Effective Orientation Control of Pb(Zr 0.4 Ti 0.6 )O 3 Thin Films Using A New Ti/Pb(Zr 0.4 Ti 0.6 )O 3 Seeding Layer

The effect of thin Ti/PbZr 0.4 Ti 0.6 O 3 seed layers on the properties of PbZr 0.4 Ti 0.6 O 3 (PZT) capacitors has been investigated. The seed layer is based on a bi-layer of thin Ti and thin PZT with a total thickness ranging from 10 to 25 nm, which was deposited on Ir/Pt or Ir/IrO 2 /Pt by sputtering. After crystallization of the seed layers the main 130-nm-thick PZT film was deposited and crystallized. As a result, a highly preferred (111)-orientation of the PZT was obtained on a 10-nm-thick seed layer, where the peak intensity ratios of (111)/{100} and (111)/{110} are about 100 and 20, respectively. The 10-nm-thick seed forms a pyrochlore phase with a very smooth surface, where the formation of the pyrochlore phase is attributed to Pb diffusion, resulting in a Pb deficient stoichiometry. The seed layer transformed to the perovskite phase during the main PZT crystallization. It is shown that an IrO 2 layer beneath the Pt can prevent Pt layer degradation related to the volume expansion due to the oxidation of Ir during the main PZT crystallization. Capacitors with the 10-nm-thick seed layer fabricated on the Ir/Pt and Ir/IrO 2 /Pt substrates showed typical 2 Pr values of 44.0 μC/cm 2 and 41.2 μC/cm 2 , respectively. The voltage found for 90%-polarization saturation is about 3.0 V, and the capacitors are fatigue-free at least up to 10 10 switching cycles.