The effect of stress-induced voiding on electromigration

Abstract

Stress‐induced voids present a serious reliability problem in the integrated‐circuit industry for near‐micrometer technologies. Reliability degradation has been previously evaluated from the viewpoint of open circuits caused by the mechanism of stress‐induced voiding. We present a study of the effect of stress‐induced voids on electromigration in 1.25‐μm AlSiCu metal runners over a wide range of temperatures and void size/density. Median time to fail decreases with increasing void size and density, except for cases of severe voiding where metal microstructure strongly influences failure. For void sizes ≤25% of the linewidth, failure rates remain low, implying that acceptable reliability may still be achieved for relatively low levels of voiding. Failure rates increase with void size up to 50% of the linewidth and then saturate. These results indicate that provided the time for an open circuit due to stress voiding alone exceeds the operational life of the device, then the primary reliability degradation of stress‐voided metallization will result from electromigration.