The electromigration short — Length effect and its impact on circuit reliability

The short-length effect, whereby electromigration is eliminated due a mechanical stress-gradient induced backflow has a profound impact on the characteristics of electromigration failure. Here we review our recent studies of electromigration failure at short lengths in Cu/low-k interconnects. We show that voiding failures can occur at current densities below the critical value. We develop a model that accurately predicts failure distributions as a function of stress variables, conductor geometry, and presence of passive reservoirs. We also discuss the scaling of electromigration at short - lengths, and show that failure times decrease even more rapidly than long-lengths with technology scaling.