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

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 (SnO 2 ) 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 …