Fabrication of a novel resonant pressure sensor based on SOI wafer

A novel resonant pressure sensor for pressure detection is designed and fabricated based on the siliconon-insulator(SOI) wafer. The resonator suspended by four beams at four points on the diaphragm is encapsulated between two glass lids. To prevent the undesired etching of resonator during the wet etching, a triple-layer protective process using silicon nitride and silicon oxide is adopted. Experiments show that after several hours wet etching in tetramethyl ammonium hydroxide (TMAH) solution,the resonator is successfully released. This protection technology proved to be highly effective for the release of a movable microstructure by wet silicon etchants. Initial performance test results of the device yield a natural frequency of 9. 932 kHz under the standard atmospheric pressure and the Q factor of 34.