Adjustment of a metrology apparatus or a measurement thereby based on a characteristic of a target measured

Patent metadata

Field	Value
Publication number	US-10670975-B2
Application number	US-201616061209-A
Country	US
Kind code	B2
Filing date	Nov 29, 2016
Priority date	Dec 17, 2015
Publication date	Jun 2, 2020
Grant date	Jun 2, 2020

Abstract

A method of adjusting a metrology apparatus, the method including: spatially dividing an intensity distribution of a pupil plane of the metrology apparatus into a plurality of pixels; and reducing an effect of a structural asymmetry in a target on a measurement by the metrology apparatus on the target, by adjusting intensities of the plurality of pixels.

First claim

The invention claimed is:

1. A method for adjusting a metrology apparatus, the method comprising:
obtaining an intensity distribution of radiation for a pupil plane of the metrology apparatus spatially divided into a plurality of pixels; and
reducing an effect of a structural asymmetry in a target on a measurement by the metrology apparatus on the target, by adjusting, by a hardware computer system, a characteristic of illumination radiation for the target so as to adjust an optical characteristic of the radiation of one or more pixels of the plurality of pixels.

2. The method of claim 1 , wherein the pupil plane is an illumination pupil or a detection pupil.

3. The method of claim 1 , wherein the measurement measures overlay, focus, aberration or a combination selected therefrom.

4. The method of claim 1 , wherein the structural asymmetry comprises one or more selected from: a difference in side wall angle (SWA), floor tilt, and/or etch depth.

5. The method of claim 1 , wherein adjusting the optical characteristic of the radiation comprises computing a cost function that represents the effect and that is a function of intensities of the plurality of pixels.

6. The method of claim 5 , wherein adjusting the optical characteristic of the radiation further comprises finding values of intensities that locally or globally minimizes or maximizes the cost function, or wherein the cost function is constrained.

7. The method of claim 1 , further comprising:
identifying one or more pixels from the plurality of pixels, wherein the one or more identified pixels do not contribute to a signal used by the metrology apparatus in the measurement or wherein the contribution of the one or more identified pixels to the signal is below a threshold, and
adjusting the optical characteristic of the radiation at the one or more identified pixels.

8. The method of claim 7 , wherein the measurement is an overlay measurement and the one or more identified pixels do not contribute to a diffraction order used in the overlay measurement.

9. The method of claim 1 , wherein adjusting the optical characteristic of one of more pixels of the plurality of pixels comprises adjusting polarization at the one or more pixels of the plurality of pixels, and/or comprises adjusting bandwidth at the one or more pixels of the plurality of pixels, and/or comprises adjusting wavelength at the one or more pixels of the plurality of pixels.

10. The method of claim 1 , wherein adjusting the optical characteristic of one of more pixels of the plurality of pixels comprises adjusting intensity at the one or more pixels of the plurality of pixels.

11. A computer program product comprising a non-transitory computer-readable medium having instructions thereon, the instructions, when executed by a computer system, configured to cause the computer system to at least:
obtain an intensity distribution of radiation of a pupil plane of a metrology apparatus spatially divided into a plurality of pixels; and
reduce an effect of a structural asymmetry in a target on a measurement by the metrology apparatus on the target, by adjustment of a characteristic of illumination radiation for the target so as to adjust an optical characteristic of the radiation of one or more pixels of the plurality of pixels.

12. The computer program product of claim 11 , wherein the pupil plane is an illumination pupil or a detection pupil.

13. The computer program product of claim 11 , wherein the measurement measures overlay, focus, aberration or a combination selected therefrom.

14. The computer program product of claim 11 , wherein the structural asymmetry comprises one or more selected from: a difference in side wall angle (SWA), floor tilt, and/or etch depth.

15. The computer program product of claim 11 , wherein the instructions configured to adjust the optical characteristic of the radiation are further configured to compute a cost function that represents the effect and that is a function of intensities of the plurality of pixels.

16. The computer program product of claim 11 , wherein the instructions are further configured to cause the computer system to:
identify one or more pixels from the plurality of pixels, wherein the one or more identified pixels do not contribute to a signal used by the metrology apparatus in the measurement or wherein the contribution of the one or more identified pixels to the signal is below a threshold, and
adjust the optical characteristic of the radiation at the one or more identified pixels.

17. The computer program product of claim 11 , wherein the instructions configured to adjust the optical characteristic of the radiation are configured to adjust intensity at the one or more pixels of the plurality of pixels, and/or adjust polarization at the one or more pixels of the plurality of pixels, and/or adjust bandwidth at the one or more pixels of the plurality of pixels, and/or adjust wavelength at the one or more pixels of the plurality of pixels.

18. A method comprising:
setting a characteristic of a target to a value based on which a parameter of a metrology apparatus or of a measurement by the metrology apparatus on the target is adjusted; and
fabricating the target with the set characteristic on a substrate.

19. The method of claim 18 , wherein setting the characteristic comprises computing a cost function that is a function of the characteristic of the target.

20. A computer program product comprising a non-transitory computer-readable medium having instructions thereon, the instructions, when executed by a computer system, configured to cause the computer system to at least:
obtain a simulated intensity distribution of radiation of a pupil plane of a metrology apparatus, the simulated intensity distribution divided into a plurality of pixels; and
adjust an intensity of radiation at one or more pixels of the plurality of pixels to reduce an effect of a structural asymmetry in a measurement target on a measurement by a metrology apparatus of the measurement target by adjusting a characteristic of illumination radiation for the target.

Assignees

• Asml Netherlands Bv

Inventors

• Socha Robert John
• Den Boef Arie Jeffrey
• Pandey Nitesh

Classifications

• G03F7/70633 Primary

  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 title

• G01N21/956

  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 H10P74/20)} · CPC title

• G01N2021/8848

  Polarisation of light · CPC title

• G01N21/8806

  Specially adapted optical and illumination features · CPC title

• G03F7/706

  Aberration measurement · CPC title