# US 2008/0187869 A1 · Exposure control for phase shifting photolithographic masks

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- Number: US 2008/0187869 A1
- Document ID: US20080187869A1
- Status: Published application
- Kind: A1
- Application number: 12/080,886
- Filed: 2008-04-07
- Published: 2008-08-07
- Earliest claimed: 2001-06-08
- Assignees: Synopsys, Inc.
- Inventors: Christophe Pierrat; Michel Luc Cote
- Web page: https://patentgrep.com/patent/US20080187869A1

## CPC

- G03F 7/70466: {Multiple exposures, e.g. combination of fine and coarse exposures, double patterning or multiple exposures for printing a single feature (stitching G03F7/70475)}
- G03F 1/26: Phase shift masks [PSM]; PSM blanks; Preparation thereof
- 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 7/70425: {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 7/70433: {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 7/70558: {Dose control, i.e. achievement of a desired dose}
- 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

Mask and integrated circuit fabrication approaches are described to facilitate use of so called “full phase” masks. This facilitates use of masks where substantially all of a layout is defined using phase shifting. More specifically, exposure settings including relative dosing between the phase shift mask and the trim masks are described. Additionally, single reticle approaches for accommodating both masks are considered. In one embodiment, the phase shifting mask and the trim mask are exposed using the same exposure conditions, except for relative dosing. In another embodiment, the relative dosing between the phase and trim patterns is 1.0:r, 2.0<r<4.0. These approaches facilitate better exposure profiles for the resulting ICs and can thus improve chip yield and increase throughput by reducing the need to alter settings and/or switch reticles between exposures.

## Claims

### Claim 1

A method of manufacturing an integrated circuit (IC) product comprising:
exposing a pattern in at least one layer of material in the IC using at least two mask patterns, the first mask pattern comprising a phase shifting pattern and the second mask pattern comprising a trim pattern, the phase shifting pattern defining substantially all of the pattern of the layer of material and the trim pattern protecting the pattern defined using the phase shifting pattern and clearing phase shifting artifacts;
said exposing using an optical lithography exposure system having a setting of values of changeable optical parameters that control characteristics of exposures, to the first mask pattern and the second mask pattern, where said setting of values is substantially the same while exposing the first and second mask patterns.

### Claim 2 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein the first mask pattern comprises a “full phase” mask.

### Claim 3 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein the pattern on the layer of material can be characterized by having at least ninety-five percent (95%) of the pattern defined by the phase shifting pattern.

### Claim 4 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein the optical lithography exposure system comprises at least one of a stepper and a scanner.

### Claim 5 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein said optical parameters consist of numerical aperture (N.A.), wavelength (λ) of radiation, partial coherency (σ), illumination configuration, and defocus.

### Claim 6 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein said optical parameters comprise two or more of numerical aperture (N.A.), wavelength (λ) of radiation, partial coherency (σ), illumination configuration, and defocus.

### Claim 7 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein substantially the same comprises within plus or minus 10%.

### Claim 8 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein the exposing further comprises using a first dosing for the first mask pattern and a second dosing for the second mask pattern, the first dosing and the second dosing being in a ratio of 1.0 to r, r>0.0.

### Claim 9 (depends on 1)

The method of manufacturing an IC product of claim 1, wherein the first mask pattern and the second mask pattern are on a single reticle.

### Claim 10 (depends on 9)

The method of manufacturing an IC product of claim 9, and wherein the exposing further comprises blading the first mask pattern and the second mask pattern on the reticle during the exposing to permit different dosing.

### Claim 11

A method for manufacturing an integrated circuit, comprising:
forming a layer of resist on a wafer;
exposing the layer to a first dose of radiation through a phase shifting pattern in a first mask, the first dose of radiation characterized by changeable parameters having values selected for exposure of the phase shifting pattern; and
exposing the layer to a second dose of radiation through a trim pattern in a second mask protecting a pattern defined using the phase shifting pattern and clearing phase shifting artifacts, the second dose of radiation characterized by said changeable parameters having substantially the same values as the changeable parameters selected for exposure of the phase shifting pattern with the first dose of radiation, wherein substantially the same values comprises within plus or minus 10%.

### Claim 12 (depends on 11)

The method of claim 11, wherein said parameters includes a parameter indicating partial coherence a of the first and second doses of radiation at the layer.

### Claim 13 (depends on 11)

The method of claim 11, wherein said parameters includes a parameter indicating a numerical aperture NA of the first and second doses of radiation at the layer.

### Claim 14 (depends on 11)

The method of claim 11, wherein said parameters includes a parameter indicating an axis of propagation of the first and second doses of radiation at the layer.

### Claim 15 (depends on 11)

The method of claim 11, wherein said parameters includes a parameter indicating an illumination configuration of the first and second doses of radiation.

### Claim 16 (depends on 11)

The method of claim 11, wherein said parameters includes a parameter indicating defocus of the first and second doses of radiation at the layer.

### Claim 17 (depends on 11)

The method of claim 11, wherein said parameters includes parameters indicating numerical aperture NA of the first and second doses of radiation at the layer, partial coherence σ of the first and second doses of radiation at the layer, an axis of propagation of the first and second doses of radiation at the layer, an illumination configuration of the first and second doses of radiation, and defocus of the first and second doses of radiation at the layer.

### Claim 18 (depends on 11)

The method of claim 11, wherein said first dose and said second dose are different.

### Claim 19 (depends on 11)

The method of claim 11, wherein said phase shifting pattern and said trim pattern are on a single mask.

### Claim 20 (depends on 11)

The method of claim 11, wherein a pattern is exposed on the layer which can be characterized by one or more of the following: at least eighty percent (80%) of the portions of the pattern that do not form memory devices are defined by the phase shifting pattern; at least eighty percent (80%) of a floorplan in the pattern is defined by the phase shifting pattern; at least ninety percent (90%) of the pattern is defined by the phase shifting pattern; all features in the pattern except those features that are not phase shifted due to phase conflicts are defined by the phase shifting pattern; all features in the pattern that are not test structures are defined by the phase shifting pattern; and all features in the pattern that are not dummy structures are defined by the phase shifting pattern.

### Claim 21 (depends on 11)

The method of claim 11, wherein a pattern is exposed on the layer which can be characterized by having at least ninety-five percent (95%) of the pattern defined by the phase shifting pattern.

### Claim 22 (depends on 11)

The method of claim 11, wherein said parameters comprises parameters that are changed by a mechanical adjustment of an optical element.

### Claim 23

A method for manufacturing an integrated circuit, comprising:
forming a layer of resist on a wafer in a first process station;
moving the wafer to a second process station including a radiation source, a mask and an optical path for exposing the wafer to radiation, the optical path being characterized by optical parameters;
exposing, in the second process station, the layer to a first dose of radiation through a phase shifting pattern in said mask using a first setting of changeable values for the optical parameters; and
exposing, in the second process station, the layer to a second dose of radiation through a trim pattern in said mask using said first setting of changeable values, said trim pattern protecting a pattern defined using the phase shifting pattern and clearing phase shifting artifacts.

### Claim 24 (depends on 23)

The method of claim 23, wherein said optical parameters includes the numerical aperture and partial coherence σ.

### Claim 25 (depends on 23)

The method of claim 23, wherein said optical parameters includes the numerical aperture NA, partial coherence σ, the illumination configuration, and the defocus.

### Claim 26 (depends on 23)

The method of claim 23, wherein said optical parameters includes partial coherence σ as the coherence parameter.

### Claim 27 (depends on 23)

The method of claim 23, wherein said first dose and said second dose have different dosage levels.

### Claim 28 (depends on 23)

The method of claim 23, wherein a pattern is exposed on the layer which can be characterized by one or more of the following: at least eighty percent (80%) of the portions of the pattern that do not form memory devices are defined by the phase shifting pattern; at least eighty percent (80%) of a floorplan in the pattern is defined by the phase shifting pattern; at least ninety percent (90%) of the pattern is defined by the phase shifting pattern; all features in the pattern except those features that are not phase shifted due to phase conflicts are defined by the phase shifting pattern; all features in the pattern that are not test structures are defined by the phase shifting pattern; and all features in the pattern that are not dummy structures are defined by the phase shifting pattern.

### Claim 29 (depends on 23)

The method of claim 23, wherein a pattern is exposed on the layer which can be characterized by having at least ninety-five percent (95%) of the pattern defined by the phase shifting pattern.

### Claim 30 (depends on 23)

The method of claim 23, wherein said optical parameters comprises parameters that are changed by a mechanical adjustment of an optical element.