Novel micromachined vibrating rate-gyroscope with optical sensing and electrostatic actuation

This paper reports the fabrication and preliminary characterization of a novel vibratory rate-sensor. The sensor employs the modulated integrative differential optical sensing (MIDOS) to detect the output mode amplitude. The mechanical part of the sensor is fabricated by bulk micromachining using a double side anisotropic wet etching process. A CMOS chip containing the detecting photodiodes and their readout electronics is fabricated through MOSIS. Electrical and mechanical integration of the two parts is achieved by using the indium bumps technology. The proof mass is aligned with the detecting photodiodes, so that when at rest, equal portions of the two photodiodes are exposed. Several prototypes have been fabricated and tested on a rotating table. Good linearity (<1%) was shown on a -1000-1000°/s range and so far, a minimum detectable rate (MDR) below 1°/s was demonstrated. Future research will focus on lowering the MDR below 0.01°/s.