Recent progress in developing an extreme ultraviolet full-field exposure tool at Selete

The Selete full-field EUV exposure tool, EUV1, manufactured by Nikon, is being set up at Selete. Its lithographic performance was evaluated in exposure experiments with a static slit using line-and-space (L&S) patterns, Selete Standard Resist 03 (SSR3), a numerical aperture of 0.25, and conventional illumination (σ=0.8). The results show that 25-nm L&S patterns were resolved. Dynamic exposure experiments demonstrate that the resolution is 45 nm across the exposure field. The CD uniformity across a shot is 3 nm. Evaluation of the overlay performance of the EUV1 using alignment marks on a processed wafer revealed the repeatability to be better than 1 nm. The overlay accuracy obtained with enhanced global alignment was less than 4 nm (3σ) after linear correction. These results show that the EUV1 has attained the quality level of a typical alpha-level lithography tool and is suitable for test site verification.