Integrated Stress Sensors for Humidity Performance Drift Analysis and Compensation in Inertial Measurement Units

Microelectromechanical devices are known to be sensitive to ambient humidity. This is especially true for devices in moisture sensitive plastic packages such as consumer targeted inertial measurement units. Stress and deformation based effects are shown to be a main contributor to humidity related effects such as performance and offset drifts. This paper shows that stress sensing units embedded in the mechanically coupled electronic control circuitry can be utilized to detect and compensate stress based humidity performance drifts of plastic packaged inertial measurement units. Next to the utilized stress sensor cells themselves a compensation approach is presented, that corrects the humidity based scale factor drift of a MEMS angular rate sensor while a humidity load is applied. This is achieved by finding a symbolic compensation function, which predicts the moisture induced scale factor drift, based only on the stress values within the electronic control circuitry, utilizing genetic symbolic regression. It is demonstrated that, using stress sensors, the humidity induced scale factor drift of two different gyroscope core types can be reduced by a factor of 3, which holds true for parts coming from separate assembly lots. [2022-0013]