Optical and electrical properties of thermal Tantalum oxide films on silicon

Abstract

Tantalum pentoxide is of interest as an alternative dielectric to SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> for 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 Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> films. The conduction currents depended on the oxidation period but were comparable to or slightly better than reported for CVD Ta <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> O <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> .