# US 2014/0193591 A1 · Method for producing a reflective optical element for euv-lithography

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- Number: US 2014/0193591 A1
- Document ID: US20140193591A1
- Status: Published application
- Kind: A1
- Application number: 14/137,225
- Filed: 2013-12-20
- Published: 2014-07-10
- Earliest claimed: 2011-06-22
- Assignees: Carl Zeiss SMT GmbH
- Applicants: CARL ZEISS SMT GmbH
- Inventors: Alexey KUZNETZOV; Michael GLEESON; Robbert W. E. VAN DE KRUIJS; Frederik BIJKERK
- Web page: https://patentgrep.com/patent/US20140193591A1

## CPC

- G03F 7/70958: {Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties}
- B82Y 10/00: Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic
- C23C 14/35: by application of a magnetic field, e.g. magnetron sputtering {(C23C14/3457 takes precedence)}
- C23C 14/542: {Controlling the film thickness or evaporation rate}
- G02B 5/0875: {the reflecting layers comprising two or more metallic layers}
- G02B 5/0891: {Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06)}
- 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)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- C23C: COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL (making metal-coated products by extrusion B21C23/22; covering with metal by connecting pre-existing layers to articles, see the relevant places, e.g. B21D39/00, B23K; metallising of glass C03C; metallising mortars, concrete, artificial stone, ceramics or natural stone C04B41/00; enamelling of, or applying a vitreous layer to, metals C23D; treating metal surfaces or coating of metals by electrolysis or electrophoresis C25D; single-crystal film growth C30B; by metallising textiles D06M11/83; decorating textiles by locally metallising D06Q1/04)
- 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 method aleviating blistering, cracking and chipping in topmost layers of a multilayer system exposed to reactive hydrogen, when producing a reflective optical element (50) having a maximum reflectivity at an operating wavelength of 5 nm to 20 nm. A multilayer system (51) composed of 30-60 stacks (53) is applied to a substrate (52). Each stack has a layer (54) of thickness dMLs composed of a high refractive index material and a layer (55) of thickness dMLa composed of a low refractive index material. The thickness ratio is dMLa/(dMLa+dMLs)=ΓML. Two to five further stacks (56) are applied to the multilayer system. at least one further stack having a layer (54) of thickness ds composed of a high refractive index material and a layer (55) of thickness da composed of a low refractive index material, wherein the thickness ratio is da/(da+ds)=Γ and wherein Γ≠ΓML.

## Claims

### Claim 1

A method for producing a reflective optical element for extreme ultraviolet (EUV) lithography, which element has a maximum reflectivity at an operating wavelength in the range of 5 nm to 20 nm, comprising:
applying to a substrate a multilayer system composed of thirty to sixty stacks arranged one above another, wherein each stack has a layer having a thickness dMLs composed of a material having a higher real part of the refractive index at the operating wavelength, and a layer having a thickness dMLa composed of a material having a lower real part of the refractive index at the operating wavelength, wherein the thickness ratio is dMLa/(dMLa+dMLs)=ΓML,
applying two, three, four or five further stacks to the multilayer system, said at least two further stacks each having a layer having a thickness ds composed of a material having a higher real part of the refractive index at the operating wavelength, and a layer having a thickness da composed of a material having a lower real part of the refractive index at the operating wavelength, wherein the thickness ratio is da/(da+ds)=Γ and Γ>1.2*ΓML or Γ<0.8*ΓML.

### Claim 2 (depends on 1)

The method according to claim 1, wherein at least one layer of the further stacks is applied via electron beam evaporation or magnetron sputtering with thermal particles or ion beam assisted coating.

### Claim 3 (depends on 1)

The method according to claim 1, wherein at least one layer of the further stacks is not ion beam polished or is polished with an ion beam whose energy is set such that the ion beam penetrates entirely through the at least one layer of the further stacks.

### Claim 4 (depends on 1)

The method according to claim 1, wherein at least one of the materials of which the layers of the stacks of the multilayer system are composed is the same as at least one of the materials of which the layers of the further stacks are composed.

### Claim 5 (depends on 1)

The method according to claim 1, wherein the layers of both the stacks of the multilayer system and the further stacks are composed of silicon as the material having the higher real part of the refactive index at the operating wavelength, and the layers of both the stacks of the multilayer system and the further stacks are composed of molybdenum as the material having the lower real part of the refactive index at the operating wavelength.

### Claim 6 (depends on 1)

The method according to claim 1, wherein the materials having the higher real part of the refractive index at the operating wavelength differ respectively in the layers of the stacks of the multilayer syetem and in the layers of the further stacks, and the materials having the lower real part of the refractive index at the operating wavelength differ respectively in the layers of the stacks of the multilayer syetem and in the layers of the further stacks.

### Claim 7 (depends on 1)

The method according to claim 1, further comprising applying an additional layer as diffusion barrier in each of the further stacks between the layer having the lower refractive index at the operating wavelength and the layer having the higher refractive index at the operating wavelength.

### Claim 8 (depends on 1)

The method according to claim 1, further comprising applying a layer composed of a material having a low density and low stress on the further stacks.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the layer applied on the further stacks is composed of a material from the group consisting of silicon, silicon nitride, silicon oxide, silicon carbide, boron, boron carbide, boron nitride, beryllium, and carbon.

### Claim 10 (depends on 1)

The method according to claim 1, further comprising applying a further layer composed of the material from the group consisting of ruthenium, cerium, yttrium, molybdenum silicide, yttrium oxide, molybdenum sulfide, zirconium, niobium, molybdenum carbide, zirconium oxide, rhenium, and rhodium on the further stacks.