Apparatus of plural charged-particle beams
A multi-beam apparatus for observing a sample with high resolution and high throughput is proposed. In the apparatus, a source-conversion unit changes a single electron source into a virtual multi-source array, a primary projection imaging system projects the array to form plural probe spots on the sample, and a condenser lens adjusts the currents of the plural probe spots. In the source-conversion unit, the image-forming means is on the upstream of the beamlet-limit means, and thereby generating less scattered electrons. The image-forming means not only forms the virtual multi-source array, but also compensates the off-axis aberrations of the plurality of probe spots.
1. A source-conversion unit, comprising:
an image-forming element including:
a first layer with a first set of multi-pole structures, and
a second layer with a second set of multi-pole structures respectively corresponding to the first set of multi-pole structures,
wherein multi-pole structures of the first set of multi-pole structures are aligned with the respective multi-pole structures of the second set of multi-pole structures to form a plurality of pairs of multi-pole structures,
wherein a pair of multi-pole structures functions as at least a micro-deflector to deflect a beamlet of a charged particle beam generated by a charged particle source to form a virtual image of the charged particle source.
2. The source-conversion unit of claim 1 , wherein the pair of multi-pole structures functions as the micro-deflector, and at least one of a micro-lens to focus the beamlet to a desired degree and a micro-stigmator to add a desired amount of astigmatism aberration to the beamlet.
3. The source-conversion unit of claim 1 , further comprising:
a beamlet-limit element disposed below the image-forming element and including a plurality of beam-limit openings respectively corresponding to the plurality of pairs of multi-pole structures to limit a plurality of beamlets deflected by the plurality of pairs of multi-pole structures.
4. The source-conversion unit of claim 3 , wherein each one of the plurality of beam-limit openings is aligned with a corresponding pair of the plurality of pairs of multi-pole structures.
5. The source-conversion unit of claim 1 , wherein the first layer is an upper layer, and the second layer is a lower layer disposed below the first layer.
6. The source-conversion unit of claim 1 , wherein each multi-pole structure of the first set of multi-pole structures and the second set of multi-pole structures is a 4-pole structure.
7. The source-conversion unit of claim 6 , wherein in each pair of multi-pole structures, a multi-pole structure of the first layer and a multi-pole structure of the second layer have a 45° difference in azimuth.
8. The source-conversion unit of claim 1 , further comprising:
a first electric conduction plate with a plurality of through-holes, each through-hole is aligned with a corresponding pair of the plurality of pairs of multi-pole structures.
9. The source-conversion unit of claim 8 , wherein the first electric conduction plate is disposed below the plurality of pairs of multi-pole structures.
10. The source-conversion unit of claim 8 , wherein the first electric conduction plate is disposed above the plurality of pairs of multi-pole structures.
11. The source-conversion unit of claim 10 , further comprising:
a second electric conduction plate disposed below the plurality of pairs of multi-pole structures.
12. The source-conversion unit of claim 1 , wherein the charged particle source is an electron source, and the charged particle beam is an electron beam.
13. A multi-beam apparatus, comprising the source-conversion unit of claim 1 .
14. A method to configure a source-conversion unit, comprises:
providing an image-forming element including:
a first layer with a first set of multi-pole structures; and
a second layer with a second set of multi-pole structures respectively corresponding to the first set of multi-pole structures,
wherein multi-pole structures of the first set of multi-pole structures are aligned with the respective multiple-pole structures of the second set of multi-pole structures to form a plurality of pairs of multi-pole structures,
wherein a pair of multi-pole structures functions as a micro-deflector to deflect a beamlet of a charged particle beam generated by a charged particle source to form a virtual image of the charged particle source.
15. The method of claim 14 , wherein the pair of multi-pole structures functions as the micro-deflector, and at least one of a micro-lens to focus the beamlet to a desired degree and a micro-stigmator to add a desired amount of astigmatism aberration to the beamlet.
16. The method of claim 14 , further comprising:
providing a beamlet-limit element disposed below the image-forming element and including a plurality of beam-limit openings respectively corresponding to the plurality of pairs of multi-pole structures to limit a plurality of beamlets deflected by the plurality of pairs of multi-pole structures.
17. The method of claim 16 wherein each one of the plurality of beam-limit openings is aligned with a corresponding pair of the plurality of pairs of multi-pole structures.
18. The method of claim 14 , wherein the first layer is an upper layer, and the second layer is a lower layer disposed below the first layer.
19. The method of claim 14 , wherein each multi-pole structure of the first set of multi-pole structures and the second set of multi-pole structures is a 4-pole structure.
20. The method of claim 19 , wherein in each pair of multi-pole structures, a multi-pole structure of the first layer and a multi-pole structure of the second layer have a 45° difference in azimuth.
21. The method of claim 14 , further comprising:
providing a first electric conduction plate with a plurality of through-holes, each through-hole is aligned with a corresponding pair of the plurality of pairs of multi-pole structures.
22. The method of claim 21 , wherein the first electric conduction plate is disposed below the plurality of pairs of multi-pole structures.
23. The method of claim 21 , wherein the first electric conduction plate is disposed above the plurality of pairs of multi-pole structures.
24. The method of claim 23 , further comprising:
providing a second electric conduction plate disposed below the plurality of pairs of multi-pole structures.
25. The method of claim 24 , wherein the charged particle source is an electron source, and the charged particle beam is an electron beam.
26. A source-conversion unit, comprising:
an image-forming element including:
a first layer with a first set of multi-pole structures, and
a second layer with a second set of multi-pole structures,
wherein the first set of multi-pole structures are aligned with the second set of multi-pole structures to function as at least one of a micro-deflector to deflect a beamlet of charged particles, a micro-lens to focus the beamlet, and a micro-stigmator to add a desired amount of astigmatism aberration to the beamlet.