Structural and dielectric characterization of atomic layer deposited HfO2 and TiO2 as promising gate oxides

Tetrakis (diethylamino) hafnium (TDEAH), tetrakis (diethylamino) titanium (TDEAT) and H
₂
O were used for the atomic layer deposition of HfO
₂
and TiO
₂
films on silicon substrates. X-ray Photoelectron Spectroscopy showed that after a short Ar
⁺
sputtering for removing surface contaminants, both HfO
₂
and TiO
₂
films were found to be essentially carbon free. While HfO
₂
remained at +4 chemical state after the surface sputtering, TiO
₂
partially changed into Ti
⁺³
(Ti
₂
O
₃
) and Ti
⁺²
(TiO), suggesting a preferential sputtering of O over Ti. Phase-shift interferometry (PSI) was applied to probe the surface morphology of both as-deposited and post annealed films, which were later examined by Grazing Incidence X-ray Diffraction (GIXRD). From both PSI and GIXRD results, as-deposited HfO
₂
and TiO
₂
films were found to be amorphous with smooth surfaces but began to crystallize with roughened surfaces after annealing at 600 °C, with HfO
₂
crystallizing into a monoclinic structure and TiO
₂
crystallizing into an anatase structure. C-V and I-V measurement were performed after electron beam evaporation of Al metal contacts on the dielectric layers. The calculated dielectric constant (k) value of TiO
₂
is almost three times higher than that of HfO
₂
and the measured leakage current densities for the metal oxides are below 10
^-5
A/cm
²
at the applied voltage of 1 V.