12 April 2016 Toward defect-free fabrication of extreme ultraviolet photomasks
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Abstract
Defect-free fabrication of extreme ultraviolet (EUV) masks relies on the appropriate detection of native defects and subsequent strategies for their elimination. Commercial unavailability of actinic mask-blank inspection systems motivates the identification of an optical inspection methodology most suitable for finding relevant EUV blank defects. Studies showed that 193-nm wavelength inspection found the greatest number of printable defects as compared with rival higher-wavelength systems, establishing deep ultraviolet inspections as the blank defectivity baseline for subsequent mitigation strategies. Next, defect avoidance via pattern shifting was explored using representative 7-nm node metal/contact layer designs and 193-nm mask-blank inspection results. It was found that a significant percentage of native defects could be avoided only when the design was limited to active patterns (i.e., layouts without dummy fill). Total pattern-defect overlap remained ≤5 when metal layer blanks were chosen from the top 35% least defective substrates, while the majority of blanks remained suitable for contacts layers due to a lower active pattern density. Finally, nanomachining was used to address remaining native/multilayer defects. Native catastrophic defects were shown to recover 40% to 70% of target critical dimension after nanomachining, demonstrating the enormous potential for compensating multilayer defects.
© 2016 Society of Photo-Optical Instrumentation Engineers (SPIE)
Zhengqing John Qi, Jed H. Rankin, Mark Lawliss, Karen D. Badger, Christina Turley, "Toward defect-free fabrication of extreme ultraviolet photomasks," Journal of Micro/Nanolithography, MEMS, and MOEMS 15(2), 023502 (12 April 2016). https://doi.org/10.1117/1.JMM.15.2.023502 . Submission:
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