Intrinsic study of current crowding and current density gradient effects on electromigration in BEOL copper interconnects

The intrinsic effects of current crowding and current density gradients on electromigration in back end of line copper interconnects have been investigated using a simple single layer test structure, where the electromigration performance of standard straight structures is compared to structures with a 90° angle. Using finite element modeling, it is demonstrated that locally higher current crowding and current density gradients are indeed present in these angled structures. As electromigration lifetimes are comparable between the straight and the angled structures and no void formation is observed in or close to the angle, we conclude that the intrinsic impact of current crowing and current density gradients in via-electromigration is negligible.