The Impacts Of Small-scale Effects On MOSFET

The feature dimension of MOSFET is significantly scaled down because of the continuous increasing of IC integration density and gradually approaches to its physical limits. This thesis concentrates on studying the impacts of small-scale effects on the gate leakage current,the electron transport and threshold voltages.For the gate leakage current in small-scale MOSFET : the influences of the oxygen vacancy on the gate leakage current have been theoretically investigated because the oxygen vacancy is one of the most important defects which influences the reliability of the gate-oxide layer. The mechanism and situation of the gate leakage current in small-scale MOS device were analyzed. Thus the influences of oxygen vacancy with its position distribution being random on the gate leakage current were calculated. The simulations show that the influence of the single oxygen vacancy on the gate leakage current decreases as the gate oxide thickness increasing. When the oxide thickness increase to a fixed value at a special oxide field, the gate leakage current increasing which caused by a single oxygen vacancy can be neglected.For the influence of the small-scale effect on the carrier transport in the channel of MOSFET: The influence of the nonparabolic parameter of the silicon band structure to the carrier transport in the channel of MOSFET has been calculated via full band Monte Carlo technique .The results show that nonparabolic parameter of the silicon band structure has a large effect on the carrier transport for the small-scale device whereas it can be neglected for the conventional large-scale devices. It implies that, the influence of the nonparabolic parameter of the silicon band structure to the carrier transport must be considered for current MOSFET.For the quantum mechanism effects of the small-scale MOSFET: An analytical 2D model taking into account the quantum mechanism (QM) effects for the threshold voltages characteristics of short-channel MOS transistors was proposed on the basis of the solution to the developed quantum correction Poisson equation. This model can clearly illustrate the increasing of the threshold voltage caused by QM effects and the short-channel effects becomes more obvious after QM effects were considered. The attractive feature of this model is that no addition fitting parameter is used.