Electromagnetic lens and charged-particle optical apparatus

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 priority under the Paris Convention with respect to European Patent Application No. 21185599.4, filed on July 14, 2021, the entire contents of which are incorporated herein by reference and are set forth herein.

[0002] The present invention relates to an electromagnetic lens configured to modify a charged particle beam of a charged particle optical apparatus for lithographic imaging and similar processing purposes, including nanopatterning (pattern formation). Such a lens comprises a passage for a charged particle beam along a longitudinal direction. The longitudinal direction will correspond to the propagation direction of the charged particle beam itself, but will usually be adjusted (aligned) to be concentric with the optical axis of the charged particle optical apparatus. The present invention also relates to a charged particle optical apparatus including an electromagnetic lens of the above type.

Background Art

[0003] The applicant has already realized a charged particle multi-beam apparatus (plural) including one or more electromagnetic lenses of the above type, and has already developed corresponding charged particle optical components, pattern defining (prescribing) devices, and a drawing method for multi-beams, and has already launched a 50 keV electron multi-beam writer called eMET (electron mask exposure tool) or MBMW (multi-beam mask writer) used to realize any photomask for 193 nm immersion lithography and (any) mask for EUV lithography and (any) template for nanoimprint lithography. The applicant's system is also referred to as PML2 (Projection Mask-Less Lithography) for application of an electron beam direct writer (EBDW) to a substrate.

[0004] Particularly with respect to maskless lithography and direct writing onto substrates (e.g., wafers), increasing throughput in mass industrial production requires increasing the current carried by the charged particle beam passing through a charged particle nanopatterning apparatus; this usually comes at the cost of resolution limitations due to Coulomb interaction between charged particles, requiring corresponding compensation by reducing the magnitude of optical aberrations introduced by the apparatus through other mechanisms. For this purpose, the applicant has already developed a charged particle multibeam apparatus comprising multiple parallel optical columns combined in a multi-column configuration, each column having a reduced ("slim") cross-sectional diameter. Such a multibeam apparatus, one embodiment of which is discussed below with reference to Figure 4, enables extremely large charged particle beam currents while overcoming the limitations of the trade-off between current and optical aberrations found in single-column systems. This is based on the fact that the total current supplied to the target is divided across multiple optical axes, while the resolution limitation is governed by (or influenced by) the amount of current per optical axis. This type of single column is well known in the prior art, such as the applicant's US 6,768,125, EP 2 187 427 A1 (=US 8,222,621) and EP 2 363 875 A1 (=US 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 [Overview of the project] [Problems that the invention aims to solve]

[0006] A typical multi-column system includes multiple optical subcolumns, each containing an illumination system that supplies a broad, telecentric charged particle beam to a pattern demarcation system, which is then back-loaded (downstream) by a charged particle projection optical system, for example, containing multiple electrostatic and / or electromagnetic lenses. To use such a system as a high-throughput wafer direct writing machine, a considerable number of subcolumns, e.g., on the order of 100, are needed above a single semiconductor wafer. However, this requires each subcolumn to have a diameter that is a fraction of the wafer's 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 for generating the desired magnetic field because reducing the column diameter would correspond to generating extremely large amounts of Joule heat due to the large current required to drive the coils for generating a significantly stronger magnetic field. Due to the tight space requirements, there is insufficient space for a proper temperature control system, including high-precision sensors and isotropic, uniform cooling, which may be required for traditional coil-type magnetic lenses. Furthermore, the tight space requirements, which arise from the target diameter of the slim columns and their arrangement in a suitable multi-column system, will hinder the manufacture of a suitable coil-type magnetic lens. The above limitations, determined by thermal and geometric requirements, are severe but 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 the possible embodiments of the present invention. However, such a permanent magnet system cannot be recalibrated after the completion of the manufacturing and assembly process, which represents a serious disadvantage compared to a coil-type magnetic lens whose magnetic field can be controlled by readjusting the current flowing through the coil, especially considering the inherent limitations on the accuracy of the target magnetic field based on manufacturing and assembly precision.The current accuracy limit corresponds to a deviation of approximately ±1.0% from the target magnetic field, but this cannot be compensated for without several additional components that allow for compensation of the lack of required magnetic field accuracy.

[0007] Electromagnetic lenses based on permanent magnets and high-permeability housing bodies combined with electrostatic elements for fine adjustment are known in prior art such as US 7,067,820, but these do not include high-precision adjustment means such as multipole or charged particle collection calibration apertures, and therefore cannot provide a means to change the beam shape, calibrate its position, and generate a desired pattern. US 9,165,745 describes a permanent magnet 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 field of the magnetic lenses of the above prior art is not sufficiently confined (localized) to the space of the lens itself, and therefore serious cross-effects occur when multiple lenses are placed side by side.

[0008] From the above perspective, the object of the present invention is to provide an electromagnetic lens that includes a permanent magnet but allows for high-precision adjustment of optical properties (e.g., focal length). At the same time, it is desirable that the effects of stray magnetic fields be limited. [Means for solving the problem]

[0009] In a first aspect of the present invention, an electromagnetic lens is provided configured to modify a charged particle beam in a charged particle optical apparatus, the electromagnetic lens having a passage hole that extends along the longitudinal axis and allows the passage of the charged particle beam. The aforementioned electromagnetic lens is • A magnetic circuit assembly including at least one ring magnet and a yoke body; and • Sleeve insert Includes, The sleeve insert surrounds the passage hole and extends along the longitudinal axis between the first and second ends of the passage hole, and the sleeve insert includes at least one conductive electrode element, each electrode element being configured to have its respective electrical potential (voltage) applied via a power supply to generate an electrostatic field inside the passage hole. The yoke body includes an outer yoke shell and an inner yoke shell, arranged around the longitudinal axis and containing a magnetic permeable material, the inner yoke shell is positioned to surround at least the 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 is positioned 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 magnet material which is magnetically oriented such that one of its two magnetic poles points toward the inner yoke shell and the other points toward 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, the closed magnetic circuit having at least two gaps positioned at the axial ends of the inner yoke shell pointing to corresponding portions of the outer yoke shell, reaching into the passage hole radially inward, and generating a magnetic field that spatially overlaps with the electrostatic field generated by the electrode elements of the sleeve insert. It is characterized by (Form 1). A second aspect of the present invention is provided, a charged particle optical apparatus including an electromagnetic lens according to the present invention, configured to affect a charged particle beam of the apparatus that propagates through the electromagnetic lens along the longitudinal axis of the apparatus, wherein the electromagnetic lens is part of the projection optical system of the apparatus. The charged particle device is a multi-column system including a plurality of particle optical columns, and each particle optical column includes a respective projection optical system that uses a respective particle beam and includes a respective electromagnetic lens (Embodiment 15).

Embodiments for Carrying Out the Invention

[0010] (Embodiment 1) Refer to the first perspective of the present invention described above. (Embodiment 2) In the electromagnetic lens of Embodiment 1, the magnetic circuit has two gaps, the two gaps are respectively positioned at the axial ends of the inner yoke shell that direct to the respective corresponding parts of the outer yoke shell, each gap generates a defined (defined or limited: defined) magnetic field that reaches into the passage hole inward (in the radial direction), it is preferable that 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. (Embodiment 3) In the electromagnetic lens of Embodiment 1 or 2, the electromagnetic lens has an overall rotationally symmetric shape along the longitudinal axis, it is preferable that the inner yoke shell and the outer yoke shell are concentric with each other. (Embodiment 4) In the electromagnetic lens of any one of Embodiments 1 to 3, the inner yoke shell extends between its two axial ends along a passage space for receiving 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. (Embodiment 5) In the electromagnetic lens of any one of Embodiments 1 to 4, it is preferable that the at least one ring magnet has a magnetization oriented substantially in the radial direction. (Form 6) In the electromagnetic lens according to any one of Forms 1 to 5, it is preferable that the at least one ring magnet is composed of two or more layers stacked along the longitudinal axis. (Form 7) In the electromagnetic lens according to any one of Forms 1 to 6, the at least one ring magnet is composed of three or more sectors arranged evenly along the circumferential direction around the longitudinal axis, preferably, the (magnet) sector is an element having a substantially wedge shape (a shape that tapers to a V shape in cross section but has no sharp-angled part at the tip) that forms a sector (radially divided around the longitudinal axis) with respect to the longitudinal axis. (Form 8) In the electromagnetic lens according to any one of Forms 1 to 7, the electrode element(s) is configured to form a particle optical lens in cooperation with the magnetic field inside the passage hole in one or more of the gaps, preferably in each gap, it is preferable that the focal length of the particle optical lens is adjustable by changing the electric potential (voltage) applied to the electrode element(s). (Form 9) In the electromagnetic lens according to any one of Forms 1 to 8, it is preferable that the electrode element(s) is configured to form at least one singlet lens. (Form 10) In the electromagnetic lens according to any one of Forms 1 to 9, it is preferable that at least one of the electrode elements includes an electrostatic multipole electrode including a plurality of sub-electrodes arranged evenly along the circumferential direction around the longitudinal axis. (Form 11) In the electromagnetic lens according to any one of Forms 1 to 10, the electrode element(s) includes a beam aperture element that forms a boundary defining aperture having a defined diameter around the longitudinal axis, and the boundary defining aperture preferably limits the lateral width of the charged particle beam propagating along the longitudinal axis. (Form 12) In the electromagnetic lens of Form 11, Preferably, the beam aperture element is connected to a current measuring device that measures the amount of charged particle beam absorbed by the beam aperture element. (Form 13) In the electromagnetic lens of Form 11 or 12, Preferably, an electrostatic multipole electrode is positioned in front of the beam aperture element in the direction of beam propagation along the vertical axis, and which includes a plurality of sub-electrodes evenly arranged circumferentially around the vertical axis, and is preferably configured to determine the lateral position (radial position) of the beam with respect to the vertical axis. (Form 14) In any of the electromagnetic lenses of Forms 1 to 13, Preferably, the sleeve insert includes a ceramic body on which electrode elements (multiple) are arranged, each composed of a conductive coating having a limited shape and area. (Embodiment 15) Refer to the second viewpoint of the present invention described above.

[0011] The above problems are solved by an electromagnetic lens configured to modify (e.g., shape, focus / defocus or otherwise manipulate) the charged particle beam of a charged particle optics. The electromagnetic lens includes a passage hole extending along the longitudinal axis and allowing the passage of the charged particle beam, and includes 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 the first and second ends of the passage hole, the sleeve insert including one or more, preferably at least two, conductive electrode elements, the electrode element(s) being configured to have an applied electrical potential (voltage) (relative to the electrical potential (potential) of the housing equal to the earth potential (earth potential)) to generate an electrostatic field inside the passage hole, the yoke body includes an outer yoke shell and an inner yoke shell, arranged around the longitudinal axis and containing a permeable material, the inner yoke shell is positioned to surround at least the central portion of the sleeve insert, and the outer yoke shell is positioned around the inner yoke shell and sleeve insert The magnetic circuit assembly comprises a permanent magnet material which surrounds the inner yoke shell, and at least one ring magnet is positioned around the inner yoke shell and between the inner yoke shell and the outer yoke shell, wherein at least one ring magnet is magnetically oriented such that one of its two poles points toward the inner yoke shell and the other points toward the outer yoke shell, and the inner yoke shell, at least one ring magnet, and the outer yoke shell form a closed magnetic circuit which has at least one gap, preferably at least two gaps, positioned at the axial ends of the inner yoke shell which point toward the corresponding (inner) portions of the outer yoke shell, and which are configured to generate a defined magnetic field which extends (radially) inward into the passage hole and spatially overlaps with the 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, and the electrical potential (voltage) applied to these electrode elements may be determined (defined) with respect to and / or to the housing or other external components.

[0013] Thus, an electromagnetic lens according to the present invention will include (1) a magnetic circuit assembly and (2) an electrostatic inlay. The magnetic circuit assembly (1) generates a static magnetic field that can exert a lensing effect on a charged particle beam propagating through the electromagnetic lens. The magnetic circuit assembly includes one or more cylindrical permanent magnets, which are preferably stacked (arranged vertically) along and concentrically with respect to the optical axis of the system, housed inside 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 or limited portion of the passage hole, in particular to a portion corresponding to one, two or three or more gaps provided (formed) in the housing body. The electrostatic inlay (2) is provided to generate an electric field that can be used to fine-tune the lensing effect of the electromagnetic lens on a transverse (longitudinal) charged particle beam, and further, 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 into which the electromagnetic lens is to be incorporated. Furthermore, a wiring system may be used to connect the elements of the electrostatic inlay, such as liners and multipole rods, to external power supply units for individual voltage regulation in order to operate the electromagnetic lens.

[0014] The inlay according to the present invention enables the generation of an electrostatic field superimposed on the above-mentioned magnetic field, thereby compensating for the above-mentioned deviation of the magnetic field from the design (target) target by enabling in-situ fine-tuning of the focal length of the (electromagnetic) lens with high precision, for example, on the order of 10 ppm or less, and control of specific properties of the charged particle beam, such as shape and optical aberrations. Accordingly, the present invention significantly facilitates the layout, assembly, fine-tuning, and control of writing machine tools, particularly multi-column multi-beam mask writing machine tools.

[0015] Unlike US 9,165,745, the electromagnetic lens of the present invention has a completely closed magnetic loop except for a few air gaps in the housing body, which allows the magnetic field to be concentrated in a desired region of the optical axis, thereby greatly reducing the effect (adverse influence) of stray fields (magnetic fields) that degrade the performance of electromagnetic lenses, such as those employed in charged particle multibeam nanopatterning apparatuses. 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, here as well because permanent magnets are used. Therefore, by using (at least) two gaps to the optical axis, and by a layout that generates two (or more) magnetic fields acting as magnetic lenses in these regions, which are spatially sharply (narrowly) confined in opposite directions along the axial direction, the layout can satisfy Ampere's law without generating additional undesirable stray fields (magnetic fields). In contrast, for a single-gap layout that generates only one axial magnetic field that is spatially sharply confined in one direction along the optical axis, Ampere's law predicts the presence of additional axial stray magnetic fields (or more) in the opposite direction along the optical axis. These magnetic fields are problematic in charged particle optics because these (stray) magnetic fields are not spatially sharply confined and therefore cause undesirable interactions with the beam, and thus aberrations (or more) in the system. Therefore, a layout in which the generated axial magnetic fields (or more) along the longitudinal direction intentionally cancel each other out (overall) minimizes the presence of stray magnetic fields. Otherwise, stray magnetic fields would affect not only each subcolumn but also, in some cases, adjacent subcolumns(s), thus introducing non-rotationally symmetrical distortions to the entire system. These distortions would make the system unsuitable for the industrial high-tech node-precision rendering quality requirements.This approach of minimizing stray magnetic fields is not employed in the aforementioned prior art systems.

[0016] For at least the reasons stated above, the present invention and its application in lithography tools such as a multi-column multi-beam charged particle nanopattern formation system for direct lithography of substrates propose a unique combination of magnetic, electrical, and calibration components, which 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 positioned at the axial ends of the inner yoke shell, each pointing to a corresponding portion of the outer yoke shell, and each gap extends (radially) inward into the passage hole and generates a defined magnetic field that spatially overlaps with the electrostatic field generated by the electrode element(s) of the sleeve insert. However, it will be apparent that the number of gaps may be more than three, four, or five, depending on the industrial application of the electromagnetic lens.

[0018] Advantageously, electromagnetic lenses often have a shape that is rotationally symmetrical overall along the vertical axis. The inner yoke shell and the outer yoke shell will be positioned concentrically with respect to each other.

[0019] According to one preferred geometric layout, the inner yoke shell may extend between its two axial ends along a passage space for receiving a sleeve insert, and the outer yoke shell may surround the inner yoke shell radially outward, while extending to the sides corresponding to the two axial ends of the inner yoke shell, respectively.

[0020] In many embodiments, at least one ring magnet may have substantially radially oriented magnetization and / or may be realized (configured) as a radially magnetized ring magnet. Furthermore, at least one ring magnet may consist of three or more (e.g., four, six, or eight) magnet portions uniformly arranged circumferentially around a longitudinal axis. Generally, ring magnets typically have the shape of a hollow cylinder or a hollow polygonal prism, while at least one ring magnet may have a general ring shape in which multiple ring portions are distributed circumferentially around a longitudinal axis; this may also include gaps(s) between the ring portions having some angular extension. For example, the magnet portions(s) may be substantially wedge-shaped elements that form sectors (divided radially around the longitudinal axis) relative to the longitudinal axis (where "substantially" means that the tapered shape formed by, for example, two sides toward the central axis of a hollow cylinder lacks the portion corresponding to the hollow space of the hollow cylinder). Alternatively, or in combination with this, a ring magnet (or some or all of the magnetic parts) may consist of two or more layers (segments) stacked (arranged vertically) along the vertical axis.

[0021] A highly advantageous aspect of the present invention is that the electrode elements may be configured to form a particle optical lens in one of the gaps, in each of several of the gaps, or preferably in each gap, in conjunction with the magnetic field inside the passage hole, and in the case of multiple gaps, a particle optical lens may be formed in each of these gaps. The focal lengths of such (one or more) particle optical lenses can 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 single 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 comprising a plurality of sub-electrodes uniformly arranged circumferentially around a longitudinal axis.

[0023] In many embodiments of the (electromagnetic) lens of the present invention, particularly when the (electromagnetic) lens is intended to be used in conjunction with a PD system, there may be a beam aperture element that forms a delimiting opening between (enclosed by) electrode elements, having a radius defined around the longitudinal axis, the delimiting opening restricts the lateral width of the charged particle beam propagating along the longitudinal axis. This delimiting opening can be used as a particle collection calibration aperture to collect (recover) particles, including those that have been intentionally deflected in the PD system, so as to prevent such deflected particles from reaching the target of the charged particle beam. Furthermore, the beam aperture element may be connected to a current measuring device, for example, which can be used to measure the amount of charged particle beam absorbed in the beam aperture element. It is often advantageous to provide an electrostatic multipole electrode configured to determine the lateral position (radial position) of the beam relative to the vertical axis by applying different appropriate electrostatic potentials to the sub-electrodes (multiple) in front of the beam aperture element, when viewed in the direction of beam propagation along the longitudinal axis.

[0024] In some advantageous embodiments, the sleeve insert may include a ceramic body on which electrode elements are arranged, each of which are realized (configured) as conductive coatings having a limited shape and area.

[0025] A further aspect of the present invention is a charged particle optics 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 the longitudinal axis of the apparatus, and the electromagnetic lens is directed toward the apparatus constituting a part of the projection optics system of the apparatus. In particular, the charged particle optics apparatus may preferably realize a multi-column system including a plurality of particle optical columns, each particle optical column using its own particle beam and including its own electromagnetic lens, and at least one, preferably several, and most preferably all of the plurality of particle optical columns including their respective projection optics systems.

[0026] Below, for further explanation of the present invention, we discuss some exemplary and non-limiting embodiments shown in the drawings. [Brief explanation of the drawing]

[0027] [Figure 1] A longitudinal cross-sectional view of an example of an electromagnetic lens according to the first embodiment of the present invention. [Figure 2] An example of the axial components of the magnetic field (solid line) and electric field (dashed line) at the position of the central axis c1 as a function of the y-coordinate; the y-coordinate is the same as in Figure 1 (and especially the same scale). [Figure 3] A magnified detail view of an example of a calibration aperture and upstream multipole as components (multiple) of the sleeve insert of an electromagnetic lens shown in Figure 1. [Figure 3A] A magnified detail view of the lower portion of an example of a modified sleeve insert that includes a corrective liner to allow for the modification of multiple optical aberrations. [Figure 4] A longitudinal section view of an example of a multi-column plotting tool, including several specific examples of electromagnetic lenses shown in Figure 1. [Figure 5] A cross-sectional view of an example of a multipole electrode with eight sub-electrodes. [Figure 5A] A close-up detail of an example of a gap area between two of several rods. [Figure 6] A perspective view of one modified example of a multipole electrode having four sub-electrodes. [Figure 7] A schematic overview of an example of voltage supply units connected to sleeve insert elements of an electromagnetic lens shown in Figure 1. [Figure 8] An embodiment of a ring magnet composed of multiple ring elements having radial magnetization. (A) is a perspective view; (B) is a longitudinal section view; (C) is a cross-sectional view. [Figure 9] A cross-sectional view of one embodiment of a divided ring magnet. [Figure 10] A cross-sectional view of another embodiment of a divided ring magnet. [Figure 11] A cross-sectional view of another embodiment of a divided ring magnet. [Examples]

[0028] The detailed discussion of the exemplary embodiments of the Invention given below discloses the basic idea, embodiment, and further advantageous developments of the Invention. It will be apparent to those skilled in the art that some or all of the embodiments discussed herein may be arbitrarily combined as they are deemed suitable for a particular application of the Invention. Throughout this disclosure, terms such as “advantageous,” “exemplary,” or “preferred” describe elements or dimensions that are particularly suitable (but not essential) for the Invention or one embodiment thereof, and can be modified unless expressly required, if deemed suitable by those skilled in the art. It goes without saying that the Invention is not limited to the exemplary embodiments discussed below, which are given for illustrative purposes and merely present preferred embodiments of the Invention. Within the scope of this disclosure, terms relating to the vertical direction, such as “up” or “down,” should be understood as relating to the direction of a particle beam traversing an electromagnetic lens that is considered to travel downward (“perpendicularly”) along the central axis (or longitudinal axis). This longitudinal axis is generally the same as the Z direction, which is intersected by the X and Y directions.

[0029] Electromagnetic lens

[0030] Figure 1 shows a longitudinal section of an example of an electromagnetic lens 10 according to a first embodiment of the present invention, i.e., a view along a cross-section passing through (including) its central axis c1. For clarity, the components are not shown in dimensional terms. When used as an objective lens, lens 10 may be used to embody the final lens 414 of the drawing machine tool 401 in Figure 4 (see below), but it will be apparent that it is suitable for use in many other particle optics devices that can embody multi-column or single-column architectures, such as those disclosed in the applicant's US 9,443,699 and US 9,495,499. The disclosures of these documents 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 an "inlay". The magnetic circuit assembly 11 includes one or more ring magnets 101, 102 made of permanent magnet material having an outer radius of 10-13 mm, a (radial) thickness of 2-5 mm, a length of approximately 25 mm, and typically having a residual magnetism of 1 T; and a housing body 13 which also serves as a yoke body for the ring magnets. Such a housing body consists of two concentric cylinders having an inner radius of approximately 5 mm and an outer radius of approximately 15 mm, each of which has a thickness of 2-5 mm and a length of 50-100 mm. The sleeve insert 12, which is also referred to as a beam control inlay or simply an "inlay", has an outer diameter of less than 5 mm and a length of 1 mm-20 mm, as will be discussed in detail below, and includes several electrically active and passive components that function as electrostatic electrodes, apertures, or field-termination caps. The electromagnetic lens 10 is typically positioned in a particle beam exposure system (such as the drawing machine tool 401 in Figure 4), so that its central axis c1 coincides with the optical axis of the exposure system; however, as will be apparent to those skilled in the art, other relative positional relationships may be selected depending on the application of the electromagnetic lens according to the present invention. The dashed line 100 shows the envelope of the particle beam as it propagates through the electromagnetic lens 10 inside the particle beam exposure system.

[0032] Magnetic circuit assembly

[0033] The magnetic circuit assembly 11 is discussed below. The housing body 13 includes an inner portion and an outer portion, respectively referred to as the inner yoke shell 103 and the outer yoke shell 104, the outer yoke shell 104 (completely) enclosing the ring magnets 101, 102, the inner yoke shell 103 and the inlay 12 when incorporated into the electromagnetic lens 10. Both the ring magnets 101, 102 and the housing body 13 are concentric with respect to the central axis c1. The ring magnets 101, 102 preferably have the shape of a rotationally symmetric ring or ring sector (a portion of a ring divided radially (partial ring or partial annular): ring sectors). The size of the ring magnets is selected to be appropriate for each application and charged particle device; in the illustrated embodiments (multiple), 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). Preferably, multiple magnets may be used, arranged in a manner that stacks continuously along the longitudinal axis of the system (Figure 8A).

[0034] In a preferred embodiment of the present invention, the permanent magnets constituting the ring magnets 101, 102 exhibit radial magnetization (see the following discussion relating to Figures 8 and 9). The ring magnets function as flux sources for the magnetic circuit realized in the magnetic circuit assembly 11. The inner yoke shell 103 is realized (configured) as, for example, a hollow cylinder having sufficient length to protrude from the stacked ring magnets at both ends. The outer yoke shell 104 is realized (configured) as having a cylindrical symmetrical shape with two U-shaped longitudinal 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 having a larger radius, and two disc-shaped end portions 141, 142 having a central hole, coupled to the longitudinal ends of the central body portion 143. The central hole of each end portion 141, 142 preferably has the same inner radius as the inner radius of the hollow cylinder body of the inner yoke shell 103. Therefore, the central bore(s) and the hollow space of the inner yoke shell enclose a passage space 200 (with radius r1) that traverses (longitudinally) 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 these cylinders (parts) cover (enclose) the magnets 101, 102 (radially) inward and outward; these cylinders (parts) advantageously contact the corresponding surfaces of the magnets in such a way that they minimize, or preferably avoid, the gap between the magnets and the corresponding surface areas of the cylinder bodies. On the other hand, gaps 14a, 14b are formed between the end surfaces 103a, 103b of the inner yoke shell representing the pole-pieces of the magnetic circuit 11 and the corresponding inner surfaces 141a, 142b of the end portions of the outer yoke shell. The radial thickness of the hollow cylinders is typically, and without loss of generalization (but not limited to), on the order of several millimeters.The inner yoke shell 103 and outer yoke shell 104 of the housing body 13 are made of a permeable material, preferably of high permeability (such as a ferrimagnetic or ferromagnetic material); the housing body 13 can enhance and focus the magnetic flux generated by the magnet, based on its shape. Around the regions of the gaps 14a and 14b, the magnetic flux of the magnetic circuit will also form a defined (defined or limited) magnetic field of the magnetostatic type that extends radially inward into the passage space 200 in certain portions of the central axis c1. Accordingly, according to the present invention, the housing body functions as a yoke for the magnetic lens, and its magnetic flux distribution is formed by the pole pieces 103a, 103b, 141a, and 142b. In particular, with respect to the passage space 200, the magnetic field generated by the magnetic circuit 11 is limited to two regions: namely, the upper region inside the gap 14a formed by the pole piece surfaces 103a and 141a; and the lower region inside the gap 14b formed by the pole piece surfaces 103b and 142b. Thus, two magnetic lenses are formed (each) in the vertical axis portion(s) corresponding to the gaps 14a and 14b. The magnetic field includes an axial component and a radial component; the radial component is of little importance, while the magnetic field B. Z The resulting axial component is utilized for the lens effect (action) of the electromagnetic lens. The magnetic field B at the position of the central axis c1 as a function of the vertical coordinate. Z The magnitude (intensity) of the axial component of the magnetic field B is shown in Figure 2 (solid line); magnetic field B ZThe typical peak value of is on the order of 0.1T in the application where the charged particle is an electron. Thus, the magnetic circuit will form two regions with (fairly) high magnetic field strengths, which will function as two sequentially arranged magnetic lenses with clearly defined focal lengths and optical aberrations. The magnetic coupling of the two magnetic lenses via the common yoke 13 will greatly reduce the effect of stray (leak) magnetic fields in regions other than the gaps 14a and 14b, but in other respects it will inevitably be associated with permanent magnets in particle lenses of a traditional layout.

[0035] Inlay

[0036] The magnetic lens 10 further includes a sleeve insert or inlay 12 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, which include one or more electrically active elements used to generate an adjustable electrostatic field 202 (dashed line in Figure 2) that superimposes a static magnetic field 201 (solid line in Figure 2) in the passage space. The beam control elements are generally ring-shaped components that function as electrically active elements, stacked along the central axis c1, oriented so that their geometric axes (lines) are 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 (longitudinally) 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 element includes, from the bottom of the plane of Figure 1, a first liner 106, two multipole electrodes 108 and 110, and a second liner 112—all made of conductive material. The multipole electrodes 108 and 110 are each realized as composite metal rings composed of multiple sections of equal arc length, as will be discussed further below with reference to Figure 6, for example; their (radial) thickness is, for example, less than 2 mm, and their length is 5 mm to 20 mm. Furthermore, preferably, an electrically passive ring 109 is interposed between the two multipole electrodes 108 and 110; this component is referred to as a calibration aperture, which will be discussed further below. The multipoles 108 and 110 consist of multiple sector (radial division) components arranged circumferentially around a central axis c1 (for example, and without loss of generalization, four, six, or eight sector components, each), whereas all other inlay elements are preferably configured rotationally symmetric with respect to the central axis c1.The electrically active elements 106, 108, 110, and 112 are preferably connected to power sources 726, 728, 730, and 732, each having an electrostatic voltage, so that their electrostatic potentials can be individually adjusted (Figure 7); in one variant, the power sources(s) may be combined to form a common power supply that provides individual supply voltages. Finally, the electrically active elements 106, 108, 110, and 112 are electrically isolated from each other and terminated at both ends by elements referred to as field termination caps 105, 107, 111, and 113, which have the same electrical potential as the housing body 13. The field termination caps 105, 107, 111, and 113 serve to restrict the electric field to the internal space 120 of the inlay; thus, they provide a clearly defined "field boundary" of the inlay to surrounding components (such as other particle optical columns 409, see Figure 4). The spaces between the field termination caps 105, 107, 111, 113 and their respective adjacent electrically active elements 106, 108, 110, 112 are electrically insulating, and are realized, for example, as a vacuum or as a filler using a non-conductive, preferably dielectric, material such as ceramics. The various elements 105-113 of the inlay are supported and held together by a hollow cylindrical support ring body (between radii r1 and r2) and are made of an electrically insulating material such as ceramic or plastic, symbolically shown in Figure 1 as two dashed rectangles. The electrode elements can be realized (embodied) as separate (discrete) ring-shaped elements, for example, coupled and held together within the ring body, or as a conductive coating formed on the inner surface of the ring body, each having a limited shape and area. The electric field E as a function of coordinates along axis c1. Z The intensity (magnitude) of the axial component (i.e., the component along the Z direction) is shown in Figure 2; electric field E Z A typical peak value is 10 5 It is on the order of V / m.

[0037] In a typical configuration, the first liner 106 and the second liner 112 have a length of 2 mm to 10 mm and a small radial thickness, for example, less than 2 mm. Each liner 106, 112 is positioned corresponding to one of the magnetic flux regions of the gap 14a, 14b, which functions as a magnetostatic lens, respectively. In particular, the liners 106, 112 are positioned to overlap, for example, the magnetic field 201. 5 The liner 202 can be used as a single lens (Einzel lens) to generate an electrostatic field of the order of V / m. This allows for fine adjustment of the focal length of the corresponding magnetic lens, and thus the system has a certain range of adjustment for focal length. Without the liner 106, 112, the accuracy of the focal length would be degraded by the limited precision of the mechanical manufacture of the permanent magnets 101, 102, the limitations of assembly precision and magnetization precision, which are typically on the order of 0.5% to 1%. However, for the purpose 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 an aging effect, that is, the magnetic field often weakens over time and its strength changes depending on temperature. Therefore, appropriate compensation means for these various effects are necessary for using permanent magnets in charged particle optics applications. The present invention also enables the electric field to be adjusted and controlled with ppm (parts-per-million) regime accuracy, thereby overcoming all the above limitations regarding manufacturing, assembly, magnetization strength, and aging effects, by including an integrated correction means. Furthermore, the voltage of the liners is adjustable in combination with other optical and electrical active elements of the system to change the properties of the particle beam lithography apparatus with respect to optical aberrations and / or to change the height of the image plane relative to the target generated by the magnetic lens.

[0038] Referring to Figures 1 and 3, the inlay 12 may preferably include a passive element called a calibration aperture 109, which functions as a stopping component for any deviating or deflected portions of the particle beam. Figure 3 shows an enlarged detail view of a longitudinal section of an example of a calibration aperture. The calibration aperture (member) 601 has an inner ring structure that protrudes toward axis c1, thus forming an aperture of a small diameter d6. The aperture has the function of limiting the size (diameter) of the beam 600 traversing (longitudinally) the inlay 12 by absorbing portions of the beam 606 that travel outside the diameter d6. In a preferred embodiment of the present invention, one of the preceding (upstream) inlay elements, for example, a multipole electrode 602, is configured to guide (direct) the beam 600 along the transverse direction to axis c1 by applying a dipole field (electric field) (typically using a voltage in the range of ±50V, for example). The multipole electrode 602 allows for the lateral position of beams 600, 606 relative to the vertical axis c1 to be defined by changing the dipole voltage applied to selected electrodes of the multipole electrode in at least two linearly independent directions, and this can also be used for beam alignment. In the particle beam column of the drawing tool 401 described above, the particle beam is divided 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 to define the drawing pattern. The deflected beamlets will reach an area adjacent to the calibration aperture 601 rather than proceeding through it, and will therefore be absorbed in the calibration aperture 601 without causing unwanted charge-ups in other parts of the system that could otherwise generate unwanted stray electric fields. For this purpose, the beam calibration aperture is configured, for example, as a cylinder having a hook-shaped (longitudinal) cross-section with a length of approximately 20 mm and a minimum diameter of several hundred micrometers at its bottom (605).Absorption in the beam portion 606 would cause charge generation in the elements forming the calibration aperture 601, which can be removed, or rather, discharged, through the electrical connections of the beam aperture towards the measuring device 720, as discussed below with reference to Figure 7. The inlay 12 is typically inserted into the passage space 200 of the housing body 13 such 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 such that the system's aberrations are intentionally varied or kept constant within a defined range of the supply voltage. To achieve this, one or more relative electrodes may have a modified shape such that they have a (longitudinal) cross-section with a pointed tip toward the longitudinal axis, thus achieving a reduced (gradually shortened) inner diameter, and an appropriate electrical potential is applied relative to the earth potential.

[0040] Figure 3A shows an exemplary embodiment of an inlay 12' including a liner 212 having a reduced inner diameter. Figure 3A shows details of an example of the “bottom” of the inlay 12'. Due to the reduced inner width, i.e., the reduced diameter d3, the liner 212 allows for aberration changes. In particular, if the diameter of the beam in the region of the liner 212 is approximately 70% or more of the diameter d3, significant spherical aberration is generated, which can then be used to change, for example, radial space or angular distortion, or field curvature. In other respects, the inlay 12' corresponds to the inlay 12 described above, and in particular, field end caps 211, 213 having an inner diameter d2 = 2·r2 on both sides of the liner 212 (top and bottom of the paper in Figure 3A) can be realized (configured) identically to field end caps 111, 113.

[0041] Lithography device

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

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

[0044] The multi-column optical system 402 includes a plurality of sub-columns 409 (the number of columns shown in the illustration has been reduced for clarity and represents a much larger number of columns than those actually included in multi-column devices in real-world examples). Preferably, the sub-columns 409 have the same setup and are arranged side by side so that their axes are parallel to each other. 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 optical system 411c, which supplies a broad, telecentric charged particle beam to a reduced charged particle projection optical system 416 consisting of a plurality of sequentially arranged electro-magneto-optical projector stages, which include a pattern definition (PD) system 412 (beam shaping device) adapted to allow only the apertures that define the shape of the sub-beam ("beamlet") that passes through each of the plurality of apertures to pass through the beam, and preferably electrostatic and / or magnetic lenses, and optionally other particle optics devices. In the embodiment shown in Figure 4, the projection optical system 416 includes, for example, a first lens 413 which is an accelerating electrostatic multi-electrode lens, while a second lens 414 located downstream of the first lens is implemented (configured) using an electromagnetic lens according to the present invention, such as lens 10 in the first embodiment (Figure 1).

[0045] In each sub-column 409, the first lens 413 of the projection optical system forms a first crossover of the particle beam, while the second lens 414 forms a second crossover. The second lens has a beam aperture 415 (corresponding to the beam aperture 605 in Figure 3) configured to remove beam portions that are deflected in the PD system and deviate from their respective optical axes. Each second lens 414 of a sub-column may preferably be mounted on a reference plate 417, which is attached to the column base plate 404 by appropriate fixing means 418. The reference plate 417 is fitted with parts 419 of an off-axis optical alignment system.

[0046] The reference plate is manufactured from a suitable raw material having low thermal expansion properties, such as a silicon oxide or aluminum oxide-based ceramic material, and has the advantages of being lightweight, having a high modulus of elasticity and high thermal conductivity, and can be appropriately coated with a conductive film, at least in its relevant parts, to avoid static charge buildup (by allowing static charge to escape).

[0047] The PD system 412 has the function of forming multiple so-called beamlets from a particle beam, which contain information about the patterns to be transferred to the target. The structure, operation, and data processing of the PD system are disclosed in the applicant's US 9,443,699 and US 9,495,499. The disclosures in these documents are incorporated herein by reference and are used herein.

[0048] Multipole electrodes

[0049] As described above, the inlay includes multipole electrodes 108 and 110. Each multipole electrode 108 and 110 consists of three or more metallic ring sectoral components, each functioning as an electrode(s) (sub-electrode(s)) of the multipole electrode, also referred to hereafter as rod(s). Preferably, the rod(s) have the same geometric shape. Figure 5 shows a depiction of an example of a multipole electrode 511 having eight rods 508 (sectorial electrodes) in a cross-sectional view; Figure 5A shows a magnified view detailing the gap region between two of these rods. Figure 6 shows a modified example of a multipole electrode 540 having four sector electrodes 544. The preferred number of rods inside the multipole electrode is four, six, eight, twelve, or sixteen, depending on the desired effect to be achieved.

[0050] Referring to Figure 5, the rods 508 are arranged inside a surrounding sleeve that functions as a support member 501. Each rod 508 can have an electrical potential (voltage) individually applied by its own external power supply unit 728, 730 (Figure 7). Additionally, a global offset voltage may be applied to cause them to act as additional electrostatic lenses. By applying different voltages to the individual rods 508, various field configurations consisting of dipoles, quadrupoles, or higher-order electrostatic fields can be realized, thereby shaping the particle beam intersecting the corresponding transverse sections of the optical axis 503. For typical applications relating to the embodiments in Figures 1-3, the voltages applied to the rods 508 are typically on the order of 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 accuracy. In this regard, a multipole can correct the beam position relative to the optical axis 503 when used as a dipole (multiple) whose orientation (multiple) in the plane defined by X and Y is arbitrary, provided that at least four different voltages +V1 (rods hatched with diagonal lines on the right side of the page in Figure 5), -V1 (rods hatched with diagonal lines on the left side of the page in Figure 5), +V2 (rods hatched with the upper grid lines on the page in Figure 5), and -V2 (rods hatched with the lower grid lines on the page in Figure 5) are applied to the rods (multiple). Additionally, when a multipole is used as a quadrapole (four poles) or a higher-order multipole, astigmatism or other higher-order distortions can be compensated by the multipole (multiple) in the same way as with a dipole (two poles) by applying appropriate voltages to each rod (multiple). For liners 106 and 112, the common offset potential of the multipole electrodes 108 and 110 can also be adjusted to tune the optical aberrations of the magnetic lenses (multiple) formed by lens 10.The gaps 505 between the sector electrodes forming the rods 508 are advantageously bent (or zigzag, forming a "labyrinth"), so that particles 504 that deviate from the beam propagating in the central space of the multipole electrode would collide with the surface of the rods but could proceed outside the multipole electrode, and in some cases (adversely) affect the support member 501 or other external components. Outside the rods 508, the gaps 505 form a pouch that has the function of collecting particles and discharging the charge of the particles to a drain electrode (not shown). This helps to avoid the generation or build-up of charge and associated stray electric fields that could otherwise (adversely) affect the charged particle beam propagating through the multipole electrode 511.

[0051] Furthermore, by appropriately selecting the position and shape of the electrical multipole and rods, and applying an appropriate common supply voltage to all rods of the multipole electrode, it becomes possible to achieve a change in the focal length of one or both of the magnetic lenses corresponding to the two gaps 14a and 14b formed by the yoke(s).

[0052] Referring again to Figure 1, advantageously, two magnetic lenses can be used to realize the so-called crossover cv of the particle beam. In Figure 1, the dotted (dashed) envelope 100 shows the evolution (change) of the beam size (diameter) (diameter of the cross section) along the optical axis (c1). As previously described, the first magnetic lens is formed at the level (height) of the first gap 14a, and this first lens can be used to focus the beam so that the beam is focused to the crossover cv, i.e., to the position or region where the width of the beam is minimized. The magnetic lens is advantageously configured to form the crossover cv at a position located vertically to or near (e.g., 10 mm or less) the calibration aperture 109. The beam then expands again and crosses (passes through) the second magnetic lens formed at the level (height) of the second gap 14b, which preferably has the effect (action) of making the beam telecentric again (relative to the source of the particle beam). Therefore, the beam forms images of the apertures that shape the beam in the PD system 412, and thus the images are generated on the target 407. Thus, it is extremely desirable that the focal lengths of the two lenses be precisely matched for successful image formation on the target. In this sense, the liners 106 and 112 are extremely important elements for the system's correction function. Focusing the beam at the position (location) of the calibration aperture 109 makes the calibration aperture 109 particularly useful for beam alignment processing, in which case the beam 600 can be scanned across the aperture 605, while the corresponding current measurement 720 (or charge accumulation measurement) helps monitor the beam position to align the beam with the optical axis c1.

[0053] Figure 7 schematically shows an example of a voltage supply device 701 for the 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, depending on the application, as (quasi)static elements or as dynamic elements, i.e., as having time-varying voltages. In fact, the upper multipole electrode 108 may 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 makes it possible to keep the beam in the correct position relative to the target 407 on the moving stage 405. Those skilled in the art will understand that the above use of beam control elements is mentioned as an illustrative application and not as a limitation on the functions achievable by the present invention.

[0054] Ring Magnet

[0055] Figure 8 shows one embodiment of a ring magnet 80 suitable for use as a component of a lens magnetic circuit according to the present invention (for example, as one of the ring magnets 101, 102 in Figure 1). Figure 8(A) is a schematic perspective view thereof, Figure 8(B) is a schematic longitudinal section thereof along the longitudinal axis c8, and Figure 8(C) is a corresponding schematic transverse section; however, the dimensions are not to scale. The ring magnet 80 consists of a plurality of ring magnet elements 81 stacked concentrically along a common longitudinal axis c8. Each of the ring magnet elements 81 has radially oriented magnetization, as shown by the dashed arrows in Figure 8(C), and thus has, for example, a "north" pole (N pole) N formed toward the internal space of the ring magnet 80, while the outside represents a "south" pole (S pole) type S of magnetization. Ring magnet elements having radial magnetization as shown in the figure are commercially available and consist of ferromagnetic materials such as sintered NdFeB, SmCo5, or ferrite. The ring magnet elements(s) are joined together by adhesive, crimping, or any other suitable means. The number of ring magnet elements 81 in a (single) ring magnet 80 can be any number, for example, one, two, three, or four or more, depending on the dimensions of these elements (in particular the height (thickness)) and the desired dimensions of the ring magnet 80.

[0056] Each ring magnet or ring magnet element may be realized (configured) by a combination of multiple, for example, four or eight, ring-sector ((radially divided) partial ring) components at each level, as shown in Figures 9 to 11. Figures 9 to 11 show unfolded views of the sector-structured ring magnet, and the magnetization of each is indicated by dashed arrows pointing from the "south" pole (S pole) to the "north" pole (N pole). In particular, Figure 9 shows a ring magnet 90 composed of eight ring sectors (partial rings) 98; Figure 10 shows a ring magnet 91 composed of four ring sectors 94 magnetized radially with respect to a vertical axis c9 at the center of the ring; and Figure 11 shows a ring magnet 99 composed of four ring sectors 95 having linear magnetization, oriented, for example, along (parallel to) the line of symmetry in the center of each (ring sector). In these embodiments, the ring sectors are magnetized radially (Figures 9 and 10) or linearly (Figure 11) to approximate an ideal radially magnetized ring magnet. Note that the gaps between the ring sectors shown in Figures 9-11 are illustrated for better clarity only; these gaps do not exist in one actual embodiment, as they are closed or minimized by direct contact between adjacent parts, achieved by bonding, crimping, or other suitable joining methods of the sector (partially ring) elements 98, 94, and 95.

[0057] All or part of the above embodiments may be described as follows, but are not limited to them. [Note 1] An electromagnetic lens configured to modify the charged particle beam of a charged particle optics device. The electromagnetic lens has a passage hole that extends along the vertical axis and allows the passage of a charged particle beam. The electromagnetic lens includes a magnetic circuit assembly comprising at least one ring magnet and a yoke body, and a sleeve insert. The sleeve insert surrounds the passage hole and extends along the longitudinal axis between the first and second ends of the passage hole. The sleeve insert includes at least one conductive electrode element. Each electrode element is configured to have its respective electrical potential (voltage) applied via a power source(s) to generate an electrostatic field inside the passage hole. The yoke body includes an outer yoke shell and an inner yoke shell, arranged around a longitudinal axis and containing a magnetic permeable material. The inner yoke shell is positioned to enclose at least the central portion of the sleeve insert, and the outer yoke shell encloses both the inner yoke shell and the sleeve insert. At least one ring magnet is positioned around the inner yoke shell and between the inner yoke shell and the outer yoke shell. The at least one ring magnet includes a permanent magnet material that is magnetically oriented such that one of its two magnetic poles points toward the inner yoke shell and the other points toward the outer yoke shell. In a magnetic circuit assembly, an inner yoke shell, at least one ring magnet, and an outer yoke shell form a closed magnetic circuit, the closed magnetic circuit having at least two gaps positioned at the axial ends of the inner yoke shell pointing to corresponding portions of the outer yoke shell, and configured to reach into the passage holes radially inward and generate a magnetic field that spatially overlaps with the electrostatic field generated by the electrode element(s) of the sleeve insert. [Note 2] In the above electromagnetic lens, The magnetic circuit has two gaps. The two gaps are located at the axial ends of the inner yoke shell, each pointing towards the corresponding portion of the outer yoke shell. Each gap generates a defined magnetic field that reaches the passage hole radially inward. The electrostatic field generated by at least one of the electrode elements of the sleeve insert is configured to overlap at least partially with the magnetic field. [Note 3] In the above electromagnetic lens, Electromagnetic lenses have a shape that is rotationally symmetrical along the vertical axis. The inner yoke shell and the outer yoke shell are concentric with each other. [Note 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 and extends to each side corresponding to the two axial ends of the inner yoke shell. [Note 5] In the above electromagnetic lens, At least one ring magnet has a magnetization that is substantially oriented radially. [Note 6] In the above electromagnetic lens, At least one ring magnet consists of two or more layers stacked along the vertical axis. [Note 7] In the above electromagnetic lens, At least one ring magnet consists of three or more sectors evenly distributed circumferentially around a vertical axis. Preferably, the (magnet) sector is a substantially wedge-shaped element that forms a sector relative to the longitudinal axis. [Note 8] In the above electromagnetic lens, The electrode elements (multiple) are configured to form a particle optical lens in one or more of the gaps, preferably in each gap, in cooperation with the magnetic field inside the passage hole. The focal length of a particle optical lens can be adjusted by changing the electrical potential (voltage) applied to the electrode elements (multiple). [Note 9] In the above electromagnetic lens, The electrode elements are configured to form at least one single lens. [Note 10] In the above electromagnetic lens, At least one of the electrode elements includes an electrostatic multipole electrode comprising a plurality of sub-electrodes evenly distributed along the circumferential direction around the longitudinal axis. [Note 11] In the above electromagnetic lens, The electrode elements include beam aperture elements that form a boundary delimitation aperture with a defined diameter around the vertical axis. The boundary delimitation aperture limits the lateral width of the charged particle beam propagating along the vertical axis. [Note 12] In the above electromagnetic lens, The beam aperture element is connected to a current measuring device that measures the amount of charged particle beam absorbed within the beam aperture element. [Note 13] In the above electromagnetic lens, An electrostatic multipole electrode is positioned in front of the beam aperture element, as viewed in the direction of beam propagation along the vertical axis, and preferably configured to determine the lateral position (radial position) of the beam with respect to the vertical axis, including a plurality of sub-electrodes evenly arranged circumferentially around the vertical axis. [Note 14] In the above electromagnetic lens, The sleeve insert includes a ceramic body on which electrode elements (multiple) are arranged, each composed of a conductive coating having a limited shape and area. [Note 15] A charged particle optical apparatus including an electromagnetic lens according to the present invention, configured to influence the charged particle beam of the apparatus that propagates through the electromagnetic lens along the vertical axis of the apparatus. The electromagnetic lens constitutes a 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 its own particle beam and comprising its own projection optical system including its own electromagnetic lens.

[0058] Within the framework of the full disclosure of the present invention (including the claims and drawings), further modifications and adjustments to the embodiments are possible based on the fundamental technical concept. Furthermore, within the framework of the full disclosure of the present invention, various combinations or 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 the full disclosure, including the claims and drawings, and various modifications and alterations that a person skilled in the art could make in accordance with the technical concept of the present invention. In particular, with respect to the numerical ranges described herein, any numerical value or sub-range included within that range should be interpreted as being specifically described, even if not otherwise stated.

[0059] Furthermore, the reference numerals in the drawings included in the claims are solely for the purpose of aiding the understanding of the invention, and are not intended to limit the present invention to the embodiments and illustrated examples.

[0060] Furthermore, the full contents of each of the above-mentioned documents are incorporated into this book through reference and are included herein.

Claims

1. an electromagnetic lens configured to modify a charged particle beam of a charged particle optical device (401), the electromagnetic lens extends along a longitudinal axis (c1) and comprises a passage hole (120) for allowing the passage of a 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 electrode element configured to have a respective electrical potential applied thereto 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 arranged circumferentially about the longitudinal axis and include 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 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 magnet 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 (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 are oriented toward the corresponding portions (141a, 142b) of the outer yoke shell, and configured to generate a magnetic field (201) that reaches 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 comprising:

2. 2. The electromagnetic lens according to claim 1, The magnetic circuit has two gaps (14a, 14b), The two gaps are located 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 (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 comprising:

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 comprising:

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

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

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 comprising:

7. 2. The electromagnetic lens according to claim 1, the at least one ring magnet (101, 102) is comprised of three or more sectors evenly spaced circumferentially around the longitudinal axis; The sector is a substantially wedge-shaped element that forms a sector relative to the longitudinal axis (c9). An electromagnetic lens comprising:

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

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 comprising:

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 about the longitudinal axis. An electromagnetic lens comprising:

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

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

13. 12. The electromagnetic lens of claim 11, an electrostatic multipole electrode (602) is arranged in front of the beam aperture element (601) in the direction of propagation of the beam along the longitudinal axis, the 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 comprising:

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 comprising:

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 comprising:

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 comprising:

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