Atomic layer deposition and electrical properties of SrTi O3 thin films grown using Sr (C11 H19 O2) 2, Ti (Oi- C3 H7) 4, and H2 O

Atomic layer deposited SrTi O3 (STO) thin films were grown using Sr (C11 H19 O2) 2 and Ti (Oi- C3 H7) 4 with a remote plasma activated or thermal H2 O vapor as oxidant at growth temperatures ranging from 190 to 270°C. The as-grown films were amorphous and showed a low effective dielectric constant of ∼20 with a low leakage current density (< 10-7 A cm2 at 1 V). The chemical binding status of the Sr ions varied with the degree of crystallization of the STO film. A reasonable film growth rate and stoichiometric cation composition were obtained when the vaporization temperature of Sr-precursor was <200°C with the thermal H2 O vapor. The low density of the as-grown film induced a large shrinkage in the film thickness which caused microcracking of the crystallized films during postannealing, even with the increased H2 O supply. Adoption of thin (∼5 nm) crystallized seed layer before the main layer STO growth improved the microstructure after the crystallization and the leakage current performance. As a result of the process optimization, the best electrical properties of an STO film grown on a Ru electrode were 0.45 nm for the equivalent oxide thickness and 1× 10-3 A cm2 for the leakage current density at 1 V.