Charged particle optics

Abstract

An electro-optical projection device for projecting multiple charged particle beams toward a sample, the device comprising a stack of plates including beam guide elements configured to project multiple charged particle beams toward a sample position on the sample, wherein at least one plate of the stack has a planar optical member configured to direct a stimulating light toward the sample position, aligning the stimulating light with the multiple charged particle beams, and preferably aligning it with the paths of the multiple charged particle beams toward the sample position, and preferably, multiple apertures for each path of the multiple electro-optical beams are defined within at least one plate including the optical member.

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims the priority of European Patent Application Publication No. 22204243.4 filed on October 27, 2022 and European Patent Application Publication No. 23158846.8 filed on February 27, 2023, and the entire contents of both applications are incorporated herein by reference.

[0002]

[0002] Embodiments provided herein generally relate to charged particle optical devices and methods for evaluating samples.

Background Art

[0003]

[0003] When manufacturing semiconductor integrated circuit (IC) chips, for example, unwanted pattern defects caused by optical effects or accompanying particles inevitably occur on the substrate (i.e., wafer) or mask during the manufacturing process, thereby reducing the yield. Therefore, monitoring the degree of unwanted pattern defects is an important process in the manufacture of IC chips. More generally, inspection and / or measurement of the surface of a substrate, or other object / material, is an important process during and / or after its manufacture.

[0004]

[0004] Pattern inspection tools using charged particle beams have been used to inspect objects, for example, to detect pattern defects. These tools typically use electron microscopy techniques such as scanning electron microscopes (SEMs). In an SEM, a primary electron beam of relatively high-energy electrons is directed to a target in the final deceleration phase so that it is incident on the sample with relatively low incident energy. The electron beam is focused onto the sample as a probe spot. Interaction between the material structure of the probe spot and the incident electrons from the electron beam causes electrons to be emitted from the surface, which are, for example, secondary electrons, backscattered electrons, or Auger electrons, and may also be called signal particles. The generated secondary electrons may be emitted from the material structure of the sample. By scanning the sample surface as a probe spot with the primary electron beam, secondary electrons can be made to be emitted across the entire sample surface. By collecting these emitted secondary electrons from the sample surface, the pattern inspection tool can obtain an image that represents the characteristics of the material structure of the sample surface. The intensity of the electron beam, including backscattered and secondary electrons, may vary based on the characteristics of the internal and external structure of the sample, thereby indicating whether the sample has defects.

[0005]

[0005] When scanning a sample with a primary electron beam, the high beam current can cause charge to accumulate on the sample, which can affect the image quality. Material structures can be illuminated with light and / or flooded with electrons to improve defect contrast during defect inspection. For example, to adjust the accumulated charge on a sample, an Advanced Charge Controller (ACC) module can be used to irradiate the sample with a light beam, such as a laser beam, and control the accumulated charge by effects such as photoconductivity, photoelectricity, or thermal effects. In the following description, the term ACC is used as an abbreviation for illumination with a light beam. The term ACC should generally be understood to refer to illumination with a light beam. Irradiating a sample with a light beam can be difficult. For example, the dimensions of a pattern inspection tool may make it difficult to get the light beam to reach the sample. [Overview of the Initiative]

[0006]

[0006] The object of this disclosure is to provide embodiments that enable the evaluation and simultaneous illumination of the sample with light to provide improved defect contrast.

[0007]

[0007] According to a first aspect of the present invention, a plate for an electro-optical device configured to project a plurality of charged particle beams toward a sample is provided, the device comprising the plate within a plate lamination, Within the plate, multiple apertures are defined for each path of multiple charged particle beams. The plate includes a planar optical element configured to direct stimulating light towards the sample and align the stimulating light with the paths of multiple charged particle beams heading toward the sample.

[0008]

[0008] According to a second aspect of the present invention, a stimulation module is provided for use in an electro-optical projection device for projecting a plurality of charged particle beams toward a sample, the module being The planar optical member includes a planar optical member configured to direct a stimulating light toward a sample and to align the stimulating light with multiple charged particle beams, wherein multiple apertures are defined within the plate for each path of the multiple charged particle beams, and preferably the planar optical member consists of a plate from, for example, a stack of plates arranged along the paths of the multiple charged particle beams toward the sample.

[0009]

[0009] According to a third aspect of the present invention, an electro-optical projection device is provided for projecting a plurality of charged particle beams toward a sample, the device being It includes a stack of plates containing beam guidance elements configured to project multiple charged particle beams toward a specific sample location on the sample, At least one plate of the laminate includes a planar optical member configured to direct a stimulating light toward its sample position, aligning the stimulating light with a plurality of charged particle beams, preferably with the paths of the plurality of charged particle beams toward its sample position, wherein a plurality of apertures are defined for each path of the plurality of charged particle beams, preferably in the at least one plate including the optical member.

[0010]

[0010] According to a fourth aspect of the present invention, an evaluation charged particle optical apparatus or a preparation charged particle optical apparatus is provided, which preferably includes the above-mentioned device, in which case a planar optical element is arranged in the beam upstream direction of the device.

[0011]

[0011] According to a fifth aspect of the present invention, an evaluation method using the above-described device is provided.

[0012]

[0012] The above and other aspects of the present disclosure will become more apparent from reading the description of the exemplary embodiments in conjunction with the accompanying drawings. [Brief explanation of the drawing]

[0013] [Figure 1]

[0013] This is a schematic diagram showing an exemplary electron beam inspection apparatus. [Figure 2]

[0014] It is a schematic diagram showing an exemplary multi-beam electron optical device which is a part of the exemplary electron beam inspection device of FIG. 1. [Figure 3]

[0015] It is a schematic diagram of an exemplary multi-beam electron optical device. [Figure 4]

[0016] It is a schematic diagram of an exemplary electron optical device including a macro collimator and a macro scan deflector. [Figure 5]

[0017] It is a schematic diagram of an exemplary multi-beam electron optical device according to an embodiment. [Figure 6]

[0018] It is a schematic diagram of a part of the multi-beam electron optical device of FIG. 5. [Figure 7]

[0019] It is a schematic cross-sectional view of an objective lens array of an electron optical device according to an embodiment. [Figure 8]

[0020] It is a bottom view of a modified type of the objective lens array of FIG. 7. [Figure 9]

[0021] It is an enlarged schematic cross-sectional view of a detector incorporated in the objective lens array of FIG. 7. [Figure 10]

[0022] It is a bottom view of a detection element of the detector. [Figure 11]

[0023] It is a schematic diagram of an electron optical device for evaluating a sample. [Figure 12]

[0024] It is a schematic cross-sectional view of a planar optical member incorporated in an electron optical device. [Figure 13]

[0025] It is a schematic cross-sectional view of another planar optical member incorporated in an electron optical device. [Figure 14]

[0026] It is a schematic cross-sectional view of another planar optical member incorporated in an electron optical device. [Figure 15]

[0027] It is an enlarged cross-sectional view of the configuration of FIG. 13. [Figure 16]

[0028] This is a schematic plan view of an optical system configuration featuring waveguides incorporated into an electro-optical device. [Figure 17]

[0029] This is a schematic plan view of an optical system configuration featuring optical fibers incorporated into an electro-optical device. [Figure 18]

[0030] This is an enlarged cross-sectional view of the configuration shown in Figure 17. [Figure 19]

[0031] This is a schematic cross-sectional view of an electro-optical device featuring an optical fiber outside the electro-optical column. [Figure 20]

[0032] This is a schematic plan view of the configuration shown in Figure 19. [Modes for carrying out the invention]

[0014]

[0033] The schematic and general diagrams show the components described below. However, the components shown in the diagrams are not to scale.

[0015]

[0034] Hereafter, exemplary embodiments will be referenced in detail, examples of which are shown in the accompanying drawings. The following description relates to the accompanying drawings, where, unless otherwise noted, the same numbers in different drawings represent the same or similar elements. The implementations described below in the exemplary embodiments do not represent all implementations that are consistent with the present invention. Rather, these are merely examples of apparatus and methods that are consistent with the aspects of the present invention enumerated in the accompanying claims.

[0016]

[0035] The improvement in the computing power of electronic devices, which in turn reduces the physical size of the devices, can be achieved by significantly increasing the density of circuit components such as transistors, capacitors, and diodes on an IC chip. This is made possible by higher resolution, which allows for the fabrication of even smaller structures. For example, a smartphone IC chip, which is thumbnail-sized and became available before 2019, can contain over 2 billion transistors, each transistor being less than 1 / 1000th the size of a human hair. Therefore, it is not surprising that the manufacturing of semiconductor ICs is a complex and time-consuming process involving hundreds of individual steps. Even a single error in one step can dramatically affect the functionality of the final product. A single "killer defect" can cause a device to fail. The goal of the manufacturing process is to improve the overall yield. For example, to achieve a 75% yield in a 50-step process (where one step can indicate the number of layers formed on a wafer), the yield in each individual step must be higher than 99.4%. Even if the yield of each individual process is 95%, the overall yield of the process will likely be a low 7%.

[0017]

[0036] While high process yield is desirable in IC chip manufacturing facilities, maintaining high substrate (i.e., wafer) throughput, defined as the number of substrates processed per hour, is also crucial. High process yield and high substrate throughput can be affected by the presence of defects. This is especially true when operator intervention is required for defect inspection. Therefore, to maintain high yield and low costs, high-performance detection and identification of microscale to nanoscale defects using inspection tools (such as scanning electron microscopes ("SEMs")) is essential.

[0018]

[0037] A SEM includes a scanning device and a detector. The scanning device includes an illumination device, which includes an electron source for generating primary electrons and a projection device for scanning a sample, such as a substrate, with one or more focused beams of primary electrons. At least the illumination device or illumination system and the projection device or projection system together may be called an electron-optical system or apparatus. Primary electrons interact with the sample and generate secondary electrons. The detector captures secondary electrons from the sample while it is being scanned, thereby allowing the SEM to create an image of the scanned area of ​​the sample. For high-performance inspection, some inspection devices use multiple focused beams of primary electrons, i.e., multibeams. The component beams of a multibeam may be called subbeams or beamlets. A multibeam can scan different parts of a sample simultaneously. Therefore, a multibeam inspection device can inspect a sample much faster than a single-beam inspection device.

[0019]

[0038] The following describes known implementation configurations of multibeam inspection systems.

[0020]

[0039] The figures are schematic. Therefore, the relative dimensions of the components in the figures are exaggerated for clarity. In the following description relating to the drawings, identical or similar reference numerals refer to identical or similar components or entities, describing only the differences relating to individual embodiments. While the description and drawings relate to electron optics, it should be understood that the embodiments are not used to limit this disclosure to specific charged particles. Therefore, references to electrons throughout this specification may be considered more broadly as references to charged particles, where charged particles are not necessarily electrons. For example, references to electron-optical devices may be considered more broadly as references to charged particle devices.

[0021]

[0040] Referring now to Figure 1, which is a schematic diagram showing an exemplary electron beam inspection apparatus 100. The electron beam inspection apparatus 100 in Figure 1 includes a main chamber 10, a load lock chamber 20, an electron-optics apparatus 40 (which may also be called an electron evaluation apparatus, electron beam system, or tool), an Equipment Front End Module (EFEM) 30, and a controller 50. The electron-optics apparatus 40 is located inside the main chamber 10.

[0022]

[0041] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b can, for example, accept a substrate Front Opening Unified Pod (FOUP), which contains a substrate (a semiconductor substrate or a substrate made of other materials) or a sample to be inspected (hereinafter, substrates, wafers, and samples are collectively referred to as "samples"). One or more robotic arms (not shown) within the EFEM 30 transport the sample to the load lock chamber 20.

[0023]

[0042] The load lock chamber 20 is used to remove gas from around the sample. This creates a vacuum, which is a local gas pressure lower than the ambient pressure. The load lock chamber 20 may be connected to a load lock vacuum pump system (not shown) that removes gas particles from within the load lock chamber 20. The operation of the load lock vacuum pump system allows the load lock chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles from within the main chamber 10, thereby bringing the pressure around the sample to a second pressure lower than the first pressure. After reaching the second pressure, the sample is transported to an electro-optical device 40, by which it may be examined. The electro-optical device 40 includes an electro-optical device 41 (which may be called a charged particle device). The electron-optical device 41 may include an electron-optical column configured to project at least one electron beam toward the sample 208, and / or an objective lens module configured to focus at least one electron beam onto the sample 208. The electron-optical device 41 may also include a detector module configured to detect electrons emitted from the sample 208 and / or a control lens module configured to adjust the electron-optical parameters of at least one electron beam. In some embodiments, the electron-optical column may include the objective lens module and the detector module, and optionally the control lens module. In some embodiments, the electron-optical device includes an objective lens assembly that may be included in the electron-optical column. The objective lens assembly includes an objective lens array associated with (e.g., integrated with) one or more other electron-optical components, such as a detector array and optionally a control lens array. The electron-optical device 41 may be a multibeam electron-optical device 41 for multiple beams projected toward the sample 208.In one embodiment, the electron-optical device 41 includes a multi-device (or column) comprising multiple electron-optical devices configured to project each electron beam or electron multibeam toward the sample 208.

[0024]

[0043] The controller 50 is electronically connected to the electro-optical component of the electro-optical device 41 of the electro-optical apparatus 40. The controller 50 may be a processor (such as a computer) configured to control the electron beam inspection apparatus 100. The controller 50 may also include processing circuits configured to perform various signal and image processing functions. In Figure 1, the controller 50 is shown outside the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, but it should be understood that the controller 50 may be part of this structure. The controller 50 may be located in one of the components of the electron beam inspection apparatus 100, or it may be distributed among at least two of these components. The controller may be considered part of the electro-optical device 41. While this disclosure provides an example of a main chamber 10 housing an electron beam inspection tool, it should be noted that aspects of this disclosure are not limited in their broadest sense to chambers housing electron beam inspection tools. Rather, it should be understood that the principles described above may also apply to other tools and other apparatus configurations operating under a second pressure.

[0025]

[0044] Next, referring to Figure 2, this is a schematic diagram showing an exemplary electron-optical device 40, which includes a multibeam electron-optical device 41, which is part of the exemplary electron beam inspection apparatus 100 of Figure 1. The multibeam electron-optical device 41 includes an electron source 201 and a projection device 230. The electron-optical device 40 further includes a motorized stage 209 and a sample holder 207. The projection device 230 may be referred to as the electron-optical device 41. The sample holder 207 is supported by the motorized stage 209 and holds a sample 208 (e.g., a substrate or a mask) for inspection. The multibeam electron-optical device 41 may further include a detector 240 (e.g., an electron detection device).

[0026]

[0045] The electron source 201 may include a cathode (not shown) and an extraction electrode or anode (not shown). During operation, the electron source 201 is configured to emit electrons from the cathode as primary electrons. The primary electrons are extracted or accelerated by the extraction electrode and / or anode to form a primary evaluation electron beam 202. The electron source 201 may include multiple electron sources as described in European Patent Application Publication 20184161.6, which is incorporated herein by reference with respect to at least multiple electron sources and how they relate to multiple columns and associated electron optics.

[0027]

[0046] The projection device 230 is configured to convert the primary evaluation electron beam 202 into multiple evaluation sub-beams 211, 212, and 213, and direct each sub-beam towards the sample 208. While three sub-beams are shown for simplicity, tens, hundreds, or even thousands of sub-beams may exist. Sub-beams may be referred to as beamlets.

[0028]

[0047] The controller 50 can be connected to various components of the electron beam inspection apparatus 100 shown in Figure 1. The controller 50 can also be connected to various components of the electron-optical apparatus 40 shown in Figure 2, which are, for example, the electron source 201, the detector 240, the projection device 230, and the motorized stage 209 (or operating stage). The controller 50 can perform various data, image, and / or signal processing functions. The controller 50 can also generate various control signals to control the operation of the electron beam inspection apparatus 100, including the multi-beam electron-optical apparatus 40.

[0029]

[0048] The projection device 230 may be configured to focus evaluation subbeams 211, 212, and 213 onto the sample 208 for inspection, and may also form three probe spots 221, 222, and 223 on the surface of the sample 208. The projection device 230 may be configured to deflect the evaluation subbeams 211, 212, and 213 to scan individual scanning regions within a section of the surface of the sample 208 with the probe spots 221, 222, and 223. In response to the incidence of the evaluation subbeams 211, 212, and 213 onto the probe spots 221, 222, and 223 on the sample 208, signal-charged particles (e.g., signal electrons), including secondary signal particles and backscattered signal particles, are generated (i.e., emitted) from the sample 208. The signal particles emitted from the sample, e.g., secondary electrons and backscattered electrons, may otherwise be called charged particles, e.g., secondary charged particles and backscattered charged particles. The signal beam is formed by signal particles emitted from the sample. Generally, any signal beam emitted from sample 208 will be understood to travel in a direction having a component substantially opposite to that of the charged particle beam (i.e., the primary beam), or to have a direction with a component opposite to that of the primary beam. The signal particles emitted by sample 208 can also pass through the electrodes of the objective lens and will be affected by the electric field.

[0030]

[0049] Secondary electrons typically have an electron energy of ≤50 eV. While actual secondary electrons may have energies less than 5 eV, all with energies less than 50 eV are generally treated as secondary electrons. Backscattered electrons typically have electron energies between 0 eV and the incident energies of evaluation subbeams 211, 212, and 213. Since electrons detected with energies less than 50 eV are generally treated as secondary electrons, some actual backscattered electrons are counted as secondary electrons. Secondary signal particles may more specifically be called secondary electrons and are interchangeable with secondary electrons. Backscattered signal particles may more specifically be called backscattered electrons and are interchangeable with backscattered electrons. Those skilled in the art will understand that backscattered signal particles can be described more broadly as secondary signal particles. However, for the purposes of this disclosure, backscattered signal particles are considered distinct from secondary signal particles, for example, having higher energies. In other words, secondary signal particles are understood to be particles whose kinetic energy is ≤50 eV when emitted from the sample, and backscattered signal particles are understood to be particles whose kinetic energy is greater than 50 eV when emitted from the sample. In practice, signal particles can be accelerated before detection, and therefore the energy range associated with signal particles can be slightly higher. For example, secondary signal particles are understood to be particles whose kinetic energy is ≤200 eV when detected by the detector, and backscattered signal particles are understood to be particles whose kinetic energy is greater than 200 eV when detected by the detector. Note that the value of 200 eV can vary depending on the degree of acceleration of the particle, and could be, for example, about 100 eV or 300 eV. Secondary signal particles with such values ​​are still considered to have a sufficient energy, different from backscattered signal particles.

[0031]

[0050] The detector 240 is configured to detect (e.g., capture) signal particles such as secondary electrons and / or backscattered electrons, generate a corresponding signal, which is transmitted to a signal processing system 280 to form an image of the corresponding scanned area of, for example, sample 208. The detector 240 may be incorporated into the projection device 230. The detector array may otherwise be called a sensor array, and the terms “detector,” “sensor,” and “sensor unit” are used interchangeably throughout this application.

[0032]

[0051] The signal processing system 280 may include circuitry (not shown) configured to process signals from the detector 240 to form an image. The signal processing system 280 may also be called an image processing system. The signal processing system may be incorporated into a component of the multibeam electron-optical apparatus 40, such as the detector 240 (as shown in Figure 2). However, the signal processing system 280 may be incorporated into any component of the electron beam inspection apparatus 100 or the multibeam electron-optical apparatus 40, such as part of the projection device 230 or the controller 50. The signal processing system 280 may be located outside the structure including the main chamber shown in Figure 1. The signal processing system 280 may include an image acquisition unit (not shown) and a storage device (not shown). For example, the signal processing system may include a processor, computer, server, mainframe host, terminal, personal computer, any kind of mobile computing device, or a combination thereof. The image acquisition unit may include at least some of the processing functions of the controller. Therefore, the image acquisition unit may include at least one processor. The image acquisition unit can be communicatively coupled to the detector 240 to enable signal communication, which may be, for example, a conductor, optical fiber cable, portable storage medium, IR, Bluetooth, the internet, a wireless network, a wireless radio, or a combination thereof. The image acquisition unit can receive signals from the detector 240, process the data contained in those signals, and form an image from them. Thus, the image acquisition unit can acquire an image of sample 208. The image acquisition unit can also perform various post-processing functions, such as contour generation and overlaying indicators onto the acquired image. The image acquisition unit may be configured to adjust the brightness and contrast of the acquired image. Storage may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), or other types of computer-readable memory. Storage may be coupled to the image acquisition unit and used to store scanned raw image data as the original image and the post-processed image.

[0033]

[0052] The signal processing system 280 may include a measurement circuit (e.g., an analog-to-digital converter) to acquire the distribution of detected secondary electrons. The electron distribution data collected during the detection time window is used in combination with the corresponding scan path data of the evaluation sub-beams 211, 212, and 213 incident on the sample surface to reconstruct an image of the sample structure under inspection. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 208. Thus, the reconstructed image can be used to reveal any defects that may be present in the sample.

[0034]

[0053] The controller 50 can control the motorized stage 209 to move the sample 208 during inspection of the sample 208. The controller 50 can ensure that the motorized stage 209 moves the sample 208 in a certain direction, preferably continuously, for example, at a constant speed, at least during sample inspection. The controller 50 can control the movement of the motorized stage 209 to vary the speed of movement of the sample 208 according to various parameters. For example, the controller 50 can control the stage speed (including its direction) according to the characteristics of the inspection step of the scanning process.

[0035]

[0054] Known multibeam systems, such as the aforementioned electron-optical device 40 and electron beam inspection device 100, are disclosed in U.S. Patent Publication Nos. 2020118784, 20200203116, 2019 / 0259570, and 2019 / 0259564, which are incorporated herein by reference.

[0036]

[0055] The components of the electro-optical apparatus 40 that may be used in the present invention will be described below with reference to Figure 3, which is a schematic diagram of the electro-optical apparatus 40. The electro-optical apparatus 40 in Figure 3 may correspond to the aforementioned electro-optical apparatus 40 (which may also be called a system or tool).

[0037]

[0056] An electron source 201 directs electrons to an array of condenser lenses 231 (otherwise referred to as a condenser lens array). The electron source 201 is preferably a high-brightness thermal field emitter having a good compromise between brightness and total emitted current. There can be tens, hundreds, or thousands of condenser lenses 231. The condenser lenses 231 may include multipole lenses and have a structure based on European Patent Publication 1602121A1, which is incorporated herein by reference, in particular, with respect to a disclosure of a lens array for splitting, for example, an electron beam from an electron source into multiple sub-beams, providing one lens for each sub-beam. The array of condenser lenses 231 can take the form of at least two plates that function as electrodes, the apertures of each plate being aligned with each other to correspond to the positions of the sub-beams. At least two of the plates are held at different potentials during operation to achieve a desired lensing effect.

[0038]

[0057] In one configuration, the array of condenser lenses 231 is formed of three plate arrays having the same energy as charged particles enter and exit each lens; this configuration may be called an Einzel lens. Thus, dispersion occurs only within the Einzel lens itself (between the inlet and outlet electrodes of the lens), thereby limiting off-axis chromatic aberration. If the thickness of the condenser lens is thin, e.g., a few millimeters, the effect of such aberration is small or negligible. More generally, the condenser lens 231 may have two or more plate electrodes, each having an array of apertures that are aligned. Each plate electrode array is mechanically connected to and electrically isolated from adjacent plate electrode arrays by insulating elements such as spacers, which may include ceramic or glass. The condenser lenses may be connected and / or separated by insulating elements such as spacers to adjacent charged particle optical elements, preferably electrostatic charged particle optical elements, as described elsewhere in this specification.

[0039]

[0058] The condenser lens may be separated from the module containing the objective lens (such as the objective lens array assembly described elsewhere in this specification). If the potential applied to the bottom surface of the condenser lens differs from the potential applied to the top surface of the module containing the objective lens, an insulating element (e.g., a spacer) can be used to separate the condenser lens from the module containing the objective lens. If the potentials are equal, a conductive element can be used to separate the condenser lens from the module containing the objective lens.

[0040]

[0059] Each condenser lens 231 in the array directs electrons to their respective evaluation subbeams 211, 212, and 213, which are focused to their respective intermediate foci downstream of the beam in the condenser lens array. Each subbeam is projected along its respective subbeam path 220. The subbeams diverge with respect to each other. The subbeam path 220 diverges downstream of the beam in the condenser lens 231. In one embodiment, a deflector 235 is provided at the intermediate focal. The deflector 235 is positioned in the subbeam path at or at least around the corresponding intermediate focal or focal point (i.e., the focusing point). The deflector 235 is positioned in or near the subbeam path in the intermediate image plane of the relevant subbeam. The deflector 235 is configured to operate for each of the evaluation subbeams 211, 212, and 213. The deflector 235 is configured to bend each of the evaluation subbeams 211, 212, and 213 by an amount effective in ensuring that the principal rays (also called beam axes) are incident on the sample 208 substantially perpendicular to the surface (i.e., substantially at 90° with respect to the nominal surface of the sample). The deflector 235 may also be called a collimator or collimator deflector. The deflector 235 actually collimates the paths of the subbeams, causing the subbeam paths to diverge with respect to each other before the deflector. Downstream of the beams of the deflector, the subbeam paths are substantially parallel with respect to each other, i.e., substantially collimated. A suitable collimator is the deflector disclosed in European Patent Application No. 20156253.5, filed on 7 February 2020, which is incorporated herein by reference with respect to the application of deflectors to multibeam arrays. The collimator may include a macrocollimator 270 (for example, shown in Figure 4) instead of, or in addition to, the deflector 235. Thus, the macrocollimator 270, described later with respect to Figure 4, may have the features of Figure 3. This is generally less desirable than when the collimator array is provided as the deflector 235.

[0041]

[0060] Below the deflector 235 (i.e., downstream of the beam or further away from the electron source 201) is a control lens array 250. The evaluation sub-beams 211, 212, and 213, having passed through the deflector 235, are substantially parallel as they enter the control lens array 250. The control lenses prefocus the sub-beams (e.g., apply focusing action to the sub-beams before they reach the objective lens array 241). Prefocusing can reduce the divergence of the sub-beams or increase their convergence rate. The control lens array 250 and the objective lens array 241 work together to provide a combined focal length. This cooperative action, without the use of intermediate focal points, can reduce the risk of aberrations.

[0042]

[0061] More specifically, it is desirable to determine the incident energy using the control lens array 250. However, in addition, it is possible to control the incident energy using the objective lens array 241. In such cases, the potential difference on the objective lens changes when a different incident energy is selected. One example of a situation where it is desirable to partially change the incident energy by changing the potential difference on the objective lens is to prevent the focus of the sub-beam from being too close to the objective lens. In such a situation, there is a risk that the components of the objective lens array 241 would have to be made too thin to manufacture. The same can be said for detectors at this position, for example, within the objective lens, on the objective lens, or otherwise associated with the objective lens. This situation can occur, for example, when the incident energy decreases. This is because the focal length of the objective lens roughly corresponds to the incident energy used. By reducing the potential difference on the objective lens, and thereby reducing the electric field inside the objective lens, the focal length of the objective lens increases again, and as a result the focal position is located further below the objective lens. Note that when using only the objective lens, the control of magnification is limited. In such a configuration, the reduction ratio and / or aperture angle cannot be controlled. Furthermore, using the objective lens to control the incident energy may mean that the objective lens operates at a magnetic field strength that is not optimal for it. This occurs when the mechanical parameters of the objective lens (such as the spacing between its electrodes) cannot be adjusted, for example, by changing the objective lens.

[0043]

[0062] The control lens array 250 includes a plurality of control lenses. Each control lens includes at least one electrode, preferably two electrodes (e.g., two or three electrodes), which are connected to their respective electron sources. The control lens array 250 may include one or more (e.g., three) plane electrode arrays connected to their respective electron sources. The control lens array electrodes may be spaced several millimeters apart (e.g., 3 mm). The control lens array 250 is associated with the objective lens array 241 (e.g., two arrays are positioned close to each other and / or mechanically connected to each other and / or controlled together as a unit). Each control lens may be associated with its respective objective lens. The control lens array 250 is positioned upstream of the beam of the objective lens array 241. Upstream can be defined as being closer to the electron source 201. Upstream can also be defined as being further away from the sample 208. The control lens array 250 may be in the same module as the objective lens array 241, i.e., it may form an objective lens array assembly or objective lens configuration, or it may be in a separate module. In this case, the configuration can be described as four or more lens electrodes that are a plate. On the plate, apertures may be defined, for example, as aperture arrays, which are aligned with multiple subbeams in the corresponding beam array. The electrodes may be divided into, for example, two or more electrodes that provide a group of control electrodes and a group of objective lens electrodes. In one configuration, the group of target lens electrodes has at least three electrodes, and the group of control electrodes has at least two electrodes. Alternatively, when the control lens array 250 and the objective lens array 240 are separated, the gap between the control lens array 241 and the objective lens array 250 (i.e., the gap between the lower electrode of the control lens array 250 and the upper electrode of the objective lens 241) can be selected from a wide range, for example, 2 mm to 200 mm or more. Smaller separation makes alignment easier, and larger separation allows for the use of weaker lenses to reduce aberrations.

[0044]

[0063] Each plate electrode of the control lens array 250 is preferably mechanically connected to and electrically isolated from an adjacent plate electrode array by an insulating element, such as a spacer, which may include ceramic or glass. Each plate electrode of the objective lens array is preferably mechanically connected to and electrically isolated from an adjacent plate electrode array by an insulating element, such as a spacer, which may include ceramic or glass. The insulating element may also be called an insulating structure and may be provided to isolate any electrodes provided, such as the objective lens array 240, the condenser lens array (shown in Figure 3), and / or the control lens array 250. If three or more electrodes are provided, multiple insulating elements (i.e., insulating structures) may be provided. For example, a series of insulating structures may exist.

[0045]

[0064] The control lens array 250 can be considered as one or more additional electrodes to the electrodes of the objective lens array 241. The control lens array 250 provides more degrees of freedom for controlling the sub-beam. The more electrodes included in the control lens array 250, the more degrees of freedom are provided. For example, these additional electrodes may enable incident energy and / or magnification control independent of the electric field strength of the objective lens array 241. Therefore, depending on the design, the control lens may be part of the objective lens. Thus, references to such electrodes may be made as part of the objective lens rather than as a separate lens such as a control lens. References to the control lens in such a configuration are references to the functionally equivalent electrodes of the objective lens.

[0046]

[0065] The control lens array 250 includes control lenses for each evaluation sub-beam 211, 212, and 213. The control lenses increase the optical degrees of freedom depending on the associated objective lens. A control lens may include one or more electrodes or plates. The addition of each electrode may provide even greater control degrees of freedom for the charged particle optics of the associated objective lens. In one configuration, the function of the control lens array 250 is to optimize the beam opening angle with respect to beam reduction and / or to control the beam energy delivered to the objective lens that directs each of the evaluation sub-beams 211, 212, and 213 toward the sample 208. The objective lens array 241 may be located at or near the base of the electron-optical system 41. More specifically, the objective lens array may be located at or near the base of the projection system 230. The control lens array 250 is optional but preferred for optimizing the sub-beams upstream of the objective lens array 241.

[0047]

[0066] For illustrative purposes, lens arrays are schematically represented in this specification by an elliptical array (illustrated in Figure 3). Each ellipse represents one of the lenses in the lens array. By convention, the ellipse is used to represent lenses by analogy to the biconvex shape often employed in optical lenses. However, it should be understood that, in relation to charged particle configurations such as those discussed herein, lens arrays typically operate electrostatically and therefore may not require any physical elements to employ a biconvex shape. Instead, a lens array may consist of multiple plates having apertures.

[0048]

[0067] Optionally, an array of scan deflectors 260 is provided between the array of control lenses 250 and the array of objective lenses 234. The array of scan deflectors 260 includes scan deflectors for each evaluation sub-beam 211, 212, and 213. Each scan deflector is configured to deflect its respective evaluation sub-beam 211, 212, and 213 in one or two directions, thereby scanning the sample 208 with the sub-beams in one or two directions.

[0049]

[0068] Figure 4 is a schematic diagram of an exemplary electron-optical apparatus 40 including a macrocollimator 270 and a macroscan deflector 265. The electron source 201 directs its electrodes toward the macrocollimator 270. The electron source 201 is preferably a high-brightness thermal field emitter that has a good compromise between brightness and total emitted current.

[0050]

[0069] A subbeam can be acquired from the beam, for example, using a subbeamforming array 252 (also known as a beam limiting aperture array) that defines an array of beam limiting apertures. The beam can be separated into a subbeam when it strikes the control lens array 250, which is described below. The subbeam is substantially parallel as it is incident on the control lens array 250.

[0051]

[0070] The macrocollimator 270 acts on the beam from the electron source 201 before the beam is split into multiple beams. The macrocollimator 270 bends each portion of the beam by an amount effective enough to ensure that the beam axis of each subbeam obtained from the beam is incident on the sample 208 substantially perpendicular to the surface (i.e., substantially at 90° with respect to the nominal surface of the sample 208). Thus, the path of each subbeam is intended to be at least perpendicular to the surface of the sample 208. The macrocollimator 270 applies macroscopic collimation to the beam. Thus, the macrocollimator 270 may act on the entire beam rather than including an array of collimator elements, each configured to act on different individual portions of the beam. The macrocollimator 270 may include a magnetic lens or magnetic lens configuration including multiple magnetic lens subunits (e.g., multiple electromagnets forming a multipole configuration). Alternatively or additionally, the macrocollimator may be implemented at least partially electrostatically. The macrocollimator may include an electrostatic lens or electrostatic lens configuration including multiple electrostatic lens subunits. The MacroCollimator 270 can use a combination of magnetic and electrostatic lenses.

[0052]

[0071] In other configurations (not shown), the macrocollimator 270 may be replaced in part or in whole by a collimator element array located downstream of the beam of the sub-beamforming array. Each collimator element collimates its respective sub-beam. The collimator element array may be formed using MEMS fabrication techniques to be spatially compact. The collimator element array may be the first deflection or focusing electron-optics array element in the beampath downstream of the electron source 201. The collimator element array may be located upstream of the control lens array 250. The collimator element array may be in the same module as the control lens array 250.

[0053]

[0072] As shown in Figure 4, in one embodiment, the electro-optical device 41 includes an objective lens array 241. The objective lens array 241 includes a plurality of objective lenses. The objective lens array 241 may be a replaceable module. The replaceable module may feature other electro-optical elements such as a detector array and / or a control lens array.

[0054]

[0073] Below the macrocollimator 270 (i.e., downstream of the beam or further away from the electron source 201) is a control lens array 250. The control lens array 250 is configured to apply a focusing action to the sub-beam before it reaches the objective lens array. Prefocusing can reduce the divergence of the sub-beam or increase the convergence rate of the sub-beam. The control lens array 250 and the objective lens array 241 work together to provide a combined focal length. The combined action without the use of an intermediate focus can reduce the risk of aberrations. Additionally or alternatively, control lenses within the control lens array 250 are configured to control the sub-beam opening angle and / or control the sub-beam reduction (i.e., expansion) and / or control the incident energy.

[0055]

[0074] The control lens array 250 may be the one described above in relation to Figure 3. The control lens array 250 can be considered as one or more electrodes in addition to the electrodes of the objective lens array 241. The control lens array 250 provides a greater degree of freedom for controlling the sub-beam. The more electrodes included in the control lens array 250, the greater the degree of freedom. For example, these additional electrodes may enable control of the incident energy and / or magnification independently of the electric field strength of the objective lens array 241. Therefore, depending on the design, the control lens may be part of the objective lens. Thus, references to such electrodes may be made as part of the objective lens, rather than as a separate lens such as a control lens.

[0056]

[0075] The control lens array 250 includes control lenses for each evaluation sub-beam 211, 212, and 213. The function of the control lens array 250 is to optimize the beam opening angle with respect to beam reduction and / or to control the beam energy delivered to the objective lens array 241 that directs the evaluation sub-beams 211, 212, and 213 onto the sample 208. The objective lens array 241 may be located at or near the base of the electro-optical device 41. The control lens array 250 is preferred for optimizing the sub-beams upstream of the objective lens array 241.

[0057]

[0076] In the embodiment shown in Figure 4, a macroscan deflector 265 is provided to scan the sample 208 with a sub-beam. The macroscan deflector 265 deflects each portion of the beam to scan the sample 208 with the sub-beam. In one embodiment, the macroscan deflector 265 includes a macroscopic multi-pole deflector having, for example, eight or more poles. The deflection is, for example, to cause the sub-beam obtained from the beam to scan the sample 208 in one direction (e.g., parallel to a single axis such as the X-axis) or in two directions (e.g., with respect to two non-parallel axes such as the X-axis and the Y-axis). The macroscan deflector 265 acts macroscopically on the entire beam, rather than including an array of deflector elements, each configured to act on different individual portions of the beam. In the embodiment shown in the figure, the macroscan deflector 265 is located between the macrocollimator 270 and the control lens array 250.

[0058]

[0077] In other configurations (not shown), the macro scan deflector 265 may be replaced in part or in whole by a scan deflector array. The scan deflector array includes multiple scan deflectors. The scan deflector array may be formed using MEMS fabrication techniques. Each scan deflector scans over the sample 208 with its respective sub-beam. Thus, the scan deflector array may include a scan deflector for each sub-beam. Each scan deflector can deflect the sub-beam in one direction (e.g., parallel to a single axis such as the X-axis) or in two directions (e.g., with respect to two non-parallel axes such as the X-axis and Y-axis). The deflection causes the sub-beam to scan over the sample 208 in one or two directions (i.e., one-dimensional or two-dimensional). The scan deflector array may be located upstream of the objective lens array 241. The scan deflector array may be located downstream of the control lens array 250. While a single sub-beam associated with a scan deflector is mentioned, a group of sub-beams may be associated with a scan deflector. In one embodiment, a scan deflector described in European Patent No. 2425444 may be used to implement a scan deflector array, and that document, in whole, is incorporated by reference to this application, particularly with respect to scan deflectors. A scan deflector array (e.g., formed using MEMS manufacturing techniques as described above) may be more spatially compact than a macro scan deflector. The scan deflector array may be in the same module as the objective lens array 241.

[0059]

[0078] In other embodiments, both a macro-scan deflector 265 and a scan deflector array are provided. In such a configuration, scanning of the sample surface with a sub-beam can be achieved by controlling the macro-scan deflector and the scan deflector array together, preferably synchronously.

[0060]

[0079] In some embodiments, the electron-optical device 41 further includes a sub-beamforming array 252. The sub-beamforming array 252 defines an array of beam-limiting apertures. The sub-beamforming array 252 may be called an upper beam-limiting aperture array or an upstream beam-limiting aperture array. The sub-beamforming array 252 may include a plate (which may be a plate-like body) having a plurality of apertures. The sub-beamforming array 252 forms a subbeam from a beam of electrons emitted by the electron source 201. The portion of the beam that does not contribute to the formation of the subbeam may be blocked (e.g., absorbed) by the sub-beamforming array 252 so as not to interfere with the downstream subbeam. The sub-beamforming array 252 may be called a sub-beam-limiting aperture array or an upper beam limiter. The aperture diameter 72 of the subbeamforming array 252 (see Figure 12) may be at least 20 μm, optionally at least 50 μm, optionally at least 100 μm, and optionally 120 μm. The aperture pitch may be equal to that of the aperture of the beam aperture 406.

[0061]

[0080] In some embodiments, as illustrated in Figure 4, the electro-optical device 41 is an objective lens array assembly (which is a unit including the objective lens array 241) and includes a beam shaping aperture array 262. The beam shaping aperture array 262 defines an array of beam limiting apertures. The beam shaping aperture array 262 may be called the lower beam limiter, lower beam limiting aperture array, or final beam limiting aperture array. The beam shaping aperture array 262 may include a plate (which may be a plate-like body) having multiple apertures. The beam shaping aperture array 262 may be located downstream of the beam from at least one electrode (optionally from all electrodes) of the control lens array 250. In some embodiments, the beam shaping aperture array 262 is located downstream of the beam from at least one electrode (optionally from all electrodes) of the objective lens array 241.

[0062]

[0081] In one configuration, the beam shaping aperture array 262 is structurally integrated with the electrodes of the objective lens array 241. Preferably, the beam shaping aperture array 262 is positioned in a region of low electrostatic field intensity. Each beam limiting aperture is aligned with the corresponding objective lens in the objective lens array 241. The alignment is such that a portion of the subbeam from the corresponding objective lens can pass through the beam limiting aperture and strike the sample 208. Each beam limiting aperture has a beam limiting effect so that only a selected portion of the subbeam incident on the beam shaping aperture array 262 can pass through the beam limiting aperture. The selected portion may be such that only a portion of each subbeam passing through the central portion of each aperture in the objective lens array reaches the sample. The central portion may have a circular cross-section and / or be centered on the beam axis of the subbeam.

[0063]

[0082] Any of the electron-optical devices 40 described herein may further include a detector 240. The detector 240 detects signal particles, such as electrons, emitted from the sample 208. The detected electrons may include any electrons detected by the SEM, including secondary electrons and / or backscattered electrons emitted from the sample 208. An exemplary structure of the detector 240 is shown in Figure 7 and will be described in more detail later with reference to Figures 8-10.

[0064]

[0083] Figure 5 schematically shows an electron-optical apparatus 40 according to one embodiment. The same reference numerals are used for features identical to those described above. For brevity, such features will not be described in detail with respect to Figure 5. For example, the electron source 201, macrocollimator 270, objective lens array 241, and sample 208 may be as described above.

[0065]

[0084] In one embodiment, the electron-optical apparatus 40 includes an array of condenser lenses 231. There may be tens, hundreds, or thousands of condenser lenses 231. The condenser lenses 231 include multipole lenses and may have a structure based on European Patent No. 1602121A1, which is incorporated herein by reference, particularly with respect to the disclosure of a lens array for splitting an electron beam into a plurality of sub-beams and the array providing a lens for each sub-beam. The array of condenser lenses 231 may take the form of at least two plates that function as electrodes, the apertures of each plate being aligned with each other and corresponding to the positions of the sub-beams. At least two of the plates are held at different potentials during operation to achieve a desired lensing effect.

[0066]

[0085] In one configuration, the array of condenser lenses 231 is formed from three plate arrays, and electrons have the same energy as they enter and exit each lens; this configuration can be called an Einzel lens. Therefore, dispersion occurs only within the Einzel lens itself (between the inlet and outlet electrodes of the lens), thereby limiting off-axis chromatic aberration. When the thickness of the condenser lens is thin, for example a few millimeters, the effect of such aberrations is small or negligible.

[0067]

[0086] As described above, in one embodiment, the detector 240 is located between the objective lens array 241 and the sample 208. The detector 240 may face the sample 208. Alternatively, as shown in Figure 5, in one embodiment, the objective lens array 241, which includes multiple objective lenses, is located between the detector 240 and the sample 208.

[0068]

[0087] In one embodiment, the deflector array 95 is located between the detector 240 and the objective lens array 241. In another embodiment, the deflector array 95 includes a Wien filter, and the deflector array may be called a beam separator. The deflector array 95 is configured to provide a magnetic field for separating electrons projected onto the sample 208 from secondary electrons from the sample 208.

[0069]

[0088] In one embodiment, the detector 240 is configured to detect signal particles based on the energy of the electrons, i.e., dependent on the band gap. Such a detector 240 is sometimes called an indirect current detector. Secondary electrons emitted from the sample 208 gain energy from the electric field between the electrodes. The secondary electrodes have sufficient energy once they reach the detector 240.

[0070]

[0089] Figure 6 is an enlarged view of a portion of the electron-optical apparatus 40 shown in Figure 5. In one embodiment, the detector 240 includes an electron-photon converter array 91. The electron-photon converter array 91 includes a plurality of fluorescent strips 92. Each fluorescent strip 92 is positioned in the plane of the electron-photon converter array 91. At least one fluorescent strip 92 is positioned between two adjacent electron beams projected toward the sample 208.

[0071]

[0090] In one embodiment, the fluorescent strip 92 extends substantially horizontally. Alternatively, the electron-photon converter array 91 may include a plate of fluorescent material having an aperture 93 for the projected electron beam.

[0072]

[0091] In Figure 6, the projected electron beam, shown by the dashed line, is projected through the aperture 93 between the fluorescence strips 92, through the plane of the electron-photon converter array 91, and toward the deflector array 95.

[0073]

[0092] In one embodiment, the deflector array 95 includes a magnetic deflector 96 and an electrostatic deflector 97. The electrostatic deflector 97 is configured to counteract the deflection of the magnetic deflector 96 with respect to the projected electron beam transmitted toward the sample 208. Thus, the projected electron beam may be shifted to a small extent in the horizontal plane. The beam downstream of the deflector array 95 is substantially parallel to the beam upstream of the deflector array 95.

[0074]

[0093] In one embodiment, the objective lens array 241 includes multiple plates for guiding secondary electrons generated in the sample 208 toward the deflector array 95. For secondary electrons traveling in the opposite direction to the projected electron beam, the electrostatic deflector 97 does not counteract the deflection of the magnetic deflector 96. Instead, the deflection of the secondary electrons by the electrostatic deflector 97 and the magnetic deflector 96 is summed up. Thus, the secondary electrons are deflected to propagate at an angle with respect to the optical axis in order to transmit them onto the fluorescence strip 92 of the detector 240.

[0075]

[0094] In the fluorescent strip 92, photons are generated when secondary electrons are incident on it. In one embodiment, the photons are transmitted from the fluorescent strip 92 to a photodetector (not shown) via a photon transmission unit. In one embodiment, the photon transmission unit includes an array of optical fibers 98. Each optical fiber 98 includes an end that is positioned adjacent to or attached to one of the fluorescent strips 92 to couple photons from the fluorescent strip 92 to the optical fiber 98, and another end that is positioned to project photons from the optical fiber 98 onto the photodetector.

[0076]

[0095] In any embodiment, the objective lens array 241 may include at least two electrodes in which aperture arrays are defined. In other words, the objective lens array includes at least two electrodes having a plurality of holes or apertures. Adjacent electrodes of the objective lens array 241 are spaced apart from each other along the sub-beam path. The distance between adjacent electrodes along the beam path, in which insulating structures may be placed as described below, is smaller than the size of the objective lens (along the beam path, i.e., between the furthest upstream and furthest downstream electrodes of the objective lens array). Figure 7 shows electrodes 242, 243, each having aperture arrays 245, 246, which are part of an exemplary objective lens array 241. The position of each aperture in one electrode corresponds to the position of the corresponding aperture in the other electrode. The corresponding apertures operate for the same beam, sub-beam, or beam group in a multi-beam during use. In other words, corresponding apertures in at least two electrodes are aligned with and positioned along one of the sub-beam paths, i.e., one of the sub-beam paths 220. Thus, each electrode is provided with an aperture through which the respective evaluation sub-beams 211, 212, and 213 propagate.

[0077]

[0096] The aperture arrays 245, 246 of the objective lens array 241 may consist of a plurality of apertures having substantially uniform diameters d, preferably. However, some variability may be allowed to optimize aberration correction, as described in European Patent Application No. 20207178.3, filed November 12, 2020, and that application is incorporated by reference to this application, at least with respect to corrections achieved by varying the aperture diameter. The diameter d of the aperture of at least one electrode may be less than about 400 μm. Preferably, the diameter d of the aperture of at least one electrode is about 30 to 300 μm. Smaller aperture diameters allow for larger detectors in the detector array 240 at the same aperture pitch, increasing the chances of capturing backscattered signal particles. Thus, the signal of backscattered signal particles may be improved. However, apertures that are too small risk causing aberrations in the main subbeam. The plurality of apertures within the electrode may be spaced apart from each other by a pitch P. The pitch P is defined as the distance from the center of one aperture to the center of an adjacent aperture. The pitch between adjacent apertures on at least one electrode may be less than about 600 μm. Preferably, the pitch between adjacent apertures on at least one electrode is about 50 μm to about 500 μm. Preferably, the pitch between adjacent apertures on each electrode is substantially uniform. The diameter and / or pitch values ​​described above can be determined for at least one electrode, multiple electrodes, or all electrodes in the objective lens array. Preferably, the dimensions mentioned and described apply to all electrodes provided in the objective lens array.

[0078]

[0097] The objective lens array 241 may include two electrodes, three electrodes, or more electrodes (not shown), as shown in Figure 7. An objective lens array 241 with only two electrodes may have fewer aberrations than an objective lens array 241 with more electrodes, and therefore may have a smaller risk and / or impact of aberrations. A tripole objective lens allows for a larger potential difference between electrodes, thus enabling a stronger lens. Additional electrodes (i.e., three or more electrodes) provide greater freedom to control electron trajectories, for example, secondary electrons and focusing the incident beam. Such additional electrodes may be considered to form a control lens array 250. An advantage of a dipole lens over an Einzel lens is that the energy of the incident beam is not necessarily the same as that of the exit beam. Beneficially, the potential difference on such a dipole lens array allows it to function as either an accelerating or decelerating lens array.

[0079]

[0098] The adjacent electrodes of the objective lens array 241 are spaced apart from each other along the sub-beam path. The distance between adjacent electrodes is greater than that of the objective lens, and insulating structures may be positioned within them as described below. The objective lens array 241 can be configured to reduce the charged particle beam by more than 10 times, preferably in the range of 50 to 100 times or more. Each element within the objective lens array 240 may be a microlens that operates different sub-beams or groups of sub-beams within a multi-beam system.

[0080]

[0099] Preferably, each electrode provided in the objective lens array 241 is a plate. Electrodes can also be described as flat sheets. Preferably, each electrode is planar. In other words, each electrode is preferably provided as a thin, flat plate in a planar form. Of course, electrodes do not need to be planar. For example, electrodes can bend due to forces resulting from high electrostatic fields. Providing planar electrodes is preferable because it facilitates the manufacture of planar electrodes, as known manufacturing methods can be used. Planar electrodes may also be preferable because they allow for more precise alignment of apertures between different electrodes.

[0081]

[0100] The objective lens array 241 can be configured to reduce the electron beam by more than 10 times, preferably in the range of 50 to 100 times or more.

[0082]

[0101] Detector 240 is provided to detect secondary and / or backscattered electrons emitted from sample 208. Detector 240 is positioned between objective lens 234 and sample 208. Detector 240 may also be referred to as a detector array or sensor array, and the terms “detector” and “sensor” are used interchangeably throughout this application.

[0083]

[0102] In one embodiment, the electron-optical device 41 is configured to project a beam of electrons toward the sample 208. The electron-optical device 41 may include an objective lens array 241. The electron-optical device 41 may include a detector 240. The array of objective lenses (i.e., the objective lens array 241) may correspond to either an array of detectors (i.e., the detector 240) and / or a beam (i.e., a subbeam).

[0084]

[0103] An exemplary detector 240 is described below. However, any reference to detector 240 may be a single detector (i.e., at least one detector) or multiple detectors as needed. Detector 240 may comprise a detection element 405 (e.g., a sensor element such as a capture electrode). Detector 240 may include any suitable type of detector. For example, a capture electrode may be used to directly detect, for example, electric charge, scintillator, or PIN element. Detector 240 may be a direct current detector or an indirect current detector. Detector 240 may be a detector as described later with respect to Figures 8-10.

[0085]

[0104] The detector 240 may be positioned between the objective lens array 241 and the sample 208. The detector 240 is configured to be in close proximity to the sample 208. The detector 240 may be in very close proximity to the sample 208. Alternatively, there may be a larger gap between the detector 240 and the sample 208. The detector 240 may be positioned within the device so as to face the sample 208. Alternatively, the detector 240 may be positioned at another location within the electro-optical device 41 such that the portion of the electro-optical device facing the sample 208 is not the detector, and therefore not the detector. For example, the detector 240 may have at least a portion associated with the electrodes of the objective lens array 241.

[0086]

[0105] In the multibeam systems of the type shown in Figures 2-5, the distance between the electron-optical column and the sample 208 is preferably about 50 μm or less. This distance is defined as the distance from the surface of the sample 208 facing the electron-optical column and the surface of the electron-optical column facing the sample 208.

[0087]

[0106] Figure 8 is a bottom view of a detector 240 including a substrate 404 on which multiple detection elements 405, each surrounding a beam aperture 406, are mounted. The beam aperture 406 can be formed by etching the substrate 404. In the configuration shown in Figure 8, the beam aperture 406 is a dense hexagonal array. The beam aperture 406 can also be arranged in a different configuration, such as a rectangular array. The hexagonal beam arrangement in Figure 8 can be denser than a square beam arrangement. The detection elements 405 can be arranged in a rectangular or hexagonal array.

[0088]

[0107] In one embodiment, the pitch P of the beam aperture 406 is at least 50 μm, optionally at least 100 μm, optionally at least 200 μm, and optionally at least 210 μm. A larger pitch allows for a larger diameter d of the beam aperture 406. In one embodiment, the pitch P of the beam aperture 406 is up to 1000 μm, optionally at least 500 μm, and optionally at least 250 μm. The pitch of the beam aperture 406 determines the pitch of the sub-beams of the electron multibeam projected toward the sample 208. In one embodiment, the pitch of the sub-beams of the electron multibeam is at least 50 μm, optionally at least 100 μm, optionally at least 200 μm, and optionally at least 210 μm. In one embodiment, the diameter d of the beam aperture 406 is smaller than the pitch P. In one embodiment, the diameter d of the beam aperture 406 is at least 10 μm, and optionally at least 20 μm. In another embodiment, the diameter d of the beam aperture 406 is up to 100 μm, optionally up to 50 μm, and optionally up to 30 μm. A smaller diameter d improves resolution and allows for the detection of smaller defects.

[0089]

[0108] Figure 9 shows a larger-scale cross-section of a portion of the detector 240. The detection element 405 forms the bottom of the detector 240, i.e., the portion closest to the surface of the sample 208. A logic layer 407 may be provided between the detection element 405 and the main body of the substrate 404. At least a portion of the signal processing system may be incorporated into the logic layer 407.

[0090]

[0109] The wiring layer 408 is located on the back surface of the substrate 404 or inside it and is connected to the logic layer 407 by through-substrate vias 409. The number of through-substrate vias 409 does not need to be the same as the number of beam apertures 406. In particular, if electrode signals are digitized in the logic layer 407, a small number of through-silicon vias may be sufficient to provide the data bus. The wiring layer 408 may include control lines, data lines, and power lines. Note that even with beam apertures 406, there is sufficient space for all necessary connections. The detection module 402 may also be fabricated using bipolar or other manufacturing techniques. A printed circuit board and / or other semiconductor chips may be provided on the back surface of the detector 240.

[0091]

[0110] The aforementioned integrated detector array is particularly advantageous when used with a tool that has a configurable incident energy, because secondary electron trapping can be optimized for a certain range of incident energies.

[0092]

[0111] The detector 240 can be implemented by integrating a CMOS chip detector into the lower electrode of the objective lens array 241. Integrating the detector 240 into the objective lens array 241 or other components of the electro-optical device 41 enables detection of electrons emitted in relation to each of several sub-beams. The CMOS chip is preferably oriented facing the sample (due to the small distance between the sample and the bottom of the electro-optical column, e.g., 50 μm or less). In one embodiment, a detector element 405 for capturing secondary electrons is formed on the surface metal layer of the CMOS device. The detector element 405 may be formed on other layers. Power and control signals for the CMOS can be connected to the CMOS via through-silicon vias. For robustness, preferably, a perforated passive silicon substrate shields the CMOS chip from high electric fields.

[0093]

[0112] To maximize detection efficiency, it is desirable to make the surface area of ​​the detection element 405 as large as possible so that substantially all of the area of ​​the objective lens array 240 (excluding the aperture) is occupied by the detection element 405. Additionally or alternatively, the diameter of each detection element 405 is substantially equal to the array pitch (i.e., the aperture array pitch described above with respect to the electrodes of the objective lens assembly 241). Thus, the diameter of each detection element may be less than about 600 μm, preferably about 50 μm to about 500 μm. As described above, the pitch may be selected depending on the desired distance between the sample 208 and the detector 240. In some embodiments, the outline of the detection element 405 is circular, but this can be square to maximize the detection area. The diameter of the substrate through-via 409 can also be reduced. The typical size of the electron beam is on the order of 5 to 15 micrometers.

[0094]

[0113] In one embodiment, a single detection element 405 surrounds each beam aperture 406. In other embodiments, multiple detection elements 405 are provided around each beam aperture 406. Electrons captured by the detection elements 405 surrounding one beam aperture 406 can be coupled to a single signal or used to generate independent signals. The detection element 405 can be divided radially. The detection element 405 can form multiple concentric annular sections or rings. The detection element 405 can be divided angularly. The detection element 405 can form multiple sector-shaped sections or segments. The segments may have similar angular sizes and / or similar areas. The electrode elements can be separated radially and angularly, or by any other convenient method.

[0095]

[0114] However, the larger the surface area of ​​the detection element 405, the greater the parasitic capacitance, resulting in a lower bandwidth. Therefore, it is sometimes desirable to limit the outer diameter of the detection element 405. This is especially true when a larger detection element 405 only slightly improves detection efficiency while significantly increasing capacitance. A circular (ring-shaped) detection element 405 can offer a good compromise between collection efficiency and parasitic capacitance.

[0096]

[0115] Increasing the outer diameter of the detection element 405 can lead to an increase in crosstalk (sensitivity to signals from adjacent holes). This may also be a reason to decrease the outer diameter of the detection element 405, especially if a larger detector element 405 only slightly improves detection efficiency while significantly increasing crosstalk.

[0097]

[0116] The electron current collected by the detection element 405 is amplified by an amplifier, such as a TIA.

[0098]

[0117] In one embodiment, the objective lens array 241 is a replaceable module, either on its own or in combination with other elements such as the control lens array 250 and / or the detector 240 and / or the beam shaping aperture array 262 and / or the sub-beamforming array 252. The replaceable module may be field-replaceable, i.e., the module can be replaced with a new module by a field engineer. In one embodiment, a plurality of replaceable modules are housed in a tool and can be exchanged between an operational position and a non-operational position without opening the electro-optical device 40.

[0099]

[0118] In one embodiment, the interchangeable module includes an electro-optical component, which may specifically be an electro-optical device, and is placed on a stage that can be operated for positioning the component. In one embodiment, the interchangeable module includes a stage. In one arrangement, the stage and the interchangeable module may be an integral part of the tool 40. In one configuration, the interchangeable module is limited to a stage and a device, such as the electro-optical device it supports. In one configuration, the stage is removable. In an alternative design, the interchangeable module including the stage is removable. A portion of the electro-optical apparatus 40 for the interchangeable module is separable, i.e., this portion of the electro-optical apparatus 40 is defined by a valve upstream and a valve downstream of the interchangeable module. These valves can be operated to isolate the environment between the valves from the vacuum upstream and downstream of the valves, respectively, thereby allowing the interchangeable module to be removed from the electro-optical apparatus 40 while maintaining the vacuum upstream and downstream of the portion of the electro-optical apparatus 40 associated with the interchangeable module. In one embodiment, the interchangeable module includes a stage. The stage is configured to support a device, such as an electro-optical device, with respect to the beam path. In one embodiment, the module includes one or more actuators. The actuators are associated with the stage. The actuators are configured to move the device with respect to the beam path. Such operation can be used to align the device and the beam path with respect to each other.

[0100]

[0119] In one embodiment, the interchangeable module is a micro-electromechanical system (MEMS) module. MEMS are miniaturized mechanical and electromechanical elements manufactured using microfabrication techniques. In one embodiment, the interchangeable module is configured to be interchangeable within the electro-optical device 40. In one embodiment, the interchangeable module is configured to be field-exchangeable. Field-exchangeable means that the electro-optical tool 40 can remove the module and replace it with the same or a different module while maintaining the vacuum within it. Only a portion of the electro-optical device 40 is ventilated, which corresponds to the ventilation of the module for the module to be removed and then returned or replaced.

[0101]

[0120] The control lens array 250 may be located in the same module as the objective lens array 241, i.e., it may form an objective lens array assembly or objective lens configuration, or it may be located in a separate module.

[0102]

[0121] In some embodiments, one or more aberration correctors are provided to reduce one or more aberrations in the subbeam. In any embodiment, one or more aberration correctors may be provided, for example, as part of an electro-optical device and / or as part of an optical lens array assembly and / or as part of an evaluation system. In some embodiments, each of at least a subset of aberration correctors is positioned at or directly adjacent to one of the corresponding intermediate foci (e.g., in or adjacent to the intermediate image plane). The subbeam has the smallest cross-sectional area in or near the focal plane, such as the intermediate plane. This provides more space for aberration correctors than is available elsewhere, i.e., upstream or downstream of the intermediate plane (or in alternative configurations without an intermediate image plane).

[0103]

[0122] In one embodiment, an aberration correction device positioned at or directly adjacent to the intermediate focal point (or intermediate image plane) includes a deflector for correcting electron sources 201 that appear to be in different positions for different beams. The correction device can be used to correct macroscopic aberrations from the electron sources that would interfere with good alignment between each sub-beam and the corresponding objective lens.

[0104]

[0123] Aberration correctors can correct aberrations that interfere with proper column alignment. Such aberrations can also lead to misalignment between the sub-beam and the corrector. For this reason, it may be desirable to position the aberration correctors additionally or alternatively near the condenser lens 231 (for example, each of such aberration correctors may be integrated with or directly adjacent to one or more of the condenser lenses 231). This is desirable because, near the condenser lens 231, the condenser lens is nearly perpendicular to or coincides with the beam aperture, so the corresponding sub-beam has not yet been shifted by the aberration. However, a challenge associated with positioning the correctors near the condenser lens is that each of the sub-beams has a relatively larger cross-sectional area and a relatively smaller pitch at this position than at further downstream (or beam downstream) positions. The aberration correction device may be a CMOS-based individual programmable deflector as disclosed in European Patent No. 2702595A1 or an array of multi-pole deflectors as disclosed in European Patent No. 2715768A2, the descriptions of beamlet manipulators in both of these documents are incorporated herein by reference.

[0105]

[0124] In some embodiments, each of at least a subset of aberration correction devices is integrated with or directly adjacent to the objective lens array 241. In some embodiments, these aberration correction devices reduce one or more of the following: field curvature, focus error, and astigmatism. Additionally or alternatively, one or more scan deflectors (not shown) may be integrated with or directly adjacent to the objective lens array 241 for scanning the sample 208 with evaluation subbeams 211, 212, and 213. In some embodiments, a scan deflector described in U.S. Patent Application Publication 2010 / 0276606 may be used, the entirety of which is incorporated herein by reference.

[0106]

[0125] A detector may comprise multiple parts, more specifically, multiple detection parts. A detector comprising multiple parts may be associated with one of the evaluation sub-beams 211, 212, and 213. Thus, multiple parts of a single detector 240 may be configured to detect signal particles emitted from a sample 208 in relation to one of the primary beams (which may otherwise be called evaluation sub-beams 211, 212, and 213). In other words, a detector comprising multiple parts may be associated with one of the apertures of at least one electrode of the electrodes of an objective lens assembly. More specifically, a detector comprising multiple parts 405 may be arranged around a single aperture 406, as shown in Figure 10, which provides an example of such a detector.

[0107]

[0126] As shown in Figure 10, the detector element 405, configured to define an aperture 406 and allow an electron beam to pass through, includes an inner detection portion 405A and an outer detection portion 405B. The inner detection portion 405A surrounds the aperture 406 of the detector. The outer detection portion 405B is radially outward from the inner detection portion 405A. The shape of the detector can generally be circular. Therefore, the inner and outer detection portions may be concentric rings.

[0108]

[0127] The present invention can be applied to various different tool architectures. For example, the electron-optical apparatus 40 may include multiple multi-beam electron-optical columns. The electron-optical columns may also include the electron-optical devices 41 described in any of the embodiments or aspects described above. As multiple electron-optical columns (or multi-column tools), the devices may be arranged in arrays that may have 2 to 100 or more electron-optical columns. The electron-optical apparatus 40 may take the form of the embodiments described and depicted in relation to Figure 4, or described and depicted in relation to Figure 5. The electron-optical columns may optionally include electron sources.

[0109]

[0128] As mentioned above, to enhance the contrast of electron beam inspection, the surface of sample 208 can be illuminated with light before inspection. This process may be called advanced charge control. Such illumination can excite electrons within sample 208. Such excited electrons within sample 208 are more likely to interact with collision electrons from the accompanying primary subbeam of the multibeam. As a result, such illumination can be used to further enhance the intensity of the signal particle signal. Light illumination can improve the contrast of the detected signal.

[0110]

[0129] Figure 11 shows an electron-optical apparatus for evaluating sample 208 using charged particles (e.g., electrons). The apparatus includes a backup electron-optical device 102, an evaluation electron-optical device 106, and a control system 500. The evaluation electron-optical device 106 may include an electron-optical device 41, for example, described with respect to Figures 2-6, as described elsewhere in this specification. The control system 500 controls the apparatus to perform various functions described later. The control system 500 includes, or may consist of, a controller 50 in any form already described with respect to Figure 1. The control system 500 may include a single unit configured to perform all control functions, or it may include a distributed system of units that can collectively achieve the required functions. The control system 500 may be implemented at least partially by computer. Any suitable combination of elements (e.g., CPU, RAM, data storage, data connectivity, sensors, etc.) can be provided and appropriately programmed to achieve some, or even all, of the specified functions. In this specification, a reference to an apparatus, device, or system being configured to perform a function includes cases where the control system 500 is configured to realize that function (for example, by being appropriately programmed to provide control signals that cause the function to occur).

[0111]

[0130] In one embodiment, exposure of a target region includes flood exposure. The pre-electro-optical device 102 may include a flood column configured to provide flood exposure. Figure 11 shows an exemplary configuration of a flood column in the pre-electro-optical device 102, but other electro-optical designs of the flood column may also be used. In this example, the flood column includes a charged particle source 301, a condenser lens 320, a blanker electrode 330, an objective lens 340, and an aperture body 350. The flood column may also include additional components for manipulating the pre-charged particle beam 302, such as a scanning element (not shown) and a field lens (not shown). The components of the flood column may be arranged substantially along the axis 304.

[0112]

[0131] The charged particle source 301 may be an electron source. The charged particle source 301 may include a charged particle emission electrode (e.g., a cathode) and an accelerating electrode (e.g., an anode). Charged particles are extracted or accelerated from the charged particle emission electrode by the accelerating electrode to form a pre-charged particle beam 302. The pre-charged particle beam 302 may propagate along a pre-beam path 302. The pre-beam path 302 may include the axis 304, for example, in situations where the pre-charged particle beam 302 is not deflected away from the axis 304.

[0113]

[0132] The condenser lens 320 is positioned downstream of the beam of the charged particle source 301; that is, the condenser lens 320 is positioned downstream of the beam with respect to the charged particle source 301. The condenser lens 320 can focus or defocus the pre-charged particle beam 302. As shown in Figure 11, the condenser lens 320 can be used to collimate the pre-charged particle beam 302. However, the condenser lens 320 can also be used to control the pre-charged particle beam 302 to generate a divergent or convergent beam.

[0114]

[0133] The aperture body 350 may be positioned downstream of the condenser lens 320. The aperture body 350 may pass through a portion of the charged particle beam propagating along axis 304, i.e., only a portion and not the entire beam. The aperture body 350 may limit the lateral range of the pre-charged particle beam 302, as shown in Figure 11. The aperture body 350 may be used to selectively block the pre-charged particle beam 302, preventing any portion of it from passing through. The aperture body 350 may define an aperture. If the lateral range (or diameter) of the pre-charged particle beam 302 is greater than the lateral range (or diameter) of the aperture, only a portion of the pre-charged particle beam 302 will pass through the aperture. Therefore, the aperture body 350 may function as a beam-limiting aperture by limiting the lateral range of the pre-charged particle beam 302.

[0115]

[0134] The blank electrode 330 can be positioned downstream of the condenser lens 320 and upstream of the aperture body 350. The blank electrode 330 can selectively deflect the pre-charged particle beam 302, for example, by deflecting it away from the axis 304. The blank electrode 330 can deflect the pre-charged particle beam 302 away from the opening of the aperture body 350, for example, toward a portion of the aperture body 350 that does not have an opening, so that no portion of the pre-charged particle beam 302 passes through the opening defined by the aperture body 350. The blank electrode 330 can block the beam so that it does not pass through the opening of the aperture body 350. However, the combination of the blank electrode 330 and the aperture body 350 can also be used to selectively block the pre-charged particle beam 302, that is, to selectively prevent at least a portion of the pre-charged particle beam 302 from passing through the aperture of the aperture body 350. In other words, the combination of the blank electrode 330 and the aperture body 350 can selectively control the proportion of the pre-charged particle beam 302 that passes through the aperture.

[0116]

[0135] The objective lens 340 is positioned downstream of the beam in the aperture body 350. The objective lens 340 can focus or defocus the pre-charged particle beam 302. As shown in Figure 11, the objective lens 320 can be used to control the pre-charged particle beam 302 to produce a divergent beam, thereby increasing the spot size on the sample 208 and increasing the area on the surface of the sample 208 that becomes flooded with charged particles. A more divergent beam can produce a beam spot with a larger field of view on the sample. However, in some situations, the objective lens 340 can be used to control the pre-charged particle beam 302 to produce a converged beam, thereby focusing the pre-charged particle beam 302 onto the sample 208. A more converged beam can produce a beam spot with a smaller field of view on the sample.

[0117]

[0136] In one embodiment, the evaluation electro-optical device 106 exposes the sample 208 with a multibeam of charged particles, where the multibeam contains multiple individual beams of charged particles. The example in Figure 11 shows a multibeam containing three individual beams, but in reality, the multibeam can contain tens, hundreds, or even thousands of beams.

[0118]

[0137] In one embodiment, the evaluation electro-optical device 106 includes an electro-optical device 41. The electro-optical device 41 can take any form already described with respect to Figures 3-7, for example, with respect to an array of electro-optical elements adjacent to the sample 208, such as an objective lens array 241 or a detector array 240. In one embodiment, the evaluation electro-optical device 106 includes an objective lens and includes multiple objective lenses for different beams of the evaluation charged particle beam. In a particular example of Figure 11, the evaluation electro-optical device 106 corresponds to, operates in, and / or takes any form already described with respect to Figure 3. During the evaluation of the sample 208, the electro-optical device 41 is used to direct charged particles onto the sample 208 and to detect signal charged particles from the sample 208.

[0119]

[0138] In one embodiment, the electro-optical apparatus is for evaluating a sample at an evaluation position. In Figure 11, the evaluation position is located below the evaluation electro-optical device 106. As shown in Figure 11, in one embodiment, the electro-optical apparatus includes an evaluation charged particle optical device 106, a backup charged particle optical device 102, and a light stimulation module 70, which in the configuration may take the form of light sources as depicted in Figure 11, for example. The evaluation charged particle optical device 106 is configured to project evaluation charged particle beams 211-213 along the evaluation beam path to the evaluation position. The evaluation charged particle beams are for evaluating a sample 208 at the evaluation position. The backup charged particle optical device 106 is configured to project a backup charged particle beam along the backup beam path. The backup charged particle beams are for preparing a sample for evaluation.

[0120]

[0139] The light stimulation module 70 is configured to generate light for light stimulation of the illuminated surface. The light stimulation module 70 may be included in an advanced charge control module, such as an ACC module. The light stimulation module 70 may be part of a projection system (i.e., an optical projection system) for illuminating the sample before evaluation of at least a portion of the sample. For example, the light source depicted in Figure 11 may irradiate the sample with a light beam.

[0121]

[0140] When the electron beam scans sample 208, a large beam current can cause charge to accumulate on sample 208, which can affect image quality. The optical stimulation module 70 can direct light 71 towards sample 208 to control the accumulated charge due to effects such as photoconductivity, the photoelectric effect, or the thermal effect.

[0122]

[0141] In one embodiment, the optical stimulation module 70 includes a light source, such as a laser light source. Laser light is coherent. However, other types of light sources can be used as alternatives. In one embodiment, the laser light source is generally configured to emit light having a wavelength in the range of 400 nm to 850 nm, preferably 450 nm to 800 nm, in the optical path 71. The selected wavelength may correspond to the wavelength absorbed by the material of the sample 208 into which the light is incident. The selected wavelength may have a tendency to excite electrons in the sample 208 when the light is incident on the sample 208.

[0123]

[0142] By irradiating sample 208 with light 71, the defect contrast is significantly improved. This technique, which may be called voltage contrast, can be used to measure whether there is a proper electrical connection between the contact and the substrate of sample 208. Depending on the secondary electron yield (<1 or >1), a reverse diode is formed by contact with an N+ or P+ doped region on the substrate. As a result, it may be impossible to distinguish between a proper electrical connection and a poor electrical connection for either the N+ contact or the P+ contact. By irradiating sample 208 with light 71 (ACC), the reverse diode becomes conductive. As a result, the contact will not be charged if there is a proper electrical connection between the contact and the substrate, but will be charged if the electrical connection is poor.

[0124]

[0143] The evaluation electro-optical device 106 may have a field of view. During sample evaluation, the field of view may be the region on the surface of the sample 208 into which electrons projected by the evaluation electro-optical device 106 can be incident. The field of view may be up to 1 mm, e.g., 5 mm, e.g., 10 mm, or even 20 mm. The evaluation electro-optical device 106 may have a large field of view. Since one or more elements of the electro-optical device, e.g., plates that can form electrodes of a lens array, may be contained within each substrate, e.g., silicon, the plate forming the most downstream surface of the device may be larger than the beam grid within the surface region. The working distance between the evaluation electro-optical device 106, e.g., the opposing surface of the evaluation electro-optical device 106 and the sample 208 may be limited for electro-optical reasons disclosed herein with respect to Figures 2-5, e.g. (e.g., having a maximum value in the range of 10-100 micrometers, as described above). These dimensions may create a gap that is limited in height (or along the direction of the beam path) or low (e.g., narrow) and wide (e.g., across or even perpendicular to the beam path). The gap may be considered narrow and wide. The gap may have a limited or restricted aspect ratio, i.e., the ratio of height (e.g., along the direction of the charged particle beam path) to width (e.g., the field of view of the beam grid). The dimensions of the gap may make it difficult to photonically illuminate the sample (or use ACC) to photostimulate the sample.

[0125]

[0144] One embodiment of the present invention is expected to realize optical stimulation (for example, an ACC by an electro-optical architecture of an evaluation electro-optical device 106, wherein the bottom surface (or opposing surface) of the device has a small displacement (i.e., a small gap) from the sample 208 and can have a large field of view).

[0126]

[0145] In one embodiment, contacts with poor electrical connection to the substrate before evaluation are charged by the backup electro-optical device 102. To ensure that both N+ and P+ contacts with proper electrical connection are not charged, the sample 208 may be illuminated by the light source 70 before evaluation. This can be done during (e.g., flooding) or after the projection of the backup beam. Since illumination with the light beam is performed before evaluation, the small gap between the evaluation electro-optical device 106 and the sample 208 is not a major issue. The light source 70 may be part of the backup electro-optical device 102, but may not be part of the evaluation electro-optical device 106.

[0127]

[0146] By controlling the incident energy of the electrons in the preliminary electron beam, poorly connected contacts can be positively or negatively charged. During evaluation, poorly connected contacts become further charged, and in addition, contacts connected to diodes with proper electrical connections but in the reverse direction become further charged. In one embodiment, the charging during the projection of the preliminary electron beam and the projection of the evaluation electron beam are in the same direction, for example, by projecting a preliminary electron beam with the same incident energy as the evaluation electron beam.

[0128]

[0147] During the projection of the preliminary electron beam (e.g., during flooding), the defective contacts are charged, the "reverse diode" contacts are charged, and the "current-carrying diode" contacts remain discharged. During the projection of light 71, the defective contacts remain charged, the "reverse diode" contacts are discharged, and the "current-carrying diode" contacts remain discharged. During the projection of the evaluation electron beam, the defective contacts become even more charged, the "reverse diode" contacts become charged, and the "current-carrying diode" contacts remain discharged. It may be possible to distinguish between the further charged defective contacts and the simply charged "reverse diode" contacts. By projecting the preliminary electron beam and the light beam, it becomes easier to distinguish between good and bad contacts. It may not be necessary to project the light beam simultaneously with the evaluation electron beam.

[0129]

[0148] When the use of optical stimulation, such as ACC, is essential for the application of a specific voltage contrast, embodiments of the present invention are expected to improve throughput by enabling the use of optical stimulation (e.g., ACC) in relation to devices with a large field of view and a small gap with sample 208.

[0130]

[0149] In one embodiment of the present invention, a preliminary electro-optical device 102 projects a preliminary beam onto the sample 208 before evaluation to charge contacts in the sample 208 that have poor electrical connections with the sample 208 (which may be called bad contacts). During or immediately after flooding, for example, between the preliminary location where the preliminary electro-optical device 102 projects a preliminary beam onto the sample 208 (e.g., flooding) and the evaluation location where the evaluation electro-optical device 106 is used to evaluate the sample 208, the sample 208 may be illuminated with light 71 suitable for ACC. This may help ensure that contacts with sound electrical connections (which may be called good contacts) are not charged.

[0131]

[0150] In one embodiment, the pre-charged particle optical device 102 is configured to project a pre-charged particle beam 302 while the photostimulation module 70 is projecting light 71 toward the illumination position. The projection of the pre-electron beam and the projection of light 71 may be performed in parallel. Alternatively, one may be performed after the other, or their periods may partially overlap.

[0132]

[0151] In one embodiment, the optical stimulation module 70 is associated with a pre-charged particle optics device 102. In another embodiment, the optical stimulation module 70 is integrated with the pre-charged particle optics device 102. Alternatively (or even additionally), in another embodiment, the optical stimulation module is associated with an evaluation-grade charged particle optics device. In another embodiment, the optical stimulation module 70 is integrated with the evaluation-grade charged particle optics device. Optical simulations using the optical stimulation module described below can be an alternative to flood exposure using a pre-charged particle optics device. Optical stimulation may be performed at the evaluation location using a charged particle device including the optical stimulation module, for example. In another embodiment, the optical stimulation module may be provided within an evaluation-grade charged particle optics device that does not have a pre-charged particle optics device, preferably requiring only the evaluation-grade charged particle device, for example, such an evaluation setup includes the optical stimulation module 70 and does not have a pre-charged particle optics device. In other cases, optical simulations using the optical stimulation module 70, as described below, can be performed in addition to flood exposure using a pre-charged particle optics device. Light stimulation at the evaluation site may be desirable for some use cases that require evaluation during or immediately after light stimulation.

[0133]

[0152] In one embodiment, optical stimulation is performed using stimulating light 71 having a wavelength in the range of 400 nm to 850 nm, preferably 450 nm to 800 nm. The selected wavelength may correspond to the wavelength absorbed by the material of sample 208. The selected wavelength may have a tendency to excite electrons in sample 208 when the light is incident on sample 208, for example, in the optical path. The selected wavelength is chosen such that the photons of the stimulating light have an energy at least the same as, preferably greater than, the band gap of the sample. Light of a wavelength selected to simulate a portion of the sample may be called stimulating light. The stimulating light can be provided throughout the entire evaluation process, and it is not necessary to modulate the intensity of the stimulating light or synchronize it with the excitation of the charged particle beam. The power demand for optical stimulation is not particularly high, and therefore, power consumption problems or undesirable heating are unlikely to occur. If the stimulating light cannot be precisely directed to the desired position, it is possible to broaden the beam and increase the output. The power density of the optical beam is 10 to 1000 mW / mm². 2 It can be on the order of this range. For a beam grid with a field of view of 20 mm on the sample surface, the magnitude of the applied power can be on the order of 50 to 5000 mW.

[0134]

[0153] One embodiment of the present invention provides a planar optical system for advanced charge control in a charged particle device, for example, as shown and described in Figures 3-5 and 11. Such a charged particle device may be included in a charged particle system, such as an evaluation system. One or more electrostatic elements of the charged particle device may be called MEMS elements. The charged particle system may be called a multibeam system, configured to project multiple charged particle beams onto a sample for evaluation, such as inspection of at least a portion of the sample's surface. Such a charged particle system is called a multibeam inspection system (or MBI system). The present invention may be embodied in an optical stimulation module 70, as described below. The optical stimulation module 70 may be a substitute for or added to the optical stimulation module 70 as shown and described in Figure 11.

[0135]

[0154] For voltage contrast, the use of Advanced Charge Control (ACC) is highly desirable. For example, defect contrast is significantly improved by illuminating the sample with a light beam 71 using, for example, an optical stimulation module, while performing sample evaluation (i.e., electron beam defect inspection). The ease of defect identification is improved by using advanced charge control techniques. A charged particle system in which ACC is implemented has a macroscopic objective lens as part of the optical system, such as an optical stimulation module. Such a lens has a working distance sufficient to direct the light beam 71 onto the sample within the gap between the sample 208 and the opposing surface of the charged particle device 41. Typically, the working distance is at least several millimeters, e.g., 1-10 mm, e.g., 5 mm or more. Also, the field of view of such an optical system is limited to <10 or 50 micrometers.

[0136]

[0155] In a charged particle system including an objective lens array (shown and described in Figures 3-5 and 11, which may be called a MEMS-based system), the working distance may be less than 500 micrometers, e.g., less than 100 micrometers, e.g., in the range of 10-70 micrometers, e.g., only 50 micrometers. The field of view may be approximately 3 mm, 5 mm, 10 mm, or 20 mm. Light directed into such a gap will have difficulty reaching the portion of the sample into which the beam grid is incident and absorbed, i.e., the portion where the light is intended to be absorbed. The angle of illumination of light into the gap may, for example, with respect to the normal to the sample surface, be such that below this angle, the illuminated light may exceed an angular threshold below which it can be absorbed by the material, i.e., the material of the sample; at angles exceeding this angular threshold, most, if not all, of the light will be reflected. Alternatively, the threshold may correspond to small angles with respect to the sample surface below which most, if not all, of the light is reflected (i.e., not absorbed). Known methods are clearly unusable in such a charged particle system with an objective lens array.

[0137]

[0156] Transmitting light onto a sample under inspection using a stack of planar elements including an electro-optical array is not a simple task due to the extremely small working distance. Several proposals have been made to guide laser light through this gap and utilize total internal reflection to illuminate a portion of the sample surface with stimulating light. Such a portion of the sample surface may have a larger surface area than the aperture array on the opposite side of the stack. (The field of view or cross-section of such an optical path on the sample surface may have dimensions corresponding to the field of view of the beam grid through the aperture array, or dimensions across the aperture array, e.g., 20 mm.) While these solutions are functional, they result in power loss due to reflection, impose a thermal load on the detector, and require specific assumptions about the sample under inspection (e.g., reflectivity, planarness). In particular, the sample may have a lattice-like topology, which completely changes the assumed reflection angles. In other solutions, the stimulating light is irradiated through a beam aperture. However, because the beam aperture required for the desired electro-optical performance of the charged particle system is very small, the stimulating light diffracts, which also results in undesirable light loss. Such diffracted light can cause undesirable heating at other undesirable locations within the charged particle device 41.

[0138]

[0157] It has been proposed to add layers for transmitting light, such as stimulating light, through total internal reflection within the layer, or within a waveguide incorporated into the laminate, or within a waveguide incorporated entirely within a separate integrated optical system (IO, also called integrated photonics) layer. The layer for transmitting light (i.e., the optical transport layer) provides photonic illumination compatible with the laminate. The layer may be called a planar optical component.

[0139]

[0158] Three embodiments of this configuration are described below and schematically shown in Figures 12-14. Note that the features may be used as alternatives or in combination as desired. The laminate may include two or more optical transmission layers of different embodiments.

[0140]

[0159] In one embodiment, a light guide plate 501 in a bottom element (or sample-facing element), for example as a layer of elements in a laminate 502, is shown in Figure 12. The layer may be planar or in the form of a slab, which is an embodiment of a planar optical member, for example. The layer may be called a slab waveguide. An additional layer that transmits visible wavelengths (either as part of an element having another function or as another element) guides the stimulating light and couples it to free space toward the sample using an output coupling mechanism such as an aperture (such as a hole) or recess (such as a dimple 503) on the surface of the additional layer.

[0141]

[0160] Since the additional layer is part of the laminate, multiple apertures may be defined within the layer to allow the charged particle beam from the beam grid and, optionally, signal particles from sample 208 to pass through. The location of aperture 504 within the layer may be the same as that of the element in which the additional layer forms part and / or other elements of the laminate. Thus, the slab waveguide can be described as having through-holes 504 (or apertures) for the passage of the charged particle beam to and from the sample.

[0142]

[0161] The thickness of the additional layer is generally several wavelengths, and total internal reflection is utilized to guide the light. However, thicknesses close to the wavelength can also be conceivable, as this can still guide light, but in that case, it is done not through total internal reflection, but by single-mode or several-mode slab-mode waveguide through refractive index contrast with the surroundings. Output coupling mechanisms such as holes and / or dimples can disrupt this total internal reflection and / or guide light locally. The light can be directed by reflection, diffraction, and / or scattering to a sample under inspection outside the slab waveguide, for example, a surface topography having regions that reflect light and direct it towards the sample, and such regions may have a sawtooth topography (or shape). Other types of output coupling mechanisms include micromirrors (which may include parabolic micromirrors) and microlenses that can be formed by focused ion beam milling or 3D printing. For example, such surface topography having regions for reflecting light is disclosed in International Publication No. 2022228943, which is incorporated into this application by reference to the extent that such surface topography is disclosed.

[0143]

[0162] The output coupling mechanism can be configured to direct the stimulating light 71 to coincide with (i.e., incident at the same location and / or time as) the charged particle beam on the sample.

[0144]

[0163] Preferably, to stimulate the sample material, the stimulating light is incident on a portion of the sample surface at the same time as, i.e., simultaneously with, the accompanying charged particles. In some cases, illumination immediately before the incidence of the charged particle beam may be effective. Preferably, the stimulating light is incident at the same location as each charged particle beam. The incident illumination (e.g., stimulating light) is preferably extended over the portion of the sample surface that will be scanned by the charged particle beam. Illumination of a portion of the sample surface may be started before that portion is scanned by the charged particle beam. Illumination may continue after that portion has been scanned by the charged particle beam (although it may be desirable to stop the illumination as soon as that portion has been scanned by the charged particle beam). Preferably, the scanning of a portion of the sample surface by the charged particle beam takes place during the photonic illumination of that portion.

[0145]

[0164] The field of view of the charged particle beam is less than 50 nm, e.g., less than 20 nm, e.g., less than 10 nm; however, the charged particle beam is continuously scanned with respect to the sample surface. For example, the charged particle beam may be scanned electrostatically, e.g., using a scan deflector, over a range of less than 10 micrometers, e.g., less than 5 micrometers, e.g., less than 1 micrometer in the scanning direction. The sample may be continuously scanned electrostatically and / or mechanically by scanning the stage, and thus the sample, in a direction different from the scanning direction of the stage. Such mechanical scanning may be performed by continuously scanning the sample with respect to the path of the beam grid (i.e., the charged particle device 41), or by scanning the sample with respect to the path of the beam grid between a series of steps of the sample with respect to the path, e.g., in a direction different from the scanning direction of the stage.

[0146]

[0165] Therefore, the incident point of the light beam, such as the light spot, preferably has dimensions larger than the electrostatic scanning range of the beam, for example, its diameter, which is, for example, larger than 1 micrometer, even 5 micrometers, or even 10 micrometers. The portion of the sample surface onto which the light beam (e.g., the light spot and / or the stimulating light as, for example, the light beam) is incident should have a cross-sectional area larger than the area scanned by the electron beam. This ensures that the material of the sample scanned by the charged particle beam is stimulated.

[0147]

[0166] Having a light spot cross-sectional area much larger than the cross-sectional area of ​​the charged particle beam is inefficient, though not an obstacle, and undesirable. Excessive exposure of the sample surface to the stimulating light is a thermal load. In some embodiments, there is a light spot for each charged particle beam in the beam grid. Therefore, the surface area of ​​the sample illuminated by the stimulating light is limited compared to known systems. Such a known system is disclosed in European Patent Application Publication No. 21171331.8, filed on 29 April 2021, which describes illuminating the entire sample surface to which a charged particle beam of a beam grid is incident, having cross-sectional areas that can be several millimeters, e.g., 1 to 20 mm, in different directions. (The entire sample surface may face the opposing surface of an electro-optical device, where an array of apertures is defined to allow the charged particle beam of the beam grid to pass through.) In the case of a light spot of 5 micrometers and a beam grid pitch of 50 micrometers according to the present invention, the thermal load can be reduced by up to two orders of magnitude (1 / 100) compared to illuminating the entire sample surface to which the charged particle beam of the beam grid is incident. Therefore, although the field of view of individual light spots is limited, the effective field of view of all the light spots of the stimulating light is at least the same size as, and preferably larger than, the field of view of the beam grid in the sample.

[0148]

[0167] While it is desirable, but not always, to illuminate the sample surface with stimulating light during scanning with each charged particle beam on the sample surface, this is not always necessary. As disclosed in European Patent Application Publication No. 22201416.9, filed October 13, 2022, stimulating light may illuminate a portion of the sample surface before the incidence of each charged particle beam. Preferably, the time between the cessation of illumination with stimulating light and the incidence of the charged particle beam should be short, i.e., as short as possible. Such a time can be in milliseconds or microseconds and may depend on the use case, the material being inspected, and any defects in the material in the area being inspected.

[0149]

[0168] Unless otherwise noted, other embodiments having the same features as the embodiments described above are shown in Figure 13. In these embodiments, light, for example, stimulating light, is output coupled at the bottom of the stack 502, preferably from a planar optical member. Elements within the laminate configured to face the sample, such as the bottom of the laminate, may include planar optical members such as optical waveguides, for example, integrated photonic waveguides, to guide the light. Such elements may be detectors, for example, detector arrays or electrode plates. For example, a layer of elements (e.g., another layer 505) may provide at least a portion of the facing surface of the laminate. The layer may include optical waveguides, for example, integrated photonic waveguides. Layer 505 may be left exposed, for example, so as not to cover some elements having electro-optical functions, such as the detection elements in the detector area. Layer 505 may have a volume sufficient to accommodate the optical waveguide. Layer 505 may be an integrated optical layer used for (1) waveguide routing and (2) coupling light from the waveguide to free space to illuminate the sample under inspection.

[0150]

[0169] The integrated optical system layer may include waveguide routing for routing the waveguide, for example, along a routing path, or through a grid between detection elements. The integrated optical system may include output couplers, such as diffraction grating couplers, for outcouple light from the waveguide routing. The integrated optical system layer may include an optical system (which may also be called an optical circuit), for example, waveguide routing and / or output couplers. The integrated optical system layer has a high refractive index layer. The high refractive index layer has upper and lower cladding with lower refractive indices to allow for the confinement and guidance of light into the waveguide.

[0151]

[0170] Figure 15 is an enlarged cross-sectional view of the embodiment shown in Figure 13. This enlarged cross-sectional view shows the elements that are detectors with defined apertures (unnumbered). As shown, the detection element 405 is located on the surface, adjacent to the aperture defined on the bottom surface of the substrate. Further outward from the aperture on the bottom surface, there is a layer 505, for example, as an integrated optical system layer. Figure 16 is a schematic diagram of the bottom surface of the detector showing the detection element 405 and the integrated optical circuit. The integrated optical circuit may be a type of optical system having a waveguide 508, a power divider 509, and a diffraction grating coupler 507 (or more generally, an output coupler).

[0152]

[0171] The integrated optical system (IO) layer includes an input coupler (not shown), a waveguide 508, a power divider 509, and an output coupler 507. The input coupler couples light from, for example, a fiber to the waveguide. The input coupler may be a diffraction grating coupler. The waveguide 508 transmits light. The power divider 509 directs the light to a plurality of output couplers 507, such as diffraction grating couplers. The output couplers 507 couple the light exiting the waveguide 508 into free space and to the sample 208 under test. The diffraction grating coupler (as an input coupler or output coupler) can accommodate multiple wavelengths.

[0153]

[0172] Light can be coupled from a fiber to a waveguide in various ways, such as edge coupling, diffraction grating coupling, and micromirrors. In edge coupling, the fiber is placed in close proximity to the waveguide in series. In diffraction grating couplers, light is coupled from the fiber to the waveguide. Micromirrors redirect the light from the fiber and focus it into the waveguide.

[0154]

[0173] Various configurations are known for splitting integrated optical waveguides, such as Y-splitters, multimode interferometers (MMIs), and directional couplers.

[0155]

[0174] As an alternative to diffraction grating couplers, mirrors can be fabricated at the ends of waveguides using focused ion beam (FIB) cutting, or 3D printed into etching holes, to direct light onto the sample surface. While fabricating such mirrors requires more effort, it allows for easier selection of illumination wavelengths, or more freedom (less restriction) in selecting the wavelength of the stimulation light. Mirrors are inherently broadband and unresponsive to wavelength, while diffraction grating couplers are dispersive and highly sensitive to wavelength.

[0156]

[0175] An integrated optical layer (or more generally, a planar optical element) can be fabricated on a sacrificial wafer. The integrated optical layer can be fixed to a stack of electro-optical elements. Since such electro-optical elements can be fabricated using MEMS processing techniques, the stack may be called a MEMS stack. The stack (e.g., a MEMS stack) may be one embodiment of the stack disclosed herein. The stack may exist such that the integrated optical layer can be fixed by adhesive bonding to an existing stack. The integrated optical layer can be fixed to elements such as planar electro-optical elements, such as electrodes. In one embodiment, the integrated optical layer may be fixed to a planar electro-optical element including a CMOS, such as a detector, for example, the integrated optical layer may be fixed to the surface of a planar electro-optical element on which a CMOS layer may be provided. In a different embodiment, the planar electro-optical element may be fixed to a side of the electro-optical element that does not have a CMOS layer, or to both sides of the electro-optical element. The integrated optical layer may be fixed to a detector array including CMOS elements, for example, around the detection elements of the detector array (for example, by adhesive bonding). The side of the electro-optical element providing the detection elements may be bonded to the surface of the CMOS layer. Sacrificial wafers can be removed by known techniques such as etching, fracturing, chemical mechanical polishing (CMP), or wafer thinning. Examples of bonding integrated optical layers operating at telecommunications wavelengths (1300-1600 nm) include the InP-membrane-on-Si (IMOS) platform from TU / e, or the WIPE project from TU / e. (For a simple example of the bonding process, see https: / / photonics-benelux.org / wp-content / uploads / pb-files / proceedings / 2018 / 39.pdf). To avoid (i.e., circumvent) the metal-containing detection elements, the integrated optical layer extends beneath the detection elements, particularly the metallic features of the detection elements, or the integrated optical layer is spaced away from the detection elements. For example, the waveguide routing path within the integrated optical layer passes between the detection elements, as shown in Figures 15 and 16. For example, the integrated optical layer may be formed within the substrate of the detector. Thus, the integrated optical layer avoids the metal of the detector, preferably the entirety.The bonding is described in relation to the integrated optical layer, but it should be noted that other types of planar optical components can similarly be fixed to the elements of the laminate.

[0157]

[0176] The integrated optical system layer can be mounted on a support substrate located within the laminate (or incorporated elsewhere). As described later, the support substrate may have electro-optical functions within the laminate.

[0158]

[0177] Materials that can form waveguides include, but are not limited to, SiO, SiN, and AlO. Waveguides can be formed by known processes using only a few lithography steps. Output couplers, such as diffraction gratings, may be formed by etching, and optionally, the trenches created by etching may be filled with materials of different refractive indices. Various waveguide structures, such as tree-like structures, can be created using dividers with various different division ratios. Waveguides can be formed in layers with other functional devices or structural properties.

[0159]

[0178] Another embodiment, unless otherwise noted, may have the same features as the embodiments described above and is shown in Figure 14. In this embodiment, stimulating light is output coupled from a planar optical element (or plate or planar optical member) and then passes through an aperture for a charged particle beam in the bottommost element of the laminate 502 shown in Figure 14. The planar optical element is here another layer 506 separated from the electro-optical elements of the laminate, thereby the planar optical element is itself an element of the laminate 502. Optionally, the planar optical element may be separated from other elements of the laminate 502, such as planar elements.

[0160]

[0179] In configurations such as that shown in Figure 14, additional optical elements may be provided to assist the propagation of stimulating light through apertures in elements of the laminate that are below the planar optical elements (i.e., closer to the sample), rather than the bottommost element of the laminate, such as a photonic integrated circuit. For example, the sides of the apertures may be treated or coated to reduce the absorption of stimulating light. Alternatively or additionally, one or more light guide structures (which may be waveguides of the type such as porous optical fibers) may be provided in and / or adjacent to each aperture, preferably without adversely affecting the electric field around the sub-beam path through the apertures. These light guide structures direct light from the planar optical elements, such as a photonic integrated circuit, to a portion of the sample surface, for example, a region of interest on the sample during evaluation, e.g., inspection. The light guide structures may include end faces, which may be within each aperture and, for example, provide at least a portion of the aperture surface through the elements of the laminate. Optical elements may be provided at the inlet and outlet of the aperture in the beam-downstream elements of the laminate, and / or at the end faces of the light guide structure, for guiding the stimulating light into and out of the aperture, for example, toward the sample. It is desirable that any optical elements provided in the aperture of the laminate do not obstruct or alter the passage of the electron beam through such aperture.

[0161]

[0180] To prevent interference with the electron beam as it is projected onto the sample, such optical features that are not part of the lowest element of the stack can be placed in a field-free region (i.e., a region without an electric field). Such a field-free region can be located upstream (or above) the objective lens 241 in any of the configurations shown in Figures 3-7, for example, between lens arrays 241 and 250 or above the control lens array 250. In such a configuration, the photonic integrated circuit and the light guide structure (such as a vacant optical fiber) are positioned upstream (e.g., above) the electrode stack. Scattering of light from the light guide element (such as a vacant fiber) can occur on downstream elements of the stack, such as plates or elements. To suppress scattering, the end faces of such light guide elements can be shaped to improve light delivery. For example, the end of a fiber can be shaped as a lens to reduce beam divergence within the limited available space. Such a lens feature may be the rim at the end of a vacant fiber.

[0162]

[0181] The optical planar element can be fixed to an adjacent element in the laminate via a spacer in which an aperture for the path of the charged particle beam of the beam grid is defined. This configuration differs from embodiments in which the integrated optical layer (or integrated optical system layer) is included within other elements of the laminate, such as a detector, for example by bonding the integrated optical system layer to the bottom element of the laminate (e.g., the detector). This configuration proposes that the integrated optical system layer, as a planar optical element such as an integrated optical element, is positioned upstream of the beam along the path of the charged particle beam of the beam grid (e.g., above the bottom element of the laminate 502). Light is coupled from the integrated optical system onto the sample through the aperture of the bottom element for the charged particle beam of the beam grid.

[0163]

[0182] The materials that can be used to form planar optical components are not limited. Such materials may include any material that sufficiently transmits the stimulating light, such as glass, plastic, quartz, or SiOx, and may depend on the selected wavelength for the stimulating light. It is desirable that the material has a relatively high refractive index at the wavelength of the stimulating light. The waveguide may be formed using two media with different refractive indices, one relatively high and the other relatively low at the wavelength of the stimulating light, with the lower refractive index material surrounding the higher refractive index material. The lower refractive index medium may be the environment surrounding the waveguide, such as air or a vacuum. Preferably, the material has low gas emission in a vacuum.

[0164]

[0183] It should be noted that the stimulating light may be selected depending on the material to be stimulated, preferably a semiconductor such as silicon or germanium that can be doped. As mentioned above, the stimulating light may have a wavelength corresponding to a photon energy greater than the band gap of the sample.

[0165]

[0184] Stimulating light can be coupled (input coupled) to a planar optical member by various types of input couplers and methods. For example, the input coupler may be a diode mounted on or incorporated within the rim (or edge) of the planar optical member. The input coupler may be provided by an input coupling mechanism such as a diffraction grating and / or relief feature on the main surface of the planar optical member. The input coupler may include, may include, or may cooperate with, an optical fiber or a prism. The input coupler may include a combination of two or more of these different features.

[0166]

[0185] Unless otherwise suggested by the context, the term “plate” is used herein to refer to a self-supporting structure that may comprise multiple layers. The layers of a plate may be functional, structural, or both, such as electrodes or integrated optical systems.

[0167]

[0186] The laminates disclosed herein in relation to the present invention may comprise at least one element, more typically a plurality of elements such as a plate which may be planar. The elements may comprise at least one detector, e.g., a detector array of detection elements, a beam shaping aperture array, one or more electrodes of a lens array, an active compensator array (e.g., comprising a plurality of apertures which may be associated with each beam or group of beams of a beam grid), or any other electro-optical elements. Such elements may be, for example, the objective lens array 241, deflector array, beam shaping array 262, control lens array 250, sub-beamforming array 252, scan deflector 260, etc., as shown and described in any of the drawings of this application, such as Figures 3-5 and 11, or otherwise associated therewith.

[0168]

[0187] Depending on the various embodiments, a planar optical member, which may be a light guide plate or a layer such as the integrated optical system layer 505, can be formed in a layer of any element of the laminate, such as electrodes of a detector, aperture array, or lens array. The element of the laminate in which the planar optical member may be formed can function as a support substrate for the planar optical member. Additionally or alternatively, the planar optical member is an element isolated from other elements of the laminate (such as another layer 506). In some embodiments, the planar optical member is the most beam-upstream element of the laminate and / or, for example, within the field-free region of the laminate during operation. Such a planar optical member may be positioned beam-upstream at the bottom of the laminate, for example beam-upstream at the bottom of a charged particle device, or beam-upstream (e.g., above) of an objective lens array. In these configurations, light may be input-coupled to the planar optical member using one or more optical waveguides, such as optical fibers or input-coupled waveguides, which will be described later herein with respect to embodiments shown in Figures 19 and 20.

[0169]

[0188] In one configuration, an input coupled optical waveguide (or a plurality of waveguides) may directly output couple light to the surface of the sample under inspection. Compared to the disclosure of European Patent Application Publication No. 21171331.8, filed on 29 April 2021, the input coupled optical waveguide may have its waveguide ends positioned close to the elemental lamination within a vacuum chamber, thereby output coupling light to the gap between the sample and the opposing surface of the charged particle device 41, i.e., the opposing surface of the lamination. The input coupled waveguide may be a single waveguide branching to have multiple ends, or a plurality of waveguides, each having one or more ends. The waveguide ends may be positioned along the periphery of the lamination, for example, at equal intervals around the periphery of the lamination. In one configuration, the waveguide may pass through the opposing element of the lamination (i.e., the element configured to face the sample), and the ends may be positioned closer to the aperture array of the opposing surface. The waveguide ends may be shaped and / or angled such that, during operation, the stimulating light is output-coupled from the waveguide ends, allowing multiple charged particle beams to illuminate the area of ​​the sample surface under inspection. These configurations allow a larger proportion of the sample surface to be illuminated with the stimulating light than other embodiments. These configurations enable the use of optical waveguides (e.g., optical fibers) to project light from a position closer to the area of ​​the sample surface under inspection with higher absorption efficiency than known illumination configurations.

[0170]

[0189] Figures 17 and 18 illustrate such a configuration in which an optical fiber 601 is used to disperse light from a planar element within the laminate, for example, on the bottom surface of the laminate, to a light-emitting point 602. Such an optical fiber 601 can be thought to be located within the laminate, associated with, or on, a detector 204 (e.g., as a plate) containing, for example, a planar element of the laminate, such as a detection element 405. The configuration shown in Figure 18 is an example of a fiber 601 on the surface of a detector 240 extending between different detection elements 405, and it should be noted that such a fiber 601 does not block the aperture associated with each detection element 405. The fiber 601 follows a winding or meandering path between the detection elements 405, as shown, for example, in Figure 17, thereby preventing any signal electrodes emitted from the sample 208 from entering the detection elements 405. The light-emitting point 602 can be formed by arranging the optical fiber 601 to create a sharp bend, or by creating surface irregularities on the optical fiber 601. To disperse the stimulating light as desired, mirrors, lenses, or other dispersion elements may be provided adjacent to the exit point 602. Such dispersion elements may include any suitable dispersion elements, such as those described in relation to any other embodiment described herein, as illustrated and described in relation thereto in Figures 12, 13, 15, and 16. When a configuration using optical fiber 601 is applied to the configuration shown in Figure 14, it may be desirable to provide an optical element at the exit point 602 to direct the light toward the aperture of the lower element of the laminate 502.

[0171]

[0190] Light from a stimulating light source (not shown) can be coupled to the optical fiber 601 by various means, for example, by extending the optical fiber 601 to the light source, by providing additional optical fibers, or, for example, in a convenient embodiment, by other optical waveguides between the light source and the optical fiber in the laminate.

[0172]

[0191] Figures 19 and 20 show an arrangement in which the optical fiber 603 is provided on the outside of the laminate 502. The laminate includes plates. Different plates form one or more charged particle optical elements. Figure 19 is a side cross-sectional view. As an example, the laminate 502 may include a control lens array 250, an objective lens array 241, a shielding plate 73, and a detector 240. The control lens array 250 and the objective lens array 241 may have a common planar electrode. Different plates of the laminate 502 may be manufactured using techniques commonly used to manufacture MEMS devices. The optical fiber 603 may extend between a light source and a planar optical member within the laminate, for example, an optical fiber 601 within the laminate. Such a planar optical member may be a transparent optical plate attached to the bottom of the laminate 502, as already described with respect to Figures 13-16, for example, a waveguide, or a fiber attached to the bottom of the laminate as shown in Figures 17 and 18. Figure 19 shows an optical fiber extending to the bottom of the laminate, but it should be noted that the optical fiber 603 may extend to any of the plates of the laminate in order to optically couple, for example, a planar optical member to a field-free region within the laminate (at least during operation) where, for example, the optical fiber 601 may be located within the laminate.

[0173]

[0192] Figure 20 is a plan view from below of the laminate 502 showing the surface of the detector 240 facing the sample position during operation. The surface of the detector 240 has a grid configuration of detection elements 405. The grid configuration is shown as hexagonal to ensure an optimal number of beams, e.g., the maximum number of beams, that can have a sufficient beam current from the electron source 201, and to ensure tessellation of adjacent surfaces scanned across the entire beam grid, but the grid configuration may also have other suitable shapes such as circular, rectangular, square, or rhombus. In a practical embodiment, there may be tens of thousands, hundreds, or thousands, e.g., tens of thousands to hundreds of thousands, of detection elements 405 at the bottom of the laminate 502.

[0174]

[0193] The ends of the optical fibers 603 are spaced apart around the outside of the laminate 502, for example, along the edges of the beam grid, and for example, there are multiple detection elements along the edges of the grid for each optical fiber 603. For example, there may be multiple elements for each optical fiber 603. There may be multiple optical fibers 603 for each side. For example, as shown in the figure, there are four fibers 603 spaced apart along each side of the hexagonal laminate 502, but this is merely a schematic diagram.

[0175]

[0194] The optical fiber 603 may be connected to one or more planar optical members, thereby enabling optical communication within the planar optical members. For example, an optical fiber outside the laminate may communicate optically with an optical element within the planar optical member, such as an optical fiber 601 within the planar optical member (or optical plate or optical element). The optical fiber 603 outside the laminate may be connected via its respective optical connection to an optical waveguide and other optical elements such as the optical fiber 601 within the optical planar member.

[0176]

[0195] Light can be dispersed through planar optical members, as described and illustrated with respect to Figure 17. In some configurations, an optical fiber can communicate optically with multiple planar optical members. There may be more or fewer fibers on each side of the grid. Preferably, the number of fibers on each side of the grid (for the laminate) is the same, and the fibers are spaced equally apart. However, the number of fibers and their spacing may be varied, for example, to accommodate mounting to elements of the laminate 502, power, or signal connections, as long as reasonably uniform illumination of sample 208 is achieved. Note that only the position of the endpoint of fiber 603 is important, for example, for coupling with planar optical members within the laminate, and the routing of the fibers to the sides of the laminate 502 can be conveniently arranged within fiber constraints, e.g., minimum bending radius.

[0177]

[0196] In one configuration, Figure 20 may be a plan view of the laminate 502 viewed from below (for example, the device viewed from the beam downstream to the beam upstream of the laminate), showing a detector 240 having a grid arrangement of detection elements 405, which may have the same features as the configuration of Figure 20 described above, unless otherwise stated. In this configuration, the ends of the optical fibers 603, schematically represented by circles 603, are positioned, for example, around the grid arrangement of detection elements 405 of the detector 240. The above description of the outer part of the optical fiber 603 with respect to the sides of the grid may apply more specifically to each end of the optical fiber 603, but is not coupled to the optical elements within the detector, such as optical planar elements located in, adjacent to, or otherwise associated with the detector 240, and, for example, the grid of the detection elements 405. The number of ends of the optical fiber 603 and their spacing may be varied, for example, to accommodate mounting to elements of the laminate 502, power, or signal connections, as long as their positions allow for reasonably uniform illumination of the sample 208. For such illumination, the position of the endpoints of the optical fiber 603 may be more important, and the routing of the fiber to the edges of the laminate 502 may be arranged to be advantageous within the constraints of the fiber, such as the minimum bending radius.

[0178]

[0197] In practical embodiments, the diameter of the stack 502 may be on the order of 1 to 20 mm, such as 100 micrometers to 300 mm, for example 3 to 5 mm. The distance between the sample 208 and the bottom of the stack may be on the order of 10 to 500 μm, for example 10 to 100 μm. Thus, the stimulating light is preferably emitted from the end of the fiber at an angle exceeding the shear angle with respect to the sample surface, for example, below which most, if not all, of the light is reflected (i.e., not absorbed by the surface material). The angle of the stimulating light with respect to the sample surface is, for example, less than about 5 degrees, for example about 1 degree. In this configuration, the illumination of the sample 208 can be described as grazing incident illumination. To achieve grazing incident illumination, the end of the fiber 603, for example the last few mm, may be directed in the direction from which the stimulating light is emitted. It is also possible to influence the angle at which the stimulating light is emitted from the fiber 603 by providing an appropriate angle or shape to the end face of the fiber 603, and / or by providing a lens, diffraction grating, or dispersion mechanism adjacent to the end of the fiber.

[0179]

[0198] Alternatively or additionally, the surface of the laminate facing the sample may have surface topography. The end of fiber 603 may be oriented toward the surface topography. Light from the end of the fiber may be reflected, diffracted, and / or scattered toward the sample under inspection. The surface topography may have regions having topography for reflection, scattering, or diffraction (such as reflective regions, scattering regions, or diffracting regions). For example, the regions may be for reflecting light toward the sample, and the regions may have a serrated topography (or shape). Such surface topography having regions for reflecting light is disclosed, for example, in International Publication No. 2022228943, which is incorporated herein by reference insofar as it relates to the disclosure of such surface topography.

[0180]

[0199] It should be noted that, in general, it is not essential that all the light emitted from the fiber is emitted at an angle that illuminates the target area of ​​sample 208. Since the required stimulation light power is not large, a considerable portion of the light emitted from fiber 603 may be incident on locations other than the desired target area on the sample, without causing excessive power consumption of the light source or excessive heat load on other parts of the sample or apparatus.

[0181]

[0200] As a variation of the configuration in Figures 19 and 20, which features the ends of optical fibers 603 for illuminating the sample surface, some or all of the optical fibers may be arranged to provide light to optical planar elements such as detectors 240, which are mounted in, adjacent to, or in relation to, other planar elements at the bottom of the laminate 502, for example, the bottom of the laminate 502, and / or other planar elements within the laminate. Such optical planar elements may be transparent optical plates, such as waveguides, or, as already described in relation to Figures 13-16, or fibers mounted on, inside, or associated with planar elements of the laminate, such as the bottom of the laminate, as shown in Figures 17 and 18. Such a configuration may be used when there is not enough space in the laminate to fit optical planar elements capable of supplying light to the entire beam grid and / or sufficiently uniformly. Optical planar elements may be used, for example, within the laminate to supply light toward the center of the beam grid. Light may be supplied directly from the end faces of fibers around the beam grid, for example, around the laminate.

[0182]

[0201] In one embodiment, the evaluation charged particle optical device and / or the backup charged particle optical device includes one or more charged particle optical elements, including a micro-electromechanical component (MEMS component). In one embodiment, the evaluation charged particle beam is a beam grid of multiple beams.

[0183]

[0202] In one embodiment, the surface of the evaluation charged particle optical device 106, configured to face the evaluation position, is an array of detectors.

[0184]

[0203] In one embodiment, the charged particle optics apparatus includes a controller configured to control one or more of the following: an evaluation charged particle optics device, a backup charged particle optics device, and a light source.

[0185]

[0204] In one embodiment, the charged particle optics apparatus includes an operable stage 209 configured to support a sample 208. In one embodiment, the operable stage 209 is configured to move the sample from an illumination position to an evaluation position. In Figure 11, the movement of the operable stage 209 between the illumination position and the evaluation position is indicated by double-ended arrows 108. In one embodiment, the operable stage 209 is configured to move the sample from the illumination position to the evaluation position after the light source has projected a light beam toward the illumination position. In one embodiment, the operable stage is configured to move the sample to the evaluation position before the evaluation charged particle optics device is ready to project an evaluation charged particle beam toward the evaluation position. In one embodiment, the operable stage is configured to move the sample to the illumination position before the evaluation charged particle optics device is ready to project an evaluation charged particle beam toward the evaluation position.

[0186]

[0205] In some embodiments, the electro-optical apparatus 40 includes, for example, a plurality of electro-optical devices as a multi-column apparatus, as shown in the figures, such as at least Figures 3 and 4, and the following comments apply. Such a multi-column apparatus may include a plurality of electro-optical columns arranged in an array such as a rectangular pattern or a hexagonal pattern. Each column of the multi-column apparatus may feature the configuration features and functions shown in Figure 3 and disclosed herein. Alternatively, the multi-column apparatus may include a plurality of columns arranged in an array having, for example, a regular pattern, and including the features and functions of the electro-optical device 41 shown in Figure 4 and described herein, but with the following differences. Such differences include, for example, having an array of collimators, such as collimated deflectors, associated with the aperture of a sub-beamforming array 252, preferably incorporated into an objective lens array assembly located immediately downstream of the beam. Each collimated deflector is assigned to each sub-beam of the multi-beam. Differences may include, for example, an array of scan deflectors incorporated into an objective lens array assembly associated with an objective lens array 241. Having scan deflector arrays and collimator arrays is advantageous because such devices are electrostatic rather than magnetic. Electro-optical column structures with magnetic devices are difficult to incorporate into multi-column configurations because the magnetic devices interfere with the surrounding columns in the multi-column configuration.

[0187]

[0206] The present invention primarily describes an evaluation charged particle device 106 illustrated and described in relation to any of Figures 3 to 5, but the present invention can also be applied to a charged particle system having a single-beam device or a multi-beam device having a common single magnetic objective lens as an evaluation charged particle device. Such a multi-beam device may have a magnetic condenser lens, an array of one or more electro-optical elements between, for example, the condenser lens and the objective lens, and a secondary column including a detector array for detecting multiple beams of charged particles from a sample. A Wien filter above the objective lens can separate charged particles from the sample in response to multiple beams from the multi-beam of charged particles directed at the sample.

[0188]

[0207] In one embodiment, the method is for evaluating sample 208 by performing a voltage contrast measurement (an example of an evaluation process). Suitable apparatus and related methods for such irradiation of the sample and / or such voltage contrast measurement are disclosed and described herein.

[0189]

[0208] The reference that a component or system of components or elements can be controlled to operate the electron beam in a particular manner includes, optionally, configuring a controller or control system or control unit to control a component to operate the electron beam in the manner described herein, as well as using other controllers or devices (e.g., voltage and current supplies) to control a component to operate the electron beam in this manner. For example, a voltage supply can be electrically connected to one or more components to supply a potential to those components, and an unrestricted list of such supplies includes a control lens array 250, an objective lens array 241, a condenser lens 231, a compensator, a collimator element array, and a scan deflector array, all under the control of a controller or control system or control unit. Actuable components such as stages may be controlled to act and therefore move relative to other components such as beampaths using one or more controllers, control systems, or control units to control the operation of the components.

[0190]

[0209] Embodiments described herein may take the form of a series of aperture arrays or electro-optical elements arranged in an array along a beam or multi-beam path. Such electro-optical elements may be electrostatic. In some embodiments, for example, all electro-optical elements from the sub-beamforming array to the last electro-optical element in the sub-beam path before the sample may be electrostatic and / or in the form of an aperture array or plate array. In some configurations, one or more of the electro-optical elements are manufactured as a micro-electromechanical system (MEMS) (i.e., using MEMS manufacturing techniques).

[0191]

[0210] References to the upper and lower sides, up and down, upward and downward, upper and lower should be understood as referring to directions parallel to the (typically but not always perpendicular) beam upstream and beam downstream directions of the electron beam or multibeam impacting Sample 208. Thus, references to the beam upstream and beam downstream are intended to refer to directions with respect to the beam path, independently of any current gravitational field and even when there is no charged particle beam, such as when the charged particle device is not operating. However, the terms upper and lower sides, up and down, upward and downward, and / or upper and lower should be understood as being more easily recognizable when there is no charged particle beam, for example when the charged particle device is away from the charged particle device, for example, a part of the laminate, for example, may be away from the charged particle device, e.g., removed, or one or more planar elements of the detector 240, for example, may be away from the laminate.

[0192]

[0211] An electron-optical apparatus according to one embodiment of the present disclosure may be a tool for qualitatively evaluating a sample (e.g., pass / fail), a tool for quantitatively measuring a sample (e.g., the size of a feature), or a tool for generating an image of a map of a sample. Examples of evaluation systems include inspection tools (e.g., for identifying defects), review tools (e.g., for classifying defects), and measurement tools, or a tool capable of performing any combination of evaluation functions related to inspection tools, review tools, or measurement tools (e.g., measurement inspection tools). An electron-optical column may be a component of an evaluation system such as an inspection tool or a measurement inspection tool, or part of an electron beam lithography tool. Any reference to a tool in this specification is intended to encompass devices, apparatus, or systems, and a tool may include, for example, various components for data processing elements, which may be co-located or not, or even located in separate rooms.

[0193]

[0212] The terms “subbeam” and “beamlet” are used interchangeably herein and should be understood to encompass any radiation obtained by separating or splitting a parent radiation beam. The term “manipulator” is used to encompass any element that affects the path of a subbeam or beamlet, such as a lens or deflector.

[0194]

[0213] When it is stated that elements are aligned along a beam path or sub-beam path, it should be understood that each element is positioned along that beam path or sub-beam path.

[0195]

[0214] Aspects of the present invention are described in the following numbered sections: Clause 1. A plate for an electro-optical device configured to project multiple charged particle beams toward a sample, wherein the device includes the plate within a plate laminate, wherein multiple apertures are defined within the plate for each path of the multiple charged particle beams, and the plate includes a planar optical member configured to direct a stimulating light toward a sample and to align the stimulating light with the paths of the multiple charged particle beams toward the sample.

[0196]

[0215] Clause 2. A laminate for an electro-optical device configured to project multiple charged particle beams toward a sample, wherein the laminate comprises at least one of the plates of Clause 1.

[0197]

[0216] Article 3. A stimulation module for use in an electro-optical projection device for projecting multiple charged particle beams toward a sample, wherein the module includes a planar optical member configured to direct stimulation light toward the sample and to align the stimulation light with the multiple charged particle beams, wherein multiple apertures are defined within the plate for each path of the multiple charged particle beams, and preferably the planar optical member consists of a plate of a laminate of plates arranged along the paths of the multiple charged particle beams toward the sample, for example.

[0198]

[0217] Article 4. An electro-optical projection device for projecting multiple charged particle beams onto a sample, wherein the device includes the laminate of Article 2 or the stimulation module of Article 3.

[0199]

[0218] Clause 5. An electro-optical projection device for projecting multiple charged particle beams toward a sample, the device comprising a laminate of plates including beam guide elements configured to project multiple charged particle beams toward a sample position on the sample, wherein at least one plate of the laminate includes a planar optical member configured to direct a stimulating light toward the sample position, aligning the stimulating light with the multiple charged particle beams, and preferably aligning it with the paths of the multiple charged particle beams toward the sample position, wherein preferably multiple apertures for each path of the multiple charged particle beams are defined within the at least one plate including the optical member.

[0200]

[0219] Clause 6. The planar optical member is configured to direct the stimulating light to incident near, or at least partially overlapping with, a portion of the individual electron beams at the sample position, and preferably the region illuminated by the stimulating light has a larger cross-sectional area at the sample position than the cross-section of the individual electron beams, as in the device of Clause 5.

[0201]

[0220] Article 7. A planar optical member configured to direct stimulating light to occur simultaneously with and / or before the incidence of a charged particle beam, as in the device of Article 5 or 6.

[0202]

[0221] Article 8. Planar optical members include transparent plates, and are devices of Article 5, 6, or 7.

[0203]

[0222] Article 9. The device according to Article 8, wherein the thickness of the transparent plate is greater than twice the wavelength of the stimulating light, and preferably in the range of 5 μm to 50 μm.

[0204]

[0223] Clause 10. A transparent plate having an output coupling mechanism configured to direct stimulating light toward a sample, preferably the output coupling mechanism comprising at least one of the following: a mirror or lens surface, for example, a projection from the surface of the transparent plate facing the sample position, a projection opposite to the sample position, a recess in the surface of the transparent plate facing the sample position, and / or a recess in the surface opposite to the sample position of the transparent plate, a diffraction grating, and a region of the transparent plate where the refractive index changes, according to Clause 8 or 9.

[0205]

[0224] Clause 11. The device of Clause 10, wherein the transparent plate has an output coupling mechanism for each of a plurality of charged particle beams, preferably the individual output coupling mechanisms are positioned adjacent to each of the apertures of the plurality of apertures, and preferably the output coupling mechanisms are configured to direct the stimulating light in the direction of the sample position along the path of the electron beam through each aperture.

[0206]

[0225] Article 12. Planar optical members are devices of Articles 5, 6, or 7, including optical systems that include, for example, waveguides, power dividers, and output couplers such as diffraction grating couplers.

[0207]

[0226] Clause 13. An optical system comprising a plurality of beampaths (preferably at least a portion of the beampaths passing between the apertures of a plurality of apertures) and a plurality of power dividers for splitting the stimulating light between the beampaths, preferably the individual power dividers on the beampaths being configured to split the beampaths, preferably at least some of the power dividers being positioned along one or more of the beampaths, and preferably the individual power dividers being configured to direct the beampaths to the individual apertures of the plurality of apertures, the device of Clause 12.

[0208]

[0227] Clause 14. The optical system includes a device of Clause 12 or 13, comprising multiple output couplers, such as diffraction gratings, configured to direct stimulating light toward a sample.

[0209]

[0228] Article 15. The optical system includes an output coupler for each of the charged particle beams, e.g., a diffraction grating, preferably each positioned adjacent to one of a plurality of apertures, as per the device of Article 14.

[0210]

[0229] Article 16. The optical system comprises a first diffraction grating and a second diffraction grating, preferably positioned adjacent to one of a plurality of apertures for each charged particle beam, wherein the first diffraction grating has a different pitch from the second diffraction grating, the device of Article 15.

[0211]

[0230] Article 17. A diffraction grating is a device of Article 14, 15, or 16, which includes overlapping diffraction gratings having different pitches and / or orientations.

[0212]

[0231] Clause 18. The optical system includes a plurality of output couplers, such as mirrors, configured to direct stimulating light toward a sample, preferably with each mirror positioned adjacent to one of the plurality of apertures, as in the device of Clause 12 or 13.

[0213]

[0232] Clause 19. A device according to any one of Clauses 5 to 18, wherein the laminate between the planar optical member and the sample position contains other plates of the laminate, preferably the planar optical member is configured to direct the stimulating light through an aperture defined in the other plates, and preferably the planar optical member is the plate furthest upstream of the beam in the device.

[0214]

[0233] Clause 20. A device according to any one of Clauses 5 to 19, wherein the planar optical member faces the sample position, and preferably the planar optical member includes a facing surface of a laminate configured to face the sample position.

[0215]

[0234] Article 21. A device according to any one of Articles 5 to 20, wherein the planar optical element includes a detector array, preferably an array of detectors, each associated with the respective aperture of a plurality of apertures.

[0216]

[0235] Article 22. Planar optical elements are devices that include electrostatic electrodes, as defined in any one of Articles 5 to 21.

[0217]

[0236] Clause 23. The electrostatic electrode is preferably a monolithic plate having a single electrical contact, or the electrostatic electrode is a plurality of electrodes, thereby the planar optical element is a device of Clause 22 including a manipulator array such as a multi-pole array.

[0218]

[0237] Clause 24. A device of any one of Clauses 1 to 23, further comprising a light source configured to generate stimulating light, preferably the light source generating stimulating light having wavelengths in the range of 450 nm to 850 nm, preferably 450 nm to 800 nm, more preferably the stimulating light having multiple wavelengths, and preferably the light source comprising one or more lasers.

[0219]

[0238] Clause 25. The device of Clause 24, further comprising an optical conduit, such as an optical fiber, configured to couple stimulating light from a light source to an optical component.

[0220]

[0239] Clause 26. A plate stack comprising a detector array configured to detect signaling particles from a sample responding to multiple charged particle beams, as a device under any one of Clauses 1 to 25.

[0221]

[0240] Article 27. A device according to any one of Articles 1 to 26, further comprising a potential supply system configured to apply potential to different plates of a laminate for projecting a charged particle beam toward a sample.

[0222]

[0241] Article 28. A device relating to any one of Articles 1 to 27, wherein one or more plates include an objective lens array for a charged particle beam.

[0223]

[0242] Article 29. A planar optical component is a device of any one of Articles 1 to 28, which is included in one of the plates and fixed to the plate, for example.

[0224]

[0243] Article 30. Planar optical components are included in the plate of the laminate closest to the sample, and are, for example, attached thereto, the devices described in Articles 1 to 29.

[0225]

[0244] Clause 31. Preferably, a planar optical element is positioned upstream of the beam of the device, an evaluation charged particle optical apparatus or a backup charged particle optical apparatus including the device of any one of Clauses 1 to 30.

[0226]

[0245] Article 32. Evaluation method using any one of the devices specified in Articles 1 to 31.

[0227]

[0246] Article 33. An electro-optical projection device for projecting multiple charged particle beams toward a sample, the device comprising: a stack of plates including beam guide elements configured to project multiple charged particle beams toward a sample position on the sample; and a plurality of optical fibers positioned outside the stack and configured to direct stimulating light toward the sample position and to align the stimulating light with the multiple charged particle beams.

[0228]

[0247] Article 34. The ends of the optical fibers are arranged at intervals around the bottom of the laminate, as in the device of Article 33.

[0229]

[0248] Article 35. Optical fiber is a device of Article 33 or 34 that emits light directly to the sample location.

[0230]

[0249] Article 36. A device under Article 33 or 34, in which an optical fiber directs light directly onto one or more other optical fibers attached to the bottom of a planar optical member or laminate.

[0231]

[0250] While the present invention has been described in relation to various embodiments, other embodiments of the present invention will become apparent to those skilled in the art from the discussion herein and the practice of the present invention disclosed herein. This specification and the examples are for illustrative purposes only, and the true scope and spirit of the present invention are set forth by the following claims.

Claims

1. An electron-optical projection device for projecting multiple charged particle beams toward a sample, The laminate comprises plates including beam guidance elements configured to project the plurality of charged particle beams toward the sample position on the sample, At least one plate of the laminate has a planar optical member configured to direct stimulating light towards the sample position and to align the stimulating light with the plurality of charged particle beams, An electron-optical projection device wherein at least one plate has multiple apertures for each path of multiple charged particle beams.

2. The planar optical member is configured to direct the stimulation light so that it is incident near, or at least partially overlapping with, a portion of the individual electron beams at the sample position. The device according to claim 1, wherein the region illuminated by the stimulating light has a larger cross-sectional area than the cross-section of the individual electron beams at the sample position.

3. The device according to claim 1 or 2, wherein the planar optical member includes a transparent plate.

4. The device according to claim 3, wherein the thickness of the transparent plate is greater than twice the wavelength of the stimulating light, and preferably in the range of 5 μm to 50 μm.

5. The transparent plate has an output coupling mechanism configured to direct the stimulating light towards the sample, preferably the output coupling mechanism is a. Mirror or lens surface, b. Diffraction grating, and c. Regions in which the refractive index of the transparent plate changes The device according to claim 3 or 4, comprising at least one of the following.

6. The device according to claim 5, wherein the transparent plate has an output coupling mechanism for each of the plurality of charged particle beams.

7. The device according to claim 1 or 2, wherein the planar optical member includes, for example, an optical system including a waveguide, a power divider, and an output coupler.

8. The optical system comprises a plurality of beam paths and a plurality of power dividers for dividing the stimulating light between the beam paths, preferably the individual power dividers on the beam paths being configured to divide the beam paths and direct the beam paths to individual apertures of the plurality of apertures, according to claim 7.

9. The device according to claim 7 or 8, wherein the optical system includes a plurality of output couplers configured to direct stimulating light towards the sample.

10. The device according to any one of claims 1 to 9, wherein there is another plate of the laminate between the planar optical member and the sample position.

11. The device according to any one of claims 1 to 10, wherein the plate includes a detector array.

12. The electrostatic electrode is either a monolithic plate having a single electrical contact, or The device according to claim 11, wherein the electrostatic electrode includes a plurality of electrodes, thereby the plate includes a manipulator array such as a multi-pole array.

13. The system further includes a light source configured to generate the aforementioned stimulating light, The device according to any one of claims 1 to 12, wherein the light source is configured to direct the stimulating light so that it is incident at the same time as and / or before the incident of the charged particle beam.

14. The device according to claim 13, further comprising an optical conduit configured to couple stimulating light from the light source to the optical member.

15. The device according to any one of claims 1 to 14, wherein the planar optical member is included in the plate of the laminate that is closest to the sample, and is, for example, attached thereto.

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