A capacitively excited and detected resonant pressure sensor with temperature compensation

Abstract A new improved resonant pressure sensor based on a balanced resonance vibration of a dual-diaphragm structure is presented, where a pressure-difference-induced static deflection of the diaphragms changes the flexural rigidity of the structure and thus the mechanical resonance frequency. The sensor is fabricated using silicon micromachining etching techniques and silicon fusion bonding. The vibration of the resonator is capacitively excited and detected using four electrodes at the resonator corners. A theoretical model of the resonator Q -factor in air is derived and used to optimize the number of ventilation holes and the electrode gap of the new sensor design. The theoretical conclusions are verified in measurements of the resonator with different electrode configurations. The new sensor has an improved and simplified support structure and electrode arrangement that yields an enhanced excitation and detection efficiency and a sufficiently high Q -factor in air of about 2600. The low and negative intrinsic temperature sensitivity to the resonance frequency of the single-crystal silicon resonator structure of about −18 ppm/°C is reduced to + 1.3 ppm/°C by using a temperature sensitivity compensation technique involving gas encapsulation in the cavity.