Design and implementation of high performance CMOS-MEMS capacitive sensors

Abstract

This study presents a novel design to improve the sensitivity and resolution of the capacitive-type CMOS-MEMS sensors. This design employs the dielectric films as the MEMS structures, and the metal films as the electrodes and sacrificial layers. There are three merits of this design, (1) the parasitic capacitance is significantly reduced by the dielectric structure, (2) very small in-plane and out-of-plane sensing gaps are realized to increase the sensitivity, and (3) plate-type instead of finger-type out-of-plane sensing electrodes is exploited to increase the sensing area. In application, 3-axis CMOS-MEMS capacitive accelerometers are demonstrated. Measurements show the sensitivities respectively reach 11.5mV/G (in X-,Y-axis) and 7.8mV/G (in Z-axis) which are near 20-fold larger than existing designs. Moreover, a much better sensing resolution of 10mG is also achieved.