Monolithic multi-aperture plate for a multi-beam electron beam system, method for manufacturing a monolithic multi-aperture plate, and multi-beam electron beam system with a monolithic multi-aperture plate

Abstract

A monolithic multi-aperture plate for shaping multiple electron beams for a multi-beam electron beam system is described. The monolithic multi-aperture plate consists of a single, monolithically constructed element with individual functional planes and a multitude of apertures. Apart from the multitude of apertures, the monolithic multi-aperture plate contains no cavities. The monolithic multi-aperture plate is designed for improved performance and extended service life.

Description

Field of invention

[0001] The invention relates to a multi-aperture plate for shaping a multitude of electron beams for a multi-beam electron beam system. State of the art

[0002] With the continuous development of increasingly smaller and more complex microstructures such as semiconductor devices, there is a need for the further development and optimization of planar fabrication techniques and inspection systems for inspecting small microstructure dimensions. Therefore, there is a need for inspection tools that can be used with high throughput to examine microstructures on wafers with high accuracy.

[0003] Typical silicon wafers used in the fabrication of semiconductor devices have diameters of up to 300 mm. Each wafer is divided into repeating regions ("dies"). A semiconductor device comprises multiple semiconductor structures fabricated in layers on the wafer's surface using planar integration techniques. Due to the fabrication processes, semiconductor wafers typically have a flat surface. The feature size of the integrated semiconductor structures ranges from a few micrometers to critical dimensions (CDs) of 5 nm, with feature sizes expected to become even smaller in the near future; future feature sizes or critical dimensions (CDs) below 3 nm, for example 2 nm, or even below 1 nm, are anticipated.For several applications, the specification requirement for the accuracy of a measurement provided by an inspection instrument is even higher, for example by a factor of two or an order of magnitude. For example, the width of a semiconductor feature must be measured with sub-1 nm accuracy, such as 0.3 nm or even less, and the relative position of semiconductor structures must be determined with a sub-1 nm superposition accuracy, such as 0.3 nm or even less.

[0004] A recent development in the field of charged particle microscopes (CPM) is a multi-beam electron beam system. A multi-beam electron beam system is disclosed, for example, in US 7,244,949 B2 and US 2019 / 0355544 A1. In a multi-beam electron beam system, or MSEM, a sample is simultaneously irradiated with a multitude of single-electron beams arranged in a field or grid. For example, 4 to 10,000 single-electron beams can be used as primary radiation, with each single-electron beam separated from an adjacent single-electron beam by a distance of 1 to 200 micrometers. For example, a multi-beam electron beam system 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.A multitude of charged single-particle beams (primary beams) are focused by a common objective lens onto the surface of a sample under investigation. The sample can be, for example, a semiconductor wafer attached to a wafer holder mounted on a movable stage. During illumination of the wafer surface with the charged primary single-particle beams, interaction products, such as secondary electrons or backscattered electrons, originate from the wafer surface. Their starting points correspond to the locations on the sample onto which the multitude of primary single-particle beams are focused. The quantity and energy of the interaction products depend, among other things, on the material composition and the topography of the wafer surface.The interaction products form several secondary single-particle beams (secondary beams), which are collected by the common objective lens and imaged by a projection imaging system of the multi-beam electron beam system onto a detector located in a detection plane. The detector comprises several detection areas, each containing several detection pixels, and the detector acquires an intensity distribution for each of the secondary single-particle beams. This results in an image field of, for example, 100 µm × 100 µm.

[0005] The prior art multi-beam electron beam system comprises a series of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable to adapt the focus position and stigmatization of the multiple charged single-particle beams. The prior art multi-beam charged-particle system also includes at least one intersection plane of the primary or secondary charged single-particle beams. Furthermore, the prior art system includes detection systems to facilitate adjustment. The prior art multi-beam electron beam system includes at least one deflection scanner for collectively scanning an area of ​​the sample surface using the multiple primary single-particle beams to obtain an image field of the sample surface.

[0006] In a prior art multi-beam electron beam system, a multitude of individual beams are generated by a first multi-aperture plate or filter plate with a multitude of first apertures in a first grid arrangement. These multiple beams are then transmitted to further multi-aperture plates, for example, a second multi-aperture plate with second apertures, such as an array of active electrostatic elements. In typical examples, in addition to the first and second multi-aperture plates, there are further multi-aperture plates with additional apertures. Examples of such an arrangement of multi-aperture plates are shown in US 11,238,054 B2, US 2022 / 0392734 A1, and WO 2023 / 016678 A1. Adjusting the multitude of individual multi-aperture plates requires special measures. Furthermore, deformation of individual, thin multi-aperture plates can occur during operation of a multi-beam microscope.This can lead to the effect, for example, that at least one individual beam no longer passes through a second aperture of a second multi-aperture plate concentrically. The manufacturing and joining of individual multi-aperture plates is therefore very prone to errors. It is known that surfaces with insulating material can locally accumulate charges. To prevent this, depressions or cavities are often formed to protect insulating surfaces, thus reducing the probability of an electron beam striking insulating material. Examples are shown in US 7,276,707 B2, where electrodes of multipole elements are separated by vacuum gaps. JP 2,816,849 B2 further shows vacuum gaps in labyrinthine form or with a cross-sectional shape similar to the letter S. Many other cross-sectional shapes are known, for example from US 5,041,731 A, US 5,401,974 A, and US 6,055,719 A.Other solutions, such as that described in US 2020 / 0203114A1, involve vacuum gaps between individual elements of multi-aperture plates. During operation, contamination can accumulate in these vacuum gaps, potentially leading to electrical short circuits.

[0007] DE 10 2022 131 862 A1, the scientific publication by I.L. Berry et al., “Programmable aperture plate for maskless high-throughput nanolithography”, Journal of Vacuum Science & Technology B 15 (1997), pp. 2382-2386, DE 10 2008 010 123 A1, the scientific publication by S. Eder-Kapl et al., “Characterization of CMOS programmable multi-beam blanking arrays as used for programmable multi-beam projection lithography and resistless nanopatterning”, Journal of Micromechanics and Microengineering 21 (2011), pp. 045038.1-8, and US 2005 / 0 242 302 A1 disclose prior art that relates to the technical background of the invention with regard to multi-beam particle beam systems with aperture plates. is. Description of the invention

[0008] One object of the invention is therefore to provide an improved multi-aperture arrangement for generating or shaping the plurality of electron beams for multi-beam electron beam systems, which is suitable for the increased requirements for resolution and accuracy during the performance of a wafer inspection task.

[0009] The improved multi-aperture arrangement according to one embodiment of the invention is provided by a monolithic multi-aperture plate for a multi-beam electron beam system. The monolithic multi-aperture plate contains a plurality of apertures that form continuous connections between a first side or top and a second side or bottom of the monolithic multi-aperture plate. Apart from the apertures, the monolithic multi-aperture plate has no gaps or cavities that could accumulate contamination and impede operation in a vacuum. The monolithic multi-aperture plate essentially consists of a first, conductive material and a second, insulating material.In one example, the monolithic multi-aperture plate is formed entirely monolithically, without any joints or cavities (except for the multiple apertures), from the first conductive material, the second insulating material, and an absorber layer. Optionally, a thin metal layer can also be present on the inner surfaces of the apertures. The monolithic multi-aperture plate is composed of more than 95% of the first conductive material (e.g., doped silicon or polysilicon) and a second insulating material (e.g., silicon dioxide). The monolithic multi-aperture plate is not stacked from individual multi-aperture plates, thus eliminating the need for error-prone alignment and assembly. This also makes it possible to integrate more functional layers, for example, more than two or three sequences of functional layers.From the first and second materials, at least one first and one second sequence of functional layers are formed, each sequence comprising an active functional layer with a plurality of embedded electrodes, at least one interconnection layer with a plurality of electrical interconnection channels, and a passive functional layer. In one example, an active functional layer of a monolithic multi-aperture plate is configured as an array of multipole elements, each with a plurality of electrodes at each aperture, where the plurality of embedded electrodes can be two, three, four, six, eight, or more. In another example, an active functional layer of a monolithic multi-aperture plate is configured as an array of lenses, each with only one ring-shaped embedded electrode at each aperture.Each embedded electrode can be individually and electrically isolated from other electrodes or other conductive structures and connected to a control unit or monitoring unit via external electrical contacts.

[0010] The monolithic multi-aperture plate also features an absorber layer on its upper surface, or the side facing the incident particle beam. The absorber layer can be made of gold, aluminum, or tungsten. The absorber layer of the monolithic multi-aperture plate can be made thicker, thus more effectively absorbing or stopping incident particles and X-rays.

[0011] In one example, the monolithic multi-aperture plate further comprises a central area in which the multitude of apertures are arranged, and a peripheral area with a multitude of electrical connection contacts on the first or top surface, which are electrically connected to the interconnection layers via a through-connection area. This through-connection area contains a multitude of mutually insulated connection channels or vias. This makes it possible to directly connect lower-lying functional layers to the top surface of the monolithic multi-aperture plate via the through-connection area. Alternatively, or additionally, electrical connection contacts can also be provided on the underside instead of the top surface, which are electrically connected to the interconnection layers via the through-connection area.

[0012] The monolithic multi-aperture plate has a thickness T in a central region between the first side or top and the second side or bottom of not less than 150 µm, preferably not less than 200 µm. In one example, the monolithic multi-aperture plate further includes a support layer S4 which contains a mechanical connection contact or flange in the peripheral region for connection to a multi-beam particle beam system.

[0013] The embedded electrodes of the monolithic multi-aperture plate are formed from the first conductive material and are each electrically insulated from further conductive structures made of the first conductive material by an insulating structure made of the second insulating material. The insulating structure of one electrode has at least one exposed surface with the inner surface of an aperture. In one example, the at least one exposed surface of the insulating structure is arranged in a recess at a distance R3 greater than the inner radius R1 of the electrode in the aperture from a beam axis of a single transmitting beam. In another example, an electrode has a tongue or spring, which forms the recess labyrinthine. In yet another example, a conductive structure above or in the beam direction in front of or above an electrode has a tongue or spring that covers at least one exposed surface.Through the monolithically integrated recesses and via tongues, springs or grooves, it is possible to protect exposed surfaces of insulating structures within the inside of the apertures from the transmitting particle beams, so that no local charges can accumulate there.

[0014] In one example, the inner surface of an electrode or conductive material on the inside of an aperture is additionally coated with metal.

[0015] In a second embodiment of the invention, a method for producing a monolithic multi-aperture plate is given. The method comprises the following steps: - Step V1 with a first photolithographic structuring of a polished silicon dioxide layer, - Step V2 of a deposition of a doped polysilicon layer, - Step V3 for the chemical-mechanical polishing (CMP) of the deposited poly-silicon layer, - Step V4 of a second photolithographic structuring of the polished poly-silicon layer, - Step V5 involves etching to structure the layer, - Step V6 with a coating of the surfaces with silicon dioxide, - Step V7 involves a chemical-mechanical polishing (CMP) of the silicon dioxide surface formed in step V6, - and step V9 of etching the apertures through the monolithic multi-aperture plate.

[0016] In one example, the process additionally includes a step V8 for coating the first side or top of the monolithic multi-aperture plate with the absorber layer.

[0017] In step V9, a thin metal layer can optionally be applied to the inner surfaces of the apertures.

[0018] In a third embodiment, a multi-beam electron beam system with a monolithic multi-aperture plate is provided. In one example, the multi-beam electron beam system further includes a first filter plate arranged in the electron beam path between the particle source and the monolithic multi-aperture plate. This pre-filters an incident electron beam and reduces the number of incident or absorbed electrons.

[0019] The various embodiments and aspects of the invention can be combined wholly or partially, provided that no technical contradictions result.

[0020] The invention will be better understood with reference to the attached figures. Fig. Figure 1 shows a multi-beam system with a monolithic multi-aperture plate Fig. Figure 2 shows another embodiment of a multi-beam system Fig. Figure 3 shows a cross-section through a monolithic multi-aperture plate Fig. Figure 4 shows the structure of a monolithic multi-aperture plate. Fig. Figure 5 shows detailed aspects of a monolithic multi-aperture plate Fig. Figure 6 shows an exemplary electrode arrangement in a monolithic multi-aperture plate Fig. Figure 7 shows individual process steps in the manufacturing of a monolithic multi-aperture plate. Fig. Figure 8 shows an example of another detail of a monolithic multi-aperture plate. Fig. Figure 9 shows an example of another detail of a monolithic multi-aperture plate. Fig. Figure 10 shows an example of a monolithic multi-aperture plate with three active layers. Fig. Figure 11 shows an example of a monolithic multi-aperture plate with a through-connection area. Fig. Figure 12 shows process steps in the production of one layer of a monolithic multi-aperture plate.

[0021] Fig. Figure 1 schematically shows a multi-beam electron beam system 1 according to one embodiment. The multi-beam electron beam system 1, hereinafter also referred to as multi-beam system 1, has a beam generating device 300 with a particle source 301 for generating charged particles, for example, an electron source. A diverging particle beam 309 is collimated by a sequence of condenser lenses 303.1 and 303.2 and strikes a monolithic multi-aperture plate 306. The multi-beam system 1 according to the first embodiment comprises exactly one monolithic multi-aperture plate 306. A plurality of single-particle beams 3 or single-electron beams 3 are generated and shaped by the monolithic multi-aperture plate 306 (also called micro-optics 306).The centers of apertures of the monolithic micro-optics 306 are arranged in a grid pattern in a first field, which is projected onto a further grid pattern formed by beam spots 5 in an object plane 101. The distance between the centers of beam spots 5 in the object plane 101 can be, for example, 5 µm, 10 µm, or 100 µm. The spacing of the apertures of the monolithic multi-aperture plate 306 is, for example, 100 µm. The diameters D of the apertures are smaller than the distance between the centers of the apertures; examples of the diameters are 0.2 times, 0.4 times, and 0.8 times the distance between the centers of the apertures.

[0022] The monolithic micro-optics 306 and the field lenses 307 and 308 are configured to generate a multitude of focal points 323 of primary beams 3 in a grid arrangement on an intermediate image surface 321. The surface 321 need not be a flat surface, but can be a spherically curved surface to accommodate field curvature of the subsequent particle optical system.

[0023] The multi-beam electron beam system 1 further comprises a system of electromagnetic lenses 103 and an objective lens 102, which reduce the size of the beam foci 323 from the intermediate image surface 321 and image them onto the object plane 101. The first individual particle beams 3 pass through the beam splitter 400 and a first collective beam deflector or scanner 110, which deflects the multitude of the first individual particle beams 3 during operation and scans the image field. The first individual particle beams 3 incident on the object plane 101 form, for example, a substantially regular field. The field formed by the point of impact 5 can, for example, exhibit rectangular or hexagonal symmetry.

[0024] The object 7 to be examined can be of any type, for example, a semiconductor wafer or a biological sample, and can comprise an arrangement of miniaturized elements or the like. The surface 25 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 object 7, for example, a wafer, is positioned on a traversing device or stage 500 with its surface 25 in the image plane 101. The surface 25 is preferably oriented perpendicular or slightly tilted to an optical axis 105 of the objective lens 102, and the plurality of individual beams 3 strike the object surface 25 substantially perpendicularly and thus parallel to the optical axis 105.The object 25 on the wafer table 500 is supplied with voltage via a power supply 503.

[0025] The primary particles of the individual beams 3 striking object 7 generate interaction products such as secondary electrons, backscattered electrons, or primary particles that have undergone a reversal of motion for other reasons. These products originate from the surface 25 of object 7 or from the first plane 101 or object plane 101. The interaction products emanating from the surface 25 of object 7 are shaped into secondary particle beams 9 by the objective lens 102. After passing through the objective lens 102, the secondary beams 9 pass through the beam splitter 400 and are directed to a projection system 200. The projection system 200 comprises an imaging system with several electrostatic or magnetic lenses 206 to 210, a contrast diaphragm 214, and a multi-particle detector 207.The impact points 15 of the second single-particle beams 9 on the detection areas of the multi-particle detector 207 are located in a third field at regular intervals. Exemplary values ​​are 10 µm, 100 µm, and 200 µm. Furthermore, the projection system includes a second collective deflector or scanner 222, which holds the impact points 15 of the second single-particle beams 9 on the multi-particle detector 207 at a constant position.

[0026] The multi-beam electron beam system 1 further comprises a computer system or control unit 800, which in turn can be designed as a single unit or as a multi-unit system, and which is designed both for controlling the individual particle-optical components of the multi-beam electron beam system 1 and for evaluating and analyzing the signals obtained with the multi-detector 207 or the detection unit 207.

[0027] Further information on such multi-beam particle beam systems or multi-beam electron beam systems 1 and components used therein, such as particle sources, multi-aperture plates and lenses, can be obtained from the international patent applications WO 2005 / 024881 A2, WO 2007 / 028595 A2, WO 2007 / 028596 A1, WO 2011 / 124352 A1 and WO 2007 / 060017 A2 and the German patent applications DE 10 2013 016 113 A1 and DE 10 2013 014 976 A1, the disclosure of which is incorporated in full by reference into the present application.

[0028] Particularly for wafer inspection, a multi-beam system 1 is subject to increased requirements. For example, the resolution of each sub-image acquired by each individual particle beam should be identical within a narrow limit, e.g., better than 3.5 nm, better than 3.0 nm, or even better. For example, the resolution should be direction-independent; that is, the resolution in an x-direction should not deviate from the resolution in a y-direction by more than 5%. These are also referred to as high-frequency (HV) differences. Furthermore, the positions of the individual beam spots 5 should be very stable so that the relative positions of the individual sub-images remain stable and do not require complex computational correction of numerous sub-image offsets.These high requirements lead, on the one hand, to increased demands on the design of the micro-optics 306 and, on the other hand, to increased demands during the operation of the micro-optics 306. A multi-beam system 1 according to one embodiment of the invention is designed to meet these increased requirements even during operation. To fulfill the increased requirements, the micro-optics 306 is designed monolithically according to this embodiment.

[0029] Fig. Figure 2 shows a further embodiment of the beam-generating device 300 according to the embodiment. Downstream of the electron source 301 are a first aperture 311 and a first multi-aperture plate or first filter plate 304 with a plurality of first apertures. The incident electron beam 309 is partially absorbed at the first filter plate 304. Following the first filter plate 304 is a collimation lens or condenser lens 303 and the monolithic multi-aperture plate 306. Following the monolithic multi-aperture plate 306 is a field lens 308 and the further components of the multi-beam system 1, with respect to which further details are described. Fig. 1 and the description therein is referenced. The multitude of primary beams are deflected by the beam splitter 400 in the direction of the optical axis 105 of the objective lens 102 by a deflection angle 109. The deflection angle 109 can be between 3° and 20°, preferably between 4° and 10°. However, larger or smaller deflection angles 109 are also possible.

[0030] The first filter plate 304 is sometimes also referred to as the pre-aperture plate 304. It can serve to reduce the stress on the monolithic micro-optics 306 caused by the incident electron current from the electron beam 309.

[0031] Particularly in wafer inspection, there are increased requirements for resolution isotropy and the uniformity of resolution of an image across multiple particle beams. Resolution isotropy means that the resolution in an x-direction differs from the resolution in a perpendicular y-direction by no more than, for example, 5%. Preferably, the deviation is even smaller, for example, 3% or less. Additionally, the resolution of a first individual beam should differ from the resolution of a second individual beam by no more than 5%, preferably by less than 3%. Such isotropy and resolution invariance are achieved when the beam cross-sections 115 in a pupil plane 117 are circular and of identical diameter for all beams. Accordingly, in a plane 111 parallel to the image plane, the (real or virtual) beam cross-sections 119 of all first individual beams 3 are identical and circular.

[0032] In Fig. Figure 3 shows a cross-section of an exemplary monolithic micro-optics 306, which is explained in more detail below. For simplicity, only four apertures 85 for forming four individual beams 3.1 to 3.4 are shown. Depending on the number of individual particle beams 3 to be generated, however, a much larger number of apertures is possible, for example, 50, 100, 300, or even more, for example, about 1000. The apertures are spaced P1 apart by approximately 100 µm or more. The arrangement of the apertures 85 can be, for example, in a Cartesian grid or in a hexagonal arrangement. Other arrangements are also possible. The apertures 85 extend between the first or upper side 313 and the second or lower side 315 of the monolithic multi-aperture plate 306. Each aperture has a diameter of about 50 µm.The monolithic multi-aperture plate 306 has a thickness T of over 100 µm, for example 150 µm or 200 µm, or more, for example 300 µm, in the central area 191, which comprises the apertures 85. In particular, the monolithic multi-aperture plate 306 does not contain any thin membranes less than 50 µm thick, as is common in the prior art. Thus, deformations of individual, thin membranes cannot occur. Furthermore, the monolithic micro-optics 306 is not stacked and does not form a stack of individual elements. Therefore, error-prone adjustment and assembly of individual elements is eliminated.

[0033] An electron beam 309 originates from an electron source 301 and is filtered by a first filter plate 304 (not shown). The monolithic multi-aperture plate 306 has a first functional layer S1 with a plurality of apertures 85. This shapes the cross-sections of the individual beams 3.1 to 3.4. Each beam cross-section of an individual beam 3.1 corresponds to the aperture shape of an aperture 85 in the first functional layer S1. The aperture shapes of the first beam-shaping apertures 85 in functional layer S1 can be individually different and, for example, be designed with different elliptical shapes. The first functional layer S1 has, for example, an absorber layer 99, which is formed from a conductive material with preferably high density or high atomic number (for example, aluminum, gold, lead, or tungsten).The absorber layer 99 of the monolithic multi-aperture plate 306 can be made very thick, for example up to 5 µm or more. This captures and absorbs the excess electrons from the pre-filtered individual beams 3 that do not pass through the apertures 85. The absorber layer 99 is connected to a large capacitance, for example to the earth (or ground). A thick absorber layer 99 is also suitable for trapping X-rays.

[0034] With the exception of this absorber layer 99 on the top surface 313, the monolithic multi-aperture plate 306 is essentially composed of a first, conductive material (for example, doped silicon or polysilicon) and a second, non-conductive material (for example, silicon dioxide). Apart from the apertures 85, the monolithic multi-aperture plate 306 has no gaps or cavities.

[0035] The individual beams 3.i then pass through further functional layers S2, S3, and S4 of the monolithic multi-aperture plate 306. In this example, the functional layers of the monolithic multi-aperture plate 306 have a double sequence of passive functional layers S2.1 and S2.2 and active functional layers S3.1 and S3.2 with electrodes 81.1 and 81.2. Finally, there is another passive functional layer S2.3 and a support layer S4, which can also be provided as an integral part of the monolithic multi-aperture plate 306. The support layer S4 contains, for example, a mechanical flange or support frame 86. Together with the support frame 86, the monolithic multi-aperture plate 306 has a thickness of, for example, approximately 0.5 mm to 1 mm.

[0036] During operation, electric fields are generated by applying voltages to the embedded electrodes 81.1 and 81.2, which have an individual beam-shaping or deflecting effect on each individual beam 3.i. For example, individual beams 3 are focused differently, deflected, or otherwise influenced in their beam shape. For this purpose, the embedded electrodes 81.1 and 81.2 are individually connected to a control unit 830 (see Fig. 2).

[0037] Fig. Figure 4 shows a simplified cross-sectional example of the monolithic multi-aperture plate 306. The monolithic multi-aperture plate 306 is predominantly (i.e., more than 50%, more than 70%, or even more than 80%) composed of a conductive material 87, for example, doped silicon. Within this conductive material 87, individual conductive structures 93 are surrounded by insulating material 89 and thus electrically isolated from one another. The insulating material 89 can be, for example, silicon dioxide. Individual conductive structures 93 are completely surrounded by insulating material or by a surface area of ​​at least one inner wall of an aperture 85. This forms individual, electrically insulated conductive structures 93 within the conductive material 87, such as the structures consisting of electrodes 81 and electrical connecting channels or conductors 75.A multitude of electrical connection channels 75 and 77 connect each electrode 81 to an associated connection contact 83, which are provided, for example, in the first functional layer S1 on the top surface 313 of the monolithic multi-aperture plate 306 for electrical connection to the control unit 830. Voltage differences can be applied between electrode 81.1 and other electrodes at the same aperture 85.1 to achieve beam deflection or stigmatization of individual beams 3. Voltage differences can also be applied to electrode 81.1 or to other electrodes 81.2 in further functional layers to achieve, for example, a focusing effect on individual beams 3.

[0038] For example, part of the conductive structure 93.1 is formed by the vertical connecting channel 75.1, which can have a diameter of approximately 5 µm. Another part of the conductive structure 93.1 is formed by the electrode 81.1, which can have a thickness of approximately up to 50 µm. A further part of the conductive structure 93.1 is formed by the horizontal connecting channel 77.1 between the electrode 81.1 and the vertical connecting channel 75.1. A horizontal connecting channel 77.1, 77.2 can have a diameter of 0.25 µm to 5 µm. Insulating material 89 between two conductive structures 93.1, 93.2, or 93.3 has a thickness of at least 0.5 µm, but can also be greater, up to 5 µm.

[0039] The diameters of the apertures 85 can differ in the individual functional layers S1 to S3. The diameter D1 in the uppermost functional layer S1 is smaller than the diameter D2 in an active functional layer S3. Conversely, the diameter D3 in a passive functional layer S2 is larger than the diameter D2. This prevents electrons from the individual electron beams 3 from contacting the inner aperture walls of the apertures 85 below the first functional layer S1.

[0040] The functional layers S1, S2 and S3 have several levels or layers, as illustrated by the example of functional layer S3.1 with levels or layers L1 to L5. Fig. Figure 5a shows an embodiment of an active functional layer S3.i with electrode 81. The first layer and the third layer L3 comprise parts of the insulating structure 89 and 91, respectively. The second layer L2 comprises parts of the electrical connecting conductor 77.1. The fourth layer L4 includes, among other things, the conductive structure 93.3 and parts of the embedded electrode 81. The fifth layer L7 comprises parts of the insulating structure 91. The insulating structures 91 and 89 electrically insulate the embedded electrode 81 from the conductive structure 93.3 in layer L4 and from the conductive structures above and below it. The conductive structure 93.3 is not completely insulated and is connected to ground, for example, via connection 95. The conductive structure 93.3 shields electric fields and thus acts as a shield between the embedded electrode 81 and other embedded electrodes (not shown).The conductive electrical connections 75.1 and 75.2 are designed as cylindrical, insulated conductor channels and are shown here in cross-section.

[0041] To insulate the embedded electrode 81 and the electrical connecting lines 75.1 and 77.1, the insulating structure 89 or 91 is provided, which has an exposed surface 73 facing the aperture 85. During operation, stray electrons can adhere to the exposed surface 73 of insulating structures 89 and generate local space charges there. To prevent the adhesion of stray electrons, the exposed surfaces 73 are arranged in a recess 71 at a distance R3 from the beam axis 121 of a single primary beam 3, where R3 is chosen to be larger than the radii R0 or R5 of a functional layer S2 arranged above or below, respectively, and in particular also larger than the radius R1 of the inner wall of the electrode 81. This avoids a direct line of sight between the exposed surface 73 and a single beam 3. Fig. Figure 5b shows another embodiment of an active functional layer S3.i with electrode 81. In this example, the active functional layer S3.i consists of nine individual levels or layers L1 to L9. The third level or layer L3 comprises parts of the insulating structure 89. The fourth layer L4 comprises the electrical connecting conductor 75.1. The fifth layer L5 comprises parts of the insulating structure 91. The sixth layer L6 includes, among other things, the conductive structure 93 and parts of the embedded electrode 81. The seventh layer L7 comprises parts of the insulating structure 91. The insulating structures 91 and 89 electrically insulate the electrode 81 from the conductive structure 93 in layer L6 and from the conductive structures above and below it.To prevent stray electrons from adhering to the exposed surface 73, the electrode 81 extends over the insulating structure in layer L2 and forms a labyrinthine gap 79.1 to the exposed surface 73 in layers L1 and L2. The labyrinthine gap or depression 79.1 is further enlarged by a tongue or spring 61 formed on the electrode 81. This prevents a direct line of sight between the exposed surface 73 and an electron beam 3, thus reducing the probability of stray electrons reaching the exposed surface 73. An additional labyrinthine vacuum gap 79.2 can be provided on the underside of the electrode 81 – in the direction of the beam – in layers L8 and L9.

[0042] In the example of the Fig. 5b The inner surfaces of the apertures 85 also have a thin metal layer 67. The metal layer 67 can be applied to the apertures 85 with a thickness of a few nm, for example 5 nm. It serves as a protective layer and can prevent local charges from adhering to the conductive structures 93 or the electrodes 81. By applying only a thin layer 67, the formation of a metal layer in the recesses 71 and 79 is prevented. The metal layer can be made of copper, aluminum, gold, or tungsten.

[0043] Fig. Figure 5c shows a further embodiment of an active functional layer S3.i with electrode 81. To prevent stray electrons from adhering to the exposed surfaces 73, the conductive structure in functional layer S2.i extends over the exposed surface 73.1 with a tongue or spring 65.1. A similar tongue or spring 65.2 is arranged below the embedded electrode 81, in the direction of radiation from top to bottom.

[0044] An electrode arrangement 81 can consist of a ring-shaped electrode to form a single lens. However, an electrode arrangement 81 can also be formed as a multipole electrode 81, with, for example, eight electrodes (81.1 to 81.8) surrounded by the insulating structure 91. Fig. Figure 6 shows an example of an electrode arrangement 81 with eight embedded electrodes 81.1 to 81.8 around an aperture 85. Between each pair of separate, embedded electrodes lies an exposed surface 73 of the insulating structure 91. To prevent scattered electrodes from reaching the exposed surface 73, the electrodes are formed with grooves 63 and springs or tongues 61, 65, such that a spring 61 of electrode 81.1 projects into a groove of an adjacent electrode 81.2 and, together with the spring 65 of the adjacent electrode 81.2, forms a labyrinthine vacuum gap 79 (see Figure 6b). A metal layer 67 may also be present on the inner surfaces of the electrodes 81.1 to 81.8.

[0045] Fig. Figure 7 shows an example of individual intermediate steps in the fabrication of a monolithic multi-aperture plate 306. In a first step, a bottom plate 171.9 made of doped silicon with an insulating silicon dioxide layer 169.9 is provided ( Fig. 7a). The silicon dioxide layer is photolithographically structured, and another doped silicon layer 171.8 is epitaxially grown and structured. A further insulating silicon dioxide layer 169.8 is then produced on top of this ( Fig. 7b). These steps are repeated ( Fig. 7c - d), and further layers 171.8 to 171.1 are formed (for simplicity, only layer 171.6 is shown). In each layer, conductive structures are photolithographically separated by insulating structures, which later form, for example, the embedded electrodes 81 and the conductive connections 75. Thus, various functional layers of the monolithic multi-aperture plate 306 are formed, with first functional layers 177 providing support, second functional layers 175 forming passive electrodes or spacers, and third functional layers 181 with active electrodes 81. Finally, the conductive absorber layer 99 made of dense material is applied and structured ( Fig. 7e). For the chemical etching of the subsequent apertures 85, an etching protection layer 173 is applied and photolithographically structured according to the subsequent apertures 85 ( Fig. 7e). Subsequently, the apertures 85 are etched into the doped silicon, with the etch protection layer 173 and the silicon dioxide structures acting as the etch protection layer 173 ( Fig. 7f). Fig. Figure 7g shows the result of the etched apertures after wet chemical removal of the exposed silicon dioxide layers. Thin metal layers 67.1 and 67.2 are deposited onto the inner surfaces of apertures 85 by deposition. Finally, the etch protection layer 173 is removed ( Fig. 7h). Fig. Figure 8 shows the uppermost layers of a monolithic multi-aperture plate 306 facing the incident electron beam 309. For reference symbols and explanations thereof, reference is made to the preceding figures and their descriptions, in particular to Fig. 4 to 6 and their description. The connecting contacts 83 for the electrical connection of the electrodes 81 are further connected to the control unit 830. This allows the many transmitting electron beams to be individually influenced during operation (e.g., including at least one focusing, beam shaping, e.g., astigmatic transformation, or beam deflection).

[0046] Fig. Figure 9 shows a further embodiment of the structures for preventing the charging of exposed surfaces of insulating structures. In this example, the uppermost doped silicon layer 171.1 is formed with a spring and tongue 65.1 that extends over the insulating layer below. This protects the underlying exposed surface 73 and reduces the probability of scattered electrons reaching it. For reference numerals and explanations thereof, reference is made to the preceding figures and their descriptions, in particular to Fig. 4 and Fig. 5 and their description.

[0047] Fig. Figure 10 shows an example of a monolithic multi-aperture plate with a total of three active functional layers 181.1 to 181.3. The active functional layers 181.1 to 181.3 enable independent and individual focusing, deflection, and beam shaping of the transmitted individual beams 3.1 and 3.2. Each of the embedded electrodes 81.1 to 81.6 is designed as a multipole electrode for this purpose. Additionally, a thin metal layer can be applied to the inner surfaces of the apertures 85 (not shown). Active elements for focusing can, for example, compensate for field curvature and image plane tilt of the downstream electron-optical system. Active elements for beam shaping can, for example, compensate for aberrations of the downstream electron-optical system.Active beam deflection elements can be used, for example, to adjust the beam spacing or to compensate for distortion in the subsequent electron-optical system. Except for the individually designed electrical connection channels 75.1 to 75.6, planes with the same function are thus largely identical, and masks for photolithographic structuring can be used multiple times. Apart from the multitude of apertures 85, the monolithic multi-aperture plate 306 has no cavities. The monolithic multi-aperture plate 306 is therefore less sensitive to thermal deformation. For further reference symbols and explanations thereof, reference is made to the preceding figures and their descriptions, in particular to [reference missing]. Fig. 4 and Fig. 5 and their description, as well as on Fig. 11 and their description.

[0048] Fig. Figure 11 shows a schematic overview of a cross-section of the monolithic multi-aperture plate 306 with three active functional layers 181.1 to 181.3 and intervening interconnection layers 183.1 to 183.6, which contain electrical connection channels 75 for electrical contacting the electrodes 81. The monolithic multi-aperture plate 306 also contains a purely passive functional layer 175.1 to 175.3, which essentially serves to create a free propagation distance for the transmitting electron beams 3.1 to 3.5. The monolithic multi-aperture plate 306 has a central region 191 with a plurality of apertures 85, of which only five are shown. Furthermore, in a peripheral area 193 of the monolithic multi-aperture plate 306, a through-connection area 195 for the electrical connection of the individual connection layers 183.1 to 183.6 is arranged with electrical contacts 83 on the top surface 313.The monolithic multi-aperture plate 306 is connected to the control unit 830 via the electrical contacts 83.

[0049] The monolithic multi-aperture plate 306 has a repeated sequence 189.1 to 189.3 of functional layers, each consisting of at least one active functional layer 181 with embedded electrodes 81, a connection layer 183, and a passive functional layer 175. For reference numerals and explanations thereof, reference is made to the preceding figures and their descriptions. In contrast to the prior art, the monolithic multi-aperture plate 306 has no gaps or cavities other than the apertures 85 that could collect contamination and impede operation in a vacuum. Also in contrast to the prior art, the monolithic multi-aperture plate 306 is not stacked from individual multi-aperture plates, thus eliminating error-prone adjustment and assembly. This also makes it possible to integrate more functional layers, for example, more than three.In contrast to the prior art, it is also possible to electrically connect deeper functional layers directly to the top surface 313 of the monolithic multi-aperture plate 306 via the through-connection area 195. Furthermore, via monolithically integrated recesses 71, 79 and via tongues, springs, or grooves 61, 63, 65, it is possible to protect exposed surfaces 73 of insulating structures within the inner surface of the apertures from the transmitting particle beams 3, thus preventing the accumulation of local charges.

[0050] Fig.Figure 12 schematically illustrates the iterative steps of the additive manufacturing process for a single layer of a monolithic multi-aperture plate 306. In step V1, an initial photolithographic structuring of a polished silicon dioxide layer is performed. In step V2, doped polysilicon is deposited. In step V3, the deposited polysilicon undergoes chemical-mechanical polishing (CMP). In step V4, a second photolithographic structuring is performed. In step V5, etching is carried out to structure the layer. In step V6, the surfaces of the etched structures are coated or filled with silicon dioxide. Finally, in step V7, the silicon dioxide surface is polished with CMP. The process steps are repeated until the monolithic multi-aperture plate 306 is completely built up (step Q).Then, in step V8, the coating with the absorber layer 99 takes place, and in step V9, the apertures are etched, and the thin metal layer 67 is introduced into the apertures 85. A list of reference symbols is provided: 1 Multi-beam electron beam system 3 single-particle beams 5 ray spots 7. Object or wafer 9 secondary particle beams 15 impact points of the secondary single-particle beams 25 Surface of the object 61 Tongue or feather 63 Nut 65 Tongue or feather 67 thin metal layer 71 In-depth study 73 exposed area 75 electrical connection channels 77 electrical connection channels 79 Labyrinth-shaped depressions 81 Electrode(s) 83 electrical connection contact 85 Aperture(s) 86 Mechanical flange 87 conductive material 89 insulating material 91 insulating structure 93 conductive structure 95 electrically conductive connection 99 Absorber layer 101 Object level 102 lens 103 electromagnetic lenses 105 optical axis 109 Deflection angle 110 collective beam deflector 111 Plane parallel to the image plane 115 beam cross-sections 117 Pupillary level 119 Beam cross-section of a first single beam 121 Beam axis of a single beam 169 Silicon dioxide layer 171 doped silicon / polysilicon 173 Etch protection layer 175 passive functional layer 181 active functional layer 183 Compound layer 189 Shift sequence 191 central area 193 peripheral area 195 through-connection area 200 projection systems 206 electrostatic or magnetic lens 207 Multi-particle detector 208 electrostatic or magnetic lens 209 electrostatic or magnetic lens 210 electrostatic or magnetic lens 214 Contrast aperture 218 beam deflectors 222 second collective distraction 300 beam generating unit 301 Particle source 303 condenser lenses 304 first filter plate 306 monolithic multi-aperture plate 307 Field lens 308 Field lens 309 Particle beam 311 first aperture 313 first or top 315 second or underside 321 Intermediate image area 323 focus points 400 beam switch 500 Moving device or stage 503 Power supply 800 control unit 830 Primary beam control unit

Claims

[1] A monolithic multi-aperture plate (306) for a multi-beam electron beam system (1), consisting of a first, conductive material (87) and a second, insulating material (89), and having a plurality of apertures (85) forming continuous connections between a first side or top side (313) and a second side or bottom side (315) of the multi-aperture plate (306), wherein at least a first and a second sequence (189.1, 189.2, 189.3) of functional layers (181, 183, 175) is formed from the first and second material, wherein each sequence (189.1, 189.2, 189.3) comprises an active functional layer (181.1, 181.2, 181.3) with a plurality of electrodes (81), at least one connecting layer (183.1 to 183.6) with a A plurality of electrical connection channels (75,77), and a passive functional layer (175.1, 175.2,175.3). [2] Monolithic multi-aperture plate (306) according to claim 1, further comprising a central region (191) in which the plurality of apertures (85) are arranged, and a peripheral region (193) with a plurality of electrical connection contacts (83) which are electrically connected to the connection layers (183.1 to 183.6) via a through-connection region (195), wherein the through-connection region (195) extends through the at least first and second sequence (189.1, 189.2, 189.3) of functional layers (181, 183, 175). [3] Monolithic multi-aperture plate (306) according to one of claims 1 or 2, wherein an electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) is formed from the first conductive material (87) and is electrically insulated from further conductive structures made of the first conductive material (87) by an insulating structure (91) made of the second insulating material (89), and wherein the insulating structure (91) has at least one exposed surface (73) with the inside of an aperture (85), and wherein the at least one exposed surface (73) is arranged in a recess (71, 71.1, 71.2, 79) with a distance R3 greater than the inner radius R1 of the aperture (81) to a beam axis (121) of a single beam (3) is arranged. [4] Monolithic multi-aperture plate (306) according to claim 3, wherein an electrode (81.1 to 81.8) has a tongue or spring (65, 65.1, 65.2) and wherein the recess (79, 79.1, 79.2) is labyrinth-shaped. [5] Monolithic multi-aperture plate (306) according to one of claims 1 to 4, wherein an electrode (81, 81.1, 81.2, 81.3, 81.4, 81.5, 81.6, 81.7, 81.8) is formed from the first conductive material (87) and is electrically insulated from further conductive structures made of the first conductive material (87) by an insulating structure (91) made of the second insulating material (89), and wherein the insulating structure (91) has at least one exposed surface (73) with the inside of an aperture (85), and wherein a conductive structure above the electrode (81.1 to 81.8) has a tongue or spring (65, 65.1) which covers the at least one exposed surface (73) of the insulating structure (91). [6] Monolithic multi-aperture plate (306) according to one of claims 1 to 5, further comprising an absorber layer (99) on the top side (313). [7] Monolithic multi-aperture plate (306) according to claim 6, wherein a material of the absorber layer (99) is gold, aluminum or tungsten. [8] Monolithic multi-aperture plate (306) according to claim 6 or 7, wherein the multi-aperture plate (306) is formed entirely and without separation points or closed cavities monolithically from the first conductive material (87), the second insulating material (89) and a material of the absorber layer (99). [9] Monolithic multi-aperture plate (306) according to one of claims 1 to 8, further comprising an overlay layer S4 containing a mechanical connection contact or flange (86). [10] Monolithic multi-aperture plate (306) according to one of claims 1 to 9, wherein the monolithic multi-aperture plate (306) has a thickness T between the first side or top side (313) and the second side or bottom side (315) of not less than 150µm, preferably not less than 200µm. [11] A method for producing a monolithic multi-aperture plate (306) according to any one of claims 1 to 10, comprising an at least twofold, iterative sequence of the steps - Step V1 with a first photolithographic structuring of a polished silicon dioxide layer, - Step V2 of deposition of a doped polysilicon layer, - Step V3 for chemical mechanical polishing (CMP) of the deposited polysilicon layer, - Step V4 of a second photolithographic structuring of the polished polysilicon layer, - Step V5 with an etching to structure the layer, - Step V6 with a coating of the surfaces with silicon dioxide, - and step V7 with a chemical mechanical polishing (CMP) of the silicon dioxide surface formed in step V6. [12] A method of manufacturing a monolithic multi-aperture plate (306) according to claim 11, further comprising a step V9 of etching the apertures (85) through the monolithic multi-aperture plate (306). [13] A method for producing a monolithic multi-aperture plate (306) according to claim 11 or 12, further comprising a step V8 for coating the first side or top side (313) of the monolithic multi-aperture plate (306) with the absorber layer (99). [14] Multi-beam electron beam system (1) comprising a monolithic multi-aperture plate (306) according to one of claims 1 to 10. [15] Multi-beam electron beam system (1) according to claim 14, further comprising a first filter plate (304) arranged in the beam path of the electron beam (309) between the particle source (301) and the monolithic multi-aperture plate (306). [16] Multi-beam electron beam system (1) according to claim 14 or 15, wherein at least one active functional layer (183.1, 183.2, 183.3) of the monolithic multi-aperture plate (306) is formed as a multipole element with a plurality of electrodes (81.1 to 81.8) at each aperture (85).

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