WO2015041506A1 - Apparatus for measuring thickness and method for measuring thickness using same - Google Patents

Abstract

The present invention relates to an apparatus for measuring a thickness. The present invention relates to an apparatus for measuring a thickness, which is an apparatus for measuring a thickness using a reflectometer, comprising: a light source for emitting light; a light filter unit for receiving the light emitted from the light source, selectively transmitting the light having a plurality of different frequencies so as to be modulated to the light having an intensity distribution, wherein a wavelength width of the light having the intensity distribution is adjusted; an optic system for irradiating an object being measured with the light modulated from the light filter unit, and receiving the light reflected from the object being measured; a light detection unit for receiving the light passing through the optic system so as to acquire reflection information; and a control unit for setting a plurality of frequencies capable of transmitting through the light filter unit so as to adjust the wavelength width of the light modulated by the light filter unit, and measuring the thickness of the target being measured by comparing pre-stored theoretical reflection information modelled by a mathematical formula, with reflection information acquired through the light detection unit.

Description

Thickness measuring device and thickness measuring method using the same

The present invention relates to a thickness measuring apparatus and a thickness measuring method using the same, and more particularly, to a thickness measuring apparatus and a thickness measuring method using the same, which can improve the thickness measuring accuracy regardless of the material or the measurement position of the measurement object. .

Transparent thin films, which are widely used in LCDs and semiconductors, have a great effect on the thickness of the transparent thin film.

In general, the thickness of the thin film can be measured by a mechanical method and an optical method using a stylus, and an interferometer and a reflectometer are widely used as an optical method.

1 is a conceptual diagram schematically illustrating a thickness measuring apparatus using a conventional reflectometry.

Referring to FIG. 1, in the case of a thickness measuring apparatus using a conventional reflective photometer, light emitted from the light source 10 passes through various lenses 21 and 22 and then enters the measurement object side through the light splitter 30. And focused by the objective lens 31. Thereafter, the light reflected by the transparent thin film S passes through the light splitter 30 and is incident to the spectrometer 40 or the camera 50. Here, the spectrometer 40 is used to obtain a reflectance distribution curve indicating a change in reflectance with respect to the wavelength of light reflected from the measurement object.

Here, in order to determine the thickness of the transparent thin film S, a method of comparing the reflectance distribution curve measured by the spectrometer 40 with the remodeling distribution curve remodeled by the equation is utilized. 10-2013-0021425).

First, a variety of transparent thin films S having different thicknesses are assumed, and a reflection distribution curve is generated for each transparent thin film S by using an equation. Then, by adopting a modeled reflectance distribution curve that most closely matches the measured reflectivity distribution curve among the plurality of modeled reflectance distribution curves, the thickness corresponding to the modeled reflectance distribution curve is determined as the thickness of the thin film layer.

By the way, in the conventional thickness measuring device, it is easy to generate the measured reflectance curve in the center of the measurement object, but the reflectance value of the reflectance distribution curve decreases toward the edge of the measurement object, making it difficult or impossible to compare with the modeled reflection distribution curve. Occurs.

In addition, the reflectance value of the reflectivity distribution curve measured from the measurement object is too high due to the material properties of the object to be measured, which makes it difficult or impossible to compare with the modeled reflectivity distribution curve.

That is, the thickness measurement accuracy is lowered depending on the material, the measurement position, and the like of the measurement object.

Accordingly, an object of the present invention is to solve such a conventional problem, and to provide a thickness measuring apparatus and a thickness measuring method using the same, which can improve the thickness measurement accuracy regardless of the material or the measurement position of the measurement object.

The above object is, according to the present invention, a thickness measuring apparatus using a reflectometer, comprising: a light source for emitting light; An optical filter unit that receives the light emitted from the light source and selectively transmits the light emitted from the light source to modulate the light having the intensity distribution, and modulates the wavelength width of the light having the intensity distribution; An optical system irradiating the light modulated from the optical filter unit to a measurement object side and receiving light reflected from the measurement object side; A light detecting unit receiving light passing through the optical system to obtain reflectance information; The wavelength range of the light modulated by the optical filter unit is adjusted by setting a plurality of frequencies that can pass through the optical filter unit, and the theoretical reflectivity information, which is modeled by the equation, is compared with the reflectance information obtained through the light detector. It is achieved by the thickness measuring apparatus comprising a; control unit for measuring the thickness of the measurement object.

Here, the optical filter unit is preferably a plurality of acoustic optical modulation filters (Acousto-Optical Tunable Filter) are spaced apart from each other along the traveling direction of the light emitted from the light source.

Here, the optical filter unit is preferably modulated so that the light transmitted from the optical filter unit has an intensity distribution by combining the predetermined plurality of frequencies in a state of maintaining the wavelength of the transmitted light.

The optical system may include a first light splitter configured to reflect light modulated by the optical filter unit or transmit light reflected from a measurement object; And a lens unit provided between the first light splitter and the measurement object to focus the light reflected from the first light splitter toward the measurement object side, and receiving the light reflected from the measurement object from the optical system. It is preferable to further include a; camera unit for obtaining information.

Here, the control unit, the frequency setting module for setting a plurality of frequencies through the optical filter unit; A storage module modeled by an equation and storing a plurality of theoretical reflectance information corresponding to each thickness; And a comparison determination module for determining a thickness of a measurement object by comparing the reflectance information measured by the light detector with the theoretical reflectance information stored in the storage module.

The control unit may further include a conversion module for converting at least one of reflectance information measured from the photodetector and theoretical reflectance information stored in the storage module in response to the frequency adjusted by the frequency setting module. The determination module preferably measures the thickness of the measurement object using at least one of the converted information of the reflectance information and the theoretical reflectance information.

On the other hand, according to the present invention, the modulating step of adjusting the wavelength width of the intensity distribution of the light modulated through the optical filter by setting a plurality of frequencies that can be transmitted through the optical filter for modulating the light emitted from the light source; A theoretical reflectance information preparing step of preparing theoretical reflectance information corresponding to each thickness through an equation; A reflectance information obtaining step of obtaining reflectance information of the measurement object by irradiating light modulated by the optical filter unit to a measurement object side; A matching step of comparing theoretical reflectance information with reflectance information and selecting theoretical reflectance information most similar to the reflectivity information among the theoretical reflectance information; And a thickness determination step of determining a thickness corresponding to the theoretical reflectance information selected in the matching step as the thickness of the measurement object.

Here, the theoretical reflectance information preparing step preferably includes a converting step of converting the theoretical reflectivity information prepared through the theoretical reflectance preparing step in consideration of a plurality of frequencies set through the modulation step.

In this case, when the theoretical reflectivity information most similar to the reflectance information cannot be selected in the matching step, it is preferable to perform the modulation step again.

According to the present invention, there is provided a thickness measuring apparatus and a thickness measuring method using the same, which can easily adjust the wavelength width of the light having an intensity distribution incident on the measurement object.

In addition, accurate thickness measurement can be performed even at the edge region of the measurement object in which the reflectance distribution curve has a low reflectance value.

In addition, even if the measurement object is formed of a material in which the reflectance value of the reflectivity distribution curve is formed too high, it is possible to perform the chemical thickness measurement.

1 is a conceptual diagram schematically showing a thickness measuring apparatus using a conventional reflectometry,

2 is a conceptual diagram schematically showing a thickness measuring apparatus according to an embodiment of the present invention,

3 is a view schematically showing an optical filter unit in the thickness measuring apparatus according to FIG. 2,

4 is a conceptual diagram schematically illustrating a configuration of a controller in the thickness measuring apparatus according to FIG. 2;

5 is a flowchart schematically showing a thickness measuring method according to an embodiment of the present invention;

FIG. 6 is a graph schematically showing the intensity of light before and after a modulation step with respect to a wavelength in the thickness measuring method according to FIG. 5;

FIG. 7 is a graph schematically illustrating reflectance information by light before and after a modulation step in the thickness measuring method according to FIG. 5;

8 is a graph schematically illustrating a conversion step in the thickness measuring method according to FIG. 5.

Hereinafter, a thickness measuring apparatus and a thickness measuring method using the same according to an embodiment of the present invention with reference to the accompanying drawings will be described in detail.

2 is a conceptual diagram schematically showing a thickness measuring apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the thickness measuring apparatus 100 according to an embodiment of the present invention modulates light into light having an intensity distribution before being incident on the measurement object S, and adjusts a wavelength width of light having an intensity distribution. It is possible to improve reflectance information measured after being reflected from the measurement object S by adjusting the light source 110, the light filter unit 120, the optical system 130, the light detector 140, and the camera unit 150. ) And the controller 160.

The light source 110 is to emit light, in one embodiment of the present invention is provided to emit white light, but is not limited thereto.

In addition, in one embodiment of the present invention, a halogen lamp is used as the light source 110, but is not limited thereto. Light sources of various sources may be used.

3 is a view schematically showing an optical filter unit in the thickness measuring apparatus according to FIG. 2, (a) an optical filter unit having three sound wave generators having different frequencies, and (b) having different frequencies 5 is a view schematically illustrating an optical filter unit including five sound wave generators.

Referring to FIG. 3, the optical filter unit 120 receives the light emitted from the light source 110 and selectively transmits the light emitted from the light source 110 to a plurality of predetermined frequencies, thereby modulating the light having the intensity distribution, and converting the light having the intensity distribution. It is to adjust the wavelength width.

Meanwhile, for convenience of description, the optical filter unit 120 illustrated in FIG. 3A will be described herein.

In one embodiment of the present invention, the optical filter unit 120 modulates the light to have a fine wavelength width through the sound wave generator 121 for emitting sound waves of a specific frequency in a direction crossing the direction of light travel.

Here, the sound wave generator 121 is disposed in a plurality along the traveling direction of the light, each sound wave generator 121 is provided to generate sound waves of different frequencies.

In an embodiment of the present invention, the sound wave generator 121 includes a first sound wave generator 121a and a second sound wave generator 121b for generating sound waves having a frequency of 120 MHz, 130 MHz, and 140 MHz, respectively, along a traveling direction of light. And the third sound wave generator 121c, but are not limited thereto. The frequency difference between the sound wave generators 121 may be increased or decreased in order to widen or narrow the wavelength width of the modulated light.

On the other hand, the light emitted from the light source 110 is modulated into light having a specific frequency but a specific wavelength through the respective sound wave generators 121a, 121b, 121c.

Here, the light through the sound wave generators 121a, 121b, and 121c is modulated into light having an intensity distribution by being combined with each specific frequency preserved.

In other words, when the light passing through the sound wave generators 121a, 121b, and 121c is combined, the light intensity distribution is obtained, but the light is not continuously connected within the range of the intensity distribution, but each light has a specific frequency. Only the lights are intermittently connected.

For this reason, it is possible to prevent noise from being generated at the same time as having the intensity distribution in the modulation of light.

On the other hand, it is preferable to adjust the intensity of the light through each of the sound wave generator (121a, 121b, 121c) so that the light modulated by the optical filter unit 120 has a desired intensity distribution.

That is, in one embodiment of the present invention, the light modulated by the second sound wave generation unit 121b is controlled to have the strongest intensity, and the first sound wave generation unit 121a and the third sound wave generation unit 121c are controlled. The light modulated by is controlled to have almost the same intensity.

In an exemplary embodiment of the present invention, the optical filter unit 120 is provided as a plurality of acoustic-optic tuneable filters spaced apart from each other along the traveling direction of light, but is not limited thereto.

The optical system 130 receives the modulated light through the above-described optical filter unit 120 and is incident to the measurement object S side, and the light reflected from the measurement object S is incident, and is a light splitter. 131, a lens unit 132, and a transflective mirror 133.

The light splitter 131 receives the modulated light through the optical filter unit 120 and reflects the light toward the measurement object S or transmits the light reflected from the measurement object S.

The lens unit 132 may be provided as an objective lens by focusing the light reflected from the light splitter 131 toward the measurement object S, but is not limited thereto.

The transflective mirror 133 guides the traveling direction toward the light detecting unit 140 or the camera unit 150 to be described later by reflecting or transmitting a part of the light reflected from the measurement object S.

On the other hand, between the light splitter 131 and the transflective mirror 133 may be provided with a second lens unit 132b for focusing the light reflected from the measurement object, but is not limited thereto.

On the other hand, since the configuration of the optical system 130 is well-known, it is not limited to the above-described configuration, and it is natural that the optical system 130 including or omitting other configurations may be used.

The light detector 140 receives light reflected from the measurement object S and passes through the optical system 130 to obtain reflectance information by analyzing a spectrum.

In one embodiment of the present invention, the reflectance information refers to a reflectance distribution curve indicating a change in reflectance of light intensity and wavelength, but is not limited thereto.

The camera unit 150 receives light reflected from the measurement object S and passes through the optical system 130 to form reflectance information as an image. In one embodiment of the present invention, the camera unit 150 may use a CCD camera (Charge coulped device) camera having a number of flowers suitable for the area to be measured, but is not limited thereto.

4 is a conceptual diagram schematically illustrating a configuration of a controller in the thickness measuring apparatus according to FIG. 2.

Referring to FIG. 4, the controller 160 adjusts a wavelength width of light modulated by the optical filter unit 120 by setting a plurality of frequencies that can pass through the optical filter unit 120, and is modeled by an equation. The thickness of the measurement object S is measured by comparing the previously stored theoretical reflectance information and the reflectance information obtained through the light detector 140, and the frequency setting module 161, the storage module 162, and the conversion module 163. And a comparison determination module 164.

The frequency setting module 161 sets a plurality of frequencies that can pass through the optical filter unit 120. According to an embodiment of the present invention, the frequency setting module 161 sets specific frequencies of sound waves emitted from each of the sound wave generators 121. It is.

Here, the wavelength width of the intensity distribution of the light modulated by the optical filter unit 120 may be changed by controlling the difference in a specific frequency of the sound waves emitted from each sound wave generator 121 or the number of generated sound waves.

Here, when the wavelength width of the intensity distribution of the light modulated by the optical filter unit 120 is changed, the reflectance value of the reflectivity information obtained from the light detector 140 is changed later, and the reflectivity is controlled by controlling the frequency setting module 161. The reflectivity value of the information can be made to have an optimal value to compare with the theoretical reflectance information.

The storage module 162 stores a plurality of theoretical reflectance information corresponding to each thickness by an equation.

Here, the equation for modeling the theoretical reflectance information is as follows.

<Equation 1>

Where R ^p (d, λ) is the total reflection coefficient of P wave parallel to the plane of incidence, r ^p ₁₂ is the Fresnel reflection coefficient of P wave at the interface between the air layer and the measurement object, and r ^p ₂₃ Is the Fresnel reflection coefficient of the P wave at the interface between the measurement object and the support layer supporting the measurement object, and β is the amount of phase change generated when light L passes through the measurement object.

<Equation 2>

Here, R ^s (d, λ) is the total reflection coefficient of the S wave perpendicular to the plane of incidence, r ^s ₁₂ is the Fresnel reflection coefficient of the S wave at the interface between the air layer 12 and the measurement object, r ^s ₂₃ is the Fresnel reflection coefficient of the S wave at the interface between the measurement object and the support layer.

<Equation 3>

는 측정대상물의 복소 굴절률이고, φ₂는 측정대상물에서의 굴절각이다.Where d is the thickness of the measurement object,

Is the complex refractive index of the measurement object, and φ ₂ is the refractive angle at the measurement object.

<Equation 4>

Here, R1 is a theoretical reflectance by mathematical modeling, I _i is the intensity of incident light L, and I _r is the intensity of reflected light L.

Substituting Equation 1 to Equation 3 into Equation 4, the theoretical reflectivity can be obtained for a certain thickness, and the theoretical reflectance distribution curve can be generated by graphing the reflectance distribution while changing the wavelength.

Meanwhile, the theoretical reflectance distribution curve may be obtained by multiplying the intensity distribution of light reflected from the measurement object by the theoretical reflectance distribution curve generated by Equation 4 above, which is calculated by the following equation.

<Equation 5>

Where R2 is the theoretical reflectance by mathematical modeling, λ ^* is the specific wavelength, I _i is the input intensity, I _r is the output intensity, I ₀ is the maximum value of the intensity at the particular wavelength, and I ₀ × F _λ is the intensity distribution curve of the specific wavelength, and R1 is the theoretical reflection curve.

That is, the storage module 162 obtains a reflection distribution curve corresponding to each thickness, and then obtains and stores an integral reflection curve corresponding to each thickness.

Meanwhile, the storage module 162 may reacquire and store theoretical reflection information using the changed intensity distribution value when the intensity distribution of the light is changed by the frequency setting module 161, but the present invention is not limited thereto. In operation 162, the previously stored theoretical reflection information may be converted.

The conversion module 163 converts at least one of reflectance information measured from the photodetector 140 or theoretical reflection information stored in the storage module 162 when the frequency is adjusted by the frequency setting module 161.

As described above, in the case of obtaining theoretical reflectance information by mathematical modeling, the luminance of incident light is assumed to be an initially set value and calculated.

In this case, when the intensity distribution of the light is changed by the frequency setting module 161, the intensity of the incident light is also changed, so that the reflectance information and the theoretical reflectance information may not be compared under the same condition. It is necessary to convert either condition.

In an embodiment of the present invention, a method of converting theoretical reflectance information previously stored in the storage module 162 is adopted, and the converted integral reflectance distribution curve is determined by the following equation.

<Equation 6>

Here, F _λ ** (λ) means an amount of change in the intensity of light with respect to the initial setting value, and other equations are as described above.

On the other hand, it is also possible to convert the theoretical reflectance information to be performed under the same conditions as the reflectance information as in one embodiment of the present invention, but the reflectivity information can be converted to be the same as the condition of the theoretical reflectivity information.

The comparison determination module 164 compares the reflectance information obtained through the light detector 140 with the theoretical reflectance information converted through the storage module 162 and the conversion module 163 to determine the thickness of the measurement object.

That is, the most similar theoretical reflectance information is searched by comparing the reflectance information obtained through the light detector 140 with the theoretical reflectance information, and the thickness value corresponding to the most similar theoretical reflectance when searching for the most similar theoretical reflectance information is obtained. Determined by the thickness.

The operation of the embodiment of the above-described thickness measuring apparatus and the thickness measuring method using the same will now be described.

Figure 5 is a flow chart schematically showing a thickness measuring method according to an embodiment of the present invention.

Referring to FIG. 5, in the thickness measuring method according to an embodiment of the present invention, the thickness measurement accuracy may be improved by adjusting the reflectivity of the reflectivity information so as to have a reflectivity that is comparable to the theoretical reflectance information. The theoretical reflectance information preparing step (S120), the converting step (S125), the reflectance information obtaining step (S130), the matching step (S140), and the thickness determining step (S150) are included.

The modulation step (S110) sets a plurality of frequencies that can pass through the optical filter unit 120 so that the light emitted from the light source 110 has an intensity distribution when modulating through the optical filter unit 120, but controls the wavelength width. Step.

Here, the wavelength width is determined based on the number and frequency values of the sound waves emitted from the sound wave generator 121 and is related to the reflectance value of the reflectivity information obtained in the reflectance information obtaining step S140 which will be described later.

6 is a graph schematically showing the intensity of light before and after a modulation step in a thickness measuring method according to FIG. 5 with respect to wavelengths, and FIG. 7 schematically shows reflectance information by light before and after a modulation step in a thickness measuring method according to FIG. 5. It is a graph shown.

Referring to FIG. 6 or 7, it can be seen that as the modulation step S110 is performed, the reflectance value in the light intensity and reflectance information is changed.

Meanwhile, in one embodiment of the present invention, the sound waves are emitted from the plurality of sound wave generators 121, that is, the number of sound wave generators 121 that operate, and the sound waves emitted from the sound wave generators 121 that operate. By separately determining the frequency of the modulation step (S110) can be performed, but is not limited thereto.

In one embodiment of the present invention operates the three sound wave generators 121 through the modulation step (S110), the sound waves emitted from each of the sound wave generators 121a, 121b, 121c are respectively 120MHz, 130MHz, 140MHz Have

Meanwhile, in one embodiment of the present invention, the sound waves emitted from each of the sound wave generators 121 are provided to increase in sequence as they move away from the light source 110, but the present invention is not limited thereto. Can be.

In addition, the greater the difference between the minimum value and the maximum value of the sound waves emitted from each of the sound wave generators 121, the wider the intensity distribution of the modulated light becomes. The narrower the difference between the minimum and maximum values, the narrower the intensity distribution of the modulated light.

On the other hand, according to an embodiment of the present invention, the sound waves emitted from each of the sound wave generators 121 are provided to increase constantly by 10 MHz as the distance from the light source 110 is not limited thereto.

The theoretical reflectance information preparing step (S120) is a step of storing theoretical reflectance information by mathematical modeling in the storage module 162 described above, and includes a modeling step (S124) and a transformation step (S125).

According to an embodiment of the present invention, the theoretical reflectance information determines light having a small wavelength of a specific frequency as an intensity value of initial light, but is not limited thereto.

Since the modeling step (S124) has been described above as determining the theoretical reflection distribution curve and the theoretical reflection reflection distribution curve according to an embodiment of the present invention, a detailed description thereof will be omitted.

FIG. 8 is a graph schematically illustrating a conversion step in the thickness measuring method according to FIG. 5, wherein (a) is a view illustrating a change in intensity of light through a modulation step, and (b) is the same according to a change in intensity of light. It is a figure which shows that the reflectivity information and theoretical reflectivity information in thickness differ, (c) is a figure which shows that the reflectivity information and theoretical reflectance information in the same thickness correspond through the conversion step.

Referring to FIG. 8, in the converting step S125, the theoretical reflectance information is modulated by light having a different intensity value from the initial light intensity value set in the theoretical reflectance information preparing step S120 through the modulating step S110. This is the step of conversion.

As described above, the theoretical reflectance information obtains a theoretical reflectance distribution curve based on the intensity value of light set in the theoretical reflectance information preparing step (S120).

Here, when the set intensity value of the light is changed, the precondition for comparing the theoretical reflectivity information and the reflectance information is deviated, and thus the accuracy of the thickness determination cannot be expected.

Accordingly, a process of converting the theoretical reflectance information based on the changed intensity value or converting the reflectivity information to the initial intensity value is required. In one embodiment of the present invention, the theoretical reflectivity information is converted based on the changed intensity value.

The reflectivity information obtaining step (S130) is a step of obtaining a reflectivity distribution curve by receiving light reflected from the measurement object S from the photodetector 140.

Since it is well known that the reflectivity distribution curve is acquired through the light detector 140 in the reflectance information acquisition step S130, detailed description thereof will be omitted.

In the matching step S140, the theoretical reflectance information obtained through the theoretical reflectance information obtaining step S120 is compared with the reflectivity information obtained through the reflecting information obtaining step S140 to search for the theoretical reflectance information most similar to the reflectance information. Step.

The most similarity is determined by calculating the error function using the least square method, and the theoretical reflectance information and the reflectance information having the minimum error are determined to be the "most similar". Since such methods are well known, the detailed description is omitted here.

However, as described above, it is natural to determine whether it is "most similar" through not only the least square method but other methods.

On the other hand, the reflectance value of the reflectivity information measured by the light detector 140 through the matching step (S140) can be measured so low or difficult to compare.

In this case, the above-described modulation step (S110) is performed again, but if the reflectance value of the reflectance information is measured too low in the modulation step (S110), the numerical value and the number of the frequency is reset so that the wavelength width of the light intensity distribution is widened, the reflectance information If the reflectivity value is too high, the modulation step (S110) resets the numerical value and the number of frequencies so as to narrow the intensity distribution wavelength width of the light.

That is, by performing the modulation step S110 again, the reflectance value is processed so that the reflectivity information and the theoretical reflectance information can be easily compared in a later matching step S150.

Here, after reacquiring and storing the theoretical reflectivity information based on the changed value through the re-modulation of the modulation step S110, the matching step S140 is performed again to retrieve the theoretical reflectance information most similar to the reflectance information.

The thickness determining step S150 selects theoretical reflectance information most similar to reflectance information, and determines the thickness corresponding to the selected theoretical reflectance information as the thickness of the measurement object.

On the other hand, if the inspection surface of the measurement object (S) is divided into a plurality of areas provided on a micro or nano scale, and the inspection results are combined for each area and the measured results are combined, the thickness, three-dimensional shape, etc. of the measurement object (S) surface, etc. Comprehensive information of the inspection surface of the measurement object (S) including a can be calculated and visualized.

The scope of the present invention is not limited to the above-described embodiment, but may be embodied in various forms of embodiments within the scope of the appended claims. Without departing from the gist of the invention claimed in the claims, it is intended that any person skilled in the art to which the present invention pertains falls within the scope of the claims described in the present invention to various extents which can be modified.

Provided is a thickness measuring apparatus capable of improving thickness measuring accuracy regardless of a material or a measuring position of a measuring object, and a thickness measuring method using the same.

Claims (9)

In the thickness measurement apparatus using a reflectometer, A light source emitting light; An optical filter unit which receives the light emitted from the light source and selectively transmits the light emitted from the light source and modulates the light having the intensity distribution while modulating the light having the intensity distribution; An optical system irradiating the light modulated from the optical filter unit to a measurement object side and receiving light reflected from the measurement object side; A light detecting unit receiving light passing through the optical system to obtain reflectance information; The wavelength range of the light modulated by the optical filter unit is adjusted by setting a plurality of frequencies that can pass through the optical filter unit, and the theoretical reflectivity information, which is modeled by the equation, is compared with the reflectance information obtained through the light detector. And a control unit for measuring the thickness of the measurement object. The method of claim 1, The optical filter unit is a thickness measuring device, characterized in that the plurality of acoustic optical modulation filters (Acousto-Optical Tunable Filter) arranged to be spaced apart from each other along the traveling direction of the light emitted from the light source. The method of claim 2, And the optical filter unit modulates the light transmitted from the optical filter unit to have an intensity distribution by combining the predetermined plurality of frequencies while maintaining the wavelength of the transmitted light. The method of claim 1, The optical system may include a first light splitter configured to reflect light modulated by the optical filter unit or transmit light reflected from an object to be measured; And a lens unit provided between the first light splitter and the measurement object to focus the light reflected from the first light splitter toward the measurement object side. And a camera unit which receives the light reflected from the measurement object from the optical system and obtains image information of the measurement object. The method of claim 1, The control unit, A frequency setting module for setting a plurality of frequencies that can pass through the optical filter unit; A storage module modeled by an equation and storing a plurality of theoretical reflectance information corresponding to each thickness; And a comparison determination module that determines the thickness of the measurement object by comparing the reflectance information measured by the light detector with the theoretical reflectance information stored in the storage module. The method of claim 5, The control unit may further include a conversion module for converting at least one of reflectance information measured from the photodetector and theoretical reflectance information stored in the storage module in response to the frequency adjusted by the frequency setting module. The comparison determination module measures the thickness of the measurement object using at least one of the converted information of the reflectivity information and the theoretical reflectivity information. Modulating a wavelength width of an intensity distribution of light modulated through the optical filter unit by setting a plurality of frequencies through which the optical filter unit modulates the light emitted from the light source; A theoretical reflectance information preparing step of preparing theoretical reflectance information corresponding to each thickness through an equation; A reflectance information obtaining step of obtaining reflectance information of the measurement object by irradiating light modulated by the optical filter unit to a measurement object side; A matching step of comparing theoretical reflectance information with reflectance information and selecting theoretical reflectance information most similar to the reflectivity information among the theoretical reflectance information; And a thickness determining step of determining a thickness corresponding to the theoretical reflectance information selected in the matching step as the thickness of the measurement object. The method of claim 7, wherein The theoretical reflectivity information preparing step includes a conversion step of converting the theoretical reflectivity information provided through the theoretical reflectivity preparing step in consideration of a plurality of frequencies set through the modulation step. The method of claim 8, And performing the modulation step again when the theoretical reflectivity information most similar to the reflectivity information cannot be selected in the matching step.

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