Current-induced wave propagation on surfaces of voids in metallic thin films with high symmetry of surface diffusional anisotropy

We report results of a systematic theoretical analysis of the electromigration driven morphological evolution of voids in metallic thin films based on self-consistent numerical simulations according to a fully nonlinear surface transport model that accounts for surface diffusional anisotropy. The analysis focuses on film planes with high symmetry of surface diffusional anisotropy. The simulations indicate that under very low anisotropy strengths, there is indeed the possibility of current driven wave propagation on the void surface. Specifically, surface waves appear prior to film failure over a broad range of electric field strengths: from very weak to quite strong. These interesting phenomena appear only at negative misorientation angles between the electric field direction and fast directions of surface diffusion for very low anisotropy strengths. However, for a slight increase in the anisotropy strength, current-induced wave propagation is observed also in the case of positive misorientation angles.