Solute effect of arsenic on the microstructure and diffusion mechanism in platinum-silicides

The growth kinetics and the microstructures of Pt2Si and PtSi on undoped and heavily arsenic-doped polycrystalline silicon have been investigated in the temperature range of 200 to 400°C. We found that on both substrate materials the silicide growth is a thermally activated process with a common activation energy for each compound. The addition of arsenic to the polycrystalline silicon was found to reduce the pre-exponential factor of the growth kinetics. To determine the diffusion mechanism in Pt-silicides we have carried out a detailed investigation of their microstructures. We report for the first time the observation of Kirkendall voids in a noble-metal silicide. The location of the voids at the Pt-silicide/Pt interface is a clear indication that the dominant diffusion mechanism in Pt-silicides is a vacancy-assisted diffusion of Pt atoms. The effect of arsenic on the pre-exponential factor is discussed by considering possible influences of arsenic atoms on the mechanism of chemical interdiffu...