Stability of phase boundaries on thin silicon layers with glass substrates

Abstract

Phase-change instabilities have been experimentally observed in the laser melting of thin silicon layers on conductive glass substrates. In this study, the polysilicon layer is bounded on the top by a thin layer of glass. This glass covering prevents the occurrence of thermocapillary flows in the silicon melt. A conductive heat-transfer mathematical model is used to predict temperature fields in both the silicon and the glass. Regions of silicon melt are shown to occur; phase-boundary locations are predicted. The stability of the predicted phase boundaries and temperature fields are studied. This analysis shows that the determining factors for stability are the laser power, the shape of the light intensity distribution, and the laser scanning speed. The effect of these parameters on the stability is evaluated. Results from the stability analysis are compared with some experimental results.