Langmuir probe measurements of plasma parameters in a planar magnetron with additional plasma confinement

Langmuir probe measurements have been carried out in a planar magnetron sputtering system with an additional plasma confinement which can be operated at low argon pressures (down to 3.4 x 10(-2) Pa) when target utilization greater than 80% can be achieved. The electron density, electron temperature, relative densities of low- and high-energy groups of electrons and the difference between the plasma and floating potential have been determined in various positions between the target and a substrate at the argon pressures in the range from 0.05 to 5 Pa. It has been proved that the additional magnetic field results, particularly in larger distances from the target at lower pressures, in the formation of structured electron energy distributions with a substantial contribution from a high-energy group of electrons, which is responsible for enhanced gas ionization and relatively high values observed for the difference between the plasma and the floating potential. (C) 1999 Elsevier Science Ltd. All rights reserved.