Ion mass-to-charge ratio in planar magnetron plasma with electron injections

The mass-to-charge ratio of ions in the plasma of a planar magnetron with central or peripheral electron injection was measured. Two modes of magnetron discharge were used: DC (up to 200 mA) and pulsed (up to 5 A, 50 µs, 300 Hz). The mass-to-charge measurements were made by using a modified quadrupole mass spectrometer. Experiments were carried out with copper magnetron cathode (target) and argon as operating gas. The analysis suggests that decreasing the operating pressure from 1.5  ×  10⁻³ to 5  ×  10⁻⁴ Torr increases the argon ion fraction by approximately 10%–30%. Increase in the amplitude of the magnetron pulsed current from 1 to 5 A increases the Cu ion fraction from 35% to 83%. At a constant operating pressure and magnetron discharge current, the ion mass-to-charge ratio of ions in plasma is little affected by injected electron current. (paper)