Working principle of PECVD vacuum coating

The working principle of PECVD (Plasma Enhanced Chemical Vapor Deposition) vacuum coating is mainly based on the method of chemical vapor phase reaction of activated chemical species in the plasma system. The following is a detailed explanation of the working principle of PECVD vacuum coating:
1. Gas supply
Firstly, it is necessary to prepare the gas mixture required for coating, such as precursors such as silane (SiH4) and dimethylsilane ((CH3) 2SiH2).
These gases are heated and premixed in the reaction chamber to ensure that they are in a state suitable for chemical reactions.
2. Plasma generation
The high-frequency electric field provided by the power supply causes the gas in the reaction chamber to form plasma. High frequency electric fields give electrons enough energy to collide with gas molecules and ionize the gas, producing positive ions and free electrons.
These charged particles (positive ions, free electrons) and neutral particles (such as non ionized gas molecules and active groups) together form a plasma, providing the necessary environment for subsequent chemical reactions.
3. Chemical reactions
Under the action of plasma, gas molecules are excited and activated, resulting in chemical reactions. For example, hydrogen atoms in silane molecules can be excited to react with low ionization energy gas molecules (such as hydrogen), producing reaction products such as silicon hydride (SiH2).
The collision between high-energy electrons in plasma and gas-phase molecules promotes the decomposition, synthesis, excitation, and ionization processes of gas molecules, generating various active groups and ions.
4. Sedimentary process
Due to the high reactivity of the reactants generated by plasma reactions, they will undergo deposition reactions on the substrate surface.
Active groups and ions adsorb on the substrate surface and undergo chemical reactions, forming a solid thin film. This process involves multiple steps such as adsorption, diffusion, reaction, and deposition of reactants on the substrate surface.
5. Control process
By controlling the plasma activation degree, temperature, gas flow rate and other parameters in the reaction chamber, the reaction rate and the composition and properties of the film can be adjusted.
The optimization of these parameters can achieve the desired coating effect, such as improving the uniformity, density, and adhesion of the film.
6. Equipment characteristics
In addition to standard CVD components, PECVD equipment is also equipped with radio frequency (RF) or microwave sources required to generate plasma.
This technology can deposit film layers at lower temperatures, protecting temperature sensitive substrates from thermal damage.
In summary, the working principle of PECVD vacuum coating is a complex and delicate process, involving multiple links such as gas supply, plasma generation, chemical reaction, deposition process, and control process. By precisely controlling the parameters and conditions in these links, thin film materials with excellent performance can be prepared.