Energy-discrimination detection device
This invention provides a method for improving performance of a reflective type energy filter for a charged particle beam, which employs a beam-adjusting lens on an entrance side of a potential barrier of the energy filter to make the charged particle beam become a substantially parallel beam to be incident onto the potential barrier. The method makes the energy filter have both a fine energy-discrimination power over a large emission angle spread and a high uniformity of energy-discrimination powers over a large FOV. A LVSEM using this method in the energy filter can obviously improve image contrast. The invention also provides multiple energy-discrimination detection devices formed by using the advantages of the method.
1. An energy-discrimination detection device for detecting a charged particle beam, comprising:
an energy filter, comprising:
a grid electrode being set at a first potential to form a potential barrier; and,
a beam-adjusting lens below said grid electrode and being excited to make said charged particle beam become a substantially parallel beam to be incident onto said potential barrier,
wherein a first plurality of particles of said charged particle beam, which has initial kinetic energies higher than a specific value and thus is able to cross said potential barrier, passes through said grid electrode and forms an exiting beam, while a second plurality of particles of said charged particle beam, which has initial kinetic energies not higher enough to be able to cross said potential barrier, is reflected back from said grid electrode and forms a reflection beam; and
a first detector above said energy filter and being excited to detect charged particles of said exiting beam,
wherein an optical axis of said beam-adjusting lens is both an optical axis of said energy filter and an optical axis of said energy-discrimination detection device.
2. The energy-discrimination detection device according to claim 1 , wherein said grid electrode is perpendicular to and aligned with said optical axis of said beam-adjusting lens.
3. The energy-discrimination detection device according to claim 2 , further comprising a shielding box covering said energy filter and said first detector, wherein said shielding box is made of electric conductor material and has an entrance plate which is below said energy filter, perpendicular to said optical axis thereof and has an entrance grid for said charged particle beam passing through.
4. The energy-discrimination detection device according to claim 3 , wherein said shielding box is set at a potential of a neighborhood where said energy-discrimination detection device is placed.
5. The energy-discrimination detection detector according to claim 4 , further comprising a beam-focusing lens between said first detector and said energy filter, wherein said beam-focusing lens is excited to reduce a beam size of said exiting beam on said first detector.
6. The energy-discrimination detection device according to claim 4 , further comprising a second detector below said entrance grid, wherein said second detector has an opening for a central part of said charged particle beam passing through and fully or partially detects other part thereof.
7. The energy-discrimination detection device according to claim 6 , further comprising a third detector being placed and excited to detect said reflection beam.
8. The energy-discrimination detection device according to claim 4 , further comprising a third detector being placed and excited to detect said reflection beam.
9. The energy-discrimination detection device according to claim 4 , further comprising a first aperture plate below said entrance grid, wherein said first aperture plate has a plurality of apertures with different radial sizes and one of said plurality of apertures is selected to block a peripheral part of said charged particle beam before passing through said entrance grid.
10. The energy-discrimination detection device according to claim 9 , further comprising a second detector below said first aperture plate, wherein said second detector has an opening for a central part of said charged particle beam passing through and fully or partially detects other part thereof.
11. The energy-discrimination detection device according to claim 10 , further comprising a second aperture plate below said second detector, wherein said second aperture plate has a plurality of apertures with different radial sizes and one of said plurality of apertures is selected to block a peripheral part of said charged particle beam before going to said second detector.
12. The energy-discrimination detection device according to claim 10 , further comprising a third detector being placed and excited to detect said reflection beam.
13. The energy-discrimination detection device according to claim 9 , further comprising a third detector being placed and excited to detect said reflection beam.
14. The energy-discrimination detection device according to claim 2 , wherein said beam-adjusting lens is an electrostatic lens comprising a first electrode, a second electrode and a third electrode,
wherein with respect to said charged particle beam, said first electrode and said second electrode are respectively on an entrance side and an exit side of said beam-adjusting lens and said third electrode is between said first electrode and said second electrode.