Preparations of PZT Thin Film Capacitors on PtRhO_x Electrodes With Various Conducting Barriers for High Density Ferroelectric Memories

Abstract

We have investigated the high quality electrode-barriers for Pb(Zr_0.35Ti_0.65)O₃ (PZT) thin film capacitors to contact directly on W-plug for COB (capacitor-over-bit line) structured high density ferroelectric memories (FRAM). A conducting oxide of 40-nm-thickness PtRhO_x was used as a fatigue free electrode for PZT capacitors. Various materials, such as Ta, NiCr (Ni with 20 wt% Cr), Cr and PtRh (Pt with 10 wt% Rh), were investigated as conducting oxygen diffusion barriers between PtRhO_x bottom electrode and W-plug. It was found that PZT capacitors with Ta-barriers of 30-nm-thickness showed superior thermal stability up to 630°C, whose remanent polarization and coercive field were typically 30 μ C/cm² and 86 kV/cm, respectively. However, their polarization fatigue behaviors are associated with the oxygen content in PtRhO_x electrodes.

Keywords:

• PZT thin films
• PtRhO_x electrodes
• Ta diffusion barriers

ACKNOWLEDGEMENT

This work has been supported by the Sangji University Program 2003.