CN118414686A

CN118414686A - Charged particle optical device and projection method

Info

Publication number: CN118414686A
Application number: CN202280083344.6A
Authority: CN
Inventors: M·斯科特兹; A·V·G·曼格努斯; 任岩; E·P·斯马克曼; J·范索伊斯特
Original assignee: ASML Holding NV
Current assignee: ASML Holding NV
Priority date: 2021-12-17
Filing date: 2022-11-22
Publication date: 2024-07-30

Abstract

A charged particle optical apparatus configured to project multiple beams of charged particles, the apparatus comprising: a charged particle device that switches between: (i) An operating configuration in which the apparatus is configured to project multiple beams to the sample along an operating beam path extending from a source of the multiple beams to the sample, and (ii) a monitoring configuration in which the apparatus is configured to project multiple beams to the detector along a monitoring beam path extending from the source to the detector; wherein the monitoring beam path is diverted halfway along the operating beam path from said inspection beam path.

Description

Charged particle optical device and projection method

Cross Reference to Related Applications

The present application claims priority from EP patent application 21215700.2 filed on 12 months 17 of 2021 and EP patent application 22196958.7 filed on 9 months 21 of 2022, which are all incorporated herein by reference.

Technical Field

Embodiments provided herein relate generally to charged particle optical devices and projection methods, and in particular, to a charged particle optical device and projection method using multiple beamlets of charged particles.

Background

In the fabrication of semiconductor Integrated Circuit (IC) chips, undesirable pattern defects often occur on a substrate (i.e., wafer) or mask during the fabrication process, thereby reducing yield. Such defects may occur due to, for example, optical effects and occasional particles and subsequent processing steps such as etching, deposition or chemical mechanical polishing. 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 to inspect objects, such as to detect pattern defects. These tools typically use electron microscopy techniques such as Scanning Electron Microscopy (SEM). In SEM, a primary electron beam of relatively high energy electrons is targeted to a final deceleration step in order to land on the sample with a relatively low landing energy. The electron beam is focused as a detection spot on the sample. Interactions between the material structure at the detection point and landing electrons from the electron beam cause 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. Secondary electrons can be emitted across the sample surface by scanning a primary electron beam as a detection point over the sample surface. By collecting these secondary electrons emitted from the sample surface, the pattern inspection tool can obtain an image representing the characteristics of the material structure of the sample surface.

There is a general need to improve the characteristics of charged particle optical devices. In particular, it is desirable to monitor various characteristics of the charged particle beam, for example to provide a basis for the beam to be controlled to have the desired characteristics. This is a process that needs improvement.

Disclosure of Invention

Embodiments provided herein disclose a charged particle optical apparatus and projection method.

According to a first aspect of the present invention there is provided a charged particle optical apparatus configured to project a multi-beam of charged particles, the apparatus comprising:

Charged particle devices, can be switched between: (i) An operating configuration in which the apparatus is configured to project multiple beams to the sample along an operating beam path extending from the source of multiple beams to the sample, and (ii) a monitoring configuration in which the apparatus is configured to project multiple beams to the detector along a monitoring beam path extending from the source to the detector;

Wherein the monitoring beam path is diverted midway along the operating beam path from the inspection beam path.

According to a second aspect of the present invention there is provided a charged particle optical apparatus configured to project multiple beams of charged particles to a sample, the apparatus comprising:

A source configured to output a source beam for generating a plurality of beams;

An aperture array configured to form a plurality of beams of the multiple beams from the source beam by blocking a proportion of the source beam from projecting toward the sample; and

A detector configured to measure at least a parameter of at least a portion of the blocked proportion of the source beam.

According to a third aspect of the present invention there is provided a charged particle optical apparatus configured to project multiple beams of charged particles to a sample, the apparatus comprising:

Charged particle apparatus comprising:

an objective lens array configured to project multiple beams onto a location on a sample;

a plurality of converters configured to receive signal particles emitted from the sample and generate light in response to the received signal particles; and

A light guide arrangement comprising a mirror defining a plurality of apertures to allow the multiple beams to pass through the mirror towards the sample; and

A light sensing assembly to which the light guide arrangement is configured to guide light generated by the converter, wherein the light sensing assembly comprises:

An evaluation sensor and a detector configured to detect the light generated by the converter, respectively; and

A beam splitter configured to split the light generated by the converter into beams for evaluation of the sensor and the detector.

According to a fourth aspect of the present invention there is provided a method of projecting multiple beams of charged particles, the method comprising:

Using a charged particle device in an operating configuration to project multiple beams to a sample along an operating beam path from a source of the multiple beams to the sample; and

Using the apparatus in a monitoring configuration to project multiple beams to a detector along a monitoring beam path extending from a source to the detector;

Wherein the monitoring beam path is diverted midway along the operating beam path from the operating beam path.

According to a fifth aspect of the present invention there is provided a method of projecting multiple beams of charged particles, the method comprising:

in an operating configuration, projecting the multiple beams to the sample along an operating beam path from a source of the multiple beams to the sample; and

In the monitoring configuration, multiple beams are projected to the detector along a monitoring beam path from the source to the detector, and the monitoring beam path is diverted midway along the operating beam path from the operating beam path.

According to a sixth aspect of the present invention there is provided a method of projecting multiple beams of charged particles onto a sample, the method comprising:

outputting a multi-beam source beam using a source;

Using an aperture array to form a plurality of beams of the multiple beams from the source beam by blocking a proportion of the source beam from projection towards the sample; and

A detector is used to measure at least a parameter of at least a portion of the blocked proportion of the source beam.

According to a seventh aspect of the present invention there is provided a method of projecting multiple beams of charged particles onto a sample, the method comprising:

outputting a multi-beam source beam from a source;

forming a plurality of beams of the multiple beams from the source beam by blocking a proportion of the source beam from projecting toward the sample at the aperture array; and

A detector is desirably used to measure at least a portion of the blocked proportion of the source beam.

According to an eighth aspect of the invention there is provided a method of projecting multiple beams of charged particles onto a sample, the method comprising:

Using an array of objective lenses configured to project multiple beams onto locations on a sample;

Using a plurality of converters, desirably scintillators, to receive signal particles emitted from the sample and generate light in response to the received signal particles;

Using a light guiding arrangement to guide light generated by the converter to the light sensing assembly, wherein the light guiding arrangement comprises a mirror defining a plurality of apertures to allow the multiple beams to pass through the mirror towards the sample; and

Using a beam splitter to split the light generated by the converter into a plurality of light beams for evaluating the sensor and the detector; and

An evaluation sensor and detector are used to detect the light generated by the converter.

According to a ninth aspect of the present invention there is provided a method of projecting multiple beams of charged particles onto a sample, the method comprising:

Desirably using an objective lens array to project multiple beams onto locations on the sample;

Receiving signal particles emitted from a sample and generating light in response to the received signal particles, desirably using a plurality of converters, desirably scintillators;

directing the generated light to a light sensing assembly using a light guiding arrangement, wherein the light guiding arrangement comprises a mirror defining a plurality of apertures, thereby allowing multiple beams to pass through the mirror towards the sample; and

The beam splitter is desirably used to split the generated light into a plurality of light beams, preferably for evaluating the sensors and detectors; and

An evaluation sensor and detector are desirably used to detect the generated light.

Drawings

The above and other aspects of the present disclosure will become more apparent from the description of exemplary embodiments thereof, taken in conjunction 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 apparatus as part of the exemplary charged particle beam inspection apparatus of fig. 1.

Fig. 3 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 4 is a schematic cross-sectional view of an objective of an inspection device according to one embodiment.

Fig. 5 is a bottom view of the objective lens of fig. 4.

Fig. 6 is a bottom view of a modification of the objective lens of fig. 4.

Fig. 7 is an enlarged schematic cross-sectional view of a detector incorporated in the objective lens of fig. 4.

FIG. 8 is a schematic diagram illustrating a portion of an electro-optical device including a plurality of transducers and a light guide arrangement.

Fig. 9 is a schematic diagram illustrating an example location of a transducer.

Fig. 10 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 11 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 12 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 13 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 14 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 15 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 16 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 17 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 18 is a schematic diagram illustrating a portion of an electro-optical device including a plurality of transducers and a light guide arrangement.

Fig. 19 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

FIG. 20 is a schematic diagram of an exemplary monitoring component.

Fig. 21 is a schematic plan view of an exemplary monitoring component.

Fig. 22 is a schematic view of an exemplary blocking element.

Fig. 23 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 24 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment.

Fig. 25 is a schematic diagram of an exemplary detector.

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 the same reference numerals in different drawings denote the same or similar elements, unless otherwise indicated. 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 of the invention as set forth in the accompanying claims.

The enhanced computational power of electronic devices can be achieved by significantly increasing the packing density of circuit components (such as transistors, capacitors, diodes, etc.) on an IC chip, which reduces the physical size of the device. This is achieved by increasing the resolution, enabling smaller structures to be fabricated. For example, the IC chip of a smartphone (which is the size of a thumb nail and available in 2019 or before) may include over 20 hundred million transistors, each less than 1/1000 of the size of human hair. 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 greatly affect the functionality of the final product. Only one error may cause device failure. The goal of the manufacturing process is to increase the overall yield of the process. For example, to obtain a 75% yield for a 50 step process (where one step may indicate the number of layers formed on the wafer), the yield for each individual step must be greater than 99.4%. If the yield of each individual step is 95%, the overall process yield will be as low as 7%.

While high process yields are required in IC chip manufacturing facilities, it is also essential 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, detection and identification of micro-and nano-scale defects at high throughput by inspection devices such as scanning electron microscopes ('SEM') is critical to maintaining high yields and low cost.

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

An embodiment of a 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. Although the description and drawings relate to electron optical devices, it is to be understood that the embodiments are not intended to limit the disclosure to particular charged particles. Thus, references to electrons throughout this document may be more generally considered to be references to charged particles, which are not necessarily electrons.

Referring now to fig. 1, fig. 1 is a schematic diagram illustrating an exemplary charged particle beam inspection apparatus 100. The charged particle beam inspection apparatus 100 of fig. 1 includes a main chamber 10, a load lock chamber 20, an electron optical device 40, an Equipment Front End Module (EFEM) 30, and a controller 50. The electron optical device 40 is 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 port(s). The first load port 30a and the second load port 30b may, for example, receive a substrate Front Opening Unified Pod (FOUP) containing a substrate (e.g., a semiconductor substrate or a substrate made of other material (s)) or a sample (substrate, wafer, and sample are collectively referred to hereinafter as "sample"). One or more robotic arms (not shown) in the EFEM 30 transport 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 local air 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) transport the sample from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown). The main chamber vacuum pump system removes gas particles 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 transported to an electron optical device, through which the sample can be inspected. The electron optics 40 may be multi-beam electron optics.

The controller 50 is electrically connected to the electro-optical device 40. The controller 50 may be a processor (such as a computer) configured to control the charged particle beam inspection device 100. The controller 50 may also include 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 is to be understood that the controller 50 may be part of the structure. The controller 50 may be located in one of the constituent elements of the charged particle beam inspection device, or it may be distributed over at least two constituent elements. Although the present disclosure provides an example of a main chamber 10 housing an electron optical apparatus, it should be noted that the broadest aspects of the present disclosure are not limited to chambers housing electron optical apparatus. Instead, it is to be appreciated that the foregoing principles may also be applied to other tools and other arrangements of devices operating at the second pressure.

Referring now to fig. 2, fig. 2 is a schematic diagram illustrating an exemplary multi-beam electron optical device 40 that is part of the exemplary charged particle beam inspection device 100 of fig. 1. Multi-beam electron optics 40 (also referred to herein as apparatus 40) includes electron source 201, projection device 230, motorized stage 209, and sample holder 207. The electron source 201 and the projection device 230 may together be referred to as an illumination device. 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 optical apparatus 40 further comprises an electron detection device 240.

The electron source 201 may include a cathode (not shown) and an extractor or anode (not shown). During operation, the electron source 201 is configured to emit electrons from the cathode as primary electrons. The primary electrons are extracted or accelerated by an extractor and/or anode to form a source beam (or primary electron beam) 202.

The projection device 230 is configured to convert the source beam 202 into a plurality of beamlets 211, 212, 213 and direct each beamlet onto the sample 208. Although three beamlets are illustrated 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 charged particle beam inspection apparatus 100 of fig. 1, such as the electron source 201, the electron detection device 240, the projection device 230, and the motorized stage 209. The controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals to manage the operation of the charged particle beam inspection device, including the charged particle multi-beam device.

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 across respective scanning region scanning detection points 221, 222, and 223 in a section of the surface of sample 208. Electrons including secondary electrons and backscattered electrons are generated from the sample 208 in response to the primary beamlets 211, 212 and 213 being incident on detection points 221, 222 and 223 on the sample 208. The secondary electrons typically have an electron energy of 50eV or less and the electron energy of the backscattered electrons is typically between 50eV and the landing energy of the primary beamlets 211, 212 and 213.

The electron detection device 240 is configured to detect secondary electrons and/or backscattered electrons and generate corresponding signals that are sent to the controller 50 or a signal processing system (not shown), for example, to construct an image of a corresponding scanned region of the sample 208. Desirably, the electronic detection device is incorporated into the projection apparatus. Alternatively, it may be separate therefrom, with a secondary electron optical column (or device) being provided to direct secondary electrons and/or backscattered electrons to the electron detection device.

The controller 50 may include an image processing system including an image acquirer (not shown) and a storage device (not shown). For example, the controller may include a processor, computer, server, mainframe, terminal, personal computer, any kind 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 may be communicatively coupled to an electronic detection device 240 of the apparatus 40 that allows signal communication, such as an electrical conductor, fiber optic cable, portable storage medium, IR, bluetooth, internet, wireless network, radio, or the like, or a combination thereof.

The image acquirer may acquire one or more images of the sample based on the imaging signals received from the electronic detection device 240. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image including a plurality of imaging regions. The single image may be stored in a storage device. A single image may be an original image that may be divided into a plurality of regions. Each of the regions may include an imaging region containing features of the sample 208. The acquired images may include multiple images of a single imaged region of the sample 208 sampled multiple times over a period of time. The plurality of images may be stored in a storage device. The controller 50 may be configured to perform the image processing steps using multiple images of the same location of the sample 208.

The controller 50 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 corresponding 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 inspection. The reconstructed image may be used to reveal various features of internal or external structures of the sample 208. 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. The controller 50 may enable the motorized stage 209 to move the sample 208 in one direction at least during sample inspection, preferably continuously, e.g. at a constant speed. The controller 50 may control the movement of the motorized table 209 such that it varies the speed of movement of the sample 208 according to various parameters. For example, the controller may control the speed of the table (including its direction) based on the characteristics of the inspection step of the scanning process.

Fig. 3 is a schematic diagram of an evaluation device comprising an electron source 201 and an electron optical apparatus (or electron optical column). (in another arrangement, the source is part of an electro-optical device). The electro-optical device includes a plurality of electro-optical elements. An electron optical element is any element that affects (e.g., directs, shapes, or focuses) an electron beam, and an electric and/or magnetic field may be used. The electron source 201 directs electrons to an array of converging lenses 231 that form part of an electron optical device. The electron source 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 configuration based on EP1602121A1, which is incorporated herein by reference in its entirety for the disclosure of a lens array dividing an electron beam into a plurality of beamlets, wherein the array provides a lens for each beamlet. Thus, the converging lens array acts as a beam divider, beam splitter, beam generator or beam splitter. The converging lens array may take the form of at least two plates acting as electrodes, the apertures in each plate being aligned with each other and corresponding to the position of the beamlets. At least two plates are maintained at different electrical potentials during operation to achieve the desired lens effect. Thus, the plate has an array of apertures, each aperture corresponding to a path of a beamlet. The plate positioned furthest upstream is an array of apertures configured to act as a beam splitter and may be referred to as a beam limiting aperture. In a different arrangement, the beam splitter may be part of or associated with a converging lens array, having the function of being separate from the lensing of the sub-beams. Between the plates of the converging lens array are electrically insulating plates, for example made of an insulating material such as ceramic or glass, with one or more apertures for the beamlets.

In an arrangement, which may be referred to as an Einzel lens, the converging lens array is formed of three plate arrays, where the charged particles have the same energy as they enter and leave each lens. The beam energy is the same as it enters and exits the Einzel lens. Thus, chromatic dispersion occurs only within the Einzel 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 low (e.g., a few millimeters), the effect of such aberrations is small or negligible.

Each converging lens in the array directs electrons into a respective sub-beam 211, 212, 213, which is focused at a respective intermediate focus 233. The beamlets diverge with respect to each other. At intermediate focus 233 is deflector 235. The deflector 235 is positioned in the beamlet path at or at least around the location of the corresponding intermediate focus 233 or focal point (i.e., focused point). The deflector is positioned in the beamlet path at the intermediate image plane of the associated beamlet, i.e. at its focal point or focal point. 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 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 also be referred to as a collimator or collimator deflector. The deflector 235 effectively collimates the paths of the beamlets such that, upstream of the deflector, the beamlet paths diverge with respect to each other. Downstream of the deflector, the beamlet paths are substantially parallel with respect to each other, i.e. substantially collimated. A suitable collimator is the deflector disclosed in EP application 20156253.5 filed on 7, 2, 2020, which is incorporated herein by reference in its part for applying the deflector to a multi-beam array.

Below the deflector 235 (i.e. downstream of the source 201 or further from the source 201) there is a control lens array 250, which control lens array 250 comprises a control lens 251 for each beamlet 211, 212, 213. The control lens array 250 may include at least two (e.g., three) plate electrode arrays connected to respective potential sources. 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 lenses 234, each objective lens 234 in the objective lenses 234 directing a respective sub-beam 211, 212, 213 onto the sample 208. The control lens pre-focuses the beamlets (e.g., applies a focusing action to the beamlets before they reach the objective 234). Prefocusing may reduce the divergence of the beamlets or increase the convergence rate of the beamlets. The lens array and the objective lens array are controlled to operate together to provide a combined focal length. The combined operation without intermediate focus may reduce the risk of aberrations. Note that references to reduction rate and opening angle are intended to refer to variations in the same parameters. In an ideal arrangement, the product of the reduction rate and the corresponding opening angle is constant over a range of values.

The objective 234 is arranged in an objective array. The objective 234 may be configured to demagnify the electron beam by a factor greater than 10, desirably in the range of 50 to 100 or more. The objective 234 may be an Einzel lens. At least the chromatic aberration generated in the beam by the converging lens and the corresponding downstream objective lens can cancel each other out.

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

Optionally, a scanning deflector array 260 is provided between the control lens array 250 and the array of objective lenses 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.

The apparatus of fig. 3 may be configured to control landing energy of electrons on a sample. The landing energy may be selected to increase the emission and detection of secondary electrons depending on the nature of the sample being evaluated. The controller provided for controlling the objective 234 may be configured to control landing energy by varying the potential applied to the electrodes controlling the lens and the objective. The control lens and the objective lens work together and may be referred to as an objective lens assembly. The landing energy may be selected to increase the emission and detection of secondary electrons depending on the nature of the sample being evaluated. The controller may be configured to control the landing energy to any desired value or a desired one of a plurality of predetermined values within a predetermined range. In one embodiment, the landing energy may be controlled to a desired value in the range of 1000eV to 5000 eV.

Desirably, the landing energy is varied primarily by controlling the energy of electrons exiting the control lens. The potential difference within the objective lens is preferably kept constant during this change so that the electric field within the objective lens remains as high as possible. In addition, the potential applied to the control lens can be used to optimize the beam opening angle and demagnification. The control lens may also be referred to as a refocusing lens, as it may be used to correct the focus position in accordance with the change in landing energy. The use of a control lens array may enable the objective lens array to be operated at its optimal electric field strength. Details of electrode structures and potentials that may be used to control landing energy are disclosed in EPA 20158804.3, incorporated herein by reference.

The landing energy of the electrons can be controlled in the system of fig. 3 because any off-axis aberrations generated in the beamlet path are generated in the converging lens 231, or at least mainly in the converging lens 231. The objective 234 of the system shown in fig. 3 need not be an Einzel lens. This is because off-axis aberrations are not generated in the objective lens when the beam is collimated. Off-axis aberrations can be better controlled in the converging lens than in the objective 234. By making the converging lens 231 substantially thinner, the contribution of the converging lens to off-axis aberrations (particularly off-axis chromatic aberrations) can be minimized. The thickness of the converging lens 231 may be varied to tune the chromatic aberration off-axis contribution to balance the other contributions of chromatic aberration in the respective beamlet paths. Accordingly, the objective 234 may have two or more electrodes. The beam energy upon entering the objective lens may be different from the energy leaving the objective lens, for example to provide a deceleration objective lens. Furthermore, when two electrodes are used, as few electrodes as possible are used, enabling the lens array to occupy a smaller volume.

In some embodiments, the electron optical apparatus further comprises one or more aberration correctors that reduce one or more aberrations in the beamlets. In one embodiment, each of the at least a subset of the aberration correctors is positioned in or directly adjacent (e.g., in or adjacent to an intermediate image plane) to a respective one of the intermediate foci. 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 than is available elsewhere, i.e. upstream or downstream of the intermediate plane (or than is available in alternative arrangements without an intermediate image plane).

In one embodiment, an aberration corrector positioned in or directly adjacent to the intermediate focus (or intermediate image plane or focal point) comprises a deflector for correcting the source 201 which appears to be in different positions for different beams. The corrector may be used to correct for macroscopic aberrations caused by the source that prevent good alignment between each beamlet and the corresponding objective lens. In some cases, it is desirable to position the corrector as far upstream as possible. In this way, small angular corrections can produce large displacements at the sample, so that weaker correctors can be used. Desirably, the corrector is positioned to minimize the introduction of additional aberrations. Additionally or alternatively, other non-uniformities in the source beam may be corrected; that is, aberration in source beam uniformity can be corrected.

The aberration corrector may correct other aberrations that prevent proper column alignment. Such aberrations may also lead to misalignment between the beamlets and the corrector. For this reason, 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 or directly adjacent to one or more of the converging lenses 231). This is desirable because at or near the converging lens 231, aberrations also do not cause a shift of the corresponding beamlets, as the converging lens 231 is vertically close to or coincident with the beam aperture. That is, correction of any angular error by the corrector will require less positional displacement than if the corrector were positioned further downstream. Correcting such aberrations further downstream, such as at an intermediate focus, may be affected by poor alignment between the beamlets 211, 212, 213 and the corrector. However, a challenge in positioning the corrector at or near the converging lens 231 is that each beamlet has a relatively large cross-sectional area and a relatively small pitch at this location relative to a further downstream location. With a volume limitation, the corrector array or additional corrector array may be located away from these preferred positions, such as between the converging lens array and the intermediate focus position.

In some embodiments, each of at least a subset of the aberration correctors is integrated with or directly adjacent to one or more of the objective lenses 234. In one embodiment, 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 one or more of the objectives 234 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 aberration corrector may be a CMOS based individually programmable deflector as disclosed in EP2702595A1 or a multipole deflector array as disclosed in EP2715768A2, the description of the beamlet manipulator in both documents being incorporated herein by reference. There may be an aberration corrector of this design for each beamlet, i.e. a separate beamlet corrector. Individual beamlet correctors may be in an array across multiple beams, which may be referred to as a corrector array.

In one embodiment, the objective lens array mentioned in the previous embodiments is an array objective lens. Each element in the array is a microlens that operates on a different beam or group of beams in the multiple beams. The electrostatic array objective has at least two plates, each plate having a plurality of apertures or bores. The location of each hole in a plate corresponds to the location of a corresponding hole in another plate. Corresponding apertures are used on the same beam or group of beams in the multiple beams. A suitable example of a lens type for each element in the array is a dual electrode deceleration lens. Each electrode itself may be considered a lens; each electrode may be considered an electro-optical element (or electro-optical component). Between the plates (e.g. electrodes) of the objective lens array are electrically insulating plates, e.g. made of insulating material such as ceramic or glass, with one or more apertures for the beamlets.

The bottom electrode of the objective lens is a chip detector, such as a CMOS chip detector, integrated into the multi-beam manipulator array. The integration of the detector array into the objective replaces the secondary column. The chip is preferably oriented to face the sample (since the distance between the sample and the bottom of the electron optical system is small (e.g., 100 μm)). In one embodiment, a capture electrode is provided for capturing a secondary electronic signal. The capture electrodes may be formed in metal layers of devices on and/or in the chip, such as CMOS devices. The trapping electrode may form the bottom layer of the objective lens. The capture electrode may form a bottom surface in a detector chip (e.g., a CMOS chip). The CMOS chip may be a CMOS chip detector. The chip (e.g., CMOS chip) may be integrated into the sample-facing surface of the objective lens assembly. The capture electrode is an example of a sensor unit for detecting secondary electrons. The trapping electrode may be formed in other layers. The power and control signals of an integrated device (e.g., CMOS) on a chip may be connected to the integrated device through a through silicon via. For robustness, the bottom electrode is preferably composed of two elements: chips (e.g., CMOS chips) and passive Si plates with holes. The plate shields the integrated device, e.g., CMOS, from high electric fields.

An exemplary embodiment is shown in fig. 4, fig. 4 illustrates a multi-beam objective 401 in a schematic cross-section. On the output side of the objective lens 401, i.e. the side facing the sample 208, a detector module 402 is provided. The detector module 402 is one example of an electronic detection device. Fig. 5 is a bottom view of a detector module 402, the detector module 402 comprising a substrate 404, a plurality of capture electrodes 405 provided on the substrate 404, each capture electrode 405 surrounding a beam aperture 406. The beam aperture 406 is large enough not to block any primary electron beam. The capture electrode 405 may be considered as an example of a sensor unit that receives a back-scatter or secondary electrode and generates a detection signal, in this case a current. The beam aperture 406 may be formed by etching through the substrate 404. In the arrangement shown in fig. 5, the beam apertures 406 are shown in a rectangular array. The beam apertures 406 may also be arranged differently, for example in the form of a hexagonal close-packed array as depicted in fig. 6.

Fig. 7 depicts a portion of the detector module 402 on a larger scale in cross-section. The capture electrode 405 forms the bottommost (i.e., closest to the sample) surface of the detector module 402. In operation, the array of capture electrodes 405 faces the sample 208. A logic layer 407 is provided between the trapping electrode 405 and the body of the silicon substrate 404. The logic layer 407 may include amplifiers, such as transimpedance amplifiers, analog-to-digital converters, and readout logic. In one embodiment, there is one amplifier and one analog-to-digital converter per capture electrode 405. The logic layer 407 and the capture electrode 405 may be fabricated using a CMOS process, where the capture electrode 405 forms the final metallization layer.

A wiring layer 408 is provided on the back side of the substrate 404 and is connected to the logic layer 407 through a through-silicon via 409. The number of through silicon 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. Wiring layer 408 may include control lines, data lines, and power lines. It is noted that despite the beam aperture 406, there is still 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 module 402.

Fig. 4 depicts a three-electrode objective lens, but it is understood that any other form of objective lens may be used, for example, a two-electrode lens.

In another arrangement, alternatively or additionally, the detector array is associated with another electrode of the objective lens array. The detector array may additionally or alternatively be associated with another plate, such as an electrode (such as a lens electrode) associated with an objective lens integrated in the objective lens array or upstream of a proximity objective lens (such as a control lens array). In one arrangement, additionally or alternatively, the detector array is located upstream of the objective array and any electron optical elements associated with the objective. The detector elements of the detector array may be associated with respective beamlets. The detector elements may include charge detection, scintillator and PIN detection elements. In an arrangement where the detector elements comprise scintillators, the detectors may be arranged to one side of the beamlet path such that the beamlets pass to one side of the respective detector element.

The deflection element may be located between the detector array and the objective lens, such as a wien filter, e.g. a wien filter array. Such a wien filter allows the non-deflected beamlets to pass through the wien filter towards the sample, but directs signal particles from the sample to the detector element. An optical converter (e.g., an optical detector) may be positioned to convert light generated by the scintillator into an electronic signal. The optical converter may be coplanar and even in direct contact with the scintillation detector element. Such an optical converter is described in EP application 21183803.2 filed at 7/5 of 2021, which is incorporated by reference at least with respect to the optical converter associated with a scintillation detector and the architecture and use of the detector for detecting signal particles.

In an alternative embodiment, a converging lens array may not be provided. Instead, beamlets 211, 212, 213 may be generated by the source beam at the objective array or at an associated plate (e.g., electrode) associated with the objective array, upstream of the objective array, and in the vicinity of the objective array. Controlling the lens array may be one example of such an associated plate. Between the adjoining plates is an electrically insulating plate, for example made of an insulating material such as ceramic or glass, with one or more apertures for the beamlets. The objective lens array may have an upper beam limiter and a beam shaping limiter. In this arrangement, the source 201 provides a beam of charged particles (e.g., electrons). For example, a beamlet may be derived from the beam using a beam limiter (e.g., an upper beam limiter) defining an array of beam limiting apertures. The upper beam limiter defines an array of beam limiting apertures and acts as a beam splitter or sub-beamgenerator. The upper beam limiter may be located, for example, upstream of the deflector 235 in the array, for example with a deflector for each beamlet. Downstream of the upper beam limiter is a beam shaping limiter. Another electron optical element, such as an objective lens array, is located between the upper beam limiter and the beam shaping limiter. The beam shaping limiter may be closer to the surface of the electron optical device that faces the sample during operation than the objective lens array.

In some embodiments illustrated in fig. 3, deflector 235 is the first deflecting or focusing electron optical array element in the beam path downstream of source 201. In another arrangement, a macro collimator may be provided upstream of the objective array. Thus, the macro collimator operates on the beams from the source before generating the multiple beams. A magnetic lens may be used as a macro collimator. When a macro collimator is provided, the collimator deflector 235, e.g. downstream of the upper beam limiter, may be omitted.

In another arrangement, a macro-scan deflector may be provided upstream of the objective array. Thus, the macro-scan deflector operates on the beams from the source before generating the multiple beams. The macro scan deflector may be downstream of the macro collimator. When the macro scan deflector is provided, the scan deflector array 260 may be omitted.

In other embodiments, a macro-scan deflector and scan deflector array 260 is provided. In this arrangement, scanning of the beamlets over the sample surface may be achieved by controlling together (preferably synchronously) the macro-scan deflector and the scan deflector array 260.

As described above, multiple electron optics in an electron optics column (such as a multi-beam SEM or a multi-beam lithography machine) are typically required to generate multiple beams. The electron optical components form electron optical apertures, lenses, deflectors, and perform other manipulation of the beam. These electro-optical components may comprise an array of electro-optical elements (one or more of which may be in the form of MEMS elements) and need to be accurately aligned to allow all beams to land on a target (e.g. a sample or detector). Electron-optical components in close proximity to each other, such as electron-optical arrays, may be stacked on top of each other and alignable. Some techniques for aligning electron optical components include corrector components, such as, for example, corrector arrays in electron optical devices described herein. Such components may be operable to achieve improved alignment. One such electro-optical component is a collimator, which may have the functions of alignment and collimation. Additionally or alternatively, other correctors, e.g., upstream of the beam-limiting aperture array, such that the corrector operates on the source beam, present in and associated with the converging lens (e.g., converging lens array), such as proximate the converging lens, collimator (e.g., associated with intermediate focus 233), and downstream of the objective lens array.

Fig. 8 schematically depicts a scintillator-based detector approach that facilitates close packing of beams at a sample 208. For ease of depiction, fig. 8 depicts only a portion of an example electron optical device in the vicinity of the electron optical device's objective lens array 403 and sample 208. The depicted objective array 403 has two plates or electrodes 301, 302, which is the minimum number of plates of the actual objective array. However, there may be as many plates as the designer can choose, for example three, four, five, seven or ten or more. Each plate may provide an additional degree of freedom for controlling the beamlet array. In one arrangement, two or more plates may be operated as an objective lens, and the remaining plates proximate to the plate selected as an objective lens may be associated plates associated with an objective lens array, and may be designated by different names, such as controlling the lens array.

The electron optical arrangement may comprise an aperture array (to form multiple sub-beams from the source beam) and a collimator upstream of the region of the electron optical device shown in fig. 8. An aperture array generates a plurality of beams. The collimator collimates the path of the beam. The detector in this example includes a plurality of transducers 410 and light sensors 412. The converter 410 may be a scintillator. The plurality of converters 410 may be referred to as a converter array. The dashed path depicts a representative path of the beam. The transducer 410 receives signal particles emitted from the sample 208. The converter 410 generates light 411 in response to the received signal particles. The converter 410 may include a luminescent material that absorbs energy from incident particles and re-emits the absorbed energy as light. The light sensor 412 detects the light 411 generated by the converter 410, thereby indirectly detecting signal particles.

A light guide arrangement is provided which reduces or avoids the need for optical fibres. The light guide arrangement guides the light 411 generated by the converter 410 to the light sensor 412. The light guide arrangement comprises a mirror 414. The light 411 generated by the converter 410 is reflected by the mirror 414 towards the light sensor 412. (thus, the mirror is one embodiment of a radiation reflecting surface that reflects radiation having a wavelength corresponding to the scintillator). Optics 418 may be provided for controlling the propagation of reflected light between the mirror 414 and the light sensor 412. Optics 418 may, for example, image the reflected light onto light sensor 412. This arrangement allows the photosensor 412 to be positioned outside (i.e., away from) the portion of the column of devices through which the beam passes, as schematically indicated by the laterally protruding housing 420 in fig. 8. The light sensor may be remote from the electromagnetic field of the electron optical component. Electromagnetic interference between the light sensor and the electron-optical component can be reduced, if not prevented. Thus, the light sensor 412 may be provided at a radially distal position relative to the beam path. For example, the spacing between the central longitudinal axis of the plurality of beams and the radially outermost one of the beams is less than the distance from the longitudinal axis to the photosensor 412. Thus, the light sensor 412 does not limit the close packing of the beams. Furthermore, the light sensor 412 may be easily implemented because there is less spatial restriction at the location of the light sensor 412 than at locations closer to the longitudinal axis. Furthermore, the mirrors redirect light without the need for optical fibers or the like, further reducing the restriction on close packing of the beams. The light sensor 412 may be provided within or outside the vacuum region, such as providing a window or other arrangement to transmit light from the mirror 414 (in the vacuum region) to the light sensor 412 (outside the vacuum region).

For example, the photosensor 412 may be implemented using any of a variety of known devices for detecting light, such as a Charge Coupled Device (CCD). In some arrangements, the light sensor 412 includes an array of photodiodes. The photosensor 412 can be configured or selected to have a wavelength sensitivity that matches the scintillator spectrum (i.e., the wavelength spectrum of photons emitted by the scintillator element). Various known arrangements of suitable data lines 422 may be provided for extracting data representing the detected light.

In some arrangements, the light guide arrangement includes one or more optical fibers between the mirror 414 and the light sensor 412. The optical fiber collects light from the mirror and directs the light to a location remote from the portion of the column of devices through which the beam passes, e.g., remote from the path along which the beam is disposed. The use of optical fibers in this manner provides further flexibility in the positioning of the optical sensors 412 (and associated electronics and/or data lines). The light sensor 412 may be positioned farther from the column of devices. The light sensor 412 may be positioned out of direct line of sight of the mirror 412.

In some arrangements, the light guide arrangement and at least a portion of the objective lens array are structurally connected. The support of the mirror 414 may be structurally connected to and/or support at least the closest electrode of the objective array 403. For example, the support of the mirror 414 may be structurally connected to the support of the nearest electrode. In different arrangements, the mirrors have independent and separate structural supports.

To allow the plurality of beams to pass through the mirror 414, the mirror 414 is configured to define a plurality of apertures 416 through the mirror 414. Aperture 416 is positioned to allow multiple beams to pass through mirror 414 toward sample 208. Thus, each aperture 416 may correspond to (i.e., be positioned to allow the respective one or more beams to pass through) the respective one or more beams.

In some arrangements, the transducers 410 are each configured to receive signal particles arising from interactions between the sample 208 and respective individual ones of the plurality of beams from the aperture array 401. Thus, for one position of the column of devices relative to the sample 208, each transducer 410 receives signal particles from a different portion of the sample 208.

In some arrangements, the converters are arranged in an array. The array is orthogonal to the paths of the plurality of beams (i.e., substantially orthogonal to each of the paths). The array may comprise a two-dimensional pattern. The two-dimensional pattern may take the form of a grid. The arrangement may be a hexagonal or rectilinear grid. The transducer array may geometrically correspond to the beam arrays 211, 212, 213. The converter may take the form of a ring surrounding an aperture for the path of the corresponding primary beam (or more than one primary beam). Thus, the aperture may be defined by each scintillator. Each transducer element in the transducer array may have the form of a ring.

In one arrangement, the transducer 410 is positioned upstream of, or associated with, at least one electrode 302 of the objective array 403. The transducer 410 may be positioned upstream of the electrode 302 facing the sample 208. In some arrangements, as illustrated in fig. 8, the transducer 410 is supported by one of the electrodes 301 of the objective lens array 403. In the example shown, the transducer 410 is supported by the electrode 301 of the objective lens array 403 furthest from the sample 208. The transducer 410 is at the same level as the uppermost portion of the electrode 301 (furthest from the sample 208). In one embodiment, the transducer 410 is supported by the most upstream electrode associated with the objective lens array. In some arrangements, the scintillator 410 is positioned upstream of the objective array 403 (or even the most upstream electrode associated with the objective array), such as directly upstream thereof (e.g., a small distance therefrom and/or no intervening elements between the transducer 410 and the objective array 403, or the most upstream electrode associated with the objective array 403).

Fig. 9 shows other example positions of the transducer 410 relative to a portion of the example objective lens array 403. Although two electrodes 301, 302 are depicted, the position of the transducer may be applied to electrodes of an objective array having any number of electrodes and any number of electrodes that may be associated with the objective array in order to access the objective array. The vertical dashed lines depict the paths of two example beams through respective objectives in the objective array 403. Five example positions of the transducer 410 are shown. The transducer 410 may be provided at a single one of the five positions or at more than one position. Some locations are more advantageous than others. Less advantageous locations may be used in combination with other locations to capture sufficient signals. The transducer 410 may be provided below the electrode 302 of the objective lens array 403 closest to the sample 208 (e.g., facing the sample 208). The transducer 410 may be positioned above the electrode 302 closest to the sample 208 and below the electrode 301 adjacent to the electrode 302 closest to the sample 208. In this case, the transducer 410 may be closer to and/or attached to the electrode 302 closest to the sample 208. Alternatively, the transducer 410 may be closer to and/or attached to the adjacent electrode 301. Alternatively, transducer 410 may be positioned above adjacent electrode 301, either directly adjacent to adjacent electrode 301 and/or attached to adjacent electrode 301, or separated from adjacent electrode 301 and/or positioned further.

In one arrangement, each transducer 410 surrounds an aperture 417, the aperture 417 being configured to allow a respective one of the plurality of beams to pass through. The aperture 417 may be defined in the electrode of the objective lens or in a separate aperture body. Each transducer in this arrangement surrounds the path of the respective beam. Each transducer 410 may be positioned to receive signal electrons that generally propagate along the path of the beam in a direction opposite the beam. Thus, the signal electrons may impinge on the transducer 410 in the annular region. Due to the aperture for allowing the corresponding primary beam to pass in the opposite direction, the signal electrons do not impinge on the central region of the ring.

In some arrangements, each transducer 410 includes multiple sections. The different portions may be referred to as different regions. Such a translator 410 may be referred to as a partition translator. The portion of the transducer may surround an aperture defined in the transducer. The signal particles captured by the transducer portion may be combined into a single signal or used to generate separate signals.

The zone switch 410 may be associated with one of the beams 211, 212, 213. Thus, portions of one transducer 410 may be configured to detect signal particles emitted from the sample 208 that are associated with one of the beams 211, 212, 213. A transducer comprising a plurality of portions may be associated with one of the apertures in at least one electrode of the objective lens array 403. More specifically, a transducer 410 comprising multiple sections may be arranged around a single aperture.

The sections of the zone switch may be separated in a variety of different ways, such as radial, annular, or any other suitable way. Preferably, the portions have similar angular sizes and/or similar areas and/or similar shapes. The separate portions may be provided as a plurality of segments, a plurality of annular portions (e.g., a plurality of concentric rings or a plurality of rings), and/or a plurality of sector portions (i.e., radial portions or sectors). The transducer 410 may be divided radially. For example, the transducer 410 may be provided as a ring-shaped section comprising 2, 3, 4 or more sections. More specifically, the transducer 410 may include an inner annular portion surrounding the aperture and an outer annular portion radially outward of the inner annular portion. Alternatively, the converter 410 may be divided angularly. For example, the scintillator 410 can be provided as a sector portion including 2, 3, 4, or more portions (e.g., 8, 12, etc.). If the transducer 410 is provided as two sectors, each sector portion may be a semicircle. If the converter 410 is provided as four sectors, each sector portion may be a quadrant. In the example, the converter 410 is divided into quadrants, i.e., four sector portions. Alternatively, the converter 410 may be provided with at least one segmented portion.

Providing multiple sections concentrically or otherwise may be beneficial because different sections of the transducer 410 may be used to detect different signal particles, which may be smaller angle signal particles and/or larger angle signal particles or secondary signal particles and/or backscattered signal particles. This configuration of different signal particles may be suitable for a concentrically partitioned transducer 410. Different angles of the backscattered signal particles may be beneficial in providing different information. For example, for signal particles emitted from a deep hole, low angle back-scattered signal particles may come more from the bottom of the hole, while high angle back-scattered signal particles may come more from the surface and material surrounding the hole. In an alternative example, the low angle back-scattered signal particles may come more from deeper buried features, while the high angle back-scattered signal particles may come more from the sample surface or material above the buried features. Note that the arrangement of fig. 8 may have limited ability to detect back-scattered signal particles, e.g. the arrangement may be limited to detecting back-scattered signal particles with low-angle back-scattered particles. That is, the backscattered signal particles that can be detected using this arrangement are limited by the relatively large distance between the sample 208 and the transducer 401 and the relatively narrow path from the sample 208 to the respective transducer 401 (e.g., because of the respective aperture through the electrode 302). In this arrangement, the transducer is unlikely to have concentric portions because the angular range of backscattered signal particles that such a transducer can detect is low.

The transducer 410 may be provided as transducer elements, each transducer element being associated with one or more of the plurality of beams. Alternatively or additionally, the converter 410 may be provided as a monolithic converter in which a plurality of apertures are defined, each aperture corresponding to a respective one or more of the plurality of beams. In some arrangements, the converters are arranged in a stripe array. Each stripe may correspond to a set of primary beams. The beams may comprise a plurality of rows of beams, and each group may correspond to a respective row.

The description with respect to fig. 9 may be equally applicable to other types of detector elements, such as charge detector elements and semiconductor elements (such as PIN detector elements).

Fig. 10 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. The electron optical device is configured to project multiple beams of electrons. The electron optical device includes an electronic apparatus (also referred to as electron optical apparatus or electron optical device column). The electron optical device may be arranged as described in any of the embodiments described above. The arrangement shown in fig. 10 is similar to that shown in fig. 3, although the lens array 250 is not controlled. In one embodiment, the electro-optical device shown in FIG. 10 includes the control lens array (or any number of other associated plates of the objective lens array) described above. In other embodiments, the electron optical device is similar to another of the arrangements described above, such as an arrangement including a macro collimator and a macro scan deflector instead of collimator deflector 235 and scan deflector array 260. In other embodiments, the electron optical device is similar to another of the arrangements described above, such as the arrangement shown in fig. 8.

In one embodiment, the electronic device may switch between: (i) An operating configuration in which the apparatus is configured to project multiple beams to the sample 208 along an operating beam path, and (ii) a monitoring configuration in which the apparatus is configured to project multiple beams to a detector (or monitoring detection system) along a monitoring beam path. The operating beam path extends from the multi-beam source 201 to the sample 208. The monitoring beam path extends from the source 201 to the detector. The operating configuration may be used, for example, to perform an inspection of the sample 208 or to perform a metering. In an operational configuration, signal electrons emitted from a sample may be detected as described above. In the operational configuration, the detector array 240 is used to detect signal particles in the operational configuration. In one embodiment of the monitoring configuration, a monitoring detection system is used to monitor multiple beams from source 201, for example.

As shown in fig. 10, in one embodiment, the monitoring beam path is diverted midway along the operating beam path from the inspection beam path. Sample 208 may be separated from the monitoring beam path. In the monitoring configuration, multiple beams are intercepted upstream of the sample 208. Monitoring the multi-beam signal directly without interacting with the sample 208; i.e. the sub-beams in the multi-beam are monitored directly. What is monitored is the primary beam, i.e., the sub-beam (which may be referred to as the primary signal), rather than the signal particles from the sample 208, which may be referred to as the secondary signal.

In one embodiment, at least one parameter of at least a portion of the multiple beams is monitored. As shown in fig. 10, in one embodiment, beamlets 211, 212, 213 in the multiple beams are monitored. Alternatively, the multi-beam source beam 202 may be monitored (e.g., as described below with reference to fig. 16-17). In one embodiment, the uniformity of the multiple beams is monitored. The uniformity of the multiple beams may be a measure of variation across the characteristics of the multiple beams. For example, the characteristic may be intensity or focus. Additionally or alternatively, one or more aberrations of the multiple beams may be monitored. For example, field curvature, distortion and astigmatism may be monitored. Additionally or alternatively, alignment of the multiple beams may be monitored. For example, alignment of the beamlets 211, 212, 213 with a set of one or more apertures (e.g., apertures in an objective lens assembly or mirror) may be monitored. Additionally or alternatively, the focus of the multiple beams may be monitored. The monitoring may be used to correct and/or mitigate deviations from nominal by monitoring at least one parameter of at least a portion of the multiple beams.

As just one example, in one embodiment, the source current uniformity may be measured by measuring the beam intensities of the individual beamlets 211, 212, 213 outside the MEMS element (i.e., outside the converging lens array and the objective lens array). Adjustments may then be made to improve the uniformity of the multiple beams or to compensate for a known lack of uniformity of the multiple beams.

As shown in fig. 10, in one embodiment, the apparatus includes at least one movable member. The movable member is configured to move between an operating position and a monitoring position. The operating position corresponds to an operating configuration. The monitoring location corresponds to the monitoring location. This movement is illustrated by the double-ended dashed arrow in fig. 10.

In the arrangement shown in fig. 10, the movable part comprises a transducer 60. Associated with the converter is an optical detector. The transducer 60 and the optical detector together are a monitoring detection system. The optical detector is external to the converter and is positioned so as to detect the light generated by the converter 60. The transducer 60 is configured to move between an operating position, which corresponds to an operating configuration, and a monitoring position, which corresponds to a monitoring configuration. The operating position is shown above the double ended arrow. In the operating position, the transducer 60 is positioned transverse to the multiple beams, e.g. a multiple beam device (or column of devices). The transducer 60 is positioned on one side of the multibeam or adjacent to the multibeam. The multiple beams pass by the transducer 60 without interacting with the transducer 60. The multiple beams are projected onto the sample 208. In fig. 10, the movable member has a different orientation in the operating position than in the monitoring position. Particularly in the monitoring position, the transducer 60 is substantially perpendicular to the direction of the multiple beams. The transducer 60 may be planar. In the operating position, the transducer 60 may not be perpendicular to the multiple beams. For example, the transducer 60 may be oriented such that the normal to its surface is perpendicular to the multiple beams. By changing the orientation between the operating position and the monitoring position, one embodiment of the present invention desirably reduces or minimizes the volume occupied by the transducer 60. In alternative arrangements, the orientation of the movable component may be the same for the operating position and the monitoring position. For example, the movable member may be moved perpendicular to the multiple beams so as to perform the movement without tilting the movable member. For example, the movable member may be slidable between an operating position and a monitoring position. Such an operation may benefit from a simple arrangement for actuation between two positions. Such sliding may be actuated linearly. The sliding may be rotationally actuated, such as about an axis away from the path of the beamlets. The rotational actuation may reduce or minimize the volume occupied by the transducer 60 and its actuation.

The monitoring position is shown to the right of the double ended arrow. As shown in fig. 10, in one embodiment, the monitoring location is between the source 201 and the sample 208. In the monitoring position, the transducer 60 intercepts multiple beams upstream of the sample 208. The converter 60 is configured to receive multiple beams output by the source 201 and to generate light in response to the received multiple beams. Although the transducer 60 is depicted only upstream of the intermediate focus point, the transducer may be positioned in a monitoring position at a location along the beamlet path from upstream of the converging lens array or a beam limiting aperture array associated with the converging lens array to upstream of the objective lens array, for example: at any position between the converging lens array to the intermediate focus, between the intermediate focus and the objective array, e.g. downstream of one or more electrodes associated with the objective array but upstream of the objective array. Note that if the converter 60 is upstream of the beam limiting aperture array, the converter will intercept the source beam instead of multiple beamlets.

In one embodiment, the converter 60 includes a scintillator. The transducer 60 may include a conversion material such as YAG. The conversion material may comprise, for example, pure crystalline material Y ₃Al₅O₁₂, which may be doped with cerium to form YAG: ce. The converter 60 may be formed as a YAG screen. In one arrangement, the converter includes a single scintillator. In another arrangement, the converter includes a scintillator for one or more beamlets in a multi-beam. In one arrangement, the transducer includes a plurality of elements for each beamlet. The scintillator elements may be included in an array, such as a two-dimensional array, e.g., an array corresponding to beamlets in a multi-beam.

As shown in fig. 10, the movable member may be telescopic. The converter 60 may be configured to convert multiple beams into light. Light is generated by the individual electron beamlets 211, 212, 213 and may be read out by an optical detector, e.g. an external camera 61. The optical detector is remote from the transducer. The optical detector is positioned such that it can detect the light emitted by the converter 60. The optical detector generates light in response to electrons at least in a line of sight of the position of the converter 60. In one embodiment, measurements of individual beam profiles may be performed to obtain more detailed information about source emission characteristics. Such measurements may be made in an optical detector, electronics associated with the detector, remote electronics in an electron optical system (such as a remote processing rack), or a processor located somewhere between the two extremes, for example in an electron optical apparatus or electron optical device.

The converter 60 may be expected to have a longer lifetime when interacting with high energy electrons. By providing the transducer 60 and an external optical detector such as the camera 61, there is no need to locate additional electronic components inside the vacuum. This helps to simplify the design of the electron optical device.

In one embodiment, the at least one movable component comprises a light guide arrangement configured to guide light generated by the converter 60 towards the optical detector. In one embodiment, the electro-optical device includes a waveguide configured to direct light from the transducer 60 to an optical detector. This allows the generated light to be read out with an in situ fiber coupled to an ex situ optical detector. The use of optical fibers in this manner enables the optical detector to detect light generated by the converter 60 without the optical detector having to be in direct line of sight of the converter 60. For example, one or more optical fibers may be provided. This may help reduce the volume required for the converter 60 and the optical detector.

As shown in fig. 10, in one embodiment, the source 201 and the electron-optical element (such as the converging lens array 231 and the objective lens array) may remain stationary as the movable member moves between the operating position and the monitoring position. One embodiment of the present invention contemplates maintaining alignment of multiple beams.

FIG. 11 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. Features of the same arrangement as that shown in fig. 10 are not repeated below. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. As shown in fig. 11, in one embodiment, the at least one movable component includes a monitoring detector 64 (or monitoring detection system). That is, the monitoring detection system is a monitoring detector 64. Thus, there is no need to provide any external optical detector, such as the camera 61.

In one embodiment, the monitor detector 64 comprises a charge detector, such as a faraday cup array. Optionally, each charged detector, such as a faraday cup, is configured to measure a respective sub-beam. In an alternative embodiment, monitor detector 64 includes a Charge Coupled Device (CCD). Alternatively, the monitoring detector may be a semiconductor-based detector, such as a PIN detector. In an alternative embodiment, monitoring detector 64 includes a direct light detector device including a converter configured to generate light in response to charged particles and an adjacent optical detector. The adjacent optical detectors are configured to directly convert the generated optical signals generated by the converter into electrical signals. The optical detector may be in contact with the transducer.

Such a charged detector (such as a faraday cup array or CCD) or PIN detector can directly detect and read out the electron beam signal without a light conversion step in between. The direct light detector device is configured to monitor multiple beams without the need for an external camera 61. One embodiment of the present invention contemplates multi-beam monitoring without the need to view the transducer 60 from outside the vacuum using an external camera 61. Direct photodetector devices may be expected to have a longer lifetime.

In one arrangement, the monitor detector 64 includes a monitor detector element. In another arrangement, the transducer includes monitoring detector elements for one or more sub-beams of the multiple beams. In one arrangement, the monitoring detector 64 includes multiple elements for each beamlet. The monitoring detector elements may be comprised in an array, e.g. a two-dimensional array, e.g. an array corresponding to sub-beams of a multi-beam.

Fig. 12 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. Features of the same arrangement as that shown in fig. 10 are not repeated below. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. As shown in fig. 12, in one embodiment, the movable member includes a mirror 62. In a variation, the movable component may be a plurality of individually movable components or a plurality of components arranged to move together. The plurality of movable components may together comprise a mirror, which may for example be represented as mirror 62. The mirror 62 is configured in the monitoring position to direct light generated by the converter 60 to an optical detector (e.g., an external camera 61). Thus, the monitoring detection system may include a transducer 60, a mirror 62, and an optical detector.

In the monitoring configuration, mirror 62 may be positioned downstream of transducer 60. Mirror 62 may be positioned between transducer 60 and sample 208. Mirror 62 may be telescopic, for example out of the path of the beamlets. The telescoping may be linear and/or rotational, e.g. about an axis spaced from the path of the beamlets. In one embodiment, mirror 62 may be movable with transducer 60. Mirror 62 and transducer 60 may have fixed positions relative to each other. Alternatively, mirror 62 and transducer 60 may be configured to move independently of each other. This may be desirable to reduce the volume required for, for example, mirror 62 and transducer 60 when mirror 62 and transducer 60 are not in the operational position. In the monitoring configuration, mirror 62 and the transducer may have fixed positions relative to each other. In the monitoring configuration, the positions of the mirror 62 and the transducer relative to the path of the beamlets may have fixed positions.

As mentioned above, in one embodiment the movable part comprises a light guide arrangement, or alternatively the movable part comprises a light guide arrangement. The light guide arrangement is configured to guide light generated by the converter 60 towards the optical detector. The light guide arrangement may comprise a mirror 62. In one embodiment, the light guide arrangement may comprise an optical element 63 (e.g. a lens). The optical element 63 is configured to direct light onto an optical detector, which may be external to the electro-optical device (or column of devices) 41, such as the external camera 61. In one embodiment, the optical element 63 is movable between an operational configuration and a monitoring configuration. In an alternative embodiment, the optical element 63 may remain stationary as the movable member moves. For example, as shown in FIG. 12, in one embodiment, the optical element 63 is outside the operating beam path, e.g., outside the electron-optical column (or device). The optical element 63 does not have to be moved in order for the multiple beams to reach the sample 208. If the optical element and the optical detector are stationary between the operating configuration and the monitoring configuration, volume may be saved, since no corresponding actuator needs to be provided.

In contrast to the arrangement shown in fig. 10, the mirror 62 and the lens are additional optical components that are provided to assist in reading the optical signal. That is, the mirror 62 and the optical element 63 improve the transmission of the optical signal from the converter 60 to an optical detector, such as an external camera 61. Mirror 62 and optical element 63 may improve detection and/or collection efficiency.

As shown in fig. 12, in one embodiment, mirror 62 is tilted, e.g., by an optimal angle, with respect to transducer 60. For example, the mirror may be tilted between 25 degrees and 65 degrees, preferably about 45 degrees. Tilting mirror 62 helps to direct light away from the operating beam path. This allows an optical detector, such as an external camera 61, to be positioned outside of the operating beam path, such as outside of the vacuum.

In one embodiment, the pitch at the sample between beamlets may be on the order of about 70 μm pitch, e.g., between 30 μm and 100 μm. At the sample, the size of the footprint of the multiple beams of beamlets may be on the order of about 5, 10 or 15 millimeters. These dimensions may be applied to multiple beams of beamlets at any point around the collimation point, for example by a deflector 63 or downstream of the collimation of the beamlets. If the mirror is 45 degrees, in one embodiment, the mirror 62 is arranged such that its height (i.e., its dimension along the multi-beam direction) is about 15mm. Alternatively or additionally, by controlling the angle of inclination of the mirror 62, e.g. with respect to the path direction of the beamlets (or orthogonal to the direction), the dimension of the mirror in the multi-beam direction (i.e. the height dimension in the view shown in the drawing) may be controlled. In the depicted arrangement, the mirror 62 and the converter 62 are located upstream of the intermediate focus of each beamlet and collimator 235. Upstream of intermediate focal point 233, the paths of the beamlets diverge and the size across the multiple beams (e.g., their width) is small.

As shown in fig. 12, in one embodiment, the converter 60, mirror 62, optical element 63, and camera 61 are located downstream of the converging lens array 231. In an alternative embodiment, transducer 60, mirror 62, optical element 63, and camera 61 are located upstream of converging lens array 231. This may be beneficial because the mirror size may be smaller, because the beam cross-section may be smaller, because it may diverge less. If the converging lens array 231 does not have a beam limiting aperture array, then the converter 60 and mirror 62 may be located downstream of the beam limiting aperture array. The converter 60 may interact with the beamlets. A mirror may be placed between the beam limiting aperture array and the converging lens array 231. However, if the converter is upstream of the beam-limiting aperture array, the converter 60 will interact with electrons of the source beam 60, rather than with beamlets generated from the source beam. Although this may not provide information about the beamlets, the detection of electrons from the source beam may still provide information about the beamlets generated from the source beam; the beamlets have the characteristic of generating their beamlets.

Fig. 13 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. Features of the same arrangement as that shown in fig. 12 are not repeated below. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. As shown in fig. 13, mirror 62 and/or transducer 60 need not be retractable. In one embodiment, the apparatus comprises: a transducer 60 in the path of the multiple beams to generate a beam in response to the multiple beams; and a mirror 62 configured in a monitoring configuration to direct the light beam to a detector desirably in the monitoring configuration.

The transducer 60 may remain in the same position in the operational configuration and monitoring position. By having fewer moving parts, reliability may be improved and/or space occupied by the device may be reduced. One embodiment of the present invention desirably reduces the overall volume required for components used to perform multi-beam monitoring.

As shown in fig. 13, in one embodiment, a plurality of apertures 65 are defined in the transducer 60 for the passage of paths of multiple beams. The aperture 65 allows the beamlets to pass through when the electron optical apparatus is in an operational configuration.

As shown in fig. 13, in one embodiment, a plurality of openings 56 (or apertures) are defined in the mirror 62. The opening 56 is configured to allow beamlets in the multi-beam to pass through the mirror 62 toward the sample 208. The opening 56 allows the beamlets to pass through when the electron optical apparatus is in an operational configuration. Mirror 62 is configured to reflect light toward an optical detector (e.g., external camera 61). In the operating configuration, the paths of the multiple ones of the multiple beams pass through respective openings 56 defined in the mirror 62.

As shown in fig. 13, in the monitoring configuration, the paths of the multiple ones of the multiple beams are incident on the converter 60. The paths of the beamlets in the operational configuration are different from the paths of the beamlets in the monitoring configuration. In one embodiment, the apparatus comprises a deflector or a plurality of deflectors operable between an inspection setting corresponding to the operating configuration and a measurement setting corresponding to the monitoring configuration.

For example, as shown in FIG. 13, in one embodiment, the electronic device includes a switching deflector array 78. The switching deflector array 78 includes a plurality of deflectors configured to switch between an operating configuration and a monitoring configuration. Each deflector in the switching deflector array 78 may be configured to act on a respective beamlet path.

The deflectors in the switching deflector array 78 are configured to control the direction of the beamlets downstream of the converging lens array 231. The switching deflector array may be located downstream of the converging lens array 231. The switching deflector array 78 is located upstream of the converter 60.

In the operating configuration, the switching deflector array 78 is configured to direct beamlets through apertures 65 in the converter 60 and mirror 62. In the monitoring configuration, the switching deflector array 78 is configured to direct beamlets along the switching beam paths 66, 67, 68 to impinge on the converter 60. In one embodiment, the controller is configured to control the potential applied to the electrodes of the switching deflector array 78 in order to control the electronics to switch between the operating configuration and the monitoring configuration.

In one arrangement shown in fig. 13, the switching deflector 78 comprises a plurality of deflector elements to operate on paths in respective beam paths of the multiple beams. In an alternative embodiment, the switching deflector 78 comprises a macro-deflector configured to operate on all beam paths of the multiple beams. When macro-deflectors are provided, the switching deflector array may be omitted. Additionally or alternatively, the switching deflector array may have mesoscopic switching deflectors, each deflector being operable on a group of beamlets in the multi-beam.

In variations of the arrangement depicted and described with respect to fig. 13, the transducer 60 may be replaced with a monitoring detector 64, as described with respect to the embodiment shown and described with respect to fig. 11. (i.e., the monitoring detection system includes a monitoring detector 64). For example, the monitoring detector may include detector elements such as a charged detector (e.g., faraday cup or charged coupling device), a PIN detector, and/or a direct light detector device. Having a monitoring detector 64 instead of a transducer 60 means that optical elements such as mirror 62, lenses and optical detector 61 are not required. This may reduce the volume required for the monitoring system. Further, the aperture 65 and the switching deflector 78 enable the monitoring deflector 64 to be maintained in position in the operating configuration as well as in the monitoring configuration.

Fig. 14 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. Features of the same arrangement as that shown in fig. 10 are not repeated below. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. As shown in fig. 14, in one embodiment, the at least one movable component comprises one of a source 201 and an objective lens array. The objective lens array is configured in an operational configuration to project multiple beams onto the sample 208. Fig. 14 shows the electronic device in a monitoring configuration. In the operating configuration, the features of the electro-optical device will be as represented in fig. 3, wherein the transducer 60 and the optical detector 61 are positioned on one side of the electronic apparatus or device column 41. Thus, the monitoring detection system comprises a transducer 60 and an optical detector 61.

The electronic device may include a source module 69. The source module 69 includes a source 201. As shown in fig. 14, in one embodiment, the source module 69 includes a converging lens array 231. The electronics 41 may also include an objective lens array, which may be part of the downstream of the target module 70. The electronic device is configured such that the source module 69 and the target module 70 are movable relative to each other. In one embodiment, the source module 69 is configured to move while the target module 70 remains stationary, such as between an operating configuration and a monitoring configuration. In an alternative embodiment, the target module 70 is configured to move while the source module 69 remains stationary, such as between an operating configuration and a monitoring configuration. In yet another alternative embodiment, both the target module 70 and the source module 69 are configured to move between the respective configured operating and monitoring positions.

As shown in fig. 3, in one embodiment, the multiple beams are aligned with lenses 234 of the objective lens array 70 in an operational configuration. As shown in fig. 14, in one embodiment, the multiple beams are offset relative to the objective lens array 70 in a monitoring configuration. In one embodiment, the electro-optical device includes an actuator (not shown). The actuator is configured to actuate the electro-optical device between an operating configuration and a monitoring configuration. The actuator may be arranged to operate linearly or rotationally about an axis remote from the path of the beamlets, desirably parallel to the path of the beamlets.

The source module 69 or the target module 70 may be configured to move laterally. For example, as shown in fig. 14, in one embodiment, the source module 69 is configured to move laterally such that the beamlets are aligned with the transducer 60 in the monitoring configuration. The converter 60 may be configured to convert the electron beam into light. The light may be detected by an optical detector such as a camera 61. Once monitoring is complete, the source module 69 may be moved so that the beamlets are aligned with the target module 70; that is, the source module 69 moves relative to the target module 70 (e.g., the objective lens array 234). Although the embodiment described with reference to fig. 14 and shown in fig. 14 has an actuatable source module, in a different arrangement it is a target module actuatable with a transducer 60 such that the transducer 60 replaces the target module 70 downstream of the source module 69.

When the source module 69 is aligned with the transducer, it is easier to determine the characteristics of the source 201. As shown in fig. 14, in one embodiment, the source module 69 includes a converging lens array 231. This may allow the source module 69 to perform a simple lateral movement to switch between the monitoring configuration and the operating configuration. Having a converging lens array 231 or at least a beam limiting aperture array comprised in the source module 69 allows monitoring of the beamlets and characteristics of the beamlets. Although the division between the source module 69 and the target module 70 is shown upstream of the intermediate focus of the beamlets, the division may be at any point downstream of the converging lens array 231. For example, the division may be downstream of collimator array 235, e.g., downstream of one or more electrodes associated with objective array 234, and e.g., above the electrodes of the objective array.

In an alternative embodiment, source module 69 does not include converging lens array 231. The converging lens array may have a fixed position relative to the objective lens array 70. The source 201 is movable relative to the converging lens array 231 and the objective lens array 70. In the monitoring configuration, source beam 202 is incident on transducer 60. This may allow for more accurate determination of the characteristics of the source. For example, any influence of the aperture of the converging lens array 231 on the measuring beam can be avoided. Since the beamlets are generated by the source beam 202, some characteristics and features of the source beam will also be present in the beamlets. Thus, the monitoring of the source beam 202 is actually monitoring one or more characteristics of the sub-beams.

Fig. 15 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. The features of the same arrangement as that shown in fig. 14 are not repeated below. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. As shown in fig. 15, in one embodiment, the transducer 60 (and optionally the optical detector 61) is replaced by a monitoring detector 64. In this embodiment, the monitoring detection system includes a monitoring detector 64.

In one embodiment, the monitor detector 64 comprises a charge detector, such as a faraday cup array. Optionally, each faraday cup is configured to measure a respective sub-beam. In an alternative embodiment, monitor detector 64 includes a charge detector, such as a Charge Coupled Device (CCD). In an alternative embodiment, the monitoring detector 64 includes: a direct light detector device comprising a converter configured to generate light in response to charged particles; and an adjacent optical detector configured to directly convert the generated optical signal generated by the converter into an electrical signal. The optical detector may be in contact with the transducer, for example in direct contact.

Fig. 16 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. The electron optical device is configured to project multiple beams of electrons. The electron optical device may be arranged as described in any of the embodiments described above. Unless otherwise mentioned, such common features may be given the same reference numerals and descriptions. The arrangement shown in fig. 16 may include the same features as the arrangement shown in fig. 3, although additional electrodes upstream of the objective lens array 234 (which may include the control lens array 250) and/or associated with the objective lens array 234 are not shown. In one embodiment, the electron optical apparatus shown in FIG. 16 includes a control lens array and optionally other additional and associated electrodes upstream of the objective lens array 234, as described above. In other embodiments, the electron optical device is similar to another of the arrangements described above, such as an arrangement including a macro-scan deflector instead of the scan deflector array 260. In other embodiments, the electron optical device includes features of another of the arrangements described above, such as the arrangements shown in fig. 8 and 9.

As shown in fig. 16, in one embodiment, the electron optical apparatus includes a source 201, the source 201 being configured to output a source beam 202 for generating multiple beams. In one embodiment, as shown in fig. 16, the electron optical device includes an array of apertures. The aperture array is configured to form multiple beams of multiple beams from the source beam 202 by blocking a proportion of the source beam 202 from projecting toward the sample 208. Such an aperture array may be referred to as a beam limiting aperture array. In one embodiment, an aperture array is included in the converging lens array 231. In another arrangement, the aperture array is located upstream of the converging lens array 231.

As shown in fig. 16, in one embodiment, the electron optical device includes a detector (or monitoring detection system) configured to measure at least a parameter of at least a portion of the blocked fraction of the source beam 202. In one embodiment, the monitoring detection system includes an optical detector and transducer 60. The optical detector may include a camera 61. The camera is configured to detect light. In one embodiment, a converter 60 is provided to convert the source beam 202 into light that can be detected by an optical detector.

As shown in fig. 16, in one embodiment, the transducer 60 is located at an upstream surface of an aperture array, which may be a beam-limiting aperture array. In one embodiment, the received source beam 202 includes at least a portion of a proportion of the source beam blocked by the aperture array. One embodiment of the present invention desirably allows the source beam 202 to be monitored without significantly affecting the multiple beams incident on the sample 208. The source beam 202 may be monitored online, such as during an inspection or metrology process, for example, using a monitoring detector.

As shown in fig. 16, in one embodiment, the transducer 60 includes a coating 71. The coating 71 may have a plurality of individual segments, for example in an array. Each array of elements may be associated with one or more apertures in the array. Alternatively, the coating 71 may be continuous. The coating 71 is provided between the apertures of an aperture array (which may be part of the converging lens array 231). The coating 71 may comprise a material comprising YAG, for example as described above.

In one embodiment, the camera 61 is configured to read the generated light ex situ, for example outside the column of devices, such as a vacuum chamber of an electron optical apparatus. As shown in fig. 16, in one embodiment, the camera 61 and the converter 60 are arranged such that the camera 61 has a direct view of the converter 60. The transducer may be in direct line of sight of the optical detector. In one embodiment, the light is detected directly.

Fig. 17 is a schematic diagram of an exemplary multi-beam electron optical apparatus according to one embodiment. Such common features may be identified with the same reference numerals and descriptions as in fig. 16. The features of the same arrangement as that shown in fig. 16 are not repeated below. As shown in fig. 17, in one embodiment, the electron optical device includes a light reflecting element, such as a mirror 72. The mirror 72 is configured to reflect light generated by the converter 60 towards the optical detector. In this embodiment, the monitoring detection system includes a transducer 60, a mirror 72, and a light detector.

As shown in fig. 17, in one embodiment, the mirror 72 is positioned around the source 201. The mirror 72 is configured to reflect light at a location where the detector is most conveniently placed. One embodiment of the present invention desirably allows the source beam 202 to be monitored without making the device significantly more difficult or complex to mechanically manufacture.

As shown in fig. 17, in one embodiment, the mirror 72 is positioned in the upstream direction of the transducer 60. In one embodiment, mirror 72 is located between converter 60 and source 201. The mirror 72 may be located in a volume that would otherwise be relatively empty. One embodiment of the present invention desirably allows monitoring of source beam 202 without significantly affecting the mechanical design of the portion of the apparatus used during the inspection or metrology process.

As shown in fig. 17, in one embodiment, the mirror 72 includes an aperture 73. Aperture 73 may be used to receive source 201 as shown in fig. 17. Additionally or alternatively, aperture 73 may be used to house source beam 202. The mirror may be located in a downstream direction of the source 201.

Typically, the mirror 72 is positioned relative to the optical detector and the converter 60 such that the optical detector detects light generated at least in selected regions (e.g., all regions) of the surface of the converter 60. The mirror 72 need not be placed around the source 201, but rather on one side of the source and/or upstream or (as already mentioned) downstream of the source 201. The optical detector is desirably positioned in the straight path of the light from the converter 60 when reflected from the mirror 72. The mirror 72 may be curved or have more than one surface, for example, may take the form of a fresnel mirror, so long as the light emitted from the transducer 60 reaches the optical detector.

In one embodiment, the transducer 60 and camera 61 shown in fig. 16 may be replaced by a monitor detector live detector, such as a faraday cup array or a CCD, which may be arranged in an array, e.g., with one or more detectors per aperture in a beam-limiting aperture array, e.g., around one or more apertures of the beam-limiting aperture array. (thus, the monitoring detection system has a monitoring detector instead of, for example, the transducer 60, the optical detector, and the mirror 72). The device may be operated at low currents of electrons from source 201 to reduce the effects of undesirable charging of the faraday cup or CCD, which may undesirably affect multiple beams.

Fig. 18 is a schematic diagram illustrating a portion of an electro-optical device comprising a plurality of transducers 410 and a light guide arrangement. The features of the same arrangement as that shown in fig. 8 are not repeated below. The device includes an electronic device (or column of devices) and a light sensing assembly.

In all and each of the arrangements shown and described with respect to fig. 10-17, as well as the mentioned and derivable embodiments, the monitoring detection system may generate a detection signal. The detection signal generated by the optical detector 75 may be used by the controller 50 or an element of the controller to control an element or component of the electro-optical device (or column of devices) 41. The detection signal may include information about the relative positions of the beamlets within the multi-beam, such as the relative alignment of the beamlets at the transducer 60 or monitoring detector 64. The detection signal may be used for the controller or an element of the controller to align the beamlets, for example by controlling one or more correctors of the electron optical apparatus 41. The invention is described herein primarily for monitoring beamlets of a multi-beam arrangement for correcting alignment between the beamlets and electron optical components, and even between electron optical elements, along a path of the multi-beam arrangement. Additionally or in the alternative, the present invention may be used to monitor other types of features, such as aberrations, for correction or adjustment. Additionally or alternatively, the beamlets of the multi-beam arrangement may be measured for one or more of: focusing aberrations, source beam uniformity characteristics or even aberrations and off-axis aberrations such as field curvature, distortion and astigmatism. A corrector in the electro-optical device may be controlled to correct or at least reduce the magnitude of one or more of these characteristics or aberrations.

As shown in fig. 18, in one embodiment, the electronic device includes an objective lens array 403, the objective lens array 403 being configured to project multiple beams onto locations on the sample 208. In one embodiment, the electronic device includes a plurality of converters 410, the plurality of converters 410 being configured to receive signal electrons emitted from the sample 208 and to generate light in response to received signal particles. The converter 410 may be a scintillator. Transducer 410 may include the conversion material described above with respect to the material of transducer 60.

In another arrangement, the objective array 403 may additionally or alternatively be associated with another plate, such as an electrode, such as a lens electrode associated with an objective integrated in the objective array or upstream of the proximity objective (such as a control lens array). In one arrangement, additionally or alternatively, the detector array is located upstream of the objective array and any electron optical elements associated with the objective. The detector elements of the detector array may be associated with respective beamlets. The detector elements may include charge detection, scintillator and PIN detection elements. In one arrangement where the detector elements comprise scintillators, the detectors may be arranged to one side of the beamlet path such that the beamlets pass to one side of the respective detector element.

The deflection element may be located between the detector array and the objective lens, such as a wien filter, e.g. a wien filter array. Such a wien filter allows the beamlets to pass through the wien filter towards the undeflected sample, but signal particles from the sample are directed to the detector element. An optical converter (e.g., an optical detector) may be positioned to convert light generated by the scintillator into an electronic signal. The optical converter may be coplanar or even in direct contact with the scintillation detector element. Such an optical converter is described in EP application 21183803.2 filed at 7/5 of 2021, which is incorporated by reference at least with respect to the optical converter associated with the scintillation detector and the architecture and use of the detector for detecting signal particles.

As shown in fig. 18, in one embodiment, the electronic device includes a light guide arrangement that includes a mirror 414. A plurality of apertures 416 are defined in the mirror 414 to allow multiple beams to pass through the mirror 414 toward the sample 208.

The light guide arrangement is configured to guide light 411 generated by the converter 410 to the light sensing component. As shown in fig. 18, in one embodiment, the light sensing assembly includes an evaluation sensor (e.g., light sensor 412) and an optical detector 75, the evaluation sensor and the optical detector 75 being respectively configured to detect light 411 generated by the converter 410. The evaluation sensor is configured to detect the light 411, for example during an inspection or metrology process. In practice, the evaluation sensor is part of an evaluation system for detecting signal particles. The evaluation sensor is functionally equivalent to, for example, the detector 240 of fig. 3. The optical detector 75 is part of an additional branch configured to, for example, improve the inspection or metrology process.

As shown in fig. 18, in one embodiment, the light sensing assembly includes a beam splitter 77, the beam splitter 77 being configured to split light 411 generated by the converter 410 into light beams directed toward the evaluation sensor and detector 75. Both the light sensor 412 and the detector 75 may be configured to detect different portions of the light 411 simultaneously. As shown in fig. 18, in one embodiment, the light sensing assembly includes an optical element 76, such as a lens. The optical element 76 is configured to act on the light 411 directed to the detector 75. For example, the optical element 76 may focus light onto the detector 75.

In one embodiment, the apparatus includes a controller configured to match the detection signal of the evaluation sensor to the position of the projected multi-beam on the sample 208 based on the detection signal of the optical detector 75. For example, the light sensor 412 may be used in a sensor array for which it is desired to align different portions of the light beam from the converter 410 associated with signal particles generated by different beamlets with corresponding portions of the light sensor 412 (such as sensor elements of the sensor array). Monitoring by the optical detector 75 may be used to calibrate and/or improve the accuracy of the signal detected by the light sensor 412. The optical detector 75 may be used to monitor the alignment of the multiple beams, such as the position of different parts of the beam relative to the optical detector 75 and its detection elements. The position of the detection elements of the optical detector 75 may be calibrated with different portions of the light sensor 412 (e.g., sensor elements). The signal detected by the optical detector 75 (e.g., a detection signal) may be used in a subsequent process or an ongoing process to improve multi-beam alignment. The signal detected by the optical detector 75 may be used to control components of the light sensing assembly, such as the mirror 414 and/or the optics 418, which may include lenses. The components of the light sensing assembly may be controlled by the controller based on the detection signal to improve the alignment of the light from the converter 410 so that different portions thereof are better aligned with portions of the light sensor 412 (e.g., the sensor elements). The detection signal transmitted from the data line 422 more accurately distinguishes the signal particles generated by each beamlet.

Fig. 19 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment. As shown in fig. 19, in one embodiment, the electronic device 41 includes a monitoring component 190. The monitoring component 190 is in the path of the monitoring beam. In one embodiment, the monitoring component 190 is upstream of a detector (e.g., a monitoring detection system). In one embodiment, the monitoring component 190 is used to monitor (e.g., detect) the size of one or more of the multiple beams. The monitoring component 190 can be used to measure the size of one or more electron beams.

Fig. 20 is a schematic close-up view of the monitoring component 190. Fig. 20 shows one beamlet 212 of the multiple beams passing through the monitoring component 190. As shown in fig. 20, in one embodiment, the monitoring component 190 includes an array of blocking elements 194. The blocking element 194 is configured to block beamlets in the multi-beam. For example, a portion of beamlet 212 may be blocked by blocking element 194.

Fig. 20 shows a transducer 60 as part of the detector. The detector may also include a camera. Alternatively, the detector may be another component configured to detect a change in current. In one embodiment, the detector is a direct electronic detector such as a PIN detector or a current detector.

Fig. 21 is a schematic plan view of the monitoring member 190. Fig. 21 schematically shows 10 blocking elements 194 arranged as part of the monitoring component 190. The monitoring component 190 may include hundreds or thousands of blocking elements 194 in an array of blocking elements 194.

As shown in fig. 21, in one embodiment, the blocking element 194 has a similar pattern. For example, as shown in fig. 21, in one embodiment, the blocking element 194 has a ring pattern. Each blocking element 194 may be in the shape of a ring. The ring is advantageous in that it is of a particularly simple construction.

Fig. 22 is a schematic close-up view of one of the blocking elements 194 of the monitoring component 190. As shown in fig. 22, in one embodiment, the blocking element 194 has an inner edge 197. In one embodiment, the inner edge 197 of the blocking element 194 forms a knife edge (i.e., a sharp edge, sharp edge). In one embodiment, the blocking element 194 (and in particular the inner edge 197 of the blocking element 194) forms a knife edge pattern. The blade pattern may enable measurement of the maximum size of the points generated by beamlets 212. In one embodiment, the controller is configured to control the electronics 41 to scan the multiple beams relative to the blade pattern. This may be referred to as blade scanning.

As shown in fig. 22, in one embodiment, the monitoring component 190 includes an aperture array 193. The aperture array 193 is adjacent to a corresponding blocking element 194. An aperture array 193 is used to pass multiple beams therethrough. For example, as shown in fig. 20, beamlets 212 may pass through apertures 193. As shown in fig. 20-22, in one embodiment, each aperture 193 in the array of apertures corresponds to each blocking element 194 in the array of blocking elements 194. In one embodiment, the number of blocking elements 194 is equal to the number of apertures 193. Alternatively, the number of blocking elements 194 may be greater than the number of apertures 193.

As shown in fig. 21, in one embodiment, each blocking element 194 surrounds a corresponding respective aperture 193. For example, as mentioned above, in one embodiment, each blocking element 194 is annular. In one embodiment, the blocking elements 194 are concentric with the corresponding apertures 193. Alternatively, the center of blocking element 194 may be offset from the center of aperture 193.

The blocking element 194 need not be annular. In one embodiment, each blocking element 194 includes a plurality of portions that are spaced apart from one another. Portions of the blocking element 194 may be spaced apart from apertures 193 associated with the blocking element 194. The blocking element 194 may be a wire or square or another shape. Square or other shapes may surround the aperture 193. However, the blocking element 194 need not surround the aperture 193.

In one embodiment, blocking element 194 comprises a material that blocks electrons of multiple beams. For example, in one embodiment, the blocking element 194 includes one or more of tungsten, gold, and iron. In one embodiment, blocking element 194 includes an element having an atomic number at least as large as the atomic number of iron.

As best shown in fig. 22, in one embodiment, the inner edge 197 of the blocking element 194 is spaced from the edge 195 of the respective aperture 193. As the beamlets 212 in the multiple beams are scanned over the blocking element 194 of the monitoring component 190, a detector (e.g., a monitoring detection system) may be configured to detect a change in the size of the beamlets 212 reaching the detector. The rate of change may be indicative of the size of beamlet 212.

As shown in fig. 19, in one embodiment, the monitoring component 190 is near the plane of the intermediate focus 233. In one embodiment, monitoring component 190 is downstream of intermediate focus 233. For example, as shown in fig. 19, in one embodiment, the electronic device 41 includes a deflector 235 at the intermediate focus 233. In one embodiment, the deflector 235 is configured to scan the beamlets 211-213 of the multi-beam on the monitoring component 190. The monitoring component 190 may be located downstream of the deflector 235.

When the electronic device 41 is in the operational configuration, the deflector 235 may be controlled such that the beamlets 211-213 pass through the aperture 193 of the monitoring component 190. When the electronic device 41 is switched to the monitoring configuration, the deflector 235 may be controlled such that the beamlets 211 to 213 of the multibeam scan over the inner edge 197 of the blocking element 194 of the monitoring component 190. In one embodiment, the monitoring component 190 includes a blade for the respective beamlets. Scanning the beamlets over the inner edges 197 of the blocking elements 194 requires relatively little deflection. By providing an aperture 193, the monitoring component 190 can remain in place during both the monitoring configuration and the operational configuration.

As shown in fig. 20, in one embodiment, the monitoring component 190 includes a substrate having thicker regions 191 and thinner regions 192. For example, the substrate may comprise silicon. Thicker region 191 is thicker than thinner region 192. In one embodiment, thicker region 191 has a thickness (in the direction of the multiple beams) of at least 100 μm, optionally at least 200 μm, and optionally at least 500 μm. In one embodiment, thicker region 191 has a thickness of at most 1mm and optionally at most 500 μm. In one embodiment, thinner region 192 has a thickness of at least 100nm, alternatively at least 200nm, alternatively at least 500nm, and alternatively at least 1 μm. In one embodiment, the thinner region has a thickness of at most 10 μm, alternatively at most 5 μm, alternatively at most 2 μm, and alternatively at most 1 μm.

As shown in fig. 20, in one embodiment, blocking elements 194 are provided on thinner regions 192 of the substrate. As mentioned above, in one embodiment, the inner edge 197 of the blocking element 194 is spaced from the rim 195 of the respective aperture 193. In one embodiment, the thinner region 192 of the substrate includes an uncovered region 196, as best shown in fig. 22. An uncovered area 196 is located between the blocking element 194 and the aperture 193. In plan view (i.e., when viewed in a direction parallel to the electron-optical axis), the uncovered region 196 is between the inner edge 197 of the blocking element 194 and the edge 195 of the aperture 193. The detector is configured to detect the change as the beamlet 212 is scanned over the blade pattern. The detector may be configured to detect a change between when the beamlet 212 passes through the aperture 193, when the beamlet 212 is over the uncovered area 196, and when the beamlet 212 is over the blocking element 194.

In one embodiment, blocking element 194 has a thickness of at least 10nm, alternatively at least 20nm, alternatively at least 50nm, alternatively at least 100nm, and alternatively at least 200 nm. In one embodiment, the blocking element 194 has a thickness of at most 1 μm, optionally at most 500nm, and optionally at most 200 nm. By providing a thicker blocking element 194, the contrast at the detector between when the beamlets 212 are over the blocking element 194 and when the beamlets pass through the thinner region 192 of the substrate may be increased.

In one embodiment, the aperture 193 has a dimension (i.e., diameter) of at least 500nm, alternatively at least 1 μm, alternatively at least 2 μm, alternatively at least 5 μm, and alternatively at least 10 μm. In one embodiment, the aperture 193 has a dimension (i.e., diameter) of at most 100 μm, alternatively at most 50 μm, alternatively at most 20 μm, and alternatively at most 10 μm. In one embodiment, the thinner regions 192 corresponding to the respective apertures 193 have a dimension (i.e., diameter) of at least 2 μm, optionally at least 5 μm, optionally at least 10 μm, optionally at least 50 μm, and optionally at least 100 μm. In one embodiment, thinner region 192 has a dimension (i.e., diameter) of at most 1mm, optionally at most 500 μm, optionally at most 200 μm, optionally at most 100 μm, and optionally at most 50 μm.

As shown in fig. 19, in one embodiment, the detector is maintained at a distance from the monitoring component 190 along the monitoring beam path. As shown in fig. 19, in one embodiment, at least one electron optical component is located between the monitoring component 190 and the detector. For example, in one embodiment, at least one of the scanning deflector array 260, the objective lens array 234, and the electronic detection device 240 is located between the monitoring component 190 and the monitoring detection system. In one embodiment, one or more other electron optical components are located between the monitoring component 190 and the monitoring detection system. For example, a control lens array 250 (e.g., as shown in fig. 3) may be located between the monitoring component 190 and the monitoring detection system.

The embodiment electronics 41 include at least one deflector 235. The deflector 235 is operable between an inspection setting corresponding to the operating configuration and a measurement setting corresponding to the monitoring configuration. In the inspection setting, the deflector 235 is configured to direct the beamlets 211-213 through an aperture 193. In a measurement setup, deflector 235 is configured to scan beamlets 211-213 over a blade pattern (e.g., over inner edge 197 of blocking element 194). In a measurement setup, at least one deflector 253 is configured to scan multiple beams over a portion of the monitoring component 190. In one embodiment, the at least one deflector 235 is configured to scan multiple beams such that beamlets 212 are scanned across the features of each blocking element 194. For example, beamlets may be scanned over the edges of the respective blocking elements 194.

As shown in fig. 19, in one embodiment, the detector is downstream of the most downstream electro-optical element of the electronic device 41. For example, as shown in FIG. 19, in one embodiment, the most downstream electro-optical element of electronic apparatus 41 is electronic detection apparatus 240. The electronic detection device 240 is for detecting electrons when the electronic device 41 is in an operational configuration. The detector for monitoring the configuration is downstream of the electronic detection device 240.

In one embodiment, the detectors are at least 500 μm, alternatively at least 1mm, alternatively at least 2mm, and alternatively at least 5mm downstream of the monitoring component 190. By keeping the detector at a distance from the monitoring component 190, electrons scattered and escaping from the blocking element 194 can be more easily geometrically separated from directly transmitted electrons. This geometric separation makes it easier for the detector to distinguish which electrons are transmitted through the thinner region 192 of the substrate and which electrons are scattered in the blade pattern. One embodiment of the present invention is expected to improve measurement accuracy. One embodiment of the present invention is expected to increase the dimensional tolerance of the blade pattern.

As shown in fig. 19 and described above, in one embodiment, the detector includes a transducer 60 and an optical detector, such as a camera 61. The converter 60 and the optical detector (such as the camera 61 shown in fig. 19) may have the same features as those described above with respect to fig. 10, for example. As shown in fig. 19, in one embodiment, the detector may be located at the location of the sample 208. The detector may be maintained as a sample at a distance from the monitoring component 190. The detector may be supported by a support or stage, which may also support the sample holder. A transducer 60 and an optical detector may be included in the stage. When the electronic device 41 is in the operational configuration, the sample 208 may be located at a sample location. When the electronic device 41 is switched to the monitoring configuration, the sample 208 may be switched using the transducer 60. In one embodiment, the stage 209 is configured to move the sample 208 and the transducer 60.

Fig. 23 is a schematic diagram of an exemplary multi-beam apparatus according to one embodiment. The device shown in fig. 23 may have the same features as described above with respect to fig. 22, except as follows. As shown in fig. 23, in one embodiment, the detector includes a monitoring detector 64. The monitoring detector 64 may be as described above, for example, with respect to fig. 11. For example only, the monitoring detector 64 may include one or more faraday cups and/or a plurality of PIN detectors. Other types of detectors may alternatively or additionally be used. The features of the monitor detector 64 of fig. 11 are applicable to the monitor detector 64 of fig. 23 unless stated to the contrary.

FIG. 24 is a schematic diagram of an exemplary apparatus according to one embodiment. For example, the device shown in fig. 24 may have the same features as described above with respect to fig. 19. As shown in fig. 24, in one embodiment, the detector is associated with an objective lens assembly of the electronic device 41. The objective lens assembly includes an objective lens array 234. The objective 234 is configured to direct multiple beams onto the sample 208. In the embodiment shown in fig. 24, the detector includes a monitor detector 64. The detector may remain in place for both the operating configuration and the monitoring configuration of the electronic device 41. Unless stated to the contrary, the features of the monitor detector 64 of fig. 11 apply to the monitor detector 64 of fig. 24.

In one embodiment, the detector is part of the same stack as the objective 234. As shown in fig. 24, in one embodiment, the detector is located upstream of the objective lens assembly. The detector remains spaced apart from the monitoring component 190.

Fig. 25 is a schematic diagram of the detector shown in fig. 24. As shown in fig. 25, in one embodiment, the detector includes a detector substrate 642 in which an aperture array 643 is formed. In an embodiment, the detector comprises an array of detection elements 641. In one embodiment, the detection elements 641 correspond to the respective apertures 643.

In one embodiment, the detection elements 641 surround the respective apertures 643. In the operating configuration, multiple beams pass through aperture 643. In the monitoring configuration, the deflector 235 is configured to direct the beamlets to scan across the blade pattern. Electrons can be detected by the detecting element 641.

The detection element 641 may include a charge detection, a scintillator, and a PIN detection element. For example, the detection element 641 may include one or more faraday cups or CCDs. In one embodiment, the detection element 641 is configured to convert electrons into photons that can be detected by an optical detector such as a camera.

The multi-beam electron optics may include a gun aperture plate or coulomb aperture array (not shown). A gun aperture plate is a plate in which an aperture is defined. It is located in the electron optical device downstream of the source and before any other electron optical device. In fig. 3, it will be located between the light source 201 and the converging lens array 231. In operation, the gun aperture plate is configured to block peripheral electrons of the source beam 202 to reduce coulomb effects in the beam, for example, in the converging lens array or before a beam splitter associated with the converging lens array. However, the gun aperture array may have fewer apertures than the converging lens array and fewer apertures than the number of beamlets downstream in the multi-beam. Since the gun aperture array is of the aperture array type and is spaced apart from other beam limiting aperture arrays, such as converging lens arrays and objective lens arrays, it is also contemplated during alignment.

The multi-beam electron optical arrangement may comprise a plurality of electron optical devices. The multi-beam electron optical device may be a multi-device column device.

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

References to upper and lower, lowest, upward and downward, above and below should be understood to refer to directions parallel (typically but not always vertical) to the upstream and downstream of the electron beam or beams impinging on the sample 208. Thus, references to upstream and downstream are intended to refer to directions about the beam path independent of any current gravitational field.

References to elements aligned along a beam path or beamlet path are understood to refer to the positioning of the corresponding element along the beam path or beamlet path.

An evaluation tool according to one embodiment of the present invention may be a tool that performs a qualitative evaluation (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 an image of a sample map. Examples of evaluation tools 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 functionalities associated with an inspection tool, or a metrology tool (e.g., a metrology inspection tool). The electron optical device 40 (which may comprise an electron optical device column) may be a component of an evaluation tool; 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 a device, apparatus or system comprising various components, which may or may not be collocated, or even located in a separate room, particularly for example, a data processing element.

Reference to a charged particle optical apparatus may be more specifically defined as a charged particle optical column. In other words, the apparatus may be provided as a column of devices. Thus, the column of devices may comprise the objective lens array assembly described above. The column of means may thus comprise a charged particle optical system as described above, for example comprising an objective lens array and optionally a detector array and/or optionally a converging lens array. Alternatively, the charged particle device may comprise a source. The charged particle device may be included as part of a charged particle optical apparatus. Such charged particle optical apparatus comprises a charged particle device and a source (if not part of the charged particle device) and an actuatable stage for supporting the sample. The actuatable stage may be actuatable to move the sample relative to the path of charged particles from the column of devices. The charged particle device may be located on a footprint in a chip fabrication facility. The charged particle system may include a charged particle device and an environmental conditioning system and a processor, such as a processing rack, which may be remote from a portion of the system present on the footprint of the device. Such environmental conditioning system approaches include portions of thermal conditioning systems and portions of vacuum systems.

Reference to a system or element that can control a component or a component that manipulates a charged particle beam in some manner includes configuring a controller or control system or control unit to control the component to manipulate the charged particle beam in the manner described, and optionally using other controllers or devices (e.g., voltage supply and/or current supply) to control the component to manipulate the charged particle beam in this manner. For example, under the control of a controller or control system or control unit, a voltage supply may be electrically connected to one or more components to apply an electrical potential to the components, such as in a non-limiting list comprising control lens array 250, objective lens array 234, converging lens 231, corrector, and scanning deflector array 260. The actuation of the components is controlled using one or more controllers, control systems or control units, and an actuatable component such as a stage may be controllable to actuate and thus move relative to another component such as a beam path.

The embodiments described herein may take the form of a series of aperture arrays or charged particle optical elements arranged in an array along a beam or multiple beam paths. Such charged particle optical elements may be electrostatic. In one embodiment, all charged particle optical elements (e.g., the last charged particle optical element in the beamlet path from the beam-limiting aperture array to the sample front) may be electrostatic and/or may be in the form of an aperture array or a plate array. In some arrangements, one or more charged particle optical elements are fabricated as MEMS (i.e., using MEMS fabrication techniques).

The computer program may include instructions that instruct the controller 50 to perform the following steps. The controller 50 controls the charged particle beam device to project a charged particle beam towards the sample 208. In one embodiment, the controller 50 controls at least one charged particle optical element (e.g., a plurality of deflectors or an array of scanning deflectors 260) to operate on the charged particle beam in the charged particle beam path. Additionally or alternatively, in one embodiment, the controller 50 controls at least one charged particle optical element (e.g., detector 240) to operate on a charged particle beam emitted from the sample 208 in response to the charged particle beam.

Any element or collection of elements may be replaceable or field replaceable within the electro-optic device 40. One or more charged particle optical components in electron optical device 40, particularly those charged particle optical components that operate on or generate beamlets, such as an aperture array and a manipulator array, may include one or more MEMS.

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 terms.

The following clauses are provided. Clause 1: a charged particle optical apparatus configured to project multiple beams of charged particles, the apparatus comprising: charged particle device, capable of switching between: (i) An operating configuration in which a column of devices is configured to project the multiple beams to a sample along an operating beam path extending from a source of the multiple beams to the sample, and (ii) a monitoring configuration in which the apparatus is configured to project the multiple beams to a detector along a monitoring beam path extending from the source to the detector; wherein the monitoring beam path is diverted midway along the operating beam path from the inspection beam path.

Clause 2: the charged particle optical apparatus of clause 1, wherein the device comprises at least one movable component configured to move between an operating position corresponding to the operating configuration and a monitoring position corresponding to the monitoring configuration.

Clause 3: the charged particle optical apparatus of clause 2, wherein the at least one movable component comprises the detector.

Clause 4: the charged particle optical apparatus of clause 2 or 3, wherein the monitoring location is between the source and the sample.

Clause 5: the charged particle optical apparatus of any of clauses 2-4, wherein the at least one movable component comprises a converter configured to receive the multiple beams output by the source and to generate light in response to the received multiple beams.

Clause 6: the charged particle optical apparatus of clause 5, wherein the at least one movable component comprises a light guide arrangement configured to guide the light generated by the converter towards the detector.

Clause 7: the charged particle device of clause 5 or 6, wherein the at least one movable component comprises a mirror configured in the monitoring position to direct the light generated by the converter to the detector.

Clause 8: the charged particle apparatus according to any of clauses 1-4, wherein the device comprises: a transducer in the path of the multiple beams to generate a beam in response to the multiple beams; and a mirror configured to be in the monitoring configuration to direct the light beam to the detector desirably in the monitoring configuration.

Clause 9: the charged particle device of clause 7 or 8, wherein the transducer is held in the same position in the operating configuration and is located in the monitoring position.

Clause 10: the charged particle device of clause 9, wherein a plurality of apertures are defined in the converter for the passage of the paths of the multiple beams, desirably in an operational configuration.

Clause 11: the charged particle optical apparatus of any of clauses 7-10, wherein a plurality of apertures are defined in the mirror, the plurality of apertures configured to allow the multi-beam to pass through the mirror in a desired operational configuration toward a sample, wherein the mirror is configured to reflect light toward the detector.

Clause 12: the charged particle device of clause 11, wherein in the operating configuration, the paths of a plurality of the multiple beams pass through respective apertures defined in the mirror.

Clause 13: the charged particle device of clause 10 or 12, wherein in the monitoring configuration, the paths of the plurality of beams in the multi-beam are incident on the converter.

Clause 14: charged particle optical apparatus according to any of the preceding clauses, wherein the device comprises at least one deflector operable between an inspection setting corresponding to the operating configuration and a measurement setting corresponding to the monitoring configuration, wherein desirably the deflector is a macro-deflector configured to operate on all beam paths of the multi-beam or the deflector is a deflector array comprising a plurality of deflector elements for operating on paths in respective beam paths of the multi-beam.

Clause 15: the charged particle optical apparatus of any of clauses 2-14, wherein the at least one movable component comprises one of the source and an objective lens array configured in the operational configuration to project the multiple beams onto the sample.

Clause 16: the charged particle optical apparatus of clause 15, wherein in the operating configuration the multiple beams are aligned with lenses in the objective lens array, and in the monitoring configuration the multiple beams are offset relative to the objective lens array, wherein desirably the apparatus comprises an actuator configured to actuate the apparatus between the operating configuration and the monitoring configuration.

Clause 17: the charged particle optical apparatus of clause 1, wherein the device comprises a monitoring component in the monitoring beam path upstream of the detector.

Clause 18: the charged particle optical apparatus of clause 17, wherein the monitoring component comprises an array of blocking elements configured to block the multiple beams.

Clause 19: the charged particle optical apparatus of clause 18, wherein the blocking elements have a similar pattern.

Clause 20: the charged particle optical apparatus of clause 18 or 19, wherein the blocking element comprises a blade.

Clause 21: charged particle optical apparatus according to any of clauses 18-20, wherein the monitoring means comprises an aperture array adjacent to the respective blocking element for passing the multi-beam.

Clause 22: the charged particle optical apparatus of clause 21, wherein each aperture in the array of apertures corresponds to each blocking element in the array of blocking elements.

Clause 23: the charged particle optical apparatus of clause 22, wherein each blocking element surrounds a corresponding each aperture.

Clause 24: a charged particle optical apparatus according to any of clauses 21-23, wherein the respective blocking elements are annular.

Clause 25: the charged particle optical apparatus of clause 24, wherein the respective blocking element has an inner edge, desirably a knife edge, spaced apart from the edge of the respective aperture.

Clause 26: the charged particle optical apparatus of any of clauses 17-25, wherein the detector is maintained a distance from the monitoring component along the monitoring beam path.

Clause 27: charged particle optical apparatus according to any of clauses 17-26, wherein the device comprises at least one deflector operable between an inspection setting corresponding to the operating configuration and a measurement setting corresponding to the monitoring configuration.

Clause 28: the charged particle optical apparatus of clause 27, wherein in the measurement setup, the at least one deflector is configured to scan the multiple beams over a portion of the monitoring component.

Clause 29: the charged particle optical apparatus of clause 28, wherein the at least one deflector is configured to scan the multiple beams such that the beams are scanned over the features of the respective blocking element that are desired to be blades.

Clause 30: the charged particle optical apparatus of any of clauses 17-29, wherein the detector is downstream of a downstream-most charged particle optical element of the device.

Clause 31: charged particle optical apparatus according to any of clauses 17-29, wherein the detector is associated with an objective lens assembly of the device, the objective lens assembly comprising an objective lens array configured to direct the multiple beams onto the sample.

Clause 32: the charged particle optical apparatus of clause 31, wherein the detector is located at an upstream end of the objective lens assembly.

Clause 33: a charged particle optical apparatus configured to project multiple beams of charged particles to a sample, the apparatus comprising: a source configured to output a source beam for generating the multiple beams; an aperture array configured to form a plurality of the multiple beams from the source beam by blocking a proportion of the source beam from projecting toward the sample; and a detector configured to measure at least a parameter of at least a portion of the source beam of the blocked fraction.

Clause 34: the charged particle optical apparatus of clause 33, comprising a converter configured to receive the source beam output by the source and to generate light in response to the received source beam.

Clause 35: the charged particle optical apparatus of clause 34, wherein the converter is located at an upstream surface of the aperture array, wherein the source beam desirably received comprises at least a portion of the proportion of the source beam blocked by the aperture array.

Clause 36: the charged particle optical apparatus of clause 34 or 35, comprising a mirror configured to reflect light generated by the converter toward the detector.

Clause 37: the charged particle optical apparatus of clause 36, wherein the mirror is positioned in an upstream direction of the converter, wherein desirably the mirror is between the converter and the source.

Clause 38: the charged particle optical apparatus of clause 36 or 37, wherein the mirror comprises an aperture for receiving the source and/or the source beam.

Clause 39: a charged particle optical apparatus configured to project multiple beams of charged particles to a sample, the apparatus comprising: charged particle apparatus comprising: an objective lens array configured to project the multiple beams onto a location on the sample; a plurality of converters configured to receive signal particles emitted from the sample and generate light in response to the received signal particles; and a light guide arrangement comprising a mirror defining a plurality of apertures to allow the multiple beams to pass through the mirror towards the sample; and a light sensing assembly, the light guide arrangement configured to guide the light generated by the converter to the light sensing assembly, wherein the light sensing assembly comprises: an evaluation sensor and a detector, each configured to detect the light generated by the converter; and a beam splitter configured to split the light generated by the converter into light beams for evaluating the sensor and the detector.

Clause 40: the charged particle optical apparatus of clause 39, comprising a controller configured to match the detection signal of the evaluation sensor to the position on the sample onto which the multiple beams are projected based on the detection signal of the detector, wherein desirably the converter is a scintillator.

Clause 41: the charged particle optical apparatus of any of the preceding clauses, wherein the detector is configured to detect light.

Clause 42: the charged particle optical apparatus of any of clauses 1-35 and 39-41, wherein the detector is configured to detect charged particles.

Clause 43: the charged particle optical apparatus of clause 42, wherein the detector comprises one of a faraday cup array, a charge coupled device, and a direct light detector device comprising a converter configured to generate light in response to charged particles and an adjoining optical detector preferably in contact with the converter configured to directly convert the generated optical signal generated by the converter into an electrical signal.

Clause 44: the charged particle optical apparatus of any of the preceding clauses, wherein the detector is configured to measure at least one of a uniformity of the multiple beams, an alignment of the multiple beams, and an aberration of the multiple beams.

Clause 45: the charged particle optical device of clause 44, wherein the aberration is at least one of field curvature, distortion, and astigmatism.

Clause 46: the charged particle optical apparatus according to any of the preceding clauses, wherein the source is configured to emit electrons.

Clause 47: a method of projecting multiple beams of charged particles, the method comprising: using a charged particle device in an operating configuration to project the multiple beams to a sample along an operating beam path from a source of the multiple beams to the sample; and using the apparatus in a monitoring configuration to project the multiple beams to a detector along a monitoring beam path extending from the source to the detector; wherein the monitor beam path is diverted midway along the operating beam path from the operating beam path.

Clause 48: a method of projecting multiple beams of charged particles, the method comprising: in an operating configuration, projecting the multiple beams to a sample along an operating beam path from a source of the multiple beams to the sample; and in a monitoring configuration, projecting the multiple beams to a detector along a monitoring beam path from the source to the detector, and diverting the monitoring beam path partway along the operating beam path from the operating beam path.

Clause 49: a method of projecting multiple beams of charged particles onto a sample, the method comprising: outputting a source beam of the multiple beams using a source; using an aperture array to form a plurality of the multiple beams from the source beam by blocking a proportion of the source beam from projecting toward the sample; and measuring, using a detector, at least a parameter of at least a portion of the source beam of the blocked fraction.

Clause 50: a method of projecting multiple beams of charged particles onto a sample, the method comprising: outputting a source beam of the multiple beams from a source; forming a plurality of the multiple beams from the source beam by blocking a proportion of the source beam from projecting toward the sample at an aperture array; and desirably using a detector to measure at least a portion of the source beam of the blocked fraction.

Clause 51: a method of projecting multiple beams of charged particles onto a sample, the method comprising: using an array of objective lenses configured to project the multiple beams onto locations on the sample; using a plurality of converters, desirably scintillators, to receive signal particles emitted from the sample and generate light in response to the received signal particles; using a light guiding arrangement to guide the light generated by the converter to a light sensing assembly, wherein the light guiding arrangement comprises a mirror defining a plurality of apertures for allowing the multiple beams to pass through the mirror towards the sample; and using a beam splitter to split the light generated by the converter into a plurality of light beams for evaluating a sensor and a detector; and detecting the light generated by the converter using the evaluation sensor and the detector.

Clause 52: a method of projecting multiple beams of charged particles onto a sample, the method comprising: desirably using an objective lens array to project the multiple beams onto a location on the sample; desirably receiving signal particles emitted from the sample using a plurality of converters, desirably scintillators, and generating light in response to the received signal particles; directing the generated light to a light sensing assembly using a light guiding arrangement, wherein the light guiding arrangement comprises a mirror defining a plurality of apertures, thereby allowing the multiple beams to pass through the mirror towards the sample; and desirably using a beam splitter to split the generated light into a plurality of light beams, preferably for evaluating sensors and detectors; and detecting the generated light, desirably using the evaluation sensor and the detector.

Claims

1. A charged particle optical apparatus configured to project multiple beams of charged particles, the apparatus comprising:

Charged particle device, capable of switching between: (i) An operating configuration in which a column of devices is configured to project the multiple beams to a sample along an operating beam path extending from a source of the multiple beams to the sample, and (ii) a monitoring configuration in which the apparatus is configured to project the multiple beams to a detector along a monitoring beam path extending from the source to the detector;

Wherein the monitor beam path is diverted midway along the operating beam path from the inspection beam path.

2. Charged particle optical apparatus according to claim 1, wherein the device comprises at least one movable component configured to move between an operating position corresponding to the operating configuration and a monitoring position corresponding to the monitoring configuration.

3. Charged particle optical apparatus according to claim 2, wherein the at least one movable part comprises the detector.

4. A charged particle optical device according to claim 2 or 3, wherein the monitoring location is between the source and the sample.

5. Charged particle optical apparatus according to any one of claims 2 to 4, wherein the at least one movable component comprises a converter configured to receive the multiple beams output by the source and to generate light in response to the received multiple beams.

6. The charged particle optical apparatus according to claim 5, wherein the at least one movable component comprises a light guiding arrangement configured to guide the light generated by the converter towards the detector.

7. A charged particle device according to claim 5 or 6, wherein the at least one movable component comprises a mirror configured in the monitoring position to direct the light generated by the converter to the detector.

8. The charged particle device according to claim 7, wherein the transducer is held in the same position in the operating configuration and is located in the monitoring position.

9. Charged particle apparatus according to claim 8, wherein a plurality of apertures are desirably defined in the converter in an operative configuration for passage of the paths of the multiple beams.

10. Charged particle optical device according to any of claims 7-9, wherein a plurality of apertures are defined in the mirror, the plurality of apertures desirably being configured in the operating configuration to allow the multiple beams to pass through the mirror towards the sample, wherein the mirror is configured to reflect light towards the detector.

11. The charged particle device according to claim 10, wherein in the operating configuration the paths of a plurality of the multiple beams pass through respective apertures defined in the mirror.

12. Charged particle apparatus according to claim 9 or 11, wherein in the monitoring configuration the paths of a plurality of the multiple beams are incident on the converter.

13. A charged particle optical apparatus according to any preceding claim, wherein the device comprises at least one deflector operable between an inspection setting corresponding to the operating configuration and a measurement setting corresponding to the monitoring configuration.

14. Charged particle optical apparatus according to any one of claims 2 to 13, wherein the at least one movable component comprises one of the source and an objective array configured in the operating configuration to project the multiple beams onto the sample.

15. Charged particle optical apparatus according to claim 14, wherein in the operating configuration the multiple beams are aligned with lenses of the objective lens array and in the monitoring configuration the multiple beams are offset relative to the objective lens array, wherein desirably the apparatus comprises an actuator configured to actuate the apparatus between the operating configuration and the monitoring configuration.