Definition
Photolithography is the core patterning technique used to build integrated circuits. It works much like photographic printing: a light-sensitive chemical called photoresist is coated onto the wafer, then exposed to light projected through a photomask carrying the layout of one layer. The exposed pattern is developed, and subsequent etching or deposition steps transfer that pattern into the wafer. The whole sequence is repeated dozens of times to stack the transistor and interconnect layers that make up a chip.
Why it sets the limit
The smallest features a fab can print are bounded by the wavelength of the light used and the optics of the exposure tool. Pushing to ever-smaller nodes drove the industry from deep-ultraviolet light to extreme-ultraviolet (EUV) lithography, which uses far shorter wavelengths to resolve the tiny features of leading-edge nodes such as those behind the newest mining ASICs. EUV scanners are among the most complex and expensive machines ever built.
Precision and cleanliness
Because a single stray particle can ruin a die, photolithography happens in cleanrooms with tightly filtered air, and mask alignment between layers must be accurate to a tiny fraction of the feature size. Better alignment and cleaner processing are major contributors to higher yield.
Photolithography relies on the mask set created after tape-out and is one of the most critical steps performed inside a foundry.
In Simple Terms
Photolithography is the core patterning technique used to build integrated circuits. It works much like photographic printing: a light-sensitive chemical called photoresist is coated onto…