Introduction to PECVD principle
PECVD literally means: plasma (P) enhanced (E) chemical vapor deposition (CVD). The reaction gas is converted into a plasma by the radio frequency (RF) of the device to perform a chemical reaction to form a desired film material. Relatively speaking, the reaction temperature is low. The film formation density is worse than the furnace tube. But the efficiency is high and easy to maintain.
In general, when film materials are prepared by PECVD technology, the growth of the film mainly includes the following three basic processes:
First, in a non-equilibrium plasma, a primary reaction occurs between the electron and the reaction gas, causing the reaction gas to decompose to form a mixture of ions and reactive groups;
Second, various reactive groups diffusely transport to the film growth surface and the tube wall, and a secondary reaction between the reactants occurs simultaneously;
Finally, the various primary and secondary reaction products that reach the growth surface are adsorbed and reacted with the surface, accompanied by re-emission of gas phase molecules. Gases (such as SiH4, NH3, N2, etc.) are ionized into ions under the action of RF power; after collision, a large number of active groups such as SiH3-, H- are generated; these reactive groups are adsorbed on the substrate or replace the surface of the substrate. H atom; the adsorbed atom migrates on the surface of the substrate under the action of its own kinetic energy and substrate temperature, and the point with the lowest energy is stabilized; at the same time, the atoms on the substrate are constantly separated from the surrounding atoms and enter the plasma to achieve dynamic balance. When the atomic deposition rate is greater than the escape velocity, it can be continuously deposited on the surface of the substrate into the film we need.