Characterization of high-k gate dielectric/silicon interfaces

Abstract

We have shown that, for thermally evaporated Ta 2O 5 or ZrO 2 thin films on Si(1 0 0), O 2 annealing at 300–500 °C causes the formation of an interfacial silicon oxide layer as thin as 1–2 nm which can be interpreted in terms of their high permeability to oxygen. And we have demonstrated how useful the energy loss spectra of photoexcited electrons from core levels such as O 1s are to measure the energy bandgaps of very thin insulators. With the combination of measured bandgaps and valence band lineups determined for X-ray photoelectron spectroscopy valence band spectra, we have determined the energy band alignments of Ta 2O 5 and ZrO 2 with Si(1 0 0) before and after the O 2 annealing at 500 °C. In addition, we have demonstrated that total photoelectron yield spectroscopy provides us direct information to quantify the energy distributions of both the defect states in the high-k dielectrics and the dielectric/Si(1 0 0) interface states over nearly entire Si bandgap.