Effect of discrete impurities on electron transport in ultrashort MOSFET using 3D MC simulation

This paper discusses the influence of the channel impurity distribution on the transport and the drive current in short-gate MOSFETs. A careful description of electron-ion interaction suitable for the case of discrete impurities has been implemented in a three-dimensional particle Monte Carlo simulator. This transport model is applied to the investigation of 50-nm MOSFET operation. The results show that a small change in the number of doping impurities or in the position of a single discrete impurity in the inversion layer may significantly influence the drain current. This effect is not only related to threshold voltage fluctuations but also to variations in transport properties in the inversion layer, especially at high drain voltage. The results are analyzed in terms of local fluctuations of electron velocity and current density. In a set of fifteen simulated devices the drive current I_on, determined at V_GS=V_DS=0.6 V, is found to vary in a range of 23% according to the position of channel impurities.