28 May 2004 Customized illumination schemes for critical layers of 90-nm node dense memory devices in ArF lithography: comparison between simulation and experimental results
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Abstract
Current 90nm Flash memory design introduces imaging critical points in several devices levels: active, poly, contacts, and first metallization. Among standard Resolution Enhancement Techniques (RET), Off-axis illuminations play a fundamental role, because they are capable of providing better imaging contrast and improved process latitude in low K1 regime with very dense structures. Starting from the simulation study of real device layer geometries, object of this work is to propose a solution in terms of illumination schemes and mask choice (binary or halftone) for each critical layer, considering K1 around 0.35 in ArF lithography. Dedicated off-axis illuminations will be compared to standard illumination modes, underlining the benefits in terms of ultimate resolution, process window and line edge roughness improvement. Experimental data confirmed the predicted gain in process robustness and, as expected, showed great line edge roughness improvement and less marginality to pattern collapse.
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Gianfranco Capetti, Maddalena Bollin, Annalisa Pepe, Gina Cotti, Sara Loi, Umberto Iessi, "Customized illumination schemes for critical layers of 90-nm node dense memory devices in ArF lithography: comparison between simulation and experimental results", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004); doi: 10.1117/12.533707; https://doi.org/10.1117/12.533707
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