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

Abstract

A method for operating a multi-beam particle microscope in an inspection mode of operation and a related multi-beam particle microscope are disclosed. The detection unit comprises an image generation detection area with fixedly assigned detection channels and an adjustment detection area with additional detection channels. The fixedly assigned detection channels (235) and the additional detection channels (235’) are provided within the same detection surface (211). Based on the signals obtained by the additional detection channels, it is possible to accurately correct in real time the incidence position of the secondary beam on the detection unit, independent of the specific structure of the detection unit.

Description

Technical Field

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

Background Art

[0002] As ever-smaller and more complex microstructures, such as semiconductor components, are continuously developed, there is a need to further develop and optimize planar production techniques and inspection systems for producing and inspecting microstructures of small dimensions. By way of example, the development and production of semiconductor components requires monitoring the design of test wafers, and planar production techniques require process optimization for high-throughput and reliable production. More recently, there have been requirements for the analysis of semiconductor wafers in reverse engineering and for semiconductor components with respect to customer-specific individual configurations. Therefore, there is a need for inspection means that can be used with high throughput in order to examine microstructures on a wafer with high precision.

[0003] The diameter of a typical silicon wafer used in the production of semiconductor components is at most 300 mm. Each wafer is at most 800 mm 2It is divided into 30 to 60 repeating regions ("dies") having a size of. The semiconductor device includes a plurality of semiconductor structures formed in layers on the surface of the wafer by planar integration techniques. The semiconductor wafer typically has a flat surface by the production process. In this case, the structure size of the integrated semiconductor structure ranges from several μm to a critical dimension (CD) of 5 nm, and in the near future, the structure size will become even smaller. The structure size or critical dimension (CD) is expected to be less than 3 nm in the future, for example, 2 nm, or even less than 1 nm. In the case of the aforementioned small structure sizes, defects in the size of the critical dimension must be quickly identified in a very wide area. In some applications, the specification requirements regarding the measurement accuracy achieved by inspection equipment are even higher, for example, twice or one order of magnitude higher. As an example, the width of the semiconductor feature must be measured with an accuracy of less than 1 nm, for example, 0.3 nm or less, and the relative position of the semiconductor structures must be determined with an overlay accuracy of less than 1 nm, for example, 0.3 nm or less.

[0004] A multi-beam scanning electron microscope (MSEM) is a relatively newly developed instrument in the field of charged particle systems (charged particle microscopes, CPM). The multi-beam scanning electron microscope is disclosed, for example, in U.S. Patent No. 7,244,949 and U.S. Patent Application Publication No. 2019 / 0355544. In the case of a multi-beam electron microscope, i.e., an MSEM, the sample is simultaneously irradiated with a plurality of individual electron beams arranged within a field or raster. As an example, 4 to 10,000 individual electron beams can be supplied as primary radiation, and each individual electron beam is separated from an adjacent individual electron beam by a pitch of 1 to 200 micrometers. The MSEM has, for example, approximately 100 separated individual electron beams ( "beamlets"), which are arranged, for example, in a hexagonal raster, and the individual electron beams are separated by a pitch of approximately 10 μm. The plurality of charged individual particle beams (primary beams) are focused onto the surface of the test sample by a common objective lens. The sample may be, for example, a semiconductor wafer firmly held in a wafer holder mounted on a movable stage. While irradiating the wafer surface with the charged primary individual particle beams, interaction products, such as secondary electrons or backscattered electrons, are emitted from the surface of the wafer. The starting points of the interaction products all coincide with the location on the sample where the plurality of primary individual particle beams are focused. The amount and energy of the interaction products vary depending on the material composition and the surface shape of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are collected by a common objective lens and, as a result of the projection imaging system of the multi-beam inspection system, are incident on a detector arranged on the detection surface. The detector comprises a plurality of detection regions each having a plurality of detection pixels, and the detector captures the intensity distribution of each of the secondary individual particle beams. In this process, for example, an image plane of 100 μm × 100 μm is obtained.

[0005] Conventional multi-beam electron microscopes comprise a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adapt the focal positions and the aberration corrections of the plurality of charged individual particle beams. Conventional multi-beam systems with charged particles further comprise at least one crossover plane of the primary or secondary charged individual particle beams. The conventional systems further comprise a detection system to facilitate the adjustment. Conventional multi-beam particle microscopes comprise at least one beam deflector ("deflection scanner") for collectively scanning a region of the sample surface with a plurality of primary individual particle beams to obtain an image plane of the sample surface. Further details regarding multi-beam electron microscopes and methods of operating them are described in German Patent Application No. 102020206739.2 filed on May 28, 2020, and documents of the related patent family, the disclosure of which is hereby incorporated in its entirety by reference into this patent application.

[0006] The exact alignment of the secondary individual particle beam when it is incident on the detector is important for obtaining high resolution within the scope of sample inspection, particularly semiconductor sample inspection. The alignment of the raster of the second individual particle beam is typically performed by referring to the beam arranged at the center of the raster. The raster is aligned or adjusted to the optimal possible extent with respect to the detection region assigned to the raster. This alignment is usually performed before each image is recorded.

[0007] However, the alignment of the second individual particle beam may also change with respect to the detection region of the detection unit during image recording, for example as a result of drift or due to the characteristics of the sample itself. As an example, the influence of the charging of the sample may cause a slight distortion of the secondary individual beam emitted from or starting from the sample, which may prevent it from hitting the desired reference position on the detection unit. In such cases, it would be desirable to perform the correction or readjustment in real time.

[0008] In this context, German Patent Application Publication No. 102015202172 proposes the use of a detector unit composed of pixels, which are each provided for detecting a second individual particle beam and each of the detection regions assigned to the second individual particle beam comprises a plurality of detection fields. When the location of incidence of the second individual particle beam on the detector changes during inspection, the assignment of the detection fields to the detection regions is corrected. On the one hand, this procedure restricts the type of detector unit used to a detector unit composed of pixels, and on the other hand, the correction of such an assignment is extremely complex algorithmically and relatively slow.

[0009] U.S. Patent No. 10,896,800 avoids the problem of restrictions on the type of detector unit composed of pixels for image generation by using, in addition to a detector not composed of pixels, an additional detector unit composed of pixels in the form of a high-speed CCD camera (in combination with a particle detector and an optical unit downstream having an optical fiber for each detection region). For this purpose, a beam splitter is provided in the optical detection path, and a part of the optical signal is output to the CCD camera. At the position on the CCD camera, the position of the light when it is incident on the signal incident surface of the optical fiber can be assigned. Using this, it is possible to indirectly detect the shift in the position of the second individual beam when it is incident on the detector used for image generation. Thereby, in principle, high-speed position correction in the secondary path of a multi-beam particle microscope becomes possible. To correct the particle optical beam path in the secondary path itself, a rapidly controllable electrostatic lens, electrostatic deflector, and / or electrostatic stigmer are used. According to U.S. Patent No. 10,896,800, the incidence of light on the additional detector unit composed of pixels for recognizing the shift is obtained by beam splitting that attenuates the original optical signal. Furthermore, with regard to the detector unit, one is restricted to the combination of particle detection and optical detection as a result of the beam splitting required in the optical system. Furthermore, in the case of a CCD camera involving the evaluation of signals from all pixels, the signal evaluation is relatively complex algorithmically.

[0010] Furthermore, US Patent Application Publication No. 2021 / 0005423 discloses a combination for each detection region of a particle detector and an optical unit downstream with an optical fiber. A beam splitter is provided in the optical detection path, and a part of the optical signal is output to a CCD camera, and the CCD camera can be used to identify changes in the location of interaction products within the detection surface due to the charging of the sample. US Patent Application Publication No. 2021 / 0005423 further discloses a diaphragm disposed at the position of the crossover of the secondary particle beam within the detection system. The circular aperture of the diaphragm is radially surrounded by several electrodes that can function as current detectors. By detecting the asymmetry of the current or charge induced in the electrodes, the eccentricity of the charged particle beam passing through the aperture of the diaphragm can be detected and corrected as necessary. SUMMARY OF THE INVENTION PROBLEMS TO BE SOLVED BY THE INVENTION

[0011] The object of the present invention is, accordingly, to propose a method of operating a multi-beam particle microscope in an inspection mode and a related multi-beam particle microscope that enables simple and highly versatile high-speed position correction of the secondary beam when it enters the detection unit.

[0012] This object is achieved by the independent claims. Advantageous embodiments of the invention are apparent from the dependent claims.

[0013] This patent application claims the priority of German Patent Application No. 102022114923.4 filed on June 14, 2022, the disclosure of which is incorporated herein by reference in its entirety. MEANS FOR SOLVING THE PROBLEM

[0014] According to a first aspect of the present invention, the present invention relates to a method of operating a multi-beam particle microscope in an inspection mode, the method comprising Irradiating a target with a plurality of charged first individual particle beams, each first individual particle beam irradiating a separate individual field region of the target in a scanning manner; Collecting second individual particle beams that are emitted from or radiated from the target by the first individual particle beams; Focusing and projecting the second individual particle beams onto the detection regions of a detection unit such that the second individual particle beams emitted from two different individual field regions are projected onto different detection regions, with one detection channel or a predetermined plurality of detection channels fixedly assigned to each detection region; Reading the fixedly assigned detection channels and generating individual images of each individual field region based on data obtained from signals from each of the fixedly assigned one detection channel of each detection region or each of the detection regions having a plurality of fixedly assigned detection channels; Reading additional detection channels of the same detection unit that are not projected in a manner directed at the target and not assigned to any detection region, and determining the displacement of the second individual particle beam from the reference incident position when entering the detection unit based on data obtained from signals from the additional detection channels; Correcting in real time the displacement of the second individual particle beam when entering the detection unit; Including.

[0015] The first charged individual particle beam may be, for example, an electron, a positron, a muon, or an ion, or other charged particles. The individual field regions of the object assigned to each of the first individual particle beams are raster scanned, for example, row by row or column by column. In this case, it is preferable that the individual field regions are adjacent to each other or cover the object or a part of the object in a mosaic pattern. The individual field regions may be substantially separated from each other but may overlap with each other in the peripheral region. In this way, it is possible to obtain an image of the object that is as complete and continuous as possible. The individual field regions are preferably embodied as rectangles or squares. This is because it is the easiest to realize the scanning process by particle radiation. The individual field regions are preferably arranged as rectangles stacked vertically in different rows so as to result in a hexagonal structure as a whole. In the case of a hexagon, it is advantageous that the number of particle beams is 3n(n - 1)+1, where n is any natural number. Other arrangements of the individual field regions, such as a square or rectangular raster, are likewise possible.

[0016] The second individual particle beam may be backscattered electrons or, otherwise, secondary electrons. In this case, for analysis, it is preferable that low-energy secondary electrons are used for image generation. However, mirror ions / mirror electrons, that is, the first individual particle beam that is immediately upstream of the object or that is reversed at the object, may also be used as the second individual particle beam.

[0017] According to the present invention, the second individual particle beam is focused and projected onto the detection region of the detection unit, whereby the second individual particle beam emerging from or emitted from two different individual field regions is projected onto different detection regions. In this case, one detection channel or a predetermined plurality of detection channels is fixedly assigned to each detection region. The detection region may thus correspond to one detection channel, or alternatively, due to the fact that the detection region may comprise a plurality of detection channels and thus smaller units, this method can basically be applied regardless of the type of detection unit. It is not necessary to configure the detection region for each second individual particle beam with pixels or to divide it more finely. Instead, the important thing is to fixedly assign one detection channel or a predetermined plurality of detection channels to each detection region. Therefore, according to the present invention, there is no change in this assignment as described above with respect to the prior art (German Patent Application Publication No. 102015202172). The present invention thus simplifies this method as a whole, and this method becomes more generally applicable.

[0018] According to the present invention, the detection unit is in principle further modified or extended. In addition to the detection areas used to generate individual images, the detection unit comprises additional detection channels. Instead of the second individual particle beam being projected onto these additional detection channels in a targeted manner towards the target, the additional detection channels are not assigned to any detection area. Thus, when the second individual particle beam impinges on each reference incidence position of the detection unit, in principle no signal is detected by these additional detection channels. The additional detection channels detect a signal only when at least one, preferably a plurality, of the second individual particle beams are displaced from their respective reference incidence positions of one second individual particle beam / plurality of second individual particle beams. As a result, the additional detection channels function to determine the displacement. Such a displacement can thus be recognized and, optionally, characterized in more detail. This makes it possible to correct the displacement of the second individual particle beam when it impinges on the detection unit.

[0019] The additional detection channels may coincide with the detection channels also used for the generation of normal images with respect to the structure of the additional detection channels. However, it is also possible to design the additional detection channels differently. For specific exemplary embodiments, this will be discussed in more detail below.

[0020] The fixedly assigned detection channels and the additional detection channels belong to the same detection unit. The fixedly assigned detection channels and the additional detection channels are thus provided in the same detection plane. In other words, according to the present invention, the image detection plane and the displacement detection plane are identical. This identity improves the accuracy with which the displacement can be detected.

[0021] According to the present invention, the misalignment of the second individual particle beam when it enters the detection unit is corrected in real time. The means within the secondary path of the multi-beam particle microscope that can be used for this purpose are, in principle, already known in the prior art. It should be noted that the misalignment correction can be carried out while still generating individual images within the scope of real-time correction, and in particular, it can be carried out multiple times. Therefore, if necessary, multiple readjustments or corrections can be carried out for each individual image. As a result, within the scope of sample inspection, better overall resolution can be obtained.

[0022] According to a preferred embodiment of the present invention, the correction of the misalignment of the second individual particle beam includes real-time adjustment of the particle optical beam path of the second individual particle beam. Alternatively, the misalignment could also be corrected by modifying the position of the detection unit itself. However, such correction would not be carried out in real time.

[0023] According to a preferred embodiment of the present invention, this method further includes the steps of classifying the determined misalignment and correcting the misalignment based on the classification. The misalignment often relates equally or overall to the raster of the second individual particle beam. The class or type of misalignment is, for example, the overall displacement, overall rotation, overall magnification of the raster, or overall anamorphic imaging of the second individual particle beam when it enters the detection unit. In this process, it may be possible to determine only one class or one type of overall misalignment, but it is also possible to recognize multiple of the aforementioned types (as an overlay) simultaneously.

[0024] According to a preferred embodiment of the present invention, the misalignment correction includes correction of the overall displacement of the second individual particle beam when it enters the detection unit. As an example, for the purpose of correction, a high-speed deflection system can be used within the second particle optical beam path / secondary path of the multi-beam particle microscope. Only the type of beam correction in the secondary path has already been described in US Patent No. 10,896,800, the disclosure of which is incorporated herein by reference in its entirety.

[0025] According to a further preferred embodiment of the present invention, the misalignment correction includes correction of the overall rotation of the second individual particle beam when it enters the detection unit. As an example, a rotation lens can be used within the second particle optical beam path / secondary path of the multi-beam particle microscope for this overall rotation of the raster of the second individual particle beam. The rotation lens can be controlled quickly. For example, it is also possible to use rotation correction means within the second path, as described in a modification of a plurality of embodiments of German Patent Application Publication No. 102020125534. The entire disclosure of German Patent Application Publication No. 102020125534 is incorporated herein by reference.

[0026] According to a further preferred embodiment of the present invention, the misalignment correction includes correction of the expansion of the second individual particle beam in one or two directions when it enters the detection unit. In this case, the two directions may be orthogonal to each other, but this is not essential. If the expansion is the same size in both directions, this is related to the overall expansion as a misalignment as a whole. To correct, it is also possible to use a system with a high-speed electrostatic lens, for example, as described in US Patent No. 10,896,800 mentioned above.

[0027] The expansion of the raster in one direction corresponds only to anamorphic imaging. Anamorphic imaging can be corrected, for example, by a high-speed electrostatic stigmatic or aberration correction system within the secondary path, as also exemplified in US Patent No. 10,896,800.

[0028] According to a further preferred embodiment of this method, the method comprises the step of correcting in real time the individual positional deviation of at least one second individual particle beam when it is incident on the detection unit This type of correction is a more refined correction that is not carried out globally, i.e., not equally for all second individual particle beams. However, the detection unit needs to meet the fact that a further requirement, for example, the deviation of a specific second individual particle beam from its reference position is detectable only if the associated detection area is arranged adjacent to or relatively very close to an additional detection channel that detects the deviation. Examples enabling this detection are presented in more detail below. By way of example, a multi-deflector array can be used for individual positional deviation correction, and the multi-deflector array is arranged, for example, within a secondary path in the direction of the particle optical beam path after a so-called anti-scan.

[0029] According to a further preferred embodiment of the present invention, the positional deviation is corrected only when it exceeds a threshold value. This basically prevents the execution of unnecessary corrections. Even when the second individual particle beams are focused and projected onto their respective detection areas, of course, the focus does not consist of a mathematical point, but instead, although small, has a spread. Thus, strictly speaking, the intensity of each second individual particle beam has an intensity distribution when it is incident on the detection surface. Therefore, when there is a deviation, the signal may be detected only little by little or gradually by the additional detection channel. For example, most of the detection of the second individual particle beam may still be carried out correctly by the assigned detection area. If so, the detected but unimportant positional deviation may not need to be corrected. It is advantageous to actually correct the positional deviation only when it exceeds a pre-determined threshold value.

[0030] The modifications of the embodiments described above according to the first aspect of the present invention can be combined with each other completely or partially, as long as no technical contradiction results.

[0031] According to a second aspect of the present invention, the present invention relates to a computer program product having program code for executing the methods described in the above-described plurality of embodiments. The program code can, in this case, be divided into one or more partial codes. The program code can be described in any desired programming language.

[0032] According to a third aspect of the present invention, the present invention relates to a multi-beam particle microscope configured to execute a method according to any one of the foregoing exemplary embodiments.

[0033] According to a fourth aspect of the present invention, the present invention relates to a multi-beam particle microscope, the multi-beam particle microscope comprising a multi-beam particle source configured to generate a first field of a plurality of charged first individual particle beams, a first particle optical unit comprising a first particle optical beam path and configured to image the generated first individual particle beams onto an object surface such that the first individual particle beams impinge on an incident location of the object that forms a second field, a detection unit comprising a plurality of detection regions that form a third field, wherein one detection channel or a plurality of detection channels are fixedly assigned to each of these detection regions, and the same detection unit further comprises additional detection channels that are not assigned to any of the detection regions, a second particle optical unit comprising a second particle optical beam path and configured to image the second individual particle beams radiated from the incident location of the second field in a substantially focused form onto the third field of the detection regions of the detection system, The second particle optical unit includes high-speed detection position adjustment means configured to correct in real time the position of the second individual particle beam when it enters the detection unit. a second particle optical unit; an objective lens through which both the first individual particle beam and the second individual particle beam pass; a beam switch disposed in a first particle optical beam path between the multi-beam particle source and the objective lens and in a second particle optical beam path between the objective lens and the detection unit; a controller, wherein the controller is configured to control the second particle optical unit; wherein the controller is configured to generate individual images from data obtained from signals from one detection channel fixedly assigned to each or a plurality of detection channels fixedly assigned to each detection region; wherein the controller is configured to determine a positional deviation of the second individual particle beam from a reference incident position when entering the detection unit from data obtained from signals from an additional detection channel not assigned to any of the detection regions and to generate at least one correction signal that functions to correct the positional deviation; wherein the controller is configured to control the high-speed detection position adjustment means in real time using the at least one correction signal; a controller; and.

[0034] The multi-beam particle microscope according to the fourth aspect of the present invention is configured to execute the method according to the first aspect of the present invention and is suitable for execution. All explanations and definitions made in connection with the first, and / or second, and / or third aspects of the present invention also apply to the fourth aspect of the present invention.

[0035] The high-speed detection position adjustment means of the multi-beam particle microscope according to the present invention can be designed with one component or a plurality of components. Each means of the detection position adjustment means can serve to correct (main) displacement or image aberration of a specific class (for example, displacement, rotation, magnification, anamorphic imaging). By the detection position adjustment means, real-time correction of the position of the second individual particle beam when it enters the detection unit becomes possible, and as a result, real-time correction is possible even during the inspection operation, particularly while still generating one or more individual images. Therefore, it is convenient because high-frequency control of the high-speed detection position adjustment means is performed.

[0036] Similarly, the controller of the multi-beam particle microscope can be formed of one component or a plurality of components. The controller may include, for example, one or more control computers or other controllers, and may also be divided into a plurality of modules. At least one correction signal that functions to correct displacement may further represent a single signal or a superposition of a plurality of signals. What is important here is that the high-speed detection position adjustment means for position correction can be significantly controlled by one signal or a plurality of signals. For example, one signal or a set of signals is used to correct a specific image aberration or a specific class of displacement, and if necessary, one or more other correction signals or corresponding sets are used to correct other image aberrations or another class of displacement. The number of correction signals corresponds, for example, to the number of individually controllable particle optical components of the high-speed detection position adjustment means.

[0037] According to a preferred embodiment of the present invention, the detection unit comprises an image generation detection area in which all detection areas are arranged, and the detection unit comprises an adjustment detection area in which all additional detection channels are arranged. Such a division of the detection unit into two functionally different areas is always possible in principle, and in this case both the image generation detection area and the adjustment detection area can be formed as connected areas or as unconnected areas. In other words, both the image generation detection area and the adjustment detection area may comprise small areas. In particular, when each detection area of the image generation detection area comprises exactly one detection channel, the detection unit itself can comprise only similar or structurally identical detection channels, more precisely, both a normal detection channel for image recording and, furthermore, additional detection channels for adjustment purposes. In that case, the division of the detection unit, firstly into the image generation detection area and, secondly, into the adjustment detection area does not necessarily have to be carried out only on the basis of physical units or structural units, but is effected approximately by an assignment which is fixed, and thus does not change, during signal evaluation within the scope of the detection.

[0038] According to a preferred embodiment of the present invention, the image generation detection area is arc-connected and the adjustment detection area is likewise arc-connected. The term "arc-connected" is used in this context as defined in topology. In this case the definition of the area is, strictly speaking, simplified, and the area is defined as a two-dimensional space and thus

[0039]

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[0040] According to a preferred embodiment of the present invention, the adjustment detection region is arranged around the outside of the image generation detection region. The nested state of these two regions may be rotationally symmetric, or alternatively may be n-fold symmetric about the center of both regions, but this is not essential. As an alternative, for example, it is also possible for the image generation detection region to be arranged around the outside of the adjustment detection region. This is also symmetric and can be realized particularly by rotational symmetry or n-fold symmetry, but an irregular asymmetric arrangement is also possible. This is advantageous because when the adjustment detection region is symmetrically arranged around the outside of the image generation detection region, in this case, with regard to the evaluation of the signal, in terms of determining the positional deviation of the raster of the second individual particle beam, the evaluation of the signal can be carried out particularly easily. It is also relatively easy to distinguish the various classes / types of positional deviations. Furthermore, the influence of the overall positional deviation is particularly large in the edge region of the raster, and as a result, detection is particularly easy. However, of course, there are also other detection options, and ultimately, in this case, a skillful choice of the physical design of the detection unit also plays a role.

[0041] According to an embodiment of the present invention, the image generation detection region is not arc-connected, and the adjustment detection region is arc-connected but not simply connected. Here too, the terms "not arc-connected" and "simply connected" are used in the same way as in conventional topology. This embodiment of the present invention clearly explains that at least two spatially separated detection regions (domains) are incorporated into the adjustment detection region. The adjustment detection region may of course be not only two detection regions, but also all detection regions of the image generation detection region individually incorporated into the adjustment detection region. Also in this case, the resulting arrangement of the image generation detection region and the adjustment detection region as a whole may be a regular or irregular, symmetric or asymmetric design. A further example of a configuration according to a variant of this embodiment of the present invention is the cross-shaped arrangement of the adjustment detection region, whereby the image generation detection region, which is not arc-connected, is consequently divided into four small regions (four domains). Various other embodiments are possible.

[0042] According to a preferred embodiment of the present invention, each detection region is at least partially surrounded by an additional detection channel. This relatively comprehensive incorporation of the detection region into the additional detection channel for the purpose of adjustment detection enables, for example, not only the overall determination of the displacement of the entire raster of the second individual particle beam but also the individual determination of the displacement of each second individual particle beam.

[0043] According to a further preferred embodiment of the present invention, the additional detection channel is arranged such that a displacement, which is in the form of a deviation in the direction from the reference incidence position of at least one second individual particle beam, in particular the deviation in the direction from the respective reference incidence position of a plurality of second individual particle beams, can be detected. In this process, therefore, not only the absolute value of the displacement but also the direction of the displacement is determined. As an example, it is possible to infer the direction of the displacement based on the position of the additional detection channel that supplies the signal.

[0044] According to a preferred embodiment of the present invention, each detection region comprises exactly one detection channel. In this case, the structure of the entire detection unit is particularly simple.

[0045] According to a further preferred embodiment of the present invention, all detection channels are structurally identical. This therefore means that both the detection channels that define one or more detection regions and the additional detection channels for detecting displacements are structurally identical. Also in this case, the design of the entire detection unit is particularly simple.

[0046] Alternatively, it is of course possible for the detection channels to be different. As an example, it is possible to implement a detection channel fixedly assigned to a detection region according to a first structure and an additional detection channel for detecting misalignment according to a second structure, but the first structure and the second structure are not the same. In this process, it is possible to adapt the additional detection channel to a special role, specifically the identification of misalignment, with respect to the design of the additional detection channel. As an example, if the detection of the displacement of the raster of the second individual particle beam is important, this detection can be easily carried out in advance, for example using additional detection channels in the form of peripheries and bands. Those skilled in the art will find further advantageous embodiments without departing from the scope of protection of the present invention as a result.

[0047] According to a further preferred embodiment of the present invention, each detection channel comprises a signal incident surface, and the signal incident surfaces are arranged in a hexagonal shape as a whole. Such a hexagonal arrangement can be used to mosaic the surface, and in particular it is easy to create a multi-image field from individual image planes. In this process, 3n(n - 1)+1 individual particle beams are advantageously used for image generation and detection.

[0048] According to a preferred embodiment of the present invention, each detection region is fixedly assigned exactly one detection channel, and additional detection channels not assigned to any detection region are arranged in a hexagonal shape around the periphery outside the detection region. The hexagonal arrangement can thus be easily extended, and the existing concept of the detection unit only needs to be extended spatially without the need for detailed modification from a structural point of view.

[0049] According to a preferred embodiment of the present invention, the detection system comprises or consists of one or more particle detectors. Alternatively, the detection system comprises one or more particle detectors and, further, a plurality of optical detectors arranged downstream of the particle detectors. The present invention can thus be implemented with a high degree of freedom with respect to the detection system or the detection unit, and there is no fundamental constraint on the specific design of the detection system.

[0050] According to a preferred embodiment of the present invention, each detection channel comprises exactly one optical fiber, and different detection channels comprise different optical fibers.

[0051] According to an alternative embodiment of the present invention, the detection channels do not comprise optical fibers, and an array of photosensitive detectors, in particular an array comprising photomultiplier tubes, photodiodes, or avalanche photodiodes, is provided as the optical detection system. These are all examples of a highly flexible choice of detection system or detection unit.

[0052] According to a preferred embodiment of the present invention, the high-speed detection position adjustment means comprises at least one of an electrostatic lens, an electrostatic deflector, an electrostatic stigmer, a hollow coil, and a multi-deflector array. Other high-speed detection position adjustment means can also be used, and other high-speed detection position adjustment means are known to those skilled in the art. Again, reference is made to the above-mentioned documents that disclose the corresponding means.

[0053] The various embodiments and aspects of the present invention can be combined with each other completely or partially, as long as no technical contradiction results.

[0054] The present invention will be better understood by reference to the accompanying drawings.

Brief Description of the Drawings

[0055]

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Embodiments for Carrying Out the Invention

[0056] FIG. 1 is a schematic explanatory view of a particle beam system 1 in the form of a multi-beam particle microscope 1 that uses a plurality of particle beams. The particle beam system 1 generates a plurality of particle beams that are incident on a subject to generate interaction products, such as secondary electrons, that are emitted from the subject and then detected there. The particle beam system 1 is of the scanning electron microscope (SEM) type and uses a plurality of primary particle beams 3 that are incident on a plurality of locations 5 on the surface of the object 7 and generate a plurality of electron beam spots or spots that are spatially separated from each other there. The object 7 can be of any desired type, such as a semiconductor wafer or a biological sample, and can include an array of miniaturized elements or the like. The surface of the object 7 is disposed on a first plane 101 (object plane) of the objective lens 102 of the objective lens system 100.

[0057] An enlarged detail I1 of FIG. 1 shows a plan view of the object plane 101 having a regular rectangular field 103 of incident locations 5 formed on the first plane 101. In FIG. 1, the number of incident locations is 25, and these form a 5×5 field 103. The number 25, which is the number of incident locations, is a number selected to simplify the explanatory drawing. The number of beams, and thus the number of incident locations, can actually be selected to be much larger numbers, such as 20×30, 100×100, and the like.

[0058] In the illustrated embodiment, the field 103 of incident locations 5 is a substantially regular rectangular field in which the pitch P1 between adjacent incident locations is constant. Exemplary values of the pitch P1 are 1 micrometer, 10 micrometers, and 40 micrometers. However, it is also possible for the field 103 to have other symmetries, such as hexagonal symmetry.

[0059] The diameter of the beam spot formed on the first plane 101 can be made small. Exemplary values of this diameter are 1 nanometer, 5 nanometers, 10 nanometers, 100 nanometers, and 200 nanometers. The focusing of the particle beam 3 for forming the beam spot 5 is performed by the objective lens system 100.

[0060] The primary particles incident on the object generate interaction products, such as secondary electrons, backscattered electrons, or primary particles that have moved back for other reasons, and the interaction products are emitted from the surface of the object 7 or the first plane 101. The interaction products emitted from the surface of the object 7 are shaped by the objective lens 102 to form a secondary particle beam 9. The particle beam system 1 includes a particle beam path 11 that guides a plurality of secondary particle beams 9 to the detector system 200. The detector system 200 includes a particle optical unit that includes a projection lens 205 for directing the secondary particle beam 9 toward the particle multi-detector 209.

[0061] Detail I2 of FIG. 1 shows a plan view of a plane 211 in which an individual detection region 215 of the particle multi-detector 209, where the secondary particle beam 9 is incident at a location 213, is located. The incident location 213 is within a field 217 and has a regular pitch P2 with respect to each other. Exemplary values of the pitch P2 are 10 micrometers, 100 micrometers, and 200 micrometers.

[0062] The primary particle beam 3 is generated by a beam generation device 300 that includes at least one particle source 301 (e.g., an electron source), at least one collimation lens 303, a multi-aperture array 305, and a field lens 307. The particle source 301 generates a diffused particle beam 309, and the diffused particle beam is collimated or at least substantially collimated by the collimation lens 303 to form a beam 311 that irradiates the multi-aperture array 305.

[0063] Detail I3 of FIG. 1 shows a plan view of a multi-aperture array 305. The multi-aperture array 305 includes a multi-aperture plate 313, and the multi-aperture plate 313 has a plurality of openings or apertures 315 formed therein. The center points 317 of the apertures 315 are arranged in a field 319 that is imaged onto the field 103 formed by the beam spot 5 on the object plane 101. The pitch P3 between the center points 317 of the apertures 315 can have exemplary values of 5 micrometers, 100 micrometers, and 200 micrometers. The diameter D of the aperture 315 is shorter than the pitch P3 between the center points of the apertures. Exemplary values of the diameter D are 0.2×P3, 0.4×P3, and 0.8×P3.

[0064] The particles of the irradiation particle beam 311 pass through the apertures 315 to form the particle beam 3. The particles of the irradiation beam 311 incident on the plate 313 are absorbed by the plate 313 and do not contribute to the formation of the particle beam 3.

[0065] The multi-aperture array 305 focuses each of the particle beams 3 such that a beam focus 323 is formed in a plane 325 by an applied electrostatic field. The beam focus 323 can alternatively be a virtual focus. The diameter of the beam focus 323 can be, for example, 10 nanometers, 100 nanometers, and 1 micrometer.

[0066] The field lens 307 and the objective lens 102 realize a first imaging particle optical unit for imaging the plane 325 in which the beam focus 323 is formed onto the first plane 101, whereby the incident location 5 or the field 103 of the beam spot occurs on the first plane 101. When the surface of the object 7 is arranged in the first plane, a beam spot is correspondingly formed on the object plane.

[0067] The objective lens 102 and the projection lens array 205 realize a second imaging particle optical unit that images the first plane 101 onto the detection surface 211. The objective lens 102 is thus a lens that is part of both the first particle optical unit and the second particle optical unit, while the field lens 307 belongs only to the first particle optical unit and the projection lens 205 belongs only to the second particle optical unit.

[0068] The beam switch 400 is arranged in the beam path of the first particle optical unit between the multi-aperture array 305 and the objective lens system 100. The beam switch 400 is also part of the second optical unit in the beam path between the objective lens system 100 and the detector system 200.

[0069] Further information regarding such a multi-beam particle beam system and the components used therein, such as particle sources, multi-aperture plates, and lenses, can be obtained from International Application Publication No. WO 2005 / 024881, International Application Publication No. WO 2007 / 028595, International Application Publication No. WO 2007 / 028596, International Application Publication No. WO 2011 / 124352, and International Application Publication No. WO 2007 / 060017, as well as German Patent Application Publication No. DE 10 2013 016 113 and German Patent Application Publication No. DE 10 2013 014 976, the disclosures of which are hereby incorporated by reference in their entirety into this application.

[0070] The multi-particle beam system further comprises a computer system 10 configured to control the individual particle optical components of the multi-particle beam system and to evaluate and analyze the signals obtained using the multi-detector 209 or the detection unit 209. The method according to the invention can also be carried out using the computer system 10. The computer system 10 can be constructed from a plurality of individual computers or components.

[0071] FIG. 2a is a schematic explanatory diagram for exemplarily explaining the realization of the detector 209. The detector 209 includes, in this case, a scintillator plate 207 which is a particle detector, and interaction products, such as a secondary electron beam, are directed onto the scintillator plate by an electron optical unit. When this electron optical unit is integrated into the multi-beam particle microscope of FIG. 1, it includes the electron optical components of the particle optical unit that shapes the electron beam 9, that is, for example, it directs the electron beam 9 towards the detector 209, for example, towards a beam switch 400, etc., and focuses the electron beam 9 onto the surface of the scintillator plate 207, for example, onto a lens 205, etc., and includes an objective lens 102. The electron beam 9 is incident on the incident location 213 of the scintillator plate 207. Even when the electron beam 9 is focused onto the surface of the scintillator plate 207, a beam spot having a diameter that is not arbitrarily small is formed on the surface. The center point of the beam spot can be regarded as the incident locations 213 arranged at a pitch P2 (see FIG. 1) from each other.

[0072] The scintillator plate 207 contains a scintillator material that is excited by the incident electrons of the electron beam 9 to emit photons. Each of the incident locations 213 thus forms a photon source. FIG. 2a shows only the corresponding single beam path 221 radiated from the incident location 213 of the central electron beam among the five electron beams 9 shown. The beam path 221 passes through an optical unit 223 including a first lens 225, a mirror 227, a second lens 229, and a third lens 231 in the illustrated example, and then impinges on the light receiving surface 235 (signal incident surface 235) of the light detection system 237. The light receiving surface 235 is formed by the end face of an optical fiber 239, and at least a part of the photons are coupled to this end face and guided to a photodetector 241. The photodetector 241 can include, for example, a photomultiplier tube, an avalanche photodiode, a photodiode, or other types of suitable photodetectors. The optical unit 223 is configured to optically image the surface 208 of the scintillator plate 207 onto the region 243 where the light receiving surface 235 is disposed. By this optical imaging, an optical image of the incident location 213 is generated in the region 243. Separate light receiving surfaces 235 of the light detection system 237 for each of the incident locations 213 are provided in the region 243. Each of the additional light receiving surfaces 235 (signal incident surfaces 235) is formed by the end face of a light guiding portion 239 that guides the light coupled to the end face to the photodetector 241. By the optical imaging, a light receiving surface 235 is assigned to each of the incident locations 213, and the light entering each light receiving surface 235 is detected by a separate photodetector 241. The photodetector 241 outputs an electrical signal via a signal line 245. This electrical signal represents the intensity of the particle beam 9. As a result, the locations on the surface of the scintillator plate 207 imaged (image) on the light receiving surface of the photodetector 241 define different detection locations or detection regions. By the electron optical unit described above, interaction products radiated from two different individual field regions of an object, such as electrons, are also projected onto different detection regions 215 of the scintillator plate 207.In the exemplary embodiment described herein, the photo-detector 241 is arranged away from the light-receiving surface 235 on which the optical unit 223 images the scintillator plate 207, and the received light is guided to the photo-detector 241 via the optical fiber 239. However, it is also possible to directly arrange the photo-detector 241 at a location where the optical unit generates an image of the scintillator plate and the photosensitive surface of the photo-detector thus forms the light-receiving surface.

[0073] FIG. 2a only schematically illustrates some details of the detector 209 in this case. It should also be pointed out here that due to the movement of the primary particle beam scanning over the object or sample, many locations of the sample are irradiated or scanned. In this case, each primary particle beam 3 sweeps over the entire or a part of the individual field region of the object 7. In this case, an individual field region dedicated to the object is assigned to each primary particle beam 3. Next, interaction products, such as secondary electrons, are emitted from these individual field regions of the object 7. The interaction products are then projected onto the detection region 215 of the particle detector or onto the scintillator plate 207 such that the interaction products emitted from two different individual field regions are projected onto different detection regions 215 of the scintillator plate 207. When interaction products, such as secondary electrons, enter this detection region 215, an optical signal is emitted from each detection region 215 of the scintillator plate 207, and the optical signals emitted from each detection region 215 are supplied to the photo-detector 241 assigned to the respective detection regions. In other words, each primary particle beam 3 includes the detection region 215 of each primary particle beam 3 itself on the scintillator 207 and also the photo-detector 241 of each primary particle beam 3 itself, and these are integrated to form the detection channel 235 in the illustrated example. Therefore, in the illustrated example, each detection region 215 includes exactly one detection channel 235 fixedly assigned to the detection region 215.

[0074] FIG. 2b shows a variant of an alternative embodiment of the detection system 209. In this variant, the optical fiber 239 is not provided. Instead, the photons emitted from the scintillator plate 207 directly impinge on an array having a photosensitive detector 241, such as an array equipped with a photomultiplier tube, a photodiode, or an avalanche photodiode, after optical imaging.

[0075] Detection architectures other than those shown in FIGS. 2a and 2b are also suitable for performing the method according to the invention for operating the multi-beam particle microscope 1. For example, see the DED ("direct electron detection") method that does not require a photodetector and directly converts secondary electrons into an electric current signal. In this case, in particular, such a detection architecture can be used in which a plurality of detection channels 235 are fixedly assigned to each detection area. This multiple assignment of a detection channel to one detection area is particularly frequently performed with detectors composed of pixels or detectors divided into sectors.

[0076] According to the present invention, in order to supplement the detection area of the detection unit 209 used in the prior art, an additional detection channel 235' is added here. The existing detection unit 209 is advantageously extended by the additional detection channel 235' which is not assigned to any detection area 215 for this purpose. Various exemplary embodiments of the corresponding multi-beam particle microscope 1 or the associated detection unit 209 according to the present invention will be described below. The additional detection channel 235' functions as a measuring element for detecting the displacement of the second individual particle beam 9 when it enters the detection area 215. This is because it can be assumed that the second individual particle beam 9 is incident on the detection area 215 accurately enough if the additional detection channel 235' does not detect a signal or at least does not detect a significant signal (not reaching the threshold). Based on the determined displacement, for example, using the high-speed detection position adjustment means of one or more components in the secondary path of the multi-beam particle microscope 1, the displacement can be corrected in real time, especially while still recording a plurality of individual images.

[0077] Figure 3 schematically shows the controller 10 of the multi-beam particle microscope 1 for readjusting the second individual particle beam 9 in real time when it enters the detection unit 209. In the illustrated example, the controller 10 includes a controller 810 for the primary path and a controller 820 for the secondary path. The controller 820 for the secondary path further includes an adjustment control module 830 and an image generation control module 840. The controller 820 for the secondary path may further include other modules, but these are not shown in Figure 3.

[0078] The image generation control module 840 processes data obtained from signals from the detection region 215, which includes the fixedly assigned detection channel 235. Individual images that can be displayed using the image display unit 850 and composite multi-images formed by the individual images are generated by the image generation algorithm 842. The controller 10 or the controller 820 shown in FIG. 3 corresponds to a controller already known in the prior art in this regard.

[0079] According to the present invention, the adjustment control module 830 is realized within the controller 10 in this case. This adjustment control module 830 includes, as a measurement element, an additional detection channel 235' that is not assigned to any of the detection regions 215. These additional detection channels 235' instead function to detect the positional deviation of the second individual particle beam 9 when it enters the detection unit 209. The adjustment control module 830 determines the positional deviation from the reference incident position of the second individual particle beam 9 when it enters the detection unit 209 from the data obtained from the signals from each of the additional detection channels 235' that are not assigned to any of the detection regions 215, and is configured to generate at least one correction signal that functions to correct the positional deviation. The signals can be evaluated using the algorithm 832 to generate at least one correction signal. One or more detection position adjustment means 833, which are one actuator or a plurality of actuators, are controlled by one correction signal or a plurality of correction signals. This control is performed in real time, that is, while one individual image or a plurality of individual images are still being generated.

[0080] Figure 4 schematically shows an aspect of a method for operating the multi-beam particle microscope 1 in inspection mode according to the present invention. Figure 4 shows, parallel to the time axis t, first the image generation step S10 and then the misalignment identification and correction step S20. The steps or sequences of steps S10 and S20 are drawn within large arrows intended to indicate parallel processing of the steps being executed. According to the present invention, during the image generation process by the sequence of steps S10, for example, the following steps can be executed in parallel in time. In step S21, an additional detection channel 235’ is read. In the next step S22, it is determined whether there is a misalignment when the second individual particle beam 9 impinges on the detection unit 209. If not, step S21 is executed again. If not, and a misalignment is determined in S22, the method proceeds to S23 and it is determined whether a threshold is exceeded. If not, step S21 is executed again and the method continues to read the additional detection channel 235’. In contrast, if the threshold has been reached, in the next step S24 at least one correction signal is generated and used in step S25 to control one or more detection position adjustment means. Thereafter, step S21 is executed again and the additional detection channel 235’ is read again. Optionally, each time it is determined in step S23 that the threshold is exceeded, it is also possible to classify the identified misalignment. This classification can then be included in an algorithm for generating one correction signal or a plurality of correction signals in S24. The misalignments corrected in this way are, for example, displacements, rotations of the raster of the second individual particle beam 9, magnifications, or anamorphic imaging.

[0081] FIG. 5 schematically shows the detection of the focused secondary beam 9, which is known in the prior art in principle. The particle source 301 emits a diffused particle beam, which, in the example shown, passes through the condenser lens systems 303a, 303b and, in the example shown, is collimated and impinges on the multi-beam particle generator 305 and passes through the multi-beam particle generator 305. This generator can comprise, for example, a multi-aperture plate with downstream counter electrodes, but other embodiments and variations are possible. Of course, theoretically, it is also possible to use the multi-beam particle source 301 directly so that the first individual particle beam 3 does not have to be separately formed by the multi-beam particle generator 305.

[0082] In the illustrated example, in a further particle optical beam path, the first individual particle beam 3 passes through a field lens system having field lenses 307a, 307b, and 307c. Thereafter, the first individual particle beam 3 also passes through a beam switch 400 and in particular a magnetic objective lens 102, and then the first individual particle beam 3 is focused and incident on an object 7 on an object plane 101. The incidence of the first individual particle beam 3 causes the emergence of a second individual particle beam 9 from a sample or object 7. The second individual particle beam likewise passes through the objective lens 102 and the beam switch 400, and in the illustrated example also subsequently passes through a projection lens system 205a, 205b, 205c. In the projection lens system 205, a contrast stop 222 is arranged at the beam crossover of the second individual particle beam 9. The contrast stop 222 may be, for example, a circular stop or an annular stop. The contrast stop 222 may be a bright field stop or a dark field stop. The contrast stop has the role of filtering the second individual particle beam 9 according to the starting angle of the second individual particle beam 9 from the object plane 101. The second individual particle beam 9 proceeding from / to a specific starting angle range is cut out from the bundle of the second individual particle beam 9 at the beam crossover. This is schematically shown within the circle shown in the enlarged view of FIG. 5. The beam path in FIG. 5 is only schematically shown as already explained, and is therefore necessarily greatly simplified. In the normal inspection mode shown in FIG. 6, the second individual particle beam 9 is focused and incident on a detection plane 207 or a scintillator 207. A photodetector 237 is arranged downstream of the scintillator 207. In FIG. 5, the photodetector 237 is schematically shown in a hexagonal arrangement of detection channels 1 to 37, and the cross-section or signal incident surface of the detection channels is here constituted by a circle. In the case of imaging shown in FIG. 5, the object plane 101 is focused on the scintillator 207 or a plane E fIt is in the (image) state formed thereon. Further, in order to achieve the highest possible throughput during imaging, it is preferable that all individual particle beams 3, 9 are used for imaging. The detection unit 209 includes, in the illustrated example, a particle detection unit and an optical detection unit 237 downstream thereof. In this case, exactly one detection channel 235 is fixedly assigned to each detection region 215, as schematically shown in FIG. 5 based on the optical detection unit 237.

[0083] Here, FIG. 6 schematically shows the principle of misalignment correction according to the present invention. The detection unit 209 shown in FIG. 5 can be extended in principle for this purpose. However, for clarity, FIG. 6 does not show a plurality of second individual particle beams 9, and instead shows the state when the second individual particle beam 9 enters the detection unit 209 for only one such beam. The detection unit 209 exemplarily shown in FIG. 6 includes a total of seven detection channels 235, 235'. The detection channels 235, 235' are provided in the same detection plane. However, only the detection channel 235 labeled with the serial number 1 is fixedly assigned to the detection region 215, and thus only the signal generated by this channel 235 functions exclusively for image generation. The additional detection channels 235' are arranged in a ring-shaped hexagonal array around the detection region 215 or the detection channel 235 fixedly assigned to this detection region 215. FIG. 6a) shows the state when the second individual particle beam drawn exemplarily enters exactly the reference incidence position of the detection unit 209. In the schematically shown example, the beam spot 213 coincides with the detection region 215 and the detection channel 235 fixedly assigned to the detection region 215. The size relationship between one beam spot 213 and the other detection region 215 may also be different. As an example, the beam spot 213 may be considerably smaller than the detection region 215. At this point, again, refer to the fact that a plurality of detection channels 235 may be fixedly assigned to the detection region 215.

[0084] Figure 6b) shows the state when the second individual particle beam does not enter the reference position of the detection unit 209. Instead, there is a displacement of beam 9 with respect to the reference position. This is because in this case, the beam spot 213 is displaced, and the center M of the detection region 215 no longer coincides with the center of the beam spot 213. This mismatch or displacement is indicated by the arrows in Figure 6b). When there is a displacement, generally, the additional detection channel 235’ detects a signal. The displacement is related to only two of the six additional detection channels 235’ in this example. Since it is known which additional detection channel 235’ is detecting the signal, the direction of the displacement of the beam spot 213 from the reference position can be inferred. In the illustrated example, these are the additional detection channels 235’ numbered 2 and 3. The displacement is detected in the upper right direction in this case.

[0085] Figure 7 schematically shows the detection unit 209 extended by the additional detection channels 235’. The detection channels 235 and the additional detection channels 235’ are provided in the same detection plane. In this case, the raster of the second individual particle beam 9 is drawn, and the beam spots 213 of this raster are drawn darkly in Figure 7. These beam spots 213 enter the detection region 215 according to the optimal or reference position of the beam spot 213 in Figure 7a). Here too, each detection region 215 has a detection channel 235 fixedly assigned to it, but it would also be possible to fixedly assign multiple detection channels 235 to each detection region 215. In addition to the detection regions 215 to which the detection channels 235 are fixedly assigned, the detection unit 209 includes additional detection channels 235’ labeled with sequence numbers 62 to 91 in the illustrated example. In this case, the hexagonal arrangement of the detection regions 215 is extended by an additional outer shell in the illustrated example. That is, the additional detection channels 235’ are also arranged in a hexagonal pattern as a whole.

[0086] Here, FIG. 7b) shows the state when there is a positional deviation of the raster of the individual particle beam 9 when it is incident on the detection unit 209. In the illustrated example, the entire raster or all the beam spots 213 are displaced diagonally upward to the right. In the figure, three vectors V indicating the displacement are exemplarily entered. For this reason, the additional detection channels 235' with serial numbers 63 to 76 detect signals. Based on which of the additional detection channels 235' detects a signal and optionally also based on the size of the signal, it is possible to determine the size of the displacement V in the illustrated example. Therefore, in order for the second individual particle beam 9 to be incident again on the reference position within the detection region 215, position correction by the vector K is necessary.

[0087] FIG. 7 is further an example of an image generation detection region that is arc-connected and an adjustment detection region that is arc-connected. All the detection regions 215 are arranged within the image generation detection region, which is hexagonal in the illustrated example. All the additional detection channels 235' are in the adjustment detection region, which is arranged around the outside of the image generation detection region in the illustrated example. The adjustment detection region itself is, in this case, the outer shell of a hexagon.

[0088] FIG. 8 schematically shows the detection unit 209 extended by the additional detection channels 235'. The detection channels 235 and the additional detection channels 235' are provided within the same detection surface 211. Different from the detection unit 209 shown in FIG. 7, the detection unit 209 in FIG. 8 has a larger number of additional detection channels 235'. Different from FIG. 7, the detection region 215 is not arranged in an arc-connected region and thus not in a domain. In FIG. 8, instead, the image generation detection region is not arc-connected. Specifically, in the illustrated example, each detection region 215 is surrounded by six additional detection channels 235'. Similar to FIG. 7, the adjustment detection region in FIG. 8 is arc-connected but not simply connected. Therefore, it is impossible to shrink the closed path within the adjustment detection region to form a point. Specifically, this is not the case when this path is arranged around the detection region 215.

[0089] Figure 8a) shows the state when a plurality of individual particle beams 9 are incident on the reference positions of the respective individual particle beams 9 of the detection unit 209. In contrast, Figure 8b) shows the state when there is a misalignment. In the illustrated example, when there is a misalignment, various additional detection channels 235’ detect signals. For the 61 secondary beams 9 and the beam spots 213 associated with the secondary beams 9 shown, 2×61 additional detection channels 235’ detect signals that enable the estimation of misalignment. Using the configuration shown in Figure 8, it is possible to detect both the overall misalignment and, in principle, the individual misalignments of the individual particle beams 9. For this purpose, all the additional detection channels 235’ are located between two detection regions or between the respective detection channels 235 fixedly assigned to the detection regions. The corresponding distance D1 between the two detection regions 215 is also entered in Figure 8.

[0090] Figure 9 schematically shows the detection unit 209 extended by the additional detection channels 235’. The detection channels 235 and the additional detection channels 235’ are provided in the same detection plane. According to Figure 9, compared with Figure 8, even more additional detection channels 235’ are provided. The distance between the detection regions 215 is denoted as D2, and two additional detection channels 235’ are located between the two detection regions 215 or between the detection channels 235 to which exactly one is fixedly assigned. Using these additional detection channels 235’, finer misalignments can be determined, but the signal evaluation may become more complex.

[0091] Figure 10 schematically shows the displacement of the second individual particle beam 9 when it enters the detection unit 209. The detection unit 209 is roughly divided into an image generation detection area B1 and an adjustment detection area B2. In Figure 10a), the beam spot 213 that only enters the image generation detection area B1 is also shown. The image generation detection area B1 and the adjustment detection area B2 are provided in the same plane. The image generation detection area B1 and the adjustment detection area B2 may be equipped with detection channels and additional detection channels respectively in this case, but are not shown in such detail in Figure 10a).

[0092] In contrast, Figure 10b) shows a part of the image generation detection area B1 and shows a plurality of detection areas 215. In the illustrated example, these detection areas 215 are hexagonal and can have a pixelated form or a non-pixelated form. In either case, the detection area 215 is provided with a fixed number of detection channels 235 fixedly assigned to the detection area 215. The beam spot 213 enters the detection area 215 in this case. The beam spot 213 collides with the center of the detection area 215 in Example b) and collides with a displacement to the right in the horizontal direction instead of the center in Example c). However, in both cases, it is a fact that the beam spot 213 completely enters each detection area 215, and thus a slight displacement does not cause signal loss. In such a case, there is no need to correct the displacement. Correction is only required when the beam spot 213 enters a plurality of detection areas 215, and in that case, a signal large enough to exceed the threshold will be detected in the adjustment detection area B2 as appropriate.

[0093] Figure 11 schematically shows various regions or domains of the detection unit 209, and various positions / position displacements of the second individual particle beam 9 when it is incident on the detection unit 209. The image generation detection region B1 and the adjustment detection region B2 are schematically shown again in Figure 11. The image generation detection region B1 and the adjustment detection region B2 are provided in the same plane. In Figure 11, the explanatory diagram of the specific division of the region into the detection region and the (additional) detection channels is omitted. The division can be of extremely various designs, as already explained in various examples. Figure 11a) here exemplarily shows the displacement of the raster of the individual particle beam, and the raster is represented by the beam spot 213. The hexagonal outer shell type adjustment detection region B2 shows the upper and right diagonal signals, and no signal is detected in the remaining four small regions. The regions where the signal is detected are shown hatched in Figure 11. The position displacement can be corrected in real time while the image is still being recorded and can be inferred from the pattern of this obtained signal.

[0094] In contrast, Figure 11b) shows the rotation of the raster. Signals are detected at six locations in the adjustment detection region B2 (this is also shown in the hatched region of the region B2). The corresponding rotation can be corrected in real time by controlling the high-speed detection position adjustment means.

[0095] Figure 11c) shows an anamorphic imaging or anamorphic position displacement. The raster of the individual particle beam is expanded in the y direction, but this does not apply in the x direction. The signal is thus detected in two small regions (the upper and lower edges of the hexagonal outer shell) of the adjustment detection region B2. This can be used to generate a correction signal, and this correction signal can be used to control the high-speed detection position adjustment means in order to correct in real time the position of the second individual particle beam 9 when it is incident on the detection unit 209.

[0096] Figure 11d) shows the expansion of the raster of the second individual particle beam in two directions (x - direction and y - direction) when it is incident on the detection unit 209. Thus, signals are detected at all six sides of the adjusted detection region D2 over the whole. A suitable algorithm can use this to generate a control signal or a correction signal, or a set of such corresponding signals, and the misalignment can be corrected in real - time by controlling the high - speed detection position adjustment means.

[0097] Figure 12 schematically shows a detection unit 209 comprising a detection region 215 to which a plurality of detection channels 235 are fixedly assigned, and additional detection channels 235' for detecting misalignment when the second individual particle beam 9 is incident on the detection unit 209. The fixedly assigned detection channels 235 and the additional detection channels 235' are provided in the same plane. Figure 12 is an example of a detection unit 209 composed of pixels or a detection unit 209 divided into sectors. In the illustrated example, all 12 detection channels 235 are fixedly assigned to the detection region 215. When properly position - adjusted, the beam spots 213 are each completely incident within the detection region 215 of the detection unit 209. In this case, signals are not necessarily detected at each of the detection channels 235 fixedly assigned to the detection region 215. In addition to the detection channels 235 fixedly assigned to the detection region 215, mutually offset row and column portions of the additional detection channels 235' are provided. In the illustrated example, the image - generating detection region is not arc - connected. Instead, individual detection regions 215 are incorporated like islands within the adjusted detection region by the additional detection channels 235'. The misalignment, and further the type of misalignment, can be estimated for the ensemble of the second individual particle beams 9 and / or for each individual second individual particle beam 9 according to the additional detection channels 235' at which signals are detected.

[0098] FIG. 13 shows a schematic division of the detection unit 209 into various regions for determining and correcting the misalignment when the second individual particle beam 9 enters the detection unit 209. FIG. 13a) shows in this case a circle and two surrounding ring structures as an example. The imaging detection region B1 is located between the outer annular part and the central ring, and when the second individual particle beam 9 enters the detection unit 209 optimally, all beam spots 213 enter the imaging detection region. The adjustment detection region B2 is divided into sub-regions B2.1 and B2.2 instead of an arc-shaped connection. The sub-regions B2.1 and B2.2 can optionally be equipped with one or more additional detection channels 235′. FIG. 13b) shows a schematic rectangular imaging detection region B1, whereby nine beam spots 213 are depicted in the imaging detection region B1 as an example. Each of these beam spots can be assigned a detection area 215, which is not shown in detail in FIG. 13. The adjustment detection area B2 is in the form of a square shell in the illustrated example and is located at the outer periphery of the image-generating detection area B1. This adjustment detection area may comprise one or more additional detection channels 235', which are not shown in detail in FIG. 13b). Very basically, each time a signal is detected in the adjustment detection area B2 or B2.1 and / or B2.2, a deviation of the second individual particle beam entering the detection unit 209 from a desired reference position can be detected. The image-generating detection area B1 and the adjustment detection area B2 or B2.1 and / or B2.2 are provided in the same plane.

[0099] FIG. 14 schematically shows another detection unit 209 that includes a detection area 215 to which a plurality of detection channels 235 are fixedly assigned, and an additional detection channel 235' for detecting a misalignment when the second individual particle beam 9 is incident on the detection unit 209. The fixedly assigned detection channels 235 and the additional detection channels are provided in the same detection plane. The exemplary embodiment shown in FIG. 14 is an example of a slightly more complex assembly or a fixed assignment of the detection channels 235 to the detection area 215. In this example, the additional detection channels 235' for detecting misalignment can also be formed relatively far apart and not in an arcuate connection.

[0100] In summary, therefore, a method for operating the multi-beam particle microscope 1 in inspection mode operation is disclosed, and the related multi-beam particle microscope 1 is likewise disclosed. The detection unit 209 includes an image generation detection area with fixedly assigned detection channels 235 and an adjustment detection area with additional detection channels 235'. The fixedly assigned detection channels 235 and the additional detection channels 235' are provided in the same detection surface 211. Based on the signals obtained by the additional detection channels 235', it is possible to accurately correct in real time the incident position of the secondary beam 9 on the detection unit 209 regardless of the specific structure of the detection unit 209.

Description of Reference Numerals

[0101] 1 Multi-beam particle microscope 3 Primary particle beam (individual particle beam) 5 Beam spot, incident location 7 Object, sample 9 Secondary particle beam 10 Computer system, controller 11 Secondary particle beam path 13 Primary particle beam path 101 Object plane 102 Objective lens 103 Field 200 Detector System 205 Projection Lens 207 Scintillator Plate 208 Deflector for Adjustment 209 Detection System, Particle Multi-Detector, Detection Unit 211 Detection Surface 213 Incident Location 215 Detection Region 217 Field 221 Light Beam Path 222 Contrast Diaphragm 223 Optical Optical Unit 225 Lens 227 Mirror 229 Lens 231 Lens 235 Detection Channel, Light-Receiving Surface, Signal Incident Surface (Image Generation) 235’ Additional Detection Channel (Position Correction) 237 Optical Detection System 239 Optical Fiber, Optical Induction Section 241 Optical Detector 243 Region for Optical Imaging of Scintillator Surface 245 Wiring 300 Beam Generation Device 301 Particle Source 303 Collimation Lens System 305 Multi-Aperture Array 306 Micro-Optical System 307 Field Lens System 309 Diffused Particle Beam 310 Multi-Beam Generator 311 Irradiating Particle Beam 313 Multi-Aperture Plate 315 Aperture of Multi-Aperture Plate 317 Center Point of Aperture 319 Field 323 Beam Focus 325 Intermediate Image Plane 400 Beam Switch 810 Controller for Primary Path 820 Secondary path controller 830 Adjustment control module 832 Real-time algorithm for position deviation 833 Detector position adjustment means 840 Image generation control module 842 Image generation algorithm 850 Image display unit E f Focal plane M Center of the raster of the second individual particle beam V Displacement, position deviation vector K Correction vector D1 Distance between detection regions / detection channels D2 Distance between detection regions / detection channels B1 Image generation detection region B2 Adjustment detection region

Claims

1. Irradiating a target with a plurality of charged first individual particle beams, each first individual particle beam irradiating a separate individual field region of the target in a scanning manner; Collecting a second individual particle beam emitted from or radiated from the target by the first individual particle beam; Focusing and projecting the second individual particle beam onto a detection region of a detection unit such that the second individual particle beam emitted from or radiated from two different individual field regions is projected onto different detection regions, wherein one detection channel or a predetermined plurality of detection channels are fixedly assigned to each detection region; Reading the fixedly assigned detection channels and generating an individual image of each individual field region based on data obtained from signals from each of the detection regions, each of the detection regions comprising one fixedly assigned detection channel or a plurality of fixedly assigned detection channels; Reading additional detection channels of the same detection unit that are not projected in a form directed at a target and are not assigned to any detection region, and determining a displacement of the second individual particle beam from a reference incident position when the second individual particle beam enters the detection unit based on data obtained from signals from the additional detection channels; Correcting the displacement of the second individual particle beam in real time when the second individual particle beam enters the detection unit; A method of operating a multi-beam particle microscope in an inspection mode of operation, comprising:

2. The correction of the displacement of the second individual particle beam includes real-time adjustment of the particle optical beam path of the second individual particle beam; A method of operating a multi-beam particle microscope in the inspection mode of operation according to Claim 1;

3. The displacement is corrected during the generation of the individual image, in particular corrected a plurality of times; A method of operating a multi-beam particle microscope according to Claim 1 or 2;

4. Classifying the determined displacement and correcting the displacement based on the classification; A method for operating a multi-beam particle microscope according to any one of claims 1 to 3, further comprising

5. wherein the correction of the misalignment includes correction of an overall displacement of the second individual particle beam when it is incident on the detection unit, A method for operating a multi-beam particle microscope according to any one of claims 1 to 4.

6. wherein the correction of the misalignment includes correction of an overall rotation of the second individual particle beam when it is incident on the detection unit, A method for operating a multi-beam particle microscope according to any one of claims 1 to 5.

7. wherein the correction of the misalignment includes correction of an expansion of the second individual particle beam in one or two directions when it is incident on the detection unit, A method for operating a multi-beam particle microscope according to any one of claims 1 to 6.

8. The step of correcting in real time an individual misalignment of at least one second individual particle beam when it is incident on the detection unit A method for operating a multi-beam particle microscope according to any one of claims 1 to 7, further comprising

9. wherein the misalignment is corrected only when it exceeds a threshold value, A method for operating a multi-beam particle microscope according to any one of claims 1 to 8.

10. A computer program product having program code for executing the method according to any one of claims 1 to 9.

11. A multi-beam particle microscope configured to execute the method according to any one of claims 1 to 10.

12. A multi-beam particle source configured to generate a first field of a plurality of charged first individual particle beams, A first particle optical unit comprising a first particle optical beam path, configured to image the generated first individual particle beam onto an object surface such that the first individual particle beam collides with the object at an incident location forming a second field, A detection unit comprising a plurality of detection regions forming a third field, wherein one detection channel or a plurality of detection channels are fixedly assigned to each of the detection regions, and the same detection unit further comprises an additional detection channel not assigned to any of the detection regions. A second particle optical unit having a second particle optical beam path and configured to image a second individual particle beam emitted from the incidence location of the second field onto the third field of the detection region of the detection system in a substantially focused form (image). The second particle optical unit includes high-speed detection position adjustment means configured to correct the position of the second individual particle beam in real time when it enters the detection unit. A second particle optical unit An objective lens through which both the first individual particle beam and the second individual particle beam pass A beam switch disposed in the first particle optical beam path between the multi-beam particle source and the objective lens and also disposed in the second particle optical beam path between the objective lens and the detection unit A controller The controller is configured to control the second particle optical unit. The controller is configured to generate individual images from data obtained from signals from the detection region including the one detection channel fixedly assigned to each or the plurality of detection channels fixedly assigned to each. The controller is configured to determine a deviation of the second individual particle beam from a reference incidence position when entering the detection unit from data obtained from signals from the additional detection channels not assigned to any of the detection regions and to generate at least one correction signal that functions to correct the deviation. The controller is configured to control the high-speed detection position adjustment means in real time using the at least one correction signal. A controller A multi-beam particle microscope comprising.

13. The detection unit includes an image generation detection region in which all detection regions are arranged. The detection unit includes an adjustment detection region in which all additional detection channels are arranged. The multi-beam particle microscope according to claim 12.

14. The image generation detection region is arc-connected. The adjustment detection region is arc-connected. The multi-beam particle microscope according to claim 13.

15. Is the adjustment detection region arranged around the outside of the image generation detection region? or the image generation detection region is disposed around the outside of the adjustment detection region The multi-beam particle microscope according to claim 14

16. the image generation detection region is not arc-connected the adjustment detection region is arc-connected but not singly connected The multi-beam particle microscope according to claim 13

17. each detection region is at least partially surrounded by an additional detection channel The multi-beam particle microscope according to claim 16

18. the additional detection channel is arranged such that a displacement, particularly in the form of a displacement of a plurality of the second individual particle beams from their respective reference incidence positions, of at least one second individual particle beam from its reference incidence position is detectable The multi-beam particle microscope according to any one of claims 12 to 17

19. each detection region comprises exactly one detection channel The multi-beam particle microscope according to any one of claims 12 to 18

20. all detection channels are structurally identical The multi-beam particle microscope according to any one of claims 12 to 19

21. the detection channel fixedly assigned to the detection region has a structure different from that of the additional detection channel not assigned to any of the detection regions The multi-beam particle microscope according to any one of claims 12 to 19

22. each detection channel comprises a signal incidence surface the signal incidence surface is arranged in a hexagonal shape as a whole The multi-beam particle microscope according to any one of claims 12 to 21

23. each detection region has exactly one detection channel fixedly assigned thereto the additional detection channel not assigned to any of the detection regions is arranged in a hexagonal shape around the outside of the detection regions The multi-beam particle microscope according to claim 22

24. the detection system comprises or consists of one or more particle detectors The multi-beam particle microscope according to any one of claims 12 to 23

25. the detection system comprises one or more particle detectors and further a plurality of optical detectors disposed downstream of the particle detectors The multi-beam particle microscope according to any one of claims 12 to 23

26. Each detection channel comprises exactly one optical fiber, and different detection channels comprise different optical fibers. The multi-beam particle microscope according to claim 25. **Claim 27** The detection channel does not comprise an optical fiber, and an array of photosensitive detectors, particularly an array comprising a photomultiplier tube, a photodiode, or an avalanche photodiode, is provided as the light detection system. The multi-beam particle microscope according to claim 25. **Claim 28** The high-speed detection position adjustment means comprises at least one means among an electrostatic lens, an electrostatic deflector, an electrostatic stigmer, a hollow coil, and a multi-deflector array. The multi-beam particle microscope according to any one of claims 12 to 27.

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