Analytical study and compensation for temperature drifts of a bulk silicon MEMS capacitive accelerometer

An analytical study and a compensation structure for temperature drifts of bias and scale factor of a bulk silicon MEMS capacitive accelerometer are presented. The analytical model for the temperature drift of bias (TDB) and temperature drift of scale factor (TDSF) is established based on the analysis results of thermal deformation and stiffness temperature dependence. The model shows that TDB is only caused by thermal deformation, while TDSF consists of two parts caused by stiffness temperature dependence and thermal deformation, respectively. The two parts are positive and negative, respectively, but the second part has greater absolute value. First part of TDSF can be reduced by high doping. TDB and second part of TDSF can be both reduced by soft adhesive die attaching or increasing substrate thickness. In silicon structure, TDB can be reduced by middle-locating anchors for moving electrodes in sensitive direction or decreasing the stiffness asymmetry of springs, while second part of TDSF can be reduced by middle-locating anchors for fixed electrodes in sensitive direction. By middle-locating anchors both for moving electrodes and fixed electrodes, a temperature compensation structure is designed to reduce TDB and second part of TDSF. Consequently, TDSF is reduced by making the two parts of TDSF cancel each other. Experimental results show that TDB is suppressed from 1.85 mg/°C to 0.52 mg/°C, while TDSF from −162.7 ppm/°C to −50.8 ppm/°C.