Influence of the Plasma Chemistry on the Composition of ZrOx and NbOx Thin Films Deposited by Reactive Magnetron Sputtering

Abstract

The plasma chemistry of magnetron sputtered Zr and Nb in an Ar/O2 atmosphere has been measured as a function of the O2 partial pressure. The previously reported composition of films deposited onto grounded non-intentionally heated substrates was correlated with the dominant positive and negative ion populations in the plasma. While the oxygen deficient films were grown in the Ar+ dominant mode, the close-to-stoichiometric films were grown in the O+/O− dominant mode. The formation of close-to-stoichiometric ZrO2.1 is observed in the compound mode (CM), while the formation of close-to-stoichiometric Nb2O4.7 thin films was reported in addition to the CM also in the transition mode (TM). This may be understood based on the 1.5–1.9 times higher power dissipated in the Nb–Ar–O2 plasma as compared to the Zr–Ar–O2 plasma. We suggest that at larger power O2 dissociation may be more efficient and lead to the presence of sufficient atomic oxygen to fully oxidize the films. This finding may provide a pathway towards a deposition rate enhancement, since compound formation at the substrate is enabled in the TM of the higher power Nb–Ar–O2 plasma and not only in the CM, as in the case of the lower power Zr–Ar–O2 plasma.