Preparation and characterization of Pb(Zr,Ti)O-3 films deposited on Pt/RuO2 hybrid electrode for ferroelectric random access memory devices

Abstract

Polycrystalline Pb(Zr,Ti)O-3 (PZT) films were fabricated at a low temperature of 450 degreesC 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 x 10(-7) A/cm(2) at 200 kV/cm) and fatigue characteristic (P* - P-boolean AND: 9% drop after 4 x 10(9) fatigue cycles) could be obtained for the 110-run-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.