Method for increasing pulling speed of single crystal

Abstract

The invention provides a method for increasing the pulling speed of a single crystal, which comprises the following steps: in the pulling process of the single crystal, keeping the position of a guide cylinder unchanged, setting a distance between the bottom of a water-cooling inner guide and the bottom of the guide cylinder in the working steps of melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation, keeping the distance unchanged, and moving the water-cooling inner guide downwards in the working step of equal diameter, and the bottom of the water-cooling inner guide is contacted with the bottom of the guide cylinder. The device has the beneficial effects that through relative movement of the water-cooling inner sleeve and the guide cylinder, the distance between the water-cooling inner sleeve and a solid-liquid interface is reduced, the temperature gradient of a single crystal growth environment is improved, the single crystal pulling speed is increased, and the yield of the single crystal furnace is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of Czochralski single crystal pulling, and in particular relates to a method for increasing the pulling speed of a single crystal. Background Art

[0002] The thermal field of the Czochralski single crystal is composed of a graphite system, a single crystal furnace cooling system, and an argon system. Usually, the cooling process of the Czochralski single crystal is to introduce cooling gas (usually argon). Since the entire system is in an open state, the introduced argon stays in the single crystal furnace for a short time, and the heat finally taken away is 80%-85% of the total heat. The cooling effect is general and the cooling gas cost is relatively high. The growth rate of the single crystal depends on the temperature gradient of the solid-liquid interface. The larger the temperature gradient, the faster the growth rate. However, if the temperature gradient is too large, it will also cause problems such as dislocations in the crystal growth process.

[0003] In the prior art, the guide tube and the water-cooled inner guide are fixedly assembled. During the single crystal pulling process, the distance between the water-cooled inner guide and the solid-liquid interface is fixed, and the temperature gradient of the single crystal growth environment is relatively stable, which is not conducive to increasing the single crystal pulling speed. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for improving the single crystal pulling speed, which effectively solves the problem that in the prior art, the temperature gradient of the growth environment is relatively stable during the single crystal pulling process, which is not conducive to improving the single crystal pulling speed, and overcomes the shortcomings of the prior art.

[0005] The technical solution adopted by the present invention is: a method for improving the pulling speed of a single crystal, characterized in that: during the single crystal pulling process, the position of the guide tube remains unchanged, and in the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, a distance is provided between the bottom of the water-cooled inner guide and the bottom of the guide tube, and the distance remains unchanged; in the equal diameter step, the water-cooled inner guide moves downward until the bottom of the water-cooled inner guide contacts the bottom of the guide tube.

[0006] Further, in the equal diameter step, after the single crystal is pulled to a set length, the water-cooled inner sleeve starts to move downward.

[0007] Furthermore, the set length is 200-1300 mm.

[0008] Furthermore, the spacing is 0-40 mm.

[0009] Further, the water-cooled inner guide moves downward at a constant speed.

[0010] Furthermore, the water-cooled inner guide continuously decreases at the constant speed.

[0011] Further, the water-cooled inner guide intermittently descends at the constant speed.

[0012] Furthermore, the constant speed is 0-2 mm / s.

[0013] Furthermore, a reducing ring is provided at the bottom of the guide tube, and the spacing is the distance between the bottom of the water-cooled inner guide tube and the reducing ring.

[0014] The advantages and positive effects of the present invention are: due to the adoption of the above technical scheme, the distance between the water-cooled inner sleeve and the guide tube is reduced through the relative movement of the water-cooled inner sleeve and the guide tube, the temperature gradient of the single crystal growth environment is increased, the single crystal pulling speed is increased, and the output of the single crystal furnace is increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of a method for increasing single crystal pulling speed according to an embodiment of the present invention.

[0016] In the figure:

[0017] 1. Guide tube 2. Water-cooled inner guide 3. Variable diameter ring

[0018] 4. Solid-liquid interface DETAILED DESCRIPTION

[0019] An embodiment of the present invention provides a method for increasing the pulling speed of a single crystal. The embodiment of the present invention is described below with reference to the accompanying drawings.

[0020] In the description of the embodiments of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "top", "bottom", etc. is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "set" and "connect" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected, or indirectly connected through an intermediate medium, or it can be a connection between the two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0021] like Figure 1As shown, a method for improving the pulling speed of a single crystal according to an embodiment of the present invention is provided with a reducing ring 3 at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before the furnace is opened, a distance d is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other, that is, the distance d between the bottom of the water-cooled inner guide 2 and the reducing ring 3 does not change. In the equal diameter step, the water-cooled inner guide 2 moves downward along the guide tube 1 until the bottom of the water-cooled inner guide 2 contacts the reducing ring 3. In the process of the water-cooled inner guide 2 moving downward, the distance d between the bottom of the water-cooled inner guide 2 and the reducing ring 3 gradually decreases, and the distance between the water-cooled inner guide 2 and the solid-liquid interface 4 gradually shortens, thereby reducing the temperature of the solid-liquid interface 4 and increasing the temperature gradient of the single crystal growth environment, thereby improving the pulling speed of the single crystal.

[0022] At the beginning of the equal diameter step, if the single crystal pulling speed is too high, it will cause the single crystal to break or dislocate. Therefore, at the beginning of the equal diameter step, the water-cooled inner guide 2 does not move downward, so that the growth environment of the single crystal maintains a stable temperature gradient to ensure that the single crystal can be pulled normally. When the single crystal is pulled to a set length, the water-cooled inner guide 2 begins to move downward. Usually, after the length is set to 200-1300mm, that is, after the single crystal has grown 200-1300mm in equal diameter, the water-cooled inner guide 2 begins to move downward.

[0023] In order not to affect the overall cooling effect, the distance d between the bottom of the water-cooled inner guide 2 and the reducing ring 3 should not be too large, and is usually set to 0-40mm.

[0024] In order to ensure the quality of single crystal pulling, the water-cooled inner guide 2 moves downward at a constant speed. Too high a speed may easily cause the crystal to break. It is usually set to 0-2mm / s.

[0025] In some embodiments, the water-cooled inner guide 2 continuously descends at a constant speed. In some embodiments, the water-cooled inner guide 2 intermittently descends at a constant speed, that is, the water-cooled inner guide 2 first descends a certain distance at a constant speed, and then descends a certain distance at the same constant speed again after a certain interval, until the bottom of the water-cooled inner guide 2 contacts the reducer ring 3. There is no limit on the distance of each descent, the interval time, and the number of descents.

[0026] The increase in single crystal pulling speed is 0.05-0.2mm / min.

[0027] Comparative example: A method for increasing the pulling speed of a single crystal, wherein a reducing ring 3 is provided at the bottom of a guide tube 1, a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3, and the bottom of the water-cooled inner guide 2 is in contact with the reducing ring 3. After the guide tube 1 is unloaded, during the single crystal pulling process, the positions of the guide tube 1 and the water-cooled inner guide 2 do not change, that is, the distance between the bottom of the water-cooled inner guide 2 and the solid-liquid interface 4 remains unchanged. The average pulling speed of the single crystal is 1.5 mm / min.

[0028] Embodiment 1: A method for increasing the pulling speed of a single crystal. Under the same working conditions as the comparative example, a reducing ring 3 is provided at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before opening the furnace, a spacing d of 20 mm is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other. In the equal diameter step, after the single crystal is pulled 200 mm, the water-cooled inner guide 2 descends at a speed of 0.02 mm / s until the water-cooled inner guide 2 contacts the reducing ring 3. The average pulling speed of the single crystal is 1.7 mm / min, which is 0.2 mm / min higher than that of the comparative example.

[0029] Embodiment 2: A method for increasing the pulling speed of a single crystal. Under the same working conditions as the comparative example, a reducing ring 3 is provided at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before opening the furnace, a spacing d of 20 mm is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other. In the equal diameter step, after the single crystal is pulled 500 mm, the water-cooled inner guide 2 descends at a speed of 2 mm / s until the water-cooled inner guide 2 contacts the reducing ring 3. The average pulling speed of the single crystal is 1.65 mm / min, which is 0.15 mm / min higher than that of the comparative example.

[0030] Embodiment 3: A method for increasing the pulling speed of a single crystal. Under the same working conditions as the comparative example, a reducing ring 3 is provided at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before opening the furnace, a spacing d of 40 mm is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other. In the equal diameter step, after the single crystal is pulled 700 mm, the water-cooled inner guide 2 first drops 20 mm at a speed of 0.02 mm / s, and after an interval of 50S, the water-cooled inner guide 2 drops another 20 mm at a speed of 0.02 mm / s. The average pulling speed of the single crystal is 1.60 mm / min, and the pulling speed is increased by 0.1 mm / min compared with the comparative example.

[0031] Embodiment 4: A method for increasing the pulling speed of a single crystal. Under the same working conditions as the comparative example, a reducing ring 3 is provided at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before opening the furnace, a spacing d of 40 mm is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other. In the equal diameter step, after the single crystal is pulled 1000 mm, the water-cooled inner guide 2 first drops 20 mm at a speed of 2 mm / s, and after an interval of 5S, the water-cooled inner guide 2 drops another 20 mm at a speed of 2 mm / s. The average pulling speed of the single crystal is 1.55 mm / min, and the pulling speed is increased by 0.05 mm / min compared with the comparative example.

[0032] Example 5: A method for increasing the pulling speed of a single crystal. Under the same working conditions as the comparative example, a reducing ring 3 is provided at the bottom of the guide tube 1, and a water-cooled inner guide 2 is sleeved inside the guide tube 1 and arranged above the reducing ring 3. Before opening the furnace, a spacing d of 30 mm is provided between the water-cooled inner guide 2 and the reducing ring 3. After the guide tube 1 is unloaded, the position of the guide tube 1 does not change during the single crystal pulling process. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, the water-cooled inner guide 2 and the guide tube 1 do not move relative to each other. In the equal diameter step, after the single crystal is pulled 1300 mm, the water-cooled inner guide 2 continues to decrease at a speed of 1 mm / s. The average pulling speed of the single crystal is 1.67 mm / min, which is 0.17 mm / min higher than that of the comparative example.

[0033] Compared with the above-mentioned embodiment and the comparative example, the moving water-cooled inner guide during the equal diameter process improves the single crystal pulling speed to varying degrees.

[0034] The advantages and positive effects of the present invention are:

[0035] By adopting the above technical solution, the distance between the water-cooled inner sleeve and the guide tube is reduced through the relative movement of the water-cooled inner sleeve and the guide tube, the temperature gradient of the single crystal growth environment is increased, the single crystal pulling speed is increased, and the output of the single crystal furnace is increased.

[0036] The embodiments of the present invention are described in detail above, but the contents described are only preferred embodiments of the present invention and cannot be considered to limit the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of application of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A method for increasing the pulling speed of a single crystal, characterized in that: During the single crystal pulling process, the position of the guide tube remains unchanged. In the melting, temperature stabilization, seeding, shoulder expansion and shoulder rotation steps, a distance is set between the bottom of the water-cooled inner guide and the bottom of the guide tube, and the distance remains unchanged. In the equal diameter step, the water-cooled inner guide moves downward until the bottom of the water-cooled inner guide contacts the bottom of the guide tube.

2. A method for increasing the pulling speed of a single crystal according to claim 1, characterized in that: In the equal diameter step, after the single crystal is pulled to a set length, the water-cooled inner sleeve starts to move downward.

3. A method for increasing the single crystal pulling speed according to claim 2, characterized in that: The set length is 200-1300 mm.

4. A method for increasing the single crystal pulling speed according to any one of claims 1 to 3, characterized in that: The spacing is 0-40 mm.

5. A method for increasing the single crystal pulling speed according to claim 4, characterized in that: The water-cooled inner guide moves downward at a constant speed.

6. A method for increasing the single crystal pulling speed according to claim 5, characterized in that: The water-cooled inner guide continuously descends at the constant speed.

7. The method for increasing the single crystal pulling speed according to claim 5, characterized in that: The water-cooled inner guide intermittently descends at the constant speed.

8. A method for increasing the single crystal pulling speed according to any one of claims 5 to 7, characterized in that: The constant speed is 0-2 mm / s.

9. The method for increasing the single crystal pulling speed according to claim 8, characterized in that: A reducing ring is provided at the bottom of the guide tube, and the spacing is the distance between the bottom of the water-cooled inner guide tube and the reducing ring.

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