20 August 2004 Global CD uniformity improvement for CAR masks by adaptive post-exposure bake with CD measurement feedback
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Proceedings Volume 5446, Photomask and Next-Generation Lithography Mask Technology XI; (2004) https://doi.org/10.1117/12.557714
Event: Photomask and Next Generation Lithography Mask Technology XI, 2004, Yokohama, Japan
Abstract
Progress towards 65nm next-generation lithography requires unprecedented global CD uniformity, with the actual ITRS 2002 roadmap proposing 4.2nm 3σ (dense lines) for 65nm binary masks. Since resolution requirements are satisfied only by using chemically amplified resists (CARs), exposure and post-exposure bake (PEB) are key processes to successful mask making, both introducing global CD errors. Develop and etch processes potentially contribute further global CD errors. The global CD uniformity can be improved significantly by adaptive PEB, especially for CARs showing moderate to strong PEB sensitivity, like NEB22. With the 25-zone hotplate of the APB5500 bake system, facilitated through a novel calibration mask with 25 equidistant temperature sensors within the resist plane, an appropriate temperature profile can be applied during PEB. This temperature profile is automatically calculated by an adaptive optimization algorithm, based on 2-dimensional spline fitting of a CD measurement. A CD-uniformity improvement (dense lines) from 3.80nm 3σ to 3.06nm 3σ (~20%) is achieved on evaluation photomasks with an 11x11 CD measurement grid.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lothar Berger, Werner Saule, Peter Dress, Thomas M. Gairing, C.-J. Chen, Hsin-Chang Lee, Hung-Chang Hsieh, "Global CD uniformity improvement for CAR masks by adaptive post-exposure bake with CD measurement feedback", Proc. SPIE 5446, Photomask and Next-Generation Lithography Mask Technology XI, (20 August 2004); doi: 10.1117/12.557714; https://doi.org/10.1117/12.557714
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