Ultrathin Ru-N and Ru-Ta-N films (∼15 nm in thickness) deposited by reactive sputtering are applied as a diffusion barrier in the Cu/barrier/ Si O2 Si systems. After film deposition, the samples are tested before and after annealing at 200-900°C in vacuum for 30 min. The sheet resistance examined by four-point probe appraises that the Ru-Ta-N barrier would not fail until annealing at 900°C, as compared to Ru-N, which fails after annealing at 600°C. The depth distribution of elements examined by Auger electron spectroscopy confirms different degrees of Cu diffusion into underlayers for the two systems after annealing at 600°C. Also, the cross-sectional microstructures of the Cu/barrier/ Si O2 Si samples analyzed by transmission electron microscopy, the crystallinity of barrier films examined by grazing incident angle X-ray diffraction, and the chemical state of barrier characterized by X-ray photoelectron spectroscope might explain the difference in barrier performance for the ultrathin Ru-N and Ru-Ta-N films in the Cu/barrier/ Si O2 Si multilayered systems.
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