Stress-induced and electromigration voiding in nitride passivated Al interconnects

Abstract

Void nucleation in nitride passivated aluminum interconnects was studied using High Voltage Scanning Electron Microscopy (HVSEM). Extensive stress-induced voiding was observed in the line regardless of passivation thickness. Some of the stress-induced and electromigration voids formed away from the interconnect sidewall, which is contrary to images presented in other studies of void nucleation. Transmission electron microscopy showed that hydrogen from the nitride layer forms bubbles in the aluminum. These bubbles act as pre-existing defects in the aluminum, reducing the barrier for void nucleation.