Inspection device

Abstract

To provide a charged-particle assessment tool comprising multiple beam columns.SOLUTION: Each beam column comprises: a charged-particle beam source (201) configured to emit charged particles; multiple condenser lenses (231) configured to form charged particles (211, 212, 213) emitted from the charged-particle beam source into multiple charged-particle beams, the condenser lenses configured to focus the multiple charged particle beams to respective intermediate focuses (233); multiple objective lenses (234) arranged downstream of the intermediate focuses, each objective lens configured to project one of the multiple charged-particle beams onto a sample; and aberration correctors (235) configured to reduce one or more aberrations in the multiple charged particle beams. The beam columns are arranged adjacently to one another to project the charged particle beams onto adjacent regions of the sample.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This application claims the priority of European Patent Application No. 20158863.9 filed on February 21, 2020, European Patent Application No. 20184162.4 filed on July 6, 2020, and European Patent Application No. 20206987.8 filed on November 11, 2020. These patent applications are hereby incorporated by reference in their entirety.

[0002]

[0002] Embodiments provided herein generally relate to charged particle evaluation tools and inspection methods, and in particular, 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, due to optical effects and accidental particles, unwanted pattern defects inevitably occur during the manufacturing process on a substrate (i.e., a wafer) or a mask, thereby reducing the yield. Therefore, monitoring the degree of unwanted pattern defects is an important process in the manufacture of IC chips. More generally, the 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 a scanning electron microscope (SEM). In an SEM, a primary electron beam of relatively high-energy electrons is targeted at a target in a final deceleration step so as to land on a sample with a relatively low landing energy. The electron beam is focused as a probing spot on the sample. Due to the interaction between the material structure at the probing spot and the landing electrons from the electron beam, electrons such as secondary electrons, backscattered electrons, or Auger electrons are emitted from the surface. The generated secondary electrons can be emitted from the material structure of the sample. By scanning the primary electron beam as a probing spot over the sample surface, secondary electrons can be emitted over the sample surface. By collecting these emitted secondary electrons from the sample surface, the pattern inspection tool can acquire an image representing the characteristics of the material structure of the sample surface.

[0005]

[0005] There is a general need to improve the throughput and other characteristics of charged particle inspection devices.

Summary of the Invention

[0006]

[0006] Embodiments provided herein disclose a charged particle beam inspection device.

[0007]

[0007] According to a first aspect of the present invention, there is provided a charged particle evaluation tool, the charged particle evaluation tool including a plurality of beam columns, each beam column including a charged particle beam source configured to emit charged particles, a plurality of condenser lenses configured to form the charged particles emitted from the charged particle beam source into a plurality of charged particle beams, and a plurality of objective lenses, each of which is configured to project one of the plurality of charged particle beams onto a sample, The beam columns are arranged adjacent to each other so as to project a charged particle beam onto an adjacent region of the sample.

[0008]

[0008] According to a second aspect of the present invention, there is provided an inspection method, the inspection method comprising: emitting a charged particle beam toward a sample using a plurality of beam columns, each beam column including a charged particle beam source configured to emit charged particles, a plurality of condenser lenses configured to form the charged particles emitted from the charged particle beam source into a plurality of charged particle beams, and a plurality of objective lenses, each of which is configured to project one of the plurality of charged particle beams onto the sample, the beam columns being arranged adjacent to each other so as to project a charged particle beam onto an adjacent region of the sample.

[0009]

[0009] According to a third aspect of the present invention, there is provided a charged particle multi-beam column array for a charged particle tool for projecting a plurality of charged particle multi-beams toward a sample, the charged particle multi-beam column array comprising: a plurality of charged particle multi-beam columns configured to simultaneously project respective multi-beams onto different regions of the sample; a focus corrector configured to perform group focus correction on each of a plurality of groups of sub-beams of the multi-beam, each group focus correction being the same for all of the sub-beams of each group; and

[0010]

[0010] According to a fourth aspect of the present invention, there is provided an inspection method, the inspection method comprising: projecting a plurality of charged particle multi-beams toward a sample using a multi-beam column array; performing group focus correction on each of a plurality of groups of sub-beams of the multi-beam, each group focus correction being the same for all of the sub-beams of each group; and

[0011]

[0011] 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

[0012]

Figure 1

[0012] It is a schematic diagram showing an exemplary charged particle beam inspection apparatus.

Figure 2

[0013] It is a schematic diagram showing an exemplary multi-beam apparatus that is part of the exemplary charged particle beam inspection apparatus of FIG. 1.

Figure 3

[0014] It is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Figure 4

[0015] It is a schematic diagram of another exemplary multi-beam apparatus according to one embodiment.

Figure 5

[0016] It is a graph of landing energy versus spot size.

Figure 6

[0017] It is an enlarged view of the objective lens of one embodiment of the present invention.

Figure 7

[0018] It is a schematic cross-sectional view of the objective lens of an inspection apparatus according to one embodiment.

Figure 8

[0019] It is a bottom view of the objective lens of FIG. 7.

Figure 9

[0020] It is a bottom view of a modification of the objective lens of FIG. 7.

Figure 10

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

Figure 11

[0022] It is a schematic side view of an inspection tool having a plurality of adjacent optical columns.

Figure 12

[0023] It is a schematic plan view of an inspection tool having a plurality of adjacent optical columns arranged in a rectangle.

Figure 13

[0024] It is a schematic plan view of an inspection tool having a plurality of adjacent optical columns arranged in a hexagonal pattern.

Figure 14

[0025] It is a schematic side cross-sectional view of a corrector aperture array integrated with an objective lens array including two electrodes.

Figure 15

[0026] It is a schematic side cross-sectional view of a corrector aperture array integrated with an objective lens array including three electrodes.

Figure 16

[0027] It is a schematic top view of electrodes in an exemplary corrector aperture array, the electrodes including relatively wide elongated conductive strips aligned in a first direction.

Figure 17

[0028] It is a schematic top view of electrodes in another exemplary corrector aperture array, the electrodes including relatively wide elongated conductive strips aligned in a second direction.

Figure 18

[0029] It is a schematic top view of electrodes in another exemplary corrector aperture array, the electrodes including relatively narrow elongated conductive strips aligned in a first direction.

Figure 19

[0030] It is a schematic top view of electrodes in another exemplary corrector aperture array, the electrodes including relatively narrow elongated conductive strips aligned in a second direction.

Figure 20

[0031] It is a schematic top view of electrodes of another exemplary corrector aperture array, the electrodes including conductive elements having a lower aspect ratio and filling without gaps.

DETAILED DESCRIPTION OF THE INVENTION

[0013]

[0032] With this, we refer in detail to exemplary embodiments, the 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 implementation forms described in the following description of the exemplary embodiments do not represent all implementation forms that are consistent with the present invention. Instead, those implementation forms are merely examples of devices and methods that are consistent with aspects related to the present invention, as described in the appended claims.

[0014]

[0033] The improvement of the computing power of an electronic device to reduce the physical size of the device can be achieved by significantly increasing the implementation density of circuit components such as transistors, capacitors, and diodes on the IC chip. This has been made possible by the improvement in resolution that enables the fabrication of smaller structures. For example, the IC chip of a smartphone, which is the size of a fingernail, could contain over 2 billion transistors before 2019, and the size of each transistor is less than 1 / 1000 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 one error in a single step can dramatically affect the function of the final product. Just one "killer defect" can cause the device to malfunction. The goal of the manufacturing process is to improve the overall yield of the process. For example, for a process with 50 steps (where the steps could represent the number of layers formed on a wafer), to achieve a 75% yield, each individual step must have a yield of over 99.4%. If each individual step has a yield of 95%, the overall process yield is as low as 7%.

[0015]

[0034] In an IC chip manufacturing facility, while a high process yield is desirable, it is also essential to maintain a high substrate (i.e., wafer) throughput defined as the number of substrates processed per hour. High process yield and high substrate throughput can be affected by the presence of defects. This is particularly true when operator intervention is required to investigate the defects. Therefore, high-throughput detection and identification of microscale and nanoscale defects by inspection tools such as scanning electron microscopes ("SEM") are essential to maintain high yield and low cost.

[0016]

[0035] The SEM includes a scanning device and a detector device. The scanning device includes an illumination device including an electron source and a projection device. The electron source is for generating primary electrons. The projection device is 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 collectively referred to as an electron-optical system or device. The primary electrons interact with the sample to generate secondary electrons. The detection device captures secondary electrons from the sample when the sample is scanned so that the SEM can generate an image of the scanned area of the sample. For high-throughput inspection, a part of the inspection device uses a plurality of focused beams of primary electrons, i.e., a multi-beam. The component beams of the multi-beam may be referred to as sub-beams or beamlets. The multi-beam can scan different parts of the sample simultaneously. Therefore, a multi-beam inspection device can inspect a sample much faster than a single-beam inspection device.

[0017]

[0036] Embodiments of known multi-beam inspection devices will be described below.

[0018]

[0037] The figures are schematic. 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, and only the differences with respect to individual embodiments are described. The description and the drawings are directed to an electron optical device, but it is understood that the embodiments are not used to limit the present disclosure to specific charged particles. Therefore, throughout this document, references to electrons can be considered more generally as references to charged particles, which are not necessarily electrons.

[0019]

[0038] Referring now to FIG. 1, FIG. 1 is a schematic view showing an exemplary charged particle beam inspection apparatus 100. The charged particle beam inspection apparatus 100 of FIG. 1 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, an equipment front end module (EFEM) 30, and a controller 50. The electron beam tool 40 is located within the main chamber 10.

[0020]

[0039] 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 front opening unified pod (FOUP). The FOUP contains a substrate (e.g., a semiconductor substrate or a substrate made of other materials), or a sample to be inspected (hereinafter, the substrate, wafer, and sample are collectively referred to as "sample"). One or more robot arms (not shown) within the EFEM 30 carry the sample to the load lock chamber 20.

[0021]

[0040] The loading lock chamber 20 is used to remove the gas around the sample. This creates a vacuum, which is a local gas pressure lower than the pressure of the ambient environment. The loading lock chamber 20 may be connected to a loading lock vacuum pump system (not shown), which removes the gas particles within the loading lock chamber 20. By operating the loading lock vacuum pump system, the loading lock chamber can 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 the gas particles within the main chamber 10 such 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 and the sample can be inspected by the electron beam tool. The electron beam tool 40 may include a multi-beam electron optical device.

[0022]

[0041] 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 a processing circuit configured to execute various signal and image processing functions. In FIG. 1, the controller 50 is shown as external to 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 within 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. It should be noted that although the present disclosure provides an example of the main chamber 10 that houses the electron beam inspection tool, aspects of the present disclosure are not limited in a broad sense to chambers that house electron beam inspection tools. Rather, it is understood that the principles described above are also applicable to other tools and other arrangements of devices operating under a second pressure.

[0023]

[0042] Referring now to FIG. 2, FIG. 2 is a schematic diagram showing an exemplary electron beam tool 40 including a multi-beam inspection tool that is part of the exemplary charged particle beam inspection apparatus 100 of FIG. 1. The multi-beam 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 be collectively referred to as an electron optical 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 multi-beam electron beam tool 40 further includes an electron detection device 240.

[0024]

[0043] 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.

[0025]

[0044] The projection device 230 is configured to convert the primary electron beam 202 into a plurality of sub-beams 211, 212, 213 and direct each sub-beam onto the sample 208. For the sake of brevity, three sub-beams are shown, but there may be dozens, hundreds, or thousands of sub-beams. The sub-beams may be referred to as beamlets.

[0026]

[0045] The controller 50 may be connected to various parts of the charged particle beam inspection apparatus 100 of FIG. 1, such as the electron source 201, the electron detection device 240, the projection device 230, and the motorized stage 209. The controller 50 may perform various image and signal processing functions. The controller 50 can also generate various control signals for controlling the operation of the charged particle beam inspection apparatus including the charged particle multi-beam apparatus.

[0027]

[0046] The projection device 230 may be configured to focus the sub-beams 211, 212, and 213 onto the sample 208 for inspection, and may form three probe spots 221, 222, and 223 on the surface of the sample 208. The projection device 230 may be configured to deflect the 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 on the probe spots 221, 222, and 223 on the sample 208, electrons including secondary electrons and backscattered electrons are generated from the sample 208. Secondary electrons generally have an electron energy of 50 eV or less. Backscattered electrons generally have an electron energy between 50 eV and the landing energy of the primary sub-beams 211, 212, and 213.

[0028]

[0047] The electron detection device 240 is configured to detect secondary electrons and / or backscattered electrons and generate corresponding signals, and these signals are sent to the controller 50 or a signal processing system (not shown) to construct an image of the corresponding scanning area of the sample 208, for example. The electron detection device may be incorporated into the projection device or may be separated from the projection device, and a secondary optical column is provided to direct secondary electrons and / or backscattered electrons towards the electron detection device.

[0029]

[0048] 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, a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer may include at least a part of the processing function of the controller. Thus, the image acquirer may include at least one or a plurality of processors. Among others, the image acquirer may be communicatively coupled to the electronic detection device 240 of the device 40 enabling signal communication such as a conductor, an optical fiber cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, a wireless radio, or a combination thereof. The image acquirer can receive a signal from the electronic detection device 240, process the data included in the signal, and construct an image therefrom. Thus, the image acquirer can acquire an image of the sample 208. The image acquirer can also perform various post-processing functions such as contour generation and superimposition of indicators on the acquired image. The image acquirer may be configured to perform adjustments such as brightness and contrast of the acquired image. The storage may be a storage medium such as a hard disk, a flash drive, cloud storage, random access memory (RAM), or other types of computer-readable memory. The storage may be coupled to the image acquirer and can be used to store the scanned raw image data as the original image or to store the post-processed image.

[0030]

[0049] The image acquirer can acquire one or more images of the sample based on the 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 including a plurality of imaging areas. The single image can be stored in storage. The single image may be the original image that can be divided into a plurality of regions. Each region may include one imaging area including the features of the sample 208. The acquired image may include a plurality of images of a single imaging area of the sample 208 sampled multiple times over a period of time. The plurality of images can be stored in storage. The controller 50 may be configured to perform image processing steps using a plurality of images of the same location of the sample 208.

[0031]

[0050] The controller 50 may include a measurement circuit (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons. The electron distribution data collected during the detection time window can be combined with the corresponding scanning path data of each 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.

[0032]

[0051] The controller 50 can control the electric stage 209 to move the sample 208 during the inspection of the sample 208. The controller 50 may enable the electric stage 209 to move the sample 208 in a certain direction, preferably continuously, for example, at a constant speed, at least during the inspection of the sample. The controller 50 can control the movement of the electric stage 209 such that the electric 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) according to the characteristics of the inspection steps of the scanning process.

[0033]

[0052] FIG. 3 is a schematic diagram of an inspection tool according to an embodiment of the present invention. The electron source 201 directs electrodes towards an array of condenser lenses 231 that form part of the projection system 230. The electron source is desirably a high-brightness thermionic emitter having a good compromise between brightness and total emission current. There may be dozens, hundreds, or thousands of condenser lenses 231. The condenser lens is desirably an Einzel lens and may be constructed as described in European Patent Application Publication No. 1602121A1, which is incorporated herein by reference particularly for the disclosure of a lens array (this array provides one lens per beamlet) for splitting an electron beam into a plurality of multi-beams. The lens array may take the form of at least two plates. These at least two plates function as electrodes. In each of these at least two plates, apertures that are aligned with each other and correspond to the locations of the beamlets are defined. Each plate is maintained at a different potential during operation to achieve the desired lens effect. The lens array may include a beam-limiting aperture array that may be one of the at least two plates.

[0034]

[0053] In one configuration, the condenser lens array may be formed of an array of three plates where the entrance and exit of the lens have the same beam energy, and this configuration may be called an Einzel lens. This is beneficial because off-axis chromatic aberration is limited since dispersion occurs only within the Einzel lens. These aberrations can be ignored if the thickness of such a lens is on the order of a few mm.

[0035]

[0054] Each condenser lens in the array directs electrons toward respective sub-beams 211, 212, 213 that converge the electrons at respective intermediate foci 233. The sub-beams diverge from each other. The down-beams of the intermediate foci 233 are a plurality of objective lenses 234, each of which directs respective sub-beams 211, 212, 213 toward the sample 208. The objective lens 234 can be an Einzel lens. At least chromatic aberrations occurring within the beam due to the condenser lens and the corresponding down-beam objective lens may cancel each other out.

[0036]

[0055] By controlling the landing energy of electrons on the sample, it becomes possible to control the focus parameters and introduce other corrections. The landing energy can be selected to increase the emission and detection of secondary electrons. A controller provided for controlling the objective lens 234 may be configured to control the landing energy to any desired value within a predetermined range, or a desired value among a plurality of predetermined values. In one embodiment, the landing energy may be controlled to a desired value within the range of 1000 eV to 4000 eV, or even up to 5000 eV.

[0037]

[0056] The electron detection device 240 is provided between the objective lens 234 and the sample 208 and detects secondary electrons and / or backscattered electrons emitted from the sample 208. An exemplary configuration of the electron detection system will be described below.

[0038]

[0057] In the system of FIG. 3, the beamlets 211, 212, 213 propagate along a straight path from the condenser lens 231 to the sample 208. The beamlet paths diverge the down beam of the condenser lens 231. A modified configuration example is shown in FIG. 4, which is the same as the system of FIG. 3 except that the deflector 235 is provided at the intermediate focus 233. The deflector 235 is disposed in the beamlet path at the position of the corresponding intermediate focus 233 or focus point (i.e., focus location), or at least around it. The deflector is disposed in the beamlet path at the intermediate image plane of the associated beamlet, i.e., at its focus or focus point. The deflector 235 is configured to operate on each of the beamlets 211, 212, 213. The deflector 235 is configured to bend each of the beamlets 211, 212, 213 by an amount effective to ensure that the chief ray (sometimes called the beam axis) is incident on the sample 208 substantially perpendicular to it (i.e., at substantially 90° to the nominal surface of the sample). The deflector 235 is sometimes called a collimator or a collimator deflector. The deflector 235 substantially parallelizes the paths of the beamlets such that, in fact, before reaching the deflector, the beamlet paths diverge from each other. In the down beam of the deflector, the beamlet paths are substantially parallel to each other, i.e., substantially collimated. Thus, each beamlet path may be linear between the array of condenser lenses 231 and an array of collimators, e.g., the deflector 235. Each beamlet path may be linear between the array of deflectors 235 and the objective lens array 234, and optionally between the sample 208. A suitable collimator is the deflector disclosed in European Patent Application No. 20156253.5 filed on February 7, 2020, which patent application is incorporated herein by reference with respect to the application of deflectors to multi-beam arrays.

[0039]

[0058] In the system of FIG. 4, the landing energy of electrons may be more easily controlled because the off-axis aberration generated in the beamlet path occurs in, or at least mainly in, the condenser lens 231. The objective lens 234 of the system shown in FIG. 4 does not need to be an Einzel lens. This is because when the beam is collimated, no off-axis aberration occurs within the objective lens. The off-axis aberration can be better controlled in the condenser lens than in the objective lens 234. By making the condenser lens 231 substantially thinner, the contribution of the condenser lens to off-axis aberration, particularly chromatic off-axis aberration, may be minimized. The thickness of the condenser lens 231 may be varied to adjust the chromatic off-axis contribution and balance it with other contributions to chromatic aberration in each beamlet path. Therefore, the objective lens 234 may have two or more electrodes. The beam energy entering the objective lens may be different from the energy exiting the objective lens.

[0040]

[0059] FIG. 6 is a schematic enlarged view of one objective lens 300 of an array of objective lenses in a three - electrode configuration, such as an Einzel lens. The objective lens 300 may be configured to reduce an electron beam at a magnification greater than 10, desirably in the range of 50 to 100 or more. The objective lens includes a central or first electrode 301, a lower or second electrode 302, and an upper or third electrode 303. Voltage sources 351, 352, 353 are configured to apply potentials V1, V2, V3 to the first, second, and third electrodes, respectively. A further voltage source is connected to the sample to apply a fourth potential, which may be ground. The potentials may be defined with respect to the sample 208. In one embodiment, it is desirable to omit the third electrode. Such a configuration is a two - electrode objective lens, which may be used in the configuration illustrated and described with respect to FIG. 4. The first, second, and third electrodes each include an aperture through which respective sub - beams propagate. The second potential may be a potential close to the potential of the sample, for example a potential just more positive by about 50V. Alternatively, the second potential may be in the range of about + 500V to about + 1500V.

[0041]

[0060] The first and / or second potential can be changed for each aperture in order to perform focus correction.

[0042]

[0061] In order to give the objective lens 300 a deceleration function so that the landing energy can be determined, it is desirable to change the potential of the lowermost electrode and the sample. To decelerate the electrons, the lower (second) electrode is made more negative than the central electrode. When the lowest landing energy is selected, the highest electrostatic field strength is generated. The distance between the second electrode and the central electrode, the lowest landing energy, and the maximum potential difference between the second electrode and the central electrode are selected so that the resulting electric field strength is acceptable. As the landing energy becomes higher, the electrostatic field becomes lower (the deceleration over the same length is smaller).

[0043]

[0062] Since the electron optical system configuration between the electron source and the beam limiting aperture (right above the condenser lens) remains the same, the beam current remains unchanged even when the landing energy changes. When the landing energy changes, it affects the resolution, and the resolution may improve or decrease. FIG. 5 is a graph showing landing energy versus spot size in two cases. The dashed line with black circles shows the effect when only the landing energy is changed, i.e., the voltage of the condenser lens remains the same. The solid line with white circles shows the effect when the landing energy is changed and the voltage of the condenser lens (optimization of magnification versus opening angle) is re-optimized.

[0044]

[0063] When the voltage of the condenser lens is changed, the collimator no longer provides an accurate intermediate image plane for all landing energies. Therefore, it is desirable to correct the aberration induced by the collimator.

[0045]

[0064] In one embodiment, the objective lens referred to in the foregoing embodiments is an array objective lens. Each element within the array is a microlens that operates on different beams or a group of different beams in a multi-beam. The electrostatic array objective lens has at least two plates, and each plate has a plurality of holes or apertures. The position of each hole in one plate corresponds to the position of the corresponding hole in the other plate. The corresponding holes act on the same beam or a group of the same beams in the multi-beam during use. A suitable example of the lens type of each element within the array is a two-electrode decelerating lens. Additional electrodes can be provided. The bottom electrode of the objective lens is a CMOS chip detector integrated with the multi-beam manipulator array. Integrating a detector array into the objective lens replaces the secondary column. The detector array, such as a CMOS chip, is preferably oriented to face the sample (because the distance between the wafer and the bottom of the electron optical system is short (e.g., 100 μm)). In one embodiment, an electrode for capturing the secondary electron signal is formed within the upper metal layer of the CMOS device. The electrode may be formed in other layers. The power and control signals of the CMOS can be connected to the CMOS by through-silicon vias. For robustness, the bottom electrode preferably consists of two elements: a CMOS chip and a passive Si plate with holes. This plate shields the CMOS from high electric fields.

[0046]

[0065] To maximize the detection efficiency, it is desirable to make the electrode surface as large as possible so that substantially all areas of the array objective lens (excluding the apertures) are occupied by the electrodes. Each electrode has a diameter substantially equal to the array pitch. In one embodiment, the outer shape of the electrode is circular, but this may be made square to maximize the detection area. Also, the diameter of the substrate through-holes can be minimized. The typical size of the electron beam is about 5 - 15 microns.

[0047]

[0066] In one embodiment, a single electrode surrounds each aperture. In another embodiment, a plurality of electrode elements are provided around each aperture. The electrons captured by the electrode elements surrounding one aperture may be combined into a single signal or used to generate independent signals. The electrode elements may be divided radially (i.e., form a plurality of concentric rings), angularly (i.e., form a plurality of fan-shaped portions), both radially and angularly, or in any other convenient manner.

[0048]

[0067] However, an increase in the surface area of the electrode results in an increase in parasitic capacitance and thus a decrease in bandwidth. For this reason, it may be desirable to limit the outer diameter of the electrode. In particular, when the increase in the electrode only provides a slight improvement in detection efficiency but a significant increase in capacitance. Circular (annular) electrodes can provide a good compromise between collection efficiency and parasitic capacitance.

[0049]

[0068] An increase in the outer diameter of the electrode can also result in an increase in crosstalk (sensitivity to signals from adjacent holes). This can also be a reason to make the outer diameter of the electrode smaller. In particular, when the increase in the electrode only provides a slight improvement in detection efficiency but a significant increase in crosstalk.

[0050]

[0069] The current of the backscattered electrons and / or secondary electrons collected by the electrode is amplified by a transimpedance amplifier.

[0051]

[0070] An exemplary embodiment is shown in FIG. 7, and FIG. 4 shows a multi-beam objective lens 401 in a schematic cross-section. A detector module 402 is provided on the output side of the objective lens 401 (the side facing the sample 403). FIG. 8 is a bottom view of the detector module 402, and the detector module 402 includes a substrate 404 on which a plurality of capture electrodes 405 are provided, and each capture electrode 405 surrounds a beam aperture 406. The beam aperture 406 can be formed by etching through the substrate 404. In the arrangement shown in FIG. 8, the beam aperture 406 is shown as a rectangular array. The beam apertures 406 can also be arranged differently (e.g., in a hexagonal close-packed array as shown in FIG. 9).

[0052]

[0071] FIG. 10 shows a magnified view of a part of the detector module 402 in cross-section. The capture electrodes 405 form the bottom-most surface of the detector module 402, i.e., the surface closest to the sample. A logic layer 407 is provided between the capture electrodes 405 and the body of the silicon substrate 404. The logic layer 407 can include amplifiers, e.g., a transimpedance amplifier, an analog-to-digital converter, and readout logic circuitry. In one embodiment, there is one amplifier and one analog-to-digital converter per capture electrode 405. The logic layer 407 and the capture electrodes 405 can be fabricated using a CMOS process in which the capture electrodes 405 form the final metallization layer.

[0053]

[0072] The wiring layer 408 is provided on the back side of the substrate 404 and is connected to the logic layer 407 by the 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. Specifically, when the electrode signals are digitized in the logic layer 407, only a few through-silicon vias may be required to provide a data bus. The wiring layer 408 may include control lines, data lines, and power lines. You will notice that there is sufficient space for all the necessary connections regardless of the beam apertures 406. The detection module 402 can also be fabricated using bipolar or other manufacturing techniques. A printed circuit board and / or other semiconductor chips may be provided on the back side of the detector module 402.

[0054]

[0073] The integrated detector array described above is particularly advantageous when used with a tool having an adjustable landing energy, since the capture of secondary electrons can be optimized for a range of landing energies.

[0055]

[0074] It is desirable to increase the rate (area per unit time) at which a sample can be evaluated or inspected. In tools using a charged particle beam, it is generally not possible to increase the operating speed by increasing the beam intensity due to constraints on the brightness of the radiation source and the total emission current. Increasing the beam current may also increase the stochastic effects due to the mutual repulsion of the charged particles.

[0056]

[0075] As shown in FIGS. 11 to 13, it is proposed to provide a tool comprising a plurality of multi-beam columns 110-1 to 110-n adjacent to each other so as to project a plurality of charged particle beams onto the same sample. Each multi-beam column 110 includes a projection device 230 as described above. The term "multi-beam column" is used herein to represent a beam column that simultaneously directs a plurality of electron beams onto one sample. Thereby, an increased area of the sample can be evaluated at one time. In order to minimize the distance between columns, it is desirable that the condenser lens and / or the objective lens be formed as MEMS or CMOS devices. If there is a collimator, it is also desirable that the collimator be formed as an MEMS or CMOS device. The collimator may be a deflector and may be called a collimator deflector. The multi-beam columns 110-1 to 110-n may be arranged in a rectangular array as shown in FIG. 12, or may be arranged in a hexagonal array as shown in FIG. 13.

[0057]

[0076] As described above, each sub-beam of the multi-beam column 110 can scan the entire respective individual scanning area (which may be called the sub-beam addressable area) of the object plane on which the sample is placed. The sub-beam addressable areas of all the sub-beams of the multi-beam column 110 may be collectively called the column addressable area. The column addressable area is not continuous because the scanning range of the sub-beam is smaller than the pitch of the objective lens. A continuous area of the sample can be scanned by mechanically scanning the sample through the object plane. The mechanical scanning of the sample may be tortuous or may be a step-and-scan movement.

[0058]

[0077] A continuous area that includes a column-addressable area is referred to herein as a region. The region can be a circle or a polygon. The region is the smallest shape that includes the column-addressable area. The regions addressed by adjacent multi-beam columns 110 are adjacent on the sample when placed on the object plane. Adjacent regions are not necessarily in contact. The multi-beam columns 110 may be arranged to cover at least a part to all of the sample. The regions may be spaced apart so that the multi-beam columns 110 can project onto the entire part. The stage may move with respect to the multi-beam columns 110 such that the regions associated with the columns preferably cover the entire part of the sample without overlap. The footprint of the multi-beam column 110 (i.e., the projection of the multi-beam column 110 onto the object plane) is likely to be larger than the area where the multi-beam column 110 projects the sub-beams.

[0059]

[0078] In one embodiment, a focus corrector is provided for correcting the focus of individual beams or groups of beams on the sample to account for any non-flatness of the sample. The focus corrector can be electrostatic and / or mechanical. The focus corrector may include any or all of the corrections in the Z direction, Rx direction, and Ry direction. The mechanical focus corrector may include an actuator configured to tilt and / or shift the entire column or only a part of the column, such as an objective lens array. The focus corrector will be further described below.

[0060]

[0079] In one embodiment, the objective lens has an aberration corrector. The aberration corrector can be combined with the focus corrector.

[0061]

[0080] In some embodiments, the charged particle evaluation tool further includes one or more aberration correctors that reduce one or more aberrations in the sub-beam. In certain embodiments, each of at least one subset of the aberration correctors is positioned at or directly adjacent to each intermediate focus of the plurality of intermediate foci (e.g., within intermediate image planes 233, 235 or adjacent to or focused at intermediate image planes 233, 235). The sub-beam has a minimum cross-sectional area within or near the focal plane, such as an intermediate plane. This provides more space for the aberration corrector than is available elsewhere, i.e., in the up-beam or down-beam of the intermediate plane (or than is available in an alternative arrangement without an intermediate image plane).

[0062]

[0081] In certain embodiments, the aberration correctors positioned at or directly adjacent to the intermediate foci (or intermediate image planes) include deflectors for correcting a source 201 that appears to be at different positions for different beams. The corrector can be used to correct macroscopic aberrations caused by the source that impede good alignment between each sub-beam and the corresponding objective lens.

[0063]

[0082] The aberration corrector can correct aberrations that impede proper column alignment. Such aberrations can also result in misalignment between the sub-beam and the corrector. For this reason, it may be desirable to position the aberration corrector additionally or alternatively at or near the condenser lens 231 (e.g., each such aberration corrector is integrated with or directly adjacent to one or more of the condenser lenses 231). This is desirable because the condenser lens 231 is close to or coincides with the beam aperture in the direction perpendicular to the beam aperture, so that at or near the condenser lens 231, the aberration has not yet caused a shift in the corresponding sub-beam. However, an issue with positioning the corrector at or near the condenser lens 231 is that each sub-beam has a relatively large cross-sectional area and a relatively small pitch at this location compared to more downstream locations.

[0064]

[0083] In some embodiments, each of at least a subset of the aberration correctors is integrated with or directly adjacent to one or more of the objective lenses 234. In one embodiment, these aberration correctors reduce one or more of field curvature, focus error, and spherical aberration. In addition or alternatively, one or more scanning deflectors (not shown) may be integrated with or directly adjacent to one or more of the objective lenses 234 for scanning the sub-beams 211, 212, 214 across the sample 208. In one embodiment, the scanning deflector may be used as described in European Patent Application Publication No. 2425444A1 (this patent application is hereby incorporated by reference in its entirety, particularly with respect to the disclosure of the use of an aperture array as a scanning deflector).

[0065]

[0084] The aberration corrector 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, and the descriptions of the beamlet manipulators in both documents are hereby incorporated by reference.

[0066]

[0085] In one embodiment, as shown in FIG. 3, an aberration corrector, for example, the aberration corrector 126 associated with the objective lens 234, includes an astigmatism corrector that reduces astigmatism. Reducing astigmatism reduces errors caused by astigmatism, such as spherical aberration and focus error. Without correction, in embodiments where the sub-beams 211, 212, 213 propagate along a straight path between the condenser lens 231 and the objective lens 234 due to an oblique angle of incidence on the objective lens 234, a significant astigmatism aberration effect is expected to occur in the objective lens 234. The astigmatism effect can be reduced or eliminated by collimating the sub-beams 211, 212, 213 before they reach the objective lens 234. However, providing a collimator upstream of the objective lens 234 increases complexity, as related to the embodiment shown in FIG. 4. The astigmatism corrector makes it possible to avoid the collimator, thereby reducing complexity. As described above, the absence of a collimator upstream of the objective lens 234 allows the objective lens to be provided at a larger pitch, thereby further increasing the beam current.

[0067]

[0086] In one embodiment, the image plane curvature corrector is integrated with one or more of the objective lenses 234 or is directly adjacent thereto. In one embodiment, the image plane curvature corrector includes a passive corrector. The passive corrector may be implemented, for example, by varying the diameter and / or ellipticity of the aperture of the objective lens 118. The passive corrector may be implemented as described in European Patent Application Publication No. 2575143A1, which is incorporated herein by reference, particularly with respect to the disclosure of the use of an aperture pattern for correcting astigmatism. The passive nature of the passive corrector is desirable since it means that no control voltage is required. In embodiments where the passive corrector is implemented by varying the diameter and / or ellipticity of the aperture of the objective lens 118, the passive corrector provides the further desirable feature that it does not require additional elements such as additional lens elements. The problem with passive correctors is that since they are fixed, it is necessary to carefully calculate in advance the amount of correction required. In addition to or instead of this, in one embodiment, the image plane curvature corrector includes an active corrector. The active corrector can provide correction by controllably correcting charged particles. The correction applied by each active corrector may be controlled by controlling the respective potential of one or more electrodes of the active corrector. In one embodiment, the passive corrector performs a coarse correction and the active corrector performs a finer and / or adjustable correction.

[0068]

[0087] In some embodiments, as illustrated in FIGS. 14 to 20, the charged particle multi-beam column array includes a focus corrector. The focus corrector may be configured to perform focus correction on each of the individual sub-beams. In other embodiments, the focus corrector performs group focus correction on each of a plurality of groups of sub-beams of the multi-beam. The focus correction may include any or all of corrections in the Z direction, Rx direction, and Ry direction. The amount of group focus correction is the same for all of the sub-beams in each group. As described above, performing correction in groups may reduce routing requirements. In some embodiments, the focus corrector performs different corrections on sub-beams from different multi-beams. Thus, the focus correction applied to the multi-beam from a certain multi-beam column 110 may be different from the focus correction applied to the multi-beam from a different multi-beam column 110 in the same array. Accordingly, the focus corrector can correct manufacturing or installation differences between different multi-beam columns 110 and / or height differences on the surface of the sample 208 between different multi-beam columns 110. Alternatively or in addition, the focus corrector may perform different corrections on different sub-beams within the same multi-beam. Accordingly, the focus corrector provides focus correction at a finer level of granularity, thereby being able to correct, for example, manufacturing variations within the multi-beam column 110 and / or relatively small range variations in the height of the surface of the sample 208 in some cases.

[0069]

[0088] According to some embodiments, the focus corrector includes a mechanical actuator 630. The mechanical actuator 630 performs one or more of the group focus corrections at least partially by mechanical actuation of the focus adjustment element. When the focus adjustment element is mechanically actuated, a tilt and / or shift of the entire multi-beam column 110, or only a part thereof, for example the objective lens array 118, may be applied. For example, the focus adjustment element may include one or more electrodes of the objective lens array 118, and the mechanical actuator 630 may adjust the focus by moving one or more (e.g., all) of the electrodes of the objective lens array 118 (e.g., towards or away from the surface of the sample 208).

[0070]

[0089] According to some embodiments, the focus corrector performs one or more of the group focus corrections at least partially by changing the potential applied to each of one or more electrodes. According to some embodiments, as illustrated in FIGS. 14 to 20, the focus corrector includes at least one corrector aperture array 601, 602. The corrector aperture array 601 defines a plurality of groups of corrector apertures 603 (each group includes a plurality of corrector apertures 603). The corrector aperture array 601 may be integrated with the objective lens array 118 and / or be directly adjacent to the objective lens array 118. For example, the corrector aperture array 601 may be formed on an electrode (e.g., the body defining the aperture) of the objective lens array 118.

[0071]

[0090] In the example shown in FIG. 14, the corrector aperture array 601 is formed on the up-beam electrode 611 of the two-electrode objective lens array 118. In the example shown in FIG. 14, another corrector aperture array 602 is formed on the down-beam electrode 612 of the objective lens array 118. This another corrector aperture array 602 may define another plurality of groups of corrector apertures 605.

[0072]

[0091] In the example shown in FIG. 15, the corrector aperture array 601 is formed on (or forms) the up - beam surface of the central electrode of the three - electrode objective lens array 118. In the example shown in FIG. 15, another corrector aperture array 602, which defines another plurality of groups of corrector apertures 605, is formed on (or forms) the down - beam surface of the central electrode. The potential difference between the corrector aperture array 601 and the corrector aperture array 602 may be small enough to avoid any significant lens effect in the region between the two corrector aperture arrays 601, 602. The three - electrode objective lens array 118 may be configured to operate as an Einzel lens array.

[0073]

[0092] At least one of the corrector aperture arrays 601, 602 may be formed on, or form, any surface of any electrode in the objective lens array. It is desirable to provide at least one of the corrector aperture arrays 601, 602 on an electrode having a stronger lens effect than other electrodes in the objective lens array. This enables at least one of the corrector aperture arrays 601, 602 to have the strongest effect for a given applied potential difference. In the configuration of FIG. 15, typically, the central electrode has a stronger lens effect than the up - beam electrode 651 and the down - beam electrode 652, so the two corrector aperture arrays 601, 602 are associated with the central electrode.

[0074]

[0093] Each corrector aperture array 601, 602 includes respective electrode systems 621, 622. Each electrode system 621, 622 includes a plurality of electrodes. Each electrode applies a common potential to the aperture outer peripheral surface of all the apertures in different groups of a plurality of groups of corrector apertures. Each electrode in each of the electrode systems 621, 622 is electrically insulated from each other electrode in the electrode systems 621, 622. Each electrode is simultaneously electrically connected to the aperture outer peripheral surface of all the apertures in different groups of a plurality of groups of corrector apertures 603, 605. Each corrector aperture 603, 605 is aligned with a respective objective lens in the objective lens array 118 along the sub-beam path. In the examples of FIGS. 14 and 15, each objective lens in the objective lens array 118 is defined by an aperture in the electrodes that are aligned with each other along the respective sub-beam paths. Thus, each corrector aperture 603, 605 may be aligned with the apertures in the up-beam electrodes and down-beam electrodes that are aligned with each other along the respective sub-beam paths.

[0075]

[0094] In one embodiment, in one or more of each of the plurality of groups of corrector apertures 603, 605, all of the objective lenses with which the corrector apertures 603, 605 are aligned are within the same multi-beam column 110. Alternatively or in addition, in some embodiments, in one or more of each of the plurality of groups of corrector apertures 603, 605, at least a subset of the objective lenses with which the corrector apertures 603, 605 are aligned are within different multi-beam columns 110. The corrector aperture array 603 (and / or any other aperture array 605 provided) may correct a focus error using respective pluralities of electrodes. The correction is performed by controlling the electric field within the region through which the sub-beam passes using the electrodes.

[0076]

[0095] Within each corrector aperture array 601, 602, each electrode can simultaneously apply a potential to a plurality of corrector apertures 603, 605, independent of the potential applied to other apertures within the corrector aperture arrays 601, 602. Thus, fewer electrodes are required than if each electrode were connected to only one corrector aperture. Fewer electrodes facilitate electrode routing, thereby facilitating manufacturing and, optionally, allowing the pattern of corrector apertures within the electrodes to be made denser. Controlling the potential applied independently to groups of corrector apertures 603, 605 provides a higher level of control than when all of the corrector apertures, such as when the corrector apertures are formed in a monolithic metal plate, are electrically connected together. Thus, an improved balance is achieved between manufacturing ease and sub-beam operation controllability.

[0077]

[0096] In some embodiments, the electrode systems 621, 622 are each provided as a conductive layer or structure on a support structure. The electrode systems 621, 622 may be formed using a silicon-on-insulator process. The electrode systems 621, 622 may be provided as a conductive layer or structure on an insulating layer of silicon oxide. The electrode systems 621, 622 may include a metallization layer and / or a conductive semiconductor such as silicon or doped silicon. The electrode systems 621, 622 may include a metal such as molybdenum or aluminum.

[0078]

[0097] Depending on the embodiment, as illustrated in FIGS. 16 to 19, each electrode in one or more of the electrode systems 621, 622 includes an elongated conductive strip 631, 632. Each elongated conductive strip 631, 632 within each electrode system may be implemented, for example, as a series of parallel plates. The conductive strips 631, 632 of each respective electrode system 621, 622 are preferably parallel to each other and / or substantially linear. Placing the electrodes within the conductive strips 631, 632 in each respective electrode system 621, 622 makes routing easier because electrical connections to the conductive strips 631, 632 can be made at the ends of the conductive strips 631, 632. Depending on the configuration, the conductive strips 631, 632 are arranged to extend to the peripheral portions of the respective electrode systems 621, 622, as schematically shown in FIGS. 16 to 19. Extending the conductive strips 631, 632 to the peripheral portions means that electrical connections to the conductive strips 631, 632 can be made at the peripheral portions. The peripheral portions of the electrode systems 621, 622 shown in the figures are schematic. The shape and relative size of the peripheral surface may be different in an actual configuration. The peripheral surface may be dimensioned, for example, to include more corrector apertures 603, 605 than shown in the figures.

[0079]

[0098] In some embodiments, the corrector apertures 603, 605 are arranged in a regular array. The regular array has a repetition of unit cells. The regular array may include, for example, a square array, a rectangular array, or a hexagonal array. Alternatively, the corrector apertures 603, 605 may be arranged in an irregular arrangement including a plurality of apertures 603, 605, which may be referred to as an irregular array. In an arrangement having a regular array, the conductive strips 631, 632 may be parallel to each other and perpendicular to the principal axis of the array. In the examples shown in FIGS. 14 to 20, the corrector apertures 603, 605 are arranged in a square array. The regular array may have one principal axis horizontal in the plane of the page and another principal axis perpendicular in the plane of the page. Accordingly, the conductive strips 631, 632 in FIGS. 16 and 24 are parallel to each other and perpendicular to the horizontal principal axis. The conductive strips 631, 632 in FIGS. 17 and 19 are parallel to each other and perpendicular to the vertical principal axis.

[0080]

[0099] The conductive strips 631, 632 may each have a minor axis and a major axis. In the examples of FIGS. 16 and 18, each minor axis is horizontal and each major axis is vertical. In the examples of FIGS. 17 and 19, each minor axis is vertical and each major axis is horizontal. The pitch of the conductive strips 631, 632 parallel to the minor axis may be greater than the pitch of the array parallel to the minor axis. Accordingly, each vertical conductive strip may include a plurality of columns of apertures 603, 605, and / or each horizontal strip may accordingly include a plurality of rows of apertures 603, 605. This approach provides a good balance between controllability and ease of manufacture. Alternatively, the pitch of the conductive strips 631, 632 parallel to the minor axis may be equal to the pitch of the array parallel to the minor axis, which provides finer spatial control of the electric field.

[0081]

[0100] In one embodiment, a plurality of corrector aperture arrays 601, 602 are provided. The corrector aperture arrays 601, 602 may be aligned with each other along the sub-beam path. In one embodiment, a conductive strip 631 within an electrode system 621 of one of the corrector aperture arrays 601 is not parallel to, for example, is perpendicular to, a conductive strip 632 within an electrode system 621 of a different one of the corrector aperture arrays 602. This configuration may be particularly preferred, for example, when the conductive strips 631, 632 are parallel to each other in each of the electrode systems 621, 622. For example, one of the corrector aperture arrays 601, an electrode system 621 may include a conductive strip 631 as shown in FIG. 16 or FIG. 18, and a different one of the corrector aperture arrays 602, an electrode system 622 may include a conductive strip 632 as shown in FIG. 17 or FIG. 19, and vice versa. Crossing the conductive strips 631, 632 in different electrode systems 621, 622 in this way results in a wide range of possible combinations of potential differences between corresponding apertures 603, 605 within each corrector aperture array without making the routing of electrical connections to each of the conductive strips 631, 632 more difficult.

[0082]

[0101] In a further configuration, as illustrated in FIG. 20, the plurality of electrodes of the electrode systems 621, 622 include a plurality of conductive elements 633 that fill each other without gaps. In the example shown, the conductive elements 633 are square. Other gapless filling shapes may be used, such as rectangles, oblongs, parallelograms, and hexagons, and / or repetitions of a group of gapless filling shapes. This approach can increase the degree of freedom in manipulating charged particles compared to the configuration using conductive strips as described above with reference to FIGS. 16-19, but the routing of electrical signals to individual electrodes may become more complex.

[0083]

[0102] In one embodiment, the beam columns are arranged in a rectangular array.

[0084]

[0103] In one embodiment, the beam columns are arranged in a hexagonal array.

[0085]

[0104] In one embodiment, the number of beam columns is in the range of 9 to 200.

[0086]

[0105] In one embodiment, the number of condenser lenses in each beam column is in the range of 1,000 to 100,000, desirably in the range of 5,000 to 25,000.

[0087]

[0106] In one embodiment, the condenser lenses of each beam column are arranged in respective arrays having a pitch in the range of 50 to 500 μm, desirably in the range of 70 to 150 μm.

[0088]

[0107] In one embodiment, n condenser lenses and / or objective lenses are formed as MEMS or CMOS devices.

[0089]

[0108] In one embodiment, one or more aberration correctors configured to reduce one or more aberrations in the sub-beam are provided.

[0090]

[0109] In one embodiment, each of at least a subset of the aberration correctors is disposed at or in direct adjacency to each of the intermediate foci.

[0091]

[0110] In one embodiment, one or more scanning deflectors are provided for scanning the sub-beam across the sample.

[0092]

[0111] In one embodiment, one or more scanning deflectors are integrated with or in direct adjacency to one or more of the objective lenses.

[0093]

[0112] In one embodiment, the evaluation tool includes one or more collimators. The one or more collimators are one or more collimator deflectors.

[0094]

[0113] In one embodiment, one or more collimator deflectors are configured to bend each beamlet by an amount effective to ensure that the chief ray of the sub-beam is incident on the sample substantially perpendicularly.

[0095]

[0114] In one embodiment, a detector integrated with the objective lens is provided.

[0096]

[0115] An evaluation tool according to an embodiment of the present invention can be a tool for performing a qualitative evaluation (e.g., pass / fail) of a sample, or a tool for performing a quantitative measurement (e.g., size of a feature) of a sample, or a tool for generating an image of a map of the sample. Examples of evaluation tools are inspection tools and measurement tools.

[0097]

[0116] The term "adjacent" may include the meaning of "abutting".

[0098]

[0117] Embodiments described herein may take the form of a series of aperture arrays or electro-optical elements arranged in an array along the path of a single beam or a multi-beam. Such electro-optical elements may be electrostatic. In one embodiment, for example, all electro-optical elements in the sub-beam path before the sample, from the beam-limiting aperture array to the last electro-optical element, may be electrostatic and / or may be in the form of an aperture array or a plate array. In a configuration, one or more of the electro-optical elements may be fabricated as a microelectromechanical system (MEMS).

[0099]

[0118] Although the present invention has been described in connection with various embodiments, other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. This specification and examples are intended to be considered as merely exemplary, and the true scope and spirit of the invention are indicated by the following claims and clauses.

[0100]

[0119] Clause 1. A charged particle evaluation tool, comprising a plurality of beam columns, each beam column including a charged particle beam source configured to emit charged particles, a plurality of condenser lenses configured to form the charged particles emitted from the charged particle beam source into a plurality of charged particle beams, and a plurality of objective lenses, each of which is configured to project one of the plurality of charged particle beams onto a sample. The plurality of beam columns are arranged adjacent to each other so that the charged particle beams are projected onto adjacent regions of the sample. The condenser lenses may be configured to focus the plurality of charged particle beams at respective intermediate foci. The plurality of objective lenses may be configured such that the down beam of the intermediate focus becomes the plurality of objective lenses. The aberration corrector may be configured to reduce one or more aberrations in the plurality of charged particle beams. The aberration corrector may include an astigmatism corrector, a focus corrector, and / or a field curvature corrector.

[0101]

[0120] Clause 2. The tool according to Clause 1, further including a focus corrector.

[0102]

[0121] Clause 3. The tool according to Clause 1 or 2, wherein the objective lens has or includes an astigmatism corrector.

[0103]

[0122] Clause 4. The tool according to Clause 1, 2, or 3, wherein the beam columns are arranged in a rectangular array.

[0104]

[0123] Clause 5. The tool according to Clause 1, 2, or 3, wherein the beam columns are arranged in a hexagonal array.

[0105]

[0124] Clause 6. The tool according to any one of Clauses 1 to 5, wherein the number of beam columns is in the range of 9 to 200.

[0106]

[0125] Clause 7. The number of condenser lenses within each beam column is within the range of 1,000 to 100,000, preferably within the range of 5,000 to 25,000, for the tool described in any one of Clauses 1 to 6.

[0107]

[0126] Clause 8. The condenser lenses of each beam column are arranged within respective arrays having a pitch within the range of 50 to 500 μm, preferably within the range of 70 to 150 μm, for the tool described in any one of Clauses 1 to 7.

[0108]

[0127] Clause 9. The condenser lens and / or the objective lens are formed as a MEMS or CMOS device, for the tool described in any one of Clauses 1 to 8.

[0109]

[0128] Clause 10. Further includes one or more aberration correctors configured to reduce one or more aberrations in the sub-beam, for the tool described in any one of Clauses 1 to 9.

[0110]

[0129] Clause 11. Each of at least a subset of the aberration correctors is disposed at or directly adjacent to each one of the intermediate foci, for the tool described in Clause 9.

[0111]

[0130] Clause 12. Further includes one or more scanning deflectors for scanning the sub-beam across the sample, and optionally, one or more of the scanning deflectors are integrated with or directly adjacent to one or more of the objective lenses, for the tool described in any one of Clauses 1 to 11.

[0112]

[0131] Clause 13. Further includes one or more collimators, and one or more of the collimators are provided at respective intermediate foci, preferably, the collimator is one or more collimator deflectors, and optionally, one or more of the collimator deflectors are configured to bend each beamlet by an effective amount to ensure that the chief ray of the sub-beam is incident on the sample substantially perpendicularly, for the tool described in any one of Clauses 1 to 12.

[0113]

[0132] Tool according to any one of clauses 1 to 13, further comprising a detector integrated with the objective lens, preferably with the detector facing the sample.

[0114]

[0133] Inspection method, comprising emitting a charged particle beam towards a sample using a plurality of beam columns, each beam column comprising a charged particle beam source configured to emit charged particles, a plurality of condenser lenses configured to form the charged particles emitted from the charged particle beam source into a plurality of charged particle beams, and a plurality of objective lenses, each of which is configured to project one of the plurality of charged particle beams onto the sample, the beam columns being arranged adjacent to each other so as to project the charged particle beam onto an adjacent region of the sample. The condenser lenses may be configured to focus the plurality of charged particle beams on respective intermediate foci. The plurality of objective lenses may be configured such that the down beam of the intermediate focus becomes the plurality of objective lenses. The aberration corrector may be configured to reduce one or more aberrations in the plurality of charged particle beams.

[0115]

[0134] Charged particle multi-beam column array for a charged particle tool for projecting a plurality of charged particle multi-beams towards a sample, the charged particle multi-beam column array comprising a plurality of charged particle multi-beam columns configured to simultaneously project respective multi-beams onto different regions of the sample, and a focus corrector configured to perform group focus correction on each of a plurality of groups of sub-beams of the multi-beam, each group focus correction being the same for all of the sub-beams of each group.

[0116]

[0135] Multi-beam column array according to clause 16, wherein the focus corrector is configured to apply different corrections to sub-beams from different multi-beams.

[0117]

[0136] Clause 18. The focus corrector is a multi-beam column array according to Clause 16 or 17, configured to apply different corrections to different sub-beams within the same multi-beam.

[0118]

[0137] Clause 19. The focus corrector is a multi-beam column array according to any one of Clauses 16 to 18, configured to perform one or more of the group focus corrections, at least in part, by mechanical actuation of the focus adjustment element.

[0119]

[0138] Clause 20. The focus corrector is a multi-beam column array according to any one of Clauses 16 to 19, configured to perform one or more of the group focus corrections, at least in part, by changing the potential applied to each of one or more electrodes.

[0120]

[0139] Clause 21. Each multi-beam column includes a sub-beam defining aperture array configured to form sub-beams from a beam of charged particles emitted by a radiation source associated with the multi-beam column, and an objective lens array, each objective lens being configured to project the sub-beam onto a sample. The focus corrector includes a corrector aperture array in which a plurality of groups of corrector apertures are defined. The corrector aperture array is integrated with one or more of the objective lens arrays and / or is directly adjacent to them. The multi-beam column array according to Clause 20.

[0121]

[0140] Clause 22. The sub-beam defining aperture array is adjacent to the objective lens array along the path of the sub-beam. The multi-beam column array according to Clause 21.

[0122]

[0141] Clause 23. The corrector aperture array includes an electrode system including a plurality of electrodes, each electrode being electrically insulated from each of the other electrodes and being electrically connected simultaneously to the aperture outer peripheral surface of all the apertures within different groups among the plurality of groups of corrector apertures, the multi-beam column array according to Clause 21 or 22.

[0123]

[0142] Clause 24. The corrector aperture array includes an electrode system including a plurality of electrodes, each electrode being configured to apply a common potential to the aperture outer peripheral surface of all the apertures within different groups among the plurality of groups of corrector apertures, the multi-beam column array according to any one of Clauses 21 to 23.

[0124]

[0143] Clause 25. Each corrector aperture is aligned with its respective objective lens along the sub-beam path, the multi-beam column array according to any one of Clauses 21 to 24.

[0125]

[0144] Clause 26. In each one or more of the plurality of groups of corrector apertures, all the objective lenses with which the corrector apertures are aligned are within the same multi-beam column, the multi-beam column array according to Clause 25.

[0126]

[0145] Clause 27. In each one or more of the plurality of groups of corrector apertures, at least a subset of the objective lenses with which the corrector apertures are aligned are within different multi-beam columns, the multi-beam column array according to Clause 25 or 26.

[0127]

[0146] Clause 28. Each column is configured to be formed from a plurality of condenser lenses configured to form from a plurality of charged particle beams from charged particles emitted from a charged particle beam source, a collimator at each one or more intermediate foci, an aberration corrector associated with the objective lens, and one or more aberration correctors configured to reduce one or more aberrations in the sub-beams, preferably, each of at least a subset of the aberration correctors is disposed at or directly adjacent to each one of the intermediate foci, one or more aberration correctors, and one or more scanning deflectors for scanning the sub-beam across the sample, optionally, one or more scanning deflectors are integrated with or directly adjacent to one or more of the objective lenses, one or more scanning deflectors, and preferably a detector integrated with the objective lens, and further includes at least one of the multi-beam column according to any one of claims 16 to 27.

[0128]

[0147] Clause 29. An inspection method, comprising projecting a plurality of charged particle multi-beams onto a sample using a multi-beam column array, and performing group focus correction on each of a plurality of groups of sub-beams of the multi-beams, wherein each group focus correction is the same for all of the sub-beams of each group.

[0129]

[0148] Clause 30. The method according to clause 29, wherein performing group focus correction includes performing different corrections on sub-beams from different multi-beams.

[0130]

[0149] Clause 31. The method according to clause 29 or 30, wherein performing group focus correction includes performing different corrections on different sub-beams within the same multi-beam.

[0131]

[0150] Clause 32. The method according to any one of clauses 29 to 31, wherein the group focus correction is performed mechanically and / or electrostatically.

[0132]

[0151] Inspection method, comprising: using the multi-beam column array according to any one of Items 1 to 28 to project a plurality of charged particle multi-beams toward a sample; and detecting charged particles emitted from the sample.

Claims

1. A charged particle multi-beam column array for a charged particle tool for projecting a plurality of charged particle multi-beams towards a sample, comprising: a plurality of charged particle multi-beam columns configured to simultaneously project respective multi-beams onto different regions of the sample; a focus corrector configured to perform group focus correction on each of a plurality of groups of sub-beams of the multi-beams, each group focus correction being the same for all of the sub-beams of the respective group; each column having a sub-beam defining aperture array configured to form sub-beams from a beam of charged particles emitted by a radiation source associated with the charged particle multi-beam column, and an objective lens array; each objective lens being configured to project the sub-beams onto the sample; the focus corrector having a corrector aperture array in which a plurality of groups of corrector apertures are defined; the charged particle multi-beam column array, wherein the corrector aperture array is integrated with one or more of the objective lens arrays and / or is directly adjacent thereto.

2. The multi-beam column array according to claim 1, wherein the focus corrector is configured to perform different corrections on sub-beams from different multi-beams.

3. The multi-beam column array according to claim 1 or 2, wherein the focus corrector is configured to perform different corrections on different sub-beams within the same multi-beam.

4. The multi-beam column array according to claim 1 or 2, wherein the focus corrector is configured to perform at least one of the group focus corrections at least in part by mechanical actuation of a focus adjustment element.

5. The multi-beam column array according to claim 1 or 2, wherein the focus corrector is configured to perform at least one of the group focus corrections at least in part by changing the potential applied to each of one or more electrodes.

6. The multi-beam column array according to claim 1, wherein the sub-beam defining aperture array is adjacent to the objective lens array along the path of the sub-beams.

7. The corrector aperture array includes an electrode system including a plurality of electrodes, The multi-beam column array according to claim 1, wherein each electrode is electrically insulated from each of the other electrodes and is electrically connected simultaneously to the surfaces of the apertures of all the apertures within different groups of the plurality of groups of corrector apertures at the outer peripheral surfaces of the apertures.

8. The corrector aperture array includes an electrode system including a plurality of electrodes, The multi-beam column array according to claim 1, wherein each electrode is configured to apply a common potential to the surfaces of the apertures of all the apertures within different groups of the plurality of groups of corrector apertures.

9. Projecting a plurality of charged particle multi-beams towards the sample using a multi-beam column array comprising a plurality of charged particle multi-beam columns configured to simultaneously project respective multi-beams onto different regions of the sample, Performing group focus correction on each of a plurality of groups of sub-beams of the multi-beams using a focus corrector, each group focus correction being the same for all of the sub-beams of each group, Each column has a sub-beam defining aperture array configured to form sub-beams from a beam of charged particles emitted by a radiation source associated with the charged particle multi-beam column, and an objective lens array, Each objective lens is configured to project the sub-beams onto the sample, The focus corrector has a corrector aperture array in which a plurality of groups of corrector apertures are defined, The corrector aperture array is integrated with one or more of the objective lens arrays and / or is directly adjacent thereto, Inspection method.

10. The method according to claim 9, wherein performing the group focus correction includes applying different corrections to sub-beams from different multi-beams.

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