CN117813669A - Charged particle apparatus and method - Google Patents

Abstract

A charged particle apparatus configured to project a charged particle multi-beam toward a sample, comprising: a charged particle source configured to emit a charged particle beam; a light source configured to emit light; and a charged particle optical device configured to project sub-beams of a charged particle multi-beam derived from the charged particle beam towards the sample; wherein the light source is arranged such that light is projected through the charged particle optical device along the path of the beamlets so as to illuminate at least a portion of the sample.

Description

Charged particle apparatus and method

Cross Reference to Related Applications

The present application claims priority from EP application 21184292.7 filed 7 at 2021 and EP application 21189570.1 filed 8 at 2021, which are incorporated herein by reference in their entirety.

Technical Field

Embodiments provided herein relate generally to charged particle optical devices, charged particle apparatuses, and methods for projecting multiple beams of charged particles toward a sample.

Background

When manufacturing semiconductor Integrated Circuit (IC) chips, undesirable pattern defects inevitably occur on a substrate (i.e., wafer) or mask during a manufacturing process as a result of, for example, optical effects and incidental particles, thereby reducing yield. Therefore, monitoring the extent of undesired pattern defects is an important process in the manufacture of IC chips. More generally, inspection and/or measurement of the surface of a substrate or other object/material is an important process during and/or after its manufacture.

Pattern inspection tools with charged particle beams have been used for inspecting objects, for example for detecting pattern defects. These tools typically use electron microscopy techniques such as Scanning Electron Microscopy (SEM). In SEM, a primary electron beam of electrons having a relatively high energy is targeted at a final deceleration step in order to land on the sample with a relatively low landing energy. The electron beam is focused as a probe spot on the sample. The interaction between the material structure at the detection point 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 may be emitted from the material structure of the sample. By scanning the primary electron beam as a detection point over 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 that is representative of the characteristics of the material structure of the sample surface. The intensity of the electron beam, including the backscattered electrons and the secondary electrons, may vary based on the nature of the internal and external structure of the sample, and may thus indicate whether the sample has defects.

When the primary electron beam scans the sample, charge may accumulate on the sample due to the large beam current, which may affect the quality of the image. The material structure may be irradiated with light and/or flood with electrons in order to improve defect contrast during defect inspection. For example, to adjust the accumulated charge on a sample, an Advanced Charge Controller (ACC) module may be employed to irradiate a beam of light, such as a laser beam, on the sample in order to control the accumulated charge due to effects such as photoconductive, photoelectric, or thermal effects. It may be difficult to irradiate a light beam on a sample. For example, the size of the pattern inspection tool may make it difficult to reach the sample with a light beam.

Additionally or alternatively, a row of flooding means for flooding the sample with electrons may be provided. The flood column is separate from the SEM inspection column which focuses the electron beam onto the sample for inspection. Switching between the flood column and the SEM inspection column may require moving the sample so that the same portion of the sample undergoes two processes. Movement may be an important contributor to the total time spent performing the examination.

Disclosure of Invention

It is an object of the present disclosure to provide embodiments supporting increasing the amount of light impinging on a sample for inspection involving improved defect contrast.

According to a first aspect of the present invention there is provided a charged particle device configured to project a charged particle multi-beam towards a sample, the charged particle device comprising: a charged particle source configured to emit a charged particle beam; a light source configured to emit light; and a charged particle optical device configured to project sub-beams of a charged particle multi-beam derived from the charged particle beam towards the sample; wherein the light source is arranged such that light (or light path) is projected along a path of the sub-beam through the charged particle optical device so as to illuminate at least a portion of the sample.

According to a second aspect of the present invention there is provided a method for projecting a charged particle multi-beam towards a sample, the method comprising: emitting a charged particle beam; projecting a sub-beam of a charged particle multi-beam derived from the charged particle beam towards the sample using a charged particle optical device; emitting light; and projecting light (or light path) along a path of the beamlets through the charged particle optical device so as to illuminate the sample.

Drawings

The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments, which is to be read in connection with the accompanying drawings.

Fig. 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus.

Fig. 2 is a schematic diagram illustrating an exemplary multi-beam charged particle apparatus as part of the exemplary electron beam inspection apparatus of fig. 1.

Fig. 3 is a schematic diagram of an exemplary multi-beam charged particle apparatus.

Fig. 4 is a schematic diagram of an exemplary charged particle apparatus including a macro-collimator and a macro-scanning deflector.

Fig. 5 is a schematic diagram of an exemplary multi-beam charged particle apparatus according to one embodiment.

Fig. 6 is a schematic diagram of a portion of the multi-beam charged particle apparatus of fig. 5.

Fig. 7 is a schematic cross-sectional view of an objective lens array of a charged particle device according to one embodiment.

Fig. 8 is a bottom view of a modification of the objective lens array of fig. 7.

Fig. 9 is an enlarged schematic cross-sectional view of a detector incorporated in the objective lens array of fig. 7.

Fig. 10 is a bottom view of a detector element of the detector.

FIG. 11 is a schematic diagram of an exemplary electronic device, according to one embodiment.

Fig. 12 is a schematic diagram of a close-up view of a portion of the exemplary charged particle device shown in fig. 11.

Fig. 13 is a schematic cross-sectional view of a control lens array and an objective lens array of a charged particle device according to one embodiment.

Fig. 14 is a schematic diagram of an exemplary charged particle apparatus according to one embodiment.

The schematic and view shows the following components. However, the components illustrated in the drawings are not drawn to scale.

Detailed Description

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

The enhanced computational power of electronic devices (which reduces the physical size of the device) can be achieved by significantly increasing the packing density of circuit components (such as transistors, capacitors, diodes, etc.) on an IC chip. This can be achieved by increasing the resolution, enabling smaller structures to be fabricated. For example, the IC chip of a smartphone, which may include over 20 hundred million transistors, each transistor having a size less than 1/1000 of a person's hair, is the size of a thumb nail and is available in 2019 or earlier. Thus, it is not surprising that semiconductor IC fabrication is a complex and time-consuming process with hundreds of individual steps. Even errors in one step can significantly affect the functionality of the final product. Only one "fatal defect" can lead to device failure. The goal of the manufacturing process is to increase the overall yield of the process. For example, for a 50 step process (where a step may represent the number of layers formed on a wafer), each individual step must have a yield of greater than 99.4% in order to achieve a 75% yield. If each individual step has a yield of 95%, the overall process yield will be as low as 7%.

Although high process yields are required in IC chip manufacturing facilities, it is also necessary to maintain high substrate (i.e., wafer) throughput (defined as the number of substrates processed per hour). The presence of defects can affect high process yields and high substrate throughput. This is especially true if operator intervention is required to inspect the defect. Thus, high throughput detection and identification of micro-scale and nano-scale defects by inspection tools such as scanning electron microscopy ("SEM") is necessary to maintain high yields and low cost.

The SEM includes scanning means and detector means. The scanning device comprises an illumination means comprising a charged particle source for generating primary charged particles and a projection means for scanning a sample, such as a substrate, with one or more focused beams of primary charged particles. At least the illumination device or illumination system and the projection device or projection system may together be referred to as a charged particle optical system or device. The primary charged particles interact with the sample and generate secondary electrons. As the sample is scanned, the detection device captures secondary electrons from the sample so that the SEM can produce an image of the scanned area of the sample. For high throughput inspection, some inspection devices use multiple focused beams, i.e., multiple beams, of primary electrons. The component beams of the multiple beams may be referred to as sub-beams or beamlets. Multiple beams may scan different portions of the sample simultaneously. Thus, the multi-beam inspection apparatus is capable of inspecting a sample at a much higher speed than a single-beam inspection apparatus.

The implementation of the known multi-beam inspection device is described below.

The figures are schematic. Accordingly, the relative dimensions of the components in the drawings are exaggerated 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 differences with respect to the respective embodiments are described. While the description and drawings are directed to electron optical systems, it should be understood that these embodiments are not intended to limit the disclosure to particular charged particles. Thus, references to electrons throughout this document may be more generally considered references to charged particles, where the charged particles are not necessarily electrons. For example, a reference to an electronic device may be more generally considered a reference to a charged particle device.

Referring now to fig. 1, fig. 1 is a schematic diagram illustrating an exemplary electron beam inspection device 100. The electron beam inspection device 100 of fig. 1 includes a main chamber 10, a load lock chamber 20, an electronic device 40 (which may also be referred to as an electron evaluation device or electron beam system or tool), an Equipment Front End Module (EFEM) 30, and a controller 50. The electronics 40 are located within the main chamber 10.

The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. For example, the first load port 30a and the second load port 30b may receive a substrate Front Opening Unified Pod (FOUP) that contains a substrate (e.g., a semiconductor substrate or a substrate made of other materials) or a sample to be inspected (the substrate, wafer, and sample are collectively referred to below as "samples"). One or more robotic arms (not shown) in the EFEM 30 transfer samples to the load lock chamber 20.

The load lock chamber 20 is used to remove gas around the sample. This creates a vacuum with a partial gas pressure lower than the pressure in the surrounding environment. The load lock chamber 20 may be connected to a load lock vacuum pump system (not shown) that removes gas particles from the load lock chamber 20. The operation of the load lock vacuum pump system enables the load lock chamber to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transfer the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles in the main chamber 10 so that the pressure around the sample reaches a second pressure lower than the first pressure. After reaching the second pressure, the sample is transferred to the electronic device 40, through which electronic device 40 the sample can be inspected. The electronic device 40 comprises an electro-optical device 41. The electron optics 41 may be an electron optics column configured to project at least one electron beam onto the sample 208 and/or an objective lens module configured to focus the at least one electron beam onto the sample 208. The electron optical device may further comprise a detector module configured to detect electrons emitted from the sample 208 and/or a control lens module configured to adjust electron optical parameters of at least one electron beam. In one embodiment, the electron optical column may include an objective lens module and a detector module and optionally a control lens module. In one embodiment, the electron optical device includes an objective lens assembly, which may be included in an electron optical device column. The objective lens assembly includes an objective lens array associated with (e.g., integrated with) one or more other electron optical components (e.g., a detector array and an optional control lens array). The electron optics 41 may be multi-beam electron optics 41 for projecting multiple beams towards the sample 208. In one embodiment, the electron optical device 41 comprises a multi-device column comprising a plurality of electron optical device columns configured to project respective electron beams or electron multiple beams toward the sample 208.

The controller 50 is electrically connected to the electro-optical components of the electro-optical device 41 of the electronic device 40. The controller 50 may be a processor (such as a computer) configured to control the electron beam inspection device 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is shown in FIG. 1 as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it should be understood that the controller 50 may be part of the structure. The controller 50 may be located in one component element of the electron beam inspection device 100, or it may be distributed over at least two component elements. The controller may be considered to be part of the electro-optical device 41. Although the present disclosure provides an example of a main chamber 10 housing an electron beam inspection tool, it should be noted that aspects of the present disclosure are not limited in their broadest sense to chambers housing electron beam inspection tools. Instead, it should be understood that the above-described principles may also be applied to other arrangements of other tools and devices operating at the second pressure.

Referring now to fig. 2, fig. 2 is a schematic diagram illustrating an exemplary electronic device 40 including a multi-beam electron optical device 41, the multi-beam electron optical device 41 being part of the exemplary electron beam inspection device 100 of fig. 1. The multi-beam electron optics 41 comprise an electron source 201 and a projection device 230. The electronic device 40 further comprises a motorized stage 209 and a sample holder 207. The projection device 230 may be referred to as an electron optical device 41. The sample holder 207 is supported by a motorized stage 209 to hold a sample 208 (e.g., a substrate or mask) for inspection. The multi-beam electron optics 41 may also include a detector 240 (e.g., an electron detection device).

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. Primary electrons are extracted or accelerated by an extractor and/or anode to form primary electron beam 202.

The projection device 230 is configured to convert the primary electron beam 202 into a plurality of beamlets 211, 212, 213 and direct each beamlet onto the sample 208. Although three beamlets are shown for simplicity, there may be tens, hundreds or thousands of beamlets. The beamlets may be referred to as beamlets.

The controller 50 may be connected to various parts of the electron beam inspection device 100 of fig. 1, such as the electron source 201, the detector 240, the projection device 230, and the motorized stage 209. The controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals to control the operation of the electron beam inspection device 100, including the multi-beam electronic device 40.

Projection device 230 may be configured to focus beamlets 211, 212, and 213 onto sample 208 for inspection, and may form three detection points 221, 222, and 223 on the surface of sample 208. Projection device 230 may be configured to deflect primary beamlets 211, 212, and 213 to scan detection points 221, 222, and 223 across respective scanning regions in a portion of a surface of sample 208. Electrons including secondary electrons and backscattered electrons are generated from the sample 208 in response to incidence of the primary beamlets 211, 212 and 213 on detection points 221, 222 and 223 on the sample 208. The secondary electrons typically have an electron energy of 50eV or less. The actual secondary electrons may have an energy of less than 5eV, but any electrons below 50eV are typically treated as secondary electrons. The backscattered electrons typically have electron energies between 0eV and the landing energies of the primary beamlets 211, 212 and 213. Because electrons detected with an energy of less than 50eV are typically regarded as secondary electrons, a portion of the actual backscattered electrons will be regarded as secondary electrons.

The detector 240 is configured to detect signal particles, such as secondary electrons and/or backscattered electrons, and generate corresponding signals that are sent to the signal processing system 280, for example, to construct an image of a corresponding scanned region of the sample 208. The detector 240 may be incorporated into the projection device 230.

The signal processing system 280 may include circuitry (not shown) configured to process signals from the detector 240 to form an image. The signal processing system 280 may also be referred to as an image processing system. The signal processing system may be incorporated into a component of the multi-beam electronic device 40, such as the detector 240 (shown in fig. 2). However, the signal processing system 280 may be incorporated into any component of the electron beam inspection device 100 or the multi-beam electronic device 40, such as part of the projection device 230 or the controller 50. The signal processing system 280 may include an image acquirer (not shown) and a storage device (not shown). For example, the signal processing system may include a processor, a computer, a server, a mainframe, a terminal, a personal computer, any type of mobile computing device, etc., or a combination thereof. The image acquirer may include at least a portion of the processing functionality of the controller. Thus, the image acquirer may include at least one or more processors. The image acquirer is communicatively coupled to a detector 240 that allows signal communication, such as an electrical conductor, fiber optic cable, portable storage medium, IR, bluetooth, the internet, wireless network, radio, or the like, or a combination thereof. The image acquirer may receive the signal from the detector 240, may process the data included in the signal, and may construct an image therefrom. Thus, the image acquirer can acquire an image of the sample 208. The image acquirer may also perform various post-processing functions, such as generating contours, superimposing indicators on the acquired image, and the like. The image acquirer may be configured to perform adjustment of brightness, contrast, and the like of the acquired image. The storage may be a storage medium such as a hard disk, flash drive, cloud storage, random Access Memory (RAM), other types of computer readable memory, and the like. The storage may be coupled with the image acquirer and may be used to save scanned raw image data as raw images and post-processed images.

The signal processing system 280 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of the detected secondary electrons. The electron distribution data collected during the detection time window may be used in combination with the respective scan path data of each of the primary beamlets 211, 212 and 213 incident on the sample surface to reconstruct an image of the sample structure under examination. The reconstructed image may be used to reveal various features of internal or external structures of the sample 208. Thus, the reconstructed image may be used to reveal any defects that may be present in the sample.

The controller 50 may control the motorized stage 209 to move the sample 208 during inspection of the sample 208. At least during the sample examination, the controller 50 may cause the motorized stage 209 to move the sample 208 in a preferably continuous direction, e.g., at a constant speed. The controller 50 may control the movement of the motorized stage 209 such that it varies the speed of movement of the sample 208 according to various parameters. For example, the controller 50 may control the stage speed (including its direction) based on characteristics of the inspection step of the scanning process.

Known multi-beam systems, such as the electronic device 40 and the electron beam inspection device 100 described above, are disclosed in US2020118784, US20200203116, US2019/0259570 and US 2019/0259464, which are incorporated herein by reference.

As shown in fig. 2, in one embodiment, the electronic device 40 includes a projection assembly 60. The projection assembly 60 may be a module and may be referred to as an ACC module. Projection assembly 60 is arranged to direct light beam 62 such that light beam 62 enters between electron optics 41 and sample 208.

As the electron beam scans the sample 208, charge may accumulate on the sample 208 due to the large beam current, which may affect the quality of the image. To adjust the charge accumulated on the sample, the projection assembly 60 may be employed to illuminate the beam 62 on the sample 208 to control the accumulated charge due to effects such as photoconductive, photoelectric, or thermal effects.

In one embodiment, projection system 60 includes a light source 61. The light source 61 is configured as a light-emitting beam 62. In one embodiment, the light source 61 is a laser light source. The laser provides a coherent light beam 62. However, other types of light sources may alternatively be used. In one embodiment, the light source 61 is configured to emit a light beam 62 having a wavelength in the range of 450nm to 850 nm.

In one embodiment, projection assembly 60 includes an optical system 63. In one embodiment, optical system 63 is configured to focus beam 62 to be narrower in a direction perpendicular to the surface of sample 208 than in a direction parallel to the surface. In one embodiment, optical system 63 includes a cylindrical lens 64. The cylindrical lens 64 is configured to focus the light beam 62 more in one direction than in the orthogonal direction. The cylindrical lens increases the degree of freedom of design for the light source 61. In one embodiment, the light source 61 is configured to emit a light beam 62 having a circular cross-section. The cylindrical lens 64 is configured to focus the light beam 62 such that the light beam has an elliptical cross-section. In one embodiment, the optical system 63 includes reflective surfaces 65, 66, such as mirrors. For example, two reflective surfaces 65, 66 may be provided.

The components of an electronic device 40 that may be used in the present invention are described below with reference to fig. 3, fig. 3 being a schematic diagram of the electronic device 40. The electronic device 40 of fig. 3 may correspond to the electronic device 40 described above (which may also be referred to as a system or tool).

The electron source 201 directs electrons toward a converging lens array 231 (alternatively referred to as a converging lens array). The electron source 201 is desirably a high brightness thermal field emitter with a good tradeoff between brightness and total emission current. There may be tens, hundreds or thousands of converging lenses 231. The converging lens 231 may comprise a multi-electrode lens and have a construction based on EP1602121A1, which document is incorporated herein by specific reference for the disclosure of a lens array for dividing, for example, an electron beam from a source into a plurality of beamlets, the array providing a lens for each beamlet. The array of converging lenses 231 may take the form of at least two plates, as electrodes, with the apertures in each plate being aligned with each other and corresponding to the position of the beamlets. During operation, at least two plates are held at different potentials to achieve the desired lens effect.

In one arrangement, which may be referred to as a single lens (Einzel lens), the array of converging lenses 231 is formed of an array of three plates, with charged particles having the same energy as they enter and leave each lens. Thus, chromatic dispersion occurs only within the single lens itself (between the entrance and exit electrodes of the lens), thereby limiting off-axis chromatic aberration. When the thickness of the converging lens is small, e.g. a few millimeters, such aberrations have little or negligible effect.

Each converging lens 231 in the array directs electrons into a respective beamlet 211, 212, 213, the beamlets 211, 212, 213 being focused at a respective intermediate focused beam downstream of the converging lens array. The beamlets diverge with respect to each other. In one embodiment, a deflector 235 is provided at the intermediate focus. The deflector 235 is positioned in the beamlet path at or at least around the position of the corresponding intermediate focus. The deflector 235 is positioned at or near the beamlet path at the intermediate image plane of the associated beamlet. The deflector 235 is configured to operate on the respective beamlets 211, 212, 213. The deflector 235 is configured to bend the respective beamlets 211, 212, 213 an effective amount to ensure that the primary rays (which may also be referred to as beam axes) are incident on the sample 208 substantially perpendicularly (i.e., substantially 90 ° from the nominal surface of the sample). The deflector 235 may be referred to as a collimator or collimator deflector. The deflector 235 effectively collimates the paths of the beamlets such that the beamlet paths are divergent with respect to each other prior to the deflector. Downstream of the deflector, the beamlet paths are substantially parallel to each other, i.e. substantially collimated. A suitable collimator is the deflector disclosed in EP application 20156253.5 filed 2/7/2020, which is incorporated herein by reference in relation to the application of the deflector to multi-beam arrays. Instead of the deflector 235 or in addition to the deflector 235, the collimator may also comprise a macro-collimator 270 (e.g. as shown in fig. 4). Thus, the macro collimator 270 described below with respect to fig. 4 may have the features of fig. 3. This is generally less preferred than providing a collimator array as deflector 235.

Below the deflector 235 (i.e., downstream of the electron source 201 or further from the electron source 201) is a control lens array 250. The beamlets 211, 212, 213 that pass through the deflector 235 are substantially parallel when entering the steering lens array 250. The control lens pre-focuses the beamlets (e.g., applies a focusing action to the beamlets before they reach the objective lens array 241). Prefocusing may reduce the divergence of the beamlets or increase the convergence rate of the beamlets. The lens array 250 and the objective lens array 241 are controlled to work together to provide a combined focal length. The combined operation without intermediate focus may reduce the risk of aberrations.

In more detail, it is desirable to use the control lens array 250 to determine landing energy. However, the objective lens array 241 may be additionally used to control landing energy. In this case, the potential difference across the objective lens is changed when a different landing energy is selected. One example of a situation where it is desirable to change the landing energy partly by changing the potential difference over the objective lens is to prevent the focus of the beamlets from being too close to the objective lens. In this case, there is a risk that the components of the objective array 241 must be too thin to be manufactured. The same can be said about the detector at this position. This may occur, for example, in the event of a reduced landing energy. This is because the focal length of the objective lens is approximately proportional to the landing energy used. By reducing the potential difference over the objective lens, the electric field within the objective lens is reduced, causing the focal length of the objective lens to become larger again, resulting in a focal position further below the objective lens. Note that the use of only an objective lens will limit the control of the magnification. This arrangement does not allow control of the reduction and/or opening angle. Furthermore, controlling the landing energy using the objective lens may mean that the objective lens will operate away from its optimal field strength. That is, unless the mechanical parameters of the objective (such as the spacing between its electrodes) can be adjusted, for example, by changing the objective.

The control lens array 250 includes a plurality of control lenses. Each control lens comprises at least one electrode, preferably at least two electrodes (e.g. two or three electrodes) connected to a respective potential source. The control lens array 250 may include one or more (e.g., three) plate electrode arrays connected to corresponding potential sources. The control lens array 250 is associated with the objective lens array 241 (e.g., the two arrays are positioned close to each other and/or mechanically connected to each other and/or controlled together as a unit). Each control lens may be associated with a respective objective lens. The control lens array 250 is positioned upstream of the objective lens array 241.

The control lens array 250 may be considered one or more electrodes other than the electrode of the objective lens array 241. The control lens array 250 provides an additional degree of freedom for controlling the beamlets. A greater number of electrodes included in the control lens array 250 provides a greater number of degrees of freedom. For example, these additional electrodes may allow landing energy and/or magnification control independent of the field strength of the objective lens array 241. In some designs, the control lens may thus be part of the objective lens. Thus, such an electrode may be part of the objective lens, rather than a separate lens, such as a steering lens. The reference to the control lens in this arrangement is a reference to a functionally equivalent electrode of the objective lens.

The control lens array 250 comprises a control lens for each beamlet 211, 212, 213. The function of the control lens array 250 is to optimize the beam opening angle with respect to the demagnification of the beam and/or to control the beam energy delivered to the objective lens array 241, which objective lens array 241 directs the beamlets 211, 212, 213 onto the sample 208. The objective lens array 241 may be positioned at or near the base of the electron optical device 41 (or also referred to as electron optical system). The control lens array 250 is optional but is preferably used to optimize beamlets upstream of the objective lens array 241.

For ease of illustration, the lens array is schematically depicted herein as an elliptical array (as shown in FIG. 3). Each oval represents a lens in the lens array. Oval shapes are conventionally used to represent lenses, similar to the biconvex form commonly employed in optical lenses. However, in the context of charged particle devices such as those discussed herein, it should be understood that the lens array will typically operate electrostatically and therefore may not require the use of any physical elements in a biconvex shape. The lens array may alternatively comprise a plurality of plates having apertures, for example the lens array may be an electrostatic lens array, for example comprising a plurality of plates which may be considered as electrodes.

Optionally, a scanning deflector array 260 is provided between the control lens array 250 and the objective lens array 234. The scan deflector array 260 includes a scan deflector for each beamlet 211, 212, 213. Each scan deflector is configured to deflect a respective beamlet 211, 212, 213 in one or both directions in order to scan the beamlet across the sample 208 in one or both directions.

Fig. 4 is a schematic diagram of an exemplary electronic device 40 including a macro collimator 270 and a macro scan deflector 265. The electron source 201 directs the electrodes to a macrocollimator 270. The electron source 201 is desirably a high brightness thermal field emitter with a good tradeoff between brightness and total emission current.

For example, beamlets may be derived from the beam using a beamlet forming array 252 defining an array of beam limiting apertures (also referred to as a beam limiting aperture array). The beam may be split into sub-beams upon encountering the control lens array 250, as described below. The beamlets are substantially parallel when entering the control lens array 250.

The macro collimator 270 acts on the beam from the source 201 before the beam is split into multiple beams. The macro-collimator 270 bends the respective portions of the beam by an effective amount to ensure that the beam axis of each sub-beam derived from the beam is incident on the sample 208 substantially perpendicularly (i.e., substantially 90 deg. from the nominal surface of the sample 208). Thus, the path of each beamlet is at least orthogonal to the surface of the sample 208. The macrocollimator 270 applies macrocollimation to the beam. Thus, instead of comprising an array of collimator elements, the macro-collimator 270 may act on all beams, each collimator element being configured to act on a different individual portion of the beam. The macro-collimator 270 may include a magnetic lens or a magnetic lens arrangement including a plurality of magnetic lens subunits (e.g., a plurality of electromagnets forming a multipole arrangement). Alternatively or additionally, the macro-collimator may be at least partially electrostatically implemented. The macro-collimator may comprise an electrostatic lens or an electrostatic lens arrangement comprising a plurality of electrostatic lens subunits. The macro collimator 270 may use a combination of magnetic and electrostatic lenses.

In another arrangement (not shown), the macro-collimator 270 may be partially or fully replaced by an array of collimator elements disposed downstream of the beamlet-forming array. Each collimator element collimates a respective sub-beam. The array of collimator elements may be formed using MEMS fabrication techniques to be spatially compact. The array of collimator elements may be first deflecting or focusing electron optical array elements in the beam path downstream of the source 201. The array of collimator elements may be upstream of the control lens array 250. The array of collimator elements may be in the same module as the control lens array 250.

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

Below the macro-collimator 270 (i.e. downstream of the electron source 201 or further from the electron source 201) there is a control lens array 250. The steering lens array 250 is configured to apply a focusing action to the beamlets before they reach the objective lens array. Prefocusing may reduce the divergence of the beamlets or increase the convergence rate of the beamlets. The lens array 250 and the objective lens array 241 are controlled to work together to provide a combined focal length. The combined operation without intermediate focus may reduce the risk of aberrations. Additionally or alternatively, the control lenses in the control lens array 250 are configured to control the opening angle of the beamlets and/or to control the demagnification (i.e., enlargement) of the beamlets and/or to control landing energy.

The control lens array 250 may be as described above with respect to fig. 3. The control lens array 250 may be considered one or more electrodes other than the electrode of the objective lens array 241. The control lens array 250 provides an additional degree of freedom for controlling the beamlets. A greater number of electrodes included in the control lens array 250 provides a greater number of degrees of freedom. For example, these additional electrodes may allow landing energy and/or magnification control independent of the field strength of the objective lens array 241. In some designs, the control lens may thus be part of the objective lens. Thus, references to such electrodes may be made as part of the objective lens, rather than a separate lens (such as a control lens).

The control lens array 250 comprises a control lens for each beamlet 211, 212, 213. The function of the control lens array 250 is to optimize the beam opening angle with respect to the demagnification of the beam and/or to control the beam energy delivered to the objective lens array 241, which objective lens array 241 directs the beamlets 211, 212, 213 onto the sample 208. The objective lens array 241 may be positioned at or near the base of the electron optical device 41. The control lens array 250 is preferably used to optimize the beamlets upstream of the objective lens array 241.

In the embodiment of fig. 4, a macro-scan deflector 265 is provided to cause beamlets to be scanned across the sample 208. The macro-scan deflector 265 deflects a corresponding portion of the beam so that the beamlets are scanned over the sample 208. In one embodiment, macro-scan deflector 265 comprises a macro-multipole deflector, e.g., having eight or more poles. Deflection causes sub-beams derived from the beam to be scanned across the sample 208 in one direction (e.g., parallel to a single axis, such as the X-axis) or in two directions (e.g., relative to two non-parallel axes, such as the X-and Y-axes). The macro-scan deflector 265 acts macroscopically on all of the beams, rather than comprising an array of deflector elements, each deflector element being configured to act on a different, separate portion of the beam. In the illustrated embodiment, macro-scan deflector 265 is disposed between macro-collimator 270 and control lens array 250.

In another arrangement (not shown), macro scan deflector 265 may be replaced in part or in whole by an array of scan deflectors. The scan deflector array includes a plurality of scan deflectors. The scanning deflector array may be formed using MEMS fabrication techniques. Each scanning deflector scans a respective beamlet over sample 208. Thus, the scan deflector array may comprise a scan deflector for each beamlet. Each scan deflector may deflect the beamlets in one direction (e.g., parallel to a single axis, such as the X-axis) or in two directions (e.g., relative to two non-parallel axes, such as the X-and Y-axes). Deflection causes the beamlets to be scanned across the sample 208 in one or both directions (i.e., one or two dimensions). The scan deflector array may be upstream of the objective lens array 241. The scanning deflector array may be downstream of the control lens array 250. Although reference is made to a single beamlet associated with a scan deflector, a beamlet group may be associated with a scan deflector. In one embodiment, the scanning deflector described in EP2425444 may be used to implement a scanning deflector array, which document is incorporated herein by reference in its entirety, in particular with respect to the parts of the scanning deflector. The scan deflector array (e.g., formed using MEMS fabrication techniques as described above) may be more spatially compact than the macro-scan deflector. The scan deflector array may be in the same module as the objective lens array 241.

In other embodiments, a macro scan deflector 265 and a scan deflector array are provided. In such an arrangement, scanning of the sub-beams over the sample surface may be achieved by controlling the macro-and scanning deflector arrays together, preferably synchronously.

In some embodiments, the electron optical device 41 further comprises a beamlet forming array 252. Beamlet forming array 252 defines a beam limiting aperture array. Beamlet forming array 252 may be referred to as an upper beam limiting aperture array or an upstream beam limiting aperture array. The beamlet forming array 252 may comprise a plate (which may be a plate-like body) having a plurality of apertures. The beamlet-forming array 252 forms beamlets from electron beams emitted by the source 201. Portions of the beam other than those that contribute to forming the beamlets may be blocked (e.g., absorbed) by the beamlet forming array 252 so as not to interfere with downstream beamlets. Beamlet forming array 252 may be referred to as a beamlet-defining aperture array or an upper beam limiter. The aperture of the beamlet-forming array 252 may have a diameter 72 of at least 20 μm, alternatively at least 50 μm, alternatively at least 100 μm, and alternatively 120 μm (see fig. 12). The pitch of the apertures may be equal to the pitch of the apertures of beam aperture 406.

In some embodiments, as shown in fig. 4, the electron optical device 41 is an objective lens array assembly (which is a unit including an objective lens array 241) and includes a beam shaping aperture array 262 (or beam shaping array). The beam shaping array 262 defines a beam limiting aperture array. The beam shaping array 262 may be referred to as a lower beam limiter, a lower beam limiting aperture array, or a final beam limiting aperture array. The beam shaping array 262 may include a plate (which may be a plate-like body) having a plurality of apertures. The beam shaping array 262 may be downstream of at least one electrode (and optionally all electrodes) of the control lens array 250. In some embodiments, the beam shaping array 262 is downstream of at least one electrode (and optionally all electrodes) of the objective lens array 241.

In one configuration, the beam shaping array 262 is structurally integrated with the electrodes of the objective lens array 241. Ideally, the beam shaping array 262 is positioned in a region of low electrostatic field strength. Each beam limiting aperture is aligned with a corresponding objective lens in the objective lens array 241. The alignment is such that a portion of the beamlets from the corresponding objective lens may pass through the beam limiting aperture and impinge on the sample 208. Each beam limiting aperture has a beam limiting effect that allows only a selected portion of the beamlets incident on the beam shaping array 262 to pass through the beam limiting aperture. The selected portions may be such that only a portion of the central portion of the respective sub-beam passing through the respective aperture in the objective lens array reaches the sample. The central portion may have a circular cross-section and/or be centered on the beam axis of the sub-beam.

Any of the electronics 40 described herein may also include a detector 240. The detector 240 detects electrons emitted from the sample 208. The detected electrons may include any electrons detected by SEM, including secondary and/or backscattered electrons emitted from sample 208. An exemplary structure of the detector 240 is shown in fig. 7 and described in more detail below with reference to fig. 8-10.

Fig. 5 schematically depicts an electronic device 40 according to one embodiment. Features identical to those described above are denoted by identical reference numerals. For brevity, such features are not described in detail with reference to fig. 5. For example, the source 201, macro-collimator 270, objective array 241, and sample 208 may be as described above.

In one embodiment, the electronic device 40 includes an array converging lens 231. There may be tens, hundreds or thousands of converging lenses 231. The converging lens 231 may comprise a multi-electrode lens and have a configuration based on EP1602121A1, which document is incorporated herein by specific reference to the disclosure of a lens array for dividing an electron beam into a plurality of beamlets, wherein the array provides a lens for each beamlet. The array of converging lenses 231 may take the form of at least two plates, acting as electrodes, with the apertures in each plate being aligned with each other and corresponding to the position of the beamlets. During the course of operation, at least two plates are held at different potentials to achieve the desired lens effect.

In one arrangement, which may be referred to as a single lens, the array of converging lenses 231 is formed of an array of three plates, with the electrons having the same energy as they enter and leave each lens. Thus, chromatic dispersion occurs only within the single lens itself (between the entrance and exit electrodes of the lens), thereby limiting off-axis chromatic aberration. When the thickness of the converging lens is small, e.g. a few millimeters, such aberrations have little or negligible effect.

As described above, in one embodiment, the detector 240 is located between the objective lens array 241 and the sample 208. The detector 240 may face the sample 208. Alternatively, as shown in FIG. 4, in one embodiment, an objective array 241 comprising a plurality of objectives is located between the detector 240 and the sample 208.

In one embodiment, deflector array 95 is located between detector 240 and objective lens array 241. In one embodiment, the deflector array 95 includes a wien filter such that the deflector array may be referred to as a beam splitter. The deflector array 95 is configured to provide a magnetic field to separate electrons projected onto the sample 208 from secondary electrons from the sample 208.

In one embodiment, detector 240 is configured to detect signal particles by referencing the energy of electrons (i.e., depending on the bandgap). Such a detector 240 may be referred to as an indirect current detector. The secondary electrons emitted from the sample 208 gain energy from the field between the electrodes. The secondary electrode has sufficient energy once it reaches the detector 240.

Fig. 6 is a close-up view of a portion of the electronic device 40 shown in fig. 5. In one embodiment, detector 240 includes an array of electron-to-photon converters 91. The electron-photon converter array 91 includes a plurality of phosphor stripes 92. Each phosphor stripe 92 is located in the plane of the electron-photon converter array 91. At least one phosphor stripe 92 is disposed between two adjacent electron beams projected toward the sample 208.

In one embodiment, the phosphor strips 92 extend in a substantially horizontal direction. Alternatively, the electron-photon converter array 91 may comprise a plate of fluorescent material with an opening 93 for projecting an electron beam.

The projected electron beam, shown by the dashed lines in fig. 6, passes through the plane of the electron-photon converter array 91, via the openings 93 between the phosphor stripes 92, towards the deflector array 95.

In one embodiment, the deflector array 95 includes a magnetic deflector 96 and an electrostatic deflector 97. The electrostatic deflector 97 is configured to counteract deflection of the projected electron beam transmitted toward the sample 208 by the magnetic deflector 96. Thus, the projection electron beam can move in the horizontal plane to a small extent. The beam downstream of the deflector array 95 is substantially parallel to the beam upstream of the deflector array 95.

In one embodiment, the objective lens array 241 includes a plurality of plates for directing secondary electrons generated in the sample 208 toward the deflector array 95. For secondary electrons traveling in the opposite direction relative to the projected electron beam, the electrostatic deflector 97 does not counteract the deflection of the magnetic deflector 96. In contrast, the deflection of the secondary electrons caused by the electrostatic deflector 97 and the magnetic deflector 96 is added. Thus, the secondary electrons are deflected to travel at an angle relative to the optical axis so as to transfer the secondary electrons onto the phosphor stripes 92 of the detector 240.

At the phosphor stripes 92, photons are generated upon incidence of the secondary electrons. In one embodiment, photons are transmitted from phosphor strip 92 to a photodetector (not shown) via a photon transmission unit. In one embodiment, the photon transmission unit includes an array of optical fibers 98. Each optical fiber 98 includes: is arranged adjacent to or attached to one of the phosphor stripes 92 for coupling photons from the phosphor stripe 92 to an end in the optical fiber 98, and is arranged to project photons from the optical fiber 98 onto the other end of the photodetector.

The objective lens array 241 of any embodiment may comprise at least two electrodes, wherein an aperture array is defined. In other words, the objective lens array comprises at least two electrodes with a plurality of holes or apertures. Fig. 7 shows electrodes 242, 243 which are part of an exemplary objective lens array 241 having corresponding aperture arrays 245, 246. The position of each aperture in an electrode corresponds to the position of the corresponding aperture in the other electrode. The corresponding apertures operate in use on the same beam, sub-beam or group of beams in the multiple beams. In other words, the corresponding apertures in the at least two electrodes are aligned with and arranged along the beamlet path (i.e., one of beamlet paths 220). Thus, the electrodes each have an aperture through which the respective beamlets 211, 212, 213 propagate.

As shown in fig. 7, the objective lens array 241 may include two electrodes, or three electrodes, or may have more electrodes (not shown). The objective lens array 241 having only two electrodes may have lower aberration than the objective lens array 241 having more electrodes. A three-electrode objective lens can have a larger potential difference between the electrodes, enabling a stronger lens. Additional electrodes (i.e. more than two electrodes) provide additional degrees of freedom for controlling the electron trajectories, such as focusing the secondary electrons and the incident beam. Such additional electrodes may be considered to form the control lens array 250. The advantage of a double electrode lens compared to a single lens is that the energy of the incoming beam does not have to be the same as the outgoing beam. Advantageously, the potential difference across such a two-electrode lens array enables it to be used as an accelerating or decelerating lens array.

Adjacent electrodes of the objective lens array 241 are spaced apart from each other along the beamlet path. The distance between adjacent electrodes, in which the insulating structure can be positioned as described below, is larger than the objective lens.

Preferably, each electrode provided in the objective lens array 241 is a plate. The electrodes may be described further as flat plates. Preferably, each electrode is planar. In other words, each electrode will preferably be provided as a thin flat plate in planar form. Of course, the electrodes need not be planar. For example, the electrodes may bend due to the force generated by the high electrostatic field. It is preferred to provide planar electrodes as this makes the manufacture of the electrodes easier as known manufacturing methods can be used. Planar electrodes may also be preferred because they may provide more accurate aperture alignment between the different electrodes.

The objective lens array 241 may be configured to demagnify the electron beam by more than a factor of 10, desirably in the range of 50 to 100 or more.

A detector 240 is provided to detect secondary and/or backscattered electrons emitted from the sample 208. The detector 240 is positioned between the objective 234 and the sample 208. The detector 240 may be otherwise referred to as a detector array or a sensor array, and the terms "detector" and "sensor" are used interchangeably throughout the application.

In one embodiment, electron optics 41 is configured to project an electron beam toward sample 208. The electron optics 41 may include an objective lens array 241. The electron optics 41 may include a detector 240. The objective lens array (i.e., objective lens array 241) may correspond to a detector array (i.e., detector 240) and/or any beam (i.e., sub-beam).

An exemplary detector 240 is described below. However, any reference to detector 240 may be a single detector (i.e., at least one detector) or multiple detectors, as appropriate. The detector 240 may include a detector element 405 (e.g., a sensor element such as a capture electrode). The detector 240 may comprise any suitable type of detector. For example, a trapping electrode, a scintillator, or a PIN element, for example, for directly detecting electron charges may be used. The detector 240 may be a direct current detector or an indirect current detector. The detector 240 may be a detector as described below with respect to fig. 8-10.

The detector 240 may be positioned between the objective lens array 241 and the sample 208. The detector 240 is configured to be proximate to the sample 208. The detector 240 may be in close proximity to the sample 208. Alternatively, there may be a larger gap between the detector 240 and the sample 208. The detector 240 may be positioned in the device so as to face the sample 208. Alternatively, the detector 240 may be positioned elsewhere in the electron optical device 41 such that the portion of the electron optical device facing the sample 208 is different from the detector and is therefore not a detector. For example, the detector 240 may have at least a portion associated with an electrode of the objective lens array 241.

For a multi-beam system of the type shown in fig. 2-5, the distance between the electron optical column and the sample 208 is preferably less than or equal to about 50 μm. The distance is determined as the distance from the surface of the sample 208 facing the electron optical column to the surface of the electron optical column facing the sample 208.

Fig. 8 is a bottom view of the detector 240, the detector 240 including a substrate 404, a plurality of detector elements 405 disposed on the substrate 404, each detector element 405 surrounding a beam aperture 406. The beam aperture 406 may be formed by etching through the substrate 404. In the arrangement shown in fig. 8, the beam apertures 406 are hexagonal close-packed arrays. The beam apertures 406 may also be arranged differently, for example, in a rectangular array. The hexagonal arrangement of beams in fig. 8 may be more densely packed than square beam arrangements. The detector elements 405 may be arranged in a rectangular array or a hexagonal array.

In one embodiment, the beam aperture 406 has a pitch P of at least 50 μm, optionally at least 100 μm, optionally at least 200 μm and optionally 210 μm. The larger pitch allows the diameter d of the beam aperture 406 to be larger. In one embodiment, the beam aperture 406 has a pitch P of at most 1000 μm, alternatively at most 500 μm, and alternatively at most 250 μm. The pitch of the beam aperture 406 defines the pitch of the beamlets of the electron multi-beam projected toward the sample 208. In one embodiment, the beamlets of the electron multiple beam have a pitch of at least 50 μm, optionally at least 100 μm, optionally at least 200 μm and optionally 210 μm. In one embodiment, the diameter d of the beam aperture 406 is less than the pitch P. In one embodiment, the beam aperture 406 has a diameter d of at least 10 μm, and optionally at least 20 μm. In one embodiment, the beam aperture 406 has a diameter d of at most 100 μm, alternatively at most 50 μm, and alternatively at most 30 μm. Smaller diameter d increases resolution so that smaller defects can be detected.

Fig. 9 depicts a cross section of a portion of the detector 240 on a larger scale. The detector element 405 forms the bottommost part of the detector 240, i.e. the surface closest to the sample 208. A logic layer 407 may be provided between the detector element 405 and the body of the substrate 404. At least a portion of the signal processing system may be incorporated into the logic layer 407.

The wiring layer 408 is disposed on the back side or inside of the substrate 404 and is connected to the logic layer 407 through a via 409 penetrating the substrate. The number of through-substrate vias 409 need not be the same as the number of beam apertures 406. In particular, if the electrode signals are digitized in the logic layer 407, only a small number of through silicon vias may be required to provide a data bus. The wiring layer 408 may include control lines, data lines, and power lines. It should be noted that despite the beam aperture 406, there is sufficient space for all necessary connections. The detection module 402 may also be fabricated using bipolar or other fabrication techniques. A printed circuit board and/or other semiconductor chips may be provided on the back side of the detector 240.

The above-described integrated detector array is particularly advantageous when used with tools having adjustable landing energies, as the secondary electron capture can be optimized for the landing energy range.

The detector 240 may be implemented by integrating a CMOS chip detector into the bottom electrode of the objective lens array 241. Integrating the detector 240 into the objective lens array 241 or other component of the electron optical device 41 allows detection of electrons emitted in relation to a plurality of respective beamlets. The CMOS chip is preferably oriented to face the sample (since the distance between the sample and the bottom of the electron optical column is small (e.g., 50 μm or less)). In one embodiment, detector elements 405 for capturing secondary electrons are formed in a surface metal layer of a CMOS device. The detector element 405 may be formed in other layers. The power and control signals of the CMOS may be connected to the CMOS through silicon vias. For robustness, it is preferable that the passive silicon substrate with holes shield the CMOS chip from high electric fields.

In order to maximize detection efficiency, it is desirable to make the surface of the detector element 405 as large as possible so that substantially all of the area of the objective lens array 240 (except the aperture) is occupied by the detector element 405. Additionally or alternatively, each detector element 405 has a diameter substantially equal to the array pitch (i.e., the aperture array pitch described above with respect to the electrodes of the objective lens assembly 241). Thus, the diameter of each detector element may be less than about 600 μm, and preferably between about 50 μm and 500 μm. As described above, the pitch may be selected based on the expected distance between the sample 208 and the detector 240. In one embodiment, the outer shape of the detector element 405 is circular, but this may be made square to maximize the detection area. The diameter of the through-substrate via 409 may also be minimized. Typical dimensions of the electron beam are on the order of 5 to 15 microns.

In one embodiment, a single detector element 405 surrounds each beam aperture 406. In another embodiment, a plurality of detector elements 405 are provided around each beam aperture 406. Electrons captured by detector elements 405 surrounding one beam aperture 406 may be combined into a single signal or used to generate separate signals. The detector elements 405 may be radially separated. The detector elements 405 may form a plurality of concentric rings or annuli. The detector elements 405 may be angularly separated. The detector element 405 may form a plurality of segments or segments. The segments may have similar angular dimensions and/or similar areas. The electrode elements may be separated radially and angularly or in any other convenient manner.

However, a larger surface of the detector element 405 results in a larger parasitic capacitance and thus a lower bandwidth. For this reason, it may be desirable to limit the outer diameter of the detector element 405. Particularly if the larger detector element 405 gives only a slightly larger detection efficiency, but a significantly larger capacitance. The circular (annular) detector element 405 may provide a good compromise between collection efficiency and parasitic capacitance.

A larger outer diameter of the detector element 405 may also result in greater cross-talk (sensitivity to signals of adjacent holes). This may also be the reason for making the outer diameter of the detector element 405 smaller. Particularly if the larger detector element 405 gives only a slightly larger detection efficiency, but gives significantly larger cross-talk.

The electron current collected by the detector element 405 is amplified, for example, by an amplifier such as TIA.

In one embodiment, the objective lens array 241 is a replaceable module, either by itself or in combination with other elements such as the control lens array 250 and/or the detector 240 and/or the beam shaping array 262 and/or the sub-beam shaping array 252. The replaceable module may be field replaceable, i.e. the module may be replaced by a field engineer with a new module. In one embodiment, a plurality of replaceable modules are contained within the tool and are exchangeable between an operable position and an inoperable position without opening the electronic device 40.

In one embodiment, the replaceable module includes an electro-optical component, and in particular may be an electro-optical device on a stage that allows actuation to position the component. In one embodiment, the replaceable module includes a stage. In one arrangement, the stage and replaceable module may be an integral part of the tool 40. In one arrangement, the replaceable module is limited to the stage and the device it supports, such as an electron optical device. In one arrangement, the stage is detachable. In an alternative design, the replaceable module, including the stage, is removable. A portion of the electronics 40 for the replaceable module is isolatable, i.e., a portion of the electronics 40 is defined by the upstream and downstream valves of the replaceable module. The valves are operable to isolate the environment between the valves from the vacuum upstream and downstream of the valves, respectively, so that the replaceable module can be removed from the electronics 40 while maintaining the vacuum upstream and downstream of the portion of the electronics 40 associated with the replaceable module. In one embodiment, the replaceable module includes a stage. The stage is configured to support a device such as an electron optical device relative to the beam path. In one embodiment, the module includes one or more actuators. An actuator is associated with the stage. The actuator is configured to move the device relative to the beam path. Such actuation may be used to align the device and the beam path relative to each other.

In one embodiment, the replaceable module is a microelectromechanical system (MEMS) module. MEMS are miniaturized mechanical and electromechanical elements fabricated using micro-fabrication techniques. In one embodiment, the replaceable module is configured to be replaceable within the electronic device 40. In one embodiment, the replaceable module is configured to be field replaceable. By field replaceable it is meant that the module can be removed and replaced with the same or a different module while maintaining the vacuum in which the electro-optic tool 40 is placed. Only the portion of the electronic device 40 corresponding to the module is vented so that the module is removed and returned or replaced.

The control lens array 250 may be in the same module as the objective lens array 241, i.e. forming an objective lens array assembly or an objective lens arrangement, or it may be in a separate module.

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

In one embodiment, an aberration corrector positioned in or directly adjacent to the intermediate focus (or intermediate image plane) comprises a deflector to correct the source 201 that appears to the different beams to be in different positions. The corrector may be used to correct for macroscopic aberrations generated by the source that prevent good alignment between each beamlet and the corresponding objective lens.

The aberration corrector can correct aberrations that prevent correct column alignment. Such aberrations may also lead to misalignment between the beamlets and the corrector. To this end, it may be desirable to additionally or alternatively locate an aberration corrector at or near the converging lenses 231 (e.g., each such aberration corrector is integrated with one or more converging lenses 231 or directly adjacent to one or more converging lenses 231). This is desirable because at or near the converging lens 231, the aberrations also do not cause a shift of the corresponding beamlets, as the converging lens is vertically close to or coincident with the beam aperture. However, a challenge in positioning the corrector at or near the converging lens is that the beamlets each have a relatively large cross-sectional area and a relatively small pitch at that location relative to a further downstream location. The aberration corrector may be a CMOS-based independently programmable deflector as disclosed in EP2702595A1 or a multipole deflector array as disclosed in EP2715768A2, the description of the beamlet manipulator in both of which documents is incorporated herein by reference.

In some embodiments, each of at least a subset of the aberration correctors is integrated with the objective array 241 or directly adjacent to the objective array 241. In one embodiment, the aberration correctors reduce one or more of the following: field curvature; a focus error; and astigmatism. Additionally or alternatively, one or more scanning deflectors (not shown) may be integrated with or directly adjacent to the objective lens array 241 for scanning the beamlets 211, 212, 213 across the sample 208. In one embodiment, a scanning deflector as described in US2010/0276606, which is incorporated herein by reference in its entirety, may be used.

The detector may have multiple parts, more specifically, multiple detection parts. A detector comprising a plurality of portions may be associated with one of the beamlets 211, 212, 213. Thus, portions of one detector 240 may be configured to detect signal particles emitted from the sample 208 that are associated with one of the primary beams (which may otherwise be referred to as sub-beams 211, 212, 213). In other words, a detector comprising a plurality of parts may be associated with one aperture in at least one electrode of the objective lens assembly. More specifically, as shown in fig. 10, a detector 405 comprising multiple portions may be disposed around a single aperture 406, which provides one example of such a detector.

As shown in fig. 10, the detector element 405 includes an inner detection portion 405A and an outer detection portion 405B, and an aperture 406 is defined and configured in the detector element 405 for the electron beam to pass through. The inner detection portion 405A surrounds the aperture 406 of the detector. The outer detection portion 405B is located radially outward of the inner detection portion 405A. The detector may be generally circular in shape. Thus, the inner and outer detection portions may be concentric rings.

The present invention may be applied to a variety of different tool configurations. For example, the electronic device 40 may include multiple electron optical columns of multiple beams. The electron optical column may include electron optical devices 41 described in any of the above embodiments or aspects. As a plurality of electron optical columns (or multi-column tools), the devices may be arranged in an array, which may have a number of two to one hundred electron optical columns or more. The electronic device 40 may take the form of one embodiment as described and depicted with respect to fig. 4 or as described and depicted with respect to fig. 5. The electron optical column may optionally include a source.

As described above, in order to improve the contrast of the electron beam inspection, the surface of the sample 208 may be irradiated with light before the sample 208 is inspected. This process is called advanced charge control. Such irradiation may excite electrons within the sample 208. Such excitation electrons within the sample 208 are more likely to interact with impinging electrons from the incident primary beamlets of the multiple beams. As a result, such irradiation can be used to increase the intensity of the signal particles. The optical illumination may improve the contrast of the detection signal.

Fig. 11 is a schematic diagram of an electronic device 40 according to one embodiment. The electronics 40 are configured to project multiple beams of electrons toward the sample 208. As shown in fig. 11, in one embodiment, the electronic device 40 includes an electron source 201. The electron source 201 is configured to emit an electron beam. The electron source may be as described above.

In one embodiment, the electronic device 40 includes an electro-optical device 41. The electron optics 41 are configured to project sub-beams of electron multiple beams derived from the electron beam emitted by the electron source 201 towards the sample 208. The electron optical arrangement 41 may comprise one or more electron optical elements configured to act on electron multiple beams. For example, in the arrangement shown in fig. 11, the electron optical device 41 may include a sub-beam forming array 252, a control lens array 250, an objective lens array 241, and a beam forming array 262. In one embodiment, the control lens array 250 includes at least two plates defining a plurality of apertures therein, each aperture for a beamlet of the multiple beams. In one embodiment, the objective array 241 includes at least two plates defining a plurality of apertures therein, each aperture for a beamlet of the multiple beams. In one embodiment, the electro-optical device 41 further includes a macro-scan deflector 265 and a macro-collimator 270 (e.g., as described above with reference to fig. 4). Alternatively, macro-scanning deflector 265 may be a separate component from electron optics 41, or macro-collimator 270 may be a separate component from electron optics 41, or both. Although not shown in fig. 11, the electron-optical device 41 may further include a detector 240. This is shown in fig. 13. The electro-optical device 41 may have the features described above with respect to figures other than fig. 11.

As shown in fig. 11, in one embodiment, the electronic device 40 includes a light source 70. The light source 70 is configured to emit light 71 (i.e., photons). In one embodiment, the light source 70 is configured to emit light 71 generally toward the sample 208. The light 71 is used to illuminate the surface of the sample 208 in order to improve the contrast when inspecting the sample 208 for defects.

As shown in fig. 11, in one embodiment, the light source 70 is arranged such that light 71 is projected along a path of the beamlets (e.g., along the optical path) through the electron optical device 41 so as to illuminate at least a portion of the sample 208. In one embodiment, the portion of the sample 208 illuminated by the light 71 corresponds to the portion that subsequently receives the electron beam. The light 71 is projected through the objective lens array 241 of the electronic device 40. The electronic device 40 is configured to project light 71 from above the electron optical device 41 onto the surface of the sample 208.

In one embodiment, the path (or optical path) of light 71 through the aperture of the electron optical element of electron optical device 41 is substantially straight. In one embodiment, the apertures of the electron optical elements of electron optical device 41 are aligned such that the path (or optical path) along which light 71 is projected is substantially straight.

By providing the light 71 through the electron optical arrangement 41, it is not necessary to provide a separate projection system 60 for projecting the light 71 onto the sample 208, e.g. as one or more light beams. Projection system 60, such as shown in fig. 2, may be omitted. It is desirable that one embodiment of the present invention simplify the design of the electronic device 40.

A complex optical arrangement that directs light between the sample 208 and the surface of the electron optical device 41 to illuminate the sample surface may be omitted. As described above, the gap between the electron optical column and the surface of the sample 208 may be small. This makes it difficult to project light 71 sideways onto sample 208, for example, using projection system 60 shown in fig. 2. In particular, it is difficult to irradiate the light 71 over the entire width of the electron-optical device column. One embodiment of the present invention makes it easier to irradiate the light 71 over the width of the sub-beam for inspection.

As described above, the electron optical device 41 may include various electron optical elements. In one embodiment, the electronic device 40 includes at least two electron optical elements including corresponding aperture arrays. The apertures of the respective aperture arrays of the respective electron optical elements correspond to respective beamlets of the electron multibeam. The aperture of the respective aperture array of the respective one or more electron optical elements corresponds to a respective sub-beam of the electron multi-beam. The light source 70 is arranged relative to the electron optical element such that the light or light beam 71 follows the same path as, for example, electron multiple beams passing through the electron optical element, to the sample 208; that is, the optical path and the electron beam (or beamlet) path may follow substantially the same path.

As shown in fig. 11, in one embodiment, the light source 70 is adjacent to the electron source 201. The light source 70 may be disposed at a similar distance (e.g., height) from the sample 208 as the electron source 201. The distance from the electron source 201 to the sample 208 may be similar (e.g., within 10% of) the distance from the sample 208 to the light source 70. In one embodiment, the light source 70 is proximate to the electron source 201. The light source 70 may be positioned such that the path length (or optical path) of the light or beam 71 to the sample 208 is similar to the path length of electrons of an electron beamlet (e.g., incident on the sample 208) to the sample 208. By providing the light source 70 in the vicinity of the electron source 201, the electronic device 40 can be formed more compactly.

As shown in fig. 11, in one embodiment, the light source 70 is arranged such that the electron source 201 (e.g., the path of the electron beam from the source 201 toward the sample in the electron beam) is radially inward of the light or beam 71 upstream of the electron optical device 41 in plan view. For example, at a position along the charged particle beam upstream of the electron optical device 41, the electron beam is radially inward of the light or light beam 71 in plan view. The light source 70 and the electron source 201 are upstream of the electron-optical device 41. The electron optical device 41 is between the sample 208 and the light source 70 and electron source 201. A plan view refers to a view looking along the major axis of the electronic device 40 and/or along the electron and/or beam path toward the sample 208 (e.g., on the surface of the sample 208 where the electron and/or beam impinges the sample 208).

As shown in fig. 11, in one embodiment, the electron source 201 is arranged such that the electron beam can be aligned with the central axis of the electron optics device 41. That is, the path of the electron beam toward the sample 208 may be aligned with the central axis of the electron optical device 41. The electron beam from which the electron multiple beams are derived is not affected by the light source 70.

As shown in fig. 11, in one embodiment, the light source 70 is positioned between at least a portion of the electron source 201 and the sample 208. The electron source 201 may include an emitter (e.g., cathode) and an extractor electrode (e.g., anode). The light source 70 may be located between the sample 208 and the emitter and extractor of the electron source 201; the sample 208 may be positioned closer to the emitter and extractor of the electron source 201, i.e., with less displacement. The light source 70 is unobstructed by the electron source 201. That is, both the light source 70 and the electron source 201 require a clear path downstream, for example, toward the sample 208. The light source 70 and the electron source 201 should be physically separated, for example, such that the required volumes do not overlap. Thus, not only are the light sources 70 unobstructed by the electron sources 201, but each source is also unobstructed by the other, i.e., they have their own volumes and there is a clear path from each source toward the sample. When a clear path is required, the corresponding beam is not obstructed by the electron source 201; the electron beam from the electron source 201 is not blocked by the light source 70.

As described in more detail with reference to fig. 14, in one embodiment, the electron source 201 may further include an electron optical deflector 290. In one embodiment, the light source 70 is located between the sample 208 and the emitter and extractor of the electron source 201. For example, the light source 70 is positioned closer to the sample than the emitter and extractor of the electron source 201. The distance from the sample 208 to the light source 70 may be smaller than the distance from the sample 208 to the electron source 201, e.g. along the path of the electron beam from the electron source 201 towards the sample 208. In this arrangement, an electron optical deflector 290 (or a pair of electrostatic deflectors configured to operate on an electron beam from the electron source 201) is located between the sample 208 and the light source 70, for example, along the path of the electron beam from the electron source 201 to the sample 208. Deflector 290 may be positioned at a smaller distance from sample 208 than light source 70, for example along a beam path (or optical path) from light source 70 to sample 208. Alternatively, in one embodiment, the light source 70 is positioned in an axial (i.e., a direction perpendicular to the surface of the sample 208) direction between the sample 208 and the emitter, extractor, and electron optical deflector 290 of the electron source 201.

In an alternative embodiment, electron source 201 is located between light source 70 and sample 208 in an axial direction. In one embodiment, the light source 70 is offset from the central axis of the electron optical device 41. By offsetting the light source 70 from the axis, the light source 70 is unobstructed by the electron source 201.

In one embodiment, the light source 70 is located at least two positions spaced apart from the electron beam in plan view. That is, different portions of the light source 70 are located at different positions, or the light source 70 extends between different positions; the different positions are partially spaced apart from the path of the electron beam as viewed along, for example, the path of the electron beam toward the sample 208. The light source 70 may be configured to emit light 71 comprising a plurality of light beams. The light beam may be emitted from a plurality of points of the light source 70. The light sources 70 may be distributed over a plurality of locations from which light 71 is emitted. In one embodiment, the controller 50 is configured to control the light sources 70 such that the light 71 is controllably emitted from a plurality of locations simultaneously.

By distributing the light source 70 over a plurality of locations, the light source 70 may be symmetrical about a central axis while avoiding mechanical interference between the light source 70 and the electron source 201. In one embodiment, the light source 70 is arranged such that the light 71 comprises a plurality of light beams (or light paths), and the path of the electron beam is between the plurality of light beams upstream of the electron optical device 41.

There are various possible arrangements of the distributed light sources 70. In one embodiment, the locations are equally spaced from each other. Additionally or alternatively, the locations are at similar radial distances from the electron source 201. It is desirable that one embodiment of the present invention makes it easier to apply a consistent level of light illumination across the lateral dimension of the sample 208.

As shown in fig. 11, in one embodiment, these locations surround the electron source 201 in plan view. As further shown in fig. 11, in one embodiment, the locations are continuous so as to form an arc in plan view that is spaced from the electron source 201. In one embodiment, the light source 70 forms an arc radially spaced from the path of the electron beam emitted from the electron source 201. For example, in the arrangement shown in fig. 11, these positions form a ring around the electron source 201 in plan view. In one embodiment, the light source 70 forms a ring around the path of the electron beam emitted from the electron source 201. Alternatively, the arc may extend partially around the path of the electron beam emitted by the electron source 201. For example, the arc may correspond to one half of a ring or one quarter of a ring. In such an arrangement, the light generated by the light source 70 may comprise a single light beam emitted from a portion of the light source 70 that extends in length between two locations or even around a path or axis of the electron optical device 41; i.e. light is emitted along a continuous length between different positions.

Fig. 12 is a close-up view of a portion of the electronic device 40 of fig. 11. Fig. 12 shows the path (or optical path) of light 71 through only one set of apertures, i.e. the path corresponding to one of the sub-beams of the electron multi-beam.

As shown in fig. 12, the beam of light 71 widens as the beam of light 71 is projected through the apertures of the sub-beam forming arrays 252 and 262. The beam of light 71 is widened by diffraction. At the beamlet forming array 252, the diameter of the beam of light may be equal to the diameter 72 of the aperture. The beam widens to a widened diameter 73 at the beam shaping array 262. The beam shaping array 262 reduces the diameter of the beam to a diameter 74 substantially equal to the aperture of the beam shaping array 262.

As described above, in embodiments, the apertures of the beamlet-forming array 252 have a diameter 72 of at least 20 μm, alternatively at least 50 μm, alternatively at least 100 μm, and alternatively 120 μm. By providing a larger aperture, beam broadening due to diffraction through the aperture is reduced. This reduces the proportion of the light 71 in the beam that is blocked at the beam shaping array 262. This increases the proportion of light 71 reaching the sample 208. Ideally, the aperture size of the beamlet-forming array 252 may be as large as possible, so that as much light as possible reaches the sample when the sample is illuminated with the light 71 of the beam. This requirement is balanced with the electron optical requirements of the beamlet forming array when choosing the size of the aperture. Such electron optical requirements can limit the size of the aperture such that the beamlet-forming array effectively generates beamlets.

In one embodiment, the aperture of the beam shaping array 262 has a diameter 74 that is greater than 10 μm, alternatively at least 20 μm, and alternatively at least 25 μm. By providing a larger aperture, beam broadening due to diffraction through the aperture is reduced. This reduces the spot size 75 on the sample 208. Further, since the beam shaping array 262 is the smallest aperture along the path of the corresponding beam (or the optical path of the corresponding beam), the diffraction effect on the light of the beam may be greatest when passing through the aperture of the beam shaping array 262. Thus, it is desirable that the aperture of the beam shaping array 262 be at least as large as the diffraction threshold. Such a diffraction threshold may be related to or even determined by the wavelength of the light beam. Additional details of the diffraction threshold, such as its relationship to the wavelength of light used, are described below. In one embodiment, the ratio of the diameter 72 of the apertures of the beamlet forming array 252 to the diameter 74 of the apertures of the beamlet forming array 262 is at least 2, alternatively at least 3, alternatively at least 4 and alternatively at least 5. In one embodiment, the ratio of the diameter 72 of the apertures of the beamlet forming array 252 to the diameter 74 of the apertures of the beamlet forming array 262 is at most 10, alternatively at most 8, alternatively at most 5 and alternatively at most 4.

Alternatively, the electron optical elements along the path of the electron beamlets in electron optical arrangement 41 are typically defined by apertures of similar diameter, e.g., as the dimensions of beam forming array 262. Diffraction of the beam may occur as the beam passes through a corresponding aperture of a plate of the electron optical element. Diffraction inevitably causes the beam to widen along the beam path (or path of the beam) toward the sample surface. This widening of the beam cross-section results in a portion of the beam being blocked at each successive plate towards the sample, for example even though the apertures in the successive plates are substantially the same. The proportion of light 71 that can reach the sample 208 can thus be reduced with further additional plates along the beam path (or optical path). The proportion of light reaching the sample 208 may depend on the degree of diffraction, such as the selected diameter of the aperture defined in the plate and the selected wavelength of photon illumination. It should be noted that when certain wavelengths of the incident light in the light beam achieve the desired excitation of electrons in the sample, different options for the wavelength of light may come from a limited choice and thus from a limited choice.

There may be an offset between the position of the electron beamlet spot and the corresponding light spot on the sample 208. For example, if the light source 70 is positioned off-axis, the light 71 is projected through the electron optics 41 at a slight angle. Any such offset is expected to be within acceptable limits. For example, it can be calculated that if the light source 70 is 1mm off-axis and the distance from the light source 70 to the beam shaping array 262 is 100mm, then the tilt angle of the light will be about 10mrad. The light spot may have a diameter on the order of about 30 μm and the scanning range of the electron beam may be on the order of about 1 μm. If the distance from the beam shaping array 262 to the sample 208 is about 50 μm, the spot point will be about 0.5 μm off-axis. If the light source is positioned about 10mm off-axis (but the other dimensions are not changed from the above calculation), the spot point is about 5 μm off-axis. The distance of the spot off-axis is acceptable, especially considering the diameter and scanning range of the spot.

Fig. 14 shows an alternative arrangement of a light source 70 and an electron source 201 for an electronic device 40. The same features as described with reference to fig. 11 are not repeated here. In one embodiment, the electronic device 40 further includes a macro-collimator 270, such as described above with reference to fig. 4. As shown in fig. 14, in one embodiment, the light source 70 is arranged such that the path (or optical path) of the light 71 towards the sample 208 is aligned with the central axis of the electron optical device 41. That is, the path (or optical path) of the light beam from the light source 70 is aligned with the path of the electron multi-beam passing through the electron optical device 41. The light source 70 may be positioned on a central axis. This helps to simplify the design of the light source 70 of the electronic device 40. The light source 70 may form a disc centered on an axis. This may reduce the power density compared to a point light source.

As shown in fig. 14, in one embodiment, the electron source 201 is offset from the central axis of the electron optical device 41. For example, the electron source 201 may be located at one side of the light source 70. The path of the electron beam emitted by the electron source 201 is not affected by the light source 70. In one embodiment, the electron source 201 may be positioned closer to the sample 208 than the light source 70, at the same distance from the sample 208, or further from the sample 208.

In one embodiment, the electron source 201 is arranged to emit an electron beam that is angled with respect to a central axis of the electron optical device 41. This allows the path of the electron beam to include a central axis. The downstream portion of the path may be aligned with the central axis. As shown in fig. 14, in one embodiment, the electronic device 40 includes an electron optical deflector 290. The electron optical deflector 290 is configured to deflect the electron beam to be aligned with the central axis of the electron optical device 41. That is, downstream of the electron optical deflector along the electron beam from the electron source 201 towards the sample 208, the paths of the electron beam towards the sample 208 and the beam towards the sample 208 may substantially correspond or even be identical. Although the path immediately downstream of the emitter and extractor electrodes of the electron source 201 is oblique with respect to the central axis, the downstream path of the electron optical deflector 290 may be controlled to align with the central axis or the path (or optical path) of the beam toward the sample 208, or with both (e.g., if the central axis of the electron optical device 41 and the path (or optical path) of the beam toward the sample 208 correspond).

As shown in fig. 14, in one embodiment, the electron optical deflector 290 is provided as a separate component from the macro scanning deflector 265. The electron optical deflector 290 may be upstream of the macro-scanning deflector 265 along the beam path (or optical path) and/or electron beam path from the electron source 201. The electron optical deflector 290 may be in a plane perpendicular to the central axis of the electron optical apparatus 41 (i.e., perpendicular to the light beam). Alternatively, the electron optical deflector 290 may be in a plane perpendicular to the direction in which the electron beam is emitted from the electron source 201. In another alternative embodiment, the electron optical deflector 290 may be located in a plane at an angle between a plane perpendicular to the central axis of the electron optical device 41 and a plane perpendicular to the direction in which the electron beam is emitted from the electron source 201.

In one embodiment, the electron optical deflector 290 may be a multipole electrostatic deflector comprising at least two electrodes facing each other, for example across the path of the electron beam. It is not necessary to make the optical path and the electron optical deflector 290 orthogonal to each other because the optical path is not affected by the electron optical deflector 290. The electron optical deflector 290 may be inclined at any suitable angle with respect to the optical path; that is, as long as it does not block the optical path and the electron beam path. An intermediate angle may be required to take advantage of the symmetry of the design in order to eliminate deflection aberrations. Thus, in one embodiment, the electron optical deflector 290 may be positioned along the path of the electron beam from the electron source 201 toward the beam path (or optical path) toward the sample 208 and/or the axis of the electron optical device 41. In one arrangement, the electron optical deflector 290 may be disposed at any reasonable orientation, such as any angle between the path of the electron beam from the electron source 201 and the path (or optical path) of the beam from the light source 70 toward the sample 208 and/or the axis of the electron optical device 41.

With two electrodes, the deflector may deflect the path of the electron beam towards the sample 208 in one direction in a plane orthogonal to the path (or optical path) of the beam and/or the axis of the electron optical device 41. In one embodiment, the multipole deflector may comprise at least four electrodes for exciting the deflected electron beam in any direction orthogonal to the path (or optical path) of the beam and/or the axis of the electron optical device 41. The multipole deflector may have a desired number of electrodes, such as two, four, six, e.g. multiples of four, preferably eight, twelve, sixteen, twenty etc. In an alternative embodiment, the macro-scan deflector 265 is configured to function as the electron optical deflector 290. The macro-scan deflector 265 may be configured to deflect the electron beam to align with a central axis of the electron optical device 41. Such a macro-scan deflector 265 may be a multipole deflector having the features described for the electron optical deflector 290.

In an alternative embodiment (not shown), the light source 70 is offset from the central axis of the electron optical device 41. In such an arrangement, a similar distance of the light source 70 and the electron source 201 from the sample 208 may be preferred, or the light source 70 may be farther from the sample 208 than the electron source 201. For example, the light source 70 may be located on one side of the electron source 201. The electron source 201 may be aligned with the central axis as shown in fig. 11. The light source 70 is arranged to emit light 71 at an angle relative to a central axis of the electron optical arrangement 41. In an arrangement even though the light source 70 is positioned closer to the sample 208 than the electron source 201, the beam from the light source 70 intersects the axis of the electron optics 41, or the path of the electron beam toward the sample 208, or both, upstream of the first electron optical element in the path of the electron beam from the electron source 201. The electronic device 40 may include a light reflector (e.g., a mirror). The light reflector is configured to deflect the light 71 into alignment with a central axis of the electron optical apparatus 41. Although the path (or optical path) immediately downstream of the light source 70 is inclined with respect to the central axis, the path downstream of the light reflector is aligned with the central axis. The light reflector may comprise an aperture coincident with the central axis so as to allow the electron beam emitted by the electron source 201 to pass through it. Such light reflectors may be located upstream of the objective lens assembly (or the objective lens array 241, converging lens array and/or beamlet forming array 252). The light reflector may be located upstream along the path of the electron beam from the electron source 201 of at least the macro-scanning deflector 265 (and even the macro-collimator 270). In one embodiment, both the electron source 201 and the light source 70 are positioned off-axis. The above-described optical reflector and electron optical deflector 290 may be provided.

As shown in fig. 11, in one embodiment, the electron optical device 41 includes a control lens array 250 and a beam shaping array 262 in addition to the objective lens array 241 and the beam shaping array 252. Additionally, the controller 50 is connected to at least the control lens array 250. The controller 50 may be considered to be at least partially included in the electro-optical device 41.

As shown in fig. 11, the control lens array 250 includes a plurality of control lenses. The control lens is configured to adjust charged particle optical parameters of respective beamlets of the electron multi-beam, such as a focal point of the beamlets. The beamlets are focused at least by a respective downstream objective lens. For example, the beamlets may be focused by operating the respective objective lens and the control lens together.

As shown in fig. 11, the beam shaping array 262 is downstream of the control lens array. The beam shaping array 262 includes a plurality of apertures for respective sub-beams of the electron multi-beam. The beam shaping array 262 is downstream of the sub-beam shaping array 252. Thus, the aperture of the beam shaping array 252 acts on the beamlets formed by the beamlet shaping array 252. In one embodiment, the aperture of the beam shaping array 262 has a diameter 74 (see FIG. 12) of at least 10 μm, alternatively at least 20 μm, alternatively at least 25 μm.

In one embodiment, the light source 70 is configured to emit light 71 having a wavelength. For example, the light source 70 may be configured to emit light 71 having a wavelength in the range from 450nm to 850nm, preferably from 450nm to 800 nm. The selected wavelength may correspond to a wavelength absorbed by the material of the sample 208. The selected wavelength may be prone to excite electrons in the sample 208 when light is incident on the sample 208. For example, incidence of light of a selected wavelength generates electron-hole pairs in the material. The particular wavelength selected may depend on the application (e.g., use or purpose) under examination or at least evaluation. In one embodiment, the apertures of the beam shaping array 262 have a size of at least the diffraction threshold. The diffraction threshold may depend on the wavelength of the light 71 emitted by the light source 70. One embodiment of the present invention is expected to reduce diffraction of the spot 71 on the sample 208.

The aperture in the electron-optical device 41 is small. In one embodiment, the beam shaping array 262 has a minimum aperture through which the optical path extends. When light is projected through an aperture, there may be significant diffraction. Any such diffraction may reduce the power density of light on the sample 208. By providing a larger aperture for the beam shaping array 262, diffraction effects are reduced. One embodiment of the present invention contemplates increasing the proportion of the output power of the light source 70 reaching the sample 208. It is desirable for one embodiment of the present invention to reduce the output power requirements of the light source 70 while providing adequate illumination of the sample 208.

By providing a larger aperture for the beam shaping array 262, the resolution of the electronic device 40 may be degraded. Detecting smaller defects on the sample 208 may be more difficult. The smaller aperture (e.g., 25-25 μm, preferably 30 μm diameter) used for the beam shaping array 262 results in a lower total electron current on the sample 208. As the size of the aperture increases, the electron current on the sample 208 increases. In general, a greater total current on the sample 208 correlates to a greater minimum size of defects of the sample 208 that can be resolved. The relationship is approximately linear. In general, larger pore sizes increase the size of the smallest defects that can be detected. However, when a larger aperture is provided for the beam shaping array 262, larger defects may be detected.

In one embodiment, the controller 50 is configured to control the electronic device 40 so as to perform flooding of the surface of the sample 208. Flooding may be performed with illumination using light source 70. This helps detect some defects in the sample 208. That is, the controller 50 may control the operation mode of the electronic device 40 between an evaluation mode (e.g., an inspection mode) and a flood mode. In flood mode, the control lens array 250 may be used to focus the beamlets that pass through the apertures of the beam shaping array 262 such that the shaping of the apertures is sufficiently reduced to cause the current of the beamlets incident on the sample 208 to meet or exceed a threshold current. The threshold current may correspond to a minimum flood current.

As shown in fig. 11, in one embodiment, the electron optical device 41 includes an objective lens array 241. The objective lens array 241 is downstream of the control lens array 250. The control lens array 250 is configured to adjust the electron optical parameters of the beamlets, which are then focused by the objective lens array 241. As shown in fig. 11 and described above, the objective lens array 241 includes a plurality of objective lenses. The objective lens is configured to focus the respective beamlets on the sample 208 when the beamlets are shaped by the beam shaping array 262. Beam shaping array 262 may be associated with any electrode or plate of objective lens array 241. In one embodiment, as shown in fig. 4, the beam shaping array 262 is associated with an electrode of the objective array 241 positioned furthest downstream of the path of the respective beamlets, e.g., positioned downstream of the electrode of the objective array 241. During flood irradiation, no objective lens is required to focus the beamlets on the surface of the sample 208.

Fig. 13 is a schematic view of a portion of the electron optical apparatus 41 of fig. 11, for example. Fig. 13 is a close-up view of the objective lens array 241 and the control lens array 250. As shown in fig. 13, in one embodiment, a beam shaping array 262 is associated with the objective lens array 241. The beam shaping array 262 may be downstream of the objective lens array 241. For example, the beam shaping array 262 may include a plate attached to the downstream electrode 243 of the objective lens array 241. The plates of the beam shaping array 262 may be integrally formed with the downstream electrode 243 of the objective lens array 241. Alternatively, the beam shaping array 262 may be remote from the objective lens array 241. The beam shaping array 262 may be formed as a separate component from either of the electrodes 242, 243 of the objective lens array 241.

As shown in fig. 13, in one embodiment, the beam shaping array 262 is downstream of the objective lens array 241. In an alternative embodiment, the beam shaping array 262 is further upstream, such as even upstream of the objective lens array 241. For example, the beam shaping array 262 may be connected to the upstream electrode 242 of the objective lens array 241 or integrally formed with the upstream electrode 242 of the objective lens array 241. In one embodiment, beam shaping array 262 is located between objective lens array 241 and control lens array 250.

As shown in fig. 13, a control lens array 250 is associated with the objective lens array 241. As described above, the control lens array 250 may be considered to provide electrodes that are attached to the electrodes 242, 243 of the objective lens array 241. Controlling the additional electrodes of the lens array 250 allows additional degrees of freedom to control the electron optical parameters of the beamlets. In one embodiment, the control lens array 250 may be considered as an additional electrode of the objective lens array 241, implementing additional functionality of the respective objective lenses of the objective lens array 241. In one arrangement, such electrodes may be considered part of the objective lens array, providing additional functionality to the objective lenses of the objective lens array 241. In such an arrangement, the control lens is considered to correspond to a portion of the objective lens, even to the extent that the control lens is referred to as only a portion of the objective lens.

As shown in fig. 13, in one embodiment, the control lens array 250 and the objective lens array 241 share a common electrode. In the arrangement shown in fig. 13, the control lens array 250 includes three electrodes 253, 254, 255. In one embodiment, the downstream electrode 255 of the control lens array 250 and the upstream electrode 242 of the objective lens array 241 form a common electrode. The same conductive plate may be used to control the downstream electrode 255 of the lens array 250 and the upstream electrode 242 of the objective lens array 241. The common electrode arrangement allows a particularly compact objective lens assembly. In an alternative embodiment, the downstream electrode 255 of the control lens array 250 is spaced apart from the upper beam electrode 242 of the objective lens array 241. The electrodes controlling the lens array 250 may be spaced apart from the electrodes of the objective lens array 241.

In the arrangement shown in fig. 13, the control lens array 250 includes three electrodes 253, 254, 255. In alternative embodiments, the control lens array 250 may include, for example, one electrode or two electrodes.

In one embodiment, the controller 50 is configured to control the voltages applied to the intermediate electrode 254 and the downstream electrode 255 of the control lens array 250 in order to adjust the focus of the incident beamlets. The focal spot of the beamlets may be such that the beam shaping array 262 is no longer beam-limiting (or less beam-limiting). More or all of the beamlet current passes through beam shaping array 262 of electron optics 241. The size of the aperture of the beam shaping array is independent of the requirements of the flood mode. That is, the flood mode does not require the beam-shaping aperture to take any particular size. The size of the beam shaping aperture is determined at least in part by the requirements for irradiating the sample with the light beam, the electron optical specifications of the electron optical device 41 in the evaluation mode, or both.

In one embodiment, the controller 50 is configured to control the objective lenses of the objective lens array 241 to operate as an accelerating lens. The controller 50 may control the voltages applied to the electrodes 242, 243 of the objective lens array 241 such that the objective lens accelerates electrons of the beamlets towards the sample 208.

In one embodiment, the controller 50 is configured to control the objective lenses of the objective lens array 241 to operate as a deceleration lens. The controller 50 may control the voltages applied to the electrodes 242, 243 of the objective lens array 241 such that the objective lens decelerates electrons of the beamlets projected towards the sample 208.

The controller 50 is configured to adjust the voltage applied to the electrodes 242, 243 during use of the electro-optical device 41. In one embodiment, the controller 50 is configured to control the objective lens to switch between accelerating and decelerating electrons projected toward the sample 208.

As shown in fig. 13, in one embodiment, the electron optical device 41 includes a beamlet forming array 252. The beamlet forming array 252 is configured to divide the electron beam into electron multiple beams comprising beamlets. Thus, the beamlet-forming array 252 generates beamlets of the electron multi-beam from, for example, the electron beam from the electron source 201. In alternative embodiments, the geometry of the beamlet-forming array 252 may help determine the highest current applied to the sample by the beamlets during flood mode. Since the flood mode may be used in combination with light irradiation, for example for voltage contrast irradiation, the relative size between the apertures of the sub-beam forming array 252 and the beam forming array 262 may be determined by the requirements of irradiating the sample with light. This is because the aperture of the beam shaping array 262 is independent of the requirements of the flood mode; that is, the size of the aperture of the beam shaping array 262 is not determined by the requirements of the electron optical device 41 for the flood mode.

In one embodiment, the apertures of the beamlet forming array 252 define a pattern. The pattern may be a grid. The grid includes regularly arranged apertures. Alternatively, the apertures may be irregularly arranged. In one embodiment, the grid is hexagonal or rectilinear. The hexagonal grid may allow for a greater density of beamlets per unit area. The electron beams from the electron source 201 may interact with the beamlet forming array 252 to create a multi-beam arrangement or beamlet array. The multi-beam arrangement (or beamlet array) may have a pattern corresponding to the grid pattern, for example, wherein each beamlet corresponds to an aperture defined in the beamlet forming array 252.

In the arrangement shown in fig. 13, a beamlet-forming array 252 is associated with the control lens array 250. For example, the beamlet-forming array 252 may be associated with an upstream electrode 253 of the control lens array 250. In one embodiment, the beamlet-forming array 252 provides the most upstream electrode 252 that controls the lens array 250. For example, the beamlet-forming array 252 may include a plate coupled to the upstream electrode 253 or integrally formed with the upstream electrode 253. In an alternative embodiment, the beamlet-forming array 252 is provided as a physically separate component from the electrodes 253, 254, 255 of the control lens array 250.

As shown in fig. 13, in one embodiment, the beamlet-forming array 252 is upstream of the control lens array 250. As shown in fig. 13, in one embodiment, the electron optical device 41 includes a detector 240. The detector 240 may be formed as a two-dimensional detector array comprising a plurality of detector elements 405 at positions along the beam path, the plurality of detector elements 405 configured to detect signal particles emitted from the sample 208. In one embodiment, the detector elements 405 are associated with respective beamlets of the electron multi-beam.

As shown in fig. 13, in one embodiment, at least a portion of detector 240 is located between control lens array 250 and sample 208. That is, the detector 240 may include at least two arrays, each located at a different position along the primary beam path toward the sample 208. The detector arrays of such detectors 240 may thus be distributed at different locations of the electron optical column, e.g. as different two-dimensional detector arrays. In one embodiment, all detector arrays are between control lens array 250 and sample 208; that is, a detector array without detector 240 is located upstream of control lens array 250. In one embodiment, a portion of detector 240 is between control lens array 250 and sample 208, and a portion of detector 240 is upstream of control lens array 250. For example, fig. 6 shows one example in which detector 240 has a detector array (relative to the direction of the primary beam or sub-beam toward sample 208, i.e., the direction of electrons projected toward sample 208) upstream of control lens array 250. In one embodiment, all detectors 240 are upstream of control lens array 250.

As shown in fig. 13, in one embodiment, at least a portion of the detector 240 (e.g., a detector array of the detector 240) is located between the beam shaping array 262 and the sample 208. For example, as shown in fig. 13, in one embodiment, detector 240 is associated with an objective lens array 241. The detector 240 may take the form of a detector array. In a different arrangement, the detector 240 may have more than one detector array, with at least one detector array being located upstream of the detector array shown in fig. 13, and no additional detector array being shown in fig. 13. The detector 240 may form the final surface of the electron optics 241 upstream of the sample 208. The detector 240 faces the sample 208; that is, the detector elements in the detector array may face the sample 208. The detector 240 may be supported by a plate that is fixed relative to the objective lens array 241 and/or the downstream electrode 243 of the beam shaping array 262.

In one embodiment, the controller 50 is configured to control the electronics 40 to operate to detect signal particles emitted by the sample 208. In such control of the electronic device 40 with the controller 50, multiple beams are used when the beamlets are shaped by the beam shaping array 262. Such shaped beamlets may mean that electrons of each beamlet that are less than a threshold current pass through a corresponding aperture of the beam shaping array 262. When an inspection current is supplied to the sample 208, signal particles are detected. When the flood current is supplied, detection may not be performed. That is, the detector elements are controlled to be inactive, e.g., by the controller 50 (or another controller), the detector elements of the detector are controlled such that they do not transmit detection signals and/or the detection signals generated by the detector elements are not processed by a processor that processes the detector signals during the inspection mode.

As shown in fig. 13, the aperture of the beam shaping array 262 is smaller in size than the corresponding aperture of the control lens array 250. The beam shaping array 262 provides a limiting factor for electron current of the beamlets projected toward the sample 208. During inspection (i.e., inspection mode), beam shaping array 262 is preferably proximate to sample 208, which is configured to shape (e.g., confine) the beamlets.

In one embodiment, the electronic device 40 includes a plurality of electronic optical devices as a multi-device column device, as shown in the figures, e.g., at least fig. 3 and 4, subject to the following description. Such a multi-device column device may include a plurality of electron-optical device columns arranged in an array, such as a rectangular or hexagonal pattern. Each column of devices of the multi-column device may feature features and functions of the arrangement described and disclosed herein with reference to fig. 3. Alternatively, the multi-device column device includes a plurality of device columns arranged, for example, as an array having a regular pattern and including the features and functions of the electro-optical device 41 depicted and described with reference to fig. 4 subject to the following differences. Such differences include having a collimator array, such as a collimator deflector integrated into an objective lens array assembly, for example associated with the aperture of the beamlet forming array, preferably just downstream of the aperture of the beamlet forming array 252. Each collimator deflector is assigned to a respective sub-beam of the multiple beams. The differences may include a scan deflector array integrated into (e.g., associated with) the objective lens array assembly(s) 241. Having a scanning deflector array and a collimator array is advantageous because such devices are electrostatic rather than magnetic. An electron-optical column structure with magnetic devices is difficult to integrate into a multi-device column arrangement due to interference of the magnetic devices with surrounding device columns of the multi-device column arrangement.

In one embodiment, a method for projecting multiple beams of electrons toward a sample 208 is provided.

In one embodiment, a method includes emitting an electron beam. In one embodiment, the method includes projecting sub-beams of electron multiple beams derived from the electron beam toward the sample 208 using electron optics. The electron multiple beams may be used to detect defects in the sample 208.

In one embodiment, the electron beam is emitted at an angle relative to the central axis of the electron optical device 41. In one embodiment, the method includes deflecting the electron beam to align with a central axis of the electron optical device 41.

In one embodiment, a method includes emitting light. In one embodiment, the method includes projecting light along a path (or optical path) of the beamlets through electron optical device 41 in order to illuminate sample 208. In one embodiment, the method is used to prepare a sample 208 for voltage contrast measurement. This light can be used to prepare the sample 208 for voltage contrast measurement.

In one embodiment, the method includes flooding the surface of the sample 208 with charged particles. In one embodiment, both flooding (with electrons) and illuminating with light are performed in order to increase the contrast for inspecting certain defects.

In one embodiment, the method is used to prepare the sample 208 for voltage contrast measurement and perform voltage contrast measurement (i.e., through an inspection process). In one embodiment, the method is used to prepare the sample 208 for voltage contrast measurement and perform voltage contrast measurement (i.e., through an inspection process). Suitable apparatus and associated methods for such illumination of a sample and/or for such voltage contrast measurement are disclosed and described herein.

References to a component or system that can control a component or element that manipulates an electron beam in a manner include configuring a controller or control system or control unit to control the component to manipulate the electron beam in the manner described, and optionally using other controllers or devices (e.g., voltage and/or current sources) to control the component to manipulate the electron beam in this manner. For example, under the control of a controller or control system or control unit, a voltage source may be electrically connected to one or more components to apply an electrical potential to the components, such as control lens array 250, objective lens array 241, converging lens 231, corrector, collimator element array, and scanning deflector array, in a non-limiting list. An actuatable component, such as a stage, may be controllable to control actuation of the component to actuate and thus move relative to another component, such as a beam path, using one or more controllers, control systems, or control units.

Embodiments described herein may take the form of a series of aperture arrays or electron-optical elements arranged in an array along a beam or multiple beam paths. Such electron optical elements may be electrostatic. In one embodiment, all electron optical elements, for example the last electron optical element in the beamlet path from the beamlet forming array to the sample before, may be electrostatic and/or may be in the form of an array of apertures 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).

References to upper and lower, above and below are understood to refer to directions parallel (typically but not always perpendicular) to the upstream and downstream directions of the electron beam or beams striking the sample 208. Thus, references to upstream and downstream are intended to mean directions about the beam path independent of any gravitational field present.

An electronic device according to one embodiment of the present disclosure may be a tool that performs a qualitative assessment (e.g., pass/fail) of a sample, a tool that performs a quantitative measurement (e.g., size of a feature) of a sample, or a tool that generates a mapped image of a sample. Examples of evaluation systems are inspection tools (e.g., for identifying defects), inspection tools (e.g., for classifying defects), and metrology tools, or tools capable of performing any combination of evaluation functions associated with an inspection tool, or a metrology tool (e.g., a metrology inspection tool). The electron optical device column may be a component of an evaluation system; such as an inspection tool or a metrology inspection tool, or a portion of an electron beam lithography tool. Any reference herein to a tool is intended to encompass an apparatus, device or system comprising various components that may or may not be collocated, and may even be located in a separate room, particularly for a data processing element, for example.

The terms "beamlet" and "beamlet" are used interchangeably herein and are understood to include any radiation beam derived from a parent radiation beam by splitting or splitting the parent radiation beam. The term "manipulator" is used to include any element affecting the beamlets or paths of beamlets, such as lenses or deflectors.

References to elements aligned along a beam path or sub-beam path are understood to mean that the respective element is positioned along the beam path or sub-beam path.

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 from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims and clauses.

The following clauses are provided: clause 1: a charged particle device configured to project a charged particle multi-beam toward a sample, the charged particle device comprising: a charged particle source configured to emit a charged particle beam; a light source configured to emit light; and a charged particle optical device configured to project sub-beams of a charged particle multi-beam derived from the charged particle beam towards the sample; wherein the light source is arranged such that the light projects along a path of the beamlets (preferably the full length of the beam path of the beamlets), desirably along an optical path that passes through the charged particle optical device along the path of the beamlets so as to illuminate at least a portion of the sample.

Clause 2: the charged particle device of clause 1, comprising at least one, desirably two charged particle optical elements, the charged particle optical elements comprising respective arrays of apertures, the apertures of the respective arrays of apertures of the respective charged particle optical elements corresponding to respective beamlets of the charged particle multi-beam, desirably the light is projected through the apertures of the respective beamlets along the path of the beamlets, desirably the charged particle device comprises at least one, desirably two charged particle optical elements.

Clause 3: the charged particle device of clause 1 or 2, wherein the light source is adjacent to the charged particle source.

Clause 4: a charged particle apparatus according to any of the preceding clauses, wherein the light source is arranged such that, in plan view, the charged particle beam is radially inward of the light, e.g. at a position along the charged particle beam upstream of the charged particle optical device.

Clause 5: a charged particle device according to any preceding clause, wherein the charged particle source is located between the light source and the sample.

Clause 6: the charged particle device according to any of clauses 1-4, wherein the light source is located between the charged particle source and the sample.

Clause 7: a charged particle device according to any of the preceding clauses, wherein the light source is located at least two positions spaced apart from the charged particle beam in plan view, e.g. the light source comprises different parts configured to be located at different positions or the light source is configured to extend between the different positions.

Clause 8: the charged particle device of clause 7, wherein the positions are equally spaced apart from each other.

Clause 9: the charged particle device of clause 7 or 8, wherein the locations are at similar radial distances from the charged particle source.

Clause 10: the charged particle device according to any of clauses 7-9, wherein the position surrounds the charged particle source.

Clause 11: the charged particle device according to any of clauses 7-10, wherein the positions are continuous so as to form an arc spaced apart from the charged particle source in plan view.

Clause 12: the charged particle device according to any of clauses 7-10, wherein the positions form a ring around the charged particle source.

Clause 13: a charged particle apparatus according to any preceding clause, wherein the light source is arranged such that the light comprises a plurality of light beams, and the charged particle beam is between the plurality of light beams upstream of the charged particle optical device.

Clause 14: a charged particle device according to any preceding clause, wherein the light source is arranged such that the path or optical path of the light towards the sample is aligned with a central axis of the charged particle optical apparatus.

Clause 15: a charged particle apparatus according to any preceding clause, comprising a charged particle optical deflector configured to deflect the charged particle beam into alignment with a central axis of the charged particle optical device.

Clause 16: the charged particle apparatus of clause 15, wherein the charged particle source is offset from the central axis of the charged particle optical device.

Clause 17: the charged particle apparatus of clause 15 or 16, wherein the charged particle source is arranged to emit the charged particle beam at an angle relative to the central axis of the charged particle optical device.

Clause 18: the charged particle apparatus according to any of clauses 1-17, wherein the charged particle optical device comprises: an objective lens array comprising a plurality of objective lenses configured to focus respective beamlets of the charged particle multi-beam onto the sample, desirably the objective lens array is an electrostatic lens array comprising, for example, a plurality of electrodes arranged along the path of the beamlets, desirably the objective lens array comprises at least two plates having a plurality of apertures defined therein.

Clause 19: the charged particle apparatus of clause 18 (or clauses 1-17), wherein the charged particle optical device comprises: a beamlet forming array comprising a plate having an aperture defined therein, the aperture configured to divide the charged particle beam into a charged particle multi-beam comprising a plurality of beamlets.

Clause 20: the charged particle device of clause 19, wherein the apertures defined in the beamlet forming array have a diameter of at least 50 μm for respective beamlets of the charged particle multi-beam.

Clause 21: the charged particle device of clause 19 or 20, wherein the aperture of the beamlet forming array defines a pattern in the plate of the beamlet forming array.

Clause 22: the charged particle device of clause 21, wherein the pattern is a grid.

Clause 23: the charged particle device of clause 22, wherein the grid is hexagonal or rectilinear.

Clause 24: the charged particle apparatus of any of clauses 19-23 (or clauses 1-17), wherein the charged particle optical device comprises: a beam shaping array comprising a plate having a plurality of apertures defined therein, wherein the apertures of the beam shaping array are for shaping respective beamlets of the charged particle multi-beam.

Clause 25: the charged particle device of clause 24, wherein the beam shaping array is downstream of an upstream-most electrode of the objective lens array.

Clause 26: the charged particle device of clause 25, wherein the beam shaping array is downstream of the objective lens array.

Clause 27: the charged particle device of any of clauses 24-26, wherein the aperture of the beam shaping array is smaller in size than the aperture of the beamlet shaping array.

Clause 28: the charged particle device of clause 27, wherein the aperture of the beam shaping array has a diameter of at least 20 μm.

Clause 29: the charged particle device of clause 27 or 28, wherein the light source is configured to emit light having a wavelength, wherein the aperture of the beam shaping array has a size of at least a diffraction threshold, preferably dependent on the wavelength of the light source is configured to emit.

Clause 30: the charged particle apparatus of any of clauses 18-29 (or any of clauses 1-17), wherein the charged particle optical device comprises: a control lens array comprising a plurality of control lenses for manipulating respective beamlets of the charged particle multi-beam.

Clause 31: the charged particle device of clause 30, wherein the objective lens array is downstream of the control lens array, preferably wherein the beamlet forming array defines or provides an uppermost electrode of the control lens array or the objective lens array, or the beamlet forming array is upstream of the uppermost electrode of the control lens array.

Clause 32: the charged particle device of clause 31, wherein the beam shaping array is downstream of the control lens array.

Clause 33: a charged particle apparatus according to any preceding clause, wherein the charged particle optical device comprises: at least one detector array includes a plurality of detector elements configured to detect signal particles emitted from the sample.

Clause 34: the charged particle device of clause 33, wherein the detector elements are associated with respective beamlets of the charged particle multi-beam, and preferably a plurality of apertures are defined in the detector array, each aperture being assigned to a respective beamlet of the charged particle multi-beam.

Clause 35: a charged particle device according to any of the preceding clauses, wherein the portion of the sample illuminated by the light corresponds to a portion subsequently receiving a charged particle beam.

Clause 36: a charged particle device according to any preceding clause, wherein the charged particles are electrons.

Clause 37: a charged particle apparatus according to any preceding clause, wherein the path of the light through the aperture of a charged particle optical element of the charged particle optical device is substantially straight.

Clause 38: a charged particle device according to any of the preceding clauses, wherein apertures defined in charged particle optical elements of the charged particle optical apparatus (such as the beamlet forming array, the control lens array, the objective lens array, the beamlet forming array and/or the detector array) are aligned such that the path along which the light is projected is substantially straight.

Clause 39: a method for projecting a charged particle multi-beam toward a sample, the method comprising: emitting a charged particle beam; projecting a sub-beam of a charged particle multi-beam derived from the charged particle beam towards the sample using a charged particle optical device; emitting light; and projecting the light through the charged particle optical device along a path of the beamlets so as to illuminate the sample.

Clause 40: the method of clause 39, comprising flooding the surface of the sample with charged particles.

Clause 41: the method of clause 39 or 40, wherein the method is used to prepare the sample for voltage contrast measurement.

Clause 42: the method of any one of clauses 39 to 41, comprising: the charged particle beam is deflected to align with a central axis of the charged particle optical device.

Clause 43: the method of any of clauses 39 to 42, wherein the charged particle beam is emitted at an angle relative to the central axis of the charged particle optical device.

The above description is intended to be illustrative, and not restrictive. It will therefore be apparent to those skilled in the art that modifications may be made as described without departing from the scope of the claims set out below and the terms set out herein.

Claims (15)

1. A charged particle device configured to project a charged particle multi-beam toward a sample, the charged particle device comprising:

a charged particle source configured to emit a charged particle beam;

a light source configured to emit light;

a charged particle optical device configured to project sub-beams of a charged particle multi-beam derived from the charged particle beam towards the sample; the charged particle apparatus comprising at least one charged particle optical element comprising a respective array of apertures, the apertures in the respective array of apertures of the respective charged particle optical element corresponding to respective sub-beams of the charged particle multi-beam,

Wherein the light source is arranged such that the light projects along a path of the sub-beam through the charged particle optical device, thereby projecting along a path of the sub-beam through the aperture of a respective sub-beam of the at least one charged particle element so as to illuminate at least a portion of the sample.

2. The charged particle device according to claim 1, wherein the light source is adjacent to the charged particle source.

3. Charged particle device according to claim 1 or 2, wherein the light source is arranged such that: in plan view, the charged particle beam is radially inward of the light at a position along the charged particle beam upstream of the charged particle optical device.

4. A charged particle device according to any one of claims 1 to 3, wherein the charged particle source is located between the light source and the sample.

5. A charged particle device according to any one of claims 1 to 4, wherein the light source is located between the charged particle source and the sample.

6. Charged particle device according to any of claims 1-5, wherein the light source is located in at least two positions spaced apart from the charged particle beam in plan view, preferably the light source comprises different parts configured to be located at different positions.

7. A charged particle device according to claim 6 wherein the positions are equidistantly spaced from each other.

8. A charged particle device according to claim 6 or 7, wherein the location surrounds the charged particle source.

9. Charged particle device according to any of claims 6-8, wherein the at least two positions form a ring around the charged particle source, preferably the light source is configured to extend between the different positions.

10. Charged particle apparatus according to any one of claims 1 to 9, wherein the light source is arranged such that the light comprises a plurality of light beams and the charged particle beam is between the plurality of light beams upstream of the charged particle optical device.

11. A charged particle apparatus according to any one of claims 1 to 10, wherein the light source is arranged such that the path of the light towards the sample is aligned with the central axis of the charged particle optical device.

12. Charged particle apparatus according to any of claims 1 to 11, comprising a charged particle optical deflector configured to deflect the charged particle beam to be aligned with a central axis of the charged particle optical device.

13. Charged particle apparatus according to claim 12, wherein the charged particle source is arranged to emit the charged particle beam at an angle relative to the central axis of the charged particle optical device.

14. Charged particle apparatus according to any one of claims 1 to 13, wherein the charged particle optical device comprises:

an objective lens array comprising a plurality of objective lenses configured to focus respective beamlets of the charged particle multi-beam onto the sample.

15. Charged particle apparatus according to any one of claims 1 to 14, wherein the charged particle optical device comprises:

the beamlet forming array comprises a plate having an aperture defined therein, the aperture being configured to divide the charged particle beam into a charged particle multi-beam comprising a plurality of beamlets.