Multi-beam particle microscope with an aberration correction unit having geometry-based correction electrodes, and method for adjusting the aberration correction, and computer program product

Abstract

A multi-beam particle microscope with an aberration correction unit is provided. A multi-beam particle microscope is disclosed having an improved aberration correction unit for individually correcting one or more aberrations, wherein the aberration correction unit has a sequence of electrode arrays including at least one first electrode array pair, the first pair having a first electrode array and a second electrode array, the first electrode array and the second electrode array each having a plurality of geometry-based correction electrodes each having n-fold rotational symmetry about an optical axis for multipole field generation, each geometry-based correction electrode being individually controllable by exactly one supply line, the geometry-based correction electrodes in the first electrode array being rotated relative to associated geometry-based correction electrodes in the second electrode array with respect to the optical axis, and a controller configured to individually control the plurality of geometry-based correction electrodes of the first electrode array and the second electrode array of the aberration correction unit for aberration correction.

Description

[Technical Field]

[0001] The present invention relates to a multi-beam particle beam system, in particular to a multi-beam particle microscope with an aberration correction unit, and to a method for adjusting the aberration correction, and an associated computer program product. [Background technology]

[0002] With the continued development of smaller and more complex microstructures, such as semiconductor components, there is a need to further develop and optimize planar manufacturing techniques and inspection systems for producing and inspecting small-dimension microstructures. For example, the development and manufacture of semiconductor components requires design monitoring of test wafers, and planar manufacturing techniques require process optimization for high-throughput, reliable manufacturing. Furthermore, there is a recent need for analysis of semiconductor wafers for reverse engineering and for customized, individual construction of component parts. Therefore, there is a need for inspection tools that can be used at high throughput to examine the microstructures on wafers with high precision.

[0003] Typical silicon wafers used in the manufacture of semiconductor components have a diameter of up to 300 mm. Each wafer can be up to 800 mm 2The semiconductor device is divided into 30 to 60 repeating areas ("dies") with sizes of 10 ...

[0004] MSEM, or multibeam scanning electron microscope, is a relatively new development in the field of charged particle systems (charged particle microscopes, CPM). For example, multibeam scanning electron microscopes are disclosed in U.S. Pat. No. 7,244,949 and U.S. Patent Application Publication No. 2019 / 0355544. In a multibeam electron microscope, or MSEM, a sample is simultaneously illuminated by multiple individual electron beams arranged in a field or grid. For example, 4 to 10,000 individual electron beams can be provided as primary radiation, with each individual electron beam separated from adjacent individual electron beams by a pitch of 1 to 200 micrometers. For example, an MSEM has approximately 100 separate individual electron beams ("beamlets"), arranged, for example, in a hexagonal grid, with the individual electron beams separated by a pitch of approximately 10 micrometers. Multiple charged individual particle beams (primary beams) are focused onto the surface of the sample being investigated by a common objective lens. For example, the sample may be a semiconductor wafer fixed to a wafer holder mounted on a movable stage. During irradiation of the wafer surface by the charged primary particle beam, interaction products, such as secondary electrons or backscattered electrons, emerge from the wafer surface. Their origins correspond to locations on the sample where the primary particle beams converge. The amount and energy of the interaction products depend on the material composition and topology of the wafer surface. The interaction products form multiple secondary particle beams (secondary beams), which are collected by a common objective lens and incident on a detector located in a detection plane as a result of the projection imaging system of the multi-beam inspection system. The detector has multiple detection areas, each of which has multiple detection pixels, and captures the intensity distribution of each of the secondary particle beams. For example, an image field of 100 μm × 100 μm is obtained in this process.

[0005] Prior art multi-beam electron microscopes include a series of electrostatic and magnetic elements, at least some of which are adjustable to adjust the focal position and stigmation of the multiple charged individual particle beams. Prior art multi-beam systems using charged particles also include at least one intersecting plane of the primary or secondary charged individual particle beams. Prior art systems also include a detection system to facilitate adjustment. Prior art multi-beam particle microscopes also include at least one beam deflector ("deflection scanner") for collectively scanning an area of ​​the sample surface with the multiple primary individual particle beams to obtain an image field of the sample surface.

[0006] When performing inspection tasks using a multi-beam particle microscope, aberrations inevitably occur and need to be avoided or reduced. For this purpose, according to the prior art, correctors are used that enable either global or individual beam correction. Individual beam correction is particularly important when a multi-beam particle microscope has a large number of individual particle beams and thus a relatively large number of fields of view. In this regard, multi-beam particle microscopes typically suffer from field astigmatism, which cannot be corrected by a global stigmator. Instead, individual beam correctors are typically used that have an array of multipole electrodes, such as octapole electrodes. In this manner, the electrodes are segmented, resulting in a multipole electrode. In this case, each electrode of the multipole electrode can be individually controlled. In this regard, reference is made, for example, to German Patent Application Publication No. 10 2014 008 083.

[0007] In this case, the multipole electrodes can be used not only to correct astigmatism but also to correct other aberrations. For example, the octapole electrodes can also deflect or displace the focal position of individual particle beams. In addition, although somewhat counterintuitive, geometric aberrations with three-fold symmetry can also be corrected by the octapole electrodes.

[0008] Thus, a major advantage of the described multipole electrodes is that they can be used very universally for aberration correction. Nevertheless, in the case of multibeam particle microscopes, which utilize more and more individual particle beams, multipole electrodes are reaching their limits and improvements are needed.

[0009] Multipole electrodes are implemented as large arrays, making their fabrication complex and relatively expensive. Due to their complexity, multipole electrodes are inherently prone to failure, making it difficult to guarantee their quality and service life. In particular, multiple supply lines are required for each multipole electrode to apply voltage to the electrodes. For example, an octopole electrode with eight individually adjustable electrodes requires eight supply lines. For an octopole electrode array for more than 100 individual particle beams in a multibeam particle microscope, more than 800 individual lines would already be required. In reality, providing such a large number of supply lines through vacuum bushings is no longer possible. Instead, the voltages for the supply lines must be generated by devices already located in the vacuum of the multibeam particle microscope, such as application-specific integrated circuits (ASICs). However, placing them in a vacuum chamber is disadvantageous due to potential electron bombardment and the inevitable X-ray radiation generated within the chamber.

[0010] Moreover, when there are a large number of individually controllable electrodes in an array or multi-aperture plate, the supply line arrangement itself becomes problematic. In this case, a large number of lines must extend between the individual octopole electrodes or into the gaps between the openings in the multi-aperture plate. Therefore, in principle, there is a limit to the size or number of multipole electrodes in the multi-aperture plate, and the system does not have good scalability. Even if the method of laying lines in multiple planes is used, this method also involves a relatively high cost, and therefore its suitability as a solution is limited to a certain extent.

[0011] EP 4 020 565, which references EP 2 702 595 and EP 2 715 768, for example, discloses a multi-beam particle beam system with aberration correction for correcting image field curvature, focus position, and astigmatism. Multipole electrodes are used for the correction.

[0012] EP 2 339 608 A1 discloses a series of plates, each with an aperture having a specific geometric shape, for the purpose of aberration correction, thereby generating a respective multipole field. Specifically, EP 2 339 608 A1 discloses, as an example, a hexapole corrector for correcting spherical aberration. This aberration is rotationally symmetric. In the context of a multi-beam particle beam system, EP 2 339 608 A1 discloses a system with multiple tips ("emitter tips") for generating multiple particle beams. The generated particle beams each pass through a series of multiple multi-aperture plates, each with multiple apertures having a specific geometric shape. In this case, a (global) voltage is applied to each multi-aperture plate. As a result, the same aberration correction for all particle beams can be achieved. EP-A-2 339 608 does not mention electric field profiles or electric field dependent individual aberration corrections, and these are not possible with the measures described in EP-A-2 339 608. Summary of the Invention

[0013] It is therefore an object of the present invention to overcome the above-mentioned drawbacks of the prior art. In particular, it is an object of the present invention to provide a multi-beam particle microscope with aberration correction that allows individual beam corrections to be performed for a larger number of individual particle beams and / or with lower control costs. In particular, the intention is to enable electric field dependent corrections individually for each individual particle beam.

[0014] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are evident from the dependent claims.

[0015] This patent application claims priority from German Patent Application Publication No. 10 2022 131 862.1 dated December 1, 2022, the disclosure content of which is incorporated herein by reference in its entirety.

[0016] The basic concept of the present invention includes the multipole correctors used in the prior art, but their segmented electrodes, which would be controlled in a complex manner, are replaced by a different type of correction unit.

[0017] In principle, the following relationship applies for the electrostatic potential U in the multipole corrector (shown in cylindrical coordinates):

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[0018] Thus, the electrostatic potential U in the multipole corrector can in principle be expressed by a series expansion for the multipole.

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[0019] Instead of generating all the potentials required for aberration correction with a single multipole corrector, whose electrodes must be controlled in a complex manner, as in the prior art, in accordance with the present invention, each term in the series expansion is realized separately by a specific electrode pair. All terms of the correction potentials can be represented by a sequence of these specific electrode pairs. In this case, each specific electrode of an electrode pair is individually controllable, but each requires exactly one supply line, thereby reducing the number of supply lines and control costs in the overall aberration correction unit. Here, what is important for the generation of each multipole in a sequence of specific electrodes or electrode pairs is the shape of these electrodes or the cross-sectional shape of these electrodes. Therefore, they are referred to in the context of this patent application as geometry-based electrodes. Geometry-based electrodes can have, for example, an elliptical cross-section, i.e., two-fold symmetry, and thus can generate a quadrupole field. They can also have a substantially rounded equilateral triangle in cross-section, i.e., three-fold symmetry, which generates a hexapole field, and so on.

[0020] Specifically, according to a first aspect, the present invention provides a multi-beam particle microscope having the following characteristics: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a first particle-optical unit having a first particle-optical beam path configured to image the generated first individual particle beam onto the sample surface such that the first individual particle beam is incident on the sample surface in the object plane at an incidence location, thereby forming a second field; a detection system having a plurality of detection regions that form a third field; a second particle-optical unit having a second particle-optical beam path configured to image a second individual particle beam emanating from an incident location within the second field onto a third field in a detection region of the detection system; a magnetic and / or electrostatic objective lens through which both the first individual particle beam and the second individual particle beam pass; a beam switch disposed in the first particle light beam path between the multi-beam generator and the objective lens, and in the second particle light beam path between the objective lens and the detection system; an aberration correction unit for individually correcting one or more aberrations in the first particle-light beam path; Controller and Equipped with the aberration correction unit has a sequence of electrode arrays including at least one first pair of electrode arrays; the first pair having a first electrode array and a second electrode array; the first electrode array and the second electrode array each have a plurality of geometry-based correction electrodes, each having n-fold rotational symmetry about an optical axis for generating a multipole field, each individually controllable by exactly one supply line; a geometry-based correction electrode in the first electrode array is rotated relative to an associated geometry-based correction electrode in the second electrode array about the optical axis; The controller relates to a multi-beam particle microscope, wherein the controller is designed to individually control a plurality of geometry-based correction electrodes of a first electrode array and a second electrode array of an aberration correction unit for aberration correction.

[0021] The first charged individual particle beam can be, for example, electrons, positrons, muons, ions, or other charged particles. Advantageously, the number of particle beams is 3n(n-1)+1, where n is any natural number, and the particle beam arrangement in the array is preferably generally hexagonal. The second individual particle beam can be backscattered electrons or other secondary electrons. In this case, for analytical purposes, low-energy secondary electrons are preferably used for image generation. However, mirror ions / mirror electrons can also be used as the second individual particle beam, i.e., the first individual particle beam undergoes reversal immediately upstream or at the position of the object.

[0022] The aberration correction unit serves to individually correct one or more aberrations in the first particle beam path. Therefore, in this case, aberrations are individually corrected for each first particle beam. This does not involve a global correction that is equal for all first particle beams. Instead, each geometry-based correction electrode is individually controlled by exactly one line. The aberration correction unit has a sequence of electrode arrays, including at least one first pair of electrode arrays, where the first pair has a first electrode array and a second electrode array. In this case, the word sequence indicates that the electrode arrays are essentially arranged consecutively in the particle beam path. However, it is not necessarily true that the first and second electrode arrays are arranged consecutively; additional elements of the aberration correction unit, or even completely different elements, can be arranged between the first and second electrode arrays. Overall, the aberration correction unit can be embodied in one piece or in multiple parts.

[0023] The fact that the first and second electrode arrays are embodied or referred to as a pair is intended to reflect the fact that multipoles of any desired orientation can be generated by the first and second electrode arrays, and thus the term "pair" essentially relates to the interaction between the first and second electrode arrays.

[0024] The first and second electrode arrays each have a plurality of geometry-based correction electrodes, each with n-fold rotational symmetry about the optical axis for generating a multipole field, and each geometry-based correction electrode is individually controllable in each case by exactly one supply line. The multipole electrodes can be dipole, quadrupole, hexapole, octopole, decapole, decadipole, etc., according to the series expansion shown in Equation (1). Each geometry-based correction electrode of the first and second electrode arrays has the same n-fold rotational symmetry about the optical axis. In this case, a respective optical axis is considered for each first individual particle beam. The order n of rotational symmetry is defined here as is customary in mathematics. A two-dimensional geometric figure is rotationally symmetric when it has a central point and is mapped onto itself when rotated around this point. A circle or ring is rotationally symmetric in the narrower sense; it is mapped onto itself by rotation through any angle. However, a figure can also be rotated around a fixed angle.

[0025]

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[0026] According to the present invention, geometry-based correction electrodes in a first electrode array are rotated relative to associated geometry-based correction electrodes in a second electrode array with respect to the optical axis. Two consecutively arranged geometry-based correction electrodes are associated when the same first individual particle beam passes through them. Rotating the geometry-based correction electrodes relative to each other allows the generated multipoles to be aligned in any desired direction. It is preferable that the alignment of all geometry-based correction electrodes within the same electrode array be identical. This facilitates the manufacture of the electrode array. However, it is also possible for the geometry-based correction electrodes within an electrode array to have the same shape but different alignments. This different alignment should then be reflected correspondingly in the second electrode array so that the rotation angle is also the same for all pairs of geometry-based correction electrodes.

[0027] According to this preferred embodiment, the rotation angle by which the first pair of geometry-based correction electrodes are rotated relative to each other is substantially

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[0028] According to a further preferred embodiment of the present invention, the aberration correction unit comprises a second pair of electrode arrays, the second pair comprising a third electrode array and a fourth electrode array; the third electrode array and the fourth electrode array each have a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; the geometry-based correction electrodes in the third electrode array are rotated relative to associated geometry-based correction electrodes in the fourth electrode array about the optical axis; The controller is designed to individually control the plurality of geometry-based correction electrodes of the third electrode array and the fourth electrode array of the aberration correction unit for aberration correction. What applies to the second electrode array pair is substantially the same as what applies to the first electrode array pair. However, the second electrode array pair typically generates a multipole field of a different multipole expansion compared to that generated by the first electrode array pair. This is also expressed by the m-fold rotational symmetry of the geometry-based correction electrodes, where typically the following is true:

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[0029] According to one preferred embodiment of the present invention, the rotation angle by which the second pair of geometry-based correction electrodes are rotated relative to each other is substantially

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[0030] According to a further preferred embodiment of the present invention, the aberration correction unit comprises a third pair of electrode arrays, the third pair has a fifth electrode array and a sixth electrode array; the fifth electrode array and the sixth electrode array each have a plurality of geometry-based correction electrodes, each having k-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; the geometry-based correction electrodes in the fifth electrode array are rotated relative to associated geometry-based correction electrodes in the sixth electrode array about the optical axis; The controller is designed to control the plurality of geometry-based correction electrodes of the fifth electrode array and the sixth electrode array of the aberration correction unit for aberration correction. Substantially what is also true for the third electrode array pair is already described above for the first and second electrode array pairs. Thus, a total of three electrode array pairs with geometry-based correction electrodes having different orders of symmetry can realize a total of three different multipoles of the series expansion described above. It should again be emphasized that the ordinal numbers associated with the electrode arrays do not necessarily indicate the position or order of the electrode arrays within the particle-light beam path, although this may of course be the case.

[0031] According to one preferred embodiment of the present invention, the rotation angle by which the third pair of geometry-based correction electrodes are rotated relative to each other is substantially

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[0032] According to one preferred embodiment of the present invention, different electrode array pairs have different orders of symmetry for their respective geometry-based correction electrodes to generate different multipole fields. For example, a first pair can generate a dipole field, a second pair can generate a quadrupole field, a third pair can generate a hexapole field, and so on.

[0033] According to one preferred embodiment of the present invention, the geometry-based correction electrodes of the electrode array pair are embodied so as to be rounded in cross section, and each rounded correction electrode of the electrode array forming the pair is displaced in a different direction relative to the optical axis, in particular by approximately 90° orthogonal to the optical axis; The controller is configured to individually control the rounded cross-section correction electrodes for aberration correction, in particular to substantially correct static distortions of the second field of the first individual particle beam upon incidence at the object plane. As a result of the displacement of the correction electrodes embodied in a rounded cross section, there is no rotational symmetry; instead, the trivial case of n=1 for the symmetry order is true. The deflection occurs in each case due to the fact that each individual particle beam passes through a geometrically displaced correction electrode rather than centered. If the rotation of the rounded correction electrodes is approximately 90° relative to each other, this corresponds to a displacement in the x and y directions. In this case, distortion correction in the object plane can be particularly simple.

[0034] According to a further preferred embodiment of the present invention, the geometry-based correction electrodes of the electrode array pair are embodied to be substantially elliptical in cross section to generate a quadrupole field, and the substantially elliptical correction electrodes of each of the electrode arrays forming the pair are rotated relative to each other about the optical axis, in particular rotated by substantially 45° relative to each other; The controller is configured to control the elliptical correction electrodes to substantially individually correct the astigmatism of the first individual particle beams. In the case of a rotation of substantially 45° relative to each other, the two quadrupole fields that are generated are elementary quadrupole fields that can be optimized independently of each other with respect to their excitation.

[0035] According to a further preferred embodiment of the present invention, the geometry-based correction electrodes of the electrode array pair are substantially embodied as rounded triangles in cross section to generate a hexapole field, and the substantially triangular correction electrodes of each of the electrode arrays forming the pair are rotated relative to each other about the optical axis, in particular rotated by substantially 30° relative to each other; The controller is configured to individually control the substantially triangular correction electrodes to correct aberrations with substantially three-fold symmetry. These aberrations with three-fold symmetry are therefore higher-order aberrations. They may occur, in particular, as part of non-systematic aberrations in multi-beam particle microscopes. Depending on the setup of the optical system, triple astigmatism with a field profile may occur, which can be corrected by appropriately controlling the electrodes.

[0036] According to a further preferred embodiment of the present invention, the sequence of electrode arrays of the aberration correction unit comprises a further electrode array comprising a plurality of geometry-based correction electrodes having a rounded cross section and arranged so as to be centered with respect to the respective optical axis, The controller is designed to individually control the plurality of geometry-based correction electrodes of the further electrode array to substantially correct the focal position of the first individual particle beam, in particular for image field curvature correction and / or image field tilt correction. The further electrode array therefore differs from the previously described electrode array in several respects: the electrode array is not provided in pairs and its electrodes are strictly rotationally symmetric, i.e. more narrowly rotationally symmetric around the respective optical axes. In the context of the present invention, the further electrode array makes it possible to realize an offset U0 according to the multipole expansion according to equation (1).

[0037] According to a further preferred embodiment of the invention, the electrode array is integrated into the multi-aperture plate. In this case, the electrodes extend substantially through the multi-aperture plate or are arranged in the openings. According to one embodiment variant, there is now provided one electrode array per multi-aperture plate. Alternative embodiment variants are also further described below.

[0038] According to one preferred embodiment of the present invention, a standard multi-aperture plate having a plurality of passive rounded apertures is placed between two adjacent multi-aperture plates having an electrode array with individually controllable geometry-based correction electrodes integrated therein. Thus, the standard multi-aperture plate does not include an electrode array with individually controllable electrodes. Preferably, the standard multi-aperture plate is grounded, but a voltage can also be applied to the standard multi-aperture plate, with all of the rounded apertures at the same potential. The advantage of providing a standard multi-aperture plate between two adjacent multi-aperture plates having an electrode array with individually controllable geometry-based correction electrodes integrated therein is that the alignment of the multipoles generated by the paired electrode arrays can be controlled and isolated from each other. In principle, two geometry-based correction electrodes per generated multipole are required to achieve arbitrary alignment of the multipoles. Consistent with the concept of series expansion, the cosine term

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[0039] According to another preferred embodiment of the invention, the aberration correction unit comprises a standard multi-aperture plate with a plurality of passive rounded apertures, which is arranged upstream of a first multi-aperture plate with individually controllable geometry-based correction electrodes with respect to the direction of the particle-light beam path, and / or The aberration correction unit comprises a standard multi-aperture plate with multiple passive rounded apertures, which is positioned downstream of a last multi-aperture plate with individually controllable geometry-based correction electrodes, with respect to the direction of the particle-light beam path.

[0040] In this embodiment variant, the first standard multi-aperture plate in the sequence of multi-aperture plates, and also the standard multi-aperture plate that is located last in relation to the sequence of multi-aperture plates, ensures that the first generated multipole and respectively the last generated multipole are also correctly oriented, or elementary multipoles that are in fact separated from each other can also be generated by two pairs of associated multi-aperture plates having electrode arrays integrated therein.

[0041] An alternative solution to create orthogonality of the generated multipoles is to follow the directionality of changing the rotation angle between the correction electrodes based on the geometry of the electrode array pair, so that the multipoles so generated do not mix. However,

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[0042] A further preferred solution is to use an appropriate linear combination of geometry-based correction electrode excitations so that mixing of the generated multipoles is prevented. By way of example, an amplitude matrix can be generated for this purpose, which represents the relationship between the correction electrode excitations and the amplitudes of the generated elementary multipoles. This matrix can be inverted so that the required linear combination of correction electrode excitations can be determined.

[0043] According to a further preferred embodiment of the present invention, the aberration correction unit provides a carrier plate for the electrode array pairs, with the geometry-based electrodes of the first electrode array being arranged on the upper surface of the carrier plate and the geometry-based electrodes of the second electrode array being arranged on the bottom surface of the carrier plate. Therefore, in this embodiment variant, the electrodes of the electrode arrays can in fact be applied to a carrier plate that, of course, has corresponding openings. In this case, the geometry-based correction electrodes are insulated from the carrier plate itself. In this embodiment, the electrodes protrude from or extend beyond the carrier plate. In this case, the geometry-based correction electrodes of each pair of geometry-based correction electrodes are substantially separated from each other in order to provide elementary multipoles for aberration correction as accurately as possible.

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[0044] According to a further preferred embodiment of the present invention, the aberration correction unit provides a carrier plate for an electrode array pair, with the geometry-based electrodes of a first electrode array embedded in the carrier plate on the top surface and the geometry-based electrodes of a second electrode array embedded in the carrier plate on the bottom surface. In this case, the geometry-based electrodes preferably do not protrude beyond the carrier plate, but rather are preferably integrated flush with the carrier plate. In this case, the geometry-based correction electrodes are insulated from the carrier plate itself.

[0045] The aberration correction unit can be manufactured by established manufacturing methods, for example, used in MEMS manufacturing or integrated circuit manufacturing. In this case, the aberration correction unit can be manufactured, for example, as a fully or partially monolithic sandwich structure. In this case, it may be necessary to place insulating layers between the individual plates or electrode arrays of the monolithic sandwich structure. It is also possible for multiple functional layers of the aberration correction unit to be bonded together to form a monolithic plate, which are then stacked and precisely aligned with each other. Alternatively, each functional layer can be embodied as an individual plate, which are then stacked and precisely aligned with each other. Precision in the submicron range may be required for such precise alignment.

[0046] According to a further preferred embodiment of the present invention, the multi-beam particle microscope further comprises a multipole amplitude input unit, by means of which a user can input the amplitudes of the multipoles to be generated; The controller of the multi-beam particle microscope is designed to generate control signals for controlling the geometry-based correction electrodes based on user input. If the multipole is a basic multipole, by changing the corresponding excitation, the user can correct the aberrations occurring during imaging in a very targeted manner.

[0047] According to one preferred embodiment of the present invention, a controller of a multibeam particle microscope is designed to perform determination of control signals for controlling geometry-based correction electrodes for multipole field generation using an inverted amplitude matrix, where the non-inverted amplitude matrix represents the relationship between the excitation of the correction electrodes and the amplitude of the elementary multipoles generated. The inverted amplitude matrix makes it possible to determine an appropriate linear combination of excitations that results in a desired amplitude distribution of the elementary multipoles. In particular, such a procedure allows for the determination of an appropriate linear combination of excitations to generate a single (very specific) multipole.

[0048] The above-mentioned embodiment variants of the multi-beam particle microscope can be combined with one another in whole or in part, provided that no technical contradictions result.

[0049] According to a second aspect of the invention, the invention provides a method for generating elementary multipoles for aberration correction in a multibeam particle microscope, comprising the steps of: a0) providing a multi-beam particle microscope as described above in several embodiment variants; a) For all geometry-based correction electrodes in the sequence, a1) exciting only one of the geometry-based correction electrodes; a2) determining all of the amplitudes of the multipoles generated by the individual excitations; b) establishing an amplitude matrix based on the determined amplitudes, the amplitude matrix representing the relationship between the excitations of the geometry-based correction electrodes and the amplitudes of the elementary multipoles generated by these excitations; c) inverting the amplitude matrix; d) exciting geometry-based correction electrodes based on the entries of the inverted amplitude matrix; The present invention relates to a method comprising:

[0050] In principle, this involves determining separately for each geometry-based correction electrode which additional multipoles would be generated by otherwise exciting the geometry-based correction electrode in the sequence of geometry-based correction electrodes. As an example, exciting the first geometry-based correction electrode would primarily generate a dipole with amplitude A1.

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[0051] According to one preferred embodiment of the present invention, method step a2) comprises compensating for the effects of the multipoles respectively generated by a global multipole corrector, in particular by a dodecapole corrector, and determining the amplitudes respectively required for this purpose in the global multipole corrector. In this case, it is possible to provide a corresponding global multipole corrector solely for the purpose of adjusting the multibeam particle microscope, which corrector does not have to be permanently installed in the multibeam particle microscope, although it can be. However, the entries of the amplitude matrix can also be determined in some other way.

[0052] According to a further preferred embodiment of the present invention, the method comprises the steps of: e) further comprising a step of optimizing the resolution of the multi-beam particle microscope, the optimizing step comprising varying the amplitude of each multipole independently and determining the optimum amplitude for the resolution.

[0053] Of course, other imaging properties than resolution can also be correspondingly optimized. However, resolution optimization is particularly important for multibeam particle microscopes. Resolution optimization, which involves varying the amplitude of each multipole, is particularly simple if the amplitude matrix of the corrector is diagonal or if the inverse amplitude matrix has been determined. This is because, in fact, it is then possible to vary the amplitude of each multipole independently.

[0054] According to a further preferred embodiment of the present invention, the method is performed for all of the sequences of geometry-based correction electrodes, and thus for each individual particle beam, so that it is possible to individually correct the imaging aberrations of each first individual particle beam in the object plane.

[0055] According to one preferred embodiment of the present invention, field-dependent aberration correction is performed by exciting geometry-based correction electrodes, in particular, previously known field dependencies of aberrations can be corrected.

[0056] According to a third aspect, the present invention relates to a computer program product having a program code for carrying out the method as described above in several embodiment variants. In this case, the program code can be written in any desired programming language. The program code can be embodied in one part or in several parts. In particular, it is advantageous to provide separate program code solely for controlling the aberration correction unit. However, this can also be achieved in different ways.

[0057] According to a further aspect of the invention, there is provided a multi-beam particle beam system having the following features: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a particle-optical unit having a first particle-optical beam path configured to image the generated individual particle beam onto a sample surface such that the individual particle beam is incident on the sample surface in the object plane at an incidence location, thereby forming a second field; an aberration correction unit for individually correcting one or more aberrations in the particle light beam path; Controller and Equipped with the aberration correction unit has at least one electrode array; the electrode array comprises a plurality of geometry-based correction electrodes, each having n-fold rotational symmetry about the optical axis for multipole generation, each of which is individually controllable by precisely one supply line, The controller is designed to individually control a plurality of geometry-based correction electrodes of the electrode array of the aberration correction unit for aberration correction.

[0058] The multi-beam particle beam system according to the fourth aspect of the present invention represents the present invention more broadly than the multi-beam particle microscope according to the first aspect of the present invention. The multi-beam particle beam system may be a multi-beam particle microscope, but this is not necessarily the case. With regard to terms used in connection with the fourth aspect of the present invention, explicit reference is made to the definitions of the relevant terms according to the first aspect of the present invention. In particular, all embodiments of the present invention according to the first aspect can also be combined with a multi-beam particle beam system according to the fourth aspect of the present invention. To avoid unnecessary repetition, only the special features of the fourth aspect of the present invention will be discussed below.

[0059] According to a fourth aspect of the present invention, the aberration correction unit has at least one electrode array. It is therefore possible for the aberration correction unit to have exactly one electrode array, which again has a plurality of geometry-based correction electrodes each having n-fold rotational symmetry about the optical axis for multipole field generation, each individually controllable by a supply line. The controller is therefore designed to individually control the geometry-based correction electrodes of the electrode array of the aberration correction unit for aberration correction. It is still possible to perform aberration correction using only one electrode array, but this is no longer universal, since the orientation or alignment of the multipole field generated for correction is defined by the electrode array configuration. However, in principle, such aberration correction is also possible.

[0060] According to one preferred embodiment of the invention, the aberration correction unit comprises a further electrode array, the further electrode array includes a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about the optical axis for generating the multipole field, each individually controllable by a supply line; The controller is designed to individually control a plurality of geometry-based correction electrodes of the further electrode array of the aberration correction unit for aberration correction.

[0061] The at least one electrode array and the further electrode array may form an electrode array pair that generates a multipole field of the same symmetric order or order, but this does not have to be the case, in other words, n=m or else n≠m may be true.

[0062] According to a further preferred embodiment of the present invention, the aberration correction unit has one or more additional electrode arrays, which are embodied as geometrically and / or non-geometrically based. Therefore, different implementations of correction electrodes can be combined with each other in the aberration correction unit. For example, when considering the sequence of correction electrodes for the first individual particle beam, this electrode sequence can include both at least one geometrically based correction electrode and at least one non-geometrically based correction electrode. Therefore, the aberration correction unit according to the present invention can be combined with other aberration correction elements.

[0063] According to a preferred embodiment of the present invention, the aberration correction unit further includes an electrode array including segmented electrodes. The segmented electrodes are, for example, multipole electrodes, particularly octopole or decadapole electrodes, as described above in connection with the prior art. In this case, it is particularly conceivable to combine and pair correction electrodes of different types, with the multipoles being aligned with each other so as to generate elementary multipoles. For example, it is conceivable that all cosine terms in the series expansion for generating the multipole field are generated by an electrode array including geometry-based correction electrodes, and all sine terms are generated by correspondingly controlled multipole electrodes, or vice versa. In this case, by combining multipole electrodes with geometry-based correction electrodes, it may be possible to reduce the number of poles in the multipole electrodes and thus at least somewhat reduce control costs. For example, it may be sufficient to provide quadrupole segmented electrodes instead of octopole electrodes, provided that the corresponding pairing with geometry-based correction electrodes is performed in a specific sequence.

[0064] According to a further preferred embodiment, the geometry-based correction electrodes of at least one electrode array of the aberration correction unit are themselves segmented, and the controller is designed to individually control these segments of the correction electrodes. The geometry-based correction electrodes are, of course, not circularly symmetric; this solution is obvious and has been known for some time. For example, it is possible to segment the geometry-based correction electrodes themselves, each with at least two-fold rotational symmetry about the optical axis for multipole field generation. Thus, the cross-section of the geometry-based correction electrodes can be, for example, elliptical, and individually controllable segments of the correction electrodes, i.e., multipole electrodes embodied with a specific cross-section, are provided along this ellipse. It is also conceivable to insert correspondingly segmented electrodes into the geometry-based correction electrodes. Various embodiment variants have specific advantages and disadvantages with respect to aberration correction.

[0065] The various embodiments and aspects of the present invention can be combined with one another in whole or in part, provided that no technical contradictions result.

[0066] The present invention may be better understood with reference to the accompanying drawings. [Brief explanation of the drawings]

[0067] [Figure 1] FIG. 1 is a schematic diagram showing a multi-beam particle microscope. [Figure 2] FIG. 1 is a schematic diagram showing aberration correction in a multi-beam particle microscope using individually controllable segmented electrodes (here octopole electrodes). [Figure 3] FIG. 1 is a schematic diagram showing an array of octopole electrodes. [Figure 4] 1 is a schematic diagram showing the creation of quadrupoles with various orientations by using octopole electrodes. FIG. [Figure 5] FIG. 1 is a schematic diagram illustrating a geometry-based electrode pair for multipole generation in accordance with the present invention. [Figure 6] FIG. 1 is a schematic diagram illustrating geometry-based electrodes for generating focus shift. [Figure 7] FIG. 1 is a schematic diagram showing a sequence of two geometry-based electrode arrays for generating a quadrupole field. [Figure 8] FIG. 1 is a schematic diagram showing a sequence of two geometry-based electrode arrays for generating a quadrupole field. [Figure 9] FIG. 1 is a schematic diagram showing a sequence of two geometry-based electrode arrays for generating a quadrupole field. [Figure 10] FIG. 1 is a schematic diagram showing a sequence of two geometry-based electrode arrays for generating a hexapole field. [Figure 11] 1A-1C are schematic diagrams illustrating exemplary embodiments of geometry-based electrodes for quadrupole field generation. [Figure 12] 1A and 1B are schematic diagrams illustrating exemplary embodiments of geometry-based correction electrode pairs for quadrupole field generation. [Figure 13] 1A-1C are schematic diagrams illustrating exemplary embodiments of sequences from multiple geometry-based electrode arrays for aberration correction. [Figure 14] FIG. 1 is a schematic diagram showing one example of the separation of the individual generated quadrupole fields. [Figure 15] FIG. 1 is a schematic diagram illustrating a method for adjusting (orthogonalizing) the aberration correction of a multi-beam particle microscope. [Figure 16] FIG. 1 is a schematic diagram illustrating geometry-based electrode optimal excitation / amplitude tuning to optimize the imaging properties of a multi-beam particle microscope. DETAILED DESCRIPTION OF THE INVENTION

[0068] FIG. 1 schematically illustrates a multi-beam particle microscope 1. The multi-beam particle microscope 1 comprises a beam generating device 300 having a particle source 301, e.g., an electron source. A diverging particle beam 309 is collimated by a sequence of condenser lenses 303.1 and 303.2 and impinges on a multi-aperture arrangement 305. The multi-aperture arrangement 305 comprises a plurality of multi-aperture plates 306 and a field lens 308. A plurality of individual particle beams 3 or individual electron beams 3 are generated by the multi-aperture arrangement 305. The midpoints of the apertures in the multi-aperture plate arrangement are positioned within a field of view that is imaged onto a further field of view formed by a beam spot 5 in the object plane 101. The pitch between the midpoints of the apertures of the multi-aperture plates 306 can be, for example, 5 μm, 100 μm, or 200 μm. The diameter D of the apertures is less than the pitch between the midpoints of the apertures, with example diameters being 0.2, 0.4 and 0.8 times the pitch between the midpoints of the apertures.

[0069] The multi-aperture arrangement 305 and field lens 307 are configured to generate multiple focal points 323 of the primary beam 3 in a grating arrangement on a surface 325. The surface 325 does not need to be a flat surface, but can be a spherically curved surface to account for the field curvature of the subsequent particle optics.

[0070] The multi-beam particle microscope 1 further comprises a system consisting of an electromagnetic lens 103 and an objective lens 102, which reduces the size of the beam focus 323 and images it from the intermediate image plane 325 to the object plane 101. Between them, the first individual particle beams 3 pass through a beam switch 400 and a collective beam deflection system 500, which deflects the plurality of first individual particle beams 3 during operation and scans the image field. The first individual particle beams 3 are incident in the object plane 101 and, for example, form a substantially regular field, and the pitch between adjacent incident locations 5 can be, for example, 1 μm, 10 μm, or 40 μm. By way of example, the field formed by the incident locations 5 can have rectangular or hexagonal symmetry.

[0071] The object 7 to be investigated can be of any desired type, for example a semiconductor wafer or a biological sample, and can include structures such as small elements. The surface 15 of the object 7 is arranged in the objective plane 101 of the objective lens 102. The objective lens 102 can include one or more electron-optical lenses. By way of example, this can be a magnetic objective lens and / or an electrostatic objective lens.

[0072] The primary particles 3 incident on the 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 interaction products originate from the surface of the object 7 or from the first or object plane 101. The interaction products originating from the surface 15 of the object 7 are shaped by the objective lens 102 to form a secondary particle beam 9. In this process, the secondary beam 9 passes through a beam switch 400 after the objective lens 102 and is supplied to the projection system 200. The projection system 200 includes an imaging system 205 having a first lens 210 and a second lens 220, a contrast stop 222, and a multi-particle detector 209. The incidence locations of the second individual particle beam 9 on the detection area of ​​the multi-particle detector 209 are located in a third field with a regular pitch from each other. Exemplary values ​​are 10 μm, 100 μm, and 200 μm.

[0073] The multi-beam particle microscope 1 further comprises a computer system or control unit 10, which may be embodied integrally or in multiple parts, both designed to control the individual particle-optical components of the multi-beam particle microscope 1 and to evaluate and analyze the signals obtained by the multi-detector 209 or detection unit 209.

[0074] The sequence of multi-aperture plates 306, also called micro-optics, may also comprise the aberration correction unit of the multi-beam particle microscope according to the invention.

[0075] Further information relating to such multi-beam particle beam systems or multi-beam particle microscopes 1 and the components used therein, such as, for example, particle sources, multi-aperture plates and lenses, can be taken from WO 2005 / 024881, WO 2007 / 028595, WO 2007 / 028596, WO 2011 / 124352 and WO 2007 / 060017 as well as German Patent Application Publications DE 10 2013 016 113 and DE 10 2013 014 976, the entire disclosures of which are incorporated herein by reference.

[0076] FIG. 2 shows a schematic diagram of aberration correction in a multi-beam particle microscope using individually controllable segmented electrodes. The aberration correction unit can be, for example, part of the micro-optics system 306 shown in FIG. 1. FIG. 2 shows, by way of example, a detail from an array of octopole electrodes 372 (see the control in the figure and its schematic plan view). Each aperture 391 in the array is assigned an octopole electrode 372 to generate, for example, a quadrupole field acting on an individual particle beam passing through the aperture 361. Each octopole electrode 372 has eight electrodes 373, which are distributed around the aperture 361 in the circumferential direction and controlled by the controller 10. For this purpose, in the illustrated example, an electronic circuit 375 that generates adjustable voltages and supplies them to the electrodes 373 via lines 377 is arranged on the multi-aperture plate in an area spaced apart from the aperture 361. 2 shows only a small portion of the lines supplying voltage to the electrodes 372, the problem of having so many lines in a closely spaced space is easily recognized. Additionally, the electronics within the vacuum jacket 381 are exposed to particle bombardment and x-ray radiation, which adversely affect the useful life of the electronics 375.

[0077] The controller 10 controls the electronic circuit 375 by means of a serial data connection 379 passing through the vacuum jacket 381 of the multi-beam particle microscope 1. Here, a seal 382 is provided, which seals the line of the serial data connection 379 with respect to the vacuum jacket 381 of the multi-beam particle microscope 1. Providing a vacuum bushing for each individual line 377 is impractical due to the large number of lines 377. The electronic circuit 375 generates voltages that are supplied to the electrodes 373 via the lines 377 in response to data received from the controller 10 via the serial data connection 379. As a result, the controller 10 is able to generate quadrupole electric fields in each of the apertures 361, said electric fields being adjustable in terms of their strength and their orientation around the center of the aperture 361. Using these quadrupole fields, all of the individual particle beams 3 can be manipulated individually in each case. The controller 10 adjusts the quadrupole field, for example, so that it induces astigmatism in the beam 3 that compensates for astigmatism introduced by downstream optics, such as the objective lens 102 of FIG. 1, so that the beam is focused substantially astigmatism-free (aberration-free) within the objective plane 101.

[0078] 3 shows schematically an array of octopole electrodes 372. In this case, the array of octopole electrodes 372 is arranged within a multi-aperture plate 370. Although only seven octopole electrodes 372 are shown by way of example, their number can be much greater, for example, over 100 octopole electrodes 372, which are controlled or energized in each case as shown in FIG.

[0079] FIG. 4 schematically illustrates the generation of quadrupole fields with various orientations using an octopole electrode 372. The octopole electrode 372 generally has a rounded cross section or rounded opening 361. The octopole electrode 372 is segmented, with individual electrodes designated 373a-373h. FIG. 4 additionally illustrates which voltages are applied to each of the electrodes 373a-373h. Voltages with the same magnitude and sign are indicated by the same shading in FIG. 4. The same voltage -U1 is applied to each of electrodes 373a and 373e, and the same voltage +U1 is applied to each of electrodes 373c and 373g. As a result, the octopole electrode 372 generates a first quadrupole field oriented along the x and y axes, as shown in FIG. 4b. A potential +U2 is applied to each of electrodes 373b and 373f, and a potential −U2 is applied to each of electrodes 373d and 373h. As a result, these electrodes generate a second quadrupole field rotated 45° relative to the first quadrupole field. This is shown in Figure 4c. Both quadrupole fields can be superimposed together to generate a resultant quadrupole field, whose alignment is determined by the relative strengths of the two quadrupole fields. Such a resultant quadrupole field is shown in Figure 4d. Therefore, by appropriate selection of the potentials ±U1 and ±U2 or amplitudes for the quadrupole generation, it is possible to generate a resultant quadrupole field that can be oriented in any direction in the xy plane. However, control of the octopole electrodes 372 is complex, and when multiple octopole electrodes 372 are present, there is the additional problem of accommodating the lines within a very limited space. In addition, it should be taken into account that the segmentation of the octopole electrodes 373a-373h results in aberrations due to non-smooth boundary conditions when the resulting quadrupole field is close to the electrodes. As a result, it is necessary that the first individual particle beam 3 passing through the segmented octopole electrode 372 is not allowed to pass too close to the electrodes 373a-373h. In other words, the fill factor of the individual particle beam 3 passing through the octopole electrode 372 is relatively small. The space available within the octopole electrode 372 cannot be optimally utilized.Although having more poles in the multipole corrector 372, e.g., 12 poles 373, combined with a larger fill factor would result in better space utilization, doing so may actually make the situation worse due to the aforementioned constraints on the placement of the lines 377 within the multi-aperture plate 370.

[0080] According to the invention, the potentials required for the aberration correction of each individual particle beam 3 are no longer generated by a single multipole corrector per individual particle beam 3. Instead, for each individual particle beam 3, a sequence of geometry-based electrodes is used to generate the correction potentials. In this case, these geometry-based electrodes are each individually controllable and each require exactly one supply line, which reduces the number of supply lines, for example in a multi-aperture plate, and therefore also the control costs for controlling the electrodes. Now, what is important for the generation of each multipole in a sequence of geometry-based electrodes is the shape of these electrodes.

[0081] Figure 5 illustrates the principle in this case. This figure shows a schematic representation of geometry-based electrode pairs for multipole generation according to the present invention. Again, equation (1):

number

[0082] Therefore, for aberration correction, it is necessary to generate a dipole field with a desired orientation, a quadrupole field with a desired orientation, a hexapole field with a desired orientation, etc.

[0083] Figure 5a) shows a sequence of geometry-based correction electrodes 701 and 702 to generate a dipole field. Figure 5b) shows a sequence of two geometry-based correction electrodes 705 and 706 to generate a quadrupole field. Figure 5c) shows a sequence of two geometry-based correction electrodes 709 and 710 to generate a hexapole field. A geometry-based correction electrode 713 with a rounded cross section according to Figure 6 can be used to generate an offset potential U0.

[0084] In particular, for reasons of clarity and for better compatibility with the superimposed quadrupole field according to FIG. 4, the electrode configuration shown in FIG. 5b) will be described in more detail first. Instead of the quadrupole field being generated by a cross-shaped configuration and corresponding application of voltages to electrodes 373a, 373c, 373e, and 373g, the same quadrupole field can also be generated by electrodes with a specific cross-section. This is the case, for example, of an electrode with an elliptical cross-section, as shown in the left electrode 705 in FIG. 5b). Its opening 707 is elliptical and aligned with the optical axis Z. The semimajor axis of the ellipse is oriented along the y-axis in this case. In this case, the elliptical shape extends somewhat along the optical axis Z (here, into the plane of the drawing), but this extent is typically only a few μm. The geometry-based correction electrode 705 with an elliptical cross-section has two-fold rotational symmetry about the optical axis Z. The ellipse can be mapped onto itself by rotating it 180° about the optical axis Z. The geometry-based correction electrode 706, shown on the right in FIG. 5b, also has an elliptical cross section or correspondingly shaped opening 708. It, of course, also has two-fold rotational symmetry about the optical axis Z, but with a different orientation than the geometry-based correction electrode 705. The major axis of the ellipse forms a 45° angle with the y-axis. Thus, the quadrupole field generated by the geometry-based correction electrode 706 is effectively rotated by 45° relative to the quadrupole field generated by the geometry-based correction electrode 705. When an individual particle beam 3 then passes through electrodes 705 and 706 in succession, it is subjected to the effects of two quadrupole fields, and the resulting effect corresponds to an effective quadrupole field (similar to the situation in FIG. 4d). Each of the geometry-based correction electrodes of the pair 705 and 706 is supplied with a voltage by only one supply line in each case. The amplitude of this excitation can be selected individually. Thus, an effective quadrupole field effect with arbitrary or adjustable orientation can also be generated by a sequence or pair of geometry-based correction electrodes 705, 706 with two-fold rotational symmetry.

[0085] It can be seen that the situation for other multipole fields is quite similar. Figure 5c) shows a pair of geometry-based correction electrodes 709 and 710 with three-fold rotational symmetry about the optical axis Z. The geometry-based correction electrodes 709 and 710 have the same shape but different orientations. A shape with three-fold symmetry can be represented by an equilateral triangle with rounded corners. A hexapole field can be generated by this type of geometry-based electrode. The rotation angle by which the two geometry-based correction electrodes 709 and 710 of the pair are rotated relative to each other is substantially

[0086]

number

number

[0087] FIG. 5a) shows a pair of geometry-based correction electrodes 701, 702 that can be used to generate an effective dipole field effect with any orientation. In this case, the two geometry-based correction electrodes 701 and 702 are embodied so that they are rounded in cross section (see openings 703 and 704), but they are centered about the optical axis Z. Therefore, there is no rotational symmetry about the optical axis Z, and so, formally, the geometry-based correction electrodes 701 and 702 have one-fold symmetry. The rotation angle about the optical axis Z is

[0088]

number

[0089] 5 shows only one pair of geometry-based correction electrodes as an example. Multiple corresponding pairs of geometry-based correction electrodes can be used to form an electrode array having a corresponding plurality of geometry-based correction electrodes.

[0090] 7 shows a schematic diagram of a sequence of two geometry-based electrode arrays 720, 721 for generating a quadrupole. In this case, the first electrode array 720 is integrated into a multi-aperture plate 715. The second electrode array 721 is integrated into a multi-aperture plate 716. Each geometry-based correction electrode 705 of the first electrode array 720 and the geometry-based correction electrode 706 of the second electrode array 721 each have a two-fold rotational symmetry about the optical axis Z of the particle light beam path of each individual particle beam 3. In the illustrated example, the orientation of the geometry-based correction electrode 705, which is embodied in the first multi-aperture plate 715 so as to have an elliptical cross section, is identical in each case, and the same similarity applies to the geometry-based correction electrode 706 of the second multi-aperture plate 716. Each electrode 705 and 706 is supplied with a voltage by a respective individual line 717 and 718. In this case, the controller 10 is designed to individually control a plurality of geometry-based correction electrodes 705, 706 of the first electrode array 720 and the second electrode array 721 of the aberration correction unit 750 for aberration correction. This can of course also be performed by corresponding sub-units or by components of the controller 10. By individually controlling each of the geometry-based correction electrodes 705, 706 (a total of 18 individually controllable lines 717, 718), field-dependent aberration correction is possible for a plurality of individual particle beams 3.

[0091] In the case of the aberration correction unit 750, only one pair of electrode arrays 720, 721 is provided in the illustrated example. However, it is of course possible to provide additional pairs or multiple additional pairs of electrode arrays to generate multipoles of different orders or to perform additional aberration correction. In this regard, it should be understood that FIG. 7 is merely an example. However, the aberration correction unit is suitable, for example, for astigmatism correction. Incidentally, it is clear that the sequence consisting of the two electrode arrays 720 and 721 is not precisely illustrated in the perspective of FIG. 7. In fact, the two electrode arrays 720 and 721 are arranged one above the other in the illustrated example so that an array with nine first individual particle beams 3 first passes through the nine openings 707 of the first electrode array 720 and then through the nine openings 708 of the second electrode array 721. Further elements or component parts can also be arranged between the two multi-aperture plates 715 and 716 with their respective electrode arrays 720 and 721, but this does not have to be the case. The importance of the additional passive multi-aperture plate between the electrode arrays is explained in further detail below.

[0092] FIG. 8 schematically illustrates a further sequence consisting of two geometry-based electrode arrays 720 and 721 for quadrupole generation or astigmatism correction. As always, like reference numerals refer to like elements. The illustration in FIG. 8 generally corresponds to the illustration in FIG. 7. However, the alignment of the elliptical cross-section electrodes 705, 706 in the respective electrode arrays 720 and 721 is somewhat different. Within electrode array 720, the geometry-based correction electrodes 705 are identically oriented only row by row. Correspondingly, the geometry-based correction electrodes 706 in the second electrode array 721 are also identically aligned only row by row. Nevertheless, even in this embodiment variant, it is true that the geometry-based correction electrodes 705, 705a in the first electrode array 720 are rotated relative to the associated geometry-based correction electrodes 706, 706a in the second electrode array 721 with respect to the optical axis Z by the same angle in each case, i.e., substantially 45°. In any event, since the geometry-based correction electrodes are individually controlled by the controller 10, in principle only the pairwise orientation of the geometry-based correction electrodes 705, 706 and 705a, 706a respectively relative to one another is important.

[0093] Figure 9 shows a schematic representation of a further sequence of two geometry-based electrode arrays 720, 721 for quadrupole generation or astigmatism correction. Compared to the illustrations of Figures 7 and 8, the alignment of the individual geometry-based correction electrodes within each electrode array 720 and 721 or within the multi-aperture plates 715, 716 is somewhat more complex. Within each electrode array 720, 721, the alignment of the illustrated elliptical cross-sectional electrodes 705a, 705b, and 705c varies both row by row and column by column. However, in relation to pairs of geometry-based correction electrodes, i.e., for example, electrodes 705a and 706a, and 705b and 706b, 705c and 706c, it is again true that the geometry-based correction electrodes in the first electrode array 720 are rotated relative to the associated geometry-based correction electrodes in the second electrode array 721 with respect to the optical axis Z, again by the same angle in each case (here 45°).

[0094] FIG. 10 schematically illustrates a sequence of two geometry-based electrode arrays 722, 723 for generating a hexapole field or correcting aberrations of an individual particle beam 3 with three-fold symmetry. In this case, the first electrode array 722 is integrated into a first multi-aperture plate 724. The second electrode array 723 is integrated into a second multi-aperture plate 725. The geometry-based correction electrodes 726 and 728 each have three-fold rotational symmetry about the optical axis Z for generating the hexapole field. In this case, the openings 727 and 729 of each electrode 726, 728 are substantially embodied as rounded equilateral triangles. The orientation of the geometry-based correction electrode 726 in the first electrode array 722 is identical in each case. In addition, the orientation of the geometry-based correction electrode 728 in the second electrode array 723 is similarly identical. Overall, however, the geometry-based correction electrodes 726 in the first electrode array 722 are rotated relative to the associated geometry-based correction electrodes 728 in the second electrode array 723 with respect to the optical axis Z by the same angle in each case (here, 30° due to the three-fold order of symmetry). Again, the controller 10 is designed to individually control the plurality of geometry-based correction electrodes 726, 728 of the first and second electrode arrays 722, 723 of the aberration correction unit 750 for aberration correction. Of course, as described in connection with the geometry-based correction electrodes with two-fold symmetry in FIGS. 8 and 9 , the orientation of the geometry-based correction electrodes 726, 728 in the electrode arrays 722, 723 can also be made variable. In any case, however, a fixed rotational relationship applies to each associated pair of geometry-based correction electrodes 726 and 728. Again, it is of course possible for the aberration correction unit 750 to comprise further correction elements, in particular further electrode arrays, although this is not shown in FIG.

[0095] FIG. 11 shows a schematic perspective view of an exemplary embodiment of geometry-based electrodes for quadrupole field generation. FIG. 11a) shows, by way of example only, a sequence of geometry-based correction electrodes, where each electrode can be part of a corresponding electrode array, and each electrode of the array is individually controllable. The exemplary embodiment of FIG. 11a) shows a sequence of four multi-aperture plates 730, 715, 716, and 732. In this case, multi-aperture plates 730 and 732 are standard multi-aperture plates with multiple passive rounded apertures, positioned upstream and downstream, respectively, of multi-aperture plates 715 and 716, which have individually controllable geometry-based correction electrodes 705 and 706, with respect to the direction of the particle-light beam path. In the illustrated exemplary embodiment, the geometry-based correction electrodes 705, 706 are themselves integrated into the multi-aperture plates 715, 716 or extend through corresponding openings 707, 708 in the multi-aperture plates 715, 716. In this case, flat conductive portions of the electrodes 705, 706 are additionally provided on the upper surface, substantially flush with the surface of the multi-aperture plates 715, 716, at which portions the electrodes 705, 706 can contact their respective supply lines. In the illustrated example, the conductive surfaces have a circular outer contour, but they may also have a different shape with respect to their outer contour.

[0096] An alternative exemplary embodiment is shown by way of example in FIG. 11b). FIG. 11b) shows only one multi-aperture plate 715 by way of example, but instead shows the entire electrode array 720. The geometry-based correction electrodes 705 are again elliptical in cross section and extend through the thickness h of the multi-aperture plate 715. Typical thicknesses of multi-aperture plates in this case are a few μm, e.g., 5, 10, 20, or 30 μm. The orientation of the electrodes 705 is uniform within the multi-aperture plate 715, and each of the electrodes 705 can again be individually controlled (corresponding supply lines are not explicitly shown in this figure). The conductive surfaces of the geometry-based correction electrodes 705, which are provided on the upper surface of the multi-aperture plate 715 for contact purposes, are embodied in the illustrated example as hexagonal. This shape allows the individual geometry-based electrodes 705 to be regularly spaced from one another and is relatively simple to manufacture. In the case of both embodiments shown in FIG. 11, it is true that the geometrically based electrodes 705, 706 are insulated from the multi-aperture plates 715 and 716.

[0097] 12A and 12B show schematic diagrams of another embodiment of a pair of geometry-based correction electrodes for quadrupole field generation. FIG. 12A shows a carrier plate 734 into which a first geometry-based correction electrode 705 is integrated on the top surface and a second geometry-based correction electrode 706 is integrated on the bottom surface. Each of the electrodes 705, 706 is insulated from the carrier plate 734 by an insulator 735 and is individually controllable. Even in this structural embodiment variant, it is true that the two geometry-based correction electrodes 705 and 706 of each pair of geometry-based correction electrodes are rotated relative to each other around the optical axis Z, in particular by 45° in the illustrated example.

[0098] Figure 12b) shows an alternative structural configuration having a carrier plate 736 on whose top surface a geometry-based correction electrode 705 is disposed and whose bottom surface a geometry-based correction electrode 706 is disposed. Again, the two electrodes 705, 706 are insulated from the carrier plate 736. The alignment of the two elliptical correction electrodes 705, 706 is again rotated relative to each other about the optical axis, again at an angle of substantially 45°, as shown in the geometrical illustration at the bottom right of Figure 12b).

[0099] 13 schematically illustrates a further exemplary embodiment of an aberration correction unit 750 having a sequence of multiple geometry-based electrode arrays for aberration correction. In the illustrated exemplary embodiment, the aberration correction unit 750 is embodied as part of the micro-optics 306. A multi-aperture plate 304 (filter plate) for generating the first individual particle beam 3 is also shown schematically.

[0100] The aberration correction unit 750 comprises three electrode array pairs. The first pair 740 includes a first electrode array with geometry-based correction electrodes 705 and a second electrode array with geometry-based correction electrodes 706. In this case, the two arrays are integrated into a carrier plate 734a, as already described in more specific detail in connection with FIG. 12a). In the illustrated example, the geometry-based correction electrodes 705 and 706, which in each case form an associated pair and through which the same individual particle beam 3 passes, are embodied to have an elliptical cross section, with the semi-axes of the ellipse rotated substantially 45° relative to each other. Each of the geometry-based correction electrodes 705, 706 is individually controlled by the controller 10 using a separate supply line 717. In FIG. 13, the corresponding line 717 is depicted, by way of example, only for the rightmost passing beam 3. In this way, by using the first electrode array pair 740 for the first individual particle beam 3, a quadrupole field with any orientation can be generated individually in each case to correct the astigmatism of the individual particle beam 3.

[0101] A second electrode array pair 741 is arranged downstream of the first pair 740 along the particle light beam path, said second pair comprising geometrically based correction electrodes 744, 746 in the illustrated example. The latter are embodied in the illustrated example as being substantially rounded in cross section, the rounded correction electrodes 744, 746 in each pair being mutually displaced by approximately 90° orthogonally with respect to the optical axis Z in different directions. The controller 10 is again configured to individually control the rounded correction electrodes 744, 746. For example, in this case, static distortion of the second field of the first individual particle beam 3 upon incidence on the object plane 101 can be corrected.

[0102] A third electrode array pair 742 having geometry-based correction electrodes 726, 728 is arranged downstream of the second pair 741 in the direction of the particle light beam path. In the example shown, the correction electrodes 726, 728 have three-fold rotational symmetry and are rotated substantially 30° relative to each other within the pair about the optical axis Z. As a result, a hexapole field for correcting aberrations with three-fold symmetry can be formed individually for each first individual particle beam 3.

[0103] Downstream of the third electrode array pair 742, a multi-aperture plate 751 is provided having an electrode array with a plurality of geometry-based correction electrodes 749 having a rounded cross section and arranged so as to be centered with respect to the respective optical axis Z. In this case, the controller 10 is further designed to individually control the plurality of geometry-based correction electrodes 749 of this further electrode array in order to effectively correct the focal position of the first individual particle beam 3. The correction of the focal position can be used in particular for image field curvature correction and / or image field tilt correction.

[0104] It should be understood that the order of the first pair 740, the second pair 741, the third pair 742, and the multi-aperture plate 751 with the further electrode arrays as shown in FIG. 13 is merely exemplary in this case. The order of these elements can be interchanged. Moreover, it is not absolutely necessary that each pair of electrode arrays 740, 741, 742 be embodied as immediately successive electrode arrays. Instead, it is also conceivable to arrange the first electrode array of each pair first, and only thereafter arrange the second electrode array of each pair. From a structural point of view, other configurations are of course also possible, some of which have already been further described above as examples in this patent application.

[0105] Figure 14 shows, by way of example, an embodiment of the invention that allows for the generation of quadrupole fields that are linearly independent of one another. In principle, two geometry-based correction electrodes per generated multipole field are required to achieve any alignment of this multipole field. Consistent with the concept of series expansion, the cosine terms

[0106]

number

number

number

number

number

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[0107] A corresponding embodiment or detail from a corresponding aberration correction unit 750 is shown in FIG. 14 . A multi-aperture plate 730 with a circular opening 731 is positioned upstream of a first electrode array with geometry-based correction electrodes 705. Furthermore, a further multi-aperture plate 737 with a circular opening 738 is positioned between the first electrode array with correction electrodes 705 and the second electrode array with geometry-based correction electrodes 706. Similarly, a further multi-aperture plate 732 with a circular opening 733 is positioned downstream of the second electrode array with geometry-based correction electrodes 706. Standard multi-aperture plates 730, 737, and 732 are each grounded and serve as counter electrodes. The quadrupole fields generated by electrodes 705 and 706, respectively, are oriented at exactly 45° relative to each other. The orientation of the quadrupoles thus generated corresponds exactly to the orientation of electrode openings 707 and 708, respectively.

[0108] For reasons of simplicity of illustration, the exemplary embodiment shown in Figure 14 again relates to quadrupole generation for the purposes of aberration correction. However, the described concept of providing a standard multi-aperture plate with a circular opening between different electrode arrays upstream of the sequence of electrode arrays in each case is of course also applicable to other geometry-based correction electrodes and their sequences for the purposes of aberration correction. Accordingly, each standard multi-aperture plate is then also placed between such electrodes to generate multipoles with variable orders.

[0109] An alternative solution to generate linear independence of the generated multipoles is to follow the directionality of changing the rotation angle between the correction electrodes based on the geometry of the electrode array pair, so that the multipoles thus generated are not mixed or orthogonal. However, the directionality of the correction electrodes is still

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[0110] A further preferred solution is to generate an appropriate linear combination of excitations of geometry-based correction electrodes, such that mixing of elementary multipoles is prevented. Figure 15 shows a schematic diagram of a method for generating elementary multipoles for aberration correction of a multibeam particle microscope 1. A first method step S0 comprises providing a multibeam particle microscope 1 with an aberration correction unit 750 according to the invention as described above in several embodiment variants.

[0111] Method step S1 involves exciting only the first geometry-based correction electrode of the sequence of correction electrodes, which does not result exclusively in the desired multipoles but also additionally generates further multipoles, although of significantly weaker amplitudes.

[0112] A further method step S2 involves determining the amplitude of the first multipole thus generated, a further method step S3 involves determining the amplitude of the second multipole thus generated, method step S4 involves determining the amplitude of the third multipole thus generated, etc. This continues until the amplitudes of all multipoles thus generated have been determined.

[0113] Then, in method step S5, only the second geometry-based correction electrode in the sequence is excited. This second geometry-based correction electrode also typically generates not only the desired multipoles but also additional parasitic multipoles. Thus, according to the method, method step S6 involves determining the amplitude of the first multipole thus generated, method step S7 involves determining the amplitude of the second multipole thus generated, method step S8 involves determining the amplitude of the third multipole thus generated, and so on. This continues until all amplitudes of all multipoles thus generated have been determined. Thereafter, and exclusively, only the third, or generally the next, geometry-based correction electrode in the sequence is excited, and so on.

[0114] Method step S9 includes establishing an amplitude matrix based on the determined amplitudes. Method step S10 includes inverting the amplitude matrix. The amplitude matrix represents the relationship between the excitation of the correction electrodes and the amplitude of the generated elementary multipoles. By using the inverted amplitude matrix, it is possible to directly change the amplitude of the elementary multipoles without changing the proportions of other elementary multipoles through this control change. In this way, geometry-based correction electrodes can be excited based on the entries of the inverted amplitude matrix, and elementary multipoles can be generated in a targeted manner. In this way, for example, previously known field dependence of aberrations can be corrected in a targeted manner.

[0115] Of course, the described method can be performed for all sequences of geometry-based correction electrodes, in other words, the method is performed for each first individual particle beam and the aberration correction units are adjusted for all of the individual particle beams.

[0116] Equations (2) and (3) below again express the relationship between the amplitude of the generated elementary multipoles and the excitation of the geometry-based correction electrodes.

[0117]

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[0118] In this case, A denotes the amplitude matrix, and A -1 denotes the inverse amplitude matrix.

[0119] One advantage of the above-described method is that the generated multipoles are decoupled. This provides advantages in optimizing the particle-optical properties of a multi-beam particle beam system or a multi-beam particle microscope 1. For example, it is possible to optimize the resolution. Since the optimal amplitudes of each generated multipole are, to a first approximation, independent of one another, the amplitudes of these multipoles can also be optimized independently of one another. In this case, the amplitudes are varied and the imaging properties are measured in each case. FIG. 16 illustrates this process diagrammatically. First, the amplitude of multipole 1 is varied and the respective resolution is determined. As a result, the optimal amplitude of the first multipole is established. Subsequently, or independently, the amplitude of the second multipole can be varied, and in each case the resolution is measured and the optimal value is determined. Then, the amplitude of the third multipole is varied and the resolution is determined in each case to obtain the corresponding optimal value of the third multipole amplitude. This can be continued for each multipole. It is also possible to repeat this process several times to separate any residual dependencies between the amplitudes of the different multipoles.

[0120] The above descriptions have been given substantially in relation to a multi-beam particle microscope 1. However, they can of course also be varied for different types of multi-beam particle beam systems that can similarly use corresponding aberration correction units.

[0121] Furthermore, it is possible to combine the aberration correction unit according to the present invention with other aberration correction elements, or to otherwise replace some elements according to the present invention with other elements. According to one preferred embodiment of the present invention, in addition to at least one geometry-based electrode array, the aberration correction unit comprises a further electrode array including segmented electrodes. The segmented electrodes are, for example, multipole electrodes, particularly octopole or decadapole electrodes, as described above in connection with the prior art. In this case, it is particularly conceivable to combine and pair correction electrodes of different types, whose multipoles are aligned with each other so as to generate elementary multipoles. For example, it is conceivable that all cosine terms of the series expansion for generating a multipole field are generated by an electrode array including geometry-based correction electrodes, and all sine terms are generated by correspondingly controlled multipole electrodes, or vice versa. In this case, it may be possible to reduce the number of poles in the multipole electrodes and thus reduce control costs at least somewhat by combining the multipole electrodes with geometry-based correction electrodes; for example, it may be sufficient to provide quadrupole segmented electrodes instead of octopole electrodes, provided that corresponding pairing combinations with geometry-based correction electrodes are performed in a specific sequence.

[0122] According to a further preferred embodiment, the geometry-based correction electrodes of at least one electrode array of the aberration correction unit are themselves segmented, and the controller is designed to individually control these segments of the correction electrodes. The geometry-based correction electrodes are, of course, not circularly symmetric; this solution is obvious and has been known for some time. For example, it is possible to segment the geometry-based correction electrodes themselves, each with at least two-fold rotational symmetry about the optical axis for multipole field generation. Thus, the cross-section of the geometry-based correction electrodes can be, for example, elliptical, and individually controllable segments of the correction electrodes, i.e., multipole electrodes embodied with a specific cross-section, are provided along this ellipse. It is also conceivable to insert correspondingly segmented electrodes into the geometry-based correction electrodes. Various embodiment variants have specific advantages and disadvantages with respect to aberration correction.

[0123] Example 1: A multi-beam particle microscope having the following features: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a first particle-optical unit having a first particle-optical beam path configured to image the generated first individual particle beam onto the sample surface such that the first individual particle beam is incident on the sample surface in the object plane at an incidence location, thereby forming a second field; a detection system having a plurality of detection regions that form a third field; a second particle-optical unit having a second particle-optical beam path configured to image a second individual particle beam emanating from an incident location within the second field onto a third field in a detection region of the detection system; a magnetic and / or electrostatic objective lens through which both the first individual particle beam and the second individual particle beam pass; a beam switch disposed in the first particle light beam path between the multi-beam generator and the objective lens, and in the second particle light beam path between the objective lens and the detection system; an aberration correction unit for individually correcting one or more aberrations in the first particle-light beam path; Controller and and the aberration correction unit has a sequence of electrode arrays including at least one first pair of electrode arrays; the first pair having a first electrode array and a second electrode array; the first electrode array and the second electrode array each have a plurality of geometry-based correction electrodes, each having n-fold rotational symmetry about an optical axis for generating a multipole field, each individually controllable by exactly one supply line; a geometry-based correction electrode in the first electrode array is rotated relative to an associated geometry-based correction electrode in the second electrode array about the optical axis; The controller is designed to individually control the plurality of geometry-based correction electrodes of the first electrode array and the second electrode array of the aberration correction unit for aberration correction, in the multi-beam particle microscope.

[0124] Example 2: A multi-beam particle microscope as described in example 1, wherein the rotation angle by which the first pair of geometry-based correction electrodes is rotated relative to each other is substantially 90° / n.

[0125] Example 3: The aberration correction unit has a second pair of electrode arrays, the second pair has a third electrode array and a fourth electrode array; the third electrode array and the fourth electrode array each have a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; the geometry-based correction electrodes in the third electrode array are rotated relative to associated geometry-based correction electrodes in the fourth electrode array about the optical axis; 3. The multi-beam particle microscope of any one of Examples 1 or 2, wherein the controller is configured to individually control the plurality of geometry-based correction electrodes of the third electrode array and the fourth electrode array of the aberration correction unit for aberration correction.

[0126] Example 4: A multi-beam particle microscope as described in example 3, wherein the rotation angle by which the second pair of geometry-based correction electrodes is rotated relative to each other is substantially 90° / m.

[0127] Example 5: The aberration correction unit has a third electrode array pair, the third pair has a fifth electrode array and a sixth electrode array; the fifth electrode array and the sixth electrode array each have a plurality of geometry-based correction electrodes, each having k-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; the geometry-based correction electrodes in the fifth electrode array are rotated relative to associated geometry-based correction electrodes in the sixth electrode array about the optical axis; 5. The multi-beam particle microscope of any one of Examples 1 to 4, wherein the controller is designed to individually control the plurality of geometry-based correction electrodes of the fifth electrode array and the sixth electrode array of the aberration correction unit for aberration correction.

[0128] Example 6: A multi-beam particle microscope as described in example 5, wherein the rotation angle by which the third pair of geometry-based correction electrodes is rotated relative to each other is substantially 90° / k.

[0129] Example 7: A multi-beam particle microscope as described in any one of Examples 1-6, wherein different electrode array pairs have different orders of symmetry for their respective geometry-based correction electrodes to generate different multipole fields.

[0130] Example 8: The geometry-based correction electrodes of the electrode array pair are embodied to have rounded cross sections, and each rounded correction electrode of the electrode array forming the pair is displaced in a different direction relative to the optical axis, in particular by about 90° orthogonal to the optical axis; 8. The multi-beam particle microscope according to any one of Examples 1 to 7, wherein the controller is configured to individually control the rounded correction electrodes for aberration correction, in particular to control the rounded correction electrodes to substantially correct static distortions of the second field of the first individual particle beam when incident on the object plane.

[0131] Example 9: The geometry-based correction electrodes of the electrode array pair are embodied to be substantially elliptical in cross section to generate a quadrupole field, and the substantially elliptical correction electrodes of each of the paired electrode arrays are rotated relative to each other about the optical axis, in particular, rotated by substantially 45°; 9. The multi-beam particle microscope of any one of Examples 1 to 8, wherein the controller is configured to control the correction electrodes having an elliptical cross section to substantially individually correct the astigmatism of the first individual particle beams.

[0132] Example 10: The geometry-based correction electrodes of the electrode array pair are embodied to have a substantially rounded triangular cross-sectional shape to generate a hexapole field, and the correction electrodes having the substantially rounded equilateral triangular cross-sectional shape of each of the paired electrode arrays are rotated relative to each other about the optical axis, in particular, rotated by substantially 30°; The multi-beam particle microscope according to any one of Examples 1 to 9, wherein the controller is configured to individually control the correction electrodes having a substantially triangular cross-sectional shape so as to substantially correct aberrations having three-fold symmetry.

[0133] Example 11: The sequence of electrode arrays of the aberration correction unit comprises a further electrode array comprising a plurality of geometry-based correction electrodes having rounded cross-sections and arranged to be centered with respect to respective optical axes; 11. The multi-beam particle microscope according to any one of Examples 1 to 10, wherein the controller is configured to individually control a plurality of geometry-based correction electrodes of the further electrode array to substantially correct a focal position of the first individual particle beam, in particular for image field curvature correction and / or image field tilt correction.

[0134] Example 12: A multi-beam particle microscope according to any one of Examples 1 to 11, wherein the electrode arrays are each integrated into a multi-aperture plate.

[0135] Example 13: A multi-beam particle microscope as described in Example 12, wherein a standard multi-aperture plate having a plurality of passive rounded apertures is placed between two mutually adjacent multi-aperture plates having integrated therein an electrode array with individually controllable geometry-based correction electrodes.

[0136] Example 14: The aberration correction unit comprises a standard multi-aperture plate with a plurality of passive rounded apertures, which is arranged upstream of a first multi-aperture plate with individually controllable geometry-based correction electrodes with respect to the direction of the particle-light beam path; and / or 14. The multi-beam particle microscope of any one of Examples 12 and 13, wherein the aberration correction unit comprises a standard multi-aperture plate having a plurality of passive rounded apertures, which is positioned downstream of a last multi-aperture plate having individually controllable geometry-based correction electrodes, with respect to the direction of the particle light beam path.

[0137] Example 15: A multi-beam particle microscope described in any one of Examples 1 to 11, wherein the aberration correction unit provides a carrier plate for an electrode array pair, and the geometry-based electrodes of the first electrode array are arranged on the top surface of the carrier plate, and the geometry-based electrodes of the second electrode array are arranged on the bottom surface of the carrier plate.

[0138] Example 16: A multi-beam particle microscope as described in any one of Examples 1 to 11, wherein the aberration correction unit provides a carrier plate for an electrode array pair, and the geometry-based electrodes of the first electrode array are embedded in the carrier plate on the top surface and the geometry-based electrodes of the second electrode array are embedded in the carrier plate on the bottom surface.

[0139] Example 17: further comprising a multipole amplitude input unit, by which a user can input the amplitude of the multipole to be generated of the elementary multipole; 17. The multi-beam particle microscope of any one of Examples 1 to 16, wherein the controller is configured to generate a control signal for controlling the geometry-based correction electrode based on a user input.

[0140] Example 18: A multibeam particle microscope as described in any one of Examples 1 to 17, wherein the controller is designed to perform determination of control signals for controlling geometry-based correction electrodes for multipole field generation using an inverted amplitude matrix, and the non-inverted amplitude matrix represents the relationship between the excitation of the correction electrodes and the amplitude of the generated elementary multipoles.

[0141] Example 19: A method for adjusting the aberration correction of a multi-beam particle microscope according to any one of Examples 1 to 18, comprising: a) For all geometry-based correction electrodes in the sequence, a1) exciting only one of the geometry-based correction electrodes; a2) determining all of the amplitudes of the multipoles generated by the individual excitations; b) establishing an amplitude matrix based on the determined amplitudes; c) inverting the amplitude matrix; A method comprising:

[0142] Example 20: The method according to Example 19, wherein method step a2) comprises compensating for the effects of multipoles generated by a global multipole corrector, in particular by a dodecapole corrector, respectively, and determining the amplitudes required for this purpose in the global multipole corrector.

[0143] Example 21: d) The method of any one of Examples 18 to 20, further comprising optimizing the resolution of the multi-beam particle microscope, the optimizing step comprising independently varying the amplitude of each multipole and determining an optimal amplitude for the resolution.

[0144] Example 22: The method according to any one of Examples 18 to 21, wherein the method is performed for all of a sequence of geometry-based correction electrodes.

[0145] Example 23: A computer program product having a program code for performing the method according to any one of Examples 18 to 22.

[0146] Example 24: A multi-beam particle beam system, comprising: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a particle-optical unit having a first particle-optical beam path configured to image the generated individual particle beam onto a sample surface such that the individual particle beam is incident on the sample surface in the object plane at an incidence location, thereby forming a second field; an aberration correction unit for individually correcting one or more aberrations in the particle light beam path; Controller and and the aberration correction unit has at least one electrode array; the electrode array comprises a plurality of geometry-based correction electrodes, each having n-fold rotational symmetry about the optical axis for generating a multipole field, each of which is individually controllable by means of, in particular, exactly one supply line; The controller is designed to individually control a plurality of geometry-based correction electrodes of the electrode array of the aberration correction unit for aberration correction in a multi-beam particle beam system.

[0147] Example 25: The aberration correction unit has a further electrode array, the further electrode array comprises a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; 25. The multi-beam particle beam system of example 24, wherein the controller is configured to individually control a plurality of geometry-based correction electrodes of the further electrode array of the aberration correction unit for aberration correction.

[0148] Example 26: A multi-beam particle beam system described in any one of Examples 24 and 25, wherein the aberration correction unit has one further electrode array or multiple further electrode arrays, the electrodes being embodied to be geometrically based and / or non-geometrically based.

[0149] Example 27: Geometry-based correction of at least one electrode array, wherein the electrodes are themselves segmented; 27. The multi-beam particle beam system of example 26, wherein the controller is configured to individually control segments of the correction electrode. [Explanation of symbols]

[0150] 1. Multibeam particle microscope 3 Primary particle beam (individual particle beam) 5 Beam spot, incident location 7 Objects and samples 9 Secondary particle beam 10 Computer system, controller 15 Sample surface 101 Objective surface 102 Objective Lens 103 Electromagnetic Lens 105 axes 200 detector system 205 Projection Lens System 209 Detection system, particle multi-detector, detection unit 210 Lens 220 Lens 222 contrast stops 300 Beam Generator 301 Particle source 303 Collimation Lens System 304 Multi-aperture plate, filter plate 305 Multi-aperture configuration 306 Micro-Optical Systems 307 Field Lens 308 Field Lens 309 Diverging Particle Beam 323 Beam Focus 325 Intermediate image plane 361 Opening 370 Multi-Aperture Plate 372 Octopole Electrode 373 Individual electrodes of octupole electrodes 375 Electronic circuit 377 Line 379 Serial Data Connection 381 Vacuum Jacket 382 stickers 400 Beam Switch, Magnetic Configuration 500 scanning deflector 600 displacement stage or positioning device 701 Geometry-based correction electrodes 702 Geometry-based correction electrodes 703 Opening 704 Opening 705 Geometry-based correction electrodes 706 Geometry-based correction electrodes 707 Opening 708 Opening 709 Geometry-Based Correction Electrode 710 Geometry-Based Correction Electrodes 711 Opening 712 Opening 713 Geometry-based correction electrodes 714 Opening 715 Multi-Aperture Plate 716 Multi-Aperture Plate 717 Line 718 Line 720 Electrode Array 721 Electrode Array 722 Electrode Array 723 Electrode Array 724 Multi-Aperture Plate 725 Multi-Aperture Plate 726 Geometry-based Correction Electrode 727 Opening 728 Geometry-Based Correction Electrode 729 Opening 730 Standard Multi-Aperture Plate 731 Opening 732 Standard Multi-Aperture Plate 733 Opening 734 Carrier Plate 735 Insulation 736 Carrier Plate 737 Standard Multi-Aperture Plate 738 Opening 740 first electrode array pair 741 Second electrode array pair 742 Third electrode array pair 744 Geometry-based correction electrodes 738 Opening 746 Geometry-Based Correction Electrodes 747 Opening 748 Geometry-Based Correction Electrode 749 Opening 750 aberration correction unit 751 Multi-Aperture Plate h Thickness of the multi-aperture plate with electrode array Z optical axis S0 to provide a multi-beam particle microscope having an aberration correction unit according to the present invention. S1: Exciting the first geometry-based correction electrode of the sequence S2 Determine the amplitude of the first multipole thus generated S3 Determine the amplitude of the second multipole thus generated S4 Determine the amplitude of the third multipole thus generated S5. Exciting the second geometry-based correction electrode of the sequence S6 Determine the amplitude of the first multipole thus generated S7 Determine the amplitude of the second multipole thus generated S8 Determine the amplitude of the third multipole thus generated S9 Establishing an amplitude matrix based on the determined amplitudes S10 Inverting the amplitude matrix

Claims

1. A multi-beam particle microscope having the following features: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a first particle-optical unit having a first particle-optical beam path configured to image the generated first individual particle beam onto a sample surface in an object plane such that the first individual particle beam is incident on the sample surface at an incidence location, thereby forming a second field; a detection system having a plurality of detection regions that form a third field; a second particle-optical unit having a second particle-optical beam path configured to image a second individual particle beam emanating from the incidence location within the second field into the third field in the detection region of the detection system; and a magnetic and / or electrostatic objective lens through which both the first individual particle beam and the second individual particle beam pass; a beam switch disposed in the first particle beam path between the multi-beam generator and the objective lens, and in the second particle beam path between the objective lens and the detection system; an aberration correction unit for individually correcting one or more aberrations in the first particle-light beam path; Controller and and the aberration correction unit comprises a sequence of electrode arrays including at least one first pair of electrode arrays; the first pair having a first electrode array and a second electrode array; the first electrode array and the second electrode array each have a plurality of geometry-based correction electrodes, each having n-fold rotational symmetry about an optical axis for generating a multipole field, each of the geometry-based correction electrodes being individually controllable by exactly one supply line; geometry-based correction electrodes in the first electrode array are rotated relative to associated geometry-based correction electrodes in the second electrode array with respect to the optical axis; the controller is designed to individually control the plurality of geometry-based correction electrodes of the first electrode array and the second electrode array of the aberration correction unit for aberration correction.

2. 2. The multi-beam particle microscope of claim 1, wherein the rotation angle by which the geometry-based correction electrodes of the first pair are rotated relative to each other is substantially 90° / n.

3. the aberration correction unit has a second pair of electrode arrays; the second pair having a third electrode array and a fourth electrode array; the third electrode array and the fourth electrode array each have a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about an optical axis for generating a multipole field, each of the geometry-based correction electrodes being individually controllable by exactly one supply line; the geometry-based correction electrodes in the third electrode array are rotated relative to associated geometry-based correction electrodes in the fourth electrode array with respect to the optical axis; 3. The multi-beam particle microscope of claim 1, wherein the controller is designed to individually control the plurality of geometry-based correction electrodes of the third electrode array and the fourth electrode array of the aberration correction unit for aberration correction.

4. 4. The multi-beam particle microscope of claim 3, wherein the rotation angle by which the geometry-based correction electrodes of the second pair are rotated relative to each other is substantially 90° / m.

5. the aberration correction unit includes a third electrode array pair; the third pair having a fifth electrode array and a sixth electrode array; the fifth electrode array and the sixth electrode array each have a plurality of geometry-based correction electrodes, each having k-fold rotational symmetry about an optical axis for generating a multipole field, each of the geometry-based correction electrodes being individually controllable by exactly one supply line; the geometry-based correction electrodes in the fifth electrode array are rotated relative to associated geometry-based correction electrodes in the sixth electrode array with respect to the optical axis; 5. The multi-beam particle microscope according to claim 1, wherein the controller is designed to individually control the plurality of geometry-based correction electrodes of the fifth electrode array and the sixth electrode array of the aberration correction unit for aberration correction.

6. 6. The multi-beam particle microscope of claim 5, wherein the rotation angle by which the geometry-based correction electrodes of the third pair are rotated relative to each other is substantially 90° / k.

7. The multi-beam particle microscope of any one of claims 1 to 6, wherein different electrode array pairs have different orders of symmetry for their respective geometry-based correction electrodes to generate different multipole fields.

8. the geometry-based correction electrodes of the electrode array pair are embodied to have rounded cross sections, and the rounded correction electrodes of each of the electrode arrays forming the pair are displaced in different directions relative to the optical axis, in particular by approximately 90° orthogonal to the optical axis; 8. The multi-beam particle microscope according to claim 1, wherein the controller is configured to individually control the rounded correction electrodes for aberration correction, in particular to control the rounded correction electrodes to substantially correct static distortions of the second field of first individual particle beams when incident on the object plane.

9. the geometry-based correction electrodes of the electrode array pair are embodied to be substantially elliptical in cross section to generate a quadrupole field, and the substantially elliptical correction electrodes of each of the electrode arrays forming the pair are rotated relative to each other about the optical axis, in particular by substantially 45°; 9. The multi-beam particle microscope according to claim 1, wherein the controller is configured to control the correction electrodes having an elliptical cross section to substantially individually correct astigmatism of the first individual particle beams.

10. the geometry-based correction electrodes of the electrode array pair are embodied to have a substantially rounded triangular cross-sectional shape to generate a hexapole field, and the correction electrodes having the substantially rounded triangular cross-sectional shape of each of the electrode arrays forming the pair are rotated relative to each other about the optical axis, in particular by substantially 30°; The multi-beam particle microscope according to any one of claims 1 to 9, wherein the controller is configured to individually control the correction electrodes having a substantially triangular cross-sectional shape so as to correct aberrations having substantially three-fold symmetry.

11. the sequence of electrode arrays of the aberration correction unit comprises a further electrode array comprising a plurality of geometry-based correction electrodes having rounded cross-sections and each of the geometry-based correction electrodes being centered about the optical axis; 11. The multi-beam particle microscope according to any one of claims 1 to 10, wherein the controller is designed to individually control the plurality of geometry-based correction electrodes of the further electrode array to substantially correct a focal position of the first individual particle beam, in particular for image field curvature correction and / or image field tilt correction.

12. The multi-beam particle microscope according to any one of claims 1 to 11, wherein each of the electrode arrays is integrated into a multi-aperture plate.

13. 13. The multi-beam particle microscope of claim 12, wherein a standard multi-aperture plate having a plurality of passive rounded apertures is placed between two mutually adjacent multi-aperture plates having integrated therein an electrode array with individually controllable geometry-based correction electrodes.

14. the aberration correction unit comprises a standard multi-aperture plate with a plurality of passive rounded apertures, arranged upstream of a first multi-aperture plate with individually controllable geometry-based correction electrodes with respect to the direction of the particle-light beam path; and / or 14. The multi-beam particle microscope according to claim 12, wherein the aberration correction unit comprises a standard multi-aperture plate with a plurality of passive rounded apertures, which is arranged, with respect to the direction of the particle light beam path, downstream of a last multi-aperture plate with individually controllable geometry-based correction electrodes.

15. 12. The multi-beam particle microscope of claim 1, wherein the aberration correction unit provides a carrier plate for a pair of electrode arrays, the geometry-based correction electrodes of the first electrode array being arranged on a top surface of the carrier plate, and the geometry-based correction electrodes of the second electrode array being arranged on a bottom surface of the carrier plate.

16. 12. The multi-beam particle microscope of claim 1, wherein the aberration correction unit provides a carrier plate for a pair of electrode arrays, the geometry-based correction electrodes of the first electrode array being embedded in the carrier plate on a top surface and the geometry-based correction electrodes of the second electrode array being embedded in the carrier plate on a bottom surface.

17. further comprising a multipole amplitude input unit, by which a user can input the amplitude of the elementary multipole to be generated; The multi-beam particle microscope of any one of claims 1 to 16, wherein the controller is configured to generate control signals for controlling the geometry-based correction electrodes based on the user input.

18. 18. The multi-beam particle microscope according to any one of claims 1 to 17, wherein the controller is designed to perform determination of control signals for controlling the geometry-based correction electrodes for multipole field generation using an inverted amplitude matrix, the non-inverted amplitude matrix representing the relationship between the excitation of the correction electrodes and the amplitude of the generated elementary multipoles.

19. 19. The multi-beam particle microscope of any one of claims 1 to 18, wherein the controller is designed to individually control the geometry-based correction electrodes to correct previously known field-dependent aberrations.

20. 1. A method for generating elementary multipoles for aberration correction in a multibeam particle microscope, comprising: a0) providing a multi-beam particle microscope according to any one of claims 1 to 19; a) For all geometry-based correction electrodes in the sequence, a1) exciting only one of the geometry-based correction electrodes; a2) determining the amplitudes of all of the multipoles generated by said individual excitations; b) establishing an amplitude matrix based on the determined amplitudes, the amplitude matrix representing a relationship between the excitation of the geometry-based correction electrodes and the amplitudes of the elementary multipoles generated by the excitation; c) inverting the amplitude matrix; d) exciting the geometry-based correction electrodes based on entries of the inverted amplitude matrix; A method comprising:

21. 20. The method according to claim 19, wherein method step a2) comprises compensating for the effects of multipoles respectively generated by a global multipole corrector, in particular by a dodecapole corrector, and determining amplitudes respectively required for this purpose in the global multipole corrector.

22. 22. The method of claim 19, further comprising: e) optimizing a resolution of the multi-beam particle microscope, the optimizing step comprising varying the amplitude of each multipole independently and determining the amplitude that is optimal for the resolution.

23. The method of any one of claims 19 to 22, wherein the method is performed for all of the sequence of geometry-based correction electrodes.

24. 24. The method according to any one of claims 19 to 23, wherein by exciting the geometry-based correction electrodes, a field-dependent aberration correction is performed, in particular a previously known field dependence of aberrations is corrected.

25. A computer program product having a program code for performing the method according to any one of claims 19 to 24.

26. 1. A multi-beam particle beam system having the following features: a multi-beam generator configured to generate a first field of a plurality of first charged individual particle beams; a particle-optical unit having a first particle-optical beam path configured to image the generated individual particle beam onto a sample surface in an object plane such that the individual particle beam is incident on the sample surface at an incidence location, thereby forming a second field; an aberration correction unit for individually correcting one or more aberrations in the particle-light beam path; Controller and and the aberration correction unit has at least one electrode array; the electrode array comprises a plurality of geometry-based correction electrodes each having n-fold rotational symmetry about an optical axis for generating a multipole field, each of the geometry-based correction electrodes being individually controllable in particular by exactly one supply line; The controller is designed to individually control the plurality of geometry-based correction electrodes of the electrode array of the aberration correction unit for aberration correction.

27. the aberration correction unit comprises a further electrode array; the further electrode array comprises a plurality of geometry-based correction electrodes, each having m-fold rotational symmetry about the optical axis for generating a multipole field, each individually controllable by exactly one supply line; 27. The multi-beam particle beam system of claim 26, wherein the controller is designed to individually control the plurality of geometry-based correction electrodes of the further electrode array of the aberration correction unit for aberration correction.

28. 28. The multi-beam particle beam system according to any one of claims 26 and 27, wherein the aberration correction unit comprises one further electrode array or a plurality of further electrode arrays, which electrodes are embodied to be geometrically and / or non-geometrically based.

29. the geometry-based correction electrodes of at least one electrode array are themselves segmented; 30. The multi-beam particle beam system of claim 28, wherein the controller is designed to individually control the segments of the correction electrode.

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