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 I_d-V_g, pulsed I_d-V_g 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.