DE102024119459B3 - Beam generating device for a multi-particle beam system and multi-particle beam system - Google Patents

Abstract

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

Description

Field of invention

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

State of the art

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

Typical silicon wafers used in the fabrication of semiconductor devices 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 multiple semiconductor structures fabricated in layers on the wafer's surface using planar integration techniques. Due to the fabrication processes, semiconductor wafers typically have a flat surface. The feature size of the integrated semiconductor structures ranges from a few micrometers to critical dimensions (CDs) of a few nanometers, with feature sizes expected to become even smaller in the near future; it is anticipated that future feature sizes, or critical dimensions (CDs), will correspond to the 3 nm, 2 nm, or even smaller technology nodes of the International Technology Roadmap for Semiconductors (ITRS). For the aforementioned small feature sizes, defects of critical dimensions must be identified quickly over a very large area. For several applications, the specification requirement for the accuracy of a measurement provided by an inspection instrument is even higher, for example, by a factor of two or an order of magnitude. For instance, the width of a semiconductor feature must be measured with sub-1 nm accuracy, such as 0.3 nm or even less, and the relative position of semiconductor structures must be determined with a sub-1 nm superposition accuracy, such as 0.3 nm or even less.

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

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

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

Multi-particle beam systems are generally divided into single-column and multi-column systems. In single-column systems, the individual particle beams pass at least partially through the same particle optics or through one or more global particle lenses. Furthermore, in a single-column system, the individual particle beams are relatively close together. Despite the partially global particle optics, even single-column systems require individual control and/or shaping of the individual particle beams to correct imaging errors such as field curvature, field astigmatism, and other aberrations. A so-called micro-optics unit can be used for this individual control and/or shaping of the individual particle beams. The micro-optics unit often also serves as a multi-beam generator for the production and shaping of a large number of individual particle beams. The multi-beam generator, or micro-optics, comprises a sequence of several multi-aperture plates to generate a multitude of single-particle beams and to shape them so that they possess the necessary properties for subsequent particle-optical imaging. In generating the multitude of single-particle beams, a widened single-particle beam typically strikes a first multi-aperture plate or filter plate after passing through a condenser lens system and passes through its apertures, resulting in a multitude of single-particle beams instead of a single beam. Subsequent beam shaping using one or more multi-aperture plates employs electrodes, which are positioned, for example, in the aperture area of a multi-aperture plate and can be controlled collectively or individually.

For the described multi-particle beam system, high resolution and high throughput are of paramount importance for satisfactory and successful practical application. In this context, it is necessary, among other things, to adjust the intensity of the particle beams. The beam flux of the individual particle beams in a multi-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.

The US 2017/0025241 A1 This reveals a multi-particle beam system in which the current density in the particle beams is variable. Specifically, the illumination density is adjusted before multi-beams are generated from the primary electron beam. The illumination density is adjusted according to the US 2017/0025241 A1 A double collimator is used, positioned immediately behind the beam-generating unit in the beam direction. By varying the lens excitations of the double collimator, the current density of electrons passing through the apertures of a multi-aperture plate following the double collimator can be varied.

The multi-particle beam system described above reaches its limits when the number of particle beams used is further increased. To obtain sufficient beam currents for the individual beams, as many particles as possible from the particle source must be used. However, the emission characteristics of the particle source then become important, more precisely, the uniformity of the emission characteristics across the entire emission angle used. When using larger emission angles, the emission characteristics of particle sources, e.g., thermal field emission sources (TFEs), are no longer uniform. Accordingly, the illuminance at a multi-aperture plate in a corresponding particle beam system is also no longer uniform, and larger variations in the current densities occur in different individual beams. However, it is a system requirement for multi-particle inspection systems that there is only a small variation in the current intensities between the different individual beams, typically less than a few percent, so that all individual image fields of the multi-image field are illuminated with an equivalent number of particles or electrons per pixel. They are touched. This is, for example, a prerequisite for obtaining individual images with approximately the same brightness.

For inspection systems that operate with multi-beam particle beam systems, the use of particle sources with high beam angles and simultaneously high current requirements per individual beam presents a challenge due to the varying beam characteristics. Similar requirements exist for other multi-beam particle beam systems, such as multi-beam lithography systems.

When using a beam generation device, a compromise is therefore made between utilizing the largest possible emission angle of a particle emitter to generate a high total beam flux on the one hand, and ensuring beam uniformity on the other. In practice, an outer region of the charged single-particle beam generated by the particle emitter is therefore cut off by an aperture (anode aperture). In this outer region, the particle flux is significantly increased. This high beam flux in the outer region is explained by field enhancements at the outer edges of the flat front facet of an emitter tip. Due to the field enhancement, a particularly large number of charged particles are emitted at these outer edges. However, in a multi-particle beam system, only the largely uniform emission region of the particle emitter is used, i.e., only the particles or electrons emitted from the flat front facet, not the particles emitted from the region near the outer edges of the flat front facet.

Another problem is that, due to the described issues in the beam generation device, individual particle beams generated later from the emitted charged particles and located further out exhibit more aberrations compared to those arranged more centrally. This is especially true when the number of individual particle beams or their field is large or is to be increased further. It is therefore desirable to reduce the aberrations occurring in the outermost individual particle beams as well, without necessarily reducing the number of individual particle beams or using a smaller emission angle of the particle emitter for the subsequent generation of individual particle beams.

1. (a) Die Extraktorelektrode wird als sphärisch konkave Fläche ausgebildet. In der Nähe der Elektronenemissionsfläche ist bei einer sphärisch konkaven Ausbildung der Extraktorelektrode ein starker Intensitätsanstieg des elektrischen Feldes zu verzeichnen. (b) Als weitere Maßnahme zur Steigerung der elektrischen Feldstärke in der Nähe der Elektronenemissionsfläche wird eine spitzere Kathode mit einem Konuswinkel von 50° oder weniger vorgeschlagen. In der DE 11 2007 000 045 T5 wird die Nutzung eines großen Abstrahlwinkels nicht thematisiert. Es geht zudem nirgends um die Verringerung von Aberrationen. Strahlstromuniformitäten von einer Vielzahl von Elektronenstrahlen werden für das Einzelstrahlsystem der DE 11 2007 000 045 T5 ebenfalls nicht diskutiert.

DE 11 2007 000 045 T5 reveals an electron gun for a single-beam system. It is an idea of DE 11 2007 000 045 T5 , to increase the field strength at the emitter or cathode in order to reduce substance loss or sublimation at the emitter or cathode and to allow for longer use of the electron gun. To achieve this, the DE 11 2007 000 045 T5 Basically, two measures are proposed:

1. (a) The extractor electrode is designed as a spherically concave surface. Near the electron emission surface, a strong increase in the intensity of the electric field is observed with a spherically concave extractor electrode. (b) As a further measure to increase the electric field strength near the electron emission surface, a more pointed cathode with a cone angle of 50° or less is proposed. In the DE 11 2007 000 045 T5 The use of a large beam angle is not addressed. Furthermore, the reduction of aberrations is not discussed anywhere. Beam current uniformity from a multitude of electron beams is not considered for the single-beam system of the DE 11 2007 000 045 T5 also not discussed.

DE 10 2019 005 362 A1 This document discloses a method for operating a multi-particle beam system at different operating points. For each operating point, the numerical aperture can be adjusted to optimize the resolution of the multi-particle beam system. As a boundary condition, the beam spacing between adjacent single-particle beams on the sample being scanned is kept constant. No mechanical modifications to the system are required to vary the numerical aperture.

US 2019/0198284 A1 This paper discusses the formation of a tip, particularly in a Schottky emitter, within a single-beam system. The emitter is wire-like and has an electron emission surface at its tip. This electron emission surface has a specifically curved shape, which serves to make the virtual source more point-like and thus achieve a better directional beam. An extractor electrode with a spherical shape is shown, which is concentric to the spherical shape of the tip's surface. The electrical potential distribution is spherically symmetrical, and electrons are emitted in one direction. A virtual trajectory converges at a spherical center point. A spherical extractor is thus revealed here in the context of reducing the diameter of the virtual source.

US 2007/0228922 A1 The diagram reveals various types of electron guns. The structure of these electron guns includes, among other things, a so-called "beam drawing electrode" with a "convex" "Spherical shape". Various simulations for different types of electron guns are revealed.

US 4 218 635 A It reveals concave-shaped electrodes and, in particular, an anode. However, the entire electron gun is constructed completely differently from today's electron guns, such as those used in modern multi-beam particle beam systems.

Description of the invention

The object of the present invention is therefore to provide a particle beam system operating with a plurality of charged single-particle beams, which ensures high beam uniformity between the individual particle beams and reduces aberrations of the individual particle beams, even when using a large number of single-particle beams and simultaneously a high beam current for each individual particle beam. In a beam generation device for the plurality-particle beam system, a large aperture area should be illuminated as homogeneously as possible.

The problem is solved by the independent patent claims. Advantageous embodiments of the invention are described in the dependent patent claims.

The invention is based on the idea of adapting existing beam generation devices for particle beam systems specifically to the requirements of multi-particle beam systems described above. It is proposed to design an extractor electrode spherically or to shape it as a spherical cap. This allows an isotropic electric field to be generated at the particle emitter or at the emitter tip. This enables the utilization of a large aperture range of the particle emitter and, in principle, prevents the formation of spherical aberrations.

• einen Teilchenemitter mit einer Kathodenspitze zum Emittieren geladener Teilchen insbesondere mittels thermischer Feldemission, die einen geladenen Teilchenstrahl bilden;
• eine Suppressorelektrode, die den Teilchenemitter zumindest teilweise umgibt, wobei zwischen der Kathodenspitze und der Suppressorelektrode im Betrieb eine Suppressorspannung anliegt,
• eine Extraktorelektrode, die von der Kathodenspitze beabstandet ist und die die geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Extraktorelektrode im Betrieb anliegenden Extraktionsspannung aus der Kathodenspitze extrahiert; und
• eine Anodenelektrode, die von der Kathodenspitze weiter beabstandet ist als die Extraktorelektrode und die die extrahierten geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Anodenelektrode im Betrieb anliegenden Beschleunigungsspannung weiter beschleunigt,
• wobei die Extraktorelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht,
• wobei die Suppressorelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht.

According to a first aspect of the invention, this relates to a beam generating device for a plurality of particle beam system, in particular for a multi-beam particle microscope operating with a plurality of charged single-particle beams, wherein the beam generating device comprises the following:

• a particle emitter with a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam;
• a suppressor electrode that at least partially surrounds the particle emitter, with a suppressor voltage applied between the cathode tip and the suppressor electrode during operation,
• an extractor electrode spaced apart from the cathode tip, which extracts the charged particles from the cathode tip by means of an extraction voltage applied between the cathode tip and the extractor electrode during operation; and
• an anode electrode that is further away from the cathode tip than the extractor electrode and that further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip and the anode electrode during operation,
• wherein the extractor electrode has a shape that includes or consists of a spherical cap,
• wherein the suppressor electrode has a shape that includes or consists of a spherical cap.

• einen Teilchenemitter mit einer Kathodenspitze zum Emittieren geladener Teilchen, insbesondere mittels thermischer Feldemission, die einen geladenen Teilchenstrahl bilden;
• eine Extraktorelektrode, die von der Kathodenspitze beabstandet ist und die die geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Extraktorelektrode im Betrieb anliegenden Extraktionsspannung aus der Kathodenspitze extrahiert; und
• eine Anodenelektrode, die von der Kathodenspitze weiter beabstandet ist als die Extraktorelektrode und die die extrahierten geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Anodenelektrode im Betrieb anliegenden Beschleunigungsspannung weiter beschleunigt,
• wobei die Extraktorelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht,
• wobei die Anodenelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht,
• wobei die Kugelkalotte der Extraktorelektrode einen Kugelmittelpunkt ME aufweist,
• wobei die Kugelkalotte der Anodenelektrode einen Kugelmittelpunkt MA aufweist,
• wobei die Positionen der beiden Kugelmittelpunkte ME und MA miteinander übereinstimmen.

According to a second aspect of the invention, it relates to a beam generating device for a plurality of particle beam system, in particular for a multi-beam particle microscope operating with a plurality of charged single-particle beams, wherein the beam generating device comprises the following:

• a particle emitter with a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam;
• an extractor electrode spaced apart from the cathode tip, which extracts the charged particles from the cathode tip by means of an extraction voltage applied between the cathode tip and the extractor electrode during operation; and
• an anode electrode that is further away from the cathode tip than the extractor electrode and that further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip and the anode electrode during operation,
• wherein the extractor electrode has a shape that includes or consists of a spherical cap,
• wherein the anode electrode has a shape that includes or consists of a spherical cap,
• wherein the spherical cap of the extractor electrode has a spherical center ME,
• wherein the spherical cap of the anode electrode has a spherical center MA,
• where the positions of the two sphere centers ME and MA coincide.

• einen Teilchenemitter mit einer Kathodenspitze zum Emittieren geladener Teilchen insbesondere mittels thermischer Feldemission, die einen geladenen Teilchenstrahl bilden;
• eine Extraktorelektrode, die von der Kathodenspitze beabstandet ist und die die geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Extraktorelektrode im Betrieb anliegenden Extraktionsspannung aus der Kathodenspitze extrahiert; und
• eine Anodenelektrode, die von der Kathodenspitze weiter beabstandet ist als die Extraktorelektrode und die die extrahierten geladenen Teilchen mittels einer zwischen der Kathodenspitze und der Anodenelektrode im Betrieb anliegenden Beschleunigungsspannung weiter beschleunigt,
• eine Kondensorelektrode, die weiter von der Kathodenspitze beabstandet ist als die Anodenelektrode,
• wobei die Extraktorelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht,
• wobei die Anodenelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht,
• wobei die Kondensorelektrode eine Form aufweist, die eine Kugelkalotte umfasst oder aus einer Kugelkalotte besteht.

According to a third aspect of the invention, it relates to a beam generating device for a plurality of particle beam system, in particular for a multi-beam particle microscope operating with a plurality of charged single-particle beams, wherein the beam generating device comprises the following:

• a particle emitter with a cathode tip for emitting charged particles, in particular by means of thermal field emission, which form a charged particle beam;
• an extractor electrode spaced apart from the cathode tip, which extracts the charged particles from the cathode tip by means of an extraction voltage applied between the cathode tip and the extractor electrode during operation; and
• an anode electrode that is further away from the cathode tip than the extractor electrode and that further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip and the anode electrode during operation,
• a condenser electrode that is further away from the cathode tip than the anode electrode,
• wherein the extractor electrode has a shape that includes or consists of a spherical cap,
• wherein the anode electrode has a shape that includes or consists of a spherical cap,
• wherein the condenser electrode has a shape that includes or consists of a spherical cap.

The term "spherical cap" is defined in this patent application in accordance with standard mathematical practice. The requirement for the shape of a spherical cap must be essentially fulfilled. For example, the spherical cap may have one or more openings, such as for the passage of charged particles. It is also possible that only an inner or outer surface of the spherical cap has a perfect sphere. Ideally, the surface(s) of the extractor electrode will have a perfect spherical cap shape, as it is particularly important for particle optics reasons that the field lines of the electrostatic field are exactly perpendicular to this surface. Furthermore, a beam-generating device typically has a preferred direction with respect to the emitted particle beam, namely along the particle-optical axis Z. The extractor electrode then has a spherical cap shape at least in the region around the particle-optical axis Z and at least on the side facing the cathode tip. More distant regions or outer areas of the extractor electrode may have a shape other than that of a spherical cap.

The terms cathode and anode used in connection with the present patent application are not to be understood as restrictive with regard to the type of charged particles emitted by the particle emitter. For a better understanding of the invention, however, the terms are used as they are conventionally when the emitted charged particles are electrons or electron beams. According to the invention, the charged particles can also be positrons, muons, ions, or other charged particles or particle beams. The terms cathode and anode are then to be interpreted accordingly.

The particle emitter includes a cathode tip. This cathode tip is approximately point-like 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, which may, for example, be coated with a zirconium oxide layer. The zirconium oxide layer can lower the work function of the electrons leaving the tungsten cathode, so that heating the cathode to approximately 1500°C is sufficient for electrons to be emitted from the tungsten single-crystal tip (thermal field emission cathode or Schottky emitter). However, the particle emitter with its cathode tip can also be configured differently.

According to a 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. The size of this opening is such that the charged particle beam is clipped at the edge as it passes through the opening. This clips the intensity peaks of the charged particle beam, which can form at the edge of the end facet due to field enhancements, as described above. The opening of the anode electrode is thus illuminated as homogeneously as possible. This is beneficial for the subsequent formation of individual particle beams. This means that the individual particle beams can each have approximately the same beam flux.

According to a preferred embodiment of the invention, the spherical cap of the extractor electrode has a spherical center ME, and the positions of the cathode tip and the spherical center ME are substantially aligned. The tolerance of this alignment can be, for example, 50 µm, 20 µm, or 10 µm absolute, or it can be on the order of the size of the cathode tip. In 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 relatively large aperture range of the particle emitter or the cathode tip can be utilized. Because the extractor electrode is designed as a spherical cap or as (part of) a spherical lens, spherical aberrations are reduced. In general, it is true that with a point source and its imaging by perfect spherical lenses, no spherical aberrations occur due to the system's inherent properties. Specifically, this prevents the outer regions of the particle beam emitted from the cathode tip from exhibiting spherical aberrations simply as a result of the beam generation process. Therefore, it is fundamentally possible to increase the field of charged single-particle beams in the multi-particle beam system, or to arrange a greater number of charged single-particle beams within it, while still maintaining the uniformity condition for the single-particle beams.

According to a further preferred embodiment of the invention, the beam generating device further comprises a suppressor electrode that at least partially surrounds the particle emitter. During operation, a suppressor voltage is applied between the cathode tip and the suppressor electrode. The suppressor electrode has a shape that encompasses 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 peripheral regions, the suppressor electrode can also have a shape other than spherical.

According to 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 from escaping the particle emitter from other areas of the particle emitter that are not part of the cathode tip.

According to a preferred embodiment of the invention, the spherical cap of the suppressor electrode has a spherical center MS, and the spherical cap of the extractor electrode has a spherical center ME. The positions of the two spherical centers MS and ME coincide. The accuracy of this coincidence is, for example, ±50 µm or ±10 µm. Due to the described arrangement of the suppressor and extractor spherical caps relative to each other, a distance is formed between these two electrodes that is uniform across the entire spherical cap area. Electrostatic field lines between the suppressor and extractor electrodes are perpendicular to the respective electrode surfaces, and the curvature of the field lines is minimized. This arrangement also incorporates a particle-optical spherical lens, which in turn enables the reduction of spherical aberrations. In this embodiment of the invention, it is simply no longer possible for the center point ME of the extractor spherical cap to coincide with the cathode tip of the particle emitter. However, this is unnecessary if a faceted emitter is used.

According to a preferred embodiment of the invention, the following relationship applies to the minimum distance dSE between the suppressor electrode and the extractor electrode: 300 µm ≤ dSE ≤ 3000 µm, preferably 550 µm ≤ dSE ≤ 3000 µm or 1000 µm ≤ dSE ≤ 3000 µm. The minimum distance dSE can correspond to a constant distance between concentrically arranged spherical caps. However, this need not be the case, for example, if the spherical caps of the suppressor electrode and the extractor electrode have the same radii.

According to a further preferred embodiment of the invention, the anode electrode has a shape that comprises or consists of a spherical cap. At least the region of the anode electrode in the direction of, or around, the particle-optical axis Z has the shape of a spherical cap. In peripheral regions, the shape of the anode electrode may deviate from the shape of a spherical cap. This spherical cap shape of the anode electrode also has a positive effect on the reduction of aberrations, in particular spherical aberrations.

According to a further preferred embodiment of the invention, the spherical cap of the extractor electrode has a spherical center ME and the spherical cap of the anode electrode has The beam generating device has a sphere center MA. The positions of the two sphere centers ME and MA coincide. These two positions can coincide to within, for example, +/-50 µm or +/-10 µm. The beam generating device may have an alignment mechanism for aligning the extractor electrode and the anode electrode relative to each other. For example, the anode electrode can be moved in a plane orthogonal to the particle-optical axis Z of the beam generating device. Additionally or alternatively, the device may allow the anode electrode to be moved relative to the extractor electrode along the particle-optical axis Z, i.e., in the z-direction.

According to a further preferred embodiment of the invention, the beam generating device includes a condenser electrode. This electrode is positioned further from the cathode tip than the anode electrode. The condenser electrode has a shape that encompasses or consists of a spherical cap. The spherical cap shape of the condenser electrode is present at least in the region along the particle-optical axis Z of the beam generating device or the multiple particle beam system. In peripheral regions, the shape of the condenser electrode may deviate from the spherical cap shape. In this embodiment of the invention, a condenser electrode or condenser lens is thus integrated into the beam generating device. This integration is advantageous because of the spherical cap shape of the condenser electrode, particularly when the condenser electrode is specifically oriented relative to the spherical anode electrode.

According to a preferred embodiment of the invention, the spherical cap of the anode electrode has a spherical center MA, and the spherical cap of the condenser electrode has a spherical center MK. The two spherical centers MA and MK coincide. In this embodiment, the distance between the anode electrode and the condenser electrode is constant over a wide area, namely over the area of the spherical caps. This, in turn, results in the electric field lines between the anode electrode and the condenser electrode being oriented orthogonally to the surfaces of the electrodes, and the curvature of the field lines is minimized, thus generating a spherical lens effect. This measure also reduces spherical aberrations, particularly in the edge regions of the emitted particle beam.

The outer surface of the condenser electrode, however, does not necessarily have to have the shape of a spherical cap; this side of the condenser electrode faces away from the particle emitter. Instead, the shape of the outer surface of the condenser electrode can be chosen so that it best harmonizes or interacts with the particle-optical lenses located 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 they generate.

Overall, it is possible that the suppressor electrode, the extractor electrode, the anode electrode and preferably also the condenser electrode form a sequence of spherical caps whose sphere centers ideally coincide.

The spacing between the individual spherical caps can be identical, but it can also vary within a sequence of spherical caps. The following applies to all electrodes of the beam generation device that have a shape encompassing or consisting of a spherical cap: The electrodes can be manufactured in various ways. The electrodes themselves can, for example, consist of a metal sheet. This can be pressed into a cylindrical shape using a die. An electrode opening can then be created, for example, using micro-EDM (electrical discharge machining) or laser drilling. An alternative to pressing is the fabrication of the electrodes using 3D printing: A metallic 3D print can be used for manufacturing. However, it is also possible to use a plastic 3D print and subsequently coat the resulting spherical cap shape with a metallic coating. The manufacturing methods for a spherical cap electrode listed here are not exhaustive.

According to a preferred embodiment of the invention, the extractor electrode has a single opening for the passage of the charged particle beam. This opening is preferably round and can, for example, have a radius of about 150 µm, 170 µm, 190 µm, 200 µm, 210 µm, 220 µm, 300 µm, or another radius.

According to an alternative embodiment of the invention, the extractor electrode, instead of having a single opening, has a particle passage region comprising a plurality of apertures through which the charged particle beam passes, forming a plurality of single-particle beams. This embodiment, in turn, serves to reduce aberrations in the plurality-particle beam system: One cause of aberrations is the Coulomb interaction of the charged particles with each other. A large proportion of the originally generated charged particles are not actually needed for image generation in the multi-particle beam system, but are instead filtered out, for example, by a filter plate, particularly in the area of the multi-beam generator. With the described particle pass-through region in the extractor electrode, this thinning of the charged particles, or the generation of a multitude of individual particle beams, can occur earlier and closer to the source. Therefore, aberrations due to Coulomb interaction are reduced further along the particle-optical beam path. The described particle pass-through region can be used instead of a filter plate in the area of the multi-beam generator or in addition to another filter plate, particularly in the area of the multi-beam generator.

Furthermore, by providing a particle passage region instead of a singular opening, the electric field is not as strongly bent as it would be with a singular opening. The absence of bending in the field lines, in turn, makes it possible to further reduce aberrations.

According to another preferred embodiment of the invention, the suppressor electrode has a single opening. This is again the standard case.

According to a further preferred embodiment of the invention, the anode electrode, instead of having a single opening, has a particle passage region comprising a plurality of apertures through which the charged particle beam passes, forming a plurality of individual particle beams. In this embodiment of the invention, the described thinning of the charged particles and thus the suppression of Coulomb interactions also occurs effectively.

According to a preferred embodiment of the invention, a particle passage region of the extractor electrode and/or the anode electrode is essentially planar. According to an alternative embodiment, the particle passage region is essentially curved. Preferably, it follows the shape of the spherical cap of the respective electrode in which the particle passage region is arranged. Both embodiments (planar or curved) generate only minor aberrations.

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

According to a preferred embodiment of the invention, the following relationship applies 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 most preferably 7.5 mm ≤ dKA ≤ 9.5 mm.

According to a further preferred embodiment of the invention, the following relationship applies for an anode electrode opening size dA: dA ≥ 180 µm, preferably dA ≥ 200 µm, or most preferably dA ≥ 220 µm. Additionally or alternatively, the following relationship applies for a total beam current Ig passing through the anode aperture during operation: Ig ≥ 1 µA or Ig ≥ 10 µA, preferably Ig ≥ 100 µA.

The embodiments of a beam-generating device described above can be combined wholly or partially, provided that the combination does not cause any technical contradictions.

According to a second aspect of the invention, it relates to a multi-particle beam system with a beam-generating device as described above in several embodiments. The multi-particle beam system can, for example, be configured as a multi-particle microscope. It can also be configured as a multi-lithography system.

According to a preferred embodiment of the invention, the multiple particle beam system operates with a multiple N of individual particle beams, where N ≥ 61, in particular N ≥ 91 or N ≥ 100. The larger the field of the multiple individual particle beams, the more important the inventive design of the beam generation device becomes. With a multiple particle beam system that has a beam generation device according to the invention, the necessary beam uniformity can be readily achieved even with a larger number of individual particle beams, for example, 10²⁷ particle beams or even more.

• 1: zeigt ein Vielzahl-Teilchenstrahlsystem in schematischer Darstellung;
• 2: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 3: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 4: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 5: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 6: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 7: zeigt schematisch eine Strahlerzeugungsvorrichtung;
• 8: zeigt schematisch Strahltrajektorien gemäß einer ersten Ausführungsvariante;
• 9: zeigt schematisch Strahltrajektorien gemäß einer zweiten Ausführungsvariante;
• 10: zeigt schematisch eine Strahlerzeugungsvorrichtung mit einem Teilchendurchtrittsbereich zur Bildung einer Vielzahl von Einzel-Teilchenstrahlen; und
• 11: zeigt schematisch eine Strahlerzeugungsvorrichtung mit einem Teilchendurchtrittsbereich zur Bildung einer Vielzahl von Einzel-Teilchenstrahlen.

The invention will be better understood with reference to the accompanying figures. These show:

• 1 : shows a multi-particle beam system in schematic representation;
• 2 : schematically shows a beam generating device;
• 3 : schematically shows a beam generating device;
• 4 : schematically shows a beam generating device;
• 5 : schematically shows a beam generating device;
• 6 : schematically shows a beam generating device;
• 7 : schematically shows a beam generating device;
• 8 : schematically shows beam trajectories according to a first implementation variant;
• 9 : schematically shows beam trajectories according to a second implementation variant;
• 10 Figure 1 schematically shows a beam generation device with a particle passage area for the formation of a multitude of single-particle beams; and
• 11 Figure 1 schematically shows a beam generation device with a particle passage area for the formation of a multitude of single-particle beams.

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

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

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

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

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

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

The radiation generation device according to the invention can be integrated into the 1 The multi-particle beam system 1 shown can be integrated.

Further information on such multi-beam particle beam systems or multi-beam particle microscopes 1 and the components used therein, such as particle sources, multi-aperture plates and lenses, can be found in the international patent applications. WO 2005 / 024881 A2 , WO 2007 / 028595 A2 , WO 2007 / 028596 A1 , WO 2011 / 124352 A1 and WO 2007 / 060017 A 2 and the German patent application DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1 will be obtained, the disclosure of which is fully incorporated into the present application by reference.

2 Figure 1 schematically shows a beam generation device 300 according to the prior art. The beam generation device 300 comprises a particle emitter 350 with a cathode tip 351 for emitting charged particles, for example, electrons. Furthermore, the beam generation device 300 comprises an extractor electrode 353 and, optionally, a suppressor electrode 356. The particle emitter, suppressor electrode, and extractor electrode together form the so-called beam head. This is shown in 2 as indicated by the dotted rectangle 366. The suppressor electrode 356 and the extractor electrode 353 each have a cylindrical shape with a cylindrical shell and a flat front region: The flat front region 359 of the suppressor electrode 356 includes an opening 360 through which the cathode tip 351 protrudes. The extractor electrode 353 has a flat front region 357, which in turn has an opening 358. This opening is penetrated by the emitted particle beam 352. The particle beam 352 then strikes an anode electrode 354 or anode aperture 354, which is flat and has an opening 355. By means of this opening 355, the charged particle beam 352 is truncated and takes the form of the diverging particle beam 309, which is also in 1 is shown schematically.

The anode electrode 354 can be moved relative to the beam head 366, 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 multi-particle beam system 1, an extraction voltage of, for example, a few kV is applied between the cathode tip 351 and the extractor electrode 353, for example, approximately +/- 2kV, +/- 3kV, +/- 4kV or +/- 5kV.

Between the cathode tip 351 and the anode electrode 354, an accelerating voltage of several tens of kV is applied during operation, for example, ±10 kV, ±25 kV, ±27 kV, ±30 kV, ±35 kV, ±40 kV or significantly higher, for example up to ±300 kV. Preferably, the anode electrode 354 is at ground potential or is only subjected to a low voltage, while the actual high voltage is applied to the particle emitter 350.

During operation of the beam generation device 300, a suppressor voltage is applied between the optionally provided suppressor electrode 356 and the particle emitter 350, which can be, for example, several hundred volts, e.g. +/- 200V, +/- 300V, +/- 400V, +/- 500V or +/- 600V.

In 2 The described voltages between the electrodes are schematically represented for the case where the particle source emits 350 electrons. With the emission of positively charged particles, the relationships would be reversed. This is shown in 2 The example shown should therefore not be understood as restrictive. The same applies to the following figures, which again only illustrate particle emitters that emit negatively charged particles or electrons.

3 Figure 1 schematically shows an embodiment of a beam generating device 300. The beam generating device 300 in turn has a particle emitter 350 with 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 (in 3 (not explicitly shown). The beam generating device 300 further 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 applied between the cathode tip 351 and the extractor electrode 353 during operation of the beam generating device 300. The beam generating device 300 further comprises an anode electrode 354, which is spaced further apart from the cathode tip 351 than the extractor electrode 353 and which extracts the charged particles by means of an extraction voltage applied between the cathode tip 351 and the anode electrode 354 during operation of the beam generating device. The accelerating voltage applied to the electrode is further accelerated. According to the invention, the extractor electrode 353 has a shape that comprises or consists of a spherical cap. In the example shown, the shape of the extractor electrode 353 consists of a spherical cap. However, at least in the region around the particle-optical axis Z, a spherical cap shape is always provided for the extractor electrode 353. In the example shown, the extractor electrode 353 has a circular opening 358. During operation, this opening is penetrated by the charged particles emitted by the particle emitter 350. The emitted particles then strike the anode electrode 354 and are clipped by it. Only a portion of the charged particles penetrate the circular opening 355, which in the example shown has the diameter dA of the anode electrode 354.

In the example shown, the spherical cap of the extractor electrode 353 has a spherical center ME whose position corresponds to the position of the cathode tip 351. The electric field between the cathode tip 351 and the surface of the extractor electrode 353 facing the particle emitter 350 thus forms an isotropic electric field at the cathode tip 351. The charged particles emitted from the tip 351 are therefore located in the field of a spherical lens, which, due to its geometry, is free of spherical aberrations. For this reason, it is possible to utilize a larger aperture range from the particle source 351 than in the example shown. 2 The illustrated variant of a beam generating device 300. For the electrodes in 3 The same principle applies to the applied tensions as already stated in connection with 2 as described. The applied voltages are in the same range. In addition, in this embodiment, a cylindrical or, in the front region, flat suppressor electrode 356 can also be used, as described in 2 depicted as intended (in 3 (not explicitly shown).

For a size dA of the opening 355 of the anode electrode 354, the following relationship can apply in the example shown: dA ≥ 180 µm, preferably dA ≥ 200 µm, and most preferably dA ≥ 220 µm. Additionally or alternatively, for a total beam current Ig passing through the opening 355 of the anode aperture 354 during operation, the following relationship can apply: Ig ≥ 1 µA, Ig ≥ 10 µA, or Ig ≥ 100 µA.

Additionally or alternatively, the following relationship can apply 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 most preferably 7.5 mm ≤ dKA ≤ 9.5 mm. The minimum distance dKA between the cathode tip 351 is determined in 3 Measured on the particle-optical axis Z, specifically up to the beginning of aperture 355. The distances in 3 are (as in all other figures) not depicted to scale.

4 Figure 3 shows a further embodiment of the beam generating device 300 according to the invention. Unlike the one in Figure 300, the beam generating device shown in Figure 300 is shown in Figure 300. 3 In the illustrated embodiment, the anode electrode 354 has a shape that comprises or consists of a spherical cap. In the embodiment shown 4 In the illustrated embodiment, the anode electrode 354 is shaped like a spherical cap. The spherical cap has a radius r_{_A}. In contrast, the spherical cap of the extractor electrode 353 has a radius r_{_E}. The spherical cap of the extractor electrode 354 has a spherical center ME, and the spherical cap of the anode electrode has a spherical center MA. The positions of the two spherical centers ME and MA are essentially identical. In the illustrated example, the spherical centers ME and MA also essentially coincide with the position of the cathode tip 351. The specific arrangement of the spherical extractor electrode 353 and the spherical anode electrode 354 makes it possible to further reduce aberrations. The greatest contribution to this reduction, however, is due to the spherical design of the extractor electrode 353. 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 boundary regions, this constancy is not exactly given, nor does it need to be.

5 shows a further embodiment of a beam generating device 300 according to the invention. Unlike in the 4 In the illustrated embodiment, the beam generating device 300 further comprises a condenser electrode 361, which is located further from the cathode tip 351 than the anode electrode 354. The condenser electrode 361 has a shape that encompasses or consists of a spherical cap. In the illustrated example, the surface 362 of the condenser electrode 361 closest to the anode is spherical. While the surface 367 furthest from the anode is also spherical in the illustrated example, its center point does not coincide with the common center point of the spherical cap-shaped surface 362 closest to the anode. In the illustrated example, the centers of the condenser electrode MK, the anode electrode MA, and the extractor electrode ME are essentially identical. Furthermore, in the illustrated example, they coincide with the position of the cathode tip 351. Due to the coincidence of the centers MK and MA, it is also possible in the electrostatic The field between the anode electrode 354 and the extractor electrode 361 is arranged such that the field lines on the surface of the electrodes are perpendicular. This essentially creates the electrostatic field of a spherical lens, which can further reduce aberrations. Additionally, in this embodiment, a cylindrical or, in the front region, flat suppressor electrode 356 can also be used, as shown in 2 depicted as intended (in 5 (not explicitly shown).

6 Figure 1 shows another embodiment of a beam generation device 300, in which, in addition to a spherical extractor electrode 353, a spherical suppressor electrode 356 is also provided. The suppressor electrode 356 surrounds the particle emitter 350 at least partially. In the example shown, the suppressor electrode 356 has an opening 360 through which the particle emitter 350 protrudes with its cathode tip 351. 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 to consist solely of a spherical cap; this should then be the case in the region around the particle-optical axis Z. Areas of the suppressor electrode 356 located further outwards are not as critical for the particle-optical properties of the beam generation device.

In the example shown, the spherical cap of the suppressor electrode 356 has a radius r_{_S}, and the extractor electrode 353 has a radius r_{_E}. Furthermore, the spherical cap of the suppressor electrode has a spherical center MS, and the extractor electrode 353 has a spherical center ME. The positions of the two spherical centers MS and ME coincide. However, in this embodiment of the invention, the two spherical centers MS and ME no longer coincide with the position of the cathode tip 351. 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 perpendicular to the surfaces of the electrodes 353 and 356, respectively. In the example shown, the two spherically shaped electrodes 353 and 356 are combined with a non-spherically shaped anode electrode 354. The voltages applied to the beam generating device 300 essentially correspond to the voltages that are described by way of example in connection with 2 have already been described.

7 Figure 3 shows a further embodiment of a beam generating device 300 according to the invention. Unlike in Figure 300, the embodiment shown in Figure 300 is further illustrated in Figure 300. 6 The anode electrode 354 is now also spherically shaped, meaning that the anode electrode 354 has a shape that encompasses or consists of a spherical cap. In the example shown, the center point MA of the anode electrode's spherical cap corresponds to the center point ME of the spherical extractor electrode 353. In the example shown, these two centers MA and ME also correspond to the center point MS of the suppressor electrode. While the surface 364 of the anode electrode 354 furthest from the extractor is also spherically shaped in the illustrated embodiment, the center point of this sphere or spherical cap does not exactly correspond to the center point MA. However, this could be the case.

It is generally possible to vary the differences between the individual radii of the spherical caps, but these differences, or the distances between the individual caps, could also be kept constant. Considerations in the specific design of the beam generation device can include stabilization of the applied high voltages and the dielectric strength between the spherical cap electrodes.

8 Figure 1 schematically shows beam trajectories according to a first embodiment V1 of the invention. The uppermost diagram depicts the xz-plane and the lower diagram the yz-plane of the beam trajectories. In embodiment V1, a substantially spherical suppressor electrode 356 and a substantially spherical extractor electrode 353 are provided. The suppressor electrode 356 has a singular opening through which a particle emitter 350 protrudes with its cathode tip 351. The radii of curvature of the suppressor electrode 356 and the extractor electrode 353 are selected such that, in this embodiment V1, the corresponding sphere centers MS and ME (not shown) coincide. The z-coordinate was set such that the position of the cathode tip 351 is located exactly at z=0. This is shown in Figure 1. 8 The position of the anode aperture 354 is also specified, whereby the anode aperture is not spherical but planar in a central area around the anode opening. The anode electrode 354 clips the emitted particle beam 352. The position of the anode aperture, or its distance dA from the cathode tip 351, is slightly less than 11 mm.

9 schematically shows beam trajectories according to a second implementation variant V2. In contrast to the implementation variant V1 in 8 The spherical extractor electrode 353 is positioned further away from the cathode tip 351. The radius of curvature of the extractor electrode 353 was left unchanged. Therefore, it at the in 9 In the illustrated embodiment, the centers ME and MS of the spherical extractor electrode 353 and the spherical suppressor electrode 356 do not coincide. The center ME and the position of the cathode tip 351 essentially coincide. The electrostatic field emanating from the cathode tip 351 towards the extractor 353 is therefore as isotropic as possible, which minimizes the spherical aberrations of the beam-generating device 300.

In the 8 and 9 The beam trajectories shown are simulated and can be further evaluated with regard to their particle-optical properties using suitable simulation programs. Here, the two embodiments V1 and V2 were compared with each other and with an embodiment in which the shape of the extractor electrode 353 is not spherical according to the invention, but planar or flat. The emittance was investigated for these three embodiments, with the electric field strength of the extraction field being set constant for all three. The emittance of embodiments V1 and V2 is significantly reduced compared to the planar embodiment of an extractor electrode: In embodiment V1, the emittance is reduced by approximately -32%, and in embodiment V2 by approximately -21%. A reduced emittance, however, means a better directional beam (brightness). The spherical design of the extractor electrode 353 makes it possible to increase the directional beam value. This also applies to the reduced directional beam value, where the current is normalized not only to the solid angle and the area penetrated, but also to the accelerating voltage. The higher the reduced directional beam value, the better the minimum achievable resolution in a multi-particle beam system. The directional beam value is initially determined by the particle source itself, but it must be preserved as much as possible during the passage through the particle optics. Aberrations reduce the directional beam value, which is why reducing aberrations is crucial for good resolution.

10 Figure 300 schematically shows another beam generating device. The figure in 10 The depicted design variant essentially corresponds to the one shown in 6 depicted version variant. Unlike in 6 However, a particle passage region 365 is provided in the extractor electrode 353 around the particle-optical axis Z, through which the charged particle beam emitted from the cathode tip 351 passes, forming a multitude of individual particle beams (not shown). In the example shown, the particle passage region 356 is designed as a filter element or filter plate with a multitude of apertures. Providing 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 early in the particle-optical beam path, which greatly reduces the Coulomb interaction between the charged particles or electrons. The earlier this thinning occurs in the particle-optical beam path, the better it is for the subsequent imaging properties and the uniformity and quality of the generated individual particle beams.

Accordingly, in the exemplary embodiment according to 11 A particle passage region 365 is provided within the anode electrode 356. Here too, the particle passage region 365 is located in a region around the particle-optical axis Z.

Both with regard to the particle passage range 365 in 10 as well as with regard to the particle passage range 365 in 11 It is true that the surface of the particle passage region 365 can be essentially planar or essentially curved. Advantageously, the curvature should then essentially 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 356 arranged therein are dimensioned so small that the surface shape is not crucial for the reduction of aberrations. Rather, the reduction of the Coulomb interaction between different charged particles is crucial. Furthermore, providing 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 reduced or largely closed. This ensures that the electrostatic field is not distorted as it would be in the area of a (somewhat larger) singular opening. This in turn has a positive effect on beam quality and the reduction of aberrations. The apertures in the particle transmission regions 365, for example, can range in size from a few hundred nm to a few micrometers.

The embodiments of the invention described above are not to be understood as limiting the invention. Instead, they serve only to improve understanding of the invention.

Reference symbol list

1

Multi-beam particle system, multi-beam particle microscope

3

primary particle beams, first single-particle beams

5

Ray spots, points of impact

7

object, sample, wafer

9

secondary particle beams, second single-particle beams

10

Computer system, control

15

Sample surface, wafer surface

25

pixel of a second single-particle beam

101

Object level

102

objective lens

103

Field lens

105

axis

108

Beam crossing, crossover

200

Detector system

205

Projection lens system

206

Projection lens

207

Multi-particle detector

208

Projection lens

210

Projection lens

212

Beam crossing, crossover

214

Aperture filter, contrast aperture

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 focus

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

flat front area of the extractor electrode

358

singular opening of the extractor electrode

359

flat front area of the suppressor electrode

360

singular opening of the suppressor electrode

361

Condenser electrode

362

surface near the anode

363

Extractor-near surface

364

extractor-remote surface

365

Particle passage area

366

Beam head

367

Anode-distant surface

400

Beam switch, magnet arrangement

500

Scan distractor

600

Moving table or positioning device

x

Direction

y

Direction

z

Direction

Z

Particle optical axis

re

Radius extractor electrode

rA

Radius of anode electrode

rS

Radius suppressor electrode

rK

Radius condenser electrode

ME

Spherical center of the extractor electrode

MA

Spherical center of the anode electrode

MS

Spherical center of the suppressor electrode

MK

Spherical center of the condenser electrode

dSE

Distance between suppressor electrode and extractor electrode

dA

Anode opening diameter

dKA

Distance between cathode tip and anode electrode

Claims (24)

Beam generating device (300) for a plurality of particle beam system (1) operating with a plurality of charged single-particle beams (3), the beam generating device (300) comprising: A particle emitter (350) with a cathode tip (351) for emitting charged particles forming a charged particle beam (352); A suppressor electrode (356) that at least partially surrounds the particle emitter (350), wherein a suppressor voltage is applied between the cathode tip (351) and the suppressor electrode (356) during operation; An extractor electrode (353) that is spaced apart from the cathode tip (351) and that extracts the charged particles from the cathode tip (351) by means of an extraction voltage applied between the cathode tip (351) and the extractor electrode (353) during operation; and an anode electrode (354) which is further spaced from the cathode tip (351) than the extractor electrode (353) and which further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip (351) and the anode electrode (354) during operation, whereby the extractor electrode (353) has a shape that includes or consists of a spherical cap, and whereby the suppressor electrode (356) has a shape that includes or consists of a spherical cap. Beam generating device (300) according to Claim 1 , wherein the anode electrode (354) has an opening (355) through which the charged particle beam (352) passes during operation and the size of which is such that the charged particle beam (352) is clipped in a marginal region when passing through the opening (355). Beam generating device (300) according to one of the preceding claims, wherein the suppressor electrode (356) has an opening (360) through which the particle emitter (350) protrudes with the cathode tip (351). Beam generating device (300) according to one of the preceding claims, in which the spherical cap of the suppressor electrode (356) has a spherical center MS, and in which the spherical cap of the extractor electrode (353) has a spherical center ME, in which the positions of the two spherical centers MS and ME coincide. Beam generating device (300) according to one of the preceding claims, wherein the following relationship applies for a minimum distance dSE between the suppressor electrode (356) and the extractor electrode (353): 300µm ≤ dSE ≤ 3000µm, in particular 550µm ≤ dSE ≤ 800µm or 1000µm ≤ dSE ≤ 3000µm. Beam generating device (300) according to one of the preceding claims, wherein the anode electrode (354) has a shape comprising or consisting of a spherical cap. Beam generating device (300) for a plurality of particle beam system (1) operating with a plurality of charged single-particle beams (3), the beam generating device (300) comprising: a particle emitter (350) with a cathode tip (351) for emitting charged particles forming a charged particle beam (352); an extractor electrode (353) spaced apart from the cathode tip (351) and extracting the charged particles from the cathode tip (351) by means of an extraction voltage applied between the cathode tip (351) and the extractor electrode (353) during operation; and an anode electrode (354) which is spaced further away from the cathode tip (351) than the extractor electrode (353) and which further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip (351) and the anode electrode (354) during operation, whereby the extractor electrode (353) has a shape comprising or consisting of a spherical cap, whereby the anode electrode (354) has a shape comprising or consisting of a spherical cap, whereby the spherical cap of the extractor electrode (353) has a spherical center ME, whereby the spherical cap of the anode electrode (354) has a spherical center MA, wherein the positions of the two spherical centers ME and MA coincide. Beam generating device (300) according to Claim 7 , which further comprises a condenser electrode (361) which is spaced further away from the cathode tip (351) than the anode electrode (354), wherein the condenser electrode (361) has a shape comprising or consisting of a spherical cap. Beam generating device (300) according to Claim 8 , wherein the spherical cap of the anode electrode (354) has a spherical center MA, and wherein the spherical cap of the condenser electrode (361) has a sphere center MK, wherein the positions of the two sphere centers MA and MK coincide. Beam generating device (300) according to one of the Claims 7 until 9 , wherein the spherical cap of the extractor electrode (353) has a sphere center ME, and wherein the positions of the cathode tip (351) and the sphere center ME coincide. Beam generating device (300) for a plurality of particle beam system (1) operating with a plurality of charged single-particle beams (3), the beam generating device (300) comprising: A particle emitter (350) with a cathode tip (351) for emitting charged particles forming a charged particle beam (352); An extractor electrode (353) spaced apart from the cathode tip (351) and extracting the charged particles from the cathode tip (351) by means of an extraction voltage applied between the cathode tip (351) and the extractor electrode (353) during operation; and an anode electrode (354) that is further spaced from the cathode tip (351) than the extractor electrode (353) and that further accelerates the extracted charged particles by means of an accelerating voltage applied between the cathode tip (351) and the anode electrode (354) during operation, a condenser electrode (361) that is further spaced from the cathode tip (351) than the anode electrode (354), whereby the extractor electrode (353) has a shape that includes or consists of a spherical cap, whereby the anode electrode (354) has a shape that includes or consists of a spherical cap, whereby the condenser electrode (361) has a shape that includes or consists of a spherical cap Beam generating device (300) according to Claim 11 , wherein the spherical cap of the anode electrode (354) has a spherical center MA, and wherein the spherical cap of the condenser electrode (361) has a spherical center MK, the positions of the two spherical centers MA and MK being identical. Beam generating device (300) according to one of the Claims 11 until 12 , wherein the spherical cap of the extractor electrode (353) has a sphere center ME, and wherein the positions of the cathode tip (351) and the sphere center ME coincide. Beam generating device (300) according to one of the preceding claims, wherein the extractor electrode (353) has a singular opening (358) for the passage of the charged particle beam (352). Beam generating device (300) according to one of the Claims 1 until 13 , wherein the extractor electrode (353) has a particle passage area (365) comprising a plurality of apertures through which the charged particle beam passes, forming a plurality of single-particle beams. Beam generating device (300) according to one of the Claims 1 until 15 , wherein the anode electrode (354) has a singular opening (355). Beam generating device (300) according to one of the Claims 1 until 15 , wherein the anode electrode (354) has a particle passage area (365) comprising a plurality of apertures through which the charged particle beam passes, forming a plurality of single-particle beams. Beam generating device (300) according to one of the Claims 15 or 17 , wherein the particle passage region (365) is essentially planar. Beam generating device (300) according to one of the Claims 15 or 17 , wherein the particle passage region (365) is essentially curved. Beam generating device (300) according to one of the preceding claims, wherein the following relationship applies for a minimum distance dKA between the cathode tip (351) and the anode electrode (354): 5.0 mm ≤ dKA ≤ 14.0 mm, in particular 6.0 mm ≤ dKA ≤ 11.0 mm or 7.5 mm ≤ dKA ≤ 9.5 mm. Beam generating device (300) according to one of the preceding claims, wherein the anode electrode (354) has an opening (355) through which the charged particle beam (352) passes during operation and the size of which is dimensioned such that the charged particle beam (352) is clipped in a marginal region when passing through the opening (355), wherein the following relationship applies for a size dA of the opening (355) of the anode electrode (354): dA ≥ 180 µm, in particular dA ≥ 200 µm or dA ≥ 220 µm; and/or where the following relation applies for a total beam current Ig which passes through the opening (355) of the anode electrode (354) during operation: Ig ≥ 10µA, in particular Ig ≥ 100µA. Multi-particle beam system (1) with a beam generating device (300) according to one of the Claims 1 until 21 . Multi-particle beam system (1) according to Claim 22 , which operates with a plurality N of single-particle beams (3), where N ≥ 61, in particular N ≥ 91 or N ≥ 100. Multi-particle beam system (1) according to one of the Claims 22 until 23 , wherein the multi-particle beam system (1) is a multi-beam particle microscope (1).