A detection system
By setting a transmission surface on the lens element of a large numerical aperture lens, the problem of interference between the lens and the illumination optical path is solved, enabling the lens to operate normally and become lighter, and improving image quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- MATRIXTIME ROBOTICS (SHANGHAI) CO LTD
- Filing Date
- 2025-07-24
- Publication Date
- 2026-07-14
AI Technical Summary
Large numerical aperture lenses are prone to spatial interference with the illumination optical path under dark lighting conditions, which can lead to a decrease in image quality or abnormal equipment operation.
A pass-through surface is set on the lens of a large numerical aperture lens to ensure that the incident beam and the reflected beam can pass through without interference. The pass-through angle is greater than the incident angle of the incident beam, thus avoiding the propagation path of the dark field illumination light path.
Optical interference was eliminated, ensuring the proper functioning of the detection system and making the lens lighter and more compact.
Smart Images
Figure CN224500452U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of semiconductor front-end inspection technology, specifically a dark field inspection system. Background Technology
[0002] Large numerical aperture (NA) lenses, as key optical components in semiconductor processing and inspection equipment, play a crucial role in semiconductor devices such as lithography equipment, defect inspection equipment, and metrology equipment. Taking semiconductor defect inspection equipment as an example, NA lenses, through their unique high numerical aperture characteristics, can efficiently collect scattered light from submicron and even nanometer-scale defects, enabling the inspection system to achieve extremely high optical resolution and significantly improving the detection sensitivity for nanometer-scale defects on wafer surfaces.
[0003] In semiconductor testing equipment, large numerical aperture (NA) lenses, due to their short working distance, are prone to spatial interference between the lens structure edge and the illumination optical path under dark illumination conditions, leading to decreased image quality or abnormal equipment operation. Summary of the Invention
[0004] To address the aforementioned technical problems, this application provides a detection system that performs selective structural processing on a large NA lens, preserving its effective optical area while avoiding the propagation path of the dark field illumination light path, thereby eliminating optical interference and ensuring the normal operation of the detection system.
[0005] To achieve the above objectives, the technical solutions adopted in the embodiments of this application are as follows:
[0006] A detection system is provided, the system comprising: an incident light beam incident at an oblique angle to the object to be detected, forming a reflected light beam and a scattered light beam; a large numerical aperture lens disposed on the propagation path of the scattered light beam, and having a passing surface formed on the lens disposed on the incident light beam and the reflected light beam, the passing surface being a passing surface through which the incident light beam and the reflected light beam pass, the passing surface having an angle with the object to be detected being a passing angle, the passing angle being greater than or equal to the incident angle of the incident light beam.
[0007] In another feasible approach, a pass-through surface is provided on a first lens close to the object to be detected.
[0008] In another possible implementation, the circumferential angle of the through surface is greater than or equal to the projection of the incident beam object aperture angle onto the plane where the lens height is located.
[0009] In another possible implementation, the passing surface includes a first passing surface and a second passing surface arranged symmetrically for the incident beam and the reflected beam to pass through, respectively.
[0010] In another possible implementation, the centers of the first and second passing surfaces coincide with the location of the incident beam spot.
[0011] In another possible implementation, the through surface has an angle with the object to be detected.
[0012] In another possible implementation, the through-plane angle is determined by the incident angle of the incident beam and the outer diameter of the first lens.
[0013] In another possible implementation, the through surface is parallel to the cone angle of the incident beam.
[0014] In another possible implementation, the inclination angle of the through surface satisfies the following relationship: α≥θ=arcsin(D / 2d)+δ+0.5*θ c Where α is the angle of inclination of the lens, d is the distance from the first lens to the focal plane, and θ is the focal plane angle. c δ is the object square cone angle of the incident beam, δ is the set margin angle, and D is the outer diameter of the first lens.
[0015] In another possible implementation, the first lens includes an effective light-transmitting area and an edge area, the passing surface being disposed in the edge area; and the edge point of the passing surface does not exceed the boundary of the effective light-transmitting area.
[0016] The embodiments of the present invention bring the following beneficial effects:
[0017] In the technical solution provided in this application embodiment, by setting a through surface in the lens of the large numerical aperture lens, the incident beam and the reflected beam are not obstructed by the large numerical aperture lens, thereby eliminating optical interference to ensure the normal operation of the detection system. Furthermore, the setting of the through surface meets the requirements of optical imaging, avoids the limitation of the large numerical aperture lens due to the working distance, and makes the large numerical aperture lens lighter and more compact.
[0018] 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.
[0019] 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
[0020] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0021] The system shown in the accompanying drawings will be further described according to exemplary embodiments. These exemplary embodiments will be described in detail with reference to the drawings. These exemplary embodiments are non-limiting exemplary embodiments, wherein example figures represent similar mechanisms in the various views of the drawings.
[0022] Figure 1 This is a schematic diagram of the detection system structure;
[0023] Figure 2 A schematic diagram of the optical lens structure of a large numerical aperture lens;
[0024] Figure 3 This is a schematic diagram of the lens circumferential angle;
[0025] Figure 4 This is a schematic diagram of the lens tilt angle. Detailed Implementation
[0026] To better understand the above technical solutions, the technical solutions of this application will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the embodiments of this application and the specific features in the embodiments are detailed descriptions of the technical solutions of this application, rather than limitations on the technical solutions of this application. In the absence of conflict, the embodiments of this application and the technical features in the embodiments can be combined with each other.
[0027] In the detailed description below, numerous specific details are illustrated with examples to provide a comprehensive understanding of the relevant guidance. However, it will be apparent to those skilled in the art that this application can be practiced without these details. In other instances, well-known methods, procedures, systems, components, and / or circuits have been described at a relatively high level without detail to avoid unnecessarily obscuring aspects of this application.
[0028] This application uses flowcharts to illustrate the execution process performed by a system according to embodiments of this application. It should be clearly understood that the execution processes in the flowcharts may not be executed sequentially. Instead, these execution processes may be executed in reverse order or simultaneously. Additionally, at least one other execution process may be added to the flowchart. One or more execution processes may be deleted from the flowchart.
[0029] This application provides a dark field detection system for dark field detection. It detects the object by projecting a laser of a specific wavelength onto the surface of the object to be tested, forming a light spot. The object to be tested is a wafer. In this embodiment, "wafer" generally refers to a substrate formed of semiconductor or non-semiconductor materials. Examples include (but are not limited to) single-crystal silicon, gallium arsenide, gallium nitride, and indium phosphide. Such substrates are typically found and / or processed in semiconductor manufacturing facilities. In some cases, the wafer may contain only the substrate (i.e., a bare die). Alternatively, the wafer may contain one or more different material layers formed on the substrate. The one or more layers formed on the wafer may be "patterned" or "unpatterned." For example, the wafer may contain multiple dies with repeatable pattern features.
[0030] Dark-field laser scattering (DLS) is an effective detection method based on the principle of light scattering. Specifically, the device uses a high-precision laser beam to illuminate the wafer surface. When the laser encounters defects on the surface, it generates scattered light. These scattered light signals are collected and analyzed by a highly sensitive detector, thus accurately reflecting the distribution of nanoscale defects on the wafer surface.
[0031] Among them, large numerical aperture (NA) lenses, as important optical devices for dark-field laser scattering, can improve the signal-to-noise ratio, resolution, and detection sensitivity of the acquired scattering signals, becoming a key tool for identifying submicron-level defects. In existing semiconductor inspection scenarios, due to their short working distance, NA lenses are prone to spatial interference between the lens edge and the illumination optical path under dark illumination conditions, leading to decreased image quality or abnormal equipment operation.
[0032] To address the aforementioned technical problems, this application provides a detection system that, by configuring the pass angle of a large numerical aperture lens, ensures that the incident and reflected beams do not interfere with each other, thereby resolving the above-mentioned technical problems while ensuring that the large numerical aperture lens meets the configuration requirements of the detection system.
[0033] For details regarding this detection system, please refer to [link / reference]. Figure 1 As shown, the detection system 10 includes a light source that is tilted relative to the object to be detected 20 to generate an incident light beam 11. The incident light beam and the object to be detected have an incident angle. The incident light beam is reflected by the object to be detected to form a symmetrically arranged reflected light beam 12, and the reflection angle of the reflected light beam is the same as the incident angle.
[0034] In this embodiment, the object to be inspected is a wafer. The incident light beam is scattered on the wafer to form a scattered beam. In order to obtain the scattered beam, a large numerical aperture lens 13 is set in the propagation path of the scattered beam.
[0035] Specifically, a large numerical aperture lens consists of multiple lenses. To ensure that the incident and reflected beams are not interfered with by the large numerical aperture lens, and to ensure that the large numerical aperture lens can meet the requirements of the detection system for collecting scattered beams, structural modifications are necessary.
[0036] In this embodiment, the structural changes of the large numerical aperture lens are eliminated by cutting off the parts of the lens that could cause interference, thus removing the obstruction. After cutting, a through surface is formed for the large numerical aperture lens.
[0037] Since the incident and reflected beams are obliquely incident and obliquely exiting beams, the passing surface formed by the cut in this embodiment should have the same tilt characteristics and be parallel to the incident and reflected beams. That is, the passing surface should be a beveled surface, forming a passageway for the incident and reflected beams to pass through. This passing surface has an angle with the object being detected; this angle is the passing angle. To ensure the passage of the incident and reflected beams, the passing angle should be greater than or equal to the incident angle of the incident beam, allowing the large numerical aperture lens to avoid the propagation path of the dark field illumination light path.
[0038] See Figure 2 In this embodiment, the large numerical aperture lens comprises multiple lens elements. The purpose of the aforementioned through-surface 14 is to avoid the propagation paths of the incident and reflected beams, but the multiple lens elements are not entirely situated along these propagation paths. Therefore, the through-surface formation is only applied to lens elements located along the propagation paths corresponding to the incident and reflected beams. The lens arrangement is designed according to the optical requirements of the large numerical aperture lens, and will not be elaborated upon in this embodiment.
[0039] However, it is worth noting that, under normal circumstances, because dark field illumination is incident at a small angle, the angle between it and the normal of the wafer to be tested is relatively large, and the distance between multiple lenses in a large numerical aperture lens means that only the first lens will have interference with the incident beam and the reflected beam.
[0040] Therefore, in this embodiment, the formation of the through-surface is preferentially carried out on the first lens element in a large numerical aperture lens. Here, the first lens element refers to the lens element in the lens closest to the wafer to be inspected.
[0041] Furthermore, in this embodiment, the number of passing surfaces is adjusted based on the incident beam. For example, when there is only one incident beam and one corresponding reflected beam, the number of passing surfaces is two, opposite to the incident beam and the reflected beam. Since the incident beam and the reflected beam have a symmetrical optical relationship, the two passing surfaces are also symmetrically arranged. If the incident beam and the reflected beam are two beams in two different directions, the passing surfaces are also symmetrically arranged.
[0042] Furthermore, in this embodiment, the through surface is used to allow the incident and reflected light beams to pass through, thereby preventing the lens from obstructing the incident and reflected light beams. Therefore, this embodiment has specific geometric requirements for the through surface.
[0043] Specifically, in this embodiment, the circumferential angle of the through surface should be greater than or equal to the projection of the object-side aperture angle of the incident beam onto the horizontal plane where the lens height is located. For the geometric representation of the circumferential angle, please refer to 3. Figure 3 This is the geometric expression of the aperture angle on the corresponding lens under top-down conditions. The circumferential angle represents the area of the aperture surface in the circumferential direction. It can be understood that the reason for setting the circumferential angle of the aperture surface in this way is that if the aperture angle is smaller than the projection of the object-side aperture angle of the incident beam onto the plane where the lens height is located, the aperture angle of the aperture surface will be too small, potentially causing interference to the transmission of part of the incident beam through the aperture surface.
[0044] Furthermore, in this embodiment, both the incident beam and the reflected beam have passing surfaces. Therefore, the passing surfaces in this embodiment include a first passing surface and a second passing surface. The centers of the first and second passing surfaces coincide with the position of the light spot formed by the incident beam on the surface of the wafer to be tested, and the two are symmetrical.
[0045] The purpose of establishing the pass-through surface is to ensure that the NA value of the large numerical aperture lens remains constant. The location of the pass-through surface needs to be clearly defined in this embodiment. Specifically, the lens includes an effective light-passing area and an edge area. The effective light-passing area refers to the optical area through which the light beam passes, generally the central area of the lens. The edge area refers to the area surrounding the effective light-passing area, which is the non-imaging area. Therefore, in this embodiment, to avoid affecting the effective light transmission of the large numerical aperture lens, the pass-through surface is located in the edge area, and the edge point of the pass-through surface does not exceed the boundary of the effective light-passing area. This ensures that the NA value is not interfered with by the establishment of the pass-through surface, and that the NA value of the central imaging optical path remains constant.
[0046] Furthermore, the outline of the through surface in this embodiment should strictly follow the light propagation path, and its through surface should be parallel to the front cone angle of the incident beam.
[0047] In summary, the setting of the pass-through surface in the detection system of this embodiment is not based on manual experience, but should be subject to strict constraints. Therefore, to ensure that the obtained pass-through surface meets the optical requirements of the detection system, this embodiment also provides a constraint condition for the key parameters of the pass-through surface, based on the following formula: α≥θ=arcsin(D / 2d)+δ+0.5*θ c Where α is the tilt angle of the lens, d is the distance from the first lens to the focal plane, and θ is... c Let δ be the object square cone angle of the incident beam, δ be the margin angle, and D be the outer diameter of the first mirror. For the geometric representation of the object square cone angle of the incident beam, please refer again to [link to relevant documentation]. Figure 1 As shown.
[0048] The through-face tilt angle refers to the angle between the through-face and the surface of the wafer to be inspected. It characterizes the degree of opening angle of the through-face and is a key parameter. For more information on the through-face tilt angle, please refer to [link to relevant documentation]. Figure 4 As shown. The allowance angle is set to provide redundancy for the surface settings, avoiding the influence of inherent biases in certain values of the system on the results. The value of the allowance angle can be obtained using statistical methods such as linear regression, which will not be elaborated upon in this embodiment. Furthermore, the allowance angle in this embodiment ranges from 3° to 5°.
[0049] The detection system provided in this application eliminates optical interference by setting a through surface in the lens of a large numerical aperture lens, ensuring that the incident beam and reflected beam are unobstructed by the large numerical aperture lens, thereby ensuring the normal operation of the detection system. Furthermore, the setting of the through surface meets the requirements of optical imaging, avoids the limitation of the large numerical aperture lens due to the working distance, and makes the large numerical aperture lens lighter and more compact.
[0050] 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.
[0051] 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 therein. Such 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 detection system, characterized in that The system comprises: An incident light beam, which is incident at an oblique angle to the object to be detected and forms a reflected light beam and a scattered light beam; A large numerical aperture lens, which is arranged on the propagation path of the scattered light beam and has a through surface on the lens arranged on the incident light beam and the reflected light beam, the through surface being a through surface for the incident light beam and the reflected light beam, the through surface having an included angle with the object to be detected, the included angle being greater than or equal to the incident angle of the incident light beam.
2. The detection system of claim 1, wherein, The first lens has a through surface near the object to be detected.
3. The detection system according to claim 1 or 2, characterized in that The circumferential angle of the through surface is greater than or equal to the projection of the object-side aperture angle of the incident light beam on the plane in which the lens height is located.
4. The detection system of claim 1 or 2, wherein, The through surface comprises a first through surface and a second through surface arranged symmetrically, which are respectively used for the incident light beam and the reflected light beam.
5. The detection system of claim 4, wherein, The centers of the first through surface and the second through surface coincide with the position of the incident light beam spot.
6. The detection system of claim 1 or 2, wherein, The through surface has an oblique angle with the object to be detected.
7. The detection system of claim 6, wherein, The oblique angle is determined by the incident angle of the incident light beam and the outer diameter of the lens.
8. The detection system of claim 1 or 2, wherein, The through surface is parallel to the cone angle of the incident light beam.
9. The detection system of claim 7, wherein, The inclination angle of the passing surface satisfies the following relationship: a > q = arcsin(D / 2d) + d + 0.5*q c ; wherein a is the inclination angle of the passing surface, d is the distance from the first lens to the focal plane, q c is the object-side cone angle of the incident light beam, d is the setting allowance angle, and D is the outer diameter of the first lens.
10. The detection system of claim 2, wherein, The first lens comprises an effective light passing region and an edge region, the through surface is arranged in the edge region, and the edge point of the through surface does not exceed the boundary of the effective light passing region.