Investigation of anti-stiction coating for ohmic contact MEMS switches with thiophenol and 2-naphthalenethiol self-assembled monolayer |
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Authors: | Takahiro YamashitaAuthor Vitae Toshihiro ItohAuthor Vitae Tadatomo SugaAuthor Vitae |
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Affiliation: | a Department of Precision Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan b National Institute of Advanced Industrial Science and Technology, 1-2-1 Namiki, Tsukuba-shi, Ibaraki 305-8564, Japan c Core Research for Evolutional Science and Technology, Japan Science and Technology Agency, Japan |
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Abstract: | Anti-stiction coating with a conductive self-assembled monolayer (SAM) formed by π-conjugated bonds was investigated for ohmic contact microelectromechanical system (MEMS) switches with low-load contacts. SAMs of thiophenol (C6H5SH, TP) or 2-naphthalenethiol (C10H7SH, 2NT) were coated on Au samples with different surface roughness to investigate the effects of the surface asperities on the adhesion force and contact resistance. The adhesion force was measured using a silicon tipless cantilever in the relative humidity range of 10-85% and the contact resistance was measured in the contact force range of 0-70 μN using a conductive tipless cantilever coated with Au for the SAM coated samples and compared with those for a Au sample surface. The adhesion force measurements indicate that the TP and 2NT coatings can prevent a liquid meniscus from forming on device surfaces due to their hydrophobic character caused by the protruding aromatic group. In addition, it was confirmed that these coatings could reduce van der Waals forces more than Au coating. Contact resistance measurements revealed that an electric current begins to flow with smaller contact force for TP and 2NT coated samples than for Au coated samples. The measured contact resistances of the SAM and Au coated samples were comparable. Based on these results, SAMs of TP and 2NT have excellent potential as anti-stiction coating for MEMS switch contacts. |
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Keywords: | Adhesion force Atomic force microscope Contact resistance MEMS switch Self-assembled monolayer Stiction |
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