Evaluation of Partial Coherent Imaging Using the Modulation Transfer Function in Immersion Lithography

Abstract

Immersion lithography has been actively pursued as a method of extending the resolution of optical lithography beyond the 65 nm mode. Immersion lithography and the hyper numerical aperture impact the selection and optimization of various resolution enhancement techniques. These can be selected, as appropriate, for each mask pattern. When the line width on target is narrower, the fine line structure will no longer be discernible. Then, this is the resolution limit of the system. Until recent times, the traditional means of determining the quality of an optical element or system of elements was to evaluate its limit of resolution. A useful parameter in evaluating the performance of a system is the modulation transfer function, and this is analyzed for the hyper numerical aperture immersion lithography.