Ferroelectric Properties of Crystalline-Oriented Lead-Zirconate-Titanates Formed by Sol-Gel Deposition Technique

Abstract

Ferroelectric properties of lead-zirconate-titanate (PZT) films formed by the sol-gel deposition technique have been discussed from the standpoint of ferroelectric random-access memory (FRAM) and dynamic random-access memory (DRAM) applications. PZT films with <111>-preferred orientation and random orientation were formed on Pt/Ti/SiO2/Si substrates by optimizing fabrication conditions. Remanent polarization of the <111>-preferred film was 23.5 µ C/cm2 which is somewhat higher than that of the randomly oriented one. An abrupt saturation of remanent polarization was observed only for the <111>-preferred film. The voltages which provide saturations of remanent polarization densities for the <111>-preferred films are almost constant between 3.5 V to 4 V independent of thickness. The dielectric constant of the randomly oriented film was 730 which is larger than that of the <111>-preferred one and gradually decreased depending on the applied electric field. The <111>-preferred PZT film is appropriate for FRAM application, and the randomly oriented one is preferred for DRAM application.