Transcript Silicon, Circuits, and the Digital Revolution

Silicon, Circuits, and the
Digital Revolution
George Watson
Department of Physics and Astronomy
University of Delaware
[email protected]
June 1, 1999
ALLSTEL
Silicon, Circuits, and the
Digital Revolution
http://www.physics.udel.edu/~watson/scen103/
The Way it Was:
Technology on Campus
25 years ago
Slide Show
Silicon, Circuits, and the
Digital Revolution
Everything is made of something!
Atoms are comprised of nuclei and electrons.
Mass is nuclear.
Size is electronic.
Electron Energy Levels in Hydrogen
The Visible Spectrum
Photon “color”
Wavelength Energy
(nm)
(eV)
blue
430
2.9
yellow
530
2.3
red
650
1.9
Electron Energy Levels
Electronic Band Structure in Solids
Metals, Insulators, and Semiconductors
Column 4: Silicon among the elements
Band Gaps of Column 4 Elements
Element
Band Gap
(eV)
Carbon (diamond)
Silicon
Germanium
5.5
1.1
0.7
The Visible Spectrum
Photon “color”
Wavelength Energy
(nm)
(eV)
blue
430
2.9
yellow
530
2.3
red
650
1.9
Metals, Insulators, and Semiconductors
Concept Check: Band Gaps
You are admiring the color of a gemstone by
looking through it to see a nearby lamp.
Your physicist friend states that the band gap
of that particular stone is about 2.4 eV.
Does the stone appear to be:
a. red
b. blue
c. black
Band Gaps of Several Elements
Element
Carbon (diamond)
Silicon
Germanium
Band Gap
(eV)
5.5
1.1
0.7
Selenium
1.8
Silicon, Circuits, and the
Digital Revolution
Principle of photoconductivity
applied to photocopying:
xerography
(dry writing)
Slide Show
Essentials of Xerography
Pure silicon - 4 valence electrons
From sand?
Column 5: one more valence electron
Silicon doped with arsenic
n-type silicon
Column 3: one fewer valence electron
Silicon doped with gallium
p-type silicon
Effect of doping on band structure
Transistors are structured from
n-type and p-type silicon.
Concept Check: doped silicon
You physicist friend hands you a
wafer of germanium and tells
you it is doped with
phosphorus.
Is the semiconductor wafer:
a. n-type
b. p-type
Silicon, Circuits, and the
Digital Revolution
Building Transistors on
Integrated Circuits:
lithography
(stone writing)
Slide Show
MOSFET inverter
CMOS inverter
CMOS fabrication
CMOS NAND gate
4 transistors
Adder circuit
38 transistors!
Moore’s Law for Intel Microprocessors
Penetration rates of major consumer
products in U.S. households