Nanoscale Strained-Si/SiGe and Double-Gate MOSFET Modeling

Karthik Chandrasekaran
(July 24, 2002 --)


Motivation and Objective

The metal oxide semiconductor field-effect transistor (MOSFET) is currently the device of choice for integrated circuits. Advanced silicon processing technology has allowed MOSFET to be scaled to sub micron dimensions, realizing incredible gains in performance. However, as dimensions continue to decrease, certain physical constraints are being reached that limit continued scaling and performance improvements. Hence it is important to look for new methods of improving performance, while taking advantage of the current silicon materials technology base. Strained silicon is fast emerging as the technology of choice. It offers significant performance enhancement over bulk silicon as well as compatibility with robust and mature silicon technology.

The strained silicon technology is slowly taking over conventional technology in the semiconductor industry. It is quite a challenge to predict strained silicon behavior because new physical effects such as reduced band gap, band offsets, higher mobility and higher leakage current have to be considered. Given the fact that wafer costs increase drastically, alternative ways of predicting new technologies and scaling effects on the future CMOS are very important. So developing analytical models for circuit simulation that are physical, predictive, intuitive and handy for quick estimate is an attractive approach.


Developing a model is an art involving constant trade off between accuracy and simplicity. Models based on correct physical assumptions are invaluable. For such models the physical parameters after extraction will be close to the values predicted by theory. Two features of compact model that have become progressively more important are (i) the use of device models based on a precise description of the physics of device operation, and (ii) the parameter extraction should also be physically based.

 Numerical simulation and experimental data would be used to model and characterize the devices. TCAD simulation results can be used to study the physical insight into novel strained silicon structures with sufficient tuning of the different material parameters and mobility models. The general approach is to incorporate physically derived equations for each individual effect with effective quantities that contain process dependent fitting parameters. All fitting parameters used would have physical meanings. The models would have as few fitting parameters as possible and they would be linked as closely as possible to the ones related to the device structure.

Original title: Computational Investigation of Novel Device Structures and Concepts
Abstract:  This project is directed towards the numerical and analytical exploration of new device concepts beyond traditional CMOS within the mainstream silicon technology.  Potential candidate building blocks of future technologies such as vertical MOS, double-gate MOS, heterostructures and nanodevices will be studied.  Theoretical analysis and modelling of these nanoscale devices will provide important guidance to performance optimisation and experimental realisation.  Analytical modelling and formulation of these intrinsic devices, combined with numerical simulation, will allow circuit/system performance to be evaluated efficiently at a higher level of abstraction.

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