ArF Immersion Lithography Using TWINSCAN Technology

For 193-nm lithography, water proves to be a suitable immersion fluid. ArF immersion offers the potential to extend conventional optical lithography to the 45-nm node and potentially to the 32-nm node. Additionally, with existing lenses, the immersion option offers the potential to increase the focus window with 50% and more, depending on actual NA and feature type. In this paper we discuss the results on imaging and overlay obtained with immersion. Using a 0.75 NA ArF projection lens, we have built a proto-type immersion scanner using TWINSCANTM technology. First experimental data on imaging demonstrated a large gain of depth of focus (DOF), while maintaining image contrast at high scan speed. For first pilot production with immersion, a 0.85 NA ArF lens will be used. The resolution capabilities of this system will support 65 nm node semiconductor devices with a DOF significantly larger than 0.5 μm. Early imaging data of such a system confirms a significant increase in focus window.