Study of the morphological modifications induced by laser annealing of preamorphized silicon

Abstract

Atomic force microscopy was employed to characterize the morphological modifications induced by laser annealing of preamorphized silicon. Laser irradiation was performed at different fluence with fixed pulse durations of 23 ns. In all cases, the laser fluence used is above the threshold fluence that is needed to melt the preamorphized layer. Roughness measurements show that the surface roughness of the silicon samples increases when the laser fluence increases. Since the laser anneal was performed in air, the changes in morphology may be associated with the surface oxide formed. When a high fluence was employed, the extension of melting was sufficient to remove all surface features of the as-implanted sample but apparently there was not enough time to completely redistribute the material upon solidification. As a result, ripple-like periodic structures are formed on the surface. Therefore, a low laser fluence should be used whenever possible in the annealing of silicon samples.