Electron tunneling spectroscopy study of traps in high- k gate dielectrics: Determination of physical locations and energy levels of traps

It will be demonstrated that the electron tunneling spectroscopy (ETS), obtained by taking the second derivative of the current-voltage (I-V) characteristic of a tunnel barrier, is an effective technique to probe traps in ultra-thin gate dielectrics where significant tunneling currents flow. By taking the electron tunneling spectra in both polarities, one can determine the locations and energy levels of traps that appear in the ETS spectra. The procedure for the above and the associated derivation will be presented. Examples are shown to demonstrate the use of ETS to track the evolution of traps in high- k gate dielectrics under electrical stress.