Etching is a technology used at the core of present-day semiconductor manufacturing. Micron-sized patterns of wiring and transistor circuitry are printed on silicon monocrystals that comprise the substrate and other semiconductors are added in line with that pattern, while chemicals or lasers are used to remove certain parts.

Wet etching is done by immersing the wafers in an appropriate solution giving isotropic profiles. Dry etching uses inert ions and/or reactive radicals (in a plasma) to sputter and/or react with the substrate giving anisotropic (vertical) profiles.

Physical etch process is done in a plasma reactor. A simple plasma etch reactor consists of a grounded electrode which is typically connected to the chamber walls, a second electrode to which power is applied and a partially evacuated chamber which contains a low pressure gas of suitable mixture.

Sputter etching uses high a energy inert gas ions (typically Ar+) to dislodge material from the wafer surface giving a highly anisotropic process.

Reactive ion etchingIt is the most common etch technique in the manufacture of VLSI/ULSI silicon devices.

In the reactive ion etch system the wafers are placed on the powered electrode of a parallel-plate RF reactor. Horizontal surfaces are subjected to both reactant species and impinging ions, while vertical sidewalls are only subjected to reactive species. In a plasma, the average distance travelled by particles between collisions, called mean free path depends on the species and gas pressure.

In a generic reactive plasma etch process, plasma glow discharge splits the feed gas into reactive radicals, reactants are adsorption onto surface by bond-breaking which is spontaneous and ion-induced or ion-enhanced. The reactive radicals form compound (product) with material to be etched. Desorption of products from surface due to volatility is spontaneous, ion-induced or ion-enhanced. Passivation rates interplay determines etch rates, profiles etc,.