Pulsed Excimer Laser Crystallization of Evaporated Amorphous Silicon Films. The Role of SiO2 Underlayer Thickness

Abstract

Amorphous Si (a-Si) films deposited by vacuum evaporation onto oxidized Si substrates with different thicknesses of SiOz underlayer were melted and crystallized using a XeCl laser beam. The energy densities of the beam E = 150 to 450 mJ/cm2 were chosen according to the results of calculations of the temperature evolution within the samples. A-Si films were irradiated by n, = 1, 10, or 100 laser pulses. The samples were analyzed by X-ray diffraction (XRD), grazing incidence XRD (GI XRD), transmission and scanning electron microscopy. The influence of the underlying SiOz thickness on the crystallization was studied. It was shown that the complete or near-complete melting of a-Si and higher temperature gradients in the melted Si (depending on the SiOz thickness) are favourable conditions for Si crystallization. Overmelting into the oxide resulted in a lower quality of Si film crystallinity.