Preparation and Characterization of Pb(Zr,Ti)O3 Films Deposited on Pt/RuO2 Hybrid Electrode for Ferroelectric Random Access Memory Devices

Polycrystalline Pb(Zr,Ti)O3 (PZT) films were fabricated at a low temperature of 450°C by the electron cyclotron resonance plasma-enhanced chemical vapor deposition (ECR PECVD) method. Stoichiometric PZT films with the pure perovskite phase could be obtained over a wider range of deposition conditions on Pt/RuO2 hybrid electrodes than on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 hybrid electrodes showed low leakage current and superior polarization characteristics compared with those on RuO2 electrodes. PZT capacitors fabricated on Pt/RuO2 were not as fatigue-free as those on RuO2 but had higher resistance to fatigue than those on Pt. The introduction of a PbTiO3 buffer layer prior to PZT film deposition on Pt/RuO2 improved the fatigue characteristics by suppressing the formation of nonstoichiometric interfacial layers. Good leakage current property (J: 5.8 ×10-7 A/cm2 at 200 kV/cm) and fatigue characteristic (P * - P ∧: 9% drop after 4 ×109 fatigue cycles) could be obtained for the 110-nm-thick PZT film using Pt/RuO2 hybrid top and bottom electrodes. This electrode structure is thought to be promising for use as a capacitor of high-density ferroelectric random access memory (FRAM) devices. The fatigue model that can explain the fatigue characteristics of PECVD-PZT capacitors with various hybrid electrode configurations is also suggested.