Method and apparatus for angular-resolved spectroscopic lithography characterization

• US 20060033921A1
• Filed: 08/16/2004
• Published: 02/16/2006
• Est. Priority Date: 08/16/2004
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Den Boef, Arie Jeffrey, Dusa, Mircea, Marie Kiers, Antoine Gaston, Der Schaar, Maurits Van
• Granted Patent: US 7,791,727 B2
• Time in Patent Office: Days
• US Class Current: 356/446
• CPC Class Codes: G01N 21/8806 Specially adapted optical and illumination features
• CPC Class Codes: G03F 7/70341 Details of immersion lithography aspects, e.g. exposure media or control of immersion liquid supply chemical composition of immersion liquids G03F7/2041
• CPC Class Codes: G03F 7/70633 Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching
• CPC Class Codes: G03F 7/7065 Defects, e.g. optical inspection of patterned layer for defects
• CPC Class Codes: G03F 9/7034 Leveling

Abstract

An apparatus and method to determine a property of a substrate by measuring, in the pupil plane of a high numerical aperture lens, an angle-resolved spectrum as a result of radiation being reflected off the substrate. The property may be angle and wavelength dependent and may include the intensity of TM- and TE-polarized light and their relative phase difference.

Claims

1. A scatterometer configured to measure a property of a substrate, comprising:

a high numerical aperture lens; and

a detector configured to detect an angle-resolved spectrum of a radiation beam reflected from a surface of the substrate,

wherein the property of the substrate can be measured by measuring, in the pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously.

2. The scatterometer according to claim 1, wherein the numerical aperture of the lens is at least 0.9.

3. The scatterometer according to claim 1, wherein the numerical aperture of the lens is at least 0.95.

4. The scatterometer according to claim 1, wherein the property of the reflected spectrum comprises (a) an intensity of transverse magnetic and transverse electric polarized light, (b) a phase difference between transverse magnetic and transverse electric polarized light, or both (a) and (b).

5. The scatterometer according to claim 1, wherein the property of the substrate is further measured by measuring, in the pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of wavelengths simultaneously.

6. The scatterometer according to claim 5, wherein the plurality of wavelengths each has a bandwidth *8 and a spacing of at least 2*8.

7. The scatterometer according to claim 1, comprising an extended broadband radiation source configured to provide the radiation beam to the substrate surface, the radiation beam having a wavelength of at least 50 nm.

8. The scatterometer according to claim 1, wherein an overlay of two misaligned periodic structures can be measured by measuring asymmetry in the reflected spectrum, the asymmetry being related to the extent of the overlay.

9. The scatterometer according to claim 1, comprising a wavelength multiplexer between a radiation source configured to provide the radiation beam and the substrate and a demultiplexer between the substrate and the detector.

10. The scatterometer according to claim 9, wherein the wavelength multiplexer comprises a dispersive element placed at a back-projected object plane.

11. The scatterometer according to claim 10, wherein the dispersive element is a grating or prism adapted to accommodate N discrete wavelengths each with a bandwidth *8 and a spacing of at least 2*8.

12. The scatterometer according to claim 9, wherein the surface area of a radiation source configured to provide the radiation beam is split into N parts that are each coupled to the wavelength multiplexer, where N is the number of discrete wavelengths.

13. The scatterometer according to claim 9, wherein the demultiplexer comprises a dispersive element placed at a pupil plane.

14. The scatterometer according to claim 1, comprising an optical wedge in an object plane to achieve defined separation of angle-resolved spectra in the pupil plane.

15. The scatterometer according to claim 1, comprising a non-polarizing beam splitter and a tilted mirror configured to couple off a portion of the radiation beam emitted from a radiation source for separate measurement with the detector.

16. The scatterometer according to claim 15, wherein the portion of the radiation beam is used to measure an intensity of the radiation beam.

17. The scatterometer according to claim 15, adapted to compensate for fluctuations in intensity of the radiation beam.

18. The scatterometer according to claim 15, comprising a pupil stop configured to limit the size of the portion of the radiation beam and to ensure that the portion of the radiation beam is parallel to the remainder of the radiation beam

19. A scatterometer configured to measure a property of a substrate, comprising:

a high numerical aperture lens; and

a space between the substrate and the high numerical aperture lens comprising a liquid,

wherein the property of the substrate can be measured by measuring, in the pupil plane of the high numerical aperture lens, a property of an angle-resolved spectrum of a radiation beam reflected from a surface of the substrate, at a plurality of angles and a plurality of wavelengths simultaneously.

20. The scatterometer according to claim 19, wherein the liquid is water.

21. The scatterometer according to claim 19, wherein the numerical aperture of the lens is at least 0.9.

22. The scatterometer according to claim 19, wherein the numerical aperture of the lens is at least 0.95.

23. The scatterometer according to claim 19, wherein the property of the reflected spectrum comprises (a) an intensity of transverse magnetic and transverse electric polarized light, (b) a phase difference between transverse magnetic and transverse electric polarized light, or both (a) and (b).

24. The scatterometer according to claim 19, comprising a wavelength multiplexer between a radiation source configured to provide the radiation beam and the substrate and a demultiplexer between the substrate and a detector configured to measure the property of the reflected spectrum.

25. A scatterometer configured to measure a property of a substrate, comprising:

a high numerical aperture lens; and

an edge adapted to be placed in one of opposite halves of an intermediate object plane,

wherein the property of the substrate can be measured by measuring, in the pupil plane of the high numerical aperture lens, a property of an angle-resolved spectrum of a radiation beam reflected from a surface of the substrate, at a plurality of angles and a plurality of wavelengths simultaneously.

26. The scatterometer according to claim 25, wherein the edge is a Foucault knife edge.

27. The scatterometer according to claim 25, wherein the numerical aperture of the lens is at least 0.9.

28. The scatterometer according to claim 25, wherein the numerical aperture of the lens is at least 0.95.

29. The scatterometer according to claim 25, wherein the property of the reflected spectrum comprises (a) an intensity of transverse magnetic and transverse electric polarized light, (b) a phase difference between transverse magnetic and transverse electric polarized light, or both (a) and (b).

30. The scatterometer according to claim 25, comprising a wavelength multiplexer between a radiation source configured to provide the radiation beam and the substrate and a demultiplexer between the substrate and a detector configured to measure the property of the reflected spectrum.

31. A scatterometer configured to measure a property of a substrate, comprising:

a high numerical aperture lens; and

a detector configured to detect an angle-resolved radiation spectrum reflected from a surface of the substrate,

wherein the property of the substrate can be measured by measuring, in the pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles and wavelengths simultaneously.

32. The scatterometer according to claim 31, wherein the numerical aperture of the lens is at least 0.9.

33. The scatterometer according to claim 31, wherein the property of the reflected spectrum comprises (a) an intensity of transverse magnetic and transverse electric polarized light, (b) a phase difference between transverse magnetic and transverse electric polarized light, or both (a) and (b).

34. The scatterometer according to claim 31, comprising a wavelength multiplexer between a radiation source configured to provide the radiation beam and the substrate and a demultiplexer between the substrate and the detector.

35. An inspection method, comprising:

printing a pattern onto a substrate; and

measuring, in the pupil plane of a high numerical aperture lens, a reflected spectrum of the pattern.

36. The method according to claim 35, wherein measuring the reflected spectrum comprises measuring (a) a property of the reflected spectrum at a plurality of angles, (b) a plurality of wavelengths, or both (a) and (b) simultaneously.

37. The method according to claim 36, wherein the property of the reflected spectrum comprises (i) an intensity of transverse magnetic and transverse electric polarized light, (ii) a phase difference between transverse magnetic and transverse electric polarized light, or both (i) and (ii).

38. The method according to claim 35, wherein the numerical aperture of the lens is at least 0.9.

39. An inspection method, comprising:

providing two gratings layered in parallel but misaligned, thereby creating an overlay of one grating with respect to the other;

measuring a reflected spectrum of the gratings using a scatterometer; and

deriving the extent of the overlay from the asymmetry in the reflected spectrum.

40. The method according to claim 39, wherein measuring the reflected spectrum comprises measuring (a) a property of the reflected spectrum at a plurality of angles, (b) a plurality of wavelengths, or both (a) and (b) simultaneously.

41. The method according to claim 40, wherein the property of the reflected spectrum comprises (i) an intensity of transverse magnetic and transverse electric polarized light, (ii) a phase difference between transverse magnetic and transverse electric polarized light, or both (i) and (ii).

42. The method according to claim 39, wherein the numerical aperture of the lens is at least 0.9.

43. A device manufacturing method, comprising:

projecting a beam of radiation onto a target portion of a substrate,

using a scatterometer to measure, in the pupil plane of a high numerical aperture lens, a reflected spectrum of the beam through a predetermined range of angles and wavelengths simultaneously.

44. The method according to claim 43, wherein measuring the reflected spectrum comprises measuring (a) a property of the reflected spectrum, the property of the reflected spectrum comprising an intensity of transverse magnetic and transverse electric polarized light, (b) a phase difference between transverse magnetic and transverse electric polarized light, or both (a) and (b).

45. The method according to claim 43, wherein the numerical aperture of the lens is at least 0.9.

46. A method of creating an angle-resolved spectroscopic image of a grating pattern, comprising using apertures that mimic lithography exposure conditions when the grating pattern is created.