Electromagnetic composite lens structure and its pole shoe self-cleaning method and device, electron beam scanning system

Abstract

This application relates to an electromagnetic compound lens structure and its electrode shoe self-cleaning method and apparatus, as well as an electron beam scanning system. The electromagnetic compound lens structure includes an objective lens and a cleaning electrode disposed on the objective lens for proximity to the sample. The objective lens is connected to a current source, and in cleaning mode, the objective lens generates a changing magnetic field at its electrode shoes in response to a current supplied by the current source. The cleaning electrode is connected to a signal generator, and in cleaning mode, in response to a second cleaning control signal provided by the signal generator, the cleaning electrode applies a first alternating electric field to the electrode shoes. The changing magnetic field and the first alternating electric field are used to clean contaminants at the electrode shoes. This application enables online self-cleaning of the objective lens electrode shoes, effectively improving system imaging accuracy and system imaging stability.

Description

Technical Field

[0001] This application relates to the field of electro-optical equipment, and in particular to an electromagnetic composite lens structure and its pole piece self-cleaning method and apparatus, and an electron beam scanning system. Background Technology

[0002] Electron beam scanning systems play an increasingly crucial role in the design, development, process debugging, and process control of semiconductor devices. The objective lens, as the core component determining electron beam focusing performance and imaging quality, is typically constructed using magnetic lenses or electromagnetic compound lenses. However, during long-term use, the surface of the objective lens pole pieces easily adsorbs and accumulates residual gas molecules from the vacuum chamber, photoresist volatiles, and particulate contaminants emitted from the sample itself. These contaminants alter the electric and magnetic field distributions on the objective lens pole piece surface, causing the main electron beam trajectory to deviate from the electron optical axis of the electron beam scanning system. This excites significant astigmatism, coma, and distortion, resulting in a significant increase in the effective beam spot diameter and a decrease in imaging resolution. Summary of the Invention

[0003] Based on this, embodiments of this application provide an electromagnetic composite lens structure and its pole piece self-cleaning method and apparatus, as well as an electron beam scanning system, which can realize online self-cleaning of the objective lens pole piece, thereby effectively improving the imaging accuracy and imaging stability of the electron beam scanning system.

[0004] To achieve the above objectives, some embodiments of this application provide an electromagnetic compound lens structure, including: an objective lens and a cleaning electrode disposed on the objective lens for proximity to a sample. The objective lens is connected to a current source and, in cleaning mode, generates a changing magnetic field at the pole piece of the objective lens in response to a first cleaning control signal provided by the current source. The cleaning electrode is connected to a signal generator and, in cleaning mode, applies a first alternating electric field to the pole piece in response to a second cleaning control signal provided by the signal generator. The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole piece.

[0005] In some embodiments of this application, the electromagnetic composite lens structure further includes an auxiliary electrode. The auxiliary electrode is disposed around the cleaning electrode and connected to the sample stage. It is used to apply a second alternating electric field to the pole piece in response to a third cleaning control signal provided by the sample stage, thereby assisting in cleaning the pole piece. The electric field directions of the first and second alternating electric fields are different.

[0006] In some embodiments of this application, the cleaning electrode includes an outer ring electrode, an inner ring electrode, and a connecting electrode. The outer ring electrode is parallel to the surface of the electrode shoe. The inner ring electrode has a central hole, is located inside the outer ring electrode along a direction parallel to the outer ring electrode, and is located on the side of the outer ring electrode away from the objective lens along the electron beam transmission direction. The connecting electrode connects the inner edge of the outer ring electrode and the outer edge of the inner ring electrode.

[0007] In some embodiments of this application, the electromagnetic composite lens structure further includes at least one of the following solutions:

[0008] The distance between the outer ring electrode and the pole piece along the electron beam propagation direction is not less than 3 mm;

[0009] The diameter of the center hole of the inner ring electrode is smaller than the diameter of the center hole of the pole shoe;

[0010] The difference in diameter between the center holes of the pole shoe and the inner ring electrode shall not be less than 3 mm;

[0011] The distance between the cleaning electrode and the sample along the electron beam propagation direction shall not be less than 1.5 mm;

[0012] The voltage range of the first alternating electric field includes 0V to 5000V;

[0013] When the electromagnetic composite lens structure also includes auxiliary electrodes, the voltage range of the second alternating electric field includes 0V~1000V.

[0014] On the other hand, some embodiments of this application also provide a self-cleaning method for the pole shoe of an electromagnetic composite lens structure, including:

[0015] The current source responds to the cleaning command and provides a first cleaning control signal, and the objective lens responds to the first cleaning control signal and generates a changing magnetic field at the pole piece;

[0016] The signal generator responds to the cleaning command by providing a second cleaning control signal, and the cleaning electrode responds to the second cleaning control signal by applying a first alternating electric field to the pole shoe;

[0017] The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoes.

[0018] In some embodiments of this application, the electromagnetic composite lens structure further includes an auxiliary electrode disposed around the cleaning electrode and connected to the sample stage. The pole piece self-cleaning method further includes: the sample stage providing a third cleaning control signal in response to a cleaning command, and the auxiliary electrode applying a second alternating electric field to the pole piece in response to the third cleaning control signal to assist in cleaning the pole piece; wherein the electric field directions of the first alternating electric field and the second alternating electric field are different.

[0019] In some embodiments of this application, the pole shoe self-cleaning method further includes:

[0020] Acquire images for pre-cleaning inspection;

[0021] Analyze the imaging quality of the images before cleaning;

[0022] If the imaging quality of the image detected before cleaning does not meet the preset conditions, a cleaning instruction is generated.

[0023] In some embodiments of this application, the pole shoe self-cleaning method further includes:

[0024] Acquire a post-cleaning detection image; analyze the imaging quality of the post-cleaning detection image; if the imaging quality of the post-cleaning detection image does not meet the preset conditions, regenerate a cleaning command to clean again; and if the imaging quality of the post-cleaning detection image meets the preset conditions, terminate the cleaning command.

[0025] And / or, monitor the vacuum level of the vacuum chamber where the electromagnetic composite lens structure is located in real time; if the vacuum level exceeds a preset threshold, terminate the cleaning command and generate an alarm command.

[0026] Furthermore, some embodiments of this application also provide a pole shoe self-cleaning device with an electromagnetic composite lens structure for implementing the pole shoe self-cleaning method described in the above embodiments. The pole shoe self-cleaning device includes: an electromagnetic composite lens structure, a current source, a signal generator, and a control unit.

[0027] The electromagnetic compound lens structure includes an objective lens and a cleaning electrode disposed on the side of the objective lens for proximity to the sample.

[0028] A current source is connected to the objective lens to provide a first cleaning control signal in response to a cleaning command, so that the objective lens generates a changing magnetic field at the pole shoe in response to the first cleaning control signal.

[0029] A signal generator is connected to the cleaning electrode and is used to provide a second cleaning control signal in response to a cleaning command, so that the cleaning electrode applies a first alternating electric field to the pole shoe in response to the second cleaning control signal.

[0030] The control unit connects to a current source and a signal generator to generate cleaning instructions.

[0031] As described above, the changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoes.

[0032] In some embodiments of this application, the electromagnetic composite lens structure further includes an auxiliary electrode disposed around the periphery of the cleaning electrode. The pole shoe self-cleaning device also includes a sample stage. The sample stage is connected to the control unit and the auxiliary electrode, and is used to provide a third cleaning control signal in response to a cleaning command, so that the auxiliary electrode applies a second alternating electric field to the pole shoe in response to the third cleaning control signal to assist in cleaning the pole shoe. The electric field directions of the first alternating electric field and the second alternating electric field are different.

[0033] In some embodiments of this application, the self-cleaning device for the pole shoe further includes an image acquisition unit and an image quality analysis unit.

[0034] The image acquisition unit is connected to the control unit and is used to acquire images for inspection before and / or after cleaning.

[0035] The imaging quality analysis unit connects the image acquisition unit and the control unit, and is used to analyze the imaging quality of the pre-cleaning and / or post-cleaning inspection images.

[0036] Accordingly, the control unit is also configured to: generate a cleaning command in response to the fact that the imaging quality of the image detected before cleaning does not meet the preset conditions; and regenerate a cleaning command to clean again in response to the fact that the imaging quality of the image detected after cleaning does not meet the preset conditions; and terminate the cleaning command in response to the fact that the imaging quality of the image detected after cleaning meets the preset conditions.

[0037] In some embodiments of this application, the pole shoe self-cleaning device further includes a safety protection unit connected to the control unit. The safety protection unit includes a vacuum monitoring module and an alarm module. The vacuum monitoring module is used to monitor the vacuum level of the vacuum chamber containing the electromagnetic composite lens structure in real time. The control unit is also used to: terminate the cleaning command and generate an alarm command in response to a vacuum level exceeding a preset threshold. The alarm module is used to issue an alarm based on the alarm command.

[0038] In another aspect, some embodiments of this application also provide an electron beam scanning system, including the electromagnetic composite lens structure as described in any of the preceding embodiments; or, the pole shoe self-cleaning device as described in any of the preceding embodiments.

[0039] The embodiments of this application may have, or at least have, the following advantages:

[0040] In this embodiment, a cleaning electrode is added to the side of the objective lens closest to the sample, so that the objective lens and the cleaning electrode together form an electromagnetic compound lens structure. The objective lens is connected to a current source to generate a changing magnetic field at the pole piece in response to a first cleaning control signal provided by the current source in cleaning mode. At the same time, the cleaning electrode is connected to a signal generator to apply a first alternating electric field to the pole piece in response to a second cleaning control signal provided by the signal generator in cleaning mode. This not only helps to reduce the adhesion rate of particulate contaminants at the pole piece by blocking the cleaning electrode, but also enables the magnetic field oscillation at the pole piece and the electric field oscillation at the pole piece by the changing magnetic field to work synergistically in terms of field space and field intensity. This allows the magnetic force and eddy current force generated by the magnetic field oscillation and the electric field force and mechanical vibration generated by the electric field oscillation to reach their maximum values ​​simultaneously and act in combination from multiple physical dimensions to maximize the destruction of particulate contaminants and / or other attached contaminants at the pole piece. This achieves online, efficient, and non-destructive cleaning of the pole piece, thereby ensuring improved imaging accuracy and imaging stability of the electron beam scanning system.

[0041] Details of one or more embodiments of this application are set forth in the following drawings and description. Other features, objects, and advantages of this application will become apparent from the specification, drawings, and claims. Attached Figure Description

[0042] To more clearly illustrate the technical solutions in the embodiments of this application, 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 this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0043] Figure 1 A schematic diagram of the electron beam focusing path to a sample when there are no particulate contaminants, provided for some embodiments;

[0044] Figure 2 A schematic diagram illustrating the path of an electron beam focused onto a sample containing particulate contaminants, provided for some embodiments;

[0045] Figure 3 A cross-sectional structural diagram of a cleaning electrode provided for some embodiments;

[0046] Figure 4 A schematic diagram of the physical structure of a cleaning electrode provided for some embodiments;

[0047] Figure 5 A schematic diagram of an electron beam scanning system provided for some embodiments;

[0048] Figure 6 Schematic diagrams of waveforms for various second cleaning control signals provided in some embodiments;

[0049] Figure 7 A waveform diagram of a sweep signal provided for some embodiments;

[0050] Figure 8 A schematic flowchart of a self-cleaning method for pole shoes provided for some embodiments;

[0051] Figure 9 A schematic flowchart of another self-cleaning method for pole shoes provided for some embodiments;

[0052] Figure 10 A flowchart illustrating steps S10 to S30 of a self-cleaning method for pole shoes provided in some embodiments;

[0053] Figure 11 A flowchart illustrating steps S40 to S70 of a self-cleaning method for pole shoes provided in some embodiments;

[0054] Figure 12 A flowchart illustrating steps S80 and S90 of a self-cleaning method for pole shoes provided in some embodiments;

[0055] Figure 13 A flowchart illustrating the implementation process of an extreme shoe self-cleaning method from start to finish, provided for some embodiments;

[0056] Figure 14 A schematic flowchart of yet another self-cleaning method for pole shoes provided in some embodiments;

[0057] Figure 15 A structural block diagram of a self-cleaning device for pole shoes is provided for some embodiments;

[0058] Figure 16 A structural block diagram of another self-cleaning device for pole shoes provided in some embodiments;

[0059] Figure 17 A structural block diagram of yet another self-cleaning device for pole shoes provided in some embodiments;

[0060] Figure 18 A structural block diagram of another self-cleaning device for pole shoes provided in some embodiments.

[0061] Explanation of reference numerals in the attached figures:

[0062] 10 - Sample, 20 - Objective lens, 30 - Particulate contaminant, EB - Electron beam;

[0063] 40-Electromagnetic composite lens structure, 41-Pole shoe, 42-Cleaning electrode, 421-Outer ring electrode, 422-Inner ring electrode, 423-Connecting electrode, H-Central hole, 43-Auxiliary electrode;

[0064] 51-Electron gun, 52-High-voltage liner, 53-First-stage focusing lens, 54-Guns vacuum valve, 55-Second-stage focusing lens, 60-Electron detector, 70-Control unit, 71-Current source, 72-Signal generator, 73-Sample stage, 74-Image acquisition unit, 75-Imaging quality analysis unit, 76-Safety protection unit, 761-Vacuum degree monitoring module, 762-Alarm module. Detailed Implementation

[0065] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. The drawings illustrate preferred embodiments of this application. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0066] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0067] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that when the terms “comprise” and / or “comprising” are used in this specification, the presence of the stated feature, integer, step, operation, element, and / or part is established, but the presence or addition of one or more other features, integers, steps, operations, elements, parts, and / or groups is not excluded. Meanwhile, when used herein, the term “and / or” includes any and all combinations of the associated listed items.

[0068] Some embodiments of this application provide an electromagnetic composite lens structure for use in an electron beam scanning system.

[0069] For example, electron beam scanning systems include, but are not limited to, scanning electron microscopes (SEMs), which use focused high-energy electron beams to scan the surface of a sample, thereby enabling the observation of the microstructure and composition of a material by detecting various signals generated by the interaction between electrons and the sample.

[0070] In some examples, the electron beam scanning system is a critical-size scanning electron microscope (CD-SEM) used to accurately measure critical dimensions, such as the line width of a photoresist pattern, with extremely high imaging accuracy and equipment stability.

[0071] It is understandable that during long-term use, the pole pieces of the objectives in an electron beam scanning system easily adsorb and accumulate residual gas molecules, photoresist volatiles, and particulate contaminants emitted from the vacuum chamber and the sample itself. If there are no contaminants adhering to the pole pieces of the objectives, then... Figure 1 As shown, ideally, when the electron beam EB is focused onto the sample 10 by the objective lens 20, the electron beam EB is aligned with the EOS (electron optics) axis, resulting in a scanned image with minimal aberrations and the highest resolution. If contaminants adhere to the pole piece of the objective lens, then... Figure 2As shown, these contaminants alter the electric and magnetic field distributions on the pole piece surface, causing the main trajectory of the electron beam to deviate from the EOS (electron optics) axis of the electron beam scanning system. This excites significant astigmatism, coma, and distortion, resulting in a marked increase in the effective beam spot diameter and a decrease in imaging resolution. Furthermore, when the electron beam scanning system is used for critical dimension measurement, the deviation of the electron beam axis from the EOS axis causes a landing angle tilt, leading to positional drift in the scanned image and even sample discharge phenomena, all of which severely affect the measurement accuracy and equipment stability of the electron beam scanning system.

[0072] Furthermore, traditional methods for cleaning pole pieces require opening a high-vacuum chamber, removing the pole pieces from the objective lens, and then physically wiping or chemically cleaning them. However, this is not only time-consuming and labor-intensive, but also disrupts the high-vacuum environment of the electron beam scanning system, impacting production efficiency. Moreover, for high-precision CD-SEMs, frequent disassembly and maintenance can easily lead to recalibration of the electron beam scanning system's optical path, introducing new errors. Therefore, how to achieve efficient online cleaning of contaminants on the surface of objective lens pole pieces without disrupting the vacuum environment or interrupting production is a key technical problem that urgently needs to be solved in this field.

[0073] Based on this, embodiments of this application provide an electromagnetic composite lens structure and its pole piece self-cleaning method and apparatus, as well as an electron beam scanning system, which can realize online self-cleaning of the objective lens pole piece, thereby effectively improving the imaging accuracy and imaging stability of the electron beam scanning system.

[0074] Please combine Figures 3-5 Understood, in some embodiments of this application, the electromagnetic compound lens structure 40 includes: an objective lens 20 and a cleaning electrode 42 disposed on the objective lens 20 for proximity to the sample 10. The objective lens 20 is connected to a current source and, in cleaning mode, generates a changing magnetic field at the pole piece 41 of the objective lens 20 in response to a first cleaning control signal provided by the current source. The cleaning electrode 42 is connected to a signal generator and, in cleaning mode, applies a first alternating electric field to the pole piece 41 in response to a second cleaning control signal provided by the signal generator. The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole piece 41.

[0075] Optionally, objective lens 20 is a magnetic lens or an electromagnetic compound lens. The pole piece 41 of objective lens 20 is grounded.

[0076] Optionally, the first cleaning control signal is a current signal. The current signal provided by the current source changes drastically back and forth, which can generate a rapidly changing magnetic field to mainly produce magnetic force and eddy current force for cleaning magnetic particulate contaminants at the pole piece 41.

[0077] In some examples, the current signal provided by the current source fluctuates wildly between 0A and 1.5A.

[0078] Optionally, the second cleaning control signal is a pulse signal, for example... Figure 6 Some of the pulse signals shown include, but are not limited to, Figure 6 The sawtooth pulse shown in Figure (a) Figure 6 The triangular pulse shown in Figure (b) Figure 6 The square wave pulse shown in Figure (c) or Figure 6 The sinusoidal pulse shown in Figure (d) is an example. Signal generators include, but are not limited to, pulse generators, especially high-voltage pulse generators.

[0079] Optionally, the second cleaning control signal is a frequency sweep signal. A signal generator is used to generate a high-voltage electrical signal with a specific waveform, frequency, and voltage amplitude as the frequency sweep signal, for example... Figure 7 As shown, a rapidly changing non-uniform electric field can be formed between the cleaning electrode 42 and the pole piece 41 to generate electric field oscillations, such as primarily generating electric force and mechanical vibration, for cleaning electrical particulate contaminants or other attached contaminants at the pole piece 41.

[0080] In some examples, the second cleaning control signal is formed based on the modulation of a sine wave signal.

[0081] In this embodiment, a cleaning electrode 42 is added to the side of the objective lens 20 closest to the sample 10, so that the objective lens 20 and the cleaning electrode 42 together form an electromagnetic compound lens structure 40. The objective lens 20 is connected to a current source to generate a changing magnetic field at the pole piece 41 in response to a first cleaning control signal provided by the current source in cleaning mode. At the same time, the cleaning electrode 42 is connected to a signal generator to apply a first alternating electric field to the pole piece 41 in response to a second cleaning control signal provided by the signal generator in cleaning mode. This not only helps to reduce particulate contaminants at the pole piece 41 by blocking the obstruction of the cleaning electrode 42, but also... The adhesion rate can also be improved by the combined synergistic effect of the magnetic field oscillation at pole shoe 41 caused by the changing magnetic field and the electric field oscillation at pole shoe 41 caused by the first alternating electric field. This allows the magnetic force and eddy current force generated by the magnetic field oscillation, as well as the electric field force and mechanical vibration generated by the electric field oscillation, to reach their maximum values ​​simultaneously and act in combination from multiple physical dimensions. This maximizes the destruction of particulate contaminants and / or other attached contaminants at pole shoe 41, achieving online, efficient, and non-destructive cleaning of pole shoe 41, thereby ensuring improved imaging accuracy and imaging stability of the electron beam scanning system.

[0082] Furthermore, in this embodiment, the first alternating electric field is formed based on the second cleaning control signal. By selecting and controlling the waveform corresponding to the second cleaning control signal, the inherent frequencies of contaminants of different masses and sizes can be sequentially matched to achieve broad-spectrum resonant removal of contaminants of different types and / or degrees. This enhances the thoroughness and multifunctional adaptability of the self-cleaning of the pole shoe 41, thereby improving the cleaning effect. In addition, this embodiment eliminates the need for physical contact cleaning or chemical cleaning of the pole shoe 41, avoiding surface damage or secondary contamination.

[0083] For some possible implementations, please refer to Figure 4 The cleaning electrode 42 includes an outer ring electrode 421, an inner ring electrode 422, and a connecting electrode 423. The outer ring electrode 421 is parallel to the surface of the electrode shoe 41. The inner ring electrode 422 has a central hole H, is located inside the outer ring electrode 421 along a direction parallel to the outer ring electrode 421, and is located on the side of the outer ring electrode 421 away from the objective lens 20 along the electron beam transmission direction. The connecting electrode 423 connects the inner edge of the outer ring electrode 421 and the outer edge of the inner ring electrode 422, and has a slope.

[0084] Optionally, the diameter of the central hole of the inner ring electrode 422 is smaller than the diameter of the central hole of the pole shoe 41.

[0085] Optionally, the outer ring electrode 421, the inner ring electrode 422, and the connecting electrode 423 are integrated into one structure.

[0086] Optionally, the cleaning electrode 42 is made of a material that is resistant to high temperatures and has good electrical conductivity, and can undergo rigorous polishing to ensure that the surface smoothness of the cleaning electrode 42 meets the preset requirements.

[0087] In this embodiment, a cleaning electrode 42 with a morphology matching the side of the pole piece 41 closest to the sample 10 is provided. For example, both are annular structures. By selecting and setting the size of the central hole H of the inner annular electrode 422, the smooth passage of primary and secondary electron beams can be ensured, while the adhesion of particulate matter spilled from the sample 10 to the surface of the pole piece 41 can be greatly reduced. This minimizes the probability of particulate matter spilling from the sample 10 to the objective pole piece 41 while ensuring the normal and safe operation of the electromagnetic compound lens structure 40. Furthermore, by selecting and setting the tilt slope of the connecting electrode 423, this embodiment can precisely control the distance between the cleaning electrode 42 and the pole piece 41, as well as the distance between the cleaning electrode 42 and the sample 10. This ensures that no arcing occurs during the daily operation and cleaning of the electromagnetic compound lens structure 40, thereby effectively improving the safety of the electron beam scanning system.

[0088] Optionally, the voltage range of the first alternating electric field includes 0V to 5000V. The distance between the outer ring electrode 421 and the pole piece 41 along the electron beam propagation direction is not less than 3mm. In this way, a safe distance of at least 3mm can be maintained between the cleaning electrode 42 and the lower surface of the pole piece 41, so as to ensure that the cleaning electrode 42 does not spark with the objective pole piece 41 when cleaning the pole piece 41.

[0089] Optionally, the difference in the central aperture diameter between the pole piece 41 and the inner ring electrode 422 is not less than 3 mm. For example, the central aperture diameter of the pole piece 41 is 8 mm, and the central aperture diameter of the inner ring electrode 422 is 5 mm. In this way, the cleaning electrode 42 can largely block spilled particles from the sample stage, so as to prevent the spilled particles from being adsorbed onto the objective pole piece 41.

[0090] Please combine Figure 5 It is understood that in some embodiments of this application, the electromagnetic composite lens structure 40 further includes an auxiliary electrode 43. The auxiliary electrode 43 is disposed on the periphery of the cleaning electrode 42 and connected to the sample stage, and is used to apply a second alternating electric field to the pole piece 41 in response to a third cleaning control signal provided by the sample stage, so as to perform auxiliary cleaning on the pole piece 41.

[0091] Optionally, the auxiliary electrode 43 may include, but is not limited to, a titanium plate. The auxiliary electrode 43 is connected to the sample stage via a high-voltage signal line.

[0092] Optionally, the third cleaning control signal includes, but is not limited to, a voltage signal.

[0093] Optionally, the electric field directions of the first alternating electric field and the second alternating electric field are different, for example, orthogonal.

[0094] In some examples, the electric field direction of the first alternating electric field is perpendicular to that of the second alternating electric field, and the electric field direction of the second alternating electric field is horizontal.

[0095] Optionally, the voltage range of the second alternating electric field includes 0V to 1000V. The distance between the cleaning electrode 42 (i.e., the inner ring electrode 422) and the sample 10 along the electron beam transmission direction is not less than 1.5mm, which can prevent arcing between the cleaning electrode 42 and the sample and is beneficial to the safety of the lifting system and the sample stage.

[0096] In this embodiment, in addition to applying a first alternating electric field through the cleaning electrode 42, a second alternating electric field is applied through the auxiliary electrode 43. This allows the second alternating electric field to work with the first alternating electric field to enhance the electric field fluctuation intensity at the pole piece 41, thereby further improving the self-cleaning effect and efficiency of the pole piece 41.

[0097] It is worth mentioning that the embodiments of this application do not limit the specific configuration of the electron beam scanning system. Figure 5An example of a possible implementation of an electron beam scanning system is provided, but it is not limited thereto.

[0098] Please see Figure 5 In some embodiments of this disclosure, the electron beam scanning system includes: an electron gun 51, a high-voltage liner 52, a primary focusing lens 53, a gun vacuum valve 54, a secondary focusing lens 55, an electron detector 60, and an electromagnetic compound lens structure 40, arranged sequentially along the electron optical axis. The electron gun 51 provides a high-brightness, stable electron beam. The high-voltage liner 52 forms an accelerating electric field to further accelerate the initial electron beam, ensuring high-speed and stable emission. The primary focusing lens 53 controls the beam intensity by adjusting the focusing of the electron beam through magnetic force. The gun vacuum valve 54 isolates the electron optical chambers in the electron beam scanning system to protect the vacuum at the tip of the electron gun 51. The secondary focusing lens 55 controls the beam angle of the electron beam to adjust the size of the electron beam spot, thereby regulating the resolution of the scanned image. The electron detector 60 collects various signals generated by the interaction between the electron beam and the sample and converts them into electrical signals. The objective lens 20 in the electromagnetic compound lens structure 40 is used to focus the diverging electron beam onto the target point on the surface of the sample to be observed using magnetic force. The cleaning electrode 42 and auxiliary electrode 43 in the electromagnetic compound lens structure 40 can be referred to the relevant descriptions in some of the foregoing embodiments, and will not be described in detail here.

[0099] Based on the same inventive concept, some embodiments of this application also provide a self-cleaning method for the pole piece of an electromagnetic composite lens structure, applicable to the electromagnetic composite lens structure described in any of the above embodiments. This self-cleaning method also possesses all the technical advantages of the aforementioned electromagnetic composite lens structure, and will not be elaborated upon here.

[0100] Please see Figure 8 In some embodiments of this application, the self-cleaning method for the pole shoe includes the following steps S100 and S200.

[0101] S100, the current source responds to the cleaning command and provides a first cleaning control signal, and the objective lens responds to the first cleaning control signal and generates a changing magnetic field at the pole shoe.

[0102] Optionally, the first cleaning control signal may include, but is not limited to, a current signal.

[0103] S200, the signal generator responds to the cleaning command and provides a second cleaning control signal, and the cleaning electrode responds to the second cleaning control signal and applies a first alternating electric field to the pole shoe.

[0104] Optionally, the second cleaning control signal includes, but is not limited to, a pulse signal or a frequency sweep signal.

[0105] As described above, the changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoes.

[0106] Please see Figure 9 In some embodiments of this application, the electromagnetic composite lens structure further includes an auxiliary electrode disposed on the periphery of the cleaning electrode and connected to the sample stage. The electrode shoe self-cleaning method further includes the following step S300.

[0107] S300, the sample stage responds to the cleaning command and provides a third cleaning control signal, and the auxiliary electrode responds to the third cleaning control signal and applies a second alternating electric field to the pole piece to perform auxiliary cleaning of the pole piece.

[0108] Optionally, the third cleaning control signal includes, but is not limited to, a voltage signal.

[0109] Optionally, the electric field directions of the first alternating electric field and the second alternating electric field are different, including but not limited to orthogonal.

[0110] In some examples, the electric field direction of the second alternating electric field is horizontal.

[0111] Please see Figure 10 In some embodiments of this application, the self-cleaning method for the exhaust shoe further includes the following steps S10 to S30.

[0112] S10, acquire images for pre-cleaning inspection.

[0113] S20, analyze the imaging quality of the image before cleaning.

[0114] S30: In response to the fact that the imaging quality of the image detected before cleaning does not meet the preset conditions, a cleaning instruction is generated.

[0115] Optionally, the acquisition of pre-cleaning inspection images is performed during equipment standby intervals (e.g., during wafer replacement) or periodically.

[0116] In this embodiment, by acquiring a pre-cleaning detection image, a cleaning command can be generated if the imaging quality of the pre-cleaning detection image does not meet the preset conditions. Based on the cleaning command, the self-cleaning action of the pole shoe is triggered online, thereby realizing intelligent cleaning of the pole shoe. This allows for on-demand cleaning and reduces unnecessary cleaning and maintenance, thereby reducing reliance on original equipment manufacturer (OEM) engineers and losses due to human error, saving system maintenance costs, reducing system maintenance expenses, effectively avoiding economic losses caused by production interruptions, and extending the system's service life.

[0117] Please see Figure 11 In some embodiments of this application, the self-cleaning method for the exhaust shoe further includes the following steps S10 to S70.

[0118] S40, acquires images after cleaning and inspection.

[0119] S50 analyzes the imaging quality of the image after cleaning.

[0120] S60, in response to the detection that the image quality of the image after cleaning does not meet the preset conditions, a cleaning command is regenerated to clean again.

[0121] S70, in response to the fact that the imaging quality of the detected image after cleaning meets the preset conditions, terminates the cleaning command.

[0122] In this embodiment, after each cleaning of the pole piece, by acquiring a post-cleaning detection image, a cleaning command can be regenerated and the cleaning action executed again when the analysis determines that the imaging quality of the post-cleaning detection image does not meet the preset conditions. The cleaning action is completed when the analysis determines that the imaging quality of the post-cleaning detection image meets the preset conditions, thereby further improving the intelligence level of pole piece self-cleaning, which is conducive to further reducing system maintenance costs and further improving the measurement accuracy, reliability and stability of the electron beam scanning system.

[0123] Please see Figure 12 In some embodiments of this application, the self-cleaning method for the exhaust shoe further includes the following steps S80 and S90.

[0124] S80 monitors the vacuum level of the vacuum chamber containing the electromagnetic composite lens structure in real time.

[0125] Optionally, the vacuum level of the vacuum chamber is monitored based on a vacuum pressure sensor, which can determine whether the self-cleaning process of the pole shoes is safe and reliable by observing changes in the vacuum level of the vacuum chamber, thereby providing safety feedback for the electron beam scanning system.

[0126] S90: If the vacuum level exceeds the preset threshold, the cleaning command is terminated and an alarm command is generated.

[0127] Optionally, when terminating the cleaning command, closing the gun vacuum valve can directly stop the pole shoe self-cleaning process, thus ensuring the safety and reliability of the electron beam scanning system.

[0128] To better understand the self-cleaning method for pole shoes provided in the embodiments of this application, the following embodiments combine... Figure 13 and Figure 14 An exemplary implementation process of the self-cleaning method for pole boots from start to finish is provided.

[0129] Please see Figure 13 First, the triggering condition is determined by the user, for example, steps S10 to S30 mentioned above can be executed.

[0130] In specific implementation, please combine Figure 14Understanding this process involves adjusting optical parameters to target parameters. For example, after the initial cleaning of the electron beam scanning system, the imaging focus and astigmatism correction parameters can be adjusted to their optimal state at a specific target location, and a reference image (i.e., the original image under the current parameter conditions) can be acquired. Then, an image algorithm is invoked to calculate the imaging quality score of the reference image. A scoring threshold can be set based on this score, for example, setting it to 90% (the percentage of the imaging quality score). During actual machine operation, according to the manually set image detection time, the sample stage will automatically move to the acquisition position of the reference image (i.e., the target position) and acquire pre- and post-cleaning detection images based on the same optical parameters. The image algorithm is then invoked to calculate the imaging quality score of the pre- and post-cleaning detection images, thereby determining whether the imaging quality score of the pre- and post-cleaning detection images exceeds the scoring threshold, and accordingly deciding whether to execute the pole shoe self-cleaning method. For example, if the imaging quality score of the image before / after cleaning is greater than the scoring threshold, there is no need to perform pole shoe self-cleaning, and critical size measurement can continue; if the imaging quality score of the image before / after cleaning is not greater than the scoring threshold, pole shoe self-cleaning is required, which can cause the control unit to generate a cleaning command.

[0131] Then, please continue reading. Figure 13 Perform a system safety self-test, for example, by performing the aforementioned step S80, so that when the system safety self-test passes (e.g., the measured vacuum degree is less than or equal to a preset threshold), the sample stage is moved to a clean position by the control unit.

[0132] It is understandable that system safety self-tests may also include other checks, such as checking whether the communication between the various components in the electron beam scanning system is properly connected.

[0133] In some examples, the cleaning location has a deep groove to receive particulate contaminants that fall off the pole shoes during the self-cleaning process.

[0134] From the above, please continue reading Figure 13 After the sample stage is moved to the cleaning position, the system intelligently selects a second cleaning control signal. For example, it can select a normal pulse signal or a sweep frequency signal as the second cleaning control signal based on the imaging quality score of the image detected before cleaning.

[0135] For example, when the imaging quality score of the image before cleaning is between 80% and 90%, it indicates that the particulate contaminants attached to the objective lens pole piece have a relatively small impact. In this case, a common pulse signal generated by a high-voltage pulse generator can be used as the second cleaning control signal. Figure 6 The sawtooth pulse signal, triangular pulse signal, square wave pulse signal, or sine pulse signal shown are used to perform simple cleaning of the objective lens pole piece.

[0136] For example, when the imaging quality score of the image before cleaning is below 80%, it indicates that particulate contaminants attached to the objective lens pole piece have a significant impact, resulting in a marked decrease in image quality. In such cases, a suitable alternative could be selected. Figure 7 The sweep frequency signal shown serves as a second cleaning control signal to perform deep cleaning of the objective lens pole piece.

[0137] It should be added that the contaminants on the surface of the objective lens pole piece are complex, varying in mass, size, and shape, and each possesses a different inherent resonant frequency. Therefore, using a frequency sweep signal as the second cleaning control signal can cover a wide range of frequencies from high to low, ensuring that each contaminant encounters an excitation frequency that matches its resonant frequency during cleaning mode, thereby achieving maximum amplitude removal. Thus, the pole piece self-cleaning method based on the sweep signal is highly adaptable, effectively removing mixed contaminants without prior analysis of contaminant composition, and can sequentially match the inherent frequencies of contaminants of different masses and sizes to achieve broad-spectrum resonant cleaning, thereby improving the thoroughness and multi-functional adaptability of the objective lens pole piece self-cleaning.

[0138] Please continue reading afterward. Figure 13 Following the aforementioned steps S100~S300, the pole shoes are cleaned. The forces generated at the pole shoes 41 by the changing magnetic field, the first alternating electric field, and the second alternating electric field (e.g., Coulomb force, gradient force, mechanical vibration effect, and magnetic force) work synergistically to effectively remove contaminants from the pole shoes.

[0139] For example, for charged particles, the Coulomb force applied by the first alternating electric field and / or the second alternating electric field can overcome the adsorption forces such as van der Waals forces, allowing the charged particles to detach directly from the surface of the objective lens pole piece.

[0140] For example, for neutral particles adsorbed on the objective lens pole piece, the non-uniform electric field in the first alternating electric field and / or the second alternating electric field can induce the neutral particles to polarize and be subjected to a gradient force pointing in the direction of weaker electric field strength, thereby pushing them away from the pole piece surface.

[0141] For example, high-frequency changing magnetic and electric fields can subject particulate matter to alternating forces, generating a mechanical vibration effect. This can disrupt the adsorption balance between contaminants and the surface of the objective lens pole piece through micro-vibration, thereby causing the contaminants to detach from the objective lens pole piece.

[0142] For example, magnetic particles adsorbed on the objective lens pole piece can be directly attracted or repelled by the magnetic gradient force and fall off the pole piece. Furthermore, if the particle is a conductor, the changing magnetic field will generate eddy currents, which will produce eddy current repulsion within the particle (following Lenz's law, the direction of the induced current always causes the magnetic field to oppose the change in magnetic flux that caused the induced current), causing the particle to detach from the objective lens pole piece.

[0143] Furthermore, in this embodiment, the combined action of the first and second alternating electric fields transforms the change in electric field force from a one-dimensional change in intensity to a two-dimensional change in which space and intensity oscillate together, and oscillates synchronously with the changing magnetic field in both space and intensity. This not only makes the electric field changes more dramatic and the various electric field forces more significant, but also significantly expands the range of electric field influence, ensuring that the cleaning area covers the entire objective pole piece, thereby greatly improving the cleaning efficiency of the objective pole piece.

[0144] Furthermore, the particles shed during the self-cleaning process of the pole shoes can fall onto the designated collection area on the sample stage under the combined action of electric field force, magnetic force, resonance force, and gravity. The collection area is designed, for example, as a circular deep groove structure, with a layer of vacuum adhesive at the bottom of the groove, to ensure that the falling particles are adsorbed in the designated collection area and await opening for cleaning, rather than splashing around during the operation of the instrument.

[0145] Please continue reading. Figure 13 After the pole shoe self-cleaning is performed, a safety protection test is performed, such as by executing the aforementioned step S80. If the safety protection test passes (e.g., the measured vacuum degree is less than or equal to a preset threshold), an image self-test can be performed (e.g., by executing the aforementioned steps S40~S70). If the safety protection test fails (e.g., the measured vacuum degree is greater than a preset threshold), the cleaning is terminated and the gun vacuum valve is closed to ensure the safety of the objective lens pole shoe.

[0146] For example, cleaning is terminated by the control unit cutting off the output signal of the signal generator.

[0147] Furthermore, if the image self-check passes, it indicates that the pole shoe self-cleaning is complete, and normal measurement of critical dimensions can be resumed.

[0148] If the image self-check fails, the system returns to the security self-check and repeats the above process until the pole shoe self-cleaning is confirmed to be complete.

[0149] In summary, the embodiments disclosed herein have online operation capabilities and can automatically complete cleaning during equipment standby intervals (such as when changing wafers), thereby greatly improving equipment utilization.

[0150] The embodiments disclosed herein can achieve intelligent cleaning. By linking image algorithms and a system self-diagnosis system, the cleaning method can be intelligently selected according to the actual situation of the machine, so as to achieve on-demand cleaning and reduce unnecessary system maintenance.

[0151] The embodiments disclosed herein also have significant economic benefits: for example, they can reduce reliance on original equipment manufacturer (OEM) engineers, save maintenance costs, and reduce maintenance expenses; for example, they can be cleaned online to avoid economic losses caused by production interruptions; for example, they can be maintained regularly to keep the system in optimal working condition and extend the system's service life.

[0152] The embodiments disclosed herein also offer significant performance improvements: for example, they can ensure that the pole piece is in optimal working condition to guarantee the accuracy and precision of the system measurements; for example, they can reduce performance fluctuations caused by objective pole piece contamination to improve system stability; for example, they can automate the cleaning of the objective pole piece to reduce losses caused by human error and enhance system reliability.

[0153] Based on the same inventive concept, some embodiments of this application also provide a self-cleaning device for pole shoes with an electromagnetic composite lens structure, used to implement the self-cleaning method for pole shoes in the above embodiments. The self-cleaning device for pole shoes also possesses the technical advantages of the aforementioned self-cleaning method for pole shoes, and will not be elaborated here. Furthermore, the relevant features of each component module or unit in the self-cleaning device for pole shoes can be understood by referring to the relevant limitations in the foregoing embodiments.

[0154] Please see Figure 15 In some embodiments of this application, the pole shoe self-cleaning device includes: an electromagnetic composite lens structure 40, a current source 71, a signal generator 72, and a control unit 70.

[0155] The electromagnetic compound lens structure 40 includes: an objective lens 20 and a cleaning electrode 42 disposed on the side of the objective lens 20 near the sample.

[0156] Current source 71 is connected to objective lens 20 and is used to provide current in response to cleaning instructions so that objective lens 20 generates a changing magnetic field at pole shoes in response to the current provided by current source 71.

[0157] The signal generator 72 is connected to the cleaning electrode 42 and is used to provide a second cleaning control signal in response to a cleaning command, so that the cleaning electrode 42 applies a first alternating electric field to the pole shoe in response to the second cleaning control signal.

[0158] The control unit 70 is connected to the current source 71 and the signal generator 72 to generate cleaning instructions.

[0159] It is understood that the control unit 70 is used to control the start and stop of the pole shoe self-cleaning process, the relevant parameters of the signal generator 72 (such as sweep frequency range, voltage peak, duration, etc.), and the relevant parameters of the current source 71 (such as current value, current reciprocating cycle, etc.), and all of its information can be included in the cleaning command.

[0160] As described above, the changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoes.

[0161] Please see Figure 16In some embodiments of this application, the electromagnetic composite lens structure 40 further includes an auxiliary electrode 43 disposed around the periphery of the cleaning electrode 42. The electrode shoe self-cleaning device also includes a sample stage 73. The sample stage 73 is connected to the control unit 70 and the auxiliary electrode 43, and is used to provide voltage in response to a cleaning command, so that the auxiliary electrode 43 applies a second alternating electric field to the electrode shoe in response to the voltage provided by the sample stage 73, thereby assisting in cleaning the electrode shoe. The electric field directions of the first alternating electric field and the second alternating electric field are different.

[0162] Please see Figure 17 In some embodiments of this application, the self-cleaning device for the pole shoes further includes an image acquisition unit 74 and an image quality analysis unit 75. The image acquisition unit 74 is connected to the control unit 70 and is used to acquire pre-cleaning detection images and / or post-cleaning detection images. The image quality analysis unit 75 is connected to the image acquisition unit 74 and the control unit 70 and is used to analyze the image quality of the pre-cleaning detection images and / or post-cleaning detection images.

[0163] Accordingly, the control unit 70 is also configured to: generate a cleaning command in response to the fact that the imaging quality of the image detected before cleaning does not meet the preset conditions; and regenerate a cleaning command to clean again in response to the fact that the imaging quality of the image detected after cleaning does not meet the preset conditions; and terminate the cleaning command in response to the fact that the imaging quality of the image detected after cleaning meets the preset conditions.

[0164] Please see Figure 18 In some embodiments of this application, the pole shoe self-cleaning device further includes a safety protection unit 76 connected to the control unit 70. The safety protection unit 76 includes a vacuum monitoring module 761 and an alarm module 762. The vacuum monitoring module 761 is used to monitor the vacuum level of the vacuum chamber where the electromagnetic composite lens structure 40 is located in real time. The control unit 70 is also used to: terminate the cleaning command and generate an alarm command in response to a vacuum level exceeding a preset threshold. The alarm module 762 is used to issue an alarm based on the alarm command.

[0165] Based on the same inventive concept, some embodiments of this application also provide an electron beam scanning system, including the electromagnetic compound lens structure as described in any of the preceding embodiments; or, the pole shoe self-cleaning device as described in any of the preceding embodiments. This electron beam scanning system also possesses the technical advantages of the aforementioned electromagnetic compound lens structure or pole shoe self-cleaning device.

[0166] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0167] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. An electromagnetic composite lens structure, characterized in that, include: Objective lens and cleaning electrode disposed on the objective lens for proximity to the sample; The objective lens is connected to a current source; The cleaning electrode is connected to a signal generator; wherein... The objective lens is used to generate a changing magnetic field at the pole piece of the objective lens in response to a first cleaning control signal provided by the current source during cleaning mode. The cleaning electrode is used to apply a first alternating electric field to the pole shoe in response to a second cleaning control signal provided by the signal generator during cleaning mode; The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoes.

2. The electromagnetic composite lens structure according to claim 1, characterized in that, Also includes: An auxiliary electrode is disposed around the cleaning electrode and connected to the sample stage. It is used to apply a second alternating electric field to the electrode shoe in response to a third cleaning control signal provided by the sample stage, so as to perform auxiliary cleaning on the electrode shoe. The electric field directions of the first alternating electric field and the second alternating electric field are different.

3. The electromagnetic composite lens structure according to claim 1 or 2, characterized in that, The cleaning electrode includes: The outer ring electrode is parallel to the surface of the pole piece; The inner ring electrode has a central hole, is located inside the outer ring electrode along a direction parallel to the outer ring electrode, and is located on the side of the outer ring electrode away from the objective lens along the electron beam transmission direction; Connecting electrodes connect the inner edge of the outer ring electrode to the outer edge of the inner ring electrode.

4. The electromagnetic composite lens structure according to claim 3, characterized in that, It also includes at least one of the following solutions: The distance between the outer ring electrode and the pole piece along the electron beam transmission direction is not less than 3 mm; The diameter of the central hole of the inner ring electrode is smaller than the diameter of the central hole of the pole shoe; The difference in the diameter of the center hole between the pole shoe and the inner ring electrode is not less than 3 mm; The distance between the cleaning electrode and the sample along the electron beam transmission direction is not less than 1.5 mm; The voltage range of the first alternating electric field includes 0V to 5000V; When the electromagnetic composite lens structure further includes auxiliary electrodes, the voltage range of the second alternating electric field includes 0V~1000V.

5. A method for self-cleaning pole shoes of an electromagnetic composite lens structure, characterized in that, The electromagnetic composite lens structure includes an objective lens and a cleaning electrode disposed on the objective lens for proximity to the sample. The objective lens is connected to a current source; The cleaning electrode is connected to a signal generator; The self-cleaning method for the polar boots includes: The current source provides a first cleaning control signal in response to a cleaning command, and the objective lens generates a changing magnetic field at the pole shoe in response to the first cleaning control signal. The signal generator provides a second cleaning control signal in response to a cleaning command, and the cleaning electrode applies a first alternating electric field to the pole shoe in response to the second cleaning control signal. The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoe.

6. The self-cleaning method for the pole shoe of the electromagnetic composite lens structure according to claim 5, characterized in that, The electromagnetic composite lens structure also includes an auxiliary electrode disposed on the periphery of the cleaning electrode and connected to the sample stage; The self-cleaning method for the extreme boots also includes: The sample stage provides a third cleaning control signal in response to a cleaning command, and the auxiliary electrode applies a second alternating electric field to the pole piece in response to the third cleaning control signal to assist in cleaning the pole piece. The electric field directions of the first alternating electric field and the second alternating electric field are different.

7. The self-cleaning method for the pole shoe of the electromagnetic composite lens structure according to claim 5, characterized in that, Also includes: Acquire images for pre-cleaning inspection; Analyze the imaging quality of the pre-cleaning detection image; The cleaning instruction is generated in response to the fact that the imaging quality of the pre-cleaning detection image does not meet the preset conditions.

8. The self-cleaning method for the pole shoe of the electromagnetic composite lens structure according to any one of claims 5 to 7, characterized in that, Also includes: Acquire images after cleaning and inspection; Analyze the imaging quality of the cleaned and detected images; If the imaging quality of the image detected after cleaning does not meet the preset conditions, the cleaning instruction is regenerated to clean again; If the imaging quality of the image detected after cleaning meets the preset conditions, the cleaning command is terminated. And / or, monitor the vacuum level of the vacuum chamber where the electromagnetic composite lens structure is located in real time; in response to the vacuum level being greater than a preset threshold, terminate the cleaning command and generate an alarm command.

9. A self-cleaning device for pole shoes with an electromagnetic composite lens structure, characterized in that, include: An electromagnetic compound lens structure includes: an objective lens and a cleaning electrode disposed on the objective lens for proximity to the sample. A current source, connected to the objective lens, is used to provide a first cleaning control signal in response to a cleaning command, so that the objective lens generates a changing magnetic field at the pole piece of the objective lens in response to the first cleaning control signal. A signal generator, connected to the cleaning electrode, is used to provide a second cleaning control signal in response to a cleaning command, so that the cleaning electrode applies a first alternating electric field to the pole shoe in response to the second cleaning control signal; A control unit, connected to the current source and the signal generator, is used to generate the cleaning command; The changing magnetic field and the first alternating electric field are used to clean contaminants at the pole shoe.

10. The self-cleaning device for the pole shoe of the electromagnetic composite lens structure according to claim 9, characterized in that, The electromagnetic composite lens structure also includes an auxiliary electrode disposed on the periphery of the cleaning electrode; The self-cleaning device for the pole shoes also includes: The sample stage is connected to the control unit and the auxiliary electrode, and is used to provide a third cleaning control signal in response to the cleaning command, so that the auxiliary electrode applies a second alternating electric field to the pole piece in response to the third cleaning control signal to perform auxiliary cleaning of the pole piece; The electric field directions of the first alternating electric field and the second alternating electric field are different.

11. The self-cleaning device for the pole shoe of the electromagnetic composite lens structure according to claim 9, characterized in that, Also includes: An image acquisition unit, connected to the control unit, is used to acquire pre-cleaning detection images and / or post-cleaning detection images; An imaging quality analysis unit, connected to the image acquisition unit and the control unit, is used to analyze the imaging quality of the pre-cleaning detection image and / or the post-cleaning detection image; The control unit is further configured to: generate the cleaning instruction in response to the fact that the imaging quality of the pre-cleaning detection image does not meet the preset conditions; and regenerate the cleaning instruction for cleaning again in response to the fact that the imaging quality of the post-cleaning detection image does not meet the preset conditions. If the imaging quality of the image detected after cleaning meets a preset condition, the cleaning command is terminated.

12. The self-cleaning device for the pole shoe of the electromagnetic composite lens structure according to any one of claims 9 to 11, characterized in that, Also includes: The safety protection unit connected to the control unit; The security protection unit includes: The vacuum monitoring module is used to monitor the vacuum level of the vacuum chamber where the electromagnetic composite lens structure is located in real time; the control unit is also used to: terminate the cleaning command and generate an alarm command in response to the vacuum level being greater than a preset threshold. The alarm module is used to issue an alarm based on the alarm command.

13. An electron beam scanning system, characterized in that, It includes the electromagnetic composite lens structure as described in any one of claims 1 to 4; or, the pole shoe self-cleaning device of the electromagnetic composite lens structure as described in any one of claims 9 to 12.

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