Method to create a geometrically structured substrate by etching. Areas where etching is not desired are covered by an Etching Mask. The Etching mask should be fabricated from a material which is resistant against the etching medium.
For Plasma Etching anisotropic etching processes are prefered (Ion Etching, Reactive Ion Etching RIE), because a precise negative copy of the mask is created. Isotropic etching processes like etching in liquid substances and plasma etching are etching below the etching mask and therefore do not allow for high aspect ratios.
A major application for anisotropic Plasma Etching processes is the generation of electronic circuit boards. In this case the etching mask is a foto resist. The technologie for etching with foto resist masks is designated foto lithography)