KR20170032700A - Optical interferometric system for measurement of physical thickness profile and refractive index distribution of large glass panel - Google Patents

Optical interferometric system for measurement of physical thickness profile and refractive index distribution of large glass panel Download PDF

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KR20170032700A
KR20170032700A KR1020150130372A KR20150130372A KR20170032700A KR 20170032700 A KR20170032700 A KR 20170032700A KR 1020150130372 A KR1020150130372 A KR 1020150130372A KR 20150130372 A KR20150130372 A KR 20150130372A KR 20170032700 A KR20170032700 A KR 20170032700A
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measurement
beam splitter
path
optical fiber
linear motion
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KR1020150130372A
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Korean (ko)
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KR101733298B1 (en
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박정재
진종한
김재완
김종안
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한국표준과학연구원
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0242—Testing optical properties by measuring geometrical properties or aberrations
    • G01M11/0271—Testing optical properties by measuring geometrical properties or aberrations by using interferometric methods
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/02—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness
    • G01B11/06—Measuring arrangements characterised by the use of optical techniques for measuring length, width or thickness for measuring thickness ; e.g. of sheet material
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B9/00—Measuring instruments characterised by the use of optical techniques
    • G01B9/02—Interferometers
    • G01B9/02049—Interferometers characterised by particular mechanical design details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
    • G01M11/00—Testing of optical apparatus; Testing structures by optical methods not otherwise provided for
    • G01M11/02—Testing optical properties
    • G01M11/0228—Testing optical properties by measuring refractive power

Abstract

The present invention provides a thickness measuring device, capable of providing signal to noise and visibility of a high interference signal even if a continuous broadband IR light source is used. The thickness measuring device comprises: a broadband light source; a first optical fiber transferring output light of the broadband light source; a first beam divider dividing the light transmitted through the first optical fiber into a reference beam radiated in a reference path, and a measurement beam radiated in a measurement path; a reference path mirror reflecting the reference beam; a measuring path mirror reflecting the measurement beam; a second beam divider generating an interference signal by overlapping the reference beam reflected from the reference path mirror with the measurement beam; a second optical fiber transmitting the interference signal; a spectrum analyzer measuring the interference signal transmitted through the second optical fiber in accordance with a wavelength; and a processing unit processing an output signal of the spectrum analyzer, calculating a thickness of a measurement object inserted into the measurement path. The reference path and the measurement path are arranged in a square form.

Description

TECHNICAL FIELD [0001] The present invention relates to an optical interferometric system for measuring a physical thickness profile and a refractive index distribution of a large glass substrate,

TECHNICAL FIELD The present invention relates to an optical apparatus for measuring a physical thickness of an object to be measured, and more particularly, to a technique capable of calculating a physical thickness with less influence on vibration and environment change by using a broadband light source and with high accuracy.

BACKGROUND ART [0002] Generally, as the display industry, optical communication, and precision optical devices are continuously developed, accurate measurement and evaluation techniques of properties (optical thickness, thickness, and refractive index) of a measurement object such as a wafer are required. A system has been developed to measure the thickness and refractive index of a material in a variety of ways.

Recently, a semiconductor substrate is polished on the back side of a substrate for mounting. These polished substrates are stacked and mounted on each other.

Therefore, measurement of the thickness of the polished substrate is required. Further, the display element is formed on a glass substrate or a substrate made of a flexible material. Therefore, monitoring of the thickness of the glass substrate is required.

In addition, the continuous wide-band IR light source has a problem that it is difficult to calculate its characteristics by collimating the object with a wide measurement area because the space is not coherent.

In addition, since the continuous wide-band IR light source also has a small coherence distance when time coherence is reduced, interference signals of a silicon wafer having a large refractive index may be difficult to obtain.

The inventor of the present application has developed a transmission type optical fiber interferometer (Korean Patent No. 10-1544962). However, this transmission type optical fiber interferometer is sensitive to environmental changes (temperature, humidity) and has a problem of low visibility of interference signals. Also, when a part of the transmission type optical fiber interferometer moves to change the measurement position, alignment difficulty occurs, and optical path difference occurs due to bending of the optical fiber. Also, a broadband laser light source, rather than a continuous broadband IR light source, is used, which is expensive. Therefore, in order to solve such a problem, the present invention is proposed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a thickness measuring apparatus which provides visibility and signal to noise of a high interference signal despite the use of a continuous wideband IR light source and is insensitive to a measurement environment .

A thickness measuring apparatus according to an embodiment of the present invention includes a broadband light source; A first optical fiber for transmitting output light of the broadband light source; A first beam splitter for splitting the light transmitted through the first optical fiber into a reference beam traveling on a reference path and a measuring beam traveling on a measurement path; A reference path mirror for reflecting the reference beam; A measurement path mirror for reflecting the measurement beam; A second beam splitter for generating an interference signal by superimposing the reference beam reflected from the reference path mirror and the measurement beam; A second optical fiber for transmitting the interference signal; A spectrum analyzer for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processor for processing the output signal of the spectrum analyzer to calculate a thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square.

In one embodiment of the present invention, the apparatus further comprises a reference frame mounting the first beam splitter, the reference path mirror, the measurement path mirror, and the second beam splitter. Wherein the reference frame comprises a groove for inserting the object to be measured, the groove intersects between the measurement path mirror and the second beam splitter, and in a first direction in which the first beam splitter and the measurement path mirror are aligned Can be extended.

In one embodiment of the present invention, the apparatus may further include a linear motion stage for moving the reference frame in a first direction. As the reference frame moves, the measurement position of the measurement object can be changed.

In one embodiment of the present invention, the reference frame includes an elongated groove extending in the first direction to insert the measurement object; A left linear motion guide disposed on the left side with respect to the groove of the reference frame and extending in the first direction; A left slide mounted on the left linear motion guide and moving in the first direction; A right linear motion guide disposed on the right side of the reference frame and extending in the first direction; A right slide mounted on the right linear motion guide and moving in a first direction; And a left and right slide connection portion for fixing the left slide and the right slide to each other. The first beam splitter and the measurement path mirror are fixed to the left slide, and the second beam splitter and the reference path mirror can be fixed to the right slide. The grooves may extend between the measurement path mirror and the second beam splitter and extend in the first direction in which the first beam splitter and the measurement path mirror are aligned.

In one embodiment of the present invention, the driving unit is inserted into the left slide or the right slide to provide a driving force for linear motion; And a motor for providing a rotational force to the driving unit.

In one embodiment of the present invention, the reference frame includes an elongated groove extending in the first direction to insert the measurement object; A left linear motion guide extending from the left side of the reference frame in the first direction; A left slide mounted on the left linear motion guide and moving in the first direction; A right linear motion guide extending from the right side of the reference frame in the first direction; And a right slide mounted on the right linear motion guide and moving in the first direction. The first beam splitter and the reference path mirror are fixed to the reference frame, the measurement path mirror is fixed to the left slide, and the second beam splitter can be fixed to the right slide. The grooves may extend between the measurement path mirror and the second beam splitter and extend in the first direction in which the first beam splitter and the measurement path mirror are aligned.

In one embodiment of the present invention, a first driving unit inserted in the left slide and providing a driving force to linearly move the first driving unit; A second driving unit inserted in the right slide to provide a driving force to linearly move; A first motor for providing a rotational force to the first driving unit; And a second motor for providing a rotational force to the second driving unit.

In an embodiment of the present invention, an alignment light measurement unit disposed at the second beam splitter in the first direction and disposed perpendicular to a traveling direction of the interference signal, the alignment light measurement unit mounted on the right slide; And an alignment processor for generating a control signal for matching the reference beam and the measurement beam with each other using an output signal of the alignment light measurement unit. The alignment processor may drive the first motor and the second motor.

In one embodiment of the present invention, the measurement target moving means for moving the measurement target may be disposed through the grooves of the reference frame.

In one embodiment of the present invention, the broadband light source may be a super luminescent diode (SLD).

In one embodiment of the present invention, a first collimating lens disposed between the output end of the first optical fiber and the first beam splitter to provide parallel light; And a second collimator lens disposed between an input end of the second optical fiber and the second beam splitter and concentrating collimated light onto the second optical fiber, wherein the first collimator lens can determine the size of the collimated light .

A thickness measuring apparatus according to an embodiment of the present invention provides a spectral dominant transmissive Mach-Zehnder interferometer structure. As a result, it is environmentally insensitive and exhibits robust characteristics against vibration of the measurement object.

1 is a diagram illustrating a Michelson interferometer type frequency domain interferometer.
2 is a view for explaining an interference signal and a Fourier transform of a frequency domain interferometer.
3 is a conceptual diagram illustrating a thickness measuring apparatus according to an embodiment of the present invention.
4 is a view for explaining the thickness measuring apparatus of Fig.
5 is a perspective view illustrating a thickness measuring apparatus according to another embodiment of the present invention.
6 is a plan view illustrating a thickness measuring apparatus according to another embodiment of the present invention.
7 is a plan view illustrating a thickness measuring apparatus according to another embodiment of the present invention.
8 is a conceptual diagram illustrating a thickness measuring apparatus according to another embodiment of the present invention.
9 is a view for explaining the thickness measuring apparatus of Fig.

As the large area flat panel display industry evolves, the physical thickness of the bare glass panel becomes thin to realize a light and thin display device. During the fabrication process, the physical thickness of the bare glass panel used as the bare substrate must be precisely controlled. When manufacturing small pixels or patterns, the physical thickness of the bare glass panel should be uniform to suppress defective pixels. In addition, the physical thickness of the bare glass panel should be monitored in-line to obtain the desired thickness value.

The glass panel is typically transported in a specific direction by means of a glass panel transfer device, and the thickness measuring device is fixedly disposed. Thereby, as the glass panel is transported in a specific direction, the measurement position of the bare glass panel is changed. In this case, the measurement height of the glass panel is fixed, and it is difficult to measure the thickness at various heights. At various heights, in order to perform the thickness measurement, when the thickness measuring apparatus moves, the measurement accuracy decreases according to the alignment and the environmental change.

A spectral-domain interferometer can measure optical thickness at high speed with the precision of. By analyzing the nterference spectra, the optical thickness can be obtained. However, in order to extract the physical thickness from the optical thickness, the refractive index of the bare glass panel must first be known.

Since the precision of the physical thickness depends on the precision of the refractive index, the refractive index of the bare glass panel must be precisely measured. Furthermore, dispersion effects should be considered according to the wavelength of the light source being used.

In the present invention, an optical device for measuring the refractive index and physical thickness of a bare glass panel is introduced.

Michelson interferometers can measure length using the principle of interference of light. Light from the light source is split through a beam splitter into a reference path and a measurement path. The phase of the interference signal is given as a function of the optical path difference between the reference path and the measurement path with respect to the optical splitter. The interference signal fluctuates periodically every time the optical path difference becomes half the wavelength. Therefore, due to the ambiguity of the phase, when the length measurement is performed, the number of interference signals can be detected while changing the measurement path.

A spectral-domain interferometer can distinguish optical path differences without phase shift.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited to the embodiments described herein but may be embodied in other forms. Rather, the embodiments disclosed herein are being provided so that this disclosure will be thorough and complete, and will fully convey the concept of the invention to those skilled in the art. In the drawings, the components have been exaggerated for clarity. Like numbers refer to like elements throughout the specification.

1 is a diagram illustrating a Michelson interferometer type frequency domain interferometer.

2 is a view for explaining an interference signal and a Fourier transform of a frequency domain interferometer.

1 and 2, the frequency domain interferometer 50 uses a broadband light source 51 and a Michelson interferometer, and the interference signal can be measured for each wavelength through the spectrum analyzer 55. The interference signal I (z, f) according to the wavelength is Fourier transformed. The amplitude of the Fourier transform of the interference signal may have a peak in the spatial frequency domain. At a spatial frequency corresponding to the position of the peak, the phase of the peak may provide information about the light path difference.

Figure pat00001

Here, I (z, f) is the interference signal, I 0 is the background light signal, z is the optical path difference between the reference path and the measurement path, c is the speed of light in vacuum, and f is the optical frequency. Thus, an interference signal according to the frequency of the broadband light source is obtained. L 1 is the distance between the beam splitter 52 and the reference mirror 54 and L 2 is the distance between the beam splitter 52 and the measurement mirror 53. z is the optical path difference. n is the refractive index of the medium.

On the other hand, the interference signal is measured according to the position (corresponding to the frequency) by the spectrum analyzer 55. The Fourier transform of the interference signal may have a peak at a predetermined spatial frequency. The predetermined spatial frequency may be expressed by the optical path difference z. Thus, the spatial frequency at the peak can provide the light path difference z.

In the case of the frequency-domain Michelson interferometer, an interference signal is formed using the beam reflected from the measurement object 10. However, when the measurement target 10 moves, the measurement target oscillates finely. Such a vibration of the measurement object causes a sudden change in the angle of the light reflected from the measurement object, thereby reducing the intensity of the measurement light reaching the spectrum analyzer, thereby making it impossible to generate the interference signal. Therefore, a Michelson interferometer using a reflective interfering signal is not suitable for measurement of large glass panels.

In order to solve the problem of the reflection type interferometer, a frequency region transmission type optical fiber interferometer (Korean Patent No. 10-1544962) has been developed. However, the frequency-domain transmission-type optical fiber interferometer generates an interference signal using a signal transmitted through the object to be measured. Thus, the error due to the vibration of the measurement object can be reduced. However, as optical fibers are used to construct a reference path and a measurement path, a light path difference between the reference path and the measurement path occurs. Accordingly, a large light path difference requires a light source having a long interference distance. Accordingly, the light source requires expensive equipment such as a broadband laser. In addition, the characteristics of the optical fiber vary sensitively according to the surrounding environment (temperature, humidity). In order to measure a large-area glass panel, the influence of jitter increases as the length of the reference path optical fiber becomes longer, Is difficult to obtain. Specifically, in the case of a structure using an optical fiber, when the optical fiber is used as a reference path, the medium of the measurement path and the medium of the reference path are different from each other. Therefore, the reference path and the measurement path have an influence depending on the environment change. Therefore, the measurement error increases.

The present invention proposes a frequency-domain transmissive Mach-Zehnder interferometer structure for suppressing the influence due to environmental changes and providing a vibration-insensitive thickness measuring apparatus. The Mach-Zender interferometer structure has a theoretical spectral difference of zero between the reference path and the measurement path. Further, the propagation directions of the measurement beam traveling in the measurement path and the reference beam traveling in the reference path are parallel. Therefore, it is possible to receive (1) influence of environmental change (temperature, humidity, etc.) at the same time, and the influence thereof can be canceled. (2) Even if vibration occurs in the sample, the effect is minimized because it is a transmission type. (3) A light source such as an inexpensive super-luminescent diode (SLD) having no optical path difference and a short interference distance can be used. (4) There is no difference in light path, and the visibility of the interference signal is improved.

In order to measure a large glass substrate, a conventional optical fiber interferometer has a long reference beam and is greatly influenced by changes in the external environment. However, since the present invention is structurally structured so as not to have a difference in light path, it is robust against changes in the external environment.

3 is a conceptual diagram illustrating a thickness measuring apparatus according to an embodiment of the present invention.

4 is a view for explaining the thickness measuring apparatus of Fig.

3 and 4, the thickness measuring apparatus 100 includes a broadband light source 110; A first optical fiber 112 for transmitting output light of the broadband light source 110; A first beam splitter 122 for splitting the light transmitted through the first optical fiber into a reference beam traveling in a reference path L1 and a measuring beam proceeding in a measurement path L2; A reference path mirror 130 for reflecting the reference beam; A measurement path mirror (140) for reflecting the measurement beam; A second beam splitter 152 for generating an interference signal by superimposing the reference beam reflected from the reference path mirror 130 and the measurement beam reflected from the measurement path mirror 140; A second optical fiber 162 for transmitting the interference signal; A spectrum analyzer 160 for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processing unit 170 for processing the output signal of the spectrum analyzer 160 and calculating the thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square. The optical path difference between the reference path and the measurement path is substantially zero.

The measurement target 10 may be a large-area glass panel. The size of the glass panel may be several tens of centimeters or more. The thickness of the measurement object may be several millimeters or less. The measurement target 10 can be linearly moved by the measurement target conveying means 30. The measurement target conveying means 30 can clamp and transfer one end of the measurement target.

The broadband light source 110 may be a broadband light source in the infrared region. Specifically, the broadband light source 110 may be a super-luminescent diode (SLD) in the infrared region. The coherence distance of the broadband light source 110 may be several millimeters or less. Accordingly, the price of the broadband light source decreases. The broadband light source may operate in a pulsed mode.

The first optical fiber 112 may receive the output light of the broadband light source 110 and provide the output light to the first beam splitter. The first optical fiber may be a single mode optical fiber.

The first collimating lens 124 may be disposed at the front end of the first beam splitter 122. The first collimating lens 124 may be an aspherical lens. The first collimating lens 124 determines the size of the collimated beam and the size of the collimated beam can determine the measurement range of the measurement position. The size of the collimated beam may be less than a few millimeters. The first collimating lens 124 may adjust the spatial resolution of the point measurement.

The first collimating lens 124 may be mounted on the first collimating lens module 120 and the first collimating lens module 120 may include a connector capable of coupling with the optical fiber. In addition, the first collimator lens module 120 includes a tilt screw for aligning the collimated beam, and the angle of propagation of the collimated beam can be adjusted by adjusting the tilted screw.

The reference frame 104 may mount the first beam splitter 122, the reference path mirror 130, the measurement path mirror 140, and the second beam splitter 152. The reference frame 104 may include a groove 104a for inserting the measurement object 10 therein. The grooves 104a intersect the measurement path mirror 140 and the second beam splitter 152 and define a first direction in which the first beam splitter 122 and the measurement path mirror 140 are aligned x-axis direction). The reference frame 104 may include a groove extending in the first direction in the central region. A part of the measurement target 10 is inserted into the groove 104a. Thus, the measurement beam can pass through the measurement target 10. Thus, a Mach-Zehnder interferometer is constructed.

The linear motion stage 102 may move the reference frame 104 in the first direction. As the reference frame moves, the measurement position of the measurement object changes. The linear motion stage 102 may move the entire reference frame in a first direction. Therefore, the two-dimensional thickness distribution can be measured by the linear motion stage 102 and the measurement-object conveying means 30. [ The linear motion stage 102 may be disposed on the table 20.

The first beam splitter 122 may be formed of a prism or a thin plate. The first beam splitter 122 may be divided into a reference beam that is received by the collimated beam and proceeds to a reference path and a measurement beam that proceeds to a measurement path. The intensity of the reference beam and the measurement beam may be the same. The first beam splitter 122 may be mounted on the first beam splitter module 120 and the first beam splitter module 120 may be in the form of a cube. The first beam splitter module may be disassembled with the first collimating lens. The reference beam may be transmitted through the first beam splitter 122 and the measurement beam may be reflected by the first beam splitter 122.

The reference path mirror 130 may reflect the reference beam transmitted through the first beam splitter 122. The reference path mirror 122 may be spaced apart from the first beam splitter in a second direction (y direction) perpendicular to the first direction. The reference path mirror 130 may change the direction of the reference beam traveling in the second direction to a first direction.

The measurement path mirror 140 may reflect the measurement beam reflected by the first beam splitter 122. The measurement path mirror 140 may be spaced apart from the first beam splitter 122 in the first direction. The measurement path mirror 140 may change the direction of the measurement beam traveling in the first direction to a second direction.

The second beam splitter 152 may reflect the direction of the reference beam traveling in the first direction and change the direction of the reference beam in the first direction. Also, the second beam splitter 152 can maintain the direction of the measurement beam traveling in the second direction in the second direction. Accordingly, the measurement beam and the reference beam can generate an interference signal. That is, the second beam splitter 152 may be a beam combiner for combining beams. The second beam splitter 152 may be mounted to the second beam splitter module 150. The second beam splitter module 150 may have a rectangular parallelepiped shape.

The second collimating lens 154 focuses the interference signal and transmits it to the second optical fiber 162. The second collimating lens 154 may be disassembled and coupled to the second beam splitter module 150.

The second optical fiber 162 is aligned with the second collimating lens 154 and can transmit the interference signal to the spectrum analyzer. The second optical fiber 162 may be a single mode optical fiber.

The spectrum analyzer 160 can decompose the interference signal according to the wavelength and measure the intensity of the interference signal according to the wavelength.

The processing unit 170 can perform Fourier transform and signal processing on the intensity of the interference signal according to the wavelength. The interference signal I (z, f) according to the wavelength is Fourier transformed. The amplitude of the Fourier transform of the interference signal may have a peak in the spatial frequency domain. At a spatial frequency corresponding to the position of the peak, the peak may provide information about the light path difference. The processing unit 170 may control the conveying speed and position by controlling the conveying unit 30 to be measured. In addition, the processing unit 170 may control the linear motion stage 102.

In addition, the alignment light measuring unit 181 may be disposed apart from the second beam splitter 152 in the first direction. The alignment light measuring unit 181 can measure the position of the reference beam transmitted through the second beam splitter 152 and the position of the measurement beam transmitted through the second beam splitter 152, respectively. The alignment light measuring unit may be a two-dimensional image sensor or a position sensitive detector.

The alignment processing unit 182 may generate a control signal by using the output signal of the alignment light measuring unit 181 to match the reference beam and the measurement beam with each other. The alignment processor 182 may drive the first motor 183 and the second motor 184. The first motor 183 may control the position or angle of the measurement path mirror 140 and the second motor 184 may control the position or angle of the second beam splitter 152.

5 is a perspective view illustrating a thickness measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 5, the thickness measuring apparatus 100a includes a broadband light source 110; A first optical fiber 112 for transmitting output light of the broadband light source 110; A first beam splitter 122 for splitting the light transmitted through the first optical fiber into a reference beam traveling in a reference path L1 and a measuring beam proceeding in a measurement path L2; A reference path mirror 130 for reflecting the reference beam; A measurement path mirror (140) for reflecting the measurement beam; A second beam splitter 152 for generating an interference signal by superimposing the reference beam reflected from the reference path mirror 130 and the measurement beam reflected from the measurement path mirror 140; A second optical fiber 162 for transmitting the interference signal; A spectrum analyzer 160 for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processing unit 170 for processing the output signal of the spectrum analyzer 160 and calculating the thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square. The optical path difference between the reference path and the measurement path is substantially zero.

The first beam splitter 122 is fixed to the reference path mirror 130 by a first alignment column 194 extending in a second direction. The first beam splitter 122 is fixed to the measurement path mirror 140 by a second alignment column 192 extending in a first direction. Also, the reference path mirror 130 is fixed by the second beam splitter 152 and the third alignment column 196 extending in the first direction. Accordingly, the Mach-Zehnder interferometer can be mounted stably in the vertical plane, and thickness measurement can be performed at a desired measurement position. The length of the third alignment column 196 may be sufficiently longer than the length of the first alignment column 194.

The reference frame mounts the first beam splitter, the reference path mirror, the measurement path mirror, and the second beam splitter. Wherein the reference frame comprises a groove for inserting the object to be measured, the groove intersects between the measurement path mirror and the second beam splitter, and in a first direction in which the first beam splitter and the measurement path mirror are aligned .

The measurement object moves in the third direction (z-axis direction). In addition, the linear motion stage moves the reference frame in a first direction.

6 is a plan view illustrating a thickness measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 6, the thickness measuring apparatus 100b includes a broadband light source 110; A first optical fiber 112 for transmitting output light of the broadband light source 110; A first beam splitter 122 for splitting the light transmitted through the first optical fiber into a reference beam traveling in a reference path L1 and a measuring beam proceeding in a measurement path L2; A reference path mirror 130 for reflecting the reference beam; A measurement path mirror (140) for reflecting the measurement beam; A second beam splitter 152 for generating an interference signal by superimposing the reference beam reflected from the reference path mirror 130 and the measurement beam reflected from the measurement path mirror 140; A second optical fiber 162 for transmitting the interference signal; A spectrum analyzer 160 for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processing unit 170 for processing the output signal of the spectrum analyzer 160 and calculating the thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square. The optical path difference between the reference path and the measurement path is substantially zero.

The reference frame 104 includes an elongated groove 104a extending in the first direction so that the measurement target 10 is inserted.

The left linear motion guide 191a is disposed on the left side with respect to the grooves 104a of the reference frame and extends in the first direction. The left linear motion guide 191a may be a rod type or a rail type.

The left slide 192a is mounted on the left linear motion guide 191a and moves in the first direction. The left slide 192a is mounted on the left linear motion guide 191a and can linearly move.

The right linear motion guide 191b is disposed on the right side with respect to the groove of the reference frame and extends in the first direction.

The right slide 192b is mounted on the right linear motion guide 191b and moves in the first direction.

The left and right slide connection portions 192c fix the left slide 192a and the right slide 192b to each other. According to a modified embodiment of the present invention, the left slide, the right slide, and the left and right slide connection portions may be integrally formed.

The first beam splitter 122 and the measurement path mirror 140 are fixed to the left slide 192a and the second beam splitter 152 and the reference path mirror 130 are fixed to the right slide 192b, Respectively.

The grooves 104a extend between the measurement path mirror and the second beam splitter and extend in the first direction in which the first beam splitter and the measurement path mirror are aligned.

The driving portion 195 is inserted into the left slide 192a or the right slide 192b to provide a driving force for linear motion. The driving unit 195 may be a screw. Both ends of the driving unit can be fixed through bearings. The motor 196 provides rotational force to the driving unit 195.

7 is a plan view illustrating a thickness measuring apparatus according to another embodiment of the present invention.

Referring to FIG. 7, the thickness measuring apparatus 100c includes a broadband light source 110; A first optical fiber 112 for transmitting output light of the broadband light source 110; A first beam splitter 122 for splitting the light transmitted through the first optical fiber into a reference beam traveling in a reference path L1 and a measuring beam proceeding in a measurement path L2; A reference path mirror 130 for reflecting the reference beam; A measurement path mirror (140) for reflecting the measurement beam; A second beam splitter 152 for generating an interference signal by superimposing the reference beam reflected from the reference path mirror 130 and the measurement beam reflected from the measurement path mirror 140; A second optical fiber 162 for transmitting the interference signal; A spectrum analyzer 160 for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processing unit 170 for processing the output signal of the spectrum analyzer 160 and calculating the thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square. The optical path difference between the reference path and the measurement path is substantially zero.

The reference frame 104 includes an elongated groove 104a extending in the first direction so that the measurement target 10 is inserted.

The left linear motion guide 191a is disposed on the left side with respect to the grooves 104a of the reference frame and extends in the first direction. The left linear motion guide 191a may be a rod type or a rail type.

The left slide 292a is mounted on the left linear motion guide 191a and moves in the first direction. The left slide 292a can be mounted on the left linear motion guide 191a and linearly moved.

The right linear motion guide 191b is disposed on the right side with respect to the groove of the reference frame and extends in the first direction.

The right slide 292b is mounted on the right linear motion guide 191b and moves in the first direction.

The first beam splitter 122 and the reference path mirror 130 are fixed to the reference frame 104. The measurement path mirror 140 is fixed to the left slide 292a and the second beam splitter 152 is fixed to the right slide 292b. The grooves 104a extend between the measurement path mirror and the second beam splitter and extend in the first direction in which the first beam splitter and the measurement path mirror are aligned.

The first driving portion 295a is inserted into the left slide 292a to provide a driving force for linear motion. The first motor 183 provides rotational force to the first driver 295a.

The second driving portion 295b is inserted into the right slide 292b to provide a driving force for linear motion. And the second motor 184 provides rotational force to the second driver 295b.

8 is a conceptual diagram illustrating a thickness measuring apparatus according to another embodiment of the present invention.

9 is a view for explaining the thickness measuring apparatus of Fig.

8 and 9, the thickness measuring apparatus 300 includes a broadband light source 110; A first optical fiber 112 for transmitting output light of the broadband light source 110; A first beam splitter 122 for splitting the light transmitted through the first optical fiber into a reference beam traveling in a reference path L1 and a measuring beam proceeding in a measurement path L2; A reference path mirror 130 for reflecting the reference beam; A measurement path mirror (140) for reflecting the measurement beam; A second beam splitter 152 for generating an interference signal by superimposing the reference beam reflected from the reference path mirror 130 and the measurement beam reflected from the measurement path mirror 140; A second optical fiber 162 for transmitting the interference signal; A spectrum analyzer 160 for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And a processing unit 170 for processing the output signal of the spectrum analyzer 160 and calculating the thickness of the measurement object inserted in the measurement path. The reference path and the measurement path are arranged to form a square. The optical path difference between the reference path and the measurement path is substantially zero.

The reference frame 104 includes an elongated groove 104a extending in the first direction so that the measurement target 10 is inserted. The grooves 104a may be formed on the lower surface. Accordingly, the measurement target conveying means 30 for moving the measurement target 10 is arranged to penetrate the grooves of the reference frame.

The reference frame 104 may be mounted on a separate frame 32 disposed on the measurement target conveying means.

The first linear motion guide 391a is disposed on the right side with respect to the grooves 104a of the reference frame and extends in the first direction. The first linear motion guide 391a may be a bar type or a rail type.

The first slide 392a is mounted on the first linear motion guide 391a and moves in the first direction. The first slide 392a is mounted on the first linear motion guide 391a and can linearly move. The second linear motion guide 391b is disposed on the left side with respect to the grooves 104a of the reference frame 104 and extends in the first direction. The second slide 392b is mounted on the second linear motion guide 391b and moves in the first direction. The first beam splitter 122 and the reference path mirror 140 are fixed to the upper end of the reference frame 104, respectively. The measurement path mirror 140 is mounted to the first slide 392a and the second beam splitter 152 is mounted to the second slide 392b.

 The grooves 104a extend between the measurement path mirror and the second beam splitter and extend in the first direction in which the first beam splitter and the measurement path mirror are aligned.

The first driving portion 395a is inserted into the first slide 392a to provide a driving force for linear motion. The first motor 183 provides rotational force to the first driving unit 395a. The second driving portion 395b is inserted into the second slide 392b to provide a driving force for linear motion. And the second motor 184 provides rotational force to the second driving unit 395b.

The alignment light measuring unit 181 is disposed in the second beam splitter in the first direction, is disposed perpendicular to the traveling direction of the interference signal, and is mounted on the second slide 392b.

The alignment processing unit 182 generates a control signal by using the output signal of the alignment light measuring unit 181 to match the reference beam and the measurement beam with each other. The alignment processor 182 drives the first motor 183 and the second motor 184.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, And all of the various forms of embodiments that can be practiced without departing from the technical spirit.

110: broadband light source
122: first beam splitter
130: Reference path mirror
140: Measuring path mirror
152: second beam splitter
160: spectrum analyzer

Claims (11)

Broadband light source;
A first optical fiber for transmitting output light of the broadband light source;
A first beam splitter for splitting the light transmitted through the first optical fiber into a reference beam traveling on a reference path and a measuring beam traveling on a measurement path;
A reference path mirror for reflecting the reference beam;
A measurement path mirror for reflecting the measurement beam;
A second beam splitter for generating an interference signal by superimposing the reference beam reflected from the reference path mirror and the measurement beam;
A second optical fiber for transmitting the interference signal;
A spectrum analyzer for measuring an interference signal transmitted through the second optical fiber according to a wavelength; And
And a processing unit for processing the output signal of the spectrum analyzer to calculate the thickness of the measurement object inserted in the measurement path,
Wherein the reference path and the measurement path are arranged to form a quadrangle. The method according to claim 1,
Further comprising a reference frame mounting the first beam splitter, the reference path mirror, the measurement path mirror, and the second beam splitter,
Wherein the reference frame includes a groove for inserting the measurement object,
Wherein the groove intersects the measurement path mirror and the second beam splitter and extends in a first direction in which the first beam splitter and the measurement path mirror are aligned. 3. The method of claim 2,
Further comprising a linear motion stage for moving the reference frame in a first direction,
Wherein the measurement position of the measurement object changes as the reference frame moves. The method according to claim 1,
A reference frame including an elongated groove extending in a first direction to insert the measurement object;
A left linear motion guide disposed on the left side with respect to the groove of the reference frame and extending in the first direction;
A left slide mounted on the left linear motion guide and moving in the first direction;
A right linear motion guide disposed on the right side of the reference frame and extending in the first direction;
A right slide mounted on the right linear motion guide and moving in a first direction; And
Further comprising left and right slide connecting portions for fixing the left slide and the right slide to each other,
Wherein the first beam splitter and the measurement path mirror are fixed to the left slide,
Wherein the second beam splitter and the reference path mirror are fixed to the right slide,
Wherein the groove intersects between the measurement path mirror and the second beam splitter and extends in the first direction in which the first beam splitter and the measurement path mirror are aligned. 5. The method of claim 4,
A driving unit inserted into the left slide or the right slide to provide a driving force to linearly move; And
And a motor for providing a rotational force to the driving unit. The method according to claim 1,
A reference frame including an elongated groove extending in a first direction to insert the measurement object;
A left linear motion guide extending from the left side of the reference frame in the first direction;
A left slide mounted on the left linear motion guide and moving in the first direction;
A right linear motion guide extending from the right side of the reference frame in the first direction; And
And a right slide mounted on the right linear motion guide and moving in the first direction,
Wherein the first beam splitter and the reference path mirror are fixed to the reference frame,
Wherein the measurement path mirror is fixed to the left slide,
The second beam splitter being fixed to the right slide,
Wherein the groove intersects between the measurement path mirror and the second beam splitter and extends in the first direction in which the first beam splitter and the measurement path mirror are aligned. The method according to claim 6,
A first driving unit inserted in the left slide and providing a driving force to linearly move;
A second driving unit inserted in the right slide to provide a driving force to linearly move;
A first motor for providing a rotational force to the first driving unit; And
And a second motor for providing a rotational force to the second driving unit. 8. The method of claim 7,
An alignment light measuring unit disposed in the second beam splitter in the first direction and disposed perpendicular to a traveling direction of the interference signal, the alignment light measuring unit mounted on the right slide; And
Further comprising an alignment processor for generating a control signal to match the reference beam and the measurement beam using an output signal of the alignment light measurement unit,
And the alignment processor drives the first motor and the second motor. 3. The method of claim 2,
Wherein the measurement target conveying means for moving the measurement target is disposed so as to pass through the grooves of the reference frame. The method according to claim 1,
Wherein the broadband light source is a super-luminescent diode (SLD). The method according to claim 1,
A first collimating lens disposed between the output end of the first optical fiber and the first beam splitter to provide parallel light; And
Further comprising a second collimator lens disposed between an input end of the second optical fiber and the second beam splitter to concentrate collimated light onto the second optical fiber,
Wherein the first collimating lens determines the size of the parallel light.
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190091144A (en) * 2018-01-26 2019-08-05 인하대학교 산학협력단 Method measuring thickness and refractive index of planar samples based on fabry-perot interferometer
KR20200071533A (en) * 2018-12-11 2020-06-19 한국표준과학연구원 Thickness And Refractive Index Measuring Apparatus Without Non-measuring Ranges

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000111677A (en) 1998-10-07 2000-04-21 Canon Inc Positioning stage device, color filter manufacturing device and liquid crystal aligner
KR100393644B1 (en) 2001-11-16 2003-08-06 광주과학기술원 Apparatus of measuring refractive index and absorption coefficient of an optical material simultaneously
DE102011051146B3 (en) * 2011-06-17 2012-10-04 Precitec Optronik Gmbh Test method for testing a bonding layer between wafer-shaped samples

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR20190091144A (en) * 2018-01-26 2019-08-05 인하대학교 산학협력단 Method measuring thickness and refractive index of planar samples based on fabry-perot interferometer
KR20200071533A (en) * 2018-12-11 2020-06-19 한국표준과학연구원 Thickness And Refractive Index Measuring Apparatus Without Non-measuring Ranges

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