Multipole element and charged particle microscope system including the same

Abstract

To improve the positive spherical aberration and chromatic aberration coefficients of a circular lens.SOLUTION: There are provided a multipole element and a charged particle microscope system including the same. In an example, a device may include a plurality of electrodes including a first subset of shapes and a second subset of shapes. Each electrode of the first subset of shapes includes an electrode active surface having a shape that is different from the shape of each electrode of the second subset of shapes. In another example, the device can include a plurality of electrodes including a first subset of sides and a second subset of sides. Each electrode includes an electrode extension that extends along a first lateral direction or a second lateral direction. In another example, the device can include an optical column having a plurality of multipole elements that are entirely contained within a first angular envelope that defines a first angular range that is up to 50 degrees while the working distance is up to 10 mm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. S / N 18 / 478,972, filed September 29, 2023, the disclosure of which is incorporated herein by reference in its entirety.

[0002] FIELD OF THEINVENTION The present disclosure relates generally to charged particle microscope systems, and more particularly to charged particle microscopes having systems for correcting spherical and / or chromatic aberrations in a charged particle beam. [Background technology]

[0003] Particle-optical microscopes utilize round lenses to direct the electron / charged particle beam to illuminate the specimen. However, such round lenses produce positive spherical and chromatic aberration coefficients, thereby limiting the higher opening angles and suppressing the resolution and probe current. Summary of the Invention

[0004] In a representative example, the apparatus includes a plurality of electrodes disposed about and defining a central bore extending at least partially along a beam axis. Each electrode of the plurality of electrodes includes a respective electrode active surface facing the central bore. The plurality of electrodes includes a first shape subset of electrodes and a second shape subset of electrodes. The electrode active surface of each electrode of the first shape subset of electrodes has a first active surface shape when viewed along a direction parallel to the beam axis. The electrode active surface of each electrode of the second shape subset of electrodes has a second active surface shape when viewed along a direction parallel to the beam axis that is different from the first active surface shape.

[0005] In another representative example, the device includes a plurality of electrodes disposed about and defining a central bore. Each electrode of the plurality of electrodes includes a respective electrode active surface facing the central bore and a respective electrode extension extending away from the respective electrode active surface and configured to supply a voltage to the respective electrode active surface. The plurality of electrodes includes a first side subset of electrodes and a second side subset of electrodes. For each electrode of the first side subset of electrodes, the electrode extension extends away from the electrode active surface along a first lateral direction. For each electrode of the second side subset of electrodes, the electrode extension extends away from the electrode active surface along a second lateral direction opposite the first lateral direction.

[0006] In another representative example, an apparatus includes a charged particle source configured to emit a charged particle beam and an optical column configured to direct the charged particle beam at least partially along a beam axis. The optical column includes a plurality of multipole elements axially aligned with the beam axis, the plurality of multipole elements configured to focus the charged particle beam at a target focal position. The plurality of multipole elements includes a proximal multipole element that is proximal to the target focal position relative to the remaining multipole elements and spaced apart from the target focal position by a working distance. The plurality of multipole elements are entirely contained within a first angular envelope defined in a first plane including the beam axis that defines a first angular range of up to 50 degrees while the working distance is up to 10 mm.

[0007] The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description which proceeds with reference to the accompanying drawings. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic side elevation view of a charged particle microscope system according to an embodiment. [Diagram 2] FIG. 2 is a front elevation view of an electrostatic hexapole generating element according to an embodiment. [Diagram 3] FIG. 1 is a schematic side elevation view of an aberration correction system according to an embodiment. [Figure 4] FIG. 4 is a diagram of a fundamental ray of a charged particle beam relative to a linear optical axis of the aberration correction system of FIG. 3 according to an embodiment. [Diagram 5] FIG. 2 is a side perspective view of a corrector electrostatic prism according to an embodiment. [Figure 6] FIG. 2 is a side perspective view of an entrance electrostatic prism according to an embodiment. [Figure 7] FIG. 2 is a partial cross-sectional side elevation view of a corrector electrostatic prism according to an embodiment. [Figure 8] FIG. 13 is another partial cross-sectional side elevation view of a corrector electrostatic prism in accordance with an embodiment. [Figure 9] FIG. 13 is another partial cross-sectional side elevation view of a corrector electrostatic prism in accordance with an embodiment. [Figure 10] FIG. 13 is another partial cross-sectional side elevation view of a corrector electrostatic prism in accordance with an embodiment. [Figure 11] FIG. 2 is a schematic side elevation view of an aberration correction system according to another embodiment. [Figure 12] FIG. 2 is a schematic side elevation view of an aberration correction system according to another embodiment. [Figure 13] FIG. 2 is a schematic side elevation view of an aberration correction system according to another embodiment. [Figure 14] FIG. 14 is a diagram of a base ray of a charged particle beam traversing the aberration correction system of FIG. 13 according to an embodiment. [Figure 15] FIG. 2 is a schematic side elevation view of an aberration correction system according to another embodiment. [Figure 16] FIG. 16 is a schematic diagram of the aberration correction system of FIG. 15 and a fundamental ray of a charged particle beam traversing the aberration correction system according to an embodiment. [Figure 17] FIG. 16 is a schematic diagram of the aberration correction system of FIG. 15 according to another embodiment and a fundamental ray of a charged particle beam traversing the aberration correction system; [Figure 18] FIG. 1 is a schematic side elevation view of a charged particle microscope system according to an embodiment. [Figure 19] 1 is a schematic diagram of a charged particle microscope system and a fundamental ray of a charged particle beam traversing the charged particle microscope system, where chromatic and third order aberrations are corrected, according to an embodiment. [Figure 20] FIG. 2 is a front elevation view of an electrostatic multipole element having four electrodes, according to an embodiment. [Figure 21] FIG. 2 is a front elevation view of an electrostatic multipole element having eight electrodes, according to an embodiment. [Figure 22] 1 is a schematic diagram of a charged particle microscope system and a fundamental ray of a charged particle beam traversing the charged particle microscope system, according to an embodiment, where third order aberrations are corrected and the charged particle microscope system is operating at a first magnification. [Figure 23] 23 is a schematic diagram of the charged particle microscope system of FIG. 22 and a fundamental ray of a charged particle beam traversing the charged particle microscope system, according to an embodiment, where third order aberrations are corrected and the charged particle microscope system operates at a second magnification. [Figure 24] 1 is a schematic diagram of another charged particle microscope system and a fundamental ray of a charged particle beam traversing the charged particle microscope system, according to an embodiment, where third order aberrations are corrected and the charged particle microscope system operates at a first magnification. [Diagram 25] 25 is a schematic diagram of the charged particle microscope system of FIG. 24 and a fundamental ray of a charged particle beam traversing the charged particle microscope system, according to an embodiment, where third order aberrations are corrected and the charged particle microscope system operates at a second magnification. [Figure 26] FIG. 2 is a side elevation view of a first charged particle beam and a second charged particle beam focused to a common location on a sample, according to an embodiment. [Figure 27] FIG. 2 is a front elevation view of an electrostatic multipole element having eight electrodes formed as a microelectromechanical system, according to an embodiment. [Figure 28] FIG. 2 is a front elevation view of an eight-electrode electrostatic multipole element having electrode extensions extending along a first lateral direction or a second lateral direction, according to an embodiment. [Figure 29] FIG. 2 is a front elevation view of an electrostatic multipole element having eight electrodes, each of the eight electrodes being a subset of a first shape of electrodes or a subset of a second shape of electrodes, according to an embodiment. [Diagram 30]FIG. 11 is a front elevation view of an electrostatic multipole element having eight electrodes, each of the eight electrodes being a subset of a first shape of electrodes or a subset of a second shape of electrodes, according to another embodiment. [Diagram 31] 1 is a cross-sectional side elevation view of an apparatus including multiple electrostatic multipole elements configured to be contained in a first angular envelope, according to an embodiment. [Diagram 32] 1 is a cross-sectional side elevation view of an apparatus including a lens housing and multiple electrostatic multipole elements configured to be contained within a first angular envelope, according to an embodiment. [Diagram 33] FIG. 13 is a cross-sectional side elevation view of an apparatus including multiple electrostatic multipole elements configured to be contained in a second angular envelope, according to an embodiment. [Diagram 34] FIG. 13 is a cross-sectional side elevation view of an apparatus including a lens housing and multiple electrostatic multipole elements configured to be contained within a second angular envelope, according to an embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Charged particle beam systems, such as scanning electron microscopes and focused ion beam microscopes, are widely used in the semiconductor and nanotechnology industries to image, fabricate, and / or modify microstructures, such as by irradiating such structures with a charged particle beam (e.g., an electron beam or an ion beam). Such beam systems typically utilize electromagnetic lenses to focus, deflect, and focus the charged particle beam onto a sample. Like optical systems, charged particle beam systems introduce axial aberrations that increase the size of the charged particle beam spot on the sample, thereby limiting the spatial resolution of the system.

[0010] In particular, the focusing lens, also known as the objective lens, which is placed closest to the sample, contributes most to the axial aberrations of the aperture, such as chromatic and spherical aberrations (denoted Cc and Cs, respectively). As described in the publication "Über einige Fehler von Elektronenlinsen" by O. Scherzer, Z. Physik 101, 1936, electromagnetic circular lenses always produce positive chromatic and spherical aberration coefficients, so that no circular lens can fully compensate for the aberrations of another circular lens.

[0011] Furthermore, in another publication by the same author (O. Scherzer, "Spharische und chromatische Correktur von Elektronenlinsen", Optik 2, 1947, p. 114), it was shown that the aberrations of circular electromagnetic lenses can be compensated by the negative aberrations generated by multipoles. A multipole element comprises N poles (e.g. electrodes) and is configured to generate electrostatic or magnetic multipole fields with <= N-fold rotational symmetry. Thus, a multipole element can generate (combinations of) dipole, hexapole, octopole fields, etc.

[0012] An example of a current solution for correcting chromatic and spherical aberrations of electron lenses has recently been proposed in "Magnetic Cc / Cs-corrector compensating for the chromatic aberration and the spherical aberration of electron lenses" (H. Rose, A. Nejati, H. Muller, Ultramicroscopy 203, 2019, p. 139-144, hereafter referred to as Rose et al. 2019), where a purely magnetic corrector is introduced in detail. In particular, the authors describe a curved axis corrector with magnetic quadrupole and hexapole generating elements arranged in an omega-shaped design.

[0013] As described in Rose et al. 2019, the quadrupoles are configured to focus and shape the beam, and the hexapoles are adjusted to offset the positive chromatic aberration of the electro-optical system. Since the primary beam is highly astigmatic in the corrector, an octupole can be added in the appropriate places to also correct the spherical aberration. This fully magnetic imaging corrector is intended for implementation in electron microscopes, such as transmission electron microscopes (TEMs), and is specifically configured to correct chromatic and spherical aberrations for beam energies up to 1.2 MeV. However, the Cc / Cs corrector of Rose et al. 2019 utilizes only magnetic fields and is therefore not practical for ions, since ions heavier than electrons are less affected by magnetic fields.

[0014] Alternatively, purely electrostatic Cc / Cs correctors can be used for both electron and ion beams with linear axes, as described, for example, in U.S. Patent Application Publication No. 2004 / 0051985, but such correctors are complex and the transmitted beam energies are very low (up to 8 kV) and therefore ion-ion interactions are problematic.

[0015] More recently, CEOS / JEOL has developed an electrostatic corrector suitable for beam energies up to 30 keV (https: / / www.ceos-gmbh.de / en / research / electrostat). However, the proposed corrector presents major drawbacks such as the generation of large higher order aberrations and a high sensitivity to alignment errors due to the very strong focusing power of the Cc corrector. Therefore, the corrector proposed by CEOS / JEOL is only suitable for ion optics.

[0016] Examples of the disclosed technology seek to mitigate and / or overcome shortcomings and disadvantages of existing aberration correction systems. More specifically, examples herein can include an improved system for correcting axial aberrations in charged particle beam systems.

[0017] Examples of the disclosed technology can also include a corrector for axial chromatic and / or spherical aberration, such as a purely electrostatic corrector that compensates for chromatic and / or spherical aberration in a charged particle beam system.

[0018] 1 illustrates an example of a charged particle microscope system 100 that may include and / or utilize an aberration correction system as disclosed herein. In the example of FIG. 1, the charged particle microscope system 100 is configured to direct or focus a charged particle beam 104 onto a sample 132 for inspection and / or analysis of one or more properties of the sample 132. The charged particle microscope system 100 may include and / or be any of a variety of systems, such as an electron microscope (EM) setup or an electron lithography setup configured to illuminate and / or otherwise impinge the sample 132 with the charged particle beam 104.

[0019] In various embodiments, the charged particle microscope system 100 may include or be one or more different types of EM and / or charged particle microscopes. Examples of one or more different types of EM and / or charged particle microscopes include a scanning electron microscope (SEM), a scanning transmission electron microscope (STEM), a transmission electron microscope (TEM), a charged particle microscope (CPM), a dual beam microscope system, etc. Additionally, in some embodiments, a TEM can also operate as a STEM. In the example of FIG. 1, the charged particle microscope system 100 is a SEM or FIB system.

[0020] As shown in FIG. 1, the exemplary charged particle microscope system 100 includes a charged particle source 102 (e.g., a thermionic electron source, a Schottky emission source, a field emission source, a liquid metal ion source, a plasma ion source, etc.) that emits a charged particle beam 104 along an emission axis 106 toward a condenser optics 108. The condenser optics 108 may include an electrostatic gun lens, an accelerator, and / or one or more condenser lenses. The emission axis 106 may be a central axis that extends from the charged particle source 102 along the length of the exemplary charged particle microscope system 100 and through the sample 132. Additionally or alternatively, the emission axis 106 may refer to and / or include a portion of the path followed by the charged particle beam 104 that extends proximate to the charged particle source 102.

[0021] The acceleration lenses of the condenser optics 108 accelerate / decelerate, focus, and / or direct the charged particle beam 104 towards the focusing column 110. As used herein, the focusing column 110 may additionally or alternatively be referred to as the optical column 110. The focusing column 110 focuses the charged particle beam 104 for incidence on the sample 132. Additionally, the focusing column 110 corrects and / or adjusts aberrations (e.g., geometric aberrations, chromatic aberrations) of the charged particle beam 104.

[0022] 1, the focusing column 110 may be described as including, encompassing, and / or defining an optical column axis 112 along which the charged particle beam 104 travels through at least a portion of the focusing column 110. In some examples, the emission axis 106 may be described as including the optical column axis 112. Although FIG. 1 illustrates the optical column axis 112 as straight for simplicity, this is not required and it is within the scope of this disclosure that the optical column axis 112 may be curved.

[0023] 1, the focusing column 110 may include an aberration correction system 120, as described in more detail below. The focusing column 110 may further include a transfer lens 122 and an objective lens 128.

[0024] The objective lens 128 is an optical element that focuses the charged particle beam 104 to a point (e.g., a well-localized spot) on the sample 132. The objective lens 128 can produce a positive Cs. The objective lens 128 can include and / or be any of a variety of focusing elements, examples of which include a single pole lens, a magnetic-electrostatic compound lens, an electrostatic objective lens, or another type of objective lens.

[0025] 1 further illustrates the charged particle microscope system 100 including a sample holder 130 for holding a sample 132 and a detector 140 configured to detect charged particles 134 emitted from the sample 132 as a result of the charged particle beam 104 being incident on the sample 132. In addition, the charged particle microscope system 100 is illustrated as including an astigmatism correction and scanning coil 126 for directing the charged particle beam 104 to scan the surface of the sample 132. For example, the scanning coil 126 can be configured to selectively shift the direction of the charged particle beam 104 such that the charged particle beam 104 can be scanned (e.g., raster scanned) over an area of ​​the surface of the sample 132 being probed.

[0026] 1, the charged particle microscope system 100 may further include one or more computing devices 150 programmed and / or configured to control the operation of one or more aspects of the charged particle microscope system 100. As an example, the computing device(s) 150 may be programmed and / or configured to direct the charged particle beam 104 to a desired location on the sample 132, such as by translating the sample holder 130 and / or operating the scanning coil 126. Additionally or alternatively, the computing device(s) 150 may be programmed and / or configured to receive signals from the detector 140 to characterize the sample 132.

[0027] Those skilled in the art will appreciate that the computing device 150 illustrated in Figure 1 is exemplary only and is not intended to limit the scope of the present disclosure. Computing device(s) 150 can include and / or be any combination of hardware or software capable of performing the functions shown, including computers, network devices, Internet appliances, PDAs, wireless telephones, controllers, oscilloscopes, amplifiers, etc. Computing device(s) 150 can also be connected (e.g., via wired and / or wireless communication connections) to other devices not shown, or may operate as a stand-alone system.

[0028] As mentioned above, one or more components of a charged particle beam system, such as the objective lens 128 of the charged particle microscope system 100, can generate chromatic and spherical axial aberrations that limit the precision with which the charged particle beam can be focused on a sample. To clarify how a correction system, such as the aberration correction system 120, can operate to correct such aberrations, the following description considers the origin and form of such aberrations. The following description is presented primarily in the context of electron beams, but it should be understood that the principles can be applied to electron beams and ion beams, for example, by introducing sign changes in some equations. In the following description, calculations are performed in a non-relativistic approximation, which is appropriate for ion beams and for electron beams with electron energies (e.g., eU<=30 keV) representative of SEM systems.

[0029] In this disclosure, various properties of charged particle beams may be described with reference to light rays that characterize the charged particle beam. In particular, the systems described herein may be described as operating in a regime in which the constituent particles of the charged particle beam travel along substantially straight paths, provided such paths are not blocked, bent, and / or deflected by other components of the system. Thus, many principles of light ray optics may be applied to such charged particle beams.

[0030] The spatial extent of a charged particle beam may be characterized with reference to any suitable coordinate system. In this disclosure, the position of a portion of a charged particle beam (e.g., a portion of a light beam) may be described with reference to an x-component measured along an x-axis, a y-component measured along a y-axis, and a z-component measured along a z-axis. In this disclosure, the z-axis generally corresponds to the optical axis along which the charged particle beam travels, and may in some cases be a curved axis. The x-axis and y-axis may extend along any suitable direction such that the x-axis, y-axis, and z-axis are mutually perpendicular to each other.

[0031] multipole As used herein, the term "multipole element" may refer to any suitable component having multiple poles or electrodes to which respective voltages can be applied to generate a multipole field. For example, a multipole element having four poles may be configured to generate at least a quadrupole field. Similarly, a multipole element having six poles may be configured to generate at least a hexapole field. In this disclosure, a multipole element may be named and / or described in relation to the multiplicity of the multipole field it is configured to generate (e.g., as the primary or sole multipole field generated by the multipole element). For example, a "quadrupole generating element" may have four or more poles to generate at least a quadrupole field and / or may have one or more poles shaped to generate at least a quadrupole field. Similarly, a "hexapole generating element" may have six or more poles to generate at least a hexapole field and / or may have one or more poles shaped to generate at least a hexapole field.

[0032] In some examples, a multipole element may additionally or alternatively be configured to generate any of a variety of multipole fields (and / or superpositions thereof). For example, in some examples, a hexapole generating element having six poles may be configured to generate a dipole field, a quadrupole field, and / or a hexapole field. Unless otherwise specified, references herein to multipole fields (e.g., dipole fields, quadrupole fields, hexapole fields, octopole fields, etc.) generally refer to electrostatic multipole fields.

[0033] 2 shows an example of an electrostatic hexapole generating element 200 including six electrodes 202, 204, 206, 208, 210, and 212 to which respective voltages V1, V2, ..., V6 can be applied. One such hexapole generating element can be used to generate dipole and quadrupole electrostatic fields of any orientation in the xy plane, and / or hexapole fields of a fixed orientation.

[0034] Consider a Cc corrector with the curved deflector optical axes lying in one plane, and define the y-axis to be perpendicular to that plane. If we exclude the small multipole fields required to correct the effects of mechanical errors (i.e., if we neglect parasitic aberrations), then all electrostatic multipole potentials are symmetric in y, i.e., φ(x,y,z) = φ(x,-y,z). In this case, the hexapole potential is φ3(x,y,z) = a3(z)(x 3 -3xy 2 ) + the fringe field term.

[0035] 2 shows an example in which the electrostatic field generated by the hexapole generating element 200 is adjustable through the selection of the voltages applied to each electrode. In particular, a hexapole field is generated when V1=V3=V5=V and V2=V4=V6=-V. Alternatively, a dipole field E is generated when V1=V, V2=V / 2, V3=-V / 2, V4=-V, V5=-V / 2, and V6=V / 2. x is generated, and the dipole field E yis generated. Similarly, any linear combination of dipole, quadrupole, and / or hexapole fields can be generated. In other examples, the geometry of the electrodes of the multipole elements can generate multipole fields of fixed orientation corresponding to such geometry, as described in more detail below.

[0036] Symmetry condition φ m (x,y,z)=φ m The electrostatic multipole potential of multiplicity m that satisfies (x,-y,z) is given by:

[0037]

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[0038]

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[0039] Primary Ray The first order ray of a charged particle beam, also known as a Gaussian ray, can be characterized by five ray parameters. One such parameter is the relative energy spread κ = ΔU / U. The remaining four parameters are typically determined by the relative energy spread κ = ΔU / U relative to a given plane z = z S In particular, these parameters are x s and y s and the x and y components of the ray in the sample plane, denoted by

[0040]

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[0041]

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[0042] Axial geometric aberration The geometric axial aberration of a charged particle beam in the specimen plane can be defined via the phase function S(α,β), where α=x'=dx / dz and β=y'=dy / dz. In wave optics terms, this function can be expressed as exp(i2πλ -1 S(α,β)), where λ is the charged particle wavelength. Eliminating parasitic aberrations, S(α,β) contains only even powers of β due to the symmetry of the electrostatic potential, and is thus given by:

[0043]

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[0044] When parasitic aberrations are included, an extension of equation (5) is required, where C1,

[0045]

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[0050] In these formulas:

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[0053] Off-axis geometric aberrations Geometric axial aberrations are particularly relevant for the probe-forming charged particle beam, but off-axis aberrations are also relevant. For example, off-axis aberrations may determine the sensitivity of components of a charged particle microscope to drifts in the incoming charged particle beam. Furthermore, for sufficiently small off-axis aberrations, alternating current (AC) scanning can advantageously be performed partially upstream of the aberration correction system.

[0054] All geometric aberrations are expressed by the image-side perturbation eikonal function S(α,β,x S ,y S ), where the additional ray parameter x S and y S But the test piece plane z=z S The function S(α,β,0,0) is equal to the phase function S(α,β) given by equation (5).

[0055]

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[0057] For the corrector according to the present disclosure, the second order aberrations are of most concern. Neglecting parasitic aberrations, the corresponding image-side eikonal is given by:

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[0061] Beam drift on the corrector (non-zero x) is not a factor unless all three off-axis coefficients are zero. S and / or y S (resulting in: ) therefore induces defocus and / or astigmatism, i.e., aberrations that are first order in α and β. As a result of equation (10), the three off-axis aberration coefficients are determined via the angular aberration of the axial beam.

[0062]

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[0064] Third-order off-axis aberrations may also be relevant. The corresponding term in the perturbed eikonal function thus relates only to the intrinsic aberrations, α 3 x S , αβ 2 x S , α 2 βy S , and β 3 y S Also in this case, the angular aberrations of the axial beam result in these off-axis aberrations. Mirror symmetry in the xz plane results in the term

[0065]

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[0066] chromatic aberration The axial chromatic aberration of a circular lens is given by coefficient C c and the corresponding aberration is

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[0069] Alternatively, C cx ≠C cy In the example, the chromatic aberration coefficient C c =(C cx +C cy ) / 2 and chromatic astigmatism coefficient A 1κ,r =(C cx -C cy ) / 2=Re(A 1κ ) can be used, so in general,

[0070]

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[0071] The corrector according to the present disclosure can be designed such that the charged particle beam leaving the corrector is not completely dispersed. Stated differently, the dispersed rays are not completely dispersed due to the first order aberrations.

[0072]

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[0073] In the present disclosure, an aberration may be characterized by an order and / or a power. In particular, as used herein, the term "order" corresponds to the geometric part of the aberration, while the term "power" refers to the power of κ in the aberration. As an example, the chromatic aberration coefficient C crepresents an aberration of order 1 and power 1. As another example, the spherical aberration coefficient C3 represents an aberration of order 3 and power 0. Furthermore, as used herein, the term "rank" is the sum of the order and power of an aberration.

[0074] Second rank aberrations For a perfect device, all relevant second rank aberrations can be derived from the image-side perturbation eikonal:

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[0076] The second rank parasitic aberration can be expressed as:

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[0078] First rank aberrations Apart from the parasitic defocus and astigmatism C1 and A1, which can be trivially nulled, the first order parasitic dispersion is significant.

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[0080] Hexapole fields for second rank aberrations In an ideal device, the hexapole field would produce aberrations of the second rank in the axial direction

[0081]

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[0083] In a practical device subject to parasitic aberrations, it is preferable that A 2i and B. 2i Preferably, x κ An additional hexapole field may be needed to null out the chromatic astigmatism component A 1κ,i An additional hexapole field may also be required to cancel out . Thus, the corresponding hexapole potential is

[0084]

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[0085] Aberrations induced by thin multipoles. z=z M For a multipole element of relatively short length L located at , the hexapole potential of the multipole element in the approximation of the sharp cutoff (SCOFF) of the fringe field is given by:

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[0090] As an example, there is no variance (i.e., x κ (z M )=0) and the axial beam is round (i.e.,

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[0094] x a (z M )≠y a (z M ) and x κ (z M ) = 0, the astigmatism A 2r and asymmetric aberration B 2r becomes:

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[0096] In general, the nonzero dispersion in thin multipole elements (i.e., x κ ≠0), the second rank axial aberration induced by the hexapole field is A 2r , B 2r , C cx , C cy and the variance of the second frequency is

[0097]

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[0098] Chromatic aberration correction in the yz plane In most cases, the corrector midplane z=z mid In the base ray x a (z mid )=0, and y a (z mid ) and x κ (z mid ) is large there. In such an example, C c The correction is preferably performed using an adjustable hexapole generating element in the corrector midplane. The radius R is equal for all electrostatic prisms. prism Assuming that, x κ (zmid )=g1R prism where |g1|~2 for the alpha type corrector described below, and |g1|~3 for the omega type corrector described below. Combining equations (22) and (23) gives:

[0099]

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[0101] In the xz plane, the mid-plane hexapole field induces the following angles:

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[0106] Chromatic aberration correction in the xz plane In some cases, the chromatic aberration correction in the xz plane is z=z A and z=z C The method is carried out with two hexapole fields arranged at two line foci at y a (z A )=y a (z C )=0. In addition, in such an example,

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[0111] Equation (34) shows that asymmetric excitation causes the second degree of dispersion

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[0116] Such a hexapole field also has the corresponding aberration coefficients

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[0120] Example of chromatic aberration corrector Figure 3 illustrates an aberration correction system 300 that at least partially corrects axial chromatic aberration of a charged particle beam 302. The aberration correction system 300 may be described as representing an example of the aberration correction system 120 of Figure 1. Similarly, the charged particle beam 302 may include and / or be the charged particle beam 104 of Figure 1.

[0121] As shown in FIG. 3 , the aberration correction system 300 includes a deflector assembly 310 including a corrector electrostatic prism 312 and a plurality of electrostatic multipole elements 314. As shown in FIG. 3 , the deflector assembly 310 can define a deflector optical axis 308 such that the charged particle beam 302 travels along the deflector optical axis 308 as the charged particle beam 302 traverses the aberration correction system 300. Thus, the deflector assembly 310 can be configured to at least partially correct the on-axis chromatic aberration of the charged particle beam 302 as the charged particle beam 302 travels along the deflector optical axis 308. In the example of FIG. 3 , the deflector optical axis 308 is a curved axis that is circular within the corrector electrostatic prism 312. Within the corrector electrostatic prism 312, the circular path of the deflector optical axis 308 is defined by a prism radius R as measured between the central axis 301 of the corrector electrostatic prism 312 and the deflector optical axis 308. prism It can be characterized by:

[0122] The corrector electrostatic prism 312 can be configured to generate at least a portion of an electrostatic deflection field associated therewithin that directs the charged particle beam 302 along the curved deflector optical axis 308. The electrostatic deflection field can include a prism hexapole field, such as may be generated by at least a subset of the plurality of electrostatic multipole elements 314.

[0123] 3, the aberration correction system 300 further includes an entrance electrostatic prism 304 configured to direct (e.g., deflect) the charged particle beam 302, such as from an optical column axis 303, towards and / or toward a deflector optical axis 308, and an exit electrostatic prism 306 configured to direct (e.g., deflect) the charged particle beam 302 from the deflector optical axis 308 towards and / or toward the optical column axis 303. The optical column axis 303 may represent at least a portion of the optical column axis 112 of FIG. 1. In this manner, the optical column axis 303 may be described as excluding the deflector optical axis 308, such that the deflector optical axis 308 represents and / or includes the path of a portion of the charged particle beam 302 that is deflected away from the optical column axis 303.

[0124] Each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 can have any of a variety of structures and / or configurations for directing the charged particle beam 302 as described. In some examples, each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 is configured to deflect the charged particle beam 302 at an angle equal to or approximately equal to 45 degrees. However, this is not required, and in addition, it is within the scope of the present disclosure that each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 can deflect the charged particle beam 302 at an angle greater than or less than 45 degrees. Additionally or alternatively, in some examples, the entrance electrostatic prism 304 and the exit electrostatic prism 306 can be configured to deflect the charged particle beam 302 by different amounts (e.g., by respective angles that differ from one another).

[0125] In some examples, one or both of the entrance electrostatic prism 304 and the exit electrostatic prism 306 are bifocal prisms. Additionally or alternatively, in some examples, one or both of the entrance electrostatic prism 304 and the exit electrostatic prism 306 can be characterized by different focusing actions in different planes (e.g., the xz and yz planes as shown in FIG. 3).

[0126] In some examples, the entrance electrostatic prism 304 and the exit electrostatic prism 306 may be configured to selectively direct the charged particle beam 302 to travel along the deflector optical axis 308 or alternatively to bypass the corrector electrostatic prism 312 (e.g., to continue traveling along the optical column axis 303). For example, the aberration correction system 300 may be configured to selectively operate in each of a correction mode in which the entrance electrostatic prism 304 directs the charged particle beam 302 towards the deflector optical axis 308 and a linear axis mode in which the charged particle beam bypasses the deflector assembly 310. In some such examples, as shown by the dashed lines in FIG. 3, the aberration correction system 300 may be configured such that when the aberration correction system 300 is in the linear axis mode, the charged particle beam 302 proceeds through each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 without deflection. This can be accomplished, for example, by configuring each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 to include an aperture and / or passageway through which the charged particle beam 302 can pass undeflected when no deflection voltage is applied to each prism.

[0127] In the present disclosure, a particle beam (e.g., charged particle beam 104 and / or charged particle beam 302) may be described as traveling "along" a direction and / or axis (e.g., emission axis 106, optical column axis 112, optical column axis 303, and / or deflector optical axis 308) even when and / or if at least a portion of the particle beam deviates spatially from the direction and / or axis. For example, as described herein, a particle beam may be characterized by a non-zero spatial extent in a direction perpendicular to its direction of travel in at least a portion of the beam path of the particle beam. Thus, in the present disclosure, an axis along which a particle beam travels may refer to a path that is encompassed and / or surrounded by the particle beam and / or a path that characterizes the average motion of the particles of the particle beam. Additionally or alternatively, the curved axis along which the particle beam travels may be defined to coincide with the central axial ray of the particle beam, i.e., a ray of the charged particle beam that travels exactly along a straight optical axis upstream of the curved optical axis before being deflected onto the curved optical axis. Alternatively stated, this central axial ray can be described as representing the ray at the center of the axial beam cone.

[0128] Additionally, in the present disclosure, the axes (e.g., emission axis 106, optical column axis 112, optical column axis 303, and / or deflector optical axis 308) characterizing the beam path of the particle beam (e.g., charged particle beam 104 and / or charged particle beam 302) may follow a curved trajectory. In particular, in the example of FIG. 3, the deflector optical axis 308 traversing the deflector assembly 310 may be described as α-shaped (i.e., shaped similarly to the Greek letter alpha). Furthermore, in the example of FIG. 3, a portion of the deflector optical axis 308 that extends into the corrector electrostatic prism 312 follows a circular path. In the present disclosure, any example of an aberration correction system and / or its deflector assembly characterized by a deflector optical axis that is generally α-shaped may be referred to as an “alpha-type” system or assembly.

[0129] In the example of FIG. 3, the multiple electrostatic multipole elements 314 include a first hexapole generating element 320, a second hexapole generating element 322, a third hexapole generating element 324, a first quadrupole generating element 330, and a second quadrupole generating element 332.

[0130] 3, at least a subset of the plurality of electrostatic multipole elements 314 (e.g., at least a first hexapole generating element 320, a second hexapole generating element 322, and a third hexapole generating element 324) may be at least partially disposed and / or incorporated within the corrector electrostatic prism 312. In particular, while FIG. 3 illustrates each electrostatic multipole element 314 as partially overlapping the corrector electrostatic prism 312 for clarity, it should be understood that each electrostatic multipole element may be at least substantially and / or completely contained within the corrector electrostatic prism 312.

[0131] In some examples, the first hexapole generating element 320, the second hexapole generating element 322, and the third hexapole generating element 324 each include six poles for generating a respective hexapole field (e.g., as a primary or standalone multipole field). In other examples, one or more of the first hexapole generating element 320, the second hexapole generating element 322, and / or the third hexapole generating element 324 can include more than six poles (e.g., eight poles) for generating a small additional multipole field (e.g., a rotating hexapole field) to nullify parasitic aberrations caused by mechanical errors. Additionally or alternatively, one or more of the electrostatic multipole elements 314 can be configured to generate a small dipole field and / or a small quadrupole field. Such dipole fields can operate to align the central ray of the charged particle beam 302. Such a quadrupole field can operate to align the primary rays (eg, the base rays shown in FIG. 4, discussed below) of the charged particle beam 302 .

[0132] In some examples, a quadrupole generating element (e.g., the first quadrupole generating element 330 and / or the second quadrupole generating element 332) of an aberration correction system according to the present disclosure can include four poles for generating a respective quadrupole field (e.g., as a primary or single multipole field). In other examples, the quadrupole generating element can include more or less than four poles.

[0133] In some examples, the multipole elements of the aberration correction system according to the present disclosure can be configured to generate a corresponding multipole field as a result of the geometry of the multipole elements and / or corresponding structures. For example, a portion of the electrostatic prism (e.g., the corrector electrostatic prism 312, the entrance electrostatic prism 304, and / or the exit electrostatic prism 306) can be shaped such that application of a deflection voltage to the electrostatic prism produces a multipole field component in addition to the deflection electrostatic field.

[0134] As another example, a multipole element configured to generate primarily a first type of multipole field (e.g., a quadrupole field) may include poles shaped to additionally generate additional types of multipole fields (e.g., octopole fields, dodecapole fields, etc.). That is, while it is often desirable to configure a multipole element to generate a corresponding multipole field that is as "pure" as possible (e.g., to generate a hexapole field with minimal quadrupole, octopole, etc. field components), in other examples it may also be desirable to configure a single multipole element to generate a superposition of multiple multipole fields. In some examples, this can simplify the design of the system by allowing the use of fewer optical elements and / or applied voltages to generate the desired field.

[0135] In the present disclosure, the multipole fields associated with such geometries may be described as "fixed" and / or "static", in the sense that such fields are of a type and / or orientation that is fixed by the geometry of the corresponding structure. Such fields may additionally or alternatively be referred to herein as "auxiliary fields". Such auxiliary fields may be magnitude-variable by varying the voltages applied to the structures that generate such auxiliary fields. However, because such voltages are typically applied to achieve different first-order effects (e.g., deflection of a charged particle beam along well-defined directions and / or generation of different first-order multipole fields), the magnitude of the auxiliary fields is generally not independently variable. Thus, the desired configuration of the auxiliary fields must generally be achieved through careful shaping of the corresponding structures, rather than through control of the applied voltages.

[0136] 3, each of the first and second quadrupole generating elements 330, 332 can be configured to generate a corresponding auxiliary quadrupole field (e.g., as a primary or single multipole field). In particular, each of the first and second quadrupole generating elements 330, 332 can be at least partially defined by the corrector electrostatic prism 312, such as through appropriate shaping of the corrector electrostatic prism 312 such that the deflector optical axis 308 enters and exits the corrector electrostatic prism 312.

[0137] Each of the first hexapole generating element 320, the second hexapole generating element 322, and the third hexapole generating element 324 is primarily configured to generate a respective hexapole field, but may also generate smaller fine-tuning dipole and / or quadrupole fields. Specifically, the first hexapole generating element 320 is configured to generate a first hexapole field, the second hexapole generating element 322 is configured to generate a second hexapole field, and the third hexapole generating element 324 is configured to generate a third hexapole field.

[0138] Similarly, each of the first and second quadrupole generating elements 330, 332 is primarily configured to generate a respective quadrupole field. Specifically, the first quadrupole generating element 330 is configured to generate a first quadrupole field, and the second quadrupole generating element 332 is configured to generate a second quadrupole field.

[0139] In the figures of the present disclosure, electrostatic multipole elements illustrated and / or represented with solid lines, such as the first hexapole generating element 320, the second hexapole generating element 322, or the third hexapole generating element 324 in FIG. 3, represent electrostatic multipole elements configured to generate a corresponding multipole field that is adjustable (e.g., in orientation and / or magnitude). In such examples, the illustrated solid lines may additionally or alternatively be understood to represent a corresponding adjustable multipole field. In such examples, as described herein, such an adjustable multipole field may be generated and / or configured in any of a variety of ways, such as by applying independently controllable voltages to each pole of the multipole element to generate a desired multipole field having one or more degrees of freedom.

[0140] Alternatively, in figures of the present disclosure, electrostatic multipole elements illustrated and / or represented with dashed lines, such as first quadrupole generating element 330 or second quadrupole generating element 332 in Figure 3, represent electrostatic multipole elements configured to generate a corresponding auxiliary multipole field. In such examples, the illustrated dashed lines may additionally or alternatively be understood to represent a corresponding auxiliary multipole field. In such examples, such auxiliary multipole fields may be generated and / or configured in any of a variety of ways, such as through appropriate shaping of electrodes of the associated multipole element, as described herein.

[0141] 3, the charged particle beam 302, the optical column axis 303, and / or the deflector optical axis 308 may also be characterized with reference to an x-axis, a y-axis, and a z-axis. In particular, the z-axis may be defined as the direction in which the deflector optical axis 308 is oriented at a given location along the deflector optical axis 308. The x-axis may be defined as the direction that is perpendicular to the z-axis at a given location along the deflector optical axis 308 and that extends in a plane in which the deflector optical axis 308 extends within the deflector assembly 310, while the y-axis may be defined as the direction that is mutually perpendicular to each of the x-axis and z-axis.

[0142] As shown in FIG. 3, the location and / or position along the portion of the deflector optical axis 308 that extends within the corrector electrostatic prism 312 is between zero and the maximum prism angle φ max In particular, a prism angle of φ=0 may correspond to the position where the charged particle beam 302 is incident on the corrector electrostatic prism 312 along the deflector optical axis 308. On the other hand, a prism angle of φ=φ max may correspond to the position at which the charged particle beam 302 exits the corrector electrostatic prism 312 along the deflector optical axis 308. Thus, the angle φ max may be described as representing the total angular range of the corrector electrostatic prism 312 and / or the total angle through which the charged particle beam 302 is deflected as it traverses the corrector electrostatic prism 312 .

[0143] Angle φ max can assume any of a variety of values. In particular, in the example of FIG. 3, the angle φ max is equal to or approximately equal to 270 degrees. However, this is not required in all instances. In addition, the angle φ max It is within the scope of this disclosure that can be less than or greater than 270 degrees.

[0144] In various examples, the angle φ maxand the respective angles through which the entrance electrostatic prism 304 and the exit electrostatic prism 306 deflect the charged particle beam 302 are equal to or approximately equal to 360 degrees, such that the charged particle beam 302 travels along substantially the same direction upstream and downstream of the deflector assembly 310. Thus, in some examples, the corrector electrostatic prism 312 is configured to have a maximum prism angle φ max = 250 degrees, and the entrance electrostatic prism 304 and the exit electrostatic prism 306 can each be configured to deflect the charged particle beam 302 at an angle of 55 degrees. Alternatively, in some other examples, the corrector electrostatic prism 312 can be configured to deflect the charged particle beam 302 at a maximum prism angle φ max =280 degrees, and each of the entrance electrostatic prism 304 and the exit electrostatic prism 306 can be configured to deflect the charged particle beam 302 by an angle of 40 degrees.

[0145] The electrostatic multipole elements 314 of the deflector assembly 310 can have any of a variety of configurations relative to each other and / or relative to the corrector electrostatic prism 312. For example, as shown in Figure 3, a first quadrupole generating element 330 can be positioned along the deflector optical axis 308 between the entrance electrostatic prism 304 and the first hexapole generating element 320, and a second quadrupole generating element 332 can be positioned along the deflector optical axis 308 between the third hexapole generating element 324 and the exit electrostatic prism 306.

[0146] 3, the second hexapole generating element 322 is positioned proximate to the midpoint of the deflector optical axis 308 within the corrector electrostatic prism 312. In particular, in the example of FIG. max = 270 degrees, whereby the second hexapole generating element 322 is positioned and / or centered at a prism angle of φ = 135 degrees.

[0147] In addition, in the example of Fig. 3, each of the first hexapole generating element 320 and the third hexapole generating element 324 is angularly equidistant from the second hexapole generating element 322 such that the deflector assembly 310 is mirror symmetric in the mid-plane (i.e., around the center of the second hexapole generating element 322). In particular, in the example of Fig. 3, the first hexapole generating element 320 is positioned and / or centered at a prism angle of about φ=58 degrees, while the third hexapole generating element 324 is positioned and / or centered at a prism angle of about φ=212 degrees. However, such an arrangement is not required, and further, it is within the scope of this disclosure that the first hexapole generating element 320 and the third hexapole generating element 324 may be positioned at any suitable respective prism angle, such as a prism angle corresponding to a position at or near the line focus of the charged particle beam 302 in the corrector electrostatic prism 312.

[0148] FIG. 4 illustrates a diagram of fundamental rays x, labeled 402, 404, and 406, respectively, of a charged particle beam 400 traversing an aberration correction system, such as the aberration correction system 300 of FIG. a (z), y a (z) and x κ 3. In other words, the charged particle beam 400 of FIG. 4 can include and / or be at least a portion of the charged particle beam 302 of FIG. 3. FIG. 4 shows a base ray along a straight optical axis 418, which corresponds to the deflector optical axis 308 and / or the z-axis of FIG. 3. As shown in FIG. 4, a charged particle source (e.g., the charged particle source 102 of FIG. 1) generating the charged particle beam 400 is imaged onto a corrector entrance 408, and a corrector exit focal point 410 is imaged via appropriate optics to a specimen plane z S 4, such optical system includes transfer lens 440 and objective lens 442, which may be similar to transfer lens 122 and / or objective lens 128, respectively, of FIG.

[0149] 4 further illustrates the positions of the first hexapole generating element 420, the second hexapole generating element 422, the third hexapole generating element 424, the first quadrupole generating element 430, and the second quadrupole generating element 432 relative to the linear optical axis 418 and relative to the base rays 402, 404, and 406. The first hexapole generating element 420, the second hexapole generating element 422, the third hexapole generating element 424, the first quadrupole generating element 430, and the second quadrupole generating element 432 in FIG. 4 correspond to the first hexapole generating element 320, the second hexapole generating element 322, the third hexapole generating element 324, the first quadrupole generating element 330, and the second quadrupole generating element 332 in FIG. 3, respectively.

[0150] As shown in FIG. 4, the charged particle beam 400 exhibits a line focus in the xz plane near the first hexapole generating element 420 and the third hexapole generating element 424, and a line focus in the yz plane near the second hexapole generating element 422.

[0151] FIG. 4 further illustrates the positions of entrance electrostatic prism 412, exit electrostatic prism 414, and corrector electrostatic prism 416, which correspond respectively to entrance electrostatic prism 304, exit electrostatic prism 306, and corrector electrostatic prism 312 of FIG.

[0152] The corrector electrostatic prism 312 of Figure 3 and / or the corrector electrostatic prism 416 of Figure 4 may have any suitable structure for deflecting the charged particle beam 302 and / or for supporting at least a subset of the plurality of electrostatic multipole elements 314. For example, Figure 5 shows an example of a corrector electrostatic prism 500, which may be described as an example of the corrector electrostatic prism 312 of Figure 3 and / or the corrector electrostatic prism 416 of Figure 4. In the example of Figure 5, the corrector electrostatic prism 500 generally takes the form of a rotating entity about a central axis 501 (which may represent the central axis 301 of Figure 3).

[0153] 5, the corrector electrostatic prism 500 may include a corrector prism body 510 having a first corrector prism electrode 512 and a second corrector prism electrode 514 disposed radially outward of the first corrector prism electrode 512. As such, the first corrector prism electrode 512 may also be referred to as the inner corrector prism electrode 512 and / or the second corrector prism electrode 514 may also be referred to as the outer corrector prism electrode 514.

[0154] 5, the first corrector prism electrode 512 and the second corrector prism electrode 514 may be spaced apart to define an electrode gap 516 therebetween such that a deflector optical axis 508 along which the charged particle beam 502 travels extends into and / or through the electrode gap 516. The deflector optical axis 508 shown in FIG. 5 may include and / or be at least a portion of the deflector optical axis 308 of FIG. 3 and / or the charged particle beam 502 of FIG. 5 may include and / or be at least a portion of the charged particle beam 302 of FIG. 3.

[0155] The corrector electrostatic prism 500 can be configured such that when a first electrode voltage is applied to the first corrector prism electrode 512 and a second electrode voltage is applied to the second corrector prism electrode 514, the corrector electrostatic prism 500 generates an electrostatic deflection field that directs the charged particle beam 502 to travel through the corrector electrostatic prism 500 along the deflector optical axis 508. As described in more detail herein, the application of the first and second electrode voltages to the corrector electrostatic prism 500 can also function to generate one or more auxiliary multipole fields (e.g., auxiliary quadrupole fields, auxiliary hexapole fields, auxiliary octopole fields, etc.) due to, for example, the geometric shapes of the first corrector prism electrode 512 and / or the second corrector prism electrode 514.

[0156] Each of the entrance electrostatic prism 304 and / or the exit electrostatic prism 306 of FIG. 3 may also have a structure similar to the corrector electrostatic prism 500 of FIG. 5. For example, FIG. 6 shows an example of an entrance electrostatic prism 604, which may be described as an example of the entrance electrostatic prism 304 of FIG. 3. In some examples, the structure shown in FIG. 6 may additionally or alternatively function as an exit electrostatic prism, such as the exit electrostatic prism 306 of FIG. 3. As shown in FIG. 6, the entrance electrostatic prism 604 may include an entrance prism body 610 having a first entrance prism electrode 612 and a second entrance prism electrode 614 disposed radially outward of the first entrance prism electrode 612. In this manner, the first entrance prism electrode 612 may also be referred to as an inner entrance prism electrode 612 and / or the second entrance prism electrode 614 may also be referred to as an outer entrance prism electrode 614.

[0157] 6, the first entrance prism electrode 612 and the second entrance prism electrode 614 may be spaced apart to define an electrode gap 616 therebetween such that a deflector optical axis 608 along which the charged particle beam 602 travels extends into and / or through the electrode gap 616. The deflector optical axis 608 shown in FIG. 6 may include and / or be at least a portion of the deflector optical axis 308 of FIG. 3 and / or the charged particle beam 602 of FIG. 6 may include and / or be at least a portion of the charged particle beam 302 of FIG. 3.

[0158] The corrector electrostatic prism 600 can be configured such that when a first electrode voltage is applied to the first entrance prism electrode 612 and a second electrode voltage is applied to the second entrance prism electrode 614, the corrector electrostatic prism 600 generates an electrostatic deflection field that directs the charged particle beam 602 to travel along the deflector optical axis 608 through the corrector electrostatic prism 600. In some examples, the same voltage can be applied to each of the first corrector prism electrode 512 of the corrector electrostatic prism 500 and the first entrance prism electrode 612 of the entrance electrostatic prism 604, and / or the same voltage can be applied to each of the second corrector prism electrode 514 of the corrector electrostatic prism 500 and the second entrance prism electrode 614 of the entrance electrostatic prism 604. Such a configuration can enable a corresponding deflector assembly to direct the charged particle beam along the deflector optical axis with fewer independent voltages to adjust, thereby facilitating stable control of such a system.

[0159] Figure 7 is a cross-sectional view of a corrector electrostatic prism 700, which may represent the corrector electrostatic prism 312 of Figure 3, the corrector electrostatic prism 416 of Figure 4, and / or the corrector electrostatic prism 500 of Figure 5. In particular, Figure 7 represents a view of a cross-sectional plane spaced apart from any electrostatic multipole element of the corrector electrostatic prism 700, such as a view along line AA of Figure 3. The corrector electrostatic prism 700 includes a corrector prism body 710 having a first corrector prism electrode 712 and a second corrector prism electrode 714 spaced apart from the first corrector prism electrode 712 to define an electrode gap 716 therebetween.

[0160] The corrector prism body 710, the first corrector prism electrode 712, the second corrector prism electrode 714, and the electrode gap 716 may represent and / or be the corrector prism body 510, the first corrector prism electrode 512, the second corrector prism electrode 514, and the electrode gap 516 of FIG. 5, respectively.

[0161] In FIG. 7, the first electrode voltage applied to the first corrector prism electrode 712 is Vp1 and the second electrode voltage applied to the second corrector prism electrode 714 is denoted by V p2 As shown in the figure.

[0162] As shown, the cross-sectional view of Figure 7 can be described as viewed along a direction parallel to deflector optical axis 708 in electrode gap 716. Deflector optical axis 708 shown in Figure 7 can include and / or be at deflector optical axis 508 of Figure 5 and / or deflector optical axis 308 of Figure 3. Additionally, Figure 7 can be described as viewed along a plane that does not intersect any of the multipole elements of the deflector assembly.

[0163] As shown in Figure 7, the first corrector prism electrode 712 can include a first outer electrode surface 720 that faces the second corrector prism electrode 714 and a second inner electrode surface 730 that faces the first corrector prism electrode 712. In the example of Figure 7, each of the first outer electrode surface 720 and the second inner electrode surface 730 is a smooth surface (at least at a location away from the multipole elements contained within the corrector electrostatic prism 800).

[0164] In some examples, the shape of the first electrode outer surface 720 and / or the second electrode inner surface 730 can correspond to the equipotential lines of the multipole electrostatic field in the electrode gap 716. In particular, for an electrostatic prism, such as the corrector electrostatic prism 700, that is sufficiently far from the entrance and exit fringe fields, the Laplace equation for the electrostatic potential φ(x,y) can be written as:

[0165]

number

[0166]

number

[0167]

number

[0168] For the electron energy eU, the axial dipole field

[0169]

number

[0170]

number

[0171]

number

[0172]

number

[0173] In general, for any reasonable set of multipole strengths a1, a2, a3, a4, ..., one can define the profiles of the first electrode outer surface 720 and the second electrode inner surface 730 as the equipotential lines of equation (37), as shown in Figure 7, i.e., φ(x,y)=V p1 and φ(x,y)=V p2 It is. p1 / V p2 can be close to -1, and these voltages can be selected such that φ(0,0) (i.e., the electrostatic potential at the deflector optical axis 808) is zero or near zero. In practice, the beam diameter of the charged particle beam can be much smaller than the radial extent of the electrode gap 816 (i.e., 2R in the example of FIG. 7), and thus the multipole components a for m≧4 or 5 can be m The values ​​of a1, a2, and a3 are negligible. Thus, many shapes of the first electrode outer surface 720 and the second electrode inner surface 730 are possible for given values ​​of a1, a2, and a3.

[0174] The first-order focusing properties of the corrector electrostatic prism 700 in the xz and yz planes can be determined by the quadrupole field parameter a2 in Equation (37). In particular, the first-order ray equations in the electrostatic prism can be written as:

[0175]

number

[0176] In some examples, such as that of Figure 7, the electrostatic deflection field generated within the corrector electrostatic prism may be invariant with prism angle. For example, Figure 7 may be described as showing a portion of a corrector electrostatic prism 700 as viewed at a particular prism angle φ (described above with reference to Figure 3), which may show any of a variety of prism angles within a continuous range of prism angles, and / or any prism angle.

[0177] In some examples, the shapes of the first electrode outer surface 720 and the second electrode inner surface 730 (e.g., the shapes of the corresponding contours of these surfaces at a given prism angle φ) may be substantially constant within the corrector electrostatic prism 700, over a range of prism angles, e.g., over substantially the entire angular range of the corrector electrostatic prism 700, and / or at locations away from the electrostatic multipole elements within the corrector electrostatic prism 700. Thus, in some examples, the magnitude of the electrostatic deflection field and / or its prism hexapole field components within the electrode gap 716 may be constant at the prism angle φ. Stated another way, in some examples, the coefficient a in Equation (37) k and b k is independent of the prism angle φ at least away from the prism exit and entrance, ignoring field contributions from any electrostatic multipole elements associated with the corrector electrostatic prism. In some examples, this can range from 0 to φ max This applies for substantially the entire range of prism angles up to and / or at prism angles that do not correspond to the position of the electrostatic multipole elements.

[0178] Figure 8 is a cross-sectional view of another example of a corrector electrostatic prism 800, which may represent the corrector electrostatic prism 312 of Figure 3, the corrector electrostatic prism 416 of Figure 4, and / or the corrector electrostatic prism 500 of Figure 5. In particular, Figure 8 represents a view of a cross-sectional plane spaced apart from any electrostatic multipole element of the corrector electrostatic prism 800, such as a view along line AA of Figure 3. The corrector electrostatic prism 800 includes a corrector prism body 810 having a first corrector prism electrode 812 and a second corrector prism electrode 814 spaced apart from the first corrector prism electrode 812 to define an electrode gap 816 therebetween.

[0179] The corrector prism body 810, the first corrector prism electrode 812, the second corrector prism electrode 814, and the electrode gap 816 may represent and / or be the corrector prism body 510, the first corrector prism electrode 512, the second corrector prism electrode 514, and the electrode gap 516 of FIG. 5, respectively.

[0180] In FIG. 8, the first electrode voltage applied to the first corrector prism electrode 812 is V p1 and the second electrode voltage applied to the second corrector prism electrode 814 is denoted by V p2 As shown in the figure.

[0181] As shown, the cross-sectional view of Figure 8 can be described as viewed along a direction parallel to deflector optical axis 808 in electrode gap 816. Deflector optical axis 808 shown in Figure 8 can include and / or be at deflector optical axis 508 of Figure 5 and / or deflector optical axis 308 of Figure 3. Additionally, Figure 8 can be described as viewed along a plane that does not intersect any of the multipole elements of the deflector assembly.

[0182] Similar to the corrector electrostatic prism 700 of FIG. 7, the first corrector prism electrode 812 of FIG. 8 includes a first electrode outer surface 820 that faces the second corrector prism electrode 814, and the second corrector prism electrode 814 includes a second electrode inner surface 830 that faces the first corrector prism electrode 812. However, in this example, the first electrode outer surface 820 defines a first electrode groove 822 that extends along a direction parallel to the deflector optical axis 808. Similarly, the second electrode inner surface 830 defines a second electrode groove 832 that extends along a direction parallel to the deflector optical axis 808.

[0183] In some examples, the first electrode groove 822 and / or the second electrode groove 832 may be sized, shaped, and / or otherwise configured to generate a desired auxiliary electrostatic field in the electrode gap 816. For example, the first electrode groove 822 and / or the second electrode groove 832 may generate a hexapole field in the corrector electrostatic prism 800 when respective voltages are applied to the first corrector prism electrode 812 and the second corrector prism electrode 814.

[0184] In some examples, the hexapole fields generated by the first electrode groove 822 and / or the second electrode groove 832 vary along the deflector optical axis 808. This auxiliary hexapole field can be linearly scaled with the first and second electrode voltages, which can thus be related to the energy of the charged particles deflected by the first and second corrector prism electrodes 812 and 814. Thus, for a given charged particle energy, these groove-induced hexapole fields can be fixed.

[0185] Each of the first electrode groove 822 and the second electrode groove 832 can have any suitable dimension that can accommodate a desired electrostatic field in the electrode gap 816. As shown in FIG. 8, the corrector electrostatic prism has a corrector prism beam radius R 1 measured between the central axis of the first corrector prism electrode 812 (e.g., central axis 301 of FIG. 3 and / or central axis 501 of FIG. 5 ) and the deflector optical axis 808. prism The first electrode groove 822 can be characterized by a first electrode groove depth d1 measured along a radial direction parallel to the corrector prism beam radius. Similarly, the second electrode groove 832 can be characterized by a second electrode groove depth d2 measured along a radial direction. In some examples, the first electrode groove depth d1 and the second electrode groove depth d2 each correspond to a distance between the corrector prism beam radius R and the first electrode groove depth d1. prism It can be at most 1 / 50 of that.

[0186] In some examples, one or more dimensions of the first electrode groove 822 and / or the second electrode groove 832 (e.g., the first electrode groove depth d1 and / or the second electrode groove depth d2) may vary with the prism angle of the corrector electrostatic prism 800 (e.g., the prism angle φ described above in the context of FIG. 3). In such examples, the auxiliary prism multipole field also varies with the prism angle. In particular, with reference to Equation (37), varying one or more dimensions of the first electrode groove 822 and / or the second electrode groove 832 with the prism angle reduces the coefficient a, which also varies with the prism angle. k and b kIn some examples, the first electrode groove 822 and / or the second electrode groove 832 can be configured such that the axial potential (corresponding to a0) and the dipole field (corresponding to a1) remain constant or nearly constant with prism angle, while the prismatic hexapole field (corresponding to a3) follows a desired profile. In some examples, the first electrode groove 822 and / or the second electrode groove 832 can be configured such that the auxiliary octopole field (corresponding to a4) also varies with prism angle.

[0187] Additionally or alternatively, one or more dimensions of the first electrode groove 822 and / or the second electrode groove 832 (e.g., the first electrode groove depth d1 and / or the second electrode groove depth d2) may be constant over the angular range (e.g., the entire angular range) of the corrector electrostatic prism 800.

[0188] As discussed above in connection with Figure 3, one or more electrostatic multipole elements can be disposed and / or incorporated within a corrector electrostatic prism. As an example, Figure 9 is a cross-sectional view of a corrector electrostatic prism 900 having an electrostatic multipole element 950 disposed therein. In particular, Figure 9 represents a view of a cross-sectional plane intersecting the electrostatic multipole element 950, such as a view along line BB in Figure 3.

[0189] The corrector electrostatic prism 900 may represent the corrector electrostatic prism 312 of FIG. 3, the corrector electrostatic prism 416 of FIG. 4, the corrector electrostatic prism 500 of FIG. 5, the corrector electrostatic prism 700 of FIG. 7, and / or the corrector electrostatic prism 800 of FIG. 8. The corrector electrostatic prism 900 includes a corrector prism body 910 having a first corrector prism electrode 912 and a second corrector prism electrode 914 spaced apart to define an electrode gap 916 therebetween. The corrector prism body 910, the first corrector prism electrode 912, the second corrector prism electrode 914, and the electrode gap 916 may represent and / or be of corresponding structures shown in any of FIGS. 5-8. In FIG. 9, a first electrode voltage applied to the first corrector prism electrode 912 is V p1 and the second electrode voltage applied to the second corrector prism electrode 914 is denoted by Vp2 As shown in the figure.

[0190] As shown, the cross-sectional view of Figure 9 can be described as looking along a direction parallel to the deflector optical axis 908 in the electrode gap 916. The deflector optical axis 908 shown in Figure 9 can include and / or be at any of the deflector optical axes of Figures 3-8.

[0191] The first corrector prism electrode 912 can include a first electrode outer surface 920 facing the second corrector prism electrode 914, and the first electrode outer surface 920 can define a first electrode recess 922 that extends partially along a direction parallel to the deflector optical axis 908. Similarly, the second corrector prism electrode 914 can include a second electrode inner surface 930 facing the first corrector prism electrode 912, and the second electrode inner surface 930 can define a second electrode recess 932 that extends partially along a direction parallel to the deflector optical axis 908.

[0192] In the example of FIG. 9, the electrostatic multipole element 950 is an electrostatic hexapole generating element including a first hexapole electrode 952, a second hexapole electrode 954, a third hexapole electrode 956, a fourth hexapole electrode 958, a fifth hexapole electrode 960, and a sixth hexapole electrode 962. Thus, applying respective voltages to each of the hexapole electrodes of the electrostatic multipole element 950 may operate to generate dipole and quadrupole electrostatic fields of any orientation in the xy plane, and / or a hexapole field with a fixed orientation in a manner similar to the hexapole generating element 200 of FIG. 2. However, such a configuration is not required in all embodiments, and in addition, it is within the scope of the present disclosure that an electrostatic multipole element configured to generate a hexapole field may include more than six electrodes. In particular, in some examples, configuring a hexapole generating element with more than six electrodes may enable the generation of multiple multipole fields, such as a rotatable hexapole field.

[0193] As shown in FIG. 9, the first hexapole electrode 952, the second hexapole electrode 954, and the third hexapole electrode 956 may be at least partially received within the second corrector prism electrode 914 (e.g., within the second electrode recess 932), while the fourth hexapole electrode 958, the fifth hexapole electrode 960, and the sixth hexapole electrode 962 may be at least partially received within the first corrector prism electrode 912 (e.g., within the first electrode recess 922).

[0194] In some examples, the electrodes of the electrostatic multipole elements disposed within the corrector electrostatic prism can be configured such that the inner surfaces defining the electrode gaps within the corrector electrostatic prism remain substantially smooth. For example, in the example of FIG. 9, the first hexapole electrode 952, the second hexapole electrode 954, and the third hexapole electrode 956 are disposed to be flush with and / or smoothly connected to the second electrode inner surface 930 outside the second electrode recess 932, collectively defining a smoothly varying profile. Similarly, in this example, the fourth hexapole electrode 958, the fifth hexapole electrode 960, and the sixth hexapole electrode 962 are disposed to be flush with and / or smoothly connected to the first electrode outer surface 920 outside the first electrode recess 922, collectively defining a smoothly varying profile. As a result, the axial potential (a0 in Eq. 37) and the dipole field (a1 in Eq. 37) remain (almost) constant inside the prism.

[0195] In this manner, the profile collectively formed by the first outer electrode surface 920, the second inner electrode surface 930, and the hexapole electrodes of the electrostatic multipole element 950 can be substantially similar in shape to that shown in FIG. 8 and / or can correspond to the equipotential lines of Equation (37) above. Additionally or alternatively, in some such examples, the magnitude of the electrostatic deflection field and / or its prismatic hexapole field components in the electrode gap 916 can be scaled by a factor a k and b k(37) with φ=0.001, which is independent of at least the prism angle φ away from the prism exit and entrance, and ignores field contributions from any electrostatic multipole elements 950 associated with the corrector electrostatic prism 500. In some examples, this can vary from zero to φ max 3 and / or at prism angles that do not correspond to the position of electrostatic multipole element 950.

[0196] As discussed above in connection with Figure 3, one or more electrostatic multipole elements may be at least partially formed by portions of a corrector electrostatic prism shaped to generate a desired auxiliary multipole field. As an example, Figure 10 is a cross-sectional view of a corrector electrostatic prism 1000 that at least partially defines an electrostatic multipole element 1050. In particular, Figure 10 represents a view along line CC of Figure 3 and depicts the exit face of the corrector electrostatic prism 1000.

[0197] The corrector electrostatic prism 1000 may represent the corrector electrostatic prism 312 of Figure 3, the corrector electrostatic prism 416 of Figure 4, the corrector electrostatic prism 500 of Figure 5, the corrector electrostatic prism 700 of Figure 7, the corrector electrostatic prism 800 of Figure 8, and / or the corrector electrostatic prism 900 of Figure 9. The corrector electrostatic prism 1000 includes a corrector prism body 1010 having a first corrector prism electrode 1012 and a second corrector prism electrode 1014 spaced apart to define an electrode gap 1016 therebetween. The corrector prism body 1010, the first corrector prism electrode 1012, the second corrector prism electrode 1014, and the electrode gap 1016 may represent and / or be the corresponding structures shown in any of Figures 5-9. In FIG. 10, the first electrode voltage applied to the first corrector prism electrode 1012 is V p1 and the second electrode voltage applied to the second corrector prism electrode 1014 is denoted by V p2 As shown in the figure.

[0198] As shown, the cross-sectional view of Figure 10 can be described as looking along a direction parallel to the deflector optical axis 1008 in the electrode gap 1016. The deflector optical axis 1008 shown in Figure 10 can include and / or be at any of the deflector optical axes of Figures 3-9.

[0199] 10, the first corrector prism electrode 1012 includes a first electrode bump 1070 that extends toward the deflector optical axis 1008, and the second corrector prism electrode 1040 includes a second electrode groove 1072 that is recessed away from the deflector optical axis 1008. The first electrode bump 1070 and the second electrode groove 1072 can be configured (e.g., shaped and / or dimensioned) such that when a first electrode voltage is applied to the first corrector prism electrode 1012 and a second electrode voltage is applied to the second corrector prism electrode 1014, the first electrode bump 1070 and the second electrode groove 1072 act as an electrostatic multipole element 1050 to generate an auxiliary quadrupole field.

[0200] The first electrode bump 1070 and / or the second electrode groove 1072 can be localized within the corrector electrostatic prism 1000, such as in regions proximate the entrance and / or exit of the corrector electrostatic prism. The first electrode bump 1070 and the second electrode groove 1072 can have any suitable dimensions, such as relative to one or more other dimensions of the corrector electrostatic prism 1000. For example, with reference to the gap radius R shown in FIG. 10, the first electrode bump 1070 and / or the second electrode groove 1072 can have a depth 1073 approximately equal to R and / or less than R and / or less than 2R, as measured along a direction parallel to the deflector optical axis 1008. Additionally or alternatively, the first electrode bump 1070 and / or the second electrode groove may have a width 1071 that is approximately equal to R and / or less than 3R when measured along a direction perpendicular to the deflector optical axis 1008 and parallel to the central axis 1001.

[0201] 11 illustrates another example of an aberration correction system 1100 for at least partially correcting axial chromatic aberration of a charged particle beam 1102. The aberration correction system 1100 can be described as representing an example of the aberration correction system 120 of FIG. 1. Similarly, the charged particle beam 1102 can include and / or be the charged particle beam 104 of FIG. 1.

[0202] The aberration correction system 1100 of FIG. 11 is similar to the aberration correction system 300 of FIG. 3. For example, as shown in FIG. 11, the aberration correction system 1100 includes a deflector assembly 1110 including a corrector electrostatic prism 1112 and a plurality of electrostatic multipole elements 1114. Except as described below, all illustrated components of the aberration correction system 1100, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of the aberration correction system 300. For components labeled in FIG. 11, components labeled with reference numbers in the format "11XX" are intended to correspond to components labeled with reference numbers in the format "3XX" in FIG. 3. For example, the entrance electrostatic prism 1104 of FIG. 11 may correspond to and be at least substantially identical to the entrance electrostatic prism 304 of FIG. 3. Furthermore, the base rays of the charged particle beam 1102 traversing the aberration correction system 1100 may be substantially similar to the base rays 402, 404, and 406 shown in FIG.

[0203] Similar to the aberration correction system 300 of Figure 3, the aberration correction system 1100 of Figure 11 includes a first hexapole generating element 1120, a second hexapole generating element 1122, a third hexapole generating element 1124, a first quadrupole generating element 1130, and a second quadrupole generating element 1132. The first hexapole generating element 1120, the second hexapole generating element 1122, and the third hexapole generating element 1124 may be configured and / or positioned (e.g., with respect to the corrector electrostatic prism 1112) substantially similarly to the corresponding electrostatic multipole elements 314 of Figure 3. However, in contrast to the aberration correction system 300 of Figure 3, each of the first quadrupole generating element 1130 and the second quadrupole generating element 1132 is an adjustable multipole element spaced apart from the corrector electrostatic prism 1112. In particular, the first quadrupole generating element 1130 and the second quadrupole generating element 1132 can be arranged such that the respective quadrupole electrostatic fields generated by the first quadrupole generating element 1130 and the second quadrupole generating element 1132 have minimal and / or negligible overlap with the deflection electrostatic field generated by the corrector electrostatic prism 1112.

[0204] In other examples, an aberration correction system (e.g., similar to aberration correction system 300 of FIG. 3 or aberration correction system 1100 of FIG. 11) can include a first quadrupole generating element and / or a second quadrupole generating element in the form of an adjustable element that is at least partially received within a corrector electrostatic prism. For example, such an aberration correction system can include one or more quadrupole generating elements configured similarly to electrostatic multipole element 950 of FIG. 9, but with fewer than three (e.g., one or two) electrodes coupled to each of the first and second prism electrodes.

[0205] As mentioned above with reference to equation (39), the dimensionless parameter p for the fixed hexapole field in the corrector electrostatic prism is a3 = pK 3The hexapole parameter can be defined as p1 through U. For spherical prisms, p=-5 / 4. For each of the entrance and exit electrostatic prisms disclosed herein (e.g., for entrance electrostatic prisms 304 and / or 1104 and / or for exit electrostatic prisms 306 and / or 1106), the hexapole parameter can be expressed as p1. For each of the corrector electrostatic prisms 300, 500, 700, 800, 900, and / or 1100, the hexapole parameter can be expressed as p2.

[0206] For the adjustable hexapole field, the hexapole excitation parameters h(m -2 It is convenient to define the mass sigma (having units of 1000 kcal / s) as follows:

[0207]

number

[0208]

number

[0209] In this way, the hexapole excitations h1 and h2 allow for chromatic aberration correction, i.e., negative C cx =C cyOne preferred choice for the fixed hexapole parameters can be p1=-1.084 and p2=-2.012, which results in:

[0210]

number

[0211] These formulas are for radius R prism is assumed to be the same for all three electrostatic prisms of the aberration correction system (e.g., entrance electrostatic prism 304 / 1104, exit electrostatic prism 306 / 1106, and corrector electrostatic prism 142 / 1112), although this is not required in all examples. However, in some examples, all such electrostatic prisms may be configured to have a constant R / R prism (where R represents distance as shown in Figs. 7-9). This can strongly relax the corresponding voltage stability requirements for the voltage applied to each such prism. In particular, each electrostatic prism can be configured to have a common value of R / R prism In the example characterized by the same value of V, only two voltages (e.g., V and -V) need to be generated and appropriately applied to the various prism electrodes to define the deflector optical axis.

[0212] 12 illustrates another example of an aberration correction system 1200 for at least partially correcting axial chromatic aberration of a charged particle beam 1202. The aberration correction system 1200 can be described as representing an example of the aberration correction system 120 of FIG. 1. Similarly, the charged particle beam 1202 can include and / or be the charged particle beam 104 of FIG. 1.

[0213] The aberration correction system 1200 of FIG. 12 is similar to the aberration correction system 300 of FIG. 3 and the aberration correction system 1100 of FIG. 11. For example, as shown in FIG. 12, the aberration correction system 1200 includes a deflector assembly 1210 including a corrector electrostatic prism 1212 and a plurality of electrostatic multipole elements 1214. Except as described below, all illustrated components of the aberration correction system 1200, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of the aberration correction system 300 and / or the aberration correction system 1100. With respect to components labeled in FIG. 12, components labeled with reference numbers in the format "12XX" are intended to correspond to components labeled with reference numbers in the format "3XX" in FIG. 3 and / or components labeled with reference numbers in the format "11XX" in FIG. For example, entrance electrostatic prism 1204 in FIG. 12 may correspond to and be at least substantially identical to entrance electrostatic prism 304 in FIG. 3 and / or entrance electrostatic prism 1104 in FIG.

[0214] 12 shows an example in which the magnitude of the prism hexapole field in the corrector electrostatic prism 1212 varies with the prism angle φ. In particular, in this example, the hexapole parameter p defined by equation (39) is a function of the prism angle.

[0215] 12, the angular range of the corrector electrostatic prism 1200 can be divided into six sub-sectors φ1, φ2, φ3, φ4, φ5, and φ6. Such sub-sectors can be associated with corresponding prism angle intervals as follows: φ1:0<φ<=φ1; φ2:φ1<φ<=φ2; φ3:φ2<φ<=φ3; φ4:φ3<φ<=φ4; φ5:φ4<φ<=φ5; and φ6:φ5<φ<=φ6, Here, φ6=φ max and φ3=φ6 / 2.

[0216] In the example of Fig. 12, the hexapole parameters corresponding to the six subsectors φ1, φ2, φ3, φ4, φ5, and φ6 can be expressed as p2, p3, p4, p4, p3, and p2, respectively. That is, the hexapole parameters maintain mid-plane symmetry. As described above with reference to Figs. 3 and 11, the hexapole parameter p1 can correspond to each of the entrance electrostatic prism 1204 and the exit electrostatic prism 1206.

[0217] The hexapole parameters can be chosen such that for h1=h2=0 the corrector electrostatic prism 1212 is free of axial chromatic aberration.

[0218]

number

[0219] The piecewise constant hexapole parameters of the example of Figure 12 can be achieved in any of a variety of ways, such as by introducing corresponding changes in the contours of the first and second prism electrodes of the corrector electrostatic prism 1212. To this end, this can be achieved, for example, by introducing shallow grooves of corresponding shape, as shown in Figure 7.

[0220] Although Fig. 12 shows an example in which the hexapole parameters are piecewise constant with respect to prism angle, this is not required in all examples. For example, the corrector electrostatic prism can alternatively be configured to smoothly vary the hexapole parameters, such as by smoothly varying the groove dimensions (e.g., the dimensions of the first electrode groove 822 and / or the second electrode groove 832 in Fig. 8) with the prism angle. In practice, such dimensions can be selected such that a0 and a1 in Fig. (37) are constant or nearly constant at the prism angle, so that the electrostatic potential and dipole field measured at the deflector optical axis are correspondingly constant at the prism angle.

[0221] 13 illustrates another example of an aberration correction system 1300 for at least partially correcting axial chromatic aberration of a charged particle beam 1302. The aberration correction system 1300 can be described as representing an example of the aberration correction system 120 of FIG. 1. Similarly, the charged particle beam 1302 can include and / or be the charged particle beam 104 of FIG. 1.

[0222] The aberration correction system 1300 of Figure 13 is similar to the aberration correction system 300 of Figure 3, the aberration correction system 1100 of Figure 11, and the aberration correction system 1200 of Figure 12. For example, as shown in Figure 13, the aberration correction system 1300 includes a deflector assembly 1310 that includes a corrector electrostatic prism 1312 and a plurality of electrostatic multipole elements 1314. Except as described below, all illustrated components of the aberration correction system 1300, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of the aberration correction system 300, the aberration correction system 1100, and / or the aberration correction system 1200. With respect to components labeled in Figure 13, components labeled with reference numbers in the format "13XX" are intended to correspond to components labeled with reference numbers in Figure 3 in the format "3XX", components labeled with reference numbers in Figure 11 in the format "11XX", and / or components labeled with reference numbers in Figure 12 in the format "12XX". For example, entrance electrostatic prism 1304 in Figure 13 may correspond to, and be at least substantially identical to, entrance electrostatic prism 304 in Figure 3, entrance electrostatic prism 1104 in Figure 11, and / or entrance electrostatic prism 1204 in Figure 12.

[0223] Similar to the previous example, the plurality of electrostatic multipole elements 1314 of the aberration correction system 1300 includes a first hexapole generating element 1320, a second hexapole generating element 1322, and a third hexapole generating element 1324. In the example of Fig. 13, the plurality of electrostatic multipole elements further includes a fourth hexapole generating element 1326 configured to generate a fourth hexapole field (e.g., as a primary or standalone multipole field). Notably, in this example, at least four hexapole generating elements may be required to fully correct the axial chromatic aberration without introducing secondary aberrations.

[0224] 13 , the second hexapole generating element 1322 and the third hexapole generating element 1324 are disposed within the corrector electrostatic prism 1312, while the first hexapole generating element 1320 and the fourth hexapole generating element 1326 are spaced apart outside the corrector electrostatic prism 1312. However, in other examples, the first hexapole generating element 1320 and the fourth hexapole generating element 1326 can be disposed within the corrector electrostatic prism 1312.

[0225] Similar to the examples described above and as shown in Fig. 13, the plurality of electrostatic multipole elements 1314 further includes a first quadrupole generating element 1330 and a second quadrupole generating element 1332. In the example of Fig. 13, each of the first quadrupole generating element 1330 and the second quadrupole generating element 1332 is configured to generate a respective auxiliary quadrupole field (e.g., as a primary or standalone multipole field). Notably, in this example, the first quadrupole generating element is integrated into and / or at least partially defined by the exit electrostatic prism 1306, similar to the first quadrupole generating element 1230 and / or the second quadrupole generating element 1232 of Fig. 12. Similarly, the second quadrupole generating element is integrated with and / or at least partially defined by the entrance electrostatic prism 1304, similar to the first quadrupole generating element 1230 and / or the second quadrupole generating element 1232 of Figure 12. In such an example, the first quadrupole generating element 1330 and / or the second quadrupole generating element 1332 can correspond to portions of the respective electrostatic prisms shaped to generate corresponding auxiliary quadrupole fields.

[0226] However, this is not required, and it is within the scope of the present disclosure that the first quadrupole generating element 1330 and / or the second quadrupole generating element 1332 can additionally include corresponding multiple poles for generating corresponding (non-auxiliary) quadrupole fields. In such an example, each of the first quadrupole generating element 1330 and / or the second quadrupole generating element 1332 can be disposed within or spaced apart from the exit electrostatic prism 1306 and the entrance electrostatic prism 1304, respectively.

[0227] FIG. 14 illustrates a diagram of fundamental rays x, labeled 1402, 1404, and 1406, respectively, of a charged particle beam 1400 traversing an aberration correction system, such as the aberration correction system 1300 of FIG. a (z), y a (z) and x κ 13. In other words, the charged particle beam 1400 of FIG. 14 can include and / or be at least a portion of the charged particle beam 1302 of FIG. 13. FIG. 14 shows a base ray along a straight optical axis 1418, which corresponds to the deflector optical axis 1308 and / or the z-axis of FIG. 13. As shown in FIG. 14, a charged particle source (e.g., the charged particle source 102 of FIG. 1) generating the charged particle beam 1400 is imaged onto a corrector entrance 1408, and a corrector exit focal point 1410 is imaged via appropriate optics to a specimen or specimen plane z. S 1. In the example of FIG. 14, such an optical system includes a transfer lens 1440 and an objective lens 1442, which may be similar to transfer lens 122 and / or objective lens 128, respectively, of FIG.

[0228] Figure 14 further illustrates the positions of the first quadrupole generating element 1452, the second quadrupole generating element 1472, the first hexapole generating element 1462, the second hexapole generating element 1464, the third hexapole generating element 1466, and the fourth hexapole generating element 1468 relative to the linear optical axis 1418 and relative to the base rays 1402, 1404, and 1406. The first quadrupole generating element 1452 and the second quadrupole generating element 1472 in Figure 14 correspond to the first quadrupole generating element 1330 and the second quadrupole generating element 1332 in Figure 13, respectively. First hexapole generating element 1462, second hexapole generating element 1464, third hexapole generating element 1466, and fourth hexapole generating element 1468 correspond to first hexapole generating element 1320, second hexapole generating element 1322, third hexapole generating element 1324, and fourth hexapole generating element 1326, respectively, of Figure 13. Figure 14 also shows the positions of entrance electrostatic prism 1450, exit electrostatic prism 1470, and corrector electrostatic prism 1460, which correspond to entrance electrostatic prism 1304, exit electrostatic prism 1306, and corrector electrostatic prism 1312, respectively, of Figure 13.

[0229] As shown in FIG. 14, the charged particle beam 1400 (and thus the charged particle beam 1302 of FIG. 13) exhibits a point-like focus at the mid-plane position 1340 / 1430 of the deflector optical axis 1308 / 1418 in the corrector electrostatic prism 1312. Thus, as shown in FIG. 13, an energy-selecting slit 1342 can be placed at the mid-plane position 1340 to monochromatize the charged particle beam 1302. As a result, the aberration correction system 1300 of FIG. 13 can be used as a Cc corrector and / or a monochromator. Other aberration correction systems disclosed herein that provide a line focus at the mid-plane position can also be used as monochromators. However, the point-like focus produced by the aberration correction system 1300 can make this system particularly favorable for such use.

[0230] 14, the charged particle beam 1400 (and thus the charged particle beam 1302 of FIG. 13) exhibits a line focus at positions on either side of the mid-plane position 1430. In some examples, each of the second hexapole generating element 1322 and the third hexapole generating element 1324 can be positioned at or near a position along the deflector optical axis 1308 that corresponds to such a line focus position.

[0231] In the above examples, the aberration correction system 300 / 1000 / 1100 / 1200 / 1300 is configured such that the corresponding deflector optical axis 308 / 1008 / 1108 / 1208 / 1308 across the deflector assembly 310 / 1110 / 1210 / 1310 is α-shaped. However, this is not required, and in addition, it is within the scope of this disclosure that the deflector optical axis may traverse the deflector assembly through a path that is Ω-shaped (i.e., shaped similarly to the Greek letter omega). This may be accomplished, for example, by using multiple (e.g., four) 90-degree electrostatic prisms to direct the deflector optical axis through a generally Ω-shaped path, although other configurations (e.g., electrostatic prism deflection angles) may also be used. In this disclosure, any example of an aberration correction system and / or its deflector assembly that is characterized by a deflector optical axis that is generally Ω-shaped may be referred to as an “omega-type” system or assembly.

[0232] 15 shows another example embodiment of an aberration correction system 1500 including four 90 degree electrostatic prisms 1522, 1524, 1526, and 1528 configured to direct a charged particle beam 1502 along a deflector optical axis 1508, where the deflector optical axis follows a generally Ω-shaped path. The aberration correction system 1500 can be described as representing one example of the aberration correction system 120 of FIG. 1. Similarly, the charged particle beam 1502 can include and / or be the charged particle beam 104 of FIG. 1.

[0233] As shown in FIG. 15, the aberration correction system 1500 includes a deflector assembly 1520 having a first electrostatic prism 1522, a second electrostatic prism 1524, a third electrostatic prism 1526, and a fourth electrostatic prism 1528.

[0234] The first electrostatic prism 1522, the second electrostatic prism 1524, the third electrostatic prism 1526, and the fourth electrostatic prism 1528 can be arranged and / or coupled to one another in any suitable configuration. For example, at least the second electrostatic prism 1524 and the third electrostatic prism 1526 can be fixedly coupled to one another and / or can represent respective components and / or portions of a single monolithic device. Additionally or alternatively, at least the first electrostatic prism 1522 and the fourth electrostatic prism 1528 can be fixedly coupled to one another and / or can represent respective components and / or portions of a single monolithic device.

[0235] 15, each of the first electrostatic prism 1522, the second electrostatic prism 1524, the third electrostatic prism 1526, and the fourth electrostatic prism 1528 is configured to deflect the charged particle beam 1510 at an angle equal to or approximately equal to 90 degrees. However, this is not required, and in addition, it is within the scope of the present disclosure that each electrostatic prism of the deflector assembly 1520 can deflect the charged particle beam 1510 at any suitable angle. In some examples, one or more of the first electrostatic prism 1522, the second electrostatic prism 1524, the third electrostatic prism 1526, and / or the fourth electrostatic prism 1528 are bifocal prisms.

[0236] Each electrostatic prism of the deflector assembly 1520 can also be characterized by a corresponding multipole strength and / or quadrupole parameter. In particular, with reference to equation (37), the first electrostatic prism 1522 and the fourth electrostatic prism 1528 each have a quadrupole strength a2=K 2 U, and each of the second electrostatic prism 1524 and the third electrostatic prism 1526 has a quadrupole strength

[0237]

number

[0238] As shown in Figure 15, the deflector assembly 1520 further includes a plurality of electrostatic multipole elements 1530. Specifically, in the example of Figure 15, the plurality of electrostatic multipole elements 1530 includes a first multipole element 1538 configured to generate a first hexapole field, a second multipole element 1540 configured to generate a second hexapole field, and a third multipole element 1542 configured to generate a third hexapole field.

[0239] In some examples, the deflector assembly 1520 can also include one or more multipole elements configured to generate a quadrupole field. For example, as shown in FIG. 15, the plurality of electrostatic multipole elements can further include a fourth multipole element 1536 configured to generate a fourth element quadrupole field, a fifth multipole element 1544 configured to generate a fifth element quadrupole field, a sixth multipole element 1532 configured to generate a sixth element quadrupole field, a seventh multipole element 1534 configured to generate a seventh element quadrupole field, an eighth multipole element 1546 configured to generate an eighth element quadrupole field, and a ninth multipole element 1548 configured to generate a ninth element quadrupole field.

[0240] Additionally, in this example, the first multipole element 1538 can also be configured to generate a first element quadrupole field, and the third multipole element 1542 can also be configured to generate a third element quadrupole field. In this manner, each of the first multipole element 1538 and the third multipole element 1542 can be described as representative of a hexapole-generating element and a quadrupole-generating element, respectively.

[0241] The first element hexapole field and the first element quadrupole field generated by the first multipole element 1538 can at least partially overlap (e.g., in space and / or along the deflector optical axis 1508). For example, the first element hexapole field and the first element quadrupole field can correspond to and / or be respective components of the electrostatic multipole field generated by the first multipole element 1538.

[0242] The first multipole element 1538 can have any suitable structure for generating the first hexapole field and the first elementary quadrupole field. For example, the first multipole element 1538 can include a hexapole generating element configured to generate each of the first hexapole field and the first elementary quadrupole field when appropriate voltages are applied to six electrodes of the hexapole generating element, and / or can be a hexapole generating element. Additionally or alternatively, the first multipole element 1538 can include a quadrupole generating element having four electrodes and a separate hexapole generating element having six electrodes, each configured to generate the first hexapole field and the first elementary quadrupole field, respectively.

[0243] Similarly, the third hexapole field and the third element quadrupole field generated by the third multipole element 1542 can at least partially overlap (e.g., in space and / or along the deflector optical axis 1508). For example, the third hexapole field and the third element quadrupole field can correspond to and / or be respective components of the electrostatic multipole field generated by the third multipole element 1542.

[0244] The third multipole element 1542 can have any suitable structure for generating the third hexapole field and the third element quadrupole field. For example, the third multipole element 1542 can include a hexapole generating element configured to generate each of the third hexapole field and the third element quadrupole field when appropriate voltages are applied to six electrodes of the hexapole generating element, and / or can be a hexapole generating element. Additionally or alternatively, the third multipole element 1542 can include a quadrupole generating element having four electrodes and a separate hexapole generating element having six electrodes, each configured to generate the third hexapole field and the third element quadrupole field, respectively.

[0245] As with the above examples, each electrostatic multipole element 1530 shown in dashed lines in Figure 15 represents an electrostatic multipole element configured to generate a corresponding auxiliary multipole field having one or more properties fixed by the multipole geometry, and each electrostatic multipole element shown in solid lines in Figure 15 represents an electrostatic multipole element configured to generate a corresponding multipole field that is independently adjustable (e.g., in orientation and / or magnitude). Thus, in the example of Figure 15, the sixth multipole element 1532, the seventh multipole element 1534, the eighth multipole element 1546, and the ninth multipole element 1548 are each configured to generate an auxiliary multipole field, and all other electrostatic multipole elements 1530 are configured to generate adjustable multipole fields.

[0246] In some examples, the first electrostatic prism 1522 can include and / or define at least a portion of each of the sixth and seventh multipole elements 1532 and 1534. For example, an entrance and / or an exit of the first electrostatic prism 1522 can be shaped and / or otherwise configured to generate a sixth element quadrupole field and / or a seventh element quadrupole field, respectively, upon application of a deflection voltage to the first electrostatic prism 1522. In other examples, the sixth and / or seventh multipole elements 1532 and / or 1534 can be fixedly coupled to the first electrostatic prism 1522.

[0247] Similarly, in some examples, the fourth electrostatic prism 1528 can include and / or define at least a portion of each of the eighth and ninth multipole elements 1546 and 1548. For example, an entrance and / or exit of the fourth electrostatic prism 1528 can be shaped and / or otherwise configured to generate an eighth element quadrupole field and / or a ninth element quadrupole field, respectively, upon application of a deflection voltage to the fourth electrostatic prism 1528. In other examples, the eighth and / or ninth multipole elements 1546 and / or ninth multipole elements 1548 can be fixedly coupled to the fourth electrostatic prism 1528.

[0248] 15, multiple electrostatic multipole elements 1530 are arranged in a mirror symmetric configuration about a mid-plane location 1504 of a deflector optical axis 1508 in a deflector assembly 1520. For example, as shown in FIG. 15, a second multipole element 1540 can be positioned proximate to the mid-plane location 1504, and a fourth multipole element 1536, a first multipole element 1538, a third multipole element 1542, and a fifth multipole element 1544 can be arranged in a mirror symmetric configuration about the second multipole element 1540.

[0249] 4 and 14, FIG. 16 illustrates the fundamental rays x, labeled 1612, 1614, and 1616, respectively, of a charged particle beam 1610 traversing an aberration correction system 1600. a (z), y a (z) and x κ 15. The aberration correction system 1600 of Figure 16 may represent an example of the aberration correction system 1500 of Figure 15. For example, the charged particle beam 1610 of Figure 16 may include and / or be at least a portion of the charged particle beam 1502 of Figure 15. In Figure 16, the deflector optical axis 1602 is shown straight for clarity, however, it should be understood that the deflector optical axis 1602 may be at least partially curved.

[0250] 16 further illustrates various structural components of the aberration correction system 1600 at representative positions along the deflector optical axis 1602. As shown in FIG. 16, the aberration correction system 1600 includes a deflector assembly 1620 having a first electrostatic prism 1622, a second electrostatic prism 1624, a third electrostatic prism 1626, and a fourth electrostatic prism 1628. The first electrostatic prism 1622, the second electrostatic prism 1624, the third electrostatic prism 1626, and the fourth electrostatic prism 1628 may represent and / or correspond to the first electrostatic prism 1522, the second electrostatic prism 1524, the third electrostatic prism 1526, and the fourth electrostatic prism 1528, respectively, of FIG. 16 may represent the first multipole element 1538, the second multipole element 1540, the third multipole element 1542, the fourth multipole element 1536, the fifth multipole element 1544, the sixth multipole element 1532, the seventh multipole element 1534, the eighth multipole element 1546, and the ninth multipole element 1548 of FIG. 15, respectively; and / or Shown are a plurality of multipole elements 1630 including a first multipole element 1638, a second multipole element 1640, a third multipole element 1642, a fourth multipole element 1636, a fifth multipole element 1644, a sixth multipole element 1632, a seventh multipole element 1634, an eighth multipole element 1646, and a ninth multipole element 1648, which may correspond thereto.

[0251] 16, the various multipole elements are shown as two overlapping solid rectangles to represent the multiple multipole fields that may be generated by such multipole elements. For example, the two overlapping solid rectangles associated with each of the first and third multipole elements 1638 and 1642 may be understood to represent the respective hexapole and quadrupole fields generated by each element.

[0252] As shown in FIG. 16, the deflector assembly 1620 operates to generate a line focus of the charged particle beam 1610 at the mid-plane position 1604, such that the second multipole element 1640 is positioned adjacent to a position along the deflector optical axis 1602 that corresponds to this line focus position.

[0253] As further shown in FIG. 16, the deflector assembly 1620 can further include one or more circular lens elements 1660 and an objective lens element 1662. Each circular lens element 1660 can include and / or be any suitable electrostatic circular lens. In some examples, the circular lens elements 1660 can correspond to and / or be the condenser optic 108 and / or the transfer lens 122 of FIG. 1. Similarly, the objective lens element 1662 shown in FIG. 16 can correspond to and / or be the objective lens 128 of FIG. 1.

[0254] 17 shows another example embodiment of an aberration correction system 1700 including four 90 degree electrostatic prisms that direct a charged particle beam 1710 along a deflector optical axis 1702, where the deflector optical axis follows a generally Ω-shaped path. In particular, similar to FIGS. 4, 14, and 16, FIG. 17 shows the fundamental ray x, labeled 1712, 1714, and 1716, respectively, of the charged particle beam 1710 traversing the aberration correction system 1700. a (z), y a (z) and x κ 17, the deflector optical axis 1702 is shown straight for clarity, however, it should be understood that the deflector optical axis 1702 may be at least partially curved.

[0255] The aberration correction system 1700 of Figure 17 may represent another example of the aberration correction system 1500 of Figure 15. For example, the charged particle beam 1710 of Figure 17 may include and / or be at least a portion of the charged particle beam 1502 of Figure 15.

[0256] The aberration correction system 1700 of FIG. 17 is similar to the aberration correction system 1600 of FIG. 16. For example, as shown in FIG. 17, the aberration correction system 1700 includes a deflector assembly 1720 including four 90 degree electrostatic prisms and a plurality of electrostatic multipole elements 1730. Unless otherwise noted, all illustrated components of the aberration correction system 1700, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with the corresponding components of the aberration correction system 1500 of FIG. 15 and / or the aberration correction system 1600 of FIG. 16. With respect to the components labeled in FIG. 17, the components labeled with reference numbers in the format "17XX" are intended to correspond to the components labeled with reference numbers in the format "15XX" in FIG. 15 and / or "16XX" in FIG. 16. For example, first electrostatic prism 1722 may correspond to and be at least substantially identical to first electrostatic prism 1522 of FIG. 15 and / or first electrostatic prism 1622 of FIG.

[0257] 16, the fourth multipole element 1636 of the deflector assembly 1720 is further configured to generate a fourth hexapole field (in addition to the fourth element quadrupole field), and the fifth multipole element 1744 is further configured to generate a fifth hexapole field (in addition to the fifth element quadrupole field). Thus, in this example, the fourth hexapole field and the fourth element quadrupole field at least partially overlap, and the fifth hexapole field and the fifth element quadrupole field at least partially overlap.

[0258] Similar to the first multipole element 1638 and the third multipole element 1742, the fourth multipole element 1636 and the fifth multipole element 1744 can each be configured to generate corresponding quadrupole and hexapole fields in any suitable manner, such as using a single multipole (e.g., hexapole) element or using a hexapole generating element in combination with a quadrupole generating element.

[0259] By including two additional hexapole fields (i.e., a fourth hexapole field and a fifth hexapole field) in the aberration correction system 1700 of FIG. 17 relative to the aberration correction system 1600 of FIG. 16, off-axis aberrations can be reduced and therefore the aberration correction system 1600 can be made less sensitive to beam drift.

[0260] 18 illustrates another example of a charged particle microscope system 1800 that can include and / or utilize the aberration correction system disclosed herein. In particular, as described in more detail below, the charged particle microscope system 1800 corrects the spherical aberration C of a charged particle beam. S The present invention may include a plurality of quadrupole and octupole electrostatic elements that collectively act to strongly reduce or nullify the source demagnification. Such a configuration can produce large source demagnification within a relatively short optical column, which may be particularly beneficial for chromatic and / or spherical aberration corrected FIB systems and / or plasma FIB systems, since the focused probe is less blurred by Coulomb interactions in the shorter column.

[0261] The charged particle microscope system 1800 of Figure 18 is similar to the charged particle microscope system 100 of Figure 1. For example, the charged particle microscope system 1800 includes a charged particle source 1802 that emits a charged particle beam 1804 along an emission axis 1806 toward a focusing column 1810 (also referred to herein as an optical column 1810). The charged particle beam 1804 travels through the focusing column 1810 along an optical axis 1818. The optical axis 1818 can include and / or be a curved optical axis, such as any of the deflector optical axes 308 / 518 / 618 / 708 / 808 / 908 / 1008 / 1108 / 1208 / 1308 / 1418 / 1602 / 1702 disclosed herein. As shown in FIG. 18, the charged particle microscope system 1800 can include condenser optics 1808 that accelerate / decelerate, focus, and / or direct the charged particle beam 1804 toward a focusing column 1810 .

[0262] Downstream of the focusing column 1810, the charged particle microscope system 1800 includes a sample holder 1860 for holding a sample 1862 and a detector 1868 configured to detect charged particles 1864 emitted from the sample 1862 as a result of the charged particle beam 1804 being incident on the sample 1862. The charged particle microscope system 1800 may further include one or more computing devices 1870 programmed and / or configured to control the operation of one or more aspects of the charged particle microscope system 1800.

[0263] Except as described below, all illustrated components of charged particle microscope system 1800, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of charged particle microscope system 100 of Figure 1. Additionally, charged particle microscope system 1800 may include any suitable components and / or exhibit any suitable functionality disclosed herein with reference to charged particle microscope system 100 of Figure 1.

[0264] In the example of Figure 18, the optical column 1810 can be configured to at least partially correct axial spherical aberration and / or axial chromatic aberration of the charged particle beam 1804. As shown in Figure 18, the optical column 1810 includes a multipole condenser 1820 and a multipole objective lens 1840 downstream of the multipole condenser 1820. The multipole condenser 1820 includes one or more condenser quadrupole generating elements 1822, and the multipole objective lens 1840 includes multiple objective lens multipole elements 1842. In some examples, one or more beam-limiting apertures can be disposed upstream of the multipole condenser 1820.

[0265] The objective lens multipole elements 1842 may have any of a variety of configurations, examples of which are described in more detail below. Generally, the objective lens multipole elements 1842 include at least three quadrupole generating elements and at least three octupole generating elements configured to at least partially correct spherical aberration of the charged particle beam 1804. In some examples, as described in more detail below, one or more of the objective lens multipole elements 1842 may be operable to generate quadrupole and octupole fields and may therefore be described as representing both a quadrupole generating element and an octupole generating element.

[0266] 18, the optical column further includes a chromatic aberration corrector 1830 disposed between the multipole condenser 1820 and the multipole objective lens 1840. In such examples, the chromatic aberration corrector 1830 can include and / or be any suitable device for at least partially correcting on-axis chromatic aberration of the charged particle beam 1804. Examples of the chromatic aberration corrector 1830 include any of the aberration correction systems 300, 1100, 1200, 1300, 1600, and / or 1700, and / or any suitable portions and / or components thereof. In other examples, the chromatic aberration of the charged particle beam 1804 can be at least partially corrected by an emitter corrector.

[0267] 1, the charged particle microscope system 1800 may include or be one or more different types of EM and / or charged particle microscopes. Examples of one or more different types of EM and / or charged particle microscopes include scanning electron microscopes (SEM), scanning transmission electron microscopes (STEM), transmission electron microscopes (TEM), charged particle microscopes (CPM), dual beam microscope systems, etc. Thus, the charged particle source 1802 may be configured to emit the charged particle beam 1804 at any suitable accelerating voltage, such as an accelerating voltage corresponding to the type of microscopy being performed. By way of example, the charged particle source 1802 can be configured to emit a charged particle beam 1804 having an acceleration voltage that is at least 200 volts (V), at least 1,000V, at least 5,000V, at least 10,000V, at least 20,000V, at least 50,000V, up to 100,000V, up to 30,000V, up to 15,000V, up to 7,000V, up to 2,000V, and / or up to 500V.

[0268] FIG. 19 illustrates another example embodiment of a charged particle microscope system 1900, which may be described as representative of the example charged particle microscope system 1800 of FIG. 18. The charged particle microscope system 1900 of FIG. 19 includes a charged particle source 1902 that emits a charged particle beam 1904 and an optical column 1910 that directs the charged particle beam 1904 toward a sample 1960. The charged particle beam 1904 travels along an optical axis 1918 through the optical column 1910. FIG. 19 illustrates the fundamental rays x(z), y(z), and x(z), labeled 1912, 1914, and 1916, respectively, of the charged particle beam 1904 as it traverses the optical column 1910. κ Further examples of (z) are given below.

[0269] Unless otherwise specified, all illustrated components of charged particle microscope system 1900, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of charged particle microscope system 1800 of Figure 18. For components labeled in Figure 19, components labeled with reference numbers in the format "19XX" are intended to correspond to components labeled with reference numbers in Figure 18 in the format "18XX." For example, condenser optic 1908 of Figure 19 may correspond to and be at least substantially identical to condenser optic 1808 of Figure 18.

[0270] As shown in Figure 19, the charged particle microscope system 1900 includes a chromatic aberration corrector 1930, which can be described as one example of the chromatic aberration corrector 1830 of Figure 18. As shown in Figure 19, the chromatic aberration corrector 1930 includes an entrance electrostatic prism 1932, a corrector electrostatic prism 1934, an exit electrostatic prism 1936, a number of electrostatic quadrupole generating elements labeled Q1, ..., Q4, and a number of electrostatic hexapole generating elements labeled H1, ..., H3.

[0271] Chromatic aberration corrector 1930 may be similar to aberration correction system 300 of Figure 3 and / or aberration correction system 1100 of Figure 11. For example, entrance electrostatic prism 1932 and exit electrostatic prism 1936 may share any suitable features, characteristics, attributes, etc. with entrance electrostatic prism 304 / 1104 and / or entrance electrostatic prism 306 / 1106, respectively. Similarly, corrector electrostatic prism 1934 may share any suitable features, characteristics, attributes, etc. with corrector electrostatic prism 312 / 1112.

[0272] 19, the charged particle microscope system 1900 includes a multipole capacitor 1920 including a quadrupole doublet 1922. Specifically, the quadrupole doublet 1922 includes a first capacitor quadrupole generating element 1924 and a second capacitor quadrupole generating element 1926 disposed downstream of the first capacitor quadrupole generating element 1924. The first capacitor quadrupole generating element 1924 is configured to generate a first capacitor quadrupole field, and the second capacitor quadrupole generating element 1926 is configured to generate a second capacitor quadrupole field. In other examples, the multipole capacitor 1920 can include a single quadrupole generating element.

[0273] 19, the charged particle microscope system 1900 includes a multipole objective 1940 having a plurality of objective multipole elements 1942. Specifically, in the example of FIG. 19, the plurality of objective multipole elements 1942 includes a first objective multipole element 1944, a second objective multipole element 1946 located downstream of the first objective multipole element 1944, and a third objective multipole element 1948 located downstream of the second objective multipole element 1946. The first objective multipole element 1944, the second objective multipole element 1946, and the third objective multipole element 1948 are configured to generate a first objective multipole field, a second objective multipole field, and a third objective multipole field, respectively.

[0274] Each electrostatic multipole element of the charged particle microscope system 1800 and / or the charged particle microscope system 1900 can have any suitable configuration for generating a corresponding multipole field. As an example, FIG. 20 shows an example of a multipole element 2000 including a first electrode 2010, a second electrode 2020, a third electrode 2030, and a fourth electrode 2040, each configured to receive a corresponding voltage to generate a respective component of the corresponding multipole field. Thus, the multipole element 2000 may be referred to as a quadrupole generating element 2000 and / or may be configured to generate a quadrupole field. In other words, the multipole element 2000 may be configured such that the multipole field generated by the multipole element 2000 includes a quadrupole field as a primary constituent multipole field.

[0275] However, in some examples, the multipole element 2000 can also be configured such that the multipole field generated by the multipole element 2000 further includes additional multipole field components, such as an octopole field component. In particular, each of the first electrode 2010, the second electrode 2020, the third electrode 2030, and the fourth electrode 2040 can be configured (e.g., shaped) such that the total multipole field generated by the multipole element 2000 includes a quadrupole field component and an octopole field component. In some examples, the relative magnitudes and / or respective configurations of the quadrupole and octopole fields generated by the multipole element 2000 can be controlled via application of appropriate respective voltages to the electrodes of the multipole element 2000 and / or via appropriate shaping of the electrodes of the multipole element 2000.

[0276] As shown in Figure 20, the multipole element 2000 may be characterized by a multipole element inner diameter 2002, which represents the minimum separation distance between opposing electrodes, measured along a direction perpendicular to the z-axis of Figure 20. The multipole element inner diameter 2002 may additionally or alternatively be described as representing the maximum diameter of a charged particle beam passing through the multipole element 2000. The multipole element inner diameter 2002 may take any of a variety of values, such as values ​​within a range of approximately 1 to 5 millimeters (mm).

[0277] 21 illustrates another example of a multipole element 2100, which may represent any suitable multipole element of the charged particle microscope system 1800 and / or the charged particle microscope system 1900. In the example of FIG. 21, the multipole element 2100 includes a first electrode pair 2110, a second electrode pair 2120, a third electrode pair 2130, and a fourth electrode pair 2140. The first electrode pair 2110 includes a first electrode 2112 and a second electrode 2114. The second electrode pair 2120 includes a third electrode 2122 and a fourth electrode 2124. The third electrode pair 2130 includes a fifth electrode 2132 and a sixth electrode 2134, and the fourth electrode pair 2140 includes a seventh electrode 2142 and an eighth electrode 2144.

[0278] In some examples, the multipole element 2100 of Figure 21 may be configured to generate a quadrupole field as a primary multipole field. For example, the multipole element 2100 may be configured such that the first electrode pair 2110, the second electrode pair 2120, the third electrode pair 2130, and the fourth electrode pair 2140 can each receive a respective voltage to generate a corresponding quadrupole field. Thus, in such examples, the multipole element 2100 may be described as representing a quadrupole generating element.

[0279] Additionally or alternatively, the multipole element 2100 can be configured such that each of the first electrode 2112, the second electrode 2114, the third electrode 2122, the fourth electrode 2124, the fifth electrode 2132, the sixth electrode 2134, the seventh electrode 2142, and the eighth electrode 2144 can receive a respective voltage to generate a corresponding multipole field. In such an example, the multipole element 2100 can be configured to operate as a quadrupole generating element for aberration correction as described herein and to generate a small deflection field superimposed on the quadrupole field to scan the charged particle beam relative to the sample. In particular, configuring the multipole element 2100 such that a different deflection voltage can be applied to each electrode of each electrode pair facilitates generating such deflection fields while minimizing the generation of undesirable multipole fields (e.g., hexapole fields) that may introduce additional aberrations.

[0280] In some examples, the multipole element 2100 may additionally or alternatively be configured to generate an octopole field (e.g., as the primary or only multipole field). In some examples, the relative magnitudes and / or respective configurations of the octopole and quadrupole fields generated by the multipole element 2100 may be controlled via application of appropriate respective voltages to the electrodes of the multipole element 2100 and / or via appropriate shaping of the electrodes of the multipole element 2100.

[0281] As shown in Figure 21, the multipole element 2000 may be characterized by a multipole element inner diameter 2102, which represents the minimum separation distance between opposing electrodes, measured along a direction perpendicular to the z-axis of Figure 21. The multipole element inner diameter 2102 may additionally or alternatively be described as representing the maximum diameter of a charged particle beam passing through the multipole element 2100. The multipole element inner diameter 2102 may take any of a variety of values, such as values ​​within the range of approximately 1-5 mm.

[0282] 22-25 show additional example embodiments of charged particle microscope systems, respectively labeled 2200, 2300, 2400, and 2500. Each of charged particle microscope system 2200, charged particle microscope system 2300, charged particle microscope system 2400, and charged particle microscope system 2500 can be described as representing an example of charged particle microscope system 1800 of FIG.

[0283] Charged particle microscope system 2200 of FIG. 22 and charged particle microscope system 2300 of FIG. 23 can be described as representing similar or the same charged particle microscope system under different operating conditions (i.e., under different magnifications of the charged particle beam).

[0284] Thus, unless otherwise specified, all illustrated components of the charged particle microscope system 2300 of Figure 23, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of the charged particle microscope system 2200 of Figure 22. With respect to components labeled in Figure 23, components labeled with reference numbers in the format "23XX" are intended to correspond to components labeled in Figure 22 with reference numbers in the format "22XX."

[0285] Additionally, unless otherwise specified, all illustrated components of charged particle microscope system 2200 or 2300, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of charged particle microscope system 1800 of FIGURE 18. With respect to components labeled in FIGURES 22-23, components labeled with reference numbers in the format "22XX" or "23XX" are intended to correspond to components labeled in FIGURE 18 with reference numbers in the format "18XX."

[0286] 22-25, it should be understood that any of the charged particle microscope systems 2200 / 2300 / 2400 / 2500 can include and / or be used in conjunction with any of the chromatic aberration correction systems and / or any suitable components thereof disclosed herein. For example, any of the aberration correction systems 300 / 1100 / 1200 / 1300 / 1500 / 1600 / 1700 / 1800 and / or any suitable portions thereof can be positioned along the optical axis 2218 / 2318 / 2418 / 2518, similar to the chromatic aberration corrector 1830 of FIG.

[0287] Similarly, charged particle microscope system 2400 of FIG. 24 and charged particle microscope system 2500 of FIG. 25 can be described as representing similar or the same charged particle microscope system under different operating conditions (i.e., under different magnifications of the charged particle beam).

[0288] Thus, unless otherwise specified, all illustrated components of the charged particle microscope system 2500 of Figure 25, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of the charged particle microscope system 2400 of Figure 24. With respect to components labeled in Figure 25, components labeled with reference numbers in the format "25XX" are intended to correspond to components labeled in Figure 24 with reference numbers in the format "24XX."

[0289] Additionally, unless otherwise specified, all illustrated components of charged particle microscope system 2400 or 2500, whether numbered or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of charged particle microscope system 1800 of FIGURE 18. With respect to components labeled in FIGURES 24-25, components labeled with reference numbers in the format "24XX" or "25XX" are intended to correspond to components labeled in FIGURE 18 with reference numbers in the format "18XX."

[0290] 22, the charged particle microscope system 2200 includes a charged particle source 2202 that emits a charged particle beam 2204 and an optical column 2210 that directs the charged particle beam 2204 to a sample 2260. The charged particle beam 2204 travels along an optical axis 2218 through the optical column 2210. FIG. 22 further illustrates example fundamental rays x(z) and y(z) of the charged particle beam 2204, labeled 2212 and 2214, respectively, as the charged particle beam 2204 traverses the optical column 2210. In the example of FIG. 22, the charged particle microscope system 2200 further includes a plurality of beam deflectors 2252 disposed along the optical axis 2218. Such beam deflectors 2252 can be used to deflect the charged particle beam 2204 to scan the charged particle beam 2204 across the sample 2260.

[0291] As shown in Figure 22, similar to the charged particle microscope system 1900 of Figure 19, the charged particle microscope system 2200 includes a multipole capacitor 2220 having a quadrupole doublet 2222 including a first capacitor quadrupole generating element 2224 and a second capacitor quadrupole generating element 2226. In the example of Figure 22, each of the first capacitor quadrupole generating element 2224 and the second capacitor quadrupole generating element 2226 is configured to generate a respective quadrupole field. In other examples, the multipole capacitor 2220 can include a single quadrupole generating element, such as the first capacitor quadrupole generating element 2224.

[0292] 19, the charged particle microscope system 2200 further includes a multipole objective 2240 having a plurality of objective multipole elements 2242. The plurality of objective multipole elements 2242 includes a first objective multipole element 2244, a second objective multipole element 2246 located downstream of the first objective multipole element 2244, and a third objective multipole element 2248 located downstream of the second objective multipole element 2246.

[0293] The first objective multipole element 2244, the second objective multipole element 2246, and the third objective multipole element 2248 are configured to generate a first objective multipole field, a second objective multipole field, and a third objective multipole field, respectively. In particular, in the example of FIG. 22, the first objective multipole field includes a first objective quadrupole field component and a first objective field octopole field component. The second objective multipole field includes a second objective quadrupole field component and a second objective octopole field component. The third objective multipole field includes a third objective quadrupole field component and a third objective octopole field component. In this way, the plurality of objective multipole elements 2242 can be described as including exactly three quadrupole generating elements. Stated another way, in this example, exactly three objective multipole elements 2242 are configured to generate quadrupole field components.

[0294] Each of the objective lens multipole elements 2242 can have any suitable form and / or configuration for generating a corresponding objective lens multipole field. In some examples, the first objective lens multipole element 2244 and the second objective lens multipole element 2246 each include four electrodes shaped to generate an octupole field in addition to a quadrupole field. As an example, one or both of the first objective lens multipole element 2244 and the second objective lens multipole element 2246 can be similar to and / or can be the multipole element 2000 of FIG. 20.

[0295] Additionally or alternatively, in some examples, the third objective lens multipole element 2248 can include eight electrodes for generating both quadrupole and octopole fields. As an example, the third objective lens multipole element 2248 can be similar to and / or the multipole element 2100 of FIG. 21. Such a configuration can be particularly beneficial in examples where the third objective lens multipole element 2248 is used as a deflector for AC scanning of the charged particle beam 2204, possibly in combination with the beam deflector 2252. In such examples, a large and undesirable auxiliary hexapole field can accompany the deflection field. Configuring the third objective lens multipole element 2248 to include eight separate electrodes, such as the multipole element 2100 of Fig. 21, may allow for the application of eight respective deflection voltages to these electrodes, configured in a mutual ratio such that these undesired hexapole fields are cancelled due to deflection in the x- and / or y-directions. Alternatively, the third objective lens multipole element 2248 may include four electrodes, such as the multipole element 2000 of Fig. 20, and an additional multipole element may be introduced downstream of the third objective lens multipole element 2248 configured to perform AC scanning. In such an example, this additional multipole element may include eight nominally identical electrodes for generating a corrective octopole field.

[0296] However, such a configuration is not required in all examples. For example, it is within the scope of the present disclosure that one or both of the first objective lens multipole element 2244 and the second objective lens multipole element 2246 can have eight electrodes, similar to the multipole element 2100 of Figure 21. Additionally or alternatively, the third objective lens multipole element 2248 can have four electrodes shaped to generate an octupole field, similar to the multipole element 2000 of Figure 20.

[0297] As mentioned above, the charged particle microscope system 2200 of FIG. 22 and the charged particle microscope system 2300 of FIG. 23 are at least substantially identical, except for the magnifications produced in the respective charted particle beams. Specifically, FIG. 22 shows an example of a magnification of 0.02, and FIG. 23 shows an example of a magnification of 0.2. In either case, compared to the fundamental rays x(z) 2212 / 2312 and y(z) 2214 / 2314, it can be seen that the charged particle beam 2204 / 2304 lacks a midpoint intersection (where x(z)=y(z)=0) between the multipole condenser 2220 / 2320 and the multipole objective lens 2240 / 2340. As a result, such a configuration can substantially reduce undesirable Coulomb interactions between charged particles that may occur at such a point intersection.

[0298] 22-23, it can be seen that |y(z)|<=|x(z)| for the portion of the charged particle beam 2204 / 2304 that extends through the multipole objective 2240 / 2340 (e.g., for the entire beam length within the multipole objective). Furthermore, in each example, the charged particle beam 2204 / 2304 enters the multipole objective 2240 / 2340 with a non-circular beam profile (e.g., an elongated and / or elliptical beam profile) and maintains the non-circular beam profile through at least a portion of the multipole objective 2240 / 2340.

[0299] 22, the multipole condenser 2220 and the multipole objective lens 2240 are configured to null the axial spherical aberration of the charged particle beam 2204 at the sample 2260. In this example, the transverse component of the axial chromatic aberration of the charged particle beam 2204 is C cx = 41mm and C cy 23, the multipole condenser 2320 and the multipole objective lens 2340 are configured to null the axial spherical aberration of the charged particle beam 2304 at the sample 2360. In this example, the transverse component of the axial chromatic aberration of the charged particle beam 2304 is C cx = 41mm and C cy = 9 mm. Thus, in the example of Figures 22-23, axial chromatic aberration is nearly nullified in the yz plane at multiple magnifications of the charged particle beam 2204 / 2304.

[0300] The charged particle microscope system 2400 of Fig. 24 is substantially similar to the charged particle microscope system 2200 / 2300 of Fig. 22-23. However, unlike the examples of Fig. 22-23, the charged particle microscope system 2400 includes a multipole objective lens 2440 including four objective lens multipole elements 23442. Specifically, in the example of Fig. 24, the multipole objective lens 2440 includes a first objective lens multipole element 2444, a second objective lens multipole element 2446 located downstream of the first objective lens multipole element 2444, a third objective lens multipole element 2448 located downstream of the second objective lens multipole element 2446, and a fourth objective lens multipole element 2450 located downstream of the third objective lens multipole element 2448.

[0301] The first objective lens multipole element 2444, the second objective lens multipole element 2446, the third objective lens multipole element 2448, and the fourth objective lens multipole element 2450 are configured to generate a first objective lens multipole field, a second objective lens multipole field, a third objective lens multipole field, and a fourth objective lens multipole field, respectively. In particular, in the example of FIG. 24, the first objective lens multipole field includes a first objective lens quadrupole field component and a first objective lens field octopole field component. The second objective lens multipole field includes a second objective lens octopole field component. The third objective lens multipole field includes a third objective lens quadrupole field component and a third objective lens octopole field component. The fourth objective lens multipole field includes a fourth objective lens quadrupole field component. In this manner, the plurality of objective lens multipole elements 23442 can be described as including exactly three quadrupole generating elements. Stated differently, in this example, exactly three objective lens multipole elements 23442 are configured to generate quadrupole field components.

[0302] Each of the objective lens multipole elements 2442 can have any suitable form and / or configuration for generating a corresponding objective lens multipole field. In some examples, the first objective lens multipole element 2444 and the third objective lens multipole element 2448 each include four electrodes shaped to generate an octupole field in addition to a quadrupole field. As an example, one or both of the first objective lens multipole element 2444 and the third objective lens multipole element 2448 can be similar to and / or can be the multipole element 2000 of FIG. 20.

[0303] Additionally or alternatively, in some examples, the second objective lens multipole element 2446 can include eight electrodes for generating an octupole field. As an example, the second objective lens multipole element 2446 can be similar to and / or can be the multipole element 2800 of FIG. 28, which is described in more detail below.

[0304] Additionally or alternatively, in some examples, the fourth objective lens multipole element 2450 can include eight electrodes for generating both quadrupole and octopole fields. As an example, the fourth objective lens multipole element 2450 can be similar to and / or the multipole element 2100 of FIG.

[0305] However, such a configuration is not required in all examples. For example, it is within the scope of the present disclosure that one or more of the first objective lens multipole element 2444, the second objective lens multipole element 2446, and / or the third objective lens multipole element 2448 can have eight electrodes, similar to the multipole element 2100 of Figure 21. Additionally or alternatively, the fourth objective lens multipole element 2450 can have four electrodes shaped to generate an octupole field, similar to the multipole element 2000 of Figure 20.

[0306] As mentioned above, the charged particle microscope system 2400 of FIG. 24 and the charged particle microscope system 2500 of FIG. 25 are at least substantially identical, except for the magnifications produced in the respective charted particle beams. Specifically, FIG. 24 shows an example of a magnification of 0.02, and FIG. 25 shows an example of a magnification of 0.1. In either case, compared to the fundamental rays x(z) 2412 / 2512 and y(z) 2414 / 2514, it can be seen that the charged particle beam 2404 / 2504 lacks a midpoint intersection (where x(z)=y(z)=0) between the multipole condenser 2420 / 2520 and the multipole objective lens 2440 / 2540. As a result, such a configuration can substantially reduce undesirable Coulomb interactions between charged particles that may occur at such a point intersection.

[0307] 24-25, it can be seen that |y(z)|<=|x(z)| for the portion of the charged particle beam 2404 / 2504 that extends through the multipole objective lens 2440 / 2540 (e.g., for the entire beam length within the multipole objective lens). Furthermore, in each example, the charged particle beam 2404 / 2504 enters the multipole objective lens 2440 / 2540 with a non-circular beam profile (e.g., an elongated and / or elliptical beam profile) and maintains the non-circular beam profile through at least a portion of the multipole objective lens 2440 / 2540.

[0308] 24, the multipole condenser 2420 and the multipole objective lens 2440 are configured to null the axial spherical aberration of the charged particle beam 2404 at the sample 2460. In this example, the transverse component of the axial chromatic aberration of the charged particle beam 2404 is C cx = 46mm and C cy 25, the multipole condenser 2520 and the multipole objective lens 2540 are configured to null the axial spherical aberration of the charged particle beam 2504 at the sample 2560. In this example, the transverse component of the axial chromatic aberration of the charged particle beam 2504 is C cx = 51mm and C cy 24-25, the axial chromatic aberration is therefore significantly smaller in the yz plane than in the xz plane at multiple magnifications of the charged particle beam 2404 / 2504.

[0309] The disclosed apparatus and systems may also be particularly suitable for use in instances where a charged particle microscope system directs multiple charged particle beams to a sample and / or target focal position. As an example, FIG. 26 shows a configuration in which a first charged particle beam 2604 (e.g., an SEM beam) and a second charged particle beam 2614 (e.g., an FIB beam) are each focused to a common position on a sample 2630. In this example, the first charged particle beam 2604 moves along a first axis 23602 and the second charged particle beam 2614 moves along a second axis 2612.

[0310] 26, the first charged particle beam 2604 may be characterized by and / or associated with a first exclusion region 2606, which is characterized by a first exclusion region angular range 2608. For example, the first exclusion region 2606 may represent a beam profile of the first charged particle beam 2604 approaching the sample 2630, or may represent a region associated with (e.g., occupied by) a lens component that directs the first charged particle beam 2604 to the sample 2630. In the example of FIG. 26, the first exclusion region 2606 is a cone region that terminates at the sample 2630.

[0311] The first exclusion region 2606 may represent a region that cannot be occupied by the second charged particle beam 2614 or associated lens components. For example, as shown in Figure 26, the second charged particle beam 2614 may be directed to the sample 2630 by and / or through a multipole objective 2620 including a first objective multipole element 2622, a second objective multipole element 2624, and a third objective multipole element 2626, each of which must be positioned outside the first exclusion region 2606. The multipole objective 2620 may represent the multipole objective 2240 / 2340 of Figures 22-23, or any other similarly configured multipole objective.

[0312] 26, the first axis 2602 is perpendicular to the surface of the sample 2630, such that the first charged particle beam 2604 and the sample 2630 collectively confine the second charged particle beam 2614 and associated components to occupy a free space 2616 defined therebetween. This free space can be characterized, for example, by a free space angle 2618 measured in the xz plane of FIG.

[0313] In some examples, the free space angle 2618 can represent a limit on how close the multipole elements of the multipole objective lens 2620 can be positioned relative to the sample 2630. In general, it can be desirable to position the multipole elements of the multipole objective lens 2620 as close as possible to the sample 2630 to minimize chromatic and higher order geometric aberrations, both intrinsic (i.e., excluding mechanical errors) and parasitic (i.e., aberrations resulting from mechanical errors). Thus, as described in more detail below, the multipole objective lens 2620 can be configured such that the multipole objective lens 2620 can be desirably positioned close to the sample 2630 while keeping the components (e.g., multipole elements) of the multipole objective lens 2620 exclusively within the free space 172616 outside the first exclusion region 2606.

[0314] Figure 27 illustrates an objective lens multipole element 2700 similar to the multipole element 2100 of Figure 21. Specifically, the objective lens multipole element 2700 includes a first electrode pair 2710, a second electrode pair 2720, a third electrode pair 2730, and a fourth electrode pair 2740. The first electrode pair 2710 includes a first electrode active surface 2712 and a first electrode extension 2716 extending away from the first electrode active surface 2712, and a second electrode active surface 2714 and a second electrode extension 2718 extending away from the second electrode active surface 2714. The second electrode pair 2720 includes a third electrode active surface 2722 and a third electrode extension 2726 extending away from the third electrode active surface 2722, a fourth electrode active surface 2724 and a fourth electrode extension 2728 extending away from the fourth electrode active surface 2724. The third electrode pair 2730 includes a fifth electrode active surface 2732 and a fifth electrode extension 2736 extending away from the fifth electrode active surface 2732, and a sixth electrode active surface 2734 and a sixth electrode extension 2738 extending away from the sixth electrode active surface 2734. The fourth electrode pair 2740 includes a seventh electrode active surface 2742 and a seventh electrode extension 2746 extending away from the seventh electrode active surface 2742, and an eighth electrode active surface 2744 and an eighth electrode extension 2748 extending away from the eighth electrode active surface 2744.

[0315] In the example of Figure 27, each of the first electrode active surface 2712, the second electrode active surface 2714, the third electrode active surface 2722, the fourth electrode active surface 2724, the fifth electrode active surface 2732, the sixth electrode active surface 2734, the seventh electrode active surface 2742, and the eighth electrode active surface 2744 faces a central bore 2701 of the multipole element 2700. The central bore 2701 can be characterized by a multipole element inner diameter 2702 that represents the minimum separation distance between opposing electrodes, measured along a direction perpendicular to the z-axis of Figure 27. In this manner, the objective lens multipole element 2700 can be described as representing an example of the multipole element 2100 of Figure 21, the third objective lens multipole element 2626 of Figure 26, and / or any other objective lens multipole element disclosed herein. Additionally or alternatively, the multipole element 2100 of FIG. 21 may be described as representing and / or describing a portion of the objective lens multipole element 2700 of FIG.

[0316] 27, each electrode of objective lens multipole element 2700 is formed as a MEMS device. In particular, in this example, first electrode extension 2716, second electrode extension 2718, third electrode extension 2726, and eighth electrode extension 2748 are each supported by first electrode support 2750, and fourth electrode extension 2728, fifth electrode extension 2736, sixth electrode extension 2738, and seventh electrode extension 2746 are each supported by second electrode support 2760.

[0317] Configuring the electrodes of the objective lens multipole element 2700 to be formed as a MEMS device can facilitate forming the objective lens multipole element 2700 such that the multipole element inner diameter 2702 is significantly smaller than conventional electrode designs, thereby further facilitating positioning the objective lens multipole element 2700 in close proximity to a sample. Such a configuration can also facilitate production of the objective lens multipole element 2700 with reduced mechanical errors and / or tighter dimensional tolerances relative to non-MEMS systems. It should be understood that any multipole element disclosed herein, including any multipole element including more or less than eight electrodes, can also be formed as a MEMS device in the manner of the objective lens multipole element 2700.

[0318] An objective lens multipole element 2700 may also be characterized with reference to one or more linear dimensions thereof (e.g., as measured in the xy plane shown in FIG. 27). For example, as shown in FIG. 27, an objective lens multipole element 2700 has a first dimension 2706 measured along the x direction that is smaller than a second dimension 2704 measured along the y direction. As described in more detail below, such a configuration can facilitate positioning such an objective lens multipole element 2700 within a spatially constrained region in the dimension corresponding to the x direction of FIG. 27.

[0319] FIG. 28 illustrates another example of a multipole element 2800 that can be used in a spatially constrained dual beam system, such as the system of FIG. 26. The multipole element 2800 includes a plurality of electrodes 2840 defining a central bore 2830 therebetween. The central bore 2830 extends at least partially along a beam axis 2802, such as the second axis 2612 of FIG. 26 and / or another axis along which a charged particle beam (e.g., the charged particle beam 2614 of FIG. 26) may travel. Specifically, FIG. 28 illustrates a view of the multipole element 2800 in which the beam axis 2802 extends into the page. It should be understood that each electrode 2840 can have a thickness along a direction parallel to the beam axis 2802, such that the central bore 2830 defined by the electrodes 2840 can be described as extending along the beam axis 2802.

[0320] Similar to the electrostatic hexapole generating element 200 of FIG. 2, the multipole element 2800 can be configured to generate an electrostatic multipole field by applying respective voltages to the electrodes 2840. In the example of FIG. 28, the multipole element 2800 includes eight electrodes 2840 and can thus be configured to generate an octopole electrostatic field. Thus, in such an example, the multipole element 2800 can be described as representing an octopole generating element. Additionally or alternatively, the multipole element 2800 can be configured to generate any of a variety of other multipole fields, such as a quadrupole electrostatic field, a hexapole electrostatic field, etc., through application of appropriate voltages to its eight electrodes 2840. Thus, the multipole element 2800 can additionally or alternatively be referred to as an electrostatic multipole element 2800.

[0321] 28 , each electrode 2840 includes a respective electrode active surface 2842 facing and / or partially defining the central bore 2830 and a respective electrode extension 2844 extending away from the electrode active surface 2842. Each electrode extension 2844 can include and / or define a respective electrical contact location 2846 configured to be electrically coupled to another component (e.g., an electrical lead) to supply a voltage to the electrode. In this manner, each electrode active surface 2842 can generate a respective electrostatic field component based on a voltage supplied to a corresponding electrical contact location 2846 spaced from the electrode active surface 2842.

[0322] 28, each electrode extension 2844 (or at least a portion thereof) extends at least partially along a lateral direction, away from a corresponding electrode active surface 2842. Specifically, the plurality of electrodes 2840 includes a first side subset 2852 of electrodes generally disposed on the left side of FIG. 28 and a second side subset 2856 of electrodes generally disposed on the right side of FIG.

[0323] 28 , for each electrode 2840 in the first side subset 2852 of electrodes, the electrode extension 2844 extends away from the electrode active surface 2842 along a first lateral direction 2816 that is perpendicular to the beam axis 2802. Similarly, for each electrode 2840 in the second side subset 2856 of electrodes 2856, the electrode extension 2844 extends away from the electrode active surface 2842 along a second lateral direction 2818 that is perpendicular to the beam axis 2802 and opposite the first lateral direction 2816.

[0324] 28 , the electrode extensions 2844 of the electrodes 2840 of a first side subset 2852 of electrodes can be described as extending to and terminating at a first side region 2850 of the composite element 2800. Similarly, the electrode extensions 2844 of the electrodes 2840 of a second side subset 2856 of electrodes can be described as extending to and terminating at a second side region 2854 of the multipole element 2800. The first side region 2850 and the second side region 2854 can correspond to spaced apart regions of the multipole element 2800 disposed on either side of the central bore 2830.

[0325] In some examples, the first lateral direction 2816 and the second lateral direction 2818 are coplanar and / or anti-parallel to each other. Notably, in such examples, the electrodes 2840 and / or their electrode extensions 2844 can extend away from the central bore 2830 in a common plane that is at least substantially perpendicular to the beam axis 2802. However, this is not required in all examples, and it is within the scope of the present disclosure for at least a portion of the multipole element 2800 to be non-planar. For example, in some examples, as described in more detail below with reference to FIG. 31, each electrode extension 2844 can extend away from the electrode active surface 2842 along a direction that is angled with respect to each of a radial direction perpendicular to the beam axis 2802 and an axial direction parallel to the beam axis 2802.

[0326] 28, the multipole element 2800 has different linear dimensions along a direction perpendicular to the beam axis 2802. In particular, in this example, the electrodes 2840 extend away from the central bore 2830 such that the multipole element 2800 has a first dimension 2806 measured along a first direction 2804 perpendicular to the beam axis 2802 that is smaller than a second dimension 2810 of the multipole element 2800 measured along a second direction 2808 perpendicular to each of the beam axis 2802 and the first direction 2804. Such a configuration can facilitate positioning the multipole element 2800 proximate to a target focal position when the free area around the target focal position at which the multipole element 2800 can be positioned is constrained in at least one dimension. For example, with reference to Figure 26, for a given position of a multipole element (e.g., third objective multipole element 2626) along the second axis 2612, the free space 2616 in which the multipole element is positioned may have a greater angular extent in the y direction than in the x direction, and thus the multipole element may correspondingly have a greater extent along the y direction than in the x direction. Correspondingly, in an example where multipole element 2800 of Figure 28 represents third objective multipole element 2626 of Figure 26, a first direction 2804 of Figure 28 may represent the x direction of Figure 26, and a second direction 2808 of Figure 28 may represent the y direction of Figure 26.

[0327] The first dimension 2806 and second dimension 2810 of the multipole element 2800 can have any of a variety of relative ranges. By way of example, the ratio of the second dimension 2810 to the first dimension 2806 can be at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, and / or at most 1.3:1.

[0328] Although Figure 28 is directed to an example in which the multipole element 2800 includes eight electrodes 2840, it should be understood that the configurations and features described herein with reference to Figure 28 may also be applied to multipole elements including any other number of electrodes, such as four electrodes, six electrodes, twelve electrodes, sixteen electrodes, etc. Similarly, the configurations and features described herein with reference to Figure 28 may also be applied to multipole elements configured to generate quadrupole, hexapole, octopole, duodecapolar fields, etc.

[0329] Figure 29 shows another example of a multipole element 2900 that can be used in space-constrained applications, such as the dual beam system of Figure 26. Similar to the multipole element 2800 of Figure 28, the multipole element 2900 includes a plurality of electrodes 2940 defining a central bore 2930 therebetween, each of which includes a respective electrode active surface 2942 and a respective electrode extension 2944.

[0330] The configuration of FIG. 29 may be particularly useful in instances where it is desirable to generate an electrostatic multipole field with a multipole multiplicity different from the number of electrodes of the multipole element. As mentioned above, a multipole element having eight electrodes can be configured to generate a quadrupole electrostatic field by applying appropriate voltages to the eight electrodes. However, in some cases, such a quadrupole field is accompanied by an undesirable parasitic dodecapolar electrostatic field due to a large coupling between the quadrupole field and the dodecapolar field. Such parasitic electric fields can be explained as artifacts of the electrode geometry. For example, such coupling can be particularly strong when all electrodes (or their active surfaces) are identical in shape.

[0331] In various examples, such parasitic electric fields can be minimized and / or neutralized by configuring a multipole element to include a number of electrodes corresponding to the desired multiplicity of the generated multipole field. For example, configuring a multipole element to include 12 electrodes can enable the multipole element to generate a quadrupole field with a minimal parasitic dodecapole field and an octopole field with a parasitic 16-pole field of acceptable magnitude. However, in some examples, space constraints and / or other practical considerations, such as a lack of space to make and / or include the required 12 separate electrical connections, preclude the use of a dodecapole element to generate a quadrupole field and / or an octopole field. However, configuring a multipole element to include eight electrodes of various shapes can enable the generation of both quadrupole and octopole electrostatic fields while limiting the associated parasitic electric fields to an acceptably small magnitude.

[0332] As an example, FIG. 29 illustrates an example in which the electrodes 2940 are configured such that the shapes of the active surfaces 2942 of the electrodes 2940 are not all the same. In particular, in this example, the plurality of electrodes 2940 includes a first shape subset 2960 of electrodes (shown as hatched lines) and a second shape subset 2962 of electrodes (shown as stippled lines). The electrode active surface 2942 of each electrode 2940 in the first shape subset 2962 of electrodes has a first active surface shape, while the electrode active surface 2942 of each electrode 2940 in the second shape subset 2960 of electrodes has a second active surface shape that is different from the first active surface shape. As used herein, each of the first active surface shape and the second active surface shape refers to the shape of the corresponding electrode active surface 2942 when viewed along a direction parallel to the beam axis 2930 (e.g., as shown in FIG. 29). For example, with reference to Figure 29, a first active surface shape may be described as a rounded shape with a relatively large radius of curvature, while a second active surface shape may be described as a rounded shape with a relatively small radius of curvature. Additionally or alternatively, the first active surface shape may be described as being wider than the second active surface shape.

[0333] 29, the first shape subset of electrodes 2960 and the second shape subset of electrodes 2962 each include an equal number of electrodes 2940 (i.e., four electrodes 2940). Additionally, in this example, the electrodes 2940 in the first shape subset of electrodes 2960 are circumferentially interleaved with the electrodes 2940 in the second shape subset of electrodes 2962. Additionally, other configurations are within the scope of this disclosure.

[0334] 29 may depict one example of a multipole element 2900 including eight electrodes 2940 and configured to generate a quadrupole electrostatic field within a central bore 2930. In particular, configuring the electrode active surfaces 2942 with alternating shapes, through appropriate shaping of the active surfaces 2942 of the electrodes 2940 and through appropriate application of voltages to the active surfaces 2942, can facilitate the generation of a quadrupole electric field while minimizing and / or canceling the associated parasitic dodecapolar field.

[0335] In some examples, the properties of the multipole element 2900 can be characterized with reference to the relative magnitudes of the multipole field components generated by the multipole element 2900. If fringe fields are neglected, the potential of a multipole field of multiplicity m can be expressed as:

[0336]

number

[0337]

number

[0338]

number

[0339] When a multipole element having eight identical electrodes spaced equidistantly with respect to the optical axis is excited to generate a quadrupole field as given by equation (44), the multipole element also generates an associated parasitic dodecapole field as given by equation (45). In particular, in such an example, the quadrupole multipole component V2 is

[0340]

number

[0341] In contrast, when the multipole element 2900 is excited to generate a quadrupole field, the quadrupole multipole component V2 can be related to the 12-pole multipole component V6 of the parasitic 12-pole field such that |V6 / V2|<=0.1. As used herein, the quantity |V6 / V2| that characterizes the quadrupole and 12-pole multipole field components generated by a multipole element (e.g., multipole element 2900) can be referred to as a 12-pole to quadrupole component ratio. The multipole element 2900 can be characterized by any of a variety of 12-pole to quadrupole component ratios, such as a 12-pole to quadrupole component ratio that is at most 0.1, at most 0.05, at most 0.01, and / or at least 0.001. Indeed, the particular shapes of the electrodes 2940 of the first shape subset of electrodes 2960 and the second shape subset of electrodes 2962 may be specifically selected and / or configured to reduce and / or minimize parasitic aberrations and / or dodecapole to quadrupole component ratios in this manner.

[0342] Similar to the multipole element 2800 of FIG. 28, the electrodes 2940 of the multipole element 2900 may be further divided into a first side subset of electrodes 2952 and a second side subset of electrodes 2956, as described above with reference to FIG. 28. As shown in FIG. 29, the first side subset of electrodes 2952 and the second side subset of electrodes 2956 may include different numbers of electrodes 2940. In particular, FIG. 29 illustrates an example in which the first side subset of electrodes 2952 includes five electrodes 2940 that extend away from the central bore 2930 along a first lateral direction 2916, and the second side subset of electrodes 2956 includes three electrodes 2940 that extend away from the central bore 2930 along a second lateral direction 2918. In this example, the multipole element 2900 exhibits mirror symmetry with respect to a plane that includes the beam axis 2930 and is parallel to the second direction 2908.

[0343] Figure 30 shows an example of a multipole element 3000 that is substantially similar to the multipole element 2900 of Figure 29, except for the distribution of electrodes 3040 in a first side subset 3052 of electrodes and a second side subset 3056 of electrodes. In particular, in the example of Figure 30, the first side subset 3052 of electrodes and the second side subset 3056 of electrodes each include four electrodes 3040. In this example, the multipole element 3000 exhibits axial symmetry with respect to the beam axis 3002.

[0344] Unless otherwise specified, all illustrated components of multipole element 2900 of Figure 29 and multipole element 3000 of Figure 30, whether labeled or not, can share any suitable features, characteristics, attributes, etc. with corresponding components of multipole element 2800 of Figure 28 and / or with each other. For example, with respect to components labeled in Figures 29-30, components labeled with reference numbers in the format "29XX" or "30XX" are intended to correspond to components labeled in Figure 28 with reference numbers in the format "28XX".

[0345] Figure 31 shows an example of an assembly 3100 including multiple multipole elements 3110 axially aligned with respect to a beam axis 3102. Each multipole element 3110 in Figure 31 may represent an example of any suitable multipole element disclosed herein, such as multipole element 2622, 2624, or 2626 of Figure 26, multipole element 2700 of Figure 27, multipole element 2800 of Figure 28, multipole element 2900 of Figure 29, or multipole element 3000 of Figure 30.

[0346] In the example of Figure 31, the multipole element 3110 is configured to focus a charged particle beam 3150 traveling along a beam axis 3102 to a target focal position 3152, such as a position of interest on a sample (e.g., sample 2630 of Figure 26). In this example, the assembly 3100 and / or the plurality of multipole elements 3110 can be referred to as a multipole objective. By way of example, the plurality of multipole elements 3110 may correspond to and / or represent the objective multipole elements 2242 / 2342 of the multipole objective 2440 / 2540 of Figures 22-23 or the objective multipole elements 2442 / 2542 of the multipole objective 2240 / 2340 of Figures 24-25. Although FIG. 31 illustrates the assembly 3100 as including four multipole elements 3110, it will be understood that this is not required and that the features and characteristics described herein with reference to FIG. 31 may also apply to similar and / or otherwise identical assemblies including more than four multipole elements 3110 or less than four multipole elements 3110.

[0347] As shown in Figure 31, the multipole objective may be characterized by a working distance 3158 (e.g., measured along the beam axis 3102) separating a proximal multipole element 3154 and a target focal position 3152. Specifically, the proximal multipole element 3154 may refer to a multipole element 3110 positioned closer to the target focal position 3152 relative to the remaining multipole elements 3110 of the multipole objective 3100. For example, the proximal multipole element 3154 may correspond to and / or represent the third objective multipole element 2248 / 2348 of Figures 22-23 or the fourth objective multipole element 2450 / 2550 of Figures 24-25. Additionally or alternatively, the proximal multipole element 3154 may correspond to and / or represent a multipole element configured for scanning and / or astigmatism correction of the charged particle beam 3150.

[0348] The multipole objective of Figure 31 may additionally be characterized by an angular region or envelope defined relative to the beam axis 3102 and / or the target focal position 3152, within which the multipole elements 3110 are spatially contained. For example, Figure 31 shows a side view of the multipole objective projected onto an xz plane (e.g., with reference to the coordinate system of Figure 26) that includes the beam axis 3102, which may be referred to herein as a first plane 3164. As shown in Figure 31, the multiple multipole elements 3110 are entirely contained within a first angular envelope 3160 defined in the first plane 3164. Specifically, the first angular envelope 3160 represents the region of the first plane 3164 between two lines within the first plane 3164 that intersect each other and the beam axis 3102 at the target focal position 3152 and subtend a first angle 3162 (e.g., are angled relative to each other by this angle).

[0349] 26 and 31, the first angle 3162 in Fig. 31 may be understood to represent and / or correspond to the free space angle 2618 in Fig. 26. For example, the value of the free space angle 2618 may represent a maximum value of the first angle 3162 that characterizes the region (e.g., the first angle envelope 3160) into which the multiple multipole elements 3110 must fit to be accepted between the sample 2630 and the first exclusion region 2606 in Fig. 26.

[0350] In general, for a given value of the first angle 3162, a multipole element 3110 of any dimension (e.g., as measured in the x-direction in FIG. 31 ) may be contained within the first angle envelope 3160 when separated from the target focal position 3152 by a sufficiently large working distance 3158. However, in various examples, aberrations (e.g., spherical aberration) of the charged particle beam 3150 at the target focal position 3152 are related (e.g., proportional) to the working distance 3158. Thus, it may be desirable to minimize the working distance 3158 to the extent permitted by other space constraints.

[0351] In certain examples, the multipole element 3110 may be completely contained within the first angle envelope 3160 when the first angle 3162 is at least 25 degrees, at least 35 degrees, at least 45 degrees, at least 55 degrees, at most 60 degrees, at most 50 degrees, at most 40 degrees, and / or at most 30 degrees and the working distance 3158 is at least 2 mm, at least 5 mm, at least 10 mm, at least 20 mm, at most 30 mm, at most 15 mm, at most 10 mm, at most 7 mm, and / or at most 3 mm. In certain examples, the multipole element 3110 may be completely contained within the first angle envelope 3160 when the first angle is at most 50 degrees and the working distance is at most 10 mm. 31 may be characterized by and / or with reference to an aberration (e.g., spherical aberration) of the charged particle beam 3150 at the target focal position 3152. By way of example, the multiple multipole elements 3110 may be configured to operate as an objective lens to focus the charged particle beam 3150 at the target focal position 3152 with a third order spherical aberration that is one or more of at most 5 mm, at most 3 mm, at most 2 mm, at most 1 mm, and / or at least 0.1 mm.

[0352] Thus, the multipole elements 3110 can have any of a variety of features as disclosed herein to facilitate positioning the multipole elements 3110 (e.g., at least the proximal multipole element 3154) near the target focal position 3152 while maintaining the multipole element 3110 within the first angular envelope 3160. For example, each multipole element 3110 can have a linear dimension along the x-direction of FIG. 31 that is small enough to enable each multipole element 3110 to be positioned desirably close to the target focal position 3152 while maintaining each multipole element 3110 within the first angular envelope 3160.

[0353] In various examples, this can be accomplished by configuring the multipole element 3110 with one or more structural features that extend along a direction other than the x-direction of Figure 31. For example, the multipole element 3110 may be characterized by a first dimension measured along the x-direction (e.g., first dimension 2706 / 2806 / 2906 / 3006 in Figures 27-30) and a second dimension measured along a y-direction transverse to the x- and z-directions (e.g., second dimension 2704 / 2810 / 2910 / 3010 in Figures 27-30), where the second dimension is greater than the first dimension. In other words, configuring the multipole element 3110 such that a portion of the multipole element 3110 (e.g., electrode extension 2840 / 284 / 3040 in Figures 28-30) extends along the y-direction can facilitate minimizing the linear dimension of the multipole element 3110 along the x-direction.

[0354] Additionally or alternatively, as shown in FIG. 31, each multipole element 3110 may have a non-planar configuration with portions extending partially along an axial direction. In particular, FIG. 31 illustrates an example in which each multipole element 3110 includes a number of electrode active surfaces 3142 facing the central bore 3130 and a number of electrode extensions 3144 extending away from the corresponding electrode active surfaces 3142, as described above with reference to FIGS. 27-30. As shown in FIG. 31, each electrode extension 3144 can be described as extending along a direction extending away from the central bore 3130 partially along a radial direction 3112 perpendicular to the beam axis 3102 and partially along an axial direction 3114 parallel to the beam axis 3102. Stated differently, each electrode extension 3144 can be described as extending away from the corresponding electrode active surface 3142 along a direction angled with respect to each of the radial direction 3112 and the axial direction 3114. Although FIG. 31 illustrates the radial direction 3112 as parallel to the x-direction, it should be understood that the radial direction 3112 may be any other direction perpendicular to the beam axis 3102.

[0355] In various examples, the multipole elements 2700 / 2800 / 2900 / 3000 of Figures 27-30 may be partially angled away from a planar configuration in the manner shown in Figure 31. For example, the electrode extensions of any of the multipole elements of Figures 27-30 may extend away from the corresponding electrode active surface along a direction that is not perpendicular to the beam axis, similar to multipole element 3110 of Figure 31.

[0356] Additionally or alternatively, each multipole element 3110 may be characterized by its different linear dimensions at its different axial locations. For example, as shown in FIG. 31, each multipole element 3110 may be described as extending along a direction parallel to the beam axis 3102 (e.g., along an axial direction 3114) between its proximal end region 3120 and its distal end region 3124. In some examples, the proximal end region 3120 is a region proximal to the central bore 3130, and the distal end region 3124 is a region distal to the central bore 3130. In some examples, as shown in FIG. 31, each multipole element 3110 may be characterized by a first diameter 3122 at the proximal end region 3120 and a second diameter 3126 at the distal end region 3124, the second diameter 3126 being larger than the first diameter 3122. Each of the first diameter 3122 and the second diameter 3126 may be measured along a direction perpendicular to the beam axis 3102 (e.g., along the radial direction 3112). In such examples, the first diameter 3122 and the second diameter 3126 may be related in any suitable manner, such as to facilitate containing the multipole element 3110 within the first angular envelope 3160. By way of example, the ratio of the second diameter 3126 to the first diameter 3122 may be at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, and / or at most 1.3:1.

[0357] 31 can also facilitate forming electrical connections with each multipole element 3110, such as for providing an appropriate voltage to the electrode 3140 of each multipole element 3110. For example, as described above with reference to FIGS. 28-30, the electrode extension 3144 of each electrode 3140 can include electrical contact locations 3146 configured to be coupled to an electrical lead 3192 (e.g., a wire) to provide a voltage to the corresponding electrode active surface 3142.

[0358] In the example of FIG. 31 , each electrode active surface 3142 is axially offset (e.g., spaced apart along the axial direction 3114) from a corresponding electrical contact location 3146. Such a configuration can facilitate forming an electrical connection between the electrical leads 3192 and the electrical contact locations 3146 in a region that is less spatially constrained than the proximal end region 3120 of each multipole element 3110. Stated another way, because the linear range of the first angular envelope 3160 measured along the x-direction of FIG. 31 increases as the distance from the target focal location 3152 increases, electrical connections can be formed with relaxed spatial constraints and / or tolerances when such connections are formed at locations farther from the target focal location 3152 relative to the electrode active surfaces 3142.

[0359] 31 may also be characterized with reference to one or more linear dimensions of the multipole elements 3110 as measured along the axial direction 3114 and / or their relative positions. For example, each pair of adjacent multipole elements 3110 may be separated by a respective multipole element gap 3180. By way of example, each multipole element gap 3180 may be at least 0.2 mm, at least 0.5 mm, at least 1 mm, up to 1.5 mm, up to 0.7 mm, and / or up to 0.3 mm. In various examples, the multipole element gaps 3180 characterizing the multiple multipole elements 3110 may be different from one another and / or may be controlled and / or configured to limit aberrations of the charged particle beam 2050 at the target focal position 3152.

[0360] Additionally or alternatively, each multipole element 3110 may be characterized by a respective multipole element length 3182 measured along the axial direction 3114. In particular, in some examples, each multipole element 3110 includes a central region 3186 that defines a central bore 3130 (e.g., excluding electrode extensions 3144 that extend axially away from the central bore 3130), and the multipole element length 3182 is measured in the central region 3186 of the multipole element 3110. By way of example, each multipole element length 3182 may be at least 2 mm, at least 5 mm, at least 10 mm, at most 15 mm, at most 10 mm, at most 7 mm, and / or at most 3 mm. In various examples, the multipole element lengths 3182 characterizing the multiple multipole elements 3110 may differ from one another and / or may be configured to limit and / or restrict aberrations of the charged particle beam 2050 at the target focal position 3152.

[0361] Additionally or alternatively, the plurality of multipole elements 3110 may be characterized by its total stack length 3184. For example, as shown in FIG. 31 , the plurality of multipole elements 3110 may include a distal multipole element 3110 that is distal to the target focal position 3152 relative to the remaining multipole elements 3156, and the stack length 3184 may be measured along the axial direction 3114 between the proximal multipole element 3154 and the distal multipole element 3156 (e.g., between their central regions 3186). Thus, the stack length 3184 may be equal to the sum of the multipole element lengths 3182 of the multipole elements 3110 and the multipole element gaps 3180 separating each pair of adjacent multipole elements 3110. By way of example, the stack length 3184 may be at least 15 mm, at least 20 mm, at least 25 mm, at least 30 mm, at least 35 mm, at least 40 mm, at most 50 mm, at most 37 mm, at most 32 mm, at most 27 mm, at most 22 mm, and / or at most 17 mm.

[0362] 31 may be characterized by the ratio of one or more dimensions of the plurality of multipole elements 3110 to the working distance 3358. For example, the plurality of multipole elements may be positioned and / or configured such that the ratio of multipole element length 3182 to the working distance 3158 of each multipole element 3110 is at least 1:5, at least 1:2, at least 1:1, at least 2:1, at least 5:1, at least 10:1, at least 20:1, at most 30:1, at most 15:1, at most 7:1, at most 3:1, at most 1:1, and / or at most 1:3. Additionally or alternatively, the plurality of multipole elements may be positioned and / or configured such that the ratio of stack length 3184 to the working distance 3158 is at least 1:1, at least 2:1, at least 5:1, at least 10:1, at most 20:1, at most 7:1, and / or at most 3:1.

[0363] FIG. 32 illustrates an assembly 3200 including a plurality of multipole elements 3210 and a lens housing 3290 surrounding the plurality of multipole elements 3210. The assembly 3200 of FIG. 32 is substantially identical to the assembly 3100 of FIG. 31, except for the presence of the lens housing 3290. Specifically, unless otherwise specified, all illustrated components of FIG. 32, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with the corresponding components of FIG. 31. For example, with respect to components labeled in FIG. 32, components labeled with reference numbers in the format "32XX" are intended to correspond to components labeled in FIG. 31 with reference numbers in the format "31XX."

[0364] 32 can be configured to shield, support, and / or otherwise assemble multiple multipole elements 3210, such as to position the multipole elements 3210 relative to the target focal position 3252. Thus, the lens housing 3290 may be conical and / or frustoconical and / or characterized by a taper angle 3294 such that the lens housing 3910 is also completely contained within the first angle envelope 3260 when the multipole elements 3210 are operatively positioned relative to the target focal position 3252. For example, the taper angle 3294 may be less than or equal to the first angle 3262.

[0365] Figure 33 shows an assembly 3300 including a plurality of multipole elements 3310 in a side view projecting the multipole elements 3310 onto a yz plane (e.g., with reference to the coordinate system of Figures 26 and / or 31) that includes the beam axis 3302. As shown in Figure 33, the yz plane may additionally or alternatively be referred to as a second plane 3374. Thus, the second plane 3374 of Figure 33 is perpendicular to the first plane 3164 of Figure 31. In this manner, Figure 33 may be described as representing the assembly 3100 of Figure 31 in a transverse cross section.

[0366] Unless otherwise specified, all illustrated components in FIG. 33, whether numbered or not, can share any suitable features, characteristics, attributes, etc. with corresponding components in FIG. 31. For example, for components labeled in FIG. 33, components labeled with reference numbers in the format "33XX" are intended to correspond to components labeled in FIG. 31 with reference numbers in the format "31XX."

[0367] In the example of Figure 33, the multipole element 3310 is entirely contained within a second angular envelope 3370 defined in a second plane 3374. Similar to the first angular envelope 3160 of Figure 31, the second angular envelope 3370 defines therebetween a second angular envelope 3370 and defines a range of second angles 3372 measured between lines intersecting at the target focal position 3352. In certain examples, the multipole element 3310 can be completely contained within the second angle envelope 3370 when the second angle 3372 is at least 25 degrees, at least 35 degrees, at least 45 degrees, at least 55 degrees, at most 60 degrees, at most 50 degrees, at most 40 degrees, and / or at most 30 degrees, and the working distance 3358 is at least 2 mm, at least 5 mm, at least 10 mm, at least 20 mm, at most 30 mm, at most 15 mm, at most 10 mm, at most 7 mm, and / or at most 3 mm.

[0368] In some examples, the second angle 3372 in Figure 33 may be at least substantially equal to the first angle 3162 in Figure 31. In such examples, the first angle envelope 3160 in Figure 31 and the second angle envelope 3370 in Figure 33 can be described as representing cross sections of a cone envelope when viewed in transverse plane.

[0369] In other examples, the second angle 3727 in Figure 33 may be greater than the first angle 3162 in Figure 31. For example, with reference to Figure 26, a constraint that a multipole element (e.g., the third objective lens multipole element 2626) fit within free space 2616 may correspond to a constraint on the x-dimension of the multipole element, while the y-dimension of the multipole element may be relatively (or completely) unconstrained.

[0370] The increased second angle 3372 relative to the first angle 3162 can enable the multipole element 3310 to have an increased linear dimension along the y direction of Figure 33 relative to a linear dimension along the x direction of Figure 31. For example, for a given value of working distance 3158 / 3358, an increase in the second angle 3372 characterizing the second angular envelope 3370 can correspond to an increase in a linear dimension of the multipole element 3310 that can be included within the second angular envelope 3370.

[0371] 31, such as portions of the multipole element 3110 / 3310 projected onto and / or intersecting the second plane 3374. For example, the multipole element 3110 / 3310 can include an electrode extension 3144 angled away from the radial direction 3112 of FIG. 31 and an electrode extension 3344 extending perpendicular to the beam axis 3302. Alternatively, in some examples, the electrode extension 3144 / 3344 can be angled away from the radial direction 3112 in each of the first plane 3164 and the second plane 3374 in the manner shown in FIG. In other examples, the electrode extensions 3144 / 3344 can extend along a radial direction 3112 (e.g., along the y direction in FIG. 33) approximately as shown in FIG. 33 in each of the first plane 3164 and the second plane 3374.

[0372] Figure 34 shows an assembly 3400 including multiple multipole elements 3410 and a lens housing 3490 surrounding the multiple multipole elements 3410 in a side view projecting the multipole elements 3410 onto a yz plane (e.g., with reference to the coordinate systems of Figures 26 or 31-33) that includes the beam axis 3402, which may also be referred to as a second plane 3474. In this manner, Figure 34 can be described as representing the assembly 3200 of Figure 32 in cross section.

[0373] Assembly 3400 of FIG. 34 is substantially identical to assembly 3300 of FIG. 33, except for the presence of lens housing 3490. Assembly 3400 of FIG. 34 is also substantially identical to assembly 3200 of FIG. 32, except that, similar to the relationship between FIG. 31 and FIG. 33, it is viewed in the yz plane rather than the xz plane. Unless otherwise specified, all illustrated components of FIG. 34, whether labeled or not, may share any suitable features, characteristics, attributes, etc. with corresponding components of FIG. 31-FIG. 33. For example, for components labeled in FIG. 34, components labeled with reference numbers in the format "34XX" are intended to correspond to components labeled with reference numbers in the format "31XX" / "32XX" / "33XX" in FIG. 31-FIG.

[0374] 32 and 34, it can be seen that an increase in the second angle 3472 characterizing the second angle envelope 3470 relative to the first angle 3262 characterizing the first angle envelope 3260 may allow the lens housing 3490 to be formed with a correspondingly larger taper angle 3494. In particular, in some examples, the lens housing 3290 of FIG. 32 and the lens housing 3490 of FIG. 34 may represent transverse cross-sectional views of a common lens housing that may have a larger taper angle 3494 in the second plane 3474 than in the first plane 3264. For example, the lens housing may have a three-dimensional shape similar to a flattened cone (e.g., having an elliptical cross-section in the xy plane) and / or any other shape that may be characterized by different taper angles in a transverse cross-section. In such an example, the taper angle 3294 of the lens housing 3290 in the first plane 3264 shown in Figure 32 may be described as a first taper angle 3294, and the taper angle 3494 of the lens housing 3490 in the second plane 3474 shown in Figure 34 may be described as a second taper angle 3494. As discussed above with reference to Figure 26, such a configuration may facilitate positioning the lens housing in constrained free space along a direction corresponding to the smaller taper angle (e.g., along the x direction in Figures 26 and 32), thereby enabling the multipole element to be positioned desirably close to a target focal position.

[0375] General Considerations As used in this application and the claims, the singular forms "a," "an," and "the" include the plural forms unless the content clearly dictates otherwise. Furthermore, the term "includes" means "comprises." Furthermore, the term "coupled" does not exclude the presence of intermediate elements between the coupled items.

[0376] As used herein, the term "substantially" refers to the recited values ​​and / or characteristics, as well as any values ​​and / or characteristics that are at least 75% of the recited values ​​and / or characteristics. Equivalently, the term "substantially" refers to the recited values ​​and / or characteristics, as well as any values ​​and / or characteristics that differ from the recited values ​​and / or characteristics by up to 25%. For example, "substantially equal" refers to amounts that are completely equal, as well as amounts that differ from each other by up to 25%.

[0377] The systems, devices, and methods described herein should not be construed as limiting in any way. Instead, the present disclosure is directed to all novel and non-obvious features and aspects of the various disclosed embodiments, alone and in various combinations and subcombinations with each other. The disclosed systems, methods, and devices are not limited to any particular aspect or feature or combination thereof, and the disclosed systems, methods, and devices do not require that any one or more particular advantages exist or problems be solved. Any theory of operation is provided for ease of explanation, but the disclosed systems, methods, and devices are not limited to such theories of operation.

[0378] In various examples described herein, a module (e.g., a component) can be "programmed" to perform particular operations or provide particular functionality, indicating that computer-executable instructions for the module can be executed to perform such operations, cause such operations to be performed, or otherwise provide such functionality. Functionality described in terms of a software component, module, or engine can be executed as a separate software unit (e.g., program, function, class method), but need not be implemented as a separate unit. That is, functionality can be incorporated into a larger or more general program, such as one or more lines of code within the larger or more general program.

[0379] Although the principles of the disclosed technology have been described and illustrated with reference to the illustrated embodiments, it will be recognized that the illustrated embodiments may be modified in configuration and details without departing from such principles. For example, elements of the embodiments that are implemented in software may be implemented in hardware, and vice versa. Also, techniques from any embodiment may be combined with techniques described in any one or more of the other embodiments. It will be understood that the procedures and functions as described with reference to the illustrated embodiments may be implemented in a single hardware or software module, or separate modules may be provided. The particular configurations described above are provided for ease of illustration, and other configurations may be used.

[0380] Additional Examples of the Disclosed Techniques In view of the above-mentioned implementations of the disclosed subject matter, the present application discloses additional embodiments as listed below. It should be noted that a feature of a single section, or a combination of two or more features of that section, optionally in combination with one or more features of one or more additional embodiments, is also a further embodiment included in the disclosure of the present application.

[0381] Example 1. An apparatus comprising: a plurality of electrostatic elements configured to deflect an incident charged particle beam along an α-shaped path; An apparatus, wherein the plurality of electrostatic elements includes a plurality of electrostatic multipole elements configured to at least partially correct for on-axis chromatic aberration of the charged particle beam.

[0382] Example 2. The apparatus of any of the embodiments herein, particularly Example 1, further comprising a deflector assembly comprising a corrector electrostatic prism and a plurality of electrostatic multipole elements, the deflector assembly configured to deflect the charged particle beam along a deflector optical axis, and the deflector assembly configured to at least partially correct on-axis chromatic aberration in the charged particle beam using two or more hexapole fields generated in the corrector electrostatic prism.

[0383] Example 3. A plurality of electrostatic multipole elements, a first hexapole generating element configured to generate a first hexapole field; a second hexapole generating element configured to generate a second hexapole field; A third hexapole generating element configured to generate a third hexapole field.

[0384] Example 4. An apparatus as described herein in substantially any one of Examples 2-3, in particular, wherein at least two electrostatic multipole elements of the plurality of electrostatic multipole elements are at least partially contained within the corrector electrostatic prism.

[0385] Example 5. An apparatus as described in any embodiment herein, particularly any one of embodiments 1-4, wherein the deflector optical axis is a curved axis.

[0386] Example 6. An apparatus as described in any of the examples herein, particularly any one of Examples 1-5, wherein the deflector optical axis is alpha shaped.

[0387] Example 7. The apparatus of any of the examples herein, particularly any one of examples 2-6, wherein the portion of the deflector optical axis that extends within the corrector electrostatic prism follows a circular path.

[0388] Example 8. Corrector The position along the part of the deflector optical axis that extends into the electrostatic prism is in the range of 0 to φ max The apparatus according to any embodiment herein, in particular any one of embodiments 2 to 7, characterized by a prism angle φ, which can assume any value between

[0389] Example 9. The prism angle φ=0 corresponds to the position where the charged particle beam enters the corrector electrostatic prism along the deflector optical axis, and the prism angle φ=φ max corresponds to a position where the charged particle beam exits the corrector electrostatic prism along the deflector optical axis.

[0390] Example 10. Prism angle φ max The apparatus of any embodiment herein, particularly any one of embodiments 8-9, wherein the angle is equal to or approximately equal to 270 degrees.

[0391] Example 11. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-10, wherein the corrector electrostatic prism is configured to deflect the charged particle beam by an angle equal to or approximately equal to 270 degrees.

[0392] Example 12. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-11, wherein at least a subset of the plurality of electrostatic multipole elements is disposed within the corrector electrostatic prism.

[0393] Example 13. an entrance electrostatic prism configured to direct the charged particle beam from the optical column axis to the deflector optical axis; an exit electrostatic prism configured to direct the charged particle beam from the deflector optical axis toward the optical column axis; The device according to any embodiment herein, particularly any one of embodiments 2 to 12, further comprising:

[0394] Example 14. The apparatus of any of the embodiments herein, particularly example 13, wherein the entrance electrostatic prism and the exit electrostatic prism are each configured to deflect the charged particle beam at an angle equal to or approximately equal to 45 degrees.

[0395] Example 15. A device according to any of the embodiments herein, particularly any one of Examples 13-14, wherein one or both of the entrance electrostatic prism and the exit electrostatic prism are bifocal prisms.

[0396] Example 16. The apparatus of any of the embodiments herein, particularly any one of embodiments 13-15, wherein the plurality of electrostatic elements further comprises a first quadrupole generating element configured to generate a first quadrupole field and a second quadrupole generating element configured to generate a second quadrupole field, the first quadrupole generating element being defined by an entrance electrostatic prism, coupled to the entrance electrostatic prism, or both, and the second quadrupole generating element being defined by an exit electrostatic prism, coupled to the exit electrostatic prism, or both.

[0397] Example 17. The device comprises: a correction mode in which an entrance electrostatic prism directs the charged particle beam onto the deflector optical axis; a linear axial mode in which the charged particle beam bypasses the deflector assembly; The device described in any embodiment herein, particularly any one of embodiments 13 to 16, configured to be selectively operated at each of the following:

[0398] Example 18. A plurality of electrostatic elements are a first hexapole generating element configured to generate a first hexapole field; a second hexapole generating element configured to generate a second hexapole field; a third hexapole generating element configured to generate a third hexapole field; a first quadrupole generating element configured to generate a first quadrupole field; a second quadrupole generating element configured to generate a second quadrupole field; The apparatus of any embodiment herein, particularly any one of embodiments 13-17, comprising: a first quadrupole generating element disposed along the deflector optical axis between the entrance electrostatic prism and the first hexapole generating element; and a second quadrupole generating element disposed along the deflector optical axis between the third hexapole generating element and the exit electrostatic prism.

[0399] Example 19. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-18, wherein the plurality of electrostatic elements further comprises a first quadrupole generating element configured to generate a first quadrupole field and a second quadrupole generating element configured to generate a second quadrupole field, each of the first quadrupole generating element and the second quadrupole generating element being an adjustable quadrupole generating element.

[0400] Example 20. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-19, wherein the plurality of electrostatic elements further comprises a first quadrupole generating element configured to generate a first quadrupole field and a second quadrupole generating element configured to generate a second quadrupole field, each of the first quadrupole generating element and the second quadrupole generating element being spaced apart from the corrector electrostatic prism.

[0401] Example 21. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-20, wherein the plurality of electrostatic elements further comprises a first quadrupole generating element configured to generate a first quadrupole field and a second quadrupole generating element configured to generate a second quadrupole field, each of the first quadrupole generating element and the second quadrupole generating element being coupled to a corrector electrostatic prism.

[0402] Example 22. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-21, wherein the plurality of electrostatic elements further comprises a first quadrupole generating element configured to generate a first quadrupole field and a second quadrupole generating element configured to generate a second quadrupole field, each of the first quadrupole generating element and the second quadrupole generating element being at least partially contained within the corrector electrostatic prism.

[0403] Example 23. A device described in any of the embodiments herein, particularly any one of embodiments 2-22, wherein the corrector electrostatic prism comprises a corrector prism body having a first corrector prism electrode and a second corrector prism electrode disposed radially outward of the first corrector prism electrode, the first corrector prism electrode and the second corrector prism electrode defining an electrode gap therebetween, and the deflector optical axis extends within the electrode gap.

[0404] Example 24. The apparatus of any of the embodiments herein, particularly example 23, wherein the corrector electrostatic prism is configured such that when a first electrode voltage is applied to the first corrector prism electrode and a second electrode voltage is applied to the second corrector prism electrode, the corrector electrostatic prism generates an electrostatic deflection field that directs the charged particle beam to move through the corrector electrostatic prism along the deflector optical axis.

[0405] Example 25. A device described in any of the embodiments herein, particularly any one of embodiments 23-24, wherein the first corrector prism electrode has a first electrode outer surface defining a first electrode recess extending partially along a direction parallel to the deflector optical axis, the second corrector prism electrode has a second electrode outer surface defining a second electrode recess extending partially along a direction parallel to the deflector optical axis, and at least one electrostatic multipole element of the plurality of electrostatic multipole elements is at least partially disposed within each of the first electrode recess and the second electrode recess.

[0406] Example 26. One or more electrostatic multipole elements of a plurality of electrostatic multipole elements, the electrostatic multipole element comprising: A first hexapole electrode; a second hexapole electrode; a third hexapole electrode; a fourth hexapole electrode; a fifth hexapole electrode; a sixth hexapole electrode; The device of any embodiment herein, particularly embodiment 25, wherein the first hexapole electrode, the second hexapole electrode, and the third hexapole electrode are at least partially received in the second electrode recess, and the fourth hexapole electrode, the fifth hexapole electrode, and the sixth hexapole electrode are at least partially received in the first electrode recess.

[0407] Example 27. A plurality of electrostatic elements are a first hexapole generating element configured to generate a first hexapole field; a second hexapole generating element configured to generate a second hexapole field; and a third hexapole generating element configured to generate a third hexapole field.

[0408] Example 28. The apparatus of any of the embodiments herein, particularly example 27, wherein the second hexapole generating element is positioned adjacent to the midpoint of the deflector optical axis within the corrector electrostatic prism.

[0409] Example 29. The apparatus of any of the embodiments herein, particularly any one of embodiments 27-28, wherein the position along the portion of the deflector optical axis that extends within the corrector electrostatic prism is characterized by a prism angle φ that varies from 0 degrees to 270 degrees, and the second hexapole generating element is positioned within the corrector electrostatic prism at a prism angle of φ=135 degrees.

[0410] Example 30. The apparatus of any of the embodiments herein, particularly any one of embodiments 27-29, wherein each of the first hexapole generating element and the third hexapole generating element is angularly equidistant from the second hexapole generating element.

[0411] Example 31. An apparatus described in any of the embodiments herein, particularly any one of embodiments 27-30, wherein each of the first hexapole generating element and the third hexapole generating element is positioned adjacent to a position along the deflector optical axis corresponding to a linear focus of the charged particle beam.

[0412] Example 32. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-31, wherein the second hexapole generating element is positioned proximate to a position along the deflector optical axis corresponding to a linear focus of the charged particle beam.

[0413] Example 33. The apparatus of any of the embodiments herein, particularly any one of embodiments 2-32, wherein the corrector electrostatic prism is configured to generate at least a portion of the electrostatic deflection field comprising a prism hexapole field.

[0414] Example 34. Any of the embodiments herein, particularly the apparatus of Example 33, wherein a position along a portion of the deflector optical axis that extends within the corrector electrostatic prism is characterized by a prism angle φ, a position within the corrector electrostatic prism away from the deflector optical axis is characterized by a prism angle φ, a radial distance away from the deflector optical axis x, and a lateral distance away from the deflector optical axis y, and the magnitude of the prism hexapole field within the corrector electrostatic prism is a function of x and y and is constant at φ.

[0415] Example 35. A device described in any embodiment herein, particularly any one of embodiments 2 to 34, wherein the corrector electrostatic prism comprises a first corrector prism electrode and a second corrector prism electrode disposed radially outward of the first corrector prism electrode, the first corrector prism electrode comprising a first electrode outer surface facing the second corrector prism electrode, and the second corrector prism electrode comprising a second electrode inner surface facing the first corrector prism electrode, and each of the first electrode outer surface and the second electrode inner surface has a cross-sectional profile that is substantially constant within the corrector electrostatic prism away from each electrostatic multipole element, when viewed along a direction perpendicular to the deflector optical axis.

[0416] Example 36. An apparatus described in any of the embodiments herein, particularly any one of embodiments 33-35, wherein the position along the portion of the deflector optical axis that extends within the corrector electrostatic prism is characterized by a prism angle φ, and the magnitude of the prism hexapole field within the corrector electrostatic prism varies with φ.

[0417] Example 37. The apparatus of any of the embodiments herein, particularly example 36, wherein the magnitude of the prism hexapole field is proportional to a hexapole parameter p that varies with the prism angle φ.

[0418] Example 38. The hexapole parameters are (i) p = p1, 0 < φ <= φ1; (ii) p = p2, φ1 < φ <= φ2; (iii) p = p3, φ2 < φ <= φ3; (iv) p = p3, φ3 < φ <= φ4; (v) p = p2, φ4 < φ <= φ5; and (vi) p = p1, φ5 < φ <= φ6 The apparatus of any embodiment herein, particularly embodiment 37, wherein the .times. ...

[0419] Example 39. The apparatus of any embodiment herein, particularly example 38, wherein φ3=φ6 / 2.

[0420] Example 40. A device described in any embodiment herein, particularly any one of embodiments 35-39, wherein the first corrector prism electrode has a first electrode outer surface facing the second corrector prism electrode, the first electrode outer surface defining a first electrode groove extending along a direction parallel to the deflector optical axis, and the second corrector prism electrode has a second electrode inner surface facing the first corrector prism electrode, the second electrode inner surface defining a second electrode groove extending along a direction parallel to the deflector optical axis.

[0421] Example 41. The apparatus of any of the embodiments herein, particularly example 40, wherein the corrector electrostatic prism is configured such that when a first electrode voltage is applied to the first corrector prism electrode and a second electrode voltage is applied to the second corrector prism electrode, the first electrode groove and the second electrode groove generate a hexapole field within the corrector electrostatic prism.

[0422] Example 42. An apparatus described in any embodiment herein, particularly any one of embodiments 40-41, wherein the corrector electrostatic prism has a corrector prism beam radius measured between the center of the first corrector prism electrode and the deflector optical axis, the first electrode groove has a first electrode groove depth measured along a radial direction parallel to the corrector prism beam radius, and the second electrode groove has a second electrode groove depth measured along the radial direction, and each of the first electrode groove depth and the second electrode groove depth is at most 1 / 50 of the corrector prism beam radius.

[0423] Example 43. A device described in any embodiment herein, particularly any one of embodiments 40-42, wherein a position along a portion of the deflector optical axis that extends within the corrector electrostatic prism is characterized by a prism angle φ, and one or more dimensions of one or both of the first electrode groove and the second electrode groove vary with the prism angle.

[0424] Example 44. A plurality of electrostatic multipole elements, a first hexapole generating element configured to generate a first hexapole field; a second hexapole generating element configured to generate a second hexapole field; a third hexapole generating element configured to generate a third hexapole field; a fourth hexapole generating element configured to generate a fourth hexapole field; The device according to any embodiment herein, in particular any one of embodiments 1 to 43, comprising:

[0425] Example 45. Any of the embodiments herein, particularly example 44, further comprising a deflector assembly comprising a corrector electrostatic prism and a plurality of electrostatic multipole elements, the deflector assembly defining a deflector optical axis, and the deflector assembly configured to at least partially correct axial chromatic aberration in the charged particle beam as the charged particle beam travels along the deflector optical axis.

[0426] Example 46. The apparatus of any of the embodiments herein, particularly example 45, wherein each of the second hexapole generating element and the third hexapole generating element is at least partially disposed within the corrector electrostatic prism.

[0427] Example 47. An apparatus described in any of the embodiments herein, particularly any one of embodiments 45-46, wherein each of the second hexapole generating element and the third hexapole generating element is positioned adjacent to a position along the deflector optical axis corresponding to a linear focus of the charged particle beam.

[0428] Example 48. The apparatus of any of the embodiments herein, particularly any one of embodiments 2 to 47, wherein the corrector electrostatic prism is configured to generate a point-like focus of the charged particle beam proximate to a mid-plane position of the deflector optical axis within the corrector electrostatic prism.

[0429] Example 49. The apparatus of any embodiment herein, particularly any one of embodiments 2 to 48, wherein the corrector electrostatic prism is configured to function as a monochromator.

[0430] Example 50. An apparatus described in any of the embodiments herein, particularly any one of embodiments 2 to 49, further comprising an energy-selecting slit positioned proximate the mid-plane position of the deflector optical axis within the corrector electrostatic prism.

[0431] Example 51. An apparatus comprising: a plurality of electrostatic elements configured to deflect an incident charged particle beam along an Ω-shaped path; An apparatus, wherein the plurality of electrostatic elements includes a plurality of electrostatic multipole elements configured to at least partially correct for on-axis chromatic aberration of the charged particle beam.

[0432] Example 52. a deflector assembly including a plurality of corrector electrostatic prisms and a plurality of electrostatic multipole elements; A plurality of corrector electrostatic prisms A first electrostatic prism; a second electrostatic prism; a third electrostatic prism; and a fourth electrostatic prism; A plurality of electrostatic multipole elements a first multipole element configured to generate a first hexapole field; a second multipole element configured to generate a second hexapole field; and a third multipole element configured to generate a third hexapole field; An apparatus as described in any embodiment of the present specification, particularly embodiment 51, wherein the deflector assembly defines a deflector optical axis, and the deflector assembly is configured to at least partially correct axial chromatic aberration in the charged particle beam as the charged particle beam travels along the deflector optical axis.

[0433] Example 53. The device of any of the embodiments herein, particularly example 52, wherein at least a portion of the deflector optical axis is curved.

[0434] Example 54. A device described in any of the examples herein, particularly any one of Examples 52-53, wherein the deflector optical axis is Ω-shaped.

[0435] Example 55. An apparatus described in any of the embodiments herein, particularly any one of embodiments 52-54, wherein each of the first electrostatic prism, the second electrostatic prism, the third electrostatic prism, and the fourth electrostatic prism is configured to deflect the charged particle beam at an angle equal to or approximately equal to 90 degrees.

[0436] Example 56. The apparatus of any of the embodiments herein, particularly any one of embodiments 52-55, wherein the second electrostatic prism and the third electrostatic prism are fixedly coupled to one another.

[0437] Example 57. A device described in any of the examples herein, particularly any one of Examples 52-56, wherein the first electrostatic prism and the fourth electrostatic prism are fixedly coupled to each other.

[0438] Example 58. A device described in any of the embodiments herein, particularly any one of embodiments 52-57, wherein one or more of the first electrostatic prism, the second electrostatic prism, the third electrostatic prism, or the fourth electrostatic prism is a bifocal prism.

[0439] Example 59. An apparatus described in any of the embodiments herein, particularly any one of embodiments 52 to 58, wherein a plurality of electrostatic multipole elements are arranged in a mirror symmetric configuration about a mid-plane position of the deflector optical axis within the deflector assembly.

[0440] Example 60. A device described in any of the embodiments herein, particularly example 59, wherein the second multipole element is a central multipole element positioned proximate to a mid-plane position of the deflector optical axis within the deflector assembly, and the first multipole element and the third multipole element are arranged in a mirror symmetric configuration around the second multipole element.

[0441] Example 61. An apparatus described in any of the embodiments herein, particularly any one of embodiments 52-60, wherein the deflector assembly is configured to generate a linear focus of the charged particle beam, and the second multipole element is positioned adjacent to a position along the deflector optical axis corresponding to the linear focus of the charged particle beam.

[0442] Example 62. The apparatus of any of the embodiments herein, particularly any one of embodiments 52-61, wherein the first multipole element is further configured to generate a first element quadrupole field and the third multipole element is further configured to generate a third element quadrupole field.

[0443] Example 63. The deflector assembly, during use in the operation of the device, the first hexapole field and the first elementary quadrupole field at least partially overlap; The apparatus of any embodiment herein, particularly embodiment 62, wherein the third hexapole field and the third element quadrupole field are configured to at least partially overlap.

[0444] Example 64. A device described in any of the embodiments herein, particularly any one of embodiments 52-63, wherein each of the first multipole element, the second multipole element, and the third multipole element is an adjustable multipole element.

[0445] Example 65. A plurality of electrostatic multipole elements, a fourth multipole element configured to generate a fourth hexapole field; a fifth multipole element configured to generate a fifth hexapole field; and The device of any embodiment herein, particularly any one of embodiments 52 to 64, further comprising:

[0446] Example 66. The apparatus of any of the embodiments herein, particularly example 65, wherein the fourth multipole element and the fifth multipole element are arranged in a mirror symmetric configuration around the second multipole element.

[0447] Example 67. The apparatus of any of the embodiments herein, particularly any one of embodiments 65-66, wherein the fourth multipole element is further configured to generate a fourth element quadrupole field and the fifth multipole element is further configured to generate a fifth element quadrupole field.

[0448] Example 68. The apparatus of any of the embodiments herein, particularly example 67, wherein the fourth hexapole field and the fourth element quadrupole field at least partially overlap, and the fifth hexapole field and the fifth element quadrupole field at least partially overlap.

[0449] Example 69. A device described in any of the embodiments herein, particularly any one of embodiments 65-68, wherein each of the fourth multipole element and the fifth multipole element is an adjustable multipole element.

[0450] Example 70. A plurality of electrostatic multipole elements, a fourth multipole element configured to generate a fourth element quadrupole field; a fifth multipole element configured to generate a fifth element quadrupole field; The device of any embodiment herein, particularly any one of embodiments 52 to 64, further comprising:

[0451] Example 71. The apparatus of any of the embodiments herein, particularly example 70, wherein each of the fourth multipole element and the fifth multipole element is an adjustable multipole element.

[0452] Example 72. A plurality of electrostatic multipole elements are a sixth multipole element configured to generate a sixth element quadrupole field; a seventh multipole element configured to generate a seventh element quadrupole field; an eighth multipole element configured to generate an eighth element quadrupole field; a ninth multipole element configured to generate a ninth element quadrupole field; The device of any embodiment herein, particularly any one of embodiments 52 to 71, further comprising:

[0453] Example 73. The apparatus of any of the embodiments herein, particularly example 72, wherein each of the sixth multipole element, the seventh multipole element, the eighth multipole element, and the ninth multipole element is a fixed multipole element.

[0454] Example 74. An apparatus described in any of the embodiments herein, particularly any one of embodiments 72-73, wherein the first electrostatic prism comprises a sixth multipole element and a seventh multipole element.

[0455] Example 75. A device described in any of the embodiments herein, particularly any one of embodiments 72-74, wherein each of the sixth multipole element and the seventh multipole element is coupled to a first electrostatic prism.

[0456] Example 76. A device described in any of the embodiments herein, particularly any one of embodiments 72-75, wherein the fourth electrostatic prism comprises an eighth multipole element and a ninth multipole element.

[0457] Example 77. A device described in any of the embodiments herein, particularly any one of embodiments 72-76, wherein each of the eighth multipole element and the ninth multipole element is coupled to a fourth electrostatic prism.

[0458] Example 78. A charged particle microscope system, comprising: a charged particle source configured to emit a charged particle beam toward the sample; an optical column configured to focus the charged particle beam onto the sample; A charged particle microscope system, wherein the optical column comprises an apparatus according to any of the embodiments herein, in particular any one of embodiments 1 to 77.

[0459] Example 79. A charged particle microscope system, comprising: a charged particle source configured to emit a charged particle beam; an optical column configured to direct the charged particle beam towards the sample; A charged particle microscope system, wherein the optical column comprises a multipole objective lens comprising a plurality of objective multipole elements, the optical column being configured to at least partially correct spherical aberration of the charged particle beam.

[0460] Example 80. The charged particle microscope system of any of the embodiments herein, particularly example 79, further comprising a multipole capacitor having one or more capacitor quadrupole generating elements.

[0461] Example 81. One or more capacitor quadrupole generating elements include: a first capacitor quadrupole generating element configured to generate a first capacitor quadrupole field; a second capacitor quadrupole generating element disposed downstream of the first capacitor quadrupole generating element and configured to generate a second capacitor quadrupole field; The charged particle microscope system of any embodiment herein, particularly embodiment 80, comprising:

[0462] Example 82. A charged particle microscope system as described in any of the examples herein, particularly any one of Examples 81-82, wherein the multipole condenser is positioned upstream of the multipole objective lens.

[0463] Example 83. A plurality of objective lens multipole elements, at least three quadrupole generating elements; at least three octupole generating elements; A charged particle microscope system according to any embodiment of the present specification, particularly any one of embodiments 79 to 82, comprising:

[0464] Example 84. The charged particle microscope system of any of the embodiments herein, particularly example 83, wherein the octupole generating element is configured to at least partially correct spherical aberration of the charged particle beam.

[0465] Example 85. A charged particle microscope system described in any of the embodiments herein, particularly any one of embodiments 79 to 84, wherein each objective lens multipole element among the plurality of objective lens multipole elements is characterized by a multipole element inner diameter indicating the maximum diameter of the charged particle beam passing through the multipole element, and the multipole element inner diameter of each objective lens multipole element is at most 5 millimeters (mm).

[0466] Example 86. A charged particle microscope system as described in any of the embodiments herein, particularly any one of embodiments 79 to 85, wherein the charged particle source is configured to emit a charged particle beam having an acceleration voltage that is one or more of at least 200 volts (V), at least 1,000 V, at least 5,000 V, at least 10,000 V, at least 20,000 V, at least 50,000 V, up to 100,000 V, up to 30,000 V, up to 15,000 V, up to 7,000 V, up to 2,000 V, or up to 500 V.

[0467] Example 87. A charged particle microscope system as described in any of the examples herein, particularly any one of examples 79-86, wherein the optical column is configured such that the charged particle beam lacks a midpoint intersection between the multipole condenser and the multipole objective lens.

[0468] Example 88. A charged particle microscope system as described in any of the embodiments herein, particularly any one of embodiments 79 to 87, wherein the charged particle beam comprises a linear combination of a first elementary light component measured along a first direction perpendicular to an optical column axis along which the charged particle beam moves through the optical column, and a second elementary light component measured along a second direction perpendicular to each of the optical column axis and the first direction, and the charged particle microscope system is configured such that for a portion of the charged particle beam extending through the multipole objective lens, the magnitude of the first elementary light component is greater than or equal to the magnitude of the second elementary light component.

[0469] Example 89. A charged particle microscope system described in any of the examples herein, particularly any one of examples 79 to 88, wherein the optical column is configured such that the charged particle beam enters the multipole objective lens with a non-circular beam profile.

[0470] Example 90. A charged particle microscope system described in any of the examples herein, particularly any one of examples 79 to 89, wherein the optical column is configured such that the charged particle beam exits the multipole objective lens with a non-circular beam profile.

[0471] Example 91. A charged particle microscope system as described in any of the examples herein, particularly any one of examples 79-90, wherein the plurality of objective lens multipole elements comprises exactly three quadrupole generating elements.

[0472] Example 92. A charged particle microscope system as described in any of the embodiments herein, particularly any one of embodiments 79 to 91, wherein exactly three objective lens multipole elements of the plurality of objective lens multipole elements are configured to generate quadrupole field components.

[0473] Example 93. A charged particle microscope system described in any of the embodiments herein, particularly any one of embodiments 79 to 92, wherein at least one objective lens multipole element of the plurality of objective lens multipole elements has an electrode formed as a microelectromechanical system (MEMS).

[0474] Example 94. A plurality of objective lens multipole elements, a first objective multipole element configured to generate a first objective multipole field; a second objective multipole element disposed downstream of the first objective multipole element and configured to generate a second objective multipole field; a third objective multipole element disposed downstream of the second objective multipole element and configured to generate a third objective multipole field; A charged particle microscope system as described in any embodiment of the present specification, particularly any one of embodiments 79 to 93, comprising:

[0475] Example 95. A charged particle microscope system as described in any of the embodiments herein, particularly example 94, wherein the first objective lens multipole field includes a first objective lens quadrupole field component and a first objective lens octopole field component, the second objective lens multipole field includes a second objective lens quadrupole field component and a second objective lens octopole field component, and the third objective lens multipole field includes a third objective lens quadrupole field component and a third objective lens octopole field component.

[0476] Example 96. A charged particle microscope system as described in any of the examples herein, particularly any one of Examples 94-95, wherein one or more of the first objective lens multipole element, the second objective lens multipole element, or the third objective lens multipole element have four electrodes shaped to generate an octupole field and a quadrupole field.

[0477] Example 97. A charged particle microscope system as described in any of the examples herein, particularly any one of Examples 94-96, wherein the third objective lens multipole element has eight electrodes.

[0478] Example 98. A charged particle microscope system as described in any of the embodiments herein, particularly any one of embodiments 94-97, wherein one or more of the first objective lens multipole element, the second objective lens multipole element, or the third objective lens multipole element have electrodes formed as a microelectromechanical system (MEMS).

[0479] Example 99. A charged particle microscope system as described in any of the embodiments herein, particularly any one of embodiments 94 to 98, wherein the multiple objective lens multipole elements further include a fourth objective lens multipole element arranged downstream of the third objective lens multipole element and configured to generate a fourth objective lens multipole field, wherein the first objective lens multipole field includes a first objective lens quadrupole field component and a first objective lens octupole field component, the second objective lens multipole field includes a second objective lens octupole field component, the third objective lens multipole field includes a third objective lens quadrupole field component and a third objective lens octupole field component, and the fourth objective lens multipole field includes a fourth objective lens quadrupole field component.

[0480] Example 100. The charged particle microscope system of any of the embodiments herein, particularly example 99, wherein the fourth objective lens multipole element comprises eight electrodes.

[0481] Example 101. A charged particle microscope system described in any of the examples herein, particularly any one of examples 79 to 100, wherein the optical column further includes a chromatic aberration corrector disposed between the multipole condenser and the multipole objective lens.

[0482] Example 102. A charged particle microscope system as described in any embodiment herein, particularly example 101, wherein the chromatic aberration corrector comprises an apparatus as described in any embodiment herein, particularly any one of examples 1 to 77.

[0483] Example 103. A charged particle microscope system described in any of the examples herein, particularly any one of examples 79 to 102, wherein the charged particle beam is a first charged particle beam and the charged particle microscope is further configured to emit a second charged particle beam toward the sample.

[0484] Example 104. A charged particle microscope system as described in any embodiment herein, particularly example 103, wherein the charged particle microscope is configured such that the first charged particle beam and the second charged particle beam approach the sample along non-parallel directions.

[0485] Example 105. A charged particle microscope system described in any of the examples herein, particularly any one of examples 103-104, wherein the second charged particle beam has a conical beam profile as the second charged particle beam approaches the sample, and the first charged particle beam has a tapered, non-circular beam profile as the first charged particle beam approaches the sample.

[0486] Example 106. A multipole element comprising: a plurality of electrodes defining a central bore therebetween, the central bore extending at least partially along the beam axis; a multipole element, each electrode of the plurality of electrodes having a respective electrode active surface facing a central bore, the plurality of electrodes comprising a first shape subset of electrodes and a second shape subset of electrodes, the electrode active surface of each electrode of the first shape subset of electrodes having a first active surface shape when viewed along a direction parallel to the beam axis, and the electrode active surface of each electrode of the second shape subset of electrodes having a second active surface shape when viewed along a direction parallel to the beam axis that is different from the first active surface shape.

[0487] Example 107. A multipole element as described in any of the embodiments herein, particularly example 106, wherein the multiple electrodes extend away from the central bore such that the multipole element has a first dimension measured along a first direction perpendicular to the beam axis, the first dimension being smaller than a second dimension of the multipole element measured along a second direction perpendicular to each of the beam axis and the first direction.

[0488] Example 108. A multipole element as described in any of the embodiments herein, particularly example 107, wherein the ratio of the second dimension to the first dimension is one or more of at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, or at most 1.3:1.

[0489] Example 109. A multipole element described in any of the examples herein, particularly any one of examples 106-108, wherein the plurality of electrodes extend away from the central bore along a plane at least substantially perpendicular to the beam axis.

[0490] Example 110. A multipole element as described in any of the embodiments herein, particularly any one of embodiments 106-109, wherein each electrode of the plurality of electrodes comprises a respective electrode extension extending away from the respective electrode active surface and configured to supply a voltage to the respective electrode active surface, the plurality of electrodes comprising a first side subset of electrodes and a second side subset of electrodes, wherein for each electrode of the first side subset of electrodes, the electrode extension extends away from the electrode active surface along a first lateral direction, and for each electrode of the second side subset of electrodes, the electrode extension extends away from the electrode active surface along a second lateral direction opposite the first lateral direction.

[0491] Example 111. A multipole element as described in any of the embodiments herein, particularly example 110, wherein for each electrode of the plurality of electrodes, the electrode extension has an electrical contact position configured to be coupled to an electrical lead to supply a voltage to the electrode active surface.

[0492] Example 112. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 111, wherein a plurality of electrodes extend away from the central bore partially along a radial direction perpendicular to the beam axis and partially along an axial direction parallel to the beam axis.

[0493] Example 113. A multipole element extends along a direction parallel to a beam axis between a proximal end region adjacent to a central bore and a distal end region distal to the central bore, the multipole element being: a first diameter measured along a direction perpendicular to the beam axis at the proximal end region; a second diameter measured along a direction perpendicular to the beam axis at the distal end region; The multipole element of any embodiment herein, particularly any one of embodiments 106-112, wherein the first diameter is smaller than the second diameter.

[0494] Example 114. A multipole element as described in any of the embodiments herein, particularly example 113, wherein the ratio of the second diameter to the first diameter is one or more of at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, or at most 1.3:1.

[0495] Example 115. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 114, wherein each electrode of the plurality of electrodes has a respective electrode extension extending away from the respective electrode active surface and configured to supply a voltage to the respective electrode active surface, and for each electrode, each electrode extension extends away from the electrode active surface along a direction angled relative to each of a radial direction perpendicular to the beam axis and an axial direction parallel to the beam axis.

[0496] Example 116. A multipole element as described in any of the embodiments herein, particularly example 115, wherein for each electrode of the plurality of electrodes, the electrode extension has an electrical contact position configured to be coupled to an electrical lead to supply a voltage to the electrode active surface.

[0497] Example 117. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 116, wherein the multipole element is configured to generate one or more of a quadrupole electrostatic field, a hexapole electrostatic field, an octupole electrostatic field, or a dodecapole electrostatic field within the central bore.

[0498] Example 118. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106-117, wherein the plurality of electrodes is composed of one of four electrodes, six electrodes, and eight electrodes.

[0499] Example 119. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 118, wherein the plurality of electrodes comprises exactly four electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0500] Example 120. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 118, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0501] Example 121. A multipole element as described in any of the embodiments herein, particularly example 120, wherein the multipole element is configured to generate a quadrupole electrostatic field with an associated parasitic duodecapolar electrostatic field, such that the duodecapolar to quadrupole component ratio characterizing the duodecapolar and quadrupole electrostatic fields generated by the multipole element is one or more of at most 0.1, at most 0.05, at most 0.01, or at least 0.001.

[0502] Example 122. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106-118 and 120-121, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0503] Example 123. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 118, wherein the plurality of electrodes comprises exactly 16 electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0504] Example 124. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 123, wherein each of the first shape subset of electrodes and the second shape subset of electrodes includes an equal number of electrodes.

[0505] Example 125. A multipole element described in any of the embodiments herein, particularly any one of embodiments 106 to 124, wherein the electrodes of the first shaped subset of electrodes are circumferentially interleaved with the electrodes of the second shaped subset of electrodes.

[0506] Example 126. A multipole element described in any of the examples herein, particularly any one of examples 106 to 125, wherein the electrode active surface of each electrode of the first shape subset of electrodes is wider than the electrode active surface of each electrode of the second shape subset of electrodes.

[0507] Example 127. A multipole element, comprising: a plurality of electrodes defining a central bore therebetween, the central bore extending at least partially along the beam axis; A multipole element in which a plurality of electrodes extend away from a central bore partially along a radial direction perpendicular to the beam axis and partially along an axial direction parallel to the beam axis.

[0508] Example 128. A multipole element extends along a direction parallel to the beam axis between a proximal end region adjacent to the central bore and a distal end region distal to the central bore, the multipole element being: a first diameter measured along a direction perpendicular to the beam axis at the proximal end region; a second diameter measured along a direction perpendicular to the beam axis at the distal end region; The multipole element of any embodiment herein, particularly embodiment 127, wherein the first diameter is smaller than the second diameter.

[0509] Example 129. A multipole element as described in any of the embodiments herein, particularly example 128, wherein the ratio of the second diameter to the first diameter is one or more of at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, or at most 1.3:1.

[0510] Example 130. Each electrode of the plurality of electrodes is a respective electrode active surface facing the central bore; a respective electrode extension extending away from the respective electrode active surface and including an electrical contact location configured to be coupled to an electrical lead to supply a voltage to the respective electrode active surface; The multipole element of any embodiment herein, particularly any one of embodiments 127-129, wherein the electrode active surface of each electrode is offset from the electrical contact location along an axial direction parallel to the beam axis.

[0511] Example 131. A multipole element, a first dimension measured along a first direction perpendicular to the beam axis and seen along the beam axis; a second dimension measured along a second direction perpendicular to each of the beam axis and the first direction and seen along the beam axis; The multipole element of any embodiment herein, particularly any one of embodiments 127-130, wherein the first dimension is smaller than the second dimension.

[0512] Example 132. A multipole element described in any of the embodiments herein, particularly any one of embodiments 127 to 131, wherein the multipole element is configured to generate one or more of a quadrupole electrostatic field, a hexapole electrostatic field, an octupole electrostatic field, or a dodecapole electrostatic field within the central bore.

[0513] Example 133. A multipole element described in any of the examples herein, particularly any one of examples 137-132, wherein the plurality of electrodes is composed of one of four electrodes, six electrodes, and eight electrodes.

[0514] Example 134. A multipole element described in any of the embodiments herein, particularly any one of embodiments 127 to 133, wherein the plurality of electrodes comprises exactly four electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0515] Example 135. A multipole element described in any of the embodiments herein, particularly any one of embodiments 127 to 133, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0516] Example 136. A multipole element as described in any of the embodiments herein, particularly example 135, wherein the multipole element is configured to generate a quadrupole electrostatic field with an associated parasitic duodecapolar electrostatic field, such that the duodecapolar to quadrupole component ratio characterizing the duodecapolar and quadrupole electrostatic fields generated by the multipole element is one or more of at most 0.1, at most 0.05, at most 0.01, or at least 0.001.

[0517] Example 137. A multipole element described in any of the embodiments herein, particularly any one of embodiments 127 to 133 and 136, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0518] Example 138. A multipole element described in any of the embodiments herein, particularly any one of embodiments 127 to 133, wherein the plurality of electrodes comprises exactly 16 electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0519] Example 139. A multipole element as described in any of the embodiments herein, particularly any one of embodiments 127-138, wherein each electrode of the plurality of electrodes has a respective electrode active surface facing the central bore, the plurality of electrodes having a first shaped subset of electrodes and a second shaped subset of electrodes, the electrode active surface of each electrode of the first shaped subset of electrodes having a first active surface shape when viewed along a direction parallel to the beam axis, and the electrode active surface of each electrode of the second shaped subset of electrodes having a second active surface shape when viewed along a direction parallel to the beam axis that is different from the first active surface shape.

[0520] Example 140. The multipole element of any of the embodiments herein, particularly example 139, wherein the first shape subset of electrodes and the second shape subset of electrodes each include an equal number of electrodes.

[0521] Example 141. A multipole element described in any of the embodiments herein, particularly any one of embodiments 139-140, wherein the electrodes of a first shaped subset of electrodes are circumferentially interleaved with the electrodes of a second shaped subset of electrodes.

[0522] Example 142. A multipole element, a plurality of electrodes disposed about and defining a central bore; Each electrode of the plurality of electrodes is a respective electrode active surface facing the central bore; a respective electrode extension extending away from the respective electrode active surface and configured to apply a voltage to the respective electrode active surface; Equipped with a multipole element, the plurality of electrodes comprising a first side subset of electrodes and a second side subset of electrodes, wherein for each electrode of the first side subset of electrodes, an electrode extension extends away from the electrode active surface along a first lateral direction, and for each electrode of the second side subset of electrodes, an electrode extension extends away from the electrode active surface along a second lateral direction opposite the first lateral direction.

[0523] Example 143. A multipole element as described in any of the embodiments herein, particularly example 142, wherein the electrode extensions of the electrodes of a subset on a first side of the electrodes extend and terminate at a first side region of the multipole element, and the electrode extensions of the electrodes of a subset on a second side of the electrodes extend and terminate at a second side region of the multipole element, the first side region and the second side region being disposed on opposite sides of a central bore.

[0524] Example 144. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142-143, wherein for each electrode of the plurality of electrodes, the electrode extension has an electrical contact position configured to be coupled to an electrical lead to supply a voltage to the electrode active surface.

[0525] Example 145. The multipole element of any example herein, particularly any one of examples 142-144, wherein the first transverse direction and the second transverse direction are at least substantially anti-parallel to each other.

[0526] Example 146. A multipole element described in any embodiment herein, particularly any one of embodiments 142 to 145, wherein the multipole element is configured to receive a charged particle beam traveling along a beam axis extending through the central bore, and each of the first transverse direction and the second transverse direction is at least substantially perpendicular to the beam axis.

[0527] Example 147. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 146, wherein the multipole element is configured to receive a charged particle beam traveling along a beam axis extending through the central bore, and each of the first transverse direction and the second transverse direction is angled with respect to each of a radial direction perpendicular to the beam axis and an axial direction parallel to the beam axis.

[0528] Example 148. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142-147, wherein the first transverse direction and the second transverse direction extend along opposite directions with respect to the beam axis, and the first transverse direction and the second transverse direction extend away from the central bore partially along an axial direction parallel to the beam axis.

[0529] Example 149. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 148, wherein the multiple electrodes extend away from the central bore such that the multipole element has a first dimension measured along a first direction perpendicular to the beam axis, the first dimension being smaller than a second dimension of the multipole element measured along a second direction perpendicular to each of the beam axis and the first direction.

[0530] Example 150. A multipole element as described in any of the embodiments herein, particularly example 149, wherein the ratio of the second dimension to the first dimension is one or more of at least 1.2:1, at least 1.5:1, at least 2:1, at least 2.5:1, at least 3:1, at most 4:1, at most 2.7:1, at most 2.3:1, at most 1.7:1, or at most 1.3:1.

[0531] Example 151. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 150, wherein the multipole element is configured to generate one or more of a quadrupole electrostatic field, a hexapole electrostatic field, an octupole electrostatic field, or a dodecapole electrostatic field within the central bore.

[0532] Example 152. A multipole element according to any of the embodiments herein, particularly any one of embodiments 142-151, wherein the plurality of electrodes is comprised of one of four electrodes, six electrodes, and eight electrodes.

[0533] Example 153. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 152, wherein the plurality of electrodes comprises exactly four electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0534] Example 154. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 152, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate a quadrupole electrostatic field within the central bore.

[0535] Example 155. A multipole element as described in any of the embodiments herein, particularly example 154, wherein the multipole element is configured to generate a quadrupole electrostatic field with an associated parasitic duodecapolar electrostatic field, such that the duodecapolar to quadrupole component ratio characterizing the duodecapolar and quadrupole electrostatic fields generated by the multipole element is one or more of at most 0.1, at most 0.05, at most 0.01, or at least 0.001.

[0536] Example 156. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142-152 and 154-155, wherein the plurality of electrodes comprises exactly eight electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0537] Example 157. A multipole element described in any of the embodiments herein, particularly any one of embodiments 142 to 152, wherein the plurality of electrodes comprises exactly 16 electrodes and the multipole element is configured to generate an octupole electrostatic field within the central bore.

[0538] Example 158. A multipole element as described in any of the embodiments herein, particularly any one of embodiments 142 to 157, wherein each electrode of the plurality of electrodes has a respective electrode active surface facing the central bore, the plurality of electrodes having a first shaped subset of electrodes and a second shaped subset of electrodes, the electrode active surface of each electrode of the first shaped subset of electrodes having a first active surface shape when viewed along a direction parallel to the beam axis, and the electrode active surface of each electrode of the second shaped subset of electrodes having a second active surface shape when viewed along a direction parallel to the beam axis that is different from the first active surface shape.

[0539] Example 159. A multipole element as described in any of the embodiments herein, particularly example 158, wherein the first shape subset of electrodes and the second shape subset of electrodes each include an equal number of electrodes.

[0540] Example 160. A multipole element described in any of the embodiments herein, particularly any one of embodiments 158-159, wherein the electrodes of a first shaped subset of electrodes are circumferentially interleaved with the electrodes of a second shaped subset of electrodes.

[0541] Example 161. A charged particle microscope system, comprising: a charged particle source configured to emit a charged particle beam; an optical column configured to direct the charged particle beam at the sample; A charged particle microscope system, wherein the optical column comprises a multipole element according to any of the embodiments herein, particularly any one of embodiments 106 to 160.

[0542] Example 162. A charged particle microscope system as described in any of the embodiments herein, particularly example 161, wherein the optical column is configured to at least partially correct spherical aberration of the charged particle beam.

[0543] Example 163. A charged particle microscope system described in any one of the embodiments herein, particularly any one of embodiments 161 to 162, wherein the optical column comprises a multipole objective lens having a multipole element described in any one of the embodiments herein, particularly any one of embodiments 106 to 160.

[0544] Example 164. A multipole objective lens, a plurality of multipole elements axially aligned with respect to a beam axis; A multipole objective lens, comprising a plurality of multipole elements configured to focus a charged particle beam at a target focal position, the plurality of multipole elements including proximal multipole elements that are closer to the target focal position than the remaining multipole elements and spaced apart from the target focal position by a working distance, the plurality of multipole elements being completely contained within a first angular envelope defined in a first plane including the beam axis, the first angular envelope defining a range of a first angle of a maximum of 50 degrees, while the working distance is a maximum of 10 mm.

[0545] Example 165. A multipole objective lens as described in any embodiment herein, particularly example 164, wherein the plurality of multipole elements comprises at least three multipole elements, each of which is configured to generate a respective quadrupole electrostatic field and a respective octupole electrostatic field.

[0546] Example 166. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164-165, wherein the plurality of multipole elements comprises at least four multipole elements, at least three multipole elements of the plurality of multipole elements are configured to generate respective quadrupole electrostatic fields, and at least three multipole elements of the plurality of multipole elements are configured to generate respective octupole electrostatic fields.

[0547] Example 167. A multipole objective lens as described in any embodiment herein, particularly example 166, wherein at least two multipole elements of the plurality of multipole elements are configured to generate a respective quadrupole electrostatic field and a respective octupole electrostatic field.

[0548] Example 168. A multipole objective lens described in any of the examples herein, particularly any one of examples 164 to 167, wherein each pair of adjacent multipole elements of the plurality of multipole elements is separated by a respective multipole element gap that is one or more of at least 0.2 mm, at least 0.5 mm, at least 1 mm, at most 1.5 mm, at most 0.7 mm, or at most 0.3 mm.

[0549] Example 169. A multipole objective lens described in any of the examples herein, particularly any one of examples 164 to 168, wherein each multipole element of the plurality of multipole elements has a respective multipole element length, measured along a direction parallel to the beam axis, that is one or more of at least 2 mm, at least 5 mm, at least 10 mm, at most 15 mm, at most 10 mm, at most 7 mm, or at most 3 mm.

[0550] Example 170. A multipole objective lens as described in any of the embodiments herein, particularly example 169, wherein each multipole element of the plurality of multipole elements has a respective central region defining a central bore through which the beam axis extends, and the multipole element length of each multipole element is measured in its respective central region.

[0551] Example 171. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164 to 170, wherein the multipole elements include a distal multipole element that is distal to the target focal position relative to the remaining multipole elements, and the multipole elements have a stack length between the proximal and distal multipole elements, measured along a direction parallel to the beam axis, that is one or more of at least 15 mm, at least 20 mm, at least 25 mm, at least 30 mm, at least 35 mm, at least 40 mm, at most 50 mm, at most 37 mm, at most 32 mm, at most 27 mm, at most 22 mm, or at most 17 mm.

[0552] Example 172. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164 to 171, wherein a plurality of multipole elements are configured to operate as an objective lens to focus a charged particle beam at a target focal position with a third-order spherical aberration of up to 1 mm.

[0553] Example 173. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164 to 172, wherein the multiple multipole elements are completely contained within a second angular envelope defined in a second plane that includes the beam axis and is perpendicular to the first plane, the second angle range being substantially equal to the first angle while the working distance is at most 10 mm.

[0554] Example 174. The multipole objective lens of any embodiment herein, particularly example 173, wherein the second angle is at most 50 degrees.

[0555] Example 175. A multipole objective lens described in any embodiment herein, particularly any one of embodiments 164 to 174, further comprising a lens housing surrounding the multiple multipole elements, wherein the portion of the lens housing surrounding the multiple multipole elements is in the shape of a cone or a frustum of a cone.

[0556] Example 176. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164 to 175, wherein the multiple multipole elements are completely contained within a second angular envelope defined in a second plane that includes the beam axis and is perpendicular to the first plane, the second angle being greater than the first angle while the working distance is at most 10 mm.

[0557] Example 177. A multipole objective lens described in any of the embodiments herein, particularly any one of embodiments 164 to 176, further comprising a lens housing surrounding the multiple multipole elements, the portion of the lens housing surrounding the multiple multipole elements encompassing the beam axis and having a greater angular extent in a second plane perpendicular to the first plane than in the first plane.

[0558] Example 178. An apparatus comprising: a charged particle source configured to emit a charged particle beam; an optical column configured to direct the charged particle beam at least partially along a beam axis to a target focal position; Equipped with An apparatus, wherein the optical column comprises a multipole objective lens according to any one of the embodiments herein, particularly any one of embodiments 164 to 177.

[0559] Example 179. Any of the embodiments herein, particularly the apparatus of example 178, wherein the charged particle beam is a first charged particle beam, the beam axis is a first beam axis, and the apparatus is configured to direct a second charged particle beam at least partially along a second beam axis to a target focal position, the second charged particle beam extending within the excluded region, and the multipole objective lens is positioned completely outside the excluded region.

[0560] Example 180 The device of any embodiment herein, particularly example 179, wherein the excluded region comprises a conical region.

[0561] Example 181. The apparatus of any of the examples herein, particularly any one of examples 179-180, wherein the second charged particle beam at least partially defines the excluded region.

[0562] Example 182. The apparatus described in any of the embodiments herein, particularly any one of embodiments 179 to 181, wherein the optical column is a first optical column and the apparatus further comprises a second optical column configured to direct the second charged particle beam to a target focal position, the second optical column at least partially defining the excluded region.

[0563] Example 183. An apparatus described in any of the embodiments herein, particularly any one of embodiments 179-182, wherein the target focus position corresponds to a position on the sample, and the sample partially defines the excluded region.

[0564] Example 184. A device described in any of the examples herein, particularly any one of examples 179-183, wherein the excluded region at least partially defines the first angular envelope.

[0565] Example 185. The apparatus of any of the embodiments herein, particularly any one of embodiments 179-184, wherein the first angular envelope indicates an area completely outside the excluded area.

[0566] Example 186. The apparatus of any of the embodiments herein, particularly any one of embodiments 179-185, wherein the first charged particle beam is a focused ion beam and the second charged particle beam is an electron beam.

[0567] Example 187. A method of assembling and / or operating a device according to any embodiment herein, particularly any one of Examples 1-77 or Examples 178-186.

[0568] Example 188. A method of assembling and / or operating a charged particle microscope system described in any of the examples herein, particularly any one of Examples 78 to 105 or Examples 161 to 163.

[0569] Example 189. A method of assembling and / or operating a multipole element according to any of the embodiments herein, particularly any one of embodiments 106-160 or embodiments 164-177.

[0570] In view of the many possible implementations to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are merely preferred examples and should not be construed as limiting the scope. Rather, the scope of the disclosed technology is defined by the following claims. Accordingly, applicant claims all that comes within the scope of those claims.

Claims

1. 1. An apparatus comprising: a plurality of electrodes disposed about and defining a central bore, the central bore extending at least partially along a beam axis; 11. An apparatus comprising: an optical fiber array including a first shape subset of electrodes and a second shape subset of electrodes, the first shape subset of electrodes having a first active surface shape when viewed along a direction parallel to the beam axis, and the second shape subset of electrodes having a second active surface shape when viewed along a direction parallel to the beam axis that is different from the first active surface shape.

2. 10. The apparatus of claim 1, wherein the plurality of electrodes comprises exactly eight electrodes, the apparatus being configured to generate a quadrupole electrostatic field within the central bore.

3. 3. The apparatus of claim 2, wherein the apparatus is configured to generate the quadrupole electrostatic field with an associated parasitic duodecapolar field, such that a duodecapolar to quadrupole component ratio characterizing the duodecapolar and quadrupole electrostatic fields generated by the apparatus is at most 0.

1.

4. The device of claim 1 , wherein the electrode active surface of each electrode of the first shape subset of electrodes is wider than the electrode active surface of each electrode of the second shape subset of electrodes.

5. 2. The device of claim 1, wherein the first shaped subset of electrodes and the second shaped subset of electrodes each include an equal number of electrodes, and the electrodes of the first shaped subset of electrodes are circumferentially interleaved with the electrodes of the second shaped subset of electrodes.

6. 1. An apparatus comprising: a plurality of electrodes disposed about and defining a central bore; Each electrode of the plurality of electrodes is a respective electrode active surface facing said central bore; a respective electrode extension extending away from said respective electrode active surface and configured to apply a voltage to said respective electrode active surface; Equipped with a device, the plurality of electrodes comprising a first side subset of electrodes and a second side subset of electrodes, wherein for each electrode of the first side subset of electrodes, the electrode extension extends away from the electrode active surface along a first lateral direction, and for each electrode of the second side subset of electrodes, the electrode extension extends away from the electrode active surface along a second lateral direction opposite the first lateral direction of the device.

7. 7. The device of claim 6, wherein the electrode extensions of the electrodes of a first side subset of the electrodes extend and terminate at a first side region of the device and the electrode extensions of the electrodes of a second side subset of the electrodes extend and terminate at a second side region of the device, the first side region and the second side region being disposed on opposite sides of the central bore.

8. The apparatus of claim 6 , wherein the first lateral direction and the second lateral direction are at least substantially anti-parallel to one another.

9. 7. The apparatus of claim 6, wherein the apparatus is configured to receive a charged particle beam traveling along a beam axis extending through the central bore, and wherein each of the first lateral direction and the second lateral direction are angled with respect to each of a radial direction perpendicular to the beam axis and an axial direction parallel to the beam axis.

10. 7. The apparatus of claim 6, wherein the plurality of electrodes extend away from the central bore such that the apparatus has a first dimension measured along a first direction perpendicular to a beam axis extending through the central bore that is smaller than a second dimension of the apparatus measured along a second direction perpendicular to each of the beam axis and the first direction.

11. 11. The apparatus of claim 10, wherein a ratio of the second dimension to the first dimension is at least 1.5:1 and at most 4:

1.

12. 1. An apparatus comprising: a charged particle source configured to emit a charged particle beam; an optical column configured to direct the charged particle beam at least partially along a beam axis; 11. The apparatus of claim 1, wherein the optical column comprises a plurality of multipole elements axially aligned with respect to the beam axis, the plurality of multipole elements configured to focus the charged particle beam at a target focal position, the plurality of multipole elements comprising proximal multipole elements proximal to the target focal position relative to remaining multipole elements and spaced apart from the target focal position by a working distance, the plurality of multipole elements being completely contained within a first angular envelope defined in a first plane including the beam axis, the first angular envelope defining a first angular range of up to 50 degrees, the working distance being up to 10 mm.

13. The proximal multipole element comprises a plurality of electrodes defining a central bore therebetween, the central bore extending at least partially along the beam axis, the plurality of electrodes extending away from the central bore partially along a radial direction perpendicular to the beam axis and partially along an axial direction parallel to the beam axis, each electrode of the plurality of electrodes comprising: a respective electrode active surface facing said central bore; a respective electrode extension extending away from the respective electrode active surface and including an electrical contact location configured to be coupled to an electrical lead to supply a voltage to the respective electrode active surface; The apparatus of claim 12 , wherein the electrode active surface of each electrode is offset from the electrical contact location along the axial direction.

14. The proximal multipole element extends along a direction parallel to the beam axis between a proximal end region proximal to the central bore and a distal end region distal to the central bore, the proximal multipole element comprising: a first diameter measured along a direction perpendicular to the beam axis at the proximal end region; a second diameter measured along a direction perpendicular to the beam axis at the distal end region; The apparatus of claim 13 , wherein the first diameter is smaller than the second diameter.

15. 14. The device of claim 13, wherein the proximal multipole element comprises exactly eight electrodes configured to generate a quadrupole electrostatic field with an associated parasitic duodecapolar field, such that the duodecapolar and quadrupole electrostatic fields generated by the device are characterized by a duodecapolar to quadrupole component ratio of at most 0.

1.

16. 15. The apparatus of claim 14, wherein the plurality of multipole elements comprises at least four multipole elements, at least three multipole elements of the plurality of multipole elements configured to generate respective electrostatic quadrupole fields and at least three multipole elements of the plurality of multipole elements configured to generate respective electrostatic octopole fields.

17. 17. The apparatus of claim 16, wherein at least two multipole elements of the plurality of multipole elements are configured to generate each a respective electrostatic quadrupole field and a respective electrostatic octupole field.

18. (i) each pair of adjacent multipole elements of the plurality of multipole elements is separated by a respective multipole element gap that is at least 0.5 mm and at most 1.5 mm; (ii) each multipole element of the plurality of multipole elements has a respective multipole element length, measured along a direction parallel to the beam axis, that is at least 2 mm or at most 10 mm, or both; or (iii) the plurality of multipole elements comprises a distal multipole element that is distal to the target focal position relative to the remaining multipole elements, the plurality of multipole elements having a stack length, measured along a direction parallel to the beam axis between the proximal and distal multipole elements, that is at least 15 mm or at most 37 mm, or both; 15. The apparatus of claim 14, wherein the one or more of:

19. 15. The apparatus of claim 14, further comprising a lens housing surrounding the plurality of multipole elements, a portion of the lens housing surrounding the plurality of multipole elements containing the beam axis and having a greater angular extent in a second plane perpendicular to the first plane than in the first plane.

20. 15. The apparatus of claim 14, wherein the charged particle beam is a first charged particle beam, the beam axis is a first beam axis, the apparatus is configured to direct a second charged particle beam at least partially along a second beam axis to the target focal position, the second charged particle beam extending within an excluded region that at least partially defines the first angular envelope, and the plurality of multipole elements are positioned entirely outside of the excluded region.

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