Determination of secondary electron yield from insulators due to a low-kV electron beam

Abstract

A technique for the accurate determination of secondary electron (SE) yield of insulators due to low-kV electron beam is presented. It is based on a capacitatively coupled charge measurement by subjecting the insulating film to a controlled pulsed electron beam in a scanning electron microscope. SE emissions from several insulating materials employed in integrated circuit manufacturing including wet and sputtered silicon dioxide (SiO2), polyimide, and AZ1350J photoresist, have been investigated for a range of primary energies between 0.5 and 2.5 keV. Comparisons are made between experimental data for SiO2 and polyimide with previous results. The dependence of SE emission on incidence angle and topography for SiO2 was investigated. Experimental results indicate that the dependence of SE emission on surface tilt for SiO2 is in good agreement with the power law for tilt angles below 70°, while emission saturation is observed at higher tilt angles. The SE yield from sputtered oxide was found to be higher than that of wet oxide, which is related to differences in topography between the two materials.