In situ and ex situ diagnostics on melting and resolidification dynamics of amorphous and polycrystalline silicon thin films during excimer laser annealing

The liquid/solid interface motion and the temperature history of Si films during excimer laser annealing are observed by in situ experiments combining time-resolved (∼1 ns) electrical conductance, optical reflectivity/transmissivity at visible and near-infra-red wavelength, and thermal emission measurements. The existence of partial and complete melting regimes are detected. In the partial melting regime, the maximum temperature remains close to the melting point of amorphous Si (a-Si), since the laser energy is consumed by the latent heat of phase-change. In the complete melting regime, substantial supercooling, followed by spontaneous nucleation is observed. These phase transformations are consistent with the recrystallized poly-Si morphologies. It is also found that phase change temperature of poly-Si films is about 140 K higher than that of the a-Si films.