Method for producing a micro-optics for a multi-particle beam system, micro-optics and multi-particle beam system

Abstract

A method for producing a micro-optic system for a multi-particle beam system is disclosed, comprising the following steps: (a) providing a first plate of the micro-optic system that is electrically conductive; (b) providing a second plate of the micro-optic system that is electrically conductive; (c) producing a plate stack comprising stacking the first plate of the micro-optic system and the second plate of the micro-optic system on top of one another, wherein the first plate of the micro-optic system and the second plate of the micro-optic system are fixed relative to one another in the plate stack and are electrically insulated from one another; and (d) drilling through the entire produced plate stack with at least the first plate and the second plate of the micro-optic system, thereby producing both a first plurality of apertures in the first plate of the micro-optic system and a second plurality of apertures in the second plate of the micro-optic system.

Description

Field of the InventionThe invention relates generally to multiple particle beam systems and, more particularly, to multiple beam particle microscopes that operate with multiple charged single particle beams. Specifically, the invention relates to a method for producing a microoptics for a multiplicity of particle beam systems, to a microoptics and to a multiplicity of particle beam systems.Prior ArtWith the continuous development of smaller and more complex microstructures such as semiconductor devices, there is a need to further develop and optimize planar fabrication techniques and inspection systems for fabricating and inspecting small dimensions of the microstructures. For example, the development and fabrication of the semiconductor devices requires a review of the design of test wafers, and the planar fabrication techniques require process optimization for reliable, high throughput fabrication. Moreover, recently, analysis of semiconductor wafers for reverse engineering and custom individual configuration of semiconductor devices have been demanded. There is therefore a need for inspection means that can be used with high throughput for inspecting microstructures on wafers with high accuracy.Typical silicon wafers used in the manufacture of semiconductor devices have diameters of up to 300 mm. Each wafer is divided into 30 to 60 repeating regions ("dies") having a size of up to 800 mm 2. A semiconductor device includes a plurality of semiconductor structures fabricated by planar integration techniques in layers on a surface of the wafer. Due to the manufacturing processes, semiconductor wafers typically have a planar surface. The structure size of the integrated semiconductor structures extends from a few μm to the critical dimensions (CD) of a few nanometers, wherein in the near future the structure sizes become even smaller; it is expected that the structure sizes or critical dimensions (CD) will correspond in the future to the 3 nm, 2 nm or even smaller technology nodes of the international technology schedule for semiconductors (ITRS)). In the above-mentioned small feature sizes, defects in the size of critical dimensions must be identified in a very large area in a short time. For several applications, the specification requirement for the accuracy of a measurement provided by an inspection device is even higher, for example by a factor of two or an order of magnitude. For example, a width of a semiconductor feature needs to be measured with an accuracy below 1 nm, for example 0.3 nm or even less, and a relative position of semiconductor structures needs to be determined with an overlay accuracy below 1 nm, for example 0.3 nm or even less.A recent development in the charged particle microscope (CPM) field is the MSEM, a multi-beam scanning electron microscope. A multi-beam scanning electron microscope is disclosed, for example, in U.S. Pat. No. 7,244,949 B2 and in U.S. Pat. No. 2019 / 0355544 A1. In a multi-beam electron microscope or MSEM, a sample is irradiated simultaneously with a plurality of single electron beams arranged in an array. For example, 4 to 10000 individual electron beams can be provided as primary radiation, wherein each individual electron beam is separated from an adjacent individual electron beam by a distance of 1 to 200 micrometers. For example, an MSEM has approximately 100 separate beamlets ("beamlets") arranged, for example, in a hexagonal grid, the individual electron beams being separated by a distance of approximately 10 μm. The plurality of charged single particle beams (primary beams) are focused on a surface of a sample to be examined by a common objective lens. The sample may be, for example, a semiconductor wafer mounted on a wafer holder mounted on a movable stage. During the illumination of the wafer surface with the charged primary individual particle beams, interaction products, for example secondary electrons or back-scattered electrons, originate from the surface of the wafer. Their starting points correspond to the locations on the sample onto which the plurality of primary individual particle beams is in each case focused. The amount and energy of the interaction products depends on the material composition and the topography of the wafer surface. The interaction products form a plurality of secondary single particle beams (secondary beams) collected by the common objective lens and incident on a detector disposed in a detection plane through a projection imaging system of the multi-beam inspection system. The detector includes a plurality of detection regions each including a plurality of detection pixels, and the detector detects an intensity distribution for each of the secondary single particle beams. An image field of, for example, 100 μm×100 μm is obtained.The prior art multi-beam electron microscope comprises a sequence of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adjust the focus position and the triangulation of the plurality of charged single particle beams. The prior art charged particle multi-beam system also includes at least one crossover plane of the primary or secondary charged single particle beams. Furthermore, the prior art system includes detection systems to facilitate adjustment. The multi-beam particle microscope of the prior art comprises at least one beam deflector ("deflection scanner") for collectively scanning a region of the sample surface by means of the plurality of primary single particle beams in order to obtain an image field of the sample surface.For separating the particle-optical beam path of the primary beams from the particle-optical beam path of the secondary beams, a so-called beam splitter ("beam splitter" or "beam separator" or "beam divisor") is used. Separation is effected by means of special arrangements of magnetic fields and / or electrostatic fields, for example by means of a Wien filter.In the case of a plurality of particle beam systems, a distinction is fundamentally made between systems which operate with a single column and systems which operate with a plurality of columns. In systems with a single column, the passage of the single particle beams takes place at least partially through the same particle optics or through one or more global particle lenses. In addition, in the case of a single column, the single particle beams are relatively close to one another. Despite the partially global particle-optical elements, there is a need for individual influenceability and / or formability of the individual particle beams in individual columns in order to correct aberrations such as curvature of the field, astigmatism of the field and other aberrations. For this individual influencing and / or shaping of the individual particle beams, a so-called microoptical system can be used. Micro-optics are often also referred to as multi-beam particle generators for generating and shaping a plurality of individual particle beams. The multi-beam particle generator or the micro-optics comprises a sequence of a plurality of multi-aperture plates, which can be used for active beam shaping or of which at least one multi-aperture plate can be used for active beam shaping. For this purpose, electrodes can be provided, for example, in the area of the apertures, which electrodes can be controlled collectively or individually. These may be, for example, ring electrodes or multipole electrodes. According to another example, a multi-aperture plate can be monolithically formed, wherein a voltage is applied to the multi-aperture plate overall, i.e. the monolithic multi-aperture plate is then at a specific potential, so that its openings can generate a lens effect in cooperation with other particle-optical elements. Other configurations of a multi-aperture plate for active beam shaping are also possible.For the best possible individual particle beam shaping / individual particle beam influencing, it is necessary for the apertures through which an individual particle beam passes to be aligned exactly with respect to one another. For example, it may be necessary for the centers of the apertures to be situated exactly one above the other. In addition, the apertures in known multi-aperture plates are relatively small, e.g. aperture diameters are each less than 100 μm, e.g. only 90 μm or less. These two conditions - small size of aperture diameters and accurate alignment of the apertures / electrodes, including. Driving can be fulfilled by the application of MEMS techniques for producing a micro-optic. In other words, similar processes are used for producing a micro-optic or its multi-aperture plates, which can also be used in semiconductor production.The applications of semiconductor components are disclosed, for example, by combination of regions of different doping or by the influence of insulating separating layers. To meet these requirements, in the production of semiconductor components, different layers are applied in succession to a base substrate in wafer form (so-called planar technique). Silicon is used as the base substrate, for example; silicon oxide is used as the insulating layer, for example. The applied layers can then each be structured by means of lithographic methods. Integrated circuits with conductor tracks, i.e. semiconductor chips, can thus be produced-or indeed micro-optics with multi-aperture plates for multiple particle beam systems.The precise way in which microoptics are produced by means of MEMS techniques is also, there are nevertheless disadvantages in this type of production: the development time for the production of microoptics is relatively long and is frequently between half and three quarters of a year. Changes in the production process are possible only with difficulty or only with considerable time expenditure. And, overall, there are few semiconductor manufacturers, the process control of semiconductor manufacturing is challenging, and very expensive equipment is needed for semiconductor manufacturing.DESCRIPTION OF THE INVENTIONIt is therefore an object of the invention to provide an improved method for producing a micro-optic for a multiplicity of particle beam systems. The method should be faster than known methods, in particular, without thereby accepting quality losses in the micro-optics or degrading an achievable resolution in multiple particle beam systems. In addition, the method should be simple and cost-effective to implement.The object is achieved by the subject matter of the independent claims. Advantageous embodiments of the invention are evident from the dependent claims.The present invention is essentially based on two basic findings: (1) It has been found that the material silicon used for micro-optics can pose serious problems: for example, undesirable surface potentials can occur and the conductivity of the silicon can change with time. Both have an undesired influence on the charged individual particle beams during the passage of the microoptical unit and thus on the beam quality and thus in turn on the resolution which can be achieved by means of a multiplicity of particle beam systems during the operation thereof. (2) Moreover, it has surprisingly been found that the desire / trend for further miniaturization of the microoptics for the purpose of improving resolution is not always correct or always required at all. Instead, it may have true advantages to fabricate the micro-optics with somewhat larger dimensions such as larger apertures and / or thicker multi-aperture plates. Advantages are offered in particular by reduced parasitic effects such as reduced beam deflections with a comparable desired electron-optical effect and by higher voltages which can be applied to the multi-aperture plates of the micro-optics. The latter is of particular interest in micro-optics for more and more individual particle beams and for larger and larger image fields.It is therefore a basic idea of the invention to use other manufacturing processes instead of MEMS techniques, namely those which can be used in metal processing. The fact that such processes for metal processing tend to be used only for producing somewhat larger structures is not necessarily a disadvantage in this case. Instead, the processes of metal processing offer the advantage that silicon no longer has to be used quasi forcibly as material. In particular, it is possible to also produce micro-optics with the method according to the invention, which comprise one or more multi-aperture plates made of metal. In addition, with a skillful method procedure, the problem of the precise alignment of the multi-aperture plates with respect to one another can also be solved, namely independently of their material or light-optical or IR transparency; the multi-aperture plates are then namely automatically or process-inherently correctly aligned with respect to one another.According to a first aspect of the invention, the invention relates to a method for producing a micro-optic for a plurality of particle beam systems, comprising the following steps: (a) providing a first plate of the micro-optic which is electrically conductive; (b) providing a second plate of the micro-optic which is electrically conductive; (c) generating a plate stack comprising stacking the first plate of the micro-optic and the second plate of the micro-optic one above the other, wherein the first plate of the micro-optic and the second plate of the micro-optic are fixed relative to one another in the plate stack and are electrically insulated from one another; (d) piercing the entire formed stack of plates with at least the first plate and the second plate of the micro-optic, thereby creating both a first plurality of apertures in the first plate of the micro-optic and a second plurality of apertures in the second plate of the micro-optic.The term micro-optics is understood, as in the introductory description part, to mean a sequence of a plurality of multi-aperture plates, of which at least one multi-aperture plate is used during operation for the active beam shaping of the plurality of individual particle beams in the plurality of particle beam systems. Preferably, each of the apertures is traversed by exactly one individual particle beam.In claim 1, reference is first made not to a multi-aperture plate, but to a first plate of the micro-optic or a second plate of the micro-optic. This is due to the fact that the apertures are first formed in the first plate and in the second plate during the manufacturing process.The first plate of the micro-optic is electrically conductive. The entire first plate of the microoptical system can be electrically conductive or else only partial regions of the first plate. The same applies to the second plate of the micro-optic. The electrical conductivity property contributes to or is even required for many methods known from metal processing to be used for manufacturing the micro-optic for a multiple particle beam system. This will be discussed in more detail later.Generating the plate stack comprises stacking the first plate of the micro-optic and the second plate of the micro-optic one above the other, wherein the first plate of the micro-optic and the second plate of the micro-optic are fixed relative to one another in the plate stack and are electrically insulated from one another. The fixing and electrical insulation can be realized simultaneously and / or by means of the same means, but it is also possible that different means are used for fixing and electrical insulation. It is possible, for example, for electrically insulating spacers to be used or for a complete electrically insulating plate to be provided.The stack of plates includes at least a first plate of the micro-optic and a second plate of the micro-optic. The plate stack can also comprise further plates of the micro-optics. In method step (d), the drilling through of the entire generated plate stack with at least the first plate and the second plate of the microoptics is carried out in any case and thereby both a first plurality of apertures in the first plate of the microoptics and a second plurality of apertures in the second plate of the microoptics are generated. Apertures through which the same individual particle beam is to pass during operation of the micro-optics or of the multiplicity of particle beam systems are thus generated in the same method step or during the same drilling. In a correspondingly accurate embodiment of the drilling by means of a drilling means, apertures assigned to one another in the first plate of the microoptics and the second plate of the microoptics and optionally one or more further plates of the microoptics are therefore automatically aligned correctly with respect to one another.According to a preferred embodiment of the invention, the first plate of the micro-optic and / or the second plate of the micro-optic is metallic. For example, the metal can be copper, silver, iron, aluminum, tungsten, gold, brass, platinum, stainless steel or else another metal or a metal alloy or combinations of the aforementioned materials. The metal plate itself can also have a surface finish, for example a gold coating. Alternatively, it is also possible for the first plate of the micro-optic and / or the second plate of the micro-optic to consist of a semiconductor material. This semiconductor material may comprise silicon, for example.According to a further preferred embodiment of the invention, the plate stack further comprises at least one further and thus at least one third plate of the micro-optic, which is electrically conductive. In this case, the third plate of the microoptics is fixed relative to the first plate of the microoptics and the second plate of the microoptics and is in each case electrically insulated from them. When carrying out method step (d), the third plate of the microoptics is likewise jointly perforated, with the result that a third multiplicity of apertures is thereby produced in the third plate of the microoptics. This third plurality of apertures is therefore also process-inherently correctly aligned with the remaining apertures of the first plate and of the second plate.According to a preferred embodiment of the invention, the third plate of the micro-optic is made of a metal. The same applies to any further plates present. In this case, it is possible in principle for all plates of the microoptics to consist of the same material and in particular of the same metal; however, this is not necessarily the case.According to a preferred embodiment of the invention, the drilling of the plate stack in step (d) is carried out by means of laser drilling. Laser drilling is a non-machining thermal separation process. There are various types of laser drilling techniques, such as single pulse drilling, percussion drilling, trepanning and helical drilling. Single-pulse drilling is the fastest in this case; it is "shot" through the material by means of a single pulse. In percussion drilling, several pulses are set at the same point to laser a hole through the material. Trepanning is referred to as the cutting of the hole after the through bore by traversing the bore contour. In helical drilling, special optics may be required. In principle, the precision of the drilling and the smoothness of the walls of the borehole depend on the material drilled through and the type of laser radiation. Copper, for example, absorbs green and blue radiation very well, whereas common infrared does not very well. Laser drilling methods are very fast and also very efficient today: for example, it is possible to drill 200 holes per second in 1 mm thick titanium sheet using single-pulse micro drilling. A focus diameter of the laser used is, for example, 12 μm, the bore produced has a diameter of only just 80 μm. An aperture diameter of 80 μm already corresponds to the dimensions of apertures used in the prior art when these are produced by means of MEMS techniques. Thus, very small apertures can be produced by means of laser drilling, if desired, as well as far larger apertures, if necessary by means of other laser drilling techniques. In addition, the processes are very rapid. In addition, laser drilling as a production method offers the advantage that the material to be drilled through does not necessarily have to be a metal or even conductive.Insulators can also be perforated by means of laser drilling. During laser drilling, plate stacks can therefore also be drilled through with a sequence of electrically conductive and electrically insulating plates at once or by means of the same laser pulse or by means of the same multiplicity of laser pulses.According to a further preferred embodiment of the invention, the disk stack is perforated in step (d) by means of micro-EDM. Micro-EDM or micro-spark erosion is one form of EDM (Electrical Discharge Machining) and can be described as a combination of drilling erosion and counterbore erosion techniques. This technique, which is based as a machining method on spark erosion, is very well suited for making electrically conductive materials of various hardness into the correct shape with high speed and precision.EDM is a contactless method with which material can be removed over very small lengths without mechanical stresses arising in the material as a result. The material is formed by highly localized melting and evaporation due to electrical discharges between an electrode and the material to be processed. The discharges forming minute plasma channels at temperatures up to 10,0000°C locally melt very small amounts of the material. When the current flow is interrupted, the plasma generated collapses and the vacuum created draws the molten material out into the surrounding dielectric medium. In order for discharges to take place, the material must have sufficient electrical conductivity, while material hardness is of no consequence. Therefore, in principle all metals and many semiconductors are suitable for EDM and also for micro-EDM.Micro-EDM is a specific form of EDM in which the workpieces may have features as low as about 10 μm. These small features are achieved with electrodes which are also very small. The orders of magnitude of apertures which are already used for micro-optics can therefore be achieved without problems even by means of micro-EDM. In addition, the micro-EDM method is significantly faster than planar integration techniques.According to a preferred embodiment of the invention, the disk stack is perforated in step (d) by means of high-speed mechanical micro drilling. For this purpose, VHM microbreders can be used, for example. In this way, it is possible to realize borehole diameters of a few millimeters just as well as borehole diameters of only 30 μm or even only 10 μm.According to a preferred embodiment of the invention, the drilling through of the plate stack in step (d) is effected by means of vibration drilling or by means of ultrasonic drilling. The principle of vibration drilling is to generate axial oscillations or oscillations in addition to the advancement motion of the drill, so that the drill chips break up and can then be easily removed from the cutting zone. A distinction is made between self-sustaining vibration systems and forced vibration systems. In vibration drilling with natural vibration, the natural frequency of the tool is used to make it natural during cutting. The oscillations can be maintained by a mass-spring system in the tool holder itself. Another possibility is the use of a piezoelectric system for generating and controlling oscillations. These systems allow high vibration frequencies (up to 2 kHz) at small dimensions (a few μm) and are particularly suitable for drilling small holes.Ultrasonic drilling uses ultrasonic vibrations to generate a borehole. This is a material-machining method which does not work in a rotary-machining manner. It can be used in particular in the case of hard and brittle materials. The drilling tool is caused to oscillate in the direction of advance by ultrasonic waves generated in an ultrasonic transducer and also excites the grains of a fed abrasive suspension to oscillate. During a short fraction of the period of oscillation, the workpiece is ablated in micro-domains. It is also possible to supplement conventional drilling with the additional use of ultrasound to improve working parameters.According to a preferred embodiment of the invention, the piercing of the plate stack in step (d) is effected using a focused ion beam (FIB). If high-energy ions strike a sample, they sputter atoms out of the surface. Due to the sputterability, a focused ion beam can be used as a tool for micro- and nano-machining and materials in the micro- and nano-range can be changed or machined. Gallium ions are used, for example, as focused ions, but other ions can also be used. Features in the range from 10 to 15 nm can be milled by means of focused ion beams; milling of features in the micrometer range is possible over the full circumference and across all. A problem with the use of a focused ion beam is only its relatively low depth of field. Therefore, it may be difficult to bore thick disks or thick disk stacks at once. However, also for this case there are solutions, for example the division of a plate stack into a plurality of sub-stacks and then the respective drilling through of the sub-stacks by means of the FIB, in particular in the case of lens transitions at which an exact alignment of the apertures with respect to one another of different plates is very critical. Subsequently, the sub-stacks can be assembled to form an overall stack.In the drilling methods described above, the material removed by drilling must be removed from the stack of plates. According to a preferred embodiment of the invention, therefore, flushing holes can be provided in the plates of the plate stack, which flushing holes have a larger diameter than the apertures in the first plate of the micro-optic and in the second plate of the micro-optic. These flushing holes can be produced by the same or by other methods as the apertures in the first plate of the micro-optic and in the second plate of the micro-optic, the method itself is not decisive here. Instead, it is important that the diameter of the flushing holes is selected such that during a flushing process in a process chamber after the plate stack has been drilled through, the removed material can be removed or flushed out through these flushing holes by means of a flushing process. A liquid, for example, can be used as flushing agent, in particular in a metal drilling method. However, it is also possible to use a gas as flushing agent, for example after drilling by means of laser drilling or after using a focused ion beam.Flushing holes also make it possible to remove or flush out auxiliary materials used in the production of the plate stack / the microoptics. It is possible, for example, to introduce a liquid between the plates of the plate stack before a mechanical drilling operation, then cool it down until it solidifies and then carry out the drilling through of the plate stack. As a result, forces acting during the drilling can also be absorbed by the solidified liquid. After drilling through, the plate stack can be heated again, the solidified liquid / the solid is liquefied again and can then be flushed out through the flushing holes.According to a preferred embodiment of the invention, the method further comprises the following step: after the piercing according to step d), flushing the plate stack and removing drilling material through flushing holes in the first plate of the micro-optic and in the second plate of the micro-optic, wherein the following relation applies for a diameter S of the flushing holes in relation to the diameter A of the apertures in the first plate of the micro-optic and in the second plate of the micro-optic: D≥10A, preferably D≥100A.According to a further preferred embodiment of the invention, the method further comprises the following steps:before drilling according to step d)filling an intermediate space between the first plate of the micro optic and the second plate of the micro optic with a liquid flushing agent, andcooling the flushing agent and thereby solidifying the flushing agent; andafter the piercing according to step d)heating the flushing agent and thereby liquifying the flushing agent; andremoving the flushing agent from the intermediate space.For filling with the flushing agent and for removing the flushing agent, the flushing holes described above can serve.According to a further preferred embodiment of the invention, at least one of the plates of the plate stack comprises an insulating material as base material, in particular a ceramic as base material, and the method further comprises the following steps, which are carried out temporally before the method steps (a) to (d): (e) producing a plurality of coarse apertures in the at least one plate with the insulating material as base material; and (f) metallising the coarse apertures; wherein, in the later carrying out of method step (d), the metallised coarse apertures are perforated and the plurality of apertures are thus formed.In this exemplary embodiment, therefore, not the entire plate of the plate stack is conductive, but only a partial region thereof, namely the regions which are metallized around the coarse apertures. This is sufficient to be able to carry out all material processing processes which require the conductivity of the material which has to be drilled through. The diameter of the coarse apertures is naturally larger than the diameter of the apertures of the finished multi-aperture plates. The metallized coarse apertures, on the other hand, are smaller in diameter than the finished aperture diameters in the multi-aperture plate.According to a preferred embodiment of the invention, the plating of the coarse apertures is effected by means of sputtering and / or by means of electroplating.According to a preferred embodiment of the invention, in method step (d) the plurality of apertures is produced in the plates of the plate stack simultaneously. For this purpose, a plurality of drilling means can be used simultaneously. These can be, for example, a plurality of laser pulses during laser drilling or else a multiplicity of electrodes which are firmly oriented with respect to one another (so-called "manhattan electrodes") during the micro-EDM method. This way of simultaneously producing boreholes is very quick.According to an alternative embodiment of the invention, in method step (d) the plurality of apertures is successively produced in the plates of the plate stack. Thus, the entire stack of plates is first completely perforated at a first location, then it is completely perforated at a second location, and so on. In this embodiment variant, the procedure of the drilling method used is relatively simple.According to a preferred embodiment of the invention, the plurality of apertures each have a diameter A, wherein the following applies: 40 μm≤A≤400 μm, preferably 80 μm≤A≤400 μm or 110 μm≤A≤400 μm. For circular apertures, the diameter naturally corresponds to twice the radius. In the case of apertures of different shapes, for example elliptical apertures, the smallest possible distance of hole walls from one another is defined as the diameter A. In the case of ellipses, this then corresponds to twice the small half axis. In stepped apertures, which can be produced, for example, by means of stepped electrodes or by means of a plurality of drilling steps (for example first drilling a plate with a small drilling agent, then partially drilling it with a larger drilling agent), the diameter A refers to the minimum diameter.According to a preferred embodiment of the invention, the shape of the apertures in the plates of the plate stack is round, elliptical, n-count or irregular in shape. The method according to the invention is thus very flexible in this case.According to a preferred embodiment of the invention, the centers of apertures adjacent to one another in the plates of the plate stack have a distance B for which the following applies: 70 μm≤B≤400 μm, preferably 90 μm≤B≤400 μm or 120 μm≤B≤400 μm.According to a preferred embodiment of the invention, the following applies to a thickness C of a plate of the plate stack: 20 μm≤C≤500 μm, preferably 150 μm≤C≤500 μm or 250 μm≤C≤500 μm.According to a preferred embodiment of the invention, the following applies for a plate spacing D of plates of the plate stack which are directly adjacent to one another: 1 μm≤D≤100 μm, preferably 20 μm≤D≤100 μm or 40 μm≤D≤100 μm.According to a preferred embodiment of the invention, the following applies to a total height H of the plate stack: 50 μm≤H≤100 0 μm, preferably 300 μm≤H≤1000 μm or 500 μm≤H≤1000 μm.Thus, by means of the method according to the invention it is possible to bore also relatively thick plates and plates which are relatively far apart from one another, namely by means of a rapid and precise method. Particularly with the larger dimensions, the production process by means of the known planar integration techniques is very much slower.According to a preferred embodiment of the invention, the microoptics have at least one second or further plate stack. In this case, the second or further plate stack of the microoptics can be produced by means of the method steps (a) to (d). However, it is also possible for the second or further plate stack of the microoptics to be produced or have been produced by means of planar technology and / or lithographic methods. In principle, other production methods are also possible.According to a further preferred embodiment of the invention, in a method step (g) the alignment of the first plate stack and the second or further plate stack with respect to one another takes place. If several stacks of plates are aligned with one another, great precision is required. However, this subsequent alignment of plate stacks or apertures located therein is naturally less accurate than the inherent positioning of the apertures within a plate stack if associated apertures have been produced exactly by means of the same method step. It may therefore be useful to provide the alignment of plate stacks with respect to one another at transitions between different plate stacks at which, electron-optically, a greater insensitivity to misalignment exists. In this connection, reference is made once again to what is being carried out in connection with focused ion beam drilling. The sub-stacks described in this case correspond in principle to a plurality of stacks. Critical lens transitions should, as far as possible, belong to the same plate stack which has preferably been produced by means of the method according to the invention comprising steps (a) to (d).According to a further aspect of the invention, this relates to a microoptics for a multiplicity of particle beam systems which have been produced according to the method as described above in a plurality of variant embodiments.According to a further aspect of the invention, this relates to a microoptics for a multiplicity of particle beam systems, in particular for a multibeam particle microscope. In this case, the microoptics have a first multi-aperture plate consisting of metal and a second multi-aperture plate consisting of metal. For the aperture diameters A of the first multi-aperture plate and of the second multi-aperture plate, A≥150 μm applies in each case. Furthermore, the following applies in each case to the thicknesses C of the first multi-aperture plate and of the second multi-aperture plate: C≥250 μm. The following applies to the plate distance D between the first multi-aperture plate and the second multi-aperture plate: D≥30 μm.The microoptics described are therefore a relatively large microoptics which is additionally also produced from metal. Such a micro-optic can be produced with the known planar integration techniques either not at all or only with considerable time expenditure.According to a further aspect of the invention, it relates to a multiplicity of particle beam systems, in particular to a multi-beam particle microscope, having a microoptical system as described above.According to a preferred embodiment of the invention, during operation of the multiplicity of particle beam systems, a voltage U can be applied to the first multi-aperture plate and / or to the second multi-aperture plate of the microoptical unit, with U≥250 V, preferably U≥300 V or U≥350 V. The application of voltages of this high level to a multi-aperture plate is thus normally not possible in the case of the known microoptical units which are produced by means of planar integration techniques. Instead, only voltages of the order of magnitude of less than 200 V can be used there. Otherwise, flashovers occur between different multi-aperture plates. When using said high voltages, sometimes significantly more than 250 V, relatively large plate spacings D are necessary. This is normally not to be achieved by means of grown insulator layers such as, for example, silicon oxide, but already by means of other production methods, since the thicknesses of insulator layers are typically limited in terms of the method in growing methods. It is then particularly advantageous that insulators can also be drilled through by means of some of the described production methods or drilling methods according to the invention (for example by means of laser drilling).The various embodiments and aspects of the invention may be combined wholly or partly with each other, as long as no technical contradictions result thereby.The invention will be better understood with reference to the accompanying figures. The following are shown: FIG. 1 shows schematically a multiplicity of particle beam systems; FIG. 2 shows a schematic structure of a micro-optic; FIG. 3 schematically shows an alignment problem in multi-aperture plates; FIG. 4 shows schematically method steps of a production method according to the invention for a microoptics; FIG. 5 shows a flow chart of a production method according to the invention; FIG. 6 shows schematically process steps of a production process according to the invention; FIG. 7 shows schematically process steps of a production process according to the invention; FIG. 8 shows schematically aspects of a production method according to the invention; FIG. 9 : shows schematically process steps of a production process according to the invention; FIG. 10 shows schematically a Manhattan electrode and a multi-aperture plate produced therewith; FIG. 11 shows schematically multi-aperture plates of a micro-optic; FIG. 12 schematically shows aspects of a manufacturing method for a micro optic; FIG. 13 shows a further flow diagram of a production method according to the invention.FIG. 1 schematically shows a plurality of particle beam systems 1 in the form of a multi-beam particle microscope 1. A diverging particle beam 309 is collimated by a sequence of condenser lenses 303.1 and 303.2 and impinges on a multi-aperture arrangement 305 which forms a micro-optic. The multi-aperture arrangement 305 comprises a plurality of multi-aperture plates 306 and a field lens 308. A plurality of individual particle beams 3 or individual electron beams 3 is generated by the multi-aperture arrangement 305. Centers of apertures of the multi-aperture plate arrangement are arranged in a field which is imaged onto a further field which is formed by beam spots 5 in the object plane 101. The distance between centers of apertures of a multi-aperture plate 306 may be, for example, 5 μm, 100 μm and 200 μm. The diameters A of the apertures are smaller than the pitch of the centers of the apertures, examples of the diameters are 0.2 times, 0.4 times and 0.8 times the pitches between the centers of the apertures.The multi-aperture arrangement 305 and the field lens 308 are configured to generate a plurality of focal points 323 of primary beams 3 in a raster arrangement in a surface 321. The surface 321 may not be a planar surface but may be a spherically curved surface to keep a 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 image the beam focus 323 in a reduced manner from the intermediate image surface 325 into the object plane 101. The first individual particle beams 3 pass between the beam splitter 400 and a collective beam deflection system 500, with which the plurality of first individual particle beams 3 is deflected during operation and the image field is scanned. The first individual particle beams 3 impinging into the object plane 101 form, for example, an essentially regular field, wherein distances between adjacent impingement locations 5 can be, for example, 1 μm, 10 μm or 40 μm. The field formed by the impingement locations 5 can have, for example, a rectangular or a hexagonal symmetry.The object to be inspected 7 may be of any kind, for example, a semiconductor wafer or a biological sample, and may include an array 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 may include 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 the object 7 generate interaction products such as secondary electrons, back-scattered electrons or primary particles which have undergone a movement reversal for other reasons, which originate 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 into secondary particle beams 9. In this case, the secondary beams 9 downstream of the objective lens 102 pass through the beam splitter 400 and are fed to a projection system 200. The projection system 200 comprises an imaging system 205 having projection lenses 208, 209 and 210, a contrast aperture 214 and a multi-particle detector 207. Sites of impingement 25 of the second individual particle beams 9 on detection regions of the multi-particle detector 207 are situated in a third field at a regular distance from one another. Exemplary values are 10 μm, 100 μm, and 200 μm.The multi-beam particle microscope 1 furthermore has a computer system or a control unit 10, which in turn can be embodied in one part or in multiple parts, and which is embodied 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.Further information on such multi-beam particle beam systems or multi-beam particle microscopes 1 and components used therein, such as particle sources, multi-aperture 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 / 06017 A 2 and the German patent applications DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1, the disclosure of which is incorporated in its entirety by reference into the present application.The multi-aperture arrangement 305 forms a micro-optics 305, by means of which, in the example shown, during operation of the plurality of particle beam system 1, the plurality of first individual particle beams 3 are first generated at the first of the multi-aperture plates (so-called filter plate) and are also actively formed at further multi-aperture plates. The microoptics 305 themselves can be designed differently in this case.FIG. 2 shows, by way of example, a microoptical unit 305 which is designed as a multi-beam generator 305. In the example shown, the multi-beam generator 305 comprises, in the z-direction, which corresponds to the propagation direction of the individual particle beams 3, a sequence having six multi-aperture plates 304, 306.1, 306.2, 306.3, 306.4 and 310 and a global condenser lens 307. Each of the multi-aperture plates 304, 306.1 to 306.4 and 310 comprises a plurality of apertures 351 through which the plurality of individual particle beams 3 pass, respectively. The cross-section through the apertures 351 in FIG. 2 is not true to scale.The plurality of multi-aperture plates 304, 306.1, 306.2, 306.3, 306.4 and 310 are spaced apart by spacers 83.1 to 83.5. Furthermore, a spacer 86 is provided between the final multi-aperture plate 310 and the global lens electrode 307. By the impingement of a collimated particle beam or electron beam 309, the plurality of first individual particle beams 3 is generated during the passage through the first multi-aperture plate 304, which is also called a filter plate or a pre-aperture plate. The pre-aperture plate 304 comprises a metallic layer 99 on its beam input side for stopping and absorbing the electrons of the electron beam 309 impinging thereon around the plurality of apertures 85. In the example shown, the material of the pre-aperture plate 304 is made of a conductive material, e.g. of doped silicon, and is at ground potential.The next multi-aperture plate in the example shown in FIG. 2 is a multi-stigmator plate 306.1. The multi-stigmator plate 306.1 comprises a plurality of four or more electrodes 82, e.g. eight electrodes for each of the apertures. During the operation of the multi-beam particle microscope 1, different voltages, for example in the range between -20 V and +20 V, can be applied to each of these electrodes and thereby individually influence each individual particle beam 3. It is possible, for example, to deflect each individual particle beam 3 in each direction up to a few μm with an antisymmetrical voltage difference in order to precorrect a distortion correction of the illuminating unit 100. An astigmatism precorrection of each individual particle beam 3 can likewise be carried out. With an offset voltage, each multipole element can additionally function as a single lens.The multi-aperture plates 306.2, 306.3 and 306.4 can in principle be any desired trajectory correction plates which are monolithically formed and to which a voltage V 1, V 2 or V 3 is applied in each case in the example shown. It is also possible for the multi-aperture plates 306.2, 306.3 and 306.4 to form a single lens array. Different apertures 351 in the same multi-aperture plate 306.2, 3606.3 and 306.4 can be identical or different in design, for example have different diameters, in order to take account of a field dependence of the correction in the course correction of the individual particle beams 3.The multi-aperture plate 310 is a two-layered multi-aperture plate and comprises a plurality of ring electrodes 79 for the plurality of apertures, wherein each ring electrode is configured to individually change or correct a focal position of the first individual particle beam 3 passing through it. The upper layer is insulated from the layer having the ring electrodes 79 and made of a conductive material such as doped silicon.The field lens 307 comprises a ring electrode 84 to which a high voltage of, for example, 3 kV to 20 kV can be applied, e.g., 12 kV to 17 kV. In the example shown, the condenser lens 307 provides a global electrostatic lens field for global focusing of the plurality of individual particle beams 3.The micro-optics 305 illustrated in FIG. 2 or their multi-aperture plates can / can be produced in principle by means of known production methods or by means of planar integration techniques. At least some multi-aperture plates, for example the multi-aperture plates 306.2, 306.3 and 306.4, can, however, also be produced by means of the production method according to the invention. Because of the special performance of such multi-aperture plates 306.2, 306.3 and 306.4 produced according to the invention (application of very high voltages V, V2, V3 and relatively large plate spacings or large thickness of spacers / insulators 83.2, 83.3, 83.4, 83.5) it is also possible that e.g. the multi-aperture plate 310 with the ring electrodes 81 is thereby superfluous.FIG. 3 schematically shows an alignment problem in multi-aperture plates 350, which have each been produced independently of one another, i.e. each individually. Figure 3a schematically shows the provision of three plates 360 without openings. FIG. 3 bshows schematically the use of a drilling means 900, which can in principle be of any desired type. In this respect, FIG. 3 is only the principle. The direction of action of the drilling means 900 is schematically indicated in FIG. 3 b by the arrow. Openings 351 are formed in the plate 360 through the drilling means 900, whereby the plate 360 becomes a multi-aperture plate 350. It should be noted that for reasons of easier illutriability, only one opening 351 is illustrated in FIG. 3, but a plurality of openings 351 are naturally present in a multi-aperture plate 350. It is now illustrated in FIG. 3D that the three multi-aperture plates 350.1, 350.2 and 350.3 are assembled to form a multi-aperture arrangement 305 or a micro-optic 305. For this purpose, the conductive multi-aperture plates 350.1, 350.2 and 350.3 are aligned with one another and fixed and insulated. In the example shown, this is realized by the spacers 370.1 and 370.2. In this case, the openings 351.1 and 351.2 and 351.3 are not arranged exactly one above the other, i.e. not centrally one above the other. They are therefore not aligned. An exact arrangement or orientation with respect to one another is very difficult, if not impossible, for the openings 351.1, 351.2, 351.3 in the multi-aperture plates 350.1, 350.2 and 350.3. This applies in particular when the multi-aperture plates 350.1, 350.2 and 350.3 are made of metal: they are then in fact not transmissive to visible light or to infrared radiation, so that an optically based alignment, as typically used in finely positioning devices (die-bonder), is greatly made more difficult. An exchange of semiconductor-based plates of a multi-aperture arrangement 305 for metal plates is therefore not easily possible.However, one solution approach is offered by the production method according to the invention, in which, on the one hand, plates made of metal can be used to produce a microoptical 305 and, on the other hand, can also be aligned precisely enough. FIG. 4 schematically shows method steps of a production method according to the invention for a microoptics 305: FIG. 4 a shows first three plates 360.1, 360.2 and 360.3 for the micro-optics 305, which in the example shown are not only conductive but made of metal. FIG. 4b shows the arrangement of the plates 360.1, 360.2 and 360.3 relative to one another. In this case, the plates 360.1, 360.2 and 360.3 are fixed relative to one another and are electrically insulated from one another by spacers 370.1 and 370.2. The spacers 370.1 and 370.2 can be made of silicon oxide, for example. FIG. 4c now schematically shows the drilling of the plate stack with the plates 360.1, 360.2 and 360.3 by means of a drilling means 900. This is only schematically shown in FIG. 4 c, the drilling direction is indicated by the arrow. It is important that the entire stack of plates is basically drilled through at once with the same drilling means 900 during the same drilling process. FIG. 4 d shows the result of the drilling process: the apertures 351.1, 351.2 and 351.3 are perfectly aligned with one another and the centers of the apertures 351.1, 351.2 and 351.3 lie centrally on the axis Z in the example shown. In this case, in turn, a sequence of apertures 351.1, 351.2 and 351.3 is shown only by way of example; naturally, a plurality of apertures or sequences of apertures are present in the multi-aperture plates 350.1, 350.2 and 350.3.It is also conceivable that not only the plates 360.1, 360.2 and 360.3 are drilled through by means of the drilling means 900, but also insulating plates or layers. Whether this is possible depends only on the drilling method used.FIG. 5 schematically shows a flow diagram of a production method according to the invention for a micro-optics 305 for a plurality of particle beam systems 1: in a method step S 1, first a first plate 360.1 of the micro-optics 305 is provided, which is electrically conductive.In a method step S 2, a second plate 360.2 of the microoptics 305 is provided, which is electrically conductive.In a method step S 3, a plate stack is produced: the production of a plate stack comprises stacking the first plate 360.1 of the micro-optic 305 and the second plate 360.2 of the micro-optic 305 one above the other, wherein the first plate 360.1 of the micro-optic 305 and the second plate 360.2 of the micro-optic 305 are fixed relative to one another in the plate stack and are electrically insulated from one another. This can be realized, for example, by the use of insulating spacers 370.1, 370.2.Then, in a method step S 4, the drilling through of the entire generated plate stack with at least the first plate 360.1 and the second plate 360.2 of the micro-optic 305 takes place and thereby the generation of both a first plurality of apertures 351.1 in the first plate 360.1 of the micro-optic 305 and a second plurality of apertures 351.2 in the second plate 360.2 of the micro-optic 305. As a result, the sequence of apertures 350.1, 350.2 in the plates 360.1, 360.2 of the plate stack produced during the same drilling process is aligned exactly with respect to one another, namely inherent in the process. Optionally, the plate stack can further comprise at least one further and thus at least one third plate 360.3 of the micro-optic 305, which is electrically conductive. In this case, the third plate 360.3 of the microoptics 305 is fixed relative to the first plate 360.1 of the microoptics 305 and the second plate 360.2 of the microoptics 305 and is electrically insulated from them. The third plate of the microoptics 305 is also perforated when carrying out method step S 4, with the result that a third multiplicity of apertures 351.3 is thereby produced in the third plate 360.3 of the microoptics 305. One or more of the aforementioned plates of the micro-optic 305 may be made of a metal. According to a preferred embodiment of the invention, all perforated plates are made of metal. However, it is also possible that in addition to the conductive plates other plates are provided which are not conductive but consist of an insulating material, for example of silicon dioxide.The drilling through of the plate stack according to method step S 4 can be carried out in various ways: examples of the drilling methods are, for example, laser drilling, drilling by means of micro-EDM, high-speed mechanical micro-drilling, vibration drilling, ultrasonic drilling or the use of a focused ion beam (FIB). For the details of these methods, reference is made to the statements in the general description part of the invention.Optionally, in a further method step S 5, the flushing of the plate stack and a removal of drilling material can take place through flushing holes in the first plate 360.1 of the microoptics 305 and in the second plate 306.2 of the microoptics 305. In this case, the relation: D≥10A, preferably D≥100A, can apply to a diameter S of the flushing holes in relation to the diameter A of the apertures in the first plate 306.1 of the micro-optic 305 and in the second plate 306.2 of the micro-optic 305.A modified production method for a micro-optics 305 of a plurality of particle beam systems 1 is illustrated in the flow chart in FIG. 13 : First, the method steps S 1 to S 3 are carried out therein as described above. Before the plate stack according to step S 4 is drilled through, in the described exemplary embodiment in step S 11 a filling of an intermediate space between the first plate 306.1 of the microoptics 305 and the second plate 306.2 of the microoptics 305 with a liquid flushing agent takes place, and in step S 12 a cooling of the flushing agent and thereby solidification of the flushing agent takes place. A temperature control can be realized, for example, by carrying out the method within a process chamber whose internal temperature is adjustable or the liquid is supplied in heated form and then cools down by itself. Then, in step S 4, the entire disk stack is perforated. By arranging / providing the solidified flushing agent, forces acting on the plates 306.1 and 306.2 can be absorbed, distributed and dissipated better during drilling. Bending of the plates 306.1 and 306.2 can thereby be better prevented. In a further method step S 13, the flushing agent is heated and the flushing agent is thereby liquefied. In this case, for example, the entire plate stack can be heated and the flushing agent is also heated in this case. In a further method step S 14, the rinsing agent, which is now again liquid, is removed from the intermediate space. For filling with the rinsing agent and for removing the rinsing agent, the above-described rinsing holes may be used.FIG. 6 schematically shows method steps of a production method according to the invention. In the exemplary embodiment illustrated in FIG. 6, the plates 360 of the micro-optic 305 are non-conductive or not fully conductive. Their conductivity is only given in sections, namely in the region around the apertures 351 which are to be formed only in the following:Specifically, first three plates 360 that are not conductive per se are provided for the micro-optic 305. The plates 360 may include an insulating material as a base material, for example, a ceramic as a base material. Coarse apertures 361 can now be formed in these plates 360. The coarse apertures 361 are larger than the apertures 362 of the micro-optics 305 to be finally produced.In a further method step (cf. FIG. 6 c ), the coarse apertures 362 are metallized. The plating of the coarse apertures 361 can be effected, for example, by means of sputtering or by means of electroplating. Around the coarse apertures or adjacent to the coarse apertures 362, conductive regions 363 are formed. These in turn have openings 363. The diameter thereof is smaller than the diameter of the final apertures 351 of the micro-optic 305.In a further method step, the plates 360.1, 360.2 and 360.3 with the metallized coarse apertures 361 are fixed relative to one another and arranged electrically insulated from one another. The spacers 370.1 and 370.2 can be electrically insulating, but they do not necessarily have to be insulating, since the plate material of the plates 360.1, 360.2 and 360.3 as ceramic can already be sufficiently insulating. The openings 363.1, 363.2 and 363.3 are not perfectly aligned with each other. However, they do not yet have to be at this point in time of the production process:As shown in FIG. 6 e, the metallized coarse apertures 361 and the conductive regions 362.1, 362.2 and 362.3 are subsequently drilled through. In FIG. 6 e, a drilling means 900 and its direction of movement is again schematically indicated for this purpose.As shown in FIG. 6f, apertures 351.1, 351.2 and 351.3 which are aligned exactly with respect to one another are formed as a result, again perfectly or inherently within the process.By means of the production method described in FIG. 6, therefore, not only monolithic multi-aperture plates 350.1, 350.2 and 350.3 can be produced, which are already (completely) conductive per se. Instead, it is also possible to realize ring electrodes by means of the production method according to the invention. In this case, the ring electrodes are formed by the conductive regions 362.1, 362.2 and 362.3 in the example shown. The supply of lines to the individual ring electrodes must be realized in a further method step; this is more complex than in the case of monolithic multi-aperture plates 350, but can likewise be realized. For this purpose, a metal printing method is suitable, for example, already before the plate stack is joined together. It is also possible, for example, for conductor tracks to be applied by a combination of sputtering and electroplating.FIG. 7 schematically shows method steps of a production method according to the invention for a microoptics 305. The disk stack shown in FIG. 7 a, comprising the disks 360.1, 360.2 and 360.3, can be produced, for example, as described in connection with FIGS. 4 aand 4 b. However, unlike the illustration in connection with FIG. 4 c, the drilling through of the plate stack in FIG. 7 ais now different, namely with regard to the drilling direction: the plate stack is namely drilled through in a beveled manner. The resulting beveled apertures 351.1, 351.2 and 351.3 are also exactly aligned with each other, as indicated by the dotted auxiliary lines in FIG. 7B. The apertures 351.1, 351.2 and 351.3 are not exactly circular, however, but slightly elliptical, in this oblique drilling. The degree of ellipticity depends on the degree of inclination during drilling relative to the normal of the plate stack.FIG. 8 schematically shows aspects of a production method according to the invention, wherein the drilling of the plate stack is carried out using a focused ion beam (FIB). The stack of plates shown comprises a total of six membranes 360.1, 360.2, 360.3, 360.4, 360.5 and 360.6, which are clamped in a frame. This is illustrated by reference numeral 380 indicating a frame region and reference numeral 381 indicating a diaphragm region.The disk stack shown should have the functionality of, for example, a single lens after the entire disk stack has been drilled through. For this reason, voltages U1, U2 and U3 are indicated schematically in FIG. 8. However, instead of a single plate 360 having the total height H over the entire plate width, two membranes having the small thicknesses h are provided. In this case, the corresponding stress is applied to the lower and the upper membrane. Viewed electron-optically, the fact that cavities 382.1, 382.2 and 382.3 are provided between the membranes 360.1 and 360.2, between 360.3 and 360.4 and between 360.5 and 360.6 makes no appreciable difference. Spacers which are insulating, 370.1 and 370.2 are again arranged in a known manner between the respective associated membrane pairs.When drilling through the plate stack, the focused ion beam can now be used, starting from above, to initially bore through the uppermost membrane 360.1, then through the next membrane 360.2 and so forth, and in principle in the same method step or without the position of the FIB column having to be changed, in any case not in the x-direction or y-direction, that is to say the x,y-positions of the FIB column and therefore also the x,y-positions of the apertures 351 to be produced are fixed. The fact that only the thin membrane sections each have to be perforated with the height h can take account of the fact that a focused ion beam has only a relatively small depth of field and can therefore only bore through relatively thin layers. Drilling through the entire stack of plates as shown in Fig. 8 is therefore particularly suitable for stacks of plates of a small overall height, for example up to a height of a few microns.For cases in which the plate stack overall has a greater height and the low depth of focus of the focused ion beam becomes a problem, the method sequence illustrated in FIG. 9 represents a solution: the overall stack with the plates 360.1 to 360.6 is divided into four sub-stacks. In particular, the plates 360.2 and 360.3 and the plates 360.4 and 360.5 form in each case independent stacks in the sense of the definition according to patent claim 1. In this case, the stack according to FIG. 9 bconstitutes a stack in which a lens transition takes place. Here, the alignment of the apertures produced in the plates 360.2 and 360.3 is particularly critical. The same applies to the lens transition between the plates 360.4 and 360.5, as shown in FIG. 9c. The transitions within the same lens are, in contrast, not so critical. Therefore, without appreciable loss of performance of the micro-optics 305, it is possible to assemble the sub-stacks after the partial stacks (FIGS. 9 band 9C ) and the individual plates or membranes (FIGS. 9 aand 9D ) have been drilled through separately and to perform a corresponding alignment here. This assembly of the sub-stacks is indicated by the bracket in Fig. 9. This in turn produces the microoptical unit 305.In principle, it is possible for the plurality of apertures to be produced successively in the plates of a plate stack. However, it is also possible for the plurality of apertures in the plates to be produced at least partially simultaneously. An example of this is shown in FIG. 10 : FIG. 10 ashows an electrode of the manhattan type as drilling means 900. This comprises a plurality of electrodes 902 arranged on a base element 901. In principle, the manhattan-type electrode is thus a multi-electrode. With this, as it were, several openings can be produced in batches at different positions in a plate 360 simultaneously. The result of the piercing process is shown in FIG. 10 b: A multi-aperture plate 350 is shown having a plurality of circular apertures 351, the arrangement of which corresponds to the arrangement of the electrodes 902.The manhattan type electrode shown in Fig. 10 can be used, for example, in a micro-EDM method. However, the principle can also be applied to other drilling methods.FIG. 11 schematically shows a plurality of multi-aperture plates 350 of a micro-optic 305. FIG. 11 a shows a plurality of round apertures 351, each having the same diameter and being arranged in a regular manner. FIG. 11 bshows a multi-aperture plate 350 having circular apertures 351, the diameter of which however varies within the multi-aperture plate or is dependent on the position of the aperture in the respective plate 350. In the example shown, the diameter of the apertures 351 shows a radial dependence on the distance from the center C in the multi-aperture plate 350.FIG. 11 cshows a multi-aperture plate 350 with elliptical apertures 351. Its longitudinal axis I varies depending on the center M, namely with regard to orientation and size.All multi-aperture plates 350 shown in FIG. 11 are monolithic aperture plates 350, to each of which only a single voltage is applied. Because of the conductivity of the plates 350, the apertures 351 produce an effect or lens effect, the size of which is then only dependent on the size and shape of the aperture.In principle, the shape of the apertures 351 in the plates 360, 350 of the plate stack can be round, elliptical, n-count or irregular in shape. The apertures themselves are preferably arranged by means of a grid, for example by means of a hexagonal grid. However, they can also be arranged, for example, in a square or rectangular grid.According to one exemplary embodiment, mutually adjacent apertures 351 in the plates of the plate stack have a spacing B for which the following applies: 70 μm≤B≤400 μm, preferably 90 μm≤B≤400 μm or 120 μm≤B≤400 μm.For a thickness C of a plate 360, 350 of the plate stack, the following can apply, for example: 20 μm≤C≤500 μm, preferably 150 μm≤C≤500 μm or 250 μm≤C≤500 μm.According to one exemplary embodiment, the following can apply to a plate spacing D of mutually adjacent plates 350, 360 of the plate stack: 1 μm≤D≤100 μm, preferably 20 μm≤D≤100 μm or 40 μm≤D≤100 μm.According to one embodiment of the invention, the following relationship applies to a total height H of the plate stack: 50 μm≤H≤1000 μm, preferably 300 μm≤H≤1000 μm or 500 μm≤H≤1000 μm. The overall height H of the plate stack is understood to mean that height of the plate stack which is simultaneously penetrated by means of a drilling means 900. Of course, the micro-optics 305 can also have at least one second or at least one further plate stack. It is possible that the second or further plate stack of the microoptics is likewise produced by means of the described method according to the invention. However, it is also possible for the second or further plate stack of the microoptics 305 to be produced by means of other methods, for example by means of planar technology and / or lithographic methods. The second or further disk stack may then be aligned relative to the first disk stack.With a correspondingly large dimensioning of the micro-optics 305, for example with an aperture diameter A with A≥150 μm, a thickness C of the multi-aperture plates 350 with C≥250 μm and a plate spacing D between the multi-aperture plates 350 of D≥30 μm, a relatively large micro-optics 305 can be provided. Relatively large voltages U can be applied to this relatively large micro-optics 305 during operation of a plurality of particle beam systems, for example U≥250 V, preferably U≥300 V and U≥350 V. This is of great advantage in particular in the case of plurality of particle beam systems which operate with a large plurality of individual particle beams 3, since in such systems the field dependence of imaging errors, for example an image field curvature or an image field astigmatism, is particularly large, especially in edge regions of a plurality of particle beam arrangements of a large raster.FIG. 12 schematically shows aspects of a further production method for a microoptics 305. In contrast to the methods already described above, an arrangement of different plates one above the other or of different layers one above the other is no longer drilled through jointly, but instead a negative mold 910 is provided, around which different layers are first built up. The negative mold 910 is removed at the end of the process, so that apertures 911 defined by the negative mold 910 are inherently exactly aligned with one another in the process. According to this example, a complex alignment problem is thus also avoided.Specifically, in a first method step, the negative mold can be provided as such. This may have, for example, a manhattan-like structure which defines the later position of apertures 911. In addition, this negative form can also provide individual electrodes, such as ring electrodes or lines, for supplying voltage to the electrodes. This central negative shape, which defines at least the dimensions of later apertures 911, can be configured in various ways. For example, it may be photoresist, silicon dioxide, etched metal (lidar process), coated metal (for deposition purposes), and so forth. In FIG. 12 a, the negative mold 910 is schematically illustrated as a central block. This central block is disposed on a substrate 390. This can be, for example, a wafer, for example made of silicon.After providing this basic structure including the negative mold 910, various layers may be deposited on the substrate 390. In the example shown, a first metallic layer 392 may be deposited on the substrate 390, for example, by means of sputtering or by means of sputtering and electroplating.Subsequently, another layer 393 is deposited on the conductive layer 392. In principle, this is an insulating layer 393. This can either be already insulating from the beginning (for example, depositing an insulator such as silicon dioxide via sputtering), or the layer can first be electrodeposited and then lose its originally present electrical conductivity by a heat treatment and become the insulator. Electrolytic processes of insulators are known in principle from the prior art in a different context.The described alternating deposition processes of conductive and non-conductive layers may be repeated. In the example shown, a metallic layer 394 is then deposited, subsequently a further insulating layer 395 is deposited, then a further metallic layer 396 and so on follows. At the end of the method, the negative mold 910 is then removed: this is schematically illustrated in FIG. 12 b. The apertures 911 formed in this case are aligned exactly with respect to one another.The synthetic advantage in which insulators are in principle applied galvanically and become the insulator only during a heat treatment or during baking has the advantage that in principle all layers 392 to 396 can be applied galvanically. This is simpler in process management, and any machine change during the application of different layers can be dispensed with. The handling of impurities is also more unproblematic in galvanic processes than in sputtering processes.The above-described exemplary embodiments are not to be understood as restrictive for the invention, but merely serve to better understand the invention. They can be combined completely or partially with one another, provided that no technical contradictions result as a result.List of reference characters1 Multi-particle beam system, multi-beam particle microscope 3 primary particle beams, first single particle beams 5 beam spots, sites of impingement 7 object, sample, wafer 9 secondary particle beams, second single particle beams 10 computer system, controller 15 sample surface, wafer surface 25 image point of a second single particle beam 81 multipole electrode 82 ring electrode 83 spacer 84 ring electrode 85 aperture 86 spacer 99 absorbing and conducting layer 101 object plane 102 objective lens 103 field lens 105 axis 108 beam crossover, cross-over 200 detector system 205 projection lens system 206 projection lens 207 multi-particle detector 208 projection lens 209 projection lens 210 projection lens 212 beam crossover, cross-over 214 aperture filter, Contrast diaphragm 222 Collective anti-deflection system 300 Beam generating device 301 Particle source 303 Collimating lens system 304 Multi-aperture array, filter plate 305 Micro-optics, multi-aperture arrangement, multi-beam particle generator 306 Multi-aperture plate 307 Field lens, aperture plate 308 Field lens 309 Particle beam 310 Multi-aperture plate 321 Intermediate image plane 323 Beamfoki 333 Holding region 335 Membrane region 350 Multi-aperture plate 351 Aperture 360 Plate 361 Coarse aperture 362 Conductive region 363 Opening in the conductive region 370 Spacer 380 Frame region 381 Membrane region 382 Cavity 390 Wafer 391 Metallic layer 392 Layer 393 Layer 394 Layer 395 Layer 396 Layer 910 Negative mold, photoresist 400 Beam splitter, Magnet arrangement 500 Scanning deflector 600 Moving table or positioning device 900 Drilling means 901 Base element 902 Manhattan-type electrode Z Axis M Center H Height Frame section h Height Membrane x Direction y Direction z Direction I Longitudinal axisReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedU.S. Pat. No. 7,244,949 B2

[0004] US 2019 / 0355544 A1

[0004] WO 2005 / 024881 A2

[0065] WO 2007 / 028595 A2

[0065] WO 2007 / 028596 A1

[0065] WO 2011 / 124352 A1

[0065] WO 2007 / 06017 A

[0065] DE 10 2013 016 113 A1

[0065] DE 10 2013 014 976 A1

[0065]

Claims

A method of manufacturing a micro-optic for a plurality of particle beam systems, comprising the steps of: (a) providing a first plate of the micro-optic that is electrically conductive; (b) providing a second plate of the micro-optic that is electrically conductive; (c) creating a plate stack comprising stacking the first plate of the micro-optic and the second plate of the micro-optic one above the other, wherein the first plate of the micro-optic and the second plate of the micro-optic are fixed relative to each other in the plate stack and are electrically isolated from each other; and (d) piercing the entire created plate stack with at least the first plate and the second plate of the micro-optic and thereby creating both a first plurality of apertures in the first plate of the micro-optic and a second plurality of apertures in the second plate of the micro-optic.The method according to claim 1, wherein the first plate of the micro-optic and / or the second plate of the micro-optic is metallic.Method according to one of the preceding claims, wherein the plate stack further comprises at least one further or, thus, at least one third plate of the micro-optics, which is electrically conductive, and wherein the third plate of the micro-optics is fixed relative to the first plate of the micro-optics and the second plate of the micro-optics and is electrically insulated from them, and wherein the third plate of the micro-optics is likewise perforated when carrying out the method step (d), such that a third plurality of apertures is thereby produced in the third plate of the micro-optics.Method according to the preceding claim, wherein the third plate of the micro-optic is metallic.Method according to one of the preceding claims, wherein the drilling through of the plate stack in step (d) is effected by means of laser drilling.The method according to any one of claims 1 to 4, wherein the drilling of the plate stack in step (d) is effected by means of micro-EDM.The method of any one of claims 1 to 4, wherein the drilling of the stack of plates in step (d) is performed by high speed mechanical micro drilling.Method according to one of Claims 1 to 4, wherein the drilling through of the plate stack in step (d) is effected by means of vibration drilling or by means of ultrasonic drilling.The method according to any one of claims 1 to 4, wherein the piercing of the plate stack in step (d) is performed using a focused ion beam (FIB).Method according to one of the preceding claims, wherein at least one of the plates of the plate stack has an insulating material as base material, in particular a ceramic as base material, and wherein the method further comprises the following steps, which are carried out before the method steps (a) to (d): (e) generating a plurality of coarse apertures in the at least one plate with the insulating material as base material; and (f) metalizing the coarse apertures; wherein, in the later carrying out of method step (d), the metallized coarse apertures are perforated and the plurality of apertures are thus formed.Method according to the preceding claim, wherein the metallisation of the coarse apertures is effected by means of sputtering and / or by means of electroplating.The method according to any one of the preceding claims, wherein in method step (d) the plurality of apertures in the plates of the plate stack is simultaneously produced.The method according to any one of claims 1 to 10, wherein in method step (d) the plurality of apertures is successively generated in the plates of the plate stack.Method according to one of the preceding claims, wherein the plurality of apertures each have a diameter A, wherein the following applies: 40 μm ≤ A ≤ 400 μm, in particular 80 μm ≤ A ≤ 400 μm or 110 μm ≤ A ≤ 400 μm.The method of the preceding claim, wherein the shape of the apertures in the plates of the plate stack is round, elliptical, n-count, or irregular in shape.Method according to one of the preceding claims, wherein apertures adjacent to one another in the plates of the plate stack have a spacing B for which the following applies: 70 μm ≤ B ≤ 400 μm, in particular 90 μm ≤ B ≤ 400 μm or 120 μm ≤ B ≤ 400 μm.Method according to one of the preceding claims, wherein the following applies to a thickness C of a plate of the plate stack: 20 μm ≤ C ≤ 500 μm, in particular 150 μm ≤ C ≤ 500 μm or 250 μm ≤ C ≤ 500 μm.Method according to one of the preceding claims, wherein the following applies to a plate spacing D of mutually adjacent plates of the plate stack: 1 μm ≤ D ≤ 100 μm, in particular 20 μm ≤ D ≤ 100 μm or 40 μm ≤ D ≤ 100 μm.Method according to one of the preceding claims, wherein the following applies to a total height H of the plate stack: 50 μm ≤ H ≤ 1000 μm, in particular 300 μm ≤ H ≤ 1000 μm or 500 μm ≤ H ≤ 1000 μm.Method according to one of the preceding claims, further comprising the following step: after the piercing according to step d), flushing the plate stack and removing drilling material through flushing holes in the first plate of the micro-optic and in the second plate of the micro-optic, wherein the following relation applies for a diameter S of the flushing holes in relation to the diameter of the apertures in the first plate of the micro-optic and in the second plate of the micro-optic: D ≥ 10A, in particular D ≥ 100A.Method according to the preceding claim, further comprising the following steps: before the piercing according to step d) - filling an intermediate space between the first plate of the microoptics and the second plate of the microoptics with a liquid flushing agent, and - cooling the flushing agent and thereby solidifying the flushing agent; and after the piercing according to step d) - heating the flushing agent and thereby liquifying the flushing agent; and - removing the flushing agent from the intermediate space.The method according to any one of the preceding claims, wherein the micro-optic comprises at least one second or further stack of plates.Method according to the preceding claim, wherein the second or further plate stack of the microoptics is produced by means of the method steps (a) to (d); or wherein the second or further plate stack of the microoptics is produced by means of planar technology and / or lithographic methods.The method according to the preceding claim, wherein the method further comprises the following step: (g) aligning the first plate stack and the second or further plate stack with each other.Micro-optics for a plurality of particle beam system, which have been produced according to the method according to one of the preceding claims.Micro-optics for a plurality of particle beam systems, wherein the micro-optics have a first multi-aperture plate consisting of metal and a second multi-aperture plate consisting of metal, wherein the aperture diameters A of the first multi-aperture plate and the second multi-aperture plate are each as follows: A ≥ 150 μm, wherein the thicknesses C of the first multi-aperture plate and the second multi-aperture plate are each as follows: C ≥ 250 μm; and wherein the plate distance D between the first multi-aperture plate and the second multi-aperture plate is as follows: D ≥ 30 μm.A multiple particle beam system, in particular a multiple beam particle microscope, having a microoptics according to one of Claims 25 to 26.The plurality of particle beam system according to the preceding claim, wherein during operation of the plurality of particle beam system a voltage U can be applied to the first multi-aperture plate and / or to the second multi-aperture plate, with U ≥ 250V, in particular U ≥ 300V or U ≥ 350V.

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