Development of a high performance SOI fabricated gyroscope

Although vibrating microgyroscopes has been an active area of research in the last few years, the resolution requirements for high performance applications have not yet been met. This paper reports the development of a high performance comb-driven vibratory angular rate gyroscope. The gyroscope uses a rotary electrostatic actuation and differential capacitive sensing. The calculations show a resolution of about 8 deg/hr. The gyroscope is fabricated using SOI wafer with a 40 μm thick layer of single-crystal silicon. The overall size of the gyroscope is about 2.8 mm diameter. The high sensitivity of the present design is achieved by employing a large sensing area coupled with a higher layer thickness. Simply increasing the sensor area without increasing the layer thickness may yield a higher sensitivity, but lead to problems such as stiction and lower pull-in voltages. Increasing the suspension stiffness increases the pull-in voltage. However, an increase in suspension stiffness may also increase the natural frequencies which will lower the sensitivity and resolution. The design of the gyroscope involves complex and often conflicting requirements, and some of these important aspects are discussed in this paper.