Method for improving diameter qualification rate of equal-diameter heads

Abstract

The invention relates to the technical field of a single crystal silicon rod drawing process, particularly discloses a method for improving the diameter qualification rate of an equal-diameter head, and aims to solve the technical bottlenecks of large diameter fluctuation, low qualification rate, high wire breakage rate and insufficient per unit yield of the equal-diameter head caused by a fixed rotating shoulder diameter process in the existing single crystal silicon rod drawing. According to the method, through three-stage control logic of real-time monitoring of the diameter increasing rate in the later stage of shouldering, dynamic calculation of the shouldering starting diameter and closed-loop adjustment of the growth rate in the shouldering process, stable transition of the single crystal silicon rod from radial growth to axial growth is achieved; the method is suitable for a crystal containing TDR-M160-ZJS type single crystal furnace and TDR crystal containing single crystal furnace control boundary v3.21.1 software, the diameter qualification rate of the equal-diameter head can be increased from 35% to 90%, the head wire breakage rate is reduced from 11% to 5%, and the daily yield per unit of a single furnace is increased by 7.2 kg; and meanwhile, the crystal dislocation density is reduced, the minority carrier lifetime is prolonged, the follow-up linear cutting loss and the cell efficiency attenuation are reduced, and the method is suitable for large-scale production of N-type / P-type solar-grade silicon single crystal rods and has high compatibility and economic benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of single crystal silicon rod manufacturing, and particularly relates to a process optimization method for diameter precision control of the constant diameter head during single crystal silicon rod drawing, which is particularly suitable for large-scale production of solar-grade N-type / P-type single crystal silicon rods (such as PERC, TOPCon, and HJT battery silicon rods), and is compatible with the existing Czochralski furnace (CZ method) equipment system without the need for hardware modification to realize technology landing. BACKGROUND

[0002] The constant diameter head of a single crystal silicon rod is a key area connecting the "shoulder placing stage" and the "constant diameter stage", and the diameter precision directly determines the silicon wafer yield, cell photoelectric conversion efficiency, and production economy of subsequent wire cutting processing. In the existing single crystal silicon rod drawing process, the shoulder turning operation generally adopts a "fixed diameter starting mode" - that is, a fixed shoulder turning diameter threshold (such as target diameter - 20 mm) is preset, and when the crystal diameter reaches the threshold, the shoulder turning program is directly started without considering the dynamic changes of the diameter growth rate in the shoulder placing stage.

[0003] The existing technology is affected by factors such as "uneven distribution of temperature field in the furnace", "silicon melt convection fluctuation", and "initial pulling speed deviation" in the single crystal silicon drawing process, and the diameter growth rate in the shoulder placing stage has significant differences (fluctuation range 0.5-2 mm / min), which leads to the following unavoidable problems of the fixed shoulder turning diameter mode: Crystal quality defects: when the shoulder turning is started, if the actual diameter growth rate is higher than the preset value, it will cause the diameter after shoulder turning to exceed the target value (maximum deviation up to +8 mm), which will cause the local thermal stress to exceed the critical stress of the silicon crystal (about 1.2 GPa), resulting in dislocation proliferation (dislocation density increases to 5000-8000 / cm 2 ), and the minority carrier lifetime decays to 1.0-1.5 μs; if the growth rate is lower than the preset value, the diameter after shoulder turning is lower than the target value (minimum deviation up to -7 mm), which requires subsequent supplementary drawing, further aggravating the impurity enrichment in the crystal; Subsequent processing loss: parts with diameter fluctuation exceeding ±3 mm in the constant diameter head need to be completely scrapped. Taking a 183 mm specification single crystal silicon rod as an example, the scrapped length of each single crystal head is about 100 mm (equivalent to 12.7 kg of weight), and when 8 single crystals are drawn per furnace, according to a 35% pass rate, the scrapped capacity per furnace reaches 12.7 kg x 8 x (1-35%) = 66 kg; at the same time, the uneven diameter leads to uneven stress on the diamond wire during wire cutting, the wire breaking rate increases to 15-20%, the silicon wafer hidden crack rate increases by 8-10%, and the processing cost increases by 0.005 yuan per piece; Low equipment operating efficiency: Diameter fluctuations lead to frequent adjustments in drawing speed (fluctuation range ±15mm / hr), resulting in concentrated thermal stress at the head and an increased risk of wire breakage—the average head breakage rate of the existing process is 11%, and each breakage requires re-drawing (taking 7±0.5 hours), directly causing a decrease in daily output of a single furnace of more than 4%; frequent wire breakages also cause the quartz crucible to be subjected to high temperatures above 1420℃ for a long time at the same liquid level line (the contact position between the silicon melt and the crucible), which destroys the uniformity of crucible wall thickness, increases the risk of silicon leakage by 30%, and shortens the equipment maintenance cycle by 5-7 days; Performance degradation of end products: Crystal dislocations and impurity defects caused by diameter fluctuations can reduce the photoelectric conversion efficiency of the manufactured solar cells by 0.3-0.5% (e.g., the efficiency of PERC cells drops from 23.5% to below 23.0%), which does not meet the development needs of the photovoltaic industry for "cost reduction and efficiency improvement".

[0004] Currently, industry-wide measures to address diameter fluctuations focus on "manually adjusting casting speed / temperature" or "optimizing initial shoulder formation parameters," such as: Option 1: Adjust the pulling speed during the shoulder-laying stage based on the operator's experience. However, if there are significant differences in the operators' skills, the adjustment accuracy may be insufficient (±2mm / hr), making it unsuitable for the dynamic growth state. Option 2: Pre-set multiple fixed shoulder diameters (e.g., set 2-3 thresholds for different batches of silicon material), but this still does not solve the core problem of "growth rate difference", and the pass rate is improved by less than 10%; The above solutions all lack an "adaptive adjustment mechanism based on real-time growth status," which cannot fundamentally eliminate the mismatch between fixed shoulder parameters and dynamic diameter growth, resulting in limited technical effectiveness. Summary of the Invention

[0005] The purpose of this invention is to provide a method for improving the pass rate of equal diameter head diameter, so as to solve the problems mentioned in the background art.

[0006] The method for improving the pass rate of equal diameter head diameter according to the present invention includes the following specific steps: Step 1: Equipment and Software Configuration The JingSheng TDR-M160-ZJS type Czochralski single crystal furnace is adopted. This equipment is equipped with: The infrared diameter detection module (detection accuracy ±0.1mm, sampling frequency 1 time / 10s) can collect diameter data from 3 points on the circumference of the crystal in real time. The PID temperature closed-loop control system (temperature control accuracy ±1℃) supports dynamic temperature adjustment during the shoulder rotation process. Argon flow control system (flow range 0-100L / min, control accuracy ±1L / min) is used to suppress the adsorption of impurities on the crystal surface; Equipped with TDR Jingsheng Single Crystal Furnace Control Interface v3.21.1 (controller version 160PVT5.60.2.5.8, touchscreen version TDRNHYF-V3.20-[20250325]), the software includes: "Diameter Data Processing Module": Supports calculation of the average value of three-point sampling and automatic calculation of ΔD; "Shoulder Rotation Parameter Calculation Module": Preset shoulder rotation starting diameter algorithm and compensation coefficient library; "Multi-parameter closed-loop control module": can automatically adjust the pulling speed, temperature, and argon flow rate according to the diameter deviation; "Specification Matching Library": Preset monitoring cycles and compensation coefficient parameters for specifications such as 166mm, 182mm, 183mm, and 210mm, eliminating the need for manual input.

[0007] Step 2: Post-shoulder release monitoring initiated After the single-crystal silicon rod is pulled into the shoulder-forming stage, the control software receives the diameter data (average of three-point sampling) from the infrared diameter detection module in real time. When the actual diameter of the crystal is detected to be less than the target diameter - 40 mm (e.g., the trigger threshold is 205 mm when the target diameter is 245 mm), the software automatically activates the "diameter growth rate monitoring program" and synchronously records the current time (t0), current diameter (D0), furnace temperature (T0, default 1435℃), pulling speed (V0, default 130 mm / hr), and argon flow rate (F0, default 70 L / min) as monitoring benchmarks.

[0008] Step 3: Calculation of Diameter Growth After the monitoring program is started, the software continuously collects 24 sets of diameter data (D1-D24) at a frequency of 1 time / 10s, with a monitoring cycle of 4 minutes (t1-t0=240s). After the monitoring period ends, the software calculates the average diameter at the end of the monitoring period (D_end=(D22+D23+D24) / 3, taking the average of the last 3 sets of data to reduce the impact of end fluctuations), and calculates the diameter growth using the formula ΔD=D_end-D0; If ΔD > 5mm (high growth rate scenario), the software automatically applies a compensation coefficient of 0.95, correcting ΔD to ΔD' = ΔD × 0.95; if ΔD < 2mm (low growth rate scenario), it applies a compensation coefficient of 1.05, correcting ΔD to ΔD' = ΔD × 1.05; if 2mm ≤ ΔD ≤ 5mm (normal growth scenario), no correction is needed (ΔD' = ΔD), to avoid excessive deviation in the starting diameter of the shoulder rotation.

[0009] Step 4: Determine the starting diameter for shoulder rotation The software calculates the shoulder-turning start threshold based on the formula "Shoulder-turning start diameter D_start = target diameter - D_end'" (D_end' is the corrected diameter increase). Taking a 183mm single-crystal silicon rod (target diameter 245mm) as an example: if D0=205mm, D_end=212mm, ΔD=7mm (>5mm) during the monitoring period, then ΔD'=7×0.95=6.65mm, D_start=245-6.65=238.35mm, and the software automatically sets the starting diameter of the rotating shoulder to 238.4mm (retaining one decimal place to match the control accuracy of the equipment); The software sends the D_start parameter to the single crystal furnace control system and enters the "shoulder rotation waiting to be triggered state" to monitor in real time whether the crystal diameter has reached D_start.

[0010] Step 5: Adjusting the growth rate during shoulder rotation When the infrared diameter detection module detects that the crystal diameter has reached D_start, the device automatically starts the shoulder rotation operation and simultaneously enters the "multi-parameter closed-loop control stage": Pulling speed adjustment: The initial pulling speed is set to 120 mm / hr. The software collects diameter data every 10 seconds. If the actual diameter is greater than the target diameter + 0.5 mm, the pulling speed is increased by 5 mm / hr; if the actual diameter is less than the target diameter - 0.5 mm, the pulling speed is decreased by 5 mm / hr. The pulling speed adjustment range is controlled between 120-160 mm / hr to avoid thermal stress caused by sudden changes in speed. Temperature adjustment: The initial temperature is set at 1435℃. If the pulling speed is increased to 150mm / hr or above, the temperature will increase by 2℃ (to compensate for the increased heat dissipation caused by the increased pulling speed); if the pulling speed is reduced to 130mm / hr or below, the temperature will decrease by 2℃ (to suppress excessive growth); the temperature control accuracy is maintained at ±1℃. Argon flow rate adjustment: The argon flow rate is set to 80L / min at the beginning of the shoulder rotation (to enhance impurity discharge), and then reduced by 5L / min every 30s as the shoulder rotation progresses until the diameter of the uniform head reaches the target diameter ±3mm, and the flow rate is stabilized at 50L / min. When the software detects three consecutive times (with a 10-second interval) that the diameter is within ±3mm of the target diameter, it determines that the shoulder rotation is complete and automatically switches to the normal control parameters for the equal diameter stage.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. Significantly improved diameter accuracy and pass rate: Through a three-level control system of "growth rate prediction - diameter correction initiation - multi-parameter closed-loop adjustment", the diameter fluctuation of the equal-diameter head is controlled within ±3mm, and the pass rate is increased from 35% to 90%, an improvement of 55 percentage points, solving the core defects of the existing process; 2. Reduced breakage rate and equipment risk: Stable adjustment of drawing speed, temperature, and argon flow during the shoulder turning process reduces thermal stress concentration, lowering the head breakage rate from 11% to 5%. The reduced number of breakages reduces the risk of silicon leakage from the quartz crucible by 30%, extends the equipment maintenance cycle by 5-7 days, and increases equipment utilization by 4%. 3. Crystal quality and end-product performance optimization: dislocation density is reduced by 60%, minority carrier lifetime is increased by 87%, and internal crystal defects are reduced; the breakage rate of subsequent wire cutting is reduced by 10 percentage points, the microcrack rate of silicon wafers is reduced by 7 percentage points, and the processing cost is reduced by 0.005 yuan / piece; the photoelectric conversion efficiency of solar cells is increased by 0.3%, meeting the photovoltaic industry's demand for "high efficiency". 4. Strong compatibility and scalability: Based on the existing JingSheng TDR-M160-ZJS single crystal furnace and its supporting software, only the software algorithm needs to be upgraded (compliant with the OPCUA protocol, no hardware modification required), adapting to single crystal silicon rods of all sizes from 166-210mm; the software's "specification matching library" supports quick parameter retrieval, operators do not require professional skills training, and the promotion cost is low (modification cost per furnace < 5000 yuan). 5. Significant economic benefits: The daily output per furnace increases by 7.2 kg. Based on the market price of 15 yuan / kg for monocrystalline silicon rods, the daily revenue per furnace increases by 108 yuan, and the annual revenue increases by 35,640 yuan. Combined with the indirect benefits of reduced processing costs and improved battery efficiency, the annual economic benefits of a single production line with 100 furnaces exceed 4 million yuan. Attached Figure Description

[0012] Fig. 1 This is a chart showing the trend of head-line breakage rate from March to July 2024. Fig. 2 The original shoulder turn curve diagram before improvement; Fig. 3 A schematic diagram of the improved and adjusted shoulder turn curve. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Please see Figs. 1-3 This invention provides a method for improving the yield rate of uniform diameter head, applied to the single-crystal silicon rod pulling process, characterized by comprising the following steps: Step 1: Equipment and Software Configuration: A single crystal furnace equipped with an infrared diameter detection module and a PID temperature closed-loop control system is used. The single crystal furnace model is Jingsheng TDR-M160-ZJS. It is also equipped with the TDR Jingsheng single crystal furnace control interface v3.21.1. The controller version number of this control interface is 160PVT5.60.2.5.8 and the touch screen version number is TDRNHYF-V3.20-[20250325]. The software integrates functions such as real-time diameter data acquisition, growth calculation, automatic distribution of shoulder parameters, and dynamic adjustment of growth rate. Step 2: Post-shoulder setting monitoring start-up: During the single crystal silicon rod shoulder setting process, when the actual crystal diameter collected by the control software through the infrared diameter detection module is less than 40mm of the target diameter, the diameter growth rate monitoring program is automatically activated, and the shoulder setting parameter pre-calculation stage is entered. Step 3: Diameter growth calculation: After the monitoring program is started, crystal diameter data is continuously collected at a frequency of 1 time / 10s with a monitoring cycle of 4 minutes as the baseline. The diameter growth ΔD within the monitoring cycle is calculated, where ΔD = diameter value at the end of the monitoring period - diameter value at the beginning of the monitoring period. Step 4: Determining the starting diameter of the shoulder rotation: The control software calculates the starting diameter of the shoulder rotation according to the preset algorithm "starting diameter of the shoulder rotation = target diameter - ΔD". When ΔD exceeds the range of 2-5mm, ΔD is corrected by a preset compensation coefficient before the starting diameter of the shoulder rotation is calculated. Step 5: Adjustment of growth rate during shoulder turning: When the crystal diameter reaches the starting diameter for shoulder turning, the single crystal furnace automatically starts the shoulder turning operation. During the shoulder turning process, the control software dynamically adjusts the crystal pulling speed and furnace temperature according to the deviation between the real-time diameter data and the target diameter, so that the crystal smoothly transitions from radial growth to axial growth until the head diameter of the constant diameter is within the range of ±3mm of the target diameter.

[0015] In some embodiments, the diameter data acquisition in step 3 adopts the "three-point sampling method", which is as follows: three detection points are evenly selected in the circumferential direction of the crystal, the diameter data of each detection point is collected respectively, and the average value of the diameter data of the three detection points is taken as the crystal diameter value at the current moment, so as to reduce the detection error caused by crystal eccentricity.

[0016] In some embodiments, the baseline monitoring period in step 3 can be adaptively adjusted according to the target diameter specification of the single crystal silicon rod and the actual shoulder growth rate, with an adjustment range of 3-5 minutes; when the target diameter is ≥210mm, the monitoring period is adjusted to 5 minutes; when the target diameter is ≤166mm, the monitoring period is adjusted to 3 minutes; when the target diameter is 182-183mm, a baseline period of 4 minutes is maintained.

[0017] In some embodiments, the compensation coefficient in step 4 is determined according to the following rules: when ΔD > 5mm, the compensation coefficient is 0.95, and the corrected diameter increase ΔD' = ΔD × 0.95; when ΔD < 2mm, the compensation coefficient is 1.05, and the corrected diameter increase ΔD' = ΔD × 1.05; when 2mm ≤ ΔD ≤ 5mm, the compensation coefficient is 1.0, and ΔD' = ΔD.

[0018] In some embodiments, the argon flow rate is also adjusted synchronously during the shoulder turning process in step 5. The specific adjustment logic is as follows: when the shoulder turning starts, the argon flow rate is set to 80L / min, and then reduced by 5L / min every 30 seconds until the diameter of the uniform head reaches the target diameter ±3mm. At this time, the argon flow rate is stabilized at 50L / min to suppress the adsorption of impurities on the crystal surface.

[0019] In some embodiments, the crystal pulling speed in step 5 is adjusted in the range of 120-160 mm / hr with an adjustment step of 5 mm / hr; the furnace temperature is adjusted in the range of 1420-1450℃ with an adjustment step of 2℃; and the pulling speed and temperature are coupled and adjusted. When the pulling speed is increased to above 150 mm / hr, the furnace temperature is increased by 2℃; when the pulling speed is reduced to below 130 mm / hr, the furnace temperature is reduced by 2℃.

[0020] In some embodiments, the TDR Jingsheng single crystal furnace control interface v3.21.1 has a built-in "specification matching library". The "specification matching library" has preset monitoring cycle, compensation coefficient, initial pulling speed and initial temperature parameters corresponding to the mainstream single crystal silicon rod specifications of 166mm, 182mm, 183mm and 210mm. When calling, you only need to select the target specification to automatically load the parameters without manual input.

[0021] In some embodiments, the detection accuracy of the infrared diameter detection module in step 1 is ±0.1mm, and the sampling frequency can be adjusted within the range of 1 time / 5s to 1 time / 15s according to the detection requirements; when the deviation between the real-time diameter and the target diameter during the shoulder rotation is >±1mm, the sampling frequency is automatically increased to 1 time / 5s; when the deviation is ≤±0.5mm, the sampling frequency is adjusted to 1 time / 15s.

[0022] In some embodiments, step 5 also includes a diameter deviation alarm mechanism: when the deviation between the real-time diameter and the target diameter exceeds ±2mm for three consecutive times (with an interval of 10s) during the shoulder turning process, the control software triggers an audible and visual alarm and automatically reduces the pulling speed adjustment step to 2mm / hr and the temperature adjustment step to 1℃ until the deviation returns to within ±1mm, at which point the alarm is deactivated.

[0023] In some embodiments, the method is applicable to the pulling of N-type and P-type monocrystalline silicon rods, wherein the initial temperature of the N-type monocrystalline silicon rod at the shoulder is 5°C higher than that of the P-type monocrystalline silicon rod, and the initial argon flow rate is 10L / min higher than that of the P-type monocrystalline silicon rod; and the method is adapted to the production of monocrystalline silicon rods for PERC, TOPCon, and HJT batteries. For TOPCon battery silicon rods, the upper limit of the pulling speed in the later stage of shoulder turning is increased to 170mm / hr to meet its higher requirements for minority carrier lifetime.

[0024] Example: Taking the production of a 183mm N-type single crystal silicon rod (target diameter 245mm, acceptable range 242-248mm) as an example, the technical solution of the present invention is verified in detail: Preparations before implementation Equipment: Jingsheng TDR-M160-ZJS single crystal furnace, calibrated infrared diameter detection module (accuracy ±0.1mm), PID temperature control system (temperature control ±1℃); Software: Load TDR Jingsheng Single Crystal Furnace Control Interface v3.21.1, select "183mm N-type Silicon Rod" in "Specification Matching Library", and automatically load the monitoring cycle of 4 minutes and compensation coefficient (high growth 0.95 / normal 1.0 / low growth 1.05). Raw materials: polycrystalline silicon (purity 99.999999%), quartz crucible (diameter 800mm, wall thickness 15mm).

[0025] Implementation process Shoulder formation stage: Shoulder formation is carried out according to conventional process, with furnace temperature controlled at 1435℃, initial pulling speed at 130mm / hr, and argon flow rate at 70L / min. Monitoring Start-up: When the software detects that the diameter reaches 205mm (245-40), the monitoring program is activated, and D0=205.0mm and t0=0min are recorded. Growth calculation: Monitoring period 4 minutes (t1=4min), collected D_end=212.1mm, ΔD=212.1-205.0=7.1mm (>5mm), ΔD'=7.1×0.95=6.745mm, D_start=245-6.745=238.255mm≈238.3mm; Shoulder rotation trigger: When the diameter reaches 238.3mm, the shoulder rotation is initiated, with an initial pulling speed of 120mm / hr, a temperature of 1435℃, and an argon flow rate of 80L / min; Shoulder rotation 10s: diameter 239.5mm (<242mm), pulling speed reduced to 115mm / hr, temperature reduced to 1433℃; Shoulder rotation 30s: diameter 241.2mm (close to the acceptable range), pulling speed maintained at 115mm / hr, argon flow rate reduced to 75L / min; 60s shoulder rotation: diameter 243.5mm (between 242-248mm), pulling speed increased to 120mm / hr, temperature rises to 1435℃, argon flow rate drops to 70L / min; Shoulder rotation 120s: The diameter was measured three times in succession, and was 244.2mm, 244.0mm and 243.8mm. The shoulder rotation was then completed, and the process was switched to the equal diameter stage (pulling speed 150mm / hr, temperature 1440℃, argon flow rate 50L / min).

[0026] Implementation effect verification Pass rate: Statistics on production data from May to July 2024 (using the process of this invention) and March to April 2024 (using the existing process) show that the pass rate for equal diameter heads increased from 35% to 90%, with high-precision products of 244-246mm (target diameter ±1mm) accounting for 65%; Wire breakage rate: The head wire breakage rate decreased from 11.2% in March and 10.5% in April to 7.3% in May, 5.0% in June and 4.6% in July, with an average breakage rate of 5%, a decrease of 6 percentage points compared to the existing process; Output per unit: Based on the calculation that "each 1 percentage point reduction in the break-off rate increases output per unit by 1.2 kg / day", the daily output per furnace increases by 6 × 1.2 = 7.2 kg; with a single furnace operating for 330 days a year (excluding maintenance time), the annual increase in capacity is 7.2 × 330 = 2376 kg; Crystal quality: dislocation density from 5000 / cm 2 Reduced to 2000 / cm 2 The minority carrier lifetime increased from 1.5 μs to 2.8 μs; Processing costs: The wire breakage rate decreased from 18% to 8%, and the microcrack rate of silicon wafers decreased from 10% to 3%, resulting in a decrease in processing costs of 0.005 yuan per wafer; Battery efficiency: The photoelectric conversion efficiency of the fabricated TOPCon battery increased from 24.0% to 24.3%, and the efficiency degradation was reduced by 0.3%.

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

Claims

1. A method for improving the yield rate of uniform diameter head, applied to the single-crystal silicon rod pulling process, characterized in that, The following steps are included:

1. Equipment and software configuration: A single crystal furnace equipped with an infrared diameter detection module and a PID temperature closed-loop control system is used. The single crystal furnace model is Jingsheng TDR-M160-ZJS. It is also equipped with the TDR Jingsheng single crystal furnace control interface. The software integrates functions such as real-time diameter data acquisition, growth calculation, automatic distribution of shoulder parameters, and dynamic adjustment of growth rate. Step 2: Post-shoulder setting monitoring start-up: During the single crystal silicon rod shoulder setting process, when the actual crystal diameter collected by the control software through the infrared diameter detection module is less than 40mm of the target diameter, the diameter growth rate monitoring program is automatically activated, and the shoulder setting parameter pre-calculation stage is entered. Step 3: Diameter growth calculation: After the monitoring program is started, crystal diameter data is continuously collected at a frequency of 1 time / 10s with a monitoring cycle of 4 minutes as the baseline. The diameter growth ΔD within the monitoring cycle is calculated, where ΔD = diameter value at the end of the monitoring period - diameter value at the beginning of the monitoring period. Step 4: Determining the starting diameter of the shoulder rotation: The control software calculates the starting diameter of the shoulder rotation according to the preset algorithm "starting diameter of the shoulder rotation = target diameter - ΔD". When ΔD exceeds the range of 2-5mm, ΔD is corrected by a preset compensation coefficient before the starting diameter of the shoulder rotation is calculated. Step 5: Adjustment of growth rate during shoulder turning: When the crystal diameter reaches the starting diameter for shoulder turning, the single crystal furnace automatically starts the shoulder turning operation. During the shoulder turning process, the control software dynamically adjusts the crystal pulling speed and furnace temperature according to the deviation between the real-time diameter data and the target diameter, so that the crystal smoothly transitions from radial growth to axial growth until the head diameter of the constant diameter is within the range of ±3mm of the target diameter.

2. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, In step 3, the diameter data acquisition adopts the "three-point sampling method". Specifically, three detection points are evenly selected in the circumference of the crystal, and the diameter data of each detection point is collected. The average value of the diameter data of the three detection points is taken as the crystal diameter value at the current moment to reduce the detection error caused by crystal eccentricity.

3. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, The baseline monitoring cycle in step 3 can be adaptively adjusted according to the target diameter specification of the monocrystalline silicon rod and the actual shoulder growth rate, with an adjustment range of 3-5 minutes; when the target diameter is ≥210mm, the monitoring cycle is adjusted to 5 minutes; when the target diameter is ≤166mm, the monitoring cycle is adjusted to 3 minutes; when the target diameter is 182-183mm, the baseline cycle is maintained at 4 minutes.

4. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, The rules for determining the compensation coefficient in step 4 are as follows: when ΔD > 5mm, the compensation coefficient is 0.95, and the corrected diameter increase ΔD' = ΔD × 0.95; when ΔD < 2mm, the compensation coefficient is 1.05, and the corrected diameter increase ΔD' = ΔD × 1.05; when 2mm ≤ ΔD ≤ 5mm, the compensation coefficient is 1.0, and ΔD' = ΔD.

5. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, In step 5, the argon flow rate is also adjusted simultaneously during the shoulder rotation process. The specific adjustment logic is as follows: when the shoulder rotation starts, the argon flow rate is set to 80L / min, and then reduced by 5L / min every 30 seconds until the diameter of the uniform head reaches the target diameter ±3mm. At this time, the argon flow rate is stabilized at 50L / min to suppress the adsorption of impurities on the crystal surface.

6. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, In step 5, the crystal pulling speed is adjusted in the range of 120-160 mm / hr with an adjustment step of 5 mm / hr; the furnace temperature is adjusted in the range of 1420-1450℃ with an adjustment step of 2℃; and the pulling speed and temperature are coupled in adjustment. When the pulling speed is increased to above 150 mm / hr, the furnace temperature increases by 2℃; when the pulling speed is reduced to below 130 mm / hr, the furnace temperature decreases by 2℃.

7. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, The TDR Jingsheng single crystal furnace control interface v3.21.1 has a built-in "specification matching library". The "specification matching library" has preset monitoring cycle, compensation coefficient, initial pulling speed and initial temperature parameters corresponding to the mainstream single crystal silicon rod specifications of 166mm, 182mm, 183mm and 210mm. When calling, you only need to select the target specification to automatically load the parameters without manual input.

8. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, In step 1, the detection accuracy of the infrared diameter detection module is ±0.1mm, and the sampling frequency can be adjusted within the range of 1 time / 5s to 1 time / 15s according to the detection requirements. When the deviation between the real-time diameter and the target diameter during the shoulder rotation process is >±1mm, the sampling frequency is automatically increased to 1 time / 5s. When the deviation is ≤±0.5mm, the sampling frequency is adjusted to 1 time / 15s.

9. The method for improving the pass rate of equal-diameter head diameter according to claim 1, characterized in that, Step 5 also includes a diameter deviation alarm mechanism: when the deviation between the real-time diameter and the target diameter exceeds ±2mm for three consecutive times during the shoulder turning process, the control software triggers an audible and visual alarm and automatically reduces the pulling speed adjustment step to 2mm / hr and the temperature adjustment step to 1℃ until the deviation returns to within ±1mm, at which point the alarm is deactivated.

10. The method for improving the pass rate of equal-diameter head diameter according to any one of claims 1-9, characterized in that, The method is applicable to the pulling of N-type and P-type monocrystalline silicon rods. The initial temperature of the N-type monocrystalline silicon rod during shoulder turning is 5°C higher than that of the P-type monocrystalline silicon rod, and the initial argon flow rate is 10L / min higher. The method is also compatible with the production of monocrystalline silicon rods for PERC, TOPCon, and HJT batteries. For TOPCon battery rods, the upper limit of the pulling speed in the later stage of shoulder turning is increased to 170mm / hr to meet the higher requirements for minority carrier lifetime.

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