SiO_xN_y thin film deposited by plasma enhanced chemical vapor deposition at low temperature using HMDS-O₂-NH₃-Ar gas mixtures

In this study, SiO_xN_y thin film was deposited by plasma enhanced chemical vapor deposition at the temperature lower than 40 °C using hexamethyldisilazane (HMDS)/Ar while varying the ratio of O₂/NH₃. And, its physical and chemical characteristics of the deposited SiO_xN_y as a diffusion barrier to water permeation applied to organic thin film transistors (OTFTs) were investigated. When oxygen ratio (R) in O₂/NH₃ (R = O₂/(O₂ + NH₃) was lower than 0.3, due to the high remaining binding states such as -CH_x and N-H in the deposited film, the deposited film was soft and easily peeled off. With increasing R, oxygen-rich, hard, and transparent SiO_xN_y thin film was deposited with lower -CH_x and N-H. When a thin film composed of parylene (100 nm)/SiO_xN_y (60 nm)/parylene (100 nm) was formed on the polyethersulfone (PES, 200 μm) film with SiO_xN_y deposited with R = 0.5, water vapor transmission rate (WVTR) of 0.3 gm/(m² day) could be obtained. It is believed that, by using a multilayer SiO_xN_y structure, the WVTR required for OTFTs (∼ 10^{- 2} gm/(m² day) could be obtained.