Copper wetting of a tantalum silicate surface: Implications for interconnect technology

X-ray photoelectron spectroscopy data show that sputter-deposited Cu (300 K) displays conformal growth on oxidized TaSi films (TaSiO6). The TaSiO6 films, 6 Å thick, were formed by sputter deposition of Ta onto ultrathin SiO2 substrates at 300 K, followed by annealing to 600 K in 2 Torr O2. The photoelectron spectra of the films are characterized by a Si(2p) binding energy at 102.1 eV, indicative of silicate formation. Annealing the film to >900 K resulted in silicate decomposition and SiO2 formation. Cu(I) formation and conformal growth were not observed for the annealed films. The results are similar to those previously reported for oxidized TaSiN, and indicate that Si-modified Ta barriers should maintain Cu wettability under oxidizing conditions for Cu interconnect applications.