Single crystal ending process

Abstract

The invention relates to the technical field of monocrystalline silicon production, in particular to a monocrystalline ending process. The single crystal ending process adopts a Czochralski method to draw a single crystal silicon rod to an ending process, and comprises the following steps: S1, controlling crystal rise to be a first lifting speed and crystal to be a first rotating speed; stopping crucible lifting, and controlling the crucible to rotate at a first crucible rotating speed; s2, controlling the crystal lifting speed to be a second lifting speed and the crystal to be a second rotation speed of the crystal; controlling the crucible to rotate at a first crucible rotating speed; s3, crystal lifting is controlled to be at a third lifting speed, and crystal is converted into crystal at a third rotating speed; controlling the crucible to rotate at a first crucible rotating speed; wherein the first lifting speed is smaller than the third lifting speed, and the second lifting speed is smaller than the first lifting speed; the first crystal rotation speed is greater than the second crystal rotation speed which is greater than the third crystal rotation speed. By optimizing the ending process parameters, the ending shape can be obviously optimized, and the ending survival rate is greatly improved.

Description

Technical Field

[0001] The invention relates to the technical field of single crystal silicon production, and in particular to a single crystal finishing process. Background Art

[0002] When there is not much molten silicon left in the crucible, the single crystal begins to tail, that is, the diameter gradually shrinks. The tail of the single crystal has a great impact on the yield rate of the single crystal. A good tail can greatly improve the yield rate of the single crystal. When the single crystal is pulled out, due to the effect of thermal stress, a large number of dislocations will be generated at the tail, and extend upward along the single crystal. The length of the extension is approximately equal to the diameter of the single crystal tail (see the traditional tail shape). Figure 1 ). The larger the diameter of the tail of the single crystal, the longer the dislocation extends upward, and the lower the yield of the single crystal. Therefore, the diameter of the tail of the single crystal should be minimized.

[0003] The success of tail closing is mainly reflected in several aspects: First, no dislocations should occur, and no broken edges should appear within the length of the tail to prevent dislocations from extending to the equal diameter part; second, the closing time should be short, and the crystal pulling hours should not be wasted, which would reduce the yield; third, the closing length is relatively short.

[0004] In the prior art, CN 107761163 B discloses a method for rapid finishing of straight-pulled single crystal silicon, which rapidly reduces the diameter while maintaining the growth rate of the single crystal silicon crystal unchanged, and then reduces the crystal growth rate, increases the rotation speed of the crystal and the crucible, and reduces the heating power to reduce the temperature rise trend of the thermal field to avoid the breakage of the crystal tail, and finally rapidly increases the crystal pulling speed to complete the finishing, thereby greatly shortening the finishing time and greatly increasing the yield; however, the finishing length is relatively short, about 80-100mm, and there is a risk that dislocations cannot be eliminated and dislocation backcuts are increased.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] The object of the present invention is to provide a single crystal finishing process, which optimizes the finishing shape and improves the finishing survival rate by optimizing the finishing process parameters.

[0007] The present invention first provides a single crystal finishing process, which uses the Czochralski method to pull a single crystal silicon rod to a finishing process, and the finishing process includes the following steps: S1: Early stage of the end: control the crystal lifting to the first pulling speed and the crystal rotation to the first crystal rotation speed; stop the crucible lifting and control the crucible to the first crucible rotation speed; S2: Mid-term of the final stage: Control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; S3: Late stage of finishing: control the crystal lifting to the third pulling speed, the crystal rotation to the third crystal rotation speed; control the crucible to the first crucible rotation speed; Wherein, the first pulling speed is less than the third pulling speed, and the second pulling speed is less than the first pulling speed; The first rotation speed of the crystal is greater than the second rotation speed of the crystal, and the second rotation speed of the crystal is greater than the third rotation speed of the crystal.

[0008] According to the single crystal finishing process provided by the present invention, the first pulling speed is 5-9 mm / h higher than the pulling speed when the equal diameter enters the finishing; and / or, the second pulling speed is 4-8 mm / h lower than the pulling speed when the equal diameter enters the end; And / or, the third pulling speed is 30-40 mm / h higher than the first pulling speed.

[0009] According to the single crystal finishing process provided by the present invention, the first rotation speed of the crystal is 8.5-9 revolutions per minute.

[0010] According to the single crystal finishing process provided by the present invention, the first rotation speed of the crucible is 4 to 7 revolutions per minute.

[0011] According to the single crystal finishing process provided by the present invention, from the beginning of finishing to the end of finishing, the first rotation speed of the crucible is controlled to remain constant.

[0012] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the power compensation value is slowly increased to 7-10 kilowatts; and / or, in the middle of the closing phase, slowly increasing the power compensation value to 14-18 kilowatts; And / or, in the later stage of the finishing, the power compensation value is rapidly increased to 32-40 kilowatts.

[0013] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the increase rate of the power compensation value is 5-8 kilowatts / hour; and / or, in the middle of the closing period, the rate of increase of the power compensation value is 10-21 kilowatts / hour; And / or, in the later stage of the closing, the rate of increase of the power compensation value is 24-32 kilowatts per hour.

[0014] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the finishing length is 20 to 40 mm; and / or, in the mid-term of the tailing, the tailing length is 40 to 60 mm; And / or, in the later stage of finishing, the finishing length is 60 to 90 mm.

[0015] According to the single crystal finishing process provided by the present invention, the finishing process comprises the following steps: S1: Early stage of the finalization: control the crystal lifting to the first pulling speed, and the crystal rotation to the first crystal rotation speed; stop the crucible lifting, and control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 7-10 kW at 5-8 kW / h; the first pulling speed is 107-111 mm / h; the first crystal rotation speed is 7-8 rpm; S2: mid-term of the final stage: control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 14-18 kW at 10-21 kW / h; the second pulling speed is 100-104 mm / h; the second crystal rotation speed is 5.5-7 rpm; S3: Late finishing stage: control the crystal lifting to the third pulling speed, and the crystal rotation to the third rotation speed of the crystal; control the crucible to the first rotation speed of the crucible; quickly increase the power compensation value to 32~40 kW at 24~32 kW / h; the third pulling speed is 104~151 mm / h; the third rotation speed of the crystal is 5~6.5 rpm.

[0016] According to the single crystal finishing process provided by the present invention, the finishing time is 1.5 to 2 hours.

[0017] The present invention further provides a device for implementing the single crystal finishing process.

[0018] Based on the above technical solution, the beneficial effects of the present invention are: The present invention can significantly optimize the finishing shape and greatly improve the finishing survival rate by optimizing the finishing process parameters. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is a schematic diagram of the shape of the single crystal silicon rod finishing in the traditional finishing process mentioned in the background technology; Figure 2 Schematic diagram of the finishing shape of a single crystal silicon rod obtained by the finishing process described in Example 1 of the present invention; Figure 3 This is a physical picture of the finishing shape of a single crystal silicon rod obtained by the finishing process described in Example 1 of the present invention; Figure 4 This is a physical picture of the finishing shape of the single crystal silicon rod obtained by the finishing process described in Comparative Example 4 of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with the drawings 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 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.

[0022] The present invention first provides a single crystal finishing process, which uses the Czochralski method to pull a single crystal silicon rod to a finishing process, and the finishing process includes the following steps: S1: Early stage of the end: control the crystal lifting to the first pulling speed and the crystal rotation to the first crystal rotation speed; stop the crucible lifting and control the crucible to the first crucible rotation speed; S2: Mid-term of the final stage: Control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; S3: Late stage of finishing: control the crystal lifting to the third pulling speed, the crystal rotation to the third crystal rotation speed; control the crucible to the first crucible rotation speed; Wherein, the first pulling speed is less than the third pulling speed, and the second pulling speed is less than the first pulling speed; The first rotation speed of the crystal is greater than the second rotation speed of the crystal, and the second rotation speed of the crystal is greater than the third rotation speed of the crystal.

[0023] In the present invention, the crystal rise and crystal rotation are divided into the above three steps for optimization and adjustment, which can optimize the tail shape and improve the tail survival rate; at the same time, by stopping the crucible rise and the crucible rotation and lowering it in one step, the forced convection can be reduced and the liquid surface temperature can be increased.

[0024] Specifically, in the early stage of finishing, by controlling the pulling speed, the reduction of the crystal diameter can be accelerated; stopping the rise of the crucible to maintain the current melt volume and temperature; controlling the crucible speed to reduce thermal convection helps control the crystal diameter. In the middle stage of finishing, reduce the pulling speed to slow down the rate of crystal diameter reduction; the crucible speed is maintained unchanged to maintain a certain amount of thermal convection, but not to increase the crystal diameter too quickly. In the late stage of finishing, further increase the pulling speed to achieve faster diameter reduction; keep the crucible speed unchanged to maintain the necessary thermal convection conditions. At the same time, in different finishing stages, adjusting the above-mentioned crystal speed helps to achieve the desired crystal diameter reduction rate and the final crystal shape.

[0025] In the present invention, crystal rise refers to the speed of crystal lifting, that is, the speed at which the crystal is pulled out of the crucible. Crucible lifting refers to the speed at which the crucible is lifted. The volume of the melt and the height of the liquid level can be controlled by adjusting the position of the crucible. Crucible rotation refers to the rotation of the crucible (container containing molten silicon), and crystal rotation refers to the rotation of the growing single crystal silicon crystal itself.

[0026] According to the single crystal finishing process provided by the present invention, the first pulling speed is 5-9 mm / h higher than the pulling speed when the equal diameter enters the finishing; and / or, the second pulling speed is 4-8 mm / h lower than the pulling speed when the equal diameter enters the end; And / or, the third pulling speed is 30-40 mm / h higher than the first pulling speed.

[0027] According to the single crystal finishing process provided by the present invention, the first rotation speed of the crystal is 8.5-9 revolutions per minute.

[0028] According to the single crystal finishing process provided by the present invention, the first rotation speed of the crucible is 4 to 7 revolutions per minute.

[0029] According to the single crystal finishing process provided by the present invention, from the beginning of finishing to the end of finishing, the first rotation speed of the crucible is controlled to remain constant.

[0030] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the power compensation value is slowly increased to 7-10 kilowatts; and / or, in the middle of the closing phase, slowly increasing the power compensation value to 14-18 kilowatts; And / or, in the later stage of the finishing, the power compensation value is rapidly increased to 32-40 kilowatts.

[0031] In the present invention, by controlling the power compensation at different closing periods, the liquid surface temperature can be increased, further promoting the reduction of the diameter.

[0032] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the increase rate of the power compensation value is 5-8 kilowatts / hour; and / or, in the middle of the closing period, the rate of increase of the power compensation value is 10-21 kilowatts / hour; And / or, in the later stage of the closing, the rate of increase of the power compensation value is 24-32 kilowatts per hour.

[0033] In the present invention, the main power is controlled to rise slowly first and then accelerate, and the crystal rise and crystal rotation are coordinated to control the liquid surface temperature, so that the finishing survival rate can be further improved.

[0034] According to the single crystal finishing process provided by the present invention, in the early stage of the finishing, the finishing length is 20 to 40 mm; and / or, in the mid-term of the tailing, the tailing length is 40 to 60 mm; And / or, in the later stage of finishing, the finishing length is 60 to 90 mm.

[0035] According to the single crystal finishing process provided by the present invention, the finishing process comprises the following steps: S1: Early stage of the finalization: control the crystal lifting to the first pulling speed, and the crystal rotation to the first crystal rotation speed; stop the crucible lifting, and control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 7-10 kW at 5-8 kW / h; the first pulling speed is 107-111 mm / h; the first crystal rotation speed is 7-8 rpm; S2: mid-term of the final stage: control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 14-18 kW at 10-21 kW / h; the second pulling speed is 100-104 mm / h; the second crystal rotation speed is 5.5-7 rpm; S3: Late finishing stage: control the crystal lifting to the third pulling speed, and the crystal rotation to the third rotation speed of the crystal; control the crucible to the first rotation speed of the crucible; quickly increase the power compensation value to 32~40 kW at 24~32 kW / h; the third pulling speed is 104~151 mm / h; the third rotation speed of the crystal is 5~6.5 rpm.

[0036] The present invention helps to achieve uniform distribution of temperature and composition in the melt and reduce local accumulation of impurities by rotating the crucible in one step, while also helping to reduce dislocations during crystal growth; at the same time, it also helps to form a stable melt-crystal interface, which is crucial to the growth process of single crystal silicon.

[0037] The present invention can further change the heat exchange conditions between the crystal and the melt through three-step crystal rotation, reduce dislocations caused by thermal stress, and further improve the crystal quality.

[0038] According to the single crystal finishing process provided by the present invention, the finishing time is 1.5 to 2 hours.

[0039] The present invention further provides a device for implementing the single crystal finishing process.

[0040] Unless otherwise specified, all raw materials used in the examples are commercially available conventional raw materials, and the technical means used are conventional means well known to those skilled in the art.

[0041] Example 1 This embodiment provides a single crystal finishing process, which includes the following steps: S1. Rapid finishing: Rapidly increase the pulling speed to 107 mm / h, and the crystal rotation to 8 rpm; slowly increase the power compensation value to 10 kW at 21 kW / h, stop the crucible lifting, and reduce the crucible rotation to 5 rpm in one step, and confirm that the quick finishing length is 40 mm; the whole process takes 25 minutes.

[0042] S2. Slow finishing: reduce the pulling speed to 102 mm / h, and the crystal rotation is 5.5 rpm; slowly increase the power compensation rate to 18 kW at 21 kW / h, and the crucible rotation continues at 5.5 rpm, and confirm that the slow finishing length is 60 mm; the whole process takes 36 minutes.

[0043] S3. Continue to finish quickly: increase the pulling speed to 118 mm / h, and the crystal rotation to 5 rpm; quickly increase the power compensation value to 38 kW at 32 kW / h, and the crucible rotation to 5 rpm, and confirm that the quick finishing length is 70 mm; the whole process takes 36 minutes.

[0044] During the entire finishing process, the finishing parameters are optimized and the finishing shape is changed to quickly reduce the cross-sectional diameter to below 80 mm, with a finished product rate of 90%. See the actual picture of the finishing shape of the single crystal silicon rod for details. Figure 2 , see the actual picture Figure 3 .

[0045] Example 2 This embodiment provides a single crystal finishing process, which includes the following steps: S1. Rapid finishing: Rapidly increase the pulling speed to 107 mm / h, and the crystal rotation to 8 rpm; slowly increase the power compensation value to 10 kW at 8 kW / h, stop the crucible lifting, and reduce the crucible rotation to 5 rpm in one step, and confirm that the quick finishing length is 40 mm; the whole process takes 23 minutes.

[0046] S2. Slow finishing: reduce the pulling speed to 100 mm / h, and the crystal rotation is 7 rpm; slowly increase the power compensation rate to 18 kW at 21 kW / h, and the crucible rotation continues for 5 rpm, and confirm that the slow finishing length is 60 mm; the whole process takes 36 minutes.

[0047] S3. Continue to finish quickly: increase the pulling speed to 104 mm / h, the crystal rotation to 6.5 rpm; quickly increase the power compensation value to 40 kW at 32 kW / h, the crucible rotation to 5 rpm, and confirm the quick finishing length of 90 mm; the whole process takes 50 minutes.

[0048] During the entire finishing process, by optimizing the finishing parameters and changing the finishing shape, the cross-sectional diameter was quickly reduced to 80 mm, and the finished product rate was 88%.

[0049] Example 3 This embodiment provides a single crystal finishing process, which is different from Embodiment 1 only in that the increasing rate of the power compensation value in S1-S3 is the same, which is 21 kilowatts / hour.

[0050] The cross-sectional diameter was quickly reduced to 80 mm, and the yield rate was 87%.

[0051] Comparative Example 1 This embodiment provides a single crystal finishing process, which differs from Embodiment 1 only in that the crucible in S1 rotates at 7 rpm, the crucible in S2 rotates at 6.5 rpm, and the crucible in S3 rotates at 6 rpm.

[0052] The cross-sectional diameter was quickly reduced to 80 mm, and the yield rate was 85%.

[0053] Comparative Example 2 This comparative example provides a single crystal finishing process, which differs from Example 1 only in that the crystal rotation in S1 is 8 rpm, the crystal rotation in S2 is 7 rpm, and the crystal rotation in S3 is 8 rpm.

[0054] The cross-sectional diameter was quickly reduced to 80 mm, and the yield rate was 84%.

[0055] Comparative Example 3 This comparative example provides a single crystal finishing process, which differs from Example 1 only in that: in S1, the crucible rising speed is 8 mm / hour; in S2, the crucible rising speed is 5 mm / hour; in S, the crucible is stopped from rising.

[0056] The cross-sectional diameter was quickly reduced to 80 mm, and the yield rate was 84%.

[0057] Comparative Example 4 This comparative example provides a single crystal finishing process, which includes the following steps: the crucible in S1 is rotated to 7 rpm, the crucible in S2 is rotated to 6.5 rpm, the crucible in S3 is rotated to 6 rpm, the crystal rotation speed is 8 rpm throughout the process, the main power offset is 5-22 kW, and the crystal growth rate is 99 mm / hour.

[0058] The cross-sectional diameter is rapidly reduced to 75 mm, and the yield rate is 80%. See the actual picture of the final shape of the single crystal silicon rod. Figure 4 .

[0059] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A single crystal finishing process, characterized in that: The single crystal silicon rod is pulled by the Czochralski method to the finishing process, and the finishing process includes the following steps: S1: Early stage of the end: control the crystal lifting to the first pulling speed and the crystal rotation to the first crystal rotation speed; stop the crucible lifting and control the crucible to the first crucible rotation speed; S2: Mid-term of the final stage: Control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; S3: Late stage of finishing: control the crystal lifting to the third pulling speed, the crystal rotation to the third crystal rotation speed; control the crucible to the first crucible rotation speed; Wherein, the first pulling speed is less than the third pulling speed, and the second pulling speed is less than the first pulling speed; The first rotation speed of the crystal is greater than the second rotation speed of the crystal, and the second rotation speed of the crystal is greater than the third rotation speed of the crystal.

2. The single crystal finishing process according to claim 1, characterized in that: The first pulling speed is 5-9 mm / h higher than the pulling speed when the equal diameter enters the end; and / or, the second pulling speed is 4-8 mm / h lower than the pulling speed when the equal diameter enters the end; And / or, the third pulling speed is 30-40 mm / h higher than the first pulling speed.

3. The single crystal finishing process according to claim 1, characterized in that: The first rotation speed of the crystal is 8.5-9 rpm.

4. The single crystal finishing process according to any one of claims 1 to 3, characterized in that: The first rotation speed of the crucible is 4-7 rpm.

5. The single crystal finishing process according to any one of claims 1 to 3, characterized in that: From the beginning of the tailing to the end of the tailing, the first rotation speed of the crucible is controlled to remain constant.

6. The single crystal finishing process according to any one of claims 1 to 3, characterized in that: In the early stage of the closing, the power compensation value is slowly increased to 7-10 kilowatts; and / or, in the middle of the closing phase, slowly increasing the power compensation value to 14-18 kilowatts; and / or, in the later stage of the closing, rapidly increasing the power compensation value to 32-40 kilowatts; Preferably, in the early stage of the closing, the rate of increase of the power compensation value is 5-8 kilowatts / hour; and / or, in the middle of the closing period, the rate of increase of the power compensation value is 10-21 kilowatts / hour; And / or, in the later stage of the closing, the rate of increase of the power compensation value is 24-32 kilowatts per hour.

7. The single crystal finishing process according to any one of claims 1 to 3, characterized in that: In the early stage of the tailing, the tailing length is 20 to 40 mm; and / or, in the mid-term of the tailing, the tailing length is 40 to 60 mm; And / or, in the later stage of finishing, the finishing length is 60 to 90 mm.

8. The single crystal finishing process according to any one of claims 1 to 3, characterized in that: The finishing process comprises the following steps: S1: Early stage of the finalization: control the crystal lifting to the first pulling speed, and the crystal rotation to the first crystal rotation speed; stop the crucible lifting, and control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 7-10 kW at 5-8 kW / h; the first pulling speed is 107-111 mm / h; the first crystal rotation speed is 7-8 rpm; S2: mid-term of the final stage: control the crystal lifting to the second pulling speed, the crystal rotation to the second crystal rotation speed; control the crucible to the first crucible rotation speed; slowly increase the power compensation value to 14-18 kW at 10-21 kW / h; the second pulling speed is 100-104 mm / h; the second crystal rotation speed is 5.5-7 rpm; S3: Late finishing stage: control the crystal lifting to the third pulling speed, and the crystal rotation to the third rotation speed of the crystal; control the crucible to the first rotation speed of the crucible; quickly increase the power compensation value to 32~40 kW at 24~32 kW / h; the third pulling speed is 104~151 mm / h; the third rotation speed of the crystal is 5~6.5 rpm.

9. The single crystal finishing process according to claim 8, characterized in that: The finishing time is 1.0~1.2 hours.

10. A device for implementing the single crystal finishing process according to any one of claims 1 to 9.

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