Effects of oxygen-argon mixing on the electrical and physical properties of ZrTiO₄ films sputtered on silicon at low temperature

Zirconium titanate (ZrTiO₄) thin films (200-260 nm) on p-type (100) Si substrates were prepared using radio-frequency sputter deposition at room temperature in atmosphere of various O₂/Ar mixing ratio (from 0/100 to 20/80). All films exhibited a (020) preferred orientation and small grain size with increasing O₂/Ar ratio, as shown by x-ray diffraction. The variations of dielectric constant, fixed oxide charge, and interface trapped charge with O₂/Ar ratio are studied with an Al/ZrTiO₄/Si structure. The refractive index and dielectric constant varied in ranges 2.34-2.26 and 20-16 for the as-deposited films. Within the range investigated, crystallinity appears to have a stronger influence on the densities of charge-trapping centers in the films than oxygen stoichiometry, and the latter may determine the leakage current density. A remarkable two orders of magnitude decrease in leakage current to 5.6×10^-9 A/cm ² at 0.1 MV/cm and an increase in breakdown field beyond 1.2 MV/cm are observed in the film deposited without oxygen after a 400°C annealing in air for 1 h. The current transport in ZrTiO₄ film is dominated by the Poole-Frenkel mechanism.