Transient charging and discharging behaviors of border traps in the dual-layer HfO2/SiO2 high-k gate stack observed by using low-frequency charge pumping method

Abstract

Transient charging and discharging of border traps in the dual-layer HfO2/SiO2 high-kappa. gate stack have been extensively studied by the low-frequency charge pumping method with various input pulse waveforms. It has been demonstrated that the exchange of charge carriers mainly occurs through the direct tunneling between the Si conduction band states and border traps in the HfO2 high-kappa. dielectric within the transient charging and discharging stages in one pulse cycle. Moreover, the transient charging and discharging behaviors could be observed in the time scale of 10(-8)-10(-4) s and well described by the charge trapping/detrapping model with dispersive capture/emission time constants used in static positive bias stress. Finally, the frequency and voltage dependencies of the border trap area density could also be transformed into the spatial and energetic distribution of border traps as a smoothed 3-D mesh profiling.