Large thickness silicon carbide crystal growth apparatus

Abstract

The utility model relates to technical field of semiconductor material, concretely for big thickness silicon carbide crystal growth device, including graphite heat preservation layer, the graphite heater of graphite heat preservation layer is located in and the growth subassembly of graphite heater is located in, the growth subassembly includes the lower crucible of graphite heater middle and the upper crucible of upside down in lower crucible, the lower fixed of upper crucible is porous graphite cylinder, the lower part fixed of lower crucible is crucible bottom, and the recess is equipped with in the center of crucible bottom, and porous graphite cylinder inserts into recess, the middle part of lower crucible is equipped with filler bin, and the upper part of lower crucible is equipped with along the outer circumferential ring of upper crucible annular arrangement's supplementary material bin. The scheme can realize the continuous supplementary material when silicon carbide single crystal preparation, avoid heat field damage and impurity invasion, and guarantee big thickness silicon carbide crystallization quality.

Description

Technical Field

[0001] This utility model relates to the technical field of semiconductor materials, specifically to a device for growing thick silicon carbide crystals. Background Technology

[0002] Silicon carbide (SiC), as the core representative of third-generation wide bandgap semiconductor materials, has excellent properties such as large bandgap, high thermal conductivity, and strong breakdown electric field. In particular, high-quality, thick silicon carbide crystals with a thickness of more than 50 mm have irreplaceable application value in high-end fields such as power devices for new energy vehicles, traction converters for rail transit, converter valves for smart grids, and high-temperature resistant electronic equipment for aerospace.

[0003] Currently, the mainstream silicon carbide crystal growth method in the industry is the physical vapor transport method (PVT). Its core principle is to set up a graphite crucible and control the temperature conditions outside the graphite crucible through a device. The graphite crucible can be filled with silicon carbide powder, and a seed crystal is fixed on the top of the graphite crucible. By heating the graphite crucible to a certain temperature, the silicon carbide powder inside the crucible sublimates and decomposes into gaseous components such as Si, Si2C, and SiC2. These gaseous components are transported to the surface of the seed crystal, which has a lower temperature, under the drive of the temperature gradient, and crystallize on the seed crystal to form silicon carbide single crystals.

[0004] During silicon carbide growth, silicon carbide gradually accumulates on the seed crystal, causing the growth surface of silicon carbide on the seed crystal to gradually approach the surface of the silicon carbide powder below. This reduces the temperature difference between the growth surface and the powder surface, leading to a decrease in the crystallization rate and stability of silicon carbide on the growth surface. To address this issue, the existing technology "A segmented graphite crucible and a method for growing silicon carbide crystals" (Publication No.: CN117568922A) discloses a graphite crucible structure for silicon carbide growth. This graphite crucible includes an upper crucible, a lower crucible, and a lifting mechanism. A porous graphite cylinder is vertically positioned at the center of the lower crucible. The material is filled in the space between the outer wall of the porous graphite cylinder and the interior of the lower crucible. The gaseous components such as Si, Si2C, and SiC2, formed by the sublimation and decomposition of the powder, permeate through the porous graphite outer wall and then gather upwards to the seed crystal surface for crystallization. A lifting mechanism moves the upper crucible upwards. When the silicon carbide single crystal on the seed crystal surface reaches a certain thickness, the lifting mechanism controls the movement of the upper crucible to ensure that the growth surface of the silicon carbide on the seed crystal always maintains a suitable distance from the powder surface. This keeps the temperature difference in this area relatively stable and ensures that the growth surface is always within a suitable temperature gradient, thus solving the problems of low silicon carbide crystallization rate and poor crystallization stability. However, the existing technology still has the following technical problems: In existing technologies, when the lower crucible needs to be replenished with powder, the growth process must be interrupted and the crucible lid opened for replenishment. This is especially true for silicon carbide crystals with a thickness exceeding 50 mm, where the amount of powder required is even greater. Opening the crucible lid for replenishment is not only cumbersome but also disrupts the sealed and thermal environment required for crystal growth. This allows impurities such as oxygen, moisture, and dust carried by the air to enter the crucible cavity, reacting with the gaseous components at high temperatures to form oxide impurities or directly adhering to the seed crystal growth surface, forming defects such as carbon encapsulation and microtubes, thus reducing crystal purity. Simultaneously, when the high-temperature crucible is exposed to room-temperature air, the stable internal temperature gradient is broken, and the sudden temperature drop triggers thermal stress cracks within the crystal. Reheating to the target temperature requires significant time and energy, and the thermal field is difficult to restore to its initial stable state during the heating process, leading to fluctuations in the subsequent crystallization rate and poorer radial uniformity of the crystal. Furthermore, the replenishment operation interrupts the continuity of crystal growth, extending the production cycle per batch, reducing production efficiency, and potentially causing defects such as stacking faults and dislocations due to the discontinuity of the growth process, further affecting the stability of crystal quality. Utility Model Content

[0005] This invention provides a silicon carbide crystal growth device with large thickness, which can solve the problem that in the existing silicon carbide growth device, the powder replenishment process is not only cumbersome, but also easily damages the internal thermal environment of the crucible, causing impurities to enter the crucible and thus reducing the quality of the silicon carbide crystal after crystallization.

[0006] This application provides the following technical solution: a silicon carbide crystal growth apparatus with large thickness, including a graphite insulation layer, a graphite heater located within the graphite insulation layer, and a growth component located within the graphite heater; The growth assembly includes a lower crucible located in the middle of a graphite heater and an upper crucible inverted above the lower crucible; a porous graphite cylinder is fixed below the upper crucible; The lower crucible is fixed with a crucible bottom at its lower part, and a groove is provided in the center of the crucible bottom, into which a porous graphite cylinder is inserted; a filling chamber is provided in the middle of the lower crucible; and a feeding chamber is provided in the upper part of the lower crucible, arranged in a ring around the outer periphery of the upper crucible.

[0007] Beneficial effects: 1. To avoid disrupting the thermal environment during powder replenishment and ensure the quality of silicon carbide crystallization. Since the preparation of thick silicon carbide crystals requires more powder, and to avoid increasing the temperature difference inside the crucible and affecting the uniformity of the powder sublimation rate, thus reducing crystallization quality, excessively large crucibles cannot be used. Larger crucibles would hinder the heat transfer from the external heater through the crucible wall to the powder inside, making the temperature field inside the crucible more difficult to control. Therefore, powder replenishment is necessary during the growth process. This solution uses a replenishment chamber arranged in a ring around the outer periphery of the upper crucible at the top of the lower crucible. This allows the powder in the replenishment chamber to be replenished during the silicon carbide single crystal growth process. The material can be continuously replenished into the filling chamber. Compared with existing technologies, powder can be added without opening the crucible, ensuring that the stable temperature gradient inside the crucible is not disrupted. This effectively avoids problems such as internal thermal stress cracks and crystallization rate fluctuations in silicon carbide crystals caused by thermal field imbalance due to opening the crucible lid for material replenishment. At the same time, it can also prevent impurities such as oxygen, moisture, and dust carried by the outside air from entering the crucible after the crucible lid is opened, which would react with gaseous components to generate oxide impurities or directly adhere to the seed crystal growth surface, forming defects such as carbon encapsulation and microtubes. This improves the quality of silicon carbide crystals after crystallization.

[0008] 2. Improved production efficiency and crystallization stability. The growth apparatus in this solution does not require interruption of the silicon carbide growth process during material replenishment. Compared to existing technologies that require opening the crucible lid for replenishment, this solution avoids the time required for reheating after opening the lid for replenishment, thus significantly saving replenishment time and effectively improving production efficiency.

[0009] Furthermore, the interface between the lower end of the replenishment bin and the upper end of the filling bin is designed as an inverted cone shape.

[0010] Beneficial effects: Utilizing the guiding and converging effect of the inverted conical structure, the powder in the replenishment bin flows smoothly and evenly into the lower crucible packing bin along the conical surface. This not only avoids powder accumulation and blockage at the interface, ensuring the continuity and stability of replenishment, but also allows the replenished powder to be precisely guided to the inner wall and surrounding area of ​​the packing bin. This specifically compensates for the rapid volatilization loss of the powder on the inner wall of the lower crucible, preventing the consumption of the powder on the inner wall of the lower crucible from causing a sudden increase in local temperature and generating thermal stress, thereby helping to extend the service life of the lower crucible.

[0011] Furthermore, a rotating lifting rod is fixed above the upper crucible, the upper crucible is slidably connected to the feeding bin, and the outer wall of the porous graphite cylinder is slidably connected to the inner wall of the groove.

[0012] Beneficial effects: After the powder in the filling chamber sublimates into gaseous components, it is transported to the upper crucible, which has a lower temperature, and crystallizes in the growth region within the upper crucible. When the crystal grows to a certain thickness, the growth surface gradually moves closer to the filling chamber below, resulting in a smaller temperature difference between the growth surface and the filling chamber, leading to a poorer crystallization effect. The rotating lifting rod in this solution can adjust the height of the upper crucible, thereby ensuring that the growth surface of silicon carbide maintains a certain distance from the filling chamber below during the silicon carbide crystallization growth process. This prevents the growth surface from getting too close to the filling chamber, which would reduce the temperature difference and cause crystallization to stagnate, making it impossible to form a thick crystal. Therefore, by lifting the upper crucible to control the height of the crystal growth surface, the uniformity and growth stability of thick silicon carbide crystals can be improved.

[0013] Furthermore, a rotating support rod is fixed to the bottom of the lower crucible.

[0014] Beneficial effects: The rotating support rod at the bottom of the lower crucible can drive the lower crucible to rotate, making the powder in the packing chamber more evenly heated and volatilized, avoiding local material imbalance, while promoting uniform diffusion of gaseous components, reducing radial defects in crystals, and improving the growth consistency and quality stability of thick silicon carbide crystals.

[0015] Furthermore, the rotation direction of the rotating support rod is opposite to that of the rotating lifting rod.

[0016] Beneficial effects: The rotating support rod and the rotating lifting rod are designed to rotate in opposite directions, which can make the powder in the filling chamber heat up evenly, avoid local overheating caused by long-term static storage of the powder, ensure the uniform sublimation rate of the powder, and avoid the imbalance of silicon carbide component volatilization caused by local overheating; improve the radial thickness uniformity and crystal quality stability of thick silicon carbide crystals.

[0017] Furthermore, the graphite heater includes a main heater located on the outer periphery of the packing bin and an auxiliary heater located on the outer periphery of the feed bin.

[0018] Beneficial effects: The main heater precisely provides the high-temperature environment required for powder sublimation around the outer periphery of the filling chamber, while the auxiliary heater is adapted to the outer periphery of the feeding chamber to specifically regulate the temperature of the feeding chamber area. This not only avoids the cold powder added in the feeding chamber from affecting the overall thermal stability of the filling chamber due to excessively low temperature, but also avoids excessive temperature difference between the crystallization area in the upper crucible and the lower filling chamber area, which could lead to crystallization defects. This improves the radial uniformity and overall quality of the crystals after the crystallization of thick silicon carbide. Attached Figure Description

[0019] Figure 1 This is the main structural view of the present invention.

[0020] Figure 2 for Figure 1 A magnified view of the growth component. Detailed Implementation

[0021] The following detailed description illustrates the specific implementation method: The markings in the accompanying drawings include: graphite insulation layer 1, partition 101, main heater 2, filling chamber 3, feeding chamber 301, auxiliary heater 4, upper crucible 5, rotating lifting rod 6, seed crystal 7, porous graphite cylinder 8, lower crucible 9, rotating support rod 10, and crucible bottom 11.

[0022] Example 1 like Figure 1 and Figure 2 As shown, the thick silicon carbide crystal growth apparatus includes a graphite insulation layer 1, a graphite heater located within the graphite insulation layer 1, and a growth component located within the graphite heater.

[0023] The graphite insulation layer 1 is formed by side walls, a bottom surface, and a top surface. The side walls have a partition 101 that divides the interior into upper and lower regions. The graphite heater includes a main heater 2 and an auxiliary heater 4. The auxiliary heater 4 is located in the region above the partition 101, and the main heater 2 is located in the region below the partition 101. Both the main heater 2 and the auxiliary heater 4 are resistance heaters.

[0024] The growth assembly is located in the middle of the graphite heater, such as... Figure 2 As shown, the growth assembly includes a lower crucible 9 and an upper crucible 5 inverted above the lower crucible 9. A rotating lifting rod 6 is threadedly fixed to the upper part of the upper crucible 5, and a lifting device can be externally connected to the upper part of the rotating lifting rod 6. A seed crystal 7 is fixed inside the upper crucible 5. The axial region between the lower surface of the seed crystal 7 and the lower opening of the upper crucible 5 is the crystal growth region. A porous graphite cylinder 8 is threadedly connected to the lower part of the upper crucible 5.

[0025] The lower crucible 9 is threadedly fixed to a crucible bottom 11, which has a groove in the center. The bottom end of the porous graphite cylinder 8 is inserted into the groove. A filling chamber 3 is provided in the middle of the lower crucible 9. The filling chamber 3 is the space formed by the inner wall of the lower crucible 9, the outer wall of the porous graphite cylinder 8, and the upper surface of the crucible bottom 11. A feeding chamber 301 is provided in the upper part of the lower crucible 9, which is arranged in a ring around the outer periphery of the upper crucible 5. The lower end of the feeding chamber 301 is connected to the upper end of the filling chamber 3. The opening is set in an inverted cone shape, with the inverted cone opening close to the inner wall of the lower crucible 9. The guiding and converging effect of the inverted cone structure allows the powder in the feeding chamber 301 to flow smoothly and evenly into the filling chamber 3 of the lower crucible 9 along the cone surface. The outer periphery of the upper crucible 5 is slidably connected to the feeding chamber 301, and the outer wall of the porous graphite cylinder 8 is slidably connected to the inner wall of the groove of the crucible bottom 11, so that the rotating lifting rod 6 can drive the upper crucible 5 and the porous graphite cylinder 8 to move together.

[0026] The bottom of the lower crucible 9 is also threaded with a rotating support rod 10, and the lower end of the rotating support rod 10 is also externally connected to a drive device. The rotating support rod 10 rotates in the opposite direction to the rotating lifting rod 6. Figure 1 The main heater 2 is located on the outer periphery of the packing bin 3, and the auxiliary heater 4 is located on the outer periphery of the feed bin 301.

[0027] The method of using this device is as follows: High-purity silicon carbide powder is filled into the filling chamber 3 and the feeding chamber 301 of the downward crucible 9. Carbon particles are added to the silicon carbide powder to prevent the powder from solidifying after heating during the entire growth process, so that the powder in the feeding chamber 301 can fall smoothly into the filling chamber 3 to replenish the powder. Then, the main heater 2 and the auxiliary heater 4 are started. The main heater 2 heats the area of ​​the filling chamber 3 to meet the sublimation requirements of the powder, and the auxiliary heater 4 regulates the temperature of the crystal growth area inside the upper crucible 5 to form a crystal growth temperature gradient. When the internal temperature of the packing chamber 3 reaches the sublimation temperature of the powder, the powder will gradually decompose into gaseous components such as Si, Si2C, and SiC2. During this process, the rotating lifting rod 6 and the rotating support rod 10 drive the upper crucible 5 and the lower crucible 9 to rotate in opposite directions, respectively. At the same time, the gaseous components such as Si, Si2C, and SiC2 will pass through the porous graphite cylinder 8 and be transported upwards to the surface of the seed crystal 7 to form silicon carbide single crystals. Since the crystallization speed of silicon carbide is known, setting the lifting speed of the rotating lifting rod 6 to the crystallization speed of silicon carbide can ensure that the crystal growth surface is always aligned with the crystal growth surface. The packing chamber 3 maintains a relatively stable distance to stabilize the temperature difference and improve crystallization quality. Furthermore, as the powder in the packing chamber 3 is consumed, powder from the replenishment chamber 301 is smoothly replenished into the packing chamber 3 via an inverted conical interface. The volume of the packing chamber 3 is greater than or equal to the volume of the replenishment chamber 301. The volume of the packing chamber 3 is designed to be just the amount of powder needed to grow one ultra-thick silicon carbide crystal. Therefore, the replenishment chamber 301 can continuously replenish the packing chamber 3 to ensure a sufficient material supply and maintain a constant material level in the packing chamber 3 throughout the growth process. After the growth process is complete, the equipment can be stopped as required, and the single crystal can be removed.

[0028] The above are merely embodiments of this utility model, and the utility model is not limited to the field covered by this embodiment. Commonly known structures and characteristics in the solutions are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of this utility model, and these should also be considered within the scope of protection of this utility model. These modifications will not affect the effectiveness of the implementation of this utility model or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A silicon carbide crystal growth apparatus with large thickness, comprising a graphite insulation layer, a graphite heater located within the graphite insulation layer, and a growth component located within the graphite heater; characterized in that: The growth assembly includes a lower crucible located in the middle of a graphite heater and an upper crucible inverted above the lower crucible; a porous graphite cylinder is fixed below the upper crucible; The lower crucible is fixed with a crucible bottom at its lower part, and a groove is provided in the center of the crucible bottom, into which a porous graphite cylinder is inserted; a filling chamber is provided in the middle of the lower crucible; and a feeding chamber is provided in the upper part of the lower crucible, arranged in a ring around the outer periphery of the upper crucible.

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that: The interface between the lower end of the replenishment bin and the upper end of the filling bin is designed as an inverted cone shape.

3. The silicon carbide crystal growth apparatus according to claim 2, characterized in that: A rotating lifting rod is fixed above the upper crucible, the upper crucible is slidably connected to the feeding bin, and the outer wall of the porous graphite cylinder is slidably connected to the inner wall of the groove.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that: A rotating support rod is also fixed to the bottom of the lower crucible.

5. The silicon carbide crystal growth apparatus according to claim 4, characterized in that: The rotating support rod rotates in the opposite direction to the rotating lifting rod.

6. The silicon carbide crystal growth apparatus according to claim 5, characterized in that: The graphite heater includes a main heater located on the outer periphery of the packing bin and an auxiliary heater located on the outer periphery of the feed bin.

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