First Stage Of Nanoscale Imaging In Positive-Tone EUV Photoresists: The Impact Of Polymer Sequence (Berkeley Lab, Columbia Hill)

A new technical paper titled “Initial stage of nanoscale imaging in positive-tone extreme UV photoresists: the influence of polymer sequence” was published by researchers at Lawrence Berkeley National Laboratory and Columbia Hill Technical Consulting.

Abstract
“Photolithographic patterning using extreme ultraviolet (EUV, 92.5 eV) light is a radiolytic process that initially forms electrons, radical cations, anions and neutral radicals in the polymeric photoresist matrix. These species may participate in the chemical reactions that define the ultimate resolution of the printed image, and their concentrations and nm-scale stochastic variations in their formation influence printed image quality. Proposals have been made that polymer chain uniformity may be advantageous in reducing stochastics due to spatial inhomogeneities, and it is this aspect of the radiolysis examined in this work. We have simulated the initial sub-picosecond stages of the imaging process for a series of photoresist films that are identical in composition but vary in their polymer chain structures. We use detailed, physically accurate stochastic reaction-diffusion calculations to evaluate the influence of defined sequence and random copolymer structures on radiolytic spur formation, i.e. a cluster of species formed by electron-polymer interactions that defines the initial spatial characteristic of the imaging process. Predictions of electron thermalization in the present work are shown to be consistent with the literature, indicating that our overall computational approach for ultrafast, nanoscale processes is sound. The computational results show that the polymer sequence has no significant effect on spur composition. This suggests that any potential imaging improvements to be gained by sequence control must originate from post-imaging lithographic process steps.”

Find the technical paper here. October 2025. (Preprint)

Houle, Frances, William Hinsberg, Jacob Milton, Qi Zhang, Cheng Wang, and Samuel Blau. “Initial stage of nanoscale imaging in positive-tone extreme UV photoresists: the influence of polymer sequence.” (2025). Creative commons license.