Silicon carbide crystal growth apparatus

Abstract

The embodiment of the utility model relates to silicon carbide preparation technical field provides a kind of silicon carbide crystal growth device, including crucible, first heating mechanism and lifting mechanism;First heating mechanism and crucible coaxial setting;First heating mechanism surrounds outside crucible;First heating mechanism includes multiple turns coaxially arranged annular heater, multiple turns annular heater is evenly distributed in axial direction, multiple turns annular heater presents the trend that diameter gradually increases and then reduces in axial direction, from top to bottom, the largest annular heater of diameter is located 1 / 3~2 / 3 at the height of crucible;Lifting mechanism is set to the lower portion of crucible and is connected with crucible for controlling the up-and-down movement of crucible.The growth device can improve the problem of poor interface shape of existing growth device for preparing silicon carbide crystal.

Description

Technical Field

[0001] This utility model relates to the field of silicon carbide preparation technology, and more specifically, to a silicon carbide crystal growth apparatus. Background Technology

[0002] The resistance heating PVT method has mature technology and widespread industrial application in the production of 8-inch silicon carbide crystals. Specific heating structures are as follows... Figure 1 As shown in the figure, 1 is the base, 2 is the seed crystal, 3 is the insulation felt, 4 is the resistance heater, 5 is the silicon carbide powder, and 6 is the graphite crucible. The principle of resistance heating for silicon carbide growth is that the resistance heater heats the silicon carbide powder in the crucible to its volatilization temperature, causing it to diffuse to the low-temperature seed crystal at the top, where it deposits and grows into a single silicon carbide crystal on the carbon surface of the seed crystal. Due to heat conduction issues, the silicon carbide powder closer to the resistance heater receives more heat than that further away, resulting in an uneven radial temperature distribution in PVT resistance heating. This phenomenon can be explained through simulation. From the above analysis, it can be concluded that resistance heating for large-size growth exhibits a temperature distribution characteristic of low temperature in the central region and high temperature at the edges. The principle of crystal growth is that the silicon carbide powder volatilizes upon encountering high temperatures, diffuses to the low-temperature region of the top seed crystal, and then sublimates to form a silicon carbide crystal. Figure 2 The mesotherm clearly shows a higher temperature at the edges and a lower temperature at the center. When heated, the silicon carbide powder in the edge region vaporizes and evaporates first during the initial crystal growth stage, reaching the seed crystal at the edge. The crystal growth rate is faster in the early stages, while the lower temperature in the center results in less powder evaporation and slower crystal growth. Therefore, a crystal interface with a thicker edge and thinner center is easily formed in the early stages of crystal growth. After the crystal growth experiment, the silicon carbide powder distribution shows black edges and a grayish-white center. The blackened edges represent silicon carbide that has already participated in the reaction, and its main component is carbon, hence the black color. The grayish-white center represents silicon carbide powder that has partially participated in the reaction, hence its grayish-white color. The experimental silicon carbide powder distribution shows an uneven temperature distribution within the powder during crystal growth.

[0003] After a period of further crystal growth, the powder at the edges has completely reacted, while the remaining powder in the central area continues to react. This results in the crystal growth rate gradually increasing in the center and decreasing at the edges during the later stages of crystal growth. Consequently, the interface changes from concave to convex, and the interface becomes increasingly convex. A more convex interface can cause significant defects. Concave interfaces in the early stages of crystal growth are not the most desirable interface for obtaining high-quality crystals. The crystal growth interface should maintain a slightly convex shape at different stages.

[0004] In summary, current crystal growth processes often result in interfaces that change from concave to convex, and such interface shapes are not optimal for crystal quality.

[0005] In view of this, this utility model is proposed. Utility Model Content

[0006] The purpose of this invention is to provide a silicon carbide crystal growth apparatus that aims to improve at least one of the problems mentioned in the background art.

[0007] The embodiments of this utility model can be implemented as follows:

[0008] In a first aspect, this utility model provides a silicon carbide crystal growth apparatus, including a crucible, a first heating mechanism, and a lifting mechanism;

[0009] The first heating mechanism and the crucible are arranged coaxially; the first heating mechanism surrounds the crucible;

[0010] The first heating mechanism includes multiple ring heaters arranged coaxially. The multiple ring heaters are evenly distributed in the axial direction. The diameter of the multiple ring heaters gradually increases and then decreases in the axial direction, or the diameter gradually increases and then remains constant before decreasing. From top to bottom, the ring heater with the largest diameter is located at 1 / 3 to 2 / 3 of the crucible height.

[0011] The lifting mechanism is located below the crucible and connected to it to control the crucible's up and down movement.

[0012] In an optional embodiment, the outer diameter of the crucible is 300-350 mm; the length of the first heating mechanism in the axial direction is 200-500 mm longer than the length of the crucible in the axial direction; the uppermost annular heater is flush with the top of the crucible; the inner diameter of the largest annular heater in the first heating mechanism is 180-220 mm larger than the outer diameter of the crucible; and the inner diameter of the smallest annular heater in the first heating mechanism is 0-200 mm larger than the outer diameter of the crucible.

[0013] In an optional embodiment, the silicon carbide crystal growth apparatus further includes a second heating mechanism, which is coaxially arranged with the crucible and located below the bottom of the crucible, corresponding to a distance from 0 to 1 / 2 to 3 / 4 times the diameter of the bottom of the crucible.

[0014] In an optional embodiment, the height of the crucible is 250-350 mm, and the distance between the second heating mechanism and the bottom of the crucible is 200-500 mm.

[0015] In an optional embodiment, the silicon carbide crystal growth apparatus further includes a graphite disk assembly located inside the crucible. The graphite disk assembly includes a first disk body, a second disk body, a first isolation rod, and a second isolation rod. The second isolation rod, the second disk body, the first isolation rod, and the first disk body are arranged sequentially from top to bottom. The second isolation rod is disposed between the second disk body and the bottom of the crucible. Multiple through-holes are provided on both the first disk body and the second disk body.

[0016] In an optional embodiment, the length of the first isolation rod is 10-20mm, the length of the second isolation rod is 10-20mm, the thickness of the first disc is 5-10mm, the thickness of the second disc is 10-15mm, the diameter of the first disc is 100-150mm, and the diameter of the second disc is the same as that of the first disc.

[0017] In an optional embodiment, the thickness of the second disc is at least 5 mm thicker than the thickness of the first disc.

[0018] In an optional embodiment, the diameter of the first isolation bar and the second isolation bar is 10~20mm.

[0019] In an optional embodiment, the pore diameter is 1~2mm and the spacing between adjacent pores is 1~2mm.

[0020] In an optional embodiment, the heating element of the annular heater is a graphite ring, with each graphite ring having the same thickness.

[0021] The beneficial effects of the silicon carbide crystal growth apparatus provided in this embodiment of the invention include:

[0022] The silicon carbide crystal growth apparatus provided in this embodiment of the present invention includes a first heating mechanism comprising multiple annular heaters of different diameters, and a lifting mechanism. During the crystal growth process, the crucible is moved and gradually lowered, which can first increase and then decrease the distance between the heater and the crucible, thus balancing the problem of uneven temperature inside the crucible during the crystal growth process, thereby producing silicon carbide crystals with better interface uniformity. Attached Figure Description

[0023] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this utility model and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 A diagram of the thermal field structure of resistance heating in existing technology;

[0025] Figure 2 A cross-sectional schematic diagram of the silicon carbide crystal growth apparatus provided in this embodiment of the present invention;

[0026] Figure 3 This is a schematic diagram of the graphite disk assembly from a first-person perspective.

[0027] Figure 4 This is a schematic diagram of the graphite disk assembly from a second-view perspective.

[0028] Icons: 100-Silicon carbide crystal growth apparatus; 110-Crucible; 120-First heating mechanism; 121-Annular heater; 130-Second heating mechanism; 140-Graphite disk assembly; 141-First disk body; 142-Second disk body; 143-First isolation rod; 144-Second isolation rod; 145-Vacuum vent; 160-Lifting mechanism; 170-Insulation felt; 11-Seed crystal; 12-Powder; 13-Base support. Detailed Implementation

[0029] 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 with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this utility model, and not all embodiments. The components of the embodiments of this utility model described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0030] Therefore, the following detailed description of the embodiments of the present 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 present invention without inventive effort are within the scope of protection of the present invention.

[0031] 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.

[0032] In the description of this utility model, it should be noted that if terms such as "upper," "lower," "inner," or "outer" are used to indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the utility model product is usually placed during use, they are only for the convenience of describing this utility model 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 utility model.

[0033] Furthermore, the terms "first" and "second" are used only to distinguish descriptions and should not be interpreted as indicating or implying relative importance.

[0034] It should be noted that, where there is no conflict, the features in the embodiments of this utility model can be combined with each other.

[0035] like Figure 2As shown, this utility model embodiment provides a silicon carbide crystal growth apparatus 100, including a crucible 110, a first heating mechanism 120, a graphite disk assembly 140, and a lifting mechanism 160.

[0036] The first heating mechanism 120 and the crucible 110 are coaxially arranged; the first heating mechanism 120 surrounds the crucible 110.

[0037] The first heating mechanism 120 includes multiple coaxially arranged annular heaters 121. The multiple annular heaters 121 are evenly distributed in the axial direction. The diameter of the multiple annular heaters 121 gradually increases and then decreases in the axial direction, or gradually increases and then remains constant before decreasing. From top to bottom, the annular heater 121 with the largest diameter is located at 1 / 3 to 2 / 3 of the height of the crucible 110 (this position usually corresponds to the material level of the powder 12).

[0038] The graphite disk assembly 140 is located inside the crucible 110. The graphite disk assembly 140 includes a first disk body 141, a second disk body 142, a first isolation rod 143, and a second isolation rod 144. From top to bottom, the second isolation rod 144, the second disk body 142, the first isolation rod 143, and the first disk body 141 are arranged sequentially. The second isolation rod 144 is located between the second disk body 142 and the bottom of the crucible 110. The first disk body 141 and the second disk body 142 are each provided with a plurality of through vent holes 145.

[0039] The lifting mechanism 160 is located below the crucible 110 and connected to the crucible 110 to control the up and down movement of the crucible 110.

[0040] When growing silicon carbide crystals using the silicon carbide crystal growth apparatus 100 provided in this embodiment, firstly, silicon carbide powder 12 is loaded into the crucible 110, then a base 13 with a seed crystal 11 fixed on top of the crucible 110 is placed on top, and then heating is turned on to grow silicon carbide crystals.

[0041] Multiple annular heaters 121 with different diameters are used, for example, graphite rings of the same thickness. Replacing the traditional S-shaped heater with multiple coaxially arranged annular heaters 121, the different heating diameters at different heights result in different distances of heat radiation from different heights to the center, thus leading to different heat transfer rates from different locations to the center. During silicon carbide crystal growth, the seed crystal 11 is located at the top of the crucible 110, with the top of the crucible 110 flush with the annular heaters 121. Its proximity to the edge of the seed crystal 11 results in a higher temperature at the edge, which reduces the sublimation rate of the vaporized silicon carbide. This controls the high edge growth rate of silicon carbide crystals, thereby mitigating the problem of rapid edge growth and concave interfaces. As the edge powder 12 evaporates further during the later stages of crystal growth, the edge crystal growth rate decreases. At this point, a low edge temperature is required. This application takes this into consideration by setting the crucible 110 to be able to move up and down via the lifting mechanism 160. As the heater diameter increases with downward movement, the distance between the heater and the crucible 110 increases, thereby reducing the temperature. Therefore, as crystal growth progresses and the crucible 110 descends, the distance between the edge of the seed crystal 11 and the annular heater 121 at the same height increases, and the edge temperature decreases. This can alleviate the problem of slowed edge growth rate in the later stages of crystal growth caused by insufficient vaporization of the powder 12.

[0042] Specifically, the lifting mechanism 160 can be a hydraulic cylinder or a pneumatic cylinder, and the piston rod of the hydraulic cylinder or pneumatic cylinder is directly or indirectly connected to the crucible 110 to control the up and down movement of the crucible 110. In this embodiment, a support shaft is provided at the bottom of the crucible 110, and the piston rod is connected to the support shaft. Furthermore, the silicon carbide crystal growth apparatus 100 also includes a heat insulation felt 170 disposed outside the heating device.

[0043] Optionally, the outer diameter of the crucible 110 is 300~350mm, which is the current standard size range for crucibles 110 used in the preparation of silicon carbide crystals.

[0044] Optionally, to ensure the production of silicon carbide crystals with better interface quality, the length of the first heating mechanism 120 in the axial direction is 200-500 mm larger than the length of the crucible 110 in the axial direction, based on the current diameter of the crucible 110. Figure 2 In the first heating mechanism 120, the annular heater 121 at the top is flush with the top of the crucible 110. The inner diameter of the largest annular heater 121 in the first heating mechanism 120 is 180~220mm larger than the outer diameter of the crucible 110, and the inner diameter of the smallest annular heater 121 in the first heating mechanism 120 is 0~200mm larger than the outer diameter of the crucible 110. Figure 2 (s).

[0045] Furthermore, the silicon carbide crystal growth apparatus 100 also includes a second heating mechanism 130, which is coaxially arranged with the crucible 110. The second heating mechanism 130 is located below the bottom of the crucible 110, corresponding to a distance from 0 to 1 / 2 to 3 / 4 times the diameter of the bottom of the crucible 110.

[0046] The second heating mechanism 130 at the bottom serves two purposes: firstly, to directly radiate heat to the center of the powder 12, thereby further reducing the temperature difference between the edge and the center; and secondly, to increase the temperature of the powder 12 at the bottom, thus creating a temperature gradient that gradually decreases from the bottom to the top of the powder 12. This addresses the issue of the temperature distribution in traditional resistance heaters, where the temperature rises first and then falls, and the sublimation of the powder 12 is not uniform. Furthermore, as the bottom gets closer to the bottom heater, the center temperature increases, further balancing the temperature difference between the edge and the center.

[0047] Furthermore, the second heating mechanism 130 may specifically include, for example, at least two sets of concentric heaters.

[0048] Optionally, the height of the crucible 110 is 250~350mm, which is the current standard range for crucible 110 size used in the preparation of silicon carbide crystals.

[0049] Optionally, the distance between the second heating mechanism 130 and the bottom of the crucible 110 is 200~500mm. Figure 2 (H). This distance range allows for the fabrication of silicon carbide crystals with fewer interface defects.

[0050] Optionally, such as Figures 3 to 4 As shown, the silicon carbide crystal growth apparatus 100 also includes a graphite disk assembly 140, which is located inside the crucible 110. The graphite disk assembly 140 includes a first disk body 141, a second disk body 142, a first isolation rod 143, and a second isolation rod 144. From top to bottom, the second isolation rod 144, the second disk body 142, the first isolation rod 143, and the first disk body 141 are arranged sequentially. The second isolation rod 144 is located between the second disk body 142 and the bottom of the crucible 110. Both the first disk body 141 and the second disk body 142 have multiple through-holes 145.

[0051] Due to the high thermal conductivity of graphite (the thermal conductivity of isostatic graphite is 180~200 W / (m·K), while the thermal conductivity of silicon carbide powder 12 is 1.65 W / (m·K)), the graphite disk assembly 140 can help transfer heat to the central area, thus further increasing the temperature of the central area.

[0052] Furthermore, the length of the first isolation bar 143 is 10~15mm ( Figure 4(t1), the length of the second isolation rod 144 is 10~15mm ( Figure 4 (t2), the thickness of the first disc 141 is 5~10mm ( Figure 4 The thickness of the second disc body 142 is 10~15mm (Q). Figure 4 The diameter of the first disc 141 is 100~150mm (in the middle W). Figure 4 (R), the diameter of the second disk 142 is the same as that of the first disk 141.

[0053] It should be noted that the graphite disk assembly 140, including the first disk body 141, the second disk body 142, the first isolation rod 143, and the second isolation rod 144, can be connected as one unit or separate. Alternatively, the first disk body 141 and the first isolation rod 143 can be connected as one unit, and the second disk body 142 and the second isolation rod 144 can be connected as one unit. When the various parts of the graphite disk assembly 140 are not connected as one unit, the various parts can be assembled into the structure defined in this application during the loading process.

[0054] Optionally, the second plate 142 is at least 5 mm thicker than the first plate 141. This improves the heat conduction of the lower part of the second plate 142, further balancing the temperature difference between the bottom and the center.

[0055] Optionally, the diameter of the first isolation bar 143 and the second isolation bar 144 is 10~20mm. Figure 4 (R).

[0056] Optionally, to ensure more uniform gas evaporation, the pore size of pore 145 is 1~2mm. Figure 3 (r), the spacing between adjacent pores 145 is 1~2mm ( Figure 4 in u).

[0057] In summary, the silicon carbide crystal growth apparatus 100 provided in this embodiment of the present invention, due to the arrangement of the first heating mechanism 120 including multiple annular heaters 121 with different diameters, and the arrangement of the lifting mechanism 160, moves the crucible 110 to lower it during the crystal growth process, which can realize that the distance between the heater and the crucible 110 first increases and then decreases, thus balancing the problem of uneven temperature inside the crucible 110 during the crystal growth process, thereby producing silicon carbide crystals with better interface uniformity.

[0058] In a preferred embodiment, the second heating mechanism 130 is provided to further balance the temperature difference between the edge and the center.

[0059] In a preferred embodiment, the graphite disk assembly 140 helps to transfer heat to the central region, thereby further increasing the temperature of the central region, further balancing the temperature difference between the edge and the center, and further improving the morphology of the silicon carbide crystal interface.

[0060] The above are merely specific embodiments of this utility model, but the protection scope of this utility model is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this utility model should be included within the protection scope of this utility model.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, Includes a crucible, a first heating mechanism, and a lifting mechanism; The first heating mechanism and the crucible are coaxially arranged; the first heating mechanism surrounds the crucible. The first heating mechanism includes multiple ring heaters arranged coaxially. The multiple ring heaters are evenly distributed in the axial direction. The diameter of the multiple ring heaters in the axial direction gradually increases and then decreases, or gradually increases and then remains constant before decreasing. From top to bottom, the ring heater with the largest diameter is located at 1 / 3 to 2 / 3 of the height of the crucible. The lifting mechanism is located below the crucible and connected to the crucible to control the crucible's up and down movement.

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The outer diameter of the crucible is 300-350mm; the length of the first heating mechanism in the axial direction is 200-500mm longer than the length of the crucible in the axial direction; the uppermost annular heater is flush with the top of the crucible; the inner diameter of the largest annular heater in the first heating mechanism is 180-220mm larger than the outer diameter of the crucible; and the inner diameter of the smallest annular heater in the first heating mechanism is 0-200mm larger than the outer diameter of the crucible.

3. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The silicon carbide crystal growth apparatus further includes a second heating mechanism, which is coaxially arranged with the crucible and located below the bottom of the crucible, corresponding to a distance from 0 to 1 / 2 to 3 / 4 times the diameter of the bottom of the crucible.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, The height of the crucible is 250-350mm, and the distance between the second heating mechanism and the bottom of the crucible is 200-500mm.

5. The silicon carbide crystal growth apparatus according to claim 4, characterized in that, The silicon carbide crystal growth apparatus further includes a graphite disk assembly located inside the crucible. The graphite disk assembly includes a first disk body, a second disk body, a first isolation rod, and a second isolation rod. From top to bottom, the second isolation rod, the second disk body, the first isolation rod, and the first disk body are arranged sequentially. The second isolation rod is disposed between the second disk body and the bottom of the crucible. Both the first disk body and the second disk body have multiple through-holes.

6. The silicon carbide crystal growth apparatus according to claim 5, characterized in that, The length of the first isolation rod is 10~30mm, the length of the second isolation rod is 10~30mm, the thickness of the first disc is 5~10mm, the thickness of the second disc is 10~15mm, the diameter of the first disc is 100~150mm, and the diameter of the second disc is the same as that of the first disc.

7. The silicon carbide crystal growth apparatus according to claim 6, characterized in that, The thickness of the second disc is at least 5 mm thicker than the thickness of the first disc.

8. The silicon carbide crystal growth apparatus according to claim 6, characterized in that, The diameters of the first and second isolation bars are 10-20 mm.

9. The silicon carbide crystal growth apparatus according to claim 7, characterized in that, The pore diameter is 1~2mm, and the spacing between adjacent pores is 1~2mm.

10. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The heating element of the annular heater is a graphite ring, and each graphite ring has the same thickness.

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