Plasma Enhanced Chemical Vapor Deposition (PECVD)

Stoichiometry is not guaranteed in PECVD systems where depositions take place under non-thermal equilibrium conditions. Thus, instead of Si₃N₄ or SiO₂ , one obtains Si_XN_Y or SiO_X where x and y can vary resulting in amorphous Silicon to SiN/SiO₂. Due to the rapid deposition without the temperatures required for surface migration, films tend to be porous leading to lower density than thermally grown films. Post deposition anneals in either O₂ or NH₃ are required to increase the density of the films. Typically, diluted SiH₄ for the Si source combined with N₂ or NH₃ for the nitrogen source are used for nitrides depositions. Films can have very high hydrogen content. Similarly, for oxide and oxynitride depositions SiH₄ combined with and O₂ / N₂O mixtures can be used.