4 May 2005 Lithographic importance of acid diffusion in chemically amplified resists
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Since their introduction in the semiconductor industry, chemically amplified resists have proven to offer very valuable benefits to lithography processes, of which improved resist contrast and higher throughput are just two examples. However, the inherent acid diffusion mechanism starts to create some issues. For instance, the reduced chemical contrast due to pronounced acid diffusion during the post-exposure bake will decrease the exposure latitudes and would impact the ultimate resolution. On the other hand, reducing the acid diffusion length will have a negative impact on line edge roughness if one wants to simultaneously keep exposure doses and shot noise effects under control. In this paper, acid diffusion lengths in present-day photoresists at different process conditions are characterized using a lithographic technique. The observed tendencies are correlated with trends in exposure latitude, resolution and the frequency spectrum of line edge roughness. The relationship between acid diffusion length and exposure latitude as well as the relationship between acid diffusion and line edge roughness are addressed in a more fundamental way. The results of this paper highlight the major impact of acid diffusion on important lithographic process characteristics, and the investigated scaling behavior gives guidelines for optimizing exposure latitude and line edge roughness for future technology nodes.
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David Van Steenwinckel, David Van Steenwinckel, Jeroen H. Lammers, Jeroen H. Lammers, L. H. A. Leunissen, L. H. A. Leunissen, J. A. J. M. Kwinten, J. A. J. M. Kwinten, } "Lithographic importance of acid diffusion in chemically amplified resists", Proc. SPIE 5753, Advances in Resist Technology and Processing XXII, (4 May 2005); doi: 10.1117/12.598677; https://doi.org/10.1117/12.598677

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