Learn the basic properties and designs of modern VLSI devices, as well as the factors affecting performance, with this thoroughly updated second edition. The first edition has been widely adopted as a standard textbook in microelectronics in many major US universities and worldwide. The internationally-renowned authors highlight the intricate interdependencies and subtle tradeoffs between various practically important device parameters, and also provide an in-depth discussion of device scaling and scaling limits of CMOS and bipolar devices. Equations and parameters provided are checked continuously against the reality of silicon data, making the book equally useful in practical transistor design and in the classroom. Every chapter has been updated to include the latest developments, such as MOSFET scale length theory, high-field transport model, and SiGe-base bipolar devices.

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Fundamentals of Modern VLSI Devices

We present a continuous analytic current-voltage (I-V) model for cylindrical undoped (lightly doped) surrounding gate (SGT) MOSFETs. It is based on the exact solution of the Poisson's equation, and the current continuity equation without the charge-sheet approximation, allowing the inversion charge distribution in the silicon film to be adequately described. It is valid for all the operation regions (linear, saturation, subthreshold) and traces the transition between them without fitting parameters, being ideal for the kernel of SGT MOSFETs compact models. We have demonstrated that the I-V characteristics obtained by this model agree with three-dimensional numerical simulations for all ranges of gate and drain voltages.

Continuous analytic I-V model for surrounding-gate MOSFETs

In this paper, we model the electrical properties of the junctionless (JL) nanowire field-effect transistor (FET), which has been recently proposed as a possible alternative to the junction-based FET. The analytical model worked out here assumes a cylindrical geometry and is meant to provide a physical understanding of the device behavior. Most notably, it aims to clarify the motivation for its nearly ideal subthreshold slope and its excellent on-state current while being a depletion device with lower electron mobility due to impurity scattering. At the same time, the model clarifies a constraint binding the allowable value of the doping density per unit length and its impact on the overall device performance. The device variability and the parasitic source/drain resistances are identified as the most important limitations of the JL nanowire field-effect transistor.

Theory of the Junctionless Nanowire FET

We present an analytical and continuous dc model for cylindrical undoped surrounding-gate (SGT) MOSFETs in which the channel current is written as an explicit function of the applied voltages. The model is based on a new unified charge control model developed for this device. The explicit model shows good agreement with the numerical exact solution obtained from the new charge control model, which was previously validated by comparison with three-dimensional numerical simulations.

Explicit continuous model for long-channel undoped surrounding gate MOSFETs

This paper presents an analytic potential model for long-channel symmetric and asymmetric double-gate (DG) MOSFETs. The model is derived rigorously from the exact solution to Poisson's and current continuity equation without the charge-sheet approximation. By preserving the proper physics, volume inversion in the subthreshold region is well accounted for in the model. The resulting analytic expressions of the drain-current, terminal charges, and capacitances for long-channel DG MOSFETs are continuous in all operation regions, i.e., linear, saturation, and subthreshold, making it suitable for compact modeling. As no fitting parameters are invoked throughout the derivation, the model is physical and predictive. All parameter formulas are validated by two-dimensional numerical simulations with excellent agreement. The model has been implemented in Simulation Program with Integrated Circuit Emphasis version 3 (SPICE3), and the feasibility is demonstrated by the transient analysis of sample CMOS circuits.

An analytic potential model for symmetric and asymmetric DG MOSFETs

This letter presents a continuous analytic current-voltage (I-V) model for double-gate (DG) MOSFETs. It is derived from closed-form solutions of Poisson's equation, and current continuity equation without the charge-sheet approximation. The entire I/sub ds/(V/sub g/,V/sub ds/) characteristics for all regions of MOSFET operation: linear, saturation, and subthreshold, are covered under one continuous function, making it ideally suited for compact modeling. By preserving the proper physics, this model readily depicts "volume inversion" in symmetric DG MOSFETs-a distinctively noncharge-sheet phenomenon that cannot be reproduced by standard charge-sheet based I-V models. It is shown that the I-V curves generated by the analytic model are in complete agreement with two-dimensional numerical simulation results for all ranges of gate and drain voltages.

A continuous, analytic drain-current model for DG MOSFETs

Explicit continuous models for both double-gate (DG) and surrounding-gate (SG) MOSFETs are presented. These models evolve from previous DG and SG MOSFETs models, which need to solve implicit equations for intermediate parameters by numerical iteration or the table lookup method. By developing approximate explicit solutions for the intermediate parameters, we can express the drain current, terminal charge, transconductance, and transcapacitance as explicit functions of applied voltages as well as the structural parameters. High accuracy and efficiency, combined with inherited favorable features from the previous models, make these new models suitable for circuit simulation programs.

Explicit Continuous Models for Double-Gate and Surrounding-Gate MOSFETs

This paper presents an analytic charge model for surrounding-gate MOSFETs. Without the charge sheet approximation, the model is based on closed-form solution of Poisson's equation, current continuity equation, and Ward-Dutton linear charge partition. It continuously covers all the operation regions, i.e., linear, saturation, and subthreshold, with unique analytic expressions. The physics-based nature makes this model free of fitting parameters and hence predictive. In addition, it is inherently not source-referenced to avoid asymmetries. It is shown that the current-voltage characteristics generated by this model agree with the numerical simulation results

Analytic Charge Model for Surrounding-Gate MOSFETs

This paper presents a systematic study of the body doping effect on symmetric double-gate (DG) MOSFETs. Two-dimensional simulation tools are used to investigate the doping effect on long-channel and short-channel devices. Both n-type and p-type doping are studied. For long-channel devices, the threshold voltage shift due to body doping is proportional to the total dopant when the device is fully depleted. Thus, it is straightforward to include the doping effect in compact models. When the device is partially depleted, in addition to the threshold voltage shift, the subthreshold slope can be degraded. For short-channel devices, improvement of the short-channel effects is observed when the body doping concentration is close to the level that makes the device partially depleted.

https://iopscience.iop.org/article/10.1088/0268-1242/23/1/015006/pdf

Huaxin Lu

Papers

A continuous, analytic drain-current model for DG MOSFETs

An analytic potential model for symmetric and asymmetric DG MOSFETs

Explicit Continuous Models for Double-Gate and Surrounding-Gate MOSFETs

Analytic Charge Model for Surrounding-Gate MOSFETs

Effect of body doping on double-gate MOSFET characteristics