Preparation Of PLZT Thin Films And Their Fine-Patterning

Lead lanthanum zirconate titanate (PLZT) exhibits many desirable optical and electrical properties such as ferroelectricity.dielectrics and holds great promise for wide applications in ferroelectric random access memory (FRAM) and dynamic random access memory(DRAM). In this paper, PLZT thin films with excellent ferroelectric, dielectric and optical properties were expected to be prepared by Sol-Gel process. The fine patterning of the films was expected to be fabricated by a novel method. The FT-IR, TEM, modified Sawyer-Tower circuit and LCR numeral electric bridge were used to study the molecule formation in stable PLZT sol, the crystal phase and the ferroelectric and optical performance of PLZT thin films respectively. The results are listed as follows:(1) Chelate complexes were formed by the reactions between acetylacetone(AcAcH) and the precursors of Pb, Zr or Ti used in this research, which led to a stable sol. In the sol-gel processing, the mol ratio of the additives of acetic acid and ethanolamine exerted an impact on the stability of the sol and the quality of its gel films.when the mol ratio of Pb, acetic acid and ethanolamine was 1:0.15:0.1,the sol possessed the best quality.(2) When the PLZT thin films on silicon substrate have been heated at 500℃ for one hour, the films were made up of perovskite, La2O3 and PbO. When heated at 700℃ for one hour, the films were composed of peroVskite.TiO2 and PbZrO3. And when heated at 800℃ for one hour, only the perovskite phase was obtained in the fikns.(3) The PLZT thin films derived from the sol 'using methanol as solvent and Zr(OC4H9V Pb(CH3COO)2 La(NO3)2 Ti(OC4H9)4 as the starting materials had excellent ferroelectric and dielectric behaviors. The remnant polarization(Pr) and the coercive field strength(Ec) were 42.81uC/cm2 and 14.62kV/cm respectively. The dielectric constant(er) was 508 and the dissipation factor(tan5) was 0.11 when the films were tested at 20Hz.(4) Adding PbTiO3 interlayer between PLZT films and the bottom electrode led to better crystallization of the perovskite phase but reduced Pr and increased EC of the thin films. As a result, the hysteresis loop couldn't be saturated easily and the tan 6 increased.(5) The PLZT thin films prepared by Sol-Gel process had good transparence. The thin films on quartz and with a composition of 7/65/35 had the highestThis paper was funded by National Natural Science Fund of PR.China (50072018).transparence of about 90%.(6)The PLZT/AcAc gel films had obvious absorption peak at the wavelength of 312nm. The absorption peak decreased until disappeared when the films were irradiated by the ultraviolet light with the relevant wavelength, which indicated that the films were distinctly photosensitive. From such a kind of photosensitive PLZT gel films, the fine patterning has been fabricated.