Analysis of Failure in Metallic Thin-Film Interconnects Due to Stress and Electromigration-Induced Void Propagation

A theoretical analysis is presented of the morphological evolution of transgranular voids in metallic thin films driven by capillarity, stress, and electromigration. This highly nonlinear and complex dynamics is analyzed through self-consistent numerical simulations based on a two-dimensional phenomenological model of a passivated interconnect. The analysis follows a systematic exploration of a six-dimensional parameter space determined by the strengths of the electric and stress fields, surface diffusion anisotropy, and the size of the void. Our simulation results reveal a very rich nonlinear dynamical picture of void morphological evolution mechanism, including faceting, wedge void and faceted slit formation through a facet selection process, and soliton-like surface wave propagation. These results are in very good agreement with experimental observations and have important implications for interconnect failure.