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

Photo-CVD growth of thin tantalum pentoxide (Ta(2)O(5)) films on Si (1 0 0) using 172 nm radiation to excite tantalum ethoxide and nitrous oxide mixtures and the effects of ultraviolet annealing of these films were investigated by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and electrical measurements. Detailed changes of the Ta4f, O1s and Si2p peaks after the UV annealing have been specifically monitored and analysis revealed that a thin SiO(2) layer was formed on the surface of the Ta(2)O(5) 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 Ta(2)O(5). The effect of UV annealing on the reduction of the leakage current in the Ta(2)O(5) films is also discussed. Leakage current densities as low as 6.49 x 10(-9) A cm(-2) at an electric field of 0.5 MV/cm have been obtained for the films deposited at 350 degreesC and annealed at 400 degreesC. These 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) 2001 Elsevier Science Ltd. All rights reserved.