Plasma cleaning means using plasma to achieve the results that conventional cleaning methods cannot achieve. Plasma is a state of matter, also called the fourth state of matter which does not belong to the common three-state of solid, liquid and gas. Applying enough energy to the gas to ionize it becomes plasma state.
The "active" components of the plasma are ions, electrons, atoms, reactive groups, nuclides in excited state (metastasis state), photons and so on. Plasma cleaning refers to treat the surface of the sample by utilizing the properties of these active components to achieve the effects of cleaning and coating. The surface of the workpiece is treated by chemical or physical action to achieve the pollutant removal at the molecular level, thereby improving the surface activity of the workpiece. The contaminants that are removed may contain organic matter, epoxy resin, photoresist, oxides, microparticle contaminants, etc., so plasma cleaning is a kind of high-precision cleaning. Different cleaning processes should be used for different pollutants. Generally speaking, plasma cleaning is classified into chemical cleaning, physical cleaning, and physical chemical cleaning depending on the selected process gas.