Deep ultraviolet detection objective and wafer defect detection system

Abstract

The application relates to the technical field of semiconductor detection, and provides a deep ultraviolet detection objective lens and a wafer defect detection system. The deep ultraviolet detection objective lens comprises, in sequence from an object plane to an image plane along an optical axis direction: a first lens group with positive focal power; a second lens group with negative focal power; a diaphragm; a third lens group with positive focal power; and a fourth lens group with negative focal power. The first lens group, the second lens group, the third lens group and the fourth lens group form a full-transmission optical structure. Incident light sequentially passes through the first lens group, the second lens group, the diaphragm, the third lens group and the fourth lens group, and the light emitted from the fourth lens group is parallel light. The application realizes the high performance unification of a large numerical aperture and a large field of view in a deep ultraviolet wave band through a four-lens full-transmission structure and a global plane single material design, and guarantees good imaging quality and processing realizability.

Description

Technical Field

[0001] This application relates to the field of semiconductor inspection technology, and more specifically, to a deep ultraviolet inspection objective and a wafer defect inspection system. Background Technology

[0002] Currently, existing deep ultraviolet (DUV) detection objectives suffer from the dilemma of balancing high numerical aperture and large field of view. To improve resolution, the numerical aperture must be increased to collect scattered light at a wider angle; conversely, to improve detection efficiency, the field of view for a single imaging pass needs to be expanded to cover a larger scanning area. Existing solutions often compromise one aspect for the other. Currently available high-UV objectives typically have a field of view limited to within φ0.1mm, severely restricting detection speed. Furthermore, there is a conflict between high-performance requirements and system manufacturability. The available optical materials in the deep ultraviolet band are limited, and aberration correction is extremely difficult. Some designs, in pursuit of performance, introduce aspherical mirrors, reflective mirrors, or multi-material combinations. While this improves image quality, it drastically increases the difficulty of lens fabrication, raises costs, complicates assembly and adjustment, and the risk of thermal mismatch between multiple materials can affect system stability, hindering manufacturing. Therefore, there is an urgent need in the field for a deep ultraviolet detection objective that can simultaneously possess large numerical aperture, large field of view, high image quality, good manufacturability and system adaptability, in order to break through the existing technical bottlenecks and meet the needs of advanced semiconductor manufacturing for high-resolution, high-throughput defect detection. Summary of the Invention

[0003] This application aims to at least address the technical problems in the design of existing deep ultraviolet detection objectives, such as the difficulty in simultaneously achieving high numerical aperture and large field of view, and the conflict between high performance requirements and system manufacturability.

[0004] To solve the above-mentioned technical problems, this application is implemented as follows:

[0005] In a first aspect, this application provides a deep ultraviolet detection objective lens, comprising: a first lens group having positive optical power; a second lens group having negative optical power; an aperture; a third lens group having positive optical power; and a fourth lens group having negative optical power, arranged sequentially from the object plane to the image plane along the optical axis; wherein the first lens group, the second lens group, the third lens group, and the fourth lens group constitute a fully transmissive optical structure, the incident light passes sequentially through the first lens group, the second lens group, the aperture, the third lens group, and the fourth lens group, and the light emitted from the fourth lens group is parallel light.

[0006] This application provides a deep ultraviolet (DUV) detection objective lens that achieves a high-performance balance between large numerical aperture and large field of view in the DUV band through a four-lens fully transmissive architecture and a single-material global surface design, while ensuring excellent imaging quality and fabrication feasibility. In terms of optical architecture and aberration correction, the objective lens employs a fully transmissive configuration consisting of a first lens group, a second lens group, an aperture stop, a third lens group, and a fourth lens group arranged sequentially along the optical axis from the object plane. This alternating distribution of specific optical powers (positive, negative, positive, negative) and the four-group division of labor effectively distributes the aberration correction task across the entire optical path. The positive lens group primarily handles light convergence and numerical aperture enhancement, while the negative lens group specifically corrects aberrations introduced by the positive lens group, particularly field curvature and distortion. This allows the system to achieve a large numerical aperture while significantly expanding the field of view to φ1mm, effectively resolving the inherent contradiction between high resolution and a large scanning range. Regarding system manufacturability and stability, all lenses are made of fused silica material suitable for the 266nm band and are all designed as spherical surfaces. The use of a single material eliminates the problems of chromatic aberration and thermal mismatch associated with multi-material lenses, while the global surface design significantly reduces the difficulty and cost of lens processing and inspection. In particular, although the fourth lens group has an overall negative optical power, it is internally achieved by combining three positive optical power lenses with specific curvature and spacing. This design not only fulfills the aberration balancing task but also facilitates the mass production of high-performance objectives. In terms of imaging quality and system adaptability, through the synergistic optimization of the aforementioned architecture and materials, this objective achieves excellent image quality with wavefront aberration less than the diffraction limit, field curvature less than 0.4μm, and distortion less than 0.045%, ensuring clear and accurate imaging of defects. Simultaneously, the objective employs an infinity optical design, emitting parallel light from the fourth lens group. The overall system magnification can be flexibly changed by matching different focal lengths of the tube lenses, enhancing its versatility and flexibility in the inspection platform, and the parallel light path reduces the requirements for assembly and adjustment precision. In summary, the deep ultraviolet detection objective provided in this application optimizes key performance characteristics such as high numerical aperture, large field of view, high image quality, and ease of fabrication, providing a reliable optical solution for efficient and high-precision defect detection of semiconductor wafers.

[0007] Secondly, this application proposes a wafer defect detection system, including a deep ultraviolet detection objective lens as described above.

[0008] The wafer defect detection system provided in this application includes a deep ultraviolet detection objective lens as described above, and therefore has all the beneficial effects of such a deep ultraviolet detection objective lens, which will not be elaborated here.

[0009] Additional aspects and advantages of this application will become apparent in the following description or may be learned by practice of this application. Attached Figure Description

[0010] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which: Figure 1 This is a schematic diagram of the structure of a deep ultraviolet detection objective lens according to an embodiment of this application; Figure 2 This is a modulation transfer function (MTF) curve of a deep ultraviolet detection objective lens according to an embodiment of this application; Figure 3 Wavefront difference diagrams of different fields of view of a deep ultraviolet detection objective lens according to an embodiment of this application; Figure 4 This is a schematic diagram of the energy concentration of a deep ultraviolet detection objective lens according to an embodiment of this application; Figure 5 This is a field curvature diagram of a deep ultraviolet detection objective lens according to an embodiment of this application; Figure 6 This is a distortion diagram of a deep ultraviolet detection objective lens according to an embodiment of this application.

[0011] in, Figures 1 to 6 The correspondence between the reference numerals and component names in the attached drawings is as follows: 100° deep ultraviolet detection objective, 110° first lens group, 120° second lens group, 130° third lens group, 140° fourth lens group, 150° aperture, 1 first lens, 2 second lens, 3 third lens, 4 fourth lens, 5 fifth lens, 6 sixth lens, 7 seventh lens, 8 eighth lens, 9 ninth lens, 10 tenth lens, 11 eleventh lens, 12 twelfth lens, 13 thirteenth lens, 14 fourteenth lens, 15 fifteenth lens, 16 sixteenth lens, 17 seventeenth lens. Detailed Implementation

[0012] To better understand the above-mentioned objectives, features, and advantages of this application, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments and features described in these embodiments can be combined with each other.

[0013] Many specific details are set forth in the following description in order to provide a full understanding of this application. However, this application may also be implemented in other ways different from those described herein. Therefore, the scope of protection of this application is not limited to the specific embodiments disclosed below.

[0014] The following reference Figures 1 to 6 This application describes a deep ultraviolet detection objective 100 and a wafer defect detection system provided according to some embodiments of the present application.

[0015] According to the first aspect of this application, Figure 1As shown, an embodiment of this application provides a deep ultraviolet detection objective lens 100, comprising the following components arranged sequentially from the object plane to the image plane along the optical axis: a first lens group 110 with positive optical power; a second lens group 120 with negative optical power; an aperture 150; a third lens group 130 with positive optical power; and a fourth lens group 140 with negative optical power. The first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 constitute a fully transmissive optical structure. Incident light passes sequentially through the first lens group 110, the second lens group 120, the aperture 150, the third lens group 130, and the fourth lens group 140, and the light emitted from the fourth lens group 140 is parallel light.

[0016] Specifically, such as Figure 1 As shown, the deep ultraviolet detection objective lens 100 provided in this application includes a first lens group 110, a second lens group 120, an aperture 150, a third lens group 130, and a fourth lens group 140, which are arranged sequentially from the object plane to the image plane along the optical axis. The first lens group 110 has positive optical power, the second lens group 120 has negative optical power, the third lens group 130 has positive optical power, and the fourth lens group 140 has negative optical power. The first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 constitute a fully transmissive optical structure. Incident light passes sequentially through the first lens group 110, the second lens group 120, the aperture 150, the third lens group 130, and the fourth lens group 140, and the light emitted from the fourth lens group 140 is parallel light.

[0017] By placing the aperture stop 150 between the second lens 2 and the third lens group 130, this application constructs a fully transmissive optical path with balanced optical power distribution. In this structure, the positive optical power lens group is mainly responsible for converging light rays and providing the system's optical power to ensure the realization of a high numerical aperture; while the negative optical power lens group mainly undertakes the correction and balancing of various aberrations introduced by the positive lens group. This allows high-order aberrations to be effectively controlled throughout the system. At the same time, the fully transmissive structure avoids the introduction of mirrors, reducing assembly complexity; and the design of emitting parallel light from the fourth lens group 140 makes the objective lens an infinity optical system, providing a basis for connecting simplified lenses of different focal lengths to achieve system magnification transformation, thus improving the system's modularity and adaptability.

[0018] Compared with existing technologies, the deep ultraviolet detection objective lens 100 provided in this application has the following advantages: First, through the alternating arrangement of four sets of positive and negative optical powers, it achieves efficient aberration correction and balance at the system-wide level, laying the optical foundation for simultaneously obtaining large numerical aperture and a large field of view. Second, the design of a fully transmissive, global surface, and single fused silica material significantly reduces the difficulty and cost of lens processing, inspection, and system assembly while ensuring high performance in the deep ultraviolet band, thus improving engineering feasibility. Third, the infinity optical design with parallel light on the image side enhances the compatibility and combination flexibility of the objective lens with different back-end imaging systems, facilitating the construction of detection platforms with different magnifications. Fourth, it has excellent overall performance, achieving multiple advantages such as high numerical aperture (NA≥0.92), large field of view (diameter≥1mm), and high imaging quality in the deep ultraviolet band, such as 266nm.

[0019] Specifically, as semiconductor process nodes continue to evolve towards smaller dimensions, the size requirements for detecting wafer surface defects have entered the nanometer level. Deep ultraviolet (DUV) optical inspection technology, due to its short wavelength and ability to achieve higher theoretical resolution, has become a key method for advanced process defect detection. The inspection objective, as the core component of this system, directly determines the detection resolution, throughput, and accuracy. However, the design of existing DUV inspection objectives faces multiple contradictions and challenges. First, a high numerical aperture and a large field of view are difficult to achieve simultaneously. To improve resolution, the numerical aperture must be increased to collect scattered light at a larger angle; conversely, to improve detection efficiency, the field of view for a single imaging session needs to be expanded to cover a larger scanning area. Existing technical solutions often compromise one aspect for the other. Currently available high-UV objectives typically have a field of view limited to within φ0.1mm, severely restricting detection speed. Second, there is a conflict between high-performance requirements and system manufacturability. The available optical materials in the deep ultraviolet band are limited, and aberration correction is extremely difficult. Some designs, in pursuit of performance, introduce aspherical mirrors, reflective mirrors, or multi-material combinations. While this improves image quality, it significantly increases the difficulty of lens manufacturing, raises costs, and complicates assembly and adjustment. Furthermore, the risk of thermal mismatch between multiple materials can affect system stability, hindering industrial applications. Moreover, inspection systems place stringent demands on the versatility and image quality of objectives. Wafer defect detection requires objectives with excellent image plane flatness, extremely low distortion, and near-diffraction-limited imaging quality to avoid false or missed defects due to aberrations. Simultaneously, to adapt to different inspection platforms and magnification requirements, objectives ideally possess an infinity optical design interface. However, existing solutions have limitations in achieving these comprehensive performance characteristics. Therefore, there is an urgent need in the field for a deep ultraviolet inspection objective that simultaneously possesses a large numerical aperture, wide field of view, high image quality, good manufacturability, and system adaptability to overcome existing technological bottlenecks and meet the demands of advanced semiconductor manufacturing for high-resolution, high-throughput defect detection.

[0020] To address the shortcomings of existing technologies, this application provides a deep ultraviolet (DUV) detection objective 100. Through a four-lens, fully transmissive architecture and a single-material global surface design, it achieves a high-performance balance between large numerical aperture and a large field of view in the DUV band, while ensuring excellent imaging quality and engineering feasibility. Specifically, in terms of optical architecture and aberration correction, the objective employs a fully transmissive configuration consisting of a first lens group 110, a second lens group 120, an aperture stop 150, a third lens group 130, and a fourth lens group 140 arranged sequentially along the optical axis from the object plane. This alternating distribution of specific optical powers (positive, negative, positive, negative) and the four-group division of labor effectively distributes the aberration correction task across the entire optical path. The positive lens group primarily handles light convergence and numerical aperture enhancement, while the negative lens group specifically corrects aberrations introduced by the positive lens group, particularly field curvature and distortion. This allows the system to achieve a large numerical aperture while significantly expanding the entire field of view to φ1mm, effectively resolving the inherent contradiction between high resolution and a large scanning range. In terms of system manufacturability and stability, all lenses are made of fused silica material suitable for the 266nm wavelength band and are all designed as spherical. The single material eliminates the problems of multi-material chromatic aberration and thermal mismatch, while the spherical design significantly reduces the difficulty and cost of lens processing and inspection. Furthermore, although the fourth lens group 140 has an overall negative optical power, it is internally achieved by combining three positive optical power lenses with specific curvature and spacing. This design not only completes the aberration balancing task but also facilitates the mass production of high-performance objectives. In terms of imaging quality and system adaptability, through the synergistic optimization of the above architecture and materials, this objective achieves excellent image quality with wavefront aberration less than the diffraction limit, field curvature less than 0.4μm, and distortion less than 0.045%, ensuring clear and accurate defect imaging. Simultaneously, the objective adopts an infinity optical design, emitting parallel light from the fourth lens group 140. The overall system magnification can be flexibly changed by matching different focal lengths of the tube lenses, enhancing its versatility and flexibility in the inspection platform, and the parallel light path reduces the requirements for assembly and adjustment precision. In summary, the deep ultraviolet detection objective 100 provided in this application optimizes key performance characteristics such as high numerical aperture, large field of view, high image quality, and ease of fabrication, providing a reliable optical solution for efficient and high-precision defect detection of semiconductor wafers.

[0021] In some embodiments, optionally, such as Figure 1 As shown, the first lens group 110 includes a first lens 1, a second lens 2, a third lens 3, a fourth lens 4 and a fifth lens 5 arranged sequentially from the object plane to the image plane, and the first lens 1, the second lens 2, the third lens 3, the fourth lens 4 and the fifth lens 5 all have positive optical power.

[0022] Specifically, such as Figure 1As shown, the first lens group 110 consists entirely of five lenses with positive optical power arranged sequentially. This design enables the lens group to provide ample and stable positive optical power. As the front end of the entire objective lens system, its primary function is to effectively collect and initially converge large-angle light rays from the object plane, laying a solid foundation for achieving high numerical aperture in the entire system. Simultaneously, this pure positive lens configuration also helps control the angle of the principal ray at the front end of the system, providing a good basis for meeting the image-side telecentric condition.

[0023] In some embodiments, optionally, such as Figure 1 As shown, the second lens group 120 includes a sixth lens 6, a seventh lens 7 and an eighth lens 8 arranged sequentially from the object plane to the image plane. The sixth lens 6 and the eighth lens 8 have positive optical power, and the seventh lens 7 has negative optical power.

[0024] Specifically, such as Figure 1 As shown, the second lens group 120 employs a positive, negative, and positive optical power distribution. The seventh lens 7, acting as a negative lens, functions primarily to generate aberrations with opposite signs to those of the positive lenses, thus providing initial internal compensation and balance for some positive spherical aberrations and other aberrations introduced by the sixth lens 6 and others. This aberration correction design, which begins within the lens group, allows the second lens group 120 to achieve its overall negative optical power, provide necessary light divergence to control aberrations such as image plane curvature, and more effectively manage light, optimize beam shape, and create more ideal conditions for light to enter the subsequent aperture 150 and the third lens group 130, thereby improving the system's aberration correction efficiency.

[0025] In some embodiments, optionally, such as Figure 1 As shown, the third lens group 130 includes a ninth lens 9, a tenth lens 10, an eleventh lens 11, a twelfth lens 12, a thirteenth lens 13, and a fourteenth lens 14 arranged sequentially from the object plane to the image plane. The ninth lens 9, the tenth lens 10, the eleventh lens 11, the thirteenth lens 13, and the fourteenth lens 14 have positive optical power, and the twelfth lens 12 has negative optical power.

[0026] Specifically, such as Figure 1As shown, the third lens group 130 adopts a configuration with five positive-power lenses as the main body and a negative-power lens, i.e., the twelfth lens 12, embedded at a key position therein. This group undertakes the main converging power of the system and the final task of achieving a high numerical aperture. Among them, the dense arrangement of multiple positive lenses ensures a strong light-gathering ability; while the embedded negative lens serves as a delicate corrector, mainly used to cancel and balance specific high-order aberrations such as spherical aberration and coma generated by the positive lenses in this group and the previous group. This design of local compensation within a strongly positive-power group allows for the final fine-tuning of residual aberrations closer to the image plane, thereby significantly improving the overall imaging quality and resolution of the system.

[0027] In some embodiments, optionally, as Figure 1 shown, the fourth lens group 140 includes the fifteenth lens 15, the sixteenth lens 16, and the seventeenth lens 17 arranged in sequence from the object plane to the image plane, and the fifteenth lens 15, the sixteenth lens 16, and the seventeenth lens 17 all have positive powers.

[0028] Specifically, as Figure 1 shown, the fourth lens group 140 is composed of three lenses all having positive powers. Through precise curvature and spacing design, the equivalent power of this lens combination is negative. This design realizes the required negative power of the system to finally balance aberrations such as field curvature and distortion, while avoiding the use of large meniscus negative lenses or cemented negative lens groups, thereby significantly reducing the processing and alignment difficulties. As the last lens group of the system, while completing the aberration correction task, it ensures that the outgoing light is parallel light, thus realizing an infinite conjugate optical design, which provides a key guarantee for the modular connection of the objective lens and the subsequent imaging system.

[0029] In some embodiments, optionally, as Figure 1 shown, the focal length f1 of the first lens group 110 satisfies: 35mm < f1 < 45mm; the focal length f2 of the second lens group 120 satisfies: -700mm < f2 < -600mm; the focal length f3 of the third lens group 130 satisfies: 70mm < f3 < 90mm; the focal length f4 of the fourth lens group 140 satisfies: -30mm < f4 < -20mm.

[0030] Specifically, as Figure 1As shown, by precisely defining the focal lengths of the four lens groups: the first lens group 110 and the third lens group 130 respectively provide moderate and strong positive optical power, responsible for the effective convergence of light and the establishment of the total optical power of the system; the second lens group 120 is a long focal negative group, mainly providing a gentle negative optical power for pre-correction of astigmatism and field curvature; the fourth lens group 140 is a short focal negative group, responsible for the fine balance of final aberrations and the shaping of parallel outgoing light. This coordinated design of the entire set of focal length parameters is the core numerical foundation for realizing the positive, negative, positive, and negative optical power architecture and achieving global aberration balance, working distance control, and infinity imaging conditions, ensuring that each lens group has a clear function and works together efficiently.

[0031] In some embodiments, optionally, such as Figure 1 As shown, all lenses in the first lens group 110, the second lens group 120, the third lens group 130, and the fourth lens group 140 are spherical lenses.

[0032] Specifically, such as Figure 1 As shown, all seventeen lenses in the first lens group 110 to the fourth lens group 140 employ a spherical surface design. In the deep ultraviolet band, the processing, inspection, and coating of aspherical lenses present significant challenges and are extremely costly. The spherical surface design fully utilizes mature spherical grinding, polishing, and interferometry technologies to ensure the surface accuracy and quality of each lens. This not only significantly reduces the manufacturing cost and cycle time of the entire objective system but also improves production consistency and yield, providing crucial feasibility assurance for the engineering and industrial application of high-performance deep ultraviolet objectives.

[0033] In some embodiments, optionally, such as Figure 1 As shown, all spherical lenses are made of fused silica material suitable for the deep ultraviolet band.

[0034] Specifically, such as Figure 1 As shown, all spherical lenses are made of fused silica, a material suitable for the deep ultraviolet band. Fused silica exhibits extremely high transmittance and excellent optical uniformity in the deep ultraviolet band, such as 266nm, making it the most mainstream and reliable optical material in this band. The use of a single fused silica material for all lenses ensures extremely low energy loss as light passes through them, which is beneficial for improving the system's signal-to-noise ratio and detection sensitivity. Secondly, the single material completely avoids complex chromatic aberration problems such as secondary spectral variations introduced by differences in refractive indices of different materials, greatly simplifying the design of chromatic aberration correction for the system. This allows for excellent aberration balance to be achieved at the system-wide level simply through spherical design.

[0035] In some embodiments, optionally, such as Figure 1 As shown, the working wavelength of the deep ultraviolet detection objective 100 is 266nm.

[0036] Specifically, such as Figure 1 As shown, this application sets the operating wavelength of the deep ultraviolet detection objective 100 to 266 nm. This wavelength is located in the deep ultraviolet band, and compared to visible light and ultraviolet light with longer wavelengths, its shorter wavelength directly results in higher theoretical diffraction-limited resolution, which is the physical basis for realizing nanoscale wafer defect detection. Simultaneously, this wavelength matches the transmission window of the selected fused silica material, ensuring that the optical system has extremely high transmission efficiency. Furthermore, 266 nm is the output wavelength of a mature deep ultraviolet light source, facilitating stable and pure illumination, which is beneficial for improving the stability and signal-to-noise ratio of the detection system.

[0037] In some embodiments, optionally, such as Figure 1 As shown, the object-side numerical aperture NA of the deep ultraviolet detection objective 100 is ≥0.92.

[0038] Specifically, such as Figure 1 As shown, through a specific four-lens architecture and precise focal length and surface design, the deep ultraviolet detection objective 100 provided in this application embodiment achieves a high-performance index with an object-side numerical aperture (NA) of not less than 0.92. The numerical aperture directly determines the objective's ability to collect light at an angle. At a working wavelength of 266 nm, NA ≥ 0.92 ensures that the objective possesses a high spatial resolution close to the theoretical limit, enabling the resolution of finer wafer defects. This characteristic is a comprehensive reflection of the powerful light-collecting capability and excellent aberration correction level of the optical system in this application, and is the core optical guarantee for achieving high-sensitivity, high-precision defect detection.

[0039] In some embodiments, optionally, such as Figure 1 As shown, the object-side full field-of-view diameter of the deep ultraviolet detection objective lens 100 is ≥1mm.

[0040] Specifically, such as Figure 1 As shown, the deep ultraviolet detection objective lens 100 provided in this embodiment achieves an object-side full field-of-view diameter of not less than 1 mm. This large field-of-view characteristic is achieved through the alternating positive and negative optical power design of the four lens groups, particularly through effective control of field curvature and distortion. In wafer defect detection, a larger single-shot imaging field of view means fewer imaging frames required under the same scanning stroke, or a larger wafer area that can be detected per unit time, thereby significantly improving the throughput and overall efficiency of the detection system. This performance indicator, combined with the aforementioned high numerical aperture, jointly resolves the technical contradiction of balancing high resolution and high efficiency in the field of deep ultraviolet detection.

[0041] In some embodiments, optionally, such as Figure 1 As shown, the focal length of the deep ultraviolet detection objective 100 is 13.5 mm.

[0042] Specifically, such as Figure 1As shown, through optimized design, the focal length of the deep ultraviolet detection objective 100 provided in this embodiment is set to 13.5 mm. This suitable focal length is the result of a comprehensive design that balances multiple key parameters such as the overall system length, working distance, numerical aperture, and field of view. It allows the objective to accommodate multiple lenses required to achieve a large numerical aperture while maintaining a compact overall optical length, and provides sufficient design freedom for aberration correction under a large field of view. This focal length also matches the design of the rear infinity interface, facilitating combination with tube lenses of conventional focal lengths to form a complete and optimized microscopic imaging system.

[0043] In some embodiments, optionally, such as Figure 1 As shown, the total optical length of the deep ultraviolet detection objective 100 is less than 350 mm.

[0044] Specifically, such as Figure 1 As shown, this embodiment of the application controls the total optical length of the deep ultraviolet detection objective 100 to within 350 mm through optimized optical path layout and lens arrangement. This compact size design is achieved through precise balancing and compression of the focal length allocation, lens thickness, and air gap between lens groups. The shorter total length not only means a smaller physical volume, facilitating integration into space-constrained semiconductor detection devices, but also significantly improves the mechanical rigidity of the entire optical system, reduces the adverse effects of environmental vibration and thermal drift on imaging stability, and helps reduce material usage and control costs, providing an important structural foundation for the engineering application of high-performance objectives.

[0045] In some embodiments, optionally, such as Figure 1 As shown, the working distance of the deep ultraviolet detection objective lens 100 is greater than 3.5 mm.

[0046] Specifically, such as Figure 1 As shown, the deep ultraviolet detection objective 100 provided in this embodiment achieves an object-side working distance greater than 3.5 mm, i.e., the distance from the object surface to the surface of the first lens. This parameter is achieved by synergistically optimizing the object-side surface curvature, center thickness, and overall optical power of the first lens while ensuring that the first lens group 110 has a strong light-collecting capability to support a high numerical aperture. Sufficient working distance provides the necessary safe physical clearance between the objective lens tip and the wafer sample, effectively avoiding the risk of collision due to insufficient spacing during high-speed scanning detection. This not only ensures the operational safety of the equipment and sample but also reserves valuable space for integrating external illumination or introducing other auxiliary optical elements between the objective lens and the sample, improving the functional flexibility and reliability of the entire detection system.

[0047] In some embodiments, optionally, such as Figure 1 As shown, aperture stop 150 is aperture stop 150.

[0048] Specifically, such as Figure 1 As shown, aperture stop 150 is configured as the system's aperture stop. Aperture stop 150 is positioned between the second lens group 120 (with negative optical power) and the third lens group 130 (with positive optical power), a position determined after aberration optimization of the pupil. As an aperture stop, its primary function is to physically define the diameter and angle of the imaging beam, thereby ultimately determining and stabilizing the numerical aperture of the entire objective lens system. Secondly, its specific axial position, in conjunction with the optical power of each lens group, effectively controls the direction of the system's principal ray, making it nearly parallel on the image side, thus satisfying or approaching the image-side telecentric condition. This is crucial for ensuring uniformity of imaging within a large field of view and for subsequent matching with the illumination system. The introduction of this aperture stop is an indispensable key design element for balancing the system's light transmission, aberration correction, and telecentric characteristics.

[0049] In some embodiments, optionally, such as Figure 1 As shown, the parallel light emitted from the fourth lens group 140 is used to cooperate with tube lenses of different focal lengths to achieve changes in the magnification of the detection system.

[0050] Specifically, such as Figure 1 As shown, the fourth lens group 140, through a specific optical power and curvature design, ensures that its emitted light is a parallel beam. This makes the deep ultraviolet detection objective 100 a standard infinity-corrected optical system. In this architecture, the objective itself forms an independent optical module with parallel light on the image side. This parallel light path allows for flexible insertion of tube lenses with different focal lengths behind it without compromising the corrected image quality due to the introduction of additional optical path differences. The total magnification of the system is determined by the ratio of the objective lens focal length to the tube lens focal length. Therefore, by simply changing the tube lens, the magnification of the entire detection system can be quickly and conveniently switched without changing the core objective, thereby adapting to the detection needs of different resolutions and field coverages, greatly enhancing the versatility and flexibility of the detection platform.

[0051] In some embodiments, optionally, such as Figure 3 As shown, the wavefront aberration of the deep ultraviolet detection objective 100 is less than the diffraction limit of the working wavelength across the entire field of view.

[0052] Specifically, such as Figure 3As shown, through the alternating design of positive and negative optical power of four lens groups and precise aberration balancing, the wavefront aberration of the deep ultraviolet detection objective 100 is strictly controlled to a level less than the diffraction limit of the working wavelength across the entire field of view. Wavefront aberration is a core indicator for measuring how close the imaging quality of an optical system is to the ideal. A value less than the diffraction limit means that the phase information distortion of the system imaging is extremely low, and the point spread function is close to the theoretical sharpest state. This shows that the optical architecture of this application still achieves excellent correction of high-order aberrations under the constraints of a global plane and a single material. This ensures that the system can maintain high contrast even at the limit resolution, guaranteeing that the objective can accurately resolve and identify nanoscale wafer defects, and avoiding signal blurring, false detections, or missed detections caused by aberrations.

[0053] In some embodiments, optionally, such as Figure 5 and Figure 6 As shown, the field curvature of the deep ultraviolet detection objective 100 is less than 0.4 μm and the distortion is less than 0.045% across the entire field of view.

[0054] Specifically, such as Figure 5 and Figure 6 As shown, through precise control of the optical power and position of the negative optical power lens group, excellent image plane flatness and geometric fidelity are achieved, resulting in a field curvature of less than 0.4 μm and a distortion of less than 0.045% for the deep ultraviolet detection objective lens 100 across the entire field of view. Field curvature characterizes the degree to which the image plane deviates from an ideal plane. Extremely low field curvature ensures that image points are clearly focused on the same focal plane throughout the entire large field of view, eliminating the need for refocusing. This is crucial for the continuity and accuracy of high-speed, large-area scanning imaging. Distortion represents the proportion of image geometry distortion relative to the object. Extremely low distortion (below 0.045%) means almost no stretching or deformation in the image, ensuring extremely precise measurement and location of wafer defects. This avoids metrological errors caused by image distortion and provides a reliable image basis for quantitative, high-precision defect analysis and classification.

[0055] In some embodiments, optionally, such as Figure 4 As shown, at the image plane, the radius of concentration of 90% of the energy in the deep ultraviolet detection objective 100 is less than 0.45 μm across the entire field of view.

[0056] Specifically, such as Figure 4As shown, through aberration correction and optical path design, the deep ultraviolet detection objective 100 achieves a concentration radius of less than 0.45 μm for 90% of the energy across the entire field of view at the image plane. Energy concentration is a direct indicator of an optical system's ability to focus light; a smaller radius indicates a sharper imaging spot and more concentrated energy. A radius less than 0.45 μm indicates that the system has a point spread function close to the diffraction limit, ensuring high-contrast transmission of high spatial frequency information. This is crucial for wafer defect detection, meaning that weak defect-scattered light signals can be efficiently focused onto the detector pixels, significantly improving the signal-to-noise ratio and sensitivity, thus enabling more reliable detection and identification of submicron and even nanoscale defects.

[0057] In practical applications, this application provides a deep ultraviolet (DUV) inspection objective 100, which combines a large field of view, a large numerical aperture, and high resolution, thereby improving the resolution and inspection speed of a wafer defect inspection system. The DUV inspection objective 100 has a fully transmission structure with 17 lenses, all of which are spherical and free of severely bent lenses, facilitating fabrication and testing. The DUV inspection objective 100 features high resolution and high image quality, low aberrations, and a wavefront aberration less than the diffraction limit, which helps improve the accuracy of defect detection in the system. High aberration objectives reduce image contrast and blur defect signals, leading to false or missed detections of wafer defects. The DUV inspection objective 100 employs an infinity mode, with parallel light emitted from the image plane. Different magnifications can be achieved by matching different focal lengths of tube lenses to meet various magnification requirements. The DUV inspection objective 100 is applicable to the 266nm wavelength band, featuring a large field of view and a large numerical aperture (φ1mm for the entire field of view and 0.92 for the object-side numerical aperture). High resolution and low aberrations improve the resolution of wafer defect detection systems, while a large field of view (i.e., a large detection scanning target surface) increases detection speed. The deep ultraviolet (DUV) detection objective 100 has an object-side field of view radius less than or equal to 0.5 mm, meaning its entire field of view is less than or equal to φ1 mm. Currently, DUV objectives with a numerical aperture greater than 0.9 typically have a total field of view less than or equal to φ0.1 mm. Therefore, this application possesses a larger field of view, resulting in a larger detection scanning target surface and improved detection speed. The DUV detection objective 100 has a focal length of 13.5 mm, a total objective length less than 350 mm, and an object-side working distance greater than 3.5 mm.

[0058] Specifically, Table 1 provides the specific optical parameters of the deep ultraviolet detection objective 100. A positive radius value R indicates that the center of curvature is closer to the image side, while a negative radius value R indicates that the center of curvature is closer to the object side.

[0059] Table 1 shows the specific optical parameters of the deep ultraviolet detection objective lens 100:

[0060] The modulation transfer function (MTF) curve of the deep ultraviolet detection objective 100 provided in this embodiment is shown in the figure below. Figure 2 As shown, the MTF curve of the objective lens obtained through simulation analysis is close to the diffraction limit. The horizontal axis represents the spatial frequency, and the vertical axis represents different MTF values.

[0061] The wavefront aberration diagrams of the deep ultraviolet detection objective 100 at different fields of view provided in this embodiment are as follows: Figure 3 As shown, the horizontal axis represents different fields of view, and the vertical axis represents different wavefront aberrations. Through simulation analysis, it can be seen that the wavefront aberrations of each field of view of the objective lens are small and all less than the diffraction limit.

[0062] The energy concentration diagrams of different fields of view of the deep ultraviolet detection objective lens 100 provided in this embodiment are as follows: Figure 4 As shown, the horizontal axis represents the image plane diameter, and the vertical axis represents the closed energy ratio. The 90% energy concentration across the entire field of view is superior to that in a region with a radius of 0.45 μm, indicating that the deep ultraviolet objective optical system can effectively concentrate the collected wafer defect scattered light into the probe optical path.

[0063] like Figure 5 and Figure 6 As shown, the field curvature diagram of the deep ultraviolet detection objective 100 provided in this embodiment is as follows. Figure 5 As shown, the distortion image is as follows Figure 6 As shown, the meridional and sagittal field curvature of the objective lens is less than 0.4 μm, and the maximum distortion is 0.045%.

[0064] In summary, the deep ultraviolet inspection objective 100 provided in this embodiment has a large numerical aperture and a large field of view, enabling high-resolution and low-aberration inspection. This large numerical aperture and large field of view inspection objective can improve the resolution and inspection speed of the wafer defect inspection system, ensuring wafer cleanliness through high-precision, high-resolution, and high-flow-rate inspection.

[0065] According to a second aspect of this application, a wafer defect detection system is proposed, including a deep ultraviolet detection objective lens 100 as described in the above embodiments.

[0066] The wafer defect detection system provided in this application includes the deep ultraviolet detection objective lens 100 as described in the above embodiment, and therefore has all the beneficial effects of the deep ultraviolet detection objective lens 100, which will not be repeated here.

[0067] In the description of this application, the term "multiple" refers to two or more. Unless otherwise expressly defined, the terms "upper," "lower," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. The terms "connection," "installation," "fixing," etc., should be interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection or an indirect connection through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0068] In the description of this specification, the terms "one embodiment," "some embodiments," "specific embodiment," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0069] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A deep ultraviolet detection objective lens, characterized in that, Including, successively arranged along the optical axis direction from the object plane to the image plane: The first lens group, having a positive optical power; The second lens group, having a negative optical power; The aperture stop; The third lens group, having a positive optical power; The fourth lens group, having a negative optical power; Wherein, the first lens group, the second lens group, the third lens group and the fourth lens group form a fully transmissive optical structure, and incident light successively passes through the first lens group, the second lens group, the aperture stop, the third lens group and the fourth lens group, and the light emerging from the fourth lens group is parallel light.

2. The deep ultraviolet detection objective lens according to claim 1, characterized in that, The first lens group includes a first lens, a second lens, a third lens, a fourth lens and a fifth lens successively arranged from the object plane to the image plane direction, and the first lens, the second lens, the third lens, the fourth lens and the fifth lens all have positive optical power.

3. The deep ultraviolet detection objective lens according to claim 1, characterized in that, The second lens group includes a sixth lens, a seventh lens and an eighth lens successively arranged from the object plane to the image plane direction, the sixth lens and the eighth lens have positive optical power, and the seventh lens has negative optical power.

4. The deep ultraviolet detection objective lens according to claim 1, characterized in that, The third lens group includes a ninth lens, a tenth lens, an eleventh lens, a twelfth lens, a thirteenth lens and a fourteenth lens successively arranged from the object plane to the image plane direction, the ninth lens, the tenth lens, the eleventh lens, the thirteenth lens and the fourteenth lens have positive optical power, and the twelfth lens has negative optical power.

5. The deep ultraviolet detection objective lens according to claim 1, characterized in that, The fourth lens group includes a fifteenth lens, a sixteenth lens and a seventeenth lens successively arranged from the object plane to the image plane direction, and the fifteenth lens, the sixteenth lens and the seventeenth lens all have positive optical power.

6. The deep ultraviolet detection objective lens according to claim 1, characterized in that, The focal length f1 of the first lens group satisfies: 35mm < f1 < 45mm; the focal length f2 of the second lens group satisfies: -700mm < f2 < -600mm; the focal length f3 of the third lens group satisfies: 70mm < f3 < 90mm; the focal length f4 of the fourth lens group satisfies: -30mm < f4 < -20mm.

7. The deep ultraviolet detection objective according to any one of claims 1 to 6, characterized in that, All lenses in the first lens group, the second lens group, the third lens group and the fourth lens group are spherical lenses.

8. The deep ultraviolet detection objective lens according to claim 7, characterized in that, All the spherical lenses are made of fused silica material applicable to the deep ultraviolet band.

9. The deep ultraviolet detection objective lens according to claim 8, characterized in that, The working wavelength of the deep ultraviolet detection objective lens is 266nm.

10. A wafer defect detection system, characterized in that, Including the deep ultraviolet detection objective lens according to any one of claims 1 to 9.

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