Frame-based precession mapping in electron microscopy

Abstract

The method includes directing a charged particle beam across a region of a target at a first angle having a tilt angle component and an azimuth angle component to collect a first image frame generated using the beam at a selected first angle; detecting the first image frame; directing the charged particle beam across the region of the target at a second angle having a tilt angle component and / or an azimuth angle component different from the first angle to collect a second image frame generated using the beam at the selected second angle; detecting the second image frame; and combining the first image frame and the second image frame to form an image. A related apparatus is also disclosed.

Description

[0001] Cross - reference to related applications

[0002] This application claims the benefit of U.S. Provisional Application No. 63 / 427,643, filed on November 23, 2022, the entire application of which is incorporated herein by reference. Technical field

[0003] The field is charged particle beam microscopy. Background art

[0004] In many fields of electron microscopy, such as electron energy loss spectroscopy (EELS) and energy - dispersive x - ray spectroscopy (EDX), a sample is probed to determine, for example, the chemical composition of a crystalline material. However, at least in EELS and EDX, it may be difficult to determine the chemical composition because the spectral signal may vary with the sample orientation due to channeling effects of the beam through the crystal. By irradiating the sample with an electron beam in a specific pattern, the dependence of the characteristic peak signal intensity of the spectral data of the sample on the sample orientation can be reduced, in which pattern the beam scans at an oblique angle (i.e., along a conical scan path) over time at a specific sample location. In particular, the oblique angle can be optimized such that the characteristic spectral peaks are saturated and dynamic scattering is suppressed. However, existing methods include many drawbacks that limit the potential benefits of scanning at an oblique angle, and thus there is still a need for improved systems and methods. Brief description of the drawings

[0005] Figure 1 is a flow chart of various examples of a frame - based imaging method.

[0006] Figures 2A to 2B are a perspective view and a plan view of a sample receiving a beam during frame collection according to some examples, respectively.

[0007] Figure 3 is a schematic side view of an example frame - based charged particle beam imaging system according to various examples.

[0008] Figure 4 is a schematic plan view of an example scan area of a sample and associated tilt / azimuth angle data collected using a series of frames.

[0009] Figure 5 is a flow chart of a drift and / or aberration correction method according to some examples.

[0010] Figure 6 is a flow chart of an example 3D imaging method. Detailed description

[0011] Introduction to the tilt precession method and overview of frame-based techniques

[0012] In transmission electron microscope spectroscopy and imaging applications, precession of the beam during beam scanning can be used to improve performance. This is typically done by precessing the beam on a cone at each point of the scan, e.g., by residing at a position while the beam precesses through the cone and acquiring pixel data over time (hereinafter referred to as the "pixel-based" method). In various applications, precession is performed instead of on-axis imaging in order to improve imaging characteristics, e.g., to avoid channeling artifacts in spectroscopy, to separate the integral centroid of the phase shift (iCOM) effect in a crystal from field contributions, or to increase the intensity in higher order diffraction spots for more accurate strain analysis.

[0013] In this disclosure, examples are disclosed that relate to precession imaging but not necessarily to precessing a probe beam on a cone at each point of the scan. Instead, the disclosed examples of precession workflows can include frame-based collection. With frame-based collection, a particular precession (or tilt) angle and azimuth angle can be selected, and a pixel array can be recorded at the selected precession angle and azimuth angle. The recorded pixel array can correspond to a frame of the frame-based precession workflow. Then one or more additional frames can be collected using one or more respective different selected precession angles and / or azimuth angles that are changed to new angles and / or azimuth angles. In some examples, the amount of frames collected and the associated precession angle characteristics can include a dataset commensurate with the amount of data collected by precessing the beam on a cone in each individual pixel of the frame (such as using pixel-based techniques). In other words, rather than recording a dynamically tilted beam in a single pixel during a full scan of the frame, a fixed beam tilt can be used to quickly scan the frame, and then additional tilts can be used to repeat the frame scan until a tilt matrix similar to the tilt matrix obtained by the pixel-based method is sufficiently populated.

[0014] However, various frame-based examples in this disclosure can exhibit enhanced characteristics and / or permit various improvements compared to pixel-based methods. For example, frame-based methods can permit the implementation of various correction capabilities during the workflow that would be impractical or impossible with pixel-based methods. Additionally, frame-based methods can permit significantly improved imaging speeds compared to pixel-based methods and can enable new applications that would be impractical or impossible with pixel-based methods. That is, various frame-based examples can provide faster data acquisition times, improved spectroscopic image quality, improved field and strain measurements, and new applications such as atomic 3D imaging, rocking maps, jump beam aberration correction in STEM, etc.

[0015] Thus, while there are multiple applications that may benefit from precession mapping techniques, or more generally tilted beam incidence, such applications have heretofore been limited by existing precession paradigms, in which a fixed tilt amplitude is applied to a focused beam that then scans around a conical path at a particular point on the sample. In contrast, the systems and methods described herein use frame-based precession, allowing for considerable flexibility in the construction of the tilt matrix of data. This flexibility can allow precession techniques to be extended to new applications such as 3D imaging, and can open precession collection to further imaging improvements such as drift correction.

[0016] An electron microscope can be equipped with a set of deflectors for generating shifts and / or tilts of the beam at the sample. These can be achieved by placing a first deflector in a plane that is exactly conjugate to the sample, thus ensuring that the first deflector creates only a tilt (and no shift) at the sample, and by placing a second deflector in a plane that is exactly conjugate to the front focal plane of the lens forming the probe, thus ensuring that the second deflector creates only a shift (and no tilt) at the sample. However, more commonly and flexibly, the two deflectors are placed in two different planes (e.g., an upper plane and a lower plane), which are not necessarily conjugate to the sample or to the front focal plane of the objective lens, and the upper and lower deflectors are excited at two specific ratios, where the first ratio is tuned such that the two deflectors together create a pure shift at the sample, and where the second ratio is tuned such that the two deflectors together create a pure tilt at the sample. The tuning of these ratios is often referred to as "tuning the pivot point".

[0017] Due to the aberrations of the lens forming the probe, especially its spherical aberration, the focusing intensity of the lens varies to some extent with the tilt angle applied at the sample. Due to this variation, the exact position of the plane conjugate to the sample also varies to some extent with the applied tilt angle. For the same reason, the exact value of the pivot point also varies to some extent with the applied tilt. When a dynamically varying tilt is applied, the correction of these variations may require a complex compensation scheme for the pivot point. The applied tilt angle, in combination with the aberrations of the lens forming the probe, not only causes a change in focus but can also cause a change in astigmatism and / or coma, which can degrade the image resolution without correction (e.g., using an astigmatizer and additional deflection).

[0018] Each deflector can include two pairs of perpendicular magnetic coils or two pairs of electrostatic deflection plates to achieve deflection in two directions (x and y) perpendicular to the beam.

[0019] Magnetic coil-based deflectors are generally easier to construct than electrostatic deflector plates, but magnetic coils typically have a maximum scan rate that is lower than that of electrostatic deflector plates due to their self-inductance. Thus, some example microscope systems can include a combination of a magnetic deflector and an electrostatic deflector such that the magnetic deflector can be used for adjustments (such as beam tilting in accordance with the present disclosure) that can be allowed to operate at a moderate rate, and the electrostatic deflector can be used for adjustments that can benefit from the highest rate such as fast lateral scanning.

[0020] Some microscope examples can include replicating a deflector set upstream of the sample to a similar deflector set downstream of the sample such that the downstream deflector set cancels out shifts and / or tilts applied at the sample to ensure a stationary beam downstream of the detector.

[0021] In many examples, frame-based precession techniques can achieve improved performance by leveraging static tilting for fast scanning and performing multiple scans according to a user-defined tilt matrix rather than tilting at each point to complete the tilt matrix as in a pixel-based method, for example. In many frame-based examples, separate beam deflectors can be used. For example, one beam deflector provides fast lateral scanning of the probe across the sample, and another beam deflector provides a fixed (or slowly varying) tilt angle for a particular frame. In this way, the tilt shift pivot point analysis and complex compensation typically required when using only two dynamic deflector units (i.e., one dynamic deflector unit provides tilting and shifting before the sample, and one dynamic deflector unit unscans the beam after the sample) are no longer needed in most applications. Additionally, degradation of the probe beam can then be limited to only the contributions of the optical system, such as aberrations introduced by the objective lens. Such aberrations can be more easily predicted using models and can therefore be partially corrected to achieve a smaller probe size during tilting, thereby improving the optical performance for an application array.

[0022] Frame-based examples can also address the long-standing problem associated with drift of the probe at the sample. For example, in a pixel-based method, each pixel is scanned individually by a cone until a full frame is completed. During this lengthy process, the probe and the sample may drift relative to each other due to various effects on the system. This can degrade the quality of the image produced during the already time-consuming acquisition process of collecting the precession image components. In a frame-based method, drift can be more easily compensated because the acquisition speed of a single frame is much faster (higher repetition rate) than the time required to complete a full frame using a pixel-based method. Thus, drift is less likely to occur or have a significant impact across frames acquired with fast scanning at a fixed tilt. In cases where drift does have an impact, such as between frames or after several frames (e.g., after a change in azimuthal or tilt angle), drift correction can be performed. In contrast, pixel-based methods do not allow frame-based drift correction.

[0023] Pixel-based methods typically only allow for conical illumination with a fixed amplitude (e.g., a fixed tilt angle relative to the optical axis) because the pivot points (shift and tilt) depend on that amplitude. Using the frame-based examples taught herein, the additional flexibility in tilt angle and amplitude allows for the application of arbitrary tilt matrices, including, by way of example, rocking beams, random walks, precessions, etc. In precession, a fixed tilt amplitude is typically applied to the beam, and the azimuthal direction is changed with the tilt amplitude, e.g., after a full 360-degree rotation of a circle. In a rocking beam, the tilt amplitude varies, and typically runs a Cartesian square pattern of beam tilts in generally equal x, y steps (e.g., 3×3, 8×8, etc.). In a random walk precession, a Cartesian coordinate system of beam tilts is used, and the matrix is accessed randomly with different tilts. It is not necessary to fully fill the matrix, and thus a sparse scan of the tilt matrix can be performed. For a rocking beam tilt matrix, the positions in the matrix can include harmonics, Lissajous paths, or other paths across the matrix. Harmonic, Lissajous paths have the advantage that they can be scanned using a scanning coil without the flyback problems caused by a row-by-row scan of the tilt amplitude.

[0024] Using the additional compensation options available in the frame-based method, the degradation of the probe caused by the aberration of the objective lens (e.g., affecting each fixed tilt of a series of recorded frames) can be compensated, thereby further allowing for the acquisition of a 3D atomic focusing series. For example, a convergence semi-angle of 100 mrad may be required to obtain an atomic resolution depth of focus. Using current technology, this is only achieved by correcting all aberrations up to 100 mrad. Such corrections are difficult to implement or impractical. However, by tilting the beam by approximately 30 mrad in a tilt matrix (e.g., 3×3, 5×5, etc.), a maximum tilt of up to 100 mrad can be achieved. The probe aberration in each frame can be partially corrected to maintain a probe size of approximately 0.2 nm in the x, y plane. Thus, the smallest voxels in the x, y, z positions can be created, allowing for a scan in three dimensions by changing the focus in steps of approximately angstrom size.

[0025] Example frame-based method

[0026] Figure 1Is an example frame-based collection method 100. Method 100 includes initiating a frame collection method at 102. For example, a sample can be disposed in a chamber of a charged particle beam microscope, such as an electron microscope. A charged particle detection beam, such as an electron beam, is guided along the optical column of the microscope. The optical column can include an arrangement of lenses that define an optical axis. The optical axis of the system generally corresponds to the central axis of the optical column, but in some examples, the optical axis can be adjusted such that the optical axis is at an angle to the central axis. The lenses can be used to guide the detection beam along the optical axis and to focus the beam toward the sample. The sample can be disposed in the path of the beam, for example, on a fixed or movable stage. Before being irradiated on the sample, one or more detection beam deflectors (two separate beam deflectors in a representative example) can be used to direct the detection beam away from the optical axis, for example, at an angle with respect to the optical axis and / or laterally with respect to the optical axis. One or more detectors can be disposed relative to the sample to receive particle emissions in the form of a detection beam from the sample. An additional detection beam deflector can be arranged to direct the detection beam from the sample to the detector, for example, to de-tilt the emitted particles. In a representative example, the detection beam is the beam downstream of the sample, and the additional beam deflector (or deflectors) can correspond to the downstream deflector. Various frame collection steps, such as scanning, detecting, and / or changing beam parameters, are typically automated by, for example, a system controller.

[0027] To collect a frame, at 104, an inclination angle (i.e., polar angle or tilt angle) and an azimuth angle (which can be collectively referred to as one or more tilt angles) are selected for the detection beam to be irradiated on the sample. At 106, the detection beam is then scanned across the sample laterally with respect to the optical axis at the selected inclination angle and azimuth angle. When scanning the detection beam across the sample, the selected inclination angle and azimuth angle are fixed or held. In many examples, after interacting with the sample, the downstream beam is deflected using a detection beam deflector and detected at the detector. Various detectors can be used depending on the application. The collected frame can correspond to data collected using a detector associated with the beam irradiated at multiple positions on the sample using a fixed or held inclination and azimuth angle. The multiple positions can be referred to as pixels.

[0028] In some examples, at 108, after collecting a frame, beam characteristics or sample characteristics can be corrected, for example, to compensate for drift, sample perturbation, etc. At 110, a determination can be made as to whether to collect additional frames, for example, continue collecting additional frames (such as completing a tilt matrix) according to an automated process or workflow, or rescan frames based on the determination made at 108. If additional frames are to be collected, the process can revert to an earlier part of process 100 and repeat, for example, selecting or adjusting the tilt angle / azimuth angle at 104 and scanning and detecting at 106. For one or more subsequent frames, the tilt angle and / or azimuth angle can be changed to one or more different angles, which can also be maintained while the beam scans across a region of the sample when generating the one or more subsequent frames.

[0029] In additional examples, the correction at 108 can correspond to a correction associated with the aberration of the beam directed to the sample, and such correction can be more simultaneous with frame collection. Aberrations can include defocus, astigmatism, coma, etc. For example, the aberration correction at 108 can occur before collecting a frame or between frames. Such correction typically occurs based on model predictions of the expected aberration for a selected deflection angle and / or scan position. Aberrations can be corrected by adjusting existing beam deflectors and / or lens elements and additional components such as anastigmators, probe correctors, or aberration correction lenses (aberration correctors can include, but are not limited to, Cc and / or Cs correctors). Typically, the scan speed may exceed the response time capabilities of the aberration correction equipment. Thus, knowledge of the frames to be collected can allow sufficient time to adjust for aberrations, for example, during the period between the collection of two frames or during the process of frame collection. In this way, compensation can occur through specific adjustments / improvements for each angle before scanning. Thus, such aberration correction can occur without having to detect those aberrations in near real-time, as that detection part is usually not necessary. In many examples, the tilt angle / azimuth angle can be selected at 104, the aberration can be corrected for that specific angle at 108, and then the beam can be scanned across the sample and the image frame detected at 106.

[0030] In many examples, a fixed or maintained tilt angle and azimuth angle can be defined by a fixed (or sometimes slowly varying) azimuth angle in a reference plane perpendicular to the optical axis of the system and a fixed or slowly varying angle relative to a reference axis perpendicular to that reference plane. This is in contrast to pixel-based precession methods, in which the angle of incidence relative to the optical axis remains fixed (e.g., a tilt angle of 5°), while the azimuth angle varies with time for a particular pixel such that detection can occur at one or more azimuth angle positions for that pixel before the beam is shifted to an adjacent pixel to undergo a similar precession (e.g., detection at 10° azimuth angle increments). In a basic frame-based precession example, a tilt matrix can be compiled by collecting a set of frames at a selected tilt angle, where each frame varies its fixed azimuth angle by a selected amount. For example, a complete precession cycle can be collected with 36 frames, each frame collected at a 5° tilt angle and its azimuth angle stepped in 10° increments. It should be understood that a large number of tilt and azimuth angle sequences can be used in various frame-based collection examples, such as precession, harmonic, Lissajous, rocking, etc. sequences. In many examples, the frame sequence includes many tilt angles and / or azimuth angles, e.g., two or more frames, three or more frames, four or more frames, ten or more frames, fifty or more frames, etc.

[0031] In many frame-based examples, the angle of the probe beam can be maintained at the intersection with the sample. In some cases where the sample surface is flat and angled relative to the optical axis of the system (i.e., not perpendicular), a fixed tilt angle and azimuth angle can be maintained across the angled sample surface during the entire collection of frames. For example, when the z position of the sample varies across frames, a z focus adjustment can be made to the beam. In a more typical example, the sample is arranged to be generally perpendicular to the central optical axis of the system. In some examples, frames can be collected at different depths of focus (e.g., in 3D depth slicing). At 112, various post-processing of the collected frames can be performed, such as mapping pixels between frames, drift correction, shift compensation, 3D depth slicing, frame summation, etc. In many examples, especially in EDX, EELS, or spectroscopic modes, more generally, images can be summed to form an average or combined image, such as a combined diffraction image.

[0032] Figures 2A to 2BAn example of a sample 200 detected using a frame-based detection method, such as method 100, is shown. The sample 200 is disposed in a chamber of an electron microscope. A surface 202 is perpendicular to and generally centered with respect to an optical axis 204 of the electron microscope. To collect a frame, a probe beam 206 is directed to the surface 202 at a selected tilt angle θ1 (shown relative to a reference line 205 parallel to the optical axis 204) and an azimuth angle θ2 (shown relative to a reference line 207 perpendicular to the optical axis 204), and the selected tilt angle and azimuth angle generally remain fixed as the probe beam 206 is scanned across the frame. As shown, the probe beam 206 is scanned transversely across the frame through four consecutive positions 208a to 208d and through a plurality of rows. This transverse scanning can occur relatively quickly, e.g., within microseconds, which can ensure that many types of drift-related aberrations do not affect the data collected across the frame. As shown, a straight grid is depicted, but it should be understood that any grid can be selected. Although the transverse scanning across the frame can occur in a sequential manner across adjacent pixels, other patterns can be used.

[0033] Microscopy apparatus embodiments

[0034] Figure 3 An example of a frame-based precession microscope system 300 is shown. The system 300 includes a charged particle beam (CPB) source 302, such as an electron or ion emitter source. The CPB source 302 emits a beam 304 that can be directed along an optical axis 305 to a sample 306 disposed on a stage 308. The system 300 can include a beam guiding column 310 that generally includes an electrostatic lens, a magnetic lens, and / or an arrangement 312 of other components configured to shape the beam 304 and direct the beam to the sample 306. Example lenses and other components of the arrangement 312 can include condenser lens elements, objective lens elements, apertures, relay lenses, astigmators, deflectors, scanning coils, beam modulators, aberration correctors, etc. The arrangement 312 is shown at a selected location closer to the beam source 302, but this is for illustrative convenience as it should be understood that the various lenses and components can be distributed throughout the optical column 310. For example, additional lens elements can be located below the sample (such as in a STEM example) to focus transmitted or emitted particles on a detector 322.

[0035] The system 300 can include a tilt beam deflector 314 configured to adjust the angle of the beam 304 such that the beam 304 is at an angle θ with respect to the optical axis 305 IPropagates to and is received by the sample 306. The adjusted angle can be referred to as the tilt angle. The tilt beam deflector 314 can include magnetic coils and / or electrostatic plates that provide the tilt deflection, and the speed of changing the tilt can be relatively slow, e.g., once per frame, for a 512×512 pixel frame at 10 frames per second (about 0.4 μs per pixel). In some examples, the tilt beam deflector 314 is located at a plane 315 conjugate to a portion of the sample 306 (e.g., the surface of the sample 306 or a z-layer at a specified depth within the sample 306). The system 300 can include a shift beam deflector 316 configured to adjust the lateral position of the beam 304 such that the beam 304 propagates to and is received by the sample 306 at a shifted lateral position relative to the optical axis 305. In many examples, the shift beam deflector 316 can include an electrostatic deflector (typically a pair of electrodes) configured to provide a relatively fast lateral scan speed that can be significantly faster than the tilt beam deflector, e.g., an order of magnitude larger, enabling a rate such as 120 frames per second for a 512×512 pixel frame (about 30 ns per pixel). In some examples, the shift beam deflector 316 is located at a plane 317 conjugate to the front focal plane 319 of the probe-forming lens in the arrangement 312, for example.

[0036] In many examples, the sample 306 can be flat and disposed on the stage 308 such that the surface or the target sample layer is perpendicular to the optical axis 305. In additional examples, the surface or the target layer of the sample 306 can be flat and angled and / or contoured relative to the optical axis 305.

[0037] In various examples, the system 300 can focus the beam 304 onto the sample such that various types of radiation are emitted from the sample 306, including (e.g.) transmitted electrons, secondary electrons, backscattered electrons, X-rays, and / or optical radiation (e.g., cathodoluminescence). The emitted radiation to be detected caused by the interaction with the sample 306 can be referred to as the detection beam 320. In some examples, an additional beam deflector 318 can be provided to deflect the detection beam 320 such that the detection beam can be received by the detector 322. For example, the beam deflector 318 can operate in a complementary manner to the tilt beam deflector 314 so as to de-tilt the beam 304 by an angle θ O . The angle θ I , θ O are shown for illustrative convenience and need not be the same in magnitude. Additionally, the beam deflector 318 need not cause the angled detection beam 320 to propagate parallel to the optical axis 305.

[0038] Depending on the application, detector 322 can be of various types, and some example devices can include multiple types of detectors. As shown, the detector is arranged below the sample 306, but depending on the type of detection being performed, other locations can be suitable. Suitable examples of detector 322 can include a segmented STEM detector and / or a pixelated detector, which are typically arranged below the sample 306. The pixelated detector can be arranged to acquire a full diffraction pattern generated from the sample. In some pixelated examples, a full STEM image can be obtained, including a HAADF or dark field image. The pixelated STEM detector can be used for general analysis, crystal orientation mapping, and strain mapping. The segmented STEM detector can be used to acquire centroid analysis data. In some examples, detector 322 can include or correspond to an electron energy loss spectroscopy (EELS) sensor. EELS sensors are typically used in chemical analysis applications. For many EELS crystalline detections, channeling effects can adversely affect the data collected, and such channeling effects can be largely overcome by precession of the beam 304. In some examples, detector 322 can correspond to or include an x-ray energy dispersive spectroscopy (EDX) detector, an Auger electron spectroscopy (AES) detector, a secondary electron (SE) detector, and / or a backscattered electron (BSE) detector, which are typically arranged in positions not below the sample 306. Example detectors can include CMOS sensors, CCD imaging sensors, photodetectors, etc.

[0039] In some examples, an additional beam deflector 318 can be included to compensate for the shift of the diffraction image present in the detection beam 320. Correcting such a shift is useful or necessary in EELS due to the change in collection angle caused by the shift of the diffraction pattern. In EDX mapping, it is typically not required because the signal is created above the sample. In examples where 4D STEM data is recorded on a pixelated detector below each tilted sample, the diffraction shift caused by beam tilting can be corrected in software, for example, corrected individually during or after processing. In some examples, a software routine can provide shift correction by summing the collected diffraction patterns with different beam tilts at each scan point. For example, the central disk can be aligned at each pixel for all tilts, and the diffraction patterns can be added.

[0040] The different components of system 300 can be coupled and controlled by a frame-based imaging controller 324, which can correspond to or be part of the controller or control network of system 300. Controller 324 can be coupled to various components such as beam source 302, lens (etc.) arrangement 312, tilt beam deflector 314, shift beam deflector 316, and de-tilt beam deflector 318, as well as detector 322, to control the direction of the beam to sample 306 and detector 322 and the detection of beam 320. In many examples, the controller 324 can be pre-programmed with frame-based detection routines, which can include tilt deflector parameters 326 and shift deflector parameters 328, configured to adjust the characteristics of source beam 304 and detection beam 320. Shift beam deflector 316 typically operates on a much faster time scale than tilt beam deflector 314 and can provide transverse scanning of beam 304 across frames relative to sample 306. In some examples, shift beam deflector parameters 328 can include a pixel map covering a portion of sample 306.

[0041] Pixel-based precession techniques typically rely on a single scanning unit to precess the beam in each pixel. In such techniques, pivot point alignment between tilt and shift has been a long-standing problem. That is, with a single scanning unit, tilt and shift are intertwined and need to be decoupled to provide pivot point alignment of the precessing beam at the same location on the sample. For example, to provide the same tilt angle and different azimuth angles, the beam needs to be shifted to keep the probe beam at the same sample location. This results in a complex tilt matrix for scanning across the sample to compensate and ensure beam stability while the beam is precessing. Additionally, the tilt matrix needs to change significantly after changing the tilt angle. In many examples of system 300, where tilt beam deflection and shift beam deflection are provided by different deflectors 314, 316, tilt beam deflection and shift beam deflection can be advantageously decoupled from each other, greatly simplifying the workflow process for precession-based techniques and other techniques that include beam tilting. In some examples, tilt beam deflector parameters 326 can include one or more tilt angles and one or more azimuth angles that can be applied to beam 304.

[0042] Frame-based methods can utilize decoupled tilt and shift beam deflections to achieve significant improvements in workflow throughput and / or improved image quality. For example, in frame-based methods, rather than repeating the slower variations in azimuth or tilt angle for each pixel, the azimuth or tilt angle can be made fewer times (or only once) across the sample area in a single frame, and as additional frames are collected, the fast shift deflections can occur repeatedly and more quickly. Additionally, with the decoupling, there is a significant improvement in ease of use for the operator. In some examples, the operator can simply select a tilt angle and optionally optimize the tilt angle within a range (e.g., at a single pixel). After optimization and the presence of other image quality characteristics (such as no jitter), the operator can choose to continue with a full scan using a fast lateral scan of the sample. In many examples, given the fast frame scan speed, frame-based systems exhibit fewer artifacts compared to frames completed in pixel-based methods. Additionally, given the increased acquisition speed of frame-based methods and the collection of multiple frames, it can be more convenient to delete and / or re-acquire additional frames to replace substandard frames.

[0043] In some frame-based examples herein, a single beam deflector unit can be used to scan and tilt the beam, i.e., having a coupled tilt and shift pivot point, in order to obtain frames such that each frame has a fixed (or only slowly varying tilt angle) across the entire frame. Single-scan unit examples may operate less quickly or have reduced complexity, but they can be less expensive. Additionally, applying frame-based techniques using single-scan units in precession-type image collection can be simpler than the same collection using pixel-based methods. This is because frame-based methods can relax the pivot point alignment requirements. In the case of applying a fixed tilt, potential errors in shift can be more easily compensated based on the acquisition of full frames. For example, frames in a sequence can be compared, and cross-correlation or machine learning techniques can be used to detect image shifts or other image changes, which can then be corrected. Post-processing image processing 329 can include software routines that are configured to provide various image processing and / or image adjustments, including post-sampling shift compensation, image construction using the collected frames, feature detection, and the like.

[0044] The tilt deflector parameter 326 can also include a corrective de-tilt parameter for the beam deflector 318. Due to image shift or diffraction shift caused by tilting, the beam deflector 318 can provide de-tilting and stability of the diffraction pattern or image below the sample 306. It is worth noting that even if the decoupling of tilting and shifting is performed before the sample 306, in many examples, a single de-scan unit (or no scan unit) can be used after the sample 306 (since the introduced tilt does cause image shift), without the need to symmetrically arrange a second de-scan unit. In some examples, post-processing image processing 329 can be used to compensate for shifts between frames (e.g., associated with changes in tilt parameters between frames), including in some examples, without using a de-scan unit to de-tilt the collected image frames.

[0045] In some examples, the system 300 can include a drift compensator 330, which can be part of the controller 324 or coupled to the controller. During a tilt-based workflow for acquiring images using tilting, the beam 304 may become distorted, for example, due to drift, and / or the sample position may drift during the acquisition of the tilt matrix. Drift can occur due to environmental perturbations (such as external vibrations, temperature changes, sound, or pressure changes) and aberrations caused by system variations or non-linearities. The frame-based method advantageously allows the ability to compensate for aberrations or drift effects dynamically during frame acquisition or during post-processing. In some examples, the drift compensator 330 can be configured with feedback capabilities to perform corrections dynamically during frame acquisition. In some cases, drift can be detected by comparing recognizable features in a sequence of frames, and the detected movement of the recognized features can provide a basis for correction between frames. The drift compensator 330 can include computer-readable instructions that can be used by the controller 324 or another processor-based computing system or embodied in the computer-readable instructions. The drift compensator 330 can include instructions for receiving scan data, comparing image data, and adjusting the image or the relationship between images. Many existing software modules can be utilized for comparison and image correction.

[0046] By way of example, since the beam distorts due to optical aberrations when tilted, compensation that minimizes these effects can be applied for each tilt. This can result in higher lateral resolution, for example, when accumulating precession runs. In many examples, beam tilting can cause beam shifts, such as in the case of imperfect pivot point alignment. These shifts can be compensated by cross-correlating images with different tilts, resulting in higher lateral resolution of the result. In the diffraction plane, shifts of the pattern can occur, for example when the unscanning unit is not perfectly aligned. These shifts can be compensated by cross-correlation methods or similar methods before adding the diffraction patterns for further analysis. This can improve the accuracy of the results in applications such as strain, orientation mapping, or centroid analysis (e.g., field measurements, iDPC, ptychography, etc.). These compensations can be applied in real-time during acquisition or during an offline process. In contrast, these effects cannot be compensated in pixel-based precession. This can lead to blurring in the scanning plane (e.g., resulting in loss of lateral resolution) or blurring in the diffraction plane, leading to loss of measurement accuracy. That is, pixel-based methods typically produce only one blurred image and one (blurred) diffraction pattern per scanned pixel, such that these compensations cannot be performed.

[0047] Correlation compensation in pixel-based methods may also be unavailable because when the beam precesses dynamically, a single frame is acquired over a relatively long duration. Drift can occur, and this drift cannot be easily corrected without repeating the acquisition of the entire pixel-based frame. Additionally, for aberrations, even with prior knowledge of the predicted aberrations, it is generally too difficult or impossible to dynamically correct aberrations in pixel-based methods because the speed of precession exceeds the corrector capabilities. For example, modeling typically provides the predicted amount of aberration in response to the application of varying tilt amounts, and then lenses, astigmatizers, or probe correctors can be utilized to correct the desired aberrations. In some examples, the controller 324 can be configured with the predicted amount of aberration and associated commands for the arrangement 312 and deflectors 314, 316 to adjust the beam direction such that frames can be collected with reduced aberrations. Aberration correction can be performed by taking advantage of the longer duration of scanning the entire frame at a fixed tilt angle or applying fewer fixed tilt angles for the completed workflow.

[0048] Given the time provided to acquire a full frame and given that the tilt angle and azimuth angle are maintained throughout the frame, some corrections can be applied in a frame-based method by comparing features in the acquired frame. Some corrections can be made based on a model-based prediction of aberrations that can be stored in the controller memory. This can allow for the correction of desired aberrations prior to collecting frames at a selected tilt angle / azimuth angle. In contrast, with a pixel-based method, the precession speed of the beam at a pixel may exceed the tracking ability of the probe corrector, or the associated delay inserted into the process to match the corrector ability undesirably increases the length of an already lengthy workflow. Additionally, pixel-based methods build frame information pixel by pixel and thus there is no full frame information until the end of the scan process. Therefore, it is not possible to apply corrections based on, for example, a comparison of feature positions in a frame because there are no multiple frames to compare.

[0049] In some examples, a frame-based tilting method can allow for the adjustment of the number of azimuth positions and tilt angles being scanned. For example, while pixel-based methods typically require collecting hundreds of azimuth positions at pixel locations, the disclosed frame-based method can arbitrarily vary that number and can enjoy a significant reduction in workflow duration by reducing the number of azimuth positions, tilt angles, and thus the number of frames collected. For example, a lower amount may be sufficient to avoid channeling artifacts or provide compositional analysis in a field or in a strain map. Additionally, a further reduction in workflow duration can lead to a further improvement in drift reduction because there is less time for drift to occur when fewer frames are collected or fewer frames are collected more quickly.

[0050] With respect to channeling artifacts, when the crystal is in the zone axis, the atoms are aligned in straight columns relative to the beam direction. When an electron beam irradiates a sample under such conditions, electrons can channel through the material, resulting in a non-uniform distribution as they travel through the sample. As a result, columns with different atomic species see different amounts of electrons. Quantification in EDX / EELS assumes that electrons travel uniformly through the material such that the probability of an atom being excited is the same everywhere. When precession is used by tilting the electron beam away from the zone axis, the channeling effect can be minimized because the exact alignment of the beam with the atomic columns is avoided. Thus, multiple tilts can simply average this effect. Therefore, precession in mapping (e.g., rocking beam) acquisitions can lead to a more accurate compositional analysis. Additionally, precession has an advantage in COM analysis for E / B field (i.e., electric or magnetic field) measurements because the change in crystal orientation via precession depends on the tilt angle of the beam, while the COM change of the field does not change. Therefore, compared to not measuring the E / B field, the E / B field can be measured more accurately in precession mapping in 4D STEM of crystalline materials.

[0051] Example frame and matrix formation and additional methods

[0052] Figure 4 is a representation of a 4×4 pixel array 400 that shows sixteen tilt matrices 402 acquired in a frame-based precession workflow, each matrix 402 corresponding to one of the pixels in the array 400. Each tilt matrix 402 includes data for five tilt angles (1°, 3°, 5°, 7°, and 9°) at five azimuthal positions (0°, 72°, 144°, 216°, and 288°) acquired over the course of twenty-five frames. In the tilt matrix 402, the image data acquired for a particular tilt angle and azimuthal frame is specified by a frame number from 1 to 25. In many examples, the array 400 is typically larger. The tilt matrix 402 can be user-configurable or application-dependent. For example, while a series of precessions with different tilt angles can be used as shown, a variety of other tilt patterns can be used depending on the application, including non-conical patterns. By way of example, any of the beam tilt patterns described in U.S. Application 17 / 683,076, “MEASUREMENT AND CORRECTION OF OPTICAL ABERRATIONS IN CHARGED PARTICLE BEAM MICROSCOPY,” incorporated herein by reference, can be used for frame-based tilt acquisition, for example, to correct aberrations in a TEM. In additional examples, a rocking beam type pattern can be used for frame-based tilt acquisition. For example, when the beam changes tilt angle along an axis, the azimuthal change can be limited to 0° and 180°, similar to the movement of a pendulum.

[0053] Figure 5 is an example method 500 for frame collection with drift correction. At 502, the method 500 can begin. At 504, frames are collected for a series of frames. At 506, the collected frames can be reviewed to determine if there is drift or aberrations in the frames. In many examples, a comparison can be made with other collected frames, such as the immediately preceding frame. If drift is detected, the process can proceed to a check at 508 according to criteria to determine if the frame should be discarded and retaken. For example, frames that include artifacts or anomalies inconsistent with other frames can be discarded and retaken at 504. In some examples, the comparison can be made later in the frame collection process or require additional time to process, such that the determination is not available until later in the frame collection process.

[0054] In the case where no drift or aberration is detected, at 510 it can be determined whether there are any more frames to be collected, and if there are no frames to be collected, the process can end at 512. If additional frames are to be collected, at 514, the next frame can be iterated, and frame collection can continue back to 504. In the case where there are no frames to be discarded or retaken but drift is detected, at 516, a determination can be made regarding whether to adjust the frame. For example, in some cases, a drift or aberration below the drift or aberration tolerance can be detected, in which case the frame can not be adjusted, and the next frame can be iterated at 514. In some examples, at 518, the frame can be adjusted through mapping between frames. For example, in the case where the drift is sufficient, the frames can be compared to quantify the drift, for example, in the form of rotational and translational movements in a frame sequence. Other drift or aberration characteristics can be quantified, including image warping, distortion, stretching, or other aberrations. A mapping can be used such that subsequent frame-based tilt matrices can be constructed with reduced effects from drift or other aberrations.

[0055] Figure 6is an example 3D imaging method 600 that uses frame-based collection techniques. At 602, the frame-based 3D imaging method can begin. At 604, a z-layer of the sample is selected as the target. The z-layer can correspond to the depth position of the sample along the overall direction of the beam used for imaging. At 606, an inclination angle and an azimuth angle can be selected for probing the sample. Aberration correction can be provided based on the selected inclination and azimuth angles such that the aberration caused by the inclination of the beam has a reduced effect. For example, due to the inclination angle, the probe spot at the selected z-layer can be elliptical, and such ellipticity can be corrected using an aberration corrector or other lens element adjustments. At 608, frames can be collected using fixed (or slowly varying) inclination and azimuth angles that are held constant throughout an individual frame. At 610, a determination can be made as to whether any additional frames are to be collected. For example, additional z-layers or inclination angles / azimuth angles can be imaged. If additional frames are to be imaged, new z-layers and / or inclination angles / azimuth angles can be selected at 604 and / or 606. If the last frame is being imaged, at 612, the collected inclination matrix can be populated with the collected data, and the images can be summed together. Due to the inclination angle, non-target z-layers can exhibit image shifts. Thus, by summing the image data at each pixel, other non-target z-layers can be subtracted from the image based on the image shifts caused by the inclination of out-of-focus atoms in other layers. It should be understood that various frame sequences can be used in different examples. In some examples, the inclination angle / azimuth angle can be selected, and frames for the selected inclination angle / azimuth angle can be collected at various z-layer depths. In other examples, frames sequences for different selected inclination angles / azimuth angles at a selected z-layer can be imaged, and then repeated at different z-layers. In additional examples, the frame sequence can include a combination of frame orderings. The frame ordering can be customized based on various factors such as acquisition speed, reduced aberration or drift, preference, etc.

[0056] General considerations

[0057] As used in this application and the claims, the singular forms "a", "an", and "the" include plural forms unless the context clearly dictates otherwise. Additionally, the term "comprising" means "including". Further, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0058] The systems, devices, and methods described herein should not be construed as being limited in any way. Instead, the present disclosure relates to all novel and non-obvious features and aspects of the various disclosed embodiments, whether individually or in various combinations and sub-combinations formed with each other. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require the presence of any one or more particular advantages or problem solutions. Any theory of operation is for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theory of operation.

[0059] Although, for convenience of presentation, the operations of some of the methods disclosed are described in a particular order of sequence, it should be understood that such description includes rearrangements, unless the particular language described below requires a particular order. For example, the operations described in sequence may in some cases be rearranged or performed concurrently. In addition, for simplicity, the figures may not show the various ways in which the disclosed systems, methods, and devices may be used in conjunction with other systems, methods, and devices. Additionally, this description sometimes uses terms such as "generate" and "provide" 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 particular implementation and can be readily discerned by one of ordinary skill in the art.

[0060] In some examples, a value, procedure, or device is referred to as "lowest", "best", "minimum", etc. It should be understood that such descriptions are intended to indicate that a selection can be made among many alternative functions used, and such selection does not need to be better, smaller, or otherwise preferred than other selections.

[0061] The innovations may be described in the general context of computer-executable instructions, such as those included in program modules and executed in a computing system on a target real or virtual processor. Generally, program modules or components include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. The functionality of program modules may be combined or split among program modules as needed in various embodiments. The computer-executable instructions for program modules may be executed within a local or distributed computing system. Generally, a computing system or computing device may be local or distributed and may include any combination of dedicated hardware and / or general-purpose hardware and software implementing the functions described herein.

[0062] In the various examples described herein, a module (e.g., a component or an engine) may be “decoded” to perform certain operations or provide certain functions, thereby indicating that the computer-executable instructions for the module can be executed to perform such operations, cause such operations to be performed, or otherwise provide such functions. Although the functions described with respect to software components, modules, or engines may be performed as discrete software units (e.g., programs, functions, class methods), it is not necessary to implement them as discrete units. That is, the functions may be incorporated into a larger or more general program, such as one or more lines of code in a larger or general program.

[0063] For presentation, the detailed description uses terms such as “determine” and “use” to describe computer operations in a computing system. These terms are high-level abstractions of operations performed by a computer and should not be confused with actions performed by a human. The actual computer operations corresponding to these terms vary according to the specific implementation.

[0064] The algorithms described may be embodied, for example, as software or firmware instructions executed by a digital computer or a controller. For example, any of the disclosed frame-based imaging techniques, drift compensation, shift compensation, aberration correction, and / or automation techniques may be executed by one or more of a computer or other computing hardware that is part of a microscopy tool. The computer may be a computer system that includes one or more processors (processing devices) and a tangible, non-transitory computer-readable medium (e.g., one or more optical media disks, volatile memory devices such as DRAM or SRAM, or non-volatile memory or storage devices such as hard disk drives, NVRAM, and solid state drives (e.g., flash drives)). The one or more processors may execute computer-executable instructions stored on one or more tangible, non-transitory computer-readable media and thereby perform any of the disclosed techniques. For example, the software for performing any of the disclosed embodiments may be stored as computer-executable instructions on the one or more volatile non-transitory computer-readable media, which when executed by the one or more processors cause the one or more processors to perform any of the disclosed techniques or subsets of techniques. The results of the computation may be stored in one or more tangible, non-transitory computer-readable storage media and / or may also be output to a user, e.g., by displaying frame data, images (including composite images, diffraction patterns, etc.), tilt / azimuth parameters, tilt matrices, image drift, and / or image drift on a display device.

[0065] The principles of the disclosed technology have been described and illustrated with reference to the exemplary embodiments, and it should be recognized that the exemplary embodiments can be modified in arrangement and detail without departing from such principles. For example, elements of the exemplary embodiments shown in software can be implemented in hardware, and vice versa. Additionally, the techniques from any example can be combined with the techniques described in any one or more of the other examples. It should be understood that programs and functions such as those described with reference to the illustrated examples can be implemented in a single hardware or software module, or separate modules can be provided. The specific arrangements provided above are for convenience of illustration, and other arrangements can be used.

[0066] Given the many possible embodiments in which the principles of the disclosed technology can be applied, it should be recognized that the illustrated embodiments are merely representative examples and should not be considered as limiting the scope of the disclosure. The alternatives specifically presented 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 can be combined in function and use.

[0067] The following paragraphs provide various examples of the embodiments disclosed herein.

[0068] Example 1 is a method that includes: directing a charged particle beam across a region of a target at a first angle having an inclination angle component and an azimuth angle component to collect a first image frame generated using the beam at the selected first angle; detecting the first image frame; directing the charged particle beam across the region of the target at a second angle having an inclination angle component and / or an azimuth angle component different from the inclination angle component and the azimuth angle component of the first angle to collect a second image frame generated using the beam at the selected second angle; detecting the second image frame; and combining the first image frame and the second image frame to form an image.

[0069] Example 2 includes the subject matter of Example 1 and further specifies that directing the beam across the region of the target includes laterally scanning the beam using a lateral beam deflector, and wherein directing the beam at the first angle and the second angle includes adjusting to the first angle and the second angle using an inclined beam deflector.

[0070] Example 3 includes the subject matter of Example 2 and further specifies that the lateral beam deflector and the inclined beam deflector are part of the same single beam deflector unit.

[0071] Example 4 includes the subject matter according to any one of Examples 1 to 3, and further includes correcting the aberration before acquisition of a corresponding frame based on a prediction of the aberration associated with guiding the beam at the first angle and / or the second angle, wherein the correction includes adjustment of one or more astigmators, deflectors, and / or lenses upstream of the target.

[0072] Example 5 includes the subject matter according to any one of Examples 1 to 4, and further includes detecting drift or aberration between the collected frames, and compensating for the drift or aberration.

[0073] Example 6 includes the subject matter according to Example 5, and further specifies that the compensation is performed during the acquisition of the frames.

[0074] Example 7 includes the subject matter according to any one of Examples 1 to 6, and further specifies that the first angle and the second angle include a set of tilt precession parameters.

[0075] Example 8 includes the subject matter according to any one of Examples 1 to 7, and further specifies that the first angle and the second angle include a set of rocking beam, random walk, harmonic, Lissajous, and / or periodic tilt parameters.

[0076] Example 9 includes the subject matter according to any one of Examples 1 to 8, and further includes collecting image frames at multiple layer depths of the target, and summing the images based on image shifts caused by tilting of out-of-focus atoms at depths other than the target layer depth to generate a 3D image of the target.

[0077] Example 10 includes the subject matter according to any one of Examples 2 to 9, and further includes decling a detection beam emitted from the target using a separate beam deflector before detecting the first image frame and / or the second image frame.

[0078] Example 11 includes the subject matter according to any one of Examples 1 to 10, and further includes constructing a tilt matrix of the collected data by associating data collected from different image frames to a common target position.

[0079] Example 12 includes the subject matter according to any one of Examples 1 to 11, and further specifies that the first image frame and the second image frame include image frames of a diffraction pattern, and further includes: determining a shift in the first image frame and / or the second image frame associated with the corresponding first angle or second angle; and compensating for the shift when combining the first image frame and the second image frame to form the image.

[0080] Embodiment 13 includes the subject matter according to Embodiment 12, and further specifies that the diffraction pattern is part of a precessing tilt series around a circle, wherein the detection includes detecting using a pixelated sensor, and wherein the combination includes compiling the precessing tilt series to form a full precession diffraction pattern of the circle.

[0081] Embodiment 14 includes the subject matter according to Embodiment 13, and further specifies that detecting the first image frame and / or the second image frame includes receiving a downstream beam using a detector without the beam being deflected by a downstream deflector unit.

[0082] Embodiment 15 includes the subject matter according to any one of Embodiments 1 to 14, and further specifies that the first image frame and the second image frame include spectroscopic image frames, and wherein detecting the first image frame and the second image frame includes detecting a HAADF signal having a shift associated with the difference between the first angle and the second angle, and compensating for the shift by cross-correlating the image frames.

[0083] Embodiment 16 includes the subject matter according to Embodiment 15, and further specifies that the spectroscopic image frames include EDX spectra of the same region of the target, and the first angle and the second angle are configured to reduce spectral channel artifacts.

[0084] Embodiment 17 includes the subject matter according to any one of Embodiments 12 to 16, and further specifies that the shift includes shift artifacts in centroid, ptychography, or spectroscopic mapping measurements.

[0085] Embodiment 18 is an apparatus, the apparatus comprising: a microscope system configured to: emit a charged particle beam; and direct the beam across a region of a target at a first angle having an inclination angle component and an azimuth angle component to collect a first image frame generated using the beam at the selected first angle; and direct the beam across the region of the target at a second angle having an inclination angle component and / or an azimuth angle component different from the inclination angle component and the azimuth angle component of the first angle to collect a second image frame generated using the beam at the selected second angle; wherein the microscope system includes a detector configured to receive and detect the first image frame and the second image frame; and wherein the microscope system includes a controller configured to combine the first image frame and the second image frame to form an image.

[0086] Example 19 includes the subject matter according to Example 18 and further specifies that the microscope system includes a lateral beam deflector and a tilt beam deflector, the lateral beam deflector being configured to scan the beam laterally, the tilt beam deflector being separate from the lateral beam deflector, wherein the tilt beam deflector is configured to direct the beam at the first angle and the second angle.

[0087] Example 20 includes the subject matter according to any one of Examples 18 to 19 and further specifies that the controller is configured to correct the aberration by adjusting the beam guidance prior to the acquisition of a corresponding frame based on a prediction of the aberration associated with directing the beam at the first angle and / or the second angle that will be caused at the first angle and / or the second angle.

[0088] Example 21 is a method that includes: directing a charged particle beam across a region of a target at a tilt angle and an azimuth angle to collect image frames generated using the beam at the selected tilt angle and azimuth angle; and detecting the collected image frames.

[0089] Example 22 includes the subject matter according to Example 21 and further includes repeating the directing and detecting one or more times using one or more different selected tilt angles and / or azimuth angles.

[0090] Example 23 includes the subject matter according to any one of Examples 21 to 22 and further specifies that directing the beam across the region of the target includes laterally scanning the beam using a lateral beam deflector configured to provide lateral scanning, and wherein directing the beam at the tilt angle and azimuth angle includes adjusting the tilt angle and azimuth angle of the beam using a tilt beam deflector separate from the lateral beam deflector.

[0091] Example 24 includes the subject matter according to any one of Examples 21 to 23 and further includes constructing a tilt matrix of the collected data by associating data collected from different image frames to a common sample position.

[0092] Example 25 includes the subject matter according to any one of Examples 21 to 24 and further includes detecting drift or aberration between the collected frames and compensating for the drift or aberration.

[0093] Example 26 includes the subject matter according to Example 25 and further specifies that the compensation is performed during the acquisition of the frames.

[0094] Example 27 includes the subject matter according to any one of Examples 22 to 26 and further specifies that the one or more different tilt angles and / or azimuth angles include a set of tilt precession parameters.

[0095] Example 28 includes the subject matter according to any one of Examples 22 to 27, and further specifies that the one or more different tilt angles and / or azimuth angles include a set of rocking beams, random walks, harmonics, Lissajous, and / or periodic tilt parameters.

[0096] Example 29 includes the subject matter according to any one of Examples 22 to 28, and further includes collecting image frames at multiple layer depths of a sample, and summing the images based on image shifts caused by tilting of out-of-focus atoms at depths other than the target layer depth to generate a 3D image of the sample.

[0097] Example 30 includes the subject matter according to any one of Examples 23 to 29, and further includes de-tilting a detection beam emitted from the sample using a separate beam deflector before detection by a detector.

[0098] Example 31 is an apparatus that includes: a microscope system configured to emit a beam and direct the beam across a region of a target at a tilt angle and an azimuth angle to collect image frames generated using the beam at the selected tilt angle and azimuth angle; wherein the microscope system includes a detector configured to receive and detect the collected image frames.

[0099] Example 32 includes the subject matter according to Example 31, and further specifies that the microscope system is configured to repeat the directing and detecting one or more times using one or more different selected tilt angles and / or azimuth angles.

[0100] Example 33 includes the subject matter according to any one of Examples 31 to 32, and further specifies that the microscope system includes a lateral beam deflector and a tilt beam deflector, the lateral beam deflector being configured to scan the beam laterally, the tilt beam deflector being separate from the lateral beam deflector, wherein the tilt beam deflector is configured to direct the beam at the tilt angle and the azimuth angle.

[0101] Example 34 includes the subject matter according to any one of Examples 31 to 33, and further specifies that the microscope system includes a frame-based imaging controller configured to construct a tilt matrix of the collected data by associating data collected from different image frames to a common sample position.

[0102] Example 35 includes the subject matter according to any one of Examples 31 to 34, and further specifies that the microscope system includes a frame-based imaging controller configured to detect drift or aberration between the collected frames and compensate for the drift or aberration.

[0103] Example 36 includes the subject matter of Example 35 and further specifies that the frame-based imaging controller is configured to provide the compensation during the acquisition of the frame.

[0104] Example 37 includes the subject matter of any one of Examples 32 to 36 and further specifies that the one or more different tilt angles and / or azimuth angles include a set of tilt precession parameters.

[0105] Example 38 includes the subject matter of any one of Examples 32 to 37 and further specifies that the one or more different tilt angles and / or azimuth angles include a set of rocking beam, random walk, harmonic, Lissajous, and / or periodic tilt parameters.

[0106] Example 39 includes the subject matter of any one of Examples 32 to 38 and further specifies that the microscope system is configured to collect image frames at multiple layer depths of a sample and sum the images based on image shifts caused by tilting of out-of-focus atoms at depths other than the target layer depth to produce a 3D image of the sample.

[0107] Example 40 includes the subject matter of any one of Examples 33 to 39 and further includes a separate beam deflector configured to de-tilt a detection beam emitted from the sample before detection by the detector.

[0108] Example 41 includes one or more non-transitory computer-readable media having instructions that, when executed by one or more processing devices of a charged particle microscope device or a support device, cause the device to perform any one of the operations according to any one of Examples 1 to 40.

Claims

1. A method, the method comprising: Directing a charged particle beam across a region of a target at a first angle having an inclination angle component and an azimuth angle component to collect a first image frame generated using the beam at the selected first angle; Detecting the first image frame; Directing the charged particle beam across the region of the target at a second angle having an inclination angle component and / or an azimuth angle component different from the inclination angle component and the azimuth angle component of the first angle to collect a second image frame generated using the beam at the selected second angle; Detecting the second image frame; And Combining the first image frame and the second image frame to form an image.

2. The method according to claim 1, wherein directing the beam across the region of the target includes laterally scanning the beam using a lateral beam deflector, and wherein directing the beam at the first angle and the second angle includes adjusting to the first angle and the second angle using an inclined beam deflector.

3. The method according to claim 2, wherein the lateral beam deflector and the inclined beam deflector are part of the same single beam deflector unit.

4. The method according to any one of the preceding claims, the method further comprising correcting an aberration before acquisition of a corresponding frame based on a prediction of an aberration associated with directing the beam at the first angle and / or the second angle that will be caused at the first angle and / or the second angle, wherein the correction includes adjustment of one or more astigmators, deflectors, and / or lenses upstream of the target.

5. The method according to any one of the preceding claims, the method further comprising detecting drift or aberration between the collected frames, and compensating for the drift or aberration.

6. The method according to claim 5, wherein the compensation is performed during the acquisition of the frames.

7. The method according to any one of the preceding claims, wherein the first angle and the second angle include a set of tilt precession parameters.

8. The method according to any one of the preceding claims, wherein the first angle and the second angle include a set of wobbling beam, random walk, harmonic, Lissajous, and / or periodic tilt parameters.

9. The method according to any one of the preceding claims, the method further comprising collecting image frames at multiple layer depths of the target, and summing the images based on image shifts caused by tilting of out-of-focus atoms at depths other than the target layer depth to generate a 3D image of the target.

10. The method according to any one of claims 2 to 9, the method further comprising, before detecting the first image frame and / or the second image frame, de-tilting a detection beam emitted from the target using a separate beam deflector.

11. The method according to any one of the preceding claims, the method further comprising constructing a tilt matrix of the collected data by associating data collected from different image frames to a common target position.

12. The method according to any one of the preceding claims, wherein the first image frame and the second image frame include image frames of diffraction patterns, and the method further comprises: Determine the shift in the first image frame and / or the second image frame associated with the respective first angle or second angle; And Compensate for the shift when combining the first image frame and the second image frame to form the image.

13. The method according to claim 12, wherein the diffraction pattern is part of a precession tilt series around a circle, wherein the detection comprises detection using a pixelated sensor, and wherein the combining comprises compiling the precession tilt series to form a full precession diffraction pattern of the circle.

14. The method according to claim 13, wherein detecting the first image frame and / or the second image frame comprises receiving a downstream beam by a detector without the beam being deflected by a downstream deflection unit.

15. The method according to any one of the preceding claims, wherein the first image frame and the second image frame comprise spectroscopic image frames, and wherein detecting the first image frame and the second image frame comprises detecting a HAADF signal having a shift associated with the difference between the first angle and the second angle, and compensating for the shift by cross-correlating the image frames.

16. The method according to claim 15, wherein the spectroscopic image frames comprise EDX spectra or EELS spectra of the same region of the target, and the first angle and the second angle are configured to reduce spectral channel artifacts.

17. The method according to any one of claims 12 to 16, wherein the shift comprises a shift artifact in centroid, ptychography or spectroscopic mapping measurement.

18. An apparatus, the apparatus comprising: A microscope system configured to: emit a charged particle beam; And direct the beam across a region of a target at a first angle having an inclination angle component and an azimuth angle component to collect a first image frame generated using the beam at the selected first angle; And direct the beam across the region of the target at a second angle having an inclination angle component and / or an azimuth angle component different from the inclination angle component and the azimuth angle component of the first angle to collect a second image frame generated using the beam at the selected second angle; Wherein the microscope system comprises a detector configured to receive and detect the first image frame and the second image frame; Wherein the microscope system comprises a controller configured to combine the first image frame and the second image frame to form an image.

19. The apparatus according to claim 18, wherein the microscope system comprises a lateral beam deflector and a tilt beam deflector, the lateral beam deflector being configured to scan the beam laterally, the tilt beam deflector being separated from the lateral beam deflector, wherein the tilt beam deflector is configured to direct the beam at the first angle and the second angle.

20. The apparatus according to claim 18 or 19, wherein the controller is configured to correct the aberration by adjusting the beam guidance prior to acquisition of a respective frame based on a prediction of the aberration associated with guiding the beam at the first angle and / or the second angle that will be caused at the first angle and / or the second angle.

Images