Dry etching refers to the removal of material, typically a masked pattern of semiconductor material, by exposing the material to a bombardment of ions (usually a plasma of nitrogen, chlorine and boron trichloride) that dislodge portions of the material from the exposed surface. Unlike with many (but not all, see isotropic etching) of the wet chemical etchants used in wet etching, the dry etching process typically etches directionally or anisotropically.

Dry etching is used in conjunction with photolithographic techniques to attack certain areas of a semiconductor surface in order to form recesses in material, such as contact holes (which are contacts to the underlying semiconductor substrate) or via holes (which are holes that are formed to provide an interconnect path between conductive layers in the layered semiconductor device) or to otherwise remove portions of semiconductor layers where predominantly vertical sides are desired. In conjunction with semiconductor manufacturing, micromachining and display production the removal of organic residues by oxygen plasmas is sometimes correctly described as a dry etch process. However, also the term plasma ashing may be used.