Numerical Study on Different Shapes of Heat Shields in Continuous Czochralski Silicon

Abstract

Monocrystalline silicon is the core material of solar cells and integrated circuits and its quality have a direct impact on device performance. The Continuous Czochralski method is a very well know technique which can grow large-sized monocrystalline silicon, with uniform axial resistivity distribution and higher growth efficiency. However, there are still some flaws such as unstable melt flow, temperature fluctuations, and high oxygen content. A two-dimensional axisymmetric global quasi steady numerical model is proposed by Fluent software for Continuous Czochralski growth of monocrystalline silicon. Two types of heat shields are designed (SHS and IHS), and the effects of changes in heat shields on heater power, argon velocity, crystal thermal stress, oxygen impurity concentration, melt/crystal interface, melt temperature and flow fields are studied. The results show that the IHS increases the velocity of argon above the melt free surfaces about 56.3%, weaken the reflux phenomenon. The technique helps to save the heater power by 2.7%, decrease the oxygen concentration on melt-crystal interface by 10.2% and smooth the melt/crystal interface, ultimately reducing crystal production costs and improving crystal quality.