Investigations on plasma-assisted surface cleaning of aluminum contaminated with lubricants

Aluminum and silicon plates contaminated with hydrocarbon-containing lubricants were treated with Ar, O-2 and H-2 plasma at different discharge modes (d.c.: anomalous glow regime, hollow cathode regime, r.f., and silent discharge). During the plasma process the discharge was monitored by means of optical emission spectroscopy. Simultaneously, the removal of the contamination layers was observed by means of in situ ellipsometry. The temporal change of the spectral line intensities and of the ellipsometric parameters psi and Delta during the cleaning process were taken as a measure for the state of the surface. Because the thermal stress of the material is an important parameter in technological application, the energy inflow towards the substrate surface during plasma treatment has also been studied carefully.