Quantum Mechanical Simulation of Ultra Thin SOIMOSFETs

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We proposed a fully inverted SOI(Silicon-On-Jnsulator)MOSFETs which have as thin silicon top layer as inversion layer of k-3 nm. Since the thickness of the top silicon layers for this devices is 1〜3 nm, electrons in the layer are in quantum mechanical 2-D states. In the quantum mechanical modeling electron density has maximum in the midst of the silicon layer and thus the transconductance is expected to be lower than that predicted from classical modeling. The electron density distribution in the silicon layer is determined from quantum mechanical self-consistent potential distribution and the electrons produces transport phenomena with dissipative nature due to scattering under the drain voltage biasing. In order to know electrical characteristics such as threshold voltage, subthreshold characteristics and drain current under strong inversion and saturation conditions, quantum mechanical modeling is mandatory.In 2002, we improved simulation accuracy by including a field dependent mobility into our simulator which is based on lateral integration of 1D Schroedinger Poisson self-consistent solutions. In 2003, we analyzed threshold voltages of fully inverted SOIMOSFETs with thin silicon layer whose thickness is in a range of 2.5〜500 nm using our simulator. It is shown that the quantum mechanical threshold voltage shift can be explained by the ground state energy of 2D electrons shfted from the bottom of conduction band and the effective gate, oxide thickness shift produced by the quantum mechanical electron distribution.