# US 2019/0171108 A1 · Reflective optical element for euv lithography

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- Number: US 2019/0171108 A1
- Document ID: US20190171108A1
- Status: Published application
- Kind: A1
- Application number: 16/257,811
- Filed: 2019-01-25
- Published: 2019-06-06
- Earliest claimed: 2016-07-27
- Assignees: Carl Zeiss SMT GmbH
- Applicants: Carl Zeiss SMT GmbH
- Inventors: Dirk Heinrich EHM; Vitaliy SHKLOVER; Irene AMENT; Stefan-Wolfgang SCHMIDT; Moritz BECKER; Stefan WIESNER; Diana URICH; Robert MEIER; Ralf WINTER; Christof JALICS; Holger KIEREY; Eric EVA
- Web page: https://patentgrep.com/patent/US20190171108A1

## CPC

- G03F 7/702: {Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems}
- G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)}
- G03F 7/70033: {by plasma extreme ultraviolet [EUV] sources}
- G03F 7/70316: {Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements}
- G03F 7/70916: {Pollution mitigation, i.e. mitigating effect of contamination or debris, e.g. foil traps}
- G03F 7/70925: {Cleaning, i.e. actively freeing apparatus from pollutants, e.g. using plasma cleaning}
- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- G03F 7/70983: {Optical system protection, e.g. pellicles or removable covers for protection of mask}
- G21K 1/062: {Devices having a multilayer structure}
- G21K 2201/067: Construction details
- 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

In order to prevent delamination of a reflective coating from the substrate under the influence of reactive hydrogen, a reflective optical element (50) for EUV lithography is provided, which has a substrate (51) and a reflective coating (54) for reflecting radiation in the wavelength range of 5 nm to 20 nm. A functional layer (60) is arranged between the reflective coating (54) and the substrate (51). With the functional layer, the concentration of hydrogen in atom % at the side of the substrate facing the reflective coating is reduced by at least a factor of 2.

## Claims

### Claim 1

A reflective optical element for extreme ultraviolet (EUV) lithography, comprising:
a substrate and a reflective coating configured to reflect radiation in a wavelength range of 5 nm to 20 nm,
a functional layer arranged between the reflective coating and the substrate, wherein the functional layer reduces a concentration of hydrogen in atom % at a side of the substrate facing the reflective coating by at least a factor of 2, and
a microstructured layer arranged between the reflective coating and the substrate.

### Claim 2 (depends on 1)

The reflective optical element as claimed in claim 1, wherein the functional layer comprises at least one of: tin, silver, molybdenum, ruthenium, iridium, nickel, iron, cobalt, copper, aluminum, platinum, zinc, manganese, lead, gold, palladium, tungsten, tantalum, alloys, oxides, borides, and nitrides or carbides thereof.

### Claim 3 (depends on 1)

The reflective optical element as claimed in claim 1, wherein the microstructured layer comprises at least one of: nickel-phosphorus, nickel-boron, copper, silver, gold, platinum, iridium, tantalum, titanium, zirconium, tungsten, molybdenum and niobium.

### Claim 4 (depends on 1)

The reflective optical element as claimed in claim 1, wherein the functional layer is arranged between the reflective coating and the microstructured layer and/or between the microstructured layer and the substrate and/or within the microstructured layer.

### Claim 5 (depends on 1)

The reflective optical element as claimed in claim 1, further comprising a polishing layer arranged on the functional layer or on the substrate or on the microstructured layer or on the functional layer configured as a microstructured layer.

### Claim 6 (depends on 5)

The reflective optical element as claimed in claim 5, wherein the polishing layer comprises at least one of: amorphous silicon, silicon dioxide, silicon nitride, gallium nitride and aluminum nitride.

### Claim 7 (depends on 5)

The reflective optical element as claimed in claim 5, wherein the functional layer is arranged between the polishing layer and the reflective coating.

### Claim 8 (depends on 1)

The reflective optical element as claimed in claim 1, wherein the substrate comprises at least one of: silicon, silicon carbide, silicon-infiltrated silicon carbide, quartz glass, titanium-doped quartz glass, glass, and glass ceramic.

### Claim 9 (depends on 1)

The reflective optical element as claimed in claim 1, further comprising an adhesion promoter layer arranged on the substrate, wherein the adhesion promoter layer comprises at least one ply and comprises at least one of: ruthenium, chromium, platinum, iridium, copper, silver, gold, nickel, nickel-phosphorus, tantalum, titanium, zirconium, tungsten, molybdenum and niobium.

### Claim 10 (depends on 1)

The reflective optical element as claimed in claim 1, wherein the reflective coating is configured as a multilayer system comprising alternately arranged layers of a material having a lower real part of the refractive index at an operating wavelength in the wavelength range of between 5 nm and 20 nm and of a material having a higher real part of the refractive index at an operating wavelength in the wavelength range of between 5 nm and 20 nm.

### Claim 11 (depends on 1)

The reflective optical element as claimed in claim 1, configured as a collector mirror.

### Claim 12 (depends on 1)

An optical system for an EUV lithography apparatus having a reflective optical element as claimed in claim 1.

### Claim 13 (depends on 12)

An EUV lithography apparatus having an optical system as claimed in claim 12.