On the nature of the interfacial layer in ultra-thin TiN/LaLuO₃ gate stacks

We present a detailed investigation on the nature of the interfacial layer (IL) in ultra-thin TiN/LaLuO₃ (LLO) gate stacks, which is of importance to facilitate CMOS scaling. The molecular beam deposited LaLuO₃ films are found to be amorphous by high-resolution transmission electron microscopy. A ∼9 Å thick LaLuO₃/interlayer transition observed by medium energy ion scattering correlates with the presence of a dual silicate/SiO₂-like interfacial layer derived from the analysis of photoelectron line positions and electron energy loss spectra. A theoretical model is used for the dielectric transition in a bi-layer LaLuO₃/IL structure, linking physical and electrical characterization data. The obtained leakage current of 10⁻³ A/cm² at 1.5 V and equivalent oxide thickness of 0.75 nm for TiN/LaLuO₃ gate stacks are adequate for scaling in the 14-12 nm node.