Frame-based precession mapping in electron microscopy

Abstract

The method includes directing a charged particle beam over an area of ​​a target at a first angle having an oblique angular component and an azimuthal angular component, collecting a first image frame produced using the beam at the selected first angle, detecting the first image frame, directing the charged particle beam over the area of ​​the target at a second angle having an oblique angular component and / or an azimuthal angular component different from the oblique angular component and azimuthal angular component of the first angle, collecting a second image frame produced 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. Related apparatus are also disclosed.

Description

[Technical Field]

[0001] (CROSS-REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 427,643, filed November 23, 2022, the entirety of which is incorporated herein by reference.

[0002] This field is charged particle beam microscopy. [Background technology]

[0003] In many areas of electron microscopy, such as electron energy loss spectroscopy (EELS) and energy dispersive X-ray spectroscopy (EDX), samples are probed to determine the chemical composition of crystalline materials, for example. However, at least in EELS and EDX, determining chemical composition can be difficult because the spectroscopic signal can change with the orientation of the sample due to beam channeling through the crystal. The characteristic peak signal intensity of a sample's spectroscopic data can be made less dependent on the sample's orientation by impinging the electron beam on the sample in a specific pattern, in which the beam is scanned over time at specific sample positions at tilt angles, i.e., through a conical scan path. In particular, the tilt angle can be optimized so that the characteristic spectroscopic peaks are saturated and dynamic scattering is suppressed. However, existing approaches contain numerous drawbacks that limit the potential benefits of scanning at tilt angles, and therefore, improved systems and methods remain needed. [Brief explanation of the drawings]

[0004] [Figure 1] 1 is a flowchart of various embodiments of a frame-based imaging method. [Figure 2A] 1A and 1B are perspective and top views of a sample receiving a beam in a collection of frames, according to some embodiments. [Figure 2B]1A and 1B are perspective and top views of a sample receiving a beam in a collection of frames, according to some embodiments. [Figure 3] 1 is a schematic side view of an exemplary frame-based charged particle beam imaging system, in accordance with various embodiments. [Figure 4] FIG. 1 is a schematic plan view of an exemplary scan area of ​​a sample and associated tilt / orientation data collected in a series of frames. [Figure 5] 1 is a flowchart of a method for drift and / or aberration correction, according to some embodiments. [Figure 6] 1 is a flowchart of an exemplary 3D imaging method. DETAILED DESCRIPTION OF THE INVENTION

[0005] Introduction to the tilt precession approach and an overview of frame-based techniques In transmission electron microscopy and imaging applications, beam precession can be exploited as the beam is scanned to improve performance. This is typically done by precessing the beam on a cone at each point in the scan, e.g., by staying in one position and acquiring pixel data over time as the beam precesses through the cone (hereafter referred to as the "pixel-based" approach). In various applications, precession is performed instead of on-axis imaging to improve imaging properties, e.g., to avoid channeling artifacts in spectroscopy, to separate the integral center of mass (iCOM) effect of phase shifts in crystals from field contributions, or to enhance the intensity of high-order diffraction spots for more accurate strain analysis.

[0006] Disclosed herein are embodiments that include precession imaging, but do not necessarily include precessing the probe beam on a cone at each point in the scan. Rather, the disclosed precession workflow embodiments can include frame-based acquisition. In frame-based acquisition, a particular precession (or tilt) angle and azimuth angle can be selected, and an array of pixels is recorded at the selected precession angle and azimuth angle. The recorded array of pixels can correspond to a frame of the frame-based precession workflow. One or more additional frames can then be collected using one or more different selected precession angles and / or azimuth angles, which are then changed to the new angle and / or azimuth angle. In some embodiments, the amount of collected frames and associated precession angle characteristics can include a set of data corresponding to the amount of data collected by precessing the beam on a cone at each individual pixel of the frame, such as using pixel-based techniques. In other words, rather than recording a dynamically tilted beam at a single pixel during a complete scan of a frame, the frame can be rapidly scanned with a fixed beam tilt, and then the frame scan can be repeated with additional tilts until a tilt matrix similar to that obtained through the pixel-based approach is sufficiently filled.

[0007] However, various frame-based embodiments herein may exhibit enhanced characteristics and / or enable various improvements over pixel-based approaches. For example, a frame-based approach may enable the implementation of various correction capabilities in a workflow that would be impractical or impossible with a pixel-based approach. Furthermore, a frame-based approach may enable significantly improved imaging speeds over pixel-based approaches, enabling new applications that would be impractical or impossible with a pixel-based approach. That is, various frame-based embodiments may provide faster data acquisition times, improved spectroscopic image quality, improved field and strain measurements, and new applications such as atomic 3D imaging, rocking mapping, and dance beam aberration correction in STEM.

[0008] Thus, while there are multiple applications that could benefit from precession mapping techniques, or more generally, tilted beam injection, such applications have until now been limited by existing precession paradigms, in which a fixed tilt amplitude is applied to a focused beam, which is then scanned around a conical path at a specific point on the sample. In contrast, the systems and approaches described herein, which use frame-based precession, allow for considerable flexibility in constructing tilt matrices of data. This flexibility may enable precession techniques to be extended to new applications, such as 3D imaging, and may open precession acquisition to further imaging refinements, such as drift correction.

[0009] An electron microscope can be equipped with a set of deflectors to generate a beam shift and / or tilt at the sample. This can be achieved by placing a first deflector in a plane exactly conjugate to the sample, thus ensuring that this first deflector generates only a tilt (and not a shift) at the sample, and by placing a second deflector in a plane exactly conjugate to the front focal plane of the probe-forming lens, thus ensuring that this second deflector generates only a shift (and not a tilt) at the sample. However, it is more common and more flexible to place two deflectors in two separate planes (e.g., upper and lower planes) that are not necessarily conjugate to the sample or the front focal plane of the objective lens, and to excite the upper and lower deflectors at two specific ratios, where the first ratio is adjusted so that the two deflectors together generate a pure shift at the sample, and the second ratio is adjusted so that the two deflectors together generate a pure tilt at the sample. These ratio adjustments are commonly referred to as "pivot point adjustments."

[0010] The focal strength of the probe-forming lens varies somewhat with the tilt angle applied to the sample due to the aberrations of this lens, in particular its spherical aberration. Due to this variation, the exact position of the plane conjugate to the sample also varies somewhat with the applied tilt angle. For the same reason, the exact value of the pivot point also varies somewhat with the applied tilt. Correcting these variations may require sophisticated compensation schemes for the pivot point when dynamically changing tilts are applied. The applied tilt angle, when combined with the aberrations of the probe-forming lens, may not only induce variations in the focus, but also variations in astigmatism and / or coma, which, if not corrected (e.g., using a stigmator and additional deflection), will impair image resolution.

[0011] Each deflector may include two perpendicular magnetic coil pairs or two electrostatic deflection plate pairs to allow deflection in two directions (x and y) perpendicular to the beam.

[0012] Although deflectors based on magnetic coils are often easier to construct than deflectors based on electrostatic deflection plates, magnetic coils typically have a slower maximum scan speed than electrostatic deflection plates due to their self-inductance. Thus, some exemplary microscope systems can include a combination of magnetic and electrostatic deflectors, whereby the magnetic deflectors can be used for adjustments that can tolerate operating at moderate speeds (such as beam tilting according to the present disclosure) and the electrostatic deflectors can be used for adjustments that can benefit from the highest speeds, such as high-speed lateral scans.

[0013] Some microscope embodiments may include a duplicate set of deflectors upstream of the sample to a similar set of deflectors downstream of the sample, whereby the downstream set of deflectors undoes any shift and / or tilt applied to the sample to ensure a stationary beam at the downstream detector.

[0014] In many embodiments, frame-based precession techniques can achieve improved performance by rapidly scanning with static tilts, multiple times according to a user-defined tilt matrix, rather than tilting at each point and completing the tilt matrix, as in pixel-based approaches. Many frame-based embodiments can use separate beam deflectors, for example, one to provide a fast lateral scan of the probe across the sample and another to provide a fixed (or slowly varying) tilt angle for a particular frame. In this way, tilt-shift pivot point analysis and sophisticated compensation, typically required when using only two dynamic deflector units (i.e., one to provide tilt and shift before the sample and one to descan the beam after the sample), are no longer required for most applications. Furthermore, probe beam degradation can be limited to contributions solely from the optical system, such as aberrations introduced by the objective lens. Such aberrations can be more easily predicted using models and therefore partially corrected to achieve smaller probe sizes during tilting, resulting in improved optical performance for a range of applications.

[0015] Frame-based implementations can also solve long-standing problems associated with probe drift on the sample. For example, in pixel-based approaches, each pixel is scanned separately through the cone until a full frame is completed. During this lengthy process, the probe and sample may drift relative to each other due to various influences on the system. This can degrade the quality of the resulting image during the already time-consuming acquisition process of collecting precession image components. In frame-based approaches, drift can be more easily compensated for because the acquisition rate of a single frame is significantly faster (high repetition rate) than the time required to complete a full frame using a pixel-based approach. Therefore, drift is less likely to occur or have a significant impact across acquisition frames that are rapidly scanned at a fixed tilt. If drift does have an impact, such as between frames or after multiple frames (e.g., after a change in azimuth or tilt angle), drift correction can be performed. In contrast, pixel-based methods do not allow for frame-based drift correction.

[0016] Pixel-based methods typically only allow for cone illumination with a fixed amplitude (e.g., a fixed tilt angle relative to the optical axis) because the pivot point (shift and tilt) depends on this amplitude. In the frame-based embodiments taught herein, the additional flexibility of tilt angle and amplitude allows for the application of arbitrary tilt matrices, including, by way of example, rocking beam, random walk, precession, etc. In precession, a fixed tilt amplitude is typically applied to the beam, and the azimuthal direction is changed with the tilt amplitude, for example, following a full 360-degree rotation of a circle. In rocking beam, the tilt amplitude is varied, typically implementing a Cartesian squared pattern of beam tilt, typically with equal x, y steps (e.g., 3 x 3, 8 x 8, etc.). In random walk precession, a Cartesian coordinate system of beam tilt is used, and the matrix is ​​randomly visited with different tilts. The matrix does not need to be completely filled, and therefore a sparse scan of the tilt matrix can be performed. In the case of a rocking beam tilt matrix, the matrix positions can include harmonic, Lissajous, or other paths through the matrix. The harmonic Lissajous path has the advantage that it can be scanned with a scan coil without the flyback problems caused by line-by-line scanning of the gradient amplitude.

[0017] Additional compensation options available in the frame-based approach can be used to compensate for probe degradation caused by objective lens aberrations (e.g., affecting each fixed tilt in a recorded series of frames), further enabling 3D atomic focus series acquisition. For example, to obtain atomic-resolution focal depth, a convergence half angle of 100 mrad may be required. With current technology, this can only be achieved by correcting all aberrations up to 100 mrad. Such correction is difficult or impractical to achieve. 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. Probe aberrations in each frame can be partially corrected to maintain a probe size of approximately 0.2 nm in the x, y plane. Therefore, minimal voxels in the x, y, and z positions can be created, enabling scanning in three dimensions by changing the focus in approximately angstrom-sized steps.

[0018] Exemplary Frame-Based Method FIG. 1 illustrates an exemplary frame-based collection method 100. Method 100 includes starting the frame collection method at 102. For example, a sample can be placed in the chamber of a charged particle beam microscope, such as an electron microscope. A charged particle probe beam, such as an electron beam, is directed along the microscope's optical column. The optical column can include an array of lenses defining an optical axis. The system's optical axis generally corresponds to the central axis of the optical column, but in some embodiments, can be adjusted to be at an angle relative to the central axis. Lenses can be used to direct the probe beam along the optical axis and to direct and focus the beam onto the sample. The sample can be positioned within the path of the beam, for example, on a fixed or movable stage. One or more probe beam deflectors (typically two separate beam deflectors) can be used to direct the probe beam away from the optical axis, for example, at an angle relative to the optical axis and / or transversely relative to the optical axis, prior to impinging on the sample. One or more detectors can be positioned relative to the sample to receive particle emissions from the sample in the form of detection beams. An additional detection beam deflector can be positioned to direct the detection beam from the sample to a detector, for example, to detilt the emitted particles. In an exemplary embodiment, the detection beam is a beam downstream from the sample, and the additional beam deflector(s) can correspond to a downstream deflector. The various frame collection steps, such as scanning, detecting, and / or changing beam parameters, are typically automated, for example, by a system controller.

[0019] To collect a frame, at 104, a tilt angle (i.e., polar angle or tilt angle) and azimuth angle (which may collectively be referred to as one or more tilt angles) are selected for the probe beam to impinge on the sample. At 106, a probe beam deflector is used to scan the probe beam across the sample transversely to the optical axis at the selected tilt and azimuth angles. The selected tilt and azimuth angles are fixed or maintained as the probe beam is scanned across the sample. In many embodiments, after interacting with the sample, the downstream beam is deflected with a detection beam deflector and detected with a detector. Depending on the application, a variety of detectors can be used. The collected frames can correspond to data collected at the detector associated with the beam impinging on multiple locations on the sample using fixed or maintained tilt and azimuth angles. The multiple locations can be referred to as pixels.

[0020] In some embodiments, at 108, after a frame is collected, beam or sample characteristics can be corrected to compensate for, e.g., drift, sample perturbations, etc. At 110, a decision can be made whether to collect additional frames, e.g., continue to collect additional frames according to an automated process or workflow (e.g., to complete a tilt matrix), or whether to rescan frames based on the decision made at 108. If additional frames are collected, the process can return to an earlier portion of process 100, e.g., repeating the selection or adjustment of tilt / azimuth angles at 104 and the scanning and detection at 106. For one or more subsequent frames, the tilt and / or azimuth angles can be changed to one or more different angles, and the one or more different angles can also be maintained as the beam is scanned across an area of ​​the sample in generating one or more subsequent frames.

[0021] In additional embodiments, the correction at 108 can correspond to corrections related to aberrations of the beam being directed at the sample, and such corrections can be performed more simultaneously with frame collection. Aberrations can include defocus, astigmatism, coma, etc. For example, the aberration correction at 108 can be performed before a frame is collected or between frames. Such corrections are typically based on model predictions of expected aberrations for a selected deflection angle and / or scan position. Aberrations can be corrected through adjustments to existing beam deflectors and / or lens elements, as well as with additional components such as stigmators, probe correctors, or aberration correction lenses (aberration correctors can include, but are not limited to, Cc and / or Cs correctors). Often, scan speeds can exceed the response time capabilities of aberration correction devices. Therefore, command knowledge of the frames to be collected can allow sufficient time to make aberration adjustments, for example, during the period between the collection of two frames or throughout the process of frame collection. In this way, compensation can be performed with specific adjustments / improvements at each angle before scanning. Thus, such aberration correction can be done without necessarily detecting those aberrations in quasi-real time, as a detection unit is often not necessary. In many embodiments, a tilt / azimuth angle can be selected at 104, aberrations can be corrected for that particular angle at 108, and then the beam can be scanned across the sample and image frames detected at 106.

[0022] In many embodiments, fixed or maintained tilt and azimuth angles can be defined by a fixed (or sometimes slowly changing) azimuth angle in a reference plane perpendicular to the system's optical axis, and a fixed or slowly changing angle relative to a reference axis perpendicular to the reference plane. This contrasts with a pixel-based precession approach, in which the angle of incidence relative to the optical axis remains fixed (e.g., a 5° tilt angle), while the azimuth angle varies over time for a particular pixel, allowing detection to occur at one or more azimuth positions for that pixel (e.g., detection at 10° azimuth increments) before the beam is shifted to an adjacent pixel to generate a similar precession. In a basic frame-based precession embodiment, a tilt matrix can be compiled by collecting a set of frames at a selected tilt angle, each frame changing its fixed azimuth angle by a selected amount. For example, a complete precession period can be collected in 36 frames, each collected at a 5° tilt angle and with azimuth angles stepped in 10° increments. It will be appreciated that multiple tilt and azimuth angle sequences may be used in various frame-based acquisition examples, such as precessional, harmonic, Lissajous, rocking, etc. sequences. In many embodiments, the frame sequence includes many tilt 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.

[0023] In many frame-based embodiments, the angle of the probe beam can be maintained at its intersection with the sample. In some embodiments where the sample surface is flat and angled obliquely (i.e., not perpendicular) to the optical axis of the system, fixed tilt and azimuth angles can be maintained across the angled sample surface throughout the collection of a frame. For example, z-focus adjustments can be made to the beam as the z-position of the sample changes across a frame. In more typical embodiments, the sample is positioned approximately perpendicular to the central optical axis of the system. In some embodiments, frames can be collected at different focal depths, e.g., in 3D depth sectioning. At 112, various post-processing of the collected frames can be performed, such as mapping pixels between frames, drift correction, shift compensation, 3D depth sectioning, frame summation, etc. In many embodiments, particularly with EDX, EELS, or more generally with spectroscopic modalities, images can be summed to form an average or composite image, e.g., a composite diffraction image.

[0024] 2A-2B are examples of a sample 200 being probed with a frame-based probing method such as method 100. The sample 200 is placed in the chamber of an electron microscope. A surface 202 is perpendicular to and generally centered relative to the optical axis 204 of the electron microscope. To collect a frame, a probe beam 206 is directed at the surface 202 at a selected tilt angle θ1 (shown relative to a reference line 205 parallel to the optical axis 204) and azimuthal angle θ2 (shown relative to a reference line 207 perpendicular to the optical axis 204), which remain generally fixed as the probe beam 206 is scanned across the frame. As shown, the probe beam 206 is scanned laterally across the frame, through four successive positions 208a-208d, and through multiple rows. The lateral scan can be performed 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 rectilinear grid is shown, although it will be understood that any grid may be selected. Scanning across a frame may be done sequentially across adjacent pixels, although other patterns may be used.

[0025] Example of microscope device FIG. 3 illustrates an exemplary frame-based precession microscope system 300. System 300 includes a charged particle beam (CPB) source 302, such as an electron or ion emitter source. 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. System 300 can include a beam direction column 310, which typically includes an arrangement 312 of electrostatic lenses, magnetic lenses, and / or other components configured to shape and direct beam 304 to sample 306. Exemplary lenses and other components of arrangement 312 can include focusing lens elements, objective lens elements, apertures, relay lenses, stigmators, deflectors, scan coils, beam modulators, aberration correctors, etc. While arrangement 312 is shown at a selected location closer to beam source 302, it will be understood that this is for convenience of illustration and that various lenses and components can be distributed throughout optical column 310. For example, an additional lens element (such as in the case of a STEM) can be placed below the sample to focus transmitted or emitted particles onto the detector 322 .

[0026] The system 300 is configured such that the beam 304 is angled θ with respect to the optical axis 305. IThe system 300 may include a tilt beam deflector 314 configured to adjust the angle of the beam 304 so that it propagates to and is received by the sample 306 at a tilt angle relative to the optical axis 305. The adjusted angle may be referred to as the tilt angle. The tilt beam deflector 314 may include magnetic coils and / or electrostatic plates that provide the tilt deflection, and the rate at which the tilt is changed may be relatively slow, for example, once per frame, 10 frames per second (approximately 0.4 μs per pixel) for a 512×512 pixel frame. In some embodiments, the tilt beam deflector 314 is located in a conjugate plane 315 with respect to a portion of the sample 306 (e.g., a surface of the sample 306 or a z-layer located at a specified depth within the sample 306). The system 300 may include a shift beam deflector 316 configured to adjust the lateral position of the beam 304 so 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 embodiments, the shift beam deflector 316 can include an electrostatic deflector (often a pair of electrodes) configured to provide a relatively fast lateral scan speed, which can be significantly faster than a tilt beam deflector, e.g., an order of magnitude faster, enabling speeds such as 120 frames per second (approximately 30 ns per pixel) for a 512x512 pixel frame. In some embodiments, the shift beam deflector 316 is located in a conjugate plane 317 to a front focal plane 319 of the probe-forming lens in the configuration 312, for example.

[0027] In many embodiments, the sample 306 may be flat and positioned on the stage 308 such that the surface or target sample layer is perpendicular to the optical axis 305. In further embodiments, the surface or target layer of the sample 306 may be flat, positioned at an angle to the optical axis 305, and / or may have a contour.

[0028] In various embodiments, system 300 can focus beam 304 onto a sample to cause various types of radiation to be emitted from sample 306, including (for example) transmitted electrons, secondary electrons, backscattered electrons, X-rays, and / or optical radiation (e.g., cathodoluminescence). The radiation to be detected caused by interaction with sample 306 can be referred to as a detection beam 320. In some embodiments, an additional beam deflector 318 can be positioned to deflect detection beam 320 so that the detection beam can be received by detector 322. For example, beam deflector 318 can deflect beam 304 at an angle θ O The angle θ can be operated in a complementary manner with the tilt beam deflector 314 so as to de-tilt at the angle θ I , θ O are shown for convenience of illustration and do not need to be the same size. Furthermore, beam deflector 318 does not need to cause angled detection beam 320 to propagate parallel to optical axis 305.

[0029] The detector 322 can be of various types depending on the application, and some exemplary devices can include multiple types of detectors. As shown, the detector is positioned below the sample 306, although other locations may be appropriate depending on the type of detection being performed. Suitable embodiments of the detector 322 can include a segmented STEM detector and / or a pixelated detector, typically positioned below the sample 306. The pixelated detector can be positioned to acquire the complete diffraction pattern generated from the sample. In some pixelated embodiments, complete STEM images, including HAADF or dark-field images, can be acquired. A pixelated STEM detector can be used for general analysis, crystal orientation mapping, and strain mapping. A segmented STEM detector can be used to acquire center-of-mass analysis data. In some embodiments, the detector 322 can include or correspond to an electron energy loss spectroscopy (EELS) sensor. EELS sensors are often used in chemical analysis applications. In many EELS crystallographic detections, channeling effects can adversely affect the collected data, and such channeling effects can be overcome to a significant extent through precession of the beam 304. In some embodiments, the detector 322 may 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, typically located at a position not below the sample 306. Exemplary detectors may include a CMOS sensor, a CCD imaging sensor, a photodetector, etc.

[0030] An additional beam deflector 318 can be included in some embodiments to compensate for a shift in the diffraction image present in the detection beam 320. Correcting for such a shift is useful or necessary in EELS due to the change in collection angle caused by the shift in the diffraction pattern. In EDX mapping, it is not typically required because the signal is generated above the sample. In embodiments where 4D STEM data is recorded on a pixelated detector below the sample at each tilt, the diffraction shift caused by the beam tilt can be corrected in software, for example, during or separately after processing. In some embodiments, a software routine can provide shift correction by summing the collected diffraction patterns with different beam tilts at each scan point. For example, a central disk can be aligned at each pixel for all tilts, and the diffraction patterns can be added.

[0031] The different components of the system 300 can be coupled to and controlled by a frame-based imaging controller 324, which can correspond to or be part of a controller or control network of the system 300. The controller 324 can be coupled to various components, such as the beam source 302, lens (etc.) arrangement 312, tilt beam deflector 314, shift beam deflector 316, tilt-release beam deflector 318, and detector 322, to control the direction of the beam to the sample 306 and detector 322, as well as the detection of the beam 320. In many embodiments, the controller 324 can be pre-programmed with a frame-based detection routine that can include tilt deflector parameters 326 and shift deflector parameters 328 configured to adjust the characteristics of the source beam 304 and detection beam 320. The shift beam deflector 316 typically operates on a much faster timescale than the tilt beam deflector 314, and can provide a scan of the beam 304 laterally relative to the sample 306 over a frame. In some embodiments, the shift beam deflector parameters 328 may include a pixel mapping overlaid on a portion of the sample 306 .

[0032] Pixel-based precession techniques typically rely on a single scanning unit to precess the beam at each pixel. Pivot point alignment between tilt and shift in such techniques is a long-standing problem. That is, in a single scanning unit, tilt and shift are intertwined and need to be decoupled to provide pivot point alignment for beams precessing at the same location on the sample. For example, to provide the same tilt angle but different azimuth angles, the beam requires a shift to maintain 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 precesses. Furthermore, the tilt matrix requires significant changes after changing the tilt angle. In many embodiments, the system 300 provides tilt and shift beam deflections via different deflectors 314, 316, which are advantageously decoupled from each other, significantly simplifying the workflow procedures for precession-based techniques as well as other techniques involving beam tilt. In some embodiments, 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 .

[0033] Frame-based approaches can leverage decoupled tilt and shift beam deflections to achieve substantial improvements in workflow throughput and / or improved image quality. For example, in a frame-based approach, rather than repeating slower changes in azimuth or tilt angle for each pixel, the azimuth or tilt angle can be performed fewer times (or only once) within a single frame across the sample area, and rapid shift deflections can occur more quickly and iteratively as additional frames are acquired. Operator ease of use is also substantially improved by decoupling. In some embodiments, the operator can simply select a tilt angle and, optionally, optimize the tilt angle over a range, e.g., at a single pixel. After optimization and other image quality characteristics (such as a lack of jitter) exist, the operator can choose to proceed with a full scan using a rapid lateral scan across the sample. In many embodiments, frame-based systems exhibit fewer artifacts compared to completed frames in pixel-based approaches, given the rapid scanning of frames. Additionally, deleting and / or reacquiring additional frames to replace substandard frames may be more convenient given the increased acquisition speed of the frame-based approach and the multiple frames collected.

[0034] In some frame-based embodiments herein, a single beam deflector unit can be used to scan and tilt the beam, i.e., the tilt and shift pivot points can be combined to acquire frames such that each frame has a fixed (or only slowly varying tilt angle) throughout the frame. Single-scan unit embodiments may not operate as quickly or with reduced complexity, but may be less expensive. Furthermore, applying frame-based techniques using a single scan unit in precession-type image acquisition may be less complex than the same acquisition using a pixel-based approach, because the requirement for pivot point alignment can be relaxed in a frame-based approach. When a fixed tilt is applied, potential errors in shift can be more easily compensated for based on the acquisition of a complete frame. For example, frames of a sequence can be compared, and cross-correlation or machine learning techniques can be used to detect image shift or other image variations, which can then be corrected. Post-process image processing 329 can include software routines configured to provide various image processing and / or image adjustments, including post-sample shift compensation, image construction using acquired frames, feature detection, etc.

[0035] The tilt deflector parameters 326 can also include corrective de-tilt parameters for the beam deflector 318. The beam deflector 318 can provide de-tilting and stabilization of the diffraction pattern or image below the sample 306 due to tilt-induced image or diffraction shift. Notably, even with the separation of tilt and shift prior to the sample 306, in many embodiments, a single de-scan unit (or no scan unit) can be used after the sample 306, without the symmetrical need for a second de-scan unit (because the introduced tilt generates an image shift). In some embodiments, post-processing image processing 329 can be used to compensate for frame-to-frame shifts (e.g., associated with changes in tilt parameters between frames), which in some embodiments includes not using a de-scan unit to de-tilt the collected image frames.

[0036] In some embodiments, the system 300 can include a drift compensator 330 that can be part of or coupled to the controller 324. During a gradient-based workflow in which images are acquired using gradients, the beam 304 can become distorted, for example, due to drift, and / or the sample position can drift during acquisition of the gradient matrix. Drift can occur due to environmental perturbations, such as external vibrations, temperature changes, acoustic or pressure fluctuations, as well as aberrations caused by system changes or nonlinearities. A frame-based approach advantageously allows for the ability to compensate for aberrations or drift effects dynamically or in post-processing during the frame acquisition process. In some embodiments, the drift compensator 330 can be configured with feedback capabilities to dynamically make corrections during frame acquisition. In some examples, drift can be detected by comparing identifiable features in a sequence of frames, and the detected movement of the identified features can provide the basis for making corrections between frames. The drift compensator 330 can include or be embodied in computer-readable instructions that can be used by the controller 324 or another processor-based computing system. The drift compensator 330 can include instructions for receiving the scan data, comparing the image data, and making adjustments to the images or the relationships between the images. Many existing software modules can be utilized to perform the comparison and image correction.

[0037] For example, because the beam distorts due to optical aberrations when tilted, compensation to minimize these effects can be applied for each tilt. This can result in higher lateral resolution, for example, when precession runs are summed. In many embodiments, beam tilts can cause beam shifts, such as when the pivot point is imperfectly aligned. These shifts can be compensated for by cross-correlation of images with different tilts, resulting in higher lateral resolution. Pattern shifts can occur in the diffraction plane, for example, if the descanning unit is not perfectly aligned. Using cross-correlation or similar methods, these shifts can be compensated for before adding the diffraction pattern for further analysis. This can improve the accuracy of results, for example, in distortion, orientation mapping, or center-of-mass analysis applications (e.g., field measurements, iDPC, ptychography, etc.). These compensations can be applied live during acquisition or in an offline process. In contrast, these effects cannot be compensated for with pixel-based precession. This can lead to blurring of the scan plane (e.g., resulting in a loss of lateral resolution) or blurring of the diffraction plane, resulting in a loss of measurement accuracy. That is, pixel-based approaches generally produce only one blurred image and one (blurred) diffraction pattern per scanned pixel, and as a result are unable to perform compensation for these.

[0038] When the beam dynamically precesses, the associated compensation in pixel-based approaches may not be available because a single frame is acquired over a longer duration. Drift may occur that cannot be easily corrected without repeating the entire pixel-based frame acquisition. Furthermore, even with a priori knowledge of aberrations through prediction, it is often too difficult or impossible to dynamically correct aberrations in pixel-based approaches because the speed of precession exceeds the capabilities of the corrector. For example, modeling often provides predicted aberration amounts in response to applying various amounts of tilt, which can then be corrected with lenses, stigmators, or probe correctors. In some embodiments, the controller 324 can be configured to use the predicted aberration amounts and associated commands to the arrangement 312 and deflectors 314, 316 to adjust the beam direction so that a frame can be acquired with reduced aberrations. Aberration correction can be achieved by utilizing a fixed tilt angle or a longer duration of scanning an entire frame at a smaller fixed tilt angle applied to complete the workflow.

[0039] Some corrections can be applied in a frame-based approach by comparing features within acquired frames, taking into account the time provided to acquire a complete frame and that tilt and azimuth angles are maintained throughout the frame. Some corrections can be made based on model-based predictions of aberrations, which can be stored in controller memory. This allows for correction of anticipated aberrations before a frame is acquired at a selected tilt / azimuth angle. In contrast, in a pixel-based approach, the speed of beam precession at the pixel may exceed the ability of the probe compensator to track, or the associated delay inserted into the process to match the compensator's capabilities undesirably increases the length of an already long workflow. Furthermore, because pixel-based approaches build frame information pixel-by-pixel, complete frame information does not exist until the end of the scanning process. Therefore, there are no multiple frames to compare, making it impossible to apply corrections based on, for example, comparison of feature locations within frames.

[0040] In some examples, the frame-based tilt approach can allow for adjustment of the number of azimuthal positions and tilt angles scanned. For example, while pixel-based approaches typically require the collection of hundreds of azimuthal positions at pixel locations, the disclosed frame-based approach can arbitrarily vary this number, significantly reducing workflow duration by reducing the azimuthal positions, tilt angles, and therefore the number of frames collected. For example, a smaller amount may be sufficient to avoid channeling artifacts or to provide compositional analysis in in-situ or strain mapping. Furthermore, further reductions in workflow duration can lead to further improvements in drift reduction, because drift has less time to occur when fewer frames are collected or collected more quickly.

[0041] Regarding channeling artifacts, when a crystal is aligned with the zone axis, atoms are aligned in linear columns relative to the beam direction. When an electron beam strikes a sample under these conditions, the electrons pass through the material, potentially resulting in uneven distribution during their passage through the sample. As a result, columns with different atomic species see different amounts of electrons. Quantification in EDX / EELS assumes that electrons move uniformly through the material, resulting in the same probability of atom excitation everywhere. Using precession by tilting the electron beam away from the zone axis minimizes channeling because precise alignment of the beam with the atomic columns is avoided. Multiple tilts can simply average out this effect. Therefore, precession (e.g., rocking beam) acquisitions in mapping can result in more accurate compositional analysis. Precession also has advantages in COM analysis for E / B field (i.e., electric or magnetic) measurements, since the change in crystal orientation due to precession depends on the beam tilt angle, while the COM change in the field does not. Therefore, the E / B field can be measured more accurately in precession mapping in 4D STEM of crystalline materials than would be possible without it.

[0042] Exemplary Frame and Matrix Formation and Additional Methods FIG. 4 is a representation of a 4×4 pixel array 400 showing 16 tilt matrices 402 acquired in a frame-based precession workflow, with each matrix 402 corresponding to one of the pixels in the array 400. Each tilt matrix 402 contains 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 25 frames. In the tilt matrix 402, image data acquired for a particular tilt angle and azimuthal frame is designated by a frame number ranging from 1 to 25. In many embodiments, the array 400 is typically larger. The tilt matrix 402 can be configurable by the user or can vary based on the application. For example, while a series of precessions at different tilt angles can be used as shown, various other tilt patterns, including non-conical ones, can be used depending on the application. By way of example, any of the beam tilt patterns described in U.S. Patent Application No. 17 / 683,076, entitled "MEASUREMENT AND CORRECTION OF OPTICAL ABERRATIONS IN CHARGED PARTICLE BEAM MICROSCOPY," incorporated herein by reference, can be used in frame-based tilt acquisition, e.g., to correct aberrations in a TEM. In additional embodiments, rocking beam-type patterns may be used in frame-based tilt acquisition. For example, as the beam changes tilt angle along an axis, similar to the motion of a pendulum, the change in azimuthal angle can be limited to 0° and 180°.

[0043] FIG. 5 is an exemplary method 500 of frame acquisition with drift correction. At 502, method 500 may begin. At 504, frames are acquired for a series of frames. At 506, the acquired frames may be examined to determine whether drift or aberrations are present in the frames. In many embodiments, a comparison may be made with other acquired frames, such as the immediately preceding frame. If drift is detected, the process may proceed at 508 to checking against criteria to determine whether the frame should be discarded and reacquired. For example, a frame containing artifacts or anomalies that do not match other frames may be discarded and reacquired at 504. In some embodiments, the comparison may be made later in the frame acquisition process or may require additional time for processing such that the determination is not available until later in the frame acquisition process.

[0044] If no drift or aberration is detected, a determination can be made at 510 whether there are more frames to collect; if not, the process can end at 512. If additional frames are to be collected, the next frame can be repeated at 514, and frame collection can continue back at 504. If the frame should not be discarded or reacquired and drift is detected, a determination can be made at 516 regarding whether to adjust the frame. For example, in some instances, drift or aberration below an acceptable range of drift or aberration may be detected, in which case the frame is left unadjusted and the next frame can be repeated at 514. In some embodiments, frames can be adjusted at 518 through frame-to-frame mapping. For example, if drift is sufficient, frames can be compared to quantify the drift, e.g., in the form of rotation and / or translation in the sequence of frames. Other drift or aberration characteristics can be quantified, including image warping, distortion, stretching, or other aberrations. The mapping can be used so that subsequent frame-based gradient matrices can be constructed with reduced effects from drift or other aberrations.

[0045] FIG. 6 illustrates an exemplary 3D imaging method 600 using a frame-based acquisition technique. At 602, the frame-based 3D imaging method can begin. At 604, a z-layer of the sample is selected for targeting. The z-layer can correspond to a depth position of the sample along the general direction of the beam used for imaging. At 606, a tilt angle and azimuth angle can be selected for probing the sample. Aberration correction can be provided based on the selected tilt and azimuth angles so that aberrations induced by beam tilt have a reduced effect. For example, the probe spot at the selected z-layer may be elliptical due to the tilt angle; such ellipticity can be corrected using an aberration corrector or other lens element adjustment. At 608, frames can be acquired using fixed (or slowly varying) tilt and azimuth angles that are maintained throughout each frame. At 610, a determination can be made as to whether any additional frames should be acquired. For example, additional z-layers or tilt / azimuth angles may be imaged. If additional frames are to be imaged, then a new z-layer and / or tilt / azimuth angle can be selected at 604 and / or 606. If the final frame is to be imaged, then at 612, the collected tilt matrix can be filled with the collected data, and the images can be summed together. Due to the tilt 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 tilt-induced image shifts of out-of-focus atoms in the other layers. It will be appreciated that various frame sequences may be used in different embodiments. In some embodiments, a tilt / azimuth angle can be selected, and frames at the selected tilt / azimuth angle are collected at various z-layer depths. In other embodiments, a frame sequence at a different selected tilt / azimuth angle at a selected z-layer can be imaged, and then repeated at a different z-layer. In yet another embodiment, the frame sequence can include a combination of frame sequencing.Frame sequencing can be adjusted based on various factors such as acquisition speed, reduced aberration or drift, preference, etc.

[0046] General Considerations As used in this application and the claims, the singular forms "a," "an," and "the" include the plural forms unless the context clearly dictates otherwise. Additionally, the term "includes" means "comprises." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0047] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with one another. 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 that any one or more specific advantages be present or problems be solved. While any theory of operation is provided for ease of explanation, the disclosed systems, methods, and devices are not limited to such theory of operation.

[0048] Although some operations of the disclosed methods are described in a particular sequential order for convenient presentation, it should be understood that the format of the specification encompasses reordering unless a specific ordering is required by specific language set forth below. For example, operations described in sequence may, in some cases, be reordered or performed simultaneously. Moreover, for the sake of simplicity, the accompanying drawings may not show the various ways in which the disclosed systems, methods, and apparatuses may be used in conjunction with other systems, methods, and apparatuses. Additionally, the specification may use terms such as "produce" and "provide" to describe the disclosed methods. These terms are high-level abstractions of actual operations that take place. The actual operations corresponding to these terms will vary depending on the particular implementation and are readily discernible by those skilled in the art.

[0049] In some examples, values, procedures, or devices are referred to as "lowest," "best," "smallest," etc. Such descriptions are intended to indicate that a selection may be made from among many possible functional alternatives, but it will be understood that such a selection need not be better than, smaller than, or otherwise preferred to other selections.

[0050] The innovation may be described in the general context of computer-executable instructions, such as instructions included in a program module, being executed on a target real or virtual processor in a computing system. 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 the program modules may be combined or divided among program modules as desired in various embodiments. Computer-executable instructions for program modules may be executed in a local or distributed computing system. Generally, a computing system or computing element may be local or distributed and may include any combination of special-purpose hardware and / or general-purpose hardware and software that implements the functionality described herein.

[0051] In various examples described herein, a module (e.g., a component or engine) can be "coded" to perform particular operations or provide particular functionality, indicating that computer-executable instructions for the module can be executed to perform such operations, cause such operations to be performed, or otherwise provide such functionality. Functionality described in terms of a software component, module, or engine can be performed as a separate software unit (e.g., a program, function, class method), but need not be implemented as a separate unit. That is, functionality can be incorporated into a larger or more general program, such as one or more lines of code within the larger or more general program.

[0052] For purposes of 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 acts performed by a human. The actual computer operations corresponding to these terms will vary depending on the implementation.

[0053] The described algorithms may be embodied as software or firmware instructions executed by, for example, a digital computer or 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 computers or other computing hardware that are part of a microscopy tool. The computer may be a computer system that includes one or more processors (processing devices) and tangible, non-transitory computer-readable media (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 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 of the tangible, non-transitory computer-readable media, thereby implementing any of the disclosed techniques. For example, software for performing any of the disclosed embodiments may be stored on one or more volatile, non-transitory computer-readable media as computer-executable instructions that, when executed by one or more processors, cause the one or more processors to perform any of the disclosed techniques or a subset of techniques. Results of the computations may be stored in one or more tangible, non-transitory computer-readable storage media and / or may be output to a user, for example, 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.

[0054] Although the principles of the disclosed technology have been described and illustrated with reference to the illustrated embodiments, it will be recognized that the illustrated embodiments may be modified in arrangement and detail without departing from such principles. For example, elements of the illustrated embodiments shown in software may be implemented in hardware, and vice versa. Also, techniques from any embodiment may be combined with techniques described in any one or more of the other embodiments. It will be understood that procedures and functions as described with reference to the illustrated embodiments may be implemented in a single hardware or software module, or may be provided as separate modules. The particular configurations described above are provided for convenient illustration, and other configurations may be used.

[0055] In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are merely representative examples and should not be construed as limiting 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, various components of the systems described herein may be combined in function and use.

[0056] The following paragraphs provide various examples of the embodiments disclosed herein.

[0057] Example 1 is a method including: directing a charged particle beam over an area of ​​a target at a first angle having an inclination angle component and an azimuthal angle component; collecting a first image frame produced using the beam at the selected first angle; detecting the first image frame; directing the charged particle beam over the area of ​​the target at a second angle having an inclination angle component and / or an azimuthal angle component different from the inclination angle component and azimuthal angle component of the first angle; collecting a second image frame produced 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.

[0058] Example 2 includes the subject matter of Example 1, further specifying that directing the beam across the area of ​​the target includes scanning the beam laterally using a lateral beam deflector, and directing the beam at the first angle and the second angle includes adjusting to the first angle and the second angle using a tilted beam deflector.

[0059] Example 3 includes the subject matter of example 2, and further specifies that the lateral beam deflector and the tilt beam deflector are part of the same single beam deflector unit.

[0060] Example 4 includes the subject matter of any of Examples 1-3, further including correcting aberrations associated with directing the beam at the first angle and / or the second angle prior to acquisition of each frame based on a prediction of aberrations induced at the first angle and / or the second angle, where the correction includes adjusting one or more stigmators, deflectors, and / or lenses upstream of the target.

[0061] Example 5 includes the subject matter of any of Examples 1-4, further including detecting drift or aberration between collected frames, and compensating for the drift or aberration.

[0062] Example 6 includes the subject matter of example 5, and further specifies that the compensation is performed during frame acquisition.

[0063] Example 7 includes the subject matter of any of examples 1-6, further specifying that the first angle and the second angle include a set of tilt precession parameters.

[0064] Example 8 includes the subject matter of any of Examples 1-7, further specifying that the first angle and the second angle include a set of rocking beam, random walk, harmonic, Lissajous, and / or periodic tilt parameters.

[0065] Example 9 includes the subject matter of any of Examples 1-8, further including collecting image frames at multiple layer depths of the target, and summing the images to generate a 3D image of the target based on tilt-induced image shifts of out-of-focus atoms at depths other than the target layer depths.

[0066] Example 10 includes the subject matter of any of Examples 2-9, further including de-tilting the detection beam emitted from the target using a separate beam deflector prior to detecting the first image frame and / or the second image frame.

[0067] Example 11 includes the subject matter of any of Examples 1-10, further including constructing a gradient matrix of the collected data by relating the data collected from different image frames to a common target location.

[0068] Example 12 includes the subject matter of any of Examples 1-11, further specifying that the first image frame and the second image frame include image frames of a diffraction pattern, and further including determining a shift of the first image frame and / or the second image frame associated with the respective first angle or second angle, and compensating for the shift when combining the first image frame and the second image frame to form an image.

[0069] Example 13 includes the subject matter of example 12, further specifying that the diffraction pattern is part of a precession tilt series around a circle, and that detecting includes detecting with a pixelated sensor, and that combining includes compiling the precession tilt series to form a complete precession diffraction pattern of the circle.

[0070] Example 14 includes the subject matter of example 13, further specifying that detecting the first image frame and / or the second image frame includes receiving the downstream beam with the detector without the beam being deflected by the downstream deflection unit.

[0071] Example 15 includes the subject matter of any of Examples 1-14, further specifying that the first and second image frames include spectroscopic image frames, and detecting the first and second image frames includes detecting a HAADF signal having a shift associated with a difference between the first angle and the second angle, and compensating for the shift by cross-correlating the image frames.

[0072] Example 16 includes the subject matter of example 15, further specifying 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 spectroscopic channeling artifacts.

[0073] Example 17 includes the subject matter of any of Examples 12-16, further specifying that the shift includes a shift artifact in a center of mass, ptychography, or spectroscopy mapping measurement.

[0074] Example 18 is an apparatus including a microscope system configured to emit a charged particle beam, direct the beam over a target area at a first angle having an inclination angle component and an azimuthal angle component, collect a first image frame generated using the beam at the selected first angle, direct the beam over the target area at a second angle having an inclination angle component and / or azimuthal angle component different from the inclination angle component and azimuthal angle component of the first angle, and 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 the microscope system includes a controller configured to combine the first image frame and the second image frame to form an image.

[0075] Example 19 includes the subject matter of Example 18, further specifying that the microscope system comprises a lateral beam deflector configured to scan the beam laterally and a tilted beam deflector separate from the lateral beam deflector, wherein the tilted beam deflector is configured to direct the beam at a first angle and a second angle.

[0076] Example 20 includes the subject matter of any of Examples 18-19, further specifying that the controller is configured to correct aberrations associated with directing the beam at the first angle and / or the second angle by adjusting the beam directing before acquisition of each frame based on a prediction of aberrations induced at the first angle and / or the second angle.

[0077] Example 21 is a method that includes directing a charged particle beam over an area of ​​a target at an inclination angle and an azimuth angle, collecting image frames generated using the beam at the selected inclination angle and azimuth angle, and detecting the collected image frames.

[0078] Example 22 includes the subject matter of example 21, further including repeating the directing and detecting one or more times using one or more different selected tilt angles and / or azimuth angles.

[0079] Example 23 includes the subject matter of any of Examples 21-22, further specifying that directing the beam across the area of ​​the target includes scanning the beam laterally using a lateral beam deflector configured to provide a lateral scan, and directing the beam at a tilt angle and an azimuth angle includes adjusting the tilt angle and the azimuth angle of the beam using a tilt beam deflector separate from the lateral beam deflector.

[0080] Example 24 includes the subject matter of any of examples 21-23, further including constructing a gradient matrix for the collected data by relating data collected from different image frames to a common sample location.

[0081] Example 25 includes the subject matter of any of Examples 21-24, further including detecting drift or aberration between collected frames, and compensating for the drift or aberration.

[0082] Example 26 includes the subject matter of Example 25, and further specifies that the compensation is performed during acquisition of the frames.

[0083] Example 27 includes the subject matter of any of examples 22-26, further specifying that the one or more different tilt angles and / or azimuth angles include a set of tilt precession parameters.

[0084] Example 28 includes the subject matter of any of Examples 22-27, further specifying 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.

[0085] Example 29 includes the subject matter of any of Examples 22-28, further including collecting image frames at multiple layer depths of the sample and summing the images to generate a 3D image of the sample based on tilt-induced image shifts for out-of-focus atoms at depths other than the target layer depth.

[0086] Example 30 includes the subject matter of any of Examples 23-29, further including de-tilting the detection beam emitted from the sample with a separate beam deflector prior to detection with the detector.

[0087] Example 31 is an apparatus that includes a microscope system configured to emit a beam, direct the beam over a target area at an inclination angle and an azimuth angle, and collect image frames generated using the beam at the selected inclination angle and azimuth angle, the microscope system including a detector configured to receive and detect the collected image frames.

[0088] Example 32 includes the subject matter of example 31, and further specifies that the microscope system is configured to repeat the orienting and detecting one or more times using one or more different selected tilt angles and / or azimuth angles.

[0089] Example 33 includes the subject matter of any of Examples 31-32, further specifying that the microscope system includes a lateral beam deflector configured to scan the beam laterally, and a tilt beam deflector separate from the lateral beam deflector, wherein the tilt beam deflector is configured to direct the beam at a tilt angle and an azimuth angle.

[0090] Example 34 includes the subject matter of any of Examples 31-33, further specifying that the microscope system includes a frame-based imaging controller configured to construct a gradient matrix for the collected data by relating data collected from different image frames to a common sample position.

[0091] Example 35 includes the subject matter of any of Examples 31-34, further specifying that the microscope system includes a frame-based imaging controller configured to detect drift or aberration between collected frames and compensate for the drift or aberration.

[0092] Example 36 includes the subject matter of example 35, and further specifies that the frame-based imaging controller is configured to provide compensation during acquisition of the frames.

[0093] Example 37 includes the subject matter of any of examples 32-36, further specifying that the one or more different tilt angles and / or azimuth angles include a set of tilt precession parameters.

[0094] Example 38 includes the subject matter of any of Examples 32-37, further specifying 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.

[0095] Example 39 includes the subject matter of any of Examples 32-38, further specifying that the microscope system is configured to collect image frames at multiple layer depths of the sample and sum the images to generate a 3D image of the sample based on tilt-induced image shifts for out-of-focus atoms at depths other than the target layer depth.

[0096] Example 40 includes the subject matter of any of Examples 33-39, further including a separate beam deflector configured to de-tilt a detection beam emitted from the sample prior to detection with the detector.

[0097] 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 apparatus or a supporting apparatus, cause the apparatus to perform the method described in any of Examples 1-40.

Claims

1. 1. A method comprising: directing a charged particle beam across an area of ​​a target at a first angle having an inclination angle component and an azimuthal angle component and acquiring a first image frame produced 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 oblique and / or azimuthal component different from the oblique and azimuthal components of the first angle and acquiring a second image frame produced 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. 2. The method of claim 1, wherein directing the beam across the area of ​​the target comprises scanning the beam laterally using a lateral beam deflector, and directing the beam at the first angle and the second angle comprises adjusting to the first angle and the second angle using a tilted beam deflector.

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

4. 4. The method of claim 1, further comprising correcting aberrations associated with directing the beam at the first angle and / or the second angle before acquisition of each frame based on a prediction of aberrations induced at the first angle and / or the second angle, wherein the correction comprises adjusting one or more stigmators, deflectors, and / or lenses upstream of the target.

5. The method of any one of claims 1 to 4, further comprising detecting drift or aberration between collected frames and compensating for said drift or aberration.

6. The method of claim 5 , wherein the compensation is performed during frame acquisition.

7. The method of any one of claims 1 to 6, wherein the first angle and the second angle comprise a set of tilt precession parameters.

8. 8. The method of claim 1, wherein the first angle and the second angle comprise a set of rocking beam, random walk, harmonic, Lissajous, and / or periodic tilt parameters.

9. 9. The method of claim 1, further comprising collecting image frames at multiple layer depths of the target, and summing the images to generate a 3D image of the target based on tilt-induced image shifts for out-of-focus atoms at depths other than the target layer depths.

10. 10. The method of claim 2, further comprising de-tilting a detection beam emitted from the target using a separate beam deflector prior to detecting the first image frame and / or the second image frame.

11. The method of any one of claims 1 to 10, further comprising constructing a gradient matrix of the collected data by relating the data collected from different image frames to a common target location.

12. the first image frame and the second image frame include image frames of a diffraction pattern; determining a shift in the first image frame and / or the second image frame associated with the respective first angle or second angle; The method of any one of claims 1 to 11, further comprising: compensating for the shift when combining the first image frame and the second image frame to form the image.

13. 13. The method of claim 12, wherein the diffraction pattern is part of a precessional tilt series around a circle, the detecting includes detecting with a pixelated sensor, and the combining includes compiling the precessional tilt series to form a complete precessional diffraction pattern of the circle.

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

15. 15. The method of claim 1, 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 a difference between the first angle and the second angle, and compensating for the shift by cross-correlating the image frames.

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

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

18. 1. An apparatus comprising: a microscope system configured to emit a charged particle beam, direct the beam over a region of a target at a first angle having an oblique angle component and an azimuthal angle component, collect a first image frame produced using the beam at a selected first angle, direct the beam over a region of the target at a second angle having an oblique angle component and / or an azimuthal angle component different from the oblique angle component and azimuthal angle component of the first angle, and collect a second image frame produced using the beam at the selected second angle; the microscope system includes a detector configured to receive and detect the first image frame and the second image frame; The microscope system includes a controller configured to combine the first image frame and the second image frame to form an image.

19. 20. The apparatus of claim 18, wherein the microscope system comprises a lateral beam deflector configured to scan the beam laterally and a tilted beam deflector separate from the lateral beam deflector, the tilted beam deflector configured to direct the beam at the first angle and the second angle.

20. 20. The apparatus of claim 18 or 19, wherein the controller is configured to correct aberrations associated with directing the beam at the first angle and / or the second angle by adjusting the directing of the beam before acquisition of each frame based on a prediction of aberrations induced at the first angle and / or the second angle.

Images