Extreme Ultra-Violet Lithography (EUVL) keeps hurting my brain. Just when I can understand how it could be used in profitable commercial high-volume manufacturing (HVM) I hear something that seriously strains my brain. First it was the mirrors and mask in vacuum, then it was the resist and pellicle, then it was the source power and availability, and in each case scientists and engineers did amazing work and showed a way to HVM. Now we hear that EUVL might require fabs to park work-in-progress (WIP) lots of wafers behind a single critical tool with an idealistic 80% availability on a good day, and lots of downtime bad days. Horrors!
For “5nm-node” designs the maximum allowable edge placement-error (EPE) in patterning overlay is only 2nm. While the physics of ~13.5nm wavelength EUVL means that aberration in the reflecting mirrors appears as up to 3nm variation in the fidelity of projected patterns. This variation can be measured and compensated for at the physical mask level, but then each mask would only be good for one specific exposure tool. John Sturtevant—SPIE Fellow, and director of RET product development in the Design to Silicon Division at Mentor Graphics—briefly discussed this on February 26th during Nikon LithoVision held just before SPIE Advanced Lithography.
Sturtevant explained that the Zernike coefficients for EUV are inherently almost 1 order-of-magnitude higher than for DUV at 193nm wavelength, as detailed in the SemiMD article “Edge Placement Error Control in Multi-Patterning.” How the inherent physical sources of aberration must be tightened to avoid image distortion and contrast loss as they scale with wavelength was discussed by by Fenger et al. in 2013 in the article “Extreme ultraviolet lithography resist-based aberration metrology” (doi:10.1117/1.JMM.12.4.043001).
Donis Flagello, president, CEO, and COO of Nikon Research Corporation of America (NRCA), will be presented with the 2017 Frits Zernike Award for Microlithography on Monday 27 February during SPIE Advanced Lithography in San Jose, California. The award, presented annually for outstanding accomplishments in microlithography technology, recognizes Flagello’s leading role in understanding and improving image formation in optical lithography for semiconductor manufacturing.
A prominent member of the industry since the early 1980s and a longtime SPIE Fellow, Flagello has primarily focused on the rigorous application of physics to lithography modeling and problem solving. Early in his career, while at IBM T.J. Watson Research Center, he developed the first practical test for measuring flare in optical lithography tools and made major contributions to high numerical aperture (NA) modeling including vector and polarization effects, and radiometric correction. At ASML he played an important role in providing analysis of aberrations for new systems and high-NA imaging effects due to polarization.
Another notable aspect of his career, Flagello’s presentations at lithography conferences and papers in various journals have inspired a better understanding of optics and resist behavior and helped drive optical lithography forward, colleagues said. “His presentations are known for their combination of humor with a deep understanding of the complex interactions between physical optics and lithographic process technology,” said David Williamson, an NRCA Fellow and previous Frits Zernike Award winner. “His combined theoretical and practical production experience and knowledge are rare in this field.”