Atomic Layer Deposition and Electrical Properties of PbTiO[sub 3] Thin Films Using Metallorganic Precursors and H[sub 2]O

Atomic layer deposition of ferroelectric PbTiO 3 (PTO) thin films was attempted using lead bis(3-N,N-dimethyl-2-methyl-2-propanoxide) and titanium tetra(tert-butoxide) as Pb and Ti precursors, respectively, and H 2 O as the oxidant at a wafer temperature of 200°C on Ir ∕ IrO 2 ∕ SiO 2 ∕ Si substrates. Cation stoichiometric PTO thin films were grown with a growth rate of 0.064 nm ∕ cycle by a proper control of the cycle ratio of the PbO and TiO 2 cycles. A catalytic increase in the growth rate was observed for the PTO films compared to the component oxide films. The as-grown film was amorphous and postdeposition annealing at temperatures ranging from 500 to 600°C induced crystallization to the desired perovskite structure. However, the slow heating and cooling induced pyrochlore phase formation with a very fine grain size along the larger perovskite grain boundaries. Conductive atomic force microscopy showed that the pyrochlore material shows a high leakage current which adversely interferes with the ferroelectric properties. Fast heating and cooling effectively suppressed the pyrochlore phase formation. In this case, the main leakage current path was formed by the perovskite grains but the leakage current level was largely decreased. A remanent polarization of 11.2 μ C ∕ cm 2 at an applied bias voltage of 2.8 V was obtained.