Patent ID: 7378196

Claim:
A method of manufacturing a mask for use in a photolithographic process, comprising the steps of: providing a mask substrate that is transparent to exposure light of a given wavelength; forming on the mask substrate an isolated pattern feature that is substantially less transparent with respect to the exposure light than the mask substrate, whereby the isolated pattern feature will block a substantial amount of the exposure light when the exposure light is incident on the mask so that an image of the isolated pattern feature will be transmitted by the mask; and forming a plurality of phase shifters in at a first selected region of the substrate located at opposite sides of the isolated pattern feature, the phase shifters being transparent to the exposure light, and wherein the phase shifters are formed directly adjacent and alternately with non-phase shifters that are also transparent to the exposure light, and the thickness of a first transmitting region of the mask where the phase shifters are formed is different from the thickness of a second transmitting region of the mask occupied by the non-phase shifters such that the boundaries between the phase shifters and the non-phase shifters form a dummy pattern at the opposite sides of the isolated pattern feature, whereby when the exposure light is transmitted through the mask, the light transmitted through said first and second transmitting regions will have a phase difference.