Dielectric properties of unannealed ECR-sputtered (Ba, Sr) TiO₃ films under DC-bias stresses

Abstract

Changes in leakage current and polarization hysteresis loops of (Ba_0.55Sr_0.45)TiO₃ (BST) films for capacitor applications are found after +3 V and -3 V dc-bias stress tests. An electron cyclotron resonance sputtering is used for depositing those 100-nm-thick films in Pt/BST/Pt structures. Comparison of characteristics with PT/BST/Ti (2 nm) /Pt(bottom) structures suggests that barrier degradation due to oxygen deficiencies may occur near the interface of not only bottom electrodes but also top electrodes. Electron traps also seem to be generated in BST films. Polarization hysteresis data indicate that there is no clear ferroelectric hysteresis and that the shape of the loops is probably controlled by leakage current and charge trapping.