A new oxygen-reducing hot field

Abstract

The application discloses a novel oxygen-reducing hot field, wherein an upper heat preservation barrel is arranged on a middle heat preservation barrel, and the upper heat preservation barrel and the middle heat preservation barrel are coaxially arranged; the inner diameter of the upper heat preservation barrel is the same as that of the middle heat preservation barrel; when the top of a crucible is arranged in the upper heat preservation barrel, a gap between the inner wall of the upper heat preservation barrel and the outer sidewall of the crucible forms a second airflow path, and a gap between the inner wall of the middle heat preservation barrel and the outer sidewall of the crucible forms a first airflow path. The upper heat preservation barrel and the lower heat preservation barrel are coaxially arranged and have the same inner diameter, so that the width of the first airflow path and the second airflow path formed during the lifting of the crucible is kept consistent, the airflow path is not narrowed, the argon flow is not blocked, the gas in the cavities of the upper heat preservation barrel and the lower heat preservation barrel is continuously and efficiently exchanged, the oxygen impurities volatilized from the crystal pulling liquid surface can be timely and sufficiently removed, the oxygen impurity content in the monocrystalline silicon is obviously reduced, and the quality of the monocrystalline silicon is improved.

Description

Technical Field

[0001] This invention relates to crystal pulling processes, and in particular to a novel oxygen-reducing thermal field. Background Technology

[0002] As a core material in industries such as semiconductors and photovoltaics, the quality of monocrystalline silicon directly determines the performance of downstream devices. The oxygen impurity content in monocrystalline silicon is one of the key indicators for evaluating its quality. In the Czochralski process for preparing monocrystalline silicon, the thermal field structure within the furnace not only provides a stable temperature environment for growth, but its accompanying protective gas flow system also plays a crucial role in removing oxygen impurities volatilized from the silicon melt surface and maintaining furnace cleanliness. Therefore, the design of the thermal field structure and the argon gas flow path is essential for reducing the oxygen content of monocrystalline silicon and improving the crystallization rate.

[0003] Existing single crystal furnaces typically have insulation components such as upper and middle insulation barrels in their hot zone. Argon gas, as a protective gas, is blown from the guide tube to the surface of the silicon melt, carrying away oxygen impurities volatilized from the surface. It then flows along the airflow path between the outer wall of the crucible and the inner walls of the upper and middle insulation barrels, and is finally discharged from the furnace through the bottom exhaust port.

[0004] This traditional airflow path structure can achieve basic impurity removal and thermal insulation effects in the early stages of crystal pulling. However, during the continuous crystal pulling process, the inventors found that its impurity removal and thermal insulation effects would be greatly reduced, affecting the crystal formation effect.

[0005] Through long-term research, the inventors discovered that as the crucible gradually rises, the height of the upper edge of the crucible side gradually exceeds the height of the support ring of the middle insulation barrel. At this point, the airflow path between the crucible side and the upper insulation barrel is drastically narrowed, leading to a series of technical problems: On the one hand, the narrowing of the airflow path directly reduces the argon flow rate, significantly reducing the gas exchange efficiency inside the upper insulation barrel cavity. This makes it impossible to remove the oxygen impurities continuously volatilized from the surface of the silicon melt in a timely and efficient manner, causing oxygen impurities to accumulate in the furnace and ultimately resulting in excessive oxygen content in single-crystal silicon. On the other hand, the flow rate of argon gas suddenly increases after the airflow path narrows. With the surface area of ​​the crucible side remaining unchanged, the heat carried away by argon gas from the crucible side per unit time increases significantly, causing severe disturbances in the thermal field temperature during crystal pulling. This disrupts the stable temperature environment required for single-crystal silicon growth, easily leading to crystal defects, crystal breakage, and other problems, seriously affecting the crystal formation quality and production efficiency of single-crystal silicon. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a novel oxygen-reducing thermal field.

[0007] The objective of this invention is achieved through the following technical solution: a novel oxygen-reducing thermal field, comprising an upper insulating barrel, a middle insulating barrel, and a crucible side. The crucible side is located within the inner cavity of the middle insulating barrel, and its bottom is supported by a rotating lifting device. A crucible is placed inside the crucible side, containing a liquid for crystal pulling. The surface of the crystal pulling liquid in the crucible is maintained within a certain range under the lifting action of the rotating lifting device. The upper insulating barrel is placed on the middle insulating barrel, and the upper and middle insulating barrels are coaxially positioned. The inner diameter of the upper insulating barrel is the same as that of the middle insulating barrel. When the top of the crucible side enters the upper insulating barrel, the gap between the inner wall of the upper insulating barrel and the outer wall of the crucible side forms a second airflow path L2. The gap between the inner wall of the middle insulating barrel and the outer wall of the crucible side forms a first airflow path L1. The widths of the first airflow path L1 and the second airflow path L2 are consistent.

[0008] Optionally, insulation layers are installed on the outer walls of both the upper and middle insulation barrels.

[0009] Optionally, the joint between the upper and middle insulation buckets is a sealed structure, and the joint surface is a smooth, flat, and fitted structure.

[0010] Optionally, the first airflow path L1 and the second airflow path L2 are argon gas flow channels. When the top of the crucible side enters the upper insulation barrel, the argon gas flows through the second airflow path L2 and the first airflow path L1 in sequence and is discharged from the exhaust port at the bottom of the furnace body.

[0011] Optionally, a heating ring is also embedded inside the insulated container.

[0012] Optionally, the inner wall of the heating ring is flush with the inner wall of the central insulation barrel.

[0013] Optionally, the level of the crystal pulling liquid is located between the upper and lower surfaces of the heating ring.

[0014] The present invention has the following advantages: 1. The oxygen-reducing thermal field of the present invention has an upper and lower insulation barrel that are coaxial and have the same inner diameter. This ensures that the width of the first and second airflow paths formed during the lifting and lowering of the crucible sides remains consistent, avoiding the problem of narrowing of the airflow path throughout the process. This ensures that the argon flow is unobstructed and achieves continuous and efficient exchange of gas inside the upper and lower insulation barrels. This can promptly and fully remove oxygen impurities volatilized from the crystal pulling liquid surface, significantly reducing the oxygen impurity content in monocrystalline silicon and improving the quality of monocrystalline silicon.

[0015] 2. The oxygen-reducing thermal field of the present invention maintains a constant airflow path width throughout the crystal pulling process, ensuring a stable argon gas flow rate. This avoids the problem of a sudden increase in heat loss per unit time caused by abrupt changes in flow rate in the prior art, effectively reducing thermal field temperature disturbances during crystal pulling, maintaining a stable temperature environment required for monocrystalline silicon growth, reducing crystal defects, crystal breakage, and other problems, and significantly improving the crystallization rate and production efficiency of monocrystalline silicon. 3. The oxygen-reducing thermal field of the present invention eliminates the central insulation support ring. By embedding the heating ring on the central insulation barrel and making the inner wall of the heating ring flush with the inner wall of the central insulation barrel, the argon gas flow path is not affected by the heating ring. Moreover, the width of the first flow path L1 can be selected according to actual needs, thereby ensuring the heat utilization rate and reducing energy consumption. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure during the initial crystal pulling stage of the present invention; Figure 2 This is a schematic diagram of the structure during the later stage of crystal pulling in this invention; Figure 3 A schematic diagram of the structure of the heat preservation barrel with the heating ring embedded in it; In the diagram, 1-upper insulation barrel, 2-middle insulation barrel, 3-crucible side, 4-rotating lifting device, 5-insulation layer, 6-crystal pulling liquid surface, 7-heating ring. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0018] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this invention can be combined with each other.

[0020] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0021] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used for the convenience of describing this invention and simplifying the description, and do not 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 invention. In addition, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0022] In the description of this invention, it should also be noted that, unless otherwise explicitly specified and limited, the terms "set," "install," "connect," and "link" 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 invention based on the specific circumstances.

[0023] like Figure 1 and Figure 2As shown, a novel oxygen-reducing thermal field includes an upper insulating barrel 1, a middle insulating barrel 2, and a crucible side 3. Insulation layers 5 are installed on the outer walls of both the upper insulating barrel 1 and the middle insulating barrel 2 to reduce heat loss. The crucible side 3 is located inside the inner cavity of the middle insulating barrel 2, and its bottom is supported by a rotating lifting device 4. The rotating lifting device 4 is existing technology, so its rotation and lifting mechanism will not be described in detail. A crucible is placed inside the crucible side 3, containing a liquid for crystal pulling. In this embodiment, the liquid is molten silicon, and the crystal pulling liquid surface 6 in the crucible is affected by the lifting action of the rotating lifting device 4. The process is maintained within a certain range. That is, as the crystal pulling process continues, the content of molten silicon in the crucible decreases, thus lowering the level of the molten silicon. Since the position of the guide tube remains constant, it is necessary to ensure that the molten silicon level and the position of the guide tube remain relatively constant. At this time, the rotary lifting device 4 will drive the crucible side 3 upwards. As the crucible side 3 gradually rises, when the height of its upper edge exceeds the height of the central support ring, the airflow path between the crucible side 3 and the upper insulation tank 1 instantly narrows, reducing the argon flow rate and decreasing the gas exchange efficiency within the upper insulation tank 1. This is detrimental to removing the molten silicon evaporating from the crystal pulling surface 6. Gas impurities, and because the airflow path between the outer wall of the crucible side 3 and the upper insulation wall narrows during crystal pulling, the airflow velocity increases. With the surface area of ​​the crucible side 3 remaining constant, the amount of heat carried away per unit time increases, causing temperature fluctuations during crystal pulling and affecting crystal formation. Therefore, in this embodiment, the upper insulation barrel 1 is placed on the middle insulation barrel 2, and the upper insulation barrel 1 and the middle insulation barrel 2 are coaxially placed. The inner diameter of the upper insulation barrel 1 is the same as the inner diameter of the middle insulation barrel 2. Therefore, the oxygen-reducing thermal field does not require the middle insulation support ring to support the upper insulation barrel 1; instead, the upper insulation barrel 1 is directly supported by the middle insulation barrel 2. Therefore, when the crucible side... When the top of the argon gas enters the upper insulation container 1, the gap between the inner wall of the upper insulation container 1 and the outer wall of the crucible 3 forms a second airflow path L2, and the gap between the inner wall of the middle insulation container 2 and the outer wall of the crucible 3 forms a first airflow path L1. The widths of the first airflow path L1 and the second airflow path L2 can always remain consistent, thereby avoiding the narrowing of the argon gas flow path, ensuring the flow rate of argon gas, and ensuring the gas exchange efficiency in the cavity of the upper insulation container 1, which facilitates the removal of gas impurities volatilized from the liquid surface. Moreover, the airflow rate will not change, thus making the heat removed per unit time relatively stable and ensuring the crystallization effect.

[0024] In this embodiment, as Figure 1 and Figure 2As shown, the joint between the upper insulation bucket 1 and the middle insulation bucket 2 is a sealed structure, and the joint surface is a smooth flat bonding structure. When the upper insulation bucket 1 is placed on the middle insulation bucket 2, the weight of the upper insulation bucket 1 makes the joint surfaces of the upper insulation bucket 1 and the middle insulation bucket 2 completely bonded. Furthermore, under the action of the insulation layer 5, the upper insulation bucket 1 and the middle insulation bucket 2 have good sealing performance, which can prevent a large amount of heat loss from the joint surface.

[0025] In this embodiment, as Figure 1 and Figure 2 As shown, the first airflow path L1 and the second airflow path L2 are argon gas flow channels. When the top of the crucible side 3 enters the upper insulation barrel 1, the argon gas flows through the second airflow path L2 and the first airflow path L1 in sequence and is discharged from the exhaust port at the bottom of the furnace body, thus forming a continuous and stable argon gas flow loop.

[0026] In this embodiment, as Figure 1 and Figure 2 As shown, the crucible side 3 has a cylindrical structure, and the outer wall of the crucible side 3 is a smooth cylindrical surface. The smooth cylindrical surface can reduce the resistance of argon gas when it flows in the gas flow path, ensure smooth argon gas flow, and avoid sudden changes in local gas flow velocity caused by the unevenness of the outer wall of the crucible side 3, thereby further maintaining the stability of the thermal field temperature. The bottom of the crucible side 3 is a spherical surface, and the top of the rotary lifting device 4 is provided with a ring, so that the crucible side 3 can be automatically aligned and placed on the rotary lifting device 4.

[0027] In this embodiment, the oxygen-reducing thermal field eliminates the central support ring, while the original central support ring serves to support and reduce heat loss. Therefore, after long-term research, the inventors have developed a solution... Figure 3 As shown, a heating ring 7 is embedded inside the intermediate insulation barrel 2. Furthermore, the inner wall of the heating ring 7 is flush with the inner wall of the intermediate insulation barrel 2. Therefore, the distance between the crucible side 3 and the inner wall of the heating ring 7 is the same as the distance of the first airflow path L1. Thus, the airflow path of argon is not affected by the heating ring 7. Moreover, the width of the first airflow path L1 can be selected according to actual needs, thereby ensuring the utilization rate of heat and reducing energy consumption. Preferably, the horizontal height of the crystal pulling liquid surface 6 is located between the upper and lower surfaces of the heating ring 7, so that the heat generated by the heating ring 7 can better act on the silicon melt, further ensuring the utilization rate of heat and reducing energy consumption.

[0028] The working process of this invention is as follows: Figure 1As shown, before the crystal pulling process begins, the crucible is placed inside the crucible side 3. Silicon material is added to the crucible and heated to a molten state, forming a silicon melt. The height of the crucible side 3 is adjusted by the rotating lifting device 4, so that the crystal pulling liquid surface 6 is at a preset initial position. At this time, the top of the crucible side 3 is located inside the middle insulation tank 2. Argon gas is blown from the guide tube to the crystal pulling liquid surface 6 and then discharged along the first airflow path L1 between the lower insulation tank and the crucible side 3, achieving initial oxygen removal. During the continuous crystal pulling process, the rotating lifting device 4 slowly drives the crucible side 3 to rise continuously, and the crystal pulling liquid surface 6 is always maintained within the preset range under the lifting adjustment. Figure 2 As shown, when the top of the crucible side 3 rises to the inner cavity of the upper insulation barrel 1, a second airflow path L2 is formed between the crucible side 3 and the upper insulation barrel 1. Since the upper insulation barrel 1 and the lower insulation barrel have the same inner diameter and are coaxially arranged, the width of the second airflow path L2 is consistent with that of the first airflow path L1. Argon gas flows through the second airflow path L2 and the first airflow path L1 in sequence, and finally exits from the bottom of the furnace body.

[0029] From the initial stage of crystal pulling to the end of the process, the widths of the first gas flow path L1 and the second gas flow path L2 remain constant throughout the entire process. The argon gas flow rate is unobstructed and the flow rate remains stable. This ensures efficient gas exchange within the furnace, effectively removing oxygen impurities, while also preventing thermal field temperature disturbances caused by sudden changes in flow rate. This maintains a stable temperature environment for monocrystalline silicon growth until the crystal pulling process is completed, producing a high-quality monocrystalline silicon rod with low oxygen content.

[0030] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A novel oxygen-reducing thermal field, comprising an upper insulation barrel, a middle insulation barrel, and a crucible side, wherein the crucible side is located within the inner cavity of the middle insulation barrel, and the bottom of the crucible side is supported by a rotating lifting device, a crucible is placed inside the crucible side, the crucible contains a liquid for crystal pulling, and the level of the crystal pulling liquid in the crucible is maintained within a certain range under the lifting action of the rotating lifting device, characterized in that: The upper insulation bucket is placed on the middle insulation bucket, and the upper insulation bucket and the middle insulation bucket are placed coaxially. The inner diameter of the upper insulation bucket is the same as the inner diameter of the middle insulation bucket. When the top of the crucible side enters the upper insulation bucket, the gap between the inner wall of the upper insulation bucket and the outer wall of the crucible side forms a second airflow path L2, and the gap between the inner wall of the middle insulation bucket and the outer wall of the crucible side forms a first airflow path L1. The widths of the first airflow path L1 and the second airflow path L2 are consistent.

2. The novel oxygen-reducing thermal field according to claim 1, characterized in that: Both the upper and middle insulation barrels have insulation layers installed on their outer walls.

3. The novel oxygen-reducing thermal field according to claim 2, characterized in that: The joint between the upper and middle insulation buckets is a sealed structure, and the joint surface is a smooth, flat, and fitted structure.

4. The novel oxygen-reducing thermal field according to claim 3, characterized in that: The first airflow path L1 and the second airflow path L2 are argon gas flow channels. When the top of the crucible side enters the upper insulation barrel, the argon gas flows through the second airflow path L2 and the first airflow path L1 in sequence and is discharged from the exhaust port at the bottom of the furnace body.

5. A novel oxygen-reducing thermal field according to any one of claims 1 to 4, characterized in that: The insulated barrel is also equipped with a heating ring.

6. The novel oxygen-reducing thermal field according to claim 5, characterized in that: The inner wall of the heating ring is flush with the inner wall of the insulated barrel.

7. A novel oxygen-reducing thermal field according to claim 6, characterized in that: The horizontal level of the crystal pulling liquid is located between the upper and lower surfaces of the heating ring.

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