# US 10,481,499 B2 · Determination of stack difference and correction using stack difference

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- Number: US 10,481,499 B2
- Document ID: US10481499B2
- Status: Granted
- Kind: B2
- Application number: 16/413,985
- Filed: 2019-05-16
- Published: 2019-09-05
- Granted: 2019-11-19
- Earliest claimed: 2016-04-22
- Assignees: ASML Netherlands B.V.
- Applicants: Asml Netherlands B.V.
- Inventors: Arie Jeffrey Den Boef; Kaustuve Bhattacharyya
- Web page: https://patentgrep.com/patent/US10481499B2

## CPC

- G03F 7/70133: {Measurement of illumination distribution, in pupil plane or field plane}
- G01N 21/4788: {Diffraction (for sizing particles G01N15/0205)}
- G01N 21/956: Inspecting patterns on the surface of objects {(contactless testing of electronic circuits G01R31/308; testing currency G07D; manufacturing processes per se of semiconductor devices implementing a measuring step H10P74/20)}
- G03F 7/70625: {Dimensions, e.g. line width, critical dimension [CD], profile, sidewall angle or edge roughness}
- G03F 7/70633: {Overlay, i.e. relative alignment between patterns printed by separate exposures in different layers, or in the same layer in multiple exposures or stitching}
- 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)
- G01N: INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES (measuring or testing apparatus or processes other than immunoassay, involving enzymes or microorganisms C12M, C12Q)

## Abstract

A method including: obtaining a measurement of a metrology target on a substrate processed using a patterning process, the measurement having been obtained using measurement radiation; and deriving a parameter of interest of the patterning process from the measurement, wherein the parameter of interest is corrected by a stack difference parameter, the stack difference parameter representing an un-designed difference in physical configuration between adjacent periodic structures of the target or between the metrology target and another adjacent target on the substrate.

## Claims

### Claim 1

A method comprising:
obtaining first values of a stack difference parameter and second values of a stack difference parameter for a plurality of adjacent periodic structures of a measurement target or for a plurality of adjacent measurement targets, the first values of the stack difference parameter and second values of the stack difference parameter having been obtained with, respectively, measurements using first measurement radiation and second measurement radiation and the stack difference parameter representing an un-designed difference in physical configuration between adjacent periodic structures of a measurement target or between adjacent measurement targets on a substrate;
obtaining first values of a target parameter and second values of the target parameter for the plurality of adjacent periodic structures of the measurement target or for the plurality of adjacent measurement targets, the first values of the target parameter and second values of the target parameter having been obtained with, respectively, the first measurement radiation and the second measurement radiation and wherein the target parameter value comprises a part which is independent of the un-designed difference in physical configuration, and a part due to the un-designed difference in physical configuration; and
determining a relationship function describing a relationship between the first and/or second values of stack difference parameter and the difference of the first values of the target parameter and the second values of the target parameter; and
determining a part of a target parameter value which is independent of the un-designed difference in physical configuration from the relationship function.

### Claim 2 (depends on 1)

The method of claim 1, wherein the relationship function comprises a constant.

### Claim 3 (depends on 1)

The method of claim 1, wherein determining the relationship function comprises determining a first relationship function describing a substantially linear relationship between the first values of the stack difference parameter and the difference of the first values of the target parameter and the second values of the target parameter and a second relationship function describing a substantially linear relationship between the second values of the stack difference parameter and the difference of the first values of the target parameter and the second values of the target parameter.

### Claim 4 (depends on 1)

The method of claim 1, wherein determining the relationship function comprises making a 3-dimensional plot of the difference of the first values of the target parameter and the second values of the target parameter against the first values of the stack difference parameter and against the second values of the stack difference parameter.

### Claim 5 (depends on 1)

The method of claim 1, wherein determining the relationship function comprises determining a relationship function which describes a substantially linear relationship between:
the difference of the first values of target parameter and the second values of target parameter; and
the difference of the first values of stack difference parameter and the second values of stack difference parameter.

### Claim 6 (depends on 1)

The method of claim 1, comprising determining a degree of correlation of 1) the first and/or second values of stack difference parameter, and 2) the difference of the first values of target parameter and the second values of target parameter.

### Claim 7 (depends on 6)

The method of claim 6, wherein a degree of correlation is used in determining a measure of the accuracy of the determined part of a target parameter value which is independent of the un-designed difference in physical configuration.

### Claim 8 (depends on 6)

The method of claim 6, comprising an initial optimization to determine a desired target from a plurality of candidate targets, the initial optimization comprising:
obtaining plural sets of values comprising the first and second values of stack difference parameter and the first and second values of target parameter, for multiple samples of a plurality of candidate targets and a plurality of candidate measurement radiation pairs of the first measurement radiation and the second measurement radiation, each set of values relating to a different combination of one of the candidate targets and one of the candidate measurement radiation pairs;
determining a degree of correlation for each of the plural sets of values; and
selecting a desired target from one of the candidate targets based upon the determined degree of correlation for each set of values.

### Claim 9 (depends on 8)

The method of claim 8, wherein selecting a desired target comprises:
determining for each candidate target, the number of sets of values relating to that candidate target for which the determined degree of correlation is above a threshold; and
selecting as the desired target, the candidate target for which the number of sets of values having a determined degree of correlation above a threshold is greatest.

### Claim 10 (depends on 8)

The method of claim 8, wherein selecting a desired target comprises:
determining for each candidate target, an average for the determined degree of correlation for each set of values relating to that candidate target; and
selecting as the desired target, the candidate target for which the determined average is greatest.

### Claim 11 (depends on 8)

The method of claim 8, wherein selecting a desired target comprises selecting a desired combination of one of the candidate targets and one of the candidate measurement radiation pairs based upon the determined degree of correlation for each set of values.

### Claim 12 (depends on 1)

The method of claim 1, wherein the target parameter is overlay and the part of overlay value which is independent of the un-designed difference in physical configuration comprises a contribution due to a known imposed bias and a contribution due to an overlay error.

### Claim 13 (depends on 1)

The method of claim 1, wherein the target parameter is measurement beam intensity asymmetry.

### Claim 14 (depends on 1)

The method of claim 1, wherein the first measurement radiation has a selected characteristic which is different to that of the second measurement radiation, the selected characteristic of the measurement radiation comprising wavelength or polarization.

### Claim 15 (depends on 1)

The method of claim 1, comprising:
measuring the adjacent periodic structures or targets using the first measurement radiation to obtain the first values of stack difference parameter;
measuring the adjacent periodic structures or targets using the second measurement radiation to obtain the second values of stack difference parameter;
measuring the target of the adjacent periodic structures or the targets of the plurality of adjacent targets using the first measurement radiation to obtain the first values of target parameter; and
measuring the target of the adjacent periodic structures or the targets of the plurality of adjacent targets using the second measurement radiation to obtain the second values of target parameter.

### Claim 16 (depends on 15)

The method of claim 15, wherein the measuring comprises:
illuminating the adjacent periodic structures or targets with the measurement radiation and detecting the measurement radiation scattered by each periodic structure or target; and
measuring intensity asymmetry in corresponding higher orders of the scattered measurement radiation.

### Claim 17 (depends on 15)

The method of claim 15, wherein the measuring of the adjacent periodic structures or targets is performed prior to formation of a structure overlying the adjacent periodic structures or targets.

### Claim 18

A non-transitory computer program product comprising machine-readable instructions therein that, when executed by a processor system, are configured to cause the processor system to at least:
obtain first values of a stack difference parameter and second values of a stack difference parameter for a plurality of adjacent periodic structures of a measurement target or for a plurality of adjacent measurement targets, the first values of the stack difference parameter and second values of the stack difference parameter having been obtained with, respectively, measurements using first measurement radiation and second measurement radiation and the stack difference parameter representing an un-designed difference in physical configuration between adjacent periodic structures of a measurement target or between adjacent measurement targets on a substrate;
obtaining first values of a target parameter and second values of the target parameter for the plurality of adjacent periodic structures of the measurement target or for the plurality of adjacent measurement targets, the first values of the target parameter and second values of the target parameter having been obtained with, respectively, the first measurement radiation and the second measurement radiation and wherein the target parameter value comprises a part which is independent of the un-designed difference in physical configuration, and a part due to the un-designed difference in physical configuration; and
determining a relationship function describing a relationship between the first and/or second values of stack difference parameter and the difference of the first values of the target parameter and the second values of the target parameter; and determining a part of a target parameter value which is independent of the un-designed difference in physical configuration from the relationship function.

### Claim 19 (depends on 18)

A metrology system comprising:
an optical system configured to provide a beam of radiation onto a substrate;
a detector system configured to detect radiation redirected from the substrate to determine a parameter related to the substrate; and
the non-transitory computer program product of claim 18.

### Claim 20 (depends on 18)

A system comprising:
an inspection apparatus configured to provide a beam of radiation on two adjacent periodic structures or measurement targets on a substrate and to detect radiation diffracted by the targets to determine a parameter of a patterning process; and
the non-transitory computer program product of claim 18.