Numerical analysis of the formation of Si3N4 and Si2N2O during a directional solidification process in multicrystalline silicon for solar cells

Abstract We studied the mechanism of formation of Si 3 N 4 and Si 2 N 2 O 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 3 N 4 was formed on the top of the silicon ingot. Si 3 N 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 2 N 2 O 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 3 N 4 was formed after Si 2 N 2 O had been formed.