Reliability of vacuum packaged MEMS gyroscopes

The greatest challenge for the successful commercialization of MEMS (micro-electro-mechanical system) technology is proving its reliability. Of concern in particular are the reliability and long-term stability of wafer level vacuum packaged MEMS gyroscope sensors subjected to cyclic mechanical stresses at high frequencies. In this study, we carried out several reliability tests and investigated the failure mechanisms of the anodically bonded vacuum gyroscope sensors designed for commercial electronic products. Particularly we studied mechanical reliability issues such as fatigue, shock, and vibration. It was found that successful vacuum packaging could be achieved through the optimization of the bonding process by reducing leakage and the deposition of titanium coating for reducing out-gassing inside the cavity. The effects of the pre-baking process are also described in this study. The current design of the gyroscope structure is found to be safe from fatigue failure for the 1000 h of operation test. The MEMS gyroscope sensor survives the drop and vibration qualification tests for electronic products without any damage, indicating the robustness of the sensor. The reliability test results presented in this study demonstrate that the MEMS gyroscope sensor is very close to commercialization.