In the course of plasma etching we can observe a loading effect, i.e. the etch rate depends on the size of the etched surface exposed to the plasma. This phenomenon was explained according to Mogab by the plasma active etch species depletion via a rapid etch reaction. But there exist more coomplicated systems, for example SiO2-photoresist SCR17-CHF3, where the SiO2 surface can be etched and a polymer layer can grow on the photoresist surface. The etching of SiO2 is also influenced by different resists in the case of differences in their chemical structure. The degree of electrode coating with a resist influences both the etch rate of the masking layer. This may be used for the control of the etching selectivity in the SiO2-resist system independently of other process parameters.