Breakdown and Protection of ALD Moisture Barrier Thin Films

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• 作者：Frederik Nehm ; Hannes Klumbies ; Claudia Richter ; Aarti Singh ; Uwe Schroeder ; Thomas Mikolajick ; Tobias M枚nch ; Christoph Ho脽bach ; Matthias Albert ; Johann W. Bartha ; Karl Leo ; Lars M眉ller-Meskamp
• 刊名：ACS Applied Materials & Interfaces
• 出版年：2015
• 出版时间：October 14, 2015
• 年：2015
• 卷：7
• 期：40
• 页码：22121-22127
• 全文大小：352K
• ISSN：1944-8252

文摘

The water vapor barrier properties of low-temperature atomic layer deposited (ALD) AlO_x thin-films are observed to be unstable if exposed directly to high or even ambient relative humidities. Upon exposure to humid atmospheres, their apparent barrier breaks down and their water vapor transmission rates (WVTR), measured by electrical calcium tests, deteriorate by several orders of magnitude. These changes are accompanied by surface roughening beyond the original thickness, observed by atomic force microscopy. X-ray reflectivity investigations show a strong decrease in density caused by only 5 min storage in a 38 掳C, 90% relative humidity climate. We show that barrier stabilities required for device applications can be achieved by protection layers which prevent the direct contact of water condensing on the surface, i.e., the sensitive ALD barrier. Nine different protection layers of either ALD materials or polymers are tested on the barriers. Although ALD materials prove to be ineffective, applied polymers seem to provide good protection independent of thickness, surface free energy, and deposition technique. A glued-on PET foil stands out as a low-cost, easily processed, and especially stable solution. This way, 20 nm single layer ALD barriers for organic electronics are measured. They yield reliable WVTRs down to 2 脳 10^鈥? g(H₂O) m^鈥? day^鈥? at 38 掳C and 90% relative humidity, highlighting the great potential of ALD encapsulation.