Low-Hydrogen-Content SiN$_{x}$ Films Prepared Under Low-Temperature Conditions and Its Application to Encapsulation Layers for Top-Emission Organic Light-Emitting Devices

We have succeeded in obtaining transparent SiN$_{x}$ films under 110$^{\circ}$C with the water vapor transmission rate (WVTR) of less than 1x10$^{-5}$ g/m$^{2}$/d. To use the top-emission OLED encapsulation films, high transparency and low WVTR ($<$10$^{-5}$ g/m$^{2}$/d) are required in a low-temperature process. However, low-temperature-prepared SiN$_{x}$ film contains more than 30at{\%} hydrogen, which causes low density of the film. Furthermore, high-hydrogen-content film may have many hydrophilic function groups such as N-H, Si-H and O-H, which deteriorates the encapsulation property. We have developed a microwave-excited Surface-Wave-Plasma Chemical Vapor Deposition (SWP-CVD) system using SiH$_{4}$/NH$_{3}$/Ar. The hydrogen content of the SiN$_{x}$ films could be controlled from 16 to 40 at{\%} by changing the distance between the plasma and the substrate during the low-temperature deposition. It was clarified that the hydrogen content in the SiN$_{x}$ film clearly corresponded to the WVTR result. The WVTR value became smaller with decreasing hydrogen content. We also evaluate the SiH$_{4}$+N$_{2}$ series for the synthesis of low-hydrogen-content SiN$_{x}$ films. Details will be discussed at the meeting.