Patent Number: 
Section: claims

1. An electron beam apparatus for irradiating a sample with a primary electron beam, and detecting secondary electrons generated from a surface of the sample by the irradiation to evaluate the sample surface, comprising:a primary electro-optical system for focusing the primary electron beam on the sample surface and scanning it with the primary electron beam;a secondary electro-optical system comprising at least one stage of lens;an E×B separator for separating the secondary electrons generated from the sample surface and directing them to the secondary electro-optical system;a first detector for detecting the secondary electrons which have passed through the secondary electro-optical system;a second detector for detecting an exposure dose of the primary electron beam on the sample surface;a memory for storing the detected exposure doses on the sample surface; anda control apparatus adapted to calculate a unit exposure dose per unit area on the basis of the stored exposure doses, and controlling the primary electron beam such that the unit exposure dose does not exceed a predetermined level. 2. An electron beam apparatus according to claim 1, wherein the secondary electro-optical system further comprises a diaphragm. 3. An electron beam apparatus according to claim 1, wherein the primary electro-optical system comprises an aperture plate having a plurality of apertures by which a plurality of primary electron beams are formed from an electron beam emitted from an electron gun. 4. An electron beam apparatus according to claim 1, further comprising an apparatus for outputting a signal representing a position on the sample surface, at which the unit exposure dose exceeds the predetermined level. 5. An electron beam apparatus according to claim 1, whereinthe sample is a wafer;the electron beam apparatus further comprises an evaluation apparatus for evaluating the wafer surface on the basis of the detected secondary electrons, the evaluation being executed for every constant stripe width on the wafer while a stage carrying wafer is moving; andthe calculation of the unit exposure dose is executed for an area which is smaller than an area of (the stripe)×(a length of a chip in the stripe direction). 6. An electron beam apparatus according to claim 1, further comprising:a third detector for detecting a moving speed of a sample stage;a compensation apparatus included in at least one of the primary electro-optical system and the secondary electro-optical system, for compensating, in response to the moving speed of the sample stage detected by the third detector, a deflection amount of at least one of the primary electron beam and the secondary electron beam. 7. An electron beam apparatus according to claim 1, further comprising:a third detector for detecting a moving speed of a stage carrying the sample;a fourth detector for detecting a position of the stage;a compensation apparatus included in at least one of the primary electro-optical system and the secondary electro-optical system, for compensating, in response to the moving speed and the position of the sample stage detected by the third and fourth detectors, a deflection amount of at least one of the primary electron beam and the secondary electron beam. 8. An electron beam apparatus according to claim 1, whereinthe primary electron beam is irradiated on the sample surface in the form of a multi-beam; andthe minimum interval between adjacent primary electron beams on the sample surface is wider than the resolution of the secondary electro-optical system. 9. An electron beam apparatus according to claim 1, whereinthe primary electron beam is irradiated on the sample surface in the form of a multi-beam; andthe multi-beam is set such that when the beams on the sample surface are projected onto an axis perpendicular to a moving direction of a sample stage, the projected points on the axis are spaced at substantially the same interval.