Influence of atomic mixing and preferential sputtering on depth profiles and interfaces

Atomic mixing and preferential sputtering impose a depth resolution limit on the use of sputter sectioning to measure the composition of metal-semiconductor interfaces. Experimental evidence obtained with the Pt-Si system is used to .demonstrate ion-induced atomic mixing and then its effect on sputter etching and depth profiling. Starting with discrete layer structures, a relatively low ion dose (;;:: 3 X 10s cm-) first produced a mixed surface layer with a thickness comparable to the ion range. Higher ion doses then result in successive sputter etching and continual atomic mixing over a constant surface layer thickness. A model is developed that is based on a sputter-removal ( including preferential sputtering) of atoms at the surface and a uniform mixing of atoms over a constant thickness. The model predicts the influences of atomic mixing and preferential sputtering on the depth profiling of thin-film structures and interfaces.