Silicon Angular Rate Sensor for Automotive Control with Open Beam Structure

An angular rate sensor of SOI (silicon on insulator) has been developed for automotive control. The sensor detects yaw rate of automobiles. The concept of the sensor design is the open beam structure (OBS). In the OBS, excitation and detection electrodes are open toward exterior bonding pads in a plane. The OBS has high independency between excitation and detection modes. The FEM analysis was carried out and the results showed the OBS was highly independent compared to other structures. This good feature contributed to the stability of vibration mode for the sensor. The OBS also made it possible to wire from the electrodes besides the mass to the exterior bonding electrodes with mono-layer silicon of the SOI. By means of the easy wirings the process and the packaging became simple. The sensor was fabricated by surface micro machining process to miniaturize the size. The measured characteristics show the OBS is suitable for angular rate sensor to be small, highly precise, and low cost