WO2026012760A1

WO2026012760A1 - Beam generating device for a multiple particle beam system and multiple particle beam system

Info

Publication number: WO2026012760A1
Application number: PCT/EP2025/068063
Authority: WO
Inventors: Michael SEIDLING; Dirk Zeidler; Uwe Niedermayer; Markus Koch; Gero STORECK
Original assignee: Carl Zeiss Multisem GmbH
Current assignee: Carl Zeiss Multisem GmbH
Priority date: 2024-07-09
Filing date: 2025-06-26
Publication date: 2026-01-15
Anticipated expiration: 2027-01-09
Also published as: DE102024119459B3

Abstract

Beam generating device for a multiple particle beam system, in particular for a multi-beam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap. Further electrodes comprising a spherical cap or consisting of a spherical cap can be provided.

Description

Beam generating device for a multiple particle beam system and multiple particle beam system

Field of the invention

The invention relates to particle beam systems which operate with a multiplicity of particle beams.

Prior art

With the ongoing development of ever smaller and ever more complex microstructures such as semiconductor components, there is a need to further develop and optimize planar production techniques and inspection systems for producing and inspecting small dimensions of the microstructures. For instance, the development and production of the semiconductor components require monitoring of the design of test wafers, and the planar production techniques require process optimization for reliable production with high throughput. Moreover, there have been recent demands for an analysis of semiconductor wafers for reverse engineering and for a customized, individual configuration of semiconductor components. Therefore, there is a need for inspection means which can be used with high throughput to examine the microstructures on wafers with high accuracy.

Typical silicon wafers used in the production of semiconductor components have diameters of up to 300 mm. Each wafer is divided into 30 to 60 repeating regions ("dies") with a size of up to 800 mm². A semiconductor device comprises a plurality of semiconductor structures, which are produced in layers on a surface of the wafer by planar integration techniques. Semiconductor wafers typically have a plane surface on account of the production processes. The feature size of the integrated semiconductor structures in this case extends from a few pm to the critical dimensions (CD) of a few nanometres, and the feature sizes will become even smaller in the near future; the expectation is that in future the feature sizes or critical dimensions (CD) will correspond to the 3 nm, 2 nm or even smaller technology nodes of the International Technology Roadmap for Semiconductors (ITRS). In the case of the aforementioned small feature sizes, defects of the order of the critical dimensions must be identified quickly over a very large area. For multiple applications, the specification requirement regarding the accuracy of a measurement provided by an inspection device is even higher, for example by a factor of two or one order of magnitude. For instance, a width of a semiconductor feature must be measured with an accuracy of better than 1 nm, for example 0.3 nm or even less, and a relative position of semiconductor structures must be determined with an overlay accuracy of better than 1 nm, for example 0.3 nm or even less.

The mSEM, a multi-beam scanning electron microscope, is a relatively new development in the field of charged particle systems (charged particle microscopes, CPMs). For instance, a multi-beam scanning electron microscope is disclosed in US 7 244 949 B2 and in US 2019/0355544 A1. In the case of a multi-beam electron microscope or mSEM, a sample is irradiated simultaneously by a multiplicity of individual electron beams arranged in a field or grid. For instance, 4 to 10 000 individual electron beams can be provided as primary radiation, with each individual electron beam being separated from an adjacent individual electron beam by a pitch of 1 to 200 micrometres. For example, an mSEM has approximately 100 separate individual electron beams ("beamlets"), which are arranged for example in a hexagonal grid, with the individual electron beams being separated by a pitch of approximately 10 pm. The multiplicity of charged individual particle beams (primary beams) are focused on a surface of a sample to be examined by way of a common objective lens. For example, the sample can be a semiconductor wafer that is secured to a wafer holder mounted on a movable stage. When the wafer surface is illuminated by the charged primary individual particle beams, interaction products, for example secondary electrons or backscattered electrons, emanate from the surface of the wafer. Their start points correspond to those locations on the sample on which the multiplicity of primary individual particle beams are focused in each case. The amount and the energy of the interaction products depend on the material composition and the topography of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are collected by the common objective lens and, by virtue of a projection imaging system of the multi-beam inspection system, are incident on a detector arranged in a detection plane. The detector comprises a plurality of detection regions, each of which comprises a plurality of detection pixels, and the detector captures an intensity distribution for each of the secondary individual particle beams. An image field of 100 pm x 100 pm, for example, is obtained in the process.

The multi-beam electron microscope of the prior art comprises a sequence of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable in order to adapt the focus position and the stigmation of the multiplicity of charged individual particle beams. The multi-beam system with charged particles of the prior art moreover comprises at least one crossover plane of the primary or the secondary charged individual particle beams. Moreover, the prior art system comprises detection systems in order to facilitate the adjustment. The multi-beam particle microscope of the prior art comprises at least one beam deflector (deflection scanner) for collective scanning of a region of the sample surface by means of the multiplicity of primary individual particle beams in order to obtain an image field of the sample surface.

What is known as a beam splitter (or alternatively beam separator or beam divider) is used to separate the particle-optical beam path of the primary beams from the particle-optical beam path of the secondary beams. Separation is effected by means of specific arrangements of magnetic fields and/or electrostatic fields, for example by means of a Wien filter.

In the case of multiple particle beam systems, a distinction is made in principle between systems that work with a single column and systems that work with a plurality of columns. In systems with a single column, the individual particle beams at least in part pass through the same particle-optical unit or through one or more global particle lenses. In addition, in a single column, the individual particle beams are relatively close to one another. Despite the partially global particle-optical elements, there is the need for individual influenceability and/or shapeability of the individual particle beams even in the case of single columns, in order to correct imaging aberrations such as image field curvature, field astigmatism and other aberrations. A so-called micro-optical unit can be used for this individual influencing and/or shaping of the individual particle beams. The micro-optical unit often also serves as a multibeam generator for generating and shaping a multiplicity of individual particle beams. In this case, the multi-beam generator or the micro-optical unit comprises a sequence of a plurality of multi-aperture plates in order firstly to generate a multiplicity of individual particle beams and in order secondly to shape them as well, such that they have the properties required for the subsequent particle-optical imaging. During the generation of the multiplicity of individual particle beams, normally an expanded individual particle beam is incident on a first multiaperture plate or filter plate after passing through a condenser lens system and passes through the openings of said plate, such that after said beam has passed through the openings, a multiplicity of individual particle beams are present instead of the individual particle beam. During subsequent beam shaping by means of a or further multi-aperture plate(s), use is made of electrodes which for example are provided in the region of the apertures of a multi-aperture plate and which are collectively or individually controllable.

In the multiple particle beam system described, a high resolution and a high throughput are highly relevant for satisfactory and successful use in practice. In this context, it is necessary, inter alia, to set the intensity of the particle beams. The beam current of the individual particle beams of a multiple particle beam system must be as uniform as possible for all individual particle beams and aberrations must be avoided as far as possible for all individual particle beams.

US 2017/0025241 A1 discloses a multiple particle beam system in which the current density in the particle beams is variable. Specifically, in that case the irradiance is set before multibeams are formed from the primary electron beam. In accordance with US 2017/0025241 A1 , the irradiance is set using a double collimator arranged directly downstream of the beam generating unit in the beam direction. By varying the lens excitations of the double collimator, it is possible to vary the current density of the electrons which pass through the openings in a multi-aperture plate downstream of the double collimator.

The multiple particle beam system described above reaches its limits if the number of particle beams used is increased further. In order even to obtain sufficient beam currents for the individual beams, it is necessary to use as many particles from the particle source as possible. However, in that case the emission characteristic of the particle source becomes more important, more precisely a uniformity of the emission characteristic over the entire emission angle used. When using relatively large emission angles, the emission characteristic of particle sources, e.g. of thermal field emission (TFE) sources, is no longer uniform throughout. Accordingly, the irradiance at a multi-aperture plate in a corresponding particle beam system is then also no longer uniform throughout and there are relatively large variations in the current densities in different individual beams. However, in the case of multi-particle inspection systems, it is in turn a system requirement that there is only a small variation in the currents between the different individual beams, which is typically less than a few per cent, so that all individual image fields of the multi-image field are scanned with an equivalent number of particles or electrons per pixel. By way of example, this is a precondition to obtain individual images with approximately the same brightness.

Thus, the use of particle sources with large emission angles and, at the same time, significant demands on the current per individual beam presents a challenge in the case of inspection systems operating with multi-beam particle beam systems on account of the varying emission characteristic. There are similar requirements for other multiple particle beam systems as well, such as e.g. multi-beam lithography systems.

The use of a beam generating device therefore involves making a compromise between, on the one hand, using the largest possible emission angle of a particle emitter for generating a high total beam current and, on the other hand, still ensuring the beam uniformity in the process. In practice, therefore, an outer region of the charged individual particle beam generated by the particle emitter is cut off by means of a stop (anode stop). The particle current is greatly increased in this outer region. This high beam current in the outer region is explained by field boosting at the outer edges of the flat front facet of an emitter tip. A particularly large number of charged particles are emitted at these outer edges owing to the field boosting. What is used or is expediently usable in a multiple particle beam system, however, is only the largely uniform emission region of the particle emitter, i.e. only the particles or electrons emitted by the flat front facet, and not the particles that have been emitted from the region near the outer edges of the flat front facet.

A problem additionally is the fact that owing to the described problem area in the beam generating device, individual particle beams situated further outwards that are generated later from the emitted charged particles have aberrations to an increased extent in comparison with more centrally arranged individual particle beams. This holds true particularly if the number of individual particle beams or the field thereof is large or is intended to be increased even further. It is therefore desirable to reduce the aberrations that occur even in the outer individual particle beams, specifically without being forced therefore to reduce the number of individual particle beams or to use a smaller emission angle of the particle emitter for the subsequent generation of individual particle beams.

DE 11 2007 000 045 T5 and its family member US 2008/0211376 A1 are older publications concerning an electron gun for a single-beam system. The problem discussed therein concerns a loss of substance or the sublimation occurring at the emitter or cathode. This should be reduced and a longer use of the electron gun should be possible. The publications suggest to increase the field strength at the emitter or cathode. To achieve this, two concrete measures are disclosed: As a first measure, the extractor electrode is designed as a spherically concave surface. As a second measure, a more pointed cathode with a cone angle of 50° or less is suggested. The electron emitting area has no tip, but it has a diameter of 10 micrometers to 100 micrometers which is much larger than today’s tips.

US 2019/0198284 A1 discloses a formation of a tip, particularly in a Schottky emitter. The emitter is wire-like and has an electron emission surface at its tip. The electron emission surface has a surface curved in a certain way. This specific curvature serves to make the virtual source more point-like and thus to improve brightness. A spherical extractor is mentioned for grounds of explaining the effect of the specifically chosen curvature of the tip.

DE 10 2019 005 362 A1 , US 2007 I 0 228 922 A1 and US 4 218 635 A disclose further background art. Description of the invention

Therefore, the object of the present invention is to provide a particle beam system that operates with a multiplicity of charged individual particle beams, said particle beam system ensuring a high beam uniformity between the individual particle beams and reducing aberrations of the individual particle beams, even if use is made of a large number of individual particle beams and, at the same time, a high beam current for each individual particle beam. In the case of a beam generating device for the multiple particle beam system, a large aperture region is intended to be illuminated as homogeneously as possible.

The object is achieved by the independent patent claims. Advantageous embodiments of the invention are evident from the dependent patent claims.

The present patent application claims the priority of German patent application No. 10 2024 119459.6 filed on 09 July 2024, the disclosure of which in the full scope thereof is incorporated in the present patent application by reference.

The invention is based on the concept of adapting existing beam generating devices for particle beam systems specifically to the above-described requirements of multiple particle beam systems. It is proposed to design an extractor electrode in spherical fashion or to shape it as a spherical cap. As a result, an isotropic electric field can be generated at the particle emitter or at the emitter tip. As a result, firstly, a large aperture region of the particle emitter becomes usable and, secondly, the production of spherical aberrations can in principle be avoided as a result. Further electrodes having a spherical shape can be provided to further reduce spherical aberrations.

In accordance with a first aspect of the invention, the latter relates to a beam generating device for a multiple particle beam system, in particular for a multi-beam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap.

In connection with this patent application, the term spherical cap is defined as usual in mathematics. The requirement in respect of the shape of a spherical cap must be substantially satisfied here. It is possible, for example, for the spherical cap to have one or more openings for example for the passage of charged particles. It is also possible for only an inner or an outer surface of the spherical cap to have an exact sphere. Expediently, the surface(s) of the extractor electrode will have an exact spherical cap shape, at which, for particle-optical reasons, it is particularly important for the field lines of the electrostatic field to be exactly perpendicular to this surface. In addition, the beam generating device normally has a preferred direction with regard to the emitted particle beam, namely along the particle-optical axis Z. The shape of the extractor electrode as a spherical cap is then present at least in the region around the particle-optical axis Z and at least on the side facing the cathode tip. Further away regions or outer regions of the extractor electrode can also have a different shape from that of the spherical cap.

The terms cathode and anode used in connection with the present patent application should not be understood as limiting with regard to the type of charged particles emitted by the particle emitter. In order to afford a better understanding of the invention, however, the terms are used in a way that follows convention if the emitted charged particles are electrons or electron beams. According to the invention, however, the charged particles can also be positrons, muons or ions or other charged particles or particle beams. The terms cathode and anode should then be interpreted accordingly.

The particle emitter comprises a cathode tip. This cathode tip is approximately punctiform and thus forms the starting point of the emitted charged particle beam. In practice, the cathode tip can correspond to the planar end facet of a front facet of a tungsten cathode, on which for example a zirconium oxide layer can be vapour-deposited. The zirconium oxide layer can reduce a work function of the electrons from the tungsten cathode, such that heating of the cathode to approximately 1500°C is already sufficient for electrons to emerge from the tungsten single-crystal tip (thermal field emission cathode or Schottky emitter). However, the particle emitter with its cathode tip can also be formed differently. In accordance with one preferred embodiment of the invention, the anode electrode has an opening through which the charged particle beam passes during operation of the beam generating device and the size of which is dimensioned such that the charged particle beam is trimmed in a marginal region upon passing through the opening. As a result, the intensity peaks - already described above - of the charged particle beam that may form on account of field boosting at the edge of the end facet are cut off. The opening of the anode electrode is illuminated as homogeneously as possible as a result. For a subsequent formation of individual particle beams, this means that the individual particle beams can each have approximately the same beam current.

In accordance with one preferred embodiment of the invention, the spherical cap of the extractor electrode has a sphere centre point ME, and the positions firstly of the cathode tip and secondly of the sphere centre point ME substantially correspond to one another. The correspondence tolerance can have an absolute value of e.g. 50 pm or 20 pm or 10 pm or can be chosen to be of the order of magnitude of the size of the cathode tip. In the case of this arrangement, the electric field lines of the extraction field between the cathode tip and the extractor electrode are perpendicular to the surface of the extractor electrode and the curvature of the field lines from the cathode tip to the extractor is minimized. An isotropic field is therefore generated at the cathode tip itself. A comparatively large aperture region of the particle emitter or cathode tip can be used. By virtue of the fact that the extractor electrode is formed as a spherical cap or as (part of) a spherical lens, spherical aberrations are reduced. It quite generally holds true that in the case of a point source and the imaging thereof by perfect spherical lenses, no spherical aberrations occur as a matter of principle. Specifically, therefore, it is possible to prevent outer regions of the particle beam emitted by the cathode tip from already having spherical aberrations on account of beam generation. It is thus possible, in principle, in the multiple particle beam system, to enlarge the field of charged individual particle beams or to arrange a higher number of charged individual particle beams therein, such that the uniformity condition for the individual particle beams is maintained.

In accordance with a further preferred embodiment of the invention, the beam generating device furthermore has a suppressor electrode, which at least partly surrounds the particle emitter. In this case, a suppressor voltage is present between the cathode tip and the suppressor electrode during operation. The suppressor electrode has a shape which comprises a spherical cap or consists of a spherical cap. The shape of the suppressor electrode is spherical cap-shaped at least in the direction of the particle-optical axis of the beam generating device. In the marginal regions, the suppressor electrode can also be in a different form from spherical.

In accordance with a further preferred embodiment of the invention, the suppressor electrode has an opening through which the particle emitter of the cathode tip protrudes. This arrangement prevents electrons or charged particles emerging from the particle emitter from other regions of the particle emitter that are not to be ascribed to the cathode tip.

In accordance with one preferred embodiment of the invention, the spherical cap of the suppressor electrode has a sphere centre point MS and the spherical cap of the extractor electrode has a sphere centre point ME. In this case, the positions of the two sphere centre points MS and ME correspond to one another. The accuracy of this correspondence is for example +/- 50 pm or +/- 10 pm. By virtue of the described arrangement of the suppressor spherical cap and the extractor spherical cap with respect to one another, a distance that is equal substantially over the entire spherical cap region is formed between these two electrodes. Electrostatic field lines between the suppressor electrode and the extractor electrode are in turn perpendicular to the respective electrode surface and the field line curvature is minimized. Therefore, this also involves an arrangement with a particle-optical spherical lens, which in turn makes it possible to reduce spherical aberrations. This embodiment variant of the invention merely no longer makes it possible for the sphere centre point ME of the extractor spherical cap to correspond to the cathode tip of the particle emitter. However, this is in turn not necessary if a faceted emitter is used.

In accordance with one preferred embodiment of the invention, the following relation holds true for a minimum distance dSE between the suppressor electrode and the extractor electrode: 300 pm < dSE < 3000 pm, preferably 550 pm < dSE < 3000 pm or 1000 pm < dSE < 3000 pm. In this case, the minimum distance dSE can correspond to a constant distance between spherical caps arranged concentrically one inside another. This need not be the case, however; for example given identical radii of the spherical caps of suppressor electrode and extractor electrode.

In accordance with a further preferred embodiment of the invention, the anode electrode has a shape which comprises a spherical cap or consists of a spherical cap. In this case, at least the region of the anode electrode in the direction of the particle-optical axis Z or around the latter has the shape of a spherical cap. In marginal regions, the shape of the anode electrode can deviate from the shape of the spherical cap. This spherical cap shape of the anode electrode also has a positive influence on the reduction of aberrations, in particular spherical aberrations.

In accordance with a further preferred embodiment of the invention, the spherical cap of the extractor electrode has a sphere centre point ME and the spherical cap of the anode electrode has a sphere centre point MA. In this case, the positions of the two sphere centre points ME and MA correspond to one another. The two positions can match for example with a precision of +/-50 pm or +/-10 pm. It is possible for the beam generating device to have an alignment mechanism for aligning the extractor electrode and the anode electrode with respect to one another. By way of example, it is possible to displace the anode electrode in a plane orthogonal to the particle-optical axis Z of the beam generating device. Additionally or alternatively, a possibility for displacing the anode electrode relative to the extractor electrode along the particle-optical axis Z, i.e. in the z-direction, can be provided.

In accordance with a further preferred embodiment of the invention, the beam generating device has a condenser electrode. The latter is further away from the cathode tip than the anode electrode. The condenser electrode has a shape which comprises a spherical cap or consists of a spherical cap. In this case, the situation is once again such that the spherical cap shape of the condenser electrode is present at least in the region in the direction of the particle- optical axis Z of the beam generating device or of the multiple particle beam system. In marginal regions, the shape of the condenser electrode can deviate from the spherical cap shape. In this embodiment of the invention, therefore, a condenser electrode or condenser lens is integrated into the beam generating device. This integration is appropriate owing to the spherical cap shape of the condenser electrode, particularly if the condenser electrode is aligned with the spherical anode electrode in a specific manner.

In accordance with one preferred embodiment of the invention, the spherical cap of the anode electrode has a sphere centre point MA and the spherical cap of the condenser electrode has a sphere centre point MK. In this case, the positions of the two sphere centre points MA and MK correspond to one another. In this embodiment, the distance between the anode electrode and the condenser electrode is equal over a wide region, namely over the region of the spherical caps. This once again has the consequence that the electric field lines between the anode electrode and the condenser electrode are each oriented orthogonally to the surfaces of the electrodes, and that the field line curvature is minimized; consequently, the field of a spherical lens is once again generated. This measure, too, makes it possible once again to reduce spherical aberrations in particular in marginal regions of the emitted particle beam. By contrast, an outer side of the condenser electrode need not necessarily have the shape of a spherical cap; this side of the condenser electrode faces away from the particle emitter. Instead, the shaping of the outer surface of the condenser electrode can be chosen such that it best harmonizes or technically cooperates with particle-optical lenses arranged further away from the particle emitter in the particle-optical beam path of the multiple particle beam system and with the electrostatic or magnetic fields generated by said lenses.

Overall, it is possible for the suppressor electrode, the extractor electrode, the anode electrode and preferably also the condenser electrode to form a sequence of spherical caps whose sphere centre points ideally correspond to one another.

The distances between the different spherical caps can each be identical, but they can also vary within the sequence of spherical caps. The following holds true for all electrodes of the beam generating device which have a shape which comprises a spherical cap or which consists of a spherical cap: The electrodes can be produced in various ways. The electrodes themselves can consist of a metal sheet, for example. The latter can be pressed round by means of a mould. An electrode opening can then be produced for example using micro-EDM (electrical discharge machining) or by means of laser drilling. As an alternative to pressing round, the electrodes are also constructed by means of 3D printing: Firstly, metallic 3D printing can be used for production. However, it is also possible to use plastics 3D printing for production and subsequently to metallically coat the shape thus produced, the spherical cap shape. The production methods listed here for an electrode with a spherical cap shape should not be understood as exhaustive.

In accordance with one preferred embodiment of the invention, the extractor electrode has a singular opening for the passage of the charged particle beam. This opening is preferably round and can have for example a radius of approximately 150 pm, 170 pm, 190 pm, 200 pm, 210 pm, 220 pm, 300 pm or some other radius.

In accordance with an alternative embodiment of the invention, the extractor electrode has, instead of the singular opening, a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams. This embodiment serves once again to reduce aberrations in the multiple particle beam system: One cause of aberrations is the Coulomb interaction of the charged particles with one another. A large portion of the charged particles originally generated is not required at all for image generation in the multiple particle beam system, however, but rather is cut out for example by means of a filter plate, in particular in the region of the multi-beam generator. The described particle passage region in the extractor electrode enables this thinning out of the charged particles or the generation of a multiplicity of individual particle beams already to take place earlier and nearer to the source, which is why aberrations on account of Coulomb interaction are smaller in the further course of the particle-optical beam path. The described particle passage region can be provided instead of a filter plate in the region of the multi-beam generator or in addition to a further filter plate, in particular in the region of the multi-beam generator.

Moreover, it is the case that providing a particle passage region instead of the singular opening allows the electric field not to be greatly distorted, as in the case of a singular opening. The lack of distortion of the field lines in turn makes it possible to reduce aberrations even further.

In accordance with a further preferred embodiment of the invention, the suppressor electrode has a singular opening. This is in turn the standard case.

In accordance with a further preferred embodiment of the invention, the anode electrode has, instead of the singular opening, a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams. In this embodiment of the invention, the described thinning out of the charged particles and thus the suppression of Coulomb interactions are likewise effected well.

In accordance with one preferred embodiment of the invention, a particle passage region of the extractor electrode and/or of the anode electrode is formed in a substantially planar fashion. In accordance with an alternative embodiment, the particle passage region is formed in a substantially curved fashion. It preferably follows the shape of the spherical cap of the respective electrode in which the particle passage region is arranged. Both embodiment variants (planar or curved) generate only small aberrations.

In the case of a singular opening, it is also possible to choose the shape of the opening itself or the specific wall course of the opening such that aberrations caused by the opening are reduced on account of the shaping within the opening along the z-direction of the beam generating device.

In accordance with one preferred embodiment of the invention, the following relation holds true for a minimum distance dKA between the cathode tip and the anode electrode: 5.0 mm < dKA < 14.0 mm, preferably 6.0 mm < dKA < 11.0 mm and extremely preferably 7.5 mm < dKA < 9.5 mm. In accordance with a further preferred embodiment of the invention, the following relation holds true for a size dA of the opening of the anode electrode: dA > 180 pm, preferably dA > 200 pm or extremely preferably dA > 220 pm. Additionally or alternatively, the following relation holds true for a total beam current Ig passing through the opening of the anode stop during operation: Ig > 1 pA or Ig > 10 pA, preferably Ig > 100 pA.

The above-described embodiments for a beam generating device can be combined with one another in full or in part, provided that no technical contradictions arise as a result of the combination.

In accordance with a further aspect of the invention, the latter relates to a beam generating device for a multiple particle beam system, in particular for a multi-beam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation, wherein the extractor electrode optionally has a shape which comprises a spherical cap or consists of a spherical cap; an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, optionally a suppressor electrode, the suppressor electrode at least partly surrounding the particle emitter, wherein a suppressor voltage is present between the cathode tip and the suppressor electrode during operation; and optionally a condenser electrode, which is spaced apart from the cathode tip further than the anode electrode; wherein two electrodes out of a group consisting of the extractor electrode, the anode electrode, the optionally provided suppressor electrode and the optionally provided condenser electrode are directly consecutively arranged, and wherein the two electrodes each have a shape which comprises a spherical cap or consists of a spherical cap, wherein the two electrodes have two sphere centre points, wherein positions of the two sphere centre points correspond to one another. Because the two directly consecutively arranged electrodes have the spherical shape with corresponding/ coinciding centre points, the electric field lines between the two directly consecutively arranged electrodes are each oriented orthogonally to the surfaces of the two electrodes. Therefore, the field line curvature is minimized; consequently, the field of a spherical lens is once again generated. This measure, too, makes it possible once again to reduce spherical aberrations, in particular in marginal regions/ edge regions of the emitted particle beam.

The two electrodes having the spherical shape with corresponding I coinciding centre points can therefore be represented by the following pairs of electrodes: suppressor electrode and extractor electrode; extractor electrode and anode electrode; anode electrode and condenser electrode.

Of course, it is also possible that three electrodes are directly consecutively arranged and have a shape which comprises a spherical cap or consist of a spherical cap, wherein the three electrodes have three centre points, the positions of the three centre points corresponding to one another. The above-described concept can be extended to even more than three directly consecutively arranged electrodes.

In accordance with a further aspect of the invention, the latter relates to a multiple particle beam system comprising a beam generating device as described above in a plurality of embodiment variants. The multiple particle beam system can be in the form of a multiple beam particle microscope, for example. It can also be formed as a multiple beam lithography system.

In accordance with one preferred embodiment of the invention, the multiple particle beam system operates with a multiplicity N of individual particle beams, wherein it holds true that N > 61 , in particular N > 91 or N > 100. The greater the field of the multiplicity of individual particle beams, the greater the importance of the configuration of the beam generating device according to the invention. A multiple particle beam system having a beam generating device according to the invention enables good implementation of a necessary beam uniformity even of even more individual particle beams, for example of 1027 particle beams or even more particle beams.

The different embodiments and aspects of the invention can be fully or partly combined with one another, provided that no technical contradictions occur. The invention will be understood even better with reference to the accompanying figures, in which:

Figure 1 : shows a schematic illustration of a multiple particle beam system;

Figure 2: schematically shows a beam generating device;

Figure 3: schematically shows a beam generating device;

Figure 4: schematically shows a beam generating device;

Figure 5: schematically shows a beam generating device;

Figure 6: schematically shows a beam generating device;

Figure 7: schematically shows a beam generating device;

Figure 8: schematically shows beam trajectories in accordance with a first embodiment variant;

Figure 9: schematically shows beam trajectories in accordance with a second embodiment variant;

Figure 10: schematically shows a beam generating device with a particle passage region for forming a multiplicity of individual particle beams; and

Figure 11 : schematically shows a beam generating device with a particle passage region for forming a multiplicity of individual particle beams.

Figure 1 schematically shows a multiple particle beam system 1 in the form of a multi-beam particle microscope 1. The multi-beam particle microscope 1 has a beam generating apparatus 300 having a particle source, for example an electron source. By means of the beam generating device 300, charged particles or electrons are generated for example by means of thermal field emission. The emitted charged particles form a divergent particle beam 309, and the latter is collimated by a sequence of condenser lenses 303.1 and 303.2 and is incident on a multi-beam particle generator 305 having a multi-aperture arrangement. The multi-beam particle generator 305 comprises a plurality of multi-aperture plates 304, 306 and a field lens 307. The multi-beam particle generator 305 generates a multiplicity of individual particle beams 3 or individual electron beams 3, which are arranged in a field, which is imaged onto a further field formed by beam spots 5 in the object plane 101. The distance between centre points of apertures of a multi-aperture plate 306 can be for example 5 pm, 100 pm or 200 pm. The diameters D of the apertures are smaller than the distance between the centre points of the apertures; examples of the diameters are 0.2 times, 0.4 times and 0.8 times the distances between the centre points of the apertures.

The multi-aperture arrangement 305 and the field lens 308 are configured to generate a multiplicity of focal points 323 of primary beams 3 in a grid arrangement on a surface 321. The surface 321 need not be a plane surface but rather can be a spherically curved surface in order to account for an image field curvature of the subsequent particle-optical system.

The multi-beam particle microscope 1 furthermore comprises a system of electromagnetic lenses 103 and an objective lens 102, which image the beam foci 323 from the intermediate image surface 321 into the object plane 101 with reduced size. In between, the first individual particle beams 3 pass through the beam splitter 400 and a collective beam deflection system 500, by means of which the multiplicity of first individual particle beams 3 are deflected during operation and the image field is scanned. The first individual particle beams 3 incident in the object plane 101 form for example a substantially regular field, wherein distances between adjacent incidence locations 5 can be for example 1 pm, 10 pm or 40 pm. The field formed by the incidence locations 5 can have a rectangular or hexagonal symmetry, for example.

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

The primary particles 3 incident on the object 7 generate interaction products, for example secondary electrons, backscattered electrons or primary particles, which have experienced a reversal of movement for other reasons, and these interaction products emanate from the surface of the object 7 or from the first plane 101 or object plane 101. The interaction products emanating from the surface 15 of the object 7 are shaped by the objective lens 102 to form secondary particle beams 9. In the process, the secondary beams 9 pass through the beam splitter 400 downstream of the objective lens 102 and are supplied to a projection system 200. The projection system 200 comprises an imaging system 205 with projection lenses 206, 208 and 210, a contrast stop 214 and a multi-particle detector 207. Incidence locations 25 of the second individual particle beams 9 on detection regions of the multi-particle detector 207 are located with a regular pitch in a third field. Exemplary values are 10 pm, 100 pm and 200 pm.

The multi-beam particle microscope 1 furthermore comprises a computer system or control unit or controller 10, which in turn can be embodied integrally or in multipartite fashion and which is designed both to control the individual particle-optical components of the multi-beam particle microscope 1 and to evaluate and analyse the signals obtained by the multi-detector 207 or detection unit. The beam generating device according to the invention can be integrated into the multiple particle beam system 1 shown in Figure 1.

Further information relating to such multi-beam particle beam systems or multi-beam particle microscopes 1 and component parts used therein, such as, for instance, particle sources, multi-aperture plate and lenses, can be obtained from the international patent applications WO 2005/024881 A2, WO 2007/028595 A2, WO 2007/028596 A1 , WO 2011/124352 A1 and WO 2007/060017 A2 and the German patent applications DE 102013016 113 A1 and DE 102013 014976 A1 , the disclosure of which is fully incorporated by reference in the present application.

Figure 2 schematically shows a beam generating device 300 in accordance with the prior art. The beam generating device 300 comprises a particle emitter 350 having a cathode tip 351 for emitting charged particles, for example electrons. Furthermore, the beam generating device 300 comprises an extractor electrode 353 and optionally a suppressor electrode 356. Particle emitter, suppressor electrode and extractor electrode jointly form the so-called beam head. This is indicated by the dotted quadrilateral 366 in Figure 2. The suppressor electrode 356 and the extractor electrode 353 each have a cylindrical shape with a cylindrical lateral surface and a flat front region: The flat front region 359 of the suppressor electrode 356 comprises an opening 360, through which the cathode tip 351 projects. The extractor electrode 353 has a planar front region 357, which in turn has an opening 358. The emitted particle beam 352 passes through this opening. The particle beam 352 is then incident on an anode electrode 354 or anode stop 354, which is formed in a planar fashion and has an opening 355. By means of this opening 355, the charged particle beam 352 is trimmed and acquires the shape of the divergent particle beam 309 that is also illustrated schematically in Figure 1.

The anode electrode 354 can be displaced relative to the beam head 366, specifically both in the z-direction and in a plane orthogonal to the particle-optical axis Z.

During operation of the beam generating device 300 or during operation of the associated multiple particle beam system 1 , an extraction voltage of for example a few kV, for example approximately +/- 2 kV, +/- 3 kV, +/- 4 kV or +/- 5 kV, is present between the cathode tip 351 and the extractor electrode 353.

Between the cathode tip 351 and the anode electrode 354, an acceleration voltage of a few 10 kV is present during operation, for example +/- 10 kV, +/- 25 kV, +/- 27 kV, +/- 30 kV, +/- 35 kV, +/- 40 kV or significantly more, for example up to +/- 300 kV. It is preferably the case here that the anode electrode 354 is at earth potential or only a low voltage is applied to it, while the actual high voltage is present at the particle emitter 350.

Between the optionally provided suppressor electrode 356 and the particle emitter 350, during operation of the beam generating device 300 a suppressor voltage is present which can be for example a few 100 volts, e.g. +/- 200 V, +/- 300 V, +/- 400 V, +/- 500 V or +/- 600 V.

Figure 2 schematically illustrates the described voltages between the electrodes for the case where the particle source 350 emits electrons. The conditions would be reversed if positively charged particles were emitted. The example illustrated in Figure 2 should be understood as non-limiting in this respect. The same applies to the following figures, in which such particle emitters which emit negatively charged particles or electrons are also once again illustrated merely by way of example.

Figure 3 shows schematically one embodiment of a beam generating device 300 according to the invention. The beam generating device 300 once again has a particle emitter 350 having a cathode tip 351 for emitting charged particles, in particular by means of thermal field emission. The emitted charged particles form a charged particle beam (not explicitly illustrated in Figure 3). The beam generating device 300 furthermore comprises an extractor electrode

353, which is spaced apart from the cathode tip 351 and which extracts the charged particles from the cathode tip 351 by means of an extraction voltage present between the cathode tip 351 and the extractor electrode 353 during operation of the beam generating device 300. Furthermore, the beam generating device 300 comprises an anode electrode 354, which is spaced apart from the cathode tip 351 further than the extractor electrode 353 and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip 351 and the anode electrode 354 during operation of the beam generating device 300. According to the invention, the extractor electrode 353 has a shape which comprises a spherical cap or consists of a spherical cap. In the example shown, the shape of the extractor electrode 353 consists of a spherical cap. At least in the region around the particle-optical axis Z, however, a spherical cap shape of the extractor electrode 353 is always provided. In the example shown, the extractor electrode 353 has a circular opening 358. The charged particles emitted by the particle emitter 350 pass through said opening during operation. The emitted particles are then incident on the anode electrode 354 and are trimmed by the latter. Only some of the charged particles pass through the opening 355 - which is circular in the example shown - having the diameter dA of the anode electrode

354. In the example shown, the spherical cap of the extractor electrode 353 has a sphere centre point ME, the position of which corresponds to the position of the cathode tip 351. The electric field between the cathode tip 351 and that surface of the extractor electrode 353 which faces the particle emitter 350 thus forms an isotropic electric field at the cathode tip 351 . The charged particles emitted by the tip 351 are thus situated in the field of a spherical lens, which field is free of spherical aberrations as a matter of principle. It is therefore possible to use a larger aperture region of the particle source 351 in comparison with the variant of a beam generating device 300 illustrated in Figure 2. The same as has already been described in connection with Figure 2 holds true, in principle, for the voltages present at the electrodes in Figure 3. The voltages present are each found in the same range. In addition, in this exemplary embodiment, a suppressor electrode 356 that is cylindrical or flat in the front region, as illustrated in Figure 2, can also be provided (not explicitly illustrated in Figure 3).

In the example shown, the following relation can hold true for a size dA of the opening 355 of the anode electrode 354: dA > 180 pm, preferably dA > 200 pm and extremely preferably dA > 220 pm. Additionally or alternatively, the following relation can hold true for a total beam current Ig passing through the opening 355 of the anode stop 354 during operation: Ig > 1 pA or Ig > 10 pA or Ig > 100 pA.

Additionally or alternatively, the following relation can hold true for a minimum distance dKA between the cathode tip 351 and the anode electrode 354: 5.0 mm < dKA < 14.0 mm, preferably 6.0 mm < dKA < 11.0 mm or extremely preferably 7.5 mm < dKA < 9.5 mm. The minimum distance dKA between the cathode tip 351 is measured on the particle-optical axis Z in Figure 3, specifically as far as the beginning of the opening 355. The distances in Figure 3 (as well as in all the other figures) are not illustrated as true to scale.

Figure 4 shows a further embodiment of the beam generating device 300 according to the invention. In contrast to the exemplary embodiment illustrated in Figure 3, the anode electrode 354 has a shape which comprises a spherical cap or consists of a spherical cap. In the exemplary embodiment illustrated in Figure 4, the shape of the anode electrode 354 consists of a spherical cap. The spherical cap has a radius TA. By contrast, the spherical cap of the extractor electrode 353 has a radius TE. The spherical cap of the extractor electrode 354 has a sphere centre point ME and the spherical cap of the anode electrode has a sphere centre point MA. The positions of the two sphere centre points ME and MA substantially correspond to one another. In the example shown, the sphere centre points ME and MA furthermore substantially correspond to the position of the cathode tip 351 . The specific arrangement of spherical capshaped extractor electrode 353 and spherical cap-shaped anode electrode 354 makes it possible to reduce aberrations further. However, the spherical configuration of the extractor electrode 353 makes up the majority of this reduction. In the example shown, the distance between the anode electrode 354 and the extractor electrode 353 is constant at least around the region of the particle-optical axis Z. In the marginal regions, this constancy is not exactly afforded, nor need it be exactly afforded.

Figure 5 shows a further exemplary embodiment for a beam generating device 300 according to the invention. Unlike in the exemplary embodiment illustrated in Figure 4, the beam generating device 300 furthermore has a condenser electrode 361 , which is spaced apart from the cathode tip 351 further than the anode electrode 354. In this case, the condenser electrode 361 has a shape which comprises a spherical cap or consists of a spherical cap. In the example shown, the near-anode surface 362 of the condenser electrode 361 consists of a spherical cap shape. In the example shown, the anode-remote surface 367 is likewise formed in a spherical fashion, but the centre point of this sphere does not correspond to the common centre point from the spherical cap-shaped near-anode surface 362. In the example shown, the centre points of the condenser electrode MK, the anode electrode MA and the extractor electrode ME substantially correspond to one another. In the example shown, they furthermore correspond to the position of the cathode tip 351. Owing to the correspondence of the centre points MK and MA, in the electrostatic field between the anode electrode 354 and the extractor electrode 361 it is also the case that the field lines are perpendicular to the surface of the electrodes. As a result, once again substantially the electrostatic field of a spherical lens is thus formed, which can reduce aberrations even further. In addition, in this exemplary embodiment, a suppressor electrode 356 that is cylindrical or flat in the front region, as illustrated in Figure 2, can also be provided (not explicitly illustrated in Figure 5).

Figure 6 shows a further embodiment variant for a beam generating device 300, in which a spherical suppressor electrode 356 is also provided besides a spherical extractor electrode 353. The suppressor electrode 356 at least partly surrounds the particle emitter 350; in the example shown, the suppressor electrode 356 has an opening 360, through which the particle emitter 350 with the cathode tip 351 protrudes. In the example shown, the shape of the suppressor electrode 356 consists of a spherical cap. However, it is also possible for the shape of the suppressor electrode 356 only to comprise a spherical cap; this should then be the case in the region around the particle-optical axis Z. Regions of the suppressor electrode 356 that are situated further outwards are not as crucial for the particle-optical properties of the beam generating device. The spherical cap of the suppressor electrode 356 has a radius rs in the example shown, and the extractor electrode 353 has a radius TE in the example shown. Furthermore, the spherical cap of the suppressor electrode has a sphere centre point MS and the extractor electrode 353 has a sphere centre point ME. The positions of the two sphere centre points MS and ME correspond to one another. In this embodiment of the invention, however, the two sphere centre points MS and ME no longer coincide with the position of the cathode tip 351 , of course. Nevertheless, the electrostatic field formed between the suppressor electrode 356 and the extractor electrode 353 is the field of a spherical lens and the field lines are each perpendicular to the surfaces on the electrodes 353 and 356. In the example shown, the two electrodes 353 and 356 formed in a spherical fashion are combined with an anode electrode 354 formed in a non-spherical fashion. The voltages present at the beam generating device 300 substantially correspond to the voltages which have already been described by way of example in connection with Figure 2.

Figure 7 shows a further embodiment of a beam generating device 300 according to the invention. Unlike in Figure 6, the anode electrode 354 is now also formed in a spherical fashion, that is to say that the anode electrode 354 has a shape which comprises a spherical cap or consists of a spherical cap. In the example shown, a sphere centre point of the anode electrode spherical cap MA corresponds to the sphere centre point ME of the spherical extractor electrode 353. In the example shown, these two centre points MA and ME furthermore correspond to the sphere centre point MS of the suppressor electrode. In the exemplary embodiment shown, the extractor-remote surface 364 of the anode electrode 354 is also formed in a spherical fashion, but the centre point of this sphere or spherical cap does not exactly correspond to the centre point MA. This could be the case, however.

It is generally possible to vary the differences between the individual radii of the spherical caps, but the differences could also be kept constant or the distances between the individual shells can also be kept constant. Aspects to consider for the specific design of the beam generating device may be stabilization issues of the high voltages present and the breakdown strength between the spherical cap-shaped electrodes.

Figure 8 schematically shows beam trajectories in accordance with a first embodiment variant V1 of the invention. In this case, the x-z-plane is illustrated in the topmost diagram and the y- z-plane of the beam trajectories is illustrated in the lower diagram. In the embodiment variant V1 , a substantially spherical suppressor electrode 356 and also a substantially spherical extractor electrode 353 are provided. The suppressor electrode 356 has a singular opening, through which a particle emitter 350 with its cathode tip 351 protrudes. The radii of curvature of the suppressor electrode 356 and of the extractor electrode 353 are chosen such that the associated sphere centre points MS and ME (not depicted) correspond to one another in this embodiment variant V1. The z-coordinate was fixed such that the position of the cathode tip 351 is arranged exactly at z=0. Figure 8 also illustrates in each case the position of the anode stop 354, wherein the anode stop is not formed in a spherical fashion, but rather in a planar fashion in a central region around the anode opening. The anode electrode 354 in each case trims the emitted particle beam 352. The position of the anode stop or its distance dA from the cathode tip 351 is somewhat less than 11 mm.

Figure 9 schematically shows beam trajectories in accordance with a second embodiment variant V2. In contrast to the embodiment variant V1 in Figure 8, the spherical extractor electrode 353 is arranged further away from the cathode tip 351. The radius of curvature of the extractor electrode 353 was left unchanged here. As a result, in the embodiment variant illustrated in Figure 9, it is the case that the sphere centre points ME and MS of the spherical extractor electrode 353 and of the spherical suppressor electrode 356 do not correspond to one another. The sphere centre point ME and the position of the cathode tip 351 substantially correspond to one another. The electrostatic field emanating from the cathode tip 351 towards the extractor 353 is thus isotropic as well as possible, which reduces the spherical aberrations of the beam generating device 300 as well as possible.

The beam trajectories illustrated in Figure 8 and Figure 9 are simulated beam trajectories which can be evaluated further with regard to their particle-optical properties by means of suitable simulation programs. In the present case, the two embodiment variants V1 and V2 were compared firstly with one another and secondly with an embodiment variant in which the shape of the extractor electrode 353 is not configured in a spherical fashion according to the invention, but rather in a planar or flat fashion. The emittance was examined for these three embodiment variants, wherein the electric field strength of the extraction field was set as constant in all three embodiment variants. The emittance in the embodiment variants V1 and V2 is significantly reduced in each case compared with the planar embodiment variant of an extractor electrode: The emittance is reduced by approximately -32% in the embodiment variant V1, and by approximately -21% in the embodiment variant V2. However, a reduced emittance means a better brightness. The spherical embodiment of the extractor electrode 353 thus makes it possible to increase the brightness; this also applies to the reduced brightness for which the current is normalized not only to the solid angle and the area passed through, but additionally also to the acceleration voltage. The greater the reduced brightness, the better the minimum achievable resolution in a multiple particle beam system. Originally, the brightness is defined by the particle source itself, but it must be maintained as much as possible during passage through the particle-optical unit. Aberrations reduce the brightness, which is why reduction of the aberrations is very important for a good resolution.

Figure 10 shows schematically a further beam generating device 300. In this case, the embodiment variant illustrated in Figure 10 substantially corresponds to the embodiment variant illustrated in Figure 6. Unlike in Figure 6, however, a particle passage region 365 is provided in the extractor electrode 353 around the particle-optical axis Z, and the charged particle beam emitted by the cathode tip 351 passes through said particle passage region to form a multiplicity of individual particle beams (not illustrated). In the example shown, the particle passage region 365 is formed as a filter element or filter plate having a multiplicity of apertures. The provision of a particle passage region 365 within the extractor electrode 353 can further contribute to reducing aberrations: The originally emitted particle beam 352 is thinned out at an early stage in the particle-optical beam path, which greatly reduces the Coulomb interaction between the charged particles or electrons. The earlier in the particle- optical beam path this thinning out takes place, the better that is for the later imaging properties or the uniformity and quality of the individual particle beams generated.

Accordingly, in the exemplary embodiment in accordance with Figure 11 , a particle passage region 365 is provided within the anode electrode 356. Here, too, the particle passage region 365 is situated in a region around the particle-optical axis Z.

Both with regard to the particle passage region 365 in Figure 10 and with regard to the particle passage region 365 in Figure 11 , it holds true that a surface of the particle passage region 365 can be formed in a substantially planar fashion or in a substantially curved fashion. The curvature should advantageously then substantially correspond to the curvature of the corresponding spherical cap of the respective electrode 353, 356. However, the curvature can also be chosen differently. The respective openings or the dimensions of the particle passage regions 365 arranged therein are so small in their dimensioning that the surface shape is not crucial for the reduction of aberrations. What is crucial, rather, is the reduction of the Coulomb interaction between different charged particles. Moreover, the provision of a particle passage region 365 within the extractor electrode 353 or within the anode electrode 354 is advantageous because the opening within the electrode spherical shell is in each case reduced or closed to the greatest possible extent. This ensures that unlike in the region of a (somewhat larger) singular opening, the electrostatic field is not distorted. This in turn has a positive influence on the beam quality and the reduction of aberrations. The apertures in the particle passage regions 365 can be of the order of magnitude of from a few 100 nm to a few micrometres, for example. The exemplary embodiments of the invention described above should not be understood as limiting for the invention. Instead, they serve only to afford a better understanding of the invention.

Further examples of the invention are given below:

Example 1. Beam generating device for a multiple particle beam system, in particular for a multi-beam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap.

Example 2. Beam generating device according to Example 1, wherein the anode electrode has an opening through which the charged particle beam passes during operation and the size of which is dimensioned such that the charged particle beam is trimmed in a marginal region upon passing through the opening.

Example 3. Beam generating device according to either of the preceding Examples, wherein the spherical cap of the extractor electrode has a sphere centre point ME, and wherein the positions of the cathode tip and of the sphere centre point ME correspond to one another.

Example 4. Beam generating device according to either of Examples 1 and 2, which furthermore has a suppressor electrode, which at least partly surrounds the particle emitter, wherein a suppressor voltage is present between the cathode tip and the suppressor electrode during operation, and wherein the suppressor electrode has a shape which comprises a spherical cap or consists of a spherical cap.

Example 5. Beam generating device according to the preceding Example, wherein the suppressor electrode has an opening through which the particle emitter with the cathode tip protrudes.

Example 6. Beam generating device according to either of Examples 4 and 5, wherein the spherical cap of the suppressor electrode has a sphere centre point MS, and wherein the spherical cap of the extractor electrode has a sphere centre point ME, wherein the positions of the two sphere centre points MS and ME correspond to one another.

Example 7. Beam generating device according to any of Examples 4 to 6, wherein the following relation holds true for a minimum distance dSE between the suppressor electrode and the extractor electrode: 300 pm < dSE < 3000 pm, in particular 550 pm < dSE < 800 pm or 1000 pm < dSE < 3000 pm.

Example 8. Beam generating device according to any of the preceding Examples, wherein the anode electrode has a shape which comprises a spherical cap or consists of a spherical cap.

Example 9. Beam generating device according to Example 8, wherein the spherical cap of the extractor electrode has a sphere centre point ME, and wherein the spherical cap of the anode electrode has a sphere centre point MA, wherein the positions of the two sphere centre points ME and MA correspond to one another.

Example 10. Beam generating device according to either of Examples 8 and 9, which furthermore has a condenser electrode, which is spaced apart from the cathode tip further than the anode electrode, wherein the condenser electrode has a shape which comprises a spherical cap or consists of a spherical cap.

Example 11. Beam generating device according to Example 10, wherein the spherical cap of the anode electrode has a sphere centre point MA, and wherein the spherical cap of the condenser electrode has a sphere centre point MK, wherein the positions of the two sphere centre points MA and MK correspond to one another.

Example 12. Beam generating device according to any of the preceding Examples, wherein the extractor electrode has a singular opening for the passage of the charged particle beam.

Example 13. Beam generating device according to any of Examples 1 to 11 , wherein the extractor electrode has a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams.

Example 14. Beam generating device according to any of Examples 1 to 13, wherein the anode electrode has a singular opening.

Example 15. Beam generating device according to any of Examples 1 to 13, wherein the anode electrode has a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams.

Example 16. Beam generating device according to either of Examples 13 and 15, wherein the particle passage region is formed in a substantially planar fashion.

Example 17. Beam generating device according to either of Claims 13 and 15, wherein the particle passage region is formed in a substantially curved fashion.

Example 18. Beam generating device according to any of the preceding Examples, wherein the following relation holds true for a minimum distance dKA between the cathode tip and the anode electrode: 5.0 mm < dKA < 14.0 mm, in particular 6.0 mm < dKA < 11.0 mm or 7.5 mm < dKA < 9.5 mm.

Example 19. Beam generating device according to any of Examples 2 to 18, wherein the following relation holds true for a size dA of the opening of the anode electrode: dA > 180 pm, in particular dA > 200 pm or dA > 220 pm; and/or wherein the following relation holds true for a total beam current Ig passing through the opening of the anode electrode during operation: Ig > 10 pA, in particular Ig > 100 pA. Example 20. Multiple particle beam system comprising a beam generating device according to any of Examples 1 to 19.

Example 21. Multiple particle beam system according to Example 20, which operates with a multiplicity N of individual particle beams, wherein it holds true that N > 61, in particular N > 91 or N > 100.

Example 22. Multiple particle beam system according to either of Examples 20 and 21, wherein the multiple particle beam system is a multi-beam particle microscope.

List of reference signs

1 multiple particle beam system, multi-beam particle microscope

3 primary particle beams, first individual particle beams

5 beam spots, incidence locations

7 object, sample, wafer

9 secondary particle beams, second individual particle beams

10 computer system, controller

15 sample surface, wafer surface

25 image point of a second individual particle beam

101 object plane

102 objective lens

103 field lens

105 axis

108 beam crossover

200 detector system

205 projection lens system

206 projection lens

207 multi-particle detector

208 projection lens

210 projection lens

212 beam crossover

214 aperture filter, contrast stop

222 collective anti-deflection system

300 beam generating device

303 collimation lens system, condenser lens system 304 multi-aperture plate, filter plate 305 multi-beam particle generator 306 multi-aperture plate 307 field lens 308 field lens 309 particle beam 311 illuminating particle beam 321 intermediate image plane

323 beam foci 350 particle emitter 351 cathode tip 352 charged particle beam 353 extractor electrode 354 anode electrode 355 singular opening of the anode electrode 356 suppressor electrode

357 planar front region of the extractor electrode 358 singular opening of the extractor electrode 359 planar front region of the suppressor electrode 360 singular opening of the suppressor electrode 361 condenser electrode 362 near-anode surface 363 near-extractor surface 364 extractor-remote surface

365 particle passage region 366 beam head 367 anode-remote surface 400 beam splitter, magnet arrangement 500 scan deflector 600 displacement stage or positioning device x direction y direction z direction

Z particle-optical axis r_E radius of extractor electrode r_A radius of anode electrode r_s radius of suppressor electrode r_K radius of condenser electrode

ME sphere centre point of the extractor electrode

MA sphere centre point of the anode electrode

MS sphere centre point of the suppressor electrode

MK sphere centre point of the condenser electrode dSE distance between suppressor electrode and extractor electrode dA diameter of anode opening dKA distance from cathode tip to anode electrode

Claims

Patent Claims

1. Beam generating device for a multiple particle beam system, in particular for a multibeam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; a suppressor electrode, which at least partly surrounds the particle emitter, wherein a suppressor voltage is present between the cathode tip and the suppressor electrode during operation; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap; and wherein the suppressor electrode has a shape which comprises a spherical cap or consists of a spherical cap.

2. Beam generating device according to Claim 1 , wherein the anode electrode has an opening through which the charged particle beam passes during operation and the size of which is dimensioned such that the charged particle beam is trimmed in a marginal region upon passing through the opening.

3. Beam generating device according to any one of the preceding claim, wherein the suppressor electrode has an opening through which the particle emitter with the cathode tip protrudes.

4. Beam generating device according to any one of the preceding claims, wherein the spherical cap of the suppressor electrode has a sphere centre point MS, and wherein the spherical cap of the extractor electrode has a sphere centre point ME, wherein the positions of the two sphere centre points MS and ME correspond to one another.

5. Beam generating device according to any of the preceding Claims, wherein the following relation holds true for a minimum distance dSE between the suppressor electrode and the extractor electrode: 300 pm < dSE < 3000 pm, in particular 550 pm < dSE < 800 pm or 1000 pm < dSE < 3000 pm.

6. Beam generating device according to any of the preceding Claims, wherein the anode electrode has a shape which comprises a spherical cap or consists of a spherical cap.

7. Beam generating device for a multiple particle beam system, in particular for a multibeam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap; wherein the anode electrode has a shape which comprises a spherical cap or consists of a spherical cap wherein the spherical cap of the extractor electrode has a sphere centre point ME, and wherein the spherical cap of the anode electrode has a sphere centre point MA, wherein the positions of the two sphere centre points ME and MA correspond to one another.

8. Beam generating device according to Claim 7, which furthermore has a condenser electrode, which is spaced apart from the cathode tip further than the anode electrode, wherein the condenser electrode has a shape which comprises a spherical cap or consists of a spherical cap.

9. Beam generating device according to Claim 8, wherein the spherical cap of the anode electrode has a sphere centre point MA, and wherein the spherical cap of the condenser electrode has a sphere centre point MK, wherein the positions of the two sphere centre points MA and MK correspond to one another.

10. Beam generating device according to any one of Claims 7 to 9, wherein the spherical cap of the extractor electrode has a sphere centre point ME, and wherein the positions of the cathode tip and of the sphere centre point ME correspond to one another.

11. Beam generating device for a multiple particle beam system, in particular for a multibeam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation; and an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, a condenser electrode, which is spaced apart from the cathode tip further than the anode electrode; wherein the extractor electrode has a shape which comprises a spherical cap or consists of a spherical cap; wherein the anode electrode has a shape which comprises a spherical cap or consists of a spherical cap; and wherein the condenser electrode has a shape which comprises a spherical cap or consists of a spherical cap

12. Beam generating device according to Claim 11, wherein the spherical cap of the anode electrode has a sphere centre point MA, and wherein the spherical cap of the condenser electrode has a sphere centre point MK, wherein the positions of the two sphere centre points MA and MK correspond to one another.

13. Beam generating device according to any one of Claims 11 to 12, wherein the spherical cap of the extractor electrode has a sphere centre point ME, and wherein the positions of the cathode tip and of the sphere centre point ME correspond to one another.

14. Beam generating device for a multiple particle beam system, in particular for a multibeam particle microscope, operating with a multiplicity of charged individual particle beams, wherein the beam generating device has the following: a particle emitter having a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam; an extractor electrode, which is spaced apart from the cathode tip and which extracts the charged particles from the cathode tip by means of an extraction voltage present between the cathode tip and the extractor electrode during operation, wherein the extractor electrode optionally has a shape which comprises a spherical cap or consists of a spherical cap; an anode electrode, which is spaced apart from the cathode tip further than the extractor electrode and which further accelerates the extracted charged particles by means of an acceleration voltage present between the cathode tip and the anode electrode during operation, optionally a suppressor electrode, the suppressor electrode at least partly surrounding the particle emitter, wherein a suppressor voltage is present between the cathode tip and the suppressor electrode during operation; and optionally a condenser electrode, which is spaced apart from the cathode tip further than the anode electrode; wherein at least two electrodes out of a group consisting of the extractor electrode, the anode electrode, the optionally provided suppressor electrode and the optionally provided condenser electrode are directly consecutively arranged, wherein the two electrodes each have a shape which comprises a spherical cap or consists of a spherical cap, and wherein the two electrodes have two sphere centre points, wherein positions of the two sphere centre points correspond to one another.

15. Beam generating device according to any of the preceding claims, wherein the extractor electrode has a singular opening for the passage of the charged particle beam.

16. Beam generating device according to any of Claims 1 to 14, wherein the extractor electrode has a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams.

17. Beam generating device according to any of Claims 1 to 16, wherein the anode electrode has a singular opening.

18. Beam generating device according to any of Claims 1 to 16, wherein the anode electrode has a particle passage region comprising a multiplicity of apertures through which the charged particle beam passes to form a multiplicity of individual particle beams.

19. Beam generating device according to either of Claims 16 and 18, wherein the particle passage region is formed in a substantially planar fashion.

20. Beam generating device according to either of Claims 16 and 18, wherein the particle passage region is formed in a substantially curved fashion.

21 . Beam generating device according to any of the preceding claims, wherein the following relation holds true for a minimum distance dKA between the cathode tip and the anode electrode: 5.0 mm < dKA < 14.0 mm, in particular 6.0 mm < dKA < 11.0 mm or 7.5 mm < dKA < 9.5 mm.

22. Beam generating device according to any of the preceding claims , wherein the anode electrode has an opening, wherein the following relation holds true for a size dA of the opening of the anode electrode: dA > 180 pm, in particular dA > 200 pm or dA > 220 pm; and/or wherein the following relation holds true for a total beam current Ig passing through the opening of the anode electrode during operation: Ig > 10 pA, in particular Ig > 100 pA.

23. Multiple particle beam system comprising a beam generating device according to any of Claims 1 to 22.

24. Multiple particle beam system according to Claim 23, which operates with a multiplicity N of individual particle beams, wherein it holds true that N > 61 , in particular N > 91 or N > 100.

25. Multiple particle beam system according to either of Claims 23 and 24, wherein the multiple particle beam system is a multi-beam particle microscope.