TaNx films sputtered from a TaN target were used as diffusion barriers between Cu thin films and Si substrates. Material characteristics of TaNx films and metallurgical reactions of Cu/TaNx/Si systems annealed in the temperature range 400-900degreesC for 60 min were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, cross-sectional transmission electron microscopy, and sheet resistance measurements. We found that the deposition rate decreased with increasing bias. TaN, beta-Ta, and Ta2N phases appeared and/or coexisted in the films at specific biases. A step change in N/Ta ratio was observed whenever a bias was applied to the substrate. After depositing a copper overlayer, we observed that the variation percentage of sheet resistance for Cu (70 nm)/TaNx (25 nm, x = 0. 37 and 0.81)/Si systems stayed at a constant value after annealing up to 700 degreesC for 60 min; however, the sheet resistance increased dramatically after annealing above 700 and 800degreesC for Cu/TaN0.37/Si and Cu/TaN0.81/Si systems, respectively. At that point, the interface was seriously deteriorated and formation of Cu3Si was also observed. (C) 2003 Elsevier Science B.V All rights reserved.