Recent advances in organic resist materials. Part 2

Abstract

This paper discusses the newly developed multilevel resist processes that have further potential to improve line resolution. As the physics and engineering of high-resolution exposure equipment advances with the advent of excimer-laser-powered, deep-UV projection printers synchrotron and laser-pulse-powered X-ray step-and-repeat aligners; advanced electron beam exposure systems; and ion beam patterning technology, resist chemists will continue to be challenged to provide new materials that do not limit either the resolution or the productivity of these new exposure tools and are available in a timely fashion. Meeting this challenge will require continued innovation. An interesting capability, recently born from material research and pure innovation, is the generation of a third dimension in microlithographic patterning. This method, however, awaits practical implementation. Rohm & Haas laboratories have shown that doping normal DQN resist with a melamine precursor allows controlled generation of a third dimension to patterning. Photodecomposition of the diazoquinone generates a local concentration of acid which, when heated prior to development, catalyzes carbonium-ion-mediated cross-linking of the novolac through the hydroxymethyl-melamine. A combination of this chemistry with a mask that has transparent, opaque, and gray pattern elements allows generation of remarkable three-level relief structures with cantilevered beams and bridges in a resist layer. This new capability in pattern generation is a likely candidate for application to the design of novel device structures.