Overlay marks, methods of overlay mark design and methods of overlay measurements

• US 20030021465A1
• Filed: 06/26/2002
• Published: 01/30/2003
• Est. Priority Date: 08/30/2000
• Status: Active Grant

• Current Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Original Assignee: Kla-Tencor Technologies Corporation (KLA Corporation)
• Inventors: Adel, Michael, Ghinovker, Mark, Mieher, Walter Dean
• Granted Patent: US 6,985,618 B2
• Time in Patent Office: Days
• US Class Current: 382/151
• 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 9/7076 Mark details, e.g. phase grating mark, temporary mark
• CPC Class Codes: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0004 Industrial image inspection
• CPC Class Codes: G06T 7/33 using feature-based methods
• CPC Class Codes: G06V 40/171 Local features and components; Facial parts eye characteristics G06V40/18; Occluding parts, e.g. glasses; Geometrical relationships
• CPC Class Codes: Y10S 438/975 Substrate or mask aligning feature

Abstract

relative position between two or more successive layers of a substrate or between two or more separately generated patterns on a single layer of a substrate, is disclosed. The method includes optimizing the geometry of a first element of the mark according to a first scale. The method further includes optimizing the geometry of a second element of the mark according to a second scale. The method additionally includes optimizing the geometry of a third element of the mark according to a third scale.

Claims

1. A method of designing an overlay mark which is used to determine the relative position between two or more successive layers of a substrate or between two or more separately generated patterns on a single layer of a substrate, the method comprising:

optimizing the geometry of a first element of the mark according to a first scale;

optimizing the geometry of a second element of the mark according to a second scale; and

optimizing the geometry of a third element of the mark according to a third scale.

4. The method as recited in claim 1 wherein geometry is defined as size.

5. The method as recited in claim 1 wherein geometry is defined as shape.

6. The method as recited in claim 1 wherein geometry is defined as distribution.

7. The method as recited in claim 1 wherein the first scale corresponds to a metrology kernel scale, which defines the boundaries of the regions that contain information about the two different layers or patterns between which overlay is to be measured.

8. The method as recited in claim 7 wherein the metrology kernel scale is based on metrology tool limitations, process issues and circuit design criteria.

9. The method as recited in claim 7 wherein the metrology kernel scale ranges from about 4 microns to about 10 microns.

10. The method as recited in claim 1 wherein the geometry of the first element is optimized by identifying the upper and lower limits of the first scale and fine tuning the geometry of the first geometry between the upper and lower limits.

11. The method as recited in claim 10 wherein the first element corresponds to working zones, which define the different layers or patterns of the overlay mark, and which represent the actual area of the overlay mark that is used for overlay measurements.

12. The method as recited in claim 11 wherein fine-tuning is implemented by defining the perimeter of the mark and dividing the mark into a plurality of working zones that are configured to diminish the impact of non-uniformities across the mark on tool and wafer induced shifts.

13. The method as recited in claim 1 wherein the second scale corresponds to the image resolution scale, which defines the boundaries between structures within a given process layer.

14. The method as recited in claim 13 wherein image resolution scale is based on metrology tool limitations and process robustness issues.

15. The method as recited in claim 13 wherein the image resolution scale ranges from about 0.3 microns to about 2 microns.

16. The method as recited in claim 1 wherein the geometry of the second element is optimized by identifying the upper and lower limits of the second scale and fine tuning the geometry of the second element between the upper and lower limits.

17. The method as recited in claim 16 wherein the second element corresponds to a periodic structure that contains the actual spatial information regarding the relative positions of the mark components that are encoded and transferred to a metrology tool used to image the mark.

18. The method as recited in claim 17 wherein fine-tuning is implemented by balancing the image resolution of the tool with the process.

19. The method as recited in claim 1 wherein the third scale corresponds to the lithography resolution scale, which defines the boundaries of sub-structures within a given structure.

20. The method as recited in claim 19 wherein image resolution scale is based on circuit design rules, process robustness issues and metrology tool limitations.

21. The method as recited in claim 19 wherein the image resolution scale ranges from about 0.01 microns to about 0.5 microns.

22. The method as recited in claim 1 wherein the geometry of the third element is optimized by identifying the upper and lower limits of the third scale and fine tuning the geometry of the third element between the upper and lower limits.

23. The method as recited in claim 22 wherein the third element corresponds to the finely segmented elements, which contain information reflective of the circuit structures themselves.

24. The method as recited in claim 1 wherein the first element is a working zone, the second element is a periodic structure of coarsely segmented elements that are positioned within the working zones, and the third element is a plurality of finely segmented elements that form the coarsely segmented elements.

2. The method as recited in claim 2 wherein the first, second and third scales are different.

3. The method as recited in claim 2 wherein the second scale is smaller than the first scale, and wherein the third scale is smaller than the second scale.

25. A method for designing an overlay mark, the overlay mark having a perimeter that corresponds to a field of view of a metrology tool, comprising:

filling the perimeter of the overlay mark with a plurality of working zones, the geometry of the working zones being based on a first design scale;

filling each of the working zones with at least one periodic structure of coarsely segmented lines, the geometry of the coarsely segmented lines being based on a second scale that is smaller than the first scale;

separating the coarsely segmented lines into a plurality of finely segmented elements, the geometry of the finely segmented elements being based on a third scale that is smaller than the second scale.

26. A method of designing an overlay mark, the method comprising:

defining the perimeter of the overlay mark;

dividing the overlay mark into a plurality of working zones, the working zones including at least a first working zone associated with a first process and at least a second working zone associated with a second process, the second process having different characteristics than the first process;

adjusting the geometry of the working zones, the geometry of the work zones being based at least in part on a first scale;

positioning a periodic structure within each of the working zones, the periodic structure having a plurality of coarsely segmented lines;

adjusting the geometry of the periodic structures, the geometry of the periodic structures being based at least in part on a second scale, the second scale having characteristics that are different than the first scale;

separating the coarsely segmented lines into a plurality of finely segmented elements; and

adjusting the geometry of the finely segmented elements, the geometry of the finely segmented lines being based at least in part on a third scale, the third scale having characteristics that are different than the first and second scales.