Work function engineering of Hf-silicate gate stacks by using Ni/Ti metal electrodes

Abstract

In order to achieve both interfacial oxide reduction and flexible work function control by using a single gate electrode structure, we deposited Ni/Ti bi-layered metal electrodes with different Ti thicknesses on Hf-silicate films and investigated their electrical properties. A relatively small reduction of the interfacial oxide thickness (by similar to 0.5 nm) when using the reactive Ti electrode was observed, possibly due to the lower oxygen diffusivity in the Hf-silicate film than in HfO2. No interfacial reaction between Ni and Ti was observed after post-metallization heat treatments at temperatures up to 400 degrees C. The flatband voltage shift from a pure Ni to a pure Ti electrode happened below a thickness of similar to 6 inn for Ti and a gradual change of the effective work function by 0.6 eV was obtained by further decreasing the underlying Ti thickness.