Method and system for dynamic band contrast imaging

Abstract

A dynamic band contrast image (DBCI) is constructed using scatter patterns acquired at multiple scan positions of a sample using a charged particle beam. Each pixel of the DBCI is produced by integrating a corresponding scatter pattern along a diffraction band. The DBCI includes charged particle passage conditions and can be used to detect sample defects.

Description

TECHNICAL FIELD

[0001] The present disclosure relates generally to methods and systems for imaging a sample with charged particles, and more particularly, to generating dynamic band contrast images using charged particles. BACKGROUND

[0002] Electron channeling contrast imaging (ECCI) based on backscattered electrons (BSE) can be used for non-destructive observation of crystal defects. The visibility of defects in ECCI depends on the Burgers vector b of the lattice distortion produced by dislocations or stacking faults in the lattice and the diffraction vector g of the crystal. A dislocation is invisible in ECCI if g · b = g · (b x u) = 0, where u is the line direction of the dislocation. ECCI is performed by tilting the sample plane into Bragg condition and collecting BSE by scanning the sample. The sample can be tilted into Bragg condition based on a selected area channel pattern (SACP) generated by rocking the primary beam on a pivot point on the sample. Alternatively, the sample can be tilted into Bragg condition based on orientation information extracted from electron backscatter diffraction (EBSD). If multiple grains are imaged, the sample must be tilted into Bragg condition for each grain. The sample tilting process in ECCI imaging is time consuming and can require hardware not available in conventional microscopy systems (e.g., a high precision stage capable of complex stage movements or a column with beam rocking functionality). SUMMARY

[0003] In one embodiment, a method for inspecting defects of a sample includes scanning a plurality of scan locations of the sample with a charged particle beam, forming a plurality of scattering patterns with charged particles emitted from the sample, where one scattering pattern is formed at each scan location of the plurality of scan locations, determining locations of diffraction bands in the plurality of scattering patterns, and constructing a dynamic band contrast image (DBCI) from the plurality of scattering patterns based on the locations of the diffraction bands. The DBCI contains channeling information and can be used to observe defects. Furthermore, DBCIs with different channeling conditions can be constructed based on the same set of acquired scattering patterns without tilting the sample relative to the incident beam. In this way, defects of the sample can be observed quickly and reliably with low radiation damage.

[0004] It is to be understood that the above general description is intended to be illustrative only and not restrictive on the scope of the claimed subject matter. It is not intended to identify key or essential features of the claimed subject matter. The claims, as set forth below, are intended to define the scope of the claimed subject matter and are not to be limited by the elements set forth in the general description or any portion thereof. BRIEF DESCRIPTION OF DRAWINGS

[0005] Figure 1 A scanning electron microscope imaging system for acquiring a dynamic band contrast image (DBCI) is shown in accordance with some embodiments.

[0006] Figure 2 is a high level flow chart for producing a DBCI.

[0007] Figure 3 A method for producing an overview sample image is shown.

[0008] Figure 4 A method for acquiring electron backscatter patterns (EBSPs) used to construct a DBCI is shown.

[0009] Figure 5 A method for constructing a DBCI is shown.

[0010] Figure 6 A process for constructing a DBCI is shown.

[0011] Figure 7 An example of an integrated EBSP and corresponding DBCI is shown.

[0012] Throughout the drawings, like reference numerals will be used to refer to like or corresponding parts throughout the several views. DETAILED DESCRIPTION

[0013] The following description relates to systems and methods for producing a dynamic band contrast image (DBCI) using a charged particle imaging system. Scattered charged particles emitted from a sample are collected with a position sensitive detector, such as a pixelated detector, in response to a plurality of scan positions of the sample. A scattering pattern is formed at each scan position. The scattering pattern can contain a plurality of Kikuchi lines. The DBCI is constructed with the scattering patterns. Each pixel of the DBCI corresponds to a scan position. The pixel value of the DBCI is an integration of a signal along a selected diffraction band in the scattering pattern acquired at the scan position. The selected diffraction band is chosen to contain at least a portion of a Kikuchi line in the scattering pattern. The image contrast of the DBCI is produced by channeling effects of charged particles within a lattice of a particular orientation (i.e., a particular channeling condition) and can be used to detect defects in a crystal structure of the sample.

[0014] In some embodiments, the charged particle imaging system is a scanning electron microscope (SEM) system. In one example, the sample surface is positioned normal to the primary electron beam. In another example, the sample surface is positioned at a non-zero angle to the primary axis of the electron beam. For example, the angle can be less than 45 degrees. Backscattered electrons (BSE) from the sample can be collected by a position sensitive BSE detector arranged between the pole piece and the sample. An electron backscatter pattern (EBSP) is generated based on the BSE collected at the scan positions. A DBCI can be constructed by integrating the EBSP along a selected diffraction band within the EBSP. The diffraction band can be selected manually by an operator or automatically by a controller of the imaging system.

[0015] The diffraction band within the EBSP can include at least a portion of a Kikuchi line of the EBSP. Since individual EBSPs can not have sufficient contrast for identifying Kikuchi lines, the Kikuchi lines can be identified from an integrated EBSP. The integrated EBSP is generated by integrating EBSPs of multiple scan positions within a grain. The grain contains crystal structures with the same orientation, or in other words, contains crystal structures with the same distribution of Kikuchi lines / bands. The grain boundaries can be identified based on a sample image. In one example, the sample image is a SEM image. In another example, the sample image can be constructed by integrating all BSEs acquired corresponding to each scan position, or in other words, by integrating pixels of EBSPs corresponding to each scan position. If multiple grains are contained in the field of view of the DBCI, the position of the selected diffraction band is determined for each grain based on the integrated EBSP generated for the grain. The diffraction band is selected to have a selective channeling condition. In one example, the diffraction band can be an entire Kikuchi line within the EBSP. In another example, the diffraction band can be a portion or portions of the Kikuchi line within the EBSP. Thus, different diffraction bands oriented differently in the EBSP contain electron channeling information at different crystal orientations. Multiple DBCIs with different diffraction bands can be generated to demonstrate different channeling conditions with respect to the crystal orientation. The location of crystal defects can be identified from multiple DBCIs of the same sample.

[0016] To reduce radiation damage to the sample, the EBSPs can be acquired via frame integration. Multiple scan positions can be repeatedly scanned with short dwell times. After each scan, the EBSPs of each scan position are updated by adding the newly acquired BSE frames to the current EBSP. The repeated scanning can be terminated when the quality of the acquired data is satisfied, for example, when the data quality is above a threshold data quality. The data quality can be measured by a parameter such as signal-to-noise ratio or image contrast. The acquired data can be grain boundaries in a sample image, Kikuchi lines / bands in an EBSP or an integrated EBSP, or a DBCI.

[0017] In this way, DBCTs with different electron channeling conditions can be constructed based on the same set of EBSPs. The EBSPs are acquired without tilting the sample relative to the incident beam. Furthermore, high quality images can be acquired with minimal radiation damage to the sample.

[0018] Referring to the drawings Figure 1 which illustrates an example SEM system 10 capable of producing DBCTs. The SEM system 10 can include an electron beam column 110 coupled to a sample chamber 120. The electron beam column 110 includes an electron source 102 for producing a high energy electron beam along a primary axis 104. The electron beam can be manipulated by lenses (106, 108, 118), deflectors (112, 114), and a beam limiting aperture (116) to form a finely focused spot on a sample 126.

[0019] The sample chamber 120 can optionally include a gas lock 122 for introducing a sample therein and placing the sample on a sample holder 124. The sample holder 124 can rotate or translate / offset the sample so that the sample surface can be irradiated by the finely focused electron beam at selectable tilt angles. The sample chamber 120 further includes one or more detectors for receiving particles emitted from the sample. The detectors can include an energy dispersive spectroscopy (EDS) detector 140 for detecting X-rays, a BSE detector 138 for detecting backscattered electrons, and an Everhart-Thornley detector 130 for detecting secondary electrons. The SEM system can also include an electron backscatter diffraction (EBSD) detector (not shown). The BSE detector 138 can be a position sensitive detector. For example, in response to an event of a single electron hitting the detector, data related to the event, such as the time of the hit, the relative hit location on the detector, and the energy of the electron can be transmitted from the detector to a controller 132. The BSE detector can further filter received electrons based on the energy of the received electrons. In one example, the BSE detector is a pixelated detector. The BSE detector can be positioned between a pole piece 150 of the electron beam column 110 and the sample holder 124. In some examples, the BSE detector can have a hole at the center to allow the electron beam to pass through. The BSE detector can acquire frames of BSEs in response to scanning locations of the sample. Both the electron beam column 110 and the sample chamber 120 can be connected with a high vacuum pump to evacuate the enclosed volumes.

[0020] In some embodiments, the voltages and / or currents required for the operation of the (magnetic or electrostatic) lenses and the electron source are generated / controlled by column controller 134, while controller 132 generates deflection signals for the deflector and samples the signals from the detector. Controller 132 can be connected to a display unit 136 for displaying information, such as an image of the sample. Controller 132 can also receive operator input from an input device 141. The input device can be a mouse, keyboard, or touchpad. The controller can translate, shift, or tilt the sample relative to the incident beam by moving the sample holder 124. Controller 132 can scan the sample with the electron beam by adjusting the position at which the electron beam hits the sample via the deflector 112 and / or 114.

[0021] Controller 132 can include a processor 135 and a non-transitory memory 137 for storing computer-readable instructions. By executing the computer-readable instructions stored in the non-transitory memory, the controller can implement the various methods disclosed herein. For example, controller 132 can be configured to process signals received from the BSE detector and generate SEM images, EBSPs, and DBCIs of the sample. Controller 132 can also include a field programmable gate array (FPGA) configured to process signals received from the various detectors.

[0022] Although an SEM system is described by way of example, it is understood that the imaging system can be other types of charged particle microscope systems, such as a transmission electron microscope (TEM), a scanning transmission electron microscope (STEM), or a dual beam tool, such as a focused ion beam combined with a scanning electron microscope (FIB-SEM). The current discussion of the SEM system is provided as an example of only one suitable imaging system for acquiring backscattered electrons.

[0023] Figure 2 is a method 200 for generating a DBCI using a charged particle system of an SEM system such as Figure 1 Based on the position of the selected diffraction band of the EBSP, the DBCI with electron channel contrast is constructed with the EBSPs acquired from the BSE detector. The DBCI can be updated and displayed in real-time during the EBSP acquisition. During the EBSP acquisition, the sample is not tilted relative to the incident beam.

[0024] At 202, an overview image of the sample is generated by scanning a first region of interest (ROI) with an electron beam, and a grain boundary within the first ROI can be identified in the overview image. The overview image can be a sample image that shows the structure of the sample. In one example, as Figure 3As shown, an overview image is acquired by repeatedly scanning a first ROI with a short dwell time at each scan position and integrating the BSE frames until grain boundaries can be identified. In another example, the overview image can be a conventional SEM image acquired via a single scan of the first ROI. In yet another example, the sample image is acquired by a detector other than the BSE detector.

[0025] In some embodiments, grain boundaries can be identified by comparing EBSPs acquired at different scanning positions. Changes in the EBSPs can indicate whether the corresponding scanning positions belong to different grains. For example, a first EBSP and a second EBSP are acquired at a first scanning position and a second scanning position, respectively. The difference between the first and second EBSPs is calculated and compared to a threshold difference. If the difference is greater than the threshold difference, the first and second scanning positions belong to different grains. In other words, if the difference between the EBSPs is greater than the threshold difference, the grain boundary is located between the first and second scanning positions.

[0026] At 204, an EBSP is acquired at each scan position of the second ROI, and the diffraction band position is identified based on the integrated EBSP. The integrated EBSP is generated by integrating the EBSP of the same grain to increase the contrast of the Kikuchi lines / bands of the scattering pattern. Figure 4 Details for obtaining the EBSP and identifying the diffraction band positions are shown in .

[0027] The second ROI may be within the first ROI. In one example, the second ROI is a connected region within the first ROI. In another example, the second ROI includes multiple disconnected regions within the first ROI. The second ROI may include the selective grains identified in step 202. The second ROI may be scanned at a higher resolution than the first ROI. In other words, the scanning step size between at least some adjacent scanning positions in the scanning of the second ROI is smaller than that in the scanning of the first ROI at 202. If any of the scanning positions of the second ROI is the same as the scanning position of the first ROI (i.e., the scanning position is repeated), the EBSP acquired at the repeated scanning position in step 202 may be used in step 204.

[0028] At 206, the EBSP of the second ROI is used to construct a DBCI with various channel conditions. Each pixel of the DBCI is calculated by integrating the EBSP pixels along the diffraction band corresponding to the selected channel condition. The details of the DBCI construction are given in Figure 5 In display.

[0029] At 208, the DBCI is saved or displayed on a screen. If more EBSPs are acquired, the DBCI can be updated using the newly acquired EBSPs and the updated DBCI is displayed. Thus, the operator can monitor the data acquisition process and assess the data quality in real time.

[0030] At 210, the quality of the DBCI is evaluated. The DBCI quality can be measured based on parameters such as image contrast and signal-to-noise ratio. Alternatively, the DBCI quality can be measured based on the visibility of sample defects. If the DBCI quality is above a threshold DBCI quality, the crystal defects in the sample can be located at 214. Otherwise, if the DBCI quality is not above the threshold DBCI quality, the second ROI is continuously scanned and the EBSPs are updated at 212. Then, the DBCI is constructed based on the updated EBSPs.

[0031] In some examples, the DBCI quality of each grain (or sub-region of the second ROI) can be evaluated individually. In response to the DBCI quality of a particular grain (or sub-region) being below a threshold DBCI quality, only the grain (or sub-region) with the lower DBCI quality is rescanned at 212. Thus, only the lower quality DBCI (or lower quality regions of the DBCI) is subsequently updated.

[0032] In some embodiments, instead of comparing the DBCI quality to a threshold DBCI quality, the operator can determine whether to continue scanning the second ROI based on the displayed DBCI. For example, the operator can terminate the scanning in response to sample defects visible in the DBCI.

[0033] In this way, the DBCI showing different electron channel conditions is constructed with the EBSPs of the ROI. Similar electron channel information can be obtained without tilting the sample relative to the incident beam compared to conventional ECCI. The duration and complexity of the data acquisition process is greatly reduced. Furthermore, during the EBSP acquisition, the DBCI with different channel conditions can be displayed and updated in real time, thus reducing unnecessary data acquisition and sample radiation damage.

[0034] Figure 3 An example method 300 for generating a sample image using BSE detectors is shown. The sample image can be acquired by repeatedly scanning a first ROI until grain boundaries can be identified.

[0035] At 302, a plurality of scan positions within the first ROI are scanned with a short dwell time. In response to illuminating each scan position with an electron beam, a frame of BSEs is acquired with a BSE detector positioned between the deflector and the sample. In some examples, the pixelated detector can include an electron energy filtering function, and the acquired BSEs can be BSEs with electron energies above a threshold energy level. Step 302 can include initiating an EBSP for each scan position. For example, the EBSP can be initiated by setting each pixel of the EBSP to zero. After each scan of the ROI, the EBSP is updated by integrating the newly acquired frame with the current EBSP. For example, at each scan position, a plurality of BSE frames acquired during multiple scans of the scan position are summed. In other words, the signals received at each pixel of the detector during the multiple scans are summed. Integrating the BSE frames can include averaging or normalizing the BSE frames.

[0036] At 304, a sample image of the first ROI is constructed with the updated EBSP. For example, each pixel of the sample image is obtained by summing the BSEs acquired at the corresponding scan position. In other words, each pixel of the sample image is obtained by summing all the pixels in the corresponding EBSP. The sample image is similar to a conventional SEM image and reveals the structure of the sample.

[0037] At 308, method 300 determines whether a grain boundary within the first ROI can be identified or recognized in the constructed sample image. The grain boundary can be automatically identified by the directional imaging microscope. In another example, the sample image can be displayed to an operator, and the operator determines whether the grain boundary can be recognized. In yet another example, instead of determining the grain boundary based on the constructed sample image, the grain boundary can be determined based on the variation of the EBSPs. For example, if the difference between the corresponding EBSPs is greater than a threshold difference, then the two scan positions belong to different grains. If the grain boundary can be identified, the grain boundary is determined and saved at 314. Otherwise, if the grain boundary cannot be identified, method 300 moves to 310.

[0038] At 310, if the total scan duration exceeds a threshold duration, method 300 exits. Otherwise, the first ROI is continuously scanned at 312.

[0039] Figure 4 A method 400 for acquiring EBSPs for producing DBCI is shown. The diffraction band position of each EBSP is determined by integrating the EBSP.

[0040] At 402, a second ROI for DBCI is selected. The second ROI can be within the first ROI. In some embodiments, the second ROI is the same as the first ROI. The second ROI can be selected based on the grain boundaries identified in the first ROI. For example, one or more grains in the first ROI can be selected as the second ROI for further analysis.

[0041] At 404, a plurality of scan locations in the second ROI are scanned with an electron beam, and EBSPs are updated based on the received BSEs. The scan locations of the second ROI can be denser than the scan locations of the first ROI. The EBSPs can be initialized to zero, with one scan location corresponding to one EBSP. The size of each EBSP is the same as the size of the pixelated detector. Similar to step 302 of method 300, after illuminating a scan location, a BSE frame is acquired. The EBSP corresponding to the scan location is updated by integrating the newly acquired BSE frame into the current EBSP.

[0042] At 406, an integrated EBSP is formed for each grain. The integrated EBSP can be formed by integrating, e.g., summing, at least some EBSPs belonging to the same grain. By integrating the EBSPs, the contrast of the scattering patterns, e.g., the Kikuchi lines in the integrated EBSP, can be improved.

[0043] At 408, the quality of the integrated EBSP is compared to a threshold integrated EBSP quality. The quality of the integrated EBSP can be evaluated based on parameters such as image contrast and signal-to-noise ratio. If the quality of the integrated EBSP is below the threshold integrated EBSP quality, the second ROI is scanned again and the integrated EBSP is updated at 410. If the quality of the integrated EBSP is above the threshold integrated EBSP quality, the Kikuchi lines can be identified in the integrated EBSP, and the positions of the diffraction bands can be determined in the integrated EBSP at 412.

[0044] At 412, the positions of the diffraction bands in each of the EBSPs are determined. The positions of the diffraction bands in the EBSPs are the same as the diffraction band positions in the corresponding integrated EBSP. Each diffraction band is aligned with a different Kikuchi line of the integrated EBSP and represents a different channel condition. In some embodiments, the Kikuchi lines are low-intensity lines on either side of a high-intensity Kikuchi band. The diffraction bands can be portions of the Kikuchi lines. For example, the diffraction bands can be portions of the Kikuchi lines that do not intersect with other Kikuchi lines. By selecting portions of the Kikuchi lines as the diffraction bands, crosstalk between different diffraction conditions can be avoided. The width of the diffraction bands can be 2-4 pixels.

[0045] Figure 5 A method 500 for constructing DBCI with selected channel conditions using EBSPs is demonstrated.

[0046] At 502, a channel condition is selected. The channel condition corresponds to a diffraction band in the EBSP. After the channel condition is selected, a particular diffraction band in the EBSP is selected. For EBSPs belonging to different grains, the location of the diffraction band with the same channel condition can be different.

[0047] For the scan position selected at 504, the EBSP signal along the selected diffraction band is integrated (e.g., summed) to produce a pixel value of the DBCI at the scan position. For example, the grain containing the scan position is first identified. Then, the location of the selected diffraction band in the integrated EBSP of the identified grain is obtained. The location of the selected diffraction band in the EBSP is the same as the location of the selected diffraction band in the integrated EBSP of the identified grain. After all scan positions in the second ROI are processed, the DBCI image with the selected channel condition is formed at 512. Otherwise, the method 500 moves to the next scan position at 510.

[0048] At 514, the method 500 checks whether all selected channel conditions are processed. If a DBCI with another channel condition needs to be constructed, the method 500 moves to 502. Otherwise, the method 500 exits.

[0049] In some embodiments, different grains in the DBCI can have different channel conditions. That is, the diffraction bands of at least two grains in the DBCI are along different Kikuchi lines of different crystal orientations. However, for each pixel within a single grain of the DBCI, the channel condition is the same.

[0050] Figure 6 The process of constructing the DBCI 630 from the EBSPs acquired from the ROI 601 is shown. The ROI 601 can be Figure 2 the second ROI of the ROI 610. The solid circles of the ROI 610 represent scan positions. The dashed lines within the ROI represent grain boundaries. The EBSPs can be acquired from Figure 2grain boundaries in the overview image of the first ROI. Alternatively, the grain boundaries can be identified based on the BSE received during the scanning of the ROI 601. The ROI 601 contains three grains (602, 603, and 604). The EBSPs of the scan locations within each grain are integrated into integrated EBSPs. EBSP 611 is acquired from a scan location of grain 602, and EBSP 612 is acquired from a scan location of grain 604. EBSP 611 is integrated into integrated EBSP 621, and EBSP 612 is integrated into integrated EBSP 622. Integrated EBSP 621 and integrated EBSP 622 are different. A diffraction band of a Kikuchi line along a particular channeling condition is selected. The location of diffraction band 623 in integrated EBSP 621 and the location of diffraction band 624 in integrated EBSP 622 are determined. For grain 602, the location of selected diffraction band 623 in integrated EBSP 621 and in EBSP 611 is the same. Similarly, for grain 604, the location of selected diffraction band 624 in integrated EBSP 622 and in EBSP 612 is the same. The pixel values along the selected diffraction band are summed to produce a pixel value of a DBCI. For example, EBSP 640 is acquired at scan location 605 within grain 602. The pixel values along diffraction band 623 are summed to produce a pixel value of corresponding pixel 635 in DBCI 630.

[0051] Figure 7 Example DBCIs for different diffraction channeling conditions of a sample containing a single grain are shown. The locations of four diffraction bands 711-714 in integrated EBSP 701 are determined based on a selected channeling condition. Each of the diffraction bands is aligned with a different Kikuchi line. Diffraction bands 711, 712, 713, and 714 represent channeling conditions along crystal orientations (-220), (2-20), (220), and (-2-20), respectively. DBCIs 702, 703, 704, and 705 are produced by integrating the EBSP signal along diffraction bands 711, 712, 713, and 714, respectively. DBCIs 702-705 are different, which reflects the different electron channeling effects in different crystal orientations.

[0052] The technical effect of constructing a DBCI using EBSPs based on selected diffraction bands is that the electron channeling effect can be seen without tilting the sample relative to the incident electron beam. The technical effect of forming an integrated EBSP is that Kikuchi lines can be identified in the integrated EBSP even if the image contrast of individual EBSPs is low. The technical effect of integrating EBSPs along diffraction bands to form a DBCI is that BSEs received under specific diffraction conditions are extracted. The technical effect of updating the DBCI as the sample is repeatedly scanned is to reduce sample radiation damage. In addition, it enables high quality data to be acquired in reduced duration.

[0053] In one embodiment, a method for imaging a sample includes: scanning a plurality of scan locations of the sample with a charged particle beam; acquiring charged particles emitted from the sample; forming a plurality of scatter patterns with the acquired charged particles, wherein one scatter pattern is formed at each scan location of the plurality of scan locations; determining a location of a diffraction band in the plurality of scatter patterns; and constructing a dynamic band contrast image (DBCI) from the plurality of scatter patterns based on the location of the diffraction band. In a first example of the method, the method further includes: determining a grain boundary of at least one grain of the sample; and wherein determining the location of the diffraction band in the plurality of scatter patterns includes determining the location of the diffraction band by integrating the plurality of scatter patterns within the grain boundary. A second example of the method optionally includes the first example and further includes: forming a sample image by integrating the acquired charged particles from each of the plurality of scan locations; and wherein determining the grain boundary includes determining the grain boundary based on the sample image. A third example of the method optionally includes one or more of the first and second examples and further includes: scanning a region of interest with the charged particle beam; forming a sample image with charged particles emitted from the region of interest; and wherein determining the grain boundary includes determining the grain boundary based on the sample image. A fourth example of the method optionally includes one or more of the first through third examples and further includes: wherein selecting a diffraction band based on the plurality of scatter patterns includes: forming an integrated scatter pattern based on the plurality of scatter patterns; and selecting the diffraction band by selecting at least a portion of a Kikuchi line of the integrated scatter pattern. A fifth example of the method optionally includes one or more of the first through fourth examples and further includes: in response to a quality of the DBCI being below a threshold quality level, updating the plurality of scatter patterns by rescanning the plurality of scan locations; and updating the DBCI based on the updated plurality of scatter patterns and the selected diffraction band. A sixth example of the method optionally includes one or more of the first through fifth examples and further includes: wherein the plurality of scan locations belong to a plurality of grains, wherein determining the location of the diffraction band in the plurality of scatter patterns includes selecting the diffraction band for each grain of the plurality of grains based on the plurality of scatter patterns of the grains, and wherein constructing the DBCI based on the plurality of scatter patterns and the location of the diffraction band includes constructing the DBCI based on the plurality of scatter patterns and the corresponding selected diffraction bands of the plurality of grains. A seventh example of the method optionally includes one or more of the first through sixth examples and further includes: determining a location of a second diffraction band in the plurality of scatter patterns, constructing a second DBCI based on the plurality of scatter patterns and the location of the second diffraction band.The eighth example of the method optionally includes one or more of the first through seventh examples and further includes wherein the second diffraction band has different channel conditions than the diffraction band.

[0054] In one embodiment, a method for imaging a sample includes scanning a plurality of scan locations of the sample with a charged particle beam; updating a plurality of scatter patterns based on backscattered charged particles accumulated from the sample during each scan, wherein each scatter pattern of the plurality of scatter patterns corresponds to one of the plurality of scan locations; determining a location of a diffraction band in the plurality of scatter patterns; and updating a dynamic band contrast image (DBCI) with signals from the plurality of scatter patterns and the location of the diffraction band. In a first example of the method, the method further includes wherein updating the DBCI with signals from the plurality of scatter patterns and the location of the diffraction band includes updating a pixel of the DBCI by integrating signals along the diffraction band of the scatter pattern corresponding to the particular pixel. A second example of the method optionally includes the first example and further includes wherein determining the location of the diffraction band in the plurality of scatter patterns includes forming an integrated scatter pattern by summing the plurality of scatter patterns and determining the location of the diffraction band relative to the plurality of scatter patterns based on Kikuchi lines in the integrated scatter pattern. A third example of the method optionally includes one or more of the first and second examples and further includes wherein the diffraction band is disposed along one of the Kikuchi lines in the integrated scatter pattern. A fourth example of the method optionally includes one or more of the first through third examples and further includes terminating scanning of the plurality of scan locations in response to a quality of the DBCI being above a threshold quality level.

[0055] In one embodiment, a system for imaging a sample includes a charged particle source for generating a charged particle beam along a principal axis; a sample holder for holding the sample; a deflector for scanning the charged particle beam over the sample; a detector between the deflector and the sample holder for collecting backscattered charged particles from the sample; and a controller including a non-transitory memory, wherein the non-transitory memory stores instructions that, when executed by the controller, cause the controller to: scan a plurality of scan positions of the sample with the charged particle beam; form a plurality of scatter patterns based on charged particles emitted from the sample, wherein at least one of the scatter patterns is formed at each scan position of the plurality of scan positions; select a diffraction band based on the plurality of scatter patterns; and construct a dynamic band contrast image (DBCI) based on the plurality of scatter patterns and the selected diffraction band. In a first example of the system, the system further includes wherein the detector is a position sensitive detector. A second example of the system optionally includes the first example and further includes wherein the non-transitory memory stores further instructions that, when executed by the controller, cause the controller to acquire a sample image; and select the plurality of scan positions based on the sample image. A third example of the system optionally includes one or more of the first and second examples and further includes wherein the sample is not tilted relative to the principal axis while scanning the plurality of scan positions. A fourth example of the system optionally includes one or more of the first through third examples and further includes wherein the non-transitory memory stores further instructions that, when executed by the controller, cause the controller to select a second different diffraction band, and construct a second DBCI based on the plurality of scatter patterns and the second diffraction band. A fifth example of the system optionally includes one or more of the first through fourth examples and further includes wherein the non-transitory memory stores further instructions that, when executed by the controller, cause the controller to locate a sample defect based on the DBCI.

Claims

1. A method for imaging a sample, comprising: scanning a plurality of scanning positions of the sample using a charged particle beam; acquiring charged particles emitted from the sample; forming a plurality of scattering patterns using the acquired charged particles, wherein one scattering pattern is formed at each of the plurality of scanning positions; forming an integrated scattering pattern based on the plurality of scattering patterns; determining positions of diffraction bands in the plurality of scattering patterns based on Kikuchi lines in the integrated scattering pattern; as well as A dynamic zone contrast image DBCI is constructed from the plurality of scattering patterns based on the positions of the diffraction zones.

2. The method according to claim 1, further comprising: determining a grain boundary of at least one grain of the sample; and wherein determining the position of the diffraction band within the plurality of scattering patterns comprises determining the position of the diffraction band by integrating the plurality of scattering patterns within the grain boundary.

3. The method according to claim 2, further comprising: forming a sample image by integrating the acquired charged particles from each of the plurality of scanning positions; And wherein determining the grain boundary includes determining the grain boundary based on the sample image.

4. The method according to claim 2, further comprising: A region of interest is scanned using the charged particle beam; a sample image is formed using charged particles emitted from the region of interest; and wherein determining the grain boundary includes determining the grain boundary based on the sample image.

5. The method according to any one of claims 1 to 4, further comprising: in response to a quality of the DBCI being below a threshold quality level, updating the plurality of scatter patterns by rescanning the plurality of scanning positions; The DBCI is updated based on the updated plurality of scattering patterns and the selected diffraction bands.

6. The method according to any one of claims 1 to 4, wherein The multiple scanning positions belong to multiple grains, wherein determining the position of the diffraction band in the multiple scattering patterns includes selecting the diffraction band for each of the multiple grains based on the multiple scattering patterns of the grains, and wherein constructing the DBCI based on the multiple scattering patterns and the positions of the diffraction bands includes constructing the DBCI based on the multiple scattering patterns and the corresponding selected diffraction bands of the multiple grains.

7. The method according to any one of claims 1 to 4, further comprising: determining a position of a second diffraction band in the plurality of scattering patterns; A second DBCI is constructed based on the plurality of scattering patterns and the position of the second diffraction zone.

8. The method according to claim 7, wherein: The second diffraction zone has a different channel condition than the first diffraction zone.

9. A method for imaging a sample, comprising: continuously scanning a plurality of scanning positions of the sample using a charged particle beam; updating a plurality of scatter patterns based on backscattered charged particles accumulated from the sample during each scan, wherein each scatter pattern in the plurality of scatter patterns corresponds to one of the plurality of scan positions; determining a location of a diffraction band in the plurality of scattering patterns; updating a dynamic zone contrast image DBCI using signals from the plurality of scattering patterns and the positions of the diffraction zones; and Responsive to the quality of the DBCI being above a threshold quality level, scanning of the plurality of scan positions is terminated.

10. The method according to claim 9, wherein: Updating the DBCI using signals from the plurality of scattering patterns and the positions of the diffraction bands includes updating the pixel of the DBCI by integrating signals along the diffraction band of the scattering pattern corresponding to a particular pixel.

11. The method according to claim 9, wherein Determining the position of the diffraction band in the plurality of scattering patterns comprises: forming an integrated scattering pattern by summing the plurality of scattering patterns; The position of the diffraction zone relative to the plurality of scattering patterns is determined based on the Kikuchi line in the integrated scattering pattern.

12. The method according to claim 11, wherein The diffraction zone is arranged along one of the Kikuchi lines in the integrated scattering pattern.

13. A system for imaging a sample, comprising: a charged particle source for generating a charged particle beam along the principal axis; a sample holder for holding the sample; a deflector for scanning the charged particle beam over the sample; a detector positioned between the deflector and the sample holder for collecting backscattered charged particles from the sample; as well as A controller comprising a non-transitory memory, wherein the non-transitory memory stores instructions that, when executed by the controller, cause the controller to: scanning the sample at a plurality of scanning positions with the charged particle beam; forming a plurality of scattering patterns based on charged particles emitted from the sample, wherein at least one of the scattering patterns is formed at each of the plurality of scanning positions; forming an integrated scattering pattern based on the plurality of scattering patterns; selecting a diffraction band by selecting at least a portion of the Kikuchi lines in the integrated scattering pattern; as well as A dynamic band contrast image DBCI is constructed based on the plurality of scattering patterns and the selected diffraction bands.

14. The system according to claim 13, wherein: The detector is a position sensitive detector.

15. The system of claim 13, wherein the non-transitory memory stores other instructions that, when executed by the controller, cause the controller to acquire a sample image; and select the plurality of scanning positions based on the sample image.

16. The system of claim 13, wherein: The sample is not tilted relative to the principal axis while scanning the plurality of scan positions.

17. The system of claim 13, wherein the non-transitory memory stores other instructions that, when executed by the controller, cause the controller to select a second different diffraction band and construct a second DBCI based on the plurality of scattering patterns and the second different diffraction band.

18. The system according to any one of claims 13 to 17, wherein: The non-transitory memory stores other instructions that, when executed by the controller, cause the controller to locate sample defects based on the DBCI.

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