A Microgyroscope With Piezoresistance for Both High-Performance Coriolis-Effect Detection and Seesaw-Like Vibration Control

A novel piezoresistive scheme is proposed to solve the problem of piezoresistive gyros in terms of low-sensitivity and high-temperature drift. Based on the piezoresistive scheme, a micromachined vibratory gyroscope is developed. By using axially stressed piezoresistive tiny-beams, piezoresistive detection to Coriolis-acceleration can be realized with both high sensitivity and high resonant frequency, i.e., high gyro operation frequency. Thanks to the high piezoresistive sensitivity, precise frequency matching between the driving and detecting modes is unnecessary. Another four-terminal transverse piezoresistive element is used to monitor and stabilize the amplitude of the seesaw-like torsional vibration through a feedback loop. With the same feedback loop, temperature drift of the piezoresistive angular-rate sensing signal can be on-chip compensated, as the transverse piezoresistance tracks the temperature drift of the angular-rate sensing piezoresistors. The gyro is designed and fabricated by bulk micromachining. Measurement results verify the proposed piezoresistive gyro scheme and show noise-limited angular-rate resolution of 0.33deg/s for plusmn300deg/s range. Considering the mature fabrication technology and simple signal-readout for piezoresistive sensors, the piezoresistive microgyros are promising for low-cost applications