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A numerical model of the equivalent time conversion to DC stressing for electromigration failures under various current waveforms is proposed based on the vacancy diffusion and damage healing theory. The Joule heating effect and the intrinsic stress-induced voiding are included in the calculation of interconnect reliability. The simulation results show that the cumulative lifetimes are strongly affected by current frequency and vacancy lifetime and a frequency shift to the right occurs for small vacancy lifetimes under AC stressing. For pulsed-DC stressing, the temperature rise dependent on the current frequency dominates the interconnect reliability. The average temperature rise due to Joule heating is reduced by two times when the frequency is larger than approximately the reciprocal of the thermal time of interconnect structures. [ABSTRACT FROM AUTHOR]