Double-frame silicon gyroscope packaged under low pressure by wafer bonding

Abstract

A new design for a "double-frame" vibratory silicon gyroscope is described. The gyroscope consists of two frames and corresponding springs. The inner frame has electrode fingers and is suspended from the outer frame, which has sensing springs. The outer frame is linked to the substrate by driving springs. This decoupling of the lateral driving and sensing motions makes the structure easy to design and improves the S/N ratio. The gyroscope has a glass/silicon/glass structure with through-hole electrodes on one face. It is fabricated by the deep dry etching of silicon and low-pressure wafer-to-wafer anodic bonding. The noise equivalent angular rate is 0.8°/s (rms, bandwidth: 40Hz), and the linearity is less than 1% for angular rates from -250 to 250°/s. The overload resistance is over 1500G for 0.5ms, and the reliability of the package has been confirmed.