Effects of pulsed current on electromigration lifetime

Asymmetrical Cu interconnect structure, where one end of the metal-2 (M2) test line is connected to M1 while the opposite end is connected to M3, was subjected to very long periods of bipolar pulsed current (i.e. 2, 16 and 48 hours) in this study. The median-time-to-failure (150) of the samples was found to depend on the direction of electron current in the first half-period, and t(50) of samples that were subjected to direct current (D.C.) that flow upstream or downstream. Bipolar pulsed current stressed samples showed improvement in lifetimes as compared to that of D.C. stressed samples only when the half-period of bipolar pulsed current was shorter than the t(50) of D.C. stressed samples.