Improvement of the Diffusion Barrier Performance of Ru by Incorporating a WN[sub x] Thin Film for Direct-Plateable Cu Interconnects

A sputter-prepared Ru (7 nm)/ (8 nm) stacked layer was investigated as a diffusion barrier layer between Cu and Si for direct-plateable Cu interconnects, and its performance was compared with that of a Ru single layer with the same thickness (15 nm). X-ray diffractometry and sheet resistance measurements showed that the incorporation of into the Ru single layer system significantly improved the barrier performance against Cu diffusion. The bilayer barrier stack failed due to Cu diffusion attack after annealing at for 30 min, while the Ru single layer failed after annealing at by the formation of Cu silicide . A high resolution transmission electron microscopy analysis clearly suggested that this was due to the excellent diffusion barrier performance of film with a nanocrystalline structure embedded in an amorphous matrix.