# US 2025/0093557 A1 · Method for producing a substrate for an optical element, and reflective optical element

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- Number: US 2025/0093557 A1
- Document ID: US20250093557A1
- Status: Published application
- Kind: A1
- Application number: 18/962,162
- Filed: 2024-11-27
- Published: 2025-03-20
- Earliest claimed: 2018-05-17
- Assignees: Carl Zeiss SMT GmbH
- Applicants: Carl Zeiss SMT GmbH
- Inventors: Andreas SCHMEHL; Heiko SIEKMANN
- Web page: https://patentgrep.com/patent/US20250093557A1

## CPC

- G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)}
- C30B 11/14: characterised by the seed, e.g. its crystallographic orientation
- C30B 29/06: Silicon
- C30B 29/08: Germanium
- G02B 5/085: {at least one of the reflecting layers comprising metal}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- C30B: SINGLE-CRYSTAL GROWTH (by using ultra-high pressure, e.g. for the formation of diamonds, B01J3/06); UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL (zone-refining of metals or alloys C22B); PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (casting of metals, casting of other substances by the same processes or devices B22D; working of plastics B29; modifying the physical structure of metals or alloys C21D, C22F); SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE (for producing semiconductor devices or parts thereof H10); APPARATUS THEREFOR

## Abstract

A reflective optical element (11), in particular for reflecting EUV radiation (14) includes: a substrate having an optical surface on which a reflective coating (13) is applied. The substrate has a quasi-monocrystalline volume region (8). An associated method for producing the substrate (10) for the optical element (11) includes: introducing a starting material, preferably a metal or a semimetal, into a container and melting the starting material, producing a material body having a quasi-monocrystalline volume region (8) by directionally solidifying the molten starting material proceeding from a plurality of monocrystalline seed plates arranged in the region of a base of the container, and producing the substrate by processing the material body to form an optical surface (12).

## Claims

### Claim 1

A reflective optical element for reflecting extreme ultraviolet (EUV) radiation, comprising:
a substrate having an optical surface, and
a reflective coating applied onto the optical surface of the substrate,
wherein the substrate comprises a quasi-monocrystalline volume region,
wherein the substrate further comprises a monocrystalline volume region, and wherein the optical surface is formed at the monocrystalline volume region at a side of the monocrystalline volume region facing away from the quasi-monocrystalline volume region.

### Claim 2 (depends on 1)

The reflective optical element according to claim 1, wherein the substrate further comprises a polycrystalline volume region, which projects laterally beyond the quasi-monocrystalline volume region at least at one lateral side of the quasi-monocrystalline volume region.

### Claim 3 (depends on 1)

The reflective optical element according to claim 1, wherein the substrate is formed from silicon or from germanium.

### Claim 4 (depends on 2)

The reflective optical element according to claim 2, wherein the substrate is formed from silicon or from germanium.