Mechanism of dependency of EM properties on linewidth in dual damascene copper interconnects

The electromigration (EM) performance of dual damascene Cu lines has been investigated correlated with quality of Cu lines. The results on the EM test showed that the EM lifetime decreases as the linewidths decrease. Failure analysis after EM test revealed that EM properties of damascene Cu lines are dominated by the transport of Cu atoms along an interface between a Cu line and a barrier layer. It is supposed that Cu atoms are easy to migrate in the defective region in the vicinity of the interface. The narrower lines are found to be more defective by Resistance Ratio (RR) measurement and transmission electron microscopy. We assume that influence of the interface is stronger in the narrower lines, therefore EM lifetime is shelter in the narrower lines because of the fast migration of Cu atoms at the interface. The RR measurement, in which quality of Cu metal in the lines might be able to be evaluated, is a useful technique for estimating the EM lifetime of damascene Cu lines in a short time.