Measurement of Surface Vacuum Potential from the Energy Spectrum of the Secondary Electron in the Scanning Electron Microscope

Abstract

A measurement method for determining the contact potential between the specimen and the analyzer from an S-curve (an integrated curve of secondary electron energy distribution) in the scanning electron microscope is described. The measured S-curve is best-fitted to the calculated S-curve assuming the secondary electron energy distribution and the instrumental function of the analyzer. The work function of the retarding electrode in the analyzer was calibrated by the use of thermionic emission from a heated W filament. The work function of acid-cleaned Cu was 4.71 V, while that of untreated Al was 3.64 V. It is shown that the previously reported charging characteristics of an electrically floating gate in the MOS structure under electron beam irradiation are well explained by taking account of the surface vacuum potentials. The work function of insulator SiO2 was estimated to be on the order of 7 V.