Physical origins of mobility degradation in extremely scaled SiO2/HfO2 gate stacks with La and Al induced dipoles

Abstract

We demonstrate metal-gate-induced interfacial layer (IL) scaling using a HfO2 dielectric and clarify the kinetics underlying this process. The intrinsic IL scaling effect on electron mobility is separated from La and Al-induced dipole effects. We find that the mobility degradation for La-containing high-κ dielectrics is not due to the La-induced dipole but due to the intrinsic IL scaling effect, whereas the Al-induced dipole brings about additional mobility degradation. This unique nature of the La-induced dipole enables aggressive equivalent oxide thickness scaling down to 0.42 nm without extrinsic mobility degradation when combined with IL scaling.