Projection optical unit for EUV projection lithography

Patent metadata

Field	Value
Publication number	US-10545323-B2
Application number	US-201816222512-A
Country	US
Kind code	B2
Filing date	Dec 17, 2018
Priority date	Jul 11, 2016
Publication date	Jan 28, 2020
Grant date	Jan 28, 2020

Abstract

A projection optical unit for EUV projection lithography has a plurality of mirrors for imaging an object field into an image field with illumination light. At least one of the mirrors is an NI mirror and at least one of the mirrors is a GI mirror. A mirror dimension Dx of the at least one NI mirror in a plane of extent (xz) perpendicular to a plane of incidence (yz) satisfies the following relationship:

4 LLWx/IWPV max <Dx.

A mirror dimension Dy of the at least one GI mirror in the plane of incidence (yz) satisfies the following relationship:

4 LLWy /( IWPV max cos( a ))< Dy.

First claim

What is claimed is:

1. A projection optical unit, comprising:
a plurality of mirrors configured to image an object field into an image field with illumination light,
wherein:
the plurality of mirrors comprises more than six mirrors comprising an NI mirror arranged so that a reflection surface of the NI mirror is impinged upon with a maximum angle of incidence of a chief ray of a central field point;
the maximum angle of incidence is less than 45°;
a ray portion of the chief ray incident on the reflection surface and a ray portion of the chief ray emerging from the reflection surface lie in a plane of incidence (yz); and
a mirror dimension Dx of the NI mirror in a plane of extent (xz) perpendicular to the plane of incidence (yz) satisfies the following relationship:
4 LLWx/IWPV max <Dx,

wherein:
LLWx: étendue of the projection optical unit in the plane of extent (xz);
IWPV max : maximum difference between a maximum angle of incidence and a minimum angle of incidence of the illumination light, respectively, at the same location and determined on the entire reflection surface of the NI mirror; and
the projection optical unit is an EUV lithography projection optical unit.

2. The projection optical unit of claim 1 , wherein the mirror dimension Dx of the NI mirror is at least 200 mm.

3. The projection optical unit of claim 1 , wherein IWPV max is at least 3°.

4. The projection optical unit of claim 3 , wherein IWPV max is at most 10°.

5. The projection optical unit of claim 1 , wherein IWPVmax is at most 10°.

6. The projection optical unit of claim 1 , wherein the projection optical unit is telecentric on the object side.

7. The projection optical unit of claim 1 , wherein:
the image field which is spanned by a coordinate x perpendicular to a plane of incidence (yz) and a coordinate y perpendicular thereto; and
an aspect ratio x bf /y bf of the image field is greater than 13.

8. An optical system, comprising:
an illumination optical unit configured to illuminate the object field with the imaging light; and
a projection optical unit according to claim 1 .

9. A projection exposure apparatus, comprising:
an EUV light source;
an illumination optical unit configured to illuminate the object field with the imaging light; and
a projection optical unit according to claim 1 .

10. A method of using a projection exposure apparatus comprising an illumination optical unit, an imaging optical unit and an EUV light source, the method comprising:
using the illumination optical unit to illuminate a reticle with light generated by the EUV light source; and
using the projection optical unit to project at least a portion of the illuminated reticle onto a light-sensitive layer,
wherein the projection optical unit comprises a projection optical unit according to claim 1 .

11. A projection optical unit, comprising:
a plurality of mirrors configured to image an object field into an image field with illumination light,
wherein:
the plurality of mirrors comprises a GI mirror arranged so that a reflection surface of the mirror is impinged upon with a maximum angle of incidence of a chief ray of a central field point;
the maximum angle of incidence being greater than 45°, wherein a ray portion of the chief ray incident on the reflection surface and a ray portion of the chief ray emerging from the reflection surface lie in a plane of incidence (yz);
a mirror dimension Dy of the at least one GI mirror in the plane of incidence satisfies the following relationship:
4 LLWy /( IWPV max cos( a ))< Dy,

wherein:
LLWy: étendue of the projection optical unit in the plane of incidence (yz);
IWPV max : maximum difference between a maximum angle of incidence and a minimum angle of incidence of the illumination light on the reflection surface of the GI mirror;
a: angle of incidence of a chief ray of the central field point on the reflection surface of the GI mirror; and
the projection optical unit is an EUV lithography projection optical unit.

12. The projection optical unit of claim 11 , wherein the mirror dimension Dy of the at least one GI mirror is at least 100 mm.

13. The projection optical unit of claim 11 , wherein IWPV max is at least 0.25°.

14. The projection optical unit of claim 11 , wherein IWPV max is at most 4°.

15. The projection optical unit of claim 11 , wherein the plurality of mirrors further comprises an NI mirror arranged so that a reflection surface of the NI mirror is impinged upon with a maximum angle of incidence of a chief ray of a central field point,
wherein:
the maximum angle of incidence upon the NI mirror of the chief ray of the central field point is less than 45°;
a ray portion of the chief ray incident on the reflection surface of the NI mirror and a ray portion of the chief ray emerging from the reflection surface of the NIT mirror lie in a plane of incidence (yz); and
a mirror dimension Dx of the NI mirror in a plane of extent (xz) perpendicular to the plane of incidence (yz) satisfies the following relationship:
4 LLWy /( IWPV′ max cos( a ))< Dy,

wherein:
LLWx: étendue of the projection optical unit in the plane of extent (xz);
IWPV′ max : maximum difference between a maximum angle of incidence and a minimum angle of incidence of the illumination light, respectively, at the same location and determined on the entire reflection surface of the NI mirror.

16. The projection optical unit of claim 11 , wherein the projection optical unit is telecentric on the object side.

17. The projection optical unit of claim 11 , wherein:
the image field which is spanned by a coordinate x perpendicular to a plane of incidence (yz) and a coordinate y perpendicular thereto; and
an aspect ratio x bf /y bf of the image field is greater than 13.

18. An optical system, comprising:
an illumination optical unit configured to illuminate the object field with the imaging light; and
a projection optical unit according to claim 11 .

19. A projection exposure apparatus, comprising:
an EUV light source;
an illumination optical unit configured to illuminate the object field with the imaging light; and
a projection optical unit according to claim 11 .

20. A method of using a projection exposure apparatus comprising an illumination optical unit, an imaging optical unit and an EUV light source, the method comprising:
using the illumination optical unit to illuminate a reticle with light generated by the EUV light source; and
using the projection optical unit to project at least a portion of the illuminated reticle onto a light-sensitive layer,
wherein the projection optical unit comprises a projection optical unit according to claim 11 .

21. The projection optical unit of claim 1 , wherein the plurality of mirrors comprises at most 10 mirrors.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Schwab Markus
• Enkisch Hartmut
• Schicketanz Thomas

Classifications

• G02B17/0663 Primary

  off-axis or unobscured systems in which not all of the mirrors share a common axis of rotational symmetry, e.g. at least one of the mirrors is warped, tilted or decentered with respect to the other elements · CPC title

• G03F7/70233

  Optical aspects of catoptric systems, i.e. comprising only reflective elements, e.g. extreme ultraviolet [EUV] projection systems · CPC title

• G03F7/702

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

• G03F7/70958

  Optical materials or coatings, e.g. with particular transmittance, reflectance or anti-reflection properties · CPC title

• G02B5/0891

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