# US 10,310,382 B2 · Mirror, in particular for a microlithographic projection exposure apparatus

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- Number: US 10,310,382 B2
- Document ID: US10310382B2
- Status: Granted
- Kind: B2
- Application number: 15/018,316
- Filed: 2016-02-08
- Published: 2016-06-02
- Granted: 2019-06-04
- Earliest claimed: 2013-08-07
- Assignees: Carl Zeiss SMT GmbH
- Applicants: Carl Zeiss SMT GmbH
- Inventors: Martin Hermann
- Web page: https://patentgrep.com/patent/US10310382B2

## CPC

- G03F 7/702: {Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems}
- G02B 5/0816: {Multilayer mirrors, i.e. having two or more reflecting layers (G02B5/0883, G02B5/0891 take precedence)}
- G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)}
- G03F 7/70316: {Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements}
- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- G21K 1/062: {Devices having a multilayer structure}
- 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)
- 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

A mirror (10, 20, 30, 40), more particularly for a microlithographic projection exposure apparatus, has an optical effective surface (10a, 20a, 30a, 40a), a mirror substrate (11, 21, 31, 41) and a reflection layer stack (14, 24, 34, 44) for reflecting electromagnetic radiation impinging on the optical effective surface (10a, 20a, 30a, 40a), wherein a layer (13, 23, 33, 43) composed of a group III nitride is arranged between the mirror substrate (11, 21, 31, 41) and the reflection layer stack (14, 24, 34, 44), wherein the group III nitride is selected from the group containing gallium nitride (GaN), aluminum nitride (AlN) and aluminum gallium nitride (AlGaN).

## Claims

### Claim 1

A mirror having an optical effective surface, comprising
a mirror substrate;
a reflection layer stack for reflecting electromagnetic radiation impinging on the optical effective surface; and
a layer composed of a group III nitride arranged between the mirror substrate and the reflection layer stack, wherein the group III nitride comprises at least one of gallium nitride (GaN), aluminum nitride (AlN) or aluminum gallium nitride (AlGaN);
wherein the layer has a thickness of at least 0.1 μm and of at most 100 μm;
wherein said mirror is configured to be arranged in a microlithographic projection exposure apparatus; and
wherein a surface profile of the layer is configured to at least partly compensate for mechanical strain formed between layers of the reflection layer stack.

### Claim 2

A mirror having an optical effective surface, comprising
a mirror substrate;
a reflection layer stack for reflecting electromagnetic radiation impinging on the optical effective surface; and
a layer composed of a group III nitride arranged between the mirror substrate and the reflection layer stack, wherein the group III nitride comprises at least one of gallium nitride (GaN), aluminum nitride (AlN) or aluminum gallium nitride (AlGaN);
wherein the layer has a thickness of at least 0.1 μm and of at most 100 μm;
wherein said mirror is configured to be arranged in a microlithographic projection exposure apparatus; and
wherein the group III nitride is amorphous.

### Claim 3 (depends on 1)

The mirror as claimed in claim 1, wherein the layer has a thickness of at least 0.5 μm and of at most 50 μm.

### Claim 4 (depends on 1)

The mirror as claimed in claim 1, wherein the layer is arranged directly on the mirror substrate.

### Claim 5 (depends on 1)

The mirror as claimed in claim 1, further comprising a polishing layer on which the layer is arranged.

### Claim 6 (depends on 1)

The mirror as claimed in claim 1, wherein the mirror substrate is produced from a metallic material.

### Claim 7 (depends on 1)

The mirror as claimed in claim 1, wherein the mirror substrate is produced from an amorphous material.

### Claim 8 (depends on 1)

The mirror as claimed in claim 1, configured for an operating wavelength of less than 30 nm.

### Claim 9 (depends on 1)

An optical system of a microlithographic projection exposure apparatus, comprising at least one mirror as claimed in claim 1.

### Claim 10

A method for producing a mirror for a microlithographic projection exposure apparatus, comprising:
applying a layer system on a mirror substrate, said layer system having a reflection layer stack configured to reflect electromagnetic radiation impinging on the optical effective surface,
applying a layer composed of a group III nitride before the reflection layer stack is applied to the mirror substrate, wherein the group III nitride comprises at least one of gallium nitride (GaN), aluminum nitride (AlN) or aluminum gallium nitride (AlGaN), and wherein the layer has a thickness of at least 0.1 μm and of at most 100 μm, and
working a surface profile into the layer, wherein the surface profile at least partly compensates for mechanical strain formed between layers of the reflection layer stack.

### Claim 11 (depends on 10)

The method as claimed in claim 10, further comprising polishing the layer before the reflection layer stack is applied.

### Claim 12 (depends on 1)

The mirror as claimed in claim 1, further comprising an adhesion promoter layer situated on the mirror substrate and on which the layer is arranged.

### Claim 13 (depends on 7)

The mirror as claimed in claim 7, wherein the amorphous material is a titanium dioxide (TiO2)-doped quartz glass.

### Claim 14 (depends on 8)

The mirror as claimed in claim 8, configured for an operating wavelength of less than 15 nm.

### Claim 15

The optical system as claimed in 9, wherein the microlithographic projection exposure apparatus is an illumination device or a projection lens.

### Claim 16 (depends on 5)

The mirror as claimed in claim 5, wherein the polishing layer comprises amorphous silicon.

### Claim 17 (depends on 2)

The mirror as claimed in claim 2, wherein a surface profile of the layer is configured to at least partly compensate for mechanical strain formed between layers of the reflection layer stack.

### Claim 18 (depends on 1)

The mirror as claimed in claim 1, wherein the group III nitride is amorphous.

### Claim 19 (depends on 12)

The mirror as claimed in claim 12, wherein the adhesion promoter layer is comprised of a first material, wherein the substrate is comprised of a second material, and wherein the first material is different from the second material.

### Claim 20 (depends on 2)

The mirror as claimed in claim 2, wherein the mirror substrate is produced from a metallic material or from titanium dioxide (TiO2)-doped quartz glass.