Characterization of zirconium oxynitride films obtained by radio frequency magnetron reactive sputtering

Thin ZrNxOy films are deposited on Si (100) substrates by radio frequency (RF) reactive magnetron sputtering of a zirconium target in an argon–oxygen–nitrogen mixture. The ΦN2/Φ(Ar + N2 + O2) ratio was varied in the range 2.5%–100% while the oxygen flux was kept constant. The films were characterized by combining several techniques: X-ray photoelectron spectroscopy, X-ray diffraction and Secondary Ion Mass Spectroscopy. The relationship between structural and compositional properties and the sputtering parameters was investigated. Increasing nitrogen partial pressure in the gas mixture, a chemical and structural evolution happens. At lowest nitrogen flux, ZrN cubic phase is formed with a very small amount of amorphous zirconium oxynitride. At highest nitrogen flux, only crystalline ZrON phases were found. For the films obtained between these two extremes, a co-presence of ZrN and ZrON can be detected. In particular, chemical analysis revealed the co-presence of ZrO2, ZrN, ZrON and N-rich zirconium nitride which is correlated with the ΦN2/Φ(Ar + N2 + O2) values. A zirconium nitride crystal structure with metal vacancies model has been considered in order to explain the different chemical environment detected by X-ray photoelectron spectroscopy measurements. The metal vacancies are a consequence of the deposition rate decreasing due to the target poisoning. It's evident that the growth process is strongly influenced by the zirconium atoms flux. This parameter can explain the structural evolution.