Multi-objective optimization of a circular dual back-plate MEMS microphone: tradeoff between pull-in voltage, sensitivity and resonance frequency

In this study, the optimization of a circular dual back-plate condenser microphone has been done in order to increase the pull-in voltage, sensitivity and resonance frequency simultaneously. Microphone’s diaphragm is assumed as a circular micro-plate subjected to symmetric two-sided electrostatic force.

An accurate eighth order polynomial function is determined as the first mode shape of the circular micro-plate and Galerkin decomposition method is employed to find the analytical formulations for the microphone metrics performance. The analytical relations are validated by comparing them with finite element results.

Next, the applied voltage, gap size, diaphragm radius and thickness are assumed as the design variables and modified non-dominated sorting genetic algorithm is utilized for multi-objective optimization procedure. Considering low standard deviations and high mean values, a new design point is chosen among the suggested optimal points so that there is an increment in each of three objective functions.

Compare to a fabricated sample of a dual back-plate microphone, for the new design point, pull-in voltage has increased more than 3.6 times, sensitivity has improved 4% and resonance frequency has extended 24%.