| Citation: | HU Jin-ze, LI Jie, HU Jian, LI Hao, CHEN Jin-ping, GUO Xu-dong, KE Chang-jun, HAN Shenghui, YANG Guo-qiang, FAN Zhong-wei. A resolution enhancement method for line gratings based on inverse calculation of diffraction fringes[J]. Chinese Optics. doi: 10.37188/CO.2026-0009
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To enable low-cost and efficient characterization of EUV photoresists, a lithographic evaluation system based on a tabletop high-harmonic generation (HHG) source and a reflective interferometer was developed. High-order harmonics were generated in argon using a 515 nm femtosecond laser. After focusing by a toroidal mirror and spectral dispersion by a blazed grating, the 11th harmonic (46.8 nm) was selected through a slit as the EUV source. Nonchemically amplified resists based on oxime sulfonate-functionalized polystyrene (PSOS) were used as the test material, and interference exposure was performed with a Lloyd’s mirror and a symmetric dual-mirror configuration. To solve the alignment problem between the sample plane and the symmetric dual-mirror interferometer, an optical ranging method based on diffraction-fringe inversion was proposed, enabling precise positioning of the symmetric dual-mirror interferometer. The results show that the Lloyd’s mirror produces clear high-contrast line-space patterns with a period of 125 nm and enables characterization of the tested resist at the 100 nm scale. After precise positioning by diffraction-fringe inversion, the symmetric dual-mirror configuration produces line-space patterns with a period of 60 nm, significantly improving the system resolution. This evaluation system provides a low-cost and scalable experimental platform for rapid screening of photoresist materials, investigation of resolution limits, and development of related lithographic processes.
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