The instability of electromigration-induced mass transport in a thin-film conductor, and its relationship to the catastrophic growth of voids in the later stage of electromigration failure, were studied. In order to isolate the intrinsic instability of mass transport, a void-free homogeneous conductor was considered in which surface and interface diffusion were neglected. Explicit conditions were derived for linearized instability, and the effects of various diffusion mechanisms upon instability were identified. It was found that thermomigration and electromigration were major driving forces for the linear instability of uniform mass transport. Thermomigration played the predominant role in the onset of linear instability. The parameters which governed the onset of linear instability were the current density and temperature of the conductor. Linear instability could occur when Joule heating, due to current crowding, led to a sufficiently high temperature rise. It was concluded that the results provided new insight into the understanding of experiments in which catastrophic void growth was observed in the later stages of electromigration failure when the degree of mass-loss and temperature rise were sufficiently high.

Intrinsic Instability of Electromigration-Induced Mass Transport in a Two-Dimensional Conductor. C.Q.Ru: Acta Materialia, 1999, 47[13], 3571-8