Stacked Disks Resonators and Micromachined Microphones: Design and Modeling

Abstract

In this thesis, the design and modeling of two micromachined systems are presented. The two devices are a novel stacked disks resonator designed for radio frequency systems and a set of microphones with released membrane designs for photoacoustic gas sensing for CO2 monitoring in demand controlled ventilation systems. For the novel stacked disk resonator design, an analytical model for the frequency separation is derived and verified using finite element analysis. The model provides useful insight into the coupling mechanisms of two or more vertically stacked disks connected via a central stem. One unsuccessful and one incomplete fabrication trial is presented and analyzed. In addition, an analytical model for support losses adapted from a simple model for soil-structure interaction is investigated and found useful for estimating the support losses. The novelty of stacked disk resonator is vertical integration of devices previously only demonstrated integrated in-plane. Vertical integration allows smaller footprint. Although fabrication has yet proved unsuccessful, useful models have been developed and insight into the coupling mechanisms gained. Two different designs of the miniaturized microphones have been designed, fabricated and characterized. Both designs feature released membranes, but of different thickness. They are designed for high sensitivity at low frequencies. Compared to a similar microphone published in the literature, the microphones presented here feature a doubling and thirty fold improvement in sensitivity for the frequency range of interest for the two designs.