KR102220731B1 - Method for measuring fine change of thin film surface - Google Patents

Abstract

The present invention discloses a system and method for measuring microscopic changes on the surface of a thin film, which enables quick inspection of a microscopic change of a sample surface or a poor coating of a thin film on a large area by using a polarization quenching method.
The disclosed thin film surface fine change measurement system includes: a light source; A polarizer that polarizes the light output from the light source; A light corrector for correcting light polarized by the polarizer; A stage in which a reference sample or a target sample to which the light corrected by the optical corrector is incident is disposed; A polarization analyzer that polarizes and analyzes the light reflected by the reference sample or the target sample; A photo detector for detecting an image of light polarized by a polarization analyzer; And the light output from the light source is polarized and corrected to be incident on the reference sample, and the light reflected by the reference sample is linearly polarized and the first stepped value for the first image of the light detected by the photo detector, and the light output from the light source. Is polarized and corrected, the light incident on the target sample and reflected by the target sample is polarized to calculate the ratio of the second brightness value to the second image of the light detected by the photo detector, and the first brightness value and the second brightness value It characterized in that it comprises a change detection unit that detects that there is a fine change in the target sample when the ratio of the values differs by more than a certain value.

Description

System and method for measuring fine change of thin film surface {Method for measuring fine change of thin film surface}

The present invention relates to a system and method for measuring microscopic changes in the surface of a thin film, and more particularly, polarizing coating defects due to microscopic changes in the surface of an ultrafine thin film of 30 nanometers (nm) or less in the process of manufacturing a flat thin film display panel. The present invention relates to a system and method for measuring microscopic changes in the surface of a thin film, which enables fast inspection in a large area using a quenching method.

In general, when examining coating defects on ultra-fine thin films of 30 nm or less in the FPD (Flat Panel Display) process, it is impossible to inspect because the difference in reflectivity is very small with a general microscope or a thickness measuring device such as SR (Spectroscopic Reflectometry). Do.

In addition, SE (Spectroscopic Ellipsometry), which can measure the thickness of an ultra-fine thin film, is a method of measuring the change in polarization when polarized light is incident on the sample and reflected, and reacts sensitively to minute changes in the sample surface.

However, SE can measure the presence or absence of an ultra-fine thin film of 30 nm or less, but has a disadvantage in that it takes a long time to measure because a polarizer or a compensator must be measured at various angles during measurement.

In addition, SE has an advantage in measuring the thickness of a thin film due to its narrow measurement area, but it has a problem that it is difficult to use for inspecting defective coatings at a high speed over a large area.

A related prior patent document is Korean Patent Publication No. 10-1987402 (registered on June 3, 2019), and the document describes a method of measuring the shape of the surface of a thin film using an optical device.

It is an object of the present invention to solve the above-described problems, by using a polarization quenching method to quickly inspect a fine change of a sample surface or a poor coating of a thin film in a large area using a polarization quenching method. It is to provide a change measurement system and method.

It is an object of the present invention to set a reference sample to be measured, and to detect whether the surface state of the target sample to be inspected is the same as or not the same as the reference sample, so that the presence or absence of a thin film or defects in surface coating can be inspected. It is to provide a system and method for measuring fine changes in the surface of a thin film.

In addition, an object of the present invention is to determine whether the change in the polarization state when the light is reflected from the measurement target sample is the same as the change in the polarization state when the light is reflected from the reference sample, and a system and method for measuring minute changes on the surface of a thin film Is to provide.

In addition, it is an object of the present invention to provide a system for measuring minute changes in the surface of a thin film by configuring a polarization optical system to maximize the difference in the amount of light measured on a photodetector even when the light is reflected by a sample Is to do.

In addition, it is an object of the present invention is a system and method for measuring microscopic changes on the surface of a thin film capable of performing a fast inspection without having to move a polarizer or a corrector in various directions when measuring like SE, and capable of inspecting a large area using an imaging optical system and a 2D camera. Is to provide.

In addition, an object of the present invention is to provide a system and method for measuring microscopic changes in the surface of a thin film capable of detecting defects of an ultrafine thin film in a large area at high speed in FPD and semiconductor processes.

A system for measuring microscopic changes in the surface of a thin film according to an embodiment of the present invention for achieving the above object includes: a light source; A polarizer that polarizes the light output from the light source; A light corrector for correcting light polarized by the polarizer; A stage in which a reference sample or a target sample to which the light corrected by the optical corrector is incident is disposed; A polarization analyzer that polarizes and analyzes the light reflected by the reference sample or the target sample; A photo detector for detecting an image of light polarized by a polarization analyzer; And the light output from the light source is polarized and corrected to be incident on the reference sample, and the light reflected by the reference sample is linearly polarized and the first stepped value for the first image of the light detected by the photo detector, and the light output from the light source. Is polarized and corrected, the light incident on the target sample and reflected by the target sample is polarized to calculate the ratio of the second brightness value to the second image of the light detected by the photo detector, and the first brightness value and the second brightness value It may include a change detection unit that detects that there is a fine change in the target sample when the ratio of the values differs by more than a predetermined value.

In addition, the polarizer passes light in the direction of the polarization axis and absorbs the light in the direction of the extinction axis to polarize the light output from the light source, and the optical compensator converts the light polarized by the polarizer into light in the fast axis direction and the slow axis direction. A λ/4 phase difference is generated for and corrected, and the light corrected by the optical corrector may be incident on the reference sample or the target sample at an angle close to Brewster's angle or Brewster's angle.

In addition, the polarization analyzer may linearly polarize the light reflected by the reference sample and output the quenched light to the photo detector.

In addition, a first telecentric lens positioned between the light corrector and the target sample, converting the light corrected by the light corrector into planar light and irradiating the target sample; And a second telecentric lens that receives the light reflected by the target sample and outputs only the planar light to the polarization analyzer.

In addition, the photodetector, when the light reflected by the target sample is incident on the polarization analyzer by the second telecentric lens, and receives the polarized light by the polarization analyzer, the Scheimplug condition is satisfied. The second image may be obtained by receiving the polarized light by the polarization analyzer in a state that is rotated at an angle and rotated at a Scheimplug angle.

In addition, the first telecentric lens and the second telecentric lens may be lenses that do not have a change in magnification even at a distance difference from the target sample.

On the other hand, the method for measuring microscopic changes on the surface of a thin film according to an embodiment of the present invention for achieving the above object is (a) polarizing light output from a light source to irradiate a reference sample, and linearly polarizing the light reflected by the reference sample. Obtaining a first image of the detected light; (b) polarizing the light output from the light source to irradiate the target sample and polarizing the light reflected by the target sample to obtain a second image of the detected light; (c) calculating a ratio of the first brightness value for the first image and the second brightness value for the second image; And (d) detecting that there is a slight change in the target sample when the ratio of the first brightness value and the second brightness value differs by more than a predetermined value.

In addition, in step (a), the light output from the light source is polarized and corrected by the polarization generator and incident on the reference sample, and the light reflected by the reference sample is polarized by the polarization analyzer and input to the photodetector. A first image of light detected by the photo detector may be obtained.

In addition, in step (a), the light output from the light source in the direction of the polarization axis is passed by the polarizer and the light in the direction of the extinction axis is absorbed, and the phase difference with respect to the light in the fast axis direction and the slow axis direction through the optical corrector. Is generated and corrected, and then incident on the reference sample at an angle close to Brewster's angle or Brewster's angle, and the light reflected by the reference sample is linearly polarized by a polarization analyzer and input to the photodetector, and the first light detected by the photodetector The first brightness value for the image may be zero (0) or may have a value close to zero (0).

In addition, in step (b), the light output from the light source in the direction of the polarization axis is passed by the polarizer and the light in the direction of the extinction axis is absorbed, and the phase difference with respect to the light in the fast axis direction and the slow axis direction through the optical corrector. Is generated and corrected, and then incident on the target sample at an angle close to Brewster's angle or Brewster's angle, and the light reflected by the target sample is polarized by a polarization analyzer and input to the photodetector, and the second image of the light detected by the photodetector Can be obtained.

In addition, in step (b), the polarized and corrected light output from the light source is converted into planar light by the first telecentric lens to irradiate the target sample, and the second telecentric light is reflected by the target sample. Only plane light is incident on the polarization analyzer by the lens, is polarized by the polarization analyzer, and input to the photo detector, and a second image of the light detected by the photo detector can be obtained.

In addition, in step (b), only the plane light is incident on the polarization analyzer by the second telecentric lens from the light reflected by the target sample, polarized by the polarization analyzer, and input to the photo detector, and the photo detector is under the Scheimplug condition. The second image of the light detected by the photodetector rotated at the Scheim plug angle and rotated at the Scheim plug angle may be obtained so as to satisfy.

In step (b), the surface of the target sample is called the object surface, the center surface of the second telecentric lens is called the lens surface, the incident surface of the photodetector is called the sensor surface, and the second telecentric lens The center point of is called the lens center point, the center point of the photodetector is called the sensor center point, the point where the straight line connecting the lens center point and the sensor center point meets the object surface is called the reference point, and the extension line of the object surface, the extension line of the lens surface, and the sensor surface The point that satisfies the Scheim plug condition in which the extension line of is coincident is called the Scheim plug point, and the angle formed by the object surface and the lens surface is called the optical system inclination angle. When the angle at which the photodetector should be rotated to satisfy the Scheim plug angle is the angle of the sensor surface by rotating the photodetector so that the Scheim plug condition is satisfied when the optical system inclination angle is 0 and the lens surface and the sensor surface are parallel. A second image of the light detected by the photodetector adjusted to the Scheimplug angle can be obtained.

In addition, in step (b), the Scheimplug angle can be calculated by the following equation.

Here, θ is the Scheim plug angle, α is the optical system inclination angle, C is the distance between the reference point and the sensor center point, and R is the distance between the reference point and the Scheim plug point.

In addition, the first telecentric lens and the second telecentric lens may be lenses that do not have a change in magnification even at a distance difference from the target sample.

According to the present invention, by setting a reference sample to be measured and detecting whether the surface state of the target sample to be inspected is the same as or not the same as the reference sample, defects in surface coating on a large area thin film can be inspected in a short time. I can.

Further, according to the present invention, by detecting whether the change in the polarization state when the light is reflected from the measurement target sample is the same as the change in the polarization state when the light is reflected from the reference sample, it is possible to measure the minute change on the surface of the thin film.

In addition, according to the present invention, when light is reflected by a sample, the polarization optical system is configured so that the difference in the amount of light measured on the photodetector is maximized even when the light is reflected by the sample, so that minute changes in the surface of the thin film can be measured.

In addition, according to the present invention, it is possible to perform fast inspection without having to move a polarizer or a corrector in various directions during measurement, such as SE, and a large area inspection of an ultrafine thin film can be performed using an imaging optical system and a 2D camera. Therefore, rather than measuring the thickness of the ultrafine thin film, it is possible to quickly inspect a fine change on the surface of the sample, the presence or absence of a thin film, and poor coating in a large area.

Further, according to the present invention, it is possible to provide a system and method for measuring microscopic changes in the surface of a thin film capable of detecting defects of an ultrafine thin film in a large area at high speed in FPD and semiconductor processes.

1 is a block diagram schematically showing the overall configuration of a system for measuring fine changes in a thin film surface according to an embodiment of the present invention.
2 is a diagram illustrating an example in which a test target sample is disposed on a stage according to an embodiment of the present invention.
3 is a diagram illustrating an example in which light polarized through a polarization generator according to an embodiment of the present invention is incident on a reference sample at a specific angle.
4 is a diagram showing an image of light reflected by a reference sample and an image of light reflected by a target sample according to an embodiment of the present invention.
5 is a diagram showing an example of additionally configuring a telecentric lens in measuring a reference sample according to an embodiment of the present invention.
6 is a diagram showing an example of additionally configuring a telecentric lens in measuring a target sample according to an embodiment of the present invention.
7 is a diagram illustrating an example of measuring a reference sample through a telecentric lens according to an embodiment of the present invention.
8 is a diagram showing an example of detecting light passing through a telecentric lens according to an embodiment of the present invention by applying the Scheimplug principle.
9 is a diagram illustrating an operation flow chart for explaining a method of measuring fine changes on a surface of a thin film according to an embodiment of the present invention.

Advantages and features of the present invention, and a method of achieving them will become apparent with reference to the embodiments described below in detail together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in a variety of different forms, only this embodiment is to complete the disclosure of the present invention, and the general knowledge in the technical field to which the present invention pertains. It is provided to completely inform the scope of the invention to the possessor, and the invention is only defined by the scope of the claims. Accordingly, in some embodiments, well-known process steps, well-known device structures, and well-known techniques have not been described in detail in order to avoid obscuring interpretation of the present invention. The same reference numerals refer to the same components throughout the specification.

In the drawings, the thicknesses are enlarged to clearly express various layers and regions. The same reference numerals are assigned to similar parts throughout the specification. When a part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the case where the other part is "directly above", but also the case where there is another part in the middle. Conversely, when one part is "directly above" another part, it means that there is no other part in the middle. Further, when a part such as a layer, film, region, plate, etc. is said to be "under" another part, this includes not only the case where the other part is "directly below", but also the case where there is another part in the middle. Conversely, when one part is "right under" another part, it means that there is no other part in the middle.

Spatially relative terms "below", "beneath", "lower", "above", "upper", etc., as shown in the figure It may be used to easily describe the correlation between the device or components and other devices or components. Spatially relative terms should be understood as terms including different directions of the device during use or operation in addition to the directions shown in the drawings. For example, if an element shown in the figure is turned over, an element described as “below” or “beneath” of another element may be placed “above” another element. Accordingly, the exemplary term “below” may include both directions below and above. The device may be oriented in other directions, and thus spatially relative terms may be interpreted according to the orientation.

In this specification, when a part is said to be connected to another part, this includes not only the case of being directly connected but also the case of being electrically connected with another element interposed therebetween. In addition, when a part includes a certain component, it means that other components may be further included rather than excluding other components unless otherwise indicated.

In the present specification, terms such as first, second, and third may be used to describe various elements, but these elements are not limited by the terms. The terms are used for the purpose of distinguishing one component from other components. For example, without departing from the scope of the present invention, a first component may be referred to as a second or third component, and similarly, a second or third component may be alternately named.

Unless otherwise defined, all terms (including technical and scientific terms) used in the present specification may be used as meanings that can be commonly understood by those of ordinary skill in the art to which the present invention belongs. In addition, terms defined in a commonly used dictionary are not interpreted ideally or excessively unless explicitly defined specifically.

Hereinafter, an all-solid-state composite electrode based on a metal support according to a preferred embodiment of the present invention, a method of manufacturing the same, and an all-solid-state secondary battery having the same will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically showing the overall configuration of a system for measuring fine changes in a thin film surface according to an embodiment of the present invention.

Referring to FIG. 1, a system 100 for measuring microscopic changes in the surface of a thin film according to an embodiment of the present invention includes a light source 10, a stage 50, a polarization generator 60, and a polarization analyzer 70. , And a change detection unit 80 may be included.

In the embodiment of the present invention below, a system for measuring fine changes in the surface of a thin film may be described simply by denoting it as the measurement system 100 or the inspection system 100.

The light source 10 may be a broadband light source or a multi-wavelength light source that generates light in a wide wavelength range, for example, 250 to 1700 nm. Further, the light source 10 may be a wavelength tunable light source capable of varying a wavelength. Of course, the light source 10 is not limited to a broadband light source. Also, the light source 10 may be a single wavelength laser light source that generates light of one wavelength. If the light source 10 is a single wavelength laser light source, the measurement system 100 of the present invention may include a plurality of laser light sources that generate light of different wavelengths, and the light sources are replaced according to the required wavelength. Can be used. For example, the light source 10 is a light source such as a laser that emits an ultraviolet laser beam, and may emit light having a wavelength of 248 nm, 193 nm or 157 nm.

The polarization generator 60 polarizes and corrects the light output from the light source 10 and outputs it. To this end, the polarization generator 60 includes a polarizer 11 for polarizing light output from a light source; And a light compensator 12 for correcting light polarized by the polarizer.

The polarizer 11 passes light in the polarization axis direction and absorbs light in the extinction axis direction, thereby polarizing the light output from the light source.

The optical corrector 12 corrects the light polarized by the polarizer by generating a λ/4 phase difference with respect to the light in the fast axis direction and the slow axis direction.

Therefore, the light corrected by the optical corrector may be incident on the reference sample or the target sample at an angle close to the Brewster angle or the Brewster angle.

The polarizer 11 may linearly polarize and output light input from the light source 10. For example, the polarizer 11 may linearly polarize the incident light by passing only the P polarization component (or the horizontal component) or the S polarization component (or the vertical component) from the incident light.

The light corrector 12 may output the light from the polarizer 11 by performing circular polarization or elliptical polarization. The light corrector 12 may change linearly polarized light into circularly polarized light or elliptically polarized light, or from circularly polarized light into linearly polarized light by giving a phase difference to linearly polarized light. Accordingly, the optical corrector 12 is also referred to as a phase retarder. For example, the optical corrector 12 may be a quarter-wave plate.

The stage 50 is a device that arranges and fixes the reference sample 13 or the target sample 16 as an inspection object, and can move in the x direction, the y direction, and the z direction. Accordingly, the stage 50 can be referred to as an xyz stage. That is, the stage 50 is a device in which the reference sample 13 or the target sample 16 to which the light corrected by the light corrector 12 is incident is disposed.

The stage 50 can be electrically moved through a motor. By moving the inspection targets 13 and 16 through the stage 50, the inspection targets 13 and 16 may be inspected at the moved position. The inspection object may be a wafer, a semiconductor package, a semiconductor chip, a display panel, and the like. Here, the wafer may be a wafer in which a periodic pattern is formed on an upper surface or a bare wafer without a pattern.

Meanwhile, as shown in FIG. 2, a sample to be inspected may be disposed on the stage 50. 2 is a diagram illustrating an example in which a test target sample is disposed on a stage according to an embodiment of the present invention. In FIG. 2, the target sample 16 may be an Anti-Fingerprint thin film or an Anti-Reflection thin film to which a fingerprint thin film is attached. Therefore, in order to properly realize the fingerprint function, the protective film, which is the diffuse reflection coating thin film, must be free from defects. In an embodiment of the present invention, a diffuse reflection coating thin film having defects on its surface will be described as the target sample 16.

The polarization analyzer 70 may include a polarization analyzer 14 and a photo detector 15.

The polarization analyzer 14 polarizes and analyzes the light reflected by the reference sample or the target sample. That is, the polarization analyzer 14 may linearly polarize the light reflected by the reference sample and output the quenched light to the photodetector 15.

The polarization analyzer 14 may selectively pass reflected light reflected from a sample and whose polarization direction is changed. For example, the polarization analyzer 14 may be a type of linear polarizer that passes only a specific polarization component and blocks other components of incident light. When the low-magnification optical system is disposed between the sample and the polarization analyzer 14, the polarization analyzer 14 may be disposed at a rear end of the low-magnification optical system.

The low magnification optical system is a kind of imaging optics, and can image light from the polarization analyzer 14 at an equal or low magnification. Here, the low magnification may mean a magnification of 1:100 or less, including an equal magnification of 1:1. Meanwhile, a magnification exceeding 1:100 may be classified as a high magnification. The measurement system 100 of the present invention can perform defect inspection at high speed with a field of view (FOV) that is significantly wider than that of a conventional SE or SIE by using a low magnification optical system. For example, if a low magnification optical system of 1:100 has a FOV corresponding to an area of A/100, at least 100 shots may be required for defect inspection of an inspection object having an area of A. On the other hand, since the low magnification optical system of 1:10 has the FOV corresponding to the area A, it is possible to inspect the defect of the inspection object having the area A with only one shot. The low magnification optical system corrects distortion of an image caused by inclination of the surface of the object to be inspected with respect to the reflected light, so that the surface of the object to be inspected can be imaged parallel to the camera unit. For example, it may be implemented with a Scheimpflug optical system. The low magnification optical system may include at least one reflective mirror for changing a path of light or preventing distortion. The low magnification optical system can be implemented as a zoom lens system that can freely adjust the magnification from 1:1 to 1:M (1<M=100).

For reference, a system including a polarizer 11, a light corrector 12, and a polarization analyzer 14 like the measuring system 100 of the present invention is referred to as a PCSA ellipsometer system. Here, P may be a linear polarizer, C may be a light corrector, S may be a sample, and A may be a polarization analyzer. On the other hand, the measurement system 100 of the present invention is not limited to the PCSA elliptic system, but may be implemented as a PSA elliptical system, a PSCA elliptical system, or a PCSCA elliptical system. Furthermore, the measurement system 100 of the present invention may have a phase modulator instead of the optical corrector 12. When a phase modulator is employed, mechanical jitter can be eliminated to obtain accurate and stable inspection results.

The photo detector 15 detects an image of light polarized by the polarization analyzer 14. That is, the photo detector 15 acquires an optical image by capturing a pattern of polarized light output from the polarization analyzer 14. To this end, the photo detector 15 may include a camera unit. Here, the camera unit may be, for example, a CCD camera or a CMOS camera. The camera unit may include a high sensitivity first camera or a low sensitivity first camera.

The first camera may be a high sensitivity camera capable of detecting even a very weak signal. For example, the first camera may have an ISO (International Organization for Standardization) sensitivity of 3000 or higher. The first camera may be, for example, an Electron Multiplying CCD (EMCCD) camera or a Scientific CMOS (sCMOS) camera. Using such a high-sensitivity first camera, it is possible to detect very fine scattered light generated by a defect in a null condition.

The first camera may be sealed and disposed inside the box so that light from the outside may be completely blocked, and a shutter may be disposed in front of the entrance of the first camera. Such a shutter and box may be arranged to protect the pixels of the first camera sensitive to low light. For example, the shutter is closed when it is not in a null condition and is opened only when it is in a null condition, thereby protecting pixels from reflected light having strong intensity. For example, the shutter can only be opened at an illuminance of 0.05Lx or less. Of course, the open condition of the shutter is not limited to these values.

The second camera may be a general or low-sensitivity camera having a lower sensitivity than the first camera. The second camera may be used to obtain the null condition of the measurement system 100 of the present invention. Meanwhile, the first camera may be used together to more accurately obtain the null condition. For example, in the measurement for a null condition, the reflected light is measured through a second camera in the range of reflected light with strong intensity, and the reflected light is measured through the first camera with high sensitivity in the range of reflected light with relatively weak intensity close to the null condition. can do.

Meanwhile, the second camera used to obtain the null condition may be an area camera. In contrast, the first camera may be a line scan camera for high-speed inspection of an object to be inspected. Of course, the first camera may be an area step or area scan type camera.

The change detection unit 80 may be implemented by, for example, a computer. The change detection unit 80 may analyze information on the optical image input from the photo detector 15. For example, the change detection unit 80 may be a general personal computer (PC), a workstation, or a super computer equipped with an analysis process. The change detection unit 80 may determine whether a defect exists in the inspection object through analysis of the optical image. Here, the change detection unit 80 may be used as a computer to control the overall measurement system 100 of the present invention.

The change detection unit 80 calculates the ratio of the first brightness value for the first image of light reflected by the reference sample and the second brightness value for the second image reflected by the target sample, and the calculated ratio is constant. If there is a difference more than the value, it is detected that there is a slight change on the surface of the target sample.

That is, the change detection unit 80 firstly polarizes and corrects the light output from the light source and enters the reference sample, and the light reflected by the reference sample is linearly polarized to determine the first image of the light detected by the photodetector. 1 Calculate the stepping value.

Subsequently, the change detection unit 80 polarizes and corrects the light output from the light source and enters the target sample, and the light reflected by the target sample is polarized and the second brightness value for the second image of the light detected by the photo detector. Yields

Subsequently, the change detection unit 80 calculates a ratio of the first brightness value and the second brightness value, and determines whether the ratio between the first brightness value and the second brightness value differs by more than a predetermined value.

Accordingly, the change detection unit 80 detects that there is a minute change in the target sample when the ratio is different by more than a predetermined value.

3 is a view showing an example in which light polarized through a polarization generator according to an embodiment of the present invention is incident on a reference sample at a specific angle θ1.

3, the light output from the light source 10 is polarized by the polarizer 11 and corrected by the light corrector 12, and then at a specific angle θ1, for example, Brewster's angle or Brewster's angle. It is incident on the reference sample 13 at a close angle.

The light incident on the reference sample 13 is reflected from the reference sample 13 and comes out and is then input to the photo detector 15 through the polarization analyzer 14.

At this time, the polarizer 11 and the light corrector 12 adjust the angles of the polarizer 11 and the light corrector 12 so that the polarization state of the light reflected from the reference sample 13 is as close to linear polarization as possible.

In order to adjust the rotation angle with respect to the optical axis, the polarizer 11, the optical compensator 12, and the polarization analyzer 14 are installed on a rotation support (not shown) driven by a motor, and can rotate around the optical axis. have. The rotation of the polarizer 11, the optical compensator 12, and the polarization analyzer 14 may be a continuous rotation that rotates continuously, or a discontinuous rotation that rotates only predetermined angles. . In the inspection system 100 according to the embodiment of the present invention, the rotation of the polarizer 11, the light corrector 12, and the polarization analyzer 14 may be non-continuous rotation.

The polarizer 11 and the polarization analyzer 14 may be implemented as a wire-grid type or a Glan-Thompson type static linear polarizer. However, the present invention is not limited thereto, and the polarizer 11 and the polarization analyzer 14 may be implemented as electronic devices that can change the direction of polarization with an electric signal, such as a Faraday rotator. In addition, the optical compensator 12 may also be replaced with an electronic device controlled by an electric signal such as a piezoelectric phase modulator. When the polarizer 11, the light corrector 12, and the polarization analyzer 14 are implemented as electronic devices, the aforementioned rotation support for driving the motor may be omitted.

The light reflected from the reference sample 13 passes through the polarization analyzer 14 of the polarization analyzer 70, and finally, the photodetector 15 may measure the amount of light.

At this time, the angle of the polarization analyzer 14 is adjusted so that the amount of light detected by the photo detector 15 is the lowest.

If the light reflected from the reference sample 13 is linearly polarized, the amount of light of the photodetector 15 is zero.

When the Jones matrix is used to express the polarization operation of the polarization generator 60, the electric field E can be expressed as in Equation 1 below.

은 다음 수학식 2와 같이 나타낼 수 있다.Here, the matrix representing the part for the optical corrector 12

Can be expressed as in Equation 2 below.

The optical corrector 12 has a fast axis inclined by C with respect to the incident surface. Therefore, it rotates by C to generate a phase difference (δ) and rotates by -C with respect to the incident surface like the polarizer 11.

은 입사면 기준으로 P파와 S파에 대한 반사계수를 적용하여

로 표현된다.Also,

Is based on the incident surface by applying the reflection coefficient for P and S waves

Is expressed as

는 편광자(11)를 통과한 다음 선 편광된 빛을 나타낸다. 선 편광된 빛은 입사면에 대해 P만큼 기울어져 있다.In Equation 1,

Denotes linearly polarized light after passing through the polarizer 11. Linearly polarized light is inclined by P with respect to the incident surface.

로 표현될 수 있다.Since the light linearly polarized by the polarizer 11 is rotated by -P based on the incident surface,

It can be expressed as

은 기준시료(13)에서 반사되어 편광 분석자(14)를 통과한 빛에 대한 내용을 표현한 것이다. 즉, 기준시료(13)에서 반사된 P파와 S파를 편광 분석자(14)를 기준으로 판단하기 위하여 편광 분석자(14)의 위치각 A로 회전시킨 후 편광축 방향의 성분만 통과시킨 것이다.In Equation 1, the leftmost matrix

Represents the content of the light reflected from the reference sample 13 and passed through the polarization analyzer 14. That is, in order to determine the P-wave and S-wave reflected from the reference sample 13 based on the polarization analyzer 14, the polarization analyzer 14 rotates at the position angle A, and then passes only the components in the polarization axis direction.

By sequentially calculating these matrices, the strength E of the electric field can be obtained as shown in Equation 3 below.

는 편광자(11)을 통과한 전기장의 세기이고,

,

는 반사계수이다.

는 광 보정자(12)에 관련된 변수인데, 이상적인 광 보정자(12)의 경우 위상차만 발생시키므로, 다음 수학식 4와 같이 표현할 수 있다.here

Is the strength of the electric field passing through the polarizer 11,

,

Is the reflection coefficient.

Is a variable related to the optical corrector 12, and since the ideal optical corrector 12 generates only a phase difference, it can be expressed as in Equation 4 below.

로 정의하면, 빛의 밝기는 다음 수학식 5와 같이 표현할 수 있다.The brightness of light detected by the photodetector 15

If defined as, the brightness of light can be expressed as in Equation 5 below.

That is, the optical components of the polarization generator 60 are adjusted so that the light irradiated to the reference sample 13 is as close to the linear polarization as possible, and the polarization analyzer 14 of the polarization analyzer 70 is adjusted, and the photodetector ( If the amount of light detected in 15) is adjusted to be close to 0, it can be expressed as Equation 6 below.

For reference, the application range of those that can be used as the photodetector 15 is very wide.

As described above, when measuring by placing the reference sample 13 on the stage 50, the amount of light reflected by the reference sample 13 has a value close to zero.

That is, light incident on the reference sample 13 is reflected by the reference sample 13 and is input to the photodetector 15 through the polarization analyzer 14 of the polarization analyzer 70.

The photodetector 15 captures light incident from the polarization analyzer 14 to obtain a first image 13' as shown in FIG. 4. 4 is a diagram showing an image of light reflected by a reference sample and an image of light reflected by a target sample according to an embodiment of the present invention.

Accordingly, the first brightness value for the first image 13' of the light reflected by the reference sample 13 is zero or has a value close to zero.

Meanwhile, as shown in FIG. 2, on the stage 50 according to the embodiment of the present invention, a target sample 16 having a small difference from the reference sample 13 is placed, and then the amount of light is measured by the above-described process. I did.

In the photodetector 15, a 2D area camera was used, and half of the target sample 16 is the same as the reference sample 13, and the other half, unlike the reference sample 13, a thin film of about several tens of nm is deposited. In this case, it is assumed that a part of the target sample 16 has a defect.

The light output from the light source 10 is polarized by the polarizer 11 of the polarization generator 60 and corrected by the light corrector 12 to enter the target sample 16.

The light incident on the target sample 16 is reflected by the target sample and is input to the photodetector 15 through the polarization analyzer 14 of the polarization analyzer 70.

The photodetector 15 captures light incident from the polarization analyzer 14 to obtain a second image 16' as shown in FIG. 4.

The second brightness value for the second image 16' of the light reflected by the target sample 16 has a specific value other than 0 as shown in FIG. 4.

In the system 100 for measuring fine changes in the surface of a thin film according to an exemplary embodiment of the present invention, a small difference of several tens of nm can be distinguished because a sufficient difference in brightness occurs in the image as shown in FIG. 4.

In the embodiment of the present invention, when the sensitivity of the photo detector 15 is increased, the amount of light measured by the reference sample 13 is always 0, but in the case of the sample 16 to be measured slightly different from the reference sample 13, the photo detector ( According to the sensitivity of 15), the sensitivity to changes in the sample can be increased.

Meanwhile, in an embodiment of the present invention, in order to improve a narrow measurement area and a slow measurement speed, which is a problem of the existing SE (Spectroscopic Ellipsometry), the first telecentric lens 20 and the second telecentric lens ( 21) can be additionally configured.

5 is a diagram showing an example of additionally configuring a telecentric lens in measuring a reference sample according to an embodiment of the present invention, and FIG. 6 is a diagram illustrating an additional configuration of a telecentric lens in measuring a target sample according to an embodiment of the present invention. It is a diagram showing an example.

5 and 6, the system 100 for measuring fine changes in the surface of a thin film according to an exemplary embodiment of the present invention includes a first telecentric lens between the polarization generator 60 and the measurement samples 13 and 16. 20) is disposed, and a second telecentric lens 21 is disposed between the measurement samples 13 and 16 and the polarization analyzer 70.

That is, as shown in FIG. 5, the first telecentric lens 20 is disposed between the light corrector 12 of the polarization generator 60 and the reference sample 13, and the reference sample 13 and The second telecentric lens 21 is disposed between the polarization analyzers 14 of the polarization analyzer 70.

In addition, as shown in Fig. 6, the first telecentric lens 20 is disposed between the optical corrector 12 and the target sample 16, and between the target sample 16 and the polarization analyzer 14 The second telecentric lens 21 is disposed.

At this time, the first telecentric lens 20 is positioned between the light corrector 12 and the measurement samples 13 and 16, and converts the light corrected by the light corrector 12 to collimation light. The measurement samples 13 and 16 are irradiated.

The second telecentric lens 21 receives the light reflected by the measurement samples 13 and 16 and outputs only the plane light to the polarization analyzer 14.

In general, light emitted from a point light source is a spherical wave, and the direction of light vibration is not constant with respect to the direction of light. In most optical measurement methods, collimated light is used. Because collimated light is irrelevant even when viewed as a plane wave, it is advantageous in explaining polarization theoretically.

In the present invention, a telecentric lens was used as the first lens to irradiate the collimated light onto the sample. A telecentric lens was also used for the second lens that receives the light reflected from the sample.

That is, in an exemplary embodiment of the present invention, a large area telecentric lens is used, and a 2D area camera to which a large area sensor is applied as the photo detector 15 may detect minute changes in a measurement sample in a wide area.

The system 100 for measuring microscopic changes in the surface of a thin film according to an exemplary embodiment of the present invention is simply an imaging system and thus has a significantly higher measurement speed than other measurement methods. Therefore, when the measurement samples 13 and 16 are imaged through the photo detector 15, the same results as in FIG. 4 can be obtained.

7 is a diagram illustrating an example of measuring a reference sample through a telecentric lens according to an embodiment of the present invention.

Referring to FIG. 7, in the thin film surface minute change measurement system 100 according to an embodiment of the present invention, light output from the light source 10 is polarized by a polarizer 11, and After being corrected, it passes through the first telecentric lens 20. Therefore, the light passing through the first telecentric lens 20 is incident on the reference sample 13 in the form of a plane wave. At this time, the light incident on the reference sample 13 is incident at a Brewster angle θ1 or an angle close to the Brewster angle as shown in FIG.

The light reflected from the reference sample 13 passes through the second telecentric lens 21 in a form including a plane wave, and the light that has passed through the second telecentric lens 21 is a polarization analyzer ( 14) is entered. The polarization analyzer 14 linearly polarizes the light in the form of a plane wave that has passed through the second telecentric lens 21 and outputs it to the photo detector 15.

As described above, the thin-film surface micro-change measurement system 100 according to the present invention includes the first telecentric lens 20 and the second telecentric lens 21 at the front and rear ends of the measurement sample. (Double Side) It composes the telecentric imaging optical system.

However, since the light incident on the reference sample 13 is incident at the Brewster angle θ1 or at an angle close to the Brewster angle, as shown in FIG. 7, the following problems may occur.

First, the point at which the measurement specimens 13 and 16 are focused is changed. In general, the point of focus on the sample is formed horizontally on the lens surface or the sensor surface.

Here, the surface of the measurement sample is referred to as the object surface, the center surface of the second telecentric lens 21 is referred to as the lens surface, the incident surface of the photodetector 15 is referred to as the sensor surface, and the second telecentric lens The center point of (21) is called the lens center point, the center point of the photodetector 15 is called the sensor center point, and the point where the straight line connecting the lens center point and the sensor center point meets the object surface is called the reference point.

Therefore, in the system having an angle as shown in FIG. 7, the point of focus cannot be generated horizontally with the reference sample 13. In this case, if the sensor surface is tilted at a certain angle by applying the Scheim plug principle, focusing of the reference sample 13 within the lens field of view becomes possible. This is shown in Figure 8.

8 is a diagram showing an example of detecting light passing through a telecentric lens according to an embodiment of the present invention by applying the Scheimplug principle.

Referring to FIG. 8, in the system 100 for measuring microscopic changes in the surface of a thin film according to an embodiment of the present invention, the light reflected from the reference sample 13 is polarized only in the form of plane waves through the second telecentric lens 21. It is input to the analyzer 14, and the light in the form of a plane wave is linearly polarized by the polarization analyzer 14 and input to the photo detector 15.

At this time, when receiving the polarized light by the polarization analyzer 14, the photodetector 15 is rotated at the Scheimplug angle θ2 and rotated at the Scheimplug angle θ2 to satisfy the Scheimplug condition. A first image may be obtained by receiving the light polarized by the polarization analyzer 14 at.

In addition, when only plane light is incident on the polarization analyzer 14 by the second telecentric lens 21 from the light reflected by the target sample 16, and receives the polarized light by the polarization analyzer 14, The photodetector 15 is rotated at the Scheimplug angle θ2 to satisfy the Scheimplug condition, and receives the light polarized by the polarization analyzer 14 while being rotated at the Scheimplug angle θ2 to obtain a second image. Can be obtained.

That is, the center point of the lens is called the lens center point (Q), the center point of the sensor unit is called the sensor center point (P), and the point where the straight line connecting the lens center point (Q) and the sensor center point (P) meets the object surface is the reference point ( T), and the point that satisfies the Scheim plug condition is called the Scheim plug point (S), the angle between the object surface and the lens surface is called the optical system inclination angle (α), and the optical system from the state that the lens surface and the sensor surface are parallel. When the angle at which the sensor unit is to be rotated to satisfy the Scheim plug condition according to the inclination angle α is referred to as the Scheim plug angle θ, the Scheim plug angle θ can be calculated by Equation 7 below.

Here, θ is the Scheim plug angle, α is the optical system inclination angle, C is the distance between the reference point and the sensor center point, and R is the distance between the reference point and the Scheim plug point.

The Scheimplug condition is that if the object surface and the lens surface are not parallel and have a certain inclination angle, the extension lines of the object surface, lens surface, and sensor surface always intersect at one point. The object surface is a fixed surface, and therefore the Scheim plug condition can be satisfied by properly tilting the lens surface or the sensor surface. When the Scheimplug condition is satisfied, an image with good focus can be obtained even if the object surface and the lens surface are arranged obliquely.

When the distance between the reference point T and the lens center point Q is X, and the distance between the reference point T and the Scheimplug point S is R, the value of R can be expressed as Equation 8.

라 하고, 기준점(T) 및 센서중심점(P) 간 거리를 C라 할 때,

값은 제2코사인법칙에 따라 수학식 9와 같이 나타낼 수 있다.The distance between the sensor center point (P) and the Scheim plug point (S)

And when the distance between the reference point (T) and the sensor center point (P) is C,

The value can be expressed as Equation 9 according to the second cosine law.

의 연장선 및 C의 연장선이 이루는 각도를 β라 할 때, β 값은 다음 수학식 10과 같이 나타낼 수 있다.Meanwhile,

When the angle formed by the extension line of and the extension line of C is β, the value of β can be expressed as in Equation 10 below.

Substituting Equation 9 into Equation 10 and arranging for β, the following Equation 11 can be obtained.

In this case, if the Scheim plug angle θ is expressed as β, it can be expressed as in Equation 12 below.

Substituting Equation 11 into Equation 12 and arranging for θ, the value of the Scheimplug angle θ can be obtained through Equation 7 above.

On the other hand, since the light incident on the reference sample 13 is incident at an angle close to Brewster's angle (θ1) or Brewster's angle, as shown in FIG. 7, secondly, since the magnification difference occurs within the angle of view of the lens, Distortion occurs.

As shown in FIG. 7, when light is irradiated to the sample at an angle, the distances of the light reflected from the sample and traveling to the photodetector 15 vary.

This causes a difference in magnification and distortion of the image. In general, a telecentric lens is a lens designed to receive only parallel light among the reflected light from an object.

However, as in the above case, when a difference in distance occurs and a change in magnification occurs, distortion of the image occurs like other lenses. In this case, distortion of the image can be solved by using a lens that does not change the magnification of the image (image) as well as the object side.

That is, in FIG. 8, the first telecentric lens 20 and the second telecentric lens 21 do not have a magnification change even in the difference in working distance between the reference sample 13 or the target sample 16. It is to use a lens.

In the embodiment of the present invention, these two problems are solved by applying the Scheimplug principle and using a lens having no magnification change in the object side and the image (image) side.

9 is a diagram illustrating an operation flow chart for explaining a method of measuring fine changes on a surface of a thin film according to an embodiment of the present invention.

Referring to FIG. 9, the system 100 for measuring microscopic changes in the surface of a thin film according to an embodiment of the present invention first polarizes light output from a light source 10 to irradiate it on a reference sample 13, and reflects the light reflected by the reference sample. The first image 13 ′ of the detected light is obtained by linearly polarizing (S910).

That is, the light output from the light source 10 is polarized and corrected by the polarization generator 60 and incident on the reference sample 13, and the light reflected by the reference sample 13 is transmitted to the polarization analyzer 14. It is polarized by the photodetector 15 and is input to the photodetector 15 to obtain a first image 13' of the light detected by the photodetector 15.

The polarization generator 60 passes light in the direction of the polarization axis through the polarizer 11 with respect to the light output from the light source, absorbs the light in the direction of the extinction axis, and passes the light in the direction of the extinction axis. And corrected by generating a phase difference for the light in the direction of the slow axis.

Therefore, the light output from the polarization generator 60 is incident on the reference sample 13 at a Brewster angle or an angle close to the Brewster angle, and the light reflected by the reference sample 13 is linear by the polarization analyzer 14 The polarized light is input to the photodetector 15, and the first brightness value for the first image 13' of light detected by the photodetector 15 may be zero (0) or close to zero (0). .

Subsequently, the light output from the light source 10 is polarized to irradiate the target sample 16, and the light reflected by the target sample 16 is polarized to obtain a second image of the detected light (S920).

That is, the polarization generator 60 passes light in the polarization axis direction through the polarizer 11 with respect to the light output from the light source 10, absorbs the light in the extinction axis direction, and uses the optical corrector 12. Through this, a phase difference is generated and corrected for light in the fast axis direction and the slow axis direction.

Accordingly, the polarized and corrected light is incident on the target sample 16 at a Brewster angle or an angle close to the Brewster angle, and the light reflected by the target sample 16 is polarized by the polarization analyzer 14 and the photodetector 15 ), and to obtain a second image 16' of the light detected by the photo detector 15.

At this time, the polarized and corrected light output from the light source 10 is converted to collimation light by the first telecentric lens 20 and is incident on the target sample 16, and The reflected light is incident on the polarization analyzer 14 by the second telecentric lens 21, and is polarized by the polarization analyzer 14 and input to the photodetector 15. In the photodetector 15, A second image 16' of the detected light may be obtained.

In addition, the light reflected by the target sample 16 is incident on the polarization analyzer 14 by the second telecentric lens 21, and is polarized by the polarization analyzer 14 and input to the photodetector 915. do.

Here, the photodetector 15 is rotated at the Scheimplug angle to satisfy the Scheimplug condition, and the second image 16' of the detected light can be obtained from the photodetector 15 rotated at the Scheimplug angle.

The first telecentric lens 20 and the second telecentric lens 21 may be lenses in which magnification does not change even with a difference in working distance from the target sample 16.

Subsequently, a ratio of the first brightness value for the first image and the second brightness value for the second image is calculated (S930).

For example, when the first brightness value for the first image 13' is 0.0001 close to zero (0), and the second step value for the second image 16' is 5, the first brightness value The ratio of is 10,000 (1/0.0001), and the ratio of the second brightness value may be 0.2 (1/5).

Subsequently, when the ratio of the first brightness value and the second brightness value differs by more than a certain value, it is detected that there is a minute change in the target sample (S940).

Therefore, when the ratio of the first brightness value is 10,000 and the ratio of the second brightness value is 0.2 (1/5), the difference in the ratio is 50,000 times beyond the error range, so that the surface of the target sample 16 It can be detected that there is a slight change in.

As described above, according to the present invention, by setting a reference sample to be measured and detecting whether the surface state of the target sample to be inspected is the same as or not the same as the reference sample, defects in surface coating on a large-area thin film are prevented. It is possible to realize a system and method for measuring fine changes on the surface of a thin film that can be inspected in a short time.

Although the above has been described based on the embodiments of the present invention, various changes or modifications can be made at the level of a person of ordinary skill in the art to which the present invention belongs. Such changes and modifications can be said to belong to the present invention as long as it does not depart from the scope of the technical idea provided by the present invention. Accordingly, the scope of the present invention should be determined by the claims set forth below.

10: light source 11: polarizer
12: light corrector 13: reference sample
13': first image 14: polarization analyzer
15: photo detector 16: target sample
16': second image 50: stage
60: polarization generation unit 70: polarization analysis unit
80: change detection unit 100: thin film surface minute change measurement system

Claims (15)

(a) a polarization analyzer, wherein the light output from the light source is polarized and irradiated onto a reference sample, and linearly polarized light reflected by the reference sample to obtain a first image of the detected light;
(b) obtaining, by the polarization analysis unit, a second image of the detected light by polarizing the light output from the light source and irradiating it to a target sample and polarizing the light reflected by the target sample;
(c) calculating, by a change detector, a ratio of a first brightness value for the first image and a second brightness value for the second image; And
(d) detecting, by the change detection unit, that there is a minute change in the target sample when the ratio of the first brightness value and the second brightness value differs by more than a predetermined value;
Including,
When reflected and linearly polarized by the reference sample or the target sample in step (a), the electric field E is calculated according to the following equation,

The above equation for the operation of the optical corrector

Is calculated according to the following equation,

The optical compensator generates a phase difference (δ) by rotating a fast axis by C with respect to the incident surface, and rotates by -C with respect to the incident surface in the same manner as a polarizer,
In the above equation

Is applied the reflection coefficient for P and S waves based on the incident surface,
In the above equation

Represents linearly polarized light after passing through the polarizer,
In the above equation

Represents that the light linearly polarized by the polarizer is inclined by P with respect to the incident surface and is rotated by -P with respect to the incident surface,
In the above equation

Represents that only the components in the direction of the polarization axis are passed after rotating the P wave and S wave reflected from the reference sample at the position angle A of the polarization analyzer in order to determine based on the polarization analyzer,
The polarizer, the optical corrector, and the polarization analyzer are installed on a rotation support driven by a motor to rotate around an optical axis, but perform discontinuous rotation in which only predetermined angles are rotated,
The strength (E) of the electric field is calculated according to the following equation,

In the above equation

Is the strength of the electric field passing through the polarizer, and

And above

Is the reflection coefficient, above

Is a variable for the optical corrector,

And the brightness of light detected by the photodetector of the polarization analyzer (

) Is the equation

And the amount of light reflected by the reference sample is zero (0) or has a value close to zero (0).
The method of claim 1,
In the step (a), the light output from the light source is polarized and corrected by a polarization generator and incident on the reference sample, and the light reflected by the reference sample is polarized by a polarization analyzer and input to the photodetector. And obtaining the first image of the light detected by the photodetector.
The method of claim 2,
In the step (a), the light in the direction of the polarization axis is passed by the polarizer and the light in the direction of the extinction axis is absorbed, and the phase difference with respect to the light in the fast axis direction and the slow axis direction through the optical corrector. It is incident on the reference sample at an angle close to Brewster's angle or Brewster's angle after generating and correcting,
The light reflected by the reference sample is linearly polarized by a polarization analyzer and input to the photodetector, and the first brightness value of the light detected by the photodetector for the first image is zero (0) or zero (0). ) Having a value close to, a method of measuring fine changes on the surface of a thin film.
The method of claim 1,
In the step (b), in the light output from the light source, light in the polarization axis direction is passed by a polarizer, light in the extinction axis direction is absorbed, and a phase difference between the light in the fast axis direction and the slow axis direction through the optical corrector. It is incident on the target sample at an angle close to Brewster's angle or Brewster's angle after generating and correcting,
The light reflected by the target sample is polarized by a polarization analyzer and input to the photo detector, and the second image of the light detected by the photo detector is obtained.
The method of claim 1,
In the step (b), the polarized and corrected light output from the light source is converted into collimation light by a first telecentric lens and irradiated to the target sample,
Only planar light from the light reflected by the target sample is incident on a polarization analyzer by a second telecentric lens, polarized by the polarization analyzer, and input to the photodetector, and the second image of the light detected by the photodetector To obtain a thin film surface fine change measurement method.
The method of claim 5,
The step (b),
Only planar light from the light reflected by the target sample is incident on the polarization analyzer by the second telecentric lens, is polarized by the polarization analyzer, and input to the photodetector,
The photodetector is rotated at a Scheim plug angle to satisfy the Scheim plug condition,
Obtaining the second image of the light detected by the photodetector rotated at the Scheimplug angle, thin film surface fine change measurement method.
The method of claim 6,
The step (b),
The surface of the target sample is referred to as an object surface, the central surface of the second telecentric lens is referred to as a lens surface, the incident surface of the photodetector is referred to as a sensor surface, and the central point of the second telecentric lens is referred to as a lens. The center point is called a center point, the center point of the photodetector is called a sensor center point, and a point where a straight line connecting the lens center point and the sensor center point meets the object surface is called a reference point, an extension line of the object surface, an extension line of the lens surface, and The point where the extension line of the sensor surface satisfies the Scheim plug condition coincident is referred to as a Scheim plug point, and the angle formed by the object surface and the lens surface is referred to as an optical system tilt angle, and the lens surface and the sensor surface are parallel. When the angle at which the optical detector should be rotated to satisfy the Scheim plug condition according to the optical system inclination angle is referred to as the Scheim plug angle,
In a state in which the optical system inclination angle is 0 and the lens surface and the sensor surface are parallel, the photodetector is rotated so that the Scheim plug condition is satisfied, and the angle of the sensor surface is detected by the photodetector adjusted to the Scheimplug angle. A method of measuring a fine change on a thin film surface, obtaining the second image of one light.
The method of claim 6,
In the step (b), the Scheimplug angle is calculated by the following equation.

(Here, θ: Scheim plug angle, α: optical system inclination angle, C: distance between reference point and sensor center point, R: distance between reference point and Scheim plug point)
The method of claim 5,
The first telecentric lens and the second telecentric lens are lenses in which magnification does not change even with a difference in working distance from the target sample.
Light source;
A polarizer that polarizes the light output from the light source;
A light compensator for correcting the light polarized by the polarizer;
A stage in which a reference sample or a target sample into which the light corrected by the optical corrector is incident is arranged;
A polarization analyzer that polarizes and analyzes the light reflected by the reference sample or the target sample;
An optical detector for detecting an image of light polarized by the polarization analyzer; And
The light output from the light source is polarized and corrected to be incident on the reference sample, and the light reflected by the reference sample is linearly polarized and a first brightness value for a first image of light detected by the photo detector, and the light source The light output from is polarized and corrected to be incident on the target sample and the light reflected by the target sample is polarized to calculate the ratio of the second brightness value to the second image of the light detected by the photo detector, A change detector configured to detect that there is a fine change in the target sample when the ratio of the first brightness value and the second brightness value differs by more than a predetermined value;
Including,
The polarizer, the optical corrector, and the polarization analyzer are installed on a rotation support driven by a motor to rotate around an optical axis, but perform discontinuous rotation in which only predetermined angles are rotated,
When reflected by the reference sample or the target sample and linearly polarized, the electric field E is calculated according to the following equation,

In the above equation, for the operation of the optical corrector

Is calculated according to the following equation,

The optical compensator generates a phase difference (δ) by rotating a fast axis by C with respect to the incident surface and rotates by -C with respect to the incident surface in the same manner as the polarizer,
In the above equation

Is applied the reflection coefficient for P wave and S wave based on the incident surface,
In the above equation

Represents linearly polarized light after passing through the polarizer,
In the above equation

Represents that the light linearly polarized by the polarizer is inclined by P with respect to the incident surface and is rotated by -P with respect to the incident surface,
In the above equation

Represents that only the components in the direction of the polarization axis are passed after rotating the P wave and S wave reflected from the reference sample at the position angle A of the polarization analyzer in order to determine based on the polarization analyzer,
The strength (E) of the electric field is calculated according to the following equation,

In the above equation

Is the strength of the electric field passing through the polarizer, and

And above

Is the reflection coefficient, above

Is a variable for the optical corrector,

And the brightness of light detected by the photodetector of the polarization analyzer (

) Is the equation

And the amount of light reflected by the reference sample is zero (0) or has a value close to zero (0).
The method of claim 10,
The polarizer passes light in the polarization axis direction and absorbs light in the extinction axis direction to polarize the light output from the light source,
The optical corrector corrects the light polarized by the polarizer by generating a λ/4 phase difference with respect to the light in the fast axis direction and the slow axis direction,
The light corrected by the optical corrector is incident on the reference sample or the target sample at an angle close to Brewster's angle or Brewster's angle.
The method of claim 11,
The polarization analyzer linearly polarizes the light reflected by the reference sample and outputs the quenched light to the photo detector.
The method of claim 10,
A first telecentric lens positioned between the optical corrector and the target sample, converting the light corrected by the optical corrector into collimation light, and irradiating the target sample; And
A second telecentric lens for receiving the light reflected by the target sample and outputting only planar light to the polarization analyzer;
Thin film surface fine change measurement system further comprising a.
The method of claim 13,
The photo detector,
When only plane light is incident on the polarization analyzer by the second telecentric lens from the light reflected by the target sample, and receives the light polarized by the polarization analyzer, the Scheimplug angle is applied to satisfy the Scheimplug condition. A system for measuring fine changes on a thin film surface by receiving the light polarized by the polarization analyzer while being rotated and rotated at the Scheimplug angle to obtain the second image.
The method of claim 13,
The first telecentric lens and the second telecentric lens are lenses having no change in magnification even with a difference in working distance from the target sample.

Images