Thermal Oxidation of Sputtered TaN Films and Properties of the Oxidized Films

Abstract
The thermal oxidations of a sputtered TaN film and the properties of an oxidized TaN (TaNO) film were investigated. By oxidation at around 600°C in dry oxygen, conductive TaN converts into an amorphous insulator which develops, after subsequent annealing at about 800°C, to a mixed compound consisting of main hcp Ta2O5 and amorphous nitride phases. The oxidation is controlled by a diffusion process. Capacitance measurements yield a relative dielectric constant of about 20. The dielectric breakdown strength is more than 2×106 V/cm. The TaNO film was found to be very suitable as a capacitor-forming material for microwave GaAs ICs in conformity with a self-align Au/TaN/WN/GaAs gate FET process.