Immersion lithography can allow for theoretical imaging to lambda/4n ( where n is the refractive index of imaging fluid). As 193 nm and 248 nm technology is pushed toward this limit, experimental data becomes increasingly important. This paper describes research carried out to explore the limitations of water immersion lithography and its extension to higher numerical aperture values using modifications to the imaging fluid. Resist imaging to 38 nm is demonstrated using water as an imaging fluid. Several alternative fluids are presented including phosphates, sulfates, and halides, which are shown to increase the refractive index of water. (C) 2004 American Vacuum Society.