PATTERN-EDGE PLACEMENT PREDICTOR AND MONITOR FOR LITHOGRAPHIC EXPOSURE TOOL

• US 20180299795A1
• Filed: 06/21/2018
• Published: 10/18/2018
• Est. Priority Date: 09/02/2014
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Tyminski, Jacek K.
• Granted Patent: US 10,345,715 B2
• Time in Patent Office: Days
• CPC Class Codes: G03F 7/70058 Mask illumination systems
• CPC Class Codes: G03F 7/70125 Use of illumination settings tailored to particular mask patterns details of setting means G03F7/70091
• CPC Class Codes: G03F 7/70258 Projection system adjustments, e.g. adjustments during exposure or alignment during assembly of projection system
• CPC Class Codes: G03F 7/70425 Imaging strategies, e.g. for increasing throughput or resolution, printing product fields larger than the image field or compensating lithography- or non-lithography errors, e.g. proximity correction, mix-and-match, stitching or double patterning
• CPC Class Codes: G03F 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/70625 Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness
• 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: G06T 2207/30148 Semiconductor; IC; Wafer
• CPC Class Codes: G06T 7/0006 using a design-rule based approach
• CPC Class Codes: G06T 7/73 using feature-based methods

Abstract

Method and system configured to reduce or even nullify the degradation of images created by the projector tool turns on the optimization of the pattern-imaging by adjusting parameters and hardware of the projector to judiciously impact the placement of various image edges at different locations in the image field. Adjustments to the projector (exposure tool) include a change of a setup parameter of the exposure tool and/or scanning synchronization and/or a change of a signature of the optical system of the exposure tool determined as a result of minimizing the pre-determined cost function(s) that are parts of a comprehensive edge-placement error model.

Claims

1. A method for predicting and monitoring a position of an edge of an image of a reticle pattern formed on a workpiece in a lithographic exposure process in an exposure tool, the method comprising:

performing at least one wafer-exposure run in the exposure tool

to form a first image of the reticle pattern on the workpiece and

to determine, with the use of an optical detector of the exposure tool, first and second operational factors, the first operational factors representing parameters of operation of said exposure tool and including descriptors of optical imaging in said exposure tool, the second operational factors representing a shot-overlay characteristic of said exposure tool,

wherein the first image is characterized by a first difference between a position of an edge of the first image and a target position;

determining, with a computer device, a change of a position of an edge of the first image with respect to a target position based on said first operational factors and said second operational factors; and

modifying, based on a value of the change of the position, the exposure tool by changing one or more of presence, position, orientation, size, and shape of an optical component of the optical projection system to form a second image of the reticle pattern on the workpiece, the second image characterized by a second difference between a position of an edge of the second image and the target position, the second difference being smaller than the first difference.

2. A method according to claim 1, wherein said descriptors of optical imaging include (i) deviations of a surface of best focus of irradiance distribution of said first image from a surface of the workpiece and (ii) exposure dose as functions of position across a slit of said exposure tool.

3. A method according to claim 1, further comprising defining first relationships among image defocus, exposure dose, and critical dimensions of said first image at the workpiece.

4. A method according to claim 3, wherein said defining first relationships includes defining said first relationships at plural different locations of a scanner slit of said exposure tool.

5. A method according to claim 3, further comprising

calculating said critical dimensions based on said first relationships , the image defocus, and the exposure dose;

applying a blur correction based on at least one of defocus data and scan synchronization data generated by said exposure tool and

comparing calculated critical dimensions with target critical dimensions corresponding to design specification.

6. A method according to claim 1, further comprising defining second relationships among image defocus, exposure dose, and a value of lateral shift of said first image at the workpiece.

7. A method according to claim 6, wherein said defining first relationships includes defining said first relationships at plural different locations of a scanner slit of said exposure tool.

8. A method according to claim 6, further comprising calculating said value of lateral shift based on said second relationships, the image defocus, and the exposure dose.

9. A method according to claim 1, further comprising creating at least one of a defocus map and a dose map.

10. A method according to claim 9, wherein said creating includes creating a dose map based on dose integrator data.

11. A method according to claim 9, wherein said creating includes creating a defocus map based on data including at least one of (i) data acquired with the use of an interferometer of the exposure tool, (ii) total field deviation data, and (iii) focus correction data.

12. A method according to claim 9, wherein said creating includes creating a defocus map based on a vector sum of topography target errors, stage trajectory errors, and image plane excursions.

13. A method according to claim 1, further comprising creating a map of image displacement values across the workpiece, said map representing values of image shift, which values have been determined as a function of locations across the workpiece based at least on the first and the second operational factors.

14. A method according to claim 13, wherein said creating a map of image displacement includes applying a blur correction based on at least one of defocus data and scan synchronization data generated by said exposure tool.

15. A method according to claim 1, wherein said determining is performed in-situ during an exposure step of a lithographic process with said exposure tool.

16. A method according to claim 1, wherein said determining includes creating, in a computer process, a map of positions of edges of said first image across the workpiece.

17. A method according to claim 1, wherein said modifying includes changing a process of synchronization of relative scanning between the workpiece and a component of the exposure tool to reduce a contribution of a scanning synchronization error to said geometrical difference.

24. The device according to claim 13, wherein the controller is configured to determine, with the use of the third information, a correction to data representing the edge position calculated with the use of the information on the state of the exposure apparatus.

18. A device configured to assess an edge position of a pattern image formed on the substrate by an exposure apparatus, the device comprising:

input electronic circuitry configured to receive information representing a state of the exposure apparatus during operation thereof; and

a controller in operable communication with the input electronic circuitry and configured to determine said edge position based on the information,

wherein the information includes data representing a scanning synchronization error of said exposure apparatus.

19. The device according to claim 18, wherein the information includes first information that contains data representing a signal produced by an optical detector of the exposure apparatus during the operation of the exposure apparatus.

20. The device according to claim 19, wherein the first information includes data representing a dose of exposure of the substrate during the operation of the exposure apparatus.

21. The device according to claim 19, wherein the first information includes data representing a position of focus of radiation, to which the substrate is exposed during the operation of the exposure apparatus.

22. The device according to claim 18, wherein the information includes second information that contains a control signal of the exposure apparatus during the operation of the exposure apparatus.

23. The device according to claim 18, wherein the input electronic circuitry is further configured to receive third information representing a change in the edge position of the pattern image with respect to a change in the state of the exposure apparatus,

and wherein the controller is further configured to calculate the edge position of the pattern image with the use of at least the information on the state of the exposure apparatus and the third information.

25. A method for assessment of an edge position of a pattern image formed on the substrate by an exposure apparatus, the method comprising:

preparing information representing a state of the exposure apparatus during operation of the exposure apparatus; and

determining the edge position of the pattern image with the use of the information on the state of the exposure apparatus,

wherein the information on the state of the exposure apparatus includes data representing a scanning synchronization error of said exposure apparatus.

26. The method according to claim 25, wherein said preparing the information representing the state of the exposure apparatus includes acquiring, from the optical detector of the exposure apparatus, first information containing a signal produced by the optical detector during the operation of the exposure apparatus.

27. The method according to claim 26, wherein said preparing includes acquiring the first information that includes data representing a dose of exposure of the substrate during the operation of the exposure apparatus.

28. The method according to claim 26, wherein said preparing includes acquiring the first information that includes data representing a position of focus of radiation, to which the substrate is exposed during the operation of the exposure apparatus.

29. The method according to claim 25, wherein said preparing the information representing the state of the exposure apparatus includes processing, with a controller of the exposure apparatus, second information that contains a control signal of the exposure apparatus during the operation of the exposure apparatus.

30. The method according to claim 25, further comprising preparing third information representing a change in the edge position of the pattern image with respect to a change in the state of the exposure apparatus,

and wherein the determining includes calculating the edge position of the pattern image using at least the information on the state of the exposure apparatus and the third information.

31. The method according to claim 30, wherein the calculating includes correcting the edge position of the pattern image, that has been calculated based on the information on the state, with the use of the third information.

32. A method for exposing the substrate to radiation to form the pattern image thereon, the method for exposing comprising:

determining the edge position of the pattern image by using the method for calculation according to claim 25.

33. The method for exposing according to claim 32, further comprising:

with a sensor of the exposure apparatus, determining whether the edge position falls within a predetermined range of positions, and

with a controller of the exposure apparatus, generating a warning signal when the edge position of the pattern image does deviates from said predetermined range of positions.

34. A device manufacturing method comprising:

exposing the pattern image on the substrate using the method for exposing according to claim 32;

developing the substrate after said exposing to forma mask layer having a contour corresponding to the pattern image; and

processing a surface of the substrate through the mask layer.

35. A method for predicting and monitoring a position of an edge of an image of a reticle pattern formed on a wafer in a lithographic exposure process in an exposure tool, the method comprising:

calculating, with a computer processor, a change of position of said edge in comparison with a target position based on

(i) empirically-determined first parameters representing non-uniformities of optical characteristics of said exposure tool across a scanner slit of said tool and

(ii) empirically-determined second parameters representing non-uniformities of capability, of said exposure tool,

to spatially align different exposure shots on the wafer with respect to one another.

36. A system for predicting and monitoring a position of an edge of a pattern image formed on a wafer, the system comprising:

a lithographic exposure tool including

a wafer-positioning apparatus configured to support said wafer, move said wafer with respect to a chosen reference position, and register movements of said wafer with the use of an optical interferometer;

an illumination system containing

a reticle, and

an optical system configured to illuminate said reticle in a direction of said wafer;

a projection optics configured to image said reticle on said wafer; and

an optical detection unit configured to acquire a distribution of light irradiance, at a chosen plane within said exposure tool, as a function of location across at least one of said reticle and said wafer;

and

a computing device operably connected with the lithographic exposure tool and configured to;

create an exposure dose map and an image defocus map based on data that represent

optical irradiance distribution across the wafer and have been acquired, with the use of said optical detection unit, from at least one exposure run that creates said pattern image on the wafer; and

determine critical dimension and image shift values of said pattern image based on

(i) the exposure dose map,

(ii) the image defocus map,

(iii) predetermined first relationships among image defocus and exposure dose and the critical dimensions, and

(iv) predetermined second relationships among image defocus and expose dose and a the image shift.

37. A system according to claim 36, wherein the exposure dose map is created based on data generated by a dose integrator of said exposure tool, and the image defocus map is created based on a vector sum of topography target errors, stage trajectory errors, and image plane excursions of said exposure tool.