Patent ID: 8026491

Claim:
An observation apparatus using scanning electron microscope comprising: (i) a source of electrons; (ii) converging lenses for converging a primary electron beam emitted from the source of electrons; (iii) an objective lens for focusing the primary electron beam onto a sample; (iv) a detector for detecting a secondary signal in response to the irradiation by the primary electron beam; and (v) a scanning deflector disposed between the converging lenses and the objective lens, the scanning electron microscope comprising: an objective aperture disposed between the scanning deflector and the converging lenses in order to limit an irradiation amount of the primary electron beam onto the sample; an aligner for deflecting a center of the primary electron beam on the objective aperture, and a computer for obtaining optical axis correction amount of the primary electron beam by the aligner, wherein the computer utilizes a first image of the objective aperture obtained by not operating the aligner, a second image obtained by deflecting the primary electron beam a predetermined amount by said aligner in the X-direction without displacement in the Y-direction on said objective aperture, and a third image obtained by deflecting the primary electron beam a predetermined amount by the aligner in the Y-direction without displacement in the X-direction on the objective aperture so as to compensate an optical axis of the primary electron beam by way of obtaining an alignment condition of the electron beam and objective aperture that shows no movement of the center of the image depending on a relative sensitivity in the X- and Y-directions of the aligner.