Method for controlling temperature gradient of a crystal bar during a single crystal pulling-off shoulder stage

Abstract

The application belongs to the technical field of semiconductor material processing, and particularly relates to a method for controlling the temperature gradient of a crystal bar in a single crystal shoulder placement stage. The method comprises the following steps: dividing the shoulder placement process into multiple stages, setting a temperature difference threshold between the edge region and the center of the shoulder of the crystal bar according to the shoulder diameter in each stage; monitoring the temperature distribution of the shoulder surface of the crystal bar in real time to obtain detection data; obtaining temperature difference data between the edge region and the center of the shoulder of the crystal bar according to the detection data; and judging whether the temperature difference data is greater than the temperature difference threshold. If the temperature difference data is greater than the temperature difference threshold, the temperature of the shoulder surface of the crystal bar is adjusted to be within the temperature difference threshold through a temperature compensation system, so that the temperature distribution of the shoulder of the crystal bar is more uniform.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material processing technology, specifically relating to a method for controlling the temperature gradient of a crystal rod during the shoulder formation stage of a single crystal. Background Technology

[0002] In the Czochralski (CZ) single-crystal silicon growth process, the shoulder formation stage is a crucial step in forming the tapered shoulder of the crystal rod, transitioning from the seed crystal to the constant-diameter growth. The level of control during this process directly affects the crystal quality, defect density, and final crystal rod utilization rate. Traditional shoulder formation processes mainly rely on the pre-design of the overall thermal field and the natural distribution of the temperature field within the furnace, with relatively passive and rudimentary control methods. Specifically, preheating is typically achieved by adjusting heater power, crucible position, or heat shield structure. Once the shoulder formation stage begins, it becomes difficult to implement real-time and precise adjustment of the local temperature.

[0003] The thermal field structure itself exhibits asymmetry. Furthermore, the surface curvature and radial heat dissipation conditions of the crystal ingot shoulder are constantly changing during the growth process. These factors combined result in significant temperature differences between different regions of the shoulder (especially between the edges and the center), typically reaching 15-20°C. This uneven temperature distribution further induces thermal stress concentration within the crystal ingot, which can easily lead to lattice distortion, an increase in the number of dislocations, and even serious problems such as cracks.

[0004] To avoid the aforementioned defects, a relatively conservative shoulder angle strategy is often adopted in actual process operations (usually limited to between 110° and 130°). However, this approach comes at the cost of sacrificing some usable crystal volume. According to relevant statistics, due to the limited shoulder angle, the material consumed in the tapered transition region that must be formed before constant diameter growth increases significantly, ultimately leading to a reduction in the overall ingot utilization rate of approximately 8-12%. Summary of the Invention

[0005] In view of this, the present invention provides a method for controlling the temperature gradient of a crystal rod during the single crystal shoulder pulling stage, so as to solve the above-mentioned technical problems caused by the uneven temperature distribution between the edge region and the center of the crystal rod shoulder during crystal pulling in the prior art.

[0006] To achieve the above objectives, this application adopts the following approach:

[0007] A method for controlling the temperature gradient of a single crystal rod during the shoulder formation stage includes the following steps:

[0008] S10. Divide the shoulder formation process into multiple stages, and set the temperature difference threshold between the edge region and the center of the crystal rod shoulder according to the shoulder diameter in each stage;

[0009] S20. Monitor the temperature distribution on the surface of the crystal bar shoulder to obtain detection data;

[0010] S30. Obtain the temperature difference data between the edge region and the center of the crystal rod shoulder based on the detection data;

[0011] S40. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is less than the threshold, do not adjust the temperature of the crystal bar shoulder surface. If it is greater than the threshold, adjust the temperature of the crystal bar shoulder surface to within the temperature difference threshold through the temperature compensation system to make the temperature distribution of the crystal bar shoulder more uniform.

[0012] Preferably, step S20 specifically includes completing a full-range scan of the shoulder surface every 10 to 20 seconds to obtain detection data of no less than 200 to 300 points.

[0013] Preferably, the shoulder-releasing process is divided into the following three stages:

[0014] Phase 1: Shoulder diameter less than 80mm, temperature difference threshold of 3℃ in this phase;

[0015] Second stage: Shoulder diameter between 80mm and 150mm, the temperature difference threshold for this stage is 5℃;

[0016] Third stage: shoulder diameter greater than 150mm, the temperature difference threshold for this stage is 8℃.

[0017] Preferably, the temperature compensation system includes a lifting mechanism, an annular temperature regulating mechanism, and a control module. The annular temperature regulating mechanism is disposed inside the single crystal furnace, located above the quartz crucible and inside the fixed thermal field. The lifting end of the lifting mechanism is connected to the annular temperature regulating mechanism, and the fixed end of the lifting mechanism is connected to the single crystal furnace. The lifting mechanism is used to drive the annular temperature regulating mechanism to move up and down, thereby adjusting the deflection of the annular temperature regulating mechanism. The annular temperature regulating mechanism has a preset distance from the shoulder of the crystal rod. The lifting mechanism is electrically connected to the control module. The control module calculates the deflection angle value of the annular temperature regulating mechanism based on the temperature difference data and converts the deflection angle value into a deflection height value. The control module controls the lifting mechanism to drive the annular temperature regulating mechanism to deflect according to the deflection height value, so as to adjust the temperature of the surface of the shoulder of the crystal rod.

[0018] Preferably, the deflection angle value is calculated using the following formula:

[0019]

[0020] In the formula, θ is the deflection angle, ΔT is the temperature difference, I is the heat flux intensity, and k is the material constant;

[0021] In the first stage, if the deflection angle θ is greater than ±10°, the deflection height is calculated as 10°; in the second stage, if the deflection angle θ is greater than ±20°, the deflection height is calculated as 20°; in the third stage, if the deflection angle θ is greater than ±25°, the deflection height is calculated as 25°.

[0022] Preferably, the annular temperature regulating mechanism consists of at least three concave reflective heat shields, each with a fan-shaped structure. The heat-reflecting concave surfaces of the concave reflective heat shields all face the quartz crucible, and there is a flow channel between adjacent concave reflective heat shields.

[0023] Preferably, the lifting mechanism includes a height adjustment platform, a second lifting component, and a third lifting component. The number of third lifting components is the same as the number of concave reflective heat screens. Both the second and third lifting components are connected to the height adjustment platform. The second lifting component includes a hollow shaft motor and a screw. One end of the screw is coaxially connected to the hollow shaft of the hollow shaft motor, and the other end of the screw is connected to the height adjustment platform. The third lifting component includes a gear transmission mechanism, an inner connecting rod, and an outer connecting rod. One end of the inner connecting rod is connected to the center of the concave reflective heat screen, and the other end of the inner connecting rod is connected to the corresponding gear transmission mechanism. One end of the outer connecting rod is connected to the edge area of ​​the concave reflective heat screen, and the other end of the outer connecting rod is connected to the corresponding gear transmission mechanism. Both the inner and outer connecting rods are slidably connected to the height adjustment platform. Both the hollow shaft motor and the gear transmission mechanism are electrically connected to the control module.

[0024] Preferably, step S40 specifically includes the following steps:

[0025] S41. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is greater, calculate the deflection angle value of the annular temperature regulating mechanism based on the temperature difference data through the control module.

[0026] S42. The control module uses trigonometric functions to convert the deflection angle value into the deflection height value of the annular temperature regulating mechanism;

[0027] S43. The control module controls the gear transmission mechanism to start based on the deflection height value, driving the inner connecting rod and the outer connecting rod to move relative to each other, so that the concave reflective heat screen deflects the heat to reflect the heat to the low temperature region, compensate for the temperature of the low temperature region, and make the temperature distribution of the crystal bar shoulder more uniform.

[0028] Preferably, the method further includes adjusting the distance between the annular temperature regulating mechanism and the surface of the crystal bar shoulder, including the following steps;

[0029] S51. The diameter of the crystal bar shoulder is acquired in real time, the diameter data is obtained, and the diameter data is provided to the control module;

[0030] S52. The control module calculates the height adjustment value based on the diameter data;

[0031] S53. The control module controls the hollow shaft motor to start based on the height adjustment value, drives the screw to rotate, and drives the height adjustment platform to rise and fall, so as to adjust the distance between the annular temperature adjustment mechanism and the surface of the crystal bar shoulder.

[0032] Preferably, the height adjustment value is calculated according to the following formula:

[0033] H = 50 + 0.4 × D

[0034] In the formula, H: height adjustment value, D: shoulder diameter.

[0035] In the aforementioned method for controlling the temperature gradient of a single crystal ingot during the shoulder formation stage, by dividing the shoulder formation process into multiple stages and setting temperature difference thresholds for each stage, more accurate temperature control can be achieved for the growth characteristics of the ingot at different stages. This satisfies the temperature gradient requirements for ingot growth at different stages. Monitoring the surface temperature distribution of the ingot shoulder and acquiring temperature difference data allows for timely detection of temperature anomalies, and the temperature compensation system can be used to make rapid adjustments to ensure that the ingot growth environment is always at a suitable temperature. The method provided in this application can improve the radial temperature uniformity of the ingot shoulder, thereby reducing the standard deviation of the axial temperature gradient, achieving more accurate control of the ingot temperature gradient, reducing dislocation generation, improving ingot quality, and increasing the maximum shoulder angle from 130° to 160°-180° after dislocation reduction, thus increasing the ingot utilization rate by 10% to 15%. Attached Figure Description

[0036] Figure 1 This is a flowchart of the present invention.

[0037] Figure 2 This is a schematic diagram of the functional modules in this invention.

[0038] Figure 3 This is an isometric view of the system configuration in a single crystal furnace according to one embodiment of the present invention.

[0039] Figure 4 This is an external front view of the system in a single crystal furnace according to one embodiment of the present invention.

[0040] Figure 5 This is a front view of the system being installed inside a single crystal furnace according to one embodiment of the present invention.

[0041] Figure 6This is an isometric view of the system configuration inside a single crystal furnace according to one embodiment of the present invention.

[0042] Figure 7 This is a cross-sectional view of the system in a single crystal furnace according to one embodiment of the present invention.

[0043] Figure 8 This is an isometric view of the system configuration outside a single crystal furnace in another embodiment of the present invention.

[0044] Figure 9 This is an external front view of the system in another embodiment of the present invention, located within a single crystal furnace.

[0045] Figure 10 This is a front view of the system configuration inside a single crystal furnace in another embodiment of the present invention.

[0046] Figure 11 This is an isometric view of the system configuration inside a single crystal furnace in another embodiment of the present invention.

[0047] Figure 12 This is a cross-sectional view of the system in a single crystal furnace according to another embodiment of the present invention.

[0048] In the figure, there are a single crystal furnace 10, a crystal rod shoulder 20, a fixed hot zone 100, a quartz crucible 200, a temperature compensation system 300, a lifting mechanism 310, a first lifting component 311, a lifting drive motor 3111, an inner connecting rod 3112, an outer connecting rod 3113, a height adjustment platform 3114, a second lifting component 3115, a hollow shaft motor 31151, a screw 31152, a third lifting component 3116, a gear transmission mechanism 31161, an annular temperature adjustment mechanism 320, a concave reflective heat shield 321, a flow guide channel 322, a control module 330, a first calculation unit 331, a second calculation unit 332, and an execution unit 333. Detailed Implementation

[0049] 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.

[0050] 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 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.

[0051] Please refer to Figures 1 to 12 In one specific embodiment, a method for controlling the temperature gradient of a crystal rod during the shoulder formation stage of a single crystal includes the following steps:

[0052] S10. Divide the shoulder formation process into multiple stages, and set the temperature difference threshold between the edge region and the center of the crystal rod shoulder 20 according to the shoulder diameter in each stage;

[0053] S20. Monitor the temperature distribution on the surface of the crystal bar shoulder 20 to obtain detection data;

[0054] S30. Obtain the temperature difference data between the edge region and the center of the crystal rod shoulder 20 based on the detection data;

[0055] S40. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is greater, adjust the temperature of the surface of the crystal bar shoulder 20 to within the temperature difference threshold through the temperature compensation system 300, so that the temperature distribution of the crystal bar shoulder 20 is more uniform.

[0056] In the aforementioned method for controlling the temperature gradient of a single crystal ingot during the shoulder formation stage, by dividing the shoulder formation process into multiple stages and setting temperature difference thresholds for each stage, more accurate temperature control can be achieved for the growth characteristics of the ingot at different stages. This satisfies the temperature gradient requirements for ingot growth at different stages. Monitoring the surface temperature distribution of the ingot shoulder 20 and acquiring temperature difference data allows for timely detection of temperature anomalies, and the temperature compensation system 300 can quickly make adjustments to ensure that the ingot growth environment is always at a suitable temperature. The method provided in this application can improve the radial temperature uniformity of the ingot shoulder 20, thereby reducing the standard deviation of the axial temperature gradient, achieving more accurate control of the ingot temperature gradient, reducing dislocation generation, improving ingot quality, and increasing the maximum shoulder angle from 130° to 160°-180° after dislocation reduction, thus increasing ingot utilization by 10% to 15%.

[0057] Specifically, step S20 includes completing a full-range scan of the shoulder surface every 10 to 20 seconds to obtain detection data of no less than 200 to 300 points.

[0058] In this embodiment, an infrared sensor can be used to monitor the temperature distribution on the surface of the crystal rod shoulder 20. The infrared sensor can be placed outside the observation port of the single crystal furnace 10 for timely cleaning, and the observation port is sealed with a transparent material, such as glass. The infrared sensor uses dual-band infrared thermometry technology, combined with a two-dimensional galvanometer scanning system, to achieve comprehensive monitoring of the temperature distribution on the shoulder surface. The infrared sensor can complete an all-round scan of the shoulder surface every 10 seconds, acquiring detection data from no less than 200 points to construct a high-precision temperature field distribution map.

[0059] In one specific embodiment, the shoulder-relaxing process is divided into the following three stages:

[0060] The first stage involves a shoulder diameter of less than 80 mm. The temperature difference threshold for this stage is 3°C. This relatively small threshold provides a relatively uniform and stable temperature environment for crystal growth. During this stage, crystal atoms begin to arrange themselves in an orderly manner to form a lattice structure. The stable thermal field prevents atomic misalignment due to temperature fluctuations, reducing the generation of crystal defects such as dislocations and stacking faults. This lays a good foundation for subsequent crystal growth and improves the initial quality of the crystal.

[0061] Second stage: shoulder diameter between 80mm and 150mm, with a temperature difference threshold of 5℃.

[0062] The third stage: When the shoulder diameter is greater than 150mm and the temperature difference threshold is 8℃, the temperature difference threshold is relatively large. By controlling the temperature difference within a relatively large range but maintaining a smooth transition, the temperature distribution of the thermal field can be gradually adjusted so that the crystal can slowly adapt to the temperature change before the end of growth, reduce the generation of thermal stress, avoid damage to the crystal due to sudden temperature changes, and ensure that the crystal can be grown completely and with high quality.

[0063] In a preferred embodiment, the temperature compensation system 300 includes a lifting mechanism 310, an annular temperature regulating mechanism 320, and a control module 330. The annular temperature regulating mechanism 320 is disposed inside the single crystal furnace 10, located above the quartz crucible 200 and inside the fixed thermal field 100 within the single crystal furnace 10. The lifting end of the lifting mechanism 310 is connected to the annular temperature regulating mechanism 320, and the fixed end of the lifting mechanism 310 is connected to the single crystal furnace 10. The lifting mechanism 310 is used to drive the annular temperature regulating mechanism 320 to move up and down. This adjusts the deflection of the annular temperature regulating mechanism 320, which has a preset distance from the crystal bar shoulder 20. The lifting mechanism 310 is electrically connected to the control module 330. The control module 330 calculates the deflection angle of the annular temperature regulating mechanism 320 based on the temperature difference data and converts the deflection angle into a deflection height. The control module 330 controls the lifting mechanism 310 to drive the annular temperature regulating mechanism 320 to deflect according to the deflection height, so as to adjust the temperature of the surface of the crystal bar shoulder 20.

[0064] In use, first place the annular temperature regulating mechanism 320 above the quartz crucible 200 and inside the fixed thermal field 100, while ensuring that the annular temperature regulating mechanism 320 and the crystal rod shoulder 20 have a preset distance of 50-100mm; connect the fixed end of the lifting mechanism 310 to the single crystal furnace 10, specifically to the drive shaft of the seed crystal on the single crystal furnace 10, and connect the lifting end to the annular temperature regulating mechanism 320, ensuring that the lifting mechanism 310 can drive the annular temperature regulating mechanism 320 normally; finally, connect the lifting mechanism 310 to the control module 33. 0. Make an electrical connection; then, start the single crystal furnace 10 to begin the shoulder formation stage of single crystal growth. If the temperature difference data is greater than the temperature difference threshold, the control module 330 calculates the deflection angle value of the annular temperature adjustment mechanism 320 based on the temperature difference value through the built-in calculation program, and converts the deflection angle value into a deflection height value. The control module 330 sends a control command to the lifting mechanism 310 based on the deflection height value, driving the lifting mechanism 310 to drive the annular temperature adjustment mechanism 320 to deflect, so as to adjust the surface temperature of the crystal bar shoulder 20.

[0065] The control module 330 includes a first calculation unit 331 and an execution unit 333. The first calculation unit 331 is electrically connected to the execution unit 333. The first calculation unit 331 calculates the deflection angle value of the annular temperature regulating mechanism 320 based on the temperature difference data, converts the deflection angle value into the deflection height value, and provides the deflection height value to the execution unit 333. The execution unit 333 controls the gear transmission mechanism 31161 to start according to the deflection height value, driving the inner connecting rod 3112 and the outer connecting rod 3113 to move relative to each other, thereby adjusting the deflection of the annular temperature regulating mechanism 320, thereby causing the concave reflective heat shield 321 to deflect heat to the low-temperature area.

[0066] As the diameter of the crystal ingot shoulder 20 changes, the distance between the annular temperature adjustment mechanism 320 and the crystal ingot shoulder 20 needs to be adjusted to ensure that the annular temperature adjustment mechanism 320 does not affect crystal pulling. Furthermore, the temperature compensation system 300 also includes a crystal ingot shoulder 20 diameter detection device, which is electrically connected to the control module 330. During the shoulder setting process, the crystal ingot shoulder 20 diameter detection device is used to detect the diameter of the crystal ingot shoulder 20 in real time and provides the detected shoulder diameter value to the control module 330. It should be noted that this crystal ingot shoulder 20 diameter detection device can be a shoulder diameter detection device integrated into a traditional crystal pulling system. At this time, the control module 330 includes a second calculation unit 332, which is electrically connected to the crystal rod shoulder 20 diameter detection device and the execution module respectively. The second calculation unit 332 calculates the height adjustment value based on the detected shoulder diameter value. The execution unit 333 controls the hollow shaft motor 31151 to start according to the height adjustment value, drives the screw 31152 to rotate, and drives the height adjustment platform 3114 to rise and fall, so as to adjust the distance between the annular temperature adjustment mechanism 320 and the surface of the crystal rod shoulder 20.

[0067] In a preferred embodiment, the deflection angle value is calculated using the following formula:

[0068]

[0069] In the formula, θ is the deflection angle, ΔT is the temperature difference, I is the heat flux intensity, and k is the material constant;

[0070] In the first stage, if the deflection angle θ is greater than ±10°, the deflection height is calculated as 10°; in the second stage, if the deflection angle θ is greater than ±20°, the deflection height is calculated as 20°; in the third stage, if the deflection angle θ is greater than ±25°, the deflection height is calculated as 25°.

[0071] In a preferred embodiment, the annular temperature regulating mechanism 320 is composed of at least three concave reflective heat shields 321. The concave reflective heat shields 321 have a fan-shaped structure, and the heat-reflecting concave surfaces of the concave reflective heat shields 321 all face the quartz crucible 200. Furthermore, there is a flow channel 322 between two adjacent concave reflective heat shields 321.

[0072] The substrate material of the concave reflective heat shield 321 is high-purity isostatic graphite (purity > 99.999%), and the surface is machined with a diamond lathe to form a concave curved surface with a radius of curvature of 500 mm. The surface coating is a pyrolytic boron nitride coating (thickness 0.2 mm) to enhance reflectivity.

[0073] At least three concave reflective heat shields 321 with fan-shaped structures can be arranged in a ring to form a ring temperature regulation mechanism 320, ensuring that the heat-reflecting concave surface of each concave reflective heat shield 321 faces the quartz crucible 200, while ensuring that a suitable flow channel 322 is left between two adjacent concave reflective heat shields 321 so that the airflow (inert gas) in the thermal field can pass through smoothly.

[0074] In use, the lifting mechanism 310 lowers the annular temperature regulating mechanism 320 above the quartz crucible 200 and to a suitable initial height position inside the fixed thermal field 100, and keeps it at a preset distance from the crystal bar shoulder 20.

[0075] The concave reflective heat shield 321 is designed to focus and reflect heat more effectively. Each heat shield can work independently or in concert. By adjusting its angle, heat can be reflected to different areas of the edge of the crystal bar shoulder 20, thereby controlling the local temperature and better controlling the temperature gradient during the crystal bar shoulder setting stage.

[0076] In a preferred embodiment, the lifting mechanism 310 includes a height adjustment platform 3114, a second lifting assembly 3115, and a third lifting assembly 3116. The number of third lifting assemblies 3116 is the same as the number of concave reflective heat shields 321. Both the second lifting assembly 3115 and the third lifting assembly 3116 are connected to the height adjustment platform 3114. The second lifting assembly 3115 includes a hollow shaft motor 31151 and a screw 31152. One end of the screw 31152 is coaxially connected to the hollow shaft of the hollow shaft motor 31151, and the other end of the screw 31152 is connected to the height adjustment platform 3114. The third lifting assembly 3116 includes gears. The transmission mechanism 31161, the inner connecting rod 3112, and the outer connecting rod 3113 are provided. One end of the inner connecting rod 3112 is connected to the center of the concave reflective heat shield 321, and the other end of the inner connecting rod 3112 is connected to the corresponding gear transmission mechanism 31161. One end of the outer connecting rod 3113 is connected to the edge area of ​​the concave reflective heat shield 321, and the other end of the outer connecting rod 3113 is connected to the corresponding gear transmission mechanism 31161. Both the inner connecting rod 3112 and the outer connecting rod 3113 are slidably connected to the height adjustment platform 3114. The hollow shaft motor 31151 and the gear transmission mechanism 31161 are both electrically connected to the control module 330.

[0077] In this embodiment, if the distance between the concave reflective heat shield 321 and the surface of the crystal rod shoulder 20 is adjusted, the control module 330 starts the hollow shaft motor 31151 to drive the height adjustment platform 3114 to rise and fall, thereby driving each of the concave reflective heat shields 321 to rise and fall, so as to adjust the distance between the concave reflective heat shield 321 and the crystal rod shoulder 20 to a preset distance; if the angle of the concave reflective heat shield 321 is adjusted, the control module 330 only starts the corresponding gear transmission mechanism 31161. The rotation of the gear drives the relative movement of the inner connecting rod 3112 and the outer connecting rod 3113 connected to it, thereby adjusting the angle (deflection) of the concave reflective heat shield 321.

[0078] In one specific embodiment, S40 specifically includes the following steps:

[0079] S41. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is greater, the control module 330 calculates the deflection angle value of the annular temperature regulating mechanism 320 based on the temperature difference data.

[0080] S42. The control module 330 uses trigonometric functions to convert the deflection angle value into the deflection height value of the annular temperature regulating mechanism 320;

[0081] S43. The control module 330 controls the gear transmission mechanism 31161 to start based on the deflection height value, driving the inner connecting rod 3112 and the outer connecting rod 3113 to move relative to each other, so that the concave reflective heat screen 321 deflects the heat to reflect the heat to the low temperature area, compensates the temperature of the low temperature area, and makes the temperature distribution of the crystal bar shoulder 20 more uniform.

[0082] Furthermore, it also includes adjusting the distance between the annular temperature regulating mechanism 320 and the surface of the crystal bar shoulder 20, including the following steps;

[0083] S51. The diameter of the crystal bar shoulder 20 is acquired in real time, the diameter data is obtained, and the diameter data is provided to the control module 330;

[0084] S52. The control module 330 calculates the height adjustment value based on the diameter data;

[0085] S53. The control module 330 controls the hollow shaft motor 31151 to start based on the height adjustment value, drives the screw 31152 to rotate, and drives the height adjustment platform 3114 to rise and fall, so as to adjust the distance between the annular temperature adjustment mechanism 320 and the surface of the crystal bar shoulder 20.

[0086] Specifically, the height adjustment value is calculated according to the following formula:

[0087] H = 50 + 0.4 × D

[0088] In the formula, H: height adjustment value, D: shoulder diameter.

[0089] In a preferred embodiment, the lifting mechanism 310 includes a first lifting assembly 311. The number of first lifting assemblies 311 is the same as the number of concave reflective heat shields 321. Each first lifting assembly 311 corresponds to one concave reflective heat shield 321. Each set of first lifting assemblies 311 includes two lifting drive motors 3111, an inner connecting rod 3112, and an outer connecting rod 3113. Each lifting drive motor 3111 is electrically connected to the control module 330. One end of the inner connecting rod 3112 is connected to the center of the concave reflective heat shield 321, and the other end is connected to the corresponding lifting drive motor 3111. One end of the outer connecting rod 3113 is connected to the edge area of ​​the concave reflective heat shield 321, and the other end is connected to the corresponding lifting drive motor 3111.

[0090] In this embodiment, if the distance between the concave reflective heat shield 321 and the crystal rod shoulder 20 is adjusted, the control module 330 can simultaneously start the lifting drive motor 3111 to drive each of the concave reflective heat shields 321 connected to it to rise and fall, thereby achieving the purpose of adjusting the distance between the concave reflective heat shield 321 and the crystal rod shoulder 20 to a preset distance; if the angle of the concave reflective heat shield 321 is adjusted, the control module 330 only starts the lifting drive motor 3111 connected to the external connecting rod 3113, thereby adjusting the angle of the concave reflective heat shield 321.

[0091] 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.

[0092] Example

[0093] In this embodiment, the method for controlling the temperature gradient of the crystal bar during the single crystal shoulder stage provided in this application is used to pull the crystal bar. After the crystal pulling is completed, the radial temperature uniformity of the crystal bar shoulder 20 is statistically analyzed, and the maximum shoulder angle, crystal bar utilization rate and dislocation density of the crystal bar shoulder 20 are detected. The results are shown in Table 1.

[0094] Comparative Example

[0095] This comparative example uses a conventional thermal field and conventional crystal pulling method for crystal pulling. The crystal pulling process parameters are consistent with those set in the above embodiment. After crystal pulling, the radial temperature uniformity of the crystal bar shoulder 20 is statistically obtained, and the maximum shoulder angle, crystal bar utilization rate and dislocation density of the crystal bar shoulder 20 are detected. The results are shown in Table 1.

[0096] Table 1 Comparison of Experimental Results of Examples and Comparative Examples

[0097]

[0098] The data in Table 1 show that the method provided in the embodiment can improve the radial temperature uniformity of the crystal bar shoulder 20, thereby reducing the standard deviation of the axial temperature gradient, thus controlling the crystal bar temperature gradient more accurately, reducing the generation of dislocations, and improving the quality of the crystal bar. After reducing dislocations, the maximum shoulder angle of the crystal bar can be increased to 160°-180°, thereby increasing the crystal bar utilization rate by 10% to 15%.

[0099] 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 controlling the temperature gradient of a crystal rod during the shoulder formation stage of a single crystal, characterized in that, Includes the following steps: S10. The shoulder formation process is divided into multiple stages, and the temperature difference threshold between the edge region and the center of the crystal rod shoulder is set according to the shoulder diameter in each stage; S20. Monitor the temperature distribution on the surface of the crystal bar shoulder and obtain the detection data; S30. Obtain the temperature difference data between the edge region and the center of the crystal rod shoulder based on the detection data; S40. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is less than the threshold, do not adjust the temperature of the crystal bar shoulder surface. If it is greater than the threshold, adjust the temperature of the crystal bar shoulder surface to within the temperature difference threshold through the temperature compensation system to make the temperature distribution of the crystal bar shoulder more uniform. The shoulder-relaxing process is divided into the following three stages: Phase 1: Shoulder diameter less than 80mm, temperature difference threshold of 3℃ in this phase; Second stage: Shoulder diameter between 80mm and 150mm, the temperature difference threshold for this stage is 5℃; Third stage: Shoulder diameter greater than 150mm, the temperature difference threshold for this stage is 8℃; Specifically, S40 includes the following steps: S41. Determine whether the temperature difference data is greater than the temperature difference threshold. If it is greater, the control module calculates the deflection angle value of the annular temperature regulating mechanism based on the temperature difference data. S42. The control module uses trigonometric functions to convert the deflection angle value into the deflection height value of the annular temperature regulating mechanism; S43. The control module controls the gear transmission mechanism to start based on the deflection height value, driving the inner connecting rod and the outer connecting rod to move relative to each other, so that the concave reflective heat screen deflects the heat to reflect the heat to the low temperature area, compensate for the temperature of the low temperature area, and make the temperature distribution of the crystal bar shoulder more uniform. The deflection angle value is calculated using the following formula: ； In the formula, θ is the deflection angle, ΔT is the temperature difference, I is the heat flux intensity, and k is the material constant; In the first stage, if the deflection angle θ is greater than ±10°, the deflection height is calculated as 10°; in the second stage, if the deflection angle θ is greater than ±20°, the deflection height is calculated as 20°; in the third stage, if the deflection angle θ is greater than ±25°, the deflection height is calculated as 25°. The method also includes adjusting the distance between the annular temperature regulating mechanism and the surface of the crystal bar shoulder, including the following steps; S51. Real-time acquisition of the diameter of the crystal rod shoulder, obtaining diameter data, and providing the diameter data to the control module; S52. The control module calculates the height adjustment value based on the diameter data; S53. The control module starts the hollow shaft motor based on the height adjustment value, drives the screw to rotate, and drives the height adjustment platform to rise and fall, so as to adjust the distance between the annular temperature adjustment mechanism and the surface of the crystal bar shoulder.

2. The method for controlling the temperature gradient of the crystal rod during the shoulder formation stage according to claim 1, characterized in that, The S20 step specifically includes completing a full-range scan of the shoulder surface every 10 to 20 seconds to obtain detection data of no less than 200 to 300 points.

3. The method for controlling the temperature gradient of a crystal rod during the shoulder formation stage according to claim 1, characterized in that, The temperature compensation system includes a lifting mechanism, an annular temperature regulating mechanism, and a control module. The annular temperature regulating mechanism is located inside the single crystal furnace, above the quartz crucible and inside the fixed thermal field. The lifting end of the lifting mechanism is connected to the annular temperature regulating mechanism, and the fixed end of the lifting mechanism is connected to the single crystal furnace. The lifting mechanism drives the annular temperature regulating mechanism to move up and down, thereby adjusting the deflection of the annular temperature regulating mechanism. The annular temperature regulating mechanism has a preset distance from the shoulder of the crystal rod. The lifting mechanism is electrically connected to the control module. The control module calculates the deflection angle value of the annular temperature regulating mechanism based on the temperature difference data and converts the deflection angle value into a deflection height value. The control module controls the lifting mechanism to drive the annular temperature regulating mechanism to deflect according to the deflection height value, so as to adjust the temperature of the surface of the shoulder of the crystal rod.

4. The method for controlling the temperature gradient of the crystal rod during the shoulder formation stage according to claim 3, characterized in that, The annular temperature regulating mechanism consists of at least three concave reflective heat shields. The concave reflective heat shields have a fan-shaped structure, and the heat-reflecting concave surfaces of the concave reflective heat shields all face the quartz crucible. There is a flow channel between two adjacent concave reflective heat shields.

5. The method for controlling the temperature gradient of a crystal rod during the shoulder formation stage according to claim 3, characterized in that, The lifting mechanism includes a height adjustment platform, a second lifting assembly, and a third lifting assembly. The number of third lifting assemblies is the same as the number of concave reflective heat screens. Both the second and third lifting assemblies are connected to the height adjustment platform. The second lifting assembly includes a hollow shaft motor and a screw. One end of the screw is coaxially connected to the hollow shaft of the hollow shaft motor, and the other end of the screw is connected to the height adjustment platform. The third lifting assembly includes a gear transmission mechanism, an inner connecting rod, and an outer connecting rod. One end of the inner connecting rod is connected to the center of the concave reflective heat screen, and the other end of the inner connecting rod is connected to the corresponding gear transmission mechanism. One end of the outer connecting rod is connected to the edge area of ​​the concave reflective heat screen, and the other end of the outer connecting rod is connected to the corresponding gear transmission mechanism. Both the inner and outer connecting rods are slidably connected to the height adjustment platform. Both the hollow shaft motor and the gear transmission mechanism are electrically connected to the control module.

6. The method for controlling the temperature gradient of a crystal rod during the shoulder formation stage according to claim 5, characterized in that, The height adjustment value is calculated according to the following formula: H = 50 + 0.4 × D In the formula, H: height adjustment value, D: shoulder diameter.

Images