Pure oxide structure for temperature stabilization and performance enhancement of CMOS-MEMS accelerometer

In this study, the stacking of pure oxide layers as the mechanical structures for CMOS-MEMS accelerometer has been developed and demonstrated for the first time. Thus, the distribution of metal-oxide composites in CMOS-MEMS accelerometer is changed from area to line. Such design has the following advantages: (1) the initial deformation of suspended MEMS structures due to the residual stresses of metal-oxide films is reduced, (2) the thermal deformation of suspended MEMS structures due to the thermal expansion coefficient (CTE) mismatch of metal-oxide films is also suppressed, and (3) the parasitic capacitance of sensing electrodes routing underneath the proof-mass can be further reduced. Thus, the accelerometer has higher sensitivity with less thermal drift. Compare with the existing metal-oxide composites accelerometer, the pure oxide accelerometer increases sensitivity of 7-fold, and decreases the structure-deformation (measured by radius-of-curvature (ROC) of proof-mass) of 2.1-fold (by residual stresses) and 2.4-fold (by temperature change). Moreover, the noise floor reduced 4.7-fold.