Structural and electrical characteristics of (Pb1-xLax)(Zr0.5Ti0.5)O3 thin film capacitors

Electrical characteristics associated with crystal structure changes as a function of La content for (Pb1-xLax)(Zr0.5Ti0.5)O-3 (PLZT) thin films were investigated for applications in DRAM capacitors. Tetragonality of the PLZT films dramatically decreased with increasing La content. Films with La greater than or equal to 20 at% were found to be cubic. Films with La greater than or equal to 10 at% exhibited broader dielectric peaks, compared with those of bulk ceramics, and behaved as relaxer ferroelectrics. Tetragonal PLZT film with 10 at% La had a dielectric constant maximum of 1330 at room temperature and a charge storage density of similar to 18 mu C/cm(2) at 5 V. A decrease in the coercive field and remnant polarization with increasing La amount was due to the reduced dipolar response caused by the decreased crystal anisotropy. The effective permittivity values were nearly identical to the measured values for films with La greater than or equal to 14 at%, as a result of minimized remnant polarization with increasing La content. Leakage current densities < 10(-8) A/cm(2) were observed for films with La greater than or equal to 14 at%. (C) 2000 Elsevier Science Ltd. All rights reserved.