Thermal Ta2O5 films as a gate insulator for thin film capacitors

Abstract

Ta2O5 thin films (13-260nm) on p-Si have been prepared by thermal oxidation at 673-873K of RF sputtered Ta films. Conduction and dielectric properties of the layers have been studied employing Al-Ta2O5-Si capacitors. A decreasing trend in the leakage current was found upon increasing temperature from 673 to 873K. Layers with dielectric constant in the range 25-32 are easily obtained. A minimum conductivity, which corresponds to a leakage current density of about 10-7 A cm-2 at an applied field of 0.5 MV cm-1, was detected for films oxidized at the highest oxidation temperature. The oxide properties are discussed in terms of the presence of an unavoidable SiO2 layer between Si and Ta2O5 and of bond defects in the oxide.