Dry etching or plasma-assisted etching (ion beam milling, plasma etching and reactive sputter etching) has become an indispensable preparation technique for high resolution pattern transfer in IC manufacturing and other areas of microfabrication. Etching can either be due to the purely physical process of momentum transfer from ions to the solid surface (e.g. inert ion etching) or due to chemical reactions of reactive species, produced in the plasma, with the solid surface resulting in a volatile reaction product (e.g. plasma etching in a barrel reactor). However, in most dry etching methods both effects play a major role and it is possible to optimize etch selectivity and the shape of the etched profile by a proper choice of parameters.