157-nm lithography with high numerical aperture lens for sub-70 nm node
For sub-70 nm semiconductor devices, 157 nm lithography using F2 lasers is one of the most important technologies. Several candidates for critical components of 157 nm lithography, such as the exposure tool, resist materials and processing have been reported previously [J. Vac. Sci. Technol. B15 (1997) 2112; Microel. Eng. 6162 (1997) 2112; Jpn. J. Appl. Phys. 41 (2002) 4033]. In this paper, we describe the recent progress of our studies including the use of a micro-stepper with high numerical aperture (NA) lens, phase-shifting masks (PSM), fluoropolymer resists and pattern-transfer processes. As a result, it was confirmed that high NA optics are very effective for improving the resolution limit as well as process margin when combined with phase-shifting masks and high-performance fluoropolymer resists. Moreover, it was found that even higher NA lenses of more than 0.94 NA, in combination with PSM, would be needed for reaching below the 50 nm resolution limit.
157 nm lithography f2 laser phase-shifting mask fluoropolymer resist