A segmented shoulder-forming method for zone-melting silicon single crystals
By using a segmented shoulder-turning method to adjust the heating power and growth angle of the single crystal, the problem of low crystal pulling success rate caused by large fluctuations in single crystal diameter was solved, and efficient and stable single crystal production was achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- GRINM SEMICONDUCTOR MATERIALS CO LTD
- Filing Date
- 2022-12-06
- Publication Date
- 2026-06-30
Smart Images
Figure CN116065227B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a segmented shoulder-forming method for zone-melting silicon single crystals, belonging to the field of semiconductor process technology. Background Technology
[0002] The production process of zone-melted silicon single crystals generally consists of several steps: material preparation, crystal pulling, necking, shoulder formation, shoulder rotation, and finishing. The shoulder rotation process is crucial in transitioning the single crystal diameter from an increasing state to a constant diameter state. This requires simultaneous control of heating power and polycrystalline speed to ensure stable growth of the single crystal diameter. Shoulder rotation is a key step affecting the success rate of crystal pulling. Traditional automatic shoulder rotation involves gradually increasing the heating power according to the increase in single crystal diameter, while the polycrystalline speed is calculated based on the single crystal growth angle. Once the single crystal diameter reaches the target diameter, neither the heating power nor the polycrystalline speed increases further. The disadvantage is the relatively long shoulder length, resulting in a fluctuating growth process in the single crystal diameter after shoulder rotation. The maximum and minimum diameters can vary by more than 3mm. Without manual intervention, the failure rate of crystal pulling is approximately 30%. Summary of the Invention
[0003] The purpose of this invention is to provide a segmented shoulder-turning method for zone-melting silicon single crystals, which can eliminate diameter fluctuations during the shoulder-turning process, reduce the shoulder length of the single crystal, improve the success rate and yield of crystal pulling, reduce the requirements for manual operation, and improve production efficiency.
[0004] To achieve the above objectives, the present invention adopts the following technical solution:
[0005] A segmented shoulder-forming method for zone-melting silicon single crystals includes the following steps:
[0006] (1) Set the position of the segmented shoulder diameter, and the set value should be 5mm smaller than the target value;
[0007] (2) Set the single crystal heating power curve parameters and growth angle before and after the shoulder diameter respectively. Before the single crystal diameter reaches the shoulder diameter, the single crystal heating power increases with the growth of the single crystal diameter. The faster the single crystal diameter grows, the faster the single crystal heating power grows, and vice versa. After the single crystal diameter exceeds the shoulder diameter, the single crystal heating power is no longer positively correlated with the single crystal diameter, but positively correlated with the single crystal growth length.
[0008] When the single crystal diameter approaches the target diameter, the single crystal growth angle first decreases, then increases, and then gradually decreases; when the single crystal diameter reaches the target diameter, the single crystal growth angle decreases to 0.
[0009] (3) Single crystal growth is carried out according to the set heating power parameters and growth angle.
[0010] Furthermore, in step (2), the heating power W = aD in front of the rotating shoulder diameter 3 +bD 2 +cD+d, where a, b, d, and c are constants, calculated using MATLAB fitting, and D is the diameter of the single crystal;
[0011] After rotating the shoulder diameter, the heating power W = a'X 3 +b'X 2 +c'X+d', where a', b', c', and d' are constants, calculated using MATLAB fitting, and X is the single crystal length.
[0012] Furthermore, in step (2), the specific process of the single crystal growth angle first decreasing and then increasing, and then gradually decreasing is as follows: first, a decrease of 2-5°, then an increase of 1-3°, and then a decrease of 0-3°.
[0013] Preferably, in step (2), the specific process of the single crystal growth angle first decreasing and then increasing, and then gradually decreasing is as follows: first, a decrease process with an amplitude of 2-5° and a speed of 1-4° / mm; then, an increase process with an amplitude of 1-3° and a speed of 0.5-2° / mm; and then, a decrease process with an amplitude of 0-3° and a speed of 0.5-3° / mm.
[0014] Furthermore, in step (2), the single crystal diameter fluctuation is controlled within 1 mm.
[0015] The advantages of this invention are:
[0016] The segmented shoulder-growing method of this invention ensures stable and smooth diameter growth during the shoulder-growing process, with diameter fluctuations controllable within 1 mm. The success rate of shoulder-growing for zone-melting single crystals is increased from approximately 80% to over 95%, yield is improved by more than 2%, labor is completely freed up during the shoulder-growing process, labor costs are significantly reduced, and per capita production capacity is increased by more than 20%. Attached Figure Description
[0017] Figure 1 This is a schematic diagram of the structure of a zone-melted silicon single crystal obtained using the conventional shoulder-turning method.
[0018] Figure 2 This is a graph showing the relationship between heating power, single crystal growth angle, and single crystal diameter in the conventional shoulder-turning method.
[0019] Figure 3 This is a schematic diagram of the structure of a zone-melting silicon single crystal obtained using the shoulder-turning method of the present invention.
[0020] Figure 4 This is a graph showing the relationship between heating power, single crystal growth angle, and single crystal diameter in the shoulder-turning method of the present invention. Detailed Implementation
[0021] The present invention will be further described below with reference to the embodiments and accompanying drawings, but this does not imply any limitation on the scope of protection of the present invention.
[0022] The segmented shoulder-forming method for zone-melting silicon single crystals provided by this invention includes the following steps:
[0023] (1) Set the segmented shoulder diameter position; (2) Set the single crystal heating power curve parameters and growth angle before and after the shoulder diameter respectively, and calculate the polycrystalline speed according to the set single crystal growth angle; (3) Perform single crystal growth according to the set parameters.
[0024] In step (1), a shoulder diameter value needs to be set, which is generally less than the target diameter of the single crystal by 5 mm. For example, when pulling a 6-inch single crystal, the target diameter is generally 155 mm, and the shoulder diameter is set to 150 mm. The diameter range of 145-155 mm is considered to be the diameter range of the shoulder turning process in the segmented shoulder turning method of the present invention.
[0025] In step (2), before the single crystal diameter reaches the shoulder diameter, the following condition is met: heating power W = aD before the shoulder diameter. 3 +bD 2 The formula is: +cD+d, where a, b, d, and c are constants calculated using MATLAB fitting, and D is the diameter of the single crystal. The heating power of the single crystal increases with the increase of the single crystal diameter; the faster the single crystal diameter increases, the faster the heating power increases, and vice versa.
[0026] After the single crystal diameter exceeds the shoulder diameter, the following condition is satisfied: Heating power W = a'X after the shoulder diameter. 3 +b'X 2 The formula is: +c'X+d', where a', b', c', and d' are constants, calculated using MATLAB fitting, and X is the single crystal length. The single crystal heating power is no longer positively correlated with the single crystal diameter, but rather with the single crystal growth length. During this process, the single crystal heating power does not fluctuate due to the rapid decrease in the single crystal growth angle. After the single crystal diameter reaches the target diameter, it will also slowly increase with the increase of the single crystal growth length, improving the stability of the single crystal shoulder.
[0027] In step (2), the closer the single crystal diameter is to the target single crystal diameter, the smaller the single crystal growth angle. When the single crystal diameter approaches the target diameter, the single crystal growth angle will first decrease, then increase, and then gradually decrease again. When the single crystal diameter reaches the target diameter, the single crystal growth angle decreases to 0. This angle change pattern is key to reducing the fluctuation of the shoulder diameter.
[0028] The variation law of the single crystal growth angle in the segmented shoulder turning method used in this invention is as follows: after the single crystal reaches the shoulder diameter and approaches the target diameter, the single crystal growth angle will decrease by 2-5°. Figure 4 As shown, the growth angle is reduced at a rate of 1-4° / mm to weaken growth inertia. Then, the growth angle is slowly increased by 1-3° at a rate of 0.5-2° / mm to counteract the shrinkage inertia of the single crystal diameter. Subsequently, the growth angle is slowly reduced from 0-3° to zero at a rate of 0.5-3° / mm, reducing single crystal diameter fluctuations without affecting the stable increase of heating power. The reason for reducing the diameter variation is that the angle change reduces the single crystal growth inertia. Using this method, single crystal diameter fluctuations can be controlled within 1mm.
[0029] Comparative Example
[0030] Taking the pulling of 6-inch zone melting single crystals as an example, the shoulder turning process using the conventional shoulder turning method is explained. The shoulder turning process does not require setting the shoulder diameter, and the growth is carried out according to the parameters set in Table 1.
[0031] Table 1
[0032] Diameter range (mm) Growth angle (degrees) Single crystal pulling speed (mm / min) 145-147 6.5 2.6 147-149 5.5 2.6 149-151 4.5 2.6 151-152 3.5 2.6 152-152.5 3 2.6 152.5-153 2.5 2.6 153-153.5 2 2.6 153.5-154 1.5 2.6 154-154.5 1 2.6 154.5-155 0.5 2.6 》155 0
[0033] like Figure 1 As shown, when the shoulder diameter reaches 155 mm using the conventional shoulder-turning method, due to the inertia of single crystal growth, the single crystal diameter will continue to slowly increase to about 157 mm when the growth angle is 0 mm. Then it will start to slowly decrease, and can be reduced to 154 mm or even less. Then it will grow alternately around 155 mm in diameter until it stabilizes at 155 mm. During this process, due to the fluctuation of single crystal diameter, about 20% of single crystal growth will fail, which is a shortcoming of the conventional shoulder-turning method.
[0034] like Figure 2 As shown, the increase in single-crystal heating power gradually decreases with the decrease in the single-crystal growth angle. When the single-crystal diameter reaches 155mm, the single-crystal growth angle decreases to 0, the polycrystalline speed reaches its maximum value and no longer increases, and the heating power also reaches the set value and no longer increases. Because the angle change during the shoulder-turning process is slow, another significant drawback of using the conventional shoulder-turning method is that the single-crystal shoulder length will be longer (e.g., ...). Figure 1 As shown in Table 2, the probability of crystal growth failure is relatively high, and the yield of single crystals will also be somewhat lost. For specific data, please refer to Table 2.
[0035] Table 2
[0036] Serial Number Shoulder length Diameter fluctuation range length Crystal pulling results 1 75 140 success 2 75 / fail 3 75 140 success 4 75 140 success 5 75 140 success 6 75 / fail 7 75 / fail 8 75 140 success
[0037] Example
[0038] Taking the pulling of a 6-inch zone-melted single crystal as an example, the shoulder-turning process using the method of this invention is explained. The shoulder-turning process requires setting the shoulder diameter to 150mm. For single crystal diameters less than 150mm, the single crystal heating power is calculated according to the formula W = -0.00001937D. 3 +0.00524921D 2 Given -0.10891882D+45, as the single crystal growth angle gradually decreases, the increase in single crystal diameter D gradually slows down, and the increase in single crystal heating power also gradually decreases; after the single crystal diameter exceeds 150mm, the single crystal heating power is calculated according to the formula W=0.00000051X 3 -0.0002777X 2 Given +0.05065X+65, the single-crystal heating power does not increase with the diameter, but rather with the increase of the single-crystal length. The relationship between the single-crystal heating power, growth angle, and single-crystal diameter throughout the entire process is shown in the figure below. Figure 4 As shown, after the single crystal diameter reaches 155 mm, the single crystal growth angle decreases to 0, and the single crystal heating power continues to increase slowly until the single crystal diameter stabilizes at 155 mm, at which point the single crystal heating power no longer increases.
[0039] The specific relationship between the shoulder diameter and angle during the shoulder turning process is shown in Table 3. After the shoulder diameter reaches 150mm, the single crystal growth angle is rapidly reduced from 4.5° to 1° to reduce the single crystal growth inertia. Subsequently, the growth angle is increased from 1° to 3° to ensure that the single crystal diameter does not fluctuate due to polycrystalline speed deviation when it increases to 155mm. The single crystal diameter fluctuation can be controlled within 1mm (e.g., ...). Figure 3 (As shown). During this process, the heating power of the single crystal is related to the growth length of the single crystal and will not fluctuate due to the rapid decrease in the growth angle of the single crystal. After the single crystal reaches the target diameter, it will also slowly increase by a certain amount as the growth length of the single crystal increases, thereby improving the stability of the single crystal shoulder.
[0040] Table 3
[0041] Diameter range (mm) Growth angle (degrees) Single crystal pulling speed (mm / min) 145-147 6.5 2.6 147-149 5.5 2.6 149-151 4.5 2.6 151-152 2.5 2.6 152-152.5 1.5 2.6 152.5-153 1 2.6 153-153.5 1.5 2.6 153.5-154 2 2.6 154-153.5 2.5 2.6 153.5-154 3 2.6 154-154.5 2 2.6 154.5-155 0.5 2.6 》155 0 2.6
[0042] The segmented shoulder design has significantly shorter length and diameter fluctuation range than the conventional shoulder design. Specific measurement data are shown in Table 4.
[0043] Table 4
[0044] Serial Number Shoulder length Diameter fluctuation range length Crystal pulling results 1 55 33 success 2 55 33 success 3 55 33 success 4 55 33 success 5 55 33 success 6 55 33 success 7 55 33 success 8 55 33 success
Claims
1. A segmented shoulder-forming method for zone-melting silicon single crystals, characterized in that, Includes the following steps: (1) Set the position of the segmented shoulder diameter, and the set value should be 5mm smaller than the target value; (2) Set the single crystal heating power curve parameters and growth angle before and after the shoulder diameter; before the single crystal diameter reaches the shoulder diameter, the single crystal heating power increases with the increase of the single crystal diameter. The faster the single crystal diameter increases, the faster the single crystal heating power increases, and vice versa; heating power W=aD 3 +bD 2 +cD+d, where a, b, d, and c are constants, calculated using MATLAB fitting, and D is the diameter of the single crystal; Once the single crystal diameter exceeds the shoulder diameter, the single crystal heating power is no longer positively correlated with the single crystal diameter, but rather with the single crystal growth length; heating power W = a'X 3 +b'X 2 +c'X+d', where a', b', c', and d' are constants, calculated using MATLAB fitting, and X is the single crystal length; When the diameter of a single crystal approaches the target diameter, the growth angle of the single crystal will first decrease, then increase, and then gradually decrease; when the diameter of the single crystal reaches the target diameter, the growth angle of the single crystal decreases to 0. The specific process of the single crystal growth angle first decreasing and then increasing, and then gradually decreasing is as follows: first, a decrease process with an amplitude of 2-5° and a speed of 1-4° / mm; then an increase process with an amplitude of 1-3° and a speed of 0.5-2° / mm; and then a decrease process with an amplitude of 0-3° and a speed of 0.5-3° / mm. (3) Single crystal growth is carried out according to the set heating power parameters and growth angle.
2. The segmented shoulder-forming method for zone-melting silicon single crystals according to claim 1, characterized in that, In step (2), the single crystal diameter fluctuation is controlled within 1 mm.