20 October 2006 Precise and high-throughput femtopulse laser mask repair of large defects
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Abstract
As mask complexity has increased and design rules continued to shrink, the manufacturing cost per mask has steadily increased as well. Studies also show that defects are the number one issue for mask yield. Smaller defects are typically addressed through process development, or through photomask repair. The occurrence of large defects often may only be further reduced through use of expensive clean room improvements, like SMIF handling systems. The impact of each large defect therefore increases while the feasibility in their repair decreases as they can span a large number of adjoining densely packed patterns. The presence of sub-resolution features such as scatter bars and the increasing use of embedded phase-shifting masks also complicates the timely repair of such defects. Existing mask repair techniques such as nanomachining, electron beam, or focused ion beam are challenged to produce high yield repairs on such large defects within a reasonable timeframe. Often very complex repairs may in fact take longer than a rewrite of the mask! Deep UV (DUV) femtosecond pulse laser mask repair provides a unique solution to this defect repair need. Methods and results are discussed for the process optimization for the removal of large (5μm) area repair on both Cr and MoSi absorber films on quartz. Additionally, high repair throughput results are shown for unknown contamination removal, and reproduction of ≥1 μm complex unconnected patterns in a single repair run lasting a matter of minutes. Closed-loop CD feedback in-situ with the iterative repair process for such structures can readily result in an edge placement control within ±15 nm. Prior iterative CD closed-loop repairs on specific structures have reliably yielded results within ±10 nm, as confirmed by AIMS CD error, even after aggressive mask wet clean. The nanometer scale dimensional resolution and repeatability of such repairs is shown with the use of sub-pixel resolution automated pattern reconstruction using integrated high-NA DUV microscope imaging.
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Roy White, Roy White, Jeff LeClaire, Jeff LeClaire, Tod Robinson, Tod Robinson, Andrew Dinsdale, Andrew Dinsdale, Ron Bozak, Ron Bozak, David A. Lee, David A. Lee, } "Precise and high-throughput femtopulse laser mask repair of large defects", Proc. SPIE 6349, Photomask Technology 2006, 63494F (20 October 2006); doi: 10.1117/12.686361; https://doi.org/10.1117/12.686361
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