Projection lens for EUV microlithography, film element and method for producing a projection lens comprising a film element

Patent metadata

Field	Value
Publication number	US-10001631-B2
Application number	US-201414454939-A
Country	US
Kind code	B2
Filing date	Aug 8, 2014
Priority date	Feb 10, 2012
Publication date	Jun 19, 2018
Grant date	Jun 19, 2018

Abstract

A film element of an EUV-transmitting wavefront correction device is arranged in a beam path and includes a first layer of first layer material having a first complex refractive index n 1 =(1−δ 1 )+iß 1 , with a first optical layer thickness, which varies locally over the used region in accordance with a first layer thickness profile, and a second layer of second layer material having a second complex refractive index n 2 =(1−δ 2 )+iß 2 , with a second optical layer thickness, which varies locally over the used region in accordance with a second layer thickness profile. The first and second layer thickness profiles differ. The deviation δ 1 of the real part of the first refractive index from 1 is large relative to the absorption coefficient ß 1 of the first layer material and the deviation δ 2 of the real part of the second refractive index from 1 is small relative to the absorption coefficient ß 2 of the second layer material.

First claim

The invention claimed is:

1. Projection lens (PO) for imaging a pattern arranged in an object plane (OS) of the projection lens into an image plane (IS) of the projection lens with electromagnetic radiation having a working wavelength λ from the extreme ultraviolet range (EUV) comprising:
a plurality of mirrors having mirror surfaces which are arranged in a projection beam path between the object plane and the image plane such that a pattern arranged in the object plane is imaged into the image plane by the mirrors, and
a wavefront correction device (WFC) comprising a transmissive film element having a film which is arranged in the projection beam path in an operating mode of the wavefront correction device and is configured to transmit a predominant proportion of the EUV radiation impinging on an optical used region of the film through the transmissive film element at the working wavelength λ, wherein the film element comprises:
a first continuous layer (L 1 ), which consists of a first layer material having a first complex refractive index n 1 =(1−δ 1 )+iß 1 and has a first optical layer thickness which varies locally over the used region in accordance with a first layer thickness profile; and
a second continuous layer (L 2 ), which consists of a second layer material having a second complex refractive index n 2 =(1−δ 2 )+iß 2 and has a second optical layer thickness which varies locally over the used region in accordance with a second layer thickness profile,
wherein the first layer thickness profile differs from the second layer thickness profile, and
wherein δ 1 is a parameter representing a deviation of the real part of the first refractive index from 1 and is larger than ß 1 , which is a parameter representing an absorption coefficient of the first layer material,
wherein δ 2 is a parameter representing a deviation of the real part of the second refractive index from 1 and is smaller than ß 2 , which is a parameter representing an absorption coefficient of the second layer material, and
wherein the projection beam path enters the transmissive film element via a radiation entrance side and exits the transmissive film element via a radiation exit side opposite the radiation entrance side.

2. Projection lens according to claim 1 , wherein the film element is arranged in the projection beam path such that all rays of the projection beam are incident on the optical used region with angles of incidence of less than 20°.

3. Projection lens according to claim 1 , wherein the film element has a transmittance of at least 70% for the impinging EUV radiation in an entirety of the optical used region.

4. Projection lens according to claim 1 ,
wherein the projection lens has at least one pupil plane between the object plane and the image plane and
wherein the film element is arranged in the pupil plane or optically in proximity to the pupil plane.

5. Projection lens according to claim 1 , wherein at least one of:
the projection lens has a film element in optical proximity to the object plane or the image plane and
an intermediate image plane lies between the object plane and the image plane and a film element is arranged in the intermediate image plane or in optical proximity to the intermediate image plane.

6. Projection lens according to claim 1 , wherein the film element comprises a multilayer film comprising the first layer and the second layer.

7. Projection lens according to claim 1 , wherein the first layer is mounted on a first film and the second layer is mounted on a second film of the film element, said second film being physically separate from the first film.

8. Projection lens according to claim 7 , wherein at least one of:
a geometrical distance between the first film and the second film is less than ten centimeters, and
an optical distance between the first film and the second film is dimensioned such that subaperature ratios of the first and second films deviate from one another by less than 0.05.

9. Projection lens according to claim 1 , wherein at least one of:
the working wavelength is between 5 nm and 20 nm,
a first efficiency ratio V 1 =δ 1 /β 1 is greater than 5, and
a second efficiency ratio V 2 =δ 2 /β 2 is less than 0.6.

10. Projection lens according to claim 1 , wherein a first efficiency ratio V 1 =δ 1 /β 1 and a second efficiency ratio V 2 =δ 2 /β 2 and
wherein a ratio V 1 /V 2 is greater than 2.

11. Projection lens according to claim 1 , wherein the working wavelength is in a wavelength range of 7 nm to 20 nm and
wherein at least one of:
the first layer material is selected from the group: ruthenium (Ru), zirconium (Zr), molybdenum (Mo), niobium (Nb), chromium (Cr), beryllium (Be), gold (Au), yttrium (Y), yttrium silicide (Y 5 Si 3 ), zirconium silicide (ZrSi 2 ), or from a material composition which predominantly consists of one of said first-layer materials, and
the second layer material is selected from the group silicon (Si) and germanium (Ge) or a material composition which predominantly consists of one of said second-layer materials.

12. Projection lens according to claim 1 , wherein the working wavelength is in a wavelength range of 6 nm to 7 nm and
wherein at least one of:
the first layer material is selected from the group: NbOB 4 C, NbO 2 , Nb 2 O 5 , RuO 4 , MoO 2 , Rh 2 O 3 , C, Te, In, Ba, Sn, RuO 2 , MoO 3 , La, B, B 4 C, BN, ZrO 2 or from a material composition which predominantly consists of one of said first-layer materials, and the second layer material is selected from the group Y or Rb or a material composition which predominantly consists of one of said second-layer materials.

13. Projection lens according to claim 1 , wherein at least one of:
a first PV ratio between a largest local value and a smallest local value of the first optical layer thickness in the optical used region is between 2 and 6, and
a second PV ratio between a largest local value and a smallest local value of the second optical layer thickness in the optical used region is between 2 and 6.

14. Projection lens according to claim 1 , wherein the second layer thickness profile is complementary to the first layer thickness profile.

15. Projection lens according to claim 1 , wherein the layer thicknesses of the first layer and of the second layer are such that the film, in a region of maximum wavefront change, brings about a wavefront change of at least 3% of the working wavelength.

16. Projection lens according to claim 1 , wherein the second layer thickness is greater than the working wavelength at at least one position in the optical used region.

17. Projection lens according to claim 1 , wherein the first layer has in the optical used region an asymmetrical first layer thickness profile having neither a mirror symmetry nor a radial symmetry or a rotational symmetry.

18. Projection lens according to claim 1 , wherein the film has a first film surface, a second film surface and a film thickness, measured between the first and second film surfaces, of less than 1 μm, wherein the film thickness is 300 nm or less.

19. Projection lens according to claim 1 , wherein the film has at at least one film surface an outer protective layer consisting of a protective layer material that is more resistant to ambient influences than is an inner layer directly adjacent to the protective layer.

20. Projection lens according to claim 1 , wherein the film comprises only a single first layer, only a single second layer, or only a single first and a single second layer.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Bittner Boris
• Wabra Norbert
• Schneider Sonja
• Schoemer Ricarda Maria
• Wagner Hendrik
• Wald Christian
• Iliew Rumen
• Schicketanz Thomas
• Gruner Toralf
• Pauls Walter
• Schmidt Holger
• Roesch Matthias

Classifications

• Y10T29/49826

  Assembling or joining · 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

• B82Y10/00

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

• G02B17/0896

  with variable magnification or multiple imaging planes, including multispectral systems (systems with only refractive elements G02B15/14) · CPC title