SrTiO3/BaTiO3 multilayers thin films for integrated tunable capacitors applications

In this study, we propose to observe STO/BTO multilayers as tunable dielectric. These layers are deposited onto platinized Si substrate as they are dedicated to be integrated in microelectronic technologies. STO and BTO are deposited by ion beam sputtering (IBS). The number of STO/BTO bilayer, called period in the following, ranges from I to 5 with thicknesses in the 65-85 nm range. After Pt top electrode deposition, samples are annealed at temperatures between 300 and 700 degrees C. High dielectric constant value, correlated with perovskite structure, appears after a 450 degrees C annealing which is very interesting for above IC integration. SIMS shows weak interdiffusion in the stack after annealing. Dielectric constant increases from 56 to 102 as periods increase from 1 to 5. Simultaneously, tuning range gains 150% with period increasing. Temperature stability and ferroelectric behaviour also increases with periods increase. A curious drawback is apparition of holes in BTO layers after annealing, as observed by TEM. (c) 2007 Elsevier Ltd.