Nanoscsale particles removal on am Extreme Ultra-Violet Lithography (EUVL) mask layer by lasershock cleaning

Abstract

A new dry laser shock wave generated by Nd:YAG laser was applied to remove the nano sized PSL (Polystyrene latex) particles on the silicon capping layer on EUV mask. UV laser was exposed on the surface before the irradiation of laser shock waves to increase the removal efficiency of organic PSL particles. Due to the expected damages on the surfaces, the energy of UV laser was reduced to 8 mJ and the gap distance between laser shock wave and surface was increased to 10.5 mm. UV irradiation only resulted in 50% removal of particles. Continuous exposure of UV laser to three times increased the removal efficiency to 70%. Over the 95% particle removal efficiency was found when the laser shock wave was combined with UV laser. However, the removal efficiency of the particles was below 25% by laser shock wave cleaning only. Enhanced removal efficiency by UV laser might be attributed to the photo thermal and chemical effects of UV light on organic PSL particles. © 2005 The Electrochemical Society.