It uses an evacuated chamber filled with gases that it subjected to electric filled (high) so that the gas breaks down and get ionized.
The RF power is applied to the pairs of electrode to produce electric field.
Due to which they transform into plasma state.
The partially ionized gases consists of equal positive ions, negative electrons and neutral molecules is called as plasma.
Electron collides with molecules and form ions and electrons.
Under a steady state, an ion electron pair is continuously created by ionisaction and destroyed by recombination.
The physical dry etching process uses plasma of insert gases such as Ar or He. The highly energized ions the substrate atom if it strikes with energy then the bonding energy. If a single beam of ion is used for etching is called as milling.
On the other hand if the whole wafer surface is processed by the field ions it is called as sputter etching. Mask is not required in case of ion milling etching.