| dc.description.abstract | The Physical Vapor Transport (PVT) method is currently the mainstream process for growing silicon carbide single crystals. During the process, the crucible must be under low pressure and high temperature to sublimate the silicon carbide powder into reactive gases. These reactive gases are transported due to the temperature gradient and concentration difference within the chamber, moving to the cooler seed crystal surface above. When the concentration on the seed crystal surface reaches saturation, the gases solidify and form crystals. To maintain the crystal growth environment, the furnace is kept in a sealed state, making it difficult to obtain numerical data through experimental measurements.
This study optimizes the PVT method developed by predecessors and uses induction heating to grow a 6-inch silicon carbide single crystal thermal flow field model. The induction heating system is changed to a resistance heating system to make the temperature distribution more uniform and reduce the generation of thermal stress. According to industry standards, the size of the mainstream product has increased to 8 inches. Therefore, this study focuses on the 8-inch silicon carbide single crystal, improving the physical vapor transport method quasi-steady-state thermal flow field model developed previously anthors. Based on the literatures, the structure of the insulating layer on the crucible is changed to form an insulating layer structure with a different shape, which not only reduces the radial temperature difference but also improves the quality of the crystal. Then, the impact of the change of the crystal over time on the heat flow field andconcentration inside the crucible is analyzed and discussed. The study analyzes the growth rate, surface morphology, and thermal stress distribution of crystals at different times and examines methods for optimizing crystal quality and surface growth rate curves under different porosity, different input power, and changes in the structure and shape of the insulating layer to introduce them into the manufacturing process. This can reduce crystal defects and increase the growth rate.
The simulation results indicate that as the thickness of the crystal increases, the distance between the crystal and the powder decreases, resulting in a reduction of the axial temperature gradient within the cavity and causing a decrease in growth rate. Improvement suggestions for the PVT process are as follows: (1) reducing the porosity between silicon carbide powders can enhance the conduction of thermal energy to the center of the powder, thereby increasing the growth rate of the crystal; (2) adjusting the input power of the heater to improve the radial temperature difference on the crystal seed surface, which also leads to an increase in growth rate as the process temperature rises; (3) modifying the insulation layer structure on the crucible to reduce the axial temperature difference at the edge of the crystal seed, thus lowering the likelihood of polycrystalline growth at the crystal edges, reducing overall growth rate disparity, and facilitating the enhancement of growth rate in the edge region of the crystal seed. | en_US |