Application of Ru-based gate materials for CMOS technology

Together with high-κ dielectric films, metal gate electrodes have to be employed in advanced CMOS technologies. The metal gate material should be carefully selected with respect to work function, stability of metal-dielectric stack and compatibility with the CMOS process. In our investigation, Ru, RuO₂ and SrRuO₃ gate electrodes grown on thermal SiO ₂, atomic-layer deposition Al₂O₃ and HfO ₂ dielectric films have been analyzed by means of high- and low-frequency capacitance-voltage measurement as well as current-voltage characteristics on MOS capacitors. Ru-based gate materials were prepared by metal-organic chemical vapor deposition at temperatures between 300 and 500°C. Work function of the investigated gate material, leakage current, density of effective defect charge as well as density of interface traps of the gate oxide film were extracted from the measurements. These properties are discussed with regard to application of Ru-based metal gates in CMOS technology.