last updated Dec 19, 1999

Sensors, actuators, transducers, microsystems and MEMS (MicroElectroMechanical Systems) are some of the terms describing technologies that interface information processing systems with the physical world. Electrostatically actuated micromechanical devices are important building blocks in many of these technologies. Arrays of interconnected devices are especially exciting, promising breakthroughs exemplified by VLSI electronics and the World Wide Web. Examples of such arrays are found in video projection displays, fluid pumping systems, optical communications systems, tunable lasers and microwave circuits. Canonical Benchmark The entire process of calibrating an electromechanical simulator - identifying relevant parameters, designing and measuring test structures, extracting parameters using detailed electromechanical simulations, and extrapolating the behavior of an actual device - is presented. The simulation model for electrostatically-actuated beams is calibrated to a wide range of electrical and optical test structure measurements and is then used to predict the behavior of more complex dual-bias-electrode structures. Various mechanical discontinuities, and post-buckled pull-in behavior are addressed explicitly. Arbitrary fitting coefficients that limit generality are avoided. The presence of gold connections is shown to cause area-dependent material property nonuniformities. The well-characterized behavior of the dual-electrode structures can serve as verification test cases for evaluating coupled electromechanical simulators. Contact Electromechanics Using well-characterized beams as in-situ surface probes, capacitance-voltage measurements reveal that surface residue adds to the effective gap when the movable electrode contacts an underlying silicon nitride layer. A compressible contact surface model used in simulations improves the fit to measurements. In addition, the electric field across the nitride causes charge to build up in the nitride, increasing the measured capacitance over time. The rate of charging corresponds to charge injection through direct tunneling. Actuator with Extended Travel A novel actuator that can travel stably beyond one-third of the initial gap (a trademark limitation of conventional actuators) is demonstrated. A "folded capacitor" design, requiring only minimal modifications to the layout of conventional devices, reduces the parasitic capacitances and modes of deformation that limit performance. This device, useful for optical applications, can travel twice the conventional range before succumbing to a tilting instability. Compact Models Three-dimensional and even detailed two-dimensional simulation models consume enormous computing resources, especially for transient/dynamic simulations. Compact models in one-dimension and simplified quasi-two-dimensional models are very useful aids in understanding the general behavior of electrostatically actuated devices. Models implemented in Matlab are shown.