Wafers are slices of a semiconductor material used as basis for semiconductor components. Usually, the wafer consists of monocrystalline silicon, rarely of polycrystalline silicon, GaAs (gallium arsenide) or other semiconductors. Monocrystalline silicon wafers are perfectly round and are made by slicing silicon monocrystals. Ideally, the silicon monocrystals and thus the wafers consist of high-purity silicon whose properties are influenced in further processing steps, in particular by etching and doping. In these processing steps, plasma technology is widely used.