Ru/WNx Bilayers as Diffusion Barriers for Cu Interconnects

Abstract

Bilayers of Ru (7 nm)/WNx (8 nm) prepared by sputtering were investigated as diffusion barriers between Cu and Si, and their performances were compared as a function of N-2 flow rate during the deposition of WNx. The Ru/WNx bilayer diffusion barriers were stable upon annealing at up to at least 650 degrees C for 30 min while a Ru single layer (15nm in thickness) failed after annealing at 450 degrees C owing to the formation of Cu silicide. Grazing-angle X-ray diffractometry results showed that the crystallinity of the WNx film was degraded but that its nanocrystalline state preserved upon annealing at higher temperatures with increasing N-2 flow rate during the deposition. These resulted in the better performance against Cu attack of bilayer diffusion barriers with the WNx film prepared with a higher N-2 flow rate. (C) 2011 The Japan Society of Applied Physics