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

The instability of electromigration induced mass transport within a thin-hi m conductor and its relation to catastrophic growth of voids in the later s tage of electromigration failure are studied. To isolate intrinsic instabil ity of mass transport from extrinsic defects, a void-free homogeneous condu ctor is examined in which surface and interface diffusion are neglected. Ex plicit conditions are derived for linearized instability and the effects of various diffusion mechanisms on instability are identified. It is found th at thermomigration and electromigration provide the major driving forces fo r linear instability of uniform mass transport. In particular, thermomigrat ion plays the dominant role in the onset of linear instability. The paramet ers which govern the onset of linear instability are the current density an d temperature of the conductor. Linear instability can occur when Joule hea ting due to current crowding leads to sufficiently high temperature rise. T he results appear to provide new insight into the understanding of some exp eriments 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. (C) 1999 Acta Metallurgica Inc. Published by Elsevi er Science Ltd. All rights reserved.