Mirror for the EUV wavelength range, method for producing such a mirror, and projection exposure apparatus comprising such a mirror

Patent metadata

Field	Value
Publication number	US-9696632-B2
Application number	US-201414478535-A
Country	US
Kind code	B2
Filing date	Sep 5, 2014
Priority date	Mar 8, 2012
Publication date	Jul 4, 2017
Grant date	Jul 4, 2017

Abstract

A mirror ( 1 ) for the EUV wavelength range having a reflectivity of greater than 40% for at least one angle of incidence of between 0° and 25° includes a substrate (S) and a layer arrangement, wherein the layer arrangement has at least one non-metallic individual layer (B, H, M), and wherein the non-metallic individual layer (B, H, M) has a doping with impurity atoms of between 10 ppb and 10%, in particular between 100 ppb and 0.1%, providing the non-metallic individual layer (B, H, M) with a charge carrier density of greater than 6*10 10 cm −3 and/or an electrical conductivity of greater than 1*10 −3 S/m, in particular with a charge carrier density of greater than 6*10 13 cm −3 and/or an electrical conductivity of greater than 1 S/m.

First claim

The invention claimed is:

1. Mirror for the extreme ultraviolet (EUV) wavelength range having a reflectivity of greater than 40% for at least one angle of incidence of between 0° and 25°, comprising a substrate (S) and a layer arrangement,
wherein the layer arrangement comprises at least one non-metallic individual layer (B, H, M),
wherein the layer arrangement comprises at least one layer subsystem (P′) consisting of a periodic sequence of at least two periods (P) of individual layers,
wherein the periods (P) comprise two individual layers composed of different materials for a high refractive index layer (H) and a low refractive index layer (L),
wherein the materials of the two individual layers (L, H) of the at least one layer subsystem (P′) that form the periods (P) are either molybdenum and silicon or ruthenium and silicon,
wherein the individual layers of the at least one layer subsystem (P′) are separated by at least one barrier layer (B) and the barrier layer (B) consists of a material which is selected from the group of materials: B 4 C, C, Si nitrides, Si carbides, Si borides, Mo nitrides, Mo carbides, Mo borides, Ru nitrides, Ru carbides and Ru borides, and
wherein the non-metallic individual layer (B, H, M) has a doping with impurity atoms of between 10 ppb and 10%, which increases a number of free electrons in the non-metallic individual layer and provides the non-metallic individual layer (B, H, M) at least one of:
a charge carrier density of greater than 6*10 10 cm −3 and
an electrical conductivity of greater than 1*10 −3 S/m.

2. Mirror for the EUV wavelength range according to claim 1 , wherein the doping with impurity atoms of the at least one non-metallic individual layer (B, H, M) is effected with atoms of at least one element from group V of the periodic system.

3. Mirror for the EUV wavelength range according to claim 1 , wherein the layer arrangement has a total thickness of less than 200 nm and the layers for the high refractive index layer (H) of the layer subsystem (P′) have a doping with impurity atoms.

4. Mirror for the EUV wavelength range according to claim 1 ,
wherein the mirror has an optically used surface which, after irradiation with light from the EUV wavelength range between 12 nm and 14 nm with a close of more than 10 kJ/mm 2 , has an average reflection wavelength, within a reflection spectrum of the mirror, of between 12 nm and 14 nm for normal incidence such that the average reflection wavelength deviates from an average emission wavelength of the irradiation light by less than 0.25 nm.

5. Mirror for the EUV wavelength range according to claim 4 ,
configured as a collector mirror for an EUV light source or a mirror for an EUV illumination system, and wherein the deviation of the average reflection wavelength from the average emission wavelength is less than 0.05 nm.

6. Mirror for the EUV wavelength range according to claim 1 , wherein all the individual layers composed of silicon of at least 10 of the periods of the layer subsystem (P′) that are furthest from the substrate have doping with impurity atoms of between 10 ppb and 10%.

7. Mirror for the EUV wavelength range according to claim 1 , wherein the surface roughness of the layer (M) terminating the layer arrangement is less than 0.2 nm rms high spatial frequency range (HSFR).

8. Mirror for the EUV wavelength range according to claim 1 , wherein the layer arrangement further comprises a terminating layer (M) consisting of an oxide or nitride and having a doping with impurity atoms by atoms of at least one element from the group V of the periodic system.

9. Mirror for the EUV wavelength range according to claim 1 ,
wherein the layer arrangement further comprises at least one further layer subsystem (ASL) for stress compensation, wherein the further layer subsystem (ASL) consists of a periodic sequence of at least two periods (P ASL ) of individual layers, wherein the periods (P ASL ) comprise two individual layers composed of different materials for a high refractive index layer (H ASL ) and a low refractive index layer (L ASL ).

10. Mirror for the EUV wavelength range according to claim 9 ,
wherein the absolute value of a total layer stress of the layer arrangement is less than 100 MPa, wherein the absolute value of a tensile stress of the further layer subsystem (ASL) is less than 240 MPa, and wherein the layer subsystem (ASL) is arranged between the substrate and the at least one layer subsystem (P′).

11. Mirror for the EUV wavelength range according to claim 9 , wherein the further layer subsystem (ASL) has a thickness (d ASL ) of the periods (P ASL ) of 5 nm or less.

12. Mirror for the EUV wavelength range according to claim 9 , wherein a reflectivity for normal incidence is more than 60% and a number (N ASL ) of the periods (P ASL ) of the further layer subsystem (ASL) is less than 20.

13. Method for coating the mirror for the EUV wavelength range according to claim 1 , comprising, during coating of the at least one non-metallic individual layer (B, H, M) with a coating apparatus, a partial pressure of impurity atoms of greater than 10 −9 mbar is present in the coating apparatus.

14. Method for coating a mirror for the EUV wavelength range according to claim 13 , wherein the coating of the at least one non-metallic individual layer (B, H, M) is performed by magnetron sputtering at a working gas pressure of at least 10 −4 mbar.

15. At least one of an EUV light source, an EUV illumination system and an EUV projection lens for microlithography comprising a mirror according to claim 1 .

16. Projection exposure apparatus for microlithography comprising at least one of the EUV light source, the EUV illumination system and the EUV projection lens according to claim 15 .

17. Projection exposure apparatus for microlithography, comprising an EUV light source with a collector mirror, an EUV illumination system with a further mirror, and an EUV projection lens with an additional mirror, wherein the collector mirror and at least one of the further mirror and the additional mirror is according to claim 1 , wherein the collector mirror for the EUV light source has a non-metallic individual layer (B, H, M) having a doping with impurity atoms which is higher than the doping with impurity atoms of a non-metallic individual layer (B, H, M) of the further mirror or the additional mirror.

18. Projection exposure apparatus for microlithography according to claim 17 , wherein the further mirror for the EUV illumination system has a non-metallic individual layer (B, H, M) having a doping with impurity atoms which is higher than the doping with impurity atoms of a non-metallic individual layer (B, H, M) of the additional mirror for the EUV projection lens of the projection exposure apparatus.

19. Mirror for the EUV wavelength range according to claim 1 , wherein the non-metallic individual layer (B, H, M) has a doping with impurity atoms of between 100 ppb and 0.1%, to provide the non-metallic individual layer (B, H, M) at least one of:
a charge carrier density of greater than 6*10 13 cm −3 and
an electrical conductivity of greater than 1 S/m.

20. Method for coating the mirror for the EUV wavelength range according to claim 1 , comprising coating the at least one non-metallic individual layer (B, H, M) utilizing at least one sputtering target which has a doping with impurity atoms of between 10 ppb and 10%.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Huber Peter
• Von Blanckenhagen Gisela

Classifications

• B82Y10/00 Primary

  Nanotechnology for information processing, storage or transmission, e.g. quantum computing or single electron logic · CPC title

• G03F7/702 Primary

  Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems · CPC title

• G21K1/062

  Devices having a multilayer structure · CPC title

• G03F7/70316

  Details of optical elements, e.g. of Bragg reflectors, extreme ultraviolet [EUV] multilayer or bilayer mirrors or diffractive optical elements · CPC title

• C23C14/35

  by application of a magnetic field, e.g. magnetron sputtering {(C23C14/3457 takes precedence)} · CPC title