The influence of HfO2 film thickness on the interface state density and low field mobility of n channel HfO2/TiN gate MOSFETs

The influence of HfO2 thickness (1.6 to 3nm) on interface state density and low field mobility in HfO2/TiN gate n channel MOSFETs have been studied by analyzing experimental data from charge pumping, split CV, DC Id-Vg, pulsed Id-Vg and Y-function methods. It is found that there is no HfO2 thickness dependence on the interface state density, whereas there is continuous electron mobility degradation with HfO2 thickness. The devices exhibited no detectable fast transient charge trapping, allowing the relative contributions of phonon and Coulomb scattering to be examined over temperature. The dependence of the low field mobility on temperature from 50 K to 400 K indicates HfO2 remote phonon scattering as the dominant cause of the mobility degradation.