Thermal Tuning of MEMS Buckled Membrane Actuator Stiffness

The thermal tuning characteristics of a microelectromechanical systems (MEMS) buckled membrane exhibiting regions of both positive and negative stiffness is examined and analyzed using finite element method (FEM) simulation and through experimentation. The membranes are fabricated by releasing a silicon/silicon dioxide (Si/SiO2) laminated membrane from a silicon on insulator (SOI) wafer. The difference in thermal expansion coefficients between Si and SiO2 induces a compressive stress in the SiO2 layer causing out-of-plane buckling of the membrane. This structure is found to have positive and negative stiffness regions when actuated with a transverse force. It is demonstrated that the stiffness of the membrane can be tuned by introducing a thermal stress to the membrane. Comparisons between localized heating of the membrane and even heating of the entire substrate are shown to affect the direction of the membrane deflection and tuning characteristics