High-voltage cable connector with embedded current transformer

Abstract

Systems and methods for monitoring current through a high-voltage cable and locating one or more sources of electrical arcing by using a high-frequency current transformer embedded in a high voltage cable connector are disclosed herein. The current monitoring apparatus includes a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.

Description

HIGH-VOLTAGE CABLE CONNECTOR WITH EMBEDDED CURRENT TRANSFORMERCROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority of US application 63 / 737,571 which was filed on December 20, 2024 and which is incorporated herein in its entirety by reference.TECHNICAL FIELD

[0002] The embodiments provided herein generally relate to the provision of a high voltage power supply to a vacuum tool, such as a charged particle apparatus, and more particularly to, systems and methods of locating one or more sources of electrical arcing by using a high-frequency current transformer embedded in a high voltage cable connector.BACKGROUND

[0003] In manufacturing processes of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as a scanning electron microscope (SEM), can be employed for such inspection. As the complexity in device architecture increases, accurate, efficient, and high-throughput inspection of 3D structures has become more important. To achieve high throughput and high sensitivity, inspection systems, such as SEMs, may use multiple beams, voltage-contrast imaging, etc., leading to the addition of several components to perform the additional functions.SUMMARY

[0004] Some embodiments of the present disclosure provide systems and methods for monitoring electrical current passing through a high-voltage cable and for locating one or more sources of electrical arcing by using a high-frequency current transformer embedded in a high voltage cable connector.

[0005] Some embodiments of the present disclosure are directed to a current monitoring apparatus which may include a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.

[0006] Some embodiments to the present disclosure are directed to an apparatus for monitoring transient current through a cable, the apparatus comprising a connector. The connector may comprisea first channel configured to receive a vacuum feedthrough comprising a feedthrough pin and an unshielded cable extending through the vacuum feedthrough; a second channel extending in a same direction as the first channel and comprising a connector cable; a portion of the first channel configured to receive the feedthrough pin to form an electrical connection between the connector cable and the unshielded cable of the vacuum feedthrough; and a current transformer embedded in or coupled to an external surface of the connector and configured to encircle a portion of the unshielded cable of the vacuum feedthrough when the vacuum feedthrough is inserted into the first channel.

[0007] Some embodiments to the present disclosure are directed to a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.

[0008] Some embodiments to the present disclosure are directed to a cable connector comprising a first channel configured to receive a vacuum feedthrough comprising a feedthrough pin and an unshielded cable extending through the vacuum feedthrough; a second channel extending in the same direction as the first channel and comprising a connector cable; a plug electrically coupled with the connector cable and configured to receive the feedthrough pin to form an electrical connection between the connector cable and the unshielded cable of the vacuum feedthrough when the feedthrough is inserted in the first channel; and a current transformer circumferentially coupled to an external surface of the cable connector and configured to encircle a portion of the unshielded cable of the vacuum feedthrough when the vacuum feedthrough is inserted in the first channel.

[0009] Some embodiments to the present disclosure are directed to a method for monitoring current through a high-voltage cable coupled to a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber. The method may comprise monitoring current passing through the high-voltage cable using a signal measurement device embedded in or coupled to an external surface of the cable connector, wherein the signal measurement device is configured to encircle a portion of an unshielded portion of the high-voltage cable and a portion of the feedthrough placed in the channel.

[0010] Other advantages will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain example embodiments of the present invention.BRIEF DESCRIPTION OF FIGURES

[0011] The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, taken in conjunction with the accompanying drawings.

[0012] Fig. 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus.

[0013] Fig. 2 is a schematic diagram illustrating an exemplary multi-beam apparatus that is part of the exemplary charged particle beam inspection apparatus of Fig. 1.

[0014] Fig. 3 is a schematic diagram of exemplary system illustrating high voltage (HV) modules supplying high voltage for operation of a charged-particle beam inspection apparatus of Fig. 1.

[0015] Fig. 4 is a schematic diagram of an exemplary arrangement of a current transformer around a shielded high-voltage cable, consistent with some embodiments of the present disclosure.

[0016] Fig. 5 is a schematic diagram of an exemplary current transformer embedded in a high- voltage cable connector, consistent with some embodiments of the present disclosure.

[0017] Fig. 6 is a schematic view of an exemplary power interface in an unengaged arrangement, consistent with some embodiments of the present disclosure.

[0018] Fig. 7 illustrates a data plot comparing electrical signals received from a current transformer, consistent with some embodiments of the present disclosure.

[0019] Fig. 8 illustrates a process flowchart for an exemplary method for monitoring current through a high-voltage cable, consistent with embodiments of the present disclosure.DETAILED DESCRIPTION

[0020] 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 represented. The implementations set forth in the following description of exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatuses and methods consistent with aspects related to the invention as recited in the appended claims. Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing detection systems and detection methods in systems utilizing electron beams (“e-beams”). However, the disclosure is not so limited. Other types of charged-particle beams (e.g., including protons, ions, muons, or any other particle carrying electric charges) may be similarly applied. Furthermore, systems and methods for detection may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, or any imaging system.

[0021] The embodiments described throughout the present document generally apply to vacuum tools. A preferred application of embodiments is the provision of a power interface to a chargedparticle apparatus. Although the techniques of embodiments are generally described for a charged particle apparatus, embodiments may be applied to any type of vacuum tool.

[0022] The reduction of the physical size of devices, and enhancement of the computing power of electronic devices, may be accomplished by significantly increasing the packing density of circuit components, such as transistors, capacitors, diodes, etc. on an IC chip. This has been enabled by the increased resolution of photolithography systems enabling the fabrication of progressively smaller structures. For example, in 2019 an IC chip of a smart phone, which is the size of a thumbnail, could include over 2 billion transistors with the size of each transistor being less than l / 1000th of the width of a human hair. Thus, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process, with hundreds of individual steps. Errors in even one step have the potential to dramatically affect the functioning of the final product. Just one “killer defect” may cause device failure. The goal of the manufacturing process is to improve the overall yield of the process. For example, to obtain a 75% yield for a 50-step process (where a step may involve a layer being formed on a wafer), each individual step must have a yield greater than 99.4%. If an individual step has a yield of 95%, the overall process yield could be as low as 7-8%.

[0023] While high process yield is essential in an IC chip manufacturing facility, maintaining a high substrate (i.e., wafer) throughput, defined as the number of substrates processed per hour, is also essential. High process yield and high substrate throughput may be impacted by the presence of a defect. This is especially true if operator intervention is required for reviewing the defects. Thus, high throughput detection and identification of micro and nano-scale defects by inspection tools (such as a Scanning Electron Microscope (‘SEM’)) is essential for maintaining high yield and low cost.

[0024] A SEM comprises a scanning device and a detector apparatus. The scanning device comprises an illumination apparatus that comprises an electron source, for generating primary electrons, and a projection apparatus for scanning a sample, such as a substrate, with one or more focused beams of primary electrons. The primary electrons interact with the sample and generate interaction products, such as secondary electrons and backscattered electrons. The detection apparatus (which can include one or more detectors) can capture the secondary electrons and backscattered electrons from the sample as the sample is scanned so that the SEM may create an image of the scanned area of the sample. For high throughput inspection, some of the inspection apparatuses use multiple focused beams, i.e. a multi-beam, of primary electrons. The component beams of the multi-beam may be referred to as sub-beams or beamlets. A multi-beam may scan different parts of a sample simultaneously. A multi-beam inspection apparatus may therefore inspect a sample at a much higher speed than a single-beam inspection apparatus.

[0025] Several components of some single -beam or a multi-beam SEMs require high-voltage power supplies. The performance of these high-voltage power supplies is monitored using high-frequency current transformers. However, the existing designs and arrangements of high-frequency currenttransformer face several challenges in accurately and effectively determining the occurrence and location of the occurrence of an electrical discharge event, such as an electrical arcing event.

[0026] In single -beam or multi-beam inspection apparatuses (e.g., SEMs), high-voltage modules are used to supply power to components such as, but not limited to, the electron gun, electro-optical column, flooding column, detector column, electrostatic chuck, and wafer stage movement. For example, electrons emitted from an electron gun may be accelerated towards the sample by applying a high accelerating voltage in the range of 1 kV to 30 kV to penetrate deeper into the sample for subsurface information. As another example, in a multi-beam SEM, the electrons of multiple beams may be “accelerated” through a crossover region to mitigate the disturbance, and thereby the loss in resolution, caused due to the Coulomb effect. Although systems and modules may be designed to minimize high-voltage discharges, occasional discharges may still occur. Occasional high-voltage discharge in cables carrying high-voltages, also referred to as arcing or flashing, can cause damage to the cables, to components receiving the high-voltage, to the high-voltage power source, or to other connected equipment. In some cases, if undetected, an arcing event in one high-voltage channel can cause cascading secondary arcing events in other channels of the system, leading to a total equipment shutdown. Further, the sudden discharge of electric current through a component can disturb loose particles off the component surface into the system, contaminating the system and potentially creating defects on a semiconductor wafer, negatively impacting the throughput or the yield.

[0027] One of several ways to detect an arcing event and identify the channel in which arcing occurs includes installing a high-frequency current transformer (HFCT) to measure transient current in high- voltage cables, which is an indication of an occurrence of an electromagnetic disturbance. However, such transformers are currently placed around shielded portions of the high-voltage cables. The metallic shielding material of the shielded cable may attenuate the signal detected by the transformer, thereby impacting the accuracy of detecting transient current, resultantly limiting the ability to detect the arcing or even locate the channel in which arcing occurred. Therefore, it is desirable to provide systems and methods for accurately measuring and monitoring the current flowing through high- voltage cables.

[0028] Some aspects of the present disclosure may address some of the above-mentioned challenges by providing an apparatus(es) and method(s) for monitoring current through high-voltage cables to detect an electrical discharge and identify the module or component in which the electrical discharge occurs. The apparatus includes a connector to which the high-voltage cable may be coupled. An unshielded portion (i.e., the metal wire without any shielding) of the high-voltage cable is inside the connector while the shielded portion of the high-voltage cable is outside the connector. A high- frequency current transformer embedded in the external surface of the connector encircles a portion of the unshielded portion of the high-voltage cable in the connector. The high-frequency current transformer measures unattenuated signals from the unshielded portions of the high-voltage cable,thereby increasing the effectiveness of the high-frequency current transformer to monitor the current in the high-voltage cable, leading to an improved ability to locate the source of arcing.

[0029] An embodiment of the proposed high-voltage cable connector design includes a high- frequency current transformer surrounding an unshielded high-voltage cable and enables continuous monitoring of transient current through the high-voltage cable, thereby enabling detection of an arcing event at the time of occurrence and identification of the location or the channel in which the arcing event occurred. In addition to monitoring, the electrical current of the signal passing through the cable may be recorded, enabling analysis of current signal characteristics such as waveform, intensity, frequency, among other things, to determine the cause of arcing. The metal shield housing the proposed high-voltage cable connector provides safety from electrical hazards during operation of high-voltage equipment.

[0030] An implementation of a known multi-beam inspection apparatus is described below.

[0031] Relative dimensions of components in drawings may be exaggerated for clarity. Within the following description of drawings, the same or like reference numbers refer to the same or like components or entities, and only the differences with respect to the individual embodiments may be described. While the description and drawings are directed to an electron-optical apparatus, it is appreciated that the embodiments are not used to limit the present disclosure to specific charged particles. References to electrons throughout the present document may therefore be more generally be considered to be references to charged particles, with the charged particles not necessarily being electrons. Although embodiments of this disclosure are generally described for charged-particles and charged-particle apparatuses, they may not be limited as such. For example, the embodiments may be applied to any type of vacuum tool, such as a deposition tool, an etch tool, or an optical inspection tool, among other vacuum tools, using charged particles, neutral particles, ions, plasma, gases, liquids, or solids, etc. Further, although the embodiments may be generally described for semiconductor device fabrication, metrology, or inspection methods, the applications are not limited as such.

[0032] Objects and advantages of the disclosure may be realized by the elements and combinations as set forth in the embodiments discussed herein. However, embodiments of the present disclosure are not necessarily required to achieve such exemplary objects or advantages, and some embodiments may not achieve any of the stated objects or advantages.

[0033] Without limiting the scope of the present disclosure, some embodiments may be described in the context of providing systems and methods in systems utilizing electron beams (“e-beams”). However, the disclosure is not so limited. Other types of charged particle beams, ion beams, plasma, neutral particles, etc. may be similarly applied. Furthermore, systems and methods for wafer inspection or overlay measurement may be used in other imaging systems, such as optical imaging, photon detection, x-ray detection, ion detection, etc.

[0034] As used herein, unless specifically stated otherwise, the term “or” encompasses all possible combinations, except where infeasible. For example, if it is stated that a component includes A or B, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or A and B. As a second example, if it is stated that a component includes A, B, or C, then, unless specifically stated otherwise or infeasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C. Expressions such as “at least one of’ do not necessarily modify an entirety of a following list and do not necessarily modify each member of the list, such that “at least one of A, B, and C” should be understood as including only one of A, only one of B, only one of C, or any combination of A, B, and C. The phrase “one of A and B” or “any one of A and B” shall be interpreted in the broadest sense to include one of A, or one of B.

[0035] Reference is now made to Fig. 1, which is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus 100. The charged particle beam inspection apparatus 100 of Fig. 1 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, an equipment front end module (EFEM) 30 and a controller 50.

[0036] EFEM 30 includes a first loading port 30a and a second loading port 30b. EFEM 30 may include additional loading port(s). First loading port 30a and second loading port 30b may, for example, receive substrate front opening unified pods (FOUPs) that contain substrates (e.g., semiconductor substrates or substrates made of other material(s)) or samples to be inspected (substrates, wafers and samples are collectively referred to as “samples” hereafter). One or more robot arms (not shown) in EFEM 30 transport the samples to load lock chamber 20.

[0037] Load lock chamber 20 is used to remove the gas around a sample. This creates a vacuum that is a local gas pressure lower than the pressure in the surrounding environment. The load lock chamber 20 may be connected to a load lock vacuum pump system (not shown), which removes gas particles in the load lock chamber 20. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below the atmospheric pressure. After reaching the first pressure, one or more robot arms (not shown) transport the sample from load lock chamber 20 to main chamber 10. Main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas molecules in main chamber 10 so that the pressure around the sample reaches a second pressure lower than the first pressure. After reaching the second pressure, the sample is transported to the electron beam tool by which it may be subject to charged particle flooding or inspection. An electron beam tool 40 may comprise either a single beam or a multi-beam electron-optical apparatus.

[0038] Controller 50 is electronically connected to electron beam tool 40. Controller 50 may be a processor (such as a computer) configured to control the charged particle beam inspection apparatus 100. Controller 50 may also include a processing circuitry configured to execute various signal and image processing functions. While controller 50 is shown in Fig. 1 as being outside of the structurethat includes main chamber 10, load lock chamber 20, and EFEM 30, it is appreciated that controller 50 may be part of the structure. The controller 50 may be located in one of the component elements of the charged particle beam inspection apparatus or it may be distributed over at least two of the component elements. While the present disclosure provides examples of main chamber 10 housing an electron beam inspection tool, it should be noted that aspects of the disclosure in their broadest sense are not limited to a chamber housing an electron beam inspection tool. Rather, it is appreciated that the foregoing principles may also be applied to other tools and other arrangements of apparatus, that operate under the second pressure.

[0039] Reference is now made to Fig. 2, which is a schematic diagram illustrating an exemplary electron beam tool 40 including a multi-beam inspection tool that is part of the EBI system 100 of Fig. 1, consistent with embodiments of the present disclosure. In some embodiments, electron beam tool 40 may be operated as a single-beam inspection tool that is part of EBI system 100 of Fig. 1. Multi-beam electron beam tool 40 (also referred to herein as apparatus 40) comprises an electron source 201, a Coulomb aperture plate (or “gun aperture plate”) 271, a condenser lens 210, a source conversion unit 220, a primary projection system 230, a motorized stage 209, and a sample holder 207 supported by motorized stage 209 to hold a sample 208 (e.g., a wafer or a photomask) to be inspected. Multi-beam electron beam tool 40 may further comprise a secondary projection system 250 and an electron detection device 240. Primary projection system 230 may comprise an objective lens 231. Electron detection device 240 may comprise a plurality of detection elements 241, 242, and 243. A beam separator 233 and a deflection scanning unit 232 may be positioned inside primary projection system 230.

[0040] Electron source 201, Coulomb aperture plate 271, condenser lens 210, source conversion unit 220, beam separator 233, deflection scanning unit 232, and primary projection system 230 may be aligned with a primary optical axis 204 of apparatus 40. Secondary projection system 250 and electron detection device 240 may be aligned with a secondary optical axis 251 of apparatus 40.

[0041] Electron source 201 may comprise a cathode (not shown) and an extractor or anode (not shown), in which, during operation, electron source 201 is configured to emit primary electrons from the cathode and the primary electrons are extracted or accelerated by the extractor or the anode to form a primary electron beam 202 that form a primary beam crossover (virtual or real) 203. Primary electron beam 202 may be visualized as being emitted from primary beam crossover 203.

[0042] Source conversion unit 220 may comprise an image-forming element array (not shown), an aberration compensator array (not shown), a beam-limit aperture array (not shown), and a pre-bending micro-deflector array (not shown). In some embodiments, the pre-bending micro-deflector array deflects a plurality of primary beamlets 211, 212, 213 of primary electron beam 202 to normally enter the beam-limit aperture array, the image-forming element array, and an aberration compensator array. In some embodiments, apparatus 40 may be operated as a single-beam system such that a singleprimary beamlet is generated. In some embodiments, condenser lens 210 is designed to focus primary electron beam 202 to become a parallel beam and be normally incident onto source conversion unit 220. The image-forming element array may comprise a plurality of micro-deflectors or micro-lenses to influence the plurality of primary beamlets 211, 212, 213 of primary electron beam 202 and to form a plurality of parallel images (virtual or real) of primary beam crossover 203, one for each of the primary beamlets 211, 212, and 213. In some embodiments, the aberration compensator array may comprise a field curvature compensator array (not shown) and an astigmatism compensator array (not shown). The field curvature compensator array may comprise a plurality of micro-lenses to compensate field curvature aberrations of the primary beamlets 211, 212, and 213. The astigmatism compensator array may comprise a plurality of micro-stigmators to compensate astigmatism aberrations of the primary beamlets 211, 212, and 213. The beam-limit aperture array may be configured to limit diameters of individual primary beamlets 211, 212, and 213. Fig. 2 shows three primary beamlets 211, 212, and 213 as an example, and it is appreciated that source conversion unit 220 may be configured to form any number of primary beamlets. Controller 50 (shown in Fig. 1) may be connected to various parts of EBI system 100 of Fig. 1, such as source conversion unit 220, electron detection device 240, primary projection system 230, or motorized stage 209. In some embodiments, as explained in further details below, controller 109 may perform various image and signal processing functions. Controller 50 (shown in Fig. 1) may also generate various control signals to govern operations of the charged particle beam inspection system.

[0043] Condenser lens 210 is configured to focus primary electron beam 202. Condenser lens 210 may further be configured to adjust electric currents of primary beamlets 211, 212, and 213 downstream of source conversion unit 220 by varying the focusing power of condenser lens 210. Alternatively, the electric currents may be changed by altering the radial sizes of beam-limit apertures within the beam-limit aperture array corresponding to the individual primary beamlets. The electric currents may be changed by both altering the radial sizes of beam-limit apertures and the focusing power of condenser lens 210. Condenser lens 210 may be an adjustable condenser lens that may be configured so that the position of its first principal plane is movable. The adjustable condenser lens may be configured to be magnetic, which may result in off-axis beamlets 212 and 213 illuminating source conversion unit 220 with rotation angles. The rotation angles change with the focusing power or the position of the first principal plane of the adjustable condenser lens. Condenser lens 210 may be an anti-rotation condenser lens that may be configured to keep the rotation angles unchanged while the focusing power of condenser lens 210 is changed. In some embodiments, condenser lens 210 may be an adjustable anti-rotation condenser lens, in which the rotation angles do not change when the focusing power and the position of its first principal plane are varied.

[0044] Objective lens 231 may be configured to focus beamlets 211, 212, and 213 onto a sample 208 for inspection and may form, in the current embodiments, three probe spots 221, 222, and 223 on the surface of sample 208. Coulomb aperture plate 271, in operation, is configured to block off peripheralelectrons of primary electron beam 202 to reduce Coulomb effect. The Coulomb effect may enlarge the size of each of probe spots 221, 222, and 223 of primary beamlets 211, 212, 213, and therefore deteriorate inspection resolution.

[0045] Beam separator 233 may, for example, be a Wien filter comprising an electrostatic deflector generating an electrostatic dipole field and a magnetic dipole field (not shown in Fig. 2). In operation, beam separator 233 may be configured to exert an electrostatic force by electrostatic dipole field on individual electrons of primary beamlets 211, 212, and 213. The electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted by magnetic dipole field of beam separator 233 on the individual electrons. Primary beamlets 211, 212, and 213 may therefore pass at least substantially straight through beam separator 233 with at least substantially zero deflection angles.

[0046] Deflection scanning unit 232, in operation, is configured to deflect primary beamlets 211, 212, and 213 to scan probe spots 221, 222, and 223 across individual scanning areas in a section of the surface of sample 208. In response to incidence of primary beamlets 211, 212, and 213 at probe spots 221, 222, and 223 on sample 208, electrons emerge from sample 208 and generate three secondary electron beams 261, 262, and 263. Each of secondary electron beams 261, 262, and 263 typically comprise secondary electrons (having electron energy < 50eV) and backscattered electrons (having electron energy between 50eV and the landing energy of primary beamlets 211, 212, and 213). Beam separator 233 is configured to deflect secondary electron beams 261, 262, and 263 towards secondary projection system 250. Secondary projection system 250 subsequently focuses secondary electron beams 261, 262, and 263 onto detection elements 241, 242, and 243 of electron detection device 240. Detection elements 241, 242, and 243 are arranged to detect corresponding secondary electron beams 261, 262, and 263 and generate corresponding signals which are sent to controller 50 (shown in Fig. 1) or a signal processing system (not shown), e.g., to construct images of the corresponding scanned areas of sample 208.

[0047] In some embodiments, detection elements 241, 242, and 243 detect corresponding secondary electron beams 261, 262, and 263, respectively, and generate corresponding intensity signal outputs to an image processing system 290. In some embodiments, each detection element, 241, 242, and 243 may comprise one or more pixels. The intensity signal output of a detection element may be a sum of signals generated by all the pixels within the detection element.

[0048] In some embodiments, image processing system 290 may include an image acquirer 292, a storage 294, and a controller 296. Image acquirer 292 may comprise one or more processors. For example, image acquirer 292 may comprise a computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, or the like, or a combination thereof. Image acquirer 292 may be communicatively coupled to charged-particle detection device 240 of beam tool 40 through a medium such as an electric conductor, optical fiber cable, portable storage media, IR,Bluetooth, internet, wireless network, wireless radio, or a combination thereof. In some embodiments, image acquirer 292 may receive a signal from charged-particle detection device 240 and may construct an image. Image acquirer 292 may thus acquire images of sample 208. Image acquirer 292 may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, adjusting brightness and contrasts of acquired images, and the like. In some embodiments, storage 294 may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer readable memory, and the like. Storage 294 may be coupled with image acquirer 292 and may be used for saving scanned raw image data as original images, and post-processed images.

[0049] In some embodiments, image acquirer 292 may acquire one or more images of a sample based on an imaging signal received from electron detection device 240. An imaging signal may correspond to a scanning operation for conducting charged particle imaging. An acquired image may be a single image comprising a plurality of imaging areas. The single image may be stored in the storage. The single image may be an original image that may be divided into a plurality of regions. Each of the regions may comprise one imaging area containing a feature of sample 208. The acquired images may comprise multiple images of a single imaging area of sample 208 sampled multiple times over a time sequence. The multiple images may be stored in the storage. In some embodiments, image processing system 290 may be configured to perform image processing steps with the multiple images of the same location of sample 208.

[0050] In some embodiments, a controller (e.g., controller 50 of Fig. 1) may include measurement circuitries (e.g., analog-to-digital converters) to obtain a distribution of the detected secondary electrons. The electron distribution data collected during a detection time window, in combination with corresponding scan path data of each of primary beamlets 211, 212, and 213 incident on the wafer surface, can be used to reconstruct images of the wafer structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of sample 208, and thereby can be used to reveal any defects that may exist in the wafer.

[0051] In some embodiments, a controller (not shown) may control motorized stage 209 to move sample 208 during inspection of sample 208. In some embodiments, controller 50 may enable motorized stage 209 to move sample 208 in a direction continuously at a constant speed. In other embodiments, a controller may enable motorized stage 209 to change the speed of the movement of sample 208 overtime depending on the steps of scanning process.

[0052] Although Fig. 2 shows that apparatus 40 uses three primary electron beams, it is appreciated that apparatus 40 may use a greater or fewer number of primary electron beams. The present disclosure does not limit the number of primary electron beams used in apparatus 40. For example, apparatus 40 may use a 3x3 array, a 5x5 array, or a m x n array of primary electron beams orbeamlets, where m and n are positive integers. In some embodiments, apparatus 40 may be a SEM used for lithography, defect inspection, metrology, or a combination thereof.

[0053] The above-described embodiments of multi-beam inspection tools comprise a multi-beam charged particle apparatus, that may be referred to as a multi-beam charged particle optical apparatus, and that may have a single source of charged particles. The multi-beam charged particle apparatus comprises an illumination apparatus and a projection apparatus. The illumination apparatus may generate a multi-beam of charged particles from the beam of electrons from the source. The projection apparatus projects a multi-beam of charged particles towards a sample. At least part of the surface of a sample may be scanned with the multi-beam of charged particles.

[0054] A multi-beam charged particle apparatus comprises one or more electron-optical devices for manipulating the sub-beams of the multi-beam of charged particles. The applied manipulation may be, for example, a deflection of the paths of sub-beams or a focusing operation applied to the subbeams. The one or more electron-optical devices may comprise micro-electro-mechanical systems (MEMS).

[0055] The charged particle apparatus may comprise beam path manipulators located up-beam of the electron-optical device and, optionally, in the electron-optical device. Beam paths may be manipulated linearly in directions orthogonal to the charged particle axis, i.e., optical axis, by, for example, two electrostatic deflector sets operating across the whole beam. The two electrostatic deflector sets may be configured to deflect the beam path in orthogonal directions. Each electrostatic deflector set may comprise two electrostatic deflectors located sequentially along the beam path. The first electrostatic deflector of each set applies a correcting deflection, and the second electrostatic deflector restores the beam to the correct angle of incidence on the electron-optical device. The correcting deflection applied by the first electrostatic deflector may be an over correction so that the second electrostatic deflector can apply a deflection for ensuring the desired angle of incidence to the MEMS. The location of the electrostatic deflector sets could be at a number of locations up-beam of the electron-optical device. Beam paths may be manipulated rotationally. Rotational corrections may be applied by a magnetic lens. Rotational corrections may additionally, or alternatively, be achieved by an existing magnetic lens such as the condenser lens arrangement.

[0056] Embodiments of charged particle apparatus may comprise alternative or additional components on a charged particle path, such as further lenses and other components, from what is shown in, and described earlier with reference to Figs. 1 and 2. In particular, embodiments also include a charged particle projection apparatus that divides a charged particle beam from a source into a plurality of sub-beams. A plurality of respective objective lenses may project the sub-beams onto a sample. In some embodiments, a plurality of condenser lenses is provided up-beam from the objective lenses. The condenser lenses focus each of the sub-beams to an intermediate focus up-beam of the objective lenses. In some embodiments, collimators are provided up-beam from the objective lenses.Correctors may be provided to reduce focus error or aberrations. In some embodiments, such correctors are integrated into or positioned directly adjacent to the objective lenses. Where condenser lenses are provided, such correctors may additionally, or alternatively, be integrated into, or positioned directly adjacent to, the condenser lenses or positioned in, or directly adjacent to, the intermediate foci. A detector is provided to detect charged particles emitted by the sample. In some embodiments, the detector may be integrated into the objective lens . In other embodiments, the detector may be on the bottom surface of the objective lens so as to face a sample in use. The condenser lenses, objective lenses, or detector may be formed as MEMS or complementary metal- oxide semiconductor (CMOS) devices, among others.

[0057] Some embodiments of charged particle apparatus may also be implemented with a flood column. The flood column may be used to pre-charge the surface of sample 208 and set the charging conditions. For example, the flood column may pre-charge the surface of sample 208 prior to inspection by the charged particle inspection apparatus. This may enhance the voltage contrast defect signal to increase the defect detection sensitivity or throughput of the charged particle inspection apparatus. A flood column may have a large beam current, as required for quickly flooding, i.e., charging a sample. The flood column may be used to provide a relatively large amount of charged particles to charge a predefined area. The charged particle inspection apparatus may scan the precharged area of sample 208 to achieve imaging of the area.

[0058] The motorized stage 209 may move sample 208 from a position for charged particle flooding by the flood column to a position for inspection by the charged particle inspection apparatus. Put another way, motorized stage 209 may be used to move sample 208 into position for charged particle flooding. The flood column may then flood sample 208 with charged particles. Motorized stage 209 may then be used to move sample 208 into position for inspection. The charged particle inspection apparatus may then be used to inspect sample 208. Alternatively, the flood column may be part of the charged particle apparatus. The position for charged particle flooding by the flood column may coincide with the position for inspection by charged particle inspection apparatus. Sample 208 and motorized stage 209 may therefore remain substantially in place after charged particle flooding and before inspection. The flood column may be integrated with, or mechanically coupled to, the charged particle inspection apparatus. There may be an interface between the flood column and the primary column of the charged particle inspection apparatus.

[0059] Advancements in the design of charged particle apparatuses include increasing the number of components in a charged particle apparatus. For example, the number of sources may be increased in order to increase the number of beams in a multi-beam of charged particles that may be provided. The number of lenses, and other charged particle manipulators, may also need to be increased so that the increased number of source beams may be appropriately manipulated. Charged particleapparatuses therefore need to comprise more components and these need to be integrated into the architecture of the charged particle apparatus.

[0060] Fig. 3 illustrates an exemplary system 300 including high-voltage supply modules configured to supply high voltage to components of a charged-particle beam system. It is to be appreciated that the charged-particle beam system illustrated in Fig. 3 may be a single-beam inspection apparatus, a multi-beam inspection apparatus, a charged-particle beam lithography apparatus, a photolithography apparatus, a metrology apparatus, or any suitable apparatus using high-voltage power supplies.

[0061] As shown, system 300 may include, among other things, a high-voltage module control unit 302, a charged-particle source 305 (e.g., an electron gun), an electro-optical column 310, a charged- particle detection system 315 (e.g., a secondary electron detector), a flooding column 320, a substrate stage including an electrostatic chuck 325, and a high-voltage shielding plate 330. System 300 may further include an electron gun high-voltage module 350 configured to supply high voltage to charged-particle source 305, a stage high-voltage module 360 configured to supply high voltage to electro-optical column 310 or high-voltage shielding plate 330, a flooding gun high-voltage module 370 configured to supply high voltage to flooding column 320, an e-chuck high-voltage module 380 configured to supply high voltage to electrostatic chuck 325, and a detector high-voltage module 390 configured to supply high voltage to charged-particle detection system 315. System 300 may further include one or more current transformers 340 installed around a shielded high-voltage cable and configured to detect an arcing event based on the current signal passing through the high-voltage cable. It is to be appreciated that although not shown, system 300 may include other components and corresponding high-voltage modules configured to supply appropriate voltage to the components.

[0062] As previously described, in a charged-particle beam apparatus, such as a multi-beam inspection tool, multiple high-voltage modules may be used to supply high-voltage to components so that the intended functions can be performed to obtain desired results. Generally, a high-voltage power supply system includes a high-voltage power supply source, cables or connector wire assembly capable of transporting high voltage from the source to the target, and a current transformer to accurately measure transient current, among other things. Transient current refers to short-lived, oscillatory, or aperiodic current that flows in a circuit after an electromagnetic disturbance. In some instances, transient current is also referred to as a “surge,” a “spike,” a “discharge,” a “flashover,” or an “arc,” which can affect the cables, the components receiving the high voltage, performance of the components, and in some cases, may also cause circuit failure. The sudden discharge (e.g., an arc) of electric current through a component can disturb, or dislodge particles on the component, contaminating the system and potentially creating defects on a semiconductor wafer during device fabrication.

[0063] In high-voltage power supply systems used in the semiconductor device fabrication or inspection tools (e.g., a SEM), transient current may be caused by internal or external sources, such asloose connections, external faults, human errors, short circuits, among other things. In some cases, gas particles (due to imperfect vacuum) or contaminants that get dislodged from a surface and float in the vacuum can also cause arcing.

[0064] In some existing systems, high-voltage module control unit 302 may be configured to control one or more high-voltage modules. Controlling high-voltage modules may include, but is not limited to, supplying and regulating power supply to a high-voltage module, activating or deactivating a high- voltage module, communicating with a high-voltage module, performing health-checks of a high- voltage module, etc. A high-voltage module may supply high-voltage power to multiple components through corresponding channels. As an example, as shown in Fig. 3, stage high-voltage module 360 is configured to supply high-voltage power to a control electrode in electro-optical column 310, to high- voltage shielding plate 330, and to e-chuck high-voltage module 380. In such cases, while the existing detection mechanism may identify the module triggering the arcing event, determining the exact channel(s) in which the arcing occurs may be challenging. Further, though the high-voltage module may have in-built mechanisms to monitor the output voltage and current over an extended period of time and detect whether an arcing event occurs, it may be unable to identify the exact location of the arcing event and reproduce the arcing signal waveform to enable identifying the cause of arcing.

[0065] One of several techniques to detect an arcing event within a channel includes placing a high- frequency current transformer around the high-voltage cables, such as current transformer 340 (discussed with reference to Fig. 4). The high-voltage cables configured to carry high voltage to a component are shielded cables, and the shielding attenuates the high-frequency arcing signal intensity or alters the high-frequency arcing signal waveform received by the current transformer, rendering the detection of an arcing event inaccurate or difficult because the arcing signal may be indistinguishable from a non-arcing event signal. In addition to being inaccurate and inconsistent in detecting arcing events, in some existing systems, current transformer 340 may be temporarily installed to troubleshoot or perform routine maintenance. The installation of current transformer 340 often warrants a partial shutdown, which can add to equipment downtime, therefore impacting the yield or the productivity. Therefore, it may be desirable to provide systems and methods for monitoring current in high-voltage cables accurately to determine the location and time of occurrence of an arcing event.

[0066] Fig. 4 illustrates an exemplary high-voltage power supply system 400 including a high- voltage power source 450 located outside of a vacuum chamber (e.g., vacuum chamber 410, which may be main chamber 10 of Fig. 1), a shielded high-voltage cable comprising electrical wire 460 and a shield layer 470, a metal shield (e.g., a safety tower) 420, a vacuum feedthrough 430 configured to electrically connect the high-voltage power supply to component inside of vacuum chamber 410 or another component of a vacuum apparatus. High-voltage power system 400 further includes a current transformer 440 encircling the shielding 470 surrounding high-voltage cable 460 and configured to help determine which channel is causing the electrical arcing or discharge. High-voltage power source450 may be a high-voltage module (e.g., electron gun high-voltage module 350, stage high-voltage module 360, flooding gun high-voltage module 370, or an e-chuck high-voltage module 380, among others). Shielded high-voltage cable may be a coaxially shielded cable in which electrically conducting wire may comprise copper, tin plated copper, etc., and the shield may comprise braided aluminum, braided copper, foil braiding, etc.

[0067] As discussed with reference to Fig. 3, in some existing systems, during a discharge or an arcing event, the current signal detected by current transformer 440 may be reduced in intensity or altered in waveform due to the shield layer 470 of the shielded high-voltage cable, which results in an attenuated E / M field outside of shielding 470 and in resultantly reduced current being induced in current transformer 440. The placement of current transformer 440 around the shielded portion of a current-carrying cable may impact its ability to accurately detect an arcing event by sensing a change in the arcing signal intensity or in the arcing signal waveform. Further, in existing systems, multiple channels are usually monitored simultaneously and if the arcing signal waveforms are indistinguishably similar, determining the source or the reason for an electrical discharge may be challenging as well. This issue may negatively impact the diagnostic capabilities and, resultantly, preventive measures may be hard to implement.

[0068] Reference is now made to Fig. 5, which illustrates an exemplary system 500 configured to supply high-voltage power in a high-voltage system, consistent with embodiments of the present disclosure. System 500 may comprise, among other things, a chamber 510, a metal shield 520, a vacuum feedthrough 530, a current transformer 540, a high-voltage power source 550, a shielded high-voltage cable comprising electrical wire 560 and a shield layer 570, a connector 580, and a data acquisition apparatus 590. It is to be appreciated that although not explicitly illustrated, system 500 may comprise more or fewer components, as appropriate.

[0069] A chamber, as referred to herein, may be a vacuum chamber (e.g., main chamber 10 of Fig. 1) of a vacuum tool or a vacuum apparatus (e.g., charged particle beam inspection apparatus 100), or any non-vacuum chamber associated with a vacuum apparatus. As an example, chamber 510 may comprise an electro-optical column of a SEM, or chamber 510 may comprise an enclosure for a flooding gun of a SEM, or chamber 510 may comprise a secondary electron detector column of a SEM, or chamber 510 may comprise a non-vacuum enclosure housing another high-voltage module such as an e-chuck high-voltage module (e.g., e-chuck high-voltage module 380 of Fig. 3).

[0070] In some embodiments, chamber 510 may be a vacuum chamber comprising a flange 512. Other components or chambers may be connected to chamber 510 via a flange coupling. As shown in Fig. 5, a flange coupling may be formed by connecting flange 512 of chamber 510 with flange 514 of metal shield 520, thus forming a connection between metal shield 520 and chamber 510. In a high vacuum (HV) or an ultra-high vacuum (UHV) apparatus, a flange coupling may further include bolts 516 and a gasket (not shown) sandwiched between the abutting surfaces of flanges 512 and 514 toform a substantially leak-free joint between the components being connected. In some embodiments, a flange coupling may include a gasket and a clamp to secure the gasket between the abutting surfaces of two flanges.

[0071] In high-voltage systems, such as a SEM, shielding of high-voltage cables serves multiple purposes, including protection for operators or users of the equipment, reduction in stress on the insulations, prevention of damage from corona discharges, blockage of electromagnetic interference (EMI) and radio frequency interference (RFI), prevention of leakage currents, among other things. Although the metallic shields on high-voltage cables offer several benefits, one of the drawbacks of shielded high-voltage cables is signal attenuation caused by return current from the shielding layer, which can lead to inaccurate or missed detection of electrical discharge events (i.e., arcing or surging) occurring in high-voltage systems. To overcome this issue, while maintaining safety and functionality, some embodiments of this disclosure provide a high-voltage system comprising a metal shield housing an unshielded high-voltage cable configured to provide high-voltage power from a power source to a target component.

[0072] Referring to Fig. 5, system 500 may further comprise metal shield 520, also referred to herein as a safety tower, designed to enclose at least connector 580. In some embodiments, metal shield 520 may be connected with chamber 510 via one or more bolts 516 configured to secure flange 514 of metal shield 520 and flange 512 of chamber 510 to provide a leak-free connection. The connection between metal shield 520 and chamber 510 may provide a continuous passage for vacuum feedthrough 530 to be placed in. In some embodiments, metal shield 520 may comprise an opening on one end to receive shielded high-voltage cable from high-voltage power source 550. The shielded high-voltage cable may include electrical wire 560 shielded by shield layer 570. The shielding (e.g., shield layer 570) of high-voltage cables may be made of a metal or a conductive alloy, among others. Some commonly used shielding materials include, but are not limited to, copper, tinned-copper, aluminum, or other suitable electrically conducting materials.

[0073] In some embodiments, shield layer 570 of high-voltage cable may extend through the entire length of electrical wire 560 from high-voltage power source 550 to plug 586 such that there are no exposed portions of electrical wire 560 connecting high-voltage power source 550 to vacuum feedthrough 530. In some embodiments, shield layer 570 may terminate at a region in channel 584 such that the exposed portion of electrical wire 560 is confined within a region in channel 584 associated with connector 580. In some embodiments, channel 584 may extend through metal shield 520, through region 522 between connector 580 and inner walls of metal shield 520, and through a portion of connector 580. In such a design, channel 584 may comprise a cavity having a receiving open end in metal shield 520 configured to receive shielded high-voltage cable and a second end formed within connector 580.

[0074] System 500 may further comprise vacuum feedthrough 530, which may be alternatively referred to herein as a feedthrough or a feedthrough connector. Vacuum feedthrough 530 may be attachable to connector 580 so that a charged-particle apparatus is provided with a high-voltage power supply. In some embodiments, vacuum feedthrough 530 may also be detachable from connector 580. In some embodiments, vacuum feedthrough 530 may be removably attached to connector 580.

[0075] Vacuum feedthrough 530 may comprise a feedthrough insulating structure 532, also referred to as a feedthrough insulator 532. In some embodiments, feedthrough insulating structure 532 may be a single solid body made of an electrically insulating material, such as alumina (AI2O3), a plastic, or a ceramic material, among others. An advantage of using AI2O3 is that it may be fixed, e.g., brazed, in a leak tight way to a flange on the housing of a charged-particle apparatus. A refractory or a ceramic material may be preferable over the use of a plastic that cannot be brazed. A plastic feedthrough insulating structure 532 may be glued to a charged particle apparatus but the glue could possibly fail over time. Plastics can also gas out when directly exposed to a vacuum (negative pressure with respect to atmosphere) and reduce the quality of the vacuum. Unlike AI2O3, plastics may also degrade, or melt, during a bake out process to improve the vacuum. It is to be appreciated that connector 580 may be detached from vacuum feedthrough 530 during such a bake-out process and so the use of PTFE for connector 580 may be acceptable. In addition, feedthrough insulating structure 532 and connector 580 may engage with each other. The engagement between a soft PTFE and a hard AI2O3 material may be more robust than an engagement between two hard materials that may be susceptible to damage or failure.

[0076] In addition to feedthrough insulating structure 532, vacuum feedthrough 530 may comprise a feedthrough pin 535 configured to mate with a plug 586 to provide electrical continuity between high- voltage power source 550 and vacuum feedthrough 530. In some embodiments, vacuum feedthrough 530 may comprise one or more feedthrough pins 535. Feedthrough pin 535 may be arranged within a feedthrough channel in feedthrough insulating structure 532. An end of feedthrough pin 535 may be arranged so that it is received in a press fit by a corresponding plug 586 disposed in channel 584 of connector 580. In some embodiments, feedthrough pin 535 may extend, i.e., protrude out of a corresponding feedthrough channel. An end of each feedthrough pin 535 may protrude from feedthrough insulating structure 532. The protrusion may enable feedthrough pin 535 to engage with the corresponding plug 586 without interference of volume conflict with feedthrough insulating structure 532. When engaged, one or more feedthrough pins 535 may form an electrical connection with respect to one or more wires 560 to provide a high-voltage power supply to a charged-particle apparatus or a component of a charged-particle apparatus. In some embodiments, feedthrough pin 535 may be made from an electrically conducting material such as, but not limited to, copper, stainless steel, or tungsten.

[0077] When connector 580 and vacuum feedthrough 530 are connected, there may be a tight fit or a substantially tight fit between feedthrough insulating structure 532 and connector 580. A substantially tight fit, as used herein, refers to having substantially no gaps or marginal gaps between feedthrough insulating structure 532 and connector 580. The proper engagement of connector 580 and vacuum feedthrough 530 may therefore exclude substantially all of the air from within the connection power interface.

[0078] When vacuum feedthrough 530 and connector 580 are detached from each other (as shown in Fig. 6, discussed later), the creep length requirement, which is that the creep length or the creep distance between an exposed electrically conductive surface of the power supply and another electrically conductive surface must be greater than the minimum creep length required to avoid an electrical breakdown, should still be met by connector 580. The creep length or creep distance, as used herein, refers to the shortest distance between two conductive elements along the surface of an insulating material. In other words, the creep distance or the creep length is the path electricity would take if it were to travel along the surface of the insulator instead of through the air. A longer creep distance indicates better insulation and resistance to electrical breakdown at high voltages. Another condition that should be satisfied is that electrical flashover should be prevented between an electrically conductive surface of connector 580 and any object that may be in the vicinity of the electrically conductive surface. For example, flashover should be prevented to a user’s hand, or other object, placed over the end of connector 580.

[0079] In previous designs of high-voltage power supply systems, mechanisms to monitor the electrical current passing through high-voltage cables face several challenges in detecting occurrence of an arcing event, in identifying the location of the occurrence of the arcing event, and resultantly, preventive measures or diagnostic methods are harder to design and implement. The placement of a current transformer to receive unattenuated (i.e., not influenced by other interferences) E / M field signals around an unshielded high-voltage cable as exists today would render the apparatus unsafe and prone to electrical failure. Some embodiments of the present disclosure provide a new design of power interface for a charged-particle apparatus including a high-voltage cable connector and a removably attachable vacuum feedthrough.

[0080] The connector 580 has a metal outer housing or a metal shield 520. Enclosed within metal shield 520 is a connector 580, also referred to herein as a connector insulating structure 580. In some embodiments, connector insulating structure 580 may be a single solid body made from an electrically insulating material, such as Polytetrafluoroethylene (PTFE), natural rubber, synthetic rubber, or polyetheretherketone (PEEK), among other materials. Connector insulating structure 580 may comprise a first portion (e.g., base 582) and a second portion (e.g., elongated tubular structure 583) extending from the first portion. In some embodiments, tubular structure 583 may be a cylindrical hollow structure, a conical hollow structure, or a combination thereof. In some embodiments, theouter form of tubular structure 583 may have any form, shape, cross-section, or size, so long as the inner cavity forming channel 588 of tubular structure 583 can accommodate vacuum feedthrough 530. In some embodiments, tubular structure 583 may be hollow to the extent that it comprises a channel 588 for receiving vacuum feedthrough 530 and feedthrough pin 535. Channel 588 of tubular structure 583 may be linear, cylindrical, tapered, or any cross-section suitable to accommodate the corresponding structure of vacuum feedthrough 530. Channel 588 of tubular structure 583 may comprise an open end (e.g., open end 687 of Fig. 6, discussed later), for receiving the assembly of vacuum feedthrough 530 and feedthrough pin 535, and a closed end (e.g., closed end 689 of Fig. 6, discussed later) that is recessed within connector 580 to receive feedthrough pin 535. The outer form of connector 580 comprises a first cylindrical portion (e.g., tubular structure 583) and a second conical portion (e.g., base 582). As illustrated in Fig. 5 and further clarified in Fig. 6, channel 588 may extend into base 582 of connector 580 such that the length of channel 588 is substantially equal to the sum of the length of the first cylindrical portion and the second conical portion of connector 580.

[0081] In some embodiments, although not explicitly illustrated in Fig. 5, connector 580 may include a connector flange. The connector flange may be used to secure connector 580 to an outer wall of a charged-particle apparatus, such as by use of a bolt. The securing of the connector flange to the outer wall may be sealed. The connector flange may have an end surface that may substantially consist of an end surface of connector 580. The part of the charged-particle apparatus that the connector flange of connector 580 is secured to may be part of a housing of vacuum feedthrough 530, such as a corresponding feedthrough flange (not shown).

[0082] In some embodiments, connector 580 may comprise one or more connector wire assemblies, which may be referred to as, and optionally take the form of, connector pins or plugs. In some embodiments, a connector wire assembly may comprise electrical wire 560 shielded with shield layer 570 and plug 586 arranged on the end of electrical wire 560. In some embodiments, plug 586 may be at the closed end of a channel 584, and thereby recessed into connector insulating structure 580. As illustrated in Fig. 5 (and in Fig. 6), channels 584 and 588 may be on opposite ends of connector 580. Channel 584 may be configured to receive high-voltage power supply cable from high-voltage power source 550. Channel 588, as previously discussed, may be configured to receive vacuum feedthrough 530, and may be referred to herein as a vacuum feedthrough channel.

[0083] It is to be appreciated that although channels 584 and 588 are shown as having a width (i.e., diameter of a cylinder) and a length, the dimensions are not limited as such. If channel 588 is a uniform cylinder, the diameter of the cylinder may be larger than the diameter of vacuum feedthrough 530 so long as vacuum feedthrough 530 may be accommodated or inserted within channel 588. Channel 584 may comprise a uniform cylindrical hollow structure, a conical hollow structure, a tapered hollow structure, a rectangular hollow structure, or other suitable structure configured toaccommodate electrical wire 560, or to accommodate shielded electrical wire. In some embodiments, shield layer 570 may terminate at a location before entering channel 584 such that an unshielded portion of the cable (e.g., naked electrical wire 560) may be exposed in region 522 between outer surface of connector 580 and inner walls of metal shield 520. In some embodiments, high-voltage supply cable may be shielded through its entire length such that substantially no portion of the high- voltage cable is exposed.

[0084] The unshielded portion of a high-voltage cable, also referred to herein as electrical wire 560, may be connected to a high-voltage power supply, such as high-voltage power source 550. In some embodiments, a high-voltage cable, as used herein, may include a shielded portion (e.g., portion of the cable wrapped in shield layer 570) and an unshielded portion (e.g., a naked wire or a portion of the cable without shield layer 570, not shown). Electrical wire 560 may, for example, be a commercially available electrical wire with its outer jacket and braiding (e.g., shield layer 570) stripped back.

[0085] In some embodiments, current transformer 540 may be mounted on an external surface of connector 580. In some embodiments, current transformer 540 may be mounted on an external surface of connector insulating structure 580. Current transformer 540 may comprise a high-frequency current transformer (HFCT) embedded in external surface of connector 580 and encircling an unshielded portion of high-voltage cable extending through vacuum feedthrough 530. A current transformer, as used herein, refers to a device configured to transform a primary electrical current signal in terms of its magnitude and phase to a secondary electrical current signal such that in normal conditions the secondary value is substantially proportional to the primary value. A high-frequency current transformer refers to a device configured to transform a primary high-frequency current signal to a secondary current signal proportional to the primary signal.

[0086] In some embodiments, current transformer 540 may be mounted on connector 580 such that there is no signal interference (e.g., from metal shielding) between the high-voltage cable and current transformer 540. In some embodiments, current transformer 540 may comprise a ring-like structure circumferentially placed around the external surface of connector 580. Current transformer 540 may be disposed in region 522 between the inner wall of metal shield 520 and the external surface of connector 580.

[0087] System 500 may further comprise data acquisition apparatus 590, which may be configured to process the signal received from current transformer 540 and display the processed signal. In some embodiments, data acquisition apparatus 590 may be configured to monitor the signal received from current transformer 540 to detect a partial discharge or an arcing event based on the received signal. Data acquisition apparatus 590 may include circuitry configured to receive the signal (e.g., voltage or current signal) generated by current transformer 540. In some embodiments, data acquisition apparatus 590 and current transformer 540 may be connected (e.g., wired or wirelessly) to enable communication with each other such that the output signal of current transformer 540 may be receivedas an input signal by data acquisition apparatus 590. As illustrated in Fig. 5, current transformer 540 and data acquisition apparatus 590 may be connected through a wired electrical connection 545.

[0088] Data acquisition apparatus 590 may comprise circuitry further configured to process the signal received from current transformer 540. Processing the signal received from current transformer 540 may include analyzing, optimizing, correcting, converting, extracting relevant information from, or displaying the received signal or signals. As an example, data acquisition apparatus 590 may comprise an oscilloscope configured to receive signals from current transformer 540 and display the received electrical signals. An oscilloscope (analog or digital) may display the waveform of an electrical signal, enabling monitoring the frequency, amplitude, and shape of the signal waveforms, for example.

[0089] Although not explicitly shown, system 500 may include multiple data acquisition apparatuses configured to receive signals from corresponding current transformers. Alternatively, system 500 may include a single data acquisition apparatus configured to receive and display signals from multiple current transformers associated with multiple high-voltage modules. From a data analysis and signal monitoring perspective, it may be desirable to display electrical signals from different current transformers within a system (e.g., SEM including multiple current transformers) in a single display unit to allow the user to analyze and extract information.

[0090] Reference is now made to Fig. 6, which illustrates an exemplary power interface 600 in an unengaged arrangement, consistent with embodiments of the present disclosure. Power interface 600 illustrates a connector 680 (analogous to connector 580 of Fig. 5) and a vacuum feedthrough 630 (analogous to vacuum feedthrough 530 of Fig. 5). Connector 680, analogous to connector 580, may comprise a first portion (e.g., base 682) and a second portion (e.g., elongated tubular structure 683) extending from the first portion. Base 682 may be conical portion (as shown in Fig. 6), or cylindrical, or any other suitable shape.

[0091] Connector 680 of power interface 600 may comprise a channel 684 configured to receive high-voltage cable 660 from a high-voltage power source (not shown). In some embodiments, although not shown, high-voltage cable 660 may comprise a shielded portion and an unshielded portion. The shielded portion may include a shield (braided, foiled, etc.) around the cable to minimize leakage currents and to prevent electromagnetic and radio frequency interference, among other things. High-voltage cable 660 may include a plug 686 on one end of the cable, analogous to and performing similar functions as plug 586 of Fig. 5.

[0092] Connector 680 may include a second channel 688, also referred to as vacuum feedthrough channel 688, configured to receive and accommodate vacuum feedthrough 630. Channel 688 may comprise an open end 687 for receiving the assembly of vacuum feedthrough 630 and feedthrough pin 635. Open end 687 of channel 688 may allow insertion of vacuum feedthrough 630 (indicated by arrows pointing towards connector 680) so that vacuum feedthrough 630 may be engaged with plug686 to form an electrical connection with a high-voltage power source. In some embodiments, the width of open end 687 may be substantially similar or slightly larger than the diameter of vacuum feedthrough 630 to receive vacuum feedthrough 630.

[0093] In some embodiments, feedthrough pin 635 may be coupled to vacuum feedthrough 630 such that feedthrough pin 635 forms an integral part of vacuum feedthrough 630. In some embodiments, feedthrough pin 635 may be removably attached to or coupled with vacuum feedthrough 630. Feedthrough pin 635 may be partially or entirely made of an electrically conducting material such as a metal or an alloy.

[0094] Vacuum feedthrough 630 may include a flange 636 configured to be secured to a chamber flange (e.g., flange 512 of Fig. 5) such that power interface 600 may be associated with or directly connected to a charged-particle apparatus. Vacuum feedthrough 630 may further include an unshielded cable 634 extending through. In some embodiments, unshielded cable 634 may be built-in with the vacuum feedthrough during manufacturing of vacuum feedthrough 630. In some embodiments, unshielded cable 634 may be inserted after manufacturing and during assembly of vacuum feedthrough 630. Although unshielded cable 634 is shown in Fig. 6 as extending through feedthrough pin 635, it is appreciated that the configuration is not limited as such. For example, unshielded cable 634 may only extend partially through feedthrough pin 635.

[0095] Reference is now made to Fig. 7, which illustrates a data plot 700 comparing the electrical signal generated by a current transformer over a time period, consistent with embodiments of the present disclosure. Data plot 700 compares the voltage signals generated by a high-frequency current transformer placed around a shielded portion of the cable (as in previous designs, and denoted by a solid line) and by a high-frequency current transformer placed around an unshielded portion of the cable (denoted by dashed line), as proposed herein. A comparison of the data shown in data plot 700 reveals a faster response time, larger amplitude, and enhanced sensitivity for capturing high-frequency signal oscillations in an unshielded cable, caused due to changes in high-frequency current signal passing through a high-voltage cable. The shielding, as previously discussed, attenuates the signal intensity detectable by a high-frequency current transformer, and therefore, leads to inaccurate measurement of transient current through the cable. Placing a current transformer encircling an unshielded cable (e.g., current transformer 540 and 640 of Figs. 5 and 6, respectively) may allow detection of unattenuated current signal from the unshielded portion of cable, and thereby, enhancing the accuracy and reliability of detection of arcing events.

[0096] Reference is now made to Fig. 8, which illustrates a process flowchart 800 for an example method of monitoring current through a high-voltage cable, consistent with embodiments of the present disclosure.

[0097] At step 810, a feedthrough (e.g., vacuum feedthrough 532 of Fig. 5) associated with a vacuum chamber (e.g., vacuum chamber 510 of Fig. 5) may be placed in a channel (e.g., channel 588 or 688of Figs. 5 and 6, respectively) of a cable connector (e.g., connector 580 or connector 680 of Figs. 5 and 6, respectively). In some embodiments, the feedthrough may be inserted, slid, or pushed inside the channel. The channel may comprise a cavity formed by the inner walls of the cable connector. The channel may be configured to receive or accommodate the vacuum feedthrough. The vacuum feedthrough is removably coupled to the cable connector through a removable coupling mechanism such as, but not limited to, a plug, a male-female connector assembly, a plug and socket, among other mechanisms. In some embodiments, the vacuum feedthrough may include an unshielded cable (e.g., unshielded cable 634 of Fig. 6) extending through. The unshielded cable may be built-in during the manufacturing or assembly of the vacuum feedthrough.

[0098] The cable connector may include a cable (e.g., cable 660 of Fig. 6) extending through a channel (e.g., channel 684 of Fig. 6) of the cable connector. In some embodiments, the cable in the channel may be built-in during the manufacture or assembly of the cable connector. When step 810 is performed, i.e., when the vacuum feedthrough is fully inserted into the channel 688 of the cable connector, the unshielded cable 634 inside the vacuum feedthrough and the cable 660 inside the channel 684 of the cable connector are electrically connected forming a continuous path for passing electricity from a high-voltage power source to the target component. The electrical connection between the unshielded cable 634 and the cable 660 may be facilitated using, but not limited to, a plug, a male-female connector assembly, inline splice connectors, crimp terminals, push connectors, etc.

[0099] At step 820, electrical current passing through the high-voltage cable is monitored using a signal measurement device (e.g., a current transformer 540 of Fig. 5) embedded in or attached to or coupled to an external surface of the cable connector. When the signal measurement device is embedded in the external surface of the cable connector it may be embedded such that it is mostly below or flush with the external surface and does not protrude above the external surface, or it may be partially below and partially above the external surface. The signal measurement device encircles a portion of the unshielded portion of the high-voltage cable to measure unattenuated electrical signals generated by converting the electromagnetic field produced by passing current through the high- voltage cable into a measurable electrical signal. In some embodiments, the current transformer (or the high-frequency current transformer) may be connected to a signal monitoring device configured to receive and monitor, using a sensing circuit, the induced electrical signal. The signal monitoring device may include an oscilloscope, as an example. Monitoring the induced signal facilitates determination of occurrence of an electrical arcing event based on the monitored electrical signal.

[0100] The embodiments of the present disclosure may further be described using the following clauses:1. A current monitoring apparatus, comprising: a cable connector, comprising:a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.2. The apparatus of clause 1, wherein the channel comprises a cavity formed by inner walls of the cable connector.3. The apparatus of clause 2, wherein the cavity is substantially cylindrical or conical.4. The apparatus of any one of clauses 1-3, wherein the cable comprises a shielded portion outside the cable connector.5. The apparatus of any one of clauses 1-4, wherein the feedthrough is configured to be removably coupled to the connector.6. The apparatus of clause 5, wherein a removable coupling comprises a plug or a male-female connector assembly.7. The apparatus of any one of clauses 1-6, wherein the current flowing through the unshielded portion induces an electrical signal in the signal measurement device when the feedthrough is fully inserted in the channel such that an electrical connection is formed between a cable of the cable connector and the unshielded portion of the cable embedded in the feedthrough.8. The apparatus of clause 7, further comprising a signal monitoring device electrically connected to the signal measurement device and configured to monitor, via a sensing circuit, the induced electrical signal.9. The apparatus of clause 8, wherein the signal monitoring device facilitates determination of occurrence of an electrical arcing event based on the monitored electrical signal.10. The apparatus of any one of clauses 8 and 9, wherein the signal measurement device comprises a high-frequency current transformer, and wherein the signal monitoring device comprises an oscilloscope.11. The apparatus of any one of clauses 1-10, further comprising a housing configured to enclose at least a portion of the cable connector.12. The apparatus of clause 11, wherein the housing is further configured to enclose the unshielded portion of the cable and the signal measurement device.13. The apparatus of any one of clauses 11 and 12, wherein the housing comprises a metal shield.14. The apparatus of any one of clauses 11-13, wherein the housing is configured to be coupled to the vacuum chamber through a flange of the feedthrough.15. The apparatus of any one of clauses 1-14, wherein the external surface of the connector comprises an electrically insulating material.16. The apparatus of any one of clauses 1-15, wherein the cable connector is mounted on a vacuum chamber in a manner sufficiently airtight to support a vacuum in the vacuum chamber.17. An apparatus for monitoring transient current through a cable, comprising: a connector, comprising: a first channel configured to receive a vacuum feedthrough comprising a feedthrough pin and an unshielded cable extending through the vacuum feedthrough; a second channel extending in a same direction as the first channel and comprising a connector cable; a portion of the first channel configured to receive the feedthrough pin to form an electrical connection between the connector cable and the unshielded cable of the vacuum feedthrough; and a current transformer embedded in or coupled to an external surface of the connector and configured to encircle a portion of the unshielded cable of the vacuum feedthrough when the vacuum feedthrough is inserted into the first channel.18. The apparatus of clause 17, wherein the connector cable comprises a shielded portion outside the second channel and an unshielded portion inside the second channel.19. The apparatus of clause 18, wherein the connector cable is removably connected to the unshielded cable extending through the vacuum feedthrough.20. The apparatus of any one of clauses 17-19, wherein a first end of the connector cable is in electrical connection with a high-voltage power source and a second end of the connector cable is coupled with the vacuum feedthrough pin when the vacuum feedthrough is inserted into the first channel.21. The apparatus of any one of clauses 17-20, wherein a current flowing through the unshielded cable of the vacuum feedthrough induces an electrical signal in the current transformer when the feedthrough is fully inserted in the first channel such that an electrical connection is formed between the cable of the cable connector and the unshielded cable of the feedthrough.22. The apparatus of clause 21, further comprising a signal sensor electrically connected to the current transformer and configured to receive, via a sensing circuit, the induced electrical signal.23. The apparatus of clause 22, wherein the signal sensor facilitates determination of occurrence of an electrical arcing event based on the received electrical signal.24. The apparatus of any one of clauses 22 and 23, further comprising a signal monitoring device associated with the signal sensor and configured to monitor the electrical signal.25. The apparatus of any one of clauses 17-24, wherein at least the external surface of the connector comprises an electrical insulator.26. The apparatus of any one of clauses 17-25, wherein the current transformer comprises a ringlike structure.27. The apparatus of any one of clauses 17-26, wherein the current transformer comprises a high- frequency current transformer.28. The apparatus of any one of clauses 17-27, further comprising a housing configured to enclose the connector.29. The apparatus of any one of clauses 17-28, wherein the cable connector is mounted on a vacuum chamber in a manner sufficiently airtight to support a vacuum in the vacuum chamber.30. The apparatus of clause 29, wherein the housing comprises a metal shield.31. A cable connector, comprising: a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.32. A cable connector, comprising: a first channel configured to receive a vacuum feedthrough comprising a feedthrough pin and an unshielded cable extending through the vacuum feedthrough; a second channel extending in the same direction as the first channel and comprising a connector cable; a plug electrically coupled with the connector cable and configured to receive the feedthrough pin to form an electrical connection between the connector cable and the unshielded cable of the vacuum feedthrough when the feedthrough is inserted in the first channel; and a current transformer circumferentially coupled to an external surface of the cable connector and configured to encircle a portion of the unshielded cable of the vacuum feedthrough when the vacuum feedthrough is inserted in the first channel.33. A method for monitoring current through a high-voltage cable coupled to a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber, the method comprising: monitoring current passing through the high-voltage cable using a signal measurement device embedded in or coupled to an external surface of the cable connector, wherein the signal measurement device is configured to encircle a portion of an unshielded portion of the high-voltage cable and a portion of the feedthrough placed in the channel.34. The method of clause 33, wherein the feedthrough is placed in the channel using a removable coupling mechanism.35. The method of clause 34, wherein the channel includes a feedthrough that has previously been inserted in the channel such that the high-voltage cable is electrically connected to an unshielded cable of the feedthrough.36. The method of clause 34, further comprising removing the feedthrough by use of the removable coupling mechanism to break the electrical connection between the high-voltage cable and the unshielded cable of the feedthrough.37. The method of clause 34, further comprising inducing an electrical signal in the signal measurement device by passing electrical current through the high-voltage cable.38. The method of clause 37, further comprising electrically connecting a signal monitoring device to the signal measurement device, the signal monitoring device configured to monitor, via a sensing circuit, the induced electrical signal.39. The method of clause 38, wherein the signal monitoring device facilitates determination of occurrence of an electrical arcing event based on the monitored electrical signal.40. The method of any one of clauses 38 and 39, wherein the signal measurement device comprises a high-frequency current transformer, and wherein the signal monitoring device comprises an oscilloscope.

[0101] It will be appreciated that the embodiments of the present disclosure are not limited to the exact construction that has been 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 connection with various embodiments, other embodiments of the 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 exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims

CLAIMS1. A current monitoring apparatus, comprising: a cable connector, comprising: a channel configured to receive a feedthrough associated with a vacuum chamber; and a signal measurement device configured to measure a current passing through an unshielded portion of a cable embedded in the feedthrough when the feedthrough is inserted in the channel, wherein the signal measurement device is embedded in or coupled to an external surface of the cable connector and is configured to encircle a portion of the unshielded portion of the cable when the feedthrough is inserted in the channel of the cable connector.

2. The apparatus of claim 1, wherein the channel comprises a cavity formed by inner walls of the cable connector.

3. The apparatus of claim 2, wherein the cavity is substantially cylindrical or conical.

4. The apparatus of claim 1, wherein the cable comprises a shielded portion outside the cable connector.

5. The apparatus of claim 1, wherein the feedthrough is configured to be removably coupled to the connector.

6. The apparatus of claim 5, wherein a removable coupling comprises a plug or a male-female connector assembly.

7. The apparatus of claim 1, wherein the current flowing through the unshielded portion induces an electrical signal in the signal measurement device when the feedthrough is fully inserted in the channel such that an electrical connection is formed between a cable of the cable connector and the unshielded portion of the cable embedded in the feedthrough.

8. The apparatus of claim 7, further comprising a signal monitoring device electrically connected to the signal measurement device and configured to monitor, via a sensing circuit, the induced electrical signal.

9. The apparatus of claim 8, wherein the signal monitoring device facilitates determination of occurrence of an electrical arcing event based on the monitored electrical signal.

10. The apparatus of claim 8, wherein the signal measurement device comprises a high-frequency current transformer, and wherein the signal monitoring device comprises an oscilloscope.

11. The apparatus of claim 1, further comprising a housing configured to enclose at least a portion of the cable connector.

12. The apparatus of claim 11, wherein the housing is further configured to enclose the unshielded portion of the cable and the signal measurement device.

13. The apparatus of claim 1, wherein the cable connector is mounted on the vacuum chamber in a manner sufficiently airtight to support a vacuum in the vacuum chamber.

14. An apparatus for monitoring transient current through a cable, comprising: a connector, comprising: a first channel configured to receive a vacuum feedthrough comprising a feedthrough pin and an unshielded cable extending through the vacuum feedthrough; a second channel extending in a same direction as the first channel and comprising a connector cable; a portion of the first channel configured to receive the feedthrough pin to form an electrical connection between the connector cable and the unshielded cable of the vacuum feedthrough; and a current transformer embedded in or coupled to an external surface of the connector and configured to encircle a portion of the unshielded cable of the vacuum feedthrough when the vacuum feedthrough is inserted into the first channel.

15. A method for monitoring current through a high-voltage cable coupled to a cable connector comprising a channel configured to receive a feedthrough associated with a vacuum chamber, the method comprising: monitoring current passing through the high-voltage cable using a signal measurement device embedded in or coupled to an external surface of the cable connector, wherein the signal measurement device is configured to encircle a portion of an unshielded portion of the high-voltage cable and a portion of the feedthrough placed in the channel.

Images