Effects of Ion Etching and Annealing in O2 Atmosphere Following Ion Etching on Properties and Chemistry of Sr0.9Bi2.1Ta2O9+a Thin Films

Abstract

The effects of ion etching and effects of annealing in an O2 atmosphere for 60 min at 800°C following ion etching (reannealing) on the properties of Sr0.9Bi2.1Ta2O9+a (SBT) thin films for ferroelectric memory were studied. The leakage current increased by six orders of magnitude following Ar-ion etching, and it caused a bulging out of the hysteresis loop. Electron probe micro analysis (EPMA) results showed no significant change following the ion etching, whereas X-ray photoelectron spectrometry (XPS) detected a large decrease in the Bi concentration and increase in the metallic Bi to oxidic Bi ratio. Following reannealing, the electrical properties and surface compositions were restored. Thus, the electrical properties were significantly affected by the presence of metallic Bi together with a large composition deviation in the surface region. It was concluded that ion etching of the SBT thin films causes a reduction of oxidic Bi to metallic Bi and a decrease in the total Bi concentration in the surface region resulting in a high leakage current density, whereas annealing in an O2 atmosphere is effective for restoring the initial low leakage current density.