Immersion exposure system using high-index materials

Advances in Patterning Materials for 193 nm Immersion Lithography

“…From eqs and , film pulling of organic immersion fluids at low scan rates is expected given their lower surface tension-to-viscosity ratios and lower contact angles on typical resist and topcoat surfaces. ,,, In agreement with the models, film pulling of these fluids on commercial photoresist and topcoat materials is observed at very low scan rates (<200 mm/s) (see Figure ). ,,,, JSR reported a high refractive index ( n = 1.64) topcoat ( 102 , Figure ) ,, with improved contact angle performance (θ static ≈ 70°) with organic immersion fluids that enables scan rates up to ∼350 mm/s without film pulling . The incorporation of fluorine into a side chain was found to be more effective in raising the contact angles with organic immersion fluids than incorporation of fluorine into the main chain .…”

“…Another contribution to the absorbance of saturated alkanes in the deep ultraviolet region is the formation of contact charge transfer complexes between alkanes and oxygen in the deep UV. , The oxygen-induced absorbance of JSR HIL-203 at 193 nm was measured to be 0.018 cm −1 ppm −1 . For this reason, the measurements of fluid optical properties listed in Tables and were carried out using rigorously deoxygenated samples.…”

“…Additional studies with model immersion fluids such as cyclohexane show the production of a variety of photodecomposition products including unsaturated and oxidized species as well as polymeric material. , Radiation-induced fluid darkening for a number of saturated hydrocarbons is shown in Figure . In addition to increasing the absorbance of the immersion fluid, photodecomposition products also form highly absorbing graphitic deposits on the surface of the lens that can generate particles in the fluid. , In situ cleaning methods using UV−ozone − or UV−aqueous hydrogen peroxide have been shown to rapidly and effectively remove lens contaminants. More recently, the addition of small amounts of water to the immersion fluid has been found to effectively suppress lens contamination…”

“…Alternatively, topcoat-free photoresists tailored for high-index immersion using additive ( 103 ) can achieve moderate receding contact angle with organic immersion fluids (SRCA ≈ 42−48° with JSR HIL-001) . Since high index fluids cannot be contained by conventional immersion showerheads at 500+ mm/s scan rates on existing materials, alternative fluid-handling schemes were considered, including flooding the entire wafer with fluid (the wafer wet approach) or simply allowing film pulling and removing the fluid afterward. ,, Even if film pulling cannot be prevented, controlling the surface energy of the resist facilitates removal of the immersion fluid prior to postexposure bake.…”