A surface-micromachined tunable vibratory gyroscope

A tunable vibratory microgyroscope was fabricated by surface micromachining technology. The 7.5 μm-thick polysilicon structural layer was deposited using LPCVD at 625°C. The resonant frequency in the detection mode was higher than that in the driving mode so that gyroscope could be tuned to the resonant frequencies by applying the inter-plate DC bias. The gyroscope was driven in a resonant state by electrostatic force and detected the output due to a capacitance change between the plate and the polysilicon electrode. The resonant frequencies of gyroscope in the driving and detection direction were measured to be 10.48 kHz and 10.93 kHz, respectively. The resonant frequency in the detection direction could be shifted to 10.52 kHz by applying the tuning voltage of 4.0 V. The quality factor and resonant frequency of detection mode were significantly affected by ambient pressure and decreased as a function of ambient pressure. The noise equivalent rate of this device was about 0.1 deg/sec at 10^-2Torr