Photoresist characterization using a tabletop extreme ultraviolet source at 30 nm wavelength

In this paper, we investigate the viability of using ZEP520A, a commercially available electron-beam photoresist, as a positive resist for extreme ultraviolet (EUV) lithography at 30 nm wavelength. The resist characterization was performed using a tabletop, high-harmonic-generation EUV source driven by an ultrafast laser. The source produces an elliptical beam at focus, modeled as a Gaussian intensity profile to analyze the exposure dose distribution. A comprehensive protocol was developed, employing confocal microscopy to generate topography maps and extract critical dimensions of the patterned resist. AFM (atomic force microscopy) was subsequently used to measure postdevelopment resist thickness and refine estimates of the clearing dose and contrast, modeled with a binary resist approach. Experimental results show that ZEP520A exhibits a clearing dose of 35.4 mJ/cm2 and a contrast of 2.9 at 30 nm wavelength, supporting its application in EUV lithography. These findings demonstrate that ZEP520A can serve as an effective EUV resist and that a tabletop EUV source provides a practical platform for material characterization in next-generation lithography development.