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8 April 2011 EUVL dark-field exposure impact on CDs using thick and thin absorber masks
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When compared to a thick absorber mask, a thin absorber EUV mask is expected to have a comparable process window, a reduced shadowing effect, and lower MEEF. However, regardless of the mask absorber thickness, the dark-field in EUV lithography is never 100% dark. Using the same absorber stack composition, EUV masks with thinner absorbers have inherently higher leakage due to the background transmission propagating through the absorber stack. While this does act to improve resist sensitivity or throughput, the leakage reduces the image contrast and can cause CD degradation in "double" exposed regions at the edge of adjacent fields. In this study, EUVL lithographic benchmarking of both thin and thick absorber masks on the ASML Alpha Demo Tool (ADT) at IMEC is presented. Herein, we experimentally quantify the process window, EL, LWR, MEEF, Esize, ultimate resolution, and impact of dark-field background exposures on CDs for both thin and thick absorber masks. There are additional issues when field edges overlap with adjacent fields, and mitigation strategies for EUV leakage emanating from dark-field regions are discussed.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Sang H. Lee, Todd R. Younkin, Michael J. Leeson, Manish Chandhok, Guojing Zhang, John Magana, Hiroyoshi Tanabe, and Steve L. Carson "EUVL dark-field exposure impact on CDs using thick and thin absorber masks", Proc. SPIE 7969, Extreme Ultraviolet (EUV) Lithography II, 79691R (8 April 2011);


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