On the propensity of electromigration void growth from preexisting stress-voids in metal interconnects.

摘要

Thermomechanical and electrical finiteelement analyses of voided metal interconnectswere undertaken. The resulting information wasused in modeling the stress buildup and atomicflux divergence during electromigration using thefinite difference method. A simple correlationbetween the preexisting stress-void andelectromigration void growth was identified. Alarge preexisting-stress void in the metal line ismore prone to growth during electromigration thansmall voids. This is a consequence of the stressgradient along the line generated by the stress-induced voiding. Controlling stress-inducedvoiding is thus seen to be important in preventingelectromigration failure. The present modelingprovides a mechanistic rationale for previousexperimental observations. It also serves toillustrate that, in electromigration modeling,simply using a critical stress as the failurecriterion may be insufficient. Material: Al linein a silicon dioxide dielectric.