Multiple-beam particle systems with high-speed magnetic lenses, particularly multi-beam particle microscopes, and their applications

Abstract

Disclosed is a multi-beam particle microscope, comprising a magnetic lens through which multiple individual charged particle beams pass, and a controller configured to control the magnetic lens, particularly dynamically. The magnetic lens comprises a coil (701), a winding body (702) particularly equipped with a cooling line structure, and a pole element. The coil is positioned around the winding body, which is designed as a hollow body through which multiple individual particle beams pass. The coil is positioned together with the winding body within the pole element. The pole element has an aperture, through which the magnetic field generated by the magnetic lens exits the pole element and interacts with the multiple individual particle beams to obtain a lensing effect. The winding body is conductive and has a shielding section (710), which shields the conductivity of the winding body in the circumferential direction around the particle optical axis. When the magnetic lens is dynamically controlled, the generation of eddy currents in the winding body around the particle optical axis is reduced. As a result, the magnetic lens of the multi-beam system can be dynamically controlled over a wide bandwidth of up to 1500 Hz.

Description

[Technical Field]

[0001] This invention relates to a multi-particle beam system operating with multiple individual charged particle beams. Specifically, this invention relates to a multi-particle beam system having a high-speed magnetic lens, in particular to a multi-beam particle microscope, and to the use thereof. [Background technology]

[0002] Microstructures such as semiconductor components are becoming increasingly small and complex, necessitating further development and optimization of planar manufacturing techniques and inspection systems for manufacturing and inspecting these tiny dimensions. For example, the development and manufacturing of semiconductor components requires monitoring the design of test wafers, and planar manufacturing techniques require process optimization for high-throughput and reliable manufacturing. Furthermore, there is a growing demand for the analysis of semiconductor wafers for reverse engineering and for customized individual configurations of semiconductor components. Therefore, high-throughput inspection methods are needed to inspect microstructures on wafers with high precision.

[0003] Typical silicon wafers used in the manufacture of semiconductor components have a maximum diameter of 300 mm. Each wafer can be up to 800 mm. 2The wafer is divided into 30 to 60 repeating regions ("dies") of a certain size. A semiconductor device comprises multiple semiconductor structures created in layers on the surface of a wafer using planar integration techniques. Due to the manufacturing process, semiconductor wafers typically have a planar surface. In this case, the structural size of the integrated semiconductor structure ranges from a few micrometers to a critical dimension (CD) of 5 nm, and in the near future, the structural size will become even smaller, and it is expected that in the future, the structural size or critical dimension (CD) will be less than 3 nm, for example, 2 nm or less than 1 nm. With such small structural sizes as described above, it is necessary to quickly identify defects of critical dimension size over a very wide area. For some applications, the specification requirements regarding the accuracy of measurements provided by inspection equipment are even higher, for example, twice as high or an order of magnitude higher. For example, the width of a semiconductor feature needs to be measured with an accuracy of less than 1 nm, for example, less than 0.3 nm, and the relative position of a semiconductor structure needs to be determined with an overlay accuracy of less than 1 nm, for example, less than 0.3 nm.

[0004] Therefore, a general objective of the present invention is to provide a multi-particle beam system operating with charged particles and related methods for operating the multi-particle beam system at high throughput, enabling high-precision measurement of semiconductor features with accuracies of less than 1 nm, less than 0.3 nm, and even less than 0.1 nm.

[0005] Multibeam scanning electron microscopes (MSEMs) are a relatively new advance in the field of charged particle microscopes (CPMs). For example, multibeam scanning electron microscopes are disclosed in U.S. Patent No. 7,244,949 and U.S. Patent Application Publication No. 2019 / 0355544. In the case of a multibeam electron microscope, or MSEM, the sample is simultaneously irradiated with a number of individual electron beams arranged within a field of view or raster. For example, 4 to 10,000 individual electron beams can be provided as primary radiation, and each individual electron beam is separated from adjacent individual electron beams at a pitch of 1 to 200 micrometers. For example, an MSEM has about 100 separated individual electron beams ("beamlets"), which are arranged, for example, within a hexagonal raster, and the individual electron beams are separated at a pitch of about 10 μm. Multiple individual charged particle beams (primary beams) are focused onto the surface of the sample under examination via a common objective lens. For example, the sample can be a semiconductor wafer fixed in a wafer holder mounted on a movable stage. When the wafer surface is irradiated by individual primary charged particle beams, interaction products such as secondary electrons and backscattered electrons are emitted from the wafer surface. Their starting points correspond to positions on the sample where multiple individual primary particle beams are focused in each case. The amount and energy of the interaction products depend on the material composition and the topography of the wafer surface. The interaction products form multiple individual secondary particle beams (secondary beams), which are collected by a common objective lens and incident on a detector placed within the detection plane as a result of the projection imaging system of a multibeam inspection system. The detector has multiple detection regions, each of which may have multiple detection pixels, and the detector acquires an intensity distribution for each of the individual secondary particle beams. In this process, an image field of view of, for example, 100 μm × 100 μm is acquired.

[0006] Conventional multibeam electron microscopes comprise a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adapt the focal position and astigmatism correction of multiple individual charged particle beams. Furthermore, conventional multibeam systems with charged particles comprise at least one intersecting plane of primary or secondary individual charged particle beams. In addition, conventional systems comprise a detection system to facilitate adjustment. Conventional multibeam particle microscopes comprise at least one beam deflector ("deflection scanner") for scanning a region of the sample surface collectively with multiple individual primary particle beams to acquire an image field of view of the sample surface.

[0007] For scanning electron microscopes used for wafer inspection, it is desirable to maintain stable imaging conditions to ensure reliable and highly reproducible imaging. Throughput depends on several parameters, such as stage speed, readjustment speed at new measurement sites, and measurement area per unit of capture time. Throughput is determined, among other things, by dwell time on pixels, pixel size, and the number of individual particle beams. In addition, multi-beam electron microscopes may require time-consuming post-imaging processing; for example, signals generated from charged particles by the detection system of a multi-beam system must be digitally corrected before combining ("stitching") image fields from multiple image subfields or partial images.

[0008] Here, the raster positions of individual particle beams on the sample surface may deviate from the ideal raster positions in a planar arrangement. The resolution of the multibeam electron microscope may differ for each individual particle beam, and may depend on the individual positions of each particle beam within the field of view of each individual particle beam, and consequently, on the specific raster positions of those individual particle beams.

[0009] Conventional charged particle beam systems are reaching their limits due to increasing demands for resolution and throughput.

[0010] Therefore, the object of the present invention is to provide a multi-particle beam system that enables high-throughput, high-precision, and high-resolution imaging recording.

[0011] One approach to improving accuracy and resolution is the use of so-called autofocus. Here, while scanning the sample surface, the current focal position of each electron beam is continuously ("on the fly") confirmed within the field of view of the sample surface / object plane, and appropriate corrections to the focal position are made. For example, the focal setting of individual particle beams is adapted to each image field. For example, this procedure is based on the assumption that the sample model or sample properties do not change much with respect to the image field, and predicted values ​​for focal improvement can be confirmed by extrapolation or interpolation.

[0012] However, known autofocus methods are often relatively slow. This is because the focal position is optimized by changing the working distance (WD) or by different controls of the objective lens. When the objective lens or other magnetic lenses are controlled separately for the purpose of changing the focal position, this adjustment is relatively slow. Conventional techniques, particularly those utilizing magnetic objective lenses and immersion lenses, do not, in the dynamic case, track the lens's magnetic field to the lens excitation (the current flowing through the lens coil). Conventional techniques use a coil body or winding made of a material with good thermal conductivity to dissipate the heat generated by the coil. Because thermal conductivity and electrical conductivity are interrelated, the coil body acts as a short-circuit turn, and a current is induced by the dynamic lens excitation. The induced current counteracts the dynamic changes in excitation. Therefore, the dynamic changes are compensated and not transmitted to the magnetic lens field shaping poles at high frequencies. Electrical compensation of the inductance of the lens coil, aimed at controlling the desired time profile of the magnetic lens field via the lens current (dynamic closed-loop control), becomes meaningless. Therefore, conventional techniques attempt to reduce the inductance of the lens coil, but this is insufficient for powerful lenses that require cooling.

[0013] To solve the problems described above, International Patent Application Publication No. 2022 / 069073 discloses a multiple particle beam system with high-speed autofocus. For this purpose, at least one high-speed autofocus correction lens is used to quickly set the focus. This lens can have different embodiments and can be implemented, for example, as a high-speed electrostatic lens or as an air-core coil. An air-core coil is an inductive component that does not have a soft magnetic core and has relatively low inductance compared to a coil that has a soft magnetic core, so an air-core coil can also be used as a high-speed autofocus correction lens.

[0014] U.S. Patent No. 5,708,274 discloses a particle optical lens having a curved optical axis, which generates anomalies that can be corrected by a coil pair.

[0015] German Patent Application Publication No. 10044199 discloses a special magnetic lens arrangement with a corrective magnetic field, which makes it possible to offset the particle optical axis parallel to the axis of symmetry of the arrangement.

[0016] German Patent Application Publication No. 2752598 discloses a high-speed electro-optical lens. Specifically, a special arrangement is proposed in which a first magnetic lens is placed inside a second magnetic lens, and a shield in the form of a ring-shaped body made of high-permeability high-frequency ferrite is provided between the magnetic lenses.

[0017] Magnetic lenses with soft magnetic cores or polar magnetic pieces have high inductance and, according to prior art, are not considered to be rapidly controllable or dynamically operable. Therefore, the time-limiting elements in multiple particle beam systems remain known magnetic lenses, including, for example, magnetic field lenses, magnetic projection lenses, and magnetic objective lenses.

[0018] In addition to high-speed autofocus correction, there are various other problems where a system with higher throughput is desirable, for example, in the case of dynamic readjustment of a multi-particle beam system, in the case of recording a focus series, when high-speed adaptation of the detection path due to charging of the sample is required, etc. Therefore, overall, high-speed controllability, i.e., dynamic controllability, of a (powerful) magnetic lens is desirable.

Summary of the Invention

[0019] Therefore, an object of the present invention is to provide an alternative multi-particle beam system that enables high-speed dynamic control of the system. In particular, even a powerful magnetic lens that requires active cooling needs to be made quickly controllable so that additional weak lenses can be avoided without active cooling.

[0020] This object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are apparent from the dependent claims.

[0021] This patent application claims the priority of German Patent Application No. 102023116627.1 filed on June 23, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0022] The present invention breaks the established theory of particle optics that a magnetic lens with high inductance is not quickly switchable or can only be dynamically controlled at a low bandwidth of a few hertz. Therefore, avoidance measures such as switching to an electrostatic lens are not required. Instead, an intentional improvement of the existing magnetic lens has been made.

[0023] Within the scope of this invention, the inventors have investigated ferromagnetic lenses and their behavior during dynamic control in detail. It is known that so-called iron loss limits the bandwidth over which a magnetic lens can be controlled. In this case, the so-called iron loss is related to the iron core or, in the context of particle optics, to the polar elements of the magnetic lens. In the case of dynamic control, eddy currents can be generated in these polar elements that limit the bandwidth of the magnetic lens. This problem is also known from the prior art within the scope of transformer construction, and solutions to this problem exist. However, simply implementing these solutions does not lead to a definitive improvement in the control behavior of ferromagnetic lenses in particle optics.

[0024] In the case of powerful magnetic lenses, a relatively large amount of heat is generated and must be dissipated. Therefore, the coil body or winding used usually has a cooling line structure, and thus the winding itself requires good thermal conductivity. However, good thermal conductivity typically correlates with high electrical conductivity. Therefore, eddy currents are generated during the dynamic control of magnetic lenses. Thus, when designing windings according to the prior art, a compromise is made between the desired thermal conductivity on the one hand and the undesirable high electrical conductivity on the other hand. In particle optics, copper is often used as the material for the windings of magnetic lenses. In addition, supplementary measures are taken, such as the use of additional small dynamic lenses with or without small windings, and the use of materials particularly suitable for lens components and beam tubes.

[0025] However, according to the present invention, a different approach is selected to dynamically control powerful magnetic lenses, i.e., magnetic lenses requiring active cooling, over a wide range. The present invention proposes the separation of windings substantially parallel to the heat flow and perpendicular to the generated eddy currents. This reduces the generated eddy currents on the one hand, while enabling maximum cooling or heat dissipation on the other.

[0026] Specifically, according to a first aspect, the present invention relates to a multi-beam particle beam system, particularly a multi-beam particle microscope, comprising a magnetic lens through which a plurality of individual charged particle beams pass, and a controller configured to control the magnetic lens, wherein the magnetic lens comprises a coil, a winding body, and a polar magnetic piece, the coil being arranged around the winding body, the winding body being designed as a hollow body through which a plurality of individual particle beams pass, the coil being arranged together with the winding body within the polar magnetic piece, the polar magnetic piece having an aperture, through which a magnetic field generated by the magnetic lens exits the polar magnetic piece and interacts with the plurality of individual particle beams to obtain a lensing effect, the winding body being conductive, the winding body having a shielding portion through which the conductivity of the winding body is blocked in the circumferential direction around the particle optical axis, and when the magnetic lens is dynamically controlled, the generation of eddy currents within the winding body around the particle optical axis is reduced.

[0027] For example, individual charged particle beams can be electron beams, positron beams, muon beams, ion beams, or other charged particle beams. Preferably, these are electron beams.

[0028] According to the present invention, the winding has a shielding portion, which blocks the conductivity of the winding in the circumferential direction around the particle optical axis. In this case, the conductivity of the winding may be completely or partially blocked in the circumferential direction around the particle optical axis. In the case of a symmetric design of a multi-beam particle beam system, the circumferential direction around the particle optical axis usually coincides precisely with the direction in which eddy currents are generated within the winding.

[0029] According to a preferred embodiment of the present invention, the cutoff portion of the winding is in the form of a slot. For example, it is possible to appropriately trim all or part of the winding before the coil is wound.

[0030] According to a preferred embodiment of the present invention, the winding is provided with exactly one interruption section, but it is also possible to provide multiple interruptions, and to ensure that the winding is not cut in a way that divides it into two halves or causes it to fall apart during the process. For example, a first slot can be introduced into the winding from above, and another slot can be introduced into the winding from below. In this case, the two slot sections can be positioned opposite each other or displaced relative to each other in the circumferential direction. Further slot sections are also possible.

[0031] According to a preferred embodiment of the present invention, the shield in the winding is oriented from the inside out, particularly radially. In addition, or alternatively, the shield is formed along the particle optical axis, particularly parallel to the particle optical axis. In this context, radial is understood to mean the direction starting from the particle optical axis of a multibeam particle beam system and extending radially outward perpendicular to the particle optical axis. The shield extends along the particle optical axis whenever it has a certain range along the particle optical axis. This range must also be considered if the precise profile of the shield is not parallel to the particle optical axis, but for example, simply angled. However, parallelism to the particle optical axis is preferred because, due to the system symmetry that is usually present, heat transport takes place parallel to the particle optical axis within the winding. Where possible, this heat transport should not be restricted by the shield.

[0032] According to a preferred embodiment of the present invention, the blocking portion is in the form of a slot, for example, the slot width b satisfies the condition 100 μm ≤ b ≤ 1000 μm. Therefore, the slot required for the blocking portion can be made very narrow, and thus it can be manufactured very easily. However, the slot can be narrow or wide.

[0033] According to a preferred embodiment of the present invention, an insulator and / or high-resistance material is placed in or within the slots, particularly in the interlocking portion within the slots. The gap in the winding created by the interlocking portion is thus firmly, and especially completely, filled. For example, a film can be placed as an insulator in the interlocking portion. For example, the following materials can be placed in the interlocking portion: namely, plastics, particularly high-performance thermoplastics, such as PEEK (polyether ether ketone), PP (polypropylene), PA (polyamide), POM (polyoxymethylene), PET (polyethylene terephthalate), PC (polycarbonate), PES (polysulfone), or PEI (polyetherimide). Alternatively, ceramics such as aluminum oxide (Al2O3) or silicate ceramics can be placed in the interlocking portion.

[0034] By placing an insulator and / or high-resistance material in the breakpoint, the breakpoint is prevented from being bridged by adjacent metal components. This reduces the eddy currents generated, while also allowing for very thin insulating layers, thus enabling maximum cooling or dissipation. Similarly, insulators can be used to compensate for the loss of mechanical stability caused by the breakpoint or slots.

[0035] According to a preferred embodiment of the present invention, the winding also includes a cooling line structure for cooling the winding, and the interruption portion is positioned so that the cooling line structure is not interrupted by the interruption portion. Such a cooling line structure has already been used in the prior art. Therefore, the region in the winding where the cooling line structure is located forms a heat sink, and the heat flux generated in the winding is directed towards the heat sink.

[0036] According to a preferred embodiment of the present invention, the winding body comprises a plate-shaped front piece. Multiple individual charged particle beams also pass through this plate-shaped front piece, and therefore the front piece is a component of the hollow body formed by the entire winding body, which may, for example, have a central opening. The cooling line structure comprises a coolant inlet and outlet located on the outer edge of the plate-shaped front piece. The cooling line structure is arranged particularly meanderingly within the plate-shaped front piece of the winding body, and as a whole, substantially surrounds the particle optical axis once between the inlet and outlet. A barrier is then located between the inlet and outlet of the cooling line structure, and the barrier blocks the plate-shaped front piece, particularly in the radial direction. When the plate-shaped front piece is also blocked in this way, eddy currents cannot flow around the particle optical axis of the system in this plate-shaped front piece. It is not necessary to omit the cooling line structure itself in the plate-shaped front piece. The loop-shaped arrangement, or meandering arrangement, allows for the provision of a cooling line structure over the largest possible area on the plate-shaped front piece, and even when a barrier is introduced on the plate-shaped front piece, an efficient heat sink can be formed.

[0037] According to a preferred embodiment of the present invention, the controller is configured to dynamically control the magnetic lens using a control current at frequencies of 20 Hz or higher, particularly frequencies of 50 Hz or higher, 100 Hz or higher, or 1000 Hz or higher. In this case, the magnetic lens is subjected to the axial magnetic field B of the magnetic lens generated by the dynamic control. dyn The following relationships

[0038]

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[0039]

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[0040]

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[0041] The above values, i.e., greater than approximately 70.7% over a long range, were used to verify these parameters of the magnetic lens. The control was modified, or, in the case of a control current with a constant maximum amplitude, linearly increased with respect to the lens current frequency. Simultaneously, the axial magnetic field of the magnetic lens was measured inside the lens for each control frequency using a sufficiently fast, field-sensitive uniaxial measuring probe. In this case, the measured axial magnetic field extends along the particle optical axis Z, i.e., in the z direction. To control the coil with a constant current over a wide frequency range, the coil inductance was electronically compensated, i.e., the control voltage was adapted accordingly.

[0042] According to a more preferred embodiment of the present invention, the magnetic lens is controllable over a bandwidth BW such that the following relationship holds: 0Hz ≤ BW ≤ 1500Hz.

[0043] According to the present invention, dynamic magnetic field B dyn However, static magnetic field B stat Compared to, the value

[0044]

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[0045] According to a more preferred embodiment of the present invention, the multi-beam particle beam system further comprises a current source for supplying the control current described above for the magnetic lens, the current source having a bandwidth optimized for dynamic control of the magnetic lens. Due to the increase in impedance, it has been found that at high frequencies the current source limits the bandwidth behavior of the magnetic lens. By appropriately changing the control parameters of the current source, the cutoff frequency can be shifted to a higher cutoff frequency. With these measures, although the power of the current source, or the output voltage of the current source, still limits the achievable bandwidth in principle, these measures already make it possible to reach the aforementioned 1500 Hz region.

[0046] According to a preferred embodiment of the present invention, the shielding portion of the winding is complete in the direction of the particle optical axis of the multi-beam particle beam system, particularly in the direction parallel to the particle optical axis, and / or the shielding portion of the winding is complete from the inside out, particularly in the radial direction. This makes it possible to completely suppress eddy currents around the particle optical axis, and the magnetic lens can be dynamically controlled over a very wide bandwidth.

[0047] According to an alternative embodiment of the present invention, the shielding portion of the winding is incomplete in the direction of the particle optical axis of the multi-beam particle beam system, particularly in the direction parallel to the particle optical axis, and / or, the shielding portion of the winding is incomplete from the inside out, particularly in the radial direction. This incomplete shielding portion may have several advantages. By significantly reducing eddy currents, it becomes possible to set the bandwidth of the magnetic lens to a value of 50 Hz or more, or significantly above 50 Hz. However, this makes it susceptible to interference induced in the cabling. Thus, interference induced in the cabling can be input-coupled to multiple individual particle beams. This can be particularly true in the frequency range around 50 Hz or 60 Hz, as these frequencies frequently occur in laboratory environments.

[0048] Therefore, it may be advantageous to optimize the bandwidth to be fast enough for dynamic requirements, and conversely, to limit excessive bandwidth to prevent interference effects on multiple individual particle beams. Accordingly, according to a preferred embodiment of the present invention, during the dynamic control of the magnetic lens, a winding connector having a defined resistance for bandwidth limiting is provided adjacent to the cutoff portion in the direction of the particle optical axis. In other words, the winding cutoff portion is not complete in the direction of the particle optical axis. The selection of a defined connector, i.e., a connector having dimensions defined in the Z direction, i.e., in the direction of the particle optical axis, ensures a defined resistance in combination with the specific resistance of the selected material.

[0049] According to a further embodiment of the present invention, the magnetic lens comprises a switchable bridging means configured to short-circuit a winding at least partially around the particle optical axis in the case of static control of the magnetic lens, and a controller is configured to control the bridging means. According to this embodiment of the present invention, the bandwidth during static operation is limited, and a large bandwidth during static operation is not required. However, conversely, variations of this embodiment can also be used to perform dynamic control of the magnetic lens over a wide frequency range without short-circuiting.

[0050] According to a preferred embodiment of the present invention, the bridging means comprises at least one connectable turn positioned around the particle optical axis of a multi-beam particle beam system. In this case, the bridging means is surrounded by the coils of the magnetic lens, since eddy currents are generated solely for dynamic lens control.

[0051] According to a preferred embodiment of the present invention, the coil comprises at least two windings arranged on the same winding body. For example, the windings can be wound continuously and / or overlapping around the winding body. By providing multiple winding bodies, the coil excitation, and consequently the lens excitation, can be divided among multiple windings, each with a low inductance. This reduces the power required for the dynamic control of each winding and prevents potentially dangerously high control voltages in the coil, which would otherwise require special safety precautions (Low Voltage Directive EN61010).

[0052] According to a preferred embodiment of the present invention, the coil comprises a first winding having a first number of turns and a second winding having a second number of turns, wherein the first number of turns is greater than the second number of turns. Furthermore, the controller is configured to statically control the first winding and dynamically control the second winding.

[0053] Even if iron loss within the polar magnetic elements of a magnetic lens is not the primary cause of dynamic control of the magnetic lens, which was previously impossible, reducing iron loss within the polar magnetic elements is advantageous even in the dynamically controllable magnetic lenses already described. Generally, it is a fact that the operation of the magnetic core, due to changes in magnetic field polarity, causes losses in the core, so-called iron loss or core loss. These consist of hysteresis loss (also called reversal loss), eddy current loss, excess loss or additional loss, and after-effect loss. In the case of magnetic lenses in the field of particle optics, eddy current loss accounts for the majority of iron loss. These eddy currents are induced in the magnetic core or polar magnetic elements under a magnetic field that changes over time. The generated eddy currents heat the polar magnetic element material, causing losses even at low frequencies (50 Hz, 60 Hz). As a countermeasure against eddy current loss, the structure of transformers and electric motors discloses a method of realizing the magnetic core not as a solid component, but in a laminated form ("sheet-like"). In this process, punched or cut magnetic steel sheets are coated with a heat-resistant insulating lacquer and stacked in blocks or wound into rings parallel to the magnetic field lines. Therefore, the magnetic flux is dispersed among the individual fluxes within each sheet, which are separated from each other. Consequently, only very small eddy currents are generated within the sheets, and the overall power loss is significantly lower than that of solid materials. The sheet thickness is typically less than 1 mm. Thinner sheets result in lower eddy current losses or higher possible operating frequencies.

[0054] However, in the field of particle optics, it is a fact that the magnetic field that produces the lens effect needs to be shaped very precisely in the region of the aperture of the magnetic lens's pole element. Therefore, to ensure the precise shaping of the magnetic field, a homogeneous pole element material is preferred near the aperture of the pole element.

[0055] Accordingly, according to a preferred embodiment of the present invention, the pole element of a magnetic lens comprises a first region having a pole element aperture and a second region spaced apart from the pole element aperture. The first region of the pole element is composed of a first material, and the second region of the pole element is composed of a second material different from the first material. In this case, the term "material" relates first to the chemical composition of the material, but second to a specific product or composition of the material. Thus, it is also possible to select an optimal material for the first region and a different optimal material for the pole element for the second region.

[0056] According to a preferred embodiment of the present invention, the pole element is composed of a solid material in a first region comprising the pole element aperture, and the pole element is not composed of a solid material in a second region spaced apart from the pole element aperture. Here, the term "solid material" is understood in the general, conventional sense from materials science. With regard to the selection of the material for the first region of the pole element, a material with low hysteresis and a sufficient saturation magnetic field strength is preferred. Furthermore, the magnetic behavior of the material needs to be as uniform as possible. According to a variation of the embodiment, the pole element can be composed of, for example, an iron-nickel alloy such as Permenorm® in the first region, and the pole element can be composed of, for example, a powder core, a ferrite core, or a laminated sheet in the second region.

[0057] According to a preferred embodiment of the present invention, a second region of the pole piece is laminated, particularly sheeted, at least partially, such that the laminations, particularly sheets, are oriented substantially parallel to the magnetic field lines formed within the pole piece during the operation of the multi-beam particle beam system. For convenience, the laminations, particularly sheets, are arranged according to the particular shape of the pole piece. For example, if the pole piece is U-shaped, then appropriately arranged laminations, particularly sheets, are provided on all sides of the U-shape. Examples of laminated metal cores include, for example, NiFe alloy sheets with varying nickel content traded under trademark names such as Permenorm, Megaperm, Ortonol, Permax, or Mu-metal, Permalloy, Supermalloy, Cryoperm, Ultraperm, or Vacoperm.

[0058] According to a preferred embodiment of the present invention, the magnetic permeability μ of the magnetic pole piece material in the magnetic pole piece r is such that μ r > 10000 holds. For example, Permenorm (registered trademark) corresponds to this. Preferably, the magnetic pole piece material has a thickness d, and the controller of the multi-particle beam system

[0059]

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[0060]

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[0061] [[ID=,31]]

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[0062]

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[0063] In this embodiment of the present invention, this condition applies to materials with extremely high magnetic permeability (Permenorm®, 3mm thick, f s This condition is usually satisfied for non-magnetic metals (copper 3mm thick, f s At approximately 500Hz, the gap is barely filled. This leads to embodiments of the present invention in which a slot is provided in an impermeable metal and the bridging is prevented by an insulating material and by the design of a highly permeable, conductive material (for example, for pole pieces) with the smallest possible surface area.

[0064] In addition to the embodiments of the present invention described above, further measures may contribute to optimizing the bandwidth of a multi-beam particle beam system. For example, this includes the appropriate design of the beam tube through which the multiple individual particle beams are typically guided. In this context, the use of a thin, moderately conductive beam tube is known to be advantageous. Details relating to beam tubes are described, for example, in German Patent Application No. 102022124933.6, which has not yet been published at the time of this patent application, and its disclosures are fully incorporated into this patent application by reference.

[0065] As a further incidental measure, a multiple particle beam system according to a preferred embodiment of the present invention comprises a housing and a magnetic shielding unit disposed within the housing, the magnetic shielding unit substantially enclosing, at least partially, the particle light beam path of the multiple particle beam system. For this purpose, the magnetic shielding unit has at least one access opening for electrical and / or mechanical feedthrough into the magnetic shielding unit, and around the access opening, a shorting body whose material has good conductivity and is paramagnetic or diamagnetic is arranged to terminate the access opening. In this way, dynamic magnetic fields penetrating the shield are compensated by eddy currents induced in the shorting body. This is very important because it would not be possible without the access opening, and the access opening is essential for, for example, access to stop drives, feed lines, or microoptics, or for the beamhead of the multiple particle beam system. For example, a copper insert, such as a copper ring, can function as a shorting body. For example, a copper ring may be annealed to enhance its conductivity. Naturally, the concept of providing a short-circuiting element around the access opening of the magnetic shielding unit can be used independently of the present invention, that is, independently of a specially designed magnetic lens having a shielding element within the winding.

[0066] According to a preferred embodiment of the present invention, the magnetic shielding unit has at least a cylindrical form and comprises an outer cylinder and an inner cylinder. In this context, the term “cylinder” should not be understood strictly geometrically, and some deviation from the cylindrical shape is naturally possible. In this embodiment of the present invention, the outer cylinder is made of a demagnetized ferromagnetic material, and the inner cylinder is made of a material that has good conductivity and is paramagnetic or diamagnetic. In principle, it is very easy to create variations of this embodiment of the present invention. However, it is also possible that the inner cylinder is made of a demagnetized ferromagnetic material, and the outer cylinder is made of a material that has good conductivity and is paramagnetic or diamagnetic.

[0067] According to embodiments of the present invention, the outer cylinder is made of Mu-metal, and / or the inner cylinder is made of copper.

[0068] According to a preferred embodiment of the present invention, the multibeam particle beam system is a multibeam particle microscope. In this context, a magnetic lens having a shielding portion in a winding body can be placed in the primary path of the multibeam particle microscope or in the secondary path of the multibeam particle microscope.

[0069] In very general terms, a magnetic lens having a shielding section in a winding can be, for example, a condenser lens, a field lens, an objective lens, or a projection lens.

[0070] Furthermore, as has already been described in many embodiments, it is naturally possible to provide a further magnetic lens having a shielding portion in the winding body, or a plurality of further magnetic lenses having shielding portions within the winding body, in a multiple particle beam system.

[0071] As described herein, considering the various options for arranging magnetic lenses together with shielding units within a winding body in a particle light beam path, we again expressly reference to International Patent Application Publication 2022 / 069073, whose disclosure is fully incorporated by reference into this patent application. The magnetic lenses in the primary and / or secondary paths disclosed therein can optimize bandwidth, i.e., they can provide shielding units according to the present invention.

[0072] In a further aspect of the present invention, the present invention relates to the use of a multi-beam particle beam system as described above for rapid focusing of individual particle beams in a variety of embodiments. Again, in the case of a multi-beam particle microscope, this rapid focusing can be performed during the primary path, i.e., incidence to the sample, and / or during the secondary path, i.e., incidence to the detection unit.

[0073] According to a further aspect of the present invention, the present invention relates to the use of a multi-particle beam system as described above in modifications of several embodiments for recording a focal series. Once the focal series is recorded, the focal position changes very rapidly, which can be advantageous, for example, for confirming the current adjustment status of the multi-particle beam system.

[0074] According to a further aspect of the present invention, the present invention relates to the use of a multiple particle beam system for dynamic readjustment of the multiple particle beam system, as described above in the modifications of several embodiments. For example, this may be necessary for charging the sample, particularly in the secondary path of the multiple particle beam system.

[0075] According to a further aspect of the present invention, the present invention relates to the use of a multiple particle beam system, as described above in the modifications of several embodiments, for high-speed switching between various operating points of the multiple particle beam system. For example, the working distance can be changed very quickly during the process, particularly by rapid switching of high-inductance magnetic objective lenses.

[0076] The embodiments and aspects of the present invention described above can be combined in whole or in part, as long as no technical inconsistencies result.

[0077] The present invention will be better understood by referring to the accompanying drawings. [Brief explanation of the drawing]

[0078] [Figure 1] This is a schematic diagram illustrating a multi-beam particle microscope system using an example. [Figure 2] This is a schematic diagram illustrating the structure of a magnetic lens having a winding body and a cooling line structure. [Figure 3] This is a schematic diagram illustrating the generation and reduction of eddy currents. [Figure 4] This is a schematic diagram illustrating a winding body having a shutoff section and a cooling line structure. [Figure 5] This is a schematic diagram illustrating a winding body having a cooling line structure, a blocking portion in its cross-section, and a first cross-sectional direction passing through the cross-section. [Figure 6] This is a schematic diagram illustrating a winding body having a cooling line structure with an even number of cooling turns and a first cross-sectional blocking section passing through the cross-section. [Figure 7] Figure 6 shows a schematic diagram and a second cross-sectional view illustrating the cooling line structure and the winding body having the interruption section in a second cross-sectional direction. [Figure 8] This is a schematic diagram illustrating a magnetic lens having a switchable bridging mechanism. [Figure 9] This figure illustrates the measurement curves of the excitation current of a magnetic lens and the associated axial magnetic field strength during the dynamic control of the magnetic lens. [Figure 10] This is a schematic diagram illustrating the measurement results of the bandwidth achieved for high-speed magnetic lenses. [Figure 11] This is a schematic diagram illustrating the optimization of the bandwidth of the polar magnetic elements of a magnetic lens using sheet-formed polar magnetic elements in cross-section. [Figure 12] This is a schematic diagram illustrating multiple magnetic shielding units. [Figure 13] This is a schematic diagram illustrating a magnetic shielding unit having an outer cylinder and an inner cylinder. [Modes for carrying out the invention]

[0079] Figure 1 schematically illustrates a multi-particle beam system using an example of a multi-beam particle microscope 1. The multi-beam particle microscope 1 comprises a beam generator 300 having a particle source 301, such as an electron source. A divergent particle beam 309 is parallelized by a series of condenser lenses 303.1 and 303.2 and incident on a multi-aperture structure 305. The multi-aperture structure 305 comprises a plurality of multi-aperture plates 306 and a field lens 308. The multi-aperture structure 305 generates a plurality of individual particle beams 3 or individual electron beams 3. The midpoints of the apertures in the multi-aperture plate structure are located in a field of view that is imaged into another field of view formed by a beam spot 5 in the object plane 101. The pitch between the midpoints of the apertures in the multi-aperture plate 306 can be, for example, 5 μm, 100 μm, or 200 μm. The diameter D of the apertures is smaller than the pitch between the midpoints of the apertures, for example, 0.2 times, 0.4 times, or 0.8 times the pitch between the midpoints of the apertures.

[0080] The multiple aperture structure 305 and the field lens 308 are configured to generate multiple focal points 323 of the primary beam 3 in a raster arrangement on the surface 321. The surface 321 does not need to be planar, but rather can be spherically curved to take into account the image plane curvature of the subsequent particle optical system.

[0081] The multibeam particle microscope 1 further comprises a system of electromagnetic lenses 103 and objective lenses 102, which image the beam focus 323 from the intermediate image plane 325 onto the object plane 101 at a reduced size. Meanwhile, the first individual particle beams 3 pass through a beam splitter 400 and a combined beam deflection system 500, which deflects multiple first individual particle beams 3 during operation and scans the image field. For example, the first individual particle beams 3 incident on the object plane 101 form a substantially regular field of view where the pitch between adjacent incident positions 5 can be, for example, 1 μm, 10 μm, or 40 μm. For example, the field of view formed by the incident positions 5 can have rectangular or hexagonal symmetry.

[0082] The object 7 to be inspected can be of any desired type, such as a semiconductor wafer or a biological sample, and may include an array of miniaturized elements. The surface 15 of the object 7 is positioned on the object surface 101 of the objective lens 102. The objective lens 102 may comprise one or more electro-optical lenses. For example, this may be a magnetic objective lens and / or an electrostatic objective lens.

[0083] Primary particles 3 incident on object 7 generate interaction products, such as secondary electrons, backscattered electrons, or primary particles whose motion is reversed for other reasons. These interaction products originate from the surface of object 7 or from a first plane 101 or the object surface 101. Interaction products originating from the surface 15 of 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 splitter 400 downstream of the objective lens 102 and is supplied to the projection system 200. The projection system 200 comprises an imaging system 205 having projection lenses 208, 209, and 210, a contrast aperture 214, and a multi-particle detector 207. The incident positions 25 of the second individual particle beam 9 on the detection area of ​​the multi-particle detector 207 are located at regular pitches within a third field of view. Exemplary values ​​are 10 μm, 100 μm, and 200 μm.

[0084] The multibeam particle microscope 1 further comprises a computer system or control unit 10, which may have a single-component or multi-component design and is designed to control the individual particle optical components of the multibeam particle microscope 1, and to evaluate and analyze signals acquired by the multiple detector 207 or detection unit.

[0085] Further information relating to such multi-beam particle beam systems or multi-beam particle microscopes 1 and components used therein, such as particle sources, multiple aperture plates, and lenses, can be obtained from International Patent Publication Nos. 2005 / 024881, 2007 / 028595, 2007 / 028596, 2011 / 124352, and 2007 / 060017, and German Patent Publication Nos. 102013016113 and 102013014976, which are fully incorporated into this application by reference.

[0086] The multibeam particle microscope illustrated in Figure 1 can be designed as a multiple-particle beam system according to the present invention and may include one or more magnetic lenses having improved bandwidth with respect to dynamic control. For this purpose, the windings of the magnetic lenses / multiple magnetic lenses (each) can be designed with a cutoff section to reduce eddy currents.

[0087] Figure 2 schematically illustrates the structure of the magnetic lens 700. A cross-section along the particle optical axis Z is shown. The magnetic lens 700 comprises a coil 701, or a winding 701 which may have multiple turns. In Figure 2, the coil 701 is shown schematicly only as a component. The coil 701 is arranged around a winding body 702. In this case, the winding body 702 is in the form of a hollow body, i.e., it has a central opening so that multiple individual particle beams 3, 9 of the multiple particle beam system 1 can pass through the winding body 702. The coil 701 is arranged together with the winding body 702 within a pole magnetic piece 703. In the illustrated example, the pole magnetic piece 703 is divided into an upper pole magnetic piece 703a and a lower pole magnetic piece 703b. The polar magnetic piece 703 has an aperture 704 located between the upper polar magnetic piece 703a and the lower polar magnetic piece 703b. The magnetic field generated by the magnetic lens 700 is emitted from the polar magnetic piece 703 of the magnetic lens 700 through the aperture 704 and interacts with a plurality of individual particle beams 3 to obtain a lensing effect.

[0088] In the illustrated example, the winding 702 comprises a plate-shaped front piece 707, a middle piece 706, and end pieces 708. In the illustrated example, the winding 702 has good conductivity and may be made of, for example, copper. Good conductivity is accompanied by good thermal conductivity. Therefore, if a cooling line structure 705 is incorporated into the winding 702, as in the illustrated example, the winding 702 can induce or dissipate the heat it generates. In the illustrated example, such a cooling line structure 705 is located on the plate-shaped front piece 707 of the winding 702. In this case, Figure 2 shows a cross-section of the three individual cooling lines. In the example, the magnetic lens 700 shown in Figure 2 has substantially rotational symmetry about the axis or particle optical axis Z.

[0089] Now, when the magnetic lens 700 is dynamically controlled, that is, when the magnetic lens 700 is rapidly controlled, eddy currents can be generated in the magnetic lens 700, as shown in Figure 2. Figure 3a) illustrates a cross-section of the central section of a winding body 702 surrounded by a coil 701 having multiple turns. The winding body 702 corresponds to a single-turn coil due to its ring structure or hollow nature. Here, a change in the current in the winding 701 within the range of dynamic control of the magnetic lens 700 is accompanied by a change in the magnetic field or magnetic flux within the coil 701 and therefore also within the winding body 702, thereby generating eddy currents. In this case, the direction of the eddy currents is directed in the opposite direction to the current direction in the coil 701, thereby attenuating the magnetic field generated in the coil 701 overall. The eddy currents and the direction of current flow within the coil 701 are illustrated by the arrows in Figure 3a).

[0090] Figure 3b) again shows the state of the winding 702 or the associated central piece 706 itself. In the case of dynamic control of the magnetic lens 700, eddy currents are generated in the winding 702 or its central piece 706 around axis Z, and a heat flux (or thermal flux) is generated in the winding 702 along the Z axis due to the heat generated in the winding 702 or due to the heat sink provided by the cooling line structure 705. In Figure 3b), the heat flux is shown as an arrow from bottom to top as an example.

[0091] Figure 3c) schematically illustrates the basic concept of the present invention. The winding 702 has a shielding portion 710, which blocks the conductivity of the winding 702 in the circumferential direction around the particle optical axis, thereby reducing the generation of eddy currents in the winding 702 around the particle optical axis Z when the magnetic lens 700 is dynamically controlled. In Figure 3c), the reduction in eddy currents is illustrated by the strikethrough arrow. However, the thermal conductivity within the winding 702 is maintained at the same time.

[0092] In the schematic example illustrated, the shielding portion 710 extends along the particle optical axis Z, which in this case is parallel to the particle optical axis Z. In addition, the shielding portion 710 of the winding 702 is oriented from the inside out, and in this case precisely radially. Furthermore, in the illustrated example, the shielding portion 710 is complete, i.e., the winding 702 is completely shielded, and as a result, eddy currents around the particle optical axis Z are completely suppressed within the winding 702.

[0093] In the illustrated example, an insulator and / or high-resistance material is placed in the interruption section 710. For example, the following materials, plastics, especially high-performance thermoplastics, such as PEEK (polyether ether ketone), PP (polypropylene), PA (polyamide), POM (polyoxymethylene), PET (polyethylene terephthalate), PC (polycarbonate), PES (polysulfone), or PEI (polyetherimide) can be placed in the interruption section 710. Alternatively, ceramics such as aluminum oxide (Al2O3) or silicate ceramics can be placed in the interruption section 710.

[0094] Furthermore, in the illustrated example, the interruption section 710 is designed as a slot. This implementation is particularly simple. However, it is theoretically possible to provide curved or zigzag interruption sections, etc. In this context, it is sufficient to simply provide a narrow slot as the interruption section 710 in the winding 702. For example, the width b of the slot can be between 100 μm and 1000 μm. However, the width b can also be less than 100 μm or greater than 1000 μm. In this case, the depth of the slot is, for example, the same as the radial range of the winding 702.

[0095] Figure 4 schematically illustrates a winding body 702 having a plate-shaped front piece 707, a central piece 706, and end pieces 708, also of a plate-shaped design, in the illustrated example. In the example illustrated in Figure 4a), a shutoff section 710 is again provided, which extends along the particle optical axis Z and completely cuts open the winding body 702 in this direction. Furthermore, the perspective view in Figure 4a) schematically shows a cooling line structure 705 within the plate-shaped front piece 707. The cooling line structure comprises an inlet section 705a and an outlet section 705b located opposite each other in a plane perpendicular to the particle optical axis Z and separated from each other by the shutoff section 710. In the illustrated example, the cooling line structure 705 extends in a ring shape around the axis Z in the plate-shaped front piece 707. In this case, the shutoff section 710 is positioned so that the cooling line structure 705 is not cut by the shutoff section 710. Therefore, the blocking section 710 is positioned between the inlet 705a and outlet 705b of the cooling line structure 705, blocking the plate-shaped front piece 707 in the radial direction, and simultaneously extending over the entire height (Z direction) of the plate-shaped front piece 707. Figure 4b) shows a corresponding schematic plan view of the plate-shaped front piece 707.

[0096] Figure 5 schematically illustrates a further exemplary embodiment of a winding 702 having a cooling line structure 705. In this case, Figure 5a) shows a cross-section of the winding 702, and Figure 5b) shows a cross-section along line A plotted in Figure 5a). Cross-sectional line A passes through three cooling line segments 705 on the left side of the Z-axis and three further cooling line elements 705 on the right side of the Z-axis. The Z-axis itself extends through the center of the opening 709 of the winding 702.

[0097] In principle, the cross-sectional view along line A corresponds to the plan view of the winding body 702, and therefore to the plan view of the plate-shaped front piece 707. Again, the cooling line structure 705 comprises an inlet 705a and an outlet 705b. In the illustrated example, the cooling line structure 705 is arranged in a meandering manner within the plate-shaped front piece 707 of the winding body 702, and as a whole, substantially encloses the particle optical axis Z once between the inlet 705a and the outlet 705b. The meandering arrangement of the cooling line structure 705 makes more effective use of the space available for cooling within the plate-shaped front piece 707, or in principle the area of ​​the plate-shaped front piece 707, than the simple ring-shaped arrangement of the cooling line structure 705 as illustrated in Figure 4a). In the example according to Figure 5b), it is also true that a shutoff section 710 is located between the inlet 705a and the outlet 705b of the cooling line structure 705. The blocking portion 710 blocks the plate-shaped front piece 707 in the radial direction. In this case, the blocking portion 710 extends across the entire front piece 707, i.e., is complete.

[0098] Figure 6 schematically illustrates an alternative exemplary embodiment of the winding body 702 having a cooling line structure 705. In the illustrated example, the cooling line structure 705 is rearranged in a meandering manner within the plate-shaped front piece 707 of the winding body 702, and as a whole, substantially encircles the particle optical axis Z once between the inlet 705a and the outlet 705b. However, unlike the modifications of the embodiments illustrated in Figure 4 (one cooling winding) and Figure 6 (three cooling windings), the modification of this embodiment has an even number of cooling windings. When the number of cooling line turns of the cooling line structure 705 is even, the coolant inlet 705a and outlet 705b can be located on the same side of the shutoff section 710.

[0099] Figure 7 is a schematic diagram and a second cross-sectional view illustrating the winding body 702 having the cooling line structure 705 and the cutoff section 710 of Figure 5 in a second cross-sectional direction. The cross section along line B is located immediately next to the cutoff section 710. Thus, the cooling line structure 705 can only be identified on the left side of the particle optical axis Z in cross section B shown in Figure 7b). On the right side, there is the end region of the plate-like front piece 707, or this is directly adjacent to the cutoff section 710 itself. Otherwise, it again applies that the cutoff section is slot-shaped and an insulator and / or high-resistance material can be placed within the cutoff section.

[0100] In the example described above, the shielding 710 of the winding 702 was complete and precise along the Z-axis and from the inside out, particularly in the radial direction. However, it is also possible to provide an incomplete shielding 710 of the winding 702 in the direction of the particle optical axis Z of the multiple particle beam system 1, particularly parallel to the particle optical axis Z. In addition, or alternatively, it is also possible to provide an incomplete shielding 710 of the winding 702 from the inside out, particularly in the radial direction. This incomplete shielding 710 may have several advantages. By significantly reducing eddy currents, it becomes possible to set the bandwidth of the magnetic lens to a value that is partially well above 50 Hz. However, this also makes it more susceptible to interference induced in the cabling, which can consequently be input-coupled into multiple individual particle beams 3. This may be particularly true in the frequency range around 50 Hz or 60 Hz, as these frequencies frequently occur in laboratory environments. Therefore, it may be advantageous to optimize the bandwidth to be fast enough for dynamic requirements, and conversely, to actively limit excess bandwidth to prevent interference effects on multiple individual particle beams 3. Accordingly, according to a preferred embodiment of the present invention, during the dynamic control of the magnetic lens 700, a connecting piece of the winding 702 having a defined resistance for bandwidth limiting is provided adjacent to the cutoff portion 710 in the direction of the particle optical axis Z. As a result, the cutoff portion 710 of the winding 702 is not complete in the direction of the particle optical axis Z. Therefore, eddy currents in the winding 702 can flow around the Z axis in the uncut region. By selecting a defined connecting piece, i.e., a connecting piece with a defined dimension in the Z direction, a defined resistance is guaranteed.

[0101] Figure 8 schematically illustrates a magnetic lens 700, in which there is an actual change or switch between a complete blocking section 710 and an incomplete blocking section 710. For this purpose, the magnetic lens 700 includes switchable bridging means 712, 713 configured to short-circuit a winding 702 at least partially around the particle optical axis Z in the case of static control of the magnetic lens 700. In this case, the controller 10 of the multiple particle beam system 1 is configured to control the bridging means 712, 713. In the illustrated exemplary embodiment, the bridging means comprises a connectable turn 712 positioned around the particle optical axis of the multiple particle beam system 1. For switching purposes, a short-circuit switch 713 controllable by the controller 10 is provided. Other embodiments of the switchable bridging means 712, 713 are also possible.

[0102] In addition, or alternatively, the coil 701 may comprise at least two windings arranged on the same winding body 702 (not shown here). For example, the windings may be wound continuously and / or overlapping around the winding body 702. By providing multiple winding bodies, it becomes possible to divide the coil excitation, and thus the lens excitation, among multiple windings, each with a lower inductance. This reduces the power required for the dynamic control of each winding and prevents potentially dangerously high control voltages in the coil, which would otherwise require special safety precautions (Low Voltage Directive EN61010). For example, the coil 701 may comprise a first winding having a first number of turns and a second winding having a second number of turns, where the first number of turns is greater than the second number of turns. Furthermore, the controller 10 may be configured to statically control the first winding of the coil 701 and dynamically control the second winding of the coil 701.

[0103] Figure 9 illustrates the improved dynamic controllability of the multi-particle beam system 1 according to the present invention, or a special magnetic lens 700 having a cutoff section 710 on a winding body 702 located therein. Figure 9a) shows the measurement results of a magnetic lens 700 without a cutoff section 710 on the winding body 702. The graph at the top plots the normalized excitation current against the control frequency, i.e., a frequency given in Hz. In this process, the control current increased over frequency. Simultaneously, the magnetic field strength B achieved during the dynamic control of the magnetic lens 700 is shown. dyn However, it was measured inside the magnetic lens 700. Specifically, the z component of the magnetic field strength, that is, the intensity along the particle optical axis Z, was determined. Magnetic field strength B dyn Similarly, this was plotted on the curve below in a normalized manner. What is clear here is that, in the case of low-frequency control, there is only a slight decrease below the absolute maximum until control at a frequency of about 2 Hz. However, the magnetic field strength B dyn The decrease becomes even more pronounced above approximately 2Hz, and slightly above 4Hz, this decrease

[0104]

number

[0105]

number

[0106] In contrast, Figure 9b) illustrates the increase in the bandwidth of dynamic control of the magnetic lens 700 provided with the shielding section 710 according to the present invention. Magnetic field strength B dyn It tracks the excitation current over the entire range from 0Hz to 10Hz, and the magnetic field strength B dynThe performance does not decrease at all. This stability continues even at frequencies above 10 Hz, but for the sake of clarity, it is not shown further in Figure 9.

[0107] Figure 10 schematically illustrates the measured results of the achieved bandwidth BW for a high-speed magnetic lens 700, or a magnetic lens 700 having a blocking section 710 for suppressing eddy currents in the winding 702. The dynamic magnetic field strength BW was measured in the z direction. dyn Static magnetic field strength B stat The ratio to is plotted against the frequency used to dynamically excite the magnetic lens 700. Ratio B dyn / B stat It is very large and relatively stable over a very wide frequency range. Cutoff frequency f cut-off This is achieved only at a frequency of approximately 1500 Hz. Therefore, compared to the conventional magnetic lens 700, the improved magnetic lens 700 according to the present invention can achieve a bandwidth increase of up to three orders of magnitude. Thus, in the measurement example, the bandwidth BW is up to 1500 Hz.

[0108] It is also possible to further increase the bandwidth. This is because the inventors' research revealed that the current source supplying the excitation current to the magnetic lens 700 limits the bandwidth behavior of the magnetic lens 700 at frequencies above 1500 Hz. By appropriately changing the current source, the cutoff frequency can be shifted to an even higher cutoff frequency. In addition, by further changing or optimizing the power or output voltage of the current source, an even higher bandwidth can be achieved in principle.

[0109] In addition, or alternatively, it is also possible to further minimize iron loss within the pole magnetic element 703 of the magnetic lens 700. Figure 11 schematically illustrates the optimization of the bandwidth of the pole magnetic element 703 of the magnetic lens 700 by sheeting the pole magnetic element 703 in cross-section. Specifically, Figure 11a) illustrates the initial state of the pole magnetic element 703, which is composed of a solid material such as an iron-nickel alloy. During the dynamic control of the magnetic lens 700, eddy currents are formed around the magnetic field lines. This attenuates the magnetic field lines in the center of the pole magnetic element 703. However, eddy currents generated in the edge region of the pole magnetic element 703 are blocked, and as a result, the dynamically excited magnetic flux is displaced outside the pole magnetic element 703. This displacement, or the generation of eddy currents that attenuate the central magnetic field within the pole magnetic element 703, can be prevented by sheeting. Two exemplary options in this regard are illustrated in Figures 11b) and 11c). In both cases, the polar magnetic piece 703 has a first region 730 and a second region 740. The first region 730 includes a polar magnetic piece aperture 704, and the second region 740 is spaced apart from the polar magnetic piece aperture 704. In the first region 730 and the second region 740, the materials constituting the polar magnetic piece are different. The first region 730, which includes the polar magnetic piece aperture 704, is made of a solid material. The first region 730 is made of an iron-nickel alloy such as Permenorm®. Permenorm® offers a good compromise between high saturation magnetic field strength, high permeability, and low coercivity. A solid material 730 is preferred in the region of the polar magnetic piece aperture 704 because the magnetic field generated by the magnetic lens 700 needs to exit the polar magnetic piece 703 in a very clear manner in the region of this aperture. This can be well confirmed in the case of a homogeneous, especially solid, material. In contrast, the focus in region 740 can be on eddy current removal. Therefore, region 740 is laminated or sheeted here.

[0110] In both the exemplary embodiment illustrated in Figure 11b) and the exemplary embodiment illustrated in Figure 11c), the stack or sheet in this case is oriented at least partially substantially parallel to the magnetic field lines in the pole piece 703 that are formed within the pole piece 703 during the operation of the multiple particle beam system 1. In the example following Figure 11b), the region 740 is divided into four sub-regions 740a, 740b, 740c, and 740d. Each of these parts is a rectangular parallelepiped. In contrast, regions 740a, 740b, 740c, and 740d are not rectangular parallelepipeds in Figure 11c), but instead have at least partially stepped or pyramidal embodiments. In variations of this embodiment, the orientation of the sheet follows somewhat precisely the magnetic field lines at the corners of the pole piece 703. Naturally, other sub-divisions of other stacked or sheeted regions 740 into sub-regions are possible. In this regard, the example in Figure 11 illustrates only the principle of lamination or sheet formation. Various NiFe alloy sheets with different nickel content can generally be used as materials for sheets and laminations. For example, these are traded under the trademark names Permenorm, Megaperm, Ortonol, Permax, or Mu-metal, Permalloy, Supermalloy, Cryoperm, Ultraperm, or Vacoperm.

[0111] Further incidental measures to increase bandwidth during dynamic control of the magnetic lens 700 are also possible. For example, the multi-particle beam system 1 comprises a housing and a magnetic shielding unit 800 located within the housing, the magnetic shielding unit 800 substantially encloses, at least partially, the particle light beam path of the multi-particle beam system. Ideally, such a magnetic shielding unit 800 would be completely closed, becoming a closed cylinder made of a magnetic material such as Mu-metal, as illustrated in Figure 12a). However, the magnetic shield 800 is not actually completely closed, but instead has mechanical and / or electrical feedthroughs to allow the multi-particle beam system 1 to be operated within the shield 800. For example, access apertures 810 and / or 811 schematically shown in Figure 12b) are required. Lateral apertures 810 may be required, for example, for feed lines to a microoptics system comprising a multi-beam particle generator 305 and / or for aperture displacements in the particle light beam path. For example, an opening 811 from above may be required for a beam generator or beamhead equipped with a particle source 301. Thus, the magnetic shield is "porous". Therefore, a dynamic magnetic field may penetrate into the magnetic shield 800 through the access openings 810, 811 and interfere with the particle light beam path. To prevent this, shorting bodies 812, 813, whose material has good conductivity and is paramagnetic or diamagnetic, can be placed around the access openings 810, 811 so as to terminate these access openings 810, 811. For example, copper, gold, and silver are diamagnetic metals, with copper being preferred. In the example according to Figure 12c), a cylindrical shorting body 812 is placed in the region of the access opening 811, and a ring-shaped shorting body 813 is placed around the lateral passage opening 810, each shorting body being made of, for example, copper. In the case of an alternating magnetic field, eddy currents are generated in the short-circuit bodies 812 and 813, and these eddy currents attenuate the original alternating magnetic field, thus shielding the dynamic magnetic field. Therefore, this method of making the magnetic shield 800 complete utilizes the exact opposite effect of the effect used in the eddy current blocking section 710 within the winding body 702 of the magnetic lens 700.

[0112] Figure 13 schematically illustrates a further example of the magnetic shielding unit 800, which again has two access openings 810, 811 for electrical and / or mechanical feedthrough into the interior of the magnetic shielding unit 800. In this case as well, shorting bodies, whose material has good conductivity and is paramagnetic or diamagnetic, are arranged around each access opening 811, 810 so as to terminate the access openings 810, 811. However, in the illustrated example, a geometrically different concept is provided for this purpose, specifically, the formation of at least part of the magnetic shielding unit 800 as an outer cylinder 815 and an inner cylinder 816. In this case, the outer cylinder is made of a demagnetized ferromagnetic material, and the inner cylinder is made of a material that has good conductivity and is paramagnetic or diamagnetic. For example, the outer cylinder 815 may be made of Mu-metal, and the inner cylinder 816 may be made of copper. Modifications of this embodiment for improved magnetic shielding can be created particularly easily from a manufacturing standpoint. However, it is also possible to fabricate the inner cylinder from a demagnetized ferromagnetic material and the outer cylinder from a material that has good conductivity and is paramagnetic or diamagnetic.

[0113] Furthermore, the disclosure regarding improved magnetic shielding is not limited to the context of improved multi-particle beam systems or high-speed magnetic lenses 700 having a shielding section 710 in the winding 702, but can naturally be applied to multi-particle beam systems in general.

[0114] Disclosed is a multi-beam particle microscope 1, comprising a magnetic lens 700 through which multiple individual charged particle beams 3, 9 pass, and a controller 10 configured to control the magnetic lens 700, particularly dynamically. The magnetic lens 700 comprises a coil 701, a winding body 702 with a cooling line structure 705 in particular, and a pole magnetic piece 703. The coil 701 is arranged around the winding body 702, which is designed as a hollow body through which multiple individual particle beams 3, 9 pass. The coil 701 is placed together with the winding body 702 within the pole magnetic piece 703. The pole magnetic piece 703 has an aperture 704, through which the magnetic field generated by the magnetic lens 700 exits the pole magnetic piece 703 and interacts with the multiple individual particle beams 3, 9 to obtain a lensing effect. The winding 702 is conductive and has a shielding section 710, which shields the conductivity of the winding 702 in the circumferential direction around the particle optical axis. When the magnetic lens 700 is dynamically controlled, the generation of eddy currents in the winding 702 around the particle optical axis Z is reduced. As a result, the magnetic lens 700 of the multiple particle beam system 1 can be dynamically controlled over a wide bandwidth BW of up to 1500 Hz. [Explanation of symbols]

[0115] 1. Multibeam particle microscope 3. Primary particle beam, the first individual particle beam 5. Beam spot, incident position 7. Objects, samples, wafers 9. Secondary particle beam, second individual particle beam 10. Computer systems, controllers 15. Sample surface, wafer surface 25 Second image point of individual particle beams 101 Object plane 102 Objective lens 103 Field of View Lens 105 axis 200 detection systems 205 Projection Lens System 206 Projection Lens 207 Multi-particle detector 208 Projection Lens 209 Projection Lens 210 Projection Lens 212 Intersection 214 Aperture filter, contrast aperture 220 multiple aperture collectors, individual deflector arrays 222 Collective bias prevention system 300 Beam Generator 301 Particle source 303 Collimation Lens System 305 Multiple aperture structure, multi-beam particle generator 306 Microoptics with multiple aperture plates 307 Field of View Lens 308 Field of View Lens 309 Particle beam 321 Intermediate image plane 323 Beam Focus 400 beam splitter, magnet arrangement 500 scanning deflector 503 Voltage source 600 Displacement stage or positioning device 700 Magnetic Lens 701 Coil 702 Winding 703 Pole magnetic piece 704 Aperture of magnetic pole element for magnetic field 705 Cooling line structure 705a inflow 705b leak 706 Center piece 707 Plate-shaped front piece 708 End piece 709 Opening of the winding 710 Interruption section 711 Passage opening of polar magnetic piece for particle beam 712 Connectable Turns 713 Short-circuit switch 730 First region of the polar magnetic piece 740 Second region of the polar magnetic piece 800 Magnetic Shielding Unit 810 Access opening 811 Access opening 812 Short-circuiting 813 Short-circuiting element 815 Outer cylinder 816 Inner cylinder

Claims

1. Multiple particle beam systems, particularly multi-beam particle microscopes, A magnetic lens through which multiple individual charged particle beams pass, The system includes a controller configured to control the magnetic lens, The magnetic lens comprises a coil, a winding body, and a pole magnetic piece. The coil is arranged around the winding body, and the winding body is designed as a hollow body through which the plurality of individual particle beams pass. The coil is arranged together with the winding body within the pole magnetic piece. The pole magnetic piece has an opening, and the magnetic field generated by the magnetic lens exits the pole magnetic piece through the opening and interacts with the plurality of individual particle beams to obtain a lensing effect. A multi-particle beam system in which the winding is conductive, the winding has a shielding portion that blocks the conductivity of the winding in the circumferential direction around the particle optical axis, and when the magnetic lens is dynamically controlled, the generation of eddy currents within the winding around the particle optical axis is reduced.

2. The blocking portion in the winding body is directed from the inside out, particularly in the radial direction, and / or The multiple particle beam system according to claim 1, wherein the blocking portion extends along the particle optical axis, and more particularly parallel to the particle optical axis.

3. The multiple particle beam system according to claim 1 or 2, wherein the blocking portion is in the form of a slot.

4. The multiple particle beam system according to any one of claims 1 to 3, wherein the width b of the slot satisfies the condition 100 μm ≤ b ≤ 1000 μm.

5. The multiple particle beam system according to any one of claims 1 to 4, wherein an insulator and / or a high-resistance material is disposed in the blocking portion, particularly in the slot / within the slot.

6. The winding body also includes a cooling line structure for cooling the winding body. The multiple particle beam system according to any one of claims 1 to 5, wherein the blocking portion is arranged such that the cooling line structure is not cut off by the blocking portion.

7. The winding body comprises a plate-shaped front piece, The cooling line structure includes an inlet and an outlet for the coolant, which are located on the outer edge of the plate-shaped front piece. The cooling line structure is arranged in a particularly meandering manner within the plate-shaped front piece of the winding body, and as a whole, substantially surrounds the particle optical axis once between the inlet and outlet. The multi-particle beam system according to claim 6, wherein the blocking portion is disposed between the inlet and outlet of the cooling line structure, and the blocking portion blocks the plate-shaped front piece, particularly in the radial direction.

8. The controller is configured to dynamically control the magnetic lens using a control current at frequencies of 20 Hz or higher, particularly frequencies of 50 Hz or higher, 100 Hz or higher, or 1000 Hz or higher. The magnetic lens has an axial magnetic field B generated by the dynamic control of the magnetic lens. dyn The following relationship [Math 1] It is configured such that the following conditions are met: Here, B stat The multiple particle beam system according to any one of claims 1 to 7, wherein indicates a magnetic field generated in the axial direction of the magnetic lens in the case of appropriate static control of the magnetic lens.

9. The current source for providing the control current is provided, The multiple particle beam system according to any one of claims 1 to 8, wherein the current source has a bandwidth optimized for the dynamic control of the magnetic lens.

10. The multi-particle beam system according to any one of claims 1 to 9, wherein the magnetic lens is dynamically controllable over a bandwidth BW, and the bandwidth BW satisfies 0 Hz ≤ BW ≤ 1500 Hz.

11. The blocking portion of the winding body is complete in the direction of the particle optical axis of the multiple particle beam system, particularly in the direction parallel to the particle optical axis, and / or The multiple particle beam system according to any one of claims 1 to 10, wherein the shielding portion of the winding body is complete from the inside outward, particularly in the radial direction.

12. The blocking portion of the winding body is incomplete in the direction of the particle optical axis of the multiple particle beam system, particularly in the direction parallel to the particle optical axis, and / or The multiple particle beam system according to any one of claims 1 to 10, wherein the cutoff portion of the winding body is incomplete from the inside outward, particularly in the radial direction.

13. The multiple particle beam system according to claim 12, wherein, during the dynamic control of the magnetic lens, a connecting piece of the winding having a resistance defined for bandwidth limiting is provided adjacent to the blocking portion in the direction of the particle optical axis.

14. The magnetic lens includes a switchable bridge means configured to short-circuit the winding around the particle optical axis in the case of static control of the magnetic lens, The multi-particle beam system according to any one of claims 1 to 13, wherein the controller is configured to control the bridging means.

15. The multiple particle beam system according to claim 14, wherein the bridging means comprises at least one connectable turn arranged around the particle optical axis of the multiple particle beam system.

16. The multi-particle beam system according to any one of claims 1 to 15, wherein the coil comprises at least two windings arranged on the same winding body.

17. A first winding having a first number of turns and a second winding having a second number of turns are provided. The first number of turns is greater than the second number of turns. The multi-particle beam system according to claim 16, wherein the controller is configured to statically control the first winding and dynamically control the second winding.

18. The pole magnetic piece is made of a first material in the first region having the pole magnetic piece opening. The multi-particle beam system according to any one of claims 1 to 17, wherein the pole magnetic piece is composed of a second material in a second region spaced apart from the pole magnetic piece aperture, and is different from the first material and the second material.

19. The pole magnetic piece is made of a solid material in the first region having the pole magnetic piece opening. The multiple particle beam system according to any one of claims 1 to 18, wherein the pole magnetic piece is not made of a solid material in a second region spaced apart from the pole magnetic piece aperture.

20. The multiple particle beam system according to claim 19, wherein the second region of the pole magnetic piece is at least partially laminated, in particular sheets, such that the laminated sheets are oriented substantially parallel to the magnetic field lines formed within the pole magnetic piece during the operation of the multiple particle beam system.

21. Permeability μ of the polarity material within the aforementioned polarity piece r μ r A multi-particle beam system according to any one of claims 1 to 20, wherein the condition >10000 is met.

22. The aforementioned pole magnetic piece material has a thickness d, The aforementioned controller, [Math 2] The magnetic lens is configured to be dynamically controlled using a control current at a frequency f. μ 0 κ represents the vacuum permeability, κ represents the conductivity, and f s is, epidermal depth [Math 3] The multi-particle beam system according to claim 21, wherein the critical frequency is such that it matches the thickness d of the material.

23. The system further comprises a housing and a magnetic shielding unit disposed within the housing, wherein the magnetic shielding unit substantially surrounds, at least partially, the particle light beam path of the multiple particle beam system. The magnetic shielding unit has at least one access opening for electrical and / or mechanical feedthrough into the interior of the magnetic shielding unit. A multiple particle beam system according to any one of claims 1 to 22, wherein a shorting body, whose material has good conductivity and is paramagnetic or diamagnetic, is arranged around the access opening to terminate the access opening.

24. The magnetic shielding unit has at least a cylindrical embodiment and comprises an outer cylinder and an inner cylinder. The outer cylinder is made of a demagnetized ferromagnetic material. The multi-particle beam system according to claim 23, wherein the inner cylinder is made of a material that has good conductivity and is paramagnetic or diamagnetic.

25. The multi-particle beam system according to claim 24, wherein the outer cylinder is made of Mu-metal and / or the inner cylinder is made of copper.

26. The multi-particle beam system according to any one of claims 1 to 25, wherein the multi-particle beam system is a multi-beam particle microscope.

27. The multi-particle beam system according to any one of claims 1 to 26, wherein the magnetic lens is a condenser lens, a field lens, an objective lens, or a projection lens.

28. Having at least one further magnetic lens, The further magnetic lens comprises a coil, a winding, and a pole element. The coil is arranged around the winding body, and the winding body is designed as a hollow body through which the plurality of individual particle beams pass. The coil is arranged together with the winding body within the pole magnetic piece. The pole magnetic piece has an opening, and the magnetic field generated by the further magnetic lens exits the pole magnetic piece through the opening and interacts with the plurality of individual particle beams to obtain a lensing effect. The multiple particle beam system according to any one of claims 1 to 27, wherein the winding is conductive, the winding has a shielding portion that blocks the conductivity of the winding in the circumferential direction around the particle optical axis, and when the further magnetic lens is dynamically controlled, the generation of eddy currents in the winding around the particle optical axis is reduced.

29. Use of a multiple-particle beam system according to any one of claims 1 to 28 for high-speed focusing correction of individual particle beams.

30. Use of a multi-particle beam system according to any one of claims 1 to 28 for recording a focal series.

31. Use of the multiple particle beam system according to any one of claims 1 to 28 for dynamic readjustment of the multiple particle beam system.

32. Use of the multiple particle beam system according to any one of claims 1 to 28 for high-speed switching between various operating points of the multiple particle beam system.

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