Laser shock removal of nanoparticles from Si capping layer of EUV mask

As the device design rule rapidly decreases below 50 nm, EUV (Extreme Ultra Violet) lithography is being developed for the next generation lithography technology. In EUV lithography, reflective masks should be used instead of conventional transparent mask. However, EUV mask has no pellicle in order to maintain high reflectivity. EUV masks have to be cleaned at every exposure level to remove the residues or air-bone particles. Conventional RCA wet cleaning including H202 can attack and damage the metal absorber layer. In this paper, a new dry laser shock cleaning has been applied to remove nanoparticles from Si capping layer for EUV reticles.