Multi-axis magnetic lens for focusing a plurality of charged particle beams

1. A multi-axis magnetic lens, comprising:

a pair of parallel magnetic conductor plates with a plurality of through holes in pairs therein, the pair of parallel magnetic conductor plates including an upper plate and a lower plate, wherein for each paired through holes, an upper through hole in the upper plate is aligned with a corresponding lower through hole in the lower plate;

a plurality of magnetic cellular pillars in pairs inside the plurality of through holes with a plurality of first radial gaps in pairs respectively, each pair of magnetic cellular pillars forming an axial gap therebetween and having a plurality of through bores in pairs, wherein for each paired first radial gaps formed by each paired magnetic cellular pillars inside each paired through holes, a first upper radial gap is between an inner sidewall of the upper through hole and an outer sidewall of the upper magnetic cellular pillar inside the upper through hole, a first lower radial gap is between an inner sidewall of the lower through hole and an outer sidewall of the lower magnetic cellular pillar inside the lower through hole, wherein for each paired through bores inside said each paired magnetic cellular pillars, an upper through bore in the upper magnetic cellular pillar is aligned with a corresponding lower through bore in the lower magnetic cellular pillar,

thereby forming a plurality of magnetic sub-lens group modules for focusing a plurality of charged particle beams respectively, wherein each magnetic sub-lens group comprises a plurality of magnetic sub-lenses, and paired upper and lower magnetic cellular pillars of each sub-lens group module respectively function as upper and lower pole-pieces of each sub-lens of said sub-lens group; and

a common excitation coil located between the pair of parallel magnetic conductor plates for providing magnetic flux to the plurality of magnetic sub-lens group modules.

2. The multi-axis magnetic lens according to claim 1 , wherein each axial gap is vacuum or filled with non-magnetic material.

3. The multi-axis magnetic lens according to claim 2 , wherein any first radial gap can be vacuum, or filled with non-magnetic or weakly-magnetic material.

4. The multi-axis magnetic lens according to claim 2 , wherein any first radial gap can comprise an annular multilayer therein, and said annular multilayer comprises non-magnetic or weakly-magnetic annular layers and magnetic annular layers in alternate arrangement.

5. The multi-axis magnetic lens according to claim 3 , further comprising a plurality of first magnetic rings, wherein each first magnetic ring has an end adjacent to or inside one of said each paired through bores.

6. The multi-axis magnetic lens according to claim 5 , further comprising a plurality of second magnetic rings, wherein each second magnetic ring has an end adjacent to or inside the other of said each paired through bores.

7. The multi-axis magnetic lens according to claim 3 , further comprising a plurality of first magnetic rings, wherein each first magnetic ring is inserted inside one of said each paired through bores with a second radial gap therebetween.

8. The multi-axis magnetic lens according to claim 7 , wherein said second radial gap can be vacuum, or filled with non-magnetic or weakly-magnetic material.

9. The multi-axis magnetic lens according to claim 7 , wherein said second radial gap can comprise an annular multilayer therein, and said annular multilayer comprises non-magnetic or weakly-magnetic annular layers and magnetic annular layers in alternate arrangement.

10. The multi-axis magnetic lens according to claim 7 , further comprising a plurality of second magnetic rings, wherein each second magnetic ring is inserted inside the other of said each paired through bores with a third radial gap therebetween.

11. The multi-axis magnetic lens according to claim 10 , wherein said second and third radial gaps can respectively be vacuum, or filled with non-magnetic or weakly-magnetic material.

12. The multi-axis magnetic lens according to claim 10 , wherein said second and third radial gaps can respectively comprise an annular multilayer therein, and said annular multilayer comprises non-magnetic or weakly-magnetic annular layers and magnetic annular layers in alternate arrangement.

13. The multi-axis magnetic lens according to claim 1 , further comprising at least one first magnetic shielding plate located on one side of the pair of magnetic conductor plates and respectively having a plurality of first through openings, wherein said each paired through bores are aligned with one of said first through openings of said each first magnetic shielding plate.

14. The multi-axis magnetic lens according to claim 13 , further comprising at least one second magnetic shielding plate located the other side of the pair of magnetic conductor plates and respectively having a plurality of second through openings, wherein said each paired through bores are aligned with one of said second through openings of said each second magnetic shielding plate.

15. The multi-axis magnetic lens according to claim 1 , wherein said each paired through bores are circular.

16. A permeability-discontinuity unit, comprising:

one magnetic cellular layer; and

at least one non-magnetic or weakly-magnetic annular layer outside said magnetic cellular layer,

wherein permeability of each weakly-magnetic annular layer is much smaller than that of said magnetic cellular layer.

17. The permeability-discontinuity unit according to claim 16 , wherein any non-magnetic or weakly-magnetic annular layer can further comprise more than one non-magnetic or weakly-magnetic sub-layers.

18. A permeability-discontinuity unit, comprising:

one magnetic cellular layer;

at least one magnetic annular layer; and

at least one non-magnetic or weakly-magnetic annular layer,

wherein one magnetic annular layer is immediately enclosed by one non-magnetic or weakly-magnetic annular layer and/or immediately encloses one non-magnetic or weakly-magnetic annular layer, the innermost annular layer encloses said magnetic cellular layer, and permeability of each weakly-magnetic annular layer is much smaller than that of said magnetic cellular layer and magnetic annular layers.

19. The permeability-discontinuity unit according to claim 18 , wherein any non-magnetic or weakly-magnetic annular layer can further comprise more than one non-magnetic or weakly-magnetic sub-layers and any magnetic layer can further comprise more than one magnetic sub-layers.

20. A magnetic shielding device for a multi-axis magnetic lens, comprising:

at least one first magnetic shielding plate respectively having a plurality of first through openings and on one side of said multi-axis magnetic lens, wherein an optical axis of each magnetic sub-lens of said multi-axis magnetic lens is aligned with one of said first through openings of said each first magnetic shielding plate,

wherein all said first magnetic shielding plates are configured to make magnetic flux leaking out of said multi-axis magnetic lens vanish away rapidly outside the magnetic shielding device.

21. The magnetic shielding device according to claim 20 , further comprising at least one second magnetic shielding plate respectively having a plurality of second through openings and on the other side of said multi-axis magnetic lens, wherein said optical axis of said each magnetic sub-lens of said multi-axis magnetic lens is aligned with one of said second through openings of said each second magnetic shielding plate,

wherein all said second magnetic shielding plates are configured to make magnetic flux leaking out of the multi-axis magnetic lens vanish away rapidly outside the magnetic shielding device.

22. The magnetic shielding device according to claim 20 , wherein each of said first magnetic shielding plates can be kept gaps from the others and the multi-axis magnetic lens so as to make magnetic flux leaking out of the multi-axis magnetic lens vanish away more rapidly outside the magnetic shielding device.

23. The magnetic shielding device according to claim 21 , wherein each of said first and second magnetic shielding plates can be kept gaps from the others and the multi-axis magnetic lens so as to make magnetic flux leaking out of the multi-axis magnetic lens vanish away more rapidly outside the magnetic shielding device.

24. A multi-axis magnetic lens, comprising:

a pair of parallel magnetic conductor plates with a plurality of through holes in pairs therein, the pair of parallel magnetic conductor plates including an upper plate and a lower plate, wherein for each paired through holes, an upper through hole in the upper plate is aligned with a corresponding lower through hole in the lower plate;

a plurality of magnetic pillars in pairs inside the plurality of through holes with a plurality of first radial gaps in pairs respectively, each pair of magnetic pillars forming an axial gap therebetween and having a pair of through bores, wherein for each paired first radial gaps formed by each paired magnetic pillars inside each paired through holes, a first upper radial gap is between an inner sidewall of the upper through hole and an outer sidewall of the upper magnetic pillar inside the upper through hole, a first lower radial gap is between an inner sidewall of the lower through hole and an outer sidewall of the lower magnetic pillar inside the lower through hole, wherein for one paired through bores inside said each paired magnetic pillars, an upper through bore in the upper magnetic pillar is aligned with a lower through bore in the lower magnetic pillar and said upper through bore is off from a center of said upper magnetic pillar,

thereby forming a plurality of magnetic sub-lens modules for focusing a plurality of charged particle beams respectively, wherein paired upper and lower magnetic pillars of each sub-lens module respectively function as upper and lower pole-pieces of said sub-lens; and

a common excitation coil located between the pair of parallel magnetic conductor plates for providing magnetic flux to the plurality of magnetic sub-lens modules.

25. The multi-axis magnetic lens according to claim 24 , wherein each axial gap is vacuum or filled with non-magnetic material.

26. The multi-axis magnetic lens according to claim 25 , wherein any first radial gap can be vacuum, or filled with non-magnetic or weakly-magnetic material.

27. The multi-axis magnetic lens according to claim 25 , wherein any first radial gap can comprise an annular multilayer therein, and said annular multilayer comprises non-magnetic or weakly-magnetic annular layers and magnetic annular layers in alternate arrangement.

28. The multi-axis magnetic lens according to claim 27 , wherein any non-magnetic or weakly-magnetic annular layer can further comprise more than one non-magnetic or weakly-magnetic sub-layers and any magnetic layer can further comprise more than one magnetic sub-layers.

29. The multi-axis magnetic lens according to claim 24 , wherein said each paired through bores are circular.