| In recent years, the modeling and simulation technologies of the small geometry effects in MOS transistors have received extensive attention. The most important small geometric effects include the short channel effect, narrow channel effect and inverse-narrow-width-effect. The 1-D and 2-D models reported in arts, however, lack of the capability to characterize the coupling effects among them, and thus a new 3-D modeling technique is proposed in this thesis.Based on solving the 3-D Poisson's equation, a 3-D analytical model to calculate the surface potential and electric field distributions of the MOS transistors have been proposed, which offer the capability to characterize the 3-D effects of the deep sub-micron and nano MOS transistors. Then, the impacts of the device structure parameters and the bias voltage on the surface potential and surface electric field are studied in detail by the model and Silvaco---a semiconductor device . A fair agreement between the numerical and analytical results proves the accuracy of the proposed model. Based on the above surface potential model, a new unified analytical model for the threshold voltage characterizes of MOS transistors have been proposed. Then, the model is used to investigate the short channel effect, narrow channel effect, the inverse-narrow-width-effect, as well as the coupling effects among them. The critical condition to identify the narrow channel effect and the inverse-narrow-width-effect is discussed. The advanced results show that the developed model can also be applied in the large size device. Furthermore, the impacts of the drain voltage is introduced in the model to include the drain induction barrier lower (DIBL). Silvaco is employed to perform the 3-D numerical simulation and verification of the developed model.The accuracy and availability of the model is verified by a fair agreement between the simulated and modeled results. |
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