| AVS 61st International Symposium & Exhibition | |
| Thin Film | Thursday Sessions |
| Session TF-ThA |
| Session: | Thin Film for Permeation Barriers and Membranes |
| Presenter: | Paul Poodt, Holst Centre / TNO, Netherlands |
| Authors: | F. van den Bruele, Holst Centre / TNO, Netherlands F. Grob, Holst Centre / TNO, Netherlands P. Poodt, Holst Centre / TNO, Netherlands |
| Correspondent: | Click to Email |
Developments in the field of flexible electronics, such as organic light emitting diodes (OLEDs), organic photovoltaics (OPV) and other thin-film solar cells, are slowly but surely evolving from lab-scale to industrial production. Proper encapsulation of these moisture sensitive devices is critical, as exposure to moisture from the ambient will degrade these devices, reducing their efficiency, lifetime, or even lead to failure altogether. Especially for OLEDs, the barrier requirements are very challenging, with a Water Vapor Transmission Rate < 10-6 g/m2/day. Encapsulation of flexible devices is even more challenging as the encapsulation should not affect the device flexibility too much. Various flexible thin film encapsulation techniques have been recently developed, often combining one ore more thin inorganic diffusion barrier layers (e.g. SiNx, Al2O3) with an organic layer. To achieve these very low WVRTs, very high quality barrier layers are required, being pinhole free over the entire device area.
One approach to make high quality inorganic barrier films is Atomic Layer Deposition (ALD). ALD is a deposition technique capable of producing ultrathin conformal films with control of the thickness and composition of the films at the atomic level. With thin (5-100 nm) Al2O3 films deposited by ALD, excellent barrier films (WVTR ~ 10-6 g/m2/day) can readily be obtained on lab-scale. The major drawback of ALD, however, is its low deposition rate making compatibility with industrial scale processing of devices challenging. The recent development of roll-to-roll and large-area Spatial ALD technology has however spurred the interest in ALD for encapsulation and barriers and the first commercially available electronic devices with ALD encapsulation are probably not far away.
The recent developments of ALD for thin-film encapsulation will be reviewed from a point of view of material- and process development, as well as ALD equipment, with a strong focus on spatial ALD. However, producing barriers with ALD is more complex than only the deposition step itself. For this reason, special attention will be given to aspects such as up-scaling, substrate handling and planarization, managing the effects of particles, characterization and costs of the process.