Accelerometer using MOSFET with movable gate electrode: Electroplating thick nickel proof mass on flexible Parylene beam for enhancing sensitivity

摘要

This paper proposes an accelerometer based on metal-oxide-semiconductor field effect transistor (MOSFET), the gate electrode of which is movable because it is suspended by a flexible Parylene beam. When acceleration is applied, the gate is moved due to inertia force, making the change in drain current. It is notable that any external amplifying circuitry is not required, since the device itself acts as an electrical transistor besides a mechanical sensing structure. The fabrication starts from a conventional MOSFET, which is preferable in terms of CMOS compatibility and fabrication cost. For increasing the sensitivity, in the present paper, a thick nickel (Ni) proof mass was successfully electroplated on a flexible Parylene beam. It was proven that the proposed MOSFET-type accelerometer surely detects gravitational acceleration.