WO2021215621A1

WO2021215621A1 - Coaxial spectral imaging ellipsometer

Info

Publication number: WO2021215621A1
Application number: PCT/KR2020/019478
Authority: WO
Inventors: 박희재; 이승우
Original assignee: 서울대학교산학협력단
Priority date: 2020-04-23
Filing date: 2020-12-31
Publication date: 2021-10-28
Also published as: KR102316503B1

Abstract

The present invention relates to a coaxial spectral imaging ellipsometer. More particularly, a coaxial spectral imaging ellipsometer according to one embodiment of the present invention comprises: a light source; a light modulation unit for polarizing light from the light source and phase-delaying same; an objective lens for emitting, at a sample, the light modulated by the light modulation unit; an incident angle adjustment unit provided between the light source and the objective lens so as to emit the light at a specific position of the rear focal plane of the objective lens; a beam splitter for guiding the reflected beam reflected by the sample so that same changes path after passing through the objective lens; a polarization analyzer for analyzing the polarization of the reflected beam; a spectral image acquisition unit for acquiring a spectral image from the reflected beam; and a signal processing unit for extracting physical information about the sample by signal-processing the image acquired by the spectral image acquisition unit.

Description

Coaxial Spectral Imaging Ellipsometer

The present invention relates to a coaxial spectral imaging ellipsometer, and by using the properties of the back focal plane of an objective lens, a small number of light incident and reflected on a sample at a specific angle of incidence in a hardware structure composed of a coaxial optical system It relates to a coaxial spectral imaging ellipsometer, which enables accurate and simple acquisition of physical properties of a sample by acquiring a spectral ellipsometry image through a measurement sequence of

Among the thin film thickness measurement methods using optics, ellipsometry, which measures the thickness of a sample based on the polarization change characteristic of the sample, is known as the most accurate and precise thickness measurement method. The ellipsometer has an inclined incident reflection structure as shown in FIG. 1, and the polarization state generator (PSG), which is the incident stage, creates various polarizations and irradiates the sample, and the polarization state analyzer (PSA) By interpreting the reflected polarization, the change in polarization in the sample is measured. Through this process, the complex reflectance characteristic of the sample is measured, and the measured complex reflectivity is compared with the theoretical complex reflectivity (Δ, Ψ) calculated by changing the thickness and refractive index of the sample, and the theoretical thickness with the smallest error And the refractive index is calculated.

In applying such ellipsometry to industrial sites, the following four issues must be addressed. First, a small spot size and large area measurement technology through a high magnification optical system are required. The display industry is steadily developing with the goal of high resolution and large screen, and the size of the display pattern is getting smaller due to this trend, and accordingly, the demand for measurement of the fine pattern is also increasing. In order to meet these measurement requirements, a technology capable of measuring a large area while reducing the spot size by using a higher magnification optical system than before is required.

Next is the necessity of coaxial optical system configuration for high magnification application. Due to the short working distance and large numerical aperture of the high magnification lens, the oblique incident reflection structure of ellipsometry causes problems such as limited incidence angle and the risk of collision between the sample and the lens. As the magnification of the objective lens increases, the working distance becomes shorter and the numerical aperture increases, so it is difficult to apply a magnification of 10 times or more in an inclined incident reflection structure. We need a way to create the angle of incidence of light using

Next is the need for a spectral signal. The polarization characteristic of the thin film sample is a function of the incident angle and wavelength, and since the ellipsometer calculates the thickness by comparing the measurement signal and the theoretical signal, the greater the change in the measurement signal, the greater the sensitivity of the thickness measurement. Consequently, acquiring the spectral signal is advantageous for ellipsometer analysis. Finally, there is minimal polarization modulation driving. At the polarization generating stage, a polarizer or a phase retarder is mechanically rotated, or a polarization modulated for each measurement sequence is created using an electrically operated phase retarder. In the case of mechanical polarization modulation, a beam drifting error that changes the optical path occurs due to minute misalignment of optical components. This causes a phase error. As a result, in order to avoid this, it is necessary to reduce this error through minimal polarization modulation driving. The present invention intends to propose an ellipsometry capable of solving all of these issues.

The present invention has been devised to improve the above-described problems, and by using the property of the back focal plane of the objective lens to acquire a spectral image of the light entering the sample at a specific angle of incidence, the physical properties of the sample are accurately and conveniently acquired It is an object of the present invention to provide a coaxial spectral imaging ellipsometer that can do this.

The present invention uses a coaxial optical system, does not require a mechanical device for separately driving an optical modulator, and has an object to obtain a spectral image according to an incident angle to determine the physical properties of a sample.

A coaxial spectroscopic ellipsometer according to an aspect of the present invention includes: a light source; a light modulator for polarizing and retarding the light from the light source; an objective lens irradiating the light modulated by the light modulator to the sample; an incident angle adjustment unit provided between the light source and the objective lens to irradiate the light to a specific position of the rear focal plane of the objective lens; a beam splitter for guiding the reflected beam reflected on the sample to change a path after passing through the objective lens; a polarization analyzer that analyzes the polarization of the reflected beam; a spectral image acquisition unit for acquiring a spectral image from the reflected beam; and a signal processing unit for signal processing the image acquired by the spectral image acquisition unit to extract physical information of the sample.

In addition, the light modulator includes a polarization generator for polarizing the light from the light source, and a phase delayer for delaying the phase of the light polarized by the polarization generator, wherein the phase delayer is a multi-order phase delayer. Retarder) is preferred.

In addition, the spectral image acquisition unit consists of an imaging interferometer, the imaging interferometer, a light splitter for splitting the reflected beam; a first mirror for reflecting the beam of one side split from the splitter; It includes a second mirror that reflects the beam of the other side split from the splitter, and moves the first mirror or the second mirror to create an interference image due to path difference, and includes a camera for acquiring the interference image It is preferable to do

In addition, it is preferable that the spectral image acquisition unit includes a wavelength modulation filter and a camera provided with a plurality of individual filters for filtering a predetermined central wavelength, a hyperspectral camera, or a diffraction grating and a camera.

On the other hand, the coaxial spectroscopic ellipsometer according to another aspect of the present invention, a light source; a light modulator for polarizing and retarding the light from the light source; an objective lens irradiating the light modulated by the light modulator to the sample; a beam splitter for guiding the reflected beam reflected on the sample to change a path after passing through the objective lens; a polarization analyzer that analyzes the polarization of the reflected beam; a light selection unit for selecting light at a specific position on the back focal plane; a spectral image acquisition unit for acquiring a spectral image from the light selected by the light selection unit; and a signal processing unit for signal processing the image acquired by the spectral image acquisition unit to extract physical information of the sample.

Here, the light modulator includes a polarization generator for polarizing the light from the light source, and a phase delayer for delaying the phase of the light polarized by the polarization generator, wherein the phase delayer is a multi-order phase delayer. Retarder) is preferred.

Here, it is preferable to include a lens system for retreating the rear focal plane of the objective lens with respect to the reflected beam passing through the beam splitter, and the light selector selects light at a specific position on the retreated rear focal plane. .

Here, it is preferable that the light selector be an diaphragm for passing light at a specific point of the retracted back focal plane, or an optical fiber for transmitting light at the specific point.

Here, it is preferable that the light selector is an aperture provided on the rear focal plane of the objective lens to inject light at a specific position into the sample and pass the reflected beam reflected from the sample.

Here, the spectral image acquisition unit comprises an imaging interferometer, and the imaging interferometer includes: a light splitter for splitting the reflected beam; a first mirror for reflecting the beam of one side split from the splitter; It includes a second mirror that reflects the beam of the other side split from the splitter, and moves the first mirror or the second mirror to create an interference image due to path difference, and includes a camera for acquiring the interference image It is preferable to do

Here, it is preferable that the spectral image acquisition unit comprises a wavelength modulation filter and a camera provided with a plurality of individual filters for filtering a predetermined central wavelength, a hyperspectral camera, or a diffraction grating and a camera.

The coaxial spectral image ellipsometer according to the present invention acquires a spectral image with respect to the light that enters the sample at a specific angle of incidence by using the property of the back focal plane of the objective lens to accurately, simply and quickly acquire the physical properties of the sample. make it possible In particular, the present invention uses a coaxial optical system, does not require a mechanical device for separately driving the light modulator, and provides an effect of quickly and accurately acquiring the physical properties of a sample by acquiring a spectral image according to an incident angle.

1 is a conceptual diagram of a conventional ellipsometer;

2 is a view showing an ellipsometer according to an aspect of the present invention;

Figure 3 is a view showing another embodiment of Figure 2;

4 is a view showing the action of the rear focal plane of the objective lens;

5 is a view showing an ellipsometer according to another aspect of the present invention;

Figure 6 is a view showing another example of the lens system in Figure 5;

7 is a view showing another example of the light selection unit in FIG. 6;

Fig. 8 shows an example of an diaphragm disposed on the rear focal plane of the objective lens.

Embodiments of the present disclosure are exemplified for the purpose of explaining the technical spirit of the present disclosure. The scope of the rights according to the present disclosure is not limited to the embodiments presented below or specific descriptions of these embodiments.

All technical and scientific terms used in this disclosure have the meanings commonly understood by one of ordinary skill in the art to which this disclosure belongs, unless otherwise defined. All terms used in the present disclosure are selected for the purpose of more clearly describing the present disclosure and not to limit the scope of the present disclosure.

As used in this disclosure, expressions such as "comprising", "including", "having", etc. are open-ended terms connoting the possibility of including other embodiments, unless otherwise stated in the phrase or sentence in which the expression is included. (open-ended terms).

Expressions in the singular described in this disclosure may include plural meanings unless otherwise stated, and the same applies to expressions in the singular in the claims.

Hereinafter, embodiments will be described with reference to the accompanying drawings. In the accompanying drawings, identical or corresponding components are assigned the same reference numerals. In addition, in the description of the embodiments below, overlapping description of the same or corresponding components may be omitted. However, even if descriptions regarding components are omitted, it is not intended that such components are not included in any embodiment.

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

FIG. 2 is a view showing an ellipsometer according to an aspect of the present invention, and FIG. 3 is a view showing another embodiment of FIG. 4 is a view showing the action of the rear focal plane of the objective lens. 5 is a view showing an ellipsometer according to another aspect of the present invention, FIG. 6 is a view showing another example of the lens system in FIG. 5, and FIG. 7 is another example of the optical selector in FIG. It is a drawing.

As shown in FIG. 2, the coaxial spectral imaging ellipsometer according to an embodiment of the present invention includes a light source 10, a light modulator 20, an objective lens 30, an incident angle control unit 40, and a beam splitter. 50 , a polarization analyzer 60 , a spectral image acquisition unit 70 , and a signal processing unit 80 .

The light source 10 is provided to emit light. The light source 10 is a white light source 10 is used. In this embodiment, a broad-band spectrum light source is used as the light source 10 . Of course, the light source 10 of a single wavelength may be used. As the light source 10 , various sources such as a tungsten-halogen lamp and a Xe lamp may be used.

The light modulator 20 is provided to polarize and phase retard the light from the light source 10 . According to the present embodiment, the light modulator 20 includes a polarization generator 21 that polarizes light from the light source 10 and a phase retarder 22 that delays the phase of light by the polarization generator 21 . ) is included.

The polarization generator 21 polarizes the light source 10 into light having a specific component before passing through the phase retarder 22 provided at the rear end of the polarization generator 21 . The light source 10 is linearly polarized by the polarization generator 21 . The light source 10 is polarized by the polarization generator 21 because polarized light is required to modulate a component of the light to a high frequency using a phase delay.

The phase retarder 22 is provided to delay the phase of the light polarized by the polarization generator 21 . According to this embodiment, the phase retarder 22 is a multi-order retarder. The multi-order retarder is a phase retarder 22 in which the p-wave and the s-wave create a phase delay of one wavelength or more with respect to each other.

The light modulator 20 having the polarization generator 21 and the phase delay unit 22 polarizes light without a separate driving device for light modulation, and generates a phase delay of 1 wavelength or more, thereby generating a sample according to a wavelength. A signal related to Ψ (amplitude ratio of P wave and S wave) and Δ (phase difference between P wave and S wave) of (100) plays a role of being modulated into a high frequency signal in the wavelength domain.

The objective lens 30 irradiates the light modulated by the light modulator 20 to the sample 100 . After passing through the objective lens 30 , the light irradiated to the sample 100 is reflected from the sample 100 and passes through the objective lens 30 again.

The incident angle control unit 40 is provided between the light source 10 and the objective lens 30 to irradiate the light to a specific position of the rear focal plane BP of the objective lens 30 . The incident angle adjusting unit 40 is implemented using a collimated beam and a lens so that the light source 10 is irradiated only to a specific position selected on the back focal plane BP, or a spatial light modulator (SLM, beam projector, etc.) ) may be used to irradiate light to a specific position of the back focal plane BP.

As shown in FIG. 4 , the light irradiated to a specific position of the back focal plane BP passes through the objective lens 30 and enters the sample 100 at the same incident angle. Accordingly, the incident angle adjusting unit 40 irradiates light to the sample 100 at a specific angle of incidence by allowing the light to be irradiated to a specific position of the back focal plane BP of the objective lens 30 . As shown in FIG. 2 , the incident angle adjusting unit 40 is provided between the light modulating unit 20 and the beam splitter 50 . In addition, as shown in FIG. 3 , the incident angle adjusting unit 40 may be provided between the light source 10 and the light modulating unit 20 .

The beam splitter 50 induces the reflected beam reflected by the sample 100 to change a path after passing through the objective lens 30 . According to this embodiment, the beam splitter 50 is provided at the front end of the objective lens 30 . The light source 10 is incident on the sample 100 through the beam splitter 50 and the objective lens 30, and the reflected beam reflected from the sample 100 is the objective lens 30 and the beam splitter. It proceeds to the spectral image acquisition unit 70 through (50).

The polarization analyzer 60 is provided to analyze the polarization of the reflected beam passing through the back focal plane BP. According to this embodiment, the reflected beam enters the polarization analyzer 60 after passing through the beam splitter 50 . The polarization analyzer 60 can use substantially the same polarizer as the polarization generator 21, and in terms of its function, the polarization generator 21 functions to generate polarized light, and the polarization analyzer 60 converts the polarized light. interprets it.

The spectral image acquisition unit 70 is provided to acquire a spectral image from the reflected beam. According to this embodiment, the reflected beam passes through the polarization analyzer 60 and then proceeds to the spectral easy acquisition unit 70 . Of course, the spectral image acquisition unit 70 may be implemented in a form in which the functions of the polarization analyzer 60 are integrated. For example, the spectral image acquisition unit 70 may be implemented to analyze a different polarization state for each pixel of the camera using a polarization camera.

The light irradiated to a specific position of the back focal plane BP travels to the sample 100 at the same incident angle, is reflected from the sample 100, and is again collected on the back focal plane BP. The spectral image acquisition unit 70 acquires data on the incident angle for each wavelength by imaging the back focal plane BP. A lens is provided at the front or rear end of the polarization analyzer 60 at the front end of the spectral image obtaining unit 70 so that the spectral image obtaining unit 70 can see the image of the rear focal plane BP.

According to the present embodiment, the spectral image acquisition unit 70 is composed of an imaging interferometer. Specifically, the imaging interferometer includes a light splitter 71 , a first mirror 72 , a second mirror 73 , and a camera 74 .

The light splitter 71 splits the reflected beam. The first mirror 72 reflects one side of the beam split from the light splitter 71 . The second mirror 73 reflects the other side of the beam split from the light splitter 71 . By moving the first mirror 72 or the second mirror 73, a path difference of the beam split through the light splitter 71 is generated. The beams reflected by the first mirror 72 and the second mirror 73 go back to the light splitter 71 to form an interference image. The camera 74 acquires the interference image. As in the present embodiment, when an interferometer is used, there is an effect that the calculation steps required for measurement can be reduced due to the Fourier relationship between the reflected light signal and the interfering light signal.

According to this embodiment, the spectral image acquisition unit 70 has moved the imaging interferometer, but it can be implemented using a plurality of wavelength modulation filters or an acousto-optic tunable filter (AOTF) and a mono camera. . In this case, there is convenience in hardware configuration, and a spectral image can be acquired by simple driving.

In the plurality of wavelength modulation filters, a plurality of individual filters for filtering a predetermined central wavelength band are provided in the circumferential direction, and are rotated to transmit light of a wavelength corresponding to the filter among multi-wavelength light. The spectral image acquisition unit 70 may be implemented as a camera that acquires images of the plurality of wavelength modulation filters and light passing therethrough. The plurality of wavelength modulation filters may be disposed between the light source 10 and the beam splitter 50 or disposed at a rear end of the beam splitter 50 based on an optical path.

The acousto-optic modulation filter uses a wavelength modulator capable of wavelength modulation, such as a variable filter or a linear variable filter through an acoustic or electrical signal, to filter the light corresponding to the filter among multi-wavelength light. The spectral image acquisition unit 70 may be implemented as a camera that acquires an image of the acousto-optic modulation filter and the light passing therethrough. The acousto-optic modulation filter may be disposed between the light source 10 and the beam splitter 50 or disposed at a rear end of the beam splitter 50 based on an optical path.

In addition, the spectral image acquisition unit 70 may be implemented through an imaging spectrometer using a diffraction grating, or a hyperspectral camera or a multi-channel spectral camera may be used.

In the diffraction grating, a phase is divided for each wavelength while the reflected beam is transmitted (transmissive diffraction grating) or reflected (reflective grating). image can be obtained. Accordingly, the spectral image acquisition unit 70 may be implemented as a transmission-type diffraction grating and a camera, or a spray-type diffraction grating and a camera.

In the hyperspectral camera, unlike a general mono camera or RGB color camera, since the image pixels constituting one pixel can receive various wavelengths by dividing, the spectral easy support acquisition unit 70 is implemented by the hyperspectral camera can be

The signal processing unit 80 extracts the physical information of the sample 100 by signal processing the image acquired by the spectral image acquisition unit 70 . Specifically, the signal for each pixel of the image of the sample 100 obtained by the spectral image acquisition unit 70 is obtained by performing Fourier transform by the signal processing unit 80 to separate the low-frequency signal and the high-frequency signal, , by performing an inverse Fourier transform on each of the low-frequency signal and the high-frequency signal, it is possible to extract physical signals for the amount of incident light and reflectivity of the sample 100 in real time.

Hereinafter, the operation or effect of the coaxial spectroscopic imaging ellipsometer according to the above configuration will be described in detail.

As shown in FIG. 2 , the light from the light source 10 is polarized while passing through the polarization generator 21 of the light modulator 20 , and the P wave and S wave passing through the phase delay unit 22 . A phase delay occurs. The modulated light is irradiated to a specific position of the rear focal plane BP of the objective lens 30 by the incident angle adjusting unit 40 . Since the light incident on the sample 100 at a specific position of the back focal plane BP is incident at a specific angle of incidence, the reflected beam reflected from the sample 100 is the sample 100 when the wavelength is incident at a specific angle of incidence. Physical properties are reflected. The reflected beam enters the spectral image acquisition unit 70 through the beam splitter 50 and the polarization analyzer 60 .

The spectral image acquisition unit 70 acquires an image containing physical information of the sample 100 according to a specific incident angle with respect to the wavelength, and the signal processing unit 80 includes the spectral image acquisition unit 70 loaded on the acquired image. By performing Fourier transform on the signal, the low frequency and high frequency signals for the reflected beam are separated and obtained, and the inverse Fourier transform is performed on each of these to measure information about the incident angle and physical information of the sample 100 .

For example, when the polarization generator 21 of the light modulator 20 is aligned at 0° and the phase retarder 22 is disposed at 45°, incident according to the incident wavelength (σ=1/λ) The reflected light I(σ) with respect to the amount of light I ₀ (σ) is expressed by the grinding equation of the Mueller matrix and the Stokes vector, and it is summarized as follows.

[Equation 1]

I(σ)= {I ₀ (σ)/4}{1- cos(2Ψ)cos(Φ(σ)) + sin(2Ψ)sin(Δ)sin(Φ(σ))}

Here, Ψ is the amplitude ratio of the P wave and the S wave, Δ is the phase difference between the P wave and the S wave,

Φ(σ) = 2πσΔn d , d is the thickness of the birefringence retarder 22 , and Δn is the birefringence of the retarder 22 .

Equation 1 can be simply expressed as Equation 2 as follows.

[Equation 2]

I(σ) = a ₀ + a ₁ cos(Φ(σ)) + b ₁ sin(Φ(σ))

Multi-order retarder retardance

Expressed as, I(σ) of Equation 2 is Fourier transform (

) is expressed as:

As a result, the signal processing unit 80, after the Fourier transform of the reflected light I(σ), includes the DC component A ₀ (h), the real part of the signal shifted by L (A ₁ (hL)), and the imaginary number. A signal can be obtained by separating each part (B ₁ (hL)), and through the inverse Fourier transform for each _{, information on the incident light I 0} (σ), cos(2Ψ) and sin(2Ψ)sin(Δ) ), it is possible to calculate physical information (thickness, refractive index, etc.) about the sample 100 .

As such, the coaxial spectral imaging ellipsometer according to the embodiment of the present invention irradiates light to a specific position of the back focal plane BP of the objective lens 30 to be incident on the sample 100 at a specific angle of incidence, The optical system may have a coaxial optical system, and for this reason, the spatial resolution may be improved by using the high magnification objective lens 30 having a short working distance.

In addition, according to the embodiment of the present invention, a multi-order retarder is used as the phase delay 22 to modulate the Ψ, Δ signal according to the wavelength of the sample 100 into a high frequency signal in the wavelength domain, so that a separate mechanical or Overcoming the disadvantage of generating a phase delay by electrical drive.

Specifically, when the phase delay element 22 is mechanically rotated to perform polarization modulation, an error may occur due to a change in the optical path due to minute misalignment of the optical component. In addition, when the optical component is accompanied by a mechanical movement, a considerable time is required for driving or stabilizing the measuring device, and the present invention can shorten the mechanical driving or stabilization time to speed up the measurement.

In the case of electrical polarization modulation, an anchoring layer is formed for the restoring force of liquid crystal, and an error occurs in the actual polarization phase delay amount, which results in a change in the optical path to reduce the amount of light, or the intended amount. The phase delay may not occur as much as that. Embodiments of the present invention do not suffer from the disadvantages of electrical polarization modulation.

In addition, according to the embodiment of the present invention, since the pattern of the sample 100 of a large area can be imaged by the spectral image acquisition unit 70, the measurement time is shortened and the convenience is improved. Recently, since the sample 100 in the semiconductor field is highly integrated and the patterns are becoming more complex, the spatial resolution is increased by the imaging method to provide the effect that a signal can be analyzed for each pixel.

In addition, according to the embodiment of the present invention, the image acquired by the spectral image acquisition unit 70 is processed and analyzed by the signal processing unit 80 . In particular, since the signal processing unit 80 can analyze the multi-wavelength light source 10 , the accuracy and precision of the physical information of the sample 100 can be improved. More specifically, the ellipsometer compares the measured polarization signal (Ψ _m , Δ _m _{) with the theoretical signal ( Ψ t} , Δ _t ) calculated through the reflectance theory fitted to the sample (100) properties and uses a nonlinear fitting to compare the sample desired physical information (thickness of the thin film, refractive index, shape of the sample 100, etc.) is calculated. Since the measured polarization signal is a function of the wavelength of light, the angle of incidence, etc., it is more effective to analyze the multi-wavelength light source 10 in the nonlinear fitting process, and the coaxial spectral imaging ellipsometer according to this embodiment is a multi-wavelength light source ( 10) to enable the analysis.

On the other hand, as shown in FIG. 5, the coaxial spectral imaging ellipsometer according to another aspect of the present invention includes a light source 10, a light modulator 20 for polarizing and phase delaying light from the light source 10, An objective lens 30 irradiating the light modulated by the light modulator 20 to the sample 100, provided between the light modulator 20 and the objective lens 30, to the sample 100 A beam splitter 50 that guides the reflected reflected beam to change the path after passing through the objective lens 30, and a polarization analyzer 60 that analyzes the polarization of the reflected beam passing through the beam splitter 50 , a lens system 90 for retreating the rear focal plane of the objective lens 30 with respect to the reflected beam passing through the beam splitter 50, and a light for selecting light at a specific position on the retreated rear focal plane A selection unit 110, a spectral image acquisition unit 70 for acquiring a spectral image from the light selected by the light selection unit 110, and signal processing the image acquired by the spectral image acquisition unit 70, and a signal processing unit 80 for extracting physical information of the sample 100 .

In the embodiment according to Fig. 5, the same reference numerals are given to components performing the same operations as those of Fig. 5, and detailed descriptions thereof are omitted. 5, the light source 10, the light modulator 20, the objective lens 30, the beam splitter 50, the polarization analyzer 60, the spectral image acquisition unit 70, and the signal processing unit Reference numeral 80 is substantially the same in terms of construction and operation according to the embodiment of Fig. 2 .

The light modulator 20 includes a polarization generator 21 for polarizing the light from the light source 10 and a phase retarder 22 for delaying the phase of the light polarized by the polarization generator 21 . Also, the phase retarder 22 is a multi-order retarder 22, which is the same as in FIG. 2 .

According to this embodiment, unlike the embodiment of FIG. 2 , the light selection unit 110 is included. In this embodiment, when all light rays originating from a specific position on the back focal plane of the objective lens 30 are incident on the sample 100 at the same angle of incidence and reflected, the back focal point by the light selector 110 Physical information of the sample 100 is calculated by selecting the light that has passed a specific position on the surface, imaging, and signal processing.

Therefore, if the embodiment of Fig. 2 is a method of irradiating light to a specific position of the back focal plane, the embodiment of Fig. 5 irradiates the multi-wavelength light source 10 to the sample 100, and the lens system 90 and the light selection This is a method of selecting a reflected beam at a specific position of the back focal plane BP by using the unit 110 .

According to this embodiment, a lens system 90 is included. The lens system 90 retreats the rear focal plane BP of the objective lens 30 with respect to the reflected beam passing through the beam splitter 50 . As shown in FIG. 5, the lens system 90 retracts the rear focal plane of the objective lens 30 using a 4f lens system using a plurality of lenses to form a secondary rear focal plane, or As shown, the second back focal plane may be formed by retreating the back focal plane using the relay lens system. Of course, the lens system 90 is not limited to the above, and an optical system capable of retracting the rear focal plane of the objective lens 30 is sufficient.

The light selection unit 110 is provided to select light at a specific position on the retracted rear focal plane. The light selection unit 110 selects the light entering the sample 100 at a specific incident angle by selecting the light at a specific position of the retracted back focal plane. The light selected by the optical selection unit 110 is provided to the polarization analyzer 60 , the spectral image acquisition unit 70 , and the signal processing unit 80 provided at the rear end of the optical selection unit 110 . The process in which the spectral image acquisition unit 70 and the signal processing unit 80 extracts physical information about the sample 100 is as described above.

As shown in FIG. 5 or 6 , the light selection unit 110 may be an diaphragm 110 that allows light to pass through a specific point of the retracted rear focal plane. In addition, as shown in FIG. 7 , the light selection unit 110 may be an optical fiber 110 ′ that transmits light at a specific point.

In addition, according to another embodiment of the present invention, the light selector 110 is provided on the back focal plane BP of the objective lens 30 to inject light at a specific position into the sample 100 , and It may be implemented as an aperture 120 that passes the reflected beam reflected from the sample. 8 shows an example of the diaphragm 120 . Light at a characteristic position through the incident unit 121 of the stop 120 is incident on the sample 100 through the objective lens 30 , and the reflected beam reflected by the sample 100 passes through the transmission unit 122 . , it is possible to select light entering at a specific angle of incidence.

Since this method selects a reflected beam at a specific position of the back focal plane BP of the objective lens 30 , there is a similarity in terms of selecting light for a specific incident angle. The light thus selected is provided to the polarization analyzer 60 , the spectral image acquisition unit 70 , and the signal processing unit 80 .

As described above, according to the present embodiment, light is selected at a specific position from the reflected beam that enters and is reflected at a specific angle of incidence with respect to the sample 100. Compared with the embodiment of FIG. 2 , information on the reflected beam at a specific angle of incidence is selected. There is a similar aspect in terms of securing In this embodiment, the configuration and operation of the light modulator 20 , the spectral image acquisition unit 70 , and the signal processing unit 80 are the same as those of the embodiment of FIG. 2 . Accordingly, the present embodiment can provide the same effects as those of the embodiment of FIG. 2 .

In the above, the present invention has been described in detail with reference to preferred embodiments, but the present invention is not limited to the above embodiments, and various modifications may be provided without departing from the scope of the present invention.

[Explanation of code]

10... Light source 20... Light modulator

21... Polarization generator 22... Phase delay

30... Objective lens 40... Incident angle control unit

50... Beam splitter 60... Polarization analyzer

70... Spectral image acquisition unit 71... Optical splitter

72... first mirror 72... second mirror

73... Camera 80... Signal processing unit

90... lens system 100... sample

110, 110'... Optical selector 120... Aperture

121... Incident 122... Transmissive

Claims

light source;

a light modulator for polarizing and retarding the light from the light source;

an objective lens irradiating the light modulated by the light modulator to the sample;

an incident angle adjustment unit provided between the light source and the objective lens to irradiate the light to a specific position of the rear focal plane of the objective lens;

a beam splitter for guiding the reflected beam reflected on the sample to change a path after passing through the objective lens;

a polarization analyzer that analyzes the polarization of the reflected beam;

a spectral image acquisition unit for acquiring a spectral image from the reflected beam; and

and a signal processing unit for signal processing the image acquired by the spectral image acquisition unit to extract physical information of the sample.
According to claim 1,

The light modulator comprises a polarization generator for polarizing the light from the light source, and a phase delayer for delaying the phase of the light polarized by the polarization generator,

The phase retarder is a coaxial spectral imaging ellipsometer, characterized in that the multi-order retarder (Multi-order retarder).
According to claim 1,

The spectral image acquisition unit consists of an imaging interferometer,

The imaging interferometer,

a light splitter for splitting the reflected beam;

a first mirror for reflecting the beam of one side split from the splitter;

Includes; a second mirror that reflects the beam of the other side split from the splitter, and moves the first mirror or the second mirror to create an interference image due to a path difference,

Coaxial spectral imaging ellipsometer comprising a camera for acquiring the interference image.
According to claim 1,

The spectral image acquisition unit,

It consists of a wavelength modulation filter and a camera in which a plurality of individual filters for filtering a predetermined central wavelength are provided, or

consisting of a hyperspectral camera; or

A coaxial spectral imaging ellipsometer comprising a diffraction grating and a camera.
light source;

a light modulator for polarizing and retarding the light from the light source;

an objective lens irradiating the light modulated by the light modulator to the sample;

a beam splitter for guiding the reflected beam reflected by the sample to change a path after passing through the objective lens;

a polarization analyzer that analyzes the polarization of the reflected beam;

a light selection unit that selects light at a specific position on the back focal plane;

a spectral image acquisition unit for acquiring a spectral image from the light selected by the light selection unit; and

and a signal processing unit for signal processing the image acquired by the spectral image acquisition unit to extract physical information of the sample.
6. The method of claim 5,

The light modulator comprises a polarization generator for polarizing the light from the light source, and a phase delayer for delaying the phase of the light polarized by the polarization generator,

The phase retarder is a coaxial spectral imaging ellipsometer, characterized in that the multi-order retarder (Multi-order retarder).
6. The method of claim 5,

a lens system for retreating the rear focal plane of the objective lens with respect to the reflected beam passing through the beam splitter,

The coaxial spectral imaging ellipsometer, characterized in that the light selector selects the light at a specific position of the retracted back focal plane.
8. The method of claim 7,

The optical selector,

A coaxial spectral imaging ellipsometer, characterized in that it is an diaphragm passing light at a specific point of the retracted back focal plane, or an optical fiber transmitting light at the specific point.
6. The method of claim 5,

The optical selector,

Coaxial spectral imaging ellipsometer, characterized in that provided in the back focal plane of the objective lens, the diaphragm for incident light at a specific position to the sample and passing the reflected beam reflected from the sample.
6. The method of claim 5,

The spectral image acquisition unit consists of an imaging interferometer,

The imaging interferometer,

a light splitter for splitting the reflected beam;

a first mirror for reflecting the beam of one side split from the splitter;

Includes; a second mirror that reflects the beam of the other side split from the splitter, and moves the first mirror or the second mirror to create an interference image due to a path difference,

Coaxial spectral imaging ellipsometer comprising a camera for acquiring the interference image.
6. The method of claim 5,

The spectral image acquisition unit,

It consists of a wavelength modulation filter and a camera in which a plurality of individual filters for filtering a predetermined central wavelength are provided, or

consisting of a hyperspectral camera; or

A coaxial spectral imaging ellipsometer comprising a diffraction grating and a camera.