Photo-Induced Atomic Layer Deposition of Tantalum Oxide Thin Films from Ta(OC[sub 2]H[sub 5])[sub 5] and O[sub 2]

Abstract

The growth of tantalum oxide thin films by photoinduced atomic layer was investigated in the temperature range of 170-350°C using Ta(OC2H5)5 and O2 as precursors. A self-limiting growth rate of 0.37 Å/cycle was achieved at the substrate temperature range of 190-285°C. 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°C were almost stoichiometric. The refractive index (at 550 nm) and the optical bandgap were found to be ∼2.13 and ∼4.20 eV, while an average transmittance of ∼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 - 1 × 10-8 A/cm2 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.