1 research outputs found
Thickness and Post-annealing Effects of the Sputtered La-Capping Layer Inserted between the TiN Gate and Hf-Based Dielectrics
We investigated effects of the sputtered
La-capping layer inserted between TiN and Hf-based dielectrics, HfO<sub>2</sub> and HfSiO<sub>4</sub>/HfO<sub>2</sub>, mainly focusing on
effective work function (EWF) and equivalent oxide thickness (EOT)
changes by modulation of its thickness and post-metal annealing (PMA).
The use of thin La capping up to 5 Γ
showed a linear flatband
voltage (<i>V</i><sub>FB</sub>) shift of β60 mV/Γ
,
regardless of gate dielectrics. However, with the increase of the
La thickness, a slight increase in EOT was observed for HfO<sub>2</sub>, whereas a negligible change in EOT was shown for the HfSiO<sub>4</sub>/HfO<sub>2</sub> bilayer. It might be ascribed to the facile
La oxidation, which acts as an additional oxide layer on both of the
gate dielectrics. Meanwhile, high-temperature PMA exhibited slight
reduction in <i>V</i><sub>FB</sub> as well as an EOT increase
for both of the Hf-based dielectrics. On the basis of X-ray photoelectron
spectroscopy (XPS) results, the reason for the slightly decreased
EWF resulted from two competing dipoles formed by movements of oxygen
vacancies (V<sub>O</sub>) and La atoms during the PMA. Additionally,
oxygen affinity and diffusion of the La-capping layer on both of the
gate dielectrics are further discussed in conjunction with thermodynamic
analyses, and thereby, schematic energy band diagrams were proposed
by taking into account competing dipole layers by V<sub>O</sub> movement
and La diffusion