Blanker enhanced moire imaging

Abstract

In some embodiments, a scientific instrument includes an electron beam column configured to scan an electron beam across a sample. The electron beam column includes a beam blanking device configured to gate the electron beam in response to a drive signal. The scientific instrument also includes an electron detector configured to measure a flux of transmitted or scattered electrons that have interacted with the sample, and an electronic controller configured to acquire images of the sample for the plurality of electron beam scanning locations using values of the flux measured with the electron detector. The electronic controller is further configured to cause the drive signal to have a gate frequency that causes the image to have a moire pattern therein.

Description

Technical Field

[0001] Various examples relate generally, but not exclusively, to electron microscopy components, instruments, systems, and methods. Summary of the invention

[0002] Moiré is a common phenomenon where two closely related patterns give rise to a more slowly varying pattern. In scanning transmission electron microscopy (STEM), moiré patterns can be generated when the sampling interval of the microscope is relatively close to the periodicity of the sample lattice or an integer multiple thereof. The spacing and orientation of STEM moiré fringes are sensitive to the local lattice periodicity and can therefore be used, for example, to reveal strain fields in the sample.

[0003] The microelectronics industry needs effective tools to quantitatively measure strain in semiconductor devices. For example, strain in devices based on multi-compound semiconductors can be both detrimental and beneficial, as strain can affect the bonding of substituent atoms or provide a way to design electronic devices through strain engineering of band gap and / or carrier mobility. In general, for quality control purposes, it is very important to know the actual strain state of the sample. Therefore, semiconductor companies are very interested in strain mapping methods and equipment that provide suitable spatial resolution and accuracy as well as sufficiently fast data acquisition and processing.

[0004] Disclosed herein, among other things, are various examples, aspects, features, and embodiments of a scientific instrument having an electron beam column equipped with a fast pre-sampling beam blanker configured to gate the electron beam during a STEM imaging scan. In some examples, the beam blanker is advantageously used to enable acquisition of high contrast moiré patterns at high scan speeds (e.g., with a dwell time of less than about 5 μs / pixel). In some other examples, the beam blanker is advantageously used to perform focusing of an electron probe based on moiré imaging. The latter feature can be used, for example, to enable fast and accurate optical alignment of electron beam optics for dose-sensitive samples, for which alternative focusing methods can subject dose-sensitive samples to degraded high radiation doses.

[0005] One example provides a scientific instrument comprising: an electron beam column configured to scan an electron beam across a sample, the electron beam column including a beam blanker configured to gate the electron beam in response to a drive signal; an electron detector configured to measure a flux of transmitted or scattered electrons that have interacted with the sample; and an electronic controller configured to acquire an image of the sample using values ​​of the flux measured using the electron detector for a plurality of electron beam scanning positions, and further configured to cause the drive signal to have a gating frequency that causes the image to have a moiré pattern therein.

[0006] Another example provides a moiré imaging method, which includes: scanning an electron beam across a sample using an electron beam column including a beam blanker, the beam blanker being configured to gate the electron beam in response to a drive signal; measuring a flux of transmitted or scattered electrons that have interacted with the sample using an electron detector; acquiring an image of the sample using values ​​of the measured flux for a plurality of electron beam scanning positions using an electronic controller; and causing the drive signal to have a gating frequency that causes the image to have a moiré pattern therein using the electronic controller. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The foregoing aspects of the present disclosure and many of the attendant advantages will become more readily appreciated when the following detailed description is taken in conjunction with the accompanying drawings.

[0008] Figure 1 is a block diagram illustrating an example scientific instrument according to some embodiments.

[0009] Figure 2 is a diagram showing the Figure 1 Diagram of a scientific instrument used to capture moiré patterns.

[0010] FIG. 3A to FIG. 3B The diagram shows the Figure 1 Scientific instruments in Figure 2 Certain operating characteristics in the configuration shown.

[0011] Figure 4 is a diagram showing the Figure 1 Block diagram of a circuit used in scientific instruments.

[0012] Figure 5 is a diagram showing a method based on the Figure 1 Flowchart of a method for strain mapping using moiré imaging implemented in a scientific instrument.

[0013] Figure 6 is a diagram showing a method for imaging based on moiré patterns according to some embodiments. Figure 1 Flowchart of a method for low-dose tuning of electron beam optics in a scientific instrument.

[0014] Figure 7 is a block diagram of an example computing device configured to perform at least some scientific instrument support operations, according to various embodiments. DETAILED DESCRIPTION

[0015] Figure 11 is a block diagram illustrating a scientific instrument 100 according to some embodiments. The scientific instrument 100 includes a scanning transmission electron microscope (STEM) column 102 coupled to a vacuum chamber 108. The vacuum chamber 108 houses a movable sample holder 110 therein and can be vacuumed using one or more vacuum pumps (in Figure 1 In an exemplary embodiment, the sample holder 110 is capable of independent movement parallel to the XY coordinate plane and parallel to the Z coordinate axis, wherein the corresponding coordinate system is represented by Figure 1 The sample S to be interrogated using the scientific instrument 100 is mounted in the sample holder 110, as shown in FIG. Figure 1 shown.

[0016] In the example shown, the STEM column 102 includes an electron source 112 and two or more electron beam lenses, which are shown for illustration purposes. Figure 1 Only two of them are schematically shown, namely, the objective lens 106 and the condenser lens 116. In some examples, a different number (other than two) of such lenses can be used in the STEM column 102. In some embodiments, the objective lens 106 can be an ultra-high resolution (UHR) lens. In at least some embodiments, the STEM column 102 also includes a beam blanker, which is described below with reference to the beam blanker. Figure 4 Describe in more detail.

[0017] In operation, the electron source 112 generates an electron beam 114 that propagates generally along a longitudinal axis 115 of the STEM column 102. The electron beam lenses 106 and 116 operate to generate electric and magnetic fields that affect the trajectories of electrons in the electron beam 114. Control signals 152, 156 generated by the electronic controller 150 are used to change the strength and / or spatial configuration of the fields and impart desired characteristics to the electron beam 114. In general, the electron beam lenses 106 and 116, the control signals 152 and 156, and other related components of the STEM column 102 and the electronic controller 150 can be used to perform various operations and support various functions, such as beam focusing, beam gating, aberration mitigation, aperture cropping, filtering, etc. The STEM column 102 also includes a deflection unit 118 that can direct the electron beam 114 in response to the control signal 154 applied thereto by the electronic controller 150. Such beam steering may be used to move a focused portion of the electron beam 114 along a desired path across the sample S, for example, to perform a raster or vector scan thereof.

[0018] The scientific instrument 100 also includes detectors 160, 170, 180 located in the vacuum chamber 108 relatively close to the sample S. In operation, the detectors 160, 170, and 180 generate measurement streams 162, 172, and 182 received by the electronic controller 150 as corresponding output signals. The specific type of detectors 160, 170, 180 depends on the embodiment of the scientific instrument 100, and can generally be selected from a variety of detector types suitable for detecting different types of emissions and / or radiation from the sample S generated in response to the electron beam 114. Example types of emissions / radiation that can be generated in this manner include, but are not limited to, X-rays, infrared light, visible light, ultraviolet light, backscattered electrons, secondary electrons, Auger electrons, elastically scattered electrons, non-scattered (e.g., zero energy loss) electrons, and inelastically scattered electrons. In various embodiments, different (other than three) numbers of such detectors can be used in the scientific instrument 100. In some embodiments, detectors 160, 170, 180 are selected from the group consisting of: a high angle annular dark field (HAADF) detector, a medium angle annular dark field detector, an annular bright field detector, a segmented annular detector, a differential phase contrast detector, an electron energy loss spectroscopy (EELS) detector, an energy dispersive x-ray spectroscopy (EDS) detector, and a two-dimensional (e.g., pixelated or segmented) electron detector. Other detectors capable of detecting various of the above types of emissions / radiations may also be used in various additional embodiments.

[0019] Figure 2 2 is a block diagram showing a configuration 200 of a scientific instrument 100 for collecting a moiré pattern according to one example. Figure 2 The HAADF detector 180 is positioned as shown to capture the moiré pattern. In other examples, other suitable detectors that can be used with corresponding embodiments of the scientific instrument 100 can also be used (see also Figure 1 ).

[0020] In operation, as a focused portion F of the electron beam 114 is scanned across the sample S in a raster pattern 206 by the deflection unit 118, the HAADF detector 180 captures a flux 214 of scattered electrons at each pixel of the raster pattern 206 and transmits flux measurements to the electronic controller 150 via its output signal 182. The electronic controller 150 then operates to generate a pixelated image representing the moiré pattern by appropriately classifying and processing the electron flux measurement stream received via the signal 182. As used herein, the term "focused portion of the electron beam" refers to a portion of the electron beam 114 having approximately (e.g., within ±10%) a minimum lateral cross-sectional area. A person of ordinary skill in the relevant art will readily appreciate that for many modes of the scientific instrument 100, the focused portion F of the electron beam 114 needs to be relatively accurately placed on the surface of the sample S or appropriately positioned in the sample S.

[0021] The grating pattern 206 has a plurality of parallel scan lines 204 with a spacing d between them. s In this context, the spacing d between the scan lines 204 is s is called the "scanning-grating spacing". s Relatively close to the lattice spacing (d l ) or an integer multiple thereof, moiré fringes typically appear in STEM images captured using the HAADF detector 180. In some configurations of the scientific instrument 100, the scanning-grating spacing d s Smaller than the lattice spacing d l In some other configurations of the scientific instrument 100, the scanning-grating spacing d s Greater than the lattice spacing d l .

[0022] When the scan line 204 is exactly on top of the lattice atoms of the sample S, relatively strong scattering of the electron beam 114 occurs, which produces bright bands in the captured STEM image. When the scan line 204 is between the lattice planes, the scattering of the electron beam 114 is significantly reduced, which produces dark bands in the captured STEM image. Such bright and dark bands are (quasi-)periodically repeated to form moiré fringes. The contrast pattern observed with a bright field detector is essentially the opposite of that observed with a dark field detector. The corresponding moiré fringe spacing (d mf ) can be expressed as follows:

[0023]

[0024] Equation (1) shows that when d l <d s When collecting moiré patterns, the fringe spacing d mf With the lattice spacing d l When dl >d s When collecting moiré patterns, the fringe spacing d mf As mentioned above, the lattice spacing d l It can be used to reveal the strain field present in the sample S. Several examples of moiré patterns and their use for strain mapping are described in, for example, Uhyun Kim, Sungho Lee, Yoshifumi Oshima et al., “Scanning moiré fringe imaging for quantitative strain mapping in semiconductor devices”, Appl. Phys. Lett. 102, 161604 (2013), the entire contents of which are incorporated herein by reference.

[0025] FIG. 3A to FIG. 3B 200 according to some examples. First, we note that the contrast of the moiré pattern in the STEM image acquired using the configuration 200 depends on the dwell time (t d ) period, the electron beam 114 is sufficiently stationary. Thus, when the electron beam 114 is Figure 3A When the electron beam 114 moves along the scanning path in a step-like manner as indicated by the step function 310 plotted in FIG. d The troll remains in a fixed (stationary) position for a period of time and then quickly jumps a distance d s Arrives at the next fixed position, where the electron beam 114 stays for another time t d As used herein, the term "rapid jump" means that the transition between two fixed positions is substantially in a period of time shorter than the dwell time t d Such rapid jumps are repeated (usually in two dimensions, possibly with different corresponding distances d s ), until all scanned pixels of the raster pattern 206 have been interrogated. In the example implementation of the scanning electronics used in the scientific instrument 100, the time dependency of the position of the electron beam 114 represented by the idealized step function is only theoretically available, but not in practice, for example, because the frequency response of the scanning electronics to the step-like voltage transitions is slower than ideal. Therefore, the example embodiments disclosed herein are intended to provide an alternative solution that enables efficient moiré pattern acquisition, as explained in more detail below.

[0026] For a STEM image size of 512 × 512 pixels, the dwell time t d =40 μs / pixel results in an image acquisition time of about 11 seconds. For a STEM image size of 1024×1024 pixels, the same dwell time results in an image acquisition time of about 42 seconds. Disadvantageously, such long acquisition times may be unacceptable for at least some moiré imaging applications. For example, semiconductor companies appear to be targeting moiré pattern acquisition times of less than about one second. For a moiré pattern image size of 1024×1024 pixels, a target acquisition time of 1 second means that the dwell time t d It is about 1 μs / pixel.

[0027] For a dwell time of about 1 μs / pixel, t d , the finite frequency response of the deflection unit 118 and associated electronics typically results in distortion of the step function 310 . Figure 3A An example of such distortion is shown in FIG. 3 as waveform 320. Note that instead of the rapid jumps of step function 310, waveform 320 has "circular" steps, which results in pixel-to-pixel transitions during which the electron beam 114 gradually drifts between two intended fixed positions, effectively interrogating a series of consecutive positions within the lattice of sample S. A typical adverse effect of such drift is that the corresponding acquired moiré pattern image becomes blurred, e.g., has relatively low moiré fringe contrast, or fails to exhibit any usable moiré fringes at all.

[0028] Figure 3B The signal origin patterns 312, 322 corresponding to the step function 310 and the waveform 320, respectively, are graphically shown. The signal origin pattern 312 is characterized by a high degree of localization, due to which the corresponding electron flux 214 originates primarily from a plurality of equidistant discrete locations (points) within the sample S. In contrast, the signal origin pattern 322 has a relatively low degree of localization, due to which the corresponding detected electron flux 214 originates from a series of continuous locations within the sample S, wherein only a small fraction of the flux 214 originates from discrete locations belonging to the signal origin pattern 312. The latter property of the signal origin pattern 322 disadvantageously causes the corresponding moiré fringe contrast to be suboptimal at high scanning speeds.

[0029] According to one embodiment, the STEM column 102 of the scientific instrument 100 is equipped with a beam blanker that can be controllably switched between an "on" and "off" state in response to a gating signal. The gating signal acts as a control mechanism that determines when the electron beam 114 can pass through the beam blanker toward the sample S and when the electron beam 114 is blocked or diverted from propagating downstream and reaching the sample S. In one example, the gating signal is a binary signal that alternates between a first (e.g., high) level and a second (e.g., low) level. When the gating signal is at the first level, the beam blanker operates to cause the electron beam 114 to pass through the beam blanker toward the sample S. When the gating signal is at the second level, the beam blanker operates to prevent (block) the electron beam 114 from propagating downstream along the longitudinal axis 115 toward the sample S. In one example, the transition between the first level and the second level in the strobe signal is timed so that the beam blanker changes the signal origination pattern from the signal origination pattern 322 (generated without the beam blanker or with the beam blanker disabled) to Figure 3B Advantageously, signal origin pattern 324 mimics (eg, closely approximates) signal origin pattern 312 corresponding to step function 310, and thus causes a corresponding acquired moiré pattern image to have a relatively high fringe contrast.

[0030] Figure 3A An example gating signal 330 that can be used to drive the beam blanker is graphically shown. The gating signal 330 includes a sequence of gating pulses 332 synchronized with the acquisition scan, so that the electron beam 114 is only briefly de-blanked at each scanned pixel, for example, with a de-blanking duty cycle of about 10%. The gating signal 330 causes the STEM column 102 to produce an illumination pattern on the sample S that essentially consists of a sequence of discrete illumination points, even if the deflection unit 118 and the scanning electronics connected thereto produce a gradual beam scan illustrated by the waveform 320. Therefore, the signal origin pattern 322 is replaced by the signal origin pattern 324 (see Figure 3B ), where in at least some cases the resulting moiré fringe contrast advantageously approaches the optimal contrast typically associated with step function 310.

[0031] In an embodiment of the scientific instrument 100, wherein the residence time t d The reduction in the deflection unit 118 and the scanning electronics connected thereto produce a "blurred" response (compared to the Figure 3A 320 ), the strobe signal applied to the beam blanker may be phase shifted so that the electron beam 114 is de-blanked when its position is most stationary within the "blurred" response.

[0032] exist Figure 3AIn the example shown, the frequency of the gate signal 330 is phase locked to the sampling frequency of the STEM acquisition scan, wherein the selected fixed phase shift between the gate signal and the scan signal causes the gate pulse 332 to be aligned with the step transitions of the step function 310. In other examples, other values ​​of the fixed phase shift between the gate signal and the scan signal may also be selected. Generally, better results are obtained when the value of the fixed phase shift between the gate signal and the scan signal is selected so that the gate pulse 332 is aligned with the slower portion of the waveform 320 or its functional equivalent, where the position of the electron beam 114 is more stationary.

[0033] In some examples, the frequency of the gating signal applied to the beam blanker is decoupled from the sampling frequency of the STEM acquisition scan. This configuration can be used, for example, to sweep the frequency of the gating signal around an initial guess until sufficient moiré contrast appears in the STEM image in the fast scan direction. Figure 2 , the fast scan direction is represented by scan line 204, and the slow scan direction is orthogonal to scan line 204. To ensure substantially uniform illumination intensity for each scanned pixel, the frequency of the gating signal generally needs to be kept equal to or higher than the sampling frequency, and the detector output signal needs to be bandpass filtered to at least be lower than the gating frequency. Other suitable methods for uniform illumination of different scanned pixels may also be used in such examples.

[0034] In an example workflow based on this method, an experiment may begin by scanning the gating frequency until approximately maximum moiré contrast is achieved for a region of interest (ROI) or for a reference region of the sample S. In some examples, the reference region is a region of the sample S where the strain is expected to be zero. Next, a full scan of the ROI can be performed at the determined gating frequency to ensure high moiré contrast in the fast scan direction. Optionally, another frequency scan and another full scan may be performed, but with the fast scan direction and the slow scan direction interchanged to achieve independently optimized moiré contrast for the orthogonal scan directions. In some examples, a full scan may be performed using two or more slightly different gating frequencies corresponding to approximately optimal contrast. This feature can be used, for example, to resolve sign ambiguity (if any) in the strain map and to improve the accuracy and / or spatial resolution of the strain map.

[0035] Figure 4 1 is a block diagram illustrating a circuit 400 for use in a scientific instrument 100 according to some embodiments. The circuit 400 includes an electronic controller 150, circuit blocks 410, 420, 440, 450, 460, and 470, a pre-sampling beam blanker 430 and other related components of a STEM column 102, and a detector 180. The STEM column 102 includes the beam blanker 430. In the example shown, the beam blanker 430 is positioned at the electron source 112 (see Figure 1) and the electron beam lens 116. In other examples, the beam blanker 430 can be placed in another suitable pre-sampling position in the STEM column 102.

[0036] In the example shown, the pre-sampling beam blanker 430 includes an electrostatic beam deflector including a first electrode 424 and a second electrode 426. When a sufficiently strong electric field exists between the electrodes 424 and 426 (due to their proper electrical biasing), the electric field interacts with the electron beam 114, thereby deflecting the beam away from the longitudinal axis 115. The beam dump ( Figure 4 The deflected electron beam 114 is then intercepted (blocked) by the beam blanker 430 and the corresponding current is directed to a charge well, such as a ground terminal of the circuit 400. When no electric field is present between the electrodes 424 and 426, the electron beam 114 passes through the beam blanker 430 without being deflected and continues to propagate along the longitudinal axis 115 toward the sample S. In other examples, other suitable physical mechanisms for gating the electron beam 114 in the beam blanker 430 may also be implemented.

[0037] The beam blanker 430 operates to block and pass the electron beam 114 at different times in response to a drive signal 422 received from the driver circuit 420 . The driver circuit 420 operates to generate the drive signal 422 in response to a gate signal 412 received from the configurable waveform generator 410 . Figure 3A The gating signal 330 shown in FIG. 1 is an example of a gating signal 412. The electronic controller 150 is operative to set various parameters of the gating signal 412 via a control signal 408 applied to the configurable waveform generator 410. The joint control of the control signals 408 and 154 applied by the electronic controller 150 enables any desired synchronization of the gating signal 412 with the scanning signal 452 applied to the scanning coil 454 of the deflection unit 118 via the scanning pattern generator 440 and the scanning coil driver 450. As already mentioned above, in some configurations, the phase and frequency of the gating signal 412 may be decoupled from the phase and frequency of the scanning signal 452.

[0038] In some examples, the scan signal 442 generated by the scan pattern generator 440 in response to the control signal 154 includes Figure 3A The step function 310 shown in FIG. 3 is shown in FIG. 310. At a relatively low scanning speed (relatively long dwell time t d ), the corresponding scanning signal 452 generated by the scanning coil driver 450 in response to the scanning signal 442 accurately follows the step function 310. However, at relatively high scanning speeds (relatively short dwell times t d), the finite frequency response of the scan coil driver 450 may cause distortion of the step function 310, causing the corresponding scan signal 452 to become similar in nature to Figure 3A Waveform 320 shown in .

[0039] Blanking and unblanking of the electron beam 114 applied by the beam blanker 430 accordingly modulates the electron flux 214. In some examples, the signal origin pattern of the electron flux 214 resulting from such modulation may be similar to Figure 3B 324. In response to the modulated electron flux 214, the detector 180 generates a corresponding output signal 458, which is then amplified in the amplifier circuit 460. The resulting amplified signal 462 is converted to digital form in the analog-to-digital converter (ADC) 470, and the resulting digital stream 182 is directed to the electronic controller 150 for processing. Based on the received digital stream 182, the electronic controller 150 composes a STEM image, which in at least some cases may contain a moiré pattern.

[0040] Figure 5 is a flow chart illustrating a method 500 for strain mapping based on moiré imaging implemented in the scientific instrument 100 according to some embodiments. Figures 1 to 5 500. In some examples, a corresponding embodiment of the scientific instrument 100 includes a beam blanker 430 and a circuit 400 ( Figure 4 ). Example use cases for method 500 include, but are not limited to, strain mapping in silicon-based semiconductor devices, interface strain mapping in polycrystalline materials (e.g., steel) or multilayer structures, and strain mapping around precipitates or crystal defects (such as stacking faults, dislocations, etc.).

[0041] The method 500 includes appropriately orienting the sample S relative to the longitudinal axis 115 of the STEM column 102 and relative to a selected scanning direction of the grating pattern 206 (in block 502) (see also Figure 1 , Figure 2 In some examples, the orienting operation of block 502 may alternatively include orienting the scanning direction to an orientation of the sample S (e.g., about a longitudinal axis of the column). The operation of block 502 also includes the electronic controller 150 via the control signal 158 ( Figure 1 ) operates the movable sample holder 110 so that the selected area axis of the sample S becomes properly aligned for moiré imaging. In response to the control signal 158, the movable sample holder 110 can perform a movement of the sample S relative to the XYZ coordinate system (see also Figure 1 ) by appropriate translation and / or rotation.

[0042] As used herein, the term "zone axis" refers to a selected orientation among the high symmetry orientations in a crystal referenced in three dimensions to the positive lattice (as opposed to the reciprocal lattice) of the crystal. Thus, the zone axes are often indexed with positive lattice indices rather than Miller indices. Typically, the zone axes are aligned with the corresponding directions of "tunnels" that exist between atomic planes in the crystal.

[0043] The method 500 also includes the electronic controller 150 appropriately tuning the electron beam optics of the STEM column 102 for STEM imaging (in block 504). In some examples, the tuning operation of block 504 includes Ronchi pattern alignment, which involves tuning the electron beam optics based on the observed Ronchi pattern. Using Ronchi pattern alignment, both low-order aberrations and high-order aberrations can be corrected. In some implementations, after Ronchi pattern alignment, a condenser lens aperture is inserted, and then at least some residual aberrations are finely corrected to obtain a high-quality STEM image.

[0044] The method 500 also includes selecting (i) an ROI in the sample S and (ii) a set of parameter values ​​for the moiré imaging scan (in block 506). In some examples, the electronic controller 150 performs these selections in block 506 based on input from an operator of the scientific instrument 100. In some other examples, the electronic controller 150 performs these selections in block 506 in an automated manner (e.g., by running a suitable programming script). Example parameters selected in block 506 include, but are not limited to, magnification (scan amplitude) and the number of scanned pixels (e.g., 1024×1024).

[0045] The method 500 also includes the electronic controller 150 selecting a parameter value for the strobe signal 412 (in block 508). In some examples, the electronic controller 150 performs the parameter selection in block 508 based on input from an operator of the scientific instrument 100. In some other examples, the electronic controller 150 performs the parameter selection in block 506 in an automated manner (e.g., by running an appropriate programming script). Example parameters selected in block 508 include, but are not limited to, a frequency and a duty cycle of the strobe signal 412.

[0046] As explained in more detail below, the operation of block 508 is part of a processing loop including blocks 508, 510, and 512. In some examples, a first instance of block 508 includes an initial selection of a parameter value for the gate signal 412. Each of the subsequent instances of block 508 includes one or more corresponding adjustments to the previously selected parameter value, for example based on the results of blocks 510, 512. For example, in some specific implementations of the processing loop 508 / 510 / 512, block 508 is configured to implement a sweep of the gate frequency while the sampling frequency of the sweep signal 452 remains fixed. In some examples, the frequency increment of the frequency sweep has a fixed value. In some other examples, the frequency increment depends on the difference between the observed moire fringe contrast and the threshold contrast value used in the decision block 512. More specifically, a more aggressive change of the gate frequency can be performed for a relatively large contrast difference compared to a relatively small contrast difference.

[0047] The method 500 also includes the electronic controller 150 acquiring a STEM image (in block 510). Example operations of block 510 include the electronic controller 150 operating various components of the STEM column 102 and various circuit blocks of the circuit 400, for example, as described above with reference to Figure 4 As described, and receiving the corresponding digital stream 182 from the detector 180. For example, the STEM column 102 is operated using the selection made in box 506. The beam blanker 430 is driven using the gating signal 412 configured according to the selection made in box 508. In various examples, the detector used for STEM image acquisition in box 510 is selected from the group consisting of: a HAADF detector, a mid-angle annular dark field detector, an annular bright field detector, a segmented annular detector, a differential phase contrast detector, an EELS detector, an EDS detector, and a two-dimensional (e.g., pixelated or segmented) electronic detector. The operation of box 510 also includes the electronic controller 150 synthesizing a STEM image from the data transmitted by the received digital stream 182 and applying a suitable image processing algorithm to the synthesized STEM image to determine the contrast of the moiré fringe pattern contained therein.

[0048] Operations at decision block 512 of method 500 include the electronic controller 150 determining whether the contrast of the moiré pattern is acceptable. In some examples, this determination is made by comparing the moiré pattern contrast determined in block 510 to the threshold contrast value described above. When the moiré contrast has a higher value than the threshold contrast value ("yes" at decision block 512), processing of method 500 is directed to block 514. When the moiré contrast has a lower value than the threshold contrast value ("no" at decision block 512), processing of method 500 loops back to block 508.

[0049] The operation of block 514 includes the electronic controller 150 generating a strain map of the ROI of the sample S based on the moiré fringe pattern contained in the STEM image acquired in the last instance of block 510. In some examples, the electronic controller 150 first operates to determine the lattice spacing d in the ROI of the sample S by applying equation (1) to various portions of the STEM image. l Then, the electronic controller 150 is operated to use the lattice spacing d l The known relationship between the spatial variation of and the strain field is used to generate a strain map of the ROI of the sample S. After the strain map is generated, the processing of the method 500 is terminated.

[0050] In some embodiments, prior to the above-described operations at block 514, the above-described processing corresponding to blocks 502-512 of method 500 is repeated for one or more rotational scan patterns to acquire at least a second STEM image containing at least a second moiré fringe pattern corresponding to the same ROI of sample S. The operations at block 514 then include the electronic controller 150 jointly analyzing at least two moiré fringe patterns to generate a strain map of the ROI. Such a joint analysis tends to advantageously produce a strain map that is more accurate and / or more detailed than any strain map derived from a single moiré fringe pattern used in the joint analysis.

[0051] Figure 6 is a flow chart illustrating a method 600 for low-dose tuning of electron beam optics in a scientific instrument 100 based on moiré imaging, according to some embodiments. Example use cases for method 600 include, but are not limited to, STEM imaging of dose-sensitive materials such as metal organic frameworks (MOFs), organic polymers, battery materials, etc. For example, some conventional electron beam optics focusing methods for high-resolution STEM use 5× oversampling, which can disadvantageously subject dose-sensitive materials of a sample S to degraded high radiation doses. In contrast, example embodiments of method 600 advantageously enable comparable optical alignment quality to be achieved with lower oversampling or no oversampling at all (e.g., with approximately 1× sampling), thereby reducing the exposure dose by a factor of ten or more.

[0052] The method 600 includes appropriately orienting the sample S relative to the longitudinal axis 115 of the STEM column 102 and relative to the selected scanning direction of the grating pattern 206 (in block 602). In some examples, the orienting operation of block 602 may alternatively include orienting the scanning direction to an orientation of the sample S (e.g., about the longitudinal axis of the column). In some examples, the operations of block 602 are similar to the above-described operations of block 502 of method 500.

[0053] The method 600 also includes the electronic controller 150 placing the scientific instrument 100 in a live STEM image acquisition mode at high magnification (in block 604). While in the live STEM image acquisition mode, the electronic controller 150 operates the STEM column 102, associated circuitry, and the detector 180 such that the electronic controller 150 continuously acquires a sequence of STEM images of the sample S via the detector output signal 182. In some examples, the sampling step (the distance between adjacent scanned pixels) of the scan for STEM imaging is selected to be greater than the lattice spacing d of the sample S. l big.

[0054] The method 600 also includes the electronic controller 150 selecting the frequency of the gating signal 412 and activating the beam blanker 430 (in block 606). In some examples, the electronic controller 150 is operative to select the gating frequency in block 606 based on input from an operator of the scientific instrument 100. In some other examples, the electronic controller 150 is operative to select the gating frequency in block 606 in an automated manner (e.g., by running a programming script) that is configured to calculate an estimated suitable value for the gating frequency based on the scan speed and sampling (nm / pixel) used in the live STEM acquisition mode configured in block 604.

[0055] In some examples, the sampling of the lattice is set based on the field of view (FOV) and the number of pixels scanned. For atomic imaging, three to ten times oversampling of the lattice can be used. In some conventional methods, when the number of pixels is reduced, if the probe size is smaller than the pixel pitch, the scientific instrument still effectively scans the sparse area between adjacent pixels when the probe is moved from one pixel to the next. Such scanning can adversely reduce contrast and / or cause smearing effects. The use of blanking substantially avoids these adverse effects and at the same time advantageously reduces the radiation dose to which the sample S is exposed, because in the case of an activated beam blanker 430, the area between pixels is no longer exposed to radiation. Under conventional methods, similar beneficial effects may not be achieved by faster scanning, for example, because the faster the scan, the smaller the ratio of the pixel signal to the signal originating from the area between the pixels. Therefore, simply reducing the sampling rate in a fixed FOV does not provide the same benefits as using blanking. On the contrary, when used to generate moiré conditions and for focus finding applications, the use of blanking can advantageously provide the above benefits.

[0056] The method 600 also includes the electronic controller 150 tuning the electron beam optics of the STEM column 102 (in block 608). The tuning operation of block 608 is configured to move the focused portion F of the electron beam 114 vertically along the longitudinal axis 115 in an attempt to find a position in which the focused portion F is substantially in a suitable position for imaging (e.g., on the surface of the sample S), such as Figure 2 Since the moiré pattern may become visible in the continuously acquired STEM images only when the focused portion F of the electron beam 114 is sufficiently close to this position, the electronic controller 150 is also operated in block 608 to continuously evaluate the STEM images in the live sequence of STEM images for the presence of the moiré pattern.

[0057] In some examples of block 608, the increment by which the vertical position of the focused portion F of the electron beam 114 is adjusted depends on whether the moiré pattern is visible in the live STEM image. More specifically, the electronic controller 150 can be configured to use a larger vertical increment when the moiré pattern is not yet visible in the live STEM image. Once the moiré pattern becomes visible in the live STEM image, the electronic controller 150 can reduce the vertical increment and use a smaller increment to fine-tune the vertical position of the focused portion F of the electron beam 114 in order to achieve better contrast of the observed moiré pattern.

[0058] Operation of decision block 610 of method 600 includes the electronic controller 150 determining whether the contrast of the moiré pattern observed in block 608 is acceptable. In some examples, the determination is made by comparing the contrast of the moiré pattern observed in block 608 to a threshold contrast value. When the moiré contrast has a lower value than the threshold contrast value (“no” at decision block 610), processing of method 600 is directed to block 612. As used herein, the term “having a lower value” should be interpreted to encompass situations where a moiré pattern has not yet appeared in the live STEM image during the tuning operation of block 608. When the moiré contrast has a higher value than the threshold contrast value (“yes” at decision block 610), processing of method 600 is directed to block 614. Note that high moiré contrast is an indication that the electron beam 114 is focused, for example, where its focused portion F is close to the image. Figure 2 Proper vertical position shown.

[0059] The operation of block 612 includes the electronic controller 150 changing the frequency of the gating signal 412. In some examples, the electronic controller 150 operates to change the gating frequency in block 612 based on input from an operator of the scientific instrument 100. In some other examples, the electronic controller 150 operates to increment the gating frequency in block 612 in an automated manner (e.g., by running a programming script) that is configured to calculate the incremental value of the gating frequency based on auxiliary information available to the electronic controller 150. Such auxiliary information may be extracted, for example, from available information about the sample S, the current configuration of the STEM scan, and / or a live STEM image. After changing the gating frequency in block 612, processing of the method 600 is directed back to block 608.

[0060] Operations at block 614 include the electronic controller 150 deactivating the beam blanker 430, canceling the live STEM acquisition mode, and optionally entering another operating mode (eg, an operating mode in which focusing of the electron beam 114 is performed by executing the method 600). Thereafter, the method 600 terminates.

[0061] Figure 7 is a block diagram of an example computing device 700 configured to perform at least some scientific instrument support operations according to various embodiments. For example, in some embodiments, the computing device 700 executes the electronic controller 150 (see also Figure 1 and Figures 4 to 6 ) In various embodiments, the support modules of the scientific instrument 100 may be implemented by a single computing device 700 or by multiple computing devices 700.

[0062] Figure 7 The computing device 700 is illustrated as having multiple components, but any one or more of these components may be omitted or repeated depending on suitability for the application and setting. In some embodiments, some or all of the components included in the computing device 700 may be attached to one or more motherboards and packaged in a housing. In some embodiments, some of these components may be manufactured onto a single system on a chip (SoC) (e.g., the SoC may include one or more processing devices 702 and one or more storage devices 704). Additionally, in various embodiments, the computing device 700 may not include Figure 7The computing device 700 may include one or more of the components shown, but may include interface circuitry for coupling to the one or more components using any suitable interface (e.g., a universal serial bus (USB) interface, a high-definition multimedia interface (HDMI) interface, a controller area network (CAN) interface, a serial peripheral interface (SPI) interface, an Ethernet interface, a wireless interface, or any other suitable interface). For example, the computing device 700 may not include the display device 710, but may include a display device interface circuit (e.g., a connector and a driving circuit) capable of coupling to the external display device 710.

[0063] The computing device 700 includes a processing device 702 (e.g., one or more processing devices). As used herein, the term "processing device" refers to any device or portion of a device that processes electronic data from registers and / or memory to convert the electronic data into other electronic data that can be stored in registers and / or memory. In various embodiments, the processing device 702 may include one or more digital signal processors (DSPs), application specific integrated circuits (ASICs), central processing units (CPUs), graphics processing units (GPUs), server processors, or any other suitable processing devices.

[0064] The computing device 700 also includes a storage device 704 (e.g., one or more storage devices). In various embodiments, the storage device 704 may include one or more memory devices, such as a random access memory (RAM) device (e.g., a static RAM (SRAM) device, a magnetic RAM (MRAM) device, a dynamic RAM (DRAM) device, a resistive RAM (RRAM) device, or a conductive bridge RAM (CBRAM) device), a hard drive-based memory device, a solid-state memory device, a network drive, a cloud drive, or any combination of memory devices. In some embodiments, the storage device 704 may include a memory that shares a die with the processing device 702. In such an embodiment, the memory may be used as a cache memory and include, for example, an embedded dynamic random access memory (eDRAM) or a spin-transfer torque magnetic random access memory (STT-MRAM). In some embodiments, the storage device 704 may include a non-transitory computer-readable medium having instructions thereon that, when executed by one or more processing devices (e.g., the processing device 702), cause the computing device 700 to perform any appropriate method or portions of such methods disclosed herein below.

[0065] The computing device 700 also includes an interface device 706 (e.g., one or more interface devices 706). In various embodiments, the interface device 706 may include one or more communication chips, connectors, and / or other hardware and software to manage communications between the computing device 700 and other computing devices. For example, the interface device 706 may include circuitry for managing wireless communications for transmitting data to and from the computing device 700. The term "wireless" and its derivatives may be used to describe circuits, devices, systems, methods, techniques, communication channels, etc. that can transmit data via modulated electromagnetic radiation through a non-solid medium. The term does not imply that the associated device does not contain any wires, although in some embodiments it may not contain any wires. The circuitry included in the interface device 706 for managing wireless communications may implement any of a plurality of wireless standards or protocols, including but not limited to Institute of Electrical and Electronics Engineers (IEEE) standards, including Wi-Fi (IEEE 802.11 series), IEEE 802.16 standards, Long Term Evolution (LTE) projects, and any amendments, updates, and / or revisions (e.g., Advanced LTE projects, Ultra Mobile Broadband (UMB) projects (also known as "3GPP2"), etc.). In some embodiments, the circuitry included in the interface device 706 for managing wireless communications may operate according to a Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Universal Mobile Telecommunications System (UMTS), High Speed ​​Packet Access (HSPA), Evolved HSPA (E-HSPA), or LTE network. In some embodiments, the circuitry included in the interface device 706 for managing wireless communications may operate according to Enhanced Data GSM Evolution (EDGE), GSM EDGE Radio Access Network (GERAN), Universal Terrestrial Radio Access Network (UTRAN), or Evolved UTRAN (E-UTRAN). In some embodiments, the circuitry included in the interface device 706 for managing wireless communications may operate in accordance with code division multiple access (CDMA), time division multiple access (TDMA), digital enhanced cordless telecommunications (DECT), evolution data optimized (EV-DO) and its derivatives, and any other wireless protocols designated as 3G, 4G, 5G and higher. In some embodiments, the interface device 706 may include one or more antennas (e.g., one or more antenna arrays) configured to receive and / or transmit wireless signals.

[0066] In some embodiments, interface device 706 may include a circuit for managing wired communication, such as electrical communication protocol, optical communication protocol or any other suitable communication protocol. For example, interface device 706 may include a circuit supporting communication according to Ethernet technology. In some embodiments, interface device 706 may support both wireless and wired communication, and / or may support multiple wired communication protocols and / or multiple wireless communication protocols. For example, a first group of circuits of interface device 706 may be dedicated to shorter range wireless communication such as Wi-Fi or Bluetooth, and a second group of circuits of interface device 706 may be dedicated to longer range wireless communication such as global positioning system (GPS), EDGE, GPRS, CDMA, WiMAX, LTE, EV-DO, etc. In some other embodiments, a first group of circuits of interface device 706 may be dedicated to wireless communication, and a second group of circuits of interface device 706 may be dedicated to wired communication.

[0067] Computing device 700 also includes battery / power circuitry 708. In various embodiments, battery / power circuitry 708 may include one or more energy storage devices (e.g., batteries or capacitors) and / or circuitry for coupling components of computing device 700 to an energy source separate from computing device 700 (e.g., coupling to AC line power).

[0068] Computing device 700 also includes display device 710 (e.g., one or more separate display devices). In various embodiments, display device 710 may include any visual indicator, such as a heads-up display, a computer monitor, a projector, a touch screen display, a liquid crystal display (LCD), a light emitting diode display, or a flat panel display.

[0069] The computing device 700 also includes additional input / output (I / O) devices 712. In various embodiments, the I / O devices 712 may include one or more data / signal transmission interfaces, audio I / O devices (e.g., microphones or microphone arrays, speakers, headphones, earbuds, alarms, etc.), audio codecs, video codecs, printers, sensors (e.g., thermocouples or other temperature sensors, humidity sensors, pressure sensors, vibration sensors, etc.), image capture devices (e.g., one or more cameras), human interface devices (e.g., keyboards, cursor control devices such as mice, styluses, trackballs, or trackpads), and the like.

[0070] Depending on the specific implementation of the scientific instrument 100 and / or the instrument portion 200, the various components of the interface device 706 and / or the I / O device 712 may be configured to output appropriate control signals (e.g., 152, 154, 156, 408) for the various components of the scientific instrument 100, receive appropriate control / telemetry signals from the various components of the scientific instrument 100, and receive measurement streams (e.g., 162, 172, 182) from the various detectors of the scientific instrument 100. In some examples, the interface device 706 and / or the I / O device 712 include one or more analog-to-digital converters (ADCs) for converting received analog signals into digital form suitable for operations performed by the processing device 702 and / or the storage device 704. In some additional examples, the interface device 706 and / or the I / O device 712 include one or more digital-to-analog converters (DACs) for converting digital signals provided by the processing device 702 and / or the storage device 704 into analog form suitable for being communicated to the corresponding components of the scientific instrument 100.

[0071] According to one example disclosed above, for example, in the Summary section and / or with reference to Figures 1 to 7 A scientific instrument is provided, comprising: an electron beam column configured to scan an electron beam across a sample, the electron beam column including a beam blanker configured to gate the electron beam in response to a binary drive signal having a first level and a second level, the first level and the second level being selected to cause the beam blanker to pass the electron beam toward the sample through the beam blanker when the binary drive signal is at the first level and to block the electron beam when the binary drive signal is at the second level; an electron detector configured to measure a flux of transmitted scattered electrons generated by the interaction of the electron beam with the sample; and an electronic controller configured to: acquire an image of the sample using the values ​​of the measured flux for a plurality of electron beam scanning positions; and cause the binary drive signal to have a gating frequency that causes the image to have a moiré pattern therein.

[0072] In some examples of the above-mentioned scientific instrument, the scientific instrument also includes: a driver circuit, which is configured to generate a binary drive signal in response to the selection signal and is also configured to apply the binary drive signal to the beam blanker; and a waveform generator, which is configured to generate the selection signal in response to a control signal received from the electronic controller, the control signal specifying a set of parameter values ​​for the selection signal including a selection frequency.

[0073] In some examples of any one of the scientific instruments described above, the set of parameter values ​​also includes a value for a duty cycle of the strobe signal.

[0074] In some examples of any of the above scientific instruments, the set of parameter values ​​includes an incremental value for changing a gating frequency.

[0075] In some examples of any of the scientific instruments described above, the set of parameter values ​​includes signal synchronization information of a gating signal relative to a scanning signal used to operate a scanning coil of the electron beam column during scanning.

[0076] In some examples of any of the above scientific instruments, the sweep signal includes a staircase waveform.

[0077] In some examples of any of the above scientific instruments, the scanning signal is configured to achieve a dwell time of less than 2 μs / pixel (or less than 1 μs / pixel, or less than 5 μs / pixel, or less than 10 μs / pixel).

[0078] In some examples of any of the above scientific instruments, the beam blanker includes an electrostatic beam deflector.

[0079] In some examples of any of the above-mentioned scientific instruments, the electron detector is selected from the group consisting of: a high-angle annular dark field detector; a medium-angle annular dark field detector; annular bright field detector; a segmented annular detector; a secondary electron detector; a backscattered electron detector; a differential phase contrast detector; an electron energy loss spectrum detector; an energy dispersive X-ray spectrum detector; and a two-dimensional pixelated or segmented electron detector.

[0080] In some examples of any of the above scientific instruments, the electronic controller is configured to generate a strain map of the sample based on the moiré pattern.

[0081] In some examples of any of the above scientific instruments, the electronic controller is configured to tune the electron beam column based on the moiré pattern so that a focused portion of the electron beam is located at the sample.

[0082] In some examples of any of the above scientific instruments, the electronic controller is configured to implement the sweep of the gating frequency while the sampling frequency of the sweep remains fixed.

[0083] According to another example disclosed above, for example, in the Summary section and / or with reference to Figures 1 to 7A method for moiré imaging is provided, comprising: scanning an electron beam across a sample using an electron beam column including a beam blanker, the beam blanker being configured to gate the electron beam in response to a binary drive signal having a first level and a second level, the first level and the second level being selected to cause the beam blanker to pass the electron beam toward the sample through the beam blanker when the binary drive signal is at the first level and to block the electron beam when the binary drive signal is at the second level; measuring a flux of transmitted scattered electrons generated by the interaction of the electron beam with the sample using an electron detector; acquiring an image of the sample using the values ​​of the measured flux for a plurality of electron beam scanning positions using an electronic controller; and causing the binary drive signal to have a gating frequency that causes the image to have a moiré pattern therein using the electronic controller.

[0084] In some examples of the above-mentioned moiré imaging method, the moiré imaging method also includes: generating a binary drive signal in response to a gating signal; and generating the gating signal in response to a control signal received from an electronic controller, the control signal specifying a set of parameter values ​​for the gating signal including a gating frequency.

[0085] In some examples of any of the above-mentioned moiré imaging methods, the set of parameter values ​​also includes one or more of the following items: a value of a duty cycle of a gating signal; an incremental value for changing the gating frequency; and signal synchronization information of the gating signal relative to a scanning signal, which is used to operate a scanning coil of an electron beam column during scanning.

[0086] In some examples of any of the above moiré imaging methods, the scanning signal includes a staircase waveform.

[0087] In some examples of any of the above moiré imaging methods, the scanning signal is configured to achieve a dwell time of less than 2 μs / pixel (or less than 1 μs / pixel, or less than 5 μs / pixel, or less than 10 μs / pixel).

[0088] In some examples of any of the above moiré imaging methods, the moiré imaging method further includes generating a strain map of the sample based on the moiré pattern.

[0089] In some examples of any of the above moiré imaging methods, the moiré imaging method further includes tuning the electron beam column based on the moiré pattern so that a focused portion of the electron beam is located at the sample.

[0090] In some examples of any of the above moiré imaging methods, the moiré imaging method further includes scanning the gating frequency while the sampling frequency of the scanning remains fixed.

[0091] In some examples of any of the above-described moiré imaging methods, the method further includes one or more of the following: (i) scanning the gating frequency until approximately maximum moiré fringe contrast is achieved for a region of interest (ROI) or for a reference region of the sample; (ii) performing a full scan of the ROI at the determined gating frequency to ensure high moiré fringe contrast in the complementary scanning direction; and (iii) performing another frequency scan and / or another full scan with the fast scanning direction and the slow scanning direction interchanged.

[0092] In some examples of any of the above moiré imaging methods, the reference region is a region of the sample where strain is expected to be substantially zero.

[0093] In some examples of any of the above moiré imaging methods, the method further includes repeating one or more full scans at different corresponding gating frequencies.

[0094] In some examples of any of the above moiré imaging methods, the method further includes resolving sign ambiguity in the strain map based on one or more repeated full scans.

[0095] It should be understood that the above description is intended to be illustrative rather than restrictive. By reading the above description, many specific implementations and applications other than the examples provided will be apparent. The scope should not be determined with reference to the above description, but should be determined with reference to the full scope of the appended claims and the equivalents to which these claims are entitled. It is anticipated and intended that future developments will occur in the technology discussed herein, and the disclosed systems and methods will be incorporated into these future examples. In short, it should be understood that the present application is capable of modification and variation.

[0096] All terms used in the claims are intended to be given their broadest reasonable interpretations and their ordinary meanings as understood by those skilled in the art described herein, unless an explicit indication to the contrary is made herein. Specifically, use of singular articles such as "a," "the," "said," etc. should be understood to recite one or more of the indicated elements unless a claim recites an explicit limitation to the contrary.

[0097] The abstract is provided to allow the reader to quickly determine the nature of the technical disclosure. It should be observed that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing detailed description, it can be seen that various features are grouped together in various examples for the purpose of streamlining the disclosure. The method of the present disclosure should not be interpreted as reflecting the following intention: the claimed subject matter includes more features than those explicitly stated in each claim. Rather, as reflected in the following claims, the subject matter of the present invention lies in less than all the features of a single disclosed example. Therefore, the following claims are hereby incorporated into the detailed description, with each claim acting on its own as a separately claimed subject matter.

[0098] Unless expressly stated otherwise, each numerical value and range should be interpreted as approximate as if the value or range was preceded by the word "about" or "approximately".

[0099] Although elements in the following method claims, if any, are recited in a specific order with corresponding labels, these elements are not necessarily intended to be limited to being implemented in that specific order unless the claim recitation otherwise implies a specific order for implementing some or all of these elements.

[0100] Unless otherwise specified herein, the use of ordinal adjectives "first," "second," "third," etc. to refer to one of multiple similar objects merely indicates that different instances of such similar objects are being referred to, and is not intended to imply that the similar objects so referred to must be in a corresponding order or sequence in time, space, rank, or in any other manner.

[0101] Unless otherwise indicated herein, in addition to its ordinary meaning, the conjunction "if" may also or alternatively be interpreted to mean "when" or "upon" or "in response to determining" or "in response to detecting", and its interpretation may depend on the corresponding specific context. For example, the phrase "if it is determined" or "if [the condition] is detected" may be interpreted to mean "upon determination" or "in response to determination" or "upon detection of [the condition or event]" or "in response to detecting [the condition or event]".

[0102] Also for the purposes of this specification, the terms "coupled", "connected" refer to any means known in the art or later developed, in which energy is allowed to be transferred between two or more elements, and the insertion of one or more additional elements is contemplated, although not required. Conversely, the terms "directly coupled", "directly connected", etc. imply the absence of such additional elements.

[0103] The functions of the various elements shown in the drawings, including any functional blocks marked as "processors" and / or "controllers", can be provided by using dedicated hardware and hardware capable of executing software in association with appropriate software. When provided by a processor, the function can be provided by a single dedicated processor, by a single shared processor, or by multiple separate processors (some of which can be shared). In addition, the explicit use of the term "processor" or "controller" should not be interpreted as exclusively referring to hardware capable of executing software, but may implicitly include but is not limited to digital signal processor (DSP) hardware, network processors, application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), read-only memories (ROMs), random access memories (RAMs) and non-volatile storage devices for storing software. Other conventional and / or customized hardware may also be included. Similarly, any switches shown in the figure are conceptual only. Their functions can be performed by the operation of program logic, by dedicated logic, by the interaction of program control and dedicated logic, or even manually, as more specifically understood from the context, and specific techniques can be selected by the implementer.

[0104] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) a hardware circuit implementation only (such as an implementation only in analog and / or digital circuits); (b) a combination of hardware circuitry and software, such as (if applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware, and (ii) a hardware processor and software (including a digital signal processor), any portion of software and memory, which work together to cause a device such as a mobile phone or server to perform various functions; and (c) a hardware circuit and / or processor, such as a microprocessor or a portion of a microprocessor, which requires software (e.g., firmware) to operate, but when software is not required for operation, the software may not be present. This definition of circuitry applies to all uses of the term in this application, including in any claims. As another example, as used in this application, the term circuitry also covers an implementation of a hardware circuit or processor (or multiple processors) or a portion of a hardware circuit or processor and its (or their) accompanying software and / or firmware. The term "circuitry" also covers, for example and if applicable to a particular claim element, a baseband integrated circuit or a processor integrated circuit for a mobile device or a similar integrated circuit in a server, cellular network device, or other computing or networking device.

[0105] Those skilled in the art will appreciate that any block diagrams herein represent conceptual diagrams of illustrative circuits embodying the principles of the present disclosure. Similarly, it will be appreciated that any flow charts, flow diagrams, state transition diagrams, pseudocodes, etc. represent various processes that can be substantially represented in a computer-readable medium and thus executed by a computer or processor, regardless of whether such a computer or processor is explicitly shown.

Claims

1. A scientific instrument, comprising: an electron beam column configured to scan an electron beam across a sample, the electron beam column comprising a beam blanker configured to gate the electron beam in response to a drive signal; an electron detector configured to measure a flux of transmitted or scattered electrons that have interacted with the sample; and An electronic controller, the electronic controller being configured to: acquiring an image of the sample using the values ​​of the flux measured using the electron detector for a plurality of electron beam scan positions; as well as The drive signal is caused to have a gating frequency that causes the image to have a moiré pattern therein.

2. The scientific instrument of claim 1, further comprising: a driver circuit configured to generate the drive signal in response to a strobe signal and further configured to apply the drive signal to the beam blanker; and A waveform generator is configured to generate the gate signal in response to a control signal received from the electronic controller, the control signal specifying a set of parameter values ​​for the gate signal including the gate frequency.

3. The scientific instrument of claim 2, wherein the set of parameter values ​​further comprises a value for a duty cycle of the strobe signal.

4. The scientific instrument of claim 2, wherein the set of parameter values ​​includes incremental values ​​for changing the gating frequency.

5. The scientific instrument of claim 2, wherein the set of parameter values ​​includes signal synchronization information of the gating signal relative to a scan signal for operating a scan coil of the electron beam column during the scan. The scientific instrument of claim 5 , wherein the scanning signal comprises a staircase waveform.

7. The scientific instrument of claim 5, wherein the scanning signal is configured to achieve a dwell time of less than 2 μs / pixel.

8. The scientific instrument of claim 1, wherein the beam blanker comprises an electrostatic beam deflector.

9. The scientific instrument of claim 1, wherein the electron detector is selected from the group consisting of: High-angle annular dark-field detector; Medium-angle annular dark-field detector; Annular bright field detector; Segmented ring detector; Differential phase contrast detector; secondary electron detector; Backscattered electron detector; Electron energy loss spectrum detector; Energy dispersive X-ray spectrum detector; and Two-dimensional pixelated or segmented electronic detector.

10. The scientific instrument of claim 1, wherein the electronic controller is configured to generate a strain map of the sample based on the moiré pattern.

11. The scientific instrument of claim 1 , wherein the electronic controller is configured to tune the electron beam column based on the moiré pattern such that a focused portion of the electron beam is located at the sample.

12. The scientific instrument of claim 1, wherein the electronic controller is configured to effectuate the sweep of the gating frequency while a sampling frequency of the sweep remains fixed.

13. A moiré imaging method, the moiré imaging method comprising: scanning an electron beam across a sample using an electron beam column including a beam blanker configured to gate the electron beam in response to a drive signal; measuring, with an electron detector, a flux of transmitted or scattered electrons that have interacted with the sample; acquiring an image of the sample using the measured flux values ​​for a plurality of electron beam scan positions with an electronic controller; as well as [TP386467CNSEC1] The electronic controller is used to cause the drive signal to have a gating frequency that causes the image to have a moiré pattern therein.

14. The moiré imaging method according to claim 13, further comprising: generating the drive signal in response to a strobe signal; as well as The gate signal is generated in response to a control signal received from the electronic controller, the control signal specifying a set of parameter values ​​for the gate signal including the gate frequency.

15. The moiré imaging method of claim 14, wherein the set of parameter values ​​further comprises one or more of the following: a value of the duty cycle of the strobe signal; an incremental value for changing the gating frequency; and The gating signal is relative to signal synchronization information of a scanning signal for operating a scanning coil of the electron beam column during the scanning.

16. The moiré imaging method according to claim 15, wherein the scanning signal comprises a step waveform.

17. The moiré imaging method of claim 15, wherein the scanning signal is configured to achieve a dwell time of less than 5 μs / pixel.

18. The moiré imaging method of claim 13, further comprising generating a strain map of the sample based on the moiré pattern.

19. The moiré imaging method of claim 13, further comprising tuning the electron beam column based on the moiré pattern such that a focused portion of the electron beam is located at the sample.

20. The moiré imaging method of claim 13, further comprising scanning the gating frequency while a sampling frequency of the scanning remains fixed.

Images