Thermally actuated microbeam for large in-plane mechanical deflections

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 mu m; while generating force magnitudes on the order of 10 mu N. The thermally actuated beam design was accomplished with the L-Edit(R) 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(R) computer program. These analyses predicted thermal beam tip defections (0-13 mu m) consistent with experimental observations. The average tip force generated by the thermal beam was measured to be 8.5 mu N. 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. (C) 1999 American Vacuum Society. [S0734-2101(99)16904-5].