Effects of crystallinity and thickness of silicide layer and substrate orientation on the oxidation of NiSi2 on silicon

Abstract

Oxidation kinetics for both dry and wet oxidation of epitaxial NiSi2 (200 nm)/(001)Si samples as well as dry oxidation of polycrystalline NiSi2 (200 nm)/(111)Si and epitaxial NiSi2 (600 nm)/(111)Si samples have been studied by transmission electron microscopy. Comparing oxidation kinetics data of 200-nm-thick epitaxial NiSi2 on (001) and (111)Si, activation energies of the parabolic rate constants are rather close, whereas those for linear rate constants are substantially different. The orientation dependence of the linear activation energies is explained in terms of the total number of available Si atoms for oxidation as a function of the substrate orientation. Oxide growth rate was found to be higher in polycrystalline NiSi2/(111)Si samples than that in epitaxial NiSi2/(111)Si samples. Strong influence of the grain boundaries of NiSi2 on oxidation kinetics was observed with the grain boundaries serving as fast paths for oxidation. For dry oxidation of epitaxial NiSi2 (600 nm)/(111)Si samples, both parabolic and linear activation energies are higher than those of Ni(200 nm)/(111)Si samples.