The World's Highest Resolution EUV mircoscope dedicated to photomask research
Knowing that small variations in the mask pattern, the mask's flatness, and the optical properties of the imaging system can't be avoided, successful lithography relies on what's called the "process window"—it describes how much tolerance a lithography system has to changes in either the exposure level (exposure dose) or focus. When the mask pattern is defective in any way, the process window shrinks, meaning that the system's tolerance to small errors is reduced.
When a mask defect is detected, in the pattern or the multilayer coating, lithographers can turn to one of several repair strategies to repair the problems. The development of these repair strategies is currently the focus of intense research. Since the only way to evaluate and optimize the success of a repair strategy or 'recipe' is to test it with EUV light, there are only two available options. One way to test a repair strategy is to measure the process window in a lithographic printing tool, such as the (SEMATECH Berkeley Micro-Exposure Tool, MET). The other way requires an EUV microscope, such as the AIT, that emulates the behavior of a stepper lens and measures the aerial image directly.
Successful lithography techniques can tolerate small focus and exposure dosechanges (process window). The AIT records data through-focus to evaluate the performance.
Images courtesy Samsung, G. Yoon, and K. Goldberg (LBNL).
Benchmarking. Understanding the images recorded by the AIT relies on careful benchmarking experiments which evaluate the optical performance of the tool. These extensive tests, have also pointed the way toward improving the tool's performance.
Images courtesy Intel, T. Liang, E. Ultanir, and K. Goldberg (LBNL).
Project Funding comes from semiconductor companies, to support the commercialization of EUV lithography in commercial production. We collaborate with equipment suppliers and researchers worldwide.
The mask inspection team consists of Kenneth Goldberg and Anton Barty (LLNL). The SEMATECH project leaders is Hakseung Han (SEMATECH/Samsung) and formerly, Obert Wood (AMD). Project scientists who lend support and guidance include CXRO members, Yanwei Liu, Eric Gullikson, Erik Anderson, and Patrick Naulleau. Expert engineering, design, and technical support comes from Senajith Rekawa (chief engineer) C. Drew Kemp, Robert Gunion, Ron Tackaberry, Jeff Gamsby, Rene Delano, Farhad Salmassi, Paul Denham, and other members of the CXRO technical staff.
"Performance of actinic EUVL mask imaging using a zoneplate microscope," K. A. Goldberg, P. P. Naulleau, A. Barty, S. B. Rekawa, C. D. Kemp, R. F. Gunion, F. Salmassi, E. M. Gullikson, E. H. Anderson, H.-S. Han, SPIE Photomask BACUS 6730, (2007). To be published. [LINK]
"Actinic Inspection of EUV Programmed Multilayer Defects and Cross-Comparison Measurements," K. A. Goldberg, A. Barty, Y. Liu, P. Kearney, Y. Tezuka, T. Terasawa, J. S. Taylor, H.-S. Han, and O. R. Wood II, Journal of Vacuum Science and Technology B 24 (6), 2824-28 (2006). [LINK]
"Multilayer defects nucleated by substrate pits: a comparison of actinic inspection and non-actinic inspection techniques," A. Barty, K. A. Goldberg, P. Kearney, S. B. Rekawa, B. LaFontaine, O. Wood II, J. S. Taylor and H.-S. Han, Proc. SPIE 6349, (2006).
"A dual-mode actinic EUV mask inspection tool," Y. Liu, A. Barty, Proc. SPIE 5751, 660-69 (2005). [LINK]
"Actinic inspection of multilayer defects on EUV masks," A. Barty, Y. Liu, K. A. Goldberg, Proc. SPIE 5992, October (2005), presentation only.
To learn more about this research, please browse the publication list where a number papers are available, view slides from recent public presentations, or contact Kenneth A. Goldberg. Wikipedia.org has entries for photolithography, reticle, and zoneplate.
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