Investigations of electron irradiation effects on SiO2-Si surfaces using the energy distribution of secondary electrons

Surface potential changes in SiO2-Si surfaces under periodic electron bombardment were studied by using the energy distribution of secondary electrons produced by 3-10KV primary electrons. Oxides of various thickness, thermally grown by wet and dry processes on both N-type and P-type substrates of various resistivity were examined. It was found that the behavior of change in surface potential with beam chopping frequency depends very little on oxide thickness and type of oxide (dry or wet). The frequency dependence of the surface potential is interpreted as being due to radiation induced charge developed in the oxide at the oxide-semiconductor interface, greater positive charge being produced at low electron beam energies. This effect is qualitatively explained by the voltage dependence of processes that yield positive charge buildup.