Analysis of Electromigration-Induced Void Motion and Surface Oscillations in Metallic Thin-Film Interconnects

Abstract

AbstractAn analysis is presented of electromigration-induced migration and oscillatory dynamics of morphologically stable void surfaces based on self-consistent numerical simulations of morphological evolution of voids in metallic thin films. As the morphological stability limit is approached, the migration speed of a stable void deviates substantially from being inversely proportional to the void size, a well-known result that is rigorously valid in an infinite conductor with isotropic material properties. A non-linear shape function that includes both current crowding and diffusional anisotropy effects is used to rescale properly the void migration speed resulting in a universally valid relationship for the migration speed as a function of void size. Furthermore, in grains characterized by high symmetry of surface diffusional anisotropy, our analysis predicts the onset of stable time-periodic states for the void surface morphology that correspond to waves propagating on surfaces of voids that migrate along the metallic film at constant speeds.