Optimization of the low-temperature MOCVD process for PZT thin films

Pb(Zr_x Ti_{1 - x})O₃ (PZT) thin films of about 0.34 tim were successfully grown at alow temperature of 500 °C by metalorganic chemical vapor deposition with a β-diketonate complex of Pb(tmhd)₂, zirconium t-butoxide, and titanium isopropoxide as source precursors. Ferroelectric capacitors of a Pt/PZT/Pt configuration were fabricated, and their structural and electrical properties were investigated as a function of the input Pb/(Zr+Ti) and Zr/(Zr+Ti) source ratios. The structure of the as-grown films at 500 °C changed from tetragonal to pseudocubic with increasing the Zr/(Zr+Ti) ratio above an input Pb/(Zr+Ti) source ratio of 5.0 while a 2nd phase of ZrO₂ was only observed below Pb/(Zr+Ti) ratio of 5.0, regardless of the Zr/(Zr+Ti) ratio. The dielectric constant and loss of the PZT films were 150-1200 and 0.01-0.04 at 100 kHz, respectively. Leakage current densities decreased with increasing the Zr/(Zr+Ti) ratio. The process window for growing a single phase PZT is very narrow in the low-temperature MOCVD process, and control of the Pb input precursor amount is crucial for the formation of the crystalline PZT phase.