Improving the Particle Removal Efficiency of Sn Contaminants on High-NA EUV Masks via Photo-Assisted Wet Cleaning

<!-- START_ABSTRACT --> <p> The advent of high-numerical aperture (NA) extreme-ultraviolet (EUV) lithography has increased the need for advanced cleaning technologies because novel mask architectures have been developed to mitigate mask 3D effects. This study introduces photo-assisted wet cleaning, in which enhanced particle removal efficiency (PRE) without damage to the mask surface was achieved by integrating low-temperature wet cleaning with stimulated desorption. Tin dioxide (SnO2) nanoparticles (NPs) were deposited on a high-NA mask surface to simulate Sn contaminants originating from an EUV light source. Room-temperature sulfuric acid–hydrogen peroxide mixture (RT-SPM) cleaning demonstrated a higher PRE in photo-assisted wet cleaning than that using SC-1 solution owing to its extremely low pH, which maximizes electrostatic repulsion. Photo-assisted wet cleaning in RT-SPM under 530 nm visible light achieved a PRE 7.5 and 2.0 times higher than those of conventional wet cleaning under dark conditions and photo-assisted wet cleaning under 185 nm UV, respectively. The dependence of the PRE on the photon flux indicates that SnO2 NPs are physisorbed on the mask surface via weak van der Waals interactions. This study enhances the sustainability of high-NA EUV masks during repeated EUV lithography by demonstrating photo-assisted wet cleaning, contributing to a deeper understanding of Sn contaminant–mask surface interactions. </p> <!-- END_ABSTRACT --> <!-- START_TEMPLATE --> <ul> <li> Source: </li> <li> Tags: </li> </ul> <!-- END_TEMPLATE -->