A balanced dual-diaphragm resonant pressure sensor in silicon

The design and fabrication of a resonant differential pressure sensor is described. The vibrating part consists of a dual-diaphragm structure suspended inside a frame. Anisotropic silicon etching and thermal silicon bonding techniques are used to fabricate the device. The sensor is electrostatically excited to vibration in a torsional balanced mode which yields a high Q factor of 2400 in air. The pressure sensitivity is based on a torsional stiffness change of the vibrating element. Measurements show a pressure sensitivity of 19%/bar over the range -0.5 to +0.5 bar and a very low temperature sensitivity of the resonance frequency of -16 p.p.m./°C