Crucible structure for reducing silicon carbide initial crystal defects
By introducing a flow guide tube and setting a micron-level gas leakage channel in the crucible structure, the problem of polymorphism in the early stage of silicon carbide single crystal growth was solved, the yield was improved and the cracking rate was reduced, and more efficient silicon carbide single crystal growth was achieved.
Patent Information
- Application Number
- CN202520486667.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-19
- Publication Date
- 2026-02-24
- Estimated Expiration
- 2035-03-19
AI Technical Summary
Polymorphism is prone to occur in the early stages of silicon carbide single crystal growth, leading to crystal defects and low yield.
A flow guide tube is introduced into the crucible structure, and a micron-sized inclined leakage channel is set on its inner wall. The leakage channel increases the leakage rate of gaseous substances, improves the C/Si ratio, and reduces the probability of polymorphism.
It improved the yield of silicon carbide single crystals, reduced the crystal cracking rate, improved the atmosphere environment in the early stage of crystal growth, and reduced the occurrence of polymorphism.
Smart Images
Figure CN223936658U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of silicon carbide crystal growth technology, specifically to a crucible structure for reducing early-stage crystal defects in silicon carbide. Background Technology
[0002] SiC (Silicon Carbide) material, with its unique characteristics such as a large bandgap, high critical breakdown field strength, high electron mobility, and high thermal conductivity, has become an ideal material for fabricating high-temperature, high-frequency, high-power, radiation-resistant, short-wavelength light-emitting, and optoelectronic integrated devices. The unique physical properties of SiC determine its applications in important fields such as artificial satellites, rockets, radar, communications, fighter jets, interference-free electronic ignition devices, and jet engine sensors. Currently, 4H-SiC single crystals are typically grown using the PVT (Polymer Transformation) method. The main process involves: under low-pressure and high-temperature conditions, SiC powder with a relatively large particle size (>200 μm) decomposes and sublimates into various gaseous substances. Driven by a temperature gradient, these substances are transported to a seed crystal at a lower temperature for reaction deposition and recrystallization into 4H-SiC single crystals. The main chemical reactions involved in the powder sublimation are:
[0003] SiC(s)→Si(g)+C(s) (1-1)
[0004] 2SiC (s) → Si (g) + SiC2 (g) (1-2)
[0005] 2SiC(s)→C(s)+Si2C(g) (1-3)
[0006] As can be seen from the above reaction equations, the gaseous substances produced by powder sublimation contain a high amount of Si, meaning that the gas obtained from decomposition and sublimation is a gas with excessive silicon content. This is also the reason why the remaining powder becomes graphitized after long-term single crystal growth. The Si and Si₂C in the sublimated gaseous phase react with C in the graphite crucible to generate additional gaseous substances:
[0007] Si2C(g) +C(s)→2SiC(s) (1-4)
[0008] 2C(s) +Si(g)→SiC2(g) (1-5)
[0009] C(s)+2Si(g)→Si2C(g) (1-6)
[0010] Following the above reaction, the generated gaseous material is transported to the seed crystal, reacts, and deposits to obtain a 4H-SiC single crystal.
[0011] Si2C(g)+SiC2(g)→3SiC(s) (1-7)
[0012] Si (g) +SiC2g →2SiC(s) (1-8)
[0013] In the above reaction formula, the Si content of other supersaturated vapors is much higher than the supersaturated vapor pressure of other atmospheres in the early stage of growth. Therefore, during the heating process of 1700-2200℃, the Si content of vapors is always high (see the attached table for the partial pressure of Si in vapors), and the temperature fluctuates continuously, making polymorphism easy to occur in the early stage.
[0014]
[0015] The table shows the calculated partial pressures of the gaseous components Si, Si₂C, SiC₂, and SiC of solid silicon carbide under vacuum or inert gas conditions within a temperature range of 1500-2800K, and the calculated saturated vapor pressure of gaseous Si (unit: Pa, i.e., N / m³). 2 (Data source: Material Science and Engineering B, 1993.21.65.)
[0016] The theoretical explanation for the polymorphism caused by temperature fluctuations is as follows: Near the powder, the unsaturated vapor contains volatile molecules such as Si, Si₂C, and SiC₂, while the supersaturated vapor near the silicon carbide seed crystal growth interface may contain more complex Si-C molecular complexes. These unstable aggregates are often referred to as metastable or undercritical nucleation points. The crystal structure of such nucleation points should resemble the thermodynamically most favorable polymorphism. Based on thermodynamic and kinetic considerations, these metastable nucleation points should exist for a very short time; however, their adsorption probability at the silicon carbide seed crystal growth interface is non-zero. Temperature fluctuations near the silicon carbide single crystal growth interface cause fluctuations in the supersaturation of various vapor combinations, leading to the formation of metastable nuclei (excluding 4H) in the gas phase, which then adsorb at the growth interface, resulting in polymorphism. Utility Model Content
[0017] This invention overcomes the shortcomings of the prior art by proposing a crucible structure that reduces crystal defects in the early stages of silicon carbide growth and solves the problem of polymorphism easily occurring in the early stages of crystal growth.
[0018] To achieve the above objectives, this utility model is implemented through the following technical solution:
[0019] A crucible structure for reducing initial crystal defects in silicon carbide includes a crucible body, with a flow guide tube connected to the inner wall of the upper part of the crucible body, on which a seed crystal is placed; the flow guide tube is a cylindrical structure with open top and bottom, with its bottom and inner wall located within the crucible body; multiple air leakage channels are formed inside the wall of the flow guide tube, one end of which is connected to the top of the flow guide tube, and the other end is connected to the bottom or inner wall of the flow guide tube; the air leakage channels connect the internal space of the crucible body with the external space of the crucible body; the inner diameter of the air leakage channels is on the order of micrometers.
[0020] Furthermore, the lengths of the multiple leakage channels are not equal.
[0021] Furthermore, the leakage channel has an inclined structure, with the top end of the leakage channel located between the seed crystal and the crucible body, and the bottom end of the leakage channel located on the inner wall of the guide tube or on the side of the bottom of the guide tube away from the inner wall of the crucible body.
[0022] Furthermore, multiple leakage channels are evenly and symmetrically distributed around the center of the guide tube.
[0023] Furthermore, the number of leakage channels is 2n, where n is a natural number less than 10.
[0024] Furthermore, a graphite support is attached to the top of the seed crystal.
[0025] The beneficial effects of this utility model compared to the prior art are as follows:
[0026] This invention optimizes the structure of the inner wall of the crucible (flow guide tube) by adding micron-level leakage channels inside the flow guide tube. This improves the leakage rate of the Si atmosphere during the initial stage of crystal growth, improves the C / Si ratio in the atmosphere during the initial stage of crystal growth, reduces the probability of polymorphism during the initial stage of crystal growth, and thus improves the yield of silicon carbide single crystals. Simultaneously, the addition of symmetrical micron-level leakage channels improves the stress distribution in all directions of the crystal, reducing the cracking rate. Attached Figure Description
[0027] Figure 1 This is a cross-sectional view of the existing crucible crystal growth process;
[0028] Figure 2 This is a cross-sectional view of the guide tube described in Embodiment 1;
[0029] Figure 3 This is a top view of the guide tube described in Embodiment 1;
[0030] Figure 4 These are photographs of crystals grown using an existing flow tube without any leakage channels.
[0031] Figure 5This is a photograph of a crystal grown using the flow guide tube with a leakage channel as described in Example 1;
[0032] Figure 6 This is a cross-sectional view of the guide tube described in Embodiment 2;
[0033] Figure label:
[0034] 1. Crucible body; 2. Flow guide tube; 3. Seed crystal; 4. Leakage channel; 5. Graphite support. Detailed Implementation
[0035] To make the technical problem to be solved, the technical solution, and the beneficial effects of this utility model clearer, this utility model will be further described in detail with reference to the embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of this utility model and are not intended to limit it. The technical solution of this utility model will be described in detail below with reference to the embodiments and accompanying drawings, but the scope of protection is not limited thereto.
[0036] Example 1
[0037] See Figure 1 , Figure 2 and Figure 3 This embodiment proposes a crucible structure to reduce initial crystal defects in silicon carbide, including a crucible body 1, with a flow guide tube 2 connected to the inner wall of the upper part of the crucible body 1. A seed crystal 3 is placed on the flow guide tube 2, and a graphite support 5 is connected to the top of the seed crystal 3. SiC powder 6 is contained in the crucible body 1, with the seed crystal 3 located above the crucible body 1 and opposite to the SiC powder. The SiC powder decomposes and sublimates into various gaseous substances, which are transported to the lower-temperature seed crystal 3 under the drive of the temperature gradient and reacted and deposited, recrystallizing into 4H-SiC single crystals. The flow guide tube 2 serves to guide the sublimated gaseous substances, allowing them to be deposited smoothly onto the seed crystal 3.
[0038] The guide tube 2 is a cylindrical structure with open top and bottom. The bottom and inner wall of the guide tube 2 are located inside the crucible body 1. In this embodiment, four air leakage channels 4 are formed on the wall of the guide tube 2, and these four channels 4 are evenly and symmetrically distributed around the center of the guide tube 2. One end of each air leakage channel 4 is connected to the top of the guide tube 2, and the other end is connected to the bottom of the guide tube 2. The air leakage channels 4 connect the internal space of the crucible body 1 with the external space of the crucible body 1. The inner diameter of each air leakage channel 4 is on the micrometer scale.
[0039] Specifically, the leakage channel 4 is an inclined structure. The top end of the leakage channel 4 is located between the seed crystal 3 and the crucible body 1, and the bottom end of the leakage channel 4 is located at the bottom of the guide tube 2 on the side away from the inner wall of the crucible body 1. In this embodiment, the leakage channel 4 is a channel structure located inside the wall of the guide tube 2; of course, it can also be a groove structure located on the inner wall of the guide tube 2. The function of the leakage channel 4 is to increase the leakage rate of the Si atmosphere in the early stage of crystal growth, improve the C / Si ratio in the atmosphere in the early stage of crystal growth, reduce the probability of polymorphism in the early stage of crystal growth, and thus improve the yield of silicon carbide single crystal.
[0040] The air leakage channels 4 on the guide tube 2 are slotted in pairs in the symmetrical direction, which can ensure stress symmetry during crystal growth and reduce the risk of crystal cracking. At the same time, the extension length of the air leakage channels 4 can be adjusted according to the actual situation, which can shorten the length of the air leakage channels 4 and only play the role of adjusting the carbon-silicon ratio in the early stage of crystal growth.
[0041] See Figure 4 These are images of crystals grown using an existing flow tube 2 without a leakage channel 4; from Figure 4 The red box shows that after the carbon-silicon ratio became unbalanced in the early stages of growth, the proportion of polymorphism in the early crystals increased, usually extending from the lower part of the crystal towards the interior.
[0042] Figure 5 The image shows a crystal grown using the guide tube 2 with the air leakage channel 4 described in the embodiment; after opening a micron-level single groove inside the guide tube 2, the polymorphism of the grown crystal is reduced.
[0043] Example 2
[0044] See Figure 6 This embodiment proposes a crucible structure to reduce defects in the initial crystals of silicon carbide. Except for the length and position of the leakage channel 4, which are different from those in Embodiment 1, the rest are the same. Specifically, in this embodiment, four leakage channels 4 are provided on the wall of the guide tube 2. They are symmetrically positioned but have different lengths. The bottom end of one of the two opposite leakage channels 4 is connected to the bottom of the guide tube 2, and the bottom end of the other is connected to the inner wall of the guide tube 2.
[0045] The above description is a further detailed explanation of the present invention in conjunction with specific preferred embodiments. It should not be considered that the specific embodiments of the present invention are limited to this. For those skilled in the art, several simple deductions or substitutions can be made without departing from the present invention, and all such deductions or substitutions should be considered to fall within the scope of patent protection determined by the submitted claims.
Claims
1. A crucible structure for reducing initial crystal defects in silicon carbide, comprising a crucible body (1), a flow guide tube (2) connected to the inner wall above the crucible body (1), and a seed crystal (3) placed on the flow guide tube (2); characterized in that, The guide tube (2) is a cylindrical structure with open top and bottom. The bottom and inner wall of the guide tube (2) are located inside the crucible body (1). Multiple air leakage channels (4) are opened on the wall of the guide tube (2). One end of the air leakage channel (4) is connected to the top of the guide tube (2), and the other end is connected to the bottom or inner wall of the guide tube (2). The internal space of the crucible body (1) is connected to the external space of the crucible body (1) through the air leakage channel (4). The inner diameter of the air leakage channel (4) is in the micrometer range.
2. The crucible structure for reducing early crystal defects in silicon carbide according to claim 1, characterized in that, The lengths of the multiple leakage channels (4) are not equal.
3. The crucible structure for reducing early crystal defects in silicon carbide according to claim 1, characterized in that, The leakage channel (4) is an inclined structure. The top of the leakage channel (4) is located between the seed crystal (3) and the crucible body (1), and the bottom of the leakage channel (4) is located on the inner wall of the guide tube (2) or on the bottom of the guide tube (2) away from the inner wall of the crucible body (1).
4. The crucible structure for reducing early crystal defects in silicon carbide according to claim 3, characterized in that, Multiple air leakage channels (4) are evenly and symmetrically distributed around the center of the guide tube (2).
5. The crucible structure for reducing early crystal defects in silicon carbide according to claim 4, characterized in that, The number of leakage channels (4) is 2n, where n is a natural number less than 10.
6. The crucible structure for reducing early crystal defects in silicon carbide according to claim 1, characterized in that, The top of the seed crystal (3) is connected to a graphite support (5).
7. The crucible structure for reducing early crystal defects in silicon carbide according to claim 1, characterized in that, The air leakage channel (4) is a groove structure located on the inner wall of the guide tube (2) or a channel structure located in the tube wall of the guide tube (2).