AVS 50th International Symposium
    Plasma Science and Technology Thursday Sessions
       Session PS1-ThM

Paper PS1-ThM2
Selective Plasma-induced Deposition of Fluorocarbon Films on Metal Surfaces for Actuation in Microfluidics

Thursday, November 6, 2003, 8:40 am, Room 314

Session: Plasma-Surface Interactions: Deposition
Presenter: A. Tserepi, National Center for Scientific Research (NCSR) "Demokritos", Greece
Authors: P. Bayiati, National Center for Scientific Research (NCSR) "Demokritos", Greece
A. Tserepi, National Center for Scientific Research (NCSR) "Demokritos", Greece
E. Gogolides, National Center for Scientific Research (NCSR) "Demokritos", Greece
K. Misiakos, National Center for Scientific Research (NCSR) "Demokritos", Greece
Correspondent: Click to Email
Plasma-induced deposition of polymer films on surfaces is an important issue in etching plasmas, since on one hand it allows selective etching of materials,@footnote 1@@footnote 2@ while on the other it provides side wall passivation necessary for anisotropic high-aspect ratio etching. The present work focuses on the selective deposition of fluorocarbon (FC) films on metal surfaces, specifically on aluminum, over SiO@sub 2@ surfaces, in order to obtain surfaces of distinct wettability. If, in addition, the wettability of the modified metal surface can be controlled electrostatically and consequently the surface be varied from a hydrophobic to a hydrophilic one, such plasma-modified metal surfaces can be used as electrodes employing electrowetting for actuation of fluid transport in microfluidic devices.@footnote 3@ Since polymer layers on surfaces are easily formed in fluorocarbon discharges with high concentrations of radical CFx species, fluorocarbon gases such as C@sub 4@F@sub 8@ and mixtures of CHF@sub 3@/CH@sub 4@ were used in our experiments. For the selection of conditions appropriate for selective deposition of FC films on Al over SiO@sub 2@, plasma parameters such as plasma power, bias voltage, electrode temperature, and gas composition were varied. The wettability of SiO@sub 2@ and Al surfaces exposed to FC plasmas under different plasma deposition conditions was characterized by contact angle measurements (without and with voltage application). Contact angles as a function of the applied voltage were used to yield the thickness of the FC film deposited on Al, and to indicate the breakdown voltage for the films under consideration. The results demonstrate the feasible use of such plasma-deposited films on Al for electrostatic actuation with application of relatively small voltages (less than 10 V). @FootnoteText@ @footnote 1@G. Oerlein, Surface Science 386, 222 (1997); and G. Oerlein et. al., J.Vac. Sci. Technol. A 12(2), 333 (1994).@footnote 2@L.Rolland, M.C. Peignon, Ch. Cardinaud, G. Turban, Microel. Engin. 53, 375 (2000).@footnote 3@M. Pollack, R. Fair, A. Shenderov, Appl. Phys. Lett. 77(11), 1725 (2000).