| 摘要 |
A method for forming a defect-free phase shift mask includes forming a mask blank having a substrate, an etch stop layer, a phase shift layer and an opaque layer. The etch stop layer and phase shift layer are formed of chemically different materials to allow selective etching and end point detection. Initially the opaque layer is patterned and etched using a process such as e-beam lithography. Then the phase shift layer is patterned and etched using the etch stop layer as an end point. Bump defects formed in phase shift areas are then removed by exposing a resist layer to leave the phase shifters, or alternately just the defects, unprotected. During defect etching, the etch stop layer can again be used to endpoint the etch process. The etch stop layer can also be formed as a phase shift layer to permit removal of indentation defects using a process such as ion milling.
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