Mass Spectrometry Study of a Magnetron Planar Glow Discharge Excited in the Direct-Current and in the Radio-Frequency Mode: An Experimental Design Approach

Abstract

A magnetron glow discharge is studied by a differentially pumped quadrupole mass spectrometer measuring the positive ions as well their energy. The 1-in.-diameter target is made in an aluminum base alloy. An “experimental design” procedure was used to study the influence of geometrical and electrical parameters of the discharge on the intensity and the energy of the ions collected by the mass filter. The ion intensity increases, in the dc mode, by two orders of magnitude when the pressure drops from 450 mTorr to 20 mTorr, whereas, in the rf mode, a maximum is observed at 60 mTorr. For both discharge modes, the ion energy increases with a drop of the pressure and the ion intensity rises proportionally to the electric power. The energy of the ions entering into the mass filter is about 10 eV higher in the rf mode than in the dc mode for the same power and pressure. For most of the ions, their energy does not vary with the power. In the rf mode and at high pressure, a rise of their energy is observed when the target is eroded.