Monolithic multi-aperture plate for a multi-beam electron beam system

Abstract

A monolithic multi-aperture plate for forming a plurality of electron beams for a multi-beam electron beam system is described. The monolithic multi-aperture plate consists of a monolithically constructed element having individual functional planes and having a plurality of apertures. Apart from the plurality of apertures, the monolithic multi-aperture plate contains no cavities. The monolithic multi-aperture plate is designed for better performance and longer service life.

Description

[0001] Title

[0002] Monolithic multi-aperture plate for a multi-beam electron beam system

[0003] Field of the invention

[0004] The invention relates to a multi-aperture plate for forming a plurality of electron beams for a multi-beam electron beam system.

[0005] Prior art

[0006] With the ongoing development of ever smaller and ever more complex microstructures such as semiconductor components, there is a need to further develop and optimize planar production techniques and inspection systems for inspecting small dimensions of the microstructures. Therefore, there is a need for inspection means which can be used with high throughput to examine the microstructures on wafers with high accuracy.

[0007] Typical silicon wafers used in the production of semiconductor components have diameters of up to 300 mm. Each wafer is subdivided into repeating regions ("dies"). A semiconductor apparatus comprises several semiconductor structures, which are produced in layers on a surface of the wafer by planar integration techniques. Semiconductor wafers typically have a plane surface on account of the production processes. The structure size of the integrated semiconductor structures in this case extends from a few pm to the critical dimensions (CDs) of 5 nm, and the structure sizes will become even smaller in the near future; in future, structure sizes or critical dimensions (CDs) are expected to be less than 3 nm, for example 2 nm, or even less than 1 nm. For several applications, the specification requirement regarding the accuracy of a measurement provided by inspection equipment is even higher, for example by a factor of two or one order of magnitude. For instance, a width of a semiconductor feature must be measured with an accuracy of better than 1 nm, for example 0.3 nm or even less, and a relative position of semiconductor structures must be determined with an overlay accuracy of better than 1 nm, for example 0.3 nm or even less.

[0008] A multi-beam electron beam system is a relatively new development in the field of charged particle systems ("charged particle microscopes", CPMs). For instance, a multi-beam electron beam system is disclosed in US 7 244949 B2 and in US 2019 / 0355544 Al. In the case of a multi-beam electron beam system or MSEM, a sample is irradiated simultaneously with a plurality of individual electron beams, which are arranged in a field or raster. For instance, 4 to 10000 individual electron beams can be provided as primary radiation, with each individual electron beam being separated from an adjacent individual electron beam by a pitch of 1 to 200 micrometres. For example, a multi-beam electron beam system has approximately 100 separate individual electron beams ("beamlets"), which for instance are arranged in a hexagonal raster, with the individual electron beams being separated by a pitch of approximately 10 pm. The plurality of individual charged particle beams (primary beams) are focused on a surface of a sample to be examined by way of a common objective lens. For example, the sample can be a semiconductor wafer which is secured to a wafer holder mounted on a movable stage. When the wafer surface is illuminated by the primary individual charged particle beams, interaction products, for example secondary electrons or backscattered electrons, emanate from the surface of the wafer. Their start points correspond to those locations on the sample on which the plurality of individual primary particle beams are focused in each case. The amount and the energy of the interaction products depends inter alia on the material composition and the topography of the wafer surface. The interaction products form a plurality of secondary individual particle beams (secondary beams), which are collected by the common objective lens and imaged on a detector, which is arranged in a detection plane, by a projection imaging system of the multi-beam electron beam system. The detector comprises several detection regions, each of which comprises several detection pixels, and the detector captures an intensity distribution for each of the secondary individual particle beams. An image field of 100 pm x 100 pm, for example, is obtained in the process.

[0009] The state-of-the-art multi-beam electron beam system comprises a sequence of electrostatic and magnetic elements. At least some of the electrostatic and magnetic elements are adjustable in order to adapt the focus position and the stigmation of the plurality of individual charged particle beams. The state-of-the-art multi-beam system with charged particles moreover comprises at least one crossover plane of the primary or the secondary individual charged particle beams. Moreover, the state-of-the-art system comprises detection systems in order to facilitate the adjustment. The state-of-the-art multi-beam electron beam system comprises at least one beam deflector ("deflection scanner") for collective scanning of a region of the sample surface by means of the plurality of individual primary particle beams in order to obtain an image field of the sample surface.

[0010] In a state-of-the-art multi-beam electron beam system, the multiplicity of individual beams are generated using a first multi-aperture plate or filter plate with a multiplicity of first apertures in a first raster arrangement. The multiplicity of individual beams subsequently pass through further multi-aperture plates, for example a second multi-aperture plate with second apertures, for example with an array of active electrostatic elements. In typical examples, there are further multi-aperture plates with further apertures in addition to the first and second multi-aperture plates. Examples for such an arrangement of multi-aperture plates are disclosed in US 11,238,054 BB, US 2022392734 AA and WO 23016678 Al. In this case, the adjustment of the plurality of individual multi-aperture plates requires special measures. Additionally, individual, thin multi-aperture plates may deform during the operation of a multi-beam microscope. For example, this gives rise to the effect that at least one individual beam no longer passes centrally through a second aperture of a second multiaperture plate. Manufacture and joining of individual multi-aperture plates is therefore very susceptible to errors. It is known that surfaces with insulating material can accumulate charges locally. To avoid this, depressions or cavities are often formed for protecting insulating surfaces so that the probability of an electron beam impinging on an insulating material is reduced. Examples are shown in US7,276,707 B2, in which electrodes are separated from multi-pole elements by vacuum gaps. JP2816849 further shows vacuum gaps in labyrinthine form or with a cross-sectional form similar to the letter S. Further cross- sectional shapes are known from multiple sources, for example from US 5,041,731, US 5,401,974 and US 6,055,719.

[0011] Other solutions, for example that of US 20200203114 Al, provide for vacuum gaps between individual elements of multi-aperture plates. Contamination can accumulate in these vacuum gaps during operation, and electrical short circuits may arise.

[0012] DE 10 2022 131 862 Al, 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 Al, S. Eder-Kapl et al., "Characterization of CMOS programmable multi-beam blanking arrays as used for programmable multi-beam projection lithography ad resistless nanopatterning", Journal of Micromechanics and Microengineering 21 (2011), pp. 045038.1-8, and US 2005 / 0 242 302 Al disclose background art relating to multi-beam particle beam systems with aperture plates.

[0013] Description of the invention

[0014] It is therefore an object of the invention to provide an improved multi-aperture arrangement for generating or forming the plurality of electron beams for multi-beam electron beam systems, which is suitable for the increased demands in respect of resolution and accuracy when performing a wafer inspection task.

[0015] The object is solved by the independent claims. Dependent claims are directed to advantageous embodiments. The present patent application claims the priority of German patent application No. 10 2023 126 510.5 filed on 28 September 2023, the disclosure of which in the full scope thereof is incorporated in the present patent application by reference.

[0016] 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 which form continuous connections between a first side or top side and a second side or underside of the monolithic multi-aperture plate. Apart from the apertures, the monolithic multi aperture plate has no gaps or cavities where contamination could accumulate and make operation in vacuo more difficult. The monolithic multi-aperture plate essentially consists of a first, conductive material and a second, insulating material. In one example, the monolithic multiaperture plate is monolithically formed in its entirety from the first, conductive material, the second, insulating material and a material of an absorber layer, without separation points or cavities (apart from the plurality of apertures). Optionally, a thin metal layer can additionally still be present on the inner surfaces of the apertures. In this case, however, the monolithic multi-aperture plate is constructed to more than 95% from the first, conductive material (for example doped silicon or polysilicon) and a second, insulating material (for example silicon dioxide). The monolithic multi-aperture plate is not constructed in stacked fashion from individual multi-aperture plates, and so it is possible to manage without adjustment and joining, which are susceptible to errors. Hence it is also possible to integrate more functional layers, for example more than two or three sequences of functional layers. At least a first and a second sequence of functional layers are formed from the first and second material, with each sequence containing an active functional layer with a plurality of embedded electrodes, at least one connection layer with a plurality of electrical connection channels, and a passive functional layer. In one example, an active functional layer of a monolithic multi-aperture plate is formed as an array of multi-pole elements, each with a plurality of electrodes at each aperture, with the plurality of embedded electrodes being able to be two, three, four, six, eight or more. In one example, an active functional layer of a monolithic multi-aperture plate is formed as an array of lenses, each with only one ring-shaped embedded electrode at each aperture. Each embedded electrode can be connected to a control unit or monitoring unit via external electrical contacts on an individual basis and in electrically insulated fashion from other electrodes or other conductive structures.

[0017] The monolithic multi-aperture plate further comprises an absorber layer on the top side or the side on which a particle beam is incident. The material forming the absorber layer may contain gold, aluminium or tungsten. The absorber layer of the monolithic multi-aperture plate can be designed to be relatively thick, with the result that incident particles and x-ray beams are absorbed or stopped more effectively. In one example, the monolithic multi-aperture plate further contains a central region, in which the plurality of apertures are arranged, and a peripheral region with a plurality of electrical connection contacts situated on the first or top side and electrically connected via a through-connection region to the connection layers. For this purpose, the through- connection region contains a plurality of connection channels or VIAs insulated from one another. This renders possible a direct electrical connection of lower functional layers to the top side of the monolithic multi-aperture plate via the through-connection region. Rather than on the top side, electrical connection contacts electrically connected to the connection layers via the through-connection region can alternatively or additionally also be provided on the underside.

[0018] In a central region, the monolithic multi-aperture plate has a thickness T between the first side or top side and the second side or underside of no less than 100 pm, for example more than 150 pm, and preferably no less than 200 pm. In one example, the monolithic multiaperture plate further contains a support layer S4 containing, in the peripheral region, a mechanical connection contact or flange serving the connection to a multi-beam particle beam system.

[0019] The embedded electrodes of the monolithic multi-aperture plate are formed from the first, conductive material and are in each case electrically insulated from further conductive structures made of the first, conductive material by an insulating structure made of the second, insulating material. In this case, the structure insulating an electrode has at least one exposed area with the inner side of an aperture. In one example, the at least one exposed area of the insulating structure is arranged in a depression at a distance R3 greater than the inner radius R1 of the electrode in the aperture from a beam axis of a transmitted individual beam. In one example, an electrode comprises a tongue or key, whereby the depression has a labyrinthine form. In one example, a conductive structure comprises a tongue or key above or, in the beam direction, before or over an electrode, the tongue or key covering at least one exposed area. By way of the monolithically integrated depressions and by way of tongues, keys or grooves, it is possible to protect exposed areas of insulating structures within the inner side of the apertures from the transmitted particle beams, with the result that no local charges can be accumulated there.

[0020] In one example, the inner area of an electrode or conductive material on an inner side of an aperture is additionally coated with metal.

[0021] A second embodiment of the invention specifies a method for producing a monolithic multiaperture plate. The method comprises the following steps:

[0022] - step VI with first photolithographic patterning of a polished silicon dioxide layer,

[0023] - step V2 of depositing a doped polysilicon layer,

[0024] - step V3 for chemical-mechanical polishing (CMP) of the deposited polysilicon layer,

[0025] - step V4 of second, photolithographic patterning of the polished polysilicon layer,

[0026] - step V5 with etching for patterning the layer,

[0027] - step V6 with coating of the surfaces with silicon dioxide,

[0028] - step V7 with chemical-mechanical polishing (CMP) of the silicon dioxide surface formed in step V6,

[0029] - and step V9 of etching the apertures through the monolithic multi-aperture plate.

[0030] In one example, the method additionally contains a step V8 for coating the first side or top side of the monolithic multi-aperture plate with the absorber layer. In step V9, a thin metal layer can optionally still be applied to the inner surfaces of the apertures.

[0031] A third embodiment specifies a multi-beam electron beam system having a monolithic multiaperture plate. In one example, the multi-beam electron beam system further comprises a first filter plate arranged in the beam path of the electron beam between the particle source and the monolithic multi-aperture plate. This pre-filters an incident electron beam, and the number of incident or absorbed electrons is reduced.

[0032] The various embodiments and aspects of the invention can be combined wholly or partly with one another, provided that no technical contradictions arise as a result.

[0033] The invention will be understood even better with reference to the accompanying figures.

[0034] Figure 1 shows a multi-beam system having a monolithic multi-aperture plate

[0035] Figure 2 shows a further embodiment of a multi-beam system

[0036] Figure 3 shows a cross section through a monolithic multi-aperture plate

[0037] Figure 4 shows a structure of a monolithic multi-aperture plate

[0038] Figure 5a-c show detailed aspects of a monolithic multi-aperture plate

[0039] Figure 6a, b show an exemplary electrode arrangement in a monolithic multiaperture plate

[0040] Figure 7a-h show individual method steps during the manufacture of a monolithic multi-aperture plate

[0041] Figure 8 shows an example of a further detail of a monolithic multi-aperture plate Figure 9 shows an example of a further detail of a monolithic multi-aperture plate

[0042] Figure 10 shows an example of a monolithic multi-aperture plate with three active planes

[0043] Figure 11 shows an example of a monolithic multi-aperture plate with a through-connection region

[0044] Figure 12 shows method steps during the production of a plane of a monolithic multi-aperture plate

[0045] Figure 13 shows an example of a further detail of a monolithic multi-aperture plate

[0046] Figure 1 schematically shows a multi-beam electron beam system 1 according to one embodiment. The multi-beam electron beam system 1, also referred to as a multi-beam system 1 below, comprises a beam generating apparatus 300 having a particle source 301 for generating charged particles, for example an electron source. A divergent particle beam 309 is collimated by a sequence of condenser lenses 303.1 and 303.2 and incident on 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 individual particle beams 3 or individual electron beams 3 are generated and formed by the monolithic multi-aperture plate 306 (also referred to as a micro-optical unit 306). Midpoints of apertures in the monolithic micro-optical unit 306 are arranged in a raster arrangement in a first field which is imaged onto a further raster arrangement formed by beam spots 5 in an object plane 101. The distance between the midpoints of beam spots 5 in the object plane

[0047] 101 can be 5 ^m, 10 or 100 ^m, for example. The pitches of the apertures in the monolithic multi-aperture plate 306 are 100 pm, for example. The diameters D of the apertures are smaller than the pitch of the midpoints of the apertures; examples of the diameters are 0.2 times, 0.4 times and 0.8 times the pitches between the midpoints of the apertures.

[0048] The monolithic micro-optical unit 306 and the field lenses 307 and 308 are configured to generate a plurality of focus points 323 of primary beams 3 in a raster arrangement on an intermediate image surface 321. The surface 321 need not be a plane surface but rather can be a spherically curved surface in order to account for a field curvature of the subsequent particle-optical system.

[0049] The multi-beam electron beam system 1 further comprises a system of electromagnetic lenses 103 and an objective lens 102, which image the beam foci 323 from the intermediate image surface 321 in the object plane 101 with reduced size. In between, the first individual particle beams 3 pass through the beam splitter 400 and a first collective beam deflector or scanner 110, by means of which the plurality of first individual particle beams 3 are deflected during operation and the image field is scanned. For example, the first individual particle beams 3 incident in the object plane 101 form a substantially regular field. For instance, the field formed by the incidence locations 5 can have a rectangular or hexagonal symmetry.

[0050] The object 7 to be examined can be of any desired type, for instance a semiconductor wafer or a biological sample, and can comprise an arrangement of miniaturized elements or the like. The surface 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. For instance, this can be a magnetic objective lens and / or an electrostatic objective lens. The object 7, for example a wafer, is positioned on a displacement device or stage 500 with the surface 25 in the image plane 101. The surface 25 is preferably aligned perpendicular or with a slight tilt to an optical axis 105 of the objective lens 102, and the plurality of individual beams 3 are incident on the object in a manner substantially perpendicular to the object surface 25 and hence parallel to the optical axis 105. The object 25 on the wafer stage 500 is supplied with a voltage by way of a voltage supply 503.

[0051] The primary particles of the individual beams 3 incident on the object 7 generate interaction products, for example secondary electrons, backscattered electrons or primary particles which have experienced a reversal of movement for other reasons, and these interaction products emanate from the surface 25 of the object 7 or from the first plane 101 or object plane 101. The interaction products emanating from the surface 25 of the object 7 are shaped by the objective lens 102 to form secondary particle beams 9. In the process, the secondary beams 9 pass through the beam splitter 400 downstream of the objective lens 102 and are guided to a projection system 200. The projection system 200 comprises an imaging system having a plurality of electrostatic or magnetic lenses 206 to 210, a contrast stop 214 and a multi-particle detector 207. Incidence locations 15 of the second individual particle beams 9 on detection regions of the multi-particle detector 207 are located with a regular pitch in a third field. Exemplary values are 10 pm, 100 pm and 200 pm. Further, the projection system contains a second collective deflector or scanner 222 which is used to keep the incidence locations 15 of the second individual particle beams 9 on the multiparticle detector 207 at a constant position.

[0052] The multi-beam electron beam system 1 further comprises a computer system or a control unit 800, which in turn can have a single-part or multi-part design and which is designed both to control the individual particle-optical components of the multi-beam electron beam system 1 and to evaluate and analyse the signals obtained by the multi-detector 207 or the detection unit 207.

[0053] Further information relating to such multi-beam particle beam systems or multi-beam electron beam systems 1 and components used therein, such as, for instance, particle sources, multi-aperture plate and lenses, can be obtained from the international patent applications WO 2005 / 024881 A2, WO 2007 / 028595 A2, WO 2007 / 028596 Al, WO 2011 / 124352 Al and WO 2007 / 060017 A2 and the German patent applications DE 10 2013 016 113 Al and DE 10 2013 014976 Al, the disclosure of which is fully incorporated in the present application by reference.

[0054] More stringent demands are placed on a multi-beam system 1, especially for a wafer inspection. For example, the resolution of each partial image captured using each individual particle beam should be identical within a tight tolerance, for example better than 3.5 nm, better than 3.0 nm or even better. For example, the resolution should be directionally independent; i.e., for example, the resolution in an x-direction should deviate from a resolution in a y-direction by no more than 5%. In this context, reference is also made to so- called H-V differences. Further, the positions of the individual beam spots 5 should be very stable so that the relative positions of the individual partial images remain stable and need not be corrected by a complicated computational correction of many partial image offsets. These stringent demands lead firstly to increased demands on the design of the micro- optical unit 306 and secondly to increased demands during the operation of the micro- optical unit 306. A multi-beam system 1 according to an embodiment of the invention is designed to meet these increased demands even during operation. To meet the more stringent demands, the micro-optical unit 306 according to the embodiment has a monolithic design. Figure 2 shows a further design of the beam generating apparatus 300 according to the embodiment. Disposed downstream of the electron source 301 there is a first stop 311 and a first multi-aperture plate or first filter plate 304 with a multiplicity of first apertures. The incident electron beam 309 is partially absorbed at the first filter plate 304. The first filter plate 304 is followed by a collimation lens or condenser lens 303 and the monolithic multiaperture plate 306. The monolithic multi-aperture plate 306 is followed by a field lens 308 and the further components of the multi-beam system 1, in respect of which reference is made to Figure 1 and the associated description. The plurality of a primary beams are deflected through a deflection angle 109 into the direction of the optical axis 105 of the objective lens 102 by the beam splitter 400. The deflection angle 109 can be between 3° and 20°, preferably between 4° and 10°. However, smaller or larger deflection angles 109 are also possible.

[0055] The first filter plate 304 is sometimes also referred to as pre-aperture plate 304. It may serve to reduce the load on the monolithic micro-optical unit 306 due to the incident electron current from the electron beam 309.

[0056] For wafer inspection in particular, there are increased demands on the isotropy of resolution and the uniformity of resolution of imaging for the multiplicity of particle beams. Isotropy of resolution means that a resolution in an x-direction deviates from a resolution in a y- direction perpendicular thereto by no more than 5%, for example. By preference, the deviation is even less, for example 3% or even less. Additionally, the resolution of a first individual beam should deviate from a resolution of a second individual beam by no more than 5%, preferably by less than 3%. Such isotropy and invariance of the resolution is achieved when the beam cross sections 115 in a pupil plane 117 are circular and have an identical diameter for all beams. Accordingly, the (real or virtual) beam cross sections 119 of all first individual beams 3 are identical and circular in a plane 111 parallel to the image plane.

[0057] A cross section of an exemplary monolithic micro-optical unit 306 is explained in detail in Figure 3. To simplify matters, only four apertures 85 for forming four individual beams 3.1 to 3.4 are illustrated. However, a much larger number of apertures is possible, for example 50, 100, 300 or even more, for example approximately 1000, depending on the number of individual particle beams 3 to be generated. A pitch Pl between the apertures is approximately 100 pm or more. For example, the apertures 85 can be arranged in a Cartesian raster or in a hexagonal arrangement. Other arrangements are likewise possible. The apertures 85 extend between the first or top side 313 and the second side or underside 315 of the monolithic multi-aperture plate 306. Each aperture has a diameter of approximately 50 pm. In the central region 191 comprising the apertures 85, the monolithic multi-aperture plate 306 has a thickness T of more than 100 pm, for example 150 pm or 200 pm, or more, for example 300 pm. In particular, the monolithic multi-aperture plate 306 does not contain any thin membranes with a thickness of less than 50 pm as conventional in the prior art. Hence, there cannot be any deformations of individual, thin membranes. Further, the monolithic micro-optical unit 306 does not have a stacked construction and does not form a stack of individual elements. It is thus possible to manage without an adjustment and joining of individual elements, which is susceptible to errors.

[0058] An electron beam 309 emanates from an electron source 301 and is filtered at a first filter plate 304 (not depicted here). The monolithic multi-aperture plate 306 comprises a first functional layer SI with a plurality of apertures 85. This shapes the cross sections of the individual beams 3.1 to 3.4. In this case, each beam cross section of an individual beam 3.i corresponds to the aperture shape of an aperture 85 in the first functional layer SI. In this case, the aperture shapes of the first beam-shaping apertures 85 in functional layer SI can be designed to be individually different and for example have different elliptical designs. For example, the first functional layer SI comprises an absorber layer 99 formed from a conductive material preferably with a high density or high atomic number (for example aluminium, gold, lead or tungsten). The absorber layer 99 of the monolithic multi-aperture plate 306 can be designed to be very thick, for example up to 5 pm or more. Hence, the excess electrons of the pre-filtered individual beams 3 which do not pass through the apertures 85 are captured and absorbed. The absorber layer 99 is connected to a large capacitance, for example to earth (or 0 V reference potential). A thick absorber layer 99 is also suitable for blocking x-ray radiation.

[0059] With the exception of this absorber layer 99 on the top side 313, the monolithic multiaperture plate 306 is essentially constructed from a first, conductive material (for example doped silicon or polysilicon) and a second, nonconductive material (for example silicon dioxide). Apart from the apertures 85, the monolithic multi-aperture plate 306 has no gaps or cavities.

[0060] The individual beams 3.i then pass through further functional layers S2, S3 and S4 of the monolithic multi-aperture plate 306. The functional layers in the monolithic multi-aperture plate 306 have a two-fold 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 in this example. Finally, there is a further passive functional layer S2.3 and a support layer S4, which can likewise be provided as an integral constituent part of the monolithic multi-aperture plate 306. For example, the support layer S4 contains a mechanical flange or support frame 86. Together with the support frame 86, the monolithic multi-aperture plate 306 has a thickness of approximately

[0061] 0.5 mm to 1 mm, for example. During operation, electric fields that have an individual, beam-shaping or deflecting effect on each individual beam 3.i are generated by way of applied voltages at the embedded electrodes 81.1 and 81.2. For example, single individual beams 3 are focused differently, deflected differently or otherwise influenced differently in terms of their beam shape. To this end, the embedded electrodes 81.1 and 81.2 are connected on an individual basis to a control unit 830 (see Figure 2).

[0062] Figure 4 shows a simplified example of the monolithic multi-aperture plate 306 in cross section. The monolithic multi-aperture plate 306 is predominantly formed, i.e. to more than 50%, more than 70% or even more than 80%, of a conductive material 87, for example doped silicon. In this conductive material 87, individual conductive structures 93 are surrounded by insulating material 89 and hence electrically insulated from one another. For example, insulating material 89 may be provided by silicon dioxide. Individual conductive structures 93 are embedded in and surrounded by insulating material and further can be delimited by a piece of area of at least one inner wall of an aperture 85. As a result, individual conductive structures 93 which are electrically insulated, for example the structures made of electrodes 81 and electrical connection channels or lines 75, are formed in the conductive material 87. A plurality of electrical connection channels 75 and 77 connect each electrode 81 to an associated connection contact 83, the connection contacts for example being provided in the first functional layer SI on the top side 313 of the monolithic multi-aperture plate 306 for electrical connection to the control unit 830. Voltage differences can be applied between the electrode 81.1 and further electrodes on the same aperture opening 85.1 in order to obtain a beam deflection or stigmation of individual beams 3. Voltage differences can be applied to the electrode 81.1 or further electrodes 81.2 in further functional layers in order for example to obtain a focusing effect of individual beams 3.

[0063] For example, a part of the conductive structure 93.1 is formed by the vertical connection channel 75.1, which may have a diameter of approximately 5 pm. A further part of the conductive structure 93.1 is formed by the electrode 81.1, which may have a thickness of approximately up to 50 pm. A further part of the conductive structure 93.1 is formed by the horizontal connection channel 77.1 between the electrode 81.1 and the vertical connection channel 75.1. A horizontal connection channel 77.1, 77.2 can have a diameter of 0.25 pm to 5 pm. Insulating material 89 between two conductive structures 93.1, 93.2 or 93.3 has a thickness of at least 0.5 pm; however, a greater thickness of up to 5 pm may also be present.

[0064] The diameters of the apertures 85 in the individual functional layers SI to S3 can be different. The diameter DI in the uppermost functional layer SI is smaller than the diameter D2 in an active functional layer S3. By contrast, the diameter D3 in a passive functional layer S2 is designed to be larger than the diameter D2. This prevents electrons from the individual electron beams 3 from coming into contact with the inner aperture walls of the apertures 85 below the first functional layer SI.

[0065] In this case, the functional layers SI, S2 and S3 comprise a plurality of planes or laminas, as depicted using the example of the functional layer S3.1 with planes or laminas LI to L5. Figure 5a shows an embodiment of a design of an active functional layer S3.i with electrode 81. The first lamina and the third lamina L3 comprise parts of the insulating structure 89 or 91. The second lamina L2 comprises parts of the electrical connection line 77.1. The fourth lamina L4 comprises inter alia the conductive structure 93.3 and parts of the embedded electrode 81. The fifth lamina 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 lamina L4 and from the conductive structures situated thereabove and therebelow. The conductive structure 93.3 is not fully insulated and for example connected to the 0 V reference potential via connection 95. The conductive structure 93.3 shields electric fields and thus acts as a shield between the embedded electrode 81 and further embedded electrodes (not depicted here). The conductive electrical connections 75.1 and 75.2 are formed as cylindrical, insulated conduction channels and in each case shown in cross section here.

[0066] The insulating structure 89 or 91 having an exposed area 73 to the aperture 85 is provided for insulating the embedded electrode 81 and the electrical connection lines 75.1 and 77.1. Scattered electrons can adhere to the exposed insulating area 73 of insulating structures 89 during operation and can cause local space charges there. To prevent the adhesion of scattered electrons or the generation of local space charges, the exposed areas 73 are arranged in a depression 71 at a distance R3 from the beam axis 121 of an individual primary beam 3, where R3 is chosen to be larger than the radii RO and, respectively, R5 of a functional layer S2 arranged thereabove or therebelow and, in particular, also greater than the radius R1 of the inner wall of the electrode 81. Hence, a direct "line of sight" between the exposed area 73 and an individual beam 3 is avoided. The depression 71.1 has a width B in the propagation direction of the electron beam 3, given by the z-axis in Figure 5a. The width B corresponds to the layer thickness of the first lamina LI in Figure 5a. In one example, the width B is chosen to be smaller than the difference between the radius R3 of the depression 71.1 and the radius R1 of the electrode 81, such that the following applies: B < (R3 - R1).

[0067] Figure 5b shows a further embodiment of a design of an active functional layer S3.i with electrode 81. In this example, the active functional layer S3.i consists of nine individual planes or laminas LI to L9. The third plane or lamina L3 comprises parts of the insulating structure 89. The fourth lamina L4 comprises the electrical connection line 75.1. The fifth lamina L5 comprises parts of the insulating structure 91. The sixth lamina L6 comprises inter alia the conductive structure 93 and parts of the embedded electrode 81. The seventh lamina 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 lamina L6 and from the conductive structures situated thereabove and therebelow. To prevent the adhesion of scattered electrons or the formation of local charges on the exposed areas 73, the electrode 81 in lamina L2 extends over the insulating structure and forms a labyrinthine gap 79.1 with respect to the exposed area 73 in laminas LI and L2. The labyrinthine gap or depression 79.1 is further enlarged by a tongue or key 61 formed on the electrode 81. Hence there is no direct line of sight between the exposed area 73 and an electron beam 3, and the probability of scattered electrons reaching the exposed area 73 is reduced. A further labyrinthine vacuum gap 79.2 can be provided at the underside - as seen in the beam direction - of the electrode 81 in laminas L8 and L9.

[0068] In the example of Figure 5b, the inner surfaces of the apertures 85 further comprise a thin metal layer 67. The metal layer 67 can be introduced with a thickness of a few nm, for example 5 nm, into the apertures 85. It serves as a protective layer and can prevent the adhesion or formation of local charges on the conductive structures 93 or the electrodes 81. The application of only a thin layer 67 prevents a metal layer from also forming in the depressions 71 and 79. The metal layer can be formed from copper, aluminium, gold or tungsten.

[0069] Figure 5c shows a further embodiment of a design of an active functional layer S3.i with electrode 81. To prevent the adhesion of scattered electrons or the formation of local charges on the exposed areas 73, the conductive structure in functional layer S2.i extends over the exposed area 73.1 with a tongue or key 65.1. A similar tongue or key 65.2 is arranged below the embedded electrode 81 - in the beam direction from top to bottom.

[0070] An electrode arrangement 81 can consist of a ring-shaped electrode in order to form an Einzel lens. However, an electrode arrangement 81 can also be formed as a multi-pole electrode 81, for example with eight electrodes (81.1 to 81.8), which are surrounded by the insulating structure 91. Figure 6 shows an example of an electrode arrangement 81 with eight embedded electrodes 81.1 to 81.8 around an aperture 85. A respective exposed area 73 of the insulating structure 91 is situated between two respective separate, embedded electrodes. To prevent scattered electrons from reaching the exposed area 73, the electrodes are formed with grooves 63 and respective keys or tongues 61, 65 such that a key 61 of one electrode 81.1 protrudes into a groove of an adjacent electrode 81.2 and, together with the key 65 of the adjacent electrode 81.2, forms a labyrinthine vacuum gap 79 (see Figure 6b). A vacuum gap 79 further leads to a shielding of disturbance fields which can emanate from structures situated therebehind. Furthermore, a metal layer 67 can be present on the inner sides of the electrodes 81.1 to 81.8.

[0071] Figure 7 shows an example of individual intermediate steps during the manufacture of a monolithic multi-aperture plate 306. In a first step, a lowermost plate 171.9 of doped silicon is provided with an insulating silicon dioxide layer 169.9 (Figure 7a). The silicon dioxide layer is patterned by photolithography, and a further doped silicon layer 171.8 is grown epitaxially or in the plasma reactor (e.g. PECVD / plasma enhanced chemical vapour deposition) and patterned. To this end, photolithographic patterning contains a lithographic exposure and at least one etching. A further insulating silicon dioxide layer 169.8 is generated thereabove

[0072] (Figure 7b). These steps are repeated (Figures 7c-d), and further layers 171.8 to 171.1 are formed (only depicted as far as layer 171.6 for a simpler illustration). In each layer, conductive structures are photolithographically separated by insulating structures; for example, these subsequently form the embedded electrodes 81 and the conductive connections 75. Hence, different functional layers of the monolithic multi-aperture plate 306 are formed, with first functional layers 177 with a supporting function, second functional layers 175 which form passive electrodes or spacers and third functional layers 181 with active electrodes 81. At the end, the conductive absorber layer 99 made of dense material is applied and patterned (Figure 7e). For chemical through-etching of the subsequent apertures 85, an etching protection layer 173 is applied and patterned photolithographically in accordance with the subsequent apertures 85 (Figure 7e). Subsequently, the apertures 85 are etched into the doped silicon, with the etching protection layer 173 and the structures made of silicon dioxide acting as etching protection layer 173 (Figure 7f). Figure 7g shows the result of the through-etched apertures, for example after wet chemical removal of the exposed silicon dioxide layers. In the apertures 85, the thin metal layers 67.1 and 67.2 are applied to the inner areas by deposition. Finally, the etching protection layer 173 is removed (Figure 7h). Figure 8 finally shows the uppermost laminas of a monolithic multi-aperture plate 306 facing the incident electron beam 309. With regards to reference signs and explanations of same, reference is made to the figures above and their description, in particular Figures 4 to 6 and their description. The connection contacts 83 for electrically connecting the electrodes 81 are further connected to the control unit 830. Hence, the many transmitted electron beams can be influenced individually during operation (e.g. including at least one of focusing, beam shaping [e.g. astigmatic reshaping or application of higher multipole fields], or beam deflection). Figure 9 shows a further embodiment of the structures for preventing the charging of exposed areas of insulating structures. In this example, the uppermost doped silicon layer 171.1 is formed with a key and tongue 65.1 which extends over the insulating layer therebelow. Hence, the exposed area 73 therebelow is protected, and the probability of scattered electrons reaching it is reduced. With regards to reference signs and explanations of same, reference is made to the figures above and their description, in particular Figures 4 and 5 and their description.

[0073] Figure 13 shows a further embodiment. In the example of Figure 13, the uppermost absorber layer 99 has a thickness T1 of 1.5 pm, for example. For example, the absorber layer is made of gold. The layer 171.1 of doped silicon situated therebelow has a conical opening, with an angle G1 between a tangent to the conical opening in the axial direction and the perpendicular 317 to the surface 313 of the absorber layer 99. In Figure 13, the angle G1 is depicted as 7° by way of example; however, the angle G1 can also be very much larger and for example equal 30° or 35°.

[0074] On the upper side facing the absorber layer 99, the diameter of an aperture 85 in the first layer 171.1 therefore has a first diameter D3.1 that is smaller than the diameter 3.2 on the distant, lower side. For example, DI < D3.1 < D3.2 applies. Exemplary values for the diameters are DI = 25 pm, D3.1 = 26.5 pm, D3.2 = 30 pm. Alternative values for the diameters are DI = 30 pm, D3.1 = 31.5 pm, D3.2 = 35 pm. Further alternative values for the diameters are DI = 35 pm, D3.1 = 37 pm, D3.2 = 40 pm. The clear internal diameter D2 of the aperture 85 between the electrodes 81 is for example chosen between the diameters D3.1 and D3.2 such that the following applies: D3.1 < D2 < D3.2.

[0075] Further, there can be underetching 319 of the absorber layer 99 as a result of etching the aperture openings 85 through the monolithic multi-aperture plate 306. The conic design of the aperture openings 85 with diameters D3.1 < D3.2 in the uppermost layer made of doped silicon or polysilicon (171.1) following the absorber layer 99 and the optional underetching 319 bring about a further prevention with regards to the adhesion of disturbing charged particles in the interior of an aperture opening 85.

[0076] 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 allow independent and individual focusing, deflection and beam shaping of the passing individual beams 3.1 and 3.2. To this end, each of the embedded electrodes 81.1 to 81.6 is embodied as a multi-pole electrode. Additionally, a thin metal layer can be applied to the inner areas of the apertures 85 (not depicted here). For example, field curvature and an image plane tilt of the subsequent electron-optical system can be compensated for by active focusing elements. For example, aberrations of the subsequent electron-optical system can be compensated for by active beam shaping elements. For example, the beam pitch can be set or a distortion of the subsequent electron-optical system can be compensated for by active beam deflection elements. Apart from the individually designed electrical connection channels 75.1 to 75.6, planes with the same function are therefore largely identical and masks for photolithographic patterning can be used multiple times. Apart from the plurality of apertures 85, the monolithic multi-aperture plate 306 contains no cavities. Hence the monolithic multi-aperture plate 306 is less sensitive to thermal deformation. With regards to further reference signs and explanations of same, reference is made to the figures above and their description, in particular Figures 4 and 5 and their description, and to Figure 11 and its description.

[0077] Figure 11 shows a schematic overview image of a cross section of the monolithic multiaperture plate 306 with three active functional layers 181.1 to 181.3 and interposed connection layers 183.1 to 183.6 containing electrical connection channels 75 for electrical contacting of the electrodes 81. The monolithic multi-aperture plate 306 further contains at least one purely passive functional layer 175.1 to 175.3, which essentially serves to create a free propagation spacing for the transmitted electron beams 3.1 to 3.5. The monolithic multi-aperture plate 306 comprises a central region 191 with a plurality of apertures 85, only five of which are depicted. Furthermore, a peripheral region 193 of the monolithic multiaperture plate 306 contains a through-connection region 195 for electrically connecting the individual connection layers 183.1 to 183.6 to electrical contacts 83 arranged on the top side 313. The monolithic multi-aperture plate 306 is connected to the control unit 830 via the electrical contacts 83.

[0078] The monolithic multi-aperture plate 306 comprises a repeated sequence 189.1 to 189.3 of functional layers, consisting in each case of at least one active functional layer 181 with embedded electrodes 81, a connection layer 183 and a passive functional layer 175. With regards to reference signs and explanations of same, reference is made to the figures above and their description. Apart from the apertures 85, the monolithic multi-aperture plate 306, in contrast to the prior art, has no gaps or cavities where contamination could accumulate and make operation in vacuo more difficult. The monolithic multi-aperture plate 306, in contrast to the prior art, is not constructed in stacked fashion from individual multi-aperture plates, and so it is possible to manage without adjustment and joining, which are susceptible to errors. Hence it is also possible to integrate more functional layers, for example more than three functional layers. In contrast to the prior art, this also renders possible a direct electrical connection of lower functional layers to the top side 313 of the monolithic multiaperture plate 306 via the through-connection region 195. By way of monolithically integrated depressions 71, 79 and by way of tongues, keys or grooves 61, 63, 65, it is further possible to protect exposed areas 73 of insulating structures within the inner side of the apertures from the transmitted particle beams 3, i.e. particle beams 3 passing through the monolithic multi-aperture plate, with the result that no local charges can be accumulated there.

[0079] Figure 12 schematically shows the iterative steps of the additive manufacturing method for an individual layer of a monolithic multi-aperture plate 306. In step VI, there is a first, photolithographic patterning of a polished silicon dioxide layer. In step V2, there is a deposition of doped polysilicon. In step V3, there is chemical-mechanical polishing (CMP) of the deposited polysilicon. In step V4, there is second photolithographic patterning. In step V5, there is etching for patterning the layer. In step V6, the surfaces of the etched structures are provided or filled with silicon dioxide. Subsequently, in step V7, the silicon dioxide surface is polished with CMP. The method steps are repeated until the monolithic multiaperture plate 306 has been constructed in full (step Q). Then, in step V8, there is coating with the absorber layer 99, and, in step V9, there is etching of the apertures and the introduction of the thin metal layer 67 into the apertures 85.

[0080] A list of reference signs is provided:

[0081] 1 Multi-beam electron beam system

[0082] 3 Individual particle beams

[0083] 5 Beam spots

[0084] 7 Object or wafer

[0085] 9 Secondary particle beams T1

[0086] 15 Incidence locations of the secondary individual particle beams

[0087] 25 Surface of the object

[0088] 61 Tongue or key

[0089] 63 Groove 65 Tongue or key

[0090] 67 Thin metal layer

[0091] 71 Depression

[0092] 73 Exposed area

[0093] 75 Electrical connection channels 77 Electrical connection channels

[0094] 79 Labyrinthine depression

[0095] 81 Electrode or electrodes

[0096] 83 Electrical connection contact

[0097] 85 Aperture or apertures 86 Mechanical flange

[0098] 87 Conductive material

[0099] 89 Insulating material

[0100] 91 Insulating structure

[0101] 93 Conductive structure 95 Electrically conductive connection

[0102] 99 Absorber layer

[0103] 101 Object plane

[0104] 102 Objective lens 103 Electromagnetic lenses

[0105] 105 Optical axis

[0106] 109 Deflection angle

[0107] 110 Collective beam deflector

[0108] 111 Plane parallel to the image plane 115 Beam cross sections

[0109] 117 Pupil plane

[0110] 119 Beam cross section of a first individual beam

[0111] 121 Beam axis of an individual beam

[0112] 169 Silicon dioxide layer 171 Doped silicon / polysilicon

[0113] 173 Etching protection layer

[0114] 175 Passive functional layer

[0115] 181 Active functional layer

[0116] 183 Connection layer 189 Layer sequence

[0117] 191 Central region

[0118] 193 Peripheral region

[0119] 195 Through-connection region 200 Projection system

[0120] 206 Electrostatic or magnetic lens

[0121] 207 Multi-particle detector

[0122] 208 Electrostatic or magnetic lens

[0123] 209 Electrostatic or magnetic lens 210 Electrostatic or magnetic lens

[0124] 214 Contrast stop

[0125] 218 Beam deflector

[0126] 222 Second collective deflector

[0127] 300 Beam generation device 301 Particle source

[0128] 303 Condenser lenses

[0129] 304 First filter plate

[0130] 306 Monolithic multi-aperture plate

[0131] 307 Field lens 308 Field lens

[0132] 309 Particle beam

[0133] 311 First stop

[0134] 313 First or top side 315 Second side or underside

[0135] 317 Perpendicular to the top side 313

[0136] 319 Underetching

[0137] 321 Intermediate image surface

[0138] 323 Focus points 400 Beam splitter

[0139] 500 Displacement device or stage

[0140] 503 Voltage supply

[0141] 800 Control unit

[0142] 830 Control unit for the primary beam

Claims

Claims1. 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) which form continuous connections between a first side or top side (313) and a second side or underside (315) of the multiaperture plate (306), with at least one first and one second sequence (189.1, 189.2, 189.3) of functional layers (181, 183, 175) being formed from the first and second material, each sequence (189.1, 189.2, 189.3) containing an active functional layer (181.1, 181.2, 181.3) with a plurality of electrodes (81), at least one connection layer (183.1 to 183.6) with 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 via a through-connection region (195) to the connection layers (183.1 to 183.6), with the through-connection region (195) extending 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 either of Claims 1 and 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 electrically insulated from further conductivestructures 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 area (73) with the inner side of an aperture (85) and wherein the at least one exposed area (73) is arranged in a depression (71, 71.1, 71.2, 79) at a distance R3 greater than the inner radius R1 of the aperture (81) from a beam axis (121) of an individual beam (3).

4. Monolithic multi-aperture plate (306) according to Claim 3, wherein the depression (71, 71.1, 71.2, 79) has a width B with B <(R3 - Rl) in the propagation direction of an electron beam (3).

5. Monolithic multi-aperture plate (306) according to Claim 3 or 4, wherein an electrode (81.1 to 81.8) has a tongue or key (65, 65.1, 65.2) and wherein the depression (79, 79.1, 79.2) has a labyrinthine form.

6. Monolithic multi-aperture plate (306) according to any of Claims 1 to 5, 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 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 area (73) with the inner side of an aperture (85) and wherein a conductive structure above the electrode (81.1 to 81.8) comprises a tongue or key(65, 65.1) which covers the at least one exposed area (73) of the insulating structure (91).

7. Monolithic multi-aperture plate (306) according to any of Claims 1 to 6, further comprising an absorber layer (99) on the top side (313).

8. Monolithic multi-aperture plate (306) according to Claim 7, wherein a material of the absorber layer (99) is gold, aluminium or tungsten.

9. Monolithic multi-aperture plate (306) according to Claim 7 or 8, wherein the multiaperture plate (306) is monolithically formed in its entirety from the first, conductive material (87), the second, insulating material (89) and a material of the absorber layer (99), without separation points or contained cavities.

10. Monolithic multi-aperture plate (306) according to any of Claims 1 to 9, further comprising a support layer S4 containing a mechanical connection contact or flange (86).

11. Monolithic multi-aperture plate (306) according to any of Claims 1 to 10, wherein the monolithic multi-aperture plate (306) has a thickness T between the first side or top side (313) and the second side or underside (315) of more than 100 pm.

12. Monolithic multi-aperture plate (306) according to any of Claims 1 to 11, wherein the monolithic multi-aperture plate (306) has a thickness T between the first side or top side (313) and the second side or underside (315) of more than 150 pm, preferably more than 200 pm.

13. Method for producing a monolithic multi-aperture plate (306) according to any of Claims 1 to 12, comprising an at least two-fold, iterative sequence of the following steps:- step VI with first, photolithographic patterning of a polished silicon dioxide layer,- step V2 of depositing a doped polysilicon layer,- step V3 for chemical-mechanical polishing (CMP) of the deposited polysilicon layer,- step V4 of second, photolithographic patterning of the polished polysilicon layer, - step V5 with etching for patterning the layer,- step V6 with coating of the surfaces with silicon dioxide,- and step V7 with chemical-mechanical polishing (CMP) of the silicon dioxide surface formed in step V6.

14. Method for producing a monolithic multi-aperture plate (306) according to Claim 13, further comprising a step V9 of etching the apertures (85) through the monolithic multi-aperture plate (306).

15. Method for producing a monolithic multi-aperture plate (306) according to Claim 13 or 14, 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).

16. Multi-beam electron beam system (1) having a monolithic multi-aperture plate (306) according to any of Claims 1 to 12.

17. Multi-beam electron beam system (1) according to Claim 16, 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).

18. Multi-beam electron beam system (1) according to Claim 16 or 17, wherein at least one active functional layer (183.1, 183.2, 183.3) of the monolithic multi-aperture plate (306) is formed as a multi-pole element having a plurality of electrodes (81.1 to 81.8) at each aperture (85).

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