Physikalisch‐chemische Vorgänge beim Plasmaätzen mit fluorhaltigen Ätzgasen

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Abstract
Examples are given for three main processes determining the reactions in plasma etching: The interaction between plasma particles and the surfaces of solids; The conversion of the gas composition in the plasma; The transport phenomena of reaction products in the reactor and the vacuum system. In the glow discharge the behaviour of saturated and unsaturated perfluorocarbon gases is very similar. Both classes of compounds are converted in a few seconds in the homologous series of perfluoroalcanes up to products of high molecular weight. The main products are CF4, C2F6, C3F8. Unsaturated compounds lead to the deposition of thin polymer films on the walls and the electrodes, whereas saturated ones are only capable of producing films on the surface of the reaction vessel. The deposition results from the recombination of free radicals arising from the plasma interactions in the gas and at the surfaces. Vice versa sputtering of polymer fragments acts on the gas composition in the plasma. Conversion processes are controled by current density and gas pressure. The cathode fall region of the discharge is found to be the zone of the highest reaction activity.

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