Crucible and polycrystalline silicon ingot furnace
By coating the combined coating of high-purity silicon dioxide and silicon nitride layer on the inner wall of the crucible, the problem of decomposition and fall off of the silicon nitride layer during the polycrystalline silicon ingot is solved, and a better anti-stick pot effect and silicon material purity are achieved.
Patent Information
- Application Number
- CN202422273286.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-14
- Publication Date
- 2025-07-04
- Estimated Expiration
- 2034-09-14
AI Technical Summary
During the polycrystalline silicon ingot, the silicon nitride layer in the solid-liquid boundary area is prone to decomposition and fall off, causing the silicon material to react in contact with the silicon dioxide in the crucible body or high-purity layer, causing the problem of sticking the pot.
The inner wall of the crucible is coated with a first coating composed of a first high-purity silicon dioxide layer and a protective layer. The protective layer is a silicon nitride layer covering the solid-liquid boundary area, and the second coating is also a silicon nitride layer to increase the thickness and adhesion of the silicon nitride layer and prevent sticking to the pot.
It effectively prevents silicon material from contacting and reacting with silicon dioxide in the crucible body or high-purity layer, reduces the phenomenon of sticking to the pot, and improves the purity and production efficiency of polycrystalline silicon ingots.
Smart Images
Figure CN223061133U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of polysilicon ingot production equipment, in particular to a crucible and a polysilicon ingot furnace. Background Art
[0002] In the process of polysilicon ingot casting, in order to prevent impurities in the crucible body from entering the silicon material in the crucible and causing contamination, a high-purity layer is usually coated on the inner wall of the crucible body as an isolation layer, and the high-purity layer is high-purity silicon dioxide. However, under the process conditions of polysilicon purification, the silicon material in the crucible is likely to react with the silicon dioxide in the high-purity layer, resulting in sticking to the crucible.
[0003] In related technologies, in order to solve the problem of sticking to the crucible caused by the reaction between the silicon material in the crucible and the silicon dioxide in the high-purity layer, a silicon nitride layer is usually coated on the inner wall of the crucible to prevent sticking. However, the silicon nitride layer in the solid-liquid boundary region is likely to decompose under the process conditions of polysilicon purification, resulting in thinning or even disappearance of the silicon nitride layer, and the silicon nitride layer in the solid-liquid boundary region cannot play a sufficient role in preventing sticking; moreover, the silicon nitride layer in the solid-liquid boundary region is likely to fall off from the high-purity layer. Therefore, improvement is needed. Summary of the Utility Model
[0004] The utility model aims to at least solve one of the technical problems existing in the prior art. For this purpose, an object of the utility model is to provide a crucible, the inner wall of the crucible body is covered with a coating, the coating includes a first coating and a second coating stacked along the thickness direction of the coating. By making the first coating include a protective layer covering the solid-liquid boundary region, and making both the protective layer and the second coating be silicon nitride layers, the thickness of the silicon nitride layer in the solid-liquid boundary region can be increased, so that after partial decomposition of the silicon nitride layer in the solid-liquid boundary region under the process conditions, there is still enough thickness left, which can better prevent the silicon material in the crucible from contacting and reacting with the silicon dioxide in the crucible body or the high-purity layer, resulting in sticking to the crucible; by making the protective layer be a silicon nitride layer and covering the solid-liquid boundary region, the silicon nitride layer in the solid-liquid boundary region can adhere to the relatively rough crucible body with greater adhesion, so that the coating in the solid-liquid boundary region is not easy to fall off.
[0005] The utility model also provides a polysilicon ingot furnace including the above-mentioned crucible.
[0006] The crucible according to the first aspect embodiment of the present utility model is used in a polysilicon ingot casting furnace and includes: a crucible body; a coating, the coating is provided on the inner wall surface of the crucible body and includes a first coating and a second coating stacked along the thickness direction of the coating, the first coating is located between the inner wall surface of the crucible body and the second coating, the first coating includes a first high-purity layer and a protective layer, the protective layer is located above the first high-purity layer, the first high-purity layer is a high-purity silicon dioxide layer, the protective layer and the second coating are both silicon nitride layers, the crucible has a first height position line and a second height position line, the first height position line is located above the second height position line, the first height position line refers to the material level line when the silicon material contained in the crucible is in a solid state, the second height position line refers to the liquid level line when the silicon material contained in the crucible is in a liquid state, the inner wall surface of the crucible body includes a solid-liquid boundary region, the solid-liquid boundary region is in the shape of a ring extending along the circumferential direction of the crucible, the upper boundary line of the solid-liquid boundary region is the first height position line, the lower boundary line of the solid-liquid boundary region is the second height position line, and the protective layer covers the solid-liquid boundary region.
[0007] For the crucible according to the embodiment of the present utility model, the inner wall of the crucible is coated with a coating, and the coating includes a first coating and a second coating stacked along the thickness direction of the coating. By including a protective layer in the first coating and making both the protective layer and the second coating be silicon nitride layers, the thickness of the silicon nitride layer can be increased, so that after partial decomposition of the silicon nitride layer under process conditions, there is still enough thickness left to more fully prevent the silicon material from contacting the crucible body or the silicon dioxide in the high-purity layer, resulting in sticking to the pot; by making the protective layer be a silicon nitride layer and covering the solid-liquid boundary region with the protective layer, the silicon nitride layer in the solid-liquid boundary region can adhere to the relatively rough crucible body with a greater adhesion force, making the connection between the crucible body, the protective layer and the second coating tighter, and the coating is not easy to fall off.
[0008] According to some embodiments of the present utility model, the inner wall surface of the crucible body further includes a first extension region, the first extension region is in the shape of a ring extending along the circumferential direction of the crucible, the first extension region is located below the solid-liquid boundary region and extends downward from the lower boundary line of the solid-liquid boundary region, and the protective layer covers the first extension region.
[0009] According to some embodiments of the present utility model, the width of the first extension region in the up-down direction is 30 mm - 60 mm.
[0010] According to some embodiments of the present utility model, the inner wall surface of the crucible body further includes a second extension region, the second extension region is an annular shape extending along the circumferential direction of the crucible, the second extension region is located above the solid-liquid boundary region and extends upward from the upper boundary line of the solid-liquid boundary region, and the protective layer covers the second extension region.
[0011] According to some embodiments of the present utility model, the width of the second extension region in the up-down direction is 50 mm - 80 mm.
[0012] According to some embodiments of the present utility model, the surface roughness of the crucible body is greater than the surface roughness of the first high-purity layer.
[0013] According to some embodiments of the present utility model, the first coating further includes a second high-purity layer, the second high-purity layer is a high-purity silicon dioxide layer, and the second high-purity layer is located above the protective layer and extends upward to the top of the crucible body.
[0014] According to some embodiments of the present utility model, the density of the protective layer is greater than the density of the second coating.
[0015] According to some embodiments of the present utility model, the coating includes a third coating, the third coating is located on the side of the second coating away from the inner wall surface of the crucible body, the part of the second coating covering the protective layer is the boundary coating part, the third coating at least covers the boundary coating part, and the density of one of the third coating and the second coating is less than the density of the protective layer.
[0016] The polysilicon ingot furnace according to the second aspect embodiment of the present utility model includes: a crucible according to the first aspect embodiment of the present utility model.
[0017] The polysilicon ingot furnace according to the embodiment of the present utility model, by including a crucible according to the first aspect embodiment of the present utility model, the first coating in the crucible includes a protective layer covering the solid-liquid boundary region, and making both the protective layer and the second coating be silicon nitride layers, can increase the thickness of the silicon nitride layer in the solid-liquid boundary region and better prevent sticking to the pot; by making the protective layer be a silicon nitride layer and making the protective layer cover the solid-liquid boundary region, the coating in the solid-liquid boundary region is not easy to fall off.
[0018] The additional aspects and advantages of the present utility model will be partly given in the following description, partly will become obvious from the following description, or will be understood through the practice of the present utility model. Description of the Drawings
[0019] The above and / or additional aspects and advantages of the present utility model will become obvious and easy to understand from the description of the embodiments in conjunction with the following drawings, where:
[0020] Figure 1 is a sectional view of a crucible according to some embodiments of the present invention;
[0021] Figure 2 is a sectional view of a crucible according to other embodiments of the present invention.
[0022] Reference numerals:
[0023] 100, crucible;
[0024] 10, crucible body; 11, solid-liquid boundary region; 12, first extension region; 13, second extension region;
[0025] 20, coating; 21, first coating; 22, second coating; 23, first high-purity layer; 24, protective layer; 25, third coating; 26, boundary coating portion; 27, second high-purity layer;
[0026] 30, first height position line; 31, second height position line. Detailed implementation manners
[0027] Embodiments of the present invention will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.
[0028] Reference will be made below to Figure 1 - Figure 2 describe the crucible 100 according to an embodiment of the present invention.
[0029] The crucible 100 according to an embodiment of the first aspect of the present invention, with reference to Figure 1 - Figure 2 , is for a polysilicon ingot furnace and includes: a crucible body 10 and a coating 20.
[0030] Among them, the crucible body 10 is a quartz piece. Since some process conditions, such as the reaction between carbon and silicon dioxide at high temperature, it is not suitable to use a graphite crucible 100. By making the crucible body 10 a quartz piece, the chemical properties of the crucible body 10 can be made more stable, reducing the chemical reactions between the crucible 100 and the coating 20, silicon materials, etc.
[0031] The coating 20 is provided on the inner wall surface of the crucible body 10 and includes a first coating 21 and a second coating 22 stacked along the thickness direction of the coating 20. The first coating 21 is located between the inner wall surface of the crucible body 10 and the second coating 22. The first coating 21 includes a first high-purity layer 23 and a protective layer 24. The protective layer 24 is located above the first high-purity layer 23. The first high-purity layer 23 is a high-purity silica layer, and the protective layer 24 and the second coating 22 are both silicon nitride layers. Among them, the high-purity silica layer is a silica layer with a relatively high purity. The silica in the high-purity silica layer is silica with a total metal impurity content of less than one in one hundred thousand and a single non-metal impurity content of less than one in one hundred thousand. The crucible 100 has a first height position line 30 and a second height position line 31. The first height position line 30 is located above the second height position line 31. The first height position line 30 refers to the material level line when the silicon material contained in the crucible 100 is in a solid state, and the second height position line 31 refers to the liquid level line when the silicon material contained in the crucible 100 is in a liquid state. The inner wall surface of the crucible body 10 includes a solid-liquid boundary region 11. The solid-liquid boundary region 11 is an annular shape extending along the circumferential direction of the crucible 100. The upper boundary line of the solid-liquid boundary region 11 is the first height position line 30, and the lower boundary line of the solid-liquid boundary region 11 is the second height position line 31. The protective layer 24 covers the solid-liquid boundary region 11.
[0032] Since the crucible body 10 may contain impurities such as metal impurities, if the crucible body 10 directly contacts the silicon material in the crucible 100, it will cause impurities to enter the silicon material and contaminate the silicon material, reducing the purity of the silicon ingot. By making the first coating 21 include the first high-purity layer 23 and the first high-purity layer 23 be a high-purity silica layer, it can ensure that the silicon material has sufficient purity and avoid the reduction of the silicon material purity caused by the direct contact between the silicon material and the crucible body 10 containing impurities.
[0033] Under some process conditions, such as in a high-temperature environment, the silicon material in the crucible 100 may react with silica. If the silicon material is directly in contact with the high-purity silica layer and a purification process is carried out, it will cause the silicon material to stick to the high-purity silica layer and be difficult to demold, that is, it will form sticking to the pot. By making the second coating 22 be a silicon nitride layer, the silicon nitride layer does not react with the high-purity silica layer. Therefore, it can reduce the sticking of the silicon material to the pot and reduce the difficulty of the demolding process.
[0034] However, in some purification processes, such as low-pressure processes, the silicon nitride in the silicon nitride layer of the solid-liquid boundary region 11 is liable to decompose. By including a protective layer 24 covering the solid-liquid boundary region 11 in the first coating 21 and making both the protective layer 24 covering the solid-liquid boundary region 11 and the second coating 22 silicon nitride layers, the thickness of the silicon nitride layer in the solid-liquid boundary region 11 can be increased, so that after partial decomposition of the silicon nitride in the solid-liquid boundary region 11 under process conditions, there is still a sufficient thickness remaining in the coating 20, more fully preventing the silicon material in the solid-liquid boundary region 11 from contacting with silicon dioxide and causing sticking to the pot.
[0035] Since silicon nitride is liable to decompose in the solid-liquid boundary region 11, by making the protective layer 24 in the solid-liquid boundary region 11 located on the upper side of the first high-purity layer 23, that is, the silicon nitride layer in the solid-liquid boundary region 11 is thicker, the silicon nitride layer in the solid-liquid boundary region 11 at the position where decomposition is more likely to occur can be made thicker. After partial decomposition of the silicon nitride in the solid-liquid boundary region 11 under process conditions, there can still be a sufficient thickness remaining, and it can more fully prevent the silicon material in the solid-liquid boundary region 11 from contacting with silicon dioxide and sticking to the pot.
[0036] Wherein, the surface roughness of the crucible body 10 can be greater than the surface roughness of the first high-purity layer 23. Since the surface of the first high-purity layer 23 is relatively smooth and the adhesion of silicon nitride is poor, the silicon nitride in the solid-liquid boundary region 11 is liable to fall off from the first high-purity layer 23. By making the protective layer 24 cover the solid-liquid boundary region 11, the silicon nitride in the solid-liquid boundary region 11 can be attached to the relatively rough crucible body 10, with a greater adhesion force, and the coating 20 is not liable to fall off.
[0037] According to the crucible 100 of the embodiment of the present utility model, the inner wall of the crucible body 10 is covered with a coating 20. The coating 20 includes a first coating 21 and a second coating 22 stacked along the thickness direction of the coating 20. By including a protective layer 24 covering the solid-liquid boundary region 11 in the first coating 21 and making both the protective layer 24 and the second coating 22 silicon nitride layers, the thickness of the silicon nitride layer at the position of the solid-liquid boundary region 11 can be increased, so that after partial decomposition of the silicon nitride layer at the position of the solid-liquid boundary region 11 under process conditions, there is still a sufficient thickness remaining, better preventing the silicon material in the crucible 100 from contacting and reacting with silicon dioxide in the crucible body 10 or the high-purity layer and causing sticking to the pot; by making the protective layer 24 a silicon nitride layer and making the protective layer 24 cover the solid-liquid boundary region 11, the silicon nitride layer in the solid-liquid boundary region 11 can be attached to the relatively rough crucible body 10, with a greater adhesion force, making the coating 20 at the position of the solid-liquid boundary region 11 not liable to fall off.
[0038] According to some embodiments of the present utility model, referring to Figure 1 - Figure 2, the inner wall surface of the crucible body 10 further includes a first extension region 12. The first extension region 12 is an annular shape extending along the circumferential direction of the crucible 100. The first extension region 12 is located below the solid-liquid boundary region 11 and extends downward from the lower boundary line of the solid-liquid boundary region 11. The protective layer 24 covers the first extension region 12. During the process of melting silicon material into silicon liquid and performing the purification process, the liquid surface may fluctuate, and the position where the liquid surface is located may not be limited to the solid-liquid boundary region 11. By making the first extension region 12 extend downward from the lower boundary line of the solid-liquid boundary region 11 and covering the first extension region 12 with the protective layer 24, sticking to the pot can be more effectively prevented.
[0039] According to some embodiments of the present invention, referring to Figure 2 , the width of the first extension region 12 in the up-down direction is a, and the value range of a is 30 mm - 60 mm. For example, the width a of the first extension region 12 in the up-down direction can be 30 mm, 35 mm, 40 mm, 45 mm, 50 mm, 60 mm, etc. The width of the first extension region 12 is determined by the range of the fluctuation of the silicon liquid surface. By making the width a range from 30 mm to 60 mm, not only can the protection range of the first extension region be more sufficient, but also the crucible 100 at a deeper part of the silicon liquid can be coated with the first high-purity layer 23, reducing the contamination of the silicon liquid by impurities in the crucible 100 and improving the purity of the silicon ingot.
[0040] According to some embodiments of the present invention, referring to Figure 1 - Figure 2 , the inner wall surface of the crucible body 10 further includes a second extension region 13. The second extension region 13 is an annular shape extending along the circumferential direction of the crucible 100. The second extension region 13 is located above the solid-liquid boundary region 11 and extends upward from the upper boundary line of the solid-liquid boundary region 11. The protective layer 24 covers the second extension region 13. Since the surface of the solid silicon material, such as silicon powder, may not be completely flat during the process of feeding, the surface may not be completely flat during the melting process of the silicon material. By making the second extension region 13 extend upward from the upper boundary line of the solid-liquid boundary region 11 and covering the second extension region 13 with the protective layer 24, the connection between the crucible body 10, the protective layer 24 and the second coating 22 in the second extension region 13 is made more firm, and the coating 20 is not easily peeled off, enabling the protective layer 24 to more fully protect the surface area of the silicon material.
[0041] According to some embodiments of the present invention, referring to Figure 2 , the width of the second extension region 13 in the up-down direction is b, and the value range of b is 50 mm - 80 mm. The range of the second extension region 13 is determined by the range of the unevenness of the silicon material surface. By making the width b of the second extension region in the up-down direction range from 50 mm to 80 mm, it can ensure that the protection range of the second extension region is more sufficient.
[0042] According to some embodiments of the present utility model, with reference to Figure 1 , the first coating 21 further includes a second high-purity layer 27. The second high-purity layer 27 is a high-purity silicon dioxide layer. The second high-purity layer 27 is located above the protective layer 24 and extends upward to the top of the crucible body 10. By making the second high-purity layer 27 located above the protective layer 24 and extending upward to the top of the crucible body 10, the distribution area of the high-purity silicon dioxide layer can be larger and the distribution range can be wider, which can more fully ensure that the silicon material has sufficient purity and prevent impurities in the crucible body 10, such as metal impurities, from entering the silicon material and causing contamination.
[0043] According to some embodiments of the present utility model, with reference to Figure 1 - Figure 2 , the density of the protective layer 24 is greater than the density of the second coating 22. By making the density of the protective layer 24 greater than the density of the second coating 22, the amount of silicon nitride in the protective layer 24 can be relatively sufficient, and after partial decomposition of the protective layer 24 under process conditions, there can still be a sufficient thickness remaining, which can more fully prevent the silicon material from contacting the silicon dioxide in the crucible body 10 or the high-purity silicon dioxide layer and causing sticking to the pot.
[0044] According to some embodiments of the present utility model, with reference to Figure 1 - Figure 2 , the coating 20 includes a third coating 25. The third coating 25 is located on the side of the second coating 22 away from the inner wall surface of the crucible body 10. The part of the second coating 22 covering the protective layer 24 is the boundary coating 20 part, and the third coating 25 at least covers the boundary coating 20 part. The density of one of the third coating 25 and the second coating 22 is less than the density of the protective layer 24. For example, the density of silicon nitride in both the third coating 25 and the second coating 22 is less than the density of silicon nitride in the protective layer 24. By making the density of silicon nitride in one of the third coating 25 and the second coating 22 less than the density of the protective layer 24, under some process conditions, such as low-pressure conditions, a silicon protective film will climb on the loose silicon nitride surface in the solid-liquid boundary region 11. The silicon protective film will protect the silicon nitride and reduce the decomposition of the silicon nitride, which can more fully prevent the silicon material in the solid-liquid boundary region 11 from contacting the silicon dioxide in the crucible body 10 or the high-purity silicon dioxide layer and causing sticking to the pot. Since the silicon nitride layer near the boundary coating 20 part is more likely to decompose, by making the third coating 25 at least cover the boundary coating 20 part, the part where the silicon nitride layer is more likely to decompose can be protected, preventing the silicon nitride layer in the solid-liquid boundary region 11 from decomposing at the part where it is more likely to decompose and causing the silicon material to contact the silicon dioxide in the crucible body 10 or the high-purity silicon dioxide layer and causing sticking to the pot.
[0045] The polysilicon ingot furnace according to the second aspect embodiment of the present utility model includes: the crucible 100 according to the first aspect embodiment of the present utility model.
[0046] According to the polysilicon ingot furnace of the embodiment of the present utility model, by including the crucible 100 according to the embodiment of the first aspect of the present utility model, the first coating 21 in the crucible 100 includes a protective layer 24 covering the solid-liquid boundary region 11, and both the protective layer 24 and the second coating 22 are silicon nitride layers, which can increase the thickness of the silicon nitride layer in the solid-liquid boundary region 11 and better prevent sticking to the pot; by making the protective layer 24 a silicon nitride layer and making the protective layer 24 cover the solid-liquid boundary region 11, the coating 20 in the solid-liquid boundary region 11 is not easily detached.
[0047] In the description of the present utility model, it should be understood that the orientation or positional relationship indicated by 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. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present utility model and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present utility model.
[0048] In the description of the present utility model, the "first feature" and "second feature" may include one or more of such features.
[0049] In the description of the present utility model, the meaning of "a plurality" is two or more.
[0050] In the description of the present utility model, the first feature being "above" or "below" the second feature may include the first and second features being in direct contact, or may include the first and second features not being in direct contact but being in contact through additional features therebetween.
[0051] In the description of the present utility model, the first feature being "above", "above the top" and "on the top" of the second feature includes the first feature being directly above and obliquely above the second feature, or merely indicating that the horizontal height of the first feature is higher than that of the second feature.
[0052] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "schematic embodiments", "examples", "specific examples", or "some examples", etc. means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.
[0053] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the claims and their equivalents.
Claims
1. A crucible, characterized in that, For a polysilicon ingot furnace and comprising: A crucible body, the crucible body being a quartz piece; A coating, the coating being provided on the inner wall surface of the crucible body and comprising a first coating and a second coating stacked along the thickness direction of the coating. The first coating is located between the inner wall surface of the crucible body and the second coating. The first coating comprises a first high-purity layer and a protective layer. The protective layer is located above the first high-purity layer. The first high-purity layer is a high-purity silicon dioxide layer. The protective layer and the second coating are both silicon nitride layers. The crucible has a first height position line and a second height position line. The first height position line is located above the second height position line. The first height position line refers to the material level line when the silicon material accommodated in the crucible is in a solid state. The second height position line refers to the liquid level line when the silicon material accommodated in the crucible is in a liquid state. The inner wall surface of the crucible body comprises a solid-liquid boundary region. The solid-liquid boundary region is an annular shape extending along the circumferential direction of the crucible. The upper boundary line of the solid-liquid boundary region is the first height position line, and the lower boundary line of the solid-liquid boundary region is the second height position line. The protective layer covers the solid-liquid boundary region.
2. The crucible according to claim 1, wherein The inner wall surface of the crucible body further comprises a first extension region. The first extension region is an annular shape extending along the circumferential direction of the crucible. The first extension region is located below the solid-liquid boundary region and extends downward from the lower boundary line of the solid-liquid boundary region. The protective layer covers the first extension region.
3. The crucible according to claim 2, wherein The width of the first extension region in the vertical direction is 30 mm - 60 mm.
4. The crucible according to claim 1, characterized in that, The inner wall surface of the crucible body further comprises a second extension region. The second extension region is an annular shape extending along the circumferential direction of the crucible. The second extension region is located above the solid-liquid boundary region and extends upward from the upper boundary line of the solid-liquid boundary region. The protective layer covers the second extension region.
5. The crucible according to claim 4, characterized in that, The width of the second extension region in the vertical direction is 50 mm - 80 mm.
6. The crucible according to claim 1, characterized in that, The surface roughness of the crucible body is greater than the surface roughness of the first high-purity layer.
7. The crucible according to claim 1, characterized in that, The first coating further comprises a second high-purity layer. The second high-purity layer is a high-purity silicon dioxide layer. The second high-purity layer is located above the protective layer and extends upward to the top of the crucible body.
8. The crucible according to claim 1, characterized in that, The density of the protective layer is greater than the density of the second coating.
9. The crucible according to any one of claims 1-8, characterized in that, The coating comprises a third coating. The third coating is located on the side of the second coating away from the inner wall surface of the crucible body. The part of the second coating covering the protective layer is the boundary coating part. The third coating at least covers the boundary coating part. The density of one of the third coating and the second coating is less than the density of the protective layer.
10. A polysilicon ingot casting furnace, characterized in that, Comprising: The crucible according to any one of claims 1 - 9.