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1 April 2008 Immersion exposure system using high-index materials
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ArF water immersion systems with a numerical aperture (NA) of over 1.3 have already introduced for the node up to 45- nm half-pitch production. For the next generation of lithography, we focus on ArF immersion lithography using high-index materials. At present, LuAG (n=2.14) is the most promising candidate as a high-index lens material. Second-generation fluids (n=1.64) have the sufficient performance as a high-index immersion fluid. The combination of LuAG and a second-generation fluid can enhance the NA up to 1.55 and the exposure system would be available for the 34-nm half-pitch node when k1 is 0.27. Although high-index immersion lithography is attractive since it is effective in raising resolution, there are some issues not encountered in water immersion system. The issues of LuAG are its availability and the intrinsic birefringence. Fluid degradation induced by dissolved oxygen or laser irradiation, lens contamination, and residual fluid on a wafer are the specific issues of the immersion system. In this article, we introduce the current status for the above issues and discuss the feasibility of ArF immersion system using high-index materials.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Keita Sakai, Yuichi Iwasaki, Sunao Mori, Akihiro Yamada, Makoto Ogusu, Keiji Yamashita, Tomofumi Nishikawara, Takatoshi Tanaka, Noriyasu Hasegawa, Shin-ichi Hara, and Yutaka Watanabe "Immersion exposure system using high-index materials", Proc. SPIE 6924, Optical Microlithography XXI, 69242H (1 April 2008);

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