Plasma Enhanced Chemical Vapor Deposition (PECVD) allows thin films (coatings) to be deposited at lower temperatures when compared to the standard process of Chemical Vapor Deposition (CVD). PECVD uses the capacitive coupling between two parallel electrodes (a grounded + a RF-energized electrode) to excite reactant gases between the electrodes into a plasma. The process results in a chemical reaction, and the product of the reaction is deposited as a coating on a substrate, which has been heated to 250°C to 350°C, depending on which film is being deposited. CVD requires much higher temperatures – 600°C to 800°C, which is problematic. The higher temperatures of CVD can damage the devices being fabricated in some cases, necessitating the use of the lower-temperature process used in PECVD.
Applications of PECVD
PECVD is normally used to deposit the following films:
- Silicon nitride (SixNy)
Silicon dioxide (SiO2)
- Silicon oxy-nitride (SiOxNy)
- Silicon carbide (SiC)
- Amorphous silicon (a-Si).
Silicon, or rather Silane (siH4 – the source gas of silicon) turns into silicon dioxide in combination with oxygen-source gas, or silicon nitride in combination with a nitrogen-source gas, both of which are insulating materials (dielectric). Dielectric materials are used to separate conductive layers and capacitors in things like electronics manufacturing, to protect substances from corrosive elements like moisture or air, and for surface passivation.