Design and Simulation of Tunable Micromirror for Two-Color Microbolometer

摘要

A tunable reflecting micromirror made up of two layers of Al and Si_3N_4 is designed to suspend between the silicon substrate and the heat sensitive membrane for measuring the actual temperature and color of an object based on comparison of two wavelength response windows, 3-5 μm and 8-12 μm. The micromirror, switching between two positions by an applied electrostatic voltage, provides a response to two wavelength windows by tuning the optical tunable resonant cavity. With different distances between the micromirror and the bottom electrode, the total capacitance of the tunable micromirror is gained based on electromagnetic analysis and theoretical equation. The pull-in voltage is calculated as 8.21 V by electrostatic-mechanical coupling analysis. But if the voltage is increased to about 9.73 V, the micromirror will touch the bottom electrode by pull-in behavior. At last, the vibration modes of the tunable micromirror are simulated using ANSYS, and the fabrication process flow of the two-color microbolometer is theoretically demonstrated.