Word: chips
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Dates: during 1970-1979
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Where will it all end? Circuits in some densely packed chips are already so close that there is sometimes electron leakage between conductors-interfering with the proper working of the chip. Is technology fast reaching the limit of miniaturization? Computer scientists think not. They point to the stupendous amounts of data contained, for example, in a DNA molecule-or in one-celled animals and plants that are visible only under a microscope. Says M.I.T.'s Michael Dertouzos...
...other manufacturing process is quite like it. Only a single speck of dust can ruin a chip, so work must be done in "clean rooms," where the air is constantly filtered and workers are swathed in surgical-type garb...
...Some 250 chips are made from one razor-thin wafer of precisely polished silicon about 3 in. in diameter. These wafers, in turn, are sliced from cylinders of extremely pure (99.9%) crystalline silicon, grown somewhat like rock candy. Why silicon? Because it can be either electrically conducting or nonconducting, depending on the impurities added to it. Thus one small area of a chip can be "doped" (as scientists say) with impurities that give it a deficiency of electrons-making it a so-called p (or electrically positive) zone, while an adjacent area gets a surplus of electrons to create...
...silk-screening, a chip's complex circuitry is created a layer at a time. It is a slow, painstaking and error-prone procedure...
...resist, a photographic-type emulsion sensitive only to ultraviolet (UV) light. (To prevent accidental exposure, clean rooms are generally bathed in UV-less yellow light.) Next, a tiny mask, scaled down photographically from a large drawing and imprinted with hundreds of identical patterns of one layer of the chip's circuitry, is placed over the wafer. Exposed to UV, the resist's shielded areas remain soft and are readily washed away in an acid bath. On the other hand, the unshielded areas harden, forming an outline of the circuit...