KR101388424B1 - Apparatus for measuring a thickness using digital light processing and method using the same - Google Patents

Abstract

The present invention relates to a thickness measuring apparatus and method using a digital optical technology, the thickness measuring apparatus and method using a digital optical technology of the present invention by a light source for emitting light, reflecting light emitted from the light source or by a measurement object A light splitter for transmitting the reflected light, a lens unit for focusing the light reflected by the light splitter to the measurement object, the light transmitted from the light splitter is provided, and at the same time the thickness measurement at a plurality of locations of the measurement object A reflection type optical path converting unit for reflecting light reflected from different measuring areas of the measurement object along different optical paths, and analyzing the light reflected from the reflective type optical path converting unit to determine thickness information of the measuring object Characterized in that it comprises a spectrometer to obtain.
Accordingly, the present invention provides a thickness measuring apparatus and method using a digital optical technology capable of minimizing the loss of light by using the reflection of light and capable of simultaneously measuring the thicknesses of a plurality of measurement areas.

Description

Thickness measuring device and method using digital optical technology {APPARATUS FOR MEASURING A THICKNESS USING DIGITAL LIGHT PROCESSING AND METHOD USING THE SAME}

The present invention relates to a thickness measuring apparatus and method using digital optical technology, and more particularly, to reflect light transmitted from the optical splitter through the reflective optical path conversion unit to minimize the light loss, and to adjust the reflection angle of the various points The present invention relates to a thickness measuring apparatus and method using digital optical technology capable of simultaneously measuring thickness.

It is essential to monitor the thickness of the thin film layer directly in the process, because the control of the thickness of the thin film layer is important among the various factors that determine the quality in the semiconductor process and the FPD process. The term 'thin film layer' refers to a base layer, that is, a layer having a very fine thickness formed on the surface of a substrate, and generally has a thickness ranging from several nm to several μm. In order to apply these thin films to specific applications, it is necessary to know the thickness, composition, roughness and other physical and optical properties of the thin films.

In particular, in recent years, in order to increase the degree of integration of semiconductor devices, it is a general trend to form ultra-thin layers on a substrate in multiple layers. In order to develop such a highly integrated semiconductor device, it is necessary to precisely control the physical properties of the film including the thickness of the thin film layer, which is a factor that greatly affects the characteristics.

A conventional thickness measuring apparatus has a configuration in which light transmitted from a light splitter passes through an LCD for transmitting light and then enters into a spectrometer.

This conventional invention may cause a problem that the loss is generated by the light transmitted through the LCD to not obtain accurate information about the thickness of the measurement object.

In addition, in order to obtain thickness information on a part of the measurement object, the thickness of the entire measurement object should be investigated. If one measurement object has a different thin film structure in each measurement area, a plurality of measurements are required. This may cause a problem.

Accordingly, an object of the present invention is to solve the conventional problems, and to provide a thickness measuring apparatus and method using a digital optical technology that can minimize the loss of light by using the reflection of light.

In addition, the thickness measuring apparatus and method using a digital optical technology that can measure the thickness of the plurality of measurement areas at the same time by controlling the reflective optical path conversion unit to enter the light incident from the plurality of different measurement areas with different spectroscopy. In providing.

The object of the present invention is to provide a light source for emitting light, a light splitter for reflecting light emitted from the light source, or a light splitter for transmitting the light reflected by the measurement object, and the light reflected by the light splitter to the measurement object. A lens unit for condensing is provided with light transmitted from the light splitter and simultaneously reflects light reflected from different measurement areas of the measurement object along different optical paths to enable thickness measurement at a plurality of positions of the measurement object. It is achieved by a thickness measuring apparatus using a digital optical technology, characterized in that it comprises a reflecting optical path converting unit for reflecting, a spectrometer for obtaining the thickness information of the measurement object by analyzing the light reflected from the reflective optical path converting unit do.

Here, a plurality of spectroscopes are provided, and the reflective optical path converting unit preferably reflects the light reflected from a plurality of different measurement regions of the measurement object to each spectroscope.

The display apparatus may further include a display unit configured to display an image of the measurement object based on the light transmitted from the light splitter.

Here, the display unit receives the light reflected from the reflective optical path converting unit and displays the image of the measurement object.

The display apparatus may further include an auxiliary light splitter disposed on an optical path between the light splitter and the reflective optical path converter to reflect or transmit light transmitted from the light splitter, and the display unit may input light transmitted from the auxiliary splitter. The image of the measurement object can be displayed.

The light absorbing unit may further include a light absorbing unit for absorbing and removing light other than the light reflected by the spectroscope from the reflective optical path converting unit.

In addition, by using the thickness measuring apparatus using the digital optical technology according to claim 3, the image storage step of storing the image of the measurement object, the image stored in the image storage step is compared with the image displayed on the display unit to measure the display area A matching step of determining whether it is displayed on the light source, a reflecting angle adjusting step of adjusting a reflection angle of the reflective optical path conversion unit so that light reflected from a plurality of different measurement areas is reflected by a plurality of spectroscopes, and based on the light obtained by the spectroscope It is achieved by a thickness measuring method comprising a thickness measuring step of measuring the thickness of the measurement object.

In addition, the matching step is repeated until all the measurement areas are displayed on the display unit. If only a part of the measurement area is displayed on the display unit, the matching step is performed after moving the measurement object so that all the measurement areas are displayed on the image displayed on the display unit. If the centering step and the measurement area to be re-executed are not displayed on the display unit, the measurement object search step may be performed by moving the measurement object in a spiral direction until some or all of the measurement area is displayed on the display unit, and then performing the matching step again.

Here, the thickness measurement step is a reflection measurement step for measuring the reflectance of the light from the spectrum of light obtained from the spectrometer and the reflectance comparison step for searching the most similar modeling by comparing the measured reflectivity and the reflectance prepared by theoretical modeling modeling searched in the reflectance comparison step It may include a thickness output step for outputting a thickness value corresponding to.

According to the present invention, there is provided a thickness measuring apparatus and method using digital optical technology that can minimize the loss of light by using the reflection of light to improve the measurement efficiency.

In addition, by controlling the micromirror of the reflective optical path conversion unit, the light reflected from the different measurement areas is incident to each spectrometer so that the thicknesses of the measurement areas may be simultaneously measured even if the thin film structures of the measurement areas are different.

In addition, the display unit may visually confirm an image of the measurement object measured from the thickness measuring device.

In addition, the light absorbing unit may absorb and remove light other than the light reflected by the spectrophotometer from the reflective optical path converter.

In addition, when all the measurement regions do not exist in the measurement range, the measurement efficiency may be improved by automatically changing the position of the lens unit or the measurement object to include all the measurement regions.

1 is a conceptual diagram schematically showing a thickness measuring apparatus using a digital optical technology according to a first embodiment of the present invention,
FIG. 2 is a conceptual diagram schematically illustrating a state in which a reflection angle of a reflective optical path conversion unit is changed in a thickness measuring apparatus using the digital optical technology of FIG. 1;
FIG. 3 is a diagram schematically illustrating a method of measuring reflectivity in two measurement regions having different thin film structures by changing a reflection angle of a portion of a reflective optical path converter in the thickness measuring apparatus using the digital optical technology of FIG. 1. , (a) is a conceptual diagram schematically showing the reflection of light from the digital micromirror to three devices at the same time, (b) is a plan view schematically showing the appearance of the measurement object, (c) is a first measurement The cross-sectional view schematically showing the thin film structure of the region and the second measurement region, (d) is a bottom view schematically showing the different control of the reflectivity for each region in the digital micromirror, (e) is a thin film structure It is a graph showing a reflectance curve after measuring two different areas simultaneously.
4 is a conceptual diagram schematically showing a thickness measuring apparatus using a digital optical technology according to a second embodiment of the present invention,
5 is a flowchart schematically showing a thickness measuring method using digital optical technology according to the first embodiment of the present invention.
6 is a flowchart schematically showing a matching step in the thickness measurement method using the digital optical technology of FIG.
FIG. 7 is a conceptual diagram schematically illustrating a direction in which a measurement area is searched in the measurement area search step of FIG. 6.

Prior to the description, components having the same configuration are denoted by the same reference numerals as those in the first embodiment. In other embodiments, configurations different from those of the first embodiment will be described do.

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

1 is a conceptual diagram schematically showing a thickness measuring apparatus using a digital optical technology according to a first embodiment of the present invention.

Referring to FIG. 1, the thickness measuring apparatus using the digital optical technology according to the first embodiment of the present invention includes a light source 110, a light splitter 120, a lens unit 130, and a reflective optical path converter 140. And a spectrometer 150 and a display unit 160.

The light source 110 emits light for measuring the thickness of the measurement object 105, and lamps of various sources including halogen lamps may be used. It may also be provided as a white light source, but is not limited thereto.

The light splitter 120 reflects light incident from the light source 110 to be incident to the lens unit 130 to be described later, or transmits light reflected from the measurement object 105 to be described later. Guide the light path to be incident on 140.

The lens unit 130 focuses the light reflected from the light splitter 120 to the measurement object 105. Since the detailed configuration of the lens unit 130 is a well-known technique, a detailed description thereof will be omitted.

The reflective optical path converting unit 140 reflects the light transmitted from the optical splitter 120 which is light having the thickness information of the measurement object 105 to be incident on the spectrometer 150 or the display unit 160 which will be described later. To guide. Surfaces where reflection occurs in the reflective optical path conversion unit 140 are each provided as a micro mirror that can be individually controlled to adjust the reflection angle of the light. According to the first exemplary embodiment 100 of the present invention, the reflective optical path converting unit 140 is provided as a digital micromirror device (DMD), but is not limited thereto. Any device that can be reflected to have can be included here.

FIG. 2 is a conceptual view schematically illustrating a state in which a reflection angle of the reflective optical path converter is changed in the thickness measuring apparatus using the digital optical technique of FIG. 1, and FIG. 3 is a reflection in the thickness measuring apparatus using the digital optical technique of FIG. 1. Figure 2 is a schematic view showing the measurement of reflectivity in two measurement areas with different thin film structures by changing the reflection angles of some areas of the fluorescence path converter. (A) In the digital micromirror, light is simultaneously reflected to three devices. (B) is a plan view schematically showing the appearance of the measurement object, (c) is a cross-sectional view schematically showing the thin film structure of the first measurement region and the second measurement region, (d) is a bottom view schematically showing how the reflectivity is controlled differently in each area in the digital micromirror, and (e) is a two-field image having different thin film structures. It is a graph showing a reflectance curve measured after the same time.

In other words, the reflection angles of the mirrors of the reflective optical path conversion unit 140 may be adjusted to be the same, and the mirrors of the reflective optical path conversion unit 140 may be adjusted to have different reflection angles. In particular, by adjusting them to have different reflection angles, even if there are a plurality of different areas to be measured on the measurement object 105, the spectrometers may be adjusted by adjusting the mirrors of the reflective light path conversion unit 140 corresponding to the corresponding areas. 150 can be incident. Therefore, even though the thin film structure is different in a plurality of different regions existing on the measurement object 105, the light reflected from each region is analyzed by a separate spectrometer 150, thereby making it possible to measure simultaneously.

The spectrometer 150 is a device for detecting the spectrum of light reflected from the measurement object 105. According to the first embodiment 100 of the present invention, the first spectroscope 151 and the second spectroscope 152 include but are not limited thereto, and three or more configurations may be possible according to a user's needs.

Referring to FIG. 3A, the first spectrometer 151 is disposed on an optical path where light is reflected at a reflection angle of 100 ° from the reflective optical path converter 140, and the second spectroscope 152 is Light is disposed on an optical path that is reflected at an angle of reflection of 80 ° from the reflective optical path converter 140. However, the present invention is not limited to this angle, and it is sufficient that each spectrometer 150 is disposed on an optical path that forms a different reflection angle from the reflective optical path converter 140.

For example, if the first measurement region 106 and the second measurement region 107 that exist on the measurement object 105 as shown in Figure 3 (b) are simultaneously measured, as shown in Figure 3 (d), the first The first reflecting unit 141 on the reflective optical path converting unit 140 corresponding to the measuring region 106 is controlled to achieve a reflection angle of 100 ° and the second reflecting unit corresponding to the second measuring region 107 ( 142 is controlled to achieve a reflection angle of 80 ° so that the light reflected from the first measurement region 106 and the first reflector 141 is incident on the first spectrometer 151, and the second measurement region 107 and Light reflected from the second reflector 142 is incident on the second spectrometer 152. Therefore, even if the thin film structures of the first measurement region 106 and the second measurement region 107 are different as shown in FIG. 3 (c), the first spectroscope 151 and the second spectrometer as shown in FIG. 3 (e). Since the spectrometer 152 can measure the spectrum of light at the same time, it becomes possible to measure the thickness in two areas at the same time.

The display unit 160 is a device for photographing the shape of the measurement object 105 to provide an image to the outside. The area photographed by the display unit 160 is the same as the measurement area to measure the thickness in the first embodiment 100 of the present invention, and the area photographed by the display unit 160 and the measurement object in the matching step S120 which will be described later. By comparing the stored images of 105, it is possible to determine whether the measurement area is within the measurement range of the first embodiment 100 of the present invention.

Referring to the arrangement of the first embodiment 100 of the present invention in detail with respect to the light path of the light emitted from the light source 110, the light is emitted from the light source 110 and reflected by the light splitter 120 to provide a lens unit. Pass 130. The light passing through the lens unit 130 is incident on the measurement object 105 and then reflected to pass through the light splitter 120. The light transmitted from the light splitter 120 is incident on the reflective optical path converter 140 and then reflected and incident on the spectrometer 150 or the display 160.

Meanwhile, a condenser lens may be provided between the optical splitter 120 and the reflective optical path converter 140 to focus light transmitted from the optical splitter 120 and to enter the reflective optical path converter 140. It is not limited.

In addition, an optical fiber for guiding the optical path or a focusing lens for focusing the light incident to each spectrometer 150 may be provided between the reflective optical path converter 140 and the spectroscope 150, but the present disclosure is not limited thereto. no.

The operation method S100 of the first embodiment of the thickness measurement apparatus using the above-described digital optical technology will now be described.

5 is a flowchart schematically showing a thickness measurement method using a digital optical technology according to a first embodiment of the present invention, Figure 6 is a flow chart schematically showing a matching step in the thickness measurement method using a digital optical technology of FIG. 7 is a conceptual diagram schematically illustrating a direction in which the measurement area is searched in the measurement area search step of FIG. 6.

Referring to FIG. 5, the thickness measuring method S100 using the digital optical technology according to the first exemplary embodiment of the present invention may include an image storing step S110, a matching step S120, a reflection angle adjusting step S130, and a thickness measuring step. It includes (S140), it is possible to measure the thickness of the measurement object 105 by performing these processes.

The image storing step (S110) is a step of storing an image of the measurement object 105 before the thickness measurement to recognize the measurement area. That is, the image itself obtained by capturing the area including the measurement area in the measurement object 105 with the optical system is stored as a standard model, and used in the matching step S120 to be described later.

The matching step S120 compares the standard model stored in the image storing step S110 with the image photographed on the display unit 160 to determine whether the measurement area is within the measurement range of the first embodiment 100 of the present invention. Determining the steps.

Referring to FIG. 6, it is preferable that the matching step S120 is repeatedly performed until all the measurement areas are displayed on the display unit 160. In the case where only a part of the measurement area is displayed or no display is performed on the display unit 160. The centering step (S121) or the measurement area search step (S122) is performed.

The centering step (S121) is performed when only a part of the measurement area is displayed on the display unit 160, and the position of the measurement object 105 or the lens unit 130 is moved so that all of the measurement area is displayed on the display unit 160. This is the step.

According to the first exemplary embodiment 100 of the present invention, the centering step S121 compares the standard model stored in the image storing step S110 with the image displayed on the display unit 160, and calculates the current measured position. The position difference with the measurement area is calculated using the calculated position value to move the measurement object 105 or the lens unit 130.

Referring to FIG. 7, the measurement area search step S122 is performed when the measurement area is not displayed on the display unit 160 at all, and since the standard model stored in the image storage step S110 is difficult to use, this process is performed. Will be performed.

The measurement area search step (S122) is a step of searching for the measurement area by moving the position of the measurement object 105 or the lens unit 130 along the spiral in the region nearest to the area displayed on the display unit. According to the first exemplary embodiment 100 of the present invention, when the measurement region is not displayed on the display unit 160, the measurement object 105 or the lens unit 130 is moved in the counterclockwise direction to take an image.

In this case, all or part of the measurement area is repeatedly performed until the display unit 160 is displayed. If all of the measurement areas are displayed, the reflection angle adjustment step S130 is performed, and when the display area is partially displayed, the centering step S121 is performed. .

 Meanwhile, even when the measurement area is two or more areas, the matching step S120 described above is performed in the same manner. If the plurality of measurement areas can be included in the measurement range, the matching step (S120) is performed until the plurality of measurement areas are all included in the measurement range, and if the plurality of measurement areas cannot be included in all the measurement range for each measurement area The matching step S120 is performed individually.

Referring to FIG. 2, in the reflection angle adjusting step S130, the reflection angle of the reflection type optical path converter 140 is adjusted to reflect the light reflected from the measurement area to the spectrometer 150. That is, when the reflection angle of the reflective optical path conversion unit 140 is adjusted to 100 °, light is incident on the first spectrometer 151, and when the reflection angle is adjusted to 80 °, light is incident on the second spectrometer 152.

In addition, referring to FIG. 3, the same applies to the case where the measurement area is two areas and light is incident on the two spectrometers 150 at the same time. As described above, the reflective surface of the reflective optical path converting unit 140 includes a myriad of small mirrors, and each mirror can be individually controlled. Using this, when the reflection angle of the first reflecting unit 141 is adjusted to 100 ° and the reflection angle of the second reflecting unit 142 is adjusted to 80 °, the light reflected from the first measuring region 106 is first spectrometer ( Light incident to the 151 and reflected from the second measurement region 107 is incident to the second spectrometer 152. Of course, even in the case where the measurement area is two areas as well as three or more areas, the spectrometer 150 is further added, and the reflection angles of a part of the reflective optical path conversion unit 140 are changed to the first reflection surface 141 and the second reflection surface. It is formed to have a different reflection angle and the reflection angle of the thickness can be measured at the same time.

The thickness measuring step (S140) is a step of measuring the reflectance of light by irradiating the spectrum of light incident on the spectroscope 150 and measuring the thickness of the measurement object 105 based on this. According to the first embodiment S100 of the present invention, the thickness measuring step S140 includes a reflectance measuring step S141, a reflectance comparison step S142, and a thickness output step S143. However, the thickness measuring step S140 is not limited to the above-described steps.

The reflectivity measuring step (S141) is to analyze the spectrum of the light incident on the spectrometer to calculate the reflectivity of the measurement area using the light amount data for each wavelength of light.

The reflectivity comparison step (S142) is a step of searching for a model having the most similar reflectivity when comparing the reflectivity of the measurement area obtained in the reflectivity measurement step (S141) with the reflectivity obtained by theoretical modeling. .

The thick output step S143 is a step of outputting a thickness value corresponding to the modeling searched in the reflectance comparison step S142.

In the thickness measurement method S100 according to the first embodiment of the present invention, the matching step S120 is performed to include the measurement area within the measurement range, thereby improving the accuracy of the thickness measurement. Could be improved.

In addition, the reflection angle of all the micromirrors included in the reflective optical path conversion unit 140 may be adjusted or only some of the reflection angles may be adjusted. In particular, when only some of the reflection angles are adjusted, the thicknesses of the plurality of measurement areas may be simultaneously measured. Measurement time can be shortened.

Next, a thickness measuring apparatus and method using a digital optical technology according to a second embodiment of the present invention will be described.

4 is a conceptual diagram schematically illustrating a thickness measurement apparatus using digital optical technology according to a second embodiment of the present invention.

Referring to FIG. 4, the thickness measuring apparatus 200 using the digital optical technology according to the second exemplary embodiment of the present invention includes a light source 110, a light splitter 120, a lens unit 130, and a reflective optical path converter. (Digital Micromirror Device, hereinafter referred to as “reflective optical path converting unit”) 140, a spectroscope 150, a display unit 160, an auxiliary light splitter 225, and a light absorbing unit 270.

The auxiliary splitter 225 is disposed on an optical path between the splitter 120 and the reflective optical path converting unit 140 to reflect the light transmitted from the splitter 120 to the display unit 160. It is transmitted to the reflective optical path conversion unit 140 side.

That is, unlike the first embodiment, the auxiliary light splitter 225 is disposed so that the light reflected by the reflective optical path converter 140 is not incident on the display unit 160, but through the auxiliary light splitter 225. The light transmitted from the light splitter 120 is reflected to the display unit 160.

The display unit 160 is provided in the same configuration as that of the display unit 160 in the first embodiment 100, but the position of the light reflected by the reflective optical path converting unit 140 as in the first embodiment 100 is Rather than being disposed at the incident position, the light reflected by the auxiliary light splitter 225 is disposed at the incident position. By such arrangement, the display unit 160 always displays an image of the measurement range without being affected by the reflection angle of the reflective optical path conversion unit 140.

 The light absorbing part 270 is a device that absorbs and removes light except the light reflected from the reflective optical path converter 140 to the spectrometer 150. This is because the reflective optical path converting unit 140 forms the first reflecting unit 141 and the second reflecting unit 142 and simultaneously the first measuring region 106 with the first spectroscope 151 or the second spectroscope 152. ) Or when the light reflected from the second measurement area 107 is reflected, the light reflected from a surface other than the first reflecting unit 141 or the second reflecting unit 142 of the reflective optical path changing unit 140. The light is reflected by the light absorbing part to remove the light.

Since the operating method (S200) of the second embodiment of the thickness measuring apparatus using the digital optical technology described above is the same as the operating method (S100) of the first embodiment, a detailed description thereof will be omitted. That is, in the second embodiment 200, the position of the measurement object 105 is changed from the light before being incident to the reflective optical path converter 140, and the light absorbs and removes the light reflected outside the measurement area. With the addition of the absorbing portion 270, only the arrangement of each component is different, performs the same function as the first embodiment 100, and the method of measuring the thickness of the measurement object 105 is the same.

The scope of the present invention is not limited to the above-described embodiments, but may be embodied in various forms of embodiments within the scope of the appended claims. It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the appended claims.

100: thickness measuring device 110: light source
120: light splitter 130: lens unit
140: reflective optical path conversion unit 150: spectrometer
160: display unit 200: thickness measuring device
225: auxiliary light splitter 270: light absorption unit
S100: Thickness Measurement Method S110: Image Storage Step
S120: matching step S121: centering step
S122: search area search step S130: reflection angle adjustment step
S140: thickness measurement step S141: reflectivity measurement step
S142: reflectivity comparison step S143: thickness output step

Claims (9)

A light source for emitting light;
A light splitter that reflects light emitted from the light source or transmits light reflected by the measurement object;
A lens unit that focuses the light reflected by the optical splitter to the measurement object;
A reflection type that receives the light transmitted from the light splitter and reflects the light reflected from different measurement areas of the measurement object along different optical paths so as to measure thickness at a plurality of positions of the measurement object. Conversion unit;
And a spectrometer for analyzing the light reflected from the reflective optical path converting unit and obtaining thickness information of the measurement target. The method of claim 1,
The spectrometer is provided in plurality,
And the reflective optical path converting unit reflects the light reflected from the plurality of different measurement areas of the measurement object to each spectrometer. 3. The method of claim 2,
And a display unit for displaying an image of the measurement object based on the light transmitted from the light splitter. The method of claim 3,
And the display unit receives the light reflected from the reflective optical path converting unit and displays an image of the measurement object. The method of claim 3,
An auxiliary light splitter disposed on an optical path between the light splitter and the reflective optical path converter to reflect or transmit light transmitted from the light splitter,
And the display unit receives the light transmitted from the auxiliary light splitter and displays an image of the measurement target. 5. The method of claim 4,
And a light absorbing unit for absorbing and removing light other than the light reflected by the spectroscope from the reflective optical path converting unit. Using the thickness measuring apparatus using the digital optical technique of any one of Claims 3-6,
An image storing step of storing an image of the measurement object;
A matching step of comparing the image stored in the image storing step with an image displayed on the display unit to determine whether a measurement area is displayed on the display unit in the measurement object;
A reflection angle adjustment step of adjusting a reflection angle of the reflection type optical path conversion unit so that the light reflected from the plurality of different measurement regions is respectively reflected by the plurality of spectroscopes;
And a thickness measurement step of measuring the thickness of the measurement object based on the light obtained by the spectrometer. 8. The method of claim 7,
The matching step is repeated until all the measurement areas are displayed on the display unit.
A centering step of repeating the matching step after moving the measurement object or the lens unit such that the entire measurement area is displayed on the image displayed on the display unit when only a part of the measurement area is displayed on the display unit; If the measurement area is not displayed on the display unit, a measurement area search step of moving the measurement object or the lens unit along the spiral direction until the display unit partially or completely displays the measurement area and then performing a matching step again; Thickness measurement method comprising the. 8. The method of claim 7,
The thickness measuring step may include: a reflectance measuring step of measuring reflectance of light from a spectrum of light obtained from the spectrometer; A reflectance comparison step of searching for the most similar modeling by comparing the measured reflectivity with reflectances prepared by theoretical modeling; And a thickness output step of outputting a thickness value corresponding to the modeling searched in the reflectance comparison step.

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