Arc-shaped slit effect of EUV lithography with anamorphic high NA system in terms of critical dimension variation

Abstract

EUV lithography is one of the promising technologies for 1X nm patterning. EUV lithography has high resolution capability because of short wavelength of source but it has some particular patterning problems which are not appeared a t optical lithography. Owing to reflective optics, EUV light incidents obliquely in mask and oblique incidence of EUV lithography leads shadow effect and arc-shaped exposure slit. The study of these particular optical problems are required for optical proximity correction (OPC). Arc-shaped exposure slit leads azimuthal angle variation, incident angle variation , and variation of shadow width. With these variations along exposure slit, patterning result is varied along the exposure slit. With understanding of these particular optical problems, lots of EUV OPC studies have been presented with 0.33 conventional NA system. However, suggested anamorphic high NA system has not only elliptical shaped mask NA and also different angle distribution. The incident angle variation as a function of azimuthal angle is different between isomorphic and anamorphic NA systems. In case of anamorphic NA system, incident angle distribution is decreased on horizontal direction but it is larger on vertical direction compared with case of isomorphic NA system. These differences make different arc-shaped slit effect. CD variation as a function of azimuthal angle is different between isomorphic and a namorphic NA systems. The study of CD variation along the exposure slit is very helpful for OPC in EUV lithography. © 2017 SPIE.