MULTI-LAYER OVERLAY METROLOGY TARGET AND COMPLIMENTARY OVERLAY METROLOGY MEASUREMENT SYSTEMS

• US 20120033215A1
• Filed: 07/19/2011
• Published: 02/09/2012
• Est. Priority Date: 08/03/2010
• Status: Active Grant

• Current Assignee: KLA-Tencor Corporation
• Original Assignee: KLA-Tencor Corporation
• Inventors: Kandel, Daniel, Levinski, Vladimir, Cohen, Guy
• Granted Patent: US 9,927,718 B2
• Time in Patent Office: Days
• US Class Current: 356/366
• 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 7/70683 Mark designs

Abstract

A multi-layer overlay target for use in imaging based metrology is disclosed. The overlay target includes a plurality of target structures including three or more target structures, each target structure including a set of two or more pattern elements, wherein the target structures are configured to share a common center of symmetry upon alignment of the target structures, each target structure being invariant to N degree rotation about the common center of symmetry, wherein N is equal to or greater than 180 degrees, wherein each of the two or more pattern elements has an individual center of symmetry, wherein each of the two or more pattern elements of each target structure is invariant to M degree rotation about the individual center of symmetry, wherein M is equal to or greater than 180 degrees.

Claims

1. A multilayer overlay target, comprising:

a plurality of target structures including three or more target structures, each target structure including a set of two or more pattern elements, wherein the target structures are configured to share a common center of symmetry upon alignment of the target structures, each target structure being invariant to N degree rotation about the common center of symmetry, wherein N is equal to or greater than 180 degrees, wherein each of the two or more pattern elements has an individual center of symmetry, wherein each of the two or more pattern elements of each target structure is invariant to M degree rotation about the individual center of symmetry, wherein M is equal to or greater than 180 degrees.

2. The multilayer overlay target of claim 1, wherein a first pattern element of the set of two or more pattern elements is suitable for overlay metrology measurements in a first direction and a second pattern element of the set of two or more pattern elements is suitable for overlay metrology measurements in a second direction different from the first direction.

3. The multilayer overlay target of claim 1, wherein a set of pattern elements suitable for overlay metrology measurements in a first direction and a second set of pattern elements suitable for overlay metrology measurements in a second direction different from the first direction have a common center of symmetry.

4. The multilayer overlay target of claim 1, wherein at least one of the two or more pattern elements of at least one of the target structures comprises:

a pattern element having two or more sub-elements, wherein the two or more sub-elements are arranged in a periodic patter or a non-periodic pattern.

5. The multilayer overlay target of claim 1, wherein the set of two or more pattern elements of each target structure are printed above or below a layer of dummy fill.

6. The multilayer overlay target of claim 1, wherein some of the plurality of target structures include an additional set of pattern elements in order to enhance contrast of the some of the plurality of target structures.

7. The multilayer overlay target of claim 1, wherein some of the target structures are disposed at different process layers.

8. The multilayer overlay target of claim 1, wherein at least two of the target structures are disposed within the same layer, each of the at least two target structures exposed in different lithographic processes.

9. A multilayer overlay target, comprising:

a plurality of target structures including three or more target structures, wherein each target structure includes a set of two or more pattern elements, wherein the target structures are configured to share a common center of symmetry upon alignment of the target structures, wherein each target structure is invariant to a 90 degree rotation about the common center of symmetry, wherein each of the two or more pattern elements has an individual center of symmetry, wherein each of the two or more pattern elements of each target structure is invariant to M degree rotation about the individual center of symmetry, wherein M is equal to or greater than 180 degrees.

10. The multilayer overlay target of claim 9, wherein a first pattern element of the set of two or more pattern elements is suitable for overlay metrology measurements in a first direction and a second pattern element of the set of two or more pattern elements is suitable for overlay metrology measurements in a second direction different from the first direction.

11. The multilayer overlay target of claim 9, wherein a set of pattern elements suitable for overlay metrology measurements in a first direction and a second set of pattern elements suitable for overlay metrology measurements in a second direction different from the first direction have a common center of symmetry.

12. The multilayer overlay target of claim 9, wherein at least one of the two or more pattern elements of at least one of the target structures comprises:

a pattern element having two or more sub-elements, wherein the two or more sub-elements are arranged in a periodic patter or a non-periodic pattern.

13. The multilayer overlay target of claim 9, wherein the set of two or more pattern elements of each target structure are printed above or below a layer of dummy fill.

14. The multilayer overlay target of claim 9, wherein some of the plurality of target structures include an additional set of pattern elements in order to enhance contrast of the some of the plurality of target structures. some of the target structures disposed at different process layers

15. The multilayer overlay target of claim 9, wherein some of the target structures are disposed at different process layers.

16. The multilayer overlay target of claim 9, wherein at least two of the target structures are disposed within the same layer, each of the at least two target structures exposed in different lithographic processes.

17. An apparatus suitable for contrast enhancement of a multi-layer overlay metrology target, comprising:

an illumination source;

a first polarizer configured to polarize at least a portion of light emanating from the illumination source;

a first beam splitter configured to direct a first portion of light processed by the first polarizer along an object path to a surface of one or more specimens and a second portion of light processed by the first polarizer along a reference path;

a detector disposed along a primary optical axis, wherein the detector is configured to collect a portion of light reflected from the surface of the one or more specimens; and

a second polarizer configured to analyze at least a portion of light reflected from the surface of the one or more specimens prior to the light impinging on the image plane of the detector, wherein the first polarizer and the second polarizer are arranged to minimize the amount of light reflected from unpattern portions of the one or more specimens reaching the detector.

18. The apparatus of claim 17, wherein a polarization axis of the first polarizer is substantially perpendicular to a polarization axis of the second polarizer.

19. The apparatus of claim 17, wherein at least one of the first polarizer or the second polarizer comprises:

a linear polarizer.

20. The apparatus of claim 17, wherein the first polarizer includes a radial polarizer and the second polarizer includes an azimuthal polarizer.

21. The apparatus of claim 17, further comprising:

a first wave plate; and

a second wave plate, wherein the first wave plate is arranged at a selected angle with respect to the first polarizer and the second wave plate is arranged at a selected angle with respect to the second polarizer.

22. An apparatus suitable for contrast enhancement of a multi-layer overlay metrology target, comprising:

an illumination source;

a detector disposed along a primary optical axis, wherein the detector is configured to collect a portion of light reflected from a surface of the one or more specimens;

an aperture positioned at a pupil plane of an illumination path, wherein the aperture is configured to select an illumination angle of illumination emanating from the illumination source, wherein the illumination angle is suitable for achieving a selected contrast level at an imaging plane of the detector; and

a first beam splitter configured to direct a first portion of light transmitted through the aperture along an object path to a surface of one or more specimens and a second portion of light transmitted through the aperture along a reference path.

23. The apparatus of claim 22, wherein the aperture comprises:

a tunable aperture, wherein the tunable aperture is configured to selectively produce one or more aperture profiles, each aperture profile suitable for producing an illumination structure.

24. The apparatus of claim 22, further comprising:

a first polarizer positioned along the illumination path; and

a second polarizer positioned along an imaging path, wherein the first polarizer, the second polarizer, and the aperture are arranged to produce a low intensity level at a point of symmetry of the multi-layer overlay metrology target.