Patent ID: 7883822

Claim:
A method of fabricating a gray scale photomask usable for patterning a radiation sensitive layer in a lithography process in the manufacture of a semiconductor device, comprising: providing a transparent substrate; forming a layer of phase shift material over the transparent substrate; patterning the layer of phase shift material to form first openings having first side edges; forming a patterned etch mask over the patterned layer of phase shift material; the patterned etch mask having second openings encompassing the first openings, the second openings having second side edges pulled back from the first side edges to expose top edges and the first side edges of the patterned layer of phase shift material; and etching the exposed top edges and first side edges of the patterned layer of phase shift material using a wet etch to undercut the second side edges and form the exposed first side edges into tapered edges, the tapered edges having a graded transparency.