Electro-optical system and detector assembly
By adjusting the design of the aperture and detector components, the large-angle signal electron beam is selectively filtered, solving the problem of accuracy and precision in high aspect ratio sample detection in existing technologies, and realizing high-precision acquisition of microscopic information of complex samples.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- ANGSTROM PRECISION INSTRUMENTS CORP
- Filing Date
- 2025-04-27
- Publication Date
- 2026-06-09
AI Technical Summary
When probing samples with high aspect ratios, existing electro-optical systems cannot meet the requirements for accurate detection with a fixed-size inner detector, and there is crosstalk between the inner and outer detectors, which affects the accuracy and reliability of sample information.
An adjustable aperture and detector assembly is used. By adjusting the aperture area and the distance between the aperture and the detector, large-angle signal electron beams are selectively filtered, and only small-angle signal electron beams are retained for detection.
It enables precise detection of features with different aspect ratios, reduces noise and interference, and improves the accuracy and reliability of acquiring surface morphology and composition information of high aspect ratio samples.
Smart Images
Figure CN224342269U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electronic detection, and in particular to an electron optical system and detector assembly. Background Technology
[0002] Electron optics systems, as important microscopic analytical instruments, are widely used in many fields such as materials science, biology, and medicine. Their basic principle is to use an electron beam source to emit an electron beam. When the electron beam irradiates a sample, it excites secondary electrons and backscattered electrons. By detecting and analyzing these signal electrons, morphological and compositional information of the sample surface can be obtained.
[0003] Figure 1 A schematic diagram of an existing electro-optical system is shown. Figure 1 As shown, the electron optics system includes an electron beam source 1 for emitting an electron beam 4, which is focused onto the sample 3 through an objective lens 2, thereby generating a signal electron beam 5. The signal electron beam 5 is then deflected by a one-way filter 6 to an electron detection assembly 7 to acquire surface morphology and composition information of the sample 3. In practical applications, acquiring microscopic information for samples with high aspect ratios faces numerous challenges. This is because the signal electron emission angle at the bottom of high aspect ratio patterns is relatively small (see...). Figure 2 Precisely detecting these small-angle signal electrons is no easy task.
[0004] Existing technology employs a dual-detector design. This design includes an inner detector 71 and an outer detector 72 located around the inner detector 71. The inner detector 71 detects the small-angle electron beam 51, while the outer detector 72 detects the large-angle electron beam 52. However, this design has significant drawbacks. Firstly, the size of the inner detector 71 is fixed, limiting its applicability to patterns with a fixed aspect ratio. For patterns with varying aspect ratios, the fixed-size inner detector 71 clearly cannot meet the requirements for accurate detection. Secondly, crosstalk may exist between the inner detector 71 and the outer detector 72. This crosstalk can contaminate the detection quality of both channels, thereby affecting the accuracy and reliability of the final sample information obtained.
[0005] Given the limitations of existing technologies, there is an urgent need to invent an electron optical system capable of accurately detecting signal electrons at different angles, so as to effectively improve the detection accuracy of features with different aspect ratios and thus better meet the needs of acquiring surface morphology and composition information of high aspect ratio samples.
[0006] The statements herein provide only background information relating to this invention and do not necessarily constitute prior art. Utility Model Content
[0007] The purpose of this invention is to provide an electro-optical system capable of accurately detecting sample information with different aspect ratios.
[0008] To achieve the above objectives, this utility model provides a detector assembly for an electro-optical system, comprising:
[0009] A detector used to detect electron beams of signals;
[0010] An aperture is located on the side of the detector that receives the signal electron beam, and a through hole is provided in its center; an adjustment mechanism is provided, which can adjust the area of the through hole and / or adjust the distance between the aperture and the detector.
[0011] Optionally, the central axis of the detector is coaxial with the central axis of the aperture.
[0012] Optionally, the aperture includes a plurality of radially movable baffles, and the adjustment mechanism can drive the baffles to move radially to adjust the area of the through hole.
[0013] Optionally, the adjustment mechanism includes:
[0014] A movable component that is movable along the central axis of the aperture, the movable component being able to adjust the distance between the aperture and the detector.
[0015] Optionally, the adjustment mechanism includes a linear motor, the drive end of which is connected to the aperture to drive the aperture away from or towards the detector.
[0016] In addition, this utility model also proposes an electro-optical system, comprising:
[0017] An electron beam source emits a main electron beam along the main optical axis from the sample and generates a signal electron beam on the sample surface.
[0018] A beam splitter is coaxially arranged with the main optical axis and located between the electron beam source and the sample. The beam splitter is used to deflect the signal electron beam.
[0019] The detector assembly is used to detect the deflected signal electron beam.
[0020] Optionally, the deflected signal electron beam has a secondary optical axis, and the central axis of the aperture is coaxially arranged with the secondary optical axis.
[0021] Optionally, it also includes an objective lens located between the beam splitter and the sample.
[0022] Optionally, the beam splitter includes a Wien filter.
[0023] Optionally, the detector assembly is configured to: adjust the aperture area of the aperture according to the aspect ratio of the structure under test, or adjust the distance between the aperture and the detector.
[0024] This invention achieves precise detection of small-angle electron beams by selectively filtering large-angle electron beams, making it particularly suitable for samples with high aspect ratios. By adjusting the area of the aperture and the distance between the aperture and the detector, electron beam detection at different diffusion angles is achieved, satisfying the need for precise detection of samples with different aspect ratios and making it suitable for characterizing samples with complex morphologies. Attached Figure Description
[0025] Figure 1 This is a simplified schematic diagram of an electro-optical system in the prior art;
[0026] Figure 2 This is a schematic diagram of a signal electronic path with a specific aspect ratio.
[0027] Figure 3 A simplified schematic diagram of an electro-optical system provided by this utility model;
[0028] Figure 4 A front view of an aperture provided by this utility model;
[0029] Figure 5 A simplified schematic diagram of another electro-optical system provided by this utility model. Detailed Implementation
[0030] The following detailed description of the electro-optical system and detector assembly proposed in this utility model, in conjunction with the accompanying drawings and specific embodiments, will further illustrate the present invention. The advantages and features of this utility model will become clearer from the following description. It should be noted that the drawings are in a very simplified form and use non-precise proportions, intended only to facilitate and clearly illustrate the embodiments of this utility model. Please refer to the drawings to make the objectives, features, and advantages of this utility model more apparent and understandable. It should be understood that the structures, proportions, sizes, etc., depicted in the accompanying drawings are only for illustrative purposes to aid those skilled in the art and are not intended to limit the implementation conditions of this utility model. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to the size, without affecting the effects and objectives achieved by this utility model, should still fall within the scope of the technical content disclosed in this utility model.
[0031] The electro-optical system provided by this invention includes at least an electron beam source 1, a beam splitter 6, and a detector assembly. The electron beam source 1 emits a main electron beam 4 along the principal optical axis onto the sample 3, exciting the sample 3 to generate a signal electron beam 5. The beam splitter 6 is coaxially arranged with the principal optical axis, located between the electron beam source 1 and the sample 3, and is used to deflect the signal electron beam 5. The detector assembly is used to detect the deflected signal electron beam 5 and form an image based on the detected signal electrons. This detector assembly has the ability to shield large-angle signal electron beams, selectively shielding large-angle signal electron beams and retaining only small-angle signal electron beams. This design has significant advantages, greatly improving the detection accuracy and flexibility of signal electron beams at specific angles.
[0032] This invention is particularly suitable for the detection of samples with complex morphologies, especially those with high aspect ratios. When it is necessary to obtain information about samples with a certain depth, such as deep holes or grooves, the electron-optical system provided by this invention can shield large-angle signal electron beams, receiving only signal electron beams at specific small angles. This enhances the signal intensity of high aspect ratio features, reduces noise and interference, and thus obtains clearer and more accurate microscopic information about samples at specific depths. This invention improves the detector assembly, which is of great significance for high-precision microstructural analysis of high aspect ratio features, especially when studying complex samples, providing more reliable data support for related research.
[0033] The signal electron beam includes secondary electrons and backscattered electrons. The secondary electrons carry information about the sample surface morphology, while the backscattered electrons carry information about the sample composition. The deflected signal electron beam 5 has a secondary optical axis, which is offset from the primary optical axis by a certain angle, entering the detector assembly from the side of the primary optical axis. Therefore, the detector assembly is offset from the primary optical axis and positioned outside it. In this paper, the signal electron beam 5 needs to be deflected by a beam splitter 6 before entering the detector assembly. Since the electrons in the signal electron beam 5 have specific energy ranges—secondary electrons have lower energy, typically less than 50 eV, while backscattered electrons have higher energy, generally greater than 50 eV—the energy of the electrons in the primary electron beam is much greater than that of the signal electrons. The beam splitter 6 can control the trajectory of the signal electron beam by generating a cross electromagnetic field, utilizing the deflection characteristics of electrons with different energies in a magnetic field to reduce the entry of non-signal electrons into the detector assembly. After passing through the beam splitter 6, the secondary optical axis of the signal electron beam 5 is aligned with the center of the detector assembly to produce better detection accuracy.
[0034] Optionally, the beam splitter 6 includes a Wien filter.
[0035] In some embodiments, the electron optics system further includes an objective lens 2 located between the beam splitter 6 and the sample 3. The objective lens 2 can generate a magnetic field to focus the main electron beam 4 by Lorentz force.
[0036] Figure 3 and Figure 5 Simplified schematic diagrams of two electron optical systems provided by this invention are shown. Each electron optical system includes an electron beam source 1, an objective lens 2, a Wien filter 6, and a detector assembly. The electron beam 4 emitted from the electron beam source 1 is focused by the objective lens 2 and reaches the sample 3, exciting the sample 3 to generate signal electrons. For samples with flat surfaces, the diffusion angle of the signal electrons is relatively uniform and easily detected by the detector assembly. For sample surfaces with complex morphologies, the diffusion angle of the signal electrons is more dispersed; for example, different morphologies such as deep holes, deep grooves, and protrusions result in different diffusion angles. Therefore, based on this principle, signal electrons within a specific diffusion angle range can be detected to characterize samples with different morphologies.
[0037] For samples with high aspect ratios, the signal electron diffusion angle is relatively small. Samples with different aspect ratios also have different signal electron diffusion angles; therefore, the detection angle needs to be adjusted accordingly. For example... Figure 2 As shown, when the aspect ratio H / D of the sample increases, the angle α of the detected electron beam needs to be reduced accordingly in order to obtain clear information on the sample surface morphology and / or composition. This is mainly because in deep-hole samples with a high aspect ratio, the electrons at the bottom of the hole can only escape from the opening at a relatively small emission angle; electrons with angles greater than this will be blocked by the hole wall and cannot reach the top of the hole. Conversely, electrons emitted from a surface flush with the top of the hole have a very wide range of emission angles, including both large and small angles.
[0038] like Figure 3 and Figure 5 As shown, the large-angle signal electron beams 52 are located around the small-angle signal electron beams 51. These large-angle signal electron beams 52 mainly originate from non-deep aperture regions and are numerous. If the detector cannot effectively distinguish the angles, it will receive far more signal electrons from the surface than from the bottom of the deep aperture, resulting in a much weaker contrast at the bottom of the deep aperture compared to the surface, even appearing as a completely dark area in the image. Current technologies cannot achieve the detection of high aspect ratio features because they cannot solve the problem of the influence of large-angle signal electrons.
[0039] In some embodiments, please refer to Figure 3A simplified schematic diagram of an electro-optical system is shown. This electro-optical system includes the detection assembly. The detection assembly includes a detector 8, an aperture 9, and an adjustment mechanism 10a. The detector 8 is used to detect a signal electron beam; the aperture 9 is located on the side of the detector 8 that receives the signal electron beam, and is used to selectively allow the signal electron beam to pass through. See also... Figure 4 The diagram shows a front view of an aperture 9. The aperture 9 has a central through-hole 91 and includes multiple radially movable baffles 92. In this example, the number of baffles 92 can be selected as five. The adjustment mechanism 10a can drive each baffle 92 to move radially to adjust the area of the through-hole 91. Therefore, the movement of the baffles 92 can be controlled by the adjustment mechanism 10a to selectively shield large-angle signal electron beams. In some embodiments, the number of baffles 92 can be increased to make the through-hole 91 increasingly closer to a circle. In some embodiments, the baffles 92 can be aperture blades; by selecting arc-shaped aperture blades, a circular or near-circular through-hole 91 can be formed.
[0040] The adjustment mechanism 10a can adjust the area of the through-hole 91. For example, to obtain sample information with a higher aspect ratio, the adjustment mechanism 10a can move multiple baffles 92 inward to reduce the area of the through-hole 91, allowing only specific small-angle signal electron beams 51 to enter the detector 8, thereby improving the detection accuracy of the small-angle signal electron beam 51. Optionally, the adjustment mechanism 10a can be integrated with the aperture 9, for example, as an electrically adjustable aperture.
[0041] In other embodiments, please refer to Figure 5 A simplified schematic diagram of another electro-optical system is shown. The detection assembly includes a detector 8, an aperture 9, and an adjustment mechanism 10b, which can adjust the distance L between the aperture 9 and the detector 8. When the distance L is increased, more large-angle signal electron beams 52 can enter the detector 8; conversely, more large-angle signal electron beams 52 are blocked.
[0042] The adjustment mechanism 10b adjusts the distance L between the aperture 9 and the detector 8 to allow the desired small-angle signal electron beam 51 to enter the detector 8. Please continue reading. Figure 5In the figure, the aperture 9 is not equipped with an adjustment mechanism 10a for adjusting the area of the through hole; instead, it is equipped with an adjustment mechanism 10b for adjusting the distance L between the aperture 9 and the detector 8. For example, when a higher aspect ratio is required, the aperture 9 is driven closer to the detector 8 via the adjustment mechanism 10b, and conversely, the aperture 9 is driven away from the detector 8. By adjusting the distance L, the signal electron beam outside the required angle is shielded. In this example, the adjustment mechanism 10b includes a linear motor movable along the central axis of the detector 8. The drive end of the linear motor is connected to the aperture 9 to drive the aperture 9 away from or closer to the detector 8. The linear motor can be a linear piezoelectric motor, which has the characteristics of ultra-high precision, energy saving, and operation in a vacuum environment, and can meet the application scenarios of this utility model. Of course, the adjustment mechanisms in the above two embodiments can be used in combination, that is, an electrically adjustable aperture can be used to simultaneously adjust the area of the through hole of the aperture 9 and the distance L between the aperture 9 and the detector 8.
[0043] In the above embodiment, the Wien filter 6 is disposed on the side of the aperture 9 that receives the signal electron beam, and is used to filter out non-signal electrons in the signal electron beam and deflect the signal electrons to the detector 8.
[0044] When the large-angle signal electron beam 52 is shielded, the small-angle signal electrons at the bottom of the deep groove or hole, together with small-angle signal electrons at other positions (such as the top of the groove), form the small-angle signal electron beam 51. After the aperture 9 is adjusted to a suitable position or a suitable aperture area, the small-angle signal electrons at different positions reach the detector 8 in similar quantities, thus avoiding the problem of different contrast after imaging. During the adjustment of the aperture 9 aperture area, the clarity of the image formed by receiving electrical signals from the detector 8 can be used as a reference. If the image clarity improves during the reduction of the aperture area, it indicates that the aperture adjustment direction is correct and the aperture area needs to be further reduced; otherwise, the adjustment is reversed. During the adjustment process, an aperture area that can form a relatively clear image is found, and then the aperture area is further fine-tuned until an ideal image is formed. The process of adjusting the distance L is similar to the process of adjusting the area and will not be described in detail here. Compared with the existing technology of setting internal and external detectors, the scheme adopted in this paper is more targeted and less susceptible to interference from large-angle signal electron beams. Furthermore, since the angle range of the received signal electron beam is adjustable, it is suitable for samples with different aspect ratios.
[0045] In some embodiments, the central axis of the detector 8 is coaxial with the central axis of the aperture 9 to maintain symmetry between them. When the signal electron beam 5 reaches the detector 8 after passing through the aperture 9, if the detector 8 and the aperture 9 are coaxial, the symmetry of the signal electron beam 5 can be guaranteed, reducing aberrations. Furthermore, it enhances the consistency of the signal electron beam 5—coaxial arrangement helps ensure a more uniform distribution of signal electrons upon reaching the detector. If the axes are not aligned, signal electrons of the same intensity or angle may produce an uneven distribution on the detector 8, leading to image distortion.
[0046] This invention achieves precise detection of small-angle signal electron beams generated by high aspect ratio features by selectively filtering large-angle signal electron beams. By adjusting the area of the aperture and the distance between the aperture and the detector, precise detection of features with different aspect ratios can be achieved, making it suitable for characterizing samples with complex morphologies.
[0047] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.
[0048] In the description of this utility model, it should be understood that the terms "center," "height," "thickness," "upper," "lower," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential," etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings and are only for the convenience of describing this utility model 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 utility model. In the description of this utility model, unless otherwise stated, "a plurality of" means two or more.
[0049] In the description of this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.
[0050] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.
[0051] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims.
Claims
1. A detector assembly for an electro-optical system, characterized in that, include: A detector used to detect electron beams of signals; An aperture is located on the side of the detector that receives the signal electron beam, and a through hole is provided in its center; An adjustment mechanism is provided, which is capable of adjusting the area of the through hole and / or adjusting the distance between the aperture and the detector.
2. The detector assembly as claimed in claim 1, characterized in that, The central axis of the detector is coaxial with the central axis of the aperture.
3. The detector assembly as claimed in claim 1, characterized in that, The aperture includes multiple radially movable baffles, and the adjustment mechanism can drive the baffles to move radially to adjust the area of the through hole.
4. The detector assembly as claimed in claim 1, characterized in that, The adjustment mechanism includes: A movable component that is movable along the central axis of the aperture, the movable component being able to adjust the distance between the aperture and the detector.
5. The detector assembly as claimed in claim 1, characterized in that, The adjustment mechanism includes a linear motor, the drive end of which is connected to the aperture to drive the aperture away from or towards the detector.
6. An electro-optical system, characterized in that, include: An electron beam source emits a main electron beam along the main optical axis from the sample and generates a signal electron beam on the sample surface. A beam splitter is coaxially arranged with the main optical axis and located between the electron beam source and the sample. The beam splitter is used to deflect the signal electron beam. The detector assembly according to any one of claims 1-5 is used to detect the deflected signal electron beam.
7. The electro-optical system as described in claim 6, characterized in that, The deflected signal electron beam has a secondary optical axis, and the central axis of the aperture is coaxial with the secondary optical axis.
8. The electro-optical system as described in claim 6, characterized in that, Also includes: The objective lens is located between the beam splitter and the sample.
9. The electro-optical system as described in claim 6, characterized in that, The beam splitter includes a Wien filter.
10. The electro-optical system as claimed in claim 6, characterized in that, The detector assembly is configured to adjust the aperture area of the aperture according to the aspect ratio of the structure being measured, or to adjust the distance between the aperture and the detector.