KR20230001611A - The thickness measurement method using a three-dimensional reflectance surface - Google Patents

Abstract

In accordance with the present invention, a thickness measurement method using a three-dimensional reflectance curved surface includes: a measured reflectance curved surface generation step of generating a three-dimensional measured reflectance curved surface with coordinate components of a wavelength, an optical path difference (OPD) and reflectance from an interference light signal measured by a spectrometer after being inputted through an interference lens module from a light source of a thickness measurement device and reflected from a specimen; a theoretical reflectance curved surface generation step of generating a three-dimensional theoretical reflectance curved surface by including a wavelength, an optical path difference and reflectance coordinate components from a calculated theoretical interference tube signal, so as to be matched with the measured reflectance curved surface; a similarity determination step of repetitively determining similarity with respect to the measured reflectance curved surface and the theoretical reflectance curved surface; and a specimen thickness calculation step of confirming the thickness of the specimen generating the theoretical reflectance curved surface corresponding to a case with the highest similarity in the similarity determination step, as the thickness of the specimen forming the measured reflectance curved surface. Therefore, the present invention is capable of precisely measuring the thickness of an ultrathin film specimen of 200 nm or less within a narrow pattern area.

Description

The thickness measurement method using a three-dimensional reflectance surface}

The present invention forms a measured three-dimensional reflectivity curve from interference light generated from a thin film sample and an interference lens module through optical axis driving and spectroscopy, and the thickness of the thin film forming the theoretical reflectance curve having the highest similarity to the measured reflectivity curve is determined as the actual thin film. It relates to a method of precisely measuring the thickness of an ultra-thin film of about 200 nm or less in a micropattern area by determining the thickness.

In semiconductor and display processes, it is essential to measure the thickness and shape of deposited thin films. In order to measure the thickness and shape of the thin film, a reflectometer, an ellipsomter, and a white light phase shift interferometer are used.

A reflectometer refers to a method and equipment for analyzing the thickness or physical properties of a sample by measuring a signal of reflected light with respect to incident light. Among thin film thickness and shape measurement methods using optics, spectroscopic reflectometry, which measures the thickness of a thin film based on the spectral reflectance characteristics of a sample, has the fastest measurement speed and is known to be applicable to mass production lines.

A spectral reflectometer is a device that measures the reflectivity of a sample by measuring the amount of incident light and the amount of reflected light.

The theoretical reflectance in FIG. 1 is defined by the following equation (1).

---- 식(1)

---- Equation (1)

The reflection coefficient in the thin film is defined by the following equation (2) in the cross-sectional structure shown in FIG.

---- 식(2)

---- Expression (2)

In Equation (2), R ^p and R ^s mean the reflection coefficients of the p-wave and the s-wave, respectively.

β included in equation (2) is a function of wavelength (λ).

Specifically, β(λ) is defined as Equation (3) below.

---- 식(3)

---- Equation (3)

In addition, the r value included in equation (2) is defined by the Fresnel equation in the following equation (4) in the cross-sectional structure shown in FIG.

---- 식(4)

---- Equation (4)

The thickness of the actual sample can be known by inferring the theoretical thickness at which the error is minimized by comparing the reflectance measured using the spectroscopic reflectometer with the theoretical reflectance. The reflectometer system shown in FIG. 3 can have a vertical incident reflection structure and can use an objective lens to measure the thickness of a narrow pattern area. However, the reflectometer system has a limitation in that it is difficult to measure the thickness of a thin film (about 200 nm or less).

An ellipsometer is a device that measures the change in polarization state of light after it is reflected or transmitted, and uses the principle that the change in polarization state is determined according to the characteristics of the measured sample (thickness, complex refractive index or dielectric function). The principle of the ellipsometer is as follows. When light is incident on a sample at an angle, a plane containing incident light and reflected light is defined as the light incident surface. According to the direction of oscillation of the electric field, parallel to the plane of incidence is called p-wave and perpendicular to it is called s-wave. The p-wave and the s-wave have independent amplitudes and phases. When light having a specific polarization state is incident on a sample at an angle, the polarization state is changed according to the characteristics of the sample. Through this, the thickness of the thin film can be measured by calculating the ellipticity parameters meaning the phase difference (Δ) and the relative amplitude change ratio (Ψ) of the p-wave and the s-wave and comparing them with theoretical signals. The ellipsometer shown in FIG. 4 has high thickness measurement accuracy even for a thin film (about 200 nm or less), but cannot use a high-magnification objective lens because of the oblique incident reflection structure. There are limitations that make it difficult to do.

The white light phase shift interferometer shown in FIG. 5 is a device for measuring the shape of a sample by utilizing light interference, and uses position scanning using white light as a light source. The white light phase shift interferometer can create an optical path difference by scanning a reference mirror, and the interfergram according to the scan position is expressed as shown in FIG. 6. The white light phase shift interferometer can use a high-magnification objective lens, so it is possible to measure even a narrow pattern area. In the white light phase shift interferometer, when the thickness of the thin film deposited on the substrate is sufficiently thick, the two peaks are separated as shown in the upper graph of FIG. 6, and the thickness of the thin film can be measured. As shown in the graph, it is difficult to measure the thickness of the thin film because the two peaks cannot be separated.

001 KR 10-2006-0052004 A (2006.05.19) 002 KR 10-2017-0142240 A (2017.12.28)

An object of the present invention has been made to solve the above-described problems, and a measured reflectivity curve is generated from a spectral signal of interference light reflected from a thin film sample, and a theoretical reflectance curve corresponding thereto is generated, and then the measured reflectivity curve and the theoretical It is to provide a method for precisely measuring the thickness of a thin film of 200 nm or less by comparing the reflectivity curves and determining the thickness forming the theoretical reflectance curve surface with the highest similarity as the thickness of the measured thin film.

In order to achieve the above object, the method for measuring thickness using a three-dimensional reflectivity curved surface according to the present invention is incident from a light source of a thickness measuring device through an interference lens module and is reflected from a sample and then measured in a spectrometer. ), an optical path difference (OPD), and a reflectance measurement step of generating a three-dimensional measurement reflectance curve with coordinate components of reflectance;

A theoretical reflectivity curve generating step of generating a three-dimensional theoretical reflectance curve by including wavelength, optical path difference, and reflectance coordinate components of the calculated theoretical interferometer signal to correspond to the measured reflectivity curve;

a similarity determination step of repeatedly determining a similarity between the measured reflectivity curved surface and the theoretical reflectivity curved surface; and

In the similarity determination step, a sample thickness calculation step of determining the thickness of the sample for generating the theoretical reflectivity curve corresponding to the case where the similarity is highest is the thickness of the sample forming the measured reflectivity curve.

Preferably, the generating of the measured reflectivity curved surface includes a scan error correction step of correcting a scan error of a piezoelectric actuator that drives the interference lens module in an optical axis direction.

The interference lens module is configured to be movable in an optical axis direction,

In the scan error correction step,

The intensity of the interfering light (I _{DC, α, φ} (k, OPD)) detected by the spectrometer is decomposed by wavelength to determine the optical path difference (OPD) and reflectance or optical path difference (OPD, Optical Path Difference). A first fitting step of fitting with a sinusoidal function composed of Difference and Intensity; and

It is preferable to include a second fitting step of repeatedly correcting the position of the interference lens module until the error between the sinusoidal function fitted in the first fitting step and the input intensity data of the interference light becomes equal to or less than a predetermined value. .

When the error converges to a predetermined value in the range of 10 ⁻³ to 10 ⁻⁴ , the scanning error correction step may be terminated.

The thickness measuring device,

a light source generating multi-wavelength light;

a first beam splitter for transmitting a part of the light generated from the light source and reflecting the rest;

an interference lens module for incident light diverged from the first beam splitter toward a sample;

a piezoelectric actuator for moving the interference lens module or sample on an optical axis; and

It is preferable to include; a spectrometer for measuring the interference light generated through the sample and the interference lens module.

The interference lens module,

an interference lens condensing light incident from the first beam splitter toward the sample;

a second beam splitter disposed below the interference lens and transmitting a part of the light incident from the interference lens and reflecting the rest; and

It is preferable to include; a reference mirror disposed between the interference lens and the second beam splitter and reflecting the light reflected from the second beam splitter toward the second beam splitter.

The present invention enables measurement of a fine pattern area through a vertical optical system configuration and presents the concept of a three-dimensional reflectivity curve that can overcome the ambiguity of the existing two-dimensional reflectivity thickness determination, thereby narrowing the narrow, which was a problem with conventional thickness measurement devices. It provides the effect of precisely measuring the thickness of an ultra-thin film sample of 200 nm or less within the pattern area.

In addition, as in the preferred embodiment of the present invention, when a process of correcting driving and vibration errors of the piezoelectric actuator is included in the white light phase shift interferometer, there is an effect of securing a higher level of measurement accuracy and stability.

1 is a diagram for defining a reflection coefficient in a thin film.
2 is a diagram for defining a Fresnel equation.
3 is a diagram showing a hardware configuration of a reflectometer.
4 is a diagram showing the hardware configuration of the ellipsometer.
5 is a diagram showing a hardware configuration of a white light phase shift interferometer.
6 is a diagram showing intensity distribution of interfering light according to a scan position of an interference lens module forming an optical path difference in a white light over-window transition interferometer.
7 is a process chart of a thickness measurement method using a three-dimensional reflectivity curved surface according to a preferred embodiment of the present invention.
8 is a configuration diagram of a thickness measuring device used in the measuring method of FIG. 7 .
9 is a view showing the shape of a reflectivity curved surface.
10 is a diagram conceptually showing an optical path difference (OPD) for calculating a theoretical reflectivity curved surface.
FIG. 11 is a plan view of the measured reflectivity curved surface as shown in FIG. 9 .
12 is a plan view of a theoretical reflectance curve calculated by assuming various thicknesses of a sample.
13 is a diagram exemplarily showing a case in which the similarity between the measured reflectivity curve and the theoretical reflectivity curve is the highest.
14 to 16 are diagrams visually showing a process in which scan error correction is performed by showing measured reflectivity decomposed by wavelength to correspond to an optical path difference and fitting it with a sine wave function.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

7 is a process chart of a thickness measurement method using a three-dimensional reflectivity curved surface according to a preferred embodiment of the present invention. 8 is a configuration diagram of a thickness measuring device used in the measuring method of FIG. 7 . 9 is a view showing the shape of a reflectivity curved surface. 10 is a diagram conceptually showing an optical path difference (OPD) for calculating a theoretical reflectivity curved surface. 11 is a plan view of the measured reflectivity curved surface as shown in FIG. 9 . 12 is a plan view of a theoretical reflectance curve calculated by assuming various thicknesses of a sample. 13 is a diagram exemplarily showing a case in which the similarity between the measured reflectivity curve and the theoretical reflectivity curve is the highest. 14 to 16 are diagrams visually showing a process in which scan error correction is performed by showing the measured reflectivity decomposed by wavelength to correspond to the optical path difference and fitting it with a sine wave function.

7 to 16, the method for measuring thickness using a three-dimensional reflectivity curved surface (hereinafter, referred to as "thickness measuring method") according to the present invention includes generating a measured reflectivity curved surface (S10) and correcting scan error (S15). ), a theoretical reflectivity curve generating step (S20), a similarity determining step (S30), and a sample thickness calculating step (S40).

First, the configuration of the thickness measuring device used in the thickness measuring method will be described.

Referring to FIG. 8 , the thickness measurement device includes a light source 100, a first beam splitter 200, an interference lens module 201, a piezoelectric actuator 205, and a spectrometer 402.

The light source 100 is a device that generates multi-wavelength light. For example, the light source 100 may generate white light. A collimator 101 may be provided as a kind of lens structure that refracts light emitted from the light source 100 to become parallel light.

The first beam splitter 200 is a component that transmits some of the light passing through the collimator 101 and reflects the rest of the light toward the sample 206 by changing the traveling direction of the light.

The interference lens module 201 is a device for incident light reflected from the first beam splitter 200 toward the specimen 206 . The interference lens module 201 may include an interference lens 202 , a second beam splitter 204 , and a reference mirror 203 .

The interference lens 202 is a lens that condenses the light reflected from the first beam splitter 200 and makes it incident toward the specimen 206 . The interference lens 202 is disposed on the path of light reflected from the first beam splitter 200 . A specimen 206 is disposed below the interference lens module 201 . The sample 206 may be, for example, a product in which a thin film is deposited on a substrate. The interference lens 202 makes the light reflected from the first beam splitter 200 incident on a specific area of the sample 206 .

The second beam splitter 204 is disposed below the interference lens 202 . The second beam splitter 204 is a component that transmits a part of the light incident from the interference lens 202 and reflects the rest toward a reference mirror 203 to be described later. In an embodiment, the second beam splitter 204 is configured to reflect half of the incident light and transmit the rest.

The reference mirror 203 reflects the light reflected by the second beam splitter 204 from the interference lens 202 back toward the second beam splitter 204, thereby reducing the light reflected from the sample 206 and It is a component that generates an interference effect on the light reflected from the sample by generating a path difference. The phase information obtained through the interference effect includes thickness information and shape information of the sample 206 . A distance between the reference mirror 203 and the sample 206 based on the second beam splitter 204 constitutes an optical path difference (OPD). Referring to FIG. 10, if the distance between the second beam splitter 204 and the reference mirror 203 is defined as L, the distance between the second beam splitter 204 and the specimen 206 may be defined as L-OPD/2. .

The piezoelectric driver 205 is a device that moves the interference lens module 201 or the specimen 206 along the optical axis. The piezoelectric actuator 205 may include a piezoelectric element. The piezoelectric actuator 205 moves the physical position of the interference lens module 201 . In this embodiment, the physical position of the interference lens module 201 is configured to be movable in the optical axis direction. This is caused by the physical characteristics of the piezoelectric actuator 205 .

The spectrometer 402 is a light sensing device that measures the interference light formed by the interference lens module 201 and the sample 206 after passing through the first beam splitter 200 . The spectrometer 402 may measure the intensity of the interference light signal for each wavelength and output it as a digital signal. The spectrometer 402 may be configured by employing a known spectrometer. In the spectrometer 402, a condensing lens 401 for condensing light may be formed as one module. The spectrometer 402 may be detachably added to a computer device for signal processing or integrally formed.

Now, the method for measuring the thickness will be sequentially described in the process order.

The measuring reflectivity curve generating step (S10) is incident from the light source 100 of the thickness measuring device through the interference lens module 201 and reflected from the sample, and then the wavelength and optical path from the interference light signal measured by the spectrometer 402. A three-dimensional measurement reflectance curve is created with coordinate components of difference (OPD) and reflectance. Referring to FIG. 9 , it can be easily understood that the measured reflectivity curved surface is formed in a three-dimensional shape. The measured reflectivity curve includes information about the unknown thickness of the sample 206, and the thickness of the sample 206 cannot be directly obtained from the measured data signal.

In the theoretical reflectivity curve generating step (S20), a theoretical reflectance curve surface is generated by calculation to correspond to the measured reflectivity curve surface. In the theoretical reflectivity curve generating step (S20), a three-dimensional theoretical reflectivity curve is generated by assuming the thickness of the sample 206 and including the coordinate components of wavelength, optical path difference, and reflectivity.

Hereinafter, a process of calculating the theoretical reflectivity will be described in detail.

, 기준 미러(203)의 반사계수를

이라 한다. 또한, 제2빔 스플리터(204)로부터 시료(206)까지의 거리를 L-OPD/2라 하면, 제2빔 스플리터(204)와 기준 미러(203)간 거리는 L로 정의된다. 도 8에 도시된 장치에서 분광계(402) 쪽으로 향하는 빛의 전기장은 다음과 같이 표현된다.FIG. 10 is a diagram conceptually representing the second beam splitter 204, the reference mirror 203, and the sample 206 in the device shown in FIG. 8 while having the same optical path for easy understanding. The reflection coefficient of the sample 206

, the reflection coefficient of the reference mirror 203

It is called In addition, if the distance from the second beam splitter 204 to the sample 206 is L-OPD/2, the distance between the second beam splitter 204 and the reference mirror 203 is defined as L. The electric field of the light directed towards the spectrometer 402 in the device shown in FIG. 8 is expressed as:

은 기준 미러의 반사계수이기 때문에 완전 반사되므로 1로 둘 수 있다.From here,

Since is the reflection coefficient of the reference mirror, it can be set to 1 because it is perfectly reflected.

Since the second beam splitter 204 transmits half of the incident light and reflects the rest, if the incident electric field is defined as 2E ₀ , the second beam splitter 204 passes through the reference mirror 203 and the specimen 206. Each thin electric field can be viewed as E ₀ .

Therefore, since the amount of light sensed by the spectrometer 402 is proportional to the square of the magnitude of the electromagnetic wave, it is expressed as follows. In the equation below, the proportionality constant is omitted.

Here, k is the wavenumber.

That is, the amount of light detected by the spectrometer 402 is a function of the reflection coefficient of the sample 206, the wavelength, and the optical path difference (OPD).

)는 아래와 같이 표현된다.Here, the reflection coefficient of the sample 206 (

) is expressed as:

,

,

,

,

,

,

)가 두께(

)를 매개로 하는 함수이므로, k와

이 특정되면

의 함수가 된다. 여기서

은 박막 시료(206)의 굴절률이며,

는 입사각을 의미한다.Therefore, the reflection coefficient (

) is the thickness (

), so k and

When this is specified

becomes a function of here

is the refractive index of the silver thin film sample 206,

is the angle of incidence.

)을 따로 측정하여

에서 나누어 주면,

가 남게 되고, 이를 반사도 곡면으로 정의할 수 있다.Standard light amount (

) is measured separately

If divided by

remains, which can be defined as a reflectivity surface.

A computer simulation of this equation can generate a theoretical reflectivity curve in the form shown in FIG. 9 .

In the similarity determination step (S30), a process of repeatedly determining the similarity between the measured reflectivity curved surface and the theoretical reflectivity curved surface is performed. In the similarity determination step (S30), a known image comparison algorithm may be employed. The plan view image of the measured reflectivity curve shown in FIG. 11 serves as a reference template. Since the range of the OPD is limited and relative due to the structure of the piezoelectric actuator 205, the OPD of the theoretical reflectivity curve shown in FIG. 12 should be set wider than the OPD of the measured reflectivity curve. Then, while moving the measured reflectivity curved surface along the OPD axis, the position with the highest degree of similarity is found. An algorithm for measuring similarity may employ a known image comparison algorithm.

는 아래 식과 같이 표현될 수 있다.When the similarity is the highest, the matching between the image of the measured reflectivity curve and the image of the theoretical reflectivity curve is maximized,

can be expressed as the formula below.

는 기준 형판(template) 이미지의 픽셀 값이며, x(r,c)는 이론 반사도 곡면의 이미지 픽셀 값으로서 소스(source) 이미지 픽셀 값이다.here,

is a pixel value of a reference template image, and x(r,c) is a source image pixel value as an image pixel value of a theoretical reflectivity curve.

In the sample thickness calculation step (S40), the thickness of the sample 206 generating the theoretical reflectance curve corresponding to the case in which the similarity is the highest in the similarity determination step (S30) is calculated as the sample 206 forming the measured reflectivity curve. determined by the thickness of In this way, the measured thickness of the thin film sample 206 may be determined through image comparison of the measured reflectivity curve and the theoretical reflectivity curve.

In addition, the step of generating the measured reflectivity curved surface (S10) preferably includes a scan error correction step (S15) of correcting a scan error of a piezoelectric actuator that drives the interference lens module in the optical axis direction.

In the scan error correction step (S15), the position error of the interference lens module 201 whose position is changed by the piezoelectric actuator 205 is corrected. In the process of obtaining the measured reflectivity curved surface shown in FIGS. 9 and 11 , the position of the interference lens module 201 is changed by driving the piezoelectric driver 205 . However, the piezoelectric actuator 205 inevitably generates errors due to driving errors and vibrations. In practice, in order to obtain meaningful data for the OPD, the scan interval of the interference lens module 201 should be about tens of nm and the scan range should be more than several hundred μm. However, in the driving process of the piezoelectric actuator 205, an error of several nm may occur in every scan. To compensate for this error, error correction is performed.

First, as described above, the interference lens module 201 is configured to be movable in the optical axis direction by the piezoelectric driver 205. When acquiring data from the spectrometer 402, the position of the interference lens module 201 is inevitably located at a discontinuous position. The position of the interference lens module 201 is referred to as Z for convenience of description, and Z is actually Z _cmd,1 ,Z _{cmd,2 .} It is defined discretely as Z _cmd,n .

More specifically, the scan error correction step (S15) includes a first fitting step (S17) and a second fitting step (S19).

In the first fitting step (S17), the intensities (I _{DC, α, φ} (k, OPD)) of the coherent light detected by the spectrometer 402 are decomposed by wavelength to determine the optical path difference (OPD) and reflectivity. It is fitted with a sinusoidal function composed of (Reflectance) or Optical Path Difference (OPD) and Intensity.

The intensity of the coherent light (I _DC,α,φ (k,OPD)) detected by the spectrometer 402 can be expressed as a sinusoidal function with respect to the OPD as follows. This can be summarized in the following way.

In the above equation, DC is a value independent of OPD.

로 정의되며,DC

is defined as,

α is the magnitude (or amplitude, amplitude) of the cos term for the OPD

로 정의된다.α

is defined as

로 정의된다.φ is the phase of the cos term, and the phase of the reflection coefficient of the sample 206 φ

is defined as

피팅을 진행한다. 이에 대한 이용 수식은 다음과 같다.When the measured reflectivity curve signal is separated for each wave number (k) and drawn according to the OPD, it is shown in FIGS. 14 to 16(a). Wavelengths of the signals shown in FIGS. 14 to 16 are different from each other. The piezoelectric driver 205 moves the position of the interference lens module 201 and converts the discretely acquired OPD and signal strength (I _measured ) data into a sinusoidal function.

proceed with the fitting. The formula used for this is:

피팅은 컴퓨터를 이용하여 빠르게 수행될 수 있다.

Fitting can be done quickly using a computer.

The second fitting step (S19) is the position of the interference lens module 201 until the error between the sinusoidal function fitted in the first fitting step (S17) and the intensity data of the input interference light becomes equal to or less than a predetermined value. Iteratively calibrate Z. As the position of the interference lens module 201 is calibrated, I _measured has different amplitudes and phases for each wavelength, but shares the same position (OPD, Z) because it is spectralized at the common position of the piezoelectric actuator 205. do. Therefore, the position of Z (OPD) is adjusted so that the error with the fitted sine wave function is minimized in all wavelength bands. Expressing this as a formula is:

피팅도 변화된다. 결과적으로 도 14 내지 도 16에 도시된 (c) 그래프와 같이 제2피팅 단계(S19)가 수행된 결과

와 I_measured가 거의 일치하는 것을 볼 수 있다.Accordingly, in the graph (b) shown in FIGS. 14 to 16, the OPD is slightly changed, and accordingly

Fitting is also changed. As a result, the result of performing the second fitting step (S19) as shown in the graph (c) shown in FIGS. 14 to 16

It can be seen that and I _measured are almost identical.

That is, the scan error correction step (S15) is preferably performed repeatedly until the following conditions are satisfied.

와 I_measured의 차이(오차)가 10^-3 내지 10^-4 범위에서 일정 값에 수렴되는 경우 상기 스캔 오차 보정 단계(S15)를 종료하는 것이 바람직하다.where ε is a very small value, practically

_{When the difference (error) between measured} I and I converges to a certain value in the range of 10 ^-3 to 10 ^-4 , it is preferable to end the scan error correction step (S15).

As described above, the thickness measurement method using a three-dimensional reflectivity curved surface according to the present invention enables measurement of a fine pattern area through a vertical optical system configuration, and can overcome the existing ambiguity in determining the thickness of two-dimensional reflectivity. By presenting the concept of a reflectivity curved surface, an effect of precisely measuring the thickness of an ultra-thin film sample of 200 nm or less within a narrow pattern area, which was a problem of conventional thickness measuring devices, is provided.

More specifically, the present invention, in order to measure the thickness of an unknown sample, after light having an optical path difference through an interference lens module is reflected on the sample, interference light is formed to form a measurement reflectance curve from a signal measured by a spectrometer, , By comparing the theoretical reflectivity curves calculated assuming the thickness to provide a method for determining the thickness of the sample forming the theoretical reflectance curve surface with the highest similarity as an unknown sample thickness, the problem of the conventional thickness measuring device is overcome and the thickness of 200 nm or less It provides the effect of precisely measuring the thickness of an ultra-thin film sample.

There is a steady demand for measuring the thickness of thin films within micropatterns of semiconductor and display samples, and for this purpose reflectometers, ellipsometers, white light phase shift interferometers, and the like have been used. However, reflectometers and white light phase shift interferometers are difficult to measure thin films less than about 200 nm thick due to limitations in measurement parameters, and ellipsometers have limitations in measuring the inside of micropatterns because their measurement area is too large. Since the thickness measurement method according to the present invention obtains a parameter called 'reflectivity curve' by spectroscopy of the interference signal, it can measure a thin film with a thickness of less than 200 nm with high accuracy, and since it inherits the hardware of the reflectometer and the white light phase shift interferometer, fine microscopic The pattern area also has the advantage of being measurable. In addition, as in the preferred embodiment of the present invention, when a process of correcting driving and vibration errors of the piezoelectric actuator in the white light phase shift interferometer is included, a higher level of measurement accuracy and stability can be secured.

In the above, the present invention has been described with preferred embodiments, but the present invention is not limited by such examples, and various types of embodiments may be embodied within a scope that does not deviate from the technical spirit of the present invention.

100: light source
101: collimator
200: first beam splitter
201: interference lens module
202: interference lens
203: reference mirror
204: second beam splitter
205: piezoelectric actuator
206: sample
401: condensing lens
402: spectrometer
S10: Measurement reflectivity curve generation step
S15: Scan error correction step
S17: First fitting step
S19: Second fitting step
S20: Theoretical reflectivity curve generation step
S30: similarity judgment step
S40: Sample thickness confirmation step

Claims (5)

Three-dimensional measurement reflectance as coordinate components of wavelength, optical path difference (OPD), and reflectance from the interference light signal measured in the spectrometer after being incident through the interference lens module from the light source of the thickness measurement device and reflected from the sample a measurement reflectivity curve generating step of generating a curved surface;
A theoretical reflectivity curve generating step of generating a three-dimensional theoretical reflectivity curve by including wavelength, optical path difference, and reflectance coordinate components of the calculated theoretical interferometer signal to correspond to the measured reflectivity curve;
a similarity determination step of repeatedly determining a similarity between the measured reflectivity curved surface and the theoretical reflectance curved surface; and
A sample thickness calculation step of determining the thickness of the sample for generating the theoretical reflectivity curve corresponding to the case in which the similarity is the highest in the similarity determination step as the thickness of the sample forming the measured reflectivity curve; Thickness measurement method using a reflectivity curved surface. According to claim 1,
The method of measuring thickness using a three-dimensional reflectivity curve, characterized in that the generating of the measured reflectivity curve comprises a scan error correction step of correcting a scan error of a piezoelectric driver that drives the interference lens module in the optical axis direction. According to claim 2,
The interference lens module is configured to be movable in an optical axis direction,
In the scan error correction step,
The intensity of the interfering light (I _{DC, α, φ} (k, OPD)) detected by the spectrometer is decomposed by wavelength to determine the optical path difference (OPD) and reflectance or optical path difference (OPD, Optical Path Difference). A first fitting step of fitting with a sinusoidal function composed of Difference and Intensity; and
and a second fitting step of repeatedly correcting the position of the interference lens module until the error between the sinusoidal function fitted in the first fitting step and the intensity data of the input interference light is equal to or less than a predetermined value. A method for measuring thickness using a 3-dimensional reflectivity curved surface. According to claim 3,
The thickness measurement method using a three-dimensional reflectivity curved surface, characterized in that the scan error correction step is terminated when the error converges to a certain value in the range of 10 ^-3 to 10 ^-4 . According to claim 1,
The thickness measuring device,
a light source generating multi-wavelength light;
a first beam splitter for transmitting a part of the light generated from the light source and reflecting the rest;
an interference lens module for incident light diverged from the first beam splitter toward a sample;
a piezoelectric actuator for moving the interference lens module or sample on an optical axis; and
Thickness measurement method using a three-dimensional reflectivity curved surface, characterized in that it comprises a; spectrometer for measuring the interference light generated through the sample and the interference lens module.

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