Non-linear dielectric constant increase with Ti composition in high-k ALD-HfTiO x films after O 2 crystallization annealing

Abstract

\ce{HfTiO_x} films deposited on \ce{TiN}, \ce{Pt} and \ce{Al2O3}/\ce{Si} bottom electrodes (BE) by Atomic Layer Deposition (ALD) method were investigated in terms of the crystallization temperature, dielectric constant and leakage current. The as-deposited films show a linear increase of dielectric constant from $20$ (\ce{HfO2}) to $40$ (\ce{TiO2}) as a function of \ce{Ti} content in the film. On the other hands, the dielectric constant of \ce{HfTiO_x} films with $64%$--$30%$ \ce{Hf} content increases up to $60$ after crystallization annealing, which strongly correlates with the appearance of the orthorhombic \ce{HfTiO4} structure. Furthermore, the thermal treatment in \ce{O2} ambient is found to have a drastic effect to decrease the leakage current density ($J_\mathrm{g}$). As a result, $10^{-8}$\,A/cm$^2$ at $V_\mathrm{g} = +1$\,V with $0.8$\,nm EOT is achieved with $30%$-\ce{Hf} contained film.