Electron beam application apparatus

1. An electron beam application apparatus, comprising,

a sample stage on which a sample is to be placed;

an electron optical system which includes an objective lens for forming an electronic image by electrons emitted from the sample and which has an optical axis perpendicular to a sample mounting surface of the sample stage; and

a camera which images the electronic image; wherein

the electron optical system includes

a mirror aberration corrector disposed perpendicular to the optical axis;

a plurality of magnetic field sectors by which an orbit of electrons passing through the objective lens is deviated from the optical axis to make the electrons incident on the mirror aberration corrector, and the orbit of the electrons emitted from the mirror aberration corrector is returned to the optical axis; and

a doublet lens disposed between adjacent magnetic field sectors along the orbit of the electrons,

each of the plurality of magnetic field sectors has a same deflection angle for deflecting the orbit of the electrons, and

the doublet lens is disposed such that an object plane and an image plane thereof are respectively central planes of the adjacent magnetic field sectors along the orbit of the electrons.

2. The electron beam application apparatus according to claim 1 , wherein

when the number of the plurality of magnetic field sectors in the electron optical system is S and the deflection angles of the plurality of magnetic field sectors are A, S and A are expressed by the following equations:

S= 4 N− 1

A=π/ 4 N [rad]

wherein N is a natural number.

3. The electron beam application apparatus according to claim 1 , wherein

the central plane of each said magnetic field sector is a plane including a line of intersection between an electron beam incidence plane and an electron beam emission plane of the magnetic field sector and a center of the magnetic field sector.

4. The electron beam application apparatus according to claim 1 , wherein

the plurality of magnetic field sectors include a first magnetic field sector and a second magnetic field sector whose centers are disposed on the optical axis,

the center of the first magnetic field sector is disposed at an intersection between an axial ray of the electrons passing through the objective lens and the optical axis, and

the center of the second magnetic field sector is disposed at an intersection between an axial ray of the electrons emitted from the mirror aberration corrector and the optical axis.

5. The electron beam application apparatus according to claim 4 , wherein

the electron optical system includes

an auxiliary objective lens, by which a field ray of the electrons passing through the objective lens is aligned in parallel with the optical axis, between the objective lens and the first magnetic field sector; and

a projection lens which magnifies and projects an electronic image, that is aberration-corrected by the mirror aberration corrector, onto an imaging surface of the camera.

6. The electron beam application apparatus according to claim 4 , wherein

the doublet lens of one stage or a plurality of stages is disposed between the first magnetic field sector and the second magnetic field sector, and

the plurality of magnetic field sectors are able to be turned off.

7. The electron beam application apparatus according to claim 6 , wherein

an electronic image is formed on the second magnetic field sector at the same magnification as an electron image formed on the first magnetic field sector regardless of whether the plurality of magnetic field sectors are turned on or off.

8. The electron beam application apparatus according to claim 1 , wherein

the magnetic field sectors include planar pole pieces facing each other with the optical axis sandwiched therebetween,

the pole piece is separated into a main pole piece and a shield magnetic pole by a first groove,

the first groove is formed so as to surround the main pole piece, and

a coil that generates a magnetic field in the magnetic field sector is disposed in the first groove.

9. The electron beam application apparatus according to claim 8 , wherein

a planar shape of the pole piece is a circular shape, and

the first groove is formed concentrically with the pole piece.

10. The electron beam application apparatus according to claim 8 , wherein

a first end surface of the pole piece is an electron beam incidence plane of the magnetic field sector, a second end surface of the pole piece is an electron beam emission plane of the magnetic field sector, and

in the optical axis from the electron beam incidence plane to a center and the optical axis from the center to the electron beam emission plane in the magnetic field sector, arrangement of the main pole piece, the first groove, and the shield magnetic pole is the same.

11. The electron beam application apparatus according to claim 8 , wherein

a second groove is formed to further separate the main pole piece into a plurality of main pole pieces,

a coil that generates a magnetic field in the magnetic field sector is disposed in each of the first groove and the second groove, and

the second groove is formed to be parallel to the central plane of the magnetic field sector.

12. The electron beam application apparatus according to claim 11 , wherein

a different magnetic field is generated for each of the plurality of separated main pole pieces.

13. The electron beam application apparatus according to claim 11 , wherein

the central plane of the magnetic field sector is a plane including a line of intersection between an electron beam incidence plane and an electron beam emission plane of the magnetic field sector and a center of the magnetic field sector.

14. The electron beam application apparatus according to claim 1 , wherein

a sample mounting surface of the sample stage is adjusted so as to be horizontal with respect to a floor surface on which the electron beam application apparatus is installed.