Development of tantalum oxynitride thin films produced by PVD: Study of structural stability

• Published in: Applied surface science Vol. 285; pp. 19 - 26
• Main Authors: Cristea, D., Crisan, A., Barradas, N.P., Alves, E., Moura, C., Vaz, F., Cunha, L.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier B.V 15.11.2013; Elsevier
• Subjects: Annealing; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Exact sciences and technology; Physics; Structural stability; Structure; Tantalum oxynitride; Annealing; Tantalum oxynitride; Structural stability; Structure; FCC lattices; Structure stability; Tetragonal lattices; Phase transformations; Thermal stability; Film growth; Deposition process; Thin films; Cracks; Magnetrons; Cathode sputtering; Tantalum; Partial pressure; Transition elements; Physical vapor deposition; Thermal annealing; Delamination; Amorphous state structure
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2013.06.061

•Growth of tantalum oxynitride thin films, by reactive magnetron sputtering, as a function of the partial pressure of the reactive gases.•Structural evolution from β-Ta, to fcc-Ta(O,N), to amorphous Ta2O5 phase with the rise of the partial pressure of the reactive gases.•High structural and morphological thermal stability, until 800°C, for the films produced with amorphous oxide structure.•Very good film stability but significant structural evolution, above T=700°C, for the film produced with lowest P(N2+O2). The purpose of this work is to study the evolution of the structure and of the thermal stability of a group of tantalum oxynitride thin films, prepared by magnetron sputtering, under the influence of vacuum annealing, up to a temperature of 800°C. When varying the partial pressure of the reactive gases (PO2+N2), during the deposition process, the films change from a structure with a combination of poorly developed crystallites of the tetragonal β-Ta and of the face centred cubic (fcc) Ta(O,N) phases, for the films deposited with low PO2+N2, to a quasi-amorphous structure, for the films deposited with highest pressures. For intermediate pressures, the films reveal the presence of the fcc-Ta(O,N) structure. This structure corresponds to O atoms substituting some of the N atoms on the fcc-TaN structure and/or N atoms substituting O atoms of the fcc-γ-TaO structure. When subjected to the thermal annealing at 700°C or higher, the film produced with lowest partial pressure revealed a remarkable structural change. New diffraction peaks appear and can only be attributed to a sub-stoichiometric hexagonal tantalum nitride structure. The film did not reveal any signs of delamination or cracks after all annealing temperatures. The two films produced with highest partial pressure proved to be the most stable. Structurally, they maintain the amorphous structure after all the annealing treatments and, in addition, no cracks or delamination were detected.