An Ultrahigh Vacuum Packaging Process Demonstrating Over 2 Million Q-Factor in MEMS Vibratory Gyroscopes

Micro resonators and vibratory gyroscopes could reach their fundamental thermo-elastic damping (TED) limit in an ultravacuum condition where the viscous damping is eliminated. This article presents a reliable and repeatable high vacuum sealing process as a standalone approach for performance evaluation of dynamic micro devices. We demonstrated a micro-Torr vacuum level in a ceramic leadless chip carrier package and achieved the Q-factor over 2 million on a quad mass gyroscope, approaching the TED limit of the device by effectively eliminating the viscous damping. The long-term vacuum stability was characterized over 1 year and demonstrated that the Q-factor does not degrade over time and even continues improving. The long-term ultrahigh vacuum condition is enabled by surface desorption prior to sealing, pumping of residual gases by passive getters, and defect-free solder reflow in the sealing area. The experimental results confirmed the reliability and repeatability of the proposed sealing procedure, which can be adapted for other Micro Electro-Mechanical Systems (MEMS) with ultrahigh vacuum requirements.