TABLE OF CONTENTS L. R. Harriott [1] and R. Hull [1] , [2]
Lithographic patterning at ever-decreasing dimensions has been a major technological driver over the past few decades, particularly in the microelectronics industry, where realization of "Moores Law" (see Section 9.2) has driven extraordinary increases in processing power and electronic data storage. However, realization of the full potential of nanotechnology requires development of a broader range of patterning techniques than the ultra-violet optical projection methods currently used in microelectronics manufacturing, to enable higher resolution, lower cost, and application to a broader range of materials and surface geometries. Nanolithography refers to the ability to define patterns on surfaces at ever-decreasing length scales. Such capabilities are central to an enormous range of research fields and emerging technologies, ranging from microelectronics1 to nanomechanical systems to biomedical applications: As such, nanolithography is a keystone of the nanotechnology revolution.
A handful of approaches dominate existing and emerging nanolithography technologies. The most prevalent approach employs exposure of resist materials, which are most usually polymeric, by energetic photons or particles (electrons or ions). Under such exposure, irradiated areas of the resist undergo structural/chemical modification such that they have differential solubility in a developing solution with respect to unexposed areas. This structural modification may reduce or enhance solubility (referred to as negative and positive resists respectively), e.g., by cross-linking or scission of polymeric chains.
Resist exposure may be accomplished in
