Electronic defect states at ultrathin SiO2/Si interfaces from photoelectron yield spectroscopy

The energy distribution of defect states for ultrathin thermally-grown SiO2 /Si(100) interfaces has been quantified by using the total photoelectron yi eld spectroscopy which enables us to detect the electronic states as low as 10(10) cm(-2) eV(-1). We have demonstrated that, for as-grown 2.5-4.5 nm-t hick SiO2/Si(100), there exist electronic defect states with a density of 1 0(11)-10(12) cm(-2) eV(-1) near midgap. It is also found that oxide thinnin g in a 0.1% HF solution at room temperature eliminates significantly the el ectronic states above midgap and subsequent 800 degrees C annealing in dry N-2 for 5 min regenerates partly the defect states. These observations sugg est the hydrogen passivation of the defect states during the dilute HF trea tment and the thermal dissociation of the hydrogen passivation by 800 degre es C annealing. (C) 1999 Elsevier Science Ltd. All rights reserved.