Critical impact of mask electromagnetic effects on optical proximity corrections performance for 45 nm and beyond

Abstract

Numerous studies have addressed the challenges ahead in optical lithography due to electromagnetic effects in photomasks (so-called emf effects), which arise from the complex interaction of the illumination with mask topography whose size now approaches the wavelength. As design critical dimensions shrink, the electromagnetic response of the reticle becomes a complicated function of the incident polarization with serious impact to printed critical dimension (CD) on the wafer. A number of modeling techniques are available to approximately account for emf in the process models employed during optical proximity correction calculations, with small to moderate runtime penalty. Among them are simple mask CD bias, the boundary layer [J. T. Azpiroz, Proc. SPIE 5040, 1611 (2003)], the domain decomposition method [K. Adam and A. Neureuther, Proc. SPIE 4562, 1051 (2001)], and techniques based on the geometrical theory of diffraction [G. K. Chua, Proc. SPIE 5377, 1267 (2004); A. Khoh, J. Opt. Soc. Am. A 21, 959 (2004)]. In this article several of these techniques are benchmarked in terms of accuracy and range of applicability. Results are compared against rigorous electromagnetic simulations. © 2007 American Vacuum Society.