Photoemission study of energy-band alignments and gap-state density distributions for high-k gate dielectrics

The determination of the energy band gaps of thin-gate insulators has been demonstrated from the onsets of the energy-loss spectra of O 1s (or N 1s) photoelectrons. The valence-band lineups of thin high-dielectric-constant (high-k) dielectrics such as Ta2O5, Al2O3, and ZrO2 formed on metals and Si(100) have also been determined by measuring the energy difference between the valence-band density-of-states curves. The energy band diagrams for metal/high-k dielectrics/Si(100) systems have been derived explicitly from considering the measured band gaps, valence-band lineups, electron affinities, and metal work functions in the systems. It is also demonstrated that total photoelectron yield spectroscopy can be used to quantify the energy distributions of both the defect states in high-k gate dielectrics and at the dielectric/Si(100) interfaces over the entire Si band gap without gate formation.