Effect of Post Thermal Annealing on Femtosecond Laser Crystallization of 500-nm-thick Amorphous Silicon Films

Abstract

Femtosecond laser interference crystallization was studied in 500-nm-thick amorphous silicon (a-Si) films prepared on glass by using plasma-enhanced chemical-vapor deposition. The efficient crystallization of 500-nm-thick a-Si films was found to require post thermal annealing as well as laser annealing. Femtosecond laser interference technique was used to produce the seed pattern for the spatially-selected crystallization of a-Si. Post thermal annealing of the seed pattern was performed at 550 degrees C for 20 hours under a nitrogen atmosphere. By applying post thermal annealing to laser-crystallized silicon, the degree of crystallization was enhanced. The femtosecond laser-induced grating can be regarded as a pattern of alternating a-Si and mu c-Si (microcrystalline silicon) bands with a period of about 2 pin. Probe-beam diffraction, micro-Raman spectroscopy, and transmission electron microscopy were used to investigate the diffraction behavior and to confirm the spatially-selected crystallization of a-Si.