Selective Area Excimer-Laser Crystallization of Amorphous Silicon Thin Films

Amorphous silicon films deposited on high quality fused-silica wafers were crystallized using an excimer laser. A unique configuration was used, which is referred to as selective-area crystallization. This was done by using surface masking of the film during standard laser irradiation. The resulting microstructure of the films was then characterized by transmission electron microscopy. The samples processed using the selective-area crystallization method resulted in one of three microstructures. Samples processed with the lower laser energy densities (200-300 mJ/cm²) demonstrated a standard microstructure consistent with regular laser annealing (grain size ∼ 200 nm). Samples processed with higher energy densities (300-470 mJ/cm²) demonstrated either enlarged grain growth (a factor of three greater than standard microstructure) or anomalous grain growth (unusual aspect ratio or geometry).