| In recent years, with the rapid development of technology, the degree of integration is more and more high. In order to meet the requirements of the development of integrated circuit, the feature size of Metal-Oxide- Semiconductor Field Effect Transistor (MOSFET) continues to decrease. The small size brings some bad results, such as seriously affecting the MOS device reliability. It also put forward higher requirements to the development of technology, such as ultra-shallow junction technology, strained channel technology and so on. At the same time, many new three-dimensional structure appeared, such as Double gate and Cylindrical Surrounding-gate(CSG)MOSFET and so on. For CSG, the entire channel is surrounded by a gate, the gate can control the channel very well, it can effectively suppress the short channel effects. With the improvement the short channel effects of CSG MOSFET’S, the transistor size can be further reduced. Those above advantages make CSG MOSFET becoming one of the most promising structure in extended nanometer CMOS circuit design。The paper embarks from the channel structure design of CSG MOSFET, mainly research the work mechanism and physical model of steeped doping channel (SC) CSG MOSFET and uniform doping channel CSG MOSFET, and then has a performance comparison between them. Then it also analysis the breakdown characteristic of MOS devices and the method to suppress hot carrier effect.Firstly, using 3d simulation software ATLAS to simulation the channel structure features of SC CSG MOSFET:different high doping concentration and the length of highly doped area. Then under different channel structure, the electric potential, electric field. Ⅰd-Ⅴds, Ⅰd-Ⅴgs and other characteristics of SC CSG MOSFET are analyzed in detail. The paper have analysis the short channel effect of SC DG MOSFET and SC CSG MOSFET, such as the threshold voltage roll-off and drain induced barrier lowering. The results show that SC CSG MOSFET have a better advantage of reducing the impact of short channel effect and hot-carrier effects compared with SC DG MOSFET.Secondly, a 3D body Potential model of SC CSG MOSFET is established under cylindrical coordinate system. In this paper, the model can describe the open field more accurately. because the run out of charge and free of charge are included at the same time. In the solving process, by using the separation variable method and Fourier inverse transformation method, the SC CSG MOSFET body potential model is obtained. Based on the 3D body Potential model, analytical model for threshold voltage of the SC CSG MOSFET are deduced.Finally, the accuracy of the model is compared and verified, with the comparison of CS CSG MOSFET modeling results and the ATLAS simulation results.The paper have an analysis the different channel structure of SCE CS CSG MOSFET on the electric potential and electric field and short channel effect. The results show that CS CSG MOSFET has a better short channel effect and hot-carrier effect and improved the breakdown characteristics also have improvement. The change of high doping density has big impact on SC CSG MOSFET, Drain induced Barrier Lowering first increases then decreases.The length of high doping have a relatively small impact on it, while have a great effect on channel mobility and carrier speed. At the end, the SC CSG MOSFET channel structure is optimized, so as to improve the reliability of the device. |
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