Effects of Ar pressure on ion flux energy distribution and ion fraction inr.f.-plasma-assisted magnetron sputtering

In r.f.-plasma-assisted sputtering, the ion fraction of the sputtered metal is thought to be enhanced by increasing Ar pressure. In this study, effect s of Ar pressure on ion energy distribution and ion fraction of the metal f lux have been investigated. The experiments have been performed by using a 55 mm diameter Ti magnetron cathode and a 60 mm diameter copper r.f. coil. The ion energy distribution of the depositing flux was measured by an energ y-resolved mass spectrometer. The experimental results show that the number of Ti-divided by ions increases with Ar pressure, whereas that of Ar-divid ed by ions decreases. The ion fraction of the Ti flux reached 80% at an Ar pressure of 4.0 Pa. The electron temperature decreased with increasing Ar p ressure as a result of plasma quenching induced by the ionization of the Ti metal atoms that have a lower ionization potential. The results emphasize the strong effects of Ar pressure on the ion fraction and plasma conditions . The Penning ionization is thought to be the dominant ionization process f or Ti atoms in the r.f.-plasma-assisted sputtering. (C) 1999 Elsevier Scien ce S.A. All rights reserved.