Phase-field simulations of electromigration-induced defects in interconnects with non-columnar grain microstructure

In this work, we utilize a phase-field model to investigate electromigration-mediated defects in non-columnar polycrystalline interconnects. We find that the misalignment of the grain boundary with respect to an externally applied electric field governs the non-linear kinetics of electromigration-induced slit evolution. We explore the mechanisms by which electromigration-induced defects propagate in interconnects comprising equiaxed and randomly distributed grains. We deduce that when atomic mobility in grain boundaries (M g b) is two orders of magnitude larger than along the surface (M s), the defect manifests as grain boundary slits, while a smaller M g b / M s promotes surface drift. By the aid of an extensive parametric study, the presence of a mixed mode at intermittent values of M g b / M s is established. Our simulations of slit formation in a network of randomly distributed grains validate our hypothesis that grain boundary alignment and the grain size distribution determine failure rates. Finally, we found that the failure rates in 3D are several times faster than in 2D, which indicates the importance of accounting the physics of three-dimensional capillarity in the present modeling approach.