The defined region may comprise a focusing region.

The microscopy system may comprise an imaging system, and the method may comprise focusing the imaging system onto the focusing region. For example, a sample may comprise a focus region as well as an exposure region and they may be displaced with respect to each other such that they are at different heights. Then, the method as described above may be used to determine the location of the focus region as well as the location of the exposure region and, based thereon, to focus the imaging system on to the focus region and the imaging beam on to the exposure region.

The defined region may comprise a tracking region configured to be imaged at a tracking magnification.

The tracking magnification may be greater than the first magnification.

The sample may comprise a plurality of defined regions, and the method may comprise determining the location in three-dimensional space of each of the plurality of defined regions.

The method may comprise determining the location in three-dimensional space of a first of the plurality of defined regions, and based thereon, determining the location in three-dimensional space of a second of the plurality of defined locations.

The method may comprise directing a beam of particles at, at least, a part of the sample.

The microscopy system may comprise a source of particles.

The determination of the location in three-dimensional space of the defined region may be based on the position of the source of particles.

According to a second aspect, the present invention relates to a microscopy system configured for acquiring tomographic images of a sample, wherein the sample comprises a defined region, and wherein the microscopy system is configured to determine a location in three-dimensional space of the defined region.

The microscopy system may be configured to illuminate at least a part of the sample by directing a beam of particles at the part of the sample.

The microscopy system may comprise a stage configured to hold the sample and to position and/or orient the sample.

The microscopy system may comprise a data processing unit.

The microscopy system may comprise an imaging system configured to capture an image of at least a part of the sample.

The microscopy system may be configured to determine the location in three-dimensional space of the defined region based on the image of the part of the sample.

The imaging system may be configured to detect emissions resulting from an interaction of the part of the sample with the beam of particles.

The imaging system may comprise a detector.

The imaging system may comprise a camera.

The microscopy system may be configured to focus the imaging system over at least a part of the sample.

The microscopy system may comprise a control unit configured to position at least a part of the sample under the beam of particles.

The microscopy system may comprise an electro-optic system configured to position the beam of particles over at least a part of the sample.

The control unit may be configured to control the electro-optic system.

The data processing unit may be configured to communicate with the imaging system.

The data processing unit may be configured to communicate with the control unit.

The data processing unit may be configured to receive a geometry of the sample.

The data processing unit may be configured to determine a projection of at least a part, that may be called a projected part, of the sample.

The data processing unit may be further configured to determine the projection of the projected part of the sample based on the geometry of the sample.

The microscopy system may comprise a source of particles and the data processing unit may be configured to receive a distance between the source of particles and a point in the projected part of the sample and, based thereon, to determine the projection of the projected part of the sample.

The stage may comprise a tilt axis.

The microscopy system may be configured to allow varying a tilt angle of the stage by rotating the sample about the tilt axis.

The data processing unit may be configured to receive the tilt angle of the stage and, based thereon, to determine the location in three-dimensional space of the defined region.

The sample may be configured to be positioned inside the stage.

Positioning the sample inside the stage may comprise substantially aligning an axis of the sample with the tilt axis of the stage.

The data processing unit may be further configured to receive an angle between the axis of the sample and the tilt axis of the stage and, based thereon, to determine the location in three-dimensional space of the defined region.

The data processing unit may be configured to send data relating to the location of the defined region to the control unit.

The microscopy system may comprise a user interface configured to at least accept an input.

The data processing unit may be configured to communicate with the user interface.

The part of the sample may comprise a feature, and the microscopy system may be configured to identify the feature in the image of the part of the sample.

The data processing unit may be configured to determine a configuration of the feature in the image of the part of the sample based on an input to the user interface.

The data processing unit may be configured to determine a configuration of the feature in the image of the part of the sample based on an artificial intelligence-based model.

The artificial intelligence-based model may comprise a supervised learning model.

An input to the artificial intelligence-based model may comprise an image of the part of the sample.

An output of the artificial intelligence-based model may comprise the configuration of the feature in the image of the part of the sample.

The supervised learning model may be trained on a dataset comprising the image of the part of the sample and the configuration of the feature.

The data processing unit may be configured to determine the configuration of the feature in the image of the part of the sample using any of edge detection, filtering, feature detection, ridge detection, or any other image processing method.

The sample may comprise a feature.

The microscopy system may be configured to determine the configuration of the feature as described above in three-dimensional space.

The data processing unit may be configured to generate a model of at least a part, that may be called a modeled part, of the sample.

The microscopy system may be configured to perform the method according to any of the preceding method embodiments.

According to a third aspect, the present invention relates to a computer program product comprising instructions, when run on a data processing unit of a microscopy system, to perform the method according to any of the preceding method embodiments.

Below method embodiments will be discussed. These are abbreviated by the letter ‘M’ followed by a number. Whenever reference is herein made to method embodiments, these embodiments are meant.

M1. A method for acquiring tomographic images of a sample in a microscopy system, wherein the sample comprises a defined region, and wherein the method comprises

- determining a location in three-dimensional space of the defined region.

M2. The method according to the preceding embodiment, wherein the method further comprises capturing an image of at least a part of the sample.

M3. The method according to the preceding embodiment, wherein the part of the sample comprises the whole sample.

M4. The method according to any of the 2 preceding embodiments, wherein the image is captured at a first magnification.

M5. The method according to any of the 3 preceding embodiments, wherein the determination of the location in three-dimensional space of the defined region is based, at least in part, on the image of the part of the sample.

M6. The method according to any of the preceding method embodiments, wherein the sample comprises a feature.

M7. The method according to any of the preceding method embodiments and with the features of embodiment M6, wherein the sample comprises a plurality of features.

M8. The method according to the preceding embodiment, wherein the sample comprises a first feature and a second feature.

M9. The method according to any of the preceding method embodiments and with the features of embodiment M6, wherein the method further comprises determining a configuration in three-dimensional space of the feature of the sample.

M10. The method according to the preceding embodiment and with the features of embodiment M7, wherein the method further comprises determining the configurations in three-dimensional space of any of the plurality of features.

M11. The method according to any of the preceding method embodiments and with the features of embodiment M8, wherein the method comprises determining the configuration of the first feature in three-dimensional space relative to the configuration of the second feature in three-dimensional space.

M12. The method according to the preceding embodiment and with the features of embodiment M2, wherein the method comprises determining a projection of the first feature on the image plane based, at least in part, on the configuration of the first feature in three-dimensional space, and a projection of the second feature on the image plane based on the configuration of the second feature in three-dimensional space, wherein the projections on the image plane lie in a projection space, and wherein the method further comprises determining the configuration of the first feature in the projection space relative to the configuration of the second feature in the projection space.

M13. The method according to any of the preceding method embodiments and with the features of embodiment M2, wherein the part of the sample comprises a feature.

M14. The method according to the preceding embodiment, wherein the part of the sample comprises a plurality of features.

M15. The method according to the preceding embodiment, wherein the part of the sample comprises a first feature and a second feature.

M16. The method according to any of the preceding method embodiments and with the features of embodiment M13, wherein the method comprises identifying the feature in the image of the part of the sample.

M17. The method according to the preceding embodiment and with the features of embodiment M14, wherein the method comprises identifying the plurality of features in the image of the part of the sample.

M18. The method according to any of the preceding method embodiments and with the features of embodiment M16, wherein the method further comprises determining a configuration in the image of the feature of the part of the sample.

M19. The method according to the preceding embodiment and with the features of embodiment M15, wherein the method comprises determining the configuration of the first feature in the image of the part of the sample relative to the configuration of the second feature in the image of the part of the sample.

M20. The method according to the preceding embodiment and with the features of embodiment M12, wherein the method comprises comparing the relative configuration of the first feature and the second feature in the image of the part of the sample to the relative configuration of the first feature and the second feature in the projection space.

M21. The method according to the preceding embodiment, wherein the determination of the location in three-dimensional space of the defined region is based, at least in part, on the comparison of the relative configuration of the first feature and the second feature in the image of the part of the sample to the relative configuration of the first feature and the second feature in the projection space.

M22. The method according to any of the preceding method embodiments, wherein the method further comprises generating a model of at least a part, that may be called a modeled part, of the sample.

M23. The method according to the preceding embodiment, wherein the modeled part comprises the whole sample.

M24. The method according to any of the 2 preceding embodiments, wherein the model is based on a geometry of the sample.

M25. The method according to any of the preceding method embodiments, wherein the method comprises determining a projection of at least a part, that may be called a projected part, of the sample.

M26. The method according to the preceding embodiment and with the features of embodiment M22, wherein the projection is based, at least in part, on the model.

M27. The method according to any of the 2 preceding embodiments and with the features of embodiment M2, wherein the method comprises capturing an image of the projected part of the sample.

M28. The method according to the preceding embodiment and with the features of embodiment M26, wherein the method comprises comparing the image and the projection of the projected part of the sample.

M29. The method according to the preceding embodiment and with the features of embodiment M22, wherein the method further comprises refining the model based on the comparison between the image and the projection of the projected part of the sample.

M30. The method according to any of the preceding embodiments and with the features of embodiment M22, wherein the determination of the location in three-dimensional space of the defined feature is based, at least in part, on the model.

Stereographic Analysis

M31. The method according to any of the preceding method embodiments and with the features of embodiment M2, wherein the method comprises capturing the image at a plurality of sample orientations.

M32. The method according to the preceding embodiment, wherein the method comprises capturing the image of at least a part of the sample at a first sample orientation.

M33. The method according to the preceding embodiment and with the features of embodiment M19, wherein the image of the part of the sample comprises the image of the part of the sample at the first sample orientation.

M34. The method according to any of the 2 preceding embodiments, wherein the method comprises capturing the image of at least a part of the sample at a second sample orientation, wherein the second sample orientation is not identical to the first sample orientation.

M35. The method according to the preceding embodiment and with the features of embodiment M19, wherein the image of the part of the sample comprises the image of the part of the sample at the second sample orientation.

M36. The method according to the preceding embodiment and with the features of embodiment M33, wherein the determination of the location in three-dimensional space of the defined region is based, at least in part, on the relative configuration of the first feature and the second feature in the image of the part of the sample at the first sample orientation and on the relative configuration of the first feature and the second feature in the image of the part of the sample at the second sample orientation.

M37. The method according to any of the preceding method embodiments and with the features of embodiments M22, M33, and M35, wherein the model of the modeled part of the sample is based, at least in part, on the relative configuration of the first feature and the second feature in the image of the part of the sample at the first sample orientation and on the relative configuration of the first feature and the second feature in the image of the part of the sample at the second sample orientation.

M38. The method according to any of the preceding method embodiments, wherein the microscopy system comprises a stage comprising a stage tilt axis and configured to position and/or orient the sample, and wherein the method comprises rotating the sample about the stage tilt axis to vary a tilt angle of the stage and change the orientation of the sample.

M39. The method according to preceding embodiment, wherein the determination of the location in three-dimensional space of the defined region is based, at least in part, on the tilt angle of the stage.

M40. The method according to any of the preceding method embodiments and with the features of embodiment M38, wherein the method further comprises positioning the sample within the stage.

M41. The method according to the preceding embodiment, wherein positioning the sample within the stage comprises substantially aligning an axis of the sample with the stage tilt axis.

M42. The method according to the preceding embodiment, wherein a result of positioning the sample within the stage is a misalignment of the axis of the sample with the stage tilt axis.

M43. The method according to any of the preceding method embodiments and with the features of embodiments M34, and M38, wherein the first sample orientation comprises a first tilt angle, the second sample orientation comprises a second tilt angle, and wherein a difference between the first tilt angle and the second tilt angle is greater than 0° and less than or equal to 90°, preferably between 10° and 80°, further preferably between 30° and 60°.

M44. The method according to the preceding embodiment, wherein each of the first tilt angle, and the second tilt angle, is between −180° and +180°, preferably between −90° and +90°, further preferably between −70° and +70°.

M45. The method according to any of the preceding method embodiments, wherein the defined region comprises an exposure region configured to be imaged at an imaging magnification.

M46. The method according to any of the preceding method embodiments, wherein the method comprises illuminating at least a part of the sample with a beam of particles.

M47. The method according to the preceding embodiment and with the features of embodiment M4, wherein the imaging magnification is greater than or equal to the first magnification.

M48. The method according to any of the 2 preceding embodiments, wherein the method comprises positioning the beam of particles over the exposure region based on the determined location in three-dimensional space of the exposure region.

M49. The method according to any of the 3 preceding embodiments, wherein the method comprises positioning the exposure region of the sample under the beam of particles.

M50. The method according to any of the preceding method embodiments, wherein the defined region comprises a focusing region.

M51. The method according to the preceding embodiment, wherein the microscopy system comprises an imaging system, and wherein the method comprises focusing the imaging system onto the focusing region.

M52. The method according to any of the preceding method embodiments, wherein the defined region comprises a tracking region configured to be imaged at a tracking magnification.

M53. The method according to the preceding embodiment and with the features of embodiment M4, wherein the tracking magnification is greater than the first magnification.

M54. The method according to any of the preceding method embodiments, wherein the sample comprises a plurality of defined regions, and wherein the method comprises determining the location in three-dimensional space of each of the plurality of defined regions.

M55. The method according to the preceding embodiment, wherein the method comprises determining the location in three-dimensional space of a first of the plurality of defined regions, and based thereon, determining the location in three-dimensional space of a second of the plurality of defined locations.

M56. The method according to any of the preceding method embodiments, wherein the method comprises directing a beam of particles at, at least, a part of the sample.

M57. The method according to the preceding embodiment, wherein the microscopy system comprises a source of particles.

M58. The method according to the preceding embodiment, wherein the determination of the location in three-dimensional space of the defined region is based on the position of the source of particles.

Below system embodiments will be discussed. These are abbreviated by the letter ‘S’ followed by a number. Whenever reference is herein made to system embodiments, these embodiments are meant.

S1. A microscopy system configured for acquiring tomographic images of a sample, wherein the sample comprises a defined region, and wherein the microscopy system is configured to

- a. determine a location in three-dimensional space of the defined region.

S2. The microscopy system according to the preceding embodiment, wherein the microscopy system is configured to illuminate at least a part of the sample by directing a beam of particles at the part of the sample.

S3. The microscopy system according to any of the preceding system embodiments, wherein the microscopy system comprises a stage configured to hold the sample and to position and/or orient the sample.

S4. The microscopy system according to any of the preceding system embodiments, wherein the microscopy system comprises a data processing unit.

S5. The microscopy system according to any of the preceding system embodiments, wherein the microscopy system comprises an imaging system configured to capture an image of at least a part of the sample.

S6. The microscopy system according to the preceding embodiment, wherein the microscopy system is configured to determine the location in three-dimensional space of the defined region based on the image of the part of the sample.

S7. The microscopy system according to the preceding embodiment and with the features of embodiment S2, wherein the imaging system is configured to detect emissions resulting from an interaction of the part of the sample with the beam of particles.

S8. The microscopy system according to any of the 3 preceding embodiments, wherein the imaging system comprises a detector.

S9. The microscopy system according to any of the 4 preceding embodiments, wherein the imaging system comprises a camera.

S10. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S6, wherein the microscopy system is configured to focus the imaging system over at least a part of the sample.

S11. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S2, wherein the microscopy system comprises a control unit configured to position at least a part of the sample under the beam of particles.

S12. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S2, wherein the microscopy system comprises an electro-optic system configured to position the beam of particles over at least a part of the sample.

S13. The microscopy system according to the preceding embodiment and with the features of embodiment S11, wherein the control unit is configured to control the electro-optic system.

S14. The microscopy system according to any of the preceding system embodiments and with the features of embodiments S4, and S6, wherein the data processing unit is configured to communicate with the imaging system.

S15. The microscopy system according to any of the preceding system embodiments and with the features of embodiments S4, and S11, wherein the data processing unit is configured to communicate with the control unit.

S16. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S4, wherein the data processing unit is configured to receive a geometry of the sample.

S17. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S4, wherein the data processing unit is configured to determine a projection of at least a part, that may be called a projected part, of the sample.

S18. The microscopy system according to the preceding embodiment and with the features of embodiment S16, wherein the data processing unit is further configured to determine the projection of the projected part of the sample based on the geometry of the sample.

S19. The microscopy system according to any of the 2 preceding embodiments and with the features of embodiment S2, wherein the microscopy system comprises a source of particles and wherein the data processing unit is configured to receive a distance between the source of particles and a point in the projected part of the sample and, based thereon, to determine the projection of the projected part of the sample.

S20. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S3, wherein the stage comprises a tilt axis.

S21. The microscopy system according to the preceding embodiment, wherein the microscopy system is configured to allow varying a tilt angle of the stage by rotating the sample about the tilt axis.

S22. The microscopy system according to the preceding embodiment and with the features of embodiment S16, wherein the data processing unit is configured to receive the tilt angle of the stage and, based thereon, to determine the location in three-dimensional space of the defined region.

S23. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S3, wherein the sample is configured to be positioned inside the stage.

S24. The microscopy system according to the preceding embodiment, wherein positioning the sample inside the stage comprises substantially aligning an axis of the sample with the tilt axis of the stage.

S25. The microscopy system according to the preceding embodiment, wherein a result of positioning the sample inside the stage is a misalignment of the axis of the sample with the tilt axis of the stage.

S26. The microscopy system according to the preceding embodiment and with the features of embodiment S16, wherein the data processing unit is further configured to receive an angle between the axis of the sample and the tilt axis of the stage and, based thereon, to determine the location in three-dimensional space of the defined region.

S27. The microscopy system according to any of the preceding system embodiments and with the features of embodiments S13, and S15, wherein the data processing unit is configured to send data relating to the location of the defined region to the control unit.

S28. The microscopy system according to any of the preceding system embodiments, wherein the microscopy system comprises a user interface configured to at least accept an input.

S29. The microscopy system according to the preceding embodiment and with the features of embodiment S4, wherein the data processing unit is configured to communicate with the user interface.

S30. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S6, wherein the part of the sample comprises a feature, and wherein the microscopy system is configured to identify the feature in the image of the part of the sample.

S31. The microscopy system according to the preceding embodiment and with the features of embodiment S4, wherein the data processing unit is configured to determine a configuration of the feature in the image of the part of the sample based on an input to the user interface.

32. The microscopy system according to any of the 2 preceding embodiments and with the features of embodiment S4, wherein the data processing unit is configured to determine a configuration of the feature in the image of the part of the sample based on an artificial intelligence-based model.

S33. The microscopy system according to the preceding embodiment, wherein the artificial intelligence-based model comprises a supervised learning model.

S34. The microscopy system according to any of the 2 preceding embodiments, wherein an input to the artificial intelligence-based model comprises an image of the part of the sample.

S35. The microscopy system according to any of the 3 preceding embodiments, wherein an output of the artificial intelligence-based model comprises the configuration of the feature in the image of the part of the sample.

S36. The microscopy system according to any of the 3 preceding embodiments, wherein the supervised learning model is trained on a dataset comprising the image of the part of the sample and the configuration of the feature.

S37. The microscopy system according to any of the preceding system embodiments and with the features of embodiments S4, and S30, wherein the data processing unit is configured to determine the configuration of the feature in the image of the part of the sample using any of edge detection, filtering, feature detection, ridge detection, or any other image processing method.

S38. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S30, wherein the microscopy system is configured to determine the configuration of the feature in three-dimensional space.

S39. The microscopy system according to any of the preceding system embodiments and with the features of embodiment S4, wherein the data processing unit is configured to generate a model of at least a part, that may be called a modeled part, of the sample.

S40. The microscopy system according to any of the preceding system embodiments, wherein the microscopy system is configured to perform the method according to any of the preceding method embodiments.

Below computer program product embodiments will be discussed. These are abbreviated by the letter ‘P’ followed by a number. Whenever reference is herein made to computer program product embodiments, these embodiments are meant.

P1. A computer program product comprising instructions, when run on a data processing unit of a microscopy system, to perform the method according to any of the preceding method embodiments.

Embodiments of the present technology will now be discussed with reference to the accompanying figures.

BRIEF DESCRIPTION OF FIGURES

FIG. 1 depicts an exemplary microscopy system;

FIG. 2 depicts an exemplary embodiment of the method according to the present technology;

FIG. 3 depicts yet another exemplary embodiment of the method according to the present technology; and

FIG. 4 depicts a further exemplary embodiment of the method according to the present technology.

For the sake of clarity, some features may only be shown in some figures, and others may be omitted. However, also the omitted features may be present, and the depicted and discussed features do not need to be present in all embodiments.

DETAILED FIGURE DESCRIPTION

FIG. 1 depicts an embodiment of a microscopy system M, particularly a charged particle microscopy system M configured to use a charged particle beam B to observe and/or characterize a sample 18. The charged particle beam B may comprise electrons or ions. In the particular case depicted in FIG. 1, it comprises electrons. Additionally, the microscopy system M depicted in FIG. 1 may comprise a transmission-type microscopy system M, wherein an image of the sample 18 is taken using the emissions in the transmission region of the microscopy system M. Thus, M may represent a Transmission Electron Microscope (TEM) or a Scanning Transmission Electron Microscope (STEM). In the Figure, within a vacuum enclosure 2, an electron source 4 produces the beam B of electrons that propagates along an electron-optical axis B′ and traverses an electron-optical illuminator 6, serving to direct/focus the electrons onto a chosen part of the sample 18 (which may, for example, be (locally) thinned/planarized).

Also depicted is a deflector 8, which (inter alia) can be used to effect scanning motion of the beam B. The sample 18 may be held on a sample holder 16 that can be positioned in multiple degrees of freedom by a positioning device/stage 14, which moves a cradle 14′ into which holder 16 is (removably) affixed; for example, the sample holder 16 may comprise a finger that can be moved (inter alia) in the XY plane (see the depicted Cartesian coordinate system; typically, motion parallel to Z and tilt about X/Y will also be possible). Such movement allows different parts of the sample 18 to be illuminated/imaged/inspected by the electron beam B traveling along axis B′ (in the Z direction) (and/or allows scanning motion to be performed, as an alternative to beam scanning). If desired, an optional cooling device (not depicted) can be brought into intimate thermal contact with the sample holder 16, so as to maintain it (and the sample 18 thereupon) at cryogenic temperatures, for example. Additionally, the positioning device/stage 14 may also effect a rotation of the sample holder 16 about an axis of rotation such that the sample 18 may be tilted and an angle between the sample 18 and the electron beam B be changed. The angle may, for example, be an angle between a normal to the sample 18 (in case the sample 18 is substantially planar), or some other direction vector that may be associated with the sample 18, and the electron beam B. The tilting of the sample 18 about the stage tilt axis may be employed to perform tomographic imaging of the sample 18 by capturing an image of the sample 18 for each tilt angle.

The electron beam B will interact with the sample 18 in such a manner as to cause various types of “stimulated” radiation to emanate from the sample 18, 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 with the aid of analysis device 22, which might be a combined scintillator/photomultiplier or EDX (Energy-Dispersive X-Ray Spectroscopy) module, for instance; in such a case, an image could be constructed using basically the same principle as in a Scanning Electron Microscope (SEM). However, alternatively or supplementally, one can study electrons that traverse (pass through) the sample 18, exit/emanate from it and continue to propagate (substantially, though generally with some deflection/scattering) along axis B′.

Such a transmitted electron flux enters an imaging system (projection lens) 24, which will generally comprise a variety of electrostatic/magnetic lenses, deflectors, correctors (such as stigmators), etc. In normal (non-scanning) TEM mode, this imaging system 24 can focus the transmitted electron flux onto a fluorescent screen 26, which, if desired, can be retracted/withdrawn (as schematically indicated by arrows 26′) so as to get it out of the way of axis B′. An image (or diffractogram) of (part of) the sample 18 will be formed by imaging system 24 on screen 26, and this may be viewed through viewing port 28 located in a suitable part of a wall of enclosure 2. The retraction mechanism for screen 26 may, for example, be mechanical and/or electrical in nature, and is not depicted here. As an alternative to viewing an image on screen 26, one can instead make use of the fact that the depth of focus of the electron flux leaving imaging system 24 is generally quite large (e.g. of the order of 1 meter). Consequently, various other types of analysis apparatus can be used downstream of screen 26, such as a TEM camera 30. At camera 30, the electron flux can form a static image (or diffractogram) that can be processed by controller/processor 20 and displayed on a display device (not depicted), such as a flat panel display, for example. When not required, camera 30 can be retracted/withdrawn (as schematically indicated by arrows 30′) so as to get it out of the way of axis B′. Note that the microscopy system M may additionally comprise a data processing unit 50 that may be configured for data processing and that may communicate with the controller 20 to effect a deflection of the beam B, for example. In other words, the data processing unit 50 may, among other things, send data relating to a location of a defined region of the sample 18 to be illuminated to the controller 20, based on which the controller may then appropriately deflect the electron beam B. Alternatively, if the stage 14 has an appropriate precision, the controller 20 may be configured to place the defined region of the sample 18 under the beam B. Similarly, the controller 20 may also be configured to position the imaging system 24 such that the defined region of the sample 18 can be brought into focus.

The analysis apparatus may further comprise a STEM camera 32. An output from camera 32 can be recorded as a function of (X,Y) scanning position of the beam B on the sample 18, and an image can be constructed that is a “map” of output from camera 32 as a function of X,Y. Camera 32 can comprise a single pixel with a diameter of e.g. 20 mm, as opposed to the matrix of pixels characteristically present in camera 30. Moreover, camera 32 will generally have a much higher acquisition rate (e.g., 10⁶points per second) than camera 30 (e.g., 10²images per second). Once again, when not required, camera 32 can be retracted/withdrawn (as schematically indicated by arrows 32′) so as to get it out of the way of axis B′ (although such retraction would not be a necessity in the case of a donut-shaped annular dark field camera 32, for example; in such a camera, a central hole would allow flux passage when the camera was not in use).

As an alternative to imaging using cameras 30 or 32, one can also invoke spectroscopic apparatus 34, which could be an electron energy loss spectrometry (EELS) module, for example. It should be noted that the order/location of items 30, 32 and 34 is not strict, and many possible variations are conceivable. For example, spectroscopic apparatus 34 can also be integrated into the imaging system 24. Note that the controller (computer processor) 20 is connected to various illustrated components via control lines (buses) 20′. This controller 20 can provide a variety of functions, such as synchronizing actions, providing setpoints, processing signals, performing calculations, and displaying messages/information on a display device (not depicted). Needless to say, the (schematically depicted) controller 20 may be (partially) inside or outside the enclosure 2, and may have a unitary or composite structure, as desired. The skilled artisan will understand that the interior of the enclosure 2 does not have to be kept at a strict vacuum; for example, in a so-called “Environmental TEM/STEM”, a background atmosphere of a given gas is deliberately introduced/maintained within the enclosure 2. The skilled artisan will also understand that, in practice, it may be advantageous to confine the volume of enclosure 2 so that, where possible, it essentially hugs the axis B′, taking the form of a small tube (e.g., of the order of 1 cm in diameter) through which the employed electron beam passes, but widening out to accommodate structures such as the source 4, sample holder 16, screen 26, camera 30, camera 32, spectroscopic apparatus 34, etc.

The microscope M may further comprise a retractable X-ray CT module 40, which can be advanced/withdrawn with the aid of positioning system 42 so as to place it on/remove it from the path of the beam B (see arrow 44). In the particular configuration illustrated here, the module 40 comprises a fork-like frame on which are mounted—a target above the plane of the sample 18, and an X-ray detector below the plane of the sample 18.

As described above, when the microscopy system M is employed to carry out tomographic imaging of a sample 18, the sample 18 is tilted about an axis by means of the stage 14. Then, the beam B is directed onto the sample 18, and a resulting image captured by the imaging system 24. The tilt angle of the stage 14, and thus of the sample 18, is varied and an image is captured at each of the tilt angles. Misalignment of the sample 18 with the stage 14 (that may comprise, for example, a misalignment of an axis of the sample 18 with the tilt axis of the stage 14) or imperfections in the fabrication process of the sample 18 may cause a precession of features in images of the sample 18 at the different tilt angles. For example, the sample 18 may comprise a significantly rod-like sample and it may be desired to perform a tomographic analysis of the sample 18 along the direction of the rod. Then, the sample 18 may be tilted and images of the sample 18 be captured. However, the axis of the rod may not be aligned accurately with the axis of the stage 14 so that a precession of the rod may be seen in images of the sample 18. Alternatively, the sample 18 may comprise a substantially planar sample that may be tilted with respect to a plane of the sample holder 16. The planes of the sample 18 and the sample holder 16 may also be misaligned leading to a precession of the image of the plane of the sample 18.

Embodiments of the present technology are directed, in a first instance, to a method for accounting for this precession. An exemplary embodiment is depicted in FIG. 2. The exemplary embodiment comprises a plurality of steps that may be of advantage in accounting for precession in images and may thus allow for faster acquisition of tomographic images.

The sample 18 may comprise a defined region corresponding to a region of interest, or the tracked feature as described above. The defined region may comprise any of an exposure region, a focusing region, or a tracking region. The microscopy system M may be configured, for example, for imaging the defined region. Owing to the misalignment of the sample 18, or imperfections in the fabrication process of the sample 18, as described above, the precise location of the defined region in three-dimensional space may be unknown. For example, the sample 18 may comprise a rod-like section that may have a length of 200 nm, and the defined region may comprise a length of 10 nm around the center of the rod-like section. Owing to misalignment of the sample 18 within the stage 14 (where, in the following, “within the stage” should be understood to comprise within the sample holder 16 that is controlled with the stage 14), the precise location in three-dimensional space of the rod-like section may not be known, even if the precise location of the sample holder 16 and the stage 14 is known. As may be appreciated, the resolution of the microscopy system M may be in the hundreds of pm, so that a precise determination of the location of the defined region may be of advantage. The step of determining the location in three-dimensional space of the defined region may comprise a “determination step” 1000 in embodiments of the present technology.

The determination step 1000 may be carried out by the data processing unit 50. The data processing unit 50 may be configured to accept an input. The input to the data processing unit 50 may be based on an image of a part of the sample 18. Capturing the image of the part of the sample 18 may comprise a step 180, that may be called an imaging step, in embodiments of the present technology. The part of the sample 18 that is imaged may or may not comprise the defined region. Preferably, the part of the sample 18 comprises the defined region. The part of the sample 18 may also comprise the whole sample 18. In other words, the whole sample 18 may be imaged and the location in three-dimensional space of the defined region may be determined based on the image of the whole sample 18.

The image of the part of the sample 18 may be obtained at a first magnification. Magnification may be understood to be in inverse relation to a diameter of the beam B at the part of the sample 18. Thus, for example, illuminating the whole sample 18 may comprise a magnification that is lower than when illuminating less than the whole of the sample 18.

The sample 18 may comprise a feature. The feature may or may not be comprised in the part of the sample 18 that is imaged as described above. The feature may comprise a zero extension, such as a point, or it may comprise a feature with a non-zero extension, such as an edge. For example, the sample 18 may comprise a rod-like section and the feature may comprise, for example, a position on the rod-like section. Or, the sample 18 may comprise a significantly planar section and the feature may comprise an edge of the planar section. Further, the feature may comprise a position in the sample 18 on which the image of the part of the sample 18 may be centered (in which case the feature may also be said to be comprised in the part of the sample 18).

The method according to embodiments of the present technology may comprise a step 160, that may be called a projection step, to determine a configuration in three-dimensional space of the feature on the sample 18. The terms “configuration” and “relative configuration” here and in the following are intended to comprise position and/or orientation with respect to some co-ordinate system that comprises an origin. That is, in particular, they may comprise either position or orientation or both. As may be appreciated, depending on the feature only one of the above may apply. For example, for a point-like feature the configuration may comprise only a position, whereas for a vector or an edge it may comprise any of a position (defined by the co-ordinates of a point through which the edge or the vector passes, for example) or an orientation (defined by the direction cosines of the edge or the vector, for example). Note also that the configuration of any of the features may not have to be determined precisely. Embodiments of the present technology relate to a relative configuration of features. This relative configuration may be precise so long as the individual configuration of each of the features is offset by the same amount. It may also be understood that for determining relative configurations, individual configurations may have to be determined with reference to the same origin and co-ordinate system. Or, in case the configurations are determined with reference to different origins or co-ordinate systems, the relative configuration of the origins and the co-ordinate systems is precisely determined.

For example, the feature may comprise a position on the rod-like section of the sample 18 and determining the configuration in three-dimensional space of the feature may comprise determining co-ordinates of the position with respect to some co-ordinate system. Or, if the feature on the sample 18 comprises an edge, determining the configuration of the feature in three-dimensional space may comprise determining any of the configuration of a point through which the edge passes or the direction cosines of the edge (with respect to some co-ordinate system).

The sample 18 may comprise a plurality of features. Any of the plurality of features may or may not be comprised in the part of the sample 18 that is imaged in step 180. In particular, the sample 18 may comprise a first feature and a second feature. The projection step 160 may then comprise determining a relative configuration of the first feature and the second feature in three-dimensional space. In other words, the configuration in three-dimensional space of the first feature relative to the configuration in three-dimensional space of the second feature may be determined. In particular, the relative configuration may be described by the distance and/or direction in three-dimensional space of the first feature relative to the second feature. The order of the features in determining the relative configuration may not be relevant.

Further, in the projection step 160, the microscopy system M, preferably the data processing unit 50, may be configured to determine a projection of the first feature and the second feature of the sample 18, based on their configurations in three-dimensional space, onto the same plane as the plane of the image, that may be called an image plane, captured in the imaging step 180. The projections of the first feature and the second feature may lie in a projection space. Step 170, that may be called a spatial configuration step, may further comprise determining a relative configuration in the projection space of the first feature and the second feature. The projection of any of the features may be further based on the relative position between the feature and the imaging beam B of the microscopy system M. It may also be based on a magnification of the beam B or any other appropriate input that may be used to determine the relative configuration of the first feature and the second feature in projection space.

The part of the sample 18 that is imaged in the imaging step 180 may also comprise a feature, or a plurality of features. In particular, it may comprise a first feature and a second feature. Note that any of the first feature and the second feature in the part of the sample 18 (that are imaged) may or may not be identical to any of the first feature and the second feature in the sample 18 (that are projected on to the projection plane) as described above. A further step 190, that may be called an image configuration step, may comprise determining the relative configuration in a pixel space of the image of the first feature and the second feature. That is, in image configuration step 190, the distance and/or direction in the image of the first feature relative to the second feature may be determined. This may comprise, for example, determining the position (in pixels) of the first feature and the second feature, in case each of the two features comprises a point-like feature.

The relative configuration in projection space of the first feature and the second feature of the sample 18, and the relative configuration in pixel space of the first feature and the second feature in the part of the sample 18 (that is imaged) may then be used in determination step 1000 to determine the location in three-dimensional space of the defined region. In other words, embodiments of the present technology aim to correct for precession of the tracked feature (that may correspond to the defined region) by accurately determining the three-dimensional location of the tracked feature. This location may be determined by comparing the projection on to an image plane of a three-dimensional vector to a captured image of a three-dimensional vector. The relative configuration of the vector that is imaged to the vector that is projected may be precisely determined such that a comparison may be made. Preferably, the vector that is imaged may be substantially parallel to the vector that is projected.