Projecting interconnect electromigration lifetime for arbitrary current waveforms

A vacancy-relaxation model is proposed. It predicts the DC lifetime, pulse DC (arbitrary unidirectional waveform) lifetime, pure AC lifetime, and AC-plus-DC-bias lifetime for all waveforms and all frequencies above 1 kHz. The predictions are verified by experiments and significantly raise the projected lifetimes beyond the widely assumed A_dc T/J_rms^m. The pure AC lifetimes of aluminum interconnect are experimentally found to be more than 10³ times larger than DC lifetime for the same current density. In addition, AC stress lifetimes are observed to follow the same dependences on current magnitude and temperature, for T<300°C, as the DC stress lifetime