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Principle of PECVD

Principle of PECVD
PECVD literally means:
plasma (P) enhanced (E) chemical vapor deposition (CVD). Reactive gases are converted into plasma under the action of radio frequency (RF) of the equipment to produce the required film materials by chemical reaction. The reaction temperature is relatively low. Film compactness is worse than furnace tube. But it is efficient and easy to maintain.

Generally speaking, when PECVD technology is used to prepare thin film materials, the growth of thin film mainly includes three basic processes:
Firstly, in non-equilibrium plasma, electrons react with reaction gases in primary order to decompose the reaction gases and form a mixture of ions and active groups.
Secondly, various active groups diffuse to the growth surface and the wall of the film, and secondary reactions occur between the reactants.
Finally, the primary and secondary reaction products reaching the growth surface are adsorbed and reacted with the surface, accompanied by the re-release of gaseous molecules. Gases (such as SiH4, NH3, N2, etc.) ionize into ions under the action of radio frequency power supply; a large number of SiH3-, H-and other active radicals are produced after repeated collisions; these active radicals are adsorbed on the substrate or replace the H atoms on the substrate surface; the adsorbed atoms migrate on the substrate surface under the action of their own kinetic energy and the temperature of the substrate, and select the lowest energy point to stabilize on the substrate;

Atoms keep breaking away from the confinement of the surrounding atoms and entering the plasma to achieve dynamic equilibrium;
when the deposition rate of atoms is greater than the escape rate, we can continuously deposit thin films on the surface of the substrate we need.


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