Photomask having line end phase anchors

Abstract

A photomask and a method for making the same in which an opaque feature (38) is formed on a transparent substrate (32) and a depression (44) is etched in the transparent substrate (32) adjacent to the opaque feature (38). The depression (44) is etched to a depth such that a phase difference between light passing through the substrate (32) outside the depression (44) and light passing through the depression is 180°. In one embodiment, the depression (44) is formed in the substrate directly adjacent to an edge of the opaque feature (38). In another embodiment, the depression (58) surrounds a mesa structure (59) formed in the substrate (50), and the opaque feature (62) resides on the mesa structure (59). The depression (58) may be laterally spaced from an edge of the opaque feature (62).

Dependencies are inferred from the claim text.