DE102023133567A1 - Method for producing a micro-optics for a multi-particle beam system, micro-optics and multi-particle beam system - Google Patents

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 invention

The invention relates generally to multi-beam particle systems and, more particularly, to multi-beam particle microscopes operating with a plurality of charged single-particle beams. Specifically, the invention relates to a method for manufacturing micro-optics for a multi-beam particle system, to micro-optics, and to a multi-beam particle system.

State of the art

With the continuous development of ever smaller and more complex microstructures such as semiconductor devices, there is a need for the further development and optimization of planar manufacturing techniques and inspection systems for the production and inspection of small dimensions of microstructures. For example, the development and manufacture of semiconductor devices requires verification of the design of test wafers, and planar manufacturing techniques require process optimization for reliable, high-throughput manufacturing. Furthermore, there is a recent demand for the analysis of semiconductor wafers for reverse engineering and customized, individual configuration of semiconductor devices. Therefore, there is a need for inspection tools that can be used at high throughput to examine 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”) with a size of up to 800 ^mm² . A semiconductor device comprises multiple semiconductor structures fabricated in layers on a wafer surface using planar integration techniques. Due to the manufacturing processes, semiconductor wafers typically have a flat surface. The feature size of the integrated semiconductor structures ranges from a few µm to critical dimensions (CD) of a few nanometers, with feature sizes becoming even smaller in the near future; it is expected that feature sizes or critical dimensions (CD) will correspond to the 3 nm, 2 nm, or even smaller technology nodes of the International Technology Roadmap for Semiconductors (ITRS) in the future. For the small feature sizes mentioned above, defects of the size of the critical dimensions must be identified in a short time over a very large area. 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 must be measured with an accuracy below 1 nm, for example, 0.3 nm or even less, and a relative position of semiconductor structures must be determined with an overlay accuracy below 1 nm, for example, 0.3 nm or even less.

A 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, for example, US 7 244 949 B2 and in US 2019/0355544 A1 disclosed. In a multibeam electron microscope, or MSEM, a sample is simultaneously irradiated with a plurality of single electron beams arranged in a field or grid. For example, 4 to 10,000 single electron beams can be provided as primary radiation, with each single electron beam separated from a neighboring single electron beam by a distance of 1 to 200 micrometers. For example, an MSEM has approximately 100 separate single electron beams (beamlets), arranged, for example, in a hexagonal grid, with the single electron beams separated by a distance of approximately 10 µm. The plurality of charged single particle beams (primary beams) are focused by a common objective lens onto a surface of a sample to be examined. The sample can be, for example, a semiconductor wafer attached to a wafer holder mounted on a movable stage. During the illumination of the wafer surface with the charged primary single-particle beams, interaction products, e.g., secondary electrons or backscattered electrons, emanate from the wafer surface. Their starting points correspond to the locations on the sample at which the plurality 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 multiple secondary single-particle beams (secondary beams), which are collected by the common objective lens and, through a projection imaging system of the multi-beam inspection system, impinge on a detector arranged in a detection plane. The detector comprises multiple detection areas, each of which comprises multiple detection pixels, and the detector records 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 stigma of the plurality of charged single-particle beams. The prior art multi-beam charged particle system further comprises at least one crossover plane of the primary or secondary charged single-particle beams. Furthermore, the prior art system comprises detection systems to facilitate adjustment. The prior art multi-beam particle microscope comprises at least one beam deflector (deflection scanner) for collectively scanning a region of the sample surface using the plurality of primary single-particle beams to obtain a field of view 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 known as a "beam separator" or "beam divider") is used. Separation is achieved using special arrangements of magnetic fields and/or electrostatic fields, for example, using a Wien filter.

Multi-particle beam systems are generally divided into systems that operate with a single column and systems that operate with multiple columns. In systems with a single column, 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, the individual particle beams are relatively close to one another. Despite the partially global particle optical elements, even with single columns there is a need for the individual particle beams to be individually influenced and/or shaped in order to correct imaging errors such as field curvature, field astigmatism, and other aberrations. So-called micro-optics can be used for this individual influence and/or shaping of the individual particle beams. Micro-optics is often also referred to as a multi-beam particle generator for generating and shaping a large number of individual particle beams. The multi-beam particle generator or micro-optics comprises a sequence of multiple multi-aperture plates that can be used for active beam shaping, or at least one of which can be used for active beam shaping. For this purpose, electrodes that can be controlled collectively or individually can be provided in the area of the apertures. These can be ring electrodes or multipole electrodes, for example. According to another example, a multi-aperture plate can be monolithic, with a voltage applied across the multi-aperture plate as a whole, i.e., the monolithic multi-aperture plate is then at a specific potential, so that its openings, in interaction with other particle-optical elements, can create a lens effect. Other designs of a multi-aperture plate for active beam shaping are also possible.

For the best possible single-particle beam shaping/influencing, it is necessary that the apertures through which a single-particle beam passes are precisely aligned. For example, it may be necessary for the centers of the apertures to be exactly aligned. Furthermore, the apertures in known multi-aperture plates are relatively small; for example, aperture diameters are each less than 100 µm, e.g., only 90 µm or less. These two conditions—small aperture diameters and precise alignment of the apertures/electrodes, including control—can be met by using MEMS technologies to manufacture micro-optics. In other words, similar processes are used to manufacture micro-optics and their multi-aperture plates that can also be used in semiconductor production.

The applications of semiconductor components are opened up, for example, by combining regions with different doping levels or by the influence of insulating separation layers. To meet these requirements, various layers are deposited sequentially on a base substrate in the form of a disc, the so-called wafer, during the production of semiconductor components (so-called planar technology). Silicon, for example, is used as the base substrate, and silicon oxide, for example, is used as the insulating layer. The deposited layers can then be structured using lithographic processes. This allows the creation of integrated circuits with conductor tracks, i.e. semiconductor chips, or even micro-optics with multi-aperture plates for multi-particle beam systems.

As precise as the production of micro-optics using MEMS techniques is, there are still disadvantages to this type of manufacturing: The development time for producing a micro-optic device is relatively long, often between six months and nine months. Changes to the manufacturing process are difficult or only possible with considerable time expenditure. And overall, there are only a few semiconductor manufacturers that can produce Process control of semiconductor manufacturing is challenging and very expensive semiconductor manufacturing equipment is required.

Description of the invention

It is therefore an object of the invention to provide an improved method for producing a micro-optic system for a multi-particle beam system. The method should be faster than known methods, without compromising the quality of the micro-optics or impairing the achievable resolution in multi-particle beam systems. Furthermore, the method should be simple and cost-effective to implement.

This object is achieved by the subject matter of the independent patent claims. Advantageous embodiments of the invention emerge from the dependent patent claims.

1. (1) Es hat sich herausgestellt, dass das für eine Mikrooptik verwendete Material Silizium durchaus ernsthafte Probleme bereiten kann: Es können z.B. unerwünschte Oberflächenpotentiale auftreten und die Leitfähigkeit des Siliziums kann sich mit der Zeit verändern. Beides hat einen unerwünschten Einfluss auf die geladenen Einzel-Teilchenstrahlen beim Durchsetzen der Mikrooptik und somit auf die Strahlqualität und dadurch wiederum auf die mittels eines Vielzahl-Teilchenstrahlsystems erzielbare Auflösung bei dessen Betrieb.
2. (2) Außerdem hat sich überraschend herausgestellt, dass der Wunsch/ der Trend zu einer weiteren Miniaturisierung der Mikrooptik zwecks Auflösungsverbesserung gar nicht immer richtig oder stets erforderlich ist. Stattdessen kann es echte Vorteile haben, die Mikrooptik mit etwas größeren Dimensionen wie beispielsweise größeren Aperturen und/ oder dickeren Multiaperturplatten herzustellen. Vorteile bieten sich insbesondere durch verringerte parasitäre Effekte wie verringerte Strahlablenkungen bei vergleichbarer erwünschter elektronenoptischer Wirkung und durch höhere Spannungen, die an den Multiaperturplatten der Mikrooptik angelegt werden können. Insbesondere Letzteres ist bei Mikrooptiken für immer mehr Einzel-Teilchenstrahlen und für immer größere Bildfelder von besonderem Interesse.

The present invention is essentially based on two fundamental findings:

1. (1) It has been shown that the silicon material used for micro-optics can pose serious problems: For example, undesirable surface potentials can occur, and the conductivity of the silicon can change over time. Both of these factors have an undesirable impact on the charged single-particle beams passing through the micro-optics, thus affecting the beam quality and, in turn, the resolution achievable with a multi-particle beam system during operation.
2. (2) Furthermore, it has surprisingly turned out that the desire/trend towards further miniaturization of micro-optics for the purpose of improving resolution is not always correct or always necessary. Instead, there can be real advantages in manufacturing micro-optics with somewhat larger dimensions, such as larger apertures and/or thicker multi-aperture plates. Advantages arise in particular from reduced parasitic effects such as reduced beam deflections with a comparable desired electron-optical effect, and from higher voltages that can be applied to the multi-aperture plates of the micro-optics. The latter is of particular interest in micro-optics for ever-increasing numbers of single-particle beams and ever-larger image fields.

It is therefore a fundamental idea of the invention to use other manufacturing processes instead of MEMS technologies, namely those that can be used in metal processing. The fact that such metal processing processes tend to be used only for the creation of somewhat larger structures is not necessarily a disadvantage. Instead, metal processing processes offer the advantage that silicon is no longer almost compulsory as a material. In particular, it is also possible to use the method according to the invention to produce micro-optics that have one or more multi-aperture plates made of metal. Furthermore, with skillful process control, the problem of precisely aligning the multi-aperture plates to one another can also be solved, regardless of their material or light-optical or IR transparency; the multi-aperture plates are then correctly aligned to one another automatically or inherently in the process.

1. (a) Bereitstellen einer ersten Platte der Mikrooptik, die elektrisch leitfähig ist;
2. (b) Bereitstellen einer zweiten Platte der Mikrooptik, die elektrisch leitfähig ist;
3. (c) Erzeugen eines Plattenstapels umfassend Stapeln der ersten Platte der Mikrooptik und der zweiten Platte der Mikrooptik übereinander, wobei die erste Platte der Mikrooptik und die zweite Platte der Mikrooptik in dem Plattenstapel relativ zueinander fixiert werden und voneinander elektrisch isoliert werden; und
4. (d) Durchbohren des gesamten erzeugten Plattenstapels mit mindestens der ersten Platte und der zweiten Platte der Mikrooptik und dadurch Erzeugen sowohl einer ersten Vielzahl von Aperturen in der ersten Platte der Mikrooptik als auch einer zweiten Vielzahl von Aperturen in der zweiten Platte der Mikrooptik.

According to a first aspect of the invention, the invention relates to a method for manufacturing a micro-optics for a multi-particle beam system, comprising the following steps:

1. (a) providing a first plate of the micro-optics which is electrically conductive;
2. (b) providing a second plate of the micro-optics which is electrically conductive;
3. (c) producing a plate stack comprising stacking the first plate of the micro-optics and the second plate of the micro-optics one above the other, wherein the first plate of the micro-optics and the second plate of the micro-optics are fixed relative to each other in the plate stack and are electrically insulated from each other; and
4. (d) drilling through the entire produced plate stack with at least the first plate and the second plate of the micro-optics and thereby producing both a first plurality of apertures in the first plate of the micro-optics and a second plurality of apertures in the second plate of the micro-optics.

As in the introductory description, the term "micro-optics" refers to a sequence of multiple multi-aperture plates, of which at least one multi-aperture plate is used during operation for actively shaping the plurality of single-particle beams in the multi-particle beam system. Preferably, each of the apertures is penetrated by exactly one single-particle beam.

In patent claim 1, the term "multi-aperture plate" is not used, but rather refers to a first micro-optic plate and a second micro-optic plate. This is due to the fact that the apertures in the first plate and in the second plate are only formed during the manufacturing process.

The first plate of the micro-optics is electrically conductive. The entire first plate of the micro-optics can be electrically conductive, or only parts of it. The same applies to the second plate of the micro-optics. The property of electrical conductivity contributes to, or is even necessary for, the use of many processes known from metal processing for the manufacture of micro-optics for a multi-particle beam system. This will be discussed in more detail later.

Creating the plate stack comprises stacking the first micro-optic plate and the second micro-optic plate on top of each other, wherein the first micro-optic plate and the second micro-optic plate are fixed relative to each other in the plate stack and are electrically insulated from each other. The fixing and electrical insulation can be achieved simultaneously and/or using the same means; however, it is also possible to use different means for fixing and electrical insulation. For example, it is possible to use electrically insulating spacers or to provide a complete electrically insulating plate.

The plate stack comprises at least a first micro-optic plate and a second micro-optic plate. However, the plate stack can also comprise further micro-optic plates. In method step (d), the entire produced plate stack is drilled through with at least the first and second micro-optic plates, thereby creating both a first plurality of apertures in the first micro-optic plate and a second plurality of apertures in the second micro-optic plate. Apertures that are to be penetrated by the same individual particle beam during operation of the micro-optic system or the multiple particle beam system are thus created in the same method step or during the same drilling process. If the drilling process is carried out with appropriate precision using a drilling means, mutually associated apertures in the first micro-optic plate and the second micro-optic plate, and optionally one or more further micro-optic plates, are automatically correctly aligned with one another.

According to a preferred embodiment of the invention, the first plate of the micro-optics and/or the second plate of the micro-optics is metallic. For example, the metal can be copper, silver, iron, aluminum, tungsten, gold, brass, platinum, stainless steel, or another metal or metal alloy, or combinations of the aforementioned materials. The metal plate itself can also have a surface finish, such as gold plating. Alternatively, it is also possible for the first plate of the micro-optics and/or the second plate of the micro-optics to consist of a semiconductor material. This semiconductor material can, for example, comprise silicon.

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-optics, which is electrically conductive. 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 each of them. When carrying out method step (d), the third plate of the micro-optics is also drilled through, thereby creating a third plurality of apertures in the third plate of the micro-optics. This third plurality of apertures is therefore also correctly aligned with the remaining apertures of the first plate and the second plate due to the nature of the process.

According to a preferred embodiment of the invention, the third plate of the micro-optics consists of a metal. The same applies to any additional plates present. It is fundamentally possible for all plates of the micro-optics to be made of the same material, and in particular, the same metal; however, this is not necessarily the case.

According to a preferred embodiment of the invention, the plate stack is drilled through in step (d) using laser drilling. Laser drilling is a non-cutting thermal cutting process. There are various types of laser drilling processes, such as single-pulse drilling, percussion drilling, trepanning, and helical drilling. Single-pulse drilling is the fastest; it "shoots" through the material using a single pulse. In percussion drilling, several pulses are applied to the same point to laser a hole through the material. Trepanning occurs when, after the through-hole has been drilled, the hole is cut out by tracing the bore contour. Helical drilling may require special optics. Generally speaking, the precision of the drilling and the smoothness of the borehole walls depend on the material being drilled through and the type of laser radiation. Copper, for example, absorbs green and blue radiation very well, but common infrared radiation not very well. Laser drilling processes are now very fast and also very efficient: For example, it is possible to drill 200 holes per second into 1 mm thick titanium sheet using single-pulse micro-drilling. The focus diameter of the laser used is, for example, For example, the aperture diameter is 12 µm, and the resulting hole has a diameter of just under 80 µm. An aperture diameter of 80 µm already corresponds to the dimensions used in the state of the art for apertures produced using MEMS technologies. Laser drilling can therefore be used to produce both very small apertures, if desired, and much larger apertures, if necessary using other laser drilling technologies. Furthermore, the processes are very fast. Furthermore, laser drilling as a manufacturing process 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 drilled through using laser drilling. Therefore, laser drilling can also drill through stacks of electrically conductive and electrically insulating plates simultaneously, using the same laser pulse, or using the same number of laser pulses.

According to a further preferred embodiment of the invention, the drilling of the plate stack in step (d) is carried out using micro-EDM. Micro-EDM, or micro-spark erosion, is a form of EDM (Electrical Discharge Machining) and can be described as a combination of drilling and sinking erosion techniques. This technique, which is based on spark erosion as a machining method, is highly suitable for shaping electrically conductive materials of various hardnesses into the correct shape at high speed and precision.

EDM is a non-contact process that can remove very small amounts of material without creating mechanical stress in the material. The material is formed by highly localized melting and evaporation as a result of electrical discharges between an electrode and the material being processed. The discharges, which form tiny plasma channels with temperatures of up to 10,000°C, locally melt very small amounts of the material. When the current flow is interrupted, the generated plasma collapses, and the resulting vacuum draws the molten material out into the surrounding dielectric medium. For discharges to occur, the material must have sufficient electrical conductivity, while material hardness is not important. Therefore, in principle, all metals and many semiconductors are suitable for EDM and also for micro-EDM.

Micro-EDM is a special form of EDM that allows workpieces to have features as small as approximately 10 µm. These small features are achieved using electrodes that are also very small. Thus, even with micro-EDM, aperture sizes of the size already used for micro-optics can be easily achieved. Furthermore, the micro-EDM process is significantly faster than planar integration techniques.

According to a preferred embodiment of the invention, the plate stack is drilled through in step (d) using mechanical high-speed micro-drilling. Solid carbide micro-drills, for example, can be used for this purpose. In this way, drill hole diameters of a few millimeters can be achieved, as well as drill hole diameters of only 30 µm or even just 10 µm.

According to a preferred embodiment of the invention, the drilling of the plate stack in step (d) is carried out by means of vibration drilling or ultrasonic drilling. The principle of vibration drilling is to generate axial vibrations or oscillations in addition to the feed movement of the drill, so that the drilling 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 cause it to vibrate naturally during cutting. The vibrations can be maintained by a mass-spring system in the tool holder itself. Another possibility is the use of a piezoelectric system to generate and control vibrations. These systems enable high vibration frequencies (up to 2 kHz) with small dimensions (a few µm) and are particularly suitable for drilling small holes.

Ultrasonic drilling uses vibrations in the ultrasonic range to create a drilled hole. It is a non-rotary material machining process. It is particularly suitable for hard and brittle materials. Ultrasonic waves generated in an ultrasonic transducer cause the drilling tool to vibrate in the feed direction, also inducing vibrations in the grains of an abrasive suspension. During a brief fraction of the vibration period, the workpiece is removed in micro-divisions. 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 drilling of the plate stack in step (d) is carried out using a focused ion beam (FIB). When high-energy ions hit a sample, they sputter atoms from the surface. Due to its sputtering capability, a focused ion beam can be used as a tool for micro- and nanomachining, and materials in the micro- and nanoscale can be modified or processed. Gallium ions, for example, are used as focused ions, but other ions can also be used. Using focused ion beams, even features in the 10 to 15 nm range can be milled, and the milling of features in the micrometer range is fully and comprehensively possible. The only problem with the use of a focused ion beam is its relatively shallow depth of field. This can make it difficult to drill through thick plates or thick plate stacks all at once. However, there are solutions for this too, such as dividing a plate stack into several sub-stacks and then drilling through each of the sub-stacks using the FIB, particularly at lens transitions where precise alignment of the apertures of different plates is very critical. The sub-stacks can then be combined to form a complete stack.

In the drilling methods described above, the material removed by drilling must be removed from the plate stack. According to a preferred embodiment of the invention, flushing holes can be provided in the plates of the plate stack, which have a larger diameter than the apertures in the first plate of the micro-optics and in the second plate of the micro-optics. These flushing holes can be created using the same or different methods as the apertures in the first plate of the micro-optics and in the second plate of the micro-optics; the method itself is not critical 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 drilling through the plate stack, 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 the flushing agent, particularly in a metal drilling process. However, it is also possible to use a gas as the flushing agent, for example after drilling through by laser drilling or after using a focused ion beam.

Flushing holes also make it possible to remove or flush out any auxiliary materials used during the production of the plate stack/micro-optics. For example, it is possible to introduce a liquid between the plates of the plate stack before a mechanical drilling process, then cool it until it solidifies, and then drill through the plate stack. This allows the forces acting during drilling to be absorbed by the solidified liquid. After drilling, the plate stack can be reheated, and the solidified liquid/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 drilling according to step d), rinsing the plate stack and removing drilling material through rinsing holes in the first plate of the micro-optics and in the second plate of the micro-optics, wherein the following relation applies to a diameter S of the rinsing holes in relation to the diameter A of the apertures in the first plate of the micro-optics and in the second plate of the micro-optics: D ≥ 10A, preferably D ≥ 100A.

• vor dem Durchbohren gemäß Schritt d)
  • - Befüllen eines Zwischenraumes zwischen der ersten Platte der Mikrooptik und der zweiten Platte der Mikrooptik mit einem flüssigen Spülmittel, und
  • - Abkühlen des Spülmittels und dadurch Erstarren des Spülmittels; und
• nach dem Durchbohren gemäß Schritt d)
  • - Erwärmen des Spülmittels und dadurch Verflüssigen des Spülmittels; und
  • - Entfernen des Spülmittels aus dem Zwischenraum.

According to a further preferred embodiment of the invention, the method further comprises the following steps:

• before drilling according to step d)
  • - filling a space between the first plate of the micro-optics and the second plate of the micro-optics with a liquid detergent, and
  • - Cooling of the detergent and thereby solidification of the detergent; and
• after drilling according to step d)
  • - Heating the detergent and thereby liquefying the detergent; and
  • - Remove the detergent from the gap.

The flushing holes described above can be used to fill and remove the detergent.

1. (e) Erzeugen einer Vielzahl von Grob-Aperturen in der mindestens einen Platte mit dem isolierenden Material als Grundmaterial; und
2. (f) Metallisieren der Grob-Aperturen;

wobei beim späteren Durchführen von Verfahrensschritt (d) die metallisierten Grob-Aperturen durchbohrt und so die Vielzahl der Aperturen gebildet werden.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 prior to method steps (a) to (d):

1. (e) creating a plurality of coarse apertures in the at least one plate with the insulating material as the base material; and
2. (f) metallizing the coarse apertures;

wherein, during the subsequent execution of process step (d), the metallized coarse apertures are pierced and thus the plurality of apertures are formed.

In this embodiment, not the entire plate of the plate stack is conductive, but only a portion of it, namely the areas metallized around the coarse apertures. This is sufficient to enable all material processing methods that require the conductivity of the material to be drilled. 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 metallization of the coarse apertures is carried out by sputtering and/or by electroplating.

According to a preferred embodiment of the invention, in process step (d), the plurality of apertures in the plates of the plate stack are created simultaneously. For this purpose, a plurality of drilling means can be used simultaneously. These can be, for example, multiple laser pulses in laser drilling or a plurality of fixedly oriented electrodes (so-called "Manhattan electrodes") in the micro-EDM process. This type of simultaneous creation of drill holes is very fast.

According to an alternative embodiment of the invention, in method step (d), the plurality of apertures in the plates of the plate stack are successively created. Thus, the entire plate stack is first completely drilled at a first location, then completely drilled at a second location, and so on. In this embodiment, the drilling process used is relatively simple.

According to a preferred embodiment of the invention, the plurality of apertures each have a diameter A, where: 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. For differently shaped apertures, such as elliptical apertures, the diameter A is defined as the smallest possible distance between the aperture walls. In the case of ellipses, this corresponds to twice the minor semi-axis. For stepped apertures, which can be created, for example, by means of stepped electrodes or by means of several drilling steps (e.g. first drilling through a plate with a small drill bit, then partially drilling out with a larger drill bit), 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-fold, or irregular. The method according to the invention is therefore very flexible.

According to a preferred embodiment of the invention, the centers of adjacent apertures 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 to a plate spacing D between directly adjacent plates of the plate stack: 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.

The method according to the invention therefore makes it possible to drill through even relatively thick plates and plates that are relatively widely spaced from one another, using a fast and precise process. Especially for larger dimensions, the manufacturing process using known planar integration techniques is much slower.

According to a preferred embodiment of the invention, the micro-optics comprises at least a second or further plate stack. The second or further plate stack of the micro-optics can be produced using method steps (a) to (d). However, it is also possible for the second or further plate stack of the micro-optics to be or have been produced using planar technology and/or lithographic processes. In principle, other manufacturing processes are also possible.

According to a further preferred embodiment of the invention, in a method step (g), the first plate stack and the second or further plate stack are aligned with each other. If several plate stacks are aligned with each other, a high degree of precision is required. However, this subsequent alignment of plate stacks or the apertures located therein is naturally less precise than the process-inherent positioning of the apertures within a plate. ten stack if related apertures have been precisely produced using the same process step. It may therefore be expedient to align plate stacks with one another at transitions between different plate stacks where there is greater electron-optical insensitivity to misalignments. In this context, reference is again made to what was said in connection with focused ion beam drilling. The sub-stacks described therein essentially correspond to several stacks. In particular, critical lens transitions should, if possible, belong to the same plate stack, which has preferably been produced using the process according to the invention comprising steps (a) to (d).

According to a further aspect of the invention, it relates to a micro-optics for a multi-particle beam system, which has been manufactured according to the method as described above in several embodiments.

According to a further aspect of the invention, this relates to a micro-optic system for a multi-particle beam system, in particular for a multi-beam particle microscope. The micro-optic system has a first multi-aperture plate made of metal and a second multi-aperture plate made of metal. For the aperture diameters A of the first multi-aperture plate and the second multi-aperture plate, A ≥ 150 µm applies. Furthermore, for the thicknesses C of the first multi-aperture plate and the second multi-aperture plate, C ≥ 250 µm applies. For the plate spacing D between the first multi-aperture plate and the second multi-aperture plate, D ≥ 30 µm applies.

The micro-optics described are therefore relatively large and made of metal. Such a micro-optics cannot be manufactured using conventional planar integration techniques, or only with considerable time expenditure.

According to a further aspect of the invention, it relates to a multi-beam particle beam system, in particular to a multi-beam particle microscope, with a micro-optics as described above.

According to a preferred embodiment of the invention, during operation of the multi-particle beam system, a voltage U with U ≥ 250 V, preferably U ≥ 300 V or U ≥ 350 V, can be applied to the first multi-aperture plate and/or to the second multi-aperture plate of the micro-optics. Applying such high voltages to a multi-aperture plate is normally not possible with known micro-optics manufactured using planar integration techniques. Instead, voltages in the order of magnitude of less than 200 V can be used there. Otherwise, arcing will occur between different multi-aperture plates. When using the aforementioned high voltages, sometimes significantly more than 250 V, relatively large plate spacings D are necessary. This is normally not possible using grown insulator layers such as silicon oxide, but it is possible using other manufacturing processes because, in growing processes, the thicknesses of insulator layers are typically limited due to process requirements. It is then particularly advantageous that insulators can also be drilled through by means of some of the described manufacturing 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 in whole or in part, provided that this does not result in technical contradictions.

• 1: zeigt schematisch ein Vielzahl-Teilchenstrahlsystem;
• 2: zeigt schematisch einen Aufbau einer Mikrooptik;
• 3: zeigt schematisch eine Ausrichtungsproblematik bei Multiaperturplatten;
• 4: zeigt schematisch Verfahrensschritte eines erfindungsgemäßen Herstellungsverfahrens für eine Mikrooptik;
• 5: zeigt ein Flussdiagramm eines erfindungsgemäßen Herstellungsverfahrens;
• 6: zeigt schematisch Verfahrensschritte eines erfindungsgemäßen Herstellungsverfahrens;
• 7: zeigt schematisch Verfahrensschritte eines erfindungsgemäßen Herstellungsverfahrens;
• 8: zeigt schematisch Aspekte eines erfindungsgemäßen Herstellungsverfahrens;
• 9: zeigt schematisch Verfahrensschritte eines erfindungsgemäßen Herstellungsverfahrens;
• 10: zeigt schematisch eine Manhattan-Elektrode und eine damit erzeugte Multiaperturplatte;
• 11: zeigt schematisch Multiaperturplatten einer Mikrooptik;
• 12: zeigt schematisch Aspekte eines Herstellungsverfahrens für eine Mikrooptik;
• 13: zeigt ein weiteres Flussdiagramm eines erfindungsgemäßen Herstellungsverfahrens.

The invention will be better understood with reference to the accompanying figures, in which:

• 1 : shows schematically a multi-particle beam system;
• 2 : shows schematically a structure of a micro-optics;
• 3 : shows schematically an alignment problem with multi-aperture plates;
• 4 : shows schematically process steps of a manufacturing process according to the invention for a micro-optic device;
• 5 : shows a flow chart of a manufacturing process according to the invention;
• 6 : shows schematically process steps of a manufacturing process according to the invention;
• 7 : shows schematically process steps of a manufacturing process according to the invention;
• 8 : shows schematically aspects of a manufacturing process according to the invention;
• 9 : shows schematically process steps of a manufacturing process according to the invention;
• 10 : shows schematically a Manhattan electrode and a multi-aperture plate produced with it;
• 11 : shows schematically multi-aperture plates of a micro-optics;
• 12 : shows schematically aspects of a manufacturing process for a micro-optic device;
• 13 : shows another flow chart of a manufacturing process according to the invention.

1 schematically shows a multi-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 301, for example an electron source. A diverging particle beam 309 is collimated by a sequence of condenser lenses 303.1 and 303.2 and impinges on a multi-aperture arrangement 305, which forms a micro-optics system. The multi-aperture arrangement 305 comprises several multi-aperture plates 306 and a field lens 308. The multi-aperture arrangement 305 generates a plurality of individual particle beams 3 or individual electron beams 3. Center points of apertures of the multi-aperture plate arrangement are arranged in a field, which is imaged 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, and 200 µm. The diameters A 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 distance 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 grid arrangement on a surface 321. The surface 321 does not have to 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 image the beam foci 323 from the intermediate image area 325 into the object plane 101 in a reduced size. The first individual particle beams 3 pass through the beam switch 400 and a collective beam deflection system 500, with which the plurality of first individual particle beams 3 are deflected during operation and the image field is scanned. The first individual particle beams 3 impinging on the object plane 101 form, for example, a substantially regular field, wherein distances between adjacent impingement points 5 can be, for example, 1 µm, 10 µm, or 40 µm. The field formed by the impingement points 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 arranged 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 the object 7 generate interaction products such as secondary electrons, backscattered electrons, or primary particles that have experienced a reversal of motion for other reasons, which emanate from the surface of the object 7 or from the first plane 101 or object plane 101. The interaction products emanating from the surface 15 of the object 7 are formed into secondary particle beams 9 by the objective lens 102. The secondary beams 9 pass through the beam switch 400 after the objective lens 102 and are fed to a projection system 200. The projection system 200 has an imaging system 205 with projection lenses 208, 209, and 210, a contrast aperture 214, and a multi-particle detector 207. The points of incidence 25 of the second single-particle beams 9 on detection areas of the multi-particle detector 207 are located in a third field at a regular distance from one another. Example values are 10 µm, 100 µm, and 200 µm.

The multi-beam particle microscope 1 further comprises a computer system or a control unit 10, which in turn can be designed as a single part or in multiple parts, and which is designed both to control the individual particle-optical components of the multi-beam particle microscope 1 and to evaluate and analyze 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 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 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-optic system 305, by means of which, in the example shown, the plurality of first individual particle beams 3 are initially generated at the first of the multi-aperture plates (so-called filter plate) during operation of the multi-aperture particle beam system 1 and are also actively shaped at additional multi-aperture plates. The micro-optic system 305 itself can be designed in various ways.

2 shows, by way of example, a micro-optics system 305 configured as a multi-beam generator 305. In the illustrated example, the multi-beam generator 305 comprises, in the z-direction, which corresponds to the propagation direction of the single-particle beams 3, a sequence with six multi-aperture plates 304, 306.1, 306.2, 306.3, 306.4, and 310, as well as 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 single-particle beams 3 pass. The cross section through the apertures 351 in 2 is not to scale.

The plurality of multi-aperture plates 304, 306.1, 306.2, 306.3, 306.4, and 310 are spaced apart from one another 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. The plurality of first individual particle beams 3 are generated by the impact of a collimated particle or electron beam 309 upon passing through the first multi-aperture plate 304, which is also called a filter plate or pre-aperture plate. The pre-aperture plate 304 includes 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., doped silicon, and is at ground potential.

The next multi-aperture plate is in the example shown in 2 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 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, thereby individually influencing each individual particle beam 3. For example, it is possible to deflect each individual particle beam 3 in any direction up to a few µm using an antisymmetric voltage difference in order to pre-correct a distortion correction of the illuminating unit 100. An astigmatism pre-correction of each individual particle beam 3 can also be performed. With an offset voltage, each multipole element can additionally function as an individual lens.

In principle, the multi-aperture plates 306.2, 306.3, and 306.4 can be any monolithic trajectory correction plates to which, in the example shown, a voltage V1, V2, and V3 is applied, respectively. 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, 306.3, and 306.4 can be identical or different, for example, they can have different diameters, in order to account for the field dependence of the correction during the trajectory correction of the individual particle beams 3.

The multi-aperture plate 310 is a two-layer multi-aperture plate and includes a plurality of ring electrodes 79 for the plurality of apertures, each ring electrode configured to individually change or correct a focal position of the first single-particle beam 3 passing through it. The upper layer is insulated from the layer or layer with the ring electrodes 79 and is 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, e.g., 12 kV to 17 kV, can be applied. In the example shown, the condenser lens 307 provides a global electrostatic lens field for global focusing of the plurality of single-particle beams 3.

The 2 The micro-optics 305 shown or its multi-aperture plates can, in principle, be manufactured using known manufacturing methods or using planar integration techniques. However, at least some multi-aperture plates, for example the multi-aperture plates 306.2, 306.3, and 306.4, can also be manufactured using the manufacturing method according to the invention. Due to the special performance of such multi-aperture plates 306.2, 306.3, and 306.4 manufactured according to the invention (ability to apply relatively 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, for example, the multi-aperture plate 310 with the ring electrodes 81 becomes superfluous.

3 shows schematically an alignment problem with multi-aperture plates 350, which have each been manufactured independently of each other, i.e. each for itself. 3a shows schematically the provision of three plates 360 without openings. 3b shows schematically the use of a drilling tool 900, which in principle can be of any type. 3 It is only a matter of principle. The direction of action of the drilling tool 900 is 3b schematically indicated by the arrow. The drilling means 900 forms openings 351 in the plate 360, whereby the plate 360 becomes a multi-aperture plate 350. It should be noted that for reasons of ease of illustration in 3 only one opening 351 is shown, but of course there are several openings 351 in a multi-aperture plate 350. In 3D It is now illustrated 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-optics 305. For this purpose, the conductive multi-aperture plates 350.1, 350.2, and 350.3 are aligned with one another, as well as fixed and insulated. In the example shown, this is achieved by the spacers 370.1 and 370.2. The openings 351.1, 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 of the openings 351.1, 351.2, and 351.3 in the multi-aperture plates 350.1, 350.2, and 350.3 is very difficult, if not impossible. This is especially true if the multi-aperture plates 350.1, 350.2, and 350.3 are made of metal: They are then impermeable to visible light or infrared radiation, making optically based alignment, as typically used in die bonders, significantly more difficult. Replacing semiconductor-based plates of a multi-aperture arrangement 305 with metal plates is therefore not readily possible.

• 4a zeigt zunächst drei Platten 360.1, 360.2 und 360.3 für die Mikrooptik 305, die im dargestellten Beispiel nicht nur leitfähig, sondern aus Metall sind.
• 4b zeigt die Anordnung der Platten 360.1, 360.2 und 360.3 relativ zueinander. Dabei sind die Platten 360.1, 360.2 und 360.3 relativ zueinander fixiert und über Abstandshalter 370.1 und 370.2 voneinander elektrisch isoliert. Die Abstandshalter 370.1 und 370.2 können beispielsweise aus Siliziumoxid hergestellt sein.
• 4c zeigt nun schematisch das Durchbohren des Plattenstapels mit den Platten 360.1, 360.2 und 360.3 mittels eines Bohrmittels 900. Dieses ist in 4c nur schematisch dargestellt, die Bohrrichtung ist durch den Pfeil angedeutet. Wichtig ist nun, dass der gesamte Plattenstapel grundsätzlich auf einmal, beim selben Bohrvorgang, mit demselben Bohrmittel 900 durchbohrt wird.
• 4d zeigt das Ergebnis des Bohrvorgangs: Die Aperturen 351.1, 351.2 und 351.3 sind perfekt zueinander ausgerichtet und die Mittelpunkte der Aperturen 351.1, 351.2 und 351.3 liegen im gezeigten Beispiel zentral auf der Achse Z. Dabei ist wiederum in 4 nur exemplarisch eine Sequenz von Aperturen 351.1, 351.2 und 351.3 dargestellt; selbstredend sind in dem Multiaperturplatten 350.1, 350.2 und 350.3 aber mehrere Aperturen beziehungsweise Sequenzen von Aperturen vorhanden.

However, the manufacturing method according to the invention offers a solution in which, on the one hand, metal plates can be used to produce a micro-optic device 305 and, on the other hand, they can also be aligned precisely enough. 4 shows schematically process steps of a manufacturing method according to the invention for a micro-optics 305:

• 4a first shows three plates 360.1, 360.2 and 360.3 for the micro-optics 305, which in the example shown are not only conductive but also made of metal.
• 4b shows the arrangement of plates 360.1, 360.2, and 360.3 relative to one another. Plates 360.1, 360.2, and 360.3 are fixed relative to one another and electrically insulated from one another by spacers 370.1 and 370.2. Spacers 370.1 and 370.2 can be made of silicon oxide, for example.
• 4c now shows schematically the drilling of the plate stack with the plates 360.1, 360.2 and 360.3 using a drilling tool 900. This is in 4c Only shown schematically; the drilling direction is indicated by the arrow. It is important that the entire stack of plates is drilled through at once, in the same drilling process, using the same 900 mm drill bit.
• 4d shows the result of the drilling process: The apertures 351.1, 351.2 and 351.3 are perfectly aligned with each other and the centers of the apertures 351.1, 351.2 and 351.3 are located centrally on the Z axis in the example shown. 4 Only one sequence of apertures 351.1, 351.2 and 351.3 is shown as an example; of course, the multi-aperture plates 350.1, 350.2 and 350.3 contain several apertures or sequences of apertures.

Furthermore, it is conceivable that drilling means 900 could be used to drill not only through plates 360.1, 360.2, and 360.3, but also through insulating plates or layers. Whether this is possible depends solely on the drilling method used.

5 shows schematically a flow diagram of a manufacturing method according to the invention for a micro-optics 305 for a multi-particle beam system 1: In a method step S1, a first plate 360.1 of the micro-optics 305, which is electrically conductive, is first provided.

In a method step S2, a second plate 360.2 of the micro-optics 305, which is electrically conductive, is provided.

In a method step S3, a plate stack is created. Creating a plate stack comprises stacking the first plate 360.1 of the micro-optics 305 and the second plate 360.2 of the micro-optics 305 one above the other, wherein the first plate 360.1 of the micro-optics 305 and the second plate 360.2 of the micro-optics 305 are fixed relative to one another in the plate stack and are electrically insulated from one another. This can be achieved, for example, by using insulating spacers 370.1, 370.2.

Then, in a method step S4, the entire produced plate stack is drilled through with at least the first plate 360.1 and the second plate 360.2 of the micro-optics 305, thereby creating both a first plurality of apertures 351.1 in the first plate 360.1 of the micro-optics 305 and a second plurality of apertures 351.2 in the second plate 360.2 of the micro-optics 305. As a result, the sequence of apertures 350.1, 350.2 in the plates 360.1, 360.2 of the plate stack created during the same drilling process is precisely aligned with one another, in a process-inherent manner. Optionally, the plate stack can further comprise at least one further and thus at least one third plate 360.3 of the micro-optics 305, which is electrically conductive. The third plate 360.3 of the micro-optics 305 is fixed relative to the first plate 360.1 of the micro-optics 305 and the second plate 360.2 of the micro-optics 305 and is electrically insulated from them. The third plate of the micro-optics 305 is also drilled through when method step S4 is carried out, so that a third plurality of apertures 351.3 is thereby created in the third plate 360.3 of the micro-optics 305. One or more of the mentioned plates of the micro-optics 305 can be made of a metal. According to a preferred embodiment of the invention, all drilled 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 silicon dioxide.

The drilling of the plate stack according to method step S4 can be carried out in various ways: Examples of drilling methods include laser drilling, drilling using micro-EDM, mechanical high-speed micro-drilling, vibration drilling, ultrasonic drilling, or the use of a focused ion beam (FIB). For details on these methods, reference is made to the explanations in the general description of the invention.

Optionally, in a further method step S5, the plate stack can be rinsed and drilling material removed through rinsing holes in the first plate 306.1 of the micro-optics 305 and in the second plate 306.2 of the micro-optics 305. For a diameter S of the rinsing holes in relation to the diameter A of the apertures in the first plate 306.1 of the micro-optics 305 and in the second plate 306.2 of the micro-optics 305, the following relation can apply: D ≥ 10A, preferably D ≥ 100A.

A modified manufacturing method for a micro-optics 305 of a multi-particle beam system 1 is shown in the flow chart in 13 shown: In it, the method steps S1 to S3 are first carried out as described above. Before drilling through the plate stack according to step S4, in the described exemplary embodiment, in step S11, a space between the first plate 306.1 of the micro-optics 305 and the second plate 306.2 of the micro-optics 305 is filled with a liquid rinsing agent, and in step S12, the rinsing agent is cooled and thereby solidifies. Temperature control can be achieved, for example, by carrying out the method within a process chamber whose internal temperature is adjustable, or the liquid is supplied heated and then cools down on its own. The entire plate stack is then drilled through in step S4. By arranging/providing the solidified rinsing agent, forces acting on the plates 306.1 and 306.2 during drilling can be better absorbed, distributed, and dissipated. This helps prevent sagging of plates 306.1 and 306.2. In a further process step S13, the rinsing agent is heated and thus liquefied. For example, the entire stack of plates can be heated, and the rinsing agent is also heated in the process. In a further process step S14, the now liquid rinsing agent is removed from the intermediate space. The rinsing holes described above can be used for filling with the rinsing agent and for removing the rinsing agent.

• Konkret werden zunächst drei an sich nichtleitende Platten 360 für die Mikrooptik 305 bereitgestellt. Die Platten 360 können ein isolierendes Material als Grundmaterial, beispielsweise eine Keramik als Grundmaterial, aufweisen. In diesen Platten 360 können nun Grob-Aperturen 361 ausgebildet werden. Die Grob-Aperturen 361 sind größer als die final herzustellenden Aperturen 362 der Mikrooptik 305.

6 shows schematically process steps of a manufacturing process according to the invention. In the 6 In the illustrated embodiment, the plates 360 of the micro-optics 305 are non-conductive, or not entirely conductive. Their conductivity is present only in sections, namely in the area around the apertures 351 that are yet to be formed:

• Specifically, three inherently non-conductive plates 360 are initially provided for the micro-optics 305. The plates 360 can have an insulating material as the base material, for example, a ceramic. Coarse apertures 361 can then be formed in these plates 360. The coarse apertures 361 are larger than the final apertures 362 of the micro-optics 305.

In a further procedural step (cf. 6c ), the coarse apertures 362 are metallized. The metallization of the coarse apertures 361 can be performed, for example, by sputtering or electroplating. Conductive regions 363 are formed around or adjacent to the coarse apertures 362. These, in turn, have openings 363. Their diameter is smaller than the diameter of the final apertures 351 of the micro-optics 305.

• Wie in 6e dargestellt, erfolgt nämlich anschließend das Durchbohren der metallisierten Grob-Aperturen 361 beziehungsweise der leitenden Bereiche 362.1, 362.2 und 362.3. In 6e ist dazu schematisch wiederum ein Bohrmittel 900 und dessen Bewegungsrichtung angedeutet.

In a further process step, the plates 360.1, 360.2, and 360.3 are fixed relative to each other with the metallized coarse apertures 361 and arranged so that they are electrically insulated from each other. The spacers 370.1 and 370.2 can be electrically insulating, but they do not necessarily have to be, since the plate material of the plates 360.1, 360.2, and 360.3, as a ceramic material, 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 have to be at this stage of the manufacturing process:

• As in 6e As shown, the metallized coarse apertures 361 and the conductive areas 362.1, 362.2 and 362.3 are subsequently drilled. 6e For this purpose, a drilling means 900 and its direction of movement are again indicated schematically.

As a result, as in 6f shown - again perfectly or process-inherently exactly aligned apertures 351.1, 351.2 and 351.3 are formed.

By means of the 6 The manufacturing method described can therefore not only be used to produce monolithic multi-aperture plates 350.1, 350.2 and 350.3, which are already (fully) conductive per se. Instead, it is also possible to realize ring electrodes using the manufacturing method according to the invention. 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 process step; this is more complex than with monolithic multi-aperture plates 350, but can also be realized. For this purpose, a metal printing process, for example, is suitable even before the plate stack is assembled. It is also possible, for example, for conductor tracks to be applied by a combination of sputtering and electroplating.

7 shows schematically process steps of a manufacturing method according to the invention for a micro-optics 305. The 7a The plate stack shown with the plates 360.1, 360.2 and 360.3 can be used, for example, as in connection with 4a and 4b Other than in connection with 4c shown, but now the drilling of the plate stack is in 7a different, namely with regard to the drilling direction: The plate stack is drilled through at an angle. The resulting angled apertures 351.1, 351.2 and 351.3 are also exactly aligned with each other, as shown by the dotted auxiliary lines in 7B However, the apertures 351.1, 351.2, and 351.3 are not exactly circular in this oblique drilling, but rather slightly elliptical. The degree of ellipticity depends on the degree of inclination during drilling relative to the normal of the plate stack.

8 schematically shows aspects of a manufacturing method according to the invention, wherein the drilling of the plate stack is carried out using a focused ion beam (FIB). The plate stack 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, which indicates a frame region, and reference numeral 381, which indicates a membrane region.

The illustrated plate stack is intended to have the functionality of, for example, a single lens after drilling through the entire plate stack. For this reason, 8 Voltages U1, U2, and U3 are indicated schematically. However, instead of a single plate 360 with a total height H across the entire plate width, two membranes with a small thickness h are provided. The corresponding voltage is applied to the lower and upper membranes, respectively. From an electron-optical perspective, the fact that cavities 382.1, 382.2, and 382.3 are provided between membranes 360.1 and 360.2, between 360.3 and 360.4, and between 360.5 and 360.6 makes no significant difference. Insulating spacers 370.1 and 370.2 are arranged between the respective pairs of membranes in a known manner.

When drilling through the plate stack, the focused ion beam can now be used in the same drilling process, starting from the top, to first drill through the uppermost membrane 360.1, then the next membrane 360.2, and so on. This can again be done in principle in the same process step or without having to change the position of the FIB column, at least not in the x-direction or y-direction. This means that the x, y positions of the FIB column and thus also the x, y positions of the apertures 351 to be created are fixed. The fact that only the thin membrane sections with the height h need to be drilled through can take into account the fact that a focused ion beam has a relatively small depth of field and can therefore only drill through relatively thin layers. Drilling through the entire plate stack as in 8 shown is therefore particularly suitable for plate stacks with a low overall height, for example up to a height of a few micrometers.

For cases where the plate stack has a greater overall height and the shallow depth of field of the focused ion beam becomes a problem, the 9 The process sequence shown represents a solution: The entire stack with the plates 360.1 to 360.6 is divided into four sub-stacks. In particular, the plates 360.2 and 360.3 as well as the plates 360.4 and 360.5 each form independent stacks as defined in patent claim 1. The individual stacks or sub-stacks are then drilled separately using the FIB or the focused ion beam. The stack forms according to 9b a stack in which a lens transition occurs. Here, the alignment of the generated apertures in plates 360.2 and 360.3 is particularly critical. The same applies to the lens transition between plates 360.4 and 360.5, as shown in 9c shown. The transitions within the same lens, on the other hand, are not so critical. Therefore, without any significant loss of performance of the micro-optics 305, it is possible to separate the sub-stacks after drilling through the partial stacks ( 9b and 9C ) as well as the individual plates or membranes ( 9a and 9D ) and perform the appropriate alignment. This assembling of the sub-stacks is done by the bracket in 9 This in turn creates the micro-optics 305.

In principle, it is possible for the multiple apertures in the plates of a plate stack to be generated successively. However, it is also possible for the multiple apertures in the plates to be generated at least partially simultaneously. An example of this is shown in 10 : 10a shows a Manhattan-type electrode as drilling means 900. This comprises a plurality of electrodes 902 arranged on a base element 901. In principle, the Manhattan-type electrode is therefore a multi-electrode. With this, several openings can be created simultaneously in batches at different positions in a plate 360. The result of the drilling process is shown in 10b : Shown is a multi-aperture plate 350 with a plurality of circular apertures 351, the arrangement of which corresponds to the arrangement of the electrodes 902.

The 10 The Manhattan-type electrode shown can be used, for example, in a micro-EDM process. However, the principle is also applicable to other drilling processes.

11 schematically shows several multi-aperture plates 350 of a micro-optics 305. 11a shows a multitude of round apertures 351, each of which has the same diameter and is regularly arranged. 11b shows a multi-aperture plate 350 with circular apertures 351, the diameter of which varies within the multi-aperture plate or depends 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 to the center C in the multi-aperture plate 350.

11c shows a multi-aperture plate 350 with elliptical apertures 351. Its longitudinal axis I varies depending on the center M, namely in terms of orientation and size.

For all in 11 The multi-aperture plates 350 shown are monolithic aperture plates 350, to each of which only a single voltage is applied. Due to the conductivity of the plates 350, the apertures 351 create an effect or lens effect, the magnitude of which then depends only 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-fold, or irregularly shaped. The apertures themselves are preferably arranged using a grid, for example, a hexagonal grid. However, they can also be arranged, for example, in a square or rectangular grid.

According to one embodiment, adjacent apertures 351 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.

For a thickness C of a plate 360, 350 of the plate stack, for example, the following can apply: 20 µm ≤ C ≤ 500 µm, preferably 150 µm ≤ C ≤ 500 µm or 250 µm ≤ C ≤ 500 µm.

According to one embodiment, the following applies to a plate spacing D between 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 total height H of the plate stack is understood to be the height of the plate stack that is simultaneously drilled through by a drilling means 900. Of course, the micro-optics 305 can also have at least a second or at least one further plate stack. It is possible for the second or further plate stack of the micro-optics to also be 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 micro-optics 305 to be produced by other methods, for example by means of planar technology and/or lithographic methods. The second or further plate stack can then be aligned relative to the first plate 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 distance 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 multi-particle beam system, for example U ≥ 250 V, preferably U ≥ 300 V and U ≥ 350 V. This is particularly advantageous in multi-particle beam systems that operate with a large number 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 in edge regions of a multi-particle beam arrangement of a large grid.

12 schematically shows aspects of another manufacturing method for a micro-optic device 305. In contrast to the methods already described above, an arrangement of different plates on top of one another or of different layers on top of one another is no longer drilled together; instead, a negative mold 910 is provided, around which various 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 precisely aligned with one another in a process-inherent manner. Thus, according to this example, a complex alignment problem is also avoided.

Specifically, in a first process step, the negative mold can be provided as such. This can, for example, have a Manhattan-like structure that defines the later position of apertures 911. Furthermore, this negative mold can also be used to provide individual electrodes, such as ring electrodes or lines for supplying voltage to the electrodes. This central negative mold, which defines at least the dimensions of later apertures 911, can be configured in various ways. For example, it can be photoresist, silicon dioxide, etched metal (lidar process), coated metal (for deposition purposes), and so on. 12a The negative mold 910 is schematically shown as a central block. This central block is arranged 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 can be deposited on the substrate 390. In the example shown, for example, a first metallic layer 392 can be deposited on the substrate 390, for example by sputtering or by sputtering and electroplating.

Subsequently, another layer 393 is deposited on the conductive layer 392. This layer is essentially an insulating layer 393. This layer can either be insulating from the outset (for example, deposition of an insulator such as silicon dioxide via sputtering), or the layer can be initially deposited electroplated and then, through heat treatment, lose its original electrical conductivity and become an insulator. Electrolytic processes for insulators are, in principle, known from the prior art in other contexts.

The described deposition processes of alternating conductive and non-conductive layers can be repeated. In the example shown, a metallic layer 394 is deposited, followed by another insulating layer 395, followed by another metallic layer 396, and so on. At the end of the process, the negative mold 910 is removed: This is shown in 12b shown schematically. The resulting apertures 911 are precisely aligned with each other.

The technique, in which insulators are essentially applied electrolytically and only become insulators upon heat treatment or baking, has the advantage that, in principle, all layers 392 to 396 can be applied electrolytically. This simplifies the process, eliminating the need for machine changes when applying different layers. Contamination is also less problematic with electroplating processes than with sputtering processes.

The exemplary embodiments described above are not intended to limit the invention, but merely serve to improve understanding of the invention. They may be combined in whole or in part, provided that no technical contradictions result.

List of reference symbols

1

Multi-beam particle system, multi-beam particle microscope

3

primary particle beams, first single particle beams

5

Beam spots, impact points

7

object, sample, wafer

9

secondary particle beams, second single particle beams

10

Computer system, control

15

Sample surface, wafer surface

25

Image point of a second single particle beam

81

Multipole electrode

82

Ring electrode

83

spacers

84

Ring electrode

85

aperture

86

spacers

99

Absorbing and conductive layer

101

Object level

102

objective lens

103

field lens

105

axis

108

Beam crossing, 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 crossing, cross-over

214

Aperture filter, contrast diaphragm

222

Collective anti-deflection system

300

Beam generating device

301

Particle source

303

Collimation lens system

304

Multi-aperture array, filter plate

305

Microoptics, multi-aperture array, 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

Beam foci

333

Holding area

335

Membrane area

350

Multi-aperture plate

351

aperture

360

plate

361

Coarse aperture

362

conductive area

363

Opening in the conductive area

370

spacers

380

Frame area

381

Membrane area

382

cavity

390

wafers

391

Metallic layer

392

layer

393

layer

394

layer

395

layer

396

layer

910

Negative form, photoresist

400

Beam switch, magnet arrangement

500

Scan deflector

600

Travel table or positioning device

900

Drilling media

901

Basic element

902

Manhattan-type electrode

Z

axis

M

Center

H

Height of frame section

h

Height of membrane

x

Direction

y

Direction

z

Direction

I

Longitudinal axis

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• US 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 / 060017 A [0065]
• DE 10 2013 016 113 A1 [0065]
• DE 10 2013 014 976 A1 [0065]

Claims (28)

A method for producing a micro-optic system for a multi-particle beam system, comprising the following steps: (a) providing a first micro-optic plate that is electrically conductive; (b) providing a second micro-optic plate that is electrically conductive; (c) creating a plate stack comprising stacking the first micro-optic plate and the second micro-optic plate one above the other, wherein the first micro-optic plate and the second micro-optic plate are fixed relative to each other in the plate stack and are electrically insulated from each other; and (d) drilling through the entire produced plate stack with at least the first and second micro-optic plates, thereby creating both a first plurality of apertures in the first micro-optic plate and a second plurality of apertures in the second micro-optic plate. Procedure according to Claim 1 , wherein the first plate of the micro-optics and/or the second plate of the micro-optics 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 micro-optic plate that is electrically conductive, and wherein the third micro-optic plate is fixed relative to the first micro-optic plate and the second micro-optic plate and is electrically insulated therefrom, and wherein the third micro-optic plate is also drilled through during the performance of method step (d), thereby creating a third plurality of apertures in the third micro-optic plate. Method according to the preceding claim, wherein the third plate of the micro-optics is metallic. Method according to one of the preceding claims, wherein the drilling of the plate stack in step (d) is carried out by means of laser drilling. Procedure according to one of the Claims 1 until 4 , wherein the drilling of the plate stack in step (d) is carried out by means of micro-EDM. Procedure according to one of the Claims 1 until 4 , wherein the drilling of the plate stack in step (d) is carried out by means of mechanical high-speed micro-drilling. Procedure according to one of the Claims 1 until 4 , wherein the drilling of the plate stack in step (d) is carried out by means of vibration drilling or by means of ultrasonic drilling. Procedure according to one of the Claims 1 until 4 , wherein the drilling of the plate stack in step (d) is carried out 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 the base material, in particular a ceramic as the base material, and wherein the method further comprises the following steps, which are carried out prior to method steps (a) to (d): (e) creating a plurality of coarse apertures in the at least one plate with the insulating material as the base material; and (f) metallizing the coarse apertures; wherein, during the subsequent implementation of method step (d), the metallized coarse apertures are drilled through, thus forming the plurality of apertures. Method according to the preceding claim, wherein the metallization of the coarse apertures is carried out by sputtering and/or by electroplating. Method according to one of the preceding claims, wherein in method step (d) the plurality of apertures in the plates of the plate stack are produced simultaneously. Procedure according to one of the Claims 1 until 10 , wherein in process step (d) the plurality of apertures in the plates of the plate stack is successively produced. Method according to one of the preceding claims, wherein the plurality of apertures each have a diameter A, where: 40µm ≤ A ≤ 400µm, in particular 80µm ≤ A ≤ 400µm or 110µm ≤ A ≤ 400µm. Method according to the preceding claim, wherein the shape of the apertures in the plates of the plate stack is round, elliptical, n-fold or irregularly shaped. Method according to one of the preceding claims, wherein adjacent apertures in the plates of the plate stack have a distance B for which the following applies: 70µm ≤ B ≤ 400µm, in particular 90µm ≤ B ≤ 400µm or 120µm ≤ B ≤ 400µm. Method according to one of the preceding claims, wherein the following applies to a thickness C of a plate of the plate stack: 20µm ≤ C ≤ 500µm, in particular 150µm ≤ C ≤ 500µm or 250µm ≤ C ≤ 500µm. Method according to one of the preceding claims, wherein the following applies to a plate spacing D between 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: 50µm ≤ H ≤ 1000µm, in particular 300µm ≤ H ≤ 1000µm or 500µm ≤ H ≤ 1000µm. A method according to any one of the preceding claims, further comprising the following step: after drilling according to step d), flushing the plate stack and removing drilling material through flushing holes in the first plate of the micro-optics and in the second plate of the micro-optics, wherein the following relationship applies to a diameter S of the flushing holes in relation to the diameter of the apertures in the first plate of the micro-optics and in the second plate of the micro-optics: D ≥ 10A, in particular D ≥ 100A. The method according to the preceding claim, further comprising the following steps: before drilling according to step d) - filling a gap between the first plate of the micro-optics and the second plate of the micro-optics with a liquid rinsing agent, and - cooling the rinsing agent and thereby solidifying the rinsing agent; and after drilling according to step d) - heating the rinsing agent and thereby liquefying the rinsing agent; and - removing the rinsing agent from the gap. Method according to one of the preceding claims, wherein the micro-optics comprises at least a second or further plate stack. Method according to the preceding claim, wherein the second or further plate stack of the micro-optics is produced by means of method steps (a) to (d); or wherein the second or further plate stack of the micro-optics is produced by means of planar technology and/or lithographic processes. A method according to the preceding claim, wherein the method further comprises the following method step: (g) aligning the first plate stack and the second or further plate stack with each other. Micro-optics for a multi-particle beam system, manufactured according to the method according to any one of the preceding claims. Micro-optics for a multi-particle beam system, wherein the micro-optics comprises a first multi-aperture plate made of metal and a second multi-aperture plate made of metal, wherein the aperture diameters A of the first multi-aperture plate and the second multi-aperture plate are each: A ≥ 150 µm, wherein the thicknesses C of the first multi-aperture plate and the second multi-aperture plate are each: C ≥ 250 µm; and wherein the plate spacing D between the first multi-aperture plate and the second multi-aperture plate is each: D ≥ 30 µm. Multi-beam particle beam system, in particular multi-beam particle microscope, with a micro-optics according to one of the Claims 25 until 26 . Multi-particle beam system according to the preceding claim, wherein during operation of the multi-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.

Images