Pt and RuO2 Bottom Electrode Effects on Pb(Zr,Ti)O3 Memory Capacitors

Abstract

This study examines the effects of bottom electrodes for metal ferroelectric metal (MFM) capacitor applications. We investigated the following parameters of bottom electrodes and Pb(Zr0.53Ti0.47)O3 (PZT) thin films: substrate temperature, rf power, gas flow rate, Ar/O2 ratio, electrode material, and post-annealing effect. Bottom electrodes grown at 300°C for Pt and 200°C for RuO2 exhibited a film resistivity of 10-4 Ω·cm, had a surface roughness of approximately 55 Å and a preferred crystal orientation. Rapid thermal annealing (RTA) treatments on a Pt electrode at 600°C for 30 s improved the resistivity to 5×10-6 Ω·cm and generated the (111) preferred crystal orientation. PZT films exhibited a strong PZT (101) peak for an optimized Pt bottom electrode and (111), (200), (112) planes without preferred PZT orientations for the RuO2 electrode. A well-fabricated Pd/PZT/Pt capacitor showed a leakage current density in the order of 6×10-5 A/cm2, a dielectric constant (εr) of 365, a remanent polarization (Pr) of 27 µC/cm2, and a coercive field (Ec) of 50.5 kV/cm. This paper discusses the bottom electrode properties as well as their recommended conditions in memory device applications of thin-film PZT capacitors.