Back-Gate Bias and Substrate Doping Influenced Substrate Effect in UTBB FD-SOI MOS Transistors: Analysis and Optimization Guidelines

In this paper, we present physical insights into the role of substrate on the anomalous frequency behavior of small-signal transconductance and output conductance in the ultrathin body and buried oxide fully depleted silicon-on-insulator MOS transistors. Using the simple dc analysis, we attribute this anomalous behavior to the negative feedback originating from both minority and majority carriers in the substrate at different frequency ranges. Through measurements and detailed TCAD simulations, we have shown that back-gate bias and substrate doping strongly modulate the frequency behavior of transconductance and output conductance. It is finally proposed that circuit/device designers can smartly use the back-gate bias and substrate doping to minimize the substrate effect and improve the frequency response of the device intrinsic gain.