Semiconductor lithography is one of the key steps in the manufacturing
of integrated silicon-based circuits. In fabricating a semiconductor
device such as a transistor, a series of hot processes consisting of
vacuum film deposition, oxidations, and dopant implantation are all
patterned into microscopic circuits by the wet processes of lithography.
Lithography, as adopted by the semiconductor industry, is the process of
drawing or printing the pattern of an integrated circuit in a resist
material. The pattern is formed and overlayed to a previous circuit
layer as many as 30 times in the manufacture of logic and memory
devices. With the resist pattern acting as a mask, a permanent device
structure is formed by subtractive (removal) etching or by additive
deposition of metals or insulators. Each process step in lithography
uses inorganic or organic materials to physically transform
semiconductors of silicon, insulators of oxides, nitrides, and organic
polymers, and metals, into useful electronic devices. All forms of
electromagnetic radiation are used in the processing. Lithography is a
mUltidisciplinary science of materials, processes, and equipment,
interacting to produce three-dimensional structures. Many aspects of
chemistry, electrical engineering, materials science, and physics are
involved. The purpose of this book is to bring together the work of many
scientists and engineers over the last 10 years and focus upon the basic
resist materials, the lithographic processes, and the fundamental
principles behind each lithographic process.