Charged particle assessment tool, inspection method

Abstract

The present disclosure relates to a charged particle assessment tool, inspection method. A charged particle tool comprising: an array of condenser lenses configured to separate a beam of charged particles into a first plurality of sub-beams along respective beam paths and focus each sub-beam to a respective intermediate focus; an array of objective lenses each configured to project one of the plurality of charged particle beams onto a sample; a corrector comprising an array of elongate electrodes extending substantially normal to the beam paths of the first plurality of sub-beams and arranged such that a second plurality of sub-beams, which is a subset of the first plurality of sub-beams, propagate between a pair of elongate electrodes; and a power supply configured to apply a potential difference between the pair of elongate electrodes to cause the second plurality of sub-beams to be deflected by a desired amount.

Description

Case Analysis

[0001] This application is a divisional application of Chinese invention patent application No. 202180026727.5, filed on April 4, 2021, entitled "Charged Particle Evaluation Tool and Inspection Method". Cross-references to related applications

[0002] This application claims priority to EP application 20168278.8, filed on April 6, 2020, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The embodiments provided herein generally relate to charged particle evaluation tools and inspection methods, and more specifically to charged particle evaluation tools and inspection methods using multiple sub-beams of charged particles, as well as to corrector arrangements for use in such tools or methods. Background Technology

[0004] In the manufacture of semiconductor integrated circuit (IC) chips, undesirable pattern defects inevitably occur on the substrate (i.e., wafer) or mask during the manufacturing process due to factors such as optical effects and stray particles, thus reducing yield. Monitoring the extent of these undesirable pattern defects is therefore a crucial process in IC chip manufacturing. More generally, the inspection and / or measurement of the surface of the substrate or other objects / materials are important processes during and / or after their manufacturing.

[0005] Pattern inspection tools with charged particle beams have been used to inspect objects, such as detecting pattern defects. These tools typically employ electron microscopy techniques, such as scanning electron microscopy (SEM). In SEM, a primary electron beam of electrons at relatively high energies targets a final deceleration step to land on the sample at a relatively low landing energy. The electron beam is focused onto the sample as a probe spot. The interaction between the material structure at the probe spot and the landing electrons from the electron beam causes electrons to be emitted from the surface, such as secondary electrons, backscattered electrons, or Auger electrons. The generated secondary electrons can be emitted from the material structure of the sample. By scanning the primary electron beam as a probe 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 characteristics of the material structure of the sample surface.

[0006] It is usually necessary to improve the throughput and other characteristics of charged particle inspection devices. Summary of the Invention

[0007] The embodiments provided herein disclose a charged particle beam inspection device.

[0008] According to a first aspect of the present invention, a charged particle tool is provided, comprising:

[0009] A focusing lens array is configured to separate the beam of charged particles into a plurality of sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0010] An array of objectives, each objective being configured to project one of a plurality of charged particle beams onto the sample;

[0011] A corrector comprising an array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0012] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0013] According to a second aspect of the present invention, a charged particle tool is provided, comprising:

[0014] A focusing lens array is configured to separate the beam of charged particles into multiple sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0015] An objective array, configured to project beams of multiple charged particles onto the sample;

[0016] A corrector array comprising a plurality of elongated electrodes arranged substantially orthogonal to the beam path and located in pairs on either side of a row of beam paths; and

[0017] The corrector array is controllable to apply a potential difference between elongated electrode pairs to deflect the beam path by a desired amount.

[0018] According to a third aspect of the present invention, a charged particle tool is provided, comprising:

[0019] A focusing lens array is configured to separate the beam of charged particles into multiple sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0020] An objective array, configured to project multiple charged particle beams onto the sample;

[0021] A corrector array comprising a plurality of elongated electrodes arranged substantially orthogonal to the beam path and located in pairs on either side of each beam path; and

[0022] The corrector array is controllable to apply macroscopic aberration correction to a sub-beam orthogonal to the elongation direction of the slender electrode.

[0023] According to a fourth aspect of the present invention, an inspection method is provided, comprising:

[0024] The beam of charged particles is divided into multiple sub-beams;

[0025] Focus each sub-beam onto its corresponding center focus;

[0026] Use a corrector to skew the sub-beam to correct macroscopic aberrations; and

[0027] Multiple objectives are used to project multiple charged particle beams onto the sample; wherein the corrector comprises an array of elongated electrodes that extend substantially perpendicular to the beam paths of a first plurality of sub-beams and are arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams.

[0028] According to a fifth aspect of the present invention, a multi-beam charged particle optical system is provided, comprising:

[0029] A focusing lens array is configured to separate the beam of charged particles into a plurality of sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0030] An array of objectives, each configured to project one of a plurality of charged particle beams onto the sample;

[0031] A corrector comprising an array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0032] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0033] According to a sixth aspect of the invention, a charged particle optical element is provided for a multi-beam projection system configured to project a plurality of charged particle beams onto a sample, the charged particle optical element comprising:

[0034] An array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0035] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0036] According to a seventh aspect of the invention, a charged particle optical element is provided for a multi-beam projection system configured to project a plurality of charged particle beams onto a sample, the last of which comprises:

[0037] The first support member includes a first plate section and a plurality of first fingers protruding from the edge of the first plate section;

[0038] The second support member includes a second plate section and a plurality of second fingers protruding from the edge of the second plate section;

[0039] The first plurality of electrodes extending from the first finger section to the second plate section; and

[0040] The second plurality of electrodes extend from the second finger section to the first plate section. Attached Figure Description

[0041] The above and other aspects of this disclosure will become more apparent from the description of exemplary embodiments in conjunction with the accompanying drawings.

[0042] Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam inspection device.

[0043] Figure 2 It is illustrated as Figure 1 A schematic diagram of an exemplary multi-beam device, representing a portion of an exemplary charged particle beam inspection apparatus.

[0044] Figure 3 This is a schematic diagram of an exemplary multibeam apparatus according to an embodiment.

[0045] Figure 4 This is a schematic diagram of a device used to detect aberrations.

[0046] Figure 5 This is a schematic side view of the array of correctors.

[0047] Figure 6 This is a schematic plan view of the corrector array.

[0048] Figure 7 This is a schematic plan view of the hexagonal array of the corrector.

[0049] Figure 8 and Figure 9 It is a calibration diagram regarding position.

[0050] Figure 10 It is a diagram that explains the voltage applied in the array of the corrector.

[0051] Figure 11 This is a diagram illustrating another arrangement of the voltages applied in the array of the correctors.

[0052] Figure 12 This is a schematic side view of a two-layer corrector array.

[0053] Figure 13 This is a schematic side view of a two-layer corrector.

[0054] Figure 14 This is a schematic side view of a three-layer corrector.

[0055] Figure 15 This is a schematic diagram of an exemplary multibeam apparatus according to an embodiment.

[0056] Figure 16 This is a schematic plan view showing the arrangement for mounting the electrodes. Specific implementation method

[0057] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise stated, the same numerals in different drawings denote the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with aspects of the invention as set forth in the appended claims.

[0058] Enhanced computing power in electronic devices can be achieved by significantly increasing the packaging density of circuit components (such as transistors, capacitors, diodes, etc.) on an IC chip, thereby reducing the physical size of the device. This is achieved through increased resolution, which enables the fabrication of smaller structures. For example, the IC chip in a smartphone could include more than 2 billion transistors, each smaller than 1 / 1000th the size of a human hair, and the IC chip was the size of a thumbnail and was available in 2019 or earlier. 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 one step can significantly affect the functionality of the final product. A single “fatal defect” can cause a device to fail. The goal of a manufacturing process is to improve the overall yield of the process. For example, for a 50-step process (where one step can indicate the number of layers formed on the wafer), to achieve a 75% yield, each individual step must have a yield greater than 99.4%. If each individual step has a yield of 95%, the overall process yield will be as low as 7%.

[0059] While high process yields are required in IC chip manufacturing facilities, maintaining high substrate (i.e., wafer) throughput (defined as the number of substrates processed per hour) is also important. The presence of defects can impact both high process yields and high substrate throughput. This is especially true in situations requiring operator intervention to inspect for defects. Therefore, high-throughput detection and identification of micron- and nanometer-scale defects using inspection tools such as scanning electron microscopy (“SEM”) is crucial for maintaining both high yields and low costs.

[0060] SEM comprises scanning equipment and detector devices. The scanning equipment includes an illumination device and a projection device. The illumination device includes an electron source for generating primary electrons, and the projection device is used to scan a sample, such as a substrate, using one or more focused beams of primary electrons. At least the illumination device or system and the projection device or system can be collectively referred to as an electron optical system or apparatus. Primary electrons interact with the sample and generate secondary electrons. As the sample is scanned, the detector captures the secondary electrons from the sample, allowing the SEM to create an image of the scanned area of ​​the sample. For high-throughput inspection, some inspection devices use multiple focused beams, i.e., multi-beam primary electrons. The component beams in the multi-beam array can be referred to as sub-beams or sub-beams. Multiple beams can scan different portions of the sample simultaneously. Sub-beams or sub-beams can be arranged within the multi-beam array, thus the multi-beam array can be referred to as having a multi-beam arrangement. The multi-beam arrangement can have a repeating pattern, which can be, for example, linear (rectangular or square) or hexagonal (e.g., regular hexagon). Therefore, multi-beam inspection devices are capable of inspecting samples at much higher speeds than single-beam inspection devices.

[0061] The following describes the known implementation methods of multi-beam inspection devices.

[0062] The accompanying drawings are schematic. Therefore, for clarity, the relative dimensions of the components in the drawings are enlarged. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only differences with respect to the various embodiments are described. Although the description and drawings relate to electro-optical devices, it should be understood that the embodiments are not intended to limit this disclosure to specific charged particles. Therefore, references to electrons in this document can be more generally considered as references to charged particles, where charged particles are not necessarily electrons.

[0063] Now for reference Figure 1 , Figure 1 This is a schematic diagram illustrating an exemplary charged particle beam inspection device 100. Figure 1 The charged particle beam inspection device 100 includes a main chamber 10, a loading and locking chamber 20, an electronic beam tool 40, an equipment front-end module (EFEM) 30, and a controller 50. The electronic beam tool 40 is located inside the main chamber 10.

[0064] EFEM 30 includes a first loading port 30a and a second loading port 30b. EFEM 30 may include additional loading ports(s). For example, the first loading port 30a and the second loading port 30b may receive a front-opening integration chamber (FOUP) containing a substrate (e.g., a semiconductor substrate or a substrate made of other materials(s)) or a sample to be inspected (substrate, wafer, and sample are collectively referred to below as “sample”). One or more robotic arms (not shown) in EFEM 30 transport the sample to loading locking chamber 20.

[0065] Loading lock chamber 20 is used to remove gas surrounding the sample. This creates a vacuum where the local gas pressure is lower than the pressure in the surrounding environment. Loading lock chamber 20 can be connected to a loading lock vacuum pump system (not shown), which removes gas particles from loading lock chamber 20. 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) transport the sample from loading lock chamber 20 to main chamber 10. Main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles from main chamber 10, causing the pressure around the sample to reach a second pressure below the first pressure. After reaching the second pressure, the sample is transported to an electron beam tool, through which the sample can be examined. Electron beam tool 40 may include multi-beam electro-optics.

[0066] The controller 50 is electrically connected to the electronic beam tool 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle beam inspection device 100. The controller 50 may also include a processing circuitry system configured to perform various signal and image processing functions. Although the controller 50 is... Figure 1 The device is shown external to the structure comprising the main chamber 10, the loading and locking chamber 20, and the EFEM 30; however, it should be understood that the controller 50 may be part of this structure. The controller 50 may be located in one of the components of the charged particle beam inspection apparatus, or it may be distributed across at least two of the components. While this disclosure provides an example of a main chamber 10 for housing an electronic beam inspection tool, it should be noted that aspects of this disclosure are not limited, in their broadest sense, to a chamber for housing an electronic beam inspection tool. Of course, it should be understood that the above principles can also be applied to other arrangements of other tools and apparatuses operating under a second pressure.

[0067] Now for reference Figure 2 , Figure 2 The diagram illustrates the inclusion of... Figure 1This is a schematic diagram of an exemplary electronic beam tool 40, including a multi-beam inspection tool, as part of an exemplary charged particle beam inspection apparatus 100. The multi-beam electronic 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 be collectively referred to as an illumination device. The sample holder 207 is supported by the motorized stage 209 to hold a sample 208 (e.g., a substrate or mask) for inspection. The multi-beam electronic beam tool 40 also includes an electronic detection device 240.

[0068] 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 the anode to form a primary electron beam 202.

[0069] The projection device 230 is configured to convert the primary electronic beam 202 into multiple sub-beams 211, 212, 213 and direct each sub-beam onto the sample 208. Although three sub-beams are illustrated for simplicity, there could be tens, hundreds, or thousands of sub-beams. Sub-beams may be referred to as beam splitters.

[0070] Controller 50 can be connected to Figure 1 The charged particle beam inspection device 100 comprises various components, 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 device (including the charged particle multi-beam device).

[0071] Projection device 230 can be configured to focus sub-beams 211, 212, and 213 onto sample 208 for inspection, and can form three probe spots 221, 222, and 223 on the surface of sample 208. Projection device 230 can be configured to deflect primary sub-beams 211, 212, and 213 to scan probe spots 221, 222, and 223 in various scanning regions of the surface of sample 208. In response to incident on the primary sub-beams 211, 212, and 213 on probe spots 221, 222, and 223 on sample 208, electrons are generated from sample 208, including secondary electrons and backscattered electrons. Secondary electrons typically have electron energies ≤50 eV, while backscattered electrons typically have electron energies between 50 eV and the landing energies of primary sub-beams 211, 212, and 213.

[0072] The electron detection device 240 is configured to detect secondary electrons and / or backscattered electrons and generate corresponding signals, which are sent to a controller 50 or a signal processing system (not shown), for example, to construct an image of the corresponding scanned area of ​​the sample 208. The electron detection device may be incorporated into or separated from the projection device, wherein a secondary optical column is provided to guide secondary electrons and / or backscattered electrons to the electron detection device.

[0073] The controller 50 may include an image processing system comprising an image acquisition unit (not shown) and a storage device (not shown). For example, the controller may include a processor, computer, server, mainframe, terminal, personal computer, any type of mobile computing device, etc., or combinations thereof. The image acquisition unit may include at least a portion of the controller's processing capabilities. Therefore, the image acquisition unit may include at least one or more processors. The image acquisition unit may be communicatively coupled to the electronic inspection device 240 of the permitted signal communication device 40, such as an electrical conductor, fiber optic cable, portable storage medium, IR, Bluetooth, the Internet, wireless network, radio, etc., or combinations thereof. The image acquisition unit may receive signals from the electronic inspection device 240, process the data included in the signals, and construct an image from them. The image acquisition unit can thus acquire an image of sample 208. The image acquisition unit may also perform various post-processing functions, such as generating contours, overlaying indicators on the acquired image, etc. The image acquisition unit may be configured to perform adjustments to the brightness and contrast, etc., of the acquired image. The storage device may be a storage medium such as a hard disk, flash drive, cloud storage, random access memory (RAM), other types of computer-readable storage, etc. The storage device can be coupled to the image acquisition device and can be used to save the initial image data of the scan as the original image and the post-processed image.

[0074] The image acquisition device can acquire one or more images of a sample based on imaging signals received from the electronic detection device 240. The imaging signals may correspond to scanning operations used for performing charged particle imaging. The acquired images may be a single image comprising multiple imaging regions. The single image may be stored in a storage device. The single image may be a raw image that can be divided into multiple regions. Each region may include an imaging area containing features of the sample 208. The acquired images may include multiple images of a single imaging region of the sample 208 sampled multiple times over a period of time. Multiple images may be stored in a storage device. The controller 50 may be configured to perform image processing steps on multiple images of the same location on the sample 208.

[0075] The controller 50 may include measurement circuitry (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 combined with corresponding scan path data of each primary sub-beam 211, 212, and 213 incident on the sample surface to reconstruct an image of the examined sample structure. The reconstructed image can be used to reveal various features of the internal or external structure of sample 208. The reconstructed image can thus be used to reveal any defects that may be present in the sample.

[0076] The controller 50 can control the movement of the motorized stage 209 during the inspection of the sample 208. The controller 50 enables the motorized stage 209 to move the sample 208 in one direction, preferably, at least during the inspection of the sample, by moving the sample 208 continuously at a constant speed. The controller 50 can control the movement of the motorized stage 209 such that it varies the speed of movement of the sample 208 depending on various parameters. For example, the controller can control the speed (including its direction) depending on the characteristics of the inspection steps in the scanning process.

[0077] Figure 3 This is a schematic diagram of the evaluation tool. An electron source 201 guides electrons toward an array of condenser lenses 231 that form part of the projection system 230. Ideally, the electron source is a high-brightness thermal field emitter with a good trade-off between brightness and total emission current. There may be tens, hundreds, or thousands of condenser lenses 231. The condenser lenses 231 may include multi-electrode lenses and have a construction based on EP1602121A1, which, by reference herein to a disclosure specifically incorporated into the lens array, splits the electron beam into multiple sub-beams, wherein the array provides a lens for each sub-beam. The lens array may take the form of at least two plates (acting as electrodes), with apertures in each plate aligned with each other and corresponding to the positions of the sub-beams. At least two of the plates are maintained at different potentials during operation to achieve the desired lensing effect.

[0078] In one arrangement, the condenser lens array is formed by three plate arrays, where charged particles have the same energy as they enter and exit each lens; this arrangement can be called an Einzel lens. The beam energy is the same when entering and exiting the Einzel lens. Therefore, dispersion occurs only within the Einzel lens itself (between the lens's entrance and exit electrodes), thus limiting off-axis chromatic aberration. When the condenser lens is very thin, such as a few millimeters, the effect of such aberration is small or negligible.

[0079] Each condenser lens in the array directs electrons into corresponding sub-beams 211, 212, 213, which are focused at a corresponding intermediate focal point 233. At the intermediate focal point 233 is a deflector 235. The deflector 235 is configured to bend the corresponding sub-beams 211, 212, 213 by a certain amount to effectively ensure that the principal ray (which may also be referred to as the beam axis) is incident substantially perpendicularly (i.e. at 90° to the nominal surface of the sample) onto the sample 208. The deflector 235 may also be referred to as a collimator. The lower beam of the intermediate focal point 233 consists of multiple objectives 234, each of which directs a corresponding sub-beam 211, 212, 213 onto the sample 208. The objectives 234 can be configured to reduce the electron beam by a factor greater than 10, ideally in the range of 50 to 100 or greater.

[0080] An electron detection device 240 is provided between the objective lens 234 and the sample 208 to detect secondary and / or backscattered electrons emitted from the sample 208. An exemplary configuration of the electron detection system is described below.

[0081] Figure 3 The system can be configured to control the landing energy of electrons on the sample. The landing energy can be selected to enhance the emission and detection of secondary electrons, depending on the properties of the sample being evaluated. A controller provided to control objective 234 can be configured to control the landing energy to any desired value within a predetermined range or a desired predetermined value among a plurality of predetermined values. In an embodiment, the landing energy can be controlled to a desired value within a range of 1000 eV to 5000 eV. Details of the electrode structure and potential that can be used to control the landing energy are disclosed in EPA 20158804.3, which is incorporated herein by reference.

[0082] In some embodiments, the charged particle assessment tool further includes one or more aberration correctors that reduce one or more aberrations in the sub-beams. In embodiments, each of at least a subset of the aberration correctors is located in or directly adjacent to a corresponding intermediate focal point (e.g., within or adjacent to the intermediate image plane). The sub-beams have a minimum cross-sectional area in or near a focal plane such as the intermediate plane. This provides more space for the aberration correctors than is available elsewhere, i.e., above or below the intermediate plane (or more space than is available in alternative arrangements without an intermediate image plane).

[0083] In an embodiment, an aberration corrector positioned in or directly adjacent to the intermediate focal point (or intermediate image plane) includes a deflector for correcting source 201, which appears to be in different positions for different beams. The corrector can be used to correct macroscopic aberrations generated by the source that hinder proper alignment between each sub-beam and its corresponding objective.

[0084] Aberration correctors can correct aberrations that prevent proper column alignment. Such aberrations can also cause misalignment between sub-beams and the corrector. For this reason, it may be desirable, additionally or alternatively, to position the aberration corrector at or near the condenser lens 231 (e.g., each such aberration corrector is integrated with or directly adjacent to one or more condenser lenses 231). This is desirable because at or near the condenser lens 231, aberrations do not cause offset of the corresponding sub-beams, since the condenser lens 231 is perpendicular to or coincides with the beam aperture. However, the challenge in positioning the corrector at or near the condenser lens 231 is that each sub-beam at that location has a relatively large cross-sectional area and a relatively small spacing compared to the location of the lower beam.

[0085] In some embodiments, each of at least a subset of aberration correctors is integrated with or directly adjacent to one or more of objectives 234. In embodiments, these aberration correctors reduce one or more of the following: field curvature; focus error; and astigmatism. Additionally or alternatively, one or more scanning deflectors (not shown) may be integrated with or directly adjacent to one or more objectives 234 for scanning sub-beams 211, 212, 214 on sample 208. In embodiments, the scanning deflectors described in US 2010 / 0276606, the entire contents of which are incorporated herein by reference.

[0086] Aberration correctors may be individual programmable deflectors based on CMOS as disclosed in EP2702595A1 or arrays of multi-pole deflectors as disclosed in EP2715768A2, the descriptions of sub-beam manipulators in both of which are incorporated herein by reference.

[0087] In the embodiments, the objectives mentioned in earlier embodiments are array objectives. Each element in the array is a microlens that operates different beams or beam groups in a multi-beam array. The electrostatic array objective has at least two plates, each plate having multiple holes or apertures. The position of each hole on one plate corresponds to the position of a corresponding hole on the other plate. The corresponding holes operate on the same beam or beam group in the multi-beam array during use. A suitable example of the type of lens used for each element in the array is a dual-electrode deceleration lens. The bottom electrode of the objective is a CMOS chip detector integrated into the multi-beam manipulator array. Integrating the detector array into the objective replaces the secondary pillar. The CMOS chip is preferably oriented to face the sample (because the distance between the wafer and the bottom of the electro-optics system is small (e.g., 100 μm)). In the embodiments, electrodes for capturing secondary electronic signals are formed in the top metal layer of the CMOS device. Electrodes may be formed in other layers. The power and control signals of the CMOS can be connected to the CMOS via through-silicon vias. For robustness, the bottom electrode preferably consists of two elements: the CMOS chip and a passive silicon substrate with vias. This board shields the CMOS from the effects of high electric fields.

[0088] To maximize detection efficiency, it is desirable to make the electrode surface as large as possible so that virtually all areas of the array objective (except the aperture) are occupied by electrodes, and each electrode has a diameter substantially equal to the array spacing. In embodiments, the outer shape of the electrodes is circular, but they can be made square to maximize the detection area. The diameter of the substrate vias can also be minimized. The typical size of the electron beam is 5 to 15 micrometers.

[0089] 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 an aperture can be combined into a single signal or used to generate independent signals. The electrode elements can be radially (i.e., forming multiple concentric rings), angularly (i.e., forming multiple fan-shaped elements), both radially and angularly, or divided in any other convenient manner.

[0090] However, a larger electrode surface area results in a larger parasitic capacitance, thus leading to a lower bandwidth. For this reason, it may be desirable to limit the outer diameter of the electrode, especially when a larger electrode only provides a slightly higher detection efficiency but a significantly larger capacitance. Circular (ring-shaped) electrodes offer a good trade-off between collection efficiency and parasitic capacitance.

[0091] A larger outer diameter of the electrode can also lead to greater crosstalk (sensitivity to signals from adjacent apertures). This may also be a reason to make the electrode outer diameter smaller, especially when a larger electrode only provides slightly greater detection efficiency but significantly greater crosstalk.

[0092] The backscattered and / or secondary electron currents collected by the electrodes are amplified by a transimpedance amplifier.

[0093] In embodiments of the invention, the corrector at the intermediate focal point 233 is embodied by a slit deflector 300. The slit deflector 300 is an example of a manipulator and may also be referred to as a slit corrector. In an arrangement, the slit deflector may comprise a portion of a collimator array (e.g., deflector array 235 as described elsewhere herein) or a portion adjacent to a collimator array or such a collimator, for example, adjacently as a corrector in the beam path. Figure 5 and Figure 6 As shown, the slit deflector 300 includes a set of elongated electrodes 301, such as parallel plates or parallel strips, defining a set of slits 302. The elongated electrodes may be electrostatic. The array of elongated electrodes may have one or more electrical connections, such as one or more electrical connections to each electrode. A potential difference may be applied to the electrodes, such as to each electrode. For alternating electrodes or at least alternating polarities, the applied potential may be similar. A set of elongated electrodes 301 or an array of elongated electrodes 301 may be in a common plane. The common plane of the array of elongated electrodes 301 may be orthogonal to, for example, the beam path of a multi-beam arrangement. The elongated electrodes may have flat surfaces, preferably directly facing the sub-beam path. The flat surfaces of the electrodes may be parallel to each other. As depicted, the electrodes may be equidistant from each other and, for example, from the sub-beams of the multi-beam arrangement. The electrodes may be orthogonal to the sub-beam path of the multi-beam arrangement, for example, when collimated. The flat surfaces of the electrodes may be substantially aligned with the path of the sub-beams of the multi-beam arrangement, for example, when collimated. Electrode 301 can be formed of silicon or metal, such as a doped silicon region of a substrate and a metallization layer formed on the substrate. Silicon electrodes can be formed by selective etching of a silicon wafer.

[0094] Figure 6 An arrangement for mounting electrodes to form an array of elongated electrodes is shown. A frame 303, such as glass or ceramic, is provided to support the electrodes. When a high voltage is applied to the electrodes, a shield 304, such as glass, can be provided at the ends of the electrodes to prevent surface creep or breakdown. As depicted, electrodes 300 extend through the frame 303, for example, between opposite sides of the frame. As depicted, the electrodes can extend across a multi-beam arrangement of sub-beams 211, for example, as a row of sub-beam paths. Potential is applied to the electrodes via conductive traces 309 (only a few are shown in the figure for clarity). Shields 304 protrude from the sides 303a, 303b of the frame 304 to which the array of electrodes is mounted. The shields are inserted between adjacent electrodes to suppress high-voltage discharge between adjacent electrodes by increasing the creep length between them.

[0095] Alternatively or additionally, the slit deflector 300, used as an aberration corrector 235a, can be positioned directly below the condenser lens 231. This can be advantageous because any angular error to be corrected will not be translated into a large positional offset. The aberration corrector 235a can correct aberrations that prevent proper column alignment. Such aberrations can also cause misalignment between sub-beams 211, 212, 213 and the corrector 235. For this reason, additionally or alternatively, the aberration corrector 235a is positioned at or near the condenser lens 231 (e.g., each such aberration corrector 235a is integrated with or directly adjacent to one or more condenser lenses 231). This is desirable because at or near the condenser lens 231, since the condenser lens 231 is perpendicularly close to or coincides with the beam aperture 111a, aberrations will not cause offsets in the corresponding sub-beams 211, 212, 213. However, the challenge in positioning the corrector 235a at or near the condenser lens 116 is that the sub-beams 212, 213, and 214 each have a relatively large cross-sectional area and a relatively small spacing at that location relative to the position of the larger beam.

[0096] A row of sub-beam paths, such as those used in tool operation, is inserted with a pair of elongated electrodes (which may be in the form of a strip array), such that a potential difference between the electrodes causes deflection of the sub-beams. The direction of deflection is determined by the relative polarity of the potential difference relative to the optical axis. The magnitude of deflection is determined by the magnitude of the potential difference, the distance between the electrodes, and the width of the electrodes in the direction parallel to the propagation of the sub-beams. These dimensions may be referred to as the width and depth of the slits, respectively. In embodiments, the slit width is in the range of 10 μm to 100 μm, preferably 50 μm. In embodiments, the slit spacing is in the range of 50 μm to 200 μm, preferably 100 μm. In embodiments, the slit depth is in the range of 50 μm to 200 μm.

[0097] In one embodiment, the electrodes are at the same potential along their length, and the slit has a constant width or depth, such that all sub-beams passing through a given slit experience substantially the same deflection because they all have substantially the same energy.

[0098] In embodiments, the slit may have a non-constant cross-section, such as variations in width or depth, to provide a predetermined deflection variation in the sub-beam based on the position of the sub-beam along the length of the slit.

[0099] In one embodiment, elongated electrodes define a set of parallel slits such that each sub-beam passes through the slits. The surface of each electrode partially defining a slit can have a flat surface that can be parallel to the sub-beam path. Therefore, the facing elongated surfaces of the respective elongated electrodes define the corresponding slits. The facing surfaces of the slits can each be flat and parallel to each other. The slits can extend through an array of sub-beam paths, for example, through a multi-beam arrangement, such as a reference array. Figure 5 exist Figure 6 As depicted in [the text]. Ideally, the potential applied to each electrode surface is individually controllable, allowing deflection to be controlled as a function of the beam position in a direction perpendicular to the slit's longitudinal direction. In embodiments, a predetermined set of voltages is applied to the electrodes to provide a predetermined set of deflections. For example, if the slit extends along the Y-axis of a Cartesian coordinate system (i.e., the elongated direction of the electrodes is in the Y direction), the deflection can be controlled as a function of the sub-beam position in the X direction.

[0100] In this embodiment, each slit is defined by two dedicated electrodes. For example, such as Figure 8 As shown, slit 302-1 is defined by the opposing surfaces of electrodes 301-1 and 301-2, slit 302-2 is defined by the opposing surfaces of electrodes 301-3 and 301-4, and so on, thus slit 301-m is defined by electrodes 301-(2m-1) and 302-2m. Opposite potentials are applied to the alternating electrodes, for example, the odd-numbered electrodes are negative and the even-numbered electrodes are positive. The amplitude of the applied potential can vary with position to provide the desired deflection, which varies with position in a direction perpendicular to the length of the electrodes. For example, as... Figure 8 As shown, the potential (indicated at the top of the figure) increases linearly, and the potential difference (indicated at the bottom of the figure) increases similarly linearly. For example, a set of electrodes, such as an even number of electrodes, can be maintained at a constant potential, such as ground potential.

[0101] In an alternative embodiment, each electrode (except the electrode at the end of the array) is used to define one side of each of the two slits. That is, generally, the opposing surfaces of electrodes extending in the direction of the beam path define partially adjacent slits. For example, as Figure 9 As shown, slit 302-1 is defined by the surfaces of electrodes 301-0 and 301-1, slit 302-2 is defined by the facing surfaces of electrodes 301-1 and 301-2, and so on, thus slit 302-n is defined by the surfaces of electrodes 301-(n-1) and 301-n. In this arrangement, the potential applied to electrode 302-n relative to the potential applied to electrode 302-0 is the sum of the potential differences applied to slits 302-1 to 302-n. Therefore, a linear increase in the potential difference results in a faster increase in the absolute potential applied to the electrode than a linear increase. Generally, in situations such as... Figure 9In the arrangement shown, the potential difference increases monotonically throughout the array.

[0102] and Figure 9 Compared to the previous arrangement, Figure 8 The advantage of this arrangement is that the amplitude of the potential applied to the electrodes does not need to exceed the potential difference required to achieve the desired deflection. Figure 8 Compared to the previous arrangement, Figure 9 The advantage of this arrangement is that it requires fewer electrodes, allowing for a more compact corrector. If the corrector is positioned close to the condenser lens 231, then... Figure 9 The arrangement is advantageous because the sub-beams are closer together and Figure 9 The arrangement can be achieved with a small distance between the slits.

[0103] In this embodiment, multiple slit deflectors are provided adjacent to each other in the beam propagation direction. Such an arrangement may be referred to as a stack of slit deflectors. The slit deflectors in the stack are oriented differently.

[0104] In an embodiment, the sub-beams are arranged in a rectangular array and two slit deflectors are provided, wherein the slit of the first slit deflector is oriented perpendicular to the slit of the second slit deflector. For example, the first slit deflector has a slit extending in the Y direction and provides deflection in the X direction, which can be controlled as a function of the sub-beam position in the X direction. The second slit deflector has a slit extending in the X direction and provides deflection in the Y direction, which can be controlled as a function of the sub-beam position in the Y direction. The slit deflectors can be provided in any order in a stack. Further details of the slit deflectors can be found in EPA20156253.5, in which a description of a multi-beam deflector device is incorporated herein by reference.

[0105] In one embodiment, the sub-beams are arranged in a hexagonal array and two slit deflectors are provided. The slit of the first slit deflector is orthogonal to the slit of the second slit detector. For example, the first slit deflector has a slit extending in the Y direction and provides deflection in the X direction, which can be controlled as a function of the sub-beam position in the X direction. The second slit deflector has a slit extending in the X direction and provides deflection in the Y direction, which can be controlled as a function of the sub-beam position in the Y direction. The second slit detector has a smaller spacing than the first slit detector, and each slit has fewer sub-beams than the first slit detector. The slit deflectors can be provided in any order in the stack.

[0106] In one embodiment, the sub-beams are arranged in a hexagonal array and provide three stacked slit deflectors. The three slit deflectors are arranged such that there is a 60° angle between the slits of the different slit detectors. For example, as... Figure 16As shown, the first slit deflector may have a slit 302a oriented parallel to the X-axis (0°), the second slit deflector may have a slit 302b at +60° to the X-axis, and the third slit deflector may have a slit 302c at -60° to the X-axis. The slit deflectors can be provided in any order in the stack. Desired deflection in any direction, as disclosed in EPA20156253.5, can be achieved by appropriately applying a potential to the electrodes defining the slits 302a, 302b, and 302c. The disclosure of a hexagonal array of three slit deflectors in that document is incorporated herein by reference. While a regular hexagonal array has been described in the arrangement, the same type of corrector can be implemented in an irregular array, wherein the deflecting slits are arranged to correspond to the three axes of the irregular hexagonal array.

[0107] Use such as Figure 7 The arrangement shown allows for the following corrections:

[0108]

[0109] in other words: • Any deflection in the 0-degree direction is a function of the position in the 0-degree direction. • Any deflection in the 60-degree direction is a function of the position in the 60-degree direction. • Any deflection in the 120-degree direction is a function of the position in the 120-degree direction.

[0110] Figure 10 and Figure 11 This shows that, for example, these degrees of freedom can be used to correct the following macroscopic aberrations: • First Order (Lens Effect): Perfect Correction • 3rd order: Perfect correction • Level 5: Reduced by 10 times

[0111] Figure 10 It describes the required and achievable angular deflection (in arbitrary units) for third-order correction as a function of position r. Figure 11 The required and achievable angular deflection (in arbitrary units) for a 5th-order correction as a function of position r is described.

[0112] Another advantage of using a three-slit deflector array (0, 60, 120 degrees) over a two-slit deflector array (0, 90 degrees) is that, for the first-order effect (perfect lens), each array only needs to deflect by 2 / 3 of the angle compared to the case with two slit deflectors.

[0113] Other arrangements of multiple slit deflectors can be provided for other arrangements of the sub-beam. For example, the slits can be arranged in a concentric hexagonal pattern.

[0114] In one embodiment of the invention, multiple beams pass through a slit defined by a pair of electrodes. This significantly reduces the number of connections required to provide the deflection potential. In multi-beam tools with hundreds or thousands of beams, it is difficult, if not impossible, to provide an independent deflection potential for each sub-beam due to limited space for leads or circuit traces (wiring). The present invention solves this problem because the number of required traces is significantly reduced. In some cases, embodiments of the invention may not fully correct aberrations, such as third-order rotationally symmetric aberrations. However, embodiments of the invention can achieve significant and useful reductions even in aberrations that cannot be fully corrected.

[0115] If the virtual source position of the electron source 201 is not constant for all emission angles, an error that can be corrected by embodiments of the present invention will occur. This effect is called source grid error. Figure 4 A device 400 for measuring source grid error is depicted. A source 201 is configured to emit electrons toward an aperture array 401. This could be an aperture array from a condenser lens array of a projection system. The aperture array 401 has a known aperture arrangement and divides the electrons emitted by the source 201 into multiple sub-beams. A fluorescent screen 402 is provided at a known location in the sub-beam path. In response to the incident electrons, the fluorescent screen 402 emits light, such as visible light. A projection lens 403 projects the image of the fluorescent screen 402 onto an imaging device 404, such as a CCD. The image captured by the imaging device 404 allows for easy determination of the source grid error, since the expected bright spot pattern can be predicted directly from the aperture arrangement in the aperture array 401 in the absence of source grid error. This arrangement can be used to measure in-situ positioning errors in source tools.

[0116] As described above, slit deflectors can introduce a slight focusing effect in the direction of beam deflection. If two or more arrays of slit deflectors with different orientations are used, focusing effects will exist in two or more directions. The magnitude of this focusing effect is proportional to the magnitude of the deflection. In some cases, this focusing effect may be undesirable.

[0117] To compensate for the focusing effect of the slit deflector, a slit lens can be added. For example... Figure 12 As shown, the slit lens 800 includes an array 300 of elongated electrodes 301 (which defines an elongated slit in a first array) and at least another array 500 of corresponding elongated electrodes 501 (depicted as 305) (which defines elongated features, such as slits, in a second array). The other array 500 of elongated electrodes 501 is shifted relative to the array 300 of elongated electrodes 301 along a corresponding beam path, such as an upper or lower beam; Figure 12In the arrangement depicted, another array is the lower beam of an array 300 of elongated electrodes. The elongated electrodes 501 of another array 500 can be aligned, preferably parallel to the corresponding elongated electrodes 301 of array 300. Each array of elongated electrodes forms a structure with a shape similar to the slit deflector mentioned earlier in this description. Lenses are fabricated by having a potential difference between the average of the two slit electrodes and the two deflecting electrodes. This is accomplished by changing the potential of the slit electrodes or by adding a voltage offset to the deflecting electrodes. The elongated electrodes 301 can be positioned at corresponding potentials, and the corresponding elongated electrodes 501 can be positioned at ground potential or at corresponding different potentials. The intensity of each slit lens can be selected such that the astigmatism is equal to the astigmatism of the slit deflector with maximum deflection. In embodiments where the corrector consists of a deflector and an array of slit lenses for each axis (typically two, one for X and one for Y), the resulting astigmatism exhibits characteristics of a microlens array.

[0118] Figure 13 This is an enlarged view showing a pair of deflector electrodes 301 and a pair of slit lens electrodes 501. The slit deflector electrodes and slit lens electrodes can be in any order. Figure 14 As shown, two pairs of slit lens electrodes 501, 502 can also be used, for example, one on either side of the slit deflector electrodes, such as an array of additional elongated electrodes 502 and another array 500 of elongated electrodes 501 on the beam of an array 300 of elongated electrodes. Figure 14 In this arrangement, the slit lens electrodes 501 and 502 can be maintained at the same potential, such as grounded or elevated, wherein the potential of the slit deflector is controlled to achieve the desired overall deflection and focusing effect. In this case, the three-lens structure is similar to an Einzel lens. The additional array 500 and the supplementary array can both be the upper or lower beam of the array 300 of the elongated electrodes 301, but this may not be as desirable as having supplementary and additional arrays on either side of the arrangement; for example, these arrays could be used as Einzel lens arrays.

[0119] Another embodiment of the charged particle evaluation tool 109 is in Figure 15The diagram is schematically illustrated. This embodiment also includes one or more aberration correctors 124, 125, 126 that reduce one or more aberrations in the sub-beams 114. In this embodiment, each of at least a subset of the aberration correctors 124 is positioned in or directly adjacent to a corresponding intermediate focus 115 (e.g., in or adjacent to the intermediate image plane 120). The sub-beams 114 have a minimum cross-sectional area in or near a focal plane such as the intermediate plane 120. This provides more space for the aberration correctors 124 than is available elsewhere, i.e., above or below the intermediate plane 120 (or more space than is available in alternative arrangements without the intermediate image plane 120).

[0120] In an embodiment, the aberration corrector 124, positioned in or directly adjacent to the intermediate focal point 115 (or intermediate image plane 120), includes a deflector for correcting the source 201, which appears to be in different positions relative to the different sub-beams 114 derived from the beam 112 emitted from the source 201. The corrector 124 can be used to correct macroscopic aberrations generated by the source 201 that hinder proper alignment between each sub-beam 114 and its corresponding objective lens 118.

[0121] Aberration corrector 124 can correct aberrations that prevent proper column alignment. Such aberrations can also cause misalignment between sub-beams 114 and corrector 124. For this reason, it may be desirable, additionally or alternatively, to position aberration corrector 125 at or near condenser lens 116 (e.g., each such aberration corrector 125 integrated with or directly adjacent to one or more condenser lenses 116). This is desirable because at or near condenser lens 116, aberrations will not cause offset of the corresponding sub-beam 114, since condenser lens 116 is perpendicularly close to or coincides with beam aperture 110. However, the challenge in positioning corrector 125 at or near condenser lens 116 is that each sub-beam 114 has a relatively large cross-sectional area and relatively small spacing at that location relative to the location of the lower beam.

[0122] In some embodiments, such as Figure 15 As illustrated, each of at least a subset of aberration correctors 126 is integrated with or directly adjacent to one or more of the objectives 118. In embodiments, these aberration correctors 126 reduce one or more of the following: field curvature; focus error; and astigmatism.

[0123] exist Figure 15 In the device, any or all correctors 124, 125, 126 can be slit deflectors as described above.

[0124] Figure 16An alternative arrangement of elongated electrodes for mounting electrodes to form an array for a slit deflector or slit lens is depicted. Frame 303 is provided with two sets of fingers 307 that project inwardly from a base 306 on opposite sides of the frame. That is, the opposite side of the frame on which the electrodes 301 are mounted has a set of fingers 307. The fingers can be integrated with the frame. The intermediate base can be considered recessed relative to one end adjacent to the fingers, for example, by providing a recessed surface 308. The fingers and recesses alternate along one side of the frame on which the electrodes 301 are mounted. Each electrode is mounted to one end of a finger 307 and to the base 306 at the other end, for example, at a recess. The electrodes are alternately connected to the frame and to the fingers at the recesses. One adjacent electrode is connected to one side of the frame via a finger, while the other is connected to the other side via a recess. Electrodes on opposite sides of the frame can be connected differently, such that each electrode is connected to the frame via a finger and a recess. For example, odd-numbered electrodes 301-1, etc., can be installed on the finger (lower side in the figure) on the first side of the frame, while even-numbered electrodes 302-2, etc., are installed on the frame (upper side in the figure) on the second side of the frame.

[0125] Electrodes can be electrically connected to the recesses via their mounting. In another arrangement, the electrodes are electrically connected to the fingers, although this may be less preferred. Since alternating electrodes are connected at the recesses or fingers, a similar potential difference can be applied to the alternating electrodes. Potential is supplied to the electrodes via conductive traces 309 (only a few are shown in the figure for clarity) connected to the electrodes at the base or recess. The creep length cl (i.e., the length of the surface where creep discharge may occur) is the lateral distance along the ends of the recesses and fingers, and the length of the fingers. The creep length is the lateral distance above the frame surface from the electrode at the recess to the finger surface extending from the frame, the length of the side surface of the finger extending from the frame, and the distance at the end of the finger from the side surface of the finger to the connection point between the finger and the adjacent electrode. Therefore, the length of the finger 307 increases, for example, the creep length between adjacent electrodes. Thus, isolation between the electrodes is improved. The risk of high-voltage discharge between the electrodes at the frame is reduced.

[0126] The frame 303 and fingers 307 are formed of an insulator, preferably ceramic, preferably silicon oxide, and preferably glass. In an embodiment, the frame is formed by selective etching of the substrate (e.g., a silicon wafer). Preferably, the frame, or at least each side, is monolithic.

[0127] An evaluation tool according to embodiments of the invention may be a tool for qualitative evaluation of a sample (e.g., pass / fail), a tool for quantitative measurement of a sample (e.g., size of a feature), or a tool for generating a map image of the sample. Examples of evaluation tools are inspection tools (e.g., for identifying defects), examination tools (e.g., for classifying defects), and metrology tools, or tools capable of performing any combination of evaluation functionalities associated with inspection, examination, or metrology tools (e.g., metrology-inspection tools). Electron beam 40 may be a component of the evaluation tool; such as an inspection tool or metrology-inspection tool, or part of an electron beam lithography tool. Any reference to tools herein is intended to cover devices, apparatus, or systems that include a variety of components, which may be juxtaposed or not, and may even be located in a separate room—especially for example, for data processing elements.

[0128] A multi-beam electronic beamforming tool may include a primary projection device, a motorized stage, and a sample holder. The primary projection device is the illumination device included in the multi-beam electronic beamforming tool. The primary projection device may include at least any one or more of the following components: an electron source, a gun aperture plate, a condenser lens, an aperture array, a beam manipulator (which may include a MEMS structure), an objective lens, and a beam splitter (e.g., a Wien filter). The sample holder is supported by the motorized stage. The sample holder is arranged to hold a sample (e.g., a substrate or mask) for inspection.

[0129] Multi-beam electronic beaming tools may also include secondary projection devices and associated electronic detection equipment. The electronic detection equipment may include multiple electronic detection elements.

[0130] A primary projection device is arranged to irradiate the sample. In response to the incident primary sub-beam or probe spot on the sample, electrons, including secondary electrons and backscattered electrons, are generated from the sample. The secondary electrons propagate in multiple secondary electron beams. These beams typically include secondary electrons (with electron energies ≤50 eV) and may also include at least some backscattered electrons (with electron energies between 50 eV and the landing energy of the primary sub-beam). A beam splitter in the primary projection device can be arranged to deflect the path of the secondary electron beams toward the secondary projection device. The secondary projection device then focuses the path of the secondary electron beams onto multiple elements of an electron detection device. The detection elements generate corresponding signals, which can be sent to a controller or signal processing system, for example, to construct an image of the corresponding scanned area of ​​the sample.

[0131] References to components or systems that can be controlled to manipulate charged particle beams in a certain manner include: configuring a controller or control system or control unit to control the component to manipulate the charged particle beam in the described manner, and optionally using other controllers or devices (e.g., voltage sources and / or current sources) to control the component to manipulate the charged particle beam in this manner. For example, a voltage source may be electrically connected to one or more components to apply a potential to components (such as objective array 234, condenser lens 231, corrector 235a, and collimator array 235 in the non-limiting list) under the control of a controller or control system or control unit. Actuable components such as stages may be controllable to be actuated using one or more controllers, control systems, or control units and thus moved relative to another component such as a beam path to control the actuation of the component.

[0132] The embodiments described herein can take the form of a series of aperture arrays or electro-optical elements arranged in an array along a beam or multi-beam path. These electro-optical elements can be electrostatic. In embodiments, all electro-optical elements, such as the last electro-optical element in the sub-beam path from the beam-limiting aperture array to the sample, can be electrostatic and / or can be in the form of an aperture array or a plate array. In some arrangements, one or more electro-optical elements are fabricated as microelectromechanical systems (MEMS) (i.e., using MEMS fabrication techniques).

[0133] Adjacent electro-optical elements along the beam path can be structurally connected to each other, for example, using electrically insulating elements such as spacers. These spacers can be made of electrically insulating materials such as ceramics (or glass).

[0134] References to upper and lower, above and below, above and below should be understood to refer to directions parallel to (usually but not always perpendicular to) the upper and lower beam directions of the electron beam or multi-beam impacting sample 208. Therefore, references to upper and lower beams are intended to refer to directions about the beam path, independent of any current gravitational field.

[0135] Exemplary embodiments of the invention are described below in the following numbered paragraphs.

[0136] 1. A charged particle tool, comprising:

[0137] A focusing lens array is configured to separate the beam of charged particles into a plurality of sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0138] An array of objectives, each objective being configured to project one of a plurality of charged particle beams onto the sample;

[0139] A corrector comprising an array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0140] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0141] 1a. A charged particle tool, comprising: an array of condenser lenses configured to split a beam of charged particles into a first plurality of sub-beams along a respective beam path and to focus each sub-beam to a respective intermediate focal point; an array of objectives, each objective configured to project one of the plurality of charged particle beams onto a sample; and a corrector including elongated electrodes of a first array and a second array along the beam path, the elongated electrodes of the second array being substantially parallel to the elongated electrodes of the first array, the first array being adjacent to the second array along the beam path, the elongated electrodes of the first array being... The electrodes extend substantially perpendicular to the beam paths of the first plurality of sub-beams and are arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes of the first array, the second plurality of sub-beams being a subset of the first plurality of sub-beams. The elongated electrodes include parallel plates extending parallel to the propagation direction of the second plurality of sub-beams. A power source is configured to apply a potential difference between the pair of elongated electrodes of the first array to deflect the second plurality of sub-beams by a desired amount. Preferably, the elongated electrodes may have a flat surface, more preferably directly facing the sub-beam paths. Preferably, the elongated electrodes are electrostatic.

[0142] 2. The tool according to embodiment 1 or 1a, wherein there are multiple pairs of elongated electrodes arranged such that corresponding second plurality of sub-beams propagate between each pair of elongated electrodes; and a power supply is configured to apply a corresponding potential difference between each pair of elongated electrodes; preferably, the pairs of elongated electrodes extend on either side of a row of second plurality of sub-beams, preferably, the row of sub-beams extends across the sub-beams; and / or preferably, the pairs of elongated electrodes extend across the sub-beams.

[0143] 3. The tool according to embodiment 2, wherein each elongated electrode has a sub-beam adjacent only to one side thereof.

[0144] 4. The tool according to embodiment 1, 1a or 2, wherein the power supply is configured to apply potentials of opposite polarity to adjacent elongated electrodes.

[0145] 5. In the tool according to embodiment 2, some of the elongated electrodes have sub-beams adjacent to their two sides, preferably with the two sides directly facing the sub-beam paths, preferably with the sub-beam paths facing either side coming from different rows of sub-beams, preferably arranged across multiple beams.

[0146] 6. The tool according to embodiment 5, wherein the power supply is configured such that the potential applied to each elongated electrode is given as a function of a continuous increase (e.g., monotonically increasing) across the position of the array of elongated electrodes.

[0147] 7. The tool according to any one of the foregoing embodiments, wherein the elongated electrode includes a parallel plate extending parallel to the propagation direction of the second plurality of sub-beams.

[0148] 8. The tool according to any one of the foregoing embodiments, wherein the corrector includes a first set of elongated electrodes and a second set of elongated electrodes along the beam path, the second set of elongated electrodes being perpendicular to the first set of elongated electrodes; or wherein the corrector includes an additional array of elongated electrodes along the beam path, the additional array of elongated electrodes being perpendicular to or parallel to the first array of elongated electrodes.

[0149] 9. The tool according to any one of embodiments 1 to 7, wherein the corrector includes a first set of elongated electrodes, a second set of elongated electrodes, and a third set of elongated electrodes, the angle between the first set of elongated electrodes and the second set of elongated electrodes is 60°, and the angle between the second set of elongated electrodes and the third set of elongated electrodes is 60°; or wherein the corrector includes a first array of elongated electrodes, the first array of elongated electrodes including a first set of elongated electrodes, a second set of elongated electrodes, and a third set of elongated electrodes, one of the first set of elongated electrodes, the second set of elongated electrodes, and the third set of elongated electrodes corresponding to the elongated electrodes of the first array, the angle between the first set of elongated electrodes and the second set of elongated electrodes is 60°, and the angle between the second set of elongated electrodes and the third set of elongated electrodes is 60°.

[0150] 10. The tool according to any of the foregoing embodiments, wherein the corrector is arranged such that the intermediate focus is located between the elongated electrodes, preferably between the elongated electrodes of the first array.

[0151] 11. The tool according to any one of embodiments 1 to 9, wherein the corrector is arranged adjacent to the condenser lens array and / or adjacent to or integrated into the objective lens array.

[0152] 11a. The tool according to any one of the foregoing embodiments, wherein the corrector is configured to reduce at least one of: field curvature; focus error; and astigmatism.

[0153] 12. The tool according to any one of the foregoing embodiments, wherein the corrector is configured to correct macroscopic aberrations of a first plurality of sub-beams.

[0154] 12a. The tool according to any one of embodiments 1 to 12 further includes an additional corrector arranged adjacent to the condenser lens array and / or adjacent to or integrated into the objective lens array.

[0155] 12b. The tool according to claim 12a, wherein the additional calibrator comprises the calibrator of any one of embodiments 1 to 10.

[0156] 13. A charged particle tool, comprising:

[0157] A focusing lens array is configured to separate the beam of charged particles into multiple sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0158] An objective array, configured to project beams of multiple charged particles onto the sample;

[0159] The corrector array includes multiple elongated electrodes arranged substantially orthogonal to the beam path and located in pairs on either side of a row of beam paths; and

[0160] The corrector array is controllable to apply a potential difference between elongated electrode pairs to deflect the beam path by a desired amount.

[0161] 13a. An inspection method comprising: dividing a beam of charged particles into a plurality of sub-beams; focusing each sub-beam to a corresponding intermediate focal point; using a corrector to deflect the beam to correct macroscopic aberrations of the sub-beams; and using a plurality of objectives to project the beams of the plurality of charged particles onto a sample; wherein the corrector includes elongated electrodes of a first array and a second array of elongated electrodes along a beam path, the elongated electrodes of the second array being substantially parallel to the elongated electrodes of the first array, the first array being adjacent to the second array along the beam path, the elongated electrodes of the first array extending substantially perpendicular to the beam path of the first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes of the elongated electrodes of the first array, the second plurality of sub-beams being a subset of the first plurality of sub-beams, the elongated electrodes including parallel plates extending parallel to the propagation direction of the second plurality of sub-beams, preferably, the elongated electrodes may have planar surfaces, more preferably, directly facing the sub-beam path.

[0162] 14. A charged particle tool, comprising:

[0163] A focusing lens array is configured to separate the beam of charged particles into multiple sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0164] An objective array, configured to project multiple charged particle beams onto the sample;

[0165] The corrector array comprises multiple elongated electrodes arranged substantially orthogonal to the beam path and located in pairs on either side of each beam path; and

[0166] The corrector array is controllable to apply macroscopic aberration correction to a sub-beam orthogonal to the elongation direction of the slender electrode.

[0167] 15. An inspection method, comprising:

[0168] The beam of charged particles is divided into multiple sub-beams;

[0169] Focus each sub-beam onto its corresponding center focus;

[0170] Use a corrector to skew the sub-beam to correct macroscopic aberrations; and

[0171] Multiple objectives are used to project multiple charged particle beams onto the sample; wherein the corrector comprises an array of elongated electrodes that extend substantially perpendicular to the beam paths of a first plurality of sub-beams and are arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams.

[0172] 16. A multi-beam charged particle optical system, comprising:

[0173] A focusing lens array is configured to separate the beam of charged particles into a plurality of sub-beams along a corresponding beam path and focus each sub-beam to a corresponding central focal point;

[0174] An array of objectives, each configured to project one of a plurality of charged particle beams onto the sample;

[0175] A corrector comprising an array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0176] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0177] 17. A charged particle optical element for a multi-beam projection system configured to project a plurality of charged particle beams onto a sample, the charged particle optical element comprising:

[0178] An array of elongated electrodes extending substantially perpendicular to the beam paths of a first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes, the second plurality of sub-beams being a subset of the first plurality of sub-beams; and

[0179] A power source is configured to apply a potential difference between a pair of elongated electrodes to deflect a second plurality of sub-beams by a desired amount.

[0180] 18. A charged particle optical element for a multi-beam projection system configured to project multiple charged particle beams onto a sample, the final charged particle optical element comprising:

[0181] The first support member includes a first plate section and a plurality of first fingers protruding from the edge of the first plate section;

[0182] The second support member includes a second plate section and a plurality of second fingers protruding from the edge of the second plate section;

[0183] The first plurality of electrodes extending from the first finger section to the second plate section; and

[0184] The second plurality of electrodes extend from the second finger section to the first plate section.

[0185] 19. The charged particle optical element according to Embodiment 18 further includes a first set of conductive traces provided on a first plate segment and connected to a second plurality of electrodes; and a second set of conductive traces provided on a second plate segment and connected to a first plurality of electrodes.

[0186] 20. A charged particle optical element according to embodiment 18 or 19, wherein the first support member and the second support member are integral parts of the substrate.

[0187] 21. The charged particle optical element according to Example 20, wherein the first support member and the second support member have been formed by selective etching of the substrate.

[0188] 22. The charged particle optical element according to any one of embodiments 19 to 21, wherein the first plate segment and the second plate segment include a recess between adjacent fingers.

[0189] 23. The charged particle optical element according to any one of Examples 19 to 22, wherein the support member comprises an insulator, preferably ceramic, preferably silicon oxide, and preferably glass.

[0190] The terms “sub-beam” and “split-beam” are used interchangeably herein and are both understood to encompass any radiation beam derived from a parent radiation beam by dividing or splitting it. The term “manipulator” is used to encompass any element, such as a lens or deflector, that affects the path of a sub-beam or split-beam.

[0191] While the invention has been described in conjunction with various embodiments, other embodiments of the invention will be apparent to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. The specification and examples are intended to be illustrative only, and the true scope and spirit of the invention are indicated by the appended claims.

Claims

1. A charged particle tool, comprising: An array of objectives, each objective being configured to project one of a plurality of charged particle beams onto the sample; The manipulator includes elongated electrodes of a first array and a second array along the beam path, the elongated electrodes of the second array being substantially parallel to the elongated electrodes of the first array, the first array being adjacent to the second array along the beam path, the elongated electrodes of the first array extending substantially perpendicular to the beam path of the first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes of the first array, the second plurality of sub-beams being a subset of the first plurality of sub-beams, the elongated electrodes including parallel plates extending parallel to the propagation direction of the second plurality of sub-beams; as well as A power supply is configured to apply a potential difference between the pair of elongated electrodes in the first array to deflect the second plurality of sub-beams by a desired amount. The manipulator further includes a first set of elongated electrodes, a second set of elongated electrodes, and a third set of elongated electrodes, one of which corresponds to the elongated electrodes of the first array. The angle between the first set of elongated electrodes and the second set of elongated electrodes is 60°, and the angle between the second set of elongated electrodes and the third set of elongated electrodes is 60°.

2. The tool of claim 1, wherein the parallel plate has a planar surface directly facing the sub-beam path.

3. The tool according to claim 1 or 2, wherein there are multiple pairs of elongated electrodes arranged such that corresponding second plurality of sub-beams propagate between each pair of elongated electrodes; and the power supply is configured to apply a corresponding potential difference between each pair of elongated electrodes.

4. The tool of claim 3, wherein the elongated electrode extends on either side of a row of the second plurality of sub-beams, the plurality of sub-beams being arranged in a multi-beam arrangement, the row extending across the multi-beam arrangement of the sub-beams.

5. The tool according to claim 3 or 4, wherein each of the elongated electrodes has a sub-beam adjacent only to one side of the elongated electrode.

6. The tool according to any one of claims 3 to 5, wherein the power source is configured to apply a potential of opposite polarity to adjacent elongated electrodes.

7. The tool according to claim 3 or 4, wherein some of the elongated electrodes have sub-beams adjacent to both sides of the elongated electrode.

8. The tool of claim 7, wherein the plurality of sub-beams are arranged in a multi-beam arrangement, wherein the sub-beam paths facing either side of some of the elongated electrodes originate from sub-beams spanning different rows of the multi-beam arrangement.

9. The tool according to claim 7 or 8, wherein the power source is configured such that the potential applied to each of the elongated electrodes is given as a function of the position of the array of elongated electrodes increasing sequentially.

10. An inspection method, comprising: Manipulators are used to deflect multiple charged particle sub-beams to correct macroscopic aberrations of the sub-beams; as well as Multiple objectives are used to project multiple charged particle beams onto the sample; wherein the manipulator includes a first array of elongated electrodes and a second array of elongated electrodes along the beam path, the elongated electrodes of the second array being substantially parallel to the elongated electrodes of the first array, the first array being adjacent to the second array along the beam path, the elongated electrodes of the first array extending substantially perpendicular to the beam path of the first plurality of sub-beams and arranged such that a second plurality of sub-beams propagate between a pair of elongated electrodes of the first array, the second plurality of sub-beams being a subset of the first plurality of sub-beams, the elongated electrodes including parallel plates extending parallel to the propagation direction of the second plurality of sub-beams. The manipulator further includes a first set of elongated electrodes, a second set of elongated electrodes, and a third set of elongated electrodes, one of which corresponds to the elongated electrodes of the first array. The angle between the first set of elongated electrodes and the second set of elongated electrodes is 60°, and the angle between the second set of elongated electrodes and the third set of elongated electrodes is 60°.

Images