Facet mirror

• US 10,599,041 B2
• Filed: 10/31/2014
• Issued: 03/24/2020
• Est. Priority Date: 05/23/2012
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Inventors: Bieling, Stig, Deguenther, Markus, Wangler, Johannes
• Primary Examiner(s): Riddle, Christina A
• Application Number:
  US14/529,844
• Publication Number:
  US 20150049321A1
• Time in Patent Office: 1,971 Days
• Field of Search: 355 52, 355 53, 355 55, 355 67- 71, 355 77, 2504921, 2504922, 25049222, 2504931, 250548, 359601, 359605, 359606, 359850, 359853, 359864, 359904, 359599
• CPC Class Codes: G02B 17/002 Arrays of reflective systems
• CPC Class Codes: G02B 19/0023 at least one surface having optical power
• CPC Class Codes: G02B 19/0047 for use with a light source G02B19/009, G02B19/0095 take precedence; details of lighting devices in general F21V; non-semiconductor lasers having optical devices external to the laser cavity H01S3/005
• CPC Class Codes: G02B 19/0095 for use with ultraviolet radiation
• CPC Class Codes: G02B 27/425 in illumination systems mask illumination systems in photolithographic systems G03F7/70158
• CPC Class Codes: G02B 5/0891 Ultraviolet [UV] mirrors apparatus for microlithography exposure G03F7/70; X-ray multilayer structures G21K1/06
• CPC Class Codes: G02B 5/1861 Reflection gratings characterised by their structure, e.g. step profile, contours of substrate or grooves, pitch variations, materials G02B5/1809, G02B5/1828, G02B5/1833, G02B5/1838 and G02B5/1847 take precedence
• CPC Class Codes: G03F 7/70075 Homogenization of illumination intensity in the mask plane by using an integrator, e.g. fly's eye lens, facet mirror or glass rod, by using a diffusing optical element or by beam deflection
• CPC Class Codes: G03F 7/70191 Optical correction elements, filters or phase plates for controlling intensity, wavelength, polarisation, phase or the like
• CPC Class Codes: G03F 7/702 Reflective illumination, i.e. reflective optical elements other than folding mirrors, e.g. extreme ultraviolet [EUV] illumination systems
• CPC Class Codes: G03F 7/70575 Wavelength control, e.g. control of bandwidth, multiple wavelength, selection of wavelength or matching of optical components to wavelength

Abstract

Illumination optical unit for illuminating an object field in a projection exposure apparatus, comprising a first facet mirror with a structure, which has a spatial frequency of at least 0.2 mm⁻¹ in at least one direction, and a second facet mirror, comprising a multiplicity of facets, wherein the facets are respectively provided with a mechanism for damping spatial frequencies of the structure of the first facet mirror.

Claims

1. A pupil facet mirror, comprising:

a multiplicity of pupil facets respectively configured to damp spatial frequencies above 1 mm<sup>−

1</sup>,

wherein;

the pupil facets comprise at least one member selected from the group consisting of a targeted defocusing in a cross-scan direction only and a scattering function configured to damp spatial frequencies;

pupil facets comprise one dimensional cylinders configured to provide the scattering function;

the one dimensional cylinders are aligned parallel to each other;

the cylinders have a property selected from the group consisting of a uniform radius of curvature and different widths, different radii of curvature and a uniform width b, and different radii of curvature and different widths; and

the pupil facet mirror is a microlithography pupil facet mirror.

2. The pupil facet mirror of claim 1, wherein, for at least some of the pupil facets, the pupil facet comprises a scattering function configured to damp the spatial frequencies above the specific limit frequency.

3. The pupil facet mirror of claim 2, wherein the scattering function is a one-dimensional scattering function.

4. The pupil facet mirror of claim 2, wherein the scattering function has a scattering angle of at least 0.1 mrad.

5. An illumination optical unit, comprising:

a first facet mirror comprising a structure having a spatial frequency of at least 0.2 mm<sup>−

1</sup> in at least one dimension; and

a pupil facet mirror according to claim 1,

wherein the illumination optical unit is a microlithography illumination optical unit.

6. The illumination optical unit of claim 5, wherein mechanisms to damp the spatial frequencies of the pupil facets of the pupil facet mirror are matched to the structure of the facets of the first facet mirror so the spatial frequencies of the structure have a contrast of at most 1% in a region of an object field.

7. The illumination optical unit of claim 5, wherein the structure of the first facet mirror defines a binary phase grating.

8. The illumination optical unit of claim 7, wherein the binary phase grating has a groove depth corresponding to a quarter of a wavelength of radiation to be blocked out.

9. The illumination optical unit of claim 7, wherein the binary phase grating has a grating period matched to a configuration of the pupil facets of the pupil facet mirror so that, during use of the illumination optical unit, the 1^st and −

1^st order of diffraction of radiation with a wavelength to be blocked out is imaged on pupil facets of the pupil facet mirror that lie adjacent to a facet on which the image of the radiation rests.

10. An illumination optical unit, comprising:

a pupil facet mirror according to claim 1,

wherein the illumination optical unit is a microlithography illumination optical unit.

11. An illumination system, comprising:

an EUV radiation source; and

an illumination optical unit comprising a pupil facet mirror according to claim 1.

12. The illumination system of claim 11, wherein the illumination optical unit comprises an additional facet mirror comprising a structure having a spatial frequency of at least 0.2 mm⁻

1 in at least one dimension.

13. An apparatus, comprising:

an illumination optical unit comprising a pupil facet mirror according to claim 1; and

a projection optical unit,

wherein the apparatus is a microlithography projection exposure apparatus.

14. The apparatus of claim 13, wherein the illumination optical unit comprises an additional facet mirror comprising a structure having a spatial frequency of at least 0.2 mm⁻

1 in at least one dimension.

15. A method of using a projection exposure apparatus comprising an illumination optical unit and a projection optical unit, the method comprising:

using the illumination optical unit to illuminate structures of a reticle in an object plane of the projection optical unit; and

using the projection optical unit to project at least some of the illuminated structures of the reticle onto a light-sensitive material in an image plane of the projection optical unit,

wherein the illumination optical unit comprises a pupil facet mirror according to claim 1.

16. The pupil facet mirror of claim 1, wherein radii of curvature of the pupil facets are configured to provide the targeted defocusing.

17. The pupil facet mirror of claim 1, wherein the pupil facets are respectively configured to damp spatial frequencies above 1.33 mm⁻

1.

18. A pupil facet mirror, comprising:

a multiplicity of pupil facets respectively configured to damp spatial frequencies above 1 mm<sup>−

1</sup>,

wherein;

the pupil facets comprise at least one member selected from the group consisting of a targeted defocusing in a cross-scan direction only and a scattering function configured to damp spatial frequencies;

pupil facets comprise one dimensional cylinders configured to provide the scattering function;

the one dimensional cylinders are aligned parallel to each other;

the cylinders are rotated by an angle in the region of 0°

to 15°

relative to a direction parallel to a scanning direction; and

the pupil facet mirror is a microlithography pupil facet mirror.

19. The pupil facet mirror of claim 18, wherein, for at least some of the pupil facets, the pupil facet comprises a scattering function configured to damp the spatial frequencies above the specific limit frequency.

20. The pupil facet mirror of claim 19, wherein the scattering function is a one-dimensional scattering function.

21. The pupil facet mirror of claim 19, wherein the scattering function has a scattering angle of at least 0.1 mrad.

22. An illumination optical unit, comprising:

a first facet mirror comprising a structure having a spatial frequency of at least 0.2 mm<sup>−

1</sup> in at least one dimension; and

a pupil facet mirror according to claim 18,

wherein the illumination optical unit is a microlithography illumination optical unit.

23. An illumination optical unit, comprising:

a pupil facet mirror according to claim 18,

wherein the illumination optical unit is a microlithography illumination optical unit.

24. An illumination system, comprising:

an EUV radiation source; and

an illumination optical unit comprising a pupil facet mirror according to claim 18.