Patent ID: 7374865

Claim:
A method for patterning contacts, comprising; illuminating a chromeless phase shift lithography (CPL) mask, the mask comprising a quartz reticle having a pattern of a plurality of phase-shifting features comprising recesses interspersed with non-phase-shifting areas, wherein each recess is to pattern a separate contact wherein the phase-shifting features are to pattern contacts, wherein the CPL mask is illuminated with a deep ultra-violet (DUV) wavelength light source, wherein light passing through the phase-shifting features is phase-shifted one hundred eighty degrees relative to light passing through the non-phase-shifted areas of the CPL mask; and passing the phase-shifted and non-phase-shifted light through projection optics to project an aerial image onto a layer of a negative tone resist applied over a semiconductor substrate to pattern the contacts in the negative tone resist, wherein the contacts are patterned using a single exposure of the DUV wavelength light source.