Charging method for optimizing crystal growth interface and preparation method of silicon carbide crystal
By laying graphite columns and porous graphite tubes in the graphite crucible and optimizing the loading method of silicon carbide crystals, the problem of uneven interface caused by uneven temperature distribution in the induction heating method was solved, and better interface morphology and crystal quality were achieved.
Patent Information
- Application Number
- CN202511047609.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-07-29
- Publication Date
- 2025-10-17
AI Technical Summary
When the induction heating method is used to grow silicon carbide crystals, there is an uneven radial temperature distribution, which results in thick edges and thin centers in the early stages of crystal growth, fast growth in the early stages and slow growth at the edges in the middle and late stages, forming an uneven interface and affecting the crystal quality.
Multiple graphite columns are laid in the lower part of the graphite crucible, and graphite tubes with air holes are laid in the upper part. Graphite columns and tubes of different thicknesses are combined to optimize the loading method to control the volatilization amount and temperature distribution of the powder.
By optimizing the charging method, the flatness of the crystal growth interface is improved, the volatilization rate in the central area is reduced, and the interface morphology quality of the crystal ingot is improved.
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Figure CN120797183A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the technical field of silicon carbide crystal preparation, in particular to a loading method for optimizing a crystal growth interface and a silicon carbide crystal preparation method. BACKGROUND
[0002] The PVT method of inductive heating has mature technology and industrial application in the production of 8-inch silicon carbide crystals. The specific heating structure is shown in Figure 1 , wherein 1 is silicon carbide powder, 2 is porous graphite, 3 is a seed crystal, 4 is an induction coil, and 5 is a graphite crucible. The principle of inductive heating of silicon carbide is that the induction coil generates a magnetic field, the magnetic field induces the graphite crucible, an electric current is generated in the graphite crucible, the electric current causes the graphite crucible to heat up, and the crucible becomes a heat source. The heat source heats the silicon carbide powder in the crucible to the evaporation temperature and diffuses to the top low-temperature seed crystal position to deposit and grow into a silicon carbide single crystal on the carbon surface of the seed crystal. Due to the strength of the induction heating magnetic field coil, the graphite parts close to the coil heat up more, and the induction heating of the parts far from the coil is less, so it causes the radial temperature distribution of the PVT inductive heating to be uneven, and the central region far from the induction heating site has a lower temperature. This phenomenon can be explained by simulation, as shown in Figure 2 .
[0003] From the above analysis, it can be concluded that the inductive heating growth of large sizes has the temperature distribution characteristics of low temperature in the center and high temperature at the edge. The principle of crystal growth is that the silicon carbide powder volatilizes when it meets high temperature and diffuses to the top low-temperature seed crystal to sublimate and form a silicon carbide crystal. Figure 2 The high-temperature region caused by inductive heating is in the black dashed box. In the edge region of the powder, the center region is far from the heat source, and the temperature is low. Therefore, the powder in the edge region will first gasify and volatilize to the edge seed crystal at the initial stage of crystal growth, the crystal growth speed is faster at the initial stage of crystal growth, the temperature in the center region is low, the powder volatilization is less, and the crystal growth in the center region is slow. Therefore, a concave interface shape with thick edges and thin center will be easily formed at the initial stage of crystal growth. In order to verify this conclusion, a crystal growth test was conducted using a seed crystal-free bottom support. After 20h of crystal growth test, a concave interface shape with thick edges and thin center was obtained, the middle thickness was 7.40mm, the edge thickness was 8.55mm, and the difference was 1.15mm, which was relatively large. Figure 3 The figure is a distribution diagram of the silicon carbide powder after 20h of test. The black powder in the edge has participated in the reaction, and the main component is carbon, so it appears black. The grayish white powder in the center has participated in the reaction to some extent, and it appears grayish white. The center region is green, which is the original color of the silicon carbide powder and has not yet reacted. This figure also fully proves the reliability of the temperature distribution.
[0004] After further crystal growth for a period of time, the powder at the edge is completely reacted, and the remaining center area is further reacted, so that the center crystal growth rate gradually increases and the edge crystal growth rate gradually decreases in the middle and later stages of crystal growth, so that the interface is concave at the edge and convex, and the interface becomes more and more convex, which causes more defects. The interface in the initial stage of crystal growth is also not the most desired interface for obtaining high-quality crystals. The interface in the initial stage of crystal growth should be a slightly convex interface. Based on the 20h crystal growth test, the multi-crystal crystal is further grown, and the thickness of the middle and edge is 16.00mm and 20.25mm respectively, with a difference of 5.75mm, which is a large difference.
[0005] In summary, the interface shape will change from concave to convex during crystal growth, which is not the best interface for crystal quality. Therefore, the present application is proposed. SUMMARY
[0006] The present application aims to provide a loading method for optimizing the crystal growth interface and a preparation method of silicon carbide crystals, and aims to improve at least one problem mentioned in the background art.
[0007] The present application is implemented as follows: In a first aspect, the present application provides a loading method for optimizing the crystal growth interface, comprising: uniformly laying a plurality of graphite columns in the middle of the lower part of the graphite crucible, and then loading the graphite columns to the top of the graphite columns; uniformly laying a plurality of graphite tubes on the lower part of the loading, and then loading the remaining material; Each graphite tube is provided with a plurality of air holes uniformly distributed on the peripheral wall of the graphite tube.
[0008] In an optional embodiment, the plurality of graphite tubes comprises at least one first-diameter graphite tube and a plurality of second-diameter graphite tubes; The at least one first-diameter graphite tube is arranged at the center of the graphite crucible, and the plurality of second-diameter graphite tubes are arranged around the at least one first-diameter graphite tube; The diameter of each first-diameter graphite tube is greater than that of each second-diameter graphite tube.
[0009] In an optional embodiment, the plurality of graphite columns comprises at least one first-diameter graphite column and a plurality of second-diameter graphite columns; The at least one first-diameter graphite column is arranged at the center of the graphite crucible, and the plurality of second-diameter graphite columns are arranged around the at least one first-diameter graphite column; The diameter of each first-diameter graphite column is greater than that of each second-diameter graphite column.
[0010] In an optional embodiment, when preparing an 8-inch silicon carbide crystal, the inner diameter of the graphite crucible is 230-250mm, and the total loading amount is 3-6kg.
[0011] In an optional embodiment, the inner diameter of the first coarse graphite tube is 15-20 mm, the tube wall thickness is 1-2 mm, and the height is 30-40 mm; the inner diameter of the second coarse graphite tube is 5-10 mm, the tube wall thickness is 1-2 mm, and the height is 30-40 mm.
[0012] In an optional embodiment, the distance between the second coarse graphite tube and the center of the graphite crucible is 100-120 mm, and the distance between the first coarse graphite tube and the center of the graphite crucible is 50-60 mm. When the loading amount is less than 3 kg, the number of the first coarse graphite tube is n, and the number of the second coarse graphite tube is n-(n+2), and n is 1-3. When the loading amount is 3-6 kg, the number of the first coarse graphite tube is m, and the number of the second coarse graphite tube is m-(m+2), and m is 2-5.
[0013] In an optional embodiment, the pore diameter of the air hole is 1-2 mm, and the spacing between adjacent air holes is 1-2 mm.
[0014] In an optional embodiment, the diameter of the first coarse graphite column is 15-20 mm, the diameter of the second coarse graphite column is 5-10 mm, and the height of all the graphite columns is the same, being 90-95 mm.
[0015] In an optional embodiment, the distance between the second coarse graphite column and the center of the graphite crucible is 100-120 mm, and the distance between the first coarse graphite column and the center of the graphite crucible is 50-60 mm. When the loading amount is less than 3 kg, the number of the first coarse graphite column is x, and the number of the second coarse graphite column is x-(x+2), and n is 1-3. When the loading amount is 3-6 kg, the number of the first coarse graphite column is y, and the number of the second coarse graphite column is y-(y+2), and m is 2-5.
[0016] In a second aspect, the application provides a method for preparing silicon carbide crystal, comprising the loading method according to any one of the preceding embodiments.
[0017] The application has the following beneficial effects: The loading method provided by the application can increase the volatilization amount of the central area in the initial growth stage by uniformly laying the graphite tube with air holes on the upper part of the powder, and the porous graphite tube is only added in the central area, so that the volatilization amount of the central area is increased in the later growth stage; in order to avoid the problem of the central area protruding in the middle due to the increase of the volatilization amount of the central area in the later growth stage, the solid graphite column is added in the middle and lower part of the powder, and the solid graphite column mainly plays a role of reducing the loading amount of the powder in the central area, and the radiation area is not increased, so that the volatilization speed of the central area in the middle and later growth stages can be reduced. Therefore, the growth of the silicon carbide crystal after loading by the loading method provided by the application can obtain a crystal ingot with better interface flatness. BRIEF DESCRIPTION OF DRAWINGS
[0018] In order to more clearly illustrate the technical solutions of the embodiments of the application, the following will briefly introduce the drawings needed to be used in the embodiments. It should be understood that the following drawings only show some of the embodiments of the application, and therefore should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can also be obtained without creative labor.
[0019] Figure 1 It is a current PVT induction heating thermal field structure diagram; Figure 2 It is a thermal field temperature distribution simulation diagram; Figure 3 It is a silicon carbide powder diagram after 20h reaction; Figure 4 It is a schematic diagram of the position of the graphite tube and the graphite column in the powder after loading; Figure 5 It is a structure schematic diagram of the graphite tube; Figure 6 It is a practical schematic diagram of placing the graphite column in the middle and lower part of the crucible; Figure 7 It is a practical schematic diagram of placing the graphite tube in the upper part of the crucible.
[0020] Figure legend: 10-graphite column; 11-first thickness graphite column; 12-second thickness graphite column; 20-graphite tube; 21-first thickness graphite tube; 22-second thickness graphite tube; 23-air hole. DETAILED DESCRIPTION
[0021] In order to make the purpose, technical solutions and advantages of the embodiments of the application more clear, the technical solutions in the embodiments of the application will be clearly and completely described below. If the specific conditions are not specified in the embodiments, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.
[0022] The features and performances of the present application are further described in detail below in combination with embodiments.
[0023] As shown in Figure 4 and Figure 5 The present application provides a loading method for optimizing the long crystal interface, comprising: A plurality of graphite columns 10 are evenly laid in the middle of the middle and lower part of the graphite crucible, and then the loading is performed to the top of the graphite columns 10; A plurality of graphite tubes 20 are evenly laid on the lower part of the loading, and then the remaining material is loaded; A plurality of air holes 23 are evenly arranged on the peripheral wall of each graphite tube 20.
[0024] Considering the problem of large volatilization of the powder at the edge of the initial long crystal, a porous area is arranged in the central area of the powder. Because the powder particles are small, the hole will collapse immediately after being dug, so the graphite tube 20 with the air hole 23 is buried in the powder. The radiation area of the graphite tube 20 is increased, the volatilization amount of the central area in the initial long crystal is increased, the speed of the central area in the initial long crystal is increased, and the degree of the concave interface in the initial long crystal is slowed down. If only the porous graphite tube 20 is increased in the central area, the volatilization amount of the central area in the late long crystal will be increased. In addition to the porous graphite tube 20 in the upper part of the powder, the solid graphite column 10 is increased in the middle and lower parts. The solid graphite column 10 mainly plays a role in reducing the amount of powder loading in the central area of the powder, and the radiation area is not increased, so it can play a role in reducing the volatilization speed of the central area in the middle and late long crystal. Therefore, the silicon carbide crystal prepared by the loading method provided by the embodiment of the present application has a better interface morphology.
[0025] Further, the plurality of graphite tubes 20 include at least one first-diameter graphite tube 21 and a plurality of second-diameter graphite tubes 22; the at least one first-diameter graphite tube 21 is arranged at the center of the graphite crucible, and the plurality of second-diameter graphite tubes 22 are arranged around the at least one first-diameter graphite tube 21; the diameter of each first-diameter graphite tube 21 is greater than that of each second-diameter graphite tube 22.
[0026] The volatilization amount of the powder in the center is smaller, and the graphite tube 20 in the center is set to be thicker to better increase the volatilization amount of the powder in the center.
[0027] Further, to better avoid the problem that the volatilization amount of the area in the center is more in the late long crystal, the plurality of graphite columns 10 include at least one first-diameter graphite column 11 and a plurality of second-diameter graphite columns 12; the at least one first-diameter graphite column 11 is arranged at the center of the graphite crucible, and the plurality of second-diameter graphite columns 12 are arranged around the at least one first-diameter graphite column 11; the diameter of each first-diameter graphite column 11 is greater than that of each second-diameter graphite column 12.
[0028] Optionally, when preparing 8-inch silicon carbide crystals, the inner diameter of the graphite crucible is 230-250 mm (for example, 230 mm, 240 mm, or 250 mm), and the total amount of the charge is 3-6 kg (for example, 3 kg, 4 kg, 5 kg, or 6 kg).
[0029] Further, the outer diameter of the first-diameter graphite tube 21 is 15-20 mm (for example, 15 mm, 17 mm, or 20 mm), the tube wall thickness is 1-2 mm (for example, 1 mm, 1.5 mm, or 2 mm), and the height is 30-40 mm (for example, 30 mm, 35 mm, or 40 mm); the inner diameter of the second-diameter graphite tube 22 is 5-10 mm (for example, 5 mm, 7 mm, or 10 mm), the tube wall thickness is 1-2 mm (for example, 1 mm, 1.5 mm, or 2 mm), and the height is 30-40 mm (for example, 30 mm, 35 mm, or 40 mm).
[0030] Further, the distance of the second-diameter graphite tube 22 from the center of the graphite crucible is 100-120 mm (for example, 100 mm, 110 mm, or 120 mm), and the distance of the first-diameter graphite tube 21 from the center of the graphite crucible is 50-60 mm (for example, 50 mm, 55 mm, or 60 mm). When the amount of the charge is less than 3 kg, the number of the first-diameter graphite tubes 21 is n, and the number of the second-diameter graphite tubes 22 is n-(n+2), where n is 1-3. When the amount of the charge is 3-6 kg, the number of the first-diameter graphite tubes 21 is m, and the number of the second-diameter graphite tubes 22 is m-(m+2), where m is 2-5 (for example, 2, 3, 4, or 5).
[0031] When the number of the first-diameter graphite tubes 21 and the number of the second-diameter graphite tubes 22 are the same, to make the interface of the prepared silicon carbide ingot more uniform, the first-diameter graphite tubes 21 and the second-diameter graphite tubes 22 are preferably arranged staggered, i.e., for example, each second-diameter graphite tube 22 is on the crucible diameter line between two adjacent first-diameter graphite tubes 21.
[0032] Optionally, the pore diameter of the air hole 23 is 1-2 mm (for example, 1 mm, 1.5 mm, or 2 mm), and the spacing between adjacent air holes 23 is 1-2 mm (for example, 1 mm, 1.5 mm, or 2 mm).
[0033] Further, to make the silicon carbide crystals have a better interface shape in the later growth stage, the diameter of the first-diameter graphite column 11 is 15-20 mm (for example, 15 mm, 18 mm, or 20 mm), the diameter of the second-diameter graphite column 12 is 5-10 mm (for example, 5 mm, 8 mm, or 10 mm), and the height of all the graphite columns 10 is the same, being 90-95 mm (for example, 90 mm, 93 mm, or 95 mm).
[0034] Further, the distance between the second thickness graphite column 12 and the center of the graphite crucible is 100-120 mm (for example, 100 mm, 110 mm or 120 mm), and the distance between the first thickness graphite column 11 and the center of the graphite crucible is 50-60 mm (for example, 50 mm, 55 mm or 60 mm); When the loading amount is less than 3 kg, the number of the first thickness graphite column 11 is x, the number of the second thickness graphite column 12 is x-(x+2), and n is 1-3 (for example, 1, 2 or 3); When the loading amount is 3-6 kg, the number of the first thickness graphite column 11 is y, the number of the second thickness graphite column 12 is y-(y+2), and m is 2-5 (for example, 2, 3, 4 or 5).
[0035] When the number of the first thickness graphite column 11 and the number of the second thickness graphite column 12 are the same, in order to make the interface of the prepared silicon carbide ingot more uniform, the first thickness graphite column 11 and the second thickness graphite column 12 are preferably arranged staggered, that is, for example, each second thickness graphite column 12 is located on the crucible diameter line between two adjacent first thickness graphite columns 11.
[0036] The embodiment of the present application also provides a preparation method of silicon carbide crystal, which comprises the loading method provided by the embodiment of the present application.
[0037] Embodiment The graphite crucible is provided, and the inner diameter of the graphite crucible is 235 mm; The first thickness graphite column 11 is provided, and the diameter of the first thickness graphite column 11 is 18 mm, and the height of the first thickness graphite column 11 is 93 mm; The second thickness graphite column 12 is provided, and the diameter of the second thickness graphite column 12 is 8 mm, and the height of the second thickness graphite column 12 is 93 mm; The first thickness graphite tube 21 is provided, and the inner diameter of the first thickness graphite tube 21 is 18 mm, the wall thickness of the first thickness graphite tube 21 is 1 mm, the height of the first thickness graphite tube 21 is 35 mm, the pore diameter of the air hole 23 is 1 mm, and the distance between adjacent air holes 23 is 1 mm; The second thickness graphite tube 22 is provided, and the inner diameter of the second thickness graphite tube 22 is 8 mm, the wall thickness of the second thickness graphite tube 22 is 1 mm, the height of the second thickness graphite tube 22 is 35 mm, the pore diameter of the air hole 23 is 1 mm, and the distance between adjacent air holes 23 is 1 mm.
[0038] As shown in Figure 4 and Figure 6 The graphite column 10 is first laid in the graphite crucible, the first thickness graphite column 11 is 4, the 4 graphite columns 10 are on the same ring, the distance between the center of each graphite column 10 and the center of the graphite crucible is 50 mm, the second thickness graphite column 12 is 6, and the 6 graphite columns 10 are on the same ring, and the distance between the center of each graphite column 10 and the center of the graphite crucible is 100 mm.
[0039] As shown in Figure 4 andFigure 7 As shown, the graphite crucible is charged with the material, and the material is charged to be flush with the graphite column 10; The graphite tubes 20 are laid on the lower material charge, 1st thickness graphite tubes 21, 3 tubes on the same ring, the distance from the center of each graphite tube 20 to the center of the graphite crucible is 50 mm; 2nd thickness graphite tubes 22, 4 graphite tubes 20 on the same ring, the distance from the center of each graphite tube 20 to the center of the graphite crucible is 100 mm.
[0040] The remaining material is continuously charged into the graphite crucible.
[0041] The total amount of the material charge is 5 kg.
[0042] After the preparation work of each unit of the material charging end device is completed, the graphite crucible is heated to grow the silicon carbide crystal.
[0043] According to the present embodiment, the crystal growth is carried out, and after 20 h (initial stage), the thickness of the edge and center of the ingot is tested, which is 15.29 mm and 15.57 mm, respectively, and the thickness difference is 0.28 mm; in the later stage, the thickness of the edge and center of the ingot is tested, which is 20.27 mm and 21.29 mm, respectively, and the thickness difference is 1.02 mm; the thickness of the middle and edge of the ingot in the initial stage and the later stage is very small.
[0044] Comparative Example 1 The present comparative example is basically the same as the embodiment 1, and the difference is only that the graphite tubes 20 and the graphite columns 10 are not laid during the material charging process.
[0045] Comparative Example 2 The present comparative example is basically the same as the embodiment 1, and the difference is only that the graphite columns 10 are not laid during the material charging process.
[0046] The thickness of the edge and center of the ingot in the initial stage and the later stage of the crystal growth of the embodiment and the comparative example is recorded, as shown in Table 1.
[0047] Table 1 Thickness of the middle and edge of the ingot during the crystal growth of the embodiment and the comparative example
[0048] As can be seen from Table 1, the interface flatness of the silicon carbide crystal grown after the material charging according to the embodiment of the present application is obviously better than that of Comparative Example 1 and Comparative Example 2, which indicates that the material charging method provided by the present application can improve the problem of interface unevenness in the process of growing the silicon carbide crystal in the prior art.
[0049] In summary, the loading method provided by the present application can increase the volatilization amount of the central area in the initial growth stage by uniformly laying the graphite tube 20 with the air hole 23 on the upper part of the powder, and the porous graphite tube 20 is only added in the central area, so that the volatilization amount of the central area in the later growth stage is increased. In order to avoid the problem of the protrusion of the central area caused by the increase of the volatilization amount of the central area in the later growth stage, the solid graphite column 10 is added in the middle and lower parts of the powder, and the solid graphite column 10 mainly plays a role of reducing the loading amount of the powder in the central area, and the radiation area is not increased, so that the volatilization speed of the central area in the middle and later growth stages can be reduced. Therefore, the crystal ingot with better interface flatness can be prepared by the growth of the silicon carbide crystal after the loading by the loading method provided by the present application.
[0050] The preferred embodiments of the present application have been described above with reference to the drawings, but the present application is not limited to the above examples, and various modifications and changes can be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Claims
1. A charging method for optimizing crystal growth interface, characterized in that: include: Evenly laying a plurality of graphite columns in the middle of the lower middle part of the graphite crucible, and then filling the crucible until it is flush with the top of the graphite columns; Evenly lay multiple graphite tubes on the lower loading, and then load the remaining material; A plurality of evenly distributed air holes are formed on the peripheral wall of each graphite tube.
2. The charging method according to claim 1, characterized in that The plurality of graphite tubes include at least one graphite tube of a first thickness and a plurality of graphite tubes of a second thickness; The at least one graphite tube of the first thickness is arranged at the center of the graphite crucible, and the plurality of graphite tubes of the second thickness are arranged around the at least one graphite tube of the first thickness; The diameter of each graphite tube with the first thickness is larger than that of each graphite tube with the second thickness.
3. The charging method according to claim 2, characterized in that: The plurality of graphite pillars include at least one graphite pillar of a first thickness and a plurality of graphite pillars of a second thickness; The at least one graphite column of the first thickness is arranged at the center of the graphite crucible, and the plurality of graphite columns of the second thickness are arranged around the at least one graphite column of the first thickness; The diameter of each graphite column having the first thickness is larger than that of each graphite column having the second thickness.
4. The charging method according to claim 3, characterized in that When preparing an 8-inch silicon carbide crystal, the inner diameter of the graphite crucible is 230-250 mm, and the total charge amount is 3-6 kg.
5. The charging method according to claim 4, characterized in that: The inner diameter of the graphite tube with the first thickness is 15-20 mm, the wall thickness is 1-2 mm, and the height is 30-40 mm; the inner diameter of the graphite tube with the second thickness is 5-10 mm, the wall thickness is 1-2 mm, and the height is 30-40 mm.
6. The charging method according to claim 5, characterized in that: The distance between the second graphite tube and the center of the graphite crucible is 100 to 120 mm, and the distance between the first graphite tube and the center of the graphite crucible is 50 to 60 mm; When the charge amount is less than 3 kg, the number of graphite tubes with the first thickness is n, and the number of graphite tubes with the second thickness is n to (n+2), where n is 1 to 3; When the charge amount is 3-6 kg, the number of graphite tubes with the first thickness is m, the number of graphite tubes with the second thickness is m-(m+2), and m is 2-5.
7. The charging method according to claim 5, characterized in that: The diameter of the pores is 1-2 mm, and the distance between adjacent pores is 1-2 mm.
8. The charging method according to claim 5, characterized in that: The diameter of the graphite column with the first thickness is 15-20 mm, the diameter of the graphite column with the second thickness is 5-10 mm, and the height of all graphite columns is the same, which is 90-95 mm.
9. The charging method according to claim 8, characterized in that: The distance between the second-thickness graphite column and the center of the graphite crucible is 100-120 mm, and the distance between the first-thickness graphite column and the center of the graphite crucible is 50-60 mm; When the charge amount is less than 3 kg, the number of graphite columns with the first coarseness is x, the number of graphite columns with the second coarseness is x to (x+2), and n is 1 to 3; When the charge amount is 3-6 kg, the number of graphite columns with the first thickness is y, the number of graphite columns with the second thickness is y-(y+2), and m is 2-5.
10. A method for preparing silicon carbide crystals, characterized in that: The method comprises the charging method as described in any one of claims 1 to 9.