Mask topography simulation for EUV lithography

Abstract

This paper introduces a methodology for rigorous computation of electric fields in the neighborhood of reflective masks employed in EUV lithography. Specifically, the media used in this application place stringent requirements on the spatial and temporal grids in order to achieve a stable and accurate Finite-Difference, Time-Domain calculation. An analytical expression for the electric field reflectivity off the multilayer is harnessed to define effective media that can decrease run times by as much as an order of magnitude. This framework is then used to analyze the effect of the absorber thickness on image linewidth and quality.