Scanning electron microscope objective system and scanning focusing method

Abstract

The embodiment of the present disclosure provides a scanning electron microscope objective lens system and a scanning focusing method, wherein the objective lens system comprises a magnetic lens, a first deflection device, a detection device, a second deflection device and a sample stage; wherein: the magnetic lens comprises a main body part and a magnetic pole shoe; the first deflection device is located between the inner wall of the main body part and the optical axis of the electron beam, and is used for changing the movement direction of the incident electron beam; the detection device is located between the first deflection device and the second deflection device, and is used for receiving signal electrons generated by the electron beam acting on a sample to be measured on the sample stage; the second deflection device is located between the main body part and the magnetic pole shoe, and is used for changing the movement direction of the electron beam; the detection device, the second deflection device, the magnetic pole shoe and the sample stage form an electric lens; and the electric lens and the magnetic lens form a compound objective lens, which is used for converging the electron beam.

Description

Technical Field

[0001] This disclosure relates to the field of scanning electron microscopy, and to, but is not limited to, a scanning electron microscope objective system and a scanning focusing method. Background Technology

[0002] Scanning electron microscopes (SEMs) are widely used in various fields requiring fine observation of material structures due to their higher resolution compared to optical microscopes, including semiconductors, biomedicine, and materials science. However, because most SEMs use magnetic lenses to focus the electron beam, and the magnetic field of these lenses is not zero at the sample (i.e., immersion objectives), when observing magnetic or ferromagnetic materials, the magnetic field covering the sample is interfered with, resulting in unclear images and causing various inconveniences. Summary of the Invention

[0003] This disclosure provides a scanning electron microscope objective system and a scanning focusing method.

[0004] In a first aspect, embodiments of this disclosure provide a scanning electron microscope objective system, comprising: a magnetic lens, a first deflection device, a detection device, a second deflection device, and a sample stage; wherein: the magnetic lens includes a main body and a magnetic pole piece; the first deflection device is located between the inner wall of the main body and the optical axis of the electron beam, and is used to change the direction of motion of the incident electron beam; the detection device is located between the first deflection device and the second deflection device, and is used to receive signal electrons generated by the electron beam acting on the sample to be tested on the sample stage; the second deflection device is located between the main body and the magnetic pole piece, and is used to change the direction of motion of the electron beam; the detection device, the second deflection device, the magnetic pole piece, and the sample stage form an electric lens; the electric lens and the magnetic lens form a composite lens for converging the electron beam.

[0005] In some embodiments, the opening of the magnetic pole shoe faces the sample to be tested, and the extension direction of the end of the magnetic pole shoe is horizontal, the same as the extension direction of the end of the magnetic housing of the main body.

[0006] In some embodiments, the maximum magnetic field strength of the magnetic lens is located between the opening of the magnetically conductive housing of the main body and the opening of the magnetically conductive pole shoe; the magnetic field strength of the magnetic lens at the location of the sample to be tested is 0.

[0007] In some embodiments, the voltage V1 of the magnetic pole shoe and the voltage V2 of the sample stage are related as follows: V2-5 kV ≤ V1 ≤ V2+5 kV, the voltage V2 of the sample stage is in the range of -15 kV to 0 kV, and the voltage of the magnetic housing is 0 kV.

[0008] In some embodiments, the diameter of the central hole of the magnetic pole shoe, the diameter of the central hole of the second deflection device, and the diameter of the central hole of the detection device decrease sequentially.

[0009] In some embodiments, the objective system further includes: a first isolation structure for isolating the main body portion and the magnetic pole shoe; and / or a second isolation structure for isolating the second deflection device, the detection device, and the main body portion.

[0010] Secondly, embodiments of this disclosure provide a scanning focusing method, comprising: when an incident electron beam passes through the central axis of a scanning electron microscope objective system, the electron beam is focused by a compound lens system, and the direction of motion of the electron beam is changed by applying voltages to a first deflection device and a second deflection device to obtain an electron beam acting on a sample on a sample stage; wherein, the compound lens includes a magnetic lens and an electric lens; the electric lens includes, from top to bottom, a detection device, a second deflection device, a magnetic pole piece of the magnetic lens, and the sample stage.

[0011] In some embodiments, the voltage applied to the first deflection device and the second deflection device is one of the following: the voltage applied to the first deflection device and the second deflection device is an alternating voltage; the voltage applied to the first deflection device is an alternating voltage and the voltage applied to the second deflection device is a constant voltage; wherein the voltage range of the constant voltage is -5kV to 5kV; the voltage applied to the first deflection device is an alternating voltage and the voltage applied to the second deflection device is a superposition of a constant voltage and a constant deflection voltage.

[0012] In some embodiments, the method further includes: after the electron lens reverses the acceleration of the signal electrons generated by the electron beam acting on the sample under test and changes the direction of motion of the signal electrons, the method receives the signal electrons through a detection device.

[0013] In this embodiment, firstly, the magnetic field distribution of the magnetic lens is changed by setting a magnetic pole shoe in the magnetic lens, so that the magnetic field strength at the position of the sample to be tested is 0, that is, the objective lens system is non-immersion. Such a scanning electron microscope objective lens system can observe not only non-magnetic samples to be tested, but also magnetic samples to be tested, and can obtain high-quality images in both cases. Secondly, a first deflection device is set between the inner wall of the main body of the magnetic lens and the optical axis of the electron beam, and a second deflection device is set between the main body and the magnetic pole shoe. The detection device, the second deflection device, the magnetic pole shoe and the sample stage form an electric lens, and the electric lens and the magnetic lens form a composite lens. In this way, the composite lens focuses and converges the incident electron beam, and the electric lens decelerates the converged electron beam. The decelerated electron beam scans on the sample to be tested under the deflection field generated by the second deflection device and the second deflection device to generate signal electrons, and the detection device collects the signal electrons. Attached Figure Description

[0014] In the accompanying drawings (which are not necessarily drawn to scale), similar reference numerals may describe similar parts in different views. Similar reference numerals with different letter suffixes may indicate different examples of similar parts. The drawings illustrate, by way of example and not limitation, the various embodiments discussed herein.

[0015] Figure 1 This is a schematic diagram of the composition of a scanning electron microscope objective system provided in an embodiment of the present disclosure;

[0016] Figure 2 This is a schematic diagram of the electric and magnetic field distributions in a scanning electron microscope objective system according to an embodiment of the present disclosure;

[0017] Figure 3 This is a schematic diagram of the shape of a second deflection device provided in an embodiment of the present disclosure;

[0018] Figure 4 This is a schematic diagram of the shape of another second deflection device provided in an embodiment of this disclosure;

[0019] Figure 5 This is a schematic diagram illustrating the voltage conditions of various parts of an electric lens according to an embodiment of the present disclosure;

[0020] Figure 6 A schematic diagram showing the size relationship between the center hole of the magnetic pole shoe, the center hole of the second deflection device, and the center hole of the detection device provided in an embodiment of this disclosure;

[0021] Figure 7 A schematic diagram illustrating the implementation process of a scanning focusing method provided in this embodiment of the present disclosure;

[0022] Figure 8 This is a schematic diagram of a first scanning focusing method provided in an embodiment of the present disclosure;

[0023] Figure 9 This is a schematic diagram of a second scanning and focusing method provided in an embodiment of the present invention;

[0024] Figure 10 This is a schematic diagram of a third scanning and focusing method provided in an embodiment of the present invention. Detailed Implementation

[0025] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the specific embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art.

[0026] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of this disclosure. However, it will be apparent to those skilled in the art that this disclosure may be practiced without one or more of these details. In other instances, to avoid confusion with this disclosure, certain technical features well-known in the art have not been described; that is, not all features of actual embodiments are described herein, nor are well-known functions and structures described in detail.

[0027] In the accompanying drawings, for clarity, the dimensions of layers, areas, and elements, as well as their relative dimensions, may be exaggerated. The same reference numerals denote the same elements throughout.

[0028] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit this disclosure. When used herein, the singular forms “a,” “an,” and “the” are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprise” and / or “comprising,” when used in this specification, identify the presence of the stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups. When used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0029] In view of this, embodiments of this disclosure provide a non-immersion objective lens system such that the magnetic field of the magnetic lens is zero at the sample under test, meaning the sample under test is not within the focusing magnetic field region formed by the magnetic lens. Therefore, when observing magnetic or ferromagnetic samples, the electron beam is not affected by the magnetic permeability of the sample under test, thereby enabling the acquisition of high-quality images on magnetic samples.

[0030] This disclosure provides a scanning electron microscope objective system, with reference to... Figure 1The objective lens system includes a magnetic lens, a first deflection device 103, a second deflection device 104, a detection device 105, and a sample stage 106; wherein:

[0031] The magnetic lens includes a main body 101 and a magnetic pole shoe 102;

[0032] The first deflection device 103 is located between the inner wall of the main body 101 and the optical axis of the electron beam, and is used to change the direction of motion of the incident electron beam.

[0033] The second deflection device 104 is located between the main body 101 and the magnetic pole shoe 102, and is used to change the direction of motion of the electron beam;

[0034] The detection device 105 is located between the first deflection device 103 and the second deflection device 104, and is used to receive the signal electrons generated by the electron beam acting on the sample to be tested on the sample stage.

[0035] The detection device 105, the second deflection device 104, the magnetic pole shoe 102, and the sample stage 106 form an electric lens; the electric lens and the magnetic lens form a composite lens for focusing the electron beam.

[0036] During use, the incident electron beam is converged by the compound lens when it passes through the central axis 109 of the objective lens system, and the direction of motion of the electron beam is changed by the voltage applied to the first deflection device 103 and the second deflection device 104, so as to obtain the electron beam acting on the sample to be tested on the sample stage; the detection device collects the signal electrons generated by the electron beam acting on the sample to be tested.

[0037] In this embodiment, firstly, the magnetic field distribution of the magnetic lens is changed by setting a magnetic pole shoe in the magnetic lens, so that the magnetic field strength at the position of the sample to be tested is 0, that is, the objective lens system is non-immersion. Such a scanning electron microscope objective lens system can observe not only non-magnetic samples to be tested, but also magnetic samples to be tested, and can obtain high-quality images in both cases. Secondly, a first deflection device is set between the inner wall of the main body of the magnetic lens and the optical axis of the electron beam, and a second deflection device is set between the main body and the magnetic pole shoe. The detection device, the second deflection device, the magnetic pole shoe and the sample stage form an electric lens, and the electric lens and the magnetic lens form a composite lens. In this way, the composite lens focuses and converges the incident electron beam, and the electric lens decelerates the converged electron beam. The decelerated electron beam scans on the sample to be tested under the deflection field generated by the second deflection device and the second deflection device to generate signal electrons, and the detection device collects the signal electrons.

[0038] It should be noted that the composite lens is used to focus the electron beam; wherein, the electron beam is generated by an electron source and incident on the objective lens system. Electron sources are divided into field emission sources and thermal emission sources. Field emission sources are further divided into hot field and cold field types, while thermal emission sources include tungsten filaments, lanthanum hexaboride, etc. In the embodiments of this disclosure, the electron source can be any type of electron source used to generate the electron beam.

[0039] In some embodiments, reference Figure 1 The main body 101 of the magnetic lens may include an excitation coil 101a and a magnetic housing 101b. The magnetic housing 101b is made of a magnetically conductive material, which may include a soft magnetic material, such as iron, iron alloys, or other relatively high permeability materials used to provide a low magnetic reluctance path for the magnetic field generated by the excitation coil.

[0040] The excitation coil 101a can be formed by winding stranded wire; in practice, the focusing characteristics of the magnetic lens can be changed by changing the current in the excitation coil 101a.

[0041] The openings of the magnetic housing 101b facing the sample under test are the inner pole shoe 101c and the outer pole shoe 101d. The pole shoe closer to the optical axis or the central axis 109 of the objective lens system is the inner pole shoe 101c, and the pole shoe farther from the optical axis is the outer pole shoe 101d. The optical axis refers to the optical central axis of the electron beam.

[0042] In some embodiments, continue to refer to Figure 1 The opening of the magnetic pole piece 102 faces the sample to be tested (or the sample stage 106), and the extension direction of the end of the magnetic pole piece 102 is horizontal, the same as the extension direction of the end of the magnetic housing 101b of the main body 101 (or the outer pole piece 101d). This ensures that the direction of the magnetic field generated by the magnetic housing is the same as the placement direction of the magnetic pole piece, which helps maintain a smooth magnetic circuit, reduces magnetic field leakage, and improves the non-immersion effect.

[0043] The function of the magnetic pole shoes is to conduct magnetism and change the magnetic field distribution, thereby making the magnetic field strength at the sample under test zero, which means that the magnetic lens is a non-immersion magnetic lens. (Reference) Figure 2 Curve B(z)120 is a schematic diagram of the magnetic field distribution of the magnetic lens on the optical axis. It can be seen that the maximum magnetic field strength of the magnetic lens is located between the opening of the magnetic housing and the opening of the magnetic pole shoe; the magnetic field strength of the magnetic lens at the position of the sample to be tested is 0.

[0044] It should be noted that the magnetic pole shoe is not only part of the magnetic lens, but also part of the electric lens; that is, the magnetic pole shoe belongs to both magnetic lenses and electric lenses.

[0045] In some embodiments, the voltage V1 of the magnetic pole shoe and the voltage V2 of the sample stage are related as follows: V2 - 5kV ≤ V1 ≤ V2 + 5kV, and the voltage V2 of the sample stage ranges from -15kV to 0kV; the voltage of the magnetic housing is 0kV. Here, the voltage V2 of the magnetic pole shoe can be an adjustable voltage; the magnetic housing can be grounded. In this way, the electric lens generates a deceleration field between the magnetic lens and the sample stage (or the sample to be tested), reducing the speed of the electron beam and allowing the electron beam to obtain lower landing point energy when it reaches the sample, thereby reducing the charge effect of the non-conductive sample.

[0046] In practice, the range of the second voltage V2 can be -15kV≤V2≤0kV; the range of the first voltage V1 can be V2-5kV≤V1≤V2+5kV, that is, -20kV≤V1≤5kV.

[0047] Continue to refer to Figure 1 The first deflection device 103 is located inside the main body 101 of the magnetic lens. In implementation, the first deflection device 103 may include at least one sub-deflector, for example, the first deflection device 103 includes two sub-deflectors, namely a first sub-deflector 103a and a second sub-deflector 103b. The first sub-deflector 103a is located above the second sub-deflector 103b. The first sub-deflector 103a and the second sub-deflector 103b may be entirely electric deflectors, entirely magnetic deflectors, or a combination of electric and magnetic deflectors.

[0048] In some embodiments, the first deflection device may include multiple sub-deflectors arranged sequentially from top to bottom along the central axis of the objective lens system. Furthermore, when the multiple sub-deflectors are a combination of electrical and magnetic deflectors, the positions of the electrical and magnetic deflectors are not limited. For example, when the first deflection device includes four sub-deflectors, they may be arranged sequentially from top to bottom along the central axis of the objective lens system: an electrical deflector, an electrical deflector, a magnetic deflector, and a magnetic deflector; or they may be arranged sequentially from top to bottom along the central axis of the objective lens system: an electrical deflector, a magnetic deflector, an electrical deflector, and a magnetic deflector; or they may be arranged sequentially from top to bottom along the central axis of the objective lens system: a magnetic deflector, a magnetic deflector, and an electrical deflector. Of course, there are various combinations of the types and positions of the multiple sub-deflectors, which will not be detailed here.

[0049] In some embodiments, the first deflection device or the second deflection device has an eight-petal structure; or, the first deflection device or the second deflection device has a twelve-petal structure. In implementation, both the first deflection device and the second deflection device can be eight-petal structures; or, both can be twelve-petal structures; or, the first deflection device has an eight-petal structure and the second deflection device has a twelve-petal structure; or, the second deflection device has an eight-petal structure and the first deflection device has a twelve-petal structure. This disclosure does not limit the structure of the first deflection device and the second deflection device.

[0050] Continue to refer to Figure 1 The second deflection device 104 is located below the opening of the magnetic lens body 101, and the second deflection device 104 can be an electric deflector. In implementation, the electric deflector is as follows: Figure 3 The eight-lobed electrical deflector 104a shown, or as... Figure 4 The electric deflector 104b with a twelve-lobed structure is shown. The more lobes an electric deflector has, the closer its structural shape is to a circle and the more symmetrical it is, resulting in more precise deflection and thus a better deflection effect.

[0051] When an incident electron beam interacts with a sample, it generates signal electrons. These signal electrons, produced by the electron beam's interaction with the sample, include secondary electrons and backscattered electrons. Backscattered electrons are high-energy electrons that escape from the sample surface again after the incident electrons interact with the sample (elastic and inelastic scattering). Secondary electrons are generated when the incident electrons interact with the sample, causing ionization of the outer electrons (valence band or conduction band electrons) of sample atoms.

[0052] In practice, the detection device is grounded, meaning its voltage is 0. The detection device can be a circular semiconductor detector with a central hole, an avalanche detector, or a detector composed of a scintillator and a light guide. The detection device 105 is located between the inner pole shoe 101c and the second deflection device 104, that is, the second deflection device 104 is located below the detection device 105 and above the magnetic pole shoe 102.

[0053] The sample stage holds the sample to be tested, which can be a magnetic sample or a non-magnetic sample.

[0054] In this embodiment of the disclosure, the electro-optic lens includes a detection device, a second deflection device, a magnetic pole shoe, and a sample stage, used to focus the electron beam, simultaneously reverse-accelerate the signal electrons and change their trajectory, thereby improving collection efficiency. In some embodiments, the potential diagrams of the various parts of the electro-optic lens are shown below. Figure 5 As shown, the detection device 105 is grounded, and the second deflection device 104 is connected to a constant voltage V. pThe magnetic pole shoe 102 is connected to a voltage V1, and the sample stage 106 is connected to a voltage V2. (Reference) Figure 2 Curve E1(z)121 is a schematic diagram of the electric field formed by the magnetic pole shoe under an adjustable voltage V1, and curve E1(z)122 is a schematic diagram of the electric field formed by the second deflection device under voltage V1. p A schematic diagram of the electric field formed below. Thus, each part of the electric lens has a potential, and they work together to decelerate, focus, and deflect the incident electron beam, while accelerating and collecting the signal electron beam.

[0055] In some embodiments, continue to refer to Figure 5 The electron lens accelerates the signal electrons 110 generated by the electron beam acting on the sample toward the detection device 105, and the trajectory becomes a convergence shape, which can pass through the magnetic pole shoe 102 and the central hole of the second deflection device 104 and be efficiently collected by the detection device 105.

[0056] It should be noted that the magnetic pole shoe, the second deflection device, and the detection device all have a central hole. In some implementations, refer to... Figure 6 The diameters of the central holes of the magnetic pole shoe 102 (D1), the second deflection device 104 (D2), and the detection device 105 (D3) decrease sequentially, i.e., D3 < D2 < D1. Since the effect of the electric lens is related to the size of the central hole, this arrangement allows for better lens performance and facilitates the passage of signal electrons, enabling efficient collection by the detection device.

[0057] Since the main body 101 is grounded and the magnetic pole shoe 102 is connected to an adjustable voltage, the voltages of the two are different, therefore an isolation structure is needed between them. In some embodiments, refer to Figure 1 The objective lens system further includes:

[0058] A first isolation structure 108 is used to isolate the main body 101 and the magnetic pole shoe 102. In practice, the material of the first isolation structure 108 can be a non-conductive material, such as ceramic. The magnetic housing 101b and the magnetic pole shoe 102 are isolated by the first isolation structure 108.

[0059] And / or, a second isolation structure 107 is used to isolate the second deflection device 104, the detection device 105, and the main body portion 101. In implementation, the material of the second isolation structure 107 may also be ceramic; the second deflection device 104, the detection device 105, and the main body portion 101 are isolated by the second isolation structure 107.

[0060] This disclosure also provides a scanning focusing method, referring to... Figure 7 The method includes the following steps S701:

[0061] Step S701: When the incident electron beam passes through the central axis of the scanning electron microscope objective system, the electron beam is focused by the composite lens system, and the direction of motion of the electron beam is changed by applying voltage to the first deflection device and the second deflection device to obtain an electron beam acting on the sample to be tested on the sample stage.

[0062] The composite mirror includes a magnetic lens and an electric lens; the electric lens, from top to bottom, includes a detection device, a second deflection device, a magnetic pole shoe of the magnetic lens, and the sample stage.

[0063] It should be noted that the incident electron beam passing through the central axis refers to the process from the electron beam's incident on the main body of the objective lens system to its arrival at the sample under test. In practice, the composite lens system can converge the electron beam as it passes through the central axis, while simultaneously applying voltage to the first and second deflection devices to change the direction of the electron beam's movement; alternatively, voltage can be continuously applied to the first and second deflection devices. The timing of voltage application is not limited in this embodiment.

[0064] In this embodiment, the electron beam is converged by the composite lens (including a magnetic lens and an electric lens) as it passes through the central axis of the objective system. The electric lens decelerates the beam, and the first and second deflection devices change the direction of motion before the beam acts on the sample, generating signal electrons. Because the magnetic lens incorporates magnetic pole shoes to alter the magnetic field distribution, the magnetic field strength at the sample location is zero, meaning the objective system is non-immersive. This scanning electron microscope objective system can observe both non-magnetic and magnetic samples, and obtain high-quality images in both cases.

[0065] In some embodiments, the voltage applied to the first deflection device and the second deflection device is one of the following:

[0066] The voltage applied to the first deflection device and the second deflection device is an alternating voltage;

[0067] The voltage applied to the first deflection device is an alternating voltage, and the voltage applied to the second deflection device is a constant voltage; wherein the constant voltage has a voltage range of -5kV to 5kV;

[0068] The voltage applied to the first deflection device is an alternating voltage, and the voltage applied to the second deflection device is a superposition of a constant voltage and a constant deflection voltage.

[0069] It should be noted that alternating voltage can be a constant voltage V. p The voltage obtained after making changes to the original voltage.

[0070] refer to Figure 8 An alternating voltage is simultaneously applied to the first deflection device 103 and the second deflection device 104, causing both sets of deflection devices to deflect the electron beam simultaneously. The trajectory of the electron beam is as follows: Figure 8 As shown by the dashed line, when the electron beam passes through the first sub-deflector 103a in the first deflection device 103, the electron beam is deflected away from the optical axis; when the electron beam passes through the second sub-deflector 103b in the first deflection device 103, the electron beam is deflected closer to the optical axis; when the electron beam passes through the second deflection device 104, the electron beam is deflected away from the optical axis. This results in a large deflection field (i.e., large-field observation is possible), allowing the converged electron beam to scan the sample.

[0071] When a constant voltage is applied, the second deflection device cannot deflect the electron beam, meaning it cannot change the direction of the electron beam's movement. (Reference) Figure 9 The second deflection device 104 can apply only a constant voltage V. p However, without applying an alternating voltage, the first deflection device 103 applies an alternating voltage, and in this case, only the first deflection device 103 deflects the electron beam. The trajectory of the electron beam is as follows: Figure 9 As shown by the dashed line, the first sub-deflector 103a and the second sub-deflector 103b in the first deflection device 103 deflect the electron beam once. The deflection field is small, so that the converged electron beam scans the sample. At this time, the deflection field matches the objective lens, which helps to reduce the distortion of the electron beam and improve the resolution of the scanning electron microscope.

[0072] refer to Figure 10 An alternating voltage is applied to the first deflection device, and a superposition of a constant voltage and a constant deflection voltage is applied to the second deflection device 104. The function of the second deflection device is to produce a constant tilt of the electron beam, which is then scanned and imaged by the first deflection device. This can be used when it is necessary to observe the sample at an angle.

[0073] In some embodiments, the method further includes: after the electron lens reverses the acceleration of the signal electrons generated by the electron beam acting on the sample under test and changes the direction of motion of the signal electrons, the method receives the signal electrons through a detection device. This can improve the collection efficiency of the signal electrons.

[0074] After the detection device receives the signal electrons, it can process the signal electrons in different detection areas and then output them to the image processing device for processing to form an image, thereby obtaining an image that includes the morphology of the sample to be tested.

[0075] In the several embodiments provided in this disclosure, it should be understood that the disclosed devices and methods can be implemented in a non-target manner. The device embodiments described above are merely illustrative; for example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods, such as: multiple units or components may be combined, or integrated into another system, or some features may be ignored or not executed. Furthermore, the various components shown or discussed may be coupled or directly coupled to each other.

[0076] The units described above as separate components may or may not be physically separate. The components shown as units may or may not be physical units, that is, they may be located in one place or distributed across multiple network units. Some or all of the units may be selected to achieve the purpose of this embodiment according to actual needs.

[0077] The features disclosed in the several method or device embodiments provided in this disclosure can be arbitrarily combined without conflict to obtain new method or device embodiments.

[0078] The above descriptions are merely some embodiments of this disclosure, but the protection scope of this disclosure is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this disclosure should be included within the protection scope of this disclosure. Therefore, the protection scope of this disclosure should be determined by the scope of the claims.

Claims

1. A scanning electron microscope objective system, characterized in that, It includes a magnetic lens, a first deflection device, a detection device, a second deflection device, and a sample stage; wherein: The magnetic lens includes a main body, a first isolation structure, and a magnetic pole piece; the first isolation structure is used to isolate the main body and the magnetic pole piece. The first deflection device is located between the inner wall of the main body and the optical axis of the electron beam, and is used to change the direction of motion of the incident electron beam. The detection device is located between the first deflection device and the second deflection device, and is used to receive the signal electrons generated by the electron beam acting on the sample to be tested on the sample stage. The second deflection device is located between the main body and the magnetic pole shoe, and is used to change the direction of motion of the electron beam; The detection device, the second deflection device, the magnetic pole shoe, and the sample stage form an electric lens; the electric lens and the magnetic lens form a composite mirror for focusing the electron beam. The opening of the magnetic pole shoe faces the sample to be tested, and the extension direction of the end of the magnetic pole shoe is horizontal, which is the same as the extension direction of the end of the magnetic shell of the main body; the magnetic field strength of the magnetic lens is 0 at the position of the sample to be tested. The relationship between the voltage V1 of the magnetic pole shoe and the voltage V2 of the sample stage is: V2-5kV≤V1≤V2+5kV, the voltage V2 of the sample stage is in the range of -15kV to 0kV; the voltage of the magnetic housing is 0kV; the voltage V1 of the magnetic pole shoe is an adjustable voltage.

2. The objective lens system according to claim 1, characterized in that, The maximum magnetic field strength of the magnetic lens is located between the opening of the magnetic housing of the main body and the opening of the magnetic pole shoe.

3. The objective lens system according to claim 1 or 2, characterized in that, The diameters of the central holes of the magnetic pole shoe, the second deflection device, and the detection device decrease sequentially.

4. The objective lens system according to claim 3, characterized in that, The objective lens system also includes: The second isolation structure is used to isolate the second deflection device, the detection device, and the main body.

5. A scanning focusing method, characterized in that, The method of using the scanning electron microscope objective system of claim 1 includes: When the incident electron beam passes through the central axis of the scanning electron microscope objective system, it is focused by the composite lens system, and the direction of motion of the electron beam is changed by the voltage applied to the first deflection device and the second deflection device, so as to obtain the electron beam acting on the sample to be tested on the sample stage. The composite mirror includes a magnetic lens and an electric lens; the electric lens, from top to bottom, includes a detection device, a second deflection device, a magnetic pole shoe of the magnetic lens, and the sample stage.

6. The method according to claim 5, characterized in that, The voltage applied to the first deflection device and the second deflection device is one of the following: The voltage applied to the first deflection device and the second deflection device is an alternating voltage; The voltage applied to the first deflection device is an alternating voltage, and the voltage applied to the second deflection device is a constant voltage; wherein the constant voltage has a voltage range of -5kV to 5kV; The voltage applied to the first deflection device is an alternating voltage, and the voltage applied to the second deflection device is a superposition of a constant voltage and a constant deflection voltage.

7. The method according to claim 5 or 6, characterized in that, The method further includes: after the electron lens accelerates the signal electrons generated by the electron beam acting on the sample under test in the opposite direction and changes the direction of motion of the signal electrons, the signal electrons are received by a detection device.

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