Approaching the Numerical Aperture of Water - Immersion Lithography at 193nm

As immersion nanolithography gains acceptance for next generation device applications, experimental data becomes increasingly important. The behavior of resist materials, fluids, coatings, sources, and optical components in the presence of a water immersion media presents conditions unique compared to convention “dry” lithography. Several groups have initiated fundamental studies into the imaging, fluids, contamination, and integration issues involved with water immersion lithography at 193nm. This paper will present the status and results of the next stage of the development efforts carried out at RIT. The status of two systems are presented; a small field projection microstepper utilizing a 1.05 catadioptric immersion objective lens and a 0.50 to 1.26NA interferometric immersion exposure system based on a compact Talbot prism lens design. Results of the fundamental resolution limits of resist materials and of imaging optics are presented. Additionally, an exploration into the benefits of increasing the refractive index of water is addressed through the use of sulfate and phosphate additives. The potential of KrF, 248nm immersion lithography is also presented with experimental resist imaging results