Application of Si₃N₄Thin Film as a Humidity Protection Layer for Organic Light Emitting Diode

Abstract

In this paper, we studied WVTR(water vapor transmission rate) properties of Si3N4 thin film that was deposited using TCP-CVD (transformer coupled plasma chemical vapor deposition) method for the possibility of OLED(organic light emitting diode) encapsulation. Considering the conventional OLED processing temperature limit of below 80℃, the Si3N4 thin films were deposited at room temperature. The Si3N4 thin films were prepared with the process conditions: SiH4 and N2, as reactive gases; working pressure below 15 mTorr; RF power for TCP below 500 W. Through MOCON test for WVTR, we analyzed water vapor permeation per day. We obtained that WVTR property below 6~0.05 gm/㎡/day at process conditions. The best preparation condition for Si3N4 thin film to get the best WVTR property of 0.05 gm/㎡/day were SiH4:N2 gas flow rate of 10:200 sccm, working pressure of 10 mTorr, working distance of 70 ㎜, TCP power of 500 W and film thickness of 200 ㎚. respectively. The proposed results indicates that the Si3N4 thin film could replace metal or glass as encapsulation for flexible OLED.