Electrical characteristics and interface structure of HfAlO∕SiON∕Si(001) stacks

The electrical characteristics of RuO2∕HfAlO∕SiON∕Si(001) capacitors prepared by thermal nitridation of the Si substrate previously to HfAlO ultrathin film deposition were determined. A dielectric constant of 19 and a gate current density of 67mA∕cm2 for an equivalent oxide thickness of 1.1nm have been determined, whereas non-nitrided capacitors gave substantially lower dielectric constant and higher gate current density. The structure and integrity of the stacks after thermal annealing were accessed by means of spectroscopic ellipsometry and x-ray reflectometry, indicating that thermal N incorporation into the gate dielectric stacks forms an effective diffusion barrier, leading to a smoother, SiO2-like interface. The HfAlO films grown on nitrided substrates were seen also to have lower porosity, percentage of voids, and density of oxygen vacancies.