Alleviating the Adverse Effects of Residual Stress in RF MEMS Switches

This paper presents two methods for counteracting the unwanted deflection due to warping or buckling effects, which are serious potential problems in many fabrication processes of microelectromechanical (MEMS) structures due to thin film phenomena. This study is primarily suited for electrostatically actuated RF MEMS switches whose RF and DC performance can be significantly deteriorated by out of plane warping. It can also be applied to MEMS accelerometers, resonators and other similar systems. The first technique focuses on modifying the support structure and the spring constant of the switch, while the second involves a more complicated fabrication process, which selectively increases the switch thickness. Both these techniques yield switches with two to ten times less warping under the same fabrication conditions. The second method, however, presents the additional advantage of maintaining the actuation voltage almost unaffected.