Phase Transformation Mechanism in Pulsed Excimer Laser Crystallization of Amorphous Silicon Thin Films
Melting and resolidification dynamics of amorphous silicon thin films on glass substrate have been investigated by time-resolved optical reflectivity and transmissivity measurements during excimer laser crystallization (ELC). The laser-annealed microstructures were characterized by optical microscopy, field-emission scanning electron microscopy, and high-resolution transmission electron microscopy. The recrystallization mechanisms for both frontside and backside ELCs are the same. The recrystallization mechanism of a-Si thin film significantly depends on the irradiated excimer laser fluence, which influences the thickness of the liquid silicon layer and the melt duration. The disk grains were observed in the complete melting regime because part of Si thin films did not melt completely, showing the recrystallization mechanism for disk grain and SLG are the same. The grain size of poly-Si films with a diameter of approximately 1 μm can be fabricated for the 90-nm-thick a-Si thin films using ELC.
Keywords: Silicon; excimer laser; crystallization; recrystallization mechanisms.