# US 11,906,281 B2 · Device and method for measuring thickness and refractive index of multilayer thin film by using angle-resolved spectral reflectometry

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- Number: US 11,906,281 B2
- Document ID: US11906281B2
- Status: Granted
- Kind: B2
- Application number: 16/610,692
- Filed: 2018-01-26
- Published: 2021-11-04
- Granted: 2024-02-20
- Earliest claimed: 2017-08-07
- Assignees: Korea Research Institute of Standards and Science
- Applicants: Korea Research Institute of Standards and Science
- Inventors: Young-sik Ghim; Hyug-gyo Rhee
- Web page: https://patentgrep.com/patent/US11906281B2

## CPC

- G01B 11/0641: {with measurement of polarization}
- G01B 11/0675: {using interferometry}
- G01B 9/02044: {Imaging in the frequency domain, e.g. by using a spectrometer}
- G01J 3/02: Details
- G01N 21/21: Polarisation-affecting properties (G01N21/19 takes precedence)
- G01N 21/55: Specular reflectivity
- G02B 27/14: operating by reflection only
- G02B 27/145: {having sequential partially reflecting surfaces}
- G02B 27/283: {used for beam splitting or combining}
- G06T 7/60: Analysis of geometric attributes
- G01B 2290/70: Using polarization in the interferometer
- G01N 2021/213: {Spectrometric ellipsometry}
- G01B: MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
- G01J: MEASUREMENT OF INTENSITY, VELOCITY, SPECTRAL CONTENT, POLARISATION, PHASE OR PULSE CHARACTERISTICS OF INFRARED, VISIBLE OR ULTRAVIOLET LIGHT; COLORIMETRY; RADIATION PYROMETRY (light sources F21, H01J, H01K, H05B; investigating properties of materials by optical means G01N)
- 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)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
- G06T: IMAGE DATA PROCESSING OR GENERATION, IN GENERAL

## Abstract

The present disclosure relates to an apparatus and method for measuring the thickness and refractive index of a multilayer thin film by measuring angle-resolved spectral reflectance according to light polarization. According to an exemplary embodiment of the present disclosure, the apparatus and method for measuring the thickness and refractive index of a multilayer structure using angle-resolved spectroscopic reflectometry is capable of measuring and analyzing thickness and refractive index of each layer of a structure having a multilayer thin film through an s-polarized imaging and a p-polarized imaging of the reflective light located in a back focal plane of an objective lens which are acquired through an angle-resolved spectral imaging acquisition part.

## Claims

### Claim 1

A method for measuring a thickness and refractive index of measurement object coated with a multilayer thin film, wherein
the method for measuring thickness and refractive index of a multilayer structure using angle-resolved spectroscopic reflectometry comprises steps of:
emitting light from a broad band light source of an illuminant optical module, wherein the illuminant optical module comprises:
the broad band light source emitting light; and
an illuminant optical system emitting light having an even light intensity distribution through the objective lens from light which is emitted from the broad band light source;
reflecting part of the light which is emitted from the illuminant optical module by a first beam splitter;
allowing the light reflected in the first beam splitter to be incident on the measurement object composed of a multilayer thin film through an objective lens;
reflecting part of the reflective light of the light incident on the measurement object by a third beam splitter, followed by allowing a reflective light reflected in the third beam splitter to be incident on an imaging acquisition part, so as to acquire an imaging of the measurement object;
allowing a reflective light transmitted through the third beam splitter to be incident on an image-rotating prism, followed by rotating an input reflective light according to rotation of the image-rotating prism about an optical axis, so as to emit an output reflective light; and
acquiring a first polarized angle-resolved spectral imaging or a second polarized angle-resolved spectral imaging by polarizing an output reflective light transmitted through the image-rotating prism;
wherein the acquiring the first polarized angle-resolved spectral imaging or the second polarized angle-resolved spectral imaging by polarizing the output reflective light transmitted through the image-rotating prism comprises:
imaging, to a first slit, the reflective light reflected in the second beam splitter and located in the back focal plane of the objective lens;
transmitting, by the first slit, only first polarized light in the reflective light in the back focal plane in the first imaging optical system; and
acquiring, by a first imaging spectrometer, the first polarized angle-resolved spectral imaging or the second polarized angle-resolved spectral imaging.

### Claim 2 (depends on 1)

The method for measuring a thickness and refractive index of measurement object coated with a multilayer thin film of claim 1,
an analysis means measures and analyzes thickness and refractive index of the measurement object from the imaging acquired from the imaging acquisition part, the first polarized angle-resolved spectral imaging and the second polarized angle-resolved spectral imaging.