Key Words

photoresist, pellicle, high-index fluid, phase shift, double patterning Optical immersion lithography utilizes liquids with refractive indices>1 (the index of air) below the last lens element to enhance numerical aper-ture and resolution, enabling sub-40-nm feature patterning. This shift from conventional dry optical lithography introduces numerous challenges re-quiring innovations in materials at all imaging stack levels. In this article, we highlight the recent materials advances in photomasks, immersion fluids, topcoats, and photoresists. Some of the challenges encountered include the fluids ’ and photomask materials ’ UV durability, the high-index liquids ’ com-patibility with topcoats and photoresists, and overall immersion imaging and defectivity performance. In addition, we include a section on novel materi-als and methods for double-patterning lithography—a technique that may further extend immersion technology by effectively doubling a less dense pattern’s line density. 93 A nn u. R e