The chips that make computers 'think'

Semiconductors are the minute silicon chips that are the ''thinking part'' of a computer.

You've seen them illustrated by the inevitable photographs of a chip floating on the whorls of a man's fingerprint like a tiny barge caught on the high seas.

Under a powerful microscope, the intricate patterns of the circuits, in metallic colors, make the chips look like miniaturized floor plans of Byzantine palaces.

These chips can take the echo out of overseas phone calls, guide your jet in for a smooth landing, or relay ''photographs'' from outer space. Researchers are vying to produce even smaller chip circuits.

The production process begins with silicon crystals, ''grown'' into cylindrical ingots looking like smoky glass. The ingots are sliced into wafers on which the circuits are photographically etched, layer after layer.

The wafers are also ''doped'' with certain impurities that alter the electrical conductivity of the silicon -- hence the term ''semiconductor.'' The chips are individually packaged and outfitted with tiny aluminum ''leads'' to connect them to electronic component in such things as telephone exchanges, video games, or calculators.

This production work is done in a ''clean room,'' where the air contains fewer than 100 particles per cubic foot - in contrast with a hospital room, say, which allows 10,000 particles per cubic foot.