Patent ID: 7329889

Claim:
An electron beam apparatus, comprising: a table which mounts a specimen and is movable in three dimensional directions; an electron beam optical unit including an electron beam source, an element for deflecting an electron beam emitted from the electron beam source, an objective lens for converging and irradiating the electron beam deflected by the deflection element onto a specimen mounted on the table, and a detector for detecting a secondary electron emanated from the specimen by the irradiation of the electron beam; a first projection optical unit for projecting a first light onto a surface of the specimen in the vicinity of a beam axis of the electron beam optical unit from a first projection direction to the surface of the specimen; a second projection optical unit for projecting a second light onto the surface of the specimen in the vicinity of the beam axis of the electron beam optical unit from a second projection direction to the surface of the specimen, in which the second projection direction has a substantially opposite azimuth angle to the first projection direction and has a substantially same elevation angle from the surface of the specimen with respect to the first projection direction; a first detection optical unit for detecting an image of the first light projected onto the surface of the specimen by the first projection optical system and outputting information of a position of the image of the first light; a second detection optical unit for detecting an image of the second light projected onto the surface of the specimen by the second projection optical system and outputting information of a position of the image of the second light; a height detection unit for calculating a height of the surface of the specimen by using information outputted from the first detection optical unit and the second detection optical unit; and a focus control system for controlling a relative position between a focus position of the electron beam optical system and the table in accordance with information of the height from the height detection unit.