Thermal Oxidation of Transition Metal Silicides on Si: Summary

Thin films of almost all transition metal silicides, on a Si substrate, oxidize and form on their surfaces upon annealing in an oxidizing ambient. In applications of these silicides as interconnects in integrated circuits, the oxidation characteristics of a silicide and the growth rate are important. A compilation of the available data concerning silicide oxidation kinetics is presented. Generalization based on the data as presented is difficult. In this summary, we explore the processes controlling the oxidation of metal silicides and point out commonalities and differences between different silicides. We review the four steps controlling silicide oxidation: oxidant transport through the oxide, reaction at the silicide/ oxide interface, net transport of Si atoms with respect to metal atoms in the silicide, and reaction at the silicide/Si interface. The diffusing species through the silicide during oxidation correlates with the moving species in silicide formation. A discussion of a mechanism which explains why the oxidation rate of some silicides on a Si substrate is faster than that of bare Si is presented. It is concluded that silicides formed via metal diffusion oxidize faster than silicides formed via Si diffusion.