# US 10,480,997 B1 · Optical measurement apparatus and optical measurement method

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- Number: US 10,480,997 B1
- Document ID: US10480997B1
- Status: Granted
- Kind: B1
- Application number: 16/414,798
- Filed: 2019-05-17
- Published: 2019-11-21
- Granted: 2019-11-19
- Earliest claimed: 2018-05-18
- Assignees: Otsuka Electronics Co., Ltd.
- Applicants: Otsuka Electronics Co., Ltd.
- Inventors: Toshiki Shinke; Shiro Kawaguchi; Nobuyuki Inoue
- Web page: https://patentgrep.com/patent/US10480997B1

## CPC

- G01B 9/02044: {Imaging in the frequency domain, e.g. by using a spectrometer}
- G01J 3/0254: {Spectrometers, other than colorimeters, making use of an integrating sphere}
- G01B 9/0209: Low-coherence interferometers
- G01B 11/0608: {Height gauges}
- G01B 11/0625: {with measurement of absorption or reflection}
- G01B 11/0675: {using interferometry}
- G01B 11/306: {for measuring evenness}
- G01J 3/46: Measurement of colour; Colour measuring devices, e.g. colorimeters (measuring colour temperature G01J5/60)
- G02B 27/0977: {Reflective elements}
- G01B 2210/42: with one or more detectors on a single side of the object to be measured and with a backing surface of support or reference on the other side
- G01B 2210/48: for measurement of a wafer
- 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)
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

An optical measurement apparatus includes: a probe including a transmissive optical member having a reference surface, the probe being configured to irradiate a sample with light through the reference surface, and receive a first reflected light from the reference surface, a second reflected light from a front side of the sample, and a third reflected light from a back side of the sample; and a calculator configured to calculate a first distance from the reference surface to the front side of the sample with use of a first reflection interference light to be generated by the first reflected light and the second reflected light, and to calculate a thickness of the sample with use of a second reflection interference light to be generated by the second reflected light and the third reflected light.

## Claims

### Claim 1

An optical measurement apparatus, comprising:
a probe including a transmissive optical member having a reference surface, the probe being configured to irradiate a sample with light through the reference surface, and to receive a first reflected light from the reference surface, a second reflected light from a front side of the sample, and a third reflected light from a back side of the sample;
a spectrometer configured to measure a spectrum of measurement reflected light including a first reflection interference light to be generated by the first reflected light and the second reflected light, and a second reflection interference light to be generated by the second reflected light and the third reflected light; and
a calculator, which is configured to calculate a first distance from the reference surface to the front side of the sample with use of the first reflection interference light, and to calculate a thickness of the sample with use of the second reflection interference light,
the transmissive optical member having an optical thickness that is larger than an upper limit value of a coherent optical thickness, which is defined by an upper limit value of a measurement wavelength range of the spectrometer and by a wavelength resolution of the spectrometer.

### Claim 2 (depends on 1)

The optical measurement apparatus according to claim 1, wherein the light has a wavelength that is transmitted through the sample.

### Claim 3 (depends on 1)

The optical measurement apparatus according to claim 1, wherein the optical measurement apparatus is configured to:
move at least one of a stage having the sample placed thereon or the probe in a first direction;
irradiate, by the probe, the sample with the light to receive the first reflected light, the second reflected light, and the third reflected light at a plurality of positions in the first direction; and
calculate, by the calculator, the first distance and the thickness of the sample at the plurality of positions in the first direction.

### Claim 4 (depends on 3)

The optical measurement apparatus according to claim 3, wherein the optical measurement apparatus is configured to:
move at least one of the stage or the probe in a second direction, which intersects the first direction;
irradiate, by the probe, the sample with the light to receive the first reflected light, the second reflected light, and the third reflected light at a plurality of positions in the second direction; and
calculate, by the calculator, the first distance and the thickness of the sample at the plurality of positions in the second direction.

### Claim 5

An optical measurement apparatus, comprising:
a probe including a transmissive optical member having a reference surface, the probe being configured to irradiate a sample with light through the reference surface, and to receive a first reflected light from the reference surface, a second reflected light from a front side of the sample, and a third reflected light from a back side of the sample; and
a calculator, which is configured to calculate a first distance from the reference surface to the front side of the sample with use of a first reflection interference light to be generated by the first reflected light and the second reflected light, and to calculate a thickness of the sample with use of a second reflection interference light to be generated by the second reflected light and the third reflected light,
the optical measurement apparatus being configured to:
irradiate, under a state in which the sample is not placed on a stage, by the probe, the stage with the light through the reference surface to receive the first reflected light, and a fourth reflected light from a surface of the stage;
calculate, by the calculator, a second distance from the reference surface to the stage with use of a third reflection interference light to be generated by the first reflected light and the fourth reflected light; and
calculate, by the calculator, a third distance between the back side of the sample and the stage with the second distance being an additive element, and with the first distance and the thickness of the sample being subtractive elements.

### Claim 6 (depends on 5)

The optical measurement apparatus according to claim 5,
wherein the optical measurement apparatus is configured to, under the state in which the sample is not placed on the stage:
move at least one of the stage or the probe in a first direction; and
irradiate, by the probe, the stage with the light to receive the first reflected light and the fourth reflected light at a plurality of positions in the first direction,
wherein the optical measurement apparatus is configured to, under a state in which the sample is placed on the stage,
move at least one of the stage or the probe in the first direction; and
irradiate, by the probe, the sample with the light to receive the first reflected light, the second reflected light, and the third reflected light at a plurality of positions corresponding to the plurality of positions at which the fourth reflected light is received, and
calculate, by the calculator, the thickness of the sample, the first distance, the second distance, and the third distance at the plurality of positions in the first direction.

### Claim 7 (depends on 6)

The optical measurement apparatus according to claim 6,
wherein the optical measurement apparatus is configured to, under the state in which the sample is not placed on the stage:
move at least one of the stage or the probe in a second direction, which intersects the first direction; and
irradiate, by the probe, the stage with the light to receive the first reflected light and the fourth reflected light at a plurality of positions in the second direction,
wherein the optical measurement apparatus is configured to, under the state in which the sample is placed on the stage,
move at least one of the stage or the probe in the second direction; and
irradiate, by the probe, the sample with the light to receive the first reflected light, the second reflected light, and the third reflected light at a plurality of positions corresponding to the plurality of positions at which the fourth reflected light is received, and
calculate, by the calculator, the thickness of the sample, the first distance, the second distance, and the third distance at the plurality of positions in the second direction.

### Claim 8 (depends on 5)

The optical measurement apparatus according to claim 5, further comprising a spectrometer, which is configured to measure a spectrum of measurement reflected light including the first reflection interference light and the second reflection interference light, and to output a result of the measurement to the calculator,
wherein the transmissive optical member has an optical thickness that is larger than an upper limit value of a coherent optical thickness, which is defined by an upper limit value of a measurement wavelength range of the spectrometer and by a wavelength resolution of the spectrometer.

### Claim 9

An optical measurement method, which is performed with use of a probe including a transmissive optical member having a reference surface, and a spectrometer, the optical measurement method comprising:
irradiating a sample with light through the reference surface with use of the probe;
receiving, by the probe, a first reflected light from the reference surface, a second reflected light from a front side of the sample, and a third reflected light from a back side of the sample;
measuring, with use of the spectrometer, a spectrum of measurement reflected light including a first reflection interference light to be generated by the first reflected light and the second reflected light, and a second reflection interference light to be generated by the second reflected light and the third reflected light; and
calculating a first distance from the reference surface to the front side of the sample with use of the first reflection interference light, and calculating a thickness of the sample with use of the second reflection interference light,
the transmissive optical member having an optical thickness that is larger than an upper limit value of a coherent optical thickness, which is defined by an upper limit value of a measurement wavelength range of the spectrometer and by a wavelength resolution of the spectrometer.

### Claim 10 (depends on 9)

The optical measuring method according to claim 9, wherein the light has a wavelength that is transmitted through the sample.

### Claim 11 (depends on 9)

The optical measuring method according to claim 9, further comprising:
moving at least one of a stage, on which the sample is placed, or the probe in a first direction;
irradiating, by the probe, the sample with the light to receive, by the probe, the first reflected light, the second reflected light, and the third reflected light at a plurality of positions in the first direction; and
calculating the first distance and the thickness of the sample at the plurality of positions in the first direction.

### Claim 12 (depends on 11)

The optical measuring method according to claim 11, further comprising:
moving at least one of the stage or the probe in a second direction, which intersects the first direction;
irradiating, by the probe, the sample with the light to receive, by the probe, the first reflected light, the second reflected light, and the third reflected light at a plurality of positions in the second direction; and
calculating the first distance and the thickness of the sample at the plurality of positions in the second direction.

### Claim 13

An optical measurement method, which is performed with use of a probe including a transmissive optical member having a reference surface, the optical measurement method comprising:
irradiating a sample with light through the reference surface with use of the probe;
receiving, by the probe, a first reflected light from the reference surface, a second reflected light from a front side of the sample, and a third reflected light from a back side of the sample;
calculating a first distance from the reference surface to the sample with use of a first reflection interference light to be generated by the first reflected light and the second reflected light, and calculating a thickness of the sample with use of a second reflection interference light to be generated by the second reflected light and the third reflected light;
irradiating, under a state in which the sample is not placed on a stage, the stage with the light through the reference surface with use of the probe to receive, by the probe, the first reflected light, and a fourth reflected light from a surface of the stage;
calculating a second distance from the reference surface to the stage with use of a third reflection interference light to be generated by the first reflected light and the fourth reflected light; and
calculating a third distance between the back side of the sample and the stage with the second distance being an additive element, and with the first distance and the thickness of the sample being subtractive elements.

### Claim 14 (depends on 13)

The optical measuring method according to claim 13, further comprising:
moving, under the state in which the sample is not placed on the stage, at least one of the stage or the probe in a first direction;
irradiating, by the probe, under the state in which the sample is not placed on the stage, the stage with the light to receive, by the probe, the first reflected light and the fourth reflected light at a plurality of positions in the first direction;
moving, under a state in which the sample is placed on the stage, at least one of the stage or the probe in the first direction;
irradiating, by the probe, under the state in which the sample is placed on the stage, the sample with the light to receive, by the probe, the first reflected light, the second reflected light, and the third reflected light at a plurality of positions corresponding to the plurality of positions at which the fourth reflected light is received; and
calculating the thickness of the sample, the first distance, the second distance, and the third distance at the plurality of positions in the first direction.

### Claim 15 (depends on 14)

The optical measuring method according to claim 14, further comprising:
moving, under the state in which the sample is not placed on the stage, at least one of the stage or the probe in a second direction, which intersects the first direction;
irradiating, by the probe, under the state in which the sample is not placed on the stage, the stage with the light to receive, by the probe, the first reflected light and the fourth reflected light at a plurality of positions in the second direction;
moving, under the state in which the sample is placed on the stage, at least one of the stage or the probe in the second direction;
irradiating, by the probe, under the state in which the sample is placed on the stage, the sample with the light to receive, by the probe, the first reflected light, the second reflected light, and the third reflected light at a plurality of positions corresponding to the plurality of positions at which the fourth reflected light is received; and
calculating the thickness of the sample, the first distance, the second distance, and the third distance at the plurality of positions in the second direction.

### Claim 16 (depends on 13)

The optical measurement method according to claim 13, further comprising measuring a spectrum of measurement reflected light including the first reflection interference light and the second reflection interference light with use of a spectrometer,
wherein the transmissive optical member has an optical thickness that is larger than an upper limit value of a coherent optical thickness, which is defined by an upper limit value of a measurement wavelength range of the spectrometer and by a wavelength resolution of the spectrometer.