Effects of High Nitrogen Pressure and Thermal Treatment on Adhesion to Amorphous Silicon/Silicon Nitride/Polyethersulfone Substrate during Excimer Laser Annealing
ABSTRACTPECVD amorphous silicon films deposited at different temperatures on low cost glass substrates have been treated by a Single Shot Excimer Laser Annealing (SSELA) at various energy densities. The influence of a thermal treatment at medium temperature (400°C) prior to the SSELA treatment was also investigated. Spectroscopie ellipsometry and Raman characterizations show that hydrogen contamination produces an important roughness increase with very little polycrystalline grains (650nm) after laser treatment. The thermal treatment prior laser annealing improves drastically the structural quality of the films. Structural results are correlated with the electrical performances of the TFT produced on these films.
ABSTRACTWe have performed molecular-dynamics simulations of heating, melting and recrystallization processes in amorphous silicon (a-Si) thin films deposited on glass during excimer laser annealing. By partially heating the a-Si surface region with 2 nm depth and removing thermal energy from the bottom of the glass substrate, a steady-state temperature profile was obtained in the a-Si layer with the thickness of 15 nm and only the surface region was melted. It was found that nucleation predominantly occurred in the a-Si region as judged by the coordination numbers and diffusion constants of atoms in the region. The results suggest that nucleation occurs in unmelted residual a-Si region during the laser irradiation and then crystal growth proceeds toward liquid Si region under the near-complete melting condition.
Effects of High Nitrogen Pressure and Thermal Treatment on Adhesion to Amorphous Silicon/Silicon Nitride/Polyethersulfone Substrate during Excimer Laser Annealing