A CMOS-MEMS Accelerometer with U-Channel Suspended Gate SOI FET

There have always been demands for the development of microscale sensors with integrated miniature electronics circuitry. Requirement of external amplification for the conventional MEMS accelerometer poses limitation on scaling, design, fabrication and on-chip Integrated Circuit (IC) compatibility. These limitations could be surpassed by the implementation of integrated CMOS-MEMS architectures for sensors and actuators. Here a novel U-channel suspended gate silicon on insulator field effect transistor (USG-SOIFET) is proposed to circumvent the pseudo short channel effects (P-SCE) present in the suspended gate field effect transistor (SGFET). In the proposed USG-SOIFET, the source and drain are separated by an air-gap and thereby ensuring effective screening of drain electric field penetration into source region. The gate length (L) of USG-SOIFET is 4 times lower than the conventional planar channel SGFET for the same performance of the device. Since the same performance is achieved with a smaller length, this results in a smaller device. Finite Element Modeling (FEM) of USG-SOIFET z-axis accelerometer using CoventerMP1.3 and TCAD process, device modeling and simulation of the USG-SOIFET using Synopsys Sentaurus are presented here. The sensitivity of the accelerometer is 4.185 μ A/g with a non-linearity of 4.96% for ± 5 g detection range. The bandwidth of the accelerometer is 100 Hz and the cross-axis sensitivity is found to be 3.52%. A fabrication process integration scheme for realizing USG-SOIFET has also been discussed along with process simulation to demonstrate the feasibility of realizing this new device architecture. This device platform is a potential candidate for monolithic integration with CMOS.