Objective lens system of scanning electron microscope and detection method

Abstract

The invention provides a scanning electron microscope objective lens system and a detection method, and relates to the technical field of scanning electron microscopes. The magnetic lens device is used for focusing an incident electron beam; the deflection device, the anastigmator, the Wien analyzer group and the detection device are all located in an accommodating space in the magnetic lens device; the deflection device, the anastigmator and the Wien analyzer group are arranged along the optical axis of the incident electron beam and are arranged around the optical axis; the deflection device and the anastigmator are respectively used for adjusting the movement direction and shape of the incident electron beam so as to scan a to-be-tested sample through the incident electron beam, so that the to-be-tested sample generates signal electrons; the Wien analyzer group is used for adjusting the movement direction of the signal electrons to enable the signal electrons to enter the detection device; the detection device is located on the side, close to the magnetic lens device, of the deflection device, the anastigmator and the Wien analyzer set and used for generating a detection signal according to the signal electrons and achieving surface imaging of the to-be-detected sample. The imaging precision and the detection efficiency of the objective lens system are improved.

Description

A scanning electron microscope objective system and detection method Technical Field

[0001] This invention relates to the field of scanning electron microscopy, and more particularly to a scanning electron microscope objective system and detection method. Background Technology

[0002] Scanning electron microscopy (SEM) is an important tool for analyzing the microstructure of materials based on the principle of electron beam scanning. It is widely used in materials science, electronic devices, biomedicine, and many other fields. Its basic measurement method is as follows: an incident electron beam scans the surface of the sample under test, and the surface of the sample is imaged by detecting the signal electrons reflected from the sample.

[0003] Existing scanning electron microscope objective systems typically include a magnetic lens system and a deflection device, which are used to control the focusing and scanning path of the incident electron beam, respectively. To simplify the system structure, the deflection device in the objective system usually serves both to control the scanning path of the incident electron beam on the sample surface and to guide the signal electrons into the detector. However, due to the differences in energy, divergence angle, and path characteristics between the incident electron beam and the signal electrons, sharing a deflection device makes it difficult to achieve precise control over the motion directions of both, which can easily cause the signal electrons to deviate from the optimal detection path, affecting the imaging accuracy and detection efficiency of the objective system. Summary of the Invention

[0004] This invention provides a scanning electron microscope objective system and detection method. By setting up a rotating device and a Wien analyzer group, it achieves independent and precise control of the motion direction of the incident electron beam and signal electrons, thereby improving the imaging accuracy and detection efficiency of the objective system.

[0005] The first aspect of the present invention provides a scanning electron microscope objective system, the scanning electron microscope objective system comprising:

[0006] Magnetic lens assembly, deflection device, astigmatism corrector, Wien analyzer assembly, and detection device;

[0007] The magnetic lens device is used to focus the incident electron beam;

[0008] The magnetic lens device includes a housing space, in which the deflection device, the astigmatism corrector, the Wien analyzer group, and the detection device are all located;

[0009] The deflection device, the astigmatism corrector, and the Wien analyzer group are arranged along the optical axis of the incident electron beam and are all arranged around the optical axis; the astigmatism corrector is located below the deflection device, and the Wien analyzer group is located below the astigmatism corrector;

[0010] The deflection device is used to adjust the direction of motion of the incident electron beam, the astigmatism reducer is used to adjust the shape of the incident electron beam so as to scan the sample under test through the incident electron beam and make the sample under test generate signal electrons; the Wien analyzer group is used to adjust the direction of motion of the signal electrons so as to make the signal electrons enter the detection device.

[0011] The detection device is located on the side of the deflection device, the astigmatism reducer and the Wien analyzer group near the magnetic lens device. The detection device is used to generate a detection signal based on the signal electrons to achieve surface imaging of the sample to be tested.

[0012] Optionally, the magnetic lens device includes a first upper pole shoe, a second upper pole shoe, a lower pole shoe, and a coil assembly;

[0013] The second upper pole piece and the first upper pole piece are arranged along the optical axis and are both arranged around the optical axis; the second upper pole piece is located opposite to and above the first upper pole piece; the second upper pole piece and the first upper pole piece are insulated from each other;

[0014] The lower pole shoe is arranged around the first upper pole shoe and part of the second upper pole shoe, and the lower pole shoe and the second upper pole shoe are connected;

[0015] The first upper pole shoe, the second upper pole shoe, and the lower pole shoe constitute a coil receiving cavity; the coil assembly is located within the coil receiving cavity, and the coil assembly is arranged around a portion of the second upper pole shoe;

[0016] The polarity of the first upper pole shoe is different from that of the second upper pole shoe and the lower pole shoe.

[0017] Optionally, the first upper pole shoe includes a first stepped surface; the second upper pole shoe includes a second stepped surface;

[0018] The first step surface and the second step surface are arranged opposite to each other; an insulating material is provided in the gap between the first step surface and the second step surface.

[0019] Optionally, the incident electron beam deflection device includes a first deflector and a second deflector;

[0020] The first deflector, the second deflector, and the astigmatism reducer are arranged along the optical axis; the second deflector is located above the astigmatism reducer, and the first deflector is located above the second deflector.

[0021] Optionally, the scanning electron microscope objective system further includes: an electron converter; the signal electrons include backscattered electrons and secondary electrons;

[0022] The Wien analyzer group includes a first Wien analyzer and a second Wien analyzer.

[0023] The electron converter, the first Wien analyzer, and the second Wien analyzer are arranged along the optical axis; the first Wien analyzer is located above the second Wien analyzer, and the electron converter is located above the first Wien analyzer.

[0024] The first Wien analyzer is used to adjust the motion direction of the backscattered electrons so that the backscattered electrons irradiate the electron converter; the electron converter is used to convert the backscattered electrons into converted secondary electrons; the first Wien analyzer is also used to adjust the motion direction of the converted secondary electrons so that the converted secondary electrons enter the detection device.

[0025] The second Wien analyzer is used to adjust the direction of motion of the secondary electrons so that the secondary electrons enter the detection device.

[0026] Optionally, the detection device includes a backscattered electron detection device and a secondary electron detection device;

[0027] The backscattered electron detection device and the secondary electron detection device are located on opposite sides of the optical axis, and the backscattered electron detection device is positioned higher than the secondary electron detection device.

[0028] The backscattered electron detection device is used to generate a backscattered electron detection signal based on the converted secondary electrons whose motion direction has been adjusted by the first Wien analyzer.

[0029] The secondary electron detection device is used to generate a secondary electron detection signal based on the secondary electrons whose motion direction has been adjusted by the second Wien analyzer.

[0030] Optionally, the backscattered electron detection device includes a first scintillator, a first light guide, and a first photomultiplier tube; the secondary electron detection device includes a second scintillator, a second light guide, and a second photomultiplier tube.

[0031] The first scintillator is used to generate a first fluorescence signal under the excitation of the converted secondary electrons; the first light guide is used to transmit the first fluorescence signal to the first photomultiplier tube; the first photomultiplier tube is used to convert the first fluorescence signal into an electrical signal to generate the backscattered electron detection signal;

[0032] The second scintillator is used to generate a second fluorescence signal under the excitation of the secondary electrons; the second light guide is used to transmit the second fluorescence signal to the second photomultiplier tube; the second photomultiplier tube is used to convert the second fluorescence signal into an electrical signal to generate the secondary electron detection signal.

[0033] Optionally, the length of the first optical guide along the optical axis is less than the length of the second optical guide along the optical axis;

[0034] The length of the first photomultiplier tube along the optical axis is greater than the length of the second photomultiplier tube along the optical axis.

[0035] Optionally, the scanning electron microscope objective system further includes: a secondary electron extraction electrode; the signal electrons include backscattered electrons and secondary electrons;

[0036] The secondary electron absorption electrode is arranged around the optical axis and is located below the Wien analyzer group;

[0037] The secondary electron absorption electrode is used to accelerate the movement of the secondary electrons.

[0038] A second aspect of the present invention provides a detection method based on a scanning electron microscope objective system, the detection method comprising:

[0039] The incident electron beam moves from top to bottom into the scanning electron microscope objective system, so that the incident electron beam moves along the optical axis toward the sample to be tested.

[0040] The incident electron beam is focused by a magnetic lens device, deflected by a deflection device, and its shape is adjusted by an astigmatism reducer before scanning the sample to be tested, so that the sample to be tested generates signal electrons.

[0041] The signal electrons move along the optical axis away from the sample to be tested, and enter the detection device after being deflected by the Wien analyzer group.

[0042] The detection device generates a detection signal based on the signal electrons to achieve surface imaging of the sample to be tested.

[0043] The technical solution of this invention, by incorporating a magnetic lens device, a deflection device, an astigmatism corrector, a Wien analyzer group, and a detection device into a scanning electron microscope objective system, enables the incident electron beam to move along the optical axis toward the sample under test. The incident electron beam is focused by the magnetic lens device, and by housing the deflection device, astigmatism corrector, Wien analyzer group, and detection device within the internal space of the magnetic lens device, the structural size of the objective system is effectively reduced. By arranging the deflection device, astigmatism corrector, and Wien analyzer group around the optical axis and along the optical axis of the incident electron beam, good electromagnetic field uniformity is maintained. By placing the astigmatism corrector below the deflection device and the Wien analyzer group below the astigmatism corrector, the direction of motion of the incident electron beam can be adjusted by the deflection device, and the shape of the incident electron beam can be adjusted by the astigmatism corrector. This allows the incident electron beam to scan the sample under test, the sample to generate signal electrons, and the direction of motion of the signal electrons can be adjusted by the Wien analyzer group to precisely guide the signal electrons into the detection device. By optimizing the deflection paths of the incident electron beam and the signal electrons using the incident electron beam deflection device and the Wien analyzer group, respectively, the flexibility and accuracy of electron beam trajectory adjustment are improved. Furthermore, by placing the detector device on the side of the deflection device, astigmatism corrector, and Wien analyzer group close to the magnetic lens device, a detection signal is generated based on the signal electrons, enabling surface imaging of the sample under test. This improves the imaging accuracy and detection efficiency of the objective lens system.

[0044] It should be understood that the description in this section is not intended to identify key or essential features of the embodiments of the present invention, nor is it intended to limit the scope of the invention. Other features of the invention will become readily apparent from the following description. Attached Figure Description

[0045] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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 the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0046] Figure 1 is a schematic diagram of a scanning electron microscope objective system provided in an embodiment of the present invention;

[0047] Figure 2 is a schematic diagram of another scanning electron microscope objective system provided in an embodiment of the present invention;

[0048] Figure 3 is a schematic diagram of a detection device provided in an embodiment of the present invention;

[0049] Figure 4 is a schematic flowchart of a detection method based on a scanning electron microscope objective system provided in an embodiment of the present invention. Detailed Implementation

[0050] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0051] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0052] Figure 1 is a schematic diagram of a scanning electron microscope objective system provided in an embodiment of the present invention. As shown in Figure 1, the scanning electron microscope objective system includes: a magnetic lens device 1, a deflection device 2, an astigmatism corrector 3, a Wien analyzer group 4, and a detection device 5; the magnetic lens device 1 is used to focus the incident electron beam; the magnetic lens device 1 includes a receiving space, and the deflection device 2, the astigmatism corrector 3, the Wien analyzer group 4, and the detection device 5 are all located within the receiving space; the deflection device 2, the astigmatism corrector 3, and the Wien analyzer group 4 are arranged along the optical axis of the incident electron beam and are all arranged around the optical axis; the astigmatism corrector 3... Located below the deflection device 2, the Wien analyzer group 4 is located below the astigmatism reducer 3. The deflection device 2 is used to adjust the direction of motion of the incident electron beam, and the astigmatism reducer 3 is used to adjust the shape of the incident electron beam so as to scan the sample under test through the incident electron beam and make the sample under test generate signal electrons. The Wien analyzer group 4 is used to adjust the direction of motion of the signal electrons so as to make the signal electrons enter the detection device 5. The detection device 5 is located on the side of the deflection device 2, the astigmatism reducer 3 and the Wien analyzer group 4 close to the magnetic lens device 1. The detection device 5 is used to generate a detection signal based on the signal electrons so as to realize the surface imaging of the sample under test.

[0053] Specifically, the incident electron beam can move from top to bottom into the scanning electron microscope objective system, allowing it to move along the optical axis toward the sample. The magnetic lens device 1 may include a pole piece structure and a coil assembly to generate a magnetic field, thereby enabling precise focusing control of the incident electron beam to obtain a smaller incident electron beam spot and improve the resolution of sample scanning.

[0054] The magnetic lens assembly 1 includes a housing space within which the deflection device 2, astigmatism corrector 3, Wien analyzer group 4, and detector 5 are all located. This effectively reduces the structural dimensions of the objective lens system in both the axial and radial directions, facilitating the miniaturization and modular design of scanning electron microscope equipment. The deflection device 2, astigmatism corrector 3, and Wien analyzer group 4 are arranged along the optical axis of the incident electron beam and are all positioned around the optical axis, which helps maintain good electromagnetic field uniformity, thereby aiding in precise control of the motion direction of the incident electron beam and signal electrons. The deflection device 2 may include, for example, an electric deflector or a magnetic deflector, and the astigmatism corrector 3 may include, for example, a quadrupole lens or an octupole astigmatism corrector structure. The astigmatism corrector 3 is located below the deflection device 2, so that when the incident electron beam moves along the optical axis toward the sample under test, its movement direction can be adjusted by the deflection device 2. For example, the deflection device 2 can control the movement direction of the incident electron beam to be adjusted along the X-axis and Y-axis directions respectively, and can correct the non-axisymmetric defocusing phenomenon of the incident electron beam caused by electromagnetic focusing or deflection by the astigmatism corrector 3, so as to ensure that the incident electron beam can be focused on the surface of the sample under test in an ideal shape, such as a circle or Gaussian distribution, so that the surface of the sample under test can be scanned by the incident electron beam. After the incident electron beam bombards the surface of the sample under test, the sample under test will generate signal electrons accordingly. The sample under test can also be connected to a negative voltage, so that the electron energy of the incident electron beam incident on the surface of the sample under test can be adjusted by adjusting the negative voltage connected to the sample under test.

[0055] The signal electrons move along the optical axis away from the sample under test, and their direction of motion can be adjusted by the Wien analyzer group 4, which is located below the astigmatism reducer 3. The Wien analyzer group 4 can include multiple Wien analyzers, thereby enabling the signal electrons to be precisely guided to the detection device 5, improving detection efficiency. Understandably, the separate setup of the deflection device 2 and the Wien analyzer group 4 allows the objective system to optimize the deflection paths of the incident electron beam and the signal electrons separately, avoiding the problems of electric field interference and control coupling when using the same deflection device to deflect both the incident electron beam and the signal electrons simultaneously, thus improving the flexibility and accuracy of electron beam trajectory adjustment.

[0056] The detection device 5 is located on the side of the deflection device 2, astigmatism corrector 3, and Wien analyzer group 4 near the magnetic lens device 1, which further reduces the structural dimensions of the objective lens system in the axial and radial directions, facilitating detection over short working distances. The detection device 5 generates a detection signal based on the signal electrons to achieve surface imaging of the sample under test. The detection device 5 can be, for example, an Everhart-Thornley (ET) detector. Specifically, it converts the signal electrons into an electrical signal and transmits this electrical signal to image processing software for image reconstruction, thereby achieving surface imaging of the sample under test. It is also understood that the signal electrons can include backscattered electrons and secondary electrons. Backscattered electrons reflect the compositional differences in different regions of the sample under test, suitable for analyzing compositional distribution and material contrast; secondary electrons reflect the microstructure and edge structure of the sample surface, suitable for observing three-dimensional contours and surface morphology. The detection device 5 converts the backscattered electrons and secondary electrons generated by the sample under test into backscattered electron detection signals and secondary electron detection signals, respectively. The detection device 5 can also transmit the backscattered electron detection signal and the secondary electron detection signal to the image processing software respectively, so that the backscattered electron image and the secondary electron image can be reconstructed and compared and analyzed respectively. This enables the coordinated detection of the sample surface in two dimensions: composition distribution and morphological features, improving the imaging accuracy and detection efficiency of the objective lens system, and enabling the objective lens system to meet the high-resolution imaging requirements of complex micro-nano structure samples.

[0057] In this embodiment, by incorporating a magnetic lens device, a deflection device, an astigmatism corrector, a Wien analyzer group, and a detection device into the scanning electron microscope objective system, the incident electron beam is directed towards the sample along the optical axis. The incident electron beam is focused by the magnetic lens device, and by housing the deflection device, astigmatism corrector, Wien analyzer group, and detection device within the internal space of the magnetic lens device, the structural size of the objective system is effectively reduced. By arranging the deflection device, astigmatism corrector, and Wien analyzer group around the optical axis and aligned with the optical axis of the incident electron beam, good electromagnetic field uniformity is maintained. By placing the astigmatism corrector below the deflection device and the Wien analyzer group below the astigmatism corrector, the direction of motion of the incident electron beam can be adjusted by the deflection device, and the shape of the incident electron beam can be adjusted by the astigmatism corrector. This allows the incident electron beam to scan the sample, the sample to generate signal electrons, and the direction of motion of the signal electrons can be adjusted by the Wien analyzer group to precisely guide the signal electrons into the detection device. By optimizing the deflection paths of the incident electron beam and the signal electrons using the incident electron beam deflection device and the Wien analyzer group, respectively, the flexibility and accuracy of electron beam trajectory adjustment are improved. Furthermore, by placing the detector device on the side of the deflection device, astigmatism corrector, and Wien analyzer group close to the magnetic lens device, a detection signal is generated based on the signal electrons, enabling surface imaging of the sample under test. This improves the imaging accuracy and detection efficiency of the objective lens system.

[0058] Optionally, Figure 2 is a schematic diagram of another scanning electron microscope objective system provided in an embodiment of the present invention. As shown in Figure 2, the magnetic lens device 1 includes a first upper pole piece 11, a second upper pole piece 12, a lower pole piece 13, and a coil assembly 14; the second upper pole piece 12 and the first upper pole piece 11 are arranged along the optical axis and are both arranged around the optical axis; the second upper pole piece 12 is located above the first upper pole piece 11; the second upper pole piece 12 and the first upper pole piece 11 are insulated from each other; the lower pole piece 13 is arranged around the first upper pole piece 11 and part of the second upper pole piece 12, and the lower pole piece 13 is connected to the second upper pole piece 12; the first upper pole piece 11, the second upper pole piece 12, and the lower pole piece 13 constitute a coil receiving cavity; the coil assembly 14 is located in the coil receiving cavity and is arranged around part of the second upper pole piece 12; the polarity of the first upper pole piece 11 is different from the polarity of the second upper pole piece 12 and the lower pole piece 13.

[0059] Specifically, in the magnetic lens device 1, the second upper pole piece 12 and the first upper pole piece 11 are arranged along the optical axis and both are arranged around the optical axis, that is, the first upper pole piece 11 and the second upper pole piece 12 are both hollow cylindrical structures arranged around the optical axis. The second upper pole piece 12 is located above the first upper pole piece 11, and the second upper pole piece 12 and the first upper pole piece 11 are insulated from each other to avoid current interference caused by potential difference. For example, the material of the first upper pole piece 11 may include a high magnetic permeability material, such as permalloy; the material of the second upper pole piece 12 may include pure iron; the insulating material between the first upper pole piece 11 and the second upper pole piece 12 may include polytetrafluoroethylene. The lower pole piece 13 is arranged around the first upper pole piece 11 and part of the second upper pole piece 12, and the lower pole piece 13 is connected to the second upper pole piece 12 so that the first upper pole piece 11, the second upper pole piece 12, and the lower pole piece 13 can form a coil receiving cavity. For example, the material of the lower pole piece 13 may include pure iron. The coil assembly 14 is located inside the coil receiving cavity and is arranged around the second upper pole piece 12, thereby enabling the magnetic lens device 1 to form a stable magnetic lens magnetic field, which in turn enables the magnetic lens device 1 to perform fine focusing control on the incident electron beam to obtain a smaller incident electron beam spot and improve the resolution of sample scanning.

[0060] In an exemplary embodiment, the first upper shoe 11 can be connected to a high potential voltage, such as 5kV, to apply an electric field to accelerate the incident electron beam, allowing it to accelerate along the optical axis into the sample region. The second upper shoe 12 is electrically connected to and grounded with the lower shoe 13, forming a low potential region relative to the first upper shoe 11. This allows the coil assembly 14 to form an axisymmetric magnetic field in the region between the first upper shoe 11 and the second upper shoe 12 and lower shoe 13 after being energized, enabling magnetic lens focusing of the incident electron beam by the magnetic lens device 1. Since the polarity of the first upper shoe 11 is opposite to that of the second upper shoe 12 and lower shoe 13, a steeper magnetic field gradient can be formed, further improving focusing accuracy, reducing the electron beam spot size, and contributing to improved spatial resolution of sample imaging.

[0061] Optionally, referring to Figure 2, the first upper pole shoe 11 includes a first stepped surface 01; the second upper pole shoe 12 includes a second stepped surface 02; the first stepped surface 01 and the second stepped surface 02 are disposed opposite to each other; an insulating material is disposed in the gap between the first stepped surface 01 and the second stepped surface 02.

[0062] Specifically, the first upper pole piece 11 includes a first stepped surface 01, and the second upper pole piece 12 includes a second stepped surface 02. The first stepped surface 01 and the second stepped surface 02 are arranged opposite to each other, that is, the first stepped surface 01 and the second stepped surface 02 form a gap region between the first upper pole piece 11 and the second upper pole piece 12, and this gap region is filled with insulating material. It can be understood that by setting the first stepped surface 01 and the second stepped surface 02, while ensuring the electrical insulation between the first upper pole piece 11 and the second upper pole piece 12, the facing area of ​​the first upper pole piece 11 and the second upper pole piece 12 in the opposite direction can be increased, thereby expanding the area for the insulating material to be arranged. This helps to improve the electrical insulation strength between the first upper pole piece 11 and the second upper pole piece 12, reduces the risk of electrical breakdown of the magnetic lens device 1, and further improves the performance and stability of the objective lens system.

[0063] Optionally, referring to Figure 2, the deflection device 2 includes a first deflector 201 and a second deflector 202; the first deflector 201, the second deflector 202, and the astigmatism reducer 3 are arranged along the optical axis; the second deflector 202 is located above the astigmatism reducer 3, and the first deflector 201 is located above the second deflector 202.

[0064] Specifically, the first deflector 201, the second deflector 202, and the astigmatism reducer 3 are arranged along the optical axis, with the second deflector 202 positioned above the astigmatism reducer 3 and the first deflector 201 positioned above the second deflector 202. This arrangement ensures that when the incident electron beam moves along the optical axis toward the sample, it passes sequentially through the first deflector 201, the second deflector 202, and the astigmatism reducer 3. The first deflector 201 may include, for example, an electric deflector or a magnetic deflector, for performing a first-stage deflection control on the initially incident electron beam, enabling it to deflect towards a predetermined angle or scanning path. The second deflector 202 may also include, for example, an electric deflector or a magnetic deflector, for further fine control of the incident electron beam after it has been deflected by the first deflector 201, thereby improving the positioning accuracy and scanning consistency of the incident electron beam.

[0065] By setting a first deflector 201, a second deflector 202, and an astigmatism reducer 3 arranged sequentially along the optical axis in the deflection device 2, a multi-level control structure for the incident electron beam is formed, which enables independent control of the trajectory and beam shape of the incident electron beam in stages. This helps to improve the scanning accuracy and response speed of the incident electron beam when scanning the surface of the sample to be tested, and further improves the imaging accuracy and detection efficiency of the objective lens system.

[0066] Optionally, continuing to refer to Figure 2, the scanning electron microscope objective system further includes: an electron converter 6; signal electrons include backscattered electrons and secondary electrons; a Wien analyzer group 4 includes a first Wien analyzer 401 and a second Wien analyzer 402; the electron converter 6, the first Wien analyzer 401, and the second Wien analyzer 402 are arranged along the optical axis; the first Wien analyzer 401 is located above the second Wien analyzer 402, and the electron converter 6 is located above the first Wien analyzer 401; the first Wien analyzer 401 is used to adjust the direction of motion of the backscattered electrons so that the backscattered electrons irradiate the electron converter 6; the electron converter 6 is used to convert the backscattered electrons into converted secondary electrons, and the first Wien analyzer 401 is also used to adjust the direction of motion of the converted secondary electrons so that the converted secondary electrons enter the detection device 5; the second Wien analyzer 402 is used to adjust the direction of motion of the secondary electrons so that the secondary electrons enter the detection device 5.

[0067] Specifically, the electron converter 6, the first Wien analyzer 401, and the second Wien analyzer 402 are arranged along the optical axis, with the first Wien analyzer 401 positioned above the second Wien analyzer 402, and the electron converter 6 positioned above the first Wien analyzer 401. The first Wien analyzer 401 can be understood as an electromagnetic composite field deflection device, which simultaneously applies a perpendicular electric field and a magnetic field, with the electric and magnetic forces in opposite directions. This allows the first Wien analyzer 401 to selectively transmit electrons with specific velocities or energies. Therefore, the first Wien analyzer 401 can first maintain the direction of motion of the incident electron beam moving along the optical axis towards the sample, and can be used to control the trajectory of backscattered electrons generated after the sample is scanned by the incident electron beam, ensuring that the backscattered electrons are accurately guided to the electron converter 6. Because backscattered electrons have high energy, they cannot be directly deflected to the detection device 5 by the first Wien analyzer 401. Therefore, the high-energy backscattered electrons are first converted into lower-energy secondary electrons by an electron converter 6. For example, the electron converter 6 may include a conversion target material. After the backscattered electrons collide with the conversion target material, they excite the secondary electrons. The secondary electrons have lower energy and are easier for the detection device 5 to collect efficiently, effectively improving the signal-to-noise ratio and imaging consistency. After the electron converter 6 excites the secondary electrons, the first Wien analyzer 401 can further adjust the direction of motion of the secondary electrons to ultimately guide them precisely into the detection device 5.

[0068] The second Wien analyzer 402 is structurally similar to the first Wien analyzer 401. The second Wien analyzer 402 can also be used to maintain the direction of motion of the incident electron beam moving along the optical axis towards the sample under test, and can be used to control the trajectory of secondary electrons generated after the sample under test is scanned by the incident electron beam. This ensures that the secondary electrons can be accurately guided to the detection device 5, which helps improve the collection efficiency of weak signals and the imaging sensitivity. It is understood that backscattered electrons and secondary electrons have significant differences in energy, divergence angle, and signal characteristics. By setting two independent first Wien analyzers 401 and second Wien analyzers 402 in the Wien analyzer group 4, the first Wien analyzer 401 and the second Wien analyzer 402 can respectively control the paths of the two types of electron beams, allowing the backscattered electrons and secondary electrons to converge to the detection device 5, thereby avoiding signal aliasing and improving the imaging accuracy and detection efficiency of the objective lens system.

[0069] Optionally, referring to Figure 2, the detection device 5 includes a backscattered electron detection device 51 and a secondary electron detection device 52; the backscattered electron detection device 51 and the secondary electron detection device 52 are located on opposite sides of the optical axis, and the position of the backscattered electron detection device 51 is higher than the position of the secondary electron detection device 52; the backscattered electron detection device 51 is used to generate a backscattered electron detection signal based on the converted secondary electrons whose motion direction has been adjusted by the first Wien analyzer 401; the secondary electron detection device 52 is used to generate a secondary electron detection signal based on the secondary electrons whose motion direction has been adjusted by the second Wien analyzer 402.

[0070] Specifically, the backscattered electron detection device 51 generates a backscattered electron detection signal based on the converted secondary electrons whose motion direction has been adjusted by the first Wien analyzer 401. The backscattered electron detection device 51 is suitable for converted secondary electrons with higher energy, longer propagation paths, and stronger directionality. The secondary electron detection device 52 generates a secondary electron detection signal based on the secondary electrons whose motion direction has been adjusted by the second Wien analyzer 402. The secondary electron detection device 52 is suitable for secondary electrons with lower energy and stronger divergence. It can be understood that by setting the backscattered electron detection device 51 and the secondary electron detection device 52 on opposite sides of the optical axis, and setting the position of the backscattered electron detection device 51 higher than the position of the secondary electron detection device 52, the backscattered electron detection device 51 can receive the converted secondary electrons deflected by the first Wien analyzer 401 located at a higher position. Simultaneously, the secondary electron detection device 52 is close to the output port of the second Wien analyzer 402 to match the incident path of the secondary electrons. By arranging the backscattered electron detector 51 and the secondary electron detector 52 in a relatively staggered manner, physical isolation is achieved between them in the reception of backscattered electrons and secondary electrons, effectively avoiding problems such as signal overlap and mutual interference. The backscattered electron detector 51 and the secondary electron detector 52 can also transmit the backscattered electron detection signal and the secondary electron detection signal to image processing software respectively, enabling image reconstruction and comparative analysis of the backscattered electron image and the secondary electron image. This allows for coordinated detection of both the compositional distribution and morphological characteristics of the sample surface, improving the imaging accuracy and detection efficiency of the objective lens system.

[0071] Optionally, Figure 3 is a schematic diagram of a detection device provided in an embodiment of the present invention. As shown in Figures 2 and 3, the backscattered electron detection device 51 includes a first scintillator 501, a first light guide 502, and a first photomultiplier tube 503; the secondary electron detection device 52 includes a second scintillator 504, a second light guide 505, and a second photomultiplier tube 506; the first scintillator 501 is used to generate a first fluorescence signal under the excitation of converted secondary electrons; the first light guide 502 is used to transmit the first fluorescence signal to the first photomultiplier tube 503; the first photomultiplier tube 503 is used to convert the first fluorescence signal into an electrical signal to generate a backscattered electron detection signal; the second scintillator 504 is used to generate a second fluorescence signal under the excitation of secondary electrons; the second light guide 505 is used to transmit the second fluorescence signal to the second photomultiplier tube 506; the second photomultiplier tube 506 is used to convert the second fluorescence signal into an electrical signal to generate a secondary electron detection signal.

[0072] Specifically, the backscattered electron detection device 51 includes a first scintillator 501, a first light guide 502, and a first photomultiplier tube 503, while the secondary electron detection device 52 includes a second scintillator 504, a second light guide 505, and a second photomultiplier tube 506. The first scintillator 501 and the second scintillator 504 have high electron-photon conversion efficiency, respectively used to convert the kinetic energy of secondary electrons into band transitions within the material when secondary electrons collide with the surface, thereby generating a first fluorescence signal or a second fluorescence signal. The first light guide 502 and the second light guide 505 can be understood as optical waveguide channels composed of transparent media, used to guide the first fluorescence signal or the second fluorescence signal from the first scintillator 501 or the second scintillator 504 to the first photomultiplier tube 503 or the second photomultiplier tube 506, respectively. The first light guide 502 and the second light guide 505 can utilize the principle of total internal reflection to transmit the fluorescence signal efficiently within the channel, thereby ensuring maximum preservation of signal strength and directionality even in space-constrained or bent layouts. The first photomultiplier tube 503 and the second photomultiplier tube 506 may specifically include a photocathode, a multiplying electrode, and an electrical signal output terminal. The first photomultiplier tube 503 and the second photomultiplier tube 506 are used to control the fluorescent signal input from the first photomultiplier tube 503 or the second photomultiplier tube 506 to strike the photocathode to release primary photoelectrons. The primary photoelectrons can be successively struck by the multiplying electrode to release more secondary electrons, thereby realizing exponential current amplification and finally outputting an electrical signal that can be used for image reconstruction.

[0073] Understandably, ET detectors offer high signal collection efficiency and fast detection speed. By configuring both the backscattered electron detection device 51 and the secondary electron detection device 52 as ET detectors, high-quality image reconstruction of the sample surface can be achieved. Furthermore, backscattered electrons and secondary electrons differ in energy, scattering angle, and timing. By independently setting up dual detection links, backscattered electrons and secondary electrons can be responded to and detected separately, enabling the objective lens system to collaboratively meet the imaging requirements of the sample's material composition and surface morphology.

[0074] Optionally, referring to Figures 2 and 3, the length of the first light guide 502 along the optical axis is less than the length of the second light guide 505 along the optical axis; the length of the first photomultiplier tube 503 along the optical axis is greater than the length of the second photomultiplier tube 506 along the optical axis.

[0075] It is understandable that the position of the backscattered electron detection device 51 is higher than that of the secondary electron detection device 52, which makes the distance between the first optical guide 502 and the electron beam exit side 02 greater than the distance between the second optical guide 505 and the electron beam exit side 02. Therefore, by setting the length of the first optical guide 502 along the optical axis to be less than the length of the second optical guide 505 along the optical axis, the height difference between the backscattered electron detection device 51 and the secondary electron detection device 52 can be compensated, so that the first photomultiplier tube 503 and the second photomultiplier tube 506 are approximately on the same horizontal plane.

[0076] It is also understandable that the first fluorescence signal excited by the converted secondary electrons in the first scintillator 501 typically has a low intensity, making a long photomultiplier tube with a wider response band and higher amplification suitable. Conversely, the second fluorescence signal excited by the secondary electrons in the second scintillator 504 has a strong fluorescence response, allowing for the use of a short photomultiplier tube with a smaller size and faster response, thus optimizing timing control and image acquisition speed. Therefore, by appropriately setting the length of the first photomultiplier tube 503 along the optical axis to be greater than that of the second photomultiplier tube 506 along the optical axis, the characteristics of the converted secondary electrons and the secondary electrons themselves can be matched, thereby achieving synergistic optimization of the detection path and detection sensitivity, and improving the imaging quality and integration performance of the objective lens system.

[0077] Optionally, continuing to refer to Figure 2, the scanning electron microscope objective system also includes: a secondary electron absorption electrode 7; the signal electrons include backscattered electrons and secondary electrons; the secondary electron absorption electrode 7 is arranged around the optical axis and is located below the Wien analyzer group 4; the secondary electron absorption electrode 7 is used to accelerate the movement of secondary electrons.

[0078] Understandably, the secondary electrons excited on the surface of the sample have low energy, slow speed, and diffuse trajectories, making them susceptible to interference from stray electromagnetic fields or re-adsorption. Therefore, a secondary electron absorption electrode 7 is also provided around the optical axis, and this electrode 7 is located below the Wien analyzer group 4, meaning it is positioned in the path of the secondary electrons before they are deflected by the second Wien analyzer 402. A positive potential can be applied to the secondary electron absorption electrode 7, thereby establishing a collecting electric field above the sample. This accelerates and guides the low-energy secondary electrons rapidly toward the second Wien analyzer 402, reducing energy loss and diffusion loss, increasing the number of secondary electrons entering the second Wien analyzer 402, and thus enhancing the signal strength of the secondary electron detection signal. This further improves the imaging accuracy and detection efficiency of the objective lens system.

[0079] Based on the same inventive concept, this invention also provides a detection method applicable to the scanning electron microscope objective system described above. Figure 4 is a flowchart illustrating a detection method based on a scanning electron microscope objective system provided by this invention. As shown in Figure 4, the detection method includes:

[0080] S101. The incident electron beam moves from top to bottom into the scanning electron microscope objective system, so that the incident electron beam moves along the optical axis toward the sample to be tested.

[0081] S102. The incident electron beam is focused by a magnetic lens device, deflected by a deflection device, and its shape is adjusted by an astigmatism reducer before scanning the sample to be tested, so that the sample to be tested generates signal electrons.

[0082] S103, the signal electrons move along the optical axis away from the sample to be tested, and after being deflected by the Wien analyzer group, they enter the detection device.

[0083] S104. The detection device generates a detection signal based on the signal electronics to achieve surface imaging of the sample to be tested.

[0084] Specifically, the incident electron beam enters the scanning electron microscope objective system from top to bottom, allowing it to move along the optical axis towards the sample. The magnetic lens device 1 generates a magnetic field, enabling precise focusing control of the incident electron beam to obtain a smaller beam spot and improve sample scanning resolution. The astigmatism reducer 3, located below the deflection device 2, allows the direction of the incident electron beam along the optical axis towards the sample to be adjusted by the deflection device 2, and its shape can be adjusted by the astigmatism reducer 3, thus enabling the incident electron beam to scan the sample surface. After the incident electron beam bombards the sample surface, the sample generates signal electrons. These signal electrons move along the optical axis away from the sample. The Wien analyzer group 4, located below the astigmatism reducer 3, allows the direction of the signal electrons to be adjusted, precisely guiding them to the detection device 5 and improving detection efficiency. The detection device 5 is used to generate a detection signal based on the signal electrons to achieve surface imaging of the sample under test. The detection device 5 can convert the backscattered electrons and secondary electrons generated by the sample under test into backscattered electron detection signals and secondary electron detection signals, respectively. The detection device 5 can also transmit the backscattered electron detection signals and secondary electron detection signals to image processing software, enabling image reconstruction and comparative analysis of the backscattered electron image and the secondary electron image, respectively. This allows for coordinated detection of both the compositional distribution and morphological features of the sample surface, improving the imaging accuracy and detection efficiency of the objective lens system.

[0085] It should be understood that the various forms of processes shown above can be used to reorder, add, or delete steps. For example, the steps described in this invention can be executed in parallel, sequentially, or in different orders, as long as the desired result of the technical solution disclosed in this invention can be achieved, and this is not limited herein.

[0086] The specific embodiments described above do not constitute a limitation on the scope of protection of this invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this invention should be included within the scope of protection of this invention.

Claims

1. A scanning electron microscope objective system, characterized in that, include: Magnetic lens assembly, deflection device, astigmatism corrector, Wien analyzer assembly, and detection device; The magnetic lens device is used to focus the incident electron beam. The magnetic lens device includes a receiving space within which the deflection device, the astigmatism corrector, the Wien analyzer group, and the detection device are all located. The deflection device, the astigmatism corrector, and the Wien analyzer group are arranged along the optical axis of the incident electron beam and are all positioned around the optical axis. The astigmatism corrector is located below the deflection device, and the Wien analyzer group is located below the astigmatism corrector. The deflection device is used to adjust the direction of motion of the incident electron beam, and the astigmatism corrector is used to adjust the shape of the incident electron beam to scan the sample under test and generate signal electrons from the sample. The Wien analyzer group is used to adjust the direction of motion of the signal electrons so that the signal electrons enter the detection device. The detection device is located on the side of the deflection device, the astigmatism corrector, and the Wien analyzer group closest to the magnetic lens device. The detection device is used to generate a detection signal based on the signal electrons to achieve surface imaging of the sample under test.

2. The scanning electron microscope objective system according to claim 1, characterized in that, The magnetic lens device includes a first upper pole piece, a second upper pole piece, a lower pole piece, and a coil assembly; the second upper pole piece and the first upper pole piece are arranged along the optical axis and are both arranged around the optical axis; the second upper pole piece is located above the first upper pole piece; the second upper pole piece and the first upper pole piece are insulated from each other; the lower pole piece is arranged around the first upper pole piece and part of the second upper pole piece, and the lower pole piece is connected to the second upper pole piece; the first upper pole piece, the second upper pole piece, and the lower pole piece constitute a coil receiving cavity; the coil assembly is located in the coil receiving cavity and is arranged around part of the second upper pole piece; the polarity of the first upper pole piece is different from the polarity of the second upper pole piece and the lower pole piece.

3. The scanning electron microscope objective system according to claim 2, characterized in that, The first upper pole shoe includes a first stepped surface; the second upper pole shoe includes a second stepped surface; the first stepped surface and the second stepped surface are disposed opposite to each other; an insulating material is disposed in the gap between the first stepped surface and the second stepped surface.

4. The scanning electron microscope objective system according to claim 1, characterized in that, The deflection device includes a first deflector and a second deflector; the first deflector, the second deflector, and the astigmatism reducer are arranged along the optical axis; the second deflector is located above the astigmatism reducer, and the first deflector is located above the second deflector away from the astigmatism reducer.

5. The scanning electron microscope objective system according to claim 1, characterized in that, Also includes: An electron converter; the signal electrons include backscattered electrons and secondary electrons; the Wien analyzer group includes a first Wien analyzer and a second Wien analyzer; the electron converter, the first Wien analyzer, and the second Wien analyzer are arranged along the optical axis; The first Wien analyzer is located above the second Wien analyzer, and the electron converter is located above the first Wien analyzer. The first Wien analyzer is used to adjust the direction of motion of the backscattered electrons so that the backscattered electrons irradiate the electron converter. The electron converter is used to convert the backscattered electrons into converted secondary electrons. The first Wien analyzer is also used to adjust the direction of motion of the converted secondary electrons so that the converted secondary electrons enter the detection device. The second Wien analyzer is used to adjust the direction of motion of the secondary electrons so that the secondary electrons enter the detection device.

6. The scanning electron microscope objective system according to claim 5, characterized in that, The detection device includes a backscattered electron detection device and a secondary electron detection device; the backscattered electron detection device and the secondary electron detection device are located on opposite sides of the optical axis, and the backscattered electron detection device is positioned higher than the secondary electron detection device; the backscattered electron detection device is used to generate a backscattered electron detection signal based on the converted secondary electrons whose motion direction has been adjusted by the first Wien analyzer; the secondary electron detection device is used to generate a secondary electron detection signal based on the secondary electrons whose motion direction has been adjusted by the second Wien analyzer.

7. The scanning electron microscope objective system according to claim 6, characterized in that, The backscattered electron detection device includes a first scintillator, a first light guide, and a first photomultiplier tube; the secondary electron detection device includes a second scintillator, a second light guide, and a second photomultiplier tube; the first scintillator is used to generate a first fluorescence signal under the excitation of the converted secondary electrons; The first light guide is used to transmit the first fluorescence signal to the first photomultiplier tube; The first photomultiplier tube is used to convert the first fluorescence signal into an electrical signal to generate the backscattered electron detection signal; the second scintillator is used to generate a second fluorescence signal under the excitation of the secondary electrons; The second light guide is used to transmit the second fluorescence signal to the second photomultiplier tube; The second photomultiplier tube is used to convert the second fluorescence signal into an electrical signal to generate the secondary electron detection signal.

8. The scanning electron microscope objective system according to claim 7, characterized in that, The length of the first light guide along the optical axis is less than the length of the second light guide along the optical axis; the length of the first photomultiplier tube along the optical axis is greater than the length of the second photomultiplier tube along the optical axis.

9. The scanning electron microscope objective system according to claim 1, characterized in that, It also includes: a secondary electron absorption electrode; the signal electrons include backscattered electrons and secondary electrons; the secondary electron absorption electrode is arranged around the optical axis and is located below the Wien analyzer group; the secondary electron absorption electrode is used to accelerate the movement of the secondary electrons.

10. A detection method based on a scanning electron microscope objective system, characterized in that, include: The incident electron beam moves from top to bottom into the scanning electron microscope objective system, so that the incident electron beam moves along the optical axis toward the sample to be tested. The incident electron beam is focused by a magnetic lens device, deflected by a deflection device, and shaped by an astigmatism reducer before scanning the sample to be tested, so that the sample to be tested generates signal electrons; the signal electrons move along the optical axis away from the sample to be tested, and enter the detection device after being deflected by the Wien analyzer group. The detection device generates a detection signal based on the signal electrons to achieve surface imaging of the sample to be tested.

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