Research On Quantization Characteristics And Threshold Voitage Of Uniaxial Strained Si NMOS

With the development of MOS devices to deep sub-micron stage, uniaxialstrained Si has been widely used as the mainstream strained silicon technology. Itmainly introduce the stress in the traditional MOSFET channel. The performance ofuniaxial strained Si device is significantly enhanced, and the produce is easy.Therefore,the theoretical study of the uniaxial strain Si on conduction band E(k)-k relationship,characteristics of the inversion layer quantization and threshold voltage is particularlyimportant.As of the theoretical basis of the Quantization characteristics and thresholdvoltage, in this paper, the coupling of Δ1and Δ2’bands at the X point, and the influenceof that band-band coupling on the minimum of energy valley are firstly respectivelydiscussed under the action of shear strain. On that basis, the dispersion relation close tothe minimum is obtained. According to this dispersion relation, the effective massparallel and perpendicular to the stress direction are obtained.Secondly, the thesis had a research of the Quantization characteristics in siliconnMOSFET with the influence of uniaxial tensile stress, and the quantitative calculationis completed. We reached a conclusion that the tensile stress reduced Quantizationcharacteristics in strained silicon MOS devices by making a comparison withrelaxation condition in characteristics such as intrinsic carrier concentration、Eigenenergies、electron occupancies and inversion layer penetration.Finally, based on the energy band structure and Quantization characteristics, thethreshold voltage model is then proposed by solving the2-D Poisson’s equation andalso by taking short channel effects, quantum mechanical effects and other secondaryeffects into consideration. Our analytical results agree with experimental datatheoretical data in the literature.