Reactive ion etching is a versatile dry-etching technology which can be used on almost all materials commonly found in electronics and optoelectronics. The surface of the workpiece is bombarded with charged particles of the plasma which remove it layer by layer in a reproducible and anisotropic manner. Reactive ion etching is used primarily for anisotropic structuring of silicon, organic and inorganic dielectrics, metallic barrier materials and polymers for electronic and opto-electronic applications. (SH) For removing silicon or silicon-containing layers, primarily fluorine-based etching gases such as CF4 and SF6 are used. For etching organic molecules or removing inorganic layers of organic residues, oxygen plasma or gas mixtures of O2 and CF4 are used. Metallic layers are primarily removed by physical etching (mechanical breaking off of atoms/molecules), for example by means of argon plasmas.