Optical and electrical properties of thermal Tantalum oxide films on silicon

Tantalum pentoxide is of interest as an alternative dielectric to SiO2for MOS devices. In the present work, RF-sputtered tantalum films on silicon substrates were thermally oxidized at 500°C. Ellipso-metric measurements showed that films made in this way were uniform in refractive index except for a narrow region of tapered index at the silicon interface. Capacitance measurements gave a relative permittivity of about 26, in the range shown by anodic Ta2O5films. The conduction currents depended on the oxidation period but were comparable to or slightly better than reported for CVD Ta2O5.