Numerical investigation of carbon contamination during the melting process of Czochralski silicon crystal growth

Czochralski (CZ) growth of single silicon (Si) crystals is invariably accompanied by transport of impurities such as carbon (C), oxygen (O), and related compounds produced by reactions at high temperature. To study the generation and accumulation of C during the melting process, a transient global model was developed that included coupled O and C transport. Transport phenomena of C, O, and related compounds were predicted by considering five chemical reactions in the furnace. The dynamic behavior of impurities was revealed during the melting process of the Si feedstock. It was found that C contamination is activated once the melting front contacts argon gas. For accurate control of C contamination in CZ-Si crystals, the accumulation of C during the melting stage should be considered. Parameter studies of furnace pressure and gas flow rate were conducted on the accumulation of C during the melting stage. At the gas/melt interface, pressure and flow rate affected the C flux in different ways. The results suggest that increase in gas flow rate could reduce C contamination much more effectively than decrease in pressure.