Void nucleation on intentionally added defects in Al interconnects

Void nucleation in passivated aluminum interconnects was studied using high voltage scanning electron microscopy. To test theories about stress-induced and electromigration void nucleation, Ar ions were implanted into Al specimens. The Ar atoms precipitated and formed bubbles that served as nucleation sites with high surface energy. In the implanted samples, voids formed away from the interconnect sidewalls, in contrast to voids in ordinary passivated Al interconnects. The evolution of the void volume was also affected by the reduction in the nucleation barrier. These results strongly support the theory of void nucleation on interface flaws in Al interconnects.