Single crystal furnace and monocrystalline silicon preparation method

Abstract

The invention relates to a single crystal furnace and a preparation method of monocrystalline silicon, and the single crystal furnace comprises a guide cylinder which comprises a shell and a lifting driving mechanism; the shell comprises a containing cavity with an inlet, and the inlet is used for introducing airflow into the containing cavity; the turbofan lining is rotatably arranged in the accommodating cavity and is connected with the lifting driving mechanism; the bearing is arranged at the bottom of the guide cylinder and is connected with the bottom of the turbofan lining; the stirring assembly is fixedly connected to the bottom of the turbofan lining; wherein the lifting driving mechanism drives the turbofan lining and the stirring assembly to synchronously lift, and airflow drives the turbofan lining and the stirring assembly to synchronously rotate. The reverse rotation of the turbofan lining and the stirring assembly is driven by the airflow, so that the mechanical convection superimposed effect caused by the rotation of the crucible is counteracted, the enrichment of oxygen and impurities is reduced, the purity and uniformity of a crystal bar are improved, the growth rate of a single crystal is increased, and the preparation efficiency is improved.

Description

Technical Field

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

[0002] With the development of single crystal silicon preparation technology, oxygen content and impurity control technology based on dual rotation of crucible and crystal has become mainstream. This technology uses mechanical convection to suppress impurity aggregation and regulate oxygen distribution by adjusting the crucible rotation speed and the crystal rod pulling speed. During the crystal pulling process, the silicon melt produces natural convection due to the vertical and radial temperature gradients, and the crucible rotation further introduces mechanical convection. The superposition effect of the two aggravates the melt flow disorder, causing oxygen elements and impurities to be enriched at the crystal rod-melt interface, thereby affecting the purity of the crystal rod and the uniformity of oxygen content.

[0003] In the related technologies, the industry generally adopts the strategy of optimizing the crucible rotation parameters to balance the survival rate of crystal ingot and the quality of the crystal rod: although low crucible rotation can weaken mechanical convection and reduce oxygen penetration, it will lead to poor crystallization stability in the crystal ingot stage due to the uneven temperature field of the melt; although high crucible rotation improves the thermal uniformity of the melt and increases the survival rate of crystal ingot by enhancing mechanical convection, it aggravates the transport of oxygen and impurities and damages the quality of the crystal rod. Therefore, it is difficult for the existing process to achieve high efficiency and high quality production at the same time. In addition, the traditional guide tube adopts a smooth inner wall and short tooth design. Although it can increase the pulling speed by enhancing heat dissipation, it cannot suppress melt convection and has no significant effect on oxygen content control. In addition, the argon gas flow path is single, and its convection field regulation and impurity carrying potential are not fully utilized.

[0004] In summary, the current single crystal silicon preparation has problems such as low crystal rod quality, low lead survival rate, and slow preparation rate. Summary of the invention

[0005] Based on this, it is necessary to provide a single crystal furnace and a single crystal silicon preparation method to address the current problems of low crystal rod quality, low lead survival rate, and slow preparation rate in single crystal silicon preparation.

[0006] A single crystal furnace, comprising:

[0007] The guide tube comprises a shell and a lifting drive mechanism; the shell comprises a receiving cavity with an inlet, and the inlet is used to introduce airflow into the receiving cavity;

[0008] A turbofan liner, rotatably disposed in the accommodating cavity and connected to the lifting drive mechanism;

[0009] A bearing, arranged at the bottom of the guide tube and connected to the bottom of the turbofan liner;

[0010] A stirring assembly, fixedly connected to the bottom of the turbofan liner;

[0011] Wherein, the lifting drive mechanism drives the turbofan liner and the stirring assembly to rise and fall synchronously, and the airflow drives the turbofan liner and the stirring assembly to rotate synchronously.

[0012] In one embodiment, the top end of the turbofan liner is connected to the top of the outer casing; and the stirring assembly extends downward along the axial direction of the turbofan liner.

[0013] In one embodiment, the stirring assembly includes a plurality of teeth distributed in an array, and there is a spacing between adjacent teeth; the teeth are flat strip structures, and the ends thereof are rectangular.

[0014] In one embodiment, the inner wall surface of the turbofan liner is provided with a plurality of groups of inclined blades, the height of the blades protruding from the inner wall of the turbofan liner is greater than the wall thickness of the inner wall of the turbofan liner; and the angle between the blade surface and the inner wall of the turbofan liner is an acute angle.

[0015] In one of the embodiments, the bearing is a ceramic thrust ball bearing, an outer ring of which is fixed to the bottom of the housing, and an inner ring is connected to the turbofan liner flange.

[0016] In one of the embodiments, an inner wall of the top of the outer casing is provided with an annular groove, and the top end of the turbofan liner is embedded in the annular groove.

[0017] In one embodiment, a flow guiding structure is provided on the inner wall of the shell, and the flow guiding structure is a spiral flow guiding groove extending axially along the inner wall of the shell.

[0018] The above-mentioned single crystal furnace drives the turbofan lining and the stirring assembly to rotate in the opposite direction through airflow, thereby offsetting the mechanical convection superposition effect caused by the rotation of the crucible, reducing the enrichment of oxygen and impurities, improving the purity and uniformity of the crystal rod, and increasing the growth rate of the single crystal, thereby improving the preparation efficiency.

[0019] According to another object of the present invention, there is also provided a method for preparing single crystal silicon, which is applied to the single crystal furnace as described above, comprising:

[0020] Adjusting the airflow to drive the stirring assembly to rotate, and controlling the lifting drive mechanism to adjust the depth of the stirring assembly inserted into the molten silicon;

[0021] Coordinated control of crucible rotation speed, gas flow rate and furnace pressure in stages;

[0022] Among them, the staged coordinated regulation includes at least the temperature adjustment stage, the crystal induction stage, the shoulder release stage and the equal diameter stage.

[0023] In one embodiment, the step of staged coordinated regulation includes:

[0024] The crucible rotation speed increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage;

[0025] The air flow rate decreases from the temperature adjustment stage to the shoulder release stage, and increases in the equal diameter stage;

[0026] The furnace pressure increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage.

[0027] In one of the embodiments, the step of coordinated regulation in stages includes: the crucible rotation speed is 12rpm-14rpm; the air flow rate is 150slpm-180slpm; and the furnace pressure is 5torr-7torr.

[0028] The above-mentioned method for preparing single crystal silicon reduces the enrichment of oxygen and impurities, improves the survival rate of seeding and the quality of single crystals through the reverse rotation of the turbofan lining and the stirring assembly, and reduces convection and reduces the crystal defect rate through the coordinated regulation of temperature control, seeding, shoulder release and equal diameter stages. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic diagram of the structure of a single crystal furnace.

[0030] Figure 2 This is a cross-sectional schematic diagram of a single crystal furnace.

[0031] Figure 3 This is a schematic diagram of the structure of the guide tube and the turbofan liner.

[0032] Figure 4 It is a cross-sectional schematic diagram of the guide tube and the turbofan lining.

[0033] Figure 5 This is a top view of the guide tube and the turbofan lining.

[0034] Figure 6 Schematic diagram of the structure of the turbofan lining.

[0035] Figure 7 Schematic diagram of the crystal rod preparation process.

[0036] Figure 8 The schematic diagram of the process of preparing single crystal silicon is shown in FIG.

[0037] In the figure: 1, single crystal furnace; 11, crucible; 12, liquid level; 13, heater;

[0038] 10. guide tube; 100. housing; 101. inlet; 102. accommodating chamber; 110. guide structure;

[0039] 20. Turbofan lining; 200. Fan blades;

[0040] 30. Bearings;

[0041] 40. stirring assembly; 400. tooth inserting;

[0042] 50. Crystal rod. DETAILED DESCRIPTION

[0043] 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.

[0044] 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.

[0045] 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] See also Figure 1 , Figure 2 , Figure 3 , Figure 7 , Figure 1 It is a schematic structural diagram of a single crystal furnace 1 in one embodiment of the present application. Figure 2 It is a schematic cross-sectional view of the single crystal furnace 1. Figure 3 It is a schematic structural diagram of a guide tube 10 and a turbofan liner 20 in one embodiment of the present application. Figure 7 Schematic diagram of the preparation process of the crystal rod 50.

[0050] Embodiment 1

[0051] A single crystal furnace 1 provided in one embodiment of the present application includes a guide tube 10, a turbofan liner 20, a bearing 30 and a stirring assembly 40. Through the synchronous lifting and rotation of the turbofan liner 20 and the stirring assembly 40, effective control of the flow of molten silicon is achieved, thereby improving the growth quality and efficiency of single crystal silicon.

[0052] Specifically, the guide tube 10 includes an outer shell 100 and a lifting drive mechanism; the outer shell 100 includes a accommodating cavity 102 having an inlet 101, and the inlet 101 is used to introduce airflow into the accommodating cavity 102. The turbofan liner 20 is rotatably arranged in the accommodating cavity 102 and is connected to the lifting drive mechanism. The bearing 30 is arranged at the bottom of the guide tube 10 and is connected to the bottom of the turbofan liner 20. The stirring assembly 40 is fixedly connected to the bottom of the turbofan liner 20. Among them, the lifting drive mechanism drives the turbofan liner 20 and the stirring assembly 40 to rise and fall synchronously, and the airflow drives the turbofan liner 20 and the stirring assembly 40 to rotate synchronously.

[0053] In one embodiment, the single crystal furnace 1 further includes a crucible 11 and a heater 13. The guide tube 10 is arranged above the crucible 11, and the heater 13 is arranged on the periphery of the crucible 11 to melt the polycrystalline silicon raw material in the crucible 11 to form molten silicon. The stirring assembly 40 can extend below the liquid level 12 of the molten silicon in the crucible 11 to stir the molten silicon.

[0054] In the specific implementation process, airflow is introduced into the accommodating chamber 102 through the inlet 101 of the guide tube 10, and the airflow is guided to the top of the silicon melt when passing through the turbofan liner 20. At this time, the lifting drive mechanism is started to drive the turbofan liner 20 and the stirring assembly 40 to rise and fall synchronously to a preset position. The airflow continues to drive the turbofan liner 20 and the stirring assembly 40 to rotate synchronously. The rotation of the turbofan liner 20 accelerates the flow of the airflow, and at the same time drives the stirring assembly 40 to effectively stir the silicon melt to offset the mechanical convection generated by the rotation of the crucible, thereby achieving effective control of the flow of the silicon melt.

[0055] As described above, the single crystal furnace 1 provided in this embodiment can achieve effective control of the flow of silicon melt, reduce the enrichment of oxygen elements and impurities, and improve the purity and oxygen content uniformity of the crystal rod 50. At the same time, the synchronous lifting and rotating design of the turbofan liner 20 and the stirring assembly 40 can also adjust the stirring intensity and airflow speed according to actual needs, thereby further optimizing the growth quality and efficiency of single crystal silicon.

[0056] In one embodiment, the guide tube 10 includes a housing 100 and a lifting drive mechanism.

[0057] Specifically, a housing 100 is formed inside, and an inlet 101 is provided at the top of the housing 102 for introducing a gas flow, such as argon, into the housing 102 to control the reaction environment and temperature gradient of the silicon melt. The lifting drive mechanism is connected to the turbofan liner 20, and is used to drive the turbofan liner 20 and the stirring assembly 40 connected thereto to rise and fall synchronously in the housing 102 of the guide tube 10. In this embodiment, the lifting drive mechanism can be an electric lifting mechanism, a pneumatic lifting mechanism, or a hydraulic lifting mechanism, and the specific selection depends on the overall design and operation requirements of the single crystal furnace 1.

[0058] In this embodiment, the lifting drive mechanism can also be arranged outside the guide tube 10, and the turbofan liner 20 is arranged inside the guide tube 10. The lifting drive mechanism drives the guide tube 10 to move up and down, driving the turbofan liner 20 and the connected stirring assembly 40 to rise and fall.

[0059] In one of the embodiments, the protective gas introduced into the containing cavity 102 of the flow guide tube 10 can be one or more inert gases such as argon (Ar), helium (He), neon (Ne), krypton (Kr), xenon (Xe), etc. The present application does not limit the specific type of the protective gas.

[0060] In one embodiment, the turbofan liner 20 is rotatably disposed in the accommodating cavity 102 of the guide tube 10, and the airflow entering the accommodating cavity 102 from the inlet 101 drives the turbofan liner 20 to rotate. A certain gap is maintained between the top of the turbofan liner 20 and the inner wall of the outer shell 100 of the guide tube 10 to ensure smooth passage of the airflow. The bottom of the turbofan liner 20 is connected to the bottom of the guide tube 10 through the bearing 30, thereby realizing the rotation function of the turbofan liner 20. In this embodiment, the shape and size of the turbofan liner 20 affect the fluidity of the airflow, and can be adaptively adjusted according to specific usage requirements.

[0061] In one embodiment, the bearing 30 is disposed at the bottom of the guide tube 10 and connected to the bottom of the turbofan liner 20. The bearing 30 supports the turbofan liner 20 and supports the turbofan liner 20 to rotate freely in the bearing 30. In this embodiment, the selection of the bearing 30 should take into account factors such as the weight, rotation speed and working environment of the turbofan liner 20.

[0062] In one embodiment, the stirring assembly 40 is fixedly connected to the bottom of the turbofan liner 20, and is used to stir the silicon melt through the blades 200 or similar structures of the stirring assembly 40 when the turbofan liner 20 rotates. The stirring assembly 40 can effectively promote the flow of the silicon melt, improve the temperature uniformity of the silicon melt, avoid adverse effects on the growth of the crystal rod 50, and improve the survival rate of the lead release.

[0063] In one embodiment, the stirring assembly 40 speed can be any one of 6rpm, 6.2rpm, 6.5rpm, 6.7rpm, 7rpm, 7.2rpm, 7.5rpm, 7.7rpm, 8rpm, 8.2rpm, 8.5rpm, 8.7rpm, 9rpm, 9.2rpm, 9.5rpm, 9.7rpm, 10rpm, 10.2rpm, 10.5rpm, 10.7rpm, 11rpm, 11.2rpm, 11.5rpm, 11.7rpm, and 12rpm. In other feasible embodiments, the stirring assembly 40 speed can also be other values ​​within the range of 6rpm-12rpm, and the specific value of the stirring assembly 40 speed is not limited by the present application.

[0064] In one embodiment, the length of the stirring component 40 extending into the silicon melt can be any one of 120mm, 121mm, 122mm, 123mm, 124mm, 125mm, 126mm, 127mm, 128mm, 129mm, 130mm, 131mm, 132mm, 133mm, 134mm, and 135mm. In other feasible embodiments, the length of the stirring component 40 extending into the silicon melt can also be other values ​​within the range of 120mm-135mm. The specific value of the length of the stirring component 40 extending into the silicon melt is not limited by this application.

[0065] Combination Figure 4 , Figure 5 As shown, Figure 4 A cross-sectional schematic diagram of a guide tube 10 and a turbofan liner 20 is provided in one embodiment of the present application. Figure 5 It is a schematic top view of the guide sleeve 10 and the turbofan liner 20.

[0066] In some embodiments, the top end of the turbofan liner 20 is connected to the top of the outer casing 100 .

[0067] Specifically, a housing 100 of the guide tube 10 is provided with a housing chamber 102, and the turbofan liner 20 is rotatably disposed in the housing chamber 102, and its top end is connected to the top of the housing 100 to form a semi-enclosed space. An opening is provided at the top of the housing 100, which is connected to the inlet 101 of the housing chamber 102, and is used to introduce airflow into the housing chamber 102 to drive the rotation of the turbofan liner 20.

[0068] In one embodiment, the stirring assembly 40 extends downwardly along the axial direction of the turbofan liner 20 .

[0069] Specifically, the stirring assembly 40 is fixedly connected to the bottom of the turbofan liner 20 and extends downward along the axial direction of the turbofan liner 20 so as to directly act on the molten silicon. The stirring assembly 40 effectively stirs the molten silicon to offset mechanical convection, reduce the enrichment of impurities and oxygen in the crystal production process, and improve the growth quality of the single crystal.

[0070] In one embodiment, the outer shell 100 of the guide tube 10 may be made of high temperature resistant and corrosion resistant materials, such as quartz or high purity ceramics.

[0071] In one of the embodiments, the lifting drive mechanism adopts an electric lifting mechanism, which realizes the synchronous lifting and lowering of the turbofan liner 20 and the stirring assembly 40 through a screw or chain transmission.

[0072] In one embodiment, the turbofan liner 20 is made of high temperature resistant material, such as quartz, etc., to reduce energy consumption and wear during rotation. The fan blades 200 of the stirring assembly 40 are spiral-shaped to increase stirring efficiency and uniformity.

[0073] Combination Figure 4 As shown, Figure 4 The structure diagram of the turbofan liner provided in one embodiment of the present application is shown in FIG.

[0074] Specifically, the stirring assembly 40 directly acts on the silicon melt, and the stirring assembly 40 is composed of a plurality of array-distributed inserts 400, and the inserts 400 are flat strip structures, and their ends are rectangular to increase the contact area with the silicon melt, to reduce mechanical convection, and to improve the growth efficiency of the single crystal. In this embodiment, the inserts 400 are made of high temperature resistant materials, such as quartz.

[0075] In one embodiment, there is an appropriate spacing between adjacent teeth 400 to prevent the increase of fluid resistance caused by the teeth 400 being too dense and to avoid mutual interference between the teeth 400. As the turbofan liner 20 rotates, the stirring assembly 40 rotates synchronously, and the stirring effect of the teeth 400 on the silicon melt is used to effectively promote the heat transfer in the silicon melt, achieve uniform temperature distribution, and reduce the impact of mechanical convection, reduce the precipitation and enrichment of oxygen and impurities, and improve the survival rate of the lead and the quality of the single crystal.

[0076] In this embodiment, the speed of the incoming airflow or the output of the lifting drive mechanism can be adjusted to control the rotation speed of the turbofan liner 20 and the stirring assembly 40, as well as the depth of the stirring assembly 40 extending into the silicon melt, thereby adjusting the intensity of offsetting mechanical convection to achieve improved heat transfer efficiency and uniformity of silicon melt mixing during single crystal growth under optimized airflow distribution and stirring conditions.

[0077] Combination Figure 6 As shown, Figure 6 Schematic diagram of the structure of a turbofan liner provided in an embodiment of the present application. In some embodiments, the inner wall surface of the turbofan liner 20 is provided with a plurality of groups of inclined blades 200.

[0078] Specifically, the turbofan liner 20 is arranged in the accommodating cavity 102 of the guide tube 10, and the inlet 101 of the accommodating cavity 102 is used to introduce argon gas. The turbofan liner 20 includes blades 200, and multiple groups of blades 200 are obliquely arranged on the inner wall surface of the turbofan liner 20. Among them, the height of the blades 200 protruding from the turbofan liner 20 is greater than the wall thickness of the inner wall of the turbofan liner 20, that is, the blades 200 protrude from the inner wall surface of the turbofan liner 20 and are obliquely arranged, so as to guide the airflow to drive the turbofan liner 20 to rotate, and then drive the stirring assembly 40 to stir the silicon melt.

[0079] In one of the embodiments, the angle between the surface of the fan blade 200 and the inner wall of the turbofan liner 20 is an acute angle, so as to more effectively guide the airflow and form a vortex, thereby enhancing the stirring effect on the silicon melt.

[0080] In one embodiment, the bearing 30 is a ceramic thrust ball bearing 30 , an outer ring of which is fixed to the bottom of the housing 100 , and an inner ring is flange-connected to the turbofan liner 20 .

[0081] Specifically, the bearing 30 is disposed at the bottom of the guide tube 10 and connected to the bottom of the turbofan liner 20 to support the rotation of the turbofan liner 20. In this embodiment, a high temperature resistant and corrosion resistant ceramic thrust ball bearing 30 is used, the outer ring of which is fixed to the bottom of the guide tube 10 housing 100, and the inner ring is tightly connected to the flange of the turbofan liner 20 to ensure the stability and durability of the turbofan liner 20 during high-speed rotation.

[0082] In one embodiment, an annular groove is provided on the inner wall of the top of the housing 100, and the top of the turbofan liner 20 is embedded in the annular groove to realize the connection between the turbofan liner 20 and the housing 100, and to realize that the turbofan liner 20 is set in the accommodating cavity 102 of the housing 100. The turbofan liner 20 is driven to rotate by introducing airflow into the accommodating cavity 102. In this embodiment, the inner wall of the annular groove may be provided with anti-slip patterns, etc., to enhance the stability of the connection between the turbofan liner 20 and the housing 100.

[0083] In one of the embodiments, a guide structure 110 is provided on the inner wall of the shell 100. The guide structure 110 is a spiral guide groove extending axially along the inner wall of the shell 100. The spiral guide groove can guide the airflow to flow along a specific path to form a uniformly distributed airflow field to drive the turbofan liner 20 to rotate uniformly to stir the silicon melt. In this embodiment, by adjusting the slotting direction of the spiral guide groove, the flow direction of the airflow can be changed, thereby realizing the reverse rotation of the turbofan liner 20 and the stirring assembly 40, so as to offset the mechanical convection superposition effect caused by the rotation of the crucible, reduce the enrichment of oxygen and impurities, improve the purity and uniformity of the crystal rod 50, and improve the growth rate of the single crystal.

[0084] In one embodiment, the crucible rotation speed can be any one of 6rpm, 6.5rpm, 7rpm, 7.5rpm, 8rpm, 8.5rpm, 9rpm, 9.5rpm, 10rpm, 10.5rpm, 11rpm, 11.5rpm, 12rpm, 12.5rpm, 13rpm, 13.5rpm, and 14rpm. In other feasible embodiments, the crucible rotation speed can also be other values ​​within the range of 6rpm-14rpm, and the specific value of the crucible rotation speed is not limited by this application.

[0085] In one embodiment, the air flow rate is any one of 150slpm, 150.2slpm, 150.5slpm, 150.7slpm, 160slpm, 160.2slpm, 160.5slpm, 160.7slpm, 170slpm, 170.2slpm, 170.5slpm, 170.7slpm, and 180slpm. In other feasible embodiments, the air flow rate can also be other values ​​within the range of 150slpm-180slpm, and the specific values ​​of the air flow rate are not limited in this application.

[0086] In one embodiment, the furnace pressure is any one of 5torr, 5.2torr, 5.5torr, 5.7torr, 6torr, 6.2torr, 6.5torr, 6.7torr, and 7torr. In other feasible embodiments, the furnace pressure can also be other values ​​within the range of 5torr-7torr. The specific value of the furnace pressure is not limited in this application.

[0087] As shown in the following Table 1, Table 1 shows various data of the first embodiment of the stirring assembly 40 of the present application.

[0088] Table 1

[0089]

[0090] As shown in the following Table 2, Table 2 is various data of a comparative example that does not use the stirring assembly 40 of the present application.

[0091] Table 2

[0092]

[0093] From the data analysis of Table 1 and Table 2, it can be seen that when the stirring assembly 40 is not used in the reference comparative example, the crucible rotation speed and argon flow rate are relatively small, the maximum crucible rotation speed is only 7rpm, the maximum argon flow rate is 120slpm, and the oxygen content is 10.9mmpa. And the crucible rotation speed, argon flow rate and furnace pressure in the comparative example are basically unchanged from the temperature adjustment stage to the shoulder release stage. When the stirring assembly 40 is used in Example 1, the speed and extension length of the stirring assembly 40 are adjusted in different process stages, which can reduce the influence of mechanical convection and make the crucible rotation speed and argon flow rate larger; wherein, the maximum crucible rotation speed is 8rpm, the maximum argon flow rate is 180slpm, and the oxygen content is 8mmpa. It can be seen that the stirring assembly 40 is used and the stirring assembly speed and extension length are adjusted in different process stages to stir the silicon melt, reduce the influence of mechanical convection, and can match the larger crucible rotation speed and argon flow rate, accelerate the precipitation of oxygen impurities, and reduce the oxygen content by 26.61%.

[0094] When the stirring assembly 40 is not used in the reference comparative example, the crucible rotation speed remains basically unchanged, and the maximum crucible rotation speed is only 7rpm, and the release survival rate is 94%; when the stirring assembly 40 is used in Example 1, since the stirring assembly 40 can reduce mechanical convection, the crucible rotation speed in Example 1 can be higher, and the release survival rate reaches 97%, which increases the release survival rate by 3.19%, thereby improving the stability of the process.

[0095] When the stirring assembly 40 is not used in the reference comparative example, the crucible rotation speed, argon flow rate and furnace pressure remain basically unchanged, the growth rate of the seeding stage is 228mm / h, the growth rate of the shoulder release stage is 111mm / h, the growth rate of the first equal diameter stage is 82mm / h, and the growth rate of the second equal diameter stage is 110mm / h. When the stirring assembly 40 is used in Example 1, the stirring assembly 40 rate and the insertion length are adjusted in each process stage, the growth rate of the seeding stage is 265mm / h, the growth rate of the shoulder release stage is 117mm / h, the growth rate of the first equal diameter stage is 89mm / h, and the growth rate of the second equal diameter stage is 115mm / h. It can be seen that the use of the stirring assembly 40 reduces the influence of mechanical convection, increases the crucible rotation speed, argon gas flow rate and furnace pressure, which is beneficial to increasing the growth rate. The growth rate in the seeding stage is increased by 16.23%, the growth rate in the shoulder release stage is increased by 5.41%, the growth rate in the first equal-diameter stage is increased by 8.54%, the growth rate in the second equal-diameter stage is increased by 4.55%, and the growth rate is increased by 8.68% on average.

[0096] As described above, the use of the stirring assembly 40 can achieve the effects of reducing oxygen content, improving the survival rate of the release and increasing the growth rate.

[0097] Embodiment 2 Combination Figure 7 , Figure 8 As shown, Figure 7 Schematic diagram of the preparation process of the crystal rod 50. Figure 8 The schematic diagram of the process of preparing single crystal silicon is shown in FIG.

[0098] This embodiment provides a method for preparing single crystal silicon, which is applied to the single crystal furnace 1 as described above, and comprises the following steps:

[0099] S100, adjusting the airflow to drive the stirring assembly 40 to rotate.

[0100] S200, controlling the lifting drive mechanism to adjust the depth of the stirring assembly 40 inserted into the molten silicon.

[0101] S300, coordinate and control the crucible rotation speed, air flow rate and furnace pressure in stages.

[0102] In this embodiment, the coordinated control in stages includes at least a temperature adjustment stage, a crystal seeding stage, a shoulder release stage and a diameter equalization stage.

[0103] In this embodiment, the staged coordinated control includes at least a temperature adjustment stage, a seeding stage, a shoulder release stage and a diameter equalization stage. The staged coordinated control means that in each stage of the temperature adjustment stage, the seeding stage, the shoulder release stage and the diameter equalization stage, when adjusting the speed and the insertion length of the stirring assembly 40, the crucible rotation speed, the argon gas flow rate and the furnace pressure are adjusted at the same time.

[0104] In one embodiment, in the step S300 of the coordinated control in stages, it includes: the crucible rotation speed increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage. The airflow rate decreases from the temperature adjustment stage to the shoulder release stage, and increases in the equal diameter stage. The furnace pressure increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage. Among them, the crucible rotation speed is 12rpm-14rpm; the airflow rate is 150slpm-180slpm; and the furnace pressure is 5torr-7torr.

[0105] In one embodiment, the crucible rotation speed can be any one of 12rpm, 12.2rpm, 12.5rpm, 12.7rpm, 13rpm, 13.2rpm, 13.5rpm, 13.7rpm, and 14rpm. In other feasible embodiments, the crucible rotation speed can also be other values ​​within the range of 12rpm-14rpm, and the specific value of the crucible rotation speed is not limited by this application.

[0106] In one embodiment, the air flow rate is any one of 150slpm, 150.2slpm, 150.5slpm, 150.7slpm, 160slpm, 160.2slpm, 160.5slpm, 160.7slpm, 170slpm, 170.2slpm, 170.5slpm, 170.7slpm, and 180slpm. In other feasible embodiments, the air flow rate can also be other values ​​within the range of 150slpm-180slpm, and the specific values ​​of the air flow rate are not limited in this application.

[0107] In one embodiment, the furnace pressure is any one of 5torr, 5.2torr, 5.5torr, 5.7torr, 6torr, 6.2torr, 6.5torr, 6.7torr, and 7torr. In other feasible embodiments, the furnace pressure can also be other values ​​within the range of 5torr-7torr. The specific value of the furnace pressure is not limited in this application.

[0108] In the specific implementation process, in the temperature adjustment stage, the crucible rotation speed is 12 rpm, the argon flow rate is 180 slpm, and the furnace pressure is 5 torr. At this time, the stirring rate of the stirring assembly 40 is controlled to be 10 rpm, and the length thereof extending into the silicon melt is 120 mm. Among them, a higher argon flow rate helps to quickly establish a stable inert gas environment, reduce the contamination of the silicon melt by external impurities, and enable the silicon melt to reach a stable temperature gradient.

[0109] In the seeding stage, the crucible rotation speed is gradually increased to 13 rpm, the argon gas flow rate is gradually reduced to 170 slpm, and the furnace pressure is gradually increased to 6 torr. At the same time, the stirring rate of the stirring assembly 40 is controlled to be 9 rpm, and the length of the stirring assembly 40 extending into the silicon melt is 120 mm to promote the formation of single crystal nuclei. By increasing the crucible rotation speed, the stirring speed is increased, the temperature uniformity of the silicon melt is enhanced, and the seeding survival rate is improved.

[0110] In the shoulder release stage, the crucible rotation speed continues to increase to 14rpm, the argon flow rate gradually decreases to 150slpm, and the furnace pressure gradually increases to 7torr. At the same time, the stirring assembly 40 is controlled to have a speed of 11rpm, and its length extending into the silicon melt is 120mm to promote the enlargement of the shoulder of the single crystal silicon. By increasing the stirring speed, the silicon melt is fully mixed, the temperature uniformity is improved, the mechanical convection intensity is offset, the impurity enrichment is reduced, and the survival rate of the lead release is improved. The argon flow rate is reduced to match the demand for the atmosphere environment in the shoulder release stage and save resources. Increasing the furnace pressure helps to stabilize the silicon melt interface and promote the smooth growth of the crystal.

[0111] In one embodiment, the equal diameter stage includes a first equal diameter stage and a second equal diameter stage. In the first equal diameter stage, the crucible rotation speed is gradually reduced to 13 rpm, the argon flow rate is gradually increased to 170 slpm, and the furnace pressure is gradually reduced to 6 torr. At the same time, the speed of the stirring assembly 40 is adjusted to 12 rpm, and the length thereof extending into the silicon melt is 130 mm to maintain a stable increase in the diameter of the single crystal silicon. By appropriately reducing the stirring speed, a stable growth environment is maintained. In addition, the argon flow rate is increased to enhance the carrying capacity of impurities in the silicon melt and improve the quality of the crystal rod 50. By appropriately reducing the furnace pressure, it is helpful to reduce the interference of gas molecules on the growth of the crystal rod 50 and improve the growth efficiency.

[0112] In the second equal diameter stage, the crucible rotation speed is gradually reduced to 12rpm, the argon flow rate is gradually increased to 180slpm, and the furnace pressure is gradually reduced to 5torr. At the same time, the stirring assembly 40 is maintained at a speed of 12rpm, and its length extending into the silicon melt is 130mm. By maintaining a relatively stable stirring speed, the smooth growth of the crystal rod 50 in the equal diameter stage is ensured. The argon flow rate is increased to take away more latent heat of crystallization, increase the crystal pulling speed and output. Maintain a low furnace pressure, reduce external interference, and ensure the quality of the crystal rod 50.

[0113] As shown in the following Table 3, Table 3 shows various data of Example 2 of the preparation process using the stirring assembly 40 of the present application and using stage-by-stage coordinated control of the crucible rotation speed, air flow rate and furnace pressure.

[0114] Table 3

[0115]

[0116] From the data analysis of Table 2 and Table 3, it can be seen that in the reference comparative example, when the stirring component 40 is not used and the preparation process of coordinated regulation in stages is not used, the crucible rotation speed, argon flow rate and furnace pressure are basically unchanged, the maximum argon flow rate is 120slpm, and the oxygen content is 10.7ppma; while in Example 2, the stirring component 40 is used, the speed and extension length of the stirring component 40 are regulated at each stage, and the crucible rotation speed is controlled to increase, the argon flow rate is controlled to decrease, and the furnace pressure is controlled to increase from the temperature adjustment stage to the shoulder release stage; the crucible rotation speed is controlled to decrease, the argon flow rate is controlled to increase, and the furnace pressure is controlled to decrease in the equal diameter stage, and the maximum argon flow rate is 180slpm, so that the oxygen content is reduced to 8ppma. It can be seen that the use of the stirring component 40, as well as the regulation of the stirring component 40 speed and extension length at each stage, the crucible rotation speed, the argon flow rate and the furnace pressure, can significantly reduce the influence of mechanical convection, ensure that the larger crucible rotation speed and argon flow rate can be matched, accelerate the precipitation of oxygen impurities, and reduce the oxygen content by 31.19%.

[0117] In the reference comparative example, when the stirring assembly 40 and the preparation process of coordinated regulation in stages were not adopted, the crucible rotation speed, argon gas flow rate and furnace pressure remained basically unchanged, the maximum crucible rotation speed was only 7rpm, and the release survival rate was 94%. In Example 2, the stirring assembly 40 was adopted, and the crucible rotation speed was gradually increased from the temperature adjustment stage to the shoulder release stage, and the crucible rotation speed reached a maximum of 14rpm, which increased the release survival rate to 98%. It can be seen that the use of the stirring assembly 40, as well as the regulation of the speed and extension length of the stirring assembly 40 and the regulation of the crucible rotation speed in each stage, can increase the release survival rate by 4.26%.

[0118] In the reference comparative example, the stirring assembly 40 is not used, and the preparation process of coordinated control in stages is not used. From the temperature adjustment stage to the shoulder release stage, the crucible rotation speed is basically unchanged, the argon flow rate is unchanged, and the furnace pressure is reduced; in the equal diameter stage, the crucible rotation speed, the argon flow rate and the furnace pressure are unchanged, so that the growth rate of the seeding stage is 228mm / h, the growth rate of the shoulder release stage is 111mm / h, the growth rate of the first equal diameter stage is 82mm / h, and the growth rate of the second equal diameter stage is 110mm / h. In Example 2, the stirring assembly 40 is used, and the crucible rotation speed is increased, the argon flow rate is decreased, and the furnace pressure is increased from the temperature adjustment stage to the shoulder release stage; in the equal diameter stage, the crucible rotation speed is decreased, the argon flow rate is increased, and the furnace pressure is decreased, so that the growth rate of the seeding stage is 265mm / h, the growth rate of the shoulder release stage is 118mm / h, the growth rate of the first equal diameter stage is 95mm / h, and the growth rate of the second equal diameter stage is 117mm / h. It can be seen that the use of the stirring assembly 40, as well as the regulation of the speed and insertion length of the stirring assembly 40, the crucible rotation speed, the argon flow rate and the furnace pressure, can increase the growth rate in the seeding stage by 16.23%, the growth rate in the shoulder release stage by 6.31%, the growth rate in the first equal-diameter stage by 15.85%, the growth rate in the second equal-diameter stage by 6.36%, and the average growth rate by 11.19%.

[0119] As described above, the stirring assembly 40 is used and the speed and extension length of the stirring assembly 40 are regulated, and the crucible rotation speed is controlled to increase, the argon flow rate is controlled to decrease, and the furnace pressure is controlled to increase from the temperature adjustment stage to the shoulder release stage; the crucible rotation speed is controlled to decrease, the argon flow rate is controlled to increase, and the furnace pressure is controlled to decrease in the equal diameter stage, which can reduce the influence of mechanical convection, accelerate the precipitation of oxygen impurities, and significantly reduce the oxygen content; a higher crucible rotation speed can improve the release survival rate and increase the growth rate.

[0120] The technical features of the above-described embodiments can be combined arbitrarily. In order to make the description concise, all possible combinations of the technical features in the above-described embodiments are not 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. The above-described embodiments only express several implementation methods of the present application, and the description is relatively specific and detailed, but it cannot be understood as a limitation on the scope of the patent application. It should be pointed out that for ordinary technicians in this field, without departing from the concept of the present application, several deformations and improvements can be made, which all belong to the scope of protection of the present application. Therefore, the scope of protection of the patent application of this application shall be based on the attached claims.

Claims

1. A single crystal furnace, characterized in that: include: A flow guide cylinder (10) comprises a housing (100) and a lifting drive mechanism; the housing (100) comprises a receiving chamber (102) having an inlet (101), and the inlet (101) is used to introduce airflow into the receiving chamber (102); A turbofan liner (20) is rotatably disposed in the accommodating chamber (102) and is connected to the lifting drive mechanism; A bearing (30) is arranged at the bottom of the guide tube (10) and connected to the bottom of the turbofan liner (20); A stirring assembly (40) fixedly connected to the bottom of the turbofan liner (20); The lifting drive mechanism drives the turbofan liner (20) and the stirring assembly (40) to rise and fall synchronously, and the airflow drives the turbofan liner (20) and the stirring assembly (40) to rotate synchronously.

2. The single crystal furnace according to claim 1, characterized in that: The top end of the turbofan liner (20) is connected to the top of the casing (100); the stirring assembly (40) extends downward along the axial direction of the turbofan liner (20).

3. The single crystal furnace according to claim 2, characterized in that: The stirring assembly (40) comprises a plurality of insert teeth (400) distributed in an array, with spacing between adjacent insert teeth (400); the insert teeth (400) are flat strip structures, and the ends thereof are rectangular.

4. The single crystal furnace according to claim 2, characterized in that: The inner wall of the turbofan liner (20) is provided with a plurality of groups of inclined blades (200); the height of the blades (200) protruding from the inner wall of the turbofan liner (20) is greater than the wall thickness of the inner wall of the turbofan liner (20); and the angle between the surface of the blades (200) and the inner wall of the turbofan liner (20) is an acute angle.

5. The single crystal furnace according to any one of claims 2 to 4, characterized in that: The bearing (30) is a ceramic thrust ball bearing, the outer ring of which is fixed to the bottom of the housing (100), and the inner ring is flange-connected to the turbofan liner (20).

6. The single crystal furnace according to any one of claims 2 to 4, characterized in that: An inner wall at the top of the outer casing (100) is provided with an annular groove, and the top end of the turbofan liner (20) is embedded in the annular groove.

7. The single crystal furnace according to any one of claims 2 to 4, characterized in that: The inner wall of the outer shell (100) is provided with a flow guiding structure (110), and the flow guiding structure (110) is a spiral flow guiding groove extending axially along the inner wall of the outer shell (100).

8. A method for preparing single crystal silicon, characterized in that: The single crystal furnace as claimed in any one of claims 1 to 7 comprises: Adjusting the airflow to drive the stirring assembly (40) to rotate, and controlling the lifting drive mechanism to adjust the depth of the stirring assembly (40) inserted into the molten silicon; Coordinated control of crucible rotation speed, gas flow rate and furnace pressure in stages; Among them, the staged coordinated regulation includes at least the temperature adjustment stage, the crystal induction stage, the shoulder release stage and the equal diameter stage.

9. The method for preparing single crystal silicon according to claim 8, characterized in that: The steps of the phased coordinated regulation include: The crucible rotation speed increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage; The air flow rate decreases from the temperature adjustment stage to the shoulder release stage, and increases in the equal diameter stage; The furnace pressure increases from the temperature adjustment stage to the shoulder release stage, and decreases in the equal diameter stage.

10. The method for preparing single crystal silicon according to claim 9, characterized in that: The step of coordinated regulation in stages includes: the crucible rotation speed is 12rpm-14rpm; the air flow rate is 150slpm-180slpm; and the furnace pressure is 5torr-7torr.

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