Thermal oxidation and resistivity of tantalum nitride films

Abstract

We investigated the effect of annealing on the resistance of tantalum nitride films. It was found that about 80% of the observed changes were due to surface oxidation, while the rest came from resistivity changes. Oxidation at 250–350 °C followed a quartic time law with an activation energy of 1.45 eV. Tantalum films with 31–37 at.% nitrogen and varying in structure from fine-grained body-centered cubic to hexagonal close-packed and face-centered cubic showed the same oxidation kinetics and activation energy. Long term exposure in air at 125–175 °C, after annealing at 300–350 °C, caused further resistance changes with a parabolic time dependence and activation energy of about 1.25 eV. They resulted from additional oxide growth and from resistivity changes in a region of thickness 50 Å at the oxide-metal interface.