In semiconductor device fabrication, etching refers to any technology that selectively removes material from a thin film on a substrate in order to create a pattern on the substrate. The pattern is defined by a mask that is resistant to the etching process.
Once the mask is in place, the etching of the material that is not protected by the mask process can begin. This can be done using either “wet” chemical methods or “dry” physical methods.
In the plasma etching process, also known as dry etching, plasmas or etching gases are used to remove material from the substrate. Dry etching produces gaseous products, which must be expelled by the vacuum system. There are three types of dry etching:
Chemical reactions (using a plasma or reactive gases)
Physical removal (using momentum transfer)
A combination of chemical reactions and physical removal (RIE)
Wet etching is a material removal process that uses liquid chemicals or etchants to remove materials from a wafer. The specific patterns are defined by photoresist masks on the wafer, and materials that are not protected by the mask are etched away by liquid chemicals.