Depth Profiling Chemical Changes in Chemically Amplified Resists for EUV Lithography

Published

July 1, 2026

Author(s)

Daniel Sunday, Peter Dudenas, Priyanka Ketkar, Julia Murphy, Cherno Jaye, Regis Kline, Gurpreet Singh, Eungnak Han, Lauren Doyle, Florian Gstrein

Abstract

Photoresist patterning for semiconductor manufacturing is encountering new challenges with the move the extreme ultraviolet (EUV) lithography, driven by smaller pitches, thinner resists and fewer photons. Obtaining information about the nanoscale distribution of chemical changes in the resist will provide key information to optimize processing and resist development. Soft X-rays provide sensitivity to chemical functional groups at key atomic absorption edges, including carbon, oxygen and fluorine. By conducting specular reflectivity measurements at these energies we can track the chemical depth profiles in a resist. This process is demonstrated by characterizing the optical constant profiles (which are proportional to the concentration of chemical bonds in a film at soft X-ray energies) of an EUV resist coated on a cross-linked polystyrene (XPS) mat. The resist was exposed to blanket exposures with different doses and measured at different stages of the process, including post-exposure but before the bake, after the post-exposure bake, and after development. Segregation of resist components was observed in the as-case films, with a fluorinated component aggregating at the film surface. Stratification of the chemical changes that occur in the film is observed after exposure, but before the bake and the magnitude of this stratification is dose dependent. After a post-exposure bake the stratification is no longer observed and the optical constant profile is uniform with the exception of the fluorinated components. These results are complemented by near edge X-ray absorption fine structure (NEXAFS) spectroscopy obtained with an imaging microscope. Finally, we also examine the XPS mat before and after the process, and observe evidence for chemical changes in the XPS, with the possibility of residual resist components residing in the film after development.

Citation

Journal of Micro/Nanopatterning, Materials, and Metrology

Pub Type

Journals

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Citation

Sunday, D. , Dudenas, P. , Ketkar, P. , Murphy, J. , Jaye, C. , Kline, R. , Singh, G. , Han, E. , Doyle, L. and Gstrein, F. (2026), Depth Profiling Chemical Changes in Chemically Amplified Resists for EUV Lithography, Journal of Micro/Nanopatterning, Materials, and Metrology, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=960706 (Accessed September 1, 2026)

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