Etching is the process of removing a material from the surface of another material. There are several methods of plasma treatment, but two main types of etching. One is wet etching and the second is dry etching, otherwise known as plasma etching. When a chemical or etchant is used to remove a substrate material in the etching process, it is called wet etching. On the other hand, plasma etching uses plasmas or etchant gases for the removal of substrate materials.