Date: Before 1993
Why is silicon used in making computer chips? Is it because of
special chemical properties? Could other crystals be used equally well?
Hi rita, great question! I have a few guesses in answer to this.
One thing that makes silicon desirable for manufacturing purposes is that it
is abundant (it is the second most abundant substance in the earth's crust)
and therefore cheap. Another, more directly relevant reason, is that silicon
is an "impurity semiconductor." What this means is that if you deliberately
make a sample of silicon with certain impurities lodged in the crystal, you
can control the conductivity of the sample by varying the concentration of
impurities. What is more, you can do it over a range of conductivity values
that correspond to small voltages. And best of all, you can either increase
or decrease the conductivity, depending on what kind of impurity you
introduce. Germanium (Ge) also has these properties, but is more expensive.
These properties make form the basis for a wide variety of semiconductor
devices. Also, I believe that silicon wafers can be etched by chemical
process (involving fluorine, I think) to change the conductivity along well-
defined channels in the wafer. This combination of properties makes silicon a
uniquely good choice for making computer chips . . . it has special chemical
AND physical properties. I just received this note from "Eric Peterson" who
has agreed to let me post it in this space. - robert
Great answer to the question on silicon use in chips. As an expansion, the
use of Gallium Arsenide is becoming more popular as a base material for doping
than silicon, or in conjunction with it. Gas chips are much faster because of
two reasons. 1) Wafers can be sub-micron, and therefore quicker because of
the less amount of circuitry involved, and 2) GAs substrate has a faster
charge transfer rate than does Silicon. There are several good trade
publications that delve into this subject at great length. One is called
"surface Mount Technology" and another is a weekly tabloid called "Electronics
Products News". Both are very good sources for those who are interested in
keeping up with the latest new tech stuff in chip making.
Click here to return to the Chemistry Archives
Update: June 2012