Advances in Chemical Amplification Resist Systems

The chemical amplification concept proposed in 1982 to boost resist sensitivities is now well accepted by the lithography community, which stems not only from high sensitivities that chemical amplification resist systems can offer but also from additional benefits of high contrasts and unexpectedly high resolution capabilities. The design flexibility and versatility that the use of acid as a catalytic species offers are another attractive feature of chemical amplification, giving rise to a birth of an entire family of advanced resist systems. Manufacture and prototype fabrication of DRAM's by deep UV lithography have been accomplished with use of chemical amplification resists. However, some process problems uniquely associated with chemical amplification resists have surfaced recently, which include their latent image instability due to their sensitivity toward minute amounts of air-borne contaminants. This paper reviews recent advances made in our laboratory in the field of chemical amplification resist systems and discusses 1) influence of residual casting solvent on absorption of NMP by polymer films, 2) effects of polymer end groups on resist sensitivity, and 3) new imaging mechanisms based on acid-catalyzed dehydration.