Electrical properties and Auger electron spectroscopy analysis of oxide layers formed by anodization on NbTa and NbTaN films

Abstract

Anodic oxide films formed on NbTa and NbTaN systems have interesting electrical properties because of the similarity in physicochemical properties of niobium and tantalum. NbTa films were prepared by d.c. sputtering in argon gas and NbTaN films were prepared by d.c. reactive sputtering in an Ar-10%N 2 mixture. Anodic oxidation of these films was carried out in a solution of 80% dimethylsulphoxide and 20% phosphoric acid at room temperature by the constant current-constant voltage method. It was found that the values of tan δ for oxide films formed on the NbTaN system were in the range of 0.006-0.008 for all film compositions. The magnitudes of the leakage currents for NbTaNO films were smaller than those for NbTaO films. It can therefore be concluded that the incorporation of nitrogen into the NbTa alloy system plays an important role in the improvement of the dielectric properties of NbTaO films. From Auger electron spectroscopy analysis of the NbTaO and NbTaNO systems, some relations between the dielectric properties and the thickness of the oxygen-diffused layer were found. It may be suggested that oxide films with a thicker oxygen-diffused layer have a higher donor density and that nitrogen incorporated into these films controls the generation of donors.