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KR-102963476-B1 - ELECTROMAGNETIC LENS

KR102963476B1KR 102963476 B1KR102963476 B1KR 102963476B1KR-102963476-B1

Abstract

A finely adjustable electromagnetic lens (10) for a charged particle optical device (401) comprises a magnetic circuit assembly (11) comprising one or more ring magnets (101, 102) and a sleeve insert (12) that is rotationally symmetric about a longitudinal axis (c1). The sleeve insert (12) includes a plurality of electrically conductive electrode elements (106, 108, 110, 112) configured to surround a passage opening (120) extending along the longitudinal axis (c1) and to generate an electrostatic field (202) within the passage opening. The ring magnets (101, 102) are arranged circumferentially around an inner yoke shell (103) and are surrounded by an outer yoke shell (104); then the inner yoke shell surrounds the central portion of the sleeve insert. The ring magnets are magnetized such that two magnetic poles are directed toward the inner and outer yoke shells, respectively. The inner and outer yoke shells form a magnetic circuit having at least one gap (14a, 14b) together with the ring magnet to reach into the passage opening (120) and generate a magnetic field (201) that spatially overlaps with the electrostatic field (202) generated by the sleeve insert (12).

Inventors

  • 스팽글러 매그. 크리스토프
  • 푸흐베르게르 디에트마르
  • 라이트너 요하네스
  • 아닥틸로스 테오도르
  • 에데르­카플 슈테판

Assignees

  • 아이엠에스 나노패브릭케이션 게엠베하

Dates

Publication Date
20260512
Application Date
20220712
Priority Date
20210714

Claims (16)

  1. An electromagnetic lens (10) configured to modulate a charged particle beam of a charged particle optical device (401), said electromagnetic lens having a passage opening (120) that extends along a longitudinal axis and allows the passage of said charged particle beam: - A magnetic circuit assembly (11) having at least one ring magnet (101, 102) and a yoke body (13); and - Sleeve insert (12); Includes, The sleeve insert (12) surrounds the passage opening (120) and extends along the longitudinal axis between its first and second ends, and the sleeve insert (12) comprises at least one electrically conductive electrode element (106, 108, 110, 112), and each electrode element is configured to apply a respective potential through a power source (726, 728, 730, 732) to generate an electrostatic field within the passage opening, The above yoke body (13) comprises an outer yoke shell (104) and an inner yoke shell (103) arranged circumferentially around the longitudinal axis and having a magnetic permeable material, wherein 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 circumferentially around the inner yoke shell and is arranged between the inner yoke shell and the outer yoke shell, and the at least one ring magnet is provided with a permanent magnet material such that its two magnetic poles are magnetically oriented toward the inner yoke shell and the outer yoke shell, respectively. An electromagnetic lens characterized in that, 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 having at least two gaps (14a, 14b) positioned at the axial ends (103a, 103b) of the inner yoke shell toward the respective corresponding parts (141a, 142b) of the outer yoke shell, and configured to reach inward through the passage opening (120) and generate a magnetic field (201) that spatially overlaps with the electrostatic field (202) generated by the electrode element of the sleeve insert.
  2. An electromagnetic lens according to claim 1, wherein the magnetic circuit has two gaps (14a, 14b), the gaps are located at either axial end of the inner yoke shell facing each corresponding part of the outer yoke shell, each gap generates a defined magnetic field (201) reaching inward through the passage opening (120), and the electrostatic field (202) generated by at least one of the electrode elements (106, 108, 110, 112) of the sleeve insert is configured to overlap at least partially with the magnetic field (201).
  3. An electromagnetic lens according to claim 1, characterized in that it has a shape of overall rotational symmetry along the longitudinal axis, and the inner yoke shell and the outer yoke shell are coaxial with each other.
  4. An electromagnetic lens according to claim 1, wherein the inner yoke shell extends between its two axial ends along a passage space (200) that accommodates the sleeve insert, and the outer yoke shell surrounds the inner yoke shell radially outwardly and extends to sides corresponding to the axial ends of the inner yoke shell.
  5. An electromagnetic lens according to claim 1, wherein at least one ring magnet (101, 102) has substantially radially oriented magnetization.
  6. An electromagnetic lens according to claim 1, wherein the at least one ring magnet (101, 102) is composed of two or more layers (81) stacked along the longitudinal axis.
  7. In claim 1, the at least one ring magnet (101, 102) is composed of three or more sectors uniformly arranged around the longitudinal axis along the circumferential direction, and An electromagnetic lens characterized in that the sector is a substantially wedge-shaped element (94, 95, 98) forming a sector with respect to the longitudinal axis.
  8. An electromagnetic lens according to claim 1, wherein the electrode element is configured to form a particle optical lens with the magnetic field (201) in the passage opening in one or more gaps, or in each gap, and the focal length of the particle optical lens is adjustable by modulating the potential applied to the electrode element (106, 112).
  9. An electromagnetic lens according to claim 1, characterized in that the electrode elements (106, 108, 110, 112) are configured to form at least one Einzel lens.
  10. An electromagnetic lens according to claim 1, characterized in that at least one of the electrode elements comprises an electrostatic multipole electrode having a plurality of sub-electrodes uniformly arranged around the longitudinal axis along the circumferential direction.
  11. An electromagnetic lens according to claim 1, wherein the electrode element comprises a beam aperture element (601) forming a delimiting aperture (605) having a diameter (d6) defined around the longitudinal axis, and the delimiting aperture limits the lateral width of a charged particle beam (600) propagating along the longitudinal axis.
  12. An electromagnetic lens according to claim 11, wherein the beam aperture element (601) is connected to a current measuring device (702) to measure the amount of the charged particle beam absorbed by the beam aperture element.
  13. An electromagnetic lens according to claim 11, wherein an electrostatic multipole electrode (602) is provided in front of the beam aperture element (601) when viewed in the direction of propagation of the beam along the longitudinal axis, and comprises a plurality of sub-electrodes uniformly arranged around the longitudinal axis along the circumferential direction, configured to determine the transverse position of the beam (600) with respect to the longitudinal axis.
  14. An electromagnetic lens according to claim 1, wherein the sleeve insert comprises a ceramic body in which the electrode elements are each implemented as a conductive coating having a limited shape and area.
  15. A charged particle optical device comprising an electromagnetic lens (10) according to any one of claims 1 to 14 and configured to affect a charged particle beam of a charged particle optical device (401) that propagates through the electromagnetic lens along the longitudinal axis, wherein the electromagnetic lens is part of a projection optical system of the charged particle optical device.
  16. In claim 15, the charged particle optical device is a multi-column system comprising a plurality of particle optical columns, and each column comprises a projection optical system that uses a respective particle beam and is equipped with a respective electromagnetic lens (100).

Description

Electromagnetic Lens The present invention relates to an electromagnetic lens configured to modulate a charged particle beam of a charged particle optical device for the purpose of lithographic recording and similar processing including nanopatterning. Such a lens is provided with a path for the charged particle beam along a longitudinal direction corresponding to the propagation direction of the charged particle beam itself and generally aligned concentrically with the optical axis of the charged particle optical device. The present invention also relates to a charged particle optical device comprising an electromagnetic lens of the aforementioned type. The applicant has implemented a charged particle multi-beam device comprising one or more electromagnetic lenses of the aforementioned type, developed the said charged particle optical components, pattern defining devices, and writing methods for the multi-beams, and commercialized a 50 keV electron multi-beam writer, referred to as eMET (electron mask exposure tool) or MBMW (multi-beam mask writer), which is used to implement any photomask for 193 nm immersion lithography, templates for nanoimprint lithography, and masks for EUV lithography. The applicant's system is also referred to as PML2 (Projection Mask-Less Lithography) for electron beam direct writer (EBDW) applications on substrates. In order to increase throughput in mass industrial manufacturing, particularly in relation to maskless lithography and direct writing to substrates (e.g., wafers), it is necessary to increase the current delivered by the charged particle beam passing through the charged particle nanopatterning device; this generally requires corresponding compensation by reducing the magnitude of optical aberrations introduced by the device through other mechanisms, at the cost of limiting resolution due to Coulomb interactions between charged particles. To this end, the applicant has developed a charged particle multi-beam device composed of multiple parallel optical columns coupled 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, enables significantly larger charged particle beam currents while overcoming the limitations caused by the trade-off between optical aberrations and current found in single-column systems. This is due to the fact that the total current delivered to the target is divided into multiple optical axes, while the resolution limitation is dominated by the amount of current per optical axis. Single columns of this type are 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). A typical multi-column system includes multiple optical sub-columns, each sub-column including a lighting system in which a charged particle projection optical device, for example, including multiple electrostatic and/or electromagnetic lenses, delivers a broad telecentric charged particle beam to a subsequent pattern definition system. To use a system such as a high-throughput wafer direct writer, a significant number of sub-columns, for example about 100 sub-columns, must be placed on a single semiconductor wafer. However, for this to work, each sub-column must have a diameter that is part of the wafer width, such as a diameter of 31 mm or less for a 300 mm (12") wafer, for example. On the other hand, slim-diameter magnetic lenses cannot be realized with coil-based magnetic lenses for generating the desired magnetic field, because the reduction in column diameter corresponds to very large Joule heating due to the large current required to operate the coil to generate a sufficiently strong magnetic field. Due to tight space requirements, there is insufficient space for the high-precision sensors and appropriate temperature control systems, including isotropic and uniform cooling, required for conventional coil-based magnetic lenses. Additionally, the narrow space requirements resulting from the target diameter of the slim column and the arrangement in an appropriate multi-column system hinder the fabrication of suitable coil-based magnetic lenses. Although the aforementioned limitations caused by thermal and geometric requirements are severe, they can be overcome by using a permanent magnet-based magnetic lens within a high-permeability housing body to generate a magnetic field, as in a possible embodiment of the present invention. However, such permanent magnet-based systems cannot be recalibrated after the manufacturing and assembly processes are completed, which means that its magnetic field [affects] the current passing through the coil This presents a significant disadvantage for coil-based magnetic lenses, which can be controlled by readjustment and have inherent limitations on the precision of the target magnetic field, particularly due to manufacturing and assembly accuracy.