Dynamics of transgranular voids in metallic thin films under electromigration conditions

A theoretical analysis is presented for the morphological evolution and stability of transgranular wedge-shaped voids in conductor lines with bamboo grain structure under an applied electric field. A linear stability analysis identifies void shapes that become unstable with respect to the growth of perturbations with wavelengths longer than a critical wavelength. The analysis predicts a critical wavelength that is consistent with experimental observations in unpassivated aluminum lines. The predicted changes in shape during the morphological evolution of the void surfaces are in agreement with the experimental observations.