Design Of Resonant Pressure Sensor Based On Double Side Beam Structure

The resonant pressure sensor is a MEMS device that measures pressure indirectly by detecting the change of the natural frequency of the resonator.It has the characteristics of high accuracy and strong anti-interference,and its output frequency signal is almost digital signal,which makes it easily to connect with digital interfaces such as computers and circuits to form a high-precision detection system.Resonant pressure sensor represents the top technology of MEMS pressure sensor in the world.It is very suitable for aerospace,meteorological monitoring,oil survey and other complex environments which have higher requirements on some performances such as accuracy and stability,and has broad development potential in both military and civilian fields.Therefore,In this paper,a resonant pressure sensor with electrostatic excitation/capacitance detection is proposed.The resonator and the pressure-sensitive film adopt mutually perpendicular working modes to reduce the energy coupling during the sensor's working process.The design of the side beams suppresses the Z-direction displacement of the resonator to further improve the improves the stability of the sensor.The physical model of the resonant beam,side beam and other components is derivated and established to complete the modeling of the resonator.Based on the principle that the equivalent stiffness of a resonator changes with axial stress under lateral vibrate in different pressure loads,the optimization design and modeling of the pressure sensitive film,silicon island and resonator three-body coupled sensor overall structure are finally completed.It is analyzed and verified under the ANSYSWorkbench simulation platform,The results show that the side beam can effectively suppress the Z-direction displacement of the resonator,the resonator has better positive stress characteristics in the range of 0-100 MPa.The sensor fundamental resonant frequency is 29.834 k Hz and the sensitivity is up to 29.6Hz/k Pa in the range of 0-120 k Pa,and the frequency stability is still obtained when the maximum overvoltage is 1.5×FS.Based on the design of the device structure,the etching,bonding,packaging and other processing technique were studied.Anisotropic wet etching method was used to release the silicon island and the sensitive film,and the resonator was released through the DRIE process.The sensor achieve vacuum packaging by silicon-silicon bonding between sputtered with getter and resonator structure layer,furthermore,electrical signals are drawn through the through-silicon vias,and finally the layout design of the lithography mask corresponding to the process steps is completed.