| 摘要 |
PURPOSE:To improve uniformity and reproducibility by a method wherein a Faraday cup, which has an aperture whose diameter is smaller than that of a beam, is provided to a prescribed position near a specimen and at least one of an electron gun or a lens system is controlled so as to make the detected maximum beam current constant. CONSTITUTION:A Faraday cup 11 whose aperture diameter is far smaller than that of an electron beam is provided to an edge of a stage on which a specimen 5 is placed. Captured electrons flow through an ammeter 12 and a beam current at a peak part of the beam is detected. Every time the specimen 5 is scanned, the Faraday cup 11 is scanned and the maximum value of a current signal synchronized with it is measured. This measured value is used as a feedback signal and controls lens driving circuits 8, 9 so as to make the measured value constant by optimizing a beam focus. |
