Drawing method for adapting large-size single crystal to small-size single crystal in thermal field

Abstract

The invention discloses a drawing method for adapting a large-size thermal field to a small-size single crystal, which comprises the following steps of: S1, transforming a large-size inner guide cylinder support ring to enable the inner diameter of the bottom end of the large-size inner guide cylinder support ring to be adaptive to the top end of a small-size CCD (Charge Coupled Device) ring; s2, performing single crystal growth according to the stages of welding, seeding, shouldering, rotating shoulder, equal diameter and ending in sequence; wherein in the shouldering stage, the furnace pressure is linearly reduced to 1.0 kPa from 1.3 kPa, and diameter control parameters and step-by-step power reduction are synchronously executed; the constant furnace pressure in the equal-diameter stage is 0.8 kPa, and the liquid opening distance, the crucible rotation and the pulling speed power are dynamically regulated and controlled. The preparation of small-size single crystals under the condition of a large-size thermal field is realized, the large-size thermal field does not need to be replaced, and the processing cost is reduced.

Description

Technical Field

[0001] The present application relates to the technical field of Czochralski crystal pulling, and in particular to a method for pulling a small-sized single crystal with a large-sized thermal field adapted to the crystal. Background Art

[0002] In the process of pulling single crystals, water-cooling screens of different sizes are required to pull crystal rods of different sizes. Using one size of water-cooling screen to pull crystal rods of various specifications and sizes can effectively reduce the procurement cost of the water-cooling screen and save the labor time for replacing the water-cooling screen.

[0003] Currently, in the actual crystal pulling process, there is a demand for pulling small-sized crystal rods (i.e., 11-inch single crystals), but the factory does not yet have small-sized water-cooling screens or there are not enough small-sized water-cooling screens. Purchasing matching small-sized water-cooling screens takes a long time, which delays the construction schedule. At the same time, since the demand for small-sized pulling is relatively low, purchasing matching water-cooling screens will also increase costs.

[0004] In view of this, a pulling method of adapting a large-size thermal field to a small-size single crystal is proposed. The bottom end structure of the existing large-size outer guide tube support ring is adapted to the small-size CCD ring to meet the pulling requirements of small-size single crystals. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for pulling small-sized single crystals with a large-sized thermal field adapted to the needs of the existing large-sized external guide tube support ring, so as to adapt it to the small-sized CCD ring to meet the needs of pulling small-sized single crystals and solve the above-mentioned problems existing in the prior art.

[0006] In order to solve the above technical problems, the present invention adopts the following solutions: A method for pulling a large-size thermal field-adapted small-size single crystal comprises the following steps: S1, modify the large-sized inner guide tube support ring so that its bottom inner diameter fits the top of the small-sized CCD ring; S2, performing single crystal growth in the following steps: welding, seeding, shoulder release, shoulder rotation, equal diameter, and finishing; In the shouldering stage, the furnace pressure is linearly reduced from 1.3kPa to 1.0kPa, and the diameter control parameters and step-by-step power reduction are executed synchronously; The furnace pressure in the constant diameter stage is constant at 0.8kPa, and the liquid nozzle distance, crucible rotation and casting speed power are dynamically controlled.

[0007] Furthermore, the inner ring surface of the bottom end of the large-sized inner guide tube support ring is provided with a step structure adapted to the top end of the small-sized CCD ring; The step structure includes a first step surface and a second step surface respectively engaged with the small-size CCD ring, and an assembly gap is ≤0.3 mm.

[0008] Furthermore, during the welding stage, the furnace pressure was 1.3 kPa, the argon flow rate was 100 sL / min, the crystal rotation was 8 rp / min reverse, the crucible rotation was 5 rp / min forward, and the liquid port distance was 30.5-31.5 mm; During the seeding stage, the seeding parameters are consistent with the welding parameters. When the seeding length is 230mm~270mm, the power is reduced by 0.5kW.

[0009] Furthermore, the diameter control parameters in the shoulder release stage include: for every 10mm increase in shoulder release height, the target diameter increase is ≥10mm; The diameter growth rate threshold was set as follows: when the shoulder diameter was ≤15 mm, the growth rate was ≤2 mm / min; When the shoulder diameter is ≥15mm, the growth rate is 2mm / min~4mm / min.

[0010] Furthermore, the power change in the shoulder release phase satisfies: When the shoulder height is 1mm~85mm, the power decreases linearly by 0.5kW~0.9kW; When the shoulder height is 85mm~180mm, the power decreases linearly by 0.8kW~2.0kW.

[0011] Furthermore, when the shoulder diameter is 260mm~270mm, the shoulder rotation stage is started, the argon flow rate is 100 sL / min, and after 1 minute of shoulder rotation, the furnace pressure drops to 0.8 kPa, the crystal rotation is reversed at 8 rp / min, and the crucible rotation is forward at 4.5 rp / min.

[0012] Furthermore, the liquid port distance in the equal diameter stage changes as follows: The equal diameter length is 1mm, and the target liquid port distance is 33mm; The equal diameter length is 100mm and the target liquid port distance is 31mm; The equal diameter length is 100 mm to 700 mm, and the target liquid port distance is 21 mm to 31 mm. When the equal diameter length is greater than 700 mm, the target liquid port distance is constant at 21 mm.

[0013] Furthermore, the target liquid mouth distance controls the real-time liquid mouth distance by adjusting the crucible lifting speed, so that the actual liquid mouth distance value matches the target liquid mouth distance value.

[0014] Furthermore, the crucible rotation in the isodiameter stage is changed to: The equal diameter length is 1 mm: the crucible rotates at 4.5 rp / min; The constant diameter length is 200 mm: the crucible is raised to 5 rp / min; The constant diameter length is 400 mm: the crucible is raised to 5.5 rp / min; The constant diameter length is 600 mm: the crucible is raised to 6 rp / min and kept constant.

[0015] Furthermore, the relationship between the casting speed and power in the constant diameter stage is: When the constant diameter length is 0~800mm, the pulling speed is ≤1.48mm / min, and the power decreases linearly by 0.3kW; When the equal diameter length is 800mm~3200mm, the pulling speed is 1.48mm / min~1.55mm / min, and the power increases linearly by 0.2kW~0.6kW.

[0016] The beneficial effects of the present invention are as follows: the present invention is a method for pulling a small-sized single crystal adapted to a large-sized thermal field, by modifying the inner ring surface at the bottom end of the inner guide tube support ring in the large-sized thermal field to add a step structure, which is adapted to the small-sized CCD ring, forcing the effective flow cross-sectional area of ​​the thermal field to be reduced, suppressing argon turbulence, eliminating the eddy current zone of traditional plane docking, and improving the uniformity of the argon flow rate; at the same time, the shoulder height is 170mm~180mm, the furnace pressure linearly changes from 1.3kPa to 1.0kPa, and then to 0.8kPa in the equal-diameter stage, and the crucible speed is reduced from 5 rp / min in the welding stage, the seeding stage and the shoulder stage to 4.5 rp / min in the equal-diameter stage, thereby reducing the oxygen content in the single crystal; increasing the constant argon flow rate, reducing the pulling speed in the equal-diameter stage, reducing the temperature gradient, facilitating crystal formation, reducing the break rate, and eliminating the need to replace the large-sized thermal field, thereby reducing processing costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the thermal field assembly structure after modification in the present invention; Figure 2 for Figure 1 Schematic diagram of a local enlarged structure; Figure 3 This is a bar graph showing the wire breakage rate when using this method for crystal pulling. DETAILED DESCRIPTION

[0018] To make the purpose, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the described embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0019] Unless otherwise specifically stated, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0020] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0021] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0022] Technologies, methods, and apparatus known to ordinary technicians in the relevant field may not be discussed in detail, but where appropriate, such technologies, methods, and apparatus should be considered part of the authorization specification.

[0023] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0024] Example 1 This embodiment 1 illustrates the assembly structure of a large-sized inner guide tube support ring and a small-sized CCD ring. Specifically, the inner ring surface at the bottom end of the large-sized inner guide tube support ring is provided with a step structure adapted to the top end of the small-sized CCD ring. The step structure includes a first step surface and a second step surface respectively engaged with the small-size CCD ring, and an assembly gap is ≤0.3 mm.

[0025] Reference Figure 1 and Figure 2 By adding a step structure to the inner ring surface at the bottom end of the large-size inner guide tube support ring, a mechanical positioning reference is provided for the top of the small-size CCD ring, forcing the reduction of the effective flow cross-sectional area of ​​the thermal field, suppressing argon turbulence, eliminating the eddy current zone of traditional plane docking, and improving the uniformity of the argon flow rate. This solves the problems of large flow field disturbance, low crystallization rate and high wire breakage rate when pulling small-size single crystals in a large thermal field.

[0026] Example 2 A method for pulling a large-size thermal field-adapted small-size single crystal comprises the following steps: S1, modify the large-sized inner guide tube support ring so that its bottom inner diameter fits the top of the small-sized CCD ring; The inner ring surface at the bottom end of the large-sized inner guide tube support ring is provided with a step structure adapted to the top end of the small-sized CCD ring; The step structure includes a first step surface and a second step surface respectively engaged with the small-size CCD ring, and an assembly gap is ≤0.3 mm.

[0027] S2, performing single crystal growth in the following steps: welding, seeding, shoulder release, shoulder rotation, equal diameter, and finishing; (1) During the welding stage, the furnace pressure was 1.3 kPa, the argon flow rate was 100 sL / min, the crystal rotation speed was 8 rp / min reverse, the crucible rotation speed was 5 rp / min forward, and the liquid port distance was 30.5-31.5 mm. (2) During the seeding stage, the seeding parameters are kept consistent with the welding parameters. When the seeding length is 230mm~270mm, the power is reduced by 0.5kW.

[0028] (3) During the shouldering stage, the furnace pressure is linearly reduced from 1.3kPa to 1.0kPa, and the diameter control parameters and step-by-step power reduction are executed simultaneously. This method adjusts the process of the shouldering stage in order to improve the survival rate of the shouldering; the main parameters are shown in Table 1 below: Table 1 Parameter settings for the shoulder release phase Table 1 shows that the diameter control parameters during the shouldering stage include: for every 10mm increase in shoulder height, the target diameter increases by ≥10mm; and for a shoulder height ≥170mm, the target diameter remains constant at 280mm. The shouldering height and shouldering diameter correspond to each other. The single crystal furnace platform detects the current crystal diameter via a camera, and the control system within the platform automatically adjusts the diameter growth rate based on this current crystal diameter. The diameter growth rate threshold is set as follows: when the shoulder diameter is ≤15mm, the growth rate is ≤2mm / min. When the shoulder diameter reaches 280mm, the growth rate is 4mm / min. When adjusting the growth rate, the shouldering height and shouldering diameter must correspond to each other. For example, if the shoulder height is 10mm, the shoulder diameter must be 15mm. If the shoulder diameter is detected to be less than 15mm, the system automatically reduces the lifting rate, slowing vertical growth and accelerating horizontal growth.

[0029] The crucible lifting speed (pot lifting speed) corresponds to the shoulder diameter. For example, when the diameter is 200mm, the crucible upward lifting speed is 0.048mm / min.

[0030] The shoulder height corresponds to the power change in Table 1. The power change in the shoulder stage satisfies the following conditions: when the shoulder height is 1 mm to 85 mm, the power decreases linearly by 0.5 kW to 0.9 kW; when the shoulder height is 85 mm to 180 mm, the power decreases linearly by 0.8 kW to 2.0 kW.

[0031] It should be noted that the camera in the single crystal furnace to detect the diameter and the control system to regulate the growth rate, pot lifting speed and power changes are conventional operating methods in this field and are not listed here one by one.

[0032] (5) Shoulder rotation stage: When the shoulder diameter is 260mm~270mm, the shoulder rotation stage is started, the argon flow rate is 100 sL / min, and after 1 minute of shoulder rotation, the furnace pressure drops to 0.8 kPa, the crystal rotates at 8 rp / min in reverse and the crucible rotates at 4.5 rp / min in forward direction.

[0033] (6) The furnace pressure in the constant diameter stage is constant at 0.8 kPa, and the liquid nozzle distance, crucible rotation and casting speed power are dynamically controlled. The specific control parameters are shown in Table 2.

[0034] Table 2 Parameter settings for the equal diameter stage The target liquid-inlet distance is controlled by the crucible lifting speed to control the real-time liquid-inlet distance, so that the actual liquid-inlet distance value matches the target liquid-inlet distance value. In the equal-diameter stage, the liquid-inlet distance is the distance from the lower edge of the guide tube to the silicon liquid surface. Since the silicon liquid surface in the crucible is constantly decreasing during the equal-diameter stage, the relative distance of the liquid-inlet distance needs to be kept constant during the crystal pulling process, so it is necessary to control the pot lifting speed to achieve this. Here, the pot lifting speed is the crystal lifting speed * the pot-to-heel ratio, ensuring that the liquid-inlet distance at this time is within the target liquid-inlet distance, thereby promoting the stable growth of the single crystal. The crucible-to-heel ratio is the real-time ratio of the crystal equal-diameter length growth to the synchronous lifting amount of the crucible. This real-time ratio is used to determine the specific pot lifting speed, which is not listed here one by one.

[0035] The change of the liquid mouth distance in the equal diameter stage is: The equal diameter length is 1mm, and the target liquid port distance is 33mm; The equal diameter length is 100mm and the target liquid port distance is 31mm; The equal diameter length is 100mm~700mm, the target liquid port distance is 21mm~31mm, and when the equal diameter length is greater than 700mm, the target liquid port distance is constant at 21mm, and the target liquid port distance is maintained unchanged.

[0036] In the early stage of the isodiameter stage, the single crystal just begins to grow and needs to be slow to prevent dislocations. The temperature gradient should be small, so the target liquid nozzle distance should be larger. In the late stage of the isodiameter stage, a higher single crystal growth rate is required. The temperature gradient should be larger, so a small target liquid nozzle distance should be set.

[0037] The crucible rotation in the isodiameter stage is: The equal diameter length is 1 mm: the crucible rotates at 4.5 rp / min; The constant diameter length is 200 mm: the crucible is raised to 5 rp / min; The constant diameter length is 400 mm: the crucible is raised to 5.5 rp / min; The constant diameter length is 600 mm: the crucible is raised to 6 rp / min and kept constant.

[0038] The relationship between the casting speed and power in the constant diameter stage is: When the constant diameter length is 0~800mm, the pulling speed is ≤1.48mm / min, and the power decreases linearly by 0.3kW; When the equal diameter length is 800mm~3200mm, the pulling speed is 1.48mm / min~1.55mm / min, and the power increases linearly by 0.2kW~0.6kW.

[0039] (7) Closing stage: Same as the conventional closing method.

[0040] It should be noted that the commonly used furnace pressure is a constant 1.5kPa or 1.3kPa, with a crucible speed of 6 rp / min. This method takes into account that when pulling small single crystals using a large water-cooled plate, the argon flow rate is slower due to the plate's distance from the outer diameter of the ingot, resulting in a higher oxygen content than when pulling small ingots using a conventional small water-cooled plate. Therefore, the initial furnace pressure is 1.3kPa (during the welding, seeding, and initial shouldering stages), increasing to 1.0kPa (with the shouldering height at 170mm-180mm, the furnace pressure changes linearly from 1.3kPa to 1.0kPa), and then to 0.8kPa during the equalizing stage. The crucible speed is reduced from 5 rp / min during the welding, seeding, and shouldering stages to 4.5 rp / min during the equalizing stage.

[0041] The argon flow rate is currently 80 sL / min. To improve the crystallization rate, this method uses a constant argon flow rate of 100 sL / min. The cooling rate during the shoulder release phase increases to 13.1 kW due to thermal gradient changes. The pulling speed during the constant diameter phase is also set approximately 0.1 mm / min lower than usual. This reduces the temperature gradient and facilitates crystallization by lowering the pulling speed.

[0042] By adopting this method, the inner ring surface at the bottom end of the 12-inch inner guide tube support ring is provided with a step structure adapted to the top end of the 11-inch CCD ring. The step structure includes a first step surface and a second step surface, and the assembly gap is ≤0.3mm. After the modification, an 11-inch single crystal is pulled using a 12-inch water-cooled screen. After verification by 126 single crystal furnaces, the pulling time is 30 days, of which the single crystal yield is 179kg / day, the crystallization rate is 85.49%, and the head oxygen content is 9.31ppma; the single crystal breakage situation is: the total breakage rate is 34%, the breakage rate is 8%, the breakage rate of the equal diameter length of 0~500mm is 7%, and the breakage rate of the equal diameter greater than 500mm is 19%. Figure 3 shown.

[0043] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Although the present invention has been disclosed as a preferred embodiment as above, it is not intended to limit the present invention. Any technician familiar with the present profession can make some changes or modifications to equivalent embodiments of the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for pulling a large-size thermal field-adapted small-size single crystal, characterized in that: The following steps are involved: S1, modify the large-sized inner guide tube support ring so that its bottom inner diameter fits the top of the small-sized CCD ring; S2, performing single crystal growth in the following steps: welding, seeding, shoulder release, shoulder rotation, equal diameter, and finishing; In the shouldering stage, the furnace pressure is linearly reduced from 1.3kPa to 1.0kPa, and the diameter control parameters and step-by-step power reduction are executed synchronously; The furnace pressure in the constant diameter stage is constant at 0.8kPa, and the liquid nozzle distance, crucible rotation and casting speed power are dynamically controlled.

2. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: The inner ring surface at the bottom end of the large-sized inner guide tube support ring is provided with a step structure adapted to the top end of the small-sized CCD ring; The step structure includes a first step surface and a second step surface respectively engaged with the small-size CCD ring, and an assembly gap is ≤0.3 mm.

3. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: During the welding stage, the furnace pressure was 1.3 kPa, the argon flow rate was 100 sL / min, the crystal rotation speed was 8 rp / min reverse, the crucible rotation speed was 5 rp / min forward, and the liquid port distance was 30.5-31.5 mm. During the seeding stage, the seeding parameters are consistent with the welding parameters. When the seeding length is 230mm~270mm, the power is reduced by 0.5kW.

4. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: The diameter control parameters in the shoulder release stage include: for every 10mm increase in shoulder release height, the target diameter increase is ≥10mm; The diameter growth rate threshold was set as follows: when the shoulder diameter was ≤15 mm, the growth rate was ≤2 mm / min; When the shoulder diameter is ≥15mm, the growth rate is 2mm / min~4mm / min.

5. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: The power change in the shoulder release phase satisfies: When the shoulder height is 1mm~85mm, the power decreases linearly by 0.5kW~0.9kW; When the shoulder height is 85mm~180mm, the power decreases linearly by 0.8kW~2.0kW.

6. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: When the shoulder diameter is 260mm~270mm, the shoulder rotation stage is started, the argon flow rate is 100 sL / min, and after 1 minute of shoulder rotation, the furnace pressure drops to 0.8kPa, the crystal rotates in the reverse direction at 8 rp / min, and the crucible rotates in the forward direction at 4.5 rp / min.

7. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 1, characterized in that: The change of the liquid mouth distance in the equal diameter stage is: The equal diameter length is 1mm, and the target liquid port distance is 33mm; The equal diameter length is 100mm and the target liquid port distance is 31mm; The equal diameter length is 100 mm to 700 mm, and the target liquid port distance is 21 mm to 31 mm. When the equal diameter length is greater than 700 mm, the target liquid port distance is constant at 21 mm.

8. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 6, characterized in that: The target liquid port distance controls the real-time liquid port distance by adjusting the crucible lifting speed, so that the actual liquid port distance value matches the target liquid port distance value.

9. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 6, characterized in that: The crucible rotation in the isodiameter stage is: The equal diameter length is 1 mm: the crucible rotates at 4.5 rp / min; The constant diameter length is 200 mm: the crucible is raised to 5 rp / min; The constant diameter length is 400 mm: the crucible is raised to 5.5 rp / min; The constant diameter length is 600 mm: the crucible is raised to 6 rp / min and kept constant.

10. The method for pulling a large-size thermal field-adapted small-size single crystal according to claim 6, characterized in that: The relationship between the casting speed and power in the constant diameter stage is: When the constant diameter length is 0~800mm, the pulling speed is ≤1.48mm / min, and the power decreases linearly by 0.3kW; When the equal diameter length is 800mm~3200mm, the pulling speed is 1.48mm / min~1.55mm / min, and the power increases linearly by 0.2kW~0.6kW.

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