Compositional Control of Tantalum–Aluminum Alloy Films by a dc Biased, ac Sputtering Technique

Abstract

The deposition of a wide range of controlled compositions from a fixed electrode and substrate geometry is demonstrated for Ta–Al alloy films using a unique dc biased 60-Hz ac sputtering technique. Sputtering takes place from sets of water-cooled Ta and Al tubular rods which alternate as anode and cathode during a high voltage ac cycle. Alloy compositions over the range of 72–5 at.% Al were obtained by systematically varying a series dc bias applied to the Ta rods from 0 to −1600 V. Reproducibility at a given bias voltage was found to be approximately ±3 at.% Al. Possible mechanisms by which the dc bias affects film composition are discussed.