EUV photoresist performance results from the VNL and the EUV LLC

Abstract

If EUV lithography is to be inserted at the 65-nm node of the 2001 International Technology Roadmap for Semiconductors, beta-tool resists must be ready in 2004. These resists should print 35-65 nm lines on a 130-nm pitch with LER below 4 nm 3δ. For throughput considerations, the sizing dose should be below 4 mJ/cm2. The VNL and EUV LLC resist development program has measured the resolution, LER, and sizing dose of approximately 60 ESCAP photoresists with the 10 X exposure tools at Sandia National Laboratories. The NA of these tools is 0.088, and every resist measured would support the beta-tool resolution requirement if the resolution scales with NA as predicted by optics. 50-nm dense lines have been printed with monopole off-axis illumination, but 35-nm resolution on a 130-nm pitch remains to be demonstrated. Only one photoresist met the LER specification, but its sizing dose of 22 mJ/cm2 is over five times too large. The power spectral density of the roughness of every resist has a Lorentzian line shape, and most of the roughness comes from frequencies within the resolution of the exposure tools. This suggests a strong contribution from mask and optics, but more work needs to be done to determine the source of the roughness. Many resists have sizing doses below the 4 mJ/cm2 target, and neither resolution nor LER degrades with decreasing sizing dose, suggesting that shot noise is not yet affecting the results. The best overall resist resolved 80-nm dense lines (NA = 0.088) with 5.3 nm 3δ LER on 100-nm dense lines at a sizing dose of 3.2 mJ/cm2. Thus, it comes close to, but does not quite meet, the beta-tool resist targets. © 2002 SPIE · 0277-786X/02/$15.00.