How is Vacuum Technology Important in the Mechanism of Vacuum Thin Film Coating

Posted by ryan on August 20th, 2019

Vacuum technology is an enabling technology for vacuum coating not only because it creates an environment of the atomistic deposition process but also because it affects the unit cost, reproducibility, and functionality of the end product. The vacuum technology began to evolve in the mid-1600s with the onset of barometer and the piston-type vacuum pumps, many of which were derived from the water pumps then in use.

Vacuum coating processes make use of vacuum technology to create sub-atmospheric pressure environment and an atomic or molecular condensable vapor source to deposit the thin films and coatings. The source of vapor may be solid or liquid surface, or from a chemical vapor precursor. Usually, there are two methods of forming a thin film in the vacuum thin-film coating technology:

Physical Vapor Deposition- utilizes the physical movement of particles

Chemical Vapor Deposition- Utilizes a chemical reaction

The evaporation method is the easiest way to form a thin film, where the material of the film is heated, dissolved, and evaporated in a vacuum and holds fast to the object.
On the contrary, the sputtering method applies a voltage of around hundred volts between the vacuum chamber and an electrode made of film material. If you add a small amount of inert gas to the chamber, electricity is discharged. As a result, the particles of the gas assume a positive charge by the energy of the electricity. These positively charged particles are pulled by the strong power of negative electrode and they collide with the electrode. The shock flicks a part of the material and it becomes particles, thus forming a film on the target.

Form a Thin Film of High Quality

This simple method, however, fail to produce a quality thin film with high degree of purity and adhesiveness. However, the significant point is to maintain a vacuum in the chamber while forming a film. For instance, if you form a film in the atmosphere or in low vacuum, particles of the film material try to move forward the object on the ceiling of the chamber but are hindered by vapor, oxygen, nitrogen and carbon-di-oxide in the air. Therefore, they hardly reach the object and fail to form a film. Moreover, even if the articles reach the object, it creates a number of problems where the adhesiveness of the film is weak. The ultimate solution here is to maintain a high vacuum chamber to eliminate unwanted substances. And this eventually helps produce a quality thin film of high degree or purity and adhesiveness.