Refractory binary metal nitride films, (Ti, Zr)N-x, were prepared by direct current reactive magnetron sputtering from a Ti-5 at.% Zr alloy target in N-2/Ar gas mixtures and then used as diffusion barriers between Cu and Si substrates. In order to investigate the thermal stability of Cu (60 nm)/(Ti, Zr)N-x (6 nm)/Si contact systems, sheet resistance measurement, X-ray diffraction, scanning electron microscopy, cross-section transmission electron microscopy, and X-ray photoelectron spectroscopy depth profile were performed. Experimental results indicate that the barrier performance are significantly, affected by the chemical composition of (Ti, Zr)N-x films, N/(Ti, Zr) atomic ratio. Besides, our results also suggest that the refractory binary metal nitride film, (Ti, Zr)N-x, can be used as a superior diffusion barrier for Cu metallization as compared to the well-known TaN film. (c) 2005 Elsevier B.V. All rights reserved.