Device for preparing silicon carbide crystals by liquid phase method with uniform flow field

Abstract

The utility model provides a device for preparing silicon carbide crystals by a liquid phase method with a uniform flow field, which comprises a graphite crucible and a seed crystal rod, a notch is arranged on a top plate of the graphite crucible, the lower end of the seed crystal rod extends into an inner cavity of the graphite crucible from the notch of the graphite crucible and is provided with seed crystals, a graphite column is further arranged in the inner cavity of the graphite crucible, and the graphite column is connected with the seed crystal rod. The axial direction of the graphite column extends in the left-right direction and is located below the seed crystal, the left end and the right end of the graphite column are suspended and supported through graphite supports respectively, and the graphite rotating shaft is driven by a driving mechanism to rotate. Compared with the prior art, the graphite crucible has the advantages that the rotatable graphite column is arranged in the inner cavity of the graphite crucible, and the transversely arranged graphite column can generate an upward stream in the rotating process, so that the convection intensity of the center of raw material melt in the graphite crucible can be enhanced; the problem that the produced silicon carbide crystals are not uniform due to non-uniform doping elements is effectively solved. And meanwhile, the graphite column can supplement a carbon source, so that the service life of the graphite crucible is prolonged.

Description

Technical Field

[0001] This utility model relates to the technical field of silicon carbide crystal material growth apparatus, and more specifically to an apparatus for preparing silicon carbide crystals by a liquid phase method with uniform flow field. Background Technology

[0002] Silicon carbide (SiC) is one of the third-generation semiconductor materials, possessing excellent hardness, high melting point, superior thermal conductivity, and corrosion resistance. It is used to manufacture electronic devices operating at high temperatures, high frequencies, and high power, and also plays a significant role in fields such as machinery and aerospace. Due to its excellent chemical and physical properties, silicon carbide is considered one of the important directions for the development of future high-tech materials.

[0003] Due to the advantages of high quality and low cost, silicon carbide crystals grown by liquid phase have received widespread attention in the industry in recent years. Liquid phase growth is a method that utilizes chemical reactions in a molten silicon solution to grow crystals. During the growth process, carbon is dissolved in the molten silicon at high temperatures, and the recrystallization of silicon carbide crystals on the seed crystal growth surface is promoted by controlling the temperature, concentration, and flow rate of the molten silicon.

[0004] In the preparation of silicon carbide crystals, doping with certain elements, such as nitrogen or aluminum, is often required. However, in existing growth apparatuses, the flow field is not uniform enough. At the liquid surface where silicon carbide is grown, the central fluid flow is weak, leading to uneven doping and affecting the quality of crystal growth. Utility Model Content

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus for preparing silicon carbide crystals by liquid phase method with uniform flow field, in order to change the liquid flow rate, achieve more uniform element doping, improve the growth quality of silicon carbide crystals, and at the same time replenish the lost carbon source.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] An apparatus for preparing silicon carbide crystals using a liquid-phase method with uniform flow field includes a graphite crucible and a seed crystal rod. The top plate of the graphite crucible has a slot. The lower end of the seed crystal rod extends from the slot into the inner cavity of the graphite crucible and is provided with a seed crystal. The inner cavity of the graphite crucible is also provided with a graphite column. The axial direction of the graphite column extends in the left-right direction and is located below the seed crystal. The left and right ends of the graphite column are respectively suspended and supported by graphite supports, and the graphite shaft is driven to rotate by a driving mechanism.

[0008] As a preferred embodiment of the above-mentioned device, a first rotating shaft and a second rotating shaft are fixed at the left and right ends of the graphite column, respectively. The first rotating shaft is a rotating shaft that is coaxially and fixedly connected to the graphite column. The second rotating shaft is composed of a first horizontal section, a vertical section, and a second horizontal section connected in sequence. The first horizontal section of the second rotating shaft is coaxially and fixedly connected to the graphite column. The second horizontal section of the second rotating shaft is parallel to the first horizontal section and eccentrically arranged. The graphite supports connected to the first rotating shaft and the second rotating shaft are the first graphite support and the second graphite support, respectively. The first rotating shaft is rotatably supported at the lower end of the first graphite support. The upper end of the first graphite support extends above the graphite crucible and is fixed. The second horizontal section of the second rotating shaft is rotatably supported at the lower end of the second graphite support. The upper end of the second graphite support extends above the graphite crucible and is connected to the output end of the drive mechanism. The drive mechanism drives the second graphite support to perform circular motion, thereby driving the graphite column to rotate through the second rotating shaft.

[0009] As a preferred embodiment of the above-mentioned device, the driving mechanism is a motor, and the output end of the motor is provided with an eccentric output shaft. The eccentric output shaft of the motor is rotatably connected to the upper end of the second graphite support. The eccentric output shaft of the motor drives the second graphite support to make circular motion, thereby driving the graphite column to rotate.

[0010] As a preferred embodiment of the above-mentioned device, the lower end of the first graphite support has a first mounting hole, and the first rotating shaft is rotatably installed in the first mounting hole of the first graphite support; the lower end and the upper end of the second graphite support have a second mounting hole and a third mounting hole, respectively, the second horizontal section of the second rotating shaft is rotatably installed in the second mounting hole of the second graphite support, and the eccentric output shaft of the motor is rotatably connected to the third mounting hole of the second graphite support.

[0011] As a preferred embodiment of the above-mentioned device, the graphite column is located at the center of the crucible cavity along the horizontal plane.

[0012] As a preferred embodiment of the above-mentioned device, the graphite crucible is provided with an insulation layer.

[0013] Compared with existing technologies, the beneficial effects of this utility model are reflected in:

[0014] This invention provides an apparatus for preparing silicon carbide crystals using a liquid-phase method with uniform flow field. By placing a rotatable graphite column inside a graphite crucible, the horizontally positioned graphite column generates an upward flow stream during rotation, thereby enhancing the convection intensity at the center of the molten raw material within the graphite crucible. This avoids the problem of lower convection at the center of the molten raw material compared to the edges during crystal growth, effectively solving the problem of uneven silicon carbide crystal production caused by uneven doping elements. Furthermore, since the graphite column is made of graphite, it can replenish the carbon source, reducing wear and tear on the graphite crucible and extending its service life. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the structure of this utility model.

[0016] Figure 2 This is a schematic diagram of the structure of the graphite column of this utility model, in which both ends are connected to two graphite supports.

[0017] Figure 3 This is a simulation diagram of the flow field of the raw material melt when no graphite column is placed inside the graphite crucible.

[0018] Figure 4 This is a simulation diagram of the flow field of the raw material melt with graphite columns inside the graphite crucible of this utility model.

[0019] The following numbers are labeled in the diagram: 1. Graphite crucible; 2. Insulation layer; 3. Heating coil; 4. Groove; 5. Seed crystal rod; 6. Seed crystal; 7. Graphite column; 8. First rotating shaft; 9. Second rotating shaft; 10. First horizontal section; 11. Vertical section; 12. Second horizontal section; 13. First graphite support; 14. Second graphite support; 15. First mounting hole; 16. Motor; 17. Eccentric output shaft; 18. Second mounting hole; 19. Third mounting hole; 20. Raw material molten liquid. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below in conjunction with the embodiments of this utility model. Obviously, the described embodiments are only some embodiments of this utility model, not all embodiments. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.

[0021] Please refer to Figures 1 to 4 This embodiment provides an apparatus for preparing silicon carbide crystals using a liquid-phase method with uniform flow field. The apparatus includes a graphite crucible 1 and a seed crystal rod 5. The inner cavity of the graphite crucible 1 holds the raw material. An insulation layer 2 is provided outside the graphite crucible 1, and a heating coil 3 is located outside the insulation layer 2. Electromagnetic induction heating is used to melt the raw material inside the graphite crucible 1. A slot 4 is formed on the top plate of the graphite crucible 1. The lower end of the seed crystal rod 5 extends from the slot 4 into the inner cavity of the graphite crucible 1 and is fitted with a seed crystal 6. The seed crystal 6 can be bonded and fixed to the lower end of the seed crystal rod 5. A graphite column 7 is also provided inside the graphite crucible 1. The graphite column 7 is cylindrical, extending axially in the left-right direction and located below the seed crystal 6. The graphite column 7 is located at the center of the crucible's inner cavity along the horizontal plane. The left and right ends of the graphite column 7 are suspended and supported by graphite supports, and a driving mechanism drives the graphite shaft to rotate.

[0022] A first rotating shaft 8 and a second rotating shaft 9 are fixed to the left and right ends of the graphite column 7, respectively. The first rotating shaft 8 is a rotating shaft that is coaxially and fixedly connected to the graphite column 7. The second rotating shaft 9 is composed of a first horizontal section 10, a vertical section 11, and a second horizontal section 12 connected in sequence. The first horizontal section 10 of the second rotating shaft 9 is coaxially and fixedly connected to the graphite column 7. The second horizontal section 12 of the second rotating shaft 9 is parallel to the first horizontal section 10 and eccentrically arranged. The graphite supports connected to the first rotating shaft 8 and the second rotating shaft 9 are a first graphite support 13 and a second graphite support 14, respectively. The first rotating shaft 8 is rotatably supported by the first vertical section 8. The lower end of a graphite support 13 and the upper end of the first graphite support 13 extend above the graphite crucible 1 and are fixed to the top of the insulation layer 2. The lower end of the first graphite support 13 has a first mounting hole 15, and the first rotating shaft 8 is rotatably installed in the first mounting hole 15 of the first graphite support 13. The second horizontal section 12 of the second rotating shaft 9 is rotatably supported at the lower end of the second graphite support 14. The upper end of the second graphite support 14 extends above the graphite crucible 1 and is connected to the output end of the drive mechanism. The drive mechanism drives the second graphite support 14 to make circular motion, thereby driving the graphite column 7 to rotate through the second rotating shaft 9. The driving mechanism is a motor 16, which is mounted on top of the insulation layer 2. An eccentric output shaft 17 is provided on the output end of the motor 16, and this eccentric output shaft 17 is rotatably connected to the upper end of the second graphite support 14. The lower and upper ends of the second graphite support 14 are respectively provided with a second mounting hole 18 and a third mounting hole 19. The second horizontal section 12 of the second rotating shaft 9 is rotatably mounted in the second mounting hole 18 of the second graphite support 14, and the eccentric output shaft 17 of the motor 16 is rotatably connected to the third mounting hole 19 of the second graphite support 14. The eccentric output shaft 17 of the motor 16 drives the second graphite support 14 to perform circular motion, thereby causing the graphite column 7 to rotate. The rotational speed of the graphite column 7 can be controlled by the motor 16. By setting the eccentricity of the eccentric output shaft 17 of the motor 16 to be equal to the eccentricity of the second rotating shaft 9, the circular motion of the eccentric output shaft 17 of the motor 16 can be transmitted to the second rotating shaft 9 through the second graphite bracket 14, pushing the second horizontal section 12 of the second rotating shaft 9 to make the same circular motion, thereby driving the graphite column 7 to rotate around its own axis through the eccentric second rotating shaft 9.

[0023] In this device, the graphite crucible 1 provides the main carbon source. However, since the graphite column 7 is also composed of graphite, it can provide carbon elements to the center of the flow field while the graphite column 7 rotates to obtain a uniform flow field. As a supplementary carbon source, it can reduce the demand for carbon source from the graphite crucible 1, reduce the wear of the graphite crucible 1, and thus improve the service life of the graphite crucible 1.

[0024] During operation, heating coil 3 is energized at a frequency of approximately 2kHz. The raw material inside graphite crucible 1 is heated and melted via medium-frequency induction heating, forming a raw material molten liquid 20. The seed crystal 6 at the bottom of the seed crystal rod 5 contacts and rotates with the raw material molten liquid 20, thus growing silicon carbide crystals. Simultaneously, graphite column 7 is immersed in the raw material molten liquid 20. Motor 16 is started, and its eccentric output shaft 17 drives the second graphite support 14 to perform circular motion. The second graphite support 14 transmits this circular motion to the second horizontal section 12 of the second rotating shaft 9, causing the second horizontal section 12 to perform circular motion. Because the second horizontal section 12 of the second rotating shaft 9 is eccentrically positioned with respect to the graphite column 7, the graphite column 7 rotates around its own axis. The graphite column 7 can be controlled by motor 16 to rotate around its own axis at a speed of 2-10 RPM. During the rotation of the graphite column 7, an upward flow stream is generated, which strengthens the convection intensity at the center of the raw material melt 20 in the graphite crucible 1. This solves the problem that the flow rate of the raw material melt 20 at the center of the graphite crucible 1 is lower than that at the edge. This can improve the problem of non-uniformity of silicon carbide crystals caused by uneven doping elements, thereby improving the uniformity of silicon carbide crystal growth and the quality of silicon carbide crystal growth.

[0025] See Figure 3 In traditional devices, the graphite crucible 1 does not contain graphite pillars 7. The flow rate of the silicon carbide melt in the middle of the graphite crucible 1 is significantly lower than that at the two edges, which may lead to uneven silicon carbide doping.

[0026] See Figure 4 In this embodiment, a rotatable graphite column 7 is set in the graphite crucible 1. The graphite column 7 rotates around its own axis at a speed of 2 to 10 RPM. The raw material molten liquid 20 rises from the center and moves to the left and right edges after reaching the vicinity of the liquid surface. After reaching the edge, the fluid velocity increases significantly under the action of gravity, which is the reason for the stronger fluid velocity on both sides. After introducing the rotatable graphite column 7, the upward momentum of the raw material molten liquid 20 can be significantly improved. Therefore, the fluid intensity in the center of the raw material molten liquid 20 can be improved, which improves the problem of slow fluid velocity in the middle of the silicon carbide molten liquid and makes the fluid velocity in the entire raw material molten liquid 20 more uniform, thereby improving the quality of silicon carbide production.

[0027] The above are merely preferred embodiments of the present utility model and are not intended to limit the present utility model. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present utility model should be included within the protection scope of the present utility model.

Claims

1. An apparatus for preparing silicon carbide crystals using a liquid-phase method with uniform flow field, comprising a graphite crucible and a seed crystal rod, wherein a slot is formed on the top plate of the graphite crucible, and the lower end of the seed crystal rod extends from the slot into the inner cavity of the graphite crucible and is provided with a seed crystal, characterized in that: The inner cavity of the graphite crucible is also provided with graphite pillars. The graphite pillars extend axially in the left-right direction and are located below the seed crystal. The left and right ends of the graphite pillars are respectively suspended and supported by graphite supports, and the graphite shaft is driven to rotate by a drive mechanism.

2. The apparatus for preparing silicon carbide crystals using a liquid-phase method with a uniform flow field as described in claim 1, characterized in that: The graphite column is fixed with a first rotating shaft and a second rotating shaft at its left and right ends, respectively. The first rotating shaft is fixedly connected to the graphite column coaxially. The second rotating shaft is composed of a first horizontal section, a vertical section, and a second horizontal section connected in sequence. The first horizontal section of the second rotating shaft is fixedly connected to the graphite column coaxially. The second horizontal section of the second rotating shaft is parallel to the first horizontal section and eccentrically set. The graphite supports connected to the first and second rotating shafts are the first graphite support and the second graphite support, respectively. The first rotating shaft is rotatably supported at the lower end of the first graphite support. The upper end of the first graphite support extends above the graphite crucible and is fixed. The second horizontal section of the second rotating shaft is rotatably supported at the lower end of the second graphite support. The upper end of the second graphite support extends above the graphite crucible and is connected to the output end of the drive mechanism. The drive mechanism drives the second graphite support to perform circular motion, thereby driving the graphite column to rotate through the second rotating shaft.

3. The apparatus for preparing silicon carbide crystals using a liquid-phase method with a uniform flow field as described in claim 2, characterized in that: The driving mechanism is a motor, and the output end of the motor is provided with an eccentric output shaft. The eccentric output shaft of the motor is rotatably connected to the upper end of the second graphite support. The eccentric output shaft of the motor drives the second graphite support to make circular motion, thereby driving the graphite column to rotate.

4. The apparatus for preparing silicon carbide crystals using a liquid-phase method with a uniform flow field as described in claim 3, characterized in that: The first graphite support has a first mounting hole at its lower end, and the first rotating shaft is rotatably installed in the first mounting hole of the first graphite support; the second graphite support has a second mounting hole and a third mounting hole at its lower and upper ends, respectively, and the second horizontal section of the second rotating shaft is rotatably installed in the second mounting hole of the second graphite support; the eccentric output shaft of the motor is rotatably connected to the third mounting hole of the second graphite support.

5. The apparatus for preparing silicon carbide crystals using a liquid-phase method with a uniform flow field as described in any one of claims 1 to 4, characterized in that: The graphite column is located at the center of the crucible cavity along the horizontal plane.

6. The apparatus for preparing silicon carbide crystals using a liquid-phase method with a uniform flow field as described in any one of claims 1 to 4, characterized in that: The graphite crucible is provided with an insulation layer.

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