Edge-profile materials and protective coating effects on image quality

摘要

Rigorous simulation of electromagnetic diffraction with TEMPEST is used to explore the impact of edge profiles, phase-shifting materials, protective coatings and reflective masks on projection printed image quality. The TEMPEST massively-parallel finite-difference time-domain scattering analysis program has been extended to generate diffraction efficiencies for transmitted as well as reflected fields. The mask materials and geometries are input through specifying turning points along the polygonal boundaries of the chrome, phase- shifting materials, overcoating, etc. Plane waves in the TE orientation are then used to illuminate the mask, and a postprocessor is used synthesize the image from diffracted fields. To identify problematic situations and survey interesting technology approaches, a variety of proto-typical mask geometries are considered. The fundamental problems of the effects of rounding of chrome edges are investigated using optical parameters at 248 nm. Phenomena which might contribute to improved image quality with overcoating are studied using planar, conformal and inhomogeneous coating models at i-line. Effects from large (0.365 nm) vertical and overcut edges in phase-shifting layers are also explored. Finally, for the reflective mask technology, the effects of mask edge angles and the use of built-in materials-based phase-shifting are explored.