Lithography And Integrated Circuits
The same lithographic concepts used to reprint text and pictures on paper can be used to manufacture integrated circuits. In this case, a polymer resist is used to repel the subsequently applied layers of metal conductors, semiconductor materials, and dielectric insulators which are the "ink." An integrated circuit is a tiny version of a conventional electrical circuit. Thin films of various materials act as insulators between conductive material and the silicon metal substrate, or protect existing layers from implantation of other atoms. These devices are built by coating a silicon wafer with patterned layers of material, designed to allow the insulators or protective barriers to be applied, or to leave holes in the barrier layer permitting electrical contact. Sophisticated circuits may require 20 or more layers. Small features and narrow lines must be precisely placed, and the absence of material in a given spot is as critical as the presence of it somewhere else.
There are several ways lithography is used to make integrated circuits, including visible and ultraviolet lithography (forms of photolithography), electron beam patterning, ion beam patterning, and x-ray lithography. The most common method is photolithography, which is well suited to high volume production of consumer electronics.