EUV mask substrate flatness improvement by laser irradiation

摘要

We demonstrate a new technique for improvement of the flatness of the EUV mask substrate by using a pulsed laser. Laser pulses from an ArF excimer laser were focused inside a quartz mask substrate to make spots. Experiments showed that the substrate surface was locally swelled out where spots were formed just beneath the surface without making any damages on the surface. This surface shape control technique can be applied to the final adjustment of the substrate flatness control since no cleaning process is necessary afterward.