The principle of sputtering is that the target is used as the cathode in the vacuum chamber, and an inert gas is introduced. A small amount of free electrons in the gas is subjected to an applied electric field, and the electrons are accelerated in the electric field to obtain energy, and the average free-diameter ratio between the low-pressure molecules is obtained. The atmospheric pressure is long, so the electrons have a long acceleration distance to obtain high energy, and the high-energy electrons transfer the kinetic energy to the inert gas via the collision motion, so that the gas molecules are ionized to form a plasma, due to the electric field, The positive ions in the gas are attracted by the cathode target end and accelerate against the surface of the target. Based on the principle of momentum conversion, ion bombardment produces secondary electrons that additionally hit the target atoms and deposit them on the workpiece. This action is called sputtering.