AVS 52nd International Symposium
    MEMS and NEMS Monday Sessions
       Session MN-MoM

Paper MN-MoM7
Surface Chemistry of Organosilanes as a Vapor Phase Lubricant for Si-based MEMS Applications

Monday, October 31, 2005, 10:20 am, Room 207

Session: Processing & Characterization of Materials for MEMS & NEMS
Presenter: D. Kim, Carnegie Mellon University
Authors: D. Kim, Carnegie Mellon University
A.J. Gellman, Carnegie Mellon University
Correspondent: Click to Email
Microelectromechanical systems (MEMS) offer the opportunity to improve a number of technologies and to develop devices that are significantly smaller and more lightweight than those in current use. Unfortunately, the long term operation of MEMS devices requires some form of lubrication for components in sliding contact. While traditional liquid lubricants cannot be used, vapor phase lubrication may be an effective solution. MEMS devices are made from single-crystal silicon and polycrystalline silicon, the surfaces of which are covered with a thin film of silicon dioxide, SiO@sub 2@, when exposed to air. The lubrication of MEMS materials requires both the replenishment of SiO@sub 2@ from the worn surfaces and the application of a lubricant film that will minimize wear. Organosilanes, R@sub n@Si(OR)@sub 4-n@, such as triethoxyphenylsilane, (C@sub 6@H@sub 5@)Si(OCH@sub 2@CH@sub 3@)@sub 3@, are proposed as vapor phase lubricants that can perform both functions. The surface chemistry of triethoxyphenylsilane on Si(100) and SiO@sub 2@ surfaces has been studied, using temperature programmed reaction spectroscopy and Auger electron spectroscopy. This chemistry was compared to that of tetraethoxysilane, (CH@sub 3@CH@sub 2@O)@sub 4@Si, which is widely used as a precursor for SiO@sub 2@ film deposition. Triethoxyphenylsilane decomposed readily, depositing SiO@sub 2@ and graphitic carbon on Si(100) and SiO@sub 2@ surfaces. Triethoxyphenylsilane formed more graphitic surface films than tetraethoxysilane on Si(100) surface at T=300-600 K. Triethoxyphenylsilane decomposes by C-O cleavage to ethyl groups which desorb as ethylene via @beta@ -hydride elimination. The remainder produces phenyl groups which desorb as benzene or decompose further to deposit graphitic carbon onto the surface. These results suggest that lubrication of MEMS materials could be accomplished, using vapor phase organosilanes such as triethoxyphenylsilane.