ELECTRICAL-PROPERTIES FOR CAPACITORS OF DYNAMIC RANDOM-ACCESS MEMORY ON (PB, LA)(ZR, TI)O-3 THIN-FILMS BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

Lanthanum-modified lead zirconate titanate (PLZT) thin films (0.2-0.35 mu m) have been prepared on Pt/SiO2/Si substrates at 650 degrees C by the metalorganic chemical vapor deposition (MOCVD) method. The electrical properties of the films were examined as a function of lanthanum content in the range of 0-22 at.%. The remanent polarization and coercive field decreased as the La content increased in the range of 0-14 at.%, whereas they were maintained at constant values of 1 mu C/cm(2) and 20 kV/cm, respectively, even in the paraelectric region where La content exceeds 15 at.% in ceramics. The effective dielectric constant of 1200 was obtained at La = 10 at.%, and the effective charge densities were about 30 fF/mu m(2) when La=8-22 at.%. It has been suggested that the breakdown of the films does not occur up to about 1 x 10(15) cycles at an access voltage of 3 V by the unipolar acceleration test.