The effect of passivation on the observation of voltage contrast in the scanning electron microscope

Abstract

Measurements of the energies of electrons emitted from the surface of a silicon dioxide film thermally grown on a silicon substrate are reported. The results indicate that significant charging of the oxide surface occurs at low beam energy but when the beam completely penetrates the oxide layer little or no charging occurs following the predictions of a recently developed theory of electron-beam-induced conductivity. Further measurements showing the effect of substrate potential on the energies of the back-scattered electrons suggest that voltage measurements and the observation of voltage contrast in the scanning electron microscope should both be possible on passivated devices if the beam completely penetrates the insulating passivation layer. At lower beam energies these measurements are only possible for short periods of time after the commencement of irradiation.