Stress Migration Followed by Electromigration Reliability Testing.

Electromigration (EM) and Stress Migration (SM) are reliability concerns for modern day integrated circuits. However, neither mechanism is completely independent of the other, but instead they have a combined impact on the failure behavior of copper interconnects. Due to the differences in the coefficient of thermal expansion (CTE), thermally induced stress is ‘quenched in’ the conductors during processing. The presence of this thermal stress may reduce the amount of stress needed for electromigration to cause failure; hence, reduce lifetime of the interconnect. For this study, we investigated the effect of a temperature anneal on electromigration lifetime. It was found that stress migration may play a significant role in the distribution of the first failure mode or the early failures of the electromigration failure. However, with stress anneals at $250^{\circ}\text{C}$ up to 500 hours, it did not have a significant effect on the second failure mode associated with electromigration failure.