Improvement in the moisture barrier properties and flexibility by reducing hydrogen dangling bonds in SiNx thin films with plasma surface treatment.

In this study, silicon nitride (SiN x) thin films were deposited by inductively coupled plasma chemical vapor deposition using trisilylamine (TSA, N(SiH 3) 3) and ammonia (NH 3) plasma, and their moisture barrier properties were improved by plasma post-treatment. Ar, N 2 , and O 2 plasmas were applied to the SiN x films after deposition. After O 2 plasma treatment, the reduction of hydrogen in -NH x was confirmed by FT-IR analysis. Mass spectroscopic results showed a distinct hydrogen peak in the O 2 plasma processes. Hydrogen was speculated to be removed from the SiN x surface, and the reduced hydrogen on the surface was attributed to the densification of the SiN x thin films. The increased film density reduced the moisture permeability of the SiN x thin films. The water vapor transmission rate (WVTR) of 120-nm thick single SiN x thin films was reduced by 77% to 3.0 × 10−3 g/m2-day from 1.3 × 10−2 g/m2-day with O 2 plasma treatment. The increase of WVTR evaluated using a bending test was adopted to estimate flexibility. The increase of WVTR reduced to 71% in O 2 -plasma treated SiN x single layers from 88% with untreated SiN x single layers after bending the film at a bending radius of 1.5 cm. Multilayer moisture barrier films were fabricated using the O 2 -plasma treated SiN x layers and hydrocarbon plasma polymer layers made of cyclohexane plasma to further improve the moisture barrier properties and flexibility. The increase of WVTR reduced by approximately five times in the multilayer structure with O 2 plasma treated SiN x /hydrocarbon plasma polymer after the bending test. A WVTR of 7.6 × 10−4 g/m2-day was obtained with an alternating nine-layer structure. In this study, we demonstrated that plasma post-treatment processes can improve the moisture barrier properties and flexibility by reducing the hydrogen dangling bonds and hydrogen concentration inside SiN x thin films. • O 2 plasma treatment was applied to SiN x deposited at room temperature. • WVTR of SiN x single layer was reduced by 77% and flexibility was increased by 24%. • Strong H 2 peak was detected during O 2 plasma treatment with mass spectroscopy. • Hydrogen dangling bonds is believed to be reduced significantly from SiN x films. • The improvement of moisture barrier properties is attributed to the reduced H concentration by O 2 plasma treatment. [ABSTRACT FROM AUTHOR]