# US 10,309,913 B2 · Pattern inspection method using charged particle beam

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- Number: US 10,309,913 B2
- Document ID: US10309913B2
- Status: Granted
- Kind: B2
- Application number: 15/909,485
- Filed: 2018-03-01
- Published: 2018-11-22
- Granted: 2019-06-04
- Earliest claimed: 2017-05-19
- Assignees: Toshiba Memory Corporation
- Applicants: Toshiba Memory Corporation
- Inventors: Osamu Nagano
- Web page: https://patentgrep.com/patent/US10309913B2

## CPC

- G01N 23/2251: using incident electron beams, e.g. scanning electron microscopy [SEM]
- H01J 37/244: Detectors; Associated components or circuits therefor
- H01J 37/265: {Controlling the tube; circuit arrangements adapted to a particular application not otherwise provided, e.g. bright-field-dark-field illumination}
- H01J 37/28: with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)}
- H01J 2237/221: Image processing
- H01J 2237/24514: Beam diagnostics including control of the parameter or property diagnosed (H01J2237/30472 takes precedence)
- H01J 2237/2817: Pattern inspection
- 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)
- H01J: ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS (spark-gaps H01T; electric arc lamps H05B31/00; particle accelerators H05H)

## Abstract

A pattern inspection method includes scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images, determining a distribution of gray level values for each of the acquired N SEM images, selecting M gray levels from the distributions of the N gray levels, selecting a first gray level value from a first one of the M distributions, and comparing it to the corresponding first gray level value of the of the other M−1 distributions, and determining that an abnormality has occurred in the charged particle beam corresponding to the first one of the M distributions when the difference between the first value of the first one of the M distributions and the other M−1 distributions is greater than a predetermined threshold value.

## Claims

### Claim 1

A pattern inspection method, comprising:
scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images;
determining a distribution of gray level values for each of the acquired N SEM images;
selecting M, where M is a whole number equal to or less than N, gray levels from the distributions of the N gray levels for each of the acquired N SEM images;
selecting a first gray level value from a first one of the M distributions, and comparing it to the corresponding first gray level value of the of the other M−1 distributions; and
determining that an abnormality has occurred in the charged particle beam corresponding to the first one of the M distributions when the difference between the first value of the first one of the M distributions and the first value of the other M−1 distributions is greater than a predetermined threshold value.

### Claim 2 (depends on 1)

The pattern inspection method according to claim 1, wherein M is an odd whole number greater than one.

### Claim 3 (depends on 1)

The pattern inspection method according to claim 1, wherein the first value is a maximum gray level value in each distribution.

### Claim 4 (depends on 1)

The pattern inspection method according to claim 1, wherein the first value is an average of the gray level value in each distribution.

### Claim 5 (depends on 1)

The pattern inspection method according to claim 1, wherein the first value is the half-width value of each distribution.

### Claim 6 (depends on 1)

The pattern inspection method according to claim 1, wherein the first value is a minimum gray level value in each distribution.

### Claim 7 (depends on 1)

The pattern inspection method according to claim 1, wherein the first value is a derivative of the gray level value in each distribution.

### Claim 8

A pattern inspection method, comprising:
scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images used to determine the presence of a defect in the pattern and concurrently;
determining a related gray level value for each of the acquired N SEM images;
selecting M gray levels from the distributions of the N gray levels for each of the acquired N SEM images;
comparing the related gray level value of each of the M gray levels;
determining which related gray level values, from among the M related gray level values, have a similar gray level value within a preset range of deviation of the gray level value, and determining which, if any of the related gray level values from among the M related gray level values have a value outside of a preset range of deviation from the other of the M gray level values; and
stopping use of any charged particle beam corresponding to the gray level value, from among the M gray level values, having a value outside of a preset range of deviation from the other of the M gray level values.

### Claim 9 (depends on 8)

The method according to claim 8, wherein the related gray level value is the gray level distribution of a SEM image.

### Claim 10 (depends on 8)

The method according to claim 8, wherein the related gray level value is a derivative of the gray level distribution of a SEM image.

### Claim 11 (depends on 8)

The method according to claim 8, wherein the related gray level value is the minimum gray level value of a SEM image.

### Claim 12 (depends on 8)

The method according to claim 8, wherein the related gray level value is the maximum gray level value of a SEM image.

### Claim 13 (depends on 8)

The method according to claim 8, wherein the related gray level value is the half width gray level value of a SEM image.

### Claim 14 (depends on 8)

The method according to claim 8, wherein M is an odd whole number greater than one.

### Claim 15

A pattern inspection method, comprising:
scanning a plurality of patterns on a substrate with N charged particle beams and detecting secondary electrons respectively generated from each of the plurality of patterns to acquire N SEM images useful for determining the presence of a defect in the pattern, and concurrently;
selecting M images from the N SEM images;
comparing a property of an N SEM image with the remaining N−1 SEM images; and
determining whether the property of the selected N SEM image is different from that same property in the remaining N−1 SEM images by more than a preset threshold amount; and
if the property of the selected N SEM image is different from that same property in the remaining N−1 SEM images by more than the preset threshold amount, stopping use of the charged particle beam corresponding to the SEM image having the property which is different from that same property in the remaining N−1 SEM images by more than the preset threshold amount.

### Claim 16 (depends on 15)

The pattern inspection method according to claim 15, wherein the property is a pattern in the SEM images.

### Claim 17 (depends on 15)

The pattern inspection method according to claim 15, wherein the property is a maximum gray scale value in the SEM images.

### Claim 18 (depends on 15)

The pattern inspection method according to claim 15, wherein the property is a minimum gray scale value in the SEM images.

### Claim 19 (depends on 15)

The pattern inspection method according to claim 15, wherein the property is a distribution of the gray scale values in the SEM images.

### Claim 20 (depends on 15)

The pattern inspection method according to claim 15, further comprising:
after comparing a property of an N SEM image with the remaining N−1 SEM images; and
determining whether the property of the selected N SEM image is different from that same property in the remaining N−1 SEM images by more than a preset threshold amount; and
if the property of the selected N SEM image is different from that same property in the remaining N−1 SEM images by more than the preset threshold amount, stopping use of the charged particle beam corresponding to the selected SEM;
comparing a property of a another of the N SEM image with the remaining N−1 SEM images; and
determining whether the property of the another of the N SEM image is different from that same property in the remaining N−1 SEM images by more than a preset threshold amount; and
if the property of the another N SEM image is different from that same property in the remaining N−1 SEM images by more than the preset threshold amount, stopping use of the charged particle beam corresponding to the another N SEM image.