Metallic tin reactive sputtering in a mixture Ar-O2:: Comparison between an amplified and a classical magnetron discharge

In this work, we have studied the tin reactive sputtering in a pure magnetron and an amplified (rf coil located between the target and the substrate) magnetron discharge. The rf coil allows us to increase the plasma reactivity (plasma amplification) and consequently to favor the substrate oxidation process. It is known that the thin film synthesis occurs by sputtered material condensation on the substrate followed by the condensed material oxidation by the reactive species present in the discharge, especially the atomic oxygen. In this study, we show by deposition rate and discharge voltage measurements that the transition between the metallic and the poisoned mode of the target is not influenced by the plasma amplification (40% O-2 in our experimental conditions). Nevertheless, we have observed that the discharge composition (mass spectrometry) and the films stoichiometry (x-ray photoelectron spectroscopy) depend on the amplification. We observe clearly an increase of the oxidation process on the substrate when the plasma is amplified (magnetron +coil). Consequently, it is concluded that it is possible to prepare fully oxidized tin film while the target is still in the metallic mode. For example, for a gas mixture of 10% in 02, we get in a pure magnetron discharge a film stoichiometry corresponding to SnO1.0, while in an amplified discharge with 200 W rf power applied to the coil, we obtain a more oxidized film with the SnO1.8 stoichiometry. (C) 2004 American Vacuum Society.