Effect of Substrate Temperature on Electrical Characteristics of (Pb, La)(Zr, Ti)O3 Ultrathin Films Deposited by Metalorganic Chemical Vapor Deposition

Lanthanum-modified lead zirconate titanate (PLZT) thin films (50-200 nm) were deposited on Pt/SiO2/Si substrates by metalorganic chemical vapor deposition (MOCVD). The electrical properties of the films were investigated as functions of the La content and substrate temperature. Ferroelectric PZT films were obtained at a substrate temperature as low as 500° C, and their electric characteristics were improved with increasing substrate temperature. La was adequately solid-dissolved into the PZT above 650° C. PLZT(15/45/55) films having a thickness of 100 nm were found to have good properties for application to capacitors of dynamic random access memory (DRAM), i.e., effective charge density of 80 fF/µ m2, dielectric constant of 1000, SiO2 equivalent thickness of 0.4 nm and leakage current density of 5×10-8 A/cm2. La addition to PZT was effective in reducing the leakage current with an increase in the registration rate.