Method and apparatus for angular-resolved spectroscopic lithography characterization

• US 20060066855A1
• Filed: 08/15/2005
• Published: 03/30/2006
• 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: Van Kraaij, Markus Gerardus Martinus, Bleeker, Arno Jan, Luehrmann, Paul Frank, Dusa, Mircea, Kiers, Antoine Gaston Marie, Grouwstra, Cedric Desire, Pellemans, Henricus Petrus Maria, Schaar, Maurits Van Der, Boef, Arie Jeffrey Maria Den, Laurentius Maria Van Dommelen, Youri Johannes
• Granted Patent: US 7,791,732 B2
• Time in Patent Office: Days
• 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 radiation 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 a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously, the scatterometer further comprising;

a reflector;

a detector configured to detect and combine at least two images reflected from the reflector; and

a processor configured to create a differential equation based on the images from which the illumination profile of the radiation beam may be determined.

2. The scatterometer according to claim 1, wherein the illumination profile is used to correct a measurement of the property of the reflected spectrum at higher diffraction orders.

3. The scatterometer according to claim 1, wherein the reflector comprises a concave mirror and the scatterometer comprises a mechanism for moving the radiation beam over the surface of the mirror in order to obtain a plurality of reflection angles.

4. The scatterometer according to claim 1, wherein the reflector comprises a convex mirror and the scatterometer is configured to move the radiation beam over the surface of the mirror in order to obtain a plurality of reflection angles.

5. The scatterometer according to claim 1, wherein the reflector comprises a flat mirror and the scatterometer is configured to tilt the mirror through a plurality of angles.

6. The scatterometer according to claim 1, comprising a plurality of mirrors at different tilt angles.

7. The scatterometer according to claim 1, wherein the measured reflection angle is in a radial direction.

8. The scatterometer according to claim 1, wherein the measured reflection angle is in an azimuthal direction.

9. An inspection method, comprising:

measuring, in a pupil plane of a high numerical aperture lens, a property of a spectrum of a radiation beam reflected from a surface of a substrate;

normalizing the radiation beam by reflecting it off one or more mirrors;

measuring and combining at least two images created from different reflection angles of the radiation beam off the one or more mirrors; and

creating a differential equation to reconstruct the illumination profile of the radiation beam.

10. 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 a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously, the scatterometer further comprising;

a first polarizer configured to linearly polarize the radiation beam;

a beam splitter configured to split the radiation beam into two orthogonal beam components;

a second polarizer configured to polarize the reflected beam;

a variable compensator positioned between the first and second polarizers configured to vary the optical path difference between the orthogonal beam components; and

a 2-dimensional detector configured to detect sinusoidal intensity variation of the beam components.

11. The scatterometer according to claim 10, wherein the compensator is placed in an illumination branch of the scatterometer.

12. The scatterometer according to claim 10, wherein the compensator is positioned between the beam splitter and the high numerical aperture lens.

13. 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 a pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of angles simultaneously, the scatterometer further comprising

a second detector branch configured to carry out coarse overlay measurements.

14. The scatterometer according to claim 13, wherein the second detector branch is configured to measure in an image plane of the substrate.

15. The scatterometer according to claim 13, wherein the second detector branch is configured to measure an overlay on a substrate, the overlay being equal to an integer number multiplied by a pitch of a substrate grating.

16. 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;

deriving an extent of the overlay from the asymmetry in the reflected spectrum; and

carrying out a coarse overlay measurement of the gratings, comprising determining whether the overlay is greater than a grating pitch.

17. The method according to claim 16, comprising:

carrying out two image plane measurements of a radiation beam to determine the presence of an overlay greater than the grating pitch; and

if the determined overlay is below a threshold, carrying out a pupil plane measurement of the radiation beam.

18. A scatterometer configured to detect local distortions in a grating, comprising:

a high numerical aperture lens;

a grating configured to scatter a radiation beam in a specular direction; and

a detector configured to detect an angle-resolved spectrum of the scattered beam at various angles outside the specular direction,

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

19. The scatterometer according to claim 18, wherein the radiation beam comprises annular illumination.

20. A scatterometer configured to simultaneously measure a property of multiple targets on a substrate, comprising:

a high numerical aperture lens;

a projector configured to project a plurality of illumination spots onto a substrate; and

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

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

21. The scatterometer according to claim 20, comprising a divider configured to create two identically polarized illumination spots.

22. A device manufacturing method, comprising:

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

dividing the beam into a plurality of beams before the beam reaches the substrate; and

using a scatterometer to measure, in a pupil plane of a high numerical aperture lens, a reflected spectrum of the plurality of beams through a range of angles and wavelengths simultaneously in order to simultaneously measure multiple targets on the substrate.

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

a high numerical aperture lens;

an illuminator configured to produce a radiation beam having an annular intensity distribution in a conjugate plane to the substrate; and

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

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

24. An inspection method, comprising:

projecting a radiation beam comprising an annular intensity distribution in a conjugate plane to a substrate, onto the substrate; and

measuring, in a pupil plane of a high numerical aperture lens, a spectrum of the radiation beam reflected from a pattern printed on the substrate.

25. An apparatus to calculate variations in tilt of a substrate, comprising:

an illuminator configured to create a radiation beam with an annular distribution in a conjugate plane to the substrate;

a shaped obscuration configured to be in the radiation beam;

a detector configured to detect a change in a width, shape, or both of an image of the shaped obscuration on the substrate caused by a variation in the substrate tilt; and

a processor configured to calculate the variation in the substrate tilt based on the change detected by the detector.

26. A method of detecting bubble defects of a substrate from an immersion lithographic apparatus, comprising:

measuring, in a pupil plane of a high numerical aperture lens, a reflected spectrum of a pattern printed on the substrate; and

determining from the reflected spectrum whether a defect is present in the pattern caused by a bubble in a liquid contained in the immersion lithographic apparatus.