Reproducing subthreshold characteristics of metal-oxide-semiconductor field effect transistors under shallow trench isolation mechanical stress using a stress-dependent diffusion model

Abstract

N-channel metal-oxide-semiconductor field effect transistors (MOSFETs) with a lightly doped well exhibit subthreshold current versus voltage (I-V) characteristics that are sensitive to shallow trench isolation (STI) mechanical stress. Such striking dependencies offer the opportunity to validate a proposed two-dimensional (2D) process model that relates the impurity diffusion to the mechanical stress throughout the substrate. With the assistance of sophisticated process/device simulations, the model appears to satisfactorily reproduce subthreshold I-V characteristics for different active area lengths and different substrate biases. The stress-dependent point defect equilibrium concentration and diffusion model are also implemented to evaluate the stress effect on transient enhanced diffusion.