A multi-view backscattered electron imaging device and method for a low-voltage scanning electron microscope

Abstract

This invention belongs to the field of scanning electron microscopy and discloses a multi-view backscattered electron imaging device and method for low-voltage scanning electron microscopy. It employs a design where a ring-shaped microchannel plate is placed between the objective lens and the sample, aligned with the optical axis. A central through-hole allows the primary electron beam to pass through. The input surface faces the sample, and the output surface is close to the readout anode unit. The readout anode unit is divided into multiple concentric rings to distinguish polar angle signals, and each ring is further uniformly divided into multiple independent fan-shaped surfaces to capture azimuth information. This device significantly improves the signal-to-noise ratio and image quality of low-voltage imaging. It is compatible with large, flat samples without requiring sample tilting, avoiding the geometric defects of traditional side-mounted detectors. Multi-view signal separation provides rich angular information, enhances image stereoscopicity and shadow effects, supports simple 3D reconstruction to infer surface morphology features, and reduces information waste, meeting the high-precision analysis needs of surface-sensitive materials and non-conductive samples.

Description

Technical Field

[0001] This invention belongs to the field of scanning electron microscopy technology, and particularly relates to a multi-view backscattered electron imaging device and method for a low-voltage scanning electron microscope. Background Technology

[0002] Scanning electron microscopy (SEM), an indispensable surface analysis tool in modern scientific research and industry, is widely used in materials characterization due to its advantages such as high resolution, large depth of field, and ability to be coupled with various analytical accessories to achieve functions like micro-area composition analysis and grain orientation analysis. Among these, low-voltage imaging technology (incident electron energy typically below 5 keV) has become an important direction for the analysis of surface-sensitive materials and non-conductive samples because it can protect heat-sensitive or insulating samples (such as biological tissues and synthetic fibers) from damage by high-energy electron beams and allows direct observation of samples without conductive treatment. Microchannel plates (MCPs), as two-dimensional array electron multipliers with advantages of high gain, fast response, and low noise, can effectively compensate for the defects of low signal-to-noise ratio and blurred imaging under low beam current conditions. Related studies have confirmed their feasibility as SEM electron detectors, and by dividing them into concentric circle arrays, grain orientation contrast can be obtained, providing an important foundation for the optimization of low-voltage SEM imaging technology.

[0003] Currently, existing low-voltage SEM imaging technology and related detectors have many shortcomings: traditional SEM is prone to problems such as low beam current and low signal-to-noise ratio under low voltage conditions, and long exposure can lead to image degradation due to disturbances such as stray magnetic fields and irregular vibrations in the external environment; the mainstream Everhart-Thornley detector has geometric defects due to its side-mounted configuration, which requires tilting the sample and makes it unable to accommodate large, flat samples, and the long transmission path of the low-energy electron beam is susceptible to interference from stray electromagnetic fields. At the same time, it can only provide information from a single viewpoint and cannot infer information such as surface normal and slope through comparison of multi-view images to achieve simple 3D reconstruction; when the MCP is used as a whole detector, the omnidirectional collection of signal electrons results in no shadow effect in the imaging, lack of angular information, and weak 3D stereoscopic effect ("flattening"); even if the MCP is divided into concentric ring collectors, although the polar angle dimension information can be separated to obtain grain orientation contrast, the azimuth dimension information still overlaps with each other, which cannot effectively improve the stereoscopic effect of the image and still has the problem of information waste.

[0004] It is evident that existing low-voltage scanning electron microscopy imaging technologies cannot simultaneously meet the sample protection requirements of low-voltage imaging while also taking into account the needs for imaging signal-to-noise ratio, imaging quality, image stereoscopicity, and multi-view information acquisition to achieve simple three-dimensional reconstruction. This limits their application in scenarios involving the fine morphology analysis of surface-sensitive materials and non-conductive samples. Summary of the Invention

[0005] This invention provides a multi-view backscattered electron imaging device and method for low-voltage scanning electron microscopes. Using this device, the requirements for sample protection in low-voltage imaging can be met simultaneously with the requirements for imaging signal-to-noise ratio, imaging quality, image stereoscopic effect, and acquisition of multi-view information to achieve simple three-dimensional reconstruction. This promotes the application of low-voltage SEM imaging technology in the fine morphology analysis of surface-sensitive materials and non-conductive samples.

[0006] To achieve the above objectives, the present invention employs the following technical content:

[0007] A multi-view backscattered electron imaging device for a low-voltage scanning electron microscope includes: an annular microchannel plate;

[0008] The annular microchannel plate is positioned between the objective lens and the sample of the low-voltage scanning electron microscope and is aligned with the optical axis.

[0009] The annular microchannel plate has a through hole at its center, through which the primary electron beam passes.

[0010] The input surface of the annular microchannel plate is oriented towards the sample.

[0011] A readout anode unit is attached to the output surface of the annular microchannel plate; the readout anode unit is used to receive the amplified backscattered electron signal output by the annular microchannel plate; the amplified backscattered electron signal is obtained by amplifying the backscattered electron signal emitted from the sample surface through the annular microchannel plate.

[0012] The readout anode unit is divided into multiple concentric rings along the polar angle direction of the annular microchannel plate. The concentric rings are used to collect amplified backscattered electron signals emitted within a preset polar angle range.

[0013] Each concentric ring is uniformly divided into multiple independent sector surfaces along the diameter of the annular microchannel plate. These independent sector surfaces are used to collect amplified backscattered electron signals emitted within a preset azimuth angle.

[0014] Furthermore, it also includes an image acquisition unit;

[0015] The image acquisition unit is connected to the output terminal of the readout anode unit and is used to receive the amplified backscattered electron signal generated by the readout anode unit and form multiple multi-view sub-images based on the amplified backscattered electron signal; wherein, each multi-view sub-image represents the intensity of the backscattered electron signal emitted from the sample surface to the corresponding solid angle at the scanning position.

[0016] Furthermore, it also includes an image synthesis unit;

[0017] The image synthesis unit is connected to the output of the image acquisition unit and is used to restore multiple multi-view sub-images into the true three-dimensional shape of the sample.

[0018] Furthermore, it also includes a mode switching unit;

[0019] The mode switching unit is connected to the image synthesis unit and is used to switch the image synthesis unit between multiple modes, including multi-view imaging mode, crystallographic contrast mode, and full microchannel plate imaging mode.

[0020] Furthermore, in the multi-view imaging mode, the image acquisition unit is used to perform multi-view imaging with a fixed viewing angle based on the response intensity differences of the partitioned microchannel plates to form multiple multi-view sub-images; the image synthesis unit is used to compare the response intensity of each partitioned microchannel plate to the same scanning point, obtain the surface tilt angle information of this scanning point according to the comparison result of the response intensity, and generate a tilt gradient map of the scanning area; based on the tilt gradient map, the true three-dimensional morphology of the sample is reconstructed by the integral method or the least squares optimization method.

[0021] The image synthesis unit is also used to sum the amplified backscattered electronic signals within the same sector to improve the signal-to-noise ratio of the multi-view sub-image.

[0022] Furthermore, in the crystallographic contrast mode, the image synthesis unit is used for:

[0023] The amplified backscattered electron signals of all located in the same concentric ring are summed to obtain the omnidirectional backscattered image at the corresponding polar angle.

[0024] Grain orientation contrast is obtained by comparing omnidirectional backscattered images at different polar angles.

[0025] Furthermore, in the full microchannel plate imaging mode, the image synthesis unit is used for:

[0026] All the received amplified backscattered electronic signals are summed in real time to obtain the full microchannel plate imaging result. The full microchannel plate imaging result is used to improve the image signal-to-noise ratio and is used as a background signal to correct the multi-view sub-image.

[0027] A multi-view backscattered electron imaging method for a low-voltage scanning electron microscope, implemented based on the aforementioned multi-view backscattered electron imaging device for the low-voltage scanning electron microscope, includes:

[0028] Place the annular microchannel plate between the objective lens and the sample of the low-voltage scanning electron microscope, and align it with the optical axis;

[0029] A primary electron beam is emitted to the sample surface through a through-hole in the center of the annular microchannel plate.

[0030] The amplified backscattered electron signal emitted within a preset polar angle range is collected by multiple concentric rings of the readout anode unit, and the amplified backscattered electron signal emitted within a preset azimuth angle is collected synchronously by independent fan-shaped surfaces.

[0031] Furthermore, after collecting the amplified backscattered electron signal emitted within a preset polar angle range by multiple concentric rings of the readout anode unit, and synchronously collecting the amplified backscattered electron signal emitted within a preset azimuth angle by independent fan-shaped surfaces, the process also includes:

[0032] The image acquisition unit receives the amplified backscattered electron signal generated by the anode unit and forms multiple sub-images from multiple perspectives based on the electrical signal.

[0033] The image synthesis unit restores the true three-dimensional shape of the sample from multiple sub-images from multiple perspectives, so as to output the imaging results from any perspective.

[0034] Furthermore, after collecting backscattered electron signals emitted within a preset polar angle range by multiple concentric rings of the readout anode unit, and synchronously collecting backscattered electron signals emitted within a preset azimuth angle by independent sector surfaces, the method further includes:

[0035] The image synthesis unit switches between multiple modes—multi-view imaging mode, crystallographic contrast mode, and full microchannel plate imaging mode—through a mode switching unit.

[0036] In the multi-view imaging mode, the image acquisition unit is used to perform multi-view imaging with a fixed viewing angle based on the response intensity difference of the partitioned microchannel plate, so as to form multiple multi-view sub-images.

[0037] The image synthesis unit is used for:

[0038] The response intensity of each partitioned microchannel plate to the same scanning point is compared. Based on the comparison results of the response intensity, the surface tilt angle information of this scanning point is obtained and a tilt gradient map of the scanning area is generated. Based on the tilt gradient map, the true three-dimensional morphology of the sample is reconstructed by the integral method or the least squares method optimization method.

[0039] The image synthesis unit is also used to sum the amplified backscattered electronic signals within the same sector to improve the signal-to-noise ratio of the multi-view sub-images.

[0040] In the crystallographic contrast mode, the image synthesis unit is used for:

[0041] The amplified backscattered electron signals of all located in the same concentric ring are summed to obtain the omnidirectional backscattered image at the corresponding polar angle.

[0042] Grain orientation contrast is obtained by comparing omnidirectional backscattered images at different polar angles;

[0043] In full microchannel plate imaging mode, the image synthesis unit is used for:

[0044] All the received amplified backscattered electronic signals are summed in real time to obtain the full microchannel plate imaging result; wherein, the full microchannel plate imaging result is used to improve the image signal-to-noise ratio and is used as a background signal to correct the multi-view sub-image.

[0045] Compared with the prior art, the present invention has the following beneficial effects:

[0046] This invention provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope (SEM). It employs a design with a ring-shaped microchannel plate positioned between the objective lens and the sample, aligned with the optical axis. A central through-hole in the ring-shaped microchannel plate allows the primary electron beam to pass through. The input surface faces the sample, while the output surface is flush with the readout anode unit. The readout anode unit is divided into multiple concentric rings to distinguish signals within polar angle intervals. Each ring is further divided into multiple independent fan-shaped surfaces to capture azimuth information. This device, through dual segmentation of polar and azimuth angles, can simultaneously distinguish backscattered electron signals emitted from different angles. The ring-shaped microchannel plate is directly above the sample, significantly shortening the electron transmission path, reducing stray electromagnetic fields and vibration interference, and improving signal acquisition efficiency. This device significantly improves the signal-to-noise ratio and image quality of low-voltage imaging. It is compatible with large, flat samples without requiring sample tilting, avoiding the geometric defects of traditional side-mounted detectors. Multi-view signal separation provides rich angular information, enhancing image stereoscopicity and shadow effects, supporting simple 3D reconstruction to infer surface morphology features, while reducing information waste. This effectively meets the high-precision analysis requirements of surface-sensitive materials and non-conductive samples.

[0047] This invention also provides a multi-view backscattered electron imaging method for low-voltage scanning electron microscopes. Based on the aforementioned multi-view backscattered electron imaging device for low-voltage scanning electron microscopes, this method places an annular microchannel plate between the objective lens and the sample, aligning the optical axis. A primary electron beam is emitted to the sample surface via a central through-hole, and backscattered electron signals in a preset polar angle range are simultaneously distinguished by multiple concentric rings of the readout anode unit. Simultaneously, a preset azimuth angle signal is distinguished by independent fan-shaped surfaces. The annular microchannel plate, acting as a detector directly above the sample, shortens the electron transmission path, reducing stray electromagnetic fields and vibration interference, and improving signal stability. The dual segmentation design of polar and azimuth angles enables simultaneous acquisition of multi-angle signals, overcoming the shortcomings of traditional methods such as single viewing angle and overlapping azimuth information. This method significantly improves the signal-to-noise ratio and image quality of low-voltage imaging, accommodates large, flat samples without tilting the sample, enhances image stereoscopicity and shadow effects, supports simplified three-dimensional surface topography reconstruction, and reduces information waste, thus meeting the needs for fine analysis of surface-sensitive materials and non-conductive samples. Attached Figure Description

[0048] Figure 1 This is a schematic diagram of the principle of a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope provided in an embodiment of the present invention;

[0049] Figure 2 A working diagram of a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope provided in an embodiment of the present invention;

[0050] Figure 3 The following is a response diagram of each unit of the microchannel plate in a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope provided in an embodiment of the present invention; wherein, (a) is the energy and position of all backscattered electron signals hitting the microchannel plate when the low-voltage scanning electron microscope scans a certain point; (b) is the response intensity of each microchannel plate detection unit when scanning the point;

[0051] Figure 4 This is an image of a full microchannel plate provided in an embodiment of the present invention;

[0052] Figure 5 The image provided in this embodiment of the invention is an image of each microchannel plate after segmentation, namely, a partition response diagram of 3 rings × 4 sectors. Detailed Implementation

[0053] To make the technical problems solved by the present invention, the technical solutions, and the beneficial effects clearer, the following specific embodiments provide a further detailed description of the present invention. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of the invention.

[0054] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments 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, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0055] Therefore, the following detailed description of the embodiments of the invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the invention without inventive effort are within the scope of protection of the invention.

[0056] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0057] The technical terms involved in this invention are explained as follows:

[0058] SEM stands for Scanning Electron Microscope.

[0059] MCP stands for Microchannel plate.

[0060] BSE: short for Back-Scattered Electron.

[0061] 3D: Three-Dimensional.

[0062] Everhart-Thornley: A secondary electron detector used in scanning electron microscopy.

[0063] As mentioned in the background section, when performing low-energy scanning electron microscopy (SEM) imaging, if the microchannel plate detector is treated as a whole to receive backscattered electron signals, the detector will indiscriminately collect all signals from approximately the entire hemisphere above the sample (regardless of its initial emission angle). This causes it to lose the directional information carried in the signal, which is directly related to the surface normal angle. The final image is a superposition projection of all angular signals, and the three-dimensional morphological features such as surface tilt and shadow contours are severely weakened, resulting in information waste and an image with far less stereoscopic depth than a side-mounted Everhart-Thornley detector. While ring-cutting the readout anode unit at the rear end of the microchannel plate separates the polar angle dimension information, allowing the detector to obtain grain orientation contrast, the azimuth dimension information still overlaps. Since the azimuth dimension contains multi-view imaging information essential for image stereoscopic depth, ring-cutting alone cannot significantly improve the image stereoscopic depth. While the traditional Everhart-Thornley detector offers good stereoscopic vision, it can only provide information from a single perspective. It cannot infer surface normals, slopes, or other information by comparing contrast changes in images from different perspectives, nor can it perform simple 3D reconstruction. This limits its application value in scenarios requiring detailed topographic analysis.

[0064] To address the aforementioned objectives, this embodiment provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope. By simultaneously dividing the readout anode unit at the rear end of the annular microchannel plate radially and angularly, multiple sets of concentric rings and fan-shaped surfaces are formed. This effectively solves the defects of the microchannel plate electron detector in current low-voltage scanning electron microscopes, such as a single imaging viewpoint and weak stereoscopic effect, thereby achieving multi-view imaging of the morphology.

[0065] For example, this embodiment provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope, including an annular microchannel plate disposed between the objective lens and the sample of the low-voltage scanning electron microscope; the annular microchannel plate is aligned with the optical axis.

[0066] The annular microchannel plate has a through hole at its center, through which the primary electron beam passes; the input surface of the annular microchannel plate is oriented towards the sample.

[0067] A readout anode unit is attached to the output surface of the annular microchannel plate; the readout anode unit is used to receive the amplified backscattered electron signal emitted from the sample surface;

[0068] The readout anode unit is divided into multiple concentric rings along the polar angle direction of the annular microchannel plate. The concentric rings are used to collect the amplified backscattered electron signals emitted within the preset polar angle range.

[0069] Each concentric ring is uniformly divided into multiple independent sector surfaces along the diameter of the annular microchannel plate. The independent sector surfaces are used to collect amplified backscattered electron signals emitted within a preset azimuth angle.

[0070] As can be seen, this embodiment provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope, and its main technical core is as follows:

[0071] First, the core design and multi-view imaging principle: The ring-shaped MCP detector is placed above the sample with the optical axis aligned coaxially, dividing the readout anode unit into multiple independent "fan-shaped-ring" detection units, with different detection units having different observation and imaging perspectives.

[0072] The imaging has a three-dimensional effect: the surface morphology of the sample makes the angular distribution of backscattered electrons directional, and the segmented detector can identify the angular distribution characteristics of backscattered electrons and manifest them as three-dimensional shadows in the image.

[0073] Second, multiple imaging modes: Different combinations of the acquired N×M dimensional data can construct different imaging modes and achieve different functions. For example, in multi-view imaging mode, polar angle dimension information can be summed, retaining only the orientation angle dimension information, which can improve the image signal-to-noise ratio and increase scanning speed while preserving the stereoscopic effect of images from different perspectives. The crystallographic contrast mode sums the azimuth angle dimension information, which can be used to distinguish between crystals and amorphous materials and obtain grain orientation contrast. The high-sensitivity fast imaging mode sums the polar angle and azimuth angle dimensions, has the highest collection efficiency and signal-to-noise ratio, and can correct the interference of atomic number contrast (Z contrast) on multi-view imaging. N×M dimensional data blocks can also be used to calculate the surface tilt angle of scanned micro-areas and for three-dimensional topography reconstruction.

[0074] The testing machine provided in this embodiment will be further described in detail below with reference to the accompanying drawings:

[0075] like Figure 1 As shown, this embodiment provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope, including an annular microchannel plate, also known as an annular MCP detector, which serves as a detector. In this embodiment, the annular MCP is placed below the objective lens and aligned with the optical axis, with a central opening for the primary electron beam to pass through. Its input surface faces the sample and is used to receive and amplify the backscattered electron (BSE) signal emitted from the sample surface.

[0076] Combination Figure 2As shown, low-energy primary electrons generated and focused by the electron optical column exit the objective lens, pass through the central ring of the microchannel plate, and bombard the sample surface, exciting backscattered electron signals. These backscattered electron signals escape from the surface with different initial kinetic energies and directions (θ, φ), and after a period of flight, land at a corresponding coordinate position (r, φ) on the MCP. The backscattered electrons enter the MCP channel, triggering avalanche multiplication, with a gain reaching 10⁻⁶. 4 ~10 6 The multiplied electron cloud (amplified backscattered electron signal) is emitted from the MCP output surface and immediately collected by the adjacent, pre-divided readout anode unit. The readout anode unit is divided into N (e.g., N=3) concentric rings along the polar angle direction. Each concentric ring corresponds to collecting the amplified backscattered electron signal emitted within a specific polar angle (θ) interval. Within each concentric ring, it is further divided into M (e.g., M=4) independent sectors along the MCP diameter direction. Each sector corresponds to collecting the amplified backscattered electron signal emitted within a specific azimuth angle (φ) interval (e.g., every 90° interval).

[0077] For example, due to the angle-position mapping relationship, an electron cloud (composed of several amplified backscattered electron signals) emitted from a specific (θ, φ) direction is mapped to the MCP plate position (r, φ) and then collected by the corresponding (ring i, sector j) unit on the anode. Figure 3 As shown, Figure 3 In Figure (a), the energy and position of all electrons hitting the microchannel plate when a point is scanned by SEM are shown. If a backscattered electron falls within a detector cell of the microchannel plate, the signal strength (electron count) of that detector cell will increase, as shown in Figure (a). Figure 3 As shown in Figure (b), Figure (b) represents the response intensity (i.e., the number of electron counters) of each microchannel plate detection unit when scanning this point. The backscattered electron signals generated by N×M anode units, after being synchronously acquired, will form N rings, each with M sectors, generating a total of N×M multi-view sub-images. Each multi-view sub-image I... {i，j}(x，y) This represents the emission from the sample surface to a specific point (θ) at the scan position (x, y). i φ j The intensity of backscattered electrons within the solid angle of the direction, specifically as follows: Figure 5 As shown.

[0078] For example, this embodiment provides a multi-view backscattered electron imaging device for a low-voltage scanning electron microscope, further comprising: an image acquisition unit connected to the output terminal of a readout anode unit, used to receive backscattered electron signals generated by the readout anode unit and form multiple multi-view sub-images based on the electrical signals, wherein the image acquisition unit performs multi-view imaging with a fixed viewing angle based on the response intensity differences of the partitioned microchannel plate to form multiple multi-view sub-images. It also includes an image synthesis unit and a mode switching unit; wherein: the image synthesis unit is connected to the output terminal of the image acquisition unit, used to restore the multiple multi-view sub-images to the true three-dimensional morphology of the sample, so as to output imaging results from any viewing angle; the mode switching unit is connected to the image synthesis unit, used to switch the image synthesis unit between multiple modes such as multi-view imaging mode, crystallographic contrast mode, and full microchannel plate imaging mode.

[0079] In multi-view imaging mode, the image synthesis unit is used to: compare the response intensity of each partition microchannel plate to the same scanning point, obtain the surface tilt angle information of this scanning point based on the comparison result of the response intensity, and generate a tilt gradient map of the scanning area; and reconstruct the true three-dimensional morphology of the sample based on the tilt gradient map by the integral method or the least squares optimization method.

[0080] The image synthesis unit is also used to sum the amplified backscattered electronic signals within the same sector to improve the signal-to-noise ratio of the multi-view sub-images;

[0081] The true three-dimensional morphology of the sample is reconstructed based on the tilt gradient map using the integral method or the least squares optimization method.

[0082] In crystallographic contrast mode, the image synthesis unit is used to: sum all amplified backscattered electron signals located in the same concentric ring to obtain an omnidirectional backscattered image at the corresponding polar angle; and obtain grain orientation contrast by comparing omnidirectional backscattered images at different polar angles.

[0083] In full microchannel plate imaging mode, the image synthesis unit is used for:

[0084] All the received amplified backscattered electronic signals are summed in real time to obtain the full microchannel plate imaging result; wherein, the full microchannel plate imaging result is used to improve the image signal-to-noise ratio and is used as a background signal to correct the multi-view sub-image.

[0085] like Figure 4 As shown, Figure 4 To obtain imaging results by collecting backscattered electrons from a microchannel plate as a whole; for example... Figure 5As shown, after dividing the MCP plate into three concentric rings (corresponding to three different polar angle views) and four sector surfaces (corresponding to four different azimuth angle views), the imaging results of each sub-MCP plate are shown. It can be seen that the imaging results of different sub-MCP plates are equivalent to observing the same sample geometry from different viewpoints, and the imaging exhibits shadows related to the 3D morphology. By comparing the imaging results from different viewpoints, the true 3D morphology of the sample can be easily reconstructed. Figure 5 In the middle, from top left to bottom right, the shapes are a sphere, a frustum, a cone, and a cube.

[0086] Therefore, the multi-view backscattered electron signal imaging device provided in this embodiment, in addition to achieving multi-view imaging through an N×M partitioned microchannel plate, can also realize the following imaging modes based on the acquired N×M dimensional data:

[0087] Mode 1, Multi-view Imaging Mode: This mode combines 3D topography reconstruction and rapid multi-view imaging. The angular distribution of backscattered electron signals in space reflects the surface topography characteristics of the sample (e.g., surface tilt angle). The segmented readout anode units can identify the directionality of the backscattered electron signals. Therefore, by comparing the response intensity of each partitioned readout anode unit (i, j) to the same scanning point (x, y), the surface tilt angle information of that scanning point can be obtained, and a tilt gradient map of the scanning area can be generated. Based on the tilt gradient map, algorithms such as integration or least squares optimization can be used to reconstruct the 3D topography of the imaging surface. Furthermore, since obtaining a sense of depth relies more on distinguishing BSE signals with different azimuth angles φ (distinguishing different polar angles θ does not significantly improve the sense of depth in imaging, see reference...), the 3D topography reconstruction of the imaging surface can be achieved. Figure 5 Therefore, by adding all polar angle signals (all annular signals) within the same sector (same azimuth angle φ), full polar angle BSE imaging can be performed. Compared with imaging each partition readout anode unit (i, j) separately, this mode has a larger equivalent detection area and can improve the signal-to-noise ratio of the image while maintaining scanning speed and image stereoscopic effect.

[0088] Mode 2, Crystallographic Contrast Mode: This mode, also known as material crystallographic contrast imaging, sums the electrical signals from all sectors with different azimuth angles within the same radial ring (same polar angle interval) to obtain an "omnidirectional" backscattered image at the corresponding polar angle. This image is sensitive to atomic number and crystal orientation; grain orientation contrast can be obtained by comparing different "omnidirectional" backscattered images. Due to the high collection efficiency and low noise of MCP, this mode achieves a signal-to-noise ratio far exceeding that of traditional crystal or semiconductor backscattered electron (BSE) detectors under low-voltage SEM.

[0089] Mode 3, Full Microchannel Plate Imaging Mode: Real-time summation of signals from all N×M channels enables full MCP imaging. In this mode, the device is equivalent to a complete large-area MCP detector, offering the highest collection efficiency and signal-to-noise ratio. It is suitable for low-dose, rapid scanning or preliminary observation of weak signals. Since the full MCP imaging signal intensity is strongly correlated with the sample's atomic number, using it as a background signal to correct multi-view images with a sense of depth (e.g., dividing the brightness of corresponding points in the multi-view image by the brightness of corresponding points in the full MCP image, i.e., performing a "normalization" operation on the multi-view image) can eliminate the interference of atomic number contrast (Z-contrast) on multi-view morphology imaging when the sample material is inhomogeneous.

[0090] In summary, this invention provides a multi-view backscattered electron imaging device and method for low-voltage scanning electron microscopes, which has the following advantages compared with existing imaging methods for low-voltage scanning electron microscopes:

[0091] First, this invention is the first to simultaneously acquire the complete two-dimensional angular distribution (polar angle θ × azimuth angle φ) of backscattered electron signals in a single scan, solving the fundamental defects of traditional imaging techniques that lose all angular information (overall MCP), lose azimuth information (only ring segmentation), or have a single viewing angle.

[0092] Secondly, in this invention, the same hardware platform can quickly switch between multiple modes such as high stereoscopic morphology imaging, material crystallographic contrast imaging mode, surface normal quantitative analysis, and high-sensitivity survey imaging through software processing without any mechanical adjustment.

[0093] Third, the complete angular distribution data cube obtained can provide a data foundation for subsequent advanced analysis work such as automatic phase identification and more complex 3D reconstruction combined with machine learning.

[0094] The above embodiments are merely one of the implementation methods for achieving the technical solution of the present invention. The scope of protection claimed by the present invention is not limited to this embodiment, but also includes any variations, substitutions and other implementation methods that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention.

Claims

1. A multi-view backscattered electron imaging device for a low-voltage scanning electron microscope, characterized in that, include: Annular microchannel plate; The annular microchannel plate is positioned between the objective lens and the sample of the low-voltage scanning electron microscope and is aligned with the optical axis. The annular microchannel plate has a through hole at its center, through which the primary electron beam passes. The input surface of the annular microchannel plate is oriented towards the sample. A readout anode unit is attached to the output surface of the annular microchannel plate; the readout anode unit is used to receive the amplified backscattered electron signal output by the annular microchannel plate; the amplified backscattered electron signal is obtained by amplifying the backscattered electron signal emitted from the sample surface through the annular microchannel plate. The readout anode unit is divided into multiple concentric rings along the polar angle direction of the annular microchannel plate. The concentric rings are used to collect amplified backscattered electron signals emitted within a preset polar angle range. Each concentric ring is uniformly divided into multiple independent sector surfaces along the diameter of the annular microchannel plate. These independent sector surfaces are used to collect amplified backscattered electron signals emitted within a preset azimuth angle.

2. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 1, characterized in that, It also includes an image acquisition unit; The image acquisition unit is connected to the output terminal of the readout anode unit and is used to receive the amplified backscattered electron signal generated by the readout anode unit and form multiple multi-view sub-images based on the amplified backscattered electron signal; wherein, each multi-view sub-image represents the intensity of the backscattered electron signal emitted from the sample surface to the corresponding solid angle at the scanning position.

3. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 2, characterized in that, It also includes an image synthesis unit; The image synthesis unit is connected to the output of the image acquisition unit and is used to restore multiple multi-view sub-images into the true three-dimensional shape of the sample.

4. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 3, characterized in that, It also includes a mode switching unit; The mode switching unit is connected to the image synthesis unit and is used to switch the image synthesis unit between multiple modes, including multi-view imaging mode, crystallographic contrast mode, and full microchannel plate imaging mode.

5. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 4, characterized in that, In the multi-view imaging mode, the image acquisition unit is used to perform multi-view imaging with a fixed viewing angle based on the response intensity differences of the partitioned microchannel plates to form multiple multi-view sub-images; the image synthesis unit is used to compare the response intensity of each partitioned microchannel plate to the same scanning point, obtain the surface tilt angle information of this scanning point according to the comparison result of the response intensity, and generate a tilt gradient map of the scanning area; based on the tilt gradient map, the true three-dimensional morphology of the sample is reconstructed by the integral method or the least squares optimization method. The image synthesis unit is also used to sum the amplified backscattered electronic signals within the same sector to improve the signal-to-noise ratio of the multi-view sub-image.

6. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 4, characterized in that, In the crystallographic contrast mode, the image synthesis unit is used for: The amplified backscattered electron signals of all located in the same concentric ring are summed to obtain the omnidirectional backscattered image at the corresponding polar angle. Grain orientation contrast is obtained by comparing omnidirectional backscattered images at different polar angles.

7. The multi-view backscattered electron imaging device for a low-voltage scanning electron microscope according to claim 4, characterized in that, In the full microchannel plate imaging mode, the image synthesis unit is used for: All the received amplified backscattered electronic signals are summed in real time to obtain the full microchannel plate imaging result. The full microchannel plate imaging result is used to improve the image signal-to-noise ratio and is used as a background signal to correct the multi-view sub-image.

8. A multi-view backscattered electron imaging method for a low-voltage scanning electron microscope, implemented based on the multi-view backscattered electron imaging device of the low-voltage scanning electron microscope according to any one of claims 1-7, characterized in that, include: Place the annular microchannel plate between the objective lens and the sample of the low-voltage scanning electron microscope, and align it with the optical axis; A primary electron beam is emitted to the sample surface through a through-hole in the center of the annular microchannel plate. The amplified backscattered electron signal emitted within a preset polar angle range is collected by multiple concentric rings of the readout anode unit, and the amplified backscattered electron signal emitted within a preset azimuth angle is collected synchronously by independent fan-shaped surfaces.

9. The multi-view backscattered electron imaging method for a low-voltage scanning electron microscope according to claim 8, characterized in that, After collecting amplified backscattered electron signals emitted within a preset polar angle range by multiple concentric rings of the readout anode unit, and then synchronously collecting amplified backscattered electron signals emitted within a preset azimuth angle by independent sector surfaces, the process further includes: The image acquisition unit receives the amplified backscattered electron signal generated by the anode unit and forms multiple sub-images from multiple perspectives based on the electrical signal. The image synthesis unit restores the true three-dimensional shape of the sample from multiple sub-images from multiple perspectives, so as to output the imaging results from any perspective.

10. A multi-view backscattered electron imaging method for a low-voltage scanning electron microscope according to claim 8, characterized in that, After collecting backscattered electron signals emitted within a preset polar angle range by multiple concentric rings of the readout anode unit, and synchronously collecting backscattered electron signals emitted within a preset azimuth angle by independent sector surfaces, the process also includes: The image synthesis unit switches between multiple modes—multi-view imaging mode, crystallographic contrast mode, and full microchannel plate imaging mode—through a mode switching unit. In the multi-view imaging mode, the image acquisition unit is used to perform multi-view imaging with a fixed viewing angle based on the response intensity difference of the partitioned microchannel plate, so as to form multiple multi-view sub-images. The image synthesis unit is used for: The response intensity of each partitioned microchannel plate to the same scanning point is compared. Based on the comparison results of the response intensity, the surface tilt angle information of this scanning point is obtained and a tilt gradient map of the scanning area is generated. Based on the tilt gradient map, the true three-dimensional morphology of the sample is reconstructed by the integral method or the least squares method optimization method. The image synthesis unit is also used to sum the amplified backscattered electronic signals within the same sector to improve the signal-to-noise ratio of the multi-view sub-images. In the crystallographic contrast mode, the image synthesis unit is used for: The amplified backscattered electron signals of all located in the same concentric ring are summed to obtain the omnidirectional backscattered image at the corresponding polar angle. Grain orientation contrast is obtained by comparing omnidirectional backscattered images at different polar angles; In full microchannel plate imaging mode, the image synthesis unit is used for: All the received amplified backscattered electronic signals are summed in real time to obtain the full microchannel plate imaging result; wherein, the full microchannel plate imaging result is used to improve the image signal-to-noise ratio and is used as a background signal to correct the multi-view sub-image.

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