Strain induced variability study in Gate-All-Around vertically-stacked horizontal nanosheet transistors

Using physics-based predictive technology CAD simulations, we show the improvements possible in device performance via strain engineering in vertically-stacked horizontal gate-all-around nanosheet Field-Effect transistors (NSFETs), which may outperform conventional FinFETs beyond 7 nm technology node. Effects of mechanical strain on NSFET variability is reported for the first time. We present a novel simulation approach for the analyses of random dopant fluctuation (RDF) and metal grain granularity (MGG) dependent variability in nanosheet transistors. The study encompasses topography simulation, which realistically reproduces a reported experimental nanosheet transistor. Device simulations are based on sub-band Boltzmann transport with 2D Schrodinger equation in the nanosheet cross-section and 1D Boltzmann transport along the nanosheet channel. The effects of mechanical stress and geometry dependence of the electrical characteristics are also reported. Critical design issues are outlined.