High Sensitivity Mems Z-Axis Accelerometer with In-Plane Differential Readout

This paper reports the innovative design and a preliminary experimental characterization of a miniaturized z-axis accelerometer. For the first time in a MEMS accelerometer, a motion conversion mechanism is implemented to allow an electrostatic readout based on in-plane comb fingers, thus overcoming the main limitations of out-of-plane parallel plate detection, e.g. nonlinearities, trade-off between sensitivity and full-scale range, pull-in, etc. The first prototype fabricated by exploiting the features of the Thelma-Double fabrication process shows an experimental sensitivity of 12.9 fF/g which agrees well with numerical predictions computed by considering nominal geometric dimension of the sensor.