Iodinated underlayer for enhanced chemically amplified resist performance

초록

High-numerical-aperture (NA) extreme ultraviolet lithography (EUVL) is essential for next-generation semiconductor manufacturing, requiring advanced photoresists (PRs) that can function effectively in ultra-thin films. However, ultra-thin PR films-primarily needed to meet stringent depth-of-focus constraints-face several challenges, including low photon absorption and reduced etch resistance. Additionally, as feature sizes shrink, the diminished PR-substrate contact area exacerbates pattern collapse issues in high NA EUVL. To mitigate these challenges, underlayers are increasingly employed to enhance patterning performance. In this study, we propose a supportive underlayer (SUL) to enhance the sensitivity of chemically-amplified photoresists (CARs) and improve adhesion between the CAR film and the SUL. As a preliminary step, we introduced a simple experimental protocol to identify high-absorption elements that could be more effective in the CAR system, exploiting a PR film-overcoat bi-layer structure. Overcoats containing hydrogen (H), iodine (I), and tin (Sn) were readily prepared on top of the CAR film by the help of solvent orthogonality. Our findings revealed that iodine atoms significantly reduced the exposure threshold compared to hydrogen or tin. Based on these results, hydrophobic iodinated materials were selected as SUL candidates, and a few materials were synthesized with different iodine contents. After fabricating the bi-layer stack, we evaluated the solubility changes of PR films under both positive- and negative-tone development (PTD and NTD) conditions. The incorporation of an iodinated SUL beneath the CAR films enhanced both lithographic sensitivity and substrate adhesion, regardless of the development type, with higher iodine content further amplifying these effects. These findings provide a promising pathway for implementing EUV underlayers specifically tailored for high-NA EUVL. © 2025 SPIE.

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