Optimization of a novel structure for micromachined resonant pressure sensor

A novel resonant pressure sensor structure is proposed to achieve better performance in quality factor (Q) and output stability. Diffused silicon (15um) is used for the resonator, thus the resonator and the pressure diaphragm can be fabricated on the same silicon substrate without bonding. A differential detection tri-resonator structure is adopted to reduce the output drift and increase the sensitivity. To optimize the structure, a simplified 2-D model is set up for the theoretical analysis. In addition, 3-D models of the 'H' style beam and the entire structure which is composed of a diaphragm and three groups of beam respectively doubly supported by the anchors are constructed for the ansys-FEA simulation. Through the theoretical analysis and the simulation, the structure parameters (beam length, beam thickness, diaphragm thickness etc) are optimized. The natural frequency of the optimized model is 86.7 KHz, and the sensitivity is 19 KHz per 0.1MPa. The sensor is fabricated with the optimized parameters. The test experiments show that the results basically correspond with the simulation results except the effect of the wet etching in the fabrication process. The quality factor is 10000 in low vacuum, and the resolution is 1/10000.