Thermally actuated microbeam for large in-plane mechanical deflections

Abstract

The design, finite-element analysis, and experimental performance evaluation of a microelectromechanical systems (MEMS) device, known as a thermally actuated beam, is presented. The behavior of the thermal beam has been characterized so that it can be considered as an actuator in future MEMS applications. A MEMS polysilicon thermally actuated beam uses resistive (Joule) heating to generate thermal expansion and movement. To be a useful MEMS device, a thermally actuated beam will need to produce in-plane tip deflections that span 0–10 μm; while generating force magnitudes on the order of 10 μN. The thermally actuated beam design was accomplished with the L-Edit® software program. The devices were fabricated using the Multi-User Microelectromechanical Systems Process foundry service at the Microelectronics Center of North Carolina. The finite-element modeling analysis was accomplished with the IntelliCAD® computer program. These analyses predicted thermal beam tip deflections (0–13 μm) consistent with experimental observations. The average tip force generated by the thermal beam was measured to be 8.5 μN. The resonant frequency associated with in-plane motion, without damping, was calculated to be 75.16 kHz. The average resonant frequency measured in ambient air was 69.73 kHz. As a relative measure of reliability, it was observed that the thermal beam could be activated well in excess of three million cycles.