# US 10,119,925 B2 · Methods and systems for measuring periodic structures using multi-angle X-ray reflectance scatterometry (XRS)

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- Number: US 10,119,925 B2
- Document ID: US10119925B2
- Status: Granted
- Kind: B2
- Application number: 15/451,104
- Filed: 2017-03-06
- Published: 2017-06-22
- Granted: 2018-11-06
- Earliest claimed: 2014-01-23
- Assignees: Nova Measuring Instruments Ltd.
- Applicants: Nova Measuring Instruments Inc.
- Inventors: Heath A. Pois; David A. Reed; Bruno W. Schueler; Rodney Smedt; Jeffrey T. Fanton
- Web page: https://patentgrep.com/patent/US10119925B2

## CPC

- G01N 23/201: by measuring small-angle scattering
- G01N 23/207: Diffractometry using detectors, e.g. using a probe in a central position and one or more displaceable detectors in circumferential positions
- G01N 2223/054: small angle scatter
- H10P 74/203: {Structural properties, e.g. testing or measuring thicknesses, line widths, warpage, bond strengths or physical defects}
- 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)
- H10P: GENERIC PROCESSES OR APPARATUS FOR THE MANUFACTURE OR TREATMENT OF DEVICES COVERED BY CLASS H10

## Abstract

Methods and systems for measuring periodic structures using multi-angle X-ray reflectance scatterometry (XRS) are disclosed. For example, a method of measuring a sample by X-ray reflectance scatterometry involves impinging an incident X-ray beam on a sample having a periodic structure to generate a scattered X-ray beam, the incident X-ray beam simultaneously providing a plurality of incident angles and a plurality of azimuthal angles. The method also involves collecting at least a portion of the scattered X-ray beam.

## Claims

### Claim 1

A method to characterize a sample using an X-ray reflectance scatterometry, the method comprising:
impinging an incident low energy X-ray beam having an energy of 1keV or less on a sample having a periodic structure to generate a first scattered X-ray beam, wherein the incident low energy X-ray beam is converging in an incidence and azimuth planes thereby providing simultaneously a plurality of incident angles and a plurality of azimuthal angles and having a range of incident angles that is greater than a range of azimuthal angles; and
collecting at least a portion of the first scattered X-ray beam.

### Claim 2 (depends on 1)

The method of claim 1, wherein the range of incident angles is from +30 degrees to −30 degrees, and the range of azimuthal angles is from +10 degrees to −10 degrees.

### Claim 3 (depends on 1)

The method of claim 1, wherein the converging incident X-ray beam has a converging angle in a range of from 20 degrees to 40 degrees.

### Claim 4 (depends on 1)

The method of claim 1, wherein a central axis of the converging X-ray beam has a fixed azimuthal angle of zero relative to the sample.

### Claim 5 (depends on 1)

The method of claim 1, wherein a central axis of the converging X-ray beam has a fixed non-zero incident angle in a range of 10 degrees to 15degrees from a horizontal plane.

### Claim 6 (depends on 2)

The method of claim 2, wherein a central axis of the converging X-ray beam has a fixed non-zero azimuthal angle relative to the sample.

### Claim 7 (depends on 2)

The method of claim 2, wherein a central axis of the converging X-ray beam has a fixed non-zero incident angle in a range of 10 degrees to 15degrees from a horizontal plane.

### Claim 8 (depends on 7)

The method of claim 7, wherein the central axis of the converging X-ray beam has a fixed non-zero azimuthal angle relative to the sample.

### Claim 9 (depends on 8)

The method of claim 8, further comprising:
positioning the central axis of the converging X-ray beam to the fixed non-zero azimuthal angle at the fixed non-zero incident angle relative to the sample; and, subsequently,
impinging the converging X-ray beam on the sample to generate a second scattered X-ray beam; and
collecting at least a portion of the second scattered X-ray beam.

### Claim 10 (depends on 9)

The method of claim 9, wherein collecting the portion of the scattered X-ray beam comprises collecting 0th order but not 1st order diffraction data for the sample, and wherein collecting the portion of the second scattered X-ray beam comprises collecting 1st order but not 0th order diffraction data for the sample.

### Claim 11 (depends on 1)

The method of claim 1, further comprising
generating the incident X-ray beam from a source selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).

### Claim 12 (depends on 1)

The method of claim 1, further comprising:
prior to the impinging, focusing the incident X-ray beam using a multilayer monochromator to generate the converging incident X-ray beam.

### Claim 13 (depends on 12)

The method of claim 12, wherein the incident X-ray beam is not collimated between the focusing and the impinging.

### Claim 14 (depends on 1)

The method of claim 1, the range of incident angles is less than the angle of a nominal first-order angle at zero degrees.

### Claim 15 (depends on 1)

The method of claim 1, wherein the range of incident angles of from +20 degrees to −20 degrees is provided using a toroidal multilayer monochromator.

### Claim 16 (depends on 1)

The method of claim 1, further comprising:
estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the sampled scattered signal intensity.

### Claim 17 (depends on 1)

The method of claim 1, wherein the converging incident X-ray beam has a wavelength that is less than a periodicity of the periodic structure.

### Claim 18

A method to measure a sample using an X-ray reflectance scatterometry, the method comprising:
impinging an incident low energy X-ray beam having an energy of 1keV or less on a sample having a periodic structure to generate a scattered X-ray beam, wherein the incident low energy X-ray beam is converging in an incidence and azimuth planes thereby providing simultaneously a plurality of incident angles and a plurality of azimuthal angles and having a range of incident angles that is greater than a range of azimuthal angles; and
collecting at least a portion of the scattered X-ray beam using a two-dimensional detector to simultaneously sample a scattered signal intensity of the at least the portion of the scattered X-ray beam that is scattered from the range of incident angles and the range of azimuthal angles.

### Claim 19

A system to measure a sample using an X-ray reflectance scatterometry, the system comprising:
an X-ray source for generating an X-ray beam having an energy of 1 keV or less;
a sample holder for positioning a sample having a periodic structure;
a monochromator positioned between the X-ray source and the sample holder, the monochromator for focusing the X-ray beam to impinge an incident low energy X-ray beam on the sample to generate a scattered X-ray beam, wherein the incident low energy X-ray beam is converging in an incident angles and a plurality of azimuthal angles and having a range of incident angles that is greater than a range of azimuthal angles; and
a 2-D detector for collecting at least a portion of the scattered X-ray beam from the sample.

### Claim 20 (depends on 19)

The system of claim 19, wherein the X-ray source comprises an electron gun directed at an anode comprising a material selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).

### Claim 21 (depends on 19)

The system of claim 19, wherein the monochromator is a toroidal monochromator to provide the range of incident angles from +20 degrees to −20degrees.

### Claim 22 (depends on 19)

The system of claim 19, wherein there is no intervening collimator between the monochromator and the sample holder.

### Claim 23 (depends on 19)

The system of claim 19, wherein the sample holder is rotatable to change an azimuth angle of a central axis of the X-ray beam relative to the periodic structure of the sample.

### Claim 24 (depends on 19)

The system of claim 19, wherein the sample holder is rotatable to provide an orthogonal operation with an eucentric rotation enabling two or more sample rotations per measurement.

### Claim 25 (depends on 19)

The system of claim 19, further comprising:
a processor coupled to the two-dimensional detector, the processor for estimating a shape of the periodic structure by inversion of scattering solutions relative to the sampled scattered signal intensity.