Particle-beam microscope
A particle beam microscope includes an illumination system generating a particle beam having a ring-shaped conical configuration. A selective detection system is configured to selectively detect one of two groups of particles having traversed the object region. The first group of particles includes the particles that traversed the object region un-scattered or scattered by a small scattering amount. The second group of particles includes particles scattered in the object region by a greater scattering amount.
1. A particle beam microscope having a beam path that traverses an object region, the particle beam microscope comprising:
an illumination system located in the beam path upstream of the object region, the illumination system comprising a first particle optical lens, and the illumination system being configured to direct particles to the object region such that the particles are incident at the object region only from directions oriented under an angle, relative to a main axis of the beam path, which is greater than an inner apex angle; and
a detection system located in the beam path downstream of the object region and configured to detect only one group of particles among first and second groups of particles that traversed the object region, the first group of particles comprising only particles that traversed the object region along a straight line and particles scattered at the object region by an angle smaller than a scattering limit angle, and the second group of particles comprising only particles scattered at the object region by a scattering angle greater than the scattering limit angle,
wherein the detection system comprises an aperture plate having an aperture with a radial inner edge located a distance from an optical axis of the particle beam microscope.
2. The particle beam microscope according to claim 1 , wherein the illumination system is configured to direct particles to the object region such that the particles are incident at the object region only from directions oriented under an angle, relative the main axis of the beam path, which is smaller than an outer apex angle.
3. The particle beam microscope according to claim 1 , wherein the inner apex angle is greater than 30 mrad.
4. The particle beam microscope according to claim 2 , wherein a ratio of the outer apex angle and the inner apex angle is less than or equal to 1.1.
5. The particle beam microscope according to claim 2 , wherein a difference between the outer apex angle and inner apex angle is greater than 0.1 mrad.
6. The particle beam microscope according to claim 1 , wherein a difference between the outer apex angle and inner apex angle is less than or equal to 20 mrad.
7. The particle beam microscope according to claim 1 , wherein the illumination system is configured to direct the particles onto an extended region within an object plane located in the object region.
8. The particle beam microscope according to claim 1 , wherein the illumination system is configured to focus the particles at a focus location within the object region.
9. The particle beam microscope according to claim 8 , wherein the illumination system comprises a deflector configured to displace the focus location in a direction transverse to the main axis of the beam path.
10. The particle beam microscope according to claim 1 , wherein the illumination system comprises a deflector configured to change a direction of the main axis of the beam path relative to an optical axis of a focusing lens of the illumination system.
11. The particle beam microscope according to claim 2 , wherein the illumination system is configured to change an angle by more than 0.1 mrad, the angle being selected from the group consisting of the inner apex angle and the outer apex angle.
12. The particle beam microscope according to claim 1 , wherein the illumination system comprises an aperture plate having an aperture with a radial inner edge located at a distance from the optical axis of the particle beam microscope.
13. The particle beam microscope according to claim 12 , wherein the illumination system comprises a focusing lens, and the aperture plate of the illumination system is positioned in a plane selected from the group consisting of a front focal plane of the particle optical lens and a plane conjugate to the front focal plane of the particle optical lens.
14. The particle beam microscope according to claim 1 , wherein the aperture of the aperture plate has a radial outer edge.
15. The particle beam microscope according to claim 1 , wherein the detection system comprises a first detector located downstream of the aperture plate.
16. The particle beam microscope according to claim 1 , wherein the aperture plate includes a second detector.
17. The particle beam microscope according to claim 1 , wherein the aperture of the aperture plate is dimensioned such that it can be traversed only by particles of the first group.
18. The particle beam microscope according to claim 1 , wherein:
the aperture of the aperture plate is dimensioned such that at least one of first and second sub-groups of particles is incident on the aperture plate;
at least one of the first group of particles and only one of the first and second sub-groups of particles traverse the aperture of the aperture plate;
the first sub-group of particles comprises only particles scattered at the object region towards an optical axis of the particle beam microscope; and
the second sub-group of particles comprises only particles scattered at the object region away from the optical axis of the particle beam microscope.
19. The particle beam microscope according to claim 1 , wherein the aperture plate has first and second aperture portions, and a radial inner edge of the second aperture portion is located a greater distance from the optical axis than is a radial outer edge of the first aperture portion.
20. The particle beam microscope according to claim 1 , wherein the detection system comprises a particle optical lens configured to image an object plane located within the object region into an image plane.
21. The particle beam microscope according to claim 20 , wherein the aperture plate is positioned in a plane selected from the group consisting of a back focal plane of the particle optical lens of the detection system and a plane conjugate to the back focal plane of the particle optical lens of the detection system.
22. The particle beam microscope according to claim 20 , wherein the detection system comprises a second deflector positioned in one of the image plane and a plane conjugate to the image plane.
23. A particle beam microscope having a beam path that traverses an object region, the particle beam microscope comprising:
an illumination system located in the beam path upstream of the object region, the illumination system comprising a first particle optical lens, and the illumination system being configured to direct particles to the object region such that the particles are incident at the object region only from directions oriented under an angle, relative to a main axis of the beam path, which is greater than an inner apex angle; and
a detection system located in the beam path downstream of the object region and configured to detect only one group of particles among first and second groups of particles that traversed the object region, the first group of particles comprising only particles that traversed the object region along a straight line and particles scattered at the object region by an angle smaller than a scattering limit angle, and the second group of particles comprising only particles scattered at the object region by a scattering angle greater than the scattering limit angle;
wherein:
the detection system comprises a first aperture plate having an aperture with a radial outer edge located at a distance from an optical axis of the particle beam microscope;
the detection system comprises a second aperture plate having an aperture with a radial outer edge located at a distance from an optical axis of the particle beam microscope;
wherein the first aperture plate is positioned upstream of the second aperture plate in the beam path; and
the first and second aperture plates are positioned such and the apertures of the first and second aperture plates are dimensioned such and particles having traversed the aperture of the first aperture plate are incident on the second aperture plate.
24. The particle beam microscope according to claim 23 , wherein the detection system comprises a particle optical lens configured to image an object plane located within the object region into an image plane.
25. The particle beam microscope according to claim 24 , wherein the at least one of the first and second aperture plates is positioned in a plane selected from the group consisting of a back focal plane of the particle optical lens of the detection system and a plane conjugate to the back focal plane of the particle optical lens of the detection system.
26. The particle beam microscope according to claim 24 , wherein the first aperture plate is positioned upstream of the image plane, and the second aperture plate is positioned downstream of the image plane.
27. The particle beam microscope according to claim 23 , wherein the illumination system is configured to direct particles to the object region such that the particles are incident at the object region only from directions oriented under an angle, relative the main axis of the beam path, which is smaller than an outer apex angle.
28. The particle beam microscope according to claim 23 , wherein the inner apex angle is greater than 30 mrad.
29. The particle beam microscope according to claim 23 , wherein the illumination system is configured to direct the particles onto an extended region within an object plane located in the object region.
30. The particle beam microscope according to claim 23 , wherein the illumination system is configured to focus the particles at a focus location within the object region.
31. The particle beam microscope according to claim 30 , wherein the illumination system comprises a deflector configured to displace the focus location in a direction transverse to the main axis of the beam path.
32. The particle beam microscope according to claim 23 , wherein the illumination system comprises an aperture plate and a focusing lens, the aperture plate of the illumination system has an aperture with a radial inner edge located at a distance from the optical axis of the particle beam microscope, and the aperture plate of the illumination system is positioned in a plane selected from the group consisting of a front focal plane of the particle optical lens of the illumination system and a plane conjugate to the front focal plane of the particle optical lens of the illumination system.
33. The particle beam microscope according to claim 23 , wherein the detection system comprises a first detector located downstream of the second aperture plate.
34. The particle beam microscope according to claim 23 , wherein at least one of the first aperture plate and the second aperture plate includes a second detector.
35. The particle beam microscope according to claim 23 , wherein the aperture of the first aperture plate is dimensioned such that it can be traversed by particles of the first group.