A new approach for sensitivity improvement of MEMS capacitive accelerometer using electrostatic actuation

This paper presents a new approach for sensitivity improvement of MEMS Capacitive Accelerometer using electrostatic actuation. In comb type capacitive accelerometer structure a few set of actuation fingers are incorporated in addition to the regular sense and movable fingers for electrostatic actuation or self test purpose. The driving voltage applied between static actuation finger and movable finger generates an electrostatic force which is inversely proportional to the square of the effective gap between the fingers. In our proposed approach the device is actuated both mechanically and electrically in same direction. As the mechanical acceleration increases, the gap between the combs decreases and it causes the increase in electrostatic force that in turn improves the overall sensitivity of the device for measurement of primarily static acceleration. The increase in sensitivity is more prominent for higher applied voltage and higher mechanical acceleration. Basic theoretical background supported by simulation results are provided for this concept.