Evaporation vacuum coating machine and physical principle

The evaporation vacuum coating machine is mainly composed of a vacuum coating chamber and a vacuum pumping system. There are evaporation sources (ie evaporation heaters), substrates and substrate holders, electrode rods, power supplies, crucibles, substrate heaters, exhaust systems, etc. in the vacuum chamber. 

The coating material is placed in the evaporation source in the vacuum chamber. Under high vacuum conditions, the evaporation source is heated to evaporate it. When the mean free path of the vapor molecules is greater than the linear size of the vacuum chamber, the atoms and molecules of the film vapor will evaporate from the evaporation source. After the source surface escapes, it is rarely collided and hindered by other molecules or atoms, and can directly reach the surface of the substrate to be plated. Due to the low temperature of the substrate, the vapor particles of the film material condense on it to form a film.

In order to improve the adhesion between the evaporated molecules and the substrate, the substrate can be activated by appropriate heating or ion cleaning. The physical process of vacuum evaporation coating from material evaporation, transportation to deposition and film formation is as follows:

1. Use various methods to convert other forms of energy into heat energy, heat the film material to evaporate or sublime, and become gaseous particles (atoms, molecules or atomic groups) with a certain energy (0.1~0.3eV):

2. The gaseous particles leave the surface of the membrane material and are transported to the surface of the substrate in a straight line with a substantial movement speed without collision;

3. The gaseous particles reaching the surface of the substrate condense and nucleate and grow into a solid film;

4. The atoms that make up the film are reorganized and arranged or chemically bonded.