Accurate investigation of the high-k soft phonon scattering mechanism in metal gate MOSFETs

We report an experimental study of the mobility in TiN/HfO/sub 2/ gate stacks focused on the accurate determination of the HfO/sub 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/sub x/ interfacial layer (IL) thicker than 9-10/spl Aring/. For a IL thickness of 7/spl ring/A, this mechanism degrades the electron mobility at high effective fields by /spl sim/16% at 300K and /spl sim/13%at 400K.