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) normalPbfalse(normalZr,normalTifalse)O3 (PZT) films were deposited on normalIr/TaOx/SiO2/normalSi 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 false[normalPbfalse(THD)2false], tetrakis1-methoxy-2-methyl-2-propoxy-Ti false[normalTifalse(MMP)4false] and tetrakis1-methoxy-2-methyl-2-propoxy-Zr false[normalZrfalse(MMP)4false], 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 normalPb/false(normalZr+normalTifalse) ratio of the deposited film is independent of the input normalPb/false(normalZr+normalTifalse) 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 false(>500°Cfalse) 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 false(Pnormalr>30 μC/cm2 at 4 V), small coercive voltage (∼0.6 V at 4.5 V), and low voltage (∼4 V), Pnormalr saturation behavior after postannealing at 650°C. The remaining Pnormalr value after the fatigue test of 1010 cycles was >90% of the initial value even with a simple Pt top electrode. © 2004 The Electrochemical Society. All rights reserved.

Characteristics of Polycrystalline SrRuO[sub 3] Thin-Film Bottom Electrodes for Metallorganic Chemical-Vapor-Deposited Pb(Zr[sub 0.2]Ti[sub 0.8])O[sub 3] Thin Films

“…A schematic diagram and detailed features of the dome-type MOCVD system were reported previously. 13 Bis-tetramethylheptanedionato-Pb ͓Pb͑THD͒ 2 ͔, tetrakis 1-methoxy-2-methyl-2-propoxy-Zr ͓Zr͑MMP͒ 4 ͔, and tetrakis 1-methoxy-2-methyl-2-propoxy-Ti ͓Ti͑MMP͒ 4 ͔ dissolved in an ethylcyclohexane ͑ECH͒ solvent ͑con-centration of 0.1 M͒ were used as Pb, Zr, and Ti precursors, respectively, and O 2 was used as an oxidant. The typical PZT film thickness was 70 nm.…”

“…Therefore, an Ir layer was adopted because this is the most commonly adopted bottom electrode layer for the MOCVD of PZT films in integrated FeRAM devices. [13][14][15][16] SRO has a too high resistivity to be used as a bottom electrode of highly integrated FeRAMs. For the fabrication of FeRAMs with a higher density ͑Ͼ32 Mbit͒ a lower height of the capacitor stack is necessary due to the difficult etching of the stack with a vertical side wall shape.…”