Transmission electron microscopy of the formation of nickel silicides

The formation of Ni2Si, Nisi and NiSi2 on Si has been studied by TEM, particularly with cross-sectional specimens and by high-resolution imaging. Both Ni2Si and Nisi showed an oriented growth on 111) substrates, while NiSi2 grew epitaxially on {111 and 100 Si. Ni2Si assumed two different pseudo-hexagonal orientations whereas Nisi was found to be truly hexagonal instead of orthorhombic on 111 Si. TEM of cross-sectional specimens showed that all the silicide-Si interfaces were quite rough, except in the case of Nisi2 where it was highly facetted. When Ni2Si and Nisi were present simultaneously, they often were separated by an interfacial layer, ∼3 nm thick, which might be related to Kirkendall voids or to remainders of the native oxide on the Si substrate. Cross-sectional views of misfit dislocations in the epitaxial interfaces have been obtained and analysed in terms of their Burgers vector and spacing.