ATOMIC-FORCE MICROSCOPY STUDY OF THE MORPHOLOGICAL MODIFICATIONS INDUCED BY LASER PROCESSING OF SI(1-X)GEX SI SAMPLES/

Atomic force microscopy topography and power spectral density analysis of the recorded images were used to obtain a thorough characterizatio n of the morphological modifications determined by laser processing of Si(1-x)Ge-x/Si (100) structures grown by ultrahigh vacuum chemical va por deposition (CVD). Two irradiation modalities were considered. In t he first case, several samples differing in alloy film thickness and m orphology were irradiated by KrF laser pulses at 248 nm after the CVD growth. Alternatively, the laser pulses were used to assist the CVD gr owth itself. In both cases laser irradiation determined primarily a se vere smoothing of the surface roughness. However for the post-growth i rradiation the achieved flatness was strictly dependent on the initial surface features (i.e., roughness and grain dimensions). The comparis on between the results obtained in the two irradiation modalities demo nstrated that, as far as surface flatness is concerned, laser-assisted deposition results a superior technique, since it allows the achievem ents of structureless surfaces, with roughness as low as 0.3 nm. (C) 1 998 American Vacuum Society.