A Closed-Loop In-Plane Movable Suspended Gate FET (CLIP-SGFET) Sensor With a Dynamically Reconfigurable Charge Pump

This article proposes a single-axis, highperformance Complementary Metal Oxide Semiconductor- Microelectromechanical System (CMOS-MEMS) closed-loop accelerometer, implemented using in-plane movable suspended gate-field-effect transistor (IP-SGFET). The IPSGFET's gate is embedded within a movable proof mass supported by flexible folded beams. The external acceleration displaces the proofmass, which changes the drain current of IP-SGFET. The change in current is read out with the help of a simple differential amplifier which is constructed with the IP-SGFET. The differential amplifier's output voltage is used througha closed-loopintegral controland a high-voltage dynamically reconfigurable charge pump, which generates a high-voltage differential drive of up to 10.5 ± 5.12 V, to drive an actuator that brings the gate back to its resting position. The actuator used is a comb-drive type electromechanical actuator. In this work, two tools, viz., MEMS+ and Technology Computer Aided Design (TCAD) device simulation tools are used in a sequential manner to handle the electrostatics coupled with the micro-mechanical domain present in the suspended gate field effect transistors (SGFET). The results obtained are then used as look-up-tables for the design and simulation of the entire system, including the control circuits, in SPECTRE. Appropriate design of the MEMS suspended structure, the field effect transistor (FET) device, and interface circuit results in a open-loop sensitivity of 927 mV/g with a near-zero cross-axis sensitivity. Using the actuator and the reconfigurable charge pump, closed-loop operation is realized with a dynamic range of ±4 g at a supply voltage of 3.3 V.