Resist-based polarization monitoring for 193nm high-numerical aperture lithography

Abstract

A third generation phase shift polarization monitor reticle is reported with improved resolution within the pupil and across the slit. The polarization state of illumination can be measured for lithography systems with NA up to 1.45. A double-reticle concept is proposed to expose both polarization test patterns and SEM alignment marks and polarimeter coordinates in the resist to optimize exposure for each independently. Both SEM imaging and polarization calculation is improved with the double reticle scheme. The single-exposure approach previously employed which can only measure three polarization states (X, Y and unpolarized) has been enhanced by a novel reciprocal exposure technique. The new exposure approach allows lithography engineers to vary effective polarization and measure at multiple custom polarization settings. Experimental results show that the sensitivity of the new reticle to polarization has more than doubled compared to the previous generation. © 2008 SPIE.