Patent ID: 6986972

Claim:
A method for fabricating an alternating aperture phase-shift mask, the method comprising: providing a optically transparent substrate having an opaque pattern formed thereon, the opaque pattern defining a pattern of phase-shift regions on the substrate; damaging the phase-shift regions of the substrate by implanting ions into the phase-shift regions of the substrate to a selected implantation depth, the damaged material of the phase-shift regions being more easily etched than undamaged portions of the substrate the ion implantation further comprising implanting ions into the phase-shift regions of the substrate at an angle so that the damaged material in the phase-shift region undercuts portions of the opaque pattern; and removing damaged material from the phase-shift regions to a predetermined depth associated with the selected implantation depth, thereby forming phase-shift recesses having the predetermined depth in the phase-shift regions thereby forming an alternating aperture phase-shift mask.