Apparatus and Method of Measuring a Property of a Substrate

• US 20110102753A1
• Filed: 04/20/2009
• Published: 05/05/2011
• Est. Priority Date: 04/21/2008
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Fuchs, Andreas, Coogans, Martyn John, Van Der Schaar, Maurits, Van De Kerkhof, Marcus Adrianus
• Granted Patent: US 8,786,825 B2
• Time in Patent Office: Days
• US Class Current: 355/27
• 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 21/4788 Diffraction for sizing particles G01N15/0205
• CPC Class Codes: G01N 21/9501 Semiconductor wafers manufacturing processes per se of semiconductor devices implementing a measuring step H01L22/10
• 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 7/70633 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 9/7049 Technique, e.g. interferometric
• CPC Class Codes: G03F 9/7088 Alignment mark detection, e.g. TTR, TTL, off-axis detection, array detector, video detection

Abstract

The present invention makes the use of measurement of a diffraction spectrum in or near an image plane in order to determine a property of an exposed substrate. In particular, the positive and negative first diffraction orders are separated or diverged, detected and their intensity measured to determine overlay (or other properties) of exposed layers on the substrate.

Claims

1. An inspection apparatus configured to determine a property of a substrate, comprising:

a radiation source configured to output a radiation beam, the radiation beam directed to a surface of the substrate;

a collimator configured to collimate and focus the radiation beam once reflected from the surface of the substrate, and to separate diffraction orders of the reflected radiation beam; and

a detector configured to detect a spectrum of the reflected radiation beam,

wherein the property of the substrate is determined by measuring a property of the spectrum in a plane positioned in a range from where the radiation beam is converging toward an image plane of the collimator to where the radiation beam is diverging from the image plane.

2. The inspection apparatus according to claim 1, wherein the plane is positioned between an image plane and a pupil plane of the collimator, where, in use, the reflected radiation beam converges towards the image plane.

3. The inspection apparatus according to claim 1, wherein the plane is positioned downstream of a plane conjugate to the image plane, where, in use, the reflected radiation beam diverges from the image plane.

4. The inspection apparatus according to claim 1, wherein the plane is positioned on an image plane of the collimator.

5. The inspection apparatus according to claim 1, wherein the plane is positioned near an image plane of the collimator.

6. The inspection apparatus according to claim 1, further comprising a spatial filter between the substrate and the detector that is configured to block a zeroth diffraction order of the spectrum.

9. The inspection apparatus according to claim 1, further comprising an optical device configured to diverge positive and negative first diffraction orders of the spectrum before the spectrum is detected by the detector.

11. The inspection apparatus according to claim 1, wherein the detector is arranged to detect positive and negative first diffraction orders of the spectrum substantially simultaneously.

12. The inspection apparatus according to claim 1, wherein the property of the substrate to be measured is the overlay of a first layer with respect to a second layer on the substrate.

13. The inspection apparatus according to claim 12, wherein the overlay is measured by comparing the intensities of detected positive and negative first diffraction orders of the reflected radiation beam.

14. The inspection apparatus according to claim 1, wherein the property of the substrate is a measurement parameter of an object on the substrate.

15. The inspection apparatus according to claim 1, further comprising an optical device configured to separate the spectrum into two or more sub-beams, at least two of the sub-beams comprising non-zero diffraction orders of the reflected beam.

16. The inspection apparatus according to claim 15, further comprising a processor configured to determine, from the intensity of the two first diffraction orders detected by the detector, an overlay of a first layer on the substrate with respect to a second layer.

17. The inspection apparatus according to claim 1, further comprising a spatial filter positioned in an intermediate image plane of the collimator, the spatial filter being configured to prevent stray radiation from reaching the detector, the stray radiation originating from outside of a target on the substrate from which the radiation beam is reflected.

21. The inspection apparatus according to claim 1, wherein the collimator includes an area between the substrate and a lens that is filled with a fluid configured to create a higher effective numerical aperture of the lens.

22. The inspection apparatus according to claim 1, wherein the detector is configured to detect the reflected spectrum for a plurality of wavelengths and a plurality of incident angles of the radiation beam substantially simultaneously.

23. The inspection apparatus according to claim 1, wherein the detector is configured to measure defocused images of the surface of the substrate and the property to be measured is determined by analyzing the defocused images.

7-8. -8. (canceled)

10. (canceled)

18-20. -20. (canceled)

24. (canceled)

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

a radiation source configured to output a radiation beam, the radiation beam directed to a surface of the substrate;

a collimator configured to collimate and focus the radiation beam once reflected from the surface of the substrate, and to separate diffraction orders of the reflected radiation beam; and

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

wherein the property of the substrate is measured by measuring a property of the spectrum in a plane positioned in a range from where the radiation beam is converging toward an image plane of the collimator to where the radiation beam is diverging from the image plane.

26. A method of measuring a property of a substrate, comprising:

irradiating a target on a substrate with a radiation beam;

reflecting the radiation beam from the target;

collimating and focusing the reflected radiation beam using a collimator;

diverging first diffraction orders of the reflected radiation beam;

detecting the intensity of the first diffraction orders in a plane positioned within a range from where the reflected radiation beam is converging toward an image plane of the collimator to where the reflected radiation beam is diverging from the image plane; and

determining, from the intensity of the first diffraction orders, a property of the target of the substrate.

27. The method according to claim 26, further comprising blocking a zeroth diffraction order from the reflected radiation beam.

28. A lithographic apparatus comprising:

an illumination system arranged to illuminate a pattern;

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

an inspection apparatus configured to determine a property of the substrate, the inspection apparatus including

a radiation source configured to output a radiation beam, the radiation beam directed to a surface of the substrate;

a collimator configured to collimate and focus the radiation beam once reflected from the surface of the substrate, and to separate diffraction orders of the reflected radiation beam; and

a detector configured to detect a spectrum of the reflected radiation beam,

wherein the property of the substrate is determined by measuring a property of the spectrum in a plane positioned in a range from where the radiation beam is converging toward an image plane of the collimator to where the radiation beam is diverging from the image plane.

29. A lithographic cell comprising:

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

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

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

an inspection apparatus configured to determine a property of the substrate, the inspection apparatus including

a radiation source configured to output a radiation beam, the radiation beam directed to a surface of the substrate;

a collimator configured to collimate and focus the radiation beam once reflected from the surface of the substrate, and to separate diffraction orders of the reflected radiation beam; and

a detector configured to detect a spectrum of the reflected radiation beam,

wherein the property of the substrate is determined by measuring a property of the spectrum in a plane positioned in a range from where the radiation beam is converging toward an image plane of the collimator to where the radiation beam is diverging from the image plane.

30. A device manufacturing method comprising:

using a lithographic apparatus to form a pattern on a substrate; and

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

irradiating a target on a substrate with a radiation beam;

reflecting the radiation beam from the target;

collimating and focusing the reflected radiation beam using a collimator;

diverging first diffraction orders of the reflected radiation beam;

detecting the intensity of the first diffraction orders in a plane positioned within a range from where the reflected radiation beam is converging toward an image plane of the collimator to where the reflected radiation beam is diverging from the image plane; and

determining, from the intensity of the first diffraction orders, a property of the target of the substrate.

31. The device manufacturing method according to claim 30, further comprising blocking a zeroth diffraction order from the reflected radiation beam.