ECE162-Lecture-20-Long-Channel-MOS-Transistors

ECE162-Lecture-20-Long-Channel-MOS-Transistors - ECE 162...

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ECE 162 FUNDAMENTALS OF MICROELECTRONIC DEVICES Lecture 20 BASIC THEORY OF LONG-CHANNEL METAL-GATE MOS TRANSISTORS Professor Hisham Z. Massoud Department of Electrical and Computer Engineering Fitzpatrick Building, Room 3521 Duke University, Durham, NC 27708–0291 [email protected] https://courses.duke.edu/webapps/portal/frameset.jsp ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.1
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LECTURE 20 – TOPICS 1. Introduction 2. Integrated-Circuit MOSFET Structures 3. Types of MOSFETs 4. Static Drain-Current Characteristics 4.1. Definitions 4.2. Assumptions and Approximations 4.3. Mobility Degradation due to the Oxide Field 4.4. The Distributed Analysis 4.5. SPICE Level-2 MOSFET Model ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.2
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1. INTRODUCTION What we end up doing is really selling real estate. We’ve sold an area of the silicon wafer for about a billion dollar an acre. Gordon Moore E. O. Wilson, the famous Harvard biologist who is an expert on ants, estimates that there are about 10 16 ants on earth. This year, we’ve made one transistor for every ant. Gordon Moore ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.3
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1. INTRODUCTION Number of transistors made in one year = 10 9 transistors wafer × 100 , 000 wafers day × 250 days year = 2 . 5 × 10 16 transistors Area of California = 200 × 400 × (5 , 280) 2 × (12) 2 = 10 14 sq.in. Number of rain drops per sq.in. = 10 in. of rain / (0 . 01 cu.in./drop) = 10 3 drops/sq.in. Total number of rain drops on California per year = 10 3 × 10 14 = 10 17 drops/year . Total number of papers published on silicon are 50,505 (1970–79), 84,202 (1980–89), and 135,562 (1990–99). ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.4
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2. INTEGRATED-CIRCUIT MOSFET STRUCTURES ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.5
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3. TYPES OF MOSFETS N-Channel vs P-Channel MOSFETs : N-Channel MOSFETs are fabricated on p -type substrates. P-Channel MOSFETs are fabricated on n -type substrates. Enhancement-Mode vs Depletion-Mode MOSFETs : Enhancement-mode MOSFETs are off with zero gate bias. Their minority-carrier concentration in the channel must be enhanced or increased to start current conduction. Depletion-mode MOSFETs are conducting with zero gate bias. Their minority-carrier concentration in the channel must be depleted or decreased to stop current conduction. ECE 162 Chapter 14 – Basic Theory of Long-Channel Metal-Gate MOS Transistors Lecture 20.6
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3. TYPES OF MOSFETS The determination of whether a MOSFET is an enhancement- or depletion- mode MOSFET depends on the values of the flat-band voltage V FB and the threshold voltage V T : If an inversion layer exists between the source and drain regions at V GB = 0, the MOSFET is then a depletion-mode MOSFET, because the minority carriers that already exist at the gate-oxide/substrate interface must be depleted to bias the channel at the onset of strong inversion.
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