
Plasma, often referred to as the fourth state of matter, distinct from the solid, liquid, and gaseous states is estimated to make up about 99% of the visible universe. Plasma is a collection of positively charged ions, negatively charged electrons, and neutral particles exhibiting collective behaviour and forming an overall electrically neutral system. In space, the dominant plasma formation mechanism is photoionization, in which high-energy solar radiation ionizes neutral atoms and molecules. The ionosphere, lightning, and fire represent classic natural plasma phenomena on Earth. Heating a gas to very high temperatures in the laboratory can ionize it and create a plasma. Plasmas play a critical role in semiconductor fabrication, enabling processes such as PECVD and etching. The primary challenge in plasma-based industries, particularly in semiconductor manufacturing, is achieving process repeatability and uniformity at nanoscale dimensions. This challenge is addressed by measuring key plasma parameters, with plasma diagnostic tools playing a central role in enabling accurate parameter measurement and ensuring industrial process repeatability.