Fabricating Transistors and Electronic Chips
Date: Summer 2012
How is it possible that we have made transistor gates that are so small that we cannot even see them? How did we make the machines that are capable of doing such tiny building?
There are many steps in the making of a transistor. Rather than me writing a long treatise on the subject, have a look at this site that allows you to see, one click at a time, each of the steps....
Note that the "mask" they refer to is created by a precision laser that allows such miniature features to be resolved.
The process for making these microscopic circuits is called
"photolithography". Basically, it is like a projector you might see in
a classroom, but instead of projecting large pictures on a wall, it
uses a special kind of light and projects tiny pictures onto materials
(the outlines of the transistors and other circuits being made). The
process is very complicated, but it is all very well documented, and
you can read about it online -- just look up "photolithography" (there
are many hits). Although our eyes cannot see things that small, you
can still see them using other tools (like an electron microscope).
Hope this helps,
Most of the ideas that make this possible are probably familiar to
you in other contexts:
1) When you take a photograph with a film camera, you get a tiny
picture of something large. You can use the same idea to get an
extremely tiny picture of something small.
2) The process of printing a picture - shining light through a
negative onto light-sensitive paper - can be used for things other
than making pictures to look at. The image you make can be
functional as well. The light you shine through the negative could
be used to alter the chemical properties of the thing you're
illuminating. A photoresist is a substance that is changed by light
so that it no longer can be dissolved as easily as unexposed
resist. This allows you to make a tiny, detailed mask that in turn
can be used to modify a semiconductor only in certain areas.
3) For very small features, the wavelength of light limits the
resolution you can achieve, but you can use a shorter wavelength to
get around this problem.
These are made by photolithographic process. one sees transistors with three legs or terminals. these transistors occupy much space. The interconnections in an array are done by photolithography and one transistor gets connected to another as you can see in
The die is about 5mm*5mm and has an area of just 33 sq mm. there are many (256) transistors in this array. you might read this article to learn more.
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Update: November 2011