Characterizing extreme ultraviolet photoresists using a tabletop source

The semiconductor industry is continually looking for ways to shrink device sizes and produce finer features. Often, that means employing higher-energy lasers with shorter wavelengths, which necessitates new resist materials to interact with them.

For extreme ultraviolet (EUV) lithography, developing new resists often means rare and costly time at a synchrotron source. Flores et al. employed a tabletop EUV source to characterize ZEP520A, an electron beam resist, for use in EUV applications.

“The key barrier [to developing a new EUV resist] is the turnaround time in testing of new resist chemistry,” said author Ethan Flores. “Tabletop systems can help rapidly test materials for EUV development.”

Their tabletop testing suite features a tabletop high-harmonic generation EUV source using an ultrafast laser, along with a confocal microscope and an atomic force microscope to probe the topography of the resist surface, characterize resist thickness, and estimate clearing dose and contrast. Although their equipment is less powerful than a synchrotron source, it is vastly more accessible.

“Unlike a synchrotron, which delivers EUV at higher power and can expose large areas, our system has lower flux,” said Flores. “Therefore, our pattern area is relatively small (100 µm range) but is sufficiently large to perform meaningful resist characterization tests.”

Using their equipment, they found that ZEP520A exhibits a clearing dose of 35.4 mJ/cm² and a contrast of 2.9 at 30 nm wavelength, making it well-suited to EUV lithography.

The authors plan to use their new testing protocol to evaluate open-source EUV resists to benchmark their results against tests performed with synchrotron sources. They hope that their approach will increase the availability of new EUV resist materials.

Source: “Photoresist characterization using a tabletop extreme ultraviolet source at 30nm wavelength,” by Ethan Flores, Saurav Mohanty, Richard Mitchell, Andrew Tunell, Mehmet Kepenekci, and Chih-Hao Chang, Journal of Vacuum Science and Technology B (2025). The article can be accessed at https://doi.org/10.1116/6.0004950 .

This paper is part of the Papers from the 68th International Conference on Electron, Ion and Photon Beam Technology and Nanofabrication (EIPBN 2025) Collection, learn more here .