ABSTRACT
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Microlithography is a manufacturing process for producing highly accurate, microscopic,
2-dimensional patterns in a photosensitive resist material. These patterns are optically
projected replicas of a master pattern on a durable photomask, and they are typically
made of a thin patterned layer of chromium on a transparent glass plate. At the end of
the lithographic process, the patterned photoresist is used to create a useful structure in
the device that is being built. For example, trenches can be etched into an insulator, or a
uniform coating of metal can be etched to leave a network of electrical wiring on the
surface of a semiconductor chip. Microlithography is used at every stage of the semicon-
ductor manufacturing process. An advanced chip design can have 50 or more masking
levels, and approximately 1/3 of the total cost of semiconductor manufacture can be
attributed to microlithographic processing.
