AVS 53rd International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS2-ThM

Paper PS2-ThM6
Plasma-Assisted Growth of Moisture Diffusion Barriers on Polymers: From Chemical Vapor Deposition to Atomic Layer Deposition

Thursday, November 16, 2006, 9:40 am, Room 2011

Session: Plasmas and Polymers
Presenter: M. Creatore, Eindhoven University of Technology, The Netherlands
Authors: M. Creatore, Eindhoven University of Technology, The Netherlands
E. Langereis, Eindhoven University of Technology, The Netherlands
I. Volintiru, Eindhoven University of Technology, The Netherlands
A. Milella, Eindhoven University of Technology, The Netherlands
W.M.M. Kessels, Eindhoven University of Technology, The Netherlands
M.C.M. Van De Sanden, Eindhoven University of Technology, The Netherlands
Correspondent: Click to Email
Polymer- based technologies are rapidly growing in fields such as flexible solar cells and OLEDs, but long-term stability devices are desired and, therefore, high moisture diffusion barrier films are required (water vapor transmission rates (WVTRs) as low as 10@super -6@ g/m@super 2@day). Sputtering and plasma-enhanced chemical vapor deposition (PE-CVD) are the most investigated technologies for the deposition of barrier films, although only µm-thick multi-layer systems appear to meet the above-mentioned requirements. Very recently, however, Atomic Layer Deposition (ALD) has been addressed as an attractive route towards excellent and thinner barriers. Also in this case, plasmas can assist the growth (plasma assisted ALD, PA-ALD) by providing a radical source, which replaces one (molecular) deposition precursor (e.g., O radicals replacing H@sub 2@O for Al@sub 2@O@sub 3@ deposition). Here we address the PA-ALD deposition of Al@sub 2@O@sub 3@, consisting of cycles of trimethylaluminum dosing alternating with O@sub 2@ plasma exposure. WVTR values as low as 0.005 g/m@super 2@day are reported for thin (20 nm) PA-ALD Al@sub 2@O@sub 3@ on polyesters, while 100 nm- thick oxides (SiO@sub 2@ and Al@sub 2@O@sub 3@) deposited by means of PE-CVD in a remote plasma configuration are characterized by WVTR values of 0.15 g/m@super 2@day. The superiority of the PA-ALD layers is attributed to the control of the film microstructure during the growth: chemical (XPS), optical (spectroscopic ellipsometry) and morphological (atomic force microscopy) analyses have pointed out towards lower hydrogen content-, higher refractive index- and smoother PA-ALD films in comparison with PE-CVD layers. Routes for the microstructure control in PE-CVD will be also addressed: ion bombardment (via an external rf bias), in terms of ion energy and ion-to-radical flux ratio, was found to be a key parameter in tuning the film microstructure and improving the moisture permeation barrier properties.