A low-cost micromechanical accelerometer with integrated solid-state sensor

Accelerometers are probably the most common application of MEMS technology as they only require sensing the movement of a mass subject to acceleration. Still, because of the irrelatively high cost, the potential of accelerometers is not fully utilized. This paper discusses the performance of the Direct Integration (DI) of stress sensors made of pn diodes and MOS transistors with Micromachined accelerometer. The accelerometers are made of beam with cross-section of 2 mu m X 20 mu m connected to proof mass. The stress sensors are fabricated at the root of the beam and respond to stress developed as a result of mechanical excitation. This stress modulates the silicon band gap energy and thus affects the I-V transfer function of the sensor. The sensors and the supporting ICs are fabricated by a conventional micro fabrication facility and the mechanical part is fabricated subsequently, using SCREAM (Single Crystal Reactive Ion Etching and Metallization) process that adds only one Lithography step to the IC's Lithography steps. This low-cost integration may reduce the cost of accelerometers and increase their potential use. (C) 2000 Elsevier Science S.A. All rights reserved.