Electronic detection device and scanning electron microscope

Abstract

An electronic detection device (10) and a scanning electron microscope (100), relating to the technical field of scanning electron microscopes (100). The electronic detection device (10) comprises: a reflective energy analyzer (101) comprising, successively arranged in an electron beam incident direction, a first control electrode (1011) and a second control electrode (1012), the first control electrode (1011) being used for generating a first electric field between the first control electrode (1011) and the second control electrode (1012); a first detector (102) arranged on the side of the second control electrode (1012) away from the first control electrode (1011); a second detector (103) arranged on the side of the first control electrode (1011) away from the second control electrode (1012); a conductive shielding tube (104) arranged to pass through the first control electrode (1011) and the second control electrode (1012) in the electron beam incident direction and used for shielding an electric field generated by the reflective energy analyzer (101), so as to allow electron beams to pass through and to be transmitted to a target sample (20), the first electric field being used for guiding secondary electrons to the first detector (102).

Description

Electronic detection device and scanning electron microscope

[0001] Cross-references to related applications

[0002] This disclosure claims priority to Chinese patent application No. 202410490804.8, filed on April 23, 2024, entitled "Electron Detection Device and Scanning Electron Microscope", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This disclosure relates to the field of scanning electron microscopy, and in particular to an electronic detection device and a scanning electron microscope. Background Technology

[0004] Scanning electron microscopy (SEM) uses a focused electron beam to scan and image the surface of a sample for characterization and analysis, enabling observation of sample surfaces or cross-sections in numerous fields. The interaction between the electron beam and the sample generates signal electrons such as secondary electrons (SE) and backscattered electrons (BSE). Secondary electrons have emission energies of approximately 0-50 eV, while backscattered electrons have emission energies above 50 eV.

[0005] Secondary electrons can reflect information about the surface morphology of a sample, while backscattered electrons can reflect information about the sample's composition and crystal structure. Furthermore, backscattered electrons of different energies carry different types of information. For example, backscattered electrons generated by perfectly elastic scattering at the sample surface with almost no energy loss contain not only compositional information but also information about the surface morphology. Therefore, the goal of a scanning electron microscope's signal detector is to effectively distinguish between different types / energy signal electrons, improve the separation of different types / energy signal electrons, and simultaneously increase collection efficiency (collecting as many signal electrons as possible) to enhance signal analysis capabilities and efficiency.

[0006] Traditional detectors are typically located in the sample chamber area outside the scanning electron microscope (SEM) tube (e.g., Everhart-Thornley detectors, insertion backscatter detectors, etc.). The space occupied by these detectors significantly increases the working distance (the distance between the pole piece and the sample surface under the objective lens), leading to reduced resolution. Furthermore, spatial constraints, especially at shorter working distances, make detector installation difficult or inaccurate. Additionally, most electrons enter the tube along the principal optical axis and cannot be collected by the external detector, resulting in reduced collection efficiency. Particularly for semiconductor-type backscatter detectors, the low energy of backscattered electrons under low landing voltage conditions (1-3 kV) leads to insufficient detector signal strength.

[0007] Summary of the Invention

[0008] This disclosure aims to at least partially address one of the technical problems in the related art. Therefore, the purpose of this disclosure is to provide an electron detection device and a scanning electron microscope to improve the separation and collection efficiency of backscattered electrons and secondary electrons.

[0009] To achieve the above objectives, a first aspect of this disclosure provides an electron detection device, comprising: a reflective energy analyzer including a first control electrode and a second control electrode arranged sequentially along the electron beam incident direction, wherein the first control electrode generates a first electric field between itself and the second control electrode; a first detector disposed on the side of the second control electrode away from the first control electrode, for receiving secondary electrons generated by the electron beam acting on a target sample; a second detector disposed on the side of the first control electrode away from the second control electrode, for receiving backscattered electrons generated by the electron beam acting on the target sample; and a conductive shielding tube disposed along the electron beam incident direction, penetrating the first control electrode and the second control electrode, for shielding the electric field generated by the reflective energy analyzer, thereby allowing the electron beam to pass through and be incident on the target sample; wherein the first electric field guides the secondary electrons to the first detector.

[0010] To achieve the above objectives, a second aspect of this disclosure provides a scanning electron microscope, the scanning electron microscope comprising: an electron source for generating an electron beam; and an electron detection device as described in the first aspect of the embodiment, for detecting secondary electrons and backscattered electrons generated by the electron beam acting on a target sample.

[0011] The electron detection device and scanning electron microscope of this disclosure, by sequentially arranging the first and second control electrodes of a reflective energy analyzer along the electron beam incident direction, and placing the first detector on the side of the second control electrode away from the first control electrode, and the second detector on the side of the first control electrode away from the second control electrode, can guide secondary electrons to the first detector through the first electric field generated between the first and second control electrodes, while backscattered electrons move to the second detector in the opposite direction to the first detector. Thus, by guiding the secondary electrons to move in the opposite direction to the backscattered electrons and receiving them with the corresponding detectors, the separation and collection efficiency of backscattered electrons and secondary electrons can be improved, and high-resolution BSE imaging at short working distances can be achieved, increasing the signal strength of backscattered electrons under low landing voltage conditions. Attached Figure Description

[0012] Figure 1 is a schematic diagram of the structure of a reflective energy analyzer according to an embodiment of the present disclosure;

[0013] Figure 2 is a schematic diagram of the structure of a reflective energy analyzer according to another embodiment of the present disclosure;

[0014] Figure 3 is a schematic diagram of the motion trajectories of secondary electrons and backscattered electrons according to an embodiment of the present disclosure;

[0015] Figure 4 is a schematic diagram of the motion trajectories of paraxial and faraxial secondary electrons according to an embodiment of the present disclosure.

[0016] Figure 5 is a schematic diagram of the structure of an electronic detection device according to another embodiment of the present disclosure;

[0017] Figure 6 is a schematic diagram of multiple electronic trajectories according to an embodiment of the present disclosure;

[0018] Figure 7 is a schematic diagram showing the relationship between the voltage of the first control electrode and the collection efficiency according to an embodiment of the present disclosure;

[0019] Figure 8 is a schematic diagram of the structure of a scanning electron microscope according to an embodiment of the present disclosure;

[0020] Figure 9 is a schematic diagram of the trajectories of secondary electrons, high-angle backscattered electrons, and medium / low-angle backscattered electrons according to an embodiment of the present disclosure.

[0021] Figure label:

[0022] 100. Scanning electron microscope;

[0023] 10. Electronic detection device; 20. Target sample; 30. Electron source; 40. Objective lens; 50. Condenser lens; 60. Voltage tube.

[0024] 101. Reflective energy analyzer; 102. First detector; 103. Second detector; 104. Conductive shielding tube.

[0025] 1011, First control electrode; 1012, Second control electrode; 1013, Third control electrode. Detailed Implementation

[0026] Embodiments of this disclosure are described in detail below, examples of which are illustrated in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this disclosure, and should not be construed as limiting this disclosure.

[0027] This disclosure proposes an electron detection device. The device is provided with a first control electrode and a second control electrode arranged sequentially along the incident direction of the electron beam to generate a first electric field. The first electric field guides secondary electrons to move in the opposite direction to backscattered electrons, guiding the backscattered electrons and secondary electrons to two opposing detectors, thereby improving the separation degree and collection efficiency of the two electrons.

[0028] The electronic detection apparatus and scanning electron microscope of embodiments of the present disclosure are described below with reference to the accompanying drawings.

[0029] Figure 1 is a schematic diagram of the structure of an electronic detection device according to an embodiment of the present disclosure.

[0030] As shown in Figure 1, the electron detection device 10 includes a reflective energy analyzer 101, a first detector 102, a second detector 103, and a conductive shielding tube 104. The reflective energy analyzer 101 includes a first control electrode 1011 and a second control electrode 1012 arranged sequentially along the electron beam incident direction. The first control electrode 1011 generates a first electric field between itself and the second control electrode 1012. The first detector 102 is located on the side of the second control electrode 1012 away from the first control electrode 1011 and is used to receive secondary electrons generated when the electron beam acts on the target sample 20. The second detector 103 is located on the side of the first control electrode 1011 away from the second control electrode 1012 and is used to receive backscattered electrons generated when the electron beam acts on the target sample 20. The conductive shielding tube 104 penetrates the first control electrode 1011 and the second control electrode 1012 along the electron beam incident direction and is used to shield the electric field generated by the reflective energy analyzer 101 (which may include the first electric field mentioned above) to allow the electron beam to pass through and be incident on the target sample 20. The first electric field is used to guide secondary electrons to the first detector 102.

[0031] Specifically, as shown in Figure 1, the electron beam is generated by the electron source 30 of the scanning electron microscope and moves along the incident direction to act on the target sample 20 below, generating upward-moving signal electrons (including secondary electrons and backscattered electrons). The electron detection device 10 is disposed between the electron source 30 and the target sample 20. The second detector 103 is disposed close to the electron source 30, the first detector 102 is disposed close to the target sample 20, and the first control electrode 1011 is disposed close to the second detector 103, and the second control electrode 1012 is disposed close to the first detector 102.

[0032] In use, the first control electrode 1011 and the second control electrode 1012 are set to opposite potentials, thereby generating a first electric field between the first control electrode 1011 and the second control electrode 1012. Since the secondary electrons and backscattered electrons have different energies, the secondary electrons and backscattered electrons in the upward-moving signal electrons can be separated under the action of the first electric field. The secondary electrons with lower energy are guided to the lower first detector 102 for reception under the action of the first electric field, while the backscattered electrons with higher energy can pass through the first electric field and move to the upper second detector 103 for reception. Therefore, by guiding the secondary electrons to move in the opposite direction to the backscattered electrons, the separation degree and collection efficiency of the secondary electrons and backscattered electrons can be improved.

[0033] It should be noted that the aforementioned different potentials do not mean opposite potentials, but rather different potentials; both the first control electrode 1011 and the second control electrode 1012 can be at positive potentials. Furthermore, the energy threshold of the backscattered electrons can be changed by adjusting the potential voltage of the first control electrode 1011, thereby enabling energy analysis of the backscattered electrons.

[0034] In some examples, after the secondary electrons are emitted upwards, they are bent by the first electric field generated by the reflective energy analyzer 101, moving in the opposite direction of emission (i.e., downwards), and can form a converging effect at a specific distance below the second control electrode 1012, thus being received by the first detector 102. After passing through the first electric field, the backscattered electrons form a certain divergence angle and continue to move upwards to the second detector 103, where they are received by the second detector 103.

[0035] As an example, the second detector 103 can be either an energy-free filter or an energy filter to selectively allow backscattered electrons of different energies to pass through.

[0036] The electron detection device 10 of this embodiment guides secondary electrons to move in the opposite direction to backscattered electrons via a reflective energy analyzer 101. The secondary electrons exit the first electric field in the opposite direction of the emission direction and continue moving in the direction of exiting the first electric field, while the backscattered electrons move in the direction of exiting the first electric field. This achieves high efficiency in distinguishing and detecting secondary electrons and backscattered electrons, and also achieves high purity. Because backscattered electrons and secondary electrons can be distinguished and detected with high collection efficiency and purity, the imaging signal-to-noise ratio is improved. Simultaneously, since the backscatter detector (i.e., the second detector 103) no longer occupies the space between the objective lens and the sample, the target sample 20 can be imaged at a smaller working distance (the distance from the lower end face of the objective lens), thereby improving the imaging resolution.

[0037] In some embodiments of this disclosure, as shown in FIG2, the reflective energy analyzer 101 further includes a third control electrode 1013, which is disposed on the side of the first control electrode 1011 away from the second control electrode 1012 along the electron beam incident direction and is penetrated by a conductive shielding tube 104.

[0038] The first control electrode 1011 is located between the third control electrode 1013 and the second control electrode 1012. The second detector 103 is disposed on the side of the third control electrode 1013 away from the first control electrode 101. The first control electrode 1011 is also used to generate a second electric field between itself and the third control electrode 1013. The second electric field is used to guide backscattered electrons to the second detector 103.

[0039] Specifically, referring to Figure 2, the conductive shielding tube 104 sequentially passes through the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012 along the electron beam incident direction, to shield the electric field (including the aforementioned first and second electric fields) generated by the reflective energy analyzer 101. The third control electrode 1013 and the second control electrode 1012 can be set to the same potential, while the first control electrode 1011 and the third control electrode 1013 can be set to opposite potentials, thereby generating a first electric field between the first control electrode 1011 and the second control electrode 1012, and a second electric field between the third control electrode 1013 and the first control electrode 1011. Since the secondary electrons and backscattered electrons have different energies, the secondary electrons and backscattered electrons in the upward-moving signal electrons can be separated under the action of the first and second electric fields. The secondary electrons with lower energy are guided to the lower first detector 102 for reception under the action of the lower first electric field, while the backscattered electrons with higher energy can pass through the first electric field and enter the second electric field, where they are guided to the upper second detector 103 for reception under the action of the second electric field. Therefore, by guiding secondary electrons and backscattered electrons to move in opposite directions, the separation and collection efficiency of secondary electrons and backscattered electrons can be improved.

[0040] In some examples, as shown in Figure 3, after the secondary electrons are emitted upwards, they are bent by the first electric field generated by the reflective energy analyzer 101, moving in the opposite direction of emission (i.e., downwards), and can form a converging effect at a specific distance below the second control electrode 1012, thus being received by the first detector 102. After passing through the first electric field, the backscattered electrons form a certain divergence angle and continue to move upwards, entering the second electric field; under the action of the second electric field, the backscattered electrons form a larger divergence angle and continue to move along the direction of exiting the second electric field to the second detector 103, where they are received by the second detector 103.

[0041] Thus, the electron detection device 10 guides secondary electrons and backscattered electrons to move in opposite directions through the reflective energy analyzer 101. The secondary electrons exit the first electric field in the opposite direction of the emission direction and continue to move in the direction of exiting the first electric field. The backscattered electrons exit the second electric field at a certain divergence angle and continue to move in the direction of exiting the second electric field. This achieves the differentiation and detection of secondary electrons and backscattered electrons with higher efficiency than the embodiment shown in Figure 1, and also has higher purity.

[0042] In some embodiments of this disclosure, referring to Figures 1, 2, and 3, the first control electrode 1011 adopts an axisymmetric structure with a through-hole at its center for the electron beam to pass through. The centerline of the through-hole coincides with the axis of symmetry. The first control electrode 1011 extends outward from the axis of symmetry as its center point, and the extending surface is a downward-opening curved surface (the cross-sectional shape of the curved surface can be a parabola, a circular arc, a Bezier curve, etc.). The end of the curved surface away from the axis of symmetry points towards the first detector 102, where the axis of symmetry is the axis along which the electron beam incident direction is located. The second control electrode 1012 has the same shape as the first control electrode 1011 and together with the first control electrode 1011, defines a sandwich layer so that the first electric field formed in the sandwich layer guides the secondary electrons to deflect onto the first detector 102 and be received by the first detector 102.

[0043] Specifically, referring to Figures 2 and 3, the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012 can all adopt an axisymmetric structure, with the axis of symmetry being the axis along which the electron beam incident direction lies. The third control electrode 1013 can be a flat plate structure, such as a circular plate; the cross-sections of the second control electrode 1012 and the first control electrode 1011, which are coplanar with the axis of symmetry, can have an approximately M-shaped structure, with the opening of the approximately M-shaped structure facing the first detector 102. This allows lower-energy secondary electrons to move to the first detector 102 along the secondary electron trajectory shown in Figure 3 under the influence of the first electric field, while higher-energy backscattered electrons pass through the first electric field and move to the second detector 103 along the backscattered electron trajectory shown in Figure 3 under the influence of the second electric field. This improves the separation between secondary electrons and backscattered electrons.

[0044] In some embodiments of this disclosure, the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012 are mesh structures or porous structures.

[0045] In this embodiment, the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012, which have a mesh structure or a porous structure, can allow most of the secondary electrons and backscattered electrons to pass through while generating the first electric field and the second electric field.

[0046] In some embodiments of this disclosure, as shown in FIG3, the conductive shielding tube 104 is symmetrically arranged along the axis of the electron beam incident direction (i.e., it is on the same axis of symmetry as the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012), and can be at the same potential as the voltage tube of the scanning electron microscope (e.g., both are positive potentials).

[0047] In this embodiment, the conductive shielding tube 104 maintains an equipotential region on the electron beam path to avoid the influence of the electric field generated by the reflective energy analyzer 101 on the electron beam.

[0048] In some embodiments of this disclosure, the portion of the conductive shielding tube 104 near the target sample 20 adopts a conical structure with an opening. The outer surface of the conical structure has a reflective function and may be plated with a metal to improve reflection efficiency. This reflects signal electrons incident on the outer surface of the conical structure, and the reflected signal electrons can partially enter the reflective energy analyzer 101 for detection. This reduces electron leakage through the central hole and improves electron collection efficiency.

[0049] As an example, the portion of the conductive shielding tube 104 near the electron source 30 can be a hollow cylindrical structure, the diameter of which can be set as needed. For instance, increasing the diameter makes it less likely for the incident electron beam to be blocked as it passes through the conductive shielding tube 104 from top to bottom, thereby reducing the difficulty of assembling and aligning the structure. The diameter of the opening at the tip of the cone can be less than 2 mm to reduce the number of signal electrons entering the conductive shielding tube 104 and increase the number of signal electrons entering the reflective energy analyzer 101, thereby improving electron collection efficiency.

[0050] Specifically, secondary electrons and backscattered electrons are incident on the outer surface of the conical structure at a small angle, and have a high probability of undergoing elastic or inelastic scattering. The scattering angle is along the direction of reflection of the conical surface or close to the direction of reflection of the conical surface. Taking secondary electrons as an example, as shown in Figure 4, paraxial secondary electrons are scattered by the outer surface of the conical structure and then enter the first electric field, while off-axis secondary electrons directly enter the first electric field.

[0051] Therefore, by setting the portion of the conductive shielding tube 104 near the target sample 20 into a conical structure, the conical structure reduces the aperture at the bottom of the tube with the same inner diameter of the conductive shielding tube 104, reducing the number of signal electrons leaking from the inside of the conductive shielding tube 104, allowing more signal electrons (secondary electrons and backscattered electrons) to collide with the outer surface of the conical structure, so that the collided signal electrons are ejected into the reflective energy analyzer 101, thereby improving the collection efficiency of signal electrons and mitigating the central black hole effect caused by the change in the collection efficiency of signal electrons with the magnitude of the scanning current.

[0052] In this embodiment, the first detector 102 and the second detector 103 can adopt a hollow annular structure, which can be symmetrical along the axis of the electron beam incident direction. The hollow diameter can be relatively large, as long as it does not affect the incident electron beam, and precise alignment is not required.

[0053] In particular, due to the structure of the electron detection device 10 adopted in this disclosure, the central aperture of the first detector 102 that receives secondary electrons can be set to be larger, thereby allowing high-angle backscattered electrons to pass through. This avoids the situation in the prior art where the central aperture of the first detector 102 is reduced in order to receive as many secondary electrons as possible. When the aperture is reduced, the influence of high-angle backscattered electrons will also be received accordingly. As a result, the signal data received by the first detector 102 is mixed with secondary electrons and backscattered electrons, thereby reducing the purity of the secondary electron received data and causing errors in subsequent data analysis and image forming.

[0054] For the first detector 102, a larger central opening allows signal electrons over a wider angular range to enter the reflective energy analyzer 101 (i.e., more signal electrons enter the reflective energy analyzer 101), and these electrons are then received by the first detector 102 and the second detector 103 under the action of the reflective energy analyzer 101, thus improving the collection efficiency and purity of the signal electrons. In contrast, scanning electron microscopes with coaxial detectors within the microscope tube in related technologies require very small central openings to ensure collection efficiency. This small central opening necessitates precise alignment of the detector with the principal optical axis (i.e., the axis containing the electron beam incident direction), increasing assembly and debugging difficulty. Therefore, the structure disclosed in this invention, compared to related technologies, improves the collection efficiency and purity of the signal electrons, and eliminates the need for precise detector alignment, reducing assembly and alignment difficulty.

[0055] In some embodiments of this disclosure, as shown in FIG5, the electron detection device 10 further includes a third detector 105. The third detector 105 is disposed on the side of the first detector 102 away from the second control electrode 1012, and is used to receive backscattered electrons generated by the electron beam acting on the target sample 20, wherein the emission angle of the backscattered electrons received by the third detector 105 is smaller than the emission angle of the backscattered electrons received by the second detector 103.

[0056] Specifically, the third detector 105 can be used to receive backscattered electrons at medium and low angles, the second detector 103 can be used to receive backscattered electrons at high angles, and the first detector 102 is used to receive secondary electrons reversed by the first electric field. The motion trajectories of each electron are shown in Figure 6.

[0057] In this embodiment, referring to Figures 5 and 6, the third detector 105, like the second detector 103 and the first detector 102, can also adopt a hollow ring structure. This hollow ring structure can also be symmetrical along the axis where the electron beam incident direction is located, and the size of its central opening can be set as needed to avoid affecting the collection of secondary electrons and high-angle backscattered electrons.

[0058] As an example, the second detector 103, the first detector 102, and the third detector 105 can be any one of the following: scintillator + light guide + photomultiplier tube type detector, scintillator + photon detector, and semiconductor type detector.

[0059] The electron collection efficiency of the electron detection device 10 of this disclosure is illustrated below with reference to Figure 7:

[0060] Taking a voltage of -3KV to 3KV for the first control electrode 1011, a working distance of 1mm, and a landing voltage of 1kV as an example, the secondary electron collection efficiency, backscattered electron collection efficiency, secondary collection of backscattered electrons, backscattered collection of secondary electrons, and low-to-medium angle backscattered electron collection efficiency were obtained. As shown in Figure 7, under short-distance operation, backscattered electrons and secondary electrons are separated by the third control electrode 1013, the first control electrode 1011, and the second control electrode 1012, and then the backscattered electrons and secondary electrons are collected separately. The collection efficiency of secondary electrons can reach more than 70%, and the collection efficiency of backscattered electrons can reach more than 35%.

[0061] Corresponding to the electronic detection device in the above embodiments, this disclosure also proposes a scanning electron microscope.

[0062] Figure 8 is a schematic diagram of the structure of a scanning electron microscope according to an embodiment of the present disclosure.

[0063] As shown in Figure 8, the scanning electron microscope 100 includes an electron source 30 and the aforementioned electron detection device 10. The electron source 30 is used to generate an electron beam; the electron detection device 10 is used to detect secondary electrons and backscattered electrons generated by the target sample 20 under the action of the electron beam.

[0064] As an example, the emission mode of the electron source 30 can be one of thermal emission, thermal field emission, or cold field emission.

[0065] The scanning electron microscope 100 of this embodiment can improve the separation and collection efficiency of backscattered electrons and secondary electrons by means of the electron detection device 10.

[0066] In some embodiments of this disclosure, as shown in FIG8, the scanning electron microscope 100 further includes an objective lens 40, a condenser lens 50, and a voltage tube 60. The voltage tube 60 has a receiving cavity for accommodating the electron detection device 10 (i.e., the electron detection device 10 is disposed within the microscope tube of the scanning electron microscope 100). The condenser lens 50 surrounds the voltage tube 60 and is located between the electron source 30 and the electron detection device 10, for focusing the electron beam; the objective lens 40 surrounds the voltage tube 60 and is located between the electron detection device 10 and the target sample 20, for focusing the electron beam onto the target sample 20.

[0067] In this embodiment, the voltage tube 60 is used to accelerate the electron beam before it enters the voltage tube 60, and after the electron beam passes through the electron detection device 10, the electron beam is decelerated by the deceleration electric field formed between the voltage tube 60 and the objective lens 40. The deceleration electric field also accelerates the signal electrons generated by the target sample 20 in the opposite direction.

[0068] As an example, the condenser lens 50 and the objective lens 40 can be one of a magnetic lens, an electric lens, or an electromagnetic compound lens.

[0069] In some embodiments of this disclosure, as shown in FIG9, the electron detection device 10 further includes a conductive shielding tube 104. The conductive shielding tube 104 is disposed through the third control electrode 1013, the first control electrode 1011 and the second control electrode 1012 along the electron beam incident direction and is symmetrical along the axis of the electron beam incident direction. The conductive shielding tube 104 is at the same potential as the voltage tube 60 and is used to shield the electric field generated by the reflective energy analyzer 101 so as to allow the electron beam to pass through and be incident on the target sample 20 without interference.

[0070] In some embodiments of this disclosure, the objective lens 40 is at ground potential, the target sample 20 is at ground potential or negative potential, and the voltage transistor 60 is at positive potential, thereby generating an electric field between the objective lens 40 and the target sample 20, and also between the target sample 20 and the voltage transistor 60. Both electric fields are generated at the end of the voltage transistor 60, enabling the voltage transistor 60 to simultaneously accelerate the secondary electrons and backscattered electrons generated by the target sample 20 through the aforementioned decelerating electric field, and simultaneously accelerate the secondary electrons and backscattered electrons generated by the target sample 20 through the aforementioned two electric fields generated with the target sample 20.

[0071] It should be noted that the objective lens 40 has low spherical aberration and chromatic aberration, which can greatly improve the resolution under low landing voltage. At the same time, for the signal electrons originating from the surface of the target sample 20, the electric field at the end of the high voltage tube (i.e., voltage tube 60) can accelerate the signal electrons, causing them to accelerate along the optical axis. The direction of the signal electrons is opposite to the direction of the electron beam generated by the electron source 30, so that the signal electrons have high energy when they reach the electron detection device 10, thereby improving the signal strength.

[0072] The working process of the scanning electron microscope 100 of this disclosure is explained below with reference to Figure 9:

[0073] An electron source 30 generates an electron beam that is incident on the surface of the target sample 20 through a conductive shielding tube 104. The target sample 20 generates secondary electrons and backscattered electrons traveling in the same direction. Backscattered electrons at medium / low angles are detected by a third detector 105, while secondary electrons and high-angle backscattered electrons continue to travel through the central hole of the third detector 105. Some secondary electrons and high-angle backscattered electrons are reflected by the outer surface of the conical structure of the conductive shielding tube 104 and enter the reflective energy analyzer 101, while others directly enter the reflective energy analyzer 101. The reflective energy analyzer 101 separates the secondary electrons and high-angle backscattered electrons. The first detector 102 receives the separated secondary electrons, and the second detector 103 receives the separated high-angle backscattered electrons.

[0074] It should be noted that, in the description of this specification, the references to terms such as "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this disclosure. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0075] In the description of this disclosure, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this disclosure and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this disclosure.

[0076] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this disclosure, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0077] In this disclosure, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise expressly limited. Those skilled in the art can understand the specific meaning of the above terms in this disclosure according to the specific circumstances.

[0078] Although embodiments of the present disclosure have been shown and described above, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present disclosure. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present disclosure.

Claims

1. An electronic detection device, characterized in that, include: A reflective energy analyzer includes a first control electrode and a second control electrode arranged sequentially along the electron beam incident direction, wherein the first control electrode is used to generate a first electric field between itself and the second control electrode. The first detector is disposed on the side of the second control electrode away from the first control electrode, and is used to receive secondary electrons generated by the electron beam acting on the target sample; The second detector is disposed on the side of the first control electrode away from the second control electrode, and is used to receive backscattered electrons generated by the electron beam acting on the target sample; A conductive shielding tube is disposed along the incident direction of the electron beam, penetrating the first control electrode and the second control electrode, to shield the electric field generated by the reflective energy analyzer, so as to allow the electron beam to pass through and be incident on the target sample; The first electric field is used to guide the secondary electrons to the first detector.

2. The electronic detection device according to claim 1, characterized in that, The reflective energy analyzer further includes a third control electrode, which is disposed on the side of the first control electrode away from the second control electrode along the electron beam incident direction and is penetrated by the conductive shielding tube. The second detector is disposed on the side of the third control electrode away from the first control electrode, and the first control electrode is also used to generate a second electric field between itself and the third control electrode. The second electric field is used to guide the backscattered electrons to the second detector.

3. The electronic detection device according to claim 2, characterized in that, The first control electrode adopts an axisymmetric structure with a through hole in the center for the electron beam to pass through. The center line of the through hole coincides with the axis of symmetry. The first control electrode extends outward from the axis of symmetry as the center point, and the extension surface is a curved surface with the opening facing downward. The side of the curved surface away from the axis of symmetry points towards the first detector. The axis of symmetry is the axis along which the electron beam incident direction is located. The second control electrode has the same shape as the first control electrode and together with the first control electrode define a sandwich layer, so that the first electric field formed in the sandwich layer guides the secondary electrons to deflect onto the first detector and be received by the first detector.

4. The electronic detection device according to claim 2 or 3, characterized in that, The third control electrode, the first control electrode, and the second control electrode have a mesh structure or a porous structure.

5. The electronic detection device according to any one of claims 1-4, characterized in that, The conductive shielding tube is symmetrically arranged along the axis of the electron beam incident direction.

6. The electronic detection device according to claim 5, characterized in that, The portion of the conductive shielding tube closest to the target sample has a conical structure with an opening.

7. The electronic detection device according to claim 6, characterized in that, Also includes: A third detector is disposed on the side of the first detector away from the second control electrode, and is used to receive backscattered electrons generated by the electron beam acting on the target sample. The emission angle of the backscattered electrons received by the third detector is smaller than the emission angle of the backscattered electrons received by the second detector. The third detector, the second detector and the first detector adopt a hollow ring structure, and the hollow ring structure is symmetrical along the axis of the electron beam incident direction.

8. A scanning electron microscope, characterized in that, include: An electron source, used to generate an electron beam; The electron detection device according to any one of claims 1-7 is used to detect secondary electrons and backscattered electrons generated by the electron beam acting on the target sample.

9. The scanning electron microscope according to claim 8, characterized in that, Also includes: A voltage tube having a receiving cavity for accommodating the electronic detection device; A condenser lens, surrounding the voltage tube and located between the electron source and the electron detection device, is used to focus the electron beam; An objective lens, surrounding the voltage tube and positioned between the electron detection device and the target sample, is used to focus the electron beam onto the target sample; The voltage tube is also used to accelerate the electron beam before it reaches the electron detection device, and to decelerate the electron beam after it passes through the electron detection device by the decelerating electric field formed between the voltage tube and the objective lens, and to accelerate the secondary electrons and backscattered electrons generated by the target sample in the opposite direction.

10. The scanning electron microscope according to claim 9, characterized in that, The electron detection device further includes a conductive shielding tube, which is disposed through the first control electrode and the second control electrode along the electron beam incident direction and is symmetrical along the axis of the electron beam incident direction. The conductive shielding tube is at the same potential as the voltage tube and is used to shield the electric field generated by the reflective energy analyzer so as to allow the electron beam to pass through and be incident on the target sample.

11. The scanning electron microscope according to claim 9 or 10, characterized in that, The objective lens has a ground potential, the target sample has a ground potential or a negative potential, and the voltage tube has a positive potential.

Images