Mechanisms of electromigration under AC and pulsed-DC stress in Cu/low-k dual damascene interconnects

We examine electromigration mass transport under pulsed-DC (PDC) and AC conditions by measuring the Cu drift velocity. We observed drift velocities that are constant as a function of duty ratio, confirm that there is no recovery of electromigration damage during current reversal, or off-cycles. Failure time distributions under PDC conditions can be accurately modeled by a void growth mechanism with an effective current density given by the average of the waveform.