A method of controlling temperature uniformity in a crystal pulling process

Abstract

The application provides a method for controlling temperature consistency of a crystal pulling process, comprising: monitoring a silicon solution liquid surface temperature in a temperature stabilization process, judging whether the silicon solution liquid surface temperature meets a first preset condition; if yes, judging whether a temperature change value from an initial temperature to the measured liquid surface temperature meets a second preset condition; if yes, adjusting a thermal field temperature according to the measured liquid surface temperature, so that the thermal field temperature is close to or equal to the measured liquid surface temperature; calculating a thermal field coefficient; and adjusting a thermal field temperature change value at any time point after the temperature stabilization process according to the thermal field coefficient. The application has the beneficial effect of adjusting the thermal field temperature change value according to the thermal field coefficient and the set liquid surface temperature change value in the crystal pulling system, so as to ensure that different single crystal furnaces can completely ensure the temperature consistency in the single crystal pulling process under the condition of different temperature stabilities, and avoid the temperature instability in the crystal pulling process caused by the different temperature rising and falling amplitudes due to the difference in thermal field temperature stability.

Description

Technical Field

[0001] This invention belongs to the field of single crystal pulling technology, and in particular relates to a method for controlling the temperature consistency during the crystal pulling process. Background Technology

[0002] In the process of pulling single crystals in a single crystal furnace, it is impossible to accurately measure the liquid surface temperature to adjust the heater power. It is often necessary to control the heater power value by controlling the thermal field temperature to ensure that the crystallization temperature in the single crystal furnace is in dynamic equilibrium.

[0003] In the parameters for pulling single crystals, the cooling range refers to the temperature value of the thermal field. For example, if the temperature is reduced or increased by 10°C (thermal field temperature), this instruction will not directly affect the power control of the heater. It needs to be indirectly controlled by measuring the temperature value of the thermal field.

[0004] Due to factors such as inconsistent insulation performance of single crystal furnaces, thermal aging, and differences in temperature measurement locations, it is difficult to ensure that the heater power, which indirectly controls the temperature of the thermal field, is consistent with the temperature rise and fall range specified in the parameters. This leads to a discrepancy between the trend of temperature change in the thermal field and the actual trend of temperature change at the liquid surface. For example, if the parameter requires a temperature drop of 20°C, different single crystal furnaces will often produce different results. Single crystal furnaces with good insulation performance will show smaller actual temperature rise and fall ranges than those with poor insulation performance. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for controlling the temperature consistency of the crystal pulling process, so as to solve the above or other problems existing in the prior art.

[0006] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for controlling the temperature uniformity during the crystal pulling process, comprising:

[0007] During the temperature stabilization process, the surface temperature of the silicon solution is monitored to determine whether the surface temperature of the silicon solution meets the first preset condition.

[0008] If so, determine whether the temperature change value of the liquid surface temperature from the initial temperature to the measured liquid surface temperature meets the second preset condition;

[0009] If so, adjust the thermal field temperature according to the measured liquid surface temperature so that the thermal field temperature is close to or equal to the measured liquid surface temperature.

[0010] Calculate the thermal field coefficient;

[0011] The change in thermal field temperature at any point in time after the temperature stabilization process is adjusted according to the thermal field coefficient.

[0012] Furthermore, the silicon solution surface temperature meets the first preset condition as follows: the measured silicon solution surface temperature is between the preset lower limit value and the preset upper limit value of the surface temperature.

[0013] Furthermore, the preset lower limit for liquid surface temperature is 1440℃-1450℃, and the preset upper limit for liquid surface temperature is 1455℃-1465℃.

[0014] Furthermore, if the surface temperature of the silicon solution does not meet the first preset condition, the surface temperature of the silicon solution will continue to be monitored to determine whether the surface temperature of the silicon solution meets the first preset condition.

[0015] Furthermore, when adjusting the thermal field temperature based on the measured liquid surface temperature, the measured liquid surface temperature is used as the target temperature, and the thermal field temperature is increased or decreased according to a preset adjustment time, which is 10-20 minutes.

[0016] Furthermore, the temperature change value of the liquid surface temperature satisfies the second preset condition: the temperature change value of the liquid surface temperature is greater than the preset liquid surface temperature change value.

[0017] Furthermore, the preset liquid surface temperature change value is not less than 10℃.

[0018] Furthermore, if the temperature change of the liquid surface does not meet the second preset condition, the liquid surface temperature of the silicon solution will continue to be monitored to determine whether the liquid surface temperature of the silicon solution meets the first preset condition.

[0019] Furthermore, the thermal field coefficient is the ratio of the temperature change at the liquid surface to the temperature change in the thermal field.

[0020] Furthermore, the formula for calculating the thermal field coefficient is: Thermal field coefficient = [(initial liquid surface temperature - final liquid surface temperature) / initial liquid surface temperature] / [(initial thermal field temperature - final thermal field temperature) / initial thermal field temperature].

[0021] Furthermore, in the step of adjusting the change value of the thermal field temperature at any time point after the temperature stabilization process according to the thermal field coefficient, the change value of the thermal field temperature at any time point is the product of the set change value of the liquid surface temperature at that time point and the thermal field coefficient.

[0022] Furthermore, the liquid surface temperature change value is set to 5-15℃.

[0023] By adopting the above technical solution, during the crystal pulling process, the thermal field temperature is adjusted according to the liquid surface temperature during the automatic temperature stabilization stage based on the different thermal field insulation properties, and the thermal field coefficient is calculated. In the subsequent automatic temperature stabilization stage, the thermal field temperature change value is adjusted according to the thermal field coefficient and the liquid surface temperature change value set in the crystal pulling system. This ensures that the temperature consistency during the single crystal pulling process can be fully guaranteed even when different single crystal furnaces have different insulation properties. It avoids temperature instability during the crystal pulling process caused by different heating and cooling amplitudes due to differences in thermal field insulation properties, reduces quality defects and breakage caused by unsuitable temperature during single crystal pulling, improves single crystal quality, and increases output. Attached Figure Description

[0024] Figure 1 This is a logic flowchart of an embodiment of the present invention. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0026] Figure 1 The diagram shows a logic flowchart of an embodiment of the present invention. This embodiment relates to a method for controlling the temperature consistency during the crystal pulling process. The method controls the temperature change of the thermal field according to the change of the silicon solution surface temperature. It can ensure that the liquid surface temperature is adjusted according to the parameter setting trend based on the different thermal field insulation performance. This ensures that the temperature consistency during the single crystal pulling process can be fully guaranteed even when different single crystal furnaces have different insulation performance, and avoids temperature instability during the crystal pulling process due to different heating and cooling amplitudes caused by differences in thermal field insulation performance.

[0027] A method for controlling temperature consistency during crystal pulling involves adjusting the thermal field temperature based on the surface temperature of the silicon solution during temperature stabilization, and controlling the change in thermal field temperature at any subsequent time point based on the changes in the silicon solution surface temperature and the changes in the thermal field temperature, thereby controlling temperature consistency during crystal pulling. Specifically, this method for controlling temperature consistency during crystal pulling includes... Figure 1 As shown, it includes:

[0028] During the temperature stabilization process, the surface temperature of the silicon solution is monitored to determine whether it meets the first preset condition. After receiving the thermal field temperature adjustment command, the single crystal pulling system automatically starts monitoring the surface temperature of the silicon solution. At this time, during the seed crystal lowering process in the early stage of temperature stabilization, the silicon solution temperature can be directly measured to obtain the initial temperature of the silicon solution surface when entering the temperature stabilization stage. Then, the surface temperature of the silicon solution is monitored. During the monitoring process, it is determined whether the surface temperature of the silicon solution measured at any time meets the first preset condition. The first preset condition is that the measured surface temperature of the silicon solution is between the preset lower limit and the preset upper limit of the surface temperature, so as to avoid the surface temperature of the silicon solution being too low, causing crystallization on the surface of the silicon solution, which would affect the surface temperature measurement. When the temperature does not reach the preset lower limit and upper limit of the liquid surface temperature, the system will normally perform the automatic temperature stabilization process. The temperature range between the preset lower limit and upper limit of the liquid surface temperature coincides with the temperature range required for automatic temperature stabilization, and no additional operation is required. In the early stage of automatic temperature stabilization, when the liquid surface temperature is low and in the heating state, no adjustment of the thermal field temperature is performed. When the silicon solution liquid surface temperature reaches or exceeds the preset lower limit of the liquid surface temperature, the crystal pulling system begins to control the thermal field temperature and adjusts the thermal field temperature according to the liquid surface temperature.

[0029] The preset lower limit of the liquid surface temperature is 1440℃-1450℃. This preset lower limit of the liquid surface temperature can be any temperature value within the range of 1440℃-1450℃, such as 1440℃, 1442℃, 1445℃, 1447℃ or 1450℃. It can be selected and set according to actual needs, and no specific requirements are made here.

[0030] The preset upper limit of the liquid surface temperature is 1455℃-1465℃. The preset lower limit of the liquid surface temperature can be any temperature value within the range of 1455℃-1465℃, such as 1455℃, 1457℃, 1460℃, 1463℃ or 1465℃. It can be selected and set according to actual needs, and no specific requirements are made here.

[0031] If the surface temperature of the silicon solution does not meet the first preset condition, continue to monitor the surface temperature of the silicon solution and repeat the above steps to determine whether the surface temperature of the silicon solution meets the first preset condition, until the surface temperature of the silicon solution meets the first preset condition.

[0032] At this point, the temperature of the silicon solution surface that meets the first preset condition is the final temperature of the silicon solution surface.

[0033] If the surface temperature of the silicon solution meets the first preset condition, then it is determined whether the temperature change value of the surface temperature from the initial temperature to the measured surface temperature meets the second preset condition. During the monitoring of the surface temperature of the silicon solution, the surface temperature of the silicon solution changes from the initial temperature to the final temperature, and the surface temperature of the silicon solution has a certain temperature change value. To ensure that the temperature change value of the surface temperature meets the second preset condition and to ensure the accuracy of the thermal field temperature adjustment, the temperature change value of the surface temperature meets the second preset condition as follows: the temperature change value of the surface temperature is greater than the preset surface temperature change value, and the preset surface temperature change value is not less than 10℃. The preset surface temperature change value is selected and set according to actual needs, and no specific requirements are made here.

[0034] If the temperature change of the liquid surface does not meet the second preset condition, the temperature of the silicon solution surface continues to be monitored to determine whether the temperature of the silicon solution surface meets the first preset condition. The above steps are repeated until the temperature change of the liquid surface meets the second preset condition. At this point, the final temperature of the silicon solution surface can be obtained.

[0035] The temperature change values ​​of the liquid surface temperature mentioned above include both the temperature change values ​​during heating and the temperature change values ​​during cooling.

[0036] If the temperature change of the liquid surface temperature meets the second preset condition, the thermal field temperature is adjusted according to the measured liquid surface temperature to reduce the difference between the thermal field temperature and the measured liquid surface temperature, making the thermal field temperature close to or equal to the measured liquid surface temperature. When adjusting the thermal field temperature according to the measured liquid surface temperature, the measured liquid surface temperature is used as the target temperature, and the thermal field temperature is increased or decreased according to a preset adjustment time. When adjusting the thermal field temperature, the temperature of the thermal field at this time is first obtained, which is the initial temperature of the thermal field. The initial temperature of the thermal field can be large. The measured surface temperature of the silicon solution, or the initial temperature of the thermal field (which may be lower than the measured surface temperature of the silicon solution), is used as the target temperature. The thermal field temperature is adjusted by raising or lowering it to bring it closer to the measured surface temperature of the silicon solution, ensuring that the final temperature of the thermal field is close to or equal to the measured surface temperature of the silicon solution. The difference between the final temperature of the thermal field and the measured surface temperature of the silicon solution is close to or equal to zero. During automatic temperature stabilization, adjusting the surface temperature of the silicon solution often takes time. Therefore, during the adjustment of the thermal field temperature to the measured surface temperature, a preset adjustment time is used. Within this preset adjustment time, the final temperature of the thermal field is adjusted to be close to or equal to the measured surface temperature of the silicon solution. This preset adjustment time is 10-20 minutes, and the specific setting is not specified here.

[0037] The temperature of the thermal field is adjusted within a preset adjustment time, from the initial temperature to the final temperature of the thermal field. Therefore, the final temperature of the thermal field can be the same as the measured surface temperature of the silicon solution, or it can be that the final temperature of the thermal field does not reach the measured surface temperature of the silicon solution, depending on the preset adjustment time.

[0038] After the temperature of the thermal field is adjusted to the final temperature, the thermal field coefficient is calculated. This thermal field coefficient is the ratio of the temperature change of the liquid surface to the temperature change of the thermal field. Specifically, the thermal field coefficient is calculated based on the measured initial and final temperatures of the liquid surface and the initial and final temperatures of the thermal field. The calculation formula is as follows:

[0039] Thermal field coefficient = [(initial liquid surface temperature - final liquid surface temperature) / initial liquid surface temperature] / [(initial thermal field temperature - final thermal field temperature) / initial thermal field temperature].

[0040] The change in thermal field temperature at any point in time after the temperature stabilization process is adjusted based on the calculated thermal field coefficient. This is to control the temperature inside the single crystal furnace during the crystal pulling process. The change in thermal field temperature at any point in time is the product of the set change in liquid surface temperature at that point in time and the thermal field coefficient. The set change in liquid surface temperature is 5-15℃, which can be selected and set according to actual needs. No specific requirements are specified here.

[0041] By using the above-mentioned method to control the temperature consistency during crystal pulling, the temperature inside the single crystal furnace during crystal pulling can be controlled according to the different thermal insulation properties. This ensures that the liquid surface temperature can be adjusted according to the parameter settings, and that different single crystal furnaces with different insulation properties can completely guarantee the temperature consistency during crystal pulling. This avoids temperature instability during crystal pulling caused by different heating and cooling amplitudes due to differences in thermal insulation properties.

[0042] The following is a specific embodiment for illustration.

[0043] Example 1

[0044] In the crystal pulling system, the preset upper limit of liquid surface temperature is 1460℃, the preset lower limit of liquid surface temperature is 1445℃, the preset adjustment time is 15min, and the preset liquid surface temperature change value is 10℃.

[0045] Automatic temperature stabilization is performed. At the beginning of the temperature stabilization stage, the initial temperature of the silicon solution is measured to be 1460℃. Then, the temperature is stabilized. During the temperature stabilization process, the surface temperature of the silicon solution is monitored.

[0046] When the liquid surface temperature is 1450℃, the liquid surface temperature is between the preset upper limit value and the preset lower limit value of the liquid surface temperature, and the current liquid surface temperature meets the first preset condition.

[0047] The liquid surface temperature at this time is the final temperature of the silicon solution. The temperature change of the liquid surface is calculated. The temperature change of the liquid surface is 10℃, which satisfies the second preset condition.

[0048] The temperature of the hot zone is adjusted, and the temperature of the hot zone is measured at this time to obtain the initial temperature of the hot zone, which is 1465℃. Within the preset adjustment time, the temperature of the hot zone is adjusted with the current liquid surface temperature as the target temperature. After the set time is reached, the temperature adjustment of the hot zone is completed, and the final temperature of the hot zone is 1453℃.

[0049] The temperature change of the silicon solution surface was calculated. Based on the initial and final temperatures of the silicon solution surface, the temperature change of the silicon solution surface was found to be 10℃.

[0050] The temperature change of the thermal field is calculated. Based on the initial and final temperatures of the thermal field, the temperature change is found to be 12℃.

[0051] Calculate the thermal field coefficient: Thermal field coefficient = [(Initial liquid surface temperature - Final liquid surface temperature) / Initial liquid surface temperature] / [(Initial thermal field temperature - Final thermal field temperature) / Initial thermal field temperature] = 0.836

[0052] After the automatic temperature stabilization is completed and the subsequent process begins, the temperature rise or fall during thermal field temperature adjustment is calculated by multiplying the liquid surface temperature rise / fall range set in the parameters by the thermal field coefficient, such as:

[0053] During the crystal pulling process, if the temperature change of the liquid surface is set to -5.0℃, then the temperature change of the thermal field will be -4.18℃.

[0054] During the expansion process, if the temperature change of the liquid surface is set to -1.0℃, then the temperature change of the thermal field will be -0.84℃.

[0055] During the shoulder rotation process, if the temperature change of the liquid surface is set to -2.0℃, then the temperature change of the thermal field will be -1.67℃.

[0056] During the constant diameter process, if the temperature change of the liquid surface is set to -5.0℃, then the temperature change of the thermal field is -4.18℃.

[0057] During the final stage, if the temperature change of the liquid surface is set to +5.0℃, then the temperature change of the thermal field will be +4.18℃.

[0058] Complete the temperature control throughout the entire crystal pulling process.

[0059] When using the above process for crystal pulling, the thermal field temperature and liquid surface temperature at various stages of the crystal pulling process in different single crystal furnaces are shown in the table below:

[0060] Single crystal furnace 1:

[0061] Liquid surface temperature / °C 1450.0 1445.0 1445.0 1440.0 1450.0 Thermal field temperature / ℃ 1450.0 1445.5 1445.5 1441.0 1450.0

[0062] Single crystal furnace 2:

[0063] Liquid surface temperature / °C 1450.0 1445.0 1445.0 1440.0 1450.0 Thermal field temperature / ℃ 1450.0 1444.0 1444.0 1438.0 1450.0

[0064] Single crystal furnace 3:

[0065] Liquid surface temperature / °C 1450.0 1445.0 1445.0 1440.0 1450.0 Thermal field temperature / ℃ 1450.0 1447.0 1447.0 1444.0 1450.0

[0066] As can be seen from the above three tables, the above process method is used to control the temperature of the thermal field during the crystal pulling process, so that the temperature consistency during the crystal pulling process can be fully guaranteed even when different single crystal furnaces have different heat preservation properties.

[0067] By adopting the above technical solution, during the crystal pulling process, the thermal field temperature is adjusted according to the liquid surface temperature during the automatic temperature stabilization stage based on the different thermal field insulation properties, and the thermal field coefficient is calculated. In the subsequent automatic temperature stabilization stage, the thermal field temperature change value is adjusted according to the thermal field coefficient and the liquid surface temperature change value set in the crystal pulling system. This ensures that the temperature consistency during the single crystal pulling process can be fully guaranteed even when different single crystal furnaces have different insulation properties. It avoids temperature instability during the crystal pulling process caused by different heating and cooling amplitudes due to differences in thermal field insulation properties, reduces quality defects and breakage caused by unsuitable temperature during single crystal pulling, improves single crystal quality, and increases output.

[0068] The embodiments of the present invention have been described in detail above, but the content described is only a preferred embodiment of the present invention and should not be considered as limiting the scope of the present invention. All equivalent changes and improvements made within the scope of the present invention should still fall within the patent coverage of the present invention.

Claims

1. A method of controlling temperature uniformity in a crystal pulling process, characterized by: include: During the temperature stabilization process, the surface temperature of the silicon solution is monitored to determine whether the surface temperature of the silicon solution meets the first preset condition; If so, determine whether the temperature change value of the liquid surface temperature from the initial temperature to the measured liquid surface temperature meets the second preset condition; If so, the thermal field temperature is adjusted according to the measured liquid surface temperature so that the thermal field temperature is close to or equal to the measured liquid surface temperature. Calculate the thermal field coefficient, which is the ratio of the temperature change of the liquid surface to the temperature change of the thermal field. The change in thermal field temperature at any point in time after the temperature stabilization process is adjusted according to the thermal field coefficient.

2. The method for controlling temperature uniformity during crystal pulling according to claim 1, characterized in that: The silicon solution surface temperature meets the first preset condition as follows: the measured silicon solution surface temperature is between the preset lower limit value and the preset upper limit value of the surface temperature.

3. The method for controlling the temperature uniformity during the crystal pulling process according to claim 2, characterized in that: The preset lower limit for liquid surface temperature is 1440℃-1450℃, and the preset upper limit for liquid surface temperature is 1455℃-1465℃.

4. The method for controlling the temperature uniformity of the crystal pulling process according to any one of claims 1-3, characterized in that: If the surface temperature of the silicon solution does not meet the first preset condition, the surface temperature of the silicon solution will continue to be monitored to determine whether the surface temperature of the silicon solution meets the first preset condition.

5. The method for controlling the temperature uniformity during the crystal pulling process according to claim 4, characterized in that: When adjusting the thermal field temperature based on the measured liquid surface temperature, the measured liquid surface temperature is used as the target temperature, and the thermal field temperature is increased or decreased according to a preset adjustment time, which is 10-20 minutes.

6. The method for controlling temperature uniformity during crystal pulling according to claim 5, characterized in that: The temperature change value of the liquid surface temperature satisfies the second preset condition as follows: the temperature change value of the liquid surface temperature is greater than the preset liquid surface temperature change value.

7. The method for controlling temperature uniformity during crystal pulling according to claim 6, characterized in that: The preset liquid level temperature change value is not less than 10℃.

8. The method for controlling the temperature uniformity during the crystal pulling process according to claim 6 or 7, characterized in that: If the temperature change of the liquid surface does not meet the second preset condition, the temperature of the silicon solution surface will continue to be monitored to determine whether the temperature of the silicon solution surface meets the first preset condition.

9. The method for controlling the temperature uniformity during the crystal pulling process according to claim 1, characterized in that: The formula for calculating the thermal field coefficient is: Thermal field coefficient = [(initial liquid surface temperature - final liquid surface temperature) / initial liquid surface temperature] / [(initial thermal field temperature - final thermal field temperature) / initial thermal field temperature].

10. The method for controlling the temperature uniformity during the crystal pulling process according to claim 1, characterized in that: In the step of adjusting the change value of the thermal field temperature at any time point after the temperature stabilization process according to the thermal field coefficient, the change value of the thermal field temperature at any time point is the product of the set change value of the liquid surface temperature at that time point and the thermal field coefficient.

11. The method for controlling the temperature uniformity during the crystal pulling process according to claim 10, characterized in that: The set liquid level temperature variation value is 5-15℃.

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