阅读说明：本技术 用于动态带对比度成像的方法和系统 (Method and system for dynamic band contrast imaging ) 是由 T·维斯塔维尔 P·斯泰斯卡尔 于 2021-05-28 设计创作，主要内容包括：动态带对比度图像(DBCI)利用使用带电粒子束在样品的多个扫描位置处获取的散射图案来构造。通过沿着衍射带对对应散射图案进行积分来产生所述DBCI的每个像素。所述DBCI包含带电粒子通道条件,且可用于检测样品缺陷。(A Dynamic Band Contrast Image (DBCI) is constructed with scattering patterns acquired at multiple scan positions of a sample using a charged particle beam. Each pixel of the DBCI is generated by integrating a corresponding scattering pattern along a diffraction band. The DBCI includes charged particle channel conditions and can be used to detect sample defects.)

1. A method for imaging a sample, comprising:

scanning a plurality of scanning positions of the sample with 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 locations;

determining a location of a diffraction band 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.

2. The method of claim 1, further comprising: determining a grain boundary of at least one grain of the sample; and wherein determining the location of the diffraction zone in the plurality of scattering patterns comprises determining the location of the diffraction zone by integrating the plurality of scattering patterns within the grain boundaries.

3. The method of claim 2, further comprising: forming a sample image by integrating the acquired charged particles from each of the plurality of scan locations; and wherein determining the grain boundaries comprises determining the grain boundaries based on the sample image.

4. The method of claim 2, further comprising: scanning a region of interest with the charged particle beam; forming an image of the sample using the charged particles emitted from the region of interest; and wherein determining the grain boundaries comprises determining the grain boundaries based on the sample image.

5. The method of any of claims 1-4, wherein determining the location of a diffraction band in the plurality of scattering patterns comprises: forming an integral scattering pattern based on the plurality of scattering patterns; and determining the location of the diffraction zone relative to the plurality of scattering patterns based on the Juglans lines in the integrated scattering pattern.

6. The method of any one of claims 1 to 4, further comprising: in response to the quality of the DBCI being below a threshold quality level, updating the plurality of scattering patterns by rescanning the plurality of scan locations; and updating the DBCI based on the updated plurality of scattering patterns and the selected diffraction band.

7. The method of any of claims 1 to 4, wherein the plurality of scan locations belong to a plurality of grains, wherein determining the location of the diffraction zone in the plurality of scattering patterns comprises selecting the diffraction zone for each grain in the plurality of grains based on the plurality of scattering patterns of the grain, and wherein constructing the DBCI based on the plurality of scattering patterns and the location of the diffraction zone comprises constructing the DBCI based on the plurality of scattering patterns and corresponding selected diffraction zones of the plurality of grains.

8. The method of any one of claims 1 to 4, further comprising: determining a location of a second diffraction band in the plurality of scattering patterns; constructing a second DBCI based on the plurality of scattering patterns and the location of the second diffraction band.

9. The method of claim 8, wherein the second diffraction band has a different channel condition than the diffraction band.

10. A method for imaging a sample, comprising:

continuously scanning a plurality of scanning positions of the sample with a charged particle beam;

updating a plurality of scattering patterns during each scan based on backscattered charged particles accumulated from the sample, wherein each scattering pattern of the plurality of scattering patterns corresponds to one of the plurality of scan locations;

determining a location of a diffraction band in the plurality of scattering patterns; and

updating a Dynamic Band Contrast Image (DBCI) with signals from the plurality of scattering patterns and the location of the diffraction band.

11. The method of claim 10, wherein updating the DBCI with signals from the plurality of scattering patterns and the location of the diffraction band comprises: updating the pixels of the DBCI by integrating signals along the diffraction bands of the scattering pattern corresponding to a particular pixel.

12. The method of claim 10, wherein determining the location of the diffraction zone in the plurality of scattering patterns comprises: forming an integrated scattering pattern by summing the plurality of scattering patterns; and determining the location of the diffraction zone relative to the plurality of scattering patterns based on the Juglans lines in the integrated scattering pattern.

13. The method of claim 12, wherein the diffraction zone is disposed along one of the Kikuchi lines in the integrated scattering pattern.

14. The method of any one of claims 10 to 13, further comprising: terminating scanning of the plurality of scan locations in response to the quality of the DBCI being above a threshold quality level.

15. A system for imaging a sample, comprising:

a charged particle source for generating a beam of charged particles along a 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; 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:

scanning a plurality of scanning positions of the sample 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 locations;

selecting a diffraction band based on the plurality of scattering patterns; and

constructing a Dynamic Band Contrast Image (DBCI) based on the plurality of scattering patterns and the selected diffraction bands.

16. The system of claim 15, wherein the detector is a position sensitive detector.

17. The system of claim 15, wherein the non-transitory memory stores further instructions that, when executed by the controller, cause the controller to acquire a sample image; and selecting the plurality of scan locations based on the sample image.

18. The system of claim 15, wherein the sample is not tilted relative to the principal axis while scanning the plurality of scanning positions.

19. The system of claim 15, 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 scattering patterns and the second diffraction band.

20. The system of any of claims 15 to 19, 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.

Technical Field

The present invention relates generally to methods and systems for imaging samples with charged particles, and more particularly to generating dynamic band contrast images using charged particles.

Background

Electron Channel 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 lattice distorted berlyard vector b generated by dislocations or stacking faults in the crystal lattice and the diffraction vector g of the crystal. If g ∙ b = g ∙ (b × u) = 0, then the dislocations are not visible in the ECCI, where u is the line direction of the dislocations. ECCI is performed by tilting the sample plane into bragg conditions and collecting BSE by scanning the sample. The sample may be tilted into the bragg condition based on a Selected Area Channel Pattern (SACP) generated by rocking the main beam on a pivot point on the sample. Alternatively, the sample may be tilted into the bragg condition based on orientation information extracted from electron backscatter diffraction (EBSD). If multiple grains are imaged, the sample must be tilted into the Bragg condition for each grain. The sample tilt process in ECCI imaging is time consuming and may require hardware not available in conventional microscopy systems (e.g., a high precision stage capable of complex stage movements or a column with beam pan functionality).

Disclosure of Invention

In one embodiment, a method for inspecting a sample for defects includes: scanning a plurality of scanning positions of the sample with a charged particle beam; forming a plurality of scattering patterns with charged particles emitted from the sample, wherein one scattering pattern is formed at each of the plurality of scanning locations; determining a location of a diffraction band 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 includes channel information and can be used to observe defects. Furthermore, DBCIs with different channel conditions can be constructed based on the same set of acquired scattering patterns without tilting the sample with respect to the incident beam. In this way, sample defects can be observed quickly and reliably with low radiation damage.

It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.

Drawings

FIG. 1 illustrates a scanning electron microscope imaging system for acquiring a Dynamic Band Contrast Image (DBCI) in accordance with some embodiments.

FIG. 2 is a high level flow chart for generating a DBCI.

FIG. 3 illustrates a method for generating an overview sample image.

Fig. 4 illustrates a method for acquiring an electron backscatter pattern (EBSP) for constructing a DBCI.

Fig. 5 illustrates a method for constructing a DBCI.

Fig. 6 shows a process for constructing a DBCI.

Fig. 7 illustrates an example of integrating EBSPs and corresponding DBCIs.

Like reference numerals designate corresponding parts throughout the several views of the drawings.

Detailed Description

The following description relates to systems and methods for generating a Dynamic Band Contrast Image (DBCI) using a charged particle imaging system. Scattered charged particles emitted from the sample are collected with a position sensitive detector, such as a pixelated detector, in response to a plurality of scan positions at which the sample is scanned. A scattering pattern is formed at each scanning position. The scattering pattern may comprise a plurality of daisy-chain lines. The DBCI is constructed with a scattering pattern. Each pixel of the DBCI corresponds to a scanning position. The pixel value of the DBCI is the integral of the signal along a selected diffraction band in the scattering pattern acquired at the scan location. The diffraction bands are selected to include at least a portion of the Kikuchi lines in the scattering pattern. The image contrast of DBCI results from the channeling of charged particles within a crystal lattice in a particular orientation (i.e., a particular channel condition) and can be used to detect defects in the crystal structure of a sample.

In some embodiments, the charged particle imaging system is a Scanning Electron Microscope (SEM) system. In one example, the sample surface is positioned vertically with respect to the primary electron beam. In another example, the sample surface is positioned at a non-zero angle relative to the main axis of the electron beam. For example, the angle may be less than 45 degrees. Backscattered electrons (BSE) from the sample may be collected by a position sensitive BSE detector disposed between the pole piece and the sample. An electron backscatter pattern (EBSP) is generated based on the BSE collected at the scan location. The DBCI can be constructed by integrating the EBSP along selected diffraction bands within the EBSP. The diffraction bands may be manually selected by an operator or automatically selected by a controller of the imaging system.

The diffraction bands within an EBSP may comprise at least a portion of the cisterna line of the EBSP. Since individual EBSPs may not have sufficient contrast for identifying the tanacetum line, the tanacetum line may be identified from the integrated EBSPs. The integrated EBSP is generated by integrating the EBSP at a plurality of scanning positions within a grain. The grains contain a crystal structure with the same orientation or, in other words, with the same distribution of the daisy-chain/ribbon. Grain boundaries may be identified based on the sample image. In one example, the sample image is a SEM image. In another example, the sample image may be constructed by integrating all of the BSEs acquired corresponding to each scan location, or in other words, by integrating the pixels of the EBSPs corresponding to each scan location. If multiple grains are contained in the field of view of the DBCI, the location of the selected diffraction band is determined for each grain based on the integrated EBSP generated for the grain. The diffraction bands are selected to have selective channel conditions. In one example, the diffraction zone may be the entire Julian line within the EBSP. In another example, the diffraction zone may be a portion or portions of the Julian line within the EBSP. Thus, different diffraction bands oriented differently in an EBSP contain electron channel information at different crystal orientations. Multiple DBCIs with different diffraction bands can be generated to exhibit different channel conditions relative to the crystal orientation. The location of the crystal defect can be identified from multiple DBCIs of the same sample.

To reduce radiation damage to the sample, EBSP may be acquired via frame integration. Multiple scan locations can be repeatedly scanned with short dwell times. After each scan, the EBSP for each scan location is updated by adding the newly acquired BSE frame to the current EBSP. The repetitive scanning may be terminated when the quality of the acquired data is met, for example when the data quality is above a threshold data quality. Data quality may be measured by parameters such as signal-to-noise ratio or image contrast. The data acquired may be grain boundaries in the sample image, daisy chain/band in EBSP or integral EBSP, or DBCI.

In this way, DBCIs with different electronic channel conditions can be constructed based on the same set of EBSPs. EBSP was acquired without tilting the sample relative to the incident beam. Furthermore, high quality images can be acquired with minimal radiation damage to the sample.

Turning to fig. 1, an example SEM system 10 capable of generating DBCIs is illustrated. SEM system 10 may include an electron beam column 110 coupled to a sample chamber 120. The electron beam column 110 contains an electron source 102 for generating a high energy electron beam along a main axis 104. The electron beam may be manipulated by lenses (106, 108, 118), deflectors (112, 114) and beam limiting apertures (116) to form a finely focused spot on the sample 126.

Sample chamber 120 may optionally include a damper 122 for introducing a sample therein and placing the sample on a sample holder 124. The sample holder 124 may rotate or translate/deflect the sample so that the sample surface may be irradiated by a finely focused electron beam at a selectable tilt angle. Sample chamber 120 further includes one or more detectors for receiving particles emitted from the sample. The detectors may 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 may also include an electron backscatter diffraction (EBSD) detector (not shown). The BSE detector 138 may be a position sensitive detector. For example, in response to an event in which a single electron strikes a detector, data relating to the event, such as the time of the strike, the relative location of the strike on the detector, and the energy of the electron, may be transmitted from the detector to the controller 132. The BSE detector may further filter the received electrons based on their energy. In one example, the BSE detector is a pixilated detector. The BSE detector may be positioned between the pole piece 150 of the electron beam column 110 and the sample holder 124. In some examples, the BSE detector may have a hole at the center to allow the electron beam to pass through. The BSE detector may acquire a frame of BSE in response to a scan position of the illuminated sample. Both the electron beam column 110 and the sample chamber 120 may be connected to a high vacuum pump to evacuate the enclosed volume.

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

The controller 132 may include a processor 135 and a non-transitory memory 137 for storing computer readable instructions. The controller may implement the various methods disclosed herein by executing computer readable instructions stored in non-transitory memory. For example, the controller 132 may be configured to process signals received from the BSE detector and generate SEM images, EBSPs, and DBCIs of the sample. The controller 132 may also contain a Field Programmable Gate Array (FPGA) configured to process signals received from the various detectors.

Although SEM systems are described by way of example, it should be understood that the imaging system may be other types of charged particle microscopy systems, such as Transmission Electron Microscopy (TEM), Scanning Transmission Electron Microscopy (STEM), or dual beam tools, such as focused ion beam in combination with scanning electron microscopy (FIB-SEM). The present discussion of SEM systems is provided merely as an example of one suitable imaging system for acquiring backscattered electrons.

Fig. 2 is a top level flow diagram of a method 200 for generating a DBCI using a charged particle system, such as the SEM system of fig. 1. The EBSPs acquired from the BSE detector are used to construct a DBCI with electron channel contrast based on the location of the selected diffraction band of the EBSP. During EBSP acquisition, the DBCI may be updated and displayed in real-time. During EBSP acquisition, the sample is not tilted with respect to the incident beam.

At 202, an overview image of the sample is generated by scanning a first region of interest (ROI) with an electron beam, and grain boundaries within the first ROI may be identified in the overview image. The overview image may be a sample image showing the structure of the sample. In one example, as shown in FIG. 3, an overview image is acquired by repeatedly scanning the first ROI at each scan location with a short dwell time and integrating the BSE frame until the grain boundaries can be identified. In another example, the overview image may 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 different from the BSE detector.

In some embodiments, grain boundaries may be identified by comparing the acquired EBSPs at different scan locations. A change in EBSP may indicate whether the corresponding scan location belongs to a different die. For example, a first EBSP and a second EBSP are acquired at a first scan position and a second scan position, respectively. The difference between the first EBSP and the second EBSP is calculated and compared to a threshold difference. If the difference is greater than the threshold difference, the first scan location and the second scan location belong to different dies. In other words, if the difference between EBSPs is greater than the threshold difference, the grain boundary is located between the first scan position and the second scan position.

At 204, the EBSP at each scan position of the second ROI is acquired and diffraction zone positions are identified based on the integrated EBSP. The integrated EBSP is generated by integrating EBSPs of the same grains to increase the contrast of the daisy chain/band of the scattering pattern. Details for acquiring EBSP and identifying diffraction band positions are shown in figure 4.

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 contains a plurality of disconnected regions within the first ROI. The second ROI may contain 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 scan step size between at least some adjacent scan positions is smaller in the scan of the second ROI than in the scan of the first ROI at 202. If any of the scan positions of the second ROI is the same as the scan position of the first ROI (i.e., the scan positions are repeated), the EBSP acquired at the repeated scan position of step 202 may be used in step 204.

At 206, DBCIs with various channel conditions are constructed with EBSPs for the second ROI. Each pixel of the DBCI is computed by integrating the EBSP pixels along the diffraction band corresponding to the selected channel condition. Details of the construction of the DBCI are shown in fig. 5.

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

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, DBCI quality can be measured based on the visibility of sample defects. If the DBCI mass is above the threshold DBCI mass, crystal defects in the sample may be located at 214. Otherwise, if the DBCI quality is not above the threshold DBCI quality, then the second ROI is continuously scanned and the EBSP is updated at 212. Next, the DBCI is constructed based on the updated EBSP.

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

In some embodiments, instead the DBCI quality is compared to a threshold DBCI quality. The operator may determine whether to continue scanning the second ROI based on the displayed DBCI. For example, an operator may terminate a scan in response to a sample defect visible in the DBCI.

In this way, DBCIs showing different electronic channel conditions are constructed with the EBSP of the ROI. Similar electronic channel information can be obtained without tilting the sample with respect to the incident beam, compared to conventional ECCI. The duration and complexity of the data acquisition process is greatly reduced. Furthermore, during EBSP acquisition, DBCIs with different channel conditions can be displayed and updated in real time, thereby reducing unnecessary data acquisition and sample radiation damage.

Fig. 3 illustrates an example method 300 for generating an image of a sample using a BSE detector. An image of the sample may be acquired by repeatedly scanning the first ROI until grain boundaries can be identified.

At 302, a plurality of scan locations within a first ROI are scanned with a short dwell time. In response to irradiating each scan location with an electron beam, a frame of BSE is acquired with a BSE detector positioned between the deflector and the sample. In some examples, the pixelated detector may include an electron energy filtering function, and the acquired BSE may be a BSE having an electron energy above a threshold energy level. Step 302 may include initiating EBSPs for each scan location. For example, an EBSP may 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 location, a plurality of BSE frames acquired during a plurality of scans of the scan location are summed. In other words, the signals received at each pixel of the detector during a plurality of scans are summed. Integrating the BSE frame may include averaging or normalizing the BSE frame.

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 positions. In other words, each pixel of the sample image is obtained by summing all pixels in the corresponding EBSP. The sample image is similar to a conventional SEM image and shows the structure of the sample.

At 308, the method 300 determines whether grain boundaries within the first ROI can be identified or recognized in the constructed sample image. Grain boundaries can be automatically identified by a directional imaging microscope. In another example, the sample image may be displayed to an operator, and the operator determines whether grain boundaries can be identified. In yet another example, grain boundaries are not determined based on the constructed sample image, but may be determined based on variations in EBSP. For example, if the difference between corresponding EBSPs is greater than the threshold difference, then the two scan locations belong to different dies. If grain boundaries can be identified, the grain boundaries are determined and saved at 314. Otherwise, if the grain boundaries cannot be identified, the method 300 moves to 310.

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

Fig. 4 illustrates a method 400 for obtaining EBSPs for generating DBCIs. The diffraction band position of each EBSP is determined by the integrating EBSP.

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

At 404, a plurality of scan locations in the second ROI are scanned with the electron beam and the EBSP is updated based on the received BSE. The scan positions of the second ROI may be denser than the scan positions of the first ROI. EBSPs may be initiated as zero, with one scan position 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 the scan location, a BSE frame is acquired. The EBSP corresponding to the scan position is updated by integrating the newly acquired BSE frame as the current EBSP.

At 406, an integral EBSP is formed for each die. The integrated EBSPs may be formed by integrating, e.g., summing, at least some of the EBSPs belonging to the same grain. By integrating the EBSP, the contrast of the scattering pattern (e.g., the daisy-chain in the integrated EBSP) may be improved.

At 408, the quality of the integrated EBSP is compared to a threshold integrated EBSP quality. The quality of the integrated EBSP may 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 Julian line may be identified in the integrated EBSP and the location of the diffraction band may be determined in the integrated EBSP at 412.

At 412, the location of the diffraction band in each of the EBSPs is determined. The position of the diffraction band in the EBSP is the same as the position of the diffraction band in the corresponding integrating EBSP. Each diffraction band is aligned with a different chrysanthemic line of the integrating EBSP and represents a different channel condition. In some embodiments, the tanacetum line is a low intensity line on either side of the high intensity tanacetum belt. The diffraction band may be a portion of the Julian line. For example, the diffraction bands may be portions of the Juglans lines that do not intersect other Juglans lines. By choosing the part of the Kikuchi line as the diffraction zone, cross-talk between different diffraction conditions can be avoided. The width of the diffraction band may be 2-4 pixels.

Fig. 5 illustrates a method 500 for constructing a DBCI for a selected channel condition using EBSP.

At 502, channel conditions are selected. The channel conditions correspond to the diffraction bands in the EBSP. After the channel conditions are selected, a particular diffraction band in the EBSP is selected. For EBSPs belonging to different grains, the positions of diffraction bands having the same channel condition may be different.

For the scan location selected at 504, the EBSP signals along the selected diffraction band are integrated (e.g., summed) to produce a pixel value of DBCI at the scan location. For example, a die containing a scan location is first identified. Next, the position of the selected diffraction band in the integrated EBSP of the identified grains is obtained. The position of the selected diffraction band in the EBSP is the same as the position of the selected diffraction band in the integrated EBSP of the identified grains. After all scan locations in the second ROI are processed, a DBCI image with selected channel conditions is formed at 512. Otherwise, the method 500 moves to the next scan position at 510.

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

In some embodiments, different grains in the DBCI may have different channel conditions. That is, the diffraction bands of at least two grains in the DBCI follow the daisy chain of different crystallographic orientations. However, the channel conditions are the same for each pixel within a single grain of the DBCI.

Fig. 6 shows a process of constructing a DBCI 630 from EBSPs acquired from the ROI 601. The ROI 601 may be the second ROI of fig. 2. The filled circles of the ROI 610 represent the scan positions. The dashed lines within the ROI indicate grain boundaries. Grain boundaries may be identified from the overview image of the first ROI of fig. 2. Alternatively, grain boundaries may be identified based on the BSE received during the scan of the ROI 601. The ROI 601 includes three grains (602, 603, and 604). The EBSP of the scan location within each grain is integrated into an integrated EBSP. EBSP 611 is obtained from the scanned position of die 602 and EBSP 612 is obtained from the scanned position of die 604. EBSP 611 is integrated into integral EBSP 621 and EBSP 612 is integrated into integral EBSP 622. Integration EBSP 621 and integration EBSP 622 are different. The diffraction bands of the Kikuchi lines along a particular channel condition were selected. The location of diffraction band 623 in integrating EBSP 621 and the location of diffraction band 624 in integrating EBSP 622 are determined. The position of selected diffraction band 623 at each of integrating EBSP 621 and EBSP 611 is the same for grain 602. Similarly, for grain 604, the position of selected diffraction zone 624 is the same for each of integrated EBSP 622 and EBSP 612. The pixel values along the selected diffraction band are summed to produce a pixel value for the DBCI. For example, EBSP 640 is acquired at scan location 605 within die 602. The pixel values along the diffraction band 623 are summed to produce a pixel value for the corresponding pixel 635 in the DBCI 630.

Fig. 7 shows exemplary DBCIs for different diffraction channel conditions for samples containing a single grain. The locations of the four diffraction bands 711 and 714 in integrating EBSP 701 are determined based on the selected channel conditions. Each of the diffraction bands is aligned with a different chrysanthemic line. Diffraction bands 711, 712, 713, and 714 represent channel conditions along the crystallographic orientations (-220), (2-20), (220), and (-2-20), respectively. The DBCIs 702, 703, 704, and 705 are generated by integrating the EBSP signals along diffraction bands 711, 712, 713, and 714, respectively. The DBCI 702-705 is different, reflecting different electron channel effects in different crystal orientations.

The technical effect of constructing a DBCI using EBSP based on a selected diffraction band is that electron channeling can be seen without tilting the sample relative to the incident electron beam. The technical effect of forming the integrated EBSPs is that the daisy chain can be identified in the integrated EBSPs even if the image contrast of the individual EBSPs is low. The technical effect of integrating EBSPs along the diffraction bands to form DBCIs is to extract the BSE received under certain diffraction conditions. The technical effect of updating the DBCI when repeatedly scanning the sample is to reduce sample radiation damage. Furthermore, it enables high quality data to be acquired with reduced duration.

In one embodiment, a method for imaging a sample comprises: scanning a plurality of scanning positions of the sample with 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; determining a location of a diffraction band 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. In a first example of the method, the method further comprises: determining a grain boundary of at least one grain of the sample; and wherein determining the location of the diffraction zone in the plurality of scattering patterns comprises determining the location of the diffraction zone by integrating the plurality of scattering patterns within the grain boundaries. 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 boundaries comprises determining the grain boundaries 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 an image of the sample using the charged particles emitted from the region of interest; and wherein determining the grain boundaries comprises determining the grain boundaries 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 scattering patterns comprises: forming an integral scattering pattern based on the plurality of scattering patterns; and selecting the diffraction band by selecting at least a portion of the Julian lines of the integral scattering pattern. A fifth example of the method optionally includes one or more of the first through fourth examples and further includes: updating the plurality of scattering patterns by rescanning the plurality of scan locations in response to the quality of the DBCI being below a threshold quality level; and updating the DBCI based on the updated plurality of scattering 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 zone in the plurality of scattering patterns comprises selecting the diffraction zone for each grain of the plurality of grains based on the plurality of scattering patterns of the grain, and wherein constructing the DBCI based on the plurality of scattering patterns and the location of the diffraction zone comprises constructing the DBCI based on the plurality of scattering patterns and the corresponding selected diffraction zone 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 scattering patterns, constructing a second DBCI based on the plurality of scattering patterns and the location of the second diffraction band. An 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 a different channel condition than the diffraction band.

In one embodiment, a method for imaging a sample comprises: scanning a plurality of scanning positions of the sample with a charged particle beam; updating a plurality of scattering patterns during each scan based on the backscattered charged particles accumulated from the sample, wherein each scattering pattern of the plurality of scattering patterns corresponds to one of the plurality of scan locations; determining a location of a diffraction band in the plurality of scattering patterns; and updating a Dynamic Band Contrast Image (DBCI) using signals from the plurality of scattering patterns and the locations of the diffraction bands. In a first example of the method, the method further comprises: wherein updating the DBCI with signals from the plurality of scattering patterns and the location of the diffraction band includes updating pixels of the DBCI by integrating signals along the diffraction band of the scattering pattern corresponding to a 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 scattering patterns comprises forming an integrated scattering pattern by summing the plurality of scattering patterns and determining the location of the diffraction band relative to the plurality of scattering patterns based on Julian lines in the integrated scattering pattern. A third example of the method optionally includes one or more of the first and second examples and further includes: wherein the diffraction bands are arranged along one of the Kikuchi lines in the integrated scattering 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 the quality of the DBCI being above a threshold quality level.

In one embodiment, a system for imaging a sample, comprising: a charged particle source for generating a beam of charged particles along a principal axis; a sample holder for holding the sample; a deflector for scanning the charged particle beam over the sample; a detector located 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: scanning a plurality of scanning positions of the sample 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 locations; selecting a diffraction band based on the plurality of scattering patterns; and constructing a Dynamic Band Contrast Image (DBCI) based on the plurality of scattering patterns and the selected diffraction bands. In a first example of the system, the system further comprises: 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 selecting the plurality of scan locations 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 with respect to the principal axis while scanning the plurality of scanning 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 scattering 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 other instructions that, when executed by the controller, cause the controller to locate a sample defect based on the DBCI.