Single crystal furnace and monocrystalline silicon preparation method

Abstract

The invention relates to a single crystal furnace and a monocrystalline silicon preparation method, the single crystal furnace comprises a furnace body, a crucible, a first thermal insulation cylinder, a second thermal insulation cylinder and a main heater, one side of the bottom of the furnace body is provided with an exhaust hole; the crucible is arranged in the furnace body; the first heat preservation cylinder is located on the outer side of the crucible and wraps one side of the bottom of the crucible, the second heat preservation cylinder is arranged on the outer side of the first heat preservation cylinder at intervals, an airflow channel is formed between the second heat preservation cylinder and the first heat preservation cylinder, and the airflow channel communicates with the open end of the crucible and the exhaust hole; the main heater comprises a foot plate and a heating piece connected with the foot plate, the foot plate is arranged between the first heat preservation cylinder and the second heat preservation cylinder, and the heating piece extends out of the first heat preservation cylinder and covers one side of the top of the crucible. According to the single crystal furnace provided by the invention, the temperature uniformity of the crucible in the longitudinal direction is ensured, the disordered convection of the silicon melt in the crucible is weakened, the deposition of oxides on the growth liquid level of the silicon melt in the crucible and other thermal fields is reduced, and the oxygen content is reduced, so that the quality of a monocrystalline silicon crystal bar is improved.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal silicon manufacturing, and in particular to a single crystal furnace and a single crystal silicon preparation method. Background Art

[0002] With the continuous development of the world economy, the demand for efficient and clean energy in modernization construction is growing. Photovoltaic power generation, as a green energy and a major energy source for sustainable development of mankind, is increasingly valued and developed by countries around the world. Monocrystalline silicon, as a basic material for photovoltaic power generation, has a wide market demand.

[0003] At present, the Czochralski method is often used to grow single crystal silicon in a single crystal furnace. The single crystal furnace is a device that uses a heater to melt polycrystalline materials such as polycrystalline silicon in an inert gas (mainly argon) environment and grows single crystals without dislocation by the Czochralski method. In the existing single crystal silicon pulling process, silicon raw materials are put into the crucible, and single crystal silicon is grown by the reaction of silicon raw materials and quartz crucible. However, the convection phenomenon of silicon liquid inside the crucible is serious, resulting in a high oxygen content inside the single crystal silicon rod, which affects the quality of the single crystal silicon rod and is not conducive to improving the efficiency of solar cells. Summary of the invention

[0004] Based on this, it is necessary to provide a single crystal furnace and a single crystal silicon preparation method to address the serious problem of silicon liquid object phenomenon inside the crucible during the existing single crystal silicon growth process.

[0005] A single crystal furnace, comprising:

[0006] A furnace body, wherein one side of the bottom of the furnace body is provided with an exhaust hole;

[0007] A crucible, wherein the crucible is arranged inside the furnace body;

[0008] a first heat-insulating tube and a second heat-insulating tube, wherein the first heat-insulating tube is located outside the crucible and covers one side of the bottom of the crucible, and the second heat-insulating tube is spaced outside the first heat-insulating tube and an air flow channel is formed between the second heat-insulating tube and the first heat-insulating tube, wherein the air flow channel connects the open end of the crucible and the exhaust hole; and

[0009] The main heater includes a foot plate and a heating element connected to the foot plate, the foot plate is arranged between the first insulation tube and the second insulation tube, the heating element extends to the outside of the first insulation tube and is covered on one side of the top of the crucible.

[0010] In one embodiment, the gap between the first heat-insulating cylinder and the second heat-insulating cylinder is d1, wherein: 35mm≤d1≤45mm.

[0011] In one of the embodiments, in the longitudinal direction of the crucible, the height of the first heat-insulating cylinder is h1, and the height of the crucible is h2, wherein: 1 / 2≤h1 / h2≤2 / 3.

[0012] In one of the embodiments, the single crystal furnace further includes a thermal insulation layer, which is disposed on one side of the bottom of the furnace body and between the crucible and the furnace body.

[0013] In one embodiment, the thermal insulation layer includes a first thermal insulation layer and a second thermal insulation layer, the first thermal insulation layer and the second thermal insulation layer are spaced apart, and an air outlet channel is formed between the first thermal insulation layer and the second thermal insulation layer, and two ends of the air outlet channel are respectively connected to the airflow channel and the exhaust hole.

[0014] In one embodiment, the gap between the first thermal insulation layer and the second thermal insulation layer is d2, wherein: 55mm≤d2≤65mm.

[0015] In one embodiment, the single crystal furnace also includes a guide tube, a third insulation tube and a fourth insulation tube. The guide tube is arranged on the side of the furnace body close to the opening end of the crucible, the third insulation tube cover is arranged on the outside of the guide tube, the fourth insulation tube connects the third insulation tube and the first insulation tube, and the cover is arranged on the outside of the transition area between the guide tube and the opening end of the crucible, and the orthographic projection of the fourth insulation tube on the bottom plane of the furnace body is located on the inner side of the orthographic projection of the first insulation tube on the bottom plane of the furnace body.

[0016] A method for preparing single crystal silicon, wherein the single crystal silicon is prepared by using the single crystal furnace described in any one of the above technical solutions, and the method for preparing single crystal silicon comprises:

[0017] In the melting stage, silicon raw materials are put into the crucible, protective gas is introduced and the silicon raw materials are heated and melted to obtain silicon melt;

[0018] The seed crystal is immersed in silicon melt, and seeding, shouldering and equal diameter growth are performed in sequence to obtain the single crystal silicon;

[0019] Among them, in the melting stage, the crucible is stationary, and in the seeding, shouldering and equal diameter processes, the crucible and the single crystal silicon rod rotate synchronously and the rotation speed gradually increases, and in the melting, seeding, shouldering and equal diameter processes, the amount of protective gas introduced gradually increases, and the thermal field power and furnace pressure inside the crucible gradually decrease.

[0020] In one embodiment, in the melting stage, the heat field power inside the crucible is 85kw~105kw, the flow rate of the protective gas is 140slpm~160slpm, and the furnace pressure inside the crucible is 7.6ttor~8.5ttor;

[0021] In the seeding stage, the heat field power inside the crucible is 56kw~58kw, the protective gas flow rate is 160slpm~175slpm, the furnace pressure inside the crucible is 6.6ttor~7.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 5.6rpm~6.5rpm;

[0022] In the shoulder release stage, the heat field power inside the crucible is 54kw~56kw, the protective gas flow rate is 175slpm~185slpm, the furnace pressure inside the crucible is 5.6ttor~6.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 6.6rpm~7.5rpm;

[0023] In the equal diameter stage, the thermal field power inside the crucible is 48kw~54kw, the protective gas flow rate is 185slpm~195slpm, the furnace pressure inside the crucible is 2.6ttor~4.5ttor, and the rotation speed of the crucible and the single crystal silicon rod is 8.6rpm~10.5rpm.

[0024] In one of the embodiments, in the equal diameter stage, the equal diameter process is drawn in the 0-500 mm stage, the internal heat field power of the crucible is 52.6 kW-54 kW, the flow rate of the protective gas is 185 slpm-188 slpm, the internal furnace pressure of the crucible is 3.6 ttor-4.5 ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6 rpm-9.2 rpm;

[0025] In the equal diameter process of drawing 500mm~1500mm, the heat field power inside the crucible is 51.6kw~52.5kw, the flow rate of the protective gas is 188slpm~195slpm, the furnace pressure inside the crucible is 3.6ttor~4.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6rpm~9.6rpm;

[0026] In the equal diameter process of drawing 1500mm~2000mm, the heat field power inside the crucible is 50.6kw~51.5kw, the flow rate of the protective gas is 188slpm~195slpm, the furnace pressure inside the crucible is 3.2ttor~3.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6rpm~9.6rpm;

[0027] After drawing 2000mm in the equal diameter process, the thermal field power inside the crucible is 48kw~50.5kw, the protective gas flow rate is 188slpm~195slpm, the furnace pressure inside the crucible is 2.6ttor~3.1ttor, and the rotation speed of the crucible and the single crystal silicon rod is 9.7rpm~10.5rpm.

[0028] In the above-mentioned single crystal furnace and single crystal silicon preparation method, the first insulation tube and the second insulation tube are arranged on the outside of the crucible, which has a good insulation effect. The crucible and the external environment are isolated by the first insulation tube and the second insulation tube to prevent the heat inside the crucible from radiating to the external environment, thereby reducing the power consumption of the single crystal furnace and preventing the crucible from having a more serious heat exchange with the external environment, thereby ensuring the temperature uniformity in the longitudinal direction of the crucible; and the heating element cover is arranged on one side of the top of the crucible, so that the top side of the crucible is in the high temperature zone, the bottom side of the crucible is in the low temperature zone, and the top side of the crucible is in the low temperature zone. Compared with the bottom side of the crucible, the reaction between the silicon raw material and the quartz crucible is more intense, which can guide the molten silicon inside the crucible to convect from the top side to the bottom side, thereby reducing the disordered convection phenomenon of the molten silicon inside the crucible. Since the first insulation tube is coated on the bottom side of the crucible, the heat loss on the bottom side of the crucible can be prevented, thereby further ensuring the temperature uniformity in the longitudinal direction of the crucible. In addition, since part of the heat of the heating element will be transferred to the foot plate, the foot plate is arranged between the first insulation tube and the second insulation tube to avoid the residual heat of the foot plate from interfering with the thermal field environment inside the crucible. The single crystal furnace provided in the present application ensures the temperature uniformity of the crucible in the longitudinal direction, and guides the molten silicon inside the crucible to convect from the top side to the bottom side, thereby reducing the disordered convection of the molten silicon inside the crucible, reducing the deposition of oxides on the growth liquid surface of the molten silicon in the crucible and other thermal fields, reducing the pollution of the molten silicon by oxides, and reducing the oxygen content to improve the quality of single crystal silicon ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] FIG. 1 is a front view of a single crystal furnace provided in some embodiments.

[0030] FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1 .

[0031] FIG. 3 is a schematic diagram of the flow of protective gas in a single crystal furnace.

[0032] FIG. 4 is a schematic flow chart of a method for preparing single crystal silicon provided in some embodiments.

[0033] Reference numerals:

[0034] 100. Single crystal furnace;

[0035] 110, furnace body; 111, exhaust hole; 120, crucible; 130, first insulation tube; 140, second insulation tube; 150, air flow channel; 160, main heater; 161, foot plate; 162, heating element; 163, electrode column; 170, insulation layer; 171, first insulation layer; 172, second insulation layer; 173, air outlet channel; 180, guide tube; 181, third insulation tube; 182, fourth insulation tube. DETAILED DESCRIPTION

[0036] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth 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 violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0037] In the description of the present application, it should be understood that if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. appear, the orientation or position relationship indicated by these terms is based on the orientation or position relationship shown in the accompanying drawings, which is only for the convenience of describing the present application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application.

[0038] In addition, if the terms "first" or "second" appear, these terms are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of this application, if the term "plurality" appears, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0039] In this application, unless otherwise clearly specified and limited, if the terms "installed", "connected", "connected", "fixed" and the like appear, these terms should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0040] In the present application, unless otherwise clearly specified and limited, if there is a description that a first feature is "above" or "below" a second feature, etc., or similar descriptions appear, it may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature being "above", "above" and "above" the second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. The first feature being "below", "below" and "below" the second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0041] It should be noted that if an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. If an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. If any, the terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used in this application are for illustrative purposes only and do not represent the only implementation method.

[0042] The technical solution provided by the embodiments of the present application is described below in conjunction with the accompanying drawings.

[0043] At present, single crystal silicon is usually grown by the Czochralski method in a single crystal furnace, where the single crystal furnace is a device that uses a heating device to melt silicon raw materials in an inert gas (mainly argon) environment and grows dislocation-free single crystals by the Czochralski method. In the existing single crystal silicon pulling process, the silicon raw materials are put into the crucible, and the single crystal silicon is grown by the reaction of the silicon raw materials and the quartz crucible. However, the convection phenomenon of the silicon liquid inside the crucible is serious, resulting in a high oxygen content inside the single crystal silicon rod. Oxygen, as the impurity with the highest content in single crystal silicon, easily induces the generation of secondary defects such as lattice dislocations, stacking faults and battery concentric circles, resulting in the general quality of the single crystal silicon rod, which is not conducive to improving the efficiency of solar cells.

[0044] Based on this, referring to FIG. 1 and FIG. 2 , the present application provides a single crystal furnace 100, which includes a furnace body 110, a crucible 120, a first heat preservation tube 130, a second heat preservation tube 140 and a main heater 160. The single crystal furnace 100 is used for pulling a single crystal silicon ingot. An exhaust hole 111 is provided at one side of the bottom of the furnace body 110, and the crucible 120 is arranged inside the furnace body 110.

[0045] The first heat-insulating cylinder 130 is located outside the crucible 120, and the first heat-insulating cylinder 130 covers one side of the bottom of the crucible 120. Exemplarily, the open end of the crucible 120 is the top side of the crucible 120, and the side away from the open end of the crucible 120 is the bottom side of the crucible 120. The first heat-insulating cylinder 130 is adapted to the shape of the crucible 120, and in the longitudinal direction of the crucible 120, the height of the first heat-insulating cylinder 130 is less than the height of the crucible 120. The second heat-insulating cylinder 140 is arranged at intervals outside the first heat-insulating cylinder 130, and an airflow channel 150 is formed between the second heat-insulating cylinder 140 and the first heat-insulating cylinder 130, and the airflow channel 150 connects the open end of the crucible 120 and the exhaust hole 111. In this way, the protective gas can be guided from the crucible 120 to the exhaust hole 111 to the outside through the air flow channel 150. The protective gas can flow out of the crucible 120 in an orderly manner along the directions a and a' shown in Figure 3 in the air flow channel 150, thereby avoiding the undesirable phenomenon of turbulence of the protective gas during the flow process, and the protective gas will not take away too much heat from the crucible 120 during the outflow process, thereby ensuring that the single crystal silicon rod inside the crucible 120 has a better growth environment. In addition, the first insulation tube 130 and the second insulation tube 140 are arranged on the outside of the crucible 120, which has a good insulation effect. The crucible 120 is isolated from the external environment by the first insulation tube 130 and the second insulation tube 140, so as to avoid the heat inside the crucible 120 from radiating to the external environment, reduce the power consumption of the single crystal furnace 100, and prevent the crucible 120 from having a more serious heat exchange with the external environment, thereby ensuring the temperature uniformity in the longitudinal direction of the crucible 120, reducing the convection of the silicon melt inside the crucible 120, reducing the deposition of oxides on the growth liquid surface of the silicon melt in the crucible 120 and other thermal fields, reducing the contamination of the molten silicon melt by oxides, and reducing the oxygen content to improve the quality of single crystal silicon rods.

[0046] The main heater 160 includes a foot plate 161 and a heating element 162, and the foot plate 161 is connected to the heating element 162. For example, one end of the foot plate 161 is connected to an electrode column 163, and the other end of the foot plate 161 is connected to the heating element 162. The foot plate 161 is energized through the electrode column 163, and the foot plate 161 conducts the heating element 162, so that the heating element 162 generates heat and provides a thermal field environment for the crucible 120. The foot plate 161 is arranged between the first heat preservation tube 130 and the second heat preservation tube 140, and the heating element 162 extends to the outside of the first heat preservation tube 130, and the heating element 162 is covered on one side of the top of the crucible 120. Among them, the connection between the foot plate 161 and the heating element 162 has a bending structure to avoid the setting of the foot plate 161, so as to avoid the interference of the first heat preservation tube 130 on the setting of the main heater 160, and the heating element 162 extends to the outside of the first heat preservation tube 130, so as to avoid the first heat preservation tube 130 from isolating the heat supplied by the heating element 162 to the crucible 120. In this way, the heating element 162 is covered on the top side of the crucible 120, so that the top side of the crucible 120 is in the high temperature zone, and the bottom side of the crucible 120 is in the low temperature zone. Compared with the bottom side of the crucible 120, the reaction between the silicon raw material and the quartz crucible is more intense on the top side of the crucible 120, which can guide the silicon melt inside the crucible 120 to convect from the top side to the bottom side, and reduce the disordered convection phenomenon of the silicon melt inside the crucible 120. Since the first heat preservation tube 130 is coated on the bottom side of the crucible 120, the heat loss on the bottom side of the crucible 120 can be prevented, and the temperature uniformity in the longitudinal direction of the crucible 120 can be further ensured. In addition, since part of the heat from the heating element 162 is transferred to the foot plate 161 , the foot plate 161 is disposed between the first heat preservation tube 130 and the second heat preservation tube 140 to prevent the residual heat of the foot plate 161 from interfering with the internal thermal environment of the crucible 120 .

[0047] The above-mentioned single crystal furnace 100 ensures the temperature uniformity of the crucible 120 in the longitudinal direction and guides the molten silicon inside the crucible 120 to convect from the top side to the bottom side, thereby weakening the disordered convection of the molten silicon inside the crucible 120, reducing the deposition of oxides on the growth liquid surface of the molten silicon in the crucible 120 and other thermal fields, reducing the contamination of the molten silicon by oxides, and reducing the oxygen content to improve the quality of single crystal silicon rods.

[0048] In one embodiment, referring to FIG. 1 to FIG. 3 , the gap between the first heat-insulating tube 130 and the second heat-insulating tube 140 is d1, wherein 35 mm ≤ d1 ≤ 45 mm. Thus, the radial width of the airflow channel 150 is set to 35 mm to 45 mm in the direction perpendicular to the flow of the protective gas, which can ensure that the protective gas flows out to the outside in an orderly manner through the airflow channel 150, and can also avoid the airflow channel 150 being too wide, resulting in the undesirable phenomenon of turbulence of the protective gas in the airflow channel 150.

[0049] In specific settings, the gap d1 between the first heat-insulating tube 130 and the second heat-insulating tube 140 can be any one of 35 mm, 38 mm, 40 mm, 42 mm, and 45 mm. Of course, in other feasible embodiments, the gap d1 between the first heat-insulating tube 130 and the second heat-insulating tube 140 can also be other values ​​within the range of 35 mm to 45 mm. The specific value of the gap d1 between the first heat-insulating tube 130 and the second heat-insulating tube 140 is not limited by this application.

[0050] Further, referring to FIGS. 1 to 3 , in the longitudinal direction of the crucible 120, the height of the first heat-insulating cylinder 130 is h1, and the height of the crucible 120 is h2, wherein 1 / 2≤h1 / h2≤2 / 3. In specific settings, the ratio of h1 / h2 can be any one of 1 / 2, 8 / 15, 17 / 30, 3 / 5, 19 / 30, and 2 / 3. Of course, in other feasible embodiments, the ratio of h1 / h2 can also be other values ​​within the range of 1 / 2 to 2 / 3, and the specific value of the ratio of h1 / h2 is not limited by this application.

[0051] In this way, the ratio of the height h1 of the first insulation cylinder 130 to the height h2 of the crucible 120 is limited to between 1 / 2 and 2 / 3. When the first insulation cylinder 130 is covered on the outside of the crucible 120, the first insulation cylinder 130 only covers one side of the bottom of the crucible 120 to avoid heat loss on one side of the bottom of the crucible 120 during the pulling process of single crystal silicon, so as to ensure the temperature uniformity in the longitudinal direction of the crucible 120, weaken the disordered convection of the silicon melt inside the crucible 120, reduce the deposition of oxides on the growth liquid surface of the silicon melt in the crucible 120 and other thermal fields, reduce the contamination of the molten silicon melt by oxides, and reduce the oxygen content to improve the quality of single crystal silicon rods. Moreover, in the present embodiment, the second insulation cylinder 140 is covered on the outside of the crucible 120. For example, in the longitudinal direction of the crucible 120, the height of the second insulation cylinder 140 is the same as the height of the crucible 120, so as to isolate the crucible 120 from the external environment, avoid the internal heat of the crucible 120 from radiating to the external environment, reduce the power consumption of the single crystal furnace 100, and prevent the crucible 120 from having a more serious heat exchange with the external environment, thereby ensuring the temperature uniformity of the crucible 120 in the longitudinal direction.

[0052] Typically, the crucible 120 includes a pot clasp and a pot support. Due to installation or production process limitations, there may be a gap at the connection between the pot clasp and the pot support, causing the molten silicon inside the crucible 120 to easily seep from the gap between the pot clasp and the pot support to the outside. Since the temperature of the molten silicon is relatively high, the molten silicon that seeps to the outside can easily burn through the protective plate and even cause an explosion. Based on this, in one embodiment, referring to Figures 1 to 3, the single crystal furnace 100 also includes a thermal insulation layer 170, which is arranged on one side of the bottom of the furnace body 110, and the thermal insulation layer 170 is located between the crucible 120 and the furnace body 110. On the one hand, the thermal insulation layer 170 cooperates with the first thermal insulation tube 130 and the second thermal insulation tube 140 to improve the thermal insulation effect of the crucible 120. On the other hand, since the thermal insulation layer 170 is arranged on one side of the bottom of the furnace body 110, the molten silicon melt flowing inside the crucible 120 can drip onto the thermal insulation layer 170 under the action of gravity. The thermal insulation layer 170 receives the molten silicon melt flowing to the outside, thereby preventing the molten silicon melt from directly dripping onto the protective plate and scalding the furnace body 110, thereby improving the safety of the single crystal furnace 100.

[0053] In one embodiment, referring to FIG. 1 and FIG. 2 , the thermal insulation layer 170 includes a first thermal insulation layer 171 and a second thermal insulation layer 172. The first thermal insulation layer 171 and the second thermal insulation layer 172 are arranged at intervals, and an outlet passage 173 is formed between the first thermal insulation layer 171 and the second thermal insulation layer 172, and both ends of the outlet passage 173 are respectively connected to the air flow passage 150 and the exhaust hole 111. In this way, the outlet passage 173 is formed between the first thermal insulation layer 171 and the second thermal insulation layer 172, and while the crucible 120 is kept warm, the first thermal insulation layer 171 and the second thermal insulation layer 172 will not interfere with the outflow of the protective gas. When the protective gas needs to be discharged from the inside of the crucible 120 to the external environment, the protective gas is discharged to the outside through the air flow channel 150, the gas outlet channel 173 and the exhaust hole 111 in sequence, so that the protective gas flows out in an orderly manner. For example, the protective gas flows out to the external environment along the directions a and a' shown in Figure 3. The protective gas will not take away too much heat from the crucible 120 during the outflow process, thereby ensuring that the single crystal silicon rod inside the crucible 120 has a better growth environment.

[0054] Specifically, referring to FIGS. 1 to 3 , the gap between the first insulation layer 171 and the second insulation layer 172 is d2, wherein: 55 mm ≤ d2 ≤ 65 mm. Thus, along the direction perpendicular to the flow of the protective gas, the radial width of the gas outlet channel 173 is set to 55 mm to 65 mm, which can ensure that the protective gas flows out to the outside in an orderly manner through the gas outlet channel 173, and can also avoid the gas outlet channel 173 being too wide, resulting in turbulence of the protective gas in the gas outlet channel 173.

[0055] In specific settings, the gap d2 between the first thermal insulation layer 171 and the second thermal insulation layer 172 can be any one of 55 mm, 58 mm, 60 mm, 62 mm, and 65 mm. Of course, in other feasible embodiments, the gap d2 between the first thermal insulation layer 171 and the second thermal insulation layer 172 can also be other values ​​within the range of 55 mm to 65 mm. The specific value of the gap d2 between the first thermal insulation layer 171 and the second thermal insulation layer 172 is not limited by this application.

[0056] Further, referring to FIG. 1 and FIG. 2 , the first insulation layer 171 is located on the side close to the crucible 120, and the first insulation layer 171 has rigidity, such as the material of the first insulation layer 171 may include solidified hard felt, graphite or carbon-carbon. In this way, on the one hand, since the first insulation layer 171 is located on the side close to the crucible 120, the first insulation layer 171 can provide a good support for the crucible 120, and on the other hand, the first insulation layer 171 enables the crucible 120 to have a good insulation effect, and can receive part of the molten silicon melt that infiltrates to the outside. The second insulation layer 172 is located on the side away from the crucible 120, so as to be spaced from the first insulation layer 171 to form an outlet channel 173 for the protective gas to flow out. The second insulation layer 172 has flexibility, such as the material of the second insulation layer 172 may include silicon carbide soft felt or carbon fiber soft felt. In this way, since the flexible second insulation layer 172 has a good liquid absorption function, the second insulation layer 172 can receive more molten silicon melt that seeps to the outside, preventing the molten silicon melt from directly dripping onto the protective plate and scalding the furnace body 110, thereby improving the safety of the single crystal furnace 100.

[0057] In one embodiment, referring to FIGS. 1 to 3 , the single crystal furnace 100 further includes a guide tube 180, a third insulation tube 181 and a fourth insulation tube 182. The guide tube 180 is disposed on one side of the furnace body 110 close to the opening end of the crucible 120, and the gas outlet end of the guide tube 180 faces the crucible 120. The protective gas can enter the upper part of the crucible 120 through the guide tube 180 to avoid excessive turbulence in the protective gas flow entering the upper part of the crucible 120. The third insulation tube 181 is disposed on the outside of the guide tube 180 to insulate the protective gas entering the upper part of the crucible 120, to avoid the supercooled protective gas directly contacting the molten silicon melt inside the crucible 120 and affecting the growth of the crystal rod. The fourth insulation tube 182 connects the third insulation tube 181 and the first insulation tube 130, and the fourth insulation tube 182 is covered on the outside of the transition area between the guide tube 180 and the open end of the crucible 120 to ensure that the overall temperature of the protective gas is constant during the flow process, thereby avoiding the protective gas temperature change from contacting the molten silicon melt and affecting the growth of the single crystal silicon rod.

[0058] Moreover, the orthographic projection of the fourth insulation tube 182 on the bottom plane of the furnace body 110 is located on the inner side of the orthographic projection of the first insulation tube 130 on the bottom plane of the furnace body 110, that is, the fourth insulation tube 182 is recessed toward the side close to the crucible 120, thereby reducing the installation space of the fourth insulation tube 182. Moreover, since the fourth insulation tube 182 is close to the crucible 120, the insulation effect of the crucible 120 can be improved.

[0059] In addition, referring to FIGS. 1 to 4 , the present application also provides a method for preparing single crystal silicon. The single crystal silicon is prepared by using the single crystal furnace 100 of the above technical solution. The single crystal furnace 100 includes a furnace body 110 and a crucible 120. The crucible 120 is arranged inside the furnace body 110. The method for preparing single crystal silicon includes the following steps:

[0060] Step S110: In the melting stage, the silicon raw material is put into the crucible 120, a protective gas is introduced, and the silicon raw material is heated to melt to obtain a silicon melt. In this way, in the melting stage of the silicon raw material, a protective gas is continuously introduced into the crucible 120 to protect the silicon raw material from being oxidized in the melting stage. Among them, the protective gas can be one or more of inert gases such as helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe). The specific type of the protective gas is not limited in this application.

[0061] Step S120: The seed crystal is immersed in silicon melt, and seeding, shouldering and equal diameter growth are performed in sequence to obtain single crystal silicon. In the seeding stage, the temperature between the silicon melt and the seed crystal is balanced to guide the growth of the single crystal silicon crystal; in the shouldering stage, the single crystal silicon crystal is gradually grown to the required diameter; in the equal diameter growth stage, the single crystal silicon crystal is gradually grown to the required length; after the above series of stages, the required single crystal silicon can be obtained.

[0062] In the melting stage, the crucible 120 is stationary, which facilitates the feeding of silicon raw materials into the crucible 120. During the seeding, shouldering and equal diameter processes, the crucible 120 rotates synchronously with the single crystal silicon ingot and the rotation speed gradually increases. During the melting, seeding, shouldering and equal diameter processes, the amount of protective gas introduced gradually increases, and the thermal field power and furnace pressure inside the crucible 120 gradually decrease.

[0063] In the above-mentioned method for preparing single crystal silicon, the silicon raw material can obtain single crystal silicon through melting, seeding, shouldering and equal diameter growth in the single crystal furnace 100. In the process of preparing single crystal silicon, by gradually increasing the crucible rotation speed of the crucible 120, the molten silicon melt can be fully stirred, so that the impurities in the silicon melt are more evenly distributed, and increasing the crucible rotation speed of the crucible 120 can reduce the temperature gradient of the internal thermal field of the crucible 120 and increase the survival rate of seeding. Since the temperature uniformity of the internal thermal field of the crucible 120 is better, the convection phenomenon of the silicon melt in the crucible 120 is weakened, and oxygen impurities are not easy to gather on the growth liquid surface of the silicon melt, thereby reducing the oxygen content in the single crystal silicon ingot and improving the quality of the single crystal silicon ingot. In the process of preparing single crystal silicon, by gradually increasing the amount of protective gas introduced and reducing the furnace pressure inside the crucible 120, more oxides can be carried during the outflow of protective gas and the pumping process, reducing the deposition of oxides on the growth liquid surface of the silicon melt in the crucible 120 and other thermal fields, reducing the pollution of the molten silicon melt by oxides, and reducing the oxygen content to improve the quality of single crystal silicon ingots. In the process of preparing single crystal silicon, the power of the thermal field inside the crucible 120 is gradually reduced to avoid the influence of the melting seed crystal on the growth of the crystal ingot and improve the yield rate of the crystal ingot.

[0064] Specifically, referring to FIGS. 1 to 4 , in the melting stage, the thermal field power inside the crucible 120 is 85 kW to 105 kW, the flow rate of the protective gas is 140 slpm to 160 slpm, and the furnace pressure inside the crucible 120 is 7.6 ttor to 8.5 ttor. Among them, in the specific setting, in the melting stage, the internal thermal field power of the crucible 120 can be any one of 85kw, 87kw, 90kw, 92kw, 95kw, 97kw, 100kw, 102kw, and 105kw, the protective gas flow rate is any one of 140slpm, 142slpm, 145slpm, 147slpm, 150slpm, 152slpm, 155slpm, 157slpm, and 160slpm, and the internal furnace pressure of the crucible 120 is any one of 7.6ttor, 7.8ttor, 8.0ttor, 8.2ttor, 8.4ttor, and 8.5ttor. Of course, during the melting stage, the thermal field power inside the crucible 120, the protective gas flow rate and the furnace pressure inside the crucible 120 are not limited to the specific values ​​provided above. For example, the thermal field power inside the crucible 120 can also be other values ​​within the range of 85kw~105kw, the protective gas flow rate can also be other values ​​within the range of 140slpm~160slpm, and the furnace pressure inside the crucible 120 can also be other values ​​within the range of 7.6ttor~8.5ttor.

[0065] Moreover, in the seeding stage, the thermal field power inside the crucible 120 is 56kw~58kw, the protective gas flow rate is 160slpm~175slpm, the furnace pressure inside the crucible 120 is 6.6ttor~7.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon ingot is 5.6rpm~6.5rpm. Among them, in the specific setting, in the crystal induction stage, the internal thermal field power of the crucible 120 can be any one of 56kw, 56.5kw, 57kw, 57.5kw, and 58kw, the protective gas flow rate is any one of 160slpm, 162slpm, 165slpm, 167slpm, 170slpm, 172slpm, and 175slpm, the internal furnace pressure of the crucible 120 is any one of 6.6ttor, 6.8ttor, 7.0ttor, 7.2ttor, and 7.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 5.6rpm, 5.8rpm, 6.0rpm, 6.2rpm, 6.4rpm, and 6.5rpm. Of course, in the crystal induction stage, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speeds of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 56kw~58kw, the protective gas flow rate can also be other values ​​within the range of 160slpm~175slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 6.6ttor~7.5ttor, and the rotation speeds of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 5.6rpm~6.5rpm.

[0066] Continuing, in the shoulder release stage, the internal thermal field power of the crucible 120 is 54kw~56kw, the protective gas flow rate is 175slpm~185slpm, the internal furnace pressure of the crucible 120 is 5.6ttor~6.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon ingot is 6.6rpm~7.5rpm. Among them, in the specific setting, in the shoulder release stage, the internal thermal field power of the crucible 120 can be any one of 54kw, 54.5kw, 55kw, 55.5kw, and 56kw, the protective gas flow rate is any one of 175slpm, 177slpm, 180slpm, 182slpm, and 185slpm, the internal furnace pressure of the crucible 120 is any one of 5.6ttor, 5.8ttor, 6.0ttor, 6.2ttor, and 6.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 6.6rpm, 6.8rpm, 7.0rpm, 7.2rpm, 7.4rpm, and 7.5rpm. Of course, during the shoulder release stage, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speeds of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 54kw~56kw, the protective gas flow rate can also be other values ​​within the range of 175slpm~185slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 5.6ttor~6.5ttor, and the rotation speeds of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 6.6rpm~7.5rpm.

[0067] Finally, in the equal diameter stage, the thermal field power inside the crucible 120 is 48kw~54kw, the protective gas flow rate is 185slpm~195slpm, the furnace pressure inside the crucible 120 is 2.6ttor~4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is 8.6rpm~10.5rpm. Among them, in the specific setting, in the equal diameter stage, the internal thermal field power of the crucible 120 can be any one of 48kw, 49kw, 50kw, 51kw, 52kw, 53kw, and 54kw, the protective gas flow rate is any one of 185slpm, 187slpm, 190slpm, 192slpm, and 195slpm, the internal furnace pressure of the crucible 120 is any one of 2.6ttor, 3.0ttor, 3.4ttor, 3.8ttor, 4.2ttor, and 4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 8.6rpm, 9.0rpm, 9.4rpm, 9.8rpm, 10rpm, 10.2rpm, and 10.5rpm. Of course, in the equal diameter stage, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speeds of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 48kw~54kw, the protective gas flow rate can also be other values ​​within the range of 185slpm~195slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 2.6ttor~4.5ttor, and the rotation speeds of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 8.6rpm~10.5rpm.

[0068] In the above-mentioned single crystal silicon preparation method, during the melting stage, the internal thermal field power of the crucible 120 is set to be relatively large, which can accelerate the melting rate of the silicon raw material. Since the growth of the single crystal silicon rod has not yet been carried out at this time, the amount of protective gas introduced is set to be relatively small, and the furnace pressure is set to be relatively large. On the basis of protecting the silicon raw material from oxidation, the power consumption of the single crystal furnace 100 is reduced. During the seeding, shouldering and equal diameter stages, the power of the internal thermal field of the crucible 120 is set to a relatively small value to prevent the melting of the seed crystal from affecting the growth of the crystal rod and to improve the yield rate of the crystal rod. Since the single crystal silicon rod has begun to grow, the amount of protective gas introduced is set to a relatively large value, and the furnace pressure is set to a relatively small value, so that more oxides can be entrained to the outside of the crucible 120 during the outflow of the protective gas and the pumping process, thereby reducing the deposition of oxides on the growth liquid surface of the silicon melt in the crucible 120 and other thermal fields and reducing the pollution of the molten silicon melt by oxides, thereby reducing the oxygen content and improving the quality of the single crystal silicon rod. In addition, the crucible rotation speed of the crucible 120 and the rotation speed of the single crystal silicon rod are gradually increased to fully stir the molten silicon melt, so that the impurity distribution in the silicon melt is more uniform, and the temperature gradient of the thermal field of the crucible 120 is reduced, the seeding survival rate is increased, the convection of the silicon melt inside the crucible 120 is reduced, the oxygen content in the single crystal silicon rod is reduced, the quality of the single crystal silicon rod is improved, and the growth rate of the single crystal silicon rod is accelerated. The single crystal silicon preparation method provided in the present application can improve the quality and yield of single crystal silicon ingots by reasonably controlling the parameters of the melt, seeding, shoulder release and equal diameter stages.

[0069] Further, referring to Figures 1-4, in the equal diameter process of pulling 0~500mm stage, the internal thermal field power of the crucible 120 is 52.6kw~54kw, the protective gas flow rate is 185slpm~188slpm, the internal furnace pressure of the crucible 120 is 3.6ttor~4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is 8.6rpm~9.2rpm. Among them, in the specific setting, in the equal diameter process of drawing 0~500mm stage, the internal thermal field power of the crucible 120 can be any one of 52.6kw, 53kw, 53.4kw, 53.8kw, and 54kw, the protective gas flow rate is any one of 185slpm, 185.5slpm, 186slpm, 186.5slpm, 187slpm, 187.5slpm, and 188slpm, the internal furnace pressure of the crucible 120 is any one of 3.6ttor, 3.8ttor, 4.0ttor, 4.2ttor, 4.4ttor, and 4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon crystal rod is any one of 8.6rpm, 8.8rpm, 9.0rpm, and 9.2rpm. Of course, in the equal diameter process of drawing 0~500mm stage, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speed of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 52.6kw~54kw, the protective gas flow rate can also be other values ​​within the range of 185slpm~188slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 3.6tor~4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 8.6rpm~9.2rpm.

[0070] Moreover, during the equal diameter drawing process of 500mm~1500mm, the thermal field power inside the crucible 120 is 51.6kw~52.5kw, the protective gas flow rate is 188slpm~195slpm, the furnace pressure inside the crucible 120 is 3.6ttor~4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is 8.6rpm~9.6rpm. Among them, in the specific setting, in the equal diameter process of drawing 500mm~1500mm stage, the internal thermal field power of the crucible 120 can be any one of 51.6kw, 52kw, 52.4kw, and 52.5kw, the protective gas flow rate is any one of 188slpm, 189slpm, 190slpm, 191slpm, 192slpm, 193slpm, 194slpm, and 195slpm, the internal furnace pressure of the crucible 120 is any one of 3.6ttor, 3.8ttor, 4.0ttor, 4.2ttor, 4.4ttor, and 4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 8.6rpm, 8.8rpm, 9.0rpm, 9.2rpm, 9.4rpm, and 9.6rpm. Of course, in the equal diameter process of drawing 500mm~1500mm, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speed of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 51.6kw~52.5kw, the protective gas flow rate can also be other values ​​within the range of 188slpm~195slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 3.6tor~4.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 8.6rpm~9.6rpm.

[0071] Continuing, in the equal diameter process of pulling 1500mm~2000mm stage, the internal thermal field power of the crucible 120 is 50.6kw~51.5kw, the protective gas flow rate is 188slpm~195slpm, the internal furnace pressure of the crucible 120 is 3.2ttor~3.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is 8.6rpm~9.6rpm. Among them, in the specific setting, in the equal diameter process of drawing 1500mm~2000mm stage, the internal thermal field power of the crucible 120 can be any one of 50.6kw, 51kw, 51.4kw, and 51.5kw, the protective gas flow rate is any one of 188slpm, 189slpm, 190slpm, 191slpm, 192slpm, 193slpm, 194slpm, and 195slpm, the internal furnace pressure of the crucible 120 is any one of 3.2ttor, 3.3ttor, 3.4ttor, and 3.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 8.6rpm, 8.8rpm, 9.0rpm, 9.2rpm, 9.4rpm, and 9.6rpm. Of course, in the equal diameter process of pulling 1500mm~2000mm stage, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speed of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 50.6kw~51.5kw, the protective gas flow rate can also be other values ​​within the range of 188slpm~195slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 3.2tor~3.5ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 8.6rpm~9.6rpm.

[0072] Finally, after drawing 2000mm in the equal diameter process, the thermal field power inside the crucible 120 is 48kw~50.5kw, the protective gas flow rate is 188slpm~195slpm, the furnace pressure inside the crucible 120 is 2.6ttor~3.1ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is 9.7rpm~10.5rpm. Among them, in the specific setting, after drawing 2000mm in the equal diameter process, the internal thermal field power of the crucible 120 can be any one of 48kw, 48.5kw, 49kw, 49.5kw, 50kw, and 50.5kw, the protective gas flow rate is any one of 188slpm, 189slpm, 190slpm, 191slpm, 192slpm, 193slpm, 194slpm, and 195slpm, the internal furnace pressure of the crucible 120 is any one of 2.6ttor, 2.7ttor, 2.8ttor, 2.9ttor, 3.0ttor, and 3.1ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod is any one of 9.7rpm, 9.9rpm, 10rpm, 10.2rpm, and 10.5rpm. Of course, after drawing 2000mm in the equal diameter process, the internal thermal field power of the crucible 120, the protective gas flow rate, the internal furnace pressure of the crucible 120, and the rotation speed of the crucible 120 and the single crystal silicon rod are not limited to the specific values ​​provided above. For example, the internal thermal field power of the crucible 120 can also be other values ​​within the range of 48kw~50.5kw, the protective gas flow rate can also be other values ​​within the range of 188slpm~195slpm, the internal furnace pressure of the crucible 120 can also be other values ​​within the range of 2.6tor~3.1ttor, and the rotation speed of the crucible 120 and the single crystal silicon rod can also be other values ​​within the range of 9.7rpm~10.5rpm.

[0073] In the above-mentioned method for preparing single crystal silicon, during the equal diameter stage, as the pulling process proceeds, the growth of the single crystal silicon rod approaches the end stage, and the thermal field power inside the crucible 120 is gradually reduced to prevent the melting seed crystal from affecting the growth of the rod, and the protective gas flow rate is always maintained at a large level, and the furnace pressure inside the crucible 120 is gradually reduced to increase the content of oxides carried during the outflow of the protective gas and the pulling process, and to reduce the oxygen content to further improve the quality of the single crystal silicon rod; in addition, the rotation speed of the crucible 120 and the single crystal silicon rod is gradually increased, and on the basis of fully stirring the silicon melt, the temperature gradient of the thermal field of the crucible 120 is further reduced, the survival rate of the lead-in is increased, the oxygen content in the single crystal silicon rod is reduced, the quality of the single crystal silicon rod is improved, and the growth rate of the single crystal silicon rod is accelerated.

[0074] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, 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, they should be considered to be within the scope of this specification.

[0075] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the patent application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent application shall be subject to the attached claims.

Claims

1. A single crystal furnace, characterized in that: The single crystal furnace comprises: A furnace body, wherein one side of the bottom of the furnace body is provided with an exhaust hole; A crucible, wherein the crucible is arranged inside the furnace body; a first heat-insulating tube and a second heat-insulating tube, wherein the first heat-insulating tube is located outside the crucible and covers one side of the bottom of the crucible, and the second heat-insulating tube is spaced outside the first heat-insulating tube and an air flow channel is formed between the second heat-insulating tube and the first heat-insulating tube, wherein the air flow channel connects the open end of the crucible and the exhaust hole; and The main heater includes a foot plate and a heating element connected to the foot plate, the foot plate is arranged between the first insulation tube and the second insulation tube, the heating element extends to the outside of the first insulation tube and is covered on one side of the top of the crucible.

2. The single crystal furnace according to claim 1, characterized in that: A gap between the first heat-insulating cylinder and the second heat-insulating cylinder is d1, wherein: 35mm≤d1≤45mm.

3. The single crystal furnace according to claim 1, characterized in that: In the longitudinal direction of the crucible, the height of the first heat-insulating cylinder is h1, and the height of the crucible is h2, wherein: 1 / 2≤h1 / h2≤2 / 3.

4. The single crystal furnace according to claim 1, characterized in that: The single crystal furnace further comprises a heat-insulating layer, which is arranged on one side of the bottom of the furnace body and between the crucible and the furnace body.

5. The single crystal furnace according to claim 4, characterized in that: The thermal insulation layer includes a first thermal insulation layer and a second thermal insulation layer, the first thermal insulation layer and the second thermal insulation layer are spaced apart, and an air outlet channel is formed between the first thermal insulation layer and the second thermal insulation layer, and two ends of the air outlet channel are respectively connected to the airflow channel and the exhaust hole.

6. The single crystal furnace according to claim 5, characterized in that: The gap between the first thermal insulation layer and the second thermal insulation layer is d2, wherein: 55mm≤d2≤65mm.

7. The single crystal furnace according to claim 1, characterized in that: The single crystal furnace also includes a guide tube, a third insulation tube and a fourth insulation tube. The guide tube is arranged on one side of the furnace body close to the opening end of the crucible, the third insulation tube cover is arranged on the outside of the guide tube, the fourth insulation tube connects the third insulation tube and the first insulation tube, and the cover is arranged on the outside of the transition area between the guide tube and the opening end of the crucible, and the orthographic projection of the fourth insulation tube on the bottom plane of the furnace body is located on the inner side of the orthographic projection of the first insulation tube on the bottom plane of the furnace body.

8. A method for preparing single crystal silicon, characterized in that: The single crystal silicon is prepared by using the single crystal furnace according to any one of claims 1 to 7, and the single crystal silicon preparation method comprises: In the melting stage, silicon raw materials are put into the crucible, protective gas is introduced and the silicon raw materials are heated and melted to obtain silicon melt; The seed crystal is immersed in silicon melt, and seeding, shouldering and equal diameter growth are performed in sequence to obtain the single crystal silicon; Among them, in the melting stage, the crucible is stationary, and in the seeding, shouldering and equal diameter processes, the crucible and the single crystal silicon rod rotate synchronously and the rotation speed gradually increases, and in the melting, seeding, shouldering and equal diameter processes, the amount of protective gas introduced gradually increases, and the thermal field power and furnace pressure inside the crucible gradually decrease.

9. The method for preparing single crystal silicon according to claim 8, characterized in that: In the melting stage, the heat field power inside the crucible is 85kw~105kw, the flow rate of the protective gas is 140slpm~160slpm, and the furnace pressure inside the crucible is 7.6ttor~8.5ttor; In the seeding stage, the heat field power inside the crucible is 56kw~58kw, the protective gas flow rate is 160slpm~175slpm, the furnace pressure inside the crucible is 6.6ttor~7.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 5.6rpm~6.5rpm; In the shoulder release stage, the heat field power inside the crucible is 54kw~56kw, the protective gas flow rate is 175slpm~185slpm, the furnace pressure inside the crucible is 5.6ttor~6.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 6.6rpm~7.5rpm; In the equal diameter stage, the thermal field power inside the crucible is 48kw~54kw, the protective gas flow rate is 185slpm~195slpm, the furnace pressure inside the crucible is 2.6ttor~4.5ttor, and the rotation speed of the crucible and the single crystal silicon rod is 8.6rpm~10.5rpm.

10. The method for preparing single crystal silicon according to claim 9, characterized in that: In the equal diameter stage, the equal diameter process is drawn in the 0-500 mm stage, the internal heat field power of the crucible is 52.6 kW-54 kW, the flow rate of the protective gas is 185 slpm-188 slpm, the internal furnace pressure of the crucible is 3.6 ttor-4.5 ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6 rpm-9.2 rpm; In the equal diameter process of drawing 500mm~1500mm, the heat field power inside the crucible is 51.6kw~52.5kw, the flow rate of the protective gas is 188slpm~195slpm, the furnace pressure inside the crucible is 3.6ttor~4.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6rpm~9.6rpm; In the equal diameter process of drawing 1500mm~2000mm, the heat field power inside the crucible is 50.6kw~51.5kw, the flow rate of the protective gas is 188slpm~195slpm, the furnace pressure inside the crucible is 3.2ttor~3.5ttor, and the rotation speed of the crucible and the single crystal silicon ingot is 8.6rpm~9.6rpm; After drawing 2000mm in the equal diameter process, the thermal field power inside the crucible is 48kw~50.5kw, the protective gas flow rate is 188slpm~195slpm, the furnace pressure inside the crucible is 2.6ttor~3.1ttor, and the rotation speed of the crucible and the single crystal silicon rod is 9.7rpm~10.5rpm.

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