Patent ID: 8222601

Claim:
A scanning electron microscope comprising: a first condenser lens for converging an electron beam emitted from an electron beam source; an electrode having an axisymmetric shape and disposed in a magnetic field produced by the first condenser lens; a second condenser lens for converging the electron beam which has been passed through the first condenser lens after being emitted from the electron beam source; an aperture plate disposed in a region containing an optical axis between the first and second condenser lenses; an objective lens for focusing the converged electron beam into a very small spot onto a 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 acting to accelerate a primary electron beam reaching from the electron beam source; and a control unit for controlling an amount of the primary electron beam passed through the aperture plate by applying a given voltage to the electrode.