Method for operating a charged particle gun, charged particle gun for a charged particle beam device, and charged particle beam device

Abstract

A method of operating a charged particle gun (102) is described. The method includes: providing an emitter (122) at a first emitter potential within the charged particle gun, and providing a capture electrode (142) at a first electrode potential within the charged particle gun, wherein the first emitter potential and the first electrode potential are configured to have a substantially zero electric field at the emitter and at the capture electrode; switching the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential to generate an electrostatic capture field at the capture electrode; and after switching the capture electrode from the first electrode potential to the second electrode potential, turning on the electrostatic emission field at the emitter.

Description

Technical Field

[0001] Embodiments of the present disclosure relate to particle traps for charged particle beam devices, and in particular to particle traps for ultra-high vacuum (UHV) gun chambers. In addition, embodiments relate to charged particle guns or gun chambers and charged particle beam devices. Embodiments also relate to cleaning of charged particle beam devices, for example, cleaning of charged particle guns or gun chambers of charged particle beam devices. Embodiments particularly relate to methods of operating charged particle guns, charged particle guns, and charged particle beam devices. Background Art

[0002] Charged particle beam devices have many functions in multiple industrial fields, including but not limited to electron beam inspection (electron beam inspection, EB), measurement of critical dimensions (criticaldimension, CD) of semiconductor devices during manufacturing, defect review (defect review, DR) of semiconductor devices during manufacturing, exposure systems, detection devices and test systems for lithography. Therefore, there is a high demand for structuring, testing and inspection of samples in micrometer and nanometer scales. Micrometer and nanometer scale process control, inspection or structuring can be performed using charged particle beams (such as electron beams) generated and focused in charged particle beam devices (such as electron microscopes). Charged particle beams provide excellent spatial resolution compared to photon beams generated by, for example, short wavelengths.

[0003] In order to operate a charged particle beam device in the industry (i.e., according to industrial standards), the acceleration of the system and the maintenance of the system need to be considered. In particular, the total throughput of the system is affected by downtime. Therefore, it is beneficial to start the system operation quickly and reliably. For the first start-up or after maintenance, dust particles may remain in the charged particle beam device (e.g., the gun chamber) even after careful cleaning. In particular, in the gun chamber, particles may cause arcing and emitter damage.

[0004] Currently, time consuming cleaning is provided and possibly several attempts to bias the emitter are provided.After the arc, the gun chamber can be opened again and can be re-inspected to find and remove residual particles.

[0005] In view of the above, an improved method of operating a charged particle gun or a gun chamber of a charged particle beam apparatus, as well as an improved charged particle gun and an improved charged particle beam apparatus would be beneficial. Summary of the invention

[0006] In view of the above, a method of operating a charged particle gun, a charged particle gun and a charged particle beam apparatus according to the independent claims are provided. Further aspects, advantages and features are apparent from the dependent claims, the description and the drawings.

[0007] According to one embodiment, a method of operating a charged particle gun is provided. The method includes: providing an emitter at a first emitter potential within the charged particle gun, and providing a capture electrode at a first electrode potential within the charged particle gun, wherein the first emitter potential and the first electrode potential are configured to have a substantially zero electric field at the emitter and at the capture electrode; switching the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential to generate an electrostatic capture field at the capture electrode; and after switching the capture electrode from the first electrode potential to the second electrode potential, turning on the electrostatic emission field at the emitter.

[0008] According to one embodiment, a charged particle gun for a charged particle beam device is provided. The charged particle gun includes: a gun housing; an emitter disposed in the gun housing, the emitter configured to emit a charged particle beam along an axis; an emitter power supply connected to the emitter; a capture electrode disposed in the gun housing, the capture electrode at least partially surrounding the axis; a capture power supply connected to the capture electrode; and a shielding element, the shielding element shielding an electrostatic field of the capture electrode from the axis during operation of the gun housing.

[0009] According to one embodiment, a charged particle beam apparatus is provided. The charged particle beam apparatus comprises: a charged particle gun according to any of the embodiments described herein; and a charged particle beam train for directing charged particles on a sample.

[0010] Embodiments also relate to devices for performing the disclosed methods and include device portions for performing each described method aspect. These method aspects can be performed by hardware components, computers programmed by appropriate software, by any combination of the two, or in any other manner. In addition, embodiments according to the present disclosure also relate to methods for operating the described devices. The methods include method aspects for performing each function of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] In order to understand the above features of the present disclosure in detail, a more specific description of the present disclosure (which has been briefly summarized above) can be provided by referring to the embodiments. The accompanying drawings are related to the embodiments of the present disclosure and are described below:

[0012] Figure 1A shows a schematic diagram of a portion of a charged particle beam apparatus according to embodiments described herein and including electrodes for capturing particles;

[0013] Figure 1B Shows Figure 1A a cross-sectional view of said portion of the charged particle beam apparatus shown;

[0014] FIG. 2A to FIG. 2C shows a schematic diagram of a portion of a charged particle beam apparatus illustrating operation for capturing particles according to further embodiments described herein;

[0015] Figure 3 A schematic diagram of a charged particle beam device including a particle trap according to an embodiment of the present disclosure is shown;

[0016] Figure 4 a flow chart showing a method of operating a portion of a charged particle beam apparatus according to an embodiment of the present disclosure; and

[0017] Figure 5 A schematic diagram of a part of a charged particle beam device according to embodiments described herein and comprising an electrode for trapping particles and a further trapping electrode is shown. DETAILED DESCRIPTION

[0018] Reference will now be made in detail to various embodiments of the present disclosure, one or more examples of which are illustrated in the accompanying drawings. In the following description of the drawings, the same reference numerals refer to the same components. Only the differences with respect to individual embodiments are described. Each example is provided in a manner to explain the present disclosure and is not intended to limit the present disclosure. In addition, features illustrated or described as part of one embodiment may be used in other embodiments or used in combination with other embodiments to produce yet another embodiment. The description is intended to include such modifications and variations.

[0019] Without limiting the scope of protection of the present application, hereinafter, a charged particle beam device or its components will be exemplarily referred to as a charged particle beam device using electrons as charged particles. However, other types of primary charged particles, such as ions, may be used. After the sample or sample is irradiated by a charged particle beam (also referred to as a "primary charged particle beam"), signal charged particles such as secondary electrons (SE) are generated, which can carry information about the configuration, chemical composition and / or electrostatic potential and other information about the sample. Secondary electrons may include at least one of backscattered electrons, secondary electrons and Auger electrons.

[0020] The charged particle beam device is operated under high vacuum. Specifically, a charged particle gun including an emitter can be operated at ultrahigh vacuum (UHV) pressure. In order to operate the emitter, a high voltage is applied while the gun housing is at ultrahigh vacuum pressure. Various cleaning procedures are applied before and during the evacuation of the gun housing. After the gun housing (i.e., the UHV chamber of the charged particle gun) is initially evacuated, particles (such as dust particles) may remain in the chamber or housing of the charged particle gun.

[0021] The tip of the emitter releases charged particles, such as electrons. According to some embodiments that can be combined with other embodiments described herein, the charged particles emitted by the emitter can be electrons or ions. In the following, reference will be made to charged particles being electrons. For example, the charged particle beam device can be a scanning electron microscope with a single beam or with multiple beamlets. However, similar embodiments can be provided for the charged particles being ions. Please note that embodiments describing potentials for electron beam devices will utilize potentials of different polarity in the case of ion beam devices.

[0022] Particles that may remain in the gun housing of a charged particle gun may adhere to the tip of the emitter, particularly when the emitter voltage is turned on. This small radius of curvature of the tip of the emitter results in a high field strength at the emitter, which may further increase the likelihood of particles adhering to the emitter. For example, particles (such as dust particles) may be electrostatically adsorbed to a negatively biased emitter. In addition, particles at the emitter tip may cause arcs, or even damage the emitter. The arc at the emitter may be triggered by the further increased field strength of particles (such as dust particles) adhering to the emitter. Therefore, once an arc is detected during the acceleration of the charged particle gun (i.e., in particular, applying an operating potential to the emitter), the acceleration of the system is stopped and further cleaning measures may be applied. For example, during the installation of a new system or after maintenance of an existing system, it may be time-consuming to attempt to accelerate the cycle of each additional cleaning of the charged particle gun.

[0023] Embodiments of the present disclosure provide a particle trap for particles (such as dust particles) in a vacuum chamber, particularly in a UHV chamber (such as a gun housing of a charged particle gun, the gun housing housing housing an emitter). The particle trap can reduce or avoid arcing in a UHV charged particle gun (e.g., an electron gun, particularly a UHV electron gun).

[0024] According to some embodiments of the present disclosure, an electrode is provided in the gun housing and a voltage is applied to the electrode before turning on the emitter located in the gun housing. Therefore, particles remaining in the gun housing (e.g., dust particles dispersed in the UHV chamber (i.e., the gun housing) of the charged particle gun) are electrostatically adsorbed to the electrode. The particles remain adsorbed at the electrode. Only thereafter, an operating voltage for the charged particle gun, in particular an operating voltage for the emitter, is applied.

[0025] In view of the above, embodiments of the present disclosure allow for faster acceleration of charged particle guns. Additionally or alternatively, the risk of arcing and emitter damage during acceleration of charged particle guns is reduced.

[0026] Figure 1A A portion of a charged particle beam device 100 is shown. The charged particle beam device 100 includes a charged particle gun 102. The charged particle beam device further includes a charged particle source 120. The charged particle source 120 includes an emitter 122 and an emitter power supply 124. A voltage for biasing the emitter 122 can be provided by a power supply using a conductor 121. For example, a high voltage can be provided to a vacuum chamber 110 of the charged particle gun 102 using a conductor 128 supported by an insulator 126. The charged particle gun 102 includes a vacuum chamber 110 provided by a gun housing 111. The emitter 122 is disposed within the gun housing 111, i.e., within the vacuum chamber 110. In order to control the electron beam generated by the charged particle source, the emitter voltage of the emitter 122 can be controlled by the emitter power supply 124. The electron beam can be further controlled by a suppressor electrode 125, an extractor 132, and an anode 152.

[0027] The extractor potential of the extractor 132 may be controlled by the extractor power supply 134. The anode potential of the anode 152 may be controlled by the anode power supply 154. For example, the anode 152 may be arranged between the vacuum chamber 110 and a further vacuum chamber 112 of a column of the charged particle beam device 100. According to some embodiments, the anode may be at least partially arranged within the gun housing 111.

[0028] According to an embodiment of the present disclosure, a capture electrode 142 is disposed in the gun housing 111. A capture power supply 144 is connected to the capture electrode for biasing the capture electrode. The electron beam emitted from the emitter 122 travels substantially along the axis 123. According to some embodiments, which can be combined with other embodiments described herein, the capture electrode at least partially surrounds the axis 123.

[0029] According to one embodiment, a charged particle gun for a charged particle beam device is provided. The charged particle gun 102 includes a gun housing and an emitter disposed in the gun housing. The emitter can be configured to emit a charged particle beam along an axis 123. The charged particle gun 102 further includes an emitter power supply connected to the emitter. A capture electrode is disposed in the gun housing, the capture electrode at least partially surrounding the axis. The capture power supply is connected to the capture electrode. The charged particle gun 102 further includes a shielding element that shields a potential provided from the capture power supply to the capture electrode from the axis during operation of the gun chamber.

[0030] According to some embodiments, which can be combined with other embodiments described herein, the emitter can be a field emitter, such as a thermal field emitter (TFE), a Schottky emitter, or a cold field emitter (CFE). Embodiments of the present disclosure can be particularly advantageous for CFEs, since CFEs can be even more sensitive to arcing that can cause emitter damage.

[0031] exist Figure 1A In an exemplary embodiment of the present invention, the shielding element may be provided by the anode 152. This may also be Figure 1B As can be seen in the cross-sectional schematic diagram. Figure 1B The diagram shows a cross-sectional view of the gun housing 111, the capture electrode 142, and the anode 152. The capture electrode 142 surrounds the anode 152. The anode 152 extends from Figure 1B The center of the rotationally symmetrical arrangement shown screens the potential of the capture electrode 142 .

[0032] According to an embodiment of the present disclosure, the shielding element reduces or avoids the influence of the potential of the capture electrode on the electron beam traveling along the axis 123. According to yet further additional or alternative modifications, the capture electrode may be rotationally symmetric, in particular annular. For example, rotational symmetry may be provided around the axis 123. Thus, a potential residual influence of the capture electrode potential on the electron beam may be provided in a symmetrical manner. According to yet further optional implementations, the charged particle gun may further include an extractor electrode located within the gun housing, a suppressor electrode located within the gun housing, and an anode located at least partially within the gun housing, such as Figure 1A shown.

[0033] According to some embodiments, which can be combined with other embodiments described herein, the charged particle gun 102 and / or the charged particle beam device 100 may include a controller 190. Figure 1A As illustrated, the controller 190 may be connected to the emitter power supply 124, the extractor power supply 134, the capture power supply 144, and the anode power supply 154. According to some embodiments, which may be combined with other embodiments described herein, the controller 190 may be connected to one or more of the power supplies of the charged particle beam device and / or the charged particle gun to control the operation of the charged particle beam.

[0034] According to some embodiments, which can be combined with other embodiments described herein, a charged particle gun comprises a controller having a processor and a memory storing instructions which, when executed by the processor, cause the device to perform a method according to any of the embodiments of the present disclosure.

[0035] According to some embodiments, which can be combined with other embodiments described herein, the charged particle beam device may further include a substrate support ( Figure 1A122 ), in particular a substrate support connected to a power supply for providing a sample voltage during operation of the charged particle beam device. The controller 190 can also control the sample potential. Thus, the landing energy of the electrons on the sample can be controlled by the potential difference between the sample and the emitter 122.

[0036] Controller 190 includes a central processing unit (CPU), a memory, and, for example, a support circuit. In order to facilitate control of the charged particle beam device and / or the charged particle gun, the CPU may be one of any form of general purpose computer processor, which may be used in industrial settings to control various chambers and subprocessors. The memory is coupled to the CPU. The memory or computer readable medium may be one or more readily available memory devices, such as random access memory, read-only memory, floppy disk, hard disk, or any other form of digital memory (local or remote). The support circuit may be coupled to the CPU for supporting the processor in a conventional manner. Such circuits include cache, power supply, clock circuit, input / output circuit and related subsystems, etc. Imaging process instructions and / or instructions for operating and cleaning the charged particle beam device (or respectively, the charged particle gun) are typically stored in the memory as software routines commonly referred to as recipes. The software routine may also be stored in and / or executed by a second CPU (not shown), which is remotely located from the hardware being controlled by the CPU. The software routines, when executed by the CPU, convert a general-purpose computer into a special-purpose computer (controller) that controls the operation of the device, such as a special-purpose computer for controlling, in particular, one or more power supplies of a charged particle beam device and / or a charged particle gun. Although the methods and / or processes of the present disclosure are discussed as being implemented as software routines, some of the method steps disclosed therein may be performed in hardware and may be performed by a software controller. Thus, embodiments may be implemented in software as being executed on a computer system, and may be implemented in hardware as an application specific integrated circuit or other type of hardware implementation, or in a combination of software and hardware. The controller may execute or perform a method of operating a charged particle gun or a method of operating a charged particle beam device according to an embodiment of the present disclosure.

[0037] Embodiments allow arc protection of an electron gun, such as an electron gun of a scanning electron microscope (SEM). Due to particle capture, the need for further reduction of particle contamination can be reduced. In addition, the risk of arcing when operating the emitter in a UHV environment, for example after maintenance of the electron gun, can be reduced.

[0038] According to an embodiment of the present disclosure, a capture electrode provides an additional electrode in the gun housing 111. That is, an electrode other than the electrode for charged particle beam guidance or charged particle beam influence is introduced. The electrode for charged particle beam guidance can be selected from the group consisting of: a suppressor, an extractor, an anode, an electrode of a lens, an electrode of a deflector for a charged particle beam, and an electrode of a beam aberration correction element. For example, the additional electrode or the capture electrode may be an annular electrode. According to some embodiments that may be combined with other embodiments described herein, the capture electrode may be disposed at the bottom of the vacuum chamber 110 or the gun housing 111, respectively, or close to the emitter.

[0039] In order to operate a charged particle gun or a charged particle beam device, the capture electrode is biased to a positive potential or a negative potential (e.g., positive or negative hundreds of volts to several kV) to adsorb contaminated particles, respectively. An electrostatic capture field is generated at the capture electrode. The capture electrode is switched to a potential before turning on the high voltage to operate the emitter or gun, respectively. Thereafter, in a second step, the other voltages of the charged particle gun are turned on. An electrostatic emission field is generated at the emitter after the electrostatic capture field is generated. According to some embodiments that may be combined with other embodiments described herein, after turning on the electrostatic emission field, the direction of the electrostatic capture field remains the same at the captured electrons. Particles adsorbed at the capture electrode remain on the capture electrode. The risk of arcing is reduced.

[0040] According to some embodiments that can be combined with other embodiments described herein, after maintenance or before operation of the accelerated charged particle gun, there is no electric field at the emitter and / or in the charged particle gun. The electric field is substantially zero. The first electric field or electrostatic field provided in the charged particle gun (e.g. in the gun housing and / or adjacent to the emitter) is an electrostatic capture field. Only thereafter, a further electrostatic field, such as an electrostatic emission field, is provided in the charged particle gun or the gun housing, respectively. The direction of the electrostatic capture field at the capture electrode is maintained after the further electrostatic field is added. Therefore, the particles remain at the capture electrode.

[0041] FIG. 2A to FIG. 2C The diagram shows Figure 4 The charged particle gun 102 during operation of the method of operating a charged particle gun illustrated in the flowchart shown. At operation 602, the voltage within the charged particle gun 102 is at a non-operating value. For example, the electric field is substantially zero at the emitter and at the capture electrode. The non-operating value may be, for example, the same as the value during maintenance or the same as the value during evacuation of the vacuum chamber 110. For example, the emitter 122, the extractor 132, the anode 152, and the capture electrode 142 may be at ground potential. FIG. 2A to FIG. 2CIn the illustrated example, the charged particle beam column is also at ground potential as indicated by reference numeral 214. The emitter power supply 124, the extractor power supply 134, the anode power supply 154, and the capture power supply 144 may be turned off, for example. After cleaning the gun housing (i.e., the vacuum chamber of the charged particle gun 102) to reduce contamination inside the gun housing, particles 202 may remain in the vacuum chamber.

[0042] According to some embodiments, which can be combined with other embodiments described herein, the particle 202 may be a dust particle or other contamination particle, which may adhere to the tip of the emitter 122 when not captured.

[0043] At operation 604, the capture electrode is turned on. The capture power supply 144 provides a voltage to the capture electrode 142 to generate an electrostatic capture field, which attracts the particle 202 to the capture electrode 142. Figure 2B As shown in the figure. For example, for an electron beam gun, the voltage applied to the capture electrode 142 may be positive or negative hundreds of volts to thousands of volts, for example 100V to 9kV or -100V to -9kV, such as about -6kV. In order to capture particles, one or more of the other components of the charged particle gun are not switched to the operating voltage. The electrostatic capture field is the only field in the gun chamber. Specifically, the emitter and / or extractor are not at the operating voltage, and for example, they can be biased to ground potential. Switching of the capture electrode causes particles in the gun housing to be adsorbed to the capture electrode and away from the emitter. Additionally or alternatively, switching the capture electrode causes particles to be adsorbed to the capture electrode and away from other components in the gun chamber, particularly other components that can increase the arc when particles adhere to it. Such components may be other electrodes or beam guiding elements, such as an anode, a suppressor, a lens electrode, or a component of the gun housing.

[0044] During operation of the charged particle gun or charged particle beam device, one or more components may be biased to ground potential even if an electrostatic emission field is provided at the emitter. In addition, multiple components may be biased to ground potential during maintenance. Therefore, there may be an overlap between the maintenance voltage and the operating voltage, and for example, components that are biased to ground potential during operation may also be at ground potential during operation 604 (i.e., when the capture electrode is turned on). According to some embodiments of the present disclosure, no electric field is provided at the emitter and / or in the charged particle gun. The electric field is substantially zero. The first electric field or electrostatic field provided in the charged particle gun (e.g., in the gun housing and / or adjacent to the emitter) is an electrostatic capture field. Only thereafter, a further electrostatic field, such as an electrostatic emission field, is provided in the charged particle gun or the gun housing, respectively. According to some embodiments that may be combined with other embodiments described herein, the capture electrode 142 is switched to a second electrode potential to capture particles without all other components being at operating voltage or most of the components being not at operating voltage. In particular, the capture electrode may be switched to the second electrode potential to generate an electrostatic capture potential to capture particles, while only one further component of the charged particle gun is potentially at an operating voltage of the one further component (e.g. ground), wherein the operating potential (e.g. ground) does not provide a further electric field. More particularly, the operating voltage of the one further component may be at ground potential.

[0045] At operation 606, one or more of the remaining components (particularly the emitter 122) are switched to an operating voltage. For example, the emitter power supply 124 can be used to bias the emitter to +8kV to +12kV. In addition, the extractor 132 can be biased to -3kV to -7kV using the extractor power supply 134, and the anode 152 can be biased to a potential close to the ground potential. According to some embodiments that can be combined with other embodiments described herein, for embodiments in which the anode 152 is always kept at ground, the anode power supply 154 can be omitted. The capture electrode 142 remains biased to, for example, +3kV to +9kV. The particle 202 remains captured at the capture electrode. When other voltages are turned on in the gun, the electric field at the capture electrode also remains negative at the surface of the capture electrode.

[0046] According to some embodiments that can be combined with other embodiments described herein, the relative potentials of the charged particle gun can be set as follows: the operational emitter potential is -0.3kV to -2kV, the potential of the extractor electrode is +5kV to +10kV, the operational anode potential is +10kV to +100kV, and the potential of the suppressor electrode is -0.6kV to -2.3kV, and the potential of the sample is at ground, wherein the relative potentials can be offset together, in particular, offset by about -15kV to -45kV.

[0047] According to one embodiment, a method of operating a charged particle gun is provided. The method includes: setting an emitter at a first emitter potential within the charged particle gun and setting a capture electrode at a first electrode potential within the charged particle gun, wherein the first emitter potential and the first electrode potential are set to have a substantially zero electric field at the emitter and at the capture electrode (e.g., see operation 602). The method further includes: switching the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential to generate an electrostatic capture field at the capture electrode (e.g., see operation 602). After switching the capture electrode from the first electrode potential to the second electrode potential, turning on the electrostatic emission field at the emitter (e.g., see operation 606).

[0048] According to an embodiment, a method of operating a charged particle gun is provided. The method includes: setting an emitter at a first emitter potential within the charged particle gun, and setting a capture electrode at a first electrode potential within a gun housing (e.g., see operation 602). The method further includes: switching the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential (e.g., see operation 602). After switching the capture electrode, the method further includes switching the emitter to an operational emitter potential of the charged particle gun, the operational emitter potential being different from the first emitter potential. According to further optional modifications and implementations, other components of the charged particle gun 102 may be included to have similar switching behavior. For example, the method may include: setting an anode at a first anode potential and setting a gun housing of the charged particle gun at a first housing potential. After switching the capture electrode, the anode may be switched to an operational anode potential of the charged particle gun, the operational anode potential being different from the first anode potential.

[0049] According to some embodiments, which can be combined with other embodiments described herein, the first emitter potential, the first electrode potential, the first anode potential, and the first gun housing potential may correspond to respective potentials during maintenance.

[0050] Back to Figure 1A and Figure 1B , the anode 152 is disposed between the capture electrode 142 and the axis 123. The electron beam travels along the axis 123. Therefore, the anode shields the electron beam from the electric field provided by the capture electrode. According to some embodiments that may be combined with other embodiments described herein, the geometry of the capture electrode and / or the design of the capture electrode are selected to reduce or avoid affecting the portion of the electrons in the beam path, i.e., the electron beam that travels substantially along the axis. According to some embodiments that may be combined with other embodiments described herein, a rotationally symmetric design of the capture electrode is advantageous. Potentially residual effects on the electrons will be rotationally symmetric.

[0051] According to some embodiments, which can be combined with other embodiments described herein, a shielding element may be provided for shielding the electrostatic field of the capture electrode. As described above, the anode or another beam guiding element may act as a shielding element. Furthermore, further shielding elements may be provided.

[0052] Figure 5 An embodiment according to the present disclosure is shown, wherein a shielding element 712 is provided to shield electrons along the beam path. Furthermore, a capture electrode 142 (i.e. a first capture electrode) is provided and a second capture electrode is provided. The capture electrode 142 and the further capture electrode 742 may be positioned at different positions along the axis 123. According to yet further additional or alternative implementations, the further capture electrode 742 may have a different outer diameter than the capture electrode 142, may have a different inner diameter than the capture electrode 142, and / or may have a different cross-sectional shape.

[0053] According to some embodiments, which can be combined with other embodiments described herein, the design and / or position of one or more capture electrodes may be selected such that when other voltages are turned on in the charged particle gun 102, the electric field also remains negative at the surface of the one or more capture electrodes.

[0054] In order to allow contamination particles to be captured at one or more capture electrodes even when other voltages are turned on for operating the charged particle gun, the one or more capture electrodes may be arranged in a cross section parallel to the axis 123 (e.g., Figure 5 The capture electrode may have a curved surface in the cross section shown, in particular a cross section of one side of the annular capture electrode. For example, the shape of the one or more capture electrodes may be set so that the electric field remains at the same polarity for different voltages for the emitter during maintenance, acceleration and operation. According to some embodiments that can be combined with other embodiments described herein, the capture electrode may have a radius of curvature of 20 mm or less, in particular 10 mm or less. The radius of curvature affects the field strength of the electrostatic capture field. Therefore, the smaller the radius of curvature, the smaller the second electrode potential that generates the electrostatic capture field may be. Regarding the maximum radius of curvature, it should be understood that the radius of curvature of a plane or line is infinite, in particular much larger than 20 mm.

[0055] Figure 3 A schematic diagram of a charged particle beam device 100 according to an embodiment described herein is shown. The charged particle beam device 100 may be an electron microscope, such as a scanning electron microscope (SEM). The charged particle beam device 100 includes a charged particle gun according to an embodiment of the present disclosure. The charged particle beam device 100 further includes a column 302 for directing an electron beam onto a sample 324. The sample 324 may be supported on a sample stage 322.

[0056] The charged particle beam device 100 includes a charged particle source 120 and a capture electrode 142 configured to emit a (primary) charged particle beam as described herein. The controller 190 can control the voltage during acceleration of the charged particle beam 102 and during operation of the charged particle gun. As described above, before operating the charged particle source 120, a capture potential is provided to the capture electrode 142 by a capture power supply 144.

[0057] The charged particle beam device may comprise a condenser lens arrangement 304 and an alignment deflector 306 for aligning the charged particle beam with the axis 123. According to some embodiments, which may be combined with other embodiments described herein, the axis 123 may be an optical axis of the objective lens 310.

[0058] Figure 3 A direct view system is shown. The alignment deflector 306 can also be used to provide a non-direct view system. For example, a first deflector can be used to generate a tilt of the charged particle beam and a second deflector can be used to redirect the beam to be perpendicular to the surface of the sample 324. In particular, for a magnetic second deflector, a spacing between the primary electron beam and the signal beam can be provided.

[0059] like Figure 3 As shown, objective lens 310 focuses the electron beam onto sample 324. One or more scanning deflectors 312 disposed within or upstream of the objective lens can scan the electron beam over the sample for image generation. Signal particles generated when the primary electron beam is incident on the sample can be detected by detector 308. Figure 3 As shown, the detector may be an on-axis detector. Additionally or alternatively, an off-axis detector may be provided.

[0060] According to some embodiments that can be combined with other embodiments described herein, the objective lens 310 can be an electrostatic magnetic composite lens, in particular an electrostatic magnetic composite lens having an electrostatic lens that reduces the energy within the column from high energy within the column to a lower landing energy.

[0061] Figure 3 A single beam scanning electron microscope is shown. According to yet further embodiments, which may be combined with other embodiments described herein, embodiments of the present disclosure including capture electrodes may also be used in a multi-beam scanning electron microscope or a multi-beam lithography system. A multi-beam charged particle beam device or a multi-beam system may be provided with a magnetic lens, an electrostatic magnetic compound lens, or with an electrostatic lens having individual lens openings for individual beamlets of the multi-beam system.

[0062] According to one embodiment, a charged particle beam device is provided. The charged particle beam device comprises: a charged particle gun according to any one of the embodiments of the present disclosure and a charged particle beam train for guiding charged particles on a sample.

[0063] In view of the above, a plurality of embodiments can be provided. The embodiments are particularly as follows. Embodiment 1: A method of operating a charged particle gun, the method comprising: setting an emitter at a first emitter potential in the charged particle gun, and setting a capture electrode at a first electrode potential in the charged particle gun, wherein the first emitter potential and the first electrode potential are set to have a substantially zero electric field at the emitter and at the capture electrode; switching the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential to generate an electrostatic capture field at the capture electrode; and after switching the capture electrode from the first electrode potential to the second electrode potential, turning on the electrostatic emission field at the emitter.

[0064] Embodiment 2: The method of embodiment 1, wherein turning on the electrostatic emitter field comprises switching the emitter from a first emitter potential to an operational emitter potential.

[0065] Embodiment 3: The method as described in Embodiment 2 further comprises: setting an anode at a first anode potential; setting a gun housing of a charged particle gun at a first housing potential; and after switching the capture electrode, switching the anode to an operational anode potential of the charged particle gun, the operational anode potential being different from the first anode potential.

[0066] Embodiment 4: The method as described in Embodiment 3, wherein the first emitter potential, the first electrode potential, the first anode potential and the first shell potential correspond to respective potentials during maintenance.

[0067] Embodiment 5: The method of any one of embodiments 1 to 4, wherein switching of the capture electrode causes particles in the gun housing to be attracted to the capture electrode and away from the emitter or other components in the gun chamber.

[0068] Embodiment 6: The method of any one of Embodiments 1 to 5, wherein after switching the emitter to the operational emitter potential, the second electrode potential provides a field strength at the capture electrode to capture particles on the capture electrode.

[0069] Embodiment 7: The method of any one of Embodiments 1 to 6, wherein the electrostatic trapping field has a first direction before turning on the electrostatic emission field at the emitter and after turning on the electrostatic emission field at the emitter.

[0070] Embodiment 8: A method as described in any one of Embodiments 1 to 7, wherein the relative potentials of the charged particle gun can be provided as follows: the operational emitter potential is -0.3 kV to -2 kV, the potential of the extractor electrode is +5 kV to +10 kV, the operational anode potential is +10 kV to +100 kV, and the potential of the suppressor electrode is -0.6 kV to -2.3 kV, and the potential of the sample is at ground, wherein the relative potentials can be offset together, in particular, offset by about -15 kV to -45 kV.

[0071] Embodiment 9: A charged particle gun for a charged particle beam device, comprising: a gun housing; an emitter disposed in the gun housing, the emitter being configured to emit a charged particle beam along an axis; an emitter power supply connected to the emitter; a capture electrode disposed in the gun housing, the capture electrode at least partially surrounding the axis; a capture power supply connected to the capture electrode; and a shielding element, the shielding element shielding the electrostatic field of the capture electrode from the axis during operation of the gun housing.

[0072] Embodiment 10: The charged particle gun of Embodiment 9 further comprises: an extractor electrode located within the gun housing; a suppressor electrode located within the gun housing; and an anode located at least partially within the gun housing.

[0073] Embodiment 11: A charged particle gun as described in Embodiment 10, wherein the shielding element is provided by an anode at least partially arranged between the capture electrode and the axis.

[0074] Embodiment 12: The charged particle gun as described in any one of Embodiments 9 to 11 further comprises: a controller, the controller comprises: a processor and a memory, the memory stores instructions, and when executed by the processor, the instructions cause the charged particle gun to perform the method as described in any one of Embodiments 1 to 8.

[0075] Embodiment 13: A charged particle gun as described in any of embodiments 9 to 12, wherein the capture electrode is rotationally symmetric, in particular annular.

[0076] Embodiment 14: The charged particle gun of any one of Embodiments 9 to 13, wherein the capture electrode has a curved surface in a cross section parallel to the axis.

[0077] Embodiment 15: The charged particle gun of any of Embodiments 9 to 14, wherein the capture electrode is shaped so that the electrostatic field remains at the same polarity for different voltages of the emitter during maintenance, acceleration, and operation.

[0078] Embodiment 16: The charged particle gun of any one of Embodiments 9 to 15, wherein the capture electrode has a radius of curvature of 20 mm or less.

[0079] Embodiment 17: The charged particle gun as described in any one of embodiments 9 to 16 further comprises: a further capture electrode, specifically located at a different position along the axis than the capture electrode.

[0080] Embodiment 18: A charged particle gun as described in any one of Embodiments 9 to 17, wherein the emitter is a field emitter.

[0081] Embodiment 19: A charged particle beam device, comprising: a charged particle gun as described in any one of Embodiments 9 to 18; and a charged particle beam train for guiding charged particles onto a sample.

[0082] In view of the above, one or more of the following advantages can be provided. Arcing during acceleration of the charged particle gun can be reduced. Therefore, the risk of damage to the emitter (particularly the field emitter) can be reduced. In addition, the cleaning workload for accelerating the charged particle gun can be reduced. Therefore, maintenance can be accelerated and / or the operating time of the system can be increased. Therefore, the total throughput of the charged particle beam device can be improved.

[0083] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof and the scope of the disclosure is determined by the following claims.

Claims

1. A method of operating a charged particle gun (102), comprising: providing an emitter (122) at a first emitter potential within the charged particle gun, and providing a capture electrode (142) at a first electrode potential within the charged particle gun (102), wherein the first emitter potential is provided at a tip of the emitter, wherein the first emitter potential and the first electrode potential are arranged to have a substantially zero electric field at the emitter and at the capture electrode; applying a voltage to switch the capture electrode from the first electrode potential to a second electrode potential different from the first electrode potential to generate an electrostatic capture field at the capture electrode to attract contaminant particles before turning on the emitter; as well as After switching the capture electrode from the first electrode potential to the second electrode potential, the electrostatic emission field at the emitter is turned on.

2. The method of claim 1, wherein the step of turning on the electrostatic emission field comprises: The emitter is switched from the first emitter potential to an operational emitter potential.

3. The method of claim 2, further comprising: providing an anode (152) at a first anode potential; Setting a gun housing (111) of the charged particle gun (102) at a first housing potential; and After switching the capture electrode (142), the anode (152) is switched to an operational anode potential of the charged particle gun, the operational anode potential being different from the first anode potential. 4 . The method of claim 3 , wherein the first emitter potential, the first electrode potential, the first anode potential, and the first shell potential correspond to respective potentials during maintenance.

5. The method of any one of claims 3 to 4, wherein switching of the capture electrode causes particles (202) in the gun housing (111) to be attracted to the capture electrode (142) and away from the emitter (122) or other components in the gun chamber.

6. The method of any one of claims 2 to 4, wherein after switching the emitter (122) to the operational emitter potential, the second electrode potential provides a field strength at the capture electrode (142) to capture particles (202) on the capture electrode.

7. The method of any one of claims 1 to 4, wherein the electrostatic capture field has a first direction before turning on the electrostatic emission field at the emitter and after turning on the electrostatic emission field at the emitter (122).

8. The method of any one of claims 3 to 4, wherein the relative potential of the charged particle gun (102) can be provided as follows: The operational emitter potential is -0.3 kV to -2 kV, the extractor electrode potential is +5 kV to +10 kV, the operational anode potential is +10 kV to +100 kV, and the suppressor electrode (125) potential is -0.6 kV to -2.3 kV, and the potential of the sample is at ground, wherein the relative potentials can be offset together.

9. A charged particle gun (102) for a charged particle beam device (100), comprising: Gun housing (111); an emitter (122) disposed in the gun housing, the emitter being configured to emit a charged particle beam along an axis; An emitter power supply (124), the emitter power supply connected to the emitter (122); a capture electrode (142) disposed in the gun housing (111), the capture electrode (142) at least partially surrounding the axis (123), the capture electrode being configured to adsorb contamination particles; a capture power source (144), the capture power source connected to the capture electrode; as well as A shielding element shields the electrostatic field of the capture electrode from the axis during operation of the gun housing.

10. The charged particle gun of claim 9, further comprising: an extractor electrode, the extractor electrode being located in the gun housing (111); a suppressor electrode (125) located within the gun housing; as well as An anode (152) is at least partially located within the gun housing.

11. A charged particle gun as claimed in claim 10, wherein the shielding element is provided by the anode being arranged at least partially between the capture electrode and the axis.

12. The charged particle gun according to any one of claims 9 to 11, further comprising: A controller (190), the controller comprising: a processor and a memory, the memory storing instructions, which when executed by the processor cause the charged particle gun to perform the method according to any one of claims 1 to 4.

13. A charged particle gun as claimed in any one of claims 9 to 11, wherein the trapping electrode (142) is rotationally symmetric.

14. A charged particle gun as claimed in any one of claims 9 to 11, wherein the capture electrode (142) has a curved surface in a cross section parallel to the axis.

15. A charged particle gun as claimed in any one of claims 9 to 11, wherein the capture electrode (142) is shaped so that the electrostatic field remains at the same polarity for different voltages of the emitter during maintenance, acceleration and operation.

16. A charged particle gun as claimed in any one of claims 9 to 11, wherein the capture electrode (142) has a radius of curvature of 20 mm or less.

17. A charged particle gun as claimed in any one of claims 9 to 11, further comprising: A further capture electrode (142) is located at a different position along the axis than the capture electrode.

18. A charged particle gun as claimed in any one of claims 9 to 11, wherein the emitter is a field emitter.

19. A charged particle beam device (100), comprising: A charged particle gun (102) for a charged particle beam device according to any one of claims 9 to 11; as well as A charged particle beam train used to direct charged particles at a sample.

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