High-voltage energy dispersive x-ray spectrometry using a low-energy primary beam

This paper proposes a way to do energy dispersive x-ray spectroscopy (EDS) at high accelerating voltages using a low-voltage field emission scanning electron microscope (FESEM). By biasing the sample to a positive voltage, the electron landing energy (also known as the x-ray excitation energy) is increased, effectively extending the EDS capabilities of the low-voltage SEM. This positive biasing reduces the signal-to-noise ratio of the FESEM image, but it also introduces scaling and offset errors. A one-time calibration procedure is shown to compensate for these distortions allowing the user to view the unbiased image, and then do a precise superposition of the low energy image, high energy image, and EDS elemental map. The proposed solution is implemented on a commercial low-voltage FESEM with an EDS energy resolution of 130 eV.