Investigation of Paraelectric Plt Thin Films Using Reactive Magnetron Sputtering.

The study of methods to prepare paraelectric perovskite PLT (Pb_{rm 1-X} La_{rm X}Ti _{rm 1-X/4}O_3 ; x = 0.28) thin films has been important because thin films of this high dielectric strength material are required to make high density capacitors for dynamic random access memory. In this research, paraelectric PLT thin films were prepared on multi-layer (Pt/Ti/SiO_2 /Si) and MgO substrates in a unique way by the reactive magnetron sputtering method using a multi-component metal target. The individual control of each metal area on the sputtering target had considerable influence on the stoichiometry and electrical properties of the thin films. The effect of post-deposition annealing on as-deposited amorphous PLT films was studied as a function of temperature in the range of 450^circC to 750 ^circC. The inter-dependent relationship of the composition, crystalline structure and surface morphology in the films was studied as a function of annealing conditions. The chemical composition of the as-deposited and annealed films was measured by Rutherford back-scattering (RBS) and Auger electron spectroscopy (AES). The composition of PLT (28) thin film was: Pb, 0.73; La, 0.28; Ti, 0.88; O, 2.9. The dielectric constant (varepsilon _{r}) and dissipation factor (tan delta) at low electric field measurement (500 V/cm) of the capacitors with the highest dielectric properties were 1216 and 0.018, respectively. Single crystal film at 650^circC were smooth and had the lowest leakage current density, 0.1 muA/cm^2, at the electric field of 0.25 MV/cm. However, the highest dielectric constant, 1216, and the highest charge storage density, 12.5 muC/cm^2, obtained with an annealing temperature of 750^circ C. The research showed that magnetron sputtering can be used to prepare paraelectric perovskite PLT (28) thin films with high dielectric constant, large charge storage density and relatively low leakage current for capacitor applications in active DRAM cells.