Novel chemistry for surface engineering in MEMS

It is well recognized that controlling surface forces is one of the key issues in the design, fabrication, and operation of miscroelectromechanical systems (MEMS). Since the majority of MEMS devices are made of silicon from surface micromaching, an attractive approach is to use the well-known alkyltrichlorosilane self-assembled monolayers (SAM) on oxidized silicon surfaces to control surface energy. While this approach has enjoyed some success in reducing adhesion in model MEMS structures, a major impediment to its implementation in a manufacturing setting is that it is highly irreproducible and very sensitive to a number of experimental parameters. In this report we present a novel strategy for the efficient assembly of organic monolayers directly onto the silicon surface via Si-O linkages. This is achieved by the reaction between an alcohol functional group and a chlorinated Si surface. The resulting molecular monolayers are thermally and chemically stable and are successfully demonstrated in adhesion reduction in a model MEMS structure, namely, a cantilever beam array (CMA). Polycrystalline beams with length up to 1.5 mm can be released. Major advantages of this new approach for surface control in MEMS include simplicity, reproducibility, and reliability.