Scaling impacts on electromigration in narrow single-damascene Cu interconnects

In this paper, we present scaling impacts on electromigration-induced mass transport in narrow single-damascene Cu interconnects. Linewidths ranging from 0.12 mm to 0.20 mm were used to demonstrate the impacts. Lifetimes that are determined by resistance degradation decrease according to decreasing linewidth at a fixed current density. This is caused by a decrease in effective incubation time and an increase in drift velocity. The,product of drift velocity and the square of the linewidth has a linear dependence on current density. The activation energy is 1.2eV for the effective incubation time, and 1.1 eV for the drift velocity. The values are independent of the linewidth. The activation energy suggests that the effective incubation time is the time to void growth from the Cu/SiCN interface to the trench bottom through Cu grain boundaries. The grain boundaries provide nucleation sites for void growth in bamboo structures. Similarly, interface diffusion at the Cu/metal liner on the sidewalls of the line contributes to void growth.