Patent ID: 8293430

Claim:
A method of forming a photomask, comprising: providing a film stack in a processing chamber, the film stack having an optically transparent silicon based material having a molybdenum layer disposed thereon, a patterned light-shielding layer disposed on the molybdenum layer and a composite mask having at least a patterned first photoresist layer, wherein the patterned light shielding layer comprises a plurality of structures between a plurality of first openings in the light shielding layer exposing the molybdenum layer; plasma etching the molybdenum layer to form a molybdenum layer opening exposing the optically transparent silicon based material using the composite mask, wherein the plasma etching the molybdenum layer further comprises depositing a conformal polymer layer on the patterned first resist layer prior to forming the patterned light shielding layer; depositing a second photoresist layer on the light-shielding layer; patterning the second photoresist layer on a the light-shielding layer, wherein the second photoresist layer fills the molybdenum layer opening after patterning and wherein the second photoresist layer defines a plurality of second openings at a center portion of each of the plurality of structures; and plasma etching the light-shielding layer using the second photoresist layer as an etch mask to form the plurality of second openings exposing the molybdenum layer.