Metrology Method and Apparatus, Lithographic System, Device Manufacturing Method and Substrate

• US 20150145151A1
• Filed: 06/17/2013
• Published: 05/28/2015
• Est. Priority Date: 07/05/2012
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: Van Der Schaar, Maurits, Bhattacharyya, Kaustuve, Smilde, Hendrik-Jan Hidde
• Granted Patent: US 9,714,827 B2
• Time in Patent Office: Days
• US Class Current: 257/797
• CPC Class Codes: G01B 11/27 for testing the alignment of axes means for centering or aligning a light guide within a ferrule G02B6/3834
• CPC Class Codes: G01B 11/30 for measuring roughness or irregularity of surfaces
• CPC Class Codes: G03F 7/20 Exposure; Apparatus therefor photographic printing apparatus for making copies G03B27/00
• 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: H01L 23/544 Marks applied to semiconductor devices or parts, e.g. registration marks, alignment structures, wafer maps test patterns for characterising or monitoring manufacturing processes H01L22/00
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00

Abstract

A lithographic process is used to form a plurality of target structures (92, 94) distributed at a plurality of locations across a substrate and having overlaid periodic structures with a number of different overlay bias values distributed across the target structures. At least some of the target structures comprise a number of overlaid periodic structures (e.g., gratings) that is fewer than said number of different overlay bias values. Asymmetry measurements are obtained for the target structures. The detected asymmetries are used to determine parameters of a lithographic process. Overlay model parameters including translation, magnification and rotation, can be calculated while correcting the effect of bottom grating asymmetry, and using a multi-parameter model of overlay error across the substrate.

Claims

1. A method comprising:

using a lithographic process to form a plurality of target structures distributed at a plurality of locations across a substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the target structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values;

illuminating the target structures and detecting asymmetries in the radiation scattered by said target structures;

using the detected a symmetries to determine said parameters.

2. The method as claimed in claim 1 wherein the using the detected asymmetries to determine said parameters includes an assumed non-linear relationship between overlay error and asymmetry.

3. The method of claim 1 wherein the using the detected asymmetries to determine said parameters comprises using detected asymmetries of three or more target structures distributed at different locations across the substrate and having three or more different respective values of overlay bias to determine said parameters using knowledge of the three different overlay bias values.

7. The method as claimed in claim 2, wherein said assumed non-linear relationship is a sinusoidal function, or optionally a combination of sinusoidal functions related harmonically to one another.

8. The method as claimed in claim 1 wherein the using the detected asymmetries to determine said parameters is performed with the assumption that a contribution to overall asymmetry due to feature asymmetry within one or more of said periodic structures is constant for all values of overlay.

9. The method as claimed in claim 2 wherein the using the detected asymmetries to determine said parameters is performed with the assumption that a contribution to overall asymmetry due to feature asymmetry within one or more of said periodic structures and one or more harmonic proportionality constant describing the assumed non-linear relationship are floating.

10. The method as claimed in claim 1 wherein the different overlay bias values span a range greater than 4%, 10%, 15%, or 20%, of a respective pitch of said periodic structures.

4. A method as claimed in wherein step (c) of using the detected asymmetries to determine said parameters comprises using a multi-parameter model of overlay error across the substrate.

5. The method as claimed in claim 4 wherein said multi-parameter model of overlay error comprises parameters representing translation, magnification, rotation and substrate coordinates.

6. The method as claimed in claim 5 wherein said multi-parameter model of overlay error is an at least-six-parameter model.

11. An inspection apparatus comprising:

a support for a substrate having a plurality of target structures distributed at a plurality of locations across the substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the target structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values;

an optical system configured to illuminate the target structures and detecting asymmetries in the radiation scattered by said target structures;

a processor arranged to use the detected asymmetries to determine parameters.

12. The inspection apparatus as claimed in claim 11 wherein said processor is arranged to use the detected asymmetries to determine said parameters by including an assumed non-linear relationship between overlay error and asymmetry.

13. The inspection apparatus as claimed in claim 11 wherein said processor is arranged to use the detected asymmetries to determine said parameters by using detected asymmetries of three or more target structures distributed at different locations across the substrate and having three or more different respective values of overlay bias to determine said parameters using knowledge of the three different overlay bias values.

14. The inspection apparatus as claimed in claim 11 wherein said processor is arranged to use the detected asymmetries to determine said parameters by using a multi-parameter model of overlay error across the substrate.

15. The inspection apparatus as claimed in claim 14 wherein said multi-parameter model of overlay error comprises parameters representing translation, magnification, rotation and substrate coordinates.

16. The inspection apparatus as claimed in claim 15 wherein said multi-parameter model of overlay error is an at least-six-parameter model.

17. The inspection apparatus as claimed in claim 12 wherein said assumed non-linear relationship is a sinusoidal function, or optionally a combination of sinusoidal functions related harmonically to one another.

18. The inspection apparatus as claimed in claim 11 wherein said processor is arranged to use the detected asymmetries to determine said parameters with the assumption that a contribution to overall asymmetry due to feature asymmetry within one or more of said periodic structures is constant for all values of overlay.

19. The inspection apparatus as claimed in claim 12 wherein said processor is arranged to use the detected asymmetries to determine said parameters with the assumption that a contribution to overall asymmetry due to feature asymmetry within one or more of said periodic structures and one or more harmonic proportionality constant describing the assumed non-linear relationship are floating.

20. The inspection apparatus as claimed in claim 11 wherein the different overlay bias values span a range greater than 4%, 10%, 15%, or 20%, of a respective pitch of said periodic structures.

21. A non-transitory computer readable medium having instructions stored thereon, execution of which by a computing device cause the computing device to perform operations comprising:

using a lithographic process to form a plurality of target structures distributed at a plurality of locations across a substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the target structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values;

illuminating the target structures and detecting asymmetries in the radiation scattered by said target structures;

using the detected asymmetries to determine said parameters.

22. A lithographic system comprising:

a lithographic apparatus comprising;

an illumination optical system an-anged to illuminate a pattern;

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

an inspection apparatus,

a support for a substrate having a plurality of target structures distributed at a plurality of locations across the substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the tar et structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values;

an optical system configured to illuminate the target structures and detecting asymmetries in the radiation scattered by said target structures;

a processor arranged to use the detected asymmetries to determine parameters,

wherein the lithographic apparatus is arranged to use the measurement results from the inspection apparatus in applying the pattern to further substrates.

23. A method of manufacturing devices wherein a device pattern is applied to a series of substrates using a lithographic process, the method comprising:

inspecting at least one periodic structure formed as part of or beside said device pattern on at least one of said substrates, the inspecting comprising,

using a lithographic process to form a plurality of target structures distributed at a plurality of locations across a substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the target structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values;

illuminating the target structures and detecting asymmetries in the radiation scattered by said target structures;

using the detected asymmetries to determine said parameters, and

controlling the lithographic process for later substrates in accordance with the result of the method.

24. A substrate comprising:

a plurality of target structures distributed at a plurality of locations across the substrate and having overlaid periodic structures with a number of different overlay bias values distributed across said target structures, at least some of the target structures comprising a number of overlaid periodic structures that is fewer than said number of different overlay bias values.