Adaptive dwell-time microscope

Abstract

To provide a method for using an adaptive pixel dwell time in a microscope.SOLUTION: A beam emitted from a beam source is scanned onto a sample according to a scan pattern such that the beam interacts with the sample at a first scan location according to the scan pattern. In some examples, the method includes monitoring, using at least a detector of the microscope, a first accumulated number of particles associated with a first scanned location of the sample, the first accumulated number of particles corresponding to an interaction of the beam with the sample at the first scanned location. In some examples, the method includes moving the beam to a second scan location of the sample according to the scan pattern if the signal criteria are satisfied after the first dwell time has elapsed and before the first dwell period has elapsed. The signal criterion is based on the first cumulative number of particles.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure is directed to charged particle microscope system components and methods. More particularly, the present disclosure describes adaptive dwell times in charged particle microscope systems. [Background technology]

[0002] Materials research, which involves characterizing probe properties (e.g., structure, topography, chemical composition) in the microscopic and nanoscopic regimes, can be performed through the implementation of scanning microscope systems such as scanning electron microscopes (SEMs). SEMs are configured to scan the surface of a sample with a primary beam (i.e., an electron beam) and acquire images of the sample based on various types of emissions, such as backscattered, transmitted, or secondary electron emissions. These emissions result from the interaction of the electron beam with particles (e.g., atoms) of the sample. Backscattered electrons (BSEs) arise from the primary electron beam, which, as the name suggests, are reflected (i.e., exit the sample) via elastic scattering from sample atoms. The number of backscattered electrons at each scan location on the sample depends on the number of atoms of the chemical element (e.g., mineral element) located at the corresponding scan location. Therefore, brightness changes (e.g., gray level changes) in the BSE image indicate compositional changes within the sample.

[0003] Along with backscattered electron emission, X-ray emission can also result from the interaction of the primary beam with the sample. In particular, characteristic X-rays are emitted when primary electrons eject electrons from the inner shells of sample atoms, creating electron holes. This electron hole is then filled by another electron from the outer shell of the atom through the emission of an X-ray photon. The energy of that X-ray photon corresponds to the energy difference between the outer and inner shells. Thus, the emitted X-rays have energies specific to the corresponding chemical element, and their detection reveals the chemical composition of the sample. To detect X-ray emission, SEMs may be equipped with an X-ray spectrometer configured to measure the number of detected X-rays with respect to their energy (energy dispersive spectrometer, EDS) or their wavelength (wavelength dispersive spectrometer, WDS). Material analysis (e.g., mineralogy classification) typically involves combining backscattered electron imaging processing with the application of X-ray spectroscopy. However, X-ray acquisition takes several milliseconds per scan location. Therefore, obtaining compositional information for an entire sample based on X-ray detection from tens, hundreds, or even thousands of scanning locations can be very time-consuming, requiring minutes to hours. Summary of the Invention

[0004] In some embodiments, a method for using an adaptive pixel dwell period in a microscope includes scanning a beam emitted from a beam source over a sample according to a scan pattern, such that the beam interacts with the sample at a first scan location according to the scan pattern. The method further includes monitoring, with at least a detector of the microscope, a first cumulative particle number associated with the first scan location of the sample, the first cumulative particle number being a cumulative number of particles detected at the first scan location of the scan pattern, where the first cumulative particle number may correspond to an interaction of the beam with the first scan location of the sample. In some embodiments, the method may include moving the beam to a second scan location of the scan pattern if a signal criterion is met after the first dwell time has elapsed and before the first dwell period has elapsed. The signal criterion may be based on the first cumulative particle number.

[0005] In some embodiments, the signal criteria may include a first threshold number, and the signal criteria may include a first cumulative number reaching or exceeding the first threshold number.

[0006] In some embodiments, the signal criteria may include a first threshold number. Further, the method may include determining whether a second cumulative particle number reaches or exceeds the first threshold number during a second dwell period, wherein the second dwell period may be shorter than the first dwell period.

[0007] In some embodiments, the method may include detecting X-ray photons, ultraviolet photons, visible photons, infrared photons, charged particles, or a combination thereof.

[0008] In some embodiments, the method may include determining whether a subset of particles in the first cumulative number of detected particles meets a second signal criterion during the first dwell time, and controlling the beam according to a scan pattern to continue scanning the first scan location of the sample based on the subset of particles meeting the second signal criterion during the first dwell time until i) a second dwell period and / or ii) the signal criterion is met. The method may further include moving the beam according to the scan pattern to a second scan location based on at least one of the second dwell period elapsed and the signal criterion being met given a total number of particles detected.

[0009] In some embodiments, the method may include determining that a second cumulative number of particles detected at the second scan location is less than a third threshold number within a third dwell period, and moving the beam to a third scan location in the scan pattern based on the third dwell period having elapsed.

[0010] In some embodiments, the detector may include a first detector and a second detector. Additionally, the method may further include monitoring, using at least the first detector, a second cumulative particle number, which is a cumulative number of particles detected at a second scan location, and determining that the second cumulative particle number does not meet the signal criterion. Additionally, the method may include determining that a third cumulative particle number detected at the second scan location by the second detector meets the signal criterion based on the second cumulative particle number not meeting the signal criterion. In some embodiments, the method may include moving the beam to a third scan location in the scan pattern based on the third cumulative particle number meeting the signal criterion.

[0011] In some embodiments, the method may include determining pixel intensity values ​​of the image based on the first dwell time.

[0012] In some embodiments, the scan pattern may include a variable staircase pattern, and the scan controller may have bandwidth to facilitate moving the beam according to the variable staircase pattern.

[0013] In some embodiments, a non-transitory computer-readable medium has stored thereon computer-readable instructions that, when executed by a processor, cause the processor to perform operations of controlling a beam source of a microscope to emit a beam toward a sample according to a scan pattern, such that the beam interacts with a first scan location of the sample. The operations may further include monitoring, using at least a detector of the microscope, a first cumulative particle number associated with the first scan location of the sample, the first cumulative particle number being a cumulative number of particles detected at the first scan location of the scan pattern, the first cumulative particle number corresponding to an interaction with the first scan location of the sample. In some embodiments, the operations may further include moving the beam to a second scan location of the scan pattern if a signal criterion is met after the first dwell time has elapsed and before the first dwell period has elapsed, the signal criterion may be based on the first cumulative particle number.

[0014] In some embodiments, the operations may include determining a cumulative number of first particles that meet a signal criterion by the first time and storing pixel intensity values ​​of the image as a function of the first dwell time.

[0015] In some embodiments, the operations may include monitoring, using at least a detector, a second accumulated particle number detected at the second scan location and determining that the second accumulated particle number does not meet a second signal criterion after a second dwell period has elapsed, where the second dwell period may include a total time for scanning the second scan location of the sample. In some embodiments, the operations may include storing pixel intensity values ​​of the image as a function of the second accumulated particle number.

[0016] In some embodiments, the operations may include monitoring, using at least a detector, a second cumulative number of particles detected at the second scan location and determining that the second cumulative number of particles detected at the second detector satisfies a second signal criterion. In some embodiments, the operations may include storing image pixel intensity values ​​as a function of the second cumulative number of particles, a maximum intensity, and / or a minimum intensity based on the second cumulative number of particles satisfying the second signal criterion.

[0017] In some embodiments, the detector is either a bright field detector or a dark field detector, and the second detector is the other one of the bright field detector or the dark field detector.

[0018] In some embodiments, a method for adaptive scanning in a microscope may include scanning a sample using at least a beam source of the microscope to project a beam toward the sample according to a first scan path, and determining, using at least a detector of the microscope, a first particle count associated with a first scan location on the sample and corresponding to a first pixel corresponding to the first scan location. In some embodiments, the method may include determining whether to exclude or include the first scan location in a second scan path based on a first comparison of the first particle count to a signal reference. In some embodiments, the method may include scanning the sample using the beam to project the beam toward the sample according to at least a second scan path, and generating sample acquisition data based on the total number of scan paths.

[0019] In some embodiments, the method may include determining a total number of particles detected at a first scan location for a number of previously completed scan passes, and determining a difference between the total number of particles and a signal reference. The method may include determining whether to exclude or include the first scan location from one or more additional scan passes based on the difference, which may continue until the difference is less than or equal to zero.

[0020] In some embodiments, each scan pass across the sample may expose each scan location determined to be included in the scan pass to the beam for a fixed dwell period, and exclude each scan location determined to be excluded from the scan pass from exposure to the beam.

[0021] In some embodiments, the method may include adjusting a dwell period for each scan location determined to be included in a subsequent scan pass based on a first number of particles detected at the scan location during a first scan pass.

[0022] In some embodiments, the method may include determining whether there is a change in the sample by identifying at least one of: i) expansion, ii) compression, iii) movement, or iv) cut in the image of the sample generated between the first and second scan passes, and reducing sample drift in the second image created after the second scan pass.

[0023] In some embodiments, the signal criteria is in the range of 1 to 20 charged particles. [Brief explanation of the drawings]

[0024] The foregoing features and many of the attendant advantages of the present disclosure will become more clearly understood by reference to the following detailed description when considered in conjunction with the accompanying drawings.

[0025] [Figure 1] FIG. 1 is an exemplary diagram of a portion of a microscope system currently known in the art.

[0026] [Figure 2] FIG. 2 is a schematic diagram of a charged particle microscope system, according to some embodiments.

[0027] [Figure 3] FIG. 3 is a system diagram illustrating an example of a microscope system, according to some embodiments.

[0028] [Figure 4] FIG. 4 is a diagram illustrating an example of an adaptive sawtooth staircase scan pattern, according to some embodiments.

[0029] [Figure 5] FIG. 5 is a flow diagram illustrating an example of a scanning process using adaptive dwell periods, according to some embodiments.

[0030] [Figure 6] FIG. 6 is a diagram illustrating an example of a scanning process using sub-dwell periods, according to some embodiments.

[0031] [Figure 7] FIG. 7 is a flow diagram illustrating an example of a scanning process utilizing sub-dwell periods, according to some embodiments.

[0032] [Figure 8] FIG. 8 is an example of a scanning process using adaptive bright-field and dark-field dwell periods according to some embodiments.

[0033] [Figure 9] FIG. 9 is a flow diagram illustrating an example of a scanning process for adaptive bright-field and dark-field dwell periods, according to some embodiments.

[0034] [Figure 10] FIG. 10 is an example of a scanning process using multiple scanning passes, according to some embodiments.

[0035] [Figure 11] FIG. 11 is a diagram illustrating an example of a location for rescanning a sample, according to certain embodiments of the present disclosure.

[0036] [Figure 12] FIG. 12 is a flow diagram illustrating an example of rescanning sample locations in accordance with certain aspects of the present disclosure.

[0037] [Figure 13] FIG. 13 is a flow diagram illustrating an exemplary method according to certain aspects of the present disclosure.

[0038] [Figure 14] FIG. 14 is a flow diagram illustrating an exemplary method according to certain aspects of the present disclosure.

[0039] [Figure 15] FIG. 15 is a block diagram of a controller of a microscope according to certain embodiments of the present disclosure.

[0040] In the drawings, like reference numbers refer to like parts throughout the various views unless otherwise specified. To reduce clutter in the drawings where appropriate, not every instance of an element is necessarily labeled. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles being described. DETAILED DESCRIPTION OF THE INVENTION

[0041] Embodiments of the invention are described below with respect to a microscope system. In one example, the microscope system is configured to acquire an image of a sample using a scanning pattern (e.g., a sawtooth staircase pattern). The scanning may generate an image. The scanning may be adaptive, so that the dwell time per image pixel may vary. In some cases, multiple detectors may be used to detect different modalities, such as bright-field and dark-field electrons. These and other features of the present disclosure are described below. It should be understood that the methods described herein are generally applicable to a wide variety of different methods and apparatus, including electron energy loss spectroscopy (EELS), energy-filtered transmission electron microscopy (EFTEM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) spectroscopy, scanning transmission electron microscopy, scanning probe systems, and parallel illumination systems, and are not limited to a particular apparatus type, beam type, object type, length scale, or scan trajectory.

[0042] In some embodiments, when "dwell time" or similar terms are used, they should be readily understood as the actual residence time at a location on the sample. Terms such as "first dwell time," "second dwell time," and the like are similarly not considered limiting and can be readily understood to represent a specific exposure time to one or more locations on the sample. Similarly, when "dwell period" or similar terms are used, they can be readily understood to represent a predetermined period of time, including two temporal endpoints. Terms such as "first dwell period," "second dwell period," and the like are similarly not considered limiting and can be readily understood to represent a specific time range for each dwell period. As a non-limiting example, a dwell period of 1 microsecond to 2 microseconds can be readily understood to include all times between 1 microsecond and 2 microseconds. A dwell time may represent one or more times shorter than, equal to, or longer than the dwell period. For example, a dwell period between 1 microsecond and 2 microseconds includes dwell times of 1.5 microseconds, 2 microseconds, 3 microseconds, or measurement times within or outside the predetermined period. Additionally or alternatively, the dwell time may be longer than, the same as, or shorter than the dwell period depending on the location of the sample, the number of particles detected, the desired intensity, or a combination thereof.

[0043] Some techniques for sample image acquisition (e.g., proteins, viruses, circuits, transistors, etc.) in SEM require the sample to be exposed to the electron beam for a period of time that can potentially damage the sample. Certain types of samples (e.g., biological specimens) are particularly sensitive to electron beam damage because the electrons can cause thermal expansion, structural damage, or similar damage. Conventional SEM (and other methods, such as conventional TED) may use a fixed dwell time for each sample location. For example, during a scan of a sample such as a carbon nanostructure, the electron beam may scan over a fixed number of locations on the sample. Each scan location may be fixed for a fixed time, regardless of whether it detects enough particles to form a reliable image. In at least some circumstances, such conventional microscopes may require a fixed dwell time before imaging. Additionally, some solutions may require the use of expensive blankers to unblank the beam once a certain amount of particles has reached the detector. These solutions can use the time the beam is unblanked to determine image pixel intensity values. For example, if a sample location corresponding to an image pixel is exposed for 1 ms and 5 electrons are collected over 0.5 ms, the unblank time (t unblank ) is 0.5 ms, and the blanking time is the remaining 0.5 ms. Image pixel intensity values ​​are calculated as 1 / t unblank This can result in unnecessary overexposure of the sample, leading to extended scan times. Furthermore, it may be necessary to fix the electronic gain and offset (e.g., pixel contrast and pixel brightness) before scanning the sample. This can result in certain locations of the sample being overexposed (appearing white in the image) and parts of the sample being underexposed (appearing black in the image). In addition to the limitations of pre-fixing the electronic gain and offset, electronic signal amplifiers can clip during imaging, leading to poor image quality.

[0044] The inventors have recognized that one novel solution to the above limitations is adaptively varying the dwell time for each image pixel corresponding to the location of the sample being analyzed. By presetting a desired signal-to-noise ratio, the control system can determine that enough particles (e.g., electrons) have been collected and instruct the scanning component to move to the next location on the sample before the pre-set maximum dwell period is reached, without the need for expensive beam blankers. This configuration uses the dwell time (e.g., the actual time it takes to advance to a scan location) itself as the image metric and may have a high dynamic range. For example, sample locations that produce a high signal (e.g., many particles detected) are illuminated for only a short time. This significantly reduces beam damage to the sample and shortens image acquisition times. Furthermore, in applications in bright-field scanning transmission electron microscopy (BF STEM) of biological tissues, sample locations that produce a low signal (e.g., few or no particles detected) may need to be illuminated (e.g., illuminated by the beam) for a longer period of time. However, in BF STEM, dark areas of the sample are typically stained, such as with heavy metal stains. They tend to be more susceptible to damage by the beam.

[0045] Furthermore, the inventors have recognized that this new solution allows the use of scan generators that are fast enough and have sufficient bandwidth to adjust using adaptive dwell times. For example, a sawtooth staircase pattern is particularly useful in SEM and TEM applications. By varying the length of each "step" in the x-direction (e.g., the fast scan direction), the dwell time per pixel can be adjusted in real time. Using this pattern, the aforementioned "blank" period is not required, allowing image pixels to be acquired quickly while simultaneously reducing the total sample acquisition time. Furthermore, if a sample location does not receive a certain threshold number of particles within the maximum dwell period (e.g., the longest dwell period), the sample location can be abandoned and the associated image pixel assigned a maximum value (e.g., using the dwell period itself as the image pixel intensity value) to further reduce acquisition time. In other words, the sum of the dwell times of pixels that reach a threshold number of particles within the maximum dwell period and the maximum dwell time of pixels that do not reach the threshold number of particles results in a shorter acquisition time than an approach that applies the maximum dwell period to all pixels. Additionally, or instead, pixel values ​​proportional to the number of particles detected may be assigned. Additionally, or alternatively, methods for detecting a certain number of particles within a short period of time can extend the time spent in a particular region of the pixel to quickly identify dark or non-interesting areas of the sample (such as unimportant structures or holes) to avoid unnecessary time spent in dark or non-interesting areas.

[0046] As yet another novel solution, the inventors have recognized that adding a subdwell period within a dwell period can help limit acquisition time. For example, if a predetermined number of particles are not detected for a sample location within a subdwell period, one or more image pixels may be immediately aborted and an image pixel intensity value (e.g., minimum intensity) may be assigned to the corresponding image pixel or pixels. Note that the term "location" may refer to the "scanned location of the sample," "scanned sample location," "scanned location," "location," or similar. In addition to reducing the time to obtain results for a sample, this solution may improve dose efficiency by extending the dwell period only for sample scan locations where particles are detected quickly, while aborting data acquisition at sample scan locations where a long dwell period is required to detect sufficient particles. This procedure helps prevent sample damage and shortens overall operation time. In some cases, another solution envisioned by the inventors may involve monitoring multiple detectors in addition to the adaptive dwell time solution previously described. For example, bright-field and dark-field detectors can be monitored in real time, and if a first one of the detectors does not receive particles above a threshold from a location on the sample within a dwell period (or sub-dwell period), the beam can be controlled to skip that location, shortening the dwell time at that location. This procedure can play an important role in shortening the scan time for samples with different structures and properties where scattered and unscattered electrons are important.

[0047] Yet another solution may incorporate multi-pass scanning into the dwell period to scan all positions on the sample. That is, for skipped locations (as described above), the solution may return to those specific locations for rescanning. This procedure has the advantage of reducing the sample scan time, thereby reducing drift due to sample expansion, compression, translation, shear, etc., and limiting overexposure.

[0048] FIG. 1 illustrates components of a scanning microscope system 100 currently known in the art. The scanning microscope system 100 can be configured to generate a primary beam of charged particles (such as electrons or ions). The scanning microscope system may further include a scanning electron microscope 101. In this example, the primary beam includes an electron beam 107. An electron source 102 is configured to emit an electron beam, where a voltage is applied between the electron source 102 and an anode 103. For SEM applications, the applied voltage preferably ranges from at least 2 kV to a maximum of 30 kV, and for S-TEM applications, the applied voltage preferably ranges from at least 20 kV to 300 kV. The scanning microscope system may also include an electromagnetic lens. The electromagnetic lens may be configured to control the path of the electron beam. At least one condenser lens 104 may be configured by an electromagnetic lens. The condenser lens 104 may be configured to determine the size of the electron beam. Furthermore, at least one objective lens 106 may be configured by an electromagnetic lens. The objective lens 106 may be configured to focus the electron beam at a scan location on the sample. The scan location may correspond to an electron beam spot on the sample 108. Furthermore, the size and shape of the scan location may depend on the focusing characteristics of the electromagnetic lens (e.g., applied current) and the working distance between the scanning electron microscope 101 and the sample 108. The scan coil 105 may be configured to deflect the electron beam 107 over multiple scan locations in one or two dimensions. Advantageously, this therefore enables two-dimensional scanning of the sample. The scan coil 105 may be magnetic or electrostatic.

[0049] The scanning microscope system can be configured to generate and detect first and second emissions 109, 110 from the sample. The electron beam 107 can interact with particles (such as atoms) in the sample 108. The interaction can result in the first and second emissions 109, 110. The first emission 109 can include the emission of charged particles, such as backscattered electrons. However, the first emission can also include the emission of secondary electrons, transmitted electrons, and / or Auger electrons. Additionally, the second emission 110 can include the emission of photons, such as X-rays and / or light (e.g., visible light).

[0050] The scanning microscope system 100 also includes a first detector 111, which can be configured to continuously detect the first emission 109 from the first scan location. In particular, the first detector 111 can be configured to detect the first emission at each first scan location over a first dwell time. In some examples, the first detector 111 can include a backscattered electron detector, such as a segmented silicon drift detector. However, the backscattered electron detector can also correspond to other types of solid-state detectors. Furthermore, the first detector 111 can also include a secondary electron detector, such as an Eberhart-Thornley detector, or a transmission electron detector (e.g., a CMOS detector). The transmission electron detector can be positioned below the sample 108 to detect transmitted electrons.

[0051] Additionally, the electron microscope system may include a second detector 112 configured to continuously detect the second emission 110 from the second scanning location. In particular, the second detector 112 may be configured to detect the second emission. The second detector 112 may include an X-ray detector, which may include a silicon drift detector. However, the X-ray detector may also include other types of detectors (e.g., scintillation detectors). The second detector 112 may be tilted relative to the surface of the sample 108. The angle between the centerline 114 of the second detector and the sample surface may be adjustable, ranging from 0° to a maximum of 90°.

[0052] The X-ray detector can be configured by an energy dispersive spectrometer (EDS). The energy bandwidth of the EDS can range from 0 to a maximum of 17 keV. Alternatively, the X-ray detector can be configured by a wavelength dispersive spectrometer (WDS). Furthermore, the second detector 112 can also be configured by an electron energy loss spectrometer or a cathodoluminescence spectrometer.

[0053] The sample 108 may be positioned on top of a movable stage 113. The movable stage 113 may be configured to perform two horizontal movements, a vertical movement, a tilt movement, and / or a rotation movement relative to the plane of the sample. The two horizontal movements may include selecting the field of view. The vertical movements may include changing the height of the sample, the depth of focus, and / or the image resolution.

[0054] FIG. 2 shows a schematic diagram of a charged particle microscope system according to some embodiments. The scanning microscope system 100 may further include a control unit 200a. The control unit 200a may be configured to control the power supply and operation of the focusing lens 104, the objective lens 106, the scanning coil 105, and the movable stage 113. The scanning microscope system may further include a vacuum system. The vacuum system may include a vacuum controller 200b, a mechanical pumping system 210, an ultra-high vacuum pump 220 (such as an ion pump), and a vacuum chamber 230. The vacuum controller 200b may be configured to control the operation of the mechanical pumping system 210 and the ultra-high vacuum pump 220. The mechanical pumping system 210 and the ultra-high vacuum pump 220 may be configured to provide an ultra-high vacuum within the vacuum chamber 230. The vacuum chamber may be configured to accommodate the sample 108, the movable stage 113, the first detector 111, the second detector 112, or portions thereof, and the scanning electron microscope 101, or portions thereof.

[0055] The system shown in FIG. 2 includes a scanning microscope system 100 and a data processing system 250. The data processing system 250 may include one or more processing units configured to execute computer instructions (e.g., machine-readable, executable instructions) of a program. The processing unit may be singular or plural. For example, the data processing system 250 may include at least one of a CPU, a GPU, a DSP, an APU, an ASIC, an ASIP, or an FPGA. In this example, the processing unit may be configured to form an X-ray spectrum based on the detected X-rays. In particular, in the case of an EDS method, the processing unit may be configured to count and sort the detected X-rays based on the energy of each X-ray over the duration of the dwell period. However, in the case of a wavelength-dispersive X-ray spectroscopy (WDS) method, the processing unit may be configured to count and sort the detected X-rays based on the wavelength of each X-ray.

[0056] The data processing system 250 may include memory components such as the data storage component 240. The data storage component 240 and the data processing system 250 may include at least one of main memory (e.g., RAM), cache memory (e.g., SRAM), and / or secondary memory (e.g., HDD, SDD). The data processing system 250 may include volatile and / or non-volatile memory such as SDRAM, DRAM, SRAM, flash memory, MRAM, F-RAM, or P-RAM. The data processing system 250 may include an internal communication interface (e.g., a bus) configured to facilitate electronic data exchange between components of the data processing system 250, such as communication between memory components and processing components. The data processing system 250 may include an external communication interface configured to facilitate electronic data exchange between the data processing system and a device or network external to the data processing system. In the example of FIG. 2, the external communication interface may be configured to facilitate electronic connection between the processing components of the data processing system 250 and components of the scanning microscope system 100, such as the control unit 200a. Additionally, the external communication interface can be configured to establish electronic data exchange between the processing components of the data processing system 250 and the vacuum controller 200b.

[0057] Further, the external communication interface can also be configured to establish electronic data exchange between the data processing system 250 and the first detector 111. The external communication interface can also be configured to facilitate an electronic connection between the data processing system 250 and the second detector 112. For example, the detected backscattered electron data from all first scan locations can be stored in the data storage component 240. The processing unit of the data processing system 250 can be configured to form at least one image based on the stored backscattered electron data. The backscattered electron image of the sample and the X-ray spectrum from each second scan location can be stored in the data storage component 240.

[0058] The data processing system may also include a network interface card that can be configured to connect the data processing system to a network, such as the Internet. The data processing system may be configured to transfer electronic data using a standardized communication protocol. The data processing system may be a centralized or distributed computing system. The data processing system may include a user interface, such as an output user interface and / or an input user interface. For example, the output user interface may include a screen and / or monitor configured to display visual data (e.g., a backscattered electron image or an X-ray spectrum of a sample) or a speaker configured to communicate audio data (e.g., play audio data to a user). The input user interface may include, for example, a keyboard that allows entry of text and / or other keyboard commands (e.g., that allow a user to enter instructions to the scanning microscope system or execution parameters of a data acquisition method), and / or a trackpad, mouse, touchscreen, and / or joystick (e.g., configured for navigation of a backscattered electron image or a region identified within the backscattered electron image).

[0059] In some examples, data processing system 250 is a processing unit configured to execute instructions of a program. Data processing system 250 is a system-on-chip including a processing unit, memory components, and a bus. Data processing system 250 is a personal computer, a laptop, a pocket computer, a smartphone, or a tablet computer. The data processing system can comprise a server, a server system, part of a cloud computing system, or a system emulating a server, such as a server system with appropriate software to run virtual machines. The data processing system is a personal computer, a laptop, a pocket computer, a smartphone, a tablet computer, and / or a processing unit or system-on-chip that can interface with a user interface (such as the user interfaces described above).

[0060] Data processing system 250 may also be comprised of hardware-implemented elements and software-implemented elements. An example is the use of a hardware-implemented encryption / decryption unit and software to process the decrypted data. Furthermore, data processing system 250 may comprise a dwell period adjustment component. The dwell period adjustment component may be configured to perform a dwell period adjustment procedure. More specifically, data processing system 250 may include at least one storage device on which the dwell period adjustment component is stored. Data processing system 250 includes at least one storage device and may store at least one dwell period adjustment component.

[0061] In some examples, the dwell period adjustment component may be implemented in software. The dwell period adjustment component may be a software component or at least a portion of one or more software components. Data processing system 250 may be configured to execute software components and / or to execute software including software components. In other words, a component may include one or more computer instructions (e.g., machine-readable instructions) that can be executed by a computer (e.g., data processing system 250). The dwell period adjustment component may be stored in one or more different storage devices (e.g., memory 1504 of FIG. 15). For example, the component may be stored in multiple storage components including persistent memory, e.g., multiple storage devices in a RAID system, or different types of memory, such as persistent memory (e.g., HDD, SDD, flash memory) and main memory (e.g., RAM). The component may also be implemented at least partially in hardware. For example, the dwell period adjustment component, or some of its functionality, can be implemented as a programmed and / or customized processing unit, hardware accelerator, or system-on-chip that can interface with data processing system 250, a personal computer, laptop, pocket computer, smartphone, tablet computer, and / or server.

[0062] FIG. 3 is a system diagram illustrating an example of a microscope 300, according to some embodiments. For example, the microscope 300 may include a spectrometer that functions using various techniques, such as EDX, EES, 4D scanning transmission electron microscopy (4D STEM), or the like. Furthermore, the microscope 300 is an example of a component of the microscope 100 of FIG. 1 and / or the microscope system 200 of FIG. 2. The microscope 300 can be used to acquire data from a sample 306 (e.g., a semiconductor, a protein, a molecule, a circuit, etc.) that receives a beam 302 (e.g., photons, electrons, ions, etc.) from a beam source (not shown). The beam 302 may be directed by scanning optics 374 (e.g., lenses, electro-optics, etc.), which adjusts the beam 302 according to a scan location received from a scan controller 340. The scan controller 340 may function to scan the beam in a scan pattern (e.g., raster, staircase, etc.) over the sample 306 so that an area of ​​interest on the sample 306 is detected by the beam 302 and imaged by the detector 320 (e.g., scintillator, CCD, etc.).

[0063] In some examples, different electron populations may be detected when using a charged particle beam. For example, unscattered transmitted electrons (bright field 330) may be received by detector 320 to provide a high-contrast image (e.g., light-dark contrast) between different scan positions of the imaged sample. Additionally, scattered electrons (dark field 332) may be received by a dark field detector to image features such as crystalline defects, stacking faults, etc. Depending on the sample type, sample structure, and contrast requirements, microscope 300 may use detectors 320 including a first detector for bright field 330 and / or a second detector for dark field 332, either physically separated or integrated into one structure. In some examples, detector 320 may detect charged particles such as electrons and / or ions, photons such as X-ray photons, ultraviolet photons, visible photons, red photons, or a combination thereof. Furthermore, detector 320 can be any detector with a counting or continuous integration output (e.g., a STEM detector, an EDX detector, a cathodoluminescence detector with counting capabilities, and / or a counting pixelated detector such as a camera or 4D STEM) that can be used as an input to one or more scanning processes disclosed herein.

[0064] In some examples, the detector 320 can generate an analog signal corresponding to one or more "hits" (e.g., the number of particles received by the detector). For example, the detector 320 can be configured according to a duty cycle that transmits an analog signal each time a hit is detected, or according to a predetermined scan cycle (e.g., every few microseconds). The analog signal can be received by a particle counter 322, which can convert the analog signal to a digital signal. This can include the cumulative number of particles received by the detector 320 during a dwell time (e.g., 1-100 microseconds) at a particular scan location (e.g., the location of the beam on the sample). For example, the dwell time can represent the actual time spent scanning a particular location on the sample, and the dwell period can represent any of the following: the total time allowed to scan a particular location on the sample, the maximum time allowed to scan a particular location on the sample, and / or a cutoff time according to some embodiments.

[0065] In some embodiments, the particle counter 322 communicates the accumulated particle count to the reference controller 324 for comparison. The reference controller 324 may include various software and / or hardware components to determine whether the accumulated number of particles in the digital signal reaches a signal criterion (e.g., between 1 and 100 particles). For example, the reference controller 324 may receive a digital signal from the particle counter 322 indicating that the accumulated number of particles corresponds to six particle events during a dwell time (e.g., several microseconds). In this example, the reference controller 324 may compare the six particle events to a signal criterion that may be defined by a user (e.g., using a graphical user interface to define the signal criterion for a finding). If the accumulated number of particles is equal to or greater than the signal criterion, the reference controller 324 may notify the scan controller 340 that the current scan location during the dwell period has met the threshold for a finding. If the reference controller 324 determines that the desired signal criterion has been met, the scan controller 340 may control the scanning optics to move to the next scan location in the scan pattern. In non-limiting examples, the beam can be blanked when desired signal criteria are met and / or when a maximum dwell period is reached.

[0066] In some embodiments, the scan controller 340 can communicate the dwell period 370 of the scan location corresponding to the position on the sample where the signal criterion was reached to the image rendering device 350 (e.g., hardware, software, firmware, etc.) to render the image 380. For example, for each position on the sample 306 corresponding to a unique image pixel, a unique dwell time 370 corresponding to each position is recorded when the signal criterion was reached. As an example, the dwell time (t dwell ), the image rendering device 350 calculates the signal criterion as a function of the dwell time (e.g., 1 / t dwell、 t dwell , or similar value) to assign image pixel intensity values ​​to corresponding image pixels. dwell The first pixel with a dwell time (tdwell ) may be brighter than the second pixel at 0.5 microseconds. In contrast, image pixel intensity values ​​may be calculated as 1 / t dwell If we define dwell ) may be darker than a second pixel with a 0.5 microsecond dwell time. In various examples, the image pixel intensity value may be a function of one or more dwell times in one or more scan passes. In other examples, the image pixel intensity value may be determined, at least in part, by a function of i) the dwell time and particle count 373 detected at a particular scan location (e.g., a convolution, ratio, or similar location), ii) a minimum intensity, iii) an undefined value, iv) a maximum intensity, v) one or more dwell times, vi) particle count 373, or a combination thereof. In some embodiments, the scan controller 340 may implement components such as the detector 320, the particle counter 322, the reference controller 324, and / or the image rendering device 350.

[0067] In some examples, a feedback loop may exist between the detector 320 and the scan controller 340 to maintain a nearly constant cumulative particle count per location. For example, the scan controller 340 may ensure that the particle load per scan location remains nearly constant by scanning the next scan location after a signal criterion is met. Using this configuration, the dwell time per location may represent the inverse of the imaging parameters. For example, after the image 380 is completed, the number of particles detected at each location may be substantially the same, and a digital conversion of the dwell time of each location to grayscale may be performed, allowing adjustments to the image contrast and brightness (e.g., gain and offset). Additionally, the amplifier electronics of the detector 320 may be preset to operate in an optimal operating range for the current particle count.

[0068] In some examples, a lockup prevention mechanism (not shown) may be implemented to limit the dwell period (e.g., maximum dwell period) for one or more scan locations of the sample 306 that produce little or no signal (e.g., too few or no particles detected). When the dwell period is reached, the scan controller 340 stores the scan coordinates 372 and the number of detected particles 373 in a memory (e.g., memory 1504 in FIG. 15 ) for later retrieval as needed (e.g., additional scan passes, a different detector, or similar processing). The lockup prevention mechanism ensures that the sample 306 is scanned in a timely manner and can prevent damage to the sample 306 due to excessive exposure to the beam. The dwell period can be preset (by a predictive algorithm or similar function) or dynamically determined.

[0069] FIG. 4 illustrates an example of an adaptive sawtooth staircase scan pattern 400, according to some embodiments. The pattern 400 can be implemented by one or more components of the microscope 300 of FIG. 3 . In some examples, the beam 302 can be scanned over the sample 306 according to a sawtooth staircase scan pattern. The sawtooth staircase scan pattern can include any number of sawtooth waveforms 470 to fully image the sample 306. The sawtooth waveforms 470 can be separated by one or more dead zones 450 between sawtooth waveforms to accommodate overshooting and stabilize the electronics of the scan controller 340. The beam 302 can scan the sample 306 in an x-direction (e.g., a fast scan direction) and can be controlled in a y-direction (e.g., a slow scan direction) with a phase signal. The scan controller 340 can include any suitable electronics with sufficient speed and bandwidth to accommodate a sawtooth staircase scan pattern with adaptive dwell times.

[0070] In a non-limiting example, the beam 302 can interact with a first scan location of the sample 306 and generate particles (e.g., electrons, ions, x-rays, etc.). The detector 320 can monitor particles at the first scan location corresponding to image pixel-1 410 according to a scan pattern. The detector 320 can remain at the first scan location until a signal criterion (e.g., the number of particles to be detected) is met or a dwell period (e.g., a time period of several microseconds to several milliseconds from the start of signal acquisition at the first scan location) is reached. During dwell time A 418 (corresponding to the x-direction scan time 480), the detector 320 can detect a first accumulated number of particles (e.g., five electron particles 414). If the first accumulated number of particles meets the signal criterion, the scan controller 340 can be operable to move the beam 302 to a second scan location corresponding to image pixel-2 420 according to the scan pattern before the dwell period has elapsed. The scan controller 340 may also be capable of communicating the dwell time A 418 and the scan coordinate 372 to the image rendering device 350 to generate a pixel for the image 380 of the second scan location. Upon reaching the second scan location (image pixel-2 420), the detector 320 may resume the particle monitoring process. In this example, the detector 320 may detect a second particle count (e.g., five electrons 424) during dwell time B 428 (corresponding to the x-direction scan time 482). The scan controller 340 may then receive information from the reference controller 324 that the signal criterion has been reached by the second particle count. The scan controller 340 may then communicate the dwell time B 428 and the scan coordinate 372 to the image rendering device 350. The dwell time B 428 may be shorter than, the same as, or longer than the dwell time A, but is less than or equal to the dwell period. The scan pattern 400 can use any suitable dwell time / dwell duration scheme, either alone or in combination, as shown in FIGS. 3 and 5-12.

[0071] Continuing with this non-limiting example, the scan controller 340 can control the beam 302 to interact with a third scan location on the sample according to the scan pattern. The detector 320 can detect a third number of particles (e.g., two electrons 434) at the third scan location (e.g., image pixel-3 430) during x-direction scan time 484. In this example, the scan controller 340 may determine that the dwell period has been exceeded because the signal criteria have not been met (e.g., not enough particles have been detected). In this case, the scan controller 340 ceases or halts acquisition of the signal from the location corresponding to image pixel-3 430 and communicates this information to the image rendering device 350 along with dwell time C 438 (which in this example is the same as the maximum dwell time). Additionally or alternatively, image pixel-3 430 can be associated with a dwell period (t max ) as a function of (e.g., the intensity value of an image pixel 1 / t max As such, image pixel intensity values ​​may be assigned as a function of the number of particles detected, and / or as a function of the number of particles detected. The scan controller 340 may then repeat the process to complete all remaining locations of the sample 306.

[0072] In some examples, predictive algorithms (e.g., linear regression, k-nearest neighbors, scan-by-scan algorithms, etc.) or appropriately trained artificial intelligence can improve pattern 400 in the next scan pass and / or in future scans of new samples 306. For example, for each successive scan line, only small deviations in signal strength from the current scan line to the next are expected. The predictive algorithms can record and store this information to optimize the driver electronics, especially when used in conjunction with low-bandwidth electronics.

[0073] FIG. 5 is a flow diagram illustrating an example scanning process 500 for adaptive dwell time, according to some embodiments. In some embodiments, scanning process 500 may include more or fewer steps than those shown in FIG. 5. It should be understood that the steps of scanning process 500 may be performed in any suitable order. Scanning process 500 may be implemented under the control of one or more components of microscope 300 of FIG. 3, such as scan controller 340. The flow begins at step 502, in which detector 320 detects a particle count at a position of sample 306 at a first scan location (e.g., the number of electrons at a location corresponding to image pixel −1 410). The particles may be electrons, ions, x-rays, etc. Detector 320 may detect a first cumulative particle count associated with a first scan location of a scan pattern.

[0074] The scanning process 500 proceeds to step 504, where the reference controller 324 determines whether the first cumulative particle count is greater than or equal to a signal criterion. The signal criterion may be defined by a user or determined predictively by an algorithm or historical data and represents a minimum number of particles required to proceed to the next scan location. If the first cumulative particle count is greater than or equal to the signal criterion, the reference controller 324 notifies the scan controller 340 that the signal criterion has been met, and the process proceeds to step 506. If the first cumulative particle count falls below the signal criterion and the maximum dwell period has been reached, flow continues at step 508. In some embodiments, the scan controller 340 may receive input directly from the detector 320 indicating the number of particles detected, count the number of particles, and compare the count to the signal criterion to determine whether to terminate the dwell period at the current scan location or continue dwelling at the current scan location to acquire a signal.

[0075] In step 506, the signal criteria have been met, so the scan controller 340 ends the dwell period at the current location. The scan controller 340 may communicate the current scan coordinate 372 and the dwell time elapsed at the current scan coordinate 372 to the image rendering device 350. In some examples, the scan controller 340 may reset counters and clocks for the next scan location.

[0076] In step 508, the scan controller 340 determines whether the dwell period (e.g., several milliseconds) has been reached at the current scan location. The dwell period may be preset, dictated by the particular scan pattern being used, user-defined, or set to a maximum / minimum value by default. The scan controller 340 may rely on an internal clock mechanism (e.g., software, firmware, etc.) to determine whether the dwell period has elapsed. In some embodiments, if the scan controller 340 determines that the dwell period has not expired and signal acquisition should continue at the current scan location, flow proceeds to step 502, and the process repeats. Once the dwell period has been reached, the scan controller 340 abandons the current scan location, and flow proceeds to step 510, where the scan controller 340 may proceed to scan the next position according to the scan pattern. In some embodiments, the scan process 500 may include more or fewer steps than those shown in FIG. 5. It should be understood that the steps of the scan process 500 may be performed in any suitable order. The scanning process 500 can use any suitable dwell time / dwell duration scheme, either alone or in combination, as shown in FIGS. 3-4 and 6-12.

[0077] FIG. 6 shows an example of a scanning process 600 using a subdwell period, according to some embodiments. The scanning process 600 may be performed by one or more components of the microscope 300 of FIG. 3 and may result in a scan pattern according to FIG. 4. The scanning process 600 may include scanning the beam 302 across a first scan location of the sample 306 (e.g., a location corresponding to image pixel −1 610) to generate particles that are detected by the detector 320. The scan controller 340 may monitor the particles during the subdwell period (e.g., dwell period 612A). In some embodiments, the scan controller 340 may receive the subdwell period as input from a user of the microscope 300, or the subdwell period may be dynamically determined by a predictive algorithm or historical data (e.g., historical data in memory 1504 of FIG. 15). The subdwell period may represent the time period within which a signal criterion (e.g., 1-20 charged particles) must be met in order to extend the subdwell period to include a larger dwell time (e.g., dwell time 612B). The subdwell period may be adaptive for each scan location or may be fixed for each scan location. If the particle signal criterion is not received before the subdwell period expires, the scan controller 340 may cease acquiring signals from the scan location and then instruct the image rendering device 350 to set the image pixel intensity value as a function of the dwell period 612A or a similar function. In other examples, the image pixel intensity value may be a minimum value, no value (e.g., not a number (NaN)), or a suitable function of the dwell period (t max , 1 / t max , 、 In instances where the particle signal criteria are met during the sub-dwell period, the sub-dwell period can be extended (e.g., similar to scanning process 500 of FIG. 5) until the signal criteria are met or until a maximum dwell period (not shown) is reached.

[0078] As a non-limiting example, the detector 320 can detect a subset of particles 614A (e.g., two electrons) during a first dwell period 612A for a scan location corresponding to image pixel −1 610. If the subset of particles 614A meets a signal criterion (e.g., a reference signal of two electrons) during the first dwell period 612A (e.g., 1 microsecond to 2 milliseconds), the scan controller 340 can continue scanning the first scan location of the sample 306 for a second dwell time 612B. The scan controller 340 can continue monitoring to determine whether the signal criterion is met during the second dwell time 612B by additional particles 614B (e.g., three additional electrons). When the scan controller 340 receives information from the reference controller 324 that the subset of particles 614A and one or more of the additional particles 614B, or a combination thereof (e.g., a second signal criterion), meet the signal criterion, the scan controller 340 can communicate the dwell time 612B and the scan coordinates 372 to the image rendering device 350 to form a first portion of the image 380.

[0079] Continuing with this non-limiting example, the scan controller 340 can move the beam 302 to the next scan coordinate 372 (e.g., next scan location) on the sample 306 corresponding to image pixel −2 620 based on the previous scan location corresponding to image pixel −1 610 meeting the signal criteria. Similar to the previous scan cycle, the scan controller 340 can receive information from the reference controller 324 regarding a second accumulated number of particles received during the dwell period 612A detected at the second scan location (e.g., the location corresponding to image pixel −2 620). In this example, the detector 320 can detect a number of particles 626A (e.g., three electrons) during the dwell period 612A. The reference controller 324 communicates to the scan controller 340 that three particles were detected, which causes the scan controller 340 to extend the dwell period 612A to dwell time 624C. Now, a remaining particle quantity 626B (e.g., two electrons) is required to satisfy the second signal criterion (e.g., two particles for the scan location corresponding to image pixel −2 620, because three particles were already detected during dwell period 612A). Dwell time 624C may be the same as, shorter than, or longer than dwell period 612B, but is less than or equal to a maximum dwell period (not shown). In some examples, scan controller 340 may determine that the second cumulative count does not satisfy the second signal criterion after dwell period 624C (e.g., the second dwell period) has elapsed. In this case, dwell period 624C represents the total time required to scan the second scan location of the sample. In this case, image rendering device 350 may store image pixel intensity as a function of dwell period 624C, the total time required to scan the second scan location of the sample, or a similar value.

[0080] Continuing with this non-limiting example, the scan controller 340 can move the beam 302 to the next scan coordinate 372, which corresponds to image pixel −3 630. In this example, the scan controller 340 may determine that it should stop acquiring signals from the scan location corresponding to image pixel −3 630 because not enough particles (e.g., zero electrons 638) were detected during the dwell period 612A. The scan controller 340 can communicate the dwell period 612A and the current scan coordinate 372 to the image rendering device 350. The image rendering device 350 can then determine that the result of not receiving enough particles (e.g., 1 / t max , t max ), image pixel −3 630 may be assigned a maximum value. The scan controller 340 may then move the beam 302 to the next scan location. In some examples, the sub-dwell period (e.g., dwell period 612A) may be the same at each scan location or may vary from scan location to scan location. The scan process 600 may use any suitable dwell period / dwell time scheme, alone or in combination, as shown in FIGS. 3-5 and 7-12.

[0081] FIG. 7 shows a flow diagram of an example scanning process 700 utilizing a sub-dwell period, according to some embodiments. The scanning process 700 may be implemented by one or more components, such as the scan controller 340, of the microscope 300 of FIG. 3 and may result in a scan pattern according to FIG. 4. In some embodiments, the scanning process 700 may include more or fewer steps than those shown in FIG. 7. It should be understood that the scanning process 700 may be performed in any suitable order. The scanning process 700 begins at step 702, where the scan controller 340 controls the beam 302 to dwell at the scan location for a first dwell period (e.g., 1 microsecond). The detector 320 may monitor one or more particles (e.g., x-ray, ultraviolet, light, electrons, etc.) during the first dwell period. In step 704, the scan controller 340 determines whether a first number of particles detected by the detector 320 is greater than or equal to a particle threshold (e.g., two particles) during the first dwell period. If the scan controller 340 determines that the first number of particles detected during the first dwell period is greater than or equal to the particle threshold, the scan process 700 proceeds to step 706. If the scan controller 340 determines that the first number of particles detected during the first dwell period is not greater than or equal to the particle threshold, the scan process 700 proceeds to step 714. At step 714, the scan controller 340 ends the first dwell period and instructs the image rendering device 350 to set the image pixel intensity value (e.g., a function of the first dwell period, a function of the number of particles already detected, or a similar function) as a value. In some embodiments, if the first number of particles detected by the detector 320 is greater than or equal to the threshold during the first dwell time, the scan controller 340 can proceed to step 716.

[0082] In step 706, the scan controller 340 can extend the first dwell period to a maximum dwell period that includes a second dwell time that is longer than the first dwell period. For example, the second dwell time can be less than or equal to the maximum dwell period minus the first dwell period. In step 708, the detector 320 detects a second number of particles during the second dwell period. This second number of particles is different from the first number of particles. In step 710, the scan controller 340 determines whether the first number of particles added to the second number of particles, or the second number of particles plus the first number of particles, is greater than or equal to a threshold value. For example, if the user defines the threshold number of particles as five electrons, and three electrons are detected during the first dwell period and two electrons are detected during the second dwell period, a total of five electrons will be detected during the first dwell period. The second dwell period meets the threshold requirement (e.g., by signal criteria) of five electrons. If the threshold is met, the process proceeds to step 716. In instances where the threshold is not met, the scan controller 340 may determine whether the maximum dwell period has been reached. If the threshold has not been reached, the process returns to step 708 to continue monitoring for more particles. If the maximum dwell period has been reached, the scan controller 340 stops the process of acquiring signals from the scan location and instructs the image rendering device 350 to set the pixel corresponding to the scan location as a pixel with an image pixel intensity value corresponding to the maximum dwell period, the number of particles already detected, or a similar function thereof. This is similar to step 714. In step 716, the scan controller 340 controls the beam 302 to scan to the next scan location of the sample 306 and controls the detector 320 to acquire signal data from the next scan location.

[0083] In some examples, the sub-dwell period of the first portion of sample acquisition reduces the total acquisition time of the sample 306. For example, if the detector 320 does not receive enough particles at a subset of scan locations (with corresponding image pixels) across the sample 306, signal acquisition from that subset of scan locations may be halted, and each pixel corresponding to each scan location may be assigned an image pixel intensity value. This avoids overexposing the sample 306 to the beam 302 for long, unnecessary dwell periods / dwell times, thereby providing faster results and improving dose efficiency. In some embodiments, the scanning process 700 may include more or fewer steps than those shown in FIG. 7. The scanning process 700 may use any suitable dwell period / dwell time scheme, alone or in combination, as shown in FIGS. 3-6 and 8-12. It should be understood that the steps of the scanning process 700 may be performed in any suitable order.

[0084] FIG. 8 is an example of a scanning process 800 using adaptive bright-field and dark-field dwell times, according to some embodiments. Scanning process 800 may be implemented by one or more components (e.g., scan controller 340) of microscope 300 of FIG. 3 and may result in a scan pattern according to FIG. 4. Scanning process 800 may include scanning beam 302 across a first scan location of sample 306 to generate particles for detection by detector 320. Scan controller 340 may monitor particles using detector 320. For example, bright-field detector 320 may be used to monitor bright-field 802 and / or dark-field detector 320 may be used to monitor dark-field 804. Scanning process 800 may use any suitable dwell period / dwell time scheme, alone or in combination, as shown in FIGS. 3-7 and 9-12. In some embodiments, the scan controller 340 receives the dwell period as input from a user of the microscope 300, or the dwell period can be dynamically determined by a predictive algorithm or historical data (e.g., historical data in memory 1504 of FIG. 15).

[0085] As a non-limiting example, the scan controller 340 may determine that sufficient particles (e.g., five electrons 810A) were detected during a first dwell time (e.g., the first dwell time within a first dwell period) at a first scan location of the sample 306 corresponding to bright-field (BF) pixel-1 810. In some examples, the first scan location of the sample 306 may be imaged by a dark-field microscope in addition to being imaged by a bright-field microscope, such that a dark-field (DF) pixel-1 840 also exists corresponding to the first scan location. A dark-field detector may detect multiple electrons diffracted at the first scan location (e.g., two electrons 840A) corresponding to BF pixel-1 810 simultaneously with the detection of undiffracted electrons emitted from the first scan location. Thus, the dark-field detector may collect data used to generate a dark-field image of the first scan location, and the bright-field detector may simultaneously collect data used to generate a bright-field image of the same scan location. In some cases, the dark-field and bright-field detectors may be the same detector. The scan controller 340 first monitors the bright field 802 until no particles are detected at the scan location on the sample, at which point the scan controller 340 may request information from the reference controller 324 regarding whether the dark field 804 detected any particles. In some embodiments, the scan controller 340 can monitor the dark field 804 and the bright field 802 substantially simultaneously. In either case, once sufficient particles (e.g., electrons 850A) are detected in either the bright field 802 or the dark field 804, the scan controller 340 can move the beam 302 to a second scan location on the sample 306 (e.g., corresponding to image BF pixel-2 820 and DF pixel-2 850) to scan during a second dwell period. As noted above, the scan process 800 can use any suitable dwell period / dwell time scheme, including adaptive dwell times and / or sub-dwell thresholds.

[0086] In some embodiments, during the second dwell period, the scan controller 340 can determine that enough particles (e.g., five electrons 820A) have been detected for the scan location corresponding to BF pixel-2 820 to move to a third scan location of the sample 306 (e.g., a location corresponding to image BF pixel-3 830 and DF pixel-3 860). When the scan controller 340 moves the beam 302 to the third scan location of the sample corresponding to image BF pixel-3 830, the scan controller 340 can determine that the second accumulated particle count (e.g., one electron 830A) does not meet the signal criterion detected in the bright field 802. In this case, the scan controller 340 can monitor the dark field 804 to determine whether the accumulated number of particles detected in the dark field 804 as detected by the dark field detector has reached a signal criterion, such as the need for five particles to be detected. As shown, there are eight electrons 860A at the scan location corresponding to DF pixel-3 860, meeting the signal criterion of five particles. In some examples, the scan controller 340 may stop acquiring a bright-field signal (e.g., a signal corresponding to BF pixel-3 830) if a signal acquired from a scan location of the dark-field (e.g., DF pixel-3 860) meets a signal criterion if not enough particles are detected by the bright-field detector during a dwell period at the third scan location of the sample. The scan controller 340 may determine whether a pixel at the third scan location of the sample 306 (e.g., BF pixel-3 830) meets a signal criterion. maxThe scan controller 340 may then notify the image rendering device 350 that the image pixel intensity values ​​corresponding to the DF pixel-1 840 (e.g., two electrons 840A) and the DF pixel-2 850 (e.g., two electrons 850A) should be a function of the total particle counts. According to some embodiments, the scan controller 340 can then reset a counter (e.g., the count of the particle counter 322) and a clock (e.g., a dwell period) and move the beam 302 to the fourth scan location (e.g., the next pixel, not shown) of the scan pattern. Additionally, the scan controller 340 can determine whether to continue monitoring the dark field 804 for the next scan location if acquisition of a signal corresponding to an image pixel in the bright field 802 is discontinued. Optionally, the scan controller 340 can store the particle counts for the scan location corresponding to DF pixel-1 840 (e.g., two electrons 840A) and the scan location corresponding to DF pixel-2 850 (e.g., two electrons 850A) in memory (e.g., memory 1504 of FIG. 15 ) for future reference (e.g., for generating future dark field images). It should be understood that the scan controller 340 can switch between or simultaneously monitor bright field 802 and dark field 804 based on any suitable parameter, such as dwell time, number of particles detected, user-defined settings, or the like. The scan scheme begins with bright field 802, but the scan scheme may also begin with dark field 804 based on user preference, historical data, or the like. Although bright field and dark field detectors have been described herein as complementary detectors for monitoring bright field and dark field, these are not intended to be limiting, and any number of complementary detectors, such as core-loss electron energy-loss detectors, zero-loss electron energy-loss detectors, cathodoluminescence detectors, energy dispersive X-ray spectroscopy detectors, wavelength dispersive X-ray detectors, etc., can be used alone or in combination with the detectors described herein.

[0087] FIG. 9 shows a flow diagram of an example scanning process 900 for adaptive dwell times for bright field and dark field, according to some embodiments. The scanning process 700 may be implemented by one or more components (e.g., the scan controller 340) of the microscope 300 of FIG. 3 and may result in a scan pattern according to FIG. 4. In some embodiments, the scanning process 900 may include more or fewer steps than those shown in FIG. 9. It should be understood that the steps of the scanning process 900 may be performed in any suitable order. The scanning process 900 begins with step 902, in which the scan controller 340 causes the beam 302 to dwell at a scan location on the sample 306 for a dwell time (e.g., the dwell times in FIGS. 3-8 and 10-12) that corresponds to the number of particles to be detected. In step 904, the reference controller 324 determines whether the first particle count at the first detector 320 (e.g., a bright field detector) is equal to or exceeds a signal reference during the dwell period. For example, the detector 320 may be a bright field detector and detect five electrons during the dwell period. If the reference controller 324 determines that the first number of particles detected by the first detector is greater than or equal to the signal criterion, the flow may proceed to step 912 to scan the next location of the sample 306. If the reference controller 324 determines that the first number of particles detected by the first detector is less than the signal criterion, the flow may proceed to step 906. While this non-limiting example begins with a bright field detector, it should be understood that any suitable detector may be evaluated first, or in addition to, or instead of, simultaneously with other suitable detectors.

[0088] In step 906, the scan controller 340 can monitor a second detector (e.g., a dark-field detector) to determine whether a second number of particles is detected. For example, the scan controller 340 can work with the reference controller 324 to determine whether the second detector detected dark-field particles within the same dwell time as the first scan location. In step 908, the scan controller 340 can determine whether the second number of particles is equal to or greater than a signal criterion. For example, the reference controller 324 can determine that the dark-field detector detected at least five particles. As a result, the reference controller 324 can report to the reference controller 324 that the second number of particles detected by the dark-field detector is equal to or greater than the signal criterion (e.g., five particles). The scan controller 340 can notify the image rendering device 350 that data acquisition for the first scan location in bright field has been stopped and can convert the first pixel intensities to image pixel intensity values ​​(e.g., t max The flow then proceeds to step 912 where the next scan location is scanned.

[0089] In some examples, the reference controller 324 may determine that the second particle count is not greater than or equal to the signal criterion. In this case, the scanning process 900 proceeds to step 910, where the reference controller 324 determines whether the dwell period for the first scan location of the sample 306 has been reached. If the dwell period has been reached, the reference controller 324 may signal the image rendering device 350 to set the dwell period for the corresponding pixel to a function of the number of detected particles, a maximum value, a minimum value, or a combination thereof. Further, the scanning controller 340 may control the beam 302 to move to a second scan location (e.g., the next scan location) of the sample 306 in step 912. If the dwell period has not been reached, the scanning process 900 returns to step 906 to continue monitoring the second detector. In some embodiments, the scanning process 900 may include more or fewer steps than those shown in FIG. 9 . It should be understood that the scanning process 900 may be performed in any suitable order. The scanning process 900 may use any suitable dwell period / dwell time scheme, either alone or in combination, as shown in FIGS. 3-8 and 10-12. can.

[0090] FIG. 10 illustrates an example of a scanning process 1000 using multiple scan paths, according to some embodiments. The scanning process 1000 can be implemented by one or more components of the microscope 300 of FIG. 3, such as the scan controller 340, and / or can be the result of the scan pattern of FIG. 4. The scanning process 1000 includes scanning the beam 302 over a first scan location of the sample 306 (e.g., a location corresponding to image pixel −1 1010), which can generate particles (e.g., five electrons 1010A) that are detected by the detector 320. The scan controller 340 can monitor the particles during a first dwell period. The scanning process 1000 can use any suitable dwell period / time, alone or in combination, as illustrated in FIGS. 3-9 and 10-12.

[0091] In some examples, the scanning process 1000 may include one or more scan passes (e.g., Scan 1 1002, Scan 2 1004, etc.) across the sample 306. Scan 1 1002 includes scanning several scan locations to input image data corresponding to image pixels such as image pixel-1 1010, image pixel-2 1020, and image pixel-3 1030. In this example, five electrons may be detected in Scan 1 1002 at the first scan location corresponding to image pixel-1 1010, meeting a signal criterion of five particles during the dwell period. The scan controller 340 then terminates the dwell time when the signal criterion is reached and moves the beam 302 to a second scan location (e.g., Image Pixel-2 1020). The process is repeated. However, during the scan of the second scan location, the dwell period may end before enough particles (e.g., two electrons 1020A) are counted by the reference controller 324. In this case, the scan controller 340 may store the number of particles detected during the dwell period (e.g., two electrons 1020A) in memory (e.g., memory 1504 of FIG. 15 ) for retrieval and comparison on the next scan pass. In some examples, the scan controller 340 may scan each scan location of the sample 306 using a fixed dwell period or an adaptive dwell time, as needed. If a fixed dwell period is used, the scan controller 340 scans all scan locations of the sample 306 (e.g., providing imaging data for all pixels) and determines where the signal criterion was not met (e.g., two electrons 1020A at the scan location corresponding to image pixel −2 1020 and three electrons 1030A at the second scan location corresponding to image pixel −3 1030).

[0092] In some examples, during the second scan pass, the scan controller 340 may skip some or all scan locations that met the signal criteria (e.g., five electrons 1010A at a location corresponding to pixel 11010 meet the signal criteria of five particles). In this manner, only scan locations that did not meet the signal criteria are re-scanned, such as scan locations corresponding to pixel-2 1020 and pixel-3 1030. For example, during scan 2 1004, the scan location corresponding to pixel-2 1020 may receive three additional particles (e.g., three electrons 1020B). The scan controller 340 may obtain the previous particle count (e.g., two electrons 1020A) from a previous scan (e.g., scan 1 1002) and add the previous particle count for that scan coordinate 372 to the particle count for scan 2 1004 (e.g., two electrons 1020A plus three electrons 1020B) to determine whether the signal criteria are met. As non-limiting examples, the dwell times and / or dwell durations from two scans may be added, alone or in combination, to calculate a total dwell time, and in some cases, the difference and / or ratio of the dwell durations / dwell times of some or all of the completed scan passes may be used to determine pixel intensity, future scan passes, etc. The scan controller 340 may perform this operation for all locations that do not meet the signal criteria by comparing the current scan with all previous scans (e.g., three electrons 1030A with three electrons 1030B, etc.). In some embodiments, the scan controller 340 may determine the difference between the signal criteria and the total number of particles detected to determine whether to exclude or include the scan location from one or more additional scan passes. Further, additional scan passes may continue until the difference is less than or equal to zero.

[0093] In some examples, the scan controller 340 can tally the scan locations in real time or complete the scan and calculate the particle totals for the scan locations upon completion of the scan. While only two scans are shown, any number of scans can be performed to scan the relevant scan locations of the sample 306. In some examples, a lock-up prevention mechanism (e.g., similar to or the same as the lock-up prevention mechanism of FIG. 3) may act to stop further scan passes after a certain number of scan passes have been completed. For example, if a number n of scan passes (e.g., 5 to 10) have been completed and only a certain percentage of the sample has been scanned that exhibits the desired particle load according to the signal criteria (e.g., about 76%), based on the number of scan locations that do not meet the signal criteria (e.g., about 24%), the image rendering device 350 may assign image pixel intensity values ​​(e.g., n × t) to all remaining locations that do not meet the signal criteria. max , or n × 1 / t max ) or can be assigned a value proportional to the cumulative number of particles detected at the scan location.

[0094] FIG. 11 illustrates an example pattern 1100 for rescanning a portion of a sample according to certain embodiments of the present disclosure. Pattern 1100 is implemented by one or more components of microscope 300 of FIG. 3 and may be the result of a scan pattern according to FIG. 4. Pattern 1100 may include scanning beam 302 through locations of sample 306. For simplicity, sample 306 is shown in FIG. 11 as a 4x4 grid of scan coordinates 372, although any suitable size or shape grid for sample 306 may be used within the scope of the present disclosure. Scan pattern 1100 may be configured to use any suitable dwell period / dwell time scheme, alone or in combination, as shown in FIGS. 3-10 and / or 12. Example pattern 1100 illustrates a 4x4 grid of sample sites where each scan location meets a signal criterion indicated by a check mark (e.g., scan location 1111 meets the signal criterion). Scan pattern 1100 also includes scan locations that did not meet the signal criteria, indicated by an "X," such as scan location 1112. In this example, 5 of the 16 scan locations met the signal criteria during scan 1 1102, but 11 of the 16 locations did not meet the signal criteria.

[0095] In some examples, similar to scan process 1000, scan controller 340 can identify locations that need to be scanned during scan 2 1104. After scan 2 1104 is completed, several new scan locations may be determined to meet the signal criteria (e.g., scan location 1115). For example, the second scan location in the second row (e.g., location (x,y)=(2,2)) may meet the signal criteria due to a combination of particles detected in scan 1 1102 and particles detected in scan 2 1104. In various embodiments, the second scan location in the second row may meet the signal criteria due to particles detected during scan 2 1104. Additionally, during scan 2 1104, several locations (e.g., five locations) may be determined not to meet the signal criteria (e.g., scan location 1114) and will be included in the next scan (e.g., scan 3 1106). In some cases, a scan location that previously met the signal criteria (eg, scan location 1113) may be excluded from scan 2 1104 (eg, as in FIG. 10).

[0096] In some examples, one or more additional scans (e.g., scan 3 1106) may be performed to rescan each scan location 1114 that does not meet the signal criteria to obtain the complete image 380. For example, after completing scan 3 1106, scan locations 1117 may each meet the signal criteria to form the complete image 380 (not shown). Similar to scan location 1113, scan location 1116 may be excluded from scan 3 1106. This process may be repeated as many times as appropriate to ensure each location meets the signal criteria (e.g., if 16 out of 16 pixels meet the signal criteria and the lock-up prevention mechanism is not activated).

[0097] FIG. 12 is a flow diagram illustrating an example of a scanning process 1200 for rescanning a position on a sample according to certain aspects of the present disclosure. The scanning process 1200 may be implemented by one or more components (e.g., the scan controller 340) of the microscope 300 of FIG. 3 and may result in a scan pattern according to FIG. 4. In some embodiments, the scanning process 1200 may include more or fewer steps than those shown in FIG. 12. It should be understood that the steps of the scanning process 1200 may be performed in any suitable order. The scanning process 1200 begins with step 1202, in which the scan controller 340 controls the beam 302 to dwell on a pixel (e.g., a first scan location) for a dwell period (e.g., 1 millisecond). The detector 320 may monitor one or more particles (e.g., x-ray, ultraviolet, light, electrons, etc.) during the dwell period. While a dwell period is used in this non-limiting example, it should be apparent that any adaptive dwell period scheme may be implemented alone or in combination with any suitable dwell period scheme in conjunction with the flow diagram of FIG. 12.

[0098] In step 1204, the reference controller 324 determines whether the number of particles detected by the detector 320 during the dwell period is greater than or equal to a signal criterion (e.g., 5 particles). If the number of particles detected by the detector 320 at the first scan location of the sample 306 is greater than or equal to the signal criterion, the scanning process 1200 proceeds to step 1206, where the dwell period at the first scan location ends when the signal criterion is met. On the other hand, if the number of particles detected by the detector 320 at the first scan location of the sample 306 is not greater than or equal to the signal criterion, the flow proceeds to step 1208, where the scanning controller 340 stores the number of particles detected at the first scan location in memory (e.g., memory 1504 of FIG. 15) for future reference, after which the scanning process 1200 can proceed to step 1210.

[0099] In step 1210, the scan controller 340 can determine whether all scan locations of the sample 306 have met the signal criterion. For example, the scan controller 340 can reference historical data (e.g., from memory 1504 of FIG. 15 ) to determine locations that have not met the signal criterion (e.g., using the same or similar signal criterion indicators as in FIGS. 3-11 ). If not all scan locations have met the signal criterion, the scanning process 1200 can proceed to step 1212 to scan the next scan location that has not yet met the signal criterion. In some embodiments, the image renderer 350 (e.g., image renderer 1520 of FIG. 15 ) can be capable of detecting the presence or absence of sample change by identifying at least one of expansion, compression, translation, and shear in the images of the sample generated between the first and second scan passes, thereby reducing sample drift for the second image generated after the second scan pass. In some examples, step 1214 can determine whether the next scan location has been previously scanned by referencing historical data (e.g., determining whether scan coordinate 372 produced particles in a previous scan) or by using a scan counter that counts the number of times a scan pass has been completed (e.g., if the counter is 0, this indicates this is the first scan pass, and scan controller 340 scans that location). Thus, scanning process 1200 can proceed to step 1202 if the scan location has not been scanned previously, or can proceed to step 1216, where controller 340 can add the number of particles previously detected at the scan location before step 1202, and then scan controller 340 may again dwell on the scan location for a second dwell period. Returning now to step 1210, if scan controller 340 determines that all scan locations have reached the signal criterion, scanning process 1200 can end at step 1218, where scan controller 340 ends scanning of sample 306. In some non-limiting examples, the scan controller 340 may determine whether to remove a scan location from a future scan pass and / or whether to terminate a scan based at least in part on a lockup prevention mechanism in conjunction with the signal criteria. Examples of lockup prevention mechanisms include, but are not limited to:i) a scan location that results in zero counts for a certain number of scan passes (e.g., the previous 2 to 10 consecutive or non-consecutive scan passes), ii) an incorrect wavelength (e.g., an incorrect X-ray wavelength), iii) no sample at the scan location, iv) improper calibration, v) a dwell period that is too long (e.g., 1 minute), or a combination of these.

[0100] FIG. 13 is a flow diagram illustrating an example of a method 1300 according to certain aspects of the present disclosure. Method 1300 can be implemented by one or more components of microscope 300 of FIG. 3 , such as scan controller 340. In some embodiments, method 1300 can include more or fewer steps than those shown in FIG. 13 . It should be understood that the steps of method 1300 can be performed in any suitable order. The method can begin with step 1305 of scanning beam 302 over sample 306 in a scan pattern. Beam 302 can interact with a first scan location of the sample and generate scattered electrons, unscattered electrons, ions, photons, or the like, for detection by detector 320 or a dark field detector.

[0101] In step 1310, the detector 320 may be associated with a first scan location on the sample and monitor a first cumulative number of particles detected at the first scan location of the scan pattern. In some examples, the first cumulative number of particles corresponds to an interaction of the beam with the first scan location on the sample. Further, in various examples, the monitoring using at least the detector 320 can include detecting x-ray light, ultraviolet light, visible light, infrared light, charged particles, or a combination thereof.

[0102] In step 1315, the scan controller 340 can control the beam 302 using the scanning optics 374 to move the beam 302 to a second scan location in the scan pattern before the first dwell period has elapsed if the signal criteria are met. In some examples, the signal criteria are based on a first cumulative particle count and may include a first threshold number. In some examples, the met signal criteria may include the first cumulative particle count reaching or exceeding the first threshold number. In various other examples, the method may include determining that the first cumulative particle count does not reach the first threshold number during the second dwell period, and the second dwell period may be shorter than the first dwell period.

[0103] FIG. 14 is a flow diagram illustrating an example of a method 1400 according to certain aspects of the present disclosure. Method 1400 can be implemented by one or more components of microscope 300 of FIG. 3 , such as scan controller 340. In some embodiments, method 1400 can include more or fewer steps than those illustrated in FIG. 14 . It should be understood that the steps of method 1400 can be performed in any suitable order. The method may begin with step 1405, in which scan controller 340 controls beam 302 to scan sample 306 according to a first scan path. For example, the first scan path may include scanning each scan location of sample 306 (e.g., the scan path of FIG. 11 or 12 ). In some examples, each scan path of the sample includes irradiating each scan location determined to be included in the scan path with the beam for a fixed dwell time and excluding each scan location determined to be excluded from the scan path from the scan path irradiating beam 302.

[0104] In step 1410, the detector 320 may measure a first particle count associated with a first scan location of the sample. In some examples, the detector 320 may communicate an analog signal to the particle counter 322 for digital conversion to a particle counter. The digital signal may then be communicated to the reference controller 324, which may compare the first particle count to a signal reference. The reference controller 324 may then communicate the results of the comparison to the scan controller 340.

[0105] In step 1415, the scan controller 340 may determine whether to exclude or include the first scan location from the second scan pass based on at least a comparison of the first particle count and the signal criterion. In some examples, the scan controller 340 may determine a total number of particles detected at the first scan location for the number of scan passes already completed and determine a difference between the total particle count and the signal criterion. Based on the difference, the scan controller 340 may further determine whether to exclude or include the first scan location in one or more additional scan passes. In some embodiments, the one or more additional scan passes are continued until the difference is less than or equal to zero. Sample acquisition data (e.g., image 380) may then be generated based at least in part on the total number of scan passes. In other examples, the sample acquisition data may be generated based on the triggering of a lockup prevention mechanism, which may result in a partial or incomplete image.

[0106] In step 1420, the scan controller 340 can control the beam 302 to scan the sample according to a second scan pass. In some examples, the second scan pass can be performed on some or all locations of the sample 306 that did not produce enough particles to meet the signal criteria. Additionally, the dwell period for each scan location can be adjusted based on the number of first particles detected at the same scan location during the first scan pass (e.g., if two electrons are detected in the first scan pass during 1 millisecond, the second scan pass can be reduced to 0.5 milliseconds because only three electrons need to be detected to meet the signal criteria).

[0107] FIG. 15 is a block diagram of a controller 1501 of a microscope system according to certain embodiments of the present disclosure. Examples of electron microscope systems may include the scanning microscope system 100 of FIG. 1, the microscope system 200 of FIG. 2, and / or the microscope 300 of FIG. 3. As shown, the controller 1501 includes a processor 1502 communicatively coupled to a memory 1504. The processor 1502 may include one or more processing units. Non-limiting examples of the processor 1502 include a field programmable gate array (FPGA), an application-specific integrated circuit (ASIC), a microprocessor, or a combination thereof. The processor 1502 may execute instructions 1510 stored in the memory 1504 to perform the operations of the microscopes, processes, scans, and methods of FIGS. 3-14. In some examples, the instructions 1510 may include processor-specific instructions generated by an editor or interpreter from code written in a suitable computer programming language (C, C++, C#, Python, or Java).

[0108] The memory 1504 may include one or more memory devices. The memory 1504 is non-volatile and may include any type of memory device that retains stored information even when power is removed. Non-limiting examples of the memory 1504 include electrically erasable programmable read-only memory (EEPROM), flash memory, or other types of non-volatile memory. At least a portion of the memory 1504 may include a non-transitory computer-readable medium from which the processor 1502 can read instructions 1510 via a bus 1506. The bus 1506 may be a communication and / or power bus that allows the processor 1502 to communicate with the memory 1504. The non-transitory computer-readable medium may include electronic, optical, magnetic, or other storage devices that can provide instructions 1510 or other program code to the processor 1502. Non-limiting examples of non-transitory computer-readable media include magnetic disks, memory chips, RAM, ASICs, or other media from which a computer processor can read instructions 1510.

[0109] The memory 1504 may further include information regarding parameters 1512 (e.g., calibration, tuning, stage position, beam intensity, etc.), a scan controller 1514 (e.g., scan coordinate 372, past particle count per pixel, etc.), a particle counter 1516 (e.g., sensitivity, gain, ADC conversion, etc.), a detector 1522 (e.g., detector control, sensitivity, etc.), a reference controller 1518 (e.g., DAC conversion, threshold comparison, etc.), and an image renderer 1520 (e.g., image pixel intensity values, dwell period intensity conversion, scan coordinate 372, etc.). The controller 1501 may receive information regarding operational parameters from a microscope, such as a TEM. At least some of the information regarding any of the controllers 1501 may be pre-stored and associated with various scan paths. The parameters 1512 may include operational parameters associated with the electron microscope system, such as desired / primary energy of the electron beam, energy distribution of the energy loss spectrum, lock-up mechanisms, feedback loops, etc. The controller 1501 can determine or calculate image pixel intensities based on the dwell time and / or dwell duration for each scan location. In some examples, some of the parameters 1512 can be compared to predetermined thresholds (e.g., known locations, known sample types, etc.).

[0110] In the above description, various embodiments have been described. For purposes of explanation, specific configurations and details have been set forth to provide a thorough understanding of the embodiments. However, it will be apparent to those skilled in the art that the embodiments may be practiced without the specific details. Additionally, well-known features may be omitted or simplified so as not to obscure the described embodiments. While the exemplary embodiments described herein focus on electron microscopy systems, these are intended as non-limiting exemplary embodiments. Embodiments of the present disclosure are not limited to such materials, but rather are intended to address electron beam systems that can be applied to imaging, microanalyzing, and / or processing a wide range of particles at the atomic scale. Such particles may include, but are not limited to, electrons, ions, or photons in TEM systems, SEM systems, STEM systems, ion beam systems, and / or particle accelerator systems.

[0111] Some embodiments of the present disclosure include a system including one or more data processors and / or logic circuitry. In some embodiments, the system includes a non-transitory computer-readable storage medium including instructions that, when executed on one or more data processors, cause the one or more data processors to perform some or all of one or more methods and / or some or all of one or more processes and workflows disclosed herein. Some embodiments of the present disclosure include a computer program product tangibly embodied in a non-transitory machine-readable storage medium, including instructions configured to cause one or more data processors to perform some or all of one or more methods and / or some or all of one or more processes disclosed herein, including, for example, process 1000 of FIG. 10 .

[0112] The terms and expressions that have been employed are used as terms of description rather than of limitation, and the use of such terms and expressions is not intended to exclude equivalents of the features shown and described or portions thereof, and it is recognized that various modifications are possible within the scope of the claims. Thus, while the present disclosure includes specific embodiments and optional features, it should be understood that modifications and variations of the concepts disclosed herein may be adopted by those skilled in the art, and that such modifications and variations are considered to be within the scope of the appended claims.

[0113] As used in this application and 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.

[0114] 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 or subcombinations with one another. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, nor do the disclosed systems, methods, and devices require that one or more particular advantages exist or problems be solved. While any theory of operation is for ease of explanation, the disclosed systems, methods, and devices are not limited to such theory of operation.

[0115] Although some operations of the disclosed methods are described in a particular sequential order for convenient presentation, it should be understood that this description style encompasses rearrangements unless a particular ordering is required by specific language set forth below. For example, operations described sequentially may in some cases be rearranged or performed simultaneously. Moreover, for the sake of simplicity, the accompanying figures may not show the various ways in which the disclosed systems, methods, and apparatuses can be used in conjunction with other systems, methods, and apparatuses. This document also sometimes uses terms such as "yield" and "provide" to describe the disclosed methods. These terms are high-level abstractions of the actual operations that are performed. The actual operations that correspond to these terms will vary depending on the particular embodiment and will be readily discernible to those skilled in the art.

[0116] In some instances, values, procedures, or devices are referred to as "lowest," "best," "minimum," "greater than," "less than," "equal to," etc. Such descriptions are intended to indicate that a selection may be made from among many functional alternatives used, with the understanding that such a selection is not necessarily better, less, or otherwise preferred than other selections.

[0117] The term "image" is intended to include a two-dimensional grid, which can include at least one or more portions. Each portion is characterized by its coordinates and its value (color and / or intensity). Thus, an image can refer to a visual representation of a sample in varying gray levels and / or varying colors and / or varying intensities. Furthermore, each portion in an image can correspond to a point on the sample (e.g., a scan location), a subgroup of pixels, or the like. An image portion can, for example, be a pixel or include multiple pixels.

[0118] The term "spectrum" is intended to include the distribution function of a physical quantity (e.g., energy or frequency). The measurement of a quantity can be, for example, the intensity, abundance, velocity, or flux of each quantity value. A spectrum can refer to a discrete spectrum, which can include a set of discrete spectral lines at different energy values. The peak of each spectral line at the center of the corresponding line can correspond to the maximum number of detected photons (i.e., peak intensity) across the respective linewidth. Detected photons may further refer to detected X-ray photons. Each spectral line can correspond to an electronic transition of a chemical element, and the energy value of each electronic transition can be unique for the corresponding chemical element. A spectrum can also refer to a continuous spectrum, which can refer to the intensity distribution over a range of continuous energy values. However, intensity can also be plotted with respect to the corresponding wavelength, frequency, or wavenumber.

[0119] Whenever x, y, and / or z coordinates or directions are used within this disclosure, the z direction is vertical, i.e., perpendicular to the ground. The x and y directions are orthogonal to each other and to the z direction, i.e., they are horizontal. The coordinates may form a Cartesian coordinate system.

[0120] The term "scan location" may refer to one or more (x,y) coordinates of a location on a sample or the coordinates of a corresponding image pixel. The term "scan location" is intended to include a scan location, a scan point location, within and / or on a sample. A scan location is specified by (x,y) coordinates with respect to the internal coordinate system of the sample and / or image.

[0121] For simplicity, some features may appear in only some figures and other features may be omitted, however, omitted features may be present and the features shown and discussed need not be present in all embodiments.

[0122] When a term is used without an explicit definition, it should be understood that the ordinary meaning of the term is intended unless it has a special and / or specific meaning in the field of charged particle microscope systems or other related fields. The terms “about,” “same,” “roughly,” “similar,” or “substantially” are used to indicate deviations from a stated characteristic or value, within which deviations have little or no effect on the corresponding function, characteristic, or attribute of the described structure. In examples where a dimensional parameter is described as “substantially equal” or “approximating” another dimensional parameter, the terms “substantially” or “approximate” are intended to indicate that the two dimensions being compared may not be equal within acceptable limits, such as manufacturing tolerances. With respect to dimensional values ​​such as diameter, length, and width, the term “about” can be understood to describe a deviation of up to ±10% from the stated value. For example, a dimension “about 10 mm” can describe a dimension from 9 mm to 11 mm. In this disclosure, a “subrange” refers to a range of values ​​between two stated ranges and / or a range of values ​​that includes either of the two stated degrees.

[0123] This description provides exemplary embodiments and is not intended to limit the scope, applicability, or configuration of the present disclosure. Rather, the following description of exemplary embodiments will provide those skilled in the art with an enabling description for implementing various embodiments. It will be understood that various changes can be made in the function and arrangement of elements without departing from the spirit and scope as set forth in the appended claims.

[0124] Specific details are described herein to provide a thorough understanding of the embodiments. However, it will be understood that the embodiments may be practiced without these specific details. For example, specific system components, systems, processes, and other elements of the disclosure may be shown in schematic form or omitted from illustrations so as not to obscure the embodiments in unnecessary detail. In other instances, well-known circuits, processes, components, structures, and / or techniques may be shown without unnecessary detail.

Claims

1. 1. A method of using adaptive pixel dwell times in a microscope, comprising: scanning light emitted from a beam source over a sample in a scan pattern, the beam interacting with the sample at a first scan location according to the scan pattern; monitoring, using at least a detector of the microscope, a first accumulated particle count associated with the first scan location of the sample, the first accumulated particle count corresponding to an interaction of the beam with the sample at the first scan location; after a first dwell time and before a first dwell period elapses, moving the beam to a second scan location on the sample according to the scan pattern if a signal criterion is met, the signal criterion being based on the first accumulated particle count; A method comprising:

2. the signal criteria include a first threshold; The method of claim 1 , wherein the signal criteria being met includes the first cumulative particle count reaching or exceeding a first threshold number.

3. the signal criteria include a first threshold; 2. The method of claim 1, further comprising determining whether a second cumulative particle count meets a first threshold during a second dwell period, the second dwell period being less than the first dwell period.

4. 10. The method of claim 1, wherein monitoring using at least the microscope detector comprises detecting x-ray photons, ultraviolet light photons, visible light photons, infrared light photons, charged particles, or a combination thereof.

5. determining whether a subset of particles of the first cumulative number of detected particles meets a second signal criterion during the first dwell period; based on the subset of particles that satisfy the second signal criterion during the first dwell period, controlling the beam according to the scan pattern to continue scanning the first scan location of the sample i) for a second dwell period, and / or ii) until the signal criterion is satisfied; moving the beam to the second scan location according to the scan pattern based on at least one of the second dwell period elapsed and the signal criteria being met given the total number of particles detected; The method of claim 1 further comprising:

6. determining that a second cumulative particle count, the cumulative number of particles detected at the second scan location, is less than a third threshold within a third dwell period; moving the beam to a third scan location in the scan pattern based on the passage of the third dwell period; The method of claim 5 further comprising:

7. the detectors include a first detector and a second detector; monitoring a second cumulative particle count, which is a cumulative number of particles detected at the second scan location, using at least the first detector; determining that the second cumulative particle count does not meet the signal criterion; determining, based on the second cumulative particle number not meeting the signal criterion, that a third cumulative particle number of particles detected at the second scan location by the second detector meets the signal criterion; moving the beam to a third scan location according to the scan pattern based on the third accumulated number of particles satisfying the signal criterion; The method of claim 1 further comprising:

8. The method of claim 1 , further comprising determining an image pixel intensity based on the first dwell time.

9. A non-transitory computer-readable medium storing computer-readable instructions, comprising: The instructions, when executed by a processor, cause the processor to: controlling a beam source of the microscope to emit a beam towards the sample according to a scan pattern, the beam interacting with the sample at a first scan location; monitoring, using at least a detector of the microscope, a first cumulative particle count associated with the sample at the first scan location according to the scan pattern, the first cumulative particle count corresponding to interactions with the sample at the first scan location; after a first dwell time and before a first dwell period elapses, if a signal criterion is met, moving the beam to a second scan location on the sample according to the scan pattern, the signal criterion being based on the first accumulated particle count; A non-transitory computer-readable medium for causing operations to be performed, including:

10. determining that the first cumulative particle count satisfies the signal criterion; storing pixel intensity values ​​of the image as a function of said first dwell time; 10. The non-transitory computer-readable medium of claim 9, further comprising:

11. monitoring, using at least the detector, a second cumulative particle count, which is a cumulative number of particles detected at the second scan location; determining that the second accumulated particle count does not meet a second signal criterion after a second dwell period has elapsed, the second dwell period comprising a total time for scanning the second scan location of the sample; storing image pixel intensity values ​​as a function of total time for scanning the second scan location of the sample; 10. The non-transitory computer-readable medium of claim 9, further comprising:

12. monitoring, using at least the detector, a second cumulative particle count, which is a cumulative number of particles detected at the second scan location; determining that a second cumulative particle count, which is a cumulative number of particles detected by a second detector, satisfies a second signal criterion; storing image pixel intensities as a function of the second particle cumulative number, a maximum intensity, and / or a minimum intensity based on a second particle cumulative number, which is a cumulative number of particles that meet the second signal criterion; 10. The non-transitory computer-readable medium of claim 9, further comprising:

13. the detector is either a bright field detector or a dark field detector, and the second detector is either the other of the bright field detector or the dark field detector; 13. The non-transitory computer-readable medium of claim 12.

14. 1. A method for multi-scanning in a microscope, comprising: - scanning the sample using at least a beam source of said microscope by emitting a beam towards the sample according to a first scanning path; determining a first number of particles associated with the sample at a first scan location using at least a detector of the microscope; determining whether to exclude or include the first scan location from a second scan pass based on a first comparison of the first particle count and a signal criterion; scanning the sample according to the second scan path using at least a beam source; generating sample acquisition data based on a total number of scan passes; A method comprising:

15. determining a total particle count, the total number of particles detected at the first scan location for the number of scan passes already completed; determining the difference between the total particle count and the signal criterion; determining whether to exclude or include the first scan location from one or more additional scan passes based on the difference, the one or more additional scan passes continuing until the difference is less than or equal to zero; 15. The method of claim 14, further comprising:

16. Each scan pass of the sample includes exposing each scan location determined to be included in the scan pass to the beam for a fixed dwell time, and excluding each scan location determined to be excluded from the scan pass from exposure to the beam.

15. The method of claim 14.

17. adjusting a dwell period for each scan location determined to be included in a subsequent scan pass based on the first number of particles detected at each scan location during the first scan pass; 15. The method of claim 14, further comprising:

18. determining whether there is a change in the sample by identifying at least one of i) expansion, ii) compression, iii) translation, or iv) shear in images of the sample generated between the first and second scan paths; reducing sample drift in a second image generated after the second scanning pass; 15. The method of claim 14, further comprising:

19. The method of claim 14 , wherein the signal criteria is in the range of 1 to 20 charged particles.

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