Paper TF-ThA6
Influence of Surface Topography and Defects on the Performance of Nanoscale Thin Film Moisture Permeation Barriers

Thursday, November 13, 2014, 4:00 pm, Room 307

Nanoscale moisture permeation barriers are needed for a wide range of applications including encapsulation of organic light emitting diodes, passivation of thin film photovoltaic devices, low dielectric constant Cu interconnect capping layers, hermetic food packaging, and protective coatings for biomedical devices. A variety of materials deposited by various methods have been proposed and successfully demonstrated for these diverse applications. However, it is well known (although not rigorously characterized) that surface roughness and surface particulates/defects can dramatically reduce the permeation barrier performance of all coating materials. In this presentation, we specifically investigate the impact that surface topography and defects can have on the moisture permeation barrier performance of various materials deposited by common methods such as atomic layer deposition (ALD), plasma-enhanced ALD (PEALD), and plasma-enhanced chemical vapor deposition (PECVD). We show that in the absence of significant surface topography a variety of different PECVD, PEALD, and ALD materials can serve as excellent moisture permeation barriers at thicknesses < 10 nm, but the controlled introduction of surface topography dramatically reduces the barrier performance in all cases. To simulate the presence of surface particulates and defects in a controlled manner, various barrier materials of interest were deposited on hanging trenches etched into nano-porous inorganic silicates deposited on a thick moisture absorbing SiO₂ film used for moisture permeation detection. The aspect ratios and dimensions were varied to probe the impact of surface particulates of different size and geometry. It will be shown that increasing surface topography generally increases the minimum thickness for a given material and deposition method to serve as a robust moisture permeation barrier. Over all, the surface topography barrier performance is found to strongly correlate with the step coverage and conformality of the deposition process with ALD and PEALD films out performing PECVD films.