# US 10,481,112 B2 · Methods and systems for measuring periodic structures using multi-angle X-ray reflectance scatterometry (XRS)

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- Number: US 10,481,112 B2
- Document ID: US10481112B2
- Status: Granted
- Kind: B2
- Application number: 16/181,287
- Filed: 2018-11-05
- Published: 2019-03-21
- Granted: 2019-11-19
- 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/US10481112B2

## 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 metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis;
impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to an orthogonal to the periodic structure;
performing one measurement by collecting only a first order diffraction from the sample.

### Claim 2 (depends on 1)

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

### Claim 3 (depends on 2)

The method of claim 2, wherein non-zero incident angle is set to approximately in the range of 10-15 degrees.

### Claim 4 (depends on 1)

The method of claim 1, wherein the incident converging X-ray beam has a converging angle approximately in the range of 2-10 degrees.

### Claim 5 (depends on 4)

The method of claim 4, wherein non-zero azimuthal angle is set to at least 45 degrees.

### Claim 6 (depends on 1)

The method of claim 1, further comprising performing another measurement by collecting only a zero order diffraction from the sample.

### Claim 7 (depends on 6)

The method of claim 6, wherein the another measurement is performed by impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to the horizontal plane defined by the uppermost surface of the sample, and the central axis forms a zero azimuthal angle relative to the orthogonal to the periodic structure.

### Claim 8 (depends on 1)

The method of claim 1, wherein impinging the incident converging X-ray beam comprises impinging a low energy X-ray beam having an energy of approximately 1 keV or less.

### Claim 9 (depends on 8)

The method of claim 8, wherein impinging the low energy X-ray beam comprises generating the low energy X-ray beam from a source selected from the group consisting of carbon (C), molybdenum (Mo) and Rhodium (Rh).

### Claim 10 (depends on 1)

The method of claim 1, wherein forming an incident converging X-ray beam comprises directing a low energy X-ray beam towards a toroidal multilayer monochromator.

### Claim 11 (depends on 1)

The method of claim 1, wherein collecting only a first order diffraction from the sample comprises using a two-dimensional detector to simultaneously sample scattered signal intensity of scattered X-ray beam from the sample.

### Claim 12 (depends on 11)

The method of claim 11, 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 13 (depends on 1)

The method of claim 1, wherein impinging the incident converging X-ray beam on the sample comprises impinging an X-ray beam having a wavelength less than a periodicity of the periodic structure.

### Claim 14

A metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis and simultaneously a plurality of incident angles and a plurality of azimuthal angles;
and performing the non-ordered steps of:
performing one measurement by impinging the converging X-ray beam on the sample such that the central axis of the converging X-ray beam forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a zero azimuthal angle relative to an orthogonal to the periodic structure, and collecting only a zero order diffraction from the sample; and,
performing another measurement by impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to the horizontal plane defined by the uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to the orthogonal to the periodic structure, and collecting only a first order diffraction from the sample.

### Claim 15 (depends on 14)

The method of claim 14, further comprising estimating a shape of the periodic structure of the sample by inversion of scattering solutions relative to the zero order diffraction and the first order diffraction.

### Claim 16 (depends on 14)

The method of claim 14, wherein the converging X-ray beam has a wavelength wherein λ/d<1, wherein λ is the wavelength and d is a fundamental dimension of the periodic structure.

### Claim 17 (depends on 14)

The method of claim 14, wherein non-zero incident angle is set to sine−1(1−λ/d).

### Claim 18 (depends on 14)

The method of claim 14, wherein impinging the incident converging X-ray beam comprises impinging a low energy X-ray beam having an energy of approximately 1 keV or less.

### Claim 19 (depends on 15)

The method of claim 15, wherein forming an incident converging X-ray beam comprises directing a low energy X-ray beam towards a focusing monochromator that extends in two dimensions.

### Claim 20

A metrology method of measuring a sample having a periodic structure by X-ray reflectance scatterometry, the method comprising:
forming an incident converging X-ray beam having a central axis;
impinging the converging X-ray beam on the sample such that the central axis forms a non-zero incidence angle relative to a horizontal plane defined by an uppermost surface of the sample, and the central axis forms a non-zero azimuthal angle relative to an orthogonal to the periodic structure;
performing a measurement by collecting both a zero order and a first order diffraction from the sample without order overlap.