Method for confirming optimal power ratio of thermal field structure

Abstract

The invention provides a method for confirming the optimal power ratio of a thermal field structure, and belongs to the technical field of monocrystalline silicon manufacturing. Comprising the following steps: S1, setting power ratios of a plurality of groups of different main bottom heaters, and simulating an R angle of a crucible and the temperature of the side wall of the crucible; and S2, according to the temperature range and the temperature distribution of the whole thermal field, determining the optimal power ratio range. According to the invention, a plurality of groups of different power ratios of the main bottom heater are set, and the R angle of the crucible and the temperature of the side wall of the crucible are simulated through simulation software according to different power ratios; and finally, according to the temperature range and the temperature distribution of the whole thermal field, determining the optimal power ratio range. Therefore, the actual crucible does not need to be heated, simulation is carried out through simulation software, the optimal power matching range is selected according to the simulation result, the situation of crucible deformation is avoided, and the influence on the service life of a thermal field is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon manufacturing, and in particular to a method for confirming an optimal power ratio of a thermal field structure. Background Art

[0002] At present, silicon materials account for more than 98% of semiconductor devices. With the rapid development of global informatization, people's demand for information has grown rapidly. Information technology based on large-scale or even ultra-large-scale integrated circuits has become the cornerstone of today's economic activities and social life. Integrated circuits have entered the nanoscale stage, which puts forward higher requirements and challenges for single-crystal silicon materials as the basis of integrated circuits, so that single-crystal silicon materials have developed from 4 inches to the current mass-produced 12 inches, 18 inches... large size, high integrity and high uniformity. Therefore, the structure of the thermal field is the focus of attention and design for each company. The thermal field structure of each company is different, and the process is different, which leads to differences in subsequent crystal defects. And each newly designed thermal field needs to pay attention to the ratio of its heater. The ratio of the heater affects the service life of the thermal field, the defects of the crystal rod of the crystal pulling, the quality of the crystal, etc. Therefore, how to determine the power ratio of the heater is a problem that every thermal field designer must consider.

[0003] In the past, when determining the power ratio of the heater, the crucible was heated by the actual heater, and different power ratios were tried according to the melting time, melting efficiency and the bearing capacity of the crucible. Each time an attempt was made, the heater was required to heat the crucible, causing the crucible to be heated continuously, and the temperature that the crucible could withstand was limited. If the temperature was too high or the high temperature time was too long, the softening time of the crucible would be too long, causing the crucible to deform. At the same time, if the high temperature time was too long, the graphite parts and thermal insulation materials in the heat field would be overheated, thereby affecting the service life of the heat field. Summary of the invention

[0004] In view of this, the present invention provides a method for confirming the optimal power ratio of a thermal field structure, so as to solve the technical problem that the crucible may be deformed when confirming the power ratio of the heater, thereby affecting the service life of the thermal field.

[0005] The technical solution adopted by the present invention to solve its technical problem is: A method for confirming the optimal power ratio of a thermal field structure comprises the following steps: S1. Setting multiple groups of different power ratios of the main bottom heater to simulate the R angle of the crucible and the temperature of the side wall of the crucible; S2. Determine the optimal power ratio range based on the temperature range and the temperature distribution of the overall thermal field.

[0006] Preferably, in step S1, a plurality of different power ratios of the main bottom heaters are set, specifically comprising the following steps: S11. Setting basic parameters of thermal field simulation; S12. Setting a plurality of different power ratios of the main bottom heaters based on basic parameters of the thermal field simulation.

[0007] Preferably, after step S12, the following steps are also included: S13, simulating a reference point, determining the position of the reference point and the target temperature; S14, adjusting the power of each group of main bottom heaters according to the target temperature of the reference point, and keeping the power ratio of the main bottom heaters unchanged; S15. After the power of each group of main bottom heaters is adjusted, the R angle of the crucible and the temperature of the side wall of the crucible are simulated.

[0008] Preferably, in step S2, the optimal power ratio range is determined according to the temperature range and the temperature distribution of the overall thermal field, which specifically includes the following steps: S21. Based on the simulated temperature, the melt temperature and flow rate graphs corresponding to each power ratio are respectively drawn, and the temperature distribution change trend and flow rate distribution change trend of the melt in the graphs are compared and analyzed; S22. Determine the optimal power ratio range based on the temperature distribution change trend and the flow velocity distribution change trend.

[0009] Preferably, in step S22, based on the temperature distribution change trend and the flow velocity distribution change trend, determining the optimal power ratio range includes the following steps: S221. If there is no obvious change trend in the temperature distribution and the flow rate distribution, reset the power ratio of the multiple groups of main bottom heaters different from step S1, simulate the R angle of the crucible and the temperature of the side wall of the crucible, and execute step S21 again.

[0010] Preferably, the method further comprises: S222. If the temperature distribution and flow velocity distribution have obvious changing trends, simulate the thermal field schematic diagram of the bottom of the crucible corresponding to each power ratio, and analyze the change of the gas flow velocity above the main heater and the bottom heater; S223. Based on the change in gas flow velocity, determine the optimal power ratio range.

[0011] Preferably, in step S223, based on the change in the gas flow velocity, determining the optimal power ratio range comprises the following steps: If there is a group of power ratios corresponding to the crucible bottom thermal field diagram in which eddies appear above the bottom heater, indicating that the gas flow velocity above the bottom heater of this group has a significant change, then the optimal power ratio is greater than this group of power ratios.

[0012] Preferably, after step S22, the method further comprises: pulling the crystal rod according to the optimal power ratio range, and adjusting the optimal power ratio range based on the defect conditions of the crystal rod.

[0013] Compared with the prior art, the present invention has the following beneficial effects: The present invention sets a plurality of different power ratios of the main bottom heaters. According to different power ratios, the R angle of the crucible and the temperature of the side wall of the crucible are simulated by ANSYS simulation software; finally, the optimal power ratio range is confirmed according to the temperature range and the temperature distribution of the overall thermal field. Therefore, there is no need to heat the actual crucible. Through simulation software simulation, the optimal power ratio range is selected according to the simulation results, so that the crucible will not deform, reducing the impact on the service life of the thermal field. Furthermore, the actual crystal pulling results are not needed, and the optimal solution can be found according to the simulation data, which reduces the time cost and crystal pulling cost, and enables the new thermal field to be promoted faster. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 The figure is a flow chart of the method of the present invention.

[0015] Figure 2 It is a schematic diagram of the setting of the horizontal axis of the R angle of the crucible and the simulation diagram of the crucible side wall in the embodiment.

[0016] Figure 3 It is a comparison diagram of the simulated crucible side wall temperature distribution curve corresponding to each group of power ratios in Table 2 of the embodiment.

[0017] Figure 4 It is a comparison diagram of the R angle temperature distribution curve of the simulated crucible corresponding to each group of power ratios in Table 2 of the embodiment.

[0018] Figure 5 It is a graph of melt temperature and flow rate corresponding to each power ratio in Table 2 of the embodiment.

[0019] Figure 6 It is a comparison diagram of the simulated crucible side wall temperature distribution curve corresponding to each group of power ratios in Table 3 of the embodiment.

[0020] Figure 7 It is a comparison diagram of the R angle temperature distribution curve of the simulated crucible corresponding to each group of power ratios in Table 3 of the embodiment.

[0021] Figure 8 The melt temperature and flow rate spectrum corresponding to each power ratio in Table 3 of the embodiment.

[0022] Fig. 9 This is a comparison diagram of the simulated crucible side wall temperature distribution curves corresponding to the two groups of power ratios selected in the embodiment.

[0023] Fig.10 Melt temperature and flow rate graphs corresponding to two sets of power ratios selected for the embodiment.

[0024] Fig.11 Schematic diagram of the simulated bottom thermal field corresponding to the two sets of power ratios selected for the embodiment. DETAILED DESCRIPTION

[0025] The technical solutions and technical effects of the embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings of the present invention.

[0026] Please see Figure 1 , a method for confirming the optimal power ratio of a thermal field structure, comprising the following steps: S1. Setting multiple groups of different power ratios of the main bottom heater to simulate the R angle of the crucible and the temperature of the side wall of the crucible; S2. Determine the optimal power ratio range based on the temperature range and the temperature distribution of the overall thermal field.

[0027] The present invention sets a plurality of different power ratios of the main bottom heaters. According to different power ratios, the R angle of the crucible and the temperature of the side wall of the crucible are simulated by ANSYS simulation software; finally, the optimal power ratio range is confirmed according to the temperature range and the temperature distribution of the overall thermal field. Therefore, there is no need to heat the actual crucible. Through simulation software simulation, the optimal power ratio range is selected according to the simulation results, so that the crucible will not deform, reducing the impact on the service life of the thermal field. Furthermore, the actual crystal pulling results are not needed, and the optimal solution can be found according to the simulation data, which reduces the time cost and crystal pulling cost, and enables the new thermal field to be promoted faster.

[0028] Furthermore, in step S1, a plurality of different power ratios of the main bottom heaters are set, specifically including the following steps: S11. Setting the basic parameters of thermal field simulation; wherein the basic parameters of thermal field simulation are the basic parameters of crystal pulling, including feed amount, GAP, crystal diameter, furnace pressure, melt interface position, argon flow rate, equal diameter pulling speed, crystal rotation, and crucible rotation. The melt interface position refers to the height difference between the center point of the main heater and the liquid surface.

[0029] S12. Set multiple groups of different power ratios of the main bottom heaters based on the basic parameters of the thermal field simulation. Specifically, according to the basic parameters of the thermal field simulation, combined with the power ratio of the main bottom heater in the actual material stage corresponding to the basic parameters, set multiple groups of different power ratios of the main bottom heaters and the power of the main bottom heater corresponding to each power ratio. Among them, different sizes of single crystal silicon correspond to different crystal pulling parameters. By setting the basic parameters of the thermal field simulation, the size of the simulated single crystal silicon can be limited, and then for single crystal silicon of different sizes, the optimal power ratio range corresponding to the single crystal silicon of that size can be accurately simulated.

[0030] Furthermore, after step S12, the following steps are also included: S13, simulating a reference point, and determining the position of the reference point and the target temperature; wherein the position of the reference point and the target temperature may be set randomly.

[0031] S14, adjusting the power of each group of main bottom heaters according to the target temperature of the reference point, and keeping the power ratio of the main bottom heaters unchanged; S15. After the power of each group of main bottom heaters is adjusted, the R angle of the crucible and the temperature of the side wall of the crucible are simulated.

[0032] Specifically, the simulation calculation method adjusts the power of the main bottom heater set in step S12 according to the target temperature of the reference point; the power is continuously adjusted according to the target temperature of the reference point to ensure that the temperature value of the temperature field at this point reaches the target temperature. Because the target temperature of the reference point is specified to ensure the heat input at this point, the total input power of the multiple groups of main bottom heaters after adjustment is similar. Since the power ratio of the main bottom heater must be kept unchanged during the adjustment process, the power ratio of the adjusted main bottom heater is consistent with the power ratio set in step S12, but the total power before and after the adjustment is inconsistent. By setting the reference point target temperature to adjust the power of the main bottom heater, the basic parameters and the total input power of the main bottom heater are guaranteed to remain unchanged when the simulation results are subsequently analyzed. The simulation results are only related to the power ratio, thereby improving the reliability of the simulation results and the accuracy of the optimal power ratio range.

[0033] Further, in step S2, the optimal power ratio range is determined according to the temperature range and the temperature distribution of the overall thermal field, which specifically includes the following steps: S21. Based on the simulated temperature, the melt temperature and flow rate graphs corresponding to each power ratio are respectively drawn, and the temperature distribution change trend and flow rate distribution change trend of the melt in the graphs are compared and analyzed; S22. Determine the optimal power ratio range based on the temperature distribution change trend and the flow velocity distribution change trend.

[0034] Through simulation software, based on the simulated crucible R angle and the temperature of the crucible side wall, the melt temperature and flow rate maps corresponding to each power ratio are drawn, and the temperature distribution trend and flow rate distribution trend of the melt in the map are compared and analyzed. Based on the temperature distribution trend and flow rate distribution trend of the melt in the map, the influence of different power ratios on the melting time and melting efficiency can be analyzed, so there is no need to actually heat the crucible through the main bottom heater with different power ratios to determine the influence of the power ratio on the melting time and melting efficiency, thereby reducing the time cost and crystal pulling cost, and at the same time increasing the service life of the thermal field.

[0035] Further, in step S22, based on the temperature distribution change trend and the flow velocity distribution change trend, the optimal power ratio range is determined, including the following steps: S221. If there is no obvious change trend in the temperature distribution and the flow rate distribution, reset the power ratio of the multiple groups of main bottom heaters that are different from step S1, simulate the R angle of the crucible and the temperature of the side wall of the crucible, and execute step S21 again. Specifically, if there is no obvious change trend in the temperature distribution and the flow rate distribution, it is impossible to analyze the impact of different power ratios on the material stage. Therefore, the power ratio of the multiple groups of main bottom heaters that are different from step S1 can be reset. Among them, the reset power ratio needs to be significantly different from the power ratio set in step S1 to ensure that when analyzing the temperature distribution change trend and the flow rate distribution change trend of the melt in the spectrum, the temperature distribution and the flow rate distribution change trend are more obvious, which is convenient for the subsequent confirmation of the optimal power ratio.

[0036] Furthermore, the method further comprises: S222. If the temperature distribution and flow velocity distribution have obvious changing trends, simulate the thermal field schematic diagram of the bottom of the crucible corresponding to each power ratio, and analyze the change of the gas flow velocity above the main heater and the bottom heater; S223. Based on the change in gas flow velocity, determine the optimal power ratio range.

[0037] When the temperature distribution and flow rate distribution of the melt in the graph show an obvious changing trend, it indicates that when the power ratio changes, the thermal field of the crucible in the material-making stage changes more obviously. Therefore, the thermal field schematic diagram of the bottom of the crucible corresponding to each group of power ratios can be simulated again, and the changes in the gas flow velocity above the main heater and the bottom heater can be analyzed to confirm the optimal power ratio range.

[0038] Further, in step S223, based on the change in the gas flow velocity, determining the optimal power ratio range includes the following steps: If there is a group of power ratios corresponding to the crucible bottom thermal field diagram and eddies appear above the bottom heater, indicating that the gas flow velocity above the bottom heater of this group has changed significantly, then the optimal power ratio is greater than this group of power ratios. During crystal pulling, the melt needs to have a stable flow rate and eddies should be avoided as much as possible. Therefore, when eddies appear above the bottom heater in the crucible bottom thermal field diagram corresponding to a group of power ratios, the optimal power ratio should be greater than this group of power ratios to ensure that the melt maintains a stable flow rate during the crystal pulling process.

[0039] Further, after step S22, the method further includes: pulling a crystal rod according to the optimal power ratio range, and adjusting the optimal power ratio range based on the defect conditions of the crystal rod. After confirming the optimal power ratio range, multiple crystal rods can also be pulled according to the optimal power ratio range, and the defects related to the material stage of the pulled multiple crystal rods are analyzed. When the pulled crystal rod has defects related to the material stage, the corresponding power ratio is excluded and the optimal power ratio range is narrowed. In this way, the temperature and the defect conditions of the pulled crystal rod are simulated by the simulation software to obtain a more accurate optimal power ratio range. Example

[0040] First, confirm the basic parameters of thermal field simulation as shown in Table 1: Table 1

[0041] Among them, Charge is the feed amount, Body length is the crystal pulling length (since the present invention mainly simulates the power ratio of the main bottom heater in the material-forming stage, the Body length is 0 mm), and the melt interface position is the height difference between the center point of the main heater and the liquid surface.

[0042] Secondly, determine the reference point temperature. The coordinates of the reference point in this simulation are (2, -2), and the target temperature of the reference point is 1685 K. According to the basic parameters in Table 1, the power ratios of 1-1, 1-3, 1-5, and 1-6 are set to obtain the power ratios shown in Table 2: Table 2

[0043] Furthermore, the simulation calculation method is used to adjust the power of the main bottom heaters 1-1, 1-3, 1-5, and 1-6 according to the target temperature of the reference point; the target temperature of the reference point is 1685K, and the power is continuously adjusted according to the target temperature of the reference point to ensure that the temperature value of the temperature field at this point reaches the target temperature. Because the target temperature of the reference point is specified to ensure the heat input at this point, the total input power of the multiple groups of main bottom heaters after adjustment is similar to 19.5-79.6, as shown in Table 2. Since the power ratio of the main bottom heater must be kept unchanged during the adjustment process, the power ratio of the adjusted main bottom heater is consistent with the set power ratio, but the total power before and after the adjustment is inconsistent. For example, the power ratio of 1-1 before and after the adjustment is 70.97%, but the total power before the adjustment is 155, and the total power after the adjustment is 79.6. The power of the main bottom heater is adjusted by setting the reference point target temperature, so that when the simulation results are subsequently analyzed, the basic parameters and the total input power of the main bottom heater are guaranteed to remain unchanged. The simulation results are only related to the power ratio, thereby improving the reliability of the simulation results and the accuracy of the optimal power ratio range.

[0044] Again, according to the above basic parameters and multiple groups of different power ratios, the R angle of the crucible and the temperature of the side wall of the crucible are simulated, and the following are obtained: Figure 3 and Figure 4 The comparison diagram of the temperature distribution curves of the crucible side wall and the crucible R corner is shown in FIG. Figure 3 and Figure 4 The horizontal axis is set as Figure 2 , that is, the horizontal coordinate from the crucible wall to the center point, where the horizontal coordinate of the crucible wall is 0 and the horizontal coordinate of the crucible center axis is 141.

[0045] By analyzing Figure 3 and Figure 4 It can be seen that according to the temperature distribution of the side wall of the crucible: the temperature of the R corner of the crucible is the highest; as the side power is reduced and the bottom power is increased, the temperature above the R corner becomes smaller and the temperature below the R corner becomes larger; the temperature transition point is at the R corner, and the lower the side-to-bottom power ratio, the lower the temperature transition point is at the R corner.

[0046] Next, the melt temperature and flow rate maps corresponding to each power ratio were plotted based on the simulated temperature, and the following results were obtained: Figure 5 The melt temperature and flow rate diagram shown in Figure 5 It can be seen that the temperature distribution in the melt has no obvious change trend, and the flow rate distribution in the melt has no obvious change trend. Therefore, it is not possible to analyze the impact of different power ratios on the material stage, and it is necessary to reset the power ratios of multiple groups of main bottom heaters that are different from step S1.

[0047] Therefore, another 4 groups of experiments in Table 3 were designed, and the experimental results are as follows: Table 3

[0048] Among them, the basic parameters of 3-1, 3-3, 3-5, and 3-6 also use the basic parameters shown in Table 1 to ensure that other parameters in the simulation experiment remain unchanged, and only the power ratio is different, so as to simulate the R angle of the crucible and the temperature change of the crucible side wall when the power ratio is different. In this group of simulations, the main bottom power ratio is relatively large, but the total power increase after adjustment is less than 1%, and the total power of the adjusted main bottom heater is not much different from the total power of the adjusted main bottom heater in Table 2.

[0049] Again, according to the above basic parameters and the power ratios of 3-1, 3-3, 3-5, and 3-6, the R angle of the crucible and the temperature of the side wall of the crucible are simulated, and the following is obtained: Figure 6 and Figure 7 The comparison of the temperature distribution curves of the crucible side wall and the crucible R angle is shown in the figure. Figure 6 and Figure 7 It can be seen that the temperature distribution curves of the crucible side wall and crucible R angle corresponding to 3-1, 3-3, 3-5, and 3-6 do not change much.

[0050] Based on the simulated temperature, the melt temperature and flow rate graphs corresponding to each power ratio are plotted respectively, and the following are obtained: Figure 8 The melt temperature and flow rate diagram shown in Figure 8 It can be seen that there is no obvious change trend in the temperature distribution of the melt, and there is no obvious change trend in the flow rate distribution of the melt. Therefore, it is also impossible to analyze the impact of different power ratios on the material stage.

[0051] Based on this, the inventors compared 1-6 of Table 2 with 3-1 of Table 3 and obtained the following: Fig. 9 The comparison of the crucible side wall temperature distribution curves simulated in 1-6 and 3-1, and Fig.10 The melt temperature and flow rate graphs of 1-6 and 3-1 are shown in the figure. Among them, the power ratio of the main bottom heater is reduced from 88.69% to 64.0%. Fig. 9 It can be seen that the temperature of the crucible wall temperature at the R angle decreases, the temperature below the R angle increases, and the temperature change transition point is at the R angle. Fig.10 It can be seen that when the power ratio is reduced and the reduction is relatively large, the temperature distribution of the melt has obvious differences. When the power of the main heater is high, the temperature gradient is large. When the power of the main heater is large, the high-temperature area of ​​the crucible side wall is significantly larger. When the power ratio becomes smaller, there is a difference in the flow speed. The high-speed area has a significant decrease, and the low-speed area has little change.

[0052] Furthermore, the schematic diagrams of the thermal field at the bottom of the crucible corresponding to 1-6 and 3-1 are simulated respectively, as shown in FIG. Fig.11As shown in Figure 2, the changes in gas flow velocity above the main heater and bottom heater are analyzed. Fig.11 The final simulated bottom thermal field diagram shows that the power ratio changes, but the gas flow velocity above the main heater does not change significantly. When the power ratio drops from 88.69% to 64.0%, the gas flow and flow velocity above the bottom heater change significantly, that is, at low power ratio, vortices form above the bottom heater. Since the melt needs a stable flow rate during crystal pulling and vortices are avoided as much as possible, the power ratio cannot be lower than 64.0%, that is, the optimal power ratio range is not less than 64.0%.

[0053] Furthermore, according to the optimal power ratio range, the crystal ingot was pulled. By analyzing the defects in the crystal ingot related to the material stage, it was found that when the power ratio range was 80-85%, the quality of the pulled crystal ingot was the best. Therefore, the optimal power ratio range is 80-85%.

[0054] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for confirming the optimal power ratio of a thermal field structure, characterized in that: The following steps are involved: S1. Setting multiple groups of different power ratios of the main bottom heater to simulate the R angle of the crucible and the temperature of the side wall of the crucible; S2. Determine the optimal power ratio range based on the temperature range and the temperature distribution of the overall thermal field.

2. The method for confirming the optimal power ratio of the thermal field structure according to claim 1 is characterized in that: In step S1, a plurality of different power ratios of the main bottom heaters are set, specifically including the following steps: S11. Setting basic parameters of thermal field simulation; S12. Setting a plurality of different power ratios of the main bottom heaters based on basic parameters of the thermal field simulation.

3. The method for confirming the optimal power ratio of the thermal field structure according to claim 2 is characterized in that: After step S12, the following steps are also included: S13, simulating a reference point, determining the position of the reference point and the target temperature; S14, adjusting the power of each group of main bottom heaters according to the target temperature of the reference point, and keeping the power ratio of the main bottom heaters unchanged; S15. After the power of each group of main bottom heaters is adjusted, the R angle of the crucible and the temperature of the side wall of the crucible are simulated.

4. The method for confirming the optimal power ratio of the thermal field structure according to claim 1, characterized in that: In step S2, the optimal power ratio range is determined according to the temperature range and the temperature distribution of the overall thermal field, which specifically includes the following steps: S21. Based on the simulated temperature, the melt temperature and flow rate graphs corresponding to each power ratio are respectively drawn, and the temperature distribution change trend and flow rate distribution change trend of the melt in the graphs are compared and analyzed; S22. Determine the optimal power ratio range based on the temperature distribution change trend and the flow velocity distribution change trend.

5. The method for confirming the optimal power ratio of the thermal field structure according to claim 4 is characterized in that: In step S22, based on the temperature distribution change trend and the flow velocity distribution change trend, the optimal power ratio range is determined, including the following steps: S221. If there is no obvious change trend in the temperature distribution and the flow rate distribution, reset the power ratio of the multiple groups of main bottom heaters different from step S1, simulate the R angle of the crucible and the temperature of the side wall of the crucible, and execute step S21 again.

6. The method for confirming the optimal power ratio of the thermal field structure according to claim 5 is characterized in that: The method further comprises: S222. If the temperature distribution and flow velocity distribution have obvious changing trends, simulate the thermal field schematic diagram of the bottom of the crucible corresponding to each power ratio, and analyze the change of the gas flow velocity above the main heater and the bottom heater; S223. Based on the change in gas flow velocity, determine the optimal power ratio range.

7. The method for confirming the optimal power ratio of the thermal field structure according to claim 6, characterized in that: In step S223, based on the change in the gas flow rate, determining the optimal power ratio range includes the following steps: If there is a group of power ratios corresponding to the crucible bottom thermal field diagram in which eddies appear above the bottom heater, indicating that the gas flow velocity above the bottom heater of this group has a significant change, then the optimal power ratio is greater than this group of power ratios.

8. The method for confirming the optimal power ratio of a thermal field structure according to any one of claims 1 to 7, characterized in that: After step S22, the method further includes: pulling the crystal rod according to the optimal power ratio range, and adjusting the optimal power ratio range based on the defect conditions of the crystal rod.

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