Abstract
This article discusses anti-stiction coating for DC contact MEMS switch by atomic force microscope (AFM). A commonly problem in Microelectromechanical System (MEMS) switch with metal-to-metal contact is stiction, which occurs when surface adhesion forces are higher than the mechanical restoring force of the switch contact. The attractive force arises from capillary force generated from forming a liquid meniscus by the water vapor across MEMS switch gap and stiction occurs. One attractive approach to tackle the stiction problem is to provide low-energy surface coating in the form of self-assembled monolayer (SAM) on the substrate. However, it may be not applicable to DC contact MEMS switch because the electric property of SAM is not known exactly. In this study, adhesion force was measured as a function of humidity for SiO2, Si, SAM, and Au surfaces against an AFM tip. Our measurements indicate that approximately 20 nm thick sputtered Au coating can reduce capillary force as in the case of the hydrophobic SAM surface. Therefore, Au coating is useful in preventing stiction for DC contact MEMS switch.
