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

We report an experimental study of the mobility in TiN/HfO 2 gate stacks focused on the accurate determination of the HfO 2 remote soft phonon scattering mechanism. The high-K intrinsic mechanism is clearly dissociated from Coulomb scattering which generally dominates the mobility degradation in high-K/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 Sio x interfacial layer (IL) thicker than 9-10 A. For an IL thickness of 7 A, 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.