A method for compensating the polarization aberration of projection optics in immersion lithography

Abstract

As the numerical aperture (NA) of 193nm immersion lithography projection optics (PO) increasing, polarization aberration (PA) leads to image quality degradation seriously. PA induced by large incident angle of light, film coatings and intrinsic birefringence of lens materials cannot be ignored. An effective method for PA compensation is to adjust lens position in PO. However, this method is complicated. Therefore, in this paper, an easy and feasible PA compensation method is proposed: for ArF lithographic PO with hyper NA (NA=1.2), which is designed by our laboratory, the PA-induced critical dimension error (CDE) can be effectively reduced by optimizing illumination source partial coherent factor σ out . In addition, the basic idea of our method to suppress pattern placement error (PE) is to adopt anti-reflection (AR) multi-layers MgF 2 /LaF 3 /MgF 2 and calcium fluoride CaF 2 of [111] crystal axes. Our simulation results reveal that the proposed method can effectively and quantificationally compensate large PA in the optics. In particular, our method suppresses the dynamic range of CDE from -12.7nm ~ +4.3nm to -1.1nm ~ +1.2nm, while keeping PE at an acceptable level.