ECE 440 Lecture 1 : Introduction Class Outline: •Class Information •Motivation •Background and Basics
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ECE 440Lecture 1 : Introduction
Class Outline:•Class Information•Motivation•Background and Basics
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Things you should know when you leave…
Key Questions• How does the class work?• Why should I care about
semiconductors and devices?• Why semiconductors?• Why electronics?• Why CMOS?
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Class Information
Section Time Location Office Tel. # EmailProf. K.Y. Cheng B 9:00 335 MEB 2112 MNTL 333-6642 [email protected]. L. Liu D 11:00 101 Trans B 3104 MNTL 244-4349 loganliu@Prof. K.C. Hsieh X 12:00 163 Everitt 2114 MNTL 244-1806 khsieh@Prof. E. Pop E 1:00 163 Everitt 2258 MNTL 244-2070 epop@Prof. M. Gilbert G 3:00 163 Everitt 2256 MNTL 333-3064 matthewg@TA M. NawazTA C.-C. ChengTA M. Mohamed
3249 BI1231 MNTL3203 BI
244-1964333-4053244-1919
nawaz@cheng22@mohamed@
Instructor Information:
Specific Information:
• Section G : MWF 3-3:50PM• Section Office Hours :
–Friday 10-11AM–By Appointment
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Class Information
• 3 in-class quizzes• Take ~ 20 min• Similar to homework problems
Grading Information: Quizzes
Grading Information: Exams
•Exam I: Thursday, October 01, 2009, 7-8:00 p.m., Everitt 269 and LIB 66•Exam II: Tuesday, October 27, 2009, 7-8:00 p.m., Loomis 151 and Everitt 269•Final Exam: December 11-18, 2009, to be announced
Grading Information: Grade Computation
Homework = 10%Quiz = 15%Hour Exam I = 20%Hour Exam II = 20%Final Exam = 35%----------------------------------Total = 100%
Fall 2007: 22% A‘s 25% B‘s 35% C‘s 12% D's 6% F's
Top and bottom 1/3 of grade range may be given plus and minus.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Motivation
Semiconductor devices are everywhere!
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Total Yearly Revenue ~ $ 261 billion
Motivation
Semiconductor devices = $$$
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and Basics
The first computer…
• Basics– 25,000 parts– Weighs 15 tons
• Computes values of polynomial functions.– Logarithmic and
trigonometric approximations
• Uses finite differences method.
• Accurate to 31 digits.
Created in 1832 by Professor Charles Babbage at Trinity College, Cambridge
Source: Wikipedia
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsGetting things started… Typical cathode ray tube
http://www.aip.org/history/electron/jjthomson.htm
•Apply bias across vacuum tube – it glows.•“Rays” are emitted by the cathode which lights up the glass.•“Rays” are carried by the “ether”.
J.J. Thompson – 1906 Nobel Prize in Physics for studying discharge of electricity in gasses.
•“Rays” are actually charges – electrons.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsCan we control the electron flow?
De Forest’s 1906 Audion
Normal Vacuum Tube•Use current to heat cathode.•Cathode releases electrons into a “space charge” region.•Electrons flow from cathode to anode.
Audion Vacuum Tube•Add a metal grid around the cathode.•Sweep grid bias from negative to positive •Electrons flow changes.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsThe “first” electronic computer…
1946 ENIAC – Electronic Numerical Integrator and Computer
• ENIAC statistics– 17,468 vacuum tubes– Weighed 30 tons– 8’ x 3’ x 80’– Consumed 150 kW of power– Crashed ~ 5 days
• ENIAC advantages– No moving parts– Could hold a 10 digit
decimal number in memory
– 5 KHz operation– Could branch – trigger
other operationsdepending on the computed result.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsWe have an electronic computer, so we’re done right?
RCA Triode Vacuum Tube, Type 808
• Vacuum tubes have some problems– They require a lot of power
• Bias voltages are typically in the 100’s of volts.– They are inefficient
• 40% to 70% of the input power is lost to heat.– They require vacuum
• Stray gas atoms can become ionized and begin to conduct electricity.
– They are very hard to scale
• The end result: Inefficient devices
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsBardeen changes everything!
UIUC Professor (1951-1991)
• The modern age is ushered in with the invention of the transistor– Discovered in 1947– Consisted of a germanium base with gold contacts– Bardeen realized that electrons did not all travel through
semiconductors the same way.• Surfaces are different
– Leads to more complex radios and computers
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsWhy Semiconductors?
• Why not a conductor?– No field effect
• Large number of mobile electrons screen out the field.
• Cannot modulate output current.
• Why not an insulator– No field effect
• No free carriers to carry the current.• To get charge flow we would need very large
fields.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsWhy Semiconductors?• Semiconductors are
somewhere in the middle.• Normally, they do not
conduct electricity.– Covalent bonds are all
satiated.• We can change their
properties dramatically– Doping– Temperature– Energy– Fields
• Insulators become conductors– Loose electrons start to
flow in a predictable way!
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
• Semiconductors are solid materials that may occur in a number of different CRYSTALLINE forms:
* In the CRYSTALLINE state the atoms are ORDERED into a well-defined LATTICE thatextends over very LONG distances
* POLYCRYSTALLINE materials consist of small CRYSTALLITES that are embedded inAMORPHOUS regions of material
* In the AMORPHOUS state there is little or NO evidence for long-range crystallineorder
CRYSTALLINE STATE AMORPHOUS STATEPOLYCRYSTALLINE STATE
Background and BasicsWhy Semiconductors?
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsWe can make things with discrete transistors…
Transistor radio from 1954 which uses 4 discrete transistors.
Let’s try using many INTEGRATED transistors…
Integrated circuits fabricate all transistors and metal interconnects on the same piece of semiconductor.
•Jack Kilby UIUC’47, patent TI’1959, Nobel prize 2000. Used germanium.
•Robert Noyce 1961, co-founder of Fairchild, then Intel. Used silicon
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsOk, but Bardeen built his transistor in germanium. So, we use germanium right?
Silicon has many attractive properties to those who make electronic devices
•It has a large density of states.
•It remains semiconducting at high temperatures.
•We may manipulate its electrical characteristics by introducing impurity atoms into the crystal.
•It has a native oxide (SiO2) which may be easily grown in a furnace.
•SiO2 has a relatively clean interface with Si and is an excellent insulator.
SiO2
Si
Germanium is a bit unpredictable at higher temperatures, we use silicon!
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Source Drain
Top Gate
Background and BasicsTransistors are like tiny switches…
P-MOS N-MOS
Source Drain
Top Gate
B.S. Doyle et al., IEEE TED (2003)
• Transistors usually have three gates.
• By using doping, we can control the type of carrier contributing to electrical conduction.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
P-MOS
N-MOS
Input (A) Output (Q)
1 (Vdd) 0 (Vss)
0 (Vss) 1 (Vdd)
Background and Basics•We can string multipletransistors together to traceout logical functionality.
•CMOS (Complementary MetalOxide Semiconductor) Logic
•Reproducible on large scales
•Leads to circuit design
•Left, we show the simpleconnection method fordifferent devices on the samewafer.
•Below, the connection schemefor a logical inverter.
Now let’s start to make something useful…
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsPut many of the transistors together and we get…
• The first microprocessor– Intel 4004 (1971)– 2250 transistors– 740 kHz operation
• Comperable computation with ENIAC
• Built on 2” wafers– We use 12” today
• 10 µm line widths– We use 45 nm today
• 4-bit bus width– We use > 800 kb today
• Used first in the BusicomCalculator
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsPut many of the transistors together and we get…
12” wafer filled with 100s of die.
Single die after removal and packaging.
Contents of single die before packaging.
Cross section of single element.Single transistor
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsHow small is small?
Human Hair
Influenza Virus
Transistor
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsSo how have things progressed since 1970?
•The development of the modern microelectronics industry has been made possible by the evolution of techniques for the INTEGRATION of large numbers of sub-micron sized TRANSISTORS into densely-packed integrated circuits.
•To satisfy the demand for chips with improved MEMORYand SPEED characteristics.
•The size of these transistors continues to SHRINK at a RAPID rate.
•The SCALING of transistor sizes in integrated circuits is governed by an EMPIRICAL principle known as MOORE’S LAW.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsSo how have things progressed since 1970?
• What are the benefits of continuous integration?– System performance– Cost-per-function– Power-per-function– System reliability
Clock speed – 104 increase in 30 yrs.
Cost – 103 decrease in 30 yrs.
Cost per function– 104 decrease in 30 yrs.
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
Background and BasicsHelp!! We are running out of time!!
M. J. Gilbert ECE 440 – Lecture 1 8/24/09
ITRS, 2005
Background and BasicsHelp!! We are running out of time!!
(ECE 444)
Processing•Zone refining•Epitaxial growth•Photolithography•Resist (positive/negative)•Encapsulation (CVD, sputtering)•Ion etching•Ion implantation and diffusion
ECE 440
Devices•P-N diode•Schottky barrier•Bipolar junction transistor•Metal-oxide-semiconductor field-effect transistor (MOSFET)•Solar cells•Photodiodes
Materials•Fundamental properties•Crystal structure•Charge carriers•Energy bands•Optical absorption (direct/indirect)•Electrical properties (drift/diffusion)•Mobility and diffusion
Physics
Circuits
M. J. Gilbert ECE 440 – Lecture 1
Background and BasicsWhat we’ll learn…
8/24/09
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