Metallorganic CVD of High-Quality PZT Thin Films at Low Temperature with New Zr and Ti Precursors Having MMP Ligands

Abstract

Thin (70-80 nm) (PZT) films were deposited on substrates by metallorganic chemical vapor deposition (MOCVD) at temperatures ranging from 450 to 525°C using a dome-type CVD chamber with a double-cocktail precursor solution liquid delivery system. The precursors used were bis-tetramethylheptanedionato-Pb tetrakis1-methoxy-2-methyl-2-propoxy-Ti and tetrakis1-methoxy-2-methyl-2-propoxy-Zr for the Pb, Ti, and Zr, respectively. These new Zr and Ti precursors showed stable vaporization characteristics at 230°C and allowed film deposition in the low-temperature range. A self-regulation mechanism in cation composition control, where the ratio of the deposited film is independent of the input ratio of the precursor solutions, was observed at temperatures as low as 475°C. The self-regulation behavior became more evident with increasing temperature. However, the films grown at higher temperatures showed a larger leakage current and degraded ferroelectric performance because of the increased interfacial reaction. A 70 nm thick PZT film grown at 475°C on an Ir electrode exhibited good ferroelectric performance, such as high remanent polarization at 4 V), small coercive voltage (∼0.6 V at 4.5 V), and low voltage (∼4 V), saturation behavior after postannealing at The remaining value after the fatigue test of cycles was >90% of the initial value even with a simple Pt top electrode. © 2004 The Electrochemical Society. All rights reserved.