Method of 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 of operating a multi-beam particle microscope, an associated computer program product, and a multi-beam particle microscope. [Background technology]

[0002] As smaller and more complex microstructures, such as semiconductor components, continue to be developed, planar manufacturing techniques and inspection systems for producing and inspecting small-dimension microstructures need to be further developed and optimized. For example, the development and production of semiconductor components requires design monitoring of test wafers, and planar manufacturing techniques require process optimization for reliable production at high throughput. More recently, there has been a demand for analysis of semiconductor wafers in reverse engineering and for individual, customer-specific configuration of semiconductor components. Therefore, there is a need for inspection tools that can be used at high throughput to examine the microstructures on wafers with high accuracy.

[0003] Typical silicon wafers used in the production of semiconductor components have a diameter of up to 300 mm. Each wafer can be up to 800 mm 2The semiconductor device comprises a plurality of semiconductor structures produced in layers on the surface of a wafer by planar integration techniques. The semiconductor wafer typically has a flat surface due to the production process. The structure sizes of the integrated semiconductor structures range from a few microns to 5 nm in critical dimension (CD), with even smaller structure sizes expected in the near future. Structure sizes or critical dimensions (CD) are expected to be less than 3 nm, e.g., 2 nm, or even less than 1 nm in the future. With these small structure sizes, defects of the critical dimension size must be quickly identified over a very large area. In some applications, the specification requirements for the measurement accuracy achieved by the inspection equipment are even higher, e.g., two times or an order of magnitude higher. For example, the width of semiconductor features must be measured with an accuracy of less than 1 nm, e.g., 0.3 nm or better, and the relative positions of semiconductor structures must be determined with an overlay accuracy of less than 1 nm, e.g., 0.3 nm or better.

[0004] Multi-beam scanning electron microscopes (MSEMs) are a relatively new development in the field of charged particle systems (charged particle microscopes, CPMs). Examples of multi-beam scanning electron microscopes are disclosed in U.S. Pat. No. 7,244,949 and U.S. Patent Application Publication No. 2019 / 0355544. In a multi-beam electron microscope, or MSEM, a sample is simultaneously illuminated with multiple individual electron beams arranged in a field or raster. For example, 4 to 10,000 individual electron beams can be provided as primary radiation, with each individual electron beam separated from its neighbor by a pitch of 1 to 200 micrometers. For example, an MSEM has approximately 100 separated individual electron beams ("beamlets") arranged in a hexagonal raster, with the individual electron beams separated by a pitch of approximately 10 micrometers. The multiple 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 secured to a wafer holder mounted on a movable stage. During irradiation of the wafer surface with a charged primary particle beam, interaction products, such as secondary electrons or backscattered electrons, are emitted from the wafer surface. The starting points of the interaction products all correspond to locations on the sample where multiple primary particle beams are focused. The amount and energy of the interaction products vary depending on the material composition and surface topography of the wafer surface. The interaction products form multiple secondary particle beams (secondary beams), which are collected by a common objective lens and incident on a detector located at the detection plane as a result of the projection imaging system of the multi-beam inspection system. The detector has multiple detection areas, each with multiple detection pixels, and captures the intensity distribution of each of the secondary particle beams. This process results in an image plane of, for example, 100 μm × 100 μm.

[0005] Prior art multi-beam electron microscopes include a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adapt the focal positions and astigmatism correction of the multiple charged individual particle beams. Prior art charged particle multi-beam systems further include at least one crossover plane for the primary or secondary charged individual particle beams. Prior art systems also include a detection system that facilitates adjustment. Prior art multi-beam particle microscopes include at least one beam deflector ("deflection scanner") for simultaneously scanning an area of ​​the sample surface with multiple primary individual particle beams to obtain an image plane of the sample surface. Further details regarding multi-beam electron microscopes and methods for operating them are described in German Patent Application No. 102020206739.2, filed May 28, 2020, and related patent family documents, the disclosures of which are incorporated herein by reference in their entirety.

[0006] Accurate alignment of the secondary individual particle beam when it strikes the detector is crucial for achieving high resolution within the scope of sample inspection, especially semiconductor sample inspection. Alignment of the raster of the second individual particle beam is typically performed by referencing it with respect to a beam located at the center of the raster. The raster is aligned or adjusted to the best extent possible with respect to the detection area assigned to the raster. This alignment is usually performed before recording each image.

[0007] However, the alignment of the second individual particle beam may change with respect to the detection area of ​​the detection unit while the image is being recorded, for example as a result of drift or due to the sample properties themselves. For example, the effect of sample charging may cause a slight distortion of the second individual beam emanating from or originating from the sample, which may cause it to not be incident on the desired reference position on the detection unit. In such cases, it may be desirable to perform corrections or readjustments in real time.

[0008] In this context, German Patent Application No. 10 2015 202 172 proposes the use of pixelated detection units, each of which is provided for the detection of a second individual particle beam, and whose detection areas allocated to the second individual particle beam each comprise a plurality of detection fields. If the point of incidence of the second individual particle beam on the detector changes during the examination, the allocation of detection fields to the detection areas is corrected. On the one hand, this procedure limits the type of detection unit used to pixelated detection units; on the other hand, correcting such an allocation is algorithmically very complex and relatively slow.

[0009] U.S. Pat. No. 10,896,800 circumvents the limitation on the type of pixelated detector used for image generation by using, in addition to the non-pixelated detector, an additional pixelated detector in the form of a high-speed CCD camera for image generation (combination of a particle detector with a downstream optical optical unit equipped with an optical fiber for each detection area). For this purpose, a beam splitter is provided in the optical detection path, and part of the optical signal is output to the CCD camera. The position of the light incident on the CCD camera can be assigned to the position of the light when it enters the signal entrance face of the optical fiber. This can be used to indirectly detect the positional deviation of the second individual beam when it enters the detector used for image generation. This, in principle, allows for fast position correction in the secondary path of a multi-beam particle microscope. Rapidly controllable electrostatic lenses, electrostatic deflectors, and / or electrostatic stigmators are used to correct the particle light beam path in the secondary path itself. According to U.S. Pat. No. 10,896,800, the incidence of light on the additional pixelated detector for positional deviation detection is achieved by a beam splitter that attenuates the original optical signal. Furthermore, with regard to the detection unit, one is limited to a combination of particle detection and light detection as a result of the beam distribution required in the light-optical system. Furthermore, in the case of a CCD camera, which involves the evaluation of signals from all pixels, the signal evaluation is algorithmically relatively complex.

[0010] Furthermore, U.S. Patent Application Publication No. 2021 / 0005423 discloses a combination of a particle detector and a downstream optical optical unit equipped with an optical fiber for each detection region. A beam splitter is provided in the optical detection path, and a portion of the optical signal is output to a CCD camera, which can be used to identify changes in the location of interaction products in the detection plane due to sample charging. U.S. Patent Application Publication No. 2021 / 0005423 further discloses an aperture located at the crossover position of the secondary particle beam within the detection system. The circular opening of the aperture is radially surrounded by several electrodes that can function as current detectors. By detecting asymmetry in the current or charge induced in the electrodes, eccentricity of the charged particle beam passing through the aperture of the aperture can be detected and corrected if necessary. Summary of the Invention [Problem to be solved by the invention]

[0011] The object of the invention is therefore to propose a method for operating a multi-beam particle microscope in inspection mode, and an associated multi-beam particle microscope, which allows a simple, versatile and fast position correction of the secondary beams when they enter the detection unit.

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

[0013] This patent application claims priority from German Patent Application No. 102022114923.4, filed June 14, 2022, the disclosure of which is incorporated by reference in its entirety into this patent application. [Means for solving the problem]

[0014] According to a first aspect of the invention, the invention relates to a method of operating a multi-beam particle microscope in an inspection mode, the method comprising: irradiating an object with a plurality of charged first individual particle beams, each first individual particle beam irradiating a separate individual field region of the object in a scanning manner; collecting a second individual particle beam that is emanated from or emitted from the object by the first individual particle beam; focusing and projecting the second individual particle beams onto detection regions of the detection unit such that the second individual particle beams emerging from two different individual field regions are projected onto different detection regions, wherein one detection channel or a predetermined number of detection channels are fixedly assigned to each detection region; reading the fixedly assigned detection channels and generating a separate image of each of the separate field regions based on data obtained by signals from one fixedly assigned detection channel of each of the detection regions or from each of the detection regions comprising a plurality of fixedly assigned detection channels of each of the detection regions; reading an additional detection channel of the same detection unit, in which the second individual particle beam is not projected in a manner directed toward the target and is not assigned to any detection region, and determining a positional deviation of the second individual particle beam from a reference incident position when it is incident on the detection unit based on data obtained by signals from the additional detection channel; correcting in real time a positional deviation of the second individual particle beam when it is incident on the detection unit; Includes:

[0015] The first charged individual particle beams may be, for example, electrons, positrons, muons, ions, or other charged particles. The individual field areas of the object assigned to each first individual particle beam are, for example, raster-scanned row by row or column by column. Preferably, the individual field areas are adjacent to one another or cover the object or parts of the object in a mosaic-like fashion. The individual field areas may be substantially separate from one another but overlap each other in peripheral regions. In this way, it is possible to obtain as complete and continuous an image of the object as possible. The individual field areas are preferably embodied as rectangles or squares, since this is the easiest way to realize the scanning process with particle radiation. The individual field areas are preferably arranged as rectangles one above the other in different rows, resulting in a hexagonal structure overall. In the case of a hexagon, the number of particle beams is advantageously 3n(n-1)+1, where n is any natural number. Other arrangements of the individual field areas, such as square or rectangular rasters, are also possible.

[0016] The second individual particle beam can be backscattered electrons or else secondary electrons. In this case, for analytical purposes, it is preferable to use low-energy secondary electrons for image generation. However, it is also possible to use mirror ions / mirror electrons, i.e., a first individual particle beam that is reversed immediately upstream of or at the object, as the second individual particle beam.

[0017] According to the present invention, the second individual particle beam is focused and projected onto a detection region of the detection unit, so that the second individual particle beams emerging or emanating from two different individual field regions are projected onto the different detection regions. In this case, one or a predetermined number of detection channels is fixedly assigned to each detection region. The fact that a detection region can therefore correspond to one detection channel or can comprise multiple detection channels, and thus smaller units, essentially makes the method applicable regardless of the type of detection unit. The detection region for each second individual particle beam does not need to be pixelated or divided into smaller parts. Instead, what is important is the fixed assignment of one or a predetermined number of detection channels to each detection region. Therefore, according to the present invention, there is no need to change this assignment, as explained above with reference to the prior art (DE 10 2015 202 172 A1). The present invention therefore simplifies the method overall, making it more universally applicable.

[0018] According to the present invention, the detection unit can, in principle, be further modified or expanded. The detection unit comprises additional detection channels in addition to the detection areas used to generate the individual images. The second individual particle beams are not projected onto these additional detection channels in a manner directed toward the target, but rather the additional detection channels are not assigned to any detection areas. Therefore, in principle, no signal is detected in these additional detection channels when the second individual particle beams are incident on the detection unit at their respective reference incident positions. The additional detection channels detect a signal only when at least one of the second individual particle beams, preferably several of the second individual particle beams, deviates from the respective reference incident positions of the second individual particle beam / s. The additional detection channels consequently serve to determine the positional deviation. Such a positional deviation can thus be recognized and, optionally, characterized in more detail. This allows for the positional deviation of the second individual particle beams when they are incident on the detection unit to be corrected.

[0019] The additional detection channels may correspond in structure to the detection channels also used for generating the normal image. However, it is also possible for the additional detection channels to be designed differently. Specific exemplary embodiments will be discussed in more detail subsequently below.

[0020] The fixedly assigned detection channel and the additional detection channel belong to the same detection unit. The fixedly assigned detection channel and the additional detection channel are therefore arranged in the same detection plane. In other words, according to the present invention, the image detection plane and the position shift detection plane are identical. This identity improves the accuracy with which a position shift 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. Means usable for this purpose in the secondary path of a multi-beam particle microscope are already known in principle in the prior art. It should be noted that the correction of the misalignment can be performed, in particular multiple times, while still generating individual images within the scope of the real-time correction. Therefore, multiple readjustments or corrections can be performed for each individual image, if necessary. As a result, an overall better resolution can be achieved within the scope of sample inspection.

[0022] According to a preferred embodiment of the present invention, the correction of the misalignment of the second individual particle beam comprises a real-time adjustment of the particle light beam path of the second individual particle beam. Alternatively, the misalignment could be corrected by a modification of the position of the detection unit itself. However, such a correction would not be performed in real-time.

[0023] According to a preferred embodiment of the present invention, the method comprises: Classifying the determined misalignment and correcting the misalignment based on the classification. The misregistration often relates equally or globally to the raster of the second individual particle beam. A class or type of misregistration can be, for example, a global displacement, a global rotation, a global magnification of the raster, or a global anamorphic imaging of the second individual particle beam when it enters the detection unit. In this process, it may be possible to determine just one class or type of global misregistration, although it is also possible to recognize several of the aforementioned types simultaneously (as a superposition).

[0024] According to a preferred embodiment of the present invention, the correction of the misalignment comprises correction of the overall displacement of the second individual particle beam when it enters the detection unit. By way of example, a high-speed deflection system can be used in the second particle light beam path / secondary path of the multi-beam particle microscope for correction purposes. Only this type of beam correction in the secondary path has been previously described in U.S. Pat. No. 10,896,800, the disclosure of which is incorporated by reference in its entirety into this patent application.

[0025] According to a further preferred embodiment of the invention, the correction of the misalignment comprises a correction of the global rotation of the second individual particle beam when it enters the detection unit. For example, a rotating lens can be used in the second particle light beam path / secondary path of the multi-beam particle microscope for this global rotation of the raster of the second individual particle beam. The rotating lens can be rapidly controlled. It is also possible to use a rotation correction means in the second path, as described, for example, in several embodiment variants of DE 10 20 20 12 5 5 34 A1. The entire disclosure content of DE 10 20 20 12 5 5 34 A1 is incorporated by reference into the present patent application.

[0026] According to a further preferred embodiment of the present invention, the correction of the misalignment 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 perpendicular to each other, but this is not necessary. If the expansion is the same size in both directions, this relates to the overall expansion as a whole, as a misalignment. For correction, it is also possible to use a system with fast electrostatic lenses, as described, for example, in the above-mentioned U.S. Pat. No. 10,896,800.

[0027] The expansion of the raster in one direction corresponds only to anamorphic imaging, which can be corrected, for example, by a high-speed electrostatic stigmator or an astigmatism correction system in the secondary path, as also exemplarily described previously in U.S. Pat. No. 10,896,800.

[0028] According to a further preferred embodiment of the method, the method comprises: correcting in real time an individual misalignment of the at least one second individual particle beam when it is incident on the detection unit; This type of correction is an even finer correction that is not performed globally, i.e. not equally for all second individual particle beams. However, the detection unit must meet further requirements, such as the fact that a deviation of a particular second individual particle beam from its reference position can only be detected if the associated detection area is arranged adjacent to or relatively very close to an additional detection channel that detects the deviation. An example that allows this detection is presented in more detail below. By way of example, a multi-deflector array can be used for the individual position deviation correction, which multi-deflector array is arranged, for example, in a secondary path in the direction of the particle light beam path after the so-called anti-scan.

[0029] According to a further preferred embodiment of the present invention, misalignment is corrected only if it exceeds a threshold value. This essentially prevents unnecessary corrections. Even if the second individual particle beams are focused and projected onto the respective detection areas, it is of course true that the focal points are not mathematical points but instead have a spread, albeit a small spread. Strictly speaking, the intensity of each second individual particle beam has an intensity distribution when it is incident on the detection surface. Therefore, if there is a misalignment, the signal may only be detected gradually or gradually by the additional detection channel. For example, the majority of the detection of the second individual particle beams may still be performed correctly by the assigned detection area. If this is the case, a detected but insignificant misalignment may not need to be corrected. It is advantageous to actually correct the misalignment only if it exceeds a threshold value, which may be predetermined.

[0030] The above-described embodiment variants according to the first aspect of the present invention can be combined with each other, either fully or in part, as long as no technical contradictions result.

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

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

[0033] According to a fourth aspect of the present invention, the present invention relates to a 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 beam onto an object plane such that the first individual particle beam impinges on the object at an incidence location forming a second field; a detection unit comprising a plurality of detection areas forming a third field, each of which is fixedly assigned one or more detection channels, the same detection unit further comprising an additional detection channel that is not assigned to any of the detection areas; a second particle-optical unit comprising a second particle-optical beam path and configured to image a second individual particle beam emanating from an incidence location in the second field onto a third field of a detection region of the detection system in a substantially focused manner, the second particle-optical unit comprising high-speed detector position adjustment means configured to correct in real time the position of the second individual particle beam when it is incident on the detection unit; a second particle-optical unit; and 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 in the second particle-optical beam path between the objective lens and the detection unit; a controller, a controller configured to control the second particle-optical unit; a controller configured to generate individual images from data obtained by signals from detection regions each having one fixedly assigned detection channel or each having a plurality of fixedly assigned detection channels; the controller is configured to determine, from data obtained by signals from additional detection channels not assigned to any of the detection regions, a positional deviation of the second individual particle beam from a reference incident position when it is incident on the detection unit, and to generate at least one correction signal operable to correct the positional deviation; the controller is configured to control the high speed detection position adjustment means in real time using the at least one correction signal; Controller and It is equipped with:

[0034] A multibeam particle microscope according to the fourth aspect of the invention is configured and suitable for carrying out a method according to the invention according to the first aspect of the invention. All explanations and definitions given in relation to the first and / or second and / or third aspects of the invention also apply to the fourth aspect of the invention.

[0035] The high-speed detector position adjustment means of the multi-beam particle microscope according to the invention can be designed in one component or in several components. Each component of the detector position adjustment means can serve for the (main) correction of a certain class of positional deviation or image aberration (e.g., displacement, rotation, magnification, anamorphic imaging). The detector position adjustment means allows for real-time correction of the position of the second individual particle beam when it enters the detection unit, and consequently real-time correction during the inspection operation, in particular even while one or more individual images are still being generated. Advantageously, high-frequency control of the high-speed detector position adjustment means is therefore provided.

[0036] The controller of the multi-beam particle microscope can similarly be formed of one or more components. For example, the controller may include one or more control computers or other controllers, and may be divided into multiple modules. The at least one correction signal that functions to correct the misalignment may further represent a single signal or a superposition of multiple signals. What is important here is that the high-speed detection and position adjustment means for position correction can be meaningfully controlled by one or more signals. For example, one signal or a set of signals can be used to correct a specific image aberration or a specific class of misalignment, and one or more other correction signals or corresponding sets can be used to correct other image aberrations or different classes of misalignment, as needed. The number of correction signals, for example, corresponds to the number of individually controllable particle-optical components of the high-speed detection and position adjustment means.

[0037] According to a preferred embodiment of the present invention, the detection unit comprises an imaging detection area in which all detection regions are arranged, and an adjustment detection area in which all additional detection channels are arranged. Such a division of the detection unit into two functionally distinct areas is always possible in principle, and in this case, both the imaging detection area and the adjustment detection area can be formed as connected or unconnected areas. In other words, both the imaging detection area and the adjustment detection area can comprise sub-areas. In particular, if each detection area of ​​the imaging detection area comprises exactly one detection channel, it is possible for the detection unit itself to comprise only similar or structurally identical detection channels, namely, both the normal detection channel for image recording and the additional detection channel for adjustment purposes. In this case, the division of the detection unit into, first, the imaging detection area and, second, the adjustment detection area does not have to be based solely on physical or structural units, but is essentially carried out by a fixed, and therefore unchanging, assignment during signal evaluation within the detection range.

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

[0039]

number

number

[0040] According to a preferred embodiment of the present invention, the adjustment detection area is arranged around the outside of the imaging detection area. The nesting of these two areas may be rotationally symmetric or n-fold symmetric about the center of both areas, but this is not required. Alternatively, for example, the imaging detection area can be arranged around the outside of the adjustment detection area. This can also be realized symmetrically, particularly rotationally symmetric or n-fold symmetrically, but irregular, asymmetric arrangements are also possible. This is advantageous because a symmetric arrangement of the adjustment detection area around the outside of the imaging detection area simplifies signal evaluation, in this case determining the misalignment of the raster of the second individual particle beam. It is also relatively easy to distinguish between different classes / types of misalignment. Furthermore, the effect of the overall misalignment is particularly large in the edge regions of the raster and, as a result, is particularly easy to detect. However, of course, other detection options are also possible, and ultimately, the skillful selection of the physical design of the detection unit also plays a role in this case.

[0041] According to an embodiment of the present invention, the imaging detection areas are not arc-connected, and the adjustment detection areas are arc-connected but not simply connected. Again, the terms "not arc-connected" and "simply connected" are used as conventional in topology. This embodiment of the present invention clearly describes at least two spatially separated detection areas (domains) incorporated into the adjustment detection areas. The adjustment detection areas can, of course, not just be two detection areas, but all of the detection areas of the imaging detection areas individually incorporated into the adjustment detection areas. Again, the resulting overall arrangement of the imaging detection areas and adjustment detection areas can be regular or irregular, symmetric or asymmetric in design. A further example of a configuration according to a variation of this embodiment of the present invention is a cross-shaped arrangement of the adjustment detection areas, resulting in the division of the imaging detection area, which is not arc-connected, into four sub-areas (four domains). Various other embodiments are possible.

[0042] According to a preferred embodiment of the invention, each detection region is at least partially surrounded by an additional detection channel. This relatively comprehensive integration of the detection regions into the additional detection channels for the purpose of coordinated detection allows, for example, not only a global determination of the misalignment of the entire raster of second individual particle beams, but also an individual determination of the misalignment of each second individual particle beam.

[0043] According to a further preferred embodiment of the invention, the additional detection channels are arranged in such a way that they are able to detect a misalignment in the form of a misalignment of at least one second individual particle beam from a reference incident position, in particular a misalignment of a plurality of second individual particle beams from their respective reference incident positions. In this process, therefore, not only the absolute value of the misalignment but also the direction of the misalignment can be determined. For example, the position of the additional detection channels providing signals makes it possible to infer the direction of the misalignment.

[0044] According to a preferred embodiment of the invention, each detection area comprises exactly one detection channel, in which case the construction of the entire detection unit is particularly simple.

[0045] According to a further preferred embodiment of the invention, all detection channels are structurally identical. This means that both the detection channels that define the detection area(s) and the additional detection channels for detecting misalignment are structurally identical. In this case too, the design of the overall detection unit is particularly simple.

[0046] Alternatively, the detection channels can of course be different. For example, a first structure can be implemented with a detection channel that is fixedly assigned to the detection region, and a second structure can be implemented with an additional detection channel for detecting misalignment, but the first and second structures are not identical. In this process, the additional detection channel can be adapted to a specific role, specifically the identification of misalignment, in terms of its design. For example, if it is important to detect the raster displacement of the second individual particle beam, this detection can be easily performed in advance, for example, using peripheral and strip-like additional detection channels. Those skilled in the art will consequently discover further advantageous embodiments without departing from the scope of protection of the present invention.

[0047] According to a further preferred embodiment of the present invention, each detection channel has a signal incidence surface, which is generally arranged in a hexagonal pattern. Such a hexagonal arrangement can be used to tessellate the surface, and in particular to easily create multiple image fields from separate image planes. In this process, 3n(n-1)+1 separate particle beams are advantageously used for image generation and detection.

[0048] According to a preferred embodiment of the present invention, each detection area is fixedly assigned exactly one detection channel, and additional detection channels that are not assigned to any detection area are arranged in a hexagonal pattern around the outside of the detection areas. The hexagonal arrangement can be easily extended in this way, and the existing concept of the detection unit only needs to be expanded spatially, without any detailed modifications from a structural point of view.

[0049] According to a preferred embodiment of the present invention, the detection system comprises one or more particle detectors or consists of one or more particle detectors. Alternatively, the detection system comprises one or more particle detectors and furthermore a plurality of photodetectors arranged downstream of the particle detectors. The present invention can therefore be realized with a high degree of freedom with regard to the detection system or detection unit, and is not principally bound to a specific design of the detection system.

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

[0051] According to an alternative embodiment of the invention, the detection channel does not comprise an optical fiber, but an array of light-sensitive detectors, in particular an array comprising photomultiplier tubes, photodiodes or avalanche photodiodes, is provided as the optical detection system, all of which are examples of a flexible choice of detection system or detection unit.

[0052] According to a preferred embodiment of the present invention, the fast detector position adjustment means comprises at least one of the following means: an electrostatic lens, an electrostatic deflector, an electrostatic stigmator, an air-core coil, a multi-deflector array. Other fast detector position adjustment means can also be used and are known to those skilled in the art. Reference is again made to the above-mentioned documents which disclose corresponding means.

[0053] The various embodiments and aspects of the present invention may be combined with one another in whole or in part, unless this results in a technical contradiction.

[0054] The present invention may be better understood with reference to the accompanying drawings. [Brief explanation of the drawings]

[0055] [Figure 1] FIG. 1 is a schematic diagram of a multi-beam particle microscope (MSEM). [Figure 2a] FIG. 1 shows a schematic diagram of a detection system for a multi-beam particle microscope. [Figure 2b] FIG. 1 shows a schematic diagram of a detection system for a multi-beam particle microscope. [Figure 3] FIG. 10 shows a schematic diagram of a controller of a multi-beam particle microscope for real-time readjustment of a second individual particle beam as it enters the detection unit. [Figure 4] 1 shows a schematic diagram of an embodiment of a method according to the present invention; [Figure 5] FIG. 10 shows a schematic diagram of detection of a focused secondary beam in normal inspection mode. [Figure 6] FIG. 2 is a diagram illustrating the principle of positional deviation correction. [Figure 7] FIG. 10 shows a schematic diagram of a detection unit extended with an additional detection channel. [Figure 8] FIG. 10 shows a schematic diagram of a detection unit extended with an additional detection channel. [Figure 9] FIG. 10 shows a schematic diagram of a detection unit extended with an additional detection channel. [Figure 10] FIG. 10 shows a schematic representation of the misalignment of the second individual particle beam when it enters the detection unit. [Figure 11] FIG. 10 shows a schematic representation of different areas of the detection unit and different positions / misalignments of the second individual particle beam when it is incident on the detection unit. [Figure 12] FIG. 10 shows a schematic diagram of a detection unit comprising a detection area to which multiple detection channels are fixedly assigned, and an additional detection channel for detecting a misalignment when a second individual particle beam is incident on the detection unit. [Figure 13] FIG. 10 shows a schematic diagram of the division of the detection unit into different regions for determining and correcting the misalignment when the second individual particle beam is incident on the detection unit. [Figure 14] FIG. 10 shows a schematic diagram of another detection unit comprising a detection region to which multiple detection channels are fixedly assigned, and an additional detection channel for detecting misalignment when a second individual particle beam is incident on the detection unit. DETAILED DESCRIPTION OF THE INVENTION

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

[0057] Enlarged detail I1 in Figure 1 shows a plan view of an object plane 101 with a regular rectangular field 103 of incidence locations 5 formed in a first plane 101. In Figure 1, the number of incidence locations is 25, forming a 5 x 5 field 103. The number of incidence locations, 25, is chosen to simplify the illustration. The number of beams, and therefore the number of incidence locations, can in practice be chosen to be much higher, e.g., 20 x 30, 100 x 100, etc.

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

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

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

[0061] Detail I2 of Figure 1 shows a plan view of plane 211 in which the individual detection areas 215 of particle multi-detector 209 are located, at which secondary particle beam 9 is incident at locations 213. The incident locations 213 lie within field 217 and have a regular pitch P2 relative to one another. Exemplary values ​​for pitch P2 are 10 micrometers, 100 micrometers and 200 micrometers.

[0062] The primary particle beam 3 is generated in a beam generating device 300 comprising 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 diffuse particle beam 309, which is collimated, or at least substantially collimated, by the collimation lens 303 to shape a beam 311 that illuminates the multi-aperture array 305.

[0063] Detail I3 of FIG. 1 shows a plan view of the multi-aperture array 305. The multi-aperture array 305 includes a multi-aperture plate 313 having a plurality of openings or apertures 315 formed therein. Center points 317 of the openings 315 are located in a field 319 that is imaged onto a field 103 formed by the beam spots 5 at 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 apertures 315 is less 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] Particles of the illumination particle beam 311 pass through the aperture 315 and form the particle beam 3. Particles of the illumination beam 311 that are 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 an applied electrostatic field forms a beam focus 323 at a plane 325. The beam focus 323 may alternatively be a virtual focus. The diameter of the beam focus 323 may 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 a plane 325 where the beam focus 323 is formed onto the first plane 101, whereby a field 103 of incidence locations 5 or beam spots results in the first plane 101. If the surface of the object 7 is arranged in the first plane, a corresponding beam spot is formed on the object plane.

[0067] The objective lens 102 and the projection lens array 205 realize a second imaging particle-optical unit, which images the first plane 101 onto the detection plane 211. The objective lens 102 is therefore 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 disposed 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 on such multi-beam particle beam systems and the components used therein, such as particle sources, multi-aperture plates, and lenses, can be found in WO 2005 / 024881, WO 2007 / 028595, WO 2007 / 028596, WO 2011 / 124352, and WO 2007 / 060017, as well as DE 102013016113 and DE 102013014976, the disclosure content of which is hereby incorporated by reference in its entirety into the present application.

[0070] The multiple particle beam system further comprises a computer system 10 configured to control the individual particle optical components of the multiple particle beam system and to evaluate and analyze the signals obtained using the multi-detector 209 or detection unit 209. The computer system 10 can also be used to perform the method according to the invention. The computer system 10 can be built by several individual computers or components.

[0071] FIG. 2a is a schematic diagram for illustratively illustrating the implementation of a detector 209. The detector 209 in this case comprises a scintillator plate 207, which is a particle detector, on which an interaction product, e.g., a secondary electron beam, is directed by an electron-optical unit. When integrated into the multi-beam particle microscope of FIG. 1, this electron-optical unit comprises electron-optical components of the particle-optical unit that shape the electron beam 9, i.e., the objective lens 102, which directs the electron beam 9 towards the detector 209, e.g., towards the beam switch 400, and focuses the electron beam 9 onto the surface of the scintillator plate 207, e.g., via the lens 205. The electron beam 9 is incident on an incident location 213 of the scintillator plate 207. Even when the electron beam 9 is focused on 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 points of the beam spots can be considered to be the incident locations 213, which are arranged at a mutual pitch P2 (see FIG. 1).

[0072] The scintillator plate 207 contains a scintillator material that is excited by incident electrons of the electron beam 9 to emit photons. Each of the incident locations 213 therefore forms a photon source. FIG. 2a shows only a single corresponding beam path 221 emanating from the incident location 213 of the central electron beam of the five electron beams 9 shown. The beam path 221 passes through an optical optical unit 223, which in the illustrated example comprises a first lens 225, a mirror 227, a second lens 229, and a third lens 231, and then impinges on a light receiving surface 235 (signal entrance surface 235) of a light detection system 237. The light receiving surface 235 is formed at the end surface of an optical fiber 239, at which at least a portion of the photons are coupled and directed to a photodetector 241. The photodetector 241 may include, for example, a photomultiplier tube, an avalanche photodiode, a photodiode, or any other type of suitable photodetector. The optical optical unit 223 is configured to optically image the surface 208 of the scintillator plate 207 onto an area 243 in which the light receiving surfaces 235 are arranged. This optical imaging generates an optical image of the incident locations 213 in the area 243. A separate light receiving surface 235 of the light detection system 237 is provided in the area 243 for each of the incident locations 213. Each of the further light receiving surfaces 235 (signal incident surfaces 235) is formed at an end surface of a light guide 239, which guides light coupled into the end surface to a light detector 241. By optical imaging, each of the incident locations 213 is assigned a light receiving surface 235, and light entering each light receiving surface 235 is detected by a separate light detector 241. The light detector 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 that are imaged onto the light receiving surface of the photodetector 241 define different detection locations or detection areas. By means of the electron optical unit described above, interaction products, e.g., electrons, emitted from two different individual field regions of the object are also imaged onto different detection areas 215 of the scintillator plate 207.In the exemplary embodiment described herein, the photodetector 241 is located away from the light receiving surface 235 onto which the light-optical unit 223 images the scintillator plate 207, and the received light is guided to the photodetector 241 via an optical fiber 239. However, it is also possible to position the photodetector 241 directly at the location where the light-optical unit forms the image of the scintillator plate, with the light-sensitive surface of the photodetector thus forming the light receiving surface.

[0073] 2a only schematically illustrates some details of the detector 209 in this case. It should also be pointed out here that the scanning movement of the primary particle beams over the object or sample illuminates or scans many locations on the sample. Each primary particle beam 3 sweeps over all or part of an individual field area of ​​the object 7 in this case. Each primary particle beam 3 is assigned an individual field area dedicated to the object. From these individual field areas of the object 7, interaction products, for example secondary electrons, are then emitted from the object 7. The interaction products are then projected onto the detection area 215 of the particle detector or onto the scintillator plate 207, such that interaction products emitted from two different individual field areas are projected onto different detection areas 215 of the scintillator plate 207. When interaction products, for example secondary electrons, are incident on this detection area 215, an optical signal is emitted from each detection area 215 of the scintillator plate 207, and the optical signal emitted from each detection area 215 is supplied to a photodetector 241 assigned to the respective detection area. In other words, each primary particle beam 3 has its own detection area 215 on the scintillator 207 and its own photodetector 241, which together form a detection channel 235 in the illustrated example. Therefore, in the illustrated example, each detection area 215 has exactly one detection channel 235 that is fixedly assigned to the detection area 215.

[0074] 2b shows a variant of an alternative embodiment of the detection system 209. In this variant, there is no optical fiber 239, and instead the photons emitted from the scintillator plate 207, after optical imaging, directly impinge on an array with photosensitive detectors 241, for example an array comprising photomultiplier tubes, photodiodes or avalanche photodiodes.

[0075] 2a and 2b are also suitable for carrying out the method according to the invention for operating a multi-beam particle microscope 1. See, for example, the method of DED ("direct electron detection"), which does not require a photodetector but converts secondary electrons directly into a current signal. In this case, in particular, such detection architectures can be used, in which each detection area is fixedly assigned a number of detection channels 235. This assignment of multiple detection channels to one detection area is particularly frequent in pixelated or sectored detectors.

[0076] According to the invention, an additional detection channel 235′ is now added to supplement the detection area of ​​the detection unit 209 used in the prior art. Advantageously, the existing detection unit 209 is extended for this purpose by an additional detection channel 235′ that is not assigned to any detection area 215. Various exemplary embodiments of the corresponding multi-beam particle microscope 1 or the associated detection unit 209 according to the invention will be described below. The additional detection channel 235′ serves as a measuring element that detects a positional deviation of the second individual particle beam 9 when it enters the detection area 215. This is because, if the additional detection channel 235′ does not detect a signal, or at least does not detect a significant signal (the threshold value is not reached), it can be assumed that the second individual particle beam 9 is sufficiently accurately incident on the detection area 215. Based on the determined positional deviation, it is possible to correct the positional deviation in real time, in particular while multiple individual images are still being recorded, for example by using a single- or multiple-component high-speed detection position adjustment means in the secondary path of the multi-beam particle microscope 1.

[0077] 3 shows a schematic representation of a controller 10 of a multi-beam particle microscope 1 for real-time readjustment of the second individual particle beam 9 as it enters the detection unit 209. The controller 10 in the example shown comprises a controller 810 for the primary path and a controller 820 for the secondary path. The controller 820 for the secondary path further comprises an adjustment control module 830 and an image generation control module 840. The controller 820 for the secondary path may further comprise further modules, which are not shown in FIG. 3.

[0078] An image generation control module 840 processes data obtained by signals from the detection area 215 with fixedly assigned detection channels 235. Individual images and composite multi-images of the individual images that can be displayed using an image display unit 850 are generated by an image generation algorithm 842. In this respect, the controller 10 or controller 820 shown in Figure 3 corresponds to controllers already known in the prior art.

[0079] According to the invention, the adjustment control module 830 is realized in this case in the controller 10. This adjustment control module 830 comprises, as measurement elements, additional detection channels 235' that are not assigned to any of the detection areas 215. These additional detection channels 235' serve instead to detect a positional deviation of the second individual particle beam 9 when it is incident on the detection unit 209. The adjustment control module 830 is configured to determine, from data obtained with signals from each of the additional detection channels 235' that are not assigned to any of the detection areas 215, a positional deviation of the second individual particle beam 9 from a reference incident position when it is incident on the detection unit 209, and to generate at least one correction signal that serves to correct the positional deviation. An algorithm 832 can be used to evaluate the signals and to generate at least one correction signal. One or more detector position adjustment means 833, which are an actuator or actuators, are controlled by the correction signal or signals. This control is performed in real time, i.e., while an individual image or images are still being generated.

[0080] FIG. 4 shows a schematic diagram of an embodiment of a method for operating a multi-beam particle microscope 1 in inspection mode according to the present invention. FIG. 4 shows, parallel to the time axis t, first an image generation step S10 and then a misalignment identification and correction step S20. The steps or sequence of steps S10 and S20 are depicted within large arrows intended to indicate the parallel processing of the steps performed. According to the present invention, during the image generation process according to the sequence of step S10, for example, the following steps can be performed in parallel in time: In step S21, the additional detection channel 235′ is read. In the following step S22, it is determined whether there is a misalignment when the second individual particle beam 9 is incident on the detection unit 209. If not, step S21 is performed again. If a misalignment is otherwise determined in S22, the method proceeds to S23, where it is determined whether a threshold value is exceeded. If not, step S21 is performed again, and the method continues with reading out the additional detection channel 235′. In contrast, if the threshold has been reached, then at least one correction signal is generated in the next step S24, which is used to control one or more detector position adjustment means in step S25. Step S21 is then performed again, and the additional detector channel 235' is read out again. Optionally, each time a threshold is determined to be exceeded in step S23, the identified misalignment can be classified. This classification can then be included in an algorithm for generating one or more correction signals in S24. Misalignments that are corrected in this way are, for example, a displacement, a rotation of the raster of the second individual particle beam 9, a magnification, or an anamorphic imaging.

[0081] 5 shows a schematic diagram of the detection of a focused secondary beam 9, which is known in principle from the prior art. A particle source 301 emits a diffuse particle beam, which in the example shown passes through a focusing lens system 303 a, 303 b and, in the example shown, is collimated before impinging on and passing through a multibeam particle generator 305. This generator can, for example, comprise a multi-aperture plate with a downstream counter electrode, although other embodiment variants are also possible. In theory, of course, it would also be possible to use the multibeam particle source 301 directly, so that the first individual particle beam 3 does not have to be formed separately by the multibeam particle generator 305.

[0082] In the illustrated example, in the further particle light beam path, the first individual particle beam 3 passes through a field lens system having field lenses 307 a, 307 b, and 307 c. The first individual particle beam 3 then passes through a beam switch 400 and in particular a magnetic objective lens 102, after which the first individual particle beam 3 is focused and incident on the object 7 in the object plane 101. The incidence of the first individual particle beam 3 causes the emergence of a second individual particle beam 9 from the sample or object 7. The second individual particle beam similarly passes through the objective lens 102 and the beam switch 400 and, also in the illustrated example, subsequently passes through a projection lens system 205 a, 205 b, 205 c. 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, for example, be a circular or ring stop. The contrast stop 222 may be a bright-field or dark-field stop. Its role is to filter the second individual particle beam 9 depending on its starting angle from the object plane 101. The second individual particle beams 9 traveling from / to a specific starting angle range are separated from the bundle of second individual particle beams 9 at the beam crossover. This is shown schematically in the enlarged circle in FIG. 5. As already explained, the beam paths in FIG. 5 are shown only schematically and are therefore necessarily greatly simplified. In the normal inspection mode shown in FIG. 6, the second individual particle beam 9 is focused and enters the detection surface 207 or scintillator 207. A photodetector 237 is arranged downstream of the scintillator 207. In FIG. 5, the photodetector 237 is shown schematically as a hexagonal array of detection channels 1 to 37, with the cross-section or signal entrance surface of the detection channels being circular. In the imaging case shown in FIG. 5, the object plane 101 is focused onto the scintillator 207 or onto the plane E f5. In this case, the detection area 215 is imaged onto the particle beam 3, 9. Furthermore, in order to achieve the highest possible throughput during imaging, it is preferred that all individual particle beams 3, 9 are used for imaging. In the illustrated example, the detection unit 209 comprises a particle detection unit and a downstream optical detection unit 237. In this case, exactly one detection channel 235 is fixedly assigned to each detection area 215, as is shown schematically in FIG. 5 based on the optical detection unit 237.

[0083] FIG. 6 illustrates the principle of misalignment correction according to the present invention. The detection unit 209 illustrated in FIG. 5 can, in principle, be extended for this purpose. However, for clarity, FIG. 6 does not show multiple second individual particle beams 9, but instead shows only one such beam as it enters the detection unit 209. The detection unit 209 illustrated exemplarily in FIG. 6 includes a total of seven detection channels 235, 235′. The detection channels 235, 235′ are arranged in the same detection plane. However, only the detection channel 235 labeled with the sequence number 1 is permanently assigned to the detection region 215, and therefore, only the signal generated by this channel 235 functions exclusively for image generation. The additional detection channels 235′ are arranged in a ring-like hexagonal arrangement around the detection region 215 or the detection channel 235 permanently assigned to this detection region 215. 6a) shows the situation when the exemplarily depicted second individual particle beam is exactly incident on the nominal incident position of the detection unit 209, where in the schematic example the beam spot 213 coincides with the detection area 215 and the detection channel 235 fixedly assigned to the detection area 215. The size relationship between one beam spot 213 and the other detection area 215 may also be different, for example the beam spot 213 may be much smaller than the detection area 215. At this point, reference is again made to the fact that the detection area 215 may also have multiple detection channels 235 fixedly assigned to it.

[0084] FIG. 6b) shows the situation when the second individual particle beam is not incident on the reference position of the detection unit 209, but instead there is a misalignment of the 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 area 215 no longer coincides with the center of the beam spot 213. This misalignment or displacement is indicated by the arrow in FIG. 6b). When a misalignment exists, the additional detection channels 235′ generally detect a signal. In this example, the misalignment concerns only two of the six additional detection channels 235′. Knowing which additional detection channels 235′ are detecting the signal allows us to infer the direction of the misalignment of the beam spot 213 from the reference position. In the illustrated example, these are the additional detection channels 235′ with order numbers 2 and 3. The misalignment is detected in this case in the upper right direction.

[0085] FIG. 7 shows a schematic diagram of a detection unit 209 extended by additional detection channels 235′. The detection channels 235 and the additional detection channels 235′ are arranged in the same detection plane. In this case, a raster of the second individual particle beam 9 is depicted, whose beam spots 213 are depicted dark in FIG. 7. These beam spots 213 are incident on the detection areas 215 according to the optimal or reference positions of the beam spots 213 in FIG. 7a). Each detection area 215 is again fixedly assigned a detection channel 235, although it would also be possible to fixedly assign multiple detection channels 235 to each detection area 215. In addition to the detection areas 215 with fixedly assigned detection channels 235, the detection unit 209 comprises additional detection channels 235′, designated in the illustrated example by the sequential numbers 62 to 91. In this case, the hexagonal arrangement of the detection areas 215 is extended by further outer shells in the illustrated example. That is, the additional detection channels 235' are also arranged in a hexagonal shape overall.

[0086] FIG. 7b) shows the situation when there is a positional deviation of the raster of the individual particle beam 9 when it enters the detection unit 209. In the illustrated example, the entire raster or all beam spots 213 are displaced diagonally to the upper right. Three vectors V indicating the displacement are exemplarily plotted in the figure. Therefore, the additional detection channels 235′ with the sequential numbers 63 to 76 detect signals. Based on which additional detection channel 235′ detects a signal, and optionally also based on the signal size, it is possible to determine the size of the displacement V in the illustrated example. Therefore, a positional correction by the vector K is required so that the second individual particle beam 9 can again enter the detection area 215 at the reference position.

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

[0088] FIG. 8 schematically illustrates a detection unit 209 expanded with additional detection channels 235′. The detection channels 235 and the additional detection channels 235′ are located within the same detection plane 211. Unlike the detection unit 209 illustrated in FIG. 7, the detection unit 209 illustrated in FIG. 8 has a greater number of additional detection channels 235′. Unlike FIG. 7, the detection regions 215 are not arranged in arc-connected regions and therefore not in domains. In FIG. 8, this is not the case; the imaging detection regions are not arc-connected. Specifically, in the illustrated example, each detection region 215 is surrounded by six additional detection channels 235′. Like FIG. 7, the adjusted detection regions in FIG. 8 are arc-connected, but not simply connected. Therefore, it is not possible to shrink a closed path within the adjusted detection region to form a point. Specifically, this is not the case if this path were arranged around the detection region 215.

[0089] FIG. 8a) shows the situation when multiple individual particle beams 9 are incident on the detection unit 209 at their respective reference positions. FIG. 8b) shows, by contrast, the situation when misalignment is present. In the illustrated example, various additional detection channels 235′ detect signals when misalignment is present. For the illustrated 61 secondary beams 9 and their associated beam spots 213, 2 × 61 additional detection channels 235′ detect signals that allow for inference of the misalignment. Using the configuration shown in FIG. 8, it is possible to detect both the overall misalignment and, in principle, the individual misalignment of the individual particle beams 9. For this purpose, each additional detection channel 235′ is located between two detection areas or between the respective detection channels 235 fixedly assigned to a detection area. The corresponding distance D1 between two detection areas 215 is also plotted in FIG. 8.

[0090] 9 shows a schematic diagram of the detection unit 209 extended with additional detection channels 235'. The detection channel 235 and the additional detection channel 235' are arranged in the same detection plane. According to FIG. 9, even more additional detection channels 235' are provided compared to FIG. 8. The distance between the detection areas 215 is denoted as D2, and two additional detection channels 235' are located between two detection areas 215 or between exactly one fixedly assigned detection channel 235. Using these additional detection channels 235', even finer misalignments can be determined, but the signal evaluation may become more complex.

[0091] Figure 10 shows a schematic representation of the displacement of the second individual particle beam 9 when it enters the detection unit 209. The detection unit 209 is generally divided into an imaging detection area B1 and a conditioning detection area B2. Figure 10a) also shows the beam spot 213, which is incident only on the imaging detection area B1. The imaging detection area B1 and the conditioning detection area B2 are arranged in the same plane. The imaging detection area B1 and the conditioning detection area B2 may in this case each be equipped with a detection channel and an additional detection channel, but this is not shown in detail in Figure 10a).

[0092] In contrast, FIG. 10b) shows a portion of the image-generating detection area B1, depicting multiple detection areas 215. In the illustrated example, these detection areas 215 are hexagonal and may have a pixelated or non-pixelated form. In both cases, the detection area 215 has a fixed number of detection channels 235 that are fixedly assigned to the detection area 215. In this case, the beam spot 213 is incident on the detection area 215. In example b), the beam spot 213 strikes the center of the detection area 215, while in example c), it strikes the detection area 215 displaced laterally to the right. However, in both cases, the beam spot 213 is fully incident on each detection area 215, so a slight misalignment does not cause signal loss. In such cases, there is no need to correct the misalignment. Correction is only necessary when the beam spot 213 strikes multiple detection areas 215, in which case a sufficiently large signal exceeding the threshold will be detected in the appropriately adjusted detection area B2.

[0093] FIG. 11 schematically illustrates the various regions or domains of the detection unit 209 and the various positions / misalignments of the second individual particle beam 9 when it enters the detection unit 209. The image-generating detection region B1 and the conditioning detection region B2 are again shown schematically in FIG. 11. The image-generating detection region B1 and the conditioning detection region B2 are arranged in the same plane. In FIG. 11, the specific division of the regions into detection regions and (additional) detection channels is omitted. The division can have a wide variety of designs, as already explained in various examples. FIG. 11a) here exemplarily illustrates the raster displacement of the individual particle beam, represented by the beam spot 213. The hexagonal shell-type conditioning detection region B2 exhibits signals diagonally above and to the right, while no signal is detected in the remaining four subregions. The regions where a signal is detected are indicated by hatching in FIG. 11. The misalignment can be corrected in real time while the image is still being recorded and can be inferred from the resulting signal pattern.

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

[0095] Figure 11c) shows anamorphic imaging or anamorphic misalignment. The raster of the individual particle beams is expanded in the y direction, but this is not the case in the x direction. Signals are therefore detected in two small areas of the adjusted detection area B2 (at the upper and lower edges of the hexagonal shell). This can be used to generate a correction signal, which can be used to control the fast detection position adjustment means in order to correct in real time the position of the second individual particle beam 9 when it enters the detection unit 209.

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

[0097] FIG. 12 schematically illustrates a detection unit 209 including a detection region 215 to which multiple detection channels 235 are fixedly assigned, and an additional detection channel 235′ for detecting a misalignment when the second individual particle beam 9 enters the detection unit 209. The fixedly assigned detection channels 235 and the additional detection channel 235′ are arranged in the same plane. FIG. 12 illustrates an example of a pixelated detection unit 209 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 correctly aligned, each beam spot 213 falls entirely within the detection region 215 of the detection unit 209. In this case, signals are not necessarily detected in 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 imaging detection area is not an arc connection, but instead the individual detection areas 215 are embedded like islands in the coordinated detection area by the additional detection channels 235'. The misalignment, and also the type of misalignment, can be estimated for the ensemble of second individual particle beams 9 and / or for each individual second individual particle beam 9 depending on the additional detection channel 235' whose signal is detected.

[0098] FIG. 13 shows a schematic division of the detection unit 209 into various regions for determining and correcting misalignment of the second individual particle beam 9 when it is incident on the detection unit 209. FIG. 13a) shows a circular and two surrounding ring structures as an example in this case. The imaging detection region B1 is located between the outer annular portion and the central ring, and when the second individual particle beam 9 is optimally incident on the detection unit 209, all beam spots 213 are incident on the imaging detection region. The adjustment detection region B2 is not arc-shaped but is divided into sub-regions B2.1 and B2.2. 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, with nine beam spots 213 depicted in the imaging detection region B1 by way of 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, in the illustrated example in the form of a square shell, is located at the outer periphery of the image generation 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 the desired reference position can be detected. The image generation detection area B1 and the adjustment detection area B2 or B2.1 and / or B2.2 are arranged in the same plane.

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

[0100] In summary, therefore, a method for operating a multi-beam particle microscope 1 in an inspection mode of operation is disclosed, as is an associated multi-beam particle microscope 1. The detection unit 209 comprises an image-generating detection area with a fixedly assigned detection channel 235 and an adjustment detection area with an additional detection channel 235'. The fixedly assigned detection channel 235 and the additional detection channel 235' are provided in the same detection plane 211. Based on the signal obtained by the additional detection channel 235', it is possible to accurately correct the position of incidence of the secondary beam 9 on the detection unit 209 in real time, independently of the specific structure of the detection unit 209. [Explanation of symbols]

[0101] 1. Multibeam particle microscope 3 Primary particle beam (individual particle beam) 5 Beam spot, incident point 7 Objects and samples 9 Secondary particle beam 10 Computer system, controller 11 Secondary particle beam path 13 Primary particle beam path 101 Object surface 102 Objective Lens 103 Field 200 detector system 205 Projection Lens 207 Scintillator Plate 208 Deflectors for adjustment purposes 209 Detection system, particle multi-detector, detection unit 211 Detection surface 213 Incidence location 215 detection area 217 Field 221 Optical Beam Path 222 contrast aperture 223 Light Optical Unit 225 lens 227 Mirror 229 Lens 231 Lens 235 Detection channel, light receiving surface, signal incident surface (image generation) 235' additional detection channels (position correction) 237 Optical Detection System 239 Optical fiber, light guide section 241 Photodetector 243 Area for optical imaging of scintillator surface 245 Wiring 300 Beam Generator 301 Particle source 303 Collimation Lens System 305 Multi-aperture array 306 Micro-Optical Systems 307 Field Lens System 309 Diffuse Particle Beam 310 Multi-beam generator 311 Irradiation Particle Beam 313 Multi-aperture plate 315 Multi-aperture plate opening 317 Center point of opening 319 Field 323 Beam Focus 325 Intermediate image plane 400 Beam Switch 810 Primary path controller 820 Secondary Path Controller 830 Adjustment Control Module 832 Real-time Algorithm for Position Misalignment 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, displacement vector K correction vector D1 Distance between detection areas / detection channels D2 Distance between detection areas / detection channels B1 Image generation and detection area B2 Adjustment detection area

Claims

1. irradiating an object with a plurality of charged first individual particle beams, each first individual particle beam irradiating a separate individual field region of the object in a scanning manner; collecting a second individual particle beam that is emanated from or emitted from the object by the first individual particle beam; focusing and projecting the second individual particle beams onto detection regions of a detection unit such that the second individual particle beams emerging or emanating from two different individual field regions are projected onto different detection regions, wherein one detection channel or a predetermined number of detection channels are fixedly assigned to each detection region; reading the fixedly assigned detection channels and generating individual images of each of the individual field regions based on data obtained by signals from each of the detection regions, each of which comprises one fixedly assigned detection channel for each of the detection regions, or a plurality of fixedly assigned detection channels for each of the detection regions; reading an additional detection channel of the same detection unit, which is not projected by the second individual particle beam in a manner directed toward a target and is not assigned to any detection region, and determining a positional deviation of the second individual particle beam from a reference incident position when it is incident on the detection unit based on data obtained by signals from the additional detection channel; correcting in real time the misalignment of the second individual particle beam when it is incident on the detection unit; 1. A method of operating a multi-beam particle microscope in an inspection mode of operation, comprising:

2. the correcting the misalignment of the second individual particle beam comprises adjusting a particle light beam path of the second individual particle beam in real time.

10. A method for operating a multi-beam particle microscope in an inspection mode of operation according to claim 1.

3. the misregistration is corrected during the generation of the individual images, in particular multiple times, 10. A method of operating a multi-beam particle microscope according to claim 1.

4. classifying the determined misalignment and correcting the misalignment based on the classification.

10. The method of operating a multi-beam particle microscope of claim 1, further comprising:

5. the correction of the misalignment comprises correcting a global displacement of the second individual particle beam when it is incident on the detection unit.

10. A method of operating a multi-beam particle microscope according to claim 1.

6. the correction of the misalignment includes correction of a global rotation of the second individual particle beam when it is incident on the detection unit.

10. A method of operating a multi-beam particle microscope according to claim 1.

7. the correction of the misalignment comprises correction of the expansion of the second individual particle beam in one or two directions when it is incident on the detection unit.

10. A method of operating a multi-beam particle microscope according to claim 1.

8. correcting in real time an individual misalignment of at least one second individual particle beam when incident on said detection unit; 10. The method of operating a multi-beam particle microscope of claim 1, further comprising:

9. The misalignment is corrected only if it exceeds a threshold value.

10. A method of operating a multi-beam particle microscope according to claim 1.

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

11. A multi-beam particle microscope configured to carry out the method according to any one of claims 1 to 9.

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 and configured to image the generated first individual particle beam onto an object plane such that the first individual particle beam impinges on the object at an incidence location forming a second field; a detection unit comprising a plurality of detection areas forming a third field, each of said detection areas being fixedly assigned one or more detection channels, said detection unit further comprising an additional detection channel not assigned to any of said detection areas; a second particle-optical unit comprising a second particle-optical beam path and configured to image a second individual particle beam emanating from the incidence location of the second field onto the third field of the detection area of ​​the detection system in a substantially focused manner, the second particle-optical unit comprises a high-speed detector position adjustment means configured to correct in real time the position of the second individual particle beam when it is incident on the detection unit. a second particle-optical unit; and 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 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 by signals from the detection regions comprising the respective fixedly assigned one detection channel or the respective fixedly assigned multiple detection channels; the controller is configured to determine a positional deviation of the second individual particle beam from a reference incident position when it is incident on the detection unit from data obtained by signals from the additional detection channels not assigned to any of the detection regions, and to generate at least one correction signal operable to correct the positional deviation; the controller is configured to use the at least one correction signal to control the high speed detection position adjustment means in real time. Controller and A multi-beam particle microscope comprising:

13. the detection unit comprises an image-generating detection area in which all detection areas are arranged; the detection unit comprises a coordinated detection area in which all additional detection channels are arranged; 13. A multi-beam particle microscope according to claim 12.

14. the image generating detection area is arc-connected; The adjusted detection area is an arc-shaped connection; 14. A multi-beam particle microscope according to claim 13.

15. the adjustment detection area is disposed around the outside of the image generation detection area; or the image generation detection area is disposed around the outside of the adjustment detection area; 15. A multi-beam particle microscope according to claim 14.

16. The image generating and detecting area is not connected in an arc shape; The adjusted detection region is arc-connected but not simply connected; 14. A multi-beam particle microscope according to claim 13.

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

18. the additional detection channel is arranged to be able to detect a misalignment in the form of a misalignment of at least one second individual particle beam from a reference incident position, in particular a misalignment of a plurality of second individual particle beams from their respective reference incident positions.

13. A multi-beam particle microscope according to claim 12.

19. each detection region comprises exactly one detection channel; 13. A multi-beam particle microscope according to claim 12.

20. All detection channels are structurally identical; 13. A multi-beam particle microscope according to claim 12.

21. the detection channels fixedly assigned to the detection regions have a different structure than the additional detection channels not assigned to any of the detection regions; 13. A multi-beam particle microscope according to claim 12.

22. each detection channel having a signal incidence face; The signal incidence surfaces are generally arranged in a hexagonal shape.

13. A multi-beam particle microscope according to claim 12.

23. Each detection region is fixedly assigned exactly one detection channel; the additional detection channels not assigned to any detection region are arranged in a hexagonal pattern around the outside of the detection region; 23. A multi-beam particle microscope according to claim 22.

24. the detection system comprises or consists of one or more particle detectors; 13. A multi-beam particle microscope according to claim 12.

25. the detection system comprising one or more particle detectors and further comprising a plurality of photodetectors disposed downstream of the particle detectors; 13. A multi-beam particle microscope according to claim 12.

26. each detection channel comprises exactly one optical fiber, and different detection channels comprise different optical fibers; 26. A multi-beam particle microscope according to claim 25.

27. the detection channels do not comprise optical fibers, but an array of photosensitive detectors, in particular an array comprising photomultiplier tubes, photodiodes or avalanche photodiodes, is provided as the optical detection system; 26. A multi-beam particle microscope according to claim 25.

28. the high-speed detection position adjusting means comprises at least one of an electrostatic lens, an electrostatic deflector, an electrostatic stigmator, an air-core coil, and a multi-deflector array; A multi-beam particle microscope according to any one of claims 12 to 27.

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