A NOVEL RESONANT SILICON ACCELEROMETER IN BULK-MICROMACHINING TECHNOLOGY

The fabrication and characterization of a resonant accelerometer made in bulk-micromachining technology are reported. The device consists of a silicon seismic mass suspended by two hinges from one side. Between them, a load sensitive silicon beam is located, clamped to the bulk and to the mass. The beam is driven electrothermally and sensed piezoresistively. A double-diffusion electrochemical etch stop process was employed in order to fabricate a sensor structure, permitting elongation and compression of the beam under an out-of-plane load, with a single wafer bulk-micromachining fabrication process. Initial device measurements show a sensitivity of 200 Hz g(-1) to out-of-plane accelerations at a beam oscillation frequency of 90 kHz. Operation of the sensor in a closed-loop circuit with an external automatic gain control circuit was successfully verified.