Electromagnetic lenses and charged particle optical devices

Abstract

To provide an electromagnetic lens which includes permanent magnets but allows for adjusting the optical properties with high precision.SOLUTION: A fine-adjustable electromagnetic lens for a charged-particle optical apparatus comprises: a magnetic circuit assembly including one or more ring magnets; and a sleeve insert of generally rotational symmetry around a longitudinal axis. The sleeve insert comprises several electrically conductive electrode elements configured to generate an electrostatic field within a passage opening. The ring magnets are arranged circumferentially around an inner yoke shell and surrounded by an outer yoke shell; the inner yoke shell surrounds a central portion of the sleeve insert. The ring magnets are magnetized such that the two magnetic poles are oriented towards the inner and outer yoke shell, respectively. The shells form a magnetic circuit having at least one gap, in order to generate a magnetic field spatially overlapping with the electrostatic field generated by the sleeve insert.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] This application claims the benefit of Paris Convention priority of European Patent Application No. 21185599.4, filed July 14, 2021, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to an electromagnetic lens configured to modify a charged particle beam of a charged particle optical device for lithographic imaging and similar processing purposes, including nanopatterning. Such a lens provides a passage for the charged particle beam along a longitudinal direction, which may correspond to the propagation direction of the charged particle beam itself and which will typically be aligned concentrically with the optical axis of the charged particle optical device. The present invention also relates to a charged particle optical device including an electromagnetic lens of the above type. [Background technology]

[0003] The applicant has already realized charged particle multi-beam devices including one or more of the above-mentioned types of electromagnetic lenses, has already developed corresponding charged particle optical components, pattern definition devices and writing methods for the multiple beams, and has already marketed a 50 keV electron multi-beam writer called eMET (electron Mask Exposure Tool) or MBMW (multi-beam mask writer) that is used to realize any photomask for 193 nm immersion lithography, any mask for EUV lithography and any template for nanoimprint lithography. The applicant's system is also called PML2 (Projection Mask-Less Lithography) for electron beam direct writer (EBDW) applications on substrates.

[0004] To increase throughput in mass industrial production, particularly for maskless lithography and direct writing to substrates (e.g., wafers), it is necessary to increase the current carried by the charged particle beam passing through a charged particle nanopatterning device; this usually comes at the expense of limited resolution due to Coulomb interactions between the charged particles, and requires corresponding compensation by reducing the magnitude of optical aberrations introduced by the device through other mechanisms. To this end, applicant has already developed a charged particle multi-beam device comprising multiple parallel optical columns combined in a multi-column manner, each column having a reduced (“slim”) cross-sectional diameter. Such a multi-beam device, one embodiment of which is discussed below with reference to FIG. 4, allows for significantly higher charged particle beam currents while overcoming the limitations imposed by the trade-off between current and optical aberrations found in single-column systems. This is due to the fact that the total current delivered to the target is split among multiple optical axes, while the resolution limit is governed by the amount of current per optical axis. Single columns of this type are well known in the prior art, such as in the applicant's US Pat. No. 6,768,125, EP 2 187 427 A1 (=US Pat. No. 8,222,621) and EP 2 363 875 A1 (=US Pat. No. 8,378,320). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] US 6,768,125 [Patent Document 2] EP 2 187 427 A1 [Patent Document 3] US 8,222,621 [Patent Document 4] EP 2 363 875 A1 [Patent Document 5] US 8,378,320 [Patent Document 6] US 7,067,820 [Patent Document 7] US 9,165,745 Summary of the Invention [Problem to be solved by the invention]

[0006] A typical multi-column system includes multiple optical subcolumns, each of which includes an illumination system that delivers a broad, telecentric charged particle beam to a pattern definition system followed by a downstream charged particle projection optics system, e.g., including multiple electrostatic and / or electromagnetic lenses. To use such a system as a high-throughput direct-write wafer system, a significant number of subcolumns—e.g., on the order of 100—must be positioned above a single semiconductor wafer. However, this requires each subcolumn to have a diameter that is a fraction of the wafer width, e.g., 31 mm or less for a 300 mm (12-inch) wafer. On the other hand, slim-diameter magnetic lenses cannot be realized by coil-type magnetic lenses to generate the desired magnetic field because a reduction in the column diameter would result in significant Joule heating due to the large currents required to drive the coils to generate significantly stronger magnetic fields. Due to tight space requirements, there is insufficient space for a suitable temperature control system, including a high-precision sensor and isotropic, uniform cooling, as would be required for a traditional coil-type magnetic lens. Furthermore, the tight space requirements, which arise from the target diameter of the slim columns and their placement in a suitable multi-column system, would preclude the fabrication of a suitable coil-type magnetic lens. While the above limitations, determined by thermal and geometric requirements, are severe, they can be overcome by employing a magnetic lens based on permanent magnets inside a highly permeable housing body to generate a magnetic field, as in possible embodiments of the present invention. However, such permanent magnet systems cannot be recalibrated after the manufacturing and assembly process is complete. This represents a serious disadvantage compared to coil-type magnetic lenses, whose magnetic field can be controlled by readjusting the current flowing through the coil, especially considering the inherent limitations on the precision of the target magnetic field based on manufacturing and assembly accuracy.The current precision limit corresponds to approximately ±1.0% deviation from the target magnetic field, which cannot be compensated for without some additional components that allow compensation for the lack of required magnetic field precision.

[0007] Electromagnetic lenses based on permanent magnets and highly permeable housing bodies combined with electrostatic elements for fine adjustment are known in the prior art, such as US 7,067,820, but they do not include high-precision adjustment means such as multipoles or charged particle collection calibration apertures, and therefore cannot provide means for changing the beam shape, calibrating its position, and generating a desired pattern. US 9,165,745 describes a permanent magnet-type electromagnetic lens combined with a coil-type magnetic lens for fine adjustment, but this has the thermal and geometric problems mentioned above. Furthermore, the magnetic fields of the above prior art magnetic lenses are poorly confined to the space of the lens itself, which causes serious cross-effects when multiple lenses are placed side by side.

[0008] In view of the above, it is an object of the present invention to provide an electromagnetic lens that includes a permanent magnet but allows for high precision adjustment of optical properties (e.g., focal length), while at the same time limiting the effects of stray magnetic fields. [Means for solving the problem]

[0009] According to a first aspect of the present invention, there is provided an electromagnetic lens configured to modify a charged particle beam of a charged particle optical device, the electromagnetic lens having a passage hole extending along a longitudinal axis and allowing the passage of the charged particle beam. The electromagnetic lens is a magnetic circuit assembly including at least one ring magnet and a yoke body; and Sleeve insert Including, the sleeve insert surrounds the passage hole and extends along the longitudinal axis between a first end and a second end of the passage hole, the sleeve insert including at least one conductive electrode element, each electrode element configured to receive a respective electrical potential (voltage) via a power source to generate an electrostatic field within the passage hole; the yoke body includes an outer yoke shell and an inner yoke shell, the outer yoke shell being circumferentially arranged about the longitudinal axis and including a magnetically permeable material, the inner yoke shell being arranged to surround at least a central portion of the sleeve insert, and the outer yoke shell surrounding the inner yoke shell and the sleeve insert; the at least one ring magnet is disposed around the inner yoke shell and between the inner yoke shell and the outer yoke shell, the at least one ring magnet including a permanent magnetic material magnetically oriented such that one of its two magnetic poles faces the inner yoke shell and the other faces the outer yoke shell; In the magnetic circuit assembly, the inner yoke shell, the at least one ring magnet, and the outer yoke shell form a closed magnetic circuit, and the closed magnetic circuit has at least two gaps positioned at axial ends of the inner yoke shell facing the corresponding portions of the outer yoke shell, extending radially inward into the passage hole and configured to generate a magnetic field that spatially overlaps with the electrostatic field generated by the electrode element of the sleeve insert. (Form 1). According to a second aspect of the invention, there is provided a charged particle optical device including an electromagnetic lens according to the invention, adapted to influence a charged particle beam of the device propagating through said electromagnetic lens along a longitudinal axis of the device. An apparatus is provided, comprising: The electromagnetic lens is part of the projection optical system of the device (Mode 15) . According to a third aspect of the present invention there is provided a charged particle optical apparatus including an electromagnetic lens according to the present invention configured to influence a charged particle beam of the apparatus propagating through the electromagnetic lens along a longitudinal axis of the apparatus.The charged particle device is a multi-column system including a plurality of particle optical columns, each of which uses a respective particle beam and includes a respective projection optical system including a respective electromagnetic lens (see form). 16 ). DETAILED DESCRIPTION OF THE INVENTION

[0010] (Mode 1) See the first aspect of the present invention above. (Feature 2) In the electromagnetic lens of feature 1, the magnetic circuit has two gaps; the two gaps are respectively positioned at axial ends of the inner yoke shell facing the corresponding portions of the outer yoke shell, each gap generates a defined magnetic field directed radially inward into the passage hole; Preferably, the electrostatic field generated by at least one of the electrode elements of the sleeve insert is configured to at least partially overlap with the magnetic field. (Form 3) Form 1 of In an electromagnetic lens, the electromagnetic lens has a generally rotationally symmetric shape along the longitudinal axis; The inner yoke shell and the outer yoke shell are preferably concentric with each other. (Form 4) Form 1 of In an electromagnetic lens, the inner yoke shell extends between its two axial ends along a passage space that receives the sleeve insert; It is preferable that the outer yoke shell surrounds the inner yoke shell radially outward of the inner yoke shell and extends to each side corresponding to the two axial ends of the inner yoke shell. (Form 5) Form 1 of In an electromagnetic lens, Preferably, the at least one ring magnet has a substantially radially oriented magnetization. (Form 6) Form 1 of In an electromagnetic lens, Preferably, said at least one ring magnet is made up of two or more layers stacked along said longitudinal axis. (Form 7) Form 1 of In an electromagnetic lens, The at least one ring magnet is composed of three or more sectors evenly spaced circumferentially around the longitudinal axis. 、 before Preferably, the (magnet) sectors are substantially wedge-shaped elements (thicker in a V-shape in cross section but without a sharp tip) that form sectors (divided radially around the longitudinal axis) relative to the longitudinal axis. (Form 8) Form 1 of In an electromagnetic lens, The electrode elements are or each gap configured to form a particle-optical lens in cooperation with the magnetic field within the passage hole; Preferably, the focal length of the particle-optical lens is adjustable by varying the electrical potential (voltage) applied to the electrode elements. (Form 9) Form 1 of In an electromagnetic lens, Preferably, the electrode elements are configured to form at least one single lens. (Form 10) Form 1 of In an electromagnetic lens, At least one of the electrode elements preferably comprises an electrostatic multipole electrode including a plurality of sub-electrodes evenly spaced circumferentially around the longitudinal axis. (Form 11) Form 1 of In an electromagnetic lens, Preferably, the electrode elements include a beam aperture element that forms a demarcating opening having a defined diameter about the longitudinal axis, the demarcating opening limiting the lateral width of the charged particle beam propagating along the longitudinal axis. (Feature 12) In the electromagnetic lens of feature 11, The beam aperture element is preferably connected to a current measuring device which measures the amount of charged particle beam absorbed in the beam aperture element. (Form 13)Form 1 1 of In an electromagnetic lens, a plurality of sub-electrodes disposed circumferentially evenly around the longitudinal axis in front of the beam aperture element as viewed in the direction of propagation of the beam along the longitudinal axis; ,before Preferably, electrostatic multipole electrodes are arranged to determine the lateral (radial) position of the beam relative to the longitudinal axis. (Form 14) Form 1 of In an electromagnetic lens, The sleeve insert preferably includes a ceramic body having disposed thereon electrode elements configured as conductive coatings each having a defined shape and area. (Mode 15) See the second aspect of the present invention above. (Mode 16) See the third aspect of the present invention above.

[0011] The above-mentioned problems are solved by an electromagnetic lens configured to modify (e.g., shape, focus / defocus, or otherwise manipulate) a charged particle beam of a charged particle optical device. The electromagnetic lens has a passage hole extending along a longitudinal axis and allowing the passage of the charged particle beam, the electromagnetic lens including a magnetic circuit assembly including at least one ring magnet and a yoke body, and a sleeve insert, the sleeve insert surrounding the passage hole and extending along the longitudinal axis between a first end and a second end of the passage hole, the sleeve insert including one or more, preferably at least two, conductive electrode elements configured to have respective electric potentials (voltages) applied thereto (relative to an electric potential of the housing equal to earth potential) to generate an electrostatic field inside the passage hole, the yoke body including an outer yoke shell and an inner yoke shell, circumferentially arranged about the longitudinal axis and including a magnetically permeable material, the inner yoke shell being arranged to surround at least a central portion of the sleeve insert, the outer yoke shell being arranged to surround at least a central portion of the inner yoke shell and the sleeve insert, The sleeve insert includes a magnetic circuit assembly, in which at least one ring magnet is disposed around the inner yoke shell and between the inner yoke shell and the outer yoke shell, the at least one ring magnet including a permanent magnetic material magnetically oriented such that one of its two magnetic poles faces the inner yoke shell and the other faces the outer yoke shell, and in the magnetic circuit assembly, the inner yoke shell, the at least one ring magnet, and the outer yoke shell form a closed magnetic circuit, the closed magnetic circuit being positioned at axial ends of the inner yoke shell facing the corresponding (inner surface) portions of the outer yoke shell, and having at least one gap, preferably at least two gaps, configured to generate a defined magnetic field that extends radially inward and reaches into the passage hole and spatially overlaps with an electrostatic field generated by the electrode elements of the sleeve insert.

[0012] In many embodiments, the sleeve insert includes at least two conductive electrode elements, the electrical potential (voltage) applied to these electrode elements can be defined relative to the housing or other external component and / or relative to each other.

[0013] Thus, an electromagnetic lens according to the present invention may include (1) a magnetic circuit assembly and (2) an electrostatic inlay. The magnetic circuit assembly (1) generates a static magnetic field capable of exerting a lensing effect on a charged particle beam propagating through the electromagnetic lens. The magnetic circuit assembly includes one or more cylindrical permanent magnets, preferably stacked concentrically along the optical axis of the system and housed within a housing body made of a highly permeable material, and configured to direct magnetic field lines to a target portion of the optical axis, i.e., a defined portion of the passage hole, particularly a portion corresponding to one, two, or more gaps provided in the housing body. The (2) electrostatic inlay is provided to generate an electric field that can be used to fine-tune the lensing effect of the electromagnetic lens on the transverse charged particle beam, and, if desired, to change the shape and deflection of the particle beam relative to the optical axis, and possibly to correct optical aberrations introduced by the electromagnetic lens itself and / or the charged particle beam optics in which it is to be incorporated. Furthermore, a wiring system can be used to connect the elements of the electrostatic inlay, such as the liner and multipole rods, to external power supply units for individual voltage adjustment to operate the electromagnetic lens.

[0014] The inlay according to the present invention allows for the generation of an electrostatic field superimposed on the magnetic field, thus compensating for the deviation of the magnetic field from the design (target) by enabling in-situ fine tuning of the focal length of the (electromagnetic) lens with high precision, e.g., on the order of 10 ppm or less, and control of certain properties of the charged particle beam, such as shape and optical aberrations. Thus, the present invention significantly facilitates the layout, assembly, fine tuning and control of writer tools, especially multi-column multi-beam mask writer tools.

[0015] Unlike U.S. Pat. No. 9,165,745, the electromagnetic lens of the present invention has a completely closed magnetic loop except for some air gaps in the housing body, which allows the magnetic field to be concentrated in a desired region of the optical axis, thereby significantly reducing the effects of stray fields that degrade the performance of electromagnetic lenses such as those employed in charged particle multi-beam nanopatterning devices. This fact can be easily understood in terms of Ampere's circuital law. According to Ampere's law, the line integral of the magnetic field around a closed curve is proportional to the total current flowing across the surface enclosed by such a closed curve, which is equal to zero in a current-free system, since permanent magnets are also used here. Therefore, by using (at least) two gaps on the optical axis and by using a layout that generates two (or more) magnetic fields that act as magnetic lenses in these regions and are sharply (narrowly) confined in opposite directions in the axial direction, the layout satisfies Ampere's law without producing additional undesired stray fields. In contrast, for a single-gap layout that generates only one axial magnetic field that is sharply (narrowly) confined in one direction along the optical axis, Ampere's law predicts the existence of additional axial stray magnetic fields in the opposite direction along the optical axis. These fields are problematic in charged particle optics because they are not sharply confined in space and therefore cause undesired interactions with the beam and therefore aberrations in the system. Therefore, a layout in which the generated axial magnetic fields along the longitudinal direction intentionally cancel each other out minimizes the presence of stray magnetic fields. Otherwise, the stray magnetic fields would affect not only each sub-column but possibly adjacent sub-columns as well, thereby causing non-rotationally symmetric distortions in the entire system, which would make the system unsuitable for the industrial high-tech node-precision imaging quality requirements.This approach to minimizing stray magnetic fields is not taken in the prior art systems mentioned above.

[0016] For at least the above reasons, the present invention and its application in writer tools such as multi-column, multi-beam charged particle nanopatterning systems for direct writing of substrates offers a unique combination of magnetic, electrical, and calibration components that is expected to have a significant impact on the development of high throughput industrial processes for integrated circuits.

[0017] In many embodiments, the magnetic circuit has two gaps located at the axial ends of the inner yoke shell facing respective portions of the outer yoke shell, each gap generating a defined magnetic field that reaches radially inward into the passage hole and spatially overlaps with the electrostatic field generated by the electrode elements of the sleeve insert, although it will be apparent that the number of gaps may be greater, such as three, four, five, or more, depending on the industrial application of the electromagnetic lens.

[0018] Advantageously, the electromagnetic lens often has a generally rotationally symmetric shape along its longitudinal axis; The inner and outer yoke shells will be concentric with each other.

[0019] According to one preferred geometric layout, the inner yoke shell may extend between its two axial ends along a passage space that receives the sleeve insert, and the outer yoke shell may surround the inner yoke shell radially outward from the inner yoke shell while extending to each side that corresponds to the two axial ends of the inner yoke shell.

[0020] In many embodiments, at least one ring magnet may have a substantially radially oriented magnetization and / or may be realized as a radially magnetized ring magnet. Furthermore, at least one ring magnet may be composed of three or more (e.g., four, six, or eight) magnet segments uniformly distributed circumferentially around the longitudinal axis. While ring magnets generally have the shape of a hollow cylinder or hollow polygonal prism, at least one ring magnet may have a generally ring shape with multiple ring segments distributed circumferentially around the longitudinal axis; this may also include gaps with some angular extension between the ring segments. For example, the magnet segments may be substantially wedge-shaped elements forming sectors (radially divided about the longitudinal axis) relative to the longitudinal axis (where "substantially" means, for example, that the tapered shape formed by the two sides toward the central axis of the hollow cylinder lacks a portion corresponding to the hollow space of the hollow cylinder). Alternatively or in combination with this, the ring magnet (or some or all of the magnet portions) may be made up of two or more layers (segments) stacked (placed one above the other) along the longitudinal axis.

[0021] In one highly advantageous aspect of the invention, the electrode elements may be configured to form a particle-optical lens in cooperation with the magnetic field inside the passage hole at one of the gaps, at each one of some of the gaps, or preferably at each gap, and in the case of multiple gaps, a particle-optical lens may be formed at each of these gaps. The focal length of such particle-optical lens(es) may be adjusted by modifying (changing) the electrical potential applied to the electrode elements. For example, the electrode elements may often be configured (mechanically and electrically) to form at least one simple lens (Einzel lens).

[0022] Furthermore, in many embodiments of the present invention, at least one of the electrode elements may include an electrostatic multipole electrode including a plurality of sub-electrodes uniformly spaced circumferentially around the longitudinal axis.

[0023] In many embodiments of the (electromagnetic) lens of the present invention, particularly when the (electromagnetic) lens is intended for use in conjunction with a PD system, there may be a beam aperture element between (surrounded by) the electrode elements, forming a delimiting opening with a defined radius about the longitudinal axis, which limits the lateral width of the charged particle beam propagating along the longitudinal axis. This delimiting opening may be used as a particle collection calibration aperture used to collect particles, including intentionally deflected particles, in the PD system to prevent the deflected particles from reaching the charged particle beam target. Furthermore, the beam aperture element may be connected to a current measurement device, which may be used, for example, to measure the amount of charged particle beam absorbed in the beam aperture element. It is often advantageous to provide an electrostatic multipole electrode in front of the beam aperture element, as seen in the direction of propagation of the beam along the longitudinal axis, comprising a plurality of sub-electrodes evenly spaced circumferentially around the longitudinal axis, preferably configured to determine the lateral (radial) position of the beam relative to the longitudinal axis by applying different appropriate electrostatic potentials to the sub-electrodes.

[0024] In advantageous embodiments, the sleeve insert may comprise a ceramic body on which are arranged electrode elements, each realized as a conductive coating having a defined shape and area.

[0025] A further aspect of the present invention is a charged particle optical apparatus including an electromagnetic lens according to the present invention, configured to influence a charged particle beam of the apparatus propagating through the electromagnetic lens along a longitudinal axis of the apparatus, the electromagnetic lens being directed towards a device forming part of a projection optical system of the apparatus. In particular, the charged particle optical apparatus may preferably realize a multi-column system including a plurality of particle optical columns, each particle optical column using a respective particle beam and including a respective electromagnetic lens, and at least one, preferably some, and most preferably all, of the plurality of particle optical columns including a respective projection optical system.

[0026] To further explain the present invention, exemplary and non-limiting embodiments illustrated in the drawings will now be discussed. [Brief explanation of the drawings]

[0027] [Figure 1] 1 is a longitudinal sectional view of an example of an electromagnetic lens according to a first embodiment of the present invention. [Figure 2] Intensity of the axial component of an example of the magnetic field (solid line) and electric field (dashed line) at the position of the central axis c1 as a function of the ordinate; the ordinate is the same (in particular the same scale) as in FIG. [Figure 3] 2 is an enlarged detail view of an example of a calibration aperture and an upstream multipole as components of a sleeve insert of the electromagnetic lens of FIG. 1; [Figure 3A] FIG. 10 is an enlarged detail view of the lower portion of an example sleeve insert in one variation that includes a corrective liner that allows for variation of optical aberrations. [Figure 4] 2 is a cross-sectional view of an example multi-column writer tool including multiple embodiments of the electromagnetic lens of FIG. 1; [Figure 5] FIG. 1 is a cross-sectional view of an example of a multipole electrode having eight sub-electrodes. [Figure 5A] FIG. 10 is an enlarged detail view of an example of a gap region between two rods of the plurality of rods. [Figure 6] FIG. 10 is a perspective view of a variation of a multipole electrode having four sub-electrodes. [Figure 7] 2 is a schematic overview of an example of voltage supplies connected to sleeve insert elements of the electromagnetic lens of FIG. 1; [Figure 8] 1 shows an embodiment of a ring magnet consisting of ring elements with radial magnetization: (A) perspective view; (B) longitudinal cross section; (C) transverse cross section. [Figure 9] FIG. 10 is a cross-sectional view of one embodiment of a segmented ring magnet. [Figure 10] FIG. 10 is a cross-sectional view of a further embodiment of a segmented ring magnet. [Figure 11] FIG. 10 is a cross-sectional view of another embodiment of a divided ring magnet. [Example]

[0028] The detailed discussion of exemplary embodiments of the present invention provided below discloses the basic idea, implementation, and further advantageous developments of the present invention. It should be clear to those skilled in the art to combine any or all of the embodiments discussed herein as deemed suitable for a particular application of the present invention. Throughout this disclosure, terms such as "advantageous," "exemplary," or "preferred" refer to elements or dimensions that are particularly suitable (but not essential) for the present invention or an embodiment thereof, and can be modified, unless explicitly required, if deemed suitable by those skilled in the art. It is understood that the present invention is not limited to the exemplary embodiments discussed below, which are provided for illustrative purposes and merely present preferred embodiments of the present invention. Within the scope of this disclosure, terms relating to the vertical (perpendicular) direction, such as "up" or "down," should be understood as referring to the direction of a particle beam traversing an electromagnetic lens, which is considered to travel downward ("vertically") along the central (or vertical) axis. This vertical axis is generally identical to the Z direction, which is intersected by the X and Y directions.

[0029] Electromagnetic Lens

[0030] FIG. 1 illustrates an example of an electromagnetic lens 10 according to a first embodiment of the present invention in longitudinal section, i.e., in (along) a section passing through (including) its central axis c1. For clarity, components are not drawn to scale. When used as an objective lens, lens 10 may be used to embody the final lens 414 of writer tool 401 of FIG. 4 (see below), but it should be appreciated that lens 10 is also suitable for use in many other particle-optical devices that may embody multi-column or single-column architectures such as those disclosed in applicant's U.S. Pat. Nos. 9,443,699 and 9,495,499, the disclosures of which are incorporated herein by reference.

[0031] The electromagnetic lens 10 includes a magnetic circuit assembly 11 and a sleeve insert 12, also referred to as a beam control inlay or simply "inlay." The magnetic circuit assembly 11 includes one or more ring magnets 101, 102 made of permanent magnetic material, each having an outer radius of 10-13 mm, a radial thickness of 2-5 mm, and a length of approximately 25 mm, typically resulting in a remanence of 1 T; and a housing body 13, which also serves as a yoke body for the ring magnets. Such a housing body is composed of two concentric cylinders with an inner radius of approximately 5 mm and an outer radius of approximately 15 mm, each having a thickness of 2-5 mm and a length of 50 mm-100 mm. The sleeve insert 12, also referred to as a beam control inlay or simply "inlay," has an outer diameter of less than 5 mm and a length of 1 mm-20 mm, and includes several electrically active and passive components that function as electrostatic electrodes, apertures, or field-termination caps, as discussed in detail below. Electromagnetic lens 10 is typically disposed in a particle beam exposure system (such as writer tool 401 in FIG. 4) so ​​that its central axis c1 coincides with the optical axis of the exposure system; however, those skilled in the art will recognize that other relative positions may be selected depending on the application of the electromagnetic lens according to the present invention. Dashed line 100 indicates the envelope of a particle beam as it propagates through electromagnetic lens 10 within a particle beam exposure system.

[0032] Magnetic Circuit Assembly

[0033] The magnetic circuit assembly 11 is discussed below. The housing body 13 includes inner and outer portions, referred to as the inner yoke shell 103 and outer yoke shell 104, respectively. The outer yoke shell 104 completely surrounds the ring magnets 101 and 102, the inner yoke shell 103, and the inlay 12 when assembled into the electromagnetic lens 10. The ring magnets 101 and 102 and the housing body 13 are all concentric about a central axis c1. The ring magnets 101 and 102 preferably have the shape of rotationally symmetric rings or ring sectors. The size of the ring magnets is selected as appropriate for the respective application and charged particle device; in the illustrated embodiments, the geometric dimensions are typically on the order of a few millimeters (e.g., outer radius 12 mm, thickness 3 mm, length approximately 25 mm). Multiple magnets may also be used, preferably arranged in a stacked configuration along the longitudinal axis of the system (FIG. 8A).

[0034] In a preferred embodiment of the present invention, the permanent magnets constituting the ring magnets 101, 102 exhibit radial magnetization (see the discussion below regarding Figures 8 and 9). The ring magnets function as a magnetic flux source for the magnetic circuit implemented in the magnetic circuit assembly 11. The inner yoke shell 103 is implemented (configured), for example, as a hollow cylinder having a length sufficient to protrude at both ends from the stacked ring magnets. The outer yoke shell 104 is implemented (configured), for example, to have a cylindrically symmetric shape with two U-shaped longitudinal cross sections. In other words, the outer yoke shell 104 includes a central body portion 143 configured as a hollow cylinder concentric with the hollow cylinder of the inner yoke shell 103 but with a larger radius, and two disk-shaped end portions 141, 142 with a central hole connected to both longitudinal ends of the central body portion 143. The central hole of each end portion 141, 142 preferably has an inner radius equal to the inner radius of the hollow cylinder body of the inner yoke shell 103. Thus, the central holes and the hollow space of the inner yoke shell enclose a passage space 200 (with a radius r1) that crosses the magnetic circuit assembly 11 along the central axis c1. The geometric dimensions of the hollow cylinder portions 103, 143 are appropriately selected so that they radially surround the magnets 101, 102 inward and outward; these cylinder portions advantageously contact the corresponding faces of the magnets to minimize or preferably avoid gaps between the magnets and the corresponding surface areas of the cylinder bodies. On the other hand, gaps 14a, 14b are formed between the end faces 103a, 103b of the inner yoke shell, which represent the pole pieces of the magnetic circuit 11, and the corresponding inner faces 141a, 142b of the end portions of the outer yoke shell. The radial thickness of the hollow cylinders is typically, and without loss of generality (and without limitation thereto), on the order of a few millimeters.The inner yoke shell 103 and the outer yoke shell 104 of the housing body 13 are made of a magnetically permeable material (such as a ferrimagnetic or ferromagnetic material), preferably with high magnetic permeability; the housing body 13, based on its shape, is able to intensify and focus the magnetic flux generated by the magnet. Around the area of ​​the gaps 14a, 14b, the magnetic flux of the magnetic circuit will also form a defined magnetic field of the magnetostatic type that reaches the passage space 200 radially inward at certain portions of the central axis c1. Thus, according to the present invention, the housing body functions as the yoke of a magnetic lens, the distribution of which magnetic flux is formed by the pole pieces 103a, 103b, 141a, 142b. In particular, with respect to the passage space 200, the magnetic field generated by the magnetic circuit 11 is limited to two regions: an upper region within the gap 14a formed by the pole piece faces 103a and 141a; and a lower region within the gap 14b formed by the pole piece faces 103b and 142b. Thus, two magnetic lenses are formed in the portions of the longitudinal axis corresponding to the gaps 14a and 14b, respectively. The magnetic field includes an axial component and a radial component; while the radial component is of little importance, the magnetic field B. Z The resulting axial component is used for the lensing effect of the electromagnetic lens. The magnetic field B at the position of the central axis c1 as a function of the ordinate Z The magnitude (intensity) 201 of the axial component of the magnetic field B is shown in FIG. 2 (solid line). ZTypical values ​​for the peak value of πf are on the order of 0.1 T in applications where the charged particles are electrons. The magnetic circuit thus forms two regions with (fairly) high magnetic field strengths, which act as two consecutive magnetic lenses with well-defined focal lengths and optical aberrations. The magnetic coupling of the two magnetic lenses via the common yoke 13 greatly reduces the effects of stray magnetic fields in regions other than the regions of the gaps 14a, 14b, but would otherwise be necessarily associated with permanent magnets in a particle lens of traditional layout.

[0035] Inlay

[0036] The magnetic lens 10 further includes a sleeve insert or inlay 12 that is inserted into the passage space 200 of the housing body 13 along the optical axis c1. Accordingly, the physical dimensions of the inlay 12 are appropriately selected with respect to the housing body 13 as described above. The inlay 12 includes a plurality of beam control elements, including one or several electrically active elements, that are used to generate an adjustable electrostatic field 202 (dashed lines in FIG. 2 ) that superimposes a static magnetic field 201 (solid lines in FIG. 2 ) in the passage space. The beam control elements are generally ring-shaped components that function as electrically active elements, stacked along a central axis c1, oriented with their geometric axes (lines) concentric and parallel to the central axis c1, and have a common inner radius r2; thus, the beam control elements define a passage hole 120 that traverses the lens 10 along the central axis c1 and functions as a channel for the beam path during operation of the magnetic lens. In the embodiment shown in Figure 1, the beam control elements include, from the bottom of the page, a first liner 106, two multipole electrodes 108, 110, and a second liner 112, all made of a conductive material. Each of the multipole electrodes 108, 110 is realized, for example, as a composite metal ring composed of multiple sections of equal arc length, as discussed further below with reference to Figure 6; their (radial) thickness is, for example, less than 2 mm, and their length is between 5 mm and 20 mm. Furthermore, an electrically passive ring 109 is preferably interposed between the two multipole electrodes 108, 110; this component is referred to as a calibration aperture, and will be discussed further below. The multipoles 108 and 110 are composed of a plurality of sector components (e.g., and without loss of generality (but not limited to), four, six or eight sector components, respectively) arranged circumferentially around the central axis c1, while all other inlay elements are preferably configured rotationally symmetrically with respect to the central axis c1.The electrically active elements 106, 108, 110, 112 are preferably connected to respective power supplies 726, 728, 730, 732 with electrostatic voltages so that their electrostatic potentials can be adjusted individually (FIG. 7); in a variant, the power supplies can be combined to form a common power supply providing individual supply voltages. Finally, the electrically active elements 106, 108, 110, 112 are electrically isolated from each other and terminated at both ends by elements called field termination caps 105, 107, 111, 113, which have the same electrical potential as the housing body 13. The field termination caps 105, 107, 111, 113 have the function of limiting the electric field to the interior space 120 of the inlay; they therefore provide a clearly defined "field boundary" of the inlay relative to surrounding components (such as other particle-optical columns 409, see FIG. 4). The spaces between the field termination caps 105, 107, 111, 113 and the adjacent electrically active elements 106, 108, 110, 112 are electrically insulating, realized for example as a vacuum or a filler using a non-conductive, preferably voltage-resistant, material such as ceramics. The various elements 105-113 of the inlay are supported and held together by a hollow cylindrical supporting ring body (between radii r1 and r2) and made of an electrically insulating material such as ceramic or plastic, symbolically shown by two dashed rectangles in FIG. 1. The electrode elements may be realized (embodied) as separate (discrete) ring-shaped elements joined and held together inside the ring body, or as a conductive coating formed on the inner surface of the ring body, each having a limited shape and area. Effect of the electric field E as a function of coordinate along axis c1. Z The intensity (magnitude) 202 of the electric field E Z A typical peak value of 5 It is on the order of V / m.

[0037] In one exemplary embodiment, the first liner 106 and the second liner 112 are between 2 mm and 10 mm in length and have a small radial thickness, e.g., less than 2 mm. Each liner 106, 112 is positioned corresponding to one of the magnetic flux regions of the gaps 14a, 14b, which respectively function as a magnetostatic lens. In particular, the liners 106, 112 are positioned corresponding to the magnetic flux regions of the gaps 14a, 14b that overlap the magnetic field 201, e.g., 5 The permanent magnets 101 and 102 can be used as single lenses (Einzel lenses) to generate an electrostatic field 202 on the order of V / m. This allows for fine adjustment of the focal length of the corresponding magnetic lens, thus providing the system with a certain adjustment range for the focal length. Without the liners 106 and 112, the accuracy of the focal length would be compromised by the limited precision of the mechanical manufacturing of the permanent magnets 101 and 102, the limited assembly precision, and the limited magnetization precision, which is typically on the order of 0.5% to 1%. However, for the purposes of magnetic lenses as intended by the applicant, even an accuracy of less than 0.1% would be desirable. Furthermore, permanent magnets are known to have aging effects; i.e., the magnetic field often becomes weaker over time and its strength changes depending on the temperature. Therefore, in order to use permanent magnets in charged particle optics applications, appropriate compensation means for these various effects are required. The present invention, also by including built-in correction means, makes it possible to overcome all the above limitations related to manufacturing, assembly, magnetization strength and ageing effects, since the electric field can be adjusted and controlled with precision in the parts-per-million (ppm) regime. Furthermore, the voltage of the liners can be adjusted in combination with other optical and electrical active elements of the system to change the properties of the particle beam exposure device with regard to optical aberrations and / or to change the height of the image plane generated by the magnetic lens relative to the target.

[0038] 1 and 3, the inlay 12 may preferably include a passive element called a calibration aperture 109 that functions as a stopping component for stray or deflected portions of the particle beam. FIG. 3 shows an example of a calibration aperture in enlarged detail, in longitudinal section. The calibration aperture 601 has an inner ring structure that protrudes toward the axis c1, thus forming an aperture with a small diameter d6. The aperture functions to limit the size of the beam 600 traversing the inlay 12 by absorbing the portion 606 of the beam traveling outside the diameter d6. In a preferred embodiment of the present invention, one of the leading (upstream) inlay elements, e.g., the multipole electrode 602, is configured to guide the beam 600 along a direction transverse to the axis c1 by applying a dipole field (typically using a voltage in the range of ±50 V, for example). The multipole electrode 602 allows the lateral position of the beams 600, 606 relative to the longitudinal axis c1 to be defined by varying dipole voltages applied to selected electrodes of the multipole electrode in at least two linearly independent directions, which can also be used for beam alignment. In the particle beam column of the writer tool 401, the particle beam is split into a bundle of beamlets that can selectively pass through the pattern definition system 412 with or without additional deflection introduced by the pattern definition system 412. Such deflection is introduced to prevent the beamlets from reaching the target and thus define the writing pattern. Rather than traveling through the calibration aperture 601, the deflected beamlets will reach areas beside the calibration aperture 601 and will therefore be absorbed in the calibration aperture 601 without causing unwanted charging up of other components of the system that could otherwise generate unwanted stray fields. For this purpose, the beam calibration aperture is configured, for example, as a cylinder with a hook-shaped (longitudinal) cross section, approximately 20 mm long and with a minimum diameter of a few hundred micrometers at the bottom (605).Absorption of beam portion 606 will cause the generation of an electric charge in the elements forming calibration aperture 601, which can be removed, i.e., bled off, via the electrical connections of the beam aperture, for example towards a measuring device 720 as discussed below with reference to Figure 7. The inlay 12 is normally inserted into the passage space 200 of the housing body 13 so that its longitudinal axis c3 coincides with the central axis c1 of the housing body 13.

[0039] In one variation of the inlay, one or more of the electrode elements of the inlay may be geometrically shaped so that the aberrations of the system are intentionally varied or kept constant within a defined range of applied voltages. To this end, the respective electrode(s) may have a modified shape with a tapered cross section towards the longitudinal axis, thus achieving a reduced internal diameter, and a suitable electrical potential is applied relative to earth.

[0040] FIG. 3A shows an exemplary embodiment of an inlay 12′ including a liner 212 with a reduced inner diameter. FIG. 3A shows a detail of an example of the “bottom” of the inlay 12′. Due to its reduced inner width, or diameter d3, the liner 212 allows for aberration variation. In particular, if the beam diameter in the area of ​​the liner 212 is approximately 70% or greater than the diameter d3, significant spherical aberration is generated, which can then be used to vary, for example, radial spatial or angular distortion or field curvature. In other respects, the inlay 12′ corresponds to the inlay 12 described above; in particular, the field end caps 211, 213, each with an inner diameter d2 = 2·r2 on either side of the liner 212 (above and below the plane of FIG. 3A), can be realized (configured) identically to the field end caps 111, 113.

[0041] Lithography equipment

[0042] 4 shows a schematic (longitudinal) cross-sectional view of a multi-column writer tool 401 incorporating an exemplary electromagnetic lens according to one embodiment of the present invention. The writer tool uses a charged particle beam formed from charged particles, which can be electrons or ions (e.g., positively charged ions).

[0043] The writer tool 401 includes a vacuum housing 410 for a multi-column charged particle optics 402 and a target chamber 403 in which the multi-column charged particle optics is mounted by a column base plate 404. Inside the target chamber 403 is an XY stage 405, e.g., a laser interferometer-controlled air-bearing vacuum stage, onto which a substrate chuck 406, preferably an electrostatic chuck, is mounted by a suitable handling system. The chuck 406 holds a substrate 407 that serves as a target, such as a silicon wafer with an electron or ion beam-sensitive resist layer.

[0044] The multi-column optics 402 includes multiple sub-columns 409 (the number of columns shown is reduced for clarity and represents the much larger number of columns that would be included in an actual implementation). Preferably, the sub-columns 409 have identical setups and are arranged side-by-side with their axes parallel to one another. Each sub-column has an illumination system 411 including an electron or ion source 411a, an extraction system 411b, and an electrostatic multi-electrode condenser optics 411c, which delivers a wide, telecentric charged particle beam to a reduced charged particle projection optics 416 consisting of multiple sequentially arranged electro-magneto-optical projector stages, preferably including electrostatic and / or magnetic lenses and possibly other particle-optical devices. In the embodiment shown in FIG. 4, the projection optics 416 comprises a first lens 413, which is for example an accelerating electrostatic multi-electrode lens, while a second lens 414, arranged downstream of the first lens, is realized (configured) using an electromagnetic lens according to the invention, such as lens 10 of the first embodiment (FIG. 1).

[0045] In each sub-column 409, a first lens 413 of the projection optics forms a first crossover of the particle beam, while a second lens 414 forms a second crossover. In the second lens, a beam aperture 415 (corresponding to beam aperture 605 in FIG. 3) is configured to remove beam portions that deviate from the respective optical axis due to deflection in the PD system. Each second lens 414 of a sub-column may preferably be mounted to a reference plate 417, which is attached to the column base plate 404 by suitable fixing means 418. Parts 419 of an off-axis optical alignment system are attached to the reference plate 417.

[0046] The reference plate is manufactured from a suitable raw material with low thermal expansion, such as a ceramic material based on silicon oxide or aluminum oxide, has the advantages of light weight, high modulus of elasticity and high thermal conductivity, and may be suitably coated, at least in its relevant parts, with a conductive coating to avoid charging (by allowing static charges to drain away).

[0047] The PD system 412 functions to form from the particle beam a plurality of so-called beamlets that contain information about the pattern to be transferred to the target. The structure, operation, and data processing of PD systems are described in commonly-assigned U.S. Pat. Nos. 9,443,699 and 9,495,499, the disclosures of which are incorporated herein by reference.

[0048] Multipole Electrodes

[0049] As described above, the inlay includes multipole electrodes 108 and 110. Each of the multipole electrodes 108, 110 is composed of three or more metallic ring sectorial components, hereinafter also referred to as rods, that function as electrodes (sub-electrodes) of the multipole electrode. Preferably, the rods have the same geometric shape. A depiction of an example of a multipole electrode 511 having eight rods 508 (sector electrodes) in cross section is shown in FIG. 5; FIG. 5A shows an enlarged view of the gap area between two of these rods. FIG. 6 shows a variation of a multipole electrode 540 having four sector electrodes 544. The preferred number of rods within a multipole electrode is 4, 6, 8, 12, or 16, depending on the desired effect to be achieved.

[0050] Referring to FIG. 5, rods 508 are disposed within an enclosing sleeve that functions as support member 501. Electric potentials (voltages) can be applied to rods 508 individually by respective external power supply units 728, 730 (FIG. 7). Additionally, a global offset voltage can be applied to cause them to act as additive electrostatic lenses. By applying different voltages to individual rods 508, various field configurations consisting of dipoles, quadrupoles, or higher-order electrostatic fields can be realized, thereby shaping the particle beam intersecting each corresponding transverse section of optical axis 503. For typical applications related to the embodiments of FIGS. 1-3, the voltages applied to rods 508 are typically on the order of up to several tens of volts. Such beam shaping can be used to compensate for errors due to imperfections in the optical system, such as magnetic inhomogeneities, mechanical manufacturing, and / or assembly inaccuracies. In this regard, when multipoles are used as dipoles whose orientations in the plane defined by X and Y can be arbitrary, provided that at least four different voltages are applied to the rods: +V1 (rods hatched with diagonal lines on the right hand side of FIG. 5), −V1 (rods hatched with diagonal lines on the left hand side of FIG. 5), +V2 (rods hatched with grid lines on the top side of FIG. 5), and −V2 (rods hatched with grid lines on the bottom side of FIG. 5). Additionally, when multipoles are used as quadrupoles or higher order multipoles, the multipoles can compensate for astigmatism or other higher order distortions in a manner similar to that of dipoles, by applying appropriate voltages to the individual rods. For liners 106, 112, the common offset potential of multipole electrodes 108, 110 may also be adjusted to tune the optical aberrations of the magnetic lenses formed by lens 10.The gaps 505 between the sector electrodes forming the rods 508 are advantageously bent (or zigzag-shaped, "labyrinth") so that particles 504 that deviate from the beam propagating in the central space of the multipole electrode will strike the surface of the rod but are prevented from traveling outside the multipole electrode and possibly affecting the support member 501 or other external components. Outside the rods 508, the gaps 505 form pouches whose function is to collect particles and drain their charge to a drain electrode (not shown). This helps to avoid the build-up of charges and associated stray electric fields that could otherwise affect the charged particle beam propagating through the multipole electrode 511.

[0051] Furthermore, by appropriately selecting the position and shape of the electric multipole and rods and applying a suitable common supply voltage to all the rods of the multipole electrode, it is possible to achieve a change in the focal length of one or both of the magnetic lenses corresponding to the two gaps 14a, 14b formed by the yokes.

[0052] Referring again to FIG. 1, two magnetic lenses can be advantageously used to realize the so-called crossover cv of the particle beam. In FIG. 1, the dotted (dashed) envelope 100 shows the evolution of the beam size (diameter) along the optical axis (c1). As mentioned above, a first magnetic lens is formed at the level of the first gap 14a and can be used to focus the beam so that it converges at the crossover cv, i.e., at the position or area where the beam's lateral width is at its minimum. The magnetic lens is advantageously configured to form the crossover cv at a position located at or close to the vertical position of the calibration aperture 109 (for example, 10 mm or less). The beam then expands again and traverses a second magnetic lens formed at the level of the second gap 14b, which preferably has the effect of making the beam telecentric again (with respect to the source of the particle beam). The beam therefore forms an image of the beam-shaping apertures in the PD system 412, and thus an image is generated on the target 407. It is therefore highly desirable to ensure accurate matching of the focal lengths of the two lenses for successful imaging on the target. In this sense, the liners 106, 112 are crucial elements for the correction function of the system. The focusing of the beam at the position of the calibration aperture 109 makes it particularly useful for beam alignment procedures, in which the beam 600 can be scanned across the aperture 605, while a corresponding current measurement 720 (or measurement of charge accumulation) serves to monitor the beam position in order to center the beam relative to the optical axis c1.

[0053] FIG. 7 shows a schematic overview of an example of a voltage supply 701 for an inlay 703 and a monitoring device 702 for performing current measurement 720. It should be noted that the multipole electrodes 108, 110 can be used as (quasi-)static or dynamic elements, i.e., with time-varying voltages, depending on the application. Indeed, the upper multipole electrode 108 can be used in a time-varying dipole configuration to deflect the beam during scanning across the calibration aperture 605. Furthermore, the lower multipole electrode 110 allows the beam to be correctly positioned relative to the target 407 on the moving stage 405. Those skilled in the art will appreciate that the above uses of beam control elements are mentioned as exemplary applications and not as limitations on the functionality achievable by the present invention.

[0054] Ring Magnet

[0055] FIG. 8 illustrates one embodiment of a ring magnet 80 suitable for use as a component of the magnetic circuit of a lens according to the present invention (e.g., as one of the ring magnets 101, 102 of FIG. 1). FIG. 8(A) is a schematic perspective view thereof, FIG. 8(B) is a schematic longitudinal cross-sectional view thereof along a longitudinal axis c8, and FIG. 8(C) is a corresponding schematic cross-sectional view; the dimensions are not to scale. The ring magnet 80 is composed of multiple ring magnet elements 81 stacked concentrically along a common longitudinal axis c8. Each of the ring magnet elements 81 has a radially oriented magnetization, as indicated by the dashed arrows in FIG. 8(C), so that, for example, it has a "north" pole (N) oriented toward the interior space of the ring magnet 80, while the outside exhibits a "south" pole (S) type of magnetization. Ring magnet elements with radial magnetization as shown are commercially available and are made of ferromagnetic materials such as sintered NdFeB, SmCo5 or ferrite. The ring magnet elements are bonded by gluing or crimping or any other suitable means. The number of ring magnet elements 81 in a ring magnet 80 can be any number, for example, one, two, three, four or more, depending on the dimensions of these elements (especially their height (thickness)) and the desired dimensions of the ring magnet 80.

[0056] Each ring magnet or ring magnet element may be realized (configured) by combining multiple, for example, four or eight, ring sector (partial ring) components at each level, as shown in FIGS. 9 to 11. Note that FIGS. 9 to 11 show sector-structured ring magnets in exploded views, with the respective magnetizations indicated by dashed arrows pointing from the "South" pole to the "North" pole. In particular, FIG. 9 shows a ring magnet 90 configured with eight ring sectors (partial rings) 98; FIG. 10 shows a ring magnet 91 configured with four ring sectors 94 radially magnetized with respect to a longitudinal axis c9 at the center of the ring; and FIG. 11 shows a ring magnet 99 configured with four ring sectors 95 with linear magnetizations oriented, for example, along (parallel to) the central symmetry line of each (ring sector). In these embodiments, the ring sectors are radially (FIGS. 9 and 10) or linearly (FIG. 11) magnetized to approximate an ideal radially magnetized ring magnet. Note that the gaps between the ring sectors shown in FIGS. 9-11 are shown merely for better clarity; in an actual embodiment, these gaps do not exist because the sector (partial ring) elements 98, 94, 95 are bonded by gluing, crimping, or other suitable bonding method, thereby closing or minimizing the direct contact between adjacent parts.

[0057] All or part of the above embodiments can be described as the following supplementary notes, but are not limited thereto. [Appendix 1] An electromagnetic lens configured to modify a charged particle beam in a charged particle optical device. The electromagnetic lens extends along a longitudinal axis and includes a passage aperture for permitting the passage of the charged particle beam. The electromagnetic lens includes a magnetic circuit assembly including at least one ring magnet and a yoke body, and a sleeve insert. The sleeve insert surrounds the passage hole and extends along a longitudinal axis between the first and second ends of the passage hole. The sleeve insert includes at least one conductive electrode element, each configured to receive a respective electrical potential (voltage) via a power source(s) to generate an electrostatic field within the passage hole. The yoke body includes an outer yoke shell and an inner yoke shell, the outer yoke shell being circumferentially arranged about a longitudinal axis and containing a magnetically permeable material, the inner yoke shell being disposed to surround at least a central portion of the sleeve insert, and the outer yoke shell surrounding the inner yoke shell and the sleeve insert. At least one ring magnet is disposed around the inner yoke shell and between the inner yoke shell and the outer yoke shell, and includes a permanent magnetic material magnetically oriented such that one of its two magnetic poles faces the inner yoke shell and the other faces the outer yoke shell. In the magnetic circuit assembly, the inner yoke shell, at least one ring magnet, and the outer yoke shell form a closed magnetic circuit, and the closed magnetic circuit has at least two gaps positioned at axial ends of the inner yoke shell that point toward corresponding portions of the outer yoke shell, and configured to generate a magnetic field that extends radially inward into the passage hole and spatially overlaps with the electrostatic field generated by the electrode elements of the sleeve insert. [Note 2] In the above electromagnetic lens, The magnetic circuit has two gaps. The two gaps are respectively positioned at axial ends of the inner yoke shell that face the corresponding portions of the outer yoke shell. Each gap generates a defined magnetic field that extends radially inward into the passage hole. The electrostatic field generated by at least one of the electrode elements of the sleeve insert is configured to at least partially overlap with the magnetic field. [Appendix 3] In the above electromagnetic lens, The electromagnetic lens has a generally rotationally symmetric shape along its longitudinal axis. The inner yoke shell and the outer yoke shell are concentric with each other. [Appendix 4] In the above electromagnetic lens, The inner yoke shell extends between its two axial ends along a passage space that receives the sleeve insert, and the outer yoke shell surrounds the inner yoke shell radially outward of the inner yoke shell and extends to each side that corresponds to the two axial ends of the inner yoke shell. [Appendix 5] In the above electromagnetic lens, At least one ring magnet has a magnetization oriented substantially radially. [Appendix 6] In the above electromagnetic lens, At least one ring magnet is comprised of two or more layers stacked along a longitudinal axis. [Appendix 7] In the above electromagnetic lens, At least one ring magnet is comprised of three or more sectors evenly spaced circumferentially around a longitudinal axis. Preferably, the (magnet) sectors are substantially wedge-shaped elements that form a sector relative to the longitudinal axis. [Appendix 8] In the above electromagnetic lens, The electrode elements are configured to cooperate with the magnetic field within the passage hole to form a particle-optical lens in one or more, and preferably each, of the gaps. The focal length of the particle-optical lens is adjustable by changing the electrical potential (voltage) applied to the electrode elements. [Appendix 9] In the above electromagnetic lens, The electrode elements are configured to form at least one single lens. [Appendix 10] In the above electromagnetic lens, At least one of the electrode elements includes an electrostatic multipole electrode including a plurality of sub-electrodes evenly spaced circumferentially about the longitudinal axis. [Appendix 11] In the above electromagnetic lens, The electrode elements include a beam aperture element that defines a delimiting aperture having a defined diameter about the longitudinal axis, the delimiting aperture limiting the lateral width of the charged particle beam propagating along the longitudinal axis. [Appendix 12] In the above electromagnetic lens, The beam aperture element is connected to a current measuring device that measures the amount of the charged particle beam absorbed in the beam aperture element. [Appendix 13] In the above electromagnetic lens, In front of the beam aperture element as viewed in the direction of propagation of the beam along the longitudinal axis, an electrostatic multipole electrode is arranged, which includes a plurality of sub-electrodes evenly spaced circumferentially around the longitudinal axis and is preferably configured to determine the lateral position (radial position) of the beam relative to the longitudinal axis. [Appendix 14] In the above electromagnetic lens, The sleeve insert includes a ceramic body having disposed thereon electrode elements configured as conductive coatings each having a defined shape and area. [Appendix 15] A charged particle optical device including an electromagnetic lens according to the invention, configured to influence a beam of charged particles of the device propagating through the electromagnetic lens along a longitudinal axis of the device. The electromagnetic lens forms part of the projection optical system of the device. Preferably, the apparatus is a multi-column system comprising a plurality of particle-optical columns, each particle-optical column using a respective particle beam and comprising a respective projection optical system including a respective electromagnetic lens.

[0058] Within the scope of the entire disclosure of the present invention (including the claims and drawings), modifications and adjustments of the embodiments are possible based on the basic technical concept thereof. Furthermore, within the scope of the entire disclosure of the present invention, various combinations and selections (including "non-selection") of various disclosed elements (including each element of each claim, each element of each embodiment, each element of each drawing, etc.) are possible. In other words, the present invention naturally includes various modifications and alterations that would be possible by a person skilled in the art in accordance with the entire disclosure, including the claims and drawings, and the technical concept of the present invention. In particular, with regard to the numerical ranges described herein, any numerical value or subrange included within the range should be construed as being specifically described, even if not otherwise specified.

[0059] Furthermore, the reference numerals in the drawings attached in the claims are intended solely to aid in the understanding of the invention and are not intended to limit the invention to the embodiments and examples shown.

[0060] Furthermore, the entire contents of each of the above references are incorporated herein by reference.

Claims

1. an electromagnetic lens configured to modify a charged particle beam of a charged particle optical device (401), the electromagnetic lens having a passage hole (120) extending along a longitudinal axis (c1) and allowing passage of the charged particle beam; The electromagnetic lens is a magnetic circuit assembly (11) including at least one ring magnet (101, 102) and a yoke body (13); and Sleeve insert (12) Including, the sleeve insert (12) surrounds the passage hole (120) and extends along the longitudinal axis (c1) between a first end and a second end of the passage hole (120), the sleeve insert (12) including at least one conductive electrode element (106, 108, 110, 112), each configured to receive a respective electrical potential via a power source (726, 728, 730, 732) to generate an electrostatic field within the passage hole; The yoke body (13) includes an outer yoke shell (104) and an inner yoke shell (103), which are circumferentially arranged about the longitudinal axis and contain a magnetically permeable material, the inner yoke shell is arranged to surround at least a central portion of the sleeve insert, and the outer yoke shell surrounds the inner yoke shell and the sleeve insert. the at least one ring magnet (101, 102) is arranged around the inner yoke shell and between the inner yoke shell and the outer yoke shell, and the at least one ring magnet includes a permanent magnetic material magnetically oriented so that one of its two magnetic poles faces the inner yoke shell and the other faces the outer yoke shell; In the magnetic circuit assembly (11), the inner yoke shell, the at least one ring magnet, and the outer yoke shell form a closed magnetic circuit, and the closed magnetic circuit has at least two gaps positioned at axial ends (103a, 103b) of the inner yoke shell that face the corresponding portions (141a, 142b) of the outer yoke shell, and configured to generate a magnetic field (201) that extends inward into the passage hole (120) and spatially overlaps with an electrostatic field (202) generated by the electrode element of the sleeve insert. An electromagnetic lens characterized by:

2. 2. The electromagnetic lens according to claim 1, The magnetic circuit has two gaps (14a, 14b), the two gaps are respectively positioned at axial ends of the inner yoke shell facing the corresponding portions of the outer yoke shell, Each gap generates a defined magnetic field (201) directed inwardly into the passage hole (120); the electrostatic field (202) generated by at least one of the electrode elements (106, 108, 110, 112) of the sleeve insert is configured to at least partially overlap with the magnetic field (201); An electromagnetic lens characterized by:

3. 2. The electromagnetic lens according to claim 1, the electromagnetic lens has a generally rotationally symmetric shape along the longitudinal axis (c1); The inner yoke shell and the outer yoke shell are concentric with each other. An electromagnetic lens characterized by:

4. 2. The electromagnetic lens according to claim 1, The inner yoke shell extends between its two axial ends along a passage space (200) that receives the sleeve insert; The outer yoke shell surrounds the inner yoke shell radially outward of the inner yoke shell and extends to each side corresponding to two axial ends of the inner yoke shell. An electromagnetic lens characterized by:

5. 2. The electromagnetic lens according to claim 1, the at least one ring magnet (101, 102) has a magnetization oriented substantially radially; An electromagnetic lens characterized by:

6. 2. The electromagnetic lens according to claim 1, said at least one ring magnet (101, 102) being composed of two or more layers (81) stacked along said longitudinal axis (c8); An electromagnetic lens characterized by:

7. 2. The electromagnetic lens according to claim 1, the at least one ring magnet (101, 102) is composed of three or more sectors evenly spaced circumferentially around the longitudinal axis; The sectors are substantially wedge-shaped elements that form sectors relative to the longitudinal axis (c9). An electromagnetic lens characterized by:

8. 2. The electromagnetic lens according to claim 1, the electrode elements are configured to form a particle-optical lens in cooperation with the magnetic field (201) inside the passage hole at one or more of the or each gap; the focal length of said particle-optical lens is adjustable by changing the electrical potential applied to said electrode elements (106, 112); An electromagnetic lens characterized by:

9. 2. The electromagnetic lens according to claim 1, the electrode elements (106, 108, 110, 112) are configured to form at least one single lens; An electromagnetic lens characterized by:

10. 2. The electromagnetic lens according to claim 1, At least one of the electrode elements includes an electrostatic multipole electrode including a plurality of sub-electrodes evenly spaced circumferentially around the longitudinal axis. An electromagnetic lens characterized by:

11. 2. The electromagnetic lens according to claim 1, The electrode elements include a beam aperture element (601) that defines a demarcating aperture (605) having a defined diameter (d6) about the longitudinal axis (c3), the demarcating aperture limiting the lateral width of the charged particle beam (600) propagating along the longitudinal axis. An electromagnetic lens characterized by:

12. 12. The electromagnetic lens of claim 11, The beam aperture element (601) is connected to a current measuring device (702) that measures the amount of charged particle beam absorbed in the beam aperture element. An electromagnetic lens characterized by:

13. 12. The electromagnetic lens of claim 11, In front of the beam aperture element (601) as seen in the direction of propagation of the beam along the longitudinal axis, there is arranged an electrostatic multipole electrode (602) including a plurality of sub-electrodes evenly arranged circumferentially around the longitudinal axis and configured to determine the lateral position of the beam (600) relative to the longitudinal axis (c3). An electromagnetic lens characterized by:

14. 2. The electromagnetic lens according to claim 1, The sleeve insert includes a ceramic body having disposed thereon electrode elements configured as conductive coatings each having a defined shape and area. An electromagnetic lens characterized by:

15. Charged particle optical device comprising an electromagnetic lens (10) according to any one of claims 1 to 14, 1. An apparatus configured to influence a charged particle beam of the apparatus propagating through said electromagnetic lens along a longitudinal axis (c1) of the apparatus, comprising: the electromagnetic lens being part of the projection optical system of the device; An apparatus characterized by:

16. A charged particle optical device comprising an electromagnetic lens (10) according to any one of claims 1 to 14, 1. An apparatus configured to influence a charged particle beam of the apparatus propagating through said electromagnetic lens along a longitudinal axis (c1) of the apparatus, comprising: The apparatus is a multi-column system including a plurality of particle-optical columns, each of which uses a respective particle beam and includes a respective projection optical system including a respective electromagnetic lens (10). An apparatus characterized by:

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