On the mobility in high-κ/metal gate MOSFETs: Evaluation of the high-κ phonon scattering impact

We report an experimental study of the mobility in TiN/HfO2 gate stacks focused on the accurate determination of the HfO2 remote soft phonon scattering mechanism. The high-κ intrinsic mechanism is clearly dissociated from Coulomb scattering which generally dominates the mobility degradation in high-κ/metal gate stacks. The temperature dependence of this additional phonon scattering mechanism is nearly linear. This scattering mechanism is shown to be negligible with a metal gate for a SiOx interfacial layer (IL) thicker than 9–10 Å. For an IL thickness of 7 Å, this mechanism degrades the electron mobility at high effective fields (1 MV/cm) by ∼13–16% at 300 K and ∼10–12% at 400 K.