Numerical analysis of the formation of Si_3N_4 and Si_2N_2O during a directional solidification process in multicrystalline silicon for solar cells

摘要

We studied the mechanism of formation of Si_3N_4 and Si_2N_2O during the solidification process of multicrystalline silicon by numerical analysis with a phase diagram of the Si(l)-N-O system. Concentrations of oxygen and nitrogen were almost the same as reported values of measurements. Si_3N_4 was formed on the top of the silicon ingot. Si_3N_4 was also formed at the middle stage of the solidification process at the center of the ingot. It was clarified from the results that Si_2N_2O was first formed near the melt-crystal interface, since oxygen concentration in the melt decreases and nitrogen concentration in the melt increases with solidification of the molten silicon. Si_3N_4 was formed after Si_2N_2O had been formed.