Impact of uniaxial strain on the capacitance-voltage characteristics of high-k double gate mosfet

Abstract

Suppression of short-channel effects (SCE) will be key challenges for transistor scaling. High-k Double-Gate MOSFET may eventually be needed to meet performance requirements in the sub-20nm gate length regime because SCE can be effectively suppressed without the need for high channel doping concentrations, resulting in enhanced carrier mobilities. Strained-Si has also been considered as a key technology for enhancing carrier mobilities via modification of the electronic band structure of the channel material and effective masses of the electron. In this work, to accurately simulate the DG MOSFET self-consistent fully-coupled1D Schrodinger and Poisson’s equation model has been used. Quantum mechanical effects have been considered by incorporating wave function penetration effect and open boundary conditions at the Si/HfO2 interfaces. It has been found that, the uniaxial strain increases the gate capacitance as it reduces eigen energy levels of longitudinal valleys of Si, thereby increasing the total charge. Moreover, the uniaxial strain reduces the threshold voltage, shifts the inversion channel towards the Si/HfO2 interfaces and reduces the gate leakage current.