Moore’s law and the silicon revolution - The Computing Universe: A Journey through a Revolution - page 120

7 Moore's law and the silicon revolution

As I prepared for this event, I began to have serious
doubts about my sanity. My calculations were
telling me that, contrary to all the current lore
in the field, we could scale down the technology
such that everything got better : the circuits got
more complex, they ran faster, and they took less
power - WOW!
Carver Mead 1

Silicon and semiconductors

When we left the early history of computers in Chapter 2 , we had seen
that logic gates were first implemented using electromechanical relays - as in
the Harvard Mark 1 - and then with vacuum tubes - as in the ENIAC and the
first commercial computers. These early computers with many thousands of
vacuum tubes actually worked much better and more reliably than many engi-
neers had expected. Nevertheless, the hunt was on for a more dependable tech-
nology. After World War II, Bell Labs ( Fig. 7.1 ) initiated a research program to
develop solid-state devices as a replacement for vacuum tubes. The focus of the
program was not on materials that were metals or insulators but on strange,
“in-between” materials called semiconductors .
In a solid, it is the flow of electrons that gives rise to electric currents when
a voltage is applied. One of the great successes of quantum physics has been
in giving us an understanding of the way in which different types of solids -
metals, insulators, and semiconductors - conduct electricity. This quantum
mechanical understanding of materials has led directly to the present techno-
logical revolution, with its accompanying avalanche of stereo systems, color
TVs, computers, and mobile phones. A good conductor, such as copper, must
have many conduction electrons that are able to move and thus constitute a cur-
rent when a voltage is applied. By contrast, an insulator such as glass or carbon
has very few conduction electrons, and little or no current flows when a voltage
is applied. Semiconductors are solids that conduct electricity much better than
insulators but much worse than metals. The elements germanium and silicon
are two examples. The importance of silicon for computer technology is evi-
dent in the naming of California's “Silicon Valley,” home to many of the earliest
electronic component manufacturers ( Fig. 7.2 ).
The properties of a solid depend not only on what element it is made of,
but also on the way the atoms or molecules are stacked together. Many solid

Fig. 7.1. An aerial view of AT&T Bell
Labs in Holmdel, New Jersey. The
building was designed by the architect
Eero Saarinen and for forty-four years it
was the home of an advanced research
laboratory owned successively by Bell
Telephone, AT&T, Lucent, and Alcatel.

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