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Journal of the Electrochemical Society, Vol.151, No.1, C52-C55, 2004
Photo-induced atomic layer deposition of tantalum oxide thin films from Ta(OC2H5)(5) and O-2
The growth of tantalum oxide thin films by photoinduced atomic layer deposition was investigated in the temperature range of 170-350degreesC using Ta(OC2H5)(5) and O-2 as precursors. A self-limiting growth rate of 0.37 Angstrom/cycle was achieved at the substrate temperature range of 190-285degreesC. All the films grown in this temperature range were amorphous and very smooth (<0.31 nm root-mean-square) as examined by X-ray diffractometer and atomic force microscopy. X-ray photoelectron spectroscopy analysis showed that the films grown at 260-350&DEG;C were almost stoichiometric. The refractive index (at 550 nm) and the optical bandgap were found to be &SIM;2.13 and &SIM;4.20 eV, while an average transmittance of &SIM;90% in the visible region was obtained. Electrical measurements performed on Pt/Ta2O5(10 nm)/Ru/SiO2/Si capacitors exhibited high dielectric constant (22-25) and a remarkably low leakage current density of 0.8-1x10(-8) A/cm(2) at an applied field of 1 MV/cm, probably due to the presence of reactive oxygen atom species. The low leakage current was dominated by the Poole-Frenkel emission mechanism. (C)2003 The Electrochemical Society.