Abstract
This thesis reports a study of certain aspects of ion beam mixing in amorphous silicon. The amorphous silicon films are deposited by RF sputter deposition technique, and heavy metal markers of gold and tantalum are used to section these films. Mixing in the amorphous silicon films is brought about by energetic argon ions of various energies (100 keV to 300 keV) and an estimate of mixing is made by observing the shift and broadening in the marker profile using Rutherford backscattering spectrometry. Mixing versus depth as a function of the angle of incidence is investigated experimentally, by implanting at ten different angles (0° to 85°), films, with the marker at various depths. A comparison of the experimental results is made with the Wilson and Webb model, the average diffusion model, and a computer simulation code TRIM-Cascade. All the comparisons show evidence of radiation enhanced diffusion in the experiment. The presence of radiation enhanced diffusion is confirmed when a double marker technique is employed to determine the effect of sputtering, contraction and swelling, in an amorphous silicon film, due to mass transport under argon ion irradiation, both at room temperature and at LN2 temperature. Finally, as an application of the ion beam mixing process, silicide formation at the interface of a Ni-Si and an Fe-Si system is considered. The need to form useful silicides is evident from the recent developments in VLSI technology where transition metal silicides have been explored for interconnect metallization, gate metallization and low resistivity contacts. In the research work presented here, it is found that both the Ni-Si and Fe-Si systems show cascade type of mixing but silicide formation is more evident in the Ni-Si system.