Lens suitable for deep ultraviolet band

Abstract

A lens suitable for a deep ultraviolet band is suitable for microscopic imaging or photoetching, and sequentially comprises a first lens and a positive meniscus lens along an optical axis, the second lens is a positive meniscus lens; the third lens is a negative biconcave lens; a fourth lens which is a negative biconcave lens; the fifth lens is a negative meniscus lens; the sixth lens is a negative meniscus lens; a seventh lens which is a negative biconcave lens; the eighth lens is a positive biconvex lens; the ninth lens is a positive biconvex lens; the tenth lens is a positive biconvex lens; an eleventh lens which is a positive biconvex lens; the twelfth lens is a positive meniscus lens; the thirteenth lens is a positive meniscus lens; the fourteenth lens is a negative meniscus lens; and the fifteenth lens is a positive meniscus lens. According to the utility model, the lens with a multi-lens combination design is easy to process, has a high numerical aperture design, combines the short wavelength characteristic of deep ultraviolet light, improves the resolution limit of a traditional optical microscope, and can be used for finely observing micro structures.

Description

Technical Field

[0001] The utility model relates to the technical field of optical lenses, in particular to a lens suitable for deep ultraviolet bands. Background Art

[0002] The field of submicron-scale line width measurement of integrated circuits places extremely high demands on microscopic imaging objectives. In this field, microscopic imaging objectives not only need to work in the deep ultraviolet band to achieve accurate observation of tiny structures, but also need to have a large numerical aperture (NA value > 0.7) to ensure sufficient resolution and light flux. In addition, in order to obtain consistent magnification at different line depths, the objective must also have a high object-space telecentricity, that is, the angle between the main light and the object surface normal should remain constant to avoid image distortion caused by depth changes. However, in the deep ultraviolet band, the choice of highly transparent and stable optical materials is limited. Among them, although CaF2 has excellent light transmittance, it has extremely high requirements on machinability, which increases the difficulty of manufacturing.

[0003] Currently, traditional microscope imaging objectives face numerous challenges. First, insufficient object-space telecentricity leads to inconsistent magnification at different line depths, severely impacting measurement accuracy and reliability.

[0004] To address the above issues, Japanese patent JP2000155267A discloses a structural type of deep ultraviolet (DUV) microscope objective lens. This objective lens is made of fused quartz and has an operating wavelength of 248nm. However, to ensure clarity within the object field of view, the patent requires that the last lens closest to the object to be detected has a very large curvature. While this design helps improve imaging quality, it also places extremely high demands on the processability of the lens, increases manufacturing costs and cycle time, and brings certain difficulties to manufacturing. Therefore, it is necessary to further optimize the design of the microscope imaging objective lens while maintaining high imaging quality to improve its processability and practicality.

[0005] To this end, we propose a lens suitable for the deep ultraviolet band. Utility Model Content

[0006] In response to the shortcomings of the above-mentioned existing production technology, this application provides a lens suitable for the deep ultraviolet band. Through a multi-lens combination design, it exhibits excellent performance in terms of resolution, clarity, processability, object space telecentricity, etc.

[0007] The technical solutions adopted in this utility model are as follows:

[0008] A lens suitable for deep ultraviolet band, suitable for microscopic imaging or photolithography of light with a wavelength of 190-270nm. The lens group is waist-drum-shaped and includes the following components along the optical axis:

[0009] The first lens is a positive meniscus lens;

[0010] The second lens is a positive meniscus lens;

[0011] The third lens is a negative biconcave lens;

[0012] The fourth lens is a negative biconcave lens;

[0013] The fifth lens is a negative meniscus lens;

[0014] The sixth lens is a negative meniscus lens;

[0015] The seventh lens is a negative biconcave lens;

[0016] The eighth lens is a positive biconvex lens;

[0017] The ninth lens is a positive biconvex lens;

[0018] The tenth lens is a positive biconvex lens;

[0019] The eleventh lens is a positive biconvex lens;

[0020] The twelfth lens is a positive meniscus lens;

[0021] The thirteenth lens is a positive meniscus lens;

[0022] The fourteenth lens is a negative meniscus lens;

[0023] The fifteenth lens is a positive meniscus lens, the left side curvature radius of the lens is 3.2-3.5 mm, the right side curvature radius is 6.0-6.7 mm, and the sagittal height is 1.8-2.2 mm.

[0024] Furthermore, the first lens group is 29.5mm to 32.6mm, the right side curvature radius is 7.0mm to 7.8mm, and the thickness is 10mm to 13mm.

[0025] Furthermore, the left side curvature radius of the second lens is 367.0 mm to 405.7 mm, and the right side curvature radius is 9.9 mm to 10.9 mm.

[0026] Furthermore, the left side curvature radius of the third lens is -22.3 mm to -20.2 mm, and the right side curvature radius is 26.8 mm to 29.6 mm.

[0027] Furthermore, the left side curvature radius of the fourth lens is -1170.7 mm to -1059.2 mm, and the right side curvature radius is 34.2 mm to 37.8 mm.

[0028] Furthermore, the left side curvature radius of the fifth lens is -33.8 mm to -30.6 mm, and the right side curvature radius is -19.5 mm to -17.7 mm.

[0029] Furthermore, the left side curvature radius of the sixth lens is -61.1 mm to -55.3 mm, and the right side curvature radius is -25.9 mm to -23.4 mm.

[0030] Furthermore, the left side curvature radius of the seventh lens is -3744.6 mm to -3387.9 mm, and the right side curvature radius is 18.2 mm to 20.2 mm.

[0031] Furthermore, the left side curvature radius of the eighth lens is 87.9 mm to 97.2 mm, and the right side curvature radius is -124.1 mm to -112.3 mm.

[0032] Furthermore, the left side curvature radius of the ninth lens is 51.3 mm to 56.7 mm, and the right side curvature radius is -91.1 mm to -82.4 mm.

[0033] Furthermore, the left side curvature radius of the tenth lens is 53.9 mm to 59.6 mm, and the right side curvature radius is -138.9 mm to -125.7 mm;

[0034] Furthermore, the left side curvature radius of the eleventh lens is 39.2 mm to 43.3 mm, and the right side curvature radius is -101.6 mm to -91.9 mm;

[0035] Furthermore, the left side curvature radius of the twelfth lens is 24.4 mm to 27.0 mm, and the right side curvature radius is 2222.7 mm to 2456.7 mm.

[0036] Furthermore, the left side curvature radius of the thirteenth lens is 12.4 mm to 13.7 mm, and the right side curvature radius is 106.4 mm to 117.5 mm;

[0037] Furthermore, the left side curvature radius of the fourteenth lens is -68.1 mm to -61.6 mm, and the right side curvature radius is -289.1 mm to -261.6 mm.

[0038] Furthermore, the lens operates at a wavelength of 248 nm.

[0039] Furthermore, the distance between adjacent lenses is 1 to 4 mm.

[0040] Furthermore, the lens is made of fused quartz.

[0041] As a further improvement of the above technical solution:

[0042] The lens is a microscope imaging objective lens or a photolithography imaging lens; when the lens is a microscope imaging objective lens, the left side of the lens is the image plane and the right side is the object plane; when the lens is a photolithography imaging lens, the left side of the lens is the object plane and the right side is the image plane.

[0043] The beneficial effects of the utility model are as follows:

[0044] The utility model has a compact structure. Through the multi-lens combination design, the lens has a high numerical aperture design. Combined with the short wavelength characteristics of deep ultraviolet light, it improves the resolution limit of traditional optical microscopes and can observe tiny structures in detail. In addition, the principal light of the objective lens is parallel to the optical axis and has a high telecentricity, which ensures a consistent magnification in a deeper object space, improves the accuracy and reliability of the measurement, and meets the lithography requirements of deep ultraviolet lithography lenses and the observation requirements of microscope lenses. Finally, by limiting the curvature radius and sagittal height of the last lens, the application avoids the lens from becoming a super-hemispherical shape, and the structure is easier to process. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 This is a schematic diagram of the lens assembly structure of Example 1 of the present utility model.

[0046] Figure 2 This is a comparison diagram of the MTF curve and the diffraction limit of the objective lens in Example 1 of the present utility model.

[0047] Figure 3 This is a distribution diagram of the diffuse spots of the objective lens of Example 1 of the present utility model.

[0048] Figure 4 This is a structural diagram of the lens assembly of comparative example 1 of the present invention.

[0049] Figure 5 This is a comparison diagram of the MTF curve and diffraction limit of the objective lens of comparative example 1 of the present invention.

[0050] Figure 6 This is a distribution diagram of the diffuse spots of the objective lens of comparative example 1 of the present invention.

[0051] in:

[0052] 1. First lens group; 2. Second lens group; 3. Third lens group; 4. Fourth lens group; 5. Fifth lens group; 6. Sixth lens group; 7. Seventh lens group; 8. Eighth lens group; 9. Ninth lens group; 10. Tenth lens group; 11. Eleventh lens group; 12. Twelfth lens group; 13. Thirteenth lens group; 14. Fourteenth lens group; 15. Fifteenth lens group. DETAILED DESCRIPTION

[0053] The specific implementation of the present utility model will be described below with reference to the accompanying drawings.

[0054] like Figure 1 As shown, this embodiment discloses a lens suitable for deep ultraviolet band. The objective lens is suitable for microscopic imaging of light with a wavelength of 190nm-270nm. In particular, in this embodiment, it is mainly used for deep ultraviolet light with a wavelength of 248nm. The objective lens can be used as a microscopic imaging objective lens or a photolithography imaging lens. Figure 1 When the lens is a microscope imaging objective lens, the left side of the lens is the image plane and the right side is the object plane; when the lens is a lithography imaging lens, the left side of the lens is the object plane and the right side is the image plane.

[0055] The following is explained using a microscope objective lens, see Figure 1 The microscope imaging objective lens of the present application is in the shape of a waist drum and includes a total of fifteen lenses. From the image plane (left side) to the object plane (right side), along the optical axis, it includes the first lens 1, which is a positive meniscus lens; the second lens 2, which is a positive meniscus lens; the third lens 3, which is a negative biconcave lens; the fourth lens 4, which is a negative biconcave lens; the fifth lens 5, which is a negative meniscus lens; the sixth lens 6, which is a negative meniscus lens; the seventh lens 7, which is a negative biconcave lens; the eighth lens 8, which is a positive biconvex lens; the ninth lens 9, which is a positive biconvex lens; the tenth lens 10, which is a positive biconvex lens; the eleventh lens 11, which is a positive biconvex lens; the twelfth lens 12, which is a positive meniscus lens; the thirteenth lens 13, which is a positive meniscus lens; the fourteenth lens 14, which is a negative meniscus lens; and the fifteenth lens 15, which is a positive meniscus lens. The left curvature radius of the lens is 3.2-3.5 mm, the right curvature radius is 6.0-6.7 mm, and the sagittal height is 1.8-2.2 mm. The lens combination has excellent performance with an object-side field of view of 0.3mm, a maximum lens diameter of 27mm, and an object-side numerical aperture NA=0.75, meeting the requirements of microscopic imaging in the deep ultraviolet band.

[0056] In addition, the fifteenth lens 15 of the present application limits its curvature radius and sagitta, limiting the curvature radius of the left side of the fifteenth lens to 3.2-3.5 mm, the curvature radius of the image side to 6.0-6.7 mm, and the sagitta to 1.8-2.2 mm, which meets the angle requirements of the incident light and the outgoing light. At the same time, the curvature radius and sagitta of the last lens are limited. Compared with the last lens in the comparative document JP2000155267A, the curvature radius of the present application is larger, avoiding the formation of a super hemisphere, making the lens easier to process.

[0057] Each objective lens in this embodiment is made of fused quartz. As a high-quality optical material, fused quartz offers excellent light transmission and stability in the deep ultraviolet (DUV) band. Compared to CaF2, it is also relatively easy to work with, meeting the requirements of high-precision manufacturing. Furthermore, the objective lens in this embodiment does not contain a cemented lens, as cemented lenses reduce light transmittance and, under prolonged exposure to DUV light, can easily degrade the optical adhesive, thus reducing the lifespan of the objective lens.

[0058] In some specific embodiments, the curvature radius of the left side of the first lens 1 ranges from 29.5 mm to 32.6 mm, the curvature radius of the right side ranges from 7.0 mm to 7.8 mm, and the thickness ranges from 10 mm to 13 mm.

[0059] In some specific embodiments, the curvature radius of the left side of the second lens 2 ranges from 367.0 mm to 405.7 mm, the curvature radius of the right side ranges from 9.9 mm to 10.9 mm, and the thickness ranges from 2.0 mm to 2.5 mm.

[0060] The left side of the third lens 3 has a curvature radius ranging from -22.3 mm to -20.2 mm, the right side has a curvature radius ranging from 26.8 mm to 29.6 mm, and the thickness ranges from 2.5 mm to 3.2 mm.

[0061] The curvature radius of the left side of the fourth lens 4 ranges from -1170.7 mm to -1059.2 mm, the curvature radius of the right side ranges from 34.2 mm to 37.8 mm, and the thickness ranges from 2.0 mm to 3.0 mm.

[0062] The curvature radius of the left side of the fifth lens 5 ranges from -33.8 mm to -30.6 mm, the curvature radius of the right side ranges from -19.5 mm to -17.7 mm, and the thickness ranges from 1.8 mm to 2.5 mm.

[0063] The curvature radius of the left side of the sixth lens 6 ranges from -61.1 mm to -55.3 mm, the curvature radius of the right side ranges from -25.9 mm to -23.4 mm, and the thickness ranges from 1.9 mm to 2.4 mm.

[0064] The curvature radius of the left side of the seventh lens 7 ranges from -3744.6 mm to -3387.9 mm, the curvature radius of the right side ranges from 18.2 mm to 20.2 mm, and the thickness ranges from 1.8 mm to 2.2 mm.

[0065] The left side of the eighth lens 8 has a curvature radius ranging from 87.9 mm to 97.2 mm, the right side has a curvature radius ranging from -124.1 mm to -112.3 mm, and the thickness ranges from 2.0 mm to 2.8 mm.

[0066] The curvature radius of the left side of the ninth lens 9 ranges from 51.3 mm to 56.7 mm, the curvature radius of the right side ranges from -91.1 mm to -82.4 mm, and the thickness ranges from 2.8 mm to 3.4 mm.

[0067] The curvature radius of the left side of the tenth lens 10 ranges from 53.9 mm to 59.6 mm, the curvature radius of the right side ranges from -138.9 mm to -125.7 mm, and the thickness ranges from 2.2 mm to 2.6 mm.

[0068] The curvature radius of the left side of the eleventh lens 11 ranges from 39.2 mm to 43.3 mm, the curvature radius of the right side ranges from -101.6 mm to -91.9 mm, and the thickness ranges from 3.2 mm to 4.0 mm.

[0069] The curvature radius of the left side of the twelfth lens 12 ranges from 24.4 mm to 27.0 mm, the curvature radius of the right side ranges from 2222.7 mm to 2456.7 mm, and the thickness ranges from 3.7 mm to 4.2 mm.

[0070] The curvature radius of the left side of the thirteenth lens 13 ranges from 12.4 mm to 13.7 mm, the curvature radius of the right side ranges from 106.4 mm to 117.5 mm, and the thickness ranges from 5.5 mm to 6.0 mm.

[0071] The curvature radius of the left side of the fourteenth lens 14 ranges from -68.1 mm to -61.6 mm, the curvature radius of the right side ranges from -289.1 mm to -261.6 mm, and the thickness ranges from 3.2 mm to 4.0 mm.

[0072] The first, second, and third lenses 1, 2, and 3 can be considered the "waist" of the entire lens; the tenth, eleventh, and twelfth lenses 10, 11, and 12 can be considered the "drum" of the lens. This combination of negative optical power in the "waist" and positive optical power in the "drum" effectively reduces the system's Petzval sum, fundamentally minimizing field curvature. The fourth through ninth lenses 9 serve as a link within the "waist and drum," smoothing the passage of light through the lens and preventing excessive refraction angles from impacting image quality.

[0073] Example 1

[0074] like Figure 1 As shown in Figure 1, this is a lens combination where all lenses are made of fused silica (F-SILICA). The specific lens composition is shown in Table 1. The spacing between adjacent lenses refers to the spacing between the lens and the next lens. For example, if the spacing between the first lens is 1mm, it means the spacing between the first and second lenses is 1mm. If the spacing between the fifteenth lens is 1.361mm, it means the distance between the fifteenth lens and the object plane is 1.361mm.

[0075] Table 1

[0076]

[0077] Table 2

[0078] Angle between the chief ray and the object surface normal (°) On-axis field of view 0 0.3 field of view 0.0052 0.5 field of view 0.0086 0.7 field of view 0.012 Full field of view 0.016

[0079] This application uses a lens combination consisting of fifteen lenses to make the final lens group appear waist drum-shaped. As shown in Table 2, the angle between the main ray of the on-axis field of view and the object plane normal is 0°, and the angle between the main ray and the object plane normal under the full field of view is 0.016°, which makes the objective lens have a high telecentricity in the entire object space, ensuring consistent magnification at different line depths, and improving the accuracy and reliability of measurement and lithography. In addition, this application conducted MTF tests at 0°, 2.1°, and 3° fields of view, as shown in Table 2. Figure 2 As shown in the figure, the meridian and sagittal curves of each field of view are highly consistent, which fully reflects that the lens still has good image quality when it reaches the diffraction limit within the entire field of view, and has high-resolution and high-definition imaging effects. Figure 3 The following are spot diagrams of the lens. The images show fields of view of 0°, 2.1°, and 3°, respectively. The diffuse spots in all three images are concentrated in the center and form Airy spots, indicating that the lens has reached the diffraction limit. At the diffraction limit, the light spot is concentrated and does not diffuse.

[0080] Example 2

[0081] This embodiment discloses a lens combination different from that of Example 1. The shape and arrangement of the lenses of Example 2 are the same as those of Example 1. The only difference is the curvature radius, thickness, and spacing between adjacent lenses. The specific lens combination is shown in Table 3:

[0082] Table 3

[0083]

[0084] Comparative Example 1

[0085] like Figure 4 As shown, Comparative Example 1 is a microscopic imaging objective lens with fourteen lenses, which can achieve microscopic imaging at a wavelength of 248nm. From left to right, the data shapes and data of each lens group are shown in Table 4 below:

[0086] Table 4

[0087] The imaging objective lens with fourteen lenses is also suitable for microscopic imaging of 248nm light waves, and the overall

[0088]

[0089] It also presents a waist drum shape, but the obvious ratio of "waist" and "drum" is different from that of the present application, and its imaging quality is not as good as that of the present application. Figure 5 As shown, the separation of the meridian and sagittal curves of the 0°, 2.1°, and 3° fields of view indicates that the imaging performance of the fourteen-element lens is poor. Figure 6 In the figure, the spot diagrams of the lens at 0°, 2.1°, and 3° fields of view are shown. The diffuse spots in these three figures are scattered and do not form Airy spots, indicating that the optical system has spot diffusion, which also proves that the imaging quality of this lens is poor.

[0090] In summary, this application utilizes a carefully designed lens combination and parameter optimization to design a fifteen-element lens, resulting in a small number of lenses. This not only achieves high-resolution, high-definition imaging, but also possesses excellent object-space telecentricity. Furthermore, the curvature of the final lens is minimal, reducing manufacturing difficulty and cost. Furthermore, the design of the entire objective lens also takes into account feasibility during the manufacturing process, ensuring efficient production and widespread application of the objective lens.

[0091] In summary, the deep ultraviolet microscopy objective lens disclosed in this embodiment demonstrates excellent performance in terms of resolution, clarity, object-space telecentricity, workability, and long-term stability. This objective lens is not only suitable for submicron linewidth measurement of integrated circuits and lithography imaging, but can also be widely used in high-precision microscopy applications in a variety of fields, including nanotechnology, biomedicine, and materials science.

[0092] The above description is an explanation of the utility model, not a limitation of the utility model. The scope of the utility model is defined by the claims. Any form of modification can be made within the scope of protection of the utility model.

Claims

1. A lens suitable for deep ultraviolet band, suitable for microscopic imaging or photolithography of light with a wavelength of 190nm-270nm, characterized in that: The lens group is in the shape of a waist drum and includes the following components in sequence along the optical axis: The first lens is a positive meniscus lens; The second lens is a positive meniscus lens; The third lens is a negative biconcave lens; The fourth lens is a negative biconcave lens; The fifth lens is a negative meniscus lens; The sixth lens is a negative meniscus lens; The seventh lens is a negative biconcave lens; The eighth lens is a positive biconvex lens; The ninth lens is a positive biconvex lens; The tenth lens is a positive biconvex lens; The eleventh lens is a positive biconvex lens; The twelfth lens is a positive meniscus lens; The thirteenth lens is a positive meniscus lens; The fourteenth lens is a negative meniscus lens; The fifteenth lens is a positive meniscus lens, the left side curvature radius of the lens is 3.2mm ~ 3.5mm, the right side curvature radius is 6.0mm ~ 6.7mm, and the sagittal height is 1.8mm ~ 2.2mm.

2. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The first lens group is 29.5mm to 32.6mm, with a right side curvature radius of 7.0mm to 7.8mm and a thickness of 10mm to 13mm.

3. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The left side curvature radius of the second lens is 367.0 mm to 405.7 mm, and the right side curvature radius is 9.9 mm to 10.9 mm; And / or, the left side curvature radius of the third lens is -22.3 mm to -20.2 mm, and the right side curvature radius is 26.8 mm to 29.6 mm.

4. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The left side curvature radius of the fourth lens is -1170.7mm to -1059.2mm, and the right side curvature radius is 34.2mm to 37.8mm; the left side curvature radius of the fifth lens is -33.8mm to -30.6mm, and the right side curvature radius is -19.5mm to -17.7mm; the left side curvature radius of the sixth lens is -61.1mm to -55.3mm, and the right side curvature radius is -25.9mm to -23.4mm.

5. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The left side curvature radius of the seventh lens is -3744.6mm to -3387.9mm, and the right side curvature radius is 18.2mm to 20.2mm; the left side curvature radius of the eighth lens is 87.9mm to 97.2mm, and the right side curvature radius is -124.1mm to -112.3mm; the left side curvature radius of the ninth lens is 51.3mm to 56.7mm, and the right side curvature radius is -91.1mm to -82.4mm.

6. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The left side curvature radius of the tenth lens is 53.9 mm to 59.6 mm, and the right side curvature radius is -138.9 mm to -125.7 mm; The left side curvature radius of the eleventh lens is 39.2 mm to 43.3 mm, and the right side curvature radius is -101.6 mm to -91.9 mm; The left side curvature radius of the twelfth lens is 24.4mm~27.0mm, and the right side curvature radius is 2222.7mm~2456.7mm.

7. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The left side curvature radius of the thirteenth lens is 12.4 mm to 13.7 mm, and the right side curvature radius is 106.4 mm to 117.5 mm; And / or, the left side curvature radius of the fourteenth lens is -68.1 mm to -61.6 mm, and the right side curvature radius is -289.1 mm to -261.6 mm.

8. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The operating wavelength of the lens is 248nm.

9. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The distance between adjacent lenses is 1~4mm; And / or, the lens is made of fused quartz.

10. The lens suitable for deep ultraviolet band according to claim 1, characterized in that: The lens is a microscopic imaging objective lens or a photolithography imaging lens; When the lens is a microscope imaging objective lens, the left side of the lens is the image plane and the right side is the object plane; When the lens is a photolithography imaging lens, the left side of the lens is the object plane, and the right side of the lens is the image plane.

Images