PROJECTION OBJECTIVE OF A MICROLITHOGRAPHIC PROJECTION EXPOSURE APPARATUS

• US 20110019169A1
• Filed: 10/01/2010
• Published: 01/27/2011
• Est. Priority Date: 07/25/2005
• Status: Active Grant

• Current Assignee: CARL Zeiss SMT GmbH (Carl-Zeiss-Stiftung)
• Original Assignee: Carl Zeiss AG (Carl-Zeiss-Stiftung)
• Inventors: Hauf, Markus, Holderer, Hubert, Bittner, Boris, Kazi, Arif, Weber, Jochen, Conradi, Olaf, Hummel, Wolfgang, Tayebati, Payam, Bleidistel, Sascha, Schwaer, Baerbel
• Granted Patent: US 7,990,622 B2
• Time in Patent Office: Days
• US Class Current: 355/30
• CPC Class Codes: G02B 27/0068 having means for controlling the degree of correction, e.g. using phase modulators, movable elements controlling the phase of light using moving or deformable elements G02B26/06
• CPC Class Codes: G02B 3/14 of variable focal length
• CPC Class Codes: G03F 7/70266 Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction
• CPC Class Codes: G03F 7/70825 Mounting of individual elements, e.g. mounts, holders or supports workpiece or mask holders G03F7/707

Abstract

A projection objective of a microlithographic projection exposure apparatus comprises a manipulator for reducing rotationally asymmetric image errors. The manipulator in turn contains a lens, an optical element and an interspace formed between the lens and the optical element, which can be filled with a liquid. At least one actuator acting exclusively on the lens is furthermore provided, which can generate a rotationally asymmetric deformation of the lens.

Claims

1. An apparatus, comprising:

a first optical element that is refractive;

a second element;

a liquid between the first optical element and the second element; and

an actuator coupled to the first optical element such that operation of the actuator causes a rotationally asymmetric deformation of the first optical element substantially without causing a deformation of the second element,

wherein the apparatus is a microlithographic projection exposure apparatus.

2. An apparatus according to claim 1, wherein the first optical element is a plane-parallel plate.

3. An apparatus according to claim 1, wherein the first optical element is a meniscus lens.

4. An apparatus according to claim 1, wherein the first optical element is a membrane.

5. An apparatus according to claim 1, wherein the interspace has, in a direction along an optical axis of the projection objective, a maximum thickness of less than 1 mm.

6. An apparatus according to claim 5, wherein the maximum thickness is less than 2 μ

m.

7. An apparatus according to claim 1, wherein the deformation of the first optical element has an m-fold symmetry or a superposition of a plurality of m-fold symmetries with m being an even, positive integer.

8. An apparatus according to claim 1, comprising at least two actuators that are configured to exert bending moments on the first optical element.

9. An apparatus according to claim 8, wherein the at least two actuators are arranged along a circumference of the first optical element.

10. An apparatus according to claim 8, wherein the actuators are configured such that at least two deformations of the first optical element can be generated having a different m-fold symmetry.

11. An apparatus according to claim 1, wherein the second element is reflective.

12. An apparatus according to claim 1, wherein the second element is refractive.

13. An apparatus according to claim 12, wherein the second element is a meniscus lens or a plane-parallel plate.

14. An apparatus according to claim 1, comprising a second actuator configured to act exclusively on the second element to generate a deformation of the second element.

15. An apparatus according to claim 14, wherein the deformation of the second element is rotationally asymmetric.

16. An apparatus according to claim 14, wherein the deformation of the second element is rotationally symmetric.

17. An apparatus according to claim 1, comprising a pressure equalizer configured to maintain a constant pressure of the liquid in the immersion space.

18. An apparatus according to claim 1, wherein the first optical element is arranged in or in close proximity of a pupil plane.

19. An apparatus according to claim 1, wherein the actuator is fastened to a front or a rear surface of the first optical element, and wherein the actuator is configured to produce on the first optical element compressive and/or tensile forces along directions that are at least substantially tangential to the surface.

20. An apparatus according to claim 19, wherein the actuator is formed by a layer which is applied to the surface, the layer having a variable dimension along at least one direction.

21. An apparatus according to claim 20, wherein the layer comprises a piezo electric material.

22. An apparatus according to claim 20, wherein the layer comprises a material having a coefficient of thermal expansion that is different from the coefficient of thermal expansion of the first optical element.

23. An apparatus according to claim 22, comprising a device configured to controllably change the temperature of the layer.

24. An apparatus according of claim 23, wherein the device is configured to direct radiation onto the layer.

25. An apparatus according of claim 23, wherein the device is configured to apply a voltage to the layer.

26. An apparatus according to claim 20, wherein a plurality of layers have the shape of ring segments, the ring segments forming a circular ring which is centered with respect to an optical axis of the projection objective.

27. An apparatus according to claim 26, wherein the ring segments are spaced apart by gaps.

28. An apparatus according claim 19, wherein a plurality of actuators are distributed over the surface within an area through which projection light propagates.

29. An apparatus according to claim 28, wherein the plurality of actuators are at least substantially transparent at the wavelengths of the projection light.

30. An apparatus according to claim 28, wherein the plurality of actuators are opaque at the wavelengths of the projection light, and wherein the manipulator is arranged in or in close proximity to a pupil plane of the projection objective.

31. An apparatus according to claim 1, comprising a sensor that is fastened to a front or rear surface of the first optical element, wherein the sensor is configured to measure a deformation of the first optical element produced by the actuator.

32. An apparatus according to claim 31, wherein the sensor is configured to produce an output signal which depends on the amount of compressive and/or tensile forces produced in the sensor by a deformation of the first optical element.

33. An apparatus according to claim 1, wherein a plurality of actuators are distributed over an area, through which projection light is allowed to propagate, of a surface of the first optical element which is opposite to a surface which is in contact with the liquid.

34. An apparatus according to claim 33, comprising a further optical element that is refractive on which the plurality of actuators rest.

35. An apparatus according to claim 1, further comprising:

a third optical element; and

means for deforming the third optical element,

wherein there is an interspace between the second element and a third optical element, both the second element and the third optical element are refractive.

36. An apparatus according to claim 1, comprising a device configured to change the pressure of the liquid.

37. An apparatus according to claim 1, wherein the first optical element has a shape in its undeformed state which is rotationally asymmetric.

38. An apparatus according to claim 37, wherein the first optical element has a thickness distribution in its undeformed state which is rotationally asymmetric.

39. An apparatus according to claim 38, wherein the first optical element has a first surface, which is in contact to the liquid and has a rotationally asymmetric shape, and a second surface opposite the first surface, wherein the second surface has a rotationally symmetric shape.

40. An apparatus according to claim 1, further comprising:

a controller configured to drive the at least one actuator; and

a sensor arrangement connected to the controller, the sensor arrangement being configured to determine the image errors.

41. The apparatus of claim 40, wherein the sensor arrangement comprises a CCD sensor, which is positionable in an image plane of the projection objective or in a field plane conjugate therewith.

42. The apparatus of claim 41, wherein the manipulator, the controller and the sensor arrangement form a closed feedback loop.

44. A method, comprising:

using an apparatus to produce a microstructured component, the apparatus being selected from the group consisting of an apparatus according to claim 1 and an apparatus according to claim 43.

45. A method according to claim 44, further comprising:

arranging a mask in an object plane of the projection objective; and

projecting the mask onto a photosensitive layer which is arranged in an image plane of the projection objective.

43. An apparatus, comprising:

a first optical element that is refractive, the first optical element having a thickness distribution in its undeformed state which is rotationally asymmetric,

a second element,

a fluid between the first optical element and the second element; and

means for deforming the first optical element,

wherein the apparatus is a microlithographic projection exposure apparatus.

46. An apparatus, comprising:

a first optical element that is refractive;

a second element;

a liquid between the first optical element and the second element; and

an actuator coupled to the first optical element such that operation of the actuator causes a rotationally asymmetric deformation of the first optical element substantially without causing a deformation of the second element,

wherein a ratio between the refractive index of the first optical element and the refractive index of the liquid is between 0.9 and 1.1, and the apparatus is a microlithographic projection exposure apparatus.

47. An apparatus according to claim 46, wherein the ratio between the refractive index of the first optical element and the refractive index of the liquid is between 0.99 and 1.01.