Defect behavior in aluminum interconnect lines deformed thermomechanically by cyclic joule heating

Al–1wt.% Si lines were deformed thermomechanically by cyclic joule heating induced by applying an AC current. Scanning electron microscopy revealed arrays of wavelike surface intrusions/extrusions aligned along low-index crystallographic directions after a few thousand thermal cycles. Transmission electron microscopy observations of cross-sections of selected regions shows that in grains that developed intrusions/extrusions, dislocations nucleated at the film–substrate interface, glided to the surface, and escaped. The densities of dislocations and prismatic loops observed here are similar to those observed in mechanical fatigue experiments on bulk aluminum.