EUV mirror and optical system comprising EUV mirror

Patent metadata

Field	Value
Publication number	US-10203435-B2
Application number	US-201615215123-A
Country	US
Kind code	B2
Filing date	Jul 20, 2016
Priority date	Jan 20, 2014
Publication date	Feb 12, 2019
Grant date	Feb 12, 2019

Abstract

An EUV mirror has a multilayer arrangement applied on a substrate. The multilayer arrangement includes a first layer group having ten or more first layer pairs. Each first layer pair has a first layer composed of a high refractive index first layer material having a first layer thickness, has a second layer composed of a low refractive index second layer material having a second layer thickness and has a period thickness corresponding to the sum of the layer thicknesses of all the layers of a first layer pair. The layer thicknesses of one of the layer materials are defined, depending on the period number, by a simply monotonic first layer thickness profile function, e.g. by a linear, quadratic or exponential layer thickness profile function. The layer thicknesses of the other of the layer materials vary, depending on the period number, in accordance with a second layer thickness profile function.

First claim

What is claimed is:

1. A mirror for extreme ultraviolet (EUV) radiation comprising:
a substrate and
a multilayer arrangement on the substrate and arranged to reflect the EUV radiation having a wavelength (λ), wherein:
the multilayer arrangement comprises a multiplicity of layer pairs having alternating layers composed of a high refractive index layer material and a low refractive index layer material, wherein the high refractive index layer material has a larger real part of the refractive index than does the low refractive index layer material at the wavelength (λ);
the multilayer arrangement comprises a first layer group (LG 1 ) having a reflective effect for the EUV radiation and having ten or more first layer pairs;
each first layer pair comprises a first layer (H) composed of a high refractive index first layer material having a first layer thickness and a second layer (L) composed of a low refractive index second layer material having a second layer thickness and has a respective period thickness (P) totaling a sum of the layer thicknesses of all the layers of each first layer pair;
the layer thicknesses of one of the layer materials are defined, depending on the period number, by a simply monotonic first layer thickness profile function which is completely defined by one, two or three layer thickness parameters;
the layer thicknesses of the other of the layer materials vary, depending on the period number, in accordance with a second layer thickness profile function; and
the first layer thickness profile function is a linearly rising or linearly falling function, such that the layer thicknesses of one of the layer materials increase linearly or decrease linearly over an entirety of first layer group (LG 1 ).

2. The EUV mirror as claimed in claim 1 , wherein the first layer group (LG 1 ) comprises fifteen or more first layer pairs.

3. The EUV mirror as claimed in claim 2 , wherein the first layer group (LG 1 ) comprises 50 or more first layer pairs.

4. The EUV mirror as claimed in claim 1 , wherein the second layer thickness profile function proceeds in a direction opposite to the first layer thickness profile function.

5. An optical system comprising at least one EUV mirror as claimed in claim 1 .

6. The optical system as claimed in claim 5 , wherein the optical system is a projection lens or an illumination system for a microlithographic projection exposure apparatus.

7. The EUV mirror as claimed in claim 1 , wherein the second layer thickness profile function is a linearly rising or linearly falling function.

8. A mirror for extreme ultraviolet (EUV) radiation comprising:
a substrate and
a multilayer arrangement on the substrate and arranged to reflect the EUV radiation having a wavelength (λ), wherein:
the multilayer arrangement comprises a multiplicity of layer pairs having alternating layers composed of a high refractive index layer material and a low refractive index layer material, wherein the high refractive index layer material has a larger real part of the refractive index than does the low refractive index layer material at the wavelength (λ);
the multilayer arrangement comprises a first layer group (LG 1 ) having a reflective effect for the EUV radiation and having ten or more first layer pairs;
each first layer pair comprises a first layer (H) composed of a high refractive index first layer material having a first layer thickness and a second layer (L) composed of a low refractive index second layer material having a second layer thickness and has a respective period thickness (P) totaling a sum of the layer thicknesses of all the layers of each first layer pair;
the layer thicknesses of one of the layer materials are defined, depending on the period number, by a simply monotonic first layer thickness profile function which is completely defined by one, two or three layer thickness parameters;
the layer thicknesses of the other of the layer materials vary, depending on the period number, in accordance with a second layer thickness profile function; and
the second layer thickness profile function is a linearly rising or linearly falling function.

9. The EUV mirror as claimed in claim 8 , wherein the first layer thickness profile function is a quadratic or an exponential function.

10. The EUV mirror as claimed in claim 8 , wherein the second layer thickness profile function proceeds in a direction opposite to the first layer thickness profile function.

11. The EUV mirror as claimed in claim 9 , wherein the second layer thickness profile function proceeds in a direction opposite to the first layer thickness profile function.

12. The EUV mirror as claimed in claim 8 , wherein the second layer thickness profile function proceeds in a direction opposite to the first layer thickness profile function.

13. A mirror for extreme ultraviolet (EUV) radiation comprising:
a substrate and
a multilayer arrangement on the substrate and arranged to reflect the EUV radiation having a wavelength (λ), wherein:
the multilayer arrangement comprises a multiplicity of layer pairs having alternating layers composed of a high refractive index layer material and a low refractive index layer material, wherein the high refractive index layer material has a larger real part of the refractive index than does the low refractive index layer material at the wavelength (λ);
the multilayer arrangement comprises a first layer group (LG 1 ) having a reflective effect for the EUV radiation and having ten or more first layer pairs;
each first layer pair comprises a first layer (H) composed of a high refractive index first layer material having a first layer thickness and a second layer (L) composed of a low refractive index second layer material having a second layer thickness and has a respective period thickness (P) totaling a sum of the layer thicknesses of all the layers of each first layer pair;
the layer thicknesses of one of the layer materials are defined, depending on the period number, by a simply monotonic first layer thickness profile function which is completely defined by one, two or three layer thickness parameters;

the layer thicknesses of the other of the layer materials vary, depending on the period number, in accordance with a second layer thickness profile function;
the multilayer arrangement comprises a second layer group (LG 2 ) having a reflective effect for the radiation and having ten or more second layer pairs, wherein the first layer group (LG 1 ) is arranged between the substrate and the second layer group (LG 2 ); and
the layer thicknesses of the first layer material and of the second layer material within the first layer group (LG 1 ) and within the second layer group (LG 2 ) vary linearly in respectively opposite directions.

14. The EUV mirror as claimed in claim 13 , wherein within the second layer group (LG 2 ) the layer thicknesses of one of the layer materials are defined, depending on the period number, by a simply monotonic first layer thickness profile function and the layer thicknesses of the other of the layer materials vary, depending on the period number, in accordance with a second layer thickness profile function.

15. A mirror for extreme ultraviolet (EUV) radiation comprising:
a substrate and
a multilayer arrangement on the substrate and arranged to reflect the EUV radiation having a wavelength (λ), wherein:
the multilayer arrangement comprises a multiplicity of layer pairs having alternating layers composed of a high refractive index layer material and a low refractive index layer material, wherein the high refractive index layer material has a larger real part

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Schicketanz Thomas
• Dier Oliver
• Strobel Sebastian
• Winter Ralf

Classifications

• G02B5/08

  Mirrors {(vehicle mirrors involving special optical features B60R1/08)} · CPC title

• G02B5/0875

  the reflecting layers comprising two or more metallic layers · CPC title

• G21K1/062

  Devices having a multilayer structure · CPC title

• G02B5/0891 Primary

  Ultraviolet [UV] mirrors (apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06) · CPC title

• G02B5/0816

  Multilayer mirrors, i.e. having two or more reflecting layers (G02B5/0883, G02B5/0891 take precedence) · CPC title