Multi-detector real-time chemical imaging

Abstract

The present invention relates to multi-detector real-time chemical imaging. A method for analyzing a sample in a microscope is provided. The method comprises: acquiring a series of compound image frames using an electron detector, a first X-ray detector, and a second X-ray detector; using the electron detector to monitor a group of generated electrons emitted from multiple positions within a sample area to obtain a first image frame; using the first X-ray detector and the second X-ray detector to monitor the first group of generated X-rays and the second group of generated X-rays emitted from multiple positions, respectively, to obtain one or more second image frames, wherein the group of electrons and the first group of X-rays and the second group of X-rays are emitted from the sample substantially simultaneously; and combining the first image frame and one or more second image frames to generate a compound image frame. A system for analyzing a sample in a microscope is also provided.

Description

Technical Field

[0001] The present invention relates to a method and system for acquiring analytical imaging data of a sample in an electron microscope, which method and system use multiple X-ray detectors as well as electron detectors to improve navigation and provide elemental analysis of the sample with high data quality and at high speed. Background Art

[0002] Figure 1 A common system for exploring a sample surface in a scanning electron microscope (SEM) is shown. An electron beam is generated in a vacuum chamber and is usually focused using a combination of magnetic or electrostatic lenses. When the electron beam strikes the sample, some of the electrons scatter back from the sample (backscattered electrons or BSEs), or interact with the sample to produce secondary electrons (SEs) and many other emissions, such as X-rays.

[0003] Figure 2 A known apparatus for performing X-ray analysis in a scanning electron microscope (SEM) 100 is shown.

[0004] In conventional analysis, the X-ray spectrum is measured by sensing and measuring the energy of individual X-ray photons emitted when the sample 101 is struck by a focused electron beam 102. (Note that in this document, it is conventional that the electron beam propagates vertically downward toward the sample, which is the context of words such as "below" and "above". In practice, the electron beam can be oriented in any direction, including vertically upward.) Each X-ray photon is an energetic particle, and the energy is converted into an electric charge related to the X-ray energy, typically using a solid-state detector 105. The charge is measured so that the counts can be recorded; a bar graph of the recorded measurements represents the digitized X-ray energy spectrum. Peaks characteristic of chemical elements can be identified in the X-ray energy spectrum, and the intensity of these peaks is used as the basis for determining the elemental content in the material directly below the electron beam 102.

[0005] The X-ray detector 105, the final polepiece of the electron microscope 104 and the sample 101 are typically all within the same vacuum chamber. It is primarily necessary to accelerate the electrons to an energy of a few keV through the vacuum and focus them into a narrow beam without scattering on gas molecules. However, there are alternative configurations in which the electron beam can be focused within a vacuum region while the sample is in a region of higher pressure. The X-ray detector can be located in the same vacuum region as the electron beam, or in a region of higher pressure. In addition to the X-ray signal, the signal of the backscattered electrons (BSE) from the sample can also be used to distinguish different materials, since the fraction of electrons backscattered from a material increases with the average atomic number (Z) of the material. Therefore, a backscattered electron detector (BSED) is typically located above the sample 101 and below the pole piece 104. The BSED detector 106 typically includes one or more sensor segments arranged around a central hole through which the focused beam 102 passes to reach the sample. This positioning is designed to maximize the collection solid angle subtended by the BSED segments at the point where the focused beam strikes the sample (the "probe spot"), thereby maximizing the BSE signal. An additional detector (usually an "Everhart-Thornley" type) is mounted on one side of the chamber to detect secondary electrons generated in the sample and emitted from the surface, thereby generating the "SE" signal. The SE signal is typically much stronger than the BSE signal and is very sensitive to the orientation of the surface relative to the incident beam.

[0006] If the focused incident beam is rastered or scanned in some other pattern by magnetic or electrostatic deflection and sequentially positioned on a 2D grid of pixel locations on the sample surface, the SE or BSE signal at each location can be used to construct a digital image that can be displayed on a monitor and gives a magnified view of the sample. This is a well-known principle of operation of a scanning electron microscope (SEM), and in particular the SE image is very useful for navigating around a sample because it shows the topography of the surface. If there is any topography on the sample, any tilted surface facets will also produce a BSE signal that depends on the orientation of the facets and will be stronger in certain directions. The BSE signal is stronger for sensor areas in the tilted direction of the facets facing away from the electron beam normal, and weaker for sensors in the opposite direction. This sensitivity to surface tilt produces "topography contrast" in the image that interferes with the "atomic number contrast" or "Z contrast" produced by variations in material composition within the scanned area. In order to minimize the directional effects of topography on the BSE signal, the total sensitive area of ​​the BSE detector must be arranged symmetrically with respect to the incident electron beam. Ideally, the sensitive area would be a disk with perfect rotational symmetry around the central hole, but there are certain benefits to using multiple independent sensor segments to make up the total sensitive area while maintaining rotational symmetry. A "4-quadrant" arrangement with 4-fold rotational symmetry is common, see for example the Micron Semiconductor catalog:

[0007] http: / / 79.170.44.80 / micronsemiconductor.co.uk / wp-content / uploads / 2017 / 03 / MSL-OEM-Catalogues.pdf.

[0008] It is well known that if all segments of a multi-segment BSE detector are used to collect electrons symmetric about the beam, then "atomic number" contrast rather than topographic contrast dominates. See, for example, the Wikipedia entry:

[0009] https: / / en.wikipedia.org / wiki / Scanning_electron_microscope#Detection_of_backscattered_electrons.

[0010] Therefore, having the BSE detector located at 106 just below the pole piece not only provides good collection efficiency of the BSE signal, but also enables the collection of a signal that is more representative of the average atomic number of the material rather than local surface tilt. The BSE signal at each pixel position can be used to construct an image, where each pixel intensity represents the atomic number of the material at that position.

[0011] The same position 106 can also be used to maximize the collection solid angle of the annular X-ray detector. However, replacing the BSED with an X-ray detector at position 106 will make it impossible to detect the BSE signal that is insensitive to topography. Soltau et al. (Microsc Microanal 15 (Suppl 2), 2009, 204 5) proposed a method to overcome this problem by surrounding the ring of sensor segments of the BSE with an outer ring of X-ray sensor segments.

[0012] The BSE detector segments are closest to the central aperture and are arranged symmetrically around the central aperture, while the X-ray detector segments, which are also arranged symmetrically, are farther from the central aperture.

[0013] While this arrangement brings both the BSED and the X-ray sensor segments close to the sample and preserves the 4-fold rotational symmetry of the total sensitive area of ​​the BSED, the collection solid angle of the X-ray sensor segments is compromised by being placed away from the central hole to accommodate the BSED sensors. Furthermore, if the individual X-ray sensor segments are of the "Silicon Drift Detector" (SDD) type (see, for example, https: / / en.wikipedia.org / wiki / Silicon_drift_detector), for a given area, the best response time is obtained for a circular sensor segment, so the elongated shape of the X-ray sensor segments in a surrounding ring arrangement is not optimal for response time for a given sensitive area.

[0014] The X-ray detector segments will also be sensitive to backscattered electrons, and since there are several orders of magnitude more BSEs than X-rays striking the sensor segments, the BSE signal will typically swamp the small X-ray signal and prevent the acquisition of a useful X-ray spectrum. Therefore, a filter material of appropriate thickness needs to be inserted between the sample and the sensor to prevent the transmission of the highest energy BSEs while allowing low energy X-rays to pass through the sensor. Liebel et al. (Microsc. Microanal. 20 (Suppl 3), 2014 1118-9) propose an arrangement using a combined BSE and X-ray sensor with a filter in front of the X-ray sensor.

[0015] In a SEM with an EDS (Energy Dispersive X-ray Spectrometer) configuration, the X-ray signal is very weak compared to the electron signal. The conventional analysis method uses a real-time updating electronic image with a refresh rate fast enough that the operator can continuously observe the changing field of view on the sample as he searches around the sample surface to find potential target areas. Once the target area is located, X-ray data is collected from that area and the electron image is enhanced with chemical elemental composition information derived from the X-ray data, either as an additional image of the target field of view or usually by color blending combined with the electronic data (image brightness and contrast) in a single composite image. If the composition information shows that the area is not the target area, the search is resumed using the real-time updating electronic image. This process can be very inefficient because some areas with important compositional content may be missed because the operator can only make decisions based on the brightness and shape information conveyed by the electronic image, which is not necessarily consistent with the composition changes.

[0016] The method described in WO2019 / 016559 involves acquiring X-ray data simultaneously with electronic signal data, so that the real-time updated image can be enhanced with chemical element composition information at the same refresh rate, and thus provide more visual cues to help the operator find target areas that are more likely to be suitable for more detailed analysis.

[0017] When collecting X-ray image frames or elemental maps that refresh quickly enough and have high enough spatial resolution to display useful information about the sample to the operator when the image changes (for example, by moving the sample or changing the magnification), conventional EDS detectors can only produce sufficient signal when using very high beam currents.

[0018] The beam current that can be obtained depends on the type of electronic components. In order to obtain a high beam current, the SEM lens and aperture configuration must usually be changed, which usually results in an increase in the beam diameter and some loss of spatial resolution. In addition, high beam currents may damage some samples.

[0019] Even at a beam current where the sample is elastic and the spatial resolution is acceptable, it is desirable to obtain as much X-ray signal as possible to improve the quality of the compositional information.

[0020] One way to increase the solid angle and thus the X-ray signal is to use multiple conventional EDS detectors. Systems with up to four detectors have been used to collect data on particle separation to quantify the release of ore minerals (e.g., Pirrie et al. 2009, DOI: 10.1007 / 978-1-4020-9204-6_26). Such systems can increase throughput, but still use high beam currents because the solid angles obtained are not significantly greater than those produced by the largest single conventional EDS detector. In addition, such systems are expensive, require a dedicated electron microscope arrangement, occupy most ports, and severely limit the availability of other sensors and the operation of the electron microscope.

[0021] An X-ray detector located just above the sample and below the pole piece can provide a greater increase in X-ray signal if the X-ray detector is close enough to the sample.

[0022] However, in this location, there is usually not enough room to accommodate a magnet to deflect the backscattered electrons from the sample, and a layer of suitable material needs to be inserted between the sample and the sensitive area of ​​the detector, which, as mentioned earlier, is thick enough to prevent the backscattered electrons from overloading or damaging the X-ray detector. Unfortunately, this electronic filter will also attenuate the X-ray signal, especially for low-energy X-rays.

[0023] When the backscattered electrons strike the filter material, their absorption behavior will cause the filter to emit characteristic X-rays, some of which will be detected by the X-ray sensor. So, for example, a carbon filter will produce a carbon X-ray signature, which will highlight the signal of that element, or produce a false positive signal for that element if that element is not in the field of view.

[0024] At lower beam energies, thinner filters can be used which reduce the attenuation of low energy X-rays. However, as the filter thickness decreases, the energy of backscattered electrons that the filter is able to block from the detector will also decrease. Therefore, thinner filters generally require the use of lower beam energies. This limits the detection of many elements to lower energy lines with lower intensities and gives less accurate results.

[0025] In a scanning electron microscope, incident electrons are typically accelerated to an energy of 20 keV, and to block BSEs up to this energy, a filter such as Mylar at least 6 microns thick is required.

[0026] With such a filter, the detector will be insensitive to X-rays with energies below about 1 keV, making it difficult to identify elements with characteristic line emissions below 1 keV in the X-ray spectrum. For example, the elements Be, B, C, N, O, F, Ne, Na will be difficult to detect with such a filter.

[0027] Another problem with some existing arrangements is that because the module including the combined BSE and X-ray sensor has a larger diameter than a typical BSE detector, the module may partially or completely block the view of the sample 103 for the detector or any other auxiliary equipment mounted to the side of the microscope. Figure 2 It shows that the line of sight of the side mounted detector 105 is blocked by the large diameter detector module 106 below the microscope pole piece 104, which occurs in conventional arrangements. Therefore, existing arrangements generally preclude the use of both sensors 105, 106 simultaneously and require that only one detector component be used at a time for analysis.

[0028] WO 2014 / 202608A1 describes a scheme for detecting a wide range of X-ray energies that involves using different filters for different conditions. However, collecting instant data to study a sample requires that any element present in the field of view is accessible for detection. If the filter is made thin enough to transmit low-energy X-rays, such as those that characterize carbon, oxygen, or nitrogen, the incident beam energy must be reduced, otherwise the backscattered electrons will penetrate the filter and reach the X-ray sensor. This reduction in beam energy reduces the generation of higher energy X-rays and eliminates the collection solid angle advantage of the sub-pole detector compared to conventional detectors mounted on one side. In practice, this means that more than one filter and microscope beam configuration are required to explore a large area of ​​various chemical elements on the sample surface, making dynamic continuous detection of all elements for interactive exploration not feasible for unknown samples.

[0029] The requirement for filters can be avoided in special microscope configurations where the microscope's lenses are designed to provide a field to deflect the BSE away from the X-ray detector (US11145487

[0030] B2). This design may not be compatible with other common accessories in a scanning electron microscope. In addition, this configuration also requires the sample surface to be located close to the final part of the electron lens, and this may not be feasible when moving the sample stage to explore a sample surface that has height variations rather than being perfectly flat.

[0031] There is a need for a more efficient interactive sample analysis method that provides a continuous display of morphological information from an electron detector and provides high quality chemical composition data for various elements when the sample is explored in an electron microscope. Summary of the invention

[0032] According to a first aspect of the present invention, a method for analyzing a sample in a microscope is provided, the method comprising: acquiring a series of compound image frames using an electron detector, a first X-ray detector, and a second X-ray detector, wherein the first X-ray detector is located between the sample and an electron beam source, a focused electron beam is emitted from the electron beam source toward the sample, and a filter component is provided, the filter component is inserted between the first X-ray detector and the sample and is suitable for reducing the incidence of electrons on the first X-ray detector, wherein the second X-ray detector is provided with a deflector device, the deflector device is configured to reduce the incidence of electrons on the second X-ray detector, and wherein acquiring the compound image frame comprises: a) passing the focused electron beam through a sample area; b) using the electron detector to monitor a group of generated electrons emitted from a plurality of positions within the sample area to obtain a first image frame, the first image frame comprising a plurality of pixels corresponding to the plurality of pixels a plurality of positions, and the plurality of pixels have values ​​derived from monitoring electrons emitted from the plurality of positions; c) using the first X-ray detector and the second X-ray detector to monitor a first group of generated X-rays and a second group of generated X-rays emitted from the plurality of positions, respectively, to obtain one or more second image frames, each of which includes a plurality of pixels, the plurality of pixels corresponding to the plurality of positions and having values ​​derived from monitoring X-rays characterizing corresponding chemical elements and emitted from the plurality of positions according to a first standard, wherein the group of electrons and the first group of X-rays and the second group of X-rays are emitted from the sample substantially simultaneously; and d) combining the first image frame and the one or more second image frames to generate the compound image frame, so that the compound image frame provides data derived from monitoring electrons and X-rays emitted from a plurality of positions within the region, and displaying the series of compound image frames on a visual display, wherein the visual display is updated to display each compound image frame in sequence.

[0033] The inventors have realised that the problems associated with known detector arrangements and analysis techniques can be overcome by a new approach involving multiple detectors and deriving image data therefrom. Efficient and rapid sample navigation as well as higher quality elemental analysis visual data is achieved by using two X-ray detectors to monitor particles emitted from a sample under analysis, the first detector being arranged to have a wide collection solid angle and the second detector being provided with a deflector arrangement to mitigate the effects of incident electrons without affecting the transmission of the X-ray signal, and the monitoring X-ray data being utilised in a specific manner according to a first criterion, thereby optimising the quality of the elemental maps that can be produced and displayed.

[0034] The method offers a solution that can provide real-time imaging with a refresh rate fast enough to be used as the microscope field of view changes and can combine morphological information and high X-ray intensity for compositional information without requiring very high beam currents and avoiding the loss of low-energy information for low atomic number elements.

[0035] The side mounted detector can be provided with a deflector arrangement and usually does not require an electronic filter. Therefore, for low atomic number elements, a side mounted second detector can usually obtain a much larger signal than the first detector, which is usually a sub-pole piece detector equipped with an electronic filter.

[0036] Partial or complete occlusion of side-mounted detectors can be avoided by using smaller sub-pole detectors or increasing the working distance, but this will typically reduce the solid angle, however this problem can be alleviated by using specially shaped sub-pole detectors to achieve good line of sight, as described later in this disclosure and exemplified in WO 2022 / 008924 A.

[0037] The method may include simultaneously collecting signals from at least one electron detector, at least one sub-pole piece detector, and one or more side-mounted X-ray detectors, and using the improved low energy response of the side-mounted auxiliary detectors to provide additional information about low-Z elements.

[0038] This method also allows the use of a side mounted X-ray detector to determine the elements present in the sample. This can be done using an automatic or automated peak identification routine on the spectrum. By using a spectrum that combines (e.g. sums) all spectra obtained from several (if not all) pixels in the image, the use of a side mounted detector can produce sufficient signal to provide a signal to noise ratio (S / N) to detect the elements present, and the side mounted detector is sensitive to a wider range of elements than a sub-pole detector, especially those light elements with lower atomic numbers.

[0039] By using a side-mounted second X-ray detector for element identification, the influence of any light element artifact signals caused by X-ray fluorescence induced by backscattering of the filter on the element list identified by the system and displayed by the software can be avoided.

[0040] The method generally allows the simultaneous collection of electron and X-ray information for all elements in the sample. These data can then be processed and presented in a compound image frame on a software interface visual display or graphical user interface (GUI), for example, by displaying: an electron image, using the detector with the highest X-ray intensity for that element, an element image representing the morphology of the sample with the element image. The images can be displayed individually and / or superimposed, with each element being assigned a different color, and the electron image giving the intensity of each pixel in the image.

[0041] The method is preferably facilitated by real-time display of the combined image under a microscope to real-time tracking of the sample. The order and rapid presentation of a series of compound image frames obtained provide the operator with a "real-time" view of the sample being analyzed by the detector. In the context of the present disclosure, a series can be understood as a plurality of compound image frames that appear in succession. The series can be considered to be sequential. Typically, this is the order in which the compound image frames are obtained, or corresponds to the order in which the compound image frames are obtained, and / or the order in which their respective component frames (i.e., the first image frame and the second image frame) are obtained. Typically, the order of a series of compound image frames is the same as the order in which they are displayed.

[0042] The series does not exclude that the group of compound image frames is a subset of a larger group or series of frames. The series also does not necessarily exclude the possibility of being superimposed in time and / or superimposed with frames acquired from another group or another series relative to the compound image frames in each group or each series. The series may be interrupted, for example by other frames that are not considered part of the series. For example, interfering compound image frames may be acquired in the same or different manner, and such interruptive compound image frames will not be considered part of the series. However, preferably, the series is an uninterrupted series.

[0043] In the present disclosure, in a common embodiment, the feature of acquiring a compound image frame includes the above steps can be understood to mean that acquiring each compound image frame in the series includes these steps.

[0044] The electron detector may be a secondary electron detector. In some embodiments, the monitoring of step (b) may be performed using an electronic sensor device that may include any one or more of a secondary electron detector and a backscattered electron detector. In various embodiments, the relative position of one or more detectors relative to any other detector, microscope, or sample may vary.

[0045] Typically, the positioning of the first X-ray detector between the sample and the beam source is achieved by placing the first X-ray detector and / or a module comprising it below a pole piece of an electron beam assembly from which the focused electron beam emerges towards the sample, i.e. between the pole piece and the sample. The first X-ray detector may be horizontal to the pole piece relative to the beam axis, for example within the pole piece, or partially or completely surrounding or enclosing the pole piece.

[0046] It will be appreciated that a certain degree of electron beam focusing is typically required in a scanning electron microscope in use. This facilitates scanning of the image across the field of view. Typically, the degree of focusing applied to the focused electron beam is set or configured according to the desired or predetermined spatial resolution of any one or more of the first, second and compound image frames. In practice, the focus achieved may be affected by other factors and may differ from the configured degree. In addition, it is also envisaged that the method may be carried out with the electron beam at least to some extent defocused, and in this manner, the beam referred to in step (a) may generally be referred to as an electron beam.

[0047] The filter member can be set as a filter layer. The size, shape and / or position of the filter member are usually selected to cover all or substantially all of the first X-ray detector effective area from the following area of ​​the sample, the beam is incident on this area of ​​the sample or particles are emitted from this area of ​​the sample in response to the beam. Preferably, the filter member or filter layer has an occupied space and / or area greater than or equal to the effective area of ​​the first X-ray detector. Preferably, the filter member is arranged directly above one or more sensor elements of the first X-ray detector so as to cover them. The filter member can be referred to as an electronic filter. The filter member can be understood to be inserted to block electrons. It is usually arranged on or above at least a portion of the effective area of ​​the first X-ray detector, which can be arranged in one or more sensor elements as described above.

[0048] The filter member is adapted and / or positioned to block or shield the first X-ray detector from the influence of electrons (e.g., particularly backscattered electrons), thereby reducing the undesirable influence of these electrons on the X-ray detector, while allowing the first X-ray detector to be placed in a prescribed position to subtend a large collection solid angle at the beam spot due to the small size and space requirements of the filter member. In other words, unlike common deflector devices such as electron traps, the filter member is thin and can therefore be generally accommodated between the sample and the sub-pole detector. The filter member is preferably adapted to block at least a portion of the electrons that will be incident on the X-ray detector in use, and more preferably to block all electrons, especially those with the highest energy. The filter member generally works by blocking or preventing the transmission of these electrons through the filter material. In other words, the filter member is adapted to reduce the amount of electrons transmitted therethrough. Although the filter member is generally adapted to shield backscattered electrons, alternatively or in addition, the filter member may also be adapted to block the transmission of any one or more of visible light and infrared radiation, while allowing the transmission of X-rays with energy within the first energy range. The incidence of the above-mentioned electrons on the first X-ray detector can be considered as the incidence of those electrons on its sensor element or multiple sensor elements.

[0049] The second X-ray detector is typically a conventional X-ray detector as described earlier in the present disclosure, typically an energy dispersive detector (EDS). The second X-ray detector is typically mounted in a side port of the electron microscope in use. Since the second X-ray detector is typically positioned away from the sample and the pole piece, this allows for a larger detector arrangement, so the second X-ray detector can be protected from incident electrons in a different manner than the first X-ray detector (in particular using an electron deflector arrangement). Typically, the above-mentioned deflector arrangement includes a magnet arrangement or is configured as a magnet arrangement. The device may include one or more magnets. It may include one or both of a permanent magnet and an electromagnet, and is typically configured as a pair or array of permanent magnets.

[0050] Typically, the deflector device is configured to deflect electrons to reduce the incidence of electrons on the second X-ray detector. Typically, the deflector device is an electric and / or magnetic deflector device or includes an electric and / or magnetic deflector device. This can be configured to deflect electrons away from at least a sensitive or effective area of ​​the detector, for example by generating a field. This can include any or each of a magnetic field and an electric field (for example an electrostatic field). The field can be created or generated in a variety of ways. In a typical arrangement, the deflector device can be referred to as an electron trap. The above-mentioned incidence of electrons on the second X-ray detector, and / or in particular the incidence on its effective area, at least refers to the electron incidence that occurs during use, or the electron incidence that would occur in the absence of the deflector device.

[0051] The sample area usually corresponds to the field of view of the microscope. This can be understood as the portion of the sample surface that will appear as a visual image in the compound image frame.

[0052] The emitted electrons and X-rays are referred to as "generated electrons and generated X-rays" because they are generated by, or their emission is generated by, the electron beam interacting with the sample.

[0053] Multiple positions in the sample area can also be understood as multiple positions along the path of the beam passing through the area. They can also be referred to as sampling points or sampling positions, because the electron and X-ray signals are collected or sampled from the particles emitted due to the electron beam incident on multiple positions of the sample, and are based on the particles emitted due to the electron beam incident on multiple positions of the sample. The multiple positions are the same for monitoring electrons and monitoring X-rays. That is, preferably, the same sampling position is used to preferably simultaneously acquire electron and X-ray data. This helps to provide low-latency "real-time" imaging by this method. Each second image frame includes multiple pixels corresponding to multiple sampling positions, and the multiple sampling positions correspond to pixels in each image frame. It should be understood that, although this is preferred, there is not necessarily a one-to-one correspondence between the monitored position and the pixel. In some embodiments, in order to produce a lower resolution image frame with an improved signal-to-noise ratio, at least for some pixels, the signals at multiple positions can be combined to form a single pixel.

[0054] In at least some embodiments, a first criterion may be employed to compensate for the detrimental attenuation of low energy X-rays by the filter member. The first criterion may be configured such that X-rays from the first group of X-rays are preferentially used to derive pixel values ​​for the second image frame over those from the second group, for example, for elements having one or each characteristic peak in a higher energy spectral portion. Conversely, for elements having peaks in a lower energy spectral portion, the criterion may be configured to indicate that X-rays from the second group of X-rays are preferentially used over those from the first group.

[0055] In general, deriving pixel values ​​from monitoring X-rays characterizing the corresponding chemical elements and emitted from multiple positions can be considered to derive pixel values ​​using monitoring X-rays characterizing the corresponding chemical elements and emitted from multiple positions.

[0056] The corresponding first standard can be used for each second image frame or each corresponding element. In other words, for each frame in one or more second image frames: the corresponding first standard can be configured according to the corresponding chemical element, and the values ​​of the plurality of pixels included in the second image frame can be derived according to the corresponding first standard. Configuring the corresponding first standard for each second image frame in this way enables to define a direct relationship between a given element mapped in the second image frame and the way in which data is acquired from two X-ray sensors to image it. The advantage of configuring the first standard specific to the element mapped in a given second image frame is that the outputs from the two detectors can be processed differently for each element if appropriate, and in particular because the pixel values ​​of the X-ray image of the chemical element can be derived in a manner that can be specifically selected for the single element, thereby optimizing or enhancing the quality of the derived data. In this way, better signals and high-quality image data can be obtained over a wide range of X-ray energies and a corresponding wide range of elements. The first standard for a specific element can be implemented by applying a specific pattern of deriving pixel values ​​according to the element itself, or its properties, categories or classifications, which element itself can be identified during the method or can have been previously identified. The element-specific criteria may be implemented based on the energy values ​​of the monitoring X-rays corresponding to the chemical element, i.e. without the presence or consideration of specific elements that have been identified from the monitoring data, but based on the energy of the monitoring X-rays corresponding to the element in question.

[0057] A given first standard configured for a given second image frame may be the same or different from another first standard configured for another second image frame obtained during the acquisition of the compound image frame, and this is preferred for multiple or individual frames in the series of compound image frames. The corresponding first standard is usually configured according to one or more energy values ​​corresponding to one or more characteristic X-ray peaks of the element or a range of these values. The first standard for a specific element may be specifically configured for one or more elements or values, or may be configured so that the pixel values ​​of the second image frame are derived in a predetermined manner for any element whose characteristic peak falls within a specified or predetermined energy range, or is above or below a specified or predetermined energy threshold. In some cases, the standard may be the same for multiple second image frames, at least for a given compound image frame being acquired, in particular when the relative capabilities of the first X-ray detector and the second X-ray detector for monitoring X-rays are the same or sufficiently similar, the X-ray characteristics correspond to the corresponding multiple chemical elements of the multiple second image frames, or the characteristic peaks of the two elements have similar energies or are located within a given energy range on the X-ray spectrum. For example, the same or similar first criteria may be configured for a plurality of light elements or a plurality of elements whose characteristic peak energies are below a predetermined or specified threshold energy value, which first criteria may, for example, cause their respective second image frames to be derived primarily or entirely from the output of the second detector, based on the expectation that the second detector has better X-ray detector performance in this range than the first detector. However, different individual first criteria may be configured for any number of elements or corresponding frames.

[0058] In some embodiments, the first criterion may be referred to as a signal criterion, a signal quality criterion, or a signal strength criterion because it may be selected, configured, or calculated based on an X-ray signal or signal-to-noise ratio obtained, expected, estimated, or otherwise derived by one or each of the first and second detectors, or data derived therefrom. In particular, the criterion may be based on the relative signal performance of the two detectors for a given characteristic element peak or group thereof corresponding to a given chemical element.

[0059] The first criterion may be selected or configured as part of the method, for example based on data acquired by any one or more detectors. However, preferably the criterion is predetermined, for example based on known or estimated properties or geometry of the detector arrangement (including properties and geometry of the filter) for one or more X-ray energy ranges.

[0060] The criterion may be understood as a condition on which a specific way of deriving pixel values ​​of the second image frame is based.

[0061] In some embodiments, the use of the first criterion in deriving the content of the X-ray element frame can be considered to mean effectively deriving the pixel values ​​included in the second image frame from the corresponding third group of monitoring X-rays that characterize the corresponding chemical elements and are emitted from multiple positions, and each corresponding third group of monitoring X-rays is selected from the first group and the second group according to the first criterion. The effective selection of the third group of X-rays is completed by selecting and other processing from the data obtained from the first X-ray detector and the second X-ray detector. That is, the conceptual third group is defined by selecting from the data derived from those X-ray detectors based on the first criterion. The selection can be understood as part of obtaining the second image frame. Obtaining the second image frame typically includes processing the data obtained from the first detector and the second detector so that the third group of X-rays is selected from the first group and the second group in a specific manner, which is determined by the first criterion. In this sense, the first criterion can be called a selection criterion.

[0062] The conceptual third group, or each third group for each corresponding second image frame, can be understood as a subset of the combination or union of the first group and the second group of monitoring X-rays. In some embodiments, this criterion can be considered as a detector selection criterion, in the sense that a selection is effectively made based on this criterion as to which group or groups are used to monitor X-rays and therefore which detector or detectors are used to generate a given second image frame.

[0063] The monitoring X-rays from which the pixel values ​​of the second image frame are derived will be understood as "monitored" X-rays, meaning that they are the same as, or at least included in, those generated X-rays monitored in step (c) of the method. It will also be understood that the X-rays from which the pixel values ​​of the second image frame are derived are monitoring X-rays of the first and / or second set of monitoring X-rays.

[0064] In particular, the monitoring X-rays from which the pixel values ​​are derived are typically at least a subset of the first and second groups of monitoring X-rays. As described above, the X-rays from which the pixel values ​​of a given frame are ultimately derived can be considered as a third group of X-rays. However, in a preferred embodiment, the X-rays themselves are typically not deliberately selected. That is, the X-rays are typically not selected or manipulated in order to obtain the third group. Instead, the third group can be understood as a theoretical group that includes members of the first and / or second groups, and whose content is defined by the manner in which the pixel values ​​of the second image frame are derived. This derivation is performed according to a first standard. In other words, the third group can be defined by the type of processing performed to obtain an image frame representing a mapping of the corresponding elements corresponding to the microscope field of view. Therefore, the third group can be defined as the X-ray photons of the image frame from which the elements are derived. As a result of the first standard, the content of the group is typically selected from the first and second groups. Therefore, the first standard can be considered as defining the steps between monitoring two sets of X-ray data and generating an element map.

[0065] Monitoring X-rays as a characterization of the corresponding chemical element may be understood as those X-rays corresponding to or representing the element. In particular, these X-rays may have an energy that is a characterization of the corresponding chemical element. That is, preferably, each second image frame corresponds to the corresponding chemical element, the values ​​of its pixels may represent the X-ray signal, that is, they may be derived from monitoring X-rays received from sample positions corresponding to those pixels (optionally, on which additional processing has been performed) of the X-rays characterizing the specific element.

[0066] X-rays characterizing the corresponding chemical elements may be understood as those X-rays having an energy in a corresponding energy range or a corresponding energy range group. Thus, each second image frame may correspond to an energy range or an energy range group. Typically, these ranges correspond to respective characteristic spectral peaks or peak groups. Typically, the monitoring X-rays from which the pixel values ​​of a given second image frame are derived are located only within this energy range, that is, the X-ray photons used to generate the element map are typically limited to those in the desired peak or peak group of the element.

[0067] In some embodiments, the first standard from which the pixel values ​​of the second image frame are derived is configured to reduce the effect of changes in the height or elevation of surface features and sample surfaces that may have on the X-rays received by the detector on the acquired image frame. Therefore, in some embodiments, the first standard is configured according to the surface topography of the sample area. Therefore, the method may include obtaining sample topography information and configuring the first standard according to the surface topography information. The surface topography information can be obtained based on the data acquired by the electron detector, and can be derived, for example, from a group of electrons monitored, or can be obtained in any other way, such as from a previously performed topography analysis of the sample or its area. The surface topography information may include marks or parameters that indicate, characterize or quantify the surface topography of a surface area or one or more sub-areas thereof.

[0068] Adjustments to the topography criteria may be applied to a single chemical element or to multiple elements. For example, a sample may have a rough topography, or an area of ​​the sample may have a surface profile that may affect the X-rays emitted therefrom or their detection by the detector due to any of the following reasons: obscuration and shadowing by surface features, variations in the angle of incidence relative to the local surface orientation, and absorption of X-rays by the sample surface. The second detector, which is typically mounted in a side port, is generally affected by topography to a greater extent than the first detector. For this reason, it may be advantageous to configure the first criteria to favor increasing the output of the second detector, for example, even though the second detector may foreseeably have a poorer signal-to-noise ratio for a given element or X-ray energy.

[0069] Due to the first X-ray detector being located between the sample and the beam source, and preferably due to its geometry, the first X-ray detector is typically less strongly affected by this effect. For example, preferably the first X-ray detector is provided with an effective or sensitive area that is symmetrically arranged about the focused beam axis. As described above, such a symmetrical arrangement beneficially mitigates the effects of high surface topography. Therefore, it may be beneficial to configure the first criterion so that for at least one chemical element or the second image frame, pixel values ​​are derived preferentially, primarily or entirely based on the output of the first X-ray detector. Preferably, configuring the first criterion according to the sample surface topography includes adjusting one or more weighting coefficients, according to which data output by the first X-ray detector and the second X-ray detector is used to generate the second image frame. Typically, such an adjustment includes adjusting one or more coefficients to reduce the relative contribution of pixel values ​​to the data output of the second X-ray detector.

[0070] In cases where the sample has a significant morphology, the quality of the visual data in the generated X-ray image frame can be improved by configuring the first standard based on the sample morphology, in addition to or in lieu of any of the configuration standards listed in the present disclosure.

[0071] The first standard can be configured so that the values ​​of each pixel in the plurality of pixels included in a given second image frame are derived in the same manner. In some embodiments, the standard can be configured to change the combination mode of one or more pixels or pixel groups in the frame, for example, different weighting coefficients for combining data from the first X-ray detector and the second X-ray detector are applied to different parts of the second image frame. This is particularly advantageous in embodiments in which the first standard is configured according to surface topography, because the application mode of the pixel values ​​of a specific part of the second image frame can be adjusted according to whether the corresponding part of the sample is affected by the topography. For example, if the line of sight from one or more of a group of positions in the area of ​​the sample surface to the second X-ray detector is blocked by a protruding part of the sample surface, the first standard can be configured to establish the pixel value of the second image frame based on the data of the pixel group corresponding to the group of positions from the first X-ray detector compared to other pixels in the frame. Specifically, the configuration of the first standard for one or more pixels, pixel groups or parts of the second image frame can be performed according to the surface topography information obtained, for example, according to whether the corresponding position, position group, or part of the area on the sample indicated by the surface topography information is affected or not affected by the topography effect.

[0072] A group of electrons and a first group of X-rays and a second group of X-rays emitted from the sample substantially simultaneously, preferably simultaneously, may refer to those groups emitted simultaneously from the sample as a whole, rather than to any simultaneity between individually emitted particles within the group.

[0073] The simultaneity of the emission of the groups may be understood as corresponding groups of particles monitored by respective detectors being emitted simultaneously, or being emitted in response to the same impact of the beam on the sample.

[0074] Typically, monitoring is performed simultaneously or substantially simultaneously. That is, different detectors can be run simultaneously to capture different information about the same field of view. It should be understood that the traversal of a beam generally means that multiple positions are irradiated by the beam in sequence rather than simultaneously. Preferably, in the acquisition process of a compound image frame, the emission of each of the three particle groups (i.e., electrons and X-rays) for each of the multiple positions is simultaneous or substantially simultaneous. That is, at each sampling point or position, multiple detectors can (substantially) monitor the emitted particles simultaneously. In order to maximize the signals collected by each, it is preferred that all three detectors monitor particles during the entire residence time of each position. However, for a given sample position, one detector can monitor a longer time period than another detector, so that the former effectively monitors other particles and those particles of its corresponding group. For any detector or image frame, in order to increase the signal of the frame, this other particle can be included in the acquisition of the image frame. The emitted X-rays referred to in step (d) are generally those X-rays with energy within the corresponding peak or peak group of the element corresponding to each of the characterizing one or more second image frames.

[0075] The display of the series of compound image frames is preferably performed in real time. This can be understood to mean that there is substantially no noticeable delay between the user initiating the navigation action and the presentation of the action on the visual display. The presentation is preferably in the form of a dynamic image or video comprising the displayed series of compound image frames. The expression "dynamic image" used in the present disclosure does not necessarily refer to the change of the field of view or image content between the frames in the series. Generally, it refers to a series of images that can have a dynamic appearance or give a dynamic impression.

[0076] Each compound image frame in the series, or at least a portion thereof, is preferably displayed on a visual display within a predetermined time period after performing any one or more of steps (a), (b), (c) and (d) to acquire a compound image frame. Thus, the predetermined time period may define a delay time for the display relative to the capture of the particle signal. The time period is typically 1 s, preferably 500 ms, more preferably 300 ms, and even more preferably 100 ms. The delay may vary from frame to frame, but typically does not exceed the time period, and is preferably substantially constant for a series.

[0077] The method typically includes processing and displaying the image data once it is acquired, so that the image data is available almost immediately. In this way, the user is able to use the real-time compound image frame as feedback to guide navigation around the sample. For such real-time navigation, pages 8-10 of WO 2019 / 016559A1 describe methods for interacting with the user and examples of suitable methods for synthesizing, formatting, and displaying compound image frames. Techniques such as those described in WO 2012 / 110754A1 can be used to combine image frames into a color composite image.

[0078] The frame rate of the visual display, i.e., the rate at which successive compound image frames in the series are displayed, can vary between different embodiments and can be configurable. In some embodiments, the frame rate at which compound image frames are displayed is at least 1 frame per second, preferably at least 3 frames per second, and more preferably 20 frames per second. In some embodiments, a single compound image frame is processed at any given time. In such embodiments, the example frame rates listed above correspond to compound image acquisition times or processing times of 1 second or less, 0.3 seconds or less, and 0.05 seconds or less, respectively.

[0079] In some embodiments, the rate of acquiring and displaying the series of compound image frames is at least 10 frames per second, preferably at least 18 frames per second, more preferably at least 25 frames per second, and even more preferably at least 50 frames per second. Therefore, it is preferred that the series of compound image frames are displayed in the form of a dynamic image, and the display frame rate is preferably equal to the video frame rate.

[0080] Advantageously, the acquired images can be displayed and refreshed quickly enough to allow the operator of the microscope to track and react to changes in the image as the field of view changes.

[0081] As described in the present disclosure, the first standard can be configured to process the output of the X-ray detector in a variety of ways. In one embodiment, it can be simply configured to sum the X-ray data from both the first detector and the second detector to obtain the second image frame. Therefore, the first standard can be configured so that step (c) further includes summed data obtained by summing the data representing the first group of monitoring X-rays with the data representing the second group of monitoring X-rays, and the values ​​of the individual pixels in one or more second image frames are obtained by the summed data. As previously mentioned, the standard can be referred to as a condition, according to which the pixel values ​​of the second image frame are derived by compiling the data from the first detector and the second detector in a specific manner. The summation of data can be performed according to a weighted sum and according to a weighting coefficient. It should be understood that these weighting coefficients can be configured to have any non-negative value. Preferably, the first data and the second data relate to a variety of chemical elements, and more preferably relate to an energy range of peaks including a variety of elements. Typically, all those peaks and / or elements detected by any one or each detector are included. The first data and the second data can be respectively the same or different from the first data and the second data described in relation to the embodiment disclosed later.

[0082] In some cases, a first criterion may be selected so that representative data derived from the first and second sets of monitoring X-rays are processed to obtain corresponding estimates of monitoring emission signals of the corresponding chemical elements of the second image frame in question, wherein each value is obtained by a combination of these estimates. Thus, in some embodiments, the first criterion may be configured such that for each of one or more second image frames, step (c) (particularly deriving pixel values ​​according to the first criterion) includes processing data obtained from each of the first X-ray detector and the second X-ray detector to obtain a first set of values ​​and a second set of values ​​(e.g., a set of one or more values, such as one or more values ​​for each pixel) representing the corresponding chemical element. Pixel values ​​may be obtained from the first set of values ​​and the second set of values.

[0083] In embodiments where the first criterion is configured such that acquiring a compound image frame requires processing the first detector data and the second detector data to obtain the first set of values ​​and the second set of values, obtaining pixel values ​​therefrom may be performed in a variety of alternative ways. A given analysis program may include a first criterion that is configured such that pixel values ​​are obtained by any one or more of these methods.

[0084] First, in some embodiments, the acquisition of pixel values ​​may include summing the first set of values ​​and the second set of values. This may be true for the following situations during the acquisition of the compound image frame: only one second image frame, or for multiple second image frames, or each of them. Other combination techniques may be used for different frames and / or chemical elements. This may be applied to the pixel value acquisition method now described.

[0085] Second, in some embodiments, obtaining pixel values ​​may include obtaining pixel values ​​from one selected from the first set of values ​​and the second set of values. This may include obtaining pixel values ​​only from the selected one, or excluding the other of the first set of values ​​and the second set of values. One of the selected group values ​​may be determined or selected according to a second standard. The second standard may be the same or different from the first standard. Typically, the second standard is configured to select based on the signal-to-noise ratio of the first set of values ​​and the second set of values.

[0086] The second criterion may be configured such that the generated data has a maximum or optimal signal-to-noise ratio.

[0087] Third, obtaining pixel values ​​may include combining the first set of values ​​and the second set of values ​​according to a weighting function. For one or more second image frames of the compound image frame, the weighting may be uniform, or may be configured by configuring the first criterion to favor an estimate of a larger task signal expected to be monitored by it, or to exhibit a better signal-to-noise ratio. For a sample with a known chemical composition, the expected X-ray emission monitored by the first X-ray detector and the second X-ray detector and the uncertainty of the estimate of the emission may be calculated.

[0088] In order to optimize the combined S / N, the weighting of the function can be selected based on the possible or calculated signal-to-noise ratio of each result. In some embodiments, for one or more elements, the weighting can be configured to be equal, so that at least for those elements, the acquisition of pixel values ​​can include summing the first group and the second group as described in the first method above. The weighting function can include a weighted sum or a weighted average.

[0089] In some embodiments, a given second image frame may be created according to a function different from another second image frame obtained in step (c). Alternatively, the same function may be used for any two or more second image frames. Preferably, the same function is applied to multiple second image frames, and / or multiple compound image frames are formed. This is preferably done in such a way that the combination is weighted toward the group value representing the X-ray signal with the maximum S / N. Typically, the function depends on the estimated or calculated S / N of each of the first and second group values.

[0090] It should be understood that in some embodiments, S / N is a key factor for configuring the first standard. The standard can be configured according to the S / N performance of one or each X-ray detector (e.g., expressed as a parameter). Therefore, in some embodiments, the first standard can be based on at least one of a first signal-to-noise ratio and a second signal-to-noise ratio parameter representing a signal-to-noise ratio, which can be measured, calculated, modeled, simulated or estimated, for example, for each of the first X-ray data derived from the first group of monitoring X-rays and the second X-ray data derived from the second group of monitoring X-rays. Typically, the first standard is based on both the first signal-to-noise ratio and the second signal-to-noise ratio parameters. However, the standard can optionally be configured to rely on only one of the parameters, such as based on whether the parameter exceeds a threshold, such as to indicate the acceptable signal capability of a given element.

[0091] Alternatively, the criterion may be based on a single parameter indicating which of the two X-ray detectors has a higher signal-to-noise ratio for a given element, or is capable of producing data with a higher signal-to-noise ratio for that element.

[0092] Any of these parameters are typically provided in the form of values, such as numerical values, such as measurements or estimates of signal-to-noise ratios or signal levels, but may alternatively or additionally include qualitative representations of these characteristics. At least for a given compound image frame acquired, the first signal-to-noise ratio and the second signal-to-noise ratio parameters may be considered to represent the signal-to-noise ratios of the first X-ray detector and the second X-ray detector, respectively.

[0093] The first criterion can be based on a comparison of such a first signal-to-noise ratio and a second signal-to-noise ratio parameter, so that for the second image frame, the pixel value can be preferentially derived from the X-ray data with a higher signal-to-noise ratio for the corresponding chemical element in the first data and the second data. The comparison is usually a comparison for each second image frame, or a comparison for each chemical element from which the second image frame is obtained. The comparison is usually performed before the method is implemented. Usually, it is calculated based on a model of the S / N that can be achieved for each detector and each element. The above-mentioned preferential derivation of pixel values ​​by higher signal-to-noise ratio data can be applied to one or more second image frames respectively.

[0094] When considering the X-rays that are ultimately used to generate the second image frame (which may be referred to as the third group of X-rays), the criterion is typically based on a comparison such that, for the second image frame, the corresponding third group of X-rays preferentially includes X-rays from data that are derived from the data of the first data and the second data that have a higher signal-to-noise ratio for the corresponding chemical element. The preferential derivation of pixel values ​​from a particular one of the first data and the second data may be considered to be a pixel value derived from a preferred one of those data, the preferred data being preferred over and / or being preferred to a greater extent than data represented by X-rays monitored by one of the detectors having a lower S / N for the element. Thus, a larger proportion of the conceptual third group of X-rays may be obtained from the higher S / N detector than from the lower S / N detector.

[0095] The signal-to-noise ratio of each set of data is typically affected by a number of factors. Typically, it depends on the detector, but may also depend on any one or more of the sample, beam current, beam energy, and dwell time. For a given system, a number of factors that affect S / N are available for comparison and / or configuration of a first standard: first, the total collection solid angle subtended by the location of the sensitive area of ​​the detector on the sample as well as the incident electron beam current and electron energy; second, for X-rays with a characteristic emission energy, the transmission fraction through the filter and any signal loss during the electron detection process; third, the energy resolution or spread of apparent energies recorded in the energy histogram when the detector is exposed to monochromatic X-rays with a characteristic emission energy; and fourth, the concentration of the chemical element and any residual contribution of the bremsstrahlung background, as well as any emission from other chemical elements that was not removed by data processing.

[0096] While the first, second, and third of these considerations can usually be calculated for a particular system, the fourth factor will usually result in different S / N at locations on a sample with different chemical compositions. Therefore, the first criterion for determining how to combine the data is usually based on the S / N expected to be obtained when the beam is incident on an area with 100% chemical element concentration.

[0097] The first criterion may be configured based on the signal-to-noise ratio, for example for one or more energies or ranges, which may be more appropriate in some cases.

[0098] The filter member may have a high pass filtering effect on the transmitted X-rays, removing substantially all X-rays having an energy below a certain value. However, typically this is not a step function and the attenuation signal from the X-rays, even though increasingly weaker at lower energies, may have some value. Therefore, the first criterion is preferably configured to combine the signals output by the first X-ray detector and the second X-ray detector so that this data is taken into account when deriving the second image frame.

[0099] Alternatively or additionally, the first criterion may be selected based on the signal strength of one or each of the first and second detectors. Thus, in some embodiments, the first criterion may be configured such that for each second image frame, e.g., at least during acquisition of a compound image frame, a pixel value is derived based on an output signal of each of the first and second X-ray detectors that represents or corresponds to a detection of an incident or monitored X-ray that characterizes a chemical element corresponding to the second image frame.

[0100] Based on whether the corresponding element corresponding to the obtained second image frame has a high energy or low energy characteristic peak, the selection of X-rays from a specific detector in the first detector and the second detector, or the preferential processing of X-ray data can be achieved by a first criterion based on a threshold. In some embodiments, the first criterion is configured so that: if the energy range of the X-rays characterizing the chemical element corresponding to the second image frame is greater than a predetermined threshold, the pixel value is derived from the first group of monitoring X-rays, and if the energy range is lower than the predetermined threshold, the pixel value is derived from the second group of monitoring X-rays. The above energy range generally corresponds to one of the characteristic peaks or a group of characteristic peaks of the corresponding chemical element. For some elements and / or some thresholds, the value may be consistent with or fall within the energy range corresponding to the characteristic peak of the element in the monitoring X-ray signal. In this case, the third group of X-rays from which the pixel value is effectively derived can be preferably or exclusively selected from the first group or the second group of X-rays, or can be effectively selected as a weighted combination of the first group of X-rays and the second group of X-rays, for example, using a weighting based on the position of the threshold in the energy range corresponding to the peak or a group of peaks. Pixel values ​​derived from the first or second groups typically include those values ​​derived from the group that take precedence over the other of the first and second groups, and in some embodiments exclude the other of the first and second groups.

[0101] In some embodiments, since the above-mentioned attenuation function of the filter component generally includes a transition (e.g., continuous) function rather than a step function, a second threshold value can be used. Therefore, X-rays with energy lower than the first threshold value and the second threshold value can be acquired from only one of the detectors or the corresponding acquisition data, X-rays with energy greater than the two threshold values ​​can be acquired from only the other one, and X-rays with energy falling between the two threshold values ​​can be acquired from a combination of these data to generate a second image frame.

[0102] In some embodiments, one or both of the first and second predetermined thresholds described above may be configured based on any one or more of: the solid angle subtended by the total sensor area of ​​each of the first and second X-ray detectors at the location where the focused electron beam strikes the sample; and a filter parameter representing the X-ray transmission characteristics of the filter member. The filter parameter may alternatively or additionally include or be defined by a function, such as a function of X-ray energy. Typically, the parameter or function is configured to represent the effect on the transmission of X-rays through the filter member when the X-rays vary for different energies, typically with less transmission for lower energy X-rays.

[0103] In some preferred embodiments, the method includes identifying chemical elements present in the sample area. For example, such a list of elements can be presented as a part of a compound image frame. Usually in such an embodiment, the method also includes filling (populating), which can include creating a group of chemical elements identified, adding to a group of chemical elements identified, updating a group of chemical elements identified, or removing from a group of chemical elements identified. This can be based on the second group of X-rays monitored during at least one, preferably multiple series, and more preferably all series in a series of compound image frames. The identified chemical element group can include those chemical elements identified as being present in the X-rays monitored by the second detector. Preferably, identification is based on the X-ray spectrum collected in all or part of the field of view / sample area before or while acquiring the compound image frame.

[0104] Typically, during acquisition of at least one of the series of compound image frames, step (c) comprises acquiring a corresponding second image frame for each chemical element in the identified group of chemical elements. This preferably applies at least to the same compound image frames in the series of compound image frames as those in which the peaks were identified, or based on the second X-ray signal populating the peak list.

[0105] It should be understood that in such an embodiment, the number of second image frames obtained for the compound image frame is at least as many as the number of peaks or elements identified. Therefore, in such an embodiment, the second image frames each typically include a plurality of pixels corresponding to values ​​derived from a corresponding third set of monitored X-ray energies in a range within the identified energy range, and having values ​​derived from the third set of monitored X-ray energies. Chemical compounds can be represented by using multiple second image frames, and these frames can be optionally superimposed or otherwise combined in the compound image frame. For example, in the case where the sample field of view includes silicon dioxide, the X-ray characteristics of its two constituent elements will typically be monitored, and a second image frame will be obtained for each element. Therefore, each compound image frame will include at least a corresponding second image frame for each of silicon and oxygen. The second image frames or element maps of silicon and oxygen can be superimposed or combined to indicate the presence of elements in the compound together.

[0106] In the case of a list or group of identified elements, the method may involve configuring the first criterion so that the pixel values ​​are derived only or entirely from the first set of X-rays. Thus, in some cases, the second image frame is not derived from data acquired by the second X-ray detector, but rather uses that detector to identify the chemical elements present in the field of view. In various embodiments, such limitations on the data used for the image frame may apply to only a portion of the series, or to only a portion of the identified group of energy ranges.

[0107] In some embodiments and in some samples or analysis systems, it is advantageous to employ pixel aggregation to increase the S / N of the acquired data, so that at least one component of the acquired compound image frame can provide improved quality of analytical data at the expense of its spatial or pixel resolution. Thus, for example, for a given second image frame, i.e., for one or more second image frames acquired during the acquisition of one or more compound image frames in the series, the acquisition of the compound image frame can also include, for at least one, preferably each, of the one or more second image frames, and according to the aggregation criterion, which can be referred to as the third criterion: for each of one or more subsets of pixels in the second image frame, combining the values ​​of the pixels in the subset to obtain one or more corresponding aggregate pixel values, and replacing each pixel in a subset or subsets of the second image frame with a single aggregate pixel or superpixel, which has a value equal to the corresponding aggregate pixel value. Thus, groups of adjacent or neighboring pixels in an image frame can be merged or aggregated by summing or averaging their pixel values ​​or combining them in some way to produce merged or aggregated pixels having these values. Merged or aggregated pixels can be represented with a larger size than their constituent pixels, especially on a visual display. Typically, in such an embodiment, this is applied to multiple subsets of the pixels in the second image frame, preferably, this is applied to all or substantially all pixels in the second image frame and they correspond to aggregated pixels such that all pixels in the second image frame are aggregated into a synthesis step of superpixels.

[0108] It will be appreciated that each subset typically includes two or more pixels, so that a subset may be considered a group of pixels. One or more corresponding aggregate pixel values ​​may be referred to as a group or more superpixels having values. Each aggregate value group may preferably correspond one-to-one to a subset or group of pixels.

[0109] In these embodiments, the aggregation criterion is typically configured based on (that is, it typically depends on) the X-ray detector used to monitor the X-rays from which the pixel values ​​in the second image frame are derived. In other words, it can be based on one of the first detector and the second detector from which the pixel values ​​of the second image frame are preferentially, mainly or exclusively derived. That is, the aggregation criterion can be based on a third group of monitoring X-rays from which the second image frame is effectively selected, and in particular based on whether the third group is selected from the first group of monitoring X-rays or the second group of monitoring X-rays, or the first group of monitoring X-rays or the second group of monitoring X-rays include the third group. It can be additionally or alternatively based on the detector used to monitor the X-rays represented in the second image frame.

[0110] Each subset or group may include a number of pixels, which may be referred to as a subset size, configured according to a signal parameter value corresponding to each monitoring X-ray from which a pixel value is derived. The signal parameter value may be based on one or more characteristics associated with data representing one or more groups of monitoring X-rays, such as a measurement or estimate of signal intensity or S / N. Alternatively or in addition, the subset size may be configured according to a signal-to-noise ratio parameter value. Any or each of these parameter values ​​may be the same as the parameter value described for the aggregation criterion. The parameter value may be predetermined, for example based on whether the second image frame pixel value is preferentially derived from the first group of X-rays or the second group of X-rays. In such an embodiment, the size of the pixel group preferably depends on the source of the X-ray signal, and accordingly depends on the first detector or the second detector, and / or both detectors, for example, if the data used is from a combination thereof.

[0111] Thus, the subset size is typically configured such that for at least a subset of pixels comprised by an image frame, for lower signal strength values ​​or lower signal-to-noise ratios, the number of pixels in the group is larger.

[0112] The above-mentioned signal parameters may be configured depending on the group of monitoring X-rays from which the pixel values ​​are derived or from which the corresponding third group is selected, which may mean that the parameters are configured depending on the detector used to obtain the second image frame in question.

[0113] The signal parameters may be configured such that at least preferentially or exclusively, for a second image frame whose pixels are derived from X-rays comprised by the second set of monitoring X-rays, the subset size or said number of pixels (which may also be referred to as superpixel size) is greater than for a second image frame whose pixel values ​​are derived from X-rays comprised by the first set of monitoring X-rays. That is, a greater degree of aggregation of the X-ray data may be applied, wherein data obtained by the second detector is preferentially used instead of the first detector, or data from the first detector is not included.

[0114] The signal parameters can be configured so that the pixel size or number of pixels depends on the solid angle subtended by the total sensor area of ​​one of a first X-ray detector and a second X-ray detector, the first X-ray detector and the second X-ray detector being used to monitor X-rays at the location where the electron beam strikes the sample from which pixel values ​​of the second image frame are derived.

[0115] The signal parameters may be configured such that the group size is larger for smaller solid angles and smaller for larger solid angles.

[0116] It will be appreciated that the above-described aggregation of pixel data enables the signal-to-noise ratio of the data to be improved at the expense of spatial resolution, and that this concession may be made to different degrees for different elements and / or for different X-ray detectors (or rather the data obtained therefrom). For example, an aggregation (or what may be called pixel "binning") method may include combining a set of nearby pixel values, such as 2x2 or 4x4. This produces a smaller number of "superpixel values" (compared to the number of aggregated frame pixels) for a superpixel covering the field of view, which has substantially the same degree as unbinned or pre-binned pixels.

[0117] If the number of pixels in one second image frame is less than the number of pixels in another image frame of the compound image frame (e.g., the first image frame or another second image frame corresponding to a different chemical element), then in order to provide the same number of pixel values ​​as the other image frames, the set of pixel values ​​of the one second image frame may be increased by known techniques, such as any one or more of the following techniques: duplication, interpolation, and upscaling. Having two or more image frames of a given compound image frame consisting of an equal number of pixels facilitates the preparation of the compound image frame.

[0118] In embodiments where merging is not used, the S / N of the displayed X-ray image can still be optionally improved by low-pass spatial filtering or "smoothing" at the expense of some blurring of image detail. It should be understood that such smoothing, for example using a spatial convolution or Fourier transform filter, will generally generate an image with the same number of pixels and with an improved signal-to-noise ratio, but typically also with some blurring or loss of high spatial frequency detail. Such a smoothed image can be immediately overlaid with another image with the same number of pixels.

[0119] In some embodiments, data from both the first detector and the second detector are included in each compound image frame. Thus, in some embodiments, step (c) comprises obtaining at least two second image frames, wherein at least one of the second image frames comprises a plurality of pixels corresponding to a plurality of locations and having values ​​derived from monitoring X-rays included in at least the first group, characterizing the corresponding chemical elements and emitted from the plurality of locations according to a first criterion, and at least another of the second image frames comprises a plurality of pixels corresponding to a plurality of locations and having values ​​derived from monitoring X-rays included in the second group, characterizing the corresponding chemical elements and emitted from the plurality of locations according to a first criterion. The two corresponding chemical elements may be the same or different.

[0120] In some embodiments, the content of the compound image frames can be modified based on the identified elements present in the microscope field of view. Thus, frames of new elements (second image frames) can in some cases be added when they are identified and / or removed from the compound image frames when they are identified as no longer present in the field of view. Thus, the method can further include defining a set of chemical elements, typically a group of one or more chemical elements, for at least part of the series of compound image frames, the set corresponding to a set of spectral peaks identified based on one or both of the first and second sets of X-rays monitored during acquisition of that portion of the series.

[0121] As described above, elements already included in a given compound image frame or its corresponding second image frame may also be excluded from one or more compound image frames, for example if the elements present in the field of view are reduced or terminated. The portion of the series of compound image frames may be at least some of the series, and preferably all of the series.

[0122] The step (c) of acquiring the compound image frame may include obtaining a corresponding second image frame corresponding to each chemical element in the group of chemical elements. That is, a corresponding second image frame including a plurality of pixels corresponding to a plurality of positions and having values ​​derived from a corresponding third group of monitoring X-rays having energies within a corresponding energy range of a corresponding third group of monitoring X-rays and emitted from the plurality of positions may be acquired, each corresponding third group of monitoring X-rays being selected from the first group and the second group according to the first criterion.

[0123] In some embodiments, a pixel of a first one of the one or more second image frames has a value derived from a combination of a corresponding third group of monitoring X-rays and a corresponding fourth group of monitoring X-rays characterizing a corresponding second chemical element different from the corresponding first chemical element, wherein the respective third group of monitoring X-rays and the fourth group of monitoring X-rays are selected from the first group and the second group according to a first criterion.

[0124] It should be understood that the second image frame need not be limited to representing only a single chemical element, or having a value derived from a monitoring X-ray that only characterizes a single chemical element. In some cases, the pixel values ​​of the second image frame can represent two or more energy ranges, peaks or chemical elements. In some embodiments, the first, or more than one, or a subset (possibly all obtained second image frames) of the second image frame obtained can have a value derived from a combination of the third group and the fourth group. Any one or more second image frames can represent a fourth group, a fifth group or another group of X-rays characterizing a fourth, fifth or other chemical element, or have an energy within a corresponding energy range, or correspond to a corresponding other element peak. Each can correspond to an element with a different number of energy ranges or peaks. Two or more second image frames can have one or more peaks in common. The corresponding fourth group can be understood to correspond to the corresponding second image frame, just as the corresponding third group is usually.

[0125] In other words, when a compound image frame is acquired, a second image frame that additionally introduces data for one or more additional chemical elements may be generated. In some embodiments, by assigning a single color to a multi-element second image frame, the single color may represent a combination of more than one element, such that the presence of those multi-elements in the field of view is mapped to that color, thereby representing a multi-element mapping by that color in the compound image frame. That is, the method may include obtaining one or more second image frames, each second image frame including a plurality of pixels, the plurality of pixels corresponding to a plurality of locations, and the plurality of pixels having values ​​derived from monitoring X-rays characterizing the corresponding plurality of chemical elements and emitted from the plurality of locations according to a first criterion. Two main methods of generating a multi-element second image frame are contemplated.

[0126] First, for a given compound image frame, one or more X-ray images or second image frames can be formed, each of which individually corresponds to the sum of signals from more than one element. One or more multi-element second image frames can each be included in the formation of the compound image frame. It should be understood that in some embodiments, the inclusion of a multi-element map in a compound image frame can be equivalently achieved by the following methods: obtaining multiple second image frames, each of which corresponds to a corresponding chemical element, and combining the multiple second image frames in a single combined image frame or pixel array, and including the combined image frame in the compound image frame; and obtaining a separate second image frame for each of the multiple chemical elements to be presented in the combined image frame, and combining the multiple single-element second image frames into a combined image to generate or as part of generating a compound image frame. Any one or a variety of these methods can be used for a given series to be acquired. Therefore, any calculation and / or image processing steps involved in generating a multi-element map can be performed in step (c) and / or step (d).

[0127] Second, the element maps or second image frames of a set of individual elements can be combined according to conditions or using mathematical rules, rather than just summing. For example, if the user operating the microscope is looking for materials containing two elements A and B in significant concentrations, but is not interested in materials in which only one of the two elements is absent or present, a second image frame can be constructed from X-ray maps for A and B, which only shows non-zero pixels when the corresponding pixel values ​​in maps A and B are both above their respective thresholds. This will help the user highlight areas that may contain materials or compounds of a specific composition. Therefore, the value of such a second image frame can be derived from the monitoring X-rays that characterize the corresponding multiple chemical elements according to the element combination standard. The element combination standard can be included by the first standard or configured according to the first standard, or vice versa. That is, the two standards may be interrelated or interdependent. In some preferred embodiments, for at least one of the multiple elements, and preferably each element, the element combination standard can be configured so that for each pixel of the second image frame corresponding to the multiple elements, the pixel value is derived according to the comparison between the corresponding value characterized by the element and derived from the X-ray emitted from the position corresponding to the pixel and the threshold. For example, the element combination criterion may be configured such that if for each second image frame pixel, a threshold is exceeded in one or each of the above comparisons, i.e., for one or each element, the pixel value may be set or derived as a combination, such as the sum or average of a plurality of corresponding values ​​corresponding to a plurality of representative elements used in the comparison. In some embodiments, if the threshold is not exceeded, the pixel value may be set to a predetermined value, such as a zero value, in any or each of the above comparisons. It should be understood, however, that such predetermined values ​​are derived from monitoring X-rays characterizing the corresponding chemical elements and emitted from a plurality of locations, particularly in the sense that the independent element values ​​on which the element combination criterion and / or comparison rely are derived from those monitoring X-rays.

[0128] Different modes of combining the second image frames together when generating the compound image frame are contemplated.In some embodiments, step (c) comprises obtaining a plurality of second image frames, and generating the compound image frame comprises juxtaposing two or more second image frames.

[0129] Some embodiments involve step (c) comprising obtaining a plurality of second image frames, and generating the compound image frame may accordingly comprise superimposing two or more second image frames, such as by using known image processing techniques for combining pixel values.

[0130] According to a second aspect of the present invention, a system for analyzing a sample in a microscope is provided, the system comprising: a first X-ray detector, which is suitable for being located between the sample and an electron beam source during use, and a focused electron beam is emitted from the electron beam source toward the sample; a filter component, the filter component is arranged so that it is inserted between the first X-ray detector and the sample during use, the filter component is suitable for reducing the incidence of electrons on the first X-ray detector, a second X-ray detector, which is provided with a deflector device suitable for reducing the incidence of electrons on the second X-ray detector in use, and a control module, the control module is configured to use the electron detector, the first X-ray detector and the second X-ray detector to acquire a series of compound image frames, wherein acquiring the compound image frames comprises: a) passing the focused electron beam through a sample area; b) using the electron detector to monitor a group of generated electrons emitted from a plurality of positions within the sample area to obtain a first image frame, the first image frame comprising a plurality of pixels, the plurality of pixels corresponding to a plurality of positions and having values ​​derived from monitoring electrons emitted from the plurality of positions; c) using the first X-ray detector and the second X-ray detector to monitor a first group of generated X-rays and a second group of generated X-rays emitted from the plurality of positions, respectively, to obtain one or more second image frames, each of which includes a plurality of pixels, the plurality of pixels corresponding to the plurality of positions and having values ​​derived from monitoring X-rays characterizing corresponding chemical elements and emitted from the plurality of positions according to a first standard, wherein the group of electrons and the first group of X-rays and the second group of X-rays are emitted from the sample substantially simultaneously; and d) combining the first image frame and the one or more second image frames to generate the compound image frame, so that the compound image frame provides data derived from monitoring electrons and X-rays emitted from the plurality of positions within the region, and a display module, the display module being configured to display the series of compound image frames on a visual display, wherein the visual display is updated to display each compound image frame in sequence.

[0131] It is particularly advantageous to use a detector or detector module comprising a first X-ray detector having one or more sensor elements, the sensor elements being arranged to subtend a large collection solid angle at the beam spot during use. The use of a detector or module having such a configuration can significantly improve the navigation and analysis of samples in an electron microscope. Preferably, this is achieved by allowing an arrangement to maintain a large total solid angle for collecting X-rays and backscattered electron detectors, preferably while ensuring that the module comprising such a detector does not obstruct the line of sight of the point at which the electron beam of the second X-ray detector strikes the sample, which is typically located on one side of the electron beam assembly. Typically a filter member is configured, positioned, placed or located so that it is inserted between the first X-ray detector and the sample during use. This is typically achieved by placing a filter member as a material layer on the surface of the first X-ray detector facing the sample.

[0132] The control module may be configured to control the microscope, in particular its electron beam assembly. Typically, an electron detector, preferably caused by the control module, for monitoring a set of electrons generated is usually separate from the system. However, the electron detector is usually in data communication with it so that the system can control the detector.

[0133] Preferably, the system includes a detector module, the detector module including a first X-ray detector. More preferably, the detector module is adapted to be positioned below a pole piece of the electron beam assembly such that the detector module receives X-rays and backscattered electrons generated by the interaction between the electron beam and the sample. In a preferred embodiment, the first X-ray detector includes a plurality of X-ray sensor elements configured to monitor the energy of a single X-ray photon received by any X-ray sensor element. Preferably, the plurality of X-ray sensor elements of the first X-ray detector have a diameter greater than 20 mm. 2 Preferably, for at least a first portion of the detector modules, the radial extent of the detector modules relative to the electron beam axis is less than 10 mm. In this way, limiting the radial extent of the detector modules relative to the beam axis may include modules having cutout portions, notches or apertures to provide a line of sight to the beam spot for the second X-ray detector.

[0134] Examples of suitable detector modules are described in International Patent Application No. PCT / GB2021 / 051752, the contents of which are incorporated herein by reference in their entirety.

[0135] As described above, in some embodiments, the system includes a detector module, the detector module is suitable for being located between the sample and the pole piece of the electron beam assembly during use, and the focused electron beam is emitted from the electron beam assembly toward the sample, and the detector module includes the first X-ray detector and the filter member. More commonly, the module can be suitable for being located between the sample and the electron beam source, so that it can be above, around or inside the pole piece, similar to the arrangement described for the first aspect. The detector module may preferably further include an electron detector. The electron detector may be an electron detector for monitoring a group of electrons. Alternatively, the electron detector may be other detectors different from the detector for monitoring a group of electrons, such as a secondary electron detector. The electron detector included by the module may include one or more sensor elements, which may be arranged as one or more discrete or separated effective sensor areas.

[0136] In some preferred embodiments, in addition to the first X-ray detector, the space below the pole piece is also shared with a backscattered electron detector or sensor element (BSE). It has been found that BSE detectors with irregular shapes can be used to obtain a large solid angle while maintaining the above-mentioned notch or cutout in the detector module to ensure a line of sight between the location where the electron beam strikes the sample and any auxiliary detectors. In this way, the line of sight to the side-mounted detector (which may include a second X-ray detector) that may be included in some embodiments is retained. In general, it is important to maintain the symmetry of the BSE sensor to ensure that the signal strength due to shading effects on non-planar samples is not affected by the geometry of the sensor module. This will be described in more detail later in this disclosure.

[0137] The deflector device may include a magnet device for generating a magnetic field to deflect electrons away from the second X-ray detector. The magnet device may include any one or more of a permanent magnet and an electromagnet. Any one or more of such magnets may be close to the second X-ray detector. This typically constitutes such magnets that, taking into account the strength and range of the magnetic field they generate, are close enough to reduce the incidence of electrons on one or more X-ray sensor elements by electromagnetic deflection (but preferably without deflecting the electron beam). Typically, at least one magnet is coupled or fixed to the second X-ray detector. Both the second X-ray detector and the deflector device may preferably be located at this part of the detector module, for example connected together as part of a single device.

[0138] In some embodiments, the second X-ray detector utilizes a stray magnetic field generated by one or more components of the electron microscope itself (e.g., a magnetic lens suitable for focusing the electron beam) to provide at least some electron deflection functions. Therefore, in some embodiments, the magnet device includes a magnet of the electron beam assembly of the microscope. More commonly, the deflector device may include a component of the electron microscope that generates an electromagnetic field during use. It should be understood that the magnet or other components of the above-mentioned microscope do not themselves need to form part of the system according to the second aspect. The second X-ray device of the system can be provided with a deflector device, in this sense, by providing an electron deflection field to it through an X-ray detector positioned thereon or adapted to be positioned thereon during use, so that the field generated by the electron beam component acts to induce the deflection.

[0139] In addition or alternatively to magnetic deflection, an electric field may be employed to reduce or avoid impact of electrons with the second X-ray detector.Thus, the deflector arrangement may typically comprise electrode arrangement for generating an electric field to deflect electrons away from the second X-ray detector.

[0140] The deflector device is preferably adapted to deflect electrons having an energy greater than 100 eV and less than at least 99% of the configured beam energy of the focused electron beam away from the second detector. Preferably, the deflector device is specifically configured as such. For example, the device can be configured to generate a magnetic field or electric field having an average or minimum field strength at least in use, preferably at least in the field region, so as to deflect incident electrons with energies within the range. Preferably, the field has such a field strength, direction and / or extent that electrons within the energy range and having undeflected or pre-deflected trajectories coinciding with the effective region of the second X-ray detector are subjected to a deflection force attributable to the field, which causes their trajectories to become trajectories that do not coincide with the sensor region. For example, the deflected trajectory can be achieved by interaction with a generated field emanating from the sensor, or a field coinciding with another component of the system, or any other structure of the detector (e.g., a wall member or at least partially surrounding the sensor) where the electron incidence does not damage or affect. In other words, said deflection away from the second detector may be understood as the deflector means being adapted to effect a change from a trajectory incident on the detector sensor to a trajectory not incident on the detector sensor. Said proportion of electrons is preferably deflected away from the X-ray sensor area, and preferably away from the entire X-ray sensor area of ​​the second detector. The configured electron beam energy may refer to a minimum, average or maximum energy of electrons comprised by the electron beam striking the sample in use.

[0141] In some embodiments, the system further comprises an interlocking mechanism configured to control the position and / or movement of one or each of the first and second X-ray detectors and the module including the detectors to prevent collision. An interlocking mechanism can generally be understood as a device or mechanism for connecting or coordinating the functions of different devices or systems. In such an embodiment, a collision between the first and second X-ray detectors or the module including the first and second X-ray detectors and their supporting components can be prevented. For example, the interlocking mechanism can be configured so that before the first detector is retracted, if the second detector is in the way, it will automatically retract first to avoid collision. After the first detector is fully retracted, the second detector is automatically inserted through the interlocking device and returned to its initial position, i.e., its position before the interlocking device intervenes. A similar function is provided during the insertion of the detector, i.e., before the first detector is inserted, if the second detector blocks its insertion, the second detector will be fully retracted and reinserted after the first detector is inserted.

[0142] According to a third aspect of the invention, there is provided a non-transitory computer readable medium storing instructions or program code, or code configured to perform the method according to the first aspect, or having instructions or program code stored thereon, or code configured to perform the method according to the first aspect. The instructions may be executed by one or more processors, such as a processor of a system for analyzing a sample in a microscope, such as any system described with respect to the second aspect, so that the one or more processors implement a method, such as the method according to the first aspect. BRIEF DESCRIPTION OF THE DRAWINGS

[0143] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which like features are indicated by like reference numerals, and in which:

[0144] Figure 1 is a schematic diagram showing the configuration of a scanning electron microscope system for recording electron and X-ray images of a sample according to the prior art;

[0145] Figure 2 schematically shows an arrangement for X-ray analysis in an electron microscope according to the prior art;

[0146] Figure 3 is a flow chart illustrating a method according to an embodiment of the present invention;

[0147] Figure 4 is a schematic diagram showing an X-ray detector arrangement in a scanning electron microscope that can be used to perform a method according to an embodiment of the present invention;

[0148] Figure 5 is a perspective view of a portion of a system according to a first embodiment of the present invention;

[0149] Figure 6 Shows Figure 5 Side and plan views of components of the system shown, including a first embodiment detector module forming part of a first embodiment system, positioned below a final lens pole piece of a scanning electron microscope;

[0150] Figure 7 is a plan view of a second embodiment detector module that may form part of an embodiment system according to the present invention;

[0151] Figure 8 is a plan view of a third embodiment detector module that may form part of an embodiment system according to the present invention;

[0152] Fig. 9 is a bottom view of an example arrangement for implementing an example method according to the present invention in a scanning electron microscope, comprising Figure 7 The first embodiment module shown;

[0153] Fig.10 yes Fig. 9 a side view of the arrangement shown;

[0154] Fig.11 A user interface is shown showing an embodiment electronic image frame obtained by an embodiment method according to the present invention;

[0155] Fig.12 The display and Fig.11 a user interface for an example X-ray image frame corresponding to the same microscope field of view; and

[0156] Fig.13 A user interface is shown that displays an example compound image frame obtained by an example method according to the present invention. DETAILED DESCRIPTION

[0157] refer to Figure 1-13 , embodiments of a method and system for analyzing a sample in a microscope according to the present invention are now described.

[0158] The steps of the method according to the embodiment of the present invention are as follows: Figure 3 The flowchart shows step 300 for Figure 4 The illustrated embodiment apparatus captures and displays a single compound image frame in a time series of such captured frames during electron microscopy operation.

[0159] At step 311, a focused electron beam electron microscope is traversed across a region of the sample 407 that corresponds to the configured field of view of the microscope.

[0160] In response to the impact of the beam emitted from the final lens pole piece 422 of the microscope on the sample material, particles are emitted as a result of the interaction between the material and the beam. The beam spot 423 is caused to scan the area of ​​the sample 407 during step 311 so as to allow the analysis data of the entire field of view to be captured. The emitted particles generally include backscattered electrons, secondary electrons and X-rays. In steps 313 and 315, the secondary electrons and X-rays of the emitted particles are monitored simultaneously by an electron detector (not shown), a first X-ray detector 408 and a second X-ray detector 409. Since the electron beam (not shown) is caused to scan the entire area, X-rays and electrons are emitted from multiple positions within the sample field of view area, so X-rays and electrons are obtained simultaneously, allowing real-time dynamic visualization of these two types of analysis data. In step 313, the electronic data is used to obtain a first image frame. The pixels of the first image frame correspond to the above-mentioned positions in the sample area, i.e., the sampling positions, from which electron and X-ray signals are captured when the beam is caused to impact the sampling positions.

[0161] Accordingly, at least one second image frame is obtained at step 315, each second image frame visualizing an X-ray signal derived from X-rays emitted from a plurality of sampling positions.

[0162] Step 315 involves deriving the content of the second image frame using a criterion in order to optimize the data acquired by the first X-ray detector 408 and the second X-ray detector 409 based on the signal collection capabilities of the X-ray detection device. It can be seen that the collection solid angle of the second X-ray detector 409 is smaller than the collection solid angle of the first X-ray detector 408. In this embodiment, the second X-ray detector 409 is a conventional EDS detector mounted on the side port of the scanning electron microscope. The limited solid angle subtended by the area of ​​the detector at the beam spot limits the signal-to-noise ratio (S / N) of the X-ray signal derived from the sensor. However, the first X-ray detector 408 is mounted below the pole piece 422 of the electron lens and has sensors surrounding the incident electron beam and a sensing area facing the sample, so a much higher total collection solid angle can be obtained for all its sensors compared to the second detector 409. In this way, the first X-ray detector 408 can achieve a higher S / N. However, as described above, due to the sensitivity of the X-ray detector segments to high energy backscattered electrons, the first and second X-ray detectors are each provided with means for reducing the incidence of electrons on the sensor elements or regions thereof. The positioning of the second X-ray detector 409 allows the inclusion of an electron trap, in this embodiment a pair of permanent magnets, which generates a strong magnetic field capable of diverting substantially all backscattered electrons travelling towards the detector away from its sensor region. In contrast, the arrangement of the first X-ray detector 408 between the pole piece 422 and the sample 407 leaves insufficient space for the electromagnetic electron deflection means, and therefore the first X-ray detector 408 is provided with a layer of filter material arranged on the surface of the sensor region facing the sample 407. The filter material in front of the first detector 408 blocks backscattered electrons. The filter also blocks secondary electrons, although these electrons generally have lower energy. However, the filter material additionally affects the X-rays and in particular reduces the incidence of low energy X-rays on the first detector 408.

[0163] For a given compound image frame being acquired, each second image frame generated in step 315 corresponds to a specific chemical element. The first criterion can be configured and implemented in a variety of different ways to obtain a second image frame of a given chemical element, preferably so that the S / N is optimized. Typically, the criterion is selected so that a second image frame representing a chemical element whose characteristic peak is at the lower end of the X-ray spectrum is preferentially derived from the second set of X-rays (i.e., data acquired by the second X-ray detector 409), because the first detector typically obtains a lower S / N for lower energies. Conversely, for a second image frame representing an element with a higher energy characteristic peak, the first criterion is typically configured so that pixel values ​​are preferentially derived from the first X-ray detector 408 due to the large collection solid angle over which the first set of X-rays are collected and the resulting higher S / N. However, in various embodiment methods, the first criterion is configured in various different ways so that in step 315, a second image frame is obtained by various different ways of deriving pixel values ​​from the available X-ray data.

[0164] The groups of electrons monitored in steps 313 and 315 and the first and second groups of X-rays are emitted from the sample substantially simultaneously. That is, as a result of the irradiation of the sample by the electron beam in step 311, both the electrons and X-rays monitored (by any X-ray detector) are emitted simultaneously. Therefore, in general, the monitoring of steps 313 and 315 is also performed simultaneously, because the corresponding detectors receive the corresponding particle groups substantially simultaneously. Typically, the electron detector and the first and second X-ray detectors monitor the corresponding particles at each of the multiple positions simultaneously, which means that it is preferably within the duration of the residence time that focuses the electron beam on each sampling point. Therefore, the simultaneity in such an embodiment can be understood to mean that the monitoring is performed within a time frame that is simultaneous with the residence time and / or in the order of the residence time.

[0165] Once a first image frame representing the monitoring electron signal and one or more second image frames (each representing the monitoring X-ray signal of the corresponding chemical element) are acquired, the frames are combined to produce a compound image frame at step 316. The frame is then displayed on a visual display as part of a real-time updating stream, video, or series of frames at step 317 to facilitate sample analysis. Steps 311 to 317 are then repeated for each compound image frame to obtain a time series of compound image frames.

[0166] Part of the first embodiment system is as follows Figure 5As shown. The depicted portion of the embodiment system 520 includes a retractable side arm 524 supporting a downward facing X-ray detector module 508 adapted to be located below the microscope pole piece in use, and a second X-ray detector 509 provided with an integral electron trap 512. The second X-ray detector 509 is mounted in the arm 524 so that it has a clear line of sight to a detection point on the sample 507 upon which the electron beam 510 is incident. The arm 524 additionally provides an electrical connection (not shown) and a cooling path to an external heat sink (not shown). The first embodiment system also includes a control module (not shown) configured to acquire a series of compound image frames using the X-ray detectors 508, 509 and the electron detector of the electron microscope. The control module may include or be included in a computing device and may include one or more processors adapted to perform the described method steps and / or control the described components to perform the various portions of the method, and include the necessary electrical and data connections for doing so.

[0167] The electron trap 512 may comprise one or more pairs of permanent magnets, or a circular array of Halbach magnets, and is adapted to generate a strong field for deflecting backscattered electrons incident on the second detector 509 therefrom. The trap also comprises a soft iron housing to confine stray magnetic fields so that they do not interfere with the focusing object of the electron microscope (see, for example, US 8,049,182 B2). The second X-ray detector 509 is much more sensitive to low energy X-rays than the sensor elements in the first X-ray detector 508 in a module adapted for use below a microscope pole piece, which requires material filters to block backscattered electrons.

[0168] An advantage of this embodiment of mounting the second X-ray detector 509 to the support arm 524 is that only a single electron microscope port is required and the conduits in the arm can accommodate the electrical and cooling requirements of both X-ray detectors 508 .

[0169] The electron detector of the electron microscope is not shown in this embodiment, but may be located at an appropriate location within the instrument as is known in the art.

[0170] Figure 6 Shows Figure 5 Side and plan views of the components of the system shown, located below the final lens pole piece 622 of the scanning electron microscope, with the detector module 618 including the first X-ray detector 608 visible in the latter. The second detector 609 is mounted in a fixed position relative to the other components of the arm, which can be considered as a detector module included in the system, allowing the geometry of the components to be configured to ensure that all detectors have a clear line of sight to the detection point on the sample 607. The line of sight of the second detector 609 is provided by an aperture 625 in the arm 624.

[0171] In this configuration, the aperture 625 is arranged as a symmetrical cutout, which is positioned so as to maintain the two-fold rotational symmetry of the plurality of sensors included in the detector module 618. In this embodiment, the detector module 618 comprises a first X-ray sensor 608 arranged as two different sensor elements, in addition to four backscattered electron sensor elements 627 having a symmetrical arrangement.

[0172] Figure 7 The plan view in Figure 1 shows a second embodiment detector module that may form part of an embodiment system according to the present invention. The module includes two circular X-ray sensors included in a first X-ray detector 708 in the form of silicon drift detectors, and two backscattered electron sensor segments 727 having dual rotational symmetry. The outer boundary of the approximately elliptical module is configured to provide two regions in which the radial distance from the electron beam 610 axis to the periphery is reduced to reduce obstruction of the second X-ray detector or any auxiliary detector in either direction. With this arrangement, a module having a length of 21.2 mm can accommodate two silicon drift detector sensors to obtain a 14 mm 2 or greater, the minimum radial distance from the beam axis to the periphery is less than 4.5 mm. Figure 6 In the illustrated embodiment, a central hole 733 is required in the module to allow the focused electron beam to travel toward the sample. After long-term use in an electron microscope, contaminant material may accumulate on this aperture 733, and charge may accumulate on the material. If the edge of the hole is too close to the focused electron beam 610, the electron beam profile may be distorted and the quality of the microscope image may be degraded. If the module support arm 624 is inserted from the side port on the electron microscope, the hole must be carefully aligned with the electron beam axis to maximize the distance between the focused electron beam and the side walls of the holes 633, 733. The smaller the hole, the more difficult it is to align. In addition, a small portion of the electrons in the incident beam may fall outside the main focused beam and constitute a "beam tail" with an intensity far exceeding that of the main beam. If some of the beam tail falls on one side of the aperture, it may exacerbate the accumulation of contaminants. Therefore, it is beneficial to provide a central hole 733 as large as possible, thereby minimizing these potential problems. However, if the sensor elements in the module 718 are located further away from the channel to accommodate these, the solid angle subtended at the sample beam spot will be reduced, so a compromise is involved. It has been found that in most scanning electron microscopes the inner diameter of the central aperture may optimally be at least 1.5 mm, preferably greater than 2.5 mm, to avoid these effects.

[0173] Another advantage of having an X-ray sensor 708 below the pole piece is that it can detect X-rays emitted from material that is not visible to side-mounted auxiliary detectors, such as for samples with rough or angled surfaces where the focused electron beam can strike the material at a depression. X-rays emitted from the detection point can reach any part of the line of sight of the first X-ray detector and will not be blocked by the side walls of the depression. Therefore, it is desirable to have as much of the active area of ​​the sensor as possible within a small radial distance from the electron beam axis. If the surface of the sensor is 6 mm from the detection point on the sample, an X-ray emitted at an elevation angle θ of 45° relative to the horizontal will strike the sensor at a radial distance of 6 mm from the axis. It is desirable that at least half of the total active area of ​​the X-ray sensor be within 6 mm of the axis to provide some analytical capability for the material at the bottom of the depression.

[0174] Providing the BSE sensor elements 727 in the module with at least twofold rotational symmetry about the focused beam axis is advantageous because the arrangement reduces the effect of topography on the total BSE signal, making it more representative of the material composition rather than the local orientation of the surface. It is also beneficial for the first X-ray detector sensor elements to be arranged symmetrically about the focused beam axis, particularly when observing samples with high surface topography. If the incident electron beam hits an object at the bottom of a "cliff", the cliff itself may block the X-rays from advancing to one of the first X-ray detector sensor elements. However, if the other X-ray sensor element is radially opposite, it can still have a clear view of the object and thus detect X-ray emissions from the object. In addition, for samples with locally flat surfaces and both first X-ray detector sensor elements have a clear view of the detection point, the emitted X-rays will be affected by so-called "matrix" effects, such as sample self-absorption, which depends on the surface orientation. If the surface is tilted from the horizontal and the first X-ray detector sensor element has twofold rotational symmetry about the focused electron beam axis, averaging the signals from the two sensors will reduce the effect of the surface tilt on the matrix effect.

[0175] While the two-fold rotational symmetry of the sensor helps reduce topographic effects, the overall response of the sensor to the excitation signal will change when the incident electron beam is deflected to different locations on the sample surface. When the focused electron beam is deflected to an off-axis position on the sample, the collection solid angle of the electrons or X-rays is larger for sensors closer to the beam position on the sample. For positions along the line between the two sensors projected onto the sample surface, the increase in the collection solid angle of one sensor is roughly compensated by the decrease in the solid angle of the opposing sensor. However, for beam positions perpendicular to this line, the collection solid angles of both sensors decrease as the distance from the central axis increases.

[0176] The higher the SEM magnification, the smaller the maximum scan deflection across the sample covering the field of view, and the smaller any variation in signal detection efficiency at different locations within the field of view. However, for a common SEM at a fairly low 200X magnification, the field of view will be about 1.5 mm wide, and for example for Figure 7 For the design shown, variations in the collection solid angle with position can result in a variation of several percentage points in the response across the field of view. The BSE signal can distinguish between materials of different composition, so a signal threshold can be defined to elucidate regions of different materials within the field of view, but any spatial variation in the signal collection efficiency will make such elucidation unreliable when the average atomic number of the materials is similar. Therefore, the extent of this response non-uniformity is particularly important for the BSE signal. The physics of BSE emission is well known and can be simulated using Monte Carlo techniques, which allow predictions of the distribution of backscattered electrons as a function of both angle and energy. When the beam position is at the upper left or lower right of the field of view, it is closest to one or the other of the two BSE sensors, and the total response is 3.3% greater than when the position is on the central axis. When the beam position is at the upper right or lower left, it is farther from both sensors, and the total response is 3% less than the central position.

[0177] For applications where non-uniformity of response over a large field of view is unacceptable, a conventional solution would be to use a full disk or 4-fold symmetric segmented BSE detector. However, this would require moving the SDD X-ray sensor further away from the beam axis and compromise the collection solid angle for X-ray detection. The alternative approach of placing the BSE sensor ring outside the X-ray sensor would reduce the BSE signal per unit area of ​​the sensor since it is well known that the intensity of BSE electrons decreases approximately with the cosine of the emission angle with the surface normal. Increasing the diameter of the module to increase BSE or X-ray sensitivity would increase the likelihood of blocking the line of sight of other equipment in the SEM chamber or detectors mounted on one side. To avoid these compromises, systems in accordance with embodiments of the present invention advantageously achieve a more uniform BSE response over a large field of view with only elliptical modules having two-fold rotational symmetry, such as Figure 8 The module shown is exemplified as having a length of 26.5 mm.

[0178] Figure 8 A third embodiment detector module is shown in plan view, which may form part of an embodiment system according to the invention. Module 818 comprises: two circular X-ray sensor elements on either side of a central aperture 833 for forming a first X-ray detector 808, and four backscattered electron sensor segments 827a, 827b, 827c, 827d having double rotational symmetry.

[0179] BSE sensor elements 827c and 827d are closest to the central axis and are therefore most effective at detecting BSE electrons. The overall response of sensors 827c and 827d will show non-uniformity over a large field of view, with the weakest response being at the farthest ends of a line perpendicular to the vertical line connecting the sensors. Additional BSE sensors 827a and 827b on top of SDD X-ray sensor 808 help compensate for this drop in sensitivity. Figure 8 The BSE response of the sum of all sensors is calculated for the 2D module, where the inlet surface of the BSE sensor is again located 5.8 mm above the sample surface and 1.5 mm above the sample. 2 The response uniformity across the area is improved. Here, the maximum response is only 0.2% greater than at the center, and the minimum response is only 0.7% less than at the center.

[0180] The uniformity of the overall BSE response can be further improved by increasing the size of BSE sensors 827a and 827b to compensate for the reduced efficiency compared to sensors 827c and 827d due to the cosine emission response. However, the changes required to improve uniformity will necessarily increase the length of the module, which will increase the likelihood of shading other devices within the SEM chamber. Instead of increasing the diameter, the response of BSE sensors 827a and 827b can be amplified by electronic, digital, or software calculation methods to compensate for the signal loss due to the cosine emission response. For Figure 8 For the module in , if the amplification is used to obtain a result equal to 3.3 times the total response of sensors 1 and 2 plus the total response of sensors 827a and 827b, the minimum value is the same as the center position and the maximum response is only 0.2% larger.

[0181] Although uniformity is improved by this amplification of the signal from sensors 827a and 827b, the noise in that portion of the signal is also amplified. The minimum noise is fundamentally limited by the electron flux striking the sensor, and the smaller the sensor, the greater the noise. Therefore, the larger the amplification factor, the more the noise in the total response will increase, so there is a tradeoff between improving the consistency of the response with beam position and reducing the signal-to-noise ratio of the total response. The BSE sensor can be divided into more segments and different levels of amplification applied before summing the signals to further improve the uniformity of the spatial response.

[0182] According to an advantageous embodiment of the present invention, for example Fig. 9 As shown, the figure depicts the Figure 7A top view of an embodiment arrangement for implementing the method according to the present invention in a scanning electron microscope of the module shown. The sub-pole detector module 918 is shown from below, that is, from the direction of the sample (not shown), and is arranged on a support arm 924. Module 918 includes a first X-ray detector 908, which includes two circular sensor elements and two backscattered electron sensor elements 927a, 927b. The module adopts the cut-out geometry of a side-mounted detector. In this embodiment, a second X-ray detector provided as a conventional side-mounted detector 909 is shown and includes an electron trap 912. The second X-ray detector 909 is provided with a line of sight to the sample (not shown) by the cut-out 929 portion of the detector module 918. Module 918 also includes a center hole 933 so that a focused electron beam (not shown) can advance from the beam assembly through the center hole to the sample. The arrangement also includes a secondary electron detector 926 mounted to the side of the instrument.

[0183] Furthermore, the apparatus according to the present embodiment includes another X-ray detector 919 which is similar to the second X-ray detector and is arranged on the opposite side of the instrument thereto. Fig.10 A side view of the device is shown. The further X-ray detector provides a further improvement to the X-ray signals that can be monitored by the system and can be considered as part of the second X-ray detector because it includes a further X-ray sensor active area, and signals and data from the further X-ray sensor active area can be processed together with those from the second X-ray detector.

[0184] The two X-ray sensor elements of the first X-ray detector, and the two backscatter sensor elements are arranged symmetrically around an aperture that allows the electron beam from the electron source to be focused onto the sample by the electron optical column. The symmetrical arrangement of the sensors is designed so that the strength of the signal is independent of the geometry of the detector. A retractable arm 924 supporting the sub-pole piece sensor arrangement provides cooling of the sensor head via a TEC having a heat pipe for dissipating heat to an external heat sink. The arm also provides electrical connections for power, control and signal output to external pre-amplification circuitry. The shape of the arm 924 is designed so that its lower end is flush with the bottom of the sensor head, as shown in FIG. Fig.10 This means that if all samples in the microscope chamber are mounted below the height of the module head, there will be no impact on the detector when the samples are moved back and forth by the operator-controlled motorized XY stage. The arm is retracted and inserted by an external motor which moves the detector from its in-use position, under the pole piece, to a position where it is completely outside the microscope vacuum chamber wall when not in use. This allows the microscope to be used outside of conditions where a filter would protect the X-ray sensor from backscattered electrons, or where this equipment is not required, such as when using shorter working distances.

[0185] The present embodiment is advantageously provided with an interlocking device which is configured to control the position and movement of components of the system. In the present case, because the arm 1024 is arranged so that it retracts in a direction away from the second detector 1009, no collision will occur between the arm and the detector even if 1009 does not move. However, in alternative arrangements, the alignment may be different so that the components may collide when moved. For example, in an alternative arrangement in which the second X-ray detector 1009 protrudes below the height of the upper surface of the sub-pole module 1018, in the absence of an interlock, a collision with the detector would result during insertion or retraction. In this case, the interlocking of the present embodiment will operate to retract the detector 1009 before moving the arm 1024.

[0186] Before the arm of the sub-pole piece probe is retracted, the downwardly protruding probe 1009 is automatically retracted by interlocking software controlling one or more motors or actuators used to position system components to avoid any potential collision.

[0187] In front of the X-ray sensor is a filter designed to block the vast majority of backscattered electrons with energies up to 20 keV, allowing a beam energy of 20 kV to be used when using the device. Using this filter, X-rays with energies above 1 keV can be detected, as described in WO 2022 / 008924A1.

[0188] The electron trap 912, 942 with two side mounted conventional EDS detectors 909, 919 is adapted to block backscattered electrons up to the maximum energy of the electron gun (typically 30 keV). When working at the design working distance of 8.5 mm below the pole piece, the cutout is up to 150 mm in size 2 The X-ray sensor provides complete line of sight.

[0189] A secondary electron detector 926 is provided for detecting secondary elements emitted by the sample during electron bombardment. An offset collection grid in front of this detector means that a direct line of sight to the sample is not required.

[0190] Using this embodiment system, secondary electrons, backscattered electrons and X-rays can be collected simultaneously.

[0191] The signals from the detector are transmitted through a preamplifier in the detector body outside the vacuum chamber. The electron and X-ray signals are then transmitted to the signal pulse processor, which processes up to four signals (two sub-pole sensors and up to two conventional EDS detectors). The electron signal is processed separately.

[0192] In this embodiment, the image frames acquired during the method are presented on a visual display within a graphical computer user interface. Portions of the guiding user interface are as follows Figure 11-13 shown.

[0193] As the electron beam is scanned across the field of view of the sample as in step 311, the X-ray spectra of each channel and the electron intensity of each pixel are stored. The spectra from the sub-pole X-ray sensor elements are added into a single spectrum. An image is constructed by displaying the electron signal or signal intensity at each pixel of the element. The element intensity is calculated by counting all X-ray counts in a selected energy range corresponding to X-rays that characterize the element.

[0194] In normal operation, up to two first image frames (ie, electronic image frames) and multiple second image frames (ie, elemental image frames) are displayed simultaneously. The electronic image comes from the secondary electron detector 1026 and the combined signal comes from the two electronic sensor elements in the sub-pole head 1018.

[0195] Embodiment electronic image frame such as Fig.11 The left frame in the figure shows the image from the secondary electron detector, and the right frame shows the image from the backscatter sensor element below the pole piece detector.

[0196] The elements to be displayed are determined by an automatic peak identification routine. This takes the spectrum as the sum of all pixels in the field of view from the side mounted conventional detector 1009 (the sum spectrum) to form a list of elements.

[0197] For each frame, any new elements identified may be added to the element list, and any elements previously detected, for example no longer detected in a previously visited microscope field of view, may be removed.

[0198] For each element in the list a second image frame is displayed, i.e. the element image. Depending on the selection of the highest signal intensity for each element, the second image frame is formed by the data provided by the sensors under the added pole piece or by the data provided by the side mounted conventional detector. This will vary depending on the relative solid angles of the sensors, but for the present embodiment device, data for elements characterized by lines with energies greater than 1.2 keV will be derived from the first detector under the pole piece in module 1018 (because the filter used in this embodiment increasingly attenuates X-rays with energies below 1.2 KeV), and image frames for elements with spectral lines less than 1.2 keV will use data from conventional detectors 1009, 1019.

[0199] Fig.12 An example X-ray image of a second image frame is shown, which depicts Fig.11The displayed X-ray image frames C Kα1-2 and O Kα1 are calculated based on X-rays with energies less than 1.2 keV and are therefore calculated based on data obtained by the side-mounted second detector 909 and the further detector 919. Si Kα1, Al Kα1, TI Kα1 and P Kα1 are calculated based on X-rays with energies greater than 1.2 keV and are therefore calculated based on data from the sub-pole piece X-ray detector 908.

[0200] In this embodiment, the first criterion is configured such that each second image frame is derived from data selected from data output by the first X-ray detector 908 and the second X-ray detector 909 based on the monitoring X-ray energy. Implementing the criterion to achieve a threshold energy value is one way to optimize the quality of the X-ray image data, which threshold energy value determines which detector data to use when generating a given X-ray element map. However, as described earlier in this disclosure, other processing methods are contemplated.

[0201] Furthermore, the value of such a threshold may be selected based on a number of factors that affect the signals monitored by the various sensors, and may be specific to a given device, sensor assembly, and / or a particular relative arrangement thereof.

[0202] The acquired image frames can be combined in a variety of ways to produce compound image frames. They can be displayed individually. They can also be displayed as a composite image in which the intensity represents the pixel value from one image (usually the electronic image, i.e. the first image frame), and the hue of each compound image frame pixel is calculated by selecting different colors for each element image frame and mixing the hue of these element image frames with the intensity of the electronic image to produce a composite image such as Fig.13 The result shown is shown in FIG. This figure shows a user interface displaying an image frame of an example compound obtained by an example method according to the present invention.

[0203] The compound image frame includes a composite image 1337 formed by a secondary electron frame or a first image frame (determining pixel intensity) and a hue determined based on multiple element maps. The individual pixel hues are based on the contribution of the corresponding pixel values ​​of the second image frame of the specific element, where each is assigned a color, including Mg (orange), Al (blue), Si (green), Cr (yellow) and Fe (magenta). In addition, in this embodiment, the compound image frame includes a second image frame 1338 of individual elements, which includes an oxygen element map derived from the signal (energy 0.5 keV) acquired from the second side-mounted conventional EDS detector 909, 919, and other maps derived from data obtained from the first sub-pole piece X-ray detector (energy>1.2 keV) 908. Electron images 1339, 1340 from the secondary electron detector 924 and the electron sensor 927 in the sub-pole piece head 918 are also shown.

[0204] The embodiment methods and systems described in the present disclosure allow for simultaneous monitoring of information from electrons and X-rays of all elements present in a sample. As described above, the data obtained therefrom can then be processed in a variety of different ways and presented on a software interface. These can be achieved by configuring different first criteria according to which the pixel values ​​of the respective second image frames are derived.

[0205] As described above, the method of the first embodiment can be summarized as: using an X-ray detector in a first X-ray detector and a second X-ray detector that receives the highest X-ray intensity of an element or outputs data with a highest signal-to-noise ratio, obtaining an electronic image frame to display the morphology as well as the elemental image; and displaying the image frames as juxtaposed frames in a compound image frame, and / or superimposing them, wherein each element is assigned a different tone and the electronic image provides intensity.

[0206] Other display modes that can be displayed are as follows.

[0207] A second approach may involve processing the X-ray data to remove variations in the X-ray background, which may be due to large differences in average atomic number, for example. Processing may also be applicable in cases where the signals from two or more elements cannot be separated by the above processing methods.

[0208] This can be summarized as: using the detector with the highest X-ray intensity for the element, obtaining an electronic image frame showing the morphology, and processing the elemental image at each pixel to remove noise and separate closely occurring peaks; and displaying the image frames separately and / or superimposing the image frames, where the individual elements are given different hues and the electronic image provides the intensity.

[0209] A third embodiment method that can be advantageously employed includes combining the acquired analysis data by adding pixels together. For example, a 2x2 block of four pixels can each add their constituent pixels together. In this manner, for example, a 256x256 pixel array of an image frame can become a 128x128 pixel image frame with pixels of higher intensity. Thus, elemental images from X-ray data can combine their pixels to produce an image resolution lower than that of an electronic image, but with an improved S / N.

[0210] Advantageous variations of the method include merging elemental images derived from data from different detectors by varying amounts, with a greater degree of merging of images of lower intensity or lower S / N data from the side-incident second X-ray detector 909. For example, the elemental image from the side-mounted detector 909 may have a 4x4 binning pixel block, and the elemental image from the under-pole detector 908 may have a 2x2 binning pixel block, so that a greater degree of pixel aggregation and thus S / N improvement at the expense of pixel resolution is applied to the data from the smaller solid angle conventional detector 909.

[0211] This approach can be summarized as follows: an electronic image frame is obtained to show the morphology, and an X-ray elemental image is obtained using the detector with the highest X-ray intensity for the element, with the pixels additionally combined or averaged (smoothed) to different levels according to their intensity. In this way, the pixels used for the electronic image will have a higher resolution than those from the sub-pole detector. Those from the conventional detector will have the lowest intensity and therefore the highest degree of merging. The image frame will again be displayed individually and / or superimposed, with the individual elements being given different tones, and the electronic image providing the intensity.

[0212] In the fourth embodiment method, for at least some elements, it may be advantageous to combine the signals from two different types of X-ray detectors, for example where the S / N of the two detectors are similar and the difference is primarily in the signal level. This may be the case for elements with high energy lines, whereas in the previously described method, the under-pole detector 908 is used because it has the highest intensity.

[0213] This fourth method can be summarized as: obtaining an electronic image to display morphological and elemental images by summing the intensities from both the first detector 908 and the second detector 909 or from one type of X-ray detector, thereby maximizing intensity and signal-to-noise ratio; displaying image frames individually and / or superimposing image frames, where each element is given a different tone and the electronic image provides the intensity.

[0214] A fifth method includes summing the signals from the sub-pole piece backscattered electron detector 927 in the sub-pole piece detector head 918. If such an electronic sensor is included in the sub-pole piece module, the backscattered electrons can be detected to form an atomic or material contrast image. This image is advantageous for samples that have been polished and have no topography, so that the amount of useful image detail in the first image frame attributable to the signal acquired by the secondary electron detector 926 is low.

[0215] The compound image frame may include any one or more of: an electron image showing atomic number contrast for each element indicating the highest X-ray intensity, an electron image showing topography, and an element image using data from an X-ray detector. The compound image frame may again be displayed individually and / or superimposed, with each element being given a different hue and the electron image providing the intensity.

[0216] The sixth embodiment method involves a post-acquisition mode, where regions of identical composition can be selected manually or using a phase clustering method. The spectra of these regions can be calculated by adding the sum of the pixels in these regions. Using a conventional detector 909 would be advantageous because it has better spectral resolution. In addition, quantitative algorithms for determining the composition of these regions are also well established. This is a variation of the method described in WO 2022 / 008924 A1. However, in this case, the composition is determined rather than creating a new elemental image. This method can be summarized as follows: pixels of the same chemical composition identified from the X-ray image are added together to form a spectrum. The added spectrum of the individual phases entering the detector from the side can be used to determine the composition.

[0217] The present invention may be further understood by referring to the following numbers.

[0218] Terms:

[0219] Clause 1. Analyzer systems in electron microscopes,

[0220] The electron microscope comprises an electron detector for detecting secondary electrons or backscattered electrons,

[0221] The analyzer system comprises:

[0222] a first detector module disposed between the beam source and the sample, the first detector module having one or more X-ray sensor portions facing the sample and at least partially surrounding the incident charged particle beam, and one or more filters between the sample and the one or more X-ray sensors,

[0223] The second detector module, including the X-ray sensor and the electron trap,

[0224] A control part, used for controlling the electron microscope system, the first detector module and the second detector module,

[0225] an element analyzer for performing element analysis based on output signals from the first detector module and the second detector module,

[0226] The image display part uses the first detector module in combination with an electronic detector to display one or more compound images. The image display part displays a series of compound image frames on a visual display in real time as the field of view of the microscope changes.

[0227] Clause 2. The apparatus of clause 1, wherein the image display portion displays one or more compound images using a combination of the first detector module and the second detector module and an electronic detector.

[0228] Clause 3. An apparatus according to clause 2, wherein more images from the X-ray detectors are merged according to the reduced level of intensity.

[0229] Clause 4. The apparatus of clause 1, wherein the first detector module further comprises one or more electronic detectors.

[0230] Clause 5. The apparatus of clause 4, wherein the image display portion displays one or more compound images using a combination of the first and second detector modules and an electronic detector.

[0231] Clause 6. The apparatus of clause 5, wherein more images from the X-ray detectors are merged based on the level of reduction in intensity.

[0232] Clause 7. The apparatus of clause 1, wherein the positions of the two detectors are known and insertion and retraction between the two detectors are coordinated to avoid collision.

Claims

1. A method for analyzing a sample in a microscope, the method comprising: acquiring a series of compound image frames using an electron detector, a first X-ray detector, and a second X-ray detector, wherein the first X-ray detector is located between the sample and an electron beam source, a focused electron beam is emitted from the electron beam source toward the sample, and a filter member is provided, the filter member is inserted between the first X-ray detector and the sample and is adapted to reduce the incidence of electrons on the first X-ray detector, wherein the second X-ray detector is provided with a deflector device, the deflector device being configured to reduce the incidence of electrons on the second X-ray detector, And wherein acquiring the compound image frame comprises: a) passing the focused electron beam across a sample area; b) monitoring a set of generated electrons emitted from a plurality of locations within the sample region using the electron detector to obtain a first image frame, the first image frame comprising a plurality of pixels, the plurality of pixels corresponding to the plurality of locations and the plurality of pixels having values ​​derived from the monitored electrons emitted from the plurality of locations; c) using the first X-ray detector and the second X-ray detector to monitor the first group of generated X-rays and the second group of generated X-rays emitted from the plurality of positions, respectively, to obtain one or more second image frames, each of the second image frames comprising a plurality of pixels corresponding to the plurality of positions and having values ​​derived from the monitoring X-rays characterizing the respective chemical elements and emitted from the plurality of positions according to respective first standards, wherein for each of the one or more second image frames, a respective first standard is configured according to the respective chemical element, wherein the set of electrons and the first and second sets of X-rays are emitted from the sample substantially simultaneously; and d) combining the first image frame and the one or more second image frames to produce the compound image frame, such that the compound image frame provides data derived from monitoring electrons and X-rays emitted from a plurality of locations within the region, and displaying the series of compound image frames on a visual display, wherein the visual display is updated to display each compound image frame in sequence.

2. The method of claim 1, wherein the first criterion is configured such that step (c) further comprises, Summed data is obtained by summing data representing the first set of monitoring X-rays and data representing the second set of monitoring X-rays, and pixel values ​​of each of the one or more second image frames are obtained from the summed data.

3. A method according to claim 1, wherein the first standard is configured so that for each of the one or more second image frames, deriving a pixel value according to the first standard includes processing data obtained from each of the first X-ray detector and the second X-ray detector to obtain a first set of values ​​and a second set of values ​​representing corresponding chemical elements, and wherein the pixel value is obtained from the first set of values ​​and the second set of values. The method of claim 3 , wherein obtaining the pixel value comprises summing the first set of values ​​and the second set of values.

5. The method of claim 3, wherein obtaining the pixel value comprises obtaining the pixel value from a value selected from the first set of values ​​and the second set of values.

6. The method of any one of claims 3 to 5, wherein obtaining the pixel value comprises combining the first set of values ​​and the second set of values ​​according to a weighting function.

7. A method according to any one of claims 3 to 5, wherein the first standard is configured so that for each second image frame, a pixel value is derived based on the intensity of the output signals of the first X-ray detector and the second X-ray detector respectively for X-rays characterizing the chemical element corresponding to the second image frame.

8. The method of claim 7, wherein the method further comprises filling in a set of identified chemical elements based on a second set of X-rays monitored during acquisition of at least one compound image frame in the series of compound image frames, And wherein in the process of acquiring at least one of the series of compound image frames, step (c) includes obtaining respective second image frames for corresponding chemical elements in the identified group of chemical elements.

9. The method according to any one of claims 3 to 5, wherein for at least one of the one or more second image frames, acquiring a compound image frame further comprises, according to an aggregation criterion: for each of one or more subsets of pixels in the second image frame, combining the values ​​of the pixels in the subset to obtain one or more corresponding aggregate pixel values, and Each of one or more subsets of pixels in the second image frame is replaced with an aggregated pixel having a value equal to the corresponding aggregated pixel value.

10. The method of claim 9, wherein the aggregation criteria is configured according to an X-ray detector for monitoring X-rays from which pixel values ​​in the second image frame are derived.

11. The method of claim 9, wherein each of the subsets comprises a plurality of pixels configured according to signal parameter values ​​corresponding to respective monitoring X-rays from which the pixel values ​​are derived.

12. A method according to claim 11, wherein the signal parameters are configured so that the number of pixels depends on the solid angle subtended by the total sensor area of ​​one of the first X-ray detector and the second X-ray detector, the first X-ray detector and the second X-ray detector being used to monitor the following X-rays, from which the pixel values ​​of the second image frame are derived at the position where the electron beam strikes the sample.

13. The method according to any one of claims 1 to 5, wherein step (c) comprises obtaining at least two second image frames, wherein: at least one of the second image frames comprises a plurality of pixels corresponding to a plurality of locations and having values ​​derived according to the first criterion from monitoring X-rays included in the first group and characterizing the corresponding chemical elements and emitted from the plurality of locations, and At least another one of the second image frames includes a plurality of pixels corresponding to a plurality of locations and having values ​​derived according to the first criterion from monitoring X-rays included in the second group and characterizing the corresponding chemical elements and emitted from the plurality of locations.

14. The method of any one of claims 1 to 5, wherein the method further comprises defining a set of chemical elements for at least a portion of the series of compound image frames corresponding to a set of spectral peaks identified from one or both of the first and second sets of X-rays monitored during acquisition of the portion of the series, and The step (c) of acquiring compound image frames includes obtaining corresponding second image frames corresponding to each chemical element in the chemical element group.

15. The method according to any one of claims 1 to 5, wherein a pixel of the first one of the one or more second image frames has a value derived from a combination of a corresponding third group of monitoring X-rays and a corresponding fourth group of monitoring X-rays characterizing a corresponding second chemical element different from the corresponding first chemical element, and the respective corresponding third group of monitoring X-rays and fourth group of monitoring X-rays are selected from the first group and the second group according to the first criterion.

16. The method of any one of claims 1 to 5, wherein step (c) comprises obtaining a plurality of second image frames, and wherein generating the compound image frame comprises juxtaposing two or more of the second image frames.

17. The method of any one of the preceding claims 1 to 5, wherein step (c) comprises obtaining a plurality of second image frames, and wherein generating the compound image frame comprises superimposing two or more of the second image frames.

18. A system for analyzing a sample in a microscope, the system comprising: a first X-ray detector adapted, in use, to be located between a sample and an electron beam source from which a focused electron beam exits towards the sample, a filter member arranged such that, in use, it is inserted between the first X-ray detector and the sample, the filter member being adapted to reduce the incidence of electrons on the first X-ray detector, a second X-ray detector provided with deflector means adapted to reduce the incidence of electrons on the second X-ray detector in use, a control module configured to acquire a series of compound image frames using an electron detector, the first X-ray detector, and the second X-ray detector, Acquiring compound image frames includes: a) passing the focused electron beam across a sample area; b) monitoring, using the electron detector, a set of generated electrons emitted from a plurality of locations within the sample region to obtain a first image frame, the first image frame comprising a plurality of pixels corresponding to the plurality of locations and having values ​​derived from the monitored electrons emitted from the plurality of locations; c) using the first X-ray detector and the second X-ray detector to monitor the first group of generated X-rays and the second group of generated X-rays emitted from the plurality of positions, respectively, to obtain one or more second image frames, each of which includes a plurality of pixels corresponding to the plurality of positions and having values ​​derived from the monitoring X-rays characterizing the corresponding chemical elements and emitted from the plurality of positions according to the corresponding first standards, wherein for each of the one or more second image frames: a corresponding first standard is configured according to the corresponding chemical element, wherein the set of electrons and the first and second sets of X-rays are emitted from the sample substantially simultaneously; and d) combining the first image frame and the one or more second image frames to produce the compound image frame, such that the compound image frame provides data derived from monitoring electrons and X-rays emitted from the plurality of locations within the region, and a display module configured to display the series of compound image frames on a visual display, wherein the visual display is updated to display the individual compound image frames in sequence.

19. A system according to claim 18, comprising a detector module adapted to be located, in use, between a sample and a pole piece of an electron beam assembly from which a focused electron beam emerges towards the sample, the detector module comprising the first X-ray detector and the filter member.

20. The system of claim 19, wherein the detector module further comprises an electronic detector.

21. A system according to any one of claims 18 to 20, wherein the deflector arrangement comprises magnet arrangement for generating a magnetic field to deflect electrons away from the second X-ray detector.

22. The system of claim 21, wherein the magnet device comprises any one or more of a permanent magnet and an electromagnet proximate to the second X-ray detector.

23. The system of claim 21, wherein the magnet arrangement comprises a magnet of an electron beam assembly of a microscope.

24. A system according to any one of claims 18 to 20, wherein the deflector arrangement comprises electrode arrangement for generating an electric field to deflect electrons away from the second X-ray detector.

25. A system according to any one of claims 18 to 20, wherein the deflector arrangement is adapted to deflect electrons having an energy greater than 100 eV and less than at least 99% of a configured beam energy of the focused electron beam away from the second X-ray detector.

26. The system of any one of claims 18 to 20, further comprising an interlock mechanism configured to control a position of one or each of the first and second X-ray detectors to prevent collision thereof.

27. A non-transitory computer readable medium storing instructions executable by one or more processors to cause the one or more processors to perform the method according to any one of claims 1 to 17.

Images