On the formation of inhomogeneities in epitaxial CoSi2 layers grown from the interaction of Co/Ti bilayers with Si 〈100〉 substrates

Abstract

The redistribution of titanium during the formation of epitaxial CoSi2, grown from the reaction of Co(20 nm)/Ti(10 nm) bilayers with Si 〈100〉, has been investigated. Annealing of Co/Ti/Si structures, at temperatures between 850 and 1050 °C, is shown to be associated with the growth of an inhomogeneous CoSi2 layer having Ti-rich surface layer(s) on top. The formation of inhomogeneities in the CoSi2 layer is conclusively attributed to the presence of Ti-rich surface layer(s). It is shown that smooth and morphologically stable CoSi2 layers can be grown by removing these surface layers followed by a high-temperature treatment in nitrogen atmosphere. We propose that the underlying mechanism for the inhomogeneity formation within the CoSi2 layer is a nucleation-controlled process, induced by an anticipated reaction between the CoSi2 layer and Ti-rich phases near the surface.