A heat shield and single crystal furnace

Abstract

This utility model embodiment provides a heat shield and a single crystal furnace. The heat shield includes a cylindrical body, which includes a straight cylindrical section and a bottom section connected to the lower end of the straight cylindrical section. A clearance channel is provided in the middle of the straight cylindrical section and the bottom section. The bottom section includes an upper end face and a lower end face opposite to each other along the axial direction of the straight cylindrical section, with the upper end face abutting against the straight cylindrical section. Along the radial direction of the straight cylindrical section, the lower end face includes a first concave region, a second concave region, and a first planar region connected in sequence. The side of the first planar region away from the second concave region extends to the clearance channel. The first concave region is recessed towards the straight cylindrical section to form a compression groove. The second concave region is recessed towards the clearance channel to form a guide groove. The guide groove is connected to the compression groove. The guide groove is used to guide the airflow returning to the compression groove in a direction away from the clearance channel, which can increase the volatilization of impurities on the molten silicon surface and achieve the effect of reducing the oxygen content of the single crystal silicon rod.

Description

Technical Field

[0001] This utility model relates to the field of crystal pulling technology, and in particular to a heat shield and a single crystal furnace. Background Technology

[0002] The Czochralski method for growing monocrystalline silicon is currently the most widely used technology for producing monocrystalline silicon. When growing monocrystalline silicon using the Czochralski method, the oxygen content in the product directly affects the product's competitiveness.

[0003] When growing single-crystal silicon using the Czochralski method, the oxygen content mainly comes from the reaction between molten silicon and a quartz crucible to generate SiO. Most of the oxygen evaporates as SiO gas and is discharged with the gas circulation system in the furnace. The remaining part is not discharged in time and re-enters the molten silicon, accumulating on the solid-liquid crystallization surface. As the crystal grows, it enters the single-crystal silicon, leading to an increase in the oxygen content in the crystal. Utility Model Content

[0004] In view of the above problems, embodiments of the present invention are proposed to provide a heat shield and single crystal furnace that overcomes or at least partially solves the above problems.

[0005] To address the aforementioned issues, in a first aspect, this utility model discloses a heat shield, comprising: a cylindrical body, the cylindrical body including a straight cylindrical portion and a cylindrical bottom connected to the lower end of the straight cylindrical portion, wherein the middle portion of the straight cylindrical portion and the cylindrical bottom has an avoidance channel;

[0006] Along the axial direction of the straight cylindrical portion, the bottom of the cylinder includes an opposing upper end face and a lower end face, the upper end face being abutted against the straight cylindrical portion;

[0007] Along the radial direction of the straight cylindrical portion, the lower end face includes a first concave area, a second concave area, and a first planar area connected in sequence, with the side of the first planar area away from the second concave area extending to the clearance channel;

[0008] The first concave region is recessed towards the straight cylindrical portion to form a compression groove; the second concave region is recessed towards the avoidance channel to form a guide groove; the guide groove is connected to the compression groove; the guide groove is used to guide the airflow returning to the compression groove in a direction away from the avoidance channel.

[0009] Secondly, this utility model embodiment discloses a single crystal furnace, including a furnace body, a quartz crucible, and the aforementioned heat shield;

[0010] Both the quartz crucible and the heat shield are disposed inside the furnace body;

[0011] The heat shield is positioned above the quartz crucible and is coaxial with the quartz crucible.

[0012] The embodiments of this utility model have the following advantages:

[0013] During crystal pulling, the gas flow can be blown along the clearance channel to the surface of the molten silicon, and then flow radially along the straight cylinder towards the edge of the quartz crucible, exiting along the edge. In other words, the gas flow is from the gap between the lower end face of the cylinder bottom and the molten silicon surface to the edge of the quartz crucible. As the gas flow through the gap between the lower end face of the cylinder bottom and the molten silicon surface, it carries away impurities and oxygen that have volatilized from the silicon surface, thus reducing the amount of oxygen entering the melt.

[0014] In this embodiment of the invention, a first concave area, a second concave area, and a first planar area are provided on the lower end surface of the straight cylindrical section. The first concave area is recessed towards the straight cylindrical section to form a compression groove, and the second concave area is recessed towards the clearance channel to form a guide groove. In this invention, the first planar area can increase the flow velocity of the airflow between the heat shield and the liquid surface. After the airflow passes through the first concave area, part of the airflow is blown along the surface of the compression groove to the molten silicon surface and flows towards the edge of the quartz crucible before flowing out. Specifically, along the direction away from the clearance channel, the distance between the surface of the compression groove and the molten silicon surface gradually decreases, which can compress the airflow and thus increase its velocity. Furthermore, after the airflow passes through the first concave area, part of the airflow will swirl back to the second concave area, and guided by the guide groove of the second concave area, it will be blown again towards the space between the first concave area and the molten silicon surface, then flow towards the edge of the quartz crucible before flowing out, which can further increase the airflow velocity.

[0015] In this embodiment of the invention, by setting a first concave area, a second concave area, and a first planar area, a Tesla-like valve principle can be formed between the lower end face of the heat shield and the molten silicon surface. This increases the liquid flow rate and improves airflow permeability, which can remove impurities from the molten silicon surface and increase the volatilization of impurities from the molten silicon surface, thereby reducing the oxygen content of the single crystal silicon rod and improving the stability of crystal pulling. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the cross-sectional structure of a single crystal furnace according to this utility model;

[0017] Figure 2 This is a schematic diagram of the cross-sectional structure of a heat shield according to this utility model;

[0018] Figure 3 This is a partial enlarged cross-sectional view of a heat shield according to this utility model;

[0019] Figure 4 This is a partial enlarged cross-sectional view of another heat shield of this utility model;

[0020] Figure 5 This is an airflow path diagram of this utility model.

[0021] Explanation of reference numerals in the attached figures:

[0022] 100. Hot screen;

[0023] 10. Cylinder body; 11. Bottom of cylinder; 112. Lower end face; 1121. First concave area; 1121a. First sub-arc surface area; 1121b. Second sub-arc surface area; 1122. Second concave area; 1123. First planar area; 113. Compression groove; 114. Guide groove; 115. First inner wall surface; 116. First outer wall surface; 117. Annular protrusion; 12. Straight cylinder section; 121. Second outer wall surface; 122. Second inner wall surface; 13. Clearance channel; 14. Annular flange;

[0024] 20. Inner liner;

[0025] 200. Quartz crucible;

[0026] 400. Heater;

[0027] 500. Insulation container;

[0028] 600, Single crystal silicon rod;

[0029] 700, molten silicon surface. Detailed Implementation

[0030] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The terms "first" and "second" in the specification and claims of this application may explicitly or implicitly include one or more of the features. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more. Furthermore, in the specification and claims, "and / or" indicates at least one of the connected objects, and the character " / " generally indicates that the preceding and following objects are in an "or" relationship.

[0032] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0033] In the description of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model based on the specific circumstances.

[0034] This utility model discloses a heat shield 100 and a single crystal furnace. The heat shield 100 can be applied to the single crystal furnace to pull single crystal silicon using the Czochralski method. The single crystal furnace is a key piece of equipment for pulling single crystal silicon crystals and is widely used in semiconductor, photovoltaic and other fields. Its working principle is based on melt crystallization technology. By precisely controlling parameters such as temperature, airflow, and pulling speed, the silicon melt is transformed into a single crystal silicon rod 600 with a complete crystal lattice structure.

[0035] Specifically, the single crystal furnace also includes a furnace body and a quartz crucible 200, both of which are disposed within the furnace body. The heat screen 100 is positioned above the quartz crucible 200 and is coaxially arranged with the quartz crucible 200. The quartz crucible 200 contains molten silicon. During crystal pulling, a thermal environment is maintained within the furnace body, allowing the grown single crystal silicon rod 600 to pass through the clearance channel 13 on the heat screen 100.

[0036] Specifically, the role of the heat shield 100 in the crystal pulling process is as follows: 1. To block the thermal radiation from the high-temperature furnace body and molten silicon to the single crystal silicon rod 600, which is beneficial for heat dissipation of the single crystal silicon rod 600 and helps to form the temperature gradient required for the growth of the single crystal silicon rod 600, thereby increasing the growth rate of the single crystal silicon rod 600. 2. To act as a guide, on the one hand, it guides the argon gas blown down from the sub-chamber of the single crystal furnace to be sprayed directly to the vicinity of the solid-liquid interface in a more concentrated manner, promoting heat dissipation of the single crystal silicon rod 600, improving the temperature gradient required for the growth of the single crystal silicon rod 600, and increasing the growth rate of the single crystal silicon rod 600; on the other hand, it removes impurities and oxygen volatilized at the solid-liquid interface, reducing the oxygen content and impurity content in the crystal, improving crystal quality and crystal pulling stability.

[0037] During crystal pulling, the interaction between molten silicon and the quartz crucible 200 readily generates SiO, with most of the oxygen evaporating as SiO gas. During crystal pulling, argon or other inert gases are introduced into the furnace. The argon gas is blown downwards along the clearance channel 13 to the surface of the molten silicon 700, and then flows upwards along the edge of the quartz crucible 200 before exiting from the bottom of the furnace under the action of a vacuum pump. This argon gas flow carries away SiO, thereby reducing the oxygen content in the single-crystal silicon rod 600, thus reducing the impurity concentration, increasing the purity of the single-crystal silicon rod 600, and improving product quality.

[0038] Specifically, such as Figure 1 As shown, the single crystal furnace also includes a crucible side that surrounds the quartz crucible 200 and supports it. The single crystal furnace also includes a heater 400 that surrounds the quartz crucible 200 and heats the silicon material inside. The single crystal furnace also includes a heat insulation cylinder 500 that is fitted over the heat shield 100 and the quartz crucible 200 to provide a thermal environment and improve temperature stability during the crystal pulling process.

[0039] In some embodiments, the heat shield 100 may include an inner liner 20 and an outer liner. During the crystal pulling process, a cooling element may also be provided inside the inner liner. In other embodiments, the heat shield 100 may only include the outer liner. The improvement of the heat shield 100 in the embodiments of this utility model lies in the improvement of the outer liner, without specifically limiting whether it includes the inner liner 20 or the specific structure of the inner liner 20.

[0040] For example, such as Figure 1 As shown, the heat shield 100 may include a cylindrical body 10 and an inner liner 20. The cylindrical body 10 is used as the outer liner of the heat shield 100. A clearance channel 13 is provided in the middle of the cylindrical body 10. The inner liner 20 is disposed in the clearance channel 13, and a crystal pulling channel is provided in the middle of the inner liner 20. The grown single crystal silicon rod 600 can be inserted through the crystal pulling channel.

[0041] As one implementation method, such as Figure 2 As shown, the heat shield 100 of this utility model embodiment includes: a cylindrical body 10, the cylindrical body 10 including a straight cylindrical portion 12 and a cylindrical bottom 11 connected to the lower end of the straight cylindrical portion 12; the middle of the straight cylindrical portion 12 and the cylindrical bottom 11 has a clearance channel 13, the clearance channel 13 passing through the straight cylindrical portion 12 and the cylindrical bottom 11 along the axial direction of the straight cylindrical portion 12; along the axial direction of the straight cylindrical portion 12, the cylindrical bottom 11 includes an opposing upper end face and a lower end face 112, the upper end face abutting against the straight cylindrical portion 12; along the radial direction of the straight cylindrical portion 12, the lower end face 112 includes sequentially connected... The first concave region 1121, the second concave region 1122, and the first planar region 1123 extend to the avoidance channel 13 on the side away from the second concave region 1122. The first concave region 1121 is recessed towards the straight cylindrical portion 12 to form a compression groove 113, and the second concave region 1122 is recessed towards the avoidance channel 13 to form a guide groove 114. The guide groove 114 is connected to the compression groove 113 and is used to guide the airflow returning to the compression groove 113 in a direction away from the avoidance channel 13.

[0042] In this embodiment of the present invention, during the crystal pulling process, the airflow can be blown along the avoidance channel 13 to the molten silicon surface 700, and then flow radially along the straight cylinder 12 to the edge of the quartz crucible 200 and then flow out along the edge of the crucible. That is, the airflow flows from the gap between the lower end face 112 of the bottom of the cylinder 11 and the molten silicon surface 700 to the edge of the quartz crucible 200. The lower end face 112 is provided with a first concave area 1121, a second concave area 1122, and a first flat area 1123. The first concave area 1121 is recessed towards the straight cylindrical part 12 to form a compression groove 113, and the second concave area 1122 is recessed towards the avoidance channel 13 to form a guide groove 114. After the airflow passes through the first concave area 1121, part of the airflow directly blows the molten silicon surface 700 towards the edge of the quartz crucible 200 and then flows out, while part of the airflow swirls back to the second concave area 1122 and is guided by the second concave area 1122. Guided by the channel 114, the gas is blown again between the first concave area 1121 and the molten silicon surface 700, and then flows to the edge of the quartz crucible 200 and out. As the distance between the surface of the compression channel 113 and the molten silicon surface 700 gradually decreases along the direction away from the avoidance channel 13, the gas flow can be compressed, thereby increasing the flow rate and achieving the effect of increasing speed and reducing resistance. Since the gas flow process can carry away the impurities of the molten silicon surface 700, it can also increase the volatilization of impurities in the molten silicon surface 700, thereby reducing the oxygen content of the single crystal silicon rod 600.

[0043] In this embodiment of the invention, by setting a first concave region 1121, a second concave region 1122, and a first planar region 1123, a Tesla-like valve principle can be formed between the lower end face 112 of the cylinder 10 and the molten silicon surface 700. This increases the liquid flow rate and improves airflow permeability, which can remove impurities from the molten silicon surface 700 and increase the volatilization of impurities from the molten silicon surface 700, thereby reducing the oxygen content of the single crystal silicon rod and improving the stability of crystal pulling.

[0044] In this embodiment of the invention, the heat shield 100 includes a cylindrical portion 12 and a cylindrical bottom 11. The cylindrical bottom 11 is connected to the lower end of the cylindrical portion 12, such that the cylindrical bottom 11 is positioned close to the molten silicon surface 700. A clearance channel 13 extends through both the cylindrical portion 12 and the cylindrical bottom 11 along the axial direction of the cylindrical portion 12 to facilitate clearance of the growing single-crystal silicon rod 600. Since the clearance channel 13 extends through both the cylindrical portion 12 and the cylindrical bottom 11, both the cylindrical portion 12 and the cylindrical bottom 11 are hollow cylindrical structures with openings at both ends.

[0045] Specifically, such as Figure 2As shown, arrow S points in the axial direction of the straight cylindrical portion 12. The bottom of the cylinder 11 includes an upper end face and a lower end face 112. The upper end face of the bottom of the cylinder 11 can be mated with the straight cylindrical portion 12, and the lower end face 112 of the bottom of the cylinder 11 can be opposite to the molten silicon surface 700. The bottom of the cylinder 11 and the straight cylindrical portion 12 can be integrally formed, making the heat shield 100 a one-piece structure with good structural stability. In some optional embodiments, the bottom of the cylinder 11 and the straight cylindrical portion 12 can also be made into separate structures, connected by splicing and fixing.

[0046] Specifically, along the radial direction of the straight cylindrical portion 12, the lower end face 112 includes a first concave region 1121, a second concave region 1122, and a first flat region 1123 connected in sequence. The side of the first flat region 1123 away from the second concave region 1122 extends to the clearance channel 13, such that the first flat region 1123 is disposed near the inner periphery of the bottom of the cylinder 11, and the first concave region 1121 is disposed near the outer periphery of the bottom of the cylinder 11.

[0047] Specifically, the first concave region 1121 can be recessed into the straight cylindrical portion 12 to form a compression groove 113, such that the opening of the compression groove 113 is located away from the straight cylindrical portion 12, and the compression groove 113 can face the molten silicon surface 700.

[0048] Specifically, the second concave area 1122 can be recessed into the avoidance channel 13 to form a guide groove 114, such that the opening of the guide groove 114 is set away from the avoidance channel 13.

[0049] Specifically, the guide groove 114 and the compression groove 113 are connected, and the first concave region 1121 and the second concave region 1122 can be smoothly connected. Specifically, the first concave region 1121 and the second concave region 1122 can have an arc-shaped transition; or, the tangent at the connection between the first concave region 1121 and the second concave region 1122 is tangent to the second concave region 1122; or, the tangent at the connection between the second concave region 1122 and the first concave region 1121 is tangent to the first concave region 1121.

[0050] Furthermore, since the first concave region 1121, the second concave region 1122, and the first planar region 1123 are sequentially connected along the radial direction of the straight cylindrical portion 12, as follows: Figure 2As shown, the first planar region 1123 is located on the side of the second concave region 1122 away from the straight cylindrical portion 12; the first concave region 1121 is located on the side of the bottom of the compression groove 113 away from the straight cylindrical portion 12. That is, the first planar region 1123 is located below the second concave region 1122, and the side of the first concave region 1121 away from the second concave region 1122 is located below the bottom of the compression tank 113. This makes the first planar region 1123 and the side of the first concave region 1121 away from the second concave region 1122 closer to the molten silicon surface 700. In this way, during the flow of argon gas, the side of the first planar region 1123 and the side of the first concave region 1121 away from the second concave region 1122 can squeeze the argon gas to the molten silicon surface 700, which plays a converging role on the argon gas, so that more argon gas can be blown towards the molten silicon surface 700 to carry away more oxygen, thereby achieving the effect of reducing the oxygen content of the single crystal silicon rod 600.

[0051] Furthermore, during the crystal pulling process, after argon gas enters the clearance channel 13, it is blown from the gap between the clearance channel 13 and the single crystal silicon rod 600 towards the molten silicon surface 700, and then blown along the gap between the lower end face 112 and the molten silicon surface 700 towards the edge of the quartz crucible 200, wherein, combined with Figure 1 and Figure 2 As shown, a portion of the airflow flows directly from between the lower end face 112 and the molten silicon surface 700 to the edge of the quartz crucible 200. Another portion of the airflow enters the compression tank 113, is compressed, and then flows in the opposite direction. According to the tangential guiding principle, the airflow in the compression tank 113 is guided by the tank wall to the guide tank 114. Since the opening of the guide tank 114 is far from the avoidance channel 13, the airflow can flow back to the edge of the quartz crucible 200 in a direction away from the avoidance channel 13, preventing the airflow from escaping. In addition, the airflow guided by the guide tank 114 merges with the airflow passing between the first plane area 1123 and the molten silicon surface 700, which can improve the airflow environment, reduce airflow resistance, increase the airflow velocity, and make the airflow flow more smoothly. This further removes more oxygen, reduces the oxygen content of the monocrystalline silicon rod 600, improves the product quality of the monocrystalline silicon rod 600, and also improves the stability of crystal pulling.

[0052] Specifically, the principle of tangential flow guidance is to guide the fluid by making it flow along a specific tangential direction, utilizing the fluid's inertia, centrifugal force, and other properties to increase airflow velocity and avoid airflow blockage.

[0053] Specifically, such as Figure 5As shown, after the argon gas flows out from the clearance channel 13, it first passes under the first planar area 1123. Part of the gas flow directly flows to the edge of the quartz crucible 200. Since the first concave area 1121 is far from the second concave area 1122, the gas flow is constricted on the side away from the second concave area 1122. Part of the gas flow flows to the compression groove 113. Since the opening of the guide groove 114 is far from the clearance channel 13, the guide groove 114 can guide the gas flow in a direction away from the clearance channel 13. This can prevent the gas flow from flowing back to the clearance channel 13, thereby preventing the gas flow from blocking the gas flow from the clearance channel 13 and ensuring the smooth flow of argon gas.

[0054] In some optional embodiments of this utility model, see Figure 3 As shown, the depth of the compression groove 113 along the axial direction of the straight cylindrical portion 12 is h1, where 2mm ≤ h1 ≤ 200mm. Specifically, the depth of the compression groove 113 along the axial direction of the straight cylindrical portion 12 refers to the maximum axial depth of the compression groove 113 from the outer end of the compression groove 113 near the heat shield to the bottom of the compression groove 113 within the straight cylindrical portion 12. In this embodiment, by setting the depth of the compression groove 113, the airflow velocity can be adjusted. If the depth is too large, airflow vortices will intensify and affect airflow stability; if the depth is too small, the guiding effect will be lost, and the guiding effect cannot be achieved.

[0055] In some optional embodiments of this utility model, the radial depth of the guide groove 114 along the straight cylindrical portion 12 is h2, where 2mm ≤ h2 ≤ 50mm. Specifically, the radial depth of the guide groove 114 along the straight cylindrical portion 12 refers to the maximum radial depth of the guide groove 114 from the bottom end near the heat shield to the bottom of the guide groove 114 within the straight cylindrical portion 12. In this embodiment, by setting the depth of the guide groove 114, the return flow angle can be adjusted. Too large a depth will affect the overall structural strength and stability, while too small a depth will result in a loss of guiding effect and failure to achieve airflow acceleration.

[0056] In some alternative embodiments, the plane containing the first planar region 1123 may be perpendicular to the axis of the straight cylindrical portion 12, so as to ensure that the first planar region 1123 compresses the airflow to the molten silicon surface 700, so that the argon gas can be blown toward the molten silicon surface 700 to carry away more oxygen.

[0057] In some alternative embodiments, the first planar region 1123 may also be inclined away from the straight cylinder 12 in the direction away from the avoidance channel 13. In this way, the first planar region 1123 gets closer and closer to the molten silicon surface 700 in the direction away from the avoidance channel 13, which makes it easier for the first planar region 1123 to compress the gas flow, so that the argon gas can be blown toward the molten silicon surface 700 to carry away more oxygen.

[0058] Specifically, in combination Figure 2 and Figure 4As shown, the second concave region 1122 extends to the first flat region 1123 from the side away from the first concave region 1121. The tangent line passing through the connection between the second concave region 1122 and the first flat region 1123, and tangent to the second concave region 1122, forms an angle θ with the plane containing the first concave region 1121. If the angle θ is too large, there is a risk that the airflow will flow in the opposite direction to the area below the first flat region 1123, easily causing blockage of the airflow out of the avoidance channel 13 and resulting in poor airflow. Therefore, in some optional embodiments of this invention, controlling 0°≤θ≤45° can effectively ensure that the guide groove 114 guides the airflow in a direction away from the avoidance channel 13, so that the argon gas flow process carries away more oxygen.

[0059] Specifically, the depth of the guide groove 114 can be designed to be larger or smaller, and this embodiment of the present invention does not impose a specific limitation on it.

[0060] Specifically, the cross-sectional shape of the guide groove 114 parallel to the axial direction of the straight cylindrical portion 12 includes at least one of C-shaped, V-shaped and U-shaped, making the structure of the guide groove 114 more diverse.

[0061] Specifically, the cross-sectional shape of the guide groove 114 parallel to the axial direction of the straight cylinder 12 can be an arc shape, a curve shape, a C-shape, a V-shape, a U-shape, or an irregular shape, etc., and this embodiment of the present invention does not make specific limitations on this.

[0062] In some optional embodiments of this utility model, the bottom of the cylinder 11 includes a first inner wall surface 115 and a first outer wall surface 116 in the radial direction of the straight cylinder portion 12. The first inner wall surface 115 is used to enclose and form an avoidance channel 13. The lower end surface 112 of the bottom of the cylinder 11 is provided with an annular protrusion 117. A portion of the first concave area 1121 and the first outer wall surface 116 constitute two opposing sides of the annular protrusion 117.

[0063] In this embodiment of the present invention, the side of the first concave region 1121 away from the second concave region 1122 is smoothly connected to the first outer wall surface 116, and an annular protrusion 117 can be formed at the connection between the side of the first concave region 1121 away from the second concave region 1122 and the first outer wall surface 116; along the axial direction of the straight cylindrical portion 12, the end of the annular protrusion 117 away from the straight cylindrical portion 12 is located on the side of the bottom of the compression groove 113 away from the straight cylindrical portion 12.

[0064] In this embodiment of the invention, during the crystal pulling process, the minimum distance from the annular protrusion 117 to the molten silicon surface 700 is less than or equal to the minimum distance from the first concave region 1121 to the molten silicon surface 700. This facilitates the compression of the airflow by the annular protrusion 117, which forces the argon gas to the molten silicon surface 700. This can improve the dead zone of airflow at the edge of the quartz crucible 200, reduce energy loss caused by airflow dispersion, and further promote the volatilization of impurities on the molten silicon surface 700, thereby reducing the oxygen content in the single crystal silicon rod 600.

[0065] In some optional embodiments, along the axial direction of the straight cylindrical portion 12, the end of the annular protrusion 117 away from the straight cylindrical portion 12 is located between the straight cylindrical portion 12 and the first planar region 1123. The minimum straight-line distance from the end of the annular protrusion 117 away from the straight cylindrical portion 12 to the first planar region 1123 is ΔH1. When ΔH1 is large, it is easy to affect the compression effect of the annular protrusion 117 on the airflow, resulting in an insignificant oxygen reduction effect on the monocrystalline silicon rod 600. Therefore, in some optional embodiments of this utility model, by controlling 0≤ΔH1≤250mm, the compression effect of the annular protrusion 117 on the airflow is ensured, so that argon gas can be blown toward the molten silicon surface 700 to carry away more oxygen, thereby enhancing the oxygen reduction effect on the monocrystalline silicon rod 600. In this embodiment, the end of the annular protrusion 117 is located between the straight cylindrical portion 12 and the first planar region 1123. Specifically, along the axial direction of the straight cylindrical portion, the end of the annular protrusion 117 is located between the straight cylindrical portion 12 and the extended plane of the first planar region 1123.

[0066] For example, ΔH1 can be 0mm, 20mm, 50mm, 100mm, 160mm, 200mm or 250mm.

[0067] Specifically, such as Figure 2 As shown, along the axial direction of the straight cylindrical portion 12, the minimum straight-line distance from the end of the annular protrusion 117 away from the straight cylindrical portion 12 to the first planar region 1123 is ΔH1. In this embodiment of the present invention, along the axial direction of the straight cylindrical portion 12, the minimum straight-line distance from the annular protrusion 117 to the top of the cylindrical body 10 is L1, and the minimum straight-line distance from the first planar region 1123 to the top of the cylindrical body 10 is L2, where L2-L1=ΔH1. Therefore, when obtaining ΔH1, it can be obtained by obtaining L2 and L1 and taking the difference.

[0068] In some alternative embodiments, along the axial direction of the straight cylindrical portion 12, the end of the annular protrusion 117 away from the straight cylindrical portion 12 is located on the side of the first planar region 1123 away from the straight cylindrical portion 12; the minimum straight-line distance from the end of the annular protrusion 117 away from the straight cylindrical portion 12 to the first planar region 1123 is ΔH2. When ΔH2 is small, it will cause the minimum distance between the annular protrusion 117 and the molten silicon surface 700 to be too close, which is not conducive to the smoothness of airflow, resulting in the argon gas not being able to carry away more oxygen, which is not conducive to reducing the oxygen content of the pulled silicon rod. Specifically, in this embodiment, during crystal pulling, the end of the annular protrusion 117 is closer to the liquid surface than the first planar region 1123. Therefore, in some optional embodiments of this utility model, by controlling 0≤ΔH2≤15mm, the annular protrusion 117 can be kept away from the molten silicon surface 700, so that the airflow is smoother, the argon gas can carry away more oxygen, the oxygen content of the pulled silicon rod can be reduced, and the stability of the pulled single crystal silicon rod 600 can be guaranteed.

[0069] For example, ΔH2 can be 0mm, 5mm, 6mm, 9mm, 10mm, 12mm or 15mm.

[0070] Specifically, in this embodiment of the present invention, along the axial direction of the straight cylindrical portion 12, the minimum straight distance from the annular protrusion 117 to the top of the cylindrical body 10 is L3, and the minimum straight distance from the first planar region 1123 to the top of the cylindrical body 10 is L4. L4-L3=ΔH2. Therefore, when obtaining ΔH2, it is possible to obtain L4 and L3 and take the difference.

[0071] Optionally, the cross-sectional shape of the compression groove 113 parallel to the axial direction of the straight cylindrical portion 12 includes at least one of C-shaped, V-shaped and U-shaped, which makes the structure of the compression groove 113 more diverse and facilitates the compression of the airflow within the compression groove 113, so as to compress more argon gas to the molten silicon surface 700, remove more oxygen, and effectively reduce the oxygen content of the single crystal silicon rod 600.

[0072] For example, such as Figure 3 As shown, the compression groove 113 has a V-shaped cross-section parallel to the axial direction of the straight cylindrical portion 12. The first concave region 1121 is composed of a first sub-arc surface region 1121a and a second sub-arc surface region 1121b. The second sub-arc surface region 1121b connects the first sub-arc surface region 1121a and the second concave region 1122. The distance between the first sub-arc surface region 1121a and the molten silicon surface 700 decreases in the direction away from the second sub-arc surface region 1121b, which can play the role of compressing the airflow. The distance between the second sub-arc surface region 1121b and the molten silicon surface 700 decreases in the direction away from the first sub-arc surface region 1121a. The second sub-arc surface region 1121b can also guide the airflow in the compression groove 113 to the guide groove 114.

[0073] Specifically, the included angle between the first sub-arc surface region 1121a and the second sub-arc surface region 1121b can be an acute angle or an obtuse angle, etc., and this embodiment of the present invention does not make specific limitations on this.

[0074] Specifically, the first planar region 1123 has a certain width along the radial direction of the straight cylindrical portion 12, which is beneficial to compress and guide the airflow flowing out from the avoidance channel 13, so that argon gas can be blown toward the molten silicon surface 700, and also carries away more oxygen, thus improving the oxygen content problem of the single crystal silicon rod 600.

[0075] Specifically, during the crystal pulling process, it is necessary to obtain the gate distance, which refers to the distance from the first planar region 1123 to the molten silicon surface 700. This distance is crucial for creating a suitable thermal environment, and its value affects the temperature distribution near the growth interface of the single crystal silicon rod 600. The gate distance affects the crystal pulling speed, crystal appearance, and crystal quality during the crystal pulling process. Precise control of the gate distance plays an important role in improving the constant diameter pulling speed capability. Moreover, capturing the gate distance allows for real-time monitoring of its value. When the gate distance is less than a set threshold, an alarm can be triggered and the crucible lifting can be stopped, thereby preventing the hot shield 100 from immersing in the molten silicon and avoiding equipment failure and production accidents.

[0076] Optionally, the width of the first planar region 1123 along the radial direction of the straight cylindrical portion 12 is D1, and the outer diameter of the straight cylindrical portion 12 is D2. When the width D1 of the first planar region 1123 along the radial direction of the straight cylindrical portion 12 is small, the width of the first planar region 1123 becomes too narrow, making it difficult to capture the liquid outlet distance. Furthermore, a narrow width D1 results in a narrow airflow surface, preventing argon from effectively carrying away the volatilized oxygen. Conversely, a large width D1 of the first planar region 1123 along the radial direction of the straight cylindrical portion 12 easily leads to poor airflow, making the process of pulling the single-crystal silicon rod 600 more difficult. Therefore, in this embodiment of the invention, by controlling 1 / 15 ≤ D1 / D2 ≤ 1 / 5, the width D1 of the first planar region 1123 along the radial direction of the straight cylindrical portion 12 is now within a reasonable range to ensure smooth airflow and thus ensure stability during the process of pulling the single-crystal silicon rod 600.

[0077] For example, D1 / D2 can be equal to 1 / 15, 1 / 13, 1 / 10, 1 / 9, 1 / 6, or 1 / 5, etc.

[0078] In this embodiment of the invention, by utilizing the cooperation of the compression groove 113 and the guide groove 114, and ensuring the width of the first planar area 1123 in the radial direction of the straight cylinder 12, this design not only improves the stability of airflow but also significantly enhances the overall heat preservation performance of the heat shield 100. Furthermore, the linkage of each component causes the airflow to expand after passing through the horizontal plane. Part of the airflow directly blows onto the molten silicon surface 700 and flows out directly, while part of the airflow comes into contact with the first concave area 1121 and is then compressed and blows onto the molten silicon again. The liquid surface 700 increases the airflow velocity. The swirling vortex in the compression tank 113 can be guided by the second concave area 1122 to blow towards the molten silicon surface 700, compressing the expanding airflow to the molten silicon surface 700 and increasing the airflow velocity at the same time. This achieves the effect of increasing the speed and reducing the resistance of the airflow, so that when the airflow blows on the molten silicon surface 700, it can carry away more impurities and effectively reduce the oxygen content of the monocrystalline silicon rod 600. The oxygen content of the monocrystalline silicon rod 600 can be reduced by 0.8 ppm or more than 1 ppm. In some optional embodiments of this utility model, the straight cylindrical portion 12 is a hollow cylindrical structure with openings at both ends. The straight cylindrical portion 12 includes opposing second inner wall surfaces 122 and second outer wall surfaces 121 along the radial direction of the straight cylindrical portion 12. The second inner wall surface 122 is used to enclose and form a clearance channel 13. The diameter of the first outer wall surface 116 is the same as the diameter of the second outer wall surface 121. The first inner wall surface 115 is connected to the second inner wall surface 122. The first inner wall surface 115 includes an inverted conical surface area, and the diameter of the first inner wall surface 115 decreases in the direction away from the second inner wall surface 122.

[0079] In this embodiment of the utility model, the diameter of the first outer wall surface 116 is the same as the diameter of the second outer wall surface 121, and one end of the inverted conical surface area is connected to the first inner wall surface 115, so that the edge side of the bottom of the cylinder 11 is thicker, which facilitates the enhancement of the heat insulation performance of the bottom of the cylinder 11.

[0080] Specifically, such as Figure 2 As shown, the angle between the inverted conical surface area and the plane axis of the first plane area 1123 is β. β can be an acute angle. In this embodiment of the present invention, the specific value of β is not limited.

[0081] Optionally, the first inner wall surface 115 also includes a second planar region connected to the end of the inverted conical surface region away from the second inner wall surface 122. The second planar region is perpendicular to the axial direction of the straight cylinder portion 12, which facilitates the support and installation of other thermal field components.

[0082] In some alternative embodiments, an annular flange 14 is provided at the end of the straight cylindrical portion 12 away from the bottom 11 of the cylinder. The annular flange 14 has a mounting hole to facilitate the installation of the heat shield 100 with the furnace body of the single crystal furnace.

[0083] The heat shield described in this embodiment of the present invention has at least the following advantages:

[0084] In this embodiment of the invention, a first concave area, a second concave area, and a first planar area are provided on the lower end surface of the straight cylindrical section. The first concave area is recessed towards the straight cylindrical section to form a compression groove, and the second concave area is recessed towards the clearance channel to form a guide groove. In this invention, the first planar area can increase the flow velocity of the airflow between the heat shield and the liquid surface. After the airflow passes through the first concave area, part of the airflow is blown along the surface of the compression groove to the molten silicon surface and flows towards the edge of the quartz crucible before flowing out. Specifically, along the direction away from the clearance channel, the distance between the surface of the compression groove and the molten silicon surface gradually decreases, which can compress the airflow and thus increase its velocity. Furthermore, after the airflow passes through the first concave area, part of the airflow will swirl back to the second concave area, and guided by the guide groove of the second concave area, it will be blown again towards the space between the first concave area and the molten silicon surface, then flow towards the edge of the quartz crucible before flowing out, which can further increase the airflow velocity.

[0085] In this embodiment of the invention, by setting a first concave area, a second concave area, and a first planar area, a Tesla-like valve principle can be formed between the lower end face of the heat shield and the molten silicon surface. This increases the liquid flow rate and improves airflow permeability, which can remove impurities from the molten silicon surface and increase the volatilization of impurities from the molten silicon surface, thereby reducing the oxygen content of the single crystal silicon rod and improving the stability of crystal pulling.

[0086] Example 1: Single-crystal silicon rods were prepared using the CZ (Czochralski) single-crystal pulling process. The CZ single-crystal pulling process includes stages such as melting, crystal pulling, shoulder formation, equal diameter pulling, and finishing. The single-crystal silicon rod produced during the equal diameter pulling stage is the one required for production. The crystal pulling process parameters used in the equal diameter pulling stage include: argon flow rate 70-100 slpm, furnace pressure 4-10 Pa, crystal rotation speed 8-10 r / min, crucible rotation speed 5-9 r / min, and liquid nozzle distance 10-20 mm. A heat shield designed in this application was used for crystal pulling, and the oxygen content of the equal diameter head was measured.

[0087] Comparative Example 1: Single-crystal silicon rods were prepared using the same Czochralski (CZ) single-crystal pulling process. Comparative Example 1 employed the exact same constant-diameter process, silicon material, and thermal conditions as Example 1. The only difference was that the comparative example used an existing hot-screen structure, which lacks flow channels and compression grooves. After crystal pulling, the oxygen content of the constant-diameter head was measured.

[0088] Data Comparison: After drawing 50 silicon rods, the average oxygen content at the head of the rod under different implementation methods was obtained. Comparative analysis showed that the heat shield solution in Example 1 effectively reduced the oxygen content of the monocrystalline silicon rod 600, with the oxygen content at the head of the monocrystalline silicon rod 600 being reduced by more than 1 ppm compared to the average oxygen content at the head of Comparative Example 1.

[0089] Although preferred embodiments of the present invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of the present invention.

[0090] Finally, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or terminal device that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or terminal device. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or terminal device that includes said element.

[0091] The above provides a detailed description of the heat shield and single crystal furnace provided by this utility model. Specific examples have been used to illustrate the principle and implementation of this utility model. The description of the above embodiments is only for the purpose of helping to understand the method and core idea of ​​this utility model. At the same time, for those skilled in the art, there will be changes in the specific implementation and application scope based on the idea of ​​this utility model. Therefore, the content of this specification should not be construed as a limitation of this utility model.

Claims

1. A heat shield (100), characterized in that, include: The cylindrical body (10) includes a straight cylindrical section (12) and a cylindrical bottom (11) connected to the lower end of the straight cylindrical section (12); the middle of the straight cylindrical section (12) and the cylindrical bottom (11) has a clearance passage (13); Along the axial direction of the straight cylindrical portion (12), the bottom of the cylinder (11) includes an opposing upper end face and a lower end face (112), the upper end face being abutted against the straight cylindrical portion (12); Along the radial direction of the straight cylindrical portion (12), the lower end face (112) includes a first concave region (1121), a second concave region (1122), and a first planar region (1123) connected in sequence, wherein the first planar region (1123) extends to the clearance channel (13) on the side away from the second concave region (1122). The first concave area (1121) is recessed toward the straight cylindrical part (12) to form a compression groove (113); the second concave area (1122) is recessed toward the avoidance channel (13) to form a guide groove (114); the guide groove (114) is connected to the compression groove (113).

2. The heat shield (100) according to claim 1, characterized in that, The compression groove (113) has a depth of h1 along the axial direction of the straight cylindrical portion (12), wherein 2mm≤h1≤200mm; the guide groove (114) has a depth of h2 along the radial direction of the straight cylindrical portion (12), wherein 2mm≤h2≤50mm.

3. The heat shield (100) according to claim 1, characterized in that, The tangent line passing through the connection between the second concave area (1122) and the first planar area (1123), and tangent to the second concave area (1122), forms an angle θ with the plane containing the first planar area (1123), where 0°≤θ≤45°.

4. The heat shield (100) according to claim 1, characterized in that, The bottom of the cylinder (11) includes a first inner wall surface (115) and a first outer wall surface (116) in the radial direction of the straight cylinder (12), the first inner wall surface (115) being used to enclose the clearance channel (13); The lower end face (112) of the bottom (11) of the cylinder is provided with an annular protrusion (117), and a portion of the first concave area (1121) and the first outer wall surface (116) constitute two opposite sides of the annular protrusion (117).

5. The heat shield (100) according to claim 4, characterized in that, Along the axial direction of the straight cylindrical portion (12), the annular protrusion (117) is located away from the end of the straight cylindrical portion (12) and between the straight cylindrical portion (12) and the first planar region (1123); The minimum straight-line distance from the end of the annular protrusion (117) away from the straight cylindrical portion (12) to the first planar region (1123) is ΔH1, where 0 ≤ ΔH1 ≤ 250 mm.

6. The heat shield (100) according to claim 4, characterized in that, Along the axial direction of the straight cylindrical portion (12), the annular protrusion (117) is located away from the end of the straight cylindrical portion (12) and on the side of the first planar region (1123) away from the straight cylindrical portion (12); The minimum straight-line distance from the end of the annular protrusion (117) away from the straight cylindrical part (12) to the first planar area (1123) is ΔH2, 0≤ΔH2≤15mm.

7. The heat shield (100) according to claim 1, characterized in that, The cross-sectional shape of the compression groove (113) or the guide groove (114) parallel to the axial direction of the straight cylindrical part (12) includes at least one of C-shaped, V-shaped and U-shaped.

8. The heat shield (100) according to claim 1, characterized in that, The width of the first planar region (1123) along the radial direction of the straight cylindrical portion (12) is D1, and the outer diameter of the straight cylindrical portion (12) is D2; wherein, 1 / 15≤D1 / D2≤1 / 5.

9. The heat shield (100) according to claim 1, characterized in that, The plane containing the first planar region (1123) is perpendicular to the axis of the straight cylindrical portion (12).

10. The heat shield (100) according to claim 4, characterized in that, The straight cylindrical part (12) is a hollow cylindrical structure with openings at both ends. The straight cylindrical part (12) includes opposing second inner wall surfaces (121) and second outer wall surfaces (122) along its radial direction. The second inner wall surface (121) is used to enclose the avoidance channel (13). The diameter of the first outer wall surface (116) is the same as the diameter of the second outer wall surface (122); The first inner wall surface (115) is connected to the second inner wall surface (121). The first inner wall surface (115) includes an inverted conical surface area. The diameter of the first inner wall surface (115) decreases in the direction away from the second inner wall surface (121).

11. A single crystal furnace, characterized in that, Includes a furnace body, a quartz crucible (200), and a heat shield (100) as described in any one of claims 1-10; The quartz crucible (200) and the heat shield (100) are both disposed inside the furnace body; The heat shield (100) is disposed above the quartz crucible (200), and the heat shield (100) and the quartz crucible (200) are coaxially arranged.

Images