Physical properties of a planar magnetron glow discharge

Abstract

Continued work with a planar magnetron glow discharge plasma device which uses permanent magnets located behind a planar cathode to trap plasma electrons in circular orbits parallel to the cathode surface is described. This results in a significant reduction in plasma voltage, and stable operation is achieved over an extended range of pressures and cathode current densities. The plasma has the form of a ring extending from the cathode surface to several millimeters from the surface. The plasma geometry is determined by the locus of greatest magnetic field strength. Cathode current density values greater than 100 mA/cm2 are easily achieved for pressures in the range 0.0007 Torr (0.093 Pa) to over 2.5 Torr (330 Pa). Over this range, the plasma voltage is under 500 V. Spatially-resolved emission spectral data are presented showing the effects of plasma current and pressure on line intensities from plasma gas species as well as from cathodically-sputtered species. Data are presented for a pure Cu cathode and for a Zn-based alloy used as a standard reference material.