Intrinsic problem affecting contact hole resolution in hyper NA era

The lifetime of optical lithography has been extended beyond most expectations by extremely high numerical aperture (NA), eccentric illumination, polarization control, and immersion lithography. An ArF interferometric system with a 1.20 NA achieved resolution of 40-nm half-pitch line and space (L&S) patterns 111. It is also well known that resolution of vertical L&S can be greatly enhanced by the combination of X-oriented dipole illumination and Ypolarization. Furthermore, the double exposure (two masks) method and advanced polarization control such as azimuthal type 121 were proposed for more complex mask patterns. Representative illumination mode and polarization control methods are shown in Figs. 1 and 2. The effectiveness of hyper NA has been supported by a lot of simulation results.