# US 10,481,501 B2 · Method for producing a reflective optical element, reflective optical element, and use of a reflective optical element

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- Number: US 10,481,501 B2
- Document ID: US10481501B2
- Status: Granted
- Kind: B2
- Application number: 15/650,141
- Filed: 2017-07-14
- Published: 2017-11-02
- Granted: 2019-11-19
- Earliest claimed: 2015-01-22
- Assignees: Carl Zeiss SMT GmbH
- Applicants: Carl Zeiss SMT GmbH
- Inventors: Markus Bauer; Ulrich Bingel; Willi Anderl
- Web page: https://patentgrep.com/patent/US10481501B2

## CPC

- G03F 7/70266: {Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction}
- C25D 7/08: Mirrors; Reflectors
- G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)}
- G02B 5/1847: {Manufacturing methods}
- G02B 7/1815: {with cooling or heating systems (cooling arrangements for laser mirrors H01S3/0401)}
- G21K 1/067: {using surface reflection, e.g. grazing incidence mirrors, gratings (multilayer mirrors G21K1/062)}
- G21K 2201/065: provided with cooling means
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G21K: HANDLING OF PARTICLES OR IONISING RADIATION NOT OTHERWISE PROVIDED FOR; IRRADIATION DEVICES; GAMMA RAY OR X-RAY MICROSCOPES

## Abstract

The disclosure provides a method that includes filling a cavity in a substrate with a second material, wherein the substrate includes a first material. The method also includes using galvanic and/or chemical deposition of a third material to apply an overcoating to a first surface of the substrate in a region of the cavity. The method further includes removing the second material from the cavity. In addition, the method includes, before or after removing the second material from the cavity, applying a reflective layer to the overcoating. The disclosure also provides related optical articles and systems.

## Claims

### Claim 1

A method of processing a substrate comprising a first material, the substrate comprising a cavity extending from a first surface of the substrate, the method comprising:
filling the cavity in the substrate with a second material;
using galvanic and/or chemical deposition of a third material to apply an overcoating to the first surface of the substrate in a region of the cavity;
removing the second material from the cavity; and
before or after removing the second material from the cavity, applying a reflective layer to the overcoating,
wherein the method forms an article.

### Claim 2 (depends on 1)

The method of claim 1, further comprising forming the article into a reflective optical element having an optically effective surface, wherein, before filling the cavity with the second material, the first surface of the substrate is preformed to form a surface shape corresponding to a basic shape of the optically effective surface of the reflective optical element.

### Claim 3 (depends on 1)

The method of claim 1, wherein the second material is liquefiable by applying heat, and/or the second material is soluble in a solvent.

### Claim 4 (depends on 1)

The method of claim 1, wherein the second material is electrically conductive.

### Claim 5 (depends on 3)

The method of claim 3, wherein the second material comprises at least one material selected from the group consisting of a wax, a polymer and a salt.

### Claim 6 (depends on 1)

The method of claim 1, further comprising, between filling the cavity and applying the overcoating, applying an electrically conductive layer to the first surface of the substrate.

### Claim 7 (depends on 1)

The method of claim 1, further comprising, after applying the overcoating or after removing the second material from the cavity, fine-machining the surface of the overcoating in accordance with a fine form of an optically effective surface that is to be achieved.

### Claim 8 (depends on 7)

The method of claim 7, further comprising smoothing the fine-machined surface of the overcoating.

### Claim 9 (depends on 7)

The method of claim 7, further comprising correcting a shape of the fine-machined surface of the overcoating.

### Claim 10 (depends on 7)

The method of claim 7, further comprising, while fine-machining the overcoating, subjecting the cavity to pressure.

### Claim 11 (depends on 1)

The method of claim 1, wherein the overcoating is applied so that the overcoating has a nonuniform thickness distributed over the first surface of the substrate.

### Claim 12 (depends on 1)

The method of claim 1, wherein the third material is varied continuously or incrementally during overcoating.

### Claim 13 (depends on 1)

The method of claim 1, further comprising processing the article to provide an optical element comprising the substrate supporting an optically effective surface of a reflective layer.

### Claim 14

A method, comprising:
filling a cavity in a substrate with a second material, the substrate comprising a first material;
using galvanic and/or chemical deposition of a third material to apply an overcoating to a first surface of the substrate in a region of the cavity;
removing the second material from the cavity; and
before or after removing the second material from the cavity, applying a reflective layer to the overcoating,
wherein the method forms an optical element, which comprises:
the substrate;
the overcoating on the first surface of the substrate;
the cavity; and
the reflective layer,
wherein:
the reflective layer comprises an optically effective surface;
the cavity is near the first surface of the substrate;
the overcoating extends over the cavity;
the cavity is free of material of the overcoating; and
the reflective layer is on a surface of the overcoating that faces away from the substrate.

### Claim 15 (depends on 14)

The method of claim 14, wherein the cavity comprises at least one channel.

### Claim 16 (depends on 14)

The method of claim 14, wherein cavity comprises a plurality of channels, and the channels have a width which is in the range from a few micrometers to around one millimeter.

### Claim 17 (depends on 14)

The method of claim 14, wherein the cavity comprises an opening that leads into the optically effective surface of the reflective layer.

### Claim 18 (depends on 14)

The method of claim 14, wherein the substrate comprises steel.

### Claim 19 (depends on 14)

The method of claim 14, wherein the overcoating comprises copper, nickel and/or nickel with phosphorus.

### Claim 20 (depends on 14)

The method of claim 14, wherein the materials of the substrate and of the overcoating have an at least approximately identical coefficient of thermal expansion.

### Claim 21 (depends on 14)

The method of claim 14, wherein the material(s) of the overcoating (16) have a coefficient of thermal expansion which is greater than a coefficient of thermal expansion of the material(s) of the substrate.

### Claim 22 (depends on 14)

The method of claim 14, wherein the overcoating has a uniform thickness, or wherein the overcoating has a thickness that varies over the first surface of the substrate.

### Claim 23 (depends on 14)

The method of claim 14, wherein:
a mirror comprises the optical element;
the mirror is in an optical system; and
the optical system is configured to be used in the VUV, EUV or even shorter-wave spectral range or for material processing with high-intensity light.

### Claim 24 (depends on 14)

The method of claim 14, wherein:
a collector mirror comprises the optical element; and
the collector mirror is in an EUV microlithography system.

### Claim 25 (depends on 14)

The method of claim 14, wherein:
an article comprises the optical element;
the article comprises an optical compensator and/or manipulator; and
the cavity is subjectable to variable pressure to compensate for an undesired deformation of the optically effective surface to produce a desired deformation in the optically effective surface.