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Fundamental characteristics of DRAM capacitor application of PLZT ultrathin films prepared by MOCVD
Author(s) -
Goto Hideo,
Sato Atsushi,
Okada Masaru
Publication year - 1998
Publication title -
electrical engineering in japan
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.136
H-Index - 28
eISSN - 1520-6416
pISSN - 0424-7760
DOI - 10.1002/(sici)1520-6416(19980115)122:1<25::aid-eej4>3.0.co;2-u
Subject(s) - materials science , metalorganic vapour phase epitaxy , lead zirconate titanate , ferroelectricity , dielectric , annealing (glass) , capacitor , chemical vapor deposition , thin film , permittivity , composite material , substrate (aquarium) , optoelectronics , electrode , analytical chemistry (journal) , electronic engineering , nanotechnology , epitaxy , electrical engineering , voltage , layer (electronics) , oceanography , chemistry , chromatography , geology , engineering
Lanthanum‐modified lead zirconate titanate (PLZT) thin films (50 nm to 200 nm) were deposited on Pt/SiO 2 /Si substrate by metal‐organic chemical vapor deposition (MOCVD). The electrical properties of the films were investigated as a function of the La content or the substrate temperature. Ferroelectric PZT(0/50/50) films were obtained at substrate temperatures as low as 500 °C; their electrical characteristics improved with increasing substrate temperature. La exhibited adequate solid solution in the PZT above 650 °C. PLZT(15/45/55) films with a thickness of 100 nm were found to have good properties for application to the capacitors of dynamic random access memory (DRAM), namely, an effective charge density of 80 fF/μm 2 , a permittivity of 1000, an SiO 2 equivalent thickness of 0.4 nm, and a leakage current density of 5 × 10 −8 A/cm. Addition of La to PZT was effective in reducing the leakage current with an increase in the registration rate. RuO 2 and/or IrO 2 bottom electrodes for ferroelectric PLZT films were also investigated. The RuO 2 films were found effective as diffusion barriers for PLZT and MgO. Significant interdiffusion at RuO 2 /Si and RuO 2 /SiO 2 interfaces occurred during the deposition of PLZT films. Annealing of the RuO 2 film considerably depressed interface reactions. © 1998 Scripta Technica. Electr Eng Jpn, 122(1): 25–36, 1998