Effect of current crowding on vacancy diffusion and void formation in electromigration

In multilevel interconnects, current crowding occurs whenever the current changes direction, such as when passing through a via. We propose that in current crowding, the current-density gradient can exert a driving force strong enough to cause excess vacancies (point defects) to migrate from high to low current-density regions. This leads to void formation in the latter. This is a key feature of electromigration-induced damage in very large scale integrated interconnects.