Method for drawing 12-inch silicon single crystal by using adjusted 8-inch crystal pulling system

Abstract

The invention belongs to the technical field of semiconductor material preparation, and particularly relates to a method for drawing a 12-inch silicon single crystal by using an adjusted 8-inch crystal drawing system, which is beneficial to optimizing temperature distribution and heat transfer efficiency in a heat field by adjusting the size and angle of a heat shield, expanding the space of the heat field, moving the position of a heater upwards and optimizing the arrangement of a heat preservation material. And a more suitable thermal field environment is created for drawing 12-inch silicon single crystals. Parameter adjustment is optimized from multiple aspects of crystal and crucible rotating speed, liquid opening distance, inert gas flow, crystal bar pulling speed, magnetic field and the like, so that the crystal growth process can be better controlled, and the production feasibility of 12-inch silicon single crystals in an 8-inch crystal pulling system is improved; through combination of the two, indexes such as the crystal forming rate, the number of times of drawing and releasing and the qualified rate approach or even reach the average production level of a 12-inch single crystal furnace as much as possible, and the requirement of the market for 12-inch heavily-doped single crystals is met.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material preparation technology, specifically relating to a method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system. Background Technology

[0002] Single-crystal materials play a crucial role in fields such as semiconductors. In recent years, the heavily doped single-crystal market has shown a continuous expansion trend. With the booming development of the domestic semiconductor industry, domestic manufacturers' demand for heavily doped substrates and epitaxy is increasing. This demand growth is particularly evident in the order volume of 8-inch and 12-inch heavily doped single crystals, with the order volume of 12-inch heavily doped single crystals increasing month by month, while the order volume of 8-inch heavily doped single crystals is decreasing month by month.

[0003] In semiconductor manufacturing, 12-inch wafers, due to their larger area, enable higher production efficiency and lower unit costs, making them a key direction for industry development, with many manufacturers expanding their 12-inch capacity. However, during this capacity expansion, a pressing issue has emerged: the demand generated by the expansion of 12-inch capacity has created an urgent need in the market to produce 12-inch heavily doped single crystals using 8-inch single crystal furnaces.

[0004] When producing silicon single crystals using 12-inch single crystal furnaces with 12-inch crystal pulling parameters, the average crystal formation rate is approximately 71%, the average number of pulls is approximately 4.5, and the average yield rate below 2.5mΩ is approximately 41%. When producing 12-inch single crystals using 8-inch single crystal furnaces with 8-inch crystal pulling parameters, the average crystal formation rate is 25%, the average number of pulls is approximately 11, the average yield rate below 2.5mΩ is 0%, and the head resistance is 0.004240mΩ. Furthermore, when producing 12-inch single crystals using 8-inch single crystal furnaces with 12-inch crystal pulling parameters, the average crystal formation rate is approximately 31%, the average number of pulls is approximately 9, and the average yield rate below 2.5mΩ is approximately 0%. Based on the production data, when using 8-inch single crystal furnaces to pull 12-inch silicon single crystals, the crystal formation rate, number of pulls, and yield rate below 2.5mΩ are all significantly lower than the average production levels of 12-inch single crystal furnaces, failing to meet the expected production requirements. Summary of the Invention

[0005] In view of this, the present invention provides a method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system, in order to solve the technical problems of low crystal formation rate, number of triggering cycles and product qualification rate in the production of 12-inch heavily doped single crystals using existing 8-inch single crystal furnaces.

[0006] To achieve the above objectives, this application adopts the following approach: A method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system includes adjusting the original 8-inch crystal pulling system and adjusting the parameters for pulling 8-inch silicon single crystals. The adjusted 8-inch crystal pulling system, combined with the adjusted 8-inch silicon single crystal parameters, is used to pull 12-inch silicon single crystals. The adjusted 8-inch crystal pulling system includes a single crystal furnace, a quartz crucible, a heater, a heat shield, and insulation material. The quartz crucible is placed inside the single crystal furnace, the heater is arranged around the outside of the quartz crucible, the insulation material is arranged around the heater, and the heat shield is placed above the quartz crucible. The heat shield includes an inner screen and an outer screen. The inner screen includes an upper section, a middle section, and a lower section. The outer screen includes... The outer screen consists of an upper section, a middle section, and a lower section. The upper section of the inner screen and the upper section of the outer screen are inclined to the side away from the quartz crucible. The middle section of the inner screen and the middle section of the outer screen are vertically arranged. The lower section of the inner screen and the lower section of the outer screen are inclined to one side of the quartz crucible, and the inclination angle of the lower section of the inner screen and the lower section of the outer screen is a predetermined angle. The size of the hot screen is changed to a preset range. Based on the original 8-inch crystal pulling system, the hot field space is expanded to a predetermined position. The position of the heater is moved upward according to the expanded hot field space. The distance of the insulation material is adjusted for the heating area of ​​the heater to match the heating area of ​​the heater, and the thickness of the insulation material is reduced. Adjusting the parameters for pulling 8-inch silicon single crystals includes: reducing the crystal rotation speed to a first predetermined speed, reducing the crucible rotation speed to a second predetermined speed, increasing the liquid outlet distance to a predetermined height, increasing the inert gas flow rate to a predetermined flow rate, reducing the minimum pulling speed of the crystal rod, adjusting the magnetic field position, and controlling the magnetic field strength.

[0007] Preferably, the "changing the size of the hot screen to a preset range" includes changing the outer diameter, inner diameter, and height of the hot screen, so that the ratio of the inner diameter of the quartz crucible to the outer diameter of the hot screen is between 0.9 ± 0.02, the ratio of the inner diameter of the quartz crucible to the inner diameter of the hot screen is between 0.5 ± 0.02, and the inner diameter of the hot screen is greater than 1.15 times the diameter of the single crystal, and the height of the hot screen is greater than the height of the quartz crucible.

[0008] Preferably, the "inclination angle of the lower section of the inner screen and the lower section of the outer screen being tilted is a predetermined angle" includes making the angle between the lower section of the outer screen of the hot screen and the horizontal line > 15°, and making the angle between the lower section of the inner screen of the hot screen and the horizontal line > 25°.

[0009] Preferably, the predetermined position is a position where the lower edge of the heat shield is ≥200mm from the crucible zero position.

[0010] Preferably, the heater is moved upward by a distance ≤80mm.

[0011] Preferably, the "adjusting the distance of the insulation material for the heating zone of the heater" includes increasing the distance of the central insulation material corresponding to the main heating zone, and this distance is ≤80mm.

[0012] Preferably, the thickness of the insulation material corresponding to the original hot zone is reduced to 80% of the original thickness.

[0013] Preferably, the first predetermined rotation speed is 7-10 rpm, the second predetermined rotation speed is 0.5-2 rpm, the predetermined height is 45-55 mm, the predetermined flow rate is 130-180 slm or more, the minimum pulling speed of the crystal rod is reduced to below 0.55 mm / min, the magnetic field position is adjusted within a range of ±40 mm at the level with the solution, and the magnetic field strength is controlled at 4000-4500 GS.

[0014] Preferably, the inert gas is argon.

[0015] Preferably, the pressure of the inert gas is determined by the opening of the pressure valve, and the minimum opening of the pressure valve during crystal growth is 25°-40°.

[0016] The above-described method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system optimizes the temperature distribution and heat transfer efficiency within the thermal field by adjusting the size and angle of the hot shield, expanding the thermal field space, moving the heater position upwards, and optimizing the insulation material settings. This creates a more suitable thermal environment for pulling 12-inch silicon single crystals. Parameter adjustments optimize various aspects, including crystal and crucible rotation speed, liquid outlet distance, inert gas flow rate, crystal rod pulling speed, and magnetic field. This allows for better control of the crystal growth process and improves the feasibility of producing 12-inch silicon single crystals in an 8-inch crystal pulling system. The combination of these two approaches ensures that indicators such as crystal formation rate, number of lead-outs, and yield are as close as possible to, or even reach, the average production level of a 12-inch single crystal furnace, meeting market demand for heavily doped 12-inch single crystals. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the overall structure of the original 8-inch crystal pulling system.

[0018] Figure 2 This is a schematic diagram of the adjusted 8-inch crystal pulling system.

[0019] Figure 3 This is a schematic diagram of the thermal screen structure in the adjusted 8-inch crystal pulling system.

[0020] Figure 4 This is a comparison diagram of the head resistivity of silicon single crystals in the examples and comparative examples.

[0021] Figure 5 This is a comparison chart of the number of times silicon single crystals are released in the examples and comparative examples.

[0022] Figure 6 This is a comparison chart of the crystallization rate of silicon single crystals in the examples and comparative examples.

[0023] Figure 7This is a comparison chart showing the yield rate of silicon single crystals below 2.5mΩ in the examples and comparative examples.

[0024] In the diagram, there are: hot screen 100, outer screen 110, upper section of outer screen 111, middle section of outer screen 112, lower section of outer screen 113, first included angle 114, inner screen 120, upper section of inner screen 121, middle section of inner screen 122, lower section of inner screen 123, second included angle 124, quartz crucible 200, heater 300, insulation material 400, and crucible zero position 500. Detailed Implementation

[0025] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are also given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0027] Please refer to Figure 1 and Figure 3In one specific embodiment, a method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system includes adjusting the original 8-inch crystal pulling system and adjusting the parameters for pulling 8-inch silicon single crystals. The adjusted 8-inch crystal pulling system, combined with the adjusted 8-inch silicon single crystal parameters, is used to pull 12-inch silicon single crystals. The adjusted 8-inch crystal pulling system includes a single crystal furnace, a quartz crucible 200, a heater 300, a heat shield 100, and insulation material 400. The quartz crucible 200 is disposed inside the single crystal furnace, the heater 300 is arranged around the outside of the quartz crucible 200, the insulation material 400 is disposed around the heater 300, and the heat shield 100 is disposed above the quartz crucible 200. The heat shield 100 includes an inner screen 120 and an outer screen 110. The inner screen 120 includes an upper section 121, a middle section 122, and a lower section 123. The screen 110 includes an upper outer screen section 111, a middle outer screen section 112, and a lower outer screen section 113. The upper inner screen section 121 and the upper outer screen section 111 are inclined to the side away from the quartz crucible 200. The middle inner screen section 122 and the middle outer screen section 112 are vertically arranged. The lower inner screen section 123 and the lower outer screen section 113 are inclined to the side of the quartz crucible 200, and the inclination angle of the lower inner screen section 123 and the lower outer screen section 113 is a predetermined angle. The size of the hot screen 100 is changed to a preset range. Based on the original 8-inch crystal pulling system, the hot field space is expanded to a predetermined position. The position of the heater 300 is moved up according to the expanded hot field space. The distance of the insulation material 400 is adjusted for the heating area of ​​the heater 300 to match the heating area of ​​the heater 300, and the thickness of the insulation material 400 is reduced. Adjusting the parameters for pulling 8-inch silicon single crystals includes: reducing the crystal rotation speed to a first predetermined speed, reducing the crucible rotation speed to a second predetermined speed, increasing the liquid outlet distance to a predetermined height, increasing the inert gas flow rate to a predetermined flow rate, reducing the minimum pulling speed of the crystal rod, adjusting the magnetic field position, and controlling the magnetic field strength.

[0028] This method revolves around pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system, mainly covering two key aspects: thermal field modification and pulling parameter adjustment. The thermal field modification steps are as follows: First, the heat shield 100 in the original 8-inch crystal pulling system is modified by changing its size to a preset range and adjusting the angle of the lower section of the heat shield 100 to a predetermined angle to increase the axial temperature gradient of the thermal field. Next, the thermal field space is expanded to a predetermined position. Due to the expansion of the thermal field space, the position of the heater 300 is moved up accordingly. Finally, for the heating area of ​​the heater 300, the distance of the insulation material 400 is adjusted to match the heating area, and the thickness of the insulation material 400 is reduced to reduce the radial temperature gradient of the thermal field. This ensures that the modified crystal pulling system will not be damaged by the temperature gradient mismatch during the subsequent crystal growth process, thus preventing the destruction of the single crystal structure.

[0029] For larger, heavily doped single crystals grown within a relatively small quartz crucible 200, the large size ratio between the crucible and the single crystal leads to increased natural and forced convection within the crucible 200. This results in more uneven impurity distribution at the solid-liquid interface, increasing the difficulty of crystal growth and causing a decrease in crystallization rate and an increase in the number of pull-out cycles. Therefore, the crystal pulling parameters are adjusted to reduce convection intensity and make the solid-liquid interface shape more flat. Specific adjustments to the parameters for pulling 8-inch silicon single crystals include: reducing the crystal rotation speed to a first predetermined speed, reducing the crucible rotation speed to a second predetermined speed, increasing the liquid outlet distance to a predetermined height, increasing the inert gas flow rate to a predetermined flow rate, reducing the minimum pulling speed of the crystal rod, and adjusting the magnetic field position and controlling the magnetic field strength.

[0030] This application optimizes the temperature distribution and heat transfer efficiency within the thermal field by adjusting the size and angle of the heat shield 100, expanding the thermal field space, moving the heater 300 upwards, and optimizing the insulation material 400. This creates a more suitable thermal environment for pulling 12-inch silicon single crystals. Parameter adjustments optimize various aspects, including crystal and crucible rotation speed, liquid outlet distance, inert gas flow rate, crystal rod pulling speed, and magnetic field. This allows for better control of the crystal growth process, improving the feasibility of producing 12-inch silicon single crystals in an 8-inch crystal pulling system. It ensures that the crystal formation rate, number of pulls, and yield are as close as possible to, or even reach, the average production level of a 12-inch single crystal furnace, meeting market demand for heavily doped 12-inch single crystals.

[0031] The "changing the size of the hot screen 100 to a preset range" includes changing the outer diameter, inner diameter, and height of the hot screen 100, so that the ratio of the inner diameter of the quartz crucible 200 to the outer diameter of the hot screen 100 is between 0.9 ± 0.02, the ratio of the inner diameter of the quartz crucible 200 to the inner diameter of the hot screen 100 is between 0.5 ± 0.02, and the inner diameter of the hot screen 100 is greater than 1.15 times the diameter of the single crystal, and the height of the hot screen 100 is greater than the height of the quartz crucible 200. Through these dimensional adjustments, a reasonable spatial layout and heat exchange relationship are ensured between the hot screen 100, the quartz crucible 200, and other hot field components, so that the hot screen 100 can better adapt to the size and growth requirements of the 12-inch silicon single crystal, and ensure that the 12-inch silicon single crystal that meets the quality requirements can be successfully pulled in the modified 8-inch crystal pulling system.

[0032] When using an 8-inch crystal pulling system to pull 12-inch silicon single crystals, the lower angle of the hot screen 100 has a significant impact on the airflow organization and heat distribution within the thermal field. The lower angle of the hot screen 100 in the original 8-inch crystal pulling system was set according to the requirements of pulling 8-inch silicon single crystals. However, when pulling 12-inch silicon single crystals, due to the increased crystal size, the thermal field environment needs to be adjusted accordingly. In a specific embodiment, the "inclination angle of the lower section of the inner screen and the lower section of the outer screen being tilted is a predetermined angle" includes making the angle (first angle 114) between the lower section 113 of the outer screen 100 and the horizontal line > 15°, increasing the axial temperature gradient between the liquid surfaces, and making the angle (second angle 124) between the lower section 123 of the inner screen 100 and the horizontal line > 25°.

[0033] Adjusting the angles of the outer screen 110 and the lower section 123 of the inner screen helps optimize the heat transfer path, making the heat more evenly distributed near the crystal growth interface. The uniform heat distribution is conducive to the stable growth of the crystal according to the predetermined crystal structure, reducing crystal defects caused by uneven temperature, such as dislocations and stacking faults, thereby improving the quality and crystallization rate of 12-inch silicon single crystal.

[0034] In the process of pulling 12-inch silicon single crystals using an 8-inch crystal pulling system, the proper setting of the thermal field space is crucial. The thermal field space of the original 8-inch crystal pulling system was designed based on the requirements of pulling 8-inch silicon single crystals. When pulling 12-inch silicon single crystals, due to the increase in crystal size, it is necessary to expand the thermal field space to meet the requirements of 12-inch silicon single crystal growth. In a preferred embodiment, the predetermined position is a position where the lower edge of the thermal screen 100 is 500 mm or more away from the crucible zero position. That is, expanding the thermal field space to a position where the lower edge of the thermal screen 100 is 500 mm or more away from the crucible zero position is to provide a sufficient and suitable spatial environment for the growth of 12-inch silicon single crystals, ensuring that various physical and chemical processes can proceed smoothly during crystal growth.

[0035] In the process of modifying an 8-inch crystal pulling system for pulling 12-inch silicon single crystals, the heat distribution and heat transfer relationship within the thermal field have changed due to the expansion and adjustment of the thermal field space. As the core heating component of the thermal field, the rationality of the heater 300's position plays a key role in the temperature uniformity and stability of the thermal field. In a preferred embodiment, the heater 300 is moved upward by ≤80mm. The purpose is to readjust the position of the heater 300 after expanding the thermal field space so that it can better adapt to the new thermal field environment and provide suitable temperature conditions for the growth of 12-inch silicon single crystals.

[0036] Moving the heater 300 upwards, with the upward movement distance controlled within 80mm, allows for a more rational distribution of the heat generated by the heater 300 within the new thermal field. This avoids excessively high or low local temperatures within the thermal field due to excessive adjustment of the heater 300's position, thus maintaining the uniformity of the thermal field temperature. This creates a favorable temperature environment for the stable growth of 12-inch silicon single crystals, reduces crystal defects caused by temperature unevenness, and improves the yield rate. Furthermore, a reasonable heater 300 position helps improve heat transfer efficiency. Within the specified upward movement distance range, the heater 300 can more effectively transfer heat to the quartz crucible 200 and the silicon melt, ensuring that the silicon melt undergoes crystal growth at a suitable temperature, improving energy utilization efficiency, and also contributing to improved growth quality and crystallization rate of the 12-inch silicon single crystal.

[0037] The insulation material 400 of the original 8-inch crystal pulling system was designed based on the thermal field requirements of 8-inch silicon single crystal pulling. When used for pulling 12-inch silicon single crystals and after the thermal field has been modified, the distance between the insulation material 400 and the heating area of ​​the heater 300 needs to be adjusted. In a preferred embodiment, the "adjustment of the distance of the insulation material 400 for the heating area of ​​the heater 300" includes increasing the distance of the middle insulation material 400 corresponding to the main heating area. This distance is ≤80mm to optimize the heat distribution in the thermal field, so that the heat can be applied more effectively to the silicon melt and crystal growth area, and meet the strict temperature requirements for 12-inch silicon single crystal growth.

[0038] In the process of pulling 12-inch silicon single crystals using an 8-inch crystal pulling system, the radial temperature gradient has a critical impact on the crystal growth quality. The original thermal insulation material thickness of 400 mm in the hot zone is designed according to the requirements of pulling 8-inch silicon single crystals. When pulling 12-inch silicon single crystals, due to the increase in crystal size and the change in thermal environment, the original radial temperature gradient may no longer be suitable for the growth of 12-inch silicon single crystals. In a preferred embodiment, the thickness of the thermal insulation material 400 mm corresponding to the original hot zone is reduced to 80% of the original thickness. For example, if the original thickness of the thermal insulation material is 100 mm, it can be reduced to 80 mm. After reducing the thickness of the thermal insulation material 400 mm, the radial temperature gradient is reduced, which can reduce defects and faults in the crystal growth process and improve the crystallization rate of 12-inch silicon single crystals.

[0039] In one specific embodiment, the first predetermined rotational speed is 7-10 rpm, the second predetermined rotational speed is 0.5-2 rpm, the predetermined height is 45-55 mm, the predetermined flow rate is above 130-180 slm, the minimum crystal rod pulling speed is reduced to below 0.55 mm / min, the magnetic field position is adjusted within a range of ±40 mm at the level with the solution, and the magnetic field strength is controlled at 4000-4500 GS, wherein the maximum crystal rod pulling speed is 1.1-1.2 mm / min.

[0040] Furthermore, the inert gas is argon.

[0041] Furthermore, the pressure of the inert gas is determined by the opening of the pressure valve, and the minimum opening of the pressure valve during crystal growth is 20°-40°.

[0042] The following specific experimental examples further illustrate the technical solution and effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention. Example

[0043] The modified 8-inch crystal pulling system provided in this application was used to pull 12-inch silicon single crystals. The goal was to pull the crystals with a head resistivity of 2.5 mΩ. The crystal pulling parameters are shown in Table 1. Five parallel examples were made (for ease of description, they are referred to as Example 1, Example 2, Example 3, Example 4 and Example 5). Five single crystals were pulled through these five examples.

[0044] Comparative Example The original 8-inch crystal pulling system was used to pull 12-inch silicon single crystals. The goal was to pull the crystals with a head resistivity of 2.5 mΩ. The crystal pulling parameters are shown in Table 1. Five sets of parallel comparative examples were made (for ease of description, they are referred to as Comparative Example 1, Comparative Example 2, Comparative Example 3, Comparative Example 4 and Comparative Example 5). Five single crystals were pulled from each of these five sets of comparative examples.

[0045] Table 1 Comparison of parameters between the examples and comparative examples

[0046] The head resistivity, number of pulls, crystallization rate, and yield of silicon single crystals below 2.5 mΩ were tested in the five sets of examples and the five sets of comparative examples above. The test results are as follows: Figure 4 , Figure 5 , Figure 6 and Figure 7 As shown.

[0047] Depend on Figure 4 It can be seen that the head resistance of the silicon single crystal in the five comparative examples is greater than or equal to 0.0035mΩ, while the head resistance of the silicon single crystal in the five examples is less than 0.0035mΩ. Depend on Figure 5 It can be seen that when pulling silicon single crystals using the method provided in the comparative example, the minimum number of pulls is 7 and the maximum is 15. However, when pulling silicon single crystals using the method provided in the implementation, the number of pulls is greatly reduced, averaging about 4. Depend on Figure 6It can be seen that when silicon single crystals are pulled using the method provided in the comparative example, the crystallization rate does not exceed 30%, while when silicon single crystals are pulled using the method provided in the implementation, the crystallization rate can reach more than 65%. Depend on Figure 7 It can be seen that when silicon single crystals are pulled using the method provided in the comparative example, the yield rate of silicon single crystals with a 2.5mΩ or lower is zero, while when silicon single crystals are pulled using the method provided in the implementation example, the average yield rate of silicon single crystals with a 2.5mΩ or lower is about 37%.

[0048] In summary, when using the method provided in this application to pull 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system, the head resistance of the silicon single crystal can be reduced, the number of times it is detonated can be greatly reduced, the crystal formation rate and the yield rate below 2.5mΩ can be significantly improved, and the quality level and degree of pulling 12-inch silicon single crystals using a 12-inch crystal pulling system can be achieved.

[0049] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for pulling 12-inch silicon single crystals using an adjusted 8-inch crystal pulling system, characterized in that, This involves adjusting the original 8-inch crystal pulling system and the parameters for pulling 8-inch silicon single crystals. The adjusted 8-inch crystal pulling system, combined with the adjusted 8-inch silicon single crystal parameters, is used to pull 12-inch silicon single crystals. The adjusted 8-inch crystal pulling system includes a single crystal furnace, a quartz crucible, heaters, a heat shield, and insulation material. The quartz crucible is placed inside the single crystal furnace, the heaters are arranged around the outside of the quartz crucible, the insulation material is placed around the heaters, and the heat shield is placed above the quartz crucible. The heat shield includes an inner screen and an outer screen. The inner screen includes an upper section, a middle section, and a lower section, and the outer screen includes an upper section, a middle section, and a lower section. The inner screen upper section and the outer screen upper section are inclined to the side away from the quartz crucible, the inner screen middle section and the outer screen middle section are vertically arranged, the inner screen lower section and the outer screen lower section are inclined to one side of the quartz crucible, and the inclination angle of the inner screen lower section and the outer screen lower section is a predetermined angle. The size of the hot screen is changed to a preset range, and the hot field space is expanded to a predetermined position based on the original 8-inch crystal pulling system. The position of the heater is moved up according to the expanded hot field space, and the distance of the heat insulation material is adjusted for the heating area of ​​the heater to match the heating area of ​​the heater, and the thickness of the heat insulation material is reduced. Adjusting the parameters for pulling 8-inch silicon single crystals includes: reducing the crystal rotation speed to a first predetermined speed, reducing the crucible rotation speed to a second predetermined speed, increasing the liquid outlet distance to a predetermined height, increasing the inert gas flow rate to a predetermined flow rate, reducing the minimum pulling speed of the crystal rod, adjusting the magnetic field position, and controlling the magnetic field strength.

2. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The phrase "changing the size of the hot screen to a preset range" includes changing the outer diameter, inner diameter, and height of the hot screen, such that the ratio of the inner diameter of the quartz crucible to the outer diameter of the hot screen is between 0.9 ± 0.02, the ratio of the inner diameter of the quartz crucible to the inner diameter of the hot screen is between 0.5 ± 0.02, and the inner diameter of the hot screen is greater than 1.15 times the diameter of the single crystal, and the height of the hot screen is greater than the height of the quartz crucible.

3. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The phrase "the tilt angle of the lower section of the inner screen and the lower section of the outer screen is a predetermined angle" includes making the angle between the lower section of the outer screen of the hot screen and the horizontal line > 15°, and making the angle between the lower section of the inner screen of the hot screen and the horizontal line > 25°.

4. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The predetermined position is a position where the lower edge of the heat shield is ≥200mm from the crucible zero position.

5. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The heater is moved upward by a distance ≤80mm.

6. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The phrase "adjusting the distance of the insulation material for the heating zone of the heater" includes increasing the distance of the central insulation material corresponding to the main heating zone, which is ≤80mm.

7. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The thickness of the insulation material corresponding to the original heat zone is reduced to 80% of the original thickness.

8. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 1, characterized in that, The first predetermined rotation speed is 7-10 rpm, the second predetermined rotation speed is 0.5-2 rpm, the predetermined height is 45-55 mm, the predetermined flow rate is 130-180 slm or more, the minimum pulling speed of the crystal rod is reduced to below 0.55 mm / min, the magnetic field position is adjusted within a range of ±40 mm at the level with the solution, and the magnetic field strength is controlled at 4000-4500 GS.

9. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 8, characterized in that, The inert gas is argon.

10. The method for pulling 12-inch silicon single crystals using an 8-inch crystal pulling system according to claim 8, characterized in that, The pressure of the inert gas is determined by the opening of the pressure valve, and the minimum opening of the pressure valve during crystal growth is 25°-40°.

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