Plasma Cleaning Terminology

Plasma Etching

Plasma: A gas with electrons removed from a significant fraction of the atoms. These atoms with missing electrons are Ions.

Plasma Sheath: The region between plasma and a solid surface. This is also sometimes called the “dark zone” for its appearance. In the sheath there are few electrons and many ions. The sheath is established as ions are much heavier than electrons. There is also a large voltage drop across the sheath, but not in the plasma.

Substrate Bias: Can be voltage externally applied to the target, but can also be naturally generated by manipulating the ratio of RF to ground size or the operating pressure.

Primary Processing: When a material is directly immersed in plasma so that a sheath is established on its surface.

Downstream Processing: When the material is shielded from the high energy electrons. An example would be a faraday cage enclosure.