Magnetron sputter deposition with high levels of metal ionization

Abstract

A new deposition technique has been developed which combines conventional magnetron sputter deposition with a rf inductively coupled plasma (RFI). The RFI plasma is located in the region between the magnetron cathode and the sample position, and is set up by a metal coil immersed in the plasma. A large fraction of the metal atoms sputtered from the magnetron cathode are ionized in the RFI plasma. By placing a negative bias on the sample, metal ions are then accelerated across the sample sheath and deposited at normal incidence. Results from a gridded energy analyzer configured with a microbalance collector and located at the sample position indicate the level of ionization is low at a few mTorr and rises to ≳80% at pressures in the 25-35 mTorr range. Optical measurements of metal ion and neutral emission lines show scaling of the relative ionization to higher discharge powers. Significant cooling of the plasma electron temperature is observed when high concentrations of metal atoms were sputtered into the plasma.