Overview of Nanoelectronic Devices <s> A. Structure and Operation of a MOSFET <s> Although the title of our article addresses engineering limits, we do not mean to convey a grim outlook. Over the past 20 years, the technology of computer systems has advanced dramatically in terms of performance, cost and reliability. There is every reason to expect this advance to continue, at a rate almost as shocking as we have experienced to date. However, the advance already achieved has pushed the mechanisms of switching, storage and communication close enough to fundamental physical limits to bring into awareness for the first time limitations in the engineering of high‐performance systems. <s> BIB001 </s> Overview of Nanoelectronic Devices <s> A. Structure and Operation of a MOSFET <s> (NOTE: Each chapter begins with an Introduction and concludes with a Summary, To Probe Further, and Exercises and Design Problems.) I. THE FABRICS. 1. Introduction. A Historical Perspective. Issues in Digital Integrated Circuit Design. Quality Metrics of a Digital Design. 2. The Manufacturing Process. The CMOS Manufacturing Process. Design Rules-The Contract between Designer and Process Engineer. Packaging Integrated Circuits. Perspective-Trends in Process Technology. 3. The Devices. The Diode. The MOS(FET) Transistor. A Word on Process Variations. Perspective: Technology Scaling. 4. The Wire. A First Glance. Interconnect Parameters-Capitance, Resistance, and Inductance. Electrical Wire Models. SPICE Wire Models. Perspective: A Look into the Future. II. A CIRCUIT PERSPECTIVE. 5. The CMOS Inverter. The Static CMOS Inverter-An Intuitive Perspective. Evaluating the Robustness of the CMOS Inverter: The Static Behavior. Performance of CMOS Inverter: The Dynamic Behavior. Power, Energy, and Energy-Delay. Perspective: Technology Scaling and Its Impact on the Inverter Metrics. 6. Designing Combinational Logic Gates in CMOS. Static CMOS Design. Dynamic CMOS Design. How to Choose a Logic Style? Perspective: Gate Design in the Ultra Deep-Submicron Era. 7. Designing Sequential Logic Circuits. Timing Metrics for Sequential Circuits. Classification of Memory Elements. Static Latches and Registers. Dynamic Latches and Registers. Pulse Registers. Sense-Amplifier Based Registers. Pipelining: An Approach to Optimize Sequential Circuits. Non-Bistable Sequential Circuits. Perspective: Choosing a Clocking Strategy. III. A SYSTEM PERSPECTIVE. 8. Implementation Strategies for Digital ICS. From Custom to Semicustom and Structured-Array Design Approaches. Custom Circuit Design. Cell-Based Design Methodology. Array-Based Implementation Approaches. Perspective-The Implementation Platform of the Future. 9. Coping with Interconnect. Capacitive Parasitics. Resistive Parasitics. Inductive Parasitics. Advanced Interconnect Techniques. Perspective: Networks-on-a-Chip. 10. Timing Issues in Digital Circuits. Timing Classification of Digital Systems. Synchronous Design-An In-Depth Perspective. Self-Timed Circuit Design. Synchronizers and Arbiters. Clock Synthesis and Synchronization Using a Phased-Locked Loop. Future Directions and Perspectives. 11. Designing Arithmetic Building Blocks. Datapaths in Digital Processor Architectures. The Adder. The Multiplier. The Shifter. Other Arithmetic Operators. Power and Spped Trade-Offs in Datapath Structures. Perspective: Design as a Trade-off. 12. Designing Memory and Array Structures. The Memory Core. Memory Peripheral Circuitry. Memory Reliability and Yield. Power Dissipation in Memories. Case Studies in Memory Design. Perspective: Semiconductor Memory Trends and Evolutions. Problem Solutions. Index. <s> BIB002 </s> Overview of Nanoelectronic Devices <s> A. Structure and Operation of a MOSFET <s> The era of low power microelectronics began with the invention of the transistor in the late 1940's and came of age with the invention of the integrated circuit in the late 1950's. Historically, the most demanding applications of low power microelectronics have been battery operated products such as wrist watches, hearing aids, implantable cardiac pacemakers, pocket calculators, pagers, cellular telephones and prospectively the hand-held multi-media terminal However, in the early 1990's low power microelectronics rapidly evolved from a substantial tributary to the mainstream of microelectronics. The principal reasons for this transformation were the increasing packing density of transistors and increasing clock frequencies of CMOS microchips pushing heat removal and power distribution to the forefront of the problems confronting the advance of microelectronics. The distinctive thesis of this discussion is that future opportunities for low power gigascale integration (GSI) will be governed by a hierarchy of theoretical and practical limits whose levels can be codified as: (1) fundamental, (2) material, (3) device, (4) circuit, and (5) system. > <s> BIB003
The metal-oxide semiconductor FET (MOSFET) has been by far the most common type of transistor in modern microelectronic digital circuits, since Shockley's explanation of the device in 1952  ,  . Properly designed MOSFET circuits use very little power and are economical to fabricate. As shown in Fig. 1 , the field effect transistor has three terminals which are called the source, the drain, and the gate. Although the novel designs that are discussed below for nanometer-scale electronic switching devices operate according to principles quite different from a MOSFET, all retain the same essential features: a source, drain, and (usually) a gate in the same conceptual roles as in a MOSFET. The channel through which current may flow from source and drain is altered more drastically in making the transition to nanoelectronic devices. Thus, to introduce the device components in a relatively familiar context and to establish a basis for comparison with conventional technology, we briefly explain the operation of a MOSFET. (c) However, when voltage is applied to the gate electrode, the electrons (negative circles) segregate from the holes (positive circles) to form a "channel" which permits current (large white hatched arrows) to flow between the source and the drain. The name "metal-oxide-semiconductor field effect transistor" stems from its constituent materials. MOSFET's are built upon a crystalline substrate of the doped semiconductor silicon. Pure silicon is a very poor conductor, so dopant impurities, such as boron or arsenic, are introduced into the silicon to create an excess of mobile positive or negative charges. Negatively doped (N-doped) silicon contains free electrons that are able to move through the bulk semiconductor. Positively doped (P-doped) silicon contains electron vacancies, commonly known as "holes," which act as positive charges that move freely through the bulk material. A metal electrode separated from the semiconductor below by an insulating oxide barrier serves as the gate of the MOSFET, whose voltage and associated electric field controls the flow of current from the source to the drain BIB002 . This is why the device is called a "fieldeffect" transistor. When the voltage on the gate is low, the region between source and drain contains few mobile negative charges, and very little current can flow. This is shown in Fig. 1(b) . However, as illustrated in Fig. 1(c) , increasing this voltage sufficiently attracts electrons to the region under the gate, opening the channel and allowing masses of electrons to flow from the source to the drain. This corresponds to a dramatic rise in current. This distinct change in conductivity makes the MOSFET a two-state device. Since small changes of gate voltage result in large changes in conductivity, the MOSFET also can be used as an amplifier. Nanoelectronic devices for use in computers must function in these same two roles of two-state device and amplifier. In the past, the most common way to make smaller electronic circuits has been simply to shrink the dimensions of all of the circuit components by a constant factor, a process called "scaling." The MOSFET has remained popular because its operation changes very little and it maintains very favorable cost-to-performance ratios as it is scaled down to much smaller sizes. This scaling has proceeded at an exponential rate, doubling the number of transistors on a chip approximately every 18 months since the invention of the integrated circuit by Kilby in 1958. This has produced today's commercial, massproduced integrated circuits, such as Intel's Pentium chip, which contains over 3.2 million transistors with a minimum feature size of approximately 350 nm  . However, as MOSFET's reach minimum feature sizes of 100 nm and less, this rapid, cost-effective scaling of dense circuitry may not persist BIB001 , BIB003 .