The dissociative photoionization of tert-butyl methyl methacrylate, a monomer unit found in many ESCAP resists, was investigated in a gas phase photoelectron photoion coincidence experiment employing extreme ultraviolet (EUV) synchrotron radiation at 13.5 nm. It was found that the interaction of EUV photons with the molecules leads almost exclusively to dissociation. However, the ionization can also directly deprotect the ester function, thus inducing the solubility switch wanted in a resist film. These results serve as a building block to reconstruct the full picture of the mechanism in widely used chemically amplified resist thin films, provide a knob to tailor more performant resist materials, and will aid interpreting advanced ultrafast time-resolved experiments.

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Marziogiuseppe Gentile, Marius Gerlach, Robert Richter, Michiel J. van Setten, John S. Petersen, Paul van der Heide, and Fabian Holzmeier, "Dissociative photoionization of EUV lithography photoresist models," Proc. SPIE 12498, Advances in Patterning Materials and Processes XL, 124980S (Presented at SPIE Advanced Lithography + Patterning: March 01, 2023; Published: 30 April 2023); https://doi.org/10.1117/12.2657702.