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Diffraction spectral filter for use in extreme-UV lithography condenser

Imported: 23 Feb '17 | Published: 22 Oct '02

William C. Sweatt, Daniel A. Tichenor, Luis J. Bernardez

USPTO - Utility Patents

Abstract

A condenser system for generating a beam of radiation includes a source of radiation light that generates a continuous spectrum of radiation light; a condenser comprising one or more first optical elements for collecting radiation from the source of radiation light and for generating a beam of radiation; and a diffractive spectral filter for separating first radiation light having a particular wavelength from the continuous spectrum of radiation light. Cooling devices can be employed to remove heat generated. The condenser system can be used with a ringfield camera in projection lithography.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a perspective view of an EUV photolithography system showing the beams going through its set of correcting mirrors and showing the interaction of the beam with the camera;

FIG. 1B illustrates a steeply tilted biconvex mirror;

FIGS. 2A and 2B illustrate a beam segment before and after reshaping;

FIG. 3 is a side-view of the condenser system without correcting mirrors, showing the reimaging of the point source into a ringfield with the images crossing over the center line of the system;

FIG. 4 is another side-view showing the geometries of the mirrors and the beams in more detail or this embodiment;

FIGS. 5 and 7 illustrate a diffraction element;

FIGS. 6 and 8 illustrate a diffraction element in a condenser system; and

FIG. 9 illustrates blazed gratings; and

FIG. 10 illustrates a plan view of an off-axis focus blazed grating.

Claims

1. A condenser system for use with a ringfield camera comprising:

2. The condenser system of claim 1 further comprising one or more absorptive members for absorbing at least a portion of radiation light of a wavelength other than that of the first radiation light.

3. The condenser system of claim 1 wherein the first radiation light has a wavelength of about 13.4 nm.

4. The condenser system of claim 1 wherein the said collector mirrors comprise six substantially equal radial segments of a parent aspheric mirror.

5. The condenser system of claim 1 wherein said concave relay mirror shapes a beam having a chord angle of about 50 degrees into a second beam having a chord angle of about 28 degrees.

6. The condenser system of claim 5 wherein the concave relay mirror reflects radiation from the source of radiation at an angle of incidence greater than 50 degrees as measured from normal at the center of the concave relay mirror.

7. The condenser system of claim 1 wherein the one or more spectral filters is fabricated on one or more of the corresponding number of sets of correction mirror means.

8. The condenser system of claim 7 wherein the one or more spectral filters comprise a diffraction grating that has a blazed-phase configuration.

9. The condenser system of claim 8 wherein the one or more spectral filters is fabricated on one or more near normal mirrors and the diffraction grating has a spatial frequency of about 150 mm

−1 to 2000 mm

−1 and a blaze height of about 5 nm to 8 nm.

10. The condenser system of claim 8 wherein the one or more spectral filters is fabricated on one or more grazing incidence mirrors and the diffraction grating has a spatial frequency of about 70 mm

−1 to 1000 mm

−1 and a blaze height of about 25 nm to 50 nm.

11. The condenser system of claim 8 wherein the diffraction grating is a discrete profile blaze-grating.

12. The condenser system of claim 11 wherein the phase grating has more than 2 levels.

13. The condenser system of claim 8 wherein the one or more spectral filters is fabricated on one or more grazing incidence flat mirrors.

14. The condenser system of claim 13 wherein the grating is approximately a linear grating.

15. The condenser system of claim 13 wherein the grating is an off-axis section of a focusing grating.

16. The condenser system of claim 15 wherein the minimum spat frequency of the grating is large enough to separate the undiffracted light and the first diffracted order which has an EUV wavelength.

17. The condenser system of claim 7 wherein the one or more spectral filters is fabricated on one or more flat mirrors with angles of incidence less than 30 degrees.

18. The condenser system of claim 17 wherein the grating is approximately a linear grating.

19. The condenser system of claim 17 wherein the grating is an off-axis section of a focusing grating.

20. The condenser system of claim 19 wherein the minimum spatial frequency of the grating is large enough to separate the undiffracted light and the first diffracted order which has an EUV wavelength.

21. The condenser system of claim 1 wherein the one or more diffractive spectral filters comprise cooling means.

22. A condenser system for use with a ringfield camera comprising:

23. The condenser system of claim 22 further comprising one or more absorptive member for absorbing at least a portion of radiation light of a wavelength other than that of the first radiation light.

24. The condenser system of claim 22 wherein the first radiation light has a wavelength of about 13.4 nm.

25. The condenser system of claim 22 wherein the said collector mirrors comprise six substantially equal radial segments of a parent aspheric mirror.

26. The condenser system of claim 22 wherein said concave relay mirror shapes a beam having a chord angle of about 50 degrees into a second beam having a chord angle of about 28 degrees.

27. The condenser system of claim 26 wherein the concave relay mirror reflects radiation from the source of radiation at an angle of incidence greater than 50 degrees as measured from normal at the center of the concave relay mirror.

28. The condenser system of claim 22 wherein the one or more spectral filters is fabricated on one or more of the corresponding number of sets of correction mirror means.

29. The condenser system of claim 28 wherein the one or more spectral filters comprise a diffraction grating that has a blazed-phase configuration.

30. The condenser system of claim 29 wherein the diffraction grating has a spatial frequency of about 70 mm

−1 to 2000 mm

−1 and a blaze height of about 5 nm to 8 nm.

31. The condenser system of claim 29 wherein the one or more spectral filters is fabricated on one or more grazing incidence mirrors and the diffraction grating has a spatial frequency of about 70 mm

−1 to 1000 mm

−1 and a blaze height of about 25 nm to 50 nm.

32. The condenser system of claim 29 wherein the diffraction grating is a discrete profile blaze-grating.

33. The condenser system of claim 32 wherein the phase grating has more than 2 levels.

34. The condenser system of claim 29 wherein the one or more spectral filters is fabricated on one or more grazing incidence flat mirrors.

35. The condenser system of claim 34 wherein the grating is approximately a linear grating.

36. The condenser system of claim 34 wherein the grating is an off-axis section of a focusing grating.

37. The condenser system of claim 36 wherein the minimum spatial frequency of the grating is large enough to separate the undiffracted light and the first diffracted order which has an EUV wavelength.

38. The condenser system of claim 22 wherein the one or more spectral filters comprise cooling means.

39. The condenser system of claim 22 wherein the one or more spectral filters is fabricated on one or more flat mirrors with angles of incidence less than 30 degrees.

40. The condenser system in

39 wherein the grating is approximately a linear grating.

41. The condenser system in

39 wherein the grating is an off-axis section of a focusing grating.

42. The condenser system in

41 wherein the minimum spatial frequency of the grating is large enough to separate the undiffracted light and the first diffracted order which has an EUV wavelength.

43. A condenser system for generating a beam of radiation that is directed to a mask comprising:

44. The condenser system of claim 43 wherein the first radiation light has a wavelength of about 13.4 nm.

45. The condenser system of claim 43 wherein the diffraction grating is discrete profile blazed-grating.

46. The condenser system of claim 45 wherein the phase grating has more than 2 levels.

47. The condenser system of claim 43 wherein the diffractive spectral filter comprises cooling means.

48. The condenser system of claim 43 wherein the grating is approximately a linear grating.

49. The condenser system of claim 43 wherein the grating is on a curved surface.

50. A condenser system for generating a beam of radiation that is directed to a mask comprising:

51. The condenser system of claim 50 wherein the first radiation light has a wavelength of about 13.4 nm.

52. The condenser system of claim 50 wherein the diffractive spectral filter comprises cooling means.

53. A condenser system for generating a beam of radiation that is directed to a mask comprising:

54. The condenser system of claim 53 wherein the first radiation light has a wavelength of about 13.4 nm.