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

Abstract

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/cm2 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.