Micromachined polysilicon resonating xylophone bar magnetometer

The basic device principles, including response sensitivity and transduction schemes, are outlined for a resonating xylophone bar magnetometer. Advanced design emphasis is on a polysilicon version with dimensions of order microns fabricated by microelectromechanical. systems (MEMS) processing techniques. All polysilicon devices tested to date have performed extremely well in static magnetic fields and exhibit mechanical quality factors, Q, of up to 30,000 at reduced pressures. The resonance frequencies of the fundamental mode of vibration of these polysilicon xylophone bars have been found to be sensitive functions of the torsional stiffness of the support arms, in accord with an analytical model based on Bernoulli-Euler theory. The output response of the polysilicon xylophone magnetometer as a function of impressed magnetic flux density has been shown to be linear up to 150 muT; however, sensitivity is currently limited by the significant resistivity of the polysilicon xylophone bar. Various strategies are being implemented to bring the magnetometer sensitivity into the applications-dominated nT regime. (C) 2002 Elsevier Science Ltd. All rights reserved.