Multi-beam microscope and method for operating a multi-beam microscope with settings tailored to the site of examination - Patent Application 20070122999

Abstract

With the improved multi-beam system and the improved wafer inspection method using the multi-beam system, multi-beam effects that reduce the accuracy or speed of wafer inspection are corrected as a function of the inspection position. To this end, the improved multi-beam system comprises means for influencing and uniforming the extraction electric field as a function of the inspection position, e.g., as a function of the distance from the wafer edge.

Description

[Background technology]

[0001] With the continuous development of smaller and more complex microstructures, such as semiconductor components, there is a need to develop and optimize planar manufacturing techniques and inspection systems for producing and inspecting small-dimension microstructures. For example, the development and production of semiconductor components requires monitoring of wafer designs, and planar manufacturing techniques require process monitoring and process optimization for high-throughput, reliable production. Furthermore, recent years have seen a demand for analysis of semiconductor wafers for reverse engineering and for customer-specific, individualized configuration of semiconductor components. Therefore, there is a need for inspection tools that can be used with high throughput to examine the microstructures on wafers with high precision.

[0002] 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 2A semiconductor device is subdivided into 30 to 60 or more repeating regions ("dies") with sizes of 1000 to 10 ... By way of example, the width of semiconductor features must be measured with an accuracy of less than 1 nm, e.g., 0.3 nm or even less, 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 even less.

[0003] It is therefore a general object of the present invention to provide a multi-particle beam system operating with charged particles, and an associated method for operating same with high throughput, that facilitates highly precise measurements of semiconductor features with resolutions of less than 4 nm, less than 3 nm, or even less than 2 nm.

[0004] The MSEM, or multi-beam scanning electron microscope, is a relatively new development in the field of charged particle systems (charged particle microscopes, CPM). For example, U.S. Pat. No. 7,244,949 (B2) and U.S. Patent Application Publication No. 2019 / 0355544 disclose multi-beam scanning electron microscopes. In a multi-beam electron microscope or MSEM, a sample is simultaneously illuminated by multiple individual electron beams arranged in a field or raster. For example, an MSEM may provide 4 to 10,000 individual electron beams as primary radiation, each separated from adjacent individual electron beams by a pitch of 1 to 200 micrometers. For example, an MSEM may have approximately J=100 separated individual electron beams ("beamlets") arranged in a hexagonal raster, with the individual electron beams separated by a pitch of approximately 10 micrometers. A plurality of J individual charged particle beams (primary beams) are focused onto the surface of a sample under investigation through a common objective lens. For example, the sample can be a semiconductor wafer housed via a wafer chuck assembled on a movable stage. During illumination of the wafer surface by the primary individual particle beams, interaction products, such as secondary electrons or backscattered electrons, emerge from the wafer surface. Their origins correspond in each case to the locations on the sample where the J primary individual particle beams are focused. The amount and energy of the interaction products depend on the material composition and topography of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are collected by a common objective lens and directed by a projection imaging system of the multi-beam inspection system to a detector positioned in a detection plane. The detector includes multiple detection areas, each containing multiple detection pixels, and measures the intensity distribution for each of the J secondary individual particle beams. For example, a digital image of a 100 μm × 100 μm image field is acquired in the process.

[0005] Prior art multi-beam electron microscopes include a series of electrostatic and magnetic elements, at least some of which are adjustable to adapt the focal position and astigmatism correction of the multiple charged particle beams. Prior art charged particle multi-beam systems further include at least one crossover plane for the primary or individual secondary charged particle beams. Furthermore, prior art systems include a detection system for easier setup. Prior art multi-beam particle microscopes include at least one beam deflector ("deflection scanner") for simultaneous scanning of an area of ​​the sample surface with multiple individual primary particle beams to completely sweep the image field of the sample surface with multiple primary beams. Furthermore, prior art systems include a beam splitter mechanism configured to guide the primary beam bundle from the primary beam bundle generating device to the objective lens and the secondary beam bundle from the objective lens to the detection system. International Application PCT / EP2021 / 061216, filed April 29, 2021, provides further details regarding multi-beam electron microscopes and methods for operating them. The disclosure of that application is incorporated herein by reference in its entirety.

[0006] In the case of scanning electron microscopes for wafer inspection, it is desirable to maintain stable imaging conditions so that imaging can be performed with high reliability, high imaging fidelity, and high repeatability. Throughput depends on several parameters, such as the speed of repositioning the displacement stage and at a new measurement site, as well as the area measured per unit of acquisition time. The latter is determined, among other things, by the dwell time on a pixel, the pixel size, and the number of individual particle beams. In addition, for multi-beam electron microscopes, time-consuming image post-processing may be required; for example, signals generated from charged particles by the detection system of a multi-beam system must be digitally corrected before multiple image subfields or image fields from subfields are integrated ("stitching").

[0007] In general, previous methods have been found to be no longer sufficient, especially when using a multibeam microscope to inspect semiconductors, which places high demands on measurement accuracy. When semiconductors are inspected, numerous special effects occur that reduce the required high measurement accuracy. These compound effects are related to the raster arrangement of multiple charged particle beams and the different shapes or sizes of individual particle beams from the multiple charged particle beams. For example, some of these effects do not occur or cannot be observed in biological samples. Other effects are so small that they only affect semiconductor inspection with advanced measurement accuracy, such as better than 2 nm or better than 1 nm. These effects reduce resolution or signal strength during wafer inspection. Furthermore, the measurement accuracy of, for example, the dimensions or distances of structures on the wafer surface, is adversely affected when these effects occur. In principle, some of these effects can be at least partially compensated for by changing the settings of the multibeam microscope. However, previous methods for determining and setting the optimal settings of a multibeam microscope to avoid unwanted effects were too slow or too complex for high-throughput wafer inspection tasks. For example, previous methods for determining and setting the best focal plane for multiple primary beams negatively impact throughput. For example, U.S. Pat. No. 10,388,487 describes determining object characteristics in a first measurement using first setting parameters and deriving the resulting second setting parameters for measuring the object in a second measurement. For example, beam characteristics such as focal position and astigmatism correction are determined from the object characteristics. However, this method reduces throughput because a high-resolution first measurement must be performed prior to the second, improved measurement. A further example in U.S. Pat. No. 10,535,494 describes a detection system used to determine the beam shape of secondary beams but not to determine the raster arrangement of the beams themselves.DE 102018124044 B3 describes a detection system that can only compensate for the relatively small effect of local sample charging by allocating multiple secondary electron beams to detector channels. Due to the increasing demand for measurement precision better than 2 nm or even better than 1 nm, it is no longer sufficient to consider only the detection system and the secondary particle path.

[0008] Multi-beam systems are being used precisely in the context of higher throughput, but compound effects occur associated with multiple charged particle beams, e.g., a raster array of multiple charged particle beams, or different shapes or sizes of individual particle beams. With prior art multi-beam systems and methods for operating them, these compound effects require complex analysis and adjustment of the multi-beam system, which significantly reduces the throughput of the multi-beam system. Given the above background and the increasing demands for throughput / speed and precision measurement of ever-smaller structures, existing multi-beam systems and methods for operating them therefore require improvement. This is particularly true for the inspection of polished wafer surfaces with high-voltage structures. Therefore, even under the completely unrealistic assumption of the absence of system drift and the like, it is no longer sufficient to set up a multi-beam electron microscope at a predetermined operating point with an associated working distance using prior art methods.

[0009] The combined multi-beam effect of multiple primary beams cannot be determined directly without effort. The occurrence of combined multi-beam effects of the primary beams, such as distortions of the raster arrangement of the primary beams, differences in magnification of the raster arrangement of the primary beams, or deviations in the shape and size of the focal points of the primary beams, can result in defective imaging, such as inaccurate positioning of the image of the surface structure of the wafer or inaccurate measurement of the dimensions or area of ​​the surface structure. If the combined multi-beam effect of the primary beams occurs significantly, this can further result in a predicted decrease in the signal intensity of the secondary particles, even leading to a complete loss of signal intensity of the secondary particles. In particular, if known methods for fast adjustment of the detection path are applied, thus compensating for the combined multi-beam effect of the primary beams with the aim of maintaining a high signal intensity of the secondary particles, the effect of inaccurate imaging of the object remains. However, especially in the case of wafer inspection, the position and dimensions of the surface structures are critical and must be determined with a high accuracy of less than 2 nm, ideally less than 1 nm, or even less. It is therefore an object of the present invention to provide, inter alia, an improved multi-beam system and an improved method for operating a multi-beam system in which the above-mentioned combined effects are reduced or compensated for without wafer inspection throughput being reduced in the process. Summary of the Invention

[0010] The present invention provides an improved multi-beam system and an improved method for operating a multi-beam system in which complex multi-beam effects occurring during the interaction of multiple beams of charged particles with the wafer surface are compensated for. According to one embodiment of the present invention, the complex multi-beam effects can be characterized by a combination of distortions of multiple secondary beams and changes in the size and shape of the focal spot on the detector. According to further embodiments, the complex multi-beam effects occur particularly near the edge of the wafer or near a previous inspection location, or the size of a complex multi-beam effect directly depends on the distance of the inspection site from the edge of the wafer or the previous inspection location. For compensation, the complex multi-beam effects are characterized or classified, and measures are derived, such as adjustments to the primary or illumination path and the secondary or detection path. According to this derivation of measures, parameters for setting or adjusting the primary and secondary paths are derived that are suitable for counteracting the complex effects. Furthermore, the multi-beam system may be equipped with suitable means at the wafer or in the immediate vicinity of the wafer surface to minimize or compensate for the combined multi-beam effect by influencing the electric field between the wafer surface and the last electrode of the objective lens of the multi-beam system, which electric field acts simultaneously on the primary and secondary particle beams.

[0011] The multi-beam system of the present invention, and a method for operating the multi-beam system, solves the problem of high-speed wafer inspection with high imaging fidelity by determining the combined multi-beam effect of the primary and secondary beams at the inspection site and implementing measures to compensate for the combined multi-beam effect through modifying parameters of both the illumination system and the detection system components. This is particularly facilitated during routine inspection of wafers that are always similar in principle, and where similar multi-beam effects with similar causes always occur.

[0012] In one embodiment, the combined multibeam effect of the primary beam is determined by time-averaged measurement of the raster arrangement of multiple secondary beams and the shape or size of at least one focal point of the secondary beam. In this case, the influence of the surface structuring of the semiconductor wafer on the measurement signal is reduced by time averaging. Analysis of the raster arrangement of multiple secondary beams and the shape or size of at least one focal point of the secondary beam is used to deduce a reliable combined multibeam effect of the primary beam, and a correction strategy for the illumination path is introduced. In this case, the measurement method can be repeated. Thus, within the framework of wafer inspection, it is possible to determine the combined multibeam effect of the primary beam at an inspection position on a structured wafer surface purely from determining the cumulative combined multibeam effect of the secondary beams, without the need for a reference object. As a result of the time averaging of the measurement, measurements can be performed very quickly here, for example by very quickly scanning the object surface at the inspection position with multiple primary beams.

[0013] In a further embodiment, the composite multi-beam effect of the primary beam is determined from a priori information. Furthermore, it has been found that some composite multi-beam effects depend on the inspection position on the wafer surface, particularly the edge of the wafer or the distance of the inspection position from a previous inspection position. Because the inspection positions on the wafer are known in advance, this dependency can be used to compensate for the composite multi-beam effect, according to an embodiment of the present invention. By way of example, parameters for driving the multi-beam system can depend on the known inspection positions. By way of example, the sequence of inspection tasks can be modified to reduce the effect of the previous inspection position. In a further embodiment, edge effects caused by non-uniform extraction fields are reduced by additional electrodes within the periphery of the wafer-receiving area. During inspection, a compensation voltage is applied to the additional electrodes. In one example, an extraction field is established through a counter electrode formed by multiple differentially drivable electrode segments to reduce the composite multi-beam effect.

[0014] In principle, the method for determining the combined multi-beam effect can also be carried out during an inspection task, so that variable combined multi-beam effects of the primary beam or unexpected deviations of the primary beam can also be detected.

[0015] According to a first embodiment of the present invention, an improved multi-beam system includes a spatially resolved detection device configured to detect focal points of multiple secondary beams during an inspection task, regardless of the surface contrast of the wafer surface at the inspection position. The improved multi-beam system further includes a control unit having a memory and a calculation unit configured to determine a current raster arrangement of focal points of multiple primary beams from the focal points of the multiple secondary beams and to use the current raster arrangement to determine a deviation from a predetermined raster arrangement. According to one embodiment, the control unit is further configured to determine a current shape and size of at least one predetermined focal point of the multiple secondary beams. For example, different shapes or sizes of at least two focal points of the multiple secondary beams are determined. The control unit is further configured to analyze the deviation of the current raster arrangement from the predetermined raster arrangement and use this to infer the occurrence of a specific composite multi-beam effect of the primary beams. According to one embodiment, the control unit determines the deviation of the current shape and size of the at least one predetermined focal point from the predetermined shape and size of the focal point. Furthermore, the control unit is configured to determine a possible cause of the composite multi-beam effect of the primary beams. In one example, the control unit determines multiple possible causes of the compound multi-beam effect of the primary beam, sorted according to their probability of occurrence. In one example, a machine learning algorithm is applied during the determination of the possible causes of the compound multi-beam effect. The machine learning algorithm can be trained with a growing set of frequently occurring compound multi-beam effects with frequently occurring causes, for example, near a previous inspection location or close to an edge of the wafer.

[0016] The control unit is further configured to determine a strategy for adjusting the illumination path and the detection path of the multi-beam system according to the most likely cause of the combined multi-beam effect at the inspection position. Within this determination, a number of control parameters are determined, which are used to drive or set components in the illumination path and the detection path of the multi-beam system. These parameters may also be changes relative to previously set parameter values ​​of specific components of the illumination path or the detection path of the multi-beam system. Possible components include quasi-static deflectors for the multiple beams of charged particles, dynamic deflectors for scanning deflection of the multiple beams of charged particles, electrostatic or magnetic lenses with variable focusing effects for the multiple beams of charged particles, multipole elements and energy filters for the multiple beams of charged particles, or array components by which each individual beam of the multiple beams of charged particles can be affected. In one example, the adjustment means includes, in particular, parameters for setting a uniform extraction field between the object surface and the objective lens system of the multi-beam system.

[0017] In one embodiment, the control unit is connected to the unit for image evaluation and is configured to provide the unit for image evaluation with a correction signal intended to correct at least part of the composite multi-beam effect, for example by image processing. The unit for image evaluation is connected to a detection unit of the multi-beam system and is configured to perform a correction of the image information of the detection unit using the correction signal. For example, highly accurate known distortions, perspective distortions, or magnification aberrations of the raster arrangement of multiple first-order beams can be compensated for by digital image processing in downstream image evaluation. For example, positional deviations of the individual first-order beams can be taken into account when integrating the individual images ("stitching").

[0018] The multi-beam system includes a displacement stage having an object holder for a semiconductor wafer, the object holder being suitable for receiving the wafer and positioning it below an objective lens of the multi-beam system. To this end, the object holder includes a reception area or wafer chuck for receiving a substantially planar wafer having a thickness T and an outer diameter D. The reception area for the wafer includes electrical contacts to a control unit for applying a voltage difference between an electrode system of the multi-beam system and the wafer. The electrode system is located below the objective lens or is part of the objective lens and includes electrical contacts to the control unit. The control unit is configured to supply suitable voltages to the electrode system and the wafer surface during operation to create, between the wafer surface and the electrode system, a field profile of an extraction field perpendicular to the wafer surface with equipotential lines parallel to the wafer surface during operation. This field is referred to as the extraction field.

[0019] For inspection tasks without the combined multi-beam effect, it is particularly necessary for the extraction field to have a uniform shape and form a constant, predetermined field strength on the wafer surface across the inspection position. Therefore, attempts are made to generate an extraction field that is as uniform as possible through a voltage difference. However, non-uniformity of the extraction field occurs, especially near the edge of the wafer. This combined multi-beam effect is also referred to as an edge effect or boundary effect. In a second embodiment, the object holder further includes a ring-shaped correction electrode having a height DE above the receiving area, which is disposed within the periphery of the receiving area and has an inner diameter DI>D, so that when the wafer is received, a constant distance G is formed in each direction between the edge of the wafer and the ring-shaped electrode. The ring-shaped electrode is insulated from the receiving area and electrically connected to a control unit, so that a voltage difference relative to the voltage of a wafer placed on the receiving area can be applied to the ring-shaped electrode during operation. The control unit of the multi-beam system is configured to, during operation, supply a first voltage to the receiving area and a wafer disposed thereon, and supply a second voltage to the ring electrode for reducing edge effects in order to generate a uniform extraction field.

[0020] In a third embodiment, the electrode system is formed by a plurality of, for example, two, four, eight, or more, electrodes that are insulated from one another and each electrically connected to a control unit. The control unit is configured to supply different voltages to the plurality of electrodes during operation in order to generate a uniform extraction field at the test position during operation. Since measurements are only performed at one test position at any one time, it is advantageous to vary the voltage of at least one segment of the ring electrode depending on the test position.

[0021] Many effects associated with imaging using multi-beam microscopes are very strongly linked to topology conditions. For example, the wafer edge has a significant influence during wafer inspection. Since the relative position of the inspection position with respect to the wafer edge is known in advance, particularly in the context of wafer inspection, improved adjustment of both the detection path and the illumination path depending on the distance of the inspection position from the wafer edge can be performed in advance when homing in to the inspection site. In a fourth embodiment, a multi-beam system and a method for operating a multi-beam system are provided, in which parameters of the illumination path and the detection path components of the multi-beam system are set depending on the distance of the inspection position from the wafer edge or boundary. To this end, the multi-beam system includes a control unit that determines the distance of the inspection position from the wafer edge or boundary. The control unit determines the combined multi-beam effect from the distance and the current operating point of the multi-beam system. Furthermore, the control unit is configured to drive components of the illumination path and the detection path of the multi-beam system with parameters suitable for reducing or completely avoiding the combined multi-beam effect during operation of the multi-beam system at the inspection position. One embodiment of the method includes obtaining and storing parameters of the improved adjustment of the detection path and the illumination path for different inspection sites as a function of distance from the edge of the wafer. Then, during inspection of the wafer, optimal parameters of the improved adjustment of both the detection path and the illumination path are determined and set as a function of the next inspection site from the predetermined and stored parameters.

[0022] It has been found that many additional composite multi-beam effects depend on the inspection position on the surface of the wafer and can therefore, in principle, be known in advance. In a fifth embodiment, a multi-beam system and a method for operating a multi-beam system are provided, in which parameters of components of the illumination path and the detection path of the multi-beam system are set in accordance with a priori information. In one example, the multi-beam system includes a control unit for achieving this purpose, which determines the composition of an object at least at the inspection position prior to measurement or inspection at the inspection position. In this case, determining the composition of the object includes, for example, determining the material composition of the object from CAD information related to semiconductor structures formed in the wafer at the inspection position. Based on the composition, expected composite multi-beam effects are determined, and suitable parameters of the multi-beam system are set to reduce or completely avoid the composite multi-beam effects. In an alternative example, the a priori information consists of information from previous inspections of similar inspection sites on other wafers. In one example, the method includes storing dynamic corrections according to the same inspection position during successive inspections of multiple wafers.

[0023] It has been found that many further composite multi-beam effects depend on adjacent inspection positions on the surface of the wafer and can therefore, in principle, be known in advance. In a sixth embodiment, a multi-beam system and a method for operating a multi-beam system are provided, in which parameters of components of the illumination path and detection path of the multi-beam system are set depending on adjacent inspection positions. In one example, the multi-beam system includes a control unit for achieving this purpose, which determines, for example, a current charge distribution of an object at an inspection position, caused by a previous inspection on the same object, before measurement or inspection at the inspection position. Based on the current charge distribution, the expected composite multi-beam effects are determined, and the parameters of the multi-beam system are set appropriately to reduce or completely avoid the composite multi-beam effects. A special example is provided by a method for repeatedly targeting the same inspection positions on the same wafer.

[0024] According to an embodiment, the method and a multi-beam microscope designed for application of the method facilitate improved adjustment of both the detection path and the illumination path for a specific inspection location on the surface of an object. According to a seventh embodiment, the method is based on acquiring and evaluating two fundamentally different items of information regarding the multi-beam microscope and its interaction with the object. First, the raster arrangement of multiple secondary beams is detected and evaluated. Second, the shape and size of at least one focus of the secondary beams is detected and evaluated. It is also possible to evaluate the shape and size of multiple foci of the secondary beams, for example, at least three foci.

[0025] Both items of information are acquired during scanning imaging of a portion of the object's surface. In this case, a plurality of J focal points of J primary beams are moved in a scanning manner across the object's surface, and a plurality of J scanning positions on the object's surface are simultaneously illuminated. To this end, a first deflection unit for the scanning deflection of the plurality of J primary beams is provided in the primary or illumination path. Each incident location of the J focal points of the J primary beams forms a source location for secondary electrons, which are collected and imaged on a detector during a short period of scanning irradiation with the J primary beams. The plurality of J source locations of the secondary electrons move synchronously across the object surface in accordance with the scanning irradiation with the J primary beams. Therefore, a second deflection unit for the scanning deflection of the J secondary beams emanating from the J source locations is provided in the imaging path of the secondary electrons, also referred to as the detection or secondary path, so that the focal points of the J secondary beams on the detector remain at the same J detection locations. In this case, the second deflection unit in the secondary path is synchronized with the first deflection unit in the primary path.

[0026] As a result of scanning illumination using multiple J primary beams and acquiring signals from multiple J secondary beams synchronized with the scanning illumination, multiple J time-series data streams are acquired, which are converted into multiple J two-dimensional digital image information items. Each image information item represents a spatially resolved generation rate of secondary electrons due to spatially resolved illumination of the object surface by the focal point of a primary beam. In this case, the secondary electron generation rate depends on the local surface conditions, for example, the local material composition of a structured wafer surface. Information regarding the shape and size of the focal point itself and the raster arrangement of the focal points for adjusting both the detection path and the illumination path is acquired in a time-averaged manner so that the effects of structuring on the object surface are reduced by averaging multiple scan positions on the surface. However, measurements can also be performed on completely unstructured wafers or unstructured test objects. Therefore, the method is possible for multiple objects, and no special measurement or calibration objects are required. In particular, the method for adjusting both the detection path and the illumination path can also be performed during an inspection task at an inspection position on the object surface.

[0027] For example, this also allows the method of adjusting both the detection path and the illumination path to be used for fast autofocus. Generally, this allows the method of adjusting both the detection path and the illumination path to be used for dynamic correction. With regard to dynamic correction, reference is made to PCT Patent Application International Application No. PCT / EP2021 / 061216, filed April 29, 2021, which is hereby incorporated by reference in its entirety into this disclosure.

[0028] In one example, determining parameters for improved adjustment of both the detection path and the illumination path according to the inspection site is performed iteratively. First, an image is recorded without correcting or changing parameters. Deviations of the raster arrangement of the multiple secondary beams from a predetermined or expected raster arrangement are detected and evaluated, and deviations of the shape and size of at least one focal spot from a predetermined or expected shape and size of the focal spot are simultaneously detected and evaluated. As described above, the deviations are detected within the framework of time averaging during scanning of the object surface with the multiple primary beams to eliminate the influence of the wafer composition. From the deviations, a probable cause of the deviations is determined, and suitable parameters for adjusting the illumination path and the detection path are determined. Detection of various deviations, in particular deviations in the raster arrangement of the multiple secondary beams and in the shape and size of the focal points, allows more targeted conclusions to be drawn regarding the cause, for example whether there is a disturbance or error in the illumination path and deviations in the multiple focal points of the primary beams are already present on the wafer surface, or whether the edge or topography of the wafer is the cause of the deviation, whether there is a global or local charging effect, or whether there is a disturbance in the detection path.

[0029] Following analysis of the raster arrangement and the combined multi-beam effect, compensation for the combined multi-beam effect is determined according to the model. Generally, the success of the compensation can be verified at a sample site, for example, of a reference sample, and fine corrections can be performed. The model for calculating the compensation can be improved by the fine corrections.

[0030] To determine the most likely cause of the deviation with even greater precision, further information, for example, from additional detectors, or a priori information, can be used. The additional detector may include a distance sensor for determining the distance of the sample surface from the reference area. The use of such a distance sensor, for example, allows for better discrimination between global charging of the object and purely mechanical defocusing. Further examples include field sensors for measuring electric or magnetic field strength near the object surface. The a priori information may include CAD information about the inspection location or stored information from previous measurements on similar objects or at similar inspection sites. For example, possible non-uniform or localized charging effects of the object may be determined from the CAD information. For example, areas of the wafer may be conductively connected, scattering charging effects beyond the inspection site. For example, areas of the wafer may include capacitance that stores charging effects over a relatively long period of time.

[0031] Generally, the position of the test site relative to the sample edge is also known a priori. Therefore, it is possible to consider distortions in the raster array through edge effects and distortions resulting from non-uniform charging. Prior measurements provide additional a priori information. For example, charges may arise due to prior measurements and may only slowly dissipate through leakage currents. Charging of adjacent test sites that have already been scanned causes distortions in the raster array, and this a priori information can be taken into account when determining the cause of the deviations.

[0032] In principle, the compensation for the combined multi-beam effect can already be performed in advance, for example, when targeting the inspection position. Once the probable cause of the deviation is determined, a correction measure or adjustment of the detection path and illumination path can be implemented. The deviation determination is then repeated. If the deviation is within a predetermined tolerance, in a next step, a portion of the object surface at the inspection site is measured or imaged. If the deviation still exceeds the predetermined tolerance, the process of determining the cause and determining new parameters for adjusting the detection path and illumination path is repeated. For example, a fine correction is determined and implemented in the second step.

[0033] The causes of deviations in the raster array and in the shape and size of the beam focus may be subject to dynamic changes. For example, the overall charging of the sample may increase when illumination by multiple primary beams increases, causing an increase in deviations in the raster array during imaging. Such dynamic effects are determined in an eighth embodiment of the present invention, for example, by taking into account the rate of change or deviation of the raster array and in the shape and size of the beam focus. This allows deviations in the raster array and in the shape and size of the beam focus to be dynamically corrected, and allows parameters for adjusting the detection path and illumination path to be dynamically changed in a predetermined manner during the capture of an image portion of the object surface.

[0034] In a ninth embodiment, a multi-beam system for inspecting a wafer includes first and second electron detectors and a beam deflector for deflecting a secondary electron beam from the first electron detector to the second electron detector. The first electron detector can detect the J secondary electron beams during an inspection task, the object contrast of the wafer, at a high data rate and with little noise. The second electron detector can detect the raster arrangement and shape or size of the focal points of the J secondary electron beams with high spatial resolution, and time averaging of the signals over multiple scan points on the surface of the wafer is performed simultaneously to suppress the object contrast. As a result, the composite multi-beam aberrations can be determined very quickly during an inspection task, and optimal parameters for a complex multi-beam system can be set. From the analysis and evaluation of the raster arrangement and shape and size of the secondary electron focal points, it is possible to infer characteristics of the illumination system, the detection system, or the inspection location on the wafer.

[0035] Generally, a multibeam system according to the present invention can be configured in such a way that it is configured to rapidly perform an inspection task related to the surface of a wafer in a first setting and to detect a composite multibeam aberration in a second setting. In this case, the composite multibeam aberration is caused by a deviation in the raster arrangement of multiple particle beams and a deviation in the shape and size of the focal point of at least one of the particle beams. In one example, the composite multibeam aberration is caused by a deviation in the raster arrangement of multiple particle beams and a deviation in the shape and size of the focal point of at least three secondary beams on a detector. In the second setting, the composite multibeam aberration is detected through time averaging over multiple raster points on the wafer surface, resulting in averaging of the object contrast. Therefore, rapid switching between the inspection task and the detection of the composite multibeam aberration is possible, resulting in high throughput. In some embodiments, the multibeam system according to the present invention is configured to detect the composite multibeam aberration while rapidly performing an inspection task related to the surface of a wafer. The composite multibeam aberration is detected through time averaging over multiple raster points on the wafer surface, resulting in averaging of the object contrast. Therefore, inspection tasks and detection of complex multi-beam aberrations can be performed simultaneously, resulting in high throughput.

[0036] The multi-beam system according to the present invention has a plurality of available primary particle beams and a plurality of secondary particle beams, and includes a spatial resolution detector, at least one deflection system for deflecting the plurality of primary and secondary particle beams for the purpose of collective scanning of a portion of the structured surface of the wafer, and a control device for driving the detector and the deflection system. The control device and the detector are designed to capture a time-averaged inspection image of the raster array of the plurality of secondary particle beams and / or to capture a digital image of a portion of the structured surface with a spatial resolution of 2 nm, 1 nm, or less. The control device, in a first operating mode for capturing a time-averaged inspection image of the raster array, rapidly scans the plurality of primary particle beams over a portion of the structured surface of the wafer within a time T1 using the deflection system, and in a second operating mode for recording a digital image of a portion of the structured surface, slowly scans the plurality of primary particle beams over a portion of the structured surface of the wafer within a time T2 using the deflection system, where T1 < T2, preferably T1 < T2 / 10, for example, T1 < T2 / 100. The detector can include a first detector and a second detector, and the multi-beam system can include a detection unit having a beam deflector configured to deflect the plurality of secondary particle beams either onto the first detector or onto the second detector during operation. The beam deflector can be additionally configured to maintain the plurality of secondary particle beams at a fixed position either on the first detector or on the second detector during operation. In an alternative example, the detector can be designed for the simultaneous capture of a time-averaged inspection image of the raster array of the plurality of secondary particle beams and a digital image of a portion of the structured surface with a high spatial resolution having a pixel size of 2 nm, nm, or less.To this end, the detector may include an electron conversion element that generates photons from electrons, and the photons are detected simultaneously using a first high-speed photodetector to capture a portion of the wafer surface and a second low-speed photodetector to capture an inspection image of the raster array.

[0037] In one example, the control device is further configured to determine, from the raster-array inspection image, a composite multi-beam effect resulting from changes in the incidence locations of the multiple particle beams and changes in the shapes and sizes of the particle beam foci, and to derive and set changes to setting parameters of the multi-beam system based on the composite multi-beam effect. In one example, the control device is connected to multiple components of the illumination path and the detection path, including components for setting a uniform extraction field, and is configured to appropriately adjust parameters of the components of the illumination path and the detection path, including components for setting a uniform extraction field, for the purpose of reducing the composite multi-beam effect.

[0038] The multi-beam system according to one embodiment comprises the following components connected to a control device for driving: - a quasi-static deflector for a plurality of primary particle beams; - a dynamic deflector for scanning deflection of the primary particle beam and the secondary particle beam; a dynamic deflector for scanning deflection of the secondary particle beam; - electrostatic or magnetic lenses with variable focusing effect; - a raster arrangement of multipole elements for influencing the primary particle beam; - a correction electrode for establishing a uniform extraction field between the wafer surface and a counter electrode of the objective lens system of the multi-beam system; In one example, the multi-beam system can further include means for generating a uniform extraction field within an edge region of the wafer, the means including a counter electrode electrical contact below the objective lens or at a portion of the objective lens for providing a first voltage difference V1 during operation. The means further includes a receiving area for receiving and positioning the wafer below the objective lens, the receiving area having an electrical contact for applying a second voltage difference V2 to the wafer during operation. The means further includes at least one correction electrode disposed within a periphery of the receiving area and having an electrical contact for providing at least one-third of the voltage difference V3 during operation.

[0039] In one example, the control unit of the multi-beam system further comprises a unit for image evaluation, wherein the control unit is configured to drive the unit for image evaluation with a correction signal intended to correct at least one part of the composite multi-beam effect.

[0040] In one embodiment, a wafer inspection multi-beam system includes a displacement stage for receiving a wafer, a spatially resolved detector, a first deflection system for deflecting multiple primary particle beams for simultaneous scanning of portions of a structured surface of the wafer, and a second deflection system for deflecting the multiple secondary particle beams to maintain a constant focus of the secondary particle beams on the detector. The multi-beam system further includes a control device configured to acquire and work through a list of inspection tasks at multiple inspection positions, and to set configuration parameters for components of the illumination path and the detection path, including components for setting a uniform extraction field, for the purpose of reducing compound multi-beam effects at the inspection positions. To this end, the control unit is configured to detect the distance of the inspection position from an edge of the wafer and compensate for compound multi-beam effects caused by the wafer edge. The control unit may be further configured to determine the composition of the wafer at the inspection position from CAD data before measurement or inspection at the inspection position and compensate for compound multi-beam effects caused by the composition. To this end, the control unit includes a memory and can determine stored parameters from a stored inspection task at a similar inspection site and can set them with the aim of reducing the combined multi-beam effect at the inspection location. The control unit can determine parameters from a previous inspection task at an adjacent inspection site and can set them with the aim of reducing the combined multi-beam effect at the actual or subsequent inspection location. The control unit can modify a scan program for driving the first and second deflection systems to at least partially compensate for the combined multi-beam effect, and the control unit is further configured to modify the scan program for driving the first and second deflection systems to at least partially compensate for the combined multi-beam effect.

[0041] A method for wafer inspection using a multi-beam system includes targeting an inspection location on a wafer and determining predetermined multi-beam microscope setting parameters for optimal imaging at the inspection location based on the inspection location. The determined setting parameters are set, and an image of a portion of the wafer surface at the inspection location is acquired. The multi-beam system setting parameters can be determined from preset setting parameters assigned to the inspection location, or the setting parameters for optimal imaging at the inspection location can be determined from at least two setting parameters assigned to two adjacent inspection locations. Additionally or alternatively, the optimized setting parameters can be determined from a priori information about the inspection location. The a priori information can include the distance of the inspection location from the edge of the wafer or from a previous image recording at a previous inspection location, or CAD information regarding the material composition at the wafer surface at the inspection location. The setting parameters include a voltage value for generating a uniform extraction field at the wafer surface, for example, a voltage value supplied to an electrode.

[0042] The present invention is not limited to specific embodiments, and variations of the embodiments are possible. While a wafer is generally referred to as the object, the present invention is also applicable to other objects, such as those used in semiconductor manufacturing. For example, the object may not be a semiconductor wafer, but a mask, such as a mask for EUV lithography. In contrast to a semiconductor wafer, such a mask is generally rectangular and has a significantly greater thickness. For example, in this case, the electrode around the object receiving area does not have a ring-shaped embodiment, but rather a rectangular embodiment. Furthermore, although the present invention is described based on a multi-beam system with multiple primary electron beams, other charged particles, such as helium ions, may also be used.

[0043] The above-described embodiments of the present invention can be fully or partially combined with each other as long as no technical contradictions result. It is obvious that those skilled in the art will consider that obvious variations of the exemplary embodiments are possible and are not excluded in this description.

[0044] The present invention will be better understood with reference to the accompanying drawings. [Brief explanation of the drawings]

[0045] [Figure 1] 1 is a diagram showing a multi-beam system according to a first embodiment. [Figure 2] FIG. 1 is a functional diagram of a multi-beam system according to a first embodiment. [Figure 3] FIG. 1 is a diagram of an inspection task using a multi-beam system. [Figure 4] FIG. 1 shows an example of a raster arrangement of multiple primary or secondary beams of a multi-beam system. [Figure 5] 10A-10C are diagrams showing examples of deviations of a current raster arrangement from a default raster arrangement, as well as examples of deviations of the beam shape or focal spot size of at least one focal point of the particle beam of the raster arrangement. [Figure 6] 1 is an illustration of a non-uniform electric extraction field at the edge of an object using the example of a wafer edge. [Figure 7] FIG. 10 is a cross-sectional view of a ring-shaped correction electrode according to a second embodiment. [Figure 8] FIG. 10 is a diagram of a segmented correction electrode and a segmented counter electrode according to a third embodiment. [Figure 9] FIG. 10 is a diagram of a method for operating a multi-beam system using parameter adjustment according to a fourth, fifth or sixth embodiment. [Figure 10] FIG. 13 is a diagram of a method for operating a multi-beam system using parameter adjustment according to a seventh embodiment. [Figure 11] 10 is a diagram of the dynamic behavior with an example of sample charging and dynamic change of tuning parameters of the multi-beam system. [Figure 12] FIG. 13 is a diagram showing a multi-beam system according to a ninth embodiment. [Figure 13] FIG. 2 illustrates a method for operating a multi-beam system according to a first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0046] In the following, the same reference signs refer to the same features, even if these are not explicitly mentioned in the text.

[0047] FIG. 1 is a schematic diagram of a multi-beam system 1 using multiple particle beams. The particle beam system 1 generates multiple J primary particle beams 3 that impinge on an object 7 under investigation to generate interaction products, e.g., secondary electrons, at the object 7, which emanate from the object 7 and are subsequently detected. The multi-beam system 1 is of the scanning electron microscope (SEM) type, using multiple primary particle beams 3 that impinge on the surface of the object 7 at multiple locations and generate multiple, spatially separated electron beam spots, or spots 5, thereon. The object 7 under investigation can be of any desired form, such as a semiconductor wafer, particularly a semiconductor wafer with an HV structure (i.e., with a horizontal and / or vertical structure), or a semiconductor mask, which may include an array of micropatterning elements or the like. The surface 25 of the object 7 is located in a first plane 101 (object plane) of an objective lens 102 of the illumination system 100. The optical axis 105 of the objective lens 102 is aligned perpendicular to the surface 25 of the object 7 and parallel to the path of the beam through the objective lens 102 .

[0048] The multiple beam foci 5 of the primary beams form a regular raster array of incident locations formed in the first plane 101. The number of incident locations J can be 5, 25, or more. In fact, the number of beams J, and thus the number of incident locations 5, can be chosen to be significantly larger, for example, J=10×10, J=20×30, or J=100×100. Exemplary values ​​for the pitch P1 between the incident locations are 1 micrometer, 10 micrometers, and 40 micrometers, or more.

[0049] The diameter of the smallest beam spot or focal point 5 formed in the first plane 101 can be small. Exemplary values ​​for this diameter are less than 4 nanometers, for example, 3 nm or less. The focusing of the particle beam 3 to form the beam spot 5 is performed by an objective lens system 102. In this case, the objective lens system 102 can include, for example, a magnetic immersion lens. Further examples of focusing means are described in DE 102020125534 A1, filed September 30, 2020, the entire contents of which are incorporated by reference in this disclosure.

[0050] Primary particles 3 impinging on object 7 generate interaction products, such as secondary electrons, backscattered electrons, or primary particles that have undergone a reversal of motion for other reasons, that emanate from the surface of object 7. The interaction products emanating from surface 25 of object 7 are shaped by objective lens 102 to form secondary particle beams 9. Particle beam system 1 provides detection beam paths 11 for guiding multiple secondary particle beams 9 to detection system 200. Detector system 200 includes a particle-optical unit having at least one projection objective lens 205 for directing secondary particle beams 9 toward a spatially resolved particle detector 207. In this case, imaging using the detection system is strongly magnified, so that both the raster pitch of the primary beams on the wafer surface and the size and shape of the focal spot of the primary beams are imaged in a greatly magnified manner. For example, the magnification is 100× to 300×, so that 1 nm on the wafer surface is imaged as 100 nm to 300 nm. In the process, for example, the image field of a multi-beam system with a diameter of 100 μm is expanded to approximately 30 mm. With sufficient signal strength, small changes in the center of gravity of the particle beam's focal point on the detector 207 can be determined with high precision. For example, in the case of a multi-beam system with F beams along one direction, scale errors become visible with a larger image field, magnified by a factor F. Therefore, the combined multi-beam effect of the particle beam, in particular deviations from the specified raster arrangement, for example at the opposite focal point located farthest from the optical axis 105, can be determined with high precision.

[0051] The primary particle beam 3 is generated in a beam generator 300, which includes at least one particle source 301 (e.g., an electron source), at least one collimation lens 303.1 and 303.2, a multi-aperture arrangement 305, and a field lens 307 or a field lens system made of multiple field lenses. The particle source 301 generates at least one diverging particle beam 309, which is collimated or at least substantially collimated by the at least one collimation lens 303 and illuminates the multi-aperture arrangement 305. The multi-aperture arrangement 305 includes at least one multi-aperture plate 306.1 having a plurality of J openings formed in a raster array therein. Particles of the illumination particle beam pass through the J apertures or openings, forming a plurality of J primary beams 3. Particles of the illumination beam that impinge on the plate 306.1 are absorbed by the plate 306.1 and do not contribute to the formation of the primary beams 3. The multi-aperture arrangement typically comprises at least a further multi-aperture plate 306.2, for example a lens array, an astigmatism corrector array or an array of deflection elements.

[0052] Together with the field lens 307 and the second field lens 308, the multi-aperture mechanism 305 focuses each of the primary beams 3 in such a way that a beam focus 311 is formed in the intermediate image plane 321. Alternatively, the beam focus 311 can be virtual. The diameter of the beam focus 311 can be, for example, 10 nanometers, 100 nanometers, and 1 micrometer. A further multi-aperture plate 390, for example in the form of a deflector array, can be arranged in the intermediate image plane 321.

[0053] The field lenses 103.1 and 103.2 and the objective lens 102 provide a first imaging particle-optical unit for imaging the plane 321, where the beam focus 311 is formed, onto the first plane 101, so that a raster array of incident locations or focal points 5 occurs there. If the surface 25 of the object 7 is located in the first plane 101, the focal points 5 are correspondingly formed on the object surface 25 (see also FIG. 2 ). The multiple primary beams form a crossover point 108, near which a high-speed deflector 110 is located. The latter is used to synchronously deflect the multiple primary beams 3 collectively so that the multiple focal points 5 are moved simultaneously over the object surface 25. The deflector 110 is driven by the control unit 800 so that the surface 25 of the object 7 is scanned with the multiple focal points 5 and multiple two-dimensional image data of the surface 25 can be acquired. In addition, a further quasi-static deflector 107 is arranged, the latter being able to align the multiple primary beams 3 in a centred manner around the optical axis 105 .

[0054] The objective lens 102 and the projection lens arrangement 205 of the projection system 200 provide a second imaging particle-optical unit for imaging the first plane 101 onto the detection plane. The objective lens 102 is therefore a lens or lens system that is part of both the first and second particle-optical units, while the field lenses 103, 307 and 308 belong only to the first particle-optical unit, or illumination path 13, and the projection lens 205 belongs only to the second particle-optical unit, or detection path 11.

[0055] A beam splitter 400 is arranged in the beam path of the first particle-optical unit between the field lens 103 and the objective system 102. The beam splitter 400 is also part of the second optical unit in the beam path between the objective system 102 and the projection objective 205. The beam splitter 400 additionally comprises at least a correction element 420 in the illumination beam path 13 which can be used to compensate for aberrations of the beam splitter 400.

[0056] The detection system 200 includes several additional components, such as an electrostatic lens 206 and several additional magnetic lenses 208 and 209. Together with the projection lens 210, the lenses focus the secondary beams onto a spatially resolved detector, compensating for the resulting imaging scale and distortion of the beams so that the raster arrangement of the focal points 15 of the secondary beams 9 on the detector plane 207 remains constant. In this case, the first and second magnetic lenses 208 and 209 are designed inversely to each other and have magnetic fields in opposite directions. By appropriately driving the magnetic lenses 208 and 209, Larmor rotation of the secondary electron beams can be compensated. Additionally, a further crossover point 212 of the secondary beams, at which an aperture stop 214 is located, is located within the projection objective 205. Furthermore, the detection system 200 has available a second global beam deflector 222 arranged near the crossover point of the secondary beam 9 and operated synchronously with the first beam deflector 110 to compensate for the beam deflection of the primary beam 3 so that the focal point 15 of the secondary beam 9 remains in a fixed position on the detection plane 207. The detection system 200 has available further correction elements, such as a multi-aperture plate 216 and a further third deflection system 218.

[0057] Further information relating to such multi-beam particle beam systems and the components used therein, such as, for example, particle sources, multi-aperture plates, and lenses, can be gleaned from the international patent applications WO 2005 / 024881, WO 2007 / 028595, WO 2007 / 028596, WO 2011 / 124352, and WO 2007 / 060017, as well as the German patent applications with publication numbers DE 102013016113 and DE 102013014976, the disclosures of which applications are incorporated in their entirety into the present application by reference.

[0058] The multiple particle beam system further comprises a computer system or control system 800 configured for both controlling the individual particle-optical components of the multiple particle beam system and for evaluating and analyzing the signals acquired by the multi-detector 207. In this case, the control or controller system 800 may be built from multiple individual computers or components. By way of example, the control unit 800 has a first control module 820 available for the detection system 200 and a second control unit 830 for the illumination system 100.

[0059] Furthermore, the control unit 800 has a control module 503 that can be used to supply a voltage to the sample 7, which will hereinafter also be referred to as the sample voltage. In use, an electric field 113 is generated between the objective lens 102 and the surface 25 of the object 7, for example of a wafer. In use, the electric field 113 decelerates the primary particles of the primary beam 3 before they reach the sample surface 25, generating a further focusing effect on the plurality of primary beams 3. At the same time, this electric field 113, in use, serves to accelerate secondary particles emerging from the surface 25 of the object 7. The electric field 113 is therefore also referred to as the extraction field 113, although at this point explicit reference is made to the fact that the extraction field 113 has two effects: first, the effect of decelerating and focusing the primary beam 3, and second, the effect of aligning and accelerating the secondary electron beam 9. The extraction field 113, or the strength and uniformity of the extraction field 113, therefore has a significant influence on the raster alignment of the primary particle beam 3 and on the shape and size of the focal spot 5 of the primary particle beam 3, as well as on the yield of secondary particles and the shape and direction of the secondary particles 9. In the ideal case, the secondary particles are extracted perpendicularly, or perpendicular to the object surface 25. A non-uniform extraction field 113 can, for example, lead to deviations in the direction of the secondary beam 9, which, together with further aberrations, lead to deviations in the raster alignment of the secondary beam 9 in the detection path 13 or to changes in the size and shape of the focal spot 15 of the secondary beam 9 on the detector 207. A non-uniform extraction field 113 already leads to an earlier deflection of the primary particles and thus to deviations in the raster alignment of the illumination beam 3 and changes in the shape and size of the focal spot 5 of the primary beam 3 on the object surface 25. Therefore, non-uniformities in the extraction field 113 overlap and amplify each other in a two-fold manner. Global variations in the extraction field 113 can occur due to global effects, such as tilt or z-offset of the object 7, or uniform charging of the object 7. Local variations in the extraction field 113 can occur due to local effects, such as differences in general height of the object 7 caused by the object edge, or edge of the wafer, object topography, or local charging. The variations in the extraction field 113 can be static or time-varying.For example, static variations arise from the unchanging topography or edges of the object 7. Time-varying variations arise from time-varying charging effects. In particular, the raster array is very sensitive to variations in the extraction field 113 at the object 7 or between the object surface 25 and the electrodes in the objective lens 102 of the multi-beam microscope 1.

[0060] 2 shows a cross-sectional view of a multi-beam system 1 according to a first embodiment of the present invention. The illumination system 100 includes a particle source 301, a multi-beam generating device 300 having a slow compensator 330 of the multi-beam generating device 300, and a fast compensator 332 of the multi-beam generating device 300. By way of example, the magnetic condenser lenses 303.1 and 303.2, which allow the beam intensity at the entrance to the multi-aperture plate 305 to be varied, are the slow compensator 330. By way of example, the deflector array 306.2, which can rapidly deflect multiple primary beams, is the fast compensator 332. The illumination system 100 further includes a slow compensator 130, e.g., magnetic lenses 103.1 and 103.2, or a further quasi-static beam deflector 107. The slow compensator 130 is further formed by a magnetic lens of the objective lens system 102, a beam splitter 400, and a correction element 420 of the beam splitter. The illumination system 100 further comprises a fast compensator 132, e.g. a deflector array 390 or a fast electrostatic focusing lens in the objective lens system 102. The objective lens 102 may additionally comprise further rapidly drivable electrode segments according to a third embodiment of the invention for setting a uniform extraction field. The drivable components (301, 330, 332, 130, 132) of the illumination system 100 are connected to a control unit of the illumination device 830 and are driven by the latter during operation. Furthermore, the illumination system 100 comprises a first fast beam deflector 110 for fast collective beam deflection of the primary beam 3. The beam deflector 110 is driven by a scanning module 860.

[0061] In addition to the spatially resolved detector 207, the detection system 200 of the multi-beam system 1 further includes a slow compensator 230 of the detection system 200 and a fast compensator 232 of the detection system 200. For example, the magnetic lenses 208 and 209 and the magnetic lens 210 are the slow compensators 230. For example, the beam deflector 214 or the electrostatic lens 206 is the fast compensator 232. The detection system 200 further includes a second fast beam deflector 222 for fast collective beam deflection of the secondary beam 9. The second beam deflector 222 is driven synchronously with the first beam deflector 110 by the scanning module 860. The secondary beam 9 passes through both the first beam deflector 110 and the second beam deflector 222. The second beam deflector 222 is designed to perform a so-called anti-scan, compensating for a scanning movement of the secondary beam 9 that would otherwise occur upon incidence on the detection unit 207. The detection system 200 further has available a further sensor 238, for example arranged in the periphery of the aperture stop 214.

[0062] The semiconductor wafer 7 is positioned below the objective lens 102 by a displacement stage 500. The displacement stage 500 can be a six-axis displacement stage capable of positioning the surface 25 of the sample 7 in the object plane or first plane 101 with six degrees of freedom. In this case, the positional accuracy in the z-direction is less than 50 nm, for example, better than 30 nm. The position of the displacement stage 500 is monitored and controlled in this case by a sensor 520 of the control unit 880. The sample voltage for a uniform extraction field is controlled via the control module 820 of the detection unit 820 together with the slow and fast compensators 230, 232 of the detection module 200. In addition, according to the second exemplary embodiment, it is possible to drive at least one further correction electrode arranged in the periphery of the wafer 7.

[0063] The detection unit 207 may include at least one scintillator for converting secondary electrons into light and multiple photo-optical detectors. Such detectors may be CMOS or CCD sensors or may be formed by multiple photodiodes, e.g., avalanche photodiodes. The sensor may be located directly behind the scintillator, or an optical imaging system or light guide may be located between the scintillator and the sensor. It is also possible to use a sensor that directly detects electrons and converts them into an electrical signal. A special form of the detection unit is described in German Patent Application No. DE 102018124044, the disclosure of which is incorporated herein by reference in its entirety. There, the detection unit 207 consists of a scintillator on which multiple focal points 15 of the secondary particle beam are formed. The generated light is imaged onto a fiber bundle via an imaging system, each fiber being coupled to a photodiode. The imaging system further includes a beam splitter that directs a portion of the generated light onto the CMOS sensor. This sensor can be used to monitor the raster array as well as the shape and size of the individual foci 15. Instead of using a beam splitter to outcouple part of the light, it is alternatively possible to capture and evaluate the light emitted by the scintillator in the reverse direction, i.e. in the direction of the incident particle beam, through a CMOS camera.

[0064] The detection unit 207 is connected to an image data converter 280, which converts analog electrical signals, e.g., time series of sensor voltages, into time series of digital signals. For example, the image data converter 280 for the J secondary beams can be implemented using a parallel computer architecture. In this case, the image data converter 280 includes parallel-connected analog-to-digital converters, which can be designed, for example, as parallel-connected ASICs. The scanning frequency FS of the two deflection systems 110 and 222 roughly corresponds to the reciprocal of the dwell time of the primary beam 3 at the focal point 5 on the sample surface 25. This dwell time is typically 50 ns. However, dwell times of 10 ns, 20 ns, or 100 ns are also possible. During image recording, the readout frequency, or frequency FC of data conversion by the image data converter 280, corresponds to the scanning frequency FS. Thus, digital image data for multiple image pixels are acquired for multiple focal points with FS = FC. A typical clock rate for the deflection system and analog-to-digital conversion using image data converter 280 in this case is FS=FC=10 MHz to 100 MHz, although higher clock rates above 100 MHz are also possible.

[0065] The control unit 800 has available a control module 830 for controlling the illumination device 100, a control module 880 for controlling the displacement stage 500, and a control module 820 for controlling the detection unit 200. A data acquisition device 810 is connected firstly to the image data converter 280 and secondly to an image data memory 814. In addition, a digital image processing unit 812 is arranged between the image data memory 814 and the data acquisition device 810. A sensor data module 818 receives time-averaged data of the raster array of the secondary beam 9 and other sensor signals, for example from the further sensor 238 of the detection module 200 or from the control module of the displacement stage 500 with the position sensor 520. The control unit 800 further has available a control processor 840 that evaluates the sensor data of the sensor data module 818 and determines corresponding control signals, for example parameters for setting components of the illumination system 100 and the detection system 200.

[0066] In a multi-beam particle beam system 1 as per Figure 2, the sample 7 is at a potential for generating the above-mentioned extraction field 113 which firstly decelerates the primary particles and secondly accelerates the secondary particles emerging from the sample. To set the sample potential, the receiving stage for the sample or wafer 7 is connected to a voltage supply 503 for the object voltage.

[0067] A method for wafer inspection is described with reference to FIG. 3. FIG. 3 shows a surface 25 of a wafer 7 having a series of first, second, and third inspection positions 33, 34, and 35. The third inspection position is located at a distance 47 from the wafer edge 43. With its top surface 25, the wafer is positioned in a first plane or object plane 101 of the multi-beam system 1. In this case, the wafer is positioned in the optimal focal plane of the multiple primary beams 3. In this example, the multiple J primary beams 3 have a rectangular raster arrangement 41. The center 21.1 of the first image field 17.1 scanned by the multiple primary beams 3 is approximately aligned with the symmetry axis 105 of the objective lens 102. The image fields 17.1 to 17.k correspond to different inspection positions for a series of wafer inspection tasks. For example, the predetermined first and second inspection positions 33 and 34 are read from a control file. In this example, the first inspection site 33 is adjacent to the second inspection position, and the image fields 17.1 and 17.2 have a first center position 21.1 and a second center position 21.2. The first center position 21.1 of the first inspection position 33 is then initially aligned under the axis 105 of the objective lens 102. In this case, methods for detecting the coordinate system of the wafer and for aligning the wafer are known from the prior art.

[0068] Next, the J primary beams 3 are deflected together by scanning the deflector 110 across each of the smaller subfields 31.11 to 31.MN, with each beam scanning a different subfield, e.g., subfield 31.mm or subfield 31.m(n+1), in the process. Exemplary scanning patterns or scan paths 27.11 and 27.MN are shown diagrammatically within the first subfield 31.11 and the last subfield 31.MN. Furthermore, by way of example, the focal points 5.11, ..., 5.MN of each different primary beam are shown in the upper left corner of their assigned subfield. Furthermore, each subfield 31 has a center, and the centers 29.mn of the subfields 31.mn are illustratively labeled with crosses. Here, the multiple subfields 31.11, ..., 31.MN are scanned in parallel by multiple J primary beams, each having a focal point 5.11-5.MN. Digital image data records are acquired for each of the J subfields 31.11-31.MN, each containing, for example, 8000 x 8000 pixels. In this case, the pixel size can be specified, for example, 2 nm x 2 nm. However, different pixel counts are possible, ranging from 4000 x 4000 to 10000 x 10000 pixels or more, and other pixel sizes, for example, 3 nm, 1 nm, or smaller, can be set. Once the digital image data for the first image field 17.1 have been acquired, the image data for the individual subfields 31.1-31.MN of the first image field 17.1 are combined to form an image data record. Then, a second inspection position 34 is positioned below the axis of the objective lens 102, and digital image data for the second image field 17.2 is acquired. The procedure continues, for example, with a second inspection position 35 having an image field 17.k. Naturally, the raster arrangement 41 of the primary beam 3 is not limited to a rectangular raster arrangement; other raster arrangements include, for example, a hexagonal raster, or an arrangement of the primary beams in concentric rings or in a single ring. In this case, the lateral resolution of the digital image data is essentially determined by the diameter of the focus 5 of the primary beam 3 on the object surface 25.4 shows a typical raster array 41 having an arrangement of a plurality of J=91 primary beams 3 with a hexagonal raster having a pitch p of, for example, 10 μm on a surface 25. Some beams along one direction are indicated by 5.11, 5.21, 5.31, 5.41, and 5.51. For illustrative purposes, the outer foci at the periphery are additionally connected by lines 45, which indicate the edges of an ideal raster array.

[0069] During an inspection task, the raster array 41 is synchronously displaced across the object surface 25 and image data of the surface 25 of the wafer 7 is acquired. Anti-scanning using the deflection device 222 ensures that the raster array 41 of the secondary beam 9 remains fixed in position or remains stationary on the detector 207. However, there may be changes in the raster array 41 in the detection plane of the detector 207 before or during the inspection task, which changes significantly disrupt the position and reproduction fidelity of the semiconductor structures on the object surface 25. In this case, a disruptive change in the raster array 41 occurs in the primary beam 11, resulting in a change in the raster array 41 of the focal point 5 of the primary beam 3. The change in the raster array 41 of the primary beam leads to a corresponding change in the raster array 41 of the secondary beam 9, the latter of course occurring at the focal point 5 of the primary beam 3 on the object surface 25. The variation in the raster arrangement 41 of the secondary beams 9 is further amplified in the secondary path and may ultimately result in, for example, a varied raster arrangement 41a-41g of the foci 15 of the secondary beams 9 in the plane of the detector 207. The varied raster arrangement of the foci 15 of the secondary beams 9 together with the varied shape and size of the foci 15 is also referred to as a composite multi-beam effect.

[0070] To obtain a raster array 41 of a plurality of J secondary beams 9, the multi-beam system 1 according to the present invention can be configured to implement various methods. In a first method, signal temporal averaging is performed by an image data converter 280 through temporal integration of an image signal. To achieve this purpose, the image data converter 280 is operated at a data conversion frequency FC that is significantly lower than the scanning frequency FS, i.e., FC < FS, whereby the averaging of the image data is performed over a plurality of foci on the object surface 25. As an example, the data conversion frequency FC can be 1 / 10 of the scanning frequency, FC < FS / 10, or even smaller, for example, FC < FS / 100, or FC < FS / 1000, or even significantly smaller than that. In one example, image data acquisition is performed using two detectors in parallel. The first detector is operated for high-resolution imaging using a first image data converter at a first data conversion frequency FC1 = FS equal to the scanning frequency, and the second detector is operated using a second image data converter at an image evaluation frequency. Therefore, only a few or only one image of the raster array is determined during the high-resolution imaging of the image portion at the inspection position using the first detector. In one example, the high-resolution image includes 8000 × 8000 pixels and has a dwell time of 50 ns or a scanning frequency of FS = 20 MHz, which results in an image recording time T2 of approximately 3.2 s. As an example, the second detector camera can be a CMOS sensor having a frame rate of 10 to 100 frames per second with an image recording time T1 of, for example, 0.1 s to 10 ms, or an image frequency of 1 Hz to approximately 0.1 kHz. Therefore, approximately 30 to 300 inspection images of the raster array can be generated while recording the high-resolution image.

[0071] As an alternative to reducing the data conversion frequency FC, the scanning frequency can be increased. For example, the scanning frequency for measuring the raster array 41 can be increased tenfold, from 50 MHz to 500 MHz. For example, the scanning frequency FS can be increased to FS=10×FC or FS>100×FC. In a first method, signal time averaging is performed by the sensor data module 818, which evaluates an average value for each secondary beam from the spatially resolved digital image data to detect changes in the raster array. In a second method, signal time averaging is performed by high-speed scanning using the scanning deflectors 110 and 222.

[0072] FIG. 5 shows several examples of variations in the raster array 41 relative to the ideal raster array 45. FIG. 5 illustrates deviations in the raster array and shape and size of the focal points 15 of the secondary beams on the detector 207. FIG. 5a illustrates variations in the pitch of beams with a spacing or pitch of pr > ps. As mentioned above, the ideal pitch is, for example, ps = 10 μm. Variations in the imaging scale result in variations in the spacing or pitch of, for example, 0.1%, or even less, for example, 2 nm. The scale error accumulates between the most widely spaced beam focal points in the raster array 41a due to the change in pitch multiplied by the number of beams, accumulating up to 18 nm in the example of FIG. 5a with a maximum of nine beams along the diagonal. Through magnification of the imaging of the raster array on the object surface 25 onto the detector 207 by 100× to 300×, the error accumulates up to 2 μm to 5 μm. 5a shows a magnification of the raster array 41a with an increased pitch pr, although the pitch pr could also be reduced. A very large magnification change is shown for illustrative purposes.

[0073] Through the magnification of the detection path, the compound multi-beam effect is imaged in a magnified manner onto the detection camera. In addition, the causes of the compound multi-beam effect (charges on the wafer, edges, tilt, etc.) also affect the secondary electrons. For example, in this case, the lower energy secondary electrons react more sensitively to variations in the extraction field than the higher energy primary electrons, and further distortions are added to the deviations of the primary beam, e.g. due to sample effects.

[0074] FIG. 5b shows a raster array 41b offset laterally by an offset vector d. The offset, displacement, or movement of the raster array results in an offset in the digital image data, which can cause aberrations, for example, when stitching multiple image portions. FIG. 5c shows a compressed raster array 41c. The compression of the raster array corresponds to a change in spacing or pitch in only one direction, e.g., the x-direction, as indicated here by the altered pitch prx. Additionally, local effects can occur, resulting in only local beam deflections of individual beams within the raster array 41d. This is illustrated in FIG. 5d using the example of five beams, specifically the target and actual positions 15.is and 15.ir of the beams, as well as the local displacement 61 of the spot positions. FIG. 5e shows the effect of a deviated beam shape of at least one beam within the raster array 41f. Beam 15.jr has an ideal beam shape, from which, for example, beam 15.ir deviates in size, and further beam 15.ka deviates in shape. Figure 5e shows a simplified example of systematic deviations in the shape or size of the focal points across the raster array. In this example, a profile can be inferred from at least three shapes or sizes for at least three focal points, thus making it possible to distinguish between local effects and global effects such as tilt. This example reveals the effect of an oblique tilt of the focal plane or best setting plane 101 relative to the wafer surface 25, with focus 15.ua positioned closer to the objective lens than focus 15.qa. For example, by detecting the shapes and sizes of foci 15.qa and 15.ua as well as the central focus 15.00, systematic tilt can be distinguished from other causes of deviations in the shape and size of the beam focus. However, in principle, it is also possible to determine deviations in the shape and size of all focal points.

[0075] Finally, FIG. 5f shows a twisted raster array, twisted at an angle A relative to the ideal raster array 45.

[0076] Other deviations in the raster arrangement are also possible, for example trapezoidal distortion. Furthermore, deviations usually occur as a combination or superposition of individual deviations.

[0077] The multi-beam system 1 is configured using predetermined parameters for the inspection task. The control processor 840 is configured to determine various predetermined parameters for the inspection task during operation and use them to drive the components of the multi-beam system 1. The components driven by the parameters include, for example, the slow and fast compensators 130, 132 of the illumination system 100, the slow and fast compensators 330, 332 of the multi-beam generating device 300, the slow and fast compensators 230, 232 of the detection system 200, or the displacement stage 500. For example, the spacing or pitch ps of the individual beam focal points 5 on the surface 25 of the wafer 7 is set through these parameters, and the focal points are set within an optimal focal plane within the plane 101. Further variable parameters include the beam intensity, which can be set using, for example, the condenser lens 303. Noise performance can be set through the beam intensity and dwell time. The parameters determining the strength of the extraction field further affect the resolution and the kinetic energy of the secondary electrons. Some twisting of the raster array on the object surface occurs through the focusing effect of the magnetic lenses of the objective lens system 102. The scanning program is set using further parameters. Further components of the detection system are driven by the parameters so that the multiple focal points 15 of the secondary beams 9 are incident on the detector 207 at predefined positions and held constant there, so that image data can be acquired in a time-series sequence. Collectively, the set of parameters is also referred to as an operating point. The control processor 840 of the multi-beam system 1 according to the first embodiment is designed to operate the multi-beam system 1 at multiple different predefined operating points.

[0078] For example, the sensor data module 818 (see FIG. 2 ) is designed to average object contrast through time averaging of image data during operation and measure the focal position 15 of the current raster array 41 of the secondary beam 9. Additionally, the shape and size of at least one of the focal points 15, for example, focal point 15.ir or focal point 15.ka, can be determined. The sensor data module 818 is configured to transmit the current raster array 41 and the shape and size of the at least one focal point 15 to the control processor 840. The control processor 840 is configured to determine from them deviations of the current raster array 41 from an ideal raster array 45 at a preset operating point, as well as deviations of the shape and size of the at least one focal point 15. The control processor 840 is configured to infer disruptive effects from the deviations and determine corresponding parameter changes suitable for reducing the disruptive effects. Deviations of the shape and size of the raster array 41 and of the at least one focal point 15 of the secondary beam 9 corresponding to disruptive effects can be predetermined. Similarly, required changes in the parameters of the operating points suitable for reducing disruptive effects can be predetermined and stored. To this end, control processor 840 includes a storage module in which parameters for various operating points as well as parameter changes suitable for reducing particular disruptive effects are stored.

[0079] Several destructive effects or causes for changes in raster alignment and changes in focal spot shape and size are listed below.

[0080] Mechanical defocus, for example, as a result of a wafer's varying thickness, can result in a change in the magnification or pitch of the focal spot within the raster array, resulting in an increased spot diameter for the raster array 41a. Additionally, there can be a change in the size of the focal spot, as shown, for example, in FIG. 5e, based on focal spot 5.ir. Mechanical defocus can be compensated for by z-movement of the stage or displacement stage 500. Alternatively, or in addition, the strength of the extraction field 113 can be changed, and additional electrostatic components in the illumination and detection paths can be configured to focus onto the defocused object surface. Extraction fields are described below. Changing the excitation of a magnetic lens, e.g., the objective lens 102, provides a further option for compensating for mechanical defocus.

[0081] For example, local tilt of the sample surface, when the wafer is bowed, causes a uniform gradient of the extraction field, offsetting the raster array 41b relative to the raster array 41b. Additionally, typical astigmatism, e.g., constant astigmatism, can occur across multiple beams, resulting in a constant elliptical beam shape, such as the beam shape of beam 5.ka in FIG. 5e. As a correction strategy, tilting the wafer 7 is possible. Alternatively, it is possible to generate a targeted uniform field gradient in the extraction field 113 that counteracts the effect of tilting the object surface 25 or the field gradient of the extraction field 113. The extraction field is described below. The offset of the raster array 41b of the primary beam 3 on the wafer surface 25 can be compensated for by the deflector 107 in the primary path. Alternatively, or in addition, appropriate correction of astigmatism can be performed, for example, using available fast and slow correction elements 130, 132 and deflection systems 110, 222.

[0082] The effect of the non-uniform extraction field 113 at the edge of the wafer, combined with constant astigmatism, causes a shift or offset of the raster array 41b. Below, measures for correcting the edge effect are described. The combined multi-beam effect at the edge of the wafer 7 and the effect resulting from tilt can be very similar. Compensation strategies can be similar. However, at the edge of the wafer, aberrations occur that vary more across the image field; for example, there is no constant offset and uniform astigmatism across the image field, but rather there is some distortion of the position of the focus or a more complex field dependence of the astigmatism.

[0083] Uniform charging of the sample surface 25 similarly results in a change in magnification and an enlarged spot diameter. At the same time, a lateral displacement of the raster array 41b occurs, corresponding to FIG. 5b. In this case, the extraction field 113 can be dynamically increased in a manner synchronous with the charging, for example, to counteract the charging. To achieve this, the sample potential is dynamically and synchronously adapted, for example, via voltage V2, to maintain the extraction field constant and counteract the sample charging. Potentials V1 and V3, which depend on the sample potential or voltage V2, are also similarly adapted to maintain the extraction field constant (see FIGS. 6-8 and the following discussion). In addition, additional electrostatic components in the illumination path 13 and detection path 11 can be configured for focusing the primary beam onto the charged object surface 25. The offset of the raster array 41b of the primary beam can be compensated for by a beam deflector 107 in the illumination system. Charging of the object surface 25 can also cause a change in the kinetic energy of the extracted secondary electrons 9 and therefore a changed rotation of the raster array 41 of the secondary electron beam 9, as shown in Figure 5f. The rotation of the raster array 41 of the secondary electron beam 9 can be compensated for by driving the magnetic lens pairs differently.

[0084] Local charging of portions of the sample surface at the inspection positions (33, 35) relative to the image field 17 of the raster array 41 of the primary beam 3 also causes a change in magnification in conjunction with a lateral offset. But in addition, a change in the shape of the focal points 5 of the edge beams of the raster array 41 occurs. Edge beams are those beams that no longer have adjacent beams in one direction. The effect of the change in shape and size of the focal points 5 is particularly noticeable at the corners of the raster array 41.

[0085] Inspection positions, such as inspection positions 33 and 35, are affected by latent charging of preceding or adjacent inspection positions or adjacent image fields. This can occur, particularly when inspection position 33 is stitched together from two image fields 17.1 and 17.2, as in the example of FIG. 3. This results in a non-uniform gradient of extraction field 113 and a raster array offset corresponding to raster array 41b. In addition, a raster array distortion corresponding to raster array 41c occurs. Furthermore, a linearly increasing profile of astigmatism can occur across multiple beams, resulting in an elliptical beam shape, such as the beam shape of beam 5.ka in FIG. 5e. For example, these effects can be influenced by changing the sequence of inspection positions.

[0086] Local charging only distorts the individual spot positions or spot shapes, as shown in FIG. 5d. Local charging effects can be influenced by optimizing the operating point or by changing the scanning strategy. In this case, adjusting the operating point can include adjusting the landing energy or the beam current. In this case, changing the scanning strategy can include fast scanning combined with averaging over many frames generated with short dwell times (also known as “frame averaging”). In this case, the beam current can be further reduced, and the number of images averaged can be increased. A further scanning strategy consists in decomposing the subfield 31 into smaller subfields that are scanned individually in succession and then stitched together. A further option involves the targeted introduction of a discharge process during image generation; such a discharge process can be generated by a temporary pause during imaging or by stimulated discharge, for example, by operating a multi-beam system in what is known as mirror mode. In a further example, the test position of the measurement object can be pre-charged by prior irradiation. For example, the scanning procedure at the inspection position can be performed at a lower speed and with a smaller exposure dose in order to reduce or compensate for local charging effects. Further measures are the adjustment of the subfield size through the deflection scanner 110 and the digital correction of the lateral position of the individual digital images of the individual subfields according to the beam offset 61 of the individual primary beams, e.g., primary beam 15.ir in Fig. 5d.

[0087] The control processor 840 is configured to store a predetermined relationship of destructive effects or causes for composite multi-beam aberrations. A composite multi-beam aberration is understood to mean a change in the raster array 41 as well as a change in the shape and size of at least one focus, e.g., three focuses, or all focuses. Furthermore, the control processor 840 is configured to store predetermined parameters for correcting or compensating for the destructive effects. The control processor is further configured to infer the destructive effects or causes from the currently determined composite multi-beam aberrations. In this case, the control processor relies on the stored relationship of the destructive effects or causes and appropriately alters the parameters to correct or compensate for the destructive effects or causes, and drives the multi-beam system 1 using the altered parameters.

[0088] Therefore, a first embodiment of the multi-beam system includes an improved method for operating the multi-beam system 1 for inspecting an object 7, preferably a semiconductor wafer. The method is shown in Figure 13 and includes the following steps:

[0089] Step 1: A substantially planar object 7 is placed on the receiving area 505 of the displacement stage 500, and the displacement stage 500 is used to position the object surface 25 of the object 7 within the object plane 101.

[0090] Step 2: Illuminate the object surface 25 with a plurality of J focal points 5 generated by a plurality of J primary beams 3 in a predefined raster arrangement 41 .

[0091] Step 3: Scan the object surface 25 with a plurality of J focal points 5 by synchronously deflecting the plurality of J primary beams 3 of the predetermined raster arrangement 41 over a first plurality of scan positions.

[0092] Step 4: Collect the secondary particles generated from the object surface 25 at the multiple focal points 5 of the primary beam 3 and focus the secondary particles onto a spatially resolved detector 207.

[0093] Step 5: Detect the secondary particle signals using the spatially resolved detector 207 to generate an image of multiple secondary particle foci 15. In one example, detecting the signals includes time averaging the secondary particle signals over the second multiple scan positions.

[0094] Step 6: Determine a composite multi-beam effect consisting of a variation in the raster arrangement 41 of the multiple focal points 15 of the secondary particles relative to a predetermined raster arrangement 45 from the image of the multiple focal points 15 of the secondary particles. In one example, determining the variation in the raster arrangement 41 additionally includes determining a deviation in the beam shape of at least one focal point 15 of the multiple focal points 15 of the secondary particles, the deviation in the beam shape including a deviation in ellipticity or diameter.

[0095] In this case, the deviations of the raster array 41 include at least one of the following errors: scale error 41 a, offset error 41 b, distortion 41 c, twist 41 g, or local deviations 41 d of only individual beams of the raster array 41.

[0096] The change in shape and size of the focal point 15 includes at least one of the following aberrations: constant astigmatism, linear astigmatism with a linear dependence of the astigmatism on the position in the raster array 41, constant focus aberration, linear focus aberration with a linear dependence of the focus aberration on the position in the raster array 41.

[0097] Step 7: Determine at least one cause of variation in the raster array 41, where the variation in the raster array 41 includes offset error, isotropic scale difference, distortion or magnification difference between two non-parallel directions, rotation, or keystone distortion.

[0098] In a further step, a decomposition of the variations in the raster array 41 can be performed according to global and local variations in the raster array.

[0099] Step 8: Determine optimized parameters for driving components of the multi-beam system to compensate for the change in raster alignment, and drive the multi-beam system using the optimized parameters.

[0100] In this case, the determination is performed, for example, using a stored table of parameter changes appropriate for compensating for the individual normalized effects of the combined multi-beam effect. The optimized parameters are then calculated, for example, by multiplying the magnitude of the raster array change by the associated stored parameter change. A specific example of the first embodiment includes determining a local tilt error of the planar object surface 25 from a combination of an offset error of the raster array 41 and a beam shape deviation in the form of ellipticity. In a further example, the first embodiment includes determining a spacing error of the planar object surface 25 from a combination of a scale difference of the raster array 41 and a beam shape deviation in the form of a diameter deviation of at least one focal point. In a further example, the first embodiment includes determining a global charging effect of the planar object surface 25 from a combination of a scale error of the raster array 41 and an offset of the raster array 41 in the case of a virtually constant beam diameter. In a further example, the first embodiment includes determining a distance from a topographical feature, e.g., an edge of the object 43, from an offset of the raster array 41 and a distortion in the direction of the offset or a magnification difference between two non-parallel directions. In a further example, the first embodiment includes determining a local charging effect from an irregular variation of the raster array, the irregular variation consisting of at least two different positional deviations of at least two focal points from a predetermined raster array. In a further example, the first embodiment includes determining a local charging effect from an irregular variation of the raster array, the irregular variation consisting of at least two deviations of the at least two focal points, the deviations including at least one beam shaping deviation and at least one positional deviation from a predetermined raster array.

[0101] Step 9: Set the optimized parameters of the multibeam microscope in the illumination system, of the extraction field, and, if needed, also of the detection system, and capture a high-resolution image of the object surface.

[0102] The optimized setting parameters include parameters of components in the illumination path 13 and the detection path 11 of the multi-beam system 1, and may also include realignment of the wafer 7 with the displacement stage 500 at the first inspection position (33, 35). Furthermore, an extraction field 113 is disposed in the illumination path and the detection path, and setting the optimized parameters of the multi-beam microscope includes driving a correction electrode to influence the extraction field 113 at the inspection position (33, 35) on the surface 15 of the wafer 7. The compensator includes a deflection device 107 to compensate for the offset of the raster array 41 on the surface 25 of the wafer 7, as well as changing the operating point of the multi-beam system 1, changing the scanning program for the beam deflector 110, and changing the digital image evaluation, for example, to set the scale of the raster array 41.

[0103] Between steps 8 and 9, there may optionally be a switch from the second operating method for obtaining a composite multi-beam effect to the first operating mode for rapid and high-resolution image capture of a portion of the object surface in step STU.

[0104] Therefore, a method for determining the composite multi-beam effect 41 includes recording a time-averaged inspection image of the raster array 41 of multiple particle beams 9 using a detector camera 207 by scanning a portion of the structured surface 25 of the wafer 7 and averaging the image contrast of the surface structures of the wafer 7, and analyzing the inspection image with the aim of determining deviations of at least one of the raster array 41 of the incidence locations 15 of the multiple particle beams from a predetermined or ideal raster array 45, as well as changes in the shape and size of the focal points 15 of the particle beams.

[0105] In one example, averaging the image contrast is achieved by rapidly scanning a portion of the surface 25 of the wafer 7 with an image recording time of T1 < T2, preferably T1 < T2 / 10, for example, T1 < T / 100. Here, T2 corresponds to the time for recording an image of a portion of the surface 25 with high spatial resolution and a pixel size of 2 nm, 1 nm, or less. T1 is typically less than 100 ms, preferably less than 10 ms. In one example, averaging the image contrast of the surface structure of the wafer 7 is performed by temporally averaging the detection signal.

[0106] Particularly, at the edge of the object, it has been found that a multi-beam effect occurs as a result of the non-uniform extraction electric field. As an example, electrons are deflected in the direction of the wafer edge. FIG. 6 shows an example. A plurality of focal points are formed within the image field 17 in the vicinity of the edge 43 of the wafer 7 by a plurality of primary beams 3a. The counter electrode 151 forms the lower end of the objective lens unit 102 and is at a voltage V1. As an example, the voltage V1 can be at ground potential or V1 = 3 kV. The voltage difference between the wafer surface 25 and the counter electrode 151 is typically 20 kV to 35 kV, for example, 30 kV. As an example, the wafer is at a voltage of -27 kV.

[0107] The objective lens unit includes a solenoid 149 for forming a focusing magnetic field intended to focus the primary beam on the wafer surface 25. A voltage V2 ranging from 1 kV to 4 kV, e.g., 2 kV, is supplied to the wafer 7 or wafer surface 25 through a wafer receiving area 505 in the displacement stage 500. An extraction field 113a is generated between the counter electrode 151 and the wafer surface 25 through a voltage difference V2-V1. The extraction field 113 typically has a field strength of 1 to 5 kV / mm at the wafer surface 25, resulting in the deceleration of the primary electrons 3. In this case, the wafer receiving area 505 is insulated from the wafer stage 500, which is at ground potential or 0 kV. The extraction field 113a is schematically represented by equipotential surfaces. However, at the edge 43 of the wafer 7, a height difference DW exists, and near the edge 43 of the wafer, the equipotential surface no longer extends parallel to the surface 25 of the wafer 7, and the primary beam 3a is deflected. As a result of the non-uniform edge field, the raster array of the primary beams therefore experiences distortions similar to those shown in FIG. 5c. Additionally, further effects may occur. According to a second embodiment of the present invention, the effects in the edge region are compensated for by an additional electrode in the periphery of the wafer 7. This second embodiment is shown in FIG. 7. A correction electrode 153, supplied with a voltage V3 and insulated from the receiving area 505 via an insulating material 155, is positioned in the periphery around the wafer 7. A correction field is generated in the periphery around the wafer 7 through voltage V3, resulting in a uniform extraction field 113b. The correction electrode 153 has a distance G from the wafer 7 and a height DE above the wafer receiving area 505. The distance G may vary around the circumference of the wafer. The strength of voltage V3 is set based on the different thicknesses DW of the wafer 7, the local distance G between the wafer edge and the compensation electrode 153, and the distance 47 between the test position 35 and the wafer edge 43 so that non-uniformity of the extraction field 113b is minimized. In this case, the thickness DW of the wafer 7 is approximately 0.7 mm, with a deviation of approximately 50 μm to 100 μm. For example, the height DE of the electrode 153 is less than the thickness DW of the wafer 7, and the difference between the compensation voltage V3 and voltage V1 is selected to be larger than the difference between voltage V2 and voltage V1.For example, the thickness is selected so that DE<0.5DW or even less. For example, V3 is set to -2 kV to -4 kV. For example, the wafer 7 is at a voltage difference of |V1-V2| = 28 kV absolute value relative to the counter electrode 151. For example, the correction electrode 153 is at a voltage difference of |V2-V3| = 3 to 6 kV absolute value relative to the wafer 7. The voltage difference V2-V3 is set so that it forms an additional electric field contribution between the wafer edge 43 and the electrode 153, the effect of which is shown by the additional equipotential lines 113c. This electric field contribution ensures smoothing and uniformity of the extraction field 113b between the wafer surface 25 and the objective lens 102. Ideally, the distance G is selected to be as small as possible, for example, 0.5 mm, 0.2 mm, or less. For a consistent extraction field 113b, the wafer 7 must be very accurately centered and must have no variations in thickness DW along its periphery. Local variations in thickness DW, in the height DE of the correction electrode, and in the distance G can be taken into account for each test position by optimally adjusting the setting of the correction voltage V3. Generally, the correction voltage for a uniform extraction field can be set based on the distance of the test position from the wafer edge. In one embodiment, the correction voltage of successive correction electrodes is locally adjusted to the current test position based on an evaluation of the raster-arrayed test image, e.g., based on a previous test position near the wafer edge.

[0108] FIG. 8 illustrates a third embodiment of the present invention. In this third embodiment, the correction electrode 153 is embodied in the form of a plurality of segments, e.g., eight segments 153.1 to 153.8. Furthermore, the counter electrode 151 is embodied in the form of a plurality of segments, e.g., eight segments 151.1 to 151.8. By supplying, e.g., eight different voltages to the correction electrode segments 153.1 to 153.8 or the counter electrode segments 151.1 to 151.8, an extraction field that is as uniform as possible is obtained. The voltage V3.2 for the correction electrode 153.2 is shown in an exemplary manner. In the second and third embodiments, the control unit 800 is configured to make available, via the voltage supply unit 503, both a sample voltage V2 and at least one correction voltage V3, V3.2 for at least one correction electrode 153, 153.2 to achieve uniformity of the extraction field. Furthermore, the control unit 800, in particular the control unit of the illumination device 830, is configured to supply at least one counter voltage 151 to the objective lens system 102 in order to provide a uniform extraction field. The sample voltage V2, the at least one counter voltage V1 and the at least one correction voltage V3 or V3.2 form rapidly variable parameters for driving the multi-beam system 1.

[0109] Accordingly, one embodiment of the present invention comprises a displacement stage 500 for a multibeam microscope 1, the displacement stage 500 having a receiving area 505 for receiving a wafer 7 having an edge 43 and a diameter D, by which a voltage V2 can be applied to the wafer 7 during operation. Furthermore, a ring electrode 153 is disposed on the displacement stage 500 within the periphery of the receiving area 505. The ring electrode 153 has an inner diameter DI>D, which forms a distance between the edge 43 of the wafer 7 and the ring electrode 153 when the wafer 7 is received. The ring electrode 153 is insulated from the receiving area 505 so that a voltage V3 can be applied to the ring electrode 153 during operation. In one example, the ring electrode 153 is formed from a plurality of mutually insulated electrode segments, for example, two, four, eight, or more, to which at least one first voltage V3 can be applied.

[0110] Many effects associated with imaging using a multibeam microscope are very strongly linked to topology. As shown with reference to FIG. 6 , the edge 43 of the wafer 7 or object generally has a significant influence. Since the relative position of the inspection position with respect to the edge 43 of the wafer 7 is known in advance, particularly in the context of wafer inspection, improved adjustments of both the detection path and the illumination path, including the uniform extraction field 113, depending on the distance of the inspection position from the wafer edge can be performed in advance when targeting the inspection site. In a fourth embodiment, a multibeam system and a method for operating a multibeam system are provided, in which parameters of the illumination and detection path components of the multibeam system are set depending on the distance of the inspection position from the edge or boundary of the object. A control unit 800 of the multibeam system 1 is configured to determine the distance of the inspection position from the boundary or edge 43 of the object. The control unit 800 is further configured to determine a combined multibeam effect from the distance and the current operating point of the multibeam system 1. Furthermore, the control unit 800 is configured to determine parameters for operating the multi-beam system 1 at the inspection site, the parameters being suitable for reducing or fully compensating for the composite multi-beam effect. Furthermore, while performing an inspection task with the multi-beam system 1 at the inspection position, the control unit 800 is configured to use the parameters to drive components of the illumination system 100 and the detection system 200 of the multi-beam system 1, including the extraction field 113, and to supply a sample voltage V2 and at least one correction voltage V3 to electrodes on the displacement stage 500 as additional parameters that together are suitable for reducing or fully compensating for the composite multi-beam effect.

[0111] Therefore, the second and third embodiments of the present invention describe a displacement stage 500 having a receiving area 505 for receiving a substantially planar object 7 having an edge 43, a thickness DW, and an outer diameter D, and a ring electrode 153 having a height DE above the receiving area 505. The latter is arranged within the periphery of the receiving area 505 and has an inner diameter DI>D, so that when the object 7 is received, a distance G is formed between the edge 43 and the ring electrode 153. In this case, the electrode 153 is insulated from the receiving area 505 so that different voltage differences can be applied to the ring electrode 153 during operation.

[0112] The second and third embodiments further describe a multi-beam system comprising a displacement stage 500, a measurement device for determining edge effects, and a control unit configured to, during operation, supply a first voltage V2 to the received object and a second voltage V3 at the ring electrode to generate a voltage difference and reduce the edge effects.

[0113] In a third embodiment, the electrode 153 has a plurality of available segments 153.1 to 153.8 to which a plurality of different voltages V3.1 to V3.8 can be applied. In a further embodiment, the objective lens system 102 of the multi-beam system 1 according to the third embodiment has a plurality of available counter electrodes 151.1 to 151.8 to which a plurality of different voltages V1.1 to V1.8 can be applied. The electrode voltage supplies, together with the object voltage, are thus designed to generate a uniform extraction field 113 between the objective lens system 102 and the object surface 25.

[0114] It has been found that many composite multibeam effects depend on the inspection position on the wafer surface 25 and can therefore, in principle, be known in advance. FIG. 9 illustrates an improved method for operating the multibeam system 1 based on this. Using this method, parameters for operating the multibeam system 1, such as the parameters of the components of the illumination system or illumination path 100, the detection system or detection path 200, and the sample or compensation voltage for the uniform extraction field 113, are optimally set. In combination, the parameters for operating the multibeam system 1 are adapted to reduce or completely compensate for the composite multibeam effects at the inspection position. In a first step SI, the wafer 7 is received on the wafer receiving area 505 of the displacement stage 500, and the coordinate system of the wafer 7 is registered. A list of inspection tasks is acquired, and for example, the first inspection task is performed. To this end, the first inspection position of the wafer 7 is centered relative to the optical axis 105 of the multibeam system 1, and the surface 25 of the wafer 7 is aligned within the setting or focal plane 101 of the multibeam system 1. The method for operating the multi-beam system 1 will now be shown in an exemplary manner for a second or subsequent inspection task, but this can also be any inspection task, in particular the first inspection task.

[0115] In a next step SE, a composite multi-beam effect is predicted for the next inspection task. The composite multi-beam effect prediction can be compiled from multiple components, and the composite multi-beam effect can be caused by multiple causes. The composite multi-beam effect refers to the effect shown in the context of FIG. 5, which includes both a deviation of the raster arrangement of multiple primary or secondary beams from a predetermined raster arrangement, as well as a deviation of the shape or size of at least one of the focal points of the primary or secondary beams, for example, three or all of the primary or secondary beams.

[0116] In step SER, the combined multi-beam effect VKR is predicted from the distance of the inspection location from the edge 43 of the wafer 7. Generally, the location of the inspection site relative to the sample edge 43 is known in advance. It is therefore possible to take into account distortions of the raster array 41 through edge effects and distortions as a result of non-uniform charging.

[0117] An example of a method according to the fourth embodiment involves detecting and storing parameters for improved adjustment of the detection path and the illumination path, and setting a voltage for a uniform extraction field for different inspection sites based on the distance from the edge of the object. Then, during inspection of the wafer, optimal parameters for improved adjustment of both the detection path and the illumination path, including setting a voltage for a uniform extraction field, are determined and set according to the next inspection site from the predetermined and stored parameters.

[0118] In step SED, the composite multi-beam effect VKA is predicted from a priori information about the inspection location, for example, from design information, CAD information, or prior measurements.

[0119] In a fifth embodiment, a multi-beam system and a method for operating the multi-beam system are provided, in which parameters of components of the illumination path and the detection path, as well as voltages for the uniform extraction field of the multi-beam system, are set in response to a priori information. In one example, step SED includes determining the composition of the object at least at the next inspection position. In this case, determining the composition of the object includes determining the material composition of the object, for example, from CAD information about semiconductor structures formed in the wafer at the inspection position. For example, possible non-uniform or localized charging effects of the object 7 can be determined from the CAD information. Based on the composition, expected combined multi-beam effects are determined, and appropriate parameters of the multi-beam system are set to reduce or completely avoid the combined multi-beam effects. Alternatively, the a priori information may consist of information from previous inspections of similar inspection sites on other wafers.

[0120] Previous measurements provide additional a priori information. For example, charges may arise from previous measurements and only slowly dissipate through leakage currents. Charging of adjacent, already scanned inspection sites can cause distortions in the raster array, and this information can be taken into account when determining the cause of the deviation. In step SEH, the combined multibeam effect VKS is predicted from information from a previous inspection task, e.g., detection of the current state of the multibeam system 1, or from the expected wafer charging effect from a previous measurement at a previous inspection position. In this case, for example, the position and distance of the next inspection position relative to the previous inspection position can be determined and evaluated. In addition, a time difference relative to the previous inspection task can be evaluated to take into account discharge effects from previous sample charging.

[0121] It has been found that many additional composite multi-beam effects depend on adjacent inspection locations on the wafer surface 25 and can therefore, in principle, be known in advance. In a sixth embodiment, a multi-beam system and a method for operating the multi-beam system are provided, in which parameters of illumination and detection path components, including voltages for a uniform extraction field 113 of the multi-beam system, are set in response to adjacent inspection locations or a previous inspection task. In one example, the multi-beam system includes a control unit for achieving this purpose, which determines, prior to measurement or inspection at the inspection location, a current charge distribution on the object at the inspection location, caused by a previous inspection on the same object. In one example, step SEH includes determining a current charge distribution on the object surface at the inspection location, caused by a previous inspection on the same object. For example, an area of ​​the wafer may be conductively connected, scattering charging effects beyond the inspection site. For example, the area of ​​the wafer may include a capacitance that stores charging effects over a relatively long period of time. Based on the current charge distribution, the expected composite multi-beam effects are determined and appropriate parameters of the multi-beam system are set to reduce or completely avoid the composite multi-beam effects. A special case is formed by a method of repeatedly targeting the same inspection location on the same wafer.

[0122] In step SEC, the predicted VKR, VKA, or VKS from the distance of the test location from the edge, a priori information, or information from a previous test task is combined to predict the combined composite multi-beam effect VKK.

[0123] In step PE, optimized parameters are determined for driving the multi-beam system 1. Starting from an operating point AP of the multi-beam system 1, the multi-beam system is operated with a specific set of parameters. The parameters of the operating point AP describe, for example, the beam current, the beam pitch or a predetermined magnification, the scanning program, the size of the extraction field, or the currents or voltages of electromagnetic or electrostatic components for setting the focal position, as examples.

[0124] In step PEI, standard parameters for the operating point AP are determined according to the next test task at the ideal test position.

[0125] In step PEC, a change in the value of at least one of the parameters is determined from the predicted composite multi-beam effect VKK. Examples of parameter changes suitable for minimizing the composite multi-beam effect are further listed above in conjunction with the first embodiment of the present invention. For example, the determination is performed based on previously determined and stored optimal parameter values, from which the change in the parameter value is determined, for example, by interpolation.

[0126] In step PC, the current parameters PA relating to the operating point AP and including the parameter changes in step PEC are transmitted according to the next inspection task at the next inspection position, and the multibeam microscope 1 is driven using the determined parameter values.

[0127] In step IN, the next inspection task at the next inspection position is performed. To this end, the next inspection position of the wafer 7 is centered with respect to the optical axis 105 of the multi-beam system 1, and the surface 25 of the wafer 7 is aligned in the setting or focal plane 101 of the multi-beam system 1. The multi-beam system 1 is operated using the current parameter values ​​PA, and the inspection task is performed. By way of example, an image portion of the wafer surface at the inspection position is captured with a high resolution and imaging fidelity of better than 5 nm, better than 2 nm, or even better than 1 nm.

[0128] Simultaneously with step IN, in step M, the raster arrangement of the secondary particle beam and the shape or size of at least one focus of the secondary beam path are monitored. The monitoring is performed by acquiring a time-averaged signal from the spatially resolved detector 207 of the multi-particle system 1. As a result of the time averaging during the scanning of the object surface 25, area averaging of the secondary particle signals over multiple object structures on the object surface 25 is achieved, and the current raster arrangement of the secondary particle beam and the shape or size of at least one focus of the secondary particle beam can be reliably detected with a high accuracy of less than 1 nm. The acquisition of the current raster arrangement of the secondary particle beam and the shape or size of at least one focus of the secondary particle beam can be performed multiple times during the inspection task, for example, 10 or 100 times.

[0129] In step Q, the current combined multi-beam effect is determined from the monitoring results of step M. If the current combined multi-beam effect during the inspection task exceeds a predetermined threshold, a signal is issued to step PE to continuously change or update the setting parameters of the multi-beam system 1, and step PE is repeated during the inspection task of step IN. As an example, this therefore also allows a method for driving both the detection path and the illumination path, including voltages for uniform extraction fields, to be used for fast autofocus. Generally, this allows a method for adjusting both the detection path and the illumination path to be used for dynamic correction. Regarding dynamic correction, reference is made to International Patent Application WO2021239380, which is incorporated herein by reference.

[0130] In step ES, the result, e.g., a digital image of the portion of the wafer surface at the inspection position, is finally stored. In this example, the digital image information is stored together with ongoing information from the monitoring step M. The ongoing information regarding the raster arrangement of the secondary particle beam and the shape or size of at least one focal point of the secondary particle beam is taken into account in the subsequent step DV of digital image processing and data evaluation.

[0131] The multi-beam system 1 according to the first embodiment and the method for using the multi-beam system 1 according to FIG. 9 facilitate improved tuning of both the detection path 11 and the illumination path 13, including setting voltages for a uniform extraction field 113, for a specific inspection location on the surface 25 of the object 7. A method for determining improved parameters for setting the multi-beam system 1 at an operating point AP for performing an inspection task is described in the seventh embodiment. This method is based on acquiring and evaluating two fundamentally different items of information regarding the multi-beam microscope and its interaction with the object. First, a raster array 41 of multiple secondary beams 9 is detected and evaluated. Second, the shape and size of at least one focal point 15 of the secondary beams 9 is detected and evaluated. It is also possible to evaluate the shape and size of multiple focal points 15 of the secondary beams 9, for example, at least three focal points. Together, these deviations are referred to as the combined multi-beam effect.

[0132] Both items of information are acquired during scanning imaging of a portion of the surface 25 of the object 7. In this case, a plurality of J focal points 5 of the J primary beams 3 are moved in a scanning manner over the surface 25 of the object 7, so that a plurality of J scanning positions on the object surface 25 are illuminated simultaneously. To this end, a first deflection unit 110 for the scanning deflection of the plurality of J primary beams 3 is provided in the primary or illumination path 13. Each incidence location of the J focal points 5 of the J primary beams 3 forms a source location for secondary electrons, which are collected and imaged on the detector 207 during a short period of scanning irradiation with the J primary beams 3. The plurality of J source locations of the secondary electrons move synchronously over the object surface in accordance with the scanning irradiation with the J primary beams. Therefore, a second deflection unit 222 for scanning deflection of the J secondary beams 9 emanating from the J source locations is installed in the imaging path of the secondary electrons, also called detection path or secondary path 11, so that the focal points 15 of the J secondary beams on the detector remain at the same J detection locations. In this case, the second deflection unit 222 in the secondary path is synchronized with the first deflection unit 110 in the primary path.

[0133] As a result of the scanning illumination using the J primary beams 3 and the acquisition of the J secondary beams 9 signals synchronized with the scanning illumination, a plurality of J time-series data streams are acquired, which are converted into a plurality of J two-dimensional digital image information items. Each image information item represents a spatially resolved generation rate of secondary electrons due to spatially resolved illumination of the object surface 25 by the focal point 5 of the primary beam 3. In this case, the secondary electron generation rate depends on the local surface conditions, e.g., the local material composition of the structured wafer surface. Information regarding the shape and size of the focal point itself and the focal point raster arrangement 41 for adjusting both the detection path and the illumination path is acquired in a time-averaged manner so that the effects of the structuring of the object surface are reduced by averaging multiple scan positions on the surface. Therefore, this method is possible for multiple objects, and no special measurement or calibration objects are required. In particular, the method for adjusting both the detection path and the illumination path can also be performed during an inspection task at an inspection position on the object surface.

[0134] In one example of the method, the assigned inspection position is assigned the selected setting parameters and the assignment is stored. The wafer inspection method then includes targeting the next inspection position in step SI, followed by determining setting parameters of the multibeam microscope for optimal imaging at the inspection position based on the next inspection position in step SE, and setting the determined setting parameters in step PE. In this case, step SE further includes loading default setting parameters of the multibeam microscope assigned to at least one inspection position. In one example, step SE includes determining default setting parameters of the multibeam microscope at the next inspection position. In one example, interpolation of setting parameters for optimal imaging at the next inspection position is performed from at least two setting parameters assigned to two adjacent inspection positions. Thus, the method is preferably suitable for repeatedly inspecting portions of an object, in particular a surface 25 of a wafer 7, at repeated or similar inspection positions.

[0135] In a further embodiment, optimization of the inspection positions is performed based on different predetermined setting parameters of the multibeam microscope, each assigned to an inspection position. Therefore, frequent changes to the setting parameters of the multibeam microscope 1 can be prevented. As an example, optimization of a series of inspection positions is performed based on different predetermined setting parameters of the multibeam microscope, each assigned to a large number of inspection positions. As an example, optimization of a series of inspection positions is performed based on local charging effects. In one case, consecutive inspection positions can be positioned adjacent to each other in a targeted manner to have long-term compensation of existing local charges. In another case, consecutive inspection positions could be positioned with maximum spacing in a targeted manner to allow local charges causing charging effects to be discharged as long as possible through leakage currents.

[0136] The method for wafer inspection using a multi-beam system 1 having a plurality of primary and secondary particle beams (3, 9) comprises the following steps: - receiving the wafer 7 using the displacement stage 500; - determining a series of inspection tasks at a series of inspection locations (33, 35) on the surface 25 of the wafer 7; - determining, based on the inspection positions (33, 35) of an inspection task, setting parameters of the multi-beam system 1 for optimal imaging at the inspection positions (33, 35); - changing the setting parameters of the multi-beam system 1 to the determined setting parameters of the inspection task; - performing an inspection task by scanning the inspection locations (33, 35) with high resolution and with an image recording time T2>100 ms; Includes.

[0137] In one example, the step of determining the setting parameters includes defining a target at the inspection positions (33, 35), and recording an image of a time-averaged first inspection image of the raster array 41 of the plurality of secondary particle beams 9 using the detector camera 207 by rapidly scanning the inspection positions with an image recording time of T1<T2, preferably, T1<T2 / 100, or T1<T2 / 1000. The first inspection image is analyzed to determine the composite multi-beam effect, and then the setting parameters are determined such that the composite multi-beam effect is at least partially compensated.

[0138] In one example, the step of determining the setting parameters further includes defining a target at a reference position, and recording an image of a time-averaged first reference image of the raster array 41 of the plurality of secondary particle beams 9 using the detector camera 207 by rapidly scanning the reference position with an image recording time of T1. The analysis of the first inspection image of the raster array 41 includes a comparison with the reference image of the raster array 41. The reference position can be a previous inspection position or a reference position on a reference object additionally arranged on the displacement stage 500.

[0139] In one example, the method may include recording a second time-averaged inspection image of the raster array 41 by rapidly scanning the inspection positions (33, 35) using the determined setting parameters. The success of the compensation may be determined from an analysis of the second inspection image. Residual composite multi-beam effects may be determined, and updated determination of improved setting parameters may be performed so that the residual composite multi-beam effects are at least partially compensated for. The determined setting parameters may be applied to the inspection positions (33, 35) and stored so that repeated inspections, e.g., of at least one second wafer, may be performed at the same inspection positions (33, 35) using the setting parameters applied to the inspection positions (33, 35). Generally, predefined or stored setting parameters of the multi-beam microscope 1 may be used for the wafer inspection task. In one example, the setting parameters may be determined by interpolating at least two predefined or stored setting parameters at at least two adjacent reference positions. Furthermore, at least one item of previously known information may be taken into account when determining the setting parameters, the previously known information including CAD information regarding the composition of the wafer 7 at the inspection location (33, 35) in addition to information from previous measurements at or adjacent inspection locations (33, 35). Additionally, the method may include determining the distance of the inspection location (33, 35) from the edge of the wafer 7.

[0140] Within the framework of optimizing a series of inspection tasks, the determination of a series of setting parameters of the multi-beam system 1 for optimal imaging for each of a series of inspection positions (33, 35) can be changed so that the number of changes in the setting parameters of the multi-beam system 1 is minimized.

[0141] In one example, the parameters for improved adjustment of both the detection and illumination paths, including voltage settings for a uniform extraction field, are determined iteratively depending on the inspection location. This method is illustrated in FIG. 10. The first step SI is identical to step SI according to FIG. 9. Following step SI, an image is acquired (M1) without correcting or changing parameters at the next inspection location in step SM. Deviations of the raster arrangement 41 of the multiple secondary beams 9 from a predetermined or expected raster arrangement are detected and evaluated, and deviations of the shape and size of at least one focal point 15 from the predetermined or expected shape and size of the focal points 15 are simultaneously detected and evaluated. Typically, deviations of the shapes and sizes of at least three focal points 15 from the predetermined or expected shape and size of three focal points 15 are detected. As described above, the deviations are detected within the framework of time averaging during scanning of the object surface 25 with the multiple primary beams 3 to eliminate the influence of the composition of the object 7.

[0142] During the inspection step IN, the raster array 41 is synchronously displaced across the object surface 25, and image data of the object surface 25, e.g., of a wafer, is acquired. Anti-scanning using the deflection device 222 ensures that the raster array 41 remains fixed or stationary in position on the detector 207. This parallel acquisition of a plurality J of image data points is performed, for example, at a scanning frequency FS of 100 MHz. Further examples of conventional scanning frequencies are specified above.

[0143] In one example, the scanning frequency is increased during step M1. By way of example, the scanning frequency FS may be increased by a factor of 10, e.g., from 50 MHz to 500 MHz, or from 100 MHz to 1 GHz. The increased scanning frequency results in averaging of data records over a larger focal area on the object surface 15.

[0144] From the deviations, a probable cause of the deviations is determined in step Q1. In step PE, suitable parameters for adjusting the illumination and detection paths are determined, including voltages for a uniform extraction field 113. Detection of various deviations, in particular deviations of the raster arrangement 41 of the multiple secondary beams and of the shape and size of the focal points 15, allows more targeted conclusions regarding the cause to be drawn, for example, whether a disturbance in the illumination path 13 is present and deviations of the multiple focal points 15 of the primary beam 3 are already present on the object surface 25, or whether the edge 43 or topography of the object 7 is the cause of the deviation, whether there are global or local charging effects, or whether there are disturbances in the detection path 11.

[0145] In step ZS, further information, for example from an additional detector, or a priori information, can be used to determine the probable cause of the deviation. The further detector may include a distance sensor for determining the distance of the sample surface from the reference area. The use of such a distance sensor, for example, allows for better discrimination between global charging of the object 7 and purely mechanical defocusing. Further examples include field sensors for measuring the electric or magnetic field strength in the vicinity of the object surface 25. A priori information is described above in the context of FIG. 9 and may include CAD information regarding the test position or stored information from previous measurements of similar objects or similar test sites.

[0146] After determining the probable cause of the deviation, in step PE, a correction strategy or adjustment of the detection and illumination paths, including voltages for uniform extraction fields, is determined. Steps SM and PE may also be performed multiple times in an iterative manner. For example, fine corrections are calculated in a second step. Finally, in step IN, the multi-beam system is driven with the changed parameters and an inspection is performed at the same inspection site.

[0147] Simultaneously with the inspection step IN, the determination of the deviations can be repeated again in step M. If the deviations exceed predetermined tolerance limits, the determination of the cause and the determination of new parameters for adjusting the detection and illumination paths are repeated in step Q. This is followed by the above-mentioned steps ES and DV.

[0148] In a further example of the seventh embodiment, a method for setting up a multibeam microscope to inspect an object includes variations of the steps recited above. In step SM, a time-averaged first reference image of a raster array of multiple primary beams is first acquired using a detector camera by rapidly scanning a reference position of the object within a first period T1, e.g., a period T1 that is 1 / 10, 1 / 100, 1 / 1000, or 1 / 10,000 times shorter than the second period T2, the second period corresponding to a period for recording a high-resolution image of a portion of the surface of the object. For example, the first period T1 can be 1 ms to 100 ms. For example, the second period T2 can be approximately 0.8 s, 1 s, or longer.

[0149] A time-averaged second inspection image of the raster array of the multiple primary beams is recorded using a detector camera by rapidly scanning the inspection position within, for example, T1, 1 ms to 100 ms. The second inspection image of the raster array is compared with a first, or reference, image of the raster array, and deviations or differences of the raster array relative to the reference image are analyzed in step Q1 or step Q. In step PE, a determination is made to change selected setting parameters of the multibeam microscope to adapt the multibeam microscope to the inspection site. The changes in the selected setting parameters are implemented as a correction strategy. Following implementation of the correction strategy, the method may additionally include updated recording of the time-averaged second reference image of the raster array of the multiple primary beams using a detector camera by rapidly scanning the inspection position within, for example, 1 ms to 100 ms, and updated analysis and determination of optimized setting parameters of the multibeam system. In step IN, an inspection image of the surface 25 of the object 7 is recorded with high spatial resolution by slowly scanning the inspection position within, for example, 100 ms to 2000 ms. In this case, the selected configuration parameters are: - realignment of the wafer 7 using the displacement stage 500; - driving the electrodes (151, 153, 505) to influence the field profile of the extraction field 113 at the surface 25 of the wafer 7; - driving the beam deflectors (107, 110, 222) to compensate for the offset of the raster array 41; - changing the operating point of the multi-beam system in order to adjust the scale of the raster array 41; - changing the rating of the digital image; may include at least one of:

[0150] Therefore, a method for setting up a multi-beam system 1 to inspect a wafer 7 comprises the following steps: - Detecting the reference position on the wafer 7 within the first time T1 by rapidly scanning it, and using the detector camera 207 to record an image of the time-averaged first reference image of the raster array 41 of the plurality of particle beams; - Defining a target at the inspection positions (33, 35); - Detecting the inspection positions (33, 35) within the first time T1 by rapidly scanning them, and using the detector camera 207 to record an image of the time-averaged first inspection image of the raster array 41 at the inspection positions (33, 35); - Analyzing the first inspection image of the raster array 41 and the first reference image of the raster array 41, and deriving selected setting parameters for adjusting the multi-beam system 1 for the purpose of optimal imaging at the inspection sites (33, 35); - Setting the multi-beam system 1 using the selected setting parameters; - Recording an inspection image of the surface 25 of the wafer 7 with high spatial resolution by slowly scanning the inspection positions (33, 35) within the second time T2, where T1 < T2, preferably T1 < T2 / 10, for example, T1 < T2 / 100; including.

[0151] Optionally, to verify the success of the changed adjustment parameters, after setting the multi-beam system 1 using the selected setting parameters, the reference position can be rapidly scanned within the first time T1, and an image of the time-averaged second reference image of the raster array 41 of the plurality of primary beams can be recorded again using the detector camera 207. Instead of the reference position, the updated image can be recorded even at the inspection positions (33, 35) for the time-averaged second inspection image of the raster array 41.

[0152] The causes of deviations in the raster array and in the shape and size of the beam focus may be subject to dynamic changes. For example, the overall charging of the sample may increase when illumination by multiple primary beams increases, causing an increase in deviations in the raster array during imaging. Such dynamic effects are determined in the eighth embodiment of the present invention, taking into account, for example, the rate of change or deviation of the raster array and in the shape and size of the beam focus. This allows deviations in the raster array and in the shape and size of the beam focus to be dynamically corrected, and allows parameters for adjusting the detection path and illumination path to be dynamically changed in a predetermined manner during the capture of an image portion of the object surface. An example is shown in FIG. 11. FIG. 11a shows the time-varying charging effect, which causes distortion and offset of the raster array, for example, at the edge of the wafer. Before an inspection task is performed, charge 903 from a previous inspection task is already present, and the charge is slowly decreasing as a result of discharge effects. With the start of image data acquisition at time t0, new charging 905 of the object surface 25 begins simultaneously as a result of illumination of the wafer surface by multiple primary beams and the emission of secondary particles from the object surface 25. The charging may also transition to saturation toward the end of image data acquisition at time t1. Complex multi-beam effects increase in parallel with the charging. Complex multi-beam effects can be at least partially compensated for during the inspection task period Ts, for example, by suitable synchronous driving of the quasi-static deflector 107. To this end, a control signal as a variable parameter for the quasi-static deflector 107 is determined from the expected time profile of the charge 905 and supplied to the quasi-static deflector 107. An example of the synchronous control signal 907 is shown in FIG. 11b.

[0153] To measure the raster array of multiple secondary beams and at least one shape or size of the focal points of the secondary beams, the present invention uses time-averaged measurement signals that can be acquired during the inspection task. In this case, the measurement can be performed by the same detector that is also used for high-resolution imaging, and the time averaging, performed as described above, is set via the sampling rate of the analog-to-digital converter, the scanning frequency, or both. Alternatively, in the case of a detection system that first converts the secondary electron signal to light through a scintillator, a beam splitter or deflector can be inserted in the light-optical unit arranged downstream of the converter to direct at least a portion of the generated light onto the CMOS camera. CMOS cameras typically have a lower refresh rate, for example, 10 to 100 frames per second, so that averaging can be achieved with a reduced refresh rate. Alternatively, in the ninth embodiment, the electron-optical path can be split within the projection optical unit 205, for example, via a modified deflection system 224. 12 shows the detection system of the multi-beam system 1, which includes a projection optical unit 205 including a beam deflector 224. During image capture, the beam deflector 224 is set so that the J secondary electron beams 9 are directed toward a first detector 207a, forming a focal spot 15a on the detection area. By way of example, the detector 207a may include a highly sensitive photodiode array with just one photodiode for each of the J secondary beams. To detect the raster array and the shape and size of the focal spot, the J secondary beams are directed toward a second detector 207b using the deflector 224, which may be formed, for example, by a high-resolution CMOS camera with a scintillator layer. Thus, the shape and size of the raster array and the focal spot 15b can be detected with high resolution. The imaging scales in the two detection arms can be set differently in the process, for example, using lenses 201 a and 210 b and using the spacing, so that the illumination of the second detector 207 b is matched to the diameter of the second detector 207 b. In this case, switching between the projection systems 205 a and 205 b can be performed very quickly through the electrostatic deflector 224.

[0154] The present invention can be described by the following clauses. However, the present invention is not limited to the clauses. Clause 1: A wafer inspection method using a multi-beam system (1) having a plurality of particle beams (3, 9), the method comprising the following steps: - receiving a wafer 7 using a displacement stage 500; - determining a series of inspection tasks at a series of inspection positions (33, 35) on the surface (25) of the wafer (7); - determining setting parameters of the multi-beam system (1) for an optimal imaging at the inspection positions (33, 35) based on the inspection positions (33, 35) of the inspection tasks; - changing the setting parameters of the multi-beam system (1) to the determined setting parameters of the inspection tasks at the inspection positions; - performing the inspection tasks by scanning the inspection positions (33, 35) with high resolution and an image recording time T2>100 ms. A method comprising the above steps. Clause 2: The step of determining the setting parameters comprises the following steps: - defining a target at a first inspection position (33, 35); - recording an image of a time-averaged first inspection image of a raster array (41) of a plurality of particle beams (3, 9) using a detector camera (207) by rapidly scanning the inspection position with an image recording time of T1<T2, preferably T1<T2 / 100, or T1<T2 / 1000; - analyzing the first inspection image for determining a composite multi-beam effect, the composite multi-beam effect including a distortion of the incidence locations (5, 15) of the plurality of particle beams (3, 9) and a change in the shape and size of the foci (5, 15) of the particle beam (3); - determining the setting parameters such that the composite multi-beam effect is at least partially compensated at the first inspection position (33, 35). 2. The method according to clause 1, comprising: Clause 3: determining the configuration parameters, - targeting a reference position; - recording an image of a time-averaged reference image of the raster array (41) of the plurality of particle beams (3, 9) using the detector camera (207) by rapidly scanning the reference position with an image recording time of T1, and the step of analyzing the first inspection image of the raster array (41) includes a comparison with the reference image of the raster array (41). Clause 4: - recording a time-averaged second inspection image of the raster array (41) by rapidly scanning the first inspection position (33, 35) using the determined setting parameters; - analyzing the second inspection image to determine a combined multi-beam effect; - re-determining improved setting parameters so that the combined multi-beam effect is at least partially compensated for; 4. The method of clause 2 or 3, further comprising: Article 5: The method according to any one of clauses 1 to 4, further comprising: applying the determined setting parameters to the first test position (33, 35) and storing the application of the setting parameters. Article 6: 6. The method of clause 5, further comprising repeating inspection of at least one second wafer at the first inspection position (33, 35) using the setting parameters assigned to the first inspection position (33, 35). Article 7: - the method according to clause 1, further comprising loading default setting parameters of the multi-beam microscope (1), the default setting parameters being applied to each reference position on the wafer, and the setting parameters for the inspection positions (33, 35) being determined from the default setting parameters. Article 8: 8. The method of clause 7, wherein the configuration parameters are determined by interpolating at least two predefined configuration parameters at at least two adjacent reference positions. Article 9: The sequence of inspection tasks is determined in the following steps: - determining a set of setting parameters of the multi-beam system (1) aimed at optimal imaging at each of the inspection positions (33, 35), - optimizing a set of inspection tasks based on a set of setting parameters of the multi-beam system (1) such that the number of changes to the setting parameters of the multi-beam system (1) is minimized; 2. The method according to clause 1, comprising: Article 10: 2. The method of claim 1, wherein at least one previously known item of information is taken into account when determining the setting parameters, the previously known item of information including at least one of CAD information regarding the composition of the wafer (7) at the inspection position (33, 35), a previous inspection task at an adjacent inspection position (33, 35), or a previous measurement or inspection at the inspection position (33, 35). Article 11: 2. The method of claim 1, wherein determining the setting parameters includes determining the distance of the inspection positions (33, 35) from the edge of the wafer (7). Article 12: The selected setting parameters include parameters of components in the illumination path (13) and in the detection path (11) of the multi-beam system (1), including the following parameters: - realigning the wafer (7) at the first inspection position (33, 35) using the displacement stage (500); - driving the correction electrodes to influence the extraction field (113) at the first test position (33, 35) on the surface (15) of the wafer (7); - driving a deflection device (107, 110) in the illumination path of the particle beam (3) in order to compensate for an offset of the raster array (41) on the surface (25) of the wafer (7), - Changing the operating point of the multi-beam system (1) for the purpose of adjusting the scale of the raster array (41), - Changing the evaluation of the digital image, The method according to any one of clauses 1 to 11, including at least one of the above. Clause 13: A method for determining the composite multi-beam effect (41), - Scanning a portion of the structured surface (25) of the wafer (7) and recording an image of the time-averaged inspection image of the raster array (41) of a plurality of particle beams (3, 9) using a detector camera (207) by averaging the image contrast of the surface structure of the wafer (7), - Analyzing the inspection image for the purpose of determining at least one deviation of the raster array (41) of the incident locations (5, 15) of a plurality of particle beams from a predefined raster array (41), as well as changes in the shape or size of the focus (5, 15) of the particle beams, The method including the above. Clause 14: The image contrast is averaged by rapidly scanning a portion of the surface (25) of the wafer (7) with an image recording time of T1 < T2, preferably T1 < T2 / 10, for example, T1 < T / 100, where T2 corresponds to the time for recording an image of the portion of the surface (25) with a high spatial resolution and a pixel size of 2 nm, 1 nm, or less. The method according to clause 13. Clause 15: The method according to clause 14, where T1 is less than 100 ms, preferably less than 10 ms. Clause 16: The method according to clause 13, where the averaging of the image contrast of the surface structure of the wafer (7) is performed by temporally averaging the detection signal. Clause 17: The deviation of the raster array (41) includes at least one of the following errors: scale error (41a), offset error (41b), distortion (41c), torsion (41g), local deviation (41d) of individual beams of the raster array (41). The method according to any one of clauses 13 to 16. Clause 18: A method according to any one of Clauses 13 to 17, wherein a change in the shape or size of at least three foci (5, 15) includes at least one of the following aberrations: constant astigmatism, linear astigmatism having a linear profile of astigmatism with respect to a raster array (41), constant focus error, and linear focus error having a linear profile of focus error with respect to a raster array (41). Clause 19: A multi-beam system (1) having a plurality of primary particle beams (3) and a plurality of secondary particle beams (9), - a spatial resolution detector (207), - at least one deflection system (110, 222) for deflecting a plurality of primary and secondary particle beams (3, 9) for the purpose of collectively scanning a portion of the structured surface (25) of the wafer (7), - a control device (800) for driving the detector (207) and the deflection system (110, 222), A multi-beam system (1), wherein the control device (800) and the detector (207) are configured to capture a time-averaged inspection image of the raster array (41) of the plurality of secondary particle beams (9) and / or a digital image of a portion of the structured surface (25) with a spatial resolution of 2 nm, 1 nm, or less than that. Clause 20: In a first operating mode in which the control device (800) captures a time-averaged inspection image of the raster array (41), the deflection system (110) is used to rapidly scan a plurality of primary particle beams (3) across a portion of the structured surface (25) of the wafer (7) within a time T1, and in a second operating mode for recording a digital image of a portion of the structured surface (25), the deflection system (110) is used to slowly scan a plurality of primary particle beams (3) across a portion of the structured surface (25) of the wafer (7) within a time T2, where T1 < T2, preferably T1 < T2 / 10, for example, T1 < T2 / 100. The multi-beam system (1) according to Clause 19. Clause 21: A multi-beam system (1) as described in clause 20, wherein the detector (207) comprises a first detector (207a) and a second detector (207b), and the multi-beam system (1) comprises a detection unit (200) having a beam deflector (224) driven by a control unit (800) and configured to deflect, during operation, the multiple secondary particle beams onto either the first detector (207a) or the second detector (207b). Article 22: 22. The multi-beam system (1) of claim 21, wherein the beam deflector (224) is configured to maintain the plurality of secondary particle beams in a fixed position on either the first detector (207a) or the second detector (207b) during operation. Article 23: 20. A multi-beam system according to clause 19, wherein the detector (207) is designed for simultaneous capture of a time-averaged inspection image of the raster array (41) of multiple secondary particle beams (9) and a digital image of a portion of the structured surface (25) with high spatial resolution having pixel dimensions of 2 nm, 1 nm or less. Article 24: 24. The multi-beam system of claim 23, wherein the detector (207) includes an electron conversion element that generates photons from electrons, and the photons are detected simultaneously using a first high-speed photodetector for capturing a portion of the wafer surface (25) and a second low-speed photodetector for capturing an inspection image of the raster array (41). Article 25: A multi-beam system (1) according to any one of clauses 19 to 24, wherein the control device (800) is further configured to determine a composite multi-beam effect resulting from changes in the incidence locations of the multiple particle beams (3, 9) and changes in the shape or size of the focal points of the particle beams (3, 9) from the inspection image of the raster array (41), and to derive and set changes in the setting parameters of the multi-beam system (1) based on the composite multi-beam effect. Article 26: A multi-beam system (1) as described in clause 25, wherein a control device (800) is connected to a plurality of components of the illumination path (13) and the detection path (11), including components for setting a uniform extraction field (113) of the multi-beam system (1), and is configured to drive setting parameters of the components of the illumination path (13) and the detection path (11), including components for setting a uniform extraction field (113), for the purpose of reducing composite multi-beam effects. Article 27: The multi-beam system (1) comprises the following components connected to a control device (800) for the purpose of driving: a quasi-static deflector (107) for a plurality of primary particle beams (3); a dynamic deflector (110) for scanning deflection of the primary particle beam (3) and the secondary particle beam (9); - a dynamic deflector (222, 224) for scanning deflection of the secondary particle beam (9), - electrostatic or magnetic lenses (306.2, 307, 103.2, 102) with variable focusing effect; - a raster arrangement of multipole elements (306.2) for influencing the primary particle beam (3); a correction electrode 153 for establishing a uniform extraction field (113) between the wafer surface 25 and a counter electrode 151 of the objective lens system 102 of the multi-beam system 1; 27. The multi-beam system (1) according to clause 26, further comprising: Article 28: - an electrical contact of the objective lens (102) or a counter electrode (151) below a part of the objective lens (102) for providing a first voltage difference V1 during operation; a displacement stage (500) having a receiving area (505) for receiving the wafer (7) and positioning it under the objective lens (102); - electrical contacts in the receiving area (505) for applying a second voltage difference V2 to the wafer (7) during operation; Furthermore, A multi-beam system (1) according to any one of clauses 19 to 27, wherein the displacement stage (500) further comprises at least one correction electrode (153) within the periphery of the receiving area (505) having electrical contacts for supplying at least one third voltage difference V3 for the purpose of generating an extraction field (113) that is uniform within the edge region of the wafer (7) during operation. Article 29: A multi-beam system (1) according to any one of clauses 19 to 28, wherein the control unit (800) further comprises a unit (812) for image evaluation, and the control unit (800) is configured to drive the unit (812) for image evaluation using a correction signal intended to correct at least a portion of the composite multi-beam effect. Article 30: A wafer inspection multi-beam system (1) having a plurality of primary particle beams (3) and a plurality of secondary particle beams (9), - a displacement stage (500) for receiving the wafer (7); - a spatially resolved detector (207); a first deflection system (110) for deflecting a plurality of primary particle beams (3) in order to scan them collectively over a portion of the structured surface (25) of the wafer (7); a second deflection system (222) for deflecting the plurality of secondary particle beams (9) in order to maintain a constant focal point (15) of the secondary particle beams (9) on the detector (207); - a control device (800); - a plurality of components of the illumination path (13) and the detection path (11), including components (151, 153, 505) for setting a uniform extraction field (113) of the multi-beam system (1); a control device (800) configured to obtain and work through a list of inspection tasks at a plurality of inspection locations (33, 35); A wafer inspection multi-beam system (1), wherein the control device (800) is further configured to set setting parameters of components of the illumination path (13) and the detection path (11), including components (151, 153, 505) for setting a uniform extraction electric field (113) for the purpose of reducing a compound multi-beam effect at the inspection positions (33, 35). Article 31: The multi-beam system (1) of clause 30, wherein the control unit (800) is further configured to detect a distance of the inspection position (33, 35) from an edge (43) of the wafer (7) and compensate for a compound multi-beam effect caused by the wafer edge (43). Article 32: The multi-beam system (1) of clause 30 or 31, wherein the control unit (800) is further configured to determine a composition of the wafer (7) at the inspection position (33, 35) from CAD data prior to measurement or inspection at the inspection position (33, 35) and compensate (41) for compound multi-beam effects caused by the composition. Article 33: A multi-beam system (1) according to any one of clauses 30 to 32, wherein the control unit (800) further comprises a memory and is configured to determine stored parameters from stored examination tasks at similar examination sites and to set the stored parameters with the aim of reducing the combined multi-beam effect at the examination positions (33, 35). Article 34: A multi-beam system (1) according to any one of clauses 30 to 33, wherein the control unit (800) is further configured to determine parameters from previous examination tasks at adjacent examination sites and to set the parameters with the aim of reducing the combined multi-beam effect at the examination positions (33, 35). Article 35: A multi-beam system (1) according to any one of clauses 30 to 34, wherein the control unit (800) is further configured to modify a scanning program for driving the first and second deflection systems (110, 222) to at least partially compensate for the combined multi-beam effect. Article 36: A multi-beam system (1) according to any one of clauses 30 to 35, wherein the control unit (800) is further configured to change an operating point of the multi-beam system (1) to at least partially compensate for the composite multi-beam effect. Article 37: A displacement stage (500) for a multi-beam microscope (1), comprising: a receiving area (505) for receiving a wafer (7) having an edge (43) and a diameter D, through which a voltage V2 can be applied to the wafer (7) during operation; a ring electrode (153) arranged within the periphery of the receiving area (505), the ring electrode (153) having an inner diameter DI>D, such that when the wafer (7) is received, a distance is formed between the edge (43) of the wafer (7) and the ring electrode (153); a displacement stage (500) in which the electrode (153) is insulated from the receiving area (505) so that during operation a voltage V3 can be applied to the ring electrode (153). Article 38: A displacement stage (500) as described in clause 37, wherein the ring-shaped electrode (153) is formed from a plurality of, for example, two, four, eight or more, mutually insulated electrode segments to which at least one first voltage V3 can be applied. Article 39: A multi-beam system (1) comprising a displacement stage (500) according to clause 37 or 38. Article 40: The multi-beam system (1) according to clause 39, further comprising a control unit (503) configured to set a voltage V2 and at least a first voltage V3 for the purpose of generating a uniform extraction electric field during operation. Clause 41: A method of setting a multi-beam system (1) for inspecting a wafer (7), comprising the following steps: - Detecting a reference position on the wafer 7 within a first time T1 by rapidly scanning it, and using a detector camera 207 to record an image of a time-averaged first reference image of a raster array 41 of a plurality of particle beams; - Defining a target at an inspection position (33, 35); - Detecting an inspection position (33, 35) within a first time T1 by rapidly scanning it, and using a detector camera 207 to record an image of a time-averaged first inspection image of a raster array 41 of a plurality of particle beams at the inspection position (33, 35); - Analyzing the first inspection image of the raster array (41) and the first reference image of the raster array (41), and deriving selected setting parameters for adjusting the multi-beam system (1) for the purpose of optimal imaging at the inspection site (33, 35); - Setting the multi-beam system (1) using the selected setting parameters; - Recording an inspection image of the surface (25) of the wafer (7) with high spatial resolution by slowly scanning the inspection position (33, 35) within a second time T2, where T1 < T2, preferably T1 < T2 / 10, for example, T1 < T2 / 100; A method including the above steps. Clause 42: The method according to clause 41, further comprising recording an image of a time-averaged second reference image of a raster array (41) of a plurality of primary beams using a detector camera (207) by rapidly scanning a reference position within a first time T1 after setting the multi-beam system (1) using the selected setting parameters. Clause 43: The method of clause 41, further comprising recording a time-averaged second inspection image of the raster array (41) of multiple primary beams using a detector camera (207) by rapidly scanning the inspection positions (33, 35) within a first time T1, to check the settings of the multi-beam system (1) using the selected setting parameters. Article 44: The selected configuration parameters are: - realignment of the wafer (7) using the displacement stage (500), - driving the electrodes (151, 153, 505) to influence the field profile of the extraction field 113 at the surface 25 of the wafer 7; - driving the beam deflectors (107, 110, 222) to compensate for the offset of the raster array (41); - changing the operating point of the multi-beam system in order to adjust the scale of the raster array 41; - changing the rating of the digital image; 44. The method of any one of clauses 41 to 43, comprising at least one of: Article 45: 45. The method of any one of clauses 41 to 44, further comprising applying the selected configuration parameters to the test locations (33, 35) and storing the application. Article 46: 46. ​​The method of clause 45, further comprising repeating inspection of at least a second wafer (7) at the inspection positions (33, 35) using the stored setting parameters assigned to the inspection positions (33, 35). Article 47: 47. The method according to any one of clauses 41 to 46, wherein the reference position corresponds to a previous inspection position (33, 35). Article 48: 47. The method of any one of clauses 41 to 46, wherein the reference position corresponds to a position on a reference object. Article 49: A method for wafer inspection using a multi-beam system (1), comprising the following steps: a. targeting an inspection location on a wafer (7); b. determining predetermined setting parameters of the multi-beam microscope (1) for optimal imaging at the inspection position based on the inspection position; c. setting the determined configuration parameters; d. recording an image of a portion of the surface (25) of the wafer (7) at the inspection position; A method comprising: Article 50: - loading default setting parameters of the multibeam microscope assigned to the inspection position; - interpolating setting parameters for optimal imaging at an inspection position from at least two setting parameters assigned to two adjacent inspection positions; 49. The method of claim 49, further comprising: Article 51: - determining a priori information about the inspection location, the a priori information comprising the following information items: - the distance of the inspection position from the edge (43) of the wafer (7), - CAD information on the material composition at the surface (25) of the wafer (7) at the inspection position, - the distance of the examination position from the previous image recording at the previous examination position, 49. The method of claim 49, comprising at least one of: Article 52: 52. The method according to any one of clauses 49 to 51, wherein the setting parameters include voltage values ​​for generating a uniform extraction field (143) on the surface (25) of the wafer (7) at the inspection position, the voltage values ​​being supplied to the electrodes (151, 153, 505). [Explanation of symbols]

[0155] 1 Multi-beam system 3 Primary beam or multiple primary beams 5 Focus of the primary beam 7 wafers 9 Secondary beam 11 Detection beam path 13 Lighting Path 15 Focus of the secondary beam 17 Image field 21 Center of image field and center of inspection position 25 Wafer surface 27 Primary beam scanning path 29 Center of partial field of vision 31 partial field of view 33 First inspection position 34 Second Inspection Position 35 Third Inspection Position 41 Raster Array 43 Wafer Edge 47 Distance of inspection position from wafer edge 61 Local displacement of spot position 100 Lighting System 101 object surface or first plane 102 Objective lens system 103 Field Lens 105 Optical axis of objective lens 107 Quasi-static deflector 108 Crossover Point 110 Scanning Deflector 113 Extraction Field 130 Slow Compensator for Lighting Systems 132 Fast Compensator for Lighting Systems 149 Magnetic Lens Coil 151 Counter electrode 153 Ring-shaped correction electrode 155 Insulation 200 Detection system having a detection path for imaging secondary electrons 205 Projection Lens 206 Electrostatic Lens 207 Spatially Resolved Particle Detector 208 Magnetic Lens 209 Magnetic Lens 210 Projection Lens 212 Secondary beam crossover point 214 Aperture or contrast stop 216 Multi-aperture plate 218 Third deflection system 222 Second deflection system 224 Second deflection system with switching between projection systems 205a and 205b 230 Slow Compensator for Detection Systems 232 Fast Compensator for Detection Systems 238 Sensors 280 Image Data Converter 300 Beam generating device 301 Electron source 303 Collimation Lens 305 Multi-aperture mechanism 306 Multi-aperture plate 307 Field Lens 308 Field Lens 309 Particle Beam 311 Beam focus in the intermediate image plane 321 Intermediate image plane 330 Slow Compensator for Multibeam Generator Device 332 High-speed compensator for multi-beam generating devices 390 Deflector Array 400 Beam Splitter 420 Beam Splitter Correction Element 500 displacement table 503 Voltage supply for object voltage 505 Object Receptor Area 520 Displacement table position sensor 800 Control Unit 810 Data Acquisition Device 812 Digital Image Processing Unit 814 Image data memory 818 Sensor Data Module 820 Control module for detection system 830 Lighting device control unit 840 Control Processor 860 Scanning Module 880 Displacement table control module 903 Existing charge from the previous test task 905 Increasing Charge During Inspection Task 907 Dynamically variable parameters for driving multi-beam systems during inspection tasks

Claims

1. A multi-beam system (1) having a plurality of primary particle beams (3) and a plurality of secondary particle beams (9), a spatially resolved detector (207), at least one deflection system (110, 222) for deflecting said plurality of primary and secondary particle beams (3, 9) for the purpose of scanning, in a batch, a portion of the structured surface (25) of the wafer (7); a control unit (800) for driving said detector (207) and said deflection system (110, 222), the control unit (800) and the detector (207) are configured to capture a digital image of a portion of the structured surface (25) with a spatial resolution of 2 nm or less and simultaneously capture a time-averaged inspection image of the raster arrangement (41) of the plurality of secondary particle beams (9); the time averaging comprises time averaging of signals over multiple scan points on the structured surface (25) of the wafer (7); Multi-beam system (1).

2. 2. The multi-beam system of claim 1, wherein the control unit is configured to: in a first operating mode for capturing the time-averaged inspection image of the raster array, rapidly scan the plurality of primary particle beams over a portion of the structured surface of the wafer in a time T1 using the deflection system; and in a second operating mode for recording the digital image of the portion of the structured surface, slowly scan the plurality of primary particle beams over a portion of the structured surface of the wafer in a time T2 using the deflection system, wherein T1<T2.

3. 3. The multi-beam system (1) of claim 2, wherein the detector (207) comprises a first detector (207a) and a second detector (207b), and the multi-beam system (1) comprises a detection unit (200) driven by the control unit (800) and having a beam deflector (224) configured to deflect the plurality of secondary particle beams onto either the first detector (207a) or the second detector (207b) during operation.

4. 4. The multi-beam system (1) of claim 3, wherein the beam deflector (224) is configured to maintain the plurality of secondary particle beams in a fixed position on either the first detector (207 a) or the second detector (207 b) during operation.

5. 2. The multi-beam system of claim 1, wherein the detector is designed for simultaneous capture of the time-averaged inspection image of the raster arrangement of the plurality of secondary particle beams and the digital image of the portion of the structured surface with high spatial resolution having a pixel dimension of 2 nm or less.

6. 6. The multi-beam system of claim 5, wherein the detector (207) includes an electron conversion element that generates photons from electrons, and the photons are detected simultaneously using a first high-speed photodetector for capturing a portion of the wafer surface (25) and a second low-speed photodetector for capturing the inspection image of the raster array (41).

7. 7. The multi-beam system (1) according to claim 1, wherein the control unit (800) is further configured to determine, from the inspection image of the raster array (41), a composite multi-beam effect consisting of changes in the incidence locations of the plurality of particle beams (3, 9) and changes in the shape or size of the focal points of the particle beams (3, 9), and to derive and set changes in setting parameters of the multi-beam system (1) based on the composite multi-beam effect.

8. 8. The multi-beam system of claim 7, wherein the control unit is connected to a plurality of components of the illumination path and the detection path, including components for setting a uniform extraction field of the multi-beam system, and is configured to drive the setting parameters of the components of the illumination path and the detection path, including components for setting a uniform extraction field, for the purpose of reducing the composite multi-beam effect.

9. The multi-beam system (1) comprises the following components connected to the control unit (800) for the purpose of driving: a quasi-static deflector (107) for said plurality of primary particle beams (3), a dynamic deflector (110) for the scanning deflection of the primary particle beam (3) and the secondary particle beam (9); a dynamic deflector (222, 224) for the scanning deflection of the secondary particle beam (9); - electrostatic or magnetic lenses (306.2, 307, 103.2, 102) with variable focusing effect; a raster arrangement of multipole elements (306.2) for influencing said primary particle beam (3), a correction electrode 153 for establishing a uniform extraction field (113) between the wafer surface 25 and a counter electrode 151 of the objective lens system 102 of the multi-beam system 1; 9. The multi-beam system (1) of claim 8, further comprising:

10. an electrical contact of the objective lens (102) or of a counter electrode (151) below a part of said objective lens (102) for providing a first voltage difference V1 during operation; a displacement stage (500) having a receiving area (505) for receiving a wafer (7) and positioning it under said objective lens (102); - electrical contacts in said receiving area (505) for applying a second voltage difference V2 to the wafer (7) during operation; 7. The multi-beam system (1) according to claim 1, wherein the displacement stage (500) further comprises at least one correction electrode (153) in the periphery of the receiving area (505) having electrical contacts for supplying at least one third voltage difference V3 for the purpose of generating an extraction field (113) that is uniform in the edge region of the wafer (7) during operation.

11. 8. The multi-beam system (1) of claim 7, wherein the control unit (800) further comprises a unit (812) for image evaluation, and the control unit (800) is configured to drive the unit (812) for image evaluation with a correction signal intended to correct at least a portion of the composite multi-beam effect.

12. A wafer inspection multi-beam system (1) having a plurality of primary particle beams (3) and a plurality of secondary particle beams (9), a displacement stage (500) for receiving the wafer (7); a spatially resolved detector (207), a first deflection system (110) for deflecting the primary particle beams (3) in order to scan them en bloc over a portion of the structured surface (25) of the wafer (7); a second deflection system (222) for deflecting the secondary particle beams (9) in order to maintain a constant focal point (15) of the secondary particle beams (9) on the detector (207); a control unit (800), - several components of the illumination path (13) and the detection path (11), including components (151, 153, 505) for setting a uniform extraction field (113) of said multi-beam system (1); the control unit (800) is configured to obtain a list of inspection tasks at a plurality of inspection locations (33, 35) and work through the list; the control unit (800) is further configured to set setting parameters of the components of the illumination path (13) and the detection path (11), including components (151, 153, 505) for setting the uniform extraction field (113) for the purpose of reducing a compound multi-beam effect at the inspection position (33, 35); the control unit (800) and the spatially resolved detector (207) are further configured to simultaneously capture a digital image of a portion of the structured surface (25) with a spatial resolution of 2 nm or less and a time-averaged inspection image of the raster arrangement (41) of the plurality of secondary particle beams (9); the time averaging comprises time averaging of signals over multiple scan points on the structured surface (25) of the wafer (7); Wafer inspection multi-beam system (1).

13. 13. The multi-beam system (1) of claim 12, wherein the control unit (800) is further configured to detect a distance of the inspection position (33, 35) from an edge (43) of the wafer (7) and to compensate for a compound multi-beam effect caused by the wafer edge (43).

14. 14. The multi-beam system (1) of claim 12 or 13, wherein the control unit (800) is further configured to determine the composition of the wafer (7) at the inspection position (33, 35) from CAD data before measurement or inspection at the inspection position (33, 35) and to compensate (41) for compound multi-beam effects caused by the composition.

15. 14. The multi-beam system (1) of claim 12 or 13, wherein the control unit (800) further comprises a memory and is configured to determine stored parameters from stored inspection tasks at similar inspection sites and to set the stored parameters with the aim of reducing composite multi-beam effects at the inspection positions (33, 35).

16. 14. The multi-beam system (1) of claim 12 or 13, wherein the control unit (800) is further configured to determine parameters from a previous inspection task at an adjacent inspection site and to set the parameters with the aim of reducing a combined multi-beam effect at the inspection position (33, 35).

17. 14. The multi-beam system (1) of claim 12 or 13, wherein the control unit (800) is further configured to modify a scanning program for driving the first and second deflection systems (110, 222) to at least partially compensate for a composite multi-beam effect.

18. 14. The multi-beam system (1) of claim 12 or 13, wherein the control unit (800) is further configured to change an operating point of the multi-beam system (1) to at least partially compensate for a composite multi-beam effect.

19. 1. A method of setting up a multi-beam system (1) to inspect a wafer (7), comprising the steps of: recording an image of a time-averaged first reference image of the raster array (41) of multiple particle beams using the detector camera (207) by rapidly scanning a reference position on the wafer (7) within a first time T1; - targeting the test positions (33, 35); recording a time-averaged first inspection image of the raster arrangement (41) of the plurality of particle beams at the inspection position (33, 35) using the detector camera 207 by rapidly scanning the inspection position (33, 35) within the first time T1; - analyzing the first inspection image of the raster array (41) and the first reference image of the raster array (41) and deriving selected setting parameters for adjusting the multi-beam system (1) for optimal imaging at the inspection site (33, 35); - configuring the multi-beam system (1) using the selected configuration parameters; - recording an inspection image of the surface (25) of the wafer (7) with high spatial resolution by slow scanning of the inspection locations (33, 35) within a second time T2, where T1<T2; Including, The method, wherein the time averaging comprises time averaging of signals over multiple scan points on the structured surface (25) of the wafer (7).

20. 20. The method of claim 19, further comprising recording a time-averaged second reference image of the raster arrangement of the plurality of primary beams using the detector camera by rapidly scanning the reference position within the first time T1 after configuring the multi-beam system with the selected configuration parameters.

21. 20. The method of claim 19, further comprising recording a time-averaged second inspection image of the raster arrangement of the plurality of primary beams with the detector camera by rapidly scanning the inspection positions within the first time T1, to check the settings of the multi-beam system using the selected setting parameters.

22. The selected configuration parameters include the following parameters: - realignment of said wafer (7) using the displacement stage (500); - driving the electrodes (151, 153, 505) to influence the field profile of the extraction field 113 at the surface 25 of the wafer 7; - driving the beam deflectors (107, 110, 222) to compensate for the offset of said raster array (41); - changing the operating point of the multi-beam system in order to adjust the scale of the raster array 41; - changing the rating of a digital image; The method according to any one of claims 19 to 21, comprising at least one of:

23. The method of any one of claims 19 to 21, further comprising applying said selected setting parameters to said test locations (33, 35) and storing said application.

24. 24. The method of claim 23, further comprising repeating inspection of at least a second wafer (7) at the inspection position (33, 35) using the stored setting parameters applied to the inspection position (33, 35).

25. The method according to any one of claims 19 to 21, wherein the reference position corresponds to a previous inspection position (33, 35).

26. The method of any one of claims 19 to 21, wherein the reference position corresponds to a position on a reference object.

27. A method for wafer inspection using a multi-beam system (1), comprising the following steps: a. targeting an inspection location on a wafer (7); b) determining, based on the inspection position, setting parameters of the multi-beam microscope (1), which are predetermined by the method of claim 19, for optimal imaging at the inspection position; c) setting the determined configuration parameters; d. Recording an image of a portion of the surface (25) of the wafer (7) at the inspection position; A method comprising:

28. - loading predefined setting parameters of the multibeam microscope assigned to the inspection position; - interpolating said setting parameters for optimal imaging at said inspection position from at least two setting parameters assigned to two adjacent inspection positions; 28. The method of claim 27, further comprising:

29. further comprising determining a priori information about said inspection location, said a priori information comprising the following items of information: the distance of the inspection position from the edge (43) of the wafer (7), CAD information on the material composition at the surface (25) of the wafer (7) in the inspection position, the distance of said inspection position from the previous image recording at the previous inspection position, 29. The method of claim 28, comprising at least one of:

30. 30. The method according to any one of claims 27 to 29, wherein the setting parameters include voltage values ​​for generating a uniform electric extraction field (143) on the surface (25) of the wafer (7) at the inspection position, the voltage values ​​being supplied to the electrodes (151, 153, 505).

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