An add-on secondary electron energy spectrometer for scanning electron microscopes

Abstract

This article presents an add-on secondary electron energy spectrometer for scanning electron microscopes (SEMs). The add-on unit fits on to the specimen stage of a conventional SEM, and the SEM is operated as normal. As an objective lens, the add-on unit improves the SEMs spatial resolution by around a factor of 4 at a primary beam energy of 1 keV. The add-on unit functions as a multichannel open-loop voltage contrast spectrometer by employing a bandpass deflector/filter unit whose pass energy is ramped with time. The unit is designed to deflect the secondary electrons while leaving the primary beam unaffected. Initial experimental results show that significant voltage and material contrast can be obtained. In a data acquisition time of 0.32 s, a minimum detectable voltage difference of around 54 mV was obtained. Regions of copper and brass that were indistinguishable via the normal secondary electron image, were distinguished with a signal to noise ratio of around 12 by using the add-on spectrometer. © 2001 American Institute of Physics.