Investigation of the pulsed magnetron discharge by time- and energy-resolved mass spectrometry

Abstract

The mass and energy spectra of the positive and negative ions at a substrate were measured in a pulsed magnetron (20–100 kHz) operated in argon, argon/oxygen and argon/helium mixtures. For a better understanding of the origin of high-energy ions and plasma dynamics of the pulsed dc magnetron discharge, time-resolved energy spectra were measured using gating of the ion beam in front of the orifice of the mass spectrometer. It was shown that the plasma potential is changing throughout the discharge volume on a time-scale of the electron plasma frequency. The mass spectroscopic results show that a significant fraction of the ions (both gas and sputtered–ionized atoms) have energies >150 eV and are generated at the beginning of the off phase in a duration of <1 μs. In reactive sputtering, the detailed study of the energy distribution of O − and O 2 − negative ions demonstrated that the surface oxygen concentration is decreasing during the “on” period in the metal mode while it is constant in the oxide mode and there is about 25 V drop of the voltage on the oxide layer in the oxide mode.