Method of operating a particle beam system and computer program product

Patent metadata

Field	Value
Publication number	US-2024258065-A1
Application number	US-202418424034-A
Country	US
Kind code	A1
Filing date	Jan 26, 2024
Priority date	Jan 27, 2023
Publication date	Aug 1, 2024
Grant date	—

Abstract

Particle beam systems, for example electron beam microscopes, exhibit improved resolution in a first direction by manipulating a beam of charged particles so that the beam has a non-circular beam profile in a focal plane of an objective lens. Multiple images of a sample can be recorded at different orientations of the beam profile relative to the sample, and the recorded images can be synthesized using non-uniform spatial-frequency weights to obtain an image of the sample having improved resolution in any direction. The orientation of the beam profile can be adjusted to a target orientation depending on a structure on a sample prior to recording an image of the sample, thereby making it possible to achieve highest resolution in a selected direction of interest.

First claim

1 . A method, comprising:
a) using a particle beam system to generate a beam of charged particles; b) using an objective lens of the particle beam system to focus the beam into a focal plane; c) manipulating the beam into a beam profile in which a ratio of a first interaction length to a second interaction length is at most 1:1.2; d) adjusting an orientation of the beam profile in the focal plane relative to a sample to a target orientation; e) using the manipulated beam having the adjusted orientation to record an image of the sample located in the focal plane; f) repeating d) and e) using at least one target orientation different from the previously used target orientations; and g) calculating a synthesized image of the sample based on the recorded images, wherein: the first interaction length is a distance, measured along a first direction, between a first straight line and a second straight line; the first straight line is perpendicular to the first direction; the second straight line is perpendicular to the first direction; the first straight line defines a first half-plane; the first half-plane is in the focal plane; the first half-plane contains 25% of a total intensity of the beam in the focal plane; the second straight line defines a second half-plane; the second half-plane is in the focal plane; the second half-plane contains 25% of the total intensity of the beam in the focal plane; the second half-plane does not overlap the first half-plane; the second interaction length is a distance, measured along a second direction different from the first direction, between a third straight line and a fourth straight line; the third straight line is perpendicular to the second direction; the fourth straight line is perpendicular to the second direction; the third straight line defines a third half-plane; the third half-plane is in the focal plane and contains 25% of the total intensity of the beam in the focal plane; the fourth straight line defines a fourth half-plane; the fourth half-plane is in the focal plane; the fourth half-plane and contains 25% of the total intensity of the beam in the focal plane; and the fourth half-plane and does not overlap the third half-plane.

2 . The method of claim 1 , wherein g) comprises:
weighting the recorded images using non-uniform weight distributions, wherein orientations of the weight distributions are selected to correspond to the target orientations; and merging the weighted images.

3 . The method of claim 2 , wherein:
the weight distributions w i ({right arrow over (k)}) fulfil w i ({right arrow over (k)} i,1 )>w i ({right arrow over (k)} i,2 ); i represents an index identifying an i-th one of the recorded images and ranges over all of the recorded images; w i ({right arrow over (k)} i,1 ) represents a weight for a spatial-frequency domain component of the i-th recorded image at spatial-frequency {right arrow over (k)} i,1 ; w i ({right arrow over (k)} i,2 ) represents the weight for the spatial-frequency domain component of the i-th recorded image at spatial-frequency {right arrow over (k)} i,2 ; {right arrow over (k)} i,1 represents a spatial-frequency of magnitude K in a spatial-frequency domain direction corresponding to the first direction; and {right arrow over (k)} i,2 represents a spatial-frequency of magnitude K in a spatial-frequency domain direction corresponding to the second direction.

4 . The method of claim 1 , wherein g) comprises:
convolving the recorded images using non-uniform point spread functions, wherein orientations of the point spread functions are selected to correspond to the target orientations; and merging the convolved images.

5 . The method of claim 1 , wherein the manipulating of the beam ( 3 ) (S 3 ) comprises:
generating a first multipole field acting on the beam ( 3 ), wherein the first multipole field comprises a first electric multipole field having a four-pole component and a first magnetic multipole field having a four-pole component, wherein the first electric multipole field and the first magnetic multipole field are superimposed.

6 . The method of claim 5 , wherein the first multipole field:
focuses the charged particles having a kinetic energy greater than a predetermined kinetic energy in the first direction; defocusses the charged particles having a kinetic energy less than the predetermined kinetic energy in the first direction; defocusses the charged particles having the kinetic energy greater than the predetermined kinetic energy in the second direction; and focuses the charged particles having the kinetic energy less than the predetermined kinetic energy in the second direction.

7 . The method of claim 5 , wherein the first multipole field reduces a chromatic aberration of the focusing by the objective lens in the first direction and increases the chromatic aberration of the focusing by the objective lens in the second direction.

8 . The method of claim 5 , wherein d) comprises rotating the first multipole field.

9 . The method of claim 5 , wherein, except for the first multipole field, the method comprises no other electric or magnetic fields are provided for correcting the chromatic aberration of the focusing by the objective lens in a direction different from the first direction.

10 . The method of claim 5 , wherein d) comprises:
adjusting a maximum illumination angle of the beam in a first plane to a first maximum illumination angle value, the first plane being perpendicular to the focal plane and including the first direction; and adjusting a maximum illumination angle of the beam in a second plane to a second maximum illumination angle value different from the first maximum illumination angle value, the second plane being perpendicular to the focal plane and including the second direction.

11 . The method of claim 10 , wherein d) comprises:
using an aperture stop comprising a non-circular aperture to block a first portion of the beam; and transmitting a second portion of the beam through the aperture of the aperture stop, the second portion of the beam being different from the first portion of the beam.

12 . The method of claim 11 , wherein d) comprises rotating the aperture stop.

13 . The method of claim 12 , wherein adjusting the maximum illumination angles comprises generating a second multipole field and a third multipole field, wherein:
the second and third multipole fields act on the beam the objective lens focuses the beam into the focal plane; the second multipole field comprises a second electric multipole field and a second magnetic multipole field; the second multipole field focuses the beam in the first direction with a selectable first focusing power and focuses the beam in the second direction with a selectable second focusing power different from the first focusing power; the third multipole field comprises a third electric multipole field and a third magnetic multipole field; the third multipole field focuses the beam in the first direction with a selectable third focusing power and focuses the beam in the second direction with a selectable fourth focusing power different from the third focusing power.

14 . The method of claim 13 , wherein d) comprises rotating the second multipole field and the third multipole field.

15 . The method of claim 10 , wherein adjusting the maximum illumination angles comprises:
generating a second multipole field acting on the beam before the objective lens focuses the beam in the focal plane; the second multipole field comprises a second electric multipole field and a second

Assignees

• Zeiss Carl Microscopy Gmbh

Inventors

• Preikszas Dirk
• Wicker Kai
• Gamm Bjoern
• Novikau Yauheni
• Wolleschensky Ralf

Classifications

• H01J37/21 Primary

  Means for adjusting the focus · CPC title

• H01J37/1471 Primary

  for centering, aligning or positioning of ray or beam · CPC title

• H01J37/28

  with scanning beams {(H01J37/268, H01J37/292, H01J37/2955 take precedence)} · CPC title

• H01J37/222

  Image processing arrangements associated with the tube · CPC title

• H01J2237/1534

  Aberrations · CPC title