Effect of RuO_x bottom electrode annealing temperature on sol-gel derived PZT capacitors

Abstract

The effects of bottom electrode annealing temperature on ferroelectric capacitors are examined. Temperatures between 350 and 600°C were used to anneal 2000 Å RuO_0.8/500 Å Ti electrodes deposited by ion beam sputtering. Anneals were performed in flowing O₂, N₂, ultra high purity (UHP) Ar, and air. Scanning Electron Microscope (SEM) data show that between 500 and 600°C, in air and flowing O₂, rectangular crystallites change to square crystallites. Energy Dispersive Spectroscopy (EDS) analysis shows that the square crystallites on the bottom electrodes annealed at 600°C in flowing O₂ have a higher oxygen content than the surrounding matrix. Atomic Force Microscopy (AFM) data show that the bottom electrodes annealed in air and flowing O₂ are rougher (root mean square (RMS) roughness between 50 and 80 nm) compared to the bottom electrodes that are unannealed (RMS roughness of 0.151 nm) and the bottom electrode annealed in flowing N₂ (RMS roughness of 3.8 nm). SEM data show that the 600°C bottom electrode anneal in UHP Ar resulted in a rougher surface, providing more nucleation sites for the PZT perovskite rosettes compared to the 400°C bottom electrode anneal with all other experimental parameters equal.