Intrinsic instability of electromigration induced mass transport in a two-dimensional conductor

Abstract

The instability of electromigration induced mass transport within a thin-film conductor and its relation to catastrophic growth of voids in the later stage of electromigration failure are studied. To isolate intrinsic instability of mass transport from extrinsic defects, a void-free homogeneous conductor is examined in which surface and interface diffusion are neglected. Explicit conditions are derived for linearized instability and the effects of various diffusion mechanisms on instability are identified. It is found that thermomigration and electromigration provide the major driving forces for linear instability of uniform mass transport. In particular, thermomigration plays the dominant role in the onset of linear instability. The parameters which govern the onset of linear instability are the current density and temperature of the conductor. Linear instability can occur when Joule heating due to current crowding leads to sufficiently high temperature rise. The results appear to provide new insight into the understanding of some experiments where catastrophic void growth was observed in the later stage of electromigration failure when the amount of mass loss and temperature rise were sufficiently high.