Stoichiometry and phase purity of Pb(Zr,Ti)O3 thin films deposited by metal organic chemical vapor deposition

Abstract

( Pb , Zr ) Ti O 3 (PZT) films have been prepared by metal organic chemical vapor deposition on 200mm wafers. Phase pure perovskite films were deposited in a self-correcting region where the Pb stoichiometry is relatively insensitive to increasing Pb content in the gas phase. Films deposited with Pb flows lower than those used in the self-correcting region showed second phase ZrO2 whereas films deposited at Pb flows higher than those used in the self-correcting region showed second phase PbO. The PZT grains are columnar, extending from the bottom electrode to the top electrode. In the self-correcting region, PZT films of 70nm nominal thickness show good ferroelectric behavior with switched polarization of ∼40μC∕cm2 at 1.5V and saturation voltage of ∼1.2V. The films have an average roughness of ∼4nm with grain size of ∼700Å. The impact of the deposition parameters such as deposition temperature, pressure, precursor flow, and oxygen flow during deposition on the self-correcting region was investigated. Increasing the deposition temperature increases the width of the self-correcting region whereas increasing the oxygen flow narrows it. Pressure and the precursor flow do not impact the width although variation in pressure does shift the location of the self-correcting region.