Non-linear dielectric constant increase with Ti composition in high-k ALD-HfTiOx films after O2 crystallization annealing

HfTiOx films deposited on TiN, Pt and Al2O3/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 (HfO2) to 40 (TiO2) as a function of Ti content in the film. On the other hands, the dielectric constant of HfTiOx films with 64% – 30% Hf content increases up to 60 after crystallization annealing, which strongly correlates with the appearance of the orthorhombic HfTiO4 structure. Furthermore, the thermal treatment in O2 ambient is found to have a drastic effect to decrease the leakage current density (Jg). As a result, 10−8 A/cm2 at Vg = +1V with 0.8nm EOT is achieved with 30%-Hf contained film.