High precision monitoring of outgassing species in model EUV photoresists with a cavity ring-down spectrometer
Publication Date
1-1-2025
Document Type
Conference Proceeding
Publication Title
Proceedings of SPIE the International Society for Optical Engineering
Volume
13428
DOI
10.1117/12.3050524
Abstract
Background: Extreme ultraviolet (EUV) photoresists play a pivotal role in advancing nanopatterning technologies by balancing image quality and sensitivity. The outgassing behavior of photoresist thin films under EUV and deep ultraviolet (DUV) exposure reveals chemical details relevant to their performance. Goal: This study focuses on utilizing an analytical technique not previously used in photolithography, the tabletop cavity ring-down spectrometer, to investigate outgassing dynamics in EUV photoresists, enabling precise chemical identification and deeper insights into resist processing. Approach: The spectrometer's enhanced laser path length (~20 km) and broadband absorption capabilities in the CH overtone region allow for sensitive and temporally resolved detection of outgassed species. Using a model resist comprising a polymer matrix with a photoacid generator and quencher, we analyzed the influence of time delays between exposure and post-exposure bake (PEB) as well as storage under varying environmental conditions. Results: Suppression of isobutylene outgassing and thickness loss was observed with extended delays between exposure and PEB, potentially linked to water absorption and acid deactivation. The technique proved highly effective in distinguishing subtle chemical differences between processing stages. Conclusion: Delay times and their environmental conditions, particularly humidity, reduce outgassing and thickness loss of photoresists during PEB, suggesting decreased acid-driven deprotection. This can potentially impact sensitivity, defectivity, and roughness of resist patterns, necessitating precise monitoring and control.
Funding Number
DE-AC02-05CH11231
Funding Sponsor
U.S. Department of Energy
Keywords
cavity ring down spectroscopy, EUV photoresists, EUV-induced chemistry, outgassing, resist characterization
Department
Chemical and Materials Engineering
Recommended Citation
Bernhard Lüttgenau, Caleb Arata, Honggu Im, Maximillian Mueller, Dahyun Oh, Oleg Kostko, Laura McHale, Chris Rella, John Hoffnagle, and Frances Houle. "High precision monitoring of outgassing species in model EUV photoresists with a cavity ring-down spectrometer" Proceedings of SPIE the International Society for Optical Engineering (2025). https://doi.org/10.1117/12.3050524
