E. Kusano et al., Effects of Ar pressure on ion flux energy distribution and ion fraction inr.f.-plasma-assisted magnetron sputtering, SURF COAT, 121, 1999, pp. 189-193
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.