High-resolution ellipsometric microscope and measuring method using same

Abstract

An ellipsometric microscope, according to an embodiment of the present invention, may comprise: a light source unit for emitting light that has a polarization distribution to a specimen; a combination of beam splitters including one or more beam splitters so as to transmit and reflect light without causing a change in polarization; an objective lens for focusing light that has passed through the beam splitters and directing same onto the specimen; and a detection unit including a circular polarization camera in which two adjacent pixels are covered by different polarizer patterns, and receiving light that has been reflected from the specimen and computing an image.

Description

High-resolution ellipsometry microscope and measurement method using the same

[0001] The present invention relates to an imaging ellipsometer or an ellipsometric microscope. Specifically, it relates to an ellipsometric microscope capable of high-resolution measurement and the operation thereof.

[0002] An ellipsometer is a device that measures ellipsometric parameters—which are the amount of change in polarization state that occurs when light is reflected or transmitted through a specimen—and analyzes them to derive the characteristics of the specimen. In particular, this device exhibits high sensitivity to minute differences in the thickness of thin films. Therefore, if an imaging optical system is introduced to this device, it becomes an imaging ellipsometer or an ellipsometric microscope, which can be used as a microscope for observing thickness distributions. Furthermore, by analyzing an image composed of ellipsometric parameters (ellipsometric image), it can be converted into an image composed of thickness values.

[0003] FIG. 1 is an example of an optical system constituting a conventional elliptical analysis microscope. First, structurally, an optical system composed of a light source (300) and a detector (500) forms a specific angle of incidence (θ) centered on the specimen. Light emitted from a monochromatic light source (100) is made linear by a collimation lens (110) and becomes linearly polarized as it passes through a polarizer (120). This light changes its polarization state as it is reflected from the specimen (140) through a focusing lens (130). The light reflected from the specimen (140) passes through an imaging lens (150), a quarter-wave plate (160), and an analysis polarizer (170), and then forms an optical image on a camera (190) by a tube lens (180). A low-magnification lens with a long working distance (WD) is used as the imaging lens (150) due to interference with the specimen.

[0004] In the conventional elliptical analysis microscope of Fig. 1, the imaging lens (150) is tilted relative to the specimen, and the optical component must be rotated for measurement, so the following disadvantages may occur.

[0005] First, if the working distance (WD) between the specimen (140) and the imaging lens (150) becomes short, they will collide with each other. Therefore, a high-resolution objective lens with a working distance (WD) of a few mm or less cannot be used as the imaging lens (150).

[0006] Second, since the imaging lens (150) is tilted, a distorted image is measured. That is, the ratio of the left and right lengths of the measured image is different, perspective occurs within the measured image, and there are parts that are out of focus depending on the perspective.

[0007] Third, a control device for rotating the polarizer (120), quarter-wave plate (160), or analysis polarizer (170) is required, and the measurement time is extended by the rotation time.

[0008] Fourth, due to mechanical shaking (wobbling phenomenon) accompanying the rotation of optical components, shaking occurs between optical images measured according to the rotation angle. Therefore, the spatial resolution of the elliptical analysis image, which is calculated by mathematically overlapping these optical images, is degraded. In particular, when using a high-magnification objective lens, the degree of resolution degradation is amplified by the magnification.

[0009] To solve the aforementioned problems, the present invention aims to provide an elliptical analysis microscope comprising a light source, a combination of beam splitters, a high-resolution objective lens, and a detection unit that calculates an image based on the polarization distribution of reflected light, including a circular polarization camera in which two adjacent pixels are each covered with different polarizer patterns.

[0010] An elliptical analysis microscope according to one embodiment of the present invention may include a light source unit that irradiates light having a polarization distribution onto a specimen, a combination of beam splitters that transmits and reflects light including one or more beam splitters, an objective lens that concentrates and irradiates light passing through the beam splitters onto a specimen, and a detection unit that receives light reflected from a specimen and produces an image, including a circular polarization camera in which two adjacent pixels are each covered with different polarizer patterns.

[0011] According to one embodiment, a circular polarization camera may be characterized in that, among two adjacent pixels, one measures left-circular polarization and the other measures right-circular polarization.

[0012] According to one embodiment, a circular polarization camera has a measured light quantity (I) of a left circular polarization pixel. L ) and the measured light quantity of the right-circular polarization pixel (I R Based on ), the difference between measured light intensities (|I L -I R |) and sum(I L +I R The ratio of ), the ratio of measured light intensity (I R / I L ) and the sum of light quantities (I L +IR It may be characterized by providing one or more of ).

[0013] According to one embodiment, the circular polarization camera may be characterized by being implemented through a two-dimensional sensor made of a CCD (charge-coupled device) or CMOS (complementary metal oxide semiconductor).

[0014] According to one embodiment, the detection unit may further include a tube lens.

[0015] According to one embodiment, the light source may include a short-wavelength light source, a polarizer, an incident quarter-wave plate, a micro-pattern half-wave plate, and a spatial filter.

[0016] According to one embodiment, the light source may be characterized in that a polarizing plate, an incident quarter-wave plate, and a micro-pattern half-wave plate are arranged in sequence, and the micro-pattern half-wave plate converts the incident polarization into a vortex-shaped fine polarization distribution.

[0017] According to one embodiment, the spatial filter may be characterized by blocking the central part of the light by being close to a micro-patterned half-wave plate.

[0018] According to one embodiment, the space filter may be characterized by adjusting the blocking area according to the wavelength of light and the type of specimen.

[0019] According to one embodiment, the light source may be characterized in that the angle between the polarizing plate and the incident quarter-wave plate axis is set based on the characteristics of the specimen.

[0020] According to one embodiment, the angle between the axes may be characterized as being 0 to 45 degrees.

[0021] According to one embodiment, the combination of light splitters may be characterized by including three light splitters arranged in a structure in which the directions of the interfaces are perpendicular to each other and have identical optical properties.

[0022] A measurement method according to another embodiment of the present invention relates to a measurement method for measuring an image of a specimen using any one of the above-mentioned elliptical analysis microscopes, and may include the steps of: irradiating a specimen with light having a polarization distribution from a light source unit; reflecting the light emitted from the light source unit through a combination of a beam splitter and an objective lens from the specimen; transmitting the light reflected from the specimen through an objective lens and a combination of a beam splitter to a detector unit; and calculating an image from a circularly polarized camera based on the reflected light.

[0023] The ellipsometric microscope according to the present invention has the following advantages compared to conventional systems.

[0024] First, since it is possible to mount an objective lens with a short working distance, it is possible to measure high-resolution and high-magnification ellipsometric images.

[0025] Second, since the objective lens is positioned perpendicular to the surface of the specimen, there are no issues with image distortion due to oblique incidence or focus formation problems due to perspective in the measured image, unlike in conventional systems.

[0026] Third, the introduction of a circular polarization camera eliminates rotation of optical components. Consequently, the measurement speed is fast, enabling real-time measurement.

[0027] Fourth, with the introduction of a circularly polarized camera, there is no rotation of the optical component. Therefore, there is no degradation in image resolution due to mechanical shaking (wobbling phenomenon) of the optical component.

[0028] Figure 1 is an example of the optical system of a conventional ellipsometry microscope (or imaging ellipsometry analyzer).

[0029] FIG. 2 shows the two polarization components (E) of light incident on a specimen at a specific angle of incidence (θ). p ,E s It is a conceptual diagram showing ).

[0030] Figure 3 shows the reflectance of the polarization component as a function of the angle of incidence (=reflection coefficient (r)) for silicon and glass. p , r s This is a graph showing the squared value of the magnitude of ).

[0031] FIG. 4 is a configuration diagram of an elliptical analysis microscope, which is an example of the present invention, and FIG. 5 is a configuration diagram of a light splitter combination (400).

[0032] Figure 6 is a graph showing the elliptical analysis variables (Δ, Ψ) that occur when light is transmitted through three beam splitters of the same name from a specific manufacturer.

[0033] FIG. 7 is an example of the pattern distribution of the fast axis in the micro-pattern half-wave plate (200), FIG. 8 is a polarization direction distribution in the cross-section of light when linearly polarized light passes through the micro-pattern half-wave plate (200), and FIG. 9 is a polarization direction distribution in the cross-section after passing through the spatial filter (210).

[0034] FIG. 10 (a) is a path diagram of light incident on an objective lens (230), FIG. 10 (b) is a conceptual diagram of the cross-section (235) of light formed on the back focal plane of the objective lens (230) and the angle of incidence formed on the specimen (140), FIG. 10 (c) is a conceptual diagram showing the polarization direction according to the direction of incident light when observed from the specimen, and FIG. 10 (d) is a conceptual diagram showing the polarization direction according to the direction of incident light when the micro-pattern half-wave plate (200) is not used.

[0035] FIG. 11 is an elliptical analysis image (ρ) of a silicon oxide film (width 40 μm, thickness 30 nm) formed on a silicon wafer using the present invention. S ) and enlarged image.

[0036] The advantages and features of the present invention and the methods for achieving them will become clear by referring to the embodiments described below in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below but may be implemented in various different forms. These embodiments are provided merely to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims.

[0037] The terms used in this specification will be briefly explained, and the invention will be described in detail.

[0038] The terms used in this invention have been selected based on currently widely used general terms, taking into account their functions within the invention; however, these terms may vary depending on the intent of those skilled in the art, case law, the emergence of new technologies, etc. Additionally, in specific cases, terms have been arbitrarily selected by the applicant, and in such cases, their meanings will be described in detail in the relevant description of the invention. Therefore, the terms used in this invention should be defined not merely by their names, but based on their meanings and the overall content of the invention.

[0039] When a part throughout the specification is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components. Furthermore, terms such as "part" and "module" used in the specification may refer to a unit that handles at least one function or operation.

[0040] Embodiments of the present invention are described below with reference to the attached drawings so that those skilled in the art can easily implement the invention. In addition, parts unrelated to the description are omitted in the drawings to clearly explain the invention. Terms including ordinal numbers, such as “first,” “second,” etc., may be used to describe various components, but the components are not limited by these terms. The terms are used solely for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be named the second component, and similarly, the second component may be named the first component. The term “and / or” includes a combination of multiple related items or any one of the multiple related items.

[0041]

[0042] Below, we will explain the basic contents for describing the elliptical analysis microscope.

[0043] Referring to FIG. 1, there are various methods for extracting an elliptical analysis image from an elliptical analysis microscope. For example, an elliptical analysis image with high contrast can be produced by adjusting the position angle of a polarizer (120), a quarter-wave plate (160), or an analysis polarizer (170) to extinguish the brightness of a specific part. Another method is to obtain an elliptical analysis image composed of elliptical analysis variables by performing calculations on multiple optical images obtained while rotating the polarizer (120), the quarter-wave plate (160), the analysis polarizer (170), etc.

[0044] Here, we would like to explain the elliptical analysis variables. Figure 2 shows the two polarization components (E) of light incident on a specimen at a specific angle of incidence (θ). p , E sThis is a conceptual diagram showing the light (①) incident on the specimen (140) and the reflected light (②) are placed on a plane that becomes the plane of incidence, and the polarization direction is divided into a component (Ep) parallel to the plane of incidence and a component (Es) perpendicular to it. These two polarization components change their polarization characteristics differently during the reflection process, and the difference can be expressed by elliptical analysis variables (Δ, Ψ). Here, Δ is the phase difference between the two polarization components generated by the specimen, and Ψ is a value related to the magnitude ratio. These two variables are the reflection coefficient (r), which is an optical characteristic of the specimen. p , r s It has the following relationship with ).

[0045]

[0046] Here, r p is the reflection coefficient for the horizontal component (Ep), and r s ε is the reflection coefficient for the normal component (Es), and both are complex numbers. That is, the measured elliptical analysis variables (Δ, Ψ) are the optical properties (r) of the material p , r s Reflects ).

[0047] Next, I would like to explain the characteristics of the angle of incidence (θ) in the operation of the elliptic analyzer. Figure 3 is a graph showing the reflectance of the two polarization components according to the angle of incidence for silicon and glass, which are widely used in the semiconductor industry. Here, reflectance is the reflection coefficient (r p , r s It is the squared value of the magnitude. It can be seen that the reflection characteristics for the two polarization components vary depending on the angle of incidence. In particular, for a specific angle of incidence (θ min Below ), the reflectances of the two polarization components become equal. That is, the two reflection coefficients (r p , r s Since the characteristics of ) cannot be distinguished, there is no measurement sensitivity when operating an ellipsometer at such an angle of incidence. The two reflection coefficients (r) according to such an angle of incidence p , r sThe characteristics of ) vary depending on the type of material, the thin film structure, and the wavelength used. In addition, as can be seen from the structure in Fig. 1, if the angle of incidence (θ) is too large, other problems occur, such as the optical component colliding with the specimen. Therefore, in general elliptical analyzers, an angle of incidence around 60 to 70 degrees is selected and used. On the other hand, when using an objective lens as in the present invention (Fig. 10), the maximum angle of incidence (θ max ) is determined by the characteristics of the objective lens used, and rather than a single angle of incidence, a distribution of angles of incidence occurs (θ=0~ θ max ).

[0048]

[0049] Hereinafter, the elliptical analysis microscope of the present invention will be described.

[0050] In order to solve the problem of the conventional elliptical analysis microscope described above, the present invention presents an elliptical analysis microscope having an optical system as shown in FIG. 4. FIG. 4 is a configuration diagram of the elliptical analysis microscope of the present invention according to one embodiment.

[0051] Referring to FIG. 4, since the present invention is a general optical microscope structure, the objective lens (230) to be used as an imaging lens (150) is positioned vertically above the specimen (140). Therefore, it is possible to use a high-resolution objective lens with a short working distance (WD). Light emitted from the light source unit (300) is incident on the objective lens (230) through the beam splitter combination (400) (①, solid arrow). Meanwhile, light reflected from the specimen (140) is incident on the detector unit (500) through the objective lens (230) and the beam splitter combination (400) (②, dotted arrow). In reality, the direction of incidence to the detector unit (500) is the x-direction, as shown in FIG. 5, which is the configuration diagram of the beam splitter combination.

[0052] The light source unit (300) may include a monochromatic light source (100), a collimation lens (110), a polarizer (120), an incident quarter-wave plate (220), a micro-pattern half-wave plate (200), a spatial filter (210), and a focusing lens (130). As the monochromatic light source (100), a tungsten halogen, xenon discharge, or LED lamp equipped with a monochromatic filter may be used. The micro-pattern half-wave plate (200) converts the incident polarization into a vortex-shaped fine polarization distribution. The spatial filter (210) has an opaque round dot in the center of the transparent plate to block the center of the transmitted light. The size of the round dot can be adjusted according to the specimen and the wavelength of the light used. This is a specific angle of incidence (θ) at which the measurement sensitivity of the elliptical analyzer is lost when the light passing through the objective lens (230) later forms an angle of incidence on the specimen (140). min It has the effect of blocking light below )

[0053] A non-polarizing beam splitter (410, 420, or 430 in FIG. 5) is an optical component having an interface positioned at 45 degrees relative to the path of light, so that at the interface, a portion of the light is transmitted in the original direction of propagation and the remainder is reflected in a vertical direction. Therefore, in order to direct the light (②) reflected from the specimen (140) in FIG. 4 toward the detector (500), a single beam splitter (420) may be used instead of using a combination of beam splitters (400). However, in the case of commercial products, even though they are non-polarizing beam splitters, they cause a significant change in polarization when light is transmitted or reflected at the interface (explained in FIG. 6). Since this amount of change in polarization is equally included throughout the image, it does not affect the shape of the image. In other words, it is not a major problem when used as an observation microscope. However, when quantitatively analyzing an image composed of elliptical analysis variables, the polarization changes generated by the beam splitter cause errors in the analysis values.

[0054] In the structure of FIG. 4 of the present invention, the change in polarization occurring during transmission of the beam splitter and the change in polarization occurring during reflection each occur once. However, since the change in polarization due to transmission and the change in polarization due to reflection are different, the polarization error can be eliminated by combining three identical beam splitters in a configuration as shown in FIG. 5. Here, identical beam splitters do not mean identical products (explained in FIG. 6). Referring to FIG. 5, the beam splitter combination (400) may include three beam splitters, and if the first beam splitter (410) is rotated 90 degrees around the z-axis, it becomes the direction of the second beam splitter (420). Also, if the second beam splitter (420) is rotated 90 degrees around the y-axis, it becomes the direction of the third beam splitter (430). Light incident from the light source unit (300) onto the upper part of the beam splitter combination (400) has a polarization component (p-component) parallel to the plane of incidence and a polarization component (s-component) perpendicular to it, and passes through the two beam splitters (410 and 420) sequentially (①). However, since the directions of the interfaces (415 and 425) of the two beam splitters are perpendicular to each other, the light that passes through the first interface (415) with the p-component (s-component) passes through the second interface (425) with the s-component (p-component). Therefore, the difference between the two polarization components (p-component and s-component) is canceled out. Meanwhile, when light reflected from the specimen is incident onto the lower part of the beam splitter combination (400), it is reflected sequentially from the two beam splitters (420 and 430) (②). Likewise, since the directions of the interfaces (425 and 435) of the two beam splitters are perpendicular to each other, the difference between the two polarization components (p-component and s-component) is canceled out.

[0055] I would like to explain the error in polarization change caused by the beam splitter. Figure 6 shows the measured values ​​of the elliptical variable that occurs when light passes through each beam splitter of the same product name from a specific manufacturer. Ideally, it should be (Δ=0, Ψ=45), but it can be seen that it causes severe polarization change. Furthermore, it can be seen that even though all three are the same product from the same company, they show different values. Therefore, for quantitative measurement, it is very important to select three beam splitters with identical optical characteristics at the wavelength used and use the beam splitter combination (400) presented in the present invention.

[0056] The objective lens (230) uses a numerical aperture (NA) suitable for providing the desired resolution and angle of incidence. Here, NA = sin(θ max It has a relationship of ).

[0057] The detection unit (500) may include a tube lens (180) and a circular polarizing camera (240, pixelated circular polarizing camera). The circular polarizing camera (240) uses a two-dimensional sensor made of a CCD (charge-coupled device) or CMOS (complementary metal oxide semiconductor), wherein two adjacent pixels are each covered by a left circular polarizer pattern and a right circular polarizer pattern, forming a single pixel group (250). The circular polarizer pattern is fabricated by attaching a quarter-wave plate filter at a 45-degree angle on top of a linear polarizer pattern.

[0058] Next, with reference to FIGS. 7 to 9, we intend to explain the phenomenon that occurs as light emitted from a light source unit (300) passes through a micro-pattern half-wave plate (200), which is a characteristic component of the present invention, and a spatial filter (210). FIG. 7 is an example of the pattern distribution of the fast axis in the micro-pattern half-wave plate (200), FIG. 8 is a polarization direction distribution in the cross-section of light when linearly polarized light passes through the micro-pattern half-wave plate (200), and FIG. 9 is a polarization direction distribution in the cross-section after passing through the spatial filter (210).

[0059] In FIG. 4, the angle between the axis of the polarizer (120) and the incident quarter-wave plate (220) can be set to 0 degrees or 45 degrees, so that the light passing through the two optical components can be selected as linearly polarized (0 degrees) or circularly polarized (45 degrees) depending on the characteristics of the specimen to be measured. As shown in FIG. 7, the micro-pattern half-wave plate (200) has a distribution in which the fast axis of the micro-pattern half-wave plate pattern rotates symmetrically along concentric circles. In the present invention, the axis of symmetry of the micro-pattern half-wave plate (200) has an angle of 45 degrees with the polarizer (120). Therefore, when linearly polarized light passes through the micro-pattern half-wave plate (200), the cross-section of the light has a vortex distribution of linearly polarized light with a fine region as shown in FIG. 8. That is, it becomes a distribution tilted at 45 degrees along the circumference of each concentric circle. Next, when this light is passed through a space filter (210), the center of the light is blocked, resulting in a donut-type cross-section as shown in Fig. 9.

[0060] The shape of this light has the following significance. First, there is the relationship between the shape of the light and the angle of incidence (θ) in the specimen. FIG. 10 (a) is a path diagram of light incident on the objective lens (230), FIG. 10 (b) is a conceptual diagram of the cross-section (235) of light formed on the back focal plane of the objective lens (230) and the angle of incidence formed on the specimen (140), FIG. 10 (c) is a conceptual diagram showing the polarization direction according to the direction of the incident light when observed from the specimen, and FIG. 10 (d) is a conceptual diagram showing the polarization direction according to the direction of the incident light when the micro-pattern half-wave plate (200) is not used. FIG. 10 shows the process in which the donut-shaped incident light (①) of FIG. 9 forms a donut-shaped image on the back focal plane (235) of the objective lens (230) by the focusing lens (130) and then enters the specimen (140) through the objective lens (230). Referring to the cross-section of the incident light in Fig. 10(b), θ=θ min From θ=θ max It can be seen that the incidence occurs with an angle of incidence distribution up to (hatched area). Here, referring to Fig. 3, the minimum angle of incidence with no measurement sensitivity (θ min Light below ) is blocked to prevent a decrease in the sensitivity of the elliptical analysis microscope when mixing light with no measurement sensitivity. NA = sin(θ max Since the relationship is ), the maximum angle of incidence (θ max ) can be selected as the NA value of the objective lens (230). That is, in the present invention, as shown in FIG. 3, θ=θ where measurement sensitivity exists min From θ=θ max Only light having an angle of incidence up to is used. If the amount of light from the light source (100) used is sufficient, the minimum angle of incidence (θ min You can also block low-sensitivity areas to some extent by making the size a bit larger.

[0061] Referring to Fig. 10(c), light from all directions is focused toward the specimen, and it shows that all have a polarization direction of 45 degrees regardless of the direction of incidence. Therefore, since the polarization state of all incident light is the same, the characteristics of the reflected polarization are the same regardless of direction. However, if only a polarizer (120 in Fig. 1) is used as in a conventional optical system, the polarization direction of the light incident on the specimen changes uniformly along the circumference, as shown in Fig. 10(d). In this case, since all polarization changes are combined in the reflected light, the polarization characteristics disappear from the detected image, causing the elliptical analysis microscope to lose sensitivity.

[0062] Referring again to FIG. 4, light emitted from a monochromatic light source (100) passes through a collimation lens (110) to increase the parallelism of the light. Then, if the angle between the axis of the polarizer (120) and the incident quarter-wave plate (220) is selected to be 0 degrees, the passing light becomes linearly polarized. Taking the case where linear polarization is selected as an example, if this linearly polarized light is passed through a micro-pattern half-wave plate (200), the cross-section of the light is separated into fine-sized linearly polarized light to form a concentric distribution, and the polarization direction of each linearly polarized light has an angle of 45 degrees with respect to the circumference of the concentric circle. Then, as it passes through a spatial filter (210), it has a donut-shaped cross-section and is incident on an objective lens (230) through a combination of a focusing lens (130) and a beam splitter (400) (①). This light is reflected from the specimen (140) with a specific angle of incidence distribution, and its polarization state changes, and then proceeds to the detector (500) through the beam splitter combination (400) (②). Referring to FIG. 5, the actual direction of the detector is the x-direction.

[0063] The polarization (②) incident on the detector (500) forms an image on the circular polarization camera (240) by the tube lens (180). Referring to (c) of FIG. 10, the polarization of the incident light is the same, so the shape of the polarization reflected from the specimen (140) is the same. However, since the reflected directions are all different, a circular polarization camera without directionality must be used. At this time, the amount of light (I) detected from the left circular polarization pixel in each pixel group (250) of the circular polarization camera L ) and the amount of light detected in the right-circular polarization pixel (I R By using ), it becomes possible to produce an elliptical analysis image.

[0064]

[0065] We will now explain the theoretical expression for the amount of light measured by each pixel group (250) when using the optical system of FIG. 4 of the present invention and when incident at a specific single angle of incidence (θ). The amount of light measured in the left-polarized pixel and the right-polarized pixel is, respectively (dI L , dI R If we say ), the value is as follows.

[0066]

[0067]

[0068] Here, all variables are functions of the angle of incidence (θ), and I0 is a value related to the amount of light incident on the specimen at the corresponding angle of incidence (θ). However, the measured value I in the present invention L(R) is θ=θ min From θ=θ max Since it includes all light with an angle of incidence up to, the expression is as follows.

[0069]

[0070] Measurement I L(R) Since it includes elliptic analysis variables (Δ, Ψ), using this allows defining elliptic analysis variables of a new expression as follows.

[0071]

[0072]

[0073]

[0074] FIG. 11 is an elliptical analysis image (ρ) of a silicon oxide film (width 40 μm, thickness 30 nm) formed on a silicon wafer using the present invention. S ...and an enlarged image thereof. From the detail of the enlarged image on the right, it can be seen that there is a spatial resolution of approximately 0.1 μm. In addition, from the contrast for a thickness difference of 30 nm, it can be seen that there is high thickness sensitivity. Furthermore, quantitative analysis is also possible; for example, the top of the image on the left and the graph on the right are the values ​​of the elliptical analysis variables for the horizontal and vertical cross-sections, respectively. By directly analyzing these values ​​using optical theory or comparing them with values ​​measured at various thicknesses, quantitative thickness information can be calculated.

[0075]

[0076] Although embodiments of the present invention have been described above with reference to the attached drawings, those skilled in the art will understand that the present invention may be implemented in other specific forms without changing its technical concept or essential features. Therefore, the embodiments described above should be understood as illustrative in all respects and not restrictive.

[0077]

[0078] The ellipsometric microscope according to the present invention has the following advantages over conventional systems, thus having high industrial applicability.

[0079] First, since it is possible to mount an objective lens with a short working distance, it is possible to measure high-resolution and high-magnification ellipsometric images.

[0080] Second, since the objective lens is positioned perpendicular to the surface of the specimen, there are no issues with image distortion due to oblique incidence or focus formation problems due to perspective in the measured image, unlike in conventional systems.

[0081] Third, the introduction of a circular polarization camera eliminates rotation of optical components. Consequently, the measurement speed is fast, enabling real-time measurement.

[0082] Fourth, with the introduction of a circularly polarized camera, there is no rotation of the optical component. Therefore, there is no degradation in image resolution due to mechanical shaking (wobbling phenomenon) of the optical component.

Claims

1. This relates to an elliptical analysis microscope capable of measuring images of a specimen, A light source unit that irradiates light having a polarization distribution onto the above specimen; A combination of beam splitters comprising one or more beam splitters that transmit and reflect the light; An objective lens that concentrates and irradiates the light passing through the beam splitter onto the above specimen; and A detector comprising a circular polarization camera in which two adjacent pixels are each covered with different polarizer patterns, receiving light reflected from the specimen and producing an image; Elliptical analysis microscope.

2. In Paragraph 1, The above circular polarization camera is, The above two adjacent pixels are characterized by one measuring left-circular polarization and the other measuring right-circular polarization. Elliptical analysis microscope.

3. In Paragraph 2, The above circular polarization camera is, The measured light quantity (I) of the above left-circular polarization pixel L ) and the measured light quantity of the right-circular polarization pixel (I R Based on ), the difference between the above measured light amounts (|I L -I R |) and sum(I L +I R The ratio of ), the ratio of the above measured light amounts (I R / I L ) and the sum of the measured light quantities (I L +I R Characterized by providing one or more of ) Elliptical analysis microscope.

4. In Paragraph 1, The above circular polarization camera is, Characterized by being implemented through a two-dimensional sensor made of a CCD (charge-coupled device) or CMOS (complementary metal oxide semiconductor). Elliptical analysis microscope.

5. In Paragraph 1, The above detection unit is, Includes additional tube lenses Elliptical analysis microscope.

6. In Paragraph 1, The above light source unit is, A short-wavelength light source, a polarizer, an incident quarter-wave plate, a micro-patterned half-wave plate, and a spatial filter Elliptical analysis microscope.

7. In Paragraph 6, The above light source unit is, The above polarizing plate, incident quarter-wave plate, and micro-pattern half-wave plate are arranged in sequence. The above-mentioned micro-patterned half-wave plate is, Characterized by converting incident polarization into a vortex-shaped fine polarization distribution Elliptical analysis microscope.

8. In Paragraph 6, The above spatial filter is, Characterized by blocking the central part of the light in close proximity to the above-mentioned micro-pattern half-wave plate. Elliptical analysis microscope.

9. In Paragraph 8, The above spatial filter is, Characterized by adjusting the blocking area according to the wavelength of the light and the type of specimen. Elliptical analysis microscope.

10. In Paragraph 6, The above light source unit is, Characterized by setting the angle between the polarizing plate and the incident quarter-wave plate axis based on the characteristics of the above specimen. Elliptical analysis microscope.

11. In Paragraph 10, The angle between the above axes is, Characterized by being between 0 and 45 degrees Elliptical analysis microscope.

12. In Paragraph 1, The above combination of light splitters is, Characterized by including three beam splitters arranged in a structure having identical optical properties and interface directions perpendicular to each other. Elliptical analysis microscope.

13. A measurement method for measuring an image of the specimen using an elliptical analysis microscope according to any one of claims 1 to 12, wherein A step of irradiating light onto a specimen from the above light source; A step in which light emitted from the light source unit passes through the beam splitter combination and objective lens and is reflected from the specimen; A step in which light reflected from the above specimen passes through the combination of the objective lens and beam splitter and is incident on the detection unit; and A step of producing an image from the circular polarization camera based on the reflected light; measurement method.

Images