Numerical and experimental investigation on iron contamination of 200 mm semiconductor-grade CZ-Si by bubble-free layer of quartz crucible

Abstract

The thickness of bubble-free (BF) layer of the quartz crucible is crucial for heat transfer during the crystal growth process of 200 mm semiconductor-grade CZ silicon. The effect of the BF layer thickness on the contamination of impurity Fe in the wafer was investigated through experimental and numerical simulations. The experimental results demonstrated that a crucible with a 3 mm BF layer (S1) exhibited a lower thermal conductivity (1.37 W/(K• m)) in comparison to a 6 mm BF layer (S2) with a thermal conductivity of 1.72 W/(K• m). Despite the S2 crucible requiring an additional 0.40 kW for thermal compensation, it resulted in a lower concentration of Fe impurities. Compared to S1, S2 crucible offered superior performance in stabilizing the distribution of O and C impurities, resulting in more uniform distribution and improved crystal quality. Simulations indicated that the utilization of S2 quartz crucibles had minimal effect on the velocity field of Ar gas but elevated the melt temperature, strengthened the Taylor-Proudman vortex beneath the crystal-melt interface and altered the flow direction of the secondary vortex. This study highlights the importance of crucible design in controlling the contamination of Fe impurities for the production of high-quality Si wafers.