Typically, a photosensitive surface (a photoresist) is selectively exposed to light using a template. The exposed areas are subsequently etched (carved by chemical means). "Photolithography - The technique used to produce the silicon chips that make up modern-day computers (actually, the term predates printed circuits, although that is the form we are interested in). The traditional process involves shining light through a mask onto a photosensitive polymer (photoresist) on a silicon surface, then subsequently removing the exposed areas." CMP-Cientifica
