Method for operating a particle beam microscope, particle beam microscope and computer program product

Abstract

A method for operating a particle beam microscope comprises scanning an object with a particle beam, detecting electrons generated on the object by the particle beam with a light-sensitive detector, generating a particle beam microscopic image based on the detected electrons, illuminating the object with light, and detecting light images of the object with a camera, wherein the generation of the particle beam microscopic image is based solely on the detected electrons detected during a plurality of first time intervals, wherein the illumination of the object occurs solely in a plurality of second time intervals, and wherein the first time intervals and the second time intervals overlap one another at most partially.

Description

[0001] The present invention relates to a method for operating a particle beam microscope, a particle beam microscope and a computer program product.

[0002] Particle beam microscopes, such as electron beam microscopes, generate a particle beam microscopic image by scanning an object with a particle beam from the particle beam microscope. A detector of the particle beam microscope detects electrons and / or other secondary particles, such as photons or ions, that are emitted by the object upon impact of the particle beam. For this purpose, particle beam microscopes often have several different detectors. With conventional particle beam microscopes, the user selects one of the various detectors to be operated before or during scanning to generate the particle beam microscopic image.Alternatively, in conventional particle beam microscopes, to generate multiple particle beam microscopy images, the user selects multiple detectors of the different detectors to be operated before starting or during scanning to generate the multiple particle beam microscopy images.

[0003] After the user has selected the detector for generating the particle beam microscopy image and the particle beam microscopy image has been generated, the user saves the particle beam microscopy image. They then continue their work at this or another sample location, or they move away from the particle beam microscope to perform further work on the particle beam microscopy image at their usual workstation. If the user later determines, for example, at their workstation or at another sample location, that the particle beam microscopy image from the detector used is not suitable for the work to be performed, the user must search for the previous sample location again or restart the particle beam microscope to acquire a new particle beam microscopy image using one or more different detectors of the particle beam microscope, which is tedious and time-consuming.A similar situation applies in cases where the user believes that using a different detector on the particle beam microscope might result in a more suitable particle beam microscopy image. In particular, there is also the possibility that the previous sample location is no longer suitable for acquiring a particle beam microscopy image, for example, due to damage to the sample location, making it impossible to re-image that sample location with one or more different detectors.

[0004] For the above reasons, conventional methods for operating particle beam microscopes involve a problem in that additional effort is incurred if the user subsequently considers a recorded particle beam microscope image to be unsuitable.

[0005] JP 2000 - 228 166 A discloses a particle beam system in which a light beam and a particle beam are directed simultaneously onto an object, the light beam and the particle beam extending along the same optical axis.

[0006] US 7 045 791 B2 discloses a particle beam system having an aperture plate which is transparent to a light beam and has an opening for a particle beam, so that the light beam and the particle beam can be directed simultaneously through the aperture plate onto an object.

[0007] US 2007 / 0 057 184 A1 discloses a particle beam system in which a light beam and a particle beam illuminate different areas of an object.

[0008] Accordingly, an object of the present invention is to avoid situations in which additional effort is required for restarting or relocating the sample location and adjusting the control parameters of the particle beam microscope.

[0009] To solve the above problem and achieve the objective, a method for operating a particle beam microscope is proposed below, which comprises receiving a selection by a user of the particle beam microscope of at least one detector from a plurality of detectors. The selection can be performed, for example, by prompting the user in a user interface to select one or more detectors from a predefined list. In some embodiments, the user's selection can be limited to exactly one detector.

[0010] The number of selected detectors is fewer than the number of the plurality of detectors, and the user's selection specifies which detectors' images are to be displayed. In addition, the plurality of detectors includes at least one detector for backscattered electrons and one detector for secondary electrons. Backscattered electrons are electrons that are created when the particles of the particle beam are scattered when they hit the object, causing them to move away from the object. Backscattered electrons have a similar energy to the impact energy of the particles when they hit the object. Secondary electrons are electrons that are created when electrons from the object are released by the impacting particles. Secondary electrons have an energy of < 50 eV and are therefore low-energy compared to the backscattered electrons.The backscattered electron detector is a detector that detects at least 1.1 times as many backscattered electrons as secondary electrons. On the other hand, the secondary electron detector is a detector that detects at least 1.1 times as many secondary electrons as backscattered electrons.

[0011] The method further comprises scanning an object once or repeatedly with a particle beam of the particle beam microscope, capturing a plurality of images during the single or repeated scanning of the object, wherein each image of this plurality of images is captured by a detector of the plurality of detectors, wherein each detector of the plurality of detectors captures at least one image of this plurality of images. Accordingly, particle beam microscopy images are captured multiple times with each detector.

[0012] The method further comprises displaying only the images acquired by the selected detectors during the single or repeated scan, and storing the images acquired by the selected detectors during the single or repeated scan and the images acquired by the non-selected detectors during the single or repeated scan. Since only the images acquired by the selected detector are displayed during the single or repeated scan, the images acquired by the non-selected detectors are not visible to the user during the single or repeated scan. In particular, the images acquired by the non-selected detectors are not displayed in additional windows or otherwise. This means that the user experience of the particle beam microscope is not impaired by information overload.In particular, the user can use the user interface as usual to acquire a particle beam microscopy image, but additional images invisible to the user will be acquired with the detectors not selected. All acquired images are saved so that the user can access them if they subsequently determine that the image acquired with the selected detector is not suitable for their purposes.

[0013] The method further comprises, after completion of the single or repeated scanning, receiving a selection of at least one stored image acquired by one of the non-selected detectors and displaying the selected image.

[0014] The user can select a detector with which to generate a particle beam microscopy image as usual. The particle beam microscopy image is then displayed during scanning. However, the particle beam microscope also acquires additional particle beam microscopy images invisible to the user using the unselected detectors, which are then saved together with the displayed images. This allows the user to access images from other detectors even after the user has moved away from the particle beam microscope or performed other activities on the particle beam microscope. Therefore, the user does not need to restart the particle beam microscope to scan the sample again with one or more detectors. Accordingly, this method can solve the above-mentioned problem and achieve the goal.

[0015] According to some embodiments, the method further comprises, after completion of the single or repeated scan, displaying a plurality of the stored images acquired by one of the selected detectors. Furthermore, receiving the selection of the at least one of the stored images acquired by one of the non-selected detectors comprises receiving a selection of one of the displayed images and using at least one of the stored images acquired by one of the non-selected detectors, acquired together with the selected displayed image during the same scan, as the selected stored image acquired by the at least one of the non-selected detectors.

[0016] In other words: As described above, images are acquired multiple times with each detector. This results in an acquisition sequence of the images, whereby it can be advantageous to save the acquired images in such a way that the images can be assigned to one another again according to this acquisition sequence after being loaded from a memory. In particular, it is advantageous to save the images of a detector in such a way that each image from this detector and each image from another detector can be assigned to one another based on which images of the detectors were acquired together during the same scan. Such an assignment enables selection using a simplified display for the user in which the images of the selected detector are displayed in the order in which they were acquired.The user can then select an image from the displayed image sequence and receive an image of a non-selected detector that was taken together with the selected image.

[0017] According to one embodiment, the method further comprises, during the single or repeated scan, analyzing the images acquired by the non-selected detectors during the single or repeated scan, for example, by line-by-line or image-by-image averaging or performing other mathematical operations, and generating a message to the user based on the analysis. Since the acquired images of the non-selected detectors are not visible to the user, it may be advantageous to analyze them in order to communicate important information recognizable in these images to the user. For this purpose, it may be advantageous to analyze the images of the secondary electron detector.Important information that is advantageous to determine during scanning can relate to the condition of the object and its suitability for high-quality particle beam microscopy images, such as contamination of the object or electrical charging on the object. If the analysis determines that electrical charging has occurred on the object, a warning can be issued to the user indicating this.

[0018] According to some embodiments, the method further comprises changing operating parameters of the particle beam microscope, wherein the images of at least one of the selected detectors and at least one of the non-selected detectors are analyzable to determine a measure representing an image quality of the images, wherein the operating parameters of the particle beam microscope are alterable such that an optimal measure of the image quality of the image recorded by the selected detector is achieved, wherein the measure of the image quality of the image recorded by the non-selected detector is then a given measure of the image quality, wherein the changing of the operating parameters of the particle beam microscope is carried out such thatthat the measure of image quality of the image acquired by the selected detector is lower than the optimal measure and the measure of image quality of the image acquired by the non-selected detector is better than the given measure.

[0019] The measure of image quality can, for example, represent image sharpness, image contrast, or the like. For example, the sharpness of an image can be defined by a normalized sum of edges determined by a Sobel operator. For example, the determination of image sharpness may be more successful with the non-selected detector than with the selected detector. In the case of conventional methods for operating the particle beam microscope, optimal operating parameters for the selected detector would be determined and set with regard to this measure. However, these optimal operating parameters for the selected detector often lead to unsatisfactory images from other detectors. Accordingly, it can be advantageous to set the operating parameters of the particle beam microscope so that they deviate from the optimal operating parameters.A small deviation from the optimal operating parameters is often barely noticeable in the displayed image of the selected detector, but even a small deviation can improve the images of the non-selected detectors. This can increase the likelihood that an image from a non-selected detector will be useful to the user in retrospect.

[0020] According to some embodiments, the changing of the operating parameters can be performed based on analyzing the images of the at least one of the selected detectors and the at least one of the non-selected detectors, and determining the measure representing the image quality of the analyzed image during the single or repeated scanning. According to alternative embodiments, a plurality of predetermined sets of values ​​representing operating parameters of the particle beam microscope can be stored, and one of the sets of the plurality of predetermined sets of values ​​can be selected based on the user's selection of the at least one detector. Thus, the changing of the operating parameters of the particle beam microscope can be performed based on the values ​​of the selected set of values.For example, a table can be saved in advance from which operating parameters can be determined that are not only optimal for the images of the selected detector, but also offer a compromise between the image quality of the images of the non-selected detectors and the images of the selected detector. Changing the operating parameters can also be performed in such a way that they are determined based on changes in the operating parameters that affect the non-selected detectors. Alternatively or additionally, operating parameters that affect the non-selected detectors can also be determined depending on the operating parameters that affect the selected detector. For example, corresponding dependencies can be specified in tables and / or mathematical relationships.

[0021] According to some embodiments, the plurality of detectors further comprises a radiation detector, such as an X-ray detector, and / or a detector for Auger electrons. Radiation is generated at the object, for example, by emission from an electron transition in atoms of the object or bremsstrahlung. The radiation can be detected by a detector that detects at least 1.1 times as many photons as electrons. Auger electrons are electrons emitted due to a further electron transition in atoms of the object. The Auger electrons have the energy characteristic of electron levels. The Auger electron detector is a detector that detects at least electrons in such a way that the Auger electrons can be distinguished from other electrons. The plurality of detectors can also include a camera that captures light images.

[0022] The detectors can be scintillation detectors, ionization detectors, or similar, as long as the electrons or photons corresponding to the detector can be detected in a suitable manner. The conversion of electrons into photons can also occur in a gas surrounding the sample or detector.

[0023] In conventional methods for operating the particle beam microscope, a camera can also be selected as the detector for visually assisted positioning of the object, whereby the light image from the camera is displayed and no particle beam microscopic image is recorded as long as the camera is selected. In order to record a light image from the camera, the object must be illuminated with light. The method proposed here makes it possible to record particle beam microscopic images while the light image from the camera is displayed. However, if the object is illuminated with light while particle beam microscopic images can be recorded, light-sensitive detectors, such as scintillation detectors for recording the particle beam microscopic images, are disrupted by the light.

[0024] Accordingly, according to a further embodiment, a method for operating the particle beam microscope is proposed, with which the particle beam microscopic images can be recorded by further selected or non-selected detectors without being disturbed by the illumination of the object with light. This method for operating a particle beam microscope comprises scanning an object with a particle beam, detecting electrons generated on the object by the particle beam with a light-sensitive detector, generating a particle beam microscopic image based on the detected electrons, illuminating the object with light, and detecting light images of the object with a camera. The generation of the particle beam microscopic image is based solely on the detected electrons, which are detected during a plurality of first time intervals.The object is illuminated only in a plurality of second time intervals, wherein the first time intervals and the second time intervals overlap each other at most partially, in particular substantially do not overlap each other.

[0025] Accordingly, the illumination of the object to capture the camera's light image is only carried out if the detectors other than the camera do not detect any electrons relevant for generating the particle beam microscopic images.

[0026] According to some embodiments, scanning the object with the particle beam comprises a line-by-line scan, in which the particle beam is scanned along a line during the first time intervals and in which the particle beam is returned to the beginning of a line during the second time intervals. This return is also referred to here as flyback and occurs when the particle beam is deflected from one end of one line to the beginning of another line. Since the point of incidence of the particle beam on the object is not located at a point on the lines relevant for the particle beam microscopic image during a time interval of the flyback, results from detectors other than the camera during this time interval are not taken into account for generating the image, which is why illumination performed during this time interval does not interfere with the generation of the particle beam microscopic images.It may be advantageous to expose the camera sensor over several fly-back time intervals for each camera image or to add several images together to obtain an improved image.

[0027] According to some embodiments, the scanning of the object is performed repeatedly, wherein during the second time intervals the particle beam is returned to a start of the scanning. For example, the camera's light image is recorded while scanning the object to generate a first particle microscopic image and a second particle microscopic image, the particle beam is returned from an end point of the scanning to a start point of the scanning. This return is also referred to herein as frame flyback. The time required to return the particle beam during the frame flyback can also be extended to obtain an improved light image.

[0028] According to another embodiment, a particle beam microscope comprises a particle beam source for generating a particle beam, a specimen holder for holding an object, a deflection device for deflecting the particle beam to scan the object with the particle beam, a plurality of detectors, and a controller configured to operate the particle beam microscope using the method described above. According to some embodiments, the particle beam microscope comprises one or more detectors and one or more cameras.

[0029] According to a further embodiment, a computer program product comprising instructions which, when executed by the controller of the particle beam microscope, cause the particle beam microscope to perform the method described above.

[0030] In the following, embodiments are described in detail with reference to the drawings. For ease of understanding, unselected detectors are also referred to as background detectors, and selected detectors are also referred to as live detectors. Furthermore, in the following detailed embodiments, an electron beam microscope is described. However, it should be noted that the embodiments are also suitably applicable to other particle beam microscopes, such as ion beam microscopes. Fig. 1 schematically shows an electron beam microscope according to an embodiment. Fig. 2 shows a flowchart with steps of a method for operating the Fig. 1 shown electron beam microscope according to an embodiment. Fig. 3 shows a display window of a user interface of the Fig. 2 shown procedure. Fig. 4 shows another display window of a user interface of the Fig. 2 shown procedure. Fig. 5 shows a flowchart with steps of a method for operating the Fig. 1 according to another embodiment. Fig. 6 shows an image field of the Fig. 1 shown particle beam microscope 1 with scanning points arranged in rows in the Fig. 5 shown procedures.

[0031] Fig. Figure 1 schematically shows an electron beam microscope 1 according to one embodiment. The electron beam microscope 1 comprises an electron beam source 3 that generates an electron beam 5. For example, the electron beam source 3 comprises an emission cathode (not shown) from which electrons are emitted, and an acceleration anode (not shown) that accelerates the electrons and thus forms the electron beam 5.

[0032] The electron beam 5 passes through a condenser lens 7. The condenser lens 7 is a magnetic lens that focuses the electron beam 5 by generating a magnetic field. The condenser lens 7 is preferably used to collimate the diverging electron beam 5 emitted by the electron beam source 3.

[0033] The electron beam 5 further passes through an objective lens 15. The objective lens 15 here is also a magnetic lens. The objective lens 15 is preferably used to focus the electron beam 5, collimated by the condenser lens 7, onto an object 23. The condenser lens 7 and / or the objective lens 15 do not have to be a magnetic lens, but can also be an electrostatic lens, for example.

[0034] The object 23 is held and positioned by a support mechanism 25 included in the electron beam microscope 1. The support mechanism 25 includes a stage 27 that holds the object 23 and an actuator 29. The actuator 29 can be operated such that the stage 27 is moved to different positions in the electron beam microscope 1.

[0035] The electron beam microscope 1 further comprises a vacuum jacket 31 that defines a vacuum chamber 33. The vacuum jacket 31 includes a pump nozzle 35, to which a pump (not shown) is connected, with which a vacuum can be generated in the vacuum chamber 33. The vacuum in the vacuum chamber 33 serves to reduce interactions of the electrons of the electron beam 5 with the atmosphere.

[0036] The electron beam 5 is deflected by an adjustable deflection device 37 of the electron beam microscope 1 and can thus be directed to different impact locations on the object 23. In this embodiment, the deflection device 37 is a set of coils that generate a magnetic field such that the electrons of the electron beam 5 experience a force perpendicular to the beam path of the electron beam 5 and thus impact the object 23 at a different impact location. The deflection device 37 can also be formed by a set of electrodes or the like.

[0037] The deflection device 37 is used to scan the object 23 with the electron beam 5. For example, the electron beam 5 is successively directed at predetermined grid points on the object 23. When the electron beam 5 strikes the object 23, various effects occur on the object 23, due to which electrons and radiation are emitted from the object 23. Secondary electrons are emitted from the object 23 when an interaction occurs between incident electrons of the electron beam 5 and electrons present in the object 23 in such a way that electrons present in the object 23 are released. Backscattered electrons are electrons of the electron beam 5 that interact with charged particles present in the object 23 in such a way that the electrons of the electron beam 5 exit the object 23 as backscattered electrons.Auger electrons are electrons that occur when an electron transition occurs in the object 23 due to an electron being released, such as through the generation of a secondary electron, and the resulting energy releases another electron. Radiation occurs when the electron beam 5 strikes the object 23, for example, through bremsstrahlung, which occurs when the electron in the electron beam 5 is deflected, or through an electron transition, the released energy of which is emitted as a photon.

[0038] Electrons emitted by object 23 can be accelerated along the beam path of electron beam 5, at least partially by an electrostatic field existing between object 23 and an accelerating anode 39, and then detected by detectors 41 and 43. Detector 41 is a secondary electron detector that detects the low-energy secondary electrons that scatter most widely around electron beam 5. Low-energy secondary electrons moving near electron beam 5 are repelled by an energy filter 47 and then impinge on an upper side of detector 41.

[0039] The energy filter 47 is a grid at a negative electrical potential that repels electrons, whereby only the high-energy backscattered electrons can penetrate the repulsive electrostatic field of the energy filter 47. The detector 43 is a backscattered electron detector that detects the backscattered electrons that penetrate the energy filter 47.

[0040] Detectors 41 and 43 are scintillation detectors that generate a large number of detectable photons through an interaction cascade when an electron strikes them. The detectable photons can then be detected by a CCD chip or a photomultiplier tube.

[0041] The Auger electrons are detected by a detector 45, which is designed, for example, in the form of an energy spectrometer. For this purpose, a detector structure can be provided that uses magnetic fields to deflect electrons of different energies to different locations in a detector field. This allows the Auger electrons to be detected at the characteristic energies of a material of the object 23. It should be noted that the Auger electron detector 45 does not necessarily have to be provided as a separate detector; the Auger electrons can also be determined from a signal from another detector, if this other detector is suitable for detecting the energy of the incident electrons.

[0042] It should be noted that in practice, detectors 41, 43, and 45 do not exclusively detect secondary electrons, backscattered electrons, or Auger electrons, respectively, but rather each detects a combination of these electrons. However, detectors 41, 43, and 45 are configured such that detector 41 detects the most secondary electrons, detector 43 detects the most backscattered electrons, and detector 45 detects electrons in such a way that Auger electrons can be distinguished from other electrons. For example, the ratio of secondary electrons to other electrons of detector 41 is at least 1.1, and the ratio of backscattered electrons to other electrons of detector 43 is at least 1.1.

[0043] The detector 41 generates an electrical signal based on the detected electrons and sends the electrical signal to the control device 53 via a connecting line 49 that connects the detector 41 to a computing unit 51 of a control device 53. The detector 43 generates an electrical signal based on the detected electrons and sends the electrical signal to the control device 53 via a connecting line 55 that connects the detector 43 to the computing unit 51 of the control device 53. The detector 45 generates an electrical signal based on the detected electrons and sends the electrical signal to the control device 53 via a connecting line 57 that connects the detector 45 to the computing unit 51 of the control device 53.

[0044] Although not in the Fig. 1, the electron beam microscope 1 can comprise multiple detectors of the same type. For example, the electron beam microscope 1 can have another secondary electron detector between the objective lens 15 and the object 23. The electron beam microscope 1 can also have another backscattered electron detector between the objective lens 15 and the object 23. With such a backscattered electron detector, it can also be advantageous to equip it with multiple detection surfaces, which are handled and displayed as different detectors in a user interface.

[0045] The electron beam microscope 1 further comprises an X-ray detector 59, which is connected to the processing unit 51 of the control device 53 via a connecting line 61. The X-ray detector 59 detects X-rays generated when the electron beam 5 strikes the object 23. For example, the X-ray detector 59 is formed by a scintillator material and a photomultiplier tube.

[0046] The electron beam microscope 1 further comprises a camera 63, which is connected to the computing unit 51 of the control device 53 via a connecting line 65. The camera captures light images of the object 23 and the support mechanism 25 and sends the light images to the control device 53 via the connecting line 65. For appropriately capturing the light images, the electron beam microscope 1 further comprises a lamp 67 that illuminates the object 23 with light. For this purpose, the lamp 67 is connected to the computing unit 51 of the control device 53 via an electrical connecting line 69.

[0047] The control device 53 further comprises a display 71 connected to the computing unit 51. During operation of the electron beam microscope 1, the display 71 displays a user interface via which the user can make inputs to the electron beam microscope 1 and thus carry out control.

[0048] The computing unit 51 is connected to a cloud 75 via a connection 73. The cloud 75 is connected to a workstation 79 of a workstation 81 via a connection 77. The workstation 81 also includes a display 83 connected to the workstation 79 and capable of displaying a user interface. The connections 73 and 77 can be wired or wireless. In the case of a wired connection 73 and a wired connection 77, it may be advantageous to implement a direct connection between the computing unit 51 of the electron beam microscope 1 and the workstation 79, omitting the cloud 75.

[0049] The electron beam microscope 1 is operated with a method which is described below with reference to the Fig. 2 is described. Fig. 2 shows a flowchart with steps of a method for operating the Fig. 1 according to one embodiment. The method comprises steps S1 to S9.

[0050] The operation of the electron beam microscope 1 is carried out in such a way that the object 23 is repeatedly scanned and, accordingly, particle beam microscopic images are repeatedly acquired. This means that the user interface displayed on the display 71 displays a particle beam microscopic image and updates this image by image with each new image acquisition, pixel by pixel with each scanned point, line by line with each scanned line, and / or block by block with scanned blocks. Accordingly, the displayed image is also referred to below as the live image, and the at least one selected detector from which the acquired images are displayed are referred to as live detectors. Detectors from which no images are displayed are referred to as background detectors, and the non-displayed images of the background detectors are referred to as background images.

[0051] In step S1, the computing unit 51 receives a user's selection from the detectors 41, 43, 45, and 59, wherein this selection indicates which of the detectors 41, 43, 45, and 59 a particle beam microscopic image is to be displayed. To do so, the user clicks, for example, on the secondary electron detector 41 in a list of detectors 41, 43, 45, and 59 displayed on the display by the user interface, which is subsequently registered by the computing unit 51 as a live detector. It should be noted that this is only an example. In some embodiments, the user may be given the option of clicking on multiple detectors 41, 43, 45, and 59, so that multiple live detectors are registered by the computing unit 51.

[0052] Subsequently, in step S2, the operating parameters are not adjusted so that the image quality of the live image is optimal, but rather so that the image quality of the live image is close to the optimal image quality and the image quality of the background images is improved. For example, a measure of image quality is image noise, which can be determined using an algorithm for image noise detection, image contrast, which can be determined from an intensity or color histogram of the images, and / or image sharpness, which can be determined using a suitable edge detection algorithm.

[0053] Often, the image quality of the live image under optimal operating parameters is so good that the user can hardly tell from a particle beam microscopy image whether the operating parameters deviate slightly from the optimal ones. However, the optimal operating parameters are not aligned with the background detectors, which is why the image quality of the background images is often poor. Therefore, it is advantageous to adjust the operating parameters so that they deviate slightly from the optimal operating parameters and are thus better aligned with the background detectors. This achieves a compromise between the live image and the background images.

[0054] An example of such operating parameters of the electron beam microscope 1 are an offset and an amplification of electrical signals of the detectors 41, 43, 45 and 59. In particular, the amplification for each of the detectors 41, 43, 45 and 59 must be adjusted so that the particle microscopic image of the respective detector is optimal.

[0055] Another example of such operating parameters is the voltage applied to detectors 41, 43, and 45, which is used to draw particles toward a detector surface. This voltage must be adjusted for each of detectors 41, 43, and 45 to achieve a compromise between the image quality of the particle microscopic image acquired by the live detector and the image quality of the particle microscopic images acquired by each of the background detectors. In other words, it is advantageous if the above-mentioned voltage of the background detectors is not selected so high that a large proportion of the particles are drawn into the background detectors, meaning only a few particles reach the live detector.

[0056] Another example of such operating parameters of the electron beam microscope 1 is a scanning speed of the electron beam microscope 1. As described later, the electron beam microscope 1 can scan the object 23 by directing the particle beam 5 onto a scanning point and holding it there for a predetermined dwell time. After this dwell time has elapsed, the particle beam 5 is then deflected from the scanning point to the next scanning point in a shorter transition time. In such a case, the scanning speed can be specified as scanning points per unit time.

[0057] The optimal scanning speed varies for different detector types. For example, a low scanning speed may cause object 23 to experience a greater charge input or charging, which impairs image acquisition. According to this example, a secondary electron detector may require a higher scanning speed than a backscattered electron detector, since the low-energy secondary electrons are more affected by the charge of object 23 than the high-energy backscattered electrons.

[0058] Particularly in the case described above, the scanning speed is part of a scanning strategy, which is an operating parameter of the electron beam microscope 1 and further defines at least one arrangement of the scanning points. The arrangement of the scanning points is relevant in a similar way to the scanning speed, as described above. Further relevant operating parameters represent, for example, a kinetic energy of the electrons of the electron beam 5 upon impact with the object 23, as well as a kinetic energy of the electrons of the electron beam 5 upon passing through the objective lens 15. These quantities can be an electrical voltage between the beam source 3 and the object 23, as well as an electrical potential of a beam tube (not shown), which delimits an inner diameter of the objective lens 15.

[0059] It should be noted that step S2 is not mandatory and may be omitted in some embodiments.

[0060] In step S3, the electron beam microscope 1 scans the object 23. In doing so, the electron beam microscope 1 directs the electron beam 5 successively onto each of the scanning points. Once the last scanning point is reached, the electron beam microscope 1 starts again with the first point, for example, or directs the electron beam 5, for example, in reverse or arbitrary order onto each of the scanning points. Consequently, the detectors 41, 43, and 45 receive electrons generated at the object 23, and the detector 59 receives radiation generated at the object 23. The detectors 41, 43, 45, and 59 generate a measured value. The respective measured values ​​are transmitted via the connecting lines 49, 55, 57, and 61 to the computing unit 51 and assigned to the respective scanning point, whereby a particle beam microscopic image is generated for each detector 41, 43, 45, and 59.It should be noted that the dwell time for which the electron beam 5 remains at a scanning point can be set individually for each of the scanning points. For example, the electron beam 5 can remain at a scanning point until the detector that receives the fewest electrons or photons among the detectors 41, 43, 45, and 59 has received at least a certain minimum number of electrons or photons.

[0061] The display 71 shows a live image of a selected live detector. For this description, it is assumed that the secondary electron detector 41 has been selected as the live detector. The live image shown on the display is updated in step S4 with each newly generated particle beam microscopic image of the secondary electron detector 41. Therefore, a current particle beam microscopic image of the secondary electron detector 41 is shown on the display 71. The generated particle beam microscopic images of the background detectors 43, 45, and 59 are not shown on the display 71.

[0062] In step S5, the generated particle beam microscopic images of the background detectors 43, 45, and 59 are analyzed using various algorithms to extract information from these background images that might be of interest to the user of the electron beam microscope 1 during the acquisition of the particle beam microscopic images. Such information is, for example, whether the object 23 is heavily charged due to irradiation with the electron beam 5. If a strong charge on the object 23 is not or only with difficulty recognizable in the live image, the user of the electron beam microscope 1 would like to be informed of such a charge in order to be able to make appropriate adjustments to the operation of the electron beam microscope 1 and / or to the object 23. Furthermore, such an analysis can also determine whether the object 23 is contaminated.

[0063] While the user is working on the electron beam microscope 1, in particular on the control device 53 for acquiring the particle beam microscopic images, steps S3 to S5 are repeated as often as desired. Once the user has completed their work on the control device 53 with the user interface shown on the display, in step S6 all acquired images, i.e., the images of the live detector and the images of the background detectors, are stored in the cloud 75 or on a hard disk of the computing unit 51. The acquired images can also be stored repeatedly, for example, by storing the generated images directly in the cloud 75 after each generation of the particle beam microscopic images of the detectors 41, 43, 45, and 59. The images are preferably stored in such a way that images generated in the same scan in step S3 can be associated with one another.For this purpose, a recording time can be saved together with each image, but numbering the images in a file name may be sufficient.

[0064] After the user has finished working on the control device 53, the user returns, for example, to their workstation 81. The user opens the user interface with the workstation 79, which is then displayed on the display 83. In step S7, the user interface loads the images stored in the cloud 75 and displays them. The loaded images are preferably displayed in a representation in which the user can recognize a chronological order in which the respective images were recorded. For this purpose, a timeline of the images from the live detector is first displayed in step S7. This will be described in more detail later. It should be noted that returning to the workstation 81 and opening the user interface with the workstation 79 represents an exemplary situation.The user can also use the functions of the user interface described in step S7 on the control device 53 of the electron beam microscope 1.

[0065] In step S8, the user then clicks on one of the live detector images in the timeline, causing images of the background detectors captured along with the clicked image to be displayed in step S9. This is possible because the images have been stored in such a way that images generated in the same scan in step S3 can be associated with each other.

[0066] The following describes the user interface shown on the displays 71 and 83 with reference to the Fig. 3 or the Fig. 4. The Fig. 3 shows a display window 85 of a user interface 87 of the Fig. 2. The display window 85 is a part of the user interface 87 that is displayed on the display 71 of the control device 53.

[0067] The display window 85 comprises an image area 89 for displaying the live image 91, a selection box 93 for selecting the live detector, an information field 95 for displaying the operating parameters of the electron beam microscope 1, and a notice field 97 for displaying a message about any unfavorable conditions during image acquisition. If, in one embodiment, a selection of multiple live detectors is provided, the selection box 93 allows a selection of multiple live detectors, and the image area 89 can be configured to display multiple live images side by side. The live image 91 shows features 99 of the object 23. The selection box comprises checkboxes 101, each labeled with one of the detectors 41, 43, 45, and 59. If the user of the electron beam microscope 1 clicks on one of the checkboxes, the associated detector is selected as the live detector. Fig. Figure 3 shows a case where the secondary electron detector 41 is selected as the live detector. Accordingly, the live image 91 is an image generated by the secondary electron detector 41.

[0068] The information field 95 displays information about the operating parameters of the electron beam microscope 1. The Fig. 3 shows a case in which the acceleration energy of the electrons of the electron beam 5, which is, for example, an energy kinetic energy of the electrons when passing through the objective lens 15, is 8 keV, the impact energy of the electrons of the electron beam 5 is 2 keV, the object 23 is scanned line by line and the scanning strategy provides that first every second line on the object 23 is scanned and then the remaining lines on the object 23 are scanned.

[0069] If in step S5 of the Fig. 2 that the object 23 has experienced a strong charge, a corresponding message is displayed to the user of the electron beam microscope 1 in the information field 97.

[0070] The Fig. 4 shows another display window 103 of the user interface 87 of the Fig. 2. The display window 103 comprises a timeline view 105 with a plurality of images 107, 109, and 111. The images 107, 109, and 111 show the features 99 of the object 23. Preferably, the images 107, 109, and 111 are arranged such that in steps S3 to S5, image 107 was acquired first, followed by image 109, and then image 111, so that the order of the images 107, 109, and 111 from left to right resembles the order in which the images 107, 109, and 111 were acquired. The timeline view 105 further comprises a scroll bar 113 with a slider 115 and arrow buttons 117 with which the user can move the timeline view 105 to a different position in the order in which the images were acquired.

[0071] In the timeline view 105, the user can select one of the images 107, 109 and 111 by clicking on it. In the Fig. Figure 4 shows a case where the user of the electron beam microscope 1 has selected image 109. As a result, an image 119 of the backscattered electron detector 43, an image 121 of the X-ray detector 59, and an image 123 of the Auger electron detector 45 are displayed. Specifically, images 119, 121, and 123 are those acquired together with the selected image 109. Images 119, 121, and 123 also show feature 99, but differ from images 107, 109, and 111, which is schematically represented as white and black filling of the features.

[0072] Accordingly, the user of the electron beam microscope 1 can easily compare images 109, 119, 121, and 123. Preferably, the user can also select one of the images 119, 121, and 123, allowing this image to be displayed in an enlarged format in a new display window.

[0073] Thanks to the method described above, the user does not necessarily have to restart the electron beam microscope 1, in particular the control device 53, if the images acquired by the live detector are insufficient for their purposes. In such a case, the user can first view images from the other detectors 43, 45, and 59, acquired under similar conditions, which might contain information needed for their purposes. Accordingly, the likelihood that the user will have to restart the control device 53 or revisit a previous sample location is reduced.

[0074] In the following, a further embodiment is described with reference to the Fig. 5. Typically, a light image from a camera is displayed to position an object so that the object can be positioned more easily and, in particular, does not collide with components of the electron beam microscope. According to the method described above, this can be achieved, for example, by listing the camera 63 as a selectable detector in the selection box 93 of the user interface 87. If the user of the electron beam microscope 1 selects the camera 63 as a live detector, the light image from the camera 63 is displayed in the image area 89 of the user interface 87. This also means that the detectors 41, 43, 45, and 59 continue to capture images as background detectors or as live detectors selected in addition to the camera.If the object 23 is illuminated with light for improved camera exposure and at least one of the detectors 41, 43, 45 and 59 is designed as a scintillation detector, illuminating the object 23 with light would interfere with the scintillation detector when taking images.

[0075] Accordingly, in the method of the further embodiment, the illumination of the object 23 with light is adjusted such that the illumination of the object 23 with light does not disturb the detectors 41, 43, 45 and 59. Thus, in the present method, the camera 63 can alternatively also function as a background detector. Fig. 5 shows a flowchart with steps S10 to S19 of a method for operating the Fig. 1 according to the further embodiment. The Fig. 5 shows, in particular, a generation of a light image of the camera 63 in a case where a single detector, such as the secondary electron detector 41, captures a single image.

[0076] In step S10, the object 23 is scanned along a line with the electron beam 5. The following description assumes a case in which the scanning of the object 23 along the line is carried out such that the electron beam 5 is first directed at a scanning point for a dwell time, then deflected to the next scanning point for a shorter transition time, and then directed again at this scanning point for the duration of the dwell time.

[0077] During the scanning of the object 23, the secondary electron detector detects secondary electrons generated on the object 23 in step S11. Steps S10 and S11 are performed until it is determined in step S12 that the scanning of the entire line on the object 23 is complete.

[0078] Subsequently, in step S13, it is checked whether the scanning of the entire object 23 is complete. If the scanning of the entire object 23 is complete, the process continues with steps S18 and S19.

[0079] If it is determined in step S13 that the scanning of the entire object 23 is not yet completed, the object 23 is illuminated with light in step S14. For this purpose, the lamp 67 is supplied with power by the computing unit 51. It is emphasized that this means that the object 23 is illuminated with light after a scanning of a line on the object 23 has been completed. In step S15, a detector field of the camera 63 is illuminated by light scattered and reflected by the object 23. During steps S14 and S15, the electron beam 5 is deflected from one end of a line to the beginning of a next line, which is Fig. 5. The deflection of the electron beam 5 does not have to take place during the illumination of the object 23 with light and the detection of the scattered and reflected light, but the electron beam microscope 1 can also suspend the deflection of the electron beam 5 from the end of the line to the beginning of the next line for a certain duration in order to improve the exposure of the camera 63.

[0080] If it is determined in step S17 that the electron beam 5 has reached the beginning of the next line, the electron beam microscope 1 proceeds to step S10 and performs the line scanning on the object 23 again without illuminating the object 23 with light.

[0081] In step S18, after scanning of the entire object 23 has been completed, the light image of the camera 63 is generated. The light image of the camera 63 is generated only after scanning of the entire object 23, since the time during which the electron beam 5 is deflected from one line to the next is generally too short for suitable exposure of the detector field of the camera 63. Furthermore, in step S19, the particle beam microscopic image of the secondary electron detector 41 is generated.

[0082] If the detection of light with the camera in step S15 is to be performed during a frame flyback as mentioned above, steps S10 to S19 can, for example, be repeated for multiple particle microscopic images. In such a case, steps S14 and S15 are then performed additionally or alternatively directly before step S18.

[0083] The procedure is described below with reference to the Fig. 6 explains in more detail. The Fig. 6 shows an image field 125 of the Fig. 1 shown particle beam microscope 1 with scanning points arranged in rows in the Fig. 5. The image field 125 is scanned line by line; lines I and II are named as examples. Lines I and II each have scanning points 127, as well as connecting lines 129 between the scanning points 127. When scanning line I, the electron beam 5 is directed onto a scanning point 127 for the duration of the dwell time. After the dwell time has elapsed, the electron beam 5 is deflected for the duration of the transition time via the adjacent connecting line 129 to the next scanning point 127, whereupon the electron beam 5 also remains at this scanning point 127 for the dwell time.

[0084] When the electron beam 5 has reached the last scanning point 131 of line I, the electron beam 5 remains at the last scanning point 131 for the duration of the dwell time and is then deflected along a fly-back line to the first scanning point 127 of line II, from where the scanning to line I is carried out identically. Fig. Steps S14 to S16 shown in Figure 5 are performed while the point of incidence of the electron beam 5 is located on the flyback line 133. This is advantageous because the flyback line 133 does not contain any scanning points 127, 129 and is thus not considered for generating a particle beam microscopic image. Accordingly, while the point of incidence of the electron beam 5 is located on the flyback line 133, the object 23 can be illuminated with light by the lamp 67 without affecting the particle beam microscopic image.

[0085] For appropriate exposure of the camera 63, it is advantageous to integrate a signal generated by the detector field of the camera 63 over several fly-back lines 133 in order to prevent interference effects. Accordingly, with reference to Fig. 5 only in step S18 generates the light image of the camera 63. Furthermore, the signal generated by the detector field of the camera 63 can be integrated exclusively via one or more fly-back lines 133, or additionally via connecting lines 127 and / or via scanning points 127, 131. The exposure of the camera by integrating the signal generated by the detector field of the camera 63 can be carried out in any suitable manner, as long as the illumination of the object 23 with light does not influence the scintillation detectors of the electron beam system 1, as for example in the Fig. 6 only when the point of incidence of the electron beam 5 is not located at a scanning point 127, 131 and in particular on a fly-back line 133.

[0086] The Fig.6 also shows a frame flyback line 135 between the first scanning point 127 in row I and the last scanning point 131 in row VII. After the electron beam 5 has been directed to the last scanning point 131 in row VII for the dwell time, the electron beam 5 is deflected along the frame flyback line 135, so that the electron beam 5 is returned to the start of scanning. While the electron beam 5 is deflected along the frame flyback line 135, the object 23 can be illuminated, and light can be detected by the camera 63 without disturbing the light-sensitive detectors of the detectors 41, 43, 45, and 59.Since the time required to deflect the electron beam 5 along the frame flyback line 135 is significantly longer than the time required to deflect the electron beam 5 along the flyback lines 133, it may be possible to capture a light image with the camera 63 while the electron beam 5 is deflected once along the frame flyback line 135 without requiring additional exposure time. If the time required is insufficient to capture a light image with the camera 63, the deflection of the electron beam 5 along the frame flyback line 135 can be slowed down or briefly paused so that a light image can be captured with the camera 63 without additional exposure time.It should be noted that illuminating the object 23 and detecting light with the camera 63 while deflecting the electron beam 5 along the frame flyback line 135 may be performed in addition to or alternatively to illuminating the object 23 and detecting light with the camera 63 while deflecting the electron beam 5 along the flyback lines 133.

[0087] It should be noted that steps S1 to S9, as well as steps S10 to S19, can be performed by the computing unit 51 or by the workstation 79, respectively, particularly when they execute a computer program product comprising instructions, upon execution of which the computing unit 51 or the workstation 79 performs steps S1 to S9 and / or steps S10 to S19. As already described above by way of example with regard to the storage of all images in step S6, steps can also be exchanged with one another in a suitable manner.

[0088] Embodiments of the above-disclosed method for operating the particle beam microscope, the particle beam microscope and the computer program can be summarized by the following aspects.

[0089] Aspect 1: A method for operating a particle beam microscope, the method comprising: receiving a selection by a user of the particle beam microscope of at least one detector from a plurality of detectors, wherein the number of selected detectors is less than the number of the plurality of detectors, wherein the user's selection indicates images acquired by which detectors are to be displayed, wherein the plurality of detectors comprises at least one detector for backscattered electrons and one detector for secondary electrons; scanning an object once or repeatedly with a particle beam of the particle beam microscope;Capturing a plurality of images during a scan of the single or repeated scan of the object, each image of the plurality of images being captured by a detector of the plurality of detectors, each detector of the plurality of detectors capturing at least one image of the plurality of images; displaying only the images captured by the selected detectors during the single or repeated scan; storing the images captured by the selected detectors during the single or repeated scan and the images captured by the non-selected detectors during the single or repeated scan; and upon completion of the single or repeated scan, receiving a selection of at least one stored image captured by one of the non-selected detectors and displaying the selected image.

[0090] Aspect 2: The method of aspect 1, further comprising, upon completion of the single or repeated scan, displaying a plurality of the stored images acquired by one of the selected detectors; wherein receiving the selection of the at least one of the stored images acquired by one of the non-selected detectors comprises: receiving a selection of one of the displayed images and using at least one of the stored images acquired by one of the non-selected detectors, acquired along with the selected displayed image during the same scan, as the selected stored image acquired by the at least one of the non-selected detectors.

[0091] Aspect 3: The method of aspect 1 or aspect 2, further comprising: during the single or repeated scan, analyzing the images acquired by the non-selected detectors during the repeated scan; and generating a notification to the user based on the analysis.

[0092] Aspect 4: The method of aspect 3, wherein analyzing the images acquired by the non-selected detectors during the single or repeated scan comprises analyzing the images acquired by the secondary electron detector.

[0093] Aspect 5: The method of aspect 4, wherein, based on the analysis, it is determined that an electrical charge has occurred on the object; and wherein the notification to the user comprises a warning that the electrical charge has occurred on the object.

[0094] Aspect 6: Method according to any one of aspects 1 to 4, further comprising changing operating parameters of the particle beam microscope; wherein the images of at least one of the selected detectors and at least one of the non-selected detectors are analyzable to determine a measure representing an image quality of the images; wherein the operating parameters of the particle beam microscope are alterable such that an optimal measure of the image quality of the image acquired by the selected detector is achieved, wherein the measure of the image quality of the image acquired by the non-selected detector is then a given measure of the image quality;and wherein the changing of the operating parameters of the particle beam microscope is carried out such that the measure of the image quality of the image recorded by the selected detector is lower than the optimal measure and the measure of the image quality of the image recorded by the non-selected detector is better than the given measure;

[0095] Aspect 7: The method of aspect 6, further comprising analyzing the images of the at least one of the selected detectors and the at least one of the non-selected detectors and determining the measure representing the image quality of the analyzed image during the single or repeated scanning; wherein changing the operating parameters of the particle beam microscope is performed based on the determined image qualities.

[0096] Aspect 8: The method of aspect 6, further comprising: storing a plurality of predetermined sets of values ​​representing operating parameters of the particle beam microscope; and selecting one of the plurality of predetermined sets of values ​​based on the user's selection of the at least one detector; wherein changing the operating parameters of the particle beam microscope is based on the values ​​of the selected set of values.

[0097] Aspect 9: Method according to one of aspects 1 to 8, wherein receiving the user's selection from the plurality of detectors is performed such that the selection comprises exactly one detector.

[0098] Aspect 10: The method of any one of aspects 1 to 9, wherein the plurality of detectors further comprises a radiation detector and / or an Auger electron detector.

[0099] Aspect 11: A particle beam microscope comprising: a particle beam source for generating a particle beam; an object holder for holding an object; a deflection device for deflecting the particle beam to scan the object with the particle beam; a plurality of detectors; and a controller configured to operate the particle beam microscope using the method according to any one of aspects 1 to 10.

[0100] Aspect 12: A computer program product comprising instructions which, when executed by the controller of the particle beam microscope according to aspect 12, cause the particle beam microscope to perform the method according to any one of aspects 1 to 10.

Claims

[1] Method for operating a particle beam microscope (1), the method comprising: Scanning an object (23) with a particle beam (5); Detecting electrons generated by the particle beam (5) on the object (23) with a light-sensitive detector; Generating a particle beam microscopy image based on the detected electrons; Illuminating the object (23) with light; and Detecting light images of the object (23) with a camera (63); wherein generating the particle beam microscopic image is based solely on the detected electrons detected during a plurality of first time intervals; wherein the object (23) is illuminated only in a plurality of second time intervals; where the first time intervals and the second time intervals overlap each other at most partially. [2] The method of claim 1, wherein the first time intervals and the second time intervals do not substantially overlap each other. [3] Method according to claim 1 or 2, wherein the scanning of the object (23) with the particle beam comprises a line-by-line scanning, in which during the first time intervals the particle beam (5) is scanned along a line (I, II, VII) in each case and in which during the second time intervals the particle beam (5) is returned to a beginning of a line (I, II, VII). [4] Method according to one of claims 1 to 3, wherein the scanning of the object (23) is carried out repeatedly; and wherein during the second time intervals the particle beam (5) is returned to a starting point of the scanning. [5] Particle beam microscope (1), comprising: a particle beam source (3) for generating a particle beam (5); an object holder (27) for holding an object (23); a deflection device (37) for deflecting the particle beam (5) in order to scan the object (23) with the particle beam (5); a detector (41, 43, 45, 59); a camera (63); and a controller (53) configured to operate the particle beam microscope (1) using the method according to one of claims 1 to 4. [6] Computer program product comprising instructions which, when executed by the controller (53) of the particle beam microscope (1) according to claim 5, cause the particle beam microscope (1) to carry out the method according to one of claims 1 to 4.

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