Patent ID: 8581190

Claim:
A charged particle beam apparatus, comprising: a specimen stage on which a specimen is mounted; an irradiation optical system for scanning a primary charged particle beam on the specimen mounted on the specimen stage; a detector for detecting secondary charged particles generated by the scanning of the charged particle beam; display means for displaying an output signal of the detector as an image; and an arithmetic unit for detecting aberrations; wherein the irradiation optical system comprises: an aberration corrector for correcting the aberrations of the primary charged particle beam emitted from a charged particle beam source; and an aperture for aberration measurement placed between the charged particle beam source and the aberration corrector, wherein the aperture for aberration measurement comprises: a first aperture part equipped with a central opening placed on an optical-axis of primary charged particles emitted from the charged particle beam source; and a second aperture part having a plurality of openings placed on a plurality of concentric circles with different radii around the central opening and outside the central opening each in an annular shape centered on the optical-axis, wherein the arithmetic unit is configured to acquire a first image acquired by the charged particle beam having passed through only the opening of the first aperture part, and a second image acquired in the same scanning region as that of the first image by the charged particle beam having passed through the plurality openings of the second aperture part, and configured to measure the aberrations from the first image and the second image, the second aperture has a plurality of groups of openings that are placed in an annular ring shape along the concentric circles centered on the optical-axis, and a cut or nontransparent region that serves as a mark provided at a specific phase on the annular ring for extraction of phase information.