CN-122017288-A - Multi-view angle back scattering electron imaging device and method of low-voltage scanning electron microscope

CN122017288ACN 122017288 ACN122017288 ACN 122017288ACN-122017288-A

Abstract

The invention belongs to the field of scanning electron microscopes, and discloses a multi-view back scattering electron imaging device and a method of a low-voltage scanning electron microscope, which adopt a design that an annular microchannel plate is arranged between an objective lens and a sample and the optical axis is aligned, a central through hole allows a primary electron beam to pass through, the input face faces the sample, the output face is closely attached to the read anode unit, and the read anode unit is divided into a plurality of concentric zones to distinguish polar angle interval signals, and each zone is uniformly divided into a plurality of independent sector faces to capture azimuth angle information. The multi-view signal separation can provide rich angle information, enhance the stereoscopic impression and shadow effect of images, support simple three-dimensional reconstruction to infer the surface morphology features, reduce the information waste and meet the high-precision analysis requirements of surface sensitive materials and non-conductive samples.

Inventors

KONG LINGGAO
CHEN ZHIJIN
ZHANG ZIYAN
LI YOUZHI
Xia xinmiao
ZHANG ZHIQIAN
MA JIJIE
Pu Baiqu
SONG YIFAN

Assignees

南京大学

Dates

Publication Date: 20260512
Application Date: 20260416

Claims (10)

1. A multi-view angle back scattering electron imaging device of a low voltage scanning electron microscope is characterized by comprising an annular microchannel plate; the annular microchannel plate is arranged between the objective lens of the low-voltage scanning electron microscope and the sample and is aligned with the optical axis; a through hole is formed in the center of the annular microchannel plate, and the through hole is used for the primary electron beam to pass through; the input surface of the annular microchannel plate is arranged towards the direction of the sample; The output surface of the annular microchannel plate is closely provided with a reading anode unit, and the reading anode unit is used for receiving the amplified back-scattered electronic signals output by the annular microchannel plate; the reading anode unit is divided into a plurality of concentric annular bands along the polar angle direction of the annular microchannel plate, and the concentric annular bands are used for collecting amplified back scattering electronic signals emitted in a preset polar angle interval; each concentric ring belt is uniformly divided into a plurality of independent fan-shaped surfaces along the diameter direction of the annular microchannel plate, and the independent fan-shaped surfaces are used for collecting amplified back scattering electronic signals emitted in a preset azimuth angle.
2. The multi-view back-scattered electron imaging device of claim 1, further comprising an image acquisition unit; The image acquisition unit is connected with the output end of the reading anode unit and is used for receiving the amplified back scattering electronic signals generated by the reading anode unit and forming a plurality of multi-view subgraphs according to the amplified back scattering electronic signals, wherein each multi-view subgraph represents the intensity of the back scattering electronic signals emitted from the surface of the sample to the solid angle in the corresponding direction at the scanning position.
3. The multi-view back-scattered electron imaging device of claim 2, further comprising an image synthesizing unit; The image synthesis unit is connected with the output end of the image acquisition unit and is used for restoring the multiple multi-view subgraphs into the real three-dimensional appearance of the sample.
4. A multi-view back-scattered electron imaging device for a low voltage scanning electron microscope as claimed in claim 3, further comprising a mode switching unit; The mode switching unit is connected with the image synthesis unit and used for switching the image synthesis unit among a multi-view imaging mode, a crystallography contrast mode and a full microchannel plate imaging mode.
5. The multi-view back scattering electronic imaging device of the low voltage scanning electron microscope according to claim 4, wherein in the multi-view imaging mode, the image acquisition unit is used for performing multi-view imaging with fixed view angles based on the response intensity difference of the partitioned microchannel plates to form a plurality of multi-view subgraphs, the image synthesis unit is used for comparing the response intensity of each partitioned microchannel plate to the same scanning point, acquiring the surface inclination angle information of the scanning point according to the comparison result of the response intensity and generating an inclined gradient map of a scanning area, and reconstructing the real three-dimensional morphology of the sample by an integration method or a least square optimization method based on the inclined gradient map; The image synthesis unit is also used for summing the amplified back scattering electronic signals in the same sector so as to improve the image signal-to-noise ratio of the multi-view subgraph.
6. The multi-view back-scattered electron imaging device of claim 4, wherein in said crystallographic contrast mode, said image synthesizing unit is adapted to: summing all amplified back-scattered electronic signals positioned in the same concentric ring belt to obtain an all-azimuth back-scattered image under a corresponding polar angle; Grain orientation contrast is obtained by comparing the full azimuth back-scattered images at different polar angles.
7. The multi-view back-scattered electron imaging device of claim 4, wherein in said full microchannel plate imaging mode, said image combining unit is adapted to: And adding all the received amplified back scattering electronic signals in real time to obtain a full microchannel plate imaging result, wherein the full microchannel plate imaging result is used for improving the signal to noise ratio of an image and correcting the multi-view subgraph as a background signal.
8. A multi-view back-scattered electron imaging method of a low voltage scanning electron microscope, which is realized based on the multi-view back-scattered electron imaging device of the low voltage scanning electron microscope according to any one of claims 1 to 7, comprising: placing an annular microchannel plate between an objective lens of a low-voltage scanning electron microscope and a sample and aligning with an optical axis; a primary electron beam is emitted to the surface of the sample through a through hole formed in the center of the annular microchannel plate; The amplified back-scattered electronic signals emitted in a preset polar angle interval are collected through a plurality of concentric annular bands of the read-out anode unit, and the amplified back-scattered electronic signals emitted in a preset azimuth angle are synchronously collected through independent fan-shaped surfaces.
9. The multi-view back-scattered electron imaging method of claim 8, wherein collecting the amplified back-scattered electron signals from the predetermined polar angle interval by a plurality of concentric rings of the readout anode unit and synchronously collecting the amplified back-scattered electron signals from the predetermined azimuth angle by the independent sectors, further comprises: Receiving the amplified back scattering electronic signals generated by the read anode unit by utilizing the image acquisition unit, and forming a plurality of multi-view subgraphs according to the electric signals; and restoring the multiple multi-view subgraphs into the real three-dimensional morphology of the sample through an image synthesis unit so as to output an imaging result under any view angle.
10. The method of multi-view back-scattered electron imaging of claim 8, wherein collecting back-scattered electron signals from a predetermined polar angle interval by a plurality of concentric rings of the readout anode unit and synchronously collecting back-scattered electron signals from a predetermined azimuth angle by separate sectors, further comprises: The image synthesis unit is switched among a multi-view imaging mode, a crystallographic contrast mode and a full microchannel plate imaging mode by a mode switching unit, wherein: in the multi-view imaging mode, the image acquisition unit is used for performing multi-view imaging with fixed view angles based on response intensity differences of the partitioned microchannel plates so as to form a plurality of multi-view subgraphs; the image synthesis unit is used for: Comparing the response intensity of each partition microchannel plate to the same scanning point, and obtaining the surface inclination angle information of the scanning point according to the comparison result of the response intensity and generating an inclination gradient map of a scanning area; the image synthesis unit is also used for summing the amplified back scattering electronic signals in the same sector so as to improve the image signal-to-noise ratio of the multi-view subgraph; in the crystallographic contrast mode, the image synthesis unit is configured to: summing all amplified back-scattered electronic signals positioned in the same concentric ring belt to obtain an all-azimuth back-scattered image under a corresponding polar angle; acquiring grain orientation contrast by comparing all-azimuth back-scattered images of different polar angles; in the full microchannel plate imaging mode, the image synthesis unit is configured to: and adding all the received amplified back scattering electronic signals in real time to obtain a full microchannel plate imaging result, wherein the full microchannel plate imaging result is used for improving the signal to noise ratio of an image and correcting the multi-view subgraph as a background signal.

Description

Multi-view angle back scattering electron imaging device and method of low-voltage scanning electron microscope Technical Field The invention belongs to the technical field of scanning electron microscopes, and particularly relates to a multi-view angle back scattering electron imaging device and method of a low-voltage scanning electron microscope. Background Scanning Electron Microscope (SEM) is used as an indispensable surface analysis tool in the fields of modern scientific research and industry, and is widely applied in the fields of material characterization and the like by virtue of the advantages of high resolution, large depth of field, capability of realizing functions of micro-area component analysis, grain orientation analysis and the like by combining with various analysis accessories. Among them, low voltage imaging technology (incident electron energy is usually lower than 5 keV) is an important direction for surface sensitive materials, non-conductive sample analysis, because it can protect heat sensitive or insulating samples (e.g. biological tissues, synthetic fibers) from high energy electron beams and allow the samples to be directly observed without conducting treatment. The microchannel plate (MCP) is used as a two-dimensional array electron multiplier with the advantages of high gain, quick response and low noise, can effectively overcome the defects of low signal to noise ratio and imaging ambiguity under the condition of low beam current, has proved the feasibility of the MCP as an SEM electron detector, can realize grain orientation contrast acquisition by dividing the MCP into concentric circle arrays, and provides an important basis for optimizing a low-voltage SEM imaging technology. At present, the conventional low-voltage SEM imaging technology and related detectors have various defects that the conventional SEM is easy to have the problems of small beam current and low signal to noise ratio under the low-voltage condition, image degradation is caused by disturbance such as an external environment stray magnetic field, irregular vibration and the like during long-time exposure, the side-mounted configuration of the main stream Everhart-Thornley detector has geometrical defects, a sample is required to be obliquely placed, a large-sized flat sample cannot be accommodated, a low-energy electron beam transmission path is easy to be interfered by the stray electromagnetic field, meanwhile, only single view angle information can be provided, surface normal direction, gradient and other information cannot be deduced through multi-view angle image contrast so as to realize simple three-dimensional reconstruction, when the MCP is used as an integral detector, imaging shadowless effect and lack of angle information are caused by omni-directional collection signal electrons, three-dimensional stereoscopic impression is weak ("flattened"), and even though the MCP is divided into concentric annular collectors, polar angle dimension information can be separated so as to obtain grain orientation contrast, but azimuth angle dimension information still overlaps each other, image stereoscopic impression cannot be effectively improved, and the problem of information waste still exists. Therefore, the prior low-voltage scanning electron microscope imaging related technology is difficult to meet the requirements of low-voltage imaging on sample protection, and meanwhile, the requirements of imaging signal-to-noise ratio, imaging quality, image third dimension and multi-view information acquisition on simple three-dimensional reconstruction are met, so that the application of the imaging device in surface sensitive materials and non-conductive sample fine morphology analysis scenes is limited. Disclosure of Invention The invention provides a multi-view back scattering electron imaging device and a method of a low-voltage scanning electron microscope, which can simultaneously meet the requirements of low-voltage imaging on sample protection, imaging signal-to-noise ratio, imaging quality, image third dimension and multi-view information acquisition to realize simple three-dimensional reconstruction, and promote the application of a low-voltage SEM imaging technology in surface sensitive materials and non-conductive sample fine morphology analysis scenes. In order to achieve the above purpose, the present invention adopts the following technical contents: a multi-view back-scattering electron imaging device of a low-voltage scanning electron microscope comprises an annular microchannel plate; the annular microchannel plate is arranged between the objective lens of the low-voltage scanning electron microscope and the sample and is aligned with the optical axis; a through hole is formed in the center of the annular microchannel plate, and the through hole is used for the primary electron beam to pass through; the input surface of the annular microchannel plate is arranged towards the direction of the