Method and apparatus for angular-resolved spectroscopic lithography characterization

• US 7,791,727 B2
• Filed: 08/16/2004
• Issued: 09/07/2010
• 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, Van Der Schaar, Maurits, Dusa, Mircea, Kiers, Antoine Gaston Marie
• Primary Examiner(s): Toatley, Jr.; Gregory J
• Assistant Examiner(s): Richey; Scott M
• Application Number:
  US10/918,742
• Publication Number:
  US 20060033921A1
• Time in Patent Office: 2,213 Days
• Field of Search: 356/401, 356/490, 356/515, 356/521, 250/237.G
• US Class Current: 356/401
• 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, comprising:

a lens configured to direct a radiation beam from a radiation source toward a pattern formed on a substrate; and

a detector located in a pupil plane of the lens and configured to detect an angle-resolved spectrum of the radiation beam reflected from the pattern,

wherein a property of the substrate is measured using the detector by measuring asymmetries between intensities of corresponding diffraction orders diffracted from the pattern in the reflected angle-resolved spectrum.

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

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

4. The scatterometer according to claim 1, wherein the detector is configured to measure at least one of (a) an intensity of a transverse magnetic and a transverse electric polarized light and (b) a phase difference between the transverse magnetic and the transverse electric polarized light.

5. The scatterometer according to claim 1, wherein asymmetries between intensities of corresponding diffraction orders diffracted from the pattern are a property of the reflected angle-resolved spectrum, wherein the property of the substrate is further measured by measuring, in the pupil plane of the lens, another property of the reflected angle-resolved spectrum at a plurality of wavelengths substantially simultaneously.

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

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

8. The scatterometer according to claim 1, wherein the asymmetries are related to an extent of an overlay between two misaligned periodic structures.

9. The scatterometer of claim 1, further 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 a separate measurement with the detector.

15. The scatterometer according to claim 1, further comprising an optical wedge in an object plane configured to achieve a pre-defined separation of the reflected angle-resolved spectrum in the pupil plane.

16. The scatterometer according to claim 1, wherein a portion of the radiation beam is used to measure an intensity of the radiation beam.

17. The scatterometer according to claim 1, the detector is adapted to compensate for fluctuations in an intensity pattern of the reflected radiation beam.

18. The scatterometer according to claim 1, further comprising a pupil stop configured to limit a size of a portion of the radiation beam.

10. A scatterometer, comprising:

a high numerical aperture lens configured to direct a radiation beam from a radiation source toward a substrate;

a detector located in a pupil plane of the high numerical aperture lens and configured to detect an angle-resolved spectrum of the radiation beam reflected a surface of the substrate; and

a wavelength multiplexer located between a radiation source configured to provide the radiation beam and the substrate and a wavelength demultiplexer located between the substrate and the detector,

wherein a property of the substrate is measured using the detector by measuring an asymmetry in the reflected angle-resolved spectrum at a plurality of angles substantially simultaneously.

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

12. The scatterometer according to claim 11, wherein the dispersive element is one of a grating and a prism adapted to accommodate N discrete wavelengths each having a spacing of at least twice a bandwidth of the plurality of wavelengths.

13. The scatterometer according to claim 10, wherein a surface area of the radiation source is split into N parts that are each coupled to the wavelength multiplexer, where N is a number of discrete wavelengths.

14. The scatterometer according to claim 10, wherein the wavelength demultiplexer comprises a dispersive element placed at the pupil plane.

19. A scatterometer, comprising:

a lens configured to direct a radiation beam from a radiation source toward a pattern formed on a substrate; and

a space between the substrate and the lens comprising a liquid,

wherein a property of the substrate is measured using a detector by measuring asymmetries between intensities of corresponding diffraction orders in an angle-resolved spectrum of a radiation beam diffracted from the pattern, at a plurality of angles and a plurality of wavelengths substantially simultaneously.

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

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

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

23. The scatterometer according to claim 19, wherein the detector is configured to measure at least one of (a) an intensity of a transverse magnetic and a transverse electric polarized light and (b) a phase difference between the transverse magnetic and the transverse electric polarized light.

24. The scatterometer of claim 19, further comprising a non-polarizing beam splitter and a tilted minor configured to couple off a portion of the radiation beam emitted from a radiation source for a separate measurement with the detector.

25. A scatterometer, comprising:

a high numerical aperture lens configured to direct a radiation beam from a radiation source toward a substrate;

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

a wavelength multiplexer located between a radiation source, configured to provide the radiation beam, and the substrate; and

a wavelength demultiplexer located between the substrate and the detector located in a pupil plane of the high numerical aperture lens, and configured to measure another property of the reflected spectrum,

wherein a property of the substrate is measured using a detector by measuring an asymmetry in 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 substantially simultaneously.

26. A scatterometer, comprising:

a lens configured to direct a radiation beam from a radiation source toward a pattern formed on a substrate; and

an edge adapted to be placed in one of opposite halves of an intermediate object plane associated with the lens,

wherein a property of the substrate is measured by a detector by measuring asymmetries between intensities of corresponding diffraction orders in an angle-resolved spectrum of a radiation beam diffracted from the pattern, at a plurality of angles and a plurality of wavelengths substantially simultaneously.

27. The scatterometer of claim 26, further 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 a separate measurement with the detector.

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

29. The scatterometer according to claim 26, wherein a numerical aperture of the lens is at least 0.9.

30. The scatterometer according to claim 26, wherein a numerical aperture of the lens is at least 0.95.

31. The scatterometer according to claim 26, wherein wherein the detector is configured to measure at least one of (a) an intensity of a transverse magnetic and a transverse electric polarized light and (b) a phase difference between the transverse magnetic and the transverse electric polarized light.

32. A scatterometer, comprising:

a high numerical aperture lens configured to direct a radiation beam from a radiation source toward a substrate;

an edge adapted to be placed in one of opposite halves of an intermediate object plane associated with the high numerical aperture lens;

a wavelength multiplexer located between a radiation, source configured to provide the radiation beam, and the substrate; and

a wavelength demultiplexer located between the substrate and the detector located in a pupil plane of the high numerical aperture lens, and configured to measure the property of the reflected spectrum,

wherein a property of the substrate is measured by a detector by measuring an asymmetry in 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 substantially simultaneously.