Microcuvette and microscopy system

Abstract

The application discloses a microscope tube lens and a microscope system. The microscope tube lens comprises a first lens group, a second lens group and a third lens group which are coaxially arranged in sequence along the direction from the object side to the image side. The first lens group and the second lens group are optically separated, and the second lens group and the third lens group are also optically separated. The focal length of the microscope tube lens is 370 mm, the image distance is 225.679 mm, and the optical separation between the entrance pupil and the first lens group is 490 mm. The microscope tube lens can support a large target TDI line scan camera, effectively play the advantages of the TDI camera in adapting to platform jitter, improving the signal-to-noise ratio and the scanning speed, and improve the precision and efficiency of wafer defect detection.

Description

Technical Field

[0001] This application generally relates to the field of optical equipment technology. More specifically, this application relates to a microscope tube and a microscope system. Background Technology

[0002] With the rapid development of the semiconductor industry, the manufacturing processes of wafers and semiconductor chips are constantly being refined, and the requirements for their inspection accuracy are becoming increasingly stringent. Among them, the surface defect inspection of wafer products after photolithography is particularly critical, as this step directly determines the yield of the final product. Any tiny surface defect can cause the complete failure of subsequent semiconductor products. Therefore, high-precision and high-reliability wafer defect inspection has become one of the core requirements for ensuring the stable operation of the semiconductor industry chain.

[0003] In existing wafer inspection technologies, the mainstream approach is to use an area scan camera combined with an internal coaxial point light source and an external ring light source to construct a bright-dark field inspection system. While this approach offers stable imaging pixels, it has significant technical limitations: it requires extremely high overall stability of the inspection equipment. Even slight fluctuations in the operation of the precision inspection platform can directly affect the imaging quality of the area scan camera, thereby reducing the accuracy of defect detection. To overcome this limitation, the industry has developed line scan cameras based on time-delay integration (TDI) technology. These cameras achieve multiple imaging of the same location through a multi-image-order design, effectively adapting to the operational jitter of the precision platform. Furthermore, the multiple integrations enhance the image signal-to-noise ratio, while shortening exposure time to increase scanning speed and significantly improve inspection efficiency. However, current technology lacks a suitable microscope tube and matching microscope system to match large-area TDI line scan cameras. This prevents the TDI line scan camera's performance advantages from being fully utilized in wafer inspection scenarios, making it difficult to meet the semiconductor industry's actual needs for efficient and high-precision wafer inspection.

[0004] In view of this, this application provides a microscope tube lens that supports a large-area TDI line scan camera, so as to effectively leverage the advantages of TDI cameras in adapting to platform jitter, improving signal-to-noise ratio and scanning speed, and improving the accuracy and efficiency of wafer defect detection. Summary of the Invention

[0005] In order to at least address one or more of the technical problems mentioned above, this application proposes a microscope tube lens that supports a large-area TDI line scan camera in the following aspects.

[0006] In a first aspect, this application provides a microscope tube, characterized in that it comprises a first lens group, a second lens group, and a third lens group arranged coaxially along the object-to-image direction; optical intervals exist between the first lens group and the second lens group, and between the second lens group and the third lens group; the microscope tube has a focal length of 370 mm, an image distance of 225.679 mm, and an optical interval of 490 mm between the entrance pupil and the first lens group; a total of six lenses with optical power are provided; the first lens group includes a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power; the first lens is a convex-concave lens, the second lens is a biconvex lens, and the third lens is a concave-convex lens; the second lens group includes a fourth lens with positive optical power; the fourth lens is a convex-planar lens or a convex-concave lens; the third lens group includes a fifth lens and a sixth lens, the fifth lens having positive optical power and the sixth lens having negative optical power; The fifth lens is a biconvex lens, and the sixth lens is a biconcave lens; or the fifth lens is a convex-concave lens, and the sixth lens is a convex-concave lens; the radius of curvature R5 of the fifth lens and the radius of curvature R6 of the sixth lens satisfy the following relationship: .

[0007] In some embodiments, the image-side surface of the first lens is glued and fixed to the object-side surface of the second lens, and the image-side surface of the second lens is glued and fixed to the object-side surface of the third lens.

[0008] In some embodiments, the radius of curvature R1 of the first lens satisfies: The radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens satisfy the following relationship: 2.80; The radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens satisfy the following: .

[0009] In some embodiments, the radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens satisfy the following relationship: .

[0010] In some embodiments, the image-side surface of the fifth lens is glued and fixed to the object-side surface of the sixth lens.

[0011] In a second aspect, this application provides a microscope system, characterized in that it includes: an entrance pupil; a tube lens as described in any of the first aspects and embodiments above; and an image plane; wherein the entrance pupil, tube lens, and image plane are arranged sequentially along the principal optical axis.

[0012] The microscope tube lens provided above, which supports a large-area TDI line scan camera, is designed to precisely match the imaging requirements of a large-area TDI line scan camera by arranging a first lens group, a second lens group, and a third lens group coaxially along the object-to-image direction, and maintaining optical intervals between the first and second lens groups and between the second and third lens groups. The focal length of the tube lens is set to 370mm, the image distance to 225.679mm, and the optical interval between the entrance pupil and the first lens group to 490mm. The 370mm focal length is compatible with the 60mm photosensitive target of a large-area TDI line scan camera, meeting the optical parameter requirements for large-area imaging. The 490mm entrance pupil and the distance between the first lens group can accommodate necessary optical components such as the objective lens switching nose wheel, autofocus sensor, and internal coaxial Kohler illumination system. Since the back focal length of the microscope objective is a parallel optical path, the addition of these components will not adversely affect the optical imaging. The coaxial lens group and reasonable optical spacing ensure the stability of the optical imaging, thereby effectively leveraging the advantages of TDI line scan cameras in adapting to the jitter of precision platform operation, improving image signal-to-noise ratio, and shortening exposure time to increase scanning speed. This helps to improve the accuracy and efficiency of wafer defect detection, meeting the semiconductor industry's demand for high-precision and high-efficiency defect detection of post-lithography wafer products, while also overcoming the limitations of traditional area scan camera inspection solutions that have excessively high requirements for equipment stability. Attached Figure Description

[0013] The above and other objects, features, and advantages of exemplary embodiments of this application will become readily understood by reading the following detailed description with reference to the accompanying drawings. In the drawings, several embodiments of this application are illustrated by way of example and not limitation, and the same or corresponding reference numerals denote the same or corresponding parts, wherein:

[0014] Figure 1 An exemplary structural diagram of the microscope tube of Embodiment 1 of this application is shown;

[0015] Figure 2 The distortion diagrams of the microscope tube lens of Embodiment 1 of this application at different wavelengths are shown;

[0016] Figure 3 The modulation transfer function of the microscope tube lens of Embodiment 1 of this application at different wavelengths is shown;

[0017] Figure 4 The diagram shows a dot plot of the microscope tube lens of Embodiment 1 of this application at different wavelengths;

[0018] Figure 5 An exemplary structural diagram of the microscope tube of Embodiment 2 of this application is shown;

[0019] Figure 6The distortion diagrams of the microscope tube lens of Embodiment 2 of this application at different wavelengths are shown;

[0020] Figure 7 The modulation transfer function diagrams of the microscope tube lens of Embodiment 2 of this application at different wavelengths are shown;

[0021] Figure 8 The diagram shows a dot plot of the microscope tube lens of Embodiment 2 of this application at different wavelengths;

[0022] Figure 9 An exemplary structural diagram of the microscope tube of Embodiment 3 of this application is shown;

[0023] Figure 10 The distortion diagrams of the microscope tube lens of Embodiment 3 of this application at different wavelengths are shown;

[0024] Figure 11 The modulation transfer function diagrams of the microscope tube lens of Embodiment 3 of this application at different wavelengths are shown;

[0025] Figure 12 The diagram shows a dot plot of the microscope tube lens of Embodiment 3 of this application at different wavelengths. Detailed Implementation

[0026] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0027] It should be understood that the terms "comprising" and "including" used in the specification and claims of this application indicate the presence of the described features, integrals, steps, operations, elements and / or components, but do not exclude the presence or addition of one or more other features, integrals, steps, operations, elements, components and / or collections thereof.

[0028] It should also be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. As used in this specification and claims, the singular forms “a,” “an,” and “the” are intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used in this specification and claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes such combinations.

[0029] As used in this specification and claims, the term "if" may be interpreted, depending on the context, as "when," "once," "in response to determination," or "in response to detection." Similarly, the phrase "if determined" or "if [described condition or event] is detected" may be interpreted, depending on the context, as "once determined," "in response to determination," "once [described condition or event] is detected," or "in response to detection of [described condition or event]."

[0030] It should be noted that, unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0031] In this application, unless otherwise stated, directional terms such as "upper," "lower," "top," and "bottom" are generally used in relation to the direction shown in the accompanying drawings, or in relation to the vertical, perpendicular, or gravitational direction of the component itself; similarly, for ease of understanding and description, "inner" and "outer" refer to the inner and outer contours of each component itself, but the above directional terms are not intended to limit this application.

[0032] It should be noted that in this specification, the terms "first," "second," "third," etc., are used only to distinguish one feature from another and do not imply any limitation on the features. Furthermore, in the accompanying drawings, the thickness, size, and shape of the lenses have been slightly exaggerated for ease of illustration. The drawings are for illustrative purposes only and are not strictly to scale.

[0033] In this specification, the paraxial region refers to the region near the optical axis. If the lens surface is convex and the location of that convexity is not defined, it means that the lens surface is convex at least in the paraxial region; if the lens surface is concave and the location of that concaveness is not defined, it means that the lens surface is concave at least in the paraxial region. The surface shape in the paraxial region can be determined according to the judgment method commonly known in the art, using the R value (R refers to the radius of curvature of the paraxial region, usually the R value in the lens database of optical software) to determine convexity or concavity. For the object side, when the R value is positive, it is determined to be convex, and when the R value is negative, it is determined to be concave; for the image side, when the R value is positive, it is determined to be concave, and when the R value is negative, it is determined to be convex.

[0034] In this application, the object side refers to the side of the microscope tube facing the object being photographed (not shown in the figure), and the image side refers to the side of the microscope tube facing the imaging plane (which can be simply referred to as the image plane). In the following text, the object side of a lens refers to the surface of the lens facing the object being photographed (not shown in the figure), and the image side of a lens refers to the surface of the lens facing the image plane. In the structural schematic diagram shown in this application, the left side is the object side, and the right side is the image side.

[0035] The specific embodiments of this application will now be described in detail with reference to the accompanying drawings. Invention Overview

[0037] Driven by the ever-increasing demand for precision in semiconductor wafer inspection, microscope objectives adapted for large-area imaging have emerged in the market. These large-area microscope objectives can support a maximum camera target size of 35mm, while traditional microscope objectives only support a maximum target size of 24mm. Calculations show that the target support capability of these microscope objectives is 1.45 times higher than that of traditional products, making it possible to scan wafers using large-area TDI cameras.

[0038] To further unleash the performance of large-target TDI line scan cameras and meet the dual demands of high resolution and high efficiency for wafer defect detection, the TDI line scan camera specifically adapted to the microscope tube provided in this application is configured with a 12K pixel scale, a single pixel size of 5 micrometers, and a chip photosensitive target surface size of 60mm. Based on the camera's photosensitive target surface requirements and the maximum support target surface of existing large-target microscope objectives (35mm), the required magnification of the microscope tube can be calculated through the ratio of target surface sizes: that is, the ratio of 60mm to 35mm is 1.85 times. Combining the correlation between microscope tube magnification and focal length, further calculations determine that the focal length of this microscope tube needs to be set to 370mm to ensure that the camera can acquire a clear image.

[0039] From the perspective of optical path design principles in microscopic optical systems, infinity-conjugate microscope objectives require the use of a dedicated tube lens to achieve complete imaging. In standard industry configurations, these microscope objectives are typically paired with a 200mm tube lens. In this case, the magnification of the entire microscope system is determined by the tube lens, which represents a 1X magnification. Based on this standard configuration, microscope objective manufacturers clearly indicate the supported charge-coupled device (CCD) target size when paired with a 1X tube lens. The large-target-area microscope objective adapted in this application belongs to this category, supporting a maximum CCD target size of 35mm in the 1X tube lens configuration. When adapting to a 60mm linear scanning CCD, the magnification of the tube lens needs to be adjusted according to the target size: by calculating the ratio of the 60mm to the 35mm target size, the required tube lens magnification is 1.85x. Since the focal length of a tube lens is positively correlated with its magnification, based on the conventional 200mm focal length corresponding to 1X magnification, multiplying 200mm by 1.85 will give the focal length of the tube lens adapted to a 60mm line scan CCD. The final focal length of the tube lens is determined to be 370mm.

[0040] In the actual construction of wafer inspection systems, to meet the inspection needs of multiple scenarios and the integrity of system functions, various functional components need to be added between the microscope objectives and the microscope tube. These include an objective switching nose wheel assembly, an autofocus sensor, an internal coaxial Kohler illumination system, and a marble platform. The objective switching nose wheel assembly enables rapid replacement of objectives with different parameters, the autofocus sensor can adjust the optical path in real time to ensure image clarity, the internal coaxial Kohler illumination system provides a uniform and stable illumination environment for the wafer surface, and the marble platform ensures the structural stability of the entire optical system.

[0041] Based on the installation space requirements and optical path transmission requirements of these components, calculations determined that the working distance of the microscope tube should be set to 490mm. This working distance is specifically defined as the distance between the entrance pupil of the microscope objective and the first lens at the front end of the microscope tube. Furthermore, since the back focal path of the microscope objective is a parallel optical path, this characteristic ensures that adding the aforementioned functional components between the microscope objective and the microscope tube will not significantly affect the final optical imaging quality, thus ensuring compatibility between system function expansion and imaging effects.

[0042] In industrial inspection, the microscope objectives commonly used employ an image-side parallel light path design. This design offers significant practical advantages, facilitating the flexible addition of various optical components between the microscope objective and the microscope tube. For example, filters can be added to filter specific wavelengths of light according to different inspection needs, thereby improving the accuracy of wafer surface defect identification. However, it is important to note that the image-side parallel light path itself cannot directly form a real image on the CCD target surface. The parallel light must be processed by a specialized optical focusing component to be converted into a real image. Therefore, a separate microscope tube is necessary. Through the optical focusing effect of the tube, the parallel light output from the microscope objective is precisely focused onto the target surface of the linear scanning CCD, ultimately forming a clear real image on the target surface. Only by fully integrating the microscope objective, various functional components, the microscope tube, and the linear scanning CCD can a complete microscope system with practical inspection capabilities be formed, meeting the various needs of wafer defect inspection in industrial scenarios.

[0043] The microscope tube provided in the embodiments of this application will now be described in detail.

[0044] The microscope tube of this application includes a first lens group, a second lens group, and a third lens group arranged coaxially along the object-to-image direction, with optical gaps between the first and second lens groups, and between the second and third lens groups. The microscope tube has a focal length of 370 mm and an image distance of 225.679 mm, while the optical gap between the entrance pupil and the first lens in the first lens group is 490 mm. This structural and parameter design can meet the imaging requirements of large-area TDI line scan cameras, providing an optical basis for leveraging the performance advantages of TDI cameras in subsequent wafer defect detection.

[0045] The aforementioned first lens group may include a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power. The image-side of the first lens is cemented to the object-side of the second lens, and the image-side of the second lens is cemented to the object-side of the third lens. This cementing method, which combines the three lenses into a single unit, not only reduces light reflection loss at the lens interfaces and improves the light transmittance of the optical system, but also enhances the structural stability of the first lens group and facilitates the assembly and adjustment of the entire microscope tube.

[0046] In practical applications, the first lens is a convex-concave lens, the second lens is a biconvex lens, and the third lens is a concave-convex lens. The convex-concave lens helps correct aberrations, the biconvex lens can efficiently converge light, and the concave-convex lens further adjusts the light path with its negative optical power. The surface shapes of the three lenses work together to achieve initial control of the incident light and initial correction of aberrations, laying the foundation for subsequent image optimization of the lens group.

[0047] From the perspective of radius of curvature design, the radius of curvature R1 of the first lens needs to satisfy: This range was determined after comprehensively considering the light coverage range and aberration control requirements when imaging a large target surface. Simultaneously, the radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens must satisfy the following condition. A 2.80 ratio ray; the radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens must satisfy the following condition. The proportional relationship. By controlling the proportion of these radii of curvature, the optical power distribution of each lens in the first lens group can be balanced, further optimizing the aberration correction effect, so that light can be transmitted to subsequent lens groups in a better state after passing through the first lens group.

[0048] The aforementioned second lens group may include a fourth lens with positive optical power, which can be in the form of a convex-planar lens or a convex-concave lens. These two surface types ensure a continuous positive optical power for light to achieve a converging effect while also allowing for flexible adjustment of the light propagation angle, thus better adapting to the imaging requirements of the entire optical system. Furthermore, the radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens must satisfy the following condition: The proportional relationship between the two lens groups ensures that the optical power of the light rays is coordinated between the first and second lens groups, making the light rays pass more smoothly between the two lens groups and reducing the introduction of additional aberrations.

[0049] The aforementioned third lens group may include a fifth lens and a sixth lens, wherein the fifth lens has positive optical power and the sixth lens may have negative optical power, and the image-side of the fifth lens and the object-side of the sixth lens are cemented together. This design allows the present application to perform final focusing or fine-tuning of aberrations by selecting the optical power type of the sixth lens according to specific imaging requirements, and the cemented structure also helps to improve the optical stability and transmittance of the third lens group.

[0050] In practical applications, the fifth lens can be a biconvex lens and the sixth lens a biconcave lens; alternatively, the fifth lens can be a convex-concave lens and the sixth lens can also be a convex-concave lens. These two lens combinations provide flexibility in optical design, allowing selection based on specific aberration correction requirements and imaging quality specifications, thereby ensuring clear and uniform imaging across a large target area.

[0051] From the perspective of curvature relationship, the radius of curvature R5 of the fifth lens and the radius of curvature R6 of the sixth lens must satisfy the following condition. The proportional relationship is crucial. By controlling this ratio, the final focusing capability of the third lens group and the degree of aberration correction can be precisely adjusted, so that the light passing through the preceding lens group can form a clear real image on the 60mm photosensitive target surface of the TDI line scan camera that meets the accuracy requirements for wafer defect detection, thereby fully leveraging the performance advantages of the large-target TDI camera in wafer defect detection.

[0052] In practical applications, for the different optical power requirements and aberration correction tasks of the first, second, third, fourth, fifth and sixth lenses in the microscope tube, specific glass materials can be selected for each lens, and the glass materials selected for each lens are not exactly the same, so as to ensure the imaging quality of the large target surface TDI line scan camera through the synergistic cooperation of the optical properties of the materials.

[0053] Specifically, the first lens, as the initial optical element of the first lens group, needs to be adapted to the convex / concave shape and positive optical power requirements to assist in the initial convergence of light and aberration control. Therefore, H-TF5 or H-ZBAF16 glass materials can be selected. The second lens is a biconvex lens with positive optical power, mainly responsible for the efficient convergence of light. At the same time, it needs to work with the first and third lenses to balance chromatic aberration. Therefore, H-FK71 glass material can be selected. The low dispersion characteristics of this material can effectively reduce the propagation deviation of light of different wavelengths. The third lens is a concave / convex lens with negative optical power. Its core function is to correct aberrations such as spherical aberration and coma introduced by the preceding lenses. The appropriate material needs to be selected according to the aberration correction emphasis of different tube lenses. Therefore, H-K12, H-BAK5, or H-BAK7 glass materials can be selected. Targeted aberration compensation can be achieved through the differences in refractive index and Abbe number of different materials. The fourth lens, as the second... The fifth lens, being the sole component of the lens group, needs to be compatible with the surface design of a convex-flat lens or a convex-concave lens, as well as the optical path connection requirements for positive optical power. This ensures that the light emitted from the front lens group (i.e., the first lens group) can be smoothly transmitted to the rear lens group (i.e., the third lens group). Therefore, H-ZPK7 glass material can be selected. The fifth lens has positive optical power and needs to work with the sixth lens to complete the final focusing of the light and image plane optimization. It needs to be compatible with the surface design of a biconvex lens or a convex-concave lens. Therefore, ZBAF51 or H-ZBAF4 glass material can be selected. The sixth lens needs to adjust its optical power type (negative optical power) according to the material characteristics of the fifth lens and the final imaging target of the tube lens (such as low distortion and high diffraction limit). Therefore, H-LAK51A, H-K3, or H-LAK52 glass material can be selected. By matching the material characteristics with the fifth lens, the aberration correction effect can be further optimized to ensure that the light forms a clear real image on the 60mm target surface.

[0054] The above-mentioned selection of glass materials not only makes full use of the inherent differences in refractive index and Abbe number of different materials to achieve accurate and comprehensive correction of various aberrations, but also ensures that all materials are domestically produced, effectively controlling production costs while guaranteeing optical performance, thus providing strong support for the industrial production and practical application of microscope tube lenses.

[0055] The projection module applicable to all embodiments of this application is further described below with reference to the accompanying drawings.

[0056] Example 1

[0057] Figure 1 An exemplary structural diagram of the microscope tube 100 according to Embodiment 1 of this application is shown. Figure 1As shown, the microscope tube 100 may include a first lens group 101, a second lens group 102, and a third lens group 103 arranged coaxially along the object-to-image direction, with optical gaps between the first lens group 101 and the second lens group 102, and between the second lens group 102 and the third lens group 103. The microscope tube 100 has a focal length of 370 mm, an image distance of 225.679 mm, and an optical gap of 490 mm between the entrance pupil and the first lens (i.e., the first lens 1011) in the first lens group 101.

[0058] The first lens group 101 includes a first lens 1011 with positive optical power, a second lens 1012 with positive optical power, and a third lens 1013 with negative optical power. The image-side surface of the first lens 1011 is cemented to the object-side surface of the second lens 1012, and the image-side surface of the second lens 1012 is cemented to the object-side surface of the third lens 1013. The first lens 1011 is a convex-concave lens, the second lens 1012 is a biconvex lens, and the third lens 1013 is a concave-convex lens.

[0059] The second lens group 102 includes a fourth lens 1021 with positive optical power, which is in the form of a convex-concave lens. The third lens group 103 includes a fifth lens 1031 and a sixth lens 1032, wherein the fifth lens 1031 has positive optical power and the sixth lens 1032 has negative optical power, and the image-side surface of the fifth lens 1031 and the object-side surface of the sixth lens 1032 are cemented together. The fifth lens 1031 is in the form of a biconvex lens and the sixth lens 1032 is in the form of a biconcave lens.

[0060] Table 1 below shows the optical parameters of each lens in the microscope tube 100, including radius of curvature, thickness (or optical spacing between lens groups), and glass material. The value of the radius of curvature in the table determines the optical power and aberration correction capability of the lens. The thickness parameter must match the optical properties of the material to ensure a reasonable optical path. The selection of glass material combines the difference in refractive index and Abbe number to achieve chromatic aberration balance. The value of the optical spacing must simultaneously meet the installation space requirements between lens groups and the light path transmission efficiency to ensure that each lens group works together to achieve the preset optical performance indicators.

[0061] Table 1

[0062]

[0063] As shown in Table 1, the radius of curvature R1 of the first lens is 258.769, which satisfies the condition. The radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens are related. ≈2.20, which satisfies the proportional relationship. 2.80. The distance between the radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens. ≈1.17, which satisfies the proportional relationship. The radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens are related. ≈2.23, which satisfies the proportional relationship. The radius of curvature R5 of the fifth lens is different from the radius of curvature R6 of the sixth lens. ≈0.31, which satisfies the proportional relationship. .

[0064] Figure 2 The distortion diagrams of the microscope tube 100 at different wavelengths are shown. Figure 2 In the graph, the horizontal axis represents the percentage of distortion, and the vertical axis represents the half-field of view of the microscope tube (maximum field of view is 4.75 degrees). The three curves represent the distortion of the microscope tube under three different working wavelengths, which are commonly used illumination wavelengths in wafer inspection scenarios. Figure 2 It can be seen that the maximum distortion of the microscope tube lens 100 occurs at the edge, where the maximum distortion percentage is less than 0.05%, which is an ultra-low distortion level. This characteristic ensures that the wafer pattern does not undergo geometric deformation during imaging, providing accurate image data for subsequent measurements.

[0065] Figure 3 The modulation transfer function (MTF) plots of the Fourier transform of the microscope tube lens 100 at different wavelengths are shown. Figure 3 In the graph, the horizontal axis represents spatial frequency, and the vertical axis represents the optical transfer function coefficient. The top curve is the theoretical optical transfer function curve, which represents the effect of transferring a real image to the CCD without deviation under ideal imaging conditions. Among the other curves below, the curve representing the meridional plane and the curve representing the sagittal plane reflect the image detail transfer capability in different directions, respectively. Figure 3 As can be seen, at all three wavelengths, both the curves representing the meridional plane and the curves representing the sagittal plane exhibit good convergence, with only a slight deviation from the diffraction limit. This deviation is a reasonable design trade-off made to prioritize ultra-low distortion characteristics and does not substantially affect image clarity, still meeting the requirements of wafer metrology for identifying image details.

[0066] Figure 4 The diagram shows a dot plot of the microscope tube 100 at different wavelengths. This plot reflects the diffusion of light of different wavelengths after entering the pupil through different field-of-view regions and converging onto the image plane by the microscope tube. It is a key basis for evaluating the focusing effect and chromatic aberration suppression capability of the lens. Figure 4In the diagram, the black circle represents the theoretically calculated minimum spot size at the lens's focusing position, while the points inside the circle represent the actual spot size after simulation design. The smaller and more concentrated the simulated spot, the better the lens's focusing effect, and the less the light is focused at different positions due to wavelength differences (i.e., chromatic aberration is effectively suppressed). Figure 4 As can be seen, the simulated light spots at each field of view and wavelength are all located within the black circle, and the light spot size is small and the distribution is concentrated, which proves that the focusing effect of the microscope 100 is excellent and the chromatic aberration is well controlled, which can ensure clear imaging of tiny defects or fine patterns on the wafer surface.

[0067] In summary Figures 2 to 4 The performance characterization results show that the microscope tube 100 provided in Example 1 is a low-distortion microscope tube, whose core advantage lies in meeting the application requirements of wafer pattern measurement scenarios. Since this Example 1 focuses on ultra-low distortion as its core design goal, through the synergistic optimization of lens group structure, parameters, and materials, a distortion rate of less than 0.05% is achieved. This ultra-low distortion rate ensures that the geometric dimensions of the wafer pattern are accurately reproduced during imaging, effectively improving measurement accuracy. Although its optical transfer function (MTF) will slightly deviate from the diffraction limit to ensure low distortion characteristics, this deviation is within a reasonable range and will not affect the overall image clarity and detail recognition, still meeting the basic imaging quality requirements of wafer measurement.

[0068] Example 2

[0069] Figure 5 An exemplary structural diagram of the microscope tube 200 according to Embodiment 2 of this application is shown. Figure 5 As shown, the microscope tube lens 200 may include a first lens group 201, a second lens group 202, and a third lens group 203 arranged coaxially along the object-to-image direction, with optical gaps between the first lens group 201 and the second lens group 202, and between the second lens group 202 and the third lens group 203. The microscope tube lens 200 has a focal length of 370 mm, an image distance of 225.679 mm, and an optical gap of 490 mm between the entrance pupil and the first lens (i.e., the first lens 1011) in the first lens group 201.

[0070] The first lens group 201 includes a first lens 2011 with positive optical power, a second lens 2012 with positive optical power, and a third lens 2013 with negative optical power. The image-side surface of the first lens 2011 is cemented to the object-side surface of the second lens 2012, and the image-side surface of the second lens 2012 is cemented to the object-side surface of the third lens 2013. The first lens 2011 is a convex-concave lens, the second lens 2012 is a biconvex lens, and the third lens 2013 is a concave-convex lens.

[0071] The second lens group 202 includes a fourth lens 2021 with positive optical power, which is in the form of a convex-planar lens. The third lens group 203 includes a fifth lens 2031 and a sixth lens 2032, wherein the fifth lens 2031 has positive optical power and the sixth lens 2032 has negative optical power, and the image-side surface of the fifth lens 2031 and the object-side surface of the sixth lens 2032 are cemented together. The fifth lens 2031 and the sixth lens 2032 are both in the form of a convex-concave lens.

[0072] Table 2 below shows the optical parameters of each lens in the microscope tube 200.

[0073] Table 2

[0074]

[0075] As shown in Table 2, the radius of curvature R1 of the first lens is 317.269, which satisfies the condition. The radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens are related. ≈2.80, which satisfies the proportional relationship. 2.80. The distance between the radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens. ≈2.24, which satisfies the proportional relationship. The radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens are related. ≈2.36, which satisfies the proportional relationship. The radius of curvature R5 of the fifth lens is different from the radius of curvature R6 of the sixth lens. ≈0.38, which satisfies the proportional relationship. .

[0076] Figure 6 The distortion diagrams of the microscope tube lens 200 at different wavelengths are shown. Figure 6 In the graph, the horizontal axis represents the percentage of distortion, and the vertical axis represents the half-field of view of the microscope tube (maximum field of view is 4.75 degrees). The three curves represent the distortion of the microscope tube at three different working wavelengths. Figure 6 It can be seen that the maximum distortion of the microscope tube lens 200 occurs at the edge, where the maximum distortion percentage is less than 0.2%. This distortion level is sufficient for scenarios with certain requirements for measurement accuracy, while also reserving room for improvement in imaging clarity, reflecting a balanced design approach.

[0077] Figure 7 The modulation transfer function plots of the Fourier transform of the microscope tube mirror 200 at different wavelengths are shown. Figure 7In the figure, the horizontal axis represents spatial frequency, and the vertical axis represents the optical transfer function coefficient. The top curve in the figure is the theoretical optical transfer function curve, representing the effect of the actual image being transferred to the CCD target surface without deviation under ideal imaging conditions. Among the other curves below, the curve representing the meridional plane and the curve representing the sagittal plane reflect the image detail transmission capability of the optical system in different directions, respectively. As can be seen from Figure 7, at the three wavelengths, both the meridional and sagittal plane curves show good convergence, and the overall deviation from the diffraction limit is slight. This deviation is a reasonable design trade-off for balancing distortion control and does not affect the effective transmission of image details. It can still clearly identify abnormal defects such as chipping on the wafer surface, meeting the detection accuracy requirements.

[0078] Figure 8 The diagram shows a dot plot of the microscope tube 200 at different wavelengths. This plot reflects the diffusion of light of different wavelengths after entering the pupil through different fields of view and converging onto the image plane by the microscope tube. Figure 8 In Figure 8, the black circle represents the minimum spot size calculated theoretically at the lens's focusing position. The size of this circle reflects the ideal focusing capability of the optical system. The dots inside the circle represent the actual spot size after simulation. The size and distribution of the simulated spot directly reflect the focusing accuracy and chromatic aberration control effect in actual imaging. The smaller and more concentrated the simulated spot, the better the lens's focusing effect, and the less the light is focused at different positions due to wavelength differences (i.e., chromatic aberration is effectively suppressed). As shown in Figure 8, the simulated spots at each field of view and wavelength are all within the range of the black circle, and the spot size is small and the distribution is concentrated, proving that the microscope 200 has excellent focusing effect and good chromatic aberration control, which can ensure clear imaging of tiny defects or fine patterns on the wafer surface.

[0079] In summary Figures 6 to 8 As can be seen, the microscope tube 200 provided in Example 2 achieves moderate distortion and diffraction limits, with a distortion rate of less than 0.2%. This distortion rate is slightly higher than that of the microscope tube 100 in Example 1 and slightly lower than that of the microscope tube 300 in Example 3, perfectly meeting the requirements for both measurement and detection accuracy. Compared to the microscope tube 100, the microscope tube 200 has the same number of lenses and cementing positions, ensuring universality and interchangeability in system installation. However, there are differences in the radius of curvature, lens thickness, lens spacing, and lens material of each lens. Changes in the radius of curvature adjust the optical power distribution of the lens; changes in lens thickness and spacing affect optical path transmission; and differences in lens material affect aberration correction through differences in refractive index and Abbe number. These structural differences ultimately lead to different characteristics in their MTF and distortion curves.

[0080] It should be noted that the distortion requirements differ for different application scenarios: if used for measuring the size of patterns in wafers, a microscope tube with a smaller distortion rate (such as the microscope tube 100 in Example 1) should be selected first to ensure the accuracy of the measurement data; if only photographing is required to identify anomalies such as chipping on the wafer surface in wafer inspection, an optical system with an MTF closer to the diffraction limit should be selected first to ensure imaging effect and clearly present defect details.

[0081] Example 3

[0082] Figure 9 An exemplary structural diagram of the microscope tube 300 according to Embodiment 3 of this application is shown. Figure 9 As shown, the microscope tube lens 300 may include a first lens group 301, a second lens group 302, and a third lens group 303 arranged coaxially along the object-to-image direction, with optical gaps between the first lens group 301 and the second lens group 302, and between the second lens group 302 and the third lens group 303. The microscope tube lens 300 has a focal length of 370 mm, an image distance of 225.679 mm, and an optical gap of 490 mm between the entrance pupil and the first lens (i.e., the first lens 1011) in the first lens group 301.

[0083] The first lens group 301 includes a first lens 3011 with positive optical power, a second lens 3012 with positive optical power, and a third lens 3013 with negative optical power. The image-side surface of the first lens 3011 is cemented to the object-side surface of the second lens 3012, and the image-side surface of the second lens 3012 is cemented to the object-side surface of the third lens 3013. The first lens 3011 is a convex-concave lens, the second lens 3012 is a biconvex lens, and the third lens 3013 is a concave-convex lens.

[0084] The second lens group 302 includes a fourth lens 3021 with positive optical power, which is in the form of a convex-concave lens. The third lens group 3203 includes a fifth lens 3031 and a sixth lens 3032, wherein the fifth lens 3031 has positive optical power and the sixth lens 3032 has negative optical power, and the image-side surface of the fifth lens 3031 and the object-side surface of the sixth lens 3032 are cemented together. The fifth lens 3031 is in the form of a biconvex lens and the sixth lens 3032 is in the form of a biconcave lens.

[0085] Table 3 below shows the optical parameters of each lens in the microscope tube 300.

[0086] Table 3

[0087]

[0088] As shown in Table 3, the radius of curvature R1 of the first lens is 260.569, which satisfies the condition. The radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens are related. ≈2.33, which satisfies the proportional relationship. 2.80. The distance between the radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens. ≈1.03, which satisfies the proportional relationship. The radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens are related. ≈2.32, which satisfies the proportional relationship. The radius of curvature R5 of the fifth lens is different from the radius of curvature R6 of the sixth lens. ≈0.36, which satisfies the proportional relationship. .

[0089] Figure 10 The distortion diagrams of the microscope tube lens 300 at different wavelengths are shown. Figure 10 In the graph, the horizontal axis represents the percentage of distortion, and the vertical axis represents the half-field of view of the microscope tube (maximum field of view is 4.75 degrees). The three curves represent the distortion of the microscope tube at three different working wavelengths. Figure 10 It can be seen that the maximum distortion of the microscope tube lens 300 occurs at the edge, where the maximum distortion percentage is less than 0.3%. Although this distortion level is slightly higher than that of the microscope tube lenses in Examples 1 and 2, it can meet the basic requirements of high-requirement wafer defect detection for imaging geometric realism, while reserving design space for achieving diffraction-limited imaging clarity.

[0090] Figure 11 The modulation transfer function plots of the Fourier transform of the microscope tube mirror 300 at different wavelengths are shown. Figure 11 In the graph, the horizontal axis represents spatial frequency, and the vertical axis represents the optical transfer function coefficients. The top curve is the theoretical optical transfer function curve, representing the effect of transferring the image of the object to the CCD target surface without deviation under ideal imaging conditions. Among the other curves below, the curve representing the meridional plane and the curve representing the sagittal plane reflect the image detail transmission capability of the optical system in different directions, respectively. Figure 11 As can be seen, both the meridional and sagittal curves exhibit good convergence at all three wavelengths and fully reach the diffraction limit. This means that the imaging effect of the 300-inch microscope is close to that of an ideal optical system, which can restore the detailed features of the wafer surface to the maximum extent and provide a clear image basis for the accurate identification of tiny defects.

[0091] Figure 12The diagram shows a dot plot of the microscope tube 300 at different wavelengths. This plot reflects the diffusion of light of different wavelengths after entering the pupil through different field-of-view regions and converging onto the image plane by the microscope tube. Figure 12 As can be seen, the simulated light spots under each field of view and wavelength are all completely located within the black circle, and the light spot size is extremely small and the distribution is highly concentrated, which proves that the focusing effect of the microscope 300 is excellent and the chromatic aberration control is precise. It can ensure clear imaging of tiny defects on the wafer surface and meet the high precision requirements of defect detection.

[0092] In summary Figures 10 to 12 The performance characterization results show that the modulation transfer function of the microscope tube lens 300 provided in Embodiment 3 reaches the diffraction limit, and its distortion rate is less than 0.5%. This distortion rate is slightly higher than that of the microscope tube lens 100 in Embodiment 1 and the microscope tube lens 200 in Embodiment 2, which is well-suited for applications with high requirements for wafer defect detection. Because its imaging effect is close to that of an ideal optical system, it can clearly present minute defects on the wafer surface (such as minor chipping, scratches, etc.), providing high-quality image support for accurate defect identification and judgment. It is especially suitable for the wafer inspection process after photolithography, where the sensitivity requirements for defect detection are stringent.

[0093] Considering the machining tolerances in industrial production, the three microscope tube forms provided in Examples 1, 2, and 3 above, through reasonable parameter design and material selection, ensure that they can still meet the usage requirements of large-area TDI line scan cameras within the allowable machining error range. In practical applications, all three tubes can effectively adapt to large-area TDI line scan cameras. Leveraging the advantages of multiple integration and superposition of TDI technology, they effectively improve wafer scanning and inspection speed, enhance the signal-to-noise ratio of the image, and simultaneously reduce the high-precision requirements of the precision scanning platform, thereby reducing equipment investment costs and maintenance difficulties.

[0094] Based on the microscope tube lens that supports a large target area TDI line scan camera as described above, this application embodiment also provides a microscope system, which includes an entrance pupil, a microscope tube lens as described above, and an image plane, and the entrance pupil, tube lens, and image plane are arranged sequentially along the principal optical axis.

[0095] The microscope objective employs an infinity-conjugate design, with its image plane oriented as a parallel light path. Filters and objective switching nose rollers can be flexibly added between the objective and the microscope tube. The entrance pupil, serving as the entry point for light into the system, is spaced from the first lens group of the microscope tube to accommodate the installation of various functional components. The microscope tube precisely focuses the parallel light emitted from the objective onto the image plane, which receives the imaging signal and converts it into an electrical signal, enabling the acquisition and subsequent processing of wafer images. Through the coordinated operation of its components, this microscope system constructs a complete, high-precision imaging chain with a large target area, meeting the full-process requirements of wafer inspection.

[0096] It is understood that the description of the various embodiments in this application emphasizes the differences between the various embodiments, while the similarities or corresponding parts can be referred to each other. For the sake of brevity, this application will not go into detail about each one.

[0097] Through the microscopy system provided above, this embodiment of the application organically integrates an infinity-conjugate microscope objective, a highly adaptable microscope tube, and a large-target-area TDI line scan camera, fully leveraging the performance advantages of each component: the microscope objective provides high-quality parallel light, the microscope tube accurately focuses and corrects aberrations, and the TDI camera achieves high-speed, high signal-to-noise ratio imaging; the entire system can effectively adapt to the imaging requirements of a 60mm large target area, improving scanning and inspection efficiency in wafer inspection while ensuring the accuracy and sensitivity of defect identification, and reducing dependence on precision platforms. It provides a stable and reliable technical solution for high-quality wafer inspection after photolithography in the semiconductor industry, helping to improve wafer product yield and the stability of the semiconductor industry chain.

[0098] It should be understood that the structure or architecture described above is merely exemplary, and the implementation methods and entities of this application are not limited thereto, but can be modified without departing from the spirit of this application. It is understood that the description of the various embodiments in this disclosure emphasizes the differences between the various embodiments, and their similarities or corresponding parts can be referred to mutually. For the purpose of brevity, this disclosure will not elaborate on each one.

[0099] It should be noted that although the operations of the method of this application are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the steps depicted in the flowchart can be performed in a different order. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0100] While numerous embodiments of this application have been shown and described herein, it will be apparent to those skilled in the art that such embodiments are provided by way of example only. Many modifications, alterations, and alternatives will arise for those skilled in the art without departing from the spirit and intent of this application. It should be understood that various alternatives to the embodiments of this application described herein may be employed in the practice of this application. The appended claims are intended to define the scope of protection of this application and therefore cover equivalents or alternatives within the scope of these claims.

Claims

1. A microscope tube, characterized in that, It includes a first lens group, a second lens group, and a third lens group that are coaxially arranged sequentially along the direction from the object side to the image side; There is an optical interval between the first lens group and the second lens group, and between the second lens group and the third lens group; The microscope tube lens has a focal length of 370 mm, an image distance of 225.679 mm, and an optical distance of 490 mm between the entrance pupil and the first lens group. There are a total of six lenses with optical power; the first lens group includes a first lens with positive optical power, a second lens with positive optical power, and a third lens with negative optical power; the first lens is a convex-concave lens, the second lens is a biconvex lens, and the third lens is a concave-convex lens; The second lens group includes a fourth lens with positive optical power; the fourth lens is a convex-planar lens or a convex-concave lens; The third lens group includes a fifth lens and a sixth lens, wherein the fifth lens has positive optical power and the sixth lens has negative optical power; the fifth lens is a biconvex lens and the sixth lens is a biconcave lens; or the fifth lens is a convex-concave lens and the sixth lens is a convex-concave lens; the radius of curvature R5 of the fifth lens and the radius of curvature R6 of the sixth lens satisfy the following relationship: .

2. The tube mirror according to claim 1, characterized in that, The image-side surface of the first lens is glued and fixed to the object-side surface of the second lens, and the image-side surface of the second lens is glued and fixed to the object-side surface of the third lens.

3. The tube mirror according to claim 1, characterized in that, The radius of curvature R1 of the first lens satisfies: The radius of curvature R1 of the first lens and the radius of curvature R2 of the second lens satisfy the following relationship: 2.80; The radius of curvature R1 of the first lens and the radius of curvature R3 of the third lens satisfy the following: .

4. The tube mirror according to claim 3, characterized in that, The radius of curvature R1 of the first lens and the radius of curvature R4 of the fourth lens satisfy the following relationship: .

5. The tube mirror according to claim 1, characterized in that, The image-side surface of the fifth lens is glued and fixed to the object-side surface of the sixth lens.

6. A microscopic system, characterized in that, include: Entering the pupil; The tube lens as described in any one of claims 1-5; and the image plane; The entrance pupil, tube lens, and image plane are arranged sequentially along the principal optical axis.

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