Electromigration in stress-voided Al alloy conductors

Electromigration in narrow, stress-voided AlSiCu conductors is characterized. The effect of passivation stress is investigated, because this parameter has a strong effect on stress-induced void growth. The reliabiilty implications of stress voids are studied. When the passivation stress is high, so that void growth is not saturated prior to electromigration testing, a pronounced degradation of failure time occurs. With a lower passivation stress, and saturated void growth, failure times are largely unaffected by stress voids. Examination of failed stripes shows that in metallizations with high stress passivations pre-existing voids are preferential sites for electromigration, producing slitlike open circuits. It is proposed that mechanical stress gradients generated by stress-induced void growth are important in the processes that produce these open circuits.<>