From Sand to Silicon: Manufacturing an Integrated Circuit; The Solid-State Century; Scientific American Presents; by Barrett; 6 Page(s)

The fundamental device of the digital world is the integrated circuit, a small square of silicon containing millions of transistors. It is probably the most complex of man-made products. Although it looks flat, it is in fact a three-dimensional structure made by painstakingly building up on the silicon base several microscopically thin layers of materials that both insulate and conduct electricity. Assembled according to a pattern carefully worked out in advance, these layers form the transistors, which function as switches controlling the flow of electricity through the circuit, which is also known as a chip. "On" and "off" switches manipulate the binary code that is at the core of what a computer does.

Building a chip typically requires several hundred manufacturing steps that take weeks to complete. Each step must be executed perfectly if the chip is to work. The conditions are demanding. For example, because a speck of dust can ruin a chip, the manufacturing has to be done in a "clean room" containing less than one submicron particle of dust per cubic foot of air (in contrast, the average living room has between 100,000 and one million particles per cubic foot of air). Much of the equipment needed for making chips embodies the highest of high technology, with the result that chip factories-which cost between $1 billion and $2 billion for a state-of-the-art facility-are among the costliest of manufacturing plants.