Characteristics of silicon nitride deposited by VHF (162 MHz)-plasma enhanced chemical vapor deposition using a multi-tile push–pull plasma source

Abstract

To prevent moisture and oxygen permeation into flexible organic electronic devices formed on substrates, the deposition of an inorganic diffusion barrier material such as SiNx is important for thin film encapsulation. In this study, by a very high frequency (162 MHz) plasma-enhanced chemical vapor deposition (VHF-PECVD) using a multi-tile push–pull plasma source, SiNx layers were deposited with a gas mixture of NH3/SiH4 with/without N2 and the characteristics of the plasma and the deposited SiNx film as the thin film barrier were investigated. Compared to a lower frequency (60 MHz) plasma, the VHF (162 MHz) multi-tile push–pull plasma showed a lower electron temperature, a higher vibrational temperature, and higher N2 dissociation for an N2 plasma. When a SiNx layer was deposited with a mixture of NH3/SiH4 with N2 at a low temperature of 100 °C, a stoichiometric amorphous Si3N4 layer with very low Si–H bonding could be deposited. The 300 nm thick SiNx film exhibited a low water vapor transmission rate of 1.18 × 10−4 g (m2 · d)−1, in addition to an optical transmittance of higher than 90%.