# US 10,310,386 B2 · Optimization of assist features and source

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- Number: US 10,310,386 B2
- Document ID: US10310386B2
- Status: Granted
- Kind: B2
- Application number: 15/325,428
- Filed: 2015-06-29
- Published: 2017-06-29
- Granted: 2019-06-04
- Earliest claimed: 2014-07-14
- Assignees: ASML Netherlands B.V.
- Applicants: ASML Netherlands B.V.
- Inventors: Duan-Fu Stephen Hsu; Feng-Liang Liu
- Web page: https://patentgrep.com/patent/US10310386B2

## CPC

- G03F 7/70433: {Layout for increasing efficiency or for compensating imaging errors, e.g. layout of exposure fields for reducing focus errors; Use of mask features for increasing efficiency or for compensating imaging errors}
- G03F 1/36: Masks having proximity correction features; Preparation thereof, e.g. optical proximity correction [OPC] design processes
- 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 7/70125: {Use of illumination settings tailored to particular mask patterns (details of setting means G03F7/70091)}
- 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}
- G03F 7/70441: {Optical proximity correction [OPC]}
- G03F 7/70483: {Information management; Active and passive control; Testing; Wafer monitoring, e.g. pattern monitoring}
- G03F 7/705: {Modelling or simulating from physical phenomena up to complete wafer processes or whole workflow in wafer productions}
- G03F 7/7085: {Detection arrangement, e.g. detectors of apparatus alignment possibly mounted on wafers, exposure dose, photo-cleaning flux, stray light, thermal load}
- G06F 30/398: Design verification or optimisation, e.g. using design rule check [DRC], layout versus schematics [LVS] or finite element methods [FEM] (optical proximity correction [OPC] design processes G03F1/36)
- 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)
- G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N)

## Abstract

Methods of reducing a pattern displacement error, contrast loss, best focus shift, and/or tilt of a Bossung curve of a portion of a design layout used in a lithographic process for imaging that portion onto a substrate using a lithographic apparatus. The methods include adjusting an illumination source of the lithographic apparatus, placing one or more assist features onto, or adjusting a position and/or shape of one or more existing assist features in, the portion. Adjusting the illumination source and/or the one or more assist features may be by an optimization algorithm.

## Claims

### Claim 1

A method to improve a lithographic process for imaging a portion of a design layout onto a substrate using a lithographic apparatus and a physical patterning device, the method comprising:
reducing a pattern displacement error, contrast loss, best focus shift, tilt of a Bossung curve of the portion, or a combination selected therefrom, or improving exposure latitude, or enlarging depth of focus, by adjusting a characteristic of an illumination in the lithographic apparatus;
calculating, by a hardware computer system, a continuous transmission map of the portion;
identifying numbers, positions, shapes or a combination selected therefrom, of assist features from the continuous transmission map, wherein at least two of the assist features are located in an asymmetric position with respect to a same feature of the design layout; and
placing the one or more assist features onto a pattern layout for the patterning device,
where the pattern layout is configured for implementation within the physical patterning device, and
where the lithographic process comprises a step of physically imaging the portion of the design layout onto the substrate using the physical patterning device implementing the pattern layout.

### Claim 2 (depends on 1)

The method of claim 1, comprising reducing the pattern displacement error and wherein the pattern displacement error is pattern-dependent.

### Claim 3 (depends on 1)

The method of claim 1, wherein adjusting a characteristic of an illumination changes a symmetry of a shape of the illumination.

### Claim 4 (depends on 1)

The method of claim 1, wherein the patterning device comprises a reflective patterning device.

### Claim 5 (depends on 1)

The method of claim 1, wherein the lithographic apparatus comprises non-telecentric optics.

### Claim 6

A method comprising:
reducing a pattern displacement error, contrast loss, best focus shift, tilt of a Bossung curve, or a combination selected therefrom, of a portion of a design layout for imaging onto a substrate using a physical patterning device and a lithographic apparatus, or improving exposure latitude, or enlarging depth of focus, by adjusting a characteristic of a data structure representing an illumination in the lithographic apparatus;
calculating, by a hardware computer system, a continuous transmission map of the portion of the design layout; and
generating a data structure representing a pattern layout for the patterning device, the data structure representing assist features, wherein numbers, positions, shapes or a combination selected therefrom, of the assist features are identified from the continuous transmission map and at least two of the assist features are located in an asymmetric position with respect to a same feature of the design layout,
where the pattern layout is configured for implementation within the physical patterning device, and
where the lithographic process comprises a step of physically imaging the portion of the design layout onto the substrate using the physical patterning device implementing the pattern layout.

### Claim 7 (depends on 6)

The method of claim 6, further comprising placing the assist features onto the patterning device.

### Claim 8 (depends on 6)

The method of claim 6, comprising reducing the pattern displacement error and wherein the pattern displacement error is pattern-dependent.

### Claim 9 (depends on 6)

The method of claim 6, wherein adjusting a characteristic of an illumination changes a symmetry of a shape of the illumination to asymmetric.

### Claim 10 (depends on 6)

The method of claim 6, wherein the patterning device comprises a reflective patterning device.

### Claim 11

A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions, when executed by a computer system, are configured to cause the computer system to at least:
reduce a pattern displacement error, contrast loss, best focus shift, tilt of a Bossung curve, or a combination selected therefrom, of a portion of a design layout for imaging onto a substrate using a physical patterning device and a lithographic apparatus, or improve exposure latitude, or enlarge depth of focus, by adjusting a characteristic of a data structure representing an illumination in the lithographic apparatus;
calculate a continuous transmission map of the portion of the design layout; and
generate a data structure representing a pattern layout for the patterning device, the data structure representing assist features, wherein numbers, positions, shapes or a combination selected therefrom, of the assist features are identified from the continuous transmission map and at least two of the assist features are located in an asymmetric position with respect to a same feature of the design layout,
where the pattern layout is configured for implementation within the physical patterning device, and
where the lithographic process comprises a step of physically imaging the portion of the design layout onto the substrate using the physical patterning device implementing the pattern layout.

### Claim 12 (depends on 11)

The computer program product of claim 11, wherein the instructions are configured to reduce the pattern displacement error and the pattern displacement error is pattern-dependent.

### Claim 13 (depends on 11)

The computer program product of claim 11, wherein adjusting a characteristic of the illumination changes a symmetry of the illumination.

### Claim 14 (depends on 11)

The computer program product of claim 11, wherein the patterning device comprises a reflective patterning device.

### Claim 15 (depends on 11)

The computer program product of claim 11, wherein the lithographic apparatus comprises non-telecentric optics.

### Claim 16 (depends on 11)

The computer program product of claim 11, wherein the instructions are further configured to cause placement of the one or more assist features onto the patterning device.

### Claim 17

A computer program product comprising a non-transitory computer readable medium having instructions recorded thereon, the instructions, when executed by a computer system, are configured to cause the computer system to at least:
reduce a pattern displacement error, contrast loss, best focus shift, tilt of a Bossung curve, or a combination selected therefrom, of a portion of a design layout for imaging onto a substrate using a physical patterning device and the lithographic apparatus, or improve exposure latitude, or enlarge depth of focus, by adjusting a characteristic of a data structure representing an illumination in the lithographic apparatus such that the illumination has an asymmetric shape; and
generate a data structure representing a pattern layout for the patterning device, the data structure representing assist features, wherein numbers, positions, shapes or a combination selected therefrom, of the assist features are identified based on the illumination and at least two of the assist features are located in an asymmetric position with respect to a same feature of the design layout,
where the pattern layout is configured for implementation within the physical patterning device, and
where the lithographic process comprises a step of physically imaging the portion of the design layout onto the substrate using the physical patterning device implementing the pattern layout.

### Claim 18 (depends on 17)

The computer program product of claim 17, wherein the instructions are further configured to calculate a continuous transmission map of the portion of the design layout, wherein numbers, positions, shapes or a combination selected therefrom, of the assist features are identified based on a continuous transmission map.

### Claim 19 (depends on 17)

The computer program product of claim 17, wherein the instructions are configured to reduce the pattern displacement error and the pattern displacement error is pattern-dependent.

### Claim 20 (depends on 17)

The computer program product of claim 17, wherein the patterning device comprises a reflective patterning device.