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

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