Charged particle microscope with charged particle detector

Abstract

A charged particle microscope incorporating a dual data stream output interface within its imaging system. These interfaces enable the microscope to capture and process data from the charged particle camera in two different ways, resulting in enhanced imaging capability and improved flexibility. The method has the potential of remarkably promoting the progress in the field of charged particle microscopy and being applied to various scientific and industrial environments.

Description

TECHNICAL FIELD

[0001] The present invention relates to a charged particle microscope for imaging a sample. More specifically, it relates to a system for generating detailed images of a sample using a charged particle optical column, a sample holder, a charged particle camera and an imaging system. BACKGROUND

[0002] In various scientific and industrial applications, it is often necessary to examine the microstructure and composition of a sample. Conventional optical microscopes have limitations in resolution and cannot provide sufficient detail for certain types of samples. To overcome these limitations, charged particle microscopes have been developed.

[0003] Charged particle microscopy is a well-known and increasingly important technique for imaging microscopic objects, particularly in the form of electron microscopy. Historically, the basic categories of electron microscopes have evolved into a number of well-known device types, such as transmission electron microscopes (TEM), scanning electron microscopes (SEM) and scanning transmission electron microscopes (STEM), and further into various sub-types, such as the so-called "dual beam" devices (e.g. FIB-SEM) which additionally employ a focused ion beam (FIB) allowing for safeguarding activities such as ion beam milling or ion beam induced deposition (IBID). The person skilled in the art will be familiar with the different types of charged particle microscopy.

[0004] These charged particle microscopes generally comprise several components, which will be explained in the following.

[0005] Firstly, a charged particle microscope comprises a charged particle optical column for directing a charged particle beam onto a sample. The optical column is responsible for directing and controlling the charged particles to the sample to ensure accurate imaging.

[0006] Further, a charged particle microscope comprises a sample holder for securely holding the sample in place during the imaging process. The sample holder is typically designed to accommodate various sample sizes and shapes, providing positioning stability and reproducibility.

[0007] Further, a charged particle microscope comprises a charged particle camera for capturing the charged particles that have interacted with the sample. The charged particle camera converts the energy or intensity of the charged particles into an electrical signal, which can be further processed for image generation.

[0008] A charged particle microscope further comprises an imaging system arranged for processing the signals from the charged particle camera. The imaging system receives the data from the charged particle camera and generates an image signal based on the collected information.

[0009] A charged particle microscope comprises a charged particle camera output interface capable of outputting a data stream related to the charged particle camera. In existing imaging systems, especially those incorporating a transmission electron microscope (TEM) camera, the output interface is designed to provide optimal image quality, with a focus on high reliability of the data and ensuring minimal loss of data.

[0010] In the field of charged particle microscopy, and in particular transmission electron microscopy (TEM), there are still significant challenges in certain applications, including drift active compensation based on image-based drift, continuous tilt tomography field correction, and system state measurement methods. Existing systems show limitations, especially in the context of electron counting cameras where electron counting algorithms play a key role.

[0011] Therefore, there is a need for systems and methods that effectively support these applications while not compromising the overall performance of the imaging system. SUMMARY

[0012] It is therefore an object of the present disclosure to provide an improved charged particle microscope and / or an improved method. In particular, it is an object of the present disclosure to provide a charged particle microscope that allows for real-time feedback without compromising the reliability of the data, while ensuring minimal loss of data.

[0013] To this end, the present disclosure provides a charged particle microscope as defined in claim 1. The charged particle microscope as disclosed herein comprises a charged particle optical column. The column is arranged for guiding a charged particle beam, such as an electron beam or an ion beam, onto a sample. The system further comprises a sample holder for holding a sample. The system comprises a charged particle camera and an imaging system. The imaging system generates an image signal based on information from the detector camera. The imaging system has a first output interface. This interface outputs a first data stream of data related to the camera.

[0014] As defined herein, the charged particle microscope further comprises a second charged particle camera output interface for outputting a second data stream of data related to the charged particle camera. In this sense, the charged particle microscope and the first and second charged particle camera output interfaces are arranged in such a way that the second data stream is different compared to the first data stream.

[0015] According to the present disclosure, the disclosed charged particle microscope provides an effective and innovative solution to the problem of how to provide real-time feedback while maintaining high data quality and reliability. By having two charged particle camera output interfaces arranged for providing data streams that are different compared to each other, the system allows for having two separate data streams available for different purposes.

[0016] For example, the first data stream can aim to prioritize data quality and reliability, ensuring that the data output is accurate and reliable (i.e. maintaining the high image quality standards for which charged particle microscopes are known).

[0017] The second data stream can aim to be optimized for low latency and / or fixed latency, making real-time feedback of one or more critical parameters to the charged particle system possible. The inclusion of this second output interface, and the different setup of the first data stream from the second data stream, allows for real-time feedback that is required (or even essential) for certain applications, such as image-based drift active compensation, continuous tilt tomography field correction or system state measurement methods. Thus, the dual output interface design of the charged particle microscope ensures 1) high data quality and reliability; and 2) provides real-time feedback, achieving a balance that was not possible with previous systems.

[0018] As defined herein, latency relates to the time difference between the time at which a charged particle hits a charged particle camera and the time at which information from that charged particle is ready to be used by any device located downstream of the output interface. Examples of such devices located / locatable downstream of the output interface are given by data storage devices, feedback processing devices, controllers, etc. Latency can relate to an average time difference or a maximum time difference.

[0019] In embodiments suitable for charged particle microscopy, latency is of the order of half the readout integration time of the charged particle camera. For example, if the charged particle camera (which can be a TEM camera) operates at 500 fps, then each pixel readout takes 2 milliseconds (ms). Low latency means that the data from the charged particle camera and output through the second output interface (which data can then be used, for example, by a further processing device) takes a time of the order of the pixel readout. This means that low latency should be of the order of milliseconds. Based on this example, average latency should be of the order of 1 ms and maximum latency should be of the order of 2 ms. Note that excellent results are still provided with a maximum latency of 6 ms.

[0020] Thus, low latency can relate to the frame rate of the charged particle camera, and average low latency can be of the order of half the readout integration time, and maximum latency can be of the order of the readout integration time.

[0021] In summary, the present disclosure describes a charged particle microscope with a dual output data interface that can be used for different data streams: one output interface is optimized, for example, for low latency, thereby increasing the efficiency of the real-time charged particle microscope architecture; and the other output interface is optimized for high quality, reliable data, thereby maintaining the high image quality of the charged particle microscope. The objectives of the present disclosure are thereby achieved.

[0022] Further embodiments will be set out below.

[0023] In one embodiment, the charged particle microscope is arranged in such a way that the second data stream is optimized for low latency output.

[0024] Such a low latency output can be defined with a maximum low latency output of 750 milliseconds, in particular a maximum low latency output of 250 milliseconds. In one example, the system is designed with an average latency in the range of 10 0 milliseconds to 10 1 milliseconds, such as in the order of 1 to 50 milliseconds and preferably in the range of 2 to 8 milliseconds.

[0025] As indicated above, the maximum low latency output can be related to the frame rate of the charged particle camera. For a frame rate of 500 fps, the maximum low latency is preferably in the order of 1 / 500 = 2 milliseconds. For a lower frame rate, such as 250 fps, the maximum low latency can be 1 / 250 = 4 milliseconds. Higher latencies, such as 10 times higher, thus in the order of 10 milliseconds, or even in the order of 100 milliseconds, can still be used to produce acceptable results.

[0026] Additionally or alternatively, the charged particle microscope is arranged in such a way that the second data stream has a substantially fixed low latency output. Such a fixed low latency output can have an average latency output below 100 milliseconds. In one example, the system is designed with an average latency in the range of 10 0 milliseconds to 10 1 milliseconds, such as in the order of 1 to 50 milliseconds and preferably in the range of 2 to 8 milliseconds.

[0027] In one embodiment, the charged particle microscope is arranged in such a way that the second data stream has an average low latency output below 100 milliseconds and has a maximum low latency output of 750 milliseconds, preferably 250 milliseconds or less.

[0028] As indicated above, the average low latency output can be related to the frame rate of the charged particle camera. For a frame rate of 500 fps, the average low latency is preferably in the order of 0.5*1 / 500 = 1 millisecond. For a lower frame rate, such as 250 fps, the average low latency can be 0.5*1 / 250 = 2 milliseconds.

[0029] The charged particle microscope can be arranged in such a way that the second data stream is arranged with a lower latency output compared to the first data stream. The latency of the second data stream can be at least one order of magnitude smaller compared to the latency of the first data stream. In one example, the latency of the second data stream can be two orders of magnitude smaller compared to the latency of the first data stream. In one example, the latency for storing high quality data using the first data stream can be up to several seconds (i.e. in the order of 10 3on the order of milliseconds), and the latency of the low-latency second data stream can be up to tens of microseconds (i.e. in the order of 10 1 milliseconds) or even shorter.

[0030] In one embodiment, the charged particle microscope is arranged such that the charged particle microscope and the second charged particle camera output data interface are connected and arranged to provide real-time feedback to the charged particle microscope using the image signals from the imaging system. As mentioned above, this is particularly useful in case the second charged particle camera output is arranged to provide a low-latency and / or fixed-latency output. Such a low-latency and / or fixed-latency output allows to establish a real-time feedback loop, which can be beneficial in applications such as drift active compensation based on image-based, continuous tilt tomography field correction and system state measurement methods. Other applications of real-time feedback loops as described herein are also conceivable.

[0031] In one embodiment, the first data stream is arranged to be optimized for high reliability, which in another embodiment can include that the first data stream is optimized for complete data transmission without substantial data loss. This means that data is transmitted without corrupted packets. In one embodiment, a checksum of the data packet can indicate a transmission error. The charged particle microscope and / or the imaging system can be arranged such that any transmission error indication will result in a request of the receiving side to retransmit the packet. For the second data stream, whenever low latency is required, the charged particle microscope and / or the imaging system can be arranged such that whenever a transmission error is indicated, the data stream is marked as “bad”, but this will not result in any retransmission of that data to prevent latency accumulation / variation.

[0032] In one embodiment, the charged particle microscope comprises a data processing unit upstream of the first and second charged particle camera output interfaces. The data processing unit is arranged to process raw data from the charged particle camera chip in a first step before it is sent to the camera output interface. The data processing unit can be, for example, a field programmable gate array (FPGA), an application specific integrated circuit (ASIC) and / or a graphics processing unit (GPU) that is part of the charged particle camera. Thus, the charged particle camera can comprise a charged particle camera chip that is connected to a data processing unit downstream of the charged particle camera chip. The data processing unit is connected to the second charged particle camera output interface that is provided downstream of the data processing unit.

[0033] The data processing unit can be a processing hardware comprised within the charged particle camera (e.g. a TEM camera) and can be an integral part thereof. The data processing unit can comprise one or more FPGAs, GPUs or CPUs. The data processing unit can be arranged to run processing algorithms on the raw data from the sensor chip.

[0034] The data processing unit can be arranged for processing data provided to the second charged particle camera output interface.

[0035] The data processing unit can additionally or alternatively be arranged for processing data provided to the second charged particle camera output interface.

[0036] The first charged particle camera output can be arranged for outputting said data from the data processing unit. The system can be arranged for storing data from the charged particle camera and processed by the data processing unit on a storage server system connected to the charged particle microscope via the first charged particle camera output. Data stored on the storage server system can be post-processed later, e.g. after the sample imaging experiment is completed.

[0037] In one embodiment, the charged particle microscope comprises a feedback data processing device downstream of the second charged particle camera output interface. Data from the second output data interface can be processed thereby, intended for use as feedback data for the charged particle microscope.

[0038] In one embodiment, the charged particle camera is a charged particle camera arranged for acquiring images from a sample, e.g. a TEM camera. The TEM camera can work in so-called integration mode. In another embodiment, the TEM camera can work in electron counting mode. For integration mode cameras, direct detection can be used, while for indirect detection, a scintillator layer can be used to convert electrons into photons, and the camera detects the photons. Counting cameras can produce “counted frames” or electron event representation (EER) data. Electron counting is an example of a low-level processing pipeline component with slightly increased latency. BRIEF DESCRIPTION OF DRAWINGS

[0039] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0040] Figure 1 A longitudinal cross-sectional view of a charged particle microscope, in particular a transmission charged particle microscope, is shown;

[0041] Figure 2 A longitudinal cross-sectional view of a charged particle microscope, in particular a scanning charged particle microscope, is shown;

[0042] Figure 3 An embodiment of a charged particle microscope with an imaging system as defined herein is shown;

[0043] Figure 4 Another embodiment of a charged particle microscope with an imaging system as defined herein is shown; DETAILED DESCRIPTION

[0044] Figure 1 (not to scale) is a highly schematic depiction of an embodiment of a charged particle microscope M according to an embodiment of the application. More specifically, this figure illustrates an embodiment of a transmission microscope M, in this case a TEM / STEM (although, in the context of the present application, it can equally well be a SEM (see e.g. Figure 2 ), or e.g. an ion-based microscope). In Figure 1 vacuum housing 2, an electron source 4 generates an electron beam B which propagates along an electron optical axis B' and through an electron optical illuminator 6, operative to direct / focus electrons onto a selected portion of a sample S (which can e.g. be (locally) thinned / flattened). Also depicted is a deflector 8 which can be used, inter alia, to effect a scanning motion of the beam B.

[0045] The sample S is held on a sample holder H which is positioned by a positioning device / stage A which moves a base A' to which the sample holder H (detachably) is attached; e.g. the sample holder H can comprise fingers which can be moved, inter alia, in the XY plane (see depicted Cartesian coordinate system; typically, motion parallel to Z and tilting around X / Y will also be possible). Such motion allows different portions of the sample S to be illuminated / imaged / inspected by the electron beam B which travels along the B' axis (in the Z direction) (and / or allows a scanning motion to be performed as an alternative to beam scanning). If desired, an optional cooling device (not depicted) can be brought in close thermal contact with the sample holder H, thereby e.g. maintaining the sample holder (and the sample S thereon) at cryogenic temperature.

[0046] The electron beam B will interact with the sample S in such a way as to cause various types of "stimulated" radiation to be emitted from the sample S, including, for example, secondary electrons, backscattered electrons, X-rays, and optical radiation (cathodoluminescence). If desired, one or more of these radiation types can be detected by means of an analysis device 22, which can be, for example, a combined scintillator / photomultiplier tube or an Energy-Dispersive X-Ray Spectroscopy (EDX) module; in this case, an image can be built using essentially the same principles as in a SEM. Alternatively or additionally, however, the electrons that pass through (and exit from) the sample S and continue to propagate (generally, but often with some deflection / scattering) along the axis B' can be investigated. This transmitted electron flux enters a projection system (projection lens) 24, which will typically include various electrostatic / magnetic lenses, deflectors, correctors (e.g. stigmators), etc. In normal (non-scanning) TEM mode, this projection system 24 can focus the transmitted electron flux onto a phosphor screen 26, which can be retracted / withdrawn (as schematically indicated by arrow 26') from the axis B', if desired. An image (or diffraction pattern) of the sample S (part thereof) will be formed on the screen 26 by the projection system 24, and this image can be viewed through a viewing port 28 in the appropriate part of the wall of the housing 2. The retraction mechanism of the screen 26 can be mechanical and / or electrical in nature, for example, and is not depicted here.

[0047] As an alternative to viewing the image on the screen 26, one can instead use the fact that the depth of focus of the electron flux exiting the projection system 24 is typically quite large (e.g. of the order of 1 meter). Thus, various other types of analysis devices can be used downstream of the screen 26, such as:

[0048] - a TEM detector (camera) 30. At the camera 30, the electron flux can form a static image (or diffraction pattern) that can be processed by the controller / processor 20 and displayed on a display device (not depicted), such as a flat panel display, for example. The camera 30 can be retracted / withdrawn (as schematically indicated by arrow 30') from the axis B', when not needed.

[0049] - a STEM detector (camera) 32. The output of the camera 32 can be recorded as a function of the (X,Y) scan position of the beam B on the sample S, and an image can be constructed that is a "map" of the camera 32 output as a function of X,Y. Instead of a matrix of pixels as is characteristic of the camera 30, the camera 32 can comprise a single pixel with a diameter of, for example, 20 mm. Furthermore, the camera 32 will typically have a much higher acquisition rate (e.g. 10 2 image) than the camera 30 (e.g. 106 Likewise, when not needed, the camera 32 can be retracted / withdrawn (as schematically indicated in terms of arrow 32'), so as to keep it out of the way of the axis B' (though such retraction would not be necessary, e.g., in the case of a donut-shaped annular dark-field camera 32; in such a camera, the central hole would allow flux to pass through when the camera is not in use).

[0050] - As an alternative to imaging using the camera 30 or 32, also a spectrometer detector 34 can be invoked, e.g., which spectrometer detector can be an EELS module.

[0051] It is noted that the order / position of items 30, 32 and 34 is not strict, and many possible variations can be envisaged. For example, the spectrometer detector 34 can also be integrated into the projection system 24.

[0052] In the embodiment shown, the microscope M further comprises a scalable X-ray computed tomography (CT) module, generally indicated by reference numeral 40. In computed tomography (also referred to as tomographic imaging), the source and (opposite) detector are used to view the sample along different lines of sight, so as to obtain a penetrating view of the sample from various perspectives.

[0053] It is noted that the detectors 30, 32, 34 are part of an imaging system, generally indicated by reference numeral 200. The imaging system is arranged to generate image signals based on information from the charged-particle detectors 30, 32, 34, and can be part of the detectors or separate therefrom. A controller (computer processor) 20 is connected to the various shown components via control lines (buses) 20'. This controller 20 can provide a variety of functions, such as synchronizing actions, providing set points, processing signals, performing calculations, and displaying messages / information on a display device (not depicted). Not to mention, the controller 20 (schematically depicted) can be located (partly) inside or outside the housing 2, and can have an integral or composite structure as desired.

[0054] The skilled person will appreciate that it is not necessary to keep the interior of the housing 2 at a strict vacuum; for example, in so-called "ambient TEM / STEM", a background atmosphere of a given gas is intentionally introduced / maintained inside the housing 2. The skilled person will also appreciate that, in practice, it can be advantageous to limit the volume of the housing 2, so that, where possible, it takes the form of a small tube (e.g., of the order of 1 cm in diameter) that essentially hugs the axis B' through which the electron beam used passes, but widens to accommodate structures such as the source 4, the sample holder H, the screen 26, the camera 30, the camera 32, the spectrometer detector 34, etc.

[0055] Reference is now first made to Figure 2 , showing another embodiment of an apparatus as disclosed herein.Figure 2 Fig. 1 (not to scale) is a highly schematic depiction of a charged particle microscope M; more specifically, it shows an embodiment of a non-transmission microscope M, in this case a SEM (although it can equally well be e.g. an ion-based microscope in the context of the present invention). In this figure, parts corresponding to those in Figs. 1A and 1B are indicated using the same reference numerals, and will not be discussed separately here. In addition to these (inter alia) the following parts are present: Figure 1 Figure 1

[0056] - 2a: a vacuum port, which can be opened to introduce / extract an article (assembly, sample) to / from the interior of the vacuum chamber 2, or to which e.g. an auxiliary device / module can be mounted. If desired, the microscope M can comprise multiple such ports 2a;

[0057] - 10a, 10b: lenses / optical elements schematically depicted in the illuminator 6;

[0058] - 12: a voltage source, which allows the sample holder H, or at least the sample S, to be biased (floating) to a potential with respect to ground, if desired;

[0059] - 14: a display, such as an FPD or CRT;

[0060] - 22a, 22b: a segmented electron detector 22a comprising multiple independent detection segments (e.g. quadrants) arranged around a central aperture 22b allowing the beam B to pass. Such a detector can e.g. be used to study the flux (of the angular dependence) of the output (secondary or backscattered) electrons exiting the sample S.

[0061] Thus, Figure 1 and Figure 2 The charged particle microscopes M shown in Figs. 1A and 1B each comprise a charged particle optical column O for directing a charged particle beam B onto a sample S; a sample holder H for holding the sample S; and a charged particle detector 22a, 22b, 30, 32, 34 having an imaging system 200 generating an image signal based on information from the charged particle detector.

[0062] Turning now to Figure 3 , embodiments of a charged particle microscope M are shown, including more details of a charged particle detector D and an imaging system 200 as disclosed herein. It is noted that, in general, the detector D can be any of the TEM camera 30, STEM camera 32, spectrometer detector 34 or segmented detector 22 shown in Figs. 1A or 1B, or generally any charged particle detector. Similarly to Figure 1 or 2, or generally any charged particle detector. Similarly to Figure 1 and Figure 2 ​​The charged particle microscope M comprises a detector D comprising a detector chip 31. Raw data from the detector chip 31 is sent to the input interface 100 of the imaging system 200. The imaging system 200 is arranged to generate an image signal based on the information from the charged particle detector D.

[0063] In the embodiments described herein, the charged particle detector D is a charged particle camera D arranged for acquiring an image of a sample. It is noted that the use of low latency and higher latency output interfaces is also generally applicable to charged particle detectors. For the sake of simplicity, the term detector will therefore be used. The skilled person will understand that the term detector explicitly refers to both charged particle cameras (arranged for acquiring images) and other types of detectors (arranged for acquiring other data).

[0064] As Figure 3 The imaging system 200 generally comprises, as shown in

[0065] In Figure 3 The first charged particle detector output interface 101 is arranged for transmitting data to the storage device 300. The detector D is connected via the imaging system 200 to the storage device 300 for storing high quality images from the sample. Here, the first data stream is arranged such that data quality and reliability are prioritized, ensuring that data is accurately and reliably output to the storage device 300 (i.e. maintaining the high image quality standards for which charged particle microscopes are thus renowned).

[0066] As defined herein, the imaging system further comprises a second charged particle detector output interface 102. The second charged particle detector output interface 102 is arranged for providing an output which is different compared to the first output interface 101. In particular, the second charged particle detector output interface 102 is arranged for providing a low latency output to a feedback data processing device 400 which in turn is connected to the microscope M. Thus, a feedback control loop is established which can be used for feedback control applications such as image based drift active compensation, continuous tilt tomography field correction or system state measurement methods.

[0067] In the illustrated embodiment, the imaging system 200 comprises a data processing unit 99 which is arranged for processing so-called "raw" data from the detector chip 31. It is noted that this processing unit 99 can be part of the detector D itself, and thus the imaging system 200 can also comprise part of the detector D. Other arrangement scenarios are also conceivable.

[0068] After the initial processing by the processing unit 99, the signals can be split into two different streams.

[0069] One stream is connected to the first charged particle detector output interface 101 and comprises a storage representation module 201 and a buffer 211. The storage representation module 201 and the buffer 211 are arranged for providing high quality image data from the detector D to the storage 300, while substantially no image information is lost.

[0070] The other stream is connected to the second charged particle detector output interface 102 and comprises a low latency representation module 202. The low latency representation module 202 is arranged to process the signals from the detector D (and optionally processed by the data processing unit 99) and then provide these signals to the second charged particle detector output interface 102. From there, they can be forwarded to the feedback data processing arrangement 400, where additional processing for enabling real-time feedback to the charged particle microscope M can take place. This enables the provision of low latency feedback to the charged particle microscope M, which can include stage movement and / or optical changes.

[0071] Figure 4A further embodiment of a charged particle microscope M with an imaging system 200 as disclosed herein is shown. Here, the detector D comprises a camera chip 31 and a data processing unit 99. The data processing unit 99 is arranged for performing a fast "basic" processing which in case of the detector D being an electronic detector can comprise gain correction and electron counting. This processing will normally be done with low latency. The resulting information is sent from the detector D via an output 90 to an input interface 100 of the imaging system 200. In the imaging system 200, the data is split into two different representation blocks 201, 202. These blocks 201, 202 can be arranged for converting the data into a desired output specific representation. These blocks 201, 202 can contain additional processing steps as well as data enhancement steps based on other information sources like a system clock. For example, if the user selects dose fraction storage, the storage representation block 201 will create dose fraction images, while the low latency representation block 202 can output an electron event representation stream (electron event position [x, y, time] stream) with additional timing information (like synchronized timestamps) embedded. The storage representation 201 is buffered in a block 211 to ensure no data loss in case of a short interruption of the connection to the storage 300, for example. The low latency representation 202 is transmitted without buffering (or at least without a large buffer) to prevent additional latency.

[0072] In one embodiment, this low latency representation module 202 can run independently from the earlier mentioned storage representation module 201. The low latency representation module 202 is preferably optimized for low latency, while data reliability is a lower priority: this means that a small amount of data loss is allowed as long as this situation is detectable.

[0073] A certain type of destination detector D is an electron counting camera: in this case, the electron counting algorithm is a critical algorithm. The type of data on the output data interface 201 can be an image "movie" (called dose fraction) or an electron event position (x, y, time) stream (also called electron event representation [EER]). Providing EER data on the low latency output data interface 202 allows for low latency event based processing for low dose applications. In low dose conditions, the low latency EER data will result in the best possible performance in the use scenarios mentioned above.

[0074] Returning to Figure 4 , it is shown that the low latency representation module 202 can be connected to a feedback data processing arrangement 400 which in the shown embodiment is part of the controller / processor 20. It will be clear to the skilled person that the feedback data processing arrangement 400 can also be a separate controller / processor. From here, the controller / processor 20 is able to change settings / parameters to the charged particle microscope M (e.g., as Figure 1 and Figure 2provides feedback: optical column O, sample holder H, imaging system 24 and / or charged particle detector D (which can be Figure 1 and 2 any of 22a, 22b, 30, 32, 34 as shown in Fig. 1). The feedback data processing device 400 together with the low-latency representation module 202 thus allows to provide real-time feedback to the charged-particle microscope M.

[0075] In summary, a charged-particle microscope M is described which incorporates double data stream output interfaces 101, 102 inside its imaging system 200. These interfaces enable the microscope M to capture and process data from the charged-particle detector D in two different ways, leading to enhanced imaging capabilities and improved flexibility. This is especially the case when one data stream is targeted at low-latency 102, making real-time feedback to the microscope M possible.

Claims

1. A charged particle microscope comprising: - a charged particle optical column for guiding the charged particle beam onto the sample; - Sample holder for holding samples; as well as - a charged particle camera and an imaging system for generating an image signal based on information from the charged particle camera; wherein the imaging system comprises a first charged particle camera output interface for outputting a first data stream of data associated with the charged particle camera; It is characterized in that the imaging system further includes a second charged particle camera output interface for outputting a second data stream of data related to the charged particle camera, wherein the second data stream is set to be different from the first data stream.

2. The charged particle microscope of claim 1, wherein the second data stream is optimized for low-latency output.

3. A charged particle microscope according to claim 1 or 2, wherein the second data stream is arranged to have a maximum low-latency output of 750 milliseconds, in particular 250 milliseconds or less.

4. A charged particle microscope according to claim 3, wherein the second data stream is arranged to have a substantially fixed low latency output.

5. A charged particle microscope according to claim 3 or 4, wherein the second data stream is arranged to have an average low latency output of less than 100 milliseconds.

6. The charged particle microscope according to claim 1-5, wherein the charged particle microscope is connected to a second charged particle camera output data interface and is configured to provide real-time feedback to the charged particle microscope using image signals from the imaging system.

7. The charged particle microscope of claims 1-6, wherein the first data stream is optimized for high reliability.

8. The charged particle microscope of claim 7, wherein the first data stream is optimized for complete data transmission without data loss.

9. The charged particle microscope according to claims 1-8, wherein the second charged particle camera output interface operates independently of the first charged particle camera output interface.

10. A charged particle microscope according to claims 1-9, wherein the system includes a data processing unit upstream of the first and second charged particle camera output interfaces, and wherein the data processing unit is configured to process data provided to the second charged particle camera output interface.

11. The charged particle microscope according to claim 9, wherein the charged particle camera comprises the data processing unit.

12. A charged particle microscope according to claims 1-11, wherein the charged particle microscope includes a feedback data processing device downstream of the second charged particle camera output interface (the second output data interface includes additional processing steps and data enhancement steps based on other information sources such as the system clock).

13. A method of operating a charged particle microscope according to claims 1 to 12, comprising the step of using the second charged particle camera output interface to provide low latency data.

14. The method of claim 13, comprising the step of using the low latency data to control the operation of the charged particle microscope.

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