Processing of photomask

摘要

A laser beam of a pulse width 10 to 20 nanoseconds is irradiated and scanned relatively and two-dimensionally on a metal thin film formed on a transparent substrate from the transparent substrate side and through the transparent substrate with a superposition number of laser beam spots set up to at most 15 and to thereby remove a predetermined region of the metal thin film. The irradiated metal film begins to melt from the substrate side and is removed away explosively from the substrate, leaving the substrate substantially unaffected.