Electrically benign Ru wet etching method for fabricating Ru/TiO ₂ /Ru capacitor

Ru top electrode etching techniques for Ru/Ti O₂ /Ru (RTR) thin film capacitor fabrication were examined. A dry etching process using a plasma mixture of O₂, Cl₂, and Ar gases deteriorated the leakage current properties significantly, which were not recovered by postannealing processes. The surface roughness was not a critical factor in determining the leakage characteristics. The etching damage along the etched edges was not the main cause of the leakage degradation but it was observed over the entire area, which was confirmed according to a comparison of capacitors with different perimeter/area ratios. For the wet etching of Ru films, the etch rates were evaluated using a periodic acid solution at various concentrations at 60°C. The Ru films etched using a 14 wt % periodic acid solution showed a moderate etch rate and a reasonable etching selectivity on the Ti O₂ and Al₂ O₃ films. The as-wet-etched RTR capacitors showed a lower leakage current level than the dry-etched capacitors. Furthermore, the electrical properties of the wet-etched capacitor were improved significantly by a postannealing process.