Patent ID: 7312449

Claim:
An electron beam system comprising: a primary optical system for irradiating a plurality of electron beams onto a sample; a condenser lens for focusing the plurality of electron beams into a crossover image at a point; a first deflector disposed downstream to the point for scanning the plurality of electron beams; and a second deflector disposed upstream to the point for scanning the plurality of electron beams; a dose amount calculating circuit; a CPU for controlling a voltage applied to a Wehnelt electrode; and wherein the plurality of electron beams are simultaneously blocked by a knife edge disposed at the point from passing toward the sample for measuring electric current absorbed by the knife edge when a signal is applied to the second deflector and during a fly-back, and the dose amount calculating circuit calculates a dose amount per unit area from the electric current absorbed by the knife edge, and the CPU decreases the voltage applied to the Wehnelt electrode for reducing a beam current when the dose amount exceeds a predetermined value.