# US 12,117,730 B2 · Method and apparatus for photolithographic imaging

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- Number: US 12,117,730 B2
- Document ID: US12117730B2
- Status: Granted
- Kind: B2
- Application number: 17/606,647
- Filed: 2020-04-07
- Published: 2022-07-28
- Granted: 2024-10-15
- Earliest claimed: 2019-04-30
- Assignees: ASML Netherlands B.V.
- Applicants: Asml Netherlands B.V.
- Inventors: Joern-Holger Franke; Eric Henri Jan Hendrickx; Guido Constant Simon Schiffelers
- Web page: https://patentgrep.com/patent/US12117730B2

## CPC

- G03F 7/70125: {Use of illumination settings tailored to particular mask patterns (details of setting means G03F7/70091)}
- G03F 1/70: Adapting basic layout or design of masks to lithographic process requirements, e.g., second iteration correction of mask patterns for imaging
- G03F 7/70091: {Illumination settings, i.e. intensity distribution in the pupil plane or angular distribution in the field plane; On-axis or off-axis settings, e.g. annular, dipole or quadrupole settings; Partial coherence control, i.e. sigma or numerical aperture [NA]}
- G03F 7/70116: {Off-axis setting using a programmable means, e.g. liquid crystal display [LCD], digital micromirror device [DMD] or pupil facets}
- G03F 7/705: {Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions}
- G03F 7/70516: {Calibration of components of the microlithographic apparatus, e.g. light sources, addressable masks or detectors}
- G03F: PHOTOMECHANICAL PRODUCTION OF TEXTURED OR PATTERNED SURFACES, e.g. FOR PRINTING, FOR PROCESSING OF SEMICONDUCTOR DEVICES; MATERIALS THEREFOR; ORIGINALS THEREFOR; APPARATUS SPECIALLY ADAPTED THEREFOR; (phototypographic composing devices B41B; photosensitive materials or processes for photographic purposes G03C; electrophotography, sensitive layers or processes therefor G03G)

## Abstract

A method for reducing M3D effects on imaging is described. The method includes identifying points within a source plane of the photolithography system that are associated with pattern shifts resulting from diffraction of light off a photomask under an angle of incidence between an imaging beam of radiation and the mask normal, determining pattern shifts associated with the identified source plane points, and modifying the source to reduce the determined pattern shifts.

## Claims

### Claim 1

A method comprising:
identifying points within an illumination plane of a photolithography system that are associated with pattern shifts resulting from diffraction of radiation off a patterning device due to asymmetric phase effects among diffraction orders;
determining shifts, associated with the identified points, of a pattern for imaging a feature onto a substrate using the photolithography system; and
modifying the illumination to reduce the determined pattern shifts.

### Claim 2 (depends on 1)

The method as in claim 1, wherein the modifying comprises:
determining, for the identified points, regions that pertain to each of a plurality of diffraction orders;
separating the illumination to reduce overlap of the determined regions;
determining a wavefront adjustment that will reduce the determined pattern shifts when applied to the illumination; and
performing source mask optimization using the determined wavefront adjustment.

### Claim 3 (depends on 2)

The method as in claim 2, wherein the separating the illumination comprises separating 1D diffraction orders while allowing 2D diffraction orders to overlap.

### Claim 4 (depends on 2)

The method as in claim 2, wherein the determining the wavefront adjustment comprises selecting an aberration that produces asymmetric pattern shifts that are opposed to the determined pattern shifts given by the diffraction of the patterning device.

### Claim 5 (depends on 2)

The method as in claim 2, further comprising eliminating points in the illumination source plane wherein the determined wavefront adjustment cannot be produced within a selected tolerance threshold.

### Claim 6 (depends on 2)

The method as in claim 2, wherein the modified illumination comprises a rotated dipole and the determined wavefront adjustment is an appropriately rotated astigmatism.

### Claim 7 (depends on 2)

The method as in claim 2, wherein the modified illumination is a trimmed leaf-shaped dipole and the determined wavefront adjustment is a rotated astigmatism.

### Claim 8 (depends on 1)

The method as in claim 1, wherein the modifying comprises:
decomposing an illumination source having a plurality of poles into a plurality of illumination shapes each having one pole; and
selecting a pattern shift value for each of the plurality of illumination shapes.

### Claim 9 (depends on 8)

The method as in claim 8, further comprising selecting a proportion of a total imaging dose to be assigned to each of the plurality of illumination shapes.

### Claim 10 (depends on 8)

The method as in claim 8, wherein the plurality of illumination shapes comprise a pair of opposed poles and wherein the selected pattern shift for one pole from the pair of opposed poles is in a direction opposite to a selected pattern shift for the other pole from the pair of opposed poles.

### Claim 11 (depends on 8)

The method as in claim 8, wherein the plurality of illumination shapes comprises two or more poles, wherein the poles may be grouped into two or more sets, wherein for each set, the selected pattern shift is different from each other set.

### Claim 12 (depends on 8)

The method as in claim 8, further comprising imaging using a vote taking imaging procedure.

### Claim 13 (depends on 1)

The method as in claim 1, wherein the identifying comprises single illumination point scanning and comparing a figure of merit of simulated image quality.

### Claim 14 (depends on 1)

The method as in claim 1, wherein the pattern shifts result from mask 3D effects, and/or wherein the pattern shifts are asymmetrical relative to the identified points.

### Claim 15 (depends on 1)

The method as in claim 1, further comprising using induced apodization to reduce amplitude of selected diffraction orders.

### Claim 16

A non-transitory computer-readable storage medium comprising instructions therein, the instructions, when executed by a processor system, are configured to cause the processor system to a least:
identify points within an illumination plane of a photolithography system that are associated with pattern shifts resulting from diffraction of radiation off a patterning device due to asymmetric phase effects among diffraction orders;
determine shifts, associated with the identified points, of a pattern for imaging a feature onto a substrate using the photolithography system; and
modify the illumination to reduce the determined pattern shifts.

### Claim 17 (depends on 16)

The medium of claim 16, wherein the instructions configured to cause the processor system to modify the illumination are further configured to cause the processor system to:
determine, for the identified points, regions that pertain to each of a plurality of diffraction orders;
separate the illumination to reduce overlap of the determined regions;
determine a wavefront adjustment that will reduce the determined pattern shifts when applied to the illumination; and
perform source mask optimization using the determined wavefront adjustment.

### Claim 18 (depends on 16)

The medium of claim 16, wherein the instructions configured to cause the processor system to modify the illumination are further configured to cause the processor system to:
decompose an illumination shape having a plurality of poles into a plurality of illumination shapes each having one pole; and
select a pattern shift value for each of the plurality of illumination shapes.

### Claim 19 (depends on 16)

The medium of claim 16, wherein the pattern shifts result from mask 3D effects, and/or wherein the pattern shifts are asymmetrical relative to the identified points.

### Claim 20 (depends on 16)

The medium of claim 16, wherein the instructions are further configured to cause the processor system to use induced apodization to reduce amplitude of selected diffraction orders.