Chip War: The Fight for the World's Most Critical Technology

by Chris Miller

Lathrop covered a block of germanium with one of Kodak’s photoresist chemicals that would disappear if exposed to light. Next, he turned his microscope upside down, covering the lens with a pattern so that light would only pass through a rectangle-shaped area. Light entered the pattern, shined in a rectangle shape through the lens, and was shrunk in size by the upside-down microscope as it focused onto the photoresist-coated germanium, with the rays of light creating a perfectly shaped, miniature version of the rectangular pattern. Where light struck the layer of photoresist, the chemical structure was altered, allowing it to be washed away, leaving a tiny rectangular hole, far smaller and more accurately shaped than any glob of wax could have been. Soon Lathrop discovered he could print “wires,” too, by adding an ultra-thin layer of aluminum to connect the germanium with an external power source. Lathrop called the process photolithography—printing with light. He produced transistors much smaller than had previously been possible, measuring only a tenth of