Translated Abstract
The channel of surrounding gate (SG) MOSFET is completely surrounded by the gate which results in better gate control capability and short-channel effects immunity. Besides, SG MOSFET has zero corner effect and a higher packing density, which makes it one of the attractive candidates for sub-10-nm technology nodes. It is therefore extremely necessary to develop compact models for SG MOSFETs in order to use them in nanoscale integrated circuit design and simulation. In this thesis, the two-dimensional surface potential model, short channel effects, quantum effects, and the transport models applicable in ballistic regim of the SG MOSFET have been developed.First, a two-dimensional surface potential model has been developed by solving Poisson‘s equation in cylindrical coordinates based on including both depletion charge and free charge. This model is applicable from the sub-threshold region to the strong-inversion region in different channel doping conditions. The explicit expression of the surface potential has been obtained by solving the implicit surface potential equation using mathematical method, which can greatly improve the computational efficiency of the model. The analytical models of the threshold voltage and subthreshold slope have been derived based on the surface potential model, and short channel effects of the device are also analyzed.Second, a new analytical model is developed for quantum-confinement effects of short channel SG MOSFETs. The eigenenergies and wavefunctions are obtained by solving Schrödinger’s equation with an accurate potential energy distribution. The potential energy distribution is based on the surface potential model proposed in this thesis paper. The eigenenergies obtained from the model are compared with other two quantum-confinement models, which use flat-well approximation and parabola-well approximation as the potential energy distributions, respectively. The results show that this model has a wider scope of application and is applicable from the subthreshold region to the strong-inversion region for both short channel and long channel devices. Based on this quantum-confinement model, the surface potential model is amended by a quantum correction based on the principle of the equivalent band gap, the electron density with quantum confinement effects are derived, threshold voltage is defined based on average electron density, and quantum effects on the threshold voltage are also analyzed.Third, the ballistic transport model of SG MOSFET has been proposed. The drain current expression has been derived based on the flux theory and the quantum-confinement model proposed in this thesis. And taking into account the effects of carrier scattering, the transport properties of the device are analyzed by introducing different reflection coefficients in both the ideal ballistic transport condition and the quasi-ballistic transport condition. Finally, the derived analytical models are verified by numerical simulation software, and it is found that the results of analytical models are in good agreement with numerical simulation results.
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