Patent Number: 048662801
Section: claims

1. An objective lens of an electron beam apparatus in which an electron beam emitted from an electron gun is converged onto a specimen, the reflected electron from the specimen or the secondary electron emitted therefrom is detected, and a fine pattern on the specimen is measured, said lens comprising: a magnetic circuit structure including an upper magnetic pole member having an opening to transmit the electron beam to be converged which was emitted from said electron gun, a lower magnetic pole member disposed so as to face said upper magnetic pole member, and a magnetic path member to connect the outer peripheral edges of the upper and lower magnetic pole members;  a coil, arranged in a part of said magnetic circuit structure, for generating magnetic fluxes passing through said upper and lower magnetic pole members, said magnetic path member, and the space between said opening edge and the lower magnetic pole member when said coil is excited; and  moving means which is disposed on the surface of the lower magnetic pole member opposite to the upper magnetic pole member and is movable on the plane substantially perpendicular to said electron beam in a space enclosed by said magnetic circuit structure in the state in which the specimen is put on the upper surface of said moving means. 2. An objective lens according to claim 1, further having a projecting portion in the portion of said lower magnetic pole member opposite to the opening of said upper magnetic pole member, said projecting portion projecting toward the side of said opening. 3. An objective lens according to claim 1, wherein a part of the side wall of said magnetic circuit structure has an opening portion and said specimen is disposed onto said moving means through said opening portion. 4. An objective lens according to claim 1, wherein said upper and lower magnetic pole members of said magnetic circuit structure are arranged so as to enable movement of at least one of said upper and lower magnetic pole members in the direction of the electron beam. 5. An objective lens according to claim 1, wherein said moving means has a first moving member which is movable on the upper surface of said lower magnetic pole member in the directions along one axis and a second moving member which is mounted on said first moving member and is movable in the direction along the axis perpendicular to said axis, and said specimen is disposed on said second moving member. 6. An objective lens according to claim 1, wherein said upper magnetic pole member, said lower magnetic pole member and said magnetic path member are disposed so as to delimit a chamber in which the specimen is received and which provides a magnetic shielding effect with respect to the electron beam.