Numerical analyses and experimental validations on transport and control of carbon in Czochralski silicon crystal growth

Czochralski silicon (CZ-Si) crystal growth is invariably accompanied by the generation and transport of impurities, such as carbon (C) and oxygen (O), from chemical reactions in the high-temperature range. Reduction of C contamination in the grown crystal is required for the production of a high-quality Si wafer. Therefore, we systematically performed the transient global simulations and in situ measurements of CO concentrations in argon (Ar) gas domain. Parametric studies on the furnace pressure, flow rate of argon gas, and gap width were conducted for the transport of CO and accumulation of C during the melting process of Si feedstock. SiO etching reactions on graphite and SiC coating are the major sources of CO production. The contact reaction between the crucible and susceptor is an additional source of CO and SiO. Furthermore, the control mechanisms of gas flow on the incorporation of the generated CO and the accumulation of C in Si feedstock were clarified by comparison of different parameter settings. According to the mechanisms of C transport, the final C content of the melting process depends on the contamination flux at the gas/melt interface which could be controlled by the Peclet number of the gas flow and diffusion distance of CO.