Atomic Layer Deposition for Ultra-Barrier Films

Lotus Applied Technology presented on its development of “High Speed Low Cost ALD (Atomic Layer Deposition) Ultra-Barrier on Sheets and Rolls”. Eric Dickey of Lotus began his talk by providing a description of the atomic layer deposition (ALD) process. He described ALD as being totally a surface limited reaction that can yield a (nearly) perfect conformal coating so that all holes in the underlying surface are plugged. To illustrate his point Dickey showed the image that highlights the extreme conformality and continuous pin-hole free very thin films that can be achieved using ALD, even on highly defective substrates.

Lotus’ contribution to the use of ALD for barrier films is its development of plasma process based “Spatial” ALD which offers the advantages of high speed low cost deposition in a roll-to-roll format at low substrate temperatures. Lotus has also evaluated the use of mixed metal oxide films of Al2O3:TiO2 to achieve a “more environmentally stable” film than when using Al2O3 alone. To date, Lotus has scaled its processes to a complete R2R pilot scale reactor. The firm projects coating costs ranging from less than $0.05 per sq. meter to $2.00 per sq. meter depending on application.

A common thread running through all the presentations during the Barrier Film and Encapsulation session, including the Lotus talk, was the need for improved methods to characterize the water vapor and oxygen transmission rate of barrier films. The final presentation of the session addressed precisely this need to develop equipment and methods for economically and meaningfully characterizing the performance of these barrier films.

Christine Walsh of French firm Vinci Technologies described her work on “Mass Spectrometry: High Sensitivity and Rapid Control for Permeability Optimization in Ultra High Barrier Materials”. Vinci Technologies is an independent French company, specializing in the design, manufacturing and marketing of instrumentation, for the high vacuum and oil and gas industries. Walsh describes her job at Vinci as doing product development of a series of high sensitivity permeameters designed to evaluate ultra high barrier materials using helium, oxygen, water and other gases as probe molecules (See QHV-4 Rapid Helium Permeameter here

Both the Lotus and 3M presenters during the Barrier Film and Encapsulation session had devoted considerable time during their respective presentations to the development and use of WVTR characterization techniques including the use of calcium test methods, ASTM methods with inadequate sensitivity (“we need to test barriers up to 10,000 times better”) and the MOCON Aquatran method that has become standard for testing to the mid 10-4 g/m²-day WVTR range.

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Vinci’s development of high sensitivity permeameters based on well understood methods such as are used in helium leak detectors in combination with high sensitivity mass spectrometry, are a very promising approach to what has thus far been a tough problem for the developers of barrier films. – Phil Wright