Step coverage of the barrier films deposited onto patterned photoresist

In this study, silicon oxynitride (SiO_xN_y) films and three-paired organosilicon/SiO_xN_y multilayered structures prepared by the plasma-enhanced chemical vapor deposition were respectively deposited onto the polyethylene terephthalate and silicon substrate with overcut and undercut patterned photoresist to mimic the packaging of the patterned organic light emitting diodes (OLEDs) and surface contaminants. The step coverage at the bottom and sidewall surface was conducted from the cross-sectional scanning electron microscopy observations. A methodology for investigating the position-dependent coverage at the concave region of the sidewall surface on the undercut patterns was developed. The increase in the water vapor transmission when these barrier structures were deposited onto polyethylene terephthalate substrate was linked to the decrease in their coverage at the sidewall surface, which was ascribed to the reduction in the diffusion path for water vapor permeation. It also was demonstrated that the degradation in the barrier property was significant as those structures coated onto the undercut patterns originating from the precursors hardly arrived at the concave region. However, although the film growth at the concave region of the sidewall surface was limited, paired organosilicon/SiO_xN_y structures still showed a superior barrier property to that of single SiO_xN_y film as the appearance of the organosilicon film in the paired structure was favorable to prolonging the diffusion length for water vapor permeation. The investigation into the barrier structures coated onto the patterned surface was beneficial for better understanding the package reliability on the patterned OLED devices.