Low resistive and highly reliable copper interconnects in combination of silicide-cap with Ti-barrier for 32 nm-node and beyond

Abstract

Silicide-cap for Cu interconnects is promising for enhancing electromigration (EM) performance for 32 nm-node and beyond. But the trade-off properties of silicide-cap between line resistance and EM lifetime remain to be resolved. Increasing of line resistance is caused by Si diffusion in Cu line. So, we focused on Ti barrier metal (BM), which diffuses in Cu line, and applied it in combination with silicide-cap, in order to keep Si stable at the surface of Cu line. As a result, we achieved EM median time-to-failure (MTF) 100 times longer than that of the sample w/o silicide-cap and Ta-BM while line resistance is kept lower. Activation energy (Ea of EM of 1.45 eV is achieved.