EMT 251 Introduction to IC Design (Pengantar Rekabentuk Litar Terkamir) Semester II 2011/2012 Introduction to IC design and Transistor Fundamental
Some Keywords! Very-large-scale-integration (VLSI) is defined as a technology that allows the construction and interconnection of large numbers (millions) of transistors on a single integrated circuit. Integrated circuit (IC) is a collection of one or more gates fabricated on a single silicon chip. Wafer is a thin slice of semiconductor material on which semiconductor devices are made. Also called a slice or substrate. Chip is a small piece of semiconductor material upon which miniaturized electronic circuits can be built. Die is an individual circuit or subsystem that is one of several identical chips that are produced after dicing up a wafer. If you use these key-words often, people will think that you are an expert VLSI engineer!!!
History of IC Design Invention of the transistor (BJT) 1947 Shockley, Bardeen, Brattain Bell Labs Single-transistor integrated circuit 1958 Jack Kilby Texas Instruments Invention of CMOS logic gates 1963 Wanlass & Sah Fairchild Semiconductor First microprocessor (Intel 4004) 1970 2,300 MOS transistors, 740 khz clock frequency Very Large Scale Integration 1978 Chips with more than 20,000 devices
The origin of this terminology can be traced as the logical extension to the integration techniques namely the Small Scale Integration, SSI (the ICs which functioned as logic gates, flip-flops), the Medium Scale Integration, MSI (multiplexers, decoders)., the Large Scale Integration LSI (early microprocessors, small memories, PAL, GAL Te chnology Number Of Gates / Transistor Per Chip Example Ye ar SSI 1 to 20 74XX series, 4xxx series 60 s MSI 100 to 1000 74XXX series, 45XX series 70 s LSI 1000 to 10,000/100 to 100,000* 8085, 80 s VLSI 10,000 to 100,000/1,000,000 * CPLD, FPGA, advanced µc, SoC 90 s
IC s market trend & economic impact As a result of the continuously increasing integration density and decreasing unit costs, the semiconductor industry has been one of the fastest growing sectors in the worldwide economy
Electronic Revolution Age of electronics microcontrollers, DSPs, and other VLSI chips are everywhere Electronics of today and tomorrow demand higher performance (speed) circuits low power circuits for portable applications more mixed signal emphasis wireless hardware high performance signal processing sensors and microsystems
VLSI Design Flow Design Methodologies Top Down Design coded circuit functionality for rapid design digital only covered in EKT 422 Bottom Up Design transistor-level design with focus on circuit performance digital & mixed signal covered in ECE 410
Integrated Circuit Technology Technologies for digital ICs passive (inert) circuits: resistors and capacitors only, no transistors active circuits; with transistors III-V devices (compound semic.) MOS and Bipolar devices (silicon) in EMT251 will cover only CMOS because CMOS dominates the semiconductor/ic industry Silicon is cheaper - preferred over other materials physics of CMOS is easier to understand CMOS is easier to implement/fabricate CMOS provides lower power-delay product CMOS is lowest power density: can get morecmos transistors/functions in same chip area BUT! CMOS is not the fastest technology! BJT and III-V devices are faster
CMOS technology trend Variations over time # transistors / chip: increasing with time power / transistor: decreasing with time (constant power density) device channel length: decreasing with time power supply voltage: decreasing with time Transistor/Chip Channel Length Power/Transistor Supply Voltage low power/voltage is critical for future ICs
Moore s Law In 1965, Gordon Moore realized there was a striking trend; each new generation of memory chip contained roughly twice as much capacity as its predecessor, and each chip was released within 18-24 months of the previous chip. He reasoned, computing power would rise exponentially over relatively brief periods of time. Moore's observation, now known as Moore's Law, described a trend that has continued and is still remarkably accurate. In 26 years the number of transistors on a chip has increased more than 3,200 times, from 2,300 on the 4004 in 1971 to 7.5 million on the Pentium II processor in 1998
Moore s Law for CPUs and DRAMs
Semiconductor Scaling
Processor Technology Scaling
Technology node
ITRS International Technology Roadmap for Semiconductors Predictions of the worldwide semiconductor / IC industry about its own future prospects...
Shrinking device dimension
Increasing function density
Increasing clock frequency
Increasing clock frequency
Decreasing supply voltages
Moore s law on power consumption
Moore s law on power consumption
Cross Sectional view
Real Cross Sectional view
Type of Material Conductor Material that easily permits electrical current Eg :???? Insulator Material that block electrical current Eg :??? Semiconductor In between conductor and insulator Eg : Silicon, Germanium
Semiconductor vs Conductor Conductor Very easy to conduct current Behavior can t be controlled costly Semiconductor Need to do something to make it conduct behavior can be controlled cheap This is the main reason WHY SEMICONDUCTOR IS THE LEADING TECHNOLOGY NOWADAYS
Type of semiconductor Transistor
What is MOSFET?? Most widely used field effect transistor Let s look at its structure and physical operation 3 terminal device (gate, source, drain) Additional body (or bulk) terminal (generally at DC and not used for signals) Two types: nmos and pmos
nmos Transistor Four terminal device: gate, source, drain (and body) No connection between the gate and drain/source (separated by oxide) Voltage on gate controls current flow between source and drain Gate-oxide-body stack looks like a capacitor Gate and body are conductors SiO2 (oxide) is a good insulator called Metal-Oxide-Semiconductor (MOS) capacitor Gate no longer made out of metal, but poly
Basic nmos operation Body is commonly tied to ground (0V) When the gate is at a low voltage (VG = 0): P-type body is at low voltage Source-body and drain-body diodes are OFF (reverse bias) Depletion region between n+ and p bulk No current can flow, transistor is OFF
Basic nmos operation cont When the gate is at a high voltage Positive charge on gate of MOS capacitor Negative charge attracted to oxide in the body (under the gate) Inverts channel under the gate to n-type Now current can flow through this n-type channel between source and drain Transistor is ON
pmos Transistor Similar to nmos, but doping and voltages reversed Body tied to high voltage (Vdd) Gate low: transistor is ON inverted channel of positively charged holes Gate high: transistor is OFF Bubble indicates inverted behavior of the pmos
CMOS complementary-symmetry metal oxide semiconductor (CMOS) A process technology that is the basis for modern digital integrated circuits "complementary-symmetry" = uses complementary and symmetrical pairs of PMOS and NMOS for logic functions. Complementary = arrangement where the NMOS and PMOS are connected in series such that when one is on, the other is off
CMOS example inverter nand nor
Assignment =) Answer the following questions: 1. Why CMOS are more favorable than BJT? 2. What is the meaning of CMOS process technology and give some examples? 3. What is the latest CMOS process technology has been used and who was introduced that technology? 4. What is the difference between 0.18 μm CMOS process technology and 0.09 μm CMOS process technology? 5. 90 nm and 65 nm CMOS process technology have been introduced in the year of 2005 and 2006 respectively. Based on Moore s Law, what is the CMOS process technology expected to be introduced in 2007 and 2008