Phase Defect Repair Method for Alternating Phase Shift Masks Conjugate Twin-Shifter Method

Abstract

Phase shift masks (PSMs) enable current optical exposure systems to provide significantly higher resolution in effective depth of focus (DOF). Localized phase errors, or other transparent defects in the mask phase shifter elements, can cause loss of DOF and degradation of image contrast. Transparent defects of this type have prevented PSMs from becoming practical for large-scale production of integrated circuits containing deep submicrometer features. This paper describes a new technique that is useful for repairing Alternating PSMs containing transparent defects in the phase shifter elements.