| 摘要 |
PURPOSE:To make it possible to improve S/N (signal v.s. noise) ratio of secondary electron output by cyclically and intermittently radiating electron beams, and applying lock-in amplification method, after detecting AC-modulated secondary electrons emitted from this irradiated part by a scintillator or a secondary electron multiplying tube. CONSTITUTION:Electron beams emitted from a power source 1 and an electron gun 2 reach a sample 11 through an electron lens system 3, a chopping electrode 4 to form a cyclic and intermittent wave, an aperture 5 and a scanning coil 6. Secondary electrons emitted from the sample 11 as the result of incident electron beams, is AC-demodulated by the scintillator or a secondary electron multiplying tube 8 to be detected. The AC-modulated secondary electron signal is, further, output to a CRT 10 through a lock-in amplifier 9. A secondary electron beam image with good S/N ratio is obtained by applying this kind of lock-in amplification, even if an electron beam incident current is reduced in the same way as in the case that an electron beam incident current is reduced for the purpose of preventing electrification.
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