Charged particle beam device
View Patent ↗Provided is a multifunctional charged particle beam device capable of inclining a beam with little aberration. The aberration is corrected by forming a local divergent field with a multipole, parallel current lines, or the like, matching the beam axis with the local divergent field via a conventional rotationally symmetric lens, deflector or astigmatism corrector, and counteracting an aberration occurring from another rotationally symmetric convex lens field.
1. A charged particle beam device comprising:
a charged particle source;
a rotationally symmetric lens system through which a charged particle beam generated from the charged particle source passes;
an electromagnetic field generating unit configured to generate N-fold symmetry electromagnetic field (N is a natural number of 2 or more) around the optical axis, the electromagnetic field generating unit including a pair of parallel current lines parallel to an optical axis of the charged particle beam; and
an entrance deflector arranged at a side of the electromagnetic field generating unit closer to the charged particle source than an entrance side of the electromagnetic field generating unit and configured to deflect the charged particle beam on an axis in a direction perpendicular to a line connecting the pair of parallel current lines or in a vicinity thereof in a plane perpendicular to a rotationally symmetric axis of the lens system,
wherein the entrance deflector is configured to deflect the charged particle beam passing through the lens system such that the charged particle beam enters a local divergent field formed in an off-axis region of the N-fold symmetry electromagnetic field, and
wherein the local divergent field has a range of a radius of R/3 from a center of a space through which the charged particle beam passes except for the center, where, as viewed in a plane perpendicular to the rotational symmetry axis of the lens system, the center is the position of the rotational symmetry axis, and R is a distance from the center to the parallel current lines.
2. The charged particle beam device according to claim 1 , wherein the electromagnetic field generating unit includes N parallel current lines arranged around the optical axis outside the space through which the charged particle beam passes.
3. The charged particle beam device according to claim 2 , wherein
an inside part of a toroidally wound coil functions as the parallel current lines, and the inside part of the toroidally wound coil is arranged inside a magnetic field shield, and the rest part of the toroidally wound coil is arranged outside the magnetic field shield.
4. The charged particle beam device according to claim 1 , wherein
the electromagnetic field generating unit is a magnetic field type multipole or an electrostatic type multipole.
5. The charged particle beam device according to claim 1 , wherein
the electromagnetic field generating unit generates a 2-fold symmetry electromagnetic field and a 4-fold symmetry electromagnetic field such that the respective local divergent fields overlap with each other, and the charged particle beam is made to enter the local divergent fields overlapping with each other.
6. The charged particle beam device according to claim 5 , further comprising: two parallel current lines arranged around the optical axis for generating the 2-fold symmetry electromagnetic field, and four parallel current lines arranged around the optical axis for generating the 4-fold symmetry electromagnetic field outside the space through which the charged particle beam passes, wherein a chromatic aberration and an aperture aberration of the charged particle beam are corrected based on a magnitude of current flowing through the parallel current lines.
7. The charged particle beam device according to claim 1 , wherein
the lens system includes a first lens arranged at the entrance side to the electromagnetic field generating unit, and a second lens arranged at an exit side to the magnetic field generating unit.
8. The charged particle beam device according to claim 7 , wherein
the first lens and the second lens are electrostatic lenses.
9. The charged particle beam device according to claim 7 , further comprising:
an exit deflector arranged at the exit side of the electromagnetic field generating unit.
10. The charged particle beam device according to claim 9 , wherein
an entrance angle and an exit angle are substantially symmetric to each other, while being parallel to the optical axis at substantially a midpoint of the electromagnetic field generating unit via the entrance deflector, the exit deflector, and the first lens.
11. A charged particle beam device comprising:
a charged particle source;
a rotationally symmetric lens system through which a charged particle beam generated from the charged particle source passes;
an electromagnetic field generating unit configured to generate N-fold symmetry electromagnetic field (N is a natural number of 2 or more) around the optical axis, the electromagnetic field generating unit including a pair of parallel current lines parallel to an optical axis of the charged particle beam; and
an entrance deflector arranged at a side of the electromagnetic field generating unit closer to the charged particle source than an entrance side of the electromagnetic field generating unit and configured to deflect the charged particle beam to a direction perpendicular to a line connecting the pair of parallel current lines,
wherein an aberration of the charged particle beam due to the lens system is corrected by deflecting the charged particle beam passing through the lens system via the entrance deflector to make the charged particle beam to enter a local divergent field formed in an off-axis region of the N-fold symmetry electromagnetic field, and
wherein an astigmatism corrector including two sets of parallel current lines arranged to be shifted 45 degrees from each other around the optical axis, is installed at the entrance side and an exit side to the electromagnetic field generating unit.
12. A charged particle beam device comprising:
a charged particle source;
a rotationally symmetric lens system through which a charged particle beam generated from the charged particle source passes;
an electromagnetic field generating unit configured to generate N-fold symmetry electromagnetic field (N is a natural number of 2 or more) around the optical axis, the electromagnetic field generating unit including a pair of parallel current lines parallel to an optical axis of the charged particle beam;
an entrance deflector arranged at a side of the electromagnetic field generating unit closer to the charged particle source than an entrance side of the electromagnetic field generating unit and configured to deflect the charged particle beam to a direction perpendicular to a line connecting the pair of parallel current lines; and
a first astigmatism corrector arranged at the entrance side of the electromagnetic field generating unit, and a second astigmatism corrector arranged at the exit side of the electromagnetic field generating unit,
wherein an aberration of the charged particle beam due to the lens system is corrected by deflecting the charged particle beam passing through the lens system via the entrance deflector to make the charged particle beam to enter a local divergent field formed in an off-axis region of the N-fold symmetry electromagnetic field,
wherein the lens system includes a first lens arranged at the entrance side to the electromagnetic field generating unit, and a second lens arranged at an exit side to the magnetic field generating unit, and
wherein the first lens and the second lens are electrostatic lenses.
13. A charged particle beam device comprising:
a charged particle source;
a rotationally symmetric lens system through which a charged particle beam generated from the charged particle source passes;
a correction coil unit configured to generate a local rotating magnetic field around the optical axis;
an electromagnetic field generating unit configured to generate N-fold symmetry electromagnetic field (N is a natural number of 2 or more) around the optical axis, the electromagnetic field generating unit including a pair of parallel current lines parallel to an optical axis of the charged particle beam; and
an entrance deflector arranged at the entrance side of the correction coil unit and configured to deflect the charged particle beam on an axis in a direction perpendicular to a line connecting the pair of parallel current lines or in a vicinity thereof in a plane perpendicular to a rotationally symmetric axis of the lens system,
wherein the entrance deflector is configured to deflect the charged particle beam passing through the lens system such that the charged particle beam enters the local rotating magnetic field formed with the correction coil unit, and
wherein the local rotating magnetic field has a range of a radius of R/3 from a center of a space through which the charged particle beam passes except for the center, where, as viewed in a plane perpendicular to the rotational symmetry axis of the lens system, the center is the position of the rotational symmetry axis, and R is a distance from the center to the parallel current lines.
14. A charged particle beam device comprising:
a charged particle source;
a rotationally symmetric lens system through which a charged particle beam generated from the charged particle source passes;
a correction coil unit configured to generate a local rotating magnetic field around the optical axis;
an electromagnetic field generating unit configured to generate N-fold symmetry electromagnetic field (N is a natural number of 2 or more) around the optical axis, the electromagnetic field generating unit including a pair of parallel current lines parallel to an optical axis of the charged particle beam; and
an entrance deflector arranged at the entrance side of the correction coil unit and configured to deflect the charged particle beam to a direction perpendicular to a line connecting the pair of parallel current lines, wherein
an aberration of the charged particle beam due to the lens system is corrected by deflecting the charged particle beam passing through the lens system via the entrance deflector to make the charged particle beam enter the local rotating magnetic field formed with the correction coil unit, and
the correction coil unit includes two sets of toroidally wound coils radially arranged from the optical axis, and the toroidally wound coil has a trapezoidal shape whose upper side and lower side are parallel to the optical axis and the length of the lower side far from the optical axis is longer than the length of the upper side near the optical axis, and the local rotating magnetic field is generated in a space sandwiched by the two sets of toroidally wound coils with parallel current lines configured by the upper side and the lower side.