A flat bottom guide tube for a CZ silicon single crystal furnace

Abstract

The present invention provides a flat-bottomed guide tube for a CZ silicon single crystal furnace, comprising a guide tube side wall portion, a guide tube transition portion and a guide tube flat bottom portion, wherein the guide tube side wall portion, the guide tube transition portion and the guide tube flat bottom portion are sequentially connected, wherein the guide tube side wall portion, the guide tube transition portion and the guide tube flat bottom portion are all annular structures, the diameter of the guide tube flat bottom portion is smaller than the diameter of the guide tube side wall portion, and the guide tube flat bottom portion and the guide tube side wall portion are coaxially arranged to reduce the gap between the silicon solution liquid surface and the guide tube. The present invention has the beneficial effect of having a guide tube flat bottom portion, reducing the gap between the guide tube and the liquid surface, accelerating the gas flow rate, and being able to quickly take away the volatilized oxygen, which can effectively reduce the oxygen content of large-sized single crystals and improve the quality of large-sized single crystals.

Description

Technical Field

[0001] The invention belongs to the technical field of Czochralski single crystals, and in particular relates to a flat-bottom guide tube of a Czochralski silicon single crystal furnace. Background Art

[0002] The Czochralski method for growing single crystal silicon is currently the most widely used technology for producing single crystal silicon. With the intensification of market competition, the quality requirements for single crystals have become more stringent, and the quality requirements for large-size single crystals are higher. Therefore, single crystal silicon manufacturers now need higher quality. In order to maintain the normal growth of single crystals, it is necessary to add a guide tube, so the guide tube has become one of the important systems of the current Czochralski single crystal furnace. The main functions of the guide tube are:

[0003] First, the heat radiation of the heater to the single crystal is isolated to ensure the temperature gradient required for the growth of the single crystal and to ensure the stable crystallization rate of the single crystal;

[0004] Second, ensure the flow direction of the protective gas in the furnace to avoid the formation of vortices, accelerate the gas flow rate on the liquid surface, and speed up the removal of volatile impurities;

[0005] The disadvantage is that the existing guide tube has a bowl-shaped structure with a side wall and an arc section connected to the bottom of the side wall. Therefore, there is a large gap above the liquid surface and the gas flow rate is low. When pulling large-sized single crystals, the evaporation area of ​​the liquid surface is reduced, resulting in a high oxygen content. Summary of the invention

[0006] In view of the above problems, the problem to be solved by the present invention is to provide a flat-bottomed guide tube for a direct-pull silicon single crystal furnace, which is particularly suitable for direct-pull single crystals. The guide tube has a flat bottom, the gap between the guide tube and the liquid surface is reduced, the gas flow rate is accelerated, and the volatilized oxygen can be quickly taken away, which can effectively reduce the oxygen content of large-size single crystals and improve the quality of large-size single crystals.

[0007] In order to solve the above technical problems, the technical solution adopted by the present invention is: a flat bottom guide tube of a CZ silicon single crystal furnace, comprising a guide tube side wall portion, a guide tube transition portion and a guide tube flat bottom portion, wherein the guide tube side wall portion, the guide tube transition portion and the guide tube flat bottom portion are connected in sequence, wherein:

[0008] The side wall of the guide tube, the transition part of the guide tube and the flat bottom of the guide tube are all annular structures. The diameter of the flat bottom of the guide tube is smaller than the diameter of the side wall of the guide tube, and the flat bottom of the guide tube is coaxially arranged with the side wall of the guide tube to reduce the gap between the liquid surface of the silicon solution and the guide tube.

[0009] Furthermore, the side wall of the guide tube is vertically arranged to the flat bottom of the guide tube.

[0010] Furthermore, the flat bottom of the guide tube is a planar structure, and a through hole is provided on the flat bottom of the guide tube.

[0011] Furthermore, the through hole is coaxially arranged with the side wall of the guide tube.

[0012] Furthermore, the transition portion of the guide tube includes an arc transition portion and a straight wall transition portion, wherein:

[0013] One end of the arc transition part is connected to the side wall of the guide tube, and the other end is connected to one end of the straight wall transition part, and the other end of the straight wall transition part is connected to the flat bottom of the guide tube, which facilitates the connection between the side wall of the guide tube and the flat bottom of the guide tube.

[0014] Furthermore, the connection between the side wall portion of the guide tube and the arc transition portion is arranged in the same plane as the flat bottom portion of the guide tube.

[0015] Furthermore, the connection between the side wall portion of the guide tube and the arc transition portion and the flat bottom portion of the guide tube are arranged at different planes.

[0016] Furthermore, the flat-bottomed flow guide tube also includes a connecting portion, which is connected to the side wall portion of the flow guide tube to facilitate the connection between the flat-bottomed flow guide tube and the single crystal furnace cover.

[0017] Due to the adoption of the above technical solution, the guide tube has a simple structure and a flat bottom, the distance between the guide tube and the liquid surface of the silicon solution is reduced, the gas flow speed above the liquid surface is accelerated, and the volatilized oxygen can be quickly taken away, and the rate of volatile oxygen taken away by the gas is increased, which can effectively reduce the oxygen content of large-sized single crystals and improve the quality of large-sized single crystals;

[0018] The guide tube has a flat bottom, which increases the internal space of the guide tube, can increase the insulation thickness of the guide tube, better isolate the heat radiation of the heater to the single crystal, increase the temperature gradient of the large-sized single crystal, and improve the growth pulling speed of the large-sized single crystal. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of an embodiment of the present invention;

[0020] Figure 2 It is a schematic structural diagram of a transition portion of a guide tube according to an embodiment of the present invention;

[0021] Figure 3 It is a schematic diagram of the structure of a guide tube in the prior art.

[0022] In the figure:

[0023] 1. Side wall of guide tube 2. Transition part of guide tube 3. Flat bottom of guide tube

[0024] 4. Connecting portion 20, arc transition portion 21, straight wall transition portion DETAILED DESCRIPTION

[0025] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0026] Figure 1 A structural schematic diagram of an embodiment of the present invention is shown, specifically showing the structure of this embodiment. This embodiment relates to a flat-bottomed guide tube for a direct-pull silicon single crystal furnace, which is used for direct-pull single crystals. The guide tube has a flat bottom, which reduces the gap between the guide tube and the liquid surface, accelerates the gas flow rate, and can quickly take away the volatilized oxygen, effectively reducing the oxygen content of large-sized single crystals and improving the quality of large-sized single crystals.

[0027] A flat bottom guide tube of a CZ silicon single crystal furnace, such as Figure 1 and 2 As shown, it includes a guide tube side wall portion 1, a guide tube transition portion 2 and a guide tube flat bottom portion 3. The guide tube side wall portion 1, the guide tube transition portion 2 and the guide tube flat bottom portion 3 are connected in sequence. The guide tube side wall portion 1, the guide tube transition portion 2 and the guide tube flat bottom portion 3 connected in sequence constitute the main structure of the guide tube. The guide tube is a cylindrical structure with openings on both the top and the bottom, which is convenient for heat conduction with the single crystal surface during the straight-pulling single crystal process, and the single crystal dissipates heat. The end of the guide tube side wall portion 1 connected to the single crystal furnace cover is the upper end of the guide tube, and the guide tube flat bottom portion 3 is the bottom. The guide tube side wall portion 1, the guide tube transition portion 2 and the guide tube flat bottom portion 3 are arranged in sequence from top to bottom along the upper end to the bottom end of the guide tube, forming the main structure of the guide tube, and performing heat exchange with the single crystal.

[0028] Among them, the guide tube side wall portion 1, the guide tube transition portion 2 and the guide tube flat bottom 3 are all annular structures, wherein the guide tube side wall portion 1 constitutes the height of the guide tube, and the guide tube side wall portion 1 is an annular structure with a certain length, and its length is selected according to the actual needs of the distance between the single crystal furnace cover and the crucible, and no specific requirements are made here, and the diameter of the guide tube side wall portion 1 is larger than the diameter of the single crystal, which is convenient for the single crystal to pass through the guide tube smoothly when the single crystal is pulled vertically, and it is convenient for the water-cooled inner guide and thermal insulation materials to be installed inside the guide tube. The guide tube side wall portion 1 can be an equal-diameter annular structure, or a variable-diameter annular structure, which is selected according to actual needs. Preferably, in this embodiment, the guide tube side wall portion 1 is an equal-diameter annular structure. Preferably, the guide tube side wall portion 1 is a cylindrical annular structure, which is adapted to the shape of the single crystal, and can make the guide tube side wall portion 1 as close to the surface of the single crystal as possible to accelerate the heat dissipation of the single crystal surface.

[0029] The above-mentioned guide tube transition part 2 is an annular structure, and the guide tube transition part 2 is fixedly connected to one end of the guide tube side wall part 1. The setting of the guide tube transition part 2 is convenient for connecting the guide tube side wall part 1 with the guide tube flat bottom part 3 to form the guide tube structure body. The guide tube transition part 2 includes an arc transition part 20 and a straight wall transition part 21, wherein one end of the arc transition part 20 is connected to the guide tube side wall part 1, and the other end is connected to one end of the straight wall transition part 21, and the other end of the straight wall transition part 21 is connected to the guide tube flat bottom part 3, so as to facilitate the connection between the guide tube side wall part 1 and the guide tube flat bottom part 3. The arc transition part 20 is an arc annular structure with a certain curvature, and its cross-sectional shape is an arc. The angle of the arc can be 90°, or 45°, or less than 90°, or other angles, which can be selected according to actual needs, and no specific requirements are made here.

[0030] The straight wall transition portion 21 is an annular structure, and the cross-sectional shape of the straight wall transition portion 21 is a straight line. The straight wall transition portion 21 can be set in a horizontal plane, or inclined, with a certain angle with the horizontal plane. The selection is made according to actual needs, and no specific requirements are made here.

[0031] The above-mentioned flat bottom 3 of the guide tube is an annular structure, and the diameter of the flat bottom 3 of the guide tube is smaller than the diameter of the side wall 1 of the guide tube. The flat bottom 3 of the guide tube is located at the lower part of the side wall 1 of the guide tube, and the projection of the flat bottom 3 of the guide tube in the vertical direction is covered by the side wall 1 of the guide tube. At the same time, the flat bottom 3 of the guide tube is coaxially arranged with the side wall 1 of the guide tube to reduce the gap between the silicon solution surface and the lower end of the guide tube, accelerate the gas flow speed above the silicon solution surface, increase the rate of volatile oxygen carried away by the gas, and improve the quality of large-size single crystals.

[0032] The above-mentioned guide tube side wall portion 1 is vertically arranged to the guide tube flat bottom 3, so that the guide tube body is a cylindrical tube structure, which is convenient for the silicon single crystal to pass through the guide tube. At the same time, the guide tube flat bottom 3 is a planar structure, and the guide tube flat bottom 3 is provided with a through hole, and the through hole is coaxially arranged with the guide tube side wall portion 1, that is, the guide tube flat bottom 3 is a plate-shaped circular ring structure, and the guide tube side wall portion 1 is a cylindrical ring structure. The guide tube side wall portion 1 and the guide tube flat bottom 3 are connected together through the guide tube transition portion 2, and a through hole is provided at the center position of the guide tube flat bottom 3. The diameter of the through hole is adapted to the diameter of the single crystal, which is convenient for the single crystal to pass through the through hole for lifting.

[0033] The connection between the guide tube side wall portion 1 and the arc transition portion 20 is arranged in the same plane as the guide tube flat bottom 3, that is, the guide tube flat bottom 3 is arranged in the same plane as the lower edge of the guide tube side wall portion 1. At this time, the straight wall transition portion 21 of the guide tube transition portion 2 is arranged horizontally; the connection between the guide tube side wall portion 1 and the arc transition portion 20 is arranged in different planes than the guide tube flat bottom 3, that is, the guide tube flat bottom 3 is not arranged in the same plane as the lower edge of the guide tube side wall portion 1, but is arranged in different planes. At this time, the straight wall transition portion 21 of the guide tube transition portion 2 is inclined and has a certain angle with the horizontal plane; the setting of the guide tube flat bottom 3 is selected according to actual needs, and no specific requirements are made here.

[0034] The guide tube side wall portion 1, the guide tube transition portion 2 and the guide tube flat bottom 3 are integrally formed, so that the overall structure of the guide tube is stable, not easy to deform, and has a long service life. When the guide tube is in use, the guide tube side wall portion 1 is placed vertically, and the guide tube flat bottom 3 is located above the silicon solution in the crucible, and the guide tube flat bottom 3 is arranged horizontally. Compared with the existing guide tube (such as Figure 3 As shown), the lower edge of the side wall of the guide tube is connected with an inclined tip, and the guide tube has a flat bottom 3 of the guide tube, which is a planar structure, so that the guide tube can be as close to the liquid surface of the silicon solution as possible, so that the distance between the flat bottom 3 of the guide tube and the liquid surface of the silicon solution is reduced, the gas flow speed above the liquid surface is accelerated, the rate of volatile oxygen carried away by the gas is increased, and the quality of large-sized single crystals is improved; at the same time, the guide tube has a flat bottom. Compared with the existing guide tube, the flat bottom 3 of the guide tube has a certain length, so that the internal space of the guide tube is increased, and the internal space of the guide tube is increased, which can increase the insulation thickness of the guide tube, isolate the heat radiation of the heater to the single crystal, increase the temperature gradient of the large-sized single crystal, and improve the growth pulling rate of the single crystal.

[0035] A further optimized solution is that the flat-bottomed flow guide tube also includes a connecting portion 4, which is connected to the side wall portion 1 of the flow guide tube, and the connecting portion 4 is located away from the end connected to the transition portion 2 of the flow guide tube. The setting of the connecting portion 4 facilitates the connection between the flat-bottomed flow guide tube and the single crystal furnace cover. The connecting portion 4 is connected to the connecting rod through bolts and other connecting parts, and the other end of the connecting rod is connected to the single crystal furnace cover, so that the flat-bottomed flow guide tube can rise or fall with the single crystal furnace cover, thereby realizing the installation and disassembly of the flow guide tube.

[0036] The connecting portion 4 is an annular plate structure with a connecting hole, and the connecting portion 4 is fixedly connected to the top of the guide tube side wall portion 1, and can be integrally formed, or connected by connecting parts such as bolts, or other fixed connection methods, which are selected according to actual needs. No specific requirements are made here. Preferably, the connecting portion is integrally formed with the guide tube side wall portion.

[0037] The oxygen content and single crystal growth rate of the flat-bottom guide tube and the existing guide tube used in pulling large-size single crystals are shown in the following table:

[0038] Existing guide tube Flat bottom guide tube Oxygen content (ppma) 16 14.4 Single crystal growth pulling speed (mm / h) 100 105

[0039] It can be seen from the above table that the use of the flat-bottomed guide tube can reduce the oxygen content of the single crystal by 10% and increase the single crystal growth rate by 5%, thereby improving the quality of the single crystal and reducing the production cost of single crystal manufacturing.

[0040] When the flat-bottomed flow guide tube is in use, the connecting portion 4 of the flow guide tube is connected to the single crystal furnace cover through a connecting rod, and the water-cooled inner guide is installed inside the flow guide tube. At the same time, thermal insulation materials such as carbon fiber are installed between the water-cooled inner guide and the flow guide tube to perform direct pulling of single crystals.

[0041] Due to the adoption of the above technical scheme, the guide tube has a simple structure and a flat bottom. The distance between the guide tube and the liquid surface of the silicon solution is reduced, and the gas flow speed above the liquid surface is accelerated, which can quickly take away the volatilized oxygen and increase the rate at which the volatile oxygen is taken away by the gas, thereby effectively reducing the oxygen content of large-size single crystals and improving the quality of large-size single crystals. The guide tube has a flat bottom, which increases the internal space of the guide tube and increases the insulation thickness of the guide tube, thereby better isolating the heat radiation of the heater to the single crystal, increasing the temperature gradient of the large-size single crystal, and improving the growth pulling rate of the large-size single crystal.

[0042] 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 within the scope of the present invention should still fall within the scope of the patent coverage of the present invention.

Claims

1. A flat-bottomed guide tube for a CZ silicon single crystal furnace, characterized in that: It includes a guide tube side wall portion, a guide tube transition portion and a guide tube flat bottom portion, wherein the guide tube side wall portion, the guide tube transition portion and the guide tube flat bottom portion are connected in sequence, wherein: The guide tube side wall portion, the guide tube transition portion and the guide tube flat bottom portion are all annular structures, the diameter of the guide tube flat bottom portion is smaller than the diameter of the guide tube side wall portion, and the guide tube flat bottom portion and the guide tube side wall portion are coaxially arranged to reduce the gap between the silicon solution surface and the guide tube; The side wall of the guide tube is vertically arranged with respect to the flat bottom of the guide tube; The transition portion of the guide tube includes an arc transition portion and a straight wall transition portion, wherein: One end of the arc transition portion is connected to the side wall portion of the guide tube, and the other end is connected to one end of the straight wall transition portion, and the other end of the straight wall transition portion is connected to the flat bottom portion of the guide tube, so as to facilitate the connection between the side wall portion of the guide tube and the flat bottom portion of the guide tube; The flat-bottomed flow guide tube also includes a connecting portion, which is connected to the side wall portion of the flow guide tube to facilitate the connection of the flat-bottomed flow guide tube with the single crystal furnace cover.

2. The flat-bottomed guide tube of the CZ silicon single crystal furnace according to claim 1, characterized in that: The flat bottom of the guide tube is a plane structure, and a through hole is provided on the flat bottom of the guide tube.

3. The flat-bottomed guide tube of the CZ silicon single crystal furnace according to claim 2, characterized in that: The through hole is coaxially arranged with the side wall portion of the guide tube.

4. The flat bottom guide tube of the CZ silicon single crystal furnace according to claim 1, characterized in that: The connection between the side wall portion of the guide tube and the arc transition portion and the flat bottom portion of the guide tube are arranged in the same plane.

5. The flat-bottomed guide tube of the CZ silicon single crystal furnace according to claim 1, characterized in that: The connection between the side wall portion of the guide tube and the arc transition portion is arranged at different planes from the flat bottom portion of the guide tube.

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