Charged particle beam column
AssigneeApplied Materials, Inc.
InventorPavel Adamec
Life of this patent
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Abstract
A column for directing a beam of charged particles with a finite energy spread onto a specimen surface under an oblique beam landing angle comprises: a particle source; an objective lens; a deflection unit for deflecting the beam of charged particles away from the optical axis such that the beam.of charged particles traverses the objective lens off-axis, thereby causing a chromatic aberration, a compensation unit adapted to disperse the beam of charged particles, thereby substantially compensating said chromatic aberration in the plane of the specimen surface, whereby the combined action of the objective lens and the deflection unit directs the beam of charged particles to hit the specimen surface under said large beam landing angle.
Claims15
A column for directing a beam of charged particles with a finite energy spread onto a specimen surface under an oblique beam landing angle, the column comprising:
- a particle source for providing the beam of charged particles propagating along an optical axis;
- an objective lens for focussing the beam of charged particles onto the specimen surface;
- a deflection unit for deflecting the beam of charged particles away from the optical axis such that the beam of charged particles traverses the objective lens off-axis, thereby causing a chromatic aberration,
- a compensation unit adapted to disperse the beam of charged particles, thereby substantially compensating said chromatic aberration in the plane of the specimen surface,
- whereby the combined action of the objective lens and the deflection unit directs the beam of charged particles to hit the specimen surface under said large beam landing angle.
A method for directing a beam of charged particles with a finite energy spread onto a specimen surface under an oblique beam landing angle, the method comprising the steps of:
- a) providing a beam of charged particles with a finite energy spread propagating along an optical axis;
- b) focussing the beam of charges particles onto the specimen surface with an objective lens;
- characterized in that the method further comprises the steps of
- c) selecting a beam landing angle;
- d) deflecting the beam of charged particles propagating along the optical axis away from the optical axis such that the beam of charged particles traverses the objective lens off-axis, thereby causing a first chromatic aberration, whereby the magnitude of the deflection is chosen such that the combined action of deflecting and focussing the beam directs the beam of charged particles to hit the specimen under said large beam landing angle;
- e) dispersing the beam of charged particles, thereby introducing a second chromatic aberration of substantially the same kind and magnitude but in substantially opposite direction as said first chromatic aberration to substantially compensate said first chromatic aberration in the plane of the specimen surface.
Dependencies are inferred from the claim text.