화학공학소재연구정보센터
Journal of the Electrochemical Society, Vol.151, No.5, C283-C291, 2004
Metallorganic CVD of high-quality PZT thin films at low temperature with new Zr and Ti precursors having MMP ligands
Thin (70-80 nm) Pb(Zr,Ti)O-3 (PZT) films were deposited on Ir/TaOx /SiO2 /Si substrates by metallorganic chemical vapor deposition (MOCVD) at temperatures ranging from 450 to 525degreesC using a dome-type CVD chamber with a double-cocktail precursor solution liquid delivery system. The precursors used were bis-tetramethylheptanedionato-Pb [Pb(THD)(2)], tetrakis1-methoxy-2-methyl-2-propoxy-Ti [Ti(MMP)(4)] and tetrakis1-methoxy-2-methyl-2-propoxy-Zr [Zr(MMP)(4)], for the Pb, Ti, and Zr, respectively. These new Zr and Ti precursors showed stable vaporization characteristics at 230degreesC and allowed film deposition in the low-temperature range. A self-regulation mechanism in cation composition control, where the Pb/(Zr + Ti) ratio of the deposited film is independent of the input Pb/(Zr + Ti) ratio of the precursor solutions, was observed at temperatures as low as 475degreesC. The self-regulation behavior became more evident with increasing temperature. However, the films grown at higher temperatures (>500degreesC) showed a larger leakage current and degraded ferroelectric performance because of the increased interfacial reaction. A 70 nm thick PZT film grown at 475degreesC on an Ir electrode exhibited good ferroelectric performance, such as high remanent polarization (P-r > 30 muC/cm(2) at 4 V), small coercive voltage (similar to0.6 V at 4.5 V), and low voltage (similar to4 V), P-r saturation behavior after postannealing at 650degreesC. The remaining P-r value after the fatigue test of 10(10) cycles was >90% of the initial value even with a simple Pt top electrode. (C) 2004 The Electrochemical Society.