Design Of MEMS Silicon Resonant Pressure Sensor

MEMS (Micro-Electro-Mechanical System) silicon resonant pressure sensor measures ambient pressure by detecting the change of its resonant frequency. It has many advantages, such as small volume, high precision, strong anti-interference ability. In addition, its frequency output signal is approximate to digital signal, which makes it connected to digital circuit easily. Therefore, MEMS resonant pressure sensor plays an important role in the field which need high precision of pressure measurement, such as precision control and aerospace.This dissertation presents a silicon resonant pressure sensor based on electrostatic excitation and capacitive detection. This sensor uses a composite sensitive structure which composed of resonant beam and pressure sensitive diaphragm. By making the theoretical analysis and modeling, the features of sensing structure can be obtained with simulation, such as the displacement and stress distribution of the sensing structure under an atmospheric pressure, the relationship between resonant frequency and pressure, and the relationship between maximum displacement of the beam and excitation voltage. By analyzing the simulation results, a rectangular diaphragm is selected as the pressure sensitive diaphragm, and the relative position of the resonant beam and the diaphragm are determined. In addition, the optimal size of the sensing structure and excitation voltage are also obtained. The resonance frequency of the structure is about 19 kHz. The sensitivity is 149.37 Hz/kpa. And the excitation voltage is less than 42.5 V.Based on the sensing structure, a sensorstructure model with three layers is built and the fabrication process design is made. The main contents are as follows: using high doped silicon which resistivity is 0.005?* cm to fabricate the sensor; using Si3N4 as the mask and combining wet etching and dry etching to fabricate the sensing structure;gold-silicon wafer eutectic bonding are used for wafer level package; the data of convex corner undercutting have been obtained by wet etching experiments; the mask layout have been completed.