Composition and structure variation for magnetron sputtered tantalum oxynitride thin films, as function of deposition parameters

• Published in: Applied surface science Vol. 358; pp. 508 - 517
• Main Authors: Cristea, D., Pătru, M., Crisan, A., Munteanu, D., Crăciun, D., Barradas, N.P., Alves, E., Apreutesei, M., Moura, C., Cunha, L.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2015; Elsevier
• Subjects: Affinity; Atmospheres; Constants; Density; Deposition; Engineering Sciences; Materials; Oxynitrides; Partial pressure; RBS; SEM; Sputtering; Structure; Tantalum; Tantalum oxynitride; Thin films; RBS; Tantalum oxynitride; SEM; Structure; Sputtering; Oxynitrides; Scanning electron microscopy; Grazing incidence X-ray diffraction; Deposition conditions; Structural evolution; Structure variation; Structure (composition); Grounded substrates; Tantalum compounds; Non-metallic elements; Rubidium; X ray diffraction; Thin films; Nitrides; Tantalum; Deposition Parameters; Magnetron sputtering; Partial pressure; Amorphous films; Deposition
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2015.09.022

•Structural evolution from β-Ta, to fcc-Ta(O,N), to amorphous Ta2O5 with increasing P(N2+O2).•The substrate bias influences the N content, but does not influence the O content of the films.•The structural features of the films appear at lower P(N2+O2) when produced with grounded substrate. Tantalum oxynitride thin films were produced by magnetron sputtering. The films were deposited using a pure Ta target and a working atmosphere with a constant N2/O2 ratio. The choice of this constant ratio limits the study concerning the influence of each reactive gas, but allows a deeper understanding of the aspects related to the affinity of Ta to the non-metallic elements and it is economically advantageous. This work begins by analysing the data obtained directly from the film deposition stage, followed by the analysis of the morphology, composition and structure. For a better understanding regarding the influence of the deposition parameters, the analyses are presented by using the following criterion: the films were divided into two sets, one of them produced with grounded substrate holder and the other with a polarization of −50V. Each one of these sets was produced with different partial pressure of the reactive gases P(N2+O2). All the films exhibited a O/N ratio higher than the N/O ratio in the deposition chamber atmosphere. In the case of the films produced with grounded substrate holder, a strong increase of the O content is observed, associated to the strong decrease of the N content, when P(N2+O2) is higher than 0.13Pa. The higher Ta affinity for O strongly influences the structural evolution of the films. Grazing incidence X-ray diffraction showed that the lower partial pressure films were crystalline, while X-ray reflectivity studies found out that the density of the films depended on the deposition conditions: the higher the gas pressure, the lower the density. Firstly, a dominant β-Ta structure is observed, for low P(N2+O2); secondly a fcc-Ta(N,O) structure, for intermediate P(N2+O2); thirdly, the films are amorphous for the highest partial pressures. The comparison of the characteristics of both sets of produced TaNxOy films are explained, with detail, in the text.