System and method for cleaning an electron source of a charged particle beam system - Patents.com

Abstract

A system and method for removing contaminants from an emitter tip of an electron source in an electron beam device is disclosed. The electron beam device may include an electron source including an emitter tip configured to emit electrons, and a light source configured to generate a light beam that illuminates a portion of the emitter tip to excite surface modes of the light beam, the excited surface modes facilitating the removal of contaminants from a surface of the illuminated portion of the emitter tip. The excited surface modes may include propagating surface waves or localized surface waves. The emitter tip may include a lattice structure, the properties of which match the wave vector of the light beam.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser. No. 63 / 293,615, filed December 23, 2021, which is incorporated by reference in its entirety into this specification.

[0002] FIELD OF THE DISCLOSURE

[0002] Embodiments provided herein relate to electron sources for charged particle beam systems, and more particularly to systems and methods for cleaning field emission electron sources using a light source. [Background technology]

[0003]

[0003] In the manufacturing process of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured as designed and are free of defects. Inspection systems using charged particle (e.g., electron) beam microscopes or optical microscopes, such as scanning electron microscopes (SEMs), may be used. As the physical size of IC components continues to shrink, the accuracy of defect detection, imaging resolution, and yield become more important. To address the requirements of inspection throughput, multiple charged beams may be utilized, but the imaging resolution of multiple charged beam systems may be compromised, making the inspection tool unsuitable for the desired purpose. Imaging resolution is also affected by the stability of the electron source, which is maintained by periodically decontaminating the tip of the electron emitter. Existing techniques for cleaning the tip of the electron emitter of the electron source may require partial or complete shutdown of the inspection tool, which may affect the overall inspection throughput, among other issues.

[0004]

[0004] Thus, related art systems have limitations, for example, in image resolution and electron source stability, due to contamination of the electron source. Existing methods for removing contaminants from the electron source may cause variations in the current generated after cleaning or shorten the lifetime of the electron source, making it less cost-effective or less reliable, or both. Thus, a system and method for cleaning the electron source while maintaining imaging resolution, radiation source stability, and inspection throughput is desired. Summary of the Invention

[0005]

[0005] One aspect of the present disclosure relates to an electron beam device including an electron source and a light source. The electron source may include an emitter tip configured to emit electrons, and the light source may be configured to generate a light beam that illuminates a portion of the emitter tip to excite surface modes of the light beam, the excited surface modes facilitating removal of contaminants from a surface of the illuminated portion of the emitter tip.

[0006]

[0006] Another aspect of the present disclosure relates to an electron beam device including an electron source and a light source. The electron source may include an emitter tip configured to emit electrons, and the light source may be configured to generate a light beam that illuminates a portion of the emitter tip to remove contaminants from a surface of the illuminated portion of the emitter tip.

[0007]

[0007] Another aspect of the present disclosure relates to a method for removing contaminants from an emitter tip of an electron source, the method may include activating a light source to generate a light beam and illuminating a portion of the emitter tip with the light beam to excite surface modes of the light beam, the excited surface modes facilitating removal of contaminants from a surface of the illuminated portion of the emitter tip.

[0008]

[0008] Another aspect of the present disclosure relates to a method for removing contaminants from an emitter tip of an electron source, which may include operating a light source to generate a light beam and irradiating a portion of the emitter tip with the light beam to remove contaminants bound to a surface of the irradiated portion of the emitter tip.

[0009] Another aspect of the present disclosure relates to a non-transitory computer readable medium storing a set of instructions executable by one or more processors of an electron beam device to cause the electron beam device to perform a method for removing contaminants from an emitter tip of an electron source. The method may include operating a light source to generate a light beam and illuminating a portion of the emitter tip with the light beam to excite surface modes of the light beam, the excited surface modes promoting removal of contaminants from a surface of the irradiated portion of the emitter tip.

[0010]

[0010] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0010] In the following description, by way of illustration and example, certain embodiments of the invention are set forth. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure. [Diagram 2]

[0012] FIG. 2 is a schematic diagram illustrating an example electron beam tool that may be part of the example electron beam inspection system of FIG. 1 consistent with embodiments of the present disclosure. [Diagram 3]

[0013] 1 shows a schematic diagram of an exemplary configuration of an electron source consistent with embodiments of the present disclosure. [Figure 4A]

[0014] FIG. 1 shows a schematic diagram of an emitter tip of an electron source being cleaned using a photon-contaminant resonance mechanism consistent with embodiments of the present disclosure. [Figure 4B]FIG. 1 shows a schematic diagram of an emitter tip of an electron source being cleaned using a photon-contaminant resonance mechanism consistent with embodiments of the present disclosure. [Figure 5A]

[0015] 1 shows a schematic diagram of an emitter tip of an electron source being cleaned using a localized optical radiative heating mechanism consistent with embodiments of the present disclosure. [Figure 5B]

[0015] FIG. 1 shows a schematic diagram of an emitter tip of an electron source being cleaned using a localized optical radiative heating mechanism consistent with an embodiment of the present disclosure. [Figure 6]

[0016] 6 is a process flow diagram illustrating an exemplary method 600 for removing contaminants from an emitter tip of an electron source using a light source consistent with embodiments of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012]

[0017] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which the same numbers in different drawings represent the same or similar elements unless otherwise stated. The implementations described in the following description of exemplary embodiments do not represent all implementations. Instead, the implementations are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments, as described in the appended claims. For example, although some embodiments are described in relation to the use of electron beams, the disclosure is not so limited. Other types of charged particle beams can be applied as well. Moreover, other imaging systems can be used, such as optical imaging, photo detection, x-ray detection, and the like.

[0013]

[0018] Electronic devices are built with circuits formed on a piece of silicon called a substrate. Many circuits can be formed together on the same piece of silicon and are called integrated circuits, or ICs. The size of these circuits has decreased dramatically, so that more and more circuits can fit on a substrate. For example, an IC chip in a smartphone is about the size of a thumbnail, yet can contain over 2 billion transistors, each less than 1 / 1000 the size of a human hair.

[0014]

[0019] Creating these tiny ICs is a time-consuming, complex, and expensive process, often involving hundreds of individual steps. An error in even one step can introduce defects into the finished IC, rendering it useless. Thus, one of the goals of a manufacturing process is to avoid such defects in order to maximize the number of functioning ICs produced by the process, i.e., to increase the overall yield of the process.

[0015]

[0020] One factor in improving yield is monitoring the chip creation process to ensure that it produces a sufficient number of functioning integrated circuits. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be done using a scanning electron microscope (SEM). An SEM can be used to image these extremely small structures, in effect taking a "picture" of the structure. The image can be used to determine if the structure was formed correctly, and if it was formed in the correct place. If the structure is defective, the process can be adjusted to make it less likely that the defect will reoccur.

[0016]

[0021] Obtaining high resolution images with SEM starts with using an electron source with high brightness, small energy spread, and small effective size. Although thermionic emission sources such as tungsten hairpin filaments are inexpensive and easy to use, they suffer from several drawbacks, including short lifetime, high operating temperature, low brightness, and wide beam energy spread, among others, which can result in poor image quality. In contrast, field emission sources offer higher brightness due to their significantly smaller emission area, small beam energy spread, long lifetime, and high image resolution, making them a desirable electron source for high resolution imaging in SEMs. However, there are several issues that can limit the effectiveness and usefulness of field emission sources in systems and applications that require high throughput. Some of these issues include short current decay times (less than 100 hours) even under high vacuum conditions, large variations in emission current, and ultra-high or extremely high vacuum requirements to prevent arcing at the emitter tip.

[0017]

[0022] To alleviate some of the existing problems of field emission sources, the electron source is periodically cleaned, such as by resistively heating the electron source (ohmic heating) to clean the emitting surface, or by indirectly heating the electron emitting source through radiation from a resistively heated filament located in close proximity to the electron source. Resistive heating, also known as "flashing" or "flash heating", may involve passing a large current through the filament and emitter tip to increase the overall temperature, clean the emitting surface, and restore the emission current. Flashing may involve light or heavy heating, which raises the temperature of the electron source, including non-emitting surfaces, in the range of 700°C to 2000°C. When a heavy heating procedure is performed, the inspection tool may have to be shut down and the electron optical column may have to be realigned or recalibrated, which may significantly affect throughput. Light heating procedures may be performed more frequently to extend the period between two heavy heating procedures.

[0018]

[0023] In either flushing technique, the inventors of the present disclosure have recognized that outgassing due to the overall temperature increase can be significant enough to adversely affect the vacuum conditions in the chamber enclosing the electron source, particularly the vacuum conditions around the electron emitter tip. One of several problems with poor vacuum conditions around the emitter tip is a noticeable decrease in the life of the electron source due to a higher rate of contaminant formation on the surface of the electron source, which can lead to more and more frequent flushing cycles, dulling the tip, and frequent tip replacement. In some cases, outgassing can be so severe that it can "overtax" the vacuum pumping mechanism, resulting in longer machine downtime, thereby adversely affecting throughput. It can therefore be desirable to remove contaminants from the emitting surface of the electron source while maintaining a low outgassing rate and a high inspection throughput.

[0019]

[0024] In some embodiments of the present disclosure, an electron beam device is disclosed that includes an electron source and a light source. The electron source may include an emitter tip configured to generate electrons, and the light source may be used to generate a light beam to irradiate the emitter tip and remove contaminants adsorbed on the emitter tip. When using a light beam, such as a laser beam, the wavelength may be adjusted based on the target contaminant, and the beam may be focused on a smaller portion of the tip, such as the apex of the emitter tip. Even if a laser beam of a desired wavelength, such as an infrared laser, causes heating of the emitter tip, the amount of heat generated is considerably less, which may result in significantly less outgassing in the vacuum chamber and minimal blunting of the tip. This is in contrast to existing and prior art, which heats the entire emitter tip by passing a current through the tip or by heating a filament near the tip to remove contaminants. Furthermore, the laser beam may be linearly polarized such that the electric field component of the laser beam may assist in removing the contaminants, thereby further reducing the amount of heat generated.

[0020]

[0025] In the drawings, the relative dimensions of the components may be exaggerated for clarity. Within the following description of the drawings, the same or similar reference numbers refer to the same or similar components or entities and only describe the differences for the individual embodiments. As used herein, unless specifically stated otherwise, the term "or" encompasses all possible combinations unless infeasible. For example, if it is stated that a component may include A or B, the component may include A or B or A and B, unless specifically stated otherwise or infeasible. As a second example, if it is stated that a component may include A, B, or C, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless specifically stated otherwise or infeasible.

[0021]

[0026] Reference is now made to FIG. 1, which illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. As shown in FIG. 1, the charged particle beam inspection system 100 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, and a front-end equipment module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. It should be understood that although the description and drawings are directed to electron beams, the embodiments are not used to limit the present disclosure to a particular charged particle and charged particle beam device. For example, a charged particle may refer to an electron, ion, or any positively or negatively charged particle, and a charged particle beam device may refer to an electron beam device, or an ion beam device, or any device using electrons and ions, such as a SEM, or a focused ion beam (FIB) in combination with a SEM.

[0022]

[0027] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b receive wafer front-opening integrated pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (hereinafter, wafers and samples are collectively referred to as "wafers"). One or more robotic arms (not shown) of the EFEM 30 transfer the wafers to the load-lock chamber 20.

[0023]

[0028] The load-lock chamber 20 is connected to a load / lock vacuum pumping system (not shown) that removes gas molecules in the load-lock chamber 20 to reach a first pressure below atmospheric pressure. After the first pressure is reached, one or more robot arms (not shown) transfer the wafer from the load-lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pumping system (not shown) that removes gas molecules in the main chamber 10 to reach a second pressure below the first pressure. After the second pressure is reached, the wafer is inspected by the electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam inspection tool.

[0024]

[0029] The controller 50 may be electronically connected to the electron beam tool 40 and may also be electronically connected to other components. The controller 50 may be a computer configured to perform various controls of the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is shown in FIG. 1 as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it will be understood that the controller 50 may also be part of the structure.

[0025]

[0030] In some embodiments, the controller 50 may include one or more processors (not shown). A processor may be a general-purpose or special-purpose electronic device capable of manipulating or processing information. For example, a processor may include any number or combination of a central processing unit (i.e., "CPU"), a graphics processing unit (i.e., "GPU"), an optical processor, a programmable logic controller, a microcontroller, a microprocessor, a digital signal processor, an intellectual property (IP) core, a programmable logic array (PLA), a programmable array logic (PAL), a general purpose array logic (GAL), a complex programmable logic device (CPLD), a field programmable gate array (FPGA), a system on a chip (SoC), an application specific integrated circuit (ASIC), and any type of circuit capable of processing data. A processor may be a virtual processor, including one or more processors distributed across multiple machines or devices coupled via a network.

[0026]

[0031] In some embodiments, the controller 50 may further include one or more memories (not shown). The memories may be general-purpose or special-purpose electronic devices capable of storing code and data accessible to the processor (e.g., via a bus). For example, the memories may include any number or combination of random access memory (RAM), read-only memory (ROM), optical disks, magnetic disks, hard drives, solid-state drives, flash drives, security digital (SD) cards, memory sticks, compact flash (CF) cards, or any type of storage device. The code may include an operating system (OS) and one or more application programs (i.e., "apps") for specific tasks. The memory may be a virtual memory, including one or more memories distributed across multiple machines or devices coupled via a network.

[0027]

[0032] It should be noted that while the present disclosure provides an example of a main chamber 10 housing an electron beam inspection system, aspects of the present disclosure are not limited in their broadest sense to chambers housing electron beam inspection systems, rather, it is understood that the principles discussed above may be applied to other chambers as well.

[0028]

[0033] Reference is now made to Figure 2, which shows a schematic diagram illustrating an exemplary configuration of an electron beam tool 40 that may be part of the exemplary charged particle beam inspection system 100 of Figure 1 consistent with an embodiment of the present disclosure. The electron beam tool 40 (also referred to herein as apparatus 40) may include an electron emitter that may include a cathode 203, an extraction electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 may further include a Coulomb aperture array 224, a condenser lens 226, a beam limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. The electron beam tool 40 may further include a sample holder 236 supported by a motorized stage 234 for holding a sample 250 to be inspected. It should be understood that other relevant components may be added or omitted as desired.

[0029]

[0034] In some embodiments, the electron emitter may include a cathode 203 and an anode 222, where primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 204 that forms the primary beam crossover 202. The primary electron beam 204 may be visualized as being emitted from the primary beam crossover 202.

[0030]

[0035] In some embodiments, the electron emitter, condenser lens 226, objective lens assembly 232, beam-limiting aperture array 235, and electron detector 244 may be aligned with the primary optical axis 201 of apparatus 40. In some embodiments, the electron detector 244 may be positioned off-axis from the primary optical axis 201 along a secondary optical axis (not shown).

[0031]

[0036] In some embodiments, the objective lens assembly 232 may include a modified swing objective retarding immersion lens (SORIL), which includes a pole piece 232a, a control electrode 232b, a beam manipulator assembly including deflectors 240a, 240b, 240d, and 240e, and an excitation coil 232d. In a typical imaging process, a primary electron beam 204 emitted from the tip of the cathode 203 is accelerated by an acceleration voltage applied to the anode 222. A portion of the primary electron beam 204 passes through the gun aperture 220 and the apertures of the Coulomb aperture array 224, and is focused by the condenser lens 226 to pass fully or partially through the apertures of the beam-limiting aperture array 235. Electrons passing through the apertures of the beam-limiting aperture array 235 may be focused by a modified SORIL lens to form a probe spot on the surface of the sample 250 and deflected by one or more deflectors of the beam manipulator assembly to scan the surface of the sample 250. Secondary electrons emitted from the sample surface may be collected by the electron detector 244 to form an image of the scanned area of ​​interest.

[0032]

[0037] In the objective lens assembly 232, the excitation coil 232d and the pole piece 232a may generate a magnetic field. A portion of the sample 250 scanned by the primary electron beam 204 may be immersed in this magnetic field and become electrically charged, which in turn generates an electric field. This electric field may reduce the energy of the impinging primary electron beam 204 on or near the surface of the sample 250. The control electrode 232b is electrically isolated from the pole piece 232a and may control the electric field on and above the sample 250, for example, to reduce aberrations of the objective lens assembly 232, control the focusing condition of the signal electron beam to increase detection efficiency, or avoid arcing to protect the sample. One or more deflectors of the beam manipulator assembly may deflect the primary electron beam 204 to facilitate beam scanning on the sample 250. For example, in a scanning process, deflectors 240a, 240b, 240d, and 240e may be controlled to deflect primary electron beam 204 to different locations on the top surface of sample 250 at different times to provide data for reconstructing images of different portions of sample 250. Note that in different embodiments, the order of 240a-240e may be different.

[0033]

[0038] Backscattered electrons (BSE) and secondary electrons (SE) may be emitted from a portion of the sample 250 upon receiving the primary electron beam 204. A beam separator (not shown) may direct the secondary or scattered electron beam, including the backscattered and secondary electrons, to a sensor surface of the electron detector 244. The detected secondary electron beam may form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 may generate a signal (e.g., voltage, current) representative of the intensity of the received secondary electron beam spot and provide the signal to a processing system, such as the controller 50. The intensity of the secondary or backscattered electron beam and the resulting secondary electron beam spot may vary depending on the external or internal structure of the sample 250. Also, as discussed above, the primary electron beam 204 may be deflected to different locations on the top surface of the sample 250 to generate secondary or scattered electron beams (and resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot to the location of the sample 250 , the processing system can reconstruct an image reflecting the internal or external structure of the wafer sample 250 .

[0034]

[0039] In some embodiments, the controller 50 may include an image processing system, which includes an image acquirer (not shown) and storage (not shown). The image acquirer may include one or more processors. For example, the image acquirer may include a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, and the like or combinations thereof. The image acquirer may be communicatively coupled to the electronic detector 244 of the device 40 through a medium such as electrical conductors, fiber optic cables, portable storage media, IR, Bluetooth, the Internet, a wireless network, a wireless radio, or combinations thereof, among others. In some embodiments, the image acquirer may receive signals from the electronic detector 244 and construct an image. Thus, the image acquirer may acquire an image of an area of ​​the sample 250. The image acquirer may also perform various post-processing functions such as generating contours, superimposing indicators on the acquired image, and the like. The image acquirer may be configured to perform adjustments such as brightness and contrast of the acquired image. In some embodiments, the storage may be a storage medium such as a hard disk, a flash drive, cloud storage, random access memory (RAM), other types of computer readable memory, and the like. The storage may be coupled with the image acquirer and may be used to store raw scanned image data as original images, and to store post-processed images.

[0035]

[0040] In some embodiments, the controller 50 may include measurement circuitry (e.g., analog-to-digital converters) to obtain a distribution of detected secondary and backscattered electrons. The electron distribution data collected during the detection time window, in combination with corresponding scan path data of the primary beam 204 incident on the sample (e.g., wafer) surface, may be used to reconstruct an image of the wafer structure under inspection. The reconstructed image may be used to reveal various features of the internal or external structure of the sample 250, and thus any defects that may be present in the wafer.

[0036]

[0041] In some embodiments, the controller 50 can control the motorized stage 234 to move the sample 250 during inspection. In some embodiments, the controller 50 can cause the motorized stage 234 to move the sample 250 continuously in one direction at a constant speed. In other embodiments, the controller 50 can cause the motorized stage 234 to vary the speed at which the sample 250 moves over time depending on the step of the scanning process.

[0037]

[0042] 3 illustrates an exemplary configuration 300 of an electron source in an electron beam inspection tool consistent with embodiments of the present disclosure. In the configuration 300, the apparatus 40 may include a chamber 310 including a viewport 350, a vacuum pumping mechanism 320, an electron source 330 having an emitter tip 335, an extractor electrode 338, a light source 340, a power supply 360, and a controller 50.

[0038]

[0043] In some embodiments, the chamber 310 may include a vacuum chamber or may be part of an electron optical column (not shown) of the apparatus 40. The chamber 310 may enclose the electron source 330 and the extractor electrode 338. The chamber 310 may be constructed from a high-vacuum or UHV compatible material, such as, but not limited to, stainless steel, and may be evacuated using one or more vacuum pumps of the vacuum pumping mechanism 320. In some embodiments, the chamber 310 may be pumped to ultra-high vacuum (UHV) or extreme high vacuum (XHV) conditions to provide a long mean free path for electrons traveling downstream in the electron optical column to improve the reliability and stability of the electron source and extend its operational lifetime, among other benefits.

[0039]

[0044] In some embodiments, the chamber 310 may include a viewport 350 configured to allow the light beam 345 generated by the light source 340 to pass therethrough. The viewport 350 may be attached to an exterior surface of the chamber 310 such that the passing light beam 345 may be incident unimpeded on the emitter tip 335. In some embodiments, the viewport 350 may be made of a material that is substantially transparent to a wide range of wavelengths of electromagnetic radiation. For example, the viewport 350 may be made of borosilicate glass that has a light transmission of greater than 90% over the wavelength range of 375 nm to 1900 nm. It should be understood that other materials having desirable properties may also be used, as appropriate. In some embodiments, in addition to being substantially transparent, the viewport 350 may be made of a low outgassing material that is compatible with high vacuum or UHV operating conditions.

[0040]

[0045] A vacuum pumping mechanism 320 may be in fluid communication with the chamber 310 to efficiently evacuate the chamber 310. In some embodiments, the vacuum pumping mechanism 320 may include multiple vacuum pumps, including, but not limited to, diaphragm pumps, scroll pumps, adsorption pumps, diffusion pumps, turbomolecular pumps, cryogenic pumps, ion getter pumps, titanium sublimation pumps, among other vacuum pumps. In operation, one or more pumps may be used in combination to achieve a desired vacuum level. In some embodiments, the choice of vacuum pump or combination of vacuum pumps may be based on factors including, but not limited to, the end application, the gas to be pumped, the surfaces contributing to outgassing, or the desired vacuum level.

[0041]

[0046] In existing SEMs, the electron source may include a thermionic source or a field emission source. Typically, thermionic sources include tungsten filaments, LaB 6 , or CeB 6 They rely on resistive heating to generate electrons from a cathode such as a crystal. A large current flows through a filament (cathode), which generates heat based on the resistance of the filament, thereby providing the electrons with energy to escape from the solid surface. Such electron sources are cheap and easy to maintain, but suffer from low brightness and wide energy dispersion, resulting in inadequate image quality. Field emission sources, on the other hand, use an electrostatic field to induce electron emission. This electrostatic field is applied to the apex of an emitter tip made of a conductive wire, where high-energy electrons are emitted by quantum mechanical tunneling. The emission area for field emission sources is significantly smaller than that of thermal electron sources, typically in the order of nanometers, resulting in better brightness, which in turn improves image quality, including improved spatial resolution and increased signal-to-noise ratio.

[0042]

[0047] In some embodiments, the apparatus 40 may include an electron source 330, which may include a field emission source, also referred to as a field emission gun (FEG) or cold field emitter. The electron source 330 may include an emitter tip 335 attached to a filament and shaped to have a tapered end. The apex 336 of the tapered end of the emitter tip 335 may be sharpened to a tip radius of 0.5 μm or less, 0.4 μm or less, 0.3 μm or less, 0.2 μm or less, or 0.1 μm or less, such that the electric field is approximately 10 8 The field emission current in a field emission source is due purely to tunneling and is independent of temperature.

[0043]

[0048] For field emitters such as electron source 330, it may be desirable to have a clean emitter tip surface that is substantially free of contaminants and adsorbed materials. One of several ways to maintain a clean emitter tip surface includes maintaining a high vacuum level, in some cases an extremely high vacuum, around the electron source 330. As an example, -6 At a negative pressure of 10 Torr, a monolayer of gas is adsorbed on the exposed surface every 1-2 seconds. The rate of monolayer formation is, for example, 10 -10 Although this can be extended to 5-10 minutes by operating at sub-Torr vacuum, the rate of monolayer formation is still unacceptable, leading to inefficiencies in the tool and testing process.

[0044]

[0049] Some of the existing techniques for cleaning emitter tip surface contamination include a "flashing" process, which involves resistively heating the emitter tip and the supporting filament to which it is attached for a short period of time to a temperature in the range of 700°C to 2000°C by passing an electric current through the emitter tip. Although mild flashing may be performed more frequently at lower temperatures compared to heavy flashing, which is performed at higher temperatures and may require tool shutdown, flash heating techniques have several drawbacks and challenges. Some of the challenges include, but are not limited to, increased outgassing due to a noticeable increase in the overall chamber temperature, readsorption of contaminants on the emitter tip due to temporary reductions in vacuum level, reduced operating lifetime of the electron source, instability of the emission current, or reduced current decay time of the electron source, among others. Other techniques may include radiative heating of a filament located near the emitter tip, but radiative and resistive heating involve heating techniques that increase the outgassing rate, or the risk of high voltage breakdown, or both. Therefore, it may be desirable to clean the emitter tips of field emission sources using techniques that can mitigate one or more problems associated with existing cleaning techniques while maintaining imaging resolution and inspection throughput.

[0045]

[0050] As shown in FIG. 3, the emitter tip 335 of the electron source 330 may be illuminated with a light beam 345 generated by a light source 340. In some embodiments, the light source 340 may include a photon source, including but not limited to a laser, a high intensity laser, or a monochromatic light source. In some embodiments, the light source 340 may include a tunable laser source configured to be controlled by the controller 50. Controlling the light source 340 may include but is not limited to activating the laser source, calibrating and stabilizing the laser source, directing photons along an optical axis, adjusting the wavelength, frequency, duty cycle, or intensity of the light beam, etc. The tunable laser source may be used to generate a light beam 345 having a tunable wavelength, for example, based on the target contaminant to be removed. In some embodiments, the light beam 345 may be a continuous laser beam or a pulsed laser beam.

[0046]

[0051] In some embodiments, the light source 340 may be fixedly coupled to the chamber 310 such that a light beam 345 generated from the light source 340 may pass through the viewport 350 and be incident on a portion of the tapered end of the emitter tip 335. In some embodiments, the light beam 345 may be aligned to illuminate the apex 336 of the emitter tip 335 such that, upon illumination, one or more contaminants may be removed from the exposed surface of the emitter tip 335, leaving the surface substantially clean of contaminants or adsorbed materials. Once aligned, the fixed coupling between the light source 340 and the chamber 310 may ensure that the alignment is maintained until replacement of the emitter tip 335 is authorized or until scheduled tool maintenance needs to be performed. In some embodiments, the light source 340 may include a beam polarizer (not shown). The beam polarizer may be configured to polarize the light beam 345 generated by the light source 340. In some embodiments, the light beam 345 may be linearly, circularly, elliptically, or randomly polarized. As used herein, the polarization of a beam, e.g., a light beam, refers to the direction of the electric field oscillation of the light beam. For example, in a linearly polarized light beam, the electric field oscillates in a linear direction perpendicular to the propagation axis of the light beam, and the magnetic field oscillates in a direction perpendicular to the propagation axis of the light beam and perpendicular to the electric field direction.

[0047]

[0052] In some embodiments, not shown, the apparatus 40 may include multiple light sources 340 configured to illuminate the emitter tip 335 with light beams, such as light beam 345. The multiple light sources 340 may be positioned such that multiple light beams can be incident on the apex 336 of the emitter tip 335 at different locations about the axis of the emitter tip 335. It should be appreciated that in configurations including multiple light sources 340, corresponding viewports 350 may also be included through which the corresponding light beams pass. In some embodiments, the number of light sources used may be determined based on mechanical, structural, spatial, or functional design considerations of the chamber 310.

[0048]

[0053] In some embodiments, the light beam 345 may be incident on the apex 336 of the emitter tip 335 or on a region near the apex 336 at an angle of incidence between 0° and 90° with respect to the axis of the emitter tip 335, which may be substantially coincident with the primary optical axis 301. The angle of incidence of the light beam 345 may be determined based on, among other things, the position of the light source 340, the path of the light beam 345, the position of the viewport 350, and the position of the emitter tip 335 within the chamber 310.

[0049]

[0054] In some embodiments, in configurations including multiple light sources 340, two or more light sources 340 may be configured to illuminate the emitter tip 335 with light beams that may be similar or dissimilar in characteristics such as, but not limited to, wavelength, frequency, intensity, power density, angle of incidence, among other characteristics. For example, a first light source may generate a first light beam in an ultraviolet wavelength range that is incident on a first portion of the emitter tip at a 45° angle of incidence, and a second light source may generate a second light beam in an infrared wavelength range that is incident on a second portion of the emitter tip at a 30° angle of incidence. The characteristics of the light beams 345 may be determined based on, among other things, the contaminant, the type of bond between the contaminant and the surface of the emitter tip 335, and the location of the contaminant on or around the apex 336 of the emitter tip 335. One or more light beams 345 from corresponding light sources 340 may be incident on the emitter tip 335 simultaneously or substantially simultaneously. In some embodiments, multiple light beams may sequentially illuminate the emitter tip 335 with regular or irregular timing offsets between successive incidences. Among the advantages of simultaneously illuminating the emitter tip 335 with multiple light beams from multiple light sources is that it reduces the time required to clean the emitter tip 335, thereby increasing the efficiency of cleaning and improving throughput.

[0050]

[0055] In operation of apparatus 40 for inspection or imaging, power supply 360 may be configured to generate an electrostatic field to extract electrons from emitter tip 335, or to focus the extracted electrons, or both. The extracted electrons may form an electron beam 302 traveling along primary optical axis 301. In some embodiments, power supply 360 may be controlled by controller 50. Controlling power supply 360 may include adjusting the voltage, current, or power generated by power supply 360 to adjust properties of the electron beam including, but not limited to, the number of electrons, the dispersion of the electron beam, among others.

[0051]

[0056] 4A and 4B, which show schematic diagrams of an exemplary apex of an emitter tip that has been cleaned using a photon-contaminant resonance mechanism consistent with embodiments of the present disclosure. Figures 4A and 4B show an apex 436 of an emitter tip 435, one or more contaminants 420 bound to a surface of the emitter tip 435, and a light beam 445 illuminating a portion of the apex 436. It should be understood that the emitter tip 435 and apex 436 may be substantially similar to the emitter tip 335 and apex 336 of Figure 3 and may perform substantially similar functions.

[0052]

[0057] As shown in FIG. 4A, a light beam 445 generated from a light source such as a laser (e.g., light source 340 of FIG. 3) may be directed to illuminate a portion of the apex 436. In some embodiments, illuminating a portion of the surface of the apex 436 with the light beam 445 may break bonds between the contaminants 420 and the surface of the apex 436, leaving the surface of the emitter tip 435 clean and substantially free of contaminants. In some embodiments, the contaminants 420 may include adsorbed materials, gas molecules, atoms, molecules, physically bonded atoms or molecules, chemically bonded atoms or molecules, or debris, or any combination thereof. In some embodiments, the plurality of contaminants 420 may include a monolayer formed on a portion of the surface of the emitter tip 435. The contaminants 420 may include carbon atoms, carbon monoxide, carbon dioxide, water molecules, organic molecules, or inorganic molecules. As referred to herein, adsorbed materials include atoms or molecules that may be physically adsorbed to a surface by van der Waals interactions or other intermolecular forces.

[0053]

[0058] In some embodiments, the light beam 445, upon illuminating a portion of the apex 436, may break bonds between one or more contaminants 420 and the surface of the emitter tip 435. Breaking bonds may include desorption of adsorbed molecules, or cleavage of physical or chemical bonds, or dissociation of molecules into individual atoms before removal from the surface. In some embodiments, breaking bonds may include a photon-assisted quantum process, also called photon-contaminant resonance, to remove atoms or molecules from the surface. In the example shown in FIG. 4A, the light beam 445 including photons with energy hv may impart the necessary energy for atoms to break bonds with the surface of the emitter tip 435. In some embodiments, the light beam 445 may be focused to a small area so that only the contaminants 420 within the illuminated area of ​​the apex 436 may be removed. Increasing the illuminated area by defocusing the light beam 445 may expand the target area of ​​the apex 436 to clean a larger surface area.

[0054]

[0059] In some embodiments, the photon-contaminant resonance mechanism for decontaminating the emitter tip may include tuning the wavelength of the photon-containing light beam 445 to break the bond between the contaminant 420 and the surface of the emitter tip 435 or apex 436. The wavelength may be tuned to resonate with the bond formed between the contaminant 420 and the surface of the emitter tip 435.

[0055]

[0060] In some embodiments, breaking bonds and removing contaminants 420 from the surface of the apex 436 by a photon-contaminant resonance mechanism may generate heat based on the characteristics of the light beam 445, such as power, wavelength, frequency, duration of exposure, intensity, and the like, the target material, the target contaminant, or the type of bond between the contaminant and the surface of the emitter tip, among other factors. However, the amount of heat generated may be significantly less than existing techniques of resistive or radiative heating for decontaminating emitter tips of electron sources. FIG. 4B shows the surface of the apex 436 of the emitter tip 435 substantially free of contaminants 420 when illuminated by a light beam 445 having a wavelength resonant with the contaminant bonds. Once released into the chamber space, the one or more contaminants 420 may be pumped out by a pumping mechanism (e.g., vacuum pumping mechanism 320 of FIG. 3). The number of contaminants released by the photon-assisted quantum decontamination process may be significantly less than resistive or radiative heating decontamination processes. This may be because the light beam 445 can locally target a smaller spot to selectively expose the apex 436 from which electrons can be emitted, as opposed to globally heating the filament and emitter tip in a flash heating process that would cause excessive outgassing and therefore a reduction in the vacuum level.

[0056]

[0061] In some embodiments, the propagation of an optical or light beam may be considered a wave phenomenon where light waves can be perceived as electromagnetic transverse waves, where the electric and magnetic fields oscillate orthogonally with respect to each other and with respect to the direction of light wave propagation. The light beam may be linearly, circularly, elliptically, or randomly polarized.

[0057]

[0062] Returning to FIG. 4A , the light beam 445 may comprise a linearly polarized light beam such that the electric field 448 oscillates in a direction perpendicular to the propagation of the light beam 445 and in a direction substantially parallel to the tapered edge of the emitter tip 435. In some embodiments, one or more portions of the tapered edge of the emitter tip 435 may comprise a grating structure 455. Properties of the grating structure 455 may be tailored to match or based on the wave vector of the light beam 445. The wave vector may include, among others, the wave number, the angular wave number, the wavelength, the direction of wave propagation. Properties of the grating structure 455 may include, but are not limited to, the pitch, the spacing, the height, the width, the angle of the grating, etc.

[0058]

[0063] In some embodiments, surface modes of the linearly polarized light beam 445 may be excited when illuminating a surface of the emitter tip 435 that includes the grating structure 455. The surface modes of the linearly polarized light beam 445 may include propagating surface waves 452 that may enhance absorption of light energy upon illumination of the emitter tip 445. The propagating surface waves 452 propagating along the grating structure 455 on the tapered edge of the emitter tip 435 may enable stripping of the contaminant 420 from the surface of the emitter tip 435. The propagating surface waves 452 may be excited when the linearly polarized light beam 445 is incident on the grating structure 455. One of several advantages of the propagating surface waves of the light beam 445 includes reduced reflected or scattered photons from the emitter tip 435 and therefore reduced outgassing from the area adjacent to the emitter tip 435. Although not shown, it should be understood that the grating structure 455 may be formed on one or more surfaces of the emitter tip 445. In some embodiments, the lattice structure 455 may be formed in a small area on or around the apex 446. Alternatively or in addition, the lattice structure 455 may be formed on most of the tapered edge of the emitter tip 435.

[0059]

[0064] 5A and 5B, which show schematic diagrams of an exemplary apex of an emitter tip that has been cleaned using a localized optical radiative heating mechanism consistent with embodiments of the present disclosure. Figures 5A and 5B show an apex 536 of the emitter tip 535, one or more contaminants 520 bound to a surface of the emitter tip 535, and an optical beam 545 illuminating a portion of the apex 536. It should be understood that the emitter tip 535 and apex 536 may be substantially similar to the emitter tip 335 and apex 336 of Figure 3 and may perform substantially similar functions.

[0060]

[0065] In some embodiments, the light beam 545 may irradiate a portion of the apex 536 to break bonds between the one or more contaminants 520 and the surface of the emitter tip 535. Breaking bonds between the contaminants 520 and the surface of the emitter tip 535 to clean the emitter tip 535 may include a localized optical radiation heating mechanism. In this mechanism, the light beam 545 may be focused on the apex 536 of the emitter tip 535, causing a localized increase in temperature of the apex 536 so that the one or more contaminants 520 can be desorbed from the surface. In some embodiments, the light beam 545 may include a near-infrared laser beam or a mid-infrared laser beam. The wavelength of the light beam 545 may be selected based on the type of contaminant 520 or the nature of the bonds formed between the contaminant 520 and the surface of the apex 536. For example, an infrared laser beam having a wavelength of 800 nm may be used to desorb water molecules from the apex 536, and a near infrared laser beam having a wavelength of 1500 nm may be used to remove carbon monoxide molecules bound to the apex 536. It should be understood that these exemplary wavelengths are not limiting or specific. Other laser wavelengths and intensities may be used as appropriate. Although the local temperature of the emitter tip 535 may increase due to exposure to the light beam 545, the increase in temperature is significantly less than resistive and radiative heating techniques because the heating is localized and limited to the emitting surface or apex 536 of the emitter tip 535. Furthermore, because only a small target area of ​​the emitter tip 535 (e.g., the apex 536) is cleaned, the number of contaminants released may not tax the vacuum pumping mechanism and may not cause a significant decrease in the vacuum level around the emitter tip 535. FIG. 5B shows a surface of apex 536 of emitter tip 535 that is substantially free of contaminant 520 when illuminated by light beam 545 .

[0061]

[0066] 5A , the light beam 545 may comprise a linearly polarized light beam such that the electric field 548 oscillates in a direction perpendicular to the propagation of the light beam 545 and in a direction substantially parallel to the tapered edge of the emitter tip 535. In some embodiments, when the surface of the emitter tip 535 is illuminated, a surface mode of the linearly polarized light beam 545 may be excited. The surface mode of the linearly polarized light beam 545 may comprise a localized surface wave 552. In some embodiments, the localized surface wave 552 may enable or facilitate removal of the contaminant 420 bound to the surface of the apex 536 of the emitter tip 535.

[0062]

[0067] The technique of electron emitter tip decontamination using a light beam, such as a laser, may have some or all of the following advantages discussed herein: 1. High decontamination efficiency - Unlike conventional flash heating techniques for decontaminating electron emission sources including a filament and an emitter tip supported by the filament, the use of a light beam such as a laser makes it possible to target only a small region or area of ​​the emitter tip, typically the apex, to remove contaminants or adsorbed material from the useful emitting portion of the emitter tip, which can make the decontamination process more efficient. 2. Less outgassing - Because the light beam can be targeted and localized to clean only the emitting portion of the emitter tip, less contaminants are expelled, resulting in less outgassing into the chamber space. Less outgassing can help keep the chamber surfaces and emitter tip surfaces cleaner, thus lowering vacuum level requirements. 3. High Emission-Current Stability and Current Decay Time - Field emission sources rely on a high electric field across the emitter tip to emit electrons. When a contaminant layer forms on the emitter, the emission current can become unstable and the current decay time can become short. The light beam source cleaning technique allows for more frequent cleaning, which maintains the stability of the emission current and increases the current decay time. 4. Short Decontamination Periods - Decontamination with a light beam such as a laser is very fast and efficient. For example, a decontamination cycle may involve exposing the emitter tip surface to a laser beam for a few milliseconds or less, because a small area of ​​the emitter tip can be targeted for decontamination at one time. 5.High imaging resolution --Frequent and efficient de-fouling cycles can maintain the stability of the emission current, and the current decay time can be extended, resulting in improved imaging resolution. 6. Higher Inspection Throughput – The emitter tip of the electron source can be cleaned during wafer inspection without having to shut down the tool for maintenance, improving machine start-up time and overall inspection throughput. 7. Cost-effective - Optical beam decontamination technology allows users to locally heat and decontaminate the emitter tip for a very short period of time, thus reducing the risk of tip blunting. This results in a longer operational emitter tip life, fewer tip replacements required, and increased inspection throughput.

[0063]

[0068] 6, which illustrates a process flow diagram depicting an exemplary method 600 for removing contaminants from an emitter tip of an electron source consistent with embodiments of the present disclosure. Method 600 may be performed, for example, by a controller 50 of an EBI system 100 such as that shown in FIG. 1. Controller 50 may be programmed to perform one or more steps of method 600. For example, controller 50 may operate a light source to generate a light beam, adjust characteristics of the generated light beam, or perform other functions.

[0064]

[0069] In step 610, a light source, such as a laser (e.g., light source 340 of FIG. 3), may be activated to generate a light beam (e.g., light beam 345 of FIG. 3). In some embodiments, the characteristics of the light beam may be adjusted before directing the light beam toward the electron source. The light source may be fixedly coupled to a chamber (e.g., chamber 310 of FIG. 3) that includes a viewport (e.g., viewport 350 of FIG. 3). The light source may be aligned with the chamber such that the generated light beam can pass through the viewport.

[0065]

[0070] In step 620, the light beam may be directed to illuminate a portion of the emitter tip (e.g., emitter tip 335 of FIG. 3), thereby exciting surface modes of the light beam. The excited surface modes of the light beam may facilitate removal of one or more contaminants (e.g., contaminant 420 of FIG. 4) bound or adsorbed to the emitter tip surface. Removing the one or more contaminants may include breaking bonds between the contaminants and the emitter tip surface, such that upon breaking, the contaminants are removed and ejected from the chamber, leaving the surface of the emitter tip substantially free of the contaminants. In some embodiments, the excited surface modes may include propagating surface waves (e.g., propagating surface waves 452 of FIG. 4A) or localized surface waves (e.g., localized surface waves 552 of FIG. 5A).

[0066]

[0071] In some embodiments, breaking the bond may include a photon-assisted quantum process, also referred to as photon-contaminant resonance, to remove atoms or molecules from the surface of the emitter tip. A photon-contaminant resonance mechanism for decontaminating the emitter tip may include tuning the wavelength of a light beam including photons to break bonds between the contaminant and the surface of the emitter tip or apex (e.g., apex 436 in FIG. 4). The wavelength may be tuned to resonate with bonds formed between the contaminant and the surface of the emitter tip.

[0067]

[0072] In some embodiments, breaking bonds between contaminants and the surface of the emitter tip to decontaminate the emitter tip may include a localized optical radiation heating mechanism, in which a light beam may be focused onto the apex of the emitter tip, causing a localized increase in temperature at the apex so that one or more contaminants can be desorbed from the surface. In some embodiments, the light beam may include a near-infrared laser beam or a mid-infrared laser beam.

[0068]

[0073] A non-transitory computer readable medium may be provided that stores instructions for a processor of a controller (e.g., controller 50 of FIG. 1) to perform an image inspection, perform image acquisition, activate a light source, adjust a pumping mechanism and pump, direct a light beam to be incident on an emitter tip of an electron source, adjust the wavelength or other beam characteristics of the light beam, etc. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, a hard disk, a solid state drive, a magnetic tape, or any other magnetic data storage medium, a Compact Disc Read Only Memory (CD-ROM), any other optical data storage medium, any physical medium with a pattern of holes, a Random Access Memory (RAM), a Programmable Read Only Memory (PROM), an Erasable Programmable Read Only Memory (EPROM), a FLASH-EPROM, or any other flash memory, a Non-Volatile Random Access Memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions thereof.

[0069]

[0074] The embodiments of the present disclosure can be further described using the following clauses. 1. An electron source including an emitter tip configured to emit electrons; a light source configured to generate a light beam that illuminates a portion of the emitter tip and excite surface modes of the light beam, the excited surface modes promoting removal of contaminants from a surface of the illuminated portion of the emitter tip; 23. An electron beam apparatus comprising: 2. The electron beam apparatus of clause 1, further comprising a chamber enclosing the electron source, the chamber including a viewport configured to allow the light beam to pass therethrough. 3. The electron beam apparatus of claim 2, wherein the light source is coupled to the chamber such that the generated light beam travels through a viewport toward the emitter tip. 4. An electron beam device as described in any one of clauses 1 to 3, wherein irradiation of the emitter tip with the light beam causes destruction of bonds between the contaminant and the surface of the emitter tip. 5. An electron beam apparatus as described in clause 4, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by a photon-assisted quantum process. 6. An electron beam apparatus as described in clause 4, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by localized heating of the emitter tip. 7. An electron beam apparatus as described in clause 4, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by a combination of photon-assisted quantum processes and localized heating of the emitter tip. 8. An electron beam device as described in any one of clauses 1 to 7, wherein the wavelength of the light beam illuminating a portion of the emitter tip is adjusted based on the contaminant to be removed. 9. The electron beam device of claim 8, wherein the wavelength of the light beam is further adjusted based on the binding energy of the contaminant. 10. An electron beam device as described in any one of clauses 8 to 9, wherein irradiation of the emitter tip with a light beam causes an increase in temperature of the emitter tip, the temperature of the emitter tip being affected by the wavelength of the light beam. 11. An electron beam device according to any one of clauses 1 to 10, wherein the contaminants include atoms, molecules, or gas molecules. 12. An electron beam device according to any one of clauses 1 to 11, wherein the contaminant is adsorbed on or bound to the surface of the emitter tip. 13. An electron beam device according to any one of clauses 1 to 12, wherein the light source comprises a laser source. 14. An electron beam device according to any one of clauses 1 to 13, wherein the light beam comprises a continuous laser beam or a pulsed laser beam. 15. An electron beam device according to any one of clauses 1 to 14, wherein the electron source comprises a cold field emitter or a field emission source. 16. An electron beam apparatus as described in any one of clauses 2 to 15, further comprising a vacuum pumping mechanism in fluid communication with the chamber and configured to evacuate the removed contaminants from the chamber, the pumping mechanism including a plurality of vacuum pumps. 17. An electron beam device according to any one of clauses 1 to 16, wherein the emitter tip includes a lattice structure. 18. An electron beam device as described in clause 17, wherein the characteristics of the lattice structure are matched to the wave vector of the light beam. 19. An electron beam device according to any one of clauses 1 to 18, wherein the surface mode comprises a propagating surface wave or a localized surface wave. 20. An electron beam device according to any one of clauses 1 to 19, wherein the light beam is linearly polarised. 21. A method for removing contaminants from an emitter tip of an electron source, comprising: activating a light source to generate a light beam; illuminating a portion of the emitter tip with the light beam to excite surface modes of the light beam, the excited surface modes promoting removal of contaminants bound to a surface of the illuminated portion of the emitter tip; A method comprising: 22. The method of claim 21, wherein illuminating a portion of the emitter tip includes directing a light beam through a viewport of a chamber enclosing the electron source. 23. The method of claim 22, further comprising coupling a light source to the chamber such that the generated light beam travels through a viewport towards the emitter tip. 24. The method of any one of clauses 21-23, wherein irradiating a portion of the emitter tip causes breakdown of bonds between the contaminant and a surface of the emitter tip. 25. The method of claim 24, wherein the bond breaking is assisted by a photon-assisted quantum process. 26. The method of claim 24, wherein the bond breaking is assisted by locally heating the irradiated portion of the emitter tip. 27. The method according to clause 24, wherein the bond breaking is assisted by a combination of photon-assisted quantum processes and localized heating of the irradiated portion of the emitter tip. 28. The method of any one of clauses 21-27, further comprising adjusting the wavelength of the light beam illuminating a portion of the emitter tip based on the contaminant to be removed. 29. The method of claim 28, further comprising adjusting the wavelength of the light beam based on the binding energy of the contaminant. 30. A method according to any one of clauses 28-29, wherein irradiating a portion of the emitter tip with a light beam increases the temperature of the emitter tip, the temperature of the emitter tip being affected by the wavelength of the light beam. 31. The method of any one of clauses 21 to 30, wherein the contaminant comprises an atom, a molecule, or a gas molecule. 32. The method of any one of clauses 21 to 31, wherein the contaminant is adsorbed on or bound to the surface of the emitter tip. 33. The method of any one of clauses 31-32, wherein the light source comprises a laser source. 34. The method of any one of clauses 21 to 33, wherein the light beam comprises a continuous laser beam or a pulsed laser beam. 35. The method of any one of clauses 21 to 34, wherein the electron source comprises a cold field emitter or a field emission source. 36. The method of any one of clauses 22-35, further comprising evacuating the removed contaminants from the chamber using a vacuum pumping mechanism, the vacuum pumping mechanism including a plurality of vacuum pumps. 37. The method of any one of clauses 21-36, wherein the emitter tip includes a lattice structure. 38. The method according to claim 37, wherein the characteristics of the grating structure are matched to the wave vector of the light beam. 39. The method of any one of clauses 21 to 38, wherein the surface mode comprises a propagating surface wave or a localized surface wave. 40. The method of any one of clauses 21-39, further comprising linearly polarizing the light beam. 41. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of an electron beam device to cause the electron beam device to perform a method for removing contaminants from an emitter tip of an electron source, the method comprising: activating a light source to generate a light beam; illuminating a portion of the emitter tip with the light beam to excite surface modes of the light beam, the excited surface modes promoting removal of contaminants bound to a surface of the illuminated portion of the emitter tip; A non-transitory computer readable medium comprising: 42. The non-transitory computer-readable medium of claim 41, wherein illuminating a portion of the emitter tip includes directing a light beam through a viewport of a chamber enclosing the electron source. 43. The non-transitory computer readable medium of clause 42, wherein the set of instructions executable by one or more processors of the electron beam device further causes the electron beam device to couple the light source to the chamber such that the generated light beam travels through a viewport toward the emitter tip. 44. A non-transitory computer-readable medium according to any one of clauses 41 to 43, wherein irradiating a portion of the emitter tip causes the breakdown of bonds between the contaminant and a surface of the emitter tip. 45. The non-transitory computer-readable medium of claim 44, wherein the bond breaking is assisted by a photon-assisted quantum process. 46. ​​The non-transitory computer-readable medium of clause 44, wherein breaking of the bond is assisted by locally heating the irradiated portion of the emitter tip. 47. The non-transitory computer-readable medium of claim 44, wherein the bond breaking is assisted by a combination of photon-assisted quantum processes and localized heating of the irradiated portion of the emitter tip. 48. A non-transitory computer-readable medium according to any one of clauses 41 to 47, wherein the set of instructions executable by one or more processors of the electron beam device further causes the electron beam device to adjust the wavelength of the light beam that irradiates a portion of the emitter tip based on the contaminant to be removed. 49. The non-transitory computer readable medium of clause 48, further comprising adjusting the wavelength of the light beam based on the binding energy of the contaminant. 50. A non-transitory computer-readable medium according to any one of clauses 48 to 49, wherein irradiating a portion of the emitter tip with a light beam increases the temperature of the emitter tip, the temperature of the emitter tip being affected by the wavelength of the light beam. 51. The non-transitory computer-readable medium of any one of clauses 41 to 50, wherein the contaminant comprises an atom, a molecule, or a gas molecule. 52. A non-transitory computer-readable medium according to any one of clauses 41 to 51, wherein the contaminant is adsorbed on the surface of the emitter tip or bound to the surface of the emitter tip. 53. The non-transitory computer-readable medium of any one of clauses 41 to 52, wherein the light source includes a laser source. 54. A non-transitory computer-readable medium according to any one of clauses 41 to 53, wherein the light beam comprises a continuous laser beam or a pulsed laser beam. 55. The non-transitory computer-readable medium of any one of clauses 41 to 54, wherein the electron source comprises a cold field emitter or a field emission source. 56. A non-transitory computer-readable medium according to any one of clauses 42 to 55, wherein the set of instructions executable by one or more processors of the electron beam device causes the electron beam device to further evacuate the removed contaminants from the chamber using a vacuum pumping mechanism, the vacuum pumping mechanism including a plurality of vacuum pumps. 57. The non-transitory computer-readable medium of any one of clauses 41-56, wherein the emitter tip includes a lattice structure. 58. The non-transitory computer-readable medium of clause 57, wherein the characteristics of the lattice structure match the wave vector of the light beam. 59. The non-transitory computer-readable medium of any one of clauses 41 to 58, wherein the surface mode includes a propagating surface wave or a localized surface wave. 60. A non-transitory computer-readable medium according to any one of clauses 42 to 55, wherein the set of instructions executable by one or more processors of the electron beam device further causes the electron beam device to linearly polarize the light beam. 61. An electron source including an emitter tip configured to emit electrons; a light source configured to generate a light beam that illuminates a portion of the emitter tip to remove contaminants from a surface of the illuminated portion of the emitter tip; 2. An electron beam apparatus comprising: 62. The electron beam apparatus of clause 61, further comprising a chamber enclosing the electron source, the chamber including a viewport configured to allow the light beam to pass therethrough. 63. The electron beam apparatus of clause 62, wherein the light source is coupled to the chamber such that the generated light beam travels through a viewport towards the emitter tip. 64. An electron beam device according to any one of clauses 61 to 63, wherein irradiation of the emitter tip with the light beam causes destruction of bonds between the contaminant and the surface of the emitter tip. 65. An electron beam apparatus as described in clause 64, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by a photon-assisted quantum process. 66. An electron beam apparatus as described in clause 64, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by localized heating of the emitter tip. 67. An electron beam device as described in clause 64, wherein irradiation of the emitter tip with a light beam causes bond breaking assisted by a combination of photon-assisted quantum processes and localized heating. 68. An electron beam device as described in any one of clauses 61 to 67, wherein the wavelength of the light beam illuminating a portion of the emitter tip is adjusted based on the contaminant to be removed. 69. The electron beam device of claim 68, wherein the wavelength of the light beam is further adjusted based on the binding energy of the contaminant. 70. An electron beam device as described in any one of clauses 68-69, wherein irradiation of the emitter tip by the light beam causes an increase in temperature of the emitter tip, the temperature of the emitter tip being affected by the wavelength of the light beam. 71. An electron beam device according to any one of clauses 61 to 70, wherein the contaminant comprises an atom, a molecule, or a gas molecule. 72. An electron beam device according to any one of clauses 61 to 71, wherein the contaminant is adsorbed on or bound to the surface of the emitter tip. 73. An electron beam device according to any one of clauses 61 to 72, wherein the light source comprises a laser source. 74. An electron beam device according to any one of clauses 61 to 73, wherein the light beam comprises a continuous laser beam or a pulsed laser beam. 75. An electron beam device according to any one of clauses 61 to 74, wherein the electron source comprises a cold field emitter or a field emission source.

[0070]

[0075] It will be understood that the embodiments of the present disclosure are not limited to the exact structures described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in conjunction with various embodiments, and other embodiments of the present invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as merely exemplary, with a true scope and spirit of the invention being indicated by the following claims.

[0071]

[0076] The above description is intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications can be made as described without departing from the scope of the claims set forth below.

Claims

1. an electron source including an emitter tip configured to emit electrons; a light source configured to generate a light beam that illuminates a portion of the emitter tip and excite surface modes of the light beam, the excited surface modes promoting removal of contaminants from a surface of the illuminated portion of the emitter tip; An electron beam apparatus comprising:

2. a chamber enclosing the electron source; The electron beam device of claim 1 , wherein the chamber includes a viewport configured to allow the light beam to pass therethrough.

3. The electron beam device of claim 1 , wherein the irradiation of the emitter tip with the light beam causes a breakdown of a bond between the contaminant and the surface of the emitter tip.

4. 4. The electron beam device of claim 3, wherein the illumination of the emitter tip with the light beam causes the breaking of the bonds assisted by a photon-assisted quantum process.

5. 4. The electron beam device of claim 3, wherein the irradiation of the emitter tip by the light beam causes breaking of the bonds assisted by localized heating of the emitter tip.

6. 4. The electron beam device of claim 3, wherein the irradiation of the emitter tip by the light beam causes the breaking of the bonds assisted by a combination of photon-assisted quantum processes and localized heating of the emitter tip.

7. 2. The electron beam device of claim 1, wherein a wavelength of the light beam illuminating the portion of the emitter tip is adjusted based on the contaminant to be removed.

8. The electron beam device of claim 7 , wherein the wavelength of the light beam is further adjusted based on a binding energy of the contaminant.

9. Irradiation of the emitter tip by the light beam causes an increase in temperature of the emitter tip; 8. The electron beam device of claim 7, wherein the temperature of the emitter tip is affected by the wavelength of the light beam.

10. Electron beam device according to claim 1 , wherein the contaminants comprise atoms, molecules or gas molecules.

11. 2. The electron beam device of claim 1, wherein the contaminants are adsorbed or bonded to the surface of the emitter tip.

12. the emitter tip includes a grating structure; The electron beam device of claim 1 , wherein the characteristics of the lattice structure match a wave vector of the light beam.

13. The electron beam device of claim 1 , wherein the surface mode comprises a propagating surface wave or a localized surface wave.

14. The electron beam device of claim 1 , wherein the light beam is linearly polarized.

15. 1. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of an electron beam device to cause the electron beam device to perform a method for removing contaminants from an emitter tip of an electron source, the method comprising: The method comprises: activating a light source to generate a light beam; illuminating a portion of the emitter tip with the light beam to excite surface modes of the light beam, the excited surface modes promoting removal of the contaminant bound to a surface of the illuminated portion of the emitter tip; A non-transitory computer readable medium comprising:

Images