Nonlinear propagation of void front during electromigration in alloy films

Void formation during electromigration has been observed near the anode edge of a Cu-Al zone in an Al stripe. Growth of new voids was continuous with a void front propagating along the electron flow direction at a nonlinear rate. Such motion of the void front can be quantitatively correlated to the electromigration of Cu at grain boundaries. The measured displacements of the void front were analyzed to yield the grain-boundary diffusivity and effective charge for Cu electromigration.