<title>Phase-shifting mask fabrication</title>

Abstract

The choice of a fabrication technique for phase-shifting masks is described by comparing approaches in which the shifter patterns are defined by etching the substrate (subtractive approach) or by adding a layer to the substrate (additive approach). By reviewing the various fabrication alternatives, a subtractive methodology that allows the fabrication of any type of phase-shift pattern (alternating aperture, assist-slot, rime, chromeless) on the same mask with only three lithographic steps was adopted. This process was extended to the fabrication of attenuated phase-shifting masks. The current processing capabilities are reviewed.