A high-sensitivity piezoresistive gyroscope with torsional actuation and axially-stressed detection

A piezoresistive gyroscope is presented, which is excited by electrostatic force and detected piezoresistively. With axially deformed tiny beams serving as piezoresistors to detect coriolis acceleration, the sensitivity can be much improved. With a four-terminal piezoresistive sensing element monitoring the driving-mode output versus temperature, the gyroscope temperature drift can be eliminated effectively. So the gyroscope enables a combination of self-compensation temperature drift and high sensitivity, and the gyroscope sensitivity will be so high as 3.07mV/7s/5V. Besides, the gyroscope can operate at atmosphere, as its high Q value is about 1000 in detection-mode. To verify the axially stressed detection scheme and develop fabrication technology, the detection part of the gyroscope has been fabricated in silicon-on-insulator (SOI) wafer by bulk micromachining techniques including deep-reactive-ionic-etch (DRIE). Testing results show both high resonant frequency of 1115Hz for operation and high sensitivity of 106mV/g/5V for detection. The detection scheme is proved to effectively improve the gyroscope sensitivity.