High dielectric constant TiO₂ thin films on a Ru electrode grown at 250°C by atomic-layer deposition

TiO₂ thin films with high dielectric constants (83-100) were grown on a Ru electrode at a growth temperature of 250°C using the atomic-layer deposition method. The as-deposited films were crystallized with rutile structure. Adoption of O₃ with a very high concentration (400 g/m³) was crucial for obtaining the rutile phase and the high dielectric constant. The leakage current density of a TiO₂ film with an equivalent oxide thickness of 1.0-1.5 nm was 10^-6 - 10 ^-8 A/cm² at ± 1 V. All these electrical properties were obtained after limited postannealing where the annealing temperature was <500°C, which is crucial to the structural stability of the Ru electrode. Therefore, these TiO₂ films are very promising as the capacitor dielectrics of dynamic random access memories. TiO₂ films grown on a bare Si wafer or Pt electrode by the same process had anatase structure and a dielectric constant of ∼40.