In the sense of plasma technology, contamination is understood to mean every undesirable material layer on the surface of a substrate, whether visible or not. In general, there are contaminants on all substrates, whether newly produced or stored, in the form of deposits from the environment, auxiliary materials from the production, or evaporations from the substrate itself. To ensure faultless further processing, it is almost always necessary to clean the substrates to remove contaminations. By means of plasma treatment , practically all contaminations can be removed from the substrate free of any residues. By cleaning in the oxygen plasma, hydrocarbons of any kind can be removed while cleaning in the hydrogen plasma removes oxide layers. Irrespective of their chemical properties, contaminations which cannot be removed in these processes can be cleaned off by physical etching in the noble gasplasma which is effective on practically all substances (“non-selective”).