A flow guide device for single crystal furnace

Abstract

The present application relates to a flow guide device for a single crystal furnace, the single crystal furnace comprising a furnace body, a crucible located in the furnace body for containing molten silicon liquid, and a clamping part that can be raised and lowered in the furnace body for fixing seed crystals and pulling single crystal silicon rods, the flow guide device comprising a flow guide tube and a flow guide cover, the flow guide tube is a cylindrical body with both the top and the bottom open and is located above the molten silicon liquid in the crucible; the flow guide cover is hollow inside and has an air inlet at the top and an air outlet at the bottom, and is installed to the bottom of the clamping part so that the seed crystal is located in the hollow space of the flow guide cover, and during the growth of the narrow neck, the flow guide cover is located at the bottom of the flow guide tube and forms a gap with the inner wall of the flow guide tube. The flow guide device of the present application utilizes the convergent shape of the flow guide cover to form strong convection at the solid-liquid growth interface of the seed crystal rod, and repels impurities and oxygen away from the solid-liquid growth interface.

Description

Technical Field

[0001] The present application relates to the technical field of single crystal furnaces, and in particular to a flow guide device for a single crystal furnace. Background Art

[0002] In the field of manufacturing single crystal silicon rods, the currently commonly used production process is to process the grains obtained by spontaneous nucleation, and then place the seed crystal obtained therefrom into a crucible for homoepitaxial growth, and finally obtain the desired single crystal silicon rod. In the above process, after the seed crystal is fused with the molten homogeneous substance in the crucible and reaches a stable temperature state, it is necessary to perform a neck-thinning operation to eliminate dislocations. In the production process of the thin neck, due to the segregation phenomenon, impurities will be concentrated in the single crystal liquid at the growth interface. Generally speaking, it is necessary to form convection at the cross section of the seed crystal and the molten homogeneous substance so as to drive the oxides in the surrounding atmosphere and the impurities near the growth interface in the single crystal liquid away from the solid-liquid growth interface. In the prior art, the diameter of the guide tube mouth for blowing inert gas is quite different from the diameter of the thin neck, so that a strong convection airflow will not be formed above the liquid surface of the molten homogeneous substance at the growth of the thin neck. In this way, impurities can easily enter the solid-liquid growth interface of the thin crystal rod, which reduces the survival rate of the thin neck, and the thin neck rod grown thereby has a high dislocation density and is prone to fracture. Utility Model Content

[0003] In order to overcome at least one of the defects of the above-mentioned prior art, the purpose of the present application is to provide a flow guide device for a single crystal furnace, wherein the single crystal furnace comprises a furnace body, a crucible located in the furnace body for containing molten silicon liquid, and a clamping part which can be raised and lowered in the furnace body for fixing seed crystals and pulling single crystal silicon rods, wherein the flow guide device comprises a flow guide tube and a flow guide cover, wherein the flow guide tube is a cylindrical body with both the top and the bottom open and is located above the molten silicon liquid in the crucible; the flow guide cover is hollow inside and has an air inlet at the top and an air outlet at the bottom, and is installed to the bottom of the clamping part so that the seed crystal is located in the hollow space of the flow guide cover, and during the growth of the narrow neck, the flow guide cover is located at the bottom of the flow guide tube and forms a gap with the inner wall of the flow guide tube.

[0004] In one embodiment, the air guide cover includes a flange, a radial surface and a lower part, the radial surface is connected between the flange and the lower part, a plurality of air inlets are provided on the radial surface, an opening is provided at the bottom of the lower part and the diameter is larger than the diameter of the seed crystal, and the gap between the opening at the bottom of the lower part and the seed crystal forms the air outlet.

[0005] In another embodiment, the plurality of air inlets are evenly distributed along the circumference of the spoke surface.

[0006] In yet another embodiment, the radial surface has a diameter that gradually increases from top to bottom, and the diameter of the top of the radial surface is equal to the diameter of the bottom of the flange.

[0007] In yet another embodiment, the lower portion is in a truncated cone shape and has a diameter that gradually decreases from top to bottom, and the diameter of the top of the lower portion is equal to the diameter of the bottom of the spoke.

[0008] In yet another embodiment, the clamping portion includes a weight located at an upper portion and a graphite chuck located at a lower portion, and the flange is clamped between the weight and the graphite chuck so as to mount the air duct to the clamping portion.

[0009] In yet another embodiment, the diameter of the bottom of the lower portion is greater than the diameter of any section of the graphite chuck, so that the graphite chuck passes upward from the bottom of the lower portion to be connected to the weight.

[0010] In yet another embodiment, an included angle between the radial surface and the lower portion in a cross section along the virtual central axis is less than 90°.

[0011] In some embodiments, the air shroud has a height less than 250 mm.

[0012] In some embodiments, the air deflector is configured to be transparent or translucent.

[0013] The flow guide device of the present application is provided with a flow guide hood at the lower part of the seed crystal clamping part. The diameter of the flow guide hood is smaller than the diameter of the flow guide tube. The convergence shape of the flow guide hood is used to form strong convection at the solid-liquid growth interface of the thin crystal rod, and the inert gas is concentrated to flow to the thin neck generation area, and impurities and oxides are repelled away from the solid-liquid growth interface, thereby improving the purity of the thin neck rod, reducing the dislocation density of the thin neck, and finally reducing the risk of fracture of the thin neck. Moreover, in the flow guide device of the present application, the flow guide hood is fixed on the seed crystal clamping part. In the subsequent shoulder rotation, shoulder release, and equal diameter process after the successful production of the thin neck, the flow guide hood and the seed crystal clamping part are pulled synchronously, which does not affect the flow guidance during the subsequent growth process of the single crystal silicon rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A perspective view of a fairing according to an embodiment of the present application is shown;

[0015] Figure 2 A cross-sectional view showing a flow guide device of the prior art applied to a crucible, wherein the flow guide cover is not included;

[0016] Figure 3 A cross-sectional view showing a flow guide device according to an embodiment of the present application applied to a single crystal furnace, wherein a flow guide cover is mounted to a clamping portion;

[0017] Figure 4 Shows Figure 3 A top view of the guide device shown;

[0018] Figure 5 Shows Figure 3 A cross-sectional view of the air deflector shown mounted to the clamping portion. DETAILED DESCRIPTION

[0019] Reference Figure 3 , which shows a cross-sectional view of a flow guide device according to an embodiment of the present application applied to a single crystal furnace. The single crystal furnace includes a furnace body (not shown), a crucible 5 located in the furnace body for accommodating a molten homogeneous substance (e.g., molten silicon liquid), and a clamping portion 2 that can be lifted and lowered in the furnace body for fixing seed crystals and pulling single crystal silicon rods. The flow guide device 1 includes a flow guide tube 3 and a flow guide cover 4. The flow guide tube 3 is designed as a cylindrical body with both the top and the bottom open. It should be noted that the flow guide tube 3 is arranged at a position above the molten silicon liquid in the crucible 5, and the flow guide tube 3 can be designed to be able to be lifted and lowered with the cooling device. The design can refer to the prior art in the field and will not be repeated here. The clamping portion 2 is arranged along the virtual central axis of the flow guide tube 3. In view of the fact that the clamping portion 2 needs to be lowered above the liquid level of the molten homogeneous substance during the process, it is preferably made of quartz. The flow guide cover 4 is mounted to the bottom of the clamping portion 2 so that the flow guide cover 4 can stay at the bottom of the flow guide tube 3.

[0020] Back to Figure 1 The air guide cover 4 is a hollow structure, with an air inlet at the top and an air outlet at the bottom, and when it is installed at the bottom of the clamping part 2, the seed crystal at the bottom of the clamping part 2 is just located in the hollow structure of the air guide cover, which may include a flange 41, a radial surface 43 and a lower part 44 in sequence, and the interface between the radial surface 43 and the lower part 44 is the part of the air guide cover 4 with the maximum diameter, for example, the maximum diameter is about 320mm. Further, since the radial surface 43 is connected between the flange 41 and the lower part 44, the diameter of the top of the radial surface 43 is equal to the diameter of the bottom of the flange 41; the radial surface 43 has a diameter that gradually increases from top to bottom until it is adjacent to the lower part 44. The lower portion 44 is designed to be a truncated cone that converges from top to bottom, and has a diameter that gradually decreases from top to bottom, that is, the diameter of the top of the lower portion 44 is equal to the diameter of the bottom of the spoke 43, and its bottom end, that is, the bottom end of the air guide 4, is open, and the opening diameter of the bottom of the lower portion 44 is larger than the diameter of the seed crystal, and the gap between the opening of the bottom of the lower portion and the seed crystal forms an air outlet 45. On the other hand, as Figure 5As shown, the clamping part 2 is designed as a split type, which includes a weight 21 located at the top and a graphite chuck 22 located at the bottom; the upper part of the air guide 4 is also open, so that the flange 41 can be clamped between the weight 21 and the graphite chuck 22, so as to install the air guide 4 to the clamping part 2. Preferably, the diameter of the air outlet 45 (i.e., the bottom of the lower part 44) of the air guide 4 is larger than the diameter of any section of the clamping part 2, especially any section of the graphite chuck 22, so that the graphite chuck 22 extends upward from the bottom of the air guide 4 to connect with the weight 21. Further, the radial surface 43 is provided with a plurality of air inlets 42, such as six or eight air inlets 42. No matter how many air inlets 42 the radial surface 43 has, these air inlets 42 are preferably evenly distributed on the radial surface 43 along its circumference and have equal and as large as possible apertures. For example, the aperture of the air inlet 42 can be designed to be as close as possible to the width of the annular radial surface 43. In this way, the air deflector 4 will not shake due to the small aperture of the air inlet 42 or the instability of the inert gas flow passing therethrough.

[0021] In a preferred embodiment, one of the weight 21 and the graphite chuck 22 has a stud protruding toward the other, and the other of the two has a complementary recessed screw hole, so that the weight 21 and the graphite chuck 22 can be connected by threads to fix each other. On this basis, the inner diameter of the flange 41 can be designed to be slightly larger than the thread outer diameter of the stud of one of the weight 21 and the graphite chuck 22, thereby ensuring the coaxiality of the air deflector 4 and the clamping part 2. Specifically, the diameter of the stud is smaller than the diameter of the weight 21, and the diameter of the screw hole is smaller than the diameter of the graphite chuck 22, so that a step surface is formed between the stud and the weight 21, and a corresponding step surface is formed between the screw hole and the graphite chuck 22. After the weight 21 and the graphite chuck 22 are connected to each other, a gap is formed between the two step surfaces, and the flange of the air deflector 4 can be fixed in the gap, thereby achieving fixation.

[0022] Further, the above-mentioned maximum diameter of the air deflector 4 is smaller than the inner diameter of the bottom end of the air deflector 3. Preferably, the inner surface of the air deflector 3 is configured to converge at least partially from top to bottom, and in particular, the lower inner surface of the air deflector 3 is configured so that the maximum diameter portion of the air deflector 4 (i.e., the interface between the radial surface 43 and the lower portion 44) does not interfere with the inner surface of the air deflector 3. In other words, the air deflector 3 does not serve as a mechanical stopper for the air deflector 4 or even the clamping portion 2. More preferably, in the direction along the virtual central axis, within each unit length, the convergence of the lower portion 44 of the air deflector 4 is more significant than the convergence of the inner surface of the air deflector 3.

[0023] In contrast, in order to ensure that the flow guide 4 does not move downward with the clamping part 2 beyond the flow guide tube 3 during the manufacturing process of the seed crystal growth, the flow guide 1 can be designed to be made of quartz, and in particular, to be at least translucent, preferably transparent. In this way, during the above manufacturing process, the operator can visually observe the position of the seed crystal clamped by the clamping part 2 (especially the graphite chuck) relative to the liquid surface of the molten homogeneous substance through the flow guide 4, thereby preventing the flow guide 4 and the clamping part 2 from moving downward beyond the flow guide tube 3. In particular, the operator can observe the relative position of the seed crystal and the liquid surface of the molten homogeneous substance through the air inlet 42 with a sufficiently large aperture.

[0024] The clamping portion 2 is designed to be able to perform linear movement along the virtual central axis of the guide tube 3. Since the guide cover 4 is mounted on the clamping portion 2, the guide cover 4 can move linearly relative to the guide tube 3 along its virtual central axis together with the clamping portion 2. Moreover, as mentioned above, the maximum diameter portion of the guide cover 4 is smaller than the inner diameter of the bottom end of the guide tube 3, so when the guide cover 4 moves downward with the clamping portion, the maximum diameter portion of the guide cover 4 will not abut against the inner surface of the guide tube 3, and the clamping portion 2 and the guide cover 4 have the possibility of further descending.

[0025] Reference Figure 2-3 , which respectively show the cross-sectional views of the flow guide device applied to the crucible when (the prior art) does not include the flow guide hood 4 and (the present application) has the flow guide hood 4 installed. Regardless of whether there is a flow guide hood 4, the flow guide tube 3 is always configured to guide the inert gas in the single crystal furnace. The inert gas can be, for example, argon Ar. Specifically, the flow guide tube 3 can guide the flow during the formation of the narrow neck and the subsequent equal-diameter growth. Since the diameter of the inner wall of the flow guide tube 3 is large, that is, the gap between the inner wall and the seed crystal is large, when the narrow neck is grown, the inert gas cannot be accurately transported to the position where the narrow neck grows by relying solely on the flow guide tube for guidance, such as Figure 2 As shown in FIG. 1 , under the working condition without the guide cover 4, the blown Ar does not form a strong convection above the liquid surface of the molten homogeneous material at the neck growth position, thereby affecting the production of the neck. Figure 3 As shown, under the working condition where the guide hood 4 is installed, convection can be formed inside the guide hood 4, and the gap between the gas outlet at the bottom of the guide hood 4 and the seed crystal is small, which can more accurately transport the inert gas to the narrow neck growth area, and form strong convection above the liquid surface of the molten homogeneous substance. In order to make the strong convection more intense, the guide hood 4 can be designed so that in any cross-section along the virtual central axis of the guide tube 3, the angle α between the radial surface 43 and the lower part of the guide hood 4 is less than 90°. This means that the Ar from the air inlet 42 is restrained by the lower part of the guide hood 4 and thus gathers and flows out in large quantities toward the bottom end of the guide hood 4, and finally forms the desired and more intense convection on the liquid surface of the molten homogeneous substance.

[0026] In the manufacturing process of seed crystal homoepitaxial growth, the seed crystal is clamped in the clamping part 2, and the seed crystal is located in the hollow space of the flow guide hood 4 and extends downward from the gas outlet 45. Next, the clamping part 2 and the flow guide hood 4 are linearly lowered along the virtual central axis of the flow guide tube 3 to the liquid level of the molten homogeneous material in the crucible. At this time, the flow guide hood 4 descends until it reaches the bottom of the flow guide tube 3, and a gap is formed between the flow guide hood 4 and the inner wall of the flow guide tube 3. During this period, the flow guide tube 3 continues to blow Ar from top to bottom. The flow guide hood 4, relying on the truncated cone shape of its lower part 44, concentrates Ar to the seed crystal growth location through the gap between the gas outlet 45 and the seed crystal. In this way, the strong convection of Ar repels impurities in the molten homogeneous material and oxygen in the surrounding atmosphere away from the solid-liquid growth interface. When the seed crystal is successfully welded, the flow guide hood 4 continues to rise with the clamping part 2 to generate a fine crystal rod, thereby completing the seeding growth process. It should be noted that in the subsequent process of generating fine crystal rods, the guide tube 3 mainly plays the role of guiding Ar to form strong convection on the liquid surface of the molten homogeneous material.

[0027] In addition, in the above-mentioned manufacturing process, the seed crystal is not disposable, but reusable. For this reason, the guide cover 4 can be designed to have a height of less than 250mm. The relatively low height of the guide cover 4 enables the seed crystal to be used for multiple fusion growth, that is, after the seed crystal is used to fuse the molten homogeneous material to generate the required fine crystal rod, the seed crystal and the resulting fine crystal rod are cut off at the interface, and then the remaining seed crystal is used for the next manufacturing process. For example, this design (the guide cover 4 height is less than 250mm) can enable a portion of seed crystal to be used in 7 manufacturing processes, thereby improving the utilization rate of a single portion of seed crystal and saving production costs.

Claims

1. A flow guide device for a single crystal furnace, the single crystal furnace comprising a furnace body, a crucible located in the furnace body for containing molten silicon liquid, and a clamping part movably arranged in the furnace body for fixing seed crystals and pulling single crystal silicon rods, characterized in that: The flow guide device includes a flow guide tube and a flow guide cover. The flow guide tube is a cylindrical body with open top and bottom ends and is located above the molten silicon liquid in the crucible. The flow guide cover is hollow inside and has an air inlet at the top and an air outlet at the bottom, and is installed to the bottom of the clamping part so that the seed crystal is located in the hollow space of the flow guide cover. During the growth of the narrow neck, the flow guide cover is located at the bottom of the flow guide tube and forms a gap with the inner wall of the flow guide tube.

2. The flow guide device for a single crystal furnace according to claim 1, characterized in that: The air guide cover includes a flange, a radial surface and a lower part, wherein the radial surface is connected between the flange and the lower part, wherein a plurality of air inlets are provided on the radial surface, an opening is provided at the bottom of the lower part and the diameter is larger than the diameter of the seed crystal, and the gap between the opening at the bottom of the lower part and the seed crystal forms the air outlet.

3. The flow guide device for a single crystal furnace according to claim 2, characterized in that: The plurality of air inlets are evenly distributed along the circumference of the spoke surface.

4. The flow guide device for a single crystal furnace according to claim 3, characterized in that: The radial surface has a diameter that gradually increases from top to bottom, and the diameter of the top of the radial surface is equal to the diameter of the bottom of the flange.

5. The flow guide device for a single crystal furnace according to claim 4, characterized in that: The lower portion is in a truncated cone shape and has a diameter that gradually decreases from top to bottom, and the diameter of the top of the lower portion is equal to the diameter of the bottom of the spoke.

6. The flow guide device for a single crystal furnace according to claim 5, characterized in that: The clamping portion includes a weight located at an upper portion and a graphite chuck located at a lower portion, and the flange is clamped between the weight and the graphite chuck so as to mount the air deflector to the clamping portion.

7. The flow guide device for a single crystal furnace according to claim 6, characterized in that: The diameter of the bottom of the lower part is larger than the diameter of any section of the graphite chuck, so that the graphite chuck passes upward from the bottom of the lower part to be connected with the weight.

8. The flow guide device for a single crystal furnace according to claim 7, characterized in that: The included angle between the radial surface and the lower portion in a cross section along the virtual central axis is less than 90°.

9. The flow guide device for a single crystal furnace according to any one of claims 1 to 8, characterized in that: The air deflector has a height of less than 250 mm.

10. The flow guide device for a single crystal furnace according to any one of claims 1 to 8, characterized in that: The air deflector is configured to be transparent or translucent.

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