US Patent 11914288 Photomask having recessed region

A method includes forming a photoresist layer over a wafer. The photoresist layer is exposed to a pattern of radiation using a photomask. The photoresist layer is developed after the photoresist layer is exposed to the pattern of radiation. The photomask includes a substrate and at least one opaque main feature. The substrate has a recessed region recessed from a first surface of the substrate and has a first width. The at least one opaque main feature protrudes from the first surface of the substrate and has a second width greater than the first width of the recessed region of the substrate. A height of the at least one opaque main feature is greater than a depth of the recess region of the substrate.