Design, analysis and characterization of silicon microphones.

摘要

The research topics of the dissertation involve the design and the acoustic response prediction of MEMS silicon microphones. A directional microphone and an omnidirectional microphone were designed to meet the performance targets such as the desired sensitivity, frequency response, stability and so on.;The directional microphone is inspired by the parasitoid fly Ormia Ochracea, and the omnidirectional microphone is inspired by the directional microphone. Both of them are capacitance microphones. The mass moment of inertia, resonance frequencies and mode shapes of the microphone diaphragm were acquired by using a combination of finite element analysis and approximate analytical formulas. Both of the models consider the effects of air viscosity in the back volume and the air slits on the diaphragm. The equations are developed to predict the theoretical responses of the two microphone designs under sound wave, and the experimental and predicted responses of the microphone designs are compared.;Since the microphone diaphragms are fabricated by using silicon micromachining technology, which will go through distinct temperature changes during the fabrication process, there will be a residual stress on the diaphragm structure after the fabrication. The analysis of the residual stress effects is included in this thesis.;Electrical stiffness due to the bias voltage added between the diaphragm fixed fingers and movable fingers are evaluated in the models. The influences of the electrical stiffness to the microphone's response are predicted.;Based on the comparison of the measured results and the analytical results to the microphone, the design of the microphones will be further modified to meet the essential mechanisms and requirements.