Improved design of a silicon micromachined gyroscope with piezoresistive detection and electromagnetic excitation

In this paper, an improved design of a silicon micromachined gyroscope (angular rate sensor) is presented. It is based on the tuning fork principle and realized by combining two proof masses. The gyroscope is driven by electromagnetic forces and detects the Coriolis force by means of four piezoresistors connected in a Wheatstone bridge. The main fabrication steps including advanced deep reactive ion etching (ADRIE) and a wafer scale packaging are reported. The major novelty consists in a new design to reduce output drift. Both a higher symmetric mechanical structure and a separation of the first and the second mechanical resonant frequencies have been successfully investigated. This allows both driving and sensing of the device at its first resonant frequency while not exciting the second one. Thus, better uncoupling between the sensor modes has been obtained, As main results, a bandwidth of 10 Hz has been achieved and long-term measurements have been performed which were not possible with the previous design due to the low stability of the zero rate signal. For the current design, the dynamic behavior, the temperature dependence, rotation measurement, and the sensor stability have been characterized.