A great breakthrough in large area barrier film deposition has been achieved in the M2i research project at TU/e together with FUJIFILM, Tilburg. Using the technique of atmospheric pressure glow plasmas (AP-PECVD) it has been possible to make uniform plasma depositions and synthesize high quality SiO2 films, that grown in a self-similar fashion with no change in morphology and roughness with thickness. The layers grow at very high rates (15 nm/s) and show much better barrier performances towards O2 and H2O diffusion compared to the ones of low pressure technologies.
Barrier improvement factor for O2 permeation in comparison to other low and high pressure plasma technologies.
In fabricating the barrier films for the encapsulation of flexible electronics, AP-PECVD is considered as an emerging technology. Though the technology looks appealing due to its economical and technological advantages, its industrial application is restricted because the uniform discharge is obtained generally in expensive noble gases or under quite restrictive conditions and films are often challenged with powder or particle formation.
The M2i researchers together with the team of specialists at TU/e and FUJIFILM have shown recently a technological breakthrough in high pressure plasma depositions being able to demonstrate stable plasma in N2 rich gases using ICCD fast imaging camera experiments. The developed dielectric barrier (DBD) assisted CVD produced homogeneous and high-quality SiO2 layers on large and wide area polymeric substrate at very high static and dynamic growth rates. Irrespective of precursors (TEOS or HMDSO) and reactive gases (N2 and N2 based), films grow following the topology of the substrate, with negligible roughening against thickness, in contrast to LP-PECVD technology.
A new class of film surface growth is realized in APG technology, which was never observed so far in the literature. It is found that the films grow in a self-organized structure with no dynamic roughening in vertical and horizontal growth, mimicking the surface features of the polymeric substrate (Patent Filed). These exceptional film properties led APG films to show excellent OTR and WVTR values which have never been achieved so far from either low pressure or high pressure technologies. The insights gained from the projects are directly incorporated in the larger technology fabricated at FUJIFILM, Tilburg.
Schematic of the roll-to-roll AP-PECVD set up. Conventional photograph of the discharge
Time evolution and formation of atmospheric barrier discharge recorded by ICCD camera at 5 ns gate time (a) via uniform Townsend discharge (b) via filament. Both the cases transits to uniform glow-like mode.
