Effect of La doping on dielectric constant and tetragonality of ZrO₂ thin films deposited by atomic layer deposition

The electrical properties of La-doped ZrO₂ thin films were studied for an application to cell capacitors in dynamic random-access memory. La-doped ZrO₂ thin films were deposited by changing the ratio of ZrO₂:La₂O₃ cycles using atomic layer deposition. Grazing-incidence X-ray diffraction analysis showed that the La-doped ZrO₂ thin films had a tetragonal structure. The tetragonality (c/a) of La-doped ZrO₂ thin films increased from 1.41 in undoped ZrO₂ to 1.43 in La-doped ZrO₂ with a 7.5% La content. X-ray photoelectron spectroscopy showed that the concentration of oxygen vacancies in ZrO₂ thin films increased with increasing La concentration. The dielectric constant of La-doped ZrO₂ was increased by 15% from 37 in undoped ZrO₂ to 43 at a La doping concentration of 7.5%, and the leakage current was also improved. Therefore, La-doped ZrO₂ thin films are expected to be an excellent candidate material for dynamic random-access memory cell capacitors owing to their high dielectric constant and low leakage current.