Method for passively adjusting a particle-optical component for a functional unit of a particle beam system, in particular a pole shoe for a magnetic lens, method for equipping a particle beam system with the functional unit, in particular a magnetic lens, and particle beam system

Abstract

A method for the passive adjustment of a pole shoe for a magnetic lens of a particle beam system is disclosed, comprising the following steps: providing a reference pole shoe with a predefined minimum magnetic homogeneity in a measuring device; releasably arranging the pole shoe to be adjusted relative to the reference pole shoe in a predefined reference position and thereby assembling a magnetic lens in the measuring device; exciting the magnetic lens in the measuring device; measuring characteristics of the magnetic field generated by the magnetic lens; determining a deviation of the characteristics of the generated magnetic field from corresponding characteristics of a predefined reference magnetic field; and mechanically changing the pole shoe based on the determined deviation to adjust the magnetic field that can be generated by the magnetic lens.

Description

Field of invention

[0001] The invention relates generally to particle beam systems and in particular to multiple particle beam systems that operate with a multitude of charged individual particle beams. Specifically, the invention relates to a method for passively adjusting a particle-optical component for a functional unit of a particle beam system, to a method for equipping a particle beam system with the functional unit, and to a particle beam system itself. The functional unit can, for example, be a magnetic lens. State of the art

[0002] With the continuous development of increasingly smaller and more complex microstructures, such as semiconductor devices, there is a need for the further development and optimization of planar fabrication techniques and inspection systems for the production and inspection of these small microstructures. The development and fabrication of semiconductor devices, for example, requires verification of test wafer designs, and planar fabrication techniques necessitate process optimization for reliable, high-throughput manufacturing. Furthermore, the analysis of semiconductor wafers for reverse engineering and the customized configuration of semiconductor devices is increasingly required. Therefore, there is a need for inspection tools that can be used with high throughput to examine microstructures on wafers with high accuracy.

[0003] Typical silicon wafers used in the production of semiconductor devices have diameters of up to 300 mm. Each wafer is divided into several dozen to several hundred repeating regions ("dies") with a size of up to 800 mm. 2 A semiconductor device comprises multiple semiconductor structures fabricated in layers on the surface of a wafer using planar integration techniques. Due to the manufacturing processes, semiconductor wafers typically have a flat surface.

[0004] The feature size of integrated semiconductor structures ranges from a few nanometers to critical dimensions (CDs) of a few nanometers, with feature sizes expected to become even smaller in the near future. It is anticipated that future feature sizes, or critical dimensions (CDs), will correspond to the 3 nm, 2 nm, or even smaller technology nodes of the International Technology Roadmap for Semiconductors (ITRS). At these small feature sizes, defects of critical dimension size must be identified quickly over a very large area. For several applications, the specification requirement for the accuracy of a measurement provided by an inspection instrument is even higher, for example, by a factor of two or an order of magnitude.For example, the width of a semiconductor feature must be measured with an accuracy of less than 1 nm, such as 0.3 nm or even less, and the relative position of semiconductor structures must be determined with a superposition accuracy of less than 1 nm, such as 0.3 nm or even less.

[0005] A more recent development in the field of charged particle microscopes (CPM) is the mSEM, a multi-beam scanning electron microscope. A multi-beam scanning electron microscope is disclosed, for example, in US 7,244,949 B2 and US 2019 / 0355544 A1. In a multi-beam electron microscope, or mSEM, a sample is simultaneously irradiated with a multitude of single-electron beams arranged in a field or grid. For example, 4 to 10,000 single-electron beams can be provided as primary radiation, with each single-electron beam separated from an adjacent single-electron beam by a distance of 1 to 200 micrometers. For example, an mSEM has approximately 100 separate single-electron beams (beamlets) arranged, for example, in a hexagonal grid, with the single-electron beams separated by a distance of approximately 10 µm.A multitude of charged single-particle beams (primary beams) are focused by a common objective lens onto the surface of a sample under investigation. The sample can be, for example, a semiconductor wafer mounted on a wafer holder attached to a movable stage. During illumination of the wafer surface with the charged primary single-particle beams, interaction products, such as secondary electrons or backscattered electrons, emanate from the wafer surface. Their starting points correspond to the locations on the sample onto which the multitude of primary single-particle beams are focused. The quantity and energy of the interaction products depend on the material composition and the topography of the wafer surface.The interaction products form several secondary single-particle beams (secondary beams) that are collected by the common objective lens and directed by a projection imaging system of the multi-beam inspection system onto a detector located in a detection plane. The detector comprises several detection areas, each containing several detection pixels, and the detector records an intensity distribution for each of the secondary single-particle beams. This results in an image field of, for example, 100 µm × 100 µm.

[0006] The prior art multi-beam electron microscope comprises a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adapt the focus position and stigmatization of the multiple charged single-particle beams. The prior art multi-beam charged particle system also includes at least one intersection plane of the primary or secondary charged single-particle beams. Furthermore, the prior art system includes detection systems to facilitate adjustment. The prior art multi-beam particle microscope includes at least one deflection scanner for collectively scanning an area of ​​the sample surface using the multiple primary single-particle beams to obtain an image field of the sample surface.

[0007] To separate the particle-optical beam path of the primary beams from the particle-optical beam path of the secondary beams, a so-called beam splitter (also called a beam separator or beam divider) is used. This separation is achieved by means of special arrangements of magnetic fields and / or electrostatic fields, for example, using a Wien filter.

[0008] Alignment of a multi-beam electron microscope, or more generally, a multi-beam particle microscope, is of great importance for precision applications. One aspect of alignment is the adjustment of the system's magnetic lenses. These magnetic lenses can be, in particular, so-called global magnetic lenses, which are essentially penetrated by all charged particles or all charged single-particle beams equally. These lenses therefore require especially precise alignment. Furthermore, due to the geometric dimensions of such a magnetic lens, it is not possible to deduce the magnetic field generated within the lens exactly. In other words, the magnetic field of lenses manufactured identically within the limits of manufacturing precision can differ measurably, which is why individual lens alignment is necessary.The reason for this is inhomogeneities in the magnetic material: Magnetic materials are not perfectly homogeneous, but have grain boundaries. If the magnetic materials are not homogeneous, or if some other type of material inhomogeneity has occurred, then it is possible that the magnetic flux does not emerge from the pole shoe end in a perfectly homogeneous manner. The magnetic field generated in a pole shoe opening is therefore often not perfectly symmetrical or often not free of tolerance aberrations.

[0009] Magnetic lenses for multi-beam particle beam systems are mechanically aligned for several reasons. This involves mechanically aligning the upper and lower pole pieces of the magnetic lens. The lens housing, containing a coil, and the lens cover are separately movable and mechanically adjustable, particularly in an alignment plane perpendicular to the particle-optical axis Z. The pole pieces are then fixed in place.

[0010] According to current technology, the adjustment of magnetic lenses in a multi-beam particle microscope is often purely mechanical, with experienced technicians performing the adjustment manually. Such an adjustment is time-consuming and is carried out while simultaneously observing a multi-beam particle microscope image. Screws on the outside of the multi-beam particle microscope or its housing are adjusted to align the magnetic lenses. The adjustment and subsequent fixing of the magnetic lenses is normally performed during the commissioning of the multi-beam particle microscope in production. Afterward, the adjustment usually remains unchanged and is only performed on-site at the customer's location after a module or magnetic lens replacement. Such a replacement may be necessary, for example, due to mechanical damage or a voltage surge, particularly in the case of objective lenses.Readjusting the multi-beam particle microscope after an exchange at the customer's site is more difficult, as it is often integrated into a production plant and its associated process chain. This can lead to lengthy and costly downtime in the production plant, which should be avoided.

[0011] DE 10 2022 114 098 A1 discloses an improved adjustment mechanism for magnetic lenses in a multi-beam particle microscope. For this purpose, an electrically controllable mechanical adjustment and fixing device with an actuator is provided for at least one, in particular globally adjustable, magnetic lens. This actuator is configured to mechanically adjust and fix the position of the at least one adjustable magnetic lens in the particle-optical beam path in a plane orthogonal to the optical axis of the multi-beam particle microscope. A control system is also provided, configured to electrically control the electrically controllable mechanical adjustment and fixing device. However, this improved adjustment mechanism still involves a time expenditure, albeit a smaller one. Description of the invention

[0012] The object of the present invention is therefore to enable faster adjustment of magnetic lenses for particle beam systems, and in particular for multi-beam particle beam systems. The exchange of magnetic lenses in a particle beam system, and especially in a multi-beam particle beam system, should be simplified and made faster.

[0013] The problem is solved by the subject matter of the independent patent claims. Dependent patent claims are directed to advantageous embodiments of the invention.

[0014] A fundamental aspect of the invention is to replace the active mechanical adjustment of a magnetic lens during or after its installation in a particle beam system with passive adjustment. In active adjustment, the two pole pieces of a magnetic lens are moved relative to each other within an adjustment plane. In contrast, with passive adjustment, the relative alignment of the two pole pieces in the installation or operating position is already fixed and highly precisely defined, for example, by means of a high-precision fit. This saves valuable time. Instead of active adjustment within the system itself, passive adjustment is performed prior to installation using a reference standard or a reference pole piece in a test setup.In particular, material removal processes can be used on a joining surface of the pole shoe and / or in the area of ​​a pole shoe opening for the precise positioning and alignment of a magnetic axis of the magnetic lens. The inventive concept can, in principle, also be transferred to other functional units of a particle beam system and, in particular, to a multi-particle beam system.

[0015] According to a first aspect of the invention, it relates to a method for the passive adjustment of a pole shoe for a magnetic lens of a particle beam system, comprising the following steps: Providing a reference pole piece with a predefined minimum magnetic homogeneity in a measuring device; Detachable arrangement of the pole shoe to be adjusted relative to the reference pole shoe in a predefined reference position and thereby assembly of a magnetic lens in the measuring device; Excitation of the magnetic lens in the measuring device; Measuring characteristics of the magnetic field generated by the magnetic lens; determining any deviation of the characteristics of the generated magnetic field from the corresponding characteristics of a predefined reference magnetic field; Mechanical modification of the pole shoe based on the determined deviation to adjust the magnetic field that can be generated by means of the magnetic lens.

[0016] Passive adjustment, as explained above, refers to the adjustment of two pole pieces of a magnetic lens relative to each other, without any relative movement of the two pole pieces within an adjustment plane. The magnetic lens can be any type, such as an objective lens, a condenser lens, a field lens, or a projection lens. The particle beam system can also be of any type. Preferably, it is a multi-beam particle beam system, but other configurations are also possible.

[0017] The magnetic lens consists of two pole shoes: the reference pole shoe and the pole shoe to be adjusted. Naturally, the magnetic lens can include other components, such as the winding located within it. The magnetic lens is the functional unit that requires passive adjustment.

[0018] The reference pole piece exhibits a predefined minimum magnetic homogeneity. The reference pole piece thus represents a reference standard. Normally, this reference pole piece is manufactured with considerable effort and also tested accordingly to ensure it can actually fulfill its function as a reference.

[0019] The measuring device is a device for measuring the functionality of the magnetic lens. It therefore includes the means necessary to investigate or test the function of the composite magnetic lens. For example, the measuring device may include a particle source, and in particular a multi-beam particle source. It may also include particle optics in addition to the magnetic lens. Furthermore, the measuring device may include a sample stage and a test sample, which is positioned on the sample stage with its surface in the plane of the magnetic lens, a deflection system with control electronics, and a detection system for detecting secondary particles. The measuring device may also include an evaluation unit, such as a computer system. The fundamental principle is that the measuring device should be as simple as possible while allowing for highly precise testing of the magnetic lens's functionality.The measuring device can also be integrally designed with the reference pole piece. This means that the reference pole piece is fixed and permanently arranged within the measuring device and does not need to be inserted into the measuring device for the passive adjustment procedure. The fixed arrangement of the reference pole piece within the measuring device eliminates potential sources of error during testing.

[0020] The pole shoe to be adjusted is detachably positioned relative to the reference pole shoe in a predefined reference position. This detachability is important because the measuring device is solely concerned with testing and establishing the proper functionality of the functional unit consisting of the pole shoe to be adjusted and the reference pole shoe. Subsequently, the passively adjusted pole shoe should be immediately usable in a particle beam system. The detachable positioning can be achieved, for example, by screwing the pole shoe together.

[0021] The assembled magnetic lens can now be tested. First, the magnetic lens is excited in the measuring device. Then, the characteristics of the magnetic field generated by the magnetic lens are measured, and deviations of these characteristics from those of a predefined reference magnetic field are determined. Based on the determined deviation, the pole shoe is mechanically adjusted to adapt the magnetic lens generated by the lens. Specifically, this can be done, for example, as follows: 1) The properties of the magnetic lens under transmitted light are investigated by taking an image of a reference sample using a raster scanning method. 2) This image is examined for geometric properties, e.g., distortion. If the reference magnetic field were also present in the real magnetic lens, this image would have certain known properties or would correspond to a reference image in which distortion was present. 3) Additionally, the excitation of the magnetic lens can be changed, and the resulting changes in certain image properties are measured. These properties can include distortion, rotation, magnification, shift, or other characteristics. 4) From the various analyses of the images, the difference between the axis of the electron beam and the magnetic axis can then be determined using calculation methods and, for example, iteratively minimized by shifting and / or tilting the pole pieces relative to each other. Possible characteristics of the generated magnetic field include, for example, the position and / or the

[0022] Alignment of a magnetic axis of the magnetic lens or the magnetic field it generates. These characteristics do not need to be measured directly; rather, they can be inferred from the imaging properties, as described above. However, it is also fundamentally possible to directly measure the characteristics of the magnetic field generated by the magnetic lens.

[0023] The measured characteristics of the generated magnetic field are compared with the corresponding characteristics of a predefined reference magnetic field, and any deviation between the measured or determined characteristics and those of the predefined reference magnetic field is calculated. A reference magnetic field can be defined, for example, by the position and / or orientation of the magnetic axis of the magnetic lens. Another possible characteristic of a generated magnetic field is its omnidirectional symmetry perpendicular to the axis. The roundness of the generated magnetic field can also be measured and, in principle, adjusted by mechanically modifying the pole piece.

[0024] The pole shoe is then mechanically adjusted based on the determined deviation to match the magnetic field generated by the magnetic lens. This step involves the actual passive adjustment by mechanically modifying the pole shoe. This mechanical adjustment alters the overall magnetic field generated by the magnetic lens so that its characteristics match those of the predefined reference magnetic field.

[0025] For this mechanical adjustment to be successful, it is necessary to position the pole shoe to be adjusted relative to the reference pole shoe in the predefined reference position. In this way, the desired change in the magnetic field generated by the magnetic lens can be achieved through a targeted mechanical adjustment of the pole shoe. Preferably, the mechanical adjustment of the pole shoe does not take place within the measuring device or a chamber belonging to the measuring arrangement. Instead, it is preferable that the pole shoe to be adjusted is first detached and then moved to a separate chamber for the mechanical adjustment or processing. This protects the measuring device with its inherently sensitive reference pole shoe.

[0026] According to a preferred embodiment of the invention, the method further comprises the following step: at least partial annealing of the pole shoe to homogenize its magnetic properties. Mechanical modification of the pole shoe can lead to the re-emergence of magnetic inhomogeneities within the pole shoe, for example, due to deformation or stress. Annealing the pole shoe, or at least a portion thereof, therefore contributes to the (re-)homogenization of its magnetic properties. The annealing can be carried out in a separate chamber.

[0027] According to a preferred embodiment of the invention, the pole shoe to be adjusted and the reference pole shoe can be connected to each other by means of at least one fit. A fit is defined as is customary in mechanical engineering. A fit is thus defined as the dimensional relationship between two parts that are intended to fit together without further machining. These parts usually have the same contour at the joining point, once as an inner shape and once as an outer shape. Such a fit allows the pole shoe to be positioned relative to the reference pole shoe in the predefined reference position.

[0028] According to a preferred embodiment of the invention, the at least one fit has an accuracy of 100µm, advantageously 10µm, most advantageously 1µm.

[0029] It is possible to provide more than one fit, for example two, three, four, five or six fits.

[0030] According to a preferred embodiment of the invention, the mechanical modification of the pole shoe comprises a material removal process. Examples of such material removal processes are machining processes, for example turning and / or milling.

[0031] Bending methods are also an alternative method for mechanically modifying the pole shoe.

[0032] According to a preferred embodiment of the invention, the pole shoe has an opening through which charged particles pass during operation of the magnetic lens. The opening of the pole shoe to be adjusted has a position and a shape. When mechanically adjusting the pole shoe passively, the position and / or shape of the opening is changed in this embodiment. For a circular opening, the center point of the opening can be used as the position. However, the shape of the opening can also be other than circular, for example, elliptical or an intermediate shape between a circle and an ellipse. Even then, it is possible to define a position for this shape, for example, via the position of the left edge of the opening or, in the case of an ellipse, by the position of one of its foci.By changing the shape and / or position of the opening of the pole shoe being adjusted, the position and / or orientation (angle) of the magnetic axis of the magnetic lens and / or the circular symmetry of the magnetic field can be set.

[0033] According to a preferred embodiment of the invention, the pole shoe to be adjusted has a pole shoe mounting surface, and the reference pole shoe has a reference pole shoe mounting surface. The pole shoe mounting surface and the reference pole shoe mounting surface correspond to each other. This correspondence can be direct or indirect. In any case, the pole shoe mounting surface and the reference pole shoe mounting surface correspond to each other with respect to their shape. According to this embodiment of the invention, when the pole shoe is mechanically modified, the pole shoe mounting surface is changed. This creates a new pole shoe mounting surface, which in turn corresponds to the reference pole shoe mounting surface. Thus, even after the pole shoe has been mechanically modified, the pole shoe to be adjusted and the reference pole shoe fit each other perfectly.

[0034] By mechanically modifying the pole shoe mounting surface and thereby creating a new pole shoe mounting surface, a tilt between the pole shoe and the reference pole shoe can be set, for example. According to a preferred embodiment of the invention, the pole shoe mounting surface is therefore asymmetrically milled to create a new pole shoe mounting surface that also corresponds to the reference pole shoe mounting surface. An asymmetric milling process is, for example, an angled milling of a formerly straight or straight-aligned pole shoe mounting surface. In contrast, a symmetrical milling process would only reduce the height of the pole shoe; this type of milling would otherwise have no effect on the symmetry.

[0035] According to a further preferred embodiment of the invention, the pole shoe mounting surface and the reference pole shoe mounting surface are flange-shaped and are, in particular, screwed together. This allows for a demonstrably precise and simple connection between the pole shoe mounting surface and the reference pole shoe mounting surface.

[0036] According to a further preferred embodiment of the invention, the method further comprises the following step: arranging a spacer, in particular a spacer ring, between the mechanically modified pole shoe mounting surface and the reference pole shoe mounting surface. The arrangement of a spacer is an example of how the pole shoe mounting surface and the reference pole shoe mounting surface correspond only indirectly to each other. Arranging or using a spacer may be necessary because the mechanical modification of the pole shoe is achieved predominantly by material removal. This can reduce the dimensions of the pole shoe along its main axis, particularly if material removal is performed repeatedly for passive adjustment. The spacer can be provided to compensate for this.

[0037] According to a preferred embodiment of the invention, the reference position between the pole shoe to be adjusted and the reference pole shoe is defined by means of a reference mark. Preferably, this reference mark is visible in the circumferential direction of the magnetic lens. However, a reference position can also be defined differently, for example by means of a detent or by means of one or more of the aforementioned fits.

[0038] According to a further preferred embodiment of the invention, the reference mark is designed as a stop of a kinematic suspension, and when the pole shoe is mechanically moved, the pole shoe is changed in the area of ​​the reference mark or the area that rests against the stop, so that the position of one or more openings of the pole shoe is changed. Ultimately, the mechanical change of the pole shoe results in a relative displacement of the pole shoe with respect to the reference pole shoe. However, the contact position between the pole shoe and the reference pole shoe remains precisely defined.

[0039] According to a preferred embodiment of the invention, when determining characteristics of the generated magnetic field in the measuring device, an image of a test sample is taken and this image is subjected to an image evaluation method.

[0040] According to a preferred embodiment of the invention, when determining characteristics of the generated magnetic field in the measuring device, several images of the test sample are recorded at different excitations of the magnetic lens and these are each subjected to the image evaluation procedure, wherein the different images are further compared with each other in the image evaluation procedure.

[0041] According to a further preferred embodiment of the invention, the method further comprises the following step: Providing a reference table that links deviations of magnetic fields from a reference magnetic field to measures for mechanically modifying the pole piece; the mechanical modification of the pole piece is then carried out based on this reference table. For example, if the reference is made to the position and / or the orientation or inclination of the magnetic axis of the magnetic lens, such a reference table can contain information about which measure will produce a corresponding correction in the event of a positional and / or inclination deviation from the ideal case. This makes it possible to perform the mechanical modification of the pole piece in a very targeted manner.

[0042] According to a preferred embodiment of the invention, the generated magnetic field is characterized with respect to the position of its magnetic axis, wherein the position of the magnetic axis is characterized by means of a positional deviation from a reference point and / or by means of a tilting relative to a reference axis of the reference magnetic field.

[0043] According to a further preferred embodiment of the invention, the positional deviation of the magnetic axis and / or the tilting of the magnetic axis is linked to a measure for the mechanical modification of the pole shoe, which causes a shift in the position of the pole shoe opening on the pole shoe. It is then precisely specified how the mechanical modification of the pole shoe must be designed or implemented in order to correct the positional deviation and / or tilting.

[0044] According to a preferred embodiment of the invention, the generated magnetic field is characterized with respect to its circular symmetry. Such circular symmetry is of great relevance for many applications in the field of particle optics.

[0045] According to a preferred embodiment of the invention, a deviation of the magnetic field from round symmetry is linked to a measure for material removal in the area of ​​the opening of the pole shoe, which causes a change in the ellipticity of the opening.

[0046] According to a further preferred embodiment of the invention, a tilting of the magnetic axis is combined with a measure for the mechanical modification of the pole shoe, which causes a tilting of the pole shoe relative to the reference pole shoe. This can, for example, be the already described asymmetrical removal of the pole shoe's mating surface. Alternatively, it is also possible to bend a pole shoe mating surface by means of a bending process.

[0047] The characteristics described above and their deviations from the corresponding characteristics of a predefined reference magnetic field are only examples and not exhaustive.

[0048] According to a further preferred embodiment of the invention, the method further comprises the following step: testing the mechanically modified pole shoe in the test device. Testing the mechanically modified pole shoe in the test device is intended to ensure that the mechanical modification of the pole shoe has the desired effect. If necessary, further work must be carried out. The testing preferably includes the steps of releasably arranging, operating or exciting the magnetic lens in the measuring device, remeasuring the characteristics of the magnetic field generated by the magnetic lens, and re-determining any deviation of the characteristics of the generated magnetic field from the corresponding characteristics of a predefined reference magnetic field.

[0049] According to a preferred embodiment of the invention, the method is repeatedly performed until a threshold value is undercut when determining the deviation of the characteristics of the generated magnetic field from the corresponding characteristics of the predefined reference magnetic field. The magnetic field can then be considered free of tolerance aberrations. The threshold value itself can be determined in advance from extensive tolerance calculations.

[0050] Based on the inventive method, the passively adjusted pole shoe can now be used directly in a correspondingly constructed particle beam system; no further mechanical adjustment of the pole shoe in the particle beam system itself is required.

[0051] According to another aspect of the invention, it relates to a method for equipping a particle beam system with a magnetic lens, comprising the following steps: Providing a first pole shoe using the method as described above in several embodiments; Arranging the first pole shoe in the particle beam system; Providing a second pole shoe using the method as described above in several embodiments; and releasably arranging the second pole shoe relative to the first pole shoe in the predefined reference position and thereby assembling the magnetic lens in the particle beam system.

[0052] The method for equipping a particle beam system with a magnetic lens is based on the principle that the two pole shoes installed within it have each been passively pre-aligned with respect to a reference pole shoe or reference standard. The first pole shoe can be an upper pole shoe and the second pole shoe a lower pole shoe, or vice versa. It is crucial that, prior to equipping the particle beam system with a reference pole shoe, the pole shoe to be adjusted (first or second) is passively pre-aligned.

[0053] In a particle beam system constructed as described, with a magnetic lens assembled as described, it is easily possible to replace one of the pole pieces with only a very brief interruption of operation. For example, a damaged pole piece can be removed and replaced with another pole piece that has already been passively adjusted beforehand in a suitably equipped measuring device. In this way, a considerable amount of time can be saved during the adjustment of a particle beam system.

[0054] The magnetic lens can, in principle, be any type of magnetic lens. Preferably, the magnetic lens is an objective lens. This objective lens can be damaged by external influences, such as contact with a surface in the sample chamber or by a voltage arc in the sample chamber. Specifically, it is then the lower pole piece of the objective lens that needs to be replaced.

[0055] However, the magnetic lens could also be a condenser lens, a field lens, a projection lens, or another type of magnetic lens.

[0056] Furthermore, reference is made to the explanations relating to the first aspect of the invention.

[0057] According to a third aspect of the invention, it relates to a particle beam system that has been equipped with a magnetic lens according to the described method for equipping a particle beam system. Otherwise, what has already been described in connection with the first and second aspects of the invention applies.

[0058] According to a preferred embodiment of the invention, the particle beam system comprises one element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM. This list is not exhaustive.

[0059] The aspects and embodiments of the invention described above can be combined in whole or in part, provided that this does not result in any technical contradictions.

[0060] As already indicated above, the inventive concept for the passive adjustment of a pole shoe for a magnetic lens can, in principle, also be applied to other functional units of a particle beam system, and in particular to a multi-particle beam system. Precise particle-optical alignment of elements within a functional unit may also be necessary for other functional units. Centering tasks for functional units of a particle beam system are particularly common in this context. Passive adjustment can replace the existing mechanical adjustment, which is based on relative movements within an adjustment plane, or even make adjustment of a functional unit possible for the first time.

[0061] According to a fourth aspect of the invention, it therefore relates to a method for the passive adjustment of a particle-optical element for a functional unit of a particle beam system, comprising the following steps: Providing a reference element with a reference joining surface in a measuring device; Providing the particle optical element with an element joining surface that corresponds to the reference joining surface; Detachable arrangement of the particle-optical element to be adjusted relative to the reference element in a predefined reference position and thereby assembly of a functional unit for a particle beam system in the measuring device; Operating the functional unit in the measuring device; Measuring particle-optical characteristics of the functional unit; Determining a deviation of the measured particle-optical characteristics of the functional unit from corresponding characteristics of a predefined reference functional unit; and Mechanical modification of the particle-optical element using a material-removing process based on the determined deviation to adapt the functional unit.

[0062] According to a preferred embodiment of the invention, the composite functional unit comprises exactly two elements: the reference element and the particle-optical element to be adjusted. However, it is also possible for the functional unit to be itself a component of a larger functional unit. For example, a passively adjustable particle-optical element may comprise a first element mounting surface corresponding to a first reference mounting surface and a second element mounting surface corresponding to a second reference mounting surface. In this case, it is preferred that a separate measuring device is provided for each of the (partial) functional units for testing or measuring the functional unit or sub-functional unit, respectively.

[0063] According to a preferred embodiment of the invention, when the particle-optical element is mechanically modified, the element joining surface is mechanically altered, thereby forming a new element joining surface that also corresponds directly or indirectly, or immediately or indirectly, to the reference joining surface. According to a preferred embodiment of the invention, material from an element joining surface is removed asymmetrically about a principal axis of the particle-optical element to be adjusted. This allows a tilt between the reference element and the particle-optical element to be adjusted to be precisely set.

[0064] According to a preferred embodiment of the invention, the mechanical modification of the particle-optical element comprises a machining process, in particular turning and / or milling.

[0065] According to a preferred embodiment of the invention, the particle-optical element to be adjusted and the reference element are connected to each other by means of at least one fitting. In this way, a very precise arrangement of the particle-optical element relative to the reference element can be achieved.

[0066] According to a preferred embodiment of the invention, the fit has an accuracy of 100µm, preferably 10µm or most preferably 1µm.

[0067] According to a preferred embodiment of the invention, the element joining surface and the reference joining surface are flange-shaped and, in particular, screwed together. This allows for a particularly simple and precise arrangement of the particle-optical element and the reference element relative to each other.

[0068] According to a further preferred embodiment of the invention, the method further comprises the following step: Arranging a spacer, in particular a spacer ring, between the mechanically modified element joining surface and the reference joining surface. This takes into account the fact that the mechanical modification of the element joining surface can practically only be achieved by material removal. This is particularly relevant when the method according to the invention is carried out repeatedly and / or iteratively and the material loss is comparatively large. In such cases, it may be necessary to provide a spacer.

[0069] According to a preferred embodiment of the invention, the particle-optical characteristics of the functional unit describe a centering and / or an orientation of an electrostatic field generated by the functional unit. In other words, it is possible to describe a position and / or an inclination of the electrostatic field. For example, the position of an electrostatic axis can be described. This can be characterized by a position in a specific plane and by an inclination of the axis relative to this plane.

[0070] According to a further preferred embodiment of the invention, the particle-optical characteristics of the functional unit describe a centering and / or an alignment of a magnetic field generated by the functional unit. For example, the magnetic axis can be described with respect to position and inclination.

[0071] According to a preferred embodiment of the invention, the functional unit comprises one element from the following list: an electrostatic lens, an electrostatic deflection system, an electrostatic stigmatization system, a higher-order electrostatic multipole system, a magnetic lens, a magnetic deflection system, a magnetic stigmatization system, a higher-order magnetic multipole system, an aperture arrangement with a plurality of apertures, a Wien filter, a beam splitter. This list is not exhaustive.

[0072] All functional units share the common feature that the measuring device used for the passive adjustment of a particle-optical element within a particle beam system's functional unit also performs a measurement of particle-optical properties. It is not merely a purely mechanical measurement. Therefore, the passive adjustment method is not simply a mechanical solution to any (arbitrary) adjustment problem. Instead, passive adjustment is closely linked to the function of the particle beam system's functional unit, and the proper functioning of that unit within the system is measured. Thus, the passive adjustment method for a particle-optical element within a particle beam system's functional unit is a specialized procedure that not only replaces conventional, active mechanical adjustment but can often surpass it in terms of the achievable results.This is because some adjustment errors do not result solely from manufacturing inaccuracies, but also from other sources of error that are not mechanically measurable, or at least not easily measurable, such as inhomogeneities, mechanical stresses, etc. After passive adjustment by material removal, the particle-optical element of the functional unit can also be annealed if necessary.

[0073] According to a preferred embodiment of the invention, the method is carried out in a cascade manner for a plurality of particle optical elements, wherein the particle optical elements, starting with the second particle optical element, are each assembled in a cascade manner to form an extended new particle optical element, for which the method is then carried out. This makes it possible to mount and passively adjust various particle optical elements sequentially. The cascade thus begins with a first particle optical element that has been passively adjusted. A second particle optical element is then connected to the first particle optical element, which is mounted and fitted to it. A third particle optical element is then connected to this entire unit consisting of the first and second particle optical elements, and so on.The particle-optical elements can be of different physical types. Therefore, different components of a particle beam system can be successively assembled and fitted together.

[0074] Furthermore, everything that has been stated in connection with the method for passively adjusting a pole shoe for a magnetic lens of a particle beam system also applies, in a figurative sense, to the described method for passively adjusting a particle optical element for a functional unit of a particle beam system.

[0075] The described embodiments and variants according to the fourth aspect of the invention can again be combined wholly or partially, provided that this does not result in any technical contradictions.

[0076] According to a fifth aspect of the invention, it relates to a method for equipping a particle beam system with a functional unit, comprising the following steps: Providing a first particle-optical element of the functional unit using the above-described method for passively adjusting a particle-optical element for a functional unit of a particle beam system; Arranging the first particle-optical element in the particle beam system; providing a second particle-optical element using the method for passively adjusting a particle-optical element for a functional unit of a particle beam system as described above in several embodiments; and releasably arranging the second particle-optical element relative to the first particle-optical element in the predefined reference position and thereby assembling the functional unit in the particle beam system.

[0077] In this aspect of the invention, a key principle is that the particle-optical elements to be installed have already been passively aligned using reference elements, thus eliminating the need for active mechanical alignment of the functional unit within the particle beam system. This significantly speeds up the setup of a particle beam system. The same applies if a functional unit or a particle-optical element within a functional unit needs to be replaced. This, too, can be done very quickly and without lengthy downtime of the particle beam system.

[0078] According to a sixth aspect of the invention, it relates to a particle beam system, wherein the particle beam system has been equipped with a functional unit as described above according to the method described above for equipping a particle beam system.

[0079] According to a preferred embodiment of the invention, the particle beam system comprises one element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM. The foregoing list is not exhaustive.

[0080] The aspects and embodiments of the invention described above can be combined in whole or in part, provided that this does not result in any technical contradictions.

[0081] The invention will be better understood with reference to the accompanying figures. These show: Fig. 1: schematically shows a particle beam system in the form of a multi-beam particle microscope; Fig. 2: schematically shows aspects of a mechanical adjustment of a magnetic lens; Fig. 3: schematically shows aspects of a mechanical adjustment of a magnetic lens; Fig. 4: schematically shows aspects of a mechanical adjustment of a magnetic lens; Fig. 5: schematically shows aspects of a passive adjustment of a magnetic lens; Fig. 6: schematically shows aspects of a passive adjustment of a magnetic lens; Fig. 7: schematically shows a passively adjusted pole shoe in a top view; Fig. Figure 8: schematically shows the joining surfaces of a reference pole shoe and a pole shoe to be adjusted in a perspective view; Fig. Figure 9: schematically shows the joining surfaces of a reference pole shoe and a pole shoe to be adjusted in a perspective view; Fig. 10: schematically shows a reference pole shoe and a pole shoe to be adjusted with fits in a sectional view; Fig. 11: schematically shows the fits of a pole shoe to be adjusted with a reference pole shoe in a sectional view; Fig. 12: schematically shows a top view of a reference pole shoe with fits or screw connections; Fig. 13: schematically shows a measuring device for testing pole shoes to be adjusted; Fig. 14: schematically shows the measuring device Fig. 13 in operation; Fig. Figure 15: schematically shows a method for the passive adjustment of a pole shoe for a magnetic lens of a particle beam system; Fig. Figure 16: schematically shows a method for equipping a particle beam system with a magnetic lens; Fig. Figure 17: schematically shows a method for replacing a pole shoe of a magnetic lens in a particle beam system; Fig. Figure 18: schematically shows a method for the passive adjustment of a particle optical element for a functional unit of a particle beam system; and Fig. Figure 19 schematically shows a method for equipping a particle beam system with a functional unit.

[0082] Fig. Figure 1 schematically shows a multi-beam particle beam system 1 in the form of a multi-beam particle microscope 1. The multi-beam particle microscope 1 has a beam generation device 300 with a particle source, for example, an electron source. Charged particles or electrons are generated by the beam generation device 300, for example, by thermal field emission. The emitted charged particles form a diverging particle beam 309, which is collimated by a sequence of condenser lenses 303.1 and 303.2 and strikes a multi-beam particle generator 305 with a multi-aperture arrangement. The multi-beam particle generator 305 comprises several multi-aperture plates 304, 306 and a field lens 307. A multitude of single-particle beams 3 or 3 are emitted by the multi-beam particle generator 305.Single-electron beams 3 are generated, arranged in a field which is mapped onto another field formed by beam spots 5 in the object plane 101. The distance between the centers of apertures of a multi-aperture plate 306 can be, for example, 5 µm, 100 µm, and 200 µm. The diameters D of the apertures are smaller than the distance between the centers of the apertures; examples of the diameters are 0.2 times, 0.4 times, and 0.8 times the distances between the centers of the apertures.

[0083] The multi-aperture arrangement 305 and the field lens 308 are configured to generate a multitude of focal points 323 of primary beams 3 in a grid arrangement on a surface 321. The surface 321 need not be a flat surface, but can be a spherically curved surface to accommodate field curvature of the subsequent particle optical system.

[0084] The multi-beam particle microscope 1 further comprises a system of electromagnetic lenses 103 and an objective lens 102, which reduce the size of the beam foci 323 from the intermediate image plane 321 onto the object plane 101. The first individual particle beams 3 pass through the beam splitter 400 and a collective beam deflection system 500, which deflects the multitude of the first individual particle beams 3 during operation and scans the image field. The first individual particle beams 3 incident on the object plane 101 form, for example, a substantially regular field, with distances between adjacent point locations 5 being, for example, 1 µm, 10 µm, or 40 µm. The field formed by the point locations 5 can, for example, have a rectangular or hexagonal symmetry.

[0085] The object 7 to be examined can be of any type, for example a semiconductor wafer or a biological sample, and it can comprise an array of miniaturized elements or the like. The surface 15 of the object 7 is located in the object plane 101 of the objective lens 102. The objective lens 102 can comprise one or more electron-optical lenses. It can be, for example, a magnetic objective lens and / or an electrostatic objective lens.

[0086] The primary particles 3 striking object 7 generate interaction products such as secondary electrons, backscattered electrons, or primary particles that have undergone a reversal of motion for other reasons. These products originate from the surface of object 7 or from the first plane 101 or object plane 101. The interaction products emanating from the surface 15 of object 7 are shaped into secondary particle beams 9 by the objective lens 102. After passing through the objective lens 102, the secondary beams 9 pass through the beam splitter 400 and are directed to a projection system 200. The projection system 200 has an imaging system 205 with projection lenses 206, 208 and 210, a contrast aperture 214 and a multi-particle detector 207. The impact points 25 of the second single-particle beams 9 on the detection areas of the multi-particle detector 207 are located in a third field at a regular distance from each other.Examples of values ​​are 10 µm, 100 µm and 200 µm.

[0087] The multi-beam particle microscope 1 further comprises a computer system or a control unit or controller 10, which in turn may be designed as a single unit or as a multi-part unit, and which is designed both for controlling the individual particle-optical components of the multi-beam particle microscope 1 and for evaluating and analyzing the signals obtained with the multi-detector 207 or the detection unit.

[0088] The particle-optical functional unit according to the invention, such as a magnetic lens and in particular an objective lens 102, which has been passively adjusted, can be placed in the Fig. The multi-particle beam system 1 shown can be integrated. However, the functional unit can also be integrated into another particle beam system 1.

[0089] Further information on such multi-beam particle beam systems or multi-beam particle microscopes 1 and components used therein, such as particle sources, multi-aperture plates and lenses, can be obtained from the international patent applications WO 2005 / 024881 A2, WO 2007 / 028595 A2, WO 2007 / 028596 A1, WO 2011 / 124352 A1 and WO 2007 / 060017 A2 and the German patent applications DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1, the disclosure of which is incorporated in full by reference into the present application.

[0090] Fig. Figure 2 schematically shows aspects of the mechanical adjustment of a magnetic lens 700. The magnetic lens 700 comprises a lens pot or upper pole shoe 701 and a lens cover or lower pole shoe 702. Inside the magnetic lens 700, a winding 703 is arranged, which can be excited to generate a magnetic field. During operation of the magnetic lens 700, a charged particle beam or several charged particle beams enter the magnetic lens 700 through the opening 706 of the upper pole shoe 701 and exit through the opening 707 of the lower pole shoe 702. The charged particles or the charged particle beam(s) traverse the magnetic field of the magnetic lens 700. The magnetic field of the magnetic lens 700 exits the pole shoes 701 and 702 at the openings 706 and 707 in a defined shape. The following are examples: Fig. 2a) Some field lines 708 are drawn. A section along the cutting plane C is shown in Fig. Figure 2b shows that, ideally, the magnetic field generated by the magnetic lens 700 is omnisymmetrical, as shown in Figure 2b. Fig. 2b is represented by the equipotential lines 708a. The particle-optical axis Z runs centrally through the magnetic field and the equipotential lines 708a are arranged circularly around the particle-optical axis Z.

[0091] For adjusting the magnetic lens 700, the upper pole shoe 701 and the lower pole shoe 702 are movable relative to each other: In the example shown, the lower pole shoe 702 can be moved in the x-direction. The same normally applies to a movement in the y-direction (in Fig. (2 not explicitly shown). For mechanical displacement, a mechanical adjustment element 704 is provided, which acts against a spring or against a support 705. Overall, the lower pole shoe 702 is thus movable in an adjustment plane (x, y-plane) that is oriented orthogonally to the particle-optical axis Z. This is the adjustment known from the prior art.

[0092] Fig. Figure 2 shows the ideal case of an adjustment situation: The magnetic lens 700 is perfectly manufactured and exhibits no inhomogeneities within the pole shoes or grain boundaries. In this ideal case, the particle-optical axis Z coincides with the geometric axis A of the magnetic lens. Furthermore, the upper pole shoe 701 and the lower pole shoe 702 are precisely aligned with each other; that is, the opening 706 of the upper pole shoe and the opening 707 of the lower pole shoe 702 are also exactly aligned.

[0093] Fig. Figure 3, however, shows a possible real-world case: While the pole shoe 702 is manufactured precisely within the specified tolerances, two inhomogeneities 709 are present within the pole shoe 702, which affect the magnetic flux in the pole shoe 702. This influence is in Fig. 3 schematically represented. As a result, the magnetic field lines 708 can be seen in Fig. 3a may be slightly altered. For example, the axis Z of the magnetic field that can be generated by means of the magnetic lens 700 might not coincide with the geometric axis A of the magnetic lens 700.

[0094] The in Fig. The magnetic lens 700 shown in section 3 therefore requires further adjustment: This is shown schematically in Fig. Figure 4 illustrates this. During the adjustment process, the lower pole shoe 702 was mechanically shifted in the x-direction by the amount d, in the illustrated example to the left. Using the mechanical adjusting element 704, the spring 705 was compressed slightly, and then the position of the lower pole shoe 702 was fixed (not shown). Through the relative displacement of the upper pole shoe 701 and the lower pole shoe 702, the tilt of the particle-optical axis Z was corrected by the mechanical adjustment; the particle-optical axis Z, or the axis of the magnetic field, now runs exactly perpendicular to the z-direction. In contrast, the geometric axis A is inclined relative to the z-direction. However, the crucial factor for adjustment is not the geometric axis A, but the orientation of the particle-optical axis Z.

[0095] The active mechanical adjustment described above is relatively time-consuming. Adjusting a magnetic lens 700, which can be installed in a particle beam system 1 and especially in a multi-beam particle microscope, is time-consuming. Therefore, replacing a pole piece of the magnetic lens 700 when this magnetic lens 700 is installed in a particle beam system should be avoided if possible, or the adjustment time should be kept short. This can be achieved by the passive adjustment according to the present invention: The Fig. 5 and Fig. Figure 6 shows the principle of the passive adjustment of a magnetic lens 700 according to the invention: Unlike the adjustment associated with the Fig. In accordance with the conventional mechanical adjustment described in sections 2 to 4, the two pole shoes 720, 721 of the magnetic lens 700 are detachably connected to each other in a predefined reference position. Fig. Figure 5 schematically shows a connecting element 722 for this purpose. Furthermore, according to the invention, a reference standard or a reference pole shoe 720 is used. This reference pole shoe 720 has a predefined minimum magnetic homogeneity. In other words, the reference pole shoe 720 is manufactured to a near-perfect standard and has, for example, been additionally analyzed. The pole shoe 720 thus exhibits very small inhomogeneities that would cause minimal distortion of the magnetic flux emerging from the pole shoe 720.

[0096] In contrast, the lower pole shoe 721 is a conventional pole shoe which, although manufactured using common manufacturing processes within manufacturing tolerances, nevertheless exhibits the inhomogeneities 709 already described, which adversely affects the emergence of the magnetic flux from the opening 707 of the pole shoe 721.

[0097] Based on measurements, for example within a measuring device 900, the position and orientation of the magnetic axis Z of the magnetic lens 700 can be determined. The magnetic axis Z is tilted relative to the geometric axis A, or the magnetic axis Z is not oriented in the z-direction.

[0098] Based on an analysis of the characteristics of the magnetic field generated by the magnetic lens 700 in a measuring device 900, the pole shoe 721 to be adjusted can be mechanically modified. In the example shown, area 723 of the pole shoe 721 to be adjusted was modified in the region of the pole shoe opening 707; in this example, material was removed, for example, by turning and / or milling. Reassembling the reference pole shoe 720 with the mechanically modified pole shoe 721 and subsequently operating the magnetic lens 700, as well as measuring and analyzing the characteristics of the generated magnetic field, shows a correlation between the particle-optical axis Z and the geometric axis A.

[0099] A mechanical change to the pole shoe 721 to be adjusted can be made on the one hand in the area of ​​the pole shoe opening 707 and on the other hand in the area of ​​the joining surface 731 with the reference pole shoe 720.

[0100] Fig. Figure 7 schematically shows several examples of a passively adjusted pole shoe 721 in a top view of the pole shoe 721: Specifically, it shows Fig. 7a is an initial situation, wherein the opening 707 is arranged concentrically within the outer surface 724 of the pole shoe 721. After a mechanical change, the pole shoe opening 707 is in Fig. 7b is enlarged on the one hand and shifted laterally in the x direction on the other. This is in Fig. The x,y coordinate system shown in Figure 7 serves to better illustrate this fact. Fig. In 7c, the opening 707 is still arranged concentrically within the outer surface 724 of the pole shoe 721, but the opening 707 is, compared to the situation in Fig. 7a enlarged. In Fig. Finally, in 7d, the shape of the opening 707 is no longer circular, but elliptical. This elliptical opening 707 could also be shifted within the x,y-plane, so that the center of the ellipse would no longer lie on the origin of the x,y-coordinate system.

[0101] Fig. Figure 7 shows that there are many possibilities for mechanically changing the pole shoe 721 to be adjusted in order to position and orient the magnetic field of the magnetic lens 700 generated in the interaction between the reference pole shoe 720 and the pole shoe 721 to be adjusted (angular correction or tilt correction).

[0102] The Fig. 8 and Fig. Figure 9 schematically illustrates another possibility for mechanically changing the pole shoe 721 to be adjusted in the course of the passive adjustment according to the invention. Fig. Figure 8 schematically shows the reference pole shoe 720 with its pole shoe opening 706, as well as the pole shoe 721 to be adjusted with its pole shoe opening 707. Fig. Figure 8 shows the two pole shoes 720 and 721 in relation to each other. In the perspective view, the surface 731 of the lower pole shoe 721 can be seen, which runs around the outside of the pole shoe opening 707. This surface 731 represents the pole shoe joining surface 731, which corresponds to the reference pole shoe joining surface 730 of the reference pole shoe 720. The reference pole shoe joining surface 730 thus corresponds, in the example shown, to the underside of the reference pole shoe 720. Fig. Figure 8 shows only the edge area of ​​the reference pole shoe joining surface 730. The pole shoe opening 707 and the pole shoe joining surface 731 are spaced apart from each other, so that a mechanical change to the pole shoe joining surface 731 has no influence on the pole shoe opening 707 or its magnetic homogeneity; therefore, annealing of the pole shoe 721 after machining is unnecessary.

[0103] The two pole shoes 721 and 720 are joined at the pole shoe joining surface 731 and the reference pole shoe joining surface 730. This joining or connecting process is described in Fig. 8 is also indicated by the two upward-pointing arrows. The reference pole shoe 720 and the pole shoe 721 to be adjusted are detachably arranged next to each other in a predefined reference position. This means that the position and orientation of the reference pole shoe 720 and the pole shoe 721 to be adjusted are fixed. For referencing purposes, in Fig. Figure 8 shows a reference mark 732, but this is only to be understood as an example.

[0104] According to one embodiment of the invention, the pole shoe 721 to be adjusted is mechanically modified by means of a mechanical modification of the pole shoe mounting surface 731. This surface can be machined asymmetrically, particularly with respect to the geometric axis A. A new pole shoe mounting surface 731 is created, which is inclined relative to the original pole shoe mounting surface 731 and thus also relative to the corresponding reference pole shoe mounting surface 730. This is a schematic and greatly exaggerated representation. Fig. 9 shown. The different lengths of the arrows in Fig. Figure 9 is intended to further illustrate the slight tilting of the pole shoe 721 to be adjusted when it is joined to the reference pole shoe 720. Naturally, this tilting of the pole shoe 721 to be adjusted affects the magnetic field that can be generated by a composite magnetic lens 700 comprising the reference pole shoe 720 and the pole shoe 721 to be adjusted during operation of the magnetic lens. The magnetic axis Z can be tilted, or a previously existing tilt can be corrected.

[0105] In Fig. In Figure 9, the reference mark 732 is located at the highest point of the joining surface 731. This is merely an example. Naturally, the reference mark 732 can also be located at a different point on the joining surface 731. Furthermore, it is possible to provide a reference mark 732 not on the joining surface 731 itself, but laterally or on an externally visible side wall of the pole shoe 721 to be adjusted. A corresponding reference mark is then, of course, also provided on the reference pole shoe 720.

[0106] For the inventive method for the passive adjustment of a pole shoe 721 for a magnetic lens 700, it is important that the pole shoe 721 to be adjusted can be detachably arranged in a predefined reference position relative to the reference pole shoe 720. While working with a reference mark 732 is generally possible, it does not replace the actual process of arranging or fastening the reference pole shoe 720 to the pole shoe 721 to be adjusted. A very good and practical solution for the detachable arrangement of the pole shoe 721 to be adjusted on the reference pole shoe 720 is described in Fig. Figure 10 schematically illustrates that, according to this example, a fit 733 can be used for arranging and fastening on the one hand, and for defining the reference position on the other. The term fit 733 is used in this patent application as is customary in mechanical engineering. A fit refers to the dimensional relationship between two parts that are intended to fit together without rework and with a defined residual tolerance. These parts usually have the same contour at the joining point, once as an inner shape and once as an outer shape.

[0107] In Fig. Figure 10 shows a sectional view of the reference pole shoe 720, which has a flange-like design in the area of ​​its joining surface 730, or rather a flange 734. A fit is provided on the underside of the joining surface 730, or rather the positive form 733a of the fit 733 is formed.

[0108] In the example shown, the pole shoe 721 to be adjusted is again designed as a lens cap; in this example, it is not flange-shaped, although this could be the case. The negative form 733b of the fit 733 is formed in the area of ​​the surface or joining surface 731. The positive form 733a fits very precisely into the negative form 733b. This is shown in Fig. 10 is also represented by the two arrows between the pole shoes 720 and 721. By using the fit or fits 733, the reference pole shoe 720 can be positioned very precisely relative to the pole shoe 721 to be adjusted. The clearance that the positive form 733a exhibits when sliding into the negative form 733b is very small. It can, for example, be a fit with an accuracy of 100 µm, preferably 10 µm, or most preferably 1 µm.

[0109] After joining the reference pole shoe 720 and the pole shoe 721 to be adjusted using the two fittings 733, the geometrically matching connection thus created is fixed by means of a screw connection. This is in Fig. 10 indicated by the two screws 735 and the two nuts 736.

[0110] If a mating surface 731 of the pole shoe 721 to be adjusted is mechanically altered, for example by removing material, this does indeed have an effect on the fits 733. However, the passive adjustment of a magnetic lens 700 is a precision adjustment, so the functionality of the fits 733 is not affected: This is in Fig. 11 are shown in an exemplary and schematic manner.

[0111] In Fig. Figure 11a shows the initial situation in which the axis of symmetry S of the positive form 733a and the negative form 733b of the fit 733 coincide. It can also be seen in Fig. 11a, that there is some play in the area of ​​the side walls 739a, 739b and in the area of ​​the bottom 738a, 738b. The amount of this play results from the tolerance of the fit 733.

[0112] If only a slight tilt occurs due to a chamfer on the joining surface 731 of the pole shoe 721 to be adjusted, the positive form 733a can still slide into the negative form 733b. This is ensured by the corresponding tolerance. However, it is evident that the inner side wall 739a is tilted relative to the outer side wall 739b. Furthermore, the base 738a is also tilted relative to the base 738b of the fit 733. The contact surfaces of the fit 733, which are associated with the reference pole shoe 720, still lie flat on the joining surface 731, even after the asymmetrical, mechanically altered joining surface 731. By tightening screw 735 accordingly, the fit can be fixed in its position; the angle between the axis of symmetry of the positive form 733a on the one hand and the axis of symmetry 733b of the negative form on the other hand can also be fixed in this way.

[0113] The tilt angle provided by means of the described asymmetric mechanically changing joining surface 731 is typically in the range of 0.01mrad to 5mrad.

[0114] Fig. Figure 12 schematically shows a top view of a reference pole shoe 720 with fits or screw connections 735: In Fig. 12a A total of four fits with associated screw connections 735 are arranged equidistantly from each other. In Fig. In contrast, 12b has a total of eight fits of each associated screw connection 735 arranged equidistantly to each other. Fig. Figure 12 thus shows a top view of the flange 734. The top of the reference pole shoe 721, as well as the upper pole shoe opening 706, is shown in Fig. 12 are also shown. The number and arrangement of the fits or screw connections 735 in Fig. 12 is to be understood as merely exemplary; the equidistant arrangement is also to be interpreted only as an example.

[0115] Fig. Figure 13 schematically shows a measuring device 900 for testing pole shoes 721 to be adjusted. The measuring device 900 can, for example, be configured as a test stand. In the example shown, it includes a particle source 901 for emitting charged particles, for example, electrons. Furthermore, the measuring device 900 in the example shown has a particle optic 902, which is only shown schematically. This particle optic 902 can comprise one or more components and, in particular, one or more lenses, deflectors, and / or stigmatists. The important aspect is the beam preparation of one or more charged particle beams for the functional test of the magnetic lens 700, which is composed of the reference pole shoe 720 and the pole shoe 721 to be adjusted.In addition to the beam generation and beam conditioning unit 901, 902, the measuring device 900 also includes the reference pole shoe 720, which has already been described in detail in connection with the preceding figures. In the example shown, the reference pole shoe 720 is again a lens pot or an upper pole shoe, which also includes the winding 703. However, the reference pole shoe 720 could also be a lens cover or a lower pole shoe. Therefore, the representation as a lens cover is only to be understood as an example.

[0116] In Fig. In the example shown, a sample stage 903 is arranged 13 below the reference pole piece 720. This stage can be adjustable in one or more spatial directions, but does not have to be. A test sample 904 is arranged on the sample stage 903. The nature of the sample will be selected appropriately by the person skilled in the art. In the example shown, a detection device 905 is schematically depicted above the test sample 904. This detection device 905 can be configured differently, for example, as a secondary electron detector of different designs. Furthermore, in the example, according to Fig. Figure 13 provides a control unit 906. In the example shown, the control unit 906 serves both to control the measuring device 900 itself and to evaluate the data generated by the measuring device 900. The control unit 906 can, for example, be connected to a monitor, an input unit, and a computer, or include such components. According to a preferred embodiment of the invention, the measuring device 900 includes everything required, both in terms of hardware and software, for testing a pole shoe to be adjusted.

[0117] Fig. 14 shows the in Fig. Figure 13 shows the measuring device 900 in operation: In the measuring device 900, or in the measuring stand, a pole shoe 721 to be adjusted is detachably arranged on the reference pole shoe 720 in a predefined reference position. The magnetic lens 700 is thus assembled as a functional unit. The predefined reference position is in Fig. Figure 14 is again only schematically illustrated by the connecting element 722. The connecting element 722 could, for example, be the one associated with the Fig. The fit or fits described in sections 10 to 11 refer to 733. However, the connecting element 722 can also be implemented differently.

[0118] In the operation of the measuring device 900, particle radiation is generated by means of the particle source 901; this is processed by the particle optics 902 for the actual functional test of the magnetic lens 400. This is shown schematically in Fig. Figure 14 shows a particle beam 907, which is focused onto the test sample 904 by means of the magnetic lens 700. In the example shown, this causes secondary particles and, in particular, secondary electrons to be released from the test sample 904, which are then Fig. 14 are schematically designated with the reference symbol 908. These secondary particles 908 can be detected with the detection system 905. The detected particle-optical image can be processed, evaluated and / or displayed in its entirety by means of the control unit 906.

[0119] It is of course possible to test and qualify the magnetic lens 700 using a single beam 907. However, it is also possible to qualify a magnetic lens 700 using a multi-beam particle beam system. In this case, the beam generating device 901, 902 generates a multitude of single-particle beams and processes them appropriately for the subsequent qualification of the magnetic lens 700.

[0120] To characterize the magnetic field generated by the magnetic lens 700, the already known wobble method can be used, for example. For this purpose, the excitation of the magnetic lens 700 or its coil 703 is varied, ideally resulting in a variation of the generated particle-optical image only in its sharpness, but not in its position. Any deviation from perfect positioning and / or inclination can be determined, and based on this, the pole shoe 721 can be mechanically adjusted.

[0121] The in the Fig. 13 and Fig. The 14 schematically depicted measuring devices 900 are to be understood as examples of the invention. The measuring devices 900 can, in principle, also be constructed differently. It is important that the functionality of the magnetic lens 700 in the measuring device 900 can be tested, analyzed, and evaluated in a suitable manner in order to determine how a mechanical change to the pole shoe 721 to be adjusted must be carried out in order to prequalify the pole shoe 721 to be adjusted with the required accuracy.

[0122] Furthermore, it is possible to provide a corresponding measuring device 900 for other functional units. Such functional units can, for example, include elements from the following list: an electrostatic lens, an electrostatic deflection system, an electrostatic stigmatization system, a higher-order electrostatic multipole system, a magnetic lens, a magnetic deflection system, a magnetic stigmatization system, a higher-order magnetic multipole, an apartur arrangement with a plurality of aparturs, a Wien filter, a beam splitter.

[0123] For all functional units, particle-optical characteristics are determined in a suitable measuring device; these particle-optical characteristics relate to measurements of electrostatic and / or magnetic fields. This is not a purely mechanical precision measurement or a purely positional measurement of mechanical parts.

[0124] Fig. Figure 15 schematically shows a method for the passive adjustment of a pole shoe 721 for a magnetic lens 700 of a particle beam system 1. In a first process step S1, a reference pole shoe 720 with a predefined minimum magnetic homogeneity is provided in a measuring device 900. This reference pole shoe 720 is a pole shoe that meets all quality and performance requirements and has been manufactured with particular care and precision. It is important to ensure, once, that the reference pole shoe 720 is suitable as a reference standard, for example by testing.

[0125] In a second process step S2, the pole shoe 721 to be adjusted is detachably arranged relative to the reference pole shoe 720 in a predefined reference position within the measuring device 900. This results in the assembly of a magnetic lens 700 within the measuring device 900. The reference position can be, for example, a pair of reference markings 732 and / or the provision of a fit 733 or several fits 733. However, the predefined reference position can also be provided or implemented in another way.

[0126] In process step S3, the assembled magnetic lens 700 is excited in the measuring device 900. The excitation of the magnetic lens 400 can, for example, be carried out according to the known wobble method, in which the strength of the excitation of the magnetic lens 700 is varied.

[0127] In a further process step S4, characteristics of the magnetic field generated by the magnetic lens 700 are measured. This measurement can include the acquisition and evaluation of a particle-optical image. For example, in the wobble method mentioned above, the position of a beam spot or focal point can be observed when the magnetic lens 400 is alternately excited, allowing conclusions to be drawn about the position and / or orientation of the magnetic axis of the magnetic field generated by the magnetic lens 700. Additionally or alternatively, the circular symmetry of the generated magnetic field can be measured.

[0128] In a further process step S5, the deviation of the characteristics of the generated magnetic field from the corresponding characteristics of a predefined reference magnetic field is determined. In this process step, the actual state is compared with the target state. After determining the deviation of the characteristics of the generated magnetic field from the corresponding characteristics of the predefined reference magnetic field, it can be ascertained whether any deviation is below a threshold value. If so, the process ends with the final process step S8. However, if the deviation is present and exceeds the threshold value, the process continues. In process step S6, the pole shoe 721 to be adjusted is mechanically modified based on the determined deviation to adapt the magnetic field generated by the magnetic lens 400. This process step corresponds to passive adjustment in the narrower sense. The mechanical modification of the pole shoe 721 to be adjusted is targeted; that is, the type of modification required for the pole shoe can be derived from the deviation determined in step S5. According to a preferred embodiment of the invention, the mechanical modification of the pole shoe 721 to be adjusted comprises a material removal process, for example, a machining process such as turning and / or milling. According to an alternative embodiment of the invention, a bending process can be used for the mechanical modification.However, a material removal process is preferred because, at least in connection with magnetic lenses 700 as functional units, this generates fewer stresses in the pole shoe material that can influence the properties of the magnetic material or the generated magnetic flux.

[0129] Based on the determined characteristics, or rather on the deviation of the characteristics of the generated magnetic field from the corresponding characteristics of the predefined reference magnetic field, the specific mechanical modification of the pole shoe 721 to be adjusted is carried out: For example, it is possible that the pole shoe to be adjusted is modified in the area of ​​the pole shoe opening. Additionally or alternatively, it is possible that, during the mechanical modification of the pole shoe, a pole shoe mounting surface that corresponds to a reference pole shoe mounting surface of the reference pole shoe 720 is mechanically modified. For example, during mechanical modifications of the pole shoe 721 in the area of ​​the pole shoe opening 707, the position and / or shape of the pole shoe opening 707 can be specifically changed.Specific measures for the mechanical modification can be obtained, for example, from a reference table which links deviations of the characteristics of the measured magnetic field to the characteristics of a reference magnetic field with a specific measure for mechanically modifying the pole shoe 721. For example, the magnetic field generated in the measuring device 900 can be characterized with respect to the position of its magnetic axis Z, whereby this position of the magnetic axis Z is characterized by a positional deviation from a reference point and / or by a tilt relative to a reference axis. Specifically, for example, the positional deviation of the magnetic axis and / or the tilt of the magnetic axis Z can be linked to a measure for mechanically modifying the pole shoe, which causes a displacement of the position of the opening 707 of the pole shoe 721 on the pole shoe 721.Additionally or alternatively, the generated magnetic field can be characterized with respect to its circular symmetry. For example, a deviation of the magnetic field from circular symmetry in the reference table can then be linked to a measure for material removal in the area of ​​the opening 707 of the adjusting pole shoe 721, which causes a change in the ellipticity of the opening 707. An originally round opening 707 can, for example, be made elliptical.

[0130] Additionally or alternatively, based on the deviation determined in step S5, the pole shoe joining surface 731, which corresponds to the reference pole shoe joining surface, can be mechanically modified when the pole shoe 721 to be adjusted is mechanically altered. For example, the pole shoe joining surface can be asymmetrically removed to adjust for tilt between the pole shoe 721 and the reference pole shoe 720, creating a new pole shoe joining surface 731 that also corresponds to the reference pole shoe joining surface 730. If a relatively large amount of material is removed from the pole shoe joining surface, a spacer, in particular a spacer ring, may be required between the mechanically modified pole shoe joining surface 731 and the reference pole shoe joining surface 730 to compensate for the material loss when the magnetic lens 700 is reassembled in the measuring device 900.

[0131] A mechanical modification of the pole shoe 721 to be adjusted, for example by turning and / or milling, exerts forces on the pole shoe, and stresses can occur. For this reason, it is advantageous that, in an optional process step S7, the pole shoe 721 is annealed to (re-)homogenize its magnetic properties. This annealing of the pole shoe 721 can be carried out completely or partially. The annealing should be performed at least in those areas of the pole shoe 721 where the mechanical modifications were carried out.

[0132] After the optional process step S7, process steps S2 to S5 are repeated. This repetition corresponds to testing the mechanically modified pole shoe 721 in the test device 900. It is possible that the test of the mechanically modified pole shoe 721 in the measuring device 900 will be successful after only one iteration, meaning that the mechanical modifications made were already sufficient to reduce deviations of the generated magnetic field from the corresponding characteristics of the predefined reference magnetic field below a threshold value. In this case, the process ends in process step S8. Alternatively, a further iteration can be performed, i.e., process steps S6 and S7 are carried out again.

[0133] The mechanical changes made in process step S6 can be the same as in the first pass, but it is also possible that the mechanical changes made are different. The pole shoe 721 to be adjusted can therefore be mechanically modified at a different location and / or in a different way.

[0134] The major advantage of the described method for passively adjusting a pole shoe 721 for a magnetic lens 700 of a particle beam system 1 is that a pole shoe 721 adjusted mechanically in this way is immediately ready for use in a corresponding particle beam system 1, provided the particle beam system 1 is appropriately equipped. Time-consuming active mechanical adjustment in the particle beam system 1 is therefore no longer necessary. This saves time and costs.

[0135] Fig. Figure 16 schematically shows a method for equipping a particle beam system 1 with a magnetic lens 700. In an initial process step S100, a first pole shoe is provided using the method for passively adjusting a pole shoe for a magnetic lens of a particle beam system 1, as described above in several embodiments. This first pole shoe is thus passively mechanically adjusted accordingly.

[0136] In a further process step S101, the first pole shoe is arranged in the particle beam system 1, which is to be equipped.

[0137] In a further process step S102, a second pole shoe is provided using the method for the passive adjustment of a pole shoe for a magnetic lens 700 of a particle beam system 1, as described above in several embodiments. This second pole shoe is also passively mechanically adjusted.

[0138] In a further process step S103, the second pole shoe is detachably arranged relative to the first pole shoe in the predefined reference position, thereby assembling the magnetic lens 700 in the particle beam system 1. Both the first and second pole shoes have undergone passive mechanical adjustment using a corresponding reference pole shoe. Naturally, the first pole shoe was assigned to a different reference pole shoe than the second. The first pole shoe could, for example, be an upper pole shoe and the second pole shoe a lower pole shoe. It is also possible that the first pole shoe is a lower pole shoe and the second pole shoe is an upper pole shoe. Each pole shoe was passively adjusted using its associated reference pole shoe. The first reference pole shoe can be used as a basis for manufacturing a second reference pole shoe.Nevertheless, every effort will be made to ensure that the second reference pole shoe also meets the predefined minimum requirements for magnetic homogeneity. Therefore, a second reference pole shoe can also be subjected to further tests and examinations, for example, by means of X-ray analysis. This is important to minimize the propagation of errors to the pole shoes 721 that are being adjusted.

[0139] The magnetic lens 700 can, in principle, be any magnetic lens. However, according to a preferred embodiment of the invention, it is an objective lens. Objective lenses in particle beam systems are often subject to special requirements: The objective lens is the lens with the greatest refractive power, which is why misalignment errors of the magnetic lens can have a particularly detrimental effect on the overall system. Furthermore, in some particle beam systems, for example, a multi-beam particle microscope 1, a high voltage of several kV, for example more than 25 kV, is applied to a lower pole piece of the objective lens 102. Therefore, electrical discharges can occur during the operation of such a multi-beam particle microscope 1, which could potentially damage a lower pole piece of the objective lens 102. This would then have to be replaced.Furthermore, a lower pole shoe can also suffer mechanical damage to an objective lens 101 due to its proximity to a sample 7, which can be positioned on a movable sample stage 600, which also necessitates replacement.

[0140] Alternatively, it is of course possible that the magnetic lens 700 in the particle beam system represents a condenser lens, a field lens, a projection lens, etc. Furthermore, it is of course possible to equip a particle beam system 1 with a plurality of, in particular, different magnetic lenses 700 in the manner described.

[0141] The particle beam system can, in principle, be of any type. Preferably, the particle beam system 1 comprises one element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM. This list is not exhaustive.

[0142] Fig. Figure 17 schematically shows a method for replacing a pole shoe 721 of a magnetic lens 700 in a particle beam system 1. In this method, a particle beam system 1 is first prepared according to the method described in Fig. The pole shoe 721, which is schematically depicted in Figure 16, has been equipped. In a further process step S104, the pole shoe 721 to be replaced is detached from its associated pole shoe within the particle beam system 1. The detachability of the pole shoe 721 has already been ensured in principle by the inventive method for the passive adjustment of a pole shoe for a magnetic lens 700 of a particle beam system 1. The pole shoe 721 to be replaced can therefore be removed in a very simple manner.

[0143] In a further process step S105, the provision of a replacement pole shoe 721a is again carried out using the inventive method for the passive adjustment of a pole shoe for a magnetic lens 700 of a particle beam system 1. This replacement pole shoe is therefore again passively mechanically adjusted.

[0144] In a further process step S106, the replacement pole shoe is repositioned relative to the pole shoe remaining within particle beam system 1 in the predefined reference position. This reassembles the magnetic lens 700 within particle beam system 1. A separate active mechanical adjustment is not necessary, saving valuable time when replacing a pole shoe.

[0145] The in the Fig. The methods described in sections 15 to 17 can, in principle, be transferred to other functional units of a particle beam system 1; the composite functional unit need not be a magnetic lens 700. Accordingly, it shows Fig. 18 schematically a method for the passive adjustment of a particle optical element for a functional unit of a particle beam system 1: In an initial process step S200, a reference element with a reference mounting surface is provided in a measuring device. Furthermore, in a process step S201, the particle-optical element to be passively adjusted is provided with an element mounting surface that corresponds to the reference mounting surface.

[0146] In process step S202, the particle-optical element to be adjusted is detachably arranged relative to the reference element in a predefined reference position. This completes the assembly of the functional unit for the particle beam system 1 in the measuring device.

[0147] In process step S203, the functional unit is operated in the measuring device. Preferably, the functional unit is operated in the same manner as it is intended to be operated in the particle beam system 1. However, it is also possible to modify the operation of the functional unit appropriately, as long as the operation of the functional unit in the measuring device allows conclusions to be drawn about the calibration state or characteristics of the functional unit.

[0148] In process step S204, the particle-optical characteristics of the functional unit are measured. These particle-optical characteristics of the functional unit can, for example, describe the centering and / or alignment of an electrostatic field generated by the functional unit. Additionally or alternatively, the particle-optical characteristics of the functional unit can describe the centering and / or alignment of a magnetic field generated by the functional unit.

[0149] In step S205, the deviation of measured particle-optical characteristics of the functional unit from corresponding characteristics of a predefined reference functional unit is determined. If the deviation determined is less than a predefined threshold, the procedure ends in step S208.

[0150] Otherwise – and this is the norm, at least for a first-time implementation of the procedure – Fig. In the procedure described in section 18, step S206 involves a mechanical modification of the particle-optical element using a material-removing process based on the determined deviation to adapt the functional unit. For example, the element's joining surface may be mechanically modified, creating a new element joining surface that also corresponds to the reference joining surface. This mechanical modification can include, for example, a machining process, in particular turning and / or milling. Alternatively, the element's joining surface may remain mechanically unchanged, but another area or location of the particle-optical element, which together with the reference element forms the functional unit, may be mechanically modified, in particular using a material-removing process, based on the deviation determined in step S205.

[0151] According to one example, the element joining surface for adjusting a tilt between the passively adjusted particle-optical element and the reference element can be ablated asymmetrically in such a way that a new element joining surface, which also corresponds to the reference element joining surface, is formed.

[0152] In an optional process step S207, a spacer, in particular a spacer ring, is arranged between the mechanically modified element joining surface and the reference joining surface.

[0153] Subsequently, process steps S202 to S205 are repeated, which corresponds to testing the mechanically modified element interface. If the test is successful, for example, if the measured deviation falls below the previously mentioned threshold, the process ends in step S208. Otherwise, the process can be repeated once or multiple times. The mechanical modification in process step S206 can be carried out using the same or a different mechanical method, and / or the mechanical modification can be performed at a different position or positions on the particle-optical element being adjusted.

[0154] Before the in Fig. In the method described in section 18, the particle-optical element can be connected to the reference element by means of one or more fits. The fit may, for example, have an accuracy of 100 µm, preferably 10 µm, or most preferably 1 µm.

[0155] Furthermore, it is possible that the element joining surface and / or the reference joining surface are flange-shaped and, in particular, screwed together. However, other detachable arrangements in a predefined reference position are also fundamentally possible.

[0156] This unfolds its particular strengths in Fig. The methods described in section 18 apply if the particle-optical characteristics of the functional unit describe a centering and / or an alignment of an electrostatic field generated by the functional unit. The same applies if the particle-optical characteristics of the functional unit describe a centering and / or an alignment of a magnetic field generated by the functional unit.

[0157] The functional unit of the particle beam system can comprise one element from the following list: an electrostatic lens, an electrostatic deflection system, an electrostatic stigmatization system, a higher-order electrostatic multipole system, a magnetic lens, a magnetic deflection system, a magnetic stigmatization system, a higher-order magnetic stigmatization system, an aperture array with a plurality of apertures, a Wien filter, or a beam splitter. This list is not exhaustive.

[0158] Optionally, after each mechanical change to the element joining surface, the particle optical element to be adjusted can be annealed.

[0159] According to a preferred embodiment of the invention, the method is performed according to Fig. The process is carried out in a cascade-like manner for a plurality of particle optical elements, whereby the particle optical elements, starting with the second particle optical element, are each assembled in a cascade-like fashion to form an extended new particle optical element, for which the process is carried out in each case. This makes it possible to mount and passively adjust various particle optical elements sequentially. The cascade thus begins with a first particle optical element that has been passively adjusted. A second particle optical element is attached to the first, mounted, and aligned with it. A third particle optical element is then added to this entire unit consisting of the first and second particle optical elements, and so on. The particle optical elements can be of different physical types.Therefore, different components of a particle beam system can be successively assembled and fitted together.

[0160] Fig. Figure 19 schematically shows a method for equipping a particle beam system 1 with a functional unit. In a process step S300, a first particle-optical element of the functional unit is initially provided using the method associated with Fig. 18 described procedures.

[0161] In process step S301, the first particle-optical element provided is arranged in the particle beam system 1.

[0162] Accordingly, in process step S302, a second particle-optical element is provided using the procedure according to Fig. 17.

[0163] In process step S303, the second particle-optical element is detachably arranged relative to the first particle-optical element in the position already determined by the process according to Fig. 17 predefined reference positions and thereby the assembly of the functional unit in the particle beam system 1.

[0164] Even in the Fig. In each of the methods described in section 19, a particle-optical element of the functional unit is provided by reference to a reference element. This means that the particle-optical elements are passively aligned and can be assembled directly and quickly into the functional unit in the particle beam system 1.

[0165] Replacing the first and / or second particle optical element in the particle beam system is correspondingly simple. Here, too, a passively adjusted replacement element can be used, which has been passively adjusted in a suitable measuring device.

[0166] The particle beam system can, in principle, be of any type. Preferably, it includes one element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM. This list is not exhaustive.

[0167] The invention eliminates the need for time-consuming active mechanical adjustment in a particle beam system. Using one or more reference standards and passively adjusting a particle optical element, such as a pole piece for a magnetic lens, by mechanically modifying this element saves valuable time and costs and also enables quick and easy replacement of a particle optical element in a particle beam system.

[0168] The embodiments of the invention described in the figures can be combined in whole or in part, provided that this does not result in any technical contradictions. Furthermore, the examples described in the figures are to be understood as merely illustrative of the invention and do not limit it to the examples shown in the figures. Reference symbol list 1. Multi-beam particle system, multi-beam particle microscope 3 primary particle beams, first single-particle beams 5 beam spots, points of impact 7. Object, sample, wafer 9 secondary particle beams, second single-particle beams 10 Computer system, control 15 Sample surface, wafer surface 25 pixels of a second single-particle beam 101 Object level 102 lens 103 Field lens 105 axle 108 Beam crossing, Cross-over 200 detector system 205 Projection lens system 206 Projection lens 207 Multi-particle detector 208 Projection lens 210 Projection lens 212 Beam crossing, Cross-over 214 aperture filter, contrast diaphragm 222 Collective Anti-Deflection System 300 beam generating device 303 Collimation lens system, condenser lens system 304 multi-aperture plate, filter plate 305 Multibeam Particle Generator 306 Multi-aperture plate 307 Field lens 308 Field lens 309 Particle beam 311 Illuminating particle beam 321 Intermediate image plane 323 beam foci 400 beam switch, magnetic arrangement 500 scan deflectors 600 Moving table or positioning device 700 magnetic lens 701 Lens pot, upper pole shoe 702 Lens cap, lower pole shoe 703 winding 704 mechanical adjusting element 705 spring 706 Opening of the upper pole shoe 707 Opening of the lower pole shoe 708 Magnetic field line 709 Inhomogeneity 720 Reference pole shoe 721 pole shoe to be adjusted 722 Connecting element 723 mechanically modified area 730 Reference pole shoe joining surface 731 Pole shoe joining surface 732 Reference mark 733 Fit 734 Flange 735 screw 736 mother 737 Opening 738 Floor 739 Side wall 740 Top 900 measuring device 901 particle source 902 Particle Optics 903 Sample table 904 Test sample 905 Detection device 906 Control 907 particle beam(s) 908 secondary particles x direction y direction z A direction Z particle optical axis geometric axis, principal axis d displacement of the lower pole shoe relative to the upper pole shoe QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 7 244 949 B2

[0005] US 2019 / 0355544 A1

[0005] DE 10 2022 114 098 A1

[0011] WO 2005 / 024881 A2

[0089] WO 2007 / 028595 A2

[0089] WO 2007 / 028596 A1

[0089] WO 2011 / 124352 A1

[0089] WO 2007 / 060017 A

[0089] DE 10 2013 016 113 A1

[0089] DE 10 2013 014 976 A1

[0089]

Claims

[1] Method for passive adjustment of a pole shoe for a magnetic lens of a particle beam system comprising the following steps: Providing a reference pole piece with a predefined minimum magnetic homogeneity in a measuring device; Detachable arrangement of the pole shoe to be adjusted relative to the reference pole shoe in a predefined reference position and thereby assembly of a magnetic lens in the measuring device; Excitation of the magnetic lens in the measuring device; Measuring the characteristics of the magnetic field generated by the magnetic lens; Determining a deviation of the characteristics of the generated magnetic field from corresponding characteristics of a predefined reference magnetic field; Mechanical modification of the pole shoe based on the determined deviation to adjust the magnetic field that can be generated by means of the magnetic lens. [2] A method according to any of the preceding claims, further comprising the following step: At least partial annealing of the pole shoe to homogenize its magnetic properties. [3] Method according to one of the preceding claims, wherein the pole shoe and the reference pole shoe are connected to each other by means of a fit. [4] Method according to the preceding claim, wherein the fit has an accuracy of 100µm, in particular of 10µm or of 1µm. [5] Method according to one of the preceding claims, wherein the mechanical modification of the pole shoe comprises a material removal method. [6] Method according to claim 5, wherein the mechanical modification of the pole shoe comprises a machining process, in particular turning and / or milling. [7] Method according to any one of claims 5 to 6, wherein the pole shoe has an opening which is penetrated by charged particles during operation of the magnetic lens; where the opening has a position and a shape, where the position and / or shape of the opening is changed when the pole shoe is mechanically altered. [8] Method according to any of the preceding claims, wherein the pole shoe has a pole shoe joining surface and wherein the reference pole shoe has a reference pole shoe joining surface; wherein the pole shoe joining surface and the reference pole shoe joining surface correspond to each other; and where the pole shoe joining surface is changed when the pole shoe is mechanically modified. [9] Method according to claim 8, wherein the pole shoe joining surface and / or the reference pole shoe joining surface are flange-shaped and in particular screwed together. [10] Method according to one of claims 8 to 9, wherein the pole shoe joining surface is asymmetrically removed to adjust a tilt between the pole shoe and the reference pole shoe, such that a new pole shoe joining surface is formed which also corresponds to the reference pole shoe joining surface. [11] Method according to any one of claims 8 to 10, further comprising the following step: Arranging a spacer, in particular a spacer ring, between the mechanically modified pole shoe joining surface and the reference pole shoe joining surface. [12] Method according to one of claims 8 to 9, wherein when mechanically changing the pole shoe, the pole shoe joining surface is bent by means of a bending method. [13] Method according to one of the preceding claims, wherein the reference position between the pole shoe and the reference pole shoe is determined by means of a reference mark. [14] Method according to the preceding claim, wherein the reference mark is designed as a stop of a kinematic suspension and when the pole shoe is mechanically changed, the pole shoe in the area of ​​the reference mark and thus the area that rests against the stop is changed, so that the position of the opening of the pole shoe is changed. [15] Method according to one of the preceding claims, wherein when determining characteristics of the generated magnetic field in the measuring device an image of a test sample is taken and this image is subjected to an image evaluation method. [16] Method according to the preceding claim, where, in determining the characteristics of the generated magnetic field in the measuring device, several images of the test sample are taken at different excitations of the magnetic lens and each is subjected to the image evaluation procedure, in which the different images are further compared with each other in the image evaluation process. [17] A method according to any of the preceding claims, further comprising the following step: Providing a lookup table that links deviations of magnetic fields from a reference magnetic field with measures for mechanically modifying the pole shoe; wherein the mechanical modification of the pole shoe is carried out based on the lookup table. [18] Method according to any of the preceding claims, wherein the generated magnetic field is characterized with respect to the position of its magnetic axis, where the position of the magnetic axis is characterized by a positional deviation from a reference point and / or by a tilt relative to a reference axis. [19] Method according to claims 17 and 18, wherein the positional deviation of the magnetic axis and / or the tilting of the magnetic axis is linked with a measure for mechanically changing the pole shoe, which causes a displacement of the position of the opening of the pole shoe on the pole shoe. [20] Method according to claims 17 and 18, wherein the positional deviation of the magnetic axis and / or the tilting of the magnetic axis is linked with a measure for mechanically changing the pole shoe, which causes a tilting of the pole shoe relative to the reference pole shoe. [21] Method according to one of the preceding claims, wherein the generated magnetic field is characterized with respect to its circular symmetry. [22] Method according to claims 17 and 21, wherein a deviation of the magnetic field from round symmetry is combined with a measure for material removal in the area of ​​the opening of the pole shoe, which causes a change in the ellipticity of the opening. [23] A method according to any of the preceding claims, further comprising the following step: Testing the mechanically modified pole shoe in the measuring device. [24] Method according to one of the preceding claims, wherein the method is repeatedly carried out until a threshold value is undercut when determining the deviation of the characteristics of the generated magnetic field from corresponding characteristics of the predefined reference magnetic field. [25] Method for equipping a particle beam system with a magnetic lens comprising the following steps: Providing a first pole shoe using the method according to one of the preceding claims; Arranging the first pole shoe in the particle beam system; Providing a second pole shoe using the method according to one of the preceding claims; Detachable arrangement of the second pole shoe relative to the first pole shoe in the predefined reference position and thereby assembly of the magnetic lens in the particle beam system. [26] Method according to claim 25, wherein the first pole shoe is an upper pole shoe and wherein the second pole shoe is a lower pole shoe. [27] Method according to claim 25, wherein the first pole shoe is a lower pole shoe and wherein the second pole shoe is an upper pole shoe. [28] Method according to any one of claims 25 to 27, wherein the magnetic lens is an objective lens. [29] Method according to any one of claims 25 to 27, wherein the magnetic lens in the particle beam system is one of the following: a condenser lens, a field lens, a projection lens. [30] Particle beam system, wherein the particle beam system has been equipped according to the method of any one of claims 25 to 29. [31] Particle beam system according to claim 30, wherein the particle beam system comprises an element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM. [32] Method for passive adjustment of a particle optical element for a functional unit of a particle beam system comprising the following steps: Providing a reference element with a reference joining surface in a measuring device; Providing the particle optical element with an element joining surface that corresponds to the reference joining surface; Detachable arrangement of the particle-optical element to be adjusted relative to the reference element in a predefined reference position and thereby assembly of a functional unit for a particle beam system in the measuring device; Operating the functional unit in the measuring device; Measuring particle-optical characteristics of the functional unit; Determining a deviation of the measured particle-optical characteristics of the functional unit from corresponding characteristics of a predefined reference functional unit; Mechanical modification of the particle-optical element using a material-removing process based on the determined deviation to adapt the functional unit. [33] Method according to claim 32, wherein the element joining surface is mechanically modified, thereby forming a new element joining surface which also corresponds to the reference joining surface. [34] Method according to one of claims 32 to 33, wherein the mechanical modification of the particle-optical element comprises a machining process, in particular turning and / or milling. [35] Method according to one of claims 32 to 34, wherein the element joining surface is ablated asymmetrically to adjust a tilt between the particle-optical element and the reference element, such that a new element joining surface is formed which also corresponds to the reference element joining surface. [36] Method according to any one of claims 32 to 35, wherein the particle optical element and the reference element are connected to each other by means of a fit. [37] Method according to the preceding claim, wherein the fit has an accuracy of 100µm, in particular of 10µm or 1µm. [38] Method according to any one of claims 32 to 37, wherein the element joining surface and / or the reference joining surface are flange-shaped and in particular screwed together. [39] Method according to any one of claims 32 to 38, further comprising the following step: Arranging a spacer, in particular a spacer ring, between the mechanically modified element joining surface and the reference joining surface. [40] Method according to any one of claims 32 to 39, wherein the particle-optical characteristics of the functional unit describe a centering and / or an alignment of an electrostatic field generated by the functional unit. [41] Method according to any one of claims 32 to 40, wherein the particle-optical characteristics of the functional unit describe a centering and / or an alignment of a magnetic field generated by the functional unit. [42] Method according to any one of claims 32 to 41, further comprising the following step: at least partial annealing of the particle-optical element to homogenize its magnetic properties. [43] Method according to any one of claims 32 to 42, wherein the functional unit comprises an element from the following list: an electrostatic lens, an electrostatic deflection system, an electrostatic stigmatization system, a higher-order electrostatic multipole system, a magnetic lens, a magnetic deflection system, a magnetic stigmatization system, a higher-order magnetic stigmatization system, an aperture arrangement with a plurality of apertures, a Wien filter, a beam splitter. [44] Method according to any one of claims 32 to 43, the process is carried out in a cascade-like manner for a plurality of particle-optical elements, wherein the particle-optical elements from the second particle-optical element onwards are each combined in a cascade-like manner to form an extended new particle-optical element, for which the procedure is carried out in each case. [45] Method for equipping a particle beam system with a functional unit comprising the following steps: Providing a first particle-optical element of the functional unit using the method according to one of claims 32 to 44; Arranging the first particle-optical element in the particle beam system; Providing a second particle-optical element using the method according to any one of claims 32 to 44; and Detachable arrangement of the second particle-optical element relative to the first particle-optical element in the predefined reference position and thereby assembly of the functional unit in the particle beam system. [46] Particle beam system, wherein the particle beam system has been equipped according to the method of claim 45. [47] Particle beam system according to claim 46, wherein the particle beam system comprises an element from the following list: a SEM, a TEM, a STEM, a SEM-STEM, a dual particle beam system, a multi-beam particle microscope, a mask repair system, a LEEM, a PEEM.

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