Metallic bismuth on strontium-bismuth tantalate thin films for ferroelectric memory application

Strontium-bismuth tantalate (SBT) has been actively investigated as an attr active candidate for non-volatile ferroelectric random access memories beca use of its high resistance to fatigue. However, the ferroelectric property of SET is easily affected by fabrication process parameters. The relationsh ip between the surface chemistry of SET thin films and the fabrication proc ess parameters, such as crystallization temperature, upper Pt electrode, an nealing in oxygen after Pt electrode fabrication (= the second annealing), hydrogen sintering and ion etching, were examined mainly by XPS analysis. I n all specimens, metallic Pi, which is one of the main causes for deteriora tion of their performances, was observed in addition to oxidic Pi, Sr and T a, The deposition of an upper Pt electrode resulted exclusively in an incre ase in metallic Pi content. Sintering in a hydrogen atmosphere and ion etch ing increased the ratio of metallic Pi to total Pi, The second annealing wa s effective in suppressing the metallic Pi content. Copyright (C) 2000 John Wiley & Sons, Ltd.