System and method for optical measurement of numerical aperture of objective lens

Abstract

An optical measurement system includes a hemispherical mirror including a planar portion and a spherical portion having a hemispherical recess shape in the planar portion. In the spherical portion, a latitude mark having a different reflectivity than the remaining portion of the spherical portion is formed. The system includes an optical unit having an objective lens and at least one beam splitter. The optical unit transmits the light reflected from the hemispherical mirror to the first sensor through the objective lens. The controller measures the numerical aperture of the objective lens by aligning the hemispherical mirror at the focal point of the objective lens, detecting a back focus image of the objective lens in which the latitude mark appears as a darker circular line, and performing a calculation on the image.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0106036 filed on August 14, 2023 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to an optical measurement system and a measurement method for the numerical aperture of an objective lens. Background Art

[0004] In optical measurement systems, the numerical aperture of an objective plays an important role in determining the performance and precision of the system. For example, the objective can determine the resolution of an optical measurement system. Furthermore, in the case of angle-resolved ellipsometry, which utilizes an objective to change the polarization properties of light at continuous angles of incidence, the measurement data can only be accurately interpreted if the numerical aperture of the objective is accurately identified. Therefore, the precise measurement of the numerical aperture of an objective can be decisive in an optical measurement system.

[0005] The numerical aperture of the objective lens may vary depending on production deviations of the objective lens, and when the objective lens is mounted on an optical measuring system, the numerical aperture of the objective lens may vary depending on optical conditions such as the collimation of light incident on the objective lens or environments such as temperature and pressure of the optical measuring system. Summary of the invention

[0006] The present disclosure provides an optical measurement system for measuring the numerical aperture of an objective lens in all directions in an installation environment of the objective lens, and a method for measuring the numerical aperture of the objective lens.

[0007] In an example, an optical measurement system includes: a hemispherical mirror including: a plane portion, a spherical portion having a hemispherical concave shape in the plane portion, and a plurality of latitude marks formed in the spherical portion to have a reflectivity different from that of the spherical portion; an optical unit including: an objective lens for allowing light incident from a light source to be incident on the hemispherical mirror, and at least one beam splitter for transmitting light reflected from the hemispherical mirror and incident on the objective lens to a first sensor; and a controller for measuring the numerical aperture of the objective lens using a back-focus image of the objective lens output by the first sensor when the hemispherical mirror is aligned so that the focus of the objective lens and the center of the spherical portion of the hemispherical mirror match each other.

[0008] In another example, an optical measurement system includes: a hemispherical mirror including a planar portion, a spherical portion having a hemispherical concave shape in the planar portion, and a plurality of latitude marks formed in the spherical portion to have a reflectivity different from that of the spherical portion; a stage in which a substrate chuck for loading a semiconductor substrate and an alignment system equipped with the hemispherical mirror are provided; an optical unit including an objective lens and a beam splitter, the objective lens being used to allow light incident from a light source to be incident on a target, the beam splitter being used to transmit light reflected from the target and incident on the objective lens to a first sensor; and a controller being used to set the hemispherical mirror as a target of the objective lens by adjusting a position of the stage, and to measure a numerical aperture of the objective lens using a back-focus image of the objective lens output by the first sensor.

[0009] In another example, an optical measurement system includes: a hemispherical mirror including a plurality of latitude marks in a spherical portion having a reflectivity different from that of the spherical portion; a light source; an objective lens; and a controller configured to: match the center of the spherical portion with a focus of the objective lens; allow light output from the light source to be incident on the spherical portion through the objective lens; detect a circular pattern formed by the plurality of latitude marks in a back-focus image of the objective lens; calculate a partial numerical aperture of the objective lens according to a radius of each of the circular patterns based on a radius of each of the circular patterns and a latitude indicated by the plurality of latitude marks; and determine a numerical aperture of the objective lens according to a radius of a pupil image in the back-focus image based on the partial numerical aperture according to the radius of each of the circular patterns.

[0010] In an example, an optical measurement system and method for measuring the numerical aperture of an objective lens can measure the numerical aperture of the objective lens using a light source inside the system while the objective lens is mounted on the system. Therefore, the numerical aperture of the objective lens can be measured in situ.

[0011] In an example, an optical measurement system and a measurement method of the numerical aperture of an objective lens can calculate the numerical aperture of the objective lens using images in all directions obtained by illuminating a hemispherical mirror having a plurality of latitude lines. Therefore, the numerical aperture of the objective lens in all directions can be measured, and the numerical aperture can be accurately calculated using a plurality of reference values.

[0012] Aspects to be solved by the present disclosure are not limited to the above-mentioned aspects, and other aspects not mentioned herein will be clearly understood by those skilled in the art from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other aspects, features and advantages of the present disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0014] Figure 1 is a diagram illustrating an example optical measurement system;

[0015] FIG. 2A to FIG. 2C is a diagram showing an example hemispherical mirror;

[0016] Figure 3A and Figure 3B is a diagram showing an example measurement method of the numerical aperture of an objective lens;

[0017] Figure 4 is a flow chart illustrating an example measurement method of the numerical aperture of an objective lens;

[0018] Figure 5 is a diagram illustrating an example method of processing an image on a rear focal plane;

[0019] Figure 6 is a diagram showing an example alignment system for a hemispherical mirror in an optical measurement system;

[0020] 7A to 7C is a diagram showing an example method of aligning the vertical position of a hemispherical mirror;

[0021] Fig. 8A and Figure 8B is a diagram showing an example method of aligning the horizontal position of a hemispherical mirror;

[0022] Fig. 9 is a diagram showing an example method of aligning the horizontal position of a hemispherical mirror;

[0023] Fig.10 is a diagram showing an example structure of an alignment system;

[0024] FIG. 11A to FIG. 11E is a graph showing the measured numerical aperture of the objective lens for each wavelength;

[0025] Fig.12 is a graph showing the accuracy of the measured numerical aperture of the objective lens;

[0026] Fig.13A and Fig. 13B is a diagram showing an example repeatability of a method for measuring the numerical aperture of an objective lens;

[0027] Fig.14 is a graph showing the repeatability accuracy of an example measurement method of the numerical aperture of an objective lens according to the radius of a hemispherical mirror;

[0028] Fig.15 is a graph showing the accuracy of an example measurement method of the numerical aperture of an objective lens according to the number of latitude lines formed in a hemispherical mirror; and

[0029] FIG. 16A to FIG. 16C is a diagram showing the accuracy of an example measurement method of the numerical aperture of an objective lens according to a processing error of a hemispherical mirror; and

[0030] Figures 17 to 20 is a diagram showing an example structure of a hemispherical mirror. DETAILED DESCRIPTION

[0031] Hereinafter, example embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0032] Figure 1 is a diagram illustrating an example optical measurement system.

[0033] Reference Figure 1 , the optical measurement system 100 may include an optical unit 140, a light source 130, a first image sensor 151, a second image sensor 152, a controller 160, and a hemispherical mirror 200. The optical unit 140 may include an objective lens 120, an illumination lens 141, a first beam splitter 142, a second beam splitter 143, a condenser lens 144, a first relay lens 145, and a second relay lens 146.

[0034] The light source 130 may output light incident on a target. The light may be light including a wavelength ranging from an ultraviolet wavelength band to an infrared wavelength band, or may be monochromatic light having a specific wavelength.

[0035] Light output from the light source 130 may be irradiated to the illumination lens 141. The illumination lens 141 may be a convex lens and may adjust the angular distribution of light output from the light source 130 to allow the light to be incident on the first beam splitter 142. For example, the illumination lens 141 may convert light irradiated from the light source 130 into parallel light.

[0036] The first beam splitter 142 may reflect some of the light received through the illumination lens 141 and transmit the rest of the light received through the illumination lens 141. The light reflected from the first beam splitter 142 may be incident on the objective lens 120, and the light passing through the objective lens 120 may be incident on the object.

[0037] When the light passing through the objective lens 120 is reflected from the object, the objective lens 120 may receive the reflected light. The light received from the objective lens 120 may be transmitted to the first beam splitter 142. Meanwhile, the objective lens 120 includes a front surface facing the sample and a rear surface disposed at an opposite side of the sample, and a back focal plane (BFP) may be defined at a predetermined distance from the rear surface of the objective lens 120.

[0038] The back focal plane BFP may be an XY plane defined in a first direction (X direction) and a second direction (Y direction) orthogonal to the first direction. Light passing through the objective lens 120 may be focused on the target in the form of a point, and may be reflected back from the target area, and then pass through the objective lens 120 to continue to the back focal plane BFP.

[0039] The second beam splitter 143 may transmit some of the light transmitted from the first beam splitter 142 and reflect the rest of the light transmitted from the first beam splitter 142. The first relay lens 145 and the second relay lens 146 may sequentially pass the light transmitted from the second beam splitter 143. The light passing through the second relay lens 146 may be incident on the first image sensor 151. The first image sensor 151 may obtain a back focal plane image as an image of a back focal plane BFP using the light incident from the second relay lens 146.

[0040] The condensing lens 144 may condense the light reflected from the second beam splitter 143 at one focus. The second image sensor 152 may obtain a focused image of the object lens 120 using the light condensed from the condensing lens 144.

[0041] The controller 160 may control the optical measuring system 100. For example, the controller 160 may control the light source 130, the first image sensor 151, and the second image sensor 152. In addition, the controller 160 may obtain a measurement value using an image obtained from the first image sensor 151, and perform subsequent control using an image obtained from the second image sensor 152.

[0042] Meanwhile, the numerical aperture (NA) of the objective lens 120 may determine the resolution of the optical measuring system 100 , and determine the accuracy of the measured value of the optical measuring system 100 by performing angle-resolved ellipsometry.

[0043] When the numerical aperture of the objective lens mounted on the optical measuring device varies, the resolution may vary for each optical measuring device, and it may be difficult to achieve tool-to-tool matching (TTTM) of the optical measuring device. In addition, in the optical measuring device performing the angle-resolved ellipsometry method, the accuracy of the measured value may be reduced.

[0044] The numerical aperture value provided by the manufacturer of the objective lens 120 is a design value, but this may often differ from the actual numerical aperture due to production variations of the objective lens 120. In addition, the numerical aperture may vary depending on the optical conditions under which the objective lens 120 is used or the installation environment in the optical measurement system 100. Therefore, accurate measurement of the numerical aperture of the objective lens 120 installed in the optical measurement system 100 may be required to accurately determine the as-installed numerical aperture of the objective lens.

[0045] In order to measure the numerical aperture of an objective lens in situ, a method disclosed in the present invention is proposed. The objective lens has a diffraction grating arranged on the front surface of the objective lens. The optical measurement system allows light output from an internal light source to be incident on the diffraction grating through the objective lens. In addition, the zero-order reflected light and ±n-order diffracted light (where n is a natural number) output from the diffraction grating are incident on the rear focal plane and form a pattern. Analyzing the pattern makes it possible to calculate the numerical aperture of the objective lens.

[0046] However, according to the method using the diffraction grating, since the light intensity of the diffracted light of the ±2nd order or higher is not bright enough, the numerical aperture of the objective lens may be calculated using only the pattern formed by the ±1st order diffracted light. Therefore, the number of reference values ​​used to calculate the numerical aperture of the objective lens may be insufficient. When the number of reference values ​​is insufficient, there is a high possibility that an error will occur in the calculated numerical aperture. In addition, in order to measure the numerical aperture of the objective lens in all directions, it may be necessary to obtain multiple back-focus images according to the angle of the diffraction grating while rotating the diffraction grating, which may result in a long time for measurement.

[0047] In an example embodiment, in order to measure the numerical aperture of the objective lens 120, a hemispherical mirror 200 may be provided on the front surface of the objective lens 120. The hemispherical mirror 200 may include a plurality of latitude marks formed in the spherical portion to have a reflectivity different from that of the spherical portion. Latitude may refer to an angle formed between a line passing through both a point in the spherical portion and the center of the spherical portion and the Z axis, and an example of the plurality of latitude marks may be a plurality of latitude lines formed at fixed latitude intervals in the spherical portion.

[0048] In an example embodiment, in a state where the hemispherical mirror 200 is aligned so that the center of the spherical portion of the hemispherical mirror 200 matches the focus of the objective lens 120, in an installation environment where the objective lens 120 uses a back focus image of the objective lens 120 formed by light reflected from the hemispherical mirror 200 and incident on the objective lens 120, the optical measurement system 100 can measure the numerical aperture in all directions using a plurality of reference values.

[0049] Hereinafter, an optical measurement system and a measurement method of the numerical aperture of an objective lens will be described in detail.

[0050] FIG. 2A to FIG. 2C is a diagram illustrating an example hemispherical mirror. Figure 2A is a perspective view of a hemispherical mirror, Figure 2B is a plan view indicating the hemispherical mirror in the XY plane, and Figure 2C yes Figure 2B A cross-sectional view along line AA'.

[0051] Reference FIG. 2A to FIG. 2C, the hemispherical mirror 200 may include a spherical portion 210, a plane portion 220, and a boundary line 230. The spherical portion 210 may be a surface having a hemispherical concave shape in the plane portion 220, and the boundary line 230 may be a boundary between the spherical portion 210 and the plane portion 220.

[0052] The spherical portion 210 and the plane portion 220 may be formed of a mirror surface. According to example embodiments, the spherical portion 210 and the plane portion 220 may be formed of a material having the same reflectivity.

[0053] A plurality of latitude lines 211 may be formed on the spherical portion 210. Each of the plurality of latitude lines 211 may be a line for connecting points having the same latitude on the spherical portion 210. For example, the plurality of latitude lines 211 may be formed at fixed latitude intervals.

[0054] The plurality of latitude lines 211 may be formed to have a reflectivity different from that of the spherical portion 210. For example, the plurality of latitude lines 211 may be formed by engraving the spherical portion 210, and the plurality of latitude lines 211 may scatter incident light. According to example embodiments, the plurality of intaglio latitude lines 211 may be filled with a material having a reflectivity lower than that of the spherical portion 210. The present disclosure is not limited thereto, and the plurality of latitude lines 211 may be embossed from the spherical portion 210, and the plurality of latitude lines 211 may be formed of a material having a reflectivity lower or higher than that of the spherical portion.

[0055] According to example embodiments, a plurality of longitude lines 212 may also be formed on the spherical portion 210. Each of the plurality of longitude lines 212 may be a line for connecting points having the same longitude (ie, based on an angle between the center of the spherical portion 210 and the X-axis or the Y-axis).

[0056] In example embodiments, light incident on the center of the spherical portion of the hemispherical mirror 200 through the objective lens 120 may be incident on the spherical portion 210 and the plurality of latitude lines 211 according to an incident angle. Since the spherical portion 210 and the plurality of latitude lines 211 have different reflectivities, a concentric pattern in which the plurality of latitude lines 211 are transferred may be displayed in a back-focus image. The numerical aperture of the objective lens may be calculated based on the radius of the concentric pattern displayed in the back-focus image and the latitude indicated by the plurality of latitude lines 211.

[0057] Figure 3A and Figure 3B is a diagram illustrating an example measurement method of the numerical aperture of an objective lens.

[0058] Figure 3A An objective lens 120 , a hemispherical mirror 200 , a back focal plane BFP and a back focus image 300 are shown.

[0059] Reference Figure 3A , the hemispherical mirror 200 can be aligned so that the center of the spherical part of the hemispherical mirror 200 matches the focus of the objective lens 120. In the state where the hemispherical mirror 200 is aligned, light entering the hemispherical mirror 200 from the objective lens 120 can pass through the focus of the objective lens 120 and can be incident on the spherical part 210 of the hemispherical mirror 200 and the plurality of latitude lines 211.

[0060] Pupil images having different radii according to the numerical aperture of the objective lens 120 may be displayed on the back-focus image 300. Figure 3A , a boundary line 320 of the pupil image is shown. In the pupil image, a plurality of concentric patterns 311 formed by transferring a plurality of latitude lines 211 having different reflectivities from the spherical portion 210 to the back-focus image 300 may be displayed.

[0061] On the other hand, when the center of the spherical part of the hemispherical mirror 200 and the focus of the objective lens 120 match each other, the light incident on the hemispherical mirror 200 after passing through the focus of the objective lens 120 may be vertically incident on the spherical part 210, and retro-reflection reflected in the incident direction may occur. Therefore, the latitude indicated by each of the plurality of latitude lines 211 corresponding to the plurality of concentric patterns 311 may be the same as the incident angle of the light incident on the focus in the objective lens 120.

[0062] The numerical aperture of the objective lens 120 may be calculated according to Equation 1 below.

[0063] <Equation 1>

[0064]

[0065] In equation 1, NA is the numerical aperture of the objective lens, n is the refractive index, and θ max is the maximum incident angle of the objective lens, R max is the radius of the pupil image, and f is the focal length. When the objective lens is a dry lens (ie, operating in air), the refractive index of the medium may be n = 1. Referring to Equation 1, the numerical aperture of the objective lens may be proportional to the radius of the pupil image.

[0066] In example embodiments, based on the partial numerical aperture of the objective lens 120 at each of the plurality of concentric patterns 311 , the numerical aperture of the objective lens 120 may be calculated according to the radius of the pupil image.

[0067] The back focus image 300 has a radius RBFP n The partial numerical aperture NA at the nth concentric circle n It can be calculated according to the following equation 2.

[0068] <Equation 2>

[0069]

[0070] In Equation 2, NA n is the partial numerical aperture at the nth concentric circle, θ n It can be the latitude of the nth concentric circle, R n may be the radius of the nth line of latitude of the image forming the nth concentric circle, and RSM may be the radius of the spherical part.

[0071] According to Equation 2, the controller 160 may determine the sine function value of each of the latitudes based on the radius of the plurality of latitude lines 211 and the radius of the spherical portion 210. In addition, the controller 160 may determine the partial numerical aperture of the objective lens 120 according to the radius of each of the plurality of concentric patterns 311 based on the sine function value and the radius of each of the plurality of concentric patterns 311. Based on the relationship between the radius of each of the plurality of concentric patterns 311 and the partial numerical aperture of the objective lens 120, a function of the numerical aperture of the objective lens 120 according to the radius of the pupil image may be obtained.

[0072] Reference Figure 3B , which shows the relationship between the radius of the pupil image and the numerical aperture of the objective lens 120. The objective lens at a radius R can be determined based on the partial numerical aperture at the concentric circles formed in the pupil image. max Numerical aperture NA at max .

[0073] In an example embodiment, the optical measurement system 100 may determine a partial numerical aperture NA for each of the plurality of concentric patterns 311 formed within the pupil image. n and NA n+1 The relationship between the radius of the plurality of concentric patterns 311 and the partial numerical aperture can be approximated as a linear function, which enables the optical measurement system 100 to calculate the radius R of the objective lens 120 in the pupil image. max Numerical aperture NA at max .

[0074] Figure 4 is a flow chart illustrating an example measurement method of the numerical aperture of an objective lens.

[0075] In operation S11 , the optical measuring system 100 may match the focus of the object lens 120 with the center of the hemispherical mirror 200 , and allow light to be incident on the object lens 120 using the light source 130 .

[0076] In operation S12, the optical measurement system 100 may obtain a back-focus image 300 of the objective lens 120. Figure 3AAs described above, the back-focus image 300 may be formed by light reflected from the hemispherical mirror 200 based on light incident on the object lens 120 , and may have a plurality of concentric patterns 311 formed by a plurality of latitude lines 211 .

[0077] In operation S13, the optical measurement system 100 may calculate a partial numerical aperture at a location showing the plurality of concentric patterns 311. The partial numerical aperture at a location showing a specific concentric pattern may be calculated based on a radius of a latitude line corresponding to the concentric pattern and a radius of the spherical portion 210 of the hemispherical mirror 200.

[0078] In operation S14 , the optical measuring system 100 may derive a linear function indicating the numerical aperture of the objective lens 120 according to the radius of the pupil image based on the partial numerical apertures at the plurality of concentric patterns 311 .

[0079] In operation S15 , the optical measuring system 100 may determine a numerical aperture of the objective lens 120 based on a radius of a pupil image displayed in the back-focus image 300 and a linear function.

[0080] Meanwhile, in order to determine the radius of the plurality of concentric patterns 311 and the radius of the pupil image based on the back-focus image 300 , image processing may be performed on the back-focus image 300 captured by the first image sensor 151 .

[0081] Figure 5 is a diagram illustrating an example method of processing an image on a rear focal plane.

[0082] In operation S21, the controller 160 may capture light transmitted through the relay lenses 145 and 146 using the first image sensor 151 to obtain a raw image. For example, the raw image may be a grayscale image.

[0083] exist Figure 5 In the example of , the pupil image can be displayed in a relatively brighter color than the outer part. In addition, when the plurality of latitude lines 211 and the plurality of longitude lines 212 have a reflectivity lower than the reflectivity of the spherical part 210, the portion of the pupil image where the plurality of latitude lines and the plurality of longitude lines are shifted can be displayed in a relatively dark color.

[0084] In operation S22, the optical measurement system 100 may generate a binary image by processing the original image. For example, the controller 160 may generate a binary image having only black and white according to the brightness of the grayscale image obtained from the rear focal plane image sensor as the first image sensor 151. A plurality of concentric patterns generated by shifting a plurality of latitude lines, a radial pattern generated by shifting a plurality of longitude lines, and a boundary line of the pupil image in the binary image may be emphasized.

[0085] In operation S23, the optical measurement system 100 may perform circular fitting to detect a circular pattern in the binary image, thereby approximating a plurality of concentric patterns in a circular shape. For example, the circular fitting may be performed using a circle Hough transform algorithm by the controller 160. Meanwhile, the circular fitting may be performed by assuming that the center of the radial pattern of the binary image is the center of the plurality of circular patterns.

[0086] In operation S24 , the optical measuring system 100 may calculate a radius of a circular pattern from the image in which the circle fitting is completed.

[0087] In operation S25 , the optical measuring system 100 may calculate a numerical aperture of the objective lens 120 based on the radii of the plurality of concentric patterns and the radius of the pupil image.

[0088] In example embodiments, since the optical measurement system 100 may measure the numerical aperture of the objective lens 120 using the internal light source 130 in a state where the objective lens 120 is mounted, the numerical aperture of the objective lens 120 may be measured in situ.

[0089] Furthermore, since the optical measurement system 100 can measure the numerical aperture of the objective lens 120 based on a plurality of concentric patterns appearing in the back-focus image 300, errors in measuring the numerical aperture can be corrected, thereby improving its accuracy, compared to calculating the numerical aperture using a single reference value.

[0090] In addition, the optical measurement system 100 can measure the numerical aperture of the objective lens 120 in all directions using the back focus image 300 having optical information from all directions. The numerical aperture of the objective lens 120 for each orientation may vary due to a processing error of the objective lens 120. According to an example embodiment, the optical measurement system 100 can perform ellipse fitting instead of performing circle fitting using a binary image in order to measure the numerical aperture in all directions. The optical measurement system 100 can measure the numerical aperture in all directions using the back focus image 300 obtained by capturing a single image, which will greatly improve the time required to measure the numerical aperture.

[0091] On the other hand, in order to obtain accurate aperture measurement results, it is necessary to accurately align the center of the spherical portion of the hemispherical mirror 200 with the focus of the objective lens 120. Figures 6 to 10 A method of aligning the hemispherical mirror 200 in an example embodiment is described in detail.

[0092] Figure 6 is a diagram illustrating an example alignment system of a hemispherical mirror in an optical measurement system.

[0093] The optical measurement system 100 may be a system for measuring a semiconductor substrate, and may include a substrate chuck 110 for loading a semiconductor substrate. The substrate chuck 110 may be disposed on a stage of the optical measurement system 100.

[0094] In an example embodiment, the hemispherical mirror 200 may be mounted on the alignment system 111 for tip-tilt control, and the alignment system 111 may be provided on the stage. For example, the alignment system 111 may be attached to a side surface of the substrate chuck 110. According to an embodiment, the substrate chuck 110 and the alignment system 111 may be integrally formed.

[0095] In order to align the hemispherical mirror 200, the hemispherical mirror 200 can be moved in the X direction, the Y direction, and the Z direction, and the tilt adjustment control can be further performed. For example, the stage can be moved in the X direction, the Y direction, and the Z direction, and the hemispherical mirror 200 can be moved together with the stage. In addition, the tilt adjustment control of the hemispherical mirror 200 can be performed by the alignment system 111.

[0096] 7A to 7C is a diagram illustrating an example method of aligning the vertical position of a hemispherical mirror.

[0097] Reference 7A to 7C , the optical measurement system 100 can set the position of the hemispherical mirror 200 on the XY plane so that the incident light from the objective lens 120 is irradiated to the flat portion 220 of the hemispherical mirror 200. In addition, the optical measurement system 100 can obtain a plurality of focused images 401, 402, and 403 by changing the operating distance of the objective lens 120 to the first operating distance WD1 to the third operating distance WD3. The operating distance can be defined as the distance between the objective lens 120 and the hemispherical mirror 200. For example, the optical measurement system 100 can use a reference Figure 1 The second image sensor 152 is described to obtain a plurality of focused images 401 , 402 , and 403 .

[0098] Reference Fig. 7A , in a state where the objective lens 120 is set at the first operating distance WD1, the optical measurement system 100 may obtain a first focused image 401. The first operating distance WD1 may be shorter than the focal length of the objective lens 120, and the first focused image 401 may be an image captured under an under-focused condition. The light reflected from the plane portion 220 may appear blurred on the first focused image 401.

[0099] Reference Figure 7BIn a state where the objective lens 120 is set at the second operating distance WD2, the optical measuring system 100 may obtain a second focused image 402. The second operating distance WD2 may match the focal length of the objective lens 120, and the light reflected from the plane portion 220 may appear clear on the second focused image 402.

[0100] Reference Figure 7C , when the objective lens 120 is set at the third operating distance WD3, the optical measurement system 100 can obtain a third focused image 403. The third operating distance WD3 can be longer than the focal length of the objective lens 120, and the third focused image 403 can be an image captured under an overfocus condition. The light reflected from the plane portion 220 can appear blurred on the third focused image 403.

[0101] In example embodiments, the optical measurement system 100 may capture a plurality of focused images 401 , 402 , and 403 while changing the Z-axis position of the hemispherical mirror 200 , and determine the Z-axis position showing a clear focused image as the Z-axis position of the hemispherical mirror 200 .

[0102] Fig. 8A and Figure 8B is a diagram illustrating an example method of aligning the horizontal position of a hemispherical mirror.

[0103] Reference Fig. 8A and Figure 8B , the optical measurement system 100 can obtain a plurality of focused images 404 and 405 while changing the X-axis position and the Y-axis position of the hemispherical mirror 200 in a state where the Z-axis position of the hemispherical mirror 200 is set.

[0104] When the focus of the objective lens 120 is located on the boundary between the spherical portion 210 and the plane portion 220, a relatively bright portion and a relatively dark portion may be displayed on the focused images 404 and 405. Since light incident on the plane portion 220 at the focus of the objective lens 120 may be reflected invariably and may be incident on the objective lens 120, the plane portion 220 may be displayed as a relatively bright portion on the focused images 404 and 405. On the other hand, since most of the light incident on the spherical portion 210 is reflected in a direction other than the focus of the objective lens 120, the spherical portion 210 may be displayed as a relatively dark portion on the focused images 404 and 405. On the other hand, since the light passing through the objective lens 120 forms an inverted image, a bright portion corresponding to the plane portion 220 and a dark portion corresponding to the spherical portion 210 in the focused images 404 and 405 may be displayed in a left-right inverted manner.

[0105] The controller 160 can determine the boundary position of the hemispherical mirror 200 so that the focus of the objective lens 120 is set in the boundary line, and align the horizontal position of the hemispherical mirror 200 by determining the center position of the hemispherical mirror 200 based on the boundary position so that the focus of the objective lens 120 is set at the center of the spherical part 210.

[0106] Fig. 9 is a diagram illustrating an example method of aligning the horizontal position of a hemispherical mirror.

[0107] Fig. 9 A plurality of focused images 404 to 407 captured at a boundary position of the hemispherical mirror 200 among a plurality of focused images captured while adjusting the horizontal position of the hemispherical mirror 200 are shown.

[0108] Images whose boundary lines are parallel to the Y axis (such as focused images 404 and 405) may be images captured using both ends of the spherical portion 210 in the X axis direction as the focus. In addition, images whose boundary lines are parallel to the X axis (such as focused images 406 and 407) may be images captured using both ends of the spherical portion 210 in the Y axis direction as the focus. On the other hand, in the focused images 404 to 407, the bright portion corresponding to the plane portion 220 and the dark portion corresponding to the spherical portion 210 may be displayed in a manner that is reversed left and right and upside down.

[0109] In example embodiments, the center of a boundary position of the hemispherical mirror 200 corresponding to the focused images 404 to 407 may be determined as the center position of the hemispherical mirror 200 .

[0110] On the other hand, when the hemispherical mirror 200 is tilted, the Z-axis position of the hemispherical mirror 200 may be aligned based on the flat portion 220, and even when the X-axis position and the Y-axis position of the hemispherical mirror 200 are aligned, the focus of the objective lens 120 and the center of the spherical portion of the hemispherical mirror 200 may not be correctly aligned. In addition, in a back-focus image captured to measure the numerical aperture of the objective lens 120, the shapes of a plurality of concentric patterns may be distorted, and it may be difficult to accurately measure the numerical aperture.

[0111] In an example embodiment, the controller 160 may detect the tilt of the hemispherical mirror 200 based on the sharpness of the plurality of focused images 404 to 407. For example, when the hemispherical mirror 200 tilts in the X-axis direction, Fig. 9 At least one of the fourth focused image 404 and the fifth focused image 405 shown in FIG. 4 may have an image captured in an overfocus condition or an underfocus condition. When the tilt of the hemispherical mirror 200 is detected, the controller 160 may cancel the tilt by controlling the alignment system 111 to perform tilt adjustment control of the hemispherical mirror 200.

[0112] Fig.10is a diagram illustrating the structure of an example alignment system.

[0113] Reference Fig.10 , shows an alignment system 111 in which the hemispherical mirror 200 is installed. The alignment system 111 may include a support 112, a fixing portion 113, a plurality of nuts 114a, 114b, and 114c, a plurality of adjustment bolts 115a, 115b, and 115c, and a plurality of springs 116a and 116b.

[0114] The support member 112 can be mounted on the reference Figure 6 The substrate chuck 110 is described to support the fixing portion 113. The fixing portion 113 may fix the hemispherical mirror 200. For example, the hemispherical mirror 200 may be inserted into the fixing portion 113 in a state where the planar portion 220 and the spherical portion 210 are exposed.

[0115] The plurality of nuts 114a, 114b, and 114c may penetrate the support member 112 from at least three vertical edges of the support member 112. In addition, the plurality of adjustment bolts 115a, 115b, and 115c may be fastened to the plurality of nuts 114a, 114b, and 114c to penetrate the support member 112, and the fixing portion 113 may be supported above the support member 112. The plurality of springs 116a and 116b may be connected to the support member 112 and the fixing portion 113 to pull the fixing portion 113 downward.

[0116] In example embodiments, the controller 160 may perform tilt adjustment control of the hemispherical mirror 200 fixed to the fixing portion 113 by controlling a height at which each of the plurality of adjustment bolts 115 a , 115 b , and 115 c protrudes from an upper surface of the support 112 .

[0117] In example embodiments, the center of the spherical portion of the hemispherical mirror 200 may be accurately aligned with the focus of the objective lens 120 , and the optical measurement system 100 may accurately and precisely measure the numerical aperture of the objective lens 120 .

[0118] FIG. 11A to FIG. 11E is a graph showing the measured numerical aperture of the objective lens for each wavelength.

[0119] FIG. 11A to FIG. 11E The graph may be a graph measuring the numerical aperture of the objective lens 120 according to the wavelength of the light source 130 by respectively and differently setting the wavelength of the light source 130 to 450 nm, 500 nm, 550 nm, 600 nm, and 650 nm. When the wavelengths of the light sources 130 are different from each other, the numerical aperture of the objective lens 120 may vary due to chromatic aberration of the objective lens 120.

[0120] exist FIG. 11A to FIG. 11EIn the graph of , the horizontal axis may represent the numerical aperture NA, and the vertical axis may represent the radius of the pupil image. FIG. 11A to FIG. 11E In the graph, the partial numerical aperture corresponding to the plurality of concentric patterns 311 displayed in the back-focus image 300 may be represented, the relationship between the radius of the pupil image and the numerical aperture of the objective lens 120 may be approximated as a linear function, and the numerical aperture MaxNA of the objective lens calculated based on the linear function and the radius MaxRad of the pupil image may be represented.

[0121] Reference FIG. 11A to FIG. 11E , the coefficient of determination R of the linear function derived by regression analysis 2 can have a value close to 1. Since the coefficient of determination R 2 Having a value close to 1, the accuracy of the partial numerical aperture measured based on the plurality of latitude lines 211 of the hemispherical mirror 200 and the plurality of concentric patterns 311 of the back-focus image 300 may be high.

[0122] In example embodiments, the optical measurement system 100 may accurately measure the numerical aperture of the objective lens 120 in various wavelength bands.

[0123] Fig.12 is a graph showing the accuracy of measurement of the numerical aperture of an objective lens according to an example embodiment of the present disclosure.

[0124] Fig.12 is a graph for comparing a theoretical value of the numerical aperture of the objective lens, a numerical aperture measured in the example embodiment, and a numerical aperture measured according to a comparative example different from the example embodiment of the present disclosure. Fig.12 The horizontal axis of the graph may represent the wavelength of the light source, and the vertical axis thereof may represent the numerical aperture NA.

[0125] Theoretical values ​​can be obtained from the measurement of SiO formed on the wafer surface by ellipsometry. 2 The numerical aperture value of the objective lens is determined by the results of the film, which can be accurately known using the SiO 2 The comparative example may refer to a method of measuring the numerical aperture of an objective lens using the above-mentioned diffraction grating method.

[0126] Reference Fig.12 , the reference value and the numerical aperture in the example embodiment in all measurement wavelength ranges can approximately match each other. On the other hand, the reference value and the numerical aperture according to the comparative example can vary greatly depending on the wavelength of the light source.

[0127] Since the method for measuring the numerical aperture of the objective lens in the example embodiment is based on the plurality of concentric patterns 311 displayed in the back focus image 300, the numerical aperture can be measured using various reference values ​​compared to the comparative example in which the numerical aperture is measured using only ±1-order diffraction light patterns. Therefore, the accuracy of measuring the numerical aperture can be improved.

[0128] Fig.13A and Fig. 13B is a graph illustrating the repeatability of an example measurement method of the numerical aperture of an objective lens.

[0129] Fig.13A is a graph showing the repeatability of measuring the numerical aperture of the objective lens of the hemispherical mirror 200. For example, Fig.13A The results of calculating the measurement errors caused by device vibration, camera shot noise, image processing, etc. are shown by moving the X-axis position and Y-axis position of the hemispherical mirror 200 to a position that is not aligned with the objective lens 120, and repeating the operation of capturing an image of the rear focal plane once 10 times after rearranging the X-axis position and Y-axis position of the hemispherical mirror 200 to the objective lens 120.

[0130] Reference Fig.13A , the aperture measurement error in all measurement wavelength ranges can be equal to or less than 10 -5 .

[0131] Fig. 13B is a graph showing the accuracy of measuring the numerical aperture according to the alignment error of the hemispherical mirror 200. For example, Fig. 13B The seven numerical aperture measurement values ​​according to the X-axis direction position are obtained by moving the hemispherical mirror 200 by 100 nm within the range of ±300 nm in the X-axis direction and calculating the measurement error.

[0132] Reference Fig. 13B , even if there is an alignment error in the hemispherical mirror 200, the aperture measurement error in all measurement wavelength ranges can be 10 -5 or smaller.

[0133] Reference Fig.13A and Fig. 13B , even if a measurement error occurs, the accuracy of measuring the numerical aperture of the objective lens 120 can be improved.

[0134] Fig.14 is a graph showing the accuracy of an example method of measuring the numerical aperture of an objective lens according to the radius of a hemispherical mirror.

[0135] The hemispherical mirror 200 may have a processing error. For example, when the hemispherical mirror 200 is processed using a diamond turning method, the radius of the hemispherical mirror 200 may have an error of ±1 μm, where the standard deviation is 3σ.

[0136] Fig.14 It may be a graph showing a simulation result of an aperture measurement error according to the radius of the hemispherical mirror 200 when there is an error of 1 μm in the radius of the hemispherical mirror 200. When the radius of the hemispherical mirror 200 is 5 mm, the error of the numerical aperture may be simulated as 0.0002. When the magnitude of the error of the radius of the hemispherical mirror 200 is the same 1 μm, as the radius increases, the error rate decreases, thereby reducing the error of the numerical aperture.

[0137] Meanwhile, the radius of the hemispherical mirror 200 may be determined in consideration of the aperture measurement error and the size of the space occupied by the hemispherical mirror 200 in the optical measurement system 100. For example, when the hemispherical mirror 200 has a radius of 5 mm to 10 mm, the aperture measurement error may be sufficiently low, and the hemispherical mirror 200 may occupy a smaller space than the stage of the optical measurement system 100, so that the hemispherical mirror 200 may always be mounted on the stage and may be used to measure the numerical aperture of the objective lens 120 in the mounting environment of the objective lens 120.

[0138] Fig.15 is a graph showing the accuracy of an example measurement method of the numerical aperture of an objective lens according to the number of latitude lines formed in a hemispherical mirror.

[0139] Due to a processing error of the hemispherical mirror 200, errors may also occur at the positions of the plurality of latitude lines 211 formed in the hemispherical mirror 200 and at gaps between the plurality of latitude lines 211. In example embodiments, as the number of latitude lines formed in the hemispherical mirror 200 increases, multiple reference values ​​can be obtained from the back-focus image, thereby reducing a measurement error of the numerical aperture.

[0140] Fig.15 This is a graph for simulating the measurement error of the numerical aperture according to the number of latitude lines when the latitude lines have an error of ±1μm under a standard deviation of 3σ. When the number of latitude lines is small, the measurement error of the numerical aperture may be ±0.00005 or more, but as the number of latitude lines increases, the measurement error of the numerical aperture may approach zero.

[0141] FIG. 16A to FIG. 16C is a diagram illustrating the accuracy of an example measurement method of the numerical aperture of an objective lens according to a processing error of a hemispherical mirror.

[0142] Ideally, since the spherical portion 210 is processed into a hemispherical concave shape from the planar portion 220, the center of the spherical portion 210 may be included in a plane extending the planar portion 220. That is, the height of the center may match the height of the planar portion 220.

[0143] Reference Fig.16A and Fig. 16B , the height of the center of the spherical portion 210 and the height of the plane portion 220 may be different from each other due to processing errors of the spherical portion 210 and the plane portion 220. As described with reference to FIG. 7 , when the objective lens 120 is focused based on the plane portion 220, defocusing may occur in which the focus of the objective lens 120 and the center of the spherical portion 210 do not match each other due to the processing error.

[0144] When defocusing occurs, the incident angle of light incident from the objective lens to the spherical portion 210 may be different from the reflection angle of light reflected from the spherical portion 210. When the numerical aperture of the objective lens 120 is calculated using a back focal plane image generated by allowing the light reflected from the spherical portion 210 to be incident on the back focal plane (BFP), an error may occur in the calculated numerical aperture.

[0145] Partial numerical aperture NA at the nth concentric circle of the back-focus image n It can be calculated according to the following equation 3.

[0146] <Equation 3>

[0147]

[0148] In Equation 3, defocus may represent the height difference between the center of the spherical portion 210 and the planar portion 220, RSM may represent the radius of the spherical portion 210, and θ n It can represent the latitude of the nth latitude line.

[0149] Fig. 16C The result of simulating the numerical aperture measurement error according to the degree of defocusing based on the above equation 3 is shown when the radius of the spherical portion 210 is 10 mm. The size of the hemispherical mirror 200 may have an error of ±1 μm under a standard deviation of 3σ, and the hemispherical mirror 200 with a defocusing range of ±1 μm may be used in the optical measurement system 100. Fig. 16C , when defocus of ±1 μm occurs, the numerical aperture measurement error is only 0.00005. That is, even if there is a processing error in the hemispherical mirror 200, the numerical aperture can be accurately measured.

[0150] Meanwhile, the spherical portion of the hemispherical mirror may be implemented in various structures.

[0151] Figures 17 to 20 is a diagram illustrating an example structure of a hemispherical mirror according to an embodiment of the present disclosure.

[0152] Reference Fig.17 , the hemispherical mirror 200a may have a structure similar to that of reference FIG. 2A to FIG. 2C The same spherical portion 210, planar portion 220 and boundary line 230 are described. However, Fig.17The hemispherical mirror 200a may include a plurality of first points 211a formed at predetermined latitude intervals and a plurality of second points 212a formed at predetermined longitude intervals, instead of a plurality of latitude lines 211 and a plurality of longitude lines 212. That is, the hemispherical mirror 200a may include a plurality of first points 211a as latitude markers.

[0153] The back focus image formed by light reflected from the hemispherical mirror 200a and incident on the objective lens 120 may have a plurality of points formed by shifting a plurality of first points 211a and a plurality of second points 212a. The controller 160 may detect a plurality of concentric patterns as described with reference to FIG. 3 by performing image processing on the back focus image.

[0154] Reference Fig.18 , the hemispherical mirror 200b may have a structure similar to that of reference FIG. 2A to FIG. 2C The same spherical portion 210, multiple longitude lines 212, planar portion 220 and boundary line 230 are described. However, Fig.18 The hemispherical mirror 200b may include a plurality of marking areas 211b formed in a predetermined latitude range, rather than a plurality of latitude lines 211. That is, the hemispherical mirror 200b may include a plurality of marking areas 211b as latitude marks. According to example embodiments, the plurality of marking areas 211b may be formed by grinding a partial area of ​​the spherical portion 210.

[0155] The back focus image formed by light reflected from the hemispherical mirror 200b and incident on the objective lens 120 may have a plurality of patterns formed by shifting the plurality of marking regions 211b. The controller 160 may detect a plurality of concentric patterns as described with reference to FIG. 3 by processing an image on the back focus image.

[0156] Reference Fig.19 , the hemispherical mirror 200c may include a first spherical portion 210c1, a second spherical portion 210c2, a plane portion 220, and a boundary line 230. In addition, a plurality of latitude lines 211 and a plurality of longitude lines 212 may be formed in the first spherical portion 210c1 and the second spherical portion 210c2.

[0157] The first spherical portion 210c1 and the second spherical portion 210c2 may correspond to the FIG. 2A to FIG. 2C The portion obtained by dividing the spherical portion 210 by a plane passing through the center of the spherical portion 210 and perpendicular to the plane portion 220. The first spherical portion 210c1 and the second spherical portion 210c2 may be coated with materials having different levels of reflectivity depending on the wavelength. For example, in the ultraviolet band, the reflectivity of the first spherical portion 210c1 may be higher than the reflectivity of the second spherical portion 210c2, and in the infrared band, the reflectivity of the second spherical portion 210c2 may be higher than the reflectivity of the first spherical portion 210c1.

[0158] The optical measurement system 100 may irradiate light to the hemispherical mirror 200c while adjusting the wavelength of the light source 130 to measure the numerical aperture according to the wavelength of the objective lens 120. When the light source 130 outputs light in the ultraviolet band, the semicircular portion corresponding to the first spherical portion 210c1 may be relatively brightly displayed in the pupil image included in the back-focus image, and when the light source 130 outputs light in the infrared band, the semicircular portion corresponding to the second spherical portion 210c2 may be relatively brightly displayed in the pupil image included in the back-focus image.

[0159] As the semicircular portion of the back-focus image becomes brighter, the concentric circle pattern can further contrast with the semicircular portion, thereby easily detecting the concentric pattern. Since each of the back-focus images captured by the light source 130 based on various wavelength bands can include a bright semicircular area, the optical measurement system 100 can easily measure the numerical aperture of the objective lens 120 in various wavelength bands.

[0160] Reference Fig. 20 , the hemispherical mirror 200d may have a structure similar to that of reference FIG. 2A to FIG. 2C The same spherical portion 210, multiple latitude lines 211, multiple longitude lines 212, planar portion 220 and boundary line 230 are described.

[0161] In example embodiments, the hemispherical mirror 200d may further include a liquid 240 filling a space surrounded by the spherical portion 210. The optical measurement system 100 may increase the numerical aperture of the objective lens 120, and the liquid may be used as a medium between the objective lens 120 and the sample to increase the resolution of the image, in which case the objective lens 120 may be referred to as an immersion lens.

[0162] In example embodiments, the controller 160 may measure the numerical aperture of the immersion lens by obtaining a back-focus image in a state where the hemispherical mirror 200 d is filled with the liquid 240 serving as a medium in the spherical portion 210 .

[0163] In a state where the focus of the objective lens matches the center of the spherical part of the hemispherical mirror, the optical measurement system 100 in the example embodiment can allow light from the internal light source to be incident on the spherical part of the hemispherical mirror, the hemispherical mirror having a plurality of latitude marks formed on the spherical part to have a reflectivity different from that of the spherical part, and the optical measurement system 100 in the example embodiment can measure the numerical aperture of the objective lens using the pattern of the plurality of latitude marks recorded to the back-focus image of the objective lens. Therefore, the optical measurement system 100 can measure the numerical aperture of the objective lens in situ.

[0164] In addition, the optical measurement system 100 can accurately measure the numerical aperture of the objective lens based on the detected multiple circular patterns based on the patterns of multiple latitude marks transferred to the back focus image. In addition, since the optical measurement system 100 can measure the numerical aperture of the objective lens in all directions using a single back focus image, the time to measure the numerical aperture in all directions can be improved.

[0165] Although the present disclosure includes many specific implementation details, these should not be interpreted as limitations on the scope that can be claimed. Certain features described in the context of different embodiments in the present disclosure may also be implemented in combination in a single embodiment. On the contrary, the various features described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination. In addition, although features may be described above as working in certain combinations and even initially claimed as such, one or more features from the combination may be removed from the combination in some cases, and the combination may be directed to a sub-combination or a variation of the sub-combination.

[0166] The present disclosure is not limited to the above embodiments and the accompanying drawings, but is limited by the appended claims. Therefore, those skilled in the art may make various substitutions, modifications or changes without departing from the scope of the present disclosure defined by the appended claims, and these substitutions, modifications or changes should be interpreted as being included in the scope of the present disclosure.

Claims

1. An optical measurement system, comprising: A hemispherical mirror comprising: The plane part, a spherical portion having a hemispherical concave shape in the planar portion, and a plurality of latitude marks formed in the spherical portion and having a different reflectivity than the spherical portion; An optical unit comprising: an objective lens configured to allow light incident from a light source to be incident on the hemispherical mirror, and at least one beam splitter configured to transmit light reflected from the hemispherical mirror and incident on the objective lens to a first sensor; and A controller configured to measure the numerical aperture of the objective lens using a back-focus image of the objective lens from the first sensor in a state where the hemispherical mirror is placed so that the focus of the objective lens and the center of the spherical portion of the hemispherical mirror are aligned with each other.

2. The optical measurement system according to claim 1, wherein: The controller is configured to: detecting a plurality of circular patterns in the back-focus image formed by an image of each of the plurality of latitude markers, and The numerical aperture of the objective lens is determined based on the sine function value of each of the plurality of latitudes indicated by the plurality of latitude marks, the radius of each of the plurality of circular patterns, and the radius of the pupil image in the back-focus image.

3. The optical measurement system according to claim 2, wherein: The controller is configured to: determining a sine function value for each of the plurality of latitudes based on a radius of a latitude line for each of the plurality of latitudes indicated by the plurality of latitude marks and a radius of the spherical portion, determining a partial numerical aperture of the objective lens according to the radius of each of the plurality of circular patterns based on the sine function value of each of the plurality of latitudes and the radius of each of the plurality of circular patterns, and A numerical aperture of the objective lens according to a radius of the pupil image is determined based on a partial numerical aperture of the objective lens according to a radius of each of the plurality of circular patterns.

4. The optical measurement system according to claim 1, wherein: The optical unit further includes a condenser lens configured to condense light incident on the objective lens and transmit the light to a second sensor.

5. The optical measurement system according to claim 4, wherein: The controller is configured to align a vertical position perpendicular to the plane portion using a focused image of the objective lens from the second sensor when the hemispherical mirror is positioned so that the focus of the objective lens is disposed on the plane portion.

6. The optical measurement system according to claim 5, wherein: The controller is configured to: when the vertical position of the hemispherical mirror is aligned using the focus of the objective lens, determining the boundary position of the hemispherical mirror so that the focus of the objective lens is set on a boundary line between the plane portion and the spherical portion using the focused image from the second sensor by changing the horizontal position along the plane portion, determining the center of the spherical portion based on the boundary position of the hemispherical mirror, and The horizontal position of the hemispherical mirror is aligned so that the focus of the objective lens is set at the center of the spherical part.

7. The optical measurement system according to claim 6, wherein: The controller is configured to: detecting the tilt of the hemispherical mirror based on the sharpness of the focused image obtained from the boundary position, and The tilt adjustment of the hemispherical mirror is controlled so as to counteract the tilt of the hemispherical mirror.

8. The optical measurement system according to claim 1, wherein: The spherical portion includes a first spherical portion and a second spherical portion formed of materials having different reflectivities.

9. The optical measurement system according to claim 8, wherein: The first spherical portion and the second spherical portion correspond to portions obtained by dividing the spherical portion by a plane perpendicular to the planar portion and passing through the center of the spherical portion, the first spherical portion has a higher reflectivity in an infrared wavelength band than the second spherical portion, and the second spherical portion has a higher reflectivity in an ultraviolet wavelength band than the first spherical portion.

10. The optical measurement system according to claim 1, wherein: The hemispherical mirror further includes a liquid filling a hemispherical space formed by the spherical portion.

11. The optical measurement system according to claim 1, wherein: The plurality of latitude marks include a plurality of latitude lines formed at predetermined latitude intervals.

12. The optical measurement system according to claim 11, wherein: The plurality of latitude lines are formed to have a reflectivity different from that of the spherical portion by being engraved or embossed on the spherical portion.

13. The optical measurement system according to claim 1, wherein: The plurality of latitude marks include a plurality of mark areas formed in each of a plurality of latitude ranges.

14. The optical measurement system according to claim 1, wherein: The hemispherical mirror further includes a plurality of longitude marks formed in the spherical portion to have a reflectivity different from a reflectivity of the spherical portion.

15. An optical measurement system, comprising: a hemispherical mirror including a planar portion, a spherical portion having a hemispherical concave shape in the planar portion, and a plurality of latitude marks formed in the spherical portion, the plurality of latitude marks having a reflectivity different from a reflectivity of the spherical portion; a stage in which a substrate chuck for loading a semiconductor substrate and an alignment system equipped with the hemispherical mirror are arranged; an optical unit including an objective lens configured to allow light incident from a light source to be incident on a target, and a beam splitter configured to transmit light reflected from the target and incident on the objective lens to a first sensor; as well as A controller is configured to set the hemispherical mirror as the target of the objective lens by adjusting the position of the stage, and is configured to measure the numerical aperture of the objective lens using the back focus image of the objective lens from the first sensor.

16. The optical measurement system according to claim 15, wherein: The controller is configured to align the plane portion of the hemispherical mirror to be parallel to a back focal plane of the objective lens by performing tilt adjustment control of the hemispherical mirror using the alignment system.

17. The optical measurement system according to claim 15, wherein: The alignment system comprises: a fixed part, on which the hemispherical mirror is mounted; a support member mounted on the substrate chuck and configured to support the fixing portion; a plurality of nuts penetrating the support member on at least three vertical edges of the support member; a plurality of adjustment bolts which penetrate the support member by being fastened to the plurality of nuts and are configured to support the fixing portion above the support member, and A plurality of springs are configured to connect the support member and the fixing portion.

18. The optical measurement system according to claim 17, wherein: The controller is configured to perform tilt adjustment control of the hemispherical mirror mounted to the fixing portion by controlling a height at which each of the plurality of adjustment bolts of the alignment system protrudes from an upper surface of the support.

19. The optical measurement system according to claim 15, wherein: The controller is configured to control the position of the hemispherical mirror by controlling the movement of the stage in a direction parallel to an upper surface of the stage and in a direction perpendicular to the upper surface of the stage.

20. An optical measurement system comprising: a hemispherical mirror including a plurality of latitude marks formed in a spherical portion to have a different reflectivity from that of the spherical portion; light source; Objective lens; as well as A controller configured to: matching the center of the spherical portion with the focal point of the objective lens; allowing light output from the light source to be incident on the spherical portion through the objective lens; detecting a circular pattern formed by the plurality of latitude markings in a back-focus image of the objective lens; calculating a partial numerical aperture of the objective lens according to the radius of each of the circular patterns based on the radius of each of the circular patterns and the latitudes indicated by the plurality of latitude marks; as well as Based on the partial numerical aperture according to the radius of each of the circular patterns, a numerical aperture of the objective lens according to the radius of the pupil image in the back-focus image is determined.

Images