Quantitative Analysis of Electromigration-Induced Damage in Al-Based Interconnects

Abstract

Electromigration in metal interconnect lines produces sites of damage, such as voids, hillocks and whiskers, which by definition are the sites of flux divergence in the lines. Detailed observations of damage volume and morphology, especially in relation to the local microstructure, may yield vital information about the processes which produce the damage and ultimate failure in the interconnects. We present fractographic measurements of void volumes and the spacing between voids and corresponding hillocks in Al and Al-2% Cu interconnects which have been electromigration tested until failure. It is shown that the void density as well as the shape of failure voids depend on the current density. Further it is found that the distribution of the spacings between voids and corresponding hillocks changes as a function of current density.