Optical and electrical properties of thermal Tantalum oxide films on silicon

Tantalum pentoxide is of interest as an alternative dielectric to SiO
2
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
2
O
5
films. The conduction currents depended on the oxidation period but were comparable to or slightly better than reported for CVD Ta
2
O
5
.