Benefiting from polarization effects on high-NA imaging

The onset of lithographic technology involving extreme numerical aperture (NA) values introduces critical technical issues that are now receiving particular attention. Projection lithography with NA values above 0.90 is necessary for future generation devices. The introduction of immersion lithography enables even larger angles, resulting in NA values of 1.2 and above. The imaging effects from oblique angles, electric field polarization, optical interference, optical reflection, and aberration can be significant. This paper addresses polarization considerations at critical locations in the optical path of a projection system, namely in the illuminator, at the mask, and in the photoresist. Several issues are addressed including TE and azimuthal polarized illumination, wire grid polarization effects for real thin film mask materials, and multilayer resist AR coatings for high NA and polarization.