Vlsi Circuit Simulation And Optimization

Circuit simulation has become an essential tool in circuit design and without it's aid, analogue and mixed-signal IC design would be impossible. However the applicability and limitations of circuit simulators have not been generally well understood and this book now provides a clear and easy to follow explanation of their function. The material covered includes the algorithms used in circuit simulation and the numerical techniques needed for linear and non-linear DC analysis, transient analysis and AC analysis. The book goes on to explain the numeric methods to include sensitivity and tolerance analysis and optimisation of component values for circuit design. The final part deals with logic simulation and mixed-signal simulation algorithms. There are comprehensive and detailed descriptions of the numerical methods and the material is presented in a way that provides for the needs of both experienced engineers who wish to extend their knowledge of current tools and techniques, and of advanced students and researchers who wish to develop new simulators.

Metal Oxide Semiconductor (MOS) transistors are the basic building block ofMOS integrated circuits (I C). Very Large Scale Integrated (VLSI) circuits using MOS technology have emerged as the dominant technology in the semiconductor industry. Over the past decade, the complexity of MOS IC's has increased at an astonishing rate. This is realized mainly through the reduction of MOS transistor dimensions in addition to the improvements in processing. Today VLSI circuits with over 3 million transistors on a chip, with effective or electrical channel lengths of 0. 5 microns, are in volume production. Designing such complex chips is virtually impossible without simulation tools which help to predict circuit behavior before actual circuits are fabricated. However, the utility of simulators as a tool for the design and analysis of circuits depends on the adequacy of the device models used in the simulator. This problem is further aggravated by the technology trend towards smaller and smaller device dimensions which increases the complexity of the models. There is extensive literature available on modeling these short channel devices. However, there is a lot of confusion too. Often it is not clear what model to use and which model parameter values are important and how to determine them. After working over 15 years in the field of semiconductor device modeling, I have felt the need for a book which can fill the gap between the theory and the practice of MOS transistor modeling. This book is an attempt in that direction.

This book describes new, fuzzy logic-based mathematical apparatus, which enable readers to work with continuous variables, while implementing whole circuit simulations with speed, similar to gate-level simulators and accuracy, similar to circuit-level simulators. The author demonstrates newly developed principles of digital integrated circuit simulation and optimization that take into consideration various external and internal destabilizing factors, influencing the operation of digital ICs. The discussion includes factors including radiation, ambient temperature, electromagnetic fields, and climatic conditions, as well as non-ideality of interconnects and power rails.

Circuit simulation has been a topic of great interest to the integrated circuit design community for many years. It is a difficult, and interesting, problem be cause circuit simulators are very heavily used, consuming thousands of computer hours every year, and therefore the algorithms must be very efficient. In addi tion, circuit simulators are heavily relied upon, with millions of dollars being gambled on their accuracy, and therefore the algorithms must be very robust. At the University of California, Berkeley, a great deal of research has been devoted to the study of both the numerical properties and the efficient imple mentation of circuit simulation algorithms. Research efforts have led to several programs, starting with CANCER in the 1960's and the enormously successful SPICE program in the early 1970's, to MOTIS-C, SPLICE, and RELAX in the late 1970's, and finally to SPLICE2 and RELAX2 in the 1980's. Our primary goal in writing this book was to present some of the results of our current research on the application of relaxation algorithms to circuit simu lation. As we began, we realized that a large body of mathematical and exper imental results had been amassed over the past twenty years by graduate students, professors, and industry researchers working on circuit simulation. It became a secondary goal to try to find an organization of this mass of material that was mathematically rigorous, had practical relevance, and still retained the natural intuitive simplicity of the circuit simulation subject.

A reprint of the classic text, this book popularized compact modeling of electronic and semiconductor devices and components for college and graduate-school classrooms, and manufacturing engineering, over a decade ago. The first comprehensive book on MOS transistor compact modeling, it was the most cited among similar books in the area and remains the most frequently cited today. The coverage is device-physics based and continues to be relevant to the latest advances in MOS transistor modeling. This is also the only book that discusses in detail how to measure device model parameters required for circuit simulations. The book deals with the MOS Field Effect Transistor (MOSFET) models that are derived from basic semiconductor theory. Various models are developed, ranging from simple to more sophisticated models that take into account new physical effects observed in submicron transistors used in today's (1993) MOS VLSI technology. The assumptions used to arrive at the models are emphasized so that the accuracy of the models in describing the device characteristics are clearly understood. Due to the importance of designing reliable circuits, device reliability models are also covered. Understanding these models is essential when designing circuits for state-of-the-art MOS ICs.

As MOS devices are scaled to meet increasingly demanding circuit specifications, process variations have a greater effect on the reliability of circuit performance. For this reason, statistical techniques are required to design integrated circuits with maximum yield. Statistical Modeling for Computer-Aided Design of MOS VLSI Circuits describes a statistical circuit simulation and optimization environment for VLSI circuit designers. The first step toward accomplishing statistical circuit design and optimization is the development of an accurate CAD tool capable of performing statistical simulation. This tool must be based on a statistical model which comprehends the effect of device and circuit characteristics, such as device size, bias, and circuit layout, which are under the control of the circuit designer on the variability of circuit performance. The distinctive feature of the CAD tool described in this book is its ability to accurately model and simulate the effect in both intra- and inter-die process variability on analog/digital circuits, accounting for the effects of the aforementioned device and circuit characteristics. Statistical Modeling for Computer-Aided Design of MOS VLSI Circuits serves as an excellent reference for those working in the field, and may be used as the text for an advanced course on the subject.

This book proposes a new approach to circuit simulation that is still in its infancy. The reason for publishing this work as a monograph at this time is to quickly distribute these ideas to the research community for further study. The book is based on a doctoral dissertation undertaken at MIT between 1982 and 1985. In 1982 the author joined a research group that was applying bounding techniques to simple VLSI timing analysis models. The conviction that bounding analysis could also be successfully applied to sophisticated digital MOS circuit models led to the research presented here. Acknowledgments 'me author would like to acknowledge many helpful discussions and much support from his research group at MIT, including Lance Glasser, John Wyatt, Jr. , and Paul Penfield, Jr. Many others have also contributed to this work in some way, including Albert Ruchli, Mark Horowitz, Rich Zippel, Chtis Terman, Jacob White, Mark Matson, Bob Armstrong, Steve McCormick, Cyrus Bamji, John Wroclawski, Omar Wing, Gary Dare, Paul Bassett, and Rick LaMaire. The author would like to give special thanks to his wife, Deborra, for her support and many contributions to the presentation of this research. The author would also like to thank his parents for their encouragement, and IBM for its financial support of t,I-Jis project through a graduate fellowship. THE BOUNDING APPROACH TO VLSI CIRCUIT SIMULATION 1. INTRODUCTION The VLSI revolution of the 1970's has created a need for new circuit analysis techniques.

Responding to recent developments and a growing VLSI circuit manufacturing market, Technology Computer Aided Design: Simulation for VLSI MOSFET examines advanced MOSFET processes and devices through TCAD numerical simulations. The book provides a balanced summary of TCAD and MOSFET basic concepts, equations, physics, and new technologies related to TCAD and MOSFET. A firm grasp of these concepts allows for the design of better models, thus streamlining the design process, saving time and money. This book places emphasis on the importance of modeling and simulations of VLSI MOS transistors and TCAD software. Providing background concepts involved in the TCAD simulation of MOSFET devices, it presents concepts in a simplified manner, frequently using comparisons to everyday-life experiences. The book then explains concepts in depth, with required mathematics and program code. This book also details the classical semiconductor physics for understanding the principle of operations for VLSI MOS transistors, illustrates recent developments in the area of MOSFET and other electronic devices, and analyzes the evolution of the role of modeling and simulation of MOSFET. It also provides exposure to the two most commercially popular TCAD simulation tools Silvaco and Sentaurus. • Emphasizes the need for TCAD simulation to be included within VLSI design flow for nano-scale integrated circuits • Introduces the advantages of TCAD simulations for device and process technology characterization • Presents the fundamental physics and mathematics incorporated in the TCAD tools • Includes popular commercial TCAD simulation tools (Silvaco and Sentaurus) • Provides characterization of performances of VLSI MOSFETs through TCAD tools • Offers familiarization to compact modeling for VLSI circuit simulation R&D cost and time for electronic product development is drastically reduced by taking advantage of TCAD tools, making it indispensable for modern VLSI device technologies. They provide a means to characterize the MOS transistors and improve the VLSI circuit simulation procedure. The comprehensive information and systematic approach to design, characterization, fabrication, and computation of VLSI MOS transistor through TCAD tools presented in this book provides a thorough foundation for the development of models that simplify the design verification process and make it cost effective.