Analysis of thin-film PZT/LNO stacks on an encapsulated TiN electrode

• Thin film PZT/LNO stacks on an encapsulated TiN electrode are studied.
• Promising ferroelectric behavior of these thin film layers is reported.
• A passive layer adjacent to the electrode is recognized and characterized.
• The leakage current was described by a diffusion-based model.

We realized metal-ferroelectric-metal (MFM) capacitors comprising high-quality ferroelectric lead zirconate titanate (Pb(Zr0.52Ti0.48)O3 or PZT) thin films on an LaNiO3/poly-Si/titanium nitride (TiN)/SiO2 integrated on a 100 mm Si wafer. Promising effective piezoelectric coefficient and remnant polarization of 53 pm/V and 19.2 μC/cm2, respectively, are obtained for the 100 nm-PZT/20 nm-LNO stack. Further analysis of the samples indicates the presence of a passive layer, possibly near the Ti/PZT interface at the top electrode. A leakage current model has been used to explain the obtained current density–electric field curves. In this model, diffusion limited transport has been assumed in which the injection is interface-controlled. Based on the capacitance and the leakage current measurements, the thickness and dielectric constant values of the passive layer are estimated to be 2.1 nm and 23, respectively. The observed apparent low barrier height value of 0.32 eV is attributed to ferroelectric polarization related phenomena. A good agreement between measurement and leakage current model is obtained.

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