CMOS-MEMS Nano Force Sensor with Sub-μm U-Channel Suspended Gate SOIFET

Abstract

This article presents a novel sub-μM U-channel suspended gate SOIFET (USG-SOIFET) based nano-force sensor. The pseudo short channel effect in suspended gate FET (SGFET) is discussed, and the channel length of USG-SOIFET is reduced to 0.95 μM with an air-gap of 200 nm. This helps in improving the sensitivity of USG-SOIFET and makes it a suitable candidate to detect forces in the nano-newton range. The gate is attached to the MEMS structure. A four L-shaped MEMS structure is designed with a mechanical sensitivity of 0.08 nm/ nN and a resonant frequency of 3.8 kHz. The air-gap values for different forces are obtained from the finite element method (FEM) simulation of MEMS structure and used as input to TCAD for USG-SOIFET simulations to get the final sensor response. The area of the sensor is only $(0.38 \times 0.38) \mathrm{mm}^{2}$ with a sensitivity of $0.425 \mu \mathrm{A} / \mathrm{nN}$ at an operating voltage of 3 V. The detection range of the proposed sensor is 1 nN to 1μN, and the response is highly linear with a non-linearity of about 0.4 %.