Inspection apparatus and methods, substrates having metrology targets, lithographic system and device manufacturing method

Patent metadata

Field	Value
Publication number	US-11022900-B2
Application number	US-202016931002-A
Country	US
Kind code	B2
Filing date	Jul 16, 2020
Priority date	Oct 30, 2013
Publication date	Jun 1, 2021
Grant date	Jun 1, 2021

Abstract

Disclosed is an inspection apparatus for use in lithography. It comprises a support for a substrate carrying a plurality of metrology targets; an optical system for illuminating the targets under predetermined illumination conditions and for detecting predetermined portions of radiation diffracted by the targets under the illumination conditions; a processor arranged to calculate from said detected portions of diffracted radiation a measurement of asymmetry for a specific target; and a controller for causing the optical system and processor to measure asymmetry in at least two of said targets which have different known components of positional offset between structures and smaller sub-structures within a layer on the substrate and calculate from the results of said asymmetry measurements a measurement of a performance parameter of the lithographic process for structures of said smaller size. Also disclosed are substrates provided with a plurality of novel metrology targets formed by a lithographic process.

First claim

The invention claimed is:

1. A method comprising:
measuring, using a scatterometry apparatus, a −1 st order scatterometry image of gratings on a substrate with offsets between grating populations using a first illumination mode;
measuring, using the scatterometry apparatus, a +1 st order scatterometry image of the gratings using a second illumination mode;
determining a region of interest in each of the gratings from the −1 st order and +1 st order scatterometry images;
calculating a difference image of each of the gratings from the −1 st order and +1 st order scatterometry images to determine a difference in intensity;
determining a parameter of a lithographic process between the grating populations based on the difference in intensity; and
correcting for at-resolution offsets based on the difference in intensity,
wherein the grating populations comprise an overlay grating and at least one auxiliary target,
wherein the at least one auxiliary target comprises gratings having coarse structures and fine at-resolution sub-structures with programmed offsets between the at-resolution sub-structures and the coarse structures, and
wherein the at-resolution sub-structures are not resolved by the scatterometry apparatus.

2. The method of claim 1 , wherein the gratings comprise double patterned gratings.

3. The method of claim 1 , wherein the parameter of the lithographic process comprises overlay.

4. The method of claim 1 , wherein the determining the parameter of the lithographic process is further based on a measurement of asymmetry.

5. The method of claim 1 , wherein the correcting for the at-resolution offsets is further based on a measurement of asymmetry.

6. The method of claim 1 , wherein the grating populations comprise first and second populations of structures in the gratings that are formed in different steps of the lithographic process.

7. The method of claim 1 , wherein the offsets between the grating populations comprise positional offsets between interleaved populations of structures in the gratings.

8. A metrology apparatus comprising:
a support configured to support a substrate, the substrate comprising gratings formed by a lithographic process;
an optical system configured to:

measure, using a scatterometry apparatus, a −1 st order scatterometry image of the gratings with offsets between grating populations using a first illumination mode; and
measure, using the scatterometry apparatus, a +1 st order scatterometry image of the gratings using a second illumination mode; and
a processor configured to:

determine a region of interest in each of the gratings from the −1 st order and +1 st order scatterometry images;
calculate a difference image of each of the gratings from the −1 st order and +1 st order scatterometry images to determine a difference in intensity;
determine a parameter of the lithographic process between the grating populations based on the difference in intensity; and
correct the parameter for at-resolution offsets based on the difference in intensity,
wherein the grating populations comprise an overlay grating and at least one auxiliary target,
wherein the at least one auxiliary target comprises gratings having coarse structures and fine at-resolution sub-structures with programmed offsets between the at-resolution sub-structures and the coarse structures, and
wherein the at-resolution sub-structures are not resolved by the scatterometry apparatus.

9. The metrology apparatus of claim 8 , wherein the gratings comprise double patterned gratings.

10. The metrology apparatus of claim 8 , wherein the parameter of the lithographic process comprises overlay.

11. The metrology apparatus of claim 8 , wherein the determining the parameter of the lithographic process is further based on a measurement of asymmetry.

12. The metrology apparatus of claim 8 , wherein the correcting for the at-resolution offsets is further based on a measurement of asymmetry.

13. The metrology apparatus of claim 8 , wherein the grating populations comprise first and second populations of structures in the gratings that are formed in different steps of the lithographic process.

14. The metrology apparatus of claim 8 , wherein the offsets between the grating populations comprise positional offsets between interleaved populations of structures in the gratings.

15. A non-transitory computer program product comprising machine-readable instructions for causing a processor to perform operations comprising:
measuring, using a scatterometry apparatus, a −1 st order scatterometry image of gratings on a substrate with offsets between grating populations using a first illumination mode;
measuring, using the scatterometry apparatus, a +1 st order scatterometry image of the gratings using a second illumination mode;
determining a region of interest in each of the gratings from the −1 st order and +1 st order scatterometry images;
calculating a difference image of each of the gratings from the −1 st order and +1 st order scatterometry images to determine a difference in intensity;
determining a parameter of a lithographic process between the grating populations based on the difference in intensity; and
correcting for at-resolution offsets based on the difference in intensity,
wherein the grating populations comprise an overlay grating and at least one auxiliary target,
wherein the at least one auxiliary target comprises gratings having coarse structures and fine at-resolution sub-structures with programmed offsets between the at-resolution sub-structures and the coarse structures, and
wherein the at-resolution sub-structures are not resolved by the scatterometry apparatus.

16. The non-transitory computer program product of claim 15 , wherein the gratings comprise double patterned gratings.

17. The non-transitory computer program product of claim 15 , wherein the parameter of the lithographic process comprises overlay.

18. The non-transitory computer program product of claim 15 , wherein the determining the parameter of the lithographic process is further based on a measurement of asymmetry.

19. The non-transitory computer program product of claim 15 , wherein the correcting for the at-resolution offsets is further based on a measurement of asymmetry.

20. The non-transitory computer program product of claim 15 , wherein the grating populations comprise first and second populations of structures in the gratings that are formed in different steps of the lithographic process.

Assignees

• Asml Netherlands Bv

Inventors

• Mathijssen Simon Gijsbert Josephus
• Hunsche Stefan
• Van Kraaij Markus Gerardus Martinus Maria

Classifications

• G03F9/7076

  Mark details, e.g. phase grating mark, temporary mark · CPC title

• G03F7/706835

  Metrology information management or control · CPC title

• G03F7/70683 Primary

  Mark designs · CPC title

• G03F7/70466

  Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature (stitching G03F7/70475) · CPC title

• G03F1/44

  Testing or measuring features, e.g. grid patterns, focus monitors, sawtooth scales or notched scales · CPC title