US-12626881-B2 - Aberration corrector, a charged particle beam apparatus, a method of aligning an aberration corrector and a method of correcting aberration of a charged particle beam

US12626881B2US 12626881 B2US12626881 B2US 12626881B2US-12626881-B2

Abstract

An aberration corrector. The aberration corrector including a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole. The first plurality of magnetic elements including at least a first magnetic element, the first magnetic element including a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite the proximal end; the proximal end having a tip with a tip surface in a shape of a semi-spheroid; and a contact point of the tip surface contacts the first magnetic pole.

Inventors

Florian Lampersberger
John Breuer
Matthias FIRNKES

Assignees

ICT Integrated Circuit Testing Gesellschaft für Halbleiterprüftechnik mbH

Dates

Publication Date: 20260512
Application Date: 20230420

Claims (20)

1 . An aberration corrector, comprising: a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements comprising at least a first magnetic element, the first magnetic element comprising: a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite the proximal end; the proximal end of the first magnetic rod having a tip with a tip surface in a shape of a curved semi-spheroid; and a contact point of the tip surface contacts the first magnetic pole.
2 . The aberration corrector according to claim 1 , wherein the contact point of the tip surface contacts the first magnetic pole at a contact surface of the first magnetic pole, and the contact surface has a curvature smaller than a tip curvature of the tip surface, particularly the curvature is zero.
3 . The aberration corrector according to claim 1 , wherein the first magnetic element comprises a first excitation coil disposed on the first magnetic rod.
4 . The aberration corrector according to claim 3 , wherein the first excitation coil is wound on a first carrier, the first carrier electrically insulating the first excitation coil from the first magnetic rod.
5 . The aberration corrector according to claim 1 , wherein the first magnetic element comprises a first electrical connector connected to the first magnetic rod adjacent the distal end.
6 . The aberration corrector according to claim 5 , wherein the first magnetic element comprises a spring at the proximal end contacting the first magnetic pole to provide an electrical connection between the first magnetic rod and the first magnetic pole.
7 . The aberration corrector according to claim 1 , further comprising a ring that magnetically connects the first plurality of magnetic elements with one another.
8 . The aberration corrector according to claim 7 , further comprising a foil positioned between the ring and the first plurality of magnetic elements, wherein the foil electrically insulates the ring and the first plurality of magnetic elements.
9 . The aberration corrector according to claim 1 , further comprising: a support configured to support at least the first magnetic rod.
10 . The aberration corrector according to claim 9 , wherein the support comprises a vacuum feedthrough for the first magnetic rod.
11 . The aberration corrector according to claim 1 , further comprising: a pressing element configured to adjust a contact force between the first magnetic rod and the first magnetic pole.
12 . The aberration corrector according to claim 1 , wherein each magnetic pole of the first plurality of magnetic elements is attached to an assembly ring.
13 . The aberration corrector according to claim 1 , wherein the first plurality of magnetic elements comprises 8 magnetic elements forming an 8-pole or 12 magnetic elements forming a 12-pole.
14 . The aberration corrector according to claim 1 , comprising a second stage comprising a second plurality of magnetic elements, each magnetic element of the second plurality of magnetic elements comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, wherein a first stage comprises the first plurality of magnetic elements and the second stage is stacked over the first stage.
15 . A method of correcting aberration of a charged particle beam with an aberration corrector according to claim 1 , comprising: guiding the charged particle beam through an opening of an aberration corrector; and correcting aberrations of the charged particle beam.
16 . The method of correcting aberration of a charged particle beam according to claim 15 , comprising: providing a magnetic field to the plurality of magnetic elements.
17 . The method of correcting aberration of a charged particle beam according to claim 15 , comprising: biasing a plurality of electrodes of the aberration corrector to form an electrostatic multipole.
18 . A charged particle beam apparatus, comprising: a sample stage; a charged particle source adapted to generate a charged particle beam; and a charged particle beam manipulation system including an aberration corrector, the aberration corrector comprising: a first plurality of magnetic elements, each magnetic element comprising a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole, the first plurality of magnetic elements comprising at least a first magnetic element, the first magnetic element comprising: a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite the proximal end; the proximal end of the first magnetic rod having a tip with a tip surface in a shape of a curved semi-spheroid; and a contact point of the tip surface contacts the first magnetic pole.
19 . A method of aligning an aberration corrector, the method comprising: providing a plurality of magnetic poles, the magnetic poles having a predetermined alignment; contacting the plurality of magnetic poles with a plurality of magnetic rods, wherein each of the plurality of magnetic rods is connected to a corresponding magnetic pole such that the predetermined alignment of the plurality of magnetic poles is substantially maintained; and pressing a tip surface of a first magnetic rod in a shape of a curved semi-spheroid onto a contact surface of a first magnetic pole.
20 . The method according to claim 19 , further comprising: moving at least one magnetic rod of the plurality of magnetic rods during contacting of the corresponding magnetic pole with essentially no movement of the corresponding magnetic pole.

Description

TECHNICAL FIELD Embodiments described herein relate to an aberration corrector, a charged particle system including an aberration corrector and methods for aligning a charged particle beam. BACKGROUND In charged particle beam devices such as microscopes, micro-machining apparatuses, semiconductor manufacturing apparatuses and so forth, single-stage or multi-stage multipoles (quadrupoles, hexapoles, octupoles and so forth) are used in deflectors or aberration correctors. Machining accuracies for the aforementioned apparatuses can be in the range of 10 micrometer or so. The apparatuses can perform observation with an accuracy in the nanometer range or even the sub-nanometer range. For such applications, the resolution of the apparatus is beneficially in the sub-nanometer range. Aberration correction with a multipole corrector can improve the performance of charged particle beam apparatuses. Such an aberration corrector includes one or more multipole stages. The quality of the correction depends on the precision of the on-axial multipole fields. Tolerances between pole to pole lead to a disturbed magnetic field distribution on the optical axis. In particular, in aberration correctors such as spherical aberration correctors and chromatic aberration correctors, where multipole fields involved can be strong, inaccuracies in such correctors can lead to imperfections in the electric and magnetic field profiles, which in turn generate residual aberrations that limit the attainable performance of the apparatus. Accordingly, high accuracy in manufacturing and assembling is beneficial. For example, accuracy in positioning of poles and other components that make up the magnetic circuit in an aberration corrector is advantageous. This is because such positioning inaccuracies cause parasitic multipole fields which in turn cause blurring of the beam. In addition, solutions to increase accuracy often involve increasing complexity which negatively impacts reproducibility and cost, especially in mass production. Accordingly, it would be beneficial to provide an aberration corrector, and a method of reducing or minimizing magnetic field deviations between pole to pole. SUMMARY In light of the above, an invention as defined by the claims is provided. According to aspects described herein, aberration correctors, a charged particle beam apparatus, a method of aligning an aberration corrector and a method of correcting aberration of a charged particle beam are provided. According to an embodiment, an aberration corrector is provided. The aberration corrector includes a first plurality of magnetic elements, each magnetic element including a magnetic pole and a corresponding magnetic rod for providing a magnetic field to the magnetic pole. The first plurality of magnetic elements including at least a first magnetic element, the first magnetic element including a first magnetic pole; a first magnetic rod having a proximal end adjacent to the first magnetic pole and a distal end opposite the proximal end; the proximal end having a tip with a tip surface in a shape of a semi-spheroid; and a contact point of the tip surface contacts the first magnetic pole. According to an embodiment, a charged particle beam apparatus is provided. The charged particle beam apparatus including a sample stage; a charged particle source adapted to generate a charged particle beam; and a charged particle beam manipulation system including the aberration corrector according to any of the embodiments described herein. According to an embodiment, a method of aligning an aberration corrector is provided. The method including providing a plurality of magnetic poles, the magnetic poles having a predetermined alignment; and contacting the plurality of magnetic poles with a plurality of magnetic rods, wherein each of the plurality of magnetic rods is connected to a corresponding magnetic pole such that the predetermined alignment of the plurality of magnetic poles is substantially maintained. According to an embodiment, a method of correcting aberration of a charged particle beam with an aberration corrector according to any of the embodiments described herein is provided. The method includes guiding the charged particle beam through an opening of an aberration corrector; and correcting aberrations of the charged particle beam. Further advantages, features, aspects and details that can be combined with embodiments described herein are evident from the dependent claims, the description and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of embodiments, briefly summarized above, may be had by reference to embodiments. The accompanying drawings relate to one or more embodiments and are described in the following. FIG. 1 is a section view of an aberration corrector according to embodiments described herein; FIG. 2A is a section view