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AssigneeCymer, Inc.
InventorsXiaojiang J. Pan, Richard G. Morton, Alexander I. Ershov
Estimating the term…
An overcoat protected diffraction grating. A replica grating having a thin aluminum reflective grating surface is produced by replication of a master grating or a submaster grating. The thin aluminum reflective surface may be cracked or have relatively thick grain boundaries containing oxides and hydroxides of aluminum and typically is also naturally coated with an aluminum oxide film. The grating is subsequently overcoated in a vacuum chamber with one or two thin, pure, dense aluminum overcoat layers and then also in the vacuum the aluminum overcoat layer or layers are coated with one or more thin protective layers of a material transparent to ultraviolet radiation. In preferred embodiments this protective layer is a single layer of MgF2, S1O2 or Al2O3. In other preferred embodiments the layer is a layer of MgF2 or S1O2 covered with a layer of Al2O3 and in a third preferred embodiment the protective layer is made up of four alternating layers of MgF2 and Al2O3 or four alternating layers of S1O2 and AL2O3 Preferably, the thickness of the transparent protective layers are chosen to produce a phase shift at the proposed operating wavelengths of an integral number of 27π.
A process for coating a replica of a diffraction grating defining a grating surface having grooves defining reflective faces, said process comprising:
An overcoat protected diffraction grating having a large number of parallel grooves, each groove having a reflective face, said grating comprising:
A line narrowing module as in claim 32 wherein said protective layer is configured to produce a phase shift in 193 nm ultraviolet light of an integral number of 2π.
A line narrowing module for an ArF laser comprising:
Dependencies are inferred from the claim text.