Patent ID: 7888640
Filing Date: 2011-02-15
Classification: G01N,H01J

Abstract:
1. A scanning electron microscope comprising: a specimen-holding portion for holding a specimen; an electron beam source emitting an electron beam; a condenser lens for converging the electron beam emitted from the electron beam source; a first electrode having an axisymmetric shape and mounted within a magnetic field produced by the condenser lens; an objective lens for focusing the converged beam into a very small spot onto the specimen; scan coils for scanning the electron beam over the specimen; a detector for detecting a specimen signal emanating from the specimen in response to the electron beam irradiation; an acceleration electrode mounted in the objective lens and accelerating a primary electron beam reaching from the electron beam source; and a control unit for varying a focal position of the condenser lens without modifying the focus of the objective lens by varying a voltage applied to the acceleration electrode while applying a given voltage to the first electrode.