Method for shouldering heavily doped single crystal

Abstract

The invention provides a heavily doped single crystal shouldering method, and belongs to the technical field of heavily doped crystal pulling control methods, different shouldering shoulder shapes, shouldering pulling speeds and temperature gradient change trends are obtained according to different height-diameter ratios, so that the shouldering shoulder shapes are matched with the height-diameter ratios, and the shouldering shoulder shapes are obtained by matching the shouldering pulling speeds with corresponding temperature gradients. The density difference caused by different heating of a solution is reduced, automatic convection from bottom to top due to the density difference is reduced, the strength of the automatic convection is prevented from being influenced, dislocation caused by the influence on the temperature and impurity concentration of a solid-liquid interface is further avoided, the temperature stability in the shouldering process is good, the shoulder shape control is good, and the drawing and releasing times are reduced; and the shouldering success rate is high.

Description

Technical Field

[0001] This invention relates to the technical field of methods for controlling heavily doped crystal pulling, and specifically to a method for shoulder formation in heavily doped single crystals. Background Technology

[0002] Currently, heavily doped semiconductors generally have steep shoulders. The differences lie in the process control methods and shoulder size, which are key factors in determining the number of triggers for heavy doping. This depends on the thermal field size, and the difficulty of shoulder formation gradually increases. Currently, the average number of triggers for small-sized heavily doped semiconductors can be controlled within 1-2 times, the average number of triggers for 8-inch semiconductors can be controlled within 2-3 times, while the average number of triggers for 12-inch semiconductors is generally >4 times. Reducing the average number of triggers for 12-inch semiconductors is currently a control challenge because their increasingly larger aspect ratios lead to poor temperature stability during the shoulder formation process, making shoulder control more difficult and resulting in a high number of triggers. Summary of the Invention

[0003] In view of this, the present invention provides a method for shoulder formation of heavily doped single crystals that reduces the number of triggering cycles.

[0004] The technical solution adopted by this invention to solve its technical problem is: A method for shoulder formation in heavily doped single crystals is proposed. Different shoulder shapes, shoulder pulling speeds, and temperature gradient trends are obtained based on different aspect ratios, so that the shoulder shape is adapted to the aspect ratio. The shoulder shape is obtained by matching the shoulder pulling speed with the corresponding temperature gradient, thereby suppressing the influence of melt depth and crucible radius on natural convection. The shoulder-relaxing angle of the shoulder-relaxing type is varied in a stepped manner.

[0005] Preferably, when the height-to-diameter ratio is 0.75~0.95, the shoulder shape is divided into three stages, and the shoulder angle range of the shoulder shape is 35°~45°, which is divided into stage A, stage B and stage C. The shoulder-expanding angle in stage A is 35° to 37° to 41°, and the shoulder-expanding height in stage A is 0 to 55% to 60% of the overall shoulder-expanding height. The shoulder-expanding angle in stage B is 37°~41° to 40°~44°, and the shoulder-expanding height in stage B is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle of stage C is 40°~44° to 45°, and the shoulder-expanding height of stage C is 75%~80% to 100% of the overall shoulder-expanding height.

[0006] Preferably, when the height-to-diameter ratio is 0.75~0.95, the shoulder-raising speed exhibits a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.2mm / min~1.3mm / min; the minimum shoulder-raising speed is 0.6mm / min~0.7mm / min. The temperature gradient change trend in stage A is the curve formed by 3a to 1.5a to 1.2a; The temperature gradient change trend in stage B is the curve formed by a to 1.2a to 1.2a; The temperature gradient change trend in stage C is as follows: the curve formed from 1.5a to 3a to 5a. The 'a' above refers to a certain temperature, in °C.

[0007] Preferably, the length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the stage during which the shoulder-releasing speed remains constant begins at 25% to 30% of the overall shoulder-releasing length.

[0008] Preferably, when the height-to-diameter ratio is less than 0.75, the shoulder shape is divided into one or two stages, and the shoulder angle of the shoulder shape is in the range of 35°~50°, and the shoulder angle range of the shoulder shape is divided into stage S1. The shoulder-expanding angle in stage S1 is 35° to 42° to 50°, and the shoulder-expanding height in stage S1 is 0 to 100% of the overall shoulder-expanding height. Alternatively, the range of shoulder-relaxing angles can be divided into S2 and S3 stages. The shoulder-expanding angle in stage S2 is 35° to 37° to 41°, and the shoulder-expanding height in stage S2 is 0 to 55% to 80% of the overall shoulder-expanding height. The shoulder-expanding angle in stage S3 is 37°~41° to 42°~50°, and the shoulder-expanding height in stage S3 is 55%~80% to 100% of the overall shoulder-expanding height.

[0009] Preferably, when the height-to-diameter ratio is less than 0.75, the shoulder-raising speed exhibits a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.3 mm / min to 1.6 mm / min; the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend is a curve formed by 3a to 1.5a to 1.2a, where 'a' refers to a certain temperature in °C.

[0010] Preferably, the length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the stage during which the shoulder-releasing speed remains constant begins before 20% of the overall shoulder-releasing length.

[0011] Preferably, when the height-to-diameter ratio is greater than 0.95, the shoulder shape has at least three stages, and the shoulder angle range of the shoulder shape is 32°~50°, dividing the shoulder angle range of the shoulder shape into at least a first stage, a second stage, and a third stage; The shoulder-expanding angle in the first stage is 32°~40° to 37°~41°, and the shoulder-expanding height in the first stage is 0 to 55%~60% of the overall shoulder-expanding height; The shoulder-expanding angle in the second stage is 37°~41° to 40°~44°, and the shoulder-expanding height in the second stage is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle in the third stage is 40°~44° to 44°~50°, and the shoulder-expanding height in the third stage is 75%~80% to 100% of the overall shoulder-expanding height.

[0012] Preferably, when the height-to-diameter ratio is greater than 0.95, the shoulder-raising speed shows a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.1 mm / min to 1.25 mm / min, and the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend in the first stage is the curve formed by 1.2a to 1a to 1a; The temperature gradient change trend in the second stage is the curve formed from 1a to 1.2a to 1.5a; The temperature gradient change trend in the third stage is the curve formed from 2a to 3a to 5a; The 'a' above refers to a certain temperature, in °C.

[0013] Preferably, the length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the end point of the stage during which the shoulder-releasing speed remains constant is within 60% of the overall shoulder-releasing length.

[0014] Preferably, the length at which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the end point at which the shoulder-releasing speed remains constant is within 60% of the overall shoulder-releasing length.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention obtains different shoulder shapes, shoulder casting speeds, and temperature gradient trends based on different aspect ratios, making the shoulder shape compatible with the aspect ratio. By matching the shoulder casting speed with the corresponding temperature gradient, the shoulder shape is obtained, reducing density differences in the melt due to different heating, and reducing the bottom-up automatic convection caused by the existence of density differences. This avoids affecting the intensity of automatic convection, and thus avoids dislocation caused by the temperature and impurity concentration at the solid-liquid interface. As a result, the shoulder casting process has good temperature stability, excellent shoulder shape control, fewer casting attempts, and a high shoulder casting success rate. Attached Figure Description

[0016] Figure 1 This is a graph showing the shoulder-relaxation stretching speed curve, the upper limit of shoulder-relaxation stretching speed curve, and the lower limit of shoulder-relaxation stretching speed curve in Example 1.

[0017] Figure 2 This is the temperature gradient curve of Example 1.

[0018] Figure 3 This is a comparison chart of the number of releases in Example 1 and Comparative Example 1.

[0019] Figure 4 This is a comparison chart of the head resistivity of Example 1 and Comparative Example 1.

[0020] Figure 5 This is a graph showing the shoulder-relaxation stretching speed curve, the upper limit of shoulder-relaxation stretching speed curve, and the lower limit of shoulder-relaxation stretching speed curve in Example 2.

[0021] Figure 6 This is the temperature gradient curve of Example 2.

[0022] Figure 7 This is a comparison chart of the number of releases in Example 2 and Comparative Example 2.

[0023] Figure 8 This is a comparison chart of the head resistivity of Example 2 and Comparative Example 2.

[0024] Figure 3 , Figure 4 From left to right, the examples are: Comparative Example 1, Experiment ...

[0025] Figure 7 , Figure 8 From left to right, the images are: Comparative Example 2, Experiment 1; Comparative Example 2, Experiment 2, Experiment 3; Example 2, Experiment 1; Example 2, Experiment 2, Experiment 2, Experiment 3. Detailed Implementation

[0026] The technical solution and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0027] A method for shoulder formation in heavily doped single crystals is proposed. Different shoulder shapes, shoulder pulling speeds, and temperature gradient trends are obtained based on different aspect ratios, so that the shoulder shape is adapted to the aspect ratio. The shoulder shape is obtained by matching the shoulder pulling speed with the corresponding temperature gradient, thereby suppressing the influence of melt depth and crucible radius on natural convection. The shoulder-relaxing angle of the shoulder-relaxing type is varied in a stepped manner.

[0028] Specifically, the height-to-diameter ratio refers to the ratio of the height of the solution inside the crucible to the radius of the solution.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention obtains different shoulder shapes, shoulder casting speeds, and temperature gradient trends based on different aspect ratios, making the shoulder shape compatible with the aspect ratio. By matching the shoulder casting speed with the corresponding temperature gradient, the shoulder shape is obtained, reducing density differences in the melt due to different heating, and reducing the bottom-up automatic convection caused by the existence of density differences. This avoids affecting the intensity of automatic convection, and thus avoids dislocation caused by the temperature and impurity concentration at the solid-liquid interface. As a result, the shoulder casting process has good temperature stability, excellent shoulder shape control, fewer casting attempts, and a high shoulder casting success rate.

[0030] Furthermore, by matching different aspect ratios with different shoulder shapes, shoulder pulling speeds, and temperature gradient trends, the temperature stability during the shoulder pulling process is excellent, making it suitable for crystal rods of various sizes.

[0031] Heavy doping, due to its high doping concentration and volatility, leads to unstable crystallization temperature at the solid-liquid interface, which is greatly affected by impurity concentration. By matching different aspect ratios with different shoulder shapes, shoulder pulling speeds, temperature gradient trends with different temperature zones and different melt convection intensities, the shoulder shape can be made consistent with the desired shoulder shape, thereby reducing the number of heavy doping induction times and obtaining the desired crystal pulling effect.

[0032] Furthermore, when the height-to-diameter ratio is 0.75~0.95, the shoulder shape is divided into three stages, and the shoulder angle range of the shoulder shape is 35°~45°. The shoulder angle range of the shoulder shape is divided into stage A, stage B, and stage C. The shoulder-expanding angle in stage A is 35° to 37° to 41°, and the shoulder-expanding height in stage A is 0 to 55% to 60% of the overall shoulder-expanding height. The shoulder-expanding angle in stage B is 37°~41° to 40°~44°, and the shoulder-expanding height in stage B is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle of stage C is 40°~44° to 45°, and the shoulder-expanding height of stage C is 75%~80% to 100% of the overall shoulder-expanding height.

[0033] For example, for a 12-inch heavily doped red phosphorus single crystal rod, the overall shoulder height is greater than or equal to 390mm and the overall diameter is greater than or equal to 320mm.

[0034] Furthermore, the shoulder diameter can be obtained by using D=[2tan(α / 2)]H, where D is the shoulder diameter in mm, H is the shoulder height in mm, and α is the shoulder angle.

[0035] Specifically, the aforementioned shoulder-releasing angle refers to the angle that gradually increases from the initial angle of a certain stage to the final angle of that stage. Taking stage A as an example, the shoulder-releasing angle may be 35°, 36°, 37°, etc.

[0036] Furthermore, when the height-to-diameter ratio is 0.75~0.95, the shoulder-laying speed exhibits a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-laying speed during the shoulder-laying process is 1.2mm / min~1.3mm / min; the minimum shoulder-laying speed is 0.6mm / min~0.7mm / min; the upper and lower limits of the shoulder-laying speed = the set value of the shoulder-laying speed - (0.075~0.15)mm / min.

[0037] The temperature gradient change trend in stage A is the curve formed by 3a to 1.5a to 1.2a; The temperature gradient change trend in stage B is the curve formed by a to 1.2a to 1.2a; The temperature gradient change trend in stage C is as follows: the curve formed from 1.5a to 3a to 5a. The 'a' above refers to a certain temperature, in °C.

[0038] Furthermore, the length of the shoulder pulling speed that remains constant in the middle is 35% to 45% of the overall shoulder length. The stage where the shoulder pulling speed remains constant in the middle starts from 25% to 30% of the overall shoulder length. The above-mentioned control of aspect ratio, shoulder pulling angle, shoulder pulling speed, and temperature gradient change trend are applicable to the shoulder pulling of 8 to 12-inch heavily doped single crystal rods.

[0039] The intensity of automatic convection is affected by the depth of the melt and the radius of the crucible. The greater the depth or the larger the radius, the greater the convection intensity. By matching the shoulder shape, shoulder pulling speed and temperature gradient, natural convection is suppressed, thereby reducing the number of pull-outs required to pull a 12-inch single crystal.

[0040] Furthermore, the aforementioned control method is also applicable to pulling 12-inch single crystals on 8-inch equipment, and it is also applicable to heavily doped low-resistivity products. This means that when facing the expansion of 12-inch crystal ingot production, most of the 8-inch furnaces can be modified to pull 12-inch single crystals, which greatly reduces the cost of pulling 12-inch single crystals and improves the utilization rate of equipment.

[0041] Furthermore, when the height-to-diameter ratio is less than 0.75, the shoulder shape is divided into one or two stages, and the shoulder angle of the shoulder shape is in the range of 35°~50°, dividing the shoulder angle range of the shoulder shape into stage S1. The shoulder-expanding angle in stage S1 is 35° to 42° to 50°, and the shoulder-expanding height in stage S1 is 0 to 100% of the overall shoulder-expanding height. Alternatively, the range of shoulder-relaxing angles can be divided into S2 and S3 stages. The shoulder-expanding angle in stage S2 is 35° to 37° to 41°, and the shoulder-expanding height in stage S2 is 0 to 55% to 80% of the overall shoulder-expanding height. The shoulder-expanding angle in stage S3 is 37°~41° to 42°~50°, and the shoulder-expanding height in stage S3 is 55%~80% to 100% of the overall shoulder-expanding height.

[0042] Furthermore, when the height-to-diameter ratio is less than 0.75, the shoulder-raising speed exhibits a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.3 mm / min to 1.6 mm / min; the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend is a curve formed from 3a to 1.5a to 1.2a, where 'a' refers to a certain temperature in °C.

[0043] Furthermore, the length of the shoulder pulling speed that remains constant in the middle is 35% to 45% of the overall shoulder length. The stage where the shoulder pulling speed remains constant in the middle starts before 20% of the overall shoulder length. The above-mentioned control of the height-to-diameter ratio, the shoulder pulling angle, the shoulder pulling speed, and the temperature gradient change trend are applicable to the shoulder pulling of heavily doped single crystal rods smaller than 8 inches.

[0044] Furthermore, when the height-to-diameter ratio is greater than 0.95, the shoulder shape has at least three stages, and the shoulder angle range of the shoulder shape is 32°~50°, dividing the shoulder angle range of the shoulder shape into at least a first stage, a second stage, and a third stage; The shoulder-expanding angle in the first stage is 32°~40° to 37°~41°, and the shoulder-expanding height in the first stage is 0 to 55%~60% of the overall shoulder-expanding height; The shoulder-expanding angle in the second stage is 37°~41° to 40°~44°, and the shoulder-expanding height in the second stage is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle in the third stage is 40°~44° to 44°~50°, and the shoulder-expanding height in the third stage is 75%~80% to 100% of the overall shoulder-expanding height.

[0045] Furthermore, when the height-to-diameter ratio is greater than 0.95, the shoulder-raising speed shows a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.1 mm / min to 1.25 mm / min, and the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend in the first stage is the curve formed by 1.2a to 1a to 1a; The temperature gradient change trend in the second stage is the curve formed from 1a to 1.2a to 1.5a; The temperature gradient change trend in the third stage is the curve formed from 2a to 3a to 5a; The 'a' above refers to a certain temperature, in °C.

[0046] Furthermore, the temperature gradient change time is 10 minutes.

[0047] Furthermore, the length of the shoulder pulling speed that remains constant in the middle is 35% to 45% of the overall shoulder length, and the end point of the shoulder pulling speed that remains constant in the middle is within 60% of the overall shoulder length. The above-mentioned control of the height-to-diameter ratio, the shoulder pulling angle, the shoulder pulling speed, and the temperature gradient change trend are applicable to the shoulder pulling of heavily doped single crystal rods larger than 12 inches.

[0048] Specifically, the content of the present invention will be illustrated through the following embodiments and comparative examples.

[0049] The following examples and comparative examples take the pulling of a 12-inch heavily doped red phosphorus single crystal as an example. The shoulder height is 400mm, the shoulder diameter is 320mm, the 8-inch single crystal growth equipment is used, the crucible is a 28-inch crucible with an outer diameter of 710mm, the crystal rod diameter is 310mm, and the height-to-diameter ratio is 0.89. Example 1:

[0050] The target resistivity was 1.1 mΩ. The experimental parameters were: crystal rotation: 10 rpm; crucible rotation: 2 rpm; pressure: 14 kPa; argon gas: 120 slm; MCZ; gap: 40 mm. The experiment was repeated 5 times.

[0051] The shoulder-expanding angle of stage A is 35° to 37°, and the shoulder-expanding height of stage A is 0 to 55% of the overall shoulder-expanding height; The shoulder-expanding angle in stage B is 37° to 42°, and the shoulder-expanding height in stage B is 55% to 75% of the overall shoulder-expanding height. The shoulder-expanding angle in stage C is 42° to 45°, and the shoulder-expanding height in stage B is 75% to 100% of the overall shoulder-expanding height.

[0052] Shoulder pull speed Figure 1 As shown, the temperature gradient is as follows Figure 2 As shown.

[0053] The above parameters are set in the system (FT-CZ2408S2-3212SE-PCE-Ver4.209). The specific shoulder-raising control method is consistent with the method in patent number CN118028967B. The real-time diameter is matched with the set diameter by controlling the pulling speed and temperature. The three are mutually input and output to control each other. The entire process is automatic shoulder raising. The number of times it is raised and the head resistivity are as follows. Figure 3 , 4 As shown.

[0054] Comparative Example 1 Using the scheme from Embodiment 1 of the patent disclosed in CN118028967B (which describes a control method, apparatus, and readable medium for automatic shoulder formation in heavily doped single crystals), shoulder formation was performed. Parameters not mentioned were the same as in Embodiment 1. The experiment was conducted 5 times, and the number of times the shoulder was formed and the head resistivity were as follows: Figure 3 , 4 As shown. Example 2:

[0055] The target resistivity was 2.5 mΩ. The experimental parameters were: crystal rotation: 10 rpm; crucible rotation: 2 rpm; pressure: 20 kPa; argon gas: 120 slm; MCZ; gap: 35 mm. The experiment was repeated 3 times.

[0056] The shoulder-expanding angle of stage A is 35° to 37°, and the shoulder-expanding height of stage A is 0 to 55% of the overall shoulder-expanding height; The shoulder-expanding angle in stage B is 37° to 42°, and the shoulder-expanding height in stage B is 55% to 75% of the overall shoulder-expanding height. The shoulder-expanding angle in stage C is 42° to 45°, and the shoulder-expanding height in stage B is 75% to 100% of the overall shoulder-expanding height.

[0057] Shoulder pull speed Figure 5 As shown, the temperature gradient is as follows Figure 6 As shown.

[0058] The above parameters are set in the system (FT-CZ2408S2-3212SE-PCE-Ver4.209). The specific shoulder-raising control method is consistent with the method in patent number CN118028967B. The real-time diameter is matched with the set diameter by controlling the pulling speed and temperature. The three are mutually input and output to control each other. The entire process is automatic shoulder raising. The number of times it is raised and the head resistivity are as follows. Figure 7 , 8 As stated above.

[0059] Comparative Example 2 Using the scheme from Embodiment 1 of the patent disclosed in CN118028967B (which describes a control method, apparatus, and readable medium for automatic shoulder formation in heavily doped single crystals), shoulder formation was performed. Parameters not mentioned were the same as in Embodiment 1. The experiment was conducted three times, and the number of times the shoulder was formed and the head resistivity were as follows: Figure 7 , 8 As shown.

[0060] pass Figure 3 , Figure 4 , Figure 7 , Figure 8 It can be seen that for pulling heavily doped low-resistivity red phosphorus single crystals, the number of pull-outs in Examples 1 and 2 is significantly reduced, and the head resistivity of the pulled crystal rod meets the target resistivity requirements. However, in Comparative Examples 1 and 2, the number of pull-outs for pulling large-size low-resistivity red phosphorus single crystals is high, the impurities in the furnace continue to volatilize and the amount of impurities gradually increases, the impurity concentration in the molten solution gradually decreases, and the corresponding head resistivity increases significantly, which does not meet the target requirements.

[0061] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for shoulder formation in heavily doped single crystals, characterized in that, Different shoulder shapes, shoulder casting speeds, and temperature gradient trends are obtained based on different height-to-diameter ratios, so that the shoulder shape is adapted to the height-to-diameter ratio. The shoulder shape is obtained by matching the corresponding temperature gradient with the shoulder casting speed, so as to suppress the influence of melt depth and crucible radius on natural convection. The shoulder-relaxing angle of the shoulder-relaxing type is varied in a stepped manner.

2. The method for shoulder formation in heavily doped single crystals as described in claim 1, characterized in that, When the height-to-diameter ratio is 0.75~0.95, the shoulder shape is divided into three stages, and the shoulder angle range of the shoulder shape is 35°~45°. The shoulder angle range of the shoulder shape is divided into stage A, stage B and stage C. The shoulder-expanding angle in stage A is 35° to 37° to 41°, and the shoulder-expanding height in stage A is 0 to 55% to 60% of the overall shoulder-expanding height. The shoulder-expanding angle in stage B is 37°~41° to 40°~44°, and the shoulder-expanding height in stage B is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle of stage C is 40°~44° to 45°, and the shoulder-expanding height of stage C is 75%~80% to 100% of the overall shoulder-expanding height.

3. The method for shoulder formation in heavily doped single crystals as described in claim 2, characterized in that, When the height-to-diameter ratio is 0.75~0.95, the shoulder-raising speed shows a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.2mm / min~1.3mm / min; the minimum shoulder-raising speed is 0.6mm / min~0.7mm / min. The temperature gradient change trend in stage A is the curve formed by 3a to 1.5a to 1.2a; The temperature gradient change trend in stage B is the curve formed by a to 1.2a to 1.2a; The temperature gradient change trend in stage C is as follows: the curve formed from 1.5a to 3a to 5a. The 'a' above refers to a certain temperature, in °C.

4. The method for shoulder formation in heavily doped single crystals as described in claim 3, characterized in that, The length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the stage during which the shoulder-releasing speed remains constant begins from 25% to 30% of the overall shoulder-releasing length.

5. The method for shoulder formation in heavily doped single crystals as described in claim 1, characterized in that, When the height-to-diameter ratio is less than 0.75, the shoulder shape is divided into one or two stages, and the shoulder angle of the shoulder shape is in the range of 35°~50°. The shoulder angle range of the shoulder shape is divided into stage S1. The shoulder-expanding angle in stage S1 is 35° to 42° to 50°, and the shoulder-expanding height in stage S1 is 0 to 100% of the overall shoulder-expanding height. Alternatively, the range of shoulder-relaxing angles can be divided into S2 and S3 stages. The shoulder-expanding angle in stage S2 is 35° to 37° to 41°, and the shoulder-expanding height in stage S2 is 0 to 55% to 80% of the overall shoulder-expanding height. The shoulder-expanding angle in stage S3 is 37°~41° to 42°~50°, and the shoulder-expanding height in stage S3 is 55%~80% to 100% of the overall shoulder-expanding height.

6. The method for shoulder formation in heavily doped single crystals as described in claim 5, characterized in that, When the height-to-diameter ratio is less than 0.75, the shoulder-raising speed shows a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.3 mm / min to 1.6 mm / min; the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend is a curve formed by 3a to 1.5a to 1.2a, where 'a' refers to a certain temperature in °C.

7. The method for shoulder formation in heavily doped single crystals as described in claim 6, characterized in that, The length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the stage during which the shoulder-releasing speed remains constant begins before 20% of the overall shoulder-releasing length.

8. The method for shoulder formation in heavily doped single crystals as described in claim 1, characterized in that, When the height-to-diameter ratio is greater than 0.95, the shoulder shape has at least three stages, and the shoulder angle range of the shoulder shape is 32°~50°. The shoulder angle range of the shoulder shape is divided into at least a first stage, a second stage, and a third stage. The shoulder-expanding angle in the first stage is 32°~40° to 37°~41°, and the shoulder-expanding height in the first stage is 0 to 55%~60% of the overall shoulder-expanding height; The shoulder-expanding angle in the second stage is 37°~41° to 40°~44°, and the shoulder-expanding height in the second stage is 55%~60% to 75%~80% of the overall shoulder-expanding height. The shoulder-expanding angle in the third stage is 40°~44° to 44°~50°, and the shoulder-expanding height in the third stage is 75%~80% to 100% of the overall shoulder-expanding height.

9. The method for shoulder formation in a heavily doped single crystal as described in claim 8, characterized in that, When the height-to-diameter ratio is greater than 0.95, the shoulder-raising speed shows a trend of increasing in the early stage, remaining constant in the middle stage, and decreasing in the later stage. The maximum shoulder-raising speed during the shoulder-raising process is 1.1 mm / min to 1.25 mm / min, and the minimum shoulder-raising speed is 0.6 mm / min to 0.7 mm / min. The temperature gradient change trend in the first stage is the curve formed by 1.2a to 1a to 1a; The temperature gradient change trend in the second stage is the curve formed from 1a to 1.2a to 1.5a; The temperature gradient change trend in the third stage is the curve formed from 2a to 3a to 5a; The 'a' above refers to a certain temperature, in °C.

10. The method for shoulder formation in a heavily doped single crystal as described in claim 9, characterized in that, The length during which the shoulder-releasing speed remains constant is 35% to 45% of the overall shoulder-releasing length, and the end point of the stage where the shoulder-releasing speed remains constant is within 60% of the overall shoulder-releasing length.

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