Characterisation of ultraviolet annealed tantalum oxide films deposited byphoto-CVD using 172 nm excimer lamp

Photo-CVD growth of thin tantalum pentoxide (Ta2O5) films on Si (1 0 0) usi ng 172 nm radiation to excite tantalum ethoxide and nitrous oxide mixtures and the effects of ultraviolet annealing of these films were investigated b y X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy , and electrical measurements. Detailed changes of the Ta4f, O1s and Si2p p eaks after the UV annealing have been specifically monitored and analysis r evealed that a thin SiO2 layer was formed on the surface of the Ta2O5 films . The atomic ratio of O/Ta is about 2.3 for the as-deposited films and 2.59 for the annealed films, which is close to the stoichiometric ratio of 2.5 for Ta2O5. The effect of UV annealing on the reduction of the leakage curre nt in the Ta2O5 films is also discussed. Leakage current densities as low a s 6.49 x 10(-9) A cm(-2) at an electric field of 0.5 MV/cm have been obtain ed for the films deposited at 350 degreesC and annealed at 400 degreesC. Th ese values are comparable to those obtained for films deposited by thermal or plasma-CVD at 400-500 degreesC and annealed at 600-900 degreesC. (C) 200 1 Elsevier Science Ltd. All rights reserved.