Crystallization Process of Polycrystalline Silicon by KrF Excimer Laser Annealing

Abstract

We have investigated the crystallization of a-Si films by means of pulsed KrF excimer laser annealing as a function of irradiation energy density (E L), using transmission electron microscopy (TEM), Raman scattering spectroscopy and secondary ion mass spectrometry (SIMS). The grain size increased gradually at 0.2–0.4 J/cm2, while a drastic enlargement of grains occurred with lateral growth at 0.6–0.8 J/cm2. The stress in the films decreased with a decrease in the thickness of the fine grain (FG) layer until the FG layer finally disappeared. We proposed a model in which a drastic enlargement of grains at high E L is controlled by the nucleation rate, the solidification velocity, and the nucleus density of initial growth. It was found that poly-Si films with large grains ( 0.5–0.9 µm), high purity of C ( ∼3×1016 cm-3) and low stress were obtained in the high E L regime ( 0.6–0.8 J/cm2).