Patent ID: 7351983

Claim:
A focused ion beam system comprising: an ion source for producing ions; an extraction electrode for extracting an ion beam from said ion source; a condenser lens for controlling angular aperture of the extracted ion beam; a current-limiting aperture for taking out an ion beam having a certain angle of radiation from said ion beam whose angular aperture has been controlled by said condenser lens; an electrostatic angular aperture control lens designed to be able to control the angular aperture of the ion beam passed through said current-limiting aperture without varying the amount of current of said ion beam; an electrostatic objective lens for focusing said ion beam, whose angular aperture has been controlled by said electrostatic angular aperture control lens, onto a specimen; and control means acting to control said electrostatic angular aperture control lens with a polarity with which charged particles are decelerated and to control said electrostatic objective lens with a polarity with which the charged particles are accelerated.