Lumped model for the comb-finger capacitance and electrostatic force

摘要

Comb-finger structure has been widely used in MEMS device as actuator and capacitive sensing unit. We can quite often find that the capacitance of and electrostatic force between a pair of the fingers are calculated by parallel plate model. This is certainly the simplest and the easiest solution, but with very low accuracy. The analytic method with reasonable accuracy is generally necessary for design engineers because it can give a quick estimation of the design and correct insight into the performance of the design. In this paper, the long comb-finger structure is analyzed. The multi-body-system, e.g., comb-finger above the ground, has been simplified. The fringe field effect is taken into account. Applying semi-empirical equations, we have developed analytic models for calculating capacitance and electrostatic force for various comb-finger structures. The results from the analytic models are compared with simulation results from commercial simulation software.