High dynamic range Z-axis hybrid spring MEMS capacitive accelerometer

We report on a high-sensitivity, Z-axis capacitive accelerometer with high dynamic range. The high sensitivity is achieved by implementing a varying capacitive gap method, and by maintaining a narrow air gap of 2µm between the proof-mass and the stator plates. As Z-axis vertical accelerometers are very prone to stiction to the stator plates, we add a complementary set of serpentine reliability springs in order to control the displacement during high g (g=3D9.8m/s
²
) acceleration. It is found that using such reliability springs, there is a considerable improvement in the dynamic range, pull-in voltage, mode spacing and impact durability. The device is fabricated using an Integrated Inertial MEMS 9 DOF platform from GLOBALFOUNDRIES. Results indicate a static capacitance of 8.02pF, a pull-in voltage of 9 Volts, a sensitivity of 12 fF/g, and dynamic range of 450g.