FERROELECTRIC PROPERTIES OF CRYSTALLINE-ORIENTED LEAD ZIRCONATE TITANATES FORMED BY SOL-GEL DEPOSITION TECHNIQUE

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 mu C/cm(2) 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.