EUV photoresist performance results from the VNL and the EUV LLC

摘要

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 3σ. For throughput considerations, the sizing dose should be below 4 mJ/cm~2. The VNL and EUV LLC resist development program has measured the resolution, LER, and sizing dose of approximately 60 ESCAP photoresists with the 10X 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/cm~2 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/ cm~2 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 3σ LER on 100-nm dense lines at a sizing dose of 3.2 mJ/cm . Thus, it comes close to, but does not quite meet, the beta-tool resist targets.