The influence of the target age on laterally resolved ion distributions in reactive planar magnetron sputtering

Ion energy spectra of negative oxygen ions in a reactive d.c. magnetron sputtering process were investigated with an energy-dispersive mass spectrometer facing zinc targets. The radial distribution of their flux parallel to the target normal was obtained by shifting the magnetron relative to the mass-spectrometer. A plane and an eroded target were studied in comparison. Both targets exhibit a significant radial inhomogeneity of the ion flux peaking opposite the race-track. The inhomogeneity is particularly pronounced for high-energetic ions but still observed at low energy and is much higher for the plane target. Together with a generally decreased ion flux for the eroded target it is concluded that the distribution of energetic bombardment of the substrate changes distinctly with the erosion of planar magnetron targets. The energy distribution of the low-energetic ions further suggests that they are formed in the pre-sheath of the target.