TaN or TaCN films were deposited using a single source, pentakis-diethylamido-tantalum as diffusion barrier for copper metallization. N- and Ar-ion beams with energy of 120 eV were used for bombarding the film during growth to improve the film quality. The films deposited using N-ion beam showed a resistivity of approximately 950 muOhm cm and a density of 7.65 g/cm(3). The use of the N-ion beam, however, drastically degraded the step coverage of the film (similar to5% at the 0.5 mum contact holes with aspect ratio of 3:1). On the other hand, the films deposited using an Ar-ion beam showed a resistivity of approximately 600 muOhm cm and a density of 8.26 g/cm(3). The step coverage measured at the same contact was approximately 40%. The resistivity and density of the thermally-decomposed film were also measured for comparison and were found to be approximately 10 000 muOhm cm and 5.85 g/cm(3), respectively. Finally, the diffusion barrier performance of 50 nm thick films against Cu was investigated by X-ray diffractometry. The Cu/N- or Ar-ion beam bombarded film/Si structures showed formation of eta"-Cu3Si after annealing at 650 degreesC for I h, while Cu/thermally-decomposed film/Si showed this only after annealing at 600 degreesC.