Electrical Properties for Capacitors of Dynamic Random Access Memory on (Pb, La)(Zr, Ti)O3 Thin Films by Metalorganic Chemical Vapor Deposition

Lanthanum-modified lead zirconate titanate (PLZT) thin films (0.2–0.35 µ m) have been prepared on Pt/ SiO2/Si substrates at 650° 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 µ C/cm2 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/µm2 when La=8–22 at.%. It has been suggested that the breakdown of the films does not occur up to about 1× 1015 cycles at an access voltage of 3 V by the unipolar acceleration test.