Charged-particle energy analyzer

1. A charged-particle energy analyzer apparatus comprising:

a first electically-conductive mesh with openings for passage of charged particles, the first mesh being arranged to receive the charged particles on a first side and pass the charged particles to a second side;

a first electrode arranged such that a first cavity is formed between the second side of the first mesh and the first electrode;

a second electrically-conductive mesh with openings for passage of the charged particles, the second mesh being arranged to receive the charged particles on a second side and pass the charged particles to a first side

a second electrode arranged such that a second cavity is formed between the first side of the second mesh and the second electrode;

a third electrically-conductive mesh with openings for passage of the charged particles, the third mesh being arranged to receive the charged particles on a first side and pass the charged particles to a second side; and

a position-sensitive charged-particle detector arranged to receive the charged particles after the charged particles pass through the third mesh,

wherein the first, second and third electrically-conductive meshes together form an annular central mesh.

2. The apparatus of claim 1 , wherein the first, second and third meshes are positioned on a single plane as parts of a single mesh structure of the annular central mesh.

3. The apparatus of claim 1 , wherein the first electrode comprises a first electrically-conductive plate, and the second electrode comprises a second electrically-conductive plate, further wherein the single plane lies between the first electrically-conductive plate and the second electrically-conductive plate.

4. The apparatus of claim 1 , wherein the first, second and third meshes are electrically grounded, and wherein a negative voltage is applied to the first and second electrodes.

5. The apparatus of claim 1 , further comprising:

resistor-like sidewalls electrically coupling the meshes to the electrodes.

6. The apparatus of claim 5 , wherein the resistor-like sidewalls comprise voltage step-down arrays.

7. The apparatus of claim 5 , wherein the resistor-like sidewalls comprise sidewalls with a resistive coating.

8. The apparatus of claim 1 , wherein trajectories of the charged particles enter the first cavity through the first mesh, are deflected away from the first electrode, enter the second cavity through the second mesh, are deflected away from the second electrode, and exit the second cavity through the third mesh.

9. The apparatus of claim 1 , further comprising:

a first electrically-conductive shield arranged to shield an electrostatic field in the first cavity; and a second electrically-conductive shield arranged to shield an electrostatic field in the second cavity.

10. The apparatus of claim 1 , further comprising:

a metal mesh arranged in front of a surface of the position-sensitive charged-particle detector, and

an electrostatic field created by a voltage difference between the metal mesh and the surface.

11. The apparatus of claim 1 , further comprising:

detector segments of the position-sensitive charged-particle detector.

12. The apparatus of claim 11 , wherein the detector segments comprise trapezoidal detector surfaces.

13. The apparatus of claim 11 , wherein the detector segments are rotatable in a polar direction.

14. The apparatus of claim 1 , wherein the charged particles comprise electrons, the apparatus further comprising:

an electron source configured to generate a primary electron beam;

an objective lens configured to focus the primary electron beam to a spot at a surface of a target substrate; and

a deflector configured to controllably deflect the primary electron beam over the surface of the target substrate,

wherein the primary electron beam cause emission of secondary electrons from the surface of the target substrate, and

wherein trajectories of the secondary electrons go through the first and second cavities and are detected by the position-sensitive charged-particle detector,

wherein the annular central mesh is centered on an optical axis for the primary electron beam of the apparatus.

15. A method of analyzing energies of charged particles, the method comprising:

passing the charged particles through a first electrically-conductive mesh to enter a first cavity,

deflecting the charged particles away from a first electrically-conductive plate;

passing the charged particles through a second electrically-conductive mesh to exit the first cavity and enter a second cavity;

deflecting the charged particles away from a second electrically-conductive plate;

passing the charged particles through a third electrically-conductive mesh to exit the second cavity; and

detecting the charged particles with a position-sensitive detector,

wherein the first, second and third electrically-conductive meshes together form an annular central mesh.

16. The method of claim 15 , wherein the first, second and third electrically-conductive meshes are positioned on a single plane as parts of a single mesh structure of the annular central mesh, further wherein the single plane lies between the first electrically-conductive plate and the second electrically-conductive plate.

17. The method of claim 15 , wherein the electrically-conductive meshes are electrically grounded, and wherein a negative voltage is applied to the first and second electrically-conductive plates.

18. The method of claim 17 , further comprising:

shielding the first cavity using a first electrically-conductive shield; and

shielding the second cavity with a second electrically-conductive shield.

19. The method of claim 15 , wherein the charged particles comprise electrons, the method further comprising:

generating a primary electron beam using an electron gun;

focusing the primary electron beam to a spot at a surface of a target substrate;

causing emission of secondary electrons from the surface of the target substrate; and

controllably deflecting the primary electron beam over the surface of the target substrate,

wherein trajectories of the secondary electrons emitted from the surface of the target substrate travel through the first and second cavities and are detected by the position-sensitive charged-particle detector,

wherein the annular central mesh is centered on an optical axis for the primary electron beam of the apparatus.

20. The method of claim 15 , further comprising:

applying an electrostatic field between a detector surface and a mesh in front of the detector surface so as to suppress or remove tertiary electrons generated at the detector surface.

21. The method of claim 15 , further comprising:

polar rotation of segments of the position-sensitive charged-particle detector.