A gas flow guiding structure for controlling the growth interface of silicon carbide crystals

Abstract

The utility model belongs to silicon carbide crystal preparation technical field relates to a kind of for controlling the airflow guide structure of silicon carbide crystal growth interface, including shell, upper graphite sheet, middle graphite sheet and lower graphite sheet.The utility model utilizes the spherical surface structure of lower graphite sheet lower part to guide the vaporization of edge to center convergence and from multiple third through-holes, when passing through middle graphite sheet, utilize the annular structure of middle graphite sheet to make the vaporization of center fast pass, the vaporization of edge is blocked by multiple second through-holes and slowly pass, finally make the vaporization uniform through multiple first through-holes, so that the vaporization is crystallized on the surface of seed crystal uniformly, avoid the concentration of edge vaporization greater than the concentration of center vaporization caused by the temperature of edge silicon carbide powder higher than the temperature of center silicon carbide powder, make the crystal ingot interface more uniform in the initial stage of crystal growth, improve the stability of silicon carbide crystal growth process.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide crystal preparation technology, and relates to an airflow guiding structure for controlling the growth interface of silicon carbide crystals. Background Technology

[0002] 8-inch silicon carbide crystals are an important foundation of third-generation semiconductor materials and are widely used in fields such as power electronics. The physical vapor transport method, or PVT method, is often used in the production of 8-inch silicon carbide crystals. The silicon carbide powder is sublimated by heating structure, and the vapor is driven to be transported to the seed crystal surface by temperature gradient and concentration gradient, and crystallized to form silicon carbide crystals.

[0003] Currently, the PVT thermal field devices used in existing PVT methods include... Figure 1 As shown, the device includes a graphite crucible, porous graphite, a base, and a heating structure. The base is positioned at the opening of the graphite crucible, and the lower part of the base is used to place a seed crystal. The porous graphite is positioned below the base, and the silicon carbide powder is placed inside the graphite crucible below the porous graphite. The heating structure heats the graphite crucible, causing the silicon carbide powder to sublimate and produce vapors. The porous graphite guides the vapors to the seed crystal for crystallization.

[0004] However, since the pores on porous graphite are uniformly distributed, when heating the graphite crucible, the heat will first be transferred to the silicon carbide powder at the edge, which easily causes the temperature of the silicon carbide powder at the edge to be higher than that of the silicon carbide powder in the center. Using porous graphite as the airflow guiding structure alone will easily lead to the concentration of vaporized material at the edge being greater than that in the center. This will result in the formation of a crystal interface that is thick at the edge and thin at the center in the early stage of crystal growth, which makes the silicon carbide crystal growth process less stable. This unstable growth is very likely to cause quality problems such as crystal cracking and increased dislocation density, thus reducing the quality of silicon carbide crystals. Utility Model Content

[0005] The purpose of this invention is to provide an airflow guiding structure for controlling the growth interface of silicon carbide crystals, which can prevent the concentration of edge vapors from being greater than that of the central vapors, making the concentration distribution of vapors more uniform and improving the stability of the silicon carbide crystal growth process.

[0006] To achieve the above objectives, the technical solution provided by this utility model is as follows: A gas flow guiding structure for controlling the growth interface of silicon carbide crystals, comprising: The outer shell is a cylindrical structure, vertically positioned with openings at both ends; The upper graphite sheet is horizontally set at the upper opening of the outer shell, and multiple first through holes are evenly opened on the upper graphite sheet; The middle layer graphite sheet is horizontally set inside the outer shell. The middle layer graphite sheet has a ring structure and multiple second through holes are evenly opened on the middle layer graphite sheet. The lower graphite sheet is located at the lower opening of the outer shell. The upper part of the lower layer is a planar structure, and the lower part of the lower graphite sheet is an upwardly concave spherical structure. Multiple third through holes are vertically and evenly opened on the lower graphite sheet. The spherical structure at the bottom of the lower graphite sheet guides the vaporized material at the edge to converge toward the center and pass through multiple third through holes. When passing through the middle graphite sheet, the annular structure of the middle graphite sheet allows the vaporized material at the center to pass through quickly, while the vaporized material at the edge passes through slowly due to the obstruction of multiple second through holes. Finally, the vaporized material passes through multiple first through holes evenly.

[0007] The features of this utility model also include: The diameter of multiple third through holes gradually increases from the edge of the lower graphite sheet towards the center.

[0008] The diameter of the third through hole closest to the outermost edge is 1mm to 1.5mm, and the diameter of multiple third through holes increases by 0.5mm.

[0009] The radius of the lower spherical structure of the lower graphite sheet is 250mm~500mm.

[0010] The thickness of the lower graphite sheet at the edge is 30mm~60mm.

[0011] The inner ring diameter of the middle layer graphite sheet is 80mm~120mm, and the diameter of each second through hole is 2.5mm.

[0012] The spacing between the upper and middle graphite sheets is the same as the spacing between the middle and lower graphite sheets, while the spacing between the upper and middle graphite sheets is 40mm to 60mm.

[0013] The outer shell is made of graphite.

[0014] The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to this invention has the following advantages: This invention utilizes the spherical structure at the bottom of the lower graphite sheet to guide the vaporized material at the edge towards the center and through multiple third through-holes. When passing through the middle graphite sheet, the annular structure of the middle graphite sheet allows the vaporized material at the center to pass through quickly, while the vaporized material at the edge passes through slowly due to the obstruction of multiple second through-holes. Ultimately, the vaporized material passes through multiple first through-holes evenly, thereby enabling the vaporized material to crystallize uniformly on the seed crystal surface. This avoids the situation where the temperature of the silicon carbide powder at the edge is higher than that at the center, resulting in a higher concentration of vaporized material at the edge than at the center. This optimizes the ingot interface, making the ingot interface more uniform in the early stage of crystal growth, improving the stability of the silicon carbide crystal growth process, avoiding quality problems such as ingot cracking and increased dislocation density, and ensuring the quality of silicon carbide crystals. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of an existing PVT thermal field device.

[0016] Figure 2 This is a schematic diagram of the main structure of this utility model.

[0017] Figure 3 This is a top view schematic diagram of the overall structure of this utility model.

[0018] Figure 4 This is a schematic diagram of the overall bottom view of the present invention.

[0019] Figure label: 1. Graphite crucible; 2. Base support; 3. Porous graphite; 4. Heating structure; 5. Outer shell; 6. Upper graphite sheet; 7. Middle graphite sheet; 8. Lower graphite sheet; 9. First through hole; 10. Second through hole; 11. Third through hole; 12. Insulation felt. Detailed Implementation

[0020] The technical solutions of this utility model will now be described clearly and in detail with reference to the accompanying drawings. In the description of the embodiments of this utility model, unless otherwise stated, " / " indicates "or," for example, A / B can mean A or B. "And / or" in the text is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone. Furthermore, in the description of the embodiments of this utility model, "multiple" refers to two or more. The terms "first" and "second" are used for descriptive purposes only and should not be construed as implying or suggesting relative importance or implicitly indicating the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0021] like Figure 1As shown, the existing PVT thermal field device includes a graphite crucible 1, porous graphite 3, a base 2, and a heating structure 4. The heating structure 4 is a resistance heater or an induction coil. When the heating structure 4 is a resistance heater, an insulating felt 12 is provided on the outside of the heating structure 4. When the heating structure 4 is an induction coil, the insulating felt 12 is placed on the graphite crucible 1, and the heating structure 4 is placed on the outside of the insulating felt 12. The base 2 is placed at the opening of the graphite crucible 1, and the lower part of the base 2 is used to place the seed crystal. The porous graphite 3 is placed inside the graphite crucible 1 and below the base 2. The inside of the graphite crucible 1, below the porous graphite 3, is used to place silicon carbide powder. The lower part of the porous graphite 3 is in contact with the silicon carbide powder. The heating structure 4 heats the graphite crucible, causing the silicon carbide powder to sublimate and produce vapors. The porous graphite 3 guides the vapors to the seed crystal for crystallization.

[0022] like Figure 2 , Figure 3 , Figure 4As shown, in order to solve the problem that the concentration of edge gaseous material is greater than the concentration of central gaseous material in the porous graphite 3 guiding gaseous material in the existing PVT hot field device, this utility model provides an airflow guiding structure for controlling the silicon carbide crystal growth interface. This structure is installed inside the graphite crucible 1 to replace the porous graphite 3. It includes an outer shell 5, an upper graphite sheet 6, a middle graphite sheet 7, and a lower graphite sheet 8. The outer shell 5 is a cylindrical structure, vertically arranged with openings at both ends. The outer shell 5 is located inside the graphite crucible 1 and below the base 2. The upper graphite sheet 6 is horizontally arranged at the upper opening of the outer shell 5. Multiple first through holes 9 are evenly distributed on the upper graphite sheet 6. The middle graphite sheet 7 is water-filled... The middle graphite sheet 7 is a ring structure, and multiple second through holes 10 are evenly opened on the middle graphite sheet 7. The lower graphite sheet 8 is set at the lower opening of the outer shell 5. The upper part of the lower layer is a planar structure, and the lower part of the lower graphite sheet 8 is an upwardly concave spherical structure. Multiple third through holes 11 are evenly opened vertically on the lower graphite sheet 8. The spherical structure of the lower part of the lower graphite sheet 8 guides the vaporized material at the edge to converge towards the center and pass through the multiple third through holes 11. When passing through the middle graphite sheet 7, the ring structure of the middle graphite sheet 7 allows the vaporized material in the center to pass through quickly, while the vaporized material at the edge passes through slowly after being blocked by the multiple second through holes 10, and finally passes through the multiple first through holes 9 evenly. This invention utilizes the spherical structure at the bottom of the lower graphite sheet 8 to guide the vaporized material at the edge to converge toward the center and pass through multiple third through holes 11. When passing through the middle graphite sheet 7, the annular structure of the middle graphite sheet 7 allows the vaporized material at the center to pass through quickly, while the vaporized material at the edge passes through slowly after being blocked by multiple second through holes 10. Finally, the vaporized material passes through multiple first through holes 9 evenly. This invention utilizes the spherical structure at the bottom of the lower graphite sheet 8 to guide the vaporized material at the edge towards the center and through multiple third through holes 11. When passing through the middle graphite sheet 7, the annular structure of the middle graphite sheet 7 allows the vaporized material at the center to pass through quickly, while the vaporized material at the edge passes through slowly due to the obstruction of multiple second through holes 10. Ultimately, the vaporized material passes through multiple first through holes 9 evenly, thereby allowing the vaporized material to act uniformly on the seed crystal surface for crystallization. This avoids the situation where the temperature of the silicon carbide powder at the edge is higher than that at the center, resulting in a higher concentration of vaporized material at the edge than at the center. This optimizes the ingot interface, making the ingot interface more uniform in the early stage of crystal growth, improving the stability of the silicon carbide crystal growth process, avoiding quality problems such as ingot cracking and increased dislocation density, and ensuring the quality of silicon carbide crystals.

[0023] like Figure 2 , Figure 4 As shown, the diameter of the multiple third through holes 11 gradually increases from the edge of the lower graphite sheet 8 toward the center, so that more gaseous material passes through the third through hole 11 near the center, further promoting the gaseous material to converge toward the center.

[0024] like Figure 2 , Figure 4 As shown, the diameter of the third through hole 11 near the outermost edge is 1mm~1.5mm, and the diameter of the multiple third through holes 11 increases by 0.5mm, which further increases the effect of the gasified material converging towards the center.

[0025] like Figure 2 , Figure 4 As shown, the radius of the lower spherical structure of the lower graphite sheet 8 is 250mm~500mm, which facilitates the convergence of vaporized material at the edge towards the center.

[0026] like Figure 2 As shown, the thickness of the edge of the lower graphite sheet 8 is 30mm~60mm.

[0027] like Figure 2 As shown, the inner ring diameter of the middle graphite sheet 7 is 80mm~120mm, the diameter of each second through hole 10 is 2.5mm, and the distance between two adjacent second through holes 10 is 2.5mm, so that the passage speed of the central gasified material is greater than the passage speed of the edge gasified material.

[0028] like Figure 2 As shown, the spacing between the upper graphite sheet 6 and the middle graphite sheet 7 is the same as the spacing between the middle graphite sheet 7 and the lower graphite sheet 8. The spacing between the upper graphite sheet 6 and the middle graphite sheet 7 is 40mm~60mm.

[0029] like Figure 2 As shown, the diameter of each first through hole 9 is 2mm, the spacing between two adjacent first through holes 9 is 2mm, and the thickness of the upper graphite sheet 6 and the middle graphite sheet 7 is 5mm.

[0030] The outer shell 5 is made of graphite material.

[0031] Working principle: In use, the airflow guiding structure of this invention replaces the porous graphite 3 in the existing PVT hot field device, so that the spherical structure of the lower graphite sheet 8 comes into contact with the silicon carbide powder. The heating structure 4 is activated to heat the graphite crucible 1. The silicon carbide powder sublimates to form vapors. The spherical structure at the bottom of the lower graphite sheet 8 guides the vapors at the edge to converge towards the center and pass through multiple third through holes 11. When passing through the middle graphite sheet 7, the annular structure of the middle graphite sheet 7 allows the vapors at the center to pass through quickly, while the vapors at the edge pass through slowly due to the obstruction of multiple second through holes 10. Finally, the vapors pass through multiple first through holes 9 evenly, so that the vapors act evenly on the surface of the seed crystal for crystallization. At the same time, the lower graphite sheet 8, the middle graphite sheet 7 and the upper graphite sheet 6 can also filter carbon-based impurity particles, preventing carbon-based impurity particles from adhering to the seed crystal with the vapors and being wrapped inside the growing silicon carbide crystal.

[0032] It is understood that this utility model has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of this utility model. Furthermore, under the teachings of this utility model, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this utility model are protected by this utility model.

Claims

1. A gas flow deflector structure for controlling the growth interface of silicon carbide crystals, characterized by, include: The outer shell (5) is a cylindrical structure, and the outer shell (5) is vertically arranged with open structures at both ends; The upper graphite sheet (6) is horizontally set at the upper opening of the outer shell (5), and a plurality of first through holes (9) are uniformly opened on the upper graphite sheet (6). The middle layer graphite sheet (7) is horizontally arranged inside the outer shell (5). The middle layer graphite sheet (7) has a ring structure and multiple second through holes (10) are uniformly opened on the middle layer graphite sheet (7). The lower graphite sheet (8) is set at the lower opening of the outer shell (5). The upper part of the lower layer is a planar structure, and the lower part of the lower graphite sheet (8) is an upwardly concave spherical structure. Multiple third through holes (11) are vertically and evenly opened on the lower graphite sheet (8). The spherical structure at the bottom of the lower graphite sheet (8) guides the gaseous material at the edge to converge toward the center and pass through multiple third through holes (11). When passing through the middle graphite sheet (7), the annular structure of the middle graphite sheet (7) allows the gaseous material at the center to pass through quickly, while the gaseous material at the edge passes through slowly through multiple second through holes (10), ultimately allowing the gaseous material to pass through multiple first through holes (9) evenly.

2. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The diameter of the plurality of third through holes (11) gradually increases from the edge of the lower graphite sheet (8) toward the center.

3. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 2, characterized in that, The diameter of the third through hole (11) closest to the outermost edge is 1 mm to 1.5 mm, and the diameter of the plurality of third through holes (11) increases by 0.5 mm.

4. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The radius of the lower spherical structure of the lower graphite sheet (8) is 250mm~500mm.

5. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The thickness of the edge of the lower graphite sheet (8) is 30mm~60mm.

6. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The inner ring diameter of the middle layer graphite sheet (7) is 80mm~120mm, and the diameter of each second through hole (10) is 2.5mm.

7. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The spacing between the upper graphite sheet (6) and the middle graphite sheet (7) is the same as the spacing between the middle graphite sheet (7) and the lower graphite sheet (8). The spacing between the upper graphite sheet (6) and the middle graphite sheet (7) is 40mm~60mm.

8. The airflow guiding structure for controlling the growth interface of silicon carbide crystals according to claim 1, characterized in that, The outer shell (5) is made of graphite material.

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