Substrate bias dependence of short-channel MOSFET threshold voltage-a novel approach

A simple theory to predict the threshold voltage variation of short-channel MOS transistors with substrate bias is proposed. While the basis of the model is vertical field perturbations due to the source-drain, its uniqueness depends on a definition of threshold voltage based on the amount of total free charge in the channel rather than inversion of the entire channel. The theory has been verified for transistors of three channel lengths, namely 2.70, 1.70, and 0.70 μm, fabricated with a p-well CMOS process. A comparison is made with an earlier model based on field perturbation. The validity of the arguments underlying the theory has been demonstrated by 2-D device simulations with MINIMOS