Single crystal furnace guide tube and single crystal furnace with large temperature gradient

Abstract

The present invention relates to the field of semiconductor technology, and in particular, to a single crystal furnace guide tube with a large temperature gradient and a single crystal furnace; the single crystal furnace guide tube with a large temperature gradient is used for the single crystal furnace, and the guide tube comprises an outer shell, the outer shell is provided with a receiving cavity, and an outer cylinder and an inner cylinder are provided in the receiving cavity; the outer cylinder is made of polyacrylonitrile-based graphite felt, and is sleeved on the outside of the inner cylinder and fits with the inner wall of the outer shell; the inner cylinder comprises a first insulation filling part, a second insulation filling part and a third insulation filling part which are stacked from bottom to top; the first insulation filling part comprises an adhesive-based graphite felt layer and a polyacrylonitrile-based graphite felt layer; the second insulation filling part and the third insulation filling part comprise a felt powder bonding filler, and the third insulation filling part is provided with a through hole, and the through hole penetrates the side wall of the outer shell away from the outer cylinder. The single crystal furnace guide tube with a large temperature gradient can realize the control of a large axial temperature gradient, so as to realize high-quality crystal rod growth and improve the growth efficiency of the crystal rod.

Description

Technical Field

[0001] The invention relates to the field of semiconductor technology, in particular to a single crystal furnace guide tube and a single crystal furnace with a large temperature gradient. Background Art

[0002] In the photovoltaic industry, crystal pulling is a commonly used method for preparing single crystal silicon; the single crystal furnace is the main production equipment.

[0003] The single crystal furnace provided by the related art needs to be equipped with a guide tube so that the crystal rod can grow in the inner cavity of the guide tube.

[0004] However, the guide tube provided by the related technology is difficult to form a large axial temperature gradient. After long-term use, the thermal insulation performance of the guide tube will deteriorate, making it difficult to ensure the production of high-quality crystal rods and improve the production efficiency of crystal rods. In addition, the manufacturing cost of the guide tube is high. Summary of the invention

[0005] The purpose of the present invention includes providing a single crystal furnace guide tube with a large temperature gradient and a single crystal furnace. The single crystal furnace guide tube with a large temperature gradient can be used in a single crystal furnace, and the single crystal furnace guide tube with a large temperature gradient can achieve control of a larger axial temperature gradient, has stable thermal insulation performance, can achieve high-quality crystal rod growth, and improve the growth efficiency of the crystal rod, and the manufacturing cost of the guide tube itself is lower.

[0006] The embodiments of the present invention can be implemented as follows:

[0007] In a first aspect, the present invention provides a single crystal furnace guide tube with a large temperature gradient, comprising:

[0008] The outer shell is provided with a receiving chamber, and the receiving chamber is provided with an outer cylinder and an inner cylinder; wherein,

[0009] The outer cylinder is sleeved on the outside of the inner cylinder and fits with the inner wall of the outer shell; the outer cylinder is made of polyacrylonitrile-based graphite felt;

[0010] The inner tube includes a first heat-insulating filling part, a second heat-insulating filling part and a third heat-insulating filling part; the first heat-insulating filling part, the second heat-insulating filling part and the third heat-insulating filling part are stacked in sequence from bottom to top along the axial direction of the outer shell;

[0011] The first heat-insulating filling part includes a viscose-based graphite felt layer and a polyacrylonitrile-based graphite felt layer;

[0012] The second heat-insulating filling part and the third heat-insulating filling part include felt powder bonding fillers; the third heat-insulating filling part is provided with a through hole, and the through hole penetrates the side wall of the shell away from the outer cylinder.

[0013] In an optional embodiment, the first heat-insulating filling part includes at least two filling layers, and the at least two filling layers include a first filling layer and a second filling layer; wherein,

[0014] The first filling layer includes multiple layers of polyacrylonitrile-based graphite felt layers, and the multiple layers of polyacrylonitrile-based graphite felt layers are sequentially stacked along the radial direction of the outer shell;

[0015] The second filling layer includes a viscose-based graphite felt layer stacked on the first filling layer, and the gap between the viscose-based graphite felt layer and two adjacent polyacrylonitrile-based graphite felt layers is distributed at an angle.

[0016] In an optional embodiment, the second filling layer includes multiple viscose-based graphite felt layers, which are stacked in sequence from bottom to top along the axial direction of the shell, and the bottommost viscose-based graphite felt layer is stacked above the first filling layer.

[0017] In an optional embodiment, the first thermal insulation filling part further includes a first protective layer and a second protective layer, the first protective layer is arranged between the second filling layer and the inner wall of the shell; the second protective layer and the second thermal insulation filling part are sequentially stacked on top of the second filling layer;

[0018] The materials of the first protective layer and the second protective layer are both polyacrylonitrile-based graphite felt.

[0019] In an optional embodiment, the fibers of the viscose-based graphite felt layer are distributed in the horizontal direction; the average length of the fibers of the polyacrylonitrile-based graphite felt layer is 150-160 μm; and the thickness of at least one of the viscose-based graphite felt layer and the polyacrylonitrile-based graphite felt layer is 8-12 mm.

[0020] In an optional embodiment, the third heat-insulating filling part further includes a support member, and the support member is supported on the inner wall of the through hole.

[0021] In an optional embodiment, the support member includes a tungsten-molybdenum ring and a protrusion, the protrusion is connected to the axial end of the tungsten-molybdenum ring, the tungsten-molybdenum ring is supported on the inner wall of the through hole, the protrusion is distributed toward the outside of the inner tube relative to the tungsten-molybdenum ring, and the protrusion is used to reflect heat to the outside of the inner tube.

[0022] In an optional embodiment, the third heat-insulating filling portion is provided with a plurality of through holes, and the total area of ​​the plurality of through holes accounts for 5-13% of the total area of ​​the third heat-insulating filling portion; the aperture of the through holes is 5-10 mm;

[0023] Along the axial direction of the shell, the plurality of through holes are distributed in a plurality of rows, and the apertures of the plurality of through holes gradually increase from bottom to top.

[0024] In an optional embodiment, the height of the first thermal insulation filling portion is greater than or equal to 300 mm; the height of the third thermal insulation filling portion is 145-155 mm.

[0025] In a second aspect, the present invention provides a single crystal furnace, comprising the single crystal furnace guide tube with a large temperature gradient according to any one of the aforementioned embodiments.

[0026] The beneficial effects of the single crystal furnace guide tube with a large temperature gradient provided by the embodiment of the present invention include: the single crystal furnace guide tube with a large temperature gradient provided by the embodiment of the present invention includes an outer shell, the outer shell is provided with a accommodating cavity, the accommodating cavity is provided with an outer cylinder and an inner cylinder, the outer cylinder is sleeved on the outside of the inner cylinder, and fits with the inner wall of the outer shell; the preparation material of the outer cylinder is polyacrylonitrile-based graphite felt; the inner cylinder includes a first thermal insulation filling part, a second thermal insulation filling part and a third thermal insulation filling part; the first thermal insulation filling part, the second thermal insulation filling part and the third thermal insulation filling part are stacked in sequence from bottom to top along the axial direction of the outer shell; the first thermal insulation filling part includes a viscose-based graphite felt layer and a polyacrylonitrile-based graphite felt layer; the second thermal insulation filling part and the third thermal insulation filling part include felt powder bonding fillers; the third thermal insulation filling part is provided with a through hole, and the through hole passes through the side wall of the outer shell away from the outer cylinder. The first thermal insulation filling part including a viscose-based graphite felt layer and a polyacrylonitrile-based graphite felt layer has the best thermal insulation effect, and its temperature is higher than that of the second thermal insulation filling part and the third thermal insulation filling part. The third thermal insulation filling part is provided with a through hole, and the through hole penetrates the side wall of the shell away from the outer tube, so that the heat dissipation performance of the third thermal insulation filling part is better than that of the second thermal insulation filling part, and the temperature of the third thermal insulation filling part is lower than that of the second thermal insulation filling part. In this way, different thermal insulation effects can be formed by using the first thermal insulation filling part, the second thermal insulation filling part and the third thermal insulation filling part with different filling materials and structures, thereby forming a larger temperature gradient in the axial direction of the guide tube, that is, the guide tube can be used to achieve control of a larger axial temperature gradient, so as to achieve high-quality crystal rod growth and improve the growth efficiency of the crystal rod. Polyacrylonitrile-based graphite felt has the highest price, the best thermal insulation performance, and is not easy to pulverize; viscose-based graphite felt layer has the second highest price, slightly worse thermal insulation performance, and is easier to pulverize than polyacrylonitrile-based graphite felt; felt powder bonded filler has the lowest price, is not easy to pulverize, has relatively poor thermal insulation performance, and has a stable structure; by mixing viscose-based graphite felt layers and polyacrylonitrile-based graphite felt layers in high temperature zones, the cost can be reduced while the thermal insulation performance is improved, the thermal insulation structure is also more stable, and the service life is extended. The upper low-temperature zone uses the second thermal insulation filling part and the third thermal insulation filling part with different structures to further improve the regulation of the temperature gradient, and the cost is low, the thermal insulation structure is stable, and the service life is also extended. Through the above structure, the service life of each part is extended in combination, and the use cost can be further reduced.

[0027] The single crystal furnace provided by the embodiment of the present invention includes all the beneficial effects of the aforementioned single crystal furnace guide tube with large temperature gradient, for example: using the guide tube to achieve control of a larger axial temperature gradient to achieve high-quality crystal rod growth and improve the growth efficiency of the crystal rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0029] Figure 1 It is a cross-sectional view of a guide tube of a single crystal furnace with a large temperature gradient in an embodiment of the present invention;

[0030] Figure 2 is a cross-sectional view of an inner cylinder in an embodiment of the present invention;

[0031] Figure 3 Schematic diagram of the structure of the support member in an embodiment of the present invention.

[0032] Icons: 010-guide tube of single crystal furnace with large temperature gradient; 100-outer tube; 200-inner tube; 210-outer shell; 220-first thermal insulation filling part; 221-first filling layer; 2211-polyacrylonitrile-based graphite felt layer; 2212-gap; 222-second filling layer; 2221-adhesive-based graphite felt layer; 223-first protective layer; 224-second protective layer; 230-second thermal insulation filling part; 240-third thermal insulation filling part; 241-through hole; 250-support member; 251-tungsten-molybdenum ring; 252-protrusion. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. 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.

[0035] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0036] In the description of the present invention, it should be noted that if the terms "upper", "lower", "inside", "outside", etc. appear to indicate an orientation or position relationship, they are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply 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.

[0037] In addition, the terms “first”, “second”, etc., if used, are merely used to distinguish between the descriptions and should not be understood as indicating or implying relative importance.

[0038] It should be noted that, in the absence of conflict, the features in the embodiments of the present invention may be combined with each other.

[0039] The single crystal furnace provided by the related technology has an inner guide tube between the outer guide wall and the water-cooled screen to achieve the function of thermal insulation. However, the inner guide tube provided by the related technology is difficult to adjust the axial temperature gradient, and the thermal insulation performance of the inner guide tube will deteriorate after long-term use, thereby making it difficult to ensure the production of high-quality crystal rods and to improve the production efficiency of crystal rods. The manufacturing cost of the inner guide tube itself is also high.

[0040] The present embodiment provides a single crystal furnace, which utilizes a single crystal furnace guide tube with a large temperature gradient as an inner guide tube, can achieve the regulation of a larger axial temperature gradient, has stable thermal insulation performance, can achieve high-quality crystal rod growth, and improves the growth efficiency of the crystal rod, and the guide tube has a low manufacturing cost.

[0041] The single crystal furnace guide tube and the single crystal furnace with a large temperature gradient of this embodiment will be described in detail below with reference to the accompanying drawings.

[0042] This embodiment provides a single crystal furnace for growing single crystals by pulling crystals. The single crystal furnace includes a single crystal furnace guide tube 010 (such as a single crystal furnace guide tube 010 with a large temperature gradient as an inner guide tube) Figure 1 As shown); the single crystal furnace guide tube 010 with a large temperature gradient of the guide tube can achieve the adjustment of a larger axial temperature gradient, has stable thermal insulation performance, can achieve high-quality crystal rod growth, and improve the growth efficiency of the crystal rod, and the manufacturing cost of the guide tube itself is low.

[0043] Please refer to Figure 1The single crystal furnace guide tube 010 with a large temperature gradient of this embodiment includes a double-layer structure, which includes an outer shell 210, and the outer shell 210 is provided with a accommodating cavity, in which an outer cylinder 100 and an inner cylinder 200 are arranged, and the outer cylinder 100 is sleeved on the outside of the inner cylinder 200, and the side of the outer cylinder 100 away from the inner cylinder 200 is in contact with the inner wall of one side of the outer shell 210, and the side of the inner cylinder 200 away from the outer cylinder 100 is in contact with the inner wall of the other side of the outer shell; the outer cylinder 100 is used to support and protect the inner cylinder 200, and the outer cylinder 100 fills part of the accommodating space of the outer shell 210.

[0044] Furthermore, the outer cylinder 100 is made of polyacrylonitrile-based (PAN-based) graphite felt, and the thickness of the outer cylinder 100 at various locations in the radial direction is the same, providing consistent thermal insulation performance from top to bottom, thereby providing favorable conditions for adjusting the temperature gradient of the inner cylinder 200, which is beneficial to the realization of temperature gradient adjustment of the inner cylinder 200.

[0045] In order to make the single crystal furnace guide tube 010 with large temperature gradient reliably realize axial temperature gradient control; please refer to Figure 1 and Figure 2 , the inner cylinder 200 of this embodiment includes a first thermal insulation filling part 220, a second thermal insulation filling part 230 and a third thermal insulation filling part 240; the first thermal insulation filling part 220, the second thermal insulation filling part 230 and the third thermal insulation filling part 240 are stacked in sequence from bottom to top along the axial direction of the outer shell 210 and filled in the accommodating cavity; wherein the first thermal insulation filling part 220 includes a viscose-based graphite felt layer 2221 and a polyacrylonitrile-based graphite felt layer 2211; the second thermal insulation filling part 230 and the third thermal insulation filling part 240 include felt powder bonding fillers, and the third thermal insulation filling part 240 is provided with a through hole 241, and the through hole 241 passes through the side wall of the outer shell 210 away from the outer cylinder 100, that is, the through hole 241 passes through the side wall of the outer shell 210 and the inner cylinder 200, that is, the through hole 241 passes through the shell wall on the inner side of the outer shell 210 close to the crystal rod.

[0046] The first thermal insulation filling part 220 including the viscose-based graphite felt layer 2221 and the polyacrylonitrile-based graphite felt layer 2211 has the best thermal insulation effect, and its temperature is higher than the temperatures of the second thermal insulation filling part 230 and the third thermal insulation filling part 240, and the third thermal insulation filling part 240 is provided with a through hole 241, and the through hole 241 penetrates the side wall where the outer shell 210 and the inner cylinder 200 are bonded, so that the heat dissipation performance of the third thermal insulation filling part 240 is better than that of the second thermal insulation filling part 230, and the temperature of the third thermal insulation filling part 240 is lower than that of the second thermal insulation filling part 230; in this way, different thermal insulation effects can be formed by using the first thermal insulation filling part 220, the second thermal insulation filling part 230 and the third thermal insulation filling part 240 with different filling materials and structures, thereby forming a larger temperature gradient in the axial direction of the guide tube, that is, the guide tube can be used to achieve the regulation of a larger axial temperature gradient, so as to achieve high-quality crystal rod growth and improve the growth efficiency of the crystal rod. Polyacrylonitrile-based graphite felt has the highest price, the best thermal insulation performance, and is not easy to pulverize; viscose-based graphite felt layer has the second highest price, slightly worse thermal insulation performance, and is easier to pulverize than polyacrylonitrile-based graphite felt; felt powder bonded filler has the lowest price, is not easy to pulverize, has relatively poor thermal insulation performance, and has a stable structure; by mixing viscose-based graphite felt layers and polyacrylonitrile-based graphite felt layers in high temperature zones, the cost can be reduced while the thermal insulation performance is improved, the thermal insulation structure is also more stable, and the service life can be extended. The second thermal insulation filling part and the third thermal insulation filling part with different structures are used in the upper low temperature zone to further improve the regulation of the temperature gradient, and the cost is low, the thermal insulation structure is stable, and the service life is also extended. Through the above structure, the service life of each part is extended in combination, and the use cost can be further reduced.

[0047] It should be noted that the shell 210 is made of heat-resistant metal, graphite, etc., which is not specifically limited here.

[0048] Please refer to Figure 2Optionally, the first thermal insulation filling part 220 includes at least two filling layers, and the at least two filling layers include a first filling layer 221 and a second filling layer 222; wherein the first filling layer 221 includes multiple layers of polyacrylonitrile-based (PAN-based) graphite felt, and the multiple layers of polyacrylonitrile-based graphite felt layers 2211 are stacked in sequence along the radial direction of the outer shell 210; the second filling layer 222 includes a viscose-based graphite felt layer 2221 stacked on the first filling layer 221, and the viscose-based graphite felt layer 2221 and the gap 2212 between the two adjacent polyacrylonitrile-based graphite felt layers 2211 are distributed at an angle. When the multiple polyacrylonitrile-based graphite felt layers 2211 are stacked in sequence in the accommodating cavity, since the multiple polyacrylonitrile-based graphite felt layers 2211 are stacked in sequence along the radial direction of the outer shell 210, the gap 2212 between two adjacent polyacrylonitrile-based graphite felt layers 2211 extends vertically, and the viscose-based graphite felt layer 2221 is stacked on the first filling layer 221, and the gap 2212 between the viscose-based graphite felt layer 2221 and the adjacent two polyacrylonitrile-based graphite felt layers 2211 is distributed at an angle, the gap 2212 can be blocked, which is beneficial to reduce the deep invasion of gases such as oxygen, thereby reducing the pulverization of the viscose-based graphite felt layer 2221 and the polyacrylonitrile-based graphite felt layer 2211; moreover, if the viscose-based graphite felt layer 2221 is easy to pulverize, The downward deposition of the rubber-based graphite felt layer 2221 will change the thermal insulation performance of the lower and upper parts of the guide tube. The viscose-based graphite felt layer 2221 is stacked on the first filling layer 221, and the viscose-based graphite felt layer 2221 is stacked roughly horizontally. This can reduce the deposition of relatively easy-to-powderize viscose-based graphite felt powdered particles downward, thereby helping to maintain the stability of the thermal insulation performance of the thermal insulation structure and helping to extend the service life of the inner tube 200. At the same time, the viscose-based graphite felt layer 2221 can be used to seal the gaps 2212 between the polyacrylonitrile-based graphite felt layers 2211, thereby improving the problem of local thermal field instability caused by the presence of the gaps 2212, thereby ensuring radial temperature balance and helping to improve the crystal formation rate.

[0049] Please refer to Figure 2 In this embodiment, the first thermal insulation filling part 220 includes only two filling layers, namely, the first filling layer 221 and the second filling layer 222. In the embodiment, the first filling layer 221 is arranged at the bottom of the accommodating cavity, the second filling layer 222 is stacked on the upper end of the first filling layer 221, and the second thermal insulation filling part 230 is stacked on the upper end of the second filling layer 222, that is, the second thermal insulation filling part 230 is stacked on the end of the second filling layer 222 away from the first filling layer 221. The first filling layer 221 is arranged at the bottom of the accommodating cavity, and provides better thermal insulation for places with higher temperatures with its excellent thermal insulation performance and strong material stability.

[0050] Of course, in other embodiments, the number of filling layers can be increased or decreased as needed. For example, the first heat-insulating filling part 220 includes four filling layers, which include two first filling layers 221 and two second filling layers 222. The first filling layers 221 and the second filling layers 222 are alternately arranged from bottom to top, and the bottom layer is one of the first filling layers 221. The vertically arranged first filling layer 221 is subject to greater upper pressure. The multi-layer alternating design can relieve the upper pressure and extend the service life of the vertically arranged first filling layer 221.

[0051] Furthermore, the second filling layer 222 includes a plurality of viscose-based graphite felt layers 2221, and the plurality of viscose-based graphite felt layers 2221 are stacked in sequence from bottom to top along the axial direction of the outer shell 210, and the bottom layer of viscose-based graphite felt layer 2221 is stacked above the first filling layer 221, and the top layer of viscose-based graphite felt layer 2221 is arranged below the second thermal insulation filling part 230.

[0052] Furthermore, the viscose-based graphite felt layer 2221 is perpendicular to the gap 2212 between two adjacent polyacrylonitrile-based graphite felt layers 2211, that is, the angle between the viscose-based graphite felt layer 2221 and the gap 2212 between two adjacent polyacrylonitrile-based graphite felt layers 2211 is 90°; wherein, the gap between two adjacent viscose-based graphite felt layers 2221 extends in the horizontal direction, and the gap 2212 between two adjacent polyacrylonitrile-based graphite felt layers 2211 extends in the vertical direction.

[0053] Of course, in other embodiments, the angle between the gap 2212 between the viscose-based graphite felt layer 2221 and two adjacent polyacrylonitrile-based graphite felt layers 2211 may be increased or decreased to a certain extent, which is not specifically limited here.

[0054] The number of multilayer polyacrylonitrile (PAN-based) graphite felt in the first filling layer 221 can be selected according to actual needs such as the thickness of the graphite felt and the size of the guide tube, for example: two layers, three layers, four layers, etc., which are not specifically limited here; the number of multilayer viscose-based graphite felt layers 2221 of the second filling layer 222 can be selected according to actual needs such as the thickness of the graphite felt and the size of the guide tube, for example: one layer, two layers, three layers, four layers, etc., which are not specifically limited here.

[0055] Optionally, at least one of the viscose-based graphite felt layer 2221 and the polyacrylonitrile-based graphite felt layer 2211 has a thickness of 8-12 mm, for example, 8 mm, 9 mm, 10 mm, 11 mm, 12 mm, etc., which is not specifically limited here. In this embodiment, the thickness of the viscose-based graphite felt layer 2221 and the polyacrylonitrile-based graphite felt layer 2211 are both 10 mm.

[0056] Optionally, the fibers of the viscose-based graphite felt layer 2221 are distributed in the horizontal direction; the average length of the fibers of the polyacrylonitrile-based graphite felt layer 2211 is 150-160 μm, for example, 150 μm, 155 μm, 160 μm, etc., which are not specifically limited here. In this embodiment, the average length of the fibers of the polyacrylonitrile-based graphite felt layer 2211 is 155 μm. When filling the viscose-based graphite felt layer 2221 of the second filling layer 222, the fiber configuration of the viscose-based graphite felt layer 2221 extends in the horizontal direction to combine and utilize the long fiber characteristics of the polyacrylonitrile-based graphite felt layer 2211 to improve the heat conduction effect, that is, the polyacrylonitrile-based graphite felt layer 2211 is more conducive to conducting the lower heat upward to the viscose-based graphite felt layer 2221, and the heat direction from bottom to top is perpendicular to the fiber direction of the viscose-based graphite felt layer 2221 (the fibers of the viscose-based graphite felt layer 2221 are distributed in the horizontal direction), which can increase the thermal insulation effect; at the same time, the polyacrylonitrile-based graphite felt layer 2211 of the first filling layer 221 located at the bottom of the accommodating cavity can also be used to provide a certain degree of protection for the viscose-based graphite felt layer 2221 of the second filling layer 222, so as to extend the service life of the single crystal furnace guide tube 010 with a large temperature gradient.

[0057] Please refer to Figure 1 and Figure 2 In this embodiment, the first thermal insulation filling part 220 also includes a first protective layer 223 and a second protective layer 224. The first protective layer 223 is arranged between the second filling layer 222 and the inner wall of the outer shell 210; the second protective layer 224 and the second thermal insulation filling part 230 are stacked in sequence above the second filling layer 222; the materials of the first protective layer 223 and the second protective layer 224 are both polyacrylonitrile-based graphite felt. With such a configuration, the viscose-based graphite felt layer 2221 can be wrapped with polyacrylonitrile-based graphite felt, so as to better utilize the polyacrylonitrile-based graphite felt to protect the viscose-based graphite felt layer 2221, thereby improving the problem of easy pulverization of the viscose-based graphite felt layer 2221, extending the service life, and improving the problem of deterioration of thermal insulation performance caused by pulverization of the graphite felt, thereby ensuring good thermal insulation performance; moreover, the viscose-based graphite felt layer 2221 is characterized by short fibers, which have good thermal insulation performance but poor formability. Wrapping the viscose-based graphite felt layer 2221 with polyacrylonitrile-based graphite felt can make up for the poor formability of the viscose-based graphite felt layer 2221.

[0058] Furthermore, the shell 210 has two side walls that are opposite and spaced apart, one of which is close to the crystal rod, and a first protective layer 223 is provided between the inner side of the side wall close to the crystal rod and the second filling layer 222; the inner wall of the side wall refers to: the side of one side wall facing the other side wall.

[0059] The number of the first protective layer 223 and the second protective layer 224 can be selected as needed, for example: one layer, two layers, three layers, etc., which are not specifically limited here. In this embodiment, the number of the first protective layer 223 and the second protective layer 224 are both one layer.

[0060] Please refer to Figure 2 In this embodiment, the felt powder of the felt powder bonded filler in the second thermal insulation filling part 230 and the third thermal insulation filling part 240 can be crushed waste carbonized felt; in this way, the production cost of the single crystal furnace guide tube 010 with a large temperature gradient can be reduced. Moreover, the use of felt powder bonded filler as a thermal insulation filling material has good formability and is easy to process, which is conducive to reducing costs. In addition, the carbon fibers in the felt powder bonded filler also have the characteristics of different directions, which is conducive to providing a more uniform thermal conductivity effect, and there are no gaps formed between the stacked felt layers, so the problem of localized powdering of carbon fibers is not easy to occur, thereby avoiding unexpected changes in the thermal insulation performance of the second thermal insulation filling part 230 and the third thermal insulation filling part 240, that is, improving the problem of poor controllability of the upper temperature field of the inner tube 200. The problem is solved to ensure that the upper part of the inner cylinder 200 has strong insulation stability; at the same time, the thermal insulation performance of the felt powder bonded filler is worse than that of the viscose-based graphite felt layer 2221 and the polyacrylonitrile-based graphite felt layer 2211. The felt powder bonded filler is filled at a relatively high position of the inner cylinder 200, which is convenient for maintaining a relatively low temperature at a higher position from the molten silicon liquid level, and then reliably utilizing the single crystal furnace guide tube 010 with a large temperature gradient to realize axial temperature gradient control. The larger axial temperature gradient can increase the pulling speed of the crystal, so as to improve the production capacity.

[0061] Optionally, the average length of short carbon fibers in the felt powder bonded filler and the density of the felt powder bonded filler may be selected in combination with the properties of the recycled carbon felt, and are not specifically limited herein.

[0062] It should be noted that the felt powder bonding filler can be prepared by mixing the adhesive and the felt powder through relevant processes. The specific preparation method can be to first use a mold to prepare the felt powder bonding filler of the second thermal insulation filling part 230 and the third thermal insulation filling part 240, and then assemble them in the accommodating cavity. It can also be directly prepared and cured in the accommodating cavity of the shell 210 to form the felt powder bonding filler of the second thermal insulation filling part 230, and then prepared and cured in the accommodating cavity of the shell 210 to form the felt powder bonding filler of the third thermal insulation filling part 240. Taking the use of a mold to prepare the felt powder bonding filler of the second thermal insulation filling part 230 as an example, the preparation method includes: mixing the felt powder and the adhesive to obtain a slurry, and then injecting the slurry into the mold, and putting it into an oven for curing and forming; wherein the adhesive includes a resin and a coupling agent, and the resin includes but is not limited to a cyanate resin, an unsaturated polyester resin, and a urethane resin; of course, in some embodiments, the adhesive also includes additives, such as: cellulose, fatty alcohols, fatty acids, ethers, polyacrylates, and associative polyurethane thickeners.

[0063] It should also be noted that, in this embodiment, the temperature difference between the bottom and the middle of the inner cylinder 200 is about 3°C ​​(for example, 2.5-3.5°C), that is, the temperature difference between the first heat-insulating filling part 220 and the second heat-insulating filling part 230 is about 3°C, that is, the temperature of the first heat-insulating filling part 220 is about 3°C ​​higher than that of the second heat-insulating filling part 230. A certain temperature difference (i.e., axial temperature gradient) is required between the bottom and the middle of the inner cylinder 200, but the temperature difference cannot be too large, otherwise it is easy to cause abnormal production accidents such as stick explosion.

[0064] Please refer to Figure 2 The third thermal insulation filling part 240 of this embodiment is a felt powder bonded filler filled in the upper part of the accommodating cavity of the outer shell 210, in order to ensure the axial temperature gradient of the single crystal furnace guide tube 010 with a large temperature gradient, that is, to ensure that the thermal insulation performance of the inner tube 200 gradually decreases from the lower part and the middle part to the upper part; the felt powder bonded filler of the third thermal insulation filling part 240 is provided with a through hole 241 for heat dissipation, and the through hole 241 passes through the inner shell wall of the outer shell 210 close to the crystal rod.

[0065] Optionally, the aperture of the through hole 241 is 5-10 mm, for example: 5 mm, 6 mm, 7 mm, 8 mm, 9 mm, 10 mm, etc. By optimizing the aperture of the through hole 241, the through hole 241 can be used to dissipate heat, so as to reduce the temperature of the third thermal insulation filling part 240 relative to the second thermal insulation filling part 230, while ensuring the strength of the third thermal insulation filling part 240. If the aperture is too large, the strength of the third thermal insulation filling part 240 will be reduced. If the aperture is too small, it will be difficult to form a reliable temperature gradient between the third thermal insulation filling part 240 and the second thermal insulation filling part 230.

[0066] Please refer to Figure 2 Optionally, the third thermal insulation filling part 240 is provided with a plurality of through holes 241, and the total area of ​​the plurality of through holes 241 accounts for 5-13% of the total area of ​​the third thermal insulation filling part 240, for example: 5%, 7%, 9%, 10%, 12%, 13%, etc. In this embodiment, the total area of ​​the plurality of through holes 241 accounts for 10% of the third thermal insulation filling part 240. With such a configuration, the heat dissipation of the upper part of the inner cylinder 200 can be optimized to ensure that a temperature difference is reliably formed between the middle and upper parts of the inner cylinder 200, that is, to ensure that a temperature difference is reliably formed between the second thermal insulation filling part 230 and the third thermal insulation filling part 240.

[0067] The total area of ​​the above-mentioned multiple through holes 241 accounts for 5-13% of the total area of ​​the third thermal insulation filling part 240, which means that the sum of the cross-sections of each through hole 241 in the direction perpendicular to its own axis accounts for 5-13% of the circumferential area of ​​the entire third thermal insulation filling part 240.

[0068] Optionally, along the axial direction of the shell 210, the plurality of through holes 241 are distributed in multiple rows, and the apertures of the plurality of through holes 241 gradually increase from bottom to top. Such a configuration can ensure that the thermal insulation of the upper portion (the third thermal insulation filling portion 240) of the inner cylinder 200 also presents a characteristic of gradually decreasing from bottom to top, that is, ensure that the third thermal insulation filling portion 240 itself also forms a temperature gradient in the axial direction, that is, ensure that the temperature of the third thermal insulation filling portion 240 gradually decreases from its lower end to the upper end, so as to be closer to the temperature reduction trend of the crystal from bottom to top, reduce the difficulty of controlling the axial temperature gradient, and help to increase the crystal pulling speed, so as to improve production efficiency and output.

[0069] Please refer to Figure 2 In this embodiment, along the axial direction of the single crystal furnace guide tube 010 with a large temperature gradient, a plurality of through holes 241 are distributed in four rows, and the apertures of the four rows of through holes 241 from bottom to top are 5 mm, 6 mm, 8 mm, and 10 mm, respectively.

[0070] Of course, in other embodiments, along the axial direction of the single crystal furnace guide tube 010 with a large temperature gradient, the plurality of through holes 241 may also be distributed in two rows, three rows, five rows, etc., which is not specifically limited here.

[0071] It should be noted that, in the present embodiment, the temperature difference between the middle and upper parts of the inner tube 200 is about 5°C (for example: 4.5-5.5°C), that is, the temperature of the second thermal insulation filling part 230 is about 5°C higher than the temperature of the third thermal insulation filling part 240; in this way, a higher pulling speed can be used for crystal pulling under suitable axial temperature gradient conditions to improve production efficiency.

[0072] Please refer to Figure 2 and Figure 3In this embodiment, the third heat-insulating filling part 240 further includes a support member 250, and the support member 250 is supported on the inner wall of the through hole 241. The provision of the support member 250 can improve the structural strength of the third heat-insulating filling part 240.

[0073] Furthermore, the support member 250 includes a tungsten-molybdenum ring 251 and a protrusion 252, the protrusion 252 is connected to the axial end of the tungsten-molybdenum ring 251, the tungsten-molybdenum ring 251 is supported on the inner wall of the through hole 241, and the tungsten-molybdenum ring 251 is hollow, that is, the tungsten-molybdenum ring 251 has an inner hole, which is conducive to the heat near the crystal rod to be conducted outwardly, and the protrusion 252 is distributed toward the outside of the inner cylinder 200 relative to the tungsten-molybdenum ring 251. The protrusion 252 is used to reflect heat to the outside of the inner cylinder 200. Specifically, the protrusion 252 is distributed toward the outer cylinder 100 to reflect heat to the outside of the inner cylinder 200. The tungsten-molybdenum ring 251 can enhance the structural strength of the third thermal insulation filling part 240. The raised portion 252 is arranged at the end of the tungsten-molybdenum ring 251, and can seal the inner hole of the tungsten-molybdenum ring 251 to isolate gases such as oxygen, improve the problem that the wall around the through hole 241 is easily powdered, which affects the thermal insulation performance of the third thermal insulation filling part 240, and improves the service life; moreover, the setting of the raised portion 252 also reflects heat outward, which is beneficial to improving the performance of heat dissipation in a direction away from the crystal rod, and is beneficial to lowering the temperature of the third thermal insulation filling part 240 relative to the second thermal insulation filling part 230, ensuring the temperature gradient in the middle and upper parts of the inner cylinder 200.

[0074] The single crystal furnace guide tube 010 with a large temperature gradient is used as the inner guide tube of the single crystal furnace. Its bottom (i.e., the position corresponding to the first heat-insulating filling part 220) is closer to the molten silicon liquid surface. The function of this part is mainly to block the temperature of the silicon liquid surface from being transferred to the water-cooling screen. In order to achieve this purpose, the height of the first heat-insulating filling part 220 is greater than or equal to 300 mm; for example: 300 mm, 305 mm, 310 mm, 320 mm, etc., which are not specifically limited here. In this embodiment, the height of the first heat-insulating filling part 220 is 300 mm.

[0075] In order to ensure the axial temperature gradient of the middle and upper parts of the inner tube 200, the height of the third heat-insulating filling part 240 is 145-155mm, for example: 145mm, 150mm, 155mm, etc., which is not specifically limited here. In this embodiment, the height of the third heat-insulating filling part 240 is 150mm.

[0076] Comparative Example 1

[0077] The difference between Comparative Example 1 and the embodiment is that the fillers of the second thermal insulation filling part and the third thermal insulation filling part are polyacrylonitrile-based graphite felt, and other structures and related parameters refer to the embodiment.

[0078] The temperature of the lower portion of the guide tube of Comparative Example 1 is about 1°C higher than the temperature of the middle portion, and the temperature difference between the middle portion and the upper portion of the guide tube is within 1°C.

[0079] It can be seen that the embodiment of the present application ensures the control of the axial temperature gradient by selecting the filler material at different heights of the inner cylinder.

[0080] Comparative Example 2

[0081] The difference between Comparative Example 2 and the embodiment is that the first thermal insulation filling part only includes the first filling layer, and other structures and related parameters refer to the embodiment.

[0082] When the single crystal furnace guide tube with a large temperature gradient provided in the embodiment was used for 3 months, the first filling layer and the second filling layer began to have the problem of powderization; when the guide tube of comparative example 2 was used for 1 month, the first filling layer began to have the problem of powderization.

[0083] It can be seen that the embodiment of the present application can improve the problem of easy pulverization of graphite felt by providing a second filling layer on the first filling layer so as to use the viscose-based graphite felt layer of the second filling layer to seal the gaps in the polyacrylonitrile-based graphite felt layer of the first filling layer.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and the embodiment is that the first protective layer and the second protective layer are not provided, and other structures and related parameters refer to the embodiment.

[0086] When the single crystal furnace guide tube with a large temperature gradient provided in the embodiment was used for 3 months, the first filling layer and the second filling layer began to have the problem of powdering; when the guide tube of comparative example 3 was used for 1.5 months, the second filling layer began to have the problem of powdering, and when the guide tube was used for nearly 2 months, the first filling layer began to have the problem of powdering.

[0087] It can be seen that the embodiment of the present application uses polyacrylonitrile-based graphite felt as the first protective layer and the second protective layer to protect the viscose-based graphite felt layer, which can improve the problem that the viscose-based graphite felt layer is easily pulverized, and thus simultaneously improve the problem that the gaps between the polyacrylonitrile-based graphite felt layers as the first filling layer cannot be reliably sealed after the viscose-based graphite felt layer is pulverized, and is easily pulverized.

[0088] Comparative Example 4

[0089] The difference between Comparative Example 4 and the embodiment is that the fibers of the viscose-based graphite felt layer of the second filling layer do not extend in the horizontal direction but in the vertical direction. The other structures and related parameters refer to the embodiment.

[0090] The temperature of the lower portion of the guide tube of Comparative Example 4 is about 1.5° C. higher than the temperature of the middle portion.

[0091] It can be seen that the embodiment of the present application ensures the thermal insulation performance of the lower part of the inner cylinder and ensures a relatively large temperature gradient between the lower part and the middle part of the inner cylinder by horizontally distributing the fibers of the viscose-based graphite felt layer of the second filling layer.

[0092] Comparative Example 5

[0093] The difference between Comparative Example 5 and the embodiment is that no support member is provided in the through hole, and other structures and related parameters refer to the embodiment.

[0094] After the single crystal furnace guide tube with a large temperature gradient provided in the embodiment was used for 5 months, there was no powdering phenomenon around the through hole; after the guide tube of comparative example 5 was used for 3.5 months, powdering problem occurred around the through hole.

[0095] It can be seen that the embodiment of the present application improves the problem of easy powdering of the third thermal insulation filling part by arranging a support member in the through hole.

[0096] Comparative Example 6

[0097] The difference between Comparative Example 6 and the embodiment is that the support member only includes a tungsten-molybdenum ring, that is, the inner hole of the tungsten-molybdenum ring is not blocked, and other structures and related parameters refer to the embodiment.

[0098] When the single crystal furnace guide tube with a large temperature gradient provided in the embodiment was used for 6 months, the felt powder bonded filler on the upper part of the inner tube began to powderize; when the guide tube of comparative example 6 was used for about 4 months, the felt powder bonded filler on the upper part of the inner tube began to powderize; and the temperature in the middle part of the inner tube of comparative example 6 was about 3.2°C higher than the temperature in the upper part.

[0099] It can be seen that the embodiment of the present application reduces the entry of gases such as oxygen by blocking the through holes, thereby improving the problem of easy pulverization of the felt powder bonded filling in the third thermal insulation filling part, and at the same time ensuring a reliable temperature gradient between the middle and upper parts of the inner tube.

[0100] Comparative Example 7

[0101] The difference between Comparative Example 7 and the embodiment is that the total area of ​​the porous through holes accounts for 18% of the total area of ​​the third thermal insulation filling part, and other structures and related parameters refer to the embodiment.

[0102] The temperature of the middle portion of the inner tube of the guide tube of Comparative Example 7 is about 7° C. higher than the temperature of the upper portion.

[0103] It can be seen that the embodiment of the present application optimizes the amount of through holes to achieve reliable temperature gradient adjustment between the middle and upper parts of the inner cylinder.

[0104] In summary, the single crystal furnace guide tube 010 with a large temperature gradient of the present invention can be used in a single crystal furnace, and the single crystal furnace guide tube 010 with a large temperature gradient can achieve control of a larger axial temperature gradient to achieve high-quality crystal rod growth and improve the growth efficiency of the crystal rod.

[0105] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by a technician familiar with the technical field within the technical scope disclosed by the present invention should be covered within the protection scope of the present invention.

Claims

1. A single crystal furnace guide tube with a large temperature gradient, characterized in that: include: A housing (210), wherein the housing (210) is provided with a receiving cavity, and an outer cylinder (100) and an inner cylinder (200) are provided in the receiving cavity; wherein: The outer cylinder (100) is sleeved on the outside of the inner cylinder (200) and fits the inner wall of the outer shell (210); the outer cylinder (100) is made of polyacrylonitrile-based graphite felt; The inner cylinder (200) comprises a first thermal insulation filling portion (220), a second thermal insulation filling portion (230) and a third thermal insulation filling portion (240); the first thermal insulation filling portion (220), the second thermal insulation filling portion (230) and the third thermal insulation filling portion (240) are sequentially stacked from bottom to top along the axial direction of the outer shell (210); The first heat-insulating filling portion (220) comprises a viscose-based graphite felt layer (2221) and a polyacrylonitrile-based graphite felt layer (2211); The second heat-insulating filling part (230) and the third heat-insulating filling part (240) comprise felt powder bonding fillers; the third heat-insulating filling part (240) is provided with a through hole (241), and the through hole (241) penetrates a side wall of the outer shell (210) away from the outer cylinder (100); The first heat-insulating filling portion (220) comprises at least two filling layers, wherein the at least two filling layers comprise a first filling layer (221) and a second filling layer (222); wherein: The first filling layer (221) comprises a plurality of polyacrylonitrile-based graphite felt layers (2211), and the plurality of polyacrylonitrile-based graphite felt layers (2211) are stacked in sequence along the radial direction of the outer shell (210); The second filling layer (222) comprises the viscose-based graphite felt layer (2221) stacked on the first filling layer (221), and the viscose-based graphite felt layer (2221) and the gap (2212) between two adjacent polyacrylonitrile-based graphite felt layers (2211) are distributed at an angle.

2. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The second filling layer (222) comprises a plurality of viscose-based graphite felt layers (2221), wherein the plurality of viscose-based graphite felt layers (2221) are stacked in sequence from bottom to top along the axial direction of the outer shell (210), and the bottommost viscose-based graphite felt layer (2221) is stacked above the first filling layer (221).

3. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The first thermal insulation filling portion (220) further comprises a first protective layer (223) and a second protective layer (224); the first protective layer (223) is arranged between the second filling layer (222) and the inner wall of the outer shell (210); the second protective layer (224) and the second thermal insulation filling portion (230) are sequentially stacked and arranged above the second filling layer (222); The materials of the first protective layer (223) and the second protective layer (224) are both polyacrylonitrile-based graphite felt.

4. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The fibers of the viscose-based graphite felt layer (2221) are distributed in the horizontal direction; the average length of the fibers of the polyacrylonitrile-based graphite felt layer (2211) is 150-160 μm; and the thickness of at least one of the viscose-based graphite felt layer (2221) and the polyacrylonitrile-based graphite felt layer (2211) is 8-12 mm.

5. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The third heat-insulating filling portion (240) further comprises a support member (250), wherein the support member (250) is supported on the inner wall of the through hole (241).

6. The single crystal furnace guide tube with large temperature gradient according to claim 5, characterized in that: The support member (250) comprises a tungsten-molybdenum ring (251) and a protrusion (252), wherein the protrusion (252) is connected to an axial end of the tungsten-molybdenum ring (251), the tungsten-molybdenum ring (251) is supported on the inner wall of the through hole (241), and the protrusion (252) is distributed toward the outside of the inner cylinder (200) relative to the tungsten-molybdenum ring (251), and the protrusion (252) is used to reflect heat to the outside of the inner cylinder (200).

7. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The third thermal insulation filling portion (240) is provided with a plurality of through holes (241), the total area of ​​the plurality of through holes (241) accounts for 5-13% of the total area of ​​the third thermal insulation filling portion (240); the diameter of the through holes (241) is 5-10 mm; Along the axial direction of the housing (210), the plurality of through holes (241) are distributed in multiple rows, and the apertures of the plurality of through holes (241) gradually increase from bottom to top.

8. The single crystal furnace guide tube with large temperature gradient according to claim 1, characterized in that: The height of the first thermal insulation filling portion (220) is greater than or equal to 300 mm; the height of the third thermal insulation filling portion (240) is 145-155 mm.

9. A single crystal furnace, characterized in that: A single crystal furnace guide tube with a large temperature gradient comprising the guide tube as described in any one of claims 1 to 8.

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