Illuminating system
By employing a multi-source coupled Kohler illumination system in semiconductor inspection, the problem of insufficient brightness in small areas by single-source illumination systems has been solved, achieving high brightness and high uniformity illumination, improving inspection accuracy and speed, and reducing production costs.
Patent Information
- Application Number
- CN202423103442.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-16
- Publication Date
- 2025-10-31
- Estimated Expiration
- 2034-12-16
AI Technical Summary
In existing semiconductor defect detection, single-wavelength, large-spot illumination systems cannot meet the high brightness and high uniformity detection requirements of nanometer-scale defects, especially in achieving efficient defect detection in tiny areas.
An illumination system using at least two independent light sources coupled together forms a Kohler illumination system through a double telecentric lens group, a beam splitter, and an objective lens. This system creates multiple parallel, elongated light spots on the object surface. Combined with a polarization control module and a pupil control module, it achieves high-brightness and high-uniformity illumination.
It improves the illumination brightness of small areas, enhances the accuracy and speed of defect detection, reduces production costs, and eliminates blurred edges caused by diffuse reflection, thereby improving detection accuracy.
Smart Images
Figure CN223499445U_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of optical detection technology, and in particular to an illumination system. Background Technology
[0002] In the semiconductor field, chip manufacturing involves thousands of processes. As wafer fabrication dimensions shrink to 7nm and 5nm, wafer inspection for monitoring processes, reducing yield losses, and improving efficiency becomes increasingly important. Therefore, nanometer-scale defect detection is crucial for the entire chip manufacturing process. Nanometer-scale defect detection often requires high-brightness, high-uniformity illumination within tiny areas. Furthermore, since different types of defects have varying sensitivities to different wavelengths of illumination, using multi-wavelength illumination can yield more accurate results. However, most semiconductor defect detection systems use single-wavelength, large-spot lighting, which cannot meet the demands of defect detection. Summary of the Invention
[0003] In view of this, the purpose of the present invention is to provide an illumination system that can not only achieve highly uniform illumination on an object surface, but also couple two or more light sources to achieve a large field of view and high brightness illumination in a small area on the object surface.
[0004] Specifically, embodiments of the present invention provide an illumination system, including: a light source assembly comprising at least two independent light sources for generating at least two parallel independent incident beams, wherein the at least two incident beams are coupled at a field stop; the at least two incident beams are projected onto an object surface via a double telecentric lens group, a beam splitter, and an objective lens to form a Köhler illumination system, and at least two elongated light spots corresponding to the at least two independent incident beams are formed on the object surface in a parallel distribution.
[0005] In some specific implementations, the light source assembly includes two non-co-directional first light source and second light source, which respectively generate a first incident beam and a second incident beam.
[0006] In some specific implementations, the first light source is positioned facing forward relative to the double telecardioscope group, while the second light source is positioned non-facing relative to the double telecardioscope group. The second light source uses a reflector to change the propagation path of the second incident beam, so that the second incident beam is incident forward onto the double telecardioscope group.
[0007] In some specific implementations, the first light source and the second light source are not forward-facing relative to the dual telecardioscope group. The first incident beam and the second incident beam undergo optical path changes through the first reflector and the second reflector, respectively, so that the first incident beam and the second incident beam are forward-facing into the dual telecardioscope group.
[0008] In some specific implementations, the light source assembly further includes at least two telecentric mirror groups arranged relative to at least two of the independent light sources.
[0009] In some specific implementations, a collimation module, a microlens array, and a filter module are also provided along the optical axis between the independent light source and the dual telecentric lens group of the light source.
[0010] In some specific implementations, the filtering module includes a neutral density filter and a bandpass filter, used to simultaneously control the light intensity and wavelength range of at least two independent incident beams.
[0011] In some specific implementations, a polarization control module and a pupil control module are arranged along the optical axis between the dual telecentric lens group and the beam splitter. The polarization control module is used to control the polarization state of at least two independent incident beams, and the pupil control module is used to control the convergence of at least two independent incident beams at the entrance pupil position of the objective lens.
[0012] In some specific implementations, the polarization control module includes a polarizer, an analyzer, a quarter-wave plate, and a half-wave plate that can be switched on the optical axis.
[0013] In some specific implementations, the independent light source is a point light source, including any one of LED light sources, laser light sources, mercury lamps, and xenon lamps.
[0014] The embodiments of the present invention bring the following beneficial effects:
[0015] This invention provides an illumination system that, by employing an illumination structure with at least two coupled light sources, solves the problem of insufficient illumination in small areas. It can be used simultaneously with multiple line scan cameras, improving detection speed and adapting to specific high-speed inspection scenarios, and is easily implemented. The entire illumination system has a modular structure, reducing the number of lenses and lowering production costs. The dual-telecentric Kohler illumination not only achieves high brightness and high uniformity illumination but also eliminates blurred edges caused by diffuse reflection. Furthermore, the field of view and the angle of incident light can be controlled through the field stop and pupil control modules, thereby improving the accuracy of defect detection.
[0016] Other features and advantages of this disclosure will be set forth in the following description, or some features and advantages may be inferred from the description or determined without doubt, or may be learned by practicing the techniques described above.
[0017] To make the above-mentioned objects, features and advantages of this disclosure more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description
[0018] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0019] Figure 1 This is a schematic diagram of the lighting system provided in Embodiment 1 of the present invention;
[0020] Figure 2 This is a schematic diagram of the forming spot distribution provided in an embodiment of the present invention;
[0021] Figure 3 This is a schematic diagram of the lighting system provided in Embodiment 2 of the present invention;
[0022] Figure 4 This is a schematic diagram of the lighting system provided in Embodiment 3 of the present invention;
[0023] Figure 5 This is a schematic diagram of the structure of the beam splitter provided in Embodiment 3 of the present invention;
[0024] Figure 6 This is a schematic diagram of the lighting system provided in Embodiment 4 of the present invention.
[0025] Icons: 10 - Lighting system; 20 - Object surface;
[0026] 110 - First light source; 120 - Second light source; 130 - Field stop; 140 - Dual telecentric module; 150 - Polarization control module; 160 - Pupil control module; 170 - Beam splitter; 180 - Objective lens;
[0027] 111-First collimation module; 112-First microlens array; 113-First filter module; 114-First light source dual telecentric lens group; 121-Second collimation module; 122-Second microlens array; 123-Second filter module; 124-Second light source dual telecentric lens group;
[0028] 101-Reflector; 102-Functional beam splitter; 103-First reflector; 104-Second reflector; 1021-Reflective film; 1022-Transmission film. Detailed Implementation
[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0030] The lighting device and imaging system provided in this application are applied to automated optical inspection of semiconductors, where the semiconductor products are wafer products, including patterned wafers and unpatterned wafers. In other embodiments, they can also be applied to other precision component products. By projecting an illumination beam onto the surface of the above products, surface images of the products are acquired, and the images are analyzed to determine whether the surface of the products has visible defects, damage, or other undesirable features. These defects include, but are not limited to, scratches, stains, cracks, or other irregular shapes. By performing visual defect inspection, problems that may lead to equipment malfunction or performance degradation can be detected and eliminated early, thereby ensuring the quality and reliability of the final product.
[0031] The illumination optical path is a crucial component of an optical system, and its illumination quality directly affects the performance of the entire optical system. Common illumination systems typically use xenon lamps or LED bulbs for direct illumination, or use condenser lenses to focus the light beam for direct illumination.
[0032] Currently, common optical lighting systems include: critical lighting and Kohler lighting.
[0033] Critical illumination refers to direct illumination of an object's surface by converging the light source. While this method can achieve maximum illumination brightness on the object's surface, it also causes the image of the light source to overlap with the object's surface, making it difficult to achieve a high degree of uniformity in the entire field of view.
[0034] Kohler illumination refers to an illumination method where the light source of the illumination system is imaged on the entrance pupil of the objective lens. This method effectively improves the disadvantage of uneven critical illumination brightness. The light source is imaged by the condenser lens at the aperture stop of the condenser lens, and the condenser lens then forms a second image of this image at the back focal point. In this way, no image of the light source is formed on the object surface, eliminating the influence of the light source image on the object surface detection. Furthermore, because each point of the light source acts uniformly on the entire object surface, the illumination of the field of view becomes more uniform.
[0035] This application provides a wide-band, highly uniform illumination optical path system. As an illumination system, it can not only achieve highly uniform illumination on the object surface, but also couple multiple light sources to achieve a large field of view and high brightness illumination in a small area on the object surface.
[0036] Specifically, this illumination system includes at least two independent light sources for generating at least two parallel independent incident beams, which are coupled at a field stop. The at least two independent incident beams are projected onto an object surface via a double telecentric lens group, a beam splitter, and an objective lens to form a Kohler illumination system, resulting in at least two elongated light spots on the object surface that are parallel to the at least two independent incident beams.
[0037] In this embodiment, the two independent light sources can be point light sources, including any one of LED light sources, laser light sources, mercury lamps, and xenon lamps.
[0038] This embodiment utilizes a multi-source lighting method, particularly a two-source lighting method, to address the issue of insufficient illumination in small areas. Furthermore, its use with multiple line-scan cameras enhances detection efficiency and adapts to specific rapid detection scenarios. Moreover, dual-telecentric Kohler illumination not only achieves high brightness and uniformity but also eliminates blurred edges caused by diffuse reflection. Additionally, the field of view and the angle of the incident light can be controlled via a field stop, thereby improving the accuracy of defect detection.
[0039] The light source assembly is also equipped with at least two telecentric lens groups relative to at least two independent light sources, that is, the incident beam generated by each independent light source enters the field stop after passing through the corresponding telecentric lens group.
[0040] In this embodiment, in order to achieve optical correction and optical control for at least two incident beams, a collimation module, a microlens array and a filter module are also provided along the optical axis between the independent light source and the light source dual telecentric mirror group.
[0041] The collimation module consists of multiple lenses used to correct spherical aberration and chromatic aberration. The optical lens combination can be implemented using existing lens combinations, which will not be elaborated in this embodiment.
[0042] The filter module includes a neutral density filter and a bandpass filter, which can simultaneously control the light intensity and wavelength range of at least two independent incident beams, and can be achieved by using relevant optical lenses in the existing technology.
[0043] In this embodiment, a polarization control module and a pupil control module are also provided along the optical axis between the dual telecentric lens assembly and the beam splitter. The polarization control module controls the polarization state of at least two independent incident beams, and the pupil control module controls the convergence of the two independent incident beams at the entrance pupil position of the objective lens.
[0044] The polarization control module includes a polarizer, analyzer, quarter-wave plate, and half-wave plate, all of which can be switched on the optical axis. These different types of polarization optical devices enable the control of linear, elliptical, and circular polarization states.
[0045] The above content is an overall description of the lighting system in this embodiment. This lighting system includes multiple implementations depending on the different configurations of the independent light sources and the different configurations of the incident beam. Please refer to the following embodiments for different implementations.
[0046] Example 1
[0047] See Figure 1 In this embodiment, the light source assembly includes two independent light sources, namely a first light source 110 and a second light source 120. The two independent light sources are arranged in parallel and are positively aligned with the dual telecentric lens group 140. The two independent light sources generate corresponding parallel first and second incident beams. The light source assembly also includes a first collimation module 111, a first microlens array 112, a first filter module 113, and a first light source dual telecentric lens group 114 along the optical axis of the first incident beam. The first incident beam undergoes spherical aberration and chromatic aberration correction by the first collimation module, homogenization by the first microlens array, and illumination intensity and wavelength range adjustment by the first filter module before entering the field stop through the first light source dual telecentric lens group. It also includes a second collimation module 121, a second microlens array 122, a second filter module 123, and a second light source dual telecentric lens group 124 along the optical axis of the second incident beam. The second incident beam is corrected for spherical aberration and chromatic aberration by the second collimation module, homogenized by the second microlens array, and then enters the field stop 130 through the second light source dual telecentric lens group 124 after the illumination light intensity and wavelength range are adjusted by the second filter module.
[0048] Among them, the first incident beam and the second incident beam are coupled relative to the field aperture and enter the double telecardioscope group 140.
[0049] After passing through the dual telecentric lens assembly, the first and second incident beams enter the polarization control module 150 and the pupil control module 160, respectively. The polarization control module 150 controls the polarization state of the first and second incident beams, while the pupil control module controls the first and second incident beams to converge at the entrance pupil position of the objective lens 180 via the beam splitter 170, ultimately illuminating the object plane 20. (See reference...) Figure 2 The first incident beam and the second incident beam appear as a first and second elongated light spot that are parallel to each other and highly uniform on the object surface.
[0050] Example 2
[0051] In Embodiment 1, the first and second light sources, being positioned in the same direction, cause structural congestion and interference. To address this interference, Embodiment 2 resolves the structural congestion problem by setting the first and second light sources in opposite directions.
[0052] For details regarding the structure of the lighting system in this embodiment, please refer to [link / reference needed]. Figure 3 Specifically, the first light source in this embodiment is positioned the same as the light source in Embodiment 1, meaning the first incident beam generated by the first light source is positioned relative to the dual telecentric lens group. The second light source is positioned perpendicular to the first incident light source, generating a second incident beam with an initial direction perpendicular to the dual telecentric lens group. However, unlike Embodiment 1, to couple the second incident beam with the first incident beam at the field stop, unlike Embodiment 1, after the second incident beam passes through the second collimating module, the second microlens array, the second filtering module, and the second dual telecentric lens group, an optical device is needed along the light propagation path to change the propagation direction of the second incident beam.
[0053] Specifically, a reflector 101 is also provided on the propagation path of the second incident beam to change the propagation direction of the second incident beam. The reflector changes the second incident beam from its initial perpendicular incidence relative to the double telecentric lens group to normal incidence. After the propagation path change, the second incident beam is parallel to the first incident beam, couples at the field stop, and enters the double telecentric lens group.
[0054] As in Example 1, the first and second incident beams after entering the dual telecentric lens group enter the polarization control module and the pupil control module, respectively. The polarization control module controls the polarization state of the first and second incident beams, and the pupil control module controls the first and second incident beams so that the two beams are converged at the entrance pupil position of the objective lens through the beam splitter, and finally illuminate the object surface through the objective lens.
[0055] Example 3
[0056] Regarding Embodiment 2, an embodiment that achieves the same effect is also provided. For details, please refer to... Figure 4 In this embodiment, to change the propagation direction of the second incident beam and maintain the propagation direction of the first incident beam, a functional beam splitter 102 is provided on the propagation paths of the first and second incident beams. A reflective film 1021 is provided on the side of this beam splitter facing the second incident beam, and a transmission film 1022 is provided on the side facing the first incident beam. The reflective film allows the propagation direction of the second incident beam to change, while the transmission film maintains the propagation direction of the first incident beam, thereby coupling the first and second incident beams at the field stop 130 and allowing them to enter the dual telecentric lens group 140. For details on the structure of this beam splitter, please refer to [reference needed]. Figure 5 As shown.
[0057] Example 4
[0058] This embodiment differs from the previous embodiment in that the directions of the first and second incident beams are also perpendicular to the dual telecardioscope group. For details on how the first and second incident beams enter the field stop 130 in a forward direction and couple, please refer to [link to relevant documentation]. Figure 6 In this embodiment, a first reflector 103 and a second reflector 104 are respectively provided on the propagation paths of the first incident beam and the second incident beam. The first reflector 103 is used to change the propagation direction of the first incident beam to enter the field stop in a positive direction, and the second reflector 104 is used to change the propagation direction of the second incident beam to enter the field stop in a positive direction. The first incident beam and the second incident beam are coupled at the field stop and enter the double telecentric lens group 140.
[0059] Regarding the lighting system structures corresponding to the above-mentioned various embodiments, based on the requirement of compact structure, Embodiment 3 is preferentially selected as the optimal embodiment in this application.
[0060] The illumination system provided in this application embodiment can separate the image of the light source from the object through a dual telecentric Kohler illumination optical path, thereby improving image quality and increasing the energy utilization rate of the light source. Furthermore, the dual telecentric optical path can eliminate blurred edges and simultaneously increase light intensity, resulting in a high-contrast image. By employing a dual-light-source coupling method, the problem of insufficient illumination brightness of a single light source in a small area can be solved. At the same time, the dual-spot illumination method on the object surface, used in conjunction with multiple line scan cameras, can further improve the detection rate of the optical system.
[0061] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the invention and for 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. Therefore, they should not be construed as limitations on the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.
[0062] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.
Claims
1. A lighting system, characterized in that, include: A light source assembly includes at least two independent light sources for generating at least two independent incident beams that are parallel to each other, and the at least two incident beams are coupled at a field stop. At least two incident beams are projected onto the object surface via a double telecentric lens group, a beam splitter, and an objective lens to form a Köhler illumination system, and at least two elongated light spots corresponding to the at least two independent incident beams are formed on the object surface in a parallel distribution.
2. The lighting system according to claim 1, characterized in that, The light source assembly includes two non-co-directional first light source and second light source, which respectively generate a first incident beam and a second incident beam.
3. The lighting system according to claim 2, characterized in that, The first light source is positioned facing forward relative to the double telecardioscope group, while the second light source is positioned not facing forward relative to the double telecardioscope group. The second light source changes the propagation path of the second incident beam through a reflector, so that the second incident beam is incident forward onto the double telecardioscope group.
4. The lighting system according to claim 2, characterized in that, The first light source and the second light source are not oriented forward relative to the double telecardioscope group. The first incident beam and the second incident beam undergo optical path changes through the first reflector and the second reflector, respectively, so that the first incident beam and the second incident beam are incident forward onto the double telecardioscope group.
5. The lighting system according to any one of claims 1-4, characterized in that, The light source assembly also includes at least two telecardiogram groups arranged relative to at least two independent light sources.
6. The lighting system according to claim 5, characterized in that, A collimation module, a microlens array, and a filter module are also provided along the optical axis between the independent light source and the dual telecentric lens group of the light source.
7. The lighting system according to claim 6, characterized in that, The filtering module includes a neutral density filter and a bandpass filter, which are used to simultaneously control the light intensity and wavelength range of at least two independent incident beams.
8. The lighting system according to claim 1, characterized in that, A polarization control module and a pupil control module are arranged along the optical axis between the dual telecentric lens group and the beam splitter. The polarization control module is used to control the polarization state of at least two independent incident beams, and the pupil control module is used to control the convergence of at least two independent incident beams at the entrance pupil position of the objective lens.
9. The lighting system according to claim 8, characterized in that, The polarization control module includes a polarizer, an analyzer, a quarter-wave plate, and a half-wave plate, all of which can be configured to be switched on the optical axis.
10. The lighting system according to claim 1, characterized in that, The independent light source is a point light source, including any one of LED light sources, laser light sources, mercury lamps, and xenon lamps.