| dc.description.abstract | The continuous-feeding Czochralski crystal growth method (CCz) is an improvement over the traditional Czochralski crystal growth method (Cz). In CCz crystal growth, the raw material, polycrystalline silicon granules, is added to the free melt surface at the same rate as the crystal puller, maintaining a constant melt height in a lower aspect ratio and reducing oxygen impurities. Additionally, a partition, known as the inner crucible, is placed in the middle of the melt to prevent unmelted granules from flowing into the inner melt and affecting crystallization. However, the partition also acts as a source of oxygen impurities and hampers heat transfer. To minimize the increase in oxygen impurities and improve heat transfer efficiency, this paper investigates the geometric design of the furnace, including the shape of the crucible, heater, heat shield, and insulation, using the numerical simulation method (CGSim software).
The results demonstrate that a flatter crucible bottom generates larger vortexes in the outer melt, keeping unmelted granules in the outer melt and improving heat transfer. This reduces the temperature on the crucible surface and the dissolution of oxygen impurities. By separating the side heaters and increasing the power of the upper side heater, the high temperature region shifts from the crucible bottom to the crucible side wall, enhancing the melting effect on the granules and reducing the temperature at the crucible bottom, which is the primary source of oxygen impurities at the crystal-melt interface. For improved heat efficiency, the optimized heat shield and insulation prevent heat loss from the upper furnace, saving more heater power and increasing the velocity of argon flow. This strengthens the vortex that prevents oxygen flow to the crystal-melt interface. As a result, the temperature on the crucible wall decreases, and the prevention of oxygen flow becomes stronger, reducing the oxygen concentration at the crystal-melt interface. The optimized furnace design reduces CCz crystal defects while saving 41% of heater power and reducing oxygen by 15%. | en_US |