Plasma refers to the state of matter in which energy is continuously applied to matter from the outside to dissociate it into negative and positive charged particles. Since the state of matter is solid, liquid, gas, and plasma according to the order of energy levels, plasma is habitually called the fourth state.

Plasma etching (also known as dry etching) is one of the key processes in integrated circuit manufacturing. Its purpose is to completely copy the mask pattern to the surface of the silicon wafer, and its range covers the size of the front-end CMOS gate (Gate) Control, as well as the etching of back-end metal aluminum and the etching of Via and Trench.

Plasma generator (plasma generator) uses artificial methods to obtain plasma device. Plasma produced by nature is called natural plasma (such as northern lights and lightning), and produced artificially is called laboratory plasma.

Generally speaking of plasma or plasma, everyone thinks of ionized air or high-temperature matter on the sun. However, if you carefully consider the free electron model of metals, the "gas" of free electrons moving in the background of positive ions is also a kind of "plasma".

The surface plasmon wave is a wave that exists near the two interfaces. The refractive index distribution on both sides of the interface has a great influence on the field distribution. This can be used for sensing.