Design Of Micro-machined Low-pressure Sensor

Micro-machined low-pressure sensor is an important subset of micro-machined pressure sensor, which plays important roles in many fields, such as interspaces exploration, semiconductor manufacturing, etc. The lowermost measurement range of micro-machined pressure sensor in the domestic market is 0～1000Pa and lower micro-machined pressure sensor must be imported overseas. It is significant to develop and research micro-machined pressure sensor with maximum output lower than 1000Pa which will contribute to improve the technology of micro-machined pressure sensor and promote the development of related industries.The key point of develop and research micro-machined low-pressure sensor is to improve its sensitivity and resolution. In the first, the operation principles of three typical micro-machined pressure sensors which are piezo-resistive, capacitive and resonant were analyzed and their working performances were compared, their low-pressure-orientations were reviewed. Based on those analyses, compares and reviews, the capacitive was determined to be the best choice of micro-machined low-pressure sensor because the capacitive have the following advantages: high sensitivity, good stability and easy to fabricate.Secondly, static performances of several kinds of diaphragms which are the core element of micro-machined pressure were simulated with FEM. The boundary condition is fixed and the load is distributed normal pressure. The simulation results show that corrugated diaphragm with central boss is suitable for capacitive micro-machined low-pressure sensor because it's high sensitivity and good linearity. The consistency of central boss displacement improves the sensitivity of detecting capacitor and the corrugations enhance the linearity of detecting capacitor which lowers the requirements of followed measuring circuit.Then, system design of the whole sensor was performed around its four main research difficulties, including structural design and process flow design. Two feasible structure and corresponding process flow were advised. Process flow of square flat diaphragm with central boss was simulated in special MEMS software—IntelliSuite. Simulated result demonstrated the feasibility of process flow design.Lastly, the lumped parameter model of diaphragm was constructed. Electrostatic influence on the dynamic response was discussed. The dynamic performance of circular diaphragm with central boss was performed with FEM. All these results provide the foundation for the understanding of the system dynamic performance.