The embodiments of the present disclosure relate to a flood column comprising a down-beam lens arrangement, as well as a charged particle apparatus comprising the flood column.
When manufacturing semiconductor integrated circuit (IC) chips, undesired pattern defects, as a consequence of, for example, optical effects and incidental particles, inevitably occur on a substrate (i.e. wafer) or a mask during the fabrication processes, thereby reducing the yield. Monitoring the extent of the undesired pattern defects is therefore an important process in the manufacture of IC chips. More generally, the inspection and/or measurement of a surface of a substrate, or other object/material, is an import process during and/or after its manufacture.
Pattern inspection tools with a charged particle beam have been used to inspect objects, for example to detect pattern defects. (Note: the term tool, such as inspection, measurement, or assessment tool, is intended to be interpreted as an apparatus, system, or device). These tools typically use electron microscopy techniques, such as a scanning electron microscope (SEM). In a SEM, a primary electron beam of electrons at a relatively high energy is targeted with a final deceleration step in order to land on a sample at a relatively low landing energy. The beam of electrons is focused as a probing spot on the sample. The interactions between the material structure at the probing spot and the landing electrons from the beam of electrons cause electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons. The generated secondary electrons may be emitted from the material structure of the sample. By scanning the primary electron beam as the probing spot over the sample surface, secondary electrons can be emitted across the surface of the sample. By collecting these emitted secondary electrons from the sample surface, a pattern inspection tool may obtain an image representing characteristics of the material structure of the surface of the sample.
Dedicated flood columns may be used in conjunction with an SEM to flood a large area of the surface of a substrate or other sample with charged particles for example in a beam (i.e. as a current) towards the sample, in a relatively short time. Flood columns are thus useful tools to pre-charge a wafer surface and set the charging conditions for subsequent inspection with an SEM. A dedicated flood column can enhance the voltage contrast defect signal, thereby increasing the defect detection sensitivity and/or throughput of an SEM. During charged particle flooding, the flood column is used to provide a relatively large amount of charged particles to quickly charge a predefined area. Afterwards, the primary electron source of an e-beam inspection system is applied to scan an area within the pre-charged area to achieve imaging of the area.
Embodiments of the invention are directed towards the relative positioning of an aperture body and a lens arrangement that is down-beam of the aperture body. The aperture body and lens arrangement of embodiments may be for use in a flood column.
According to some embodiments of the present disclosure, there is provided a flood column for projecting a charged particle flooding beam along a beam path towards a sample to flood the sample with charged particles prior to assessment of the flooded sample using an assessment column, the flood column comprising: a flood column housing; an anchor body arranged along the beam path; a lens arrangement arranged in a down beam part of the flood column; and a lens support arranged between the anchor body and the lens arrangement; wherein the lens support is configured to position the lens arrangement and the anchor body relative to each other and to extend between the flood column housing and the lens arrangement; the lens support comprises an electrical insulator; and the lens support is in the direct line of sight of at least a portion of the beam path in the down beam part.
According to some embodiments of the present disclosure, there is provided a charged particle assessment tool comprising: a stage configured to support a sample; a charged particle system for assessing the sample, wherein the charged particle system is configured to project a charged particle beam towards the sample and to detect charged particles emanating from the sample; and a flood column configured to project a charged particle flooding beam towards the sample so as to flood the sample, the beam path of the primary charged particle beam is spaced apart from the beam path of the charged particle beam of the flood column.
Advantages of the present invention 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 embodiments of the present invention.
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, in which:
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.
The enhanced computing power of electronic devices, which reduces the physical size of the devices, can 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 increased resolution enabling yet smaller structures to be made. For example, an IC chip of a smart phone, which is the size of a thumbnail and available in, or earlier than, 2019, may include over 2 billion transistors, the size of each transistor being less than 1/1000th 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” can 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 can indicate the number of layers 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 would be as low as 7%.
While high process yield is desirable 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 can be impacted by the presence of a defect. This is especially 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 (SEW)) is essential for maintaining high yield and low cost.
A SEM comprises a scanning device and a detector apparatus. The scanning device comprises an illumination system that comprises an electron source, for generating primary electrons, and a projection system 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 secondary electrons. A detection system captures the secondary electrons from the sample as the sample is scanned so that the SEM can 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 can scan different parts of a sample simultaneously. A multi-beam inspection apparatus can therefore inspect a sample at a much higher speed than a single-beam inspection apparatus.
The figures are schematic. Relative dimensions of components in drawings are therefore 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 are 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.
Reference is now made to
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.
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 particles in main chamber 10 so that the pressure in 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 and/or inspection.
Controller 50 is electronically connected to charged particle 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
Reference is now made to
The components for example of the primary column, that are used to generate a primary beam may be aligned with a primary electron-optical axis of the charged particle inspection tool 200. These components can include: the electron source 201, gun aperture plate 271, condenser lens 210, source conversion unit 220, beam separator 233, deflection scanning unit 232, and primary projection apparatus 230. The components of the primary column, or indeed the primary column, generate a primary beam, which may be a multibeam, towards a sample for inspection of the sample. Secondary projection system 250 and its associated electron detection device 240 may be aligned with a secondary electron-optical axis 251 of the charged particle inspection tool 200.
The primary electron-optical axis 204 is comprised by the electron-optical axis of the part of the charged particle inspection tool 200 that is the illumination system. The secondary electron-optical axis 251 is the electron-optical axis of the part of the charged particle inspection tool 200 that is a detection system (or detection column). The primary electron-optical axis 204 may also be referred to herein as the primary optical axis (to aid ease of reference) or charged particle optical axis. The secondary electron-optical axis 251 may also be referred to herein as the secondary optical axis or the secondary charged particle optical axis.
Electron source 201 may comprise a cathode (not shown) and an extractor or anode (not shown). During operation, electron source 201 is configured to emit electrons as primary electrons from the cathode. The primary electrons are extracted and accelerated by the extractor and/or the anode to form a primary electron beam 202 that forms a primary beam crossover (virtual or real) 203. Primary electron beam 202 may be visualized as being emitted from primary beam crossover 203. In an arrangement the electron source 201 may operate at a high voltage and/or high energy, for example more than 20 keV preferably more than 30 keV, 40 keV or 50 keV. The electrons from the electron source have a high landing energy for example relative to a sample 208 for example on the sample holder 207.
In this arrangement a primary electron beam, by the time it reaches the sample, and preferably before it reaches the projection system, is a multi-beam. Such a multi-beam can be generated from the primary electron beam in a number of different ways. For example, the multi-beam may be generated by a multi-beam array located before the cross-over, a multi-beam array located in the source conversion unit 220, or a multi-beam array located at any point in between these locations. A multi-beam array may comprise a plurality of electron beam manipulating elements arranged in an array across the beam path. Each manipulating element may influence the primary electron beam to generate a sub-beam. Thus the multi-beam array interacts with an incident primary beam path to generate a multi-beam path down-beam of the multi-beam array.
Gun aperture plate 271, in operation, is configured to block off peripheral electrons 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 sub-beams 211, 212, 213, and therefore deteriorate inspection resolution. A gun aperture plate 271 may also be referred to as a Coulomb aperture array.
Condenser lens 210 is configured to focus primary electron beam 202. Condenser lens 210 may be designed to focus primary electron beam 202 to become a parallel beam and be normally incident onto source conversion unit 220. Condenser lens 210 may be a movable condenser lens that may be configured so that the position of its first principle plane is movable. The movable condenser lens may be configured to be magnetic. Condenser lens 210 may be an anti-rotation condenser lens and/or it may be movable. The condenser lens 210 may comprise a plurality of static lenses that may be operated so that the position of its lens principle plane is moveable.
Source conversion unit 220 may comprise an image-forming element array, an aberration compensator array, a beam-limit aperture array, and a pre-bending micro-deflector array. The pre-bending micro-deflector array may deflect a plurality of primary sub-beams 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 this arrangement, the image-forming element array may function as a multi-beam array to generate the plurality of sub-beams in the multi-beam path, i.e. primary sub-beams 211, 212, 213. The image forming array may comprise a plurality electron beam manipulators such as micro-deflectors micro-lenses (or a combination of both) to influence the plurality of primary sub-beams 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 sub-beams 211, 212, and 213. 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 sub-beams 211, 212, and 213. The astigmatism compensator array may comprise a plurality of micro-stigmators, or multi-pole electrodes, to compensate astigmatism aberrations of the primary sub-beams 211, 212, and 213. The beam-limit aperture array may be configured to limit diameters of individual primary sub-beams 211, 212, and 213.
Condenser lens 210 may further be configured to adjust electric currents of primary sub-beams 211, 212, 213 down-beam of source conversion unit 220 by varying the focusing power of condenser lens 210. Alternatively, or additionally, the electric currents of the primary sub-beams 211, 212, 213 may be changed by altering the radial sizes of beam-limit apertures within the beam-limit aperture array corresponding to the individual primary sub-beams. The electric currents may be changed by both altering the radial sizes of beam-limit apertures and the focusing power of condenser lens 210. If the condenser lens is moveable and magnetic, off-axis sub-beams 212 and 213 may result that illuminate 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 movable condenser lens. A condenser lens 210 that is an anti-rotation condenser lens may be configured to keep the rotation angles unchanged while the focusing power of condenser lens 210 is changed. Such a condenser lens 210 that is also movable, may cause the rotation angles not change when the focusing power of the condenser lens 210 and the position of its first principal plane are varied.
Objective lens 231 may be configured to focus sub-beams 211, 212, and 213 onto a sample 208 for inspection and may form three probe spots 221, 222, and 223 on the surface of sample 208.
Beam separator 233 may be, for example, a Wien filter comprising an electrostatic deflector generating an electrostatic dipole field and a magnetic dipole field (not shown in
Deflection scanning unit 232, in operation, is configured to deflect primary sub-beams 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 sub-beams 211, 212, and 213 or probe spots 221, 222, and 223 on sample 208, electrons are generated from the sample 208 which include secondary electrons and backscattered electrons. The secondary electrons propagate in three secondary electron beams 261, 262, and 263. The secondary electron beams 261, 262, and 263 typically have secondary electrons (having electron energy ≤50 eV) and may also have at least some of the backscattered electrons (having electron energy between 50 eV and the landing energy of primary sub-beams 211, 212, and 213). The beam separator 233 is arranged to deflect the path of the secondary electron beams 261, 262, and 263 towards the secondary projection system 250. The secondary projection system 250 subsequently focuses the path of secondary electron beams 261, 262, and 263 onto a plurality of detection regions 241, 242, and 243 of electron detection device 240. The detection regions may be the separate detection elements 241, 242, and 243 that are arranged to detect corresponding secondary electron beams 261, 262, and 263. The detection regions generate corresponding signals which are sent to controller 50 or a signal processing system (not shown), e.g. to construct images of the corresponding scanned areas of sample 208.
The detection elements 241, 242, and 243 may detect the corresponding secondary electron beams 261, 262, and 263. On incidence of secondary electron beams with the detection elements 241, 242 and 243, the elements may generate corresponding intensity signal outputs (not shown). The outputs may be directed to an image processing system (e.g., controller 50). 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.
The controller 50 may comprise image processing system that includes an image acquirer (not shown) and a storage device (not shown). For example, the controller may comprise a processor, computer, server, mainframe host, terminals, personal computer, any kind of mobile computing devices, and the like, or a combination thereof. The image acquirer may comprise at least part of the processing function of the controller. Thus the image acquirer may comprise at least one or more processors. The image acquirer may be communicatively coupled to an electron detection device 240 of the apparatus 40 permitting signal communication, such as an electrical conductor, optical fiber cable, portable storage media, IR, Bluetooth, internet, wireless network, wireless radio, among others, or a combination thereof. The image acquirer may receive a signal from electron detection device 240, may process the data comprised in the signal and may construct an image therefrom. The image acquirer may thus acquire images of sample 208. The image acquirer may also perform various post-processing functions, such as generating contours, superimposing indicators on an acquired image, and the like. The image acquirer may be configured to perform adjustments of brightness and contrast, etc. of acquired images. The storage 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. The storage may be coupled with the image acquirer and may be used for saving scanned raw image data as original images, and post-processed images.
The image acquirer may acquire one or more images of a sample based on an imaging signal received from the 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 period. The multiple images may be stored in the storage. The controller 50 may be configured to perform image processing steps with the multiple images of the same location of sample 208.
The controller 50 may include measurement circuitry (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, can be used in combination with corresponding scan path data of each of primary sub-beams 211, 212, and 213 incident on the sample surface, to reconstruct images of the sample structures under inspection. The reconstructed images can be used to reveal various features of the internal or external structures of sample 208. The reconstructed images can thereby be used to reveal any defects that may exist in the sample.
The controller 50 may control motorized stage 209 to move sample 208 during inspection of sample 208. The controller 50 may enable motorized stage 209 to move sample 208 in a direction, preferably continuously, for example at a constant speed, at least during sample inspection. The controller 50 may control movement of the motorized stage 209 so that it changes the speed of the movement of the sample 208 dependent on various parameters. For example, the controller may control the stage speed (including its direction) depending on the characteristics of the inspection steps of scanning process.
Although
As shown in
The flood column 300 may comprise at least a charged particle source 301 which may be in a generator system, a condenser lens 320, a blanker electrode 330, an objective lens 340 and an aperture body 350. The flood column 300 may also comprise additional components for manipulation of the charged particle beam 302 such as a scanning element (not shown) and a field lens (not shown). The components of the flood column 300 may be arranged substantially along an axis 304. The axis 304 may be the electro-optical axis of the flood column 300. The components of the flood column 300 may be controlled by the controller 50. Alternatively, a dedicated controller may be used to control the components of the flood column 300, or the components of the flood column 300 may be controlled by multiple respective controllers. The flood column 300 may be mechanically coupled to the charged particle inspection apparatus 200. That is the flood column is connected, even coupled, to the primary column of the charged particle inspection apparatus 200. Preferably the flood column is connected to the primary column at an interface 350 between the flood column 300 and the primary column.
The charged particle source 301 may be an electron source. The charged particle source 301 may comprise a charged particle emitting electrode (e.g. a cathode) and an accelerating electrode (e.g. an anode). The charged particles are extracted and accelerated from the charged particle emitting electrode by the accelerating electrode to form a charged particle beam 302. The charged particle beam 302 may propagate along a beam path 302. The beam path 302 may comprise the axis 304, for example in situations in which the charged particle beam 302 is not deflected away from the axis 304. In an arrangement the electron source 301 operates at a high voltage, for example more than 20 keV preferably more than 30 keV, 40 keV or 50 keV. The electrons from the electron source 301 may have a high landing energy for example relative to a sample 208 for example on the sample holder 207. However, embodiments also include implementations in which the electrons do not have a high landing energy. For example, the electrons emitted from the source may be accelerated to a high beam energy of 30 keV. The electrons may then be decelerated to an energy in the range 0.3 keV to 3 keV before hitting the sample 208. Preferably the electron source 301 of the flood column operates at the same, or at least substantially the same operating voltage as the electron source 201 of primary column. Electrons from the electron source 301 of the flood column 300 desirably have the same, or at least a substantially similar landing energy to electrons emitted by the electron source 201 of the inspection tool 200.
Having the sources 201, 301 of both flood column and the primary column at substantially the same operating voltage is desirable. This is because the sample 208, and thus preferably the substrate support and desirably the moveable stage 209 are set at the same operating voltage for inspection and/or measurement and flooding. That is they may be biased to the source of the primary column during inspection and the source of the flood column during flooding. The relative potential between the primary source and the stage is high. Flood columns, such as those that are commercially available, have an operating voltage substantially less than the high voltage of the inspection tool 200. Such a stage cannot be maintained at high voltage during flooding, since the stages are biased relative to an operating source, whether of the flood column or the primary column. The biasing of the stage should therefore change to suit the source next to operate. For a commercially available flood column, the source can be set to a potential to near ground potential.
The stage may be moved between a flooding position and an inspection/measurement position (e.g. assessment position). It takes time to move the moveable stage 209 between a flooding position when the sample is in the beam path of the flood column, and an inspection position when the sample is in the beam path of the primary column. Yet the time taken to adjust the stage potential between inspection and flooding settings for a typical commercial flood column and high voltage inspection tool, may take longer than the movement between the flooding and inspection positions. The change in voltage can take as long as minutes. Therefore, there is a significant throughput improvement in having a flood column having at least a similar operating voltage to the primary column; this is even for an inspection or measurement tool with a separate flood column having its own flooding position apart from an inspection position. Another or alternative benefit is that in reducing the time between flooding and inspection and/or measurement, the flooding effect remains and the risk of it disappearing before inspection/measurement is reduced if not prevented. The path of the primary charged particle beam may be spaced apart from the path of the charged particle beam of the flood column. Desirably any influence of the charged particle beam of the flood column may be reduced or even prevented.
The condenser lens 320 is positioned down-beam of the charged particle source 301, i.e. the condenser lens 320 is positioned in a down-beam direction relative to the charged particle source 301. The condenser lens 320 may focus or defocus the charged particle beam 302. As shown in
The aperture body 350 may be positioned down-beam of the condenser lens 320. The aperture body 350 may pass a portion, or only a portion and not all, of a charged particle beam propagating along an axis 304. The aperture body 350 may limit the lateral extent of the charged particle beam 302, as depicted in
The blanking electrode 330 may be positioned down-beam of the condenser lens 320 and up-beam of the aperture body 350. The blanking electrode 330 may selectively deflect the charged particle beam 302, for example deflect the charged particle beam 302 away from the axis 304. The blanking electrode 330 may deflect the charged particle beam 302 away from the opening in the aperture body 350, for example onto a portion of the aperture body 350 that does not comprise the opening, so as to prevent any portion of the charged particle beam 302 from passing through the opening defined by the aperture body 350. The blanking electrode 330 may blank the beam so that beam does not pass through the opening of the aperture body 350. However, the combination of the blanking electrode 330 and the aperture body 350 may also be used to selectively blank the charged particle beam 302, i.e. to selectively prevent passage of at least part the charged particle beam 302 through the opening in the aperture body 350. That is, the combination of the blanking electrode 330 and the aperture body 350 may selectively control the proportion of the charged particle beam 302 that passes the opening.
The objective lens 340 is positioned down-beam of the aperture body 350. The objective lens 340 may focus or defocus the charged particle beam 302. As shown in
The flood column 300 may selectively be operated in different modes of operation, such as in a high-density mode (as schematically depicted in
The high-density mode is for charged particle flooding of a relatively small area of the sample 208. In the high-density mode, the lateral extent (or diameter) of the charged particle beam 302 incident at the sample 208, also referred to as the lateral extent (or diameter) of the beam spot herein, is relatively small. The lateral extent (or diameter) of the beam spot in the high-density mode is relatively small, in particular compared to the lateral extent (or diameter) of the beam spot in the low-density mode. As such, the charge density of the beam spot in the high-density mode is relatively high, in particular compared to the charge density of the beam spot in the low-density mode. In the high-density mode, the lateral extent (or diameter) of the beam spot may be in the range from 0 to 1000 μm, preferably between 5 μm and 500 μm. However, the spot size is dependent on the application. The typical application requirements are in the range of 25 μm to 500 μm, which is the preferred operational range. The beam spot can then be selected from the operation range during operation dependent on the application. An upper limit of the operation range is selected because above 500 μm the required current density is difficult to achieve. With available optics a lower limit to the range can be higher than 5 μm, for example 10 μm, 25 μm or 50 μm.
The low-density mode is for charged particle flooding of a relatively large area of the sample 208. In the low-density mode, the lateral extent (or diameter) of the beam spot is relatively large, in particular compared to the lateral extent (or diameter) of the beam spot in the high-density mode. As such, the charge density of the beam spot in the low-density mode is relatively low, in particular compared to the charge density of the beam spot in the high-density mode. In the low-density mode, the lateral extent (or diameter) of the beam spot may be greater than 500 μm, preferably greater than 1 mm, further preferably greater than 3 mm, particularly preferably greater than 5 mm, for example about 8 mm. The lateral extent (or diameter) of the beam spot in the low-density mode may be in the range from 500 μm to 50 mm, preferably from 1 mm to 20 mm, further preferably from 3 mm to 15 mm, particularly preferably from 5 mm to 12 mm.
As shown in
As shown in
For example,
Alternatively or additionally, for example in the low-density mode, the source lens 310 may also be controllable so as to set, or fixedly set, the beam angle α (or the amount of focus/defocus) of the charged particle beam 302 down-beam of the source lens 310. This is shown, for example, in
As shown in
Alternatively or additionally, as shown in
The aperture body 350 is preferably arranged down-beam of the condenser lens 320. The aperture body 350 may be arranged up-beam of the condenser lens and down-beam of the source lens 310. Having the aperture body 350 down beam of the condenser lens may be preferred because in that arrangement greater control of the beam and its beam spot may be achieved. The aperture body 350 is for passing at least a portion of the charged particle beam 302. The aperture body 350 may limit the lateral extent of the charged particle beam 302, for example in both the high-density mode of
Optionally, the blanking electrode 330 is arranged up-beam of the aperture body 350. The blanking electrode 330 may be arranged down-beam of the condenser lens 320. The blanking electrode 330 may deflect the charged particle beam 302 away from the axis 304 so as to prevent any portion of the charged particle beam 302 from passing the aperture body 350, for example towards sample 208.
The objective lens 340 is arranged down-beam of the aperture body 350. The objective lens 340 is controllable so as to adjust the focus of the charged particle beam 302. Using the objective lens 340 to adjust the focus of the charged particle beam 302 adjusts the lateral extent (or diameter) of the beam spot formed by the incidence of the charged particle beam 302 on the sample 208.
As shown in
Alternatively or additionally, for example in the low-density mode, the objective lens 340 may be controllable to manipulate the charged particle beam 302 such that the lateral extent (or diameter) of the beam spot is larger than the lateral extent (or diameter) of the charged particle beam 302 at the objective lens 340. This is shown, for example, in
The cross-over point C3 may be located such that the ratio d′/d of i) the distance d′, along the axis 304, between the cross-over point C3 and the surface of the sample 208 and ii) the distance d, along the axis 304, between the center of the objective lens 340 and the cross over-point C3, is greater than 1, preferably greater than 1.2, further preferably greater than 1.5, particularly preferably greater than 2. The ratio d′/d may be in the range from 1 to 10, preferably from 1.2 to 6, further preferably from 1.5 to 4, particularly preferably from 2 to 3. In other words, the magnification of the charged particle beam 302 by the objective lens 340 (from the objective lens 340 to the surface of the sample 208) may be in the range from 1 to 10, preferably from 1.2 to 6, further preferably from 1.5 to 4, particularly preferably from 2 to 3.
Optionally, the flood column 300 may comprise the scanning electrodes 360, for example a pair of scanning electrodes 360 (which may be referred to as a scanning deflector 360 or scanning element 360). The scanning electrodes 360 may be arranged or positioned down-beam of the aperture body 350. The scanning electrodes 360 may be arranged or positioned up-beam of the objective lens 340, as shown in
The scanning electrodes 360, preferably a pair of scanning electrodes 360 (i.e. a scanning deflector), may be controllable so as to scan the charged particle beam 302 across the sample 208, for example in the high-density mode. The scanning electrodes 360 may be controllable to variably deflect the charged particle beam 302, for example in one dimension (from top to bottom in
Alternatively or additionally, for example in the low-density mode, the scanning electrodes 360 may be controllable so as not to manipulate the charged particle beam 302. The scanning electrodes 360 may be controllable so as to retain or preserve the beam path of the charged particle beam 302, so as not to deflect the charged particle beam 302. The scanning electrodes 360 may be controllable in this manner, for example, in the low-density mode of operation of the flood column 300. In situations in which the beam spot on the sample 208 is relatively large (such as in the low-density mode of
There may be provided the flood column 300 for charged particle flooding of the sample 208. The flood column 300 comprises a charged particle source 301 configured to emit a charged particle beam 302 along a beam path. The flood column 300 further comprises the source lens 301 arranged down-beam of the charged particle source 301. The flood column 300 further comprises the condenser lens 320 arranged down-beam of the source lens 301. The flood column 300 further comprises the aperture body 350 arranged down-beam of the source lens 310, preferably down-beam of the condenser lens 320. The aperture body 350 is for passing a portion of the charged particle beam 302. The flood column 300 further comprises the controller 50. The controller 50 selectively operates the flood column 300 in a high-density mode for charged particle flooding of a relatively small area of the sample 208, and a low-density mode for charged particle flooding of a relatively large area of the sample 208. The source lens 301 may be controllable so as to focus the charged particle beam 302 to the cross-over point C1 up-beam of the condenser lens 320 and to variably set the position of the cross-over point C1 along a beam path.
There may be provided a method for charged particle flooding of the sample 208 using the flood column 300. The method comprises emitting the charged particle beam 302 along the beam path using the charged particle source 301. The method further comprises variably setting the beam angle α of the emitted charged particle beam 302 using the source lens 310 arranged down-beam of the charged particle source 301. The method further comprises adjusting the beam angle of the charged particle beam 302 using the condenser lens 320 arranged down-beam of the source lens 310. The method further comprises passing a portion of the charged particle beam 302 using the aperture body 350 arranged down-beam of the condenser lens 320.
There may be provided a method for charged particle flooding of the sample 208 using the flood column 300. The method comprises emitting the charged particle beam 302 along the beam path using the charged particle source 301. The method further comprises adjusting the beam angle α of the charged particle beam 302 using the condenser lens 320 arranged down-beam of the charged particle source 301. The method further comprises passing a portion of the charged particle beam 302 using the aperture body 350 arranged down-beam of the condenser lens 320. The method further comprises selectively operating the flood column 300 in a high-density mode for charged particle flooding of a relatively small area of the sample 208, and a low-density mode for charged particle flooding of a relatively large area of the sample 208.
There may be provided a method for charged particle flooding of the sample 208 using the flood column 300. The method comprises emitting the charged particle beam 302 along the beam path using the charged particle source 301. The method further comprises adjusting the beam angle α of the charged particle beam 302 using the condenser lens 320 arranged down-beam of the charged particle source 301. The method further comprises passing a portion of the charged particle beam 302 using the aperture body 350 arranged down-beam of the condenser lens 320. The method further comprises focusing the charged particle beam 302 to a cross-over point C3 up-beam of the sample 208 using the objective lens 340, such that the lateral extent of the charged particle beam 302 at the sample 208 is larger than lateral extent of the charged particle beam 302 at the objective lens 240.
As described earlier, the flood column 300 may comprise an objective lens 340 down-beam of the aperture body 350. The flood column 300 may also comprise additional components for manipulation of the charged particle beam 302 such as scanning elements 360 or scanning deflector 360 and a field lens 370 as described in reference to
The scanning deflector 501 may be arranged in the beam path 304 between the aperture body 350 and the ground plane 503. The scanning deflector 501 may be arranged to change and control the path of the flooding beam. The scanning deflector 501 may comprise electrodes for that generate electric fields for deflecting the flooding beam, according to known techniques. The scanning deflector 501 may be the same as the earlier described scanning electrodes 360 with reference to
The ground plane 503 is in the beam path between the aperture body 350 and the objective lens 504. The ground plane 503 may be an annular metallic disc with a central aperture so that the flooding beam may pass through it. The ground plane 503 may be at a local ground potential, which may be 0 V. The effect of the ground plane 503 may be to substantially shield the region down-beam from the ground plane 503 from the electric fields generated by the scanning deflector 501. If no ground plane 503 is used, the electric fields generated by the scanning deflector 501 may extend to the region between the scanning deflector 501 and the objective lens 504. This may result in the electric field in this region being rotationally asymmetric (i.e. not symmetric). A consequence of this may be that, during a flooding operation, the flooding beam spot on the sample 208 is rotationally asymmetric. This deformation of the flooding beam spot may degrade flooding beam spot. This deformation may degrade the flooding process and/or the performance of the flooding by the flooding beam spot. In particular, the asymmetry may reduce the uniformity of the current density in the beam.
In some embodiments, the ground plane 503 and scanning deflector 501 may effectively be parts of the same component for manipulating the flooding beam. That is to say, the ground plane 503 may effectively be the down-beam surface of the deflector. The presence of the ground plane 503 may therefore complement the operation of the scanning deflector 501.
As shown in
In order to provide shielding, the housing 506 walls may comprise an alloy with a high permeability. The housing 506 walls may comprise a mu-metal. The housing 506 walls may be configured to have a suitable thickness for shielding the beam. The housing 506 walls may comprise a mu metal alloy, or alternatively an alloy with a lower permeability than mu-metal but which provides sufficient shielding. Such an alloy may be less expensive than mu-metal. The thickness of the housing 506 walls may be larger than if mu-metal is used so that effective shielding is still provided. In some embodiments, the shielding may be achieved by a shielding wall within and apart from the chamber wall. However in view of limited volume such an arrangement may be impractical if not impossible. Having the chamber wall serve as a shield is therefore beneficial.
The objective lens 504 may be configured to contribute to the deceleration of the flooding beam. In the direction of the beam path 304, the objective lens 504 may have a high aspect ratio. The objective lens 504 may be an electrostatic lens, i.e. an E-field lens. The electrodes of the objective lens 504 may comprise monolithic titanium. In having a high aspect ratio, the objective lens 504 may extend along the beam path 304. The objective lens 504 thus beneficially provide electrostatic shielding to the part of the beam path 304 along which it extends. It should be noted that references to electrostatic lenses throughout the present document may more generally refer to structures which contribute to an electrostatic lensing function. The lensing function may arise due to an electrical field generated between two or more lens bodies, thus comprising by one or more lenses operated at the operating potentials thereof. This is described in more detail later.
The final lens arrangement 505 may be adjacent to the sample 208. The final lens arrangement 505 may be an electrostatic lens, i.e. an E-field lens. The electrodes of the final lens arrangement 505 may comprise monolithic titanium.
The objective lens 504 and final lens arrangement 505 may respectively be the earlier described objective lens 340 and field lens. In the direction of beam path 304, the objective lens 504 may be up-beam of the final lens arrangement 505. The objective lens 504 may be separated from the final lens arrangement 505.
The objective lens 504 and final lens arrangement 505 may together be referred to as a lens arrangement 504, 505. The lens arrangement 504, 505 is held in position by one or more lens supports 502, 507 that extend down-beam from an anchor body of the lens arrangement 504, 505. The anchor body may be an element, or arrangement of elements, which directly support or hold the lens supports 502, 507. The only function of the anchor body may be to hold the lens supports 502, 507. Alternatively, the anchor body may have other functions in addition to holding the lens supports 502, 507. The anchor body may therefore be comprised within the housing 506. The anchor body may be or comprise any component that the housing 506 comprises, such as the aperture body 350 and the ground plane 503. In particular, the one or more lens supports 502, 507 may extend down-beam from the aperture body 350 or ground plane 503, which may be part of the housing 506. The lens arrangement 504, 505 is therefore suspended from the housing 506 by the one or more lens supports 502, 507 for example connected via the anchor body. That is the anchor body may connect the lens supports 502, 507 to the housing 506. Each lens support 502, 507 may comprise a first part 502 that extends from the housing 506 to the objective lens 504. Each lens support 502, 507 may also comprise a second part 507 that extends from the objective lens 504 to the final lens arrangement 505. The first part 502 of each lens support may define the separation between the objective lens 504 and the housing 506. The second part 507 of each lens support may define the separation between the final lens arrangement 505 and the objective lens 504. The one or more lens supports 502, 507 are therefore configured to position the objective lens 504 and the final lens arrangement 505 relative to each other and the housing 506.
The one or more lens supports 502, 507 are required to hold the lens arrangement 504, 505 in its position along the beam path 304. Each lens support 502, 507 according to embodiments extends along the beam path 304 from the housing 506. The use of one or more lens supports 502, 507 according to embodiments may be preferable over other techniques for supporting the lens arrangement 504, 505. In particular, as described earlier, volume restrictions within the flood column may prevent the housing 506 from extending down-beam from the ground plane 503. That is to say, if the housing 506 extends down-beam from the ground plane 503 to the lens arrangement 504, 505, the volume occupied by the housing 506 may force substantial design and/or performance compromises on other components in the apparatus. Volume and positioning restrictions, as well as movement requirements, may also prevent other types of support structures of the lens arrangement 504, 505, such as a support structure that is orthogonal to the beam path 304.
The one or more lens supports 502, 507 according to embodiments may be configured so that their interference on the operation of the flood column is minimal. Different parts of each lens support 502, 507 may be in contact with the ground plane 503, objective lens 504 and the final lens arrangement 505. There may be large potential differences between each of the ground plane 503, objective lens 504 and the final lens arrangement 505. In order for the same lens support 502, 507 to be in contact with components at different operating voltages, each lens support 502, 507 according to embodiments may be an electrical insulator. The operation at different voltages of the ground plane 503, objective lens 504 and the final lens arrangement 505 will therefore be substantially unaffected by the physical contact with each lens support 502, 507.
The properties of the flooding beam, such as its power, flooding spot size and positioning of the spot of the flooding beam on the sample are important. The accuracy with which the properties of the flooding beam may be controlled are also important. A problem with each lens support 502, 507 being an electrical insulator is that, over time, electric charges may build-up on the surface of the lens support 502, 507. Electric fields from charge build-up on a surface near the flooding beam path 304 may potentially have an effect on the flooding beam path 304. This may adversely affect the operation of the flooding beam, such as the ability to achieve different parameters and/or settings of the flooding beam for performance specifications. Embodiments therefore include techniques for allowing a flooding beam to be controlled with sufficient accuracy, for example to achieve standards of flooding of the sample. In particular, each lens support 502, 507 according to some embodiments, may be configured so that any charge build-up on its surface may have little, or substantially no, effect on the flooding beam path 304. For example, each lens support 502, 507 according to embodiments may be a relatively narrow elongate structure. This reduces the amount of lens support 502, 507 surface, that may be charged, in the vicinity of the flooding beam path 304.
As shown in at least
Each lens support 502, 507 and the lens arrangement 504, 505 may be geometrically shaped and positioned with respect to the flooding beam path 304 and each other such that, in use, any charging of a surface of a lens support 502, 507 has no substantial influence on the flooding beam, in terms of path, focus and/or aberrations.
Embodiments include the use of a single lens support 502, 507. However, embodiments preferably use a plurality of lens supports 502, 507 because this may provide a more secure attachment of the lens arrangement 504, 505 to the housing 506. The number of lens supports 502, 507 may two, three or more.
As shown in
Accordingly, embodiments include a number of different arrangements of lens support 502, 507. In particular, embodiments include there being two lens supports 502, 507 arranged on opposing sides of the beam path 304. Alternatively, embodiments include there being three or more lens supports 502, 507 arranged around the beam path 304. The three or more lens supports 502, 507 may be arranged angularly equidistant around the beam path 304. In embodiments with a plurality of lens supports 502, 507, the lens supports 502, 507 may be substantially equidistantly radially positioned from the beam path 304. The rotationally symmetric arrangement of lens supports 502, 507 may reduce the extent that the symmetry of the flooding beam is affected by the charging of the lens supports 502, 507. Each lens support 502, 507 may have a radial surface portion most proximate to the beam path 304 and the radial surface portions of the lens supports 502, 507 may be substantially equidistantly radially positioned from the beam path 304. In embodiments with a plurality of lens supports 502, 507, the cross-sections of the lens supports 502, 507 may be similar. Accordingly, each lens support 502, 507 may have substantially the same dimensions, i.e. diameter, width and/or length.
Embodiments include a number of different configurations of the down-beam components from the aperture body 350. For example, the separation along the beam path 304 between the ground plane 503 and the most up-beam part of the objective lens 504 may be in the range 2 mm to 30 mm, and preferably 6 mm to 12 mm. The separation along the beam path 304 between the ground plane 503 and the most down-beam part of the objective lens 504 may be in the range 20 mm to 50 mm, and preferably 30 mm to 40 mm. The separation along the beam path 304 between the ground plane 503 and the most up-beam part of the final lens arrangement 505 may be in the range 30 mm to 60 mm, and preferably 25 mm to 50 mm. The separation along the beam path 304 between the objective lens 504 and the final lens arrangement 505 may be in the range 1 mm to 10 mm, and preferably 2 mm to 8 mm
When the flood column is in use, the potential difference between the ground plane 503 and objective lens 504 may be in the range 20 kV to 50 kV, and preferably 25 kV to 30 kV. The potential difference between the objective lens 504 and final lens arrangement 505 may be in the range 0 V to and preferably 3 kV to 6 kV. The potential difference between the final lens arrangement 505 and the sample 208 is in the range −5 kV to 10 kV, and preferably −2 kV to 5 kV.
The inventors found that having a flood column with down-beam components having components and a design using these numerical ranges provides a flood column with advantageous performance. Some of the performance characteristics are as herein described.
Embodiments include a number of modifications and variations to the above-described techniques.
In particular, the aperture body 350 may be any aperture body 350 that is configured to blank and/or shape the flooding beam. Accordingly, the aperture body 350 may have a different design from the aperture body 350 that is shown in
The use of the ground plane 503 as one down-beam components of the aperture body 350 is optional. Accordingly, embodiments include there being no ground plane 503. In such embodiments, the down-beam end of the housing 506 may be at the aperture body 350 or the scanning deflector 501.
Throughout the present document lenses are referred to. These may be references to the lens structures, such as electrodes, and/or the lensing effect caused by the fields generated by the lens structures. In particular, a voltage supply may be electrically connected to a component so as to supply a potential or potential difference to the component which may be different from a component adjacent in the beam path 304. For example, a lens may have a potential applied to it by a voltage supplier. The applied potential may be applied as a potential difference between a surface of the lens and the beam path 304. The surface of the lens may be generally orthogonal to the beam path 304. The potential applied to the surface of the lens, for example, may operate between the surface of the lens and a surface of an adjacent component in the beam path 304 that may be generally orthogonal to the beam path 304. The adjacent component is electrically connected, and it may be connected to a voltage supply which applies a potential to the adjacent component such that a potential is applied to the surface of the adjacent component. A controller may be connected to the voltage supplies of the lens and the adjacent component to control their operation and thus control of the beam along the beam path 304.
Embodiments may include a flood column for projecting a charged particle flooding beam along a beam path 304 towards a sample 208 to flood the sample 208 with charged particles prior to assessment of the flood sample 208 using an assessment column. The flood column comprises: an aperture body 350, an electro-magnetic shield, a lens arrangement 504, 505 and a lens support 502, 507. The aperture body is arranged in the beam path 304 and is configured to blank and/or shape the charged particle flooding beam. The electro-magnetic shield is configured to shield at least part of the beam path 304. The lens arrangement 504, 505 is arranged in the beam path 304 down-beam of the aperture body 350. The lens support 502, 507 is arranged between the aperture body 350 and the lens arrangement 504, 505 and configured to support the lens arrangement 504, 505 relative to the aperture body 350. The lens support 502, 507 may comprise an insulator. The shield may comprise an end, the shielding extending along the beam path 304 up to the end, the end positioned between the aperture body 350 and at least part of the lens arrangement 504, 505. The end of the shield may be up-beam of the lens arrangement 504, 505, preferably the end is down-beam of the aperture body 350, and preferably the end is no further down-beam than a down-beam surface of the aperture. The shield may be comprised in a chamber wall of the flood column, preferably the chamber wall comprises mu-metal or an alloy capable of electromagnetic shielding.
Embodiments may further include a charged particle assessment system e.g. a tool, comprising: a stage, a charged particle system, and a flood column. The stage is configured to support a sample 208. The charged particle system for assessing the sample 208; the charged particle assessment system is configured to project a charged particle beam towards a sample 208 and to detect charged particles emanating from the sample 208. The flood column according to the embodiments is configured to project a charged particle flooding beam towards the sample 208 so as to flood the sample 208. The flood column may be configured to project a charged particle flooding beam to the sample 208 to flood the sample 208 prior to assessment of the flood sample 208 by the charged particle system.
The primary column of the charged particle assessment tool may be as described and shown with respect to
Embodiments further include a flood column for projecting a charged particle flooding beam along a path towards a sample 208, the flood column comprising: an aperture body 350, a final lens arrangement 505, and an insulating support. The aperture body 350 is for blanking and shaping the charged particle flooding beam. The final lens arrangement 505 is adjacent the sample 208. The insulating support is between the aperture body 350 and a surface of the final lens arrangement 505, the surface facing the sample 208. The support and lens arrangement 504, 505 are geometrically shaped and positioned with respect to the beam path 304 and each other such that charging of a surface of the support has minimal influence on the flooding beam, in terms of e.g. path, focus and aberrations.
The flood column of embodiments may comprise: a charged particle source, a source lens, a condenser lens, and a controller. The charged particle source is configured to emit a charged particle beam along the beam path. The source lens is arranged down-beam of the charged particle source. The condenser lens is arranged down-beam of the source lens, wherein the aperture body is down beam of the condenser lens and is configured to pass a portion of the charged particle beam. The controller is configured to selectively operate the flood column in a high-density mode for charged particle flooding of a relatively small area of the sample, and a low-density mode for charged particle flooding of a relatively large area of the sample.
Embodiments are particularly appropriate for operation with a high energy flooding beam in which there may be substantial power dissipation in the aperture body 350. Embodiments include the electron source 301 of the flood column operating at a high voltage, for example more than 20 keV preferably more than 30 keV, 40 keV or 50 keV. The electrons from the electron source 301 have a high landing energy for example relative to a sample 208 for example on the sample holder 207. Preferably the electron source 301 of the flood column operates at the same, or at least substantially the same operating voltage as the electron source 201 of the primary column. Electrons from the electron source 301 of the flood column 300 desirably have the same, or at least a substantially similar landing energy to electrons emitted by the electron source 201 of the inspection tool 200. Having the sources 201, 301 of both flood column and the primary column at substantially the same operating voltage is desirable. This is because the sample 208, and thus preferably the substrate support and desirably the moveable stage 209 are set at the same operating voltage for inspection and/or measurement and flooding. That is they may be biased to the source of the primary column during inspection and the source of the flood column during flooding. The relative potential between the primary source the stage is set at high voltage. Flood columns, such as those that are commercially available, have an operating voltage substantially less than the high voltage of the inspection tool 200. Such a stage cannot be maintained at high voltage during flooding, since the stages are biased relative to an operating source, whether of the flood column or the primary column. The biasing of the stage should therefore change to suit the source next to operate. For a commercially available flood column, the source can be set to a potential to near ground potential.
The stage may be moved between a flooding position and an inspection/measurement position. It takes time to move the moveable stage 209 between a flooding position when the sample 208 is in the beam path 304 of the flood column, and an inspection position when the sample 208 is in the beam path 304 of the primary column. Yet the time taken to adjust the stage potential between inspection and flooding settings for a typical commercial flood column and high voltage inspection tool, may take longer than the movement between the flooding and inspection positions. The change in voltage can take as long as minutes. Therefore, there is a significant throughput improvement in having a flood column having at least a similar operating voltage to the primary column; this is even for an inspection or measurement tool with a separate flood column having its own flooding position apart from an inspection position. Another benefit is that in reducing the time between flooding and inspection and/or measurement, the flooding effect remains and the risk of it disappearing before inspection/measurement is reduced if not prevented. The path of the primary charged particle beam may be spaced apart from the path of the charged particle beam of the flood column. Desirably any influence of the charged particle beam of the flood column may be reduced or even prevented.
An assessment tool according to some embodiments may be a tool that makes a qualitative assessment of a sample 208 (e.g. pass/fail), one which makes a measurement such as a quantitative measurement (e.g. the size of a feature) of a sample 208 or one which generates an image of map of a sample 208. Examples of assessment tools are inspection tools (e.g. for identifying defects), review tools (e.g. for classifying defects) and metrology tools.
Reference of the charged particle beam 302 up-beam or down-beam of an element includes directly up-beam or directly down-beam of that element. Reference to a first element being up-beam and down-beam of a second element may mean directly up-beam or directly down-beam, but may also, where appropriate, include embodiments in which other elements are provided between the first element and the second element.
Reference to a component being controllable to manipulate the charged particle beam 302 in a certain manner includes the controller 50 controlling the component so as to manipulate the component in this manner, as well as other controllers or devices (e.g. voltage supplies) controlling the component so as to so as to manipulate the component in this manner. For example, a controller may be electrically connected to a component, a selection of the components or all the electrostatic components of the flood column. A voltage supply may be electrically connected to a component so as to supply a potential or potential difference to the component which may be different from a component adjacent in the beam path 304. For example, a lens may have a potential applied to it by a voltage supplier. The applied potential may be applied between a surface of the lens and the beam path 304. The surface of the lens may be generally orthogonal to the beam path 304. The potential applied to the surface of the lens, for example, may operate between the surface of the lens and a surface of an adjacent component in the beam path 304 that may be generally orthogonal to the beam path 304. The adjacent component is electrically connected, and it may be connected to a voltage supply which applies a potential to the adjacent component such that a potential is applied to the surface of the adjacent component. The controller may be connected to the voltage supplies of the lens and the adjacent component to control their operation and thus control of the beam along the beam path 304. Note the components of the flood column include a deflector such as a scanning deflector 501. Such a deflector may have electrodes which may be arranged around the beam path 304. The electrodes each are electrically connected. The electrodes of the deflector may be independently controlled or controlled together. The deflector electrodes may be independently connected to a voltage supply or to a common voltage supply.
Reference to a cross-over point includes a real cross-over point that is achieved by focusing the charged particle beam 302 to the cross-over point (such as the cross-over points C1, C2 and C3 in
All references to beam angles in this specification are the maximum angular displacement across the beam cross-section. An alternative definition of beam angle could be the maximum angular displacement of the beam relative to the electron-optical axis, shown in dotted lines in
Embodiments Include the Following Numbered Clauses.
An alternative, or additional, Clause 1 is: A flood column for projecting a charged particle flooding beam along a beam path towards a sample to flood the sample with charged particles prior to assessment of the flooded sample using an assessment column, the flood column comprising: an aperture body arranged in the beam path and configured to blank and/or shape the charged particle flooding beam; an electro-magnetic shield configured to shield at least part of the beam path; a lens arrangement arranged in the beam path down-beam of the aperture body; and a lens support arranged between the aperture body and the lens arrangement and configured to support the position of the lens arrangement relative to the aperture body; wherein the lens support comprises an electrical insulator; and the shield comprises a down-beam end, that is positioned between the aperture body and at least part of the lens arrangement, and the shield is configured to extend along the beam path up to the down-beam end.
While the present invention has been described in connection with various embodiments, other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the technology 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. Reference to inspection throughout this specification is intended also to refer to measurement, e.g., metrological applications.
The descriptions above are intended to be illustrative, not limiting. Thus, it will be apparent to one skilled in the art that modifications may be made as described without departing from the scope of the claims set out below.
Number | Date | Country | Kind |
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21163522.2 | Mar 2021 | EP | regional |
This application claims priority of International application PCT/EP2022/053966, filed on 17 Feb. 2022, which claims priority of EP application 21163522.2, filed on 18 Mar. 2021, all of which are incorporated herein by reference in their entireties.
Number | Date | Country | |
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Parent | PCT/EP2022/053966 | Feb 2022 | US |
Child | 18369619 | US |