Charged particle optical device, objective lens assembly, detector, detector array, and methods
The embodiments of the present disclosure provide various techniques for detecting backscatter charged particles, including accelerating charged particle sub-beams along sub-beam paths to a sample, repelling secondary charged particles from detector arrays, and providing devices and detectors which can switch between modes for primarily detecting charged particles and modes for primarily detecting secondary particles.
1. A charged particle-optical device configured to project a multi-beam of charged particles along sub-beam paths towards a sample, the multi-beam comprising sub-beams, the charged particle-optical device comprising:
an objective lens array configured to project an array of charged particle sub-beams onto the sample, wherein the objective lens array comprises at least two electrodes in which are defined aperture arrays, corresponding apertures of the aperture arrays in the at least two electrodes are aligned with and arranged along a sub-beam path of the array of charged particle sub-beams; and
a detector array configured to be proximate the sample and configured to capture charged particles emitted from the sample,
wherein the charged particle-optical device is configured to repel secondary charged particles emitted from the sample away from the detector array.
2. The charged particle-optical device of claim 1 , wherein objective lenses of the objective lens array are configured to accelerate the array of charged particle sub-beams along the sub-beam paths.
3. The charged particle-optical device of claim 1 , wherein the detector array is configured in use to have a detector array potential and the sample is configured in use to have a sample potential so that there is a potential difference between the detector array and the sample potential, and wherein the sample potential is more positive than the detector array potential.
4. The charged particle-optical device of claim 3 , wherein the potential difference between the sample potential and the detector array potential is greater than a secondary electron threshold.
5. The charged particle-optical device of claim 1 , wherein a first electrode of the at least two electrodes is up-beam of a second electrode of the at least two electrodes, the first electrode configured in use to have a first electrode potential and the second electrode configured in use to have a second electrode potential, and wherein the second electrode potential is more positive than the first electrode potential.
6. The charged particle-optical device of claim 5 , wherein the sample is configured to be at a sample potential in use, and wherein the sample potential is more positive than the second electrode potential.
7. The charged particle-optical device of claim 1 , further comprising an insulating structure separating adjacent electrodes, the insulating structure comprising a main body and a protrusion radially inwards of the main body, the main body having a first side and a second side opposing the first side, wherein one of the electrodes contacts the main body and the protrusion on the first side of the insulating structure, and the main body contacts another of the electrodes on the second side of the insulating structure and a gap is defined between the protrusion and the other of the electrodes.
8. The charged particle-optical device of claim 1 , further comprising a control lens array positioned up-beam of the objective lens array, wherein a control lens is associated with a corresponding objective lens.
9. The charged particle-optical device of claim 8 , wherein the control lens array is configured to provide an intermediate focus between the control lens and the corresponding objective lens.
10. The charged particle-optical device of claim 8 , wherein the control lens array is configured to decelerate charged particle sub-beams of the array of charged particle sub-beams along the sub-beam paths.
11. The charged particle-optical device of claim 1 , wherein the detector array is configured to detect more backscattered charged particles than secondary charged particles.
12. The charged particle-optical device of claim 1 , wherein the detector array is positioned approximately 10 μm to approximately 50 μm up-beam from the sample.
13. The charged particle-optical device of claim 1 , further comprising an electric power source configured to apply a potential difference between at least one of: two of the at least two electrodes, or at least one of the at least two electrodes and the sample, and both.
14. A charged particle-optical device configured to project a multi-beam of charged particles along sub-beam paths towards a sample, the multi-beam comprising sub-beams, the charged particle-optical device comprising:
an objective lens array configured to project an array of charged particle sub-beams onto the sample, wherein the objective lens array comprises at least two electrodes in which are defined aperture arrays, corresponding apertures of the aperture arrays in the at least two electrodes are each aligned with and arranged along a sub-beam path of the array of charged particle sub-beams; and
a detector array configured to be proximate the sample and configured to capture charged particles emitted from the sample,
wherein objective lenses of the objective lens array are further configured to accelerate the array of charged particle sub-beams along the sub-beam paths.
15. The charged particle-optical device of claim 14 , wherein the detector array is configured in use to have a detector array potential and the sample is configured in use to have a sample potential, so that there is a potential difference between the detector array and the sample potential, and wherein the sample potential is more positive than the detector array potential.
16. The charged particle-optical device of claim 15 , wherein the potential difference between the sample potential and the detector array potential is greater than a secondary electron threshold.
17. The charged particle-optical device of claim 14 , wherein a first electrode of the at least two electrodes is up-beam of a second electrode of the at least two electrodes, the first electrode configured in use to have a first electrode potential and the second electrode configured in use to have a second electrode potential, and wherein the second electrode potential is more positive than the first electrode potential.
18. An objective lens assembly for projecting a multi-beam of charged particles towards a sample, the objective lens assembly comprising:
an objective lens array comprising at least two electrodes arranged along a path of the multi-beam and in which are defined a plurality of apertures, corresponding apertures of the plurality of apertures in each of the at least two electrodes are aligned with and arranged along a sub-beam path of the path of the multi-beam; and
a detector array configured to detect charged particles emanating from the sample in response to the multi-beam incident on the sample, wherein the detector array is configured to be positionable proximate the sample and is configured to repel secondary electrons emanating from the sample away from the detector array.
19. The objective lens assembly of claim 18 , wherein the sample is set to a sample potential and the detector array is set to a detector array potential so there is a potential difference between the sample potential and the detector array potential, and the potential difference between the sample potential and the detector array potential is greater than a secondary electron threshold.
20. The objective lens assembly of claim 18 , wherein the detector array is configured to detect more backscattered electrons than secondary electrons.