Effect of Grain Boundaries and Local Variation Influence of Current Density and Temperature on the Electromigration Damage in Gold Thin Films

The value of activation energy for electromigration failure in gold thin films (0,85±0,17 e.v.) show that the grain boundary diffusion is very important. According to the elastic collisions hypothesis the electron flow promotes a normal force on the grain boundary which does not produce diffusion along the boundaries. On the opposite the electric field produces on the boundary ions a force always directed toward the cathode. Therefore the effective valence is positive, although mass accumulation on the anode side of voids is suggesting an effective negative valence for gold. This is not a contradiction: the modification of current lines around the voids results local current density and temperature variations, great enough for bulk electromigration (effective negative valence).