Silicon Resonant Angular Rate Sensor for Vehicle Stability Control

A new silicon resonant angular rate sensor which is suited for mass production is studied. The sensor consists of a glass-silicon-glass structure. The resonant portion is one silicon cantilever, which is fabricated by anisotropic wet etching and excited by an external piezo actuator. The resonant frequencies of the exciting direction and the Coriolis force direction are about 4 kHz. The thickness of the cantilever is the silicon wafer thickness itself, and only the width and length of cantilever are determined by the etching, thus frequency variation is very small. The silicon cantilever is packaged in a vacuum environment by anodic bonding of glass and silicon. In this process, smaller substrate deformation and higher bonding strength are required. We studied the conditions including applied voltage, current and temperature. The vibration caused by Coriolis force is detected by capacitance change between the silicon cantilever and the metal electrode on the glass. The sensor circuit consists of C-V converter and synchronous demodulator. The C-V converter is an ASIC (Application Specific Integrated Circuit) using switched-capacitor technology. We achieved a linearity of ±1% F.S. (full scale) within a measured range of ±200 deg/sec. In the paper we describe the design, the process details and the performance of the sensor.