-TaON thin films: production by reactive magnetron sputtering and the question of non-stoichiometry

Abstract

In this work we report on the structure, morphology, composition, chemical bonding and optical properties of tantalum oxynitride (Ta–O–N) thin films prepared by reactive direct current magnetron sputtering. The films have been investigated by grazing incidence x-ray diffraction, x-ray reflectivity, grazing incidence small angle x-ray scattering, time-of-flight elastic recoil detection analysis, x-ray photoelectron spectroscopy and spectroscopic ellipsometry. The composition and the partial pressure of the reactive atmosphere (N2 + O2) have been varied in order to find conditions suitable for the -TaON phase production. As prepared thin films are amorphous and annealing at °C is necessary to promote crystallization. We discuss the role of N2 gas on the kinetics of sputtered particles and its influence on the oxidation rate and porosity of the growing film. The anion composition in Ta–O–N films strongly depends on the reactive gas condition during the deposition. We found that the O/N ratio in -TaON films increases with more N2 or O2 gas in the chamber, whereas the corresponding absorption onset and valence band maximum show a blue shift of up to 0.5 eV. These results were related to the non-stoichiometry in -TaOxNy crystallites with x > y .