Crystal growth device and method

Abstract

The invention discloses a crystal growth device and method. The device is characterized in that a silicon carbide thermal field system is arranged in a heat-insulating chamber; the lower opening end of the supporting sleeve is lapped at the upper opening end of the crucible body, and the gas leakage rate at the joint is within a set leakage range I; the seed crystal cover covers the upper opening end of the supporting sleeve and is provided with an air passing hole; the graphite cap and the thermal insulation sleeve are vertically distributed; the graphite cap covers the supporting sleeve, and the gas leakage rate of an annular seam of the graphite cap and the supporting sleeve is within a set leakage range II; the heat preservation sleeve is made of multiple layers of graphite soft felts and arranged outside the crucible body in a sleeving mode. The method comprises the following steps: in a crystal growth process, gradually corroding the heat preservation sleeve on the outer side of the crucible body by using leaked silicon-rich gas-phase components, gradually weakening the heat preservation effect of the heat preservation sleeve on the bottom of the crucible body, guiding a high-temperature region to move upwards, and ensuring that the temperature gradient of a crystal growth region is stable. According to the invention, the utilization efficiency of the powder can be obviously improved, and the thickening and efficient growth of crystals can be realized.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a crystal growth apparatus and method. Background Technology

[0002] Physical vapor transport (PVT) is the mainstream method for growing 6- to 8-inch 4H-SiC single crystals. This method utilizes induction heating, applying an alternating current through a mid-frequency power supply to create a magnetic field. This induces a high-density current in the conductor (such as graphite) within the coil, rapidly raising the temperature to a high level. The core components of PVT crystal growth include graphite (including the crucible and its components), graphite felt (hard or soft felt used for insulation and to create temperature gradients), silicon carbide powder providing the sublimation source, and seed crystals. Under a high temperature of at least 2100°C and relatively low pressure, the bottom silicon carbide powder undergoes non-stoichiometric decomposition and sublimation, generating gaseous components such as SimCn. Due to the axial temperature gradient, these gaseous components are transported from the bottom powder source region to the growth interface, where they focus and crystallize.

[0003] During crystal growth, sintering occurs inside the silicon carbide powder at the bottom, initially forming a ceramic body with numerous channels. As the reaction progresses, due to the "skin effect" of induction heating, carbonization occurs first in the high-temperature regions near the crucible walls and bottom. For example... Figure 1 As shown, after the graphite is heated by the induction coil, the high-temperature zone is mainly concentrated on the surface and bottom of the graphite crucible. Combined with the axial temperature gradient (lower temperature at the top, higher temperature at the bottom), the powder at the bottom and near the crucible wall will be preferentially carbonized. The gaseous components generated by carbonization will converge from the bottom to the top and from the outside to the center of the carbonized area. As the growth process continues, a mixture of gases will form in the powder, such as... Figure 2 The two characteristic regions shown are: Region (a) is the residual silicon carbide polycrystalline ceramic body in the middle of the crucible, mainly 6H-SiC, with relatively large particle size, belonging to a distinct uncarbonized region. This region is formed due to the lower temperature in the upper part of the crucible, where SimCn powder, which is fully carbonized at high temperatures on the bottom and sidewalls, converges along the central channel; while in the surrounding and bottom regions of the dense ceramic body, the SiC powder particles undergo complete decomposition and sublimation, with most of the solid Si atoms transforming into gaseous Si atoms or SimCn gaseous components. These material sources converge towards the seed crystal surface along the channels in the powder under the action of the axial temperature gradient, providing raw materials for crystal growth.

[0004] Ideally, within a temperature range of 1200–2300℃, all particles in SiC powder will undergo non-stoichiometric decomposition and sublimation, with most or all of the silicon transforming into gaseous or other silicon-rich gaseous components, leaving only solid C particles. At this point, it can be considered that the SiC powder is "completely carbonized." However, in actual growth processes (such as…),… Figure 2As shown in the diagram, only the four sides and bottom of ceramic body a can achieve complete carbonization; however, in the middle to top region of the SiC powder, there are still a large number of large, regularly shaped columnar grains. These green grains are usually 6H structures and belong to incompletely carbonized and ineffectively utilized silicon carbide fractions. Therefore, the actual utilization efficiency of silicon carbide powder is usually no more than 50%. If we attempt to recycle this part of silicon carbide powder, because it is mixed with graphite powder and its particle size and shape differ significantly from the original silicon carbide powder, the recycling process requires a lot of manpower and resources. At the same time, it is difficult to ensure the purity of the powder during repeated crushing, screening, and washing, resulting in low feasibility of secondary recycling. Therefore, there is an urgent need to provide a crystal growth device and method. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides a crystal growth apparatus and method. The apparatus has a simple structure and low manufacturing cost, significantly improving the utilization efficiency of silicon carbide powder, increasing crystal growth rate and quality, and effectively reducing the secondary recovery rate of silicon carbide powder. The method is simple to implement and has low implementation cost, significantly improving powder utilization efficiency without changing the crystal growth process, and achieving efficient and thickened crystal growth.

[0006] To achieve the above objectives, the present invention provides a crystal growth apparatus, including a heat preservation chamber and a silicon carbide thermal field system; The silicon carbide thermal field system is set in the insulation room and includes a crucible body, a support sleeve, a seed crystal cover, an insulation sleeve, and a graphite cap. The lower opening end of the support sleeve overlaps the upper opening end of the crucible body, and the gas leakage rate at the connection between the two is within a set leakage range; the seed crystal cover is placed on the upper opening end of the support sleeve, and a seed crystal mounting area is provided in the center area of ​​its lower end face, and an vent hole is opened around the seed crystal mounting area. The graphite cap and the insulation sleeve are distributed vertically; the graphite cap is placed outside the support sleeve, and the gas leakage rate at the annular joint between the two is within the second leakage range; the insulation sleeve is placed outside the crucible body.

[0007] In this invention, ensuring that the gas leakage rate between the lower opening of the support sleeve and the upper opening of the crucible body is within a predetermined leakage range guarantees that the silicon-rich gaseous components generated during heating can leak to the outside of the crucible body. The presence of vent holes on the outside of the seed crystal mounting area on the seed crystal cover facilitates atmosphere control and thermal field optimization, enabling control of crystal growth rate and quality, and also helps balance pressure. A graphite cap is fitted over the outside of the support sleeve to facilitate effective heat preservation of the area where the support sleeve is located. Similarly, a heat preservation sleeve is fitted over the outside of the crucible body to facilitate effective heat preservation of the area where the crucible body is located. By arranging the graphite cap and crucible body vertically and ensuring that the gas leakage rate between the graphite cap and the support sleeve is within a predetermined leakage range, the silicon-rich gaseous components leaking from the joint between the support sleeve and the crucible body can further leak through the annular joint between the graphite cap and the support sleeve to the insulation sleeve. This allows the leaked silicon-rich gaseous components to gradually corrode the crystal, thus gradually weakening the bottom insulation during crystal growth. The high-temperature zone will gradually move towards the upper middle part of the powder due to the weakened bottom insulation. Therefore, without changing the crystal growth process, the unreacted powder can be effectively utilized, significantly improving powder efficiency and effectively reducing the formation rate of the central ceramic body. This helps ensure smoother gaseous component channels, simultaneously achieving stable crystal thickening and growth, and significantly increasing the crystal growth rate.

[0008] The device has a simple structure and low manufacturing cost. It can significantly improve the utilization efficiency of silicon carbide powder, increase the growth rate and quality of crystals, and effectively reduce the secondary recovery rate of silicon carbide powder.

[0009] Furthermore, in order to achieve stable and high-quality crystal growth, the silicon carbide thermal field system also includes: A support member is installed on the inner side of the upper end of the crucible body and has a vent hole. A graphite plate, which is covered by a support member at the upper opening end of the crucible body, and has several ventilation holes on it; A flow guiding component is disposed between the graphite plate and the seed crystal cover, with its bottom connected to the edge of the graphite plate. The flow guiding component and the graphite plate together define the single crystal growth space.

[0010] In this technical solution, vent holes are provided on the support component, allowing some of the gaseous components generated by heating to reach the periphery of the flow guiding component. These components then exit through the vent holes on the seed crystal into the graphite cap and overflow from the annular joint between the graphite cap and the support sleeve, effectively acting on the insulation sleeve. This, combined with the gaseous components overflowing from the joint between the crucible body and the support cylinder, enhances the corrosion of the insulation sleeve, thus more effectively reducing the insulation effect of the bottom insulation. Simultaneously, the gaseous components overflowing from the vent holes on the support component and exiting through the vent holes on the seed crystal cap also form a gas insulation cavity, which helps ensure a constant internal temperature for the flow guiding component, thereby effectively improving crystal growth efficiency and quality.

[0011] Furthermore, the silicon carbide thermal field system also includes graphite paper; the graphite paper is bonded to the inner surface of the top of the graphite cap; the insulation sleeve 3 is made of multiple layers of graphite soft felt. The graphite paper serves as a heat equalization layer, making the temperature distribution on the back of the seed crystal more uniform, preventing the growth interface from changing from flat to curved due to localized overheating / overcooling, thus suppressing defects such as dislocations and stacking faults. Using graphite soft felt for the insulation sleeve allows for effective corrosion of the graphite soft felt by the silicon-rich gas phase components, thinning the graphite soft felt fiber layer, enhancing pore connectivity, and drastically increasing heat radiation and heat conduction losses, thus disrupting the uniformity of the temperature field inside the furnace and effectively reducing its insulation performance.

[0012] Furthermore, in order to achieve efficient flow guidance so that the gas phase components can enter the seed crystal mounting area efficiently and in a concentrated manner, the flow guiding component is a flow guiding cylinder, which is frustum-shaped.

[0013] Furthermore, in order to facilitate the gradual increase of gas leakage rate during the growth process, a soft felt ring is also included, which is disposed between the joint between the support sleeve and the crucible body.

[0014] Furthermore, to facilitate adjustment of the gas leakage rate between the crucible body and the support sleeve, and to effectively guide the leaked gaseous components to concentrate in the area where the insulation sleeve is located, The support sleeve is made of graphite, and an annular recess is provided on the inner side of its lower end. The annular recess is threaded onto the outer side of the upper end of the crucible body.

[0015] Furthermore, in order to facilitate the adjustment of the gas leakage rate between the graphite cap and the support sleeve, and at the same time, in order to effectively guide the leaked gas phase components to concentrate in the area where the insulation sleeve is located, the support sleeve is connected to the graphite cap by a threaded fit. Furthermore, in order to facilitate real-time temperature data sensing inside the insulation chamber via temperature sensors, the insulation chamber is equipped with temperature measuring holes.

[0016] As a preferred embodiment, the insulation chamber includes an insulation cylinder, an insulation base, and an insulation cover, wherein the insulation base and the insulation cover are respectively encapsulated at the upper and lower opening ends of the insulation cylinder.

[0017] The present invention also provides a crystal growth method, employing the above-mentioned crystal growth apparatus, comprising the following steps: During crystal growth, the leaked silicon-rich gas phase components are used to gradually corrode the insulation sleeve on the outside of the crucible, gradually weakening the insulation effect of the insulation sleeve on the bottom of the crucible, guiding the high-temperature zone upward, and ensuring the stability of the temperature gradient in the crystal growth zone.

[0018] This invention utilizes leaked silicon-rich gaseous components to gradually corrode an insulating sleeve made of graphite felt during crystal growth. As crystal growth continues, the insulating sleeve is continuously corroded, gradually losing its initial insulating properties. This effectively weakens the insulating performance at the bottom of the crucible, achieving the technical effect of the high-temperature zone gradually shifting upwards as the crystal grows. Therefore, without changing the power control and other growth conditions, the high-temperature zone can gradually move towards the upper part of the powder during crystal growth. This helps eliminate the ceramic body structure initially formed in the upper part of the powder, significantly reducing the proportion of uncarbonized ceramic body, enabling more efficient use of the powder, and preventing uncarbonized ceramic body from blocking gas transport channels. This makes the gaseous component transport channels within the powder smoother, facilitating more efficient upward transport of gaseous components and increasing the crystal growth rate.

[0019] This method is simple to implement and has low implementation costs. It can significantly improve the utilization efficiency of powder without changing the crystal growth process, and can achieve efficient growth of thickened crystals. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the "skin effect" in an induction-heated graphite crucible. Figure 2 This is a schematic diagram showing the state where the powder in the central region of the induction heating field has not been effectively carbonized; Figure 3 This is a photograph of the ceramic body remaining after crystal growth. Figure 4 This is a schematic diagram of the growth device in this invention; Figure 5 This is a schematic diagram of the silicon carbide thermal field system in this invention; Figure 6 yes Figure 5 Enlarged view of part A in the middle; Figure 7 This is a schematic diagram of the state after crystal growth is completed in this invention.

[0021] In the diagram: 1. Insulation chamber, 2. Support sleeve, 3. Insulation sleeve, 4. Support component, 5. Graphite plate, 6. Seed crystal cover, 7. Flow guiding component, 8. Graphite cap, 9. Temperature measuring hole, 10. Crucible body, 11. Vent hole, 12. Vent hole, 13. Seed crystal mounting area, 14. Vent hole, 15. Seed crystal, 16. Crystal, 17. Annular recess, 18. Soft felt ring, 19. Insulation cylinder, 20. Insulation base, 21. Insulation cover plate, 22. Silicon carbide thermal field system, 23. Silicon carbide powder, 24. Graphite paper, 25. Silicon carbide ceramic body, 26. Graphitized part. Detailed Implementation

[0022] The invention will now be further described with reference to the accompanying drawings.

[0023] like Figures 4 to 6 As shown, the present invention provides a crystal growth apparatus, including a heat preservation chamber 1 and a silicon carbide thermal field system 22; The silicon carbide thermal field system 22 is set in the insulation chamber 1. The silicon carbide thermal field system 22 includes a crucible body 10, a support sleeve 2, a seed crystal cover 6, an insulation sleeve 3, and a graphite cap 8. The crucible body 10 is used to hold silicon carbide powder 23; The lower opening end of the support sleeve 2 overlaps the upper opening end of the crucible body 10. The connection between the support sleeve 2 and the crucible body 10 must ensure a certain airtightness, while allowing a certain gas leakage rate at the connection, and the gas leakage rate at the connection is within a set leakage range one; as a preferred option, the set leakage range one is 2.5-3g / h. The seed crystal cover 6 is placed on the upper open end of the support sleeve 2, and a seed crystal mounting area 13 is provided in the center area of ​​its lower end face, and an air vent 14 is opened around the seed crystal mounting area 13; as a preferred embodiment, the diameter of the air vent 14 is in the range of 1.5 to 3 mm, and more preferably, the number of air vents is 8, and they are evenly distributed in the circumference. When setting the seed crystal 15, the seed crystal 15 is attached and fixed to the seed crystal mounting area 13 on the seed crystal cover 6 by adhesive bonding. The graphite cap 8 and the insulation sleeve 3 are distributed vertically. The graphite cap 8 covers the outside of the support sleeve 2. The connection between the graphite cap 8 and the support sleeve 2 must ensure a certain degree of airtightness, while allowing a certain gas leakage rate at the annular joint. The gas leakage rate at the annular joint is within the set leakage range two. Preferably, the set leakage range two is 1.5-2 g / h. The insulation sleeve 3 is made of multiple layers of graphite soft felt and is fitted over the outside of the crucible body 10. Preferably, the insulation sleeve 3 is formed by 3 to 5 layers of graphite soft felt. Furthermore, the insulation sleeve 3 can be tied to the outside of the crucible body using graphite rope. Of course, other high-temperature resistant fixing components can also be used to fix the insulation sleeve 3 to the outside of the crucible body.

[0024] Preferably, in order to ensure that the leaked gas can directly act on the insulation sleeve 3, the annular joint between the graphite cap 8 and the support sleeve 2 is located in the area where the insulation sleeve 3 is located.

[0025] In this invention, ensuring that the gas leakage rate between the lower opening of the support sleeve and the upper opening of the crucible body is within a predetermined leakage range guarantees that the silicon-rich gaseous components generated during heating can leak to the outside of the crucible body. The presence of vent holes on the outside of the seed crystal mounting area on the seed crystal cover facilitates atmosphere control and thermal field optimization, enabling control of crystal growth rate and quality, and also helps balance pressure. A graphite cap is fitted over the outside of the support sleeve to facilitate effective heat preservation of the area where the support sleeve is located. Similarly, a heat preservation sleeve is fitted over the outside of the crucible body to facilitate effective heat preservation of the area where the crucible body is located. By arranging the graphite cap and crucible body vertically and ensuring that the gas leakage rate between the graphite cap and the support sleeve is within a predetermined leakage range, the silicon-rich gaseous components leaking from the joint between the support sleeve and the crucible body can further leak through the annular joint between the graphite cap and the support sleeve to the insulation sleeve. This allows the leaked silicon-rich gaseous components to gradually corrode the crystal, thus gradually weakening the bottom insulation during crystal growth. The high-temperature zone will gradually move towards the upper middle part of the powder due to the weakened bottom insulation. Therefore, without changing the crystal growth process, the unreacted powder can be effectively utilized, significantly improving powder efficiency and effectively reducing the formation rate of the central ceramic body. This helps ensure smoother gaseous component channels, simultaneously achieving stable crystal thickening and growth, and significantly increasing the crystal growth rate.

[0026] The device has a simple structure and low manufacturing cost. It can significantly improve the utilization efficiency of silicon carbide powder, increase the growth rate and quality of crystals, and effectively reduce the secondary recovery rate of silicon carbide powder.

[0027] To achieve stable and high-quality crystal growth, the silicon carbide thermal field system 22 further includes: The support member 4 is installed on the inner side of the upper end of the crucible body 10 and has vent holes 11. Preferably, the vent holes 11 are located in the area of ​​the support member 4 near the inner wall of the crucible body 10. The support member 4 is preferably an annular connector, and a plurality of vent holes 11 are evenly provided in the circumferential direction of the annular connector. More preferably, the diameter of the vent holes is 3 to 5 mm and the number is 36. Graphite plate 5, which is covered by support member 4 at the upper opening end of crucible body 10, has a plurality of vent holes 12. Preferably, the diameter of the vent holes 12 is 1 to 1.5 mm, and the graphite plate 5 plays the role of filtering gas phase components. A flow guiding component 7 is disposed between the graphite plate 5 and the seed crystal cover 6, with its bottom connected to the edge of the graphite plate. The flow guiding component and the graphite plate together define the single crystal growth space. Preferably, the flow guiding component 7 is located in the inner region of the vent hole 11.

[0028] In this technical solution, vent holes are provided on the support component, allowing some of the gaseous components generated by heating to reach the periphery of the flow guiding component. These components then exit through the vent holes on the seed crystal into the graphite cap and overflow from the annular joint between the graphite cap and the support sleeve, effectively acting on the insulation sleeve. This, combined with the gaseous components overflowing from the joint between the crucible body and the support cylinder, enhances the corrosion of the insulation sleeve, thus more effectively reducing the insulation effect of the bottom insulation. Simultaneously, the gaseous components overflowing from the vent holes on the support component and exiting through the vent holes on the seed crystal cap also form a gas insulation cavity, which helps ensure a constant internal temperature for the flow guiding component, thereby effectively improving crystal growth efficiency and quality.

[0029] As a preferred embodiment, the silicon carbide thermal field system 22 further includes graphite paper 24; the graphite paper 24 is bonded to the inner surface of the top of the graphite cap 8. The graphite paper serves as a heat equalization layer, resulting in a more uniform temperature distribution on the back side of the seed crystal. This prevents the growth interface from changing from flat to curved due to localized overheating / overcooling, thereby suppressing defects such as dislocations and stacking faults. Using graphite soft felt for the insulation jacket allows for effective corrosion of the graphite soft felt by the silicon-rich gas phase components, thinning the fiber layer and enhancing pore connectivity. This leads to a sharp increase in heat radiation and heat conduction losses, disrupting the uniformity of the temperature field within the furnace and effectively reducing its insulation performance.

[0030] To achieve efficient flow guidance and allow the gas phase components to enter the seed crystal mounting area efficiently and in a concentrated manner, the flow guiding component 7 is a flow guiding cylinder, which is frustoconical in shape. Preferably, the lower opening end of the flow guiding cylinder is supported on the support member 4, and its upper end extends to the bottom of the seed crystal mounting area 13, thereby playing the role of efficient flow guidance and defining the single crystal growth area; To facilitate the gradual increase of gas leakage rate during the growth process, a soft felt ring 18 is also included, which is disposed between the support sleeve 2 and the crucible body 10. Preferably, the soft felt ring 18 is clearance-fitted with both the support sleeve 2 and the crucible body 10. The soft felt ring 18 is made of graphite and does not fully contact the lower end of the support sleeve 2 and the upper end of the crucible body 10 to leave space for gas corrosion.

[0031] In order to facilitate the adjustment of the gas leakage rate between the crucible body and the support sleeve, and at the same time, in order to effectively guide the leaked gas phase components to concentrate in the area where the insulation sleeve is located; The support sleeve 2 is made of graphite, and an annular recess 17 is formed on the inner side of its lower end. The annular recess 17 is threaded onto the outer side of the upper end of the crucible body 10. In this way, the airtightness of the connection between the crucible body 10 and the support sleeve 2 can be adjusted by the thread depth and pitch in the thread structure.

[0032] To facilitate adjustment of the gas leakage rate between the graphite cap and the support sleeve, and to effectively guide the leaked gaseous components to the area where the insulation sleeve is located, the support sleeve 2 is connected to the graphite cap 8 via a threaded connection. Thus, the airtightness at the connection between the graphite cap 8 and the support sleeve 2 can be adjusted by the thread depth and pitch in the thread structure.

[0033] In order to facilitate the real-time sensing of temperature data inside the insulation chamber through temperature sensors, the insulation chamber 1 is equipped with a temperature measuring hole 9.

[0034] As a preferred embodiment, the insulation chamber 1 includes an insulation cylinder 19, an insulation base 20, and an insulation cover 21. The insulation base 20 and the insulation cover 21 are respectively encapsulated at the upper and lower opening ends of the insulation cylinder 19. As a preferred embodiment, the insulation cylinder 19, the insulation base 20, and the insulation cover 21 are all made of insulation felt. The temperature measuring hole is opened on the insulation cover 21. More preferably, the diameter of the temperature measuring hole is in the range of 15-20 mm.

[0035] The present invention also provides a crystal growth method, which employs a crystal growth apparatus and includes the following steps: During the growth of crystal 16, the leaked silicon-rich gas phase components gradually corrode the insulation sleeve 3 on the outside of the crucible body 10, gradually weakening the insulation effect of the insulation sleeve 3 on the bottom of the crucible body 10, and guiding the high-temperature zone to move upward.

[0036] Specifically, the following growth methods can be used: Step 1: Loading the furnace; fill the crucible body 10 located on the stage with silicon carbide powder, and attach the seed crystal 15 to the seed crystal mounting area 13 in the seed crystal cover 6; Step 2: Vacuuming; Vacuuming is performed on the growth chamber inside the crucible body 10. The vacuuming can be continued for 2 hours to ensure that the vacuum level of the growth chamber is less than or equal to the set vacuum threshold. Step 3: Airtight Leak Detection; Perform a 30-minute process leak detection on the growth chamber to ensure that the growth chamber's sealing meets the set sealing standard; Step 4: Inflate and pressurize; Introduce argon gas at a flow rate of 1000 sccm into the growth chamber, and increase the pressure of the growth chamber to 80000 Pa within 30 minutes. At this time, the heating power is kept at 0 kW. Step 5: Pressure Stabilization Stage; Maintain the growth chamber pressure at 80000Pa, reduce the argon flow rate to 100sccm, and continue for 30 minutes. During this time, keep the heating power at 0kW. Step 6: Depressurization and heating; maintain the argon flow rate at 100 sccm, and reduce the pressure in the growth chamber to 10000 Pa within 30 minutes. At the same time, start the heating device and adjust the heating power to 10 kW. Step 7: Growth preparation stage; maintain the pressure in the growth chamber at 10000Pa, maintain the argon flow rate at 100sccm, increase the heating power to 16kw, and continue for 3 hours; Step 8: Pressure fine-tuning and atmosphere adjustment; within 10 minutes, reduce the pressure in the growth chamber to 5000Pa and the argon flow rate to 10sccm, while simultaneously introducing nitrogen (N2) at a flow rate of 3sccm, and maintain the heating power at 16kw; Step 9: Low-pressure growth stage; within 7 hours, reduce the pressure in the growth chamber to 100 Pa, increase the argon flow rate to 100 sccm, maintain the nitrogen flow rate at 3 sccm, and keep the heating power at 16 kW. Step 10: Core growth stage; Maintain the growth chamber pressure at 100 Pa, argon flow rate at 100 sccm, adjust the nitrogen flow rate to 20 sccm, increase the heating power to 18 kW, and simultaneously control the stage to move upward at a continuous speed of 0.1 mm / h. This stage lasts for 200 hours. During this process, the graphite felt (insulation sleeve 3) on the outside of the crucible body 10 is gradually corroded by the gas phase components, which gradually weakens the bottom insulation and guides the high-temperature zone to move upward. At the same time, the leaked gaseous components gradually corrode the insulation sleeve 3 on the outside of the crucible body 10, gradually weakening the insulation effect of the insulation sleeve 3 on the bottom of the crucible body 10, and guiding the high temperature zone to move upward. Step 11: Pressure recovery stage one; within 30 minutes, increase the pressure in the growth chamber to 5000Pa, adjust the argon flow rate to 1000sccm, stop the nitrogen supply, and maintain the heating power at 18kw; Step 12: Pressure recovery stage two; within 1 hour, further increase the pressure in the growth chamber to 50000Pa, maintain the argon flow rate at 1000sccm, and turn off the heating device; Step Thirteen: Cooling and Opening the Furnace; Allow the chamber to cool naturally for 48 hours. After cooling is complete, open the growth chamber and remove the crystal.

[0037] Throughout the entire process, the core process parameters such as the relative position of the coil and crucible, power, and pressure remain constant. There is no need to dynamically adjust the coil position. The insulation is weakened only by the corrosion of the bottom graphite soft felt (insulation sleeve 3), which indirectly controls the position of the high-temperature zone and ensures the stability of the temperature gradient in the crystal growth zone.

[0038] This invention utilizes leaked silicon-rich gaseous components to gradually corrode an insulating sleeve made of graphite felt during crystal growth. As crystal growth continues, the insulating sleeve is continuously corroded, gradually losing its initial insulating properties. This effectively weakens the insulating performance at the bottom of the crucible, achieving the technical effect of the high-temperature zone gradually shifting upwards as the crystal grows. Therefore, without changing the power control and other growth conditions, the high-temperature zone can gradually move towards the upper part of the powder during crystal growth. This helps eliminate the ceramic body structure initially formed in the upper part of the powder, significantly reducing the proportion of uncarbonized ceramic body, enabling more efficient use of the powder, and preventing uncarbonized ceramic body from blocking gas transport channels. This makes the gaseous component transport channels within the powder smoother, facilitating more efficient upward transport of gaseous components and increasing the crystal growth rate.

[0039] This method is simple to implement and has low implementation costs. It can significantly improve the utilization efficiency of powder without changing the crystal growth process, and can achieve efficient growth of thickened crystals.

[0040] Working principle: The thermal field of silicon carbide single crystal growth contains a "high-temperature zone," which is the region with the highest temperature existing inside the silicon carbide powder or between the silicon carbide powder and the seed crystal. The range and stability of this zone directly determine the quality of the crystal. Adjusting the crystal growth process for this high-temperature zone is crucial and directly determines the yield rate of the crystal.

[0041] Typically, the high-temperature region of a silicon carbide thermal field depends primarily on the structural design of the thermal field; this is the most fundamental determining factor. It can be said that the physical and structural design of the thermal field directly determines the distribution of the high-temperature region. However, by adjusting the local structure, the high-temperature region can be positioned in a relatively suitable location. For example: 1. Adjusting the relative position of the induction coil and the thermal field by moving the coil or the thermal field upwards or downwards will cause a relative displacement between them, which will directly change the axial position of the high-temperature zone. Through adjustments between several furnaces in the early stage of growth, a constant relative position will be determined, and fine adjustments will be made between furnaces based on the crystal growth. 2. The structure of the insulation felt (insulation chamber 1), consisting of side insulation felt (insulation cylinder 19), bottom insulation felt (insulation base 20), and top insulation felt (insulation cover plate 21), determines heat retention and heat loss through its thickness, density, and structural design. The top insulation felt is crucial for establishing the axial temperature gradient of the thermal field. The side insulation felt is also important for maintaining relative power and temperature stability. The bottom insulation felt affects the temperature at the bottom of the silicon carbide powder. However, once the thermal field is determined, the main insulation felt system will not undergo significant adjustments during continuous crystal growth or throughout the entire growth process between furnaces.

[0042] Common technical methods for adjusting high-temperature zones: In addition to the aforementioned thermal field structure design, in terms of process technology, the position of the high-temperature zone in the thermal field is generally adjusted in a timely manner by moving the coil position (dynamic control) during crystal growth. This is because, during the long-term growth of silicon carbide crystals, the boundary conditions of the thermal field change as silicon carbide powder is consumed and the crystal grows. Dynamically and slowly raising the coil is a key technology for maintaining a stable high-temperature zone and a constant temperature gradient. If the coil is not raised, the high-temperature zone will shift downwards, leading to changes in the supersaturation of the growth interface and affecting the crystal quality. Furthermore, a more serious problem will arise, as described above in this application: the appearance of a central 6H-SiC ceramic body. The appearance of the central ceramic body, on the one hand, hinders the continuous and stable upward transport of gaseous components, and on the other hand, prevents the effective utilization of the powder.

[0043] However, the method described above, which involves moving the coil position during crystal growth to shift the high-temperature zone upwards, is a dynamic control process. This means that while adjusting the downward shift of the high-temperature zone in the powder, other positions of the thermal field / crucible must also be adjusted synchronously. This can lead to significant uncontrollable factors. In a silicon carbide thermal field, a graphite crucible typically comprises a powder-containing area and a crystal growth area in the upper part of the powder. The shape of this crystal growth area, from the upper surface of the powder to the seed crystal surface (e.g., a flow guide, graphite outer ring, porous plate, etc.), is a core component of the thermal field. The thickness, shape, and relative position of the graphite wall in this area significantly alter the heat flow path. Therefore, while dynamically adjusting the overall coil position can move the high-temperature zone within the powder upwards, it also changes the heat flow path and temperature gradient within the crystal growth area from the upper surface of the powder to the seed crystal surface. Thus, under fixed thermal field conditions, this application achieves stable crystal growth process parameters while adjusting the high-temperature zone within the powder.

[0044] The thermal field during silicon carbide crystal growth is not static; it evolves throughout the growth process. For example, the performance of insulation materials degrades. After repeated use, insulation materials such as carbon felt become brittle, shrink, and change density due to high temperatures and chemical environments, leading to alterations in their insulation performance and causing the thermal field to "drift." Therefore, this application discovers and utilizes this principle to propose a thermal field and method for improving the utilization efficiency of silicon carbide powder during single crystal growth. This thermal field can maintain constant process parameters during crystal growth, such as constant power, constant pressure, and constant relative positions of the coil and crucible. Throughout the growth process, the temperature gradient and stability of the crystal growth region from the upper surface of the powder to the seed crystal surface are maintained as much as possible. This is achieved by weakening the insulation performance of the graphite felt on the bottom powder sidewall, thus reducing the bottom insulation. This allows the high-temperature zone to gradually move upward as the crystal growth process progresses. This represents a localized dynamic adjustment of the silicon carbide powder, which effectively promotes the gradual upward movement of the high-temperature zone during crystal growth, reduces the formation of the central ceramic body, and facilitates component transport and powder utilization, thereby stabilizing the crystal growth region and increasing the crystal growth rate.

[0045] like Figure 1 As shown, the basic principle of induction heating is that when the magnetic flux through the area enclosed by a conductor loop changes, an induced electromotive force (EMF) is generated in the loop. When the loop is closed, an induced current is generated. In practical applications, when a conductor (e.g., graphite) is placed in an alternating magnetic field (induction coil and intermediate frequency power supply), an induced EMF is generated in the conductor. Because the conductor itself forms a loop, an induced current is generated in the conductor. When the alternating current passes through the conductor, the current density in the conductor cross-section is not uniformly distributed; the maximum current density appears on the surface of the conductor. This phenomenon of current accumulation is called the "skin effect." Therefore, one drawback of induction heating is that if the crucible diameter is large, the coil usually only heats the outer layer of the crucible, leaving a lower-temperature region inside the crucible. This is more pronounced in large-size crystals, such as 8-inch and 12-inch silicon carbide thermal fields. However, induction heating is also widely used in silicon carbide crystal growth due to its advantages such as rapid heating, low energy consumption, and controllable equipment costs.

[0046] like Figure 2As shown, silicon carbide powder contains a silicon carbide ceramic body 25 whose center is not completely carbonized during and after crystal growth. This ceramic body is mainly composed of 6H-SiC and is a product of the re-formation of sublimated gas phase components at the bottom and undecomposed silicon carbide components at the original location. The existence of this structure indicates that: 1. Some gas phase components react at this location but fail to be effectively transported upwards to the seed crystal surface to participate in crystal growth; 2. This structure is relatively dense, and compared to the carbonized region (loose), it severely hinders the gas phase component transport path during and after its formation, preventing components from being transported upwards through this structure. Besides reducing the crystal growth rate, this may also lead to a thicker crystal edge and a thinner center, resulting in an uneven growth surface. Figure 3 As shown.

[0047] like Figure 7 As shown, during the growth of crystal 16, the graphite felt on the outside of crucible 10 is continuously corroded by the gas phase components, ultimately achieving the technical effect that the bottom insulation is continuously weakened during the crystal growth process.

Claims

1. A crystal growth apparatus, comprising a heat preservation chamber (1) and a silicon carbide thermal field system (22), characterized in that... ； The silicon carbide thermal field system (22) is set in the insulation chamber (1). The silicon carbide thermal field system (22) includes a crucible body (10), a support sleeve (2), a seed crystal cover (6), an insulation sleeve (3), and a graphite cap (8). The lower opening end of the support sleeve (2) overlaps with the upper opening end of the crucible body (10), and the gas leakage rate at the connection between the two is within the set leakage range. The seed crystal cover (6) is placed on the upper opening end of the support sleeve (2), and a seed crystal installation area (13) is provided in the center area of ​​its lower end face, and an air vent (14) is opened around the seed crystal installation area (13). The graphite cap (8) and the insulation sleeve (3) are distributed vertically; the graphite cap (8) is placed on the outside of the support sleeve (2), and the gas leakage rate at the annular joint between the two is within the set leakage range two; the insulation sleeve (3) is placed on the outside of the crucible body (10).

2. The crystal growth apparatus according to claim 1, characterized in that, The silicon carbide thermal field system (22) also includes: Support member (4), which is installed on the inner side of the upper end of the crucible body (10) and has a vent hole (11). Graphite plate (5), the graphite plate (5) is covered on the upper opening end of the crucible body (10) by a support member (4), and several ventilation holes (12) are opened on it. A flow guiding component (7) is disposed between the graphite plate (5) and the seed crystal mounting area (13), with its bottom connected to the edge of the graphite plate (5). The flow guiding component (7) and the graphite plate (5) together define the single crystal growth space.

3. The crystal growth apparatus according to claim 2, characterized in that, The silicon carbide thermal field system (22) also includes graphite paper (24); the graphite paper (24) is attached to the inner surface of the top of the graphite cap (8); the insulation sleeve (3) is made of multi-layer graphite soft felt.

4. A crystal growth apparatus according to claim 2, characterized in that, The flow guiding component (7) is a flow guiding cylinder, which is truncated cone-shaped.

5. A crystal growth apparatus according to claim 1, characterized in that, It also includes a soft felt ring (18), which is disposed between the support sleeve (2) and the crucible body (10).

6. A crystal growth apparatus according to claim 1, characterized in that, The support sleeve (2) is made of graphite, and an annular recess (17) is provided on the inner side of its lower end. The annular recess (17) is threaded onto the outer side of the upper end of the crucible body (10).

7. A crystal growth apparatus according to claim 1, characterized in that, The support sleeve (2) is connected to the graphite cap (8) by a threaded connection.

8. A crystal growth apparatus according to claim 1, characterized in that, The insulated chamber (1) is equipped with a temperature measuring hole (9).

9. A crystal growth apparatus according to claim 8, characterized in that, The insulation chamber (1) includes an insulation cylinder (19), an insulation base (20), and an insulation cover plate (21). The insulation base (20) and the insulation cover plate (21) are respectively encapsulated at the upper opening end and the lower opening end of the insulation cylinder (19).

10. A crystal growth method, employing a crystal growth apparatus as described in any one of claims 1 to 9, characterized in that, Includes the following steps: During the crystal (16) growth process, the leaked silicon-rich gas phase components gradually corrode the heat insulation sleeve (3) on the outside of the crucible body (10), gradually weakening the heat insulation effect of the heat insulation sleeve (3) on the bottom of the crucible body (10), guiding the high temperature zone to move upward, and ensuring the stability of the temperature gradient in the crystal growth zone.

Images