Study On The Simulation Of Si_1-x Ge_x MOSFETs

Simulation techniques of the SiGe MOSFETs are related with this dissertation. Works on the paper are composed of two parts :one is to construct the model for the devices. The other is to develop a software named "SiGe-Sim", which should have a friendly interface and can display the result of the simulation with pictures. The detail contents are as follows.To construct the threshold voltage model for the surface-channel strained silicon N/P MOSFETs and quantum mechanical SiGe-channel PMOSFETs , physics-based short-channel threshold voltage models are given on this paper. Suppose the potential along channel changes with the square of the distance, two dimension possion equation can be simplified into one dimension. By this means, using Voltage-Doping transformation, conventional long-channel threshold voltage formula can be used still. In these models, Ge mole effects to the energy band, electron affinity , effective density of state and substrate bias effect are considered. Medici simulation verified the exactness of the models.To construct the universal mobility model of the surface-channel strained silicon N/P MOSFETs, A physic-based carrier mobility model of inversion layer in strained N/P MOSFETs is given on this paper. Using polynomial Parameter fitting, low-field enhance factor model of the strained MOSFETs is constructed ,which makes it possible to directly use the model in pspice ; Then, according to the essential of the device, a universal carrier mobility model is supplied. Bulk-phonon scattering , surface-phonon scattering , coulomb scattering , surface scattering and carrier-carrier scattering are all taken into account in this model. Particularly , the inversion-layer quantum effect is considered, too.To construct the universal mobility model of the quantum mechanical SiGe-channel PMOSFETs, also according to the physics of the device, Bulk-phonon scattering , surface-phonon scattering, coulomb scattering, alloy scattering and carrier-carrier scattering are all considered. Polynomial Parameter fitting also is used to establish low-field factor model. Then conventional current model is adopted. Particularly, quantum-channel PMOSFETs' patristic surface-channel current is included.Finally, software named SiGe-Sim is developed, which is composed of following Module: mobility, threshold voltage and DC Sweep.