Double telecentric lens and focusing and leveling device

Abstract

The invention discloses a double-telecentric lens and a focusing and leveling device, and belongs to the technical field of optical equipment.The double-telecentric lens comprises a front optical module, an aperture diaphragm and a rear optical module which are sequentially arranged in the optical axis direction; the front optical module is composed of three lenses and comprises a first lens, a second lens and a third lens which are sequentially arranged in the optical axis direction. The first lens and the second lens are convergent lenses with positive focal power, and the third lens is a divergent lens with negative focal power; the rear optical module is composed of four lenses and comprises a fourth lens, a fifth lens, a sixth lens and a seventh lens which are sequentially arranged in the optical axis direction. The fourth lens, the sixth lens and the seventh lens are all convergent lenses with positive focal power, and the fifth lens is a divergent lens with negative focal power.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of optical equipment, in particular to a dual-telecentric lens and a focusing and leveling device. BACKGROUND

[0002] As a core device for integrated circuit manufacturing, a photolithography machine transfers fine circuit patterns on a mask to a silicon wafer coated with photoresist through a projection objective lens. With the development of semiconductor technology, photolithography machines need to achieve higher pattern resolution, and the focusing depth of the projection objective lens decreases sharply. The focusing and leveling device, as a key subsystem to ensure exposure accuracy, adjusts the relative position of the silicon wafer and the projection objective lens in real time, so that the silicon wafer is always in the best focal plane position.

[0003] The relay detection unit is an important part of the focusing and leveling device, which accurately transmits and images the detected spot information to the detector. The imaging quality directly affects the accuracy of the subsequent algorithm for calculating the vertical position of the silicon wafer. Therefore, there is an urgent need to provide a high-precision dual-telecentric lens designed for the focusing and leveling device to meet the high-precision detection requirements of the focusing and leveling device for the vertical position of the silicon wafer. SUMMARY

[0004] The embodiments of the present application provide a dual-telecentric lens and a focusing and leveling device, which can realize uniform high-resolution imaging from the center to the edge of the spot, and meet the high-precision detection requirements of the focusing and leveling device for the vertical position of the silicon wafer, to at least partially solve the above technical problems.

[0005] To achieve the above purpose, according to the first aspect of the present application, a dual-telecentric lens is provided, which comprises: a front optical module, an aperture stop and a rear optical module arranged in sequence along the optical axis direction; The front optical module is composed of three lenses and includes a first lens, a second lens and a third lens arranged in sequence along the optical axis direction; the first lens and the second lens are converging lenses with positive focal power, and the third lens is a diverging lens with negative focal power; The rear optical module is composed of four lenses and includes a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along the optical axis direction; the fourth lens, the sixth lens and the seventh lens are converging lenses with positive focal power, and the fifth lens is a diverging lens with negative focal power.

[0006] According to the second aspect of the present application, a focusing and leveling device is provided, which comprises: The dual-telecentric lens as described in the above technical solution is configured as a relay detection unit; and The illumination unit, the projection mark, the first projection unit, the second projection unit, the relay detection unit and the detector are arranged along an optical path, the illumination unit and the first projection unit are arranged on one side of the lithography objective, and the second projection unit, the relay detection unit and the detector are arranged on the other side of the lithography objective.

[0007] In the dual-telecentric lens of the embodiment of the present application, through the above technical solution, the two positive focal power converging lenses of the first lens and the second lens in the front optical module can perform efficient preliminary convergence and accurate light path shaping on the slit light spot from the silicon wafer, so as to ensure that the light spot energy is concentrated and the initial imaging path is optimized. And by introducing the third lens negative focal power diverging lens, the spherical aberration and the field curvature generated by the first lens and the second lens are balanced, and the geometric precision and the edge response sensitivity of the position detection are increased. The fourth lens in the rear optical module can compensate for the residual spherical aberration and field curvature of the front optical module, so as to ensure that the imaging plane is closer to the ideal state. The fifth lens suppresses the magnification deviation and non-linear distortion of the edge field of view through its negative focal power divergence characteristics, and maintains the high stability of the imaging magnification. The sixth lens and the seventh lens are both positive focal power converging lenses, which cooperate to enhance the converging ability of the edge light spot, thereby further optimizing the overall imaging quality. Therefore, by using the above design, uniform high-resolution imaging from the center of the light spot to the edge can be realized, and the high-precision detection requirement of the focusing and leveling device for the vertical position of the silicon wafer can be met.

[0008] Other features and advantages of the present application will be described in detail in the following specific embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0009] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings needed in the embodiment description. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creating any labor.

[0010] In order to more completely understand the present application and its beneficial effects, the following will be described in conjunction with the drawings, wherein the same reference numerals in the following description represent the same parts.

[0011] Figure 1 is a schematic diagram of a dual-telecentric lens structure in the embodiment of the present application; Figure 2 is a design parameter table of each lens in a dual-telecentric lens in the embodiment of the present application; Figure 3 is a field curvature, astigmatism and distortion diagram of a dual-telecentric lens in the embodiment of the present application; Figure 4 is an MTF curve diagram of a dual-telecentric lens in the embodiment of the present application; Figure 5 is a point spread diagram of a double telecentric lens in an embodiment of the present application; Figure 6 is a structural diagram of another double telecentric lens in an embodiment of the present application; Figure 7 is a table of design parameters of each lens in another double telecentric lens in an embodiment of the present application; Figure 8 is a diagram of field curvature, astigmatism and distortion of another double telecentric lens in an embodiment of the present application; Figure 9 is a diagram of MTF curves of another double telecentric lens in an embodiment of the present application; Figure 10 is a point spread diagram of another double telecentric lens in an embodiment of the present application; Figure 11 is a structural diagram of a focusing and leveling device in an embodiment of the present application.

[0012] Explanation of reference signs: G1- front optical module; L1- first lens; L2- second lens; L3- third lens; 2- aperture stop; G2- rear optical module; L4- fourth lens; L5- fifth lens; L6- sixth lens; L7- seventh lens; 10- illumination unit; 20- projection mark; 30- first projection unit; 31- first lens; 32- first mirror; 33- second lens; 40- second projection unit; 41- third lens; 42- second mirror; 43- fourth lens; 50- detection mark; 60- relay detection unit; 70- detector; 80- lithography objective lens; 90- silicon wafer. DETAILED DESCRIPTION

[0013] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0014] In the description of the present application, it should be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the purpose of facilitating the description of the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0015] The terms "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implying the number of the technical features indicated. Therefore, the features defined as "first", "second", "third", "fourth", "fifth", "sixth", "seventh" and "eighth" can explicitly or implicitly include one or more of the features. In the description of the present application, unless otherwise stated, the meaning of "a plurality of" is two or more.

[0016] The present application provides a dual-telecentric lens and a focusing and leveling device. The following will be described in detail. It should be noted that the description order of the following embodiments is not limited as the preferred order of the embodiments of the present application. In the following embodiments, the description of each embodiment has its own emphasis, and the parts not described in detail in a certain embodiment can be referred to the related description of other embodiments.

[0017] As the core equipment of integrated circuit manufacturing, the lithography machine transfers the fine circuit pattern on the mask plate to the surface of the silicon wafer coated with photoresist through the projection objective lens. With the development of semiconductor technology, the lithography machine not only needs to achieve higher pattern resolution, but also the focusing depth of the projection objective lens decreases sharply. The focusing and leveling device, as a key subsystem to ensure exposure accuracy, adjusts the relative position of the silicon wafer and the projection objective lens in real time, so that the silicon wafer is always in the best focal plane position.

[0018] The relay detection unit is an important part of the focusing and leveling device, which can accurately transmit and image the detected spot information to the detector. The imaging quality directly affects the calculation accuracy of the subsequent algorithm for the vertical position of the silicon wafer. Therefore, it is urgent to provide a high-precision dual-telecentric lens designed for the focusing and leveling device to meet the high-precision detection requirements of the focusing and leveling device for the vertical position of the silicon wafer.

[0019] Please refer to Figure 1 and Figure 11 The dual-telecentric lens includes a front optical module G1, an aperture stop 2 and a rear optical module G2 arranged in sequence along the optical axis. The front optical module G1 is composed of three lenses and includes a first lens L1, a second lens L2 and a third lens L3 arranged in sequence along the optical axis. The first lens L1 and the second lens L2 are converging lenses with positive focal power, and the third lens L3 is a diverging lens with negative focal power. The rear optical module G2 is composed of four lenses and includes a fourth lens L4, a fifth lens L5, a sixth lens L6 and a seventh lens L7 arranged in sequence along the optical axis. The fourth lens L4, the sixth lens L6 and the seventh lens L7 are converging lenses with positive focal power, and the fifth lens L5 is a diverging lens with negative focal power.

[0020] In the technical solution, the two positive focal length converging lenses of the first lens L1 and the second lens L2 in the front optical module G1 can perform efficient preliminary convergence and accurate light path shaping on the slit light spot from the silicon wafer 90, ensure the concentration of light spot energy and optimize the initial imaging path. And by introducing the third lens L3 negative focal length diverging lens, the spherical aberration and field curvature generated by the first lens L1 and the second lens L2 are balanced, and the geometric accuracy and edge response sensitivity of position detection are increased. The fourth lens L4 in the rear optical module G2 can compensate for the residual spherical aberration and field curvature of the front optical module G1, ensure that the imaging plane is closer to the ideal state, and the fifth lens L5 suppresses the magnification deviation and nonlinear distortion of the edge field of view through its negative focal length divergence characteristics, and maintains the high stability of the imaging magnification. The sixth lens L6 and the seventh lens L7 are both positive focal length converging lenses, which work together to enhance the convergence ability of the edge light spot, thereby further optimizing the overall imaging quality. Therefore, by using the above design, uniform high-resolution imaging from the center to the edge of the light spot can be achieved, meeting the high-precision detection requirements of the focusing and leveling device for the vertical position of the silicon wafer 90.

[0021] Among them, the object side optical surface of the first lens L1, the second lens L2 and the third lens L3 is outwardly convex spherical surface, and the image side optical surface is inwardly concave spherical surface. The object side optical surface and the image side optical surface of the fourth lens L4, the sixth lens L6 and the seventh lens L7 are outwardly convex spherical surface. The object side optical surface and the image side optical surface of the fifth lens L5 are inwardly concave spherical surface. That is, the first lens L1, the second lens L2 and the third lens L3 are convex-concave lenses, and the fourth lens L4, the sixth lens L6 and the seventh lens L7 are double convex lenses. The fifth lens L5 is a double concave lens.

[0022] As another example, the object side optical surface of the first lens L1 and the second lens L2 is outwardly convex spherical surface, and the image side optical surface is inwardly concave spherical surface. The object side optical surface and the image side optical surface of the third lens L3 are inwardly concave spherical surface. The object side optical surface and the image side optical surface of the fourth lens L4, the sixth lens L6 and the seventh lens L7 are outwardly convex spherical surface. The object side optical surface and the image side optical surface of the fifth lens L5 are inwardly concave spherical surface.

[0023] In the front optical module G1, the convex surface (outward protrusion) of the first lens L1, the second lens L2 and the third lens L3 has a significant strong converging ability for the wide-angle incident light rays from the silicon wafer 90 (object plane), guiding the fast convergence of the divergent incident light beams to the vicinity of the optical axis, effectively reducing the burden of light path regulation of the subsequent lenses. At the same time, the concave surface (inward recess) of the image side can accurately compensate for the focusing point offset of the edge light rays, and through the reverse adjustment of the optical curvature, the light rays of different apertures (from the center to the edge) are more uniformly focused to the vicinity of the image plane, which not only can realize the efficient shaping of the primary light path, but also can inhibit the deterioration of the spherical aberration and coma of the edge light rays, and improve the sharpness and position detection accuracy of the spot edge.

[0024] In the rear optical module G2, the fourth lens L4 and the fifth lens L5 effectively eliminate the magnification deviation of the overall double-telecentric lens through the precise matching of positive and negative focal powers, and the sixth lens L6 and the seventh lens L7 enhance the converging ability of the edge light rays through their positive focal power converging characteristics, so that the imaging plane more accurately matches the ideal plane of the detector 70, and also can improve the focusing consistency of the edge field of view, inhibit the edge spot blur problem caused by the field curvature effect, and ensure the uniform high-resolution imaging from the center to the edge of the spot.

[0025] In some embodiments, the refractive indices of the third lens L3, the fifth lens L5 and the seventh lens L7 are equal and greater than the refractive indices of the first lens L1 and the fourth lens L4, and smaller than the refractive indices of the second lens L2 and the sixth lens L6. The third lens L3, the fifth lens L5 and the seventh lens L7 adopt a medium refractive index material, so that these lenses can more accurately control the deflection of light rays. The third lens L3 can balance the spherical aberration and field curvature generated by the first lens L1 and the second lens L2, and through its appropriate refractive index, the focusing point of the edge light rays can be reasonably adjusted, so that the light rays of different apertures are more uniformly focused. The fifth lens L5 is mainly used to suppress the magnification deviation and nonlinear distortion of the edge field of view, and the medium refractive index enables it to finely adjust the focusing of the edge light rays without affecting the overall imaging effect, ensuring the stability of the magnification. The seventh lens L7 plays a role in enhancing the converging ability of the edge spot and improving the overall contrast, and its refractive index can ensure sufficient converging ability for the edge light rays, while not introducing too much aberration. The first lens L1 and the fourth lens L4 adopt a low refractive index material, so that the deflection degree of light rays is relatively moderate when passing through these lenses, which helps to reduce the primary aberration. The second lens L2 and the sixth lens L6 adopt a high refractive index material to ensure their stronger deflection ability for light rays, so as to more accurately adjust the path of the edge light rays.

[0026] As an example, the Abbe numbers of the second lens L2 and the sixth lens L6 are equal and greater than the Abbe numbers of the third lens L3, the fifth lens L5 and the seventh lens L7, while being less than the Abbe numbers of the first lens L1 and the fourth lens L4. The second lens L2 and the sixth lens L6 adopt a moderate Abbe number material to appropriately introduce dispersion by moderate Abbe number to compensate for system residual chromatic aberration, while avoiding insufficient dispersion suppression due to excessively high Abbe number. The third lens L3, the fifth lens L5 and the seventh lens L7 adopt a lower Abbe number material, which can further balance the system chromatic aberration by using its stronger dispersion characteristics, and form a complement with the first lens L1 and the fourth lens L4. The high Abbe number of the first lens L1 and the fourth lens L4 can effectively suppress the basic chromatic aberration, and finally realize the dispersion cooperative control of the light rays with a working wavelength band of 600 nanometers to 1000 nanometers through the gradient distribution of the Abbe number, to ensure the imaging positions of different wavelength light spots to be consistent, so as to improve the imaging consistency required for overlay accuracy.

[0027] Exemplarily, the refractive index of the first lens L1 and the fourth lens L4 is 1.804, and the Abbe number is 46.6; the refractive index of the second lens L2 and the sixth lens L6 is 1.883, and the Abbe number is 39.2; the refractive index of the third lens L3, the fifth lens L5 and the seventh lens L7 is 1.847, and the Abbe number is 23.8. Among them, the first lens L1 and the fourth lens L4 adopt an optical material with a refractive index of 1.804 and an Abbe number of 46.6, which guides the wide-angle incident light rays to converge towards the optical axis and provides stable primary light path shaping by a higher refractive index, and the high Abbe number characteristic suppresses the axial chromatic aberration to ensure the initial focusing consistency of multi-wavelength light rays; the second lens L2 and the sixth lens L6 adopt a material with a higher refractive index of 1.883 and an Abbe number of 39.2, which strengthens the edge light ray convergence ability to compensate for higher-order spherical aberration and coma, and the moderate Abbe number further balances the residual chromatic aberration to ensure the edge sharpness of the light spot; the third lens L3, the fifth lens L5 and the seventh lens L7 adopt a material with a medium refractive index of 1.847 and the lowest Abbe number of 23.8, which uses strong dispersion characteristics to accurately control astigmatism, field curvature and distortion, wherein the third lens L3 corrects the field curvature and spherical aberration, the fifth lens L5 suppresses magnification deviation and non-linear distortion, and the seventh lens L7 enhances the edge light spot convergence and contrast, finally realizing uniform high-resolution imaging in the full field of view.

[0028] In some embodiments, the distance between the second lens L2 and the third lens L3 is L 23 , and satisfies: 1mm≤L 23 ≤4mm, thereby ensuring that the positive convergence of the second lens L2 and the negative divergence of the third lens L3 are more matched, which not only ensures the effective balance of the primary spherical aberration and field curvature, but also ensures the focusing consistency of the light spot from the center to the edge, providing a high-quality intermediate image for the rear optical module G2 and supporting high-precision detection of the vertical position of the silicon wafer 90.

[0029] As an example, the spacing between the fourth lens L4 and the fifth lens L5 is L 45 and satisfies: 0.5 mm≤L 45 ≤5 mm. With the above design, by limiting the spacing between the fourth lens L4 and the fifth lens L5 to the range of 0.5 mm to 5 mm, the accurate focusing of the edge field light rays can be ensured on the basis of inhibiting the magnification deviation and the nonlinear distortion, so as to achieve uniform high-resolution imaging from the center to the edge of the light spot, thereby providing an optical basis for high-precision detection of the vertical position of the silicon wafer 90.

[0030] In some embodiments, 1≤|f2 / f3|≤3, and / or, 0.5≤|f4 / f5|≤2.5, where f2 is the focal length of the second lens L2, f3 is the focal length of the third lens L3, f4 is the focal length of the fourth lens L4, and f5 is the focal length of the fifth lens L5.

[0031] For 1≤|f2 / f3|≤3, the focal length ratio of the two lenses (the second lens L2 and the third lens L3) ensures that the positive converging power and the negative diverging power are more matched, which can further inhibit the spherical aberration and the field curvature of the front optical module G1, and better ensure the focusing stability of the light spot from the center to the edge, thereby providing a high-quality intermediate image for the rear optical module G2.

[0032] For 0.5≤|f4 / f5|≤2.5, the positive convergence of the fourth lens L4 and the negative divergence of the fifth lens L5 form a complement, which can reduce the influence of high-order spherical aberration, coma, and distortion on the imaging quality, ensure the uniform convergence of the edge field light rays and the center light rays, and finally form an imaging effect that maintains high sharpness and geometric symmetry from the center to the edge of the light spot, thereby providing a high-precision position detection reference covering the full field of view for the focusing and leveling device.

[0033] The object-side working distance of the dual-telecentric lens is D1, and satisfies: 100 mm≤D1≤300 mm. On the object-side, the larger working distance range of 100 mm to 300 mm provides a flexible silicon wafer 90 accommodation space for the focusing and leveling device, which can cover the vertical position fluctuation of the silicon wafer 90 table in different process states (such as lifting, leveling, and thermal expansion compensation) in the lithography machine, and ensures that the silicon wafer 90 surface (object-side) and the lens object-side entrance pupil always maintain effective optical coupling.

[0034] The image-side working distance of the dual-telecentric lens is D2, and satisfies: 20 mm≤D2≤50 mm. On the image-side, the shorter working distance range of 20 mm to 50 mm can ensure that the lens image-side exit pupil and the photosensitive surface of the detector 70 maintain a compact and stable coupling, thereby ensuring that the imaging coordinates of the light spot on the detector 70 always have a strict linear mapping relationship with the vertical position of the silicon wafer 90.

[0035] The working waveband of the dual-telecentric lens is in the near-infrared range of 600 nm to 1000 nm. The reflectivity of light in this waveband is significantly lower than that in the short-wave waveband, which can greatly reduce the stray light interference caused by the surface reflection of the silicon wafer 90, ensure that the light spot signal received by the detector 70 mainly comes from the target slit projection area, and improve the contrast and edge definition of the light spot. At the same time, the transmittance of light in this waveband remains high in optical materials (such as quartz and glass), and the selection of high Abbe number materials (such as the Abbe number of 46.6 of the first lens L1 and the fourth lens L4) in the dual-telecentric lens further reduces the absorption and scattering loss of light inside the lens, so that more effective light energy is transmitted to the detector 70, and the intensity and signal-to-noise ratio of the light spot signal are enhanced.

[0036] In some embodiments, the dual-telecentric lens has a dual-telecentric structure on the object side and the image side. The chief rays of each field of view on the object side are incident on the first lens L1 and have an angle with the optical axis of less than 0.1°. The chief rays of each field of view on the image side are incident on the image plane and have an angle with the optical axis of less than 0.1°. Thus, on the object side, the telecentricity of the chief rays with an angle of less than 0.1° with the optical axis ensures that the incident light beams from different vertical heights (such as ± several millimeters) of the silicon wafer 90 (object side) have their chief rays approximately parallel to the optical axis incident on the first lens L1, thereby eliminating the influence of the position fluctuation of the silicon wafer 90 on the imaging magnification, and providing a stable basic magnification for subsequent imaging on the image side. On the image side, the telecentricity of the chief rays with an angle of less than 0.1° with the optical axis ensures that the light rays emitted from the lens to the detector 70 (image plane) are approximately parallel to the optical axis, and the stability of the imaging position is ensured.

[0037] In some embodiments, the effective field of view diameter of the dual-telecentric lens on the object side is greater than 60 mm. In the lithography process, the exposed area of the photoresist on the surface of the silicon wafer 90 usually covers a diameter range of tens of millimeters (such as the effective exposure area diameter of a 6-inch silicon wafer 90 is about 150 mm, but a single focusing and leveling detection needs to cover the key area). The effective field of view diameter of more than 60 mm on the object side can ensure that a large enough detection area (such as a composite field of view containing multiple alignment marks or feature areas) on the silicon wafer 90 can be captured by a single imaging of the lens, avoiding the efficiency loss and position matching error caused by multi-frame stitching detection of traditional small field of view lenses.

[0038] In some embodiments, the numerical aperture of the dual-telecentric lens on the object side is 0.02. The numerical aperture is a key parameter for measuring the light collection ability and resolution of the lens. A low numerical aperture of 0.02 corresponds to a very small incident angle of the light on the object side, which strictly controls the convergence ability of the incident light on the surface of the silicon wafer 90 (object side) within a very small range, thereby being able to eliminate the influence of the position fluctuation (height change) of the silicon wafer 90 on the imaging magnification to a certain extent.

[0039] In some embodiments, the magnification β of the dual-telecentric lens satisfies: -0.6≤β≤-0.4. With such a design, it can not only ensure that the spot on the detector 70 has a sufficient size to extract clear edge features (such as the straightness and width variation of the slit), but also ensure that a single imaging can cover a large enough detection area on the silicon wafer 90, meeting the collaborative requirements of the focus and level adjustment device for large field of view and high resolution.

[0040] In some embodiments, the field curvature of the dual-telecentric lens is less than or equal to 0.025 mm, and the distortion is less than or equal to 0.5%. Specifically, the field curvature, as a key indicator of the curvature of the imaging plane and the ideal plane (the plane of the detector 70), the smaller the value, the higher the matching degree of the actual imaging plane of the lens and the receiving plane of the detector 70. The distortion, as a core parameter representing the degree of geometric deformation of imaging, the lower the value, the stronger the ability of the lens to maintain the geometric features of the spot. Therefore, by strictly limiting the field curvature to within 0.025 mm (equivalent to sub-micron flatness deviation), it ensures that the focusing positions of the spots from different areas (center to edge) of the silicon wafer 90 on the detector 70 have almost no deviation from the ideal plane when focusing, avoiding the problem of blurred or position offset of edge spots caused by field curvature in traditional lenses. Moreover, by strictly limiting the distortion to within 0.5%, it ensures the consistency of the magnification of the spot from the center to the edge, and the deviation of the size of the edge spot from the center spot is minimal (for example, 0.5% distortion means that the edge of a 100 μm spot only shifts by 0.5 μm), and the geometric shape (such as the straightness and rectangularity of the slit) is almost not distorted, so that the focus and level adjustment device can accurately calculate the vertical position and tilt angle of the silicon wafer 90 based on the real geometric edges of the spot (such as the slit boundary and the corner points of the rectangular mark), avoiding false position offset or angle misjudgment caused by distortion.

[0041] According to the foregoing description, the following will be described in detail in combination with more specific embodiments and tables.

[0042] Embodiment One As shown in Figure 1 , the first lens L1 is a convex-concave positive lens, the second lens L2 is a convex-concave positive lens, the third lens L3 is a convex-concave negative lens, the fourth lens L4 is a double-convex positive lens, the fifth lens L5 is a double-concave negative lens, the sixth lens L6 is a double-convex positive lens, and the seventh lens L7 is a double-convex positive lens. Object is the object plane, Aperture stop is the aperture stop, and Image is the image plane. In this embodiment, the magnification of the dual-telecentric lens is -0.4.

[0043] As an example, please refer to Figure 2 , Figure 2The detailed design parameters of each lens assembly in the dual-telecentric lens in this embodiment are listed, including the optical property indexes and geometric structure parameters of each element. For example, the surface type, curvature radius, thickness, refractive index, Abbe number, and half aperture of each lens.

[0044] As shown in Figure 3 , Figure 3 The left side is a field curvature astigmatism graph, the horizontal axis represents the focal point offset, positive and negative represent the offset direction of the image point near the focal plane, and the numerical value represents the offset degree, and the vertical axis represents the object height. It can be seen from the graph that the field curvature astigmatism is within 0.025 mm in the range of 600 nm to 1000 nm, which indicates that the spot profile is closer to the ideal geometric shape. Figure 3 The right side is a distortion graph, the horizontal axis represents the percentage of distortion, and the vertical axis represents the object height. It can be seen from the graph that the distortion is less than 0.5%, which indicates that the degree of deformation of the imaging pattern is small.

[0045] As shown in Figure 4 , Figure 4 is the MTF curve graph of the dual-telecentric lens in this embodiment, the horizontal axis represents the spatial frequency, and the vertical axis represents the MTF value. It can be seen from the graph that the curve of F1:Diff.Limit represents the diffraction limit curve, and the other curves correspond to the MTF curves under different conditions (such as different object distances). It can be observed that the MTF curves are relatively close to the diffraction limit curve, indicating that the dual-telecentric lens has good imaging quality.

[0046] As shown in Figure 5 , Figure 5 is the spot diagram of the dual-telecentric lens in this embodiment, the horizontal axis represents the defocusing amount (DEFOCUSING), and the vertical axis represents the field position (FIELD POSITION). Under different field positions and defocusing states, the imaging formed diffraction spot is within the Airy disk range, indicating that the dual-telecentric lens has good imaging quality.

[0047] Embodiment Two As shown in Figure 6 , the first lens L1 is a convex-concave positive lens, the second lens L2 is a convex-concave positive lens, the third lens L3 is a double-concave negative lens, the fourth lens L4 is a double-convex positive lens, the fifth lens L5 is a double-concave negative lens, the sixth lens L6 is a double-convex positive lens, and the seventh lens L7 is a double-convex positive lens. Object is the object plane, Aperture stop is the stop, and Image is the image plane. In this embodiment, the magnification of the dual-telecentric lens is -0.6.

[0048] As an example, please refer to Figure 7 , Figure 7The detailed design parameters of each lens assembly in the dual-telecentric lens in this embodiment are listed, including the optical property indexes and geometric structure parameters of each element. For example, the surface type, curvature radius, thickness, refractive index, Abbe number, and half aperture of each lens.

[0049] As shown in Figure 8 , Figure 8 the left side is a field curvature astigmatism graph, the horizontal axis represents the focal point offset, positive and negative represent the offset direction of the image point near the focal plane, and the numerical value represents the offset degree, and the vertical axis represents the object height. It can be seen from the graph that the field curvature astigmatism is within 0.025 mm in the range of 600 nm to 1000 nm, indicating that the spot profile is closer to the ideal geometric shape. Figure 3 The right side is a distortion graph, the horizontal axis represents the percentage of distortion, and the vertical axis represents the object height. It can be seen from the graph that the distortion is less than 0.5%, indicating that the degree of deformation of the imaging pattern is small.

[0050] As shown in Figure 9 , Figure 9 is the MTF curve graph of the dual-telecentric lens in this embodiment, the horizontal axis represents the spatial frequency, and the vertical axis represents the MTF value. It can be seen from the graph that the curve of F1:Diff.Limit represents the diffraction limit curve, and the other curves correspond to the MTF curves under different conditions (such as different object distances). It can be observed that the MTF curves are relatively close to the diffraction limit curve, indicating that the dual-telecentric lens has good imaging quality.

[0051] As shown in Figure 10 , Figure 10 is the spot diagram of the dual-telecentric lens in this embodiment, the horizontal axis represents the defocusing amount (DEFOCUSING), and the vertical axis represents the field position (FIELD POSITION). Under different field positions and defocusing states, the imaging formed diffraction spot is within the Airy disk range, indicating that the dual-telecentric lens has good imaging quality.

[0052] Please refer to Figure 11 , in this embodiment, the focusing and leveling device includes a dual-telecentric lens as described in any of the above technical solutions, and the dual-telecentric lens is configured as a relay detection unit 60. And the illumination unit 10, the projection mark 20, the first projection unit 30, the second projection unit 40, the relay detection unit 60, and the detector 70 are arranged along the light path. The illumination unit 10 and the first projection unit 30 are arranged on one side of the lithography objective 80, and the second projection unit 40, the relay detection unit 60, and the detector 70 are arranged on the other side of the lithography objective 80. Since the dual-telecentric lens in the focusing and leveling device in this embodiment has the same technical features as the above-mentioned dual-telecentric lens, they can solve the same technical problems and achieve the same technical effects.

[0053] Please continue to refer toFigure 11 The complete workflow of the focusing and leveling device is as follows: first, a specific light source is emitted by the illumination module, and the light is accurately irradiated to the projection mark 20; then the image of the projection mark 20 is accurately projected to the surface of the silicon wafer 90 by the first projection unit 30; the light carrying height information is reflected by the surface of the silicon wafer 90, and is imaged to the detection mark 50 by the second projection unit 40; then the light at the detection mark 50 is optimally transmitted and imaged by the relay detection unit 60, and finally the light is accurately projected to the detector 70; the detector 70 calculates the defocus amount of the silicon wafer 90 by analyzing the received optical signal. That is, the detection mark 50 is also arranged between the second projection unit 40 and the relay detection unit 60 along the light path direction. The detection mark 50, the second projection unit 40 and the relay detection unit 60 are located on the same side of the lithography objective 80.

[0054] Specifically, the illumination unit 10 provides uniform and stable light source, usually a specific light source such as laser, LED, etc. will be used, and the intensity, wavelength, uniformity and other parameters of the light will be strictly controlled to meet the needs of different measurement environments. For example, in the lithography process, a specific wavelength laser is often used as the illumination light source to ensure that the projection mark 20 can be clearly imaged on the silicon wafer 90. The projection mark 20 is a specific pattern or structure located in the light path, which is the key reference object for the focusing and leveling device to measure. The projection mark 20 can be illuminated by the illumination unit 10, and then the projection mark 20 is clearly projected to the surface of the silicon wafer 90 or other measured object surface by the first projection unit 30.

[0055] The second projection unit 40 receives the reflected light from the surface of the silicon wafer 90 or other measured object surface, and accurately adjusts the angle and direction of the reflected light to ensure that the light is accurately transmitted to the detection mark 50. The detection mark 50 serves as a secondary imaging reference for the reflected light, providing a pattern feature for the detector 70 to analyze. The relay detection unit 60 further adjusts and transmits the imaged light on the detection mark 50, which uses the special optical design of the aforementioned double-telecentric lens to improve the collection efficiency and transmission quality of the light, reduce the loss and interference of the light, and ensure that the light efficiently and accurately reaches the detector 70. The detector 70 receives the light transmitted by the relay detection unit 60 and converts it into an electrical signal or a digital signal. By analyzing and processing these signals, the imaging information of the projection mark 20 on the surface of the silicon wafer 90 can be obtained, and then the vertical position and inclination angle of the silicon wafer 90 can be calculated. For example, the detector 70 includes but is not limited to a charge-coupled device (CCD), a complementary metal-oxide-semiconductor (CMOS), etc.

[0056] Exemplarily, the first projection unit 30 comprises a first lens 31, a first mirror 32 and a second lens 33 arranged in sequence along the light path. The first lens 31 and the second lens 33, as a lens assembly, respectively undertake the functions of light collimation, focusing or aberration correction, and cooperate with the light path turning of the first mirror 32 to jointly optimize the imaging quality of the projection mark 20 to the silicon wafer 90. The first mirror 32 can deflect the light refracted by the first lens 31 to the required direction (e.g., from the vertical direction to a certain angle to the silicon wafer 90), avoiding mechanical interference caused by the straight light path, so as to make the structure of the first projection unit 30 compact. Similarly, the second projection unit 40 comprises a third lens 41, a second mirror 42 and a fourth lens 43 arranged in sequence along the light path.

[0057] In the description of the present specification, specific features, structures, materials or characteristics can be combined in any one or more embodiments or examples in a suitable manner.

[0058] The above merely provides the specific implementation of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims. In addition, the specific examples are applied in the present specification to describe the principles and implementation of the present application. The above description of the embodiments is only for helping to understand the method of the present application and its core idea, and the content of the present specification should not be understood as the limitation of the present application.

Claims

1. A dual-telecentric lens characterized in that, The double telecentric lens comprises: a front optical module, an aperture diaphragm and a rear optical module arranged in sequence along an optical axis direction; the front optical module is composed of three lenses and comprises a first lens, a second lens and a third lens arranged in sequence along the optical axis direction; the first lens and the second lens are converging lenses with positive focal power, and the third lens is a diverging lens with negative focal power; the rear optical module is composed of four lenses and comprises a fourth lens, a fifth lens, a sixth lens and a seventh lens arranged in sequence along the optical axis direction; the fourth lens, the sixth lens and the seventh lens are converging lenses with positive focal power, and the fifth lens is a diverging lens with negative focal power.

2. The double telecentric lens according to claim 1, wherein: the object-side optical surface of the first lens and the second lens is an outward convex spherical surface, and the image-side optical surface is an inward concave spherical surface; the object-side optical surface of the third lens is an outward convex or inward concave spherical surface, and the image-side optical surface is an inward concave spherical surface; the object-side optical surface and the image-side optical surface of the fourth lens, the sixth lens and the seventh lens are outward convex spherical surfaces; the object-side optical surface and the image-side optical surface of the fifth lens are inward concave spherical surfaces.

3. The double telecentric lens according to claim 1 or 2, wherein: the refractive index of the third lens, the fifth lens and the seventh lens is equal and greater than the refractive index of the first lens and the fourth lens, and is less than the refractive index of the second lens and the sixth lens; and / or, the Abbe number of the second lens and the sixth lens is equal and greater than the Abbe number of the third lens, the fifth lens and the seventh lens, and is less than the Abbe number of the first lens and the fourth lens.

4. The double telecentric lens according to claim 3, wherein: the refractive index of the first lens and the fourth lens is 1.804, and the Abbe number is 46.6; the refractive index of the second lens and the sixth lens is 1.883, and the Abbe number is 39.2; the refractive index of the third lens, the fifth lens and the seventh lens is 1.847, and the Abbe number is 23.

8.

5. The dual-telecentric lens of claim 1, wherein, The distance between the second lens and the third lens is L 23 and satisfies: 1 mm ≤ L 23 ≤ 4 mm.

6. The dual-telecentric lens according to claim 1 or 5, characterized in that, The interval between the fourth lens and the fifth lens is L 45 and satisfies: 0.5 mm ≤ L 45 ≤ 5 mm.

7. The dual-telecentric lens according to claim 1 or 2, characterized in that, 1≤|f2 / f3|≤3, and / or, 0.5≤|f4 / f5|≤2.5, wherein f2 is the focal length of the second lens, f3 is the focal length of the third lens, f4 is the focal length of the fourth lens, and f5 is the focal length of the fifth lens.

8. The double telecentric lens according to claim 1 or 2, wherein: the object-side working distance of the double telecentric lens is D1, and satisfies: 100mm≤D1≤300mm; and / or, the image-side working distance of the double telecentric lens is D2, and satisfies: 20mm≤D2≤50mm.

9. The dual-telecentric lens of claim 1, wherein, the working waveband of the double telecentric lens is 600nm to 1000nm.

10. The dual-telecentric lens of claim 1, wherein, The double-telecentric lens has double-telecentric structures on the object side and the image side, the angle between the chief ray of each field of view on the object side and the optical axis is less than 0.1° when the chief ray is incident to the first lens, and the angle between the chief ray of each field of view on the image side and the optical axis is less than 0.1° when the chief ray is incident to the image plane.

11. The dual-telecentric lens of claim 1, wherein, The double-telecentric lens has an effective field of view on the object side with a diameter greater than 60 mm.

12. The dual-telecentric lens according to claim 1 or 11, characterized in that, The double-telecentric lens has a numerical aperture on the object side of 0.

02.

13. The dual-telecentric lens of claim 1, wherein, The double-telecentric lens has a magnification β satisfying -0.6≤β≤-0.

4.

14. The dual-telecentric lens of claim 1, wherein, The double-telecentric lens has a field curvature less than or equal to 0.025 mm and a distortion less than or equal to 0.5%.

15. A focus leveler device, characterized by The focusing and leveling device comprises: The double-telecentric lens according to any one of claims 1 to 14 is configured as a relay detection unit; and An illumination unit, a projection mark, a first projection unit, a second projection unit, the relay detection unit, and a detector are arranged along an optical path, the illumination unit and the first projection unit are arranged on one side of a photolithography objective lens, and the second projection unit, the relay detection unit, and the detector are arranged on the other side of the photolithography objective lens.

Images