A resist can be patterned via lithography to form a (sub)micrometer-scale, temporary mask that protects selected areas of the underlying substrate during subsequent processing steps.
Resists are generally proprietary mixtures of a polymer or its precursor and other small molecules (e.g. photoacid generators) that have been specially formulated for a given lithography technology.
For example, in the interconnect layers of a modern microprocessor, a conductive material (copper or aluminum) is inlaid in an electrically insulating matrix (typically fluorinated silicon dioxide or another low-k dielectric).
The metal patterns define multiple electrical circuits that are used to connect the microchip's transistors to one another and ultimately to external devices via the chip's pins.
Several materials may be deposited or patterned directly using techniques like soft lithography, Dip-Pen Nanolithography, evaporation through a shadow mask or stencil.