Inspection method and apparatus, lithographic apparatus, lithographic processing cell and device manufacturing method

• US 8,553,227 B2
• Filed: 06/17/2009
• Issued: 10/08/2013
• Est. Priority Date: 11/13/2007
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Jordanoska, Cvetanka
• Primary Examiner(s): Punnoose, Roy M
• Application Number:
  US12/486,449
• Publication Number:
  US 20100007863A1
• Time in Patent Office: 1,574 Days
• Field of Search: 356/369
• US Class Current: 356/369
• CPC Class Codes: G01N 21/21 Polarisation-affecting properties G01N21/19 takes precedence
• CPC Class Codes: G01N 21/47 Scattering, i.e. diffuse reflection G01N21/25, G01N21/41 take precedence G01N21/55 takes precedence
• CPC Class Codes: G01N 21/95 characterised by the material or shape of the object to be examined G01N21/89 - G01N21/91, G01N21/94 take precedence
• CPC Class Codes: G01N 21/956 Inspecting patterns on the surface of objects contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• 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

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. The radiation that is reflected off the substrate is radially polarized.

Claims

1. A scatterometer, comprising:

a radiation source configured to provide a radiation beam;

a high numerical aperture lens configured to direct the radiation beam onto a substrate; and

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

wherein the radiation source is configured to radially polarize the radiation beam.

2. The scatterometer of claim 1, wherein the radiation source comprises a liquid nematic cell configured to polarize the radiation beam.

3. The scatterometer of claim 1, further comprising:

an optical system configured to focus the radially polarized radiation beam to a focal spot with a diameter of up to about 200 nm.

4. The scatterometer of claim 1, wherein:

the detector is configured to measure an overlay of a first layer on a substrate with respect to a second layer superimposed onto the first layer; and

the detector is configured to detect at least the zeroth and first orders of the angle-resolved spectrum of the radially polarized radiation beam having been reflected from the superimposed first and second layers and to output an image of the respective intensities of the zeroth, −

1 and +1 diffraction orders, a parameter of the image indicating the extent of the overlay.

5. The scatterometer of claim 4, wherein the parameter of the image indicating the extent of the overlay comprises a value on one of a color or gray-scale pixel image.

6. The scatterometer of claim 1, wherein the detector is configured to measure the property of the substrate by further measuring, substantially simultaneously, in the pupil plane of the high numerical aperture lens, a property of the reflected spectrum at a plurality of wavelengths.

7. The scatterometer of claim 1, wherein the lens comprises a numerical aperture of at least about 0.9.

8. The scatterometer of claim 1, further comprising a space between the substrate and the high numerical aperture lens containing a liquid.

9. The scatterometer of claim 1, wherein the radiation source comprises a polarizer configured to radially polarize the radiation beam.

10. The scatterometer of claim 1, wherein a critical dimension of a structure on the substrate is measured by measuring features in the reflected spectrum, the features being comparable to a library of predetermined features associated with known critical dimensions.

11. The scatterometer of claim 1, wherein the features in the reflected spectrum include asymmetry.

12. A method, comprising

generating a pattern for printing onto a substrate through patterning a radially polarized radiation beam;

and

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

13. The method of claim 12, wherein the 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.

14. The method of claim 12, wherein:

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

wherein the measuring of the reflected spectrum of the gratings is carried out using a scatterometer; and

wherein the extent of the overlay is derived from the asymmetry in the reflected spectrum.

15. A lithographic apparatus comprising:

an illumination optical system configured to illuminate a pattern;

a projection optical system configured to project an image of the pattern on to a substrate; and

an angularly resolved scatterometer configured to measure a property of the substrate, the scatterometer comprising,

a radiation source configured to provide a radiation beam,

a high numerical aperture lens configured to direct the radiation beam on the substrate, and

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

wherein the radiation source is configured to radially polarize the radiation beam.

16. A lithographic cell, comprising:

a coater configured to coat substrates with a radiation sensitive layer;

a lithographic apparatus configured to expose images onto the radiation sensitive layer of substrates coated by the coater;

a developer configured to develop images exposed by the lithographic apparatus; and

an angularly resolved scatterometer configured to measure a property of a substrate, the scatterometer comprising,

a radiation source configured to provide a radiation beam,

a high numerical aperture lens, and

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

wherein the radiation source is configured to radially polarize the radiation beam.

17. A device manufacturing method, comprising:

forming a pattern on a substrate using a lithographic apparatus; and

determining a value related to a parameter of the pattern printed by;

providing a radiation beam;

generating a pattern for printing onto the substrate; and

measuring, in the pupil plane of a high numerical aperture lens, a reflected spectrum of the pattern, the reflected spectrum being created by the reflection of a radially polarized radiation beam from the pattern on the substrate.