DISCRETE SOURCE MASK OPTIMIZATION

• US 20150378262A1
• Filed: 02/04/2014
• Published: 12/31/2015
• Est. Priority Date: 02/25/2013
• Status: Active Grant

• Current Assignee: ASML Netherlands BV (ASML Holding NV)
• Original Assignee: ASML Netherlands BV (ASML Holding NV)
• Inventors: LIU, Xiaofeng, HOWELL, Rafael C.
• Granted Patent: US 10,191,384 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G03F 7/2008 characterised by the reflectors, diffusers, light or heat filtering means or anti-reflective means used
• CPC Class Codes: G03F 7/70116 Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets
• 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 7/705 Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions
• CPC Class Codes: G03F 7/70508 Data handling in all parts of the microlithographic apparatus, e.g. handling pattern data for addressable masks or data transfer to or from different components within the exposure apparatus

Abstract

A method for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method including: calculating a discrete pupil profile based on a desired pupil profile; selecting a discrete change to the discrete pupil profile; and applying the selected discrete change to the discrete pupil profile. The methods according to various embodiments disclosed herein may reduce the computational cost of discrete optimization from O(aⁿ) to O(n) wherein a is constant and n is the number of knobs that can generate discrete change in the pupil profile.

Claims

1. A method for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method comprising:

calculating, by a computer device, a discrete pupil profile based on a desired pupil profile;

selecting, using the computer device, a discrete change to the discrete pupil profile; and

applying, by the computer device, the selected discrete change to the discrete pupil profile.

2. The method of claim 1, wherein the desired pupil profile is a pupil profile from an optimization or an empirical pupil profile.

3. The method of claim 1, wherein the discrete pupil profile is renderable by hardware of an illumination source of the lithographic projection apparatus.

4. The method of claim 1, wherein the discrete pupil profile comprises intensities at a plurality of spatially discrete positions on a pupil plane.

5. The method of claim 1, further comprising optimizing design variables unassociated to source hardware that generates a discrete change in the discrete pupil profile.

6. The method of claim 1, further comprising iterating selecting a discrete change to the discrete pupil profile and applying the discrete change to the discrete pupil profile.

7. The method of claim 3, wherein the hardware of the illumination source comprises an array of mirrors.

8. The method of claim 1, wherein selecting a discrete change comprises calculating a plurality of gradients of a cost function, each of the plurality of gradients being with respect to intensity at one of a plurality of spatially discrete positions on a pupil plane.

9. The method of claim 8, wherein the plurality of spatially discrete positions are positions at which intensity can change by adjusting hardware of an illumination source of the lithographic projection apparatus.

10. The method of claim 1, wherein selecting a discrete change comprises selecting the discrete change from a plurality of discrete changes.

11. The method of claim 10, wherein at least one discrete change in the plurality of discrete changes is a discrete change in intensity at one or more of discrete positions of the discrete pupil profile.

12. The method of claim 10, wherein the plurality of discrete changes exclusively include those discrete changes that maintain a total intensity in the discrete pupil profile.

13. The method of claim 10, wherein the plurality of discrete changes exclusively include those discrete changes that decrease a fill ratio of the discrete pupil profile.

14. The method of claim 1, wherein the desired pupil profile is a pupil profile of an illumination source of the lithographic projection apparatus, or is a pupil profile of projection optics of the lithographic projection apparatus.

15. A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions when executed by a computer implementing the method of claim 1.

16. The method of claim 1, wherein the desired pupil profile is a pupil profile from another lithographic projection apparatus.

17. The method of claim 8, wherein the cost function is a function of intensities at the plurality of spatially discrete positions on the pupil plane.

18. The method of claim 10, wherein the plurality of discrete changes includes a discrete change having a symmetry about an optical axis of the lithographic projection apparatus.

19. The method of claim 10, wherein selecting a discrete change further comprises calculating a change in a value of a cost function for each of the plurality of discrete changes.

20. A method comprising:

executing, on a hardware processor of a computer system, one or more computer program modules configured to execute a method for improving a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic projection apparatus, the method comprising;

calculating, by the computer system, a discrete pupil profile based on a desired pupil profile;

selecting, using the computer system, a discrete change to the discrete pupil profile; and

applying, by the computer system, the selected discrete change to the discrete pupil profile; and

displaying, on an electronic display communicatively linked with the processor of the computer system, the discrete pupil profile.