Diffusion barrier properties of metalorganic chemical vapor deposition -WNx compared with other barrier materials

Tungsten nitride (WNx) is a potentially strong candidate for Cu diffusion barrier. The WNx films were deposited by chemical vapor deposition (CVD) using W(CO)6 and NH3 sources at 430°C. The diffusion barrier properties of WNx were investigated by comparison with other materials. In order to study the barrier properties, Cu/barrier/substrate structures were fabricated. A 120-nm-thick Cu film was deposited by evaporation onto various barrier materials including CVD-WNx, CVD-W, and sputter-deposited Ti,Ta, and TaN. After annealing for 1h in argon, variations in the film sheet resistances and the x-ray diffraction patterns were examined. Both results showed that a 15-nm-thick W2N film prevented Cu diffusion up to 600°C, and started to fail at 620°C, while no barrier and the CVD-W barrier samples failed at 100–150°C and 525–550°C, respectively. Also, 20nm sputtered Ti,Ta, and TaN films failed at 400–450°C, 550–575°C, and 650–700°C, respectively, in our annealing conditions. From these results, our WNx, deposited by CVD using the simple, nonfluorine precursor, W(CO)6, can be evaluated as a competent diffusion barrier candidate.