Preparations of PZT thin film capacitors on PtRhOx electrodes with various conducting barriers for high density ferroelectric memories

We have investigated the high quality electrode-barriers for Pb(Zr0.35Ti0.65)O-3 (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 PtRhOx 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 PtRhOx bottom electrode and W-plug. It was found that PZT capacitors with Ta-barriers of 30-nm-thickness showed superior thermal stability up to 630degreesC. whose remanent polarization and coercive field were typically 30 muC/cm(2) and 86 kV/cm. respectively. However, their polarization fatigue behaviors are associated with the oxygen content in PtRhOx electrodes.