Resist-based polarization monitoring with phase-shift masks at 1.35 numerical aperture

Abstract

Experimental verification of Phase Shift Mask (PSM) Polarimetry is provided at numerical apertures up to 1.35. Promising initial results of periodic monitoring of a few polarized illuminators are illustrated and track with a scanner on-board technique to within a fraction of a percent. Earlier publications have introduced the concept and provided experimental validation up to 0.93NA. This paper discusses a variety of design improvements to improve the usability, flexibility and robustness of this technique at NAs up to 1.35. The specialized test reticle, which consists of a large number of polarization-sensitive chromeless phase shifting patterns, was successfully fabricated using a commercial mask shop. Polarization sensitivity has improved by up to 7x when compared to two earlier generation reticles, helping to minimize the impact of experimental noise. Various use models, the experimental flow, and details on the experimental procedure are provided. It is concluded that this resist-based method can serve as a highly sensitive polarization monitoring system for all hyper-NA applications.