Azimuthal ion movement in HiPIMS plasmas—Part II: lateral growth fluxes

Abstract

The transport of sputtered species from the target of a magnetron plasma to a collecting surface at the circumference of the plasma is analyzed using a particle tracer technique. A small chromium insert at the racetrack position inside a titanium target is used as the source of tracer particles, which are redeposited on the collecting surface. The azimuthal velocity of the ions along the racetrack above the target is determined from the Doppler shift of the optical emission lines of titanium and chromium. The trajectories are reconstructed from an analysis of the transport physics leading to the measured deposition profiles. It is shown that a simple direct line-of-sight re-deposition model can explain the data for low-power plasmas (direct current magnetron sputtering) and for pulsed high-power impulse magnetron plasmas (HiPIMS) by using the Thompson velocity distribution from the sputtering process as starting condition. In the case of a HiPIMS plasma, the drag force exerted on the ions and neutrals by the electron Hall current has to be included causing an azimuthal displacement in E ⃗ × B ⃗ direction. Nevertheless, the Thompson sputter distribution remains preserved for 50% of the re-deposited growth flux. The implications for the understanding of transport processes in magnetron plasmas are discussed.

Azimuthal ion movement in HiPIMS plasmas—part I: velocity distribution function

“…The azimuthal movement of ions in magnetron plasmas is addressed in a two part series with part I addressing the velocity distribution functions (VDFs) of the ions inside the plasma and part II addressing the lateral deposition of species leaving the magnetic trap region [35]. This paper constitutes part I, where we investigate the azimuthal ion movement using highresolution optical emission spectroscopy.…”