Immersion lithography at 157 nm

We present a preliminary study on the feasibility of immersion lithography at 157 nm for patterning below 70 nm. This technology can enable an enhancement in resolution of ∼40% without radical changes in lasers, optics, or resist technology. We have identified a class of commercially available liquids, perfluoropolyethers, which are good candidates for use as immersion liquids. They are transparent (α≈10−3 μm−1 base 10), optically clean, chemically inert, and compatible with at least some current resist materials and with the semiconductor manufacturing environment. We have also constructed a high-resolution lensless interference immersion lithography system, preserving much of the design of a previous nonimmersion interference system. With this immersion interference tool, we have patterned resist with 30 nm dense features.