Mechanics of Out-of-Plane MEMS via Postbuckling: Model-Experiment Demonstration Using CMOS

A novel approach to out-of-plane microelectromechanical systems (MEMS) is demonstrated where elements are designed in the postbuckling regime, exploiting buckling phenomena and residual-stress control to create functional elements that extend significantly out of the wafer plane. An analytical tool for out-of-plane MEMS design is presented, based on nonlinear postbuckling of layered structures, including boundary nonideality. The analytical design tool is applied to several MEMS designs where low-order elements (e.g., beams) are controllably formed into out-of-plane shapes. Various architectures are experimentally demonstrated using CMOS processes, including one that could find application in three-axis single-heater thermal accelerometers. The on chip approach is compatible with several MEMS fabrication techniques (e.g., CMOS and micromachining), thus providing a new extension of state-of-the-art microfabrication techniques to out-of-plane elements.