Catadioptric projection objective with parallel, offset optical axes

Patent metadata

Field	Value
Publication number	US-9772478-B2
Application number	US-201514677089-A
Country	US
Kind code	B2
Filing date	Apr 2, 2015
Priority date	Jan 14, 2004
Publication date	Sep 26, 2017
Grant date	Sep 26, 2017

Abstract

A projection objective configured to image an object field in an object plane into an image field in an image field plane includes a reflective unit, a first refractive unit, and a second refractive unit. An optical axis of the first refractive unit is parallel to but displaced from an optical axis of the second refractive unit. The reflective unit includes a first curved mirror and a second curved mirror. The second curved mirror is immediately downstream from the first curved mirror in a path of light from the object plane to the image plane. The projection objective is a microlithography projection objective.

First claim

What is claimed is:

1. A projection objective configured to image an object field in an object plane into an image field in an image field plane, the projection objective comprising:
a reflective unit, comprising:
a first curved mirror; and
a second curved mirror, the second curved mirror being immediately downstream from the first curved mirror in a path of light from the object plane to the image plane;

a first refractive unit having an optical axis; and
a second refractive unit having an optical axis,
wherein:
the optical axis of the first refractive unit is parallel to the optical axis of the second refractive unit, the optical axis of the first refractive unit is a non-zero distance from the optical axis of the second refractive unit, and
the projection objective is a microlithography projection objective.

2. The projection objective of claim 1 , wherein the first refractive unit is upstream from the reflective unit in the path of light from the object plane to the image plane.

3. The projection objective of claim 2 , wherein the second refractive unit is downstream from the reflective unit in the path of light from the object plane to the image plane.

4. The projection objective of claim 1 , wherein the first curved mirror is a concave mirror.

5. The projection objective of claim 1 , wherein the second curved mirror is a concave mirror.

6. The projection objective of claim 1 , wherein the projection objective forms at least one intermediate image in a light path from the object plane to the image plane.

7. The projection objective of claim 6 , wherein the intermediate image is formed in the light path between the first refractive unit and the reflective unit.

8. The projection objective of claim 7 , wherein the projection objective forms a second intermediate image in the light path from the object plane to the image plane.

9. The projection objective of claim 8 , wherein the second intermediate image is formed in the light path between the reflective unit and the second refractive unit.

10. The projection objective of claim 1 , wherein the projection objective further comprises at least one plane mirror.

11. The projection objective of claim 10 , wherein the plane mirror is positioned in the light path from the object plane to the image plane upstream from first and second curved mirrors of the reflective unit.

12. The projection objective of claim 11 , wherein the projection objective comprises exactly two plane mirrors.

13. The projection objective of claim 12 , wherein a first of the plane mirrors is positioned upstream from the first and second plane mirrors of the reflective unit in the light path from the object plane to the image plane and a second of the plane mirrors is positioned downstream from the first and second plane mirrors of the reflective unit in the light path.

14. The projection objective of claim 1 , wherein the reflective unit has an optical axis non-parallel to the optical axis of the first refractive unit.

15. The projection objective of claim 1 , further comprising an aperture stop between the reflective unit and the image plane.

16. The projection objective of claim 1 , wherein the projection objective has an image-side numerical aperture greater than 1.

Assignees

• Zeiss Carl Smt Gmbh

Inventors

• Shafer David
• Ulrich Wilhelm
• Dodoc Aurelian
• Von Buenau Rudolf Murai
• Mann Hans-Juergen
• Epple Alexander

Classifications

• G02B17/0812 Primary

  off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry · CPC title

• G02B17/0804 Primary

  using two curved mirrors (G02B17/0864, G02B17/0896 takes precedence) · CPC title

• G02B17/0856

  comprising a refractive element with a reflective surface, the reflection taking place inside the element, e.g. Mangin mirrors · CPC title

• G02B17/08

  Catadioptric systems {(used in non-imaging applications G02B19/00)} · CPC title

• G02B17/0844

  off-axis or unobscured systems in which all of the mirrors share a common axis of rotational symmetry · CPC title