Figure correction of multilayer coated optics
AssigneeThe Regents of the University of California
InventorsHenry N. Chapman, John S. Taylor
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Abstract
A process is provided for producing near-perfect optical surfaces, for EUV and soft-x-ray optics. The method involves polishing or otherwise figuring the multilayer coating that has been deposited on an optical substrate, in order to correct for errors in the figure of the substrate and coating. A method such as ion-beam milling is used to remove material from the multilayer coating by an amount that varies in a specified way across the substrate. The phase of the EUV light that is reflected from the multilayer will be affected by the amount of multilayer material removed, but this effect will be reduced by a factor of 1−n as compared with height variations of the substrate, where n is the average refractive index of the multilayer.
Claims30
A method for correcting the figure of a multilayer coated substrate, comprising removing at least a portion of a multilayer coating from a multilayer coated substrate by an amount needed to mitigate surface height error.
An apparatus for correcting the figure of a multilayer coated substrate, comprising:
- an interferometer for measuring the figure of a multilayer coated substrate with a surface that has a height error;
- and
- a mechanism for removing material from the multilayer of said multilayer coated substrate.
The apparatus of claim 25, wherein said apparatus for depositing energy comprises a laser.
The apparatus of claim 25, wherein said apparatus for depositing energy comprises an ion beam source.
The apparatus of claim 25, wherein said apparatus for depositing energy comprises an electron beam source.
The apparatus of claim 25, wherein said apparatus for depositing energy comprises an atomic beam source.
A method for correcting the figure of a multilayer coated optic, comprising:
- measuring the figure of multilayer coated optic;
- and
- removing material from said multilayer coated optic to obtain a desired figure.
An apparatus for correcting the figure of a multilayer coated optic, comprising:
- means for measuring the figure of said optic;
- and
- means for removing material from the multilayer coating on said multilayer-coated optic to obtain a desired figure.
A method for optimizing the performance of an EUVL system having multilayer coated reflective optics, comprising:
- measuring, at a plurality of locations, the wavefront of a beam of light propagating within said EUVL system to determine figure error corrections to one or more of the mirrors that would improve the system wavefront;
- removing individual multilayer coated optics from said system;
- removing material from said individual multilayer coated optics to obtain a desired figure;
- and
- placing said individual multilayer-coated optics back into said system.
Dependencies are inferred from the claim text.