Multibeam Scanning Transmission Charged Particle Microscope

Abstract

The present invention discloses a technique for a multi-beam scanning transmission charged particle microscope. An example apparatus includes at least a charged particle beam column for generating a plurality of charged particle beams and irradiating a sample with each of the plurality of charged particle beams; and an imaging system for collecting charged particles of each of the plurality of charged particle beams that traverse the sample during the irradiation, and directing each of the plurality of charged particle beams onto a detector after traversing the sample, wherein each charged particle beam includes a centroid, and wherein the detector is disposed at an intermediate position between a back focal plane of the imaging system and an imaging plane.

Description

Technical Field

[0001] The technology disclosed herein relates generally to the field of electron microscopy, and more specifically, in some embodiments, to multi-beam scanning transmission electron microscopy. Background Art

[0002] Electron microscopy is divided into many types, each of which has advantages and disadvantages. In some cases, the advantages and disadvantages may determine which type of electron microscopy may be used. To name just a few, a few example types include scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy. Each of the types mentioned has specific disadvantages that, if overcome, may increase its adoption. For example, scanning transmission electron microscopy is adversely affected by throughput (to name just one negative example), which, if properly addressed, may increase its adoption. BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Figure 1 is a highly schematic depiction of an embodiment of a STCPM in which the disclosed technology may be implemented.

[0004] Figure 2 The operating principle of an embodiment of the present invention is shown.

[0005] Like reference numerals refer to corresponding parts throughout the several views of the drawings. DETAILED DESCRIPTION

[0006] As used in this application and claims, the singular forms "a", "an", and "the" include plural forms unless the context clearly dictates otherwise. In addition, the term "comprising" means "including". Further, the term "coupled" does not exclude the presence of intervening elements between the coupled items.

[0007] The systems, devices, and methods described herein should not be construed as limiting in any way. Rather, the present disclosure relates to all novel and non-obvious features and aspects of the various disclosed embodiments (the embodiments alone and in various combinations and sub-combinations of the embodiments with each other). The disclosed systems, methods, and devices are not limited to any specific aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require the presence of any one or more specific advantages or problems to be solved. Any theories of operation are for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theories of operation.

[0008] Although the operations of some of the disclosed methods are described in a specific sequential order for ease of presentation, it should be understood that unless the specific language set forth below requires a specific ordering, this description encompasses rearrangement. For example, in some cases, the operations described in sequence may be rearranged or performed simultaneously. In addition, for the sake of simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and devices can be used in combination with other systems, methods, and devices. In addition, this specification sometimes uses terms like "generating" and "providing" to describe the disclosed methods. These terms are high-level abstractions of the actual operations performed. The actual operations corresponding to these terms will vary depending on the specific implementation and are easily discernible by those of ordinary skill in the art.

[0009] In some instances, values, processes, or devices are referred to as "lowest," "optimal," "minimum," etc. It should be understood that such descriptions are intended to indicate that a selection can be made among a number of functional alternatives that may be used, and that such selection is not necessarily better, lesser, or otherwise preferred over other selections.

[0010] Charged particle microscopy is a well-known and increasingly important technique for imaging microscopic objects, particularly in the form of electron microscopy. Historically, the basic genus of electron microscopes has undergone a transformation into many well-known device types, such as transmission electron microscopes (TEM), scanning electron microscopes (SEM), and scanning transmission electron microscopes (STEM), and also into various sub-species, such as so-called "dual beam" devices (such as FIB-SEM), which additionally employ a "machining" focused ion beam (FIB), allowing support activities such as ion beam milling or ion beam induced deposition (IBID).

[0011] In a SEM, irradiation of the sample by a scanning electron beam causes "auxiliary" radiation, for example in the form of secondary electrons, backscattered electrons, X-rays, and cathodoluminescence (infrared, visible and / or ultraviolet photons), to be emitted from the sample; one or more components of this emitted radiation are then detected and used for image accumulation purposes.

[0012] In a TEM, the electron beam used to irradiate the sample is chosen to have a sufficiently high energy to penetrate the sample (for this purpose, the sample will generally be thinner than in the case of SEM samples); the transmitted electrons emitted from the sample can then be used to create an image. When this type of TEM is operated in scanning mode (hence a STEM), the image in question will be accumulated during the scanning movement of the irradiating electron beam over the sample. As an alternative to using electrons as the irradiating beam, charged particle microscopy can also be performed using other kinds of charged particles. In this regard, the phrase "charged particles" should be interpreted broadly to cover, for example, electrons, positive ions (such as Ga or He ions), negative ions, protons and positrons.

[0013] It should be noted that besides imaging and performing (local) surface modifications (e.g. milling, etching, deposition, etc.), charged particle microscopes may also have other capabilities, like performing spectroscopic examinations, examining diffraction patterns, etc.

[0014] In all cases, a charged particle microscope (CPM) will contain at least the following components:

[0015] A particle source, such as a Schottky electron source or an ion source.

[0016] An illuminator (charged particle beam column) which is used to manipulate the "raw" radiation beam from the source and perform operations on it, such as focusing, aberration suppression, cropping (with a diaphragm), filtering, etc. It will generally contain one or more (charged particle) lenses, and may also contain other types of (particle) optical components. If necessary, the illuminator can be provided with a deflector system that allows the outgoing beam to perform a scanning motion over the sample being studied.

[0017] A sample holder on which the sample under investigation can be held and positioned (e.g. tilted, rotated). If necessary, the holder can be moved to achieve a scanning motion of the sample relative to the beam. Generally, such a sample holder will be connected to a positioning system. When designed for holding cryogenic samples, the sample holder may include means for maintaining the sample at cryogenic temperatures, for example using a suitably connected cryogen barrel.

[0018] Detectors (for detecting radiation emitted from the irradiated sample) which may be unitary or composite / distributed in nature and which may take many different forms, depending on the radiation being detected. Examples include photodiodes, CMOS detectors, CCD detectors, photovoltaic cells, X-ray detectors (such as silicon drift detectors and Si(Li) detectors), etc. In general, a CPM may contain several different types of detectors, the selection of which may be called for in different circumstances.

[0019] In case of a transmission type microscope (e.g. (S)TEM), the CPM will additionally contain:

[0020] An imaging system, which basically takes the charged particles transmitted through the sample (plane) and directs (focuses) them onto an analytical device, such as a detection / imaging device, a spectroscopic device (such as an EELS device: EELS = Electron Energy Loss Spectroscopy), etc. As with the illuminator mentioned above, an imaging system may also perform other functions, such as aberration suppression, cropping, filtering, etc., and it usually contains one or more charged particle lenses and / or other types of particle optical components.

[0021] Hereinafter, the techniques disclosed herein may, for example, sometimes be described in the specific context of electron microscopy; however, such settings are intended for clarity / illustrative purposes only and should not be construed as limiting.

[0022] STEM is a powerful operating mode of conventional TEM, whereby a focused electron beam is scanned over a thin sample, and the transmitted / scattered electrons with different scattering angles are then collected and converted into an image. Depending on the scattering angle of the transmitted electrons, they can generate a "bright field (BF)" signal if the scattering stays within the beam opening angle; if the scattering angle is greater than the beam opening angle, they can generate a "dark field (DF)" signal. With the recent development of new imaging techniques (by the current assignee), which can be referred to as integral differential phase contrast (iDPC) imaging: for example, see US 9,312,098 and US 2016 / 0307729 A1 (incorporated herein by reference in its entirety and for all purposes), STEM has attracted new interest as an imaging method. However, for some applications, the throughput of STEM technology may not be optimal. One of the reasons is that in high-resolution STEM, the probe / input beam flow tends to be limited due to lens aberrations and Coulomb interactions. In addition, the field of view (FoV) tends to be limited by the off-axis aberrations of the imaging system. As throughput requirements become more challenging, these types of STEM defects become increasingly frustrating.

[0023] It is an object of the present disclosure to at least address the above identified problems. More specifically, it is an object of the present disclosure to describe a STCPM-based imaging technique that allows for improved throughput compared to existing STCPM-based imaging techniques. Furthermore, it is an object of the present disclosure that the techniques disclosed herein should have an increased FoV relative to conventional techniques.

[0024] These and other goals can be achieved in a microscope when:

[0025] the microscope being configured to generate a plurality of said charged particle beams and to irradiate these simultaneously onto different areas of said sample; and

[0026] In a detector plane between a back focal plane (BFP) and an imaging plane (IP) of the imaging system, a detector for detecting the multiple charged particle beams after passing through a sample is arranged, wherein the detector plane is located at a position sufficient to provide determination and detection of the center of mass of each beam in the multiple charged particle beams.

[0027] It should be noted that the detector may be a separate independent detector module (eg, multiple detector modules) for each of the multiple charged particle beams, or the detector may be a large, composite detector that detects each of the charged particle beams, eg, at different regions of the detector.

[0028] The technology disclosed herein solves the throughput problem of STEM by using multiple probes / input beams to achieve parallel processing: the sample's presentation surface is essentially subdivided into a matrix of conceptual "patches / regions / areas", and each of these patches / regions / areas is simultaneously imaged by a corresponding one of the multiple beams, thus increasing the cumulative FoV and increasing throughput. However, in such architectures, problems arise in simultaneously detecting each of the STEM signals from the corresponding input beams. Applying "conventional" diffraction pattern detection methods fails because the signals from the multiple beams overlap at the diffraction plane (also referred to herein as BFP) of the employed imaging system (objective) where the (real or virtual) detector / camera would traditionally be located, so it is impossible to separate different signals from different beams. On the other hand, it makes little sense to use a detector in the IP of the imaging system, because one detector essentially only forms a (non-overlapping) probe image at said location and can only detect the intensity of the probe (one or more) at said location. Only being able to detect the intensity of the probe image does not allow the centroid to be determined.

[0029] In contrast, the disclosed technique takes the counter-intuitive step of positioning the detector(s) at an intermediate detector plane located between the BFP and IP of the imaging system. In this intermediate detector plane, the output beams originating from multiple input beams will be separated from each other, allowing discrete detection thereof; however, the pattern registered at this location is essentially a hybrid between a diffraction pattern and a probe image (somewhat similar to a partial Fourier transform / Fresnel propagation of a real image), so conventional physical interpretation of the registered pattern would be considered challenging. However, it has been found that such hybrid patterns can be used to form satisfactory images, for example, by the iDPC technique described above.

[0030] In general, it has been shown that the location of the intensity centroid of each pattern (the center of "mass" or spatial center of each beam emerging from the sample) is proportional to the local electric field potential experienced by the associated beam during its passage through the sample. As a result, it does not matter what the pattern represents or how it looks, as long as its intensity centroid can be determined. In other words, no matter how each pattern looks, it retains angular information (through the location of its centroid) that can be used as the basis for image information. If the pattern is registered using a position-sensitive detector (such as a pixelated or segmented detector / camera), its centroid can be located relatively easily using, for example, image recognition software. Note that such position-sensitive detectors are at the heart of the differential phase contrast (DPC) technique, which derives information from the way the beam footprint is displaced (on the detection surface of the detector) from a zero / reference position (e.g., the way the beam is (asymmetrically) divided between four or more detector quadrants / segments / regions). The aforementioned iDPC technique goes a step further by converting the output from such a detector into a vector field and performing a mathematical integration step on it; hence, the iDPC technique is also called iVF (integrated vector field) imaging.

[0031] Regarding the relative scanning motion of the input beam and the sample, there are many different ways in which this can be achieved. For example:

[0032] (i) In one possible ("mechanical scanning") setup, the scanning assembly employed comprises an actuator system for generating a scanning motion of the sample holder.

[0033] (ii) in an alternative ("beam scanning") setting, the beams are scanned relative to the sample. To this end, for example, a first beam deflector system is invoked upstream of the sample to generate a scanning motion of the plurality of beams relative to the sample; and a second beam deflector system downstream of the sample and upstream of the detector plane is used to negate the scanning motion generated by the first beam deflector system.

[0034] An advantage of method (i) is that, although it will require the use of a sample holder platform capable of accurately traversing the scanning path, it is less complex / complex than method (ii); this need not present a technical obstacle as complex scanning stages are already used in fields such as lithography and are available in many different embodiments. Beam scanning is the more traditional method used in single-beam CPMs (such as SEMs and STEMs), although the current disclosure may require modification for multiple beams. Needless to say, a hybrid of methods (i) and (ii) may also be implemented if desired, in which both types of scanning are employed. Note that when method (ii) is used with a detector that is not located in the diffraction plane of the imaging system, scanning the input beam will result in a concomitant scanning motion of the output beam falling on the detector. If a reference "zero measurement" is performed without the sample in place, this "baseline" scanning effect can be subtracted from the detection results obtained with the sample in place.

[0035] With regard to the number of input beams used in the techniques disclosed herein, it should be emphasized that this is arbitrary. On the one hand, the greater the number of beams, the greater the throughput enhancement that can be achieved; on the other hand, a greater number of beams will increase the complexity of the overall system. A skilled person will be able to find a compromise between these competing effects and choose a number that is appropriate for a given scenario / use case. By way of example, a system may be constructed using 196 beams in a 14×14 array - although many other beam numbers / configurations are possible.

[0036] Those skilled in the art will also appreciate that if the detector plane used in the present invention is selected too close to the BFP of the imaging system, the patterns corresponding to the various input beams may not be sufficiently separated from each other to distinguish the centroids of the various beams. On the other hand, if the detector plane is selected too close to the IP of the imaging system, the beam paths of the input beams will be very sufficiently separated from each other, but the registered "patterns" will tend to the basic detection image, so it is impossible to determine the position and translation of their corresponding centroids, which may render the technology disclosed herein unimplementable. Between these extremes, the technician will be well able to select appropriate detector plane positions.

[0037] Figure 1 is a highly schematic depiction of an embodiment of a STCPMM in which the disclosed techniques may be implemented; more specifically, it shows an embodiment of a TEM / STEM (however, in the context of the present disclosure, it may effectively be, for example, an ion-based microscope). Figure 1In FIG. 1 , within a vacuum housing 2, an electron source 4 generates an electron beam B that propagates along an electron optical axis B' and traverses an electron optical illuminator (charged particle beam column) 6 for directing / focusing the electrons onto a selected portion of a sample S (e.g., which may be (locally) thinned / planarized). A deflector 8 is also depicted, which ( especially ) can be used to realize the scanning movement of the electron beam B.

[0038] The sample S is held on a sample holder H, which can be positioned with multiple degrees of freedom by a positioning device / platform A, which moves a bracket A' in which the holder H is (removably) fixed; for example, the sample holder H can include a ( especially ) The finger that moves in the XY plane ( See also The sample holder H is a Cartesian coordinate system as depicted; in general, movement parallel to Z and tilting about X / Y are also possible). Such movement allows different parts of the sample S to be irradiated / imaged / inspected by the electron beam B traveling along the axis B' (in the Z direction), and / or allows scanning movements to be performed as an alternative to beam scanning. If desired, an optional cooling device (not depicted) can be brought into close thermal contact with the sample holder H, for example to maintain it (and the sample S thereon) at cryogenic temperatures.

[0039] The electron beam B will interact with the sample S so that various types of "stimulated" radiation are emitted from the sample S, including (for example) secondary electrons, backscattered electrons, X-rays and optical radiation (cathodoluminescence). If desired, one or more of these radiation types can be detected with the aid of an analysis device 22, which can be, for example, a combined scintillator / photomultiplier tube or an EDX (energy dispersive X-ray spectrometer) module; in such cases, images can be constructed using essentially the same principles as in a SEM. Alternatively or additionally, however, electrons that traverse (pass through) the sample S, exit / emit from it and continue to propagate along the axis B' (basically, although usually with some deflection / scattering) can be studied. Such transmitted electron flux enters an imaging system (projection lens) 24, which typically includes various electrostatic / magnetic lenses, deflectors, correctors (such as compensators), etc. In normal (non-scanning) TEM mode, this imaging system 24 can focus the transmitted electron flux onto a fluorescent screen 26, which can be retracted / withdrawn (as schematically indicated by arrow 26') if necessary to keep it away from the axis B'. An image (or diffraction pattern) of (a portion of) the sample S will be formed by the imaging system 24 on a screen 26, and this may be viewed through a viewing port 28 located in a suitable portion of the wall of the housing 2. The retraction mechanism for the screen 26 may, for example, be mechanical and / or electrical in nature, and is not depicted herein.

[0040] As an alternative to viewing the image on screen 26, use may be made instead of the fact that the depth of focus of the electron flux leaving the imaging system 24 is typically very large (e.g., about 1 meter). Therefore, various other types of analysis equipment may be used downstream of screen 26, such as:

[0041] TEM camera 30. At the TEM camera 30, the electron flux may form a static image (or diffraction pattern) which may be processed by the controller / processor 20 and displayed on a display device (not depicted) (e.g., a flat panel display). When not needed, the TEM camera 30 may be retracted / withdrawn (as schematically indicated by arrow 30') to move it away from the axis B'.

[0042] STEM camera 32. The output from the STEM camera 32 can be recorded as a function of the (X, Y) scan position of the beam B on the sample S, and an image can be constructed that is a "map" of the output from the STEM camera 32 as a function of X, Y. In contrast to the matrix of pixels characteristically present in the TEM camera 30, the STEM camera 32 may contain a single pixel having a diameter of, for example, 20 mm. In addition, the STEM camera 32 will typically have a higher speed than the TEM camera 30 (e.g., 10 pixels per second). 2 images per second) 6 Likewise, when not needed, the STEM camera 32 can be retracted / withdrawn (as schematically indicated by arrow 32') so as to move it away from the axis B' (although such retraction is not necessary in the case of, for example, an annular dark field STEM camera 32; in such cameras, the central hole will allow flux passage when the camera is not in use).

[0043] As an alternative to imaging using cameras 30 or 32 , a spectroscopic device 34 may also be called upon, which may be an EELS module, for example.

[0044] It should be noted that the order / position of items 30 , 32 and 34 is not critical and many possible variations are contemplated. Spectroscopic device 34 may also be integrated into imaging system 24 , for example.

[0045] Note that a controller (computer processor) 20 is connected to the various components shown via control lines (buses) 20'. This controller 20 can provide a variety of functions, such as synchronizing actions, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not depicted). Needless to say, the (schematically depicted) controller 20 can be (partially) inside or outside the housing 2 and can have an integral or composite structure as desired.

[0046] The skilled person will appreciate that the interior of the enclosure 2 need not necessarily be kept in a strict vacuum; for example, in a so-called "ambient TEM / STEM", a background atmosphere of a given gas is intentionally introduced / maintained within the enclosure 2. The skilled person will also appreciate that, in practice, it may be advantageous to limit the volume of the enclosure 2 so that it substantially surrounds the axis B' where possible, in the form of a small tube (e.g., of about 1 cm in diameter) through which the electron beam used passes, but widened to accommodate structures such as the light source 4, the sample holder H, the screen 26, the TEM camera 30, the STEM camera 32, the spectroscopic device 34, etc.

[0047] In the context of the present disclosure, multiple charged particle beams are directed onto respectively different regions of a sample S, for example by subdividing the (original) beam B into multiple (product) sub-beams using suitable aperture plates (not depicted). Figure 2 An example of such a situation is shown, where:

[0048] The left part of the figure is according to the present disclosure Figure 1 A schematic elevation view of the relevant portion of which has been modified to produce multiple beams.

[0049] The right part of the figure shows a plan view of the multi-beam cross section along the Z axis at a selected particle optical plane.

[0050] In this particular example, the multi-beam architecture uses four input beams (B1, B2, B3, B4) arranged in a square quadrupole configuration; however, this is not required, and different numbers and / or geometric arrangements of beams may be implemented and are contemplated herein. Figure 2 The various parts:

[0051] OP is the object plane of the objective lens (imaging system) OL. At plane OP, each focused input beam will have a cross-section in the form of a point or a small disk, as shown in the right subplot (B) of the figure. The sample S to be imaged is placed on this plane OP and Figure 2 This is schematically shown in the right subplot (S). As shown, the sample S is conceptually subdivided into four regions (S1, S2, S3, S4) to be imaged by corresponding beams (B1, B2, B3, B4) respectively. The sample S will typically be inhomogeneous, so the regions (S1, S2, S3, S4) will appear different from each other.

[0052] BFP is the back focal plane of the objective OL. Note that in this plane, the beams (B1, B2, B3, B4) have overlapping paths, so the patterned information carried by each of the beams will also overlap and coincide at the same location, as shown by the large central "spot" on the right side of the figure. Plane BFP is separated from the objective OL by the focal length f. At this location along Z, the centroid of each beam B1, B2, B3, and B4 will not be individually discernible due to the overlap of beams B1, B2, B3, and B4, so if a detector is positioned here, the techniques disclosed herein may not be applicable.

[0053] IP is the image plane of the objective lens OL. In plane IP, each of the beams (B1, B2, B3, B4) is focused onto a spot / disk similar to the situation in plane OP. Similarly, at this position along Z, due to the composition of the probe image (e.g., spot / disk), the centroid of each beam B1, B2, B3, and B4 will not be individually discernible, and therefore the techniques disclosed herein may not be applicable.

[0054] DP is an intermediate detector plane arranged between planes BFP and IP (along Z) according to the present disclosure. DP is displaced from plane BFP by an amount ΔZ. In this plane DP, the beams (B1, B2, B3, B4) will be separated from each other - at Figure 2 , which are shown in the lower right figure of , as four different patterns that can be individually registered by corresponding multiple component detectors whose detection surfaces are arranged in plane DP; note that, as mentioned above, these component detectors can actually be different zones of a single composite detection surface, for example as presented in a camera. In each detected pattern, the intensity centroid can be identified and its position used to construct (for example) an iPDC image of sample S. In a non-limiting example, plane DP is located at a Z-position corresponding to a position where the distance between the BF disks (of a well-defined size in BFP) of two adjacent beams is approximately equal to the BF (bright field) disk radius (R BF ), so that adjacent centroids are separated by 4*R in X or Y BF distance.

[0055] The principles of the disclosed technology have been described and shown with reference to the illustrated embodiments, and it will be appreciated that the illustrated embodiments may be modified in arrangement and detail without departing from such principles. For example, the elements of the illustrated embodiments shown in software may be implemented in hardware, and vice versa. In addition, the technology from any example may be combined with the technology described in one or more of the other examples. It will be appreciated that the processes and functions described with reference to the illustrated examples may be implemented in a single hardware or software module, or a separate module may be provided. The above specific arrangements are provided for ease of explanation, and other arrangements may be used.

[0056] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be appreciated that the embodiments shown are representative examples only and should not be considered to limit the scope of the present disclosure. The alternatives specifically addressed in these sections are merely exemplary and do not constitute all possible alternatives to the embodiments described herein. For example, the various components of the systems described herein may be combined in function and use. Therefore, we claim that all are within the scope of the appended claims.

[0057] In one embodiment, a scanning transmission charged particle microscope comprises a charged particle beam column for generating a plurality of charged particle beams and irradiating a sample with each of the plurality of charged particle beams; a scanning assembly for generating a relative scanning motion of the plurality of charged particle beams relative to the sample; and an imaging system for collecting charged particles of each of the plurality of charged particle beams that traverse the sample during the irradiation, and directing each of the plurality of charged particle beams to a detector after traversing the sample, wherein each of the plurality of charged particle beams comprises a centroid, and wherein the detector is disposed at an intermediate position between a back focal plane of the imaging system and an imaging plane, the intermediate position being defined by a position where the plurality of charged particle beams coincide and a position where the centroid of each charged particle beam is no longer distinguishable. In a first example of the microscope, the microscope further comprises, wherein the detector is selected from a group comprising a bright field detector, a dark field detector, a position sensitive detector, and a combination thereof. A second instance of the method optionally includes the first instance, and further includes, wherein the detector is a position sensitive detector; and a controller included in the microscope is configured to: generate a vector field based on an output from the position sensitive detector; and apply a two-dimensional integral operation to the vector field. A third instance of the microscope optionally includes one or more of the first instance and the second instance, and further includes, wherein the scanning assembly includes an actuator system for generating a scanning motion of the sample holder. A fourth instance of the microscope optionally includes one or more of the first instance and the third instance, and further includes, wherein the scanning assembly includes a first beam deflector system upstream of the sample, which is used to generate a scanning motion of the plurality of beams; and a second beam deflector system downstream of the sample and upstream of the detector plane, which is used to invalidate the scanning motion generated by the first beam deflector system. A fifth instance of the microscope optionally includes one or more of the first instance and the fourth instance, and further includes, wherein the plurality of charged particle beams are generated by directing the raw charged particle beam onto an aperture plate having a plurality of openings within a footprint of the raw beam. A sixth instance of the microscope optionally includes one or more of the first and fifth instances, and further includes, wherein the multiple charged particle beams are generated by multiple charged particle beam columns. A seventh instance of the microscope optionally includes one or more of the first and sixth instances, and further includes, wherein the middle plane is positioned so that adjacent centers of mass of the multiple charged particle beams are separated in the middle plane by at least twice the diameter of the profile of the charged particle beam.An eighth instance of a microscope optionally includes one or more of the first and seventh instances, and further includes, wherein the intermediate plane is further defined in the direction of the back focal plane by positions where the multiple charged particle beams are sufficiently emitted from the coincident positions so that individual charged particle beams and their corresponding centers of mass can be detected separately. A ninth instance of a microscope optionally includes one or more of the first and eighth instances, and further includes, wherein the intermediate plane is further defined in the direction of the imaging plane by positions where the center of mass of each of the multiple charged particle beams is still detectable. A tenth instance of a microscope optionally includes one or more of the first and ninth instances, and further includes, wherein the intermediate plane is further defined in the direction of the imaging plane by positions where the center of mass of each of the multiple charged particle beams is still detectable.

[0058] In another embodiment, a method of using a scanning transmission charged particle microscope includes simultaneously irradiating a sample with multiple charged particle beams, wherein each of the multiple charged particle beams irradiates a corresponding area of ​​the sample; scanning the charged particle beam relative to the sample; collecting charged particles that traverse the sample during the irradiation, and directing the collected charged particles onto a detector, wherein the detector is disposed in a detector plane between a back focal plane and an imaging plane of an imaging system, and wherein an intermediate position is defined by a coincidence position of the multiple charged particle beams and a position where the center of mass of each charged particle beam is no longer distinguishable. In a first instance of the method, the method further includes, wherein the intermediate position is positioned so that the bright field disks of at least two adjacent charged particle beams in the multiple charged particle beams are separated by a distance of twice the radius of the bright field disk.

Claims

1. A scanning transmission charged particle microscope, comprising: a charged particle beam column for generating a plurality of charged particle beams and irradiating a sample with each of the plurality of charged particle beams; a scanning assembly for generating a relative scanning motion of the plurality of charged particle beams relative to the sample; and an imaging system for collecting charged particles of each of the plurality of charged particle beams traversing the sample during the irradiating and directing each of the plurality of charged particle beams onto a detector after traversing the sample, wherein each of the plurality of charged particle beams comprises a centroid, and Wherein the detector is disposed at an intermediate position between a back focal plane and an imaging plane of the imaging system, the intermediate position being defined by a coincidence position of the plurality of charged particle beams and a position where the centroid of each charged particle beam is no longer distinguishable.

2. The microscope according to claim 1, wherein the detector is selected from the group consisting of a bright field detector, a dark field detector, a position sensitive detector and combinations thereof.

3. The microscope according to claim 1, wherein: The detector is a position sensitive detector; and The controller included in the microscope is configured to: generating a vector field based on output from the position sensitive detector; and A two-dimensional integration operation is applied to the vector field.

4. Microscope according to claim 1 or 3, wherein the scanning assembly comprises an actuator system for generating a scanning movement of the sample holder.

5. The microscope according to claim 1 or 3, wherein the scanning assembly comprises: a first beam deflector system upstream of the sample for producing a scanning motion of the plurality of beams; and A second beam deflector system downstream of the sample and upstream of the detector plane for nullifying the scanning motion produced by the first beam deflector system.

6. The microscope according to any one of claims 1 to 5, wherein the plurality of charged particle beams are generated by directing a primary charged particle beam onto an aperture plate having a plurality of openings within a footprint of the primary beam.

7. The microscope according to any one of claims 1 to 5, wherein the plurality of charged particle beams are generated by a plurality of charged particle beam columns.

8. The microscope according to any one of claims 1 to 5, wherein the intermediate plane is positioned such that adjacent centroids of the plurality of charged particle beams are separated in the intermediate plane by at least two times the diameter of the profile of the charged particle beam.

9. The microscope according to any one of claims 1 to 5, wherein the intermediate plane is further defined in the direction of the back focal plane by the positions at which the multiple charged particle beams are sufficiently emitted from the coincidence positions, so that individual charged particle beams and their corresponding centers of mass can be detected separately.

10. The microscope according to any one of claims 1 to 5, wherein an intermediate plane is further defined in the direction of the imaging plane by a position at which the center of mass of each of the plurality of charged particle beams is still detectable.

11. A method of using a scanning transmission charged particle microscope, the method comprising: irradiating a sample with a plurality of charged particle beams simultaneously, wherein each charged particle beam of the plurality of charged particle beams irradiates a corresponding area of ​​the sample; scanning the charged particle beam relative to the sample; collecting charged particles that traverse the sample during the irradiation and directing the collected charged particles onto a detector, wherein the detector is arranged in a detector plane between a back focal plane and an imaging plane of the imaging system, and The intermediate position is defined by a position where the plurality of charged particle beams coincide and a position where the center of mass of each charged particle beam is no longer distinguishable. 12 . The method of claim 11 , wherein the intermediate position is positioned such that bright field disks of at least two adjacent charged particle beams of the plurality of charged particle beams are separated by a distance of twice the radius of the bright field disk.

Images