Cobalt silicide formation induced by oxygen ion bombardment

Abstract

Oxygen ion bombardment of the Co/Si and Co/SiOx/Si systems has been studied with regard to the effects on the ion-induced formation of cobalt silicides. Dose-dependence experiments have shown that with increasing total dose the phase formed upon post-bombardment annealing was Co2Si (rather than the expected disilicide). Similarly, samples annealed after bombardment at elevated temperatures were also found to result in the metal-rich phase. Conversely, post-bombardment annealing of samples bombarded at progressively higher energies indicated that the disilicide was the favoured phase. Samples bombarded at lower energies, however, were found to consist largely of Co2Si. These observations are interpreted in terms of the formation of a buried silicon oxide layer. The oxide layer subsequently acts as a barrier to the evolution of the disilicide phase by providing a high activation energy diffusion path for the mobile species. In contrast to neon bombardment, no evidence was found for surface exfoliation even at the highest oxygen doses.