Vacuum Packaged Silicon MEMS Gyroscope with Q-Factor Above 0.5 Million

Abstract

This paper reports a new dual mass vibratory MEMS z-axis rate gyroscope architecture that prioritizes the sense-mode quality factor and provides improved ordering of the mechanical vibrational modes. The proposed linearly coupled, dynamically balanced anti-phase sense-mode design minimizes substrate energy dissipation to maximize the quality factor. The levered drive-mode mechanism structurally forces the anti-phase drive-mode motion of the symmetrically decoupled tines eliminating the lower frequency spurious mode and providing true mechanical rejection of external shocks and accelerations. SOI prototypes were characterized in a vacuum chamber demonstrating drive-mode quality factor of 67,000 and ultra-high sense-mode quality factor of 125,000. A vacuum packaging technology was introduced and demonstrated a ceramic package-level sealed gyroscope with a quality factor on the order of 100,000. The high quality factor and mode ordering of the new design provide a path toward ultra-high scale factor without compromising the sensitivity to external accelerations.