Charged particle optics components and their fabrication

Abstract

The present invention is directed to an electrode component with at least two electrodes or a multipole component as generally known in the art. Each of the electrodes can be provided with a beam neighboring section or end section forming the free electrodes. This section is the section exposed to high voltages, i.e. more than 10 KV, and is intended to nevertheless work very reliable and precise with respect to the guidance and/or controlling of a beam of a charged particle beam in a microscope or lithographic apparatus. This neighboring section are positioned in the vicinity or close to a charged particle beam or even facing it. This bears the preferred advantage that high voltages can be generated by the electrodes or to the electrode component and they can withstand those high voltages. This assists in a better guidance and/or controlling of the charged beam, such as for compensating aberration etc. The beam neighboring section can have a surface configured to face the beam. This neighboring section or surface are fabricated with absolute dimensional tolerances less than a desired maximum absolute dimensional tolerance wherein the desired maximum absolute dimensional tolerance is based at least on a maximum voltage to be applied to the electrode. With such a precisely fabricated surface, a more precise and/or efficient field can be generated being able to control the charged particle beam more precisely and efficiently.

Claims

1. A device for the use in charge particle optics comprising: an electrode component (302) with at least two electrodes (302a,b), each being provided with a beam neighboring section, the beam neighboring section having an absolute dimensional tolerance less than a desired maximum absolute dimensional tolerance, wherein the desired maximum absolute dimensional tolerance is based at least on a maximum voltage to be applied to any of the at least two electrodes (302a,b).

2. The device according to claim 1, wherein the beam neighboring section of the electrode component (302) has a maximum absolute dimensional tolerance of 0.25 m, preferably a maximum absolute dimensional tolerance of 0.10 m, more preferably a maximum absolute dimensional tolerance of 0.05 m, and even more preferably a maximum absolute dimensional tolerance of 0.02 m.

3. The device according to claim 1, the beam neighboring section having a surface (302c) configured to face the beam, the surface (302c) having a maximum surface roughness of Ra 0.05 m.

4. The device according to claim 1, the surface having a maximum surface roughness of Ra 0.04 m, preferably a maximum surface roughness of Ra 0.03 m, and most preferably a maximum surface roughness of Ra 0.025 m.

5. The device according to claim 1, wherein the electrode component (302) is provided with a beam neighboring section with a minimum effective thickness that is configured to be used with a beam voltage of more than 10 KeV, more preferably more than 15 KeV, more preferably more than 30 KeV, more preferably more than 50 KeV and more preferably more than 100 KeV.

6. The device according to claim 5, wherein the desired maximum absolute dimensional tolerance is based also on the beam energy.

7. The device according to claim 1, wherein the electrode component (302) is provided with a beam neighboring section with a minimum effective thickness of at least 0.1 m, preferably 100 m, preferably 500 m, preferably 1,000 m, preferably of at least 1,250 m, more preferably of at least 1,500 m, and more preferably of at least 3,000 m.

8. The device according to claim 1, with a stack of electrodes comprising at least two layers of electrodes along an axis of the beam, wherein the effective thickness (L) of the electrodes comprises the thickness of each layer of electrodes and the distance between the electrodes.

9. The device according to claim 8, wherein the desired maximum absolute dimensional tolerance is based also on the effective thickness. The device according to claim 1, wherein the device is an aberration corrector.

11. The device according to claim 1, wherein an electrically insulating substrate (306) is fixed to the electrode component (302) and has at least one substrate beam facing surface(s) flush with the beam facing surfaces (302c).

12. The device according to claim 11, wherein the electrode component (302) and the substrate (306) are fixed together by an intermediate layer (304).

13. The device according to claim 11, wherein the electrode component (302) comprises at least two indexing markers (408) in order to align the electrode component (302) with any other component, such as the substrate (306).

14. Method of fabrication of a device for the use in charge particle optical instruments comprising the steps of forming an electrode component with at least two electrodes, each being provided with a beam neighboring section having an absolute dimensional tolerance less than a desired maximum absolute dimensional tolerance wherein the desired maximum absolute dimensional tolerance is based at least on a maximum voltage to be applied to the electrode.

15. Method of fabrication of a device for the use in charge particle optical instruments comprising the steps of forming an electrode component with at least two electrodes, each being provided with a beam neighboring section having a maximum absolute dimensional tolerance of 1 m.

16. Method for forming of a device, particularly according to claim 15, for the use in charge particle optics comprising forming at least a beam neighboring section of an electrode component (302) with high-precision forming.

17. Method according to claim 16, comprising applying any of the forming processes of lithography, deep dry etching, the forming of silicon wafers, deposit coating for forming at least the beam neighboring section of the electrode component (302).

18. Method according to claim 15, further with the step of forming at least the neighboring section of the electrodes or the entire electrodes from conductive Si-wafer material and/or semiconductor Si-wafer with a metal coating applied onto the semiconductor Si-wafer.

19. A charged particle beam assembly, particularly a charged particle beam microscope, the device comprising: an electrode component (302) with at least two electrodes (302a,b), each being provided with a beam neighboring section, the beam neighboring section having an absolute dimensional tolerance less than a desired maximum absolute dimensional tolerance, wherein the desired maximum absolute dimensional tolerance is based at least on a maximum voltage to be applied to any of the at least two electrodes (302a,b).

20. Operation of a charged particle beam assembly with a device according to claim 19, comprising generating a beam voltage of more than 50 KeV.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0217] Further potential and thus non-limiting features, details and advantages of the invention will be discussed in the following drawings.

[0218] FIG. 1 depicts a microscopy system comprising an active charged particle optics component.

[0219] FIG. 2a depicts a heuristic schematic of an active charged particle optics component.

[0220] FIG. 2b depicts a schematic setup of the active charged particle optics component.

[0221] FIG. 3 depicts an exemplary active charged particle optics component according to the present invention.

[0222] FIG. 4a depicts a step in a fabrication of the active charged particle optics component according to the present invention;

[0223] FIG. 4b depicts another step in the fabrication of the active charged particle optics component according to the present invention;

[0224] FIG. 4c depicts yet another step in the fabrication of the active charged particle optics component according to the present invention;

[0225] FIG. 4d depicts the final active charged particle optics component according to the present invention;

[0226] FIG. 5a depicts an image of the active charged particle optics component according to the present invention;

[0227] FIG. 5b depicts a zoomed-in image of the active charged particle optics component according to the present invention;

[0228] FIG. 6a depicts an image of the active charged particle optics component according to the present invention for a beam energy of 60 KeV; and

[0229] FIG. 6b depicts an image of the active charged particle optics component according to the present invention for a beam energy of 300 KeV.

[0230] FIG. 6c depicts a micro structure comprising a recess through the component with the electrodes enclosing a circular or cylindrical structure according to the invention. present invention.

[0231] FIG. 7 shows a preferred device and a way of fabrication according to the present invention.

[0232] FIG. 8a shows a preferred first step of fabrication of an aperture plate in accordance with the present invention.

[0233] FIG. 8b shows a preferred second step of fabrication of an aperture plate in accordance with the present invention.

[0234] FIG. 8c shows a preferred third step of fabrication of an aperture plate in accordance with the present invention.

[0235] FIG. 8d shows a preferred fourth step of fabrication of an aperture plate in accordance with the present invention.

[0236] FIG. 8e shows a preferred fifth step of fabrication of an aperture plate in accordance with the present invention.

[0237] FIG. 9a shows a preferred first step of fabrication of an electrode component in accordance with the present invention.

[0238] FIG. 9b shows a preferred second step of fabrication of an electrode component in accordance with the present invention.

[0239] FIG. 9c shows a preferred third step of fabrication of an electrode component in accordance with the present invention.

[0240] FIG. 9d shows a preferred fourth step of fabrication of an electrode component in accordance with the present invention.

[0241] FIG. 9e shows a preferred fifth step of fabrication of an electrode component in accordance with the present invention.

[0242] FIG. 10 shows an electrode component and a stacked one with two electrodes stacked.

[0243] FIG. 11 shows an electrode component and a stacked one with two electrodes stacked and a preferred spacer in-between the two electrodes.

[0244] FIG. 12 shows another embodiment in accordance with the present invention comprising stacked multipoles.

[0245] FIG. 13 shows an example of an aberration corrector, such as Russian Quadruplet.

[0246] FIG. 14a shows an exemplary electrode component with an exemplary fabrication error.

[0247] FIG. 14b shows another exemplary electrode component with an exemplary fabrication error.

[0248] FIG. 15 shows a spherical aberration corrector comprising two exemplary electrode components.

DETAILED DESCRIPTION

[0249] For the sake of clarity, some features may only be shown in some figures, and others may be omitted. However, also the omitted features may be present, and the depicted and discussed features do not need to be present in all embodiments. Further, in the following, embodiments of the present invention will be described with an aberration corrector or device being used as a non-limiting example of an active charged particle optics device or component.

[0250] FIG. 1 shows components of a scanning microscopy system 100. The scanning microscopy system 100 may be configured for generating a primary beam 107 of charged particles (e.g., electrons or ions). The scanning microscopy system 100 may be further configured to direct the primary beam 107 of charged particles on to a sample 108. The scanning microscopy system 100 may comprise, for example, a Scanning/Transmission Electron Microscope (SEM/TEM) 101.

[0251] In this example, the primary beam comprises an electron beam 107. The electron beam 107 may be generated by an electron source 102 configured for emitting the electron beam, wherein a voltage may be applied between the electron source 102 and an anode 103. The applied voltage may preferably range from at least 0.1 kV to 30 kV. The scanning microscopy system 100 may further comprise a directing and/or focusing assembly that may comprise, for example, electromagnetic lenses. The electromagnetic lenses may be configured for controlling the path of the electron beam 107. At least one condensing lens 104 may be comprised by the electromagnetic lenses. The condensing lens 104 may be configured for controlling the size of the beam 107. Moreover, at least one objective lens 106 may be comprised by the electromagnetic lenses. The objective lens 106 may be configured for focusing the electron beam 107 to a scan point on the sample 108. The scan point may correspond to an electron spot on the sample 108. Further, the dimensions and the shape of the scan point may depend on the focusing properties of the electromagnetic lenses (e.g., applied current) and the working distance between the SEM 101 and the sample 108. A scanning device 105 may be configured for deflecting the ion beam 107 over a plurality of scan locations in one or two dimensions. Thus, as an optional advantage, this may enable a two-dimensional scanning of the sample. The scanning device 105 may be magnetic and/or electrostatic. An aberration corrector 122 may be located between the condensing lens 104 and the scanning device 105 and may be configured for compensation and/or correcting aberrations of the microscopy system 100.

[0252] The scanning microscopy system 100 may be configured for detecting first and second emissions 109, 111, 113. The electron beam 107 may interact with particles (such as atoms) of the sample 108. This interaction may result in the first and second emissions. The first emissions may comprise emissions of charged particles, such as secondary electrons and/or secondary ions. The first emissions may also comprise emissions of backscattered, transmitted and/or Auger electrons. Further, the second emissions may comprise emissions of photons across a range of wavelengths, such as X-rays and/or light (e.g., visible light).

[0253] In the example of FIG. 1, the scanning microscopy system 100 may comprise a first detector 110, wherein the first detector 110 may be configured for detecting backscattered electrons 109 emitted from the scan locations in a sequential manner. Thus, the first detector 110 may comprise a backscattered electron detector, such as a segmented silicon drift detector. However, the backscattered electron detector may also correspond to other types of solid-state detectors. Moreover, the scanning microscopy system 100 may comprise a second detector 112, wherein the second detector 112 may be configured for detecting secondary electrons and/or secondary ions 111 emitted from the scan locations in a sequential manner. Thus, the second detector may comprise a secondary electron detector, such as an Everhart-Thornley detector. The second detector may alternatively or additionally comprise a secondary ion detector, such as a charged particle multiplier.

[0254] Further, the scanning microscopy system may comprise a third detector 114, wherein the third detector 114 may be configured for detecting photons emitted from the scan locations in a sequential manner. Thus, the third detector 114 may comprise, for example, an X-ray detector, wherein the X-ray detector may comprise, for example, a silicon drift detector. However, the third detector 114 may also comprise other types of photon detectors (e.g. scintillation detectors). The second and the third detector 112, 114 may be tilted with respect to the surface of the sample 108.

[0255] The third detector 114 may be comprised by an energy-dispersive spectrometer (EDS). The energy bandwidth of the EDS may range from 0 to 17 KeV. In another modality the third detector 114 may be comprised by a wavelength-dispersive spectrometer (WDS). Further, the third detector 114 may also be comprised by an electron energy loss spectrometer or a cathodoluminescence spectrometer.

[0256] The sample 108 may be positioned on top of a movable stage 115. The movable stage 115 may be configured for performing two horizontal movements, a vertical movement, a tilting movement, and/or a rotational movement, with respect to the plane of the sample 108. The two horizontal movements may comprise selecting a field of view. The vertical movement may comprise changing the height of the sample 108 and thus the depth of focus and/or the image resolution.

[0257] The scanning microscopy system 100 may further comprise a control unit 116. The control unit 116 may be configured for controlling the power supply and operation of the condensing lens 104, the objective lens 106, the scanning coil 105 and the movable stage 115. Further, the scanning microscopy system 100 may comprise a vacuum system. The vacuum system may comprise a vacuum controller 117, a mechanical pumping system 118, an ultra-high vacuum pump 119 (such as an ion pump) and a vacuum chamber 120. The vacuum controller 117 may be configured for controlling the operation of the mechanical pumping system 118 and the ultra-high vacuum pump 119. The mechanical pumping system 118 and the ultra-high vacuum pump 119 may be configured for providing an ultra-high vacuum within the vacuum chamber 120. The vacuum chamber 120 may be configured for housing the sample 108, the movable stage 115, the first detector 110 or parts thereof, the second detector 112 or parts thereof, the third detector 114 or parts thereof, and the SEM 101 or parts thereof.

[0258] A relevant consideration for the achievable resolution of the microscopy system 100 may be the energy, more particularly a central energy, of the electron beam 107. Higher energies may lead to shorter wavelengths thus improving the resolution of the microscopy system 100. However, higher energy of the electron beam 107 would also drive up the magnitude of the electrostatic field needed in any of the active charged particle optics components, such as the aberration corrector 122, to have an effect on the beam 107. An exemplary active charged particle optics component 200, that may be, for example, an electrostatic deflector, is depicted in FIG. 2.

[0259] A respective lithography system working similar to the microscope shown is also enclosed by the present invention.

[0260] FIG. 2 depicts the active charged particle optics device or component 200 that may be used to deflect the electron beam 107 by an angle \alpha. FIG. 2a depicts a heuristic schematic of the active charged particle optics component 200, whereas FIG. 2b depicts a schematic diagram of the active charged particle optics component 200 as may be employed in the microscopy system 100 or a lithography system.

[0261] As depicted in FIG. 2a, the active charged particle optics component 200 may comprise a pair of electrodes 202 serving as a cathode and an anode. An equal, but opposite voltage, U, may be applied to the cathode (negative) and anode (positive or ground). The resultant electric field, E_x, may be used to deflect an electron beam traveling along optics axis or in the z-direction by the angle \alpha, see also FIG. 1. The electrodes may be placed a distance, d, apart and may each have a thickness, L along the direction of motion of the electron beam 107. FIG. 2b depicts an exemplary realization of the active charged particle optics component 200. The electrodes 202 may be fabricated as films on top of a separating layer 204, that may be further supported by a membrane 206. The thickness of the electrodes 202 may be similar to the thickness of the separating layer 204 and may be, for example, 10 m, while the thickness of the membrane 206 may be 500 m. The distance, d, may be, for example, 10 m.

[0262] While the active charged particle optics component 200 with electrodes 202 of a thickness as described above may be employed in the microscopy system 100 for deflecting the electron beam 107 with a central energy less than, for example, 10 KeV, the component 200 may not be employed for an electron beam 107 of higher central energy. This is because the angle \alpha may be determined as \alpha =(E_x.Math.L)/(2 E), where E is proportional to the central energy of the electron beam 107. Thus, the larger the thickness, L, of the electrodes 202, the longer is the electron beam 107 acted upon by the active charged particle optics component 200, and the larger is the deflection angle \alpha. However, as may be appreciated from this relation, for the same thickness, L, and same voltage U (and thus E_x) applied to the electrodes 202, a higher central energy of the electron beam 107 is deflected less. In particular, the deflection angle is inversely related to the central energy of the beam 107. Thus, if the resolution of the microscopy system 100 is to be increased by increasing the energy of the electron beam 107, either a stronger electrostatic field, E_x, may have to be generated inside the active charged particle optics component 200, or the thickness, L, of the electrodes 200 may have to increased. The strength of the electrostatic field, E_x, may be limited due to its effect on the electron beam 107 but also due to limitations of arcing issues (10 KV/mm in vacuum and 1 KV/mm along the surface creepage of an insulator). A relevant consideration here may be the desired aspect ratio of the active charged particle optics component 200. For example, if a component similar to the component 200 depicted in FIG. 2 is to be used with an electron beam 107 with a central energy of 300 KeV, the aspect ratio of the electrodes 202 has to be increased by a factor of 30. Such an aspect ratio may be difficult to achieve with conventional fabrication techniques as described earlier.

[0263] According to FIG. 3, embodiments of the present invention relate to active charged particle optics components 300 with electrodes 302 that may be used in a microscopy system for beams with a high central energy of the particles. They may be of particular advantage for charged particle beam microscopy systems where the central energy of the charged particle beam is more than 10 KeV, preferably at least 15 KeV, further preferably at least 20 KeV and even considerably more. Such active charged particle optics components 300 may be created by precision manufacturing of the electrodes 302. For example, the charged particle optics component 300 may comprise at least two electrodes 302a and 302b, with a high-precision microstructure and a minimum thickness of 1 mm, preferably 1.5 mm, and further preferably 2 mm and even more. The thickness is along the inner surface 302c of the beam neighboring section of the electrode(s). Embodiments of the present invention may also be directed to fabrication of more complex active charged particle optics components 300, comprising 2N electrodes 302, where the component 300 may be used to generate an electrostatic field of N-polarity, such as 4 electrodes for generating a quadrupole electrostatic field.

[0264] FIG. 3 depicts an exemplary embodiment of an active charged particle optics component 300 according to the present invention. The component 300 comprises a pair of electrodes 302, assembled on a separating layer 304, which are then supported on a substrate or membrane 306.

[0265] The electrodes 302 may comprise any conducting and/or semi-conducting material, such as silicon wafer material or even an insulator covered with a conductive layer. The separating layer 304 may comprise any material that may insulate the electrodes 302 from the underlying membrane 306. So, for example, when the electrodes 302 comprise a metal, the separating layer 304 may comprise adhesive or glue. The substrate 306 may also comprise an electrical conductor or insulator. When an electrical conductor is used, care may be taken that there is no possibility of shorting between the membrane 306 and the electrode 302. For example, the membrane 306 may comprise glass, Pyrex and/or silica (SiO.sub.2).

[0266] The exemplary active charged particle optics component 3000 may be fabricated by employing a sequence of suitable techniques. This is depicted in FIG. 4. For example, when the electrodes 302 comprise silicon, a suitable fabrication technique may comprise etching away a block of bulk silicon so as to produce a groove in the bulk silicon. The etching technique may comprise, for example, a deep reactive ion-etching technique. A width of the groove may be chosen to correspond to the desired separation, such as 10 m or even smaller, between the electrodes 302. An advantage of using etching may be that the process may be precisely controlled. For example, the depth of the groove may be controlled by controlling the etching time and/or the etching rate (that may be known based on the etchant used). Further, the width of the groove may be controlled by choosing the etchant appropriately. If a crystalline material is used for the electrodes 302, for example, the etchant may be chosen such that the rate of etching depends on the crystal face that is exposed. A suitable choice of etchant may be such that the rate of etching is fastest in the vertical direction. A further advantage of employing an etching process may be that a surface roughness of the fabricated microstructures may be significantly low. For example, a maximum surface roughness of Ra 0.05 m may be obtained. Thus, the cavity or the surfaces between the electrodes 302 may be precisely shaped. This step is depicted in FIG. 4a, where grooves along the line 3020 are etched into bulk silicon 3000.

[0267] Note that the bulk silicon 3000 may not be etched right through so as to produce disjoint silicon electrodes 302 yet, so as to not adversely affect the spacing between the electrodes 302 that are fabricated. Rather, in a further step, depicted in FIG. 4b, the bulk silicon 3000 with the grooves may be glued on to a substrate/membrane 3060 such as glass, Pyrex, or a silicon wafer covered with an insulator (such as silica). This may help provide stability to the bulk silicon 3000 without affecting the width of the grooves 3020 (and thus the separation between the electrodes 302). The width of the separation between etched Si electrodes is getting larger when moving away from a center of active elements. This is because, at the center, the electrodes are floating in vacuum and a breakdown voltage threshold is 10 KV/mm, so the distances could be kept smaller but at the outside, when electrodes are resting on an insulator, the breakdown threshold is governed by the surface creepage distance on the insulator (which is effectively, the distance between the electrodes). Thus, it can be advantageous to make this distance larger and to not necessarily form straight lines. Any other shape can be used as well. These separations could be uses for gluing the electrodes to the insulator.

[0268] Once the bulk silicon 3000 has thus been glued on to the substrate 3060, the electrodes 302 may be separated by dicing along the grooves 3020, as depicted in FIG. 4c. Any trailing edges of the bulk silicon 3000 may also be diced away. The final charged particle optics component 300 is depicted in FIG. 4d. Dicing may be accomplished by means of a laser, or any other suitable means of dicing.

[0269] FIG. 5 depicts an image of an exemplary charged particle optics component 400 fabricated in a lab. FIG. 5a depicts a zoomed-out view of the component 400, while FIG. 5b depicts a zoomed-in view. The charged particle optics component 400 comprises 7 electrodes 402 (a through g). The 7 electrodes 402 may be used to generate two adjacent quadrupole electrostatic fields, for example. In this case the two sets of quadrupoles share one electrode, as can be seen.

[0270] Further, the component 400 comprises alignment markers 408 that may be used for aligning the charged particle optics component 400 in the microscopy system 100. These alignment markers 408 may be patterned on the electrodes 402 or on an underlying substrate 406 (not shown) thereof, using any suitable lithography technique.

[0271] FIG. 6a depicts an active charged particle optics component 500 fabricated as described above for use in a microscopy system 100 comprising an electron beam 107 with a beam energy of up to 60 KeV. FIG. 6b depicts another active charged particle optics component 600, comprising five times thicker electrodes, fabricated as described above for use in a microscopy system 100 comprising an electron beam 107 with a beam energy of up to 300 KeV. Comparing FIGS. 6a and 6b, it may be appreciated that even though the thickness of the electrodes is increased by a factor of 5, the precision of the apertures (that may correspond to the separation, d, between the electrodes 202 in FIG. 2) is similar. Thus, the present invention may allow fabrication of active charged particle optics components for use with beams 107 of energies significantly larger than 10 KeV.

[0272] FIG. 6c shows how electrodes can circumscribe a circular structure with respect to the embodiment shown in FIG. 5. This can be formed by a cross-section of a hypothetical cylinder, as a circle, in order to define a free space for a beam to pass the electrodes. In this manner two pathways, each for one charged particle beam, can be formed very efficiently.

[0273] FIG. 7 exemplifies a preferred device and its principal way of fabrication according to the present invention. In particular, an electrode component or electrode assembly 302 can be arranged at the bottom for fabrication purposes. In the example shown, it is a quadrupole assembly. On top is an aperture plate or substrate 306 that has a larger aperture than is shown in FIG. 3. This is advantageous as the charged particles beam not to influenced by the substrate. A BLA (beam limiting aperture) can be arranged on top of element 300. This can be realized in order to prevent direct interaction of the charged particle beam with the electrodes.

[0274] The process of making the BLA is depicted in FIGS. 8a-8c.

[0275] FIG. 8a shows in more detail an aperture plate or supporting structure and its preferred first step of fabrication. A wafer structure or any other material is treated to form the apertures that are aligned with electrodes in the later-described electrode component. In the example shown, the electrodes are formed by a lithography and then an etching step. The lithography can be a high-resolution lithography step, such as an EBPG lithography step. The etching can be done by a highly anisotropic (dry) deep reactive ion etching (DRIE) process.

[0276] In FIG. 8b the aperture is formed by another lithography step, such as by NUV lithography, followed by another etching, such as the DRIE etching, mentioned before.

[0277] The intermediate material is further removed, as shown in FIG. 8c. The techniques for that can be a stripping of the insulating Si oxide and a metallization of the remaining structure.

[0278] In accordance with FIG. 8d an insulator that can comprise or consist of glass can be attached and then the final structure can be obtained by dicing and cleaning according to FIG. 8e.

[0279] Alternatively or additionally, a standard (thin=thickness <1 mm) Si-Wafer can be established and in order to increase the effective thickness the first steps, such as shown in FIGS. 8a-8c, can be repeated. E.g., as many thin wafers as possible can be created and then attached together with glue or wafer bonding etc. Then the steps according to FIGS. 8d and 8e can be continued. Also an SOI wafer could be chosen.

[0280] Electrical connections, such as the ones to electrodes 302a and 302b, can be formed by accommodating electrical connections in the layer 304.

[0281] The electrode component or assembly and a possible fabrication is further exemplified by FIGS. 9a-9e. As is apparent from FIG. 9a, oxide can be formed on bare Si by a PECVD process. This is an example only. Next, according to FIG. 9b, a lithographic step, such as an EBPG step and a DRIE step, can be chosen to form the electrode structure, such as a quadrupole, with optional alignment patterns. With a lithographic step, such as a NUV lithography, considerable material can be removed, followed by a DRIE etching or other etching steps. The Si oxide can be removed by another etching, followed by a metallization, see FIG. 9c, According to FIG. 9d, a spacer can be added. FIG. 9e exemplifies the dicing and further cleaning of the electrode component or quadrupole assembly.

[0282] Practically, this can be challenging as etching such a thick wafer has never been done so far. It is referred to FIG. 10. It has recently been found with respect to the present invention that for aberration corrector applications, it is possible to use an alternative solution to a very thick electrodes and that to split the electrodes 302a and 302b into a sandwich of two thin electrodes with a drift space in between such that the effective thickness of 302c in FIG. 1 is equal to the length L of the outer dimensions of the two layers of electrodes with the gap (or insulating material) in-between. This is especially of interest for multipoles, such as hexapoles to be used for hexapole based correctors but also in general for other multipoles. In practice, making these two elements can be very similar to making thick element 300 but then there will further steps of alignments be useful, see FIGS. 4 and 5.

[0283] Alternative arrangements are also schematically depicted in FIGS. 11 and 12. The electrodes form a thickness L with different arrangements of spacers or insulators, depending on the needs. The thickness L establishes the effective thickness.

[0284] FIG. 13 is exemplifying a known corrector concept based on four quadrupoles (e.g., four multipoles, also known as a Russian Quadruplet). In such a sample an alignment of at least 1 m accuracy between the individual elements is advantageous (between Q1, Q , . . . ). Thus, the fabrication accuracy isn't only needed to make individual electrodes but also needed to align the stack with the assistance of alignment marker between different elements (different Q in above example).

[0285] Note that at least one step of the fabrication method for the electrode component (300) may be chosen based on a desired maximum absolute dimensional tolerance. The desired maximum absolute dimensional tolerance may be based on characteristics of a charged particle system comprising the device as described above. For example, it may be based on the beam energy of the beam as described above. The desired maximum absolute dimensional tolerance may be based on a maximum voltage to be applied to any of the at least two electrodes (302a, b). The desired maximum absolute dimensional tolerance may be based on the effective length of any of the at least two electrodes (302a, b). The desired maximum absolute dimensional tolerance may be based on an aberration coefficient of a lens of the charged particle system. Thus, generally, the desired maximum absolute dimensional tolerance may be determined, and based thereon, at least one step of the fabrication method may be chosen. For example, one may consider an electrostatic multipole element with a radius of R and effective length L that produces a hexapole field (disregarding the fringe field), see FIGS. 14(a, b) and FIG. 15. The hexapole potential can be written as:

[00001]${}_3\left(x,y\right)\frac{V}{R^3}\left(x^3-3{\mathrm{xy}}^2\right)$

[0286] For the maximum field E.sub.max on the electrodes, one may use the approximation:

[00002]$E_{\max }\frac{3V}{R}$

[0287] For an arbitrary error s in fabricating these elements, where s represents any error such as a shift, a parasitic potential .sub.parasitic is introduced to the main hexapole field, .sub.3. The combined effect of errors s as shown in FIG. 14 (a, b) may be estimated (where m denotes the order of anisotropy of the parasitic potential, with m=4 for parasitic octupole fields, for example):

[00003]${}_{\mathrm{parasitic}}={.Math.}_m\frac{1}{R^m}\mathrm{Re}\left[{V_m\left(x+\mathrm{iy}\right)}^m\right],\mathrm{with}.Math.V_m.Math.<\frac{Vs}{R}.$

[0288] Each (complex) Fourier component V.sub.m may lead to parasitic primary aberrations and combination aberrations. The primary parasitic aberration is m-fold astigmatism with an aberration coefficient of A.sub.m-1. This parasitic astigmatism may introduce an extra blur on the electron probe (d50 is the corresponding probe diameter which contains 50% of the probe current) at the specimen plane as:

d50=2.sup.(3-m)/2|A.sub.m-1|.sup.m-1

[0289] As an example, consider a spherical aberration corrector of the two-hexapole Rose-type sketched schematically in FIG. 15, where a round and parallel electron beam enters the hexapoles 300. A basic calculation of the parasitic m-fold astigmatism yields:

[00004]$\begin{array}{cc}.Math.A_{m-1}.Math.\frac{\mathrm{mL}{E}_{\max }s}{6U}{\left(\frac{6U^2{C}_s}{L^3{E}_{\max }^2}\right)}^m,& \left(1\right)\end{array}$

[0290] in which C.sub.s is the spherical aberration coefficient of an objective lens 1000, and U is the beam energy. Thus, the error s in fabricating elements may lead to a change in the probe diameter d50, and the change may depend on characteristics such as the effective length L of the electrodes 302(a, b), the beam energy U, or the spherical aberration coefficient of another component.

[0291] The desired maximum absolute dimensional tolerance may be determined by, for example, requiring that the probe diameter d50 does not exceed a certain threshold. For example, if the probe diameter d50 in the absence of any geometric or chromatic aberrations would be 1.25 A, one may require that the probe diameter d50 in the presence of geometric or chromatic aberrations is no greater than 2 . This may impose an upper limit on the size of |A.sub.m-1| and thus, from equation (1) above, on As when suitable values are substituted for other parameters entering equation (1). Generally, in embodiments of the present technology the fabrication process, at least in part, may thus also be based on the maximum absolute dimensional tolerance so determined.

[0292] Note that the above discussion should be considered exemplary, but non-limiting, and that it may not be possible to always determine the desired maximum absolute dimensional tolerance by means of an equation such as equation (1). It may also be possible, for example, that the desired maximum absolute dimensional tolerance may be determined based on a desired maximum variation in the effect (such as variation in the probe diameter d50 described above) of the electrode component when used e.g., in a charged particle system. In this case, other methods such as, for example, an artificial-intelligence based method, may be employed to corroborate the desired maximum absolute dimensional tolerance with the desired maximum variation in the effect of the electrode component.

[0293] Overall, embodiments of the present invention aim to thus provide an active charged particle optics component for use with high-energy beams that may be fabricated robustly, precisely, and efficiently using the processes described above. Embodiments of the present invention may thus provide an effective avenue to improving the resolution of microscopy systems.

[0294] Whenever a relative term, such as about, substantially or approximately is used in this specification, such a term should also be construed to also include the exact term. That is, e.g., substantially straight should be construed to also include (exactly) straight.

[0295] Whenever steps were recited in the above or also in the appended claims, it should be noted that the order in which the steps are recited in this text may be accidental. That is, unless otherwise specified or unless clear to the skilled person, the order in which steps are recited may be accidental. That is, when the present document states, e.g., that a method comprises steps (A) and (B), this does not necessarily mean that step (A) precedes step (B), but it is also possible that step (A) is performed (at least partly) simultaneously with step (B) or that step (B) precedes step (A). Furthermore, when a step (X) is said to precede another step (Z), this does not imply that there is no step between steps (X) and (Z). That is, step (X) preceding step (Z) encompasses the situation that step (X) is performed directly before step (Z), but also the situation that (X) is performed before one or more steps (Y1), . . . , followed by step (Z). Corresponding considerations apply when terms like after or before are used.

[0296] While in the above, preferred embodiments have been described with reference to the accompanying drawings, the skilled person will understand that these embodiments were provided for illustrative purpose only and should by no means be construed to limit the scope of the present invention, which is defined by the claims.