Modeling of electromigration-induced failure of metallic thin-film interconnects

Failure of metallic thin-film interconnects driven by electromigration is among the most challenging materials reliability problems in microelectronics. One of the most serious failure mechanisms in these films is the current-driven propagation of transgranular voids. In this paper, we present a comprehensive theoretical analysis based on self-consistent simulations of void dynamics under electromigration conditions and the simultaneous action of mechanical stress. For unpassivated films, our simulations predict void faceting, wedge-shaped void formation, propagation of slit-like features from void surfaces leading to failure, and propagation of surface waves on the voids prior to failure. For passivated films, void morphological instabilities can lead to film failure by propagation from the void surface of either faceted slits or finer-scale cracklike features depending on the strength of the electric and mechanical stress fields. More importantly, we demonstrate that in textured films, there exists a narrow range of conditions over which failure due to slit propagation can be inhibited completely.