LENS HEATING COMPENSATION SYSTEMS AND METHODS

• US 20140047397A1
• Filed: 10/28/2013
• Published: 02/13/2014
• Est. Priority Date: 06/03/2008
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: YE, Jun, Liu, Peng, Cao, Yu
• Granted Patent: US 9,746,784 B2
• Time in Patent Office: Days
• US Class Current: 716/53
• CPC Class Codes: G03F 7/70266 Adaptive optics, e.g. deformable optical elements for wavefront control, e.g. for aberration adjustment or correction
• CPC Class Codes: G03F 7/70441 Optical proximity correction [OPC]
• 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 7/70504 Optical system modelling, e.g. lens heating models
• CPC Class Codes: G03F 7/706 Aberration measurement
• CPC Class Codes: G03F 7/70891 Temperature
• CPC Class Codes: G06F 30/00 Computer-aided design [CAD]

Abstract

Methods for calibrating a photolithographic system are disclosed. A cold lens contour for a reticle design and at least one hot lens contour for the reticle design are generated from which a process window is defined. Aberrations induced by a lens manipulator are characterized in a manipulator model and the process window is optimized using the manipulator model. Aberrations are characterized by identifying variations in critical dimensions caused by lens manipulation for a plurality of manipulator settings and by modeling behavior of the manipulator as a relationship between manipulator settings and aberrations. The process window may be optimized by minimizing a cost function for a set of critical locations.

Claims

1. A method for performing optical proximity correction (OPC) on a target design for a lithographic process comprising:

obtaining a lens heating model that accounts for effects of lens heating in the lithographic process;

obtaining a set of process window conditions associated with the lithographic process;

determining pattern failures across the set of process window conditions using the lens heating model; and

performing OPC on the target design based on the determined pattern failures.

2. A method according to claim 1, further comprising:

obtaining a cold lens model associated with a cold lens state of the lithographic process,

wherein determining pattern failures is performed by combining results using the cold lens model and the lens heating model.

3. A method according to claim 2, further comprising:

identifying a plurality of hot lens states of the lithographic process,

wherein determining pattern failures is performed by accounting for the plurality of hot lens states using the cold lens model and the lens heating model.

4. A method according to claim 1, further comprising:

obtaining a set of slit positions associated with a lens of the lithographic process,

wherein determining pattern failures is further performed across the set of slit conditions.

5. A method according to claim 1, wherein the pattern failures include one or more of bridging and necking.

6. A method according to claim 1, wherein performing OPC includes adjusting edges of features in the target design.

7. A method according to claim 1, wherein the lens heating model comprises a physics-based predictive model.

8. A method according to claim 7, wherein the lens heating model is an ASCAL-based lens heating model formed using actual measurements of the lithographic process.

9. A non-transitory computer readable storage medium having instructions stored thereon which, when executed by a computer, cause the computer to implement a method for performing optical proximity correction (OPC) on a target design for a lithographic process comprising:

obtaining a lens heating model that accounts for effects of lens heating in the lithographic process;

obtaining a set of process window conditions associated with the lithographic process;

determining pattern failures across the set of process window conditions using the lens heating model; and

performing OPC on the target design based on the determined pattern failures.

10. A non-transitory computer readable storage medium according to claim 9, wherein the method further comprises:

obtaining a cold lens model associated with a cold lens state of the lithographic process,

wherein determining pattern failures is performed by combining results using the cold lens model and the lens heating model.

11. A non-transitory computer readable storage medium according to claim 10, wherein the method further comprises:

identifying a plurality of hot lens states of the lithographic process,

wherein determining pattern failures is performed by accounting for the plurality of hot lens states using the cold lens model and the lens heating model.

12. A non-transitory computer readable storage medium according to claim 9, wherein the method further comprises:

obtaining a set of slit positions associated with a lens of the lithographic process,

wherein determining pattern failures is further performed across the set of slit conditions.

13. A non-transitory computer readable storage medium according to claim 9, wherein the pattern failures include one or more of bridging and necking.

14. A non-transitory computer readable storage medium according to claim 9, wherein performing OPC includes adjusting edges of features in the target design.

15. A non-transitory computer readable storage medium according to claim 9, wherein the lens heating model comprises a physics-based predictive model.

16. A non-transitory computer readable storage medium according to claim 15, wherein the lens heating model is an ASCAL-based lens heating model formed using actual measurements of the lithographic process.

17. A method implemented by a computer comprising:

establishing a substantially linear relationship between a lithometric and lens heating in a lithographic process;

identifying a target value for the lithometric;

forming a cost function with the substantially linear relationship and the target value;

using, by the computer, the cost function to determine lens manipulator settings to achieve the target value of the lithometric over a range of lens aberrations caused by lens heating.

18. A method according to claim 17, wherein the lithometric comprises critical dimensions.

19. A method according to claim 17, wherein the lithometric comprises process window conditions.

20. A method according to claim 17, wherein substantially linear relationship is expressed as a function of Zernikes.

21. A method according to claim 20, wherein Zernike coefficients represent perturbations in the lithometric caused by the lens manipulator.

22. A non-transitory computer readable storage medium having instructions stored thereon, which when executed by a computer, cause the computer to implement a method comprising:

establishing a substantially linear relationship between a lithometric and lens heating in a lithographic process;

identifying a target value for the lithometric;

forming a cost function with the substantially linear relationship and the target value;

using, by the computer, the cost function to determine lens manipulator settings to achieve the target value of the lithometric over a range of lens aberrations caused by lens heating.

23. A non-transitory computer readable storage medium according to claim 22, wherein the lithometric comprises critical dimensions.

24. A non-transitory computer readable storage medium according to claim 22, wherein the lithometric comprises process window conditions.

25. A non-transitory computer readable storage medium according to claim 22, wherein substantially linear relationship is expressed as a function of Zernikes.

26. A non-transitory computer readable storage medium according to claim 25, wherein Zernike coefficients represent perturbations in the lithometric caused by the lens manipulator.