Photo-assisted wet cleaning of tin contaminants on high-NA EUV masks | SPIE Photomask Technology + EUV Lithography
View presentations details for Photo-assisted wet cleaning of tin contaminants on high-NA EUV masks at SPIE Photomask Technology + EUV Lithography
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The emergence of high-NA EUV lithography has intensified mask 3D effects, necessitating advanced cleaning solutions for next-generation mask components. Removal of tin (Sn) particles is crucial for maintaining mask performance, as Sn is used to generate EUV light and continuously contaminates EUV masks during lithography. This study introduces a photo-assisted wet cleaning technique designed to enhance particle removal efficiency (PRE) on Pt-based high-NA EUV masks. We evaluated the PRE of SnO2 particles deposited on mask surfaces under three conditions: dark, 185 nm UV, and 530 nm illumination during low-temperature sulfuric acid-hydrogen peroxide mixture cleaning. Our results reveal that photon illumination, particularly at 530 nm, significantly improves PRE, with higher illumination intensity further enhancing cleaning performance. Atomic force microscopy was employed to evaluate PRE by measuring the number of particles before and after cleaning. Photo-assisted wet cleaning is a viable approach for overcoming the cleaning limitations associated with high-NA EUV masks, providing a scalable solution for maintaining mask surface integrity and performance.
Real-time observation of EUV-induced blister formation at various sample temperatures in pellicle-like materials | SPIE Photomask Technology + EUV Lithography
View presentations details for Real-time observation of EUV-induced blister formation at various sample temperatures in pellicle-like materials at SPIE Photomask Technology + EUV Lithography
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In this study, we investigated degradation mechanisms on pellicle-like, semi-amorphous, 50 nm SiN thin films exposed to both isolated hydrogen radicals and isolated extreme ultraviolet (EUV) radiation in vacuum at temperatures of 50°C, 120°C, and 300°C. For EUV radiation, real-time, in-situ ellipsometry monitored surface changes without reactive gases, isolating pure EUV photon effects. For isolated hydrogen radical exposure, we have not observed any chemical and morphological changes in the thin films. For isolated EUV photons exposure, results strongly depend on temperature. At 50°C, localized and limited blistering occurred, while exposure at 120°C showed no blister formation due to atomic mobility enhancing self-healing within the amorphous matrix. At 300°C, extensive blistering was driven primarily by stress at the film-substrate interface. Contrary to the conventional idea of gradual blister growth, ellipsometric imaging revealed sudden, varied-size blister formation directly linked to local EUV dosage. In-situ XPS, TOF-SIMS, NRA, optical microscopy and SEM complemented post-exposure analyses. Our findings offer critical insights into degradation mechanisms and blister formation and evolution mechanisms, enhancing the durability and reliability of pellicles and other optical components in EUV lithography, notably for ASML EUV lithography systems.