Photoresist

n. photosensitive liquid polymer which becomes insoluble after exposure to light (used to print patterns onto integrated circuits prior to chemical etching)

Photoresist is a light-sensitive material used in several industrial processes, such as photolithography and photoengraving to form a patterned coating on a surface.
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a photo sensitive chemical resistant to acid. Photoresists may be liquids that are spun onto wafers, or solid sheets that are rolled onto printed circuit boards.