Objective lens system for fast scanning large FOV
The device includes a beam source for generating an electron beam, a beam guiding tube passed through an objective lens, an objective lens for generating a magnetic field in the vicinity of the specimen to focus the particles of the particle beam on the specimen, a control electrode having a potential for providing a retarding field to the particle beam near the specimen to reduce the energy of the particle beam when the beam collides with the specimen, a deflection system including a plurality of deflection units situated along the optical axis for deflecting the particle beam to allow scanning on the specimen with large area, at least one of the deflection units located in the retarding field of the beam, the remainder of the deflection units located within the central bore of the objective lens, and a detection unit to capture secondary electron (SE) and backscattered electrons (BSE).
1. An objective system for focusing a charged particle beam, comprising:
an objective lens for focusing the beam onto a specimen;
a beam guiding structure disposed through the objective lens for the beam;
a first deflection unit arranged in the objective lens for deflecting the beam to a first distance; and
a second deflection unit for deflecting the beam to a second distance less than the first distance,
wherein the second deflection unit is arranged below the beam guiding structure and includes a ferrite structure adjacent to the second deflection unit.
2. The system according to claim 1 , wherein the objective lens comprises a magnetic lens and an electrostatic lens, the beam guiding structure is an electrode for controlling kinetic energy of the beam, and the first deflection unit comprises a first magnetic deflector for deflecting the beam and a second magnetic deflector for swinging a compound field of the objective lens.
3. The system according to claim 2 , wherein the electrostatic lens comprises a lower end of the beam guiding structure, a control electrode disposed below the beam guiding structure, and a stage.
4. The system according to claim 2 , wherein the electrostatic lens comprises a lower end of the beam guiding structure, the second deflection unit disposed below the beam guiding structure, and a stage.
5. The system according to claim 1 , wherein the second deflection unit adjusts a beam incidence angle from a tilt incidence angle to a normal incidence angle for an edge aberration.
6. A charged particle beam device, comprising:
a beam source for generating a primary beam;
a beam guiding structure for accelerating the primary beam;
an objective lens to focus the primary beam onto a specimen;
a first deflection unit disposed in the objective lens for deflecting the primary beam to a first distance and a second deflection unit for deflecting the primary beam to a second distance less than the first distance,
wherein the second deflection unit is arranged below the beam guiding structure and includes a ferrite structure adjacent to the second deflection unit.
7. The device according to claim 6 , further comprising a plurality of apertures for limiting the primary beam.
8. The device according to claim 6 , wherein the beam guiding structure extends from an anode of the beam source downward a lower pole piece of the objective lens.
9. The device according to claim 6 , wherein the first deflection unit comprises a first magnetic deflector accommodated in an upper portion of the objective lens for pre-deflecting the primary beam and a second magnetic deflector accommodated in the objective lens for swinging the objective lens.
10. The device according to claim 6 , further comprising:
a retarding electrode disposed below the beam guiding structure for decelerating the beam; and
at least one detection unit disposed above the objective lens to detect secondary or back-scattered particles emanated from the specimen.
11. The device according to claim 10 , wherein the retarding electrode adjusts a beam incidence angle from a tilt incidence angle to a normal incidence angle for an edge aberration.
12. A method for directing a charged particle beam to a substrate, comprising the steps of:
providing, using a beam guiding structure, a guiding field along a beam path to direct the beam to the substrate;
generating, using a first deflection unit, a first deflection field within the guiding field to direct the beam in a predetermined direction; and
generating, using a second deflection unit, a second deflection field downstream of the first deflection field for deflecting the beam, wherein the second deflection unit is arranged below the beam guiding structure and includes a ferrite structure adjacent to the second deflection unit, and
further comprising an electrostatic lens, the electrostatic lens comprising the beam guiding structure, the second deflection unit, and a stage for supporting the substrate.
13. The method according to claim 12 , further comprising a swing objective lens comprising a magnetic lens and the electrostatic lens, and
wherein the first and second deflection units are magnetic.
14. The method according to claim 13 , wherein the electrostatic lens comprises the beam guiding structure, a control electrode disposed below the beam guiding structure, and a stage for supporting the substrate.
15. The method according to claim 12 , wherein the second deflection unit is spaced apart from an objective lens by the ferrite structure.