Photo-induced atomic layer deposition of tantalum oxide thin films from Ta(OC2H5)5 and O2

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 degrees C were almost stoichiometric. The refractive index (at 550 nm) and the optical bandgap were found to be similar to 2.13 and similar to 4.20 eV, while an average transmittance of similar to 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.