 353 provided in the third flow guiding portion 330 satisfies: 10° ≤ a3 ≤ 50°. The above range reflects the spiral inclination angle of the third flow guiding groove 353. Among them, the shape of the third circular edge infinitely approaching the edge of the third flow guiding groove 353 can be approximately regarded as a straight line, and the included angle between the straight line at this position and the edge of the third flow guiding groove 353 is the above-mentioned included angle a3. Satisfying the above range is beneficial to the shielding gas smoothly entering the third flow guiding groove 353, and is also beneficial to the shielding gas in the third flow guiding groove 353 smoothly entering the second flow guiding groove 352.

[0064] In some embodiments, as Figure 2 and Figure 3 shown, along the axis direction of the furnace cavity, the radial dimension of the first flow guiding portion 310 remains unchanged. The radial dimension here refers to the radial dimension of the inner sidewall of the first flow guiding portion 310, that is, the inner wall of the first flow guiding portion 310 can be in a cylindrical structure, so that the radial dimensions at each place are the same, and the corresponding first flow guiding groove 351 is recessed on the inner sidewall of the first flow guiding portion 310. Compared with the inverted cone-shaped or conical structure, the setting of the first flow guiding portion 310 with a constant radial dimension in a cylindrical structure is beneficial to making the flow direction of the shielding gas passing through the flow guiding cylinder 300 balanced and stable. Because if the shielding gas is directly spirally led out from the first flow guiding portion 310 with an inverted cone-shaped structure, obviously the shielding gas at each place will have a tendency to converge towards the middle, causing the shielding gas to be staggered and mixed, affecting the stability of the flow direction of the shielding gas on the liquid surface. And if the shielding gas is directly spirally led out from the first flow guiding portion 310 with a conical structure, obviously the shielding gas at each place will have a tendency to diffuse towards the periphery, easily causing the shielding gas to run out of the crucible 200, thereby reducing the utilization rate of the shielding gas and resulting in a poor oxygen reduction effect on the liquid surface in the crucible 200. Therefore, the setting of the first flow guiding portion 310 with a constant radial dimension in a cylindrical structure is beneficial to making the flow direction of the shielding gas passing through the flow guiding cylinder 300 balanced and stable.

[0065] In this embodiment, along the axial direction of the furnace chamber and away from the crucible 200, the radial dimensions of the second flow guiding portion 320 and the third flow guiding portion 330 both gradually increase. In this way, the overall trend of the flow guiding cylinder 300 is an inverted cone shape, which is beneficial to reducing the risk of the protective gas flowing outside the crucible 200, and making the introduced protective gas flow into the crucible 200 as much as possible. And through the two-stage flow guiding by the two flow guiding portions, it is beneficial to make the protective gas transition smoothly, which is conducive to forming a stable air flow of the protective gas and improving the crystal pulling effect.

[0066] In this embodiment, the radial dimension b1 of the first flow guiding portion 310 satisfies: 300 ≤ b1 ≤ 365. The radial dimension b2 of the second flow guiding portion 320 satisfies: 305 mm ≤ b2 ≤ 370 mm, and the radial dimension b3 of the third flow guiding portion 330 satisfies: 310 mm ≤ b3 ≤ 370 mm. Meeting the above range is beneficial to reducing air flow turbulence, reducing the risk of the protective gas directly impacting the liquid surface of the silicon liquid in the crucible 200, optimizing the path of the protective gas, forming a stable air flow of the protective gas, enabling the protective gas to pass through the liquid surface more smoothly, taking away volatile impurities, making the temperature more uniform everywhere in the furnace, and improving the oxygen reduction effect everywhere in the furnace, thereby being beneficial to improving the quality of the obtained single crystal silicon.

[0067] In this embodiment, the radial dimension of the third flow guiding portion 330 can be 310 mm, 335 mm or 360 mm. When the radial dimension b3 of the third flow guiding portion 330 is 310 mm, it is correspondingly applicable to a crystal bar 600 with a diameter of 10 inches; when the radial dimension b3 of the third flow guiding portion 330 is 335 mm, it is correspondingly applicable to a crystal bar 600 with a diameter of 11 inches; when the radial dimension b3 of the third flow guiding portion 330 is 360 mm, it is correspondingly applicable to a crystal bar 600 with a diameter of 12 inches.

[0068] In some embodiments, as Figure 1 shown, along the axial direction of the furnace chamber, the dimension H of the flow guiding cylinder 300 satisfies: 165 mm ≤ H ≤ 330 mm, the dimension h1 of the second flow guiding portion 320 satisfies: 150 mm ≤ h1 ≤ 300 mm, and the dimension h2 of the third flow guiding portion 330 satisfies: 15 mm ≤ h2 ≤ 30 mm. Meeting the above range is beneficial to making the dimensions of the flow guiding cylinder 300 and the dimensions of each flow guiding portion within a suitable range, effectively guiding the flow path of the protective gas, enabling the air flow to pass through the liquid surface more smoothly, and taking away volatile impurities. At the same time, it is beneficial to reducing the blowing force of the protective gas on the liquid surface, avoiding the change of the internal convection of the silicon liquid on the liquid surface, thereby being beneficial to improving the stability of the pulling of the crystal bar 600 of the single crystal silicon. In addition, it can effectively reduce the heat dissipation to the outside, maintain the precise temperature control in the single crystal silicon crystal growth area, and improve the energy utilization efficiency. And it can be beneficial to optimizing the temperature distribution and helping to control the single crystal silicon crystal growth rate and quality.

[0069] In some embodiments, as Figure 1 shown, the single crystal furnace 10 further includes a heat preservation cover 400. The heat preservation cover 400 is arranged around the central axis of the furnace cavity and is disposed annularly outside the guide cylinder 300. The heat preservation cover 400 and the guide cylinder 300 jointly define a heat preservation cavity, and a heat preservation material 500 is filled in the heat preservation cavity. In this embodiment, the heat preservation material 500 can be graphite felt. By arranging the heat preservation material 500 outside the guide cylinder 300, the crystal rod 600 can be effectively heat-insulated, effectively reducing the heat dissipation to the outside, which is beneficial to improving the thermal efficiency and reducing the energy consumption. The heat preservation material 500, such as graphite felt, is evenly wrapped outside the guide cylinder 300, which helps to optimize the temperature distribution of the entire thermal field, thereby facilitating the stability of the temperature gradient during the crystal growth process of single crystal silicon and improving the uniformity and quality of crystal growth.

[0070] In some embodiments, continue to refer to Figure 1 shown, the heat preservation cover 400 includes a bottom shell 410 and a side shell 420. The bottom shell 410 is connected between the side shell 420 and the guide cylinder 300. The outer side surface of the bottom shell 410 faces the opening of the crucible 200 of the crucible 200, and the included angle k between the outer side surface of the bottom shell 410 and the axial direction of the furnace cavity satisfies: 60° ≤ k ≤ 82°. The bottom shell 410 of the heat preservation cover 400 satisfying the above conditions is beneficial to limit the protective gas at the liquid surface of the crucible 200, so that the protective gas at the liquid surface of the crucible 200 stably spirally flows at the liquid surface of the crucible 200, reducing the risk of chaotic flow of the protective gas at the liquid surface of the crucible 200. And if the inclination angle of the bottom shell 410 satisfies the above range, the part of the bottom shell 410 close to the guide cylinder 300 is closer to the crucible 200 axially, and the part of the bottom shell 410 far from the guide cylinder 300 is farther from the crucible 200 axially. In this way, it is beneficial to enable the excess or the protective gas that has spirally flowed and carried impurities to diffuse around, so that the subsequently introduced protective gas blows to the liquid surface of the crucible 200. Such a design is beneficial to adjusting the pressure of the gas flow at the liquid surface of the crucible 200, helping to form a more stable pressure distribution in the furnace, and reducing the liquid surface fluctuation and gas flow instability caused by the gas flow pressure fluctuation, thereby providing a more stable environment for single crystal silicon growth.

[0071] Combined with referring to Figure 1 and Figure 4 shown, Figure 4 is a flowchart of the crystal pulling process for pulling a crystal using the single crystal furnace 10 in an embodiment of the present application. The crystal pulling process provided by the present application uses the single crystal furnace 10 in any of the above embodiments for crystal pulling. The crystal pulling process includes:

[0072] S1. Add silicon material into the crucible 200.

[0073] The specific operation is to crush high-purity polysilicon materials into appropriate sizes, clean the outer surface in a cleaning solution such as a mixed solution of nitric acid and hydrofluoric acid to remove impurities, and then add the cleaned silicon materials into the crucible 200 located in the furnace body 100. After adding the silicon materials into the crucible 200, operations such as secondary feeding can also be carried out.

[0074] S2. Introduce a protective gas into the single crystal furnace 10. The flow rate Q of the protective gas satisfies: 80 L / min ≤ Q ≤ 120 L / min, and the furnace pressure P after introducing the protective gas into the single crystal furnace 10 satisfies: 4 Torr ≤ P ≤ 6 Torr.

[0075] Before introducing the protective gas into the single crystal furnace 10, it is also necessary to evacuate the furnace body 100 of the single crystal furnace 10, and then fill it with the protective gas after evacuation. The introduced protective gas satisfies the above range, which can effectively isolate the air, reduce the risk of oxidation of the silicon liquid, and reduce the risk of impurities mixing into the silicon liquid, which is beneficial to improving the purity of the single crystal silicon. It is also beneficial for the protective gas to effectively carry away the impurities volatilized from the surface of the silicon liquid. At the same time, controlling the flow rate of the protective gas and the furnace pressure after introducing the protective gas to satisfy the above range is beneficial to optimizing the gas flow distribution in the furnace, reducing the disturbance of the gas flow to the silicon liquid, and at the same time is beneficial to further helping to maintain a stable temperature distribution, which is conducive to the uniform growth of single crystal silicon.

[0076] S3. Heat the crucible 200 to fully melt the silicon materials in the crucible 200 to form silicon liquid, so as to complete the silicon melting step. In the silicon melting step, heat the crucible 200 to melt silicon, so that the temperature r1 of the silicon liquid satisfies: 1420 °C ≤ r1 ≤ 1480 °C to melt the silicon materials in the crucible 200. And in the silicon melting step, the flow rate Q1 of the introduced protective gas satisfies: 50 L / min ≤ Q1 ≤ 150 L / min. The flow rate of the introduced protective gas can be any value within the above range, and a deviation of ±2 L / min is allowed during the introduction process. And the furnace pressure P after introducing the protective gas into the single crystal furnace 10 satisfies: 1 Torr ≤ P1 ≤ 16 Torr. A deviation of ±0.5 Torr is allowed while the furnace pressure in the single crystal furnace is within the above range. While satisfying the above range during the silicon melting process, continue to introduce the protective gas, which is beneficial for the protective gas to effectively carry away the impurities volatilized from the surface of the silicon liquid and improve the purity of the single crystal silicon.

[0077] S4. Immerse the seed crystal into the silicon liquid and successively carry out crystal seeding, shoulder formation, and equal diameter growth to obtain single crystal silicon.

[0078] During the crystal seeding process, a seed crystal of appropriate size is taken and chemically polished to remove surface damage and reduce metal contamination. The seed crystal is fixed on a rotating seed crystal rod and slowly lowered to a certain distance from the liquid surface, such as 10 mm, and paused for a moment to make the temperature of the seed crystal close to the temperature of the silicon liquid. Then the seed crystal is gently immersed in the silicon liquid to form a solid-liquid interface, and then the seed crystal is gradually pulled up to start the growth of single crystal silicon. During the crystal seeding process, the temperature r2 of the silicon liquid is maintained to satisfy: 1448 °C ≤ r2 ≤ 1452 °C, and the protective gas is continuously introduced. The flow rate Q2 of the introduced protective gas satisfies: 50 L / min ≤ Q2 ≤ 150 L / min, that is, the flow rate of the introduced protective gas can be any value within the above range, and a deviation of ±2 L / min is allowed during the introduction process. And the furnace pressure P2 after introducing the protective gas into the single crystal furnace 10 satisfies: 1 Torr ≤ P2 ≤ 16 Torr. At this time, a deviation of ±0.5 Torr is allowed while the furnace pressure in the single crystal furnace satisfies the above range. In this way, it is beneficial for the protective gas to effectively carry away the impurities volatilized from the surface of the silicon liquid and improve the purity of the single crystal silicon. It is beneficial to optimize the gas flow distribution in the furnace, reduce the disturbance of the gas flow to the silicon liquid, and at the same time help to further maintain a stable temperature distribution, which is conducive to the uniform growth of single crystal silicon.

[0079] After the crystal seeding is completed, the seed crystal is quickly pulled up to make the diameter of the newly crystallized single crystal silicon thinner to remove the dislocation-free seed crystal with surface mechanical damage and complete the necking operation. And after the crystal seeding reaches the target length, the crystal pulling speed is slowed down and the temperature is reduced to make the crystal diameter increase rapidly. By adjusting the coordination of the temperature and the diameter, the shoulder shape is controlled.

[0080] During the equal-diameter growth process, the crystal grows with a constant diameter. During the equal-diameter growth process, the temperature r3 of the silicon liquid is maintained to satisfy: 1420 °C ≤ r3 ≤ 1440 °C, and the protective gas is continuously introduced. The flow rate Q3 of the introduced protective gas satisfies: 50 L / min ≤ Q3 ≤ 150 L / min, the flow rate of the introduced protective gas can be any value within the above range, and a deviation of ±2 L / min is allowed during the introduction process. And the furnace pressure P3 after introducing the protective gas into the single crystal furnace 10 satisfies: 1 Torr ≤ P3 ≤ 16 Torr. At this time, a deviation of ±0.5 Torr is allowed while the furnace pressure in the single crystal furnace satisfies the above range. It is beneficial to reduce the disturbance of the gas flow to the silicon liquid, and at the same time help to further maintain a stable and uniform temperature distribution, which is conducive to improving the quality of single crystal silicon. At the same time, it can also effectively carry away the impurities volatilized from the surface of the silicon liquid through the helically flowing protective gas and improve the purity of the single crystal silicon.

[0081] When the crystal growth is approaching the end, the growth rate increases again. At the same time, the temperature of the silicon melt is raised so that the temperature r4 of the silicon melt in this stage satisfies: 1460 °C ≤ r4 ≤ 1480 °C, causing the crystal diameter to gradually shrink to form a conical shape. Eventually, the crystal leaves the liquid surface, completing the growth of monocrystalline silicon and obtaining the ingot 600. And in this stage, the protective gas is continuously introduced, and the flow rate Q4 of the introduced protective gas satisfies: 50 liters / minute ≤ Q4 ≤ 150 liters / minute. The flow rate of the introduced protective gas can be any value within the above range, and a deviation of ±2 liters / minute is allowed during the introduction process. And the furnace pressure P4 after introducing the protective gas into the single crystal furnace 10 satisfies: 1 Torr ≤ P4 ≤ 16 Torr. A deviation of ±0.5 Torr is allowed while the furnace pressure in the single crystal furnace satisfies the above range.

[0082] In some embodiments, during the isodiametric growth process, the rotation speed r1 of the crucible 200 is controlled to satisfy: 4 revolutions / minute ≤ r1 ≤ 5 revolutions / minute. In this way, while maintaining the stable growth of the crystal, it is beneficial to reduce the convection and fluctuation of the silicon melt, make the surface of the silicon melt more stable, facilitate the uniform growth of the crystal, and reduce the defects and stress inside the crystal. At the same time, by satisfying the above rotation speed, the oxygen content in the silicon melt can be effectively reduced, the solid-liquid interface can be kept stable, and the fluctuation and deformation of the interface can be avoided, thereby improving the uniformity and stability of crystal growth and thus improving the quality of monocrystalline silicon.

[0083] In this application, in addition to the specific structural design of the originally installed deflector 300 and the bottom shell 410 of the thermal insulation housing 400 in the equipment, the flow rate of the protective gas introduced into the furnace cavity of the single crystal furnace 10, the corresponding pressure in the furnace, and the rotation speed of the corresponding crucible 200 will also affect the condition of the spiral gas flow formed by the protective gas on the liquid surface of the crucible 200.

[0084] In some embodiments, as shown in Table 1 below, during the isodiametric growth of crystal pulling, a protective gas with a flow rate of 100 liters per minute is introduced. After introducing the protective gas, the furnace pressure inside the single crystal furnace is 5 Torr, the height of the crucible 200 is 680 mm. As the length of the grown crystal rod 600 increases, adjust the growth setting, the rotation speed of the crucible 200, the rotation speed of the crystal, the power of the bottom heater inside the single crystal furnace 10, the liquid level distance, and the maximum liquid level control to meet Table 1 below. Finally, a crystal rod 600 with a diameter of 300 mm, a head oxygen content of 8.6 ppma, and sectional oxygen contents of 7.4 ppma, 7.2 ppma, and 6.9 ppma respectively is grown. Comparing with the oxygen content of the corresponding crystal rod 600 prepared by the related technology, in the related technology, a protective gas with the same flow rate as in this application is introduced. Referring to Table 1, the related technology also sets the same growth setting, crucible rotation, and crystal rotation as in this application, and the same parameters as in Table 1 below. After introducing the protective gas with the same flow rate, the furnace pressure is 5 Torr. Then, the head oxygen content of the prepared corresponding crystal rod 600 is 10.4 ppma, and the sectional oxygen contents are 8.6 ppma, 7.4 ppma, and 7.6 ppma respectively. It can be seen that the head oxygen content of the crystal rod 600 prepared by this application is reduced by 1.8 ppma, and the single crystal furnace 10 of this application has a significant effect on reducing oxygen.

[0085] As shown in Table 1 below, the growth setting represents the upward pulling speed of the crystal rod 600 during the growth of single crystal silicon. The crucible rotation represents the rotation speed of the crucible 200, and the crystal rotation represents the rotation speed of the crystal rod 600. The rotation directions of the crystal rotation and the crucible rotation are opposite. The gas flow rate represents the flow rate of the introduced protective gas, the furnace pressure represents the pressure inside the single crystal furnace after introducing the protective gas, the power change represents the power of the bottom heater inside the single crystal furnace 10, the liquid level distance represents the distance between the crystal rod 600 and the liquid surface of the silicon liquid, and the maximum liquid level control represents the maximum limit of the liquid level height of the silicon liquid in the crucible 200 inside the crucible 200. Meeting the adjustment data in Table 1 below can obtain a crystal rod 600 with a significantly reduced oxygen content and greatly improve the quality of single crystal silicon.

[0086] Table 1

[0087]

[0088] The single crystal furnace 10 of the present application can optimize the gas flow path of the protective gas, causing the gas flow of the protective gas to generate a vortex, which makes the oxygen reduction effect on the surface of the silicon liquid better and more volatilization on the liquid surface, so as to achieve the purpose of reducing oxygen and increasing production. The protective gas of the present application is in a spiral gas flow, which can form a more complex flow pattern on the liquid surface and produce an effect similar to a vortex. On the one hand, it can make the renewal of the silicon liquid surface more sufficient, expose more of the silicon liquid surface containing oxygen to the gas phase, and is conducive to the volatilization of oxygen in the form of silicon oxide. On the other hand, the spiral gas flow will form a relatively stable gas flow rotation field above the liquid surface, which can more effectively carry away substances such as volatilized silicon oxide from near the liquid surface and reduce the possibility of their re-returning to the silicon liquid, thereby reducing the oxygen content of the ingot 600.

[0089] In addition, the optimization of the gas flow path of the protective gas in the present application is also conducive to making the temperature distribution on the surface of the silicon liquid more uniform. In the related art, the introduced protective gas impinges concentratedly on the surface of the silicon liquid, which may cause a rapid local temperature drop in the impingement area. Because the process of the protective gas carrying away heat is mainly concentrated in the area directly affected by the gas flow, a large temperature gradient will be generated between this area and the surrounding areas. For example, the temperature of the silicon liquid may drop rapidly near the gas flow impingement point, while the temperature change is smaller at a slightly farther place. However, the single crystal furnace 10 of the present application optimizes the gas flow path of the protective gas, and the spiral gas flow makes the heat transfer on the surface of the silicon liquid more uniform. It will not cause a sudden local temperature drop like direct blowing in the related art, but makes the temperature on the surface of the silicon liquid decrease more evenly. Because the spiral gas flow can make the protective gas contact with the silicon liquid in a wider area, the heat can be carried away more evenly, and the temperature distribution on the entire surface of the silicon liquid is relatively smoother.

[0090] In addition, the optimization of the gas flow path of the protective gas in the present application is also conducive to removing impurities on the surface of the silicon liquid. In the related art, the introduced protective gas forms a relatively concentrated gas flow, which can generate a large impact force. If the impurity particles are larger or the adhesion is smaller, the directly blowing gas flow may directly blow the impurities off the surface of the silicon liquid, but for some impurities with stronger adhesion or located in the area with weaker gas flow impact, the removal effect is not good. The spiral gas flow of the protective gas after the gas flow path is optimized in the present application has a wide coverage range and can act on the impurities on the surface of the silicon liquid from multiple angles. Even if the positions of the impurities are relatively scattered or the adhesion is strong, the spiral gas flow is more likely to peel off and carry away the impurities from the surface of the silicon liquid. It can more effectively stir the surface of the silicon liquid, making it easier for the impurities to be involved and carried away by the protective gas.

[0091] That is, the single crystal furnace 10 of the present application can optimize the gas flow path of the protective gas. For example, during the isodiametric growth of crystal pulling in the present application and related technologies, a protective gas with a flow rate of 100 liters per minute is used, and the furnace pressure after introducing the protective gas is controlled to be 6 Torr. Then, the oxygen content at the head of the corresponding crystal rod 600 prepared in the related technology is 10.4 ppma, and the segmented oxygen contents are 8.6 ppma, 7.4 ppma, and 7.6 ppma respectively. For the crystal rod 600 prepared in the present application, the oxygen content at the head is 8.6 ppma, and the segmented oxygen contents are 7.4 ppma, 7.2 ppma, and 6.9 ppma respectively. Obviously, the design of the gas flow of the protective gas in the single crystal furnace 10 of the present application can generate vortices, making the temperature of the silicon liquid surface more uniform, having a better oxygen reduction effect, and a better impurity removal effect.

[0092] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0093] The above-described embodiments only represent several implementation manners of the present application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present application, several modifications and improvements can still be made, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the appended claims.

Claims

1. A single crystal furnace, characterized in that: The single crystal furnace comprises: A furnace body defines a furnace cavity with an opening at the top, wherein the opening is used to introduce a protective gas into the furnace cavity; a crucible, disposed in the furnace chamber and used to contain silicon material; and A guide tube is arranged in the furnace chamber and is located on one side of the crucible along the axial direction of the furnace chamber; the guide tube is provided with a channel penetrating along the axial direction of the furnace chamber, and the protective gas flows toward the crucible through the channel; Among them, a plurality of guide grooves are opened on the inner wall of the channel, and the plurality of guide grooves are arranged at intervals along the circumference of the furnace cavity and arranged in a spiral shape; the extension direction of the guide grooves intersects with the axial direction of the furnace cavity.

2. The single crystal furnace according to claim 1, characterized in that: The guide tube includes a first guide portion, a second guide portion and a third guide portion, which are arranged in sequence along the axis direction of the furnace chamber and away from the crucible; The channel is sequentially arranged to penetrate the first guide portion, the second guide portion and the third guide portion; and the guide groove comprises a first guide groove, a second guide groove and a third guide groove which are connected to each other, the first guide groove is opened on the first guide portion, the second guide groove is opened on the second guide portion, and the third guide groove is opened on the third guide portion; Along the radial direction of the furnace cavity, a size of the first air guide portion is smaller than a size of the second air guide portion, and a size of the second air guide portion is smaller than a size of the third air guide portion.

3. The single crystal furnace according to claim 2, characterized in that: The guide groove is recessed on the inner side wall of the channel, and the recessed depth h of the guide groove satisfies: 5mm≤h≤8mm; the notch width d of the guide groove satisfies: 8mm≤d≤12mm.

4. The single crystal furnace according to claim 2, characterized in that: The guide groove comprises two groove edges which are parallel to each other, and the two groove edges are respectively located on two sides of the groove opening of the guide groove and jointly define the groove opening; The inner side wall of the first guide portion has a first circular edge on a side facing away from the second guide portion, and an included angle a1 between the first circular edge and the groove edge of the guide groove provided in the first guide portion satisfies: 10°≤a1≤50°; A second circular edge is provided at the junction of the inner side wall of the first guide portion and the inner side wall of the second guide portion, and an included angle a2 between the second circular edge and the groove edge of the guide groove provided in the second guide portion satisfies: 10°≤a2≤50°; A third circular edge is provided at a junction of an inner side wall of the third guide portion and an inner side wall of the second guide portion, and an included angle a3 between the third circular edge and the groove edge of the guide groove provided in the third guide portion satisfies: 10°≤a3≤50°.

5. The single crystal furnace according to claim 2, characterized in that: Along the axial direction of the furnace chamber, the radial dimension of the first guide portion remains unchanged, and along the axial direction of the furnace chamber and in the direction away from the crucible, the radial dimensions of the second guide portion and the third guide portion gradually increase; and the radial dimension b1 of the first guide portion satisfies: 300≤b1≤365; the radial dimension b2 of the second guide portion satisfies: 305mm≤b2≤370mm, and the radial dimension b3 of the third guide portion satisfies: 310mm≤b3≤370mm.

6. The single crystal furnace according to claim 2, characterized in that: Along the axial direction of the furnace cavity, the size H of the guide tube satisfies: 165mm≤H≤330mm, the size h1 of the second guide portion satisfies: 150mm≤h1≤300mm, and the size h2 of the third guide portion satisfies: 15mm≤h2≤30mm.

7. The single crystal furnace according to claim 1, characterized in that: The single crystal furnace further comprises a heat-insulating cover shell, which is arranged around the central axis of the furnace chamber and is arranged around the outer side of the guide cylinder; The heat-insulating cover shell and the guide tube jointly define a heat-insulating cavity, and the heat-insulating cavity is filled with heat-insulating material.

8. The single crystal furnace according to claim 7, characterized in that: The heat-insulating cover shell includes a bottom shell and a side shell, the bottom shell is connected between the side shell and the guide tube, the outer side surface of the bottom shell is arranged toward the crucible opening of the crucible, and the angle k between the outer side surface of the bottom shell and the axial direction of the furnace chamber satisfies: 60°≤k≤82°.

9. A crystal pulling process, characterized in that: A single crystal furnace according to any one of claims 1 to 8 is used to pull crystals, wherein the crystal pulling process comprises: Adding silicon material into a crucible, and placing the crucible into a furnace body of a single crystal furnace; A protective gas is introduced into the single crystal furnace, wherein a flow rate Q of the protective gas satisfies: 80 liters / minute ≤ Q ≤ 120 liters / minute, and a furnace pressure P after the protective gas is introduced into the single crystal furnace satisfies: 4 Torr ≤ P ≤ 6 Torr; Heating the crucible to fully melt the silicon material in the crucible to form silicon liquid; The seed crystal is immersed in silicon liquid, and seeding, shouldering and equal-diameter growth are carried out in sequence to obtain single crystal silicon.

10. The crystal pulling process according to claim 9, characterized in that: During the isodiameter growth process, the rotation speed r1 of the crucible is controlled to satisfy: 4 rpm≤r1≤5 rpm.

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