Charged particle evaluation tools and inspection methods

Abstract

This helps improve the throughput or other characteristics of charged particle evaluation tools. [Solution] A multibeam electron-optics system for a charged particle evaluation tool, comprising a plurality of control lenses, a plurality of objective lenses, and a controller. The plurality of control lenses are configured to control the parameters of their respective sub-beams. The plurality of objective lenses are configured to project one of a plurality of charged particle beams onto a sample. The controller controls the control lenses and objective lenses so that the charged particles are incident on the sample at a desired landing energy, reduction magnification, and / or beam opening angle.

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims the priority of European Patent Application Publication No. 20196716.3 filed on September 17, 2020, European Patent Application Publication No. 21166205.1 filed on March 31, 2021, and European Patent Application Publication No. 21191725.7 filed on August 17, 2021, and these applications are hereby incorporated herein by reference in their entirety.

[0002]

[0002] Embodiments provided herein generally relate to charged - particle evaluation tools and inspection methods, and more particularly to charged - particle evaluation tools and inspection methods using a plurality of charged - particle sub - beams.

Background Art

[0003]

[0003] When manufacturing a semiconductor integrated circuit (IC) chip, for example, as a result of optical effects and incidental particles, unwanted pattern defects inevitably occur on a substrate (i.e., a wafer) or a 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 generally use electron microscopy techniques such as scanning electron microscopes (SEMs). In an SEM, a primary electron beam of relatively high-energy electrons is targeted in a final deceleration step to land on the sample with a relatively low landing energy. The electron beam is focused onto the sample as a probing spot. The interaction between the material structure at the probing spot and the landed electrons from the electron beam causes electrons such as secondary electrons, backscattered electrons, or Auger electrons to be emitted from the surface. The generated secondary electrons may be emitted from the material structure of the sample. By scanning the primary electron beam as a probing spot across the sample surface, secondary electrons can be emitted across the sample surface. By collecting these emitted secondary electrons from the sample surface, the pattern inspection tool can obtain an image representing the material structure features of the sample surface.

[0005]

[0005] There is a general need to improve the throughput and other characteristics of charged particle evaluation tools. In particular, it is desirable to be able to easily control the landing energy of electrons incident on the sample. [Overview of the Initiative]

[0006]

[0006] The object of this disclosure is to provide embodiments that help improve the throughput or other characteristics of a charged particle evaluation tool.

[0007]

[0007] According to a first aspect of the present invention, a multibeam electron optics system for a charged particle evaluation tool, Multiple control lenses, each configured to control the parameters of a different subbeam, Multiple objective lenses, each configured to project one of several charged particle beams onto a sample, A controller configured to control the control lens and objective lens so that charged particles are incident on the sample at a desired landing energy, reduction magnification, and / or beam opening angle, A multibeam electron-optics system including this is provided.

[0008]

[0008] According to a second aspect of the present invention, a multibeam electron optics system for a charged particle evaluation tool, A control lens array comprising multiple control electrodes and configured to control the parameters of each subbeam, An objective lens array comprising multiple objective electrodes and configured to guide multiple charged particle beams onto a sample, A potential source system configured to apply a relative potential to control electrodes and objective electrodes so that charged particles are incident on a sample at a desired landing energy, reduction magnification, and / or beam opening angle, A multibeam electron-optics system including this is provided.

[0009]

[0009] According to a third aspect of the present invention, a multibeam electron optics system for a charged particle evaluation tool, An objective lens array including an objective lens configured to focus each sub-beam onto the sample surface, A control lens array including a control lens configured to control the landing energy of each subbeam on the sample surface and / or optimize the opening angle and / or magnification of each subbeam before the objective lens array operates, A multibeam electron-optics system including this is provided.

[0010]

[0010] According to a fourth aspect of the present invention, a multibeam electron-optical system for an inspection tool, An objective lens array configured to focus multiple collimated subbeams onto a sample, A control lens array located in the up beam of an objective lens array, comprising a control lens array configured to control the beam energy of each sub-beam, A multibeam electron-optics system is provided that is configured to adjust the landing energy of subbeams on a sample.

[0011]

[0011] According to a fifth aspect of the present invention, a multibeam electron-optical system for a charged particle evaluation tool, comprising an objective lens array assembly including a plurality of aperture arrays, the objective lens array assembly a) Focusing multiple subbeams onto the sample, b) Controlling another subbeam parameter, which is at least one of the subbeam's landing energy on the sample surface, the opening angle of each subbeam, and / or the magnification of each subbeam. A multibeam electron-optics system is provided that is configured to perform the following actions:

[0012]

[0012] According to a fourth aspect of the present invention, This involves using multiple control lenses to control the parameters of each of the multiple subbeams of charged particles, This involves using multiple objective lenses to project multiple charged particle beams onto the sample, Controlling the control lens and objective lens so that charged particles are incident on the sample at a desired landing energy, reduction magnification, and / or beam opening angle, A testing method including the following is provided.

[0013]

[0013] According to a fourth aspect of the present invention, there is a replaceable module configured to be replaceable in the electro-optical column of a charged particle inspection tool, the replaceable module includes an objective lens array, which includes a plurality of control lenses configured to control the reduction magnification and / or landing energy of a multibeam.

[0014]

[0014] The above and other aspects of the present disclosure will become more apparent from the description of the exemplary embodiments in conjunction with the accompanying drawings.

Brief Description of the Drawings

[0015] [Figure 1]

[0015] It is a schematic diagram showing an exemplary charged particle beam inspection apparatus. [Figure 2]

[0016] It is a schematic diagram showing an exemplary multi-beam apparatus which is a part of the exemplary charged particle beam inspection apparatus of FIG. 1. [Figure 3]

[0017] It is a schematic diagram of an exemplary multi-beam apparatus according to an embodiment. [Figure 4]

[0018] It is a graph of landing energy vs. resolution for an exemplary configuration. [Figure 5]

[0019] It is an enlarged view of an objective lens according to an embodiment of the present invention. [Figure 6]

[0020] It is a schematic cross-sectional view of an objective lens of an inspection apparatus according to an embodiment. [Figure 7]

[0021] It is a bottom view of the objective lens of FIG. 8. [Figure 8]

[0022] It is a bottom view of a modified form of the objective lens of FIG. 6. [Figure 9]

[0023] It is an enlarged schematic cross-sectional view of a detector incorporated in the objective lens of FIG. 6. [Figure 10]

[0024] It is a schematic diagram of an exemplary electron optical system including a macro collimator and a macro scan deflector. [Figure 11]

[0025] It is a schematic diagram of an exemplary electron optical system including a collimator element array and a scan deflector array. [Figure 12]

[0026] It is a schematic side cross-sectional view of a portion of an electrode forming an objective lens having a final beam limiting aperture array. [Figure 13]

[0027] Figure 12 is a schematic enlarged upper cross-sectional view in planar AA showing the aperture in the final beam limiting aperture array. [Modes for carrying out the invention]

[0016]

[0028] Herein, exemplary embodiments are given in detail, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, and unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations described below in the description of exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatus and methods consistent with embodiments related to the present invention as described in the accompanying claims.

[0017]

[0029] Reducing the physical size of devices and improving the computing power of electronic devices can be achieved by significantly increasing the mounting density of circuit components such as transistors, capacitors, and diodes on an IC chip. This has been made possible by improvements in resolution, which allows for the fabrication of even smaller structures. For example, an IC chip in a smartphone available before 2019, the size of a thumbnail, could contain more than 2 billion transistors, with each transistor being less than 1 / 1000th the size of a human hair. Therefore, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. Even an error in a single step can dramatically affect the functionality of the final product. A single "fatal defect" can cause a device to fail. The goal of the manufacturing process is to improve the overall yield of the process. For example, to achieve a 75% yield for a process with 50 steps (where a step can indicate the number of layers formed on a wafer), each individual step must have a yield of more than 99.4%. If each individual step has a yield of 95%, the overall process yield is a low 7%.

[0018]

[0030] In IC chip manufacturing equipment, while high process yield is desirable, maintaining high substrate (i.e., wafer) throughput, defined as the number of substrates processed per hour, is also essential. High process yield and high substrate throughput can be affected by the presence of defects. This is especially true when operator intervention is required to investigate defects. Therefore, high-throughput detection and identification of microscale and nanoscale defects using inspection tools (such as scanning electron microscopes ("SEM")) is essential to maintain high yield and low costs.

[0019]

[0031] A scanning electron microscope (SEM) includes a scanning device and a detector. The scanning device includes an illumination device containing 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. Together, at least the illumination device or illumination system and the projection device or projection system may be called an electron-optical system or apparatus. The primary electrons interact with the sample and generate secondary electrons. The detector captures the secondary electrons from the sample as it is scanned, so that the SEM can generate an image of the scanning area of ​​the sample. For high-throughput 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.

[0020]

[0032] The following describes known implementation configurations of multibeam inspection systems.

[0021]

[0033] The figures are schematic diagrams. Therefore, in the drawings, the relative dimensions of components are enlarged for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, illustrating only the differences to individual embodiments. While the description and drawings pertain to electron-optical devices, it should be understood that the embodiments are not used to limit this disclosure to specific charged particles. Thus, throughout this specification, references to electrons can be considered more generally to charged particles, and charged particles are not necessarily electrons.

[0022]

[0034] Referring now to Figure 1, which is a schematic diagram showing an exemplary charged particle beam inspection apparatus 100. The charged particle beam inspection apparatus 100 in Figure 1 includes a main chamber 10, a loading lock chamber 20, an electron beam tool 40, an instrument front-end module (EFEM) 30, and a controller 50. The electron beam tool 40 is located inside the main chamber 10.

[0023]

[0035] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include one or more additional loading ports. The first loading port 30a and the second loading port 30b may receive, for example, a substrate front-opening integrated pod (FOUP) containing a substrate (e.g., a semiconductor substrate or a substrate made of other materials) or a sample to be inspected (hereafter, 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 loading lock chamber 20.

[0024]

[0036] The loading 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 loading lock chamber 20 may be connected to a loading lock vacuum pump system (not shown), which removes gas particles from within the loading lock chamber 20. The operation of the loading lock vacuum pump system allows the loading lock chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) carry the sample from the loading 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 so that the pressure around the sample reaches a second pressure below the first pressure. After reaching the second pressure, the sample is carried to an electron beam tool, which can then be examined. The electron beam tool 40 may include a multibeam electron optics device.

[0025]

[0037] The controller 50 is electronically connected to the electron beam tool 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle 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 as an external component of the structure including the main chamber 10, the loading lock chamber 20, and the EFEM 30, but it is understood that the controller 50 may be part of the structure. The controller 50 may be located inside one of the component elements of the charged particle beam inspection apparatus, or the controller 50 may be distributed across at least two of the component elements. 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 a broad sense to chambers housing electron beam inspection tools. Rather, it is understood that the aforementioned principles can be applied to other tools and other arrangements of apparatus operating under a second pressure.

[0026]

[0038] Referring here to Figure 2, Figure 2 is a schematic diagram showing an exemplary electron beam tool 40, which includes a multibeam inspection tool that is part of the exemplary charged particle beam inspection apparatus 100 of Figure 1. The multibeam electron beam tool 40 (also referred to herein as apparatus 40) includes an electron source 201, a projection device 230, a motorized stage 209, and a sample holder 207. The electron source 201 and the projection device 230 may collectively be called the illumination device. The sample holder 207 is supported by the motorized stage 209 to hold a sample 208 (e.g., a substrate or a mask) for inspection. The multibeam electron beam tool 40 further includes an electron detection device 240.

[0027]

[0039] The electron source 201 may include a cathode (not shown) and an extractor 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 extractor and / or anode to form a primary electron beam 202.

[0028]

[0040] The projection device 230 is configured to convert the primary electron beam 202 into multiple sub-beams 211, 212, and 213, and to guide each sub-beam onto the sample 208. While three sub-beams are shown for simplicity, tens, hundreds, or thousands of sub-beams may exist. Sub-beams may be called beamlets.

[0029]

[0041] The controller 50 can be connected to various parts of the charged particle beam inspection apparatus 100 in Figure 1, such as the electron source 201, the electron detection device 240, the projection device 230, and the motorized stage 209. The controller 50 can perform various image and signal processing functions. The controller 50 can also generate various control signals to control the operation of the charged particle beam inspection apparatus, including a charged particle multibeam apparatus.

[0030]

[0042] The projection device 230 may be configured to focus sub-beams 211, 212, and 213 onto the sample 208 for inspection, thereby forming three probe spots 221, 222, and 223 on the surface of the sample 208. The projection device 230 may be configured to deflect the primary sub-beams 211, 212, and 213 to scan the probe spots 221, 222, and 223 across individual scanning areas within a section of the surface of the sample 208. In response to the incidence of the primary sub-beams 211, 212, and 213 onto the probe spots 221, 222, and 223 on the sample 208, electrons, including secondary and backscattered electrons, are generated from the sample 208. The secondary electrons generally have an electron energy of 50 eV or less, and the backscattered electrons generally have an electron energy between 50 eV and the landing energy of the primary sub-beams 211, 212, and 213.

[0031]

[0043] The electron detection device 240 is configured to detect secondary electrons and / or backscattered electrons and generate corresponding signals, which are sent to the controller 50 or a signal processing system (not shown) to construct, for example, an image of the corresponding scanning area of ​​the sample 208. The electron detection device may be integrated into or separate from the projection device, and the secondary optical column is provided to direct secondary electrons and / or backscattered electrons toward the electron detection device.

[0032]

[0044] The controller 50 may include an image processing system including an image acquirer (not shown) and a storage device (not shown). For example, the controller may include a processor, computer, server, mainframe host, terminal, personal computer, any type of mobile computing device, or a combination thereof. The image acquirer may include at least some of the processing functions of the controller. Therefore, the image acquirer may include at least one or more processors. The image acquirer may be communicatively coupled to an electronic detection device 240 of a signal communication device 40, such as a conductor, optical fiber cable, portable storage medium, IR, Bluetooth, the Internet, wireless network, wireless radio, or a combination thereof. The image acquirer can receive signals from the electronic detection device 240, process the data contained in the signals, and construct an image therefrom. Therefore, the image acquirer can acquire an image of sample 208. The image acquirer can also perform various post-processing functions, such as contour generation and superimposition of indicators onto the acquired image. The image acquirer may be configured to adjust the brightness and contrast of the acquired image. Storage can 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 combined with an image acquisition device and used to store scanned raw image data as the original image, or to store post-processed images.

[0033]

[0045] The image acquirer can acquire one or more images of a sample based on an imaging signal received from the electronic detection device 240. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image containing multiple imaging areas. The single image can be stored in storage. The single image may be the original image which can be divided into multiple regions. Each region may contain one imaging area containing features of sample 208. The acquired image may contain multiple images of a single imaging area of ​​sample 208 sampled multiple times over a period of time. The multiple images can be stored in storage. The controller 50 may be configured to perform image processing steps using multiple images of the same location of sample 208.

[0034]

[0046] The controller 50 may include a measurement circuit (e.g., an analog-to-digital converter) to obtain the distribution of detected secondary electrons. The electron distribution data collected during the detection time window can be used in combination with the corresponding scan path data of the primary 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.

[0035]

[0047] The controller 50 can control the motorized stage 209 to move the sample 208 during inspection of the sample 208. The controller 50 can enable the motorized stage 209 to move the sample 208 in a certain direction, preferably at a constant speed, at least continuously, during the inspection of the sample. The controller 50 can control the movement of the motorized stage 209 so that the motorized stage 209 changes the speed of the movement of the sample 208, depending on various parameters. For example, the controller can control the stage speed (including its direction) depending on the characteristics of the inspection step in the scanning process.

[0036]

[0048] Figure 3 is a schematic diagram of an evaluation tool, for example, an electron-optical column 40 of the evaluation tool. The electron-optical column 40 may include a radiation source 201. The electron-optical column 40 is an example of an electron-optical architecture that may include mechanisms such as an upper beam limiter 252, a collimator element array 271, a control lens array 250, a scan deflector array 260, an objective lens array 241, a beam shaping limiter 242, and a detector array 240, where one or more elements containing these elements may be connected to one or more adjacent elements by insulating elements such as ceramic spacers. The detector array may include detector elements associated with each sub-beam of the multi-beam system.

[0037]

[0049] The electron source 201 directs its electrodes to an array 231 of condenser lenses that form part of the projection system 230. The electron source is preferably a high-intensity thermal field emission emitter having a good compromise between luminance and total emission current. The condenser lenses 231 may number in the tens, hundreds, or thousands. The condenser lenses of the array 231 may include multi-electrode lenses and may have a structure based on European Patent Application Publication No. 1602121A1, which is incorporated herein by reference to a disclosure of a lens array for splitting an electron beam into multiple sub-beams, with each sub-beam having its own lens. The focusing lens array may take the form of at least two plates that function as electrodes, with apertures of each plate aligned with each other to correspond to the positions of the sub-beams. At least two of these plates are maintained at different potentials during operation to achieve a desired lensing effect.

[0038]

[0050] In one configuration, the focusing lens array is formed from an array of three plates in which charged particles have the same energy when entering and exiting each lens; this configuration can 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. When the thickness of the focusing lens is thin, for example a few millimeters, the effect of such aberration is small or negligible.

[0039]

[0051] The focusing lens array 231 may have two or more plate electrodes, each plate electrode comprising an array of aligned apertures. Each plate electrode array is mechanically connected to and electrically isolated from adjacent plate electrode arrays by isolation elements, such as spacers, which may include ceramic or glass. The focusing lens array may be connected to and / or separated from adjacent electro-optical elements, preferably electrostatic electro-optical elements, by isolation elements, such as spacers, as described elsewhere in this specification.

[0040]

[0052] The focusing lens is separated from the module containing the objective lens (such as the objective lens array assembly discussed below). If the potential applied to the bottom surface of the focusing lens differs from the potential applied to the top surface of the module containing the objective lens, a separation spacer is used to separate the focusing lens from the module containing the objective lens. If the potentials are equal, a conductive element can be used to separate the focusing lens from the module containing the objective lens.

[0041]

[0053] Each focusing lens in the array directs electrons to their respective sub-beams 211, 212, and 213, which are focused at their respective intermediate focal points 233. A deflector 235 is provided at the intermediate focal points 233. The deflector 235 is configured to bend each beamlet 211, 212, and 213 by an amount effective in ensuring that the principal ray (also called the beam axis) is incident on the sample 208 substantially perpendicularly (i.e., substantially at 90° with respect to the nominal surface of the sample). The deflector 235 may also be called a collimator.

[0042]

[0054] Below the deflector 235 (i.e., downbeam or away from the radiation source 201), there is a control lens array 250, which includes a control lens 251 for each sub-beam 211, 212, 213. The control lens array 250 may include two or more, for example, three, plate-shaped electrode arrays connected to their respective potential sources. Each plate-shaped electrode array is mechanically connected and electrically isolated from adjacent plate-shaped electrode arrays by insulating elements such as spacers, which may include ceramic or glass. The function of the control lens array 250 is to optimize the beam opening angle with respect to the beam reduction magnification and / or to control the beam energy delivered to the objective lens 234, each of which directs its respective sub-beam 211, 212, 213 onto the sample 208.

[0043]

[0055] Optionally, a scan deflector array 260 is provided between the control lens array 250 and the objective lens array 234. The scan deflector array 260 includes a scan deflector 261 for each sub-beam 211, 212, and 213. Each scan deflector is configured to deflect each sub-beam 211, 212, and 213 in one or two directions so as to scan the sample 208 in one or two directions with the sub-beam.

[0044]

[0056] An electron detection device 240 is provided between the objective lens 234 and the sample 208 to detect secondary electrons and / or backscattered electrons emitted from the sample 208. An exemplary structure of the electron detection system is described below. The detector and the objective lens may be part of the same structure. The detector may be connected to the lens by an insulating element or directly to the electrodes of the objective lens.

[0045]

[0057] The system in Figure 3 is configured to control the electron landing energy on the sample by changing the potential applied to the electrodes of the control lens and objective lens. The control lens and objective lens work together and are sometimes referred to as the objective lens assembly. The landing energy may be selected to increase the emission and detection of secondary electrons, depending on the properties of the sample being evaluated. The controller may be configured to control the landing energy to any desired value within a given range or to one of several predetermined values. In one embodiment, the landing energy is a given range and may be controlled to a desired value, for example, 1000 eV to 5000 eV. Figure 4 is a graph showing the resolution as a function of landing energy, assuming that the beam opening angle / reduction magnification is reoptimized in response to the change in landing energy. As can be seen from the graph, the resolution of the evaluation tool can be kept substantially constant for changes in landing energy up to the minimum value LE_min. The resolution deteriorates below LE_min because the lens intensity of the objective lens and the electric field within the objective lens must be reduced to maintain the minimum distance between the objective lens and / or detector and the sample. Furthermore, as will be detailed later, interchangeable modules may be employed to change or control the landing energy.

[0046]

[0058] The landing energy is preferably changed primarily by controlling the energy of electrons emanating from the control lens. The potential difference within the objective lens is preferably kept constant during this change in order to maintain the electric field within the objective lens as high as possible. Such a high electric field within the objective lens is called a predetermined electric field and can be set to this predetermined electric field. In addition, the potential applied to the control lens can be used to optimize the beam opening angle and reduction magnification. The control lens may function to change the reduction magnification in consideration of the change in landing energy. Each control lens preferably includes three electrodes to provide two independent control variables, as will be detailed later. For example, one electrode may be used to control the magnification, and another electrode may be used to independently control the landing energy. Alternatively, each control lens may have only two electrodes. In the case of only two electrodes, in contrast, one of the electrodes may need to control both the magnification and the landing energy.

[0047]

[0059] Figure 5 is an enlarged schematic view of one objective lens 300 of the objective lens array and one control lens 600 of the control lens array 250. The objective lens 300 may be configured to reduce the electron beam at magnifications greater than 10, preferably in the range of 50 to 100 or more. The objective lens includes a central, i.e., first electrode 301, a lower, i.e., second electrode 302, and an upper, i.e., third electrode 303. Voltage sources V1, V2, and V3 are configured to apply potentials to the first, second, and third electrodes, respectively. A further voltage source V4 is connected to the sample to apply a fourth potential, which may be ground. The potential may be defined with respect to the sample 208. The first, second, and third electrodes are each provided with apertures through which their respective subbeams propagate. The second potential may be a potential close to the sample potential, for example, a potential in the range of 50V to 200V positive than the sample. Alternatively, the second potential can be in a range of approximately +500V to +1,500V positive relative to the sample. A higher potential is useful when the detector 240 is higher in the optical column than the bottom electrode. The first and / or second potentials can be varied per aperture or per group of apertures to perform focus correction.

[0048]

[0060] In one embodiment, it is desirable to omit the third electrode. An objective lens with only two electrodes may have less aberration than an objective lens with more electrodes. A three-electrode objective lens allows for a larger potential difference between electrodes, thus enabling a more powerful lens. Additional electrodes (i.e., three or more electrodes) provide further flexibility in controlling electron trajectories, for example, to focus secondary electrons in addition to the incident beam.

[0049]

[0061] As mentioned above, it is desirable to determine the landing energy using a control lens. However, it is also possible to control the landing energy using the objective lens 300. In such cases, the potential difference across the objective lens changes when a different landing energy is selected. One example of a situation where it is desirable to partially change the landing energy by changing the potential difference across the objective lens is to prevent the focus of the subbeam from becoming too close to the objective lens. In such a situation, there is a risk that the electrodes of the objective lens would have to be made too thin to manufacture. The same can be said for the detector at this location (e.g., as a detector array). This situation can occur, for example, when the landing energy is reduced. This is because the focal length of the objective lens expands or contracts roughly with the selected landing energy. By reducing the potential difference across the objective lens, and thereby reducing the electric field inside the objective lens, the focal length of the objective lens becomes longer again, and the focal position moves further below the objective lens. Note that using only the objective lens limits the control of the magnification. In such a configuration, it is not possible to control the reduction ratio and / or the aperture angle. Furthermore, controlling the landing energy using the objective lens may mean that the objective lens operates away from the optimal electric field strength. This is true unless the mechanical parameters of the objective lens (such as the spacing between electrodes) can be adjusted, for example, by changing the objective lens.

[0050]

[0062] In the illustrated configuration, the control lens 600 includes three electrodes 601-603 connected to potential sources V5-V7. The electrodes 601-603 can be spaced a few millimeters apart (e.g., 3 mm). The distance between the control lens and the objective lens (i.e., the gap between the lower electrode 602 and the upper electrode of the objective lens) can be selected from a wide range, such as 2 mm to 200 mm or more. A smaller separation distance makes alignment easier, while a larger separation distance allows the use of weaker lenses and reduces aberrations. It is desirable that the potential V5 of the uppermost electrode 603 of the control lens 600 be maintained at the same potential as the next electro-optical element (e.g., deflector 235) in the up beam of the control lens. The potential V7 applied to the lower electrode 602 can be varied to determine the beam energy. The potential V6 applied to the intermediate electrode 601 can be varied to determine the lens intensity of the control lens 600 and thus control the beam opening angle and reduction ratio. It is desirable that the lower electrode 602 of the control lens, the uppermost electrode of the objective lens, and the sample have substantially the same potential. In one design, the upper electrode V3 of the objective lens is omitted. In this case, it is desirable that the lower electrode 602 of the control lens and the electrode 301 of the objective lens have substantially the same potential. Furthermore, even if it is not necessary to change the landing energy or if it is changed by other means, the beam opening angle can be controlled using the control lens. The position of the sub-beam focal point is determined by the combination of the actions of each control lens and each objective lens.

[0051]

[0063] For example, to obtain a landing energy in the range of 1.5kV to 2.5kV, the potentials V1, V2, V4, V5, V6, and V7 can be set as shown in Table 1 below. The potentials in this table are given as beam energy values ​​in keV units, which are equal to the electrode potential with respect to the cathode of beam source 201. In the design of an electron-optics system, there is considerable design freedom in which point within the electron-optics system is set to the ground potential, and it should be understood that the operation of the electron-optics system is determined by the potential difference, not the absolute potential.

[0052] [Table 1]

[0053]

[0064] It can be seen that the beam energies at V1, V3, and V7 are the same. In embodiments, the beam energies at these points can be 10 keV to 50 keV. If a lower potential is selected, the spacing between electrodes may be shortened, particularly in the objective lens, to limit the drop in the electric field. Note that the potential difference applied to adjacent electrodes in the objective lens array is the largest of the potential differences applied to adjacent electrodes in the objective lens configuration. To avoid a drop in the electric field within the objective lens, the electric field within the objective lens may be predetermined. The electric field within the objective lens may be optimized for desired performance of the objective lens, for example, to provide the maximum potential difference between adjacent electrodes along the beam path of any electrode in the objective lens array assembly. Fluctuations near such large potential differences can cause errors and aberrations. Substantially maintaining the potential difference between electrodes in the objective lens array and varying the potentials of other electrodes in the objective lens array configuration helps ensure that the operation of the objective lens is maintained, for example, when there is a large electric field for a short and stable focal length. Variations in the function of the objective lens configuration are achieved through variations in the potential difference applied to the other electrodes of the configuration, which reduces the risk of inducing large aberrations.

[0054]

[0065] If a control lens is used instead of the focusing lens in the embodiment of Figure 3 to correct the electron beam's aperture angle / magnification, for example, the collimator remains at an intermediate focal point, and therefore, there is no need to correct the collimator's astigmatism (in such a configuration, adjusting the magnification also adjusts the aperture angle, because the beam current remains constant along the beam path). Furthermore, the landing energy can be varied over a wide range of energies while maintaining an optimal electric field strength within the objective lens. Such an optimal electric field strength may be called a predetermined electric field strength. During operation, the electric field strength can be predetermined as the optimal electric field strength. This minimizes the aberration of the objective lens. The intensity of the focusing lens (if used) is kept constant, and further aberrations are avoided due to the collimator not being at an intermediate focal plane or a change in the path of electrons passing through the focusing lens. Furthermore, if a control lens is used that features a beam shaping limiter, as shown in Figures 10 and 11 (without a focusing lens), the opening angle / magnification can be controlled in addition to the landing energy.

[0055]

[0066] In some embodiments, the charged particle evaluation tool further includes one or more aberration correctors that reduce one or more aberrations in the subbeam. In one embodiment, each of at least a subset of aberration correctors is located at or directly adjacent to one of the intermediate focals (e.g., located at or adjacent to the intermediate image plane). The subbeam has the smallest cross-sectional area at or near the focal plane, such as the intermediate plane. This provides the aberration correctors with more space available elsewhere, i.e., in the up-beam or down-beam of the intermediate plane (or in an alternative arrangement without an intermediate image plane).

[0056]

[0067] In one embodiment, an aberration corrector positioned at or directly adjacent to an intermediate focal point (or intermediate image plane) includes a deflector for correcting radiation sources 201 that appear to be in different positions for different beams. The corrector may be used to correct macroscopic aberrations caused by the radiation sources that would interfere with good alignment between each sub-beam and the corresponding objective lens.

[0057]

[0068] Aberration correctors can correct aberrations that interfere with proper column alignment. Such aberrations can lead to misalignment between the sub-beam and the corrector. For this reason, it may be desirable, in addition to or instead, to place the aberration correctors at or near the focusing lenses of the focusing lens array 231 (for example, each of such aberration correctors may be integrated with or directly adjacent to one or more of the focusing lenses 231). This is desirable because, at or near the condenser lenses of the condenser lens array 231, the condenser lenses are nearly perpendicular or coincident with the beam aperture, so the aberrations do not result in a corresponding sub-beam shift. However, a challenge when placing the corrective optical system at or near the condenser lenses is that the sub-beams at this location have relatively large cross-sectional areas and relatively small pitches compared to locations further downstream. The aberration correction optical system may be a CMOS-based individual programmable deflector, as disclosed in European Patent Application Publication No. 2702595A1, or an array of multipole deflectors, as disclosed in European Patent Application Publication No. 2715768A2, of which the descriptions of beamlet manipulators in both documents are incorporated herein by reference. The condenser lens and the correction optical system may be part of the same structure. For example, the condenser lens and the correction optical system may be connected to each other using insulating elements or the like.

[0058]

[0069] In some embodiments, each of at least a subset of aberration-correcting optical systems is integrated with or directly adjacent to one or more objective lenses 234. In one embodiment, these aberration-correcting optical systems reduce one or more of field curvature, focusing error, and astigmatism. Additionally or alternatively, one or more scanning deflectors (not shown) may be integrated with or directly adjacent to one or more objective lenses 234 for scanning the sample 208 with subbeams 211, 212, and 214. In one embodiment, a scanning deflector as described in U.S. Patent Application Publication 2010 / 0276606 may be used, which is incorporated herein by reference in its entirety.

[0059]

[0070] In one embodiment, the objective lens mentioned in the above embodiment is an array objective lens. Each element in the array is a microlens that manipulates a different beam or group of beams in a multibeam. The electrostatic array objective lens has at least two plates, each having a plurality of holes or apertures. The position of each hole in a plate corresponds to the position of a corresponding hole in the other plate. The corresponding holes manipulate the same beam or group of beams in a multibeam when in use. A suitable example of the type of lens for each element in the array is a two-electrode deceleration lens.

[0060]

[0071] In some embodiments, the detector 240 of the objective lens array assembly includes a detector array located in the down beam of at least one electrode of the objective lens array 241. The detector array may consist of multiple detector elements. Thus, the detector may be located within the objective lens array assembly. In one embodiment, at least a portion of the detector (e.g., a detector module) is adjacent to and / or integrated with the objective lens array 240. For example, the detector array may be implemented by integrating a CMOS chip detector into the bottom electrode of the objective lens array. Integrating the detector array into the objective lens array replaces the secondary column. The CMOS chip is preferably oriented to face the wafer (because the distance between the sample and the bottom of the electro-optical system is short (e.g., 100 μm)). Regardless of the position of the detector within the objective lens array, there is a short distance between the detector and the sample. At such a distance, the sample may be within the detection range of the detector. Such a short or optimal distance between the sample and the detector may be desirable, for example, to avoid crosstalk between detector elements, or the detector signal may become too weak if the distance is too long. This optimal distance or range of the detector maintains a minimum gap between the detector and the sample (this may relate to, or be approximately equivalent to, the gap between the objective lens array and the sample). However, this short distance is not so short as to not prevent the risk of damaging components of the objective lens array assembly, such as the sample, the sample support, or the detector. In one embodiment, the electrode that captures the secondary electron signal is formed within the upper metal layer of the CMOS device (e.g., the surface of the detector facing the sample). The electrode may be formed in other layers. Power and control signals of the CMOS may be connected to the CMOS by through-silicon vias. For robustness, the bottom electrode is preferably composed of two elements: a CMOS chip and a perforated passive Si plate. The plate shields the CMOS from high electric fields.

[0061]

[0072] To maximize detection efficiency, it is desirable to make the electrode surface as large as possible so that substantially all area of ​​the objective lens array (excluding the aperture) is occupied by electrodes. Each electrode has a diameter substantially equal to the array pitch. In some embodiments, the electrode outline is circular, but this can be square to maximize the detection area. The diameter of the substrate through-holes can also be minimized. The typical size of the electron beam is about 5 to 15 microns.

[0062]

[0073] In one embodiment, a single electrode surrounds each aperture. In another embodiment, multiple electrode elements are provided around each aperture. Electrons captured by the electrode elements surrounding one aperture can be combined into a single signal or used to generate independent signals. The electrode elements can be divided radially (i.e., to form multiple concentric rings), angularly (i.e., to form multiple fan-shaped sections), both radially and angularly, or in any other convenient manner.

[0063]

[0074] However, increasing the electrode surface area leads to increased parasitic capacitance and, consequently, a decrease in bandwidth. Therefore, limiting the electrode's outer diameter is sometimes desirable, especially when increasing the electrode size only provides a slight improvement in detection efficiency but results in a significant increase in capacitance. Circular (annular) electrodes can offer a good compromise between collection efficiency and parasitic capacitance.

[0064]

[0075] Increasing the outer diameter of the electrode can also lead to an increase in crosstalk (sensitivity to signals from adjacent holes). This can be a reason to reduce the outer diameter of the electrode, especially if the enlargement of the electrode only provides a slight improvement in detection efficiency but results in a significant increase in crosstalk.

[0065]

[0076] The current of backscattered electrons and / or secondary electrons collected by the electrodes is amplified by a transimpedance amplifier.

[0066]

[0077] Figure 6 shows an exemplary embodiment of a detector incorporated into an objective lens array. Figure 6 shows a schematic cross-sectional view of a portion 401 of a multi-beam objective lens array. In this embodiment, the detector includes a detector module 402 which includes a plurality of detector elements 405 (e.g., sensor elements such as capture electrodes). Thus, the detector can be a detector array or an array of detector elements. In this embodiment, the detector array 402 is located on the output side of the objective lens array. The output side is the output side of the objective lens 401. Figure 7 is a bottom view of the detector module 402, which includes a substrate 404 on which a plurality of capture electrodes 405 are located, each of which surrounds a beam aperture 406. The beam aperture 406 can be formed by etching the substrate 404. In the configuration shown in Figure 7, the beam aperture 406 is shown as a rectangular array. Unlike this, the beam aperture 406 can also be arranged in a close-packed hexagonal array, for example, as shown in Figure 8.

[0067]

[0078] Figure 9 shows a cross-sectional view of a portion of the detector module 402 at a larger scale. The detector elements, such as the capture electrode 405, form the bottom surface of the detector module 402, i.e., the surface closest to the sample. A logic layer 407 is provided between the capture electrode 405 and the main body of the silicon substrate 404. The logic layer 407 may include amplifiers, such as transimpedance amplifiers, analog-to-digital converters, and readout logic. In one embodiment, there is one amplifier and one analog-to-digital converter for each capture electrode 405. The logic layer 407 and the capture electrode 405 can be manufactured using a CMOS process, with the capture electrode 405 forming the final metal coating layer.

[0068]

[0079] The wiring layer 408 is located on the back or inside of the substrate 404 and is connected to the logic layer 407 by through-silicon vias 409. The number of through-silicon vias 409 does not need to be the same as the number of beam apertures 406. In particular, if electrode signals are digitized within the logic layer 407, only a small number of through-silicon vias may be needed to provide a data bus. The wiring layer 408 may include control lines, data lines, and power lines. There is sufficient space for all necessary connections despite the presence of beam apertures 406. The detection module 402 can also be manufactured using bipolar or other manufacturing techniques. A printed circuit board and / or other semiconductor chips may be located on the back of the detector module 402.

[0069]

[0080] The integrated detector array described above is particularly advantageous when used with tools where the landing energy is adjustable, as it allows for the optimization of secondary electron capture within a range of landing energies. The detector array can be integrated not only with the bottom electrode array but also with other electrode arrays. Further details and alternative configurations of the detector module integrated with the objective lens are described in European Patent Application No. 20184160.8, which is incorporated herein by reference.

[0070]

[0081] Embodiments of this disclosure provide an objective lens array assembly. The objective lens array assembly may be incorporated into the electron-optical system of a charged particle evaluation tool. The charged particle evaluation tool may be configured to focus multiple beams onto a sample.

[0071]

[0082] Figure 10 is a schematic diagram of an exemplary electro-optical system having an objective lens array assembly. The objective lens array assembly includes an objective lens array 241. The objective lens array 241 includes a plurality of objective lenses. Each objective lens includes at least two electrodes (e.g., two or three electrodes) connected to its respective potential source. The objective lens array 241 may include two or more (e.g., three) plate-like electrode arrays connected to its respective potential source. Each objective lens formed by the plate-like electrode array may be a microlens that manipulates different sub-beams or groups of sub-beams in a multi-beam system. Each plate defines a plurality of apertures (also called holes). The position of each aperture in a plate corresponds to the position of a corresponding aperture (or corresponding hole) in another plate (or plurality of plates). The corresponding apertures define the objective lenses, and therefore each set of corresponding holes, when in use, manipulates the same sub-beam or group of sub-beams in a multi-beam system. Each objective lens projects each sub-beam of the multi-beam system onto the sample 208.

[0072]

[0083] For ease of explanation, lens arrays are schematically depicted in this specification as elliptical arrays. Each ellipse represents one of the lenses in the lens array. The ellipse is used to represent lenses in a manner that resembles the biconvex shape commonly used in optical lenses. However, in relation to charged particle configurations such as those discussed herein, it will be understood that lens arrays, which typically operate electrostatically, may not require physical elements employing a biconvex shape. As mentioned above, lens arrays may instead include multiple plates having apertures.

[0073]

[0084] The objective lens array assembly further includes a control lens array 250 (therefore, the objective lens array assembly may include the control lens array 250 and the objective lens array 241). The control lens array 250 includes a plurality of control lenses. Each control lens includes at least two electrodes (e.g., two or three electrodes) connected to its respective potential source. The control lens array 250 may include two or more (e.g., three) plate-shaped electrode arrays connected to its respective potential source. The control lens array 250 is associated with the objective lens array 241 (e.g., these two arrays are positioned close to each other and / or mechanically connected to each other and / or controlled together as a single unit). The control lens array 250 is positioned in the up beam of the objective lens array 241. The control lenses prefocus the subbeam (e.g., apply a focusing effect to the subbeam before it reaches the objective lens array 241). Therefore, if the objective lens array assembly consists only of the control lens array 250 and the objective lens array 241, the combined focusing of the control lens and the objective lens can be controlled to be on the sample. Prefocus can reduce the divergence of the sub-beam or increase the convergence of the sub-beam. The control lens array has a prefocus distance. The control lens array works together with the objective lens array to provide a combined focal length. Combined operation without intermediate focusing can reduce the risk of aberrations. The control lens can be controlled, for example, to focus each sub-beam onto the sample while maintaining a minimum distance between the sample and the objective lens array and / or the sample. Therefore, the control of the control lens and each objective lens can preferably determine the focusing position (e.g., each focus) of each sub-beam on the sample. Thus, the combined action of each objective lens and each control lens determines the focusing position of each sub-beam on the sample. That is, the combined lens effect of each objective lens and each control lens on each sub-beam results in focusing on the sample. This can also be described as the combined lensing effect of each sub-beam by each objective lens and each control lens resulting in focusing on the sample.In other words, each objective lens and each control lens work together to focus their respective sub-beams onto the sample. Alternatively or additionally, the controller is configured to control the objective lenses to focus each sub-beam onto the sample and to control the control lenses to control the prefocus parameters of each sub-beam, such that the prefocus of each sub-beam is before the objective lens focuses each sub-beam onto the sample.

[0074]

[0085] The control lens array 250 can be considered as providing electrodes in addition to the electrodes of the objective lens array 241 (this also applies to the control lens in the embodiment of Figure 10, as well as in the embodiments of Figures 3 and 11). The additional electrodes of the control lens array 250 allow for a greater degree of freedom in controlling the electron-optical parameters of the subbeam. In one embodiment, the control lens array 250 can be considered as additional electrodes of the objective lens array 241 that enable additional functions for each of the objective lenses of the objective lens array 241. In one configuration, such electrodes can be considered as part of the objective lens array that provides additional functions for the objective lenses of the objective lens array 241. In such a configuration, the control lens is considered to be part of the corresponding objective lens to the extent that it is only mentioned that the control lens is part of the objective lens.

[0075]

[0086] In one embodiment, an electro-optical system including an objective lens array assembly is configured to control the objective lens assembly (for example, by controlling the potential applied to the electrodes of the control lens array 250) such that the focal length of the control lens is greater than the distance between the control lens array 250 and the objective lens array 241. In this way, the control lens array 250 and the objective lens array 241 can be positioned relatively close together due to a focusing effect from the control lens array 250 that is too weak to form an intermediate focus between the control lens array 250 and the objective lens array 241. The focusing position of each subbeam by the control lens array may be a downbeam of the objective lens array. In another embodiment, the objective lens array assembly may be configured to form an intermediate focus between the control lens array 250 and the objective lens array 241. The subbeam may have an intermediate focus between the control lens array and the objective lens array.

[0076]

[0087] In one embodiment, the control lens array is a replaceable module, either on its own or in combination with other elements such as an objective lens array and / or a detector array. The replaceable module may be a field-replaceable module, i.e., the module can be swapped with a new module by a field engineer. In one embodiment, multiple replaceable modules are housed within a tool and can be swapped between an operational position and a non-operational position without opening the tool.

[0077]

[0088] In one embodiment, the interchangeable module includes an electro-optical component on a stage that enables movement for positioning the component. In one embodiment, the interchangeable module includes a stage. In one configuration, the stage and the interchangeable module may be an integral part of the electro-optical tool 40. In one configuration, the interchangeable module is limited to the stage and the electro-optical device supported by the stage. In one configuration, the stage is removable. In an alternative design, the interchangeable module including the stage is removable. The part of the electro-optical tool 40 relating to the interchangeable module is separable, i.e., this part of the electro-optical tool 40 is defined by valves on the up beam and valves on the down beam of the interchangeable module. The valves can be operated to separate the environment between the valves from the vacuum in the up beam and down beam of the valves, allowing the interchangeable module to be removed from the electro-optical tool 40, respectively, while maintaining the vacuum in the up beam and down beam of a portion of the column accompanying the interchangeable module. In one embodiment, the interchangeable module includes a stage. The stage is configured to support the electro-optical device with respect to the beam path. In one embodiment, the module includes one or more actuators of 405. The actuators are associated with a stage. The actuators are configured to move the electro-optical device relative to the beam path. Such operation may be used to align the electro-optical device and the beam path relative to each other.

[0078]

[0089] In one embodiment, the replaceable module includes a MEMS module. In one embodiment, the replaceable module is configured to be replaceable within the electro-optical tool 40. In one embodiment, the replaceable module is configured to be replaceable in the field. Field replaceability is intended to mean that the module can be removed and replaced with the same or a different module while maintaining the vacuum in which the electro-optical tool 40 is located. Only the section of the column corresponding to the module is vented, and that section is vented in order to remove and return or replace the module. When replacing a module in the column, the section of the column may be vented in order to completely remove and replace it not only from the column but also from the apparatus or tool. In another embodiment, the section may be vented so that the module in the vented section of the column can be replaced with a module stored elsewhere in the tool or apparatus. Such stored modules may be stored in one or more module compartments that are kept under vacuum. The vacuum of the compartment for storing modules may be lower than that of the column. In another embodiment, the compartment may be under the same pressure as the column, and as a result, ventilation of the section of the column in which the modules are located is not required.

[0079]

[0090] The control lens array may be in the same module as the objective lens array 241, that is, it may form an objective lens array assembly or objective lens configuration, or it may be located in a separate module.

[0080]

[0091] A power supply is provided so that the potential can be applied to the electrodes of the control lens of the control lens array 250 and the objective lens of the objective lens array 241, respectively.

[0081]

[0092] By providing a control lens array 250 in addition to the objective lens array 241, the degree of freedom for controlling the characteristics of the sub-beam is further increased. This additional degree of freedom is also provided when the control lens array 250 and the objective lens array 241 are located together relatively close to each other, for example, when no intermediate focus is formed between the control lens array 250 and the objective lens array 241. The control lens array 250 can be used to optimize the beam opening angle with respect to the beam reduction factor and / or to control the beam energy delivered to the objective lens array 241. The control lens may include two or more electrodes. If there are two electrodes, the reduction factor and landing energy are controlled together. If there are three or more electrodes, the reduction factor and landing energy can be controlled independently. Thus, the control lens may be configured to adjust the reduction factor and / or beam opening angle of each sub-beam (for example, by using a power supply to apply appropriate potentials to the electrodes of the control lens and the objective lens). This optimization can be achieved without excessively negatively impacting the number of objective lenses or excessively worsening the aberrations of the objective lenses (for example, without increasing the intensity of the objective lenses). By using a control lens array, the objective lens array can operate at its optimal electric field intensity. Thus, such operation of the control lens can make it possible to predetermine the electric field intensity of the objective lens array. Note that references to reduction magnification and aperture angle are intended to refer to variations of the same parameters. In an ideal configuration, the product of a certain range of reduction magnification and the corresponding aperture angle is constant. However, the aperture angle can be affected by the use of aperture.

[0082]

[0093] In the embodiment shown in Figure 10, the electron-optical system includes a radiation source 201. The radiation source 201 supplies a beam of charged particles (e.g., electrons). The multibeams focused onto the sample 208 are obtained from the beam supplied by the radiation source 201. Subbeams can be obtained from the beam, for example, using a beam limiter that defines an array of beam limiting apertures. The radiation source 201 is preferably a high-brightness thermal field emission emitter with a good compromise between brightness and total emission current. In the illustrated example, a collimator is provided on the upbeam of the objective lens array assembly. The collimator may include a macrocollimator 270. The macrocollimator 270 acts on the beam from the radiation source 201 before the beam is split into multibeams. The macrocollimator 270 bends each portion of the beam by an amount sufficient to ensure that the beam axis of each subbeam obtained from the beam is incident on the sample 208 substantially perpendicularly (i.e., substantially at 90° with respect to the nominal surface of the sample 208). The macrocollimator 270 collimates the beam macroscopically. Therefore, the macrocollimator 270 may act on the entire beam, rather than including an array of collimator elements, each configured to act on different individual parts 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 may use a combination of magnetic and electrostatic lenses.

[0083]

[0094] In the embodiment shown in Figure 10, the 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 256 includes, for example, a macroscopic multi-pole deflector with eight or more poles. This deflection is for scanning the sample 208 with a sub-beam obtained from the beam in one direction (e.g., parallel to a single axis such as the X-axis) or 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 illustrated embodiment, the macroscan deflector 265 is provided between the macrocollimator 270 and the control lens array 250.

[0084]

[0095] Any of the objective lens array assemblies described herein may further include a detector (e.g., including a detector module 402). The detector may include, for example, a detector array of detector elements. The detector detects charged particles emitted from the sample 208. The detected charged particles may include any of the charged particles detected by the SEM, including secondary electrons and / or backscattered electrons emitted from the sample 208. Exemplary structures of the detector module are described above in relation to Figures 6 to 9. The detector of the detector module, i.e., the detector array, may be positioned within a specified range of the sample, for example, along the beam path. The distance between the detector and the sample can be small, regardless of the position of the detector in the objective lens array or further in the objective lens array assembly. Such a small distance between the sample and the detector is the optimal distance or range for the detector, which may be desirable, for example, to avoid crosstalk between detector elements, and the detector signal may be too weak if the distance from the sample to the detector is too large. The optimal distance or range for the detector maintains a minimum gap between the detector and the sample (which also corresponds to the minimum gap between the objective lens array and the sample). However, this small distance cannot be too small to avoid, if not avoid, the risk of damage to the sample, its support, i.e., the sample holder or components of the objective lens array assembly such as the detector.

[0085]

[0096] Figure 11 shows a modification of the embodiment of Figure 10, in which the objective lens array assembly includes a scan deflector array 260. The scan deflector array 260 includes a plurality of scan deflectors. The scan deflector array 260 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 260 may include a scan deflector for each sub-beam. Each scan deflector can deflect the ray in 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 the Y-axis). This deflection causes the sub-beam to scan over the sample 208 in one or two directions (i.e., one-dimensional or two-dimensional). In one embodiment, the scan deflector described in European Patent No. 2425444 may be used to implement the scan deflector array 260, which is incorporated herein by reference in whole, particularly in relation to the scan deflector. The scan deflector array 260 is positioned between the objective lens array 241 and the control lens array 250. In the illustrated embodiment, the scan deflector array 260 is provided in place of the macro scan deflector 265. The scan deflector array 260 (e.g., formed using the MEMS fabrication techniques described above) may be more spatially compact than the macro scan deflector 265.

[0086]

[0097] In other embodiments, both a macro-scan deflector 265 and a scan deflector array 260 are provided. In such a configuration, scanning the sample surface with a sub-beam can be achieved by controlling the macro-scan deflector 265 and the scan deflector array 260 together, preferably in a synchronous manner.

[0087]

[0098] By replacing the macro-scan deflector 265 with a scan deflector array 260, aberrations from the control lens can be reduced. This is because the scanning operation of the macro-scan deflector 265 causes the beam to move in response to the beam shaping limiter (also called a lower beam limiter), which defines an array of beam limiting apertures to the down beam of at least one electrode of the control lens, and this increases the contribution of the control lens to aberrations. When the scan deflector array 260 is used instead, the beam moves by a much smaller amount over the beam shaping limiter because the distance from the scan deflector array 260 to the beam shaping limiter is much shorter. For this reason, it is preferable to position the scan deflector array 260 as close as possible to the objective lens array 241 (for example, so that the scan deflector array 260 is directly adjacent to the objective lens array 241, as shown in Figure 11). The smaller the movement over the beam shaping limiter, the smaller the portion used by each control lens. Therefore, the control lens contributes less to aberration. To minimize or at least reduce the aberrations contributed by the control lens, a beam shaping limiter is used to shape the beam in the down beam of at least one electrode of the control lens. This differs from conventional systems and architectures where the beam shaping limiter is provided only as part of a first manipulator array in the beam path or as an aperture array associated therewith, and where multiple beams are generally generated from a single beam from a radiation source.

[0088]

[0099] In some embodiments, as illustrated in Figure 10, the control lens array 250 is an electro-optical array element that exhibits a first deflection or lensing effect in the beam path of the down beam of the radiation source 201.

[0089]

[0100] In the embodiment shown in Figure 11, a collimator element array 271 is provided in place of the macrocollimator 270. Although not shown, this modification can also be applied to the embodiment shown in Figure 3 to provide an embodiment having a macroscan deflector and a collimator element array. Each collimator element collimates its respective subbeam. The collimator element array 271 (e.g., formed using MEMS fabrication techniques) may be more spatially compact than the macrocollimator 270. Therefore, space can be saved by providing the collimator element array 271 and the scan deflector array 260 together. This space saving is desirable when multiple electro-optical systems, including objective lens array assemblies, are provided in an electro-optical system array. In such embodiments, a macrocondenser lens or condenser lens array may not be present. Therefore, in this scenario, the control lens provides the possibility of optimizing the beam opening angle and magnification in response to changes in landing energy. Note that the beam shaping limiter is located in the downbeam of the control lens array. The aperture in the beam shaping limiter modulates the beam flow along the beam path so that the magnification control by the control lens functions differently with respect to the opening angle. In other words, the aperture in the beam shaping limiter breaks the direct correspondence between changes in magnification and opening angle.

[0090]

[0101] In some embodiments, as illustrated in Figure 11, the collimator element array 271 is a first deflection or focusing electron-optical array element in the beam path of the down beam of the radiation source 201.

[0091]

[0102] By avoiding deflecting or lensing electro-optical array elements (e.g., lens arrays or deflector arrays) in the up-beam of the control lens array 250 or the up-beam of the collimator element array 271, the requirements for the electro-optical system in the up-beam of the objective lens and the corrective optical system to compensate for imperfections in such optical systems are reduced. For example, some alternative configurations attempt to maximize the utilization of the radiation source current by providing a condenser lens array in addition to the objective lens array. By providing a condenser lens array and an objective lens array in this way, there is a strict requirement that the position of the virtual radiation source relative to the radiation source opening angle be uniform, or a corrective optical system is required for each sub-beam so that each sub-beam passes through the center of its corresponding objective lens downstream. Architectures such as those in Figures 10 and 11 can reduce the beam path from the first deflecting or lensing electro-optical array element to the beam shaping limiter to less than about 10 mm, preferably less than about 5 mm, and more preferably less than about 2 mm. Shortening the beam path can alleviate or eliminate the strict requirements for the position of the virtual radiation source relative to the radiation source opening angle.

[0092]

[0103] In one embodiment, an electron-optical system array is provided. The array may include any of the electron-optical systems described herein. Each electron-optical system simultaneously focuses its respective multibeam onto a different region of the same sample. Each electron-optical system may form a subbeam from beams of charged particles from different sources 201. Each of the respective sources 201 may be one source in a plurality of sources 201. At least a subset of the plurality of sources 201 may be provided as a source array. The source array may include a plurality of sources 201 provided on a common substrate. By simultaneously focusing multiple multibeams onto different regions of the same sample, the area of ​​sample 208 that is processed (e.g., evaluated) at the same time can be increased. The electron-optical systems in the array may be arranged adjacent to one another so that their respective multibeams project onto adjacent regions of sample 208. Any number of electron-optical systems may be used in the array. Preferably, the number of electron-optical systems is in the range of 9 to 200. In one embodiment, the electron-optical system consists of a rectangular array or a hexagonal array. In other embodiments, the electro-optical system is provided in an irregular array or a regular array having a geometry other than rectangular or hexagonal. Each electro-optical system in the array may consist of any of the configurations described herein when referring to a single electro-optical system. As described above, the scan deflector array 260 and the collimator element array 271 are particularly suitable for incorporation into an electro-optical system array because they are spatially compact, making it easy to position the electro-optical systems in close proximity to each other.

[0093]

[0104] In some embodiments, as illustrated in Figures 12 and 13, the objective lens array assembly further includes a beam shaping limiter 242. The beam shaping limiter 242 defines an array of beam limiting apertures 124. The beam shaping limiter 242 may be referred to as the beam shaping limiting aperture array or the final beam limiting aperture array. The beam shaping limiter 242 may include a plate (which may be a plate-like body) having multiple apertures. The beam shaping limiter 242 is down-beam from at least one electrode (optionally all electrodes) of the control lens array 250. In some embodiments, the beam shaping limiter 242 is down-beam from at least one electrode (optionally all electrodes) of the objective lens array 241. The plate of the beam limiter 242 may be connected to adjacent plate electrode arrays of the objective lenses by a separating element such as a spacer, which may include ceramic or glass.

[0094]

[0105] In one configuration, the beam shaping limiter 242 is structurally integrated with the electrodes 302 of the objective lens array 241. That is, the plate of the beam shaping limiter 242 is directly connected to the adjacent plate electrode array of the objective lens array 241. It is desirable that the beam shaping limiter 242 be positioned in a region with low or no electrostatic field strength, for example, in a region associated with an adjacent plate electrode (e.g., inside or above it) facing away from all other electrodes of the objective lens array 242. Each beam limiting aperture 124 is aligned with the corresponding objective lens in the objective lens array 241. This alignment allows a portion of the sub-beam from the corresponding objective lens to pass through the beam limiting aperture 124 and strike the sample 208. Each beam limiting aperture 124 has a beam limiting effect, allowing only a selected portion of the sub-beam incident on the beam shaping limiter 242 to pass through the beam limiting aperture 124. The selected portion may be such that only the portion of each sub-beam 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 sub-beam.

[0095]

[0106] In some embodiments, the electro-optical system further includes an upper beam limiter 252. The upper beam limiter 252 defines an array of beam limiting apertures. The upper beam limiter 252 may be called an upper beam limiting aperture array or an up-beam beam limiting aperture array. The upper beam limiter 252 may include a plate (which may be a plate-like body) having multiple apertures. The upper beam limiter 252 forms a subbeam from the beam of charged particles emitted by the radiation source 201. Beam portions other than those contributing to the formation of the subbeam may be blocked (e.g., absorbed) by the upper beam limiter 252 so as not to interfere with the down-beam subbeam. The upper beam limiter 252 may be called a subbeam defining aperture array.

[0096]

[0107] In embodiments that do not include a focusing lens array, as illustrated in Figures 10 and 11, the upper beam limiter 252 may form part of the objective lens array assembly. The upper beam limiter 252 may be adjacent to and / or integrated with the control lens array 250 (for example, as shown in Figure 13, it may be adjacent to and / or integrated with the electrode 603 of the control lens array 250 closest to the radiation source 201). The upper beam limiter 252 may be the up-up beam electrode of the control lens array 250. In one embodiment, the upper beam limiter 252 defines a beam limiting aperture that is larger (e.g., has a larger cross-sectional area) than the beam limiting aperture 124 in the beam shaping limiter 242. Therefore, the beam limiting aperture 124 of the beam shaping limiter 242 may be smaller in dimensions (i.e., smaller in area and / or diameter and / or size of other characteristics) than the corresponding aperture defined in the upper beam limiter 252 and / or in the objective lens array 241 and / or in the control lens array 250.

[0097]

[0108] In embodiments having a focusing lens array 231, as illustrated in Figure 3, the upper beam limiter 252 may be located adjacent to and / or integrated with the focusing lens array 231 (for example, adjacent to and / or integrated with the electrode of the focusing lens array 231 closest to the radiation source 201). Generally, it is desirable to configure the beam limiting aperture of the beam shaping limiter 242 to be smaller than the beam limiting apertures of all other beam limiters that define beam limiting apertures up the beam from the beam shaping limiter 242. That is, a subbeam may be derived from the beam (i.e., the beam of charged particles from the radiation source 201) using, for example, beam limiters that define an array of beam limiting apertures. The upper beam limiter 252 is a beam limiting aperture array that is associated with or can be part of the focusing lens array 231.

[0098]

[0109] The beam shaping limiter 242 is preferably configured to have a beam limiting effect (i.e., to remove a portion of each sub-beam incident on the beam shaping limiter 242). The beam shaping limiter 242 may be configured, for example, to ensure that each sub-beam exiting the objective lenses of the objective lens array 241 passes through the center of its respective objective lens. In contrast to alternative methods, this effect can be achieved using the beam shaping limiter 242 without requiring complex alignment procedures to ensure that the sub-beam incident on the objective lenses is adequately aligned with the objective lenses. Furthermore, the effect of the beam shaping limiter 242 is not hindered by column alignment operations, radiation source instability, or mechanical instability. Additionally, the beam shaping limiter 242 reduces the length over which scanning operates on the sub-beam. This distance is reduced to the length of the beam path from the beam shaping limiter 242 to the sample surface.

[0099]

[0110] In some embodiments, the ratio of the diameter of the beam limiting aperture in the upper beam limiter 252 to the diameter of the corresponding beam limiting aperture 124 in the beam shaping limiter 242 is 3 or greater, optionally 5 or greater, optionally 7.5 or greater, and optionally 10 or greater. In one configuration, for example, the beam limiting aperture in the upper beam limiter 252 has a diameter of about 50 microns, and the corresponding beam limiting aperture 124 in the beam shaping limiter 242 has a diameter of about 10 microns. In another configuration, the beam limiting aperture in the upper beam limiter 252 has a diameter of about 100 microns, and the corresponding beam limiting aperture 124 in the beam shaping limiter 242 has a diameter of about 10 microns. It is desirable that only a portion of the beam that has passed through the center of the objective lens is selected by the beam limiting aperture 124. In the example shown in Figure 13, each objective lens is formed by an electrostatic field between electrodes 301 and 302. In some embodiments, each objective lens consists of two basic lenses (each with a focal length = 4 * beam energy / electric field), namely a lens at the bottom of electrode 301 and a lens at the top of electrode 302. The primary lens may be the lens at the top of electrode 302 (because the beam energy may be small at this location, for example 2.5 kV compared to 30 kV near electrode 301, which makes that lens about 12 times more powerful than the other). The portion of the beam passing through the center of the aperture at the top of electrode 302 is preferably also passing through the beam limiting aperture 124. Because the z-direction distance between the top of electrode 302 and aperture 124 is very small (typically, for example, 100-150 microns), the correct portion of the beam is selected even when the beam angle is relatively large. The electric field intensity within the objective lens array may be a predetermined value.

[0100]

[0111] In the specific examples shown in Figures 12 and 13, the beam shaping limiter 242 is shown as an element formed separately from the bottom electrode 302 of the objective lens array 241. In other embodiments, the beam shaping limiter 242 may be formed integrally with the bottom electrode of the objective lens array 241 (for example, by lithography to etch away cavities suitable for functioning as lens apertures and beam-blocking apertures on opposing surfaces of the substrate).

[0101]

[0112] In one embodiment, the aperture 124 in the beam shaping limiter 242 may be located at a distance in the downbeam from at least a portion of the corresponding lens aperture in the bottom electrode of the corresponding objective lens array 241, at a distance in the downbeam greater than or equal to the diameter of the lens aperture, preferably at least 1.5 times greater than the diameter of the lens aperture, and preferably at least 2 times greater than the diameter of the lens aperture.

[0102]

[0113] Generally, it is desirable to position the beam shaping limiter 242 adjacent to the electrode of each objective lens having the strongest lens effect. In the examples of Figures 12 and 13, the bottom electrode 302 has the strongest lens effect, and the beam shaping limiter 242 is positioned adjacent to this electrode. If the objective lens array 241 includes three or more electrodes, such as an Einzel lens configuration with three electrodes, the electrode with the strongest lens effect is usually the central electrode. In this case, it is desirable to position the beam shaping limiter 242 adjacent to the central electrode. Therefore, at least one electrode of the objective lens array 241 may be positioned in the down beam of the beam shaping limiter 242. The electro-optical system may also be configured to control the objective lens assembly (for example, by controlling the potential applied to the electrodes of the objective lens array) so that the beam shaping limiter 242 is adjacent to or integrated with the electrode of the objective lens array 241 that has the strongest lens effect.

[0103]

[0114] Generally, it is also desirable to place the beam shaping limiter 242 in a region with a small electric field, preferably a region with virtually no electric field. This avoids or minimizes disturbances to the desired lensing effect caused by the presence of the beam shaping limiter 242.

[0104]

[0115] As illustrated in Figures 12 and 13, it is desirable to provide a beam shaping limiter 242 on the up beam of the detector (e.g., detector array 402). Providing a beam shaping limiter 242 on the up beam of the detector ensures that the beam shaping limiter 242 does not obstruct charged particles emitted from the sample 208, thereby preventing the charged particles from reaching the detector. Therefore, in embodiments in which the detector is located on the up beam of all electrodes of the objective lens array 241, it is desirable to provide the beam shaping limiter 242 on the up beam of all electrodes of the objective lens array 241, or further, on the up beam of one or more electrodes of the control lens array 250. In this scenario, it may be desirable to position the beam shaping limiter 242 on the up beam of the detector while being as close as possible to the objective lens array 241. Therefore, the beam shaping limiter 242 may be located directly adjacent to the detector in the up beam direction.

[0105]

[0116] The objective lens array assembly described above, having a beam shaping limiter 242 on the downbeam from at least one electrode of the control lens array 250 and / or at least one electrode of the objective lens array 241, is an example of a class of objective lens configurations. Embodiments of this class include objective lens configurations for an electron-optical system for focusing a multibeam onto a sample 208. The objective lens configuration includes an upbeam lens effect aperture array (e.g., electrode 302 or 121 of the objective lens array 241 closest to the radiation source 201, as shown in Figure 12). The objective lens configuration further includes a downbeam lens effect aperture array (e.g., electrode 122 of the objective lens array 241 furthest from the radiation source 201, as shown in Figure 12). The downbeam lens effect aperture array (e.g., electrode 302) and the upbeam lens effect aperture array (e.g., electrode 301) work together to provide a lens effect to the subbeams of the multibeam. A beam-limiting aperture array (e.g., beam-shaping limiter 242 shown in Figure 12) is provided, in which apertures (e.g., beam-limiting aperture 124 in Figure 12) are smaller in dimensions (i.e., smaller in area and / or diameter and / or size of other characteristics) than apertures in the up-beam lens-effect aperture array and the down-beam lens-effect aperture array. The apertures in the beam-limiting aperture array are configured to limit each sub-beam to the portion of the sub-beam that has passed through the central portion of the respective aperture in the up-beam lens-effect aperture array and the down-beam lens-effect aperture array. Thus, as described above, the beam-limiting aperture array can ensure that each sub-beam exiting the objective lens of the objective lens configuration has passed through the center of the respective lens.

[0106]

[0117] References to controllable components or systems of components or elements for manipulating a charged particle beam in a particular manner include configuring a controller or control system or control unit to manipulate the charged particle beam in the manner described above, and optionally using other controllers or devices (e.g., voltage sources and / or current sources) to control components and manipulate the charged particle beam in that manner. For example, a voltage source may be electrically connected to one or more components to apply potential to components such as, but are not limited to, a control lens array 250, an objective lens array 241, a focusing lens 231, a compensator, a collimator element array 271, and a scanning deflector array 260, under the control of a controller or control system or control unit. Actuable components such as a stage may be operated using one or more controllers, control systems or control units to control the operation of the component, and thus controllable to move relative to other components such as a beam path.

[0107]

[0118] Embodiments described herein may take the form of a series of aperture arrays or electro-optical elements arranged in an array along a single-beam or multi-beam path. Such electro-optical elements may be electrostatic and may include, for example, objective lens arrays and control lens arrays. One or more of the following elements, namely the focusing lens 231, compensator, collimator element array 271, and scanning deflector array 260 under the control of a controller or control system or control unit, may be electrostatic. In one embodiment, for example, all electro-optical elements from the beam limiting aperture array in the sub-beam path prior to the sample to the last electro-optical element 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).

[0108]

[0119] References to "upper" and "lower," "up" and "down," and "upward" should be understood to refer to directions parallel to the (usually, but not always, perpendicular) up-beam and down-beam directions of the electron beam or multibeam corresponding to Sample 208. Therefore, references to up-beam and down-beam are intended to refer to directions related to the beam path, independent of any gravitational field.

[0109]

[0120] An evaluation tool according to one embodiment of the present invention may be a tool for performing a qualitative evaluation of a sample (e.g., pass / fail), a tool for performing a quantitative measurement of a sample (e.g., feature size), or a tool for generating an image of a map of a sample. Examples of evaluation tools include inspection tools (e.g., for identifying defects), review tools (e.g., for classifying defects), and measurement tools, or tools that can perform any combination of evaluation functions related to inspection tools, review tools, or measurement tools (e.g., measurement inspection tools). The electron-optical column 40 may be a component of the evaluation tool, such as part of an inspection tool, a measurement inspection tool, or an electron beam lithography tool. References to tools herein are intended to encompass devices, apparatus, or systems, and tools include various components that may or may not be located in the same place, and in particular, for example, data processing components may even be located in separate rooms.

[0110]

[0121] The terms “subbeam” and “beamlet” are used interchangeably herein and are understood to encompass any radiation beam derived from a parent radiation beam by splitting or separating the parent radiation beam. The term “manipulator” is used to encompass any element that influences the path of a subbeam or beamlet, such as a lens or deflector. When it is said that an element is aligned along a beam path or subbeam path, it should be understood that each element is positioned along the beam path or subbeam path. When it is said that an optical system is used, it should be understood that it is an electro-optical system.

[0111]

[0122] Embodiments of the present invention are described in the following numbered clauses.

[0112]

[0123] Clause 1: A multibeam electron-optics system for a charged particle evaluation tool, comprising: a plurality of control lenses each configured to control the parameters of a respective subbeam; a plurality of objective lenses each configured to project one of a plurality of charged particle beams onto a sample; and a controller configured to control the control lenses and objective lenses so that charged particles are incident on the sample at a desired landing energy, reduction magnification and / or beam opening angle.

[0113]

[0124] Clause 2: The controller is configured to maintain a predetermined E-field, i.e., an electric field, in the objective lens, as described in Clause 1.

[0114]

[0125] Clause 3: The system according to Clause 1 or 2, wherein the control lens is configured to adjust the reduction magnification and / or beam opening angle of each subbeam and / or control the landing energy of each subbeam on the sample surface.

[0115]

[0126] Clause 4: A control lens located upstream of the objective lens and associated with the objective lens, as described in any one of Clauses 1 to 3.

[0116]

[0127] Clause 5: The controller is configured to control the prefocus parameters of each sub-beam by controlling the control lenses such that the combined effect of each objective lens and each control lens determines the focus position of each sub-beam on the sample; the combined lens effect of each objective lens and each control lens on each sub-beam results in focus on the sample; the combined lens effect of each objective lens and each control lens on each sub-beam results in focus on the sample; and each objective lens and each control lens together focus each sub-beam on the sample. Alternatively or additionally, the controller is configured to control the objective lens to focus each sub-beam onto the sample such that the prefocus of each sub-beam is before the objective lens focuses each sub-beam onto the sample, and to control the control lens to control the prefocus parameter of each sub-beam, preferably such that the position of the sample at the combined focal length (preferably along the path of each sub-beam) maintains a gap, preferably a minimum gap, between the sample and the objective lens array, and / or maintains a gap such as a minimum gap between the detector and the sample, corresponding to the distance between the detector and the sample.

[0117]

[0128] Clause 6: The control of the control lens and each objective lens determines the focusing position of each sub-beam, preferably the focusing position of each sub-beam by the control lens array may be the down beam of the objective lens array, preferably the control lens is configured to have a focal length, and preferably the resulting combined focal length of the control lens and the corresponding objective lens is controlled by the controller, as described in any one of Clauses 1 to 5.

[0118]

[0129] Clause 7: The controller is an objective lens array or objective lens configuration comprising an array of control lenses and an array of objective lenses, preferably the control lens is configured to apply a potential difference to adjacent electrodes of the objective lens configuration, which are in the up beam of the objective lens, that is the maximum potential difference between two adjacent electrodes of the objective lens and the control lens along each path of the charged particle beam, as described in any one of Clauses 1 to 6.

[0119]

[0130] Clause 8: A system according to any one of Clauses 1 to 7, wherein the multiple control lenses and / or multiple objective lenses are configured to be interchangeable, preferably in the field.

[0120]

[0131] Clause 9: The system according to Clause 8, comprising a replaceable module containing multiple control lenses and / or multiple objective lenses, such that the multiple control lenses and / or multiple objective lenses are replaceable when the replaceable module is replaced, preferably in the field.

[0121]

[0132] Clause 10: A multibeam electron-optics system for a charged particle evaluation tool, comprising: a control lens array including a plurality of control electrodes and configured to control the parameters of each subbeam; an objective lens array including a plurality of objective electrodes and configured to guide a plurality of charged particle beams onto a sample; and a potential source system configured to apply relative potentials to the control lenses and objective lenses such that charged particles are incident on the sample at a desired landing energy, reduction magnification and / or beam opening angle.

[0122]

[0133] Clause 11: A multibeam electron-optics system for a charged particle evaluation tool, comprising: an objective lens array including objective lenses configured to focus each subbeam onto a sample surface; and a control lens array including control lenses configured to control the landing energy of each subbeam on the sample surface and / or optimize the opening angle and / or magnification of each subbeam before the objective lens array operates.

[0123]

[0134] Clause 12: The control lens is part of the system described in Clause 11, comprising at least two electrodes along the beam path.

[0124]

[0135] Clause 13: The system according to Clause 12, wherein at least one electrode is configured to set the beam energy of each subbeam, preferably the electrode is downbeam from the first electrode in the beam path.

[0125]

[0136] Clause 14: The system according to Clause 12 or 13, wherein at least one electrode is configured to control the opening angle and / or magnification of each subbeam, preferably the electrode is in the downbeam from a first electrode in the beampath, and preferably the electrode is in the upbeam configured to control the beam energy.

[0126]

[0137] Clause 15: A multibeam electron-optics system for an inspection tool, comprising: an objective lens array configured to focus a plurality of collimated subbeams onto a sample; and a control lens array located up-beam of the objective lens array, configured to control the beam energy of each subbeam, and configured to adjust the landing energy of the subbeams on the sample.

[0127]

[0138] Clause 16: The multibeam electro-optical system described in Clause 15, configured to adjust the landing energy by changing the potential applied to the objective lens array while maintaining the electrostatic field at the objective lens at a pre-selected strength.

[0128]

[0139] Clause 17: The system according to Clause 15 or 16, configured to adjust the landing energy by controlling the control lens array to change the beam energy delivered to the objective lens array by the control lens array.

[0129]

[0140] Clause 18: Controlling the control lens includes re-optimizing the opening angle and reduction magnification, as described in any one of Clauses 15-17.

[0130]

[0141] Clause 19: Each objective lens is a system described in any one of Clauses 1 to 18, including two electrodes.

[0131]

[0142] Clause 20: A multibeam electron-optics system for a charged particle evaluation tool, comprising an objective lens array assembly including a plurality of aperture arrays, wherein the objective lens array assembly is configured to: a) focus a plurality of subbeams onto a sample; and b) control another parameter of the subbeams, which is at least one of the landing energy of the subbeams on the sample surface, the opening angle of each subbeam, and / or the magnification of each subbeam.

[0132]

[0143] Clause 21: The aperture array adjacent to the sample is configured to focus multiple beams onto the sample, as described in Clause 20.

[0133]

[0144] Clause 22: At least two aperture arrays are in close proximity to the sample in the system as described in Clause 21.

[0134]

[0145] Clause 23: An aperture array confirmed to control other parameters is located upstream of an aperture array configured to control the focusing of a subbeam, as described in any one of Clauses 20-22.

[0135]

[0146] Clause 24: The system described in Clause 23, wherein at least two aperture arrays are configured to control other parameters.

[0136]

[0147] Clause 25: The aperture array configured to control other parameters includes an aperture configured to control landing energy, as described in Clause 24.

[0137]

[0148] Clause 26: The system according to Clause 24 or 25, wherein aperture arrays configured to control other parameters include aperture arrays configured to optimize the opening angle and / or magnification of each subbeam, preferably the aperture arrays are the same as the apertures configured to control the landing energy.

[0138]

[0149] Clause 27: A system according to any one of Clauses 1 to 26, further comprising a detector configured to detect charged particles emitted from a sample, preferably comprising a plurality of detector elements, preferably the plurality of detector elements being associated with each subbeam, and the detectors being spaced apart from the sample by a certain distance, preferably the distance from the sample being the optimal distance or range for the detectors.

[0139]

[0150] Clause 28: The system as described in Clause 27, wherein the detector is preferably associated with an objective lens array between multiple objective lenses and the sample.

[0140]

[0151] Clause 29: At least the objective lens (or objective lens array) and the control lens (or control lens array) are electrostatic, and preferably all charged particle optical elements of the multibeam electron-optics system are electrostatic, as described in any one of Clauses 1 to 28.

[0141]

[0152] Clause 30: The charged particle is an electron, and preferably the multibeam electron-optical system includes an emission electron source for emitting the electron, as described in any one of Clauses 1 to 29.

[0142]

[0153] Clause 31: A charged particle evaluation tool comprising a multibeam electron-optical system as described in any one of Clauses 1 to 30, wherein the charged particle evaluation tool preferably comprises a condenser lens, the condenser lens being located in the upbeam of the objective lens array and the control lens array, and the condenser lens is preferably a condenser lens array or, alternatively preferably, a macrocondenser lens being magnetic.

[0143]

[0154] Clause 32: An inspection method comprising using a plurality of control lenses to control the parameters of each of a plurality of subbeams of charged particles, using a plurality of objective lenses to project the plurality of charged particle beams onto a sample, and controlling the control lenses and objective lenses so that the charged particles are incident on the sample at a desired landing energy, reduction magnification and / or beam opening angle.

[0144]

[0155] Clause 33: A method for projecting a plurality of subbeams onto a sample surface using an objective lens array assembly, comprising: a) projecting the subbeams onto the sample surface; and b) controlling the landing energy of the subbeams and / or optimizing the reduction ratio and / or beam opening angle of the subbeams.

[0145]

[0156] Clause 34: The objective lens array assembly includes an array of control lenses, each control lens for controlling the parameters of its respective sub-beam; an array of objective lenses, each objective lens for projecting its respective sub-beam onto a sample; a controller for controlling the control lenses and objective lenses; and a detector for detecting charged particles emitted from the sample, comprising a plurality of detector elements associated with each sub-beam, and positioned at a certain distance from the sample, wherein projection involves using the objective lens array, and control involves controlling the landing energy of the sub-beam so that the sub-beam is incident on the sample at a desired landing energy, the method preferably comprising: 1) the combined action of each objective lens and each control lens determining the focal position of each sub-beam on the sample; and 2) the combined action of each objective lens and each control lens on each sub-beam The method according to Clause 33, further comprising: 3) the lens effect resulting in focusing on the sample; 4) the combined lens effect of each subbeam by each objective lens and each control lens resulting in focusing on the sample; and 5) each objective lens and each control lens focusing each subbeam together on the sample (alternatively or additionally, the controller is configured to control the objective lens to focus each subbeam on the sample and to control the control lens to control the parameter of the prefocus of each subbeam, such that the prefocus of each subbeam is before the subbeam is focused on the sample by the objective lens); and detecting charged particles emitted from the sample, wherein preferably the control lens and objective lens are controlled by the controller, and preferably the detection is performed by the detector.

[0146]

[0157] Clause 35: The method according to Clause 33 or 34, wherein the objective lens array assembly includes an objective lens array configured to project a beam of charged particles onto a sample.

[0147]

[0158] Clause 36: The method according to any one of Clauses 33 to 35, comprising maintaining a predetermined electrostatic field or E-field in the objective lens array.

[0148]

[0159] Clause 37: The method according to any one of Clauses 33 to 36, further comprising adjusting the reduction factor and / or beam opening angle of each sub-beam.

[0149]

[0160] Clause 38:e) The method of any one of Clauses 33 to 37, further comprising adjusting the landing energy of each subbeam in the sample.

[0150]

[0161] Clause 39: The method according to any one of Clauses 33 to 38, further comprising detecting charged particles released from a sample.

[0151]

[0162] Clause 40: Detection is performed using a detector associated with the objective lens array assembly, as described in Clause 39.

[0152]

[0163] Clause 41: The method of Clause 40, wherein detection is between multiple objective lenses and a sample.

[0153]

[0164] Clause 42: The method according to any one of Clauses 33 to 41, wherein a minimum distance is maintained between the sample and the objective lens array and / or detector when prefocusing the control lens to focus each subbeam onto the sample.

[0154]

[0165] Clause 43: The method according to any one of Clauses 33 to 42, further comprising collimating a beam of charged particles.

[0155]

[0166] Clause 44: Collimating is to use a macrocollimator located in the up beam of the objective lens array assembly, as described in Clause 43.

[0156]

[0167] Clause 45: Collimation is performed using a collimator array located within an objective lens array assembly, as described in Clause 43.

[0157]

[0168] Clause 46: The method of any one of Clauses 33 to 45, further comprising making at least one lens element of the objective lens assembly replaceable.

[0158]

[0169] Clause 47: The method of Clause 46, comprising ventilating a section of a column, the section preferably corresponding to a module including at least lens elements of an objective lens assembly, and optionally comprising at least one of removing the module, returning the module to the section, and replacing the module, the method further comprising depressurizing the section.

[0159]

[0170] Clause 48: The method of Clause 46 or 47, which includes swapping a module, which includes at least an element, between an operable position and a non-operable position, wherein in the operable position the module is a section of a column, and optionally swapping the module with another module in a non-operable position such that the module is moved to a non-operable position, preferably to a section such that another module is in an operable position.

[0160]

[0171] Clause 49: A replaceable module configured to be replaceable in a charged particle column, such as an electro-optical column of a charged particle inspection tool, comprising an objective lens array assembly including a plurality of control lenses configured to control the parameters of each sub-beam, the parameters including the reduction magnification and / or landing energy of the multi-beam, and preferably the replaceable module is replaceable in the field.

[0161]

[0172] Clause 50: An objective lens array assembly comprises a plurality of objective lenses configured to project each charged beam of a multibeam onto a sample, and detectors configured to detect charged particles emitted from the sample, preferably comprising a plurality of detector elements associated with each subbeam, and configured to be positioned at a certain distance from the sample when the module is placed in an electro-optical column, preferably the control lens and objective lens are configured to control charged particles so that they are incident on the sample with a desired landing energy and / or reduction magnification, preferably the control lens, when the module is placed in an electro-optical column, 1) the combined action of each objective lens and each control lens determines the focal position of each subbeam on the sample, and 2) each objective lens and each control lens The interchangeable module as described in Clause 49 is preferably configured to control the control lens to control the prefocus parameter of each subbeam such that one or more of the following occur: 3) the combined lens effect on the subbeams results in focus on the sample; 4) the combined lens effect of each subbeam by each objective lens and each control lens results in focus on the sample; and 5) each objective lens and each control lens together focus each subbeam on the sample. (Alternatively or additionally, the controller is configured to control the objective lens to focus each subbeam on the sample and to control the control lens to control the prefocus parameter of each subbeam such that the prefocus of each subbeam is before focus of each subbeam on the sample by the objective lens.

[0162]

[0173] Although the present invention has been described in relation to various embodiments, other embodiments will be apparent to those skilled in the art from considering the details and practices of the invention disclosed herein. This specification and examples are intended to be merely illustrative, and the true scope and spirit of the invention are set forth by the following claims.

Claims

1. A multibeam electron optics system for a charged particle evaluation tool, Multiple control lenses that control the parameters of each subbeam, Multiple objective lenses, each projecting one of the multiple charged particle beams onto a sample, A detector for detecting charged particles emitted from the sample, comprising a plurality of detector elements associated with each subbeam, and spaced a certain distance from the sample, A controller that controls the control lens and the objective lens so that the charged particles are incident on the sample with a desired landing energy and / or reduction magnification, the controller controlling the control lens and the parameters of the prefocus of the respective sub-beams so that the combined effect of the respective objective lens and the respective control lens on the respective sub-beams determines the focusing position of the respective sub-beams on the sample, A multibeam electron-optics system, including one.

2. The system according to claim 1, wherein the controller maintains a predetermined electrostatic field in the objective lens.

3. The system according to claim 1 or 2, wherein the controller applies a potential difference, which is the maximum potential difference between two adjacent electrodes of the objective lens and the control lens along each path of the charged particle beam, to adjacent electrodes of the objective lens array.

4. The system according to any one of claims 1 to 3, wherein the control lens adjusts the reduction ratio of each subbeam and / or controls the landing energy of each subbeam on the sample surface.

5. The system according to any one of claims 1 to 4, wherein the control lens is located in the up beam of the objective lens and is associated with the objective lens.

6. The system according to any one of claims 1 to 5, wherein the plurality of control lenses and / or the plurality of objective lenses are interchangeable.

7. The system according to claim 6, comprising a replaceable module, the replaceable module comprising the plurality of control lenses and / or the plurality of objective lenses, wherein the plurality of control lenses and / or the plurality of objective lenses are replaceable when the module is replaced.

8. A method for projecting multiple subbeams onto a sample surface by using an objective lens array assembly, the objective lens array assembly comprising: an array of control lenses, each control lens for controlling the parameters of a respective subbeam; an array of objective lenses, each objective lens for projecting a respective subbeam onto a sample; a controller for controlling the control lenses and the objective lenses; and a detector for detecting charged particles emitted from the sample, comprising a plurality of detector elements associated with each subbeam and spaced a certain distance from the sample, wherein the method is: a) Projecting the sub-beam onto the surface of the sample, using the objective lens, b) Controlling the landing energy of the subbeam and / or optimizing the reduction ratio of the subbeam so that the subbeam is incident on the sample with a desired landing energy, c) Controlling the parameters by controlling the control lens such that the combined effect of each objective lens and each control lens on each sub-beam is present on the sample, including prefocusing each sub-beam, d) detecting charged particles released from the sample, The control of the control lens and the objective lens is performed by the controller. A method wherein the detection is performed by the detector.

9. The method according to claim 8, further comprising adjusting the reduction ratio of each subbeam.

10. The method according to claim 8 or 9, further comprising adjusting the landing energy of each subbeam on the sample surface.

11. The method according to any one of claims 8 to 10, wherein the detector in the detection is associated with the objective lens array assembly.

12. The method according to any one of claims 8 to 11, wherein the detection is performed between the plurality of objective lenses and the sample.

13. The method according to any one of claims 8 to 12, wherein the control lens is prefocused to focus each of the subbeams onto the sample, and the minimum distance between the sample and the objective lens array is maintained.

14. The method according to any one of claims 8 to 13, further comprising collimating the beam of charged particles.

15. A replaceable module in a charged particle optical column of a charged particle inspection tool, comprising an objective lens array assembly, the objective lens array assembly is A plurality of control lenses for controlling the parameters of each subbeam, wherein the parameters include the reduction ratio and / or landing energy of the multibeam subbeam, Multiple objective lenses for projecting each of the charged beams of the multibeam onto the sample, A detector for detecting charged particles emitted from the sample, comprising a plurality of detector elements associated with each subbeam, wherein the module is spaced a certain distance away from the sample when placed in an electron-optical column, The control lens and the objective lens are controlled so that the charged particles are incident on the sample with a desired landing energy and / or reduction magnification. The control lens is an interchangeable module, which, when the module is placed in an electro-optical column, is controlled to control the parameters of the prefocus of each sub-beam such that the combined effect of each objective lens and each control lens on each sub-beam determines the focusing position of each sub-beam on the sample.

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